Proceedings of the Junior Scientist Conference 2008

Proceedings of the 

Junior Scientist Conference 2008

Proceedings of the 

Junior Scientist Conference 2008 

Vienna University of Technology 

Vienna, Austria 

November 2008 

Edited by 

Hans K. Kaiser and Raimund Kirner

The views and opinions expressed in all the papers of this book are the author’s personal 

ones. 

The copyright of the individual papers belongs to the authors. Copies cannot be reproduced 

for commercial profit. 

Cover page design: Bettina Neunteufl 

c○2008, Copyright protected. 

ISBN 978-3-200-01612-5 

Printed in Austria.

Contents 

Welcome Message from Peter Skalicky xv 

Welcome Message from Hans K. Kaiser xvii 

Conference Organizers xix 

Conference Program xxi 

1 Information and Communication Technology 1 

Implementation of Quadrature Modulator Imbalance Compensation Method, 

Karel Povalac, Roman Marsálek ...................... 3 

Diagnostical analysis of voice, 

Pavel Sala, Milan Sigmund ......................... 5 

Realization of the OFDM coder and decoder using DSP, 

Petr Zelinka, Milan Sigmund ........................ 7 

Transmembrane Potential Measurements on Plant Cells using the Voltagesensitive 

Dye ANNINE-6, 

Bianca Flickinger, Thomas Berghöfer, Christian Eing, Wolfgang Frey ... 9 

Modeling metamaterial microwave resonators, 

Tomas Zvolensky, Zbynek Raida ...................... 11 

Bearingless Segment Motor with Buried Magnets, 

Thomas Stallinger, Wolfgang Gruber, Wolfgang Amrhein ......... 13 

Identification of tacit knowledge during realization of knowledge creation processes, 

Frantisek Babic, Ján Paralic ........................ 15 

i

Multifunctional tuned 4th order active filter, 

Roman Sotner, Tomas Dostal ........................ 17 

Active Semiconductor Devices for Millimetre Waves Applications, 

Michal Pokorný, Zbynek Raida ....................... 19 

Analysis of Power-Bus Structures Using Contour Integral Method, 

Martin Stumpf, Zbynek Raida ........................ 21 

Creating and Drawing Fonts for Graphic displays with Paged Memory Model, 

Filip Adamec, Tomas Fryza ......................... 23 

Bandwidth Comparison of Microwave Planar Hybrids, 

Petr Orság, prof. Ing. Jirí Svacina, CSc. .................. 25 

Six prot microwave vector analyzer, 

Radek Dvorák, Ing. Tomás Urbanec, Ph.D. ................ 27 

Decomposing HEX-Programs: Preliminary Results, 

Thomas Krennwallner, Thomas Eiter, Michael Fink ............ 29 

Bio-inspired Implementation of Linear Vestibulo-Ocular and Opto-Kinetic Reflexes 

in a Humanoid Robot, 

Igor Labutov, Jizhong Xiao, Theodore Raphan ............... 31 

Simulation of light environment and its application in practice, 

Anna Beneova, Marek Krupa ........................ 33 

Towards Synchronization in Multiple Antenna Systems, 

Qi Wang, Markus Rupp ........................... 35 

Technical criteria for the comparison of modern ERP system for the usage in 

orchestra companies at the case study of Dynamics AX 2009, 

Michael Gall, Christian Sterba ....................... 37 

Development Of A Quantitative Approach That Uses Fourier Transform Infrared 

Spectroscopy (FTIR) To Measure Ambient Aerosol Composition, 

Vilma Arriaran, Beth Wittig (Mentor) .................... 39 

Optimizing the Python interpreter: Identifying performance bottlenecks., 

Stefan Brunthaler, Jens Knoop, n/a ..................... 41 

Model for Comparison of Types of Traffic Intersection Control Systems, 

Jan Krcal, Michal Jerabek ......................... 43 

An integrated source-to-source approach for WCET analysis, 

Adrian Prantl, Jens Knoop ......................... 45 

Cooperative Media Access Control in Wireless Networks, 

Mathias Offner, Helmut Adam ....................... 47 

ii

Jessine: An Approach to Creating Software Applications with Rule-Based Domain 

Knowledge, 

Miroslav Sabo ................................ 49 

Coordination of Agent-based Services, 

Lubomir Wassermann ............................ 51 

Design of Self-organizing Systems Using Evolutionary Methods, 

István Fehérvári, Wilfried Elmenreich ................... 53 

Towards Automatic Design of Competitive Image Filters in FPGAs, 

Zdenek Vasícek ............................... 55 

Evaluation of a State-based Process Management Platform, 

Ekaterina Andrianova, Jürgen Dorn .................... 57 

Motor task-induced modifications of multiple spinal cord reflexes, 

Ursula Hofstoetter, Josef Ladenbauer, Karen Minassian, Milan Dimitrijevic, 

Frank Rattay ............................. 59 

Approach for a Reliable Cooperative Relaying Process, 

Melanie Schranz, Wilfried Elmenreich ................... 61 

Retrieval of Ocean Water Parameters from Satellite Imagery and their Dependence 

on Atmospheric Correction Models, 

Rushane Dyer, Sam Ahmed ......................... 63 

Fast Packet Classification Algorithm in Hardware, 

Viktor Pus .................................. 65 

Radiation of Antenna Array in Near-field Area, 

Jirí Hermany, Zdenek Novácek ....................... 67 

Ontology- and Bayesian-based Threat Probability Determination, 

Stefan Fenz, A Min Tjoa ........................... 69 

Development of Multi-Core Video Decoding Platforms based on High-Level 

Architecture Simulations, 

Florian Seitner, Michael Bleyer, Margrit Gelautz ............. 71 

Comparison between Solute transport parameters estimation from local to field 

scale, 

Mohamed Kassab, Antonio Coppola, Nicola Lamaddalena, Alberto 

Guadagini, Monica Riva .......................... 73 

A new method for identification of systems of arbitrary real order based on solution 

of fractional differential equations and orthogonal distance fitting, 

Tomas Skovranek, Vladimir Despotovic, Igor Podlubny .......... 75 

iii

Configurable Meta-search in Human Resource Domain, 

Tabbasum Naz, Jürgen Dorn ........................ 77 

The Definition of Secure Business Processes with Respect to Multiple Objectives, 

Johannes Heurix, Thomas Neubauer .................... 79 

Generalising Constraint Solving over Finite Domains, 

Markus Triska, Nysret Musliu ........................ 81 

Default Reasoning on Top of Ontologies with dl-Programs, 

Minh DAO Tran, Thomas Eiter ....................... 83 

Implementation of a Design Tool for Automated Generation of Four State 

Logic Circuits., 

Jakob Lechner, Martin Delvai ........................ 85 

Analyzing Moving Objects Behaviour and Predicting their Future Location, 

Ivana Nizetic, Kresimir Fertalj ....................... 87 

Efficient Counting with Bounded Treewidth using Datalog, 

Stefan Rümmele, Reinhard Pichler ..................... 89 

MapFace - A Graphical Editor to Support the Semantic Annotation of Medical 

Text, 

Theresia Gschwandtner, Katharina Kaiser, Silvia Miksch ......... 91 

Optimization of communication by analyzing the interlocutors wording, 

Gudrun Kellner ............................... 93 

A Simulation Environment for Distributed Real-Time Systems in the Presence 

of Malicious Attacks, 

Ekarin Suethanuwong, Christian El-Salloum ................ 95 

Filtering of Phase Shift Terrestrial Laser Scanner Point Clouds, 

Clemens Nothegger, Norbert Pfeifer .................... 97 

When and why to use the evolutionary algorithms, 

Jana Jilková, Zbynek Raida ......................... 99 

Hybrid Timing Analysis for ANSI-C Applications with Loops and Function 

Calls, 

Bernhard Rieder, Peter Puschner ......................101 

Deterministic Finite Automaton with Perfect Hashing for Fast Pattern Matching, 

Jan Kastil, Jan Korenek ...........................103 

Network Coding for Cooperative Communications, 

Gordhan Das Menghwar, Christoph F Mecklenbrauker ..........105 

iv

Graphics versus spoken language in pedestrian navigation, 

Felix Ortag, Georg Gartner .........................107 

Hardware Acceleration of Protocol Identification, 

Petr Kobierský ................................109 

Evolutionary Design of Wormhole Switched Collective Communications, 

Jiri Jaros, Josef Schwarz ..........................111 

Component Based Communication Middleware for AUTOSAR, 

Dietmar Schreiner, Karl M. Göschka, Jens Knoop .............113 

The Acquaintance of Hardware Timing Effects: A Sine Qua Non to Validate 

Temporal Requirements in Embedded Real Time Systems, 

Sven Bünte, Raimund Kirner ........................115 

Divide and Measure: CFG Segmentation for the Measurement-Based Analysis 

of Resource Consumption, 

Michael Zolda, Raimund Kirner ......................117 

Neutralizing Timing Anomalies in Complex Computer Architectures, 

Albrecht Kadlec, Raimund Kirner .....................119 

Optical Imaging Hidden Objects in Turbid Scattering Media using Principal 

Component Analysis, 

Binlin Wu, Swapan Gayen, Robert Alfano .................121 

Links between Diachronic Thinking and Temporal Cognition Tasks Observed 

in Middle Childhood, 

Brandy Moore, Patricia Brooks, Laura Rabin, Carmen Carrion ......123 

Generalizing Sudoku to Three Dimensions, 

Tiffany Lambert, Paula Whitlock ......................125 

2 Material Sciences 127 

Nonadditivity of Quantum Phases for mixed States, 

Jürgen Klepp, Stephan Sponar, Stefan Filipp, Matthias Lettner, Gerald 

Badurek, Yuji Hasegawa ..........................129 

Complexation of trivalent Cm and Eu with extraction ligands for the Partitioning 

& Transmutation strategy, 

Sascha Trumm, Petra J. Panak, Andreas Geist, Reinhardt Klenze, Thomas 

Fanghänel ..................................131 

Complexation of Cm(III) with Nitrate and Fluoride at Elevated Temperatures 

Studied by Time Resolved Laser Fluorescence Spectroscopy, 

Andrej Skerencak, Petra J. Panak, Volker Neck, Reinhardt Klenze, Thomas 

Fanghänel ..................................133 

v

Development of alpha-(Al,Cr)2O3 solid solutions by reactive magnetron sputtering, 

Dominic Diechle, Michael Stueber, Harald Leiste, Sven Ulrich ......135 

Modification of Aluminum Alkoxides with o Esters and Dialkylmalonates as 

Precursors for Sol-Gel Derived Hybrid Materials, 

Robert Lichtenberger, Stefan O. Baumann, Michael Puchberger, Ulrich 

Schubert ...................................137 

Structural Aspects of Oximate-Modified Titanium Alkoxides, 

Stefan O. Baumann, Maria Bendova, Robert Potzmann, Michael Puchberger, 

Ulrich Schubert ...........................139 

Trace Metal Speciation in Water using a Solid Phase Extraction Flow Injection 

Setup online coupled to ICP-AES, 

Christoph Puls, Andreas Limbeck .....................141 

Analysis of Snowpack Properties And Estimation of Snow Grain Size Using 

Cold Land Processes Field Experiment Data, 

Dugwon Seo, Amir Azar, Al Powell, Reza Khanbilvardi ..........143 

Supersensitive tin oxide nanosensors for gas detection, 

Alexandra Tischner, Anton Köck, Thomas Maier, Christian Edtmaier, 

Christian Gspan, Gerhard Kothleitner ...................145 

Distortion Investigation during Sintering of Copper PIM Parts, 

Ijaz Ul Mohsin, Christian Gierl, Herbert Danninger ............147 

Electron microscopy of LiAlO_2 - a promising substrate for opto-electronic 

devices, 

Walid Hetaba ................................149 

Measuring of the Vibrations of the Petrol Engine, 

Jan Diblík ..................................151 

Silver plated tungsten carbide powders for electrical contact materials with 

improved homogeneity, 

Robert Christian Hula, Christian Edtmaier ................153 

Investigation of mechanical properties of polymer-derived Si-C-N/Al2O3composites 

with low shrinkage, 

Thomas Konegger, Antje Liersch ......................155 

Preparation of Alkyne and Azide modified Spherosilicates, 

Angelika Bachinger, Guido Kickelbick ...................157 

vi

Learning more about the Gene Regulation of Hydrolytic enzyme-encoding 

Genes in an industrial relevant Fungus, 

Matthias G. Steiger, Marion E. Pucher, Astrid R. Mach-Aigner, Robert L. 

Mach ....................................159 

Investigations of Xyr1 (Xylanase regulator 1), the main transcriptional regulator 

of the xylanolytic and cellulolytic enzymes in Hypocrea jecorina 

(Trichoderma reesei), 

Marion E. Pucher, Gudrun E. Bauer, Matthias G. Steiger, Robert L. Mach, 

Astrid R. Mach-Aigner ...........................161 

Using Confocal Microscopy to Study Mechanotransduction in Renal Epithelial 

Cells, 

Yi Duan, Sheldon Weinbaum ........................163 

Low-Energy School in Indian Himalayas, 

Jan Tilinger .................................165 

Algorithm of Simulation and Optimization of Coventional Mechanical Production, 

Robert Jurcisin, Dusan Sebo ........................167 

A Computer-Controlled Joint Loading System for Quantitative Analysis of 

Mechanoresponsiveness in Articular Cartilage, 

Xiang Gu, Daniel Leong, YongHui Li, Francisco Guzman, HuiBin Sun, 

Luis Cardoso ................................169 

Induced Blood Brain Barrier Electroporation during Deep Brain Stimulation: 

In vitro endothelial monolayer model, 

Veronica Lopez, Abhisheck Datta, Ronny Amaya, John Tarbell, Marom 

Bikson ....................................171 

Colloidal gel formation dynamics: light scattering, rheometry and simulation, 

Xiujuan Cao, Herman Cummins, Jeffrey Morris (Mentor) .........173 

Synthesis Of New Isothiazole Derivatives As Potential Agents For Crop Protection, 

Radoslav Flasik, Peter Stanetty .......................175 

Site-Selective Time Resolved Laser Fluorescence Spectroscopy on Ca2+- 

Bearing Mineral Phases Doped with Europium, 

Moritz Schmidt, Thorsten Stumpf, Clemens Walther, Thomas Fanghänel, 

Horst Geckeis ................................177 

Nanofeatured carbon-copper metal matrix composites, 

Michael Kitzmantel, Christoph Eisenmenger-Sittner, Dan Cunningham . . 179 

vii

Substitution of fossil fuels by using low temperature pyrolysis of agricultural 

residues in a thermal power plant, 

Michael Halwachs .............................181 

Long Wave Instabilities in Periodic Structures, 

Melanie Todt, Thomas Daxner .......................183 

Determination of the stoichiometry of complexes of trivalent lanthanides 

and extraction-relevant ligands with nanoelectrospray ionization time-offlight 

mass-spectrometry, 

Michael Steppert, Clemens Walther, Andreas Geist, Horst Geckeis, Thommas 

Fanghänel ...............................185 

Quantum Optical Coherence Tomography, 

Pierre Bouzi, Michael Etienne, Andru Prescod, Roger Dorsinville ....187 

Studies on application strategy of salts and chitosan for controlling Penicillium 

rot of Hernandina clementine, 

Youssef Khamis, Ligorio Angela, Pentimone Isabella, Sanzani Semona, 

DOnghia Anna Maria, Nigro Franco, Ippolito Antonio ..........189 

Functionalized Cadmium Sulfide Clusters as Nanosized Building Blocks for 

Hybrid Materials - Investigation of the "[Cd10S4(SPh)12]" Cluster Structure, 

Maria Bendova, Michael Puchberger, Ulrich Schubert ..........191 

Creating building blocks for Hybrid Materials: Investigation of Adhesives for 

Zirconia Substrates, 

Christoph Lomoschitz, Guido Kickelbick ..................193 

Model Structures for the Mycotoxin Zearalenone as Mimics in Metabolite Synthesis, 

Hannes Mikula, Hans-Peter Karl, Bernhard Klösch, Christian Hametner, 

Johannes Fröhlich ..............................195 

Realization of Inversion-type GaN MOSFETs with Ar Implantation for Device 

Isolation, 

Clemens Ostermaier, Sang-Il Ahn, Kay Potzger, Manfred Helm, Stefan 

Kalchmair, Dionyz Pogany, Jong-Ho Lee, Sung-Ho Hahm, Jung-Hee Lee . 197 

Solution Stability of Trinuclear Iron Oxo Clusters, 

Robert Potzmann, Stefan O. Baumann, Maria Bendova, Michael Puchberger, 

Ulrich Schubert ...........................199 

Olefinic Bioreduction, 

Naseem Iqbal, Marko. Mihovilovic. ....................201 

viii

Intraband Auger effect in InAs/InGaAlAs/InP Quantum Dot Structures, 

Thomas Gebhard, Deborah Alvarenga, Karl Unterrainer .........203 

Effect of Various Composition and Dosage of Potassium Activator on the Properties 

of Alkali Activated Slag Mortar, 

Iva Frybortova, Pavel Rovnanik ......................205 

Impact of Mineral Dust on PM10 Levels in Austria - Seasonal and local variations 

of carbonate carbon in ambient PM10 and source samples, 

Nicole Jankowski, Hans Puxbaum .....................207 

PE-UHMW in hip implants: The influence of crosslinking on structural parameters 

and micro-mechanical properties, 

Ruth Markut-Kohl, Thomas Koch, Vasiliki-Maria Archodoulaki, Sabine 

Seidler ....................................209 

Synthesis of Organo-Electronic Compounds: A Cooperative Sparkling Science 

Research Project, 

Daniel Lumpi, Caterina Benigni, Aileen Opelt, Ernst Horkel, Johannes 

Fröhlich ...................................211 

Shadowgrahic Imaging of Femto Second Laser Induced Ablation of Al, 

Shazia Bashir, M:Shahid Rafique, Wolfgang Husinsky ...........213 

3D-analysis of neuronal and vascular networks by ultramicroscopy, 

Nina Jährling, Stefan Kalchmair, Klaus Becker, Andreas Gewies, Edgar 

R. Kramer, Hans-Ulrich Dodt ........................215 

Regioselective O-Glucuronidation of Deoxynivalenol-derived Model Compounds, 

Philipp Fruhmann, Ernst Horkel, Christian Hametner, Johannes Fröhlich 217 

Optimisation of the incoupling geometry of a pulsed solid-state laser, 

Elisabeth Schwarz, Johannes Tauer, Heinrich Kofler, Ernst Wintner ....219 

Enhancement Mode HEMTs: Evaluation of Two Approaches by Numerical 

Simulation, 

Stanislav Vitanov, Vassil Palankovski ....................221 

Simulation of Q-switched solid-state laser for ignition, 

Franz Trawniczek, Johannes Tauer, Heinrich Kofler, Margarita Deneva, 

Ernst Wintner ................................223 

Priorities in Improving of Railway Infrastructure, 

Jirí Pospísil .................................225 

Raman and Surface Enhanced Raman Spectra of, Apigenin and Luteolin, 

Charlie Corredor, John Lombardi .....................227 

ix

A Sustainable Approach in Hybrid Materials Development: Metal Nanoparticles 

Synthesis in Biobased Polymeric Systems, 

Colleen Achong, Praveen Kumar Vemula, Kareem Douglas, George John 229 

Micro-lenses Fabrication by Solvent-Casting of Chalcogenide Glass, 

Eric Sanchez, Craig Arnold .........................231 

Structure and Dynamics of the Protein P7 from Bacteriophage φ12, 

Ertan Eryilmaz, Ranajeet Ghose ......................233 

Dsh is required for the phosphorylation of Dpr1a by CKIδ, 

Evelyn Teran, Joni Seeling .........................235 

Momentum of Optical Airy Beams, 

Henry Sztul, Robert Alfano .........................237 

Electrochemistry, Optical Spectroscopy and DFT Calculations of Glutathionylcobalamin, 

Iya Likhtina, Ronald Birke .........................239 

Surface Enhanced Raman Spectroscopy of Flavanthrone, 

Jingjing Chang, Maria Vega Cañamares, John Lombardi .........241 

Nonlinear resistance of 2D electrons in crossed electric and magnetic fields, 

JingQiao Zhang, Sergey Vitkalov ......................243 

Understanding the Effects of Aerosols in Cloud Microphysics in Coastal Urban 

Environments, 

Nathan Hosannah, Jorge Gonzalez .....................245 

Derivation of a Water Potential that Parameterizes Cooperative Effects, 

Philipa Njau, Michael Green ........................247 

Real-Time Visualization And Quantification Of Glial Progenitor And Glioma 

Chemotactic Migration, 

Richard Able, Maribel Vazquez .......................249 

Surface Enhanced Raman Spectroscopy of Pyridine on CdSe/ZnBeSe Quantum 

Dots Grown by Molecular Beam Epitaxy, 

Richard Livingstone, John Lombardi ....................251 

3 Environmental Science and Energy 253 

Using RFID Technology in Pedestrian Navigation for Information Transmission 

and Data Communication Recording, 

Qing Fu, Guenther Retscher ........................255 

x

Adaptive Boundary Element Methods Based on Accurate A Posteriori Error 

Estimation, 

Samuel Ferraz-Leite, Dirk Praetorius ...................257 

Risk Habitat Megacity. Recycling Systems in Santiago de Chile, 

Tahnee Gonzalez, Klaus-Rainer Bräutigam, Helmut Seifert ........259 

Slurry sampling ICP-AES procedure for fast and accurate measurement of 

crustal elements in airborne particulate matter, 

Azam Mukhtar, Andreas Limbeck ......................261 

Effects of Environmental Degradation on the Response of Reinforced Concrete 

Structures, 

Paola Simioni, Anna Saetta .........................263 

Usage of the Global Positioning System GPS in the fields of weather forecast 

and fleet navigation, 

Ana Karabatic, Gottfried Thaler, Robert Weber ..............265 

Organically Modified Mixed-Oxide Sol-Gel Films with Macro Meso and Micro 

Porosity, 

Marina Lomoschitz, Ulrich Schubert ....................267 

Development of a New High Frequency Fatigue Testing Method for Concrete 

Bridges, 

Johannes Berger, Johann Kollegger, Bernd Koeberl ............269 

Antenna far-fields determination from phaseless measurement using the realvalued 

GA, 

Jan Puskely, Zdenek Novácek ........................271 

Catalyst loaded porous membranes for environmental applications - Smart 

Membranes, 

Bin Ren, Ilona Kretzschmar .........................273 

Presence of the Bacteria Legionella in Hot Water Distribution Systems, 

Daniela Ocipova, Zuzana Vranayova ....................275 

Development and Processing of a Multi-Filter Rotating Shadowband Radiometer 

Network for Distributed Monitoring of Aerosol Optical Depth: Comparisons 

Between Conventional Langley Regression and a Novel NASA- 

GISS Algorithm, 

Miguel Bustamante, Fred Moshary, Barry Gross, Sam Ahmed .......277 

Impact Analysis of Resort Projects in Alpine Area, 

Lu Shen ...................................279 

Random Bipartite Graphs and their Application to Cuckoo Hashing, 

Reinhard Kutzelnigg, Michael Drmota (FacultyMentor) ..........281 

xi

Adaptive hp-Finite Element Methods for Two-Dimensional Elasticity with 

Tresca Friction, 

Philipp Dörsek, Jens Markus Melenk ....................283 

Thermal Bridge in Detail of a Gully in a Warm Flat Roof, 

Petr Zahradník ...............................285 

Development of Novel Flow Sensors using SPICE Simulations, 

Samir Cerimovic, Almir Talic, Franz Keplinger ..............287 

Pre-heating Vegetable Oil as a Sustainable Energy Development Solution : A 

Biofuel-Engine Longevity Test, 

Amir Nosrat, Mostafa Morovati, Martin Nolan, Paul A. West (Mentor) . . 289 

The "G" Ring Laser in Wettzell, Germany, as an Indicator for Astronomical 

and Geophysical Disturbances of the Planet Earth, 

Lucia Plank, Mendes Cerveira P.J. .....................291 

Occurrence and Possible Origin of Humic-like substances in Vienna Airborne 

Particulate Matter, 

Barbara Klatzer, Hans Puxbaum, Heidi Bauer, Alex Caseiro .......293 

Communication Specialties between Ear and Brain: Analysis of the Cluster 

Functions in the Human Cochlea, 

Cornelia Wenger, Frank Rattay .......................295 

Spatial potentials for renewable energies, 

Hartmut Dumke, Stefan Plha, Hannes Schaffer, Andreas Dillinger ....297 

Silica nanoparticles connected through ionic linkers, 

Marco Litschauer, Marie-Alexandra Neouze ................299 

An Adaptive Solver for Parabolic Partial Differential Equations, 

Gernot Pulverer ...............................301 

ICT - The Big Picture: Intertwined Driving Potentials Innovation, Technology 

Penetration and the Global Economy, 

DI Ranja Reda ...............................303 

Activation of Neural Networks in the Human Spinal Cord with Implanted and 

Surface Electrodes: Conclusions from Finite Element Simulations, 

Josef Ladenbauer, Ursula S. Hofstötter, Karen Minassian, Milan R. Dimitrijevic, 

Frank Rattay ............................305 

Characterisation of biomass smoke particle emissions and its application to 

source apportionment, 

Christoph Schmidl, Hans Puxbaum .....................307 

xii

Observations of the surface evolution of Pinka-plain: mass movements and 

neotectonics, 

Gábor Kovács, Balázs Székely, Sándor Papp ................309 

Spray Can Geometry, 

Gwen Wilke, Andrew U. Frank .......................311 

Anammox Studies Using New York City Centrate to Correlate Performance, 

Population Dynamics, and Impact of Toxins, 

Alex Rosenthal, John Fillos, Krish Ramalingam ..............313 

Multi-Perspective Ultramicroscopy with Structured Illumination in Optically 

Dense Specimens, 

Stefan Kalchmair, Klaus Becker, Nina Jährling, Hans-Ulrich Dodt ....315 

Analytical technology for biogas production from straw by multivariate Nearinfrared 

spectroscopy, 

Chularat Krongtaew, Karin Fackler, Barbara Hinterstoisser, Kurt Messner 317 

Playing with maps: The role of webcartography in education, 

Eszter Simonné-Dombóvári .........................319 

Overtopping of Dams - A Model Approach, 

Michael Pucher, Peter Tschernutter ....................321 

Rediscovery of a Special Type of Separation Pier, 

Michael Pucher, Peter Tschernutter ....................323 

Possibilities of bentonite substitution - development of new progressive grouting 

materials and durability monitoring., 

Pavla Matulova ...............................325 

Combined Active/Passive Microwave Wavelet-Based Approach For Snowmelt 

Detection Over Antarctica Ice Shelves, 

Nicholas Steiner, Marco Tedesco ......................327 

Binary Quadratic Forms over the Modular Ring Z/nZ, 

Clyde Lewis, Rony Gouraige ........................329 

Index of Authors 331 

xiii

xiv

Welcome Message from Peter Skalicky 

By surfing in Wikipedia one finds the following definition: 

“The scientific community consists of the total 

body of scientists, its relationships and interactions.” 

And further: “Communication between the members 

is established by disseminating research work and 

hypotheses through articles in peer reviewed journals, 

or by attending conferences where new research 

is presented and ideas are exchanged and discussed.” 

So in fact - aside from publications - conferences are 

the core opportunity for young scientists to become 

part of their community, present their research, make 

contacts and make themselves a name. 

The Junior Scientist Conference at the Vienna University of Technology 

(TU Wien) is specially designed to make it easier for young researchers to 

enter this arena. So it is my pleasure to wish all of you good luck and a 

good start for the presentation of your posters and for getting into contact 

with each other. 

The Junior Scientist Conference is also a good example for the collaboration 

within the heart of Europe. Aside from our friends from New York 

where the first conference tooks place, there are participants from Austria, 

Croatia, the Czech Republic, Denmark, Germany, Hungary, Italy and Slovakia. 

The Central European Region - in short: Centrope - is a political 

commitment to overcome former borders. One promising way to reach 

this goal is the intensive collaboration between scientists. 

Peter Skalicky 

Rector at Vienna University of Technology 

xv

xvi

Welcome Message from Hans K. Kaiser 

The idea for such a Junior Scientist Conference originated 

in the discussions between a delegation from 

the City College of New York and members of the 

TU Wien during the visit of our American colleagues 

to Vienna, headed by president Gregory Williams, in 

2004. The aim of such a conference is to give young 

researchers a first possibility to present the results of 

their scientific work to a wider audience. In the centre 

of such a conference is the presentation of posters 

by young scientists. The first conference in this series 

took place in New York in March 2005, the second 

one in Vienna in 2006, and a third conference was organized in New 

York in 2007. TU Wien is happy to organize now this fourth event in a - 

hopefully - long series of similar conferences to come. There was a call 

for scientific contributions in all fields of Science and Technology both on 

Master- and PhD-level. Preference was given to posters from the area of 

Environmental Sciences, Information and Communication Technology and 

Material Sciences. We are very pleased that the announcement of our conference 

was well received both by universities in our neighbouring countries 

and our friends from the City College of New York. So we are proudly 

welcoming more than 160 young researchers from nine different countries. 

At the heart of the conference in Vienna will be the poster session. Around 

this main event there will be three mini-conferences in the area of Environmental 

Sciences, Material Sciences and Information and Communication 

Technology. Within the conference we are organizing a best poster award: 

one for posters on the Master-level and one on PhD-level. 

We wish all participants an exciting time in Vienna and a successful 

conference at the Vienna University of Technology. 

Hans K. Kaiser 

Vice Rector for International Relations at Vienna University of Technology 

xvii

xviii

Conference Organizers 

Conference Chairman 

Hans K. Kaiser Vice Rector for International Relations at TU Vienna 

Scientific Program Committee 

Ewald Benes Institute of General Physics, TU Vienna 

Jürgen Dorn Institute of Software Technology and Interactive Systems, TU Vienna 

Gerald Futschek Institute of Software Technology and Interactive Systems, TU Vienna 

Georg Gartner Institute of Geoinformation and Cartography, TU Vienna 

Hermann Hofbauer Institute of Chemical Engineering, TU Vienna 

Günther Karigl Inst.of Discrete Mathematics and Geometry, TU Vienna 

Raimund Kirner Institute of Computer Engineering, TU Vienna 

Andreas Kolbitsch Institute for Building Construction and Technology, TU Vienna 

Kurt Matyas Institute of Management Science, TU Vienna 

Helmut Rechberger Institute for Water Quality, Resources and Waste Management, TU 

Vienna 

Manfred Schrödl Institute of Electrical Drives and Machines, TU Vienna 

Organizing Committee 

Raimund Kirner Assistant Professor 

Nicole Pacher Assistant to the Vice Rector 

Edith Scharaditsch Secretary to the Vice Rectorate 

Simone Souczek Secretary to the Vice Rectorate 

Melanie Wagner Public Relations and Communication 

xix

Conference Program 

Sunday, November 16, 2008 

Time Event Location 

05.00 pm -7.00 pm Registration and Poster Setup Prechtl-Saal, Main 

Building, Ground 

(US: 1st) Floor 

07.00 pm (open end) Get together at Nelson’s Café University courtyard, 

Main Building 

Monday, November 17, 2008 

Preparation 


08.30 am - 10.00 am Registration and Poster Setup Prechtl-Saal, Main 



Morning Session 


10.00 am - 10.30 am Opening Lecture Room 8, 

Main Building, 

Ground (US: 

1st) Floor 

10.30 am - 11.15 am Keynote: Prof. Dr. Werner PURGATH- 

OFER (Institute of Computer Graphics 

and Algorithms): "Speedup Concepts 

for Realtime Computer Graphics" 

11.15 am - 12.00 pm Keynote: Prof. Dr. Karl UNTER- 

RAINER (Institute of Photonics): "Coherent 

Terahertz Generation: New Light 

for Nanostructures and Bio-Imaging" 

12.00 pm - 02.00 pm Lunch Break Mensa, Freihaus 

Bldg., Wiedner 

Hauptstr. 8-10 

xxi

Afternoon Session (Parallel Sessions) 

Session A) Environmental Sciences and Energy 


02.00 pm - 02.45 pm Plenary Speaker: Prof. Dr. Nebojsa 

NAKICENOVIC (Institute of Power 

Systems and Energy Economics): "Energy 

Perspectives and Climate Challenge" 

02.45 pm - 03.10 pm Student Presentation: Nina 

JÄHRLING (Graduate Student, Vienna 

University of Technology): 

"3D-Analysis of neuronal and vascular 

networks by ultramicroscopy (143)" 

03.10 pm - 03.35 pm Student Presentation: Daniela 

OCIPOVA (Graduate Student, Technical 

University in Kosice): "Presence of 

the Bacteria Legionella in Hot Water 

Distribution Systems (34)" 

03.35 pm - 04.00 pm Student Presentation: Chularat KRO- 

NGTAEW (Graduate Student, Vienna 

University of Technology): "Analytical 

Technology for Biogas Production from 

Straw by Multivariate Near-Infrared 

Spectroscopy" 

Lecture Room 8, 


Ground Floor 

04.00 pm - 04.20 pm Break Prechtl-Saal, Main 


Floor 

04.20 pm - 04.45 pm Student Presentation: Christoph 

SCHMIDL (Graduate Student, Vienna 

University of Technology): "Characterisation 

of Biomass Smoke Particle 

Emissions and its Application to Source 

Receptor Analysis" 

04.45 pm - 05.10 pm Student Presentation: Marina LO- 

MOSCHITZ (Graduate Student, Vienna 

University of Technology): "Sol-Gel 

Films with Macro Meso and Micro 

Porosity" 

xxii 



Ground Floor

Session B) Material Sciences 


02.00 pm - 02.45 pm Plenary Speaker: Asst. Prof. Dr. Ilse- 

Christine GEBESHUBER (Institute of 

General Physics): "Scanning Probe Microscopy 

across Dimensions" 

02.45 pm - 03.10 pm Student Presentation: Clemens OS- 

TERMAIER (Graduate Student, Vienna 

University of Technology): "Realization 

of Inversion-type Gan MOSFETs 

with Ar Implantation for Device Isolation 

(114)" 

03.10 pm - 03.35 pm Student Presentation: Michael KITZ- 

MANTEL (Graduate Student, Vienna 

University of Technology): "Nanofeatured 

Carbon-Copper Metal Matrix 

Composites (74)" 

03.35 pm - 04.00 pm Student Presentation: Melanie TODT 

(Graduate Student, Vienna University of 

Technology): "Long Wave Instabilities 

in Periodic Structures (91)" 



Ground Floor 



Floor 

04.20 pm - 04.45 pm Student Presentation: Stanislav VI- 

TANOV (Graduate Student, Vienna 

University of Technology): "Enhancement 

Mode HEMTs: Evaluation of Two 

Approaches by Numerical Simulation 

(158)" 

04.45 pm - 05.10 pm Student Presentation: Philipp 

DÖRSEK (Undergraduate Student, 

Vienna Univ. of Technology): "Adaptive 

hp-Finite Element Methods for 

Two-Dimensional Elasticity with Tresca 

Friction (49)" 

xxiii 



Ground Floor

Session C) Information, Communication and Computer Technology 


02.00 pm - 02.45 pm Plenary Speaker: Assoc. Prof. Dr. Andreas 

RAUBER (Institute of Software 

Technology and Interactive Systems): 

Topic to be announced 

02.45 pm - 03.10 pm Student Presentation: Markus 

TRISKA (Graduate Student, Vienna 

University of Technology): "Generalizing 

Constraint Solving over Finite 

Domains (121)" 

03.10 pm - 03.35 pm Student Presentation: Florian SEIT- 

NER (Graduate Student, Vienna University 

of Technology): "Development of 

Multi-Core Video Decoding Platforms 

based on High Level Architecture Simulations 

(105)" 

03.35 pm - 04.00 pm Student Presentation: Qi WANG 

(Graduate Student, Vienna University 

of Technology): "Towards Synchronization 

in Multiple Antenna Systems (42)" 



2nd (US: 3rd) 

Floor 



Floor 

04.20 pm - 04.45 pm Student Presentation: Theresia 

GSCHWANDTNER (Graduate Student, 

Vienna University of Technology): 

"Map Face - A Graphical Editor to 

Support the Semantic Annotation of 

Medical Text (139)" 

04.45 pm - 05.10 pm Student Presentation: Rushane DYER 

(Student, City College New York): 

"Retrieval of Ocean Water Parameters 

from Satellite Imagery and their Dependance 

on Atmospheric Correction Models 

(100)" 

xxiv 



2nd (US: 3rd) 

Floor

Evening Program 


07.00 pm (open end) Enjoy an evening at the Wiener Heuriger 

Fuhrgassl-Huber 

Tuesday, November 18, 2008 

1190 Wien, 

Neustift/Walde 68 


09.00 am - 10.00 am Presenting and visiting Poster Session 1 Prechtl-Saal, Main 



10.00 am - 11.00 am Presenting and visiting Poster Session 2 

11.00 am - 11.30 am Break Prechtl-Saal, Main 


Floor 

11.30 am - 12.15 pm Keynote: Prof. Dr. Manfred 

GRASSERBAUER (Institute of Chemical 

Technologies and Analytics): " ’Our 

Environment - Our Future’. Sustainable 

Development in the European Union - 

Concepts, Approaches and Challenges" 

12.15 pm - 12.45 pm Award Ceremony 

12.45 pm - 01.00 pm Closing Ceremony/End of Conference 

xxv 



Ground Floor

xxvi

Chapter 1 

Information and Communication 

Technology

Implementation of Quadrature Modulator Imbalance 

Compensation Method 

Karel Povala�, Roman Maršálek (Faculty Mentor) 

Department of Radio Electronics 

Brno University of Technology 

Brno, Czech republic 

Email: xpoval00@stud.feec.vutbr.cz, marsaler@feec.vutbr.cz 

Abstract — Quadrature modulator (demodulator) 

is used in transmitting (receiving) part of many 

devices. Modulator (demodulator) output signal can 

be influenced by unwanted amplitude, phase or DC 

offset imbalances. The implementation of basic 

method for imbalances compensation on programmable 

logic filed is a main subject of the paper. 

Development kit V2MB1000 with analogue board 

Memec P160 was chosen for this purpose. Practical 

measurements have been done with digital oscilloscope 

and digital signal analyzer. 

I. INTRODUCTION – REAL MODULATOR 

IQ imbalance problem arises when non-ideal components 

injure the power balance or phase orthogonality 

between inphase (I) and quadrature (Q) branch of 

modulator. Methods for IQ imbalance compensation 

are suitable for VHDL implementation in programable 

logic field. Figure 1 shows block diagram of 

real modulator with imbalances. 

Figure 1: Modulator with imbalances 

I and Q signals are usually produced in DSP block 

(digital signal processor). Digital signals are converted 

into analogue form by digital/analogue converters. 

Active Low Pass Filter (ALPF) can add 

unwanted amplitude imbalance (KI, KQ) or DC offset 

(a1, a2). Phase imbalance (�err) express phase difference 

between both branches, which is figured by the 

oscillator block and the phase shift block. Adder is 

the last block of quadrature amplitude modulator. 

3 

Chosen method should adaptively compensate unwanted 

above mentioned imbalances. 

II. COMPENSATION METHOD [1] 

A. MATRIX MODEL 

Choosen method was published by Ingolf Held in 

paper [1]. IQ imbalance can be characterized by two 

parameters: amplitude imbalance K as a power mismatch 

between I and Q branch, and phase imbalance 

�err as an error of orthogonality between I and Q 

branch. Situation can be characterized by the matrix 

equation: 

, 

�s � � 

0 

I k � � KI 

� � sI �k �� 

� �� 

. (1) 

� � � , 

s � � KQ sin err KQ 

cos 

Q k � � 

� � 

� � �� err� 

��sQ�k�� Where s’I and s’Q denote components of unimpaired 

signals. KI and KQ represents the amplitude 

imbalance and �err represents the phase imbalance. 

B. AMPLITUDE IMBALANCE COMPENSATION CO- 

EFICIENT 

Estimate of amplitude imbalance is based on the 

following equation 

K 

� 

L 

� 

k �1 

est, B L 

� 

k�1 

2 

Q 

2 

I 

� � 

s k 

� � 

s k 

(2) 

The long-time domain preamble has been used as 

training input sequence s consisting of sI and sQ parts. 

Parameter L denotes a number of long preamble 

samples for computing estimation. 

C. PHASE IMBALANCE COMPENSATION COEFI- 

CIENT 

Estimation of phase imbalance coefficient Pest uses 

the same data symbols s of length L. The following 

equation is used 

L 

�� 

� �� 

s k s k 

I Q 

k �1 

est � L 

2 

� sI�k� k �1 

P 

(3)

When both of compensation coefficients are found 

correction of imbalances can continue. 

III. FPGA IMPLEMENTATION 

The Xilinx ISE environment was used for implementation. 

The compensation algorithm had to be rebuilt 

for VHDL implementation. The basic blocks are 

shown on simplified schematic (Figure 2). 

Figure 2: Scheme of implemented method 

Clock speed of FPGA was 100 MHz. Digital 

Clock Manager (DCM) provided clocking for other 

blocks. Random symbols (s’I and s’Q) were generated 

by DATA generator. Data symbols passed through 

the model of imbalances. Next steps were calculating 

compensation coefficients, imbalance compensation, 

filtering signals by Square Root Raised Cosine filter 

(elimination inter symbol interferences) and modulation 

on the carrier with frequency 500 kHz. All of 

mathematic operations were done in floating point 

format. The development kit V2MB1000 has been 

used for the implementation. Almost 100% logic 

block inside FPGA were used. Signal from modulator 

has been sent into analogue board Memec P160 

with the D/A converter. Output analogue signal could 

be measured and displayed by digital oscilloscope 

and digital signal analyzer. 

IV. MEASUREMENTS AND RESULTS 

The output analogue signal was measured in time 

domain. Measuremt results corresponded with simulations. 

Digital signal analyzer (Rohde & Schwarz 

4 

FSQ3) was used for display constellation diagrams of 

signal before compensation (with amplitude imbalances 

KI = 1,1and KQ = 0,9, phase imbalance �err=� 

/10rad) and after compensation (without imbalances). 

The graphic results are shown on Figure 3. 

Figure 3: Constellation diagrams before (left) and 

after compensation (right) 

It’s evident that both of imbalances have been 

compensated. The constellation points have been 

dispersed as a consequence of shorter impulse response 

of used raised cosine filter. 

V. CONCLUSION 

Number of logic blocks used in FPGA Virtex II 

XC2V1000 reached almost 100%. Method was implemented 

together with data generation, filter for 

elimination inter symbol interferences and direct 

digital synthesizer generated carrier for modulator. 

Measured results proved right function of implemented 

method. 

ACKNOWLEDGMENTS 

Implementation described in the paper was financially 

supported by the Czech Grant Agency under 

grant No. 102/08/H027 "Advanced Methods, Structures 

and Components of Electronic Wireless Communication" 

and by the research program MSM 

0021630513 "Advanced Electronic Communication 

Systems and Technologies (ELCOM)". 

REFERENCES 

[1] I. Held, O. Klein, A. Chen and V. Ma. Low 

Complexity Digital IQ Imbalance Correction in 

OFDM WLAN Receivers. IEEE Integrated System 

Solution Corporation. Hsinchu, Taiwan, 

2004, p. 1172 – 1176

Diagnostical analysis of voice 

Pavel Sala, Milan Sigmund (Faculty Mentor) 

Faculty of Electrical Engineering and Communication 


Brno, Czech Republic 

Email: xsalap00@stud.feec.vutbr.cz, sigmund@feec.vutbr.cz 

Abstract — This paper is focused on methods for 

the estimation of glottal pulses from speech signal 

and finding appropriate criterions to describe a 

selected diagnosis. Two methods for the estimation 

of the glottal flow from the speech signal were 

programmed. Finally, attention was focused on the 

determination of criterions for the description of a 

selected pathological diagnosis and the influence of 

the stress on the glottal flow. The proposal of two 

criterions for describing the influence of the stress 

on the glottal flow is an outcome of this work. 

I. INTRODUCTION 

Parameters for the estimation of some diagnose are 

often extracted directly from a speech signal in time 

or frequency domain. A quite new approach consists 

in obtaining appropriate parameters from the estimate 

of glottal pulses. The device which can measure 

glottal pulses directly is quite expensive, and 

therefore, the development of methods for estimating 

glottal pulses from speech signal was started. 

This paper is organized as follows. After 

introductions, two methods for the estimation of 

glottal pulses that were programmed are mentioned 

in Section II. The Section III is focused on the 

description of a selected pathological diagnosis. In 

Section IV, two criterions for describing the 

influence of the stress on the glottal flow were 

suggested. Finally, concluding remarks are given in 

Section V. 

II. GLOTTAL PULSE ESTIMATION 

Both used methods are derived from the speech 

production model [1]. Block diagram of this model is 

showed in Fig. 1. 

Figure 1: The speech production model 

( ) 2 1 − 

( z) 

1/ 

1− 

exp( 

− cT ) 

G = z (1) 

5 

The equation 1 represents a glottis where c is the 

unknown parametr of the filter and T is the sampling 

period. The glottal flow goes throught the vocal tract 

V(z) which is modeled by an all-pole filter defined in 

zplaneas 

V 

( z) 

= K −i 

1+ 

∑ c ⋅ 

i= 

i z 

1 

1 (2) 

where ci are coeficients of the vocal tract model and 

K is a number of these coefficients. R(z) represents 

the lips radiation which can be described as 

−1 

R z = 1 − μ z 

(3) 

( ) 

where μ∈〈0.98; 1〉. 

The first method was published by Paavo Alku in 

1992 and its name is “Iterative Adaptive Inverse 

Filtering” (IAIF) [2]. The second method was 

published by H. Deng, H. Ward, M. P. Beddoes and 

M. Hodgson in 2006 [3]. 

III. PATHOLOGICAL DIAGNOSIS 

Three pathological diagnoses where processed: 

− reinek’s edema 

− vocal fold edema 

− vocal tremor 

The signal of 10 speakers has been available for each 

of the diagnoses. Each speech signal was splitted to 5 

sections and each section was then used for the 

estimate of the glottal pulse. Normalized forms of 

estimated glottal pulses were displayed in the same 

graph. It turned out that the shape of glottal pulses of 

different speakers (for the same pathological 

diagnose) is different. Therefore a few smaller 

groups with similar shapes of glottal pulses were 

created (for each pathological diagnosis). 

IV. STRESS 

Two speech signals of 9 speakers have been available 

[4] (the one “stressed” and the one “normal” speech 

signal of the same utterance for each speaker). Only

the first method [2] for glottal pulses estimation was 

used because of the small length of the speech signal. 

A. MONOTONICITY 

The monotonicity of each of the edges (rising and 

falling) of normalized glottal pulses was tested at 

first - concretely the number of changes of edges 

directions was observed. The threshold was 

determined when the error rate of the classification of 

the speech signal was minimal see Fig. 2. 

Figure 2: Threshold searching 

From the monotonicity observation of the falling 

edge the minimal error was achieved for the 

threshold value 8% see Fig. 3. 

type 2 error (dashed line) [%] 

60 

40 

20 

Falling edge 

0 

0 2 4 6 8 10 12 14 16 18 20 

threshold value [%] 

40 

Figure 3: Error of the classification for various 

thresholds 

B. SURFACE 

As the second classifier the surface of the rising and 

the falling edge was used. In Fig. 4 glottal pulses of 

the normal speech signal (solid line) and the stressed 

speech signal (dotted line) of all 9 speakers are 

shown. In almost all of these graphs, it is observable 

that in the right half of graphs, the surface of the 

stressed glottal pulse is smaller than the surface of 

the normal glottal pulse. If this is not accomplished, 

it is necessary to compare the left half of the graphs 

too. If the left surface of the examined glottal pulse is 

bigger than surface of the “normal” glottal pulse, it 

70 

60 

50 

type1error(solidline)[%] 

6 

can be determined that the glottal pulse is stressed. 

This method fails only in one case (speaker 1). 

0.9 

0.8 

0.7 

speaker1 

-100 -50 0 

speaker3 

50 100 

0.9 

0.8 

0.7 

-100 -50 0 

speaker5 

50 100 

0.9 

0.8 

0.7 

-100 -50 0 

speaker7 

50 100 

0.9 

0.8 

0.7 

-100 

1 

-50 0 

speaker9 

50 100 

0.8 

0.6 

-100 -50 0 50 100 

0.9 

0.8 

0.7 

speaker2 

-100 

1 

-50 0 

speaker4 

50 100 

0.8 

0.6 

-100 -50 0 

speaker6 

50 100 

0.9 

0.8 

0.7 

-100 

1 

-50 0 

speaker8 

50 100 

0.8 

0.6 

-100 -50 0 50 100 

Figure 4: Normal and stressed glottal pulses 

CONCLUSION 

Two criterions for description of the stressed speech 

signal were proposed. For improvement of the 

accuracy of these methods or for the proposition a 

new method for the stress description, more samples 

of the speech signal are needed. 

REFERENCES 

[1] J. Psutka and L. Müller and J. Matoušek and V. 

Radová. Mluvíme s počítačem česky, Academia, 

Praha, Czech Republic, 2006 

[2] H. Pulakka. Analysis of Human Voice Production 

Using Inverse Filtering. High-Speed Imaging, 

Helsinki University of Technology, Master’s 

Thesis, 2005. 

[3] H. Deng and R. K. Ward and M. P. Beddoes and 

M. Hodgson. A New Method for Obtaining 

Accurate Estimates of Vocal-Tract Filters and 

Glottal Waves from Vowel Sound. In 

Proceedings of the IEEE Transaction on audio, 

speech, and language processing. Vol. 14, No. 2. 

p. 445-455 . March 2006. 

[4] M. Sigmund. Introducing the database 

ExammStress for speech under stress. 

Proceedings of 7 th 

IEEE Nordic Signal 

Processing Symposium, 290–293, Reykjavik, 

2006.

Realization of the OFDM coder and decoder using DSP 

Petr Zelinka, Milan Sigmund (Faculty Mentor) 




Email: xzelin06@stud.feec.vutbr.cz, sigmund@feec.vutbr.cz 

Abstract — The European Standard ETSI EN 

300 744 for terrestrial digital video broadcasting 

specifies the OFDM (orthogonal frequency division 

multiplexing) for use in television broadcast stations. 

This article describes an OFDM baseband 

coder and decoder in 2K mode without errorcorrection 

capabilities constructed according to the 

above-mentioned norm. The proper function of both 

devices is verified using Matlab simulations. The 

practical realization comprises two Texas Instruments’ 

Starter Kits with TMS320C6711 digital 

signal processors (DSPs) connected through coaxial 

cables. 


Nowadays set-top-boxes and other similar devices 

use well-established application-specific integrated 

circuits (ASIC) for OFDM demodulation. These 

parts have predetermined purpose and parameters, 

hence, they can’t be used in special applications like 

hand-held equipment or computer peripherals. 

The coder and decoder described in this article are 

configured for 2K mode according to the DVB-T 

standard and therefore minimal number of carriers is 

used ensuring short symbol period. This fact allows 

fast variances of the transmission channel. The used 

algorithms could be adapted for other modes as well. 

II. OFDM BASICS 

A typical terrestrial communication channel always 

causes certain degree of signal distortion – attenuation, 

added noise, interferences and fading due to 

strong echoes. High-speed digital signals may therefore 

exhibit severe inter-symbol interferences (ISI) 

limiting the maximum data rate for one carrier. 

OFDM uses many orthogonal carriers providing 

good transmission rates within a predetermined HF 

bandwidth. The existence of a so-called guard interval 

greatly improves the immunity to the echoes. 

Individual carriers can be influenced by means of 

amplitude and phase changes therefore conveying 

desired information. 

7 

III. PROPOSED CODER 

A. SYSTEM PARAMETERS 

The system uses a 2K OFDM according to the standard 

[1] with the guard interval of ¼ (512 samples). 

Carriers are modulated using the QPSK or 16-QAM 

(uniform) to be able to study the impact of the 

channel noise on the error rate with different 

constellation point distances. The system doesn’t 

contain blocks for the forward error correction. 

B. USED PILOT SIGNALS 

The modulated carriers are interleaved with continual 

and scattered pilots (SP) on the proper positions. The 

transmission parameters signalling pilots are set to 

zero since their function is not employed in the system. 

The total number of carriers is 1705, hence the 

2048-IFFT is used for the transformation into the 

time domain. 

C. SPECTRUM ADJUSTMENT 

The power spectrum of individual carriers follows a 

sinc 2 function and their superposition composes the 

atoll-like shape. The sidelobes, however, show too 

slow fading, so an efficient filtration is needed. The 

proposed coder uses a windowing method described 

in [2] to suppress the out-of-band radiation. The only 

drawback of the method is a slight increase of the 

echo sensitivity since the guard interval is shortened 

by a small fraction to preserve the proper symbol 

period. 

IV. PROPOSED DECODER 

A. MAIN STRUCTURE 

The reception of the OFDM signal comprises of 

two parts: acquisition and tracking. When the receiver 

is switched-on it has no prior information 

about the symbol timing and there may also be a 

nonzero frequency shift. In order to be able to demodulate 

the carriers, it is necessary to compensate 

the amplitude and phase characteristics of the transmission 

channel. The block scheme of the decoder

was composed (Figure 1) in accordance with [3]. 

Some receivers use interpolation/decimation blocks 

for adjusting fractional timing offsets, nevertheless 

this feature was not applied due to its high impact on 

required memory capacity and computational power. 

baseband 

OFDM 

signal 

A/D 

frequency 

correction 

pre-FFT 

analysis: 

-symbol 

timing 

-frequency 

guard 

interval 

removal 

Figure 1: Decoder block diagram 

B. ACQUISITION 

During the initial signal acquisition the decoder performs 

a correlation of the input signal comparing the 

results against an adaptive threshold in order to find 

the beginning of an OFDM symbol. Subsequently, 

the first guess of the frequency offset is computed 

using a method described in [2] and a software converter 

is used for the necessary correction. After the 

FFT’s completion, an integer frequency calibration is 

done and pilot signals are located. Only two subsequent 

symbols are needed to attain scattered pilots’ 

pattern lock thanks to the method [4]. The final stage 

of the acquisition is the fine timing correction using 

SPs (with resolution limited to one sample period). 

C. TRACKING 

The receiver is able to perform continuous tracking 

and correcting of the timing and fractional frequency 

offset. All received symbols are treated for linear 

distortion using a fast equalizer [5] which exploits 

SPs only from the current symbol and the following 

correction is applied on this symbol. This allows fast 

channel variances. 

V. PRACTICAL REALIZATION 

post-FFT 

alalysis: 

-frequency 

-timing 

-channel 

FFT 

equalizer 

carriers 

demodulation 

output 

data 

Two Starter Kits with TMS320C6711 DSPs connected 

through coaxial cables were used. Both run 

under the DSP BIOS operating system in cooperation 

with the Code Composer Studio v. 3.0. Several libraries 

of hand-optimized assembler routines were 

used on critical parts of the program. 

8 

VI. CONCLUSION 

The proposed baseband OFDM coder and decoder 

according to the DVB-T standard were successfully 

realized using two evaluation boards with DSPs. The 

decoder is adequately resistant to noise and linear 

distortion of the communication channel. Used 

algorithms are speed-optimized efficiently employing 

hardware resources, still, computational power of the 

DSPs limits the data rate below the standardised 

value. A real-time operation would be certainly 

possible with faster fixed-point DSPs. 


This work was supported by the Czech Grant Agency 

under project No. 102/08/H027 and by the research 

program MSM 0021630513 Advanced Electronic 

Communication Systems and Technologies 

(ELCOM). 

References 

[1] European Standard ETSI EN 300 744: Digital 

Video Broadcasting (DVB); Framing structure, 

channel coding and modulation for digital terrestrial 

television [online]. Ver. 1.5.1. 11-2004. [cit. 

25.4.2007]. Available . 

[2] SCHULZE, H.; LUDERS, Ch. Theory and applications 

of OFDM and CDMA. John Wiley & 

Sons Ltd., Chichester, United Kingdom, 2005. 

ISBN-13 978-0-470-85069-5. 

[3] SPETH, M.; FECHTEL, S.; FOCK, G.; MEYR, 

H. Optimum Receiver Design for OFDM-Based 

Broadband Transmission-Part II: A Case Study. 

In IEEE Transactions on Communications, vol. 

49, issue 4, pages 571-578, 2001. 

[4] INDUSTRIAL TECHNOLOGY RESEARCH 

INSTITUTE. Time-frequency correlation-based 

synchronization for coherent OFDM receiver. 

Inventor: CHEN Ching-Yung, WANG Yi-Ting, 

HUNG Yung-Hua. United States of America. 

Patent Application Publication No. US 

2006/0088133 A1. 27. 4. 2006 [online]. [cit. 

25.4.2007]. Available . 

[5] FRESCURA, F.; PIELMEIER, S.; REALI, G.; 

BARUFFA, G.; CACOPARDI, S. DSP based 

OFDM demodulator and equalizer for professional 

DVB-T receivers. In IEEE Transactions 

on Broadcasting, vol. 45, issue 3, pages 323-332, 

1999.

Transmembrane Potential Measurements on Plant Cells using the 

Voltage-sensitive Dye ANNINE-6 

B. Flickinger, Th. Berghöfer, C. Eing, W. Frey 

Institute for Pulsed Power and Microwave Technology (IHM) 

Forschungszentrum Karlsruhe GmbH 

76344 Eggenstein-Leopoldshafen, Germany 

Email: bianca.flickinger@ihm.fzk.de 

Abstract — Recently, effects of pulsed electric 

fields on plant cells have become an interesting 

topic of research in plant electrophysiology. 

Systematic measurements using Nicotiana tabacum 

L. cv. Bright Yellow 2 (BY-2) protoplasts 

have been performed using a Pulsed Laser Fluorescence 

Microscopy (PLFM) setup with nanosecond 

time resolution. The field strength dependence 

of the protoplast’s transmembrane 

potential shows strong asymmetric saturation 

characteristics. To determine the azimuthal dependence 

of the transmembrane potential, the 

relative fluorescence change has been measured 

in angular intervals of 10° along the circumference 

of the cell. Pulse-train experiments reveal 

that a subsequent re-charging of cell membranes 

to the same voltage is possible within a few seconds 

indicating a fast recovery process of the cell 

membrane. 


The application of an external electric field to 

biological cells leads to the polarisation of the 

membrane. This charging process continues until 

the transmembrane potential reaches a critical 

value, where a fast rearrangement of the membrane’s 

molecular structure occurs, leading to the 

formation of pores. This field-induced membrane 

effect is known as “electroporation”. The created 

pores lead to an increase of membrane permeability 

for ions and even macromolecules like DNA. 

Numerous studies with different approaches have 

been performed to obtain a better understanding of 

the molecular processes involved in electroporation. 

Furthermore, theoretical models have been 

developed, e.g. the single cell electroporation 

model [1], to supply the experimental knowledge. 

But despite of all these models little is known 

about the electroporation process itself. Therefore 

a better understanding of the charging processes of 

biomembranes is needed. Pulsed laser fluorescence 

microscopy allows the examination of 

9 

membrane charging processes with high temporal 

resolution of a few ns. This knowledge is of importance, 

because it enables the adaptation of the 

electric pulse parameters for several applications 

ranging from nano- to industrial-scale processes. 

II. EXPERIMENTAL SETUP 

The experimental setup used for the presented 

experiments is equivalent to the one described by 

Frey et al. [2]. Protoplasts prepared from the cell 

line Nicotiana tabacum L. cv. Bright Yellow 2 (BY- 

2) have been stained with ANNINE-6, a fast voltage-sensitive 

dye which exhibits fluorescence 

intensity changes based on electronic transitions 

due to the molecular Stark effect within a subnanosecond 

time range [3]. For the excitation of 

the fluorescent dye, a laser pulse with a wavlength 

of 468 nm delivered by a Nd:YAG-pumped dyelaser 

has been used. The voltage pulse driving the 

external electric field is provided by a microscopebased 

Blumlein-line generator. Transmembrane 

potential dependent fluorescence changes caused 

by the applied external electric field have been 

recorded using a fast intensified CCD camera. To 

obtain the basic fluorescence F0, the fluorescence 

response of ANNINE-6 has been recorded without 

external electric field. For the measurement of the 

field strength dependent fluorescence intensity F, 

an external electric field E has been applied and 

the fluorescence image has been acquired at a 

certain point of time t relative to the onset of the 

pulse. The obtained relative fluorescence change 

F/F0 has been converted to transmembrane potential 

values �VM using a calibration curve of the 

voltage-sensitive dye obtained by spectroscopic 

measurements on leech neuron cells [4]. 

III. RESULTS AND DISCUSSION 

The experiments presented in this work have been 

performed using a 1 μs rectangular pulse with field 

strength amplitudes in a range of 0.05 kV/cm to

30 kV/cm. The recordings of the fluorescence intensity 

changes have been acquired at t = 500 ns after 

the onset of the electric field pulse. 

A. FIELD STRENGTH DEPENDENE OF THE TRANS- 

MEMBRANE POTENTIAL 

The field strength dependence of the BY-2 protoplasts 

transmembrane potential shows asymmetric 

saturation characteristics due to the high resting 

potential of plant cells. At the depolarized cell 

hemisphere (cathode) the fluorescence intensity 

decreases until an external electric field of 

~1 kV/cm is reached. With further increasing field 

strength the curve progression shows a clear saturation 

effect. At the hyperpolarized pole (anode) of 

the protoplast, the saturation of the fluorescence 

intensity sets in at a lower field strength of approximately 

0.3 kV/cm. 

With the assumption of a resting potential value of 

-150 mV the critical transmembrane potential 

where pore formation effects limit a further charging 

of the membrane could be calculated to a value 

|VM| of ~ 350 mV. 

B. AZIMUTHAL DEPENDENCE OF THE TRANSMEM- 

BRANE POTENTIAL 

To determine the azimuthal dependence of the 

transmembrane potential, the relative fluorescence 

change has been measured in angular intervals of 

10° along the circumference of the protoplast. 

The curve progressions show membrane charging 

up to values similar to the results obtained by the 

method described in (A.). The flattening and the 

drop of the curves at the depolarized cell hemisphere 

at field strengths > 1kV/cm is a clear sign 

for the limiting of the membrane charging by the 

formation of pores. Due to the high resting potential, 

the pore formation at the hyperpolarized cell 

pole starts earlier and the curves do not show the 

same amplitude compared to the cathodic cell 

pole. At an external electric field strength of 

~ 1 kV/cm, a statistically verified membrane effect 

occuring at the hyperpolarized pole could be 

observed. Recent theories explain the sudden drop 

of the transmembrane potential with an activation 

of voltage-gated ion channels. The existence of 

hyperpolarisation-activated Ca 2+ -channels plant 

cells, which control the membrane depolarisation 

needed for physiological functions, has been confirmed 

by several authors [5]. 

C. RECHARGING BEHAVIOUR OF THE MEMBRANE 

AFTER PULSE EXPOSITION 

Pulse train experiments have been performed to 

determine the charging- and recharging behaviour 

10 

of the protoplasts plasmalemma after multiple 

pulse exposition at several field strengths. The 

results show, that the membrane discharges instantaneously 

after the pulse ends to values which are 

supposed to be the resting potential of the cell. The 

membrane can be recharged to the same value a 

few seconds after the previous pulse exposition. At 

low field strengths both cell poles show the same 

amplitude of the induced transmembrane potential. 

With increasing field strength, the depolarized cell 

pole shows higher amplitudes compared to the 

hyperpolarized side. Application of electric fields 

higher than approximately 1 kV/cm leads to disruption 

of the charging- and discharging-processes 

at the hyperpolarized cell pole indicated by the 

saturation characteristics of the curve progression. 

The results of the pulse-train experiments show a 

fast recovery process of the plasmalemma with the 

depolarized pole showing characteristics of the 

formation of reversible pores whereas the curve 

progression measured at the hyperpolarized pole 

indicates the formation of irreversible pores. 


Thanks to Prof. Dr. Peter Nick and Dr. Petra 

Hohenberger from the Botanical Institute I, 

University Karlsruhe for their assistance. 

Faculty mentor: Prof. Dr. Peter Nick 

Email: 

peter.nick@uni-karlsruhe.de 

REFERENCES 

[1] W. Krassowska, P.D. Filev, Modeling Electroporation 

in a Single Cell, Biophysical Journal, 

Vol. 92, 404-417, January 2007. 

[2] W. Frey, J.A. White, R.O. Price, P.F. Blackmore, 

R.P. Joshi, R. Nuccitelli, S.J. Beebe, 

K.H. Schoenbach and J.F. Kolb, Plasma 

Membrane Voltage Changes during Nanosecond 

Pulsed Electric Field Exposure, Biophysical 

Journal, Vol. 90, 3608-3615, May 2006. 

[3] B. Kuhn, P. Fromherz, W. Denk, High Sensitivity 

of Stark-Shift Voltage-Sensing Dyes by 

One- or Two-Photon Excitation Near the Red 

Spectral Edge, Biophysical Journal, Vol. 87, 

631-639, July 2004. 

[4] B. Kuhn, P. Fromherz, Annelated Hemicyanine 

Dyes in a Neuron Membrane: Molecular 

Stark Effect and Optical Voltage Recording, J. 

Phys. Chem. B, 107, 7903-7913, 2003. 

[5] P.J. White, Calcium channels in higher plants, 

Biochimica et Biophysica Acta 1465, 171- 

189, 2000.

Modeling metamaterial microwave resonators 

Tomas Zvolensky and Zbynek Raida (Faculty Mentor) 


University of Technology 


Email: xzvole00@stud.feec.vutbr.cz, raida@feec.vutbr.cz 

Abstract — The work is aimed to verify the possibility 

of modeling, realization and measurement of 

a microwave resonator comprised of a metamaterial 

equivalent structure. The resonator is designed 

in a planar form to be easily implemented in multilayered 

planar circuits. For the resonator design, 

MATLAB scripts for calculating the dimensions of 

the planar components of the resonator were developed. 

After simulating the designed structure in 

Zeland IE3D, the metamaterial resonator was fabricated 

and measured. 


Throughout last decades, researchers have been 

dealing with metamaterials and their practical implementation 

in many fields of engineering areas. In 

principle, metamaterials are composed media having 

various forms (layered media, planar structures, 

space neatened structures, etc.). At some frequencies, 

metamaterials possess negative values of material 

constants (i.e., relative permittivity and relative permeability). 

Having negative material constants values, 

several interesting characteristics can arise (e.g., 

wave propagating through the metamaterial structure 

can have the same phase shift at the end of the structure 

as at the entrance). 

Our interest is focused on using metamaterials in 

microwave resonators design. In order to verify the 

characteristics of metamaterials, planar resonators 

were designed, simulated and measured. 

II. SUB-WAVELENGTH CAVITY RESONATOR 

Figure 1 shows geometry of a two-layer resonator 

[1]. The layer of the thickness d1 is made of 

a conventional material (positive values of material 

constants), and the layer of the thickness d2 is made 

of metamaterial. Arrows S1 and S2 show the directions 

of the Poyinting vector, arrows k1 and k2 are 

directions of the phase velocity vector. 

Metamaterials are left-handed (LH) media, and 

conventional materials are right-handed (RH) ones. 

Therefore, the direction of the Poyinting vector and 

the direction of the phase velocity vector are antiparallel 

in the metamaterial layer. 

11 

Resonators designed and investigated in this project 

are composed of a LH transmission line (TL) and 

a RH TL. These resonators are therefore called 

CRLH TL (Composite Left/Right Handed Transmission 

Lines). 

When designing such a resonator in the planar 

form, LH TL is created by series capacitors and shunt 

inductors. The resonator exhibits then a nonlinear 

phase response. The phase response can be shaped 

according to our requirements by changing the properties 

of transmission lines (adjusting RH TL length 

and changing inductance and capacity of LH TL). 

Figure 1: Two-layer resonator [1] 

Better characteristics of the planar resonator (i.e., 

higher modes spacing) can reached by decreasing the 

slope of the phase response. By increasing the slope 

of the phase response, the Q factor of the resonator 

can be increased. The advantage of this technique is 

hidden in the fact that changing the phase response 

influences both the essential parameters of resonators 

– the selectivity and the higher modes spacing. 

III. CIRCUIT MODEL VERIFICATION 

Figure 2 shows a planar resonator setup created 

by the modification of the structure published in [2]. 

Gap capacitors used in [2] were replaced interdigital 

ones in order to reach higher values of the series 

capacities. Parallel inductivities are implemented in

the form of short-end shunts. In between shunts, RH 

part of the TL is placed. 

Figure 2: Planar resonator setup 

In order to obtain proper dimensions of the shunt 

inductor and the interdigital capacitor, MATLAB 

scripts were implemented. The scripts used a local 

optimization algorithm, which changed the dimensions 

of the layout to reach the required capacity and 

inductivity. 

The described design procedure was applied considering 

the dielectric substrate Arlon D600 (the 

height h = 1.54 mm, the dielectric constant �r = 6.15, 

and the loss factor tan � = 0.003). 

When the dimensions of the resonator elements are 

known, the structure can be modeled and optimized 

in Zeland IE3D. The optimization is aimed to obtain 

the dominant resonance at frequency 6 GHz. 

0 

-5 

-10 

-15 

-20 

-25 

-30 

s11[dB] 

0 

-10 

-20 

-30 

-40 

-50 

-60 

-70 

-80 

f[GHz] 

4 4,5 5 5,5 6 6,5 7 7,5 8 

measured simulated 

f[GHz] 

4 4,5 5 5,5 6 6,5 7 7,5 8 

s21[dB] measured simulated 

Figure 3: Measurement and simulation comparison 

12 

Consequently, the optimized resonator was fabricated 

and measured. Comparison of the simulation 

and the measurement of the designed structure are 

depicted in Figure 3. 

Obviously, there is a single lower mode resonating 

below frequency 5.4 GHz, and there are a number of 

upper modes resonating above frequency 5.4 GHz. 

A detailed comparison shows that: 

� The frequency of maximum transmission for the 

measured structure is at 6.3 GHz (s21 =–8.05 dB) 

and at 6.08 GHz for the simulated one (s21 = 

–7.94 dB). The drift of the resonance frequency 

is about 3.6 %. 

� The frequency of the minimum reflections is at 

5.89 GHz for the measured structure (s11 = 

–25.12 dB) and at 6.09 GHz for the simulated 

one (s11 = –27.11 dB). The drift of resonance 

frequency is about 3.3 %. At the frequency 

6 GHz (the expected resonance), reflections of 

the measured structure reach –18.1 dB, therefore 

impedance matching can be considered as satisfactory. 

� The drift of the resonant frequency can be caused 

of the the fabrication of the structure. An extension 

of vias through the metal joint (moreover 

with a different impedance) modified parameters 

of the whole structure and shifted the resonance. 

IV. CONCLUSIONS 

In the paper, the design, modeling, fabrication 

and measurement of the metamaterial planar resonator 

is described. Obtained results are discussed 

demonstrating a relatively good agreement. 

ACKNOWLEDGEMENTS 

The described work was financially supported 

by the Czech Grant Agency by grants 102/07/0688 

and 102/08/H018. 

REFERENCES 

[1] ENGHETA, N. An idea for thin sub-wavelength 

cavity resonators using meta-materials with 

negative permittivity and permeability. IEEE Antennas 

and Wireless Propagation Letters. 2002, 

vol. 1, no. 1, p. 10–13. 

[2] ALLEN, C.A., LEONG, K., ITOH, T. Design of 

microstrip resonators using balanced and unbalanced 

composite right/left-handed transmission 

lines. IEEE Transactions on Microwave Theory 

and Techniques. 2006, vol. 54, no. 7, p. 3104 to 

3112.

Bearingless Segment Motor with Buried Magnets 

Thomas Stallinger, Wolfgang Gruber and Wolfgang Amrhein 

Institute of Electrical Drives and Power Electronics 

Johannes Kepler University 

Linz, Austria 

Email: {Thomas.Stallinger,Wolfgang.Gruber,Wolfgang.Amrhein}@jku.at 

Abstract — Bearingless motors combine contactless 

levitation and rotation in a preferably compact 

system design, because bearing as well as motor 

windings are located on the same lamination stack. 

The bearingless segment motor features concentrated 

coils on separated stator elements, which 

reduce the stator iron, weight and cost, especially 

for constructions with large diameters. In this paper 

a bearingless segment motor with buried permanent 

magnets is investigated. The mathematical model is 

presented and a proper control scheme is introduced. 

Finally, the performance of the bearingless segment 

motor with buried permanent magnets is proven by 

the comparison of simulation results with measurement 

data of the manufactured prototype. 


The advantages of bearingless drives are evident. 

Contactless levitation leads to wearless and lubrication 

free operation. Furthermore, the rotating part and 

the stator can be separated completely by the use of a 

rotor can. This leads to hermetically sealed systems 

which can satisfy high demands on cleanliness, 

chemical resistance and tightness. Therefore such 

motors are often employed in the pharmaceutical, 

biomedical, chemical, semiconductor or aerospace 

industry. 

Bearingless systems have to stabilize all six degrees 

of freedom by magnetic forces. In general these 

systems show a quite complex build-up. The bearingless 

slice motor [1] reduces the system complexity 

because three degrees of freedom (two tilting and the 

axial direction) are passively stabilized by means of 

reluctance forces. This becomes feasible due to the 

permanent magnet excited disc shaped rotor. In the 

recent past the bearingless segment motor, illustrated 

in Figure 1, was introduced [2] as a subtype of the 

bearingless slice motor. 

II. CONTROL SCHEME 

To simplify matters only the model for current injection 

is given here. The detailed deduction and the 

more complex model for voltage injection can be 

found in [4]. 

13 

Figure 1: Drawing of a bearingless segment motor 

A. FORCE AND TORQUE 

A describtion of the bearing forces (Fx, Fy) and the 

motor torque (Mz) of the system is given in [3] by 

T 

� F � � 0 0 

x x � �i� r 

s 

� T 

Fy 

�x � � � � 0 i 0 � 

r 

s MQ�xr�is 

� � T � 

(1) 

M z � �� 

� x � � 0 0 i 

r 

s � 

�M x i �M 

x . 

� � � � 

L r s N r 

Here xr��xr� yr� �r) T represents the rotor position by 

the radial deflection and rotor angle. The vector of 

the stator currents is=(is1, is2, is3, … ,ism) T is composed 

of the m phase currents. There is a quadratic (MQ), a 

linear (ML) and a term of no dependency (MN) concerning 

the stator currents. Equation (1) can be linearized 

via Taylor series approximation and yields to 

� Fx 

�� r 

� Fy�� 

� � T � � � , � � , 

r m �r is �Tc 

�r is � Kx �r 

iS� r 

� 

M z ��r�� 

x . (2) 

B. OVERALL MODEL 

Adding the mechanical equations of motion the overall 

model of the system in (2) is given by 1 

1 

� 

x�� M O 

K i 

E 

O 

� � O 

�x�� M 

T 

� O3×1 

� 

� � -1 , 

��r, �� 

�M Tc iS 

� 

On× m 

E n 

� 

� 

� i 

3×3 3 3×m 

-1 -1 S 

x��r, S� 3×3 m��r� 

(3) 

represents a zero matrix of the dimension n × m and 

stands for an identity matrix of the dimension n.

with is as the actuating variable. The state vector x is 

defined as 

x � � x y � x� y� 

� � 

r r r r r r 

T 

. (4) 

In this equation of motion M represents the diagonal 

mass matrix and Kx(�r) stands for the stiffness matrix, 

Tm(�r)� is called current-force matrix and 

Tc(�r,iS) is the reluctance matrix. 

C. CONTROL SCHEME 

For the deduced nonlinear model in (3) a proper 

control scheme has to be found. A possible choice is 

to use nonlinear feedback techniques [4]. Utilizing 

the pseudo inverse matrix of Tm(�r), which is also 

called force-current matrix Km(�r), it is possible to 

compensate all nonlinearities with an bias current 

vector, depending on the rotor angle and the current 

vector itself, leading to an overall linear and decoupled 

model 

� O E � � O 

x�� x��M T 

3×3 3 

3×m 

� -1 � 

-1 

S 

�M K � � �� x O3×3 

m r �� 

� 

III. OPTIMIZATION 

� 

i . (5) 

Finite element simulations were carried out to optimize 

bearing forces and motor torque and to minimize 

the reluctance forces and the cogging torque. 

Because of calculating capacity and time economy 

these optimizations were done in 2D by Femag� and 

then verified by Maxwell 3D�. Both the rotor and 

the stator geometry were optimized. 

IV. MANUFACTURED MOTOR 

To evaluate the functionality of the motor and the 

quality of the optimization a prototype was built, 

visible in Figure 2. The five stator elements (each 

holding a concentrated winding coil) are held among 

an aluminium framework. Inside the rotor the buried 

permanent magnets are cognizable, forming six magnetic 

pole pairs. The used Ni-coated NdFeB magnets 

feature a remanence field density BBr of 1.2T. The 

stator and rotor iron consist of laminated V270-35A 

steel plates. 

Figure 2: Bearingless segment motor prototype 

14 

The control scheme was implemented on the inexpensive 

16 bit fixed point digital signal processor 

family TMS320 by Texas Instruments. The software 

is written in ANSI C-code. The design of a proper 

electronic to evaluate the position- and the Hallsensors 

was also part of this work. 

V. MEASUREMENTS 

An orbit measurement was done while the bearingless 

segment motor was in operation. The radial 

deflection at certain speeds was measured and displayed 

in Figure 3. More measurement data is also 

given in [5]. 

Figure 3: Bearingless motor in action - orbit 


This research project was funded by the Austrian Science 

Fund (FWF) under contract P17523-N07. The authors 

thank the Austrian Government for the support. Scientific 

advisory support and parts of the control algorithms were 

kindly given by the Austrian Center of Competence in 

Mechatronics (ACCM), a K2 Centre of the COMET program 

of the Austrian Government. 

REFERENCES 

[1] Schöb R. and Barletta N., Principle and application 

of a bearingless slice motor, Proc. of the 5th 

Int. Symp. on Magnetic Bearings (ISMB5), Kanazawa, 

Japan, 1996 

[2] Gruber W. and Amrhein W., Design of a Bearingless 

Segment Motor, Proc. of the 10th Int. 

Symp. on Magnetic Bearings (ISMB10), Martigny, 

Switzerland, 2006. 

[3] Amrhein W., Silber S. and Nenninger K., Levitation 

forces in bearingless perm. magnet rotors, 

IEEE Trans. on Magnetics, Vol. 35, No. 5, 1996. 

[4] Grabner H., Dynamik und Ansteuerkonzepte 

lagerloser Drehfeld-Scheibenläufermotoren in 

radialer Bauform, Ph. D. Dissertation, Johannes 

Kepler University Linz, Trauner Verlag, 2007. 

[5] Stallinger T., Lagerloser Segmentmotor mit eingebetteten 

Magneten, Diplomarbeit, Johannes 

Kepler University Linz, 2008.

Identification of tacit knowledge during realization of knowledge 

creation processes 

František Babi� and Ján Parali� (Faculty Mentor) 

Department of Cybernetics and Artificial Intelligence 

Faculty of Electrical Engineering and Informatics, Technical University of Košice 

Košice, Slovakia 

Email: {frantisek.babic, jan.paralic}@tuke.sk 

Abstract — The aim of this paper is to present 

proposed solution for identification of tacit knowledge 

during knowledge creation processes. The 

secondary knowledge arise based on actual situations 

and have potential to simplify and solve the 

problematic points in performed processes. 

This approach is based on saving performed actions 

and activities within processes in form of logs into 

separate database in predefined format. These logs 

of events will be further analyzed with e.g. Data 

Mining methods, SNA methods, statistical methods, 

etc. 

Events are realized in collaborative system called 

KP-Lab System that has been implemented within 

integrated IST FP6 project called KP-Lab 1 (2006- 

2011). 


Knowledge creation processes are modelled and 

realized in order to acquire new knowledge; this is 

the main goal of these processes. Process models 

consist of phases and some detail parts, inputs and 

resources, participants with assigned roles, etc. During 

process execution many interactions between 

theses aspects can emerged and it can be reason for 

contradictions, deviations and exceptions. In various 

cases are these situation evaluated and negative and 

several solution are predefined. In our case, we 

evaluate these points in process as potentially place 

of change with possible tacit knowledge. 

II. LOG-BASED AWARENESS 

Proposed solution is marked as Log-based (History) 

awareness (LBA) and provides an asynchronous 

functionality that builds on persistent storage of 

events representing activities performed by users of 

various end-user tools in KP-Lab System and based 

on them supports analysis and discovery of tacit 

knowledge from previous activities. 

1 http://www.kp-lab.org/ 

15 

KP-Lab System is virtual collaborative system that 

provides many important and interesting features to 

support collaborative knowledge creation processes. 

In this system users/participants can realized their 

activities, e.g. creation of process models with further 

execution, working with shared objects of activities, 

multimedia annotation (document, video, etc.) based 

on free or ontology approach (vocabularies), conferencing 

features with creation of discussion map and 

outcomes export, collaborative semantic modelling, 

etc. KP-Lab System use ontologies as common 

communication and integration language for all applications 

and tools that are implemented and integrated 

in whole system. Semantic information (metadata, 

ontologies) are stored into knowledge repository 

within RDFSuite and content storage is implemented 

based on Jackrabbit and JSR-170 technologies. 

A. ARCHITECTURE 

LBA is integrated on the platform level under end 

user tool layer and provides several related services, 

see Figure 1. 

Figure 1: Integration of LBA related services into 

whole system 

Subscription service is responsible for a creation, 

modification and a removal of the subscriptions 

which keeps in repository. This module must communicate 

both with the users (end-user tools) to receive 

their choices or updates of their subscriptions

and with the repository in order to allow a persistent 

storage of these subscriptions. 

Role of the Notification service is to deliver the notifications 

to the corresponding users based on selected 

form: email, RSS, online message, etc. 

Repository is implemented as transactional database 

to store subscription and events for further analyses. 

LBA services have support analysis and discovery 

of (possibly tacit) knowledge from previous activities. 

B. INTEGRATION WITH KPS 

The whole process of data collection and analysis can 

be shown on an example, using Knowledge Process 

Service (KPS), and see Figure 2. 

Figure 2: Communication between KPS and envisaged 

LBA services [1] 

KPS provides a set of features and interfaces necessary 

for creation, management, and annotation of 

processes composed from various elements. This tool 

can generate several types of events as Modification 

of object metadata, Modification of object itself 

(create, delete) and Modification in process structure. 

If e.g. a user wants to be notified about changes in a 

particular Task (this means any change of Task properties 

metadata), the process is the following (see 

Figure 2). The user subscribes via KPS his/her interest 

to be notified when a particular Task changes 

(Subscription of Task changes in Figure 2). This 

subscription will be stored in the repository (Saving 

in database). Whenever any user makes a modification 

of this particular task, KPS issues an event to be 

logged (Modification of Task - Event) into repository. 

A matching algorithm will match each new event 

with all current subscriptions (see Figure 2) and all 

matching subscriptions (result of Queries in Figure 

2) will lead to notifications (Notification of realized 

event) to all their subscribers. 

Moreover, this event will be taken into account 

whenever a relevant analysis of logged events will be 

16 

performed by a user or a tool (Perform History Analysis, 

Queries, and Provide results of Analysis in 

Figure 2). 

C. ANALYTICAL APPROACH 

The analytical services have been proposed with 

several levels of complexity and granularity. For a 

start we implement basic features as identification of 

all changes within shared objects, list of performed 

actions by users, performed actions in selected time 

interval and some combinations. In the next step, 

based on further acquired logs of events, additional 

functionalities will be implemented as: 

• Visualisation of the user’s activities (e.g. identification 

of most active participant, identification 

of isolated persons in collaborative processes). 

• Sequence mining: identification of typical sequences 

of actions that users execute to reach the 

goals or solve the problem. 

• Identification of past patterns – e.g. participants 

used several relevant documents for accomplishment 

of similar type of task, so we can recommend 

which documents are suitable for actual 

task instance. 

• Support for building the user and task models for 

Help services. 

• Identification of changes in vocabularies, e.g. list 

of last changes. 

• Discovery of “best practices” in past knowledge 

processes. Based on them new templates of 

various types may be created and stored into Reuse 

library. 

• Identification of objects that were subject of 

(triggered) context-based chat – maybe problematic 

part of process that needs necessary discussion 

about next step, progress or solution. 

• Statistics of ToDo items creation – evaluation of 

individual work management (user with many 

items may be more interested in the whole process 

as user with only few items). 

III. CONCLUSION 

LBA services have provided necessary functionalities 

for identification of tacit knowledge in various 

formats to improve knowledge creation processes. 

REFERENCES 

[1] F. Babi� and J. Wagner. Awareness service based 

on events logs. 2nd Workshop on Intelligent and 

Knowledge oriented Technologies 2007, Košice, 

Slovakia, pages 106-109, 2008, ISBN 978-80- 

89284-10-8.

Multifunctional 4 th order tuned active filter 

Roman Šotner, Tomáš Dostál (Faculty Mentor) 

Department of Radioelectronics 

Faculty of Electrical Engineering and Communications, University of Technology 


Email: xsotne00@stud.feec.vutbr.cz, dostal@feec.vutbr.cz 

Abstract — The paper deals about design of 

the multifunctional active filter with operational 

transconductance amplifiers (OTA-s), 

which realize low pass (LP), band pass (BP), 

high pass (HP) and band reject (BR) transfer 

functions. Mentioned filter is studied with several 

circuits models, namely third level based 

on voltage controlled current sources and professional 

macro models of commercially available 

integrated circuits. The circuit is simulated 

by PSpice (OrCad) and adjusting parameters 

are discussed. Simulations are compared 

with experimental results. 


Some modern integrated active blocks have 

possibility to electronic control of their parameters. 

It is possible to used this principle on adjustable 

filters and oscillators [1], [3]. Typical 

block is operational transconductance amplifier, 

for example LT 1228 [5]. 

II. CIRCUIT DESIGN 

The proposed autonomous circuit in Figure 1 

was obtained with the help of symbolic analysis 

by Snap [2]. 

Figure 1: Autonomous circuit 

Characteristic equation has the following form 

Y YYY 

�YYY g �YY 

g g �Yg 

g g �g 

g g g �0. 

(1) 

1 2 3 4 

1 2 3 

4 

1 2 

3 

4 

1 2 

3 

4 

1 2 

If Y1 = sC1, Y2 = sC2, Y3 = sC3, Y4 = sC4, 

4 3 g4 

2 g3g4 

2 g2g3g 

4 g1g2g 

3g4 

D( s) 

� s � s � s � s � , (2) 

C C C C C C C C C C 

4 

3 

4 

2 

3 

4 

1 

3 

2 

4 

3 

4 

17 

and corresponding circuit diagram is shown in 

Figure 2. 

Figure 2: Multifunctional 4 th order filter 

The transfer functions are 

K BR 

g1g 

2 g 3g 

4 

K LP ( s) 

� , (3) 

D( 

s) 

2 

s C 1C 

2 g 3g 

4 

K BP ( s) 

� , (4) 

D( 

s) 

4 

s C1C 

2C 

3C 

4 

K HP ( s) 

� , (5) 

D( 

s) 

4 

s C1C 

2C 

2C 

4 g1g 

2 g 3g 

4 

( s) 

� � . (6) 

D( 

s) 

D( 

s) 

Inputs, which are not used, must be grounded. 

The filter is designed with following specification: 

the cut-off (center) frequency is 

fC = 100 kHz for pass-band with KC = -3 dB, the 

stop-band frequency is fS = 300 kHz, for 

KS = -35 dB and Butterworth approximation. 

The coefficients of the denominator of the transfer 

function (2), obtained using the computer 

tool NAF [4] are b0 = 1,56207.10 26 , 

b1 = 6,49284.10 19 , b2 = 1,34940.10 13 , 

b3 = 1,64280.10 6 , b4 = 1. The transconductances 

are: g4 = 7,72 mS, g3 = 3,87 mS, g2 = 2,24 mS, 

g1 = 1,13 mS (for C1 = C2 = C3 = C4 = 4,7 nF) . 

There is possible apply the approximate equations 

g3 = g4/2, g2 = g4/3,41, g1 = g4/6,83, then 

tuning is very simply. The transconductance

(gm) can be continuously controlled by a DC 

control current ISETm = 10.gm [5]. 

III. EXPERIMENTAL RESULTS 

The proposed circuit (Figure 2) was simulated 

by PSpice using professional macro models 

LT 1228 [5]. Resulting magnitude responses 

(LP, BP, HP, BR) are given in Figure 3. These 

responses are confirming theoretical assumptions. 

10 

K[dB] 0 

-10 

-20 

-30 

-40 

-50 

-60 

-70 

BP 

HP 

BR 

LP 

U CC = ± 15 V 

f c = 96 kHz 

I SET1 = 111 uA 

1,0E+03 1,0E+04 1,0E+05 1,0E+06 1,0E+07 

f[Hz] 

Figure 3: Magnitude responses 

Electronic tuning was tested for LP filter in 

Figure 4, changing the control current ISET1 in 

the range given to in Table 1, other types transfer 

functions were tested too. 

10 

K[dB] U CC = ± 15 V 

0 

-10 

-20 

-30 

-40 

-50 

-60 

1 2 3 4 5 

-70 

1,0E+04 1,0E+05 1,0E+06 

f[Hz] 

1,0E+07 

Figure 4: Simulation of the tuning of the LP filter 

Curve index ISET1 [uA] fC [kHz] 

1 

2 

3 

4 

5 

19 

111 

323 

559 

677 

17 

96 

280 

485 

589 

Table 1: Control current versus cut-off frequency 

18 

The proposed multifunctional 4 th order filter 

was practically realized on a solderless connecting 

field and then measured. The results 

are given to in Figure 5 and compared with 

the computer simulation above. 

simulation 

10 

f C � 96 kHz 

K [dB] 

0 

U INP (LP, HP) = 50 mV 

-10 U INP (BP) = 20 mV 

U CC = ± 15 V 

-20 R L = 1 M� 

I SET1 = 111 uA 

-30 

HP 

-40 

BP 

-50 

measurement 

f C � 105 kHz 

-60 

1,0E+03 1,0E+04 1,0E+05 f [Hz] 1,0E+06 

Figure 5: Results of simulation and measurement 

IV. CONCLUSION 

This filter has advantage in more of the type 

transfer function, simplicity in circuit design, 

large cut-off frequency range and simply tuning. 

Disadvantage is small input voltage level. 

Function of this filter was verified by computer 

simulation and by practical measurement. 


Research described in the paper was supported 

by the Grant Agency of the Czech Republic 

project under grant No. 102/08/H027. 

REFERENCES 

[1] Chen W. K. The circuits and filters handbook. 

CRC Press, Florida, 1995 

[2] Biolek D., Kolka Z. Snap – symbolic, semisymbolic 

and numerical analysis of electronic circuits, 

on www: http://snap.webpark.cz 

[3] Herencsar N., Vrba K. P�eladitelné filtry s OTA 

zesilova�i. Elektrorevue 2007/28, ISSN 1213- 

1539, 12 s., on www: http://www.elektrorevue.cz 

[4] Hajek K., Sedla�ek J., Nafid Program as Powerful 

Tool in Filter Education Area. Proc. Of International 

Conference CBLIS´97, Leicester 1997, s. 

PK4 1-10 

[5] Linear technology, LT 1228 – Current feedback 

amplifier with DC gain control. Linear Technology 

Datasheets, 1994. on www: 

http://www.linear.com 

LP

Active Semiconductor Devices for Millimetre Waves Applications 

Michal Pokorný and Zbyn�k Raida (Faculty Mentor) 



Brno, Czechia 

Email: xpokor33@stud.feec.vutbr.cz, raida@feec.vutbr.cz 

Abstract — This paper deals with advanced theory 

of dielectric waveguides and with the solid state 

physics of bulk semiconductors. The research is 

aimed to the design and numerical modeling of 

active waveguides and antennas using the unique 

property of the bulk GaAs – the negative differential 

resistance. The mathematical model is numerically 

implemented using the finite element method and 

evaluated in COMSOL Multiphysics. 


The main problem of active millimeter-wave (MW) 

systems is related to fundamental limitations of the 

convectional discrete semiconductor devices which 

output power drops drastically at frequencies of MW 

band. Therefore, alternative principles, like traveling 

wave amplification using the bulk negative differential 

resistance (NDR) that arises in A 3 B 5 semiconductors 

(e.g. GaAs), are very perspective. Also losses of 

wave-guiding MW systems are significant. Here, the 

dielectric waveguides are more promising than metallic 

ones due to lower cost, easier fabrication and 

lower propagation loss [1]. 

II. SIMPLIFIED MODEL OF WAVE PROPA- 

GATION IN EXCITED SEMICONDUCTOR 

If the uniform doping profile and low perturbation of 

GaAs sample is assumed, the gradient of the carrier 

concentration is zero, so the diffusive processes can 

be neglected and the free carrier concentration is 

always equal to the doping concentration. Under 

these simplifying considerations, the media properties 

can be simply described by conductivity σ. If the 

external voltage is applied, the electrostatic field E0 

arises, and the conductivity becomes to have an anisotropic 

character due to the reduction of the electron 

mobility caused by components of the E0. Thus the 

conductivity should be expressed as an uniaxial tensorσˆ 

. In order of further simplification, the smallsignal 

approximation can be used. That introduces 

the differential form of conductivity σD, given by 

equation (1) which can be derived from the driftdiffusion 

scheme [2] of the semiconductor physics. 

19 

( ) 

( ) 2 

3 

4 

4 

4vsatE0 

− 3�nE0 

+ �nEcrit 

4 4 

E + E 

4 

qNDE 

crit 

σ D = 

(1) 

0 crit 

Here q is the elementary charge and ND denotes 

the donor concentration, μn represents the original 

mobility, vsat is the saturation velocity, E is the component 

of the electric field in the direction of the 

current flow, and Ecrit is the threshold electric field. 

Finally, the elements of the desired tensor σˆ are D 

given by the formula (1) evaluated for the corresponding 

component of the electrostatic field E0 

( E ) 

( ) 

( )� �� 

�σ 

D x0 

� 

ˆ σ = 

� 

D � 

σ D E 

(2) 

y0 

�� 

σ D Ez 

0 � 

Considering the simplifications above, the system 

published in [1] can be reduced into a single Helmholz 

equation where the vector of current density is 

substituted by the product of the electric field vector 

and the differential conductivity tensor. Such an 

equation is easy to solve, thus the analysis of a complex 

device containing the domain of the active semiconductor 

media is less CPU-time and memory consuming. 

III. MODELS OF ACTIVE DEVICES 

The active waveguide consists of the GaAs rod, 

which is inserted into two open-ended metallic rectangular 

waveguides. The GaAs is biased through the 

ohmic contacts placed on the top and the bottom of 

the rod. 

Figure 1: FEM model of an active waveguide

The active antenna can be created by an openended 

dielectric rod, which is excited by an openended 

metallic waveguide. 

Figure 2: FEM model of an active rod antenna 

Figure 1 and Figure 2 depict the geometry of analyzed 

structures. The terminating waveguides are the 

standard type WR-10 of the length 8 mm. The cross 

section dimensions of the GaAs waveguide are 

1.10 × 0.55 mm 2 and its length is 24 mm. The donor 

concentration in the rod volume is ND = 20 ⋅ 10 18 m -3 . 

IV. RESULTS 

If the Poisson equation is solved in the domain of the 

active semiconductor media, then the solution defines 

the components of E0. Consequently, the differential 

conductivity tensor (2) can be evaluated, and 

the Helmholz equation can be solved. 

S - parameters [dB] 

10 

5 

0 

-5 

-10 

-15 

S11 

-20 

S21 

-25 

7,5E+10 8,0E+10 8,5E+10 9,0E+10 9,5E+10 1,0E+11 1,1E+11 1,1E+11 

f [Hz] 

Figure 3: Computed s-parameters of the active 

waveguide 

The computed reflection coefficient S11 and the 

transmission coefficient S21 of the active waveguide 

are depicted in Figure 3. The progress of the S21 

coefficient shows that the gain of the rod is about 

5 dB, and varies significantly at higher frequencies. 

The S11 coefficient has the resonating character: there 

are well-matched bands on one hand and strong 

resonances at higher frequencies on the other hand. 

20 

Figure 4: Computed gain radiation patterns in dB 

for vertical polarization at 88 GHz 

The computed gain radiation pattern of the active 

antenna is depicted in Figure 4. The computations 

were done for the two donor concentrations in order 

to compare a passive rod antenna ND = 0 [m -3 ] and an 

active one ND = 20⋅10 18 [m -3 ]. The gain increase is 

about 4.2 dB. In both cases, the magnitude of the 

reflection coefficient S11 at the antenna input is lower 

than –22 dB. 

CONCLUSIONS 

A simple model of electromagnetic wave propagation 

in excited semiconductor media was presented. 

The model was used in innovative design of the 

active dielectric waveguide and the active rod antenna. 

The future work will be focused on the investigation 

of the stability of structures in order to avoid 

the self-oscillation behavior (this effect is ignored in 

the presented work). Moreover, other types of NDR 

media for operating at lower current densities will be 

developed. 


Research described in this contribution was financially 

supported by the Czech Grant Agency under 

the grants no. 102/07/0688 and 102/08/H018, and by 

the research program MSM 0021630513. The research 

is a part of the COST project IC0603. 

REFERENCES 

[1] D. Lioubtchenko, S. Tretyakov and S. Dudorov. 

Millimeter-Wave Waveguides, Boston: Kluwer 

Academic Publishers, 2003 

[2] S. Selberherr. Analysis and Simulation of Semiconductor 

Device, Hiedelberg: Springer-Verlag, 

1984.

Analysis of Power-Bus Structures Using Contour Integral Method 

Martin Štumpf and Zbyn�k Raida (Faculty Mentor) 




Email: xstump00@stud.feec.vutbr.cz, raida@feec.vutbr.cz 

Abstract — The paper is focused on the analysis of 

power-bus structures on printed circuit boards 

using the contour integral method (CIM). The CIM 

was implemented in Matlab and the program is 

capable to analyze the parallel-plate structures with 

arbitrary material parameters, polygonal shape and 

number of ports. As an output the program provides 

the frequency dependent voltage distribution between 

the plates, voltage/current relations between 

the ports and the far-field radiation diagram of the 

structure. The evaluation of the far field radiation 

diagrams is based on the application of the field 

equivalence principle. All results were validated by 

measurement. 


Power-bus structures serves as the charge storage for 

the integrated circuits (IC) on printed circuit boards 

(PCB). The second essential purpose is the reduction 

of the switching noise rising from the non-ideal 

switching within IC. As a consequence of the switching 

noise and non-zero impedance of the structure, 

the power-bus structure is a source of the radiated 

electromagnetic emissions. 

All today’s analyses of power-bus structures are 

focused on the evaluation of voltage/current relations 

between the ports (e.g. in Z-matrix form) and on the 

far-field radiation diagrams [1]. Recently, several 

numerical methods were used. First group of these 

methods are restricted on simply-shaped structures 

only [1], and others are based on the full-wave numerical 

methods as finite-difference-time-domain 

method (FDTD) [2] or on the circuit extraction based 

on the mixed-potential integral equation (CEMPIE) 

[3]. The numerical approach presented here is based 

on the 2D contour integral equation [4], usually 

called as Weber’s solution for cylindrical waves [5]. 

In the presented paper, the resulting Z-matrix is converted 

into the so-called TouchStone file format, 

which allows embedding the power-bus structure 

into a network analysis. This then enables to simulate 

the behavior of the populated power-bus structures 

and design the proper decoupling. Further, the radi- 

21 

ated emissions are evaluated using the fieldequivalence 

principle [5]. 

II. FORMULATION OF THE PROBLEM 

The problem is firstly formulated as a 2D boundary 

value problem. Consequently, Green’s theorems and 

the properties of a unit source are applied, getting a 

second kind Fredholm integral equation. The voltage 

at the point Q at the periphery C of the power-bus 

structure is given by the voltage V(s) and surface 

current density iSn(s) along this periphery as [4]: 

1 

( 2) 

( 2) 

V ( Q) 

� � H ( ) ( ) cos H ( ) ( ) � 

1 

0 0 

2 � k kR V s � � j�� 

d kR iSn 

s ds 

j 

C 

( 1) 

where H0 (2) ( . ) and H1 (2) ( . ) are the zero-order and firstorder 

Hankel functions of the second kind, respectively. 

Next, j =�-1 is the imaginary unit, � is the 

angular frequency, �0 is the vacuum permeability, k 

is the complex wavenumber and � denotes the angle 

between the outward normal vector to C and vector 

in the direction of the joint line between 

source/observe points. 

The integral equation is then numerically solved 

using CIM. In short only, the boundary contour C is 

divided into the small segments and the electric and 

magnetic field are assumed to be constant over each 

segment. After a few of algebraic steps, the system of 

linear algebraic equations is obtained. From this 

system of equations, the voltages along the boundary 

contour C and voltage/current relations between the 

ports can be derived. 

A. FAR FIELD RADIATION DIAGRAMS 

The far field radiation diagrams of the parallelplate 

structure can be evaluated using the fieldequivalence 

principle. In this paper, the radiated 

electric field are numerically computed according to 

[1]: 

� jk0r 

jk0d 

e 

jkor 

'�er 

E( 

r) 

� 

( ') 

� � , 

4 � M r e e � e ds (2) 

S 

r s 

� r C 

where r a r’ denote position vectors of the observation 

and source points, respectively. Next, r is the 

distance of the observation point from the origin, er 

and es denote the unit vectors having the directions of

the observation point from the origin and of the 

equivalent magnetic surface current MS(r’) along C, 

respectively. The height of the structure is denoted as 

d. 

III. EXAMPLES OF RESULTS 

The power-bus structure depicted in Fig. 1 includes 2 

SMA ports and 13 decoupling capacitors C = 10 nF. 

As a substrate, FR-4 with the height of d = 1.6 mm, 

dielectric constant of �r = 4.35 and dielectric tangent 

loss tan� = 0.035, was used. The parasitic inductance 

and resistance of the decoupling capacitors were 

measured for one capacitor as ESL = 640 pH and 

ESR = 120 m�. 

(0, 100) 

(50, 150) 

(50, 100) 

(25, 80) 

(25, 50) 

(75, 130) (120, 130) 

(75, 80) 

(75, 50) 

(120, 80) 

(0, 0) (100, 0) 

(150, 50) 

(50, 35) (100, 50) 

(25, 20) (75, 20) 

Port1 

Figure 1: Analyzed and measured power-bus structure 

(dimensions in mm) 

The far field radiation diagram at f = 1010 MHz, 

with respect to an excitation by a unit current 

source at the position of Port2 is depicted in Fig. 

2. 

Figure 2: Far field radiation diagram at 

f = 1010 MHz 

(200, 150) 

(180, 130) 

Port2 (180, 105) 

(180, 80) 

(180, 50) 

(180, 20) 

(150, 0) 

(200, 0) 

22 

|Z12| [Ohm] 

10 2 

10 1 

10 0 

10 -1 

10 -2 

10 -3 

Measurement 

CIM 

10 

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 

-4 

f [GHz] 

Figure 3: Frequency response of the transmission 

impedance |z12| 

Fig. 3 shows the measured and analyzed transmission 

impedance |z12| between Port1 and Port2. The 

analysis was carried out, as well as measurement, 

in the frequency range (20�2000) MHz with the 

frequency step 5 MHz.As can be seen, the simulation 

results were confirmed by measurement very 

well. 

REFERENCES 

[1] M. Leone. The radiation of a rectangular powerbus 

structure at multiple cavity-mode resonances. 

IEEE Transactions on Electromagnetic Compatibility, 

vol. 45, no. 3, pp. 486-492, August 2003. 

[2] X. Ye, M. Y. Koledintseva, M. Li and J. L. 

Drewniak, DC power-bus design using FDTD 

modeling with dispersive media and surface 

mount technology components. IEEE Transactions 

on Electromagnetic Compatibility, vol. 43, 

no. 4, pp. 579-587, November 2001. 

[3] J. Fan, J. L. Drewniak, H. Shi and J. L. Knighten, 

DC power-bus modeling and design with a 

mixed-potential integral-equation formulation 

and circuit extraction. IEEE Transactions on 

Electromagnetic Compatibility, vol. 43, no. 4, 

pp. 426-436, November 2001. 

[4] T. Okoshi. Planar Circuits for Microwaves and 

Lightwaves. Berlin, Germany: Springer-Verlag, 

1985. 

[5] J. A. Stratton. Electromagnetic Theory. New 

York: McGraw-Hill, 1 st edition, 1941.

Creating and Drawing Fonts for Graphic displays with Paged 

Memory Model 

Filip Adamec (Student), Tomas Fryza (Faculty Mentor) 

Department of Radio Electronic 



Email: xadame24@stud.feec.vutbr.cz, fryza@feec.vutbr.cz 

Abstract — This abstract describes how to draw a 

character with variable font and size, on graphical 

displays with paged memory model. There are 

firstly described some restrictions for minimal draw 

algorithm demands, next how to store font data on 

desired target and finally how to create very easy 

desired font. 


In many applications (field instruments, information 

panels etc.) it is necessary to represent text information 

via graphical displays. The displays have two 

types of memory organizations, paged memory or 

linear memory organizations. I can introduce very 

easy way to create and draw text on displays with 

paged memory model. This model can be seen in 

Figure 1. 

Figure 1: Paged display RAM 

From figure 1 it is obvious, that the best way to 

write a character bitmap to the display RAM memory 

is to write it by columns. For additional simplification 

we can require the high of the character like a 

multiple of eight. With that simplification the solution 

is easy how can be seen in the following text. 

23 

II. CHARACTER FORMAT AND GENRATION 

The first problem need to be solved is how to store 

the font data. Because commonly we can write target 

application in C langue, the best way how to store 

a data is by arrays. We could use two dimensional 

arrays, where the first dimension is a character number, 

that can be the ASCII number with some offset, 

and the second dimension is the character bitmap. 

We must now consider that we can have nice characters 

with variable width. With that condition we must 

know width of each character and place it as a first 

number in character bitmap. The type of our array 

depends on the font size. For the eight pixel high font 

it will be BYTE variable, for 16 pixel WORD and for 

24, 32 DWORD. 

Now we can generate our font. Because it is very 

hard to create it by own hands, an easy program in 

Visual C++ 6.0 was created, which use fonts from 

other programs and from operation system. In this 

case many fonts with variable size could be used. 

Note that any size could be set, but we need size in 

pixel like a multiply of eight. The basic of this program 

is very easy. It prints all printable ASCII character 

to the memory bitmap on known position and 

then read it back pixel by pixel. After read back 

whole character, it prints that character into text file 

described above. In figure 2 example of generated 

font for 16 bit font size, is shown. 

const unsigned int font[224][17] = { 

……… 

{0xc,0x0,0x1c00,0x1f00,0x3c0,0x2f0,0x23c,0x2e0,0 

x23c, 0x2f0,0x3c0,0x1c00,0x1c00}, //A 

{0xc,0x0,0x0,0x1ffe,0x1ffe,0x1042,0x1042,0x1042, 

0x1042, 0x18e6,4028,1816,0x0}, //B 

{0xc,0x0,0x0,0x1e0,0x7f8,0xe1c,0x1806,0x1002,0x1 

002, 0x1002,0x1806,0xe1c,0x618}, //C 

{0xc,0x0,0x0,0x1ffe,0x1ffe,0x1002,0x1002,0x1002, 

0x1806, 0xe1c,0x7f8, 0x1e0,0x0}, //D 

……… 

}; 

Figure 2: Font example

SIZE 

WIDTH 

0x0000 

0x1c00 

0x1f00 

0x03c0 

0x02f0 

0x023c 

0x020e 

0x023c 

0x02f0 

0x03c0 

0x1f00 

0x1c00 

Figure 3: Bitmap of character “A” 

III. DRAW CHARACTER 

Now, we have everything prepared for draw our font 

on display. We must consider the last thing and it is 

if we can use a universal algorithm or not. The universal 

algorithm can print all font sizes, but is less 

exacting than the type for fixed font size. I describe 

here the universal algorithm. The algorithm needs 

three global variables, first for current text position 

titled cur_line, then for count of pixel from beginning 

of a line cur_pos and the variable that represents 

actual character position on the line cur_column. The 

algorithm must change the line if the actually printed 

character could not be printed on actual line and do 

nothing if the actual number of line is higher than 

maximum. Also the interpret character for jump to 

new line is needed. The algorithm in C language is 

following. 

void TERMIO_PutChar(char character) 

{ 

int i,j; 

char pos; 

//if jump to the new line 

if(znak == 0xa) 

{ 

cur_line++; 

cur_pos = 0; 

cur_column = 0; 

return; 

} 

//subtract the font offset 

pos = character - FONT_FIRST_CHAR; 

//could be the character printed on actual line 

if((cur_pos + font[pos][0]) > 128) 

{ 

cur_line++; 

cur_pos = 0; 

cur_column = 0; 

} 

//if we reach maximum numbers of text lines, 

//display dependent 

if(cur_line > 5) 

24 

return; 

//loop for display pages 

for(j = 0; j < FONT_BYTES; j++) 

{ 

//set display page and page position to write 

SetPageAdress(cur_line*FONT_BYTES+j); 

SetCulomAdress(cur_pos); 

//print all data to the actual selected 

//display page 

for( I = 0; I < font[pos][0]; i++) 

LCDWrite((font[pos][i+1]>>(8*j))&0xff,true); 

} 

//change the current positions 

cur_column++; 

cur_pos += font[pos][0]; 

} 

Figure 4: Proposed draw algorithm 

The macro constant FONT_FIRST_CHAR is the 

offset for ASCII character, FONT_BYTES is the 

high of basic font array type. 

IV. RESULTS 

The best character size for the tested display was 16 

pixels high. The 8 pixels high characters are badly 

visible and the higher pixels high have no meaning, 

because we can not represent useless information. 

The printed characters for 16 pixels high characters 

are shown in figures 5. 

Figure 5: Example of 16 pixels high characters 


The author would like to thank for the financial support 

of the Czech Ministry of Education, Youth and 

Sports under grants no. MSM 002 163 0513. 

REFERENCES 

[1] David J. Kruglinski, George Shepherd a Scot 

Wingo. Programujeme v Microsoft Visual C++. 

Computer press 2000, ISBN: 8072263625. 

[2] Electronic Assembly, DOGM GRAPHIC SE- 

RIS 128x64 DOTS. [online]. 2007 – 

[25.9.2008] Avaliable: http://www.lcdmodule.de/eng/pdf/grafik/dogm128e.pdf

Bandwidth Comparison of Microwave Planar Hybrids 

Petr Orság and Ji�í Sva�ina (Faculty Mentor) 



Czech Republic 

E-mail: xorsag04@stud.feec.vutbr.cz, svacina@feec.vutbr.cz 

Abstract — The paper deals with some parameters 

of microwave planar hybrids mainly from their 

attainable frequency bandwidth. The parameters 

are especially the coupling (C), insertion loss (IL), 

isolation (I), the VSWR and corresponding bandwidth. 

We compare a branch line coupler, rat-race 

coupler and De Ronde’s coupler. All three couplers 

are designed for centre frequency of 3 GHz. Their 

main common advantage is a very easy construction, 

because they consist from some microstrip 

lines eventually a slot line only. Parameters of these 

planar hybrids were simulated and compared with 

measured experimental results. 


Microwave directional couplers are used frequently 

in structures, where we need divide and/or sum microwave 

power – in dividers, attenuators, phase 

shifters, combiners and other microwave structures. 

Herat we require, that these structures didn’t have big 

return loss. Individual types of directional couplers 

have various shapes and parameters. 

Brach line coupler shown in Fig. 1 is a double reflection 

symmetrical structure with the 1st type of 

directivity. Output signals on port 2 and 3 (coupling 

and insertion loss) are in quadrate. Lengths of single 

microstrips usually opt for �g/4. 

Fig. 1. Branch line directional coupler 

The structure of a rat-race planar coupler is displayed 

in Fig. 2. By exciting the port 1 (2), output 

signals 2 and 3 (1 and 2) are in phase, by exciting the 

port 3 (4) the output signals 1 and 4 (2 and 3) are in 

opposite phase. Rat-race couplers have usually bigger 

frequency bandwidth that branch line couplers. 

25 

Fig. 2. Rat-race directional coupler 

The form of so-called composite hybrid (De 

Ronde’s coupler) is shown in Fig. 3. This hybrid 

consists of H shaped microstrip line on the top side 

of the dielectric substrate, and of an open-ended 

slotline on this opposite side. Output signals on ports 

2 and 3 are again in quadrate. 

Fig. 3. De Ronde’s directional coupler 

The main individual electrical parameters of all 

three hybrids in Fig. 1 to Fig. 3 are defined as follow: 

coupling [dB] 

P1 

1 1 

C � 10 log � 20 log � 20 log , (1) 

P S k 

21 

21

insertion loss [dB] 

IL 

P 

1 

1 � 10log 

� 20log 

� 20log 

, (2) 

P 

2 

31 S31 

and isolation [dB] 

1 

I � 

41 

41 

1 

1� 

k 

P 1 

� 10log 

20log 

, (3) 

P S 

where k is the voltage coupling coefficient of the 

structure (k < 1). 

II. RESULTS 

All three above mentioned types of planar directional 

couplers were designed on dielectric substrate 

with relative permittivity �r = 3,55 (Arlon AD-350), 

centre frequency 3 GHz, characteristic impedance of 

input lines of Z0 = 50 �, coupling C = 3 dB for 

branch line and rat-race couplers and C = 1,5 dB for 

De Ronde’s coupler. The practicable bandwidth of 

these hybrids can be examined in different ways 

depending on intended hybrid application. In Fig. 4 

the measured results of coupling frequency dependence 

are shown for individual investigated hybrids. 

The practicable bandwidth is here taken as the difference 

of frequencies for which the actual coupling 

differs from the nominal value of 1 dB. 

From the Fig. 4 we can see, that the so stated 

bandwidth is biggest for De Ronde’s hybrid with the 

value of about 99 % of the centre frequency f0. 

coupling [dB] 

0 

-2 

-4 

-6 

-8 

-10 

0 1 2 3 4 5 6 

frequency [GHz] 

Fig. 4. Frequency dependence of planar hybrid couplings 

(— rat-race hybrid, - - - De Ronde’s hybrid, 

– – branch line hybrid) 

In Tab. I the comparison of practicable bandwidths 

is shown for the three investigated planar hybrids. 

The criterions used are: the coupling value deviation 

of 1 dB, the insertion loss value deviation of 1 dB, 

the return loss > 14 dB (VSWR < 1,5), and the isola- 

26 

tion > 20 dB. From these comparison results we can 

see, that the largest bandwidth shows the De Ronde’s 

hybrid in all mentioned criterions. The reason for this 

result is, that the microstrip – slotline transitions used 

in the De Ronde’s structure are very broadband [1]. 

The smallest bandwidth shows the branch line coupler 

in our research. All couplers shown good return 

loss properties with an input VSWR < 1,2. 

The directivity (D) of the hybrids defined as 

D = I – C is for all investigated structures > 20dB at 

the centre frequency. 

For easy measurement of planar microwave directional 

couplers an universal socked was created, 

which has until frequency of 15 GHz comparable 

parameters with soldered connectors. 

Bandwidth [% of f0] 

Parameter Branch line 

Raterace 

De 

Ronde 

C ± 1 dB 56 73 99 

IL ± 1 dB 26 37 54 

RL >14 dB 

(PSV 20 dB 10 60 43 

Tab. I. Planar hybrid bandwidths comparison 


Research described in this paper was supported by 

the Science Foundation of the Czech Republic 

project under grant No. 102/08/H027 and by the 

National Research Programm No. MS 0021630513. 

REFERENCES 

[1] L. G. Maloratsky. Passive & Microwave Integrated 

Circuits. Burlington, USA, 2004, pages 117- 

164 

[2] F. C. Ronde. A new class of microstrip directional 

couplers. In 1970 IEEE MTT-S Int. Microwave 

Symposium Digest, p. 184-186 

[3] J. Sva�ina. Microwave Integrated Circuits (in 

Czech). Textbook of Brno University of Technology, 

2007

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Decomposing HEX-Programs: Preliminary Results ∗ 

Thomas Krennwallner, Thomas Eiter and Michael Fink (Faculty Mentors) 

Institute of Information Systems, Vienna University of Technology, Austria 

Email: {tkren,eiter,fink}@kr.tuwien.ac.at 

Abstract — We show a program rewriting technique for optimizing 

HEX-programs, which are nonmonotonic logic programs 

with external atoms tailored to access external knowledge 

sources. This approach decomposes a program according 

to a partition of the Herbrand universe in order to be able to 

compute the subprograms over unrelated parts and thus make 

the overall program execution faster. First experiments show 

promising results. 


The declarative logic programming paradigm [1] has received 

increasing interest in recent years. In this work, 

we are interested in logic programs (LPs) called HEXprograms 

[2] (Higher-order logic programs with EXternal 

atoms). External atoms are special devices for reasoning 

with knowledge outside of a LP, which may accept input 

from the program intended for updating this external information. 

HEX-programs are thus relevant for reasoning 

with hybrid knowledge bases, i.e., knowledge bases integrating 

different possibly incompatible semantics, and 

have been applied in many fruitful applications like Semantic 

Web reasoning. Given the inherent nonmonotonic 

flavour of LPs, in general, we are forced to compute the 

models using a highly complex reasoning process. An 

inaugural example for nonmonotonic reasoning is Reiter’s 

Nixon diamond. 

Example 1. Take the logic theory T = {r(n),q(n)} containing 

assertions about a former US president: Nixon 

(short n) was a republican (r) and was also a quaker (q). 

The Nixon diamond expresses that (i) quakers are usually 

pacifists, whereas (ii) the opposite normally holds for republicans. 

Adding (i) and (ii) as additional axioms to a 

monotonic theory like T would render it inconsistent. It 

is well-known that such exceptional information can only 

be dealt with in a nonmonotonic formalism like logic programming. 

In spirit of dl-programs [3], the HEX-program 

PN below defines the rules (2) and (3) to encode (i) and 

(ii), resp. There, a(−p, n) and a(p, n) is used to state that 

n is (not) a pacifist, resp. We operate on T using a variant 

of external atoms shown in [4] of form &dl[a, C](X), 

whose purpose is to add the extension of a to T before 

querying the concept expression C in T . 

PN : d(n). (1) 

a(p, X) ← d(X), &dl[a, r](X), not &dl[a, −p](X). (2) 

a(−p, X) ← d(X), &dl[a, q](X), not &dl[a, p](X). (3) 

∗ Supported by the Austrian Science Fund (FWF) project P20841. 

29 

&dl[a,p](X) 

&dl[a,–p](X) 

¬ e 

e e 

e ¬ C2 a(–p, X) a(p, X) 

e e 

e e 

&dl[a,r](X) &dl[a,q](X) 

d(X) 

C 1 

Figure 1: Dependency graph of PN 

PN has two models: {d(n), a(p, n)} and {d(n), 

a(−p, n)}. The meaning of the former is that Nixon is 

considered as pacifist, whereas the latter expresses the 

opposite, that Nixon is not a pacifist. 

A well-known method for incrementally computing the 

models of LPs is the splitting-set method [5]. In [2], this 

technique has been adopted to HEX-programs. The basic 

idea is to generate a dependency graph of the atoms in 

a program and split it into subprograms according to the 

connected components of the graph. The evaluation of 

the program can thus be seen as computing the models 

along a tree of smaller subprograms, hence speeding up 

the overall evaluation due to parallelizing of unrelated 

program parts. See Figure 1 for the dependency graph of 

PN from above, where C1 and C2 are two components of 

PN , and C2 depends on C1. 

The class of e-unstratified HEX-programs are those 

whose dependency graph contains at least one cycle 

through a nonmonotonic or an external atom preceded 

by not; it is thus inevitable to compute the models for 

such programs by a guess-and-check methodology. The 

program in Example 1 is an instance of such programs, 

since it contains cycles over negated external atoms. 

The efficient computation of the external atom input 

is crucial and contributes tremendously to the overall 

runtime behaviour of unstratified programs. In fact, given 

a cyclic external atom &g[p](x) with input predicate p, 

there are exponentially many updates for it which include 

a particular fact p(c) in the worst case. A parsimonious 

generation of input facts must be preferred. 

In general, one cannot decide whether an input containing 

p(c) has an effect on the outcome of the evaluation 

for &g, but with knowledge on the external computation 

source, we can drastically prune the search space by decomposing 

the subprogram containing &g into ℓ copies, 

each one referring to exactly one distinct member of a 

partitioning d1 ˙∪··· ˙∪ dℓ of the domain of the program. 

This splitting of the domain is generated by grouping in-

dividuals together using independency information for 

&g. As a consequence of this decomposition scheme, 

the extensions of p in one of the decomposed program 

components can only range over its assigned subdomain. 

Since independent individuals cannot occur in different 

components, we limit the variations of extensions of p in 

the guesses to a minimum. 

Next, we will see an outline of a program rewriting 

technique taking the above considerations into account. 

II. OPTIMIZING HEX-PROGRAMS 

Let P be a HEX-program over domain C with rules of form 

a1 ∨···∨ak ← b1,...,bm, not bm+1,...,not bn. For 

a rule r, let H(r) ={a1,...,ak} and B(r) ={b1,. . . , 

bm, not bm+1,...,not bn}. Let D ⊆Cbe a nonempty 

finite set of constant and predicate symbols. 

Let (D, �) be the partial ordering of the lattice of partitions 

of D, where � is the usual refinement order, i.e., 

a � b iff ∀x ∈ a ∃y ∈ b: x ⊆ y. 

For a partition π ∈D, let e ∈ π, and let p be an mary 

predicate symbol. We denote by p[e] the set {p(c) | 

c ∈ e m }. Furthermore, let p = p1,...,pk be a list of 

predicate symbols. We define p[e] = � 

1≤j≤k pj[e] and 

p[π] as � 

e ′ ∈π p[e′ ]. 

Let e ⊆ D, let I be an interpretation, let &g ∈ G 

be an external atom over D with associated boolean 

function f&g, and let x and c be a ground (i.e., concrete) 

input and output list, resp. We say e is a basis 

for &g if (1) f&g(I,x, c) = f&g(I ∩ x[e], x, c), and 

(2) ∀e ′ ⊇ e: f&g(I ∩ x[e], x, c) =f&g(I ∩ x[e ′ ], x, c). 

Given an external atom &g, let ∼&g be an equivalence 

relation on D defined as a ∼&g b iff {a, b} ⊆e for a basis 

e for &g. We define D/∼&g as the quotient set of D by 

∼&g, which forms a partition of D. 

Let A be a set of atoms. For B = {D/∼&b | &b ∈ A}, 

we say that π is the greatest local split of A, denoted 

gls(A), ifπ is the least upper bound of B. 

Proposition 1. Let x be a ground input list for &g, A be a 

set of atoms such that &g ∈ A, and I be an interpretation. 

Then, for all π ∈Dsuch that gls(A) � π, f&g(I,x, c) = 

f&g(I ∩ x[π], x, c). 

In the following we assume that predicate symbols ps with superscript s do not occur in C. We denote by ps (e) 

the facts {ps (c) | c ∈ e} for a set e ⊆ D. 

The i-splitting substitution in A is σi A = {p/pi | 

p(t) ∈ A}, which maps the predicate p of every ordinary 

atom p(t) in A to pi .Ani-splitting of A in P , denoted 

P i A , is given by the set of rules 

H(r)σ i A ← B(r)σi A , domi (X1),...,domi (Xr) 

for each r ∈ bA(P ), where X1,...,Xr are all output 

variables which occur in some external atoms in B(r). 

30 

k 1 2 3 4 5 6 

PN (k) 0.09 0.4 1.7 9.8 — — 

P d N (k) 0.09 0.16 0.23 0.31 0.39 0.47 

Table 1: Evaluation times in seconds for Example 1 

Given the dependency graph GP of P , let GA P = 

(A, E(GP )). We call GA P negatively e-cyclic,ifGA P contains 

a cycle through an external atom with a neg. edge. 

Let bA(P ) be the bottom of P wrt. A as in [2]. 

Let C be the set of strongly connected components 

of GP , let C ∈ C, and let gls(C) ={e1,...,eℓ}. The 

decomposition of P wrt. C, denoted dC(P ), is defined as 

� 

1≤i≤ℓ 

P i C ∪{a ← a i | a ∈ H(r),r ∈ bC(P )}∪dom i (ei) 

if G C P is negatively e-cyclic, otherwise it is bC(P ). The 

decomposition of P , denoted P d ,is � 

C∈C dC(P ). 

The following result shows the equivalence of P and 

its optimized variant P d . 

Theorem 2. There is a 1-to-1 correspondence between 

the answer sets of P and the answer sets of P d . 

III. EXPERIMENTS 

For experimental evaluation, we adapted our prototype 

implementation dlvhex, 1 a HEX-program reasoner. Synthesizing 

Example 1, we created PN (k) =PN ∪{d(ni) | 

1

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Simulation of light environment and its application in practice 

Anna Beneova, Marek Krupa, Ruzena Kralikova 

Department of environmental studies and information engineering 

Technical University in Kosice 

Kosice, Slovak republic 

Email: anna.beneova@tuke.sk, marek.krupa@tuke.sk, ruzena.kralikova@tuke.sk 

Abstract — The condition and development of 

artificial lighting it’s a way of expression economical 

and energetic situation of state, criterion of 

substantial and cultural levels of population. Following 

present experience come through that the 

enhanced parameters lighting may increase productivity 

of labour and together reach high quality 

of products in the all sectors of country economy. 

On the present, as computer technics bet more 

available and its development in the last terms has 

intensifyed yet, we more apply practices making 

use of computing graphic if we want to solve problem 

of luminosity - technical projects. Computer 

graphics after alleged methods incoming lighting 

get effective centre on calculation and modelling 

luminosity- technical (lighting) system, already in 

phase its proposal. 


Nowadays at luminosity- technical modelling 

applies access, who be based on computing visualization 

three - dimensional scenes of engineering 

lighting system. In this case realizes luminosity- 

engineering calculations with the setting precision 

without using cargo physical models. Volts computer 

visualizations, those aim photo - realistic 

reproduction, frequently models in detail and malingers 

propagation of light in the leeway. The 

modern visualization programs make it reproduce 

brightness, colour and structure surfaces complex 

threedimensional leewaies relatively feasibly, 

because calculations do include intereflection as 

well (inter - bounce) light between various surface 

in the leeway and various optical effects emergent 

by the daily, artificial or clustered alight. Simulation 

methods are established on classic optic, 

thermodynamic, or luminosity- technical models 

radiation extensions [2]. 

II. SIMULATION METHODS 

Exist two ground methods being exploited by the 

computer simulation light environment, and otherwise 

Monte Carlo method, which in applies 

technology following light beam (called raytrac- 

33 

ing, this title usually utilizes for tracking back 

raies, utilizes oneself too concept „ ray casting" 

sending light beam, when shaft of light go out 

from light source), and radiating method (called 

radiosity)[1]. From physical aspects are both methods 

similar, difference rests in algorithmization. 

Volts method following raies work with minimal 

plate in stochlastic way (results of repeated calculation 

can be little different). Volts radiating method 

work with bigger surfaces deterministic (results 

of repeated calculation are always equivalent). 

a) 

b) 

Figure 1: a) Monte Carlo method, b) Radiosity 

method (D – walls of leeway, S – lighten subject, L 

– light source, E – observer) 

III. SIMULATION SOFTWARES 

When we project lighting system we use as basic 

tool for calculation and modeling, for several 

years, specialistic computer programs. In last 

terms come the boom on the market with the luminosity- 

technical software following increase in 

availability computer technic for everybody projector. 

Turn up single programming aids and me-

thod incoming lighting bring chances accurate 

calculations of lighting system. Following hereof 

development come into being dismes luminosity- 

technical programs with various levels and purpose 

[3]. The last move by the development remembered 

result is its application not only in proposal 

lighting system for living, office and recreational 

spaces, but also its application in engineering 

working environment [4]. 

Among the most arranged programs on simulation 

light environment belongs besides by other program 

RELUX PROFESSIONAL from the Swiss 

company Relux informatic AG [5]. Program utilizes 

combination of methods Monte Carlo and 

radiating methods. Function as calculation and 

visualization of daily and artificial lighting. 

IV. APPLICATION SIMULATION IN RELUX 

PROFESSIONAL 

Last part of contribution is above all demonstration 

various ascents from specialistic software of 

product RELUX PROFESSIONAL 2007 [5]. For 

purposes this contribution was carry simulation of 

intensity artificial lighting at chosen workspace. 

Options of application simulation in Relux Professional: 

• 3D scene with all of element and elements 

interior 

• attributes illumination intensity 

• isotofic graphics illumination intensity 

• area map illumination in a given leeway 

• 3D map illumination in a given leeway 

(Fig. 3) 

• 3D rasterization graph illumination intensity 

(Fig. 4) 

• Wholes 3D sight ratios illumination in the 

under consideration leeway 

Figure 3: Three - dimensional maps illumination 

34 

Figure 4: 3D rasterization graph illumination intensity 

V. CONCLUSION 

This report was worked - out in the flow of work 

on doctoral thesis „ aplication of simulation luminosity- 

technical quantity by the optimalization 

lighting system", and within the frame project 

VEGA 1/3231/06 „ modelling factors of working 

environment and its optimalization in the specified 

condition mechanical business.", problem being 

solved on Department of environmental studies 

and information engineering at Technical University 

in Kosice. 

REFERENCES 

[1] SILION, F., PUECH, C.: Radiosity and Global 

Illumination, Morgan Kaufmann, ‘94, 149-181 

[2] HALÁSZ, Jozef - KRÁLIKOVÁ, Ružena: 

Environmentálne informa�né systémy. Košice : 

Vienala, 2002. 220 s. ISBN 80-7099-797-4. 

[3] BUDAK, V. P. : Vizualizacija raspred�lenija 

jarkosti v trjochm�rnych scenach nabljud�nija, 

Izdat�lstvo MEI, Moskva 2000 

[4] KRUPA, M., KRÁLIKOVÁ, R. : Po�íta�ová 

simulácia osvetlenosti pracovných priestorov, 

In.: Acta Mechanica Slovaca, 2-B/2005, ISSN 

1335-2393 

[5] http://www.relux.ch

Towards Synchronization in Multiple Antenna Systems 

Qi Wang and Markus Rupp (Faculty Mentor) 

Institute of Communications and Radio-Frequency Engineering 

TU Vienna 


Email: {qwang,mrupp}@nt.tuwien.ac.at 

Abstract — The presented work deals with synchronization 

issues in modern wireless systems employing orthogonal frequency 

division multiple access and multiple antenna systems. 

We show that current state of the art algorithms for timing and 

frequency offset estimation are capable of estimating and compensating 

such errors in almost perfect manner even under very 

harsh conditions. Throughput simulations of a WiMAX compliant 

standard support our theoretical statement. 


In the past 15 years multiple antenna systems, also called 

Multiple-Input Multiple-Output (MIMO) have been a research 

focus in wireless communications. Foschini and 

Gans [1] and Telatar [2] showed that a much higher 

channel capacity is available than originally anticipated. 

While many researchers in the past years came up with 

novel concepts [3]-[6] to make use of such capacity, only 

few showed in experiments what can be achieved. [7]- 

[15]. The problem lies in the technical realization of 

many underlaying assumptions. 

One of such difficulties arises from synchronization in 

frequency, phase and sample timing of transmitter and 

receiver. In simulations typically both ends are perfectly 

synchronous while in the real world such synchronization 

needs to be achieved first. With MIMO systems the 

interference of the various antenna signals becomes even 

larger and thus synchronization algorithms have to be improved 

considerably. 

Since Orthogonal Frequency Division Multiplex 

(OFDM) based transmission plays a major role in future 

communications, we concentrated on WiMAX transmissions 

to consider principle methods. Also the WiMAX 

standard supports transmission over more than one antenna. 

II. ALGORITHMIC SOLUTION 

Unfortunately, timing and frequency offset estimation 

are not independent and have to be treated jointly [16]- 

[19]. The frequency offset alone in an OFDM system 

consists of three parts, the fractional frequency offset, the 

integer frequency offset as well as the residual frequency 

offset. The following Figure 1 depicts the four steps of 

synchronization required in such system for frequency 

and symbol timing. First a coarse symbol timing estima- 

35 

ton is performed in the time domain. With the received 

signal denoted by r(n), this is achieved by a matched 

filter operation: 

M(n) = 

�Ng+64 k=0 

�Ng+64 k=0 

r(n − k)r∗ (n − k − 192) 

|r(n−k)| 2 + � , 

Ng+64 

k=0 |r(n−k−192)| 2 

(1) 

making use of the periodic structure in the training word. 

The correct timing is taken when M(n) reaches its maximum. 

In a second step the fractional frequency offset 

(εFFO) estimation is performed as well in the time domain: 

εFFO = 1 

π arg 

⎧ 

⎨Ng+64 

� 

� � 

j2πn 

r(n) exp · 

⎩ 

N 

· 

k=0 

� 

r(n − 128) exp 

� j2π(n − 128) 

Then the integer frequency offset estimation 

M(2i) = 

N 

| � 

k X1,k+2iX ∗ 2,k+2i (P1,kP ∗ 2,k )∗ | 

� 

k |X1,k+2i| 2 + � 

k 

�� ∗� 

. (2) 

|X2,k+2i| 2 , (3) 

is performed in the frequency domain, with the received 

symbol and pilot symbol in lth OFDM symbol kth subcarrier 

in frequency domain represented by Xl,k and 

Pl,k. The estimated integer frequency offset 2i appears 

when M(2i) gets the peak value. 

Eventually, the residual frequency offset εRFO is 

tracked. 

Figure 1: The four steps of timing and frequency offset 

estimation in an OFDM system.

III. RESULTS 

In the following simulation we measured the throughput 

of a WiMAX compliant OFDM system under frequency 

and timing errors when the transmission takes place over 

a typical pedestrian B channel. The result is depicted in 

Figure 2. As the figure shows, if we would only correct 

for timing or frequency and not taking the second part 

into consideration, we would loose substantial amounts 

in throughput. Only the joint approach results in almost 

perfect synchronization. The observed throughput loss 

due to synchronization estimation is very small even at 

low SNR. 

perfect synchronized 

both timing and frequency 

offset corrected 

only frequency 


only timing 


Figure 2: Achieved throughput over SNR under various 

frequency and timing estimation errors. 

IV. CONCLUSION AND OUTLOOK 

In this article we have shown that for OFDM transmission 

systems like WiMAX, synchronization algorithms 

can be applied to achieve almost optimal synchronization 

results and thus maximal throughput. In the next 

steps such algorithms will be investigated for MIMO systems 

employing several transmit and receive antennas. 

It is anticipated that such transmission will considerably 

hamper the quality of the estimation algorithms and that 

they have to be re-designed. 

REFERENCES 

[1] G.J. Foschini, Layered space-time architecture for wireless 

communication in a fading environment when using 

multiple antennas, Bell Labs Technical Journal, vol. 1, no. 

2, pp. 41-59, 1996. 

[2] E. Telatar, Capacity of multiple-antenna Gaussian channels, 

European Transactions on Telecommunications, vol. 

10, pp. 585-595, Nov. 1999. 

[3] Erik Larsson, Petre Stoica, und Girish Ganesan, Space- 

Time Block Coding for Wireless Communications, Cambridge 

University Press, 2003. 

[4] Branka Vucetic und Jinhong Yuan, Space-time Coding , 

Wiley & Sons, 2003. 

36 

[5] H.Bolcskei, D.Gesbert, A.-J. Van Der Veen, Space-Time 

Wireless Systems: From Array Processing to MIMO 

Communications,, Cambridge University Press, 2006. 

[6] G.B. Giannakis, Z.Q. Liu, Space-Time Coding for Broadband 

Wireless Communications, Wiley & Sons, 2006. 

[7] S. Caban, C. Mehlführer, R. Langwieser, A.L. Scholtz, 

M. Rupp, Vienna MIMO Testbed,; EURASIP Journal on 

Applied Signal Processing, pp. 1 – 13, 2006. 

[8] S. Caban, M. Rupp, Impact of transmit antenna spacing 

on 2 x 1 Alamouti radio transmission, Electronics Letters, 

Vol. 43, 4; pp. 198 – 199, 2007. 

[9] M. Rupp, C. Mehlführer, S. Caban, R. Langwieser, L.W. 

Mayer, A.L. Scholtz, Testbeds and Rapid Prototyping in 

Wireless System Design, EURASIP Newsletter, 17, 3; pp. 

32 – 50, 2006. 

[10] L.W. Mayer, M. Wrulich, S. Caban, ”Measurements and 

Channel Modeling for Short Range Indoor UHF Applications, 

Proc. European Conference on Antennas and Propagation 

(EuCAP 2006), France, Nov. 2006. 

[11] C. Mehlführer, S. Caban, M. Rupp, A.L. Scholtz, Effect 

of Transmit and Receive Antenna Configuration 

on the Throughput of MIMO UMTS Downlink, Proc. 

8th International Symposium on DSP and Communication 

Systems, Noosa Heads, Sunshine Coast, Australia, 

19.12.2005 - 21.12.2005. 

[12] C. Mehlführer, S. Geirhofer, S. Caban, M. Rupp, A Flexible 

MIMO Testbed with Remote Access, Proc. 13th EU- 

SIPCO European Signal Processing Conference, Antalya, 

Turkey, 04.09.2005 - 08.09.2005. 

[13] M. Rupp, S. Caban, C. Mehlführer, Challenges in Building 

MIMO Testbeds, Proc. 15th EUSIPCO European Signal 

Processing Conference, Poznan, Poland, pp. 1833 - 

1839, 03.09.2007 - 07.09.2007. 

[14] C. Mehlführer, S. Caban, M. Rupp, Experimental Evaluation 

of Adaptive Modulation and Coding in MIMO 

WiMAX with Limited Feedback, EURASIP Journal on 

Advances in Signal Processing, Article ID 837102, 2008. 

[15] M. Wrulich, S. Caban, M. Rupp, Testbed Measurements 

of Optimized Linear Dispersion Codes, ITG Workshop on 

Smart Antennas, Wien, 26.02.2007 - 27.02.2007. 

[16] W.Lei, T.Tao, J.Lu, ”A robust frequency acquisition algorithm 

for OFDM systems, The 5th International Symposium 

on Wireless Personal Multimedia Communications, 

Vol. 1, pp. 145 - 148, vol.1, 27-30 Oct. 2002. 

[17] T.Lv; J.Chen, ”ML estimation of timing and frequency 

offset using multiple OFDM symbols in OFDM systems, 

Proc. IEEE Global Telecommunications Conference, 

GLOBECOM ’03, Vol. 4, pp.2280 - 2284, vol.4, 

1-5 Dec. 2003. 

[18] L.Wei, Y.Y.Xu, Y.M.Cai, X.Xu, ”Robust frequency offset 

estimator for OFDM over fast varying multipath channel, 

Electronics Letters, Vol.43, Issue 6, pp.53 - 54, March 15 

2007. 

[19] Y.Yan; M.Tomisawa, Y.Gong; Y.L.Guan; G.Wu; 

C.L.Law, ”Joint timing and frequency synchronization for 

IEEE 802.16 OFDM systems, Mobile WiMAX Symposium, 

pp.17 21, 25-29 March 2007.

Technical criteria for the comparison of modern ERP system for 

the usage in orchestra companies at the case study of Dynamics 

AX 2009 

Abstract — Orchestra companies are companies 

with 50 (plus or minus 25) employees which do not 

create any business value out of their IT system. 

The IT systems in the company are only operating 

resources. In such a company, the implementation 

of a new ERP solution is a critical and cost intensive 

step. This research project establishes criteria 

and ratios to allow for the comparison of ERP systems 

that are suitable for use in such a company. 

The criteria will be split into the following areas: 

Customizability, integration capacity and, migration 

ability. The criteria will be validated against 

Dynamics AX 2009 to give a proof of concept. 


In the literature some criteria currently exist for the 

comparison of architectures of ERP systems. [1], [2], 

[3] However, these are usually on a very detailed 

technical level and are based primarily on the requirements 

of larger companies. This makes it difficult 

for small and medium-size enterprises, which 

have other requirements, to use these criteria to decide 

upon a particular system. The existing criteria 

applied to small and medium size companies do not 

always show the advantages or disadvantages of the 

particular system architectures clearly. An application 

of comparative criteria which have not been 

developed especially for small and medium enterprises 

leads to inadequate evaluation results. In this 

thesis, criteria for the comparison of ERP systems for 

a specific class of companies ("orchestra company") 

has been developed. 

An orchestra company is an enterprise with 25 to 

75 employees. Based on the definition of the European 

Commission they are either small or mediumsized 

enterprises. According to the definition of the 

EU, small businesses are those with less than 50 

employees. The annual turnover may not exceed 10 

million Euro. A key aspect of an orchestra company 

is the fact that the company does not gain direct 

value from its IT systems. The entire IT equipment in 

Michael Gall und Christian Sterba 

Research Group for Industrial Software (INSO) 

Technical University 


Email: e9825247@student.tuwien.ac.at 

37 

the company is only an operating resource. These 

companies do not have their own IT department. 

This paper is part of an ongoing research project. 

Based on a literary analysis of the existing methods 

for the comparison of ERP systems, the authoritative 

criteria for orchestra companies are identified and 

modified. The successful validation of this criteria 

system has been done in a case study of Microsoft 

Dynamics AX 2009. 

II. IDENTIFIED CRITERIA 

In an orchestra company decisions are usually made 

by the decision makers directly without a long and 

expensive selection process. [4] In the literature 

several approaches for the evaluation of ERP systems 

exist, but their focus is not on its application on the 

chosen enterprise class. [1], [2], [3]. The criteria 

identified in this work reflect the important decision 

criteria which are relevant for orchestra companies . 

They can be grouped as followed: 

A. CUSTOMIZABILITY 

The term customizability includes all activities where 

the functionality of the system is changed and it can 

be divided further into modifiability and extensibility. 

[5] The following ratios (including their domains) 

can be defined: 

1. What effort is necessary to rework the modifications 

when switching to a new release of the 

system? (0 – no further adjustments to 5 – 

complete reimplementation) 

2. Can modifications been done regardless of the 

subcategory (Externally visible, internally 

visible or not visible)? (Yes / No) 

3. Can modifications be done and stored centrally 

? (Yes / No) 

4. Do modifications affect the process when applying 

hot fixes, service packs or new product 

versions? (0 – no overhead to 5 – significantly 

change)

5. Does an integrated development environment 

exist? (Yes / No) 

6. Do clear interfaces exist ? (0 – no interfaces to 

5 – complete modularization) 

7. Can new features be implemented outside the 

existing system ? (‘N’ – Not possible, ‘C’ – 

costly or ‘E’ – easy) 

8. Does the system provide tools to administer 

the database schema? (Yes / No) 

9. Can the system access external data structures? 

(Yes / No) 

B. INTEGRATION CAPACITY 

For various reasons there may be a variety of other 

systems in the enterprise, which need to communicate 

with the ERP solution. A key aspect here is how 

easily is this possible. There are many separate providers 

of EAI solutions which facilitate communication 

between the various systems. By taking a few 

criteria into consideration, costly integration projects 

can be saved. 

10. For what processes are services provided? 

(‘N’ - None, ‘F’ - Framework, ‘B’ – Basic or 

‘A’ - Advanced) 

11. Can EAI platforms be integrated? (Yes / No) 

12. Are API’s available? (Yes / No) 

13. Are data integration capabilities of the database 

system supported? (Yes / No) 

14. What file formats are supported? (‘N’ - None, 

‘P’ - Proprietary or ‘C’ - Common file formats) 

15. Can the data and fields be mapped dynamically? 

(Yes / No) 

16. Do tools for monitoring a data exchange exist? 

(Yes / No) 

C. MIGRATION ABILITY 

The notion of migration is defined in this context as 

either the change from a previous system to the chosen 

ERP solution or as the switch between different 

product releases of the same solution. 

17. Do tools for data migration exist? (Yes / No) 

18. Do application tools to support the release 

change exist? (Yes / No) 

19. Do tools to migrate the modifications exist ? 

(Yes / No) 

III. CASE STUDY DYNAMICS AX 2009 

The validation of the developed criteria has been 

carried out in a case study by applying the criteria to 

the product Microsoft Dynamics AX 2009. Dynam- 

38 

ics AX, formerly known as Axapta, came through the 

acquisition of Danish software company Navision in 

the possession of Microsoft. The market placement 

of Dynamics AX is in the segment of small and / or 

medium-sized enterprises. The current product version 

is Dynamics AX 2009 which was used to validate 

the criteria and ratios. This case study proved 

the successful application of the build criteria system. 

For the given ERP product the proposed ratios could 

be answered. The results are given in “Table 1” 

Ratio AX 2009 

1 Revision Effort (0 .. 5) 

2 Independent modifications 

3 Central modifications 

4 Maintenance influence (0 .. 5) 

5 Development environment 

6 Clear interfaces (0 .. 5) 

7 External modifications (N/E/C) 

8 Schema administration 

9 External data structures 

10 Services available (N/F/B/A) 

11 EAI integration 

12 API’s available 

13 Support DB data integration 

14 File formats (N/P/C) 

15 Dynamic data mapping 

16 Monitoring 

17 Data migration tools 

18 Release change tools 

19 Modification migration tools 

3 

Y 

Y 

2 

Y 

3 

E 

Y 

Y 

B 

Y 

Y 

N 

C 

N 

Y 

N 

Y 

Y 

Table 1: Criteria applied to Dynamics AX 2009 

By applying the criteria on different ERP solutions 

a comparison to support the decision making process 

is now possible. 

REFERENCES 

[1] Kennerley, M., Neely A., A framework of the 

factors affecting the evolution of performance 

measurement systems, International Journal of 

Operations & Production Management 22(11), 

2002, S. 1222-1245 

[2] Dumslaff, U.: Ein Vorgehensmodell zur Software 

Evaluation, HMD 31, 1994, S. 89 - 105 

[3] Stefanou, C.J.: A framework for the ex-ante 

evaluation of ERP software, European Journal of 

Information Systems 10, 2001, S 204 – 215 

[4] Barbacci M., SEI Architecture Analysis Techniques 

and when to use them, Carnegie Mellon 

Software Engineering Institute, 2002 

[5] Gronau, N.. Management von Produktion und 

Logistik, 3. überarb. Aufl., Oldenbourg, 

München, 1999

DEVELOPMENT OF A QUANTITATIVE APPROACH THAT USES FOURIER 

TRANSFORM INFRARED SPECTROSCOPY (FTIR) TO MEASURE AMBIENT 

AEROSOL COMPOSITION 

Abstract —The goal of this research is to develop 

a method to collect, identify and quantify organic 

and inorganic species present in ambient aerosols. 

A sampler to collect both types of species on a 

single substrate at high efficiency will be developed, 

avoiding the artifacts that many other researchers 

have experienced. The software and 

hardware used by the FTIR spectrometer will be 

optimize to analyze the aerosols collected onto a 

substrate that is not transparent to IR light and can 

therefore mask the signal of the aerosols. Because 

FTIR is generally not used to quantify chemicals in 

solid samples, a chemical method that uses internal 

standards added to the sample or external analytical 

methods to calibrate the FTIR will be developed. 

Finally, because FTIR has not been used to quantify 

chemicals in ambient aerosols before, an algorithm 

that relates the concentration of the chemical in the 

ambient air to the FTIR absorbance area, chemical 

molar absorptivity and sampling flow rate and duration 

will be developed. This algorithm will not 

depend on the path length of the IR beam through 

the sample, because this quantity is difficult to 

estimate. 


Particulate matter (PM) is formed by condensation 

of semi-volatile gases and the coagulation of even 

smaller particles, and they play an important role in 

gas phase reactions which require a third body. 

These particles are typically formed by the condensation 

of semi-volatile gases onto smaller particles, 

by homogeneous nucleation of gases to form particles, 

and by coagulation of smaller particles. 

Exposure to ambient fine particulate matter can 

cause serious problems to public health. Because 

of their small size, fine particles may penetrate in 

the tracheobronchial and pulmonary region, 

causing a range of respiratory system responses 

from sneezing, coughing, broncho-constriction, 

rapid, shallow breathing (Boudel et al., 1994; 

Vilma Arriaran and Beth Wittig (Faculty Mentor) 

City College of New York 

City University of New York 

New York, USA 

Email: vilma@ce.ccny.cuny.edu 

39 

CCOHS, March 22 1999) to lung cancer and 

cardiopulmonary disease (Lall et al, 2004) and 

even death. For example, in London in 1952, about 

4000 people were killed in four days due to 

inhalation of excessive concentration of particles 

and SO2 that accumulated in the air due to stagnant 

weather conditions (Boudel et al, 1994). 

The environment is also adversely affected by exposure 

to PM2.5. Deposited PM can corrode stone 

buildings and damage the cellular structure of 

plants. In suspension they can impair visibility (dust 

clouds, haze) . 

Researchers have been continuously studying the 

adverse health effects of the PM and have found 

that this effect depends in part on the size of the 

PM. This prompted more studies on PM2.5 which 

creates more adverse health effects due to both 

their size and their unique chemical composition. 

U.S. EPA promulgated a new NAAQS for PM2.5 in 

1997. NAAQS set the maximum permissible 

concentration for fine particulate matter at 

15μg/m 3 on an annual basis and 35μg/m 3 on a 24 

hour basis (EPA, May 9th 2008). 

The method developed in this work will provide 

information that can be used to better identify 

sources of PM2.5 and develop more effective SIPs 

for New York state and the Northeastern US (NYS 

DEC, 2008; Solomon, 2004). The method will 

speciate and measure the concentration of the organic 

and inorganic chemical components present 

in fine PM using Fourier Transform Infrared Spectroscopy 

(FTIR). The current state of the science is 

unable to identify and quantify all of the functional 

groups in PM2.5 using a single analytical method 

and many of the available methods also require 

extraction of the sample or destroy the sample during 

analysis. While FTIR is not considered to be 

quantitative for liquid and solid samples, through 

this research internal and external standards that 

make the method quantitative will be developed.

II. EXPERIMENTS AND PRELIMINARY RE- 

SULTS 

PM must be uniformly collected into a small area on 

a substrate that can be directly analyzed by FTIR 

without introducing artifacts. This will be 

accomplished using a sample collection system. 

Sample collection systems are designed to draw a 

constant flow rate of ambient air containing PM2.5 

through a substrate for a specified period of time, 

collecting the sample on the substrate by impaction, 

filtration and sieving. 

A. SUBSTRATE SELECTION 

Ideal substrates have no signature in the MIR region. 

Second-best substrates have sharp weak 

signatures, especially in MIR regions where targeted 

inorganic and organic compounds are expected. 

Blank (i.e., clean and prepared for sampling) 

substrates will be analyzed using FTIR. 

Signatures in their MIR spectra will be observed to 

select the substrate that has a sharp and strong 

signature that does not obscure the sample signature. 

Figure 1 shows spectra of Teflon and quarts substrates 

collected by using transmission and reflectance 

spectroscopy. 

Absorbance 

7 

6 

5 

4 

3 

2 

1 

0 

3836 

3645 

Teflon Savillex-ATR 

Teflon Savillex-Transmission 

Teflon Pall-Transmission 

Quartz-ATR 

Quartz-Transmission Saturation due to 

substrate thickness 

3454 

3263 

3072 

2881 

2690 

2499 

2308 

2117 

1927 

Wavenumber (cm -1 ) 

Sharp and 

moderate peaks 

Figure 1 Blank substrate IR spectra 

B. LIGHT PATH THROUGH SAMPLE 

Identical samples will be analyzed by transmission 

and reflectance techniques to evaluate the diffrence 

in peak absorbance areas due to the depth of 

penetration of the light through the sample. 

C. REFINING ANALYSIS 

Due to the complex composition of PM2.5, its spectra 

analysis may show peaks that overlap, due to the 

interactions between functional groups that appear 

very close in the IR wavenmber range. Different 

approaches to split those peaks will be evaluated 

1736 

1545 

1354 

1163 

972 

781 

590 

399 

40 

without affecting the accuracy of their absorbance 

areas. 

D. SPECTRAL INTERPRETATION 

Functional groups present in the sample will be 

identified by wavenumber based on spectral library 

data and results from literature review. Concentrations 

of the functional groups present in the sample 

and in the actual ambient air will be determined by 

developing an algorithm that will use all parameters 

calculated after the FTIR spectral analysis 

A theoretical algorithm Equation 1 was developed, 

and will need to be validated with internal or external 

standards which concentrations are kwnon. 

C 

xa 

ABSxb 

1 

� 

ABS yb � 

� 

Q � t 

x / y 

� C 

yb 

mss 

� 

� 

s 

Equation 1 

The algorithm calculates the concentration of the 

functional group in the air by relating the absorbance 

area of the functional group and the standard, the 

relative molar absorptivity, the concentration of the 

standard in the light path, the flow and sampling 

time, the mass of the sample onto the substrate and 

the density of the particles. Measurement of the path 

length of either the sample or the standard is not 

required to validate the algorithm. Once algorithm is 

validated, it will be applied to calculate concentration 

of actual ambient PM2.5. 

REFERENCES 

[1] Boudel, R., Fox, D., Turner, B. and Stern, A., 

1994. Fundamentals of air pollution. Academic 

Press, 22-34. 

[2] Lall, R., Kendall, M., Ito, K. and Thurston, G., 

2004. Estimation of historical annual PM2.5 exposures 

for health effects assessment. Atmospheric 

Environment 38, 5217-5226. 

[3] EPA, May 9th 2008. PM Standards. EPA. 

www.epa.gov/air/particlepollution/standards.html 

[4] NYS Department of Environmental 

Conservation, 2008. Annual monitoring network 

plan: New York State ambient air monitoring 

program. 

[5] Solomon, P and Allen, D., 2004. Special Issue 

of Aerosol Science and Technology on findings 

from the fine particulate matter Supersites 

Programs. Aerosol Science and Technology 38 

(S1), 1-4. 

[6] CCOHS, March 22 1999. How do particles 

enter the respiratory system? Canadian Center for 

Occupational Health and Safety. 

http://gala.ccohs.ca/oshanswers/chemicals/how_do 

.html

Optimizing the Python interpreter: Identifying performance 

bottlenecks. 

Stefan Brunthaler and Jens Knoop (Faculty Mentor) 

Institut für Computersprachen 

TU Wien 


Email: stefan@brunthaler.net, knoop@complang.tuwien.ac.at 

Abstract — Efficient optimization of the Python interpreter 

requires detailed information about the presence and exact location 

of performance bottlenecks. This paper presents the results 

of our careful and detailed analysis, complemented by 

our selection of optimization techniques based on those observations 

to overcome these bottlenecks: Speculation and Type 

Feedback. 

I. MOTIVATION 

This abstract paper presents preliminary results of ongoing 

research. Python is a dynamically, but strongly 

typed programming language that enjoys widespread application. 

One of its main goals is simplicity, which 

is also reflected in its run-time execution environment: 

an interpreter. Python programs are compiled to byte 

code, which models a stack instruction set architecture. 

Byte-code execution uses a simple and straight forward 

switch-dispatch technique. Similar programming languages, 

like Perl share these implementation characteristics. 

While this simplicity has merits by itself—positive 

effects for maintenance and extensibility—, it is also 

detrimental to the interpreters performance. 

According to [1], there already exist some specific optimizations 

for interpreters, such as threaded code [2],[3], 

stack caching [4], and superinstructions [5]. All these 

optimizations are based on the premise that especially instruction 

dispatch, i.e. getting from one byte code implementation 

to another, is the most costly operation within 

an interpreter. This has also been reported recently in [6]. 

While this is certainly true for some cases, like Java and 

OCaml, we show that it is specifically not true for the 

Python programming language. 

In this paper we present our findings of a quantitative 

analysis of Python byte-code frequencies and execution 

times. We use these results to argue our choice in optimization 

techniques, which will be implemented in subsequent 

phases of research. 

II. QUANTITATIVE ANALYSIS 

A. HYPOTHESES 

For efficient optimization it is a prerequisite to have a 

careful and detailed analysis of the status quo. Based on 

41 

its results, estimating the potential of optimization techniques 

is possible. Specifically we are interested in determining 

whether speculation and type feedback are good 

candidates for optimizing Python. Our hypotheses for 

“measuring” their optimization potential were: 

– For verifying speculation’s potential we measure 

raw byte-code frequency in standard libraries. 

Since optimization potential is directly proportional 

to the corresponding byte code frequency, optimization 

for infrequent use, i.e. infrequent byte 

codes, yields unsatisfactory results. 

– For verifying type feedback’s potential we provide 

a detailed measurement of execution times. In order 

to make judgments of merits of optimization 

techniques, it is necessary to locate the bottlenecks 

within the execution profile. 

B. PROCEDURE 

Since we are analyzing for two separate hypotheses, we 

also need separate procedures. First we have implemented 

a byte code counting system, which recursively 

traverses library trees and counts byte code occurrences 

per file. These occurrences are grouped by enclosing 

modules/directories, in order to check whether specific 

applications, e.g. scientific modules, have different byte 

code occurrence patterns. This was done using a standard 

Python 2.5 executable as distributed with Ubuntu 

8.04. Several libraries were analyzed, such as scipy, a 

scientific computing package, PIL, the Python Imaging 

Library, and twisted, a networking library. 

For testing our second hypothesis, we used the recent 

Python 3.0 beta 3 source code. It already contains 

a high resolution timing mechanism based on Intel’s 

Time Stamp Counter feature. (Henceforth abbreviated by 

TSC.) It counts processor cycles for the interpreters main 

loop, and its switch-dispatch architecture. We extended 

the measurement to also include detailed measurement 

within the separate case/break blocks inside the switch 

statement. We used this modified interpreter version to 

collect samples on the pystone benchmark. 

Both measurements were done using an Intel Pentium 

4 CPU, clocked at 3GHz, running Xubuntu 8.04, with 

kernel version 2.6.24-19.

C. RESULTS 

For our first part, we counted the byte code instructions 

used in various libraries, e.g. we found that of 

the 664.542 byte codes we counted, 56.832 belonged 

to the CALL FUNCTION instruction. Likely candidates 

for speculation, such as CALL FUNCTION, or 

GET ITER/FOR ITER (for generator based speculation) 

instructions ranked high, i.e. all of them scored above the 

3 rd quartile of measured byte code instruction frequencies 

1 . Consequently, speculation is a viable option for 

parallelization on a chip multiprocessor. 

For the second part, we ran the pystone benchmark in 

our modified version of the Python interpreter, which collected 

9 million samples of CPU cycle counts for wholeloop, 

switch dispatch and operation execution. Figure 1 

shows a histogram of median cycle counts within those 

samples. As we can see, operation execution takes up a 

major part of the CPU cycles, about 50%. (See Table 1 

for details.) Python’s execution model relies on run-time 

binding functionality to byte codes, e.g. a BINARY ADD 

instruction will for every execution instance determine 

which actual “add” operation to execute. Several checks 

take care of properly choosing the operation implementation, 

in our addition example, the Python interpreter will 

check argument types, operation availability and implementation, 

and whether a subtype relation holds between 

the arguments. Nothing is cached and no run-time feedback 

enables to cache any of those computations. Following 

[7], the optimization potential for type feedback 

in such a case is substantial. 

Section Min 1 st Qu Median 3 rd Qu 

Op-Execution 75 568 1076 2052 

Dispatch 84 812 1296 2084 

Whole Loop 84 1576 2568 4156 

Table 1: Contains the minimum, 1 st quartile, median, and 

3 rd quartile values for measured CPU cycles per code 

section. 

III. CONCLUSIONS 

We presented the results of our quantitative analysis. 

In particular, we have shown where Pythons interpreter 

spends most of its time: in op-code execution. This is a 

contradictory result to [6]. We assume that this is due to 

the JVM instruction set having semantics closer to a real 

machine. Nevertheless, without further analysis no satisfactory 

answer can be found. As a direct consequence, 

however, techniques focusing on improving the instruction 

dispatch of the interpreter are unlikely to result in 

1 Additional material: http://www.complang.tuwien.ac. 

at/knoop/jsc08/data.html 

42 

CPU Cycles (TSC) 

0 200 400 600 800 1000 1200 

Operation Dispatch 

Code Section 

Whole Loop 

Figure 1: Histogram of median CPU cycles per code section 

expected speedups. We identified type feedback [7] to be 

particularly well suited instead. Our results on measuring 

byte code frequency also indicate that speculation is 

a viable parallelization technique for Python. Given the 

advent of chip-multiprocessors the idea of adding speculation 

to the interpreter becomes even more attractive. Interesting 

questions remain. For example, taking a second 

look at Figure 1, it is striking how many time is spent before 

and after the switch-dispatch—this requires further 

investigation. Another example would be to drill down 

costs within operation execution, e.g. how expensive is 

operand fetching or garbage collection. 

REFERENCES 

[1] M. Anton Ertl and David Gregg. The structure and 

performance of efficient interpreters. J. Instruction- 

Level Parallelism, 5, 2003. 

[2] James R. Bell. Threaded code. Commun. ACM, 

16(6):370–372, 1973. 

[3] M. Anton Ertl. Threaded code variations and optimizations. 

In EuroForth, pages 49–55, TU Wien, 

Vienna, Austria, 2001. 

[4] M. Anton Ertl. Stack caching for interpreters. In 

Proc. of the ACM SIGPLAN 1995 conf. on Programming 

language design and implementation, pages 

315–327, 1995. 

[5] M. Anton Ertl and David Gregg. Combining stack 

caching with dynamic superinstructions. In Proc. of 

the 2004 workshop on Interpreters, virtual machines 

and emulators, pages 7–14, 2004. 

[6] Yunhe Shi, Kevin Casey, M. Anton Ertl, and David 

Gregg. Virtual machine showdown: Stack versus 

registers. ACM Trans. Archit. Code Optim., 4(4):1– 

36, 2008. 

[7] Urs Hölzle and David Ungar. Optimizing 

dynamically-dispatched calls with run-time type 

feedback. In Proc. of the ACM SIGPLAN 1994 conf. 

on Programming language design and implementation, 

pages 326–336, 1994.

Model for Comparison of Types of Traffic 

Intersection Control Systems 

Jan Krcal, Michal Jerabek, Jana Kalikova (Faculty Mentor) 

Faculty of Transportation Sciences 

Czech Technical University in Prague 

Prague, Czech Republic 

Email: {krcal,jerabek,kalikova}@fd.cvut.cz 

Abstract — This article contains part of the results 

of a research which focused on finding the best way 

to manage a traffic lights controlled crossing. A 

simulation model, which includes the crossing and 

the traffic on it, has been created to achieve this. 

The simulation model has been created in a 

mathematical program "Matlab", which currently 

tests static, dynamic and fuzzy control. To assess 

the expediency of these types of control, tests under 

different levels of traffic intensity have been carried 

out. 


The percentage of automobile transport in the 

transport as such is nowadays constantly increasing. 

As a result of this development, the requirements of 

quality of either commercial or private transport are 

increasing. The classical crossings are not sufficient 

nowadays, new roundabouts and intersections 

equipped with Light Signal System (LSS) are 

therefore more and more common because they 

increase the effectiveness, traffic-carrying capacity 

and safety of these points. 

The method of designing the optimal control of the 

crossing is very important. This proposal should 

ideally enable the maximal traffic-carrying capacity 

together with the minimum of standing vehicles and 

with minimal time loss. As a consequence, it should 

also reduce the pollution of the environment caused 

by burning of fuel. 

Apart from the fluency of the transport, the 

optimal type of managing the crossing should also 

contribute to its safety and to the decrease of either 

number or seriousness of the car accidents. 

There are four known types of the controlling 

systems nowadays: static (time dependent), dynamic 

(traffic dependent), fuzzy and adaptive. The first 

three mentioned are used as the controlling systems 

of the traffic crossing, whereas the adaptive 

controlling system is used for the whole area. The 

aim of the work presented in the article is to compare 

these types of control for different levels of traffic, 

and to define and verify which type of control is 

43 

suitable for which (specific) level of traffic of the 

road. 

II. THE SIMULATION MODEL OF A TRAFFIC 

CROSSING 

In every model, not only in the modeling of a 

traffic crossing, we try to make as precise and real as 

possible. It is always necessary to accept some 

simplifying (idealizing) assumptions. Some 

assumptions were idealized even in this simulation, 

but always in a way which does not significantly 

influence the objectivity of the simulation. 

The mathematical program Matlab 6.5 of the 

company MathWorks was used for the creation of 

simulation model. The advantage of this 

mathematical instrument lies primarily in its 

additional modules, so-called toolboxes, each of 

which contains a particular part of a scientific 

interest, i.e. signal processing toolbox, image 

processing toolbox etc. 

III. INITIAL ASSUMPTION FOR THE 

SIMULATION 

For illustrative simulation of managing the 

crossing in terms of our work, we chose three 

different options of traffic intensity which consider 

traffic in various parts of the day – morning rush 

hours, noon traffic and night traffic. As a crossing 

type, we chose common four-leg intersection (see 

Figure 1), i.e. four entries and exits with following 

intensity proportion intensity (V2 = 100%, 

V1 = 0,5*V2, V3 = 0,4*V2, V4 = 0,8*V2). 

The options of traffic intensity consequently are: 

1. option I – total intensity at the entry 405 uv/h 

(Unit Vehicle per hour) (V2 = 150 uv/h) 

2. option II – total intensity at the entry 810 uv/h 

(V2 = 300 uv/h) 

3. option III – total intensity at the entry 1350 uv/h 

(V2 = 500 uv/h)

A signal program for each of the options was 

computed by the Webster's method and on the basis 

of the program were realized the simulations of the 

individual types of controlling systems. 

The length of the simulation itself was prescribed 

to 3600 seconds, i.e. 1 hour. It is highly convenient 

for the simulation because all values of saturated 

flow and intensity are given in unit vehicles per hour. 

For evaluation of the efficiency of the crossing, the 

Performance index value (PI) is used; it considers 

also the ecological aspects (fuel over-consumption, 

higher production of CO, CHx, NOx, SO2 etc.). 

Following parameters for individual entries are 

additionally evaluated in this simulation program: 

− The longest queue [uv] 

− Period of the vehicle standing in the queue for 

the longest time [seconds] 

− Period of the vehicle standing in the queue for 

the shortest time [seconds] 

− Total delay of the vehicles [seconds] 

− Number of vehicles standing in the queue [uv] 

− Number of vehicles passing without stop [uv] 

− Average delay in the queue [seconds] 

− Average delay at the entry [seconds] 

− Performance Index for individual entry 

[seconds] 

V2 

V3 

V1 

Figure 1. Model of chosen crossing type 

V4 

44 


The aim of this research was to judge the 

connection between static, dynamic and fuzzy 

controlling system of the crossing, considering the 

simulation model of the crossing. 

It was therefore inevitable to create own model 

which would enable these simulations. It is necessary 

to point out that it is not any commercial product. 

The signal program, computed by the Webster 

method, specified the Length of the Cycle (LC) for 

all intensity levels to one value LC = 40s. The 

differences could be found only between the 

proportions between signal "go" in corresponding 

phases. The values of Performance index were 

computed for each option of intensity and controlling 

system. 

As a consequence of the table data (see Table 1), 

fuzzy controlling system is the most suitable for the 

low intensity as it has 21% better results than the 

static controlling system. The dynamic has 17% 

better results. The utility of the fuzzy control 

disappears with the increasing intensity, which 

means that the result of the middle intensity is worse 

than the dynamic control and for the high intensity 

worse even that the static control. The dynamic 

controlling system has always better results than the 

static control, but it draws near the static control with 

the increasing intensity. 

The results related to the static controlling system 

(100%) in the table below. 

Intensity [uv/h] 405 810 1350 

Static control 100% 100% 100% 

Dynamic control 83% 89% 95% 

Fuzzy control 79% 96% 101% 

Table 1. Table of result of simulation 

REFERENCES 

[1] P�ibyl P., Svítek M.: Inteligentní dopravní 

systémy, BEN, Praha 2001. 

[2] Vysoký P.: Fuzzy �ízení, CVUT, Praha 1996. 

[3] Tan K.K., Khalid M., and Yusof R.: Intelligent 

Traffic Lights Control by Fuzzy Logic, 

Malaysian Journal of Computer Science, Nov. 

1995. 

[4] Trabia M. B.: A two-stage fuzzy logic controller 

for traffic signals, Transportation Research Part 

C 7 (1999), pp. 353 367. 

[5] Könönen V, Nevala R, Mäenpää, M.: 

Development of Fuzzy Signal Controller, 

Transportation Engineering, Publication 98, 

Espoo 1999, pp. 7.

An integrated source-to-source approach for WCET analysis 

Adrian Prantl and Jens Knoop (Faculty Mentor) 

Institut für Computersprachen 

Technische Universität Wien 


Email: {adrian,knoop}@complang.tuwien.ac.at 

Abstract — The safety of our everyday life depends increasingly 

on the correct functioning of embedded software systems 

that control more and more appliances. Many of these software 

systems are time-critical. Hence, computations performed 

need not only to be correct, but must also return results in a 

timely fashion. Worst-case execution time (WCET) analysis 

is concerned with computing tight upper bounds for the execution 

time of a system in order to provide formal guarantees for 

the proper timing behaviour of a system. In this paper, we introduce 

TuBound – a conceptually new approach, introducing 

source-to-source flow analysis, optimization and transformation 

of analysis information in the workflow of WCET analysis. 

I. MOTIVATION 

Embedded software systems are virtually ubiquitous today 

to control the functioning of technical devices we 

routinely use and rely on in our everyday life. With the 

emergence of safety-critical technologies like fly-by-wire 

in the avionics field or drive-by-wire, which is already 

foreseeable in the automotive field, the correct functioning 

of these software systems is more important than 

ever. 

In a safety-critical real-time system, the timeliness of 

a computation is equally important as its correctness. 

Worst-case execution time (WCET) analysis is concerned 

with providing formal guarantees for the proper timing 

behaviour of a system by computing tight upper bounds 

for the execution time of a system. 

State-of-the-art WCET analysis tools rely on supporting 

analyses and manual annotations to provide them 

with information on the execution behaviour of the program, 

such as upper bounds for loops. Usually, this is 

done on the low level binary code, which, together with 

the analysis information, is then combined with a model 

of the target hardware to formulate an optimization problem 

describing the worst-case behaviour of the program. 

While it is mandatory to perform this last step on the final 

binary code, a high-level representation, such as the 

source code, generally contains much more information, 

such as types, thus rendering possible more powerful 

analyses.. 

The TuBound approach [1], which we pursue in the 

CoSTA 1 project, is to lift annotations and the supporting 

1 Austrian science fund (FWF) project No P18925-N13: Compiler 

support for timing analysis. http://costa.tuwien.ac.at/ 

45 

analyses to the source code level of a program, while still 

performing WCET analysis on the machine code level. 

In addition to keeping the precision of low-level WCET 

analysis, this has the following benefits: 

– Convenience and Ease: For the user, annotating the 

source code is generally easier and less demanding 

as annotating the assembler output of the compiler. 

– Reuse and Portability: Source code annotations, 

which specify hardware-independent behaviour, 

can directly be reused when the program is ported 

to another target hardware. 

– Feedback and Tuning: Source code annotations can 

be used to present the results of static analyses to 

the programmer for inspection and further manual 

refinement. 

The information computed on the source level and 

annotated in the code is then conjointly transformed 

throughout the compilation and optimization of the program 

to the binary code level to make it accessible to the 

WCET analysis component of our TuBound tool. Currently, 

all optimizations are performed on the source code 

level, too. The transformed and optimized code is then 

fed into a specific WCET-aware variant of the Gnu-C 

compiler [2], which is tailored for preserving the validity 

of code annotations that are provided within the compiled 

code. The binary code it generates is finally passed to 

a retargetable WCET analysis component, which computes 

the desired upper bound of the execution time of 

the program in the worst case. Currently, this is the 

WCET analyzer CALCWCET167. 

II. THE SOURCE-TO-SOURCE APPROACH 

The heart of our high-level approach was implemented 

with the help of the source-to-source analysis and transformation 

framework SATIrE [3]. This framework integrates 

the program analyzer generator PAG and SWI- 

Prolog with the C++ source-to-source compiler framework 

LLNL-ROSE. 

A. SOURCE-TO-SOURCE ANALYSIS 

Utilizing the SATIrE framework, we have implemented 

the following supporting analyses, the results of which 

are attached as annotations to the abstract syntax tree and 

as pragma-statements in the source code:

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

CalcWCET 

GCC 

TeBo 

PAG-Interval 

ICFG 

Rose 

fibcall 

expint 

cover 

bsort100 

qurt 

lcdnum 

crc 

cnt 

TuBound: Time spent per phase 

st 

sqrt 

recursion 

Seconds/Benchmark 

ns 

matmult 

jfdctint 

fdct 

whet 

– An interprocedural interval analysis that computes 

variable-interval pairs for each sequence point in 

the program. 

– A loop-bound analysis that computes upper bounds 

for all iteration variable-based loops. 

– A generalized loop constraint analysis that uses 

constraint logic programming to calculate precise 

flow information for nested loops. 

B. FLOW CONSTRAINT TRANSFORMATION 

While fully automatic analysis is often sufficient, the programmer 

can use his knowledge about the execution environment 

in a semi-automatic process to further extend 

the power of the analysis. Traditionally, this manual annotation 

of the program is also done on the binary code. 

The philosophy of TuBound is to also lift the annotation 

process to the source level. 

Since compiler optimizations can modify the control 

flow of a program, they also have the potential to invalidate 

source code annotations describing the control flow. 

In TuBound, the FlowTrans component takes care of this 

by transforming flow constraints according to the performed 

optimizations. This is realized with the help of an 

optimization trace and a rule system that defines the correct 

transformation of flow constraints for each type of 

optimization. By performing optimizations on the source 

code, the subsequent compiler can be instructed to perform 

a direct translation to binary code, thus keeping the 

flow information intact. 

III. RESULTS 

TuBound successfully took part in the WCET Tool Challenge 

2008, a competition for academic and commercial 

WCET analysis tools; detailed results can be found 

in [4]. We also evaluated our approach using a selection 

of standardized WCET-analysis benchmarks compiled 

by Mälardalen University. In Figure 1, the upper 

graph compares the run time of the components of 

1e+09 

1e+08 

1e+07 

1e+06 

100000 

10000 

1000 

crc 

cnt 

Figure 1: Measurements 

46 

unoptimimized 

loop-opt. 

lowlevel-opt 

loop-opt+lowlevel-opt 

fibcall 

expint 

cover 

bsort100 

qurt 

lcdnum 

TuBound: Analyzed WCET 

st 

sqrt 

recursion 

Cycles/Benchmark 

ns 

matmult 

jfdctint 

fdct 

whet 

TuBound, whereas the lower graph depicts the effect of 

optimizations on the analyzed WCET of the benchmarks. 


With TuBound we have successfully demonstrated the 

feasibility of a source-to-source approach to WCET analysis, 

by combining the advantage of low level WCET 

analysis with high level source code annotations and optimizing 

compilation. The flow constraint transformation 

framework FlowTrans ensures that annotations are 

transformed according to the optimization trace as provided 

by the high-level optimizer. Recent works such 

as [5] show that better integration of optimizing compilation 

and WCET analysis is indeed of high interest for the 

community. With our source-based approach, we now 

have a portable solution to close the gap between source 

code annotations and machine-specific WCET analysis. 

REFERENCES 

[1] Adrian Prantl, Markus Schordan, and Jens Knoop. 

TuBound – A Conceptually New Tool for Worst-Case Execution 

Time Analysis. In Proc. 8th International Workshop 

on Worst-Case Execution Time Analysis (WCET 2008), 

Prague, 2008. 

[2] Raimund Kirner. Extending Optimising Compilation to 

Support Worst-Case Execution Time Analysis. PhD thesis, 

Technische Universität Wien, 2003. 

[3] Markus Schordan. Source-To-Source Analysis with 

SATIrE – an Example Revisited. In Proc. of Dagstuhl 

Seminar 08161: Scalable Program Analysis. Germany, 

Dagstuhl, April 2008. 

[4] Niklas Holsti, Jan Gustafsson, and Guillem Bernat (eds). 

WCET tool challenge 2008: Report. In Proc. 8th International 

Workshop on Worst-Case Execution Time Analysis 

(WCET 2008), Prague, 2008. 

[5] Heiko Falk, Paul Lokuciejewski, and Henrik Theiling. Design 

of a WCET-Aware C Compiler. In Soonhoi Ha and 

Samarjit Chakraborty, editors, ESTImedia, pages 121–126. 

IEEE Computer Society, 2006.

Cooperative Media Access Control in Wireless Networks 

Mathias Offner and Helmut Adam (Faculty Mentor) 

Networked and Embedded Systems 

University of Klagenfurt, Austria 

Email: moffner@edu.uni-klu.ac.at, helmut.adam@uni-klu.ac.at 

Abstract — We present CMAC/DRS, a cooperative relaying enhanced 

MAC protocol which solves mandatory tasks in cooperative 

networks in a throughput efficient way. Our main focus is the 

relay selection process; we only select relays if requested by the 

destination and try to minimize the collision probability of messages 

in this process. We compare CMAC/DRS with CMAC/ARS 

and standard non-cooperative IEEE 802.11. Our simulation results 

indicate considerable throughput benefits of CMAC/DRS 

compared to the reference protocols. 


In cooperative relaying, as depicted in Figure 1, a node denoted 

as relay R overhears the direct transmission between 

S and D and, on demand, forwards this data to D. D combines 

both messages to mitigate small scale fading effects. 

R is chosen from the common neighbors of S and D based 

on current Channel State Information (CSI) from the candidates 

to S and D. RTS and CTS messages of IEEE 802.11 

protocols can be exploited at relaying candidates to estimate 

their CSI to S and D trying to keep the overhead introduced 

by the relay selection small. Furthermore, a selected relay 

needs also to reserve the channel in its neighborhood. Thus, 

it is appealing to combine cooperative relaying protocols a 

similar to IEEE 802.11 MAC protocol [1, 2, 3]. 

The performance of cooperative relaying schemes mainly 

depends on the relay selection. Distributed relay selection 

requires the exchange of messages which are prone to collide. 

Due to collision it can happen that no relay can be 

selected and cooperation is not available. 

In this paper we introduce Cooperative Medium Access 

Control with Dynamic Relay Selection (CMAC/DRS) 

which addresses the problem of relay selection and tries to 

avoid collisions between potential relaying nodes. Furthermore, 

it only uses cooperation if required and skips relay 

selection otherwise. 

S D 

R 

Figure 1: Basic cooperative relaying scheme 

II. PROTOCOL DESCRIPTION: CMAC/DRS 

CMAC/DRS which is based on CMAC/ARS [1] works as 

depicted in Figure 2: at the beginning the source broadcasts 

an RTS frame to initiate the transmission with a certain destination 

and reserves the channel in its neighborhood for the 

time of the relay selection. The destination replies with a 

Conditional Clear to Send (CCTS) frame if it is ready to 

send and occupies the channel for the expected transmission 

time. If the direct link between source and destination is bad 

a relay is selected distributively. The current relay is confirmed 

within the data transmission of the source. The data 

packet also extends the source’s channel reservation until 

47 

planned ACK reception time. After data transmission the relay 

waits for an ACK from the destination. If the relay does 

not receive the ACK within a certain period of time, it assumes 

a failure and forwards the overheard message. At the 

end an ACK frame completes the cooperative transmission. 

A. COOPERATION ON DEMAND 

Cooperative Relaying consumes time and energy for relay 

selection and overhearing packet transmissions. However, 

cooperation is only used when the direct transmission 

from source to destination does not succeed. Thus, in 

CMAC/DRS the destination uses the RTS message to estimate 

the current Packet Error Rate (PER) of the sourcedestination 

link. If the current PER drops below an application 

depended threshold the relay selection is skipped which 

is reported via the CCTS message. Thus cooperation is only 

used on demand [4]. 

B. DISTRIBUTED RELAY SELECTION 

Relay selection is a significant topic in cooperative relaying. 

Main challenge is to choose a node that can effectively 

improve data transmission out of a set of potential relays. 

CMAC/DRS uses three busy tone slots and a static number 

of RRTS slots to solve this problem. Busy tones are used to 

signalize that there exist neighboring nodes that may help to 

send packets in a cooperative manner. Moreover those tones 

assist to separate relays into sets with different capabilities, 

e.g. relays that provide an outage rate of 0.01, 0.1 and 0.5. 

Busy tones are consulted to estimate the number of competing 

relays [5]. The estimated number of relaying candidates 

is reported by the source using a NRC (Number of Relay 

Candidates) message. Potential relays use this information 

to derive their slot transmission probability in the contention 

window. This reduces the probability of colliding RRTS 

(Relay Ready To Send) messages. For instance, if 13 relays 

are available each of them broadcast an RRTS message 

at N available slots with a probability of 1/13. This equation 

maximizes the probability that only one single frame is 

send at the same time [6]. 

III. SIMULATION 

We implemented CMAC/DRS and CMAC/ARS [1] in a 

modified version of an 802.11 simulator1 for ad hoc networks. 

CMAC/ARS has not been implemented one-to-one 

in our simulator because this approach presumes a few assumptions 

that can not be applied practically [7]. The main 

difference between both implemented cooperative protocols 

is that CMAC/ARS uses constant slot transmission probabilities 

for RRTS frames. Therefore, the number of available 

slots significantly affects the success of relay selection. 

In order to provide a fair comparison, both CMAC/DRS and 

CMAC/ARS use seven RRTS slots. 

For our simulations we randomly place nodes on an 

100 × 100 m2 area, where each 5 msec a packet with size 

1024 bytes is injected. Source and destination of this transmission 

are random. Relays perform decode and forward. 

Further assumptions are given in [7]. Figure 3 depicts a 

1 http://wiki.uni.lu/secan-lab/802.11+Network+Simulator.html

throughput comparison of CMAC/DRS, CMAC/ARS and 

802.11. IEEE 802.11 achieves a fairly low throughput 

due to many required retransmissions. Throughput of 

CMAC/ARS raises continuously from sparse networks with 

only 10 available nodes to networks with 40 radios, afterwards 

it drops instantly. The value decreases mainly because 

of collisions of RRTS frames. Consequently, relay 

selection fails and data frames cannot be sent in a cooperative 

manner. CMAC/DRS reaches at a point of 25 network 

nodes a throughput value that stays nearly constant 

around 620 kB/s. With increasing node density benefits of 

dynamic slot transmission probabilities arise, as the probability 

of RRTS frame collisions is minimized even in dense 

networks. 

throughput (kB/s) 

700 

600 

500 

400 

300 

200 

100 

0 

0 20 40 60 80 100 120 

number of network nodes 

Figure 2: CMAC/DRS frame exchange sequence 

CMAC/ARS 

CMAC/DRS 

802.11 

Figure 3: Throughput comparison 

Figure 4 illustrates the dropped packet rates of 

CMAC/DRS, CMAC/ARS and IEEE 802.11 in the given 

scenario. A packet is dropped whenever the number of retransmissions 

exceeds seven. While rates of CMAC/ARS 

and CMAC/DRS are fairly low and show a dependency on 

the network density, the packet drop rate of 802.11 is constantly 

around 0.04. Regarding CMAC/ARS we can recognize 

that the ratio of dropped packets raises at networks with 

70 or more radios. Again the reason are RRTS collisions as 

nodes have to transmit directly if relay selection fails. It appears 

that more packets are dropped at sparse networks as 

there are less potential relays available. Overall simulations 

have shown that CMAC/DRS outperforms CMAC/ARS in 

many comparison criteria by far and therefore it is a promising 

state of the art cooperative MAC layer protocol. 


This paper shows significant benefits of cooperative 

communications demonstrated by simulation results. 

CMAC/DRS represents an efficient MAC layer protocol 

to provide relaying in wireless networks. Fundamentals of 

this proposed scheme are distributed relay selection with 

48 

ratio of dropped packets 

0.1 

0.01 

0.001 

1e-04 

1e-05 

1e-06 

CMAC/ARS 

1e-07 

0 20 40 60 80 100 120 

number of network nodes 

Figure 4: Dropped packets 

802.11 

CMAC/DRS 

dynamic slot transmission probabilities and cooperation on 

demand. Evaluations demonstrate gains of CMAC/DRS by 

terms of throughput and outage. 


This work has been sponsored within the scope of the master’s 

thesis by Orange Labs. 

REFERENCES 

[1] C.-T. Chou, J. Yang, and D. Wang. Cooperative MAC 

Protocol with Automatic Relay Selection in Distributed 

Wireless Networks. In Proc. IEEE Intl. Conf. on Pervasive 

Computing and Communications Workshops,pages 

526–531, Washington, DC, USA, March 2007. 

[2] A. Azgin, Y. Altunbasak, and G. Alregib. Cooperative 

MAC and routing protocols for wireless ad hoc networks. 

In Proc. IEEE GLOBECOM, volume 3, pages 

2854–2859, November 2005. 

[3] S.Moh,C.Yu,S.M.Park,H.N.Kim,andJ.Park.CD- 

MAC: Cooperative Diversity MAC for Robust Communication 

in Wireless Ad Hoc Networks. In Proc. IEEE 

ICC, pages 3636–3641, Glasgow, Scotland, June 2007. 

[4] H. Adam, C. Bettstetter, and S. M. Senouci. Adaptive 

relay selection in cooperative wireless networks. In 

Proc. IEEE PIMRC, Cannes, France, September 2008. 

[5] Sarkar S. Khanna, S. and I. Shin. An energy measurement 

based collision resolution protocol. In Proc. of 

ITC conference, Berlin, Germany, September 2003. 

[6] S. S. Lam. Packet switching in a multi-access broadcast 

channel with application to satellite communication in 

a computer network. PhD thesis, University of California, 

Los Angeles, 1974. 

[7] M. Offner. Media access control in wireless cooperative 

relaying systems. Master’s thesis, University of 

Klagenfurt, 2008.

Jessine: An Approach to Creating Software Applications 

with Rule-Based Domain Knowledge 

Miroslav Sabo and Jaroslav Poruban (Faculty Mentor) 

Faculty of Electrical Engineering and Informatics 

Technical University of Kosice 

Kosice, Slovak Republic 

Email: {miroslav.sabo,jaroslav.poruban}@tuke.sk 

Abstract — This paper points out the problem of 

tangling of implicit knowledge about the domain 

with the core functionality in software applications. 

The presented framework called Jessine enables 

separating of rule-based knowledge and objectoriented 

functionality in order to facilitate 

independent development and evolution. An 

application programming interface is provided for 

creating, managing and customizing the necessary 

components of rule systems designed with the 

framework. Configuration of the rule systems 

implemented with Jessine is defined via external 

files outside an application code. Jessine is a 

conceptual framework written in Java and is 

utilizing full-fledged rule engine Jess. 


The complexity of software applications is steadily 

increasing and knowledge management of 

application domain is becoming more important. 

Moreover, real-world domains are subject to change 

and applications have to cope with these changes in 

order to operate properly. Current software 

engineering practices result in software applications 

containing implicit knowledge about the domain that 

is tangled with the core functionality. 

The development of such a software is a very 

complex task: the software developer, who is 

typically a software engineer but not a knowledge 

engineer, has to concentrate on two facets of software 

at the same time and manually integrate them. This 

violates the principle of separation of concerns, 

which states that the core functionality should be 

separated from other concerns or aspects, such as 

rule-based knowledge in this case. However, due to 

current software engineering methodologies, domain 

rules are expressed implicitly, strongly coupled and 

even tangled in the application code. Thus, changes 

in the domain imply invasively changing the code, 

making it hard to understand, maintain, evolve and 

reuse. 

In my work I am focusing on the integration of 

domain knowledge represented by domain rules into 

the software applications during the implementation 

49 

phase of the software development cycle. The 

following list mentions the main advantages of 

decoupling domain rules from the core application: 

� Explicit representation of domain knowledge. 

� Reuse of domain rules accross different 

processes and applications. 

� Reuse of software applications considering 

different sets of domain rules. 

� Clearer understanding of application 

behaviour. 

� Decreased maintenance and testing costs. 

II. FRAMEWORK AS A SOLUTION 

To promote the aforementioned features, I decided to 

use the rule engine for storing and processing of 

domain rules, encapsulating and separating that way 

the domain knowledge from the rest of the 

application. For seamless non-invasive integration of 

such a separated domain knowledge back to the 

application, I have designed and implemented 

specialized application framework [1]. The 

framework is utilizing full-fledged rule engine Jess 

[2], therefore the name of framework: Jessine. 

The main idea which is the framework based on is 

the elimination of writing glue code which does not 

contribute to any functionality of application, but 

serves solely to “glue together” the code of 

application and rule engine, which would not 

otherwise be compatible. The good example of glue 

code would be initialization and configuration of rule 

engine which are both performed by framework 

automatically and therefore not needed to be written 

by programmer in application code. Instead, various 

places in core functionality where some processing 

with domain knowledge is required contain simple 

method calls to Jessine, which engage the rule engine 

and appropriate action is executed or value returned. 

Moreover, in context of Aspect-Oriented Software 

Development technologies, rule systems developed 

with Jessine can be considered as implementation of 

the cross-cutting functionality concerning domain 

knowledge. Since multiple joinpoint models are

available through various AOP implementations, 

method calls to Jessine framework can be 

encapsulated into the aspects and woven into the 

application code by employing some of them. In this 

manner, by combining Jessine framework with 

AOSD technologies, programmers can integrate the 

separated domain knowledge with core functionality 

without interfering with application source code. 

III. HOW JESSINE WORKS 

One of the main objectives when designing the 

framework was automatization of tasks necessary to 

perform when using rule systems and leaving the 

programmer only to deal with application related 

coding. Another one was holding to the principle of 

loose coupling [3] between particular components of 

framework. 

The Jessine framework is provided with an 

Application Programing Interface which exposes 

both of the components that are the subjects to be 

customized by programmer for specific domain 

applications – AbstractEngine and Action. 

AbstractEngine is component wrapped around Jess 

rule engine and extends it with automatic 

initialization and configuration in accordance with 

external configuration files defined outside an 

application. Another component, Action, serves as a 

communication bridge between the rule system and 

the application context by enabling domain rules to 

access the objects from application. All of the other 

components of framework are hidden and may not be 

modified by programmer. 

There exist no explicit dependencies between 

components which make up rule systems in Jessine. 

Programmer can develop each component 

independently of the others and reuse it among many 

rule systems. Bindings between components are 

defined declaratively in Jessine configuration file 

with Jessine XML-based language. 

The framework allows to implement multiple rule 

systems in one application, each of them specialized 

in different area of domain knowledge. Every 

implementation can be packed into the library file 

and used together with Jessine library in other 

application as a plugin solution. 

It is also provided with its own exception and 

logging system. When an error occurs, an object of 

Jessine exception is created, handed off to the 

runtime system and the event is recorded to the log 

file. Besides exceptions, logging system records 

every important event within context of rule systems, 

e.g. starting the environment of framework or setting 

of configuration directory. 

50 

IV. RELATED WORKS 

When considering literature on developing software 

applications with rule-based knowledge we find that 

all advocate making rules explicit and separating 

them from the object-oriented core functionality 

[4][5][6]. Moreover, many technologies exist that are 

targeted towards these goals, although they take 

radically different approaches. First of all, rule-based 

knowledge can be represented separately in the 

object-oriented programming language itself. An 

extension to this approach is representing rule-based 

knowledge explicitly using object-oriented design 

patterns, referred to as the Rule Object Pattern [7]. 

Finally there are dozens of both commercial and 

academic hybrid systems [8][2], which integrate a 

full-fledged rule-based language with a state of the 

art object-oriented programming language. 

Nevertheless, none of them is using rule system for 

separating domain knowledge in the way I am doing 

it in my approach. 


This work was supported by VEGA Grant No. 

1/4073/07 – Aspect-oriented Evolution of Complex 

Software System. 

REFERENCES 

[1] M. Sabo. Applying Rules in Software Systems. 

Diploma thesis, Technical university in Kosice, 

Kosice, 2008. 

[2] E. Friedmann-Hill. Jess in Action: Rule-Based 

Systems in Java. Manning Publications, 2003. 

[3] J. Eder, G. Kappel, M. Schrefl. Coupling and 

Cohesion in Object-Oriented Systems. In 

Proceedings of the 1 st Conference on Information 

and Knowledge Management, 1992. 

[4] C.J. Date. What Not How: The Business Rules 

Approach to Application Development. Addison- 

Wesley, 2000. 

[5] R.G. Ross. Principles of the Business Rule 

Approach. Addison-Wesley, 2003. 

[6] B. von Halle. Business Rules Applied: Building 

Better Systems Using the Business Rules 

Approach. Wiley, 2002. 

[7] A. Arsanjani. Rule Object 2001: A Pattern 

Language for Adaptive and Scalable Business 

Rule Construction. IBM T.J. Watson Research 

Centre, 2001. 

[8] M. D’Hondt. Hybrid Aspects for Integrating 

Rule-Based Knowledge and Object-Oriented 

Functionality. PhD thesis, Vrije Universiteit 

Brussel, 2004.

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Design of Self-organizing Systems Using Evolutionary Methods 

István Fehérvári and Wilfried Elmenreich (Faculty Mentor) 

Institute for Networked and Embedded Systems / Mobile Systems Group 

University of Klagenfurt 

Klagenfurt, Austria 

Email: {ifeherva,wilfried.elmenreich}@uni-klu.ac.at 

Abstract — Having many advantages, self-organizing systems 

could mean a solution for intelligent group behavior. Until now 

there is no general methodolgy how to design and control these 

systems. In this paper we examine a genetic approach for generating 

group behavior. Related research proved that it is possible 

to create sensor based robot control program using genetically 

evolved ANNs. Extending this concept, we propose a method for 

designing self-organizing systems by extending this concept to cooperative 

behavior among the individuals. 


The power of evolutionary methods was shown in many 

applications where the implementation of artificial intelligence 

was necessary. As an example genetic algorithms 

(and so genetic programming) were used in simple and 

more complex games as proposed by Hauptman and Sipper 

[1]. Another approach is using neural networks to build 

programs capable of learning. Following this idea adaptive 

robot control can be developed at the hardware level 

for practical motion [2] or taking one step further by evolving 

neural networks in a genetic manner to get a complete 

control program of a single robot driven by sensor data. According 

to [3] the evolved network was significant better 

than the handcrafted solution. 

For self-organizing systems to get the highest satisfaction 

σsys for the system a cooperative behavior should be developed. 

This is mostly done by manually adjusting parameters 

which in case of systems with high complexity could 

be very difficult. In these systems, a small change in a parameter 

could arise unpredicted behavior due to the missing 

direct function between element and system. Thus, a lot of 

trials are necessary to find a satisfying solution. Evolutionary 

methods provide a means to automatize the testing and 

optimizing of parameters in an intelligent way. 

In this paper we present a method where the team strategy 

is not pre-programmed, but using the idea proposed 

by Elmenreich and Klinger [3], is generated by genetically 

evolving an Artifical Neural Network (ANN). The intention 

is to minimize the required human interference in creating 

the model by making it partly or fully generated by itself. 

The rest of the paper is structurized as follows: Section 2 

describes self-organizing systems while Section 3 explains 

the genetic approach and discusses the method for the given 

problem. Current work is discussed in Section 4. 

II. SELF-ORGANIZING SYSTEMS 

The term “self-organizing” was first introduced in 1947 by 

W. Ross Ashby. It refers to pattern-formation processes 

within a system caused by the behavior of its individual entities. 

Their basic feature is the way how they acquire their 

order and structure. Among the several definitions the most 

suitable could be the following: 

53 

“In self-organizing systems, pattern formation occurs 

through interactions internal to the system, without intervention 

by external directing influences.”[4, p.7] 

A good example is a team of workers acting on their own 

following a mutual understanding. If there would be common 

blueprints or a boss controlling them, it would mean an 

external influence resulting in no self-organization. Nature 

also has many examples like a school of fish where each 

individual has knowledge only about its neighbors and so 

there is no leader among them. The key part is the communication 

between the individuals satisfying their own goals 

and by doing so a pattern emerges. Through these features 

it is expected that the overall system shows many advantages 

like robustness, adaptability and scalability which 

makes self-organizing systems (SOS) an interesting option 

for controlling complex systems. However the above mentioned 

properties and the decentralized control makes an 

SOS difficult to design and control. Although, Gershenson 

[5] provides some ideas for the design of SOS for technical 

applications, there is no general methodology yet to 

explain how these should be done. 

III. THE GENETIC APPROACH 

The main idea behind genetic methods is the Darwinian selection 

process. The algorithm operates on a pool of possible 

solutions. It evaluates them based on their fitness function 

which measures their performance when applied to the 

given problem. While the best ones are kept, those with 

bad performance will be replaced by offsprings or mutations 

of the pool. For more complex problems where the 

solutions cannot be represented by variables but individual 

programs it is hard to define how to mutate or recombine 

them while keeping the syntactically correct structure. In 

these cases normal programming languages like C or Java 

do not qualify for this kind of programming, however the 

usage of ANN could solve the problem. 

A. NEURAL NETWORK MODEL 

We choose a fully connected, time-discrete, recurrent ANN 

where each neuron has a connection to every other neuron 

and also to itself via several input connectors. Based on the 

neurons activation value, the neurons output is forwarded 

via different connections to all other neurons. Each connection 

is assigned a weight and each neuron is assigned 

a bias value. There are special input and output neurons 

for the controlling interface: the input neurons produce the 

sensor data on their output independtly of their input values, 

the output neurons act like normal neurons in the network, 

but their output data is also forwarded to the actuators. 

Other nodes which are not characterized as input or 

output nodes are the so-called hidden neurons. Figure 1 

shows a schematic structure. 

In more complex systems containing many individuals 

like self-organizing systems there might be a need for dif-

Figure 1: Neural network model example 

ferently arranged sensor subsystems connected to the same 

network. Robot soccer would be a good example where one 

group of sensors watch for the ball while other groups for 

teammates or opposing partymembers. Their separate inputs 

will be connected to the common network at the input 

nodes so the output would depend on several external factors 

resulting in more compound behavior. 

B. EVOLUTION METHOD 

Evolution method means a genetic algorithm that looks for 

solutions with high fitness values to the given problem. 

During the process many solutions are created and evaluated 

in parallel while the best ones will be kept for the next 

generation. First, the genomes have to be defined for each 

entity. In our case they are represented by the weight matrix 

and the biases of each neuron. The next step is the definition 

of the fitness function which is a proper formulation of 

what we expect from the system. As proved in [3] genetic 

selection processes supporting crossover, mutation and elite 

selection have higher learning speed than the ones without 

crossover [6]. To have support of all this features we will 

use the versatile framework given by Pfandler [7]. 

IV. TESTBED 

There are several ways to test the proposed method; we 

chose the RoboCup Soccer Simulator1 as an evaluation tool. 

This open-source program is capable of simulating a soccer 

game between two teams played in real-time. See Figure 2 

for a screenshot of the simulator. As a result of each genetic 

procedure a population of ANNs will be created. These will 

be turned into robot soccer team control programs, where 

we want to rank them for further processes based on their 

in-game performance. In the soccer environment there is 

no effective way to assign fitness values to the entities by 

evaluating them one by one, so we will use a Swiss system 

tournament [8] organized among them. A standard simulated 

robot soccer game takes 12 minutes to finish if played 

in real-time. Calculating with a population of 100 it would 

take 84 minutes to finish with only one iteration. To overcome 

this problem and shorten the required time for the 

test the simulator will be modified to run as fast as possible 

using an asynchronic coupling between server and team 

clients. Further speedup can be achieved using a parallel 

evaluation on a multi-computer system. 

V. CONCLUSION AND OUTLOOK 

The success of genetically evolved ANNs used in [3] for 

autonomous mobile robot control shows a good potential 

1 http://sserver.sourceforge.net 

54 

Figure 2: Team evaluation using soccer simulator 

for applying to self-organizing systems. The goal of the 

current project is to create a simulation environment for 

self-organizing systems evolved by following the proposed 

method. Once implemented, experiments will be performed 

to optimize and to compare this solution with hand coded 

ones in robot soccer environments. 


This work was supported by the Austrian FWF project 

TTCAR under contract No. P18060-N04. 

REFERENCES 

[1] M. Sipper, Y. Azaria, A. Hauptman, and Y. Shichel. Designing 

an evolutionary strategizing machine for game 

playing and beyond. IEEE Trans. on Systems, Man and 

Cybernetics, Part C, 37(4):583–593, July 2007. 

[2] M. W. Han and P. Kopacek. Neural networks for the 

control of soccer robots. In Proceedings of the 2000 

IEEE International Symposium on Industrial Electronics, 

pages 571–575, Cholula, Mexico, August 2000. 

[3] W. Elmenreich and G. Klingler. Genetic evolution of 

a neural network for the autonomous control of a fourwheeled 

robot. In Sixth Mexican International Conference 

on Artificial Intelligence (MICAI’07), Aguascalientes, 

Mexico, November 2007. 

[4] S. Camazine, J. Deneubourg, N. R. Franks, J. Sneyd, 

G. Theraulaz, and E. Bonabeau. Self-Organization in 

Biological Systems, volume 1. Princeton University 

Press, Princeton, NJ, USA, 2nd edition, January 2001. 

[5] C. Gershenson. Design and control of self-organizing 

systems. PhD Dissertation, Vrije Universiteit Brussel, 

Brussel, Belgium, 2007. 

[6] L. A. Meeden. An incremental approach to developing 

intelligent neural network controllers for robots. IEEE 

Trans. on Systems, Man, and Cybernetics, Part B: Cybernetics, 

26(3):474–485, June 1996. 

[7] A. Pfandler. Design and implementation of a generic 

framework for genetic optimization of neural networks. 

Bachelor’s thesis, Vienna University of Technology, Vienna, 

Austria, 2007. 

[8] J. A. Bergstra and L. M. G. Feijs, editors. Algebraic 

Methods, volume 2. Springer-Verlag, New York, LLC, 

1st edition, May 1991.

Towards Automatic Design of Competitive Image Filters in FPGAs 

Zdeněk Vaˇsíček, Lukáˇs Sekanina (Faculty Mentor) 

Faculty of Information Technology 



Email: {vasicek,sekanina}@fit.vutbr.cz 

Abstract — This paper presents a new approach to the FPGA 

implementation of image filters which are utilized to remove the 

salt and pepper noise of high intensity. An evolutionary algorithm 

(EA) is utilized to find a set of image filters which can 

be employed in a bank of image filters. The main advantage of 

this approach is that the bank of evolutionary designed filters 

requires four times less resources on a chip in comparison with 

the adaptive median filter while the visual quality of filtering is 

preserved. 

In order to design image filters in reasonable time, an FPGAbased 

evolutionary platform is utilized. The proposed platform 

is based on the implementation of a search algorithm in the 

PowerPC processor which is available in Xilinx Virtex II Pro 

and newer FPGAs. As the search algorithm as well as the evaluation 

of candidate solution runs in FPGA, the evolutionary design 

of image filters needs approx. 44 times less time to design a 

human-competitive filter when compared to the same algorithm 

running on the common PC. 


The aim of this paper is to introduce a new EA-based 

approach to the image filter design. We will solely deal 

with the images corrupted by the shot noise, in particular 

salt-and-pepper noise. This type of noise is caused by 

malfunctioning pixels in camera sensors, faulty memory 

locations in hardware, or errors in the data transmission. 

Traditionally, the salt-and-pepper noise is removed by 

median filter (MF). However, when the intensity of noise 

is increasing (15-90% pixels are corrupted), simple median 

filter are not sufficient. Among others, adaptive median 

filter (AMF) provides good results and simultaneously, 

its hardware implementation is straightforward [1]. 

The problem is that these advanced techniques require 

a considerably larger area on a chip in comparison with 

simple median filters. 

It has been shown that evolutionary design techniques 

are able to generate slightly better solutions than standard 

MF for this noise intensity [2].Unfortunately, the evolutionary 

design approach which works up to 10% noise 

intensity does not work for higher noise intensities. 

In this paper, we will show that by an innovative combination 

of evolved designs and conventional designs we 

are able to significantly reduce the overall implementation 

cost on a chip in comparison to standard approaches 

based on sophisticated filtering schemes, such as AMF. 

55 

II. IMAGE FILTER GENERATOR 

In order to design image filters which can be used in the 

bank of filters, we utilize the evolutionary platform running 

on FPGA introduced in [3]. The system consists 

of a genetic unit (GU), array of reconfigurable elements 

(VRC) and fitness calculation unit (FU). The corrupted 

image is processed by a pipelined array of reconfigurable 

elements whose configuration is generated by the genetic 

unit. While candidate filters are created and evaluated 

using a user logic available on the FPGA, the genetic operations 

are carried out in the PowerPC processor which 

is available on the same FPGA. Every image operator is 

considered as a digital circuit of nine primary 8-bit inputs 

and a single 8-bit output, which processes gray-scaled 

images. The aim of the EA is to find a digital circuit 

which accomplish the requirement task. 

The VRC array consists of 2-input configurable elements 

(CEs), placed in a grid 8 columns and 4 rows. Any 

input of each CEs may be connected either to a primary 

input or to the output of a CEs placed anywhere in the 

preceding column. Each CEs can be programmed to implement 

one of 16 functions given beforehand. The evaluation 

of candidate configurations is pipelined in such 

manner as there are no idle clock cycles. As the EA directly 

operates with configurations of the VRC, a configuration 

is considered as a chromosome. 

The corrupted image, original image and filtered image 

are stored in external SRAM memories. The FU forwards 

the pixels of corrupted image to inputs of VRC 

and compares the pixels of filtered image with the pixels 

of original image. The design objective is to minimize 

the absolute difference between the filtered image and the 

original image. 

III. PROPOSED APPROACH 

In order to create a salt-and-pepper noise filter which 

generates filtered images of the same quality as an AMF 

and which is suitable for hardware implementation, we 

propose to combine several simple image filters utilizing 

the 3 × 3 window that are designed by an evolutionary 

algorithm. As Figure 2 shows the procedure has three 

steps: (1) the reduction of a dynamic range of noise, (2) 

processing using a bank of n filters and (3) deterministic 

selection of the best result. 

The first step reduces the large dynamic range of corrupted 

pixels (0/255) using a component which inverts 

all pixels with value 255, i.e. all shots are transformed to

PSNR [dB] 

45 

40 

35 

30 

25 

20 

15 

10 

MF (W =3× 3), 268 slices 

MF (W =5× 5), 1506 slices 

MF (W =7× 7), 4426 slices 

AMF (W max =5× 5), 2024 slices 

AMF (W =7× 7), 6567 slices 

max 

AMF (W =9× 9), 16395 slices 

max 

single filter, 200 slices 

3-bank filter, 843 slices 

best SW algorithm 

5 

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 

Noise intensity [%] 

Figure 1: Comparison of various image filters using a set of 25 test images corrupted by salt-and-pepper noise 

Filter kernel 3x3 

I0 

I1 

I2 

I3 

I5 

I4 

I8 

I7 

I6 

Pre− 

processing 

filter 

Filter 

1 

Filter 

2 

Filter 

n 

Buffer 

O0 

O1 

On 

I4 

Post− 

processing 

filter 

Filtered image 

Figure 2: Proposed architecture for salt-and-pepper noise 

removal circuit 

have a uniform value. This task is easy to implement in 

hardware using comparators. 

Preprocessed image then enters a bank of n filters that 

operate in parallel. The selection of suitable filters is the 

crucial step. Since we repeated the evolutionary design of 

salt-and-noise filters many times, we have gathered various 

implementations of this type of filter. Thus, we selected 

n different evolved filters which exhibit the best 

filtering quality and utilized them in the bank. These filters 

were designed by EA using the same type of noise 

and training image and with the same aim: to remove 

40% salt-and-pepper noise. 

Finally, the outputs coming from banks 1 ...ntogether 

with the original value of the central pixel are combined 

by n +1-input median filter which can easily be implemented 

using comparators. As the proposed system naturally 

forms a pipeline, the overall design can operate at 

the same frequency as a simple median filter when implemented 

in hardware. 

IV. EXPERIMENTAL RESULTS 

Filtering properties of the proposed bank of filters 

and MFs as well as AMFs (both with various filtering 

windows) were compared on 25 test images (see 

http://www.fit.vutbr.cz/ ˜vasicek/imagedb). All images 

were corrupted by salt-and-pepper noise of intensity 5- 

75%. The results were also compared to the best known 

software solution which utilizes filtering windows of unlimited 

size. Figure 1 contains the results obtained as an 

average over test set. The visual quality is measured in 

terms of the peek signal-to-noise ratio (PSNR); the higher 

56 

PSNR, the better results. 

Surprisingly, only three filters utilized in the bank are 

needed to obtain a filter which produces images of practically 

undistinguishable visual quality to the AMF utilizing 

up to 7 × 7-pixel filtering windows. 

The implementation cost of adaptive median filter is 

2024 slices for AMF which utilizes the filter window 

up to 5 × 5 pixel and 6567 slices for AMF 7 × 7 (Virtex 

II Pro considered). The implementation cost of proposed 

bank consisting of three filters (3-bank) requires 

500 slices only and 5-bank filter 843 slices only (for details 

see [4]). 

V. CONCLUSION 

The proposed solution which combines image filters designed 

by means of EA with a simple human designed 

preprocessing and post-processing unit can reach the 

quality of adaptive median filtering. The bank of three 

evolved filters which utilizes 3×3-pixel filtering window 

is able to accomplish the same task as AMF utilizing up 

to 7×7-pixel filtering windows; however, using a significantly 

lower number of FPGA resources. This can lead to 

a significant reduction of power consumption of a target 

system. 

REFERENCES 

[1] H. Hwang and R. A. Haddad. New algorithms for adaptive 

median filters. In K.-H. Tzou and T. Koga, editors, Proc. 

SPIE Vol. 1606, p. 400-407, Visual Communications and 

Image Processing ’91: Image Processing, Kou-Hu Tzou; 

Toshio Koga; Eds., pages 400–407, November 1991. 

[2] L. Sekanina. Evolvable components: From Theory to 

Hardware Implementations. Natural Computing. Springer- 

Verlag Berlin, 2004. 

[3] Zdenek Vasicek and Lukas Sekanina. An evolvable hardware 

system in xilinx virtex ii pro fpga. International Journal 

of Innovative Computing and Applications, 1(1):63–73, 

2007. 

[4] Zdenek Vasicek and Lukas Sekanina. An area-efficient alternative 

to adaptive median filtering in fpgas. In Proc. of 

the 17th Conf. on Field Programmable Logic and Applications, 

pages 1–6. IEEE Computer Society, to appear, 2007.

Evaluation of a State-based Process Management Platform 

Ekaterina Andrianova, Jürgen Dorn 

Institute of Software Technology and Interactive Systems 



Emails: Katerina.Andrianova@gmail.com 

juergen.dorn@ec.tuwien.ac.at 

Abstract — The first objective of the analysis presented 

in this paper is to define an evaluation procedure 

for Business Process Management Systems 

(BPMS) and to investigate requirements to BPMS in 

different categories according to the procedure. The 

business process life cycle, different BPM values, 

process types, infrastructure requirements and 

BPM failure reasons are explored. 

The second objective of the analysis is to investigate 

ISIS Papyrus’ BPM approach grounded on a 

state-based representation of processes and a 

learning algorithm sensitive to document content. 

We have assessed the ISIS Papyrus BPM platform 

step by step according to the developed procedure. 


A lot of efforts are usually devoted to BPM projects. 

Nevertheless, such projects fail quite often or don’t 

live up to the expectations due to a variety of reasons. 

Packaged applications such as ERP also have some 

problems for managing business processes. They 

don’t deliver the process insights and agility needed 

by the business due to [2]. 

Potential factors that can lead to a BPM project 

failure are important to be investigated. Moreover, a 

special procedure should be created in order to help a 

BPMS-customer to understand which aspects should 

be taken into account when choosing a BPMS and to 

help a BPMS-vendor to define a niche for the BPMS 

and understand its advantages and drawbacks. 

At the same time many alternative approaches to 

BPM have been proposed. One of them is ISIS Papyrus’ 

process management approach grounded on the 

state/event-based representation of processes and 

learning, sensitive to the content of documents in a 

workflow [4]. The Papyrus platform provides the 

user-trained environment (UTE) that lets execute or 

guide a process on the basis of learned user experience 

[4]. Since this approach is quite new for the 

BPMS market, it is essential to assess it and evaluate 

strengths and weaknesses and to show which BPM 

sector it can potentially occupy. 

57 

II. RESEARCH METHODOLOGY 

The evaluation procedure was created after researching 

the scientific base of BPM, i.e., the process life 

cycle, classifications of processes, and the practical 

base, i.e., how BPM is understood by companies, 

why companies initiate BPM, why BPM projects fail 

or don’t live up to the expectations. This knowledge 

provides the foundation for realizing the steps that 

are important for evaluation of BPMS. Then, each 

step of the evaluation procedure was investigated in 

order to define requirements to BPMS. Classification 

of processes was analysed in order to define specific 

requirements for each process type. The state-of-theart 

about the scientific background was acquainted 

by literature study, web-articles and white papers in 

the BPM field (for instance, [1]). Survey reports such 

as [2] and interviews with companies in Austria held 

by the authors of this paper provided the up-to-date 

view on problems considered in literature. 

The Papyrus platform was evaluated according to 

the developed procedure. Sources such as Papyrus’ 

documentation [4], workshops and discussions with 

the Papyrus team as well as partial scenario implementation 

were used for evaluation. 

III. RESEARCH RESULTS 

A. EVALUATION PROCEDURE FOR BPMS 

The developed evaluation procedure includes the 

following steps: 

1. Process life cycle support 

2. BPM values support 

3. Infrastructure requirements fulfilment 

4. Fulfilment of the requirements to different 

process types 

5. Best practices support and failure avoidance 

Each step is provided either with a chosen structure 

for evaluation (the first step) or a developed evaluation 

schema with requirements (other steps). 

The process classification for the step 4 is based 

on [2] and [3].

B. ASSESSMENT RESUTLS FOR THE PAPYRUS 

PLATFORM 

Papyrus’ approach is evaluated as very valuable for 

process life cycle support because it brings user experience 

into the system, is not restricted by modelling 

elements and lets optimize a process almost 

without human participation. Nevertheless, graphic 

representation of processes as well as optimization 

results are not visible explicitly. This, however, is 

essential for a company especially while optimization 

is not empowered with a collection of process targets. 

The Papyrus platform is assessed as oriented on 

bringing such values as cross-enterprise process 

support, agility of process changes and decreasing 

process cycle times by automating a part of the process 

and providing operational decision support as 

well as by supporting tasks delegation and removing 

delays when handed off from person to person. See 

“Figure 1”for details. 

Figure 1: BPM values support by Papyrus 

According to the evaluation, the platform is flexible 

enough, reliable and secure, and fulfils mandatory 

infrastructure requirements. 

The system suits for managing people- and document-intensive 

processes as well as for sequential 

workflow and content approval scenarios. It has good 

chances to be successful during competitions with 

other BPMS for managing these process types. 

Decision-intensive processes can be basically supported 

by Papyrus. Nevertheless, the platform is not 

empowered to support such kind of processes in the 

best way as it doesn’t provide decision support on the 

basis of business data analysis. 

Papyrus’ approach, having a state-based concept, 

is potentially very powerful for case management of 

complex processes. This could be Papyrus’ unique 

niche as typical workflow modeling BPMS must 

58 

have failed to support such kind of processes. But no 

tries have been yet undertaken to explore how system 

would operate practically under such conditions. 

See support of different process types by Papyrus 

on “Figure 2”. 

Figure 2: Different process types support by Papyrus 

The Papyrus platform with the UTE concept is especially 

efficient for: 

� Processes with high reusability of actions 

� Process flow based on documents content 

� Large enterprises with several employers having 

the same functional role 

� Processes where staff changes often or employers 

haven’t enough experience 

Since UTE is basically an approach based on inductive 

learning, the drawback of the approach is that it 

only works if enough examples exist for learning. 

Not sufficient process visibility and complexity of 

the design and deployment procedure make the platform 

not a perfect system. Nevertheless, this platform 

has a potential to avoid some failures and supports 

multiple BPM best practices. 

The analysis described in this paper was carried 

out in the master thesis and presented at Papyrus. 

REFERENCES 

[1] H. Smith, P. Finger, “Business Process Management: 

The Third Wave”, 2003. 

[2] Forrester company, www.forrester.com, the Forrester 

Wave reports concerning BPM. 

[3] Macehiter Ward-Dutton company, N. Ward- 

Dutton, report “Business process management: 

beyond technology”, December 2007. 

[4] ISIS Papyrus company, www.isis-papyrus.com, 

technical and marketing documentation.

Motor task-induced modifications of multiple spinal cord reflexes 

Ursula S. Hofstoetter, Josef Ladenbauer, Karen Minassian, 

Milan R. Dimitrijevic and Frank Rattay 

Institute of Analysis and Scientific Computing 



ursula.hofstoetter@gmail.com 

Abstract — Dynamic regulation of reflexes controlled 

by the central nervous system plays an integral 

part in neurocontrol of locomotion. Such modifications 

of sensory-motor transmission can be 

studied by conditioning a test reflex with specific 

motor tasks. In the present study, we applied a 

novel transcutaneous spinal cord stimulation (tSCS) 

technique to elicit short-latency test reflexes in 

several lower limb muscles simultaneously. During 

3 different conditioning-test paradigms in healthy 

subjects we could demonstrate that the monosynaptic 

test reflexes can be characteristically modulated 

during the execution of postural maneuvers. 


Since successful limb movement depends on effective 

interaction of sensory flow with motor plans, the 

central nervous system control of somatosensory 

transmission is an essential element for neural control 

of locomotion. For its assessment, conditioning-test 

paradigms utilizing the monosynaptic H reflex are 

commonly used [1]. However, elicitation of H reflexes 

from periphery is methodologically difficult to 

be obtained under constant stimulation conditions, 

especially during movement at the stimulation site. 

Recently we described a non-invasive method of 

tSCS effective to simultaneously elicit reflex responses 

in multiple lower limb muscles [2]. According 

to the initiation (posterior roots) and recording 

sites (surface of a muscle) these responses were 

named posterior root-muscle reflexes (PRM reflexes). 

PRM reflexes elicited by single stimuli were 

shown to be segmental monosynaptic reflexes [3]. 

We will demonstrate that PRM reflexes can be 

elicited in upright standing healthy subjects and used 

to assess the central gain control of short-latency 

reflexes at multiple segmental levels simultaneously. 

II. MATERIAL AND METHODS 

− Subjects: 

Three men with intact nervous system were recruited. 

The stimulation and recording protocols used 

59 

in this manuscript were approved by the local ethics 

committee. 

− Stimulation and recording set-up: 

tSCS was applied through surface stimulation electrodes 

placed over T11-T12 vertebral processes, with 

the indifferent electrodes over the abdomen. A constant-voltage 

stimulator was used to generate symmetric, 

biphasic rectangular pulses with widths of 2 

ms. For details see [2]. 

Electromyographic (EMG) activity was recorded 

with surface electrodes placed over bilateral quadriceps 

(Q), hamstrings (Ham), tibialis anterior (TA), 

and triceps surae (TS). 

− Study protocol: 

PRM reflexes (> 100 μV) were elicited at 0.2 Hz 

in all muscles with subjects in a standing position. 

Recordings started with 5 unconditioned PRM reflexes, 

followed by 5 responses modified by one of 

three different motor tasks: volitional unilateral dorsiand 

plantar flexion; volitional unilateral hip and knee 

flexion-extension; leaning backward/forward. 

− Data analysis: 

The amplitudes of the 5 unconditioned and the 5 

conditioned PRM reflexes were averaged. The mean 

conditioned responses were then normalized with 

respect to the unconditioned ones. 

III. RESULTS 

PRM reflexes could be elicited in all studied muscles 

while subjects were standing upright. 

As shown in Figure 1, ankle dorsiflexion distinctly 

suppressed the ipsilateral Ham and TS responses and 

facilitated the ipsilateral Q response. PRM reflexes 

showed modifications during ankle plantar flexion, 

without an overall tendency towards either facilitation 

or suppression. 

Figure 2 illustrates that Ham and TS responses of 

the moving lower limb were always distinctly suppressed 

during both flexion and extension phases of a 

volitional unilateral multi-joint movement. Attenuation 

of PRM reflexes in Ham and TS was more profound 

during flexion than extension phases.

Figure 1: (A) dorsi- and plantar flexion; (B) hip 

and knee flexion-extension. 

Leaning backward resulted in reduced Ham and 

TS response magnitudes and facilitation of Q (Figure 

3, A). Leaning forward led to the facilitation of Ham, 

TA, and TS (Figure 3, B). 

Figure 3: leaning (A) forward; (B) backward. 

60 

IV. DISCUSSION 

PRM reflexes were generally modified in a way to 

functionally meet the requirements of a particular 

motor act: For example, dorsiflexion suppressed the 

ankle and hip extensor responses and at the same 

time facilitated the relevant flexors Q and TA. 

Volitional multi-joint movements at the hip and 

knee joints reduced the response magnitudes of Ham 

and TS during flexion and extension with different 

degrees of attenuation. Hence, mechanisms underlying 

the reflex modulation do not solely hinge on 

muscle stretch and joint position but also on the 

motor task setting the role of a particular muscle. 

Leaning backward requires contraction of Q and 

TA to maintain equilibrium, as accordingly revealed 

by our tests. PRM reflexes of Ham and TS, two muscles 

that are quiescent during this task, were suppressed, 

hinting on ‘active’ inhibition. 

Leaning forward is normally accompanied by activation 

of Ham and TS to avoid falling, as detected in 

our recordings. Additionally, we found facilitation of 

TA, probably due to the necessity to increase the 

stiffness of the ankle joint for stabilization. 

The presented approach opens a new avenue to 

study how motor control is triggered and maintained 

in individuals with intact or altered nervous system 

functions. Apart from the basic sciences value of 

studying human motor control, the assessment of 

postural capacities and volitional movements will be 

crucial to design rehabilitation strategies in people 

with different neurological disorders. 


This study was supported by the Wings for Life 

Spinal Cord Research Foundation, Proj.Nr. 

WFL-FR-001/06, and the Austrian Science 

Fund (FWF), Vienna, Austria, Proj. L512-N13. 

REFERENCES 

[1] Schieppati M. The Hoffmann reflex: a means of 

assessing spinal reflex excitability and its descending 

control in man. Prog Neurobiol 1987; 

28: 345-376. 

[2] Minassian K, Persy I, Rattay F, Pinter MM, Kern 

H, Dimitrijevic MR. Human lumbar cord circuitries 

can be activated by extrinsic tonic input to 

generate locomotor-like activity. Hum Mov Sci 

2007; 26: 275-295. 

[3] Minassian K, Persy I, Rattay F, Dimitrijevic MR, 

Hofer C, Kern H. Posterior root-muscle reflexes 

elicited by transcutaneous stimulation of the human 

lumbosacral cord. Muscle Nerve 2007; 35: 

327-336.

Approach for a Reliable Cooperative Relaying Process 

Melanie Schranz and Wilfried Elmenreich (Faculty Mentor) 

Lakeside Labs/Institute for Networked and Embedded Systems 

University of Klagenfurt 

Klagenfurt, Austria 

Email: {melanie.schranz,wilfried.elmenreich}@uni-klu.ac.at 

Abstract — Cooperative relaying is a method, where nodes 

overhearing a communication help in forwarding this information 

in case the direct transmission between source and destination 

fails. In this paper we present a communication protocol 

based on cooperative relaying employing a TDMA relay selection 

and exchange of short control messages. To show its applicability, 

we implemented the described protocol on the wireless 

platform WARP as our testbed. 


Nowadays wireless networks form a powerful area that 

cannot be neglected. Primarily the task of these wireless 

networks is to deliver data, whether it is about music, 

videos, sensor data or any other information. A major 

question is, if the data packets reliably reach its destination 

in a wireless network. With applications such as 

voice communication or distributed sensing and control, 

reliable communication plays a decisive role. 

Wireless links typically suffer from effects such as 

shadowing and fading, where the latter typically can 

cause a wireless link to be unavailable for several 100 

milliseconds. Within this timespan, retransmission attempts 

issued by the source will very likely have no success. 

A transmission via a spatially different path, however, 

is typically not affected by the same fading problems 

at the same time. Thus the concept of cooperative 

relaying, where a relay node is assisting the communication 

between a source and a destination node [1], can 

greatly improve the reliability of wireless communication. 

Within the scope of this paper, we consider an approach 

where the relay node only forwards information 

in the case the direct transmission between source 

and destination fails (in contrast to relaying networks in 

many telecommunication applications, where the relays 

are used to extend the transmission range via a multi-hop 

approach). 

In this paper we present a cooperative relaying approach 

for improving a wireless multi-hop communication. 

Besides elaborating the protocol the intention is to 

evaluate it on a wireless platform called WARP, which 

is a universal multiple-input multiple-output wireless test 

platform controlled by FPGA for maximum flexibility. 

The rest of the paper is structured as follows: Section 2 

introduces to cooperative relaying concepts in more detail. 

Section 3 describes a self conceived simple relaying 

approach for 802.11-based networks while Section 4 delineates 

the hardware testbed we are using to implement 

61 

the concepts depicted in Section 3. In the end we give a 

conclusion and an outlook to future work. 

II. COOPERATIVE RELAYING 

The term ”cooperative relaying” was already explained in 

the introduction. The major advantage of using a relayed 

communication channel is that it raises the capacity of 

the network by implementing spatial diversity [1]. This 

spatial diversity establishes several independent communication 

paths. Researches on Multiple Input Multiple 

Output (MIMO) systems have depicted that the reliability 

of sending a data packet is enhanced the more independent 

paths are available [2]. 

Practically the simplest cooperative relaying network 

consists of three nodes, like shown in Figure 1. The 

source (S) has a direct communication (step 1) to destination 

(D). If the communication fails (steps 2 and 3) 

the relay (R) has to support D with information. 

Figure 1: Cooperative relaying scheme 

III. RELAYING APPROACH 

We propose the following possible solution to achieve an 

acceptable reliability in a wireless network: In case a 

packet is ready to send, the source S ”asks” the destination 

D via an RTS (ready to send) if a transmission is 

possible. When S receives a CTS (clear to send), as a 

next step it starts with the transmission. S gets an ACK 

(acknowledge) if all packets are received by D. In this 

(likely) case we have a successful direct communication 

like demonstrated in Figure 2. 

In the other case, so if a packet did not arrive, we have 

the situation illustrated in Figure 3. D sends a NACK(not 

acknowledge) to S and broadcasts a LOOKforGOODmessage. 

This message contains the header of the packet 

that could not be received. Attention should be paid to

Figure 2: Packet exchange scheme for successful direct 

transmission 

Figure 3: Packet exchange scheme for failed direct transmission 

the source S. In the case of a none received packet, also S 

works as a relay node as assistance for the data transmission. 

All the relay nodes (in our figure the situation 

is demonstrated with only one relay node R) look 

for the packet in their buffers. If the packet is in the 

buffer the relays send their ID (IDSENT) in an a priori 

defined TDMA schedule, so each node has its own 

time slot. In the next step D selects one relay node according 

to measures of the channel quality by sending a 

SELECT-message that contains the ID of the chosen relay 

node. The data will then be transmitted. In the case 

of an failed transmission again, the process would start 

once with choosing a relay node by sending a LOOKfor- 

GOOD message. 

The messages CTS, RTS, ACK, NACK, LOOKfor- 

GOOD, IDSENT and SELECT are coded with BPSK 

(Binary Phase-Shift Keying). These messages are considerably 

shorter than the data packet. The BPSK modulation 

scheme is less vulnerable to noise, so we assume 

that the control messages can be transmitted even 

in case of fading problems. The data packet is coded with 

16QAM (16 Quadrature Amplitude Modulation), which 

is more efficient than BPSK, but requires a better Signalto-Noise 

ratio than BPSK. 

IV. TESTBED 

To evaluate the described relay approach, we use a wireless 

platform called WARP board1 . The WARP board 

consist of a Virtex II Pro FPGA of Xilinx for the processing 

of the developed communication protocol, two 

radio boards for the transmission over radio frequency of 

1 For further information: http://warp.rice.edu 

62 

2.4 GHz, two antennas and respective circuitry needed 

for realizing a communication. Figure 4 depicts a WARP 

board, which has been set up to use both transmitters emulating 

two different wireless nodes. 

Figure 4: WARP-Board: Wireless platform for implementing 

the relay approach 

With these boards we have the possibility to modify 

physical layer as well as MAC layer. All programming 

work is done in C. With the comfortable detail of a serial 

output we have a chance to track the communication 

channel status with every sent packet for debugging 

purposes. Current test configuration consists of two 

WARP Boards, where each of the two wireless transmission 

units per board is programmed separately, forming a 

network of four logical nodes. 

V. CONCLUSION AND OUTLOOK 

The proposed protocol on the basis of cooperative relaying 

promises increased reliability for wireless networks 

by mitigating small-scale fading effects. A preliminary 

version of the protocol has been implemented 

on the WARP platform, but further tests have to be done 

to achieve expedient results. Though, for an efficient 

evaluation we are going to evaluate the approach on a 

larger wireless network. Further future work will also 

include researching alternative ways for relay selection, 

since the proposed TDMA approach comes with considerable 

complexity for large networks. 


This work was supported by the European Regional Development 

Fund and the Carinthian Economic Promotion 

Fund (KWF) under grant 20214/15935/23108 within the 

Lakeside Labs project. 

REFERENCES 

[1] W. Elmenreich, N. Marchenko, H. Adam, C. Hofbauer, 

G. Brandner, C. Bettstetter, and M. Huemer. 

Building blocks of cooperative relaying in wireless 

systems. Springer e&iJournal, October 2008. 

[2] H. Adam, W. Elmenreich, and S. M. Senouci. A protocol 

for cooperative relaying in wireless networks. 

submitted to EURASIP Journal on Wireless Communications 

and Networking, 2008.

Retrieval of Ocean Water Parameters from Satellite Imagery and 

their Dependence on Atmospheric Correction Models 

Rushane Dyer and Sam Ahmed (Faculty Mentor) 

Optical Remote Sensing Laboratory 

The City College of the City University of New York 

New York, USA 

Email: rdyer00@ccny.cuny.edu 

Abstract — Ocean color algorithms for the 

retrieval of chlorophyll [Chl] and mineral 

concentrations as well as water inherent optical 

properties (IOPs) from satellite reflectance 

spectra usually fail in coastal waters because of 

errors in atmospheric correction procedures. 

Recent advances in those procedures over coastal 

zones opened possibilities for more detailed 

studies of coastal areas using satellite imagery 

which includes analysis of spatial and temporal 

trends in [Chl]. We report on studies of MODIS 

data for various parameters for several years in 

Western, Central and Eastern areas of Long 

Island Sound using SeaDAS processing software 

and the SWIR and NIR atmospheric correction 

algorithms. Correlations between parameters 

retrieved using various procedures were 

calculated and analyzed. 


It is well known that in coastal regions the near infrared 

(NIR) atmospheric correction algorithm can be 

unreliable in the retrieval of parameters such as chlorophyll 

concentrations [Chl], inherent optical properties 

(IOPs) and fluorescence line height (FLH). This 

is typically due to the increase in elastic scattering of 

chlorophyll and minerals along the coast. In response 

to this problem the shortwave infrared 

(SWIR) atmospheric correction algorithm was introduced 

to be used in retrievals of ocean water parameters 

within coastal regions [1]. Generally, the SWIR 

algorithm has shown significant improvement over 

the NIR algorithm in remote sensing of coastal regions. 

Rather than just completely disregarding the 

use of the NIR algorithm along the coast, we have 

begun a thorough analysis of various parameters 

retrieved using both the NIR and SWIR algorithms 

for the region of Long Island Sound (LIS). We have 

quantified correlations between parameters retrieved 

with each algorithm and have determined the level of 

sensitivity these parameters have with respect to each 

atmospheric model. 

63 

II. SENSITIVITY OF THE RETRIEVALS 

To determine sensitivity of [Chl], FLH, and various 

other parameters to the atmospheric correction model 

we studied MODIS Aqua data of [Chl], FLH, absorption 

of colored dissolved organic matter (CDOM) 

and backscattering coefficient for several years for 

Western, Central and Eastern areas of Long Island 

Sound using SeaDAS processing software with standard 

NIR and recently developed SWIR atmospheric 

correction models [2]. The general idea is that high 

correlations between the retrieved parameters can be 

used as indicators of more accurate parameter retrieval. 

Figure 1 is a typical [Chl] map for the regions of 

LIS and NY Bight these were created for both NIR 

and SWIR models. Figures 2-3 show correlations 

between [Chl] and FLH for these 2 models. Current 

MODIS algorithms for [Chl] use wavelengths within 

the blue and green parts of the spectra, these areas are 

typically the most affected by atmospheric correction 

models. We can see that the correlation of retrieved 

[Chl] between these 2 models is extremely low, 

which is what we would expect. 

Figure 1: [Chl] map for LIS

Figure 2: Correlation between [Chl] 

Figure 3: Correlation between FLH 

Correlation between FLH, on the other hand, is 

very good. The current FLH algorithm uses wavelengths 

in the near infrared region of the spectra, it 

also uses the difference between reflectances to calculate 

its values, which is less sensitive to atmospheric 

models than ratio algorithms such as that of 

[Chl]. This analysis has been extended to parameters 

such as backscattering bb(551) and CDOM absorption 

at 412 nm ay(412) 


This work was supported by grants from NASA, 

NOAA and Office of Naval Research. 

REFERENCES 

[1] M. Wang, "Remote sensing of the ocean 

contributions from ultraviolet to nearinfrared 

using the shortwave infrared bands: 

simulations," Appl. Opt. 46, 1535-1547 

(2007) 

[2] S. Ahmed, A. Gilerson, J. Zhou, R. Dyer, S. 

Hlaing, I. Ioannou, B. Gross, F. Moshary," 

Untangling the Make-up of the NIR Reflectance 

Peak in Coastal Waters and its Impact 

64 

on Remote Sensing Retrievals of [Chl] and 

Fluorescence Height Algorithms,” Proc. of 

SPIE 7105, Remote Sensing of the Ocean, 

Sea Ice, and Large Water Regions 2008.

Fast Packet Classification Algorithm in Hardware 

Abstract — Packet classification is an important operation 

for applications such as routers, firewalls or intrusion detection 

systems. Many algorithms and hardware architectures for 

packet classification have been created, but none of them can 

compete with the speed of TCAMs in the worst case. I propose 

new hardware-based algorithm for packet classification. The 

solution is based on problem decomposition and is aimed at 

the highest network speeds. A unique property of the algorithm 

is the constant time complexity in terms of external memory accesses. 

The algorithm performs exactly two external memory 

accesses to classify a packet. Using FPGA and one commodity 

SRAM chip, a throughput of 150 million packets per second can 

be achieved. 


A classification algorithm contains a set of rules ordered 

by priority. Each rule defines a condition for all significant 

packet header fields. These fields are typically: 

Source IP Address, Destination IP Address, Source Port, 

Destination Port, Protocol. A condition may be exact 

match, prefix match (usually for IP addresses), range 

match (for ports), or a wildcard (matching any value). 

The goal of a packet classification algorithm is to find 

the matching rule with the highest priority. The output of 

the algorithm is then the number of the matched rule. 

The traditional method of classifying packets 

makes use of Ternary Content Addressable Memories 

(TCAMs). However, the TCAM is an expensive device 

with high power-consumption [1]. Therefore, algorithmic 

solutions without the use of TCAMs has become 

a research subject. I propose a new packet classification 

method which uses SRAM to store necessary data, and 

FPGA to implement the algorithm. I will show that my 

solution is fully competitive to TCAM. 

II. RELATED WORK 

As the packet classification problem is inherently hard 

from a theoretical standpoint [2], a large number of hardware 

and software solutions [3, 4] have been proposed. 

From the wide choice of available algorithms, I discuss 

only those which are related to my work. All of them 

belong to the family of decomposition-based methods. In 

decomposition methods, packet classification is divided 

into several steps. First step is the Longest Prefix Match 

(LPM) operation, which is performed independently in 

Viktor Puˇs andJanKoˇrenek (Faculty Mentor) 




Email: {ipus,korenek}@fit.vutbr.cz 

65 

each packet header field. Range conditions (such as port 

ranges) in the ruleset are converted to prefixes, so that 

LPM may be performed in all packet header fields. LPM 

operation is performed in IP packet routing, so it is well 

studied topic. Popular example of such algorithm is Tree 

Bitmap [5], but there are also many other solutions [6]. 

The next step is the search process, mapping LPM results 

to the correct rule number. This is the specific part 

of each decomposition-based method. 

III. ALGORITHM 

I propose a novel high-speed hardware-suited packet 

classification algorithm, which has a modular design and 

removes the performance drawbacks of existing solutions. 

The algorithm consists of LPM for rule fields followed 

by a mechanism to search a rule. LPM and the 

rest of the classification algorithm have a very simple 

unidirectional interface and both parts may be changed 

separately, when a better solution is available. Recent 

research results for LPM operation have outstanding results 

even over 100 Gbps [6], therefore I do not propose 

any new architecture for LPM and focus on the rule 

searching mechanism. 

The primary goal is to find a solution with the constant 

packet rate and a good scalability with the size of the rule. 

Therefore, I propose to use a perfect hashing mechanism 

to provide the Rule Table search in a constant time and 

utilize the off-chip memory to store Perfect Hash Table. 

The perfect hash function must find a correct rule number 

for every packet. Thanks to LPM used in the first step, 

the packet state space is reduced significantly. The hash 

table is stored in the off-chip memory and its construction 

was described in [7]. 

The last part of the algorithm is the comparison of 

the rule to corresponding packet header fields. As high 

throughput memory is needed to read a rule, the Rule Tableisstoredinon-chipmemories. 

IV. RESULTS 

The proposed algorithm was implemented in FPGA and 

utilizes one external static memory. I have studied several 

rulesets to get information about typical properties 

of rules, and similarly to [4] have found that the number 

of unique prefixes in each field is usually quite small. 

Therefore, the data structures for LPMs may be easily

stored in small on-chip memories, either BlockRAMs or 

distributed memories. Also the Rule Table itself is not 

greater than a few kilobytes, so the external memory is 

not needed for its storage. But the Perfect Hash Table 

may become large, therefore, I propose to use an external 

memory to store it. 

The proposed solution significantly reduces bottleneck 

caused by the speed of external memory. Only two 18-bit 

words need to be read for every packet, which is many 

times less than one whole rule (or even worse, several 

rules, [3]). Moreover, performance of the algorithm is 

not affected by the complexity of rules. Other fields (i.e. 

MAC addresses, TCP flags, etc.) can be added to rules 

and the throughput remains the same, only on-chip Rule 

Table size increases linearly. It means that the solution 

scales well with the rule size. 

Supposing 300 MHz DDR memory with the burst 

length of two words, throughput of the solution is always 

constant – 150 million packets per second for this particular 

memory. 

A. MEMORY REQUIREMENTS 

I have performed perfect hash function search for several 

rulesets from university campus network (fw) together 

with several synthetic ruleset generated by ClassBench 

[8] (synth) to determine off-chip memory requirements. 

Memory requirements are shown in Table 1. 

Ruleset Rules Memory 

fw1 32 740 

fw2 58 3 424 

fw3 171 116 356 

synth1 40 2 740 

synth2 49 5 035 

synth3 70 2 451 

synth4 100 3 827 

Table 1: Off-chip memory requirements (in Bytes) for 

several rulesets. 

The on-chip memory for my solution consists of two 

basic parts: LPM, which may be the same for all 

crossproduct-based methods, and Rule Table, which may 

be compressed with a simple prefix indexing scheme to 

less than a half of its original size. 

V. CONCLUSION 

I have proposed a novel algorithm for fast packet classification 

using perfect hash functions. The algorithm introduces 

perfect hash functions to packet classification. By 

creating custom hash function, I make sure that all packets 

are hashed to associated rule. Because only two ex- 

66 

ternal memory accesses are needed to classify a packet, 

150 million packets per second can be processed with 

commodity FPGA and SRAM. Therefore, up to 48 Gbps 

throughput can be achieved for the smallest (40 B) packets. 

Moreover, the throughput does not depend on ruleset 

complexity and is well scalable with number of external 

memories. 

According to my knowledge, the proposed algorithm 

is the first algorithm which requires reasonable amount 

of memory and has constant processing time even for 

complex ruleset. High throughput together with constant 

processing time makes the proposed algorithm fully 

competitive to widely used TCAM solutions. As the proposed 

solution uses commodity SRAM, the price and 

power consumption is significantly lower than classification 

with TCAM memory. 

REFERENCES 

[1] IDT Generic Part: 75K72100. 

http://www.idt.com/?catID=58523&genID=75K72100 

, June 2008. 

[2] F. Baboescu, S. Singh, and G. Varghese. Packet classification 

for core routers: Is there an alternative to 

CAMs? In INFOCOM, 2003. 

[3] Sarang Dharmapurikar, Haoyu Song, Jonathan 

Turner, and John Lockwood. Fast packet classification 

using Bloom filters. In ANCS ’06: Proceedings 

of the 2006 ACM/IEEE symposium on Architecture 

for networking and communications systems, pages 

61–70, New York, NY, USA, 2006. ACM. 

[4] D. Taylor and J. Turner. Scalable packet classification 

using distributed crossproducting of field labels. 

In IEEE INFOCOM 2005, 24th Annual Joint Conference 

of the IEEE Computer and Communications 

Societies., pages 269–280, July 2005. 

[5] Will Eatherton, George Varghese, and Zubin Dittia. 

Tree bitmap: hardware/software IP lookups with incremental 

updates. SIGCOMM Computer Communication 

Review, 34(2):97–122, 2004. 

[6] H Lee, W Jiang, and V K Prasanna. Scalable 

High-Throughput SRAM-Based Architecture for IP 

Lookup Using FPGA. In FPL ’08. IEEE, 2008. 

[7] Zbigniew J. Czech, George Havas, and Bohdan S. 

Majewski. An optimal algorithm for generating minimal 

perfect hash functions. Information Processing 

Letters, 43(5):257–264, 1992. 

[8] David E. Taylor and Jonathan S. Turner. Classbench: 

a packet classification benchmark. IEEE/ACM 

Trans. Netw., 15(3):499–511, 2007.

Radiation of Antenna Array in Near-field Area 

Ji�í Hermany, Zden�k Nová�ek (Faculty Mentor) 



Brno, Czech republic 

Email: xherma09@stud.feec.vutbr.cz, novacek@feec.vutbr.cz 

Abstract — The goal of this work is to analyze the 

radiation of antenna array computation methods 

and then to produce the radiation of antenna array 

computation program. The program can display the 

electrical and magnetical intensity and power density 

distribution over the planar or cylindrical surface 

in the near-field area. The aim of this paper is 

to propose some steps which were needed for building 

this program up. 


There is a description of a computation method of 

antenna array radiation in this paper. The values of 

an electrical and magnetical intensity or power density 

distribution of an electric dipole can be evaluated. 

II. THEORY 

The antenna array analyzed in this paper consists of a 

number of elementary dipoles placed in a row. A part 

of the antenna array is also a reflector which represents 

the conductive board situated in parallel to the 

row of dipoles. 

A. ELECTROMAGNETIC FIELD INTENSITY 

COMPUTATION 

The electromagnetic field radiated in the elementary 

dipole near-field area can be computed using the 

vector equations (1), (2) and (3) [1]. Its products are 

the vectors of the electrical and magnetical intensity 

and the power density in any chosen point in a space 

positioned in the near-field area. 

When the dipole and the measuring point positions 

are known it is possible to evaluate the electrical and 

magnetical intensity using equations 

� � � 

� 3 

�� 

� � � � 

k r0 

� ( r0 

� d s0 

) 3( 

r0 

� d s0 

) � r0 

� d s0 

E � � j � � 

2 2 

4�� (1) 

�� 

k r 

� 

k r 

� � � � 

3( 

r0 

� d s0 

) � r0 

� d s0 

� 

� 

� j�t 

� j 

e , 

3 � 3 � 

k r �� 

� j� 

� 1 jk � � 

� j�t 

� 

H � � e � � �d 

0 r0 

, 

2 

s � 

(2) 

4� 

� r r � 

� � 

67 

where k = 2� /� is a wave number, ds is a position of 

a dipole centre, ds0 is a dipole’s orientation and r0 is a 

vector from the dipole D to the point P (Figure 1). 

Figure 1: Point P position with regard to the position 

and orientation of dipole D 

From the values of the electrical and magnetical 

intensity vectors can be computed a power density 

vector 

* 

E H . 

(3) 

� � � 

� � � 

When the radiation values of all dipoles are 

known, it is needed to sum up the radiation elements 

of all parts of the antenna array. The reflector effect 

can be substituted by the radiation of a dipole situated 

behind the reflector which is driven by the same 

valued but inverse phased current. 

Then the radiation elements of this so-called mirrored 

dipoles are added to radiation elements of the 

dipoles in front of the reflector. 

B. SURFACES 

The next step is to define a suitable group of points 

where the electromagnetic field values will be computed. 

The basic idea is that the dipole row with the 

reflector (the antenna array) is situated in the centre 

of the Cartesian coordinate system when the reflector 

lies even with the z axis of the coordinate system. 

The first group of the suitable points in space is the 

planar surface, which is defined by its position and 

orientation with regard to the antenna array position 

and orientation. The second one is the cylindrical 

surface where the cylinder axis lies even with the z 

axis of the Cartesian coordinate system. 

Then the values of the electromagnetic field are 

computed for every point of the planar or the cylindrical 

surface.

Figure 2: Cylindrical surface with the four dipole 

antenna array in the Cartesian coordinate system 

In the Figure 2 is shown the position of the cylindrical 

surface, where the electromagnetic field intensity 

distribution is computed, regarding to dipole 

antenna array with the reflector. Similarly there can 

be the planar surface. 

C. PROGRAM 

The program for the computation of the electromagnetic 

field distribution was built in MATLAB with 

GUI (graphic user interface). It allows not only computing 

but also displaying the distribution of the 

electrical and magnetic intensity and the power density 

components of antenna array radiation on the 

planar or the cylindrical surface. 

The components can be x, y, z (for Cartesian coordinate 

system), r, �, z (for cylindrical coordinate 

system) or r, �, � (for spherical coordinate system). 

The program also allows saving computed values to 

files, saving displayed graphs as pictures, or saving 

the adjusted parameters of antenna array and/or the 

selected surface. 

Figure 3: Demonstration program window 

68 

There is a screenshot of the program window in the 

Figure 3. It allows setting the parameters of the antenna 

array under test (number of the dipoles and 

their positions and orientations) and the dimensions 

and resolution of the selected surface, where the 

electromagnetic intensity distribution will be computed. 


The program allows displaying the computed electromagnetic 

filed intensity distribution of the dipole 

antenna array on the selected planar or cylindrical 

surface. It is also possible to find out the computed 

values in concrete points from the displayed intensity 

distribution and to export computed data to graphic 

or data files. 

The created program can be used for the presentation 

of the antenna array radiation in a university 

laboratory or for the graphical representation when a 

new antenna is designed. 

REFERENCES 

[1] STRATTON, J. A.: Teorie elektromagnetického 

pole. SNTL, Praha 1961, 592 s. 

[2] �ERNOHORSKÝ, D., TICHÝ, J.: Vyza�ování a 

ší�ení rádiových vln, II. Díl Antény. Vojenská 

akademie Antonína Zápotockého, 1977. 

[3] NOVÁ�EK, Z.: Elektromagnetické vlny, antény 

a vedení. Elektronické skriptum. Brno: VUT, 

FEKT, 2003, 135 s.

Ontology- and Bayesian-based 

Threat Probability Determination 

Stefan Fenz and A Min Tjoa (Faculty Mentor) 




Email: {fenz,tjoa}@ifs.tuwien.ac.at 

Abstract — Information security risk management is crucial 

for ensuring long-term business success and thus numerous 

approaches to implementing an adequate information security 

risk management strategy have been proposed. The subjective 

threat probability determination is one of the main reasons for 

an inadequate information security strategy endangering the 

organization in performing its mission. To address the problem 

this research project proposes an ontology- and Bayesianbased 

approach for determining asset-specific and comprehensible 

threat probabilities. The elaborated concepts enable risk 

managers to comprehensibly quantify the current security status 

of their organization. 

I. THE SECURITY ONTOLOGY 

A conceptual and formal model of information security 

is required for supporting the threat probability determination 

in the information security risk management process. 

Ontologies are one possibility for modeling the information 

security domain in order to make it accessible 

to machines. Therefore, the security ontology [1, 2, 3] 

was proposed based on the security relationship model 

described in the National Institute of Standards and Technology 

Special Publication 800-12. Figure 1 shows the 

high-level concepts and corresponding relations of our 

ontology. A threat gives rise to follow-up threats, represents 

a potential danger to the organization’s assets and 

affects specific security attributes (e.g. confidentiality, 

integrity, and/or availability) as soon as it exploits a vulnerability 

in the form of a physical, technical, or administrative 

weakness, and it causes damage to certain assets. 

Additionally each threat is described by potential 

threat origins (human or natural origin) and threat sources 

(accidental or deliberate source). For each vulnerability 

a severity value and the asset on which the vulnerability 

could be exploited is assigned. Controls have to be 

implemented to mitigate an identified vulnerability and 

to protect the respective assets by preventive, corrective, 

deterrent, recovery, or detective measures (control type). 

Each control is implemented as asset concept, or as combinations 

thereof. Controls are derived from and correspond 

to best-practice and information security standard 

controls. To enrich the knowledge model with concrete 

information security knowledge the German IT Grundschutz 

Manual is superimposed on the security ontology 

and more than 500 information security concepts and 600 

69 

corresponding formal axioms are integrated into the ontological 

knowledge base. The controls are modeled on 

a highly granular level and are thus reusable for different 

standards. When implementing the controls, a compliance 

with various information security standards is implicit. 

The coded ontology follows the OWL-DL (W3C 

Web Ontology Language) standard and ensures that the 

knowledge is represented in a standardized, formal, and 

therefore machine-interpretable form. 

Control Type 

of Type implemented by 

threatens gives rise to affects 

Standard Control Control 

Severity Scale 

corresponds 

to 

Organization 

owned 

by 

requires 

Asset 

vulnerability on 

requires Level 

mitigated by exploited by 

Vulnerability 

has severity 

Threat 

Figure 1: Security relationships 

has 

source 

has origin 

Security Attribute 

Threat Source 

Threat Origin 

II. BAYESIAN THREAT PROBABILITY DE- 

TERMINATION 

This section aims at describing the connection to the security 

ontology framework, which provides a foundation 

to enrich the Bayesian network with concrete knowledge. 

Since the security ontology provides detailed knowledge 

about threat, vulnerability, and control dependencies, this 

knowledge could be utilized to build up the Bayesian network 

for the threat probability determination. Figure 2 

gives an overview of the connections between the proposed 

Bayesian threat probability determination and the 

security ontology. It is assumed that each node has exactly 

one of a finite set of probability states (expressed as 

a vector, representing the probability distribution among 

distinct states, e.g. high, medium, and low). Since the 

threat probability or influencing factors cannot be determined 

quantitatively, a qualitative rating is used in this 

approach. For each variable a three-point Likert scale 

was defined to capture the subjective impressions on the 

input variables and to represent the results on the intermediate 

and output variables. 

First of all, the approach has to set up a threat net, in-

Threat Ti 

Probability PPTi 

sec:canBeConsequenceOf 

Threat ST1Ti 

Probability PPST1Ti 

sec:exploits 

…. 

Threat Ti 

Probability PPTi 

Vulnerabilities VSTi 

Exploitation Probability 

PPVSTi 

Threat PTnTi 

Probability PPPTnTi 

... 

WPPVSTi 

Threat PT1Ti 

Probability PPPT1Ti 

Threat STnTi 

Probability PPSTnTi 

WPTnTi 

WPT1Ti 

Vulnerability V1 


PPV1 

….. 

Vulnerability Vn 


PPVn 

sec:givesRiseTo 

WPPV1 

WPPVn 

WCE1 

Control 

Implementation 

Effectiveness CE1 

sec:implementedBy 

sec:mitigatedBy 

…. 

Control Combination 

Effectiveness CCEVi 

Vulnerability Vi 


PPVi 

Attacker Motivation 

AMVi 

WCEn 

Control 

Implementation 

Effectiveness CEn 

WCCEVi 

WPPVi 

WACVi 

Attacker Capability 

ACVi 

WAMVi 

Threat Ti 

A Priori Probability 

APTi 

V 

WAPTi 

WAEVi 

Attacker Effectiveness 

ΑEVi 

Figure 2: Utilizing the security ontology for the Bayesian 

threat probability determination 

cluding the relations between the threats and their a priori 

threat probability. Since each threat modeled in the security 

ontology is connected by the relation sec:givesRiseTo 

to follow-up threats (see Figure 2) the corresponding 

threat net can easily be created. The a priori threat proba- 

bility vector � 

APTi for each threat Ti is also derived from 

the security ontology, depending on the actual physical 

location of the organization. The sec:Probability concept 

and the sec:probabilityDistribution property of the 

security ontology connect each threat of a given physical 

location with its a priori probability. Weights for all 

threat probability influencing factors (influencing threats 

and vulnerabilities) are distributed equally. 

For each threat the approach has to determine the corresponding 

vulnerabilities. In the security ontology this 

relationship is modeled by the sec:exploits relation which 

allows revealing the vulnerabilities of a given threat. As 

the vulnerabilities vector � PPVST is determined by sin- 

i 

gle vulnerabilities and their weights, the weight of each 

vulnerability which influences the intermediate vulnerabilities 

vector � PPVST was determined. Since the secu- 

i 

rity ontology provides a severity rating SVi for each vul- 

ontology regarding those control implementations effectiveness 

values which are relevant for the considered asset/vulnerability 

combination. 

With the security ontology relation sec:mitigatedBy 

(see Figure 2) the required control implementation combination 

which is necessary to mitigate the given vulnerability 

can be derived. Since each implementation 

in the recommended control combination has a different 

effectiveness � CEi, the weight WCEi differs dependently 

on the implementation’s importance for the current 

control combination. The security ontology concept 

sec:ControlImplementation represents the effectiveness 

for each control/implementation combination � CEi by a 

three-point Likert scale (high, medium, low). 

III. RESULTS 

The question is if the proposed Bayesian threat probability 

determination is the solution to the fundamental information 

security risk management problem, namely disposing 

of realistic probability values. The answer is neither 

yes nor no. The advantage of the proposed Bayesian 

threat probability determination is that it gives the risk 

manager a methodology to determine the threat probability 

in a structured and, by incorporating the security 

ontology, comprehensible way. The calculation schema 

is fully documented and each state of the Bayesian network 

can be explained and justified mathematically and 

formally taking the given input factors into consideration. 

However, the high dependence on realistic input values 

requires further research on sound methods to gather, 

store, and provide these crucial threat probability calculation 

components. 

REFERENCES 

nerability (high (3), medium (2), and low(1)), a numerical 

weight WPPV for each vulnerability can be deter- 

i 

mined by dividing the severity of the considered vulnerability 

by the severity sum of all vulnerabilities relevant 

SV 

to the threat: WPPV = � i 

n 

i 

j=1 SVj The exploitation probability of each vulnerability variable 

is determined by (1) the effectiveness of the implemented 

control combination � CCEVi , (2) the attacker’s 

effectiveness � AEVi in the case of a deliberate threat 

source or by the a priori threat probability � APTi in the 

case of an accidental threat source. By default all components, 

namely � CCEVi , � AEVi , and � APTi , are weighted 

equally. While the attacker’s effectiveness � AEVi and 

[1] Andreas Ekelhart, Stefan Fenz, Markus Klemen, and 

Edgar R. Weippl. Security ontology: Simulating 

threats to corporate assets. In A. Bagchi and V. 

Atluri, editors, Information Systems Security, Second 

International Conference, ICISS 2006, volume 

4332/2006 of Lecture Notes in Computer Science, 

pages 249–259, Kolkata, India, December 2006. 

Springer Berlin / Heidelberg. 978-3-540-68962-1. 

[2] Andreas Ekelhart, Stefan Fenz, Gernot Goluch, and 

Edgar Weippl. Ontological mapping of common 

criteria’s security assurance requirements. In H. 

Venter, M. Eloff, L. Labuschagne, J. Eloff, and R. 

von Solms, editors, Proceedings of the IFIP TC 11 

22nd International Information Security Conference, 

IFIPSec 2007, pages 85–95, Sandton, South Africa, 

May 2007. IFIP. 978-0-387-72366-2. 

[3] Thomas Neubauer, Andreas Ekelhart, and Stefan 

Fenz. Interactive selection of ISO 27001 controls under 

multiple objectives. In Proceedings of the IFIP 

the a priori threat probability � APTi are not rated on an TC 11 23rd International Information Security Con- 

asset-specific level, the control combination effectiveness ference, IFIPSec 2008, pages 477–492, Boston, July 

� 

2008. Springer. 

CCEVi is determined specifically for the considered asset. 

Therefore, reasoning algorithms query the security 

70

Development of Multi-Core Video Decoding Platforms based on 

High-Level Architecture Simulations 

Florian Seitner, Michael Bleyer (Faculty Mentor) and Margrit Gelautz (Faculty Mentor) 




Email: {seitner, bleyer, gelautz}@ims.tuwien.ac.at 

Abstract — The high computational demands of state-of-theart 

video coding standards pose serious challenges on strongly 

resource-restricted architectures. For reaching the performance 

specifications, specialized multi-core architectures for 

video processing are becoming more and more popular. In this 

work, we introduce an high-level simulator for supporting the 

development of such decoding platforms. Our system combines 

all available information such as hardware measurements, profilings 

and human expertise. Based on this input, the behaviour 

of the final architecture running a parallel video decoder is 

estimated. Using this information, adaptations of the current 

hardware or software design can be done. The simulator shall 

aid in developing efficient and application-optimized decoding 

systems. 


The H.264 video standard [1] is currently used in a wide 

range of video-related areas such as video content distribution 

and television broadcasting. Compared to preceding 

standards such as MPEG-2 and MPEG-4 SP/ASP, 

improved coding efficiency is reached by introducing 

more advanced pixel processing algorithms (e.g. quarterpixel 

motion estimation) as well as by the use of more 

sophisticated algorithms for predicting syntax elements 

from neighbouring macroblocks (e.g. context-adaptive 

VLC). These new coding tools result in significantly increased 

CPU and memory loads required for decoding 

the video stream. In environments of limited processing 

power such as embedded systems, the high computational 

demands pose a serious challenge for practical 

H.264 implementations. Multi-core systems provide an 

elegant and power-efficient solution to overcome these 

performance limitations. 

The design of such a specialized multi-processor decoding 

architecture is a non-trivial task. For exploiting 

the processing power of a multi-core system most efficiently, 

an equal workload between the cores must be 

achieved. Apart from the system’s usage this also influences 

the required buffer sizes between the cores for 

compensating differences in the workload. However, the 

significant workload differences in typical video decoding 

systems make this balancing a challenging task. 

Figure 1 visualizes the structure of the H.264 decod- 

71 

ing process. The computational complexity of a macroblock’s 

parsing and deblocking functions is strongly 

bitrate dependent. While the parsing complexity typically 

raises with the macroblock’s number of bits and 

syntax elements, the deblocking filter is applied more aggressively 

for low bitrates. For the pixel-based decoding 

tasks (e.g. intra prediction and motion compensation) a 

large variety of possible macroblock coding modes exists. 

The coding options such as the prediction type 

(i.e. for H.264 skipped, intra and inter prediction) and 

the macroblock partitioning influence the decoding complexity 

significantly. 

For multi-core video decoding systems, predicting the 

run-time behaviour is not straight forward. Differences 

in the workload, algorithmic dependencies and stalls due 

to resource limitations (e.g. size restrictions of communication 

buffers) must be considered. Furthermore, video 

decoding platforms are often based on heterogeneous architectures 

for addressing the execution behaviour of the 

individual decoding tasks more efficiently. For example, 

the highly conditional parsing and entropy decoding 

functions require processors with efficient branch execution. 

Depending on which processor a decoding task is 

executed, differences in the decoder run-time will occur. 

The dynamics and heterogeneity of video decoding 

systems often result in the following questions: 

– Can we reach the specified decoding requirements 

on a specified multi-core architecture? 

– Which architecture is required to handle a certain 

set of videos (i.e. a set of streams that represents 

the common input characteristics of an application 

such as DVB-T)? 

– What is the optimal decoder hardware and software 

partitioning for this architecture? 

These questions have a major impact on the architecture 

decisions and should be addressed before implementing 

a video decoding system. 

For solving these questions, assumptions about the architecture 

requirements regarding the computational decoding 

complexity are typically made. They allow us 

to decide on the hardware components and the software

Encoded 

Bitstream 

Stream 

Parsing 

Entropy 

Decoder 

IDCT 

Spatial 

Prediction 

Motion 

Compensation 

Reference 

Frames 

+ 

Deblocking 

Decoded 

Frame 

Figure 1: The H.264 decoding process. After parsing and entropy decoding the syntax elements of a macroblock, a 

spatial or temporal prediction of this macroblock is computed. This prediction is added to the inverse transformed 

(IDCT) residual information and a deblocking filter removes blocking artefacts introduced during the quantisation 

step. 

structure of our decoder. Complexity estimation techniques 

are therefore of prime importance. In recent years, 

advanced techniques for estimating the run-time of a program 

have evolved. 

Static algorithm analysis and path analysis techniques 

have been introduced in [2]. These techniques analyse 

an algorithm’s definition (e.g. its source code) for estimating 

the upper and lower run-time bounds of a program. 

For considering the impact of the input data on 

the program execution, dynamic profiling methods [3] 

have been developed. These methods observe the program’s 

execution behaviour during the run-time. This 

allows us to measure the complexity of the decoding 

functions for individual input data. Hardware simulations 

and HW/SW-Codesign methods [4] provide accurate 

run-time information but require labour intensive 

adaptation of the hardware and decoder software before 

first run-time estimations are possible. 

All these approaches above can provide us with information 

about the complexity requirements of our video 

decoding system. However, interpretation of the complexity 

information in the context of a multi-core system 

is not straight-forward. Algorithmic dependencies 

and resource limitations result in run-time constraints between 

the processing units. For highly dynamic multicore 

decoder systems, making predictions about the parallel 

decoding system’s behaviour is hardly possible. 

In our work, we introduce a simulator for supporting 

the development process of multi-core video decoding 

systems. It estimates the basic parameters such as the 

execution time, the memory transfers and the power consumption 

of the decoder system. Instead of running the 

partitioned decoding tasks and using exactly specified interfaces 

for connecting them together, only an abstract 

information about the macroblocks’ runtime (e.g. decoding 

complexity) is required. This is a major advantage of 

72 

our system, since the system designer typically gets this 

information without building the complete hardware architecture 

or without partitioning the software of the decoder. 

Architecture evaluations are possible before the 

decoder architecture is effectively built. Additionally, 

the Partition Assessment Tool (PAT) allows software design 

explorations for supporting the partitioning of the 

decoder software. 


This work has been supported by ON DEMAND Microelectronics 

AG [5] and the Austrian Federal Ministry of 

Transport, Innovation, and Technology under the FIT-IT 

Project 812429. 

REFERENCES 

[1] ITU-T and ISO/IEC. Advanced video coding for 

generic audiovisual services (ITU Rec. H.264 — 

ISO/IEC 14496-10). ITU-T and ISO/IEC, March 

2005. 

[2] Peter P. Puschner and Christian Koza. Calculating 

the maximum execution time of real-time programs. 

Journal of Real-Time Systems, 1(2):159–176, 1989. 

[3] Susan L. Graham, Peter B. Kessler, and Marshall K. 

McKusick. gprof: a call graph execution profiler. 

In SIGPLAN Symposium on Compiler Construction, 

pages 120–126, 1982. 

[4] Peter Voigt Knudsen and Jan Madsen. Pace: 

A dynamic programming algorithm for hardware/software 

partitioning. In Proceedings of the Int. 

Workshop on Hardware-Software Co-Design, pages 

85–92, 1996. 

[5] ON DEMAND Microelectronics. 

http://www.odmsemi.com, 2008.

Comparison between Solute transport parameters estimation from 

local to field scale 

Mohamed Kassab 1 , Antonio Coppola 2 , Nicola Lamaddalena 3 , Alberto Guadagini 1 and Monica Riva 1 

1 

Politecnico di Milano, DIIAR, Piazza L. Da Vinci, Milano, Italy, 

2 

Dept. Tecnico Economico per la Gestione del Territorio Agr. forestale, University of Basilicata, Potenza, Italy 

3 

Mediterranean Agronomic Institute of Bari (IAMB), Italy. 

Email: Mohamed.kassab@mail.polimi.it 

Abstract — The generalized transfer function 

model (GTF) and TDR based time normalized resident 

concentrations were combined to characterize 

solute transport mechanisms at local and field 

scales. A leaching experiment was conducted under 

greenhouse, where TDR probes were installed at 

three different depths at 37 sites. The field plot was 

brought to steady-state water content; a pulse application 

of 3.87 mm of KCl solution was applied. 

Measurements of water content (�) and impedance 

(Z) were simultaneously taken and the time series of 

relative resident concentrations for each site where 

effectively interpreted in terms of GTF model. The 

field scale behavior was described by calculating a 

local average and an integral average which gave 

two significantly different field scale solute transport 

behaviors. 


Sustainable management of soil and water resources 

depends largely on the ability to predict the impacts 

of current and future management practices on soil 

and groundwater quality both at local and global 

scale. 

The complex heterogeneity of soil has encouraged 

the development of transport theories based on conceptual 

models, such as the transfer function approach 

[1]. [2] presented a generalized transfer function 

models (GTF) which is a four-parameter flexible 

transfer function able to describe both the convection-dispersive 

(CD) and the stochastic-convective 

(SC) process of dispersion in a soil, and solute transport 

processes in heterogeneous soils such as those in 

which the mean travel time increase non-linearly 

with depth and when the dispersivity is a scale dependent 

function. Finally, [3] presented an analytical 

solution for time normalized resident concentration 

for the GTF model. 

This work amid at improving the link between the 

small scale variability of the local transport properties 

and large scale transport behavior by characterizing 

local solute transports mechanisms on several 

sites along transect area by using TDR probes at 

73 

different depths and in terms of GTF model, then 

integrating local scale measurement and parameters 

along a transect area and normalized for the different 

local water contents, to build a time-integral normalized 

resident concentration at each depth to be used 

as field-scale curves. 

II. MATERIALS AND METHODS 

A leaching experiment was carried out in a Terra 

Rossa (sand 23.5%, silt 58.7%, clay 17.8%) soil plot 

under greenhouse at IAMB, Bari. TDR probes were 

installed at three different depths (0-15, 20 and 40 

cm) at 37 sites 1m apart along a 40 m transect. The 

field plot was brought to steady-state water content 

by adapting the drip irrigation to apply water at the 

rate of 10 mm/day. An automatic irrigation scheduler 

was used to maintain the desired rate. A pulse application 

of 3.87 mm of KCl solution (23.5 g/l) was 

applied. Then, the fresh water was newly applied at 

10 mm/day to force the KCl solution downward into 

the soil. 

III. RESULTS AND DISCUSSIONS 

A. SOIL RESIDENT CONCENTRATIONS 

Measurements of both water content (�) and impedance 

(Z) were simultaneously taken to follow the 

KCl solution propagation through the soil profile 

“Figure 1”. 

Z(ohm) 

80.00 

70.00 

60.00 

50.00 

40.00 

0-15 cm 

20 cm 

40 cm 

30.00 

0.00 100.00 200.00 300.00 400.00 

t(hours) 

Figure 1: Soil impedance evolution of “Site 19” 

A closed-form expressions for the time normalized 

resident concentrations, Crt*, for the (GTF model) 

based on TDR measurements was applied to estimate 

solute transport parameters at both the local “Figure 

2” and field scale [4], [2] and [3].

Crt* (-) 

time normalized resident concentrations 

0.01 

0-15 cm measured 

20 cm measured 


0-15 cm simulated 

20 cm simulated 


0.00 

0 100 200 300 400 

Time(h) 

Figure 2: The time normalized resident concentrations, 

Crt*, for “Site 19” 

The GTF scales the moments of travel times E(t) and 

Var(t) according to the following relationships: 

�1 

2� 

2 2(�1� 

�2 

) 

E(t,z) z Var(t,z) z CV(t,z) l 

(1) 

� � � � 

� � 

�� 

� , �� 

� ; � 2 � � 

E(t,l) � l � Var(t,l) � l � CV(t,l) � z � 

where, �1; �2 are parameters of the time moments. 

The parameters �� and �� can be calculated from the 

�1 and �2 parameters in the previous expressions, 

considering that the mean, E, and the variance, Var, 

of the travel times, t, are related to the mean (�) and 

variance (�2) of the ln(t) through [5] as following: 

2 

E�t, z�� 

exp��0. 

5� 

� 

(2) 

z 

z 

2 

2 

Var�t, z��exp�2� 

� � ��exp��1� z z 

z 

(3) 

B. PARAMETERS AT LOCAL AND FIELD SCALES 

The field scale behavior was described by calculating 

a local and integral measurements average in terms 

of GTF model parameters. A significant different 

between the integral average (1.2) and local average 

(0.587) values was observed “Figure 3”. 

�1-�2 

1.5 

1.2 

0.9 

0.6 

0.3 

0 

0 10 20 30 

local values 

Integral average 

Local average 

Distance (m) 

Figure 3: The evolution with the distance of the 

(�� values obtained along the transect. 

The time-normalized resident concentrations and the 

dispersivity in terms of GTF parameters proposed by 

[4] were formulated by [3] as following: 

2 

2 2 

rt* 

aln( 

t) 

�a� 

� � � � � � 

z a�z 

�1 

(ln( t) 

�z 

�z) 

(4) 

C ( z, 

t) 

� exp�� 

2 � 

t�1� 

2 � 2� 

z � 

z � 

2( �1 

�� 

2 ) 

z � l � 

2 

� � � � exp��1� 

(5) 

l 

2 � z � 

Both local and integral average dispersivity values 

were significantly different although both of them 

had the same trend with soil depth “Figure 4”. An 

integral average curve “Figure 5” was obtained by 

weighting Crt*(z, t) by (�� measured at the same 

depth and time based on [6]: 

40 

74 

Z cm) 

� (cm) 

0 10 20 30 40 

0 

10 

20 

30 

40 

50 

Local average 

Integral average 

Figure 4: Local and integral average dispersivity 

values as a function of depth. 

37 

* 

� � �z, x , t � Z fT �z, x , t � (6) 

rt * 

x �1 

C �z, t � � � 37 

* 

� � � �z, x , t � Z fT �z, x , t �dt 

0 x �1 

where ZfT*(z,t) is the temperature corrected impedance 

loads, x is location along the transect. 

Mean time normal time resident 

concentration 

 

0.03 

0 

0-15 cm measured 



0-15 cm simulated 



0 100 200 300 400 

Time (h) 

Figure 5: The integral average curves for the three 

depths, along with the best fitting obtained in terms 

of GTF parameters. 

REFERENCES 

[1] W. A. Jury. Simulation of solute transport using a 

transfer function model. Water resources research, 

18: 363–368, 1982. 

[2] R. D. Zhang. Generalized transfer function model 

for solute transport in heterogeneous soils. Soil 

science society of American journal, 64:1595– 

1602, 2000. 

[3] M. Javaux and M. Vanclooster. Robust estimation 

of the generalized solute transfer function 

parameters. Soil science society of American 

journal, 67:81-91, 2003. 

[4] J. Vanderborght, M. Vanclooster, D. Mallants, J. 

Diels, and J. Feyen. Determining convective lognormal 

solute transport parameters from resident 

concentration data. Soil science society of 

American journal ,60:1306–1317, 1996. 

[5] T. B. Parkin, J. J. Meisinger, S. T. Chester, J. L 

Starr. and J. A. Robinson. Evaluation of statistical 

estimation methods for lognomally distributed 

variables. Soil science society of American 

journal, 52:323–329, 1988. 

[6] M. Javaux. Solute transport in a heterogeneous 

unsaturated subsoil: experiments and modeling. 

Ph.D. Thesis n45 . Louvain-la-Neuve. Faculte 

d'ingenierie biologique, agronomique et environnementale, 

Presses universitaires de Louvain. 

194 p., 2004.

A new method for identification of systems of arbitrary real order 

based on solution of fractional differential equations and orthogonal 

distance fitting 

Tomas Skovranek 1 , Vladimir Despotovic 2 , Igor Podlubny 1 (Faculty Mentor) 

1 Faculty of BERG, Institute of Control and Informatization of Production Processes 



2 Technical Faculty of Bor, Department of Electromechanical Engineering 

University of Belgrade 

Bor, Serbia 

Email: {tomas.skovranek,igor.podlubny}@tuke.sk; vdespotovic@tf.bor.ac.yu 

Abstract — In this paper the total least squares method 

(TLSM), the so called orthogonal distance regression (ODR) 

will be used for system identification instead of the classical regression 

based on the least squares method (LSM). The main 

reason is the fact that ODR is a suitable tool for fitting lines 

and surfaces in multidimensional space, while even the use 

of classical regression in 2D is not so natural. We apply the 

ODR to define the optimal data-fitting-line in the state space. A 

new method for Identification of systems of arbitrary real order 

based on solution of fractional differential equations and orthogonal 

distance fitting is proposed. In order to define a model 

of observed data a system of fractional-order differential equations 

will be considered, which solution represents the optimal 

fitting of given points in space. The sum of orthogonal distances 

between the data points in space and a fitting line is considered 

as the criterion for optimization. The results are presented in 

2-dimensional and 3-dimensional space. 


System identification is a general term to describe mathematical 

tools and algorithms that build dynamical models 

from experimental data. Having the model of a system is 

often very important for analysis, simulation, control system 

design etc. In this paper a new method is proposed 

for identification of systems of arbitrary real order based 

on solution of fractional differential equations. In order 

to successfully solve a problem of system identification, 

parameters of the differential equations (including orders 

of differentiation which are considered as arbitrary real or 

”fractional”) have to be evaluated, and a criterion must be 

determined, by which the estimation process will be done 

optimally. 

LSM was used for long period of time among scientists 

and researchers as an universal tool for finding bestfitting 

curve to a given set of points, although this method 

has many disadvantages, which lead to development of 

more general methods, for example TLSM or ODR [1, 2]. 

ODR uses perpendicular (orthogonal) distances between 

given points and fitting curve, what is more natural point 

of view than using vertical offsets, as in LSM. 

75 

Although the fractional calculus and the idea of fractional 

order operators is over three centuries old, the 

interest of scientists increased mainly in last decades 

[3, 4, 5]. Fractional-order differential equations (FODE) 

and their numerical solution is the topic of many authors 

(e.g. Diethelm, He, Podlubny, Lubich, Adomian, Momani, 

etc.). It is due to better possibilities of description 

of dynamical systems, as FODEs provide a powerful instrument 

for description of memory and hereditary properties 

of systems in comparison to integer-order models, 

where such effects are neglected. 

II. IDENTIFICATION OF LINEAR FRAC- 

TIONAL ORDER SYSTEMS USING OR- 

THOGONAL DISTANCE FITTING 

The main goal of this paper is the state space description 

of a dynamical system with a set of FODEs. Indeed, we 

want to define a mathematical model of this dynamical 

system, by finding a solution of a set of FODEs, which 

represents the optimal fitting of given points in space. 

Criterion of optimization is the sum of shortest distances 

between given points in space and fitting line. The analysis 

is performed in 2D and 3D space. 

A. SOLUTION TO A SYSTEM WITH OPTIMIZED COEF- 

FICIENTS IN 2D SPACE 

Let us first analyze a system of two linear FODEs. The 

analytical interpretation of this system is: 

D (α) x = a1 · x + a2 · y + C1 

D (β) y = a3 · x + a4 · y + C2, 

(1) 

where the orders of differentiation (α, β) are fractional, 

in interval 0

where the expression (−1) j� � α 

j is represented by the coefficient 

b, and can be evaluated using recurrence rela- 

tionship as in [5]: 

b (α) 

0 

=1, b(α) 

j 

= 

� 

1 − 1+α 

� 

b 

j 

(α) 

j−1 , j =1, 2, 3 .... 

(3) 

Applying definitions (2)-(3) on (1) we obtain a numerical 

expression of the system of two linear FODEs: 

(a1 − h −α · b (α) 

0 ) · xm + a2 · ym 

= h −α · � b (α) 

j 

· xm−j − C1 

a3 · xm +(a4 − h −β · b (β) 

0 

= h −β · � b (β) 

j 

) · ym 

· ym−j − C2 

Figure 1: Fitting in 2D space 

(4) 

B. SOLUTION TO A SYSTEM WITH OPTIMIZED COEF- 

FICIENTS IN 3D SPACE 

Now we will deal with a system in 3D space, which analytical 

interpretation can be written as: 

D (α) x = a1 · x + a2 · y + a3 · z + C1 

D (β) y = a4 · x + a5 · y + a6 · z + C2 

D (γ) z = a7 · x + a8 · y + a9 · z + C3. 

(5) 

The orders of differentiation (α, β, γ) are fractional, in 

interval 0

Configurable Meta-search in Human Resource Domain 

Abstract — In this paper, we propose a configurable 

meta-search engine in the human resource 

domain (HRD) to provide a platform for job and 

applicant tracking processes. The meta-search 

engine in HRD has been designed by applying semantic 

Web technologies, to solve the problems of 

job seekers. We provide the solutions for automatic 

integration of data, structures and processes in 

HRD into a meta-search by the use of domain ontology. 

Use of domain ontology, HR-XML and multiple 

matchers for generation of integrated schema 

and interface, helps in understanding the meaning 

of terms and improves the quality of the search 

interface and search results. Experiments show that 

there is improvement in schema/data matching and 

integration process, result extraction and identification 

process for meta-search engine by use of multiple 

matchers and domain ontology. 


A lot of information is available online via websites 

or databases but this information is heterogeneous 

and distributed. It is difficult for a user to visit 

every website to access this information. There must 

be a way that people can search heterogeneous and 

distributed information quickly. Primary tools to 

search the information on the Web are search engines, 

subject directories and social network search 

engines. Traditional search engines are based on 

keyword or phrase search without understanding the 

meaning of the word and are unable to provide the 

desired results to the user. Other traditional search 

tools have different index structures, low recall and 

precision and do not provide comprehensive coverage 

of the Web. In short, Internet search still needs 

improvement. To overcome all these problems, there 

exist another search tool “meta-search engine” and 

considered as an excellent choice for specific topic 

search from multiple heterogeneous search engines. 

Traditional job search engines lack the capability 

of processing structured queries and search is based 

only on statistical methods without any attempt to 

understand the meaning of the terms being used. For 

job seekers, access to large number of job search 

engines is difficult and sometimes existing job por- 

Tabbasum Naz and Jürgen Dorn (Faculty Mentor) 

Institute for Information Systems (184/2) 



Email: {naz,dorn}@dbai.tuwien.ac.at 

77 

tals produce irrelevant results. As every search portal 

has different interface style, it can be confusing for 

the job seeker in giving job search criteria. Recruiting 

organizations also need some improvements in the 

existing job search portals. 

Previous research shows that automatic integration 

of different search engines into a meta-search is 

not an easy task. There are many problems in the 

construction of meta-search engines. For example 

some cannot be automatically constructed and provide 

hard wired solutions and other involve complex 

steps for development process. Automatic schema 

matching, schema integration, data integration, 

global attributes and value selection from multiple 

search engines for the meta-search interface is a 

tricky and time consuming task that needs more 

attention. Other meta-search engines also lack the 

capability of semantically understanding the terms. 

To solve these problems in a domain, we have developed 

a prototype for a meta-search engine in the job 

domain that use modern technologies to help the job 

seekers and recruiting organizations 

II. RESEARCH METHODOLOGY 

We have developed a prototype for a configurable 

job meta-search engine to provide a platform for job 

and applicant tracking processes. We identify the 

requirements of recruiters and job seekers to improve 

the efficiency of job meta-search. The system supports 

automatic integration of interfaces, data structures 

and processes. There are two processes involved 

in the construction of job meta-search engine 

in job domain i) meta-search engine creation process 

for recruiting organization and ii) meta-search engine 

usage process for job seekers. Our approach can 

automatically extract, match and integrate individual 

schemas and job results from different job search 

engines into one. Job results are converted to a single 

format for quick and easy navigation for a job seeker. 

Use of semantic Web technologies for meta-search 

engine in HRD provides convenience to the job 

seeker and save their precious time in job search. We 

have developed domain ontology in HRD that helps 

in the translation of individual extracted schemas 

from individual job search engines to common

schema. We also introduce design patterns for common 

components of meta-search engines. Presented 

design patterns for meta-search engines and their 

components are reusable, extendable and flexible. 

Presented design patterns accelerate the development 

process in meta-search domain and other related 

domains. Moreover, it promises higher quality of 

developed solutions [1]. 

III. CONTRIBUTIONS 

Meta-search engine creation process involves components 

i.e. job search engine selector, interface 

extractor, XML schema generator, job meta-search 

query interface generator. Different search engines 

use different representation concepts, data structures 

and different granularities of knowledge, so domainontology 

is used for translation between concepts. 

Query interface generator of meta-search engine is 

responsible for integration of meta-data in three steps 

i) schema matching and integration ii) data integration 

iii) and query interface generation. Schema 

matching process is actually a process of discovering 

correspondences between two schema elements that 

correspond to each other. There can be structural, 

syntactic and semantic heterogeneity in schemas. 

Manual or semi-automatic schema matching and 

mapping is tedious, complex and time consuming 

task because of open and heterogeneity nature of 

Web data. Automatic schema matching and 

integration is always required to reduce manual 

efforts but require more researcher’s efforts to 

produce high quality techniques and results. Our 

main focus is to have an automatic schema/data 

matching and integration for meta-search engine and 

to resolve the semantic conflicts by utilizing the 

commutative techniques from database and ontology 

community. We utilize multiple matchers i.e. name 

matcher, linguistic matcher, instance level matcher 

(top down matcher), number of instances matcher, 

combinational matcher, synonym matcher, ontology 

matcher for schema/data level matching and integration. 

Our combinational matcher uses stemming 

algorithm and string distance algorithms i.e. Cosine 

similarity, Levenshtein distance and Euclidian distance 

algorithm to improve the matching results. We 

use single ontology approach and utilize our domain 

ontology as a global ontology for the schema/data 

matching and integration process. Domain ontology 

snippet is used in finding mapping between attributes 

of two interfaces. A domain-specific ontology also 

identifies the relationship between the values of two 

interfaces. Identified mappings are stored in XML 

format for further use by form generator and query 

dispatcher component. After schema/data matching 

and integration, a form for mete-search engine is 

78 

generated. The form generation is supported by 

XForms which enables the generation of the form 

from an XML schema and also the easy adaptation to 

different user clients. 

In HRD, meta-search engine usage process involves 

components including query dispatcher, information 

extractor (IE), result merger, duplicate 

result eliminator and result ranker. Above mentioned 

matchers and domain ontology is utilized again by 

the IE component, to identify the different concepts, 

data structures of a job description and job result 

attributes to convert them to a single common format 

for the job seeker. The system solves problems of 

different representational concepts in different job 

search engines [1]. 

HR domain ontology used in job meta-search engine 

construction contains job related attributes from 

HR-XML, occupations from Standard Occupation 

Classification (SOC) and skill from International Cooperation 

Europe Ltd. 

Introduced design patterns architect complex 

meta-search engines construction processes and 

provides us with flexible design philosophy. 


We have presented an approach for integrating 

schema/data from different job portals in a metasearch 

in order to support job seeking people to master 

the large number of available job portals. Our 

main focus is on the automated extraction and integration 

of the structure of provided information. This 

structure is used in meta-search to integrate the different 

sources. Application of Semantic Web technologies 

in meta-search domain proved helpful and 

provides automatic and efficient schema/data integration, 

query translation, integrated query interface 

generation and result identification. Experiments 

show that there is improvement in schema/data 

matching and integration by use of multiple matchers 

and domain ontology. It also increases the mapping 

accuracy. Integrated system provides a unified access 

to job seekers to navigate multiple search engines 

without visiting them separately and increase the 

Web coverage for them in a short time. Overall metasearch 

engine in HRD will be helpful in reducing the 

unemployment rate of a country. 

REFERENCES 

[1] T. Naz. Configurable Meta-search in Human 

Resource Domain, PhD Thesis, Institute for Information 

Systems, Vienna University of Technology, 

Austria (To publish in Dec 2008)

The Definition of Secure Business Processes with Respect to 

Multiple Objectives 

Johannes Heurix, Thomas Neubauer (Faculty Mentor) 




Email: {jheurix,tneubauer}@securityresearch.at 

Abstract — Business processes have gained more and more 

importance in today’s business environment, and their unimpeded 

execution is crucial for a company’s success. Since business 

processes are permanently exposed to several threats, organizations 

are forced to pay attention to security issues. Although 

security of business activities is widely considered as 

important, business processes and security aspects are often developed 

separately. Recent approaches for managing business 

process security focus on certain aspects only and neglect others, 

thus not providing a holistic framework for analyzing process 

security and evaluating security safeguards. Often, these 

safeguards are evaluated according to technical aspects only; 

multiple objectives are not considered. 

This work introduces a model-supported, risk-based multiobjective 

decision making methodology (MR-MOD) for the elicitation 

of security requirements of business processes, for the 

analysis of assets, threats, and vulnerabilities, and for the selection 

of appropriate security technologies. Thereby it combines 

the strengths of different methods, including process modeling, 

quantitative risk assessment, and multiobjective decision 

making techniques, for the definition of Secure Business Processes. 


In recent times, business processes have often been the 

target of a number of security hazards such as viruses, 

hacker attacks, or data theft [1]. Given the importance 

of business processes and the fact that they are permanently 

exposed to numerous vulnerabilities, it becomes 

obvious to include business processes into security considerations. 

As business processes generate value and 

their unimpeded execution is vital for the success of enterprises, 

decision makers and security experts are tasked 

with revising methods to secure them against external or 

internal threats; legal requirements and the loss of value 

sustained after a successful attack result in the demand 

for appropriate security measures. Loss of value can 

be either of monetary nature (e.g. loss of profit due to 

the interruption of business activities) and/or intangible 

(e.g. loss of reputation). A striking example illustrate 

the severity of security breaches is the Denial of Service 

(DoS) attack of February 2000 causing access problems 

of Yahoo!’s website, costing an estimated half a million 

US Dollars in just three hours [2]. 

79 

A major issue with business process security is that 

security properties are mainly considered as ’technical’ 

problems which have to be solved by dedicated security 

experts [3], while process managers are tasked with optimizing 

the core workflows, thus leading to business processes 

and security measures developed separately. Another 

problem is how to measure it. Recent approaches 

depend on the calculation of aggregated values such as 

the Annualized Loss Expectancy (ALE) [4] or Return 

on Investment (ROI) for evaluating security improving 

measures. But relying solely on a single value for measuring 

security is inappropriate, considering the multiple 

factors that may play a role in selecting the correct security 

safeguards including issues such as safeguard costs, 

effectiveness, and user acceptance. Part of this measurement 

problem is the issue of ’How much (security) is 

enough’ [5], as security does not directly generate business 

value and does not directly improve the net profit 

[1]; investing in security can only prevent negative events 

or reduce related adverse effects. Decision makers have 

to find the optimal balance between the expenditure for 

security safeguards and their ability to prevent adverse 

events. 

II. DESIGN OF A MODEL-SUPPORTED, 

RISK-BASED MULTIOBJECTIVE DECI- 

SION MAKING PROCESS 

The proposed methodology is a risk assessment process 

based on process models and security safeguard selection. 

Whereas other existing frameworks often concentrate 

on a certain aspect of security and do not address all 

requirements for the definition of secure business processes, 

this approach provides a holistic methodology 

for eliciting security-related elements based on business 

processes, measuring the risks, and choosing an optimal 

safeguard portfolio to ensure business process security. It 

is a model-supported, risk-based multiobjective decision 

making process (MR-MOD) and incorporates elements 

of different disciplines and their strengths: 

Model-based Elicitation Process Process models are 

used for deriving security relevant assets and threats 

they are exposed to.

Risk Assessment A risk assessment process provides a 

structured method to measure information security 

risks and to valuate security safeguard effectiveness. 

Workshop A workshop environment ensures consideration 

of the different opinions and expertise of different 

participating domain experts such as security 

experts, process owners, and other stakeholders. 

Multiobjective Decision Making A multiobjective decision 

making process takes multiple criteria into 

consideration and provides solutions that represent 

the best tradeoffs of opposed factors. 

The MR-MOD framework consists of three distinctive 

phases, each of them divided into several sub-steps (figure 

1): 

Phase 1: Modeling and Identification The first phase 

is tasked with the modeling and the identification 

of all security relevant entities based on business 

process models. This includes the creation of the 

process model and the identification of all participating 

assets, the identification of applicable vulnerabilities 

and threats they are exposed to, and the 

identification of possible safeguards. 

Phase 2: Workshop-based Risk Assessment 

In the next phase, risks are composed as 

asset/vulnerability/threat-tuples, cost and benefit 

categories the safeguards are measured in are 

defined, and necessary quantitative data collected 

for the evaluation process. In addition, constraints 

and interdependencies of the safeguards are 

specified. 

Phase 3: Multiobjective Decision Making The final 

phase deals with the generation of Pareto-efficient 

solutions (safeguard combinations) with respect to 

the cost/benefit categories using the data collected 

in the previous phase, the analysis of the candidate 

solutions by modifying the upper and lower 

bounds for the categories, and the final selection 

of the optimal safeguard portfolio according to the 

preferences of the decision makers. 


In this work, a model aimed to be a holistic framework 

for the elicitation of security holes and the selection of 

appropriate methods to satisfy the security requirements 

of business processes has been introduced. Its main advantage 

over other approaches is the combination of multiple 

techniques and the inheritance of their strengths to 

overcome their individual weaknesses and shortcomings. 

This methodology is supported by a software tool. 

80 

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�� 

�� 

�� 

�� 

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�� 

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Figure 1: Overview of the MR-MOD Phases 

REFERENCES 

[1] T. Neubauer, M. Klemen, and S. Biffl. Secure business 

process management: a roadmap. In ARES ’06: 

Proceedings of the First International Conference on 

Availability, Reliability and Security, page 8, 20-22 

April 2006. 

[2] P. Kedrosky. Hackers prey on our insecurities. The 

Wall Street Journal, February 2000. 

[3] G. Herrmann. Security and integrity requirements of 

business processes - analysis and approach to support 

their realisation. In Consortium on Advanced Information 

Systems Engineering, pages 36–47, 1999. 

[4] Fips Publication (65), 1979. 

[5] K. J. SooHoo. How much is enough? a riskmanagement 

approach to computer security. Technical 

report, Consortium for Research on Information 

Security and Policy (CRISP), June 2000.

Generalising Constraint Solving over Finite Domains 

Markus Triska and Nysret Musliu (Faculty Mentor) 

Institut für Informationssysteme 184/2 



Email: {triska,musliu}@dbai.tuwien.ac.at 

Abstract — Traditionally, finite domain constraint solvers 

can typically handle only rather small values. This limits their 

potential applications. In this project, we devise and study a 

generalisation of constraint solving over finite domains, where 

domains can be unbounded. We present and discuss new application 

opportunities for constraint solvers that this feature 

allows. We are also interested in proving theoretical properties 

of a new constraint solver that is implemented as part of this 

project, such as termination and correctness. 


Constraint programming is a declarative formalism for 

describing and solving combinatorial problems from various 

areas, such as planning, scheduling and allocation 

tasks. It is one of the most promising developments in 

programming languages of the last decade, and the Association 

for Computing Machinery (ACM) has identified 

it as one of the strategic directions in computing research 

[1]. 

Formally, a constraint satisfaction problem (CSP) consists 

of: 

– asetXof variables, X = {x1,...,xn} 

– for each variable xi, asetD(xi) of values that xi 

can assume, which is called the domain of xi 

– asetofconstraints, which are simply relations 

among variables in X, and which can further restrict 

their domains. 

From such a description, a constraint solver can ideally 

compute solutions without additional instructions. 

II. CLP(FD) 

In connection with combinatorial optimisation or completion 

problems, one of the most frequently used instances 

of constraint programming is constraint logic 

programming over finite domains, denoted as CLP(FD). 

This means that all domains are finite sets of integers, 

and the available constraints include at least the common 

arithmetic relations between integer expressions. 

As an example of this approach, consider the wellknown 

combinatorial problem “Sudoku”, which has recently 

gained significant attention. Figure 1 shows an 

instance of this problem. To give a visual impression of 

the values that a constraint solver can safely remove from 

81 

domains, we proceed as follows: First, we subdivide all 

free cells into 9 small regions, numbered in their natural 

order. Each region corresponds to a domain element, i.e., 

an integer between 1 and 9. In Figure 1, a dot is drawn 

in those regions that correspond to domain elements that 

can be pruned due to the given constraints. A subsequent 

search can ignore these elements. 

1 

3 

7 5 

2 7 4 

5 4 

9 6 

4 6 

7 1 

1 3 

Figure 1: Constraint propagation for a Sudoku puzzle 

III. GENERALISING CLP(FD) 

Traditionally, finite domain constraint solvers have 

mostly been used to tackle problems that involve only 

quite small values. This is the case in many scheduling, 

allocation and combinatorial optimisation tasks 

for which constraint-based approaches are very well 

suited. A well-known benchmark library for constraints, 

CSPLib [2], consists almost exclusively of such examples. 

On the other hand, the need for arbitrary precision integer 

arithmetic is widely recognised, and many common 

Prolog systems provide transparent built-in support for 

arbitrarily large integers. 

It thus seems natural to enhance a constraint solver 

over finite domains with the ability to reason over arbitrarily 

large integers. SICStus Prolog already goes in 

that direction, using the symbolic constants inf and sup 

to denote default domain limits, but internally, they still 

correspond to quite small integers: The system yields a 

representation errors when these limits are exceeded.

In this project, we implement a new constraint solver 

over finite domains, in which a software implementation 

for big integers (“bignums”) is transparently used when 

arising values exceed machine-sized integers. We accept 

the inf/sup notation of SICStus Prolog, but these atoms 

now denote the actual infinities instead of abbreviating 

underlying finite limits. 

As an example where this is useful, consider the socalled 

“7-11 problem” [3], which already surpasses the 

limits of the finite domain constraint solver of SICStus 

Prolog on 32-bit systems. This non-linear problem is also 

beyond the abilities of common CLP(Q) solvers, but can 

be solved with our solver. 

Further, a constraint solver without arbitrary limits can 

be freely advocated as a more general and more declarative 

alternative for (moded) built-in arithmetic. For example, 

consider the well known factorial function, implemented 

via finite domain constraints: 

factorial(0, 1). 

factorial(N, F) :- 

N #> 0, 

F #= F0*N, 

N1 #= N - 1, 

factorial(N1, F0). 

This relation can now be used in all directions. For 

example, given n, it can be used to compute f = n!, 

and also, given any f �= 0, it can compute all n for 

which n! =f: 

?- factorial(25, F). 

F = 15511210043330985984000000 

?- factorial(N, 120). 

N = 5 

The factorial function quickly exceeds the built-in limits 

of conventional constraint solvers, but not ours. 

IV. CURRENT RESULTS AND STATUS 

The current version of our constraint solver is included 

as library(clpfd) in the free Prolog system SWI- 

Prolog [4]. Partial descriptions of the system are already 

published in two workshop contributions ([5], [6]), 

and a further paper focusing on termination properties 

was recently submitted [7]. The solver is already being 

used in a course on logic programming at the university 

of Aachen. Other users include a group working 

on worst-case execution time analysis in a program analysis 

framework [8]. We work closely together with these 

groups and sometimes extend the solver with features 

that are especially useful for their applications. For example, 

we recently implemented a strategy that lets users 

quickly count the number of possible variable instantiations, 

without enumerating them explicitly. This feature 

82 

is needed in execution time analysis, and is also valuable 

to quickly skip solutions that are not interesting to users. 

Importantly, constraint propagation in our solver always 

terminates. While this weakens propagation in 

cases with unbounded domains, it yields a simple termination 

criterion for constraint logic programs involving a 

costly search with the built-in predicate labeling/2: 

If posting the constraints alone terminates, then this posting 

followed by labeling also terminates. Terminating 

propagation is also very valuable in automatically generated 

queries to test the solver. 

V. WORK IN PROGRESS 

Ongoing work on the constraint solver includes performance 

improvements and correctness considerations. In 

addition, we are constantly looking for new real-life tasks 

that can now be tackled with our constraint solver. 

REFERENCES 

[1] Pascal Van Hentenryck and Vijay Saraswat. Strategic 

directions in constraint programming. In ACM 

Workshop on Strategic Directions in Computing Research, 

1996. 

[2] Ian P. Gent and Toby Walsh. CSPLib: A benchmark 

library for constraints. In CP’99, volume 1713 of 

LNCS, 1999. 

[3] Paul Pritchard and David Gries. The seven-eleven 

problem. Technical Report TR83-574, Cornell University, 

Computer Science Department, September 

1983. 

[4] Jan Wielemaker. An overview of the SWI-Prolog 

programming environment. In Proc. of the 13th Int. 

Workshop on Logic Prog. Environments, pages 1–16, 

December 2003. 

[5] Ulrich Neumerkel, Markus Triska, and Jan Wielemaker. 

Declarative language extensions for Prolog 

courses. In FDPE, 2008. 

[6] Markus Triska, Ulrich Neumerkel, and Jan Wielemaker. 

A generalised finite domain constraint solver 

for SWI-Prolog. In WLP, 2008. 

[7] Markus Triska, Ulrich Neumerkel, and Jan Wielemaker. 

Better termination for Prolog with constraints. 

In WLPE (submitted), 2008. 

[8] Adrian Prantl, Jens Knoop, Markus Schordan, and 

Markus Triska. Constraint solving for high-level 

WCET analysis. In WLPE (submitted), 2008.

Default Reasoning on Top of Ontologies with dl-Programs 

DAO Tran Minh and Thomas Eiter (Faculty Mentor) 

Institute for Information Systems, Vienna University of Technology, Austria 

Email: {dao,eiter}@kr.tuwien.ac.at 

Abstract — We study the usefulness of description logic programs 

(dl-programs) in implementing Reiter’s default logic on 

top of a description logic knowledge base (DL-KB). To this 

end, we investigate transformations from default theories to dlprograms 

based on different established algorithms for computing 

default theory extensions, namely the select-defaultsand-check 

and the select-justifications-and-check algorithms. 

In each transformation, additional constraints are exploited 

to prune the search space based on conclusion-conclusion or 

conclusion-justification relations. The implementation was deployed 

as a new component in the dl-plugin for dlvhex, and 

evaluated with various experimental test ontologies, which 

showed promising results. 


Default logic [1] has been one of the most prominent 

nonmonotonic reasoning formalisms due to its close relationship 

to common-sense reasoning. Ontologies are 

a key component of the future Semantic Web and reasoning 

on top also needs to handle default information. 

However, nonmonotonic reasoning with an ontology 

alone is not possible because description logics 

(DLs) which are used as ontology languages are monotonic. 

Therefore, incorporating default reasoning into 

ontologies is an interesting topic to take into account. 

The first attempt in this field was proposed in [2] which 

imposes some restrictions regarding decidability. Moreover, 

there has not been any implementation or further 

development on this approach since then. One of the reasons 

was the lack of support from research on integrating 

rules and ontologies at that time [3]. 

In this work, we investigate the problem of enabling 

default reasoning on top of ontologies specified by DL- 

KBs, based on an available mechanism that allows for 

integrating rules and ontologies, namely dl-programs [4]. 

In addition to our theoretical results, we provide a frontend 

as a new component in the dl-plugin [5] for the 

HEX-program solver dlvhex1 [6], which implements dlprograms. 

II. EMBEDDING DEFAULTS OVER DESCRIP- 

TION LOGICS INTO DL-PROGRAMS 

In [7], we present three transformations to embed default 

reasoning into dl-programs. Due to space constraints, we 

present here only one, viz. Υ, which we illustrate in a 

simple example rather than in full details. 

1 http://www.kr.tuwien.ac.at/research/systems/dlvhex/ 

83 

Assume that we have a small DL-KB about birds and 

penguins: � � 

Flier ⊑¬NonFlier, Penguin ⊑ Bird, 

L = 

Penguin ⊑ NonFlier, Bird(t) 

and a set of defaults: 

� � 

Bird(X) :Flier(X) 

D = 

Flier(X) 

Intuitively, we have a DL-KB in which flying and nonflying 

objects are distinguished. We know that penguins, 

which are birds, do not fly. We also know that birds normally 

fly, but this fact cannot be added into L because it 

will make L inconsistent. Having a bird named Tweety, t 

for short, and no more information, we would like to conclude 

that t flies; and later if we learn that t is a penguin, 

the opposite conclusion should hold. To make this possible, 

we add a set of defaults D as about on top of L. We 

call Δ=〈L, D〉 a default theory over a DL-KB. Through 

Υ, Δ is transformed to a dl-program KB df 

Υ (Δ) = (L, P ) 

where P consists of the following dl-rules: 

cons_Flier(X) :dom(X), 

not out_cons_Flier(X). 

out_cons_Flier(X) :dom(X), 

not cons_Flier(X). 

in_Flier(X) :- cons_Flier(X), 

dom(X), DL[Flier+=in_Flier;Bird](X). 

:- cons_Flier(X), 

DL[Flier+=in_Flier;-Flier](X). 

:- not DL[Flier+=in_Flier;-Flier](X), 

out_cons_Flier(X). 

dom(t). 

These rules can be explained as follows: the first two 

guess if assuming an object can fly is consistent or not 

with the answer set, i.e., the agents’ belief set. The third 

rule aims to find which objects can fly under the consistency 

assumption above, where the atom DL[...] incorporates 

the assumption on Fliers. The last two rules 

are two constraints: the first prevents cases in which we 

guessed that an object can fly is consistent to the answer 

set but in fact we conclude that it does not fly. Similarly, 

the second constraint kills all answer sets in which we 

guessed that an object cannot fly is consistent with the 

answer set but then we could not conclude that it does 

not fly. 

With this dl-program, we have the desired answer set 

I = {dom(t), cons F lier(t), inF lier(t)} which en-

default rules 

[A(X);B(X)] 

/[C(X)] 

dl-rules 

HEX-rules 

User 

dl-rules 

C(X):-DL[ ;A](X), 

not DL[ ;-B](X). 

dfconverter 

ontology ontology 

dl-rules 

HEX-rules 

dlconverter 

HEXrules 

dlvhex 

Models/ 

Extensions 

Figure 1: Strategy for implementing the df-converter 

tails that t flies by default. If we now change to a new 

DL-KB L ′ = L ∪{P enguin(t)}, then from the dl- 

program KB df 

Υ (Δ′ )=(L ′ ,P), t can no longer be inferred 

to be able to fly, and the corresponding answer set 

is I ′ = {dom(t), out cons F lier(t)}. 

The other two transformations Π and Ω, the proof of 

correctness, and an optimizing technique using pruning 

rules are presented in [7]. 

III. FRONT-END OVERVIEW 

The architecture of the front-end is shown in Figure 1. 

Users provide input, including a set of default rules along 

with a DL-KB in an OWL file, and then get the extensions 

of the default theory in terms of answer sets. 

Other optional inputs can be either dl-rules or low-level 

HEX-rules. Recall that dlvhex is a solver for HEXprograms. 

It receives input in terms of HEX-rules and 

returns results as answer sets to the user. As dlvhex has 

a dl-plugin, dl-programs are converted transparently into 

HEX-programs, the ordinary user is unaware of HEXrules. 

However, this does not prevent experts from providing 

more sophisticated input such as constraints in 

terms of dl-rules or HEX-rules to reduce the search space 

and speed up the evaluation. In fact, we do provide a 

technique in which the user can specify more supportive 

information, i.e., typing predicates that helps our implementation 

gaining significant performance improvement. 

Details on this technique can be found in [7]. 

Utilizing the dl-plugin, we implement a df-converter 

whose input contains default rules accompanied with a 

DL-KB, optional dl-rules, or even HEX-rules. This converter 

transforms all the default rules into dl-rules based 

on different transformations, with the help of the DL- 

KB serving as the sources of individuals for the domain 

predicates to guarantee the safety condition [6]. 

Then, the transformed dl-rules, along with other input dland 

HEX-rules, are transferred to the dl-converter. The 

rest of the evaluation will be done by the dl-plugin and 

dlvhex. For more details on the implementation of the dfconverter, 

we refer to the Master’s Thesis [7] on which 

this abstract is based. The thesis also contains experimental 

results, and comparisons between different trans- 

84 

formations, which reveals interesting tasks to improve 

the overall performance of the system. 

IV. FUTURE WORK 

Concerning our implementation of the front-end, some 

issues remain for future work. Firstly, we would like to 

investigate more sophisticated pruning rules depending 

on the structure of the default theory. Secondly, a closer 

look into particular kinds of default theories such as normal 

or semi-normal default should help to find more effective 

transformations. 

As our work depends on dlvhex and the dl-plugin, the 

experimental results suggest the following tasks to increase 

the system performance. 

A caching technique which is only available now for 

dl-atoms would give additional benefit if it can be implemented 

for cq-programs [8], an extended version of 

dl-programs, and already be deployed in the dl-plugin. 

dlvhex is now using RacerPro as its only DL-reasoner. 

It would also be interesting to look at other possibilities 

interfacing dlvhex with different DL-reasoners such as 

KAON2 or Pellet, and then compare the results. 

Currently, dlvhex takes all grounded dl-programs and 

computes the answer sets. Another challenging task 

would be to automatically classify the input and do only 

necessary rules grounding for a smaller search space. 

REFERENCES 

[1] R. Reiter. A logic for default reasoning. Artificial 

Intelligence, 13(1-2):81–132, 1980. 

[2] F. Baader and B. Hollunder. Embedding defaults 

into terminological knowledge representation formalisms. 

Autom. Reasoning, 14(1):149–180, 1995. 

[3] G. Antoniou et al., Combining Rules and 

Ontologies: A survey. Technical Report 

IST506779/Linköping/I3-D3/D/PU/a1, Linköping 

University, Feb 2005. 

[4] T. Eiter, G. Ianni, Th. Lukasiewicz, R. Schindlauer, 

and H. Tompits. Combining answer set programming 

with description logics for the semantic web. 

Artificial Intelligence, 172(12-13):1495–1539, 2008. 

[5] T. Krennwallner. Integration of Conjunctive Queries 

over Description Logics into HEX-Programs. Master’s 

thesis, TU Wien, Oct 2007. 

[6] R. Schindlauer. Answer-Set Programming for the Semantic 

Web. PhD thesis, TU Wien, Dec 2006. 

[7] M. T. DAO. Default Reasoning on Top of Ontologies 

with dl-Programs. Master’s thesis, TU Wien, Jun 

2008. 

[8] T. Eiter, G. Ianni, T. Krennwallner, R. Schindlauer. 

Exploiting Conjunctive Queries in Description Logic 

Programs. Annals of Mathematics and Artificial Intelligence. 

2008.

Implementation of a Design Tool for 

Automated Generation of Four State Logic Circuits 

Jakob Lechner and Martin Delvai (Faculty Mentor) 

Institute of Computer Engineering, Embedded Computing Systems Group 



Email: {lechner,delvai}@ecs.tuwien.ac.at 

Abstract — Although asynchronous logic design is a long 

known research domain it plays a niche role in industry. One 

reason is certainly the lack of design tools that empower hardware 

designers to cope with the inherent complexity of asynchronous 

circuits. This short paper describes the development 

of a computer aided conversion process that allows designers 

to transform a given synchronous circuit description into an 

asynchronous Four State Logic design. 


In the past decades research of asynchronous circuitry 

has produced various design methodologies and concepts. 

One of these approaches is called Four State Logic 

(FSL). This short paper gives a brief overview of a master 

thesis, which targets the development of a tool-supported 

design flow for FSL circuits. For this purpose the following 

tasks were performed: 

– Provide a sound theoretical background about the 

FSL design paradigm focusing on initialisation issues. 

In contrast to synchronous designs, where all 

registers fire at the same point in time, in asynchronous 

circuits the firing is sequentially, controlled 

by (local) handshake signals. Thus, depending 

on the event sequence, the same circuit may 

produce different results. Due to the fact that the 

initialisation strongly affects this event sequence an 

in-depth analysis of FSL circuits wrt. initialisation 

and the resulting behaviour was performed. 

– Development of a CAD tool which transforms a 

conventional synchronous circuit description into 

an FSL circuit. Some steps within this transformation 

are straightforward (e.g. the replacement of a 

conventional AND gate with an FSL AND gate). 

Other tasks however require more attention such as 

the automated identification of source-sink pairs in 

complex circuit topologies and the introduction of 

appropriate handshake signals. 

In this short paper the focus is placed on the design 

tool. In the first part the basic principles of FSL are introduced 

whereas the second part presents the design flow 

and the developed tool. 

85 

II. FOUR STATE LOGIC 

Four State Logic (FSL) is a representative of the delayinsensitive 

design methodology, where no timing assumptions 

have to be made (gate and wire delays can 

be unbounded). The key concept of FSL is the idea to 

extend regular boolean data values with temporal information. 

With this additional information it’s possible to 

determine if a certain data value is valid in the current 

context. Together with acknowledge signals a “local” 

handshaking can be established between a data source 

and a data sink. Thus a global clock for coordinating 

switching actions of the circuit becomes obsolete. 

In FSL consecutive data words are encoded in alternate 

phases [1], called the even phase (ϕ0) and the odd 

phase (ϕ1). If all bits of an input vector have the same 

phase the input data is said to be consistent and can be 

considered valid. Thus, for discovering the arrival of the 

next data word the data sink only needs to check if all 

bits of the input have changed their phase. 

Figure 1 demonstrates this principle. Assume signals 

A, B, C and D make up a data word. The figure shows the 

signals’ phases over time as perceived by the recipient on 

its input ports. As you can see consistent intervals are 

interleaved with periods of time where the phase of one 

or more signals differs. 

Figure 1: Consistent and inconsistent phases. 

For representing the logical 0 (low) and logical 1 

(high) values in two phases a 2-bit encoding is needed: 

– ϕ0 : l =00,h=11 

– ϕ1 : L =01,H =10

Due to this encoding scheme it’s no longer possible to 

transmit one bit of information over a single wire. Hence, 

FSL needs to employ a “Double-Rail” logic: One single 

bit of information is sent over two rails. 

A. THE HANDSHAKE PRINCIPLE 

Registers are important components of a circuit because 

they are synchronisation points. A register is allowed 

to latch new data if two conditions are satisfied: Obviously 

new data needs to be available from the preceding 

registers (upstream stages) and the currently stored data 

word has to be consumed by the successors (downstream 

stages). Both conditions can be validated by checking 

the phases of the predecessors and the successors. The 

phases of the upstream stages can be directly derived 

from the transmitted (FSL encoded) data, the phases of 

the downstream stages are provided by additional feedback 

(or acknowledge) signals. Now a firing rule for registers 

can be formally defined: 

Definition 1 A register r is allowed to replace the currently 

stored value with its current input value if and only 

if the following two conditions are met: 

1. ∀w ∈ N + (r) :Φ(w) =Φ(r) 

2. ∀w ∈ N − (r) :Φ(w) �= Φ(r) 

N + (r) ... set of successor registers, 

N − (r) ... set of predecessor registers, 

Φ(r) ... current phase of register r 

On top of this concise model of the switching activities 

of FSL circuits the design flow including a tool for 

computer-aided conversion of synchronous circuits could 

be developed. 

III. TOOL FOR FSL CIRCUIT GENERATION 

The starting point of the conversion algorithm is a gatelevel 

netlist of the synchronous hardware circuit. This 

netlist can be produced with a properly configured synthesis 

tool (e.g. Synopsys). Subsequently the netlist 

needs to be parsed so the circuit can then be transformed 

into a directed graph, where the nodes represent the registers 

of the circuit. An edge pointing from one register 

v to another register w represents a data flow from v to 

w. This graph representation of the circuit is used for all 

further transformation steps and contains all necessary 

information for deciding about the structural extensions 

needed for building the actual FSL design. 

Since the phase relationship between two registers is 

the decisive factor rather than the actual phase of the individual 

register, the notion of tokens was introduced (see 

[2]). Thus the initialisation can be done be simply placing 

tokens at specific edges. A token placed on an edge 

between two registers indicates that the initial phases of 

86 

the connected registers are different. Thus the token denotes 

that new data is available for the sink register instantly 

after a reset of the circuit. 

As mentioned in the introduction the initialisation has 

a crucial impact on the sequence in which registers fire. 

In order to investigate the circuit’s behaviour in presence 

of different initialisations a simulation tool was also developed. 

Figure 2 shows a screenshot of the simulator. 

A token (black dots) is available on both input edges of 

register data2. Based on the firing rule this register is 

allowed to latch the new input. In the simulator the firing 

action will consume both input tokens and place a new 

token on the output edge (which then indicates new data 

for register data3). 

Figure 2: FSL simulator 

After the designer has decided about a specific token 

assignment the asynchronous FSL design is completely 

defined and can be generated from the synchronous 

netlist in several steps: First standard logic signals are 

replaced by dual-rail encoded FSL signals and combinational 

logic gates are substituted for corresponding FSL 

gates. Subsequently synchronous registers are replaced 

by asynchronous ones and the insertion of the associated 

handshaking connections is performed. The chosen initialisation 

is applied and an FSL netlist is generated. This 

netlist can be used as input for conventional place & route 

tools, Xilinx ISE or Altera Quartus e.g., and finally the 

asynchronous design can be downloaded into an FPGA. 

Concluding, the presented tool converts synchronous 

to asynchronous designs with a minimal user interaction 

required. The latter is restricted to the initialisation, 

which allows to tune the circuit to specific needs. 

REFERENCES 

[1] Anthony J. McAuley. Four state asynchronous 

architectures. IEEE Transactions on Computers, 

41(2):129–142, February 1992. 

[2] Daniel H. Linder and James C. Harden. Phased 

logic: Supporting the synchronous design paradigm 

with delay-insensitive circuitry. IEEE Transactions 

on Computers, 45(9):1031–1044, September 1996.

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Efficient Counting with Bounded Treewidth using Datalog ∗ 

Stefan Rümmele and Reinhard Pichler (Faculty Mentor) 

Database and Artificial Intelligence Group 



Email: {ruemmele,pichler}@dbai.tuwien.ac.at 

Abstract — Bounded treewidth has proven to be a key concept 

in identifying tractable fragments of inherently intractable 

problems. An important result in this context is Courcelle’s 

Theorem, stating that any property of finite structures definable 

in monadic second-order logic (MSO), becomes tractable if the 

treewidth of the structure is bounded by a constant. An extension 

of this result to counting problems was done by Arnborg 

et al. But both proofs did not yield an implementable algorithm. 

Recently Gottlob et al. presented a new approach using 

monadic datalog to close this gap for decision problems. In 

this paper, we extend this method in order to handle counting 

problems as well and apply it to the problems #SAT,#CIRCUM- 

SCRIPTION and #HORN-ABDUCTION. 


Many intractable problems can be solved efficiently if 

some parameter is bounded by a constant. Downey 

and Fellows [1] introduced the framework of parameterized 

complexity to deal with this phenomenon. One 

of the most successful concepts for such a parameter is 

bounded treewidth, where the treewidth (a measure of 

similarity to a tree) of the underlying structure is bounded 

by a constant. Although the systematic study of parameterized 

complexity basically started with Downey 

and Fellows, many ad-hoc results especially related to 

fixed-parameter tractability (FPT) have been presented 

before. One of them is Courcelle’s Theorem [2], stating 

that any property of finite structures which is expressible 

in monadic second-order logic (MSO) can be decided 

in linear time, if we restrict ourselves to structures 

with bounded treewidth. Previous methods for deriving 

a concrete algorithm from the MSO description based 

on Courcelle’s Theorem [3, 4] translate the MSO evaluation 

problem over finite structures into an evaluation 

problem over colored binary trees, which is then solved 

via a finite tree automaton (FTA). Although the theoretical 

value of these approaches is indisputable, it turned 

out that in practice they lead to a “state explosion” of the 

FTA even for very simple MSO formulae (cf. [5]). Therefore, 

it was stated in [6] that such algorithms are “useless 

for practical applications” and that the main benefit of 

Courcelle’s Theorem is in providing “a simple way to 

recognize a property as being linear time computable”. 

∗This work was supported by the Austrian Science Fund (FWF), 

project P20704-N18. 

89 

Recently Gottlob et. al. [7] have proposed an alternative 

approach for deriving linear time algorithms from a 

MSO property via monadic datalog. In particular they 

have shown the following theorem: 

Theorem 1 (Gottlob et al. [7]) Given an arbitrary but 

fixed (relational) vocabulary τ and a constant w ≥ 1. 

Then every MSO-definable unary query over τ-structures 

of treewidth w is also definable in the quasi-guarded 

fragment of monadic datalog over τ extended by predicates 

for expressing tree decompositions. 

Note that their definition of quasi-guarded programs require 

that every rule contains an extensional atom called 

guard, s.t. every variable in the rule is functionally dependent 

on the guards variables. Additionally they showed 

that such a program can be evaluated in linear time. 

Our work includes the extension of Theorem 1 to also 

account for counting problems instead of handling decision 

problems and unary queries only. The formal 

framework of counting complexity was introduced by 

Valiant [8, 9] in order to deal with counting problems, 

where one is not only interested in whether a property 

is true or false but instead one wants to count how often 

this property is fulfilled. The first formal integration of 

counting complexity into parameterized complexity theory 

was done independently by McCartin [10] and Flum 

and Grohe [11]. But again many ad-hoc results related 

to fixed-parameter tractability of counting problems have 

been presented before. One of them is a result by Arnborg 

et al. [3] extending Courcelle’s Theorem to counting 

problems, which are definable via MSO properties. 

They showed that each of these problems can be solved 

in linear time if restricted to problem instances, where 

the treewidth of the underlying structure is bounded by 

some constant. 

II. RESULTS 

Of course, the statements about implementability of the 

algorithms based on Courcelle’s Theorem, which are derived 

via colored binary trees and FTA also hold for the 

extension to counting problems. Therefore we adopted 

the idea of [7] and showed: 

Theorem 2 Given an arbitrary but fixed (relational) vocabulary 

τ and a constant w ≥ 1. Then every counting 

problem over τ-structures of treewidth w defined via

MSO properties is also definable in the quasi-guarded 

fragment of datalog over τ extended by predicates for 

expressing tree decompositions and a summation operator. 

The proof was done utilizing a technique from finite 

model theory, namely Ehrenfeucht-Fraïssé games for 

monadic second-order logic. With the help of these 

games, we could assign a so called type to each node 

in the tree decomposition, which only depends on the 

types of its child nodes. Furthermore the type of the root 

node is all we need to compute the result of our counting 

problem. Therefore we could establish the theorem 

by structural induction over the tree decomposition. We 

also showed that the evaluation of a datalog program can 

be done in linear time if restricted to the quasi-guarded 

fragment of datalog extended by a summation operator 

and assuming unit cost for arithmetic operations. Note 

that from this result and from Theorem 2 we can actually 

derive Courcelle’s Theorem for counting problems as a 

corollary. 

To put our theorem to work, we applied this datalog 

approach to solve the three counting problems #SAT, 

#CIRCUMSCRIPTION and #HORN-ABDUCTION. The 

first one (#SAT), is the problem of counting all models of 

a propositional formula whereas #CIRCUMSCRIPTION is 

the problem of counting only the (subset) minimal models. 

#HORN-ABDUCTION is the problem of counting the 

solutions of a propositional abduction problem where the 

underlying theory is restricted to Horn clauses. Note that 

the #P-completeness of #SAT was already mentioned in 

[9], whereas the #P-completeness of #HORN-ABDUC- 

TION has been shown recently in [12]. #CIRCUMSCRIP- 

TION is #NP-complete and therefore lies on the second 

level of the counting hierarchy [13]. 

III. RELATED WORK 

Part of this work will appear in [14], which contains also 

a discussion on a proof-of-concept implementation of the 

algorithm for #SAT. Other related publications include 

[15], where the counting version of Courcelle’s Theorem 

is extended to graphs with bounded clique-width (a measure 

of similarity to a clique). In [16] an algorithm for 

solving #SAT and #GENSAT (a generalization of #SAT) 

in case of bounded treewidth as well as bounded cliquewidth. 

Furthermore they provided a sketch on how to 

apply their approach based on recursive splitting to other 

#P-complete problems. An algorithm for #SAT based 

on dynamic programming was presented in [17]. 

REFERENCES 

[1] R.G. Downey and M.R. Fellows. Parameterized 

Complexity. Springer, New York, 1999. 

90 

[2] B. Courcelle. Graph rewriting: An algebraic and 

logic approach. In Handbook of Theoretical Computer 

Science, Volume B, pages 193–242. Elsevier 

and MIT Press, 1990. 

[3] S. Arnborg, J. Lagergren, and D. Seese. Easy problems 

for tree-decomposable graphs. J. Algorithms, 

12(2):308–340, 1991. 

[4] J. Flum, M. Frick, and M. Grohe. Query evaluation 

via tree-decompositions. J. ACM, 49(6):716–752, 

2002. 

[5] M. Frick and M. Grohe. The complexity of firstorder 

and monadic second-order logic revisited. In 

Proc. LICS’02, pages 215–224. IEEE Computer 

Society, 2002. 

[6] M. Grohe. Descriptive and parameterized complexity. 

In Proc. CSL’99, volume 1683 of Lecture Notes 

in Computer Science, pages 14–31. Springer, 1999. 

[7] G. Gottlob, R. Pichler, and F. Wei. Monadic datalog 

over finite structures with bounded treewidth. In 

Proc. PODS’07, pages 165–174. ACM, 2007. 

[8] L.G. Valiant. The complexity of computing the permanent. 

Theor. Comput. Sci., 8:189–201, 1979. 

[9] L.G. Valiant. The complexity of enumeration and 

reliability problems. SIAM J. Comput., 8(3):410– 

421, 1979. 

[10] C. McCartin. Parameterized counting problems. In 

Proc. MFCS’02, volume 2420 of Lecture Notes in 

Computer Science, pages 556–567. Springer, 2002. 

[11] J. Flum and M. Grohe. The parameterized complexity 

of counting problems. SIAM J. Comput., 

33(4):892–922, 2004. 

[12] M. Hermann and R. Pichler. Counting complexity 

of propositional abduction. In Proc. IJCAI’07, 

pages 417–422, 2007. 

[13] Arnaud Durand, Miki Hermann, and Phokion G. 

Kolaitis. Subtractive reductions and complete problems 

for counting complexity classes. Theor. Comput. 

Sci., 340(3):496–513, 2005. 

[14] M. Jakl, R. Pichler, S. Rümmele, and S. Woltran. 

Fast counting with bounded treewidth. In Proc. 

LPAR’08 (to appear). 

[15] B. Courcelle, J.A. Makowsky, and U. Rotics. On 

the fixed parameter complexity of graph enumeration 

problems definable in monadic second-order 

logic. Discrete Applied Mathematics, 108(1–2):23– 

52, 2001. 

[16] E. Fischer, J.A. Makowsky, and E.V. Ravve. Counting 

truth assignments of formulas of bounded treewidth 

or clique-width. Discrete Applied Mathematics, 

156(4):511–529, 2008. 

[17] M. Samer and S. Szeider. Algorithms for propositional 

model counting. In Proc. LPAR’07, volume 

4790 of LNCS, pages 484–498. Springer, 2007.

MapFace - A Graphical Editor to Support the 

Semantic Annotation of Medical Text 

Theresia Gschwandtner, Katharina Kaiser, and Silvia Miksch (Faculty Mentor) 




Email: {gschwandtner,kaiser,miksch}@ifs.tuwien.ac.at 

Abstract — The mapping of medical texts to concepts of medical 

terminology systems is a prerequisite for many tasks of automatically 

processing these documents. Due to the complex 

nature of this task, the results of mapping systems still contain 

erroneous bits of information. 

Our editor visualizes the annotation of the text and provides 

means to easily navigate and modify it. Thus we are able to 

shorten a cumbersome and time-consuming task and subsequently 

provide reliable and well-defined information for further 

processing steps. Even more, the visualization features 

support a better understanding of the medical texts. 


Medical documents contain important information, but 

they are often difficult to understand. Mapping concepts 

from medical terminology systems to the text supports 

the intelligibility and disambiguation of the text by 

adding useful metainformation. To this end, programs 

such as the MetaMap Transfer (MMTx) program [1] create 

a rough mapping of concepts from the Unified Medical 

Language System (UMLS) Metathesaurus [2] to free 

medical text. Due to the complexity of unstructured text, 

it is not always possible to automatically create a correct 

mapping. However, the complete reliability of information 

is crucial in medical care - an extremely sensitive 

discipline - which makes it necessary for medical experts 

to control and correct these results. This led us to meet 

the following challenges: 

– Enabling medical experts without special programming 

skills to handle the MMTx program. 

– Providing means to assure the correct affiliation of 

UMLS concepts to text chunks. 

– Supporting the understanding of medical concepts 

in the text as well as relations between them. 

II. THE MAPFACE EDITOR 

A variety of systems exist annotating text with medical 

concepts. In contrast to most other systems, MMTx not 

only supports exact matches between a text token and 

a UMLS concept, but also considers term variants as 

well as partial matches. Additionally, it computes matchscores 

of found candidates by combining specific mea- 

91 

sured values. For a detailed description of annotation 

systems we refer to [3]. 

The MMTx program automatically tokenizes the text 

into phrase chunks and concept chunks; additionally, it 

maps UMLS concepts to the text (see Figure 1). 

Since manually correcting these results would be an 

extremely cumbersome and time-consuming task, and as 

there has been no satisfactory tool to support it, we have 

developed the MapFace editor (see Figure 2). By means 

of this editor we are able to 

1. facilitate the handling of the MMTx program, by 

– providing a GUI, and 

– making the MMTx results easily navigable. 

2. assure a correct mapping of the text to UMLS concepts, 

by providing means to 

– correct the tokenization of the text into concept 

chunks and phrase chunks (see Figure 3), and 

to 

– edit the affiliation of UMLS concepts to these 

concept chunks (see Figure 3). 

3. support the better understanding of the text, by 

– color-coding of semantic types [4], 

– highlighting concepts or phrases accordingly, 

and 

– listing and highlighting relations among medical 

concepts in the text. 

III. EVALUATION 

In order to ensure the usability of the MapFace editor we 

conducted an evaluation study. In doing so, we went for a 

heuristic approach according to Nielsen and Molich [5]. 

Four evaluators were asked to solve typical tasks with the 

help of the MapFace editor. They noted and rated each 

usability problem they encountered. 

The study discovered 32 usability problems, of which 

78,12% could be fixed immediately. The other 21.88% 

either take more effort to fix or they require more general 

changes in the design. In any case, we will consider all 

problems carefully in order to improve the quality of the 

editor.

Figure 1: The MMTx program tokenizes the sentence 

into phrase chunks. A set of best matching UMLS concepts 

together with their associated semantic types (in 

italics) are returned for each concept identified within 

the text. The encircled objects are wrong or ambiguous 

results which have to be corrected by means of the Map- 

Face editor. 

Figure 2: For a given concept chunk a list of best matching 

UMLS concepts is displayed in the bottom pane. In 

the right-hand pane the user can select color-coded semantic 

types to highlight associated text chunks. 


The MapFace editor provides important means to navigate, 

edit, and visualize the semantic annotation of medical 

documents automatically generated by the MMTx 

program. Enabling medical experts to easily control and 

correct the semantic annotation assures the quality of the 

outcome, which in turn improves the validity of any subsequent 

processing step. 

With respect to the outcome of the usability evaluation 

we will ensure that the MapFace editor is not only an 

92 

Figure 3: Corrections accomplished by means of the 

MapFace editor are encircled (compare Figure 1). 

important and time-saving means, but also a convenient 

tool to work with. 


The research leading to these results has received funding 

from Fonds zur Förderung der wissenschaftlichen 

Forschung FWF (Austrian Science Fund), grant L290- 

N04 and from the European Community’s Seventh 

Framework Programme (FP7/2007-2013) under grant 

agreement n ◦ 216134. 

REFERENCES 

[1] A. R. Aronson. Effective mapping of biomedical text 

to the UMLS Metathesaurus: the MetaMap program. 

In Proceedings of the 25th Annual American Medical 

Informatics Association Symposium, pages 17– 

21, Washington, D.C., November 2001. 

[2] P. L. Schyler, W. T. Hole, M. S. Tuttle, and D. D. 

Sherertz. The UMLS Metathesaurus: representing 

different views of biomedical concepts. Bulletin 

of the Medical Library Association, 81(2):217–222, 

April 1993. 

[3] L. H. Reeve. Semantic Annotation and Summarization 

of Biomedical Text. PhD Thesis. Drexel University, 

College of Information Science and Technology, 

Philadelphia, Pennsylvania, 2007. 

[4] A. T. McCray and S. J. Nelson. The representation 

of meaning in the UMLS. Methods of Information in 

Medicine, 34(1-2):193–201, March 1995. 

[5] J. Nielsen and R. Molich. Heuristic evaluation of 

user interfaces. In Proceedings of the ACM Conference 

on Human Factors in Computing Systems, 

pages 249–256, Seattle, Washington, April 1990.

Optimization of communication by analyzing the interlocutor’s 

wording 

Gudrun Kellner 

E-Commerce Group, Institute of Software Technology and Interactive Systems 



Email: kellner@ec.tuwien.ac.at 

Abstract — Recent research results on communication 

science mention a relation between the interlocutor’s 

perceptional preferences, his or her mental 

representations and his or her choice of expressions. 

However, there is not any tool for analyzing 

such. 

In my research I combined lexical with computational 

linguistic methods to develop a software 

prototype that is able to analyze text on the usage of 

perceptional expressions. This analyzing tool can 

help to identify the interlocutor’s perceptional preference 

for easier meeting his or her way of thinking 

and thereby facilitate the understanding. 


All communication is based on perception. With the 

establishment of constructivism the knowledge about 

individual differences in perception spread. It seems 

reasonable to assume that the individual form of 

perception also influences the language of a person. 

Interestingly, this theory hasn’t yet shown great affects 

in the research on individual and personal language 

use. 

The Neurolinguistic Programming (NLP) offers a 

model that seems as a first step in closing this gap: 

The idea of sensual-specific perception which comes 

noticeable in the individual language use is described 

by the keyword “representational systems”. According 

to this, every person has one or two sensory systems 

preferably used to perceive his or her environment. 

From the five senses arises the classification in 

visual, auditory, kinesthetic, olfactory and gustatory 

perception modalities. Each of these perception 

classes forms a sensomotor complex, in the NLP 

called representational system. As the inner representations 

are accessed for expressing thoughts, the 

preferred sensory system of a speaker can be told by 

his or her diction and wording. 

The research about the optimization of communication 

furnished proof that the percentage of understanding 

is higher when a speaker adjusts his diction 

to the diction of his addressee – what applies with a 

high probability also to the use of perceptional 

words. 

93 

Still, for the German language, not much research 

on the relation between an individual’s perceptional 

preference and his or her language use has been done 

yet. To be able to go deeper into that idea, (1) a lexical 

corpus of perceptional expressions and (2) a 

software tool that automatically filters those expressions 

from a text are needed. Those two steps shall 

be explained in this abstract. 

II. A LEXICAL CORPUS OF PERCEPTIONAL 

EXPRESSIONS 

For a systematic analysis of the use of perceptional 

expressions, a corpus is needed, containing a collection 

of the most often used words and expressions 

that can be directly linked to one of the perceptional 

classes mentioned above. That corpus was built with 

the input of 13 different resources and contains more 

than 840 different entries with at least 200 words and 

expressions per perceptional class. For further details 

and the complete corpus see [1]. 

During the examination of the corpus it was found 

that usually only the root word is decisive for the 

assignment to a representational class, but that such a 

root word can occur in different combinations. This 

follows the fact that in the German language it is 

possible to combine words and thereby create new 

ones. That possibility causes a problem when searching 

for a semantic unit that can also be part of a compound 

word. For example, when searching for the 

signal word “rot” [red], the output should also include 

words like “Morgenrot” [dawn] and “rotgrün” 

[red and green] containing the same semantic root, 

but not words like “Brot” [bread] or “Schrot” 

[bruised grain] which include the same sequence of 

characters, but have no semantic link to the searched 

word. A search algorithm that also takes compound 

words into account would especially be helpful when 

scanning a German text for a list of signal words. 

Therefore, a search algorithm using a new model 

describing word composition was developed.

III. THE ANALYZING TOOL 

As a consequence of the multiple combining possibilities 

of root words, an appropriate analyzing tool 

should not only be able to find the expressions contained 

by the corpus, but also all possible combinations 

that are based on the same semantic root. 

To solve this problem, a model of possible word 

structures was developed. Following that model, it 

can be determined which letters or syllables may 

occur around a root word without changing its semantic 

meaning (and hence the assignment to the 

respective perceptional class). This model was introduced 

with the aim to provide a clear description of 

word composition transferable into an algorithm and, 

based on the root word, describes the structure of 

compound words as follows: 

[ [prefix] + root word + [infix] + (word joint) ] 

[prefix] + root word + [infix] + (ending) 

The following notation was used: Round brackets 

mark optional, but maximal single occurrence, square 

brackets highlight optional (even multiple) occurrence 

of elements. 

Based on the word components mentioned in the 

Duden Grammatik [2], for each element of the model 

a list of letter combinations was set up. The analyzing 

tool joins the corpus of perceptional expressions 

with the model of word structure and the lists of 

possible word composition elements. After having 

identified the searched sequence of characters in a 

word, the algorithm analyzes the characters around it. 

Step by step it checks whether the environment either 

represents a semantically inseparable part of the 

sequence of characters (which indicates a different 

word meaning) or is the rest of a compound word 

and thereby should be part of the output result. 

The tests with the tool let presume that the occurrence 

of perceptional expression depends on the sort 

of text and on the topic. A user’s test report on some 

instant food i.e., had a very high rate of gustatory 

vocabulary. 

IV. FURTHER RESEARCH 

At the moment I’m working on using this tool in user 

modeling. As in the internet (and esp. in blogs and 

forums) there is quite a lot of text which can be directly 

linked to a user, this could be a rich source for 

modeling the user’s mental representations of perceptional 

information. With such knowledge about the 

user, advertisements with a higher acceptance can be 

designed and chosen with respect to the user’s individual 

perceptional preference. 

94 

REFERENCES 

[1] G. Kellner. Wege der Kommunikationsoptimierung. 

Anwendung von NLP im Bereich der 

Künstlichen Intelligenz. Master Thesis, Wien, 

Austria, 2006. 

[2] G. Drosdowski (Ed.). Duden „Grammatik der 

deutschen Gegenwartssprache“. Duden, Mannheim, 

Germany, 1995.

A Simulation Environment for Distributed Real-Time 

Systems in the Presence of Malicious Attacks 

Ekarin Suethanuwong and Christian El-Salloum (Faculty Mentor) 

Institute of Computer Engineering 



Email: {ekarin,salloum}@vmars.tuwien.ac.at 

Abstract — The purpose of this work is to develop 

a simulation environment for distributed real-time 

systems for observing system’s behaviour after 

malicious attacks. Our simulation framework is 

targeted at systems based on the Time-triggered 

Architecture [1]. The purpose of this simulation is 

to investigate and increase the security of existing 

dependable distributed real-time systems, especially 

when these systems are connected to the Internet or 

any other open systems. 


Nowadays, distributed real-time systems tend to take 

more and more responsibilities in many application 

domains. For example in the automotive or avionics 

sector an increasing number of functions are 

controlled by embedded systems. Current and future 

embedded systems tend to be more open than they 

were in the past. For instance they might be 

connected to the Internet for remote configuration or 

maintenance. Due to these facts, distributed real-time 

systems are facing a growing potential for malicious 

attacks and security is becoming a major issue in the 

embedded domain. 

In order to investigate the effect of malicious 

attacks as well as to find out counter measures in a 

distributed real-time system, we are developing a 

simulation environment for simulating distributed 

real-time systems and malicious attacks. 

In this software, users can implement different 

algorithms, e.g. clock synchronization algorithms 

like FTA (Fault-Tolerance Average) [2] or communication 

protocols like TTP/C [3] or TT Ethernet [4]. 

The software enables users to define the structure of 

the simulated distributed real-time system and 

supports different methods to execute the simulated 

system and to perform malicious attacks. 

This paper is organized as following. In section II, 

the design of simulation framework is presented. 

Next, in section III, the simulation of malicious 

attacks is described. The last section will conclude 

the most important results. 

95 

II. DESIGN OF SIMULATION FRAMEWORK 

Our simulation framework aims to provide a tool 

to build and execute a simulation model for 

distributed real-time systems and malicious attacks. 

Users can build an arbitrary system model of distributed 

real-time systems via a user interface. The userdefined 

distributed real-time systems are executed on 

a discrete time scale. The simulation includes updating 

the internal state of nodes as well as the transmission 

and malicious manipulation of messages on the 

network (i.e. it includes the simulation of nodes, the 

network and the attacker). In the following we describe 

the model of a simulated system, its execution 

and the user interface of the simulation framework. 

A. SYSTEM MODEL 

In our model a distributed real-time systems is 

composed out of one or more clusters. Each cluster 

consists of one network and one or more connected 

nodes. The structure and the behaviour of 

the simulated system are defined by the following 

parameters: 

� Number of clusters 

� Number of nodes in each cluster 

� Topology for each cluster 

� Transmission delays w.r.t. communication 

� Jitter w.r.t. communication 

� Drift rate of local clocks 

� Behavior of each node 

The behaviour of each node is expressed in its 

reaction to the reception of a message and actions 

performed at specific instants in time with respect to 

its local clock. A reaction is either adapting the 

node’s internal state or sending a message with a 

specific content derived from its internal state. This 

behaviour can be programmed by the user of the 

simulation environment (e.g., the user can program 

the nodes of the simulated system to update their 

local clocks according to the FTA clock 

synchronization protocol).

B. EXECUTION OF THE MODEL 

The simulation model is executed on a discrete 

time scale called the simulation time. A tick in this 

time scale represents an instant of the real time and is 

called simulation tick. The length of each interval of 

two real-time instants represented by two succeeding 

simulation ticks is equal and called the granularity of 

the simulation time. The granularity of the simulation 

time can be defined by the user. A smaller 

granularity leads to a better temporal resolution of 

the simulation results but induces a higher load for 

simulating a given real-time interval. 

At each simulation tick the simulation framework 

will compute the new status of the individual nodes 

and the network taking into account the user defined 

topology and behaviour of the nodes as well as the 

characteristics of the chosen communication 

infrastructure (e.g., latency, bandwidth). 

The simulation supports different kinds of model 

execution: 

� Free-running mode: In this mode the simulation 

runs until a user stops it. 

� Break-point mode: Unlike free-running 

mode, the simulation runs until a specific 

condition is met (e.g. a specified point in 

time is reached, a collision has occurred, the 

precision exceeds a specified threshold …). 

When the simulation is stopped or paused, the user 

can observe or reenter the values of desired 

parameters. Furthermore after each stop a summary 

is created containing defined parameters of the 

distributed real-time system, e.g. precision during 

run-time, local time value of each nodes and failure 

time after the malicious attack. 

C. USER INTERFACE (UI) 

The simulation framework will provide an intuitive 

graphical user interface. Users can enter parameter 

values as well as monitoring for diagnostics and 

maintenance. For example, simulation time, local 

time of each nodes, precision value, correction term 

of local time, user-defined variable and so forth. 

III. SIMULATION OF MALICIOUS ATTACK 

In order to investigate and observe both mechanisms 

and effects from the malicious attacks in the 

simulation model for distributed real-time system, a 

priori known malicious attacks are explicitly assumed 

and emulated as shown below. 

- Injection of messages. One or more messages are 

added to the communication network. A number of 

injected messages might cause a denial of service [5]. 

The injected messages might also cause the collision 

96 

with other sending messages. So, the receiver will 

not get messages from the sender at the expected 

message receive instant. 

- Changing message content. The content of a 

message sent from the correct sender into correct 

receiver might be changed during transmission. 

- Changing message latency. The malicious 

attacker might attack a temporal accuracy of 

messages [6, pp. 102] by changing the message 

latency to be delayed or accelerated. 

IV. CONCLUSION AND FUTURE WORK 

We have purposed a framework for simulating distributed 

real-time systems in the presence of malicious 

attacks. This framework will ease the development 

of new security mechanisms and will be employed 

at our institute for the design of future safety 

critical architectures and applications. 


I am grateful to Christrian El-Salloum to guide me to 

work on this challenging research and thankful to 

Armin Wasicek and every colleagues for all useful 

comments and encouragements. 

REFERENCES 

[1] H. Kopetz and G. Bauer. The Time-Triggered 

Architecture, In Proceedings of the IEEE Special 

Issue on Modeling and Design of Embedded 

Software, October 2001. 

[2] H. Kopetz and W. Ochsenreiter. Clock Synchronization 

in Distributed Real Time Systems, Research 

Report Nr. 1/87/II, Institute of Computer 

Engineering, Vienna University of Technology, 

Vienna, Austria, March 1987. 

[3] H. Kopetz, G. Bauer and W. Steiner. Dependable 

Time Triggered Communication, published in 

2005 The Industrial Communication Technology 

Handbook, pp. 12.1-12.6, February 2005. 

[4] H. Kopetz, A.Ademaj, P. Grillinger, K. 

Steinhammer and M. Prammer. The Time- 

Triggered Ethernet (TTE) Design, In Proceeding 

s of the 8 th IEEE International Symposium on 

Object-oriented Real-time distributed Computing 

(ISORC), Seattle, Washington, USA, 2005. 

[5] J. Mirkovic, S. Dietrich, D. Dittrich, P. Reiher. 

Internet Denial of Service: Attack and Defense 

Mechanisms, Prentice Hall, January 2005. 

[6] H. Kopetz, Real-Time Systems: Design Principles 

for Distributed Embedded Applications, 

Kluwer Academic Publishers, 4 th Edition, 1997.

Filtering of Phase Shift Terrestrial Laser Scanner Point Clouds 

Clemens Nothegger and Norbert Pfeifer (Faculty Mentor) 

Christian Doppler Laboratory for ”Spatial Data from Laser Scanning and Remote Sensing” 

Institute of Photogrammetry and Remote Sensing 



Email: {cn,np}@ipf.tuwien.ac.at 

Abstract — The latest generation of phase shift scanners 

features an extremely high scanning speed and improved accuracy, 

thus making it possible to capture surface detail in the 

millimeter range. However, at the highest resolutions these 

scanners produce huge amounts of data which are quite noisy. 

We present a chain of preprocessing steps which reduces the 

amount of data and the noise without loosing detail. Effects influencing 

the filtering parameters are identified and a method 

for their estimation is described. 


Phase shift terrestrial laser scanners achieve measurement 

rates of up to 500 kHz resulting in a huge number 

of points (up to 600 mio.), which commercial of the shelf 

modeling software cannot handle directly. It is therefore 

necessary to apply thinning to reduce the size of the data. 

While being fairly homogeneous locally, the point density 

at different parts of the scan can vary significantly, 

depending mainly on the polar range and angle of incidence. 

This makes it necessary to set parameters adaptively 

if optimal results are to be achieved in the processing 

of the point cloud. This, however, is usually not 

possible without significant manual work. If this preprocessing 

is not done carefully loss of detail or even larger 

scale model deformation can occur, which can be hard to 

detect at later stages of the processing. 

In this paper we propose a chain of preprocessing steps 

for thinning and smoothing of point clouds acquired with 

such scanners. The preprocessing steps include surface 

normal estimation, surface roughness classification, outlier 

detection and removal, thinning, and smoothing. Our 

goal is to avoid loss of detail and thus achieve millimeter 

accuracy of the model. Since the processing is timeconsuming 

it can only be applied in a batch process. This 

means that all parameters of the computation must be 

known in advance. We show, how the parameters needed 

in the computation can be estimated and set adaptively. 

II. ALGORITHM 

The filtering strategy consists of a sequence of four steps: 

The first step is the analysis of the surface and a classification 

according to the local curvature. The second step 

consists of a computation of robust surface normal vec- 

97 

tors with outlier detection and elimination. The third step 

is a thinning step, which is followed by a forth and final 

smoothing step. All steps require the local neighborhood 

of a point p. As the local neighborhood of a point p we 

use the k points which are closest to p. These k points 

can be found efficiently by using the kd-tree data structure 

[1]. The choice of k is crucial, however, if consistent 

results are to be achieved. In [2] it is suggested that all 

points within a certain radius be used instead. This radius 

depends on local point density and curvature. For 

locally homogeneous point distribution, however, this is 

comparable to choosing an individual k for each point. 

The surface analysis we perform is based on the covariance 

analysis of the local neighborhood. In [3] it is 

shown that the surface variation σk - which can be computed 

from the eigenvalues of the covariance matrix - can 

be used instead of the local surface curvature for estimating 

surface roughness. The surface is then classified into 

smooth, rough and intermediate areas by using the maximum 

surface variation in the neighbourhood and applying 

thresholds. These thresholds heavily depend on the 

choice of k. 

Normal vectors can be estimated from the covariance 

analysis of the local neighborhood [4]. The problem with 

this approach is that it only works for continuous and 

smooth surfaces, i.e. surfaces not containing any sharp 

features. To address this problem, we use a robust estimator 

for the covariance. We used the highly robust 

Fast Minimum Covariance Determinant (FMCD) estimator 

[5] for estimating a covariance matrix, from which the 

surface normal vectors can be derived robustly. 

Robust estimation can also help with outlier detection 

(i.e. data not originating from the same underlying process 

as the majority of the other data), since it is not affected 

by leverage points [6]. Outliers in TLS may be 

caused for example by specular reflections, or if the laser 

beam hits multiple surfaces. For outlier determination, 

we use the result from the normal vector estimation. A 

point is classified as an outlier and deleted, if it is not contained 

in the final set of points which contains all points 

that are likely to be part of the same surface. 

In the thinning step, the estimated normal vectors are 

used to determine points having the highest probability 

of being closest to the real surface. From a randomly

selected point, neighboring points are projected to the 

point’s normal vector. Along this vector a univariate density 

is estimated and the point being closest to the mode 

of this distribution is chosen as the representative point. 

The mode of the distribution is found by applying the 

mean-shift algorithm [7]. 

III. NEIGHBORHOOD ESTIMATION 

The choice of k is crucial for consistent and reliable results 

for the entire scan. We want to choose k such that 

for all flat surfaces the surface variation is constant, i.e. 

the ratio of the smallest to the largest eigenvalue of the 

covariance matrix of the neighborhood must be constant: 

λ3/λ1 = const(withλ1 >λ2 >λ3) (1) 

For a given start point, we can compute the ratio λ3/λ1 

for increasing k. At a certain point this ratio will drop 

below a threshold. k is then chosen as the point where 

the ratio falls below the threshold τ. The value of τ can 

be chosen empirically. It depends on the error bounds for 

the normal vectors. 

For TLS the measurement noise is fairly constant, increasing 

just slightly with increasing range. The point 

density, however, decreases rapidly, proportional to the 

square of the range. Another influence is the angle of incidence. 

As the angle of incidence increases, the point 

density decreases. Some scanners do not correct the convergence 

of scan lines at the zenith and nadir, thus they 

exhibit an increased point density towards these points. 

We propose the following empirical formula to compute 

k: 

k = a · cos(α)/(r · sin(θ)) + b (2) 

where α is the angle of incidence, r is the range, θ is 

the zenith angle and a and b are coefficients. The term 

sin(θ) must only be used if the scanner does not compensate 

the convergence of scan lines. 

IV. RESULTS 

To evaluate the quality of the point cloud after preprocessing, 

we compared a triangulated model of the preprocessed 

points to the original point cloud. For a best 

fitting model we expect randomly distributed differences 

with a magnitude equal to that of the measurement noise 

level, no systematic deformations, but possibly large differences 

at erroneously measured points. 

We tested the method on two datasets, the first being 

an 80 by 40 cm part of a pillar of an arcade of 

Schönbrunn Palace. This object mainly consists of planar 

faces which are bounded by sharp edges. We chose 

this object to test our method’s behaviour at these edges. 

The second test dataset is a 45 by 35 cm part of a historic 

stove. This datasets contains surfaces of varying 

98 

curvatures, some sharp edges but no flat surfaces. We 

compared the model generated in our workflow to models 

derived using commercial software packages. While 

all models were acceptable, we were able to show that 

our approach produced the smoothest surface with the 

least deformation. 

V. CONCLUSION 

The processing of point clouds from phase shift terrestrial 

laser scanners poses a number of challenges that 

must be overcome if the full potential of the instruments 

is to be tapped. Among others the huge size of the point 

cloud and the relatively high noise level have been addressed 

in this paper. We demonstrated that our method 

achieves the goal of preserving surface detail while at 

the same time achieving significant smoothing. We also 

showed how it can be applied automatically by providing 

a method for estimating the parameters and setting them 

adaptively them according to known factors. 


We would like to thank the private management of 

Schönbrunn Palace and Steinmetzbetriebe Bamberger as 

members of the Christian Doppler-Laboratory for supporting 

our investigations. 

REFERENCES 

[1] M. de Berg, M. van Krefeld, M. Overmars, and 

O. Schwarzkopf. Computational Geometry Algorithms 

and Applications. Springer, 2000. 

[2] N.J. Mitra and A. Nguyen. Estimating surface normals 

in noisy point cloud data. In Proceedings of the 

nineteenth annual symposium on Computational geometry, 

pages 322–328. ACM New York, NY, USA, 

2003. 

[3] M. Pauly, M. Gross, L. P. Kobbelt, E. T. Hochschule, 

and S. Zurich. Efficient simplification of pointsampled 

surfaces. In IEEE Visualization ’02, pages 

163–170, 2002. 

[4] TK Dey, G. Li, and J. Sun. Normal estimation for 

point clouds: a comparison study for a Voronoi based 

method. In Point-Based Graphics, 2005. Eurographics 

Proceedings, pages 39–46, 2005. 

[5] P. J. Rousseeuw and K. van Driessen. A fast algorithm 

for the minimum covariance determinant estimator. 

Technometrics, 41(3):212–223, 1999. 

[6] P.J. Rousseeuw and A.M. Leroy. Robust Regression 

and Outlier Detection. Wiley, 1987. 

[7] Y. Cheng. Mean Shift, Mode Seeking, and Clustering. 

IEEE Transactions on Pattern Analysis and Machine 

Intelligence, pages 790–799, 1995.

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Hybrid Timing Analysis for ANSI-C Applications 

with Loops and Function Calls 

Bernhard Rieder, Peter Puschner 

Institute of Computer Engineering 



Email: {bernhard,peter}@vmars.tuwien.ac.at 

Abstract — Todays automotive industry uses an increasing 

number of electronic control units (ECUs) to perform complex 

safety-critical tasks. 

The systems used to implement these tasks are hard real-time 

systems which means that the result of a calculation is only usefull 

when it has the correct value and when it arrives on time. 

The failure of such a system may cause catastrophic results, 

such as the loss of human life. 

Worst Case Execution Time (WCET) Analysis is used to determine 

the maximum execution time of a task running on a realtime 

system, an information which required to ensure that each 

task meets its deadline. The presented work describes a hybrid 

WCET analysis method, combining static program analysis and 

dynamic execution time measurements. 


Traditionally, the execution time of an application was 

determined by manually performed end-to-end measurements 

using user-generated input data which was supposed 

to cover the execution path with the biggest execution 

time. In the last years the control applications have 

become increasingly complex. Now a control application 

for a power train has more than 10 40 possible executions 

paths ∗ which makes impossible to cover all paths using 

end-to-end measurements. 

In this article we describe a method to perform segmentation 

of applications and perform end-to-end measurements 

on the individual segments. Using the WCET 

of each Program Segment (PS) the WCET of the whole 

application is estimated. The presented work extends the 

prototype described in [1] to support loops and function 

calls. 

This article is structured as follows: Section II. describes 

how the hybrid WCET calculation method works. 

Section III. explains how it is extended to support loops 

and function calls, which is the main contribution of this 

work. Section IV. discusses topics that require further 

research and section V. describes similar work. 

II. HYBRID WCET ANALYSIS 

The hybrid WCET analysis consists of fife steps which 

are depicted in Figure 1: ➀ Static Program Analysis is 

performed to identify variables and control structures and 

∗ Code supplied from an industrial partner from the MoDECs project 

101 

to generate a Control Flow Graph (CFG). ➁ The CFG 

is split up into individual Program Segments during the 

CFG Decomposition. ➂ In the next phase, the Test Data 

Generation, model-checking is used to generate test data 

to cover all paths of each program segment. ➃ These data 

are used to perform Execution Time Measurements from 

which ➄ the WCET is derived during the WCET Calculation 

step. The individual steps of the analysis process 

are described in more detail in [1] and [2]. 

Figure 1: Hybrid WCET Analysis Framework 

Since the CFG partitioning and the test data generation 

step are key points of the hybrid WCET analysis approach, 

they shall be briefly described here. 

The CFG partitioning works by reducing the number 

of decisions and therefore paths in the analyzed code. 

When looking at a series of n+m conditional expressions 

we can observe 2 n+m execution paths. When the code is 

partitioned in two program segments PSn and PSm only 

2 n +2 m paths exist. Considering a piece of code with 16 

subsequent if-then-else constructs we can observe a total 

of 2 16 = 65536 paths while only 2 ∗ 2 8 = 512 paths 

exists if we create two program segments (PS). If the 

code is partitioned in four segments, this number drops 

to 4 ∗ 2 4 =64. In this simple idealized example the number 

of paths that need to be measured has dropped from 

65536 to 64. Figure 2 shows the effect of segmentation 

on an applications from the automotive domain [3]. The 

first column shows the number of program segments. In 

the first line this is 1, which means the programs segment 

comprises the whole application. The second column 

shows the number of paths that need to be measured after 

the segmentation. The third number is the Path bound.

The path bound is the maximum number of paths within 

a single PS and is used for the automatic partitioning algorithm. 

The last column represents the overall analysis 

time (including execution time measurements) in seconds. 

Instead of 1.9 ∗ 10 11 end-to-end measurements we 

need only 92 measurements when using 14 program segments 

and a fraction of the time. 

PS Paths Path bound Time [s] 

1 1.9E+11 unbounded - 

5 1455 1000 41402 

7 336 100 7794 

8 242 50 - 

14 92 10 957 

Figure 2: Hybrid WCET Analysis Framework 

The test data generation in step ➂ uses a heuristic stage 

to find the majority of results very quickly and a modelchecking 

stage to find the remaining data. Since modelchecking 

is complete, which means any existing solution 

will be found, we can used it not only for test data generation 

but also to identify infeasible paths. When the test 

data generation finishes we have test data for each path 

within a PS or we know that a syntactical possible path 

is semantically infeasible. This gives us the certainty that 

the worst-case execution time of each PS has been found. 

This does not mean that the local WCET path is part of 

the global WCET path which gives a chance for the overestimation 

of the global WCET. 

III. LOOPS AND FUNCTION CALLS 

While the WCET analysis framework created in [3] does 

not rely on code modifications other than inserting Instrumentation 

Points (IPs) for measurements extensive alterations 

on the source code are necessary for the measurement 

of loops and functions calls. The measurement of 

loops uses model checking to find the maximum iteration 

count of the loop[4]. After the loop bound is known, 

there are three possible ways to perform execution time 

measurements: 

α) The loop has no control flow decisions and can be 

covered like a single expression without further action. 

β) The loop has data dependent control flow and 

Paths(loop) Iterations ≤ Path Bound: The loop has to be 

unrolled for test data generation but is kept as loop for 

execution time measurements without any IPs. 

γ) The loop has data dependent control flow and 

Paths(loop) Iterations > Path Bound: Handle the loop 

like β but place an IP inside the loop and perform a measurement 

for each iteration. 

The last approach is the most invasive since measurements 

can reduce the performance considerably[2]. 

Function calls are handled similar. If it is not necessary 

to place IPs into the function when Paths(loop) ≤ 

102 

Path Bound the function is inlined in the model generation 

but kept as function for execution time measurements. 

If Paths(loop) > Path Bound then the function 

is inlined which allows the placement of IPs inside the 

function. 

IV. OPEN ISSUES AND OUTLOOK 

This work assumes that the source code CFG is equivalent 

to the CFG of the object code and that instructions 

execute with the same latency. The first assumption requires 

a mapping between object code and source code 

to check for equality. The second assumption requires 

the identification of variable latency instructions an their 

consideration in the measured execution times. 

V. RELATED WORK 

Chapter 35 of [5] gives a very complete overview of 

WCET analysis and explains different techniques of time 

acquisition (static, dynamic) as well as different methods 

of WCET calculation (tree based, path based and IPET) 

and much more. 


This work has been supported by the FIT-IT research 

project “ATDGEN - Automatic Test Data Generation 

for WCET Measurements” under project number 

812653/1729-GLE/BLC. 

REFERENCES 

[1] I. Wenzel, B. Rieder, R. Kirner, and P. Puschner. Automatic 

Timing Model Generation by CFG Partitioning 

and Model Checking. In Proc. of the Conference 

on Design, Automation and Test in Europe, pages 

606–611, 2005. 

[2] B. Rieder, I. Wenzel, K. Steinhammer, and 

P. Puschner. Using a Runtime Measurement Device 

with Measurement-Based WCET Analysis. In Proc. 

International Embedded Systems Symposium 2007, 

pages 15–26, 2007. 

[3] I. Wenzel, R. Kirner, B. Rieder, and P. Puschner. 

Measurement-Based Timing Analysis. In Proc. 3rd 

Int’l Symposium on Leveraging Applications of Formal 

Methods, Verification and Validation, 2008. 

[4] B. Rieder, P. Puschner, and I. Wenzel. Using Model 

Checking to derive Loop bounds of general Loops 

within ANSI-C applications for measurement based 

WCET analysis. In Proc. Sixth Workshop on Intelligent 

Solutions in Embedded Systems (WISES’08), 


[5] I. Lee, J. Y-T. Leung, and S. H. Son, editors. Handbook 

of Real-Time and Embedded Systems. Computer 

and Information Science Series. Chapman & 

Hall/CRC, 1 edition, 7 2007. ISBN 1-58488-678-1.

Deterministic Finite Automaton with Perfect Hashing for Fast 

Pattern Matching 

Abstract — As todays networks grow very fast, it is necessary 

to protect networks by security systems such as firewalls and 

Intrusion Detection Systems. Pattern matching is time critical 

operation on multigigabit networks for current IDS. Patterns 

are often described by regular expressions. The paper deals 

with fast regular expression matching using the Deterministic 

Finite Automata (DFA) with perfect hash function. We introduce 

decomposition of the statement to the transformation of 

the alphabet and fast DFA. We introduced perfect hash to reduce 

space/speed trade off for DFA transition table. 


In recent years, Internet becoming very popular to connect 

computers all over the world. While the availability 

of always-on communication has created many new opportunities 

it has also bring new possibilities for the malicious 

users. Therefore the importance of the network 

security is growing. Intrusion Detection Systems (IDS) 

are used for the detection of the malicious activity on the 

network. 

To define suspicious activities most modern IDS relies 

on set of rules that are applied to each input packet. The 

simplest rules are in the form of packet type and pattern 

of content. Looking for such patterns is the core operation 

for the IDS. 

Modern IDS cannot process each packet independently, 

because an attacker can possibly send part of the 

attack at the end of one packet and the other part at the beginning 

of the following packet. To identify such attacks, 

IDS must scan each network flow as one stream. For the 

stream reconstruction, we need to store some information 

for every flow. If DFA is used for pattern matching, the 

stored information is state. As the number of flows can 

be high and memory size is limited, one state has to be 

represented by only small amount of memory. 

II. PERFECT HASHING 

Under the concept of Perfect Hash a hash function that 

has no collisions in the given set of keys is understood. 

Such hash functions are rare and their identification can 

be computationally intensive. However, it allows to determine 

the position of the key in hash table in constant 

time in the worst case. This property can be very helpful 

in the implementation of the DFA, because we often 

work with very sparse and large transition table in which 

Jan Kastil and Jan Korenek (supervisor) 




Email: ikastil@fit.vutbr.cz 

103 

we need to lookup. As an disadvantage of perfect hashing, 

the fact that we need to store Perfect hash function 

in the memory can be seen. 

Many algorithms exist which aim at finding perfect 

hash function. They differ mainly in the number of bits 

which are needed to store Perfect Hash Function (PHF). 

Each hash function maps its key into integer interval. 

With PHF each key has its own number. It is often required 

the output interval to be minimal. Than we spoke 

about Minimal Perfect Hash Function (MPHF), which is 

PHF which output interval size is equal to the number of 

keys. For our research, we chose algorithm presented in 

[1] and used it for the implementation of the transition 

table. This algorithm requires only about 3 bit per key to 

store MPHF. 

III. PRINCIPLES OF THE METHOD 

In the worst case we need to examine each character of 

the input stream. Automaton in the FPGA can make one 

transition per clock cycle and work up to 200 Mhz. To 

achieve the throughput needed in modern networks we 

need to accept more than one character in each transition 

either by implementing more automata or by means 

of input stream transformation. For reducing state information 

and possible problem with coordination of many 

automata we use second approach. 

Figure 1 shows that our method consist of two independent 

steps. First, the alphabet transformation by a 

shared decoder. Second, pattern matching by DFA. 

Figure 1: Description of our method

A. PERFECT HASH AS TRANSITION FUNCTION 

We propose to use DFA as a pattern match algorithm. 

Figure 1 shows detailed logical structure of DFA. The 

computation of the next state consist of three blocks. In 

the first block, the position of the transition is computed. 

The second is transition table itself and it returns the 

value of the next state and information needed for the validation 

of the result. The third block is called next state 

logic and it validates results from the transition table. 

Each transition is represented by starting state, symbol 

and ending state. The first two values are used to address 

position in the transition table and the last is stored in addressed 

position. Our experiments show that transition 

table is extremely sparse. We use hash table to remove 

unused spaces from the table. In the first block, hash from 

input state and symbol is computed. Transition table then 

returns 3-tuple of state, symbol and next state. State and 

symbol are compared with actual state and input symbol 

in the validate block. If classical approach to hash tables 

was used, we should have several possible transitions returned 

from the transition table. In such case, all of them 

would have to be tested and time complexity of the third 

block would be linear in the worst case. We solve this 

problem by using MPH in the first block. 

When we find minimal perfect hash function for the 

transition table then every transition will have one unique 

position and no empty space will be in the table. We still 

have to solve collisions, because nonexistent transitions 

are mapped into the table and they collide with some existing 

transition. As we use MPHF we are sure that if 

actual state has outgoing transition with input symbol it 

will be situated on returned position. Therefore only one 

comparison in validate block is needed. 

Perfect hash has to be pre-computed. Perfect hash 

function has to be stored in the memory and therefore 

it increase memory requirements. Algorithm described 

in [1] is used, because its memory requirements are increasing 

linearly. 

IV. RESULTS 

Memory consumption of our approach is O(kn), where 

n is number of transitions. Due to space limit we used 

only two other methods for the comparison. In [2], 

next state logic and transition table are implemented as 

a treebitmap. The second method is called bit parallel 

and was published in [3]. 

We chose 12 rules from virus rule set from snort and 

combine then into one big automaton. We estimated 

memory needed to store this automaton by mentioned 

methods. Results are shown in table 1. 

From Table 1, it can be recognized that our method 

requires less memory than other methods. The difference 

grows with the number of symbols in the alphabet of the 

automaton. 

This result proves that our method is suitable for automata 

with big alphabets. Memory required for the alphabet 

transformation is not taken into account, because 

104 

n Alphabet 

size 

Tree 

bitmap 

[kb] 

Perfect 

Hash 

[kb] 

Bit parallel 

[kb] 

2 777 330 42 1400 

3 3213 1400 140 3600 

4 13000 6500 700 12000 

Table 1: Table shown numbers of the symbols in the alphabet 

of FA and memory in bits needed to store automaton 

it will be equal for all methods. 

Our results prove that for accepting more than one 

character per clock we have to deal with big alphabets. 

V. CONCLUSION AND FUTURE RESEARCH 

We propose new regular expression matching algorithm 

based on DFA which utilizes Perfect Hash functions for 

fast transition table look-up. Finite Automaton with Perfect 

Hash can perform transition in constant time even 

with extremely big alphabets and allows to store sparse 

transition in compact form. Our solution does not implement 

any additional compression into the transition table 

and still has better memory requirements than other 

tested solutions. Moreover, the proposed algorithm is 

scalable well even for multigigabit networks by increasing 

number of characters accepted within one clock cycle. 

The memory overhead of the perfect hash function 

is extremely small, therefore FPGA resources could be 

effectively utilized and even large automaton can fit to 

on-chip memory. 

There are many possible directions for future research. 

First, we could concentrate on the alphabet transformation. 

This would allow us to increase the number of 

characters accepted at once and increase the throughput. 

Second, we could reduce memory requirements of our 

method by introducing additional compression of records 

in transition table. It would be also possible to increase 

average throughput by skipping characters. The research 

in this area will be the core of my future work. 

REFERENCES 

[1] Fabiano C. Botelho, Rasmus Pagh, and Nivio Ziviani. 

Simple and space-efficient minimal perfect 

hash functions. In In Proc. of the 10th Intl. Workshop 

on Data Structures and Algorithms, pages 139–150. 

Springer LNCS, 2007. 

[2] Nathan Tuck, Timothy Sherwood, Brad Calder, and 

George Varghese. Deterministic memory-efficient 

string matching algorithms for intrusion detection. In 

In IEEE Infocom, Hong Kong, pages 333–340, 2004. 

[3] Gonzalo Navarro and Mathieu Raffinot. New techniques 

for regular expression searching. Algorithmica, 

41(2):89–116, November 2004.

Network Coding for Cooperative Communications 

Gordhan Das Menghwar 

Christoph Mecklenbräuker (Faculty Mentor) 

Institute of Communications and Radio Frequency Engineering 



Email: gdas@nt.tuwien.ac.at 

Abstract — In this paper, we propose network coding, as an 

efficient and low cost option for the implementation of block- 

Markov coding for cooperative communications. Cooperative 

communications is a strategy where users, besides transmitting 

their own encoded information, also relay re-encoded versions 

of other users’ information to a common destination. Our work 

is motivated by the recent information-theoretic results on user 

cooperation. These results show that cooperating users in a 

multiple access channel can improve on the classical multiple 

access channel capacity region under the same average transmit 

power constraint. Additionally, cooperation provides diversity 

gain. The proposed implementation of the above information 

theoretic coding with network coding is very simple and 

cost effective. 


Signals transmitted through radio channels are prone to 

wave propagation effects like scattering, reflection, refraction, 

and diffraction. The result of these effects is a 

faded signal received at the destination. This faded signal, 

whose receive power level varies over time, is subject 

to noise and interference which result in unreliable 

bit decisions. To counter these effects, one strategy is to 

increase the diversity order of the communications channel 

by providing several independent copies of the same 

transmitted signal. 

For this purpose many strategies like space, frequency, 

and time diversity have been used. In the line of same efforts 

of improving the signal quality at receiver, user cooperation 

was introduced by Sendonaris et al [1, 2]. Cooperative 

diversity is a communications strategy where 

users besides transmitting their encoded information also 

relay re-encoded version of other users’ information to a 

common destination. 

In our work, we use network coding [3] to implement 

block-Markov coding used by [4] to achieve diversity and 

capacity gain by user cooperation. The structure of the 

random codebooks used users u1 and u2 is as follows: 

x1 = w1 

x2 = w2 

� (α1P1)+r � (1 − α1)P1 

� (α2P2)+r � (1 − α2)P2 

(1) 

(2) 

for some 0 ≤ αi ≤ 1, where the transmission takes place 

in blocks. wi represents the fresh information in the current 

block and r is the cooperative refinement information 

depending on the fresh information sent in the previ- 

105 

ous block [4]. 

Our results show that by using network coding in cooperative 

communications we can achieve diversity gain 

and the said strategy is easy to implement practically. 

The paper is structured as follows: In section II we 

present our system model. In section III, we describe the 

network coding and receiver structure for that. Section 

IV presents our results and finally we conclude in section 

V. 

II. SYSTEM MODEL 

In our cooperative communications setup, two users u1 

and u2 wish to send information, denoted by wi where 

i = 1, 2, to single destination as shown in Figure 1. We 

Figure 1: cooperative communications setup 

assume that the channels from sources to destination and 

the inter-user channel are block-fading Rayleigh and receiver 

noise is assumed to be AWGN with zero mean and 

unit variance. Discrete-time baseband received signal at 

each receiver and at each sample time k, is 

y0[k] =h1,0x1[k]+h2,0x2[k]+n0[k] (3) 

y1[k] =h2,1x2[k]+n1[k] (4) 

y2[k] =h1,2x1[k]+n2[k] (5) 

y0[k], y1[k] and y2[k] are the received signals at destination, 

users u1 and u2 respectively. xi is the encoded 

message transmitted by the user ui, wherei =1,2. ni 

represent the Gaussian noise at the receivers with variance 

No. Fading coefficients between transmitter i and 

receiver j are represented by hi,j. The signal-to-noise 

ratio (SNR) is defined as: 

si,j = |hi,j| 2 P 2 i 

No 

(6)

In this model, we assume perfect echo cancellation on 

the basis of the fact that each user knows its own signal, 

therefore it can cancel out its own message’s effect on 

their received signal. 

Channel phase information availability at the transmitter 

side is assumed. With the help of this phase information, 

transmitters can adjust the phase of the signal at the 

transmitting side which results in coherent combination 

of the received signal at the destination. 

Furthermore, for practical reasons we impose half duplex 

constraint on the channel that both of the users can 

not send or receive at the same time. Their channel assignment 

looks like as in Figure 2. An average trans- 

u1 Transmits x1 

u2 Listens 

Destination Listens 

u2 Transmits x2 

u1 Listens 


time 

u1 Transmits r 

u2 Transmits r 


Figure 2: Proposed orthogonal cooperative communications 

protocol 

mission power constraint of Pi is imposed on the nodes, 

where i = 1, 2. For simplicity, we assume that all the terminals, 

users u1, u2 and destination are at the same distance 

d. Furthermore, we assume perfect channel knowledge 

at the receivers. 

III. NETWORK CODING FOR COOPERATIVE 

COMMUNICATIONS 

For our two user cooperative communications setup, first 

user u1 broadcasts its fresh information in first time slot 

which is received both by another user and the destination. 

Same thing is done by user u2 in the second time 

slot. Finally, in the third time slot both of the users send 

refinement information part of their message which is 

same for both of the users. This message is formed by 

taking exclusive or (XOR) operation of users’ own message 

with the message received from other cooperating 

user. User power Pi is divided between their first phase 

of fresh information and second phase of XOR operation, 

appropriately. 

At the receiver side, it detects and saves the messages 

received by both of the users during their fresh information 

transmission phase. In the refinement phase of 

transmission by users, it gets the XOR copy of both of 

the messages and uses this to get the second copy of the 

message for each user as follows: 

ˆx1 = r ⊕ ˆx2 

ˆx2 = r ⊕ ˆx1 

IV. OUTAGE PROBABILITY 

In block fading case, channels considered follow a 

Rayleigh distribution, but remain constant for some specific 

time and than they change. As a result the achievable 

rates change accordingly. Therefore it is difficult to 

(7) 

(8) 

106 

maintain constant rate, in this situation outage probability 

is better performance measure. 

Outage probability is defined as the probability that 

asystemrateR falls bellow a certain required rate R ′ . 

By using cooperative communications concept with network 

coding, we not only have capacity gain but, diversity 

gain is also in the list of potential gains provided by 

this promising scheme. For the reason of space constraint 

we only show the results for diversity gain as shown in 

Figure 3. As can be seen from the figure that with coop- 

Outage probability 

10 0 

10 −1 

10 −2 

10 

0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 

−3 

Cooperative 

Non−Cooperative 

Required rate R’ 

Figure 3: Outage probability comparison at 8 dB SNR 

erative communications we get 25 percent reduction in 

outage as compared to non-cooperative communications. 

For these results we have taken the inter-user channels 

as well as user destination channel operating at the same 

SNR level of 8 dB. 

V. CONCLUSION 

We proposed a simple XOR-based network code for 3phase 

orthogonal cooperative communications protocol. 

The simulation results indicate that we benefit from a 

22% increase in rate for outage probability of 10−2 . 

There is 25% of reduction in outage at the rate of 0.55 

bits per channel use, where inter-user and user destination 

channels are operating at SNR of 8 dB. 

REFERENCES 

[1] A. Sendonaris, E. Erkip, and B. Aazhang. User cooperation 

diversity-Part I: System description. IEEE Trans. Commun., 

51(11):1927–1938, Nov 2003. 

[2] A. Sendonaris, E. Erkip, and B. Aazhang. User cooperation 

diversity-Part II: Implementation aspects and performance analysis. 

IEEE Trans. Commun., 51(11):1939–1948, Nov 2003. 

[3] R. Ahlswede, N. Cai, S.-Y. R. Li, and R. W. Yeung. Network 

information flow. IEEE Transactions on Information Theory, 

46(4):1204–1216, July 2000. 

[4] J. N. Laneman. Cooperative Diversity in Wireless Networks: Algorithms 

and Architectures. PhD thesis, Massachusetts Institute of 

Technology, Cambridge, MA, Aug 2002.

Graphics versus spoken language in pedestrian navigation 

Felix Ortag and Georg Gartner (Faculty Mentor) 

Institute for Geoinformation and Cartography 



Email: {felix.ortag,georg.gartner}@tuwien.ac.at 

Abstract — Today’s navigations systems for pedestrians 

are mainly based on car navigation. Different 

needs of car drivers and pedestrians are in part 

obvious. Therefore it seems to be useful to do investigations 

which might help to improve pedestrian 

navigation systems. 

The abstracted diploma thesis compares two ways 

of communication between the system and its user: 

spoken instructions and graphic maps – each as 

single method. Which guides the user »better« to his 

destination? Where does he feel safer? Which 

would he prefer? How does the mental map differ? 

These questions were investigated for indoor and 

outdoor use in an empirical test with 31 test persons 

who had to walk on test routes using a prototype 

navigation system. 


The main focus of cartography lies on graphic representations 

of the real world. Other types of media are 

mostly considered as an additional improvement, but 

not as a replacement. This is because of the outstanding 

qualities of the visual media in communicating 

complex context and large amounts of information 

in a quick way [1]. [2] mentions interesting 

numbers on this: humans need 1.5 seconds to decode 

an information which was decoded verbally. In contrast 

to this it is possible to process up to 17 information 

units in 0.2 seconds when they are transported 

on the visual channel without verbal coding. 

However, this master thesis questions that a user in 

the pedestrian navigation situation needs to know so 

much about the area surrounding him. From a very 

pragmatic point of view one could argue that the 

usability of a pedestrian navigation system is as important 

as the special knowledge the user derives. 

Today there are already navigation systems for pedestrians 

sold commercially, but they are often car 

navigation systems with only slight or even no adaptations 

to the usage situation of a person moving by 

foot [3, 4]. One of the many improvements for pedestrians 

one could think of is a hands free voice only 

navigation system. The main idea of this master 

thesis was to prove this idea with empirical means. 

107 

II. THESES 

After literature research it was decided to test the 

following theses for two presentation forms: a map 

on a PDA and verbal instructions supplied via an 

earphone: 

� Subjective navigation quality. The user’s feeling 

of being on route or off route is independent of 

the presentation form. 

� Objective navigation quality. There is no difference 

in measurable parameters like walking 

speed and number of errors. 

� User acceptance. People prefer the system with 

auditory instructions. 

� Mental map. The mental map – the “map in the 

user’s head” – is better concerning topology and 

completeness when the map is used as presentation 

form. 

III. EMPIRICAL TEST 

In the empirical test 31 test persons had to use two 

different navigation systems: a PDA displaying a 

map and a route to go and a wireless earphone which 

gave verbal instructions on how to proceed. The used 

devices are shown in Figure 1. Each test person had 

to do four test routes, two of them outdoor and the 

other two indoor. In each environment the graphic 

presentation form was used on one route and the 

verbal one on the other route. The system was not a 

real navigation system with working positioning 

sensors but a simulation that only worked on the 

selected test routes and with the investigator accompanying 

the test person. 

Figure 1: Devices used for the test: a tablet PC (for 

the investigator), a PDA and a Bluetooth earphone.

After doing the navigation tasks the test persons 

were interviewed with a short questionnaire and had 

to draw sketch maps of the outdoor routes. 

IV. RESULTS 

Among the numerous results there were two interesting 

significant ones: Women were slower than men 

when graphic route presentations (maps) were used 

on the outdoor routes. In comparison, this difference 

did not appear when spoken instructions were used. 

The results from the interviews support this, as 

women overall had a more positive attitude towards 

spoken language than men. 

Another result is that for indoor use the test persons 

walked significantly faster when they were 

guided by voice. Here again the results from the 

interview support this finding. 

Concerning the theses mentioned earlier the following 

was found out: 

� Subjective navigation quality. Basically, this 

thesis was supported by the interview results, but 

there seem to be differences between indoor and 

outdoor usage and between the genders. 

� Objective navigation quality. Concerning walking 

speed and number of errors there were no 

significant differences between the two presentation 

forms. 

� User acceptance. The preference for the audio 

system seems to be true for indoor routes. For 

outdoor routes we were not able to show this. 

The idea that the preference is individually different 

seems promising. 

� Mental map. Surprisingly there was no difference 

in the quality of sketch maps in conjunction 

with the presentation form. 

V. CONCLUSION 

Maps are powerful means to communicate spatial 

information and this work – of course – did not 

change this fact. But it shows that for the usage situation 

of pedestrian navigation a map is not the only 

possibility to present a route ant that spoken language 

can be a real alternative. Some users even prefer it. 

The often discussed and claimed user adaptivity of 

location based services should also include the possibility 

to choose the presentation form. 

Another open field for further research are the verbal 

instructions itself. As there is a long tradition of 

making maps there are not that many open questions 

concerning their usage in pedestrian navigation systems, 

but for spoken instructions the opposite is true. 

Does the user prefer short statements “to the point” 

108 

or longer descriptions with a certain grade of redundancy? 

Is it important to pronounce street names? 

Aside of this considerations which mainly focus 

on the user’s needs, one could also investigate the 

economic and financial aspects of the topic. Systems 

with spoken instructions could be made cheaper and 

automated as there is no cartographic work needed. 

REFERENCES 

[1] R. Däßler. Visuelle Kommunikation mit Karten. 

In Visuelle Medienkompetenz. Fachbereich Informationswissenschaften, 

FH Potsdam, 2002. 

[2] G. Buziek. Dynamic Elements of Multimedia 

Cartography. In: W. Cartwright, M. P. Peterson 

and G. Gartner (Eds.): Multimedia Cartography, 

pages 231–245, Springer-Verlag, Berlin, Heidelberg, 

1999. 

[3] G. Gartner, A. Frank and G. Retscher. Pedestrian 

Navigation System in Mixed Indoor/Outdoor 

Environment – The Navio Project. In CORP 

2004 & Geomultimedia04 Proceedings, pages 

165–171, 2004. 

[4] F. Heidmann and F. Hermann. Benutzerzentrierte 

Visualisierung raumbezogener Informationen 

für ultraportable mobile Systeme. In Visualisierung 

und Erschließung von Geodaten. Beiträge 

des Seminars GEOVIS 2003, Kartographische 

Schriften, Band 7, pages 121–131, Deutsche Gesellschaft 

für Kartographie, Hannover, 2003.

Hardware Acceleration of Protocol Identification 

Petr Kobierský and Jan Koˇrenek (Faculty Mentor) 




Email: {ikobier,korenek}@fit.vutbr.cz 

Abstract — A dynamic grow of computer networks encourage 

rapid development of network applications and services. 

For providing sufficient network service quality it is important 

to shape network flows based on their application protocol type. 

This work analyzes current best protocol identification methods 

for use on multi-gigabit networks. Based on analysis, the hardware 

architecture which accelerates computationally intensive 

algorithms parts is proposed. Our solution is able to work on 

10 Gbps networks and export application protocol type using 

Netflow protocol. 


Internet is becoming used by more and more applications 

and services. Network has to guarantee different levels 

of quality for each network protocol. For this tasks it 

is necessary to identify application protocol in network 

flows which is seen, with respect to different protocol 

types (ciphered, corporate standards etc.), as a serious 

problem. 

Standard traffic identification methods associate the 

observed traffic with application according to the TCP or 

UDP port numbers using IANA list of registered ports. 

To avoid detection, several applications have begun to 

use dynamic port numbers and well-known ports commonly 

used by protocols, such as HTTP or SMTP so 

new detection methods had to be utilized. Current protocol 

identification techniques are based on payload analysis, 

but they can be circumvented using variable length 

padding and protocol encryption. In recent years, researchers 

solved some of this issues using statistic based 

protocol identification methods [1]. These methods are 

able to identify applications with the accuracy of about 

90 – 100 % using statistical information gathered from 

network flows. 

Current protocol identification methods are not perfect 

and each method is suitable for detection of different protocol 

types. Using a combination of these methods is 

possible to get better protocol identification accuracy for 

all types of application protocols. Unfortunately, operations 

which have to be performed during protocol identification 

are computationally intensive and performance 

of their software implementation is not sufficient for deployment 

on current networks and dedicated accelerated 

implementations are required. 

This work analyzes computational intensity of application 

protocol identification operations and allocates 

109 

them on hardware and software resources. Based on the 

allocation, selected operations are mapped on hardware 

resources with intention to accelerate current best protocol 

identification methods to 10 Gbps networks. 

II. PROTOCOL IDENTIFICATION MODEL 

Based on the knowledge of current application protocol 

identification methods the general model was created. 

Proposed model shown in Figure 1 covers all necessary 

operations for accurate protocol identification using currently 

best identification methods. The model was build 

to analyze computational intensity for individual operations 

of protocol identification. The model consists of 

several cooperating processes which are responsible for 

L2-L4 protocol layers processing, holding per-flow information, 

L3-L4 protocol reassembling and protocol identification. 

Input Interface 

L2 – L7 

Layers 

Identification 

Out-order 

packet 

storage 

Pattern Matching 

Header 

Field 

Extraction 

L3 and L4 Protocol 

Reassembling 

Flow Statistic 

Computation 

Classification 

Network 

Flow 

Identification 

Collision 

Network Flows 

Context 

Information 

Keeping 

Context 

Information 

Update 

Packets 

Application Data 

Headers 

Flow Context 

Collision 

Flow ID 

Position of L2-L7 

Figure 1: Model of application protocol identification 

Computationally intensive operations which limit usage 

of current identification methods to networks up to 

1 Gbps were identified based on performed model simulations. 

The most critical operation was regular expression 

matching with software throughput about 18 Mbps 

for 200 regular expressions. Other necessary operations 

have sufficient throughput for 1 Gbps networks but not 

for 10 Gbps networks. The results of performed simulations 

can be seen in Table 1. 

Output Interface

Operation Throughput 10GBase-TX 

L2-L4 parsing 21 Mp/s 

Reassembling 2.5 Mp/s 

Statistics computation 3 Mp/s 

Pattern matching 18 Mb/s 

Protocol classification 1 Mflows/s 

Table 1: Software throughput of selected operations 

III. PROPOSED ARCHITECTURE 

Hardware and software architecture of network probe 

were proposed based on the results of model simulations. 

This architecture consists of a hardware acceleration card 

and a host computer. The accelerator performs packet 

header analysis, per-flow statistic collection and regular 

expression matching. Information about flows (statistics, 

matched regular expressions) is exported via PCI bus for 

software processing. Software performs classification 

task and export information about flows and identified 

application protocols using Netflow v9 protocol. This 

standardized protocol can be collected by active network 

devices which can perform appropriate actions like traffic 

shaping and blocking. 

The COMBO6 1 card equipped with Xilinx Virtex II 

FPGA is used as a hardware accelerator. The firmware 

architecture comes out from existing Netflow probe design 

[2] with several modifications. For enabling statistical 

protocol identification, suitable statistics (with respect 

to hardware realization and protocol identification 

accuracy) were identified. The firmware architecture was 

adapted to be able to collect these statistics on network 

flows. The firmware was also extended with powerful 

pattern match unit which enables the usage of signature 

based protocol identification methods. The final 

firmware architecture is shown in Figure 2. 

NetCOPE 

Input 

Buffers 

Sampling 

HFE 

HFE 

HFE 

Hash 

Generator 

External 

Memory 

Flow state 

manager 

Pattern 

Match 

new 

External 

Memory 

Flow 

context 

block 

FPU 

FPU 

FPU 

modified 

SW 

Buffer 

Figure 2: Hardware accelerator firmware architecture 

1 http://www.liberouter.org 

110 

Regular expressions from open-source project L7filter 

were used for signature based protocol identification. 

Most of these signatures were transformed into 

NFA representation which can be easily mapped to 

FPGA logic and later used to pattern matching [3]. Before 

conversion to VHDL NFAs are transformed to lazy 

NFA representation which enable processing more characters 

in one transition. To save hardware resources the 

lazy NFAs are also determinized and minimized. Thanks 

to these optimization a throughput over 10 Gbps was 

achieved. 

The application protocols are identified based on extracted 

attributes using software classifier. The decision 

tree based classifier was selected after evaluation of several 

classification algorithms because of high throughput 

and ability to work with very large training set. Classifier 

was evaluated using set of pre-classified network 

traffic from Cambridge University. For very small set of 

attributes (up to 10 attributes) was able to archive 95 % 

accuracy of application protocol identification. 

IV. CONCLUSION AND FUTURE RESEARCH 

The new protocol identification model with respect to 

mapping operations between software and hardware was 

created. A new architecture of protocol identification 

probe has been proposed based on the model. Presented 

architecture combines statistic and signature based identification 

methods to archive better detection accuracy 

and it is also able to archive throughput over 10 Gbps. 

The implemented pattern match unit accelerates regular 

expression matching more than 400 times compared to 

software solutions. 

The future work will put focus mainly on hardware 

probe evaluation with various traffic samples. We also 

plan to analyze particular application protocols (mainly 

P2P networks) in detail and find suitable classification 

attributes and methods for them. 

REFERENCES 

[1] Andrew W. Moore and Denis Zuev. Internet traffic 

classification using bayesian analysis techniques. In 

Proceedings of the 2005 ACM SIGMETRICS international 

conference, volume 33, pages 50–60. ACM 

Press, June 2005. 

[2] Petr Kobierský Martin ˇZádník, Jan Koˇrenek and 

Ondˇrej Lengál. Network probe for flexible flow 

monitoring. In Proceedings of IEEE Design and Diagnostics 

of Electronic Circuits and Systems, pages 

213–218, 2008. 

[3] Jan Koˇrenek and Petr Kobierský. Intrusion detection 

system intended for multigigabit networks. In Proceedings 

of IEEE Design and Diagnostics of Electronic 

Circuits and Systems, pages 361–364, 2007.

Evolutionary Design of Wormhole Switched Collective Communications 

Jiri Jaros and Josef Schwarz (Faculty Mentor) 




Email: {jarosjir,schwarz}@fit.vutbr.cz 

Abstract — In this paper, we describe an evolutionary 

technique aimed at scheduling collective 

communications on interconnection networks of 

parallel computers. To avoid contention for links 

and associated delays, collective communications 

proceed in synchronized steps. Minimum number of 

steps is sought for the given network topology, 

wormhole (pipelined) switching, minimum routing 

and given sets of sender and/or receiver nodes. 

Used technique is able not only re-invent optimum 

schedules for known symmetric topologies like 

hyper-cubes, but it can find schedules even for any 

asymmetric or irregular topologies in case of general 

many-to-many collective communications. 


At the present time, multiprocessor systems are more 

frequently found not only in high-end servers and 

workstations, but also in small-scale parallel systems 

for high performance control, data acquisition and 

analysis, image processing, networking processors, 

wireless communication, and game computers. The 

importance of communication among CPU cores, 

processors and computers and of related interconnection 

networks is recently steadily growing. Whereas 

the lower bounds on time complexity of various 

collective communications (CC) can be mathematically 

derived for any network topology and the given 

communication pattern, finding a corresponding 

schedule of communication is much more difficult, 

and in some cases it is not known as yet. The rest of 

the paper addresses the quest for an optimal communication 

schedule based on evolutionary algorithms, 

provided that network topology and communication 

patterns are given. 

II. MODEL OF COMMUNICATION 

Any CC can be seen as a set of point-to-point communications. 

The CC scheduling problem can be 

simply described as partitioning this set into as few 

subsets as possible that follow one another in sequence 

of synchronized steps, and all communications 

in one subset proceed in parallel. 

111 

The main goal is to avoid any conflicts in shared 

resources – links (channels). Several messages between 

source-destination pairs, not necessarily the 

neighbours, can proceed concurrently, and can be 

combined into a single subset if their paths are linkdisjoint. 

If the source and destination nodes are not 

adjacent, the messages go via some intermediate 

nodes, but processors in these nodes are not aware of 

it; the messages are routed automatically by the 

routers attached to processors. 

To achieve low power consumption and chip area 

requirements, the wormhole switching and source 

based routing have been employed [1]. 

Four collective communication patterns were examined 

for their high time complexity and impact on 

the performance degradation. They were one-to-all 

broadcast (OAB), one-to-all scatter (OAS), all-to-all 

broadcast (AAB) and all-to-all scatter (AAS). 

III. OPTIMIZATION ALGORITHM 

The proposed technique makes profits from using 

evolutionary algorithms to relax the limitation of 

currently known heuristic techniques (adaptive routing, 

graph colouring, recursive division or conventional 

human design) [3]. 

A. PRE-PROCESSING PHASE 

An input data structure stores a topology description, 

a definition of CC and subsets of communicating 

nodes. After an input file is loaded, the data have to 

be pre-processed. The pre-processor takes a topology 

and finds all paths (shortest ones in the case of minimal 

routing) between all source-destination node 

pairs and stores them into a special data structure 

employing the modified Dijkstra’s algorithm. 

B. SOLUTION ENCODING 

As broadcast and scatter CC are completely different 

communication services, candidate solutions are 

encoded in separate ways. 

The OAS chromosome contains P genes equals to 

number of communicating nodes; each gene consists 

of two items: an index of one of the shortest source-

destination paths, and a communication step number. 

An index of gene represents a destination node for 

the scattered message. 

In the case of OAB, an indirect encoding has been 

used; a chromosome does not include a broadcast 

tree, but only instructions how to create it. Each 

chromosome consists of P genes, one for each destination 

node. Individual genes are composed of three 

items: a source node index, the shortest path index, 

and a step number. 

An AAB/AAS chromosome is created as by extending 

the vector to a matrix, each row of which 

corresponds to one of OAB/OAS communications. 

C. FITNESS FUNCTION DEFINITION 

The fitness function is based on counting conflicts 

between all point-to-point communications realized 

in the same steps. The numbers of conflicts from 

particular steps are summarized. The valid communication 

schedule for a given number of communication 

steps must be conflict-free, i.e. its fitness value 

has to reach zero. Valid schedules are either optimal 

(the number of steps equals the lower bound) or 

suboptimal. In practice, we start with higher number 

of possible steps and if the EA is successful then 

decrease this value. 

D. ACCELERATION HEURISTIC 

To improve the searching abilities and speed-up the 

convergence, the acceleration heuristic has been 

utilized. It is based on search space pruning taking 

into account: 

− a search space restriction due to a limited message 

injection capability of network nodes 

− injection of promising building blocks into initial 

population 

− guided broadcast tree construction 

− guided selection of message source and utilized 

path 

IV. EXPERIMENTAL RESULTS 

The proposed technique has been verified on well 

known hypercube topology, where the best known 

schedules have been reinvented again (Ho-Kao or 

double-tree schedule)[3]. Optimal schedules have 

been founded also for other easily fabricated networks 

like 2D mesh, ring, octagon, K-ring, midimew, 

ladder, etc. [5]. The special diameter-degree 

networks have been examined for their compactness, 

and the results have been published in [1]. 

Moreover, the fault-tolerance of special networks 

has been investigated under a single link or node 

fault [2]. The proposed technique has been also ap- 

112 

plied to fat topologies and irregular topologies like 

fat octagon, coated mesh or AMP [3]. 

Finally, more complex communication services 

with overlapping subsets of senders and receivers 

(many-to-many communications), never solved before, 

have been explored and their results published 

in [4]. 

Last but not least, the proposed method was declared 

as Human competitive at GECCO 2007 [6]. 

V. CONCLUSION 

Since many of optimal CC schedules are still not 

known, the proposed technique can speed-up many 

distributed systems. Moreover, it can be employed to 

repair suffered systems by isolating and deactivating 

of damaged blocks, reloading of corrected communication 

schedules and restarting the system. 


This research has been carried out under the financial 

support of the research grant “Security-Oriented 

Research in Information Technology”, MSM 

0021630528 (2007-13). 

REFERENCES 

[1] J. Jaros and V. Dvorak. An Evolutionary Design 

Technique for Collective Communications on 

Optimal Diameter-Degree Networks. In Proceedings 

of the 2008 Genetic and Evolutionary Computational 

Conference GECCO, pages 1539- 

1546, New York, US, ACM, 2008. 

[2] J. Jaros. Evolutionary Design of Fault Tolerant 

Collective Communications. In Proceeding of 

8th International Conference, ICES 2008, pages 

261-272, Berlin, DE, Springer, 2008. 

[3] J. Jaros, M. Ohlidal and V. Dvorak. An Evolutionary 

Approach to Collective Communication 

Scheduling. In Proceedings of the 2007 Genetic 

and Evolutionary Computational Conference, 

pages 2037-2044, New York, US, ACM, 2007. 

[4] J. Jaros, M. Ohlidal and V. Dvorak. Complexity 

of Collective Communications on NoCs. In Proceedings 

of the 5th International Symposium on 

Parallel Computing in Electrical Engineering, 

pages 127-132, Los Alamitos, CA 90720-1314, 

US, IEEE CS, 2006. 

[5] V. Dvorak, J. Jaros and M. Ohlidal. Optimum 

Topology-Aware Scheduling of Collective Communications. 

In Proceedings of the Sixth International 

Conference on Networking, pages 6, New 

York, US, IEEE CS, 2007. 

[6] The “Hummies” URL http://www.geneticprogramming.org/hc2007/cfe2007.html

Component Based Communication Middleware for AUTOSAR 

Dietmar Schreiner 1 , 

Karl M. Göschka 2 (Faculty Mentor), and Jens Knoop 1 (Faculty Mentor) 

1 Institute of Computer Languages, Compilers and Languages Group 

2 Institute of Information Systems, Distributed Systems Group 



Email: {schreiner,knoop}@complang.tuwien.ac.at 

Email: {k.goeschka}@infosys.tuwien.ac.at 

Abstract — Due to market demands and technological 

progress automotive electronic systems have become highly 

complex, distributed, and heterogeneous systems. In consequence, 

costs and time-to-market tend to out-grow spendable 

budgets, whereas quality seriously suffers. To overcome this situation, 

automotive manufacturers agreed upon a new standard 

for their electronic systems—AUTOSAR. In AUTOSAR applications 

are built in conformance to the component paradigm by 

assembling prefabricated application components that utilize 

standardized component middleware. Hence, AUTOSAR compliant 

systems provide increased reusability, maintainability 

and thus reduced time-to-market and over-all costs. However, 

the middleware itself is still a coarse grained layered software 

architecture that is hard to adapt and to optimize w.r.t. application 

specific needs. Within this paper we provide an overview 

on our work on how to apply the component paradigm to the 

component middleware itself, and how to capitalize on this redesigned 

middleware architecture by automatically synthesizing 

custom-tailored, light-weight middleware that still complies 

to the AUTOSAR standard. 

I. MOTIVATION 

Driven by steadily increasing requirements of innovative 

applications, automotive electronic systems have reached 

a level of complexity that requires a technological breakthrough 

in order to manage them cost efficiently and 

at high quality. In contrast to other domains, like e.g. 

avionics, automotive electronic systems are produced in 

comparatively large quantities (69,1 million vehicles in 

2006). Therefore, the price per unit has to be as low as 

possible, forcing manufacturers to assemble economical, 

and thus resource constrained electronic building blocks. 

In consequence, automotive software has to cope with 

harsh restrictions, especially with limitations of available 

memory and processing power. 

The Automotive Open System Architecture 

(AUTOSAR) [1], an upcoming industry standard 

within the automotive domain, reflects these facts by 

constituting Component Based Software Engineering 

(CBSE) [2, 3, 4] as development paradigm for automotive 

applications. CBSE is well accepted within the 

embedded systems community, as it provides a clear 

separation of concerns, and hence facilitates extensive 

software reuse. In AUTOSAR, application concerns are 

113 

Application 

Layer 

« component » 

AUTOSAR SWC 

AUTOSAR compliant BSW Interfaces 

Basic Software 


COMPASS MWC 

RTE 


AUTOSAR SWC 


COMPASS MWC 


COMPASS MWC 

AUTOSAR 

Component Model 

COMPASS 

Component Model 

Figure 1: Component based AUTOSAR middleware 

covered by software components, while infrastructural 

ones are handled within layered component middleware. 

This design leads to an increase in application quality, 

reusability, and maintainability, and consequently to a 

reduction of costs and time-to-market. However, the 

AUTOSAR component middleware is specified as layered 

software that is only customizable on a coarse-grained 

level. 

In consequence, conventional AUTOSAR middleware 

tends to be heavy-weight, which is problematic within 

resource constrained automotive embedded systems. 

Therefore, our work contributes by applying the component 

paradigm to AUTOSAR beyond the application 

layer—to the component middleware. AUTOSAR’s conventional, 

layered middleware architecture is replaced by 

a component based design that completely resembles the 

standard’s functionality, but is more flexible in terms of 

application specific customization. 

To capitalize on the benefits of a component based architecture, 

we designed a model driven development process, 

that incorporates generation of component based 

communication middleware. As a result, customtailored, 

resource saving middleware can automatically 

be synthesized from application models and prefabri-

cated, reusable middleware components. 

II. COMPONENT BASED MIDDLEWARE 

As adumbrated in Fig. 1, we aim at the construction 

of component based AUTOSAR middleware. This so 

called Basic Software is assembled from standardized 

and hence replaceable middleware components, but still 

has to provide the same interfaces as its conventional 

counterpart, to allow seamless integration into existing 

environments. 

To build component based middleware we developed 

a new component model (COMPASS CM) for the middleware, 

which can not resort to middleware itself. Our 

component model specifies a component definition, and 

a composition- and interaction-standard. Composition 

is based on procedural- and on data-interfaces (function 

calls and shared memory); interaction may adhere to 

the client-server or the sender-receiver paradigm. The 

type-system of COMPASS CM is kept close to that of 

AUTOSAR to ensure full compatibility [5]. 

III. COMPONENT IDENTIFICATION 

After specifying a sound component model for component 

based middleware, we identified standardized middleware 

building-blocks as much as pared-down versions 

for each of them. Therefore we investigated a 

full-fledged industry implementation of a Basic Software 

stack. First we did a manual decomposition based on expert 

knowledge. In a second step we developed a contextinsensitive 

static analysis that, guided by few manual 

source-code annotations, automatically identified a set 

of valid decompositions containing the manually created 

one [6, 7]. 

IV. AUTOMATED MIDDLEWARE SYNTHESIS 

One of the advantages of component architectures is the 

ability to easily replace single building-blocks by isomorphic 

ones exposing the same interfaces. Heavyweight 

components may be replaced by pared-down 

ones, if the application does not require the components’ 

full functionality. Based on this fact, we developed 

a model driven process that automatically synthesizes 

AUTOSAR middleware from prefabricated middleware 

building blocks and application models [8, 9]. The 

core of the defined model driven process is the so called 

Connector Transformation. It transforms platform independent 

models (PIMs), describing the application’s 

component architecture, into platform specific models 

(PSMs), containing application components and component 

equivalent middleware structures. The PSMs moreover 

render the system’s physical structure, so one PSM 

is created for each system node. 

114 

V. RESULTS 

To prove the proposed methodology, and to assess the 

reduction in size of the synthesized communication middleware, 

we implemented a simple automotive application. 

The read-only-memory (ROM) footprint of the application’s 

custom-tailored, synthesized communication 

middleware was compared to that of the conventional 

industry implementation to substantiate the claimed improvement. 

Results showed a reduction of the middleware’s 

ROM footprint by nearly 30% for the implemented 

application, while a worst-case scenario, where 

the full AUTOSAR’s functionality was required within 

the middleware, led to an identical footprint as that of 

the conventional one. In addition the middleware’s execution 

time was reduced by 10% due to omitting forwarding 

calls between prescribed layers. 


This work has been partially funded by the FIT-IT [embedded 

systems initiative of the Austrian Federal Ministry 

of Transport, Innovation, and Technology] and managed 

by Eutema and the Austrian Research Agency FFG 

within project COMPASS under contract 809444, and by 

the 7th EU R&D Framework Programme within project 

ALL-TIMES under contract No 215068. 

REFERENCES 

[1] AUTOSAR. Automotive Open System Architecture. http:// 

www.autosar.org/. 

[2] Clemens Szyperski. Component Software: Beyond Object- 

Oriented Programming. Addison-Wesley, January 1998. 

[3] Ivica Crnkovic and Magnus Larsson, editors. Building Reliable 

Component-Based Software Systems. Artech House, 2002. 

[4] Rob C. van Ommering, Frank van der Linden, Jeff Kramer, and 

Jeff Magee. The koala component model for consumer electronics 

software. IEEE Computer, 33(3):78–85, 2000. 

[5] Dietmar Schreiner and Karl M. Göschka. A component model 

for the AUTOSAR Virtual Function Bus. In COMPSAC ’07: Proceedings 

of the 31st Annual International Computer Software and 

Applications Conference, volume 2, pages 635–641. IEEE, 2007. 

[6] Dietmar Schreiner and Karl M. Göschka. Building component 

based software connectors for communication middleware 

in distributed embedded systems. In Proceedings of the 2007 

ASME/IEEE International Conference on Mechatronic and Embedded 

Systems and Applications (MESA07), ASME/IEEE, 2007. 

CD-ROM. 

[7] Dietmar Schreiner, Markus Schordan, Gergö Barany, and Karl M. 

Göschka. Source code based component recognition in software 

stacks for embedded systems. In Proceedings of the 2008 

IEEE/ASME International Conference on Mechatronic and Embedded 

Systems and Applications (MESA08), IEEE. IEEE, 2008. 

to appear. 

[8] Dietmar Schreiner and Karl M. Göschka. Synthesizing communication 

middleware from explicit connectors in component based 

distributed architectures. In Proceedings of the 6th International 

Symposium on Software Composition (SC 2007), LNCS. Springer, 

2007. to appear. 

[9] Dietmar Schreiner and Karl M. Göschka. Explicit connectors in 

component based software engineering for distributed embedded 

systems. In SOFSEM 2007: Theory and Practice of Computer Science, 

Proceedings, volume 4362 of LNCS, pages 923–934. LNCS, 

Springer, Jan 2007.

The Acquaintance of Hardware Timing Effects: A Sine Qua Non to 

Validate Temporal Requirements in Embedded Real Time Systems ∗ 

Sven Bünte and Raimund Kirner (Faculty Mentor) 

Real Time Systems Group 



Email: {sven,raimund}@vmars.tuwien.ac.at 

Abstract — The validation of embedded real time systems not 

only has to include the investigation of temporal behavior of the 

software but also of the hardware to a large extent. We present 

a measurement-based analysis approach in which delays due to 

hardware effects of the system under test can be captured with 

high resolution on the one hand and how to relate this information 

to a model describing the control flow of the software on 

the other hand. 


Embedded Systems are computer systems that are included 

in devices that serve a small number of dedicated 

functions. Today’s life would be quite different without 

them: The clock radio in the morning, the coffee machine 

during breakfast, MP3-Players, mobile phones, cars, airplanes 

- they all include embedded systems. Modern cars 

comprise up to 70 microcontrollers, which is just a fraction 

compared to the amount of what can be found in airplanes 

or spacecrafts. There are estimations, that 98% 1 

of all computer systems are embedded. 

For the design of embedded control software, not only 

functional requirements have to be adhered to but also 

temporal demands. An airbag for instance must be released 

in time to be useful. Systems of this kind are referred 

to as Real Time Systems. The validation of real 

time systems has to include techniques to assure that temporal 

requirements are met. There are basically two major 

methodologies: formal verification on the one hand 

and testing (i.e. performing time measurements) on the 

other hand. The former can guarantee safe and precise 

upper bounds on execution times but is not feasible for 

complex hardware or software. In contrast, the process of 

performing measurements with random test data is easy 

to conduct but will most likely miss the Worst Case Execution 

Time (WCET) for there are too many possible runs 

such that each of them will be tested eventually. 

Our research focuses a hybrid approach in which test 

cases are not generated randomly but in a systematic way 

∗ The research leading to these results has received funding from the 

Austrian Science Fund (Fonds zur Förderung der wissenschaftlichen 

Forschung) within the research project Formal Timing Analysis Suite 

of Real-Time Systems (FORTASRT) under contract P19230-N13. 

1 http://www.jimturley.com 

115 

using formal methods. The ultimate goal is to give the 

software developer a testing tool that can provide adequately 

precise timing estimations of the system under 

test in an efficient way. The programmer should be able 

to press the check button before he leaves the office in 

order to get the results by the time he gets back to work 

the next day. 

The following section describes the hybrid approach 

in more detail and illustrates what our research project is 

concerned about. The last section shows one important 

part in the big picture, namely measuring, analyzing, and 

predicting the temporal behavior of hardware effects. 

II. MEASUREMENT BASED TIMING ANALY- 

SIS 

Figure 1: Data flow within FORTAS 

The Formal Timing Analysis Suite (FORTAS) project 2 

follows a measurement-based timing analysis approach 

based on [1]. We use formal methods like model checking 

to examine the Software Under Test (SUT) and to 

generate proper test cases which form the input for measurements 

on the target platform. 

Figure 1 depicts a top-level view on our framework: an 

embedded control program written in C is translated into 

an abstract graph representation of the program’s control 

flow structure. In a next step, we use FShell [2] for generating 

a set of test cases in oder to cover feasible paths 

in the graph. The model is then iteratively refined by 

adding timing information from the measurements that 

are performed using the test cases as input. This enables 

2 http://www.fortastic.net

techniques to take timing effects of the target platform 

selectively into account. The refinement loop stops at the 

time the software developer considers the result (the Expected 

Time System) to be adequately precise. A positive 

effect of the introduced procedure is that if the software 

is locally modified, many test cases can most likely be 

reused. 

Our approach inevitably yields to large sets of test 

data. We therefore designed an architecture [3] that (a) 

stores them and (b) manages meta information in order 

to use them conveniently. 

III. THE TEMPORAL BEHAVIOR OF HARD- 

WARE 

t1 

1 

n1 CFG 

n2 n3 

n4 

n5 

Trace element 1: 

instruction info 

t 

t start 

finish 

t2 

2 

t3 

3 

t4 

4 

t5 

5 

Trace element 2: 


t 

t start 

finish 

t6 

6 

t7 

7 

t8 

8 

... 

... 

... 

Trace element k: 


t 

t start 

finish 

t 

m-2 

t m-1 

t m 

m-2 m-1 m 

Measured path 

n1 n3 n4 n5 

tbegin 

tend 

tbegin 

tend 

tbegin 

tend 

tbegin 

tend 

Trace 

CPU cycles 

Figure 2: The relation between a trace, measured path, 

and CFG 

Recall that one of our goals is to estimate the WCET 

of the system under test. The hardware has to be part of 

the analysis to get a reasonable degree of precision. As 

an example, the latency when reading data from memory 

can differ by the factor of 100, depending on whether the 

data is located in the cache or not. A similar effect can 

be observed in the processor pipeline. A precondition 

to include hardware effects of this kind into the analysis 

using the measurement-based approach is to sample an 

execution run at a high rate in order not to miss anything. 

In our experiments we perform measurements on a Infineon 

Tricore TC1796 microcontroller. It includes an instruction 

cache, a processor pipeline and the OCDS level 

2 interface which conforms to the NEXUS 3 standard. 

Using both, the on-chip debug support and the Lauterbach 

LA-7690 Powertrace device, we reproduce a trace 

of an execution run that includes cycle-accurate timing 

and control-flow information. As depicted in Figure 2, a 

trace is a sequence of references to machine instructions. 

Furthermore, trace elements are mapped to time-stamped 

CPU cycles in which the respective instructions are processed 

in the execution unit of the pipeline. As men- 

3 http://www.nexus5001.org/ 

116 

tioned, the FORTAS model relates to the Control Flow 

Graph (CFG) of the software under investigation. In order 

to get a measured path, the trace is associated with 

CFG nodes in a further step, since each node might represent 

several machine instructions. Thus, detailed timing 

information can be related to the FORTAS model in 

a flexible way. 

The demonstrated measurement and post-processing 

method has been implemented and shows positive results 

with respect to its applicability. 

A. FUTURE WORK 

As shown, we are able to capture delays due to hardware 

effects. The next step is to use the collected data for the 

generation of new test cases. This implies that we have 

to speculate on what favorable test cases could be. In 

the context of WCET analysis the goal is quite clear: we 

want to get as many cache misses and pipeline stalls as 

possible in order to discover expensive paths within our 

model. One problem is to perceive which paths that have 

not yet been measured might lead to those time consuming 

effects. Another challenge is to differentiate whether 

an observed delay results from a cache miss, a pipeline 

stall or both. 

Beside WCET analysis, we also want to provide the 

software developer with timing profiles that can be used 

for performance optimization. Here, the Average Case 

Execution Time (ACET) might be of interest as well. We 

still do not know precisely what timing information the 

programmer considers to be useful. This is also one of 

our current research topics. Once this is known, our objective 

will be to provide this information by designing 

an appropriate analysis. 

REFERENCES 

[1] Ingomar Wenzel, Bernhard Rieder, Raimund Kirner, 

and Peter Puschner. Automatic Timing Model Generation 

by CFG Partitioning and Model Checking. In 

Proc. Conference on Design, Automation, and Test in 

Europe, Mar. 2005. 

[2] Andreas Holzer, Christian Schallhart, Michael 

Tautschnig, and Helmut Veith. FShell: Systematic 

Test Case Generation for Dynamic Analysis and 

Measurement. In Proceedings of the 20th International 

Conference on Computer Aided Verification 

(CAV 2008), Lecture Notes in Computer Science, 

Princeton, NJ, USA, July 2008. Springer. 

[3] Sven Bünte and Michael Tautschnig. A Benchmarking 

Suite for Measurement-Based WCET Analysis 

Tools. In First International Conference on Software 

Testing, Verification and Validation (ICST), Lillehammer, 

Norway, April 2008. IEEE Computer Society 

Press.

Divide and Measure: CFG Segmentation for the 

Measurement-Based Analysis of Resource Consumption 

Michael Zolda and Raimund Kirner (Faculty Mentor) 

Institut für Technische Informatik 


Wien, Austria 

Email: {michaelz, raimund}@vmars.tuwien.ac.at 

Abstract — A computer system is a good computer system if 

it correctly performs the task it was intended to perform. This 

is not even half of the truth: Non-functional requirements are 

abundant in the world of software and system engineering, even 

if they are not always stated explicitly. In our work we are concerned 

with the measurement-based analysis of resource consumption. 

Examples of resources are time, energy, or memory 

space. In the context of our measurement-based approach for 

software analysis, we face the problem of breaking the software 

under examination into smaller parts of manageable size, 

a process dubbed CFG Segmentation. 


In our measurement-based approach for resourceconsumption 

of embedded software, we perform measurements 

on the real physical computer system, and subsequently 

integrate the measurement results into a resource 

consumption model that is ready for expert inspection 

or use in a higher level analysis of the system. 

In order to obtain an accurate picture of the system behavior, 

we would like to achieve full measurement coverage 

of all feasible operation sequences of the software 

under test. We therefore start from the Control Flow 

Graph (CFG) of the software under examination, a fundamental 

program representation where nodes represent 

the operations of the software, and where directed edges 

represent possible successive execution (see Figure 1 for 

an example of a CFG). Thus, each feasible sequence of 

operations of the software corresponds to a path in the 

CFG. 

In theory, it would therefore suffice to examine all 

CFG paths, but due to the huge number of paths in the 

CFGs of real software, this approach is practically infeasible. 

For example, the CFG of a simple actuator controller 

that is part of our benchmarks contains about 10 44 

paths, which is clearly beyond measurement feasibility. 

To cope with such huge numbers of paths, we split the 

CFG into connected subgraphs of manageable size (“segments”), 

deal with these subgraphs individually, and subsequently 

merge the data that was obtained for each segment 

into a global resource consumption model. 

A (simple) segment is a connected subgraph of a CFG, 

and is characterized by its sets of entry edges (edges lead- 

117 

20783664 

20850528 20795424 

27719392 

30565936 

27719552 14453136 

20795568 20850368 

13861344 13802240 

13858944 

14793904 

24922544 

17667232 

17677824 17699296 

17699248 

14955392 14955456 

17710032 

17731072 17752272 

Figure 1: A CFG with four segments (indicated by thick, 

dashed borders). Thin borders, on the other hand, mark 

intermediate segments generated by our proposed greedy 

segmentation algorithm. 

ing into the subgraph), its set of exit edges (edges leading 

out of the subgraph), and the number of segment paths 

(paths leading through the subgraph). 

Our goal is to partition the CFG into as few segments 

as possible, such that the segment path total does not exceed 

a given feasibility limit. 

To illustrate our idea, consider Figure 1, which shows 

a tiny CFG that has been partitioned into four segments. 

The total number of segment paths to be examined is 

3+6+7+8 = 24. Without segmentation we would 

have to examine all 99 CFG paths. The number of paths 

to be examined is thus lowered by a factor of 4 in this 

tiny example, but the effect is much more pronounced 

for realistically-sized CFGs, where we use segments in 

the magnitude of hundreds or thousands of paths. 

II. PROPOSED APPROACH 

In [1, 2], Wenzel et al. present an approach for CFG 

segmentation that produces segments with a single entry 

edge. Such segments are advantageous from a composi- 

17762832

14144128 

13974624 

14172032 

13911376 

14631232 

14147008 

14728752 

14742400 

14020320 

14212496 

14518304 

13847536 

14309808 

14384736 

13879344 14061328 14518496 

14122272 

14890208 

14880336 

14048752 

14894128 

14781568 14215328 

13945200 

Figure 2: A CFG with a lattice-shaped structure. 

bility point of view, but yield problems with large proper 

interval structures [3]. For example, the lattice-shaped 

CFG in Figure 2 allows only the two trivial segmentations 

of either putting everything into one single segment, 

or putting each node an individual segment. 

We therefore abandon the single entry restriction and 

allow any number of entry edges. However, for composability 

reasons, we do not want the entry/exit interface 

to become unjustifiably large. Because we later want to 

associate measurement results with all entry/exit combinations 

of a segment, a reasonable size metric for the interface 

of a segment is 

h(S) =entries(S) · exits(S). (1) 

To perform a segmentation of this more general form, 

we propose an iterative greedy algorithm that builds segments 

bottom-up from smaller segments, starting with 

single-node segments. For each iteration, the algorithm 

considers all segments that could be created by merging 

pairs of adjacent segments and picks the least-cost one. 

As costs functions, we currently consider the following 

class of functions: 

costs(S) =h(S) a · paths(S) b , (2) 

We have already mentioned that we would like to keep 

the entry/exit interfaces of segments as small as reasonably 

possible. This explains the h(S) part of the 

costs function, which is weighted by the tunable exponent 

a. On the other hand, the paths(S) part of the costs 

function assures that the algorithm will produce roughly 

equally-sized segments. Again, this part of the costs 

function can be tuned by adjusting an exponent. 

The example in Figure 1 indicates both, the final segments 

produced by our algorithm (thick, dashed borders), 

and the intermediate segments generated during the individual 

iterations (thin borders). 

118 

III. PRELIMINARY RESULTS AND FUTURE 

WORK 

We have implemented the segmentation algorithm presented 

above as a component of the timing analysis 

framework that is currently being developed within the 

FORTAS project. Our implementation is already capable 

of handling real industrial application code. A logical 

next step would be a detailed evaluation of the produced 

segments for a larger number of benchmarks and the usage 

of the obtained insight to tune the costs function presented 

above. It is even conceivable that careful examination 

of such results point at completely new forms of 

costs functions. 

Performing segmentation is just one tasks in 

measurement-based analysis of resource consumption. 

Other tasks include the generation of suitable test 

data that can trigger the execution of individual paths [1], 

performing the actual measurements, construction of the 

complete timing model, and others. All these tasks, and 

especially their integration, are important future research 

issues. 

IV. SUMMARY 

In this work, we have explained the problem of CFG segmentation, 

as it arises in the context of measurementbased 

resource consumption analysis. We have introduced 

segmentation as a possible solution to handle the 

explosion of CFG paths and have pointed at the shortcomings 

of previous segmentation approaches. Lastly, 

we have sketched a novel segmentation algorithm that 

overcomes these shortcoming. 


The research leading to these results has received funding 

from the Austrian Science Fund (Fonds zur Förderung 

der wissenschaftlichen Forschung) within the research 

project “Formal Timing Analysis Suite of Real-Time 

Systems” (FORTAS-RT) under contract P19230-N13. 

REFERENCES 

[1] Ingomar Wenzel, Bernhard Rieder, Raimund Kirner, 

and Peter Puschner. Automatic Timing Model Generation 

by CFG Partitioning and Model Checking. In 

Proc. Conference on Design, Automation, and Test in 

Europe, Mar. 2005. 

[2] Ingomar Wenzel, Raimund Kirner, Bernhard Rieder, 

and Peter Puschner. Measurement-Based Timing 

Analysis. To be presented at the 3rd Int. Symp. on 

Leveraging Applications of Formal Methods, Verification 

and Validation, Oct. 2008. 

[3] Steven S. Muchnick. Advanced Compiler Design 

and Implementation. Morgan Kaufmann, August 

1997.

Neutralizing Timing Anomalies in 

Complex Computer Architectures ∗ 

Albrecht Kadlec and Raimund Kirner (Faculty Mentor) 

Institut für Technische Informatik 

University of Technology, Vienna 


Email: albrecht@vmars.tuwien.ac.at 

Abstract — The complex designs of current computer architectures 

mostly stem from complex optimizations performed at 

run-time. The interactions of these optimizations lead to timing 

anomalies. This paper presents a first approach to actually 

eliminate timing anomalies by transforming the code in a way 

that avoids the adverse effects of timing anomalies on the processor 

state. This enables static timing analysis to be extended 

to more complex types of computer architectures. 


Safety critical real time systems have to guarantee timeliness 

in addition to correctness. To ensure this, schedulability 

analysis was established for multi-tasking systems. 

To provide schedulability analysis with hard facts on the 

Worst Case Execution Time (WCET) of a single task, 

static timing analysis was established (more precisely: 

static WCET analysis). But static WCET analysis in turn 

relies on timing composability for complexity reduction: 

it requires that single basic blocks can be analyzed separately 

and the results be added to form an overall WCET 

for a certain execution path through the program. 

Timing anomalies compromise timing composability, 

as they produce timing artefacts, that are only analyzable 

if the whole path is considered at once. This in turn drives 

up overall analysis complexity, as the number of paths is 

much larger than the number of basic blocks, with more 

analysis time needed for a path than for a single basic 

block. This easily renders timing analysis intractable, so 

timing composability must be restored. 

Timing anomalies were first described by Lundqvist 

and Stenström for out-of-order architectures [1]. They 

defined timing anomalies as unintuitive timing behaviour, 

where the local worst case does not correspond 

to the global worst case. Their work was extended among 

others by Wenzel [2], who showed the existence of timing 

anomalies for less complex architectures without outof-order 

execution. 

In [3] we identified the processor state as the carrier 

and therefore a necessary condition for late effects, and 

∗ This work has been partially supported by the Austrian Science 

Fund (Fonds zur Förderung der wissenschaftlichen Forschung) within 

the research project “Compiler-Support for Timing Analysis” (CoSTA) 

under contract P18925-N13. 

119 

listed several properties to categorize the influence of 

the various CPU state. The second necessary condition 

for timing anomalies is choice in the CPU-internal algorithms, 

i.e., the possibility of functionally identical, 

but not timing-identical decisions based on this processor 

state (e.g. all sorts of speculation). 

As a result, the processor pipeline was identified as the 

biggest obstacle for static timing analysis, as it connects 

subsystems such as cache or jump prediction, has a high 

decision density and the decisions immediately influence 

several other subsystems. 

II. THEORETICAL FOUNDATION 

Our key observation is the fact that we do not need to 

avoid timing variations in general, but that we only need 

to make sure, that the state is identical after all possible 

executions - i.e. after all possible different decisions during 

the execution of the instructions so far. 

Timing variations can be accounted for (overestimated) 

by WCET analysis. The different possible 

state of the CPU after execution of an instruction is responsible 

for the combinatorial explosion of interactions 

with later instructions, which makes WCET analysis intractable. 

However, since CPUs must be deterministic in the execution 

of the instructions, the difference in state can only 

be a difference in time. Given enough time, the CPU 

state must converge to a single output state after each 

instruction is executed. So we must make sure that the 

following instructions, which might be influenced by the 

respective state, can only observe that state after it has 

converged - when it is stable. 

This can be done by inserting NOP instructions, until 

the state has stabilized, i.e., until all effects of the instruction 

onto the CPU state have occurred. By induction this 

avoids the state space explosion in WCET analysis, no 

matter which decisions were taken in the execution of 

any instruction. The remaining small timing variations 

themselves are easily accounted-for by the WCET analysis.

III. PRACTICAL SOLUTIONS 

A. RATE NOP INSERTION 

The easiest way to achieve our goal is to exploit the fact 

that the fetch width closely resembles the average issue 

width for a given processor: making the fetch width much 

larger overly increases the costs of the memory subsystem, 

making it smaller voids the expenses for execution 

units. However, the fetch width must be somewhat larger 

to recover from pipeline break instructions, cache misses 

and mis-speculations. 

Now if we fill this overcapacity with NOPs, we can 

easily control the issuing stage of the CPU: starting with 

an empty prefetch window, each instruction that enters 

the prefetch window is immediately ready and can be executed 

without reordering. If we do not have an instruction 

to issue in this cycle, we still have to insert a NOP 

to keep the prefetch window from filling up with the following 

instructions, that may not be executed yet. 

B. SPARSE NOP INSERTION 

We implemented a sparse NOP insertion algorithm 

within a compile-time list scheduler for fictious ARMbased 

superscalar out-of-order architectures. For detailed 

evaluations, the issue-width of the fictious CPU can be 

configured as well as the depth of the prefetch window 

and the number of respective functional units. 

Now whenever a variable-time instruction is scheduled, 

the succeeding instructions, that may be scheduled 

to the same unit are marked with a minimum program 

counter before which they may not be scheduled. The 

distance to that program counter is filled with other ready 

instructions for independent functional units or NOPs. 

This mechanism makes sure that the instruction does not 

enter the prefetch window before the effects of the previous 

instructions on the state are completed. 

C. PRELIMINARY MEASUREMENTS 

First preliminary measurement indicate that there is a 

significant but acceptable penalty in code size and dynamically 

executed instructions associated with our algorithm. 

However, we cannot supply definite numbers 

yet, as the algorithm still seems to expose bugs, so the 

measurements are not yet reliable. 


We illustrated the problem of timing anomalies in the 

wider context of WCET and schedulability analysis for 

hard real time systems. In prior work we already refined 

the description of timing anomalies from the timing domain 

to the state domain. 

Now we reasoned about the necessary preconditions 

for timing anomalies to occur in the state domain, and 

separated the tolerable effects that can be handled by 

120 

static WCET analysis from the adversary effects, that 

lead to state space explosion within the WCET analysis. 

Finally we designed two algorithms that avoid these 

adversary effects and implemented one of them. First 

measurements for a fictious four way issue superscalar 

out-of-order ARM implementation seem very positive, 

but unfortunately the numbers are not reliable enough to 

be published, yet. 

We will continue on this track and evaluate the algorithm 

for different configurations of our fictious architecture 

family. We will then look for further improvements 

of the algorithm, or more efficient alternative solutions. 

REFERENCES 

[1] Thomas Lundqvist and Per Stenström. Integrating 

path and timing analysis using instruction-level simulation 

techniques. In Proc. ACM SIGPLAN Workshop 

on Languages, Compilers, and Tools for Embedded 

Systems (LCTES), pages 1–15, June 1998. 

[2] Ingomar Wenzel. Principles of timing anomalies in 

superscalar processors. Master’s thesis, Technische 

Universität Wien, Vienna, Austria, 2003. 

[3] Albrecht Kadlec and Raimund Kirner. On the 

difficulty of building a precise timing model for 

real-time programming. In 14. Kolloquium Programmiersprachen 

und Grundlagen der Programmierung, 

pages 99–105, Timmendorfer Strand, Germany, 

Oct. 2007.

Optical Imaging Hidden Objects in Turbid Scattering Media using 

Principal Component Analysis 

Binlin Wu, S. K. Gayen (Faculty Mentor) and R. R. Alfano (Faculty Mentor) 

The Institute for Ultrafast Spectroscopy and Lasers (IUSL) 

The City College of The City University of New York 

New York, USA 

Email: bwu@sci.ccny.cuny.edu 

Abstract — We have developed a new imaging 

approach for 3D localization and characterization 

of objects in turbid media using the principal component 

analysis (PCA). The aim is to develop an 

approach for imaging inside a breast using light. A 

novel algorithm is presented based on PCA for 

optical imaging (OIPCA) of objects located in scattering 

media. OIPCA can be used with any geometry 

and any forward model in steady-state or timeresolved 

imaging. We use a model medium to demonstrate 

this method using simulated data. 


Reliable and fast approaches for inverse image reconstruction 

are important. In this paper, we present 

a novel and new algorithm based on PCA for imaging. 

We refer to this approach as Optical Imaging 

using Principal Component Analysis (OIPCA). 

OIPCA determines the number and strengths of targets 

with the leading eigenvalues. The light propagations 

from different inhomogeneities to the source or 

detector planes are uncorrelated. The locations of the 

objects are retrieved by fitting principal components 

intensity distributions (PCID) to Green’s functions. 

A multi-source and multi-detector scheme is used. 

This paper focuses on using PCA as a new 

method for optical imaging of objects in scattering 

media for breast applications. 

II. ALGORITHMS AND SIMULATIONS 

A. DIFFUSION APPROXIMATION 

Using the diffusion approximation, the light intensity 

perturbation on the detector plane to the first order of 

Born Approximation can be written as [1][2] 

n 

� 

j�1 

�� 

� G( 

r , r ) � G( 

r , r ) , (1) 

sca 

d 

j 

j 

where a j cV �� and � � �DcV 

j for absorptive 

and scattering inhomogeneities respectively. 

G ( r 

d 

, r 

j 

) and G( 

r 

j 

, r 

s 

) are Green’s functions for 

j 

s 

121 

light propagation from objects to detectors and 

sources to objects respectively. The light perturbation 

can be rewritten as 

� 

x ( r , r ) � a ( r ) s ( r ) , (2) 

d 

s 

j 

j 

d 

where s j( 

rs 

) � � jG( 

rj, 

rs 

) , a j( 

rd 

) � � jG( 

rd 

, rj 

) , 

j 

� and � are scaling factors and � j � j � � j . Using 

a multi-source and multi-detector scheme, one has 

X � AS , where rows of S are virtual sources which 

are the inhomogeneities illuminated by the incident 

light and A is a mixing matrix. 

B. OPTICAL IMAGING USING PCA 

PCA [3] is a data analysis tool widely used to extract 

hidden uncorrelated signals by finding the largest 

variances (eigenvalues). We assume the virtual 

sources are not correlated. So we mean-center the 

matrix X , solve the eigenvalue equation for the 

covariance matrix. Then we sort and select principal 

components (PC) with the leading eigenvalues and 

project the matrix X onto the selected PCs with 

noise reduced. The uncorrelated matrix is the virtual 

T T �1 

source matrix S . A � XS ( SS ) . Locations of 

the targets can be found by fitting either of A and S 

or both to the respective Green’s functions using 

least squares fitting: 

{ [ 

1 

( ) ( , )] 

2 

, , 

[ 

1 

( ) ( , )] 

2 

} 

min � � 

� 

j 

s 

j 

r 

s 

� G r 

j 

r 

s 

r 

j 

� 

j 

� 

j r 

s 

. (3) 

� 

� 

� � 

j 

a 

j 

r 

d 

� G r 

d 

r 

j 

r 

d 

C. RESULTS OF SIMULATED DATA 

The sample is a 40mm thick uniform slab of scattering 

medium, as shown in Figure 1. Its absorption and 

diffusion coefficients are � a 

�1 

� 1/ 

300mm 

and 

D � 1/ 

3mm 

, respectively. An absorptive and a 

scattering objects were placed at (50, 60, 15) mm and 

(30, 30, 25) mm, respectively. The incident CW 

beam scanned at 21� 21 grid points covering 

s

2 

80 � 80mm 

area. Light on the other side was recorded 

by CCD camera at 41� 41 grid points covering 

the same area. 5% Gaussian noise was added to 

the simulated intensity change. 

Figure 1: Light intensity on one side is measured 

when a point source scans on the other side. 

The eigenvalues found by PCA were sorted and 

the leading four PCIDs on the source and detector 

planes were calculated. The absorptive object has 

only one component while the scattering object has 

one centrosymmetric and two dumbbell-shaped 

components on the source and detector planes. The 

centrosymmetric PCIDs for the scattering and absorptive 

objects are shown in Figure 2. 

By least squares fitting the intensity profiles with 

respective Green’s functions, the absorptive object is 

found to be at (50, 60, 15.3) mm and the scattering at 

(30, 30, 25.1) mm. 

(a) 

(b) 

(c) 

122 

(d) 

Figure 2: Centrosymmetric PCIDs of the scattering 

inhomogeneity are shown in (a), of the absorptive 

inhomogeneity in (c). Normalized PCIDs on the 

source plane are shown in the second columns of (a) 

and (c), and on detector plane in the first columns. 

(b) and (d) are showing the horizontal profiles of 

intensity distributions on the source and detector 

planes (circles) and their least squares fittings (solid). 

III. SUMMARY 

OIPCA can determine the number, strength and type 

of targets without any forward model, which is helpful 

to achieve a “bind test” of targets embedded in 

turbid media such as a tumor in a breast. Due to the 

high accuracy, OIPCA is a potential novel tool for 

breast cancer detection in early stages. OIPCA runs 

very fast which make it possible for in-vivo real-time 

detection. OIPCA can also be used for pre-evaluation 

or noise removal for other imaging and reconstruction 

modalities. 


The research is supported by the U. S. Army Medical 

Research and Materials Command, IUSL and The 

City University of New York (CUNY) organized 

research programs. This research by Binlin Wu is 

made possible by the support and mentoring from 

Professor S. K. Gayen and Professor R. R. Alfano. 

The author Binlin Wu thanks Dr. Cai, Dr M. Xu and 

Dr. Alrubaiee for helpful discussions. 

REFERENCES 

[1] M. A. O’Leary, D. A. Boas, B. Chance and A. G. 

Yodh, “Experimental images of heterogeneous 

turbid media by frequency-domain diffusingphoton 

tomography,” Opt. Lett. 20, 426–428 

(1995). 

[2] S. R. Arridge, “Photon-measurement density 

functions. Part I: Analytical forms”, Applied Optics, 

Vol. 34, Issue 31, pp. 7395-7409 (1995) 

[3] I. T. Jolliffe, Principal Component Analysis. 

New York: Springer, 1986.

Links between Diachronic Thinking and Temporal Cognition 

Tasks Observed in Middle Childhood 

Brandy Moore, Patricia Brooks, Laura Rabin (Faculty Mentor) and Carmen Carrion 


Graduate Center, and Brooklyn College 

New York, United States 

Email: lrabin@brooklyn.cuny.edu 

Abstract — The present study will assess 

developments in temporal language, source 

memory, and diachronic concepts of 

transformation, synthesis, and tendency in children 

ages 5 to 10. These constructs broadly refer to the 

interpretation of events and understanding of time 

in relation to the past, present, and future. Research 

has not investigated all of these constructs 

simultaneously within this age group. One-hundred 

children participated in this study. Participants 

performed a series of tasks thought to reflect an 

understanding for temporal cognition, synthesis, 

source memory, and verbal and nonverbal ability. 

Preliminary data reveals a correlation between 

most tasks of temporal cognition. The data indicates 

that temporal cognition is significantly related to 

life experience and not to children’s nonverbal 

intelligence or age. 


The construct of diachronic thinking can be thought 

of as the ability of an individual to naturally visualize 

the past, present and future. Prior research suggests 

that this developmental change occurs early on in 

childhood during the pre-school years (Atance & 

O’Neill, 2005). This learned response occurs through 

continual exposure to daily life in which children 

develop a sense of time (Nelson, 2007). At 

approximately three years of age, children begin to 

think about the not-now (the past) as a point of 

reference to something that already occurred; 

children at this stage do not possess the capacity to 

talk about specific experiences so they envision the 

future as non-existent or as unimagined (Nelson, 

1989a, 1997, 2000). This challenge elicits the 

understanding in children that one remains constant 

while still possessing the ability to project oneself to 

the past and the future (Nelson, 2000). 

According to McCormack and Hoerl (1999) these 

experiences give rise to the concept of temporal 

order. It has been predicted, however, that temporal 

order is independent of children’s nonverbal 

intelligence and that it may be further related to their 

123 

verbal capacity and experiences in daily life (Nelson, 

2007). Source memory on the other hand refers to the 

ability of an individual to recall the context by which 

information was obtained, such as when and/or 

where an object was encountered (Cycowicz, 

Friedman, Snodgrass, & Duff, 2000). The results of 

their study suggest that source memory in children 

tends to improve with age. 

The present study seeks to demonstrate that 

developments in temporal cognition, diachronic 

transformation, synthesis, are interrelated and 

independent of age and nonverbal intelligence. 

II. METHODS 

Participants in the current study were 100 children 

between the ages of 5 and 10. The children were 

recruited either from a local school or were brought 

in by Brooklyn College undergraduate students for 

course extra credit. The children were given $10 gift 

cards for their participation. Parents and guardians 

signed an informed consent sheet and children gave 

verbal assent. The children completed Boucher, 

Pons, Lind, and Williams’ (2007) diachronic thinking 

tasks: 

A. TENDENCY 

Participants were asked to draw inferences regarding 

prior and subsequent moments in time upon 

examining a picture of a man at the beach. In the first 

task participants deduced from looking at the image 

what is happening and what is going to happen in the 

picture. In task 2 the children had to determine 

whether it was summer or winter and provide reasons 

for their response. Subsequently, participants had to 

determine if a surfer at the beach is a child or an 

adult. Lastly, the children were asked to explain why 

the man on the beach was lying on a towel and also 

why he brought an umbrella with him. For the third 

task the children were shown a blank piece of paper 

and asked to think about what might be observed 

further along the beach. In the final task of this 

section, participants were asked to place six picture

cards in order depicting the man’s past and future 

activities. 

B. TRANSFORMATION 

In the first task participants were asked to draw a 

tree, and then asked to show the tree’s life cycle by 

also drawing a before and after image. In tasks 2 and 

3 participants drew qualitatively different trees and 

placed picture cards of a tree in the appropriate 

developmental stages. 

C. SYNTHESIS 

Participants were asked to synthesize a group of 

pictures. In the first task the children were shown 4 

different sets of cards (Boucher, et al., 2007). The 

pictures depicted parts of a face, house, pot plant, or 

farm. For the second task the children viewed six 

pictures depicting the day of a man at the beach. The 

first image was of the man arriving at the beach and 

the final image was of the man in his bed sleeping. 

Children were asked what do all of the pictures 

together show. The test was terminated when the 

participants showed a capacity for synthesis. 

D. OTHER TASKS AND NEUROPSYCHOLOGICAL 

TESTS 

Upon completion of these tasks, participants 

undertook Friedman’s temporal cognition tasks 

(1990; 2000) thereby judging pictured events and 

different times of the year. A similar task was also 

administered to judge the temporal order of daily 

events. The Peabody Picture Vocabulary Test-Fourth 

Edition (PPVT-4) was utilized to estimate 

participants’ verbal intelligence and the Test of 

Nonverbal Intelligence (TONI-3) was used to 

measure nonverbal reasoning skills. Participants were 

also given a recognition test to assess whether they 

recalled seeing animate versus inanimate images 

from a previous test trial. As a final point, 

participants were asked to determine where they had 

observed images that were previously presented. This 

test was given to assess participants’ source memory 

capacity. 


Pearson partial coefficients were computed using age 

and TONI-3 scores as covariates. Preliminary data 

indicates that most tasks of temporal cognition are 

inter-correlated. There were only two intercorrelations 

of diachronic thinking but no significant 

correlations between diachronic thinking and 

temporal cognition tasks. The Peabody tests of verbal 

intelligence were significantly correlated with most 

tasks of temporal order. Conversely, the TONI-3 

124 

tasks of nonverbal reasoning skills were not intercorrelated 

with temporal cognition. 

The current data support the hypothesis that temporal 

order developments are dependent upon experience 

and not upon the developmental stage. Results reveal 

that children’s temporal cognition is independent of 

their level of nonverbal intelligence and age. Data 

collection is ongoing and we expect that findings will 

enhance understanding of the typical development of 

various cognitive skills and inform treatment of 

autism spectrum and other childhood disorders. 


This work was supported in part by the New York 

City Louis Stokes Alliance. 

REFERENCES 

[1] C. M. Atance, & D. K. O'Neill, Preschoolers’ 

talk about future situations. First Language, 1, 

pages 5-18, 2005. 

[2] K. Nelson. Young Minds in Social Worlds: 

Experience, Meaning, and Memory. February 

2007. 

[3] J. Boucher, F. Pons, S. Lind, & D. Williams. 

Temporal cognition in children with autistic 

spectrum disorders: Tests of diachronic 

perspective taking. Journal of Autism and 

Developmental Disorders, 37, pages 1413-1429, 

2007. 

[4] T. McCormack, & C. Hoerl. Memory and 

Temporal Perspective: The Role of Temporal 

Frameworks in Memory Development. 

Developmental Review, 19, pages 154-182, 

March 1999. 

[5] W. J. Friedman. The development of children's 

knowledge of the times of future events. Child 

Development, 7, 1, pages 913-932, 2000. 

[6] L. Brown, R. Sherbenou, & S. Johnsen. Test of 

nonverbal intelligence, a language free measure 

of cognitive ability. (3rd ed.). Austin: Pro-ed, 

1997. 

[7] K. Nelson. Narrative, time and the emergence of 

the encultured self. Culture & Psychology, 6, 

pages 183-196, 2000. 

[8] Y. M. Cycowicz, D. Friedman, J. G. Snodgrass, 

and M. Duff. Recognition and Source Memory 

for pictures in children and adults. 

Neuropsychologia, pages 255-267, New York, 

NY, August 2000.

Generalizing Sudoku to Three Dimensions 

Abstract —The aim of this paper is to 

generalize the logic puzzle Sudoku from twodimensions 

into three-dimensions. Our 

objective is to find the most efficient way to 

generate and solve these puzzles. Some of 

our other goals are to find how many 

possible solutions exist, and if and how ca-n 

we generate logic solvable puzzles? We have 

designed a set of rules and constraints for a 

three-dimensional Sudoku puzzle and have 

found m-any unique solutions using the 

method of simulated annealing. 


Tiffany A Lambert (Dr. Paula Whitlock) 

Brooklyn College 

The City University of New York 

Brooklyn, NY, USA 

Email: LT0180@bcmail.brooklyn.cuny.edu 

Sudoku is a logic puzzle where every row, 

column and block must contain the numbers 1-9, 

which means no number can be repeated more 

than once in a row, column or block. Sudoku can 

actually be changed to consist of smaller or larger 

blocks and can easily be defined. 

The general problem of solving Sudoku is 

known to be NP-Complete [6], and there have 

been many papers and methods published that try 

to solve Sudoku optimally. The Sudoku examples 

most people are familiar with are called logicsolvable 

because a logical reasoning approach 

will lead to a solution. Others, however, can be 

solved using many other algorithms. There has 

also been plenty of computational work done to 

find the number of unique Sudoku puzzle 

possibilities [1] [5]. 

II. METHOD 

Generalizing a three-dimensional Sudoku can be 

more challenging because it has a much larger 

state-space than a regular two-dimensional 

Sudoku. Our design has 6 faces, each where n = 

4. Every face of the puzzle is an individual puzzle 

within itself and follows the traditional rules of 

Sudoku. Our added constraint was on the cube’s 

edges, which relate the faces to one another. The 

edges on each adjacent cell must be identical. 

125 

A. SIMULATED ANNEALING 

Rhyd Lewis uses a technique called Simulated 

Annealing [3] to solve Sudoku. Simulated 

Annealing is an algorithm that employs both 

iterative improvement, as well as Monte Carlo 

methods [2]. The algorithm is based on making 

random swaps toward an optimal solution. It 

calculates an initial score and accepts a new 

move if the score has decreased. The algorithm 

accepts a move based on the following probabilistic 

function: 

−ΔE 

T 

P = e (1) 

where T is the temperature and �E is the change 

in energy or cost. The cost approaches 0 as the 

algorithm approaches a solution. 

B. NEW CONSTRAINTS 

Lewis’ Sudoku solver is capable of producing a 

solution for both partially filled, as well as 

completely empty grids. We altered the 

parameters and constraints in order to 

accommodate our three-dimensional model. We 

added additional constraints that accommodated 

our new rules for the edges. When coding this, 

we used the original two-dimensional array, but 

2 2 

increased the size to 2n × 2n 

. The array was 

divided into four quadrants, one for each face, 

with the fourth quadrant unused. For practical 

purposes, we have worked with only three faces 

of the cube. 

In order to configure the edge constraint into the 

total cost, we added an edge score to the row and 

column score. For every edge cell that does not 

meet the constraint, we added one point to the 

total edge score. This edge score told us how 

close we were to a solution. 

C. COOLING SCHEDULES 

In the original paper by Lewis the temperature 

was cooled by 1% after every Markov chain, 

which was efficient for two-dimensional 9 x 9 

Sudoku grids, but after we added our new

constraints and increased the size of the statespace, 

the algorithm was no longer efficient. We 

tested several constant cooling rates less than 

99%. These faster cooling rates did improve the 

time, but if the substance was cooled to quickly, 

it did not produce the desired results. This led us 

to experiment with dynamic cooling schedules 

such that, the temperature decreases by larger 

amounts initially, and as the cooling rate 

gradually reduces, the temperature decreases at a 

much slower rate toward the end. To achieve this, 

we made the cooling rate a function of cost, so 

that as the change in cost increases from its initial 

state, so does the cooling rate. 

III. RESULTS 

The runtimes for both rule constraints produce 

similar outcomes. The average times using 

constant cooling rates are shown below. Reheats 

were performed if the algorithm could not find a 

solution on the first run within the allocated time. 

The results are near linear with the exception of 

when it reaches its cooling limit. From the figures 

above, it is clear that the anything less than 80% 

causes the system to cool too quickly. 

Trial and error led us to new cooling schedules 

that have been the most efficient thus far. This 

schedule improved the runtime by more than 

90% from the initial cooling schedule used in 

Metaheuristics [3]. 

Time (sec) 

900 

800 

700 

600 

500 

400 

300 

200 

100 

0 

Average Runtimes 

variable 80% 85% 90% 95% 99% 

Cooling Rate 

Figure 3: Average runtimes of cooling schedules 


According to Taking Sudoku seriously [1], and 

The mathematics of Sudoku [7], we know that as 

n increases, so does the number of puzzle 

combinations. Exactly how many unique puzzles 

exist is a problem that still needs to be explored. 

As we increase to three dimensions, the number 

of possibilities grows factorially, but several 

solutions can be eliminated due to repetition. 

126 

The issue of logic solvability is still a question 

that needs to be further explored. It has not been 

proven, but the smallest known amount of 

numbers given to find a unique Sudoku solution 

is 17 [7]. Computing the minimum number of 

givens for a unique solution is an optimization 

problem that is NP-complete. 

A. CONCLUSION 

From our experiments with the cooling schedule, 

we have determined that both, change in score, 

and cooling rates are key factors in finding an 

optimal solution. As the difference between the 

initial score and the current score becomes larger, 

the cooling rate should become stricter in order to 

restrict jumps to a less optimal solution. By 

changing the cooling rate dynamically, we reduce 

the amount of Marcov chains that are started, 

thus decreasing the run time. 


We acknowledge the Louis Stoke Alliance for 

Minority Participation and the National Science 

Foundation for providing us with this grant. We 

would also like to thank Dr. Murray Gross for his 

insight and recommendations. 

REFERENCES 

[1] Felgenhauer, Bertram, and Frazer Jarvis. 

"Mathematics of Sudoku I." Mathematical 

Spectrum 39(2006): 15-22. 

[2] Kirkpatrick, S., C. D. Gelatt Jr., and M. P. 

Vecchi. "Optimization by Simulated Annealing." 

Science 220(1983): 671 - 680. 

[3] Lewis, Rhyd. "Metaheuristics can solve 

Sudoku puzzles." Journal of Heuristics 13(2006): 

387-401. 

[4] Mantere, T and J. Koljonen. “Solving and 

rating Sudoku puzzles with genetic algorithms.” 

Proceedings of the 12 th Finnish Artificial 

Intelligence Conference (2006): 86-92. 

[5] Russell, Ed, and Frazer Jarvis. "Mathematics 

of Sudoku II." Mathematical Spectrum 39(2006): 

54-58. 

[6] Santos-Garcia, G. and M. Palomino. 

“Solving Sudoku Puzzles with Rewriting Rules.” 

Electronic Notes in Theoretical Computer 

Science 176(2007): 79-93. 

[7] Taalman, L. “Taking Sudoku Seriously.” 

Math Horizons 15(2007): 5-9. 

[8] “Sudoku Solver by Logic.” (2006) 

http://www.sudokusolver.co.uk

Chapter 2 

Material Sciences

Nonadditivity of Quantum Phases for mixed States 

J. Klepp, S. Sponar, S. Filipp, M. Lettner, G. Badurek and Yuji Hasegawa 

Atominstitut 



Email: {jklepp,hasegawa}@ati.ac.at 

Abstract — In a neutron polarimetry experiment mixed state 

relative phases between spin eigenstates are determined. We 

consider evolutions leading to purely geometric, purely dynamical 

and combined phases. It is experimentally demonstrated 

that the sum of the geometric and dynamical phases - both obtained 

in separate measurements - is not equal to the associated 

total phase which is obtained from a single measurement, unless 

the system is in a pure state. Therefore, surprisingly, mixed 

state phases are not additive. 


Evolving quantum systems acquire two kinds of phase 

factors: (i) the dynamical phase which depends on the 

dynamical properties of the system - like energy or time - 

during a particular evolution, and (ii) the geometric phase 

which only depends on the evolution path the system 

takes in state space on its way from the initial to the final 

state [1, 2]. Due to its robustness against noise [3] the 

geometric phase is an excellent candidate to be utilized 

for logic gate operations in quantum information science 

[4]. Thus, a rigorous investigation of all its properties is 

of great importance. 

In addition to an approach by Uhlmann [5] a new concept 

of phase for mixed input states based on interferometry 

was developed by Sjöqvist et al. [6]. Here, 

each eigenvector of the initial density matrix independently 

acquires a geometric phase. The total mixed state 

phase is a weighted average of the individual phase factors. 

This concept is of great significance for such experimental 

situations or technical applications where pure 

state theories may imply strong idealizations. Theoretical 

predictions have been tested using NMR and singlephoton 

interferometry [7, 8]. Here, we report on measurements 

of nonadiabatic and noncyclic geometric, dynamical 

and combined phases. These depend on noise 

strength in state preparation, defining the degree of polarization, 

the purity, of the neutron input state. In particular, 

our experiment demonstrates for the first time that 

the geometric and dynamical mixed state phases Φg and 

Φd, resulting from separate measurements, are not additive 

[9], because the phase resulting from a single, cumulative, 

measurement differs from Φg +Φd. These striking 

results are published in [10]. 

II. THEORETICAL CONSIDERATIONS 

A polarized neutron beam propagating in y-direction, 

interacting with static magnetic fields �B(y), undergoes 

129 

Figure 1: Schematic view of the measurement setup with 

overall guide field Bz, polarizer P, three DC-coils to im- 

plement unitary operations U1, U † 

1 ,Uφ, analyzer A and 

detector D. Greek letters denote spin rotation angles. 

Shifting the second coil induces an additional dynamical 

phase η resulting in intensity oscillations. The desired 

phase φ is determined from their minima and maxima. 

Zeeman splitting. This results in a momentum shift 

k± � k0∓Δk, where k0 is the momentum of the free particle 

and Δk = mμ|�B(y)|/¯h 2 k. Δk can be detected from 

spinor precession. We focus on the resulting evolution of 

superposed spin eigenstates sometimes described as Larmor 

precession of the polarization vector �r = 〈ϕ|�σ|ϕ〉, 

where �σ =(σx,σy,σz) is the Pauli vector operator. 

Consider the experimental setup shown in Figure 1. 

In [11] it is stated that with such an apparatus one can 

obtain the pure state Pancharatnam (total) phase [1] between 

spin eigenstates of neutrons, induced by a SU(2) 

transformation Uφ(ξ,δ,ζ). The phase can be written as 

a function of the maximum Imax and minimum Imin of the 

intensity oscillations, exhibited by applying an auxiliary 

phase shift η. The intensity only depends on the SU(2) 

parameters ξ, δ and ζ - set by choosing the spin rotation 

angles in the second coil and the additional propagation 

distance within the guide field Bz, respectively. η is varied 

by stepwise translation of the second coil. 

A neutron beam with incident purity r = |�r| along the 

+z-axis (�r =(0, 0,r)) is described by the density operator 

ρin(r) =1/2(1l + rσz). For mixed input states, 

0 ≤ r

sity, one obtains the mixed state phase [12]. For r =1, 

Figure 2: Evolutions Uφ associated to: a) Purely (noncyclic) 

geometric phase (2ξ = π/2). b) Combinations of 

dynamical and geometric phase (0 < 2ξ

Complexation of trivalent Cm and Eu with extraction ligands for the 

Partitioning & Transmutation strategy 

S. Trumm a,b , P. J. Panak a,b , A. Geist a , R. Klenze a , Th. Fanghänel b,c 

a 

Institut für Nukleare Entsorgung, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, 

Germany 

b 

Ruprecht-Karls Universität, 69120 Heidelberg, Germany 

c 

Institute for Transuranium Elements, European Commission, 76125 Karlsruhe, Germany 

The partitioning and transmutation (P&T) strategy [] i is a prosperous strategy for the treatment 

of spent nuclear fuels. The aim is to reduce the long-term radiotoxicity of the nuclear material 

by separating long-lived actinides (Np, Pu, Am and Cm isotopes) and transmuting them into 

shorter-lived isotopes by nuclear fission. In this way the long-term radiotoxicity of high-level 

nuclear wastes can be significantly reduced, which has a positive impact on the storage in 

final geological repositories. 

The separation of trivalent americium and curium from the lanthanides is a key step within 

this process. Due to their similar chemical behavior, highly selective ligands are necessary to 

separate trivalent actinides from lanthanides. This separation step, is not feasible using 

common oxygen-donor ligands extractants, only soft donor ligands bearing nitrogen or sulfur 

atoms induce the desired selectivity. 

[ ] ii 

Alkylated 2,6-Bis(1,2,4-triazine-3-yl)pyridines (BTPs) and 6,6’-Bis(1,2,4-triazin-3yl)bipyridines 

(BTBPs, figure 1) have shown high performance in the separation of trivalent 

minor actinides (americium, curium) from lanthanides and were the first N-donor extracting 

agents to extract and separate trivalent actinides and lanthanides from nitric acideous 

[ ],[ ] 

solutions. iii iv However, the origin of the observed selectivity is not yet completely 

understood. To set the foundation for the basic understanding of the selectivity, fundamental 

research towards the complexation of these ligands with trivalent actinides and lanthanides is 

necessary. 

Fig. 1: Structure of BTP and BTBP ligands 

BTP BTBP 

In this work we investigated the complexation of Cm(III) and Eu(III) using the time-resolved 

laser fluorescence spectroscopy (TRLFS). This method allows monitoring complex species in 

organic solution at very low concentrations. To quantify the differences in complexation 

between BTPs and BTBPs, complexation constants have been derived from titration 

experiments. Two new BTP ligands have been synthesized carrying substituents on the 

pyridine ring altering the electronic structure of the aromatic system. This allowed us for the 

first time to investigate the influence of electronic parameters on the complexation and 

extraction chemistry of Cm(III) and Eu(III). Further we were able to gain thermodynamic 

parameters of complexation of BTBP ligands with trivalent Cm and Eu by measuring the 

equilibrium between the complex species in solution at different temperatures. 

131

The results show a difference between the complexation constants of BTP ligands with the 

two metal ions in the range of three to five orders of magnitude, which is in excellent 

agreement with the selectivity found in extraction experiments. The complexation of Eu(III) 

shows a significant dependence on the electron density of the coordinating nitrogen atoms. 

Electron withdrawing substituents cause a decrease of complexation constants whereas 

electron donating substituents lead to higher ones. Also in extraction experiments the 

influence of the substituents is observed. This information is important for the understanding 

of selectivity and also for the optimization of extraction ligands with respect to future 

industrial processing. The results of our studies on the complexation of BTBP ligands with 

Cm(III) and Eu(III) show higher changes in the free enthalpy of complexation for Cm(III) than 

for Eu(III). The thermodynamically favored complexation of trivalent Cm is again in good 

agreement with extraction experiments. 

i 

Actinide and fission product partitioning and transmutation, status and assessment report; OECD 

Nuclear Energy Agency; Paris, 1999. 

ii 

Nash, K. L. Solvent Extr. Ion Exch. 1993, 11 (4), 729�768. 

iii 

Kolarik Z.; Müllich U.; Gassner F. Solvent Extr. Ion Exch. 1999, 17 (1), 23�32. 

iv 

Kolarik Z.; Müllich U.; Gassner F. Solvent Extr. Ion Exch. 1999, 17 (5), 1155�1170. 

132

COMPLEXATION OF Cm(III) WITH NITRATE AND FLUORIDE AT ELEVATED 

TEMPERATURES STUDIED BY 

TIME-RESOLVED LASER FLUORESCENCE SPECTROSCOPY 

A. Skerencak a,c , P. J. Panak a,c , V. Neck a , R. Klenze a , Th. Fanghänel b,c 

a Institut für Nukleare Entsorgung, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany 

b Institute for Transuranium Elements, European Commission, 76125 Karlsruhe, Germany 

c Ruprecht-Karls Universität, 69120 Heidelberg, Germany 

Fundamental understanding of the geochemical processes in the near and far field of a nuclear waste repository 

and their thermodynamic quantification is necessary for the assessment of the long-term migration behavior of 

actinides in the geosphere. The migration of the nuclides is limited by their low solubility and interaction with 

inorganic material (i.e. interaction with mineral surfaces (sorption, incorporation)). Conversely, aqueous 

complexation with proper ligands can increase their mobility. As natural waters contain a variety of inorganic 

ligands such as OH - , CO3 2- , SO4 2- , Cl - , F - , H2PO4 - , H3SiO4 - , HCO3 - , and NO3 - , the complexation of actinides with 

inorganic ligands is of particular interest for a better understanding of the migration behaviour of actinides under 

natural conditions [1] . Extensive knowledge on the participating chemical reactions and the corresponding 

thermodynamic data is needed. In the past few years considerable progress in establishing a thermodynamic 

database for lanthanides and actinides has been achieved [2] . Nevertheless, these data is mostly restricted to 

ambient temperatures. Due to the heat production in the close vicinity of radioactive waste, complexation 

reactions of actinides at elevated temperatures are of major importance for modelling the migration behaviour of 

actinides under near field conditions over a long time period. 

We utilized a newly designed high temperature and high pressure cell coupled with time resolved laser 

fluorescence spectroscopy (TRLFS). TRLFS is a versatile tool for determining the speciation of actinides in the 

submicromolar concentration range and provides information on reaction mechanisms without disturbing the 

chemical equilibrium [3] . Because of its outstanding spectroscopic properties, Cm(III) is chosen as a 

representative for trivalent actinides. In this work we have investigated the complexation of Cm(III) with 

fluoride in the temperature range of 20 to 90°C and with nitrate in the temperature region of 20 to 200°C. The 

speciation is done via peak deconvolution. The equilibrium constants are determined and extrapolated to zero 

ionic strength using linear SIT Regression. Modeling of the data is done according to the Van't Hoff equation at 

temperatures up to 90°C. Higher temperatures required an extended Van't Hoff equation for adequate modeling. 

From this approaches valuable thermodynamic data (�rH 0 m, �rS 0 m, �rG 0 m, �rC 0 p,m) is derived at elevated 

temperatures. 

The results show a strong increase in complexation of Cm(III) with increasing temperatures resulting in a 

significant increase of the stability constants at elevated temperatures. Due to high temperatures in the close 

vicinity of a nuclear waste repository, the increased complexation leads to an increased mobility of the actinides 

under near field conditions. Therefore, the determined thermodynamic data is crucial for a reliable description of 

the migration behaviour of radionuclides under near field conditions and has to be taken into account for the long 

term safety assessment of a nuclear waste repository. 

[1] Fanghänel, Th., Kim, J.-I., Journal of Alloys and Compounds, Vol. 271-273, 728-737, (1998). 

[2] Guillaumont, R., Fanghänel, Th., Neck, V., Fuger, J., Palmer, D.A., Grenthe, I., Rand, M.H., Chemical 

Thermodynamics 5, Nuclear Energy Agency, Elsevier Science Publisher, (2003). 

[3] Edelstein, N. M., Klenze, R., Fanghänel, Th., Hubert, S., Coord. Chem. Rev. 250, 948, (2006). 

133

134

Development of �-(Al,Cr)2O3 solid solutions 

by reactive magnetron sputtering 

Dominic Diechle, Michael Stüber, Harald Leiste and Sven Ulrich (Faculty Mentor) 

Institute for Materials Research I 

Forschungszentrum Karlsruhe 

Karlsruhe, Germany 

Email: dominic.diechle@imf.fzk.de 

Abstract — Hard, tough, wear and corrosion 

resistant thin film materials are very important for 

many applications such as cutting tools. We present 

a new combinatorial approach for the deposition of 

solid solution strengthened �-(Al,Cr)2O3 thin films 

grown by reactive r.f. magnetron sputtering in an 

argon-oxygen atmosphere. The deposition 

experiments are carried out with a Leybold Z 550 

PVD machine for the sputtering from a segmented 

target. The growth, phase formation and 

constitution of the thin films has been characterized 

by various methods. 


The development of superior coatings for high 

performance cutting tools is a key element for 

significant advances in metal working. Aluminum 

oxide thin films, mostly deposited by chemical 

vapour deposition (CVD) methods, are an established 

technology in this application field. Recently, the 

physical vapour deposition (PVD) synthesis of 

aluminum oxide and derivate coatings is attracting 

large scientific and technical interest. Especially 

aluminum-chromium oxide thin films are promising 

candidates for further significant improvement. 

Physical vapour deposition allows a nanoscale design 

of thin films made of ceramics, metals and their 

alloys, far away from thermodynamic equilibrium 

conditions. The “Holleck triangle” classifies hard 

materials with regard to their bonding [1]. For the 

work presented here, we intend to combine two 

predominant ionic hard materials in new coating 

structures. The bonding in aluminum oxide and 

chromium oxide is a mixture of ionic and covalent 

bonding. Thus, the properties of these materials are a 

very good compromise between thermal stability and 

chemical inertness due to the ionic bonding share and 

an excellent high temperature toughness and 

hardness due to the covalent bonding share. The 

section �-Al2O3/�-Cr2O3 in the Al-Cr-O phase 

diagram shows two important regions, refeering to a 

miscibility gap, and, to a solid solution, respectively 

[2]. In the field of the miscibility gap below 1300 °C 

135 

the phase consists of two coexisting solid states �- 

Al2O3 (corundum) and �-Cr2O3 (escolaite) [3]. 

Above the miscibility gap exists the solid solution 

(Al1-x,Crx)2O3 of �-Al2O3 and �-Cr2O3. The materials 

science approach behind the physical vapour 

deposition process is to quench the vapour phase in 

the solid solution at deposition temperatures 

significantly below 1300 °C. A metastable corundum 

type solid solution of composition (Al1-x,Crx)2O3 is 

obtained at non-equilibrium conditions. Witthaut et 

al. [4] deposited (Al1-x,Crx)2O3 coatings in corundum 

structure by reactive magnetron sputtering (where 

aluminum was sputtered in r.f. mode and chromium 

in d.c. mode simultaneously). We introduce a new 

combinatorial approach for the deposition of Al-Cr-O 

thin films in order to elaborate the conditions of (Al1x,Crx)2O3 

thin film growth in corundum structure in 

more detail. 

II. EXPERIMENTAL DETAILS 

The coatings were deposited in a Leybold Z 550 

PVD machine. The experimental setup for the 

deposition experiments was shown in Figure 1. We 

used a combinatorial approach with a segmented 

target consisting of aluminum and chromium plates. 

The diameter of the target was 75 mm, the target to 

substrate distance was 50 mm, and the cathode power 

was 500 W in r.f. mode. The total gas pressure was 

kept constant at 0.65 Pa in all experiments. The 

atmosphere consisted of 80 at.-% argon and 20 at.-% 

oxygen. During the reactive deposition process we 

controlled the substrate temperature in the range from 

180 °C to 600 °C with a heating plate (resistance 

wire) and a connected d.c. power supply. In addition 

we were able to induce a substrate bias up to -400 V 

with a second r.f. power supply. The coatings 

presented here were deposited at -100 V substrate 

bias at a substrate temperature of 500 °C. 

Commercial cemented carbide substrates and silicon 

wafers were coated. Before deposition the substrates 

were cleaned in an ultrasonic bath in acetone for 15 

minutes and plasma-etched in pure argon r.f. 

powered plasma for ten minutes. Five cemented

carbide substrates (12.7 mm x 12.7 mm in lateral 

dimension) were coated in each deposition process. 

These samples had a different chemical composition 

and thus a different microstructure, constitution and 

properties. 

N S 

N 

Al Cr 

Ar/O2 plasma 

1 2 3 4 5 

substrate holder, heatable 

Figure 1: Experimental setup 

III. CHARACTERISATION 

The coatings were characterized by determining their 

thickness by using a standard calo test, their Vickers 

micro hardness, their chemical composition by 

Electron Probe Microanalysis (EPMA) with a 

Camebax Microbeam equipment and their 

microstructure by X-Ray Diffraction (XRD) with a 

Seifert C-3000 diffractometer running in the Bragg- 

Bretano geometry using CuK� radiation. 

IV. GROWTH AND CONSTITUTION OF THE 

ALXCRYOZ THIN FILMS 

Between the AlxCryOz layer and the substrate a 

metallic adhesion interface layer of 300 nm Cr and 1 

μm Al/Cr, with a mixing ration Al/Cr according to 

the sample position under the target, was applied. 

The AlxCryOz layer had a minimum thickness of 

about 3 μm. 

The highest growth rate was 1.13 μm/h at sample 

position three and the lowest growth rate was 0.81 

μm/h at sample position one. 

The lowest Vickers micro hardness was 2150 

HV0.05 at sample position five and the highest 

Vickers micro hardness was 2620 HV0.05 at sample 

position two. Ramm et al. [5] reported values 

between 1800 and 2500 HVpl for arc evaporated Al- 

Cr-O layers. 

The chemical analysis by EPMA revealed an 

argon content lower than 0.01 at.-%. The oxygen 

content of the coatings varied between 61.14 at.-% at 

sample position one and 59.61 at.-% at sample 

position five. The aluminum + chromium-content 

varied slightly over the sample positions, 38.60 at.-% 

at sample position one and 39.92 at.-% at sample 

position five. Thus we had thin films with nearly 

136 

stoichiometric (Al1-x,Crx)2O3 composition. The 

maximum Al/(Al+Cr) ratio was 0.71 at sample 

position one and the maximum Cr/(Al+Cr) ratio was 

0.75 at sample position five. 

We used the X-Ray Diffraction in Bragg-Bretano 

geometry for the phase analysis. The cemented 

carbide substrates consisted of tungsten carbide and 

cobalt. In the XRD spectrum we clearly identified 

tungsten carbide peaks (PDF No. 25-1047 and PDF 

No. 5-728 from the ICDD-data base). A comparison 

of the measured XRD spectrum with the peaks of 

corundum (PDF No. 42-1468 from the ICDD-data 

base) and escolaite (PDF No. 38-1479 from the 

ICDD-data base) showed six Bragg peaks positioned 

between the �-Al2O3 and �-Cr2O3 peaks of the same 

crystal lattice plane. Thus we assumed corundumtype 

growth of the solid solution. 

V. CONCLUSIONS 

Thin films of corundum-type solid solutions (Al1x,Crx)2O3 

were deposited at non-equilibrium 

conditions at a deposition temperature of 500 °C with 

a new combinatorial approach by reactive magnetron 

sputtering in an atmosphere containing 20 at.-% 

oxygen. The metastable solid solutions were 

nanocrystalline with a high degree of crystallinity. 

We investigated the growth rate, chemical 

composition and the phases of the coatings. 

REFERENCES 

[1] H. Holleck. Basic principles of specific 

applications of ceramic materials as protective 

layers. Surface and Coatings Technology, 43/44: 

245–258, December 1990. 

[2] T. M. Besmann and N. S. Kulkarni. 

Thermochemical analysis and modeling of the 

Al2O3-Cr2O3, Cr2O3-SiO2, and Al2O3-Cr2O3-SiO2 

systems relevant to refractories . Journal of the 

American Ceramic Society, 89(2):638–644, 

February 2006. 

[3] W. Sitte. Investigation of the miscibility gap of 

the system chromia-alumina below 1300 °C. 

Materials Science Monographs, 28A:451-456, 

1985. 

[4] M. Witthaut, R. Cremer, K. Reichert and D. 

Neuschütz. Preparation of Cr2O3-Al2O3 solid 

solutions by reactive magnetron sputtering. 

Mikrochimica Acta, 133:191-196, 2000. 

[5] J. Ramm, M. Ante, T. Bachmann, B. Widrig, H. 

Brändle and M. Döbeli. Pulse enhanced electron 

emission (P3e) arc evaporation and the 

synthesis of wear resistant Al-Cr-O coatings in 

corundum structure. Surface and Coatings 

Technology, 202:876-883, 2007.

Modification of Aluminum Alkoxides with �-Keto Esters and 

Dialkylmalonates as Precursors for Sol-Gel Derived Hybrid 

Materials 

Robert Lichtenberger, Stefan O. Baumann, Maria Bendova, Michael Puchberger, 

and Ulrich Schubert 

Institute of Materials Chemistry 



Email: rlichten@mail.zserv.tuwien.ac.at 

Abstract — Aluminum alkoxides were modified 

with a series of �-ketoesters and dialkylmalonates 

to give complexes of the general formulas 

[Al(OR)2(�-diketonate)]2 and Al(�-diketonate)3. The 

use of ligands bearing additional functional groups 

allows synthesis of precursors for inorganicorganic 

hybrid materials were synthesized. The 

influence of varying the ester-alkoxo groups on 

structure and reactivity was studied using NMR, IR 

and XRD techniques. Transesterification as a possible 

side reaction affecting the structure of the 

products was studied and found to be crucial for the 

reaction with sterically less demanding malonates. 


Substitution of OR groups in metal alkoxides by 

organic ligands is a powerful tool for tuning the 

structural and chemical behavior of the alkoxides, 

e.g. the reactivity during hydrolysis in sol-gel processing 

[1]. The use of ligands bearing additional 

functional groups allows introducing organic functionalities 

into precursors for metal oxide based solgel 

materials. This opens new possibilities for the 

synthesis of sol-gel derived inorganic-organic hybrid 

materials, where the inorganic and organic parts of 

the material are directly linked. Understanding the 

chemistry and structures of those precursors is a 

prerequisite for the deliberate design and use in the 

preparation of novel metal oxide based materials. 

II. RESULTS 

The modification of aluminum alkoxides with a 

series of �-ketoesters and dialkylmalonates and the 

influence of variation of the ester-alkoxo groups was 

studied. Furthermore the structure, stability, and 

reactivity of the complexes was investigated, in particular 

their tendency to undergo transesterification. 

137 

For the application of �-ketoesters and dialkylmalonates 

slightly different reaction conditions had 

to be applied. 

A. MODIFICATION WITH �-KETO ESTERS 

In contrast to procedures from the literature [2] for 

the modification of aluminum alkoxides with �diketones, 

the reaction of [Al(O i Pr)3]4 with one 

equivalent of �-ketoester at room temperature yields 

exclusively Al(�-ketoesterate)3 and unreacted alkoxide 

for all ligands used (Figure 1). 

O 

meac-H 

O O 

R = 

O O O O 

O 

etac-H 

i prac-H 

R 

t buac-H aaa-H 

Figure 1: �-Keto esters used 

O 

O 

meaa-H 

To obtain the desired [Al(O i Pr)2(�-ketoesterate)]2 

complexes, three synthetic pathways were developed. 

1. In situ heating of the reaction solution containing 

Al(�-ketoesterate)3 and [Al(O i Pr)3]4 

2. Reaction of isolated Al(�-ketoesterate)3 with 

[Al(O i Pr)3]4 at elevated temperatures 

3. Pre-deoligomerization of [Al(O i Pr)3]4 at elevated 

temperatures and subsequent addition of 

�-ketoester at room temperature 

The third reaction procedure opens the possibility 

to use thermally sensitive ligands, e.g. 2- 

(methacryloyloxy)ethyl acetoacetate (meaa-H), for 

the synthesis of [Al(O i Pr)2(meaa)]2 as a potential 

precursor for inorganic-organic hybrid materials.

The crystal structure of [Al(O i Pr)2( t buac)]2 (Figure 

2) shows the dimeric nature of the compound with 

one octahedrally and one tetrahedrally coordinated 

Al center, bridged by two isopropoxo groups. 

C18 

C19 

C17 

C21 

O7 

C15 

C20 

C23 

O8 

C16 

C22 

C24 

O6 

O10 

C13 

C11 

C14 C1 

Al2 

O9 

O5 

C26 

C10 

C25 

C28 

O3 

Figure 2: Thermal ellipsoid (50% probability) plot 

of [Al(O i Pr)2( t buac)]2 

Transesterification as side reacting was only found 

to be relevant in the reaction of Al(d t bum)3 with 

liberated isopropanol at elevated temperatures. 

B. MODIFICATION WIH DIALKYLMALONATES 

Al(O i Pr)3 Al(O t Bu)3 and Al(OEt)3 were analogously 

modified with a series of dialkylmalonates (Figure 

3). 

CH 3 

dmem-H 

O4 

O O 

C7 

C8 

C27 

C2 

C12 

C9 

R R 

O O 

R = 

Al1 

O1 

O2 

detm-H d i prm-H d t bum-H 

Figure 3: Dialkylmalonates used 

The modification of [Al(O i Pr)3]4 with dialkylmalonates 

was possible without additional reagents 

for the deprotonation of malonates, but in contrast to 

the modification with �-ketoesters, elevated temperatures 

and extended reaction times were needed. 

NMR studies revealed that the complexes 

[Al(O i Pr)2(d i prm)]2 and [Al(O i Pr)2(d t bum)]2 are 

isostructural to [Al(O i Pr)2( t buac)]2 (Figure 2). 

For the reaction of Al(O i Pr)3 with dialkylmalonates 

bearing smaller alkoxo groups, viz. dmem-H 

and detm-H, transesterification was observed to a 

considerable extent. Therefore, for the preparation of 

Al(dmem)3 (Figure 4) Al(O t Bu)3 was used as a starting 

compound, giving no transesterification. 

C3 

C4 

C5 

C6 

138 

O3 

C2 

C4 

C1 

O4 

C3 

O1 

C8 

C5 

O2 

O5 

Al1 

Figure 4: Thermal ellipsoid (50% probability) plot 

of Al(dmem)3 


Aluminum alkoxides were successfully modified 

with a series of �-keto esters and dialkylmalonates. 

For both types of ligands, dimeric complexes with 

two ligands and trisubstituted monomeric compounds 

were prepared and characterized. The influence of 

the ester-alkoxo groups was studied and found to 

have no influence on the structure but to be crucial 

for the tendency to undergo transesterification. 

For the modification with �-keto esters additionally 

ligands bearing polymerizable groups were successfully 

introduced to give products applicable as 

precursors for sol-gel derived inorganic-organic 

hybrid materials. 

Transesterification was found to be a relevant side 

reaction in particular for the modification of 

Al(O i Pr)3 with sterically less demanding dialkylmalonates. 


The author thanks R. Hellein and M. Schwabl for 

their practical work in the field of the dialkylmalonate 

modification. 

REFERENCES 

[1] U. Schubert. Sol-Gel Processing of Metal Compounds. 

In Comprehensive Coordination Chemistry 

II, pages 629-656. Elsevier, Amsterdam, 

Netherlands, 2004 

[2] J. H. Wengrovius, M. F. Garbauskas, E. A. Williams, 

R. C. Going, P. E. Donahue, and J. F. 

Smith. Aluminum Alkoxide Chemistry Revisited: 

Synthesis, Structure, and Modification of 

Several Aluminum Alkoxide and Siloxide Complexes. 

J. Am. Chem. Soc., 108(5):982–989, 

1986. 

O6 

C6 

C7

Structural Aspects of Oximate-Modified Titanium Alkoxides 

Stefan O. Baumann, Maria Bendova, Robert Potzmann, 

Michael Puchberger, and Ulrich Schubert 

Institute of Materials Chemistry, Vienna University of Technology, 

Getreidemarkt 9, 1060 Vienna, Austria 

Email: sbaumann@mail.zserv.tuwien.ac.at 

Abstract — Titanium alkoxides were reacted with 

oximes in order to give modified precursors for solgel 

processing. The substituent’s influence on the 

obtained derivates was monitored in case of anisaldehyde 

oxime as crystal structures and calculated 

models were compared. The reaction of acetone 

oxime with titanium isopropoxide resulted in a 

dimeric complex and - as partial hydrolysis occurred 

– in a hexanuclear oxo cluster. 


Organically modified titanium alkoxides serve as 

precursors for sol-gel derived inorganic-organic 

hybrid materials. Substitution of alkoxo groups 

with organic ligands on the one hand lowers reactivity 

and thus facilitates control during sol-gel 

processing, and affects the material’s structure. On 

the other hand, modification of those molecular 

precursors also permits the introduction of new 

functional groups that influence the chemical 

properties and provide reactive sites, offering the 

possibility of post-synthesis modification or allowing 

later crosslinking. Understanding the influence 

of the introduced organic groups on both chemistry 

and structure of the modified alkoxide precursors 

establishes is a key requirement for the development 

of new titania based hybrid materials. 

II. RESULTS 

A lot of work has been done on the modification 

of titanium alkoxides with oxygen containing coordinating 

groups, viz. carboxylates and �-diketonates. [1] 

Nitrogen bearing ligands, e.g. oximes, have been less 

investigated, [2-4] although oximate ligands show 

interesting coordination behaviour and allow new 

ways in transition metal alkoxide modification. 

A. BINDING MODES 

The effect of altered substitution modes in o-, m- 

and p-anisaldehyde oxime on the reaction products 

with titanium isopropoxide was investigated. 

Binding of different isomers to the metal atom in 

the crystal structures (Figure 1) was compared 

139 

with the results of quantum mechanical calculations. 

Figure 1: Crystal structures of the reaction products 

of titanium isopropoxide with o-, m- and panisaldehyde 

oxime 

B. PARTIAL HYDROLYSIS PRODUCTS 

The reaction of titanium isopropoxide with acetone 

oxime yielded crystals of the dimeric complex with a 

ligand to metal ratio of 2/1. When small amounts of 

water were introduced to the system, a hexanuclear 

oxo cluster crystallized from the reaction mixture. 

The structures derived by single crystal X-ray diffraction 

(Figure 2) were correlated to NMR studies in 

solution. 

Figure 2: Crystal structures of the reaction products 

of titanium isopropoxide with acetone oxime


With regard to the synthesis of new hybrid materials 

via the sol-gel pathway the investigation of precursors 

derived by modification of metal alkoxides with 

organic ligands is a crucial point. The structural investigation 

of differently substituted anisaldehyde 

oximate derivates is as well as hydrolysis effects of 

titanium alkoxides modified with acetone oximate 

offeris new snapshots of the route from the molecular 

precursor to the final material. 


Financial support by the Austrian Fonds zur Förderung 

der wissenschaftlichen Forschung (FWF) is 

gratefully acknowledged. 

REFERENCES 

[1] U. Schubert. Chemical modification of titanium 

alkoxides for sol-gel processing. Journal of Materials 

Chemistry, 15: 3701-3715, 2005. 

[2] R. C. Mehrotra, A. K. Rai, A. K. Singh and R. 

Bohra. Oxime and hydroxylamine derivatives of 

metals and metaloids. Inorganica Chimica Acta 

13(1): 91-103, 1975. 

[3] U. Thewalt and R. Friedrich. Cp2Ti IV Complexes 

with oximato ligands. Z. Naturforsch., 46b: 475- 

482, 1991. 

[4] M. G. Davidson, A. L. Johnson, M. D. Jones, M. 

D. Lunn, M. F. Mahon. Titanium(IV) complexes 

of oximes – Novel binding modes. Polyhedron 

26(5): 975-980, 2007. 

140

Trace Metal Speciation in Water using a Solid Phase Extraction 

Flow Injection Setup online coupled to ICP-AES 

Christoph Puls and Andreas Limbeck (Faculty Mentor) 

Institute of Chemical Technologies and Analytics 

Vienna University of Technologies 


Email: e9625356@stud3.tuwien.ac.at 

Abstract — The presented speciation method employs 

a Flow-Injection (FI) system consisting of 

three different Solid-Phase-Extraction (SPE) cartridges 

that retain passing metal species, separating 

them into the fractions neutral, anionic and cationic. 

During direct elution into the detecting ICP- 

AES system, transient signals are recorded simultaneously 

for Mg, Al, Ca, Cr, Mn, Fe, Co, Cu, Zn, Cd 

and Pb. Thereby, both the total metal concentrations 

and the distribution into the three classes are 

acquired in one run. By automatization the presented 

method minimizes potential error sources. 

Due to the occurring preconcentration, enhanced 

detection limits could be achieved. 

The accuracy of the method was verified using 

standard addition series. Finally the applicability of 

the technique to molten snow samples was demonstrated. 


In environmental and especially aquatic systems, the 

determination of trace metals and assessment of their 

toxic potential cannot be reduced to the measurement 

of their total concentration, since trace metals tend to 

be complexed by varying ligands, changing their 

chemical form and thus affecting their chemical 

reactivity and biological availability [1],[2] . Due to the 

correlation of trace metal toxicity and biological 

availability to fractions retained on different sorbent 

materials [3],[4] , solid phase extraction (SPE) techniques 

have been widely employed. 

The use of flow injection (FI) techniques for all 

kinds of automatization and their adaption to enhance 

sensitivity and precision of ultra trace elemental 

analysis has been widely demonstrated [5]-[7] . Both 

chemical speciation analysis by FI-systems coupled 

on-line to varying detector systems has been comprehensively 

studied [8] and a few systems able to 

discriminate between organic and inorganic complexes 

as well as the free ionic form have been described 

[9] , but the incorporation of an SPE-system 

able to achieve this fractionation into an FI-system 

coupled on-line to a multi-elemental detector remains 

to be achieved. 

141 

II. EXPERIMENTAL 

A. REAGENTS AND MATERIALS 

High purity water was obtained by double distillation 

of deionized water and used throughout. All used 

chemicals were of p.a. grade purity or higher. Due to 

the need to reuse the SPE-cartridges and -sorbents 

several times styrene-divinylbenezene (S-DVB) 

based materials were preferred. The employed sorbent 

materials were Strata-X, Strata-X-AW and 

Strata-X-C (all from Phenomenex). All sorbents were 

delivered in cartridges containing 30 mg and space 

for 1 ml of sample solution. They were shortened and 

fitted with a male luer tip for incorporation into the 

FI-system. 

The FI-Setup included three six-port two position 

valves. All parts were connected with PTFE and 

TYGON pump tubings. The eluent and the sample 

flow were kept up through two channels of a 

SPETEC PERIMAX 12 peristaltic pump. A Spectroflame 

P ICP-AES from SPECTRO A.I. was used 

for detection. 

B. FI-PROCEDURE 

The FI-system for fractionation of metal species into 

hydrophobic organic complexes, anionic complexes 

and cations consisted of three six-port valves and 

three SPE cartridges. 

After conditioning all cartridges to neutralize the 

pH of the SPE sorbents with (NH4)2CO3 buffer solution, 

the sample was pumped through the cartridges, 

thus concentrating the analytes on the respective SPE 

sorbents. After washing all sorbent cartridges with 

buffer solution, elution of the cartridges was carried 

out consecutively in reversed order with 2 M HNO3. 

The elution sequence was automatized and controlled 

by a serial communication program (VCom). 

In course of the measuring sequence 110 data points 

were collected for each element. This transient signals 

each comprised three peaks, with peak areas 

corresponding to the respective trace metal fraction.

III. RESULTS 

A. DETECTION LIMITS AND REPRODUCIBILITY 

Statistical characterization of the total metal quantification 

was performed employing standard solutions 

spiked with different ligands to account for differing 

trace metal species. 

For determination of the reproducibility standard 

solutions were analyzed in the course of two measurement 

series occurring on different days. Within 

each series three standards were analyzed at intervals 

of 2 hours resulting in a total of six measurements. 

Detection limits calculated via the 3σ-criterion and 

relative standard deviations from reproducibility 

measurements are given in Table 1. 

Element LOD (3σ) RSD (n = 6) 

Mg 1.2 μg/l 4.8 % 

Al 3.3 μg/l 3.1 % 

Ca 3.5 μg/l 3.7 % 

Cr 0.7 μg/l 3.5 % 

Mn 0.2 μg/l 4.6 % 

Fe 1.2 μg/l 4.5 % 

Co 1.3 μg/l 2.9 % 

Cu 1.3 μg/l 4.7 % 

Zn 1.4 μg/l 5.9 % 

Cd 1.1 μg/l 3.8 % 

Pb 12 μg/l 6.4 % 

Table 1: Detection limits and relative 

standard deviations. 

B. SPECIES SEPARATION 

To investigate the separation of trace metals into the 

desired fractions, standard solutions were spiked with 

0.1 mM of different organic ligands at varying pH 

values. The investigated ligands were 

8-hydroxyquinoline, tryptophan, ethylene-diaminetetraacetate 

and nitrilotriacetic acid. 

Measurements of these synthetic samples confirmed 

the ability of the system to fractionate trace 

metal complexes according to their affinity to the 

employed SPE sorbents. 

C. SNOW SAMPLES 

Snow Samples were collected at different urban 

locations, stored frozen and molten prior to analysis. 

Analysis was carried out using the previously described 

setup, to ensure the accuracy of trace metal 

quantification, standard addition measurements were 

performed. 

Total metal concentrations were within the range 

reported previously for urban snow samples. Additionally, 

trace metals could be assigned to fractions 

according to their natural speciation. 

142 


The presented FI-system is able to separate neutral 

hydrophobic and anionic complexes from the cationic 

constituents by retaining and simultaneously 

preconcentrating each of the three fractions separately 

on the corresponding SPE-sorbent. 

Experiments involving synthetic ligand-spiked 

standard solutions confirmed the achieved separation 

efficiency. Due to the inherent preconcentration 

abilities of the presented FI-system the achievable 

limits of detection for quantification by ICP-AES 

were improved. On-line coupling of the FI-system to 

the nebulizer of the ICP-AES and automatized control 

of the employed valves minimized contamination 

risks and led to good reproducibility of determined 

results. 

To demonstrate the applicability of the developed 

method to snow samples, samples collected at different 

sites were analyzed. Observed total metal concentrations 

were within the range reported previously for 

snow samples collected at urban sites. 

REFERENCES 

[1] Hart, B. T.; Hines T., In Trace Elements In Natural 

Waters; Salbu, B.; Steinnes, E., Eds.; CRC 

Press: Boca Raton, FL, 1995; pp 203-221. 

[2] Campbell, P. G. C., In Metal Speciation and 

Bioavailability in Aquatic Systems; Tessier, A.; 

Turner, D. R., Eds.; John Wiley & Sons: New 

York, 1995 pp 45-102. 

[3] Chakrabarti, C. L. et al., Anal. Chim. Acta 267 

(1993), 47-64. 

[4] Burba, P.; Rocha, J.; Klockow, D., Fresenius J. 

Anal. Chem. 349 (1994), 800-807. 

[5] Sperling, M.; Yin, X.; Welz, B., J. Anal. At. 

Spectrom. 6 (1991), 295 – 300. 

[6] Liu, Z.-S.; Huang, S.-D., Anal. Chim. Acta 281 

(1993), 185-90. 

[7] Benkhedda, K. et al, J. Anal. At. Spectrom. 15 

(2000), 429-434. 

[8] Das, A. K.; de la Guardia, M.; Cervera, M. L., 

Talanta 55 (2001), 1-28. 

[9] Groschner, M.; Appriou, P., Anal. Chim. Acta 

297 (1994), 369-376.

Analysis of Snowpack Properties 

And Estimation of Snow Grain Size 

Using Cold Land Processes Field Experiment Data 

Dugwon Seo 1 , Amir E Azar 1 , Al Powell 1 and Reza Khanbilvardi 2 

NOAA-CREST 

The City College of New York 

New York, U.S.A. 

Email: seo59ny@gmail.com 

Abstract — We focused on analysis of snow grain 

size behavior with respect to other snow parameters 

such as snow depth, density, and temperature which 

are collected by NASA Cold-Land Process Experiment 

data. We derive a pattern which can be used 

to approximate the range of grain size variations. 

The analysis showed that the snow density, grain 

size and temperature usually increase towards the 

snow-ground interface. Overall, the grain size 

variation is highly correlated with both density and 

temperature. The correlation is generally higher 

between grain size and temperature as compared 

with grain size and density. Thus, snowpack temperature 

profile might be estimated by a linear 

function having the top and bottom temperature. 

Using snowpack temperature, the grain size evolution 

can be approximated. 


Snow albedo plays a major role in earth's energy 

balance. Seasonal snow covers more than thirty percent 

of earth’s land surface [1]. Also, estimation of 

snowpack properties is significantly important in 

regional scale for various problems such as flood 

predictions and water resource management. Melting 

snow is responsible for majority of the spring floods. 

Microwaves are sensitive to snowpack properties 

(depth, water equivalent, grain size, and wetness). 

Many studies have been conducted to establish a 

relationship between snowpack properties and microwave 

electromagnetic scattering signatures [2]. 

One of the approaches was simulation of the microwave 

emission of snowpack [3]. It proposed a single 

layer snow emission model (Helsinki University of 

Technology, HUT) for simulating the snowpack 

brightness temperature. Similarly, Wiseman and 

Matzler developed a multi-layer microwave emission 

model (MEMLS) [4]. 

In the mentioned algorithms and models, there are 

key parameters of snow such as snow depth, density, 

water content, and grain size. These parameters play 

a significant role in microwave emission and con- 

143 

tribute to the measured emission by sensors. The goal 

of this study is to analyze the behavior of snow grain 

size variations with respect to other snowpack parameters, 

which influence the microwave scattering 

of snowpack. We analyzed the data from one of the 

most comprehensive snow survey; NASA CLPX, in 

order to establish the potential relationship of snow 

pack properties with respect to each other. 

II. ANALYSIS 

A. STUDY AREAS 

The Cold Land Process Experiment (CLPX) consisted 

of multiple sites in Colorado. This study area 

(Colorado) is selected because the central Rocky 

Mountains have large physiographic gradients and 

they provide different terrain, snow, soil, and ecological 

characteristics. Study area of CLPX data 

collection is designed in one area within another, 

based on 5-level set. Different scale of level is designed 

to provide a “scale bridge” between the levels 

for better understanding at one scale to other scales. 

B. PROFILE OF SNOW PROPERTIES 

In order to have a better understanding of snowpack 

properties and their behavior with respect to each 

other, the profiles of snow depth, density, temperature, 

and grain size were analyzed. 

The profile of snow temperature, density, and 

snow grain size for various snow pits in all ISAs 

located in Fraser and Rabbit Ear were drawn. Figure 

1 illustrates changes in snowpack characteristics 

(density, temperature and grain size). It is observed 

that, with except to very top layer of snow, the 

snow temperature, density, and averaged grain size 

increase towards the snow-ground interface. The 

older snow has larger grain size and the fresh snow 

on top has smaller grain size. But, the very top 

layer of the snow (top 10cm) shows different 

characteristics. In cases, the snow grain size is 

larger in very top layer as compared with the

underlying layer. This can be explained by daily 

fluctuations air temperature. 

height(cm) 

ffsp12 snow temp 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

-8 -6 -4 -2 

snow temp(c) 

height(cm) 

ffsp12 grain sz 

80 

70 

60 

50 

40 

30 

20 

10 

0 

0 1 2 3 

snow grain size(mm) 

height(cm) 

ffsp12 density 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

0 100 200 300 

snow density(kg/m 3 ) 

Figure 1:Example of variation of snow temperature, 

grain size, and density in the snow profile 

On the other hand, the bottom layer has 

different characteristics. The average grain size, 

snow temperature, and density of the bottom layer 

are larger than other layers. In addition, the snow 

temperature in the bottom layer falls in a certain 

range with a relatively small deviation. The 

majority temperature of bottom layer is between 

0 o C and -2 o C in Rabbit Ear and Fraser. 

To quantify the variation of all snow 

parameters with respect to each other, the 

correlation coefficients between those parameters 

over the profile was calculated for all the snow 

pits within ISAs of Fraser and Rabbit Ear. 

C. METHODOLOGY 

As mentioned in the previous section, the snow 

temperature and snow grain size are highly correlated 

in the profile of snowpack. Thus, using the 

temperature, the grain size profile can be estimated. 

Also, it was mentioned that the temperature for the 

bottom layer of snow tends to be in a certain range 

(between 0 o C and -2 o C). Thus, the intercept of the 

regression line can be a fixed value which is 

determined based on the characteristics of the snow 

covered area. 

Fraser 

ƒ(snow temperature) Averaged Linear Equations 

IOP1 (Feb, 2002) Z=0.25*T + 2.4 

IOP2 (Mar, 2002) Z = 0.22*T + 2 

IOP3 (Feb, 2003) Z = 0.14*T + 1.8 

IOP4 (Mar, 2003) Z = 0.3*T + 1.4 

Rabbit Ear 

ƒ(snow temperature) Averaged Linear Equations 

IOP1 (Feb, 2002) Z = 0.12T + 1.4 

IOP2 (Mar, 2002) Z = 0.13*T + 1.2 

IOP3 (Feb, 2003) Z = 0.07*T + 1 

IOP4 (Mar, 2003) Z = 0.07*T + 0.8 

Table 1: Equations to estimate snow grain size (Z) 

using snow temperature (T). 

144 

In this study, we derived the regression line 

between snow grain size and snow temperature for 

each of the snow pits located in all ISAs for 

selected periods. Then, we defined a new 

regression line by averaging the slope of the 

regression lines for all the snow pits. Finally, we 

examined the derived regression line for 

estimating the snow grain size using snow 

temperature profile for different periods in various 

locations (Table 1). 


It was observed that, with except very top layer of 

snow, the snow temperature, density, and averaged 

grain size increase towards the snow-ground 

interface. Using the results form of the analysis, 

we equation to estimate snow grain size using 

snow temperature. The spatial changes in 

snowpack properties in this area add to the 

complexity of the problem. In addition, the 

changes in the snow profile could be due to 

existence of a very stratified layer in the bottom 

and a layer of recently fallen fresh snow on the 

top. In short, the approach for estimation of snow 

grain size using the snow temperature was 

relatively successful and the source of the errors 

was identified. 


The authors would like to thank NOAA and the City 

University of New York for funding this research 

project. 

REFERENCES 

[1] Robinson, D., Dewey, K., and Heim, R., “Global 

Snow Cover Monitoring: An Update,” Bulltin of 

Americamn Meteorological Society, vol.74, no.9, pp. 

1689-1696, 1993. 

[2] B.E. Goodison, and A.E. Walker, “Canadian 

development and use of snow cover information from 

passive microwave satellite data,” Passive microwave 

remote sensing of land- atmosphere interactions, B. J. 

Choudhury, Y. H. Kerr, E. G. Njoku and P. Pampaloni, 

VSP, pp. 245-262, 1995. 

[3] Pullianen, J. T., Grandell, J., and Hallikainen M, 

“HUT snow emission model and its applicability to 

snow water equivalent retrieval,” IEEE Transaction on 

Geosciences and Remote sensing, vol.37, no.3, pp. 

1378-1390, 1999. 

[4] Matzler, C., and Wisemann, A., “Microwave 

Emission Model of Layered Snowpack,” Remote 

Sensing of Environment, 70, pp. 307- 316, 1999.

Supersensitive tin oxide nanosensors for gas detection 

Alexandra Tischner a , Anton Köck (Faculty Mentor) a , Thomas Maier a , C. Edtmaier b , C. 

Gspan c , G. Kothleitner c 

a Nano-System-Technologies, Austrian Research Centers GbmH – ARC, 1220 Vienna, Austria 

b Institute of Chemical Technologies and Analytic, Vienna University of Technology, Austria 

c Graz Centre for Electron Microscopy, Austria 

Abstract — Supersensitive gas sensors based on 

nanocrystalline SnO2-films and single-crystalline 

SnO2-nanowires, both integrated on Si, are presented. 

The sensing mechanism is based on a 

change in the electrical conductance due to adsorption 

of gas molecules. The sensors are able to detect 

CO and CH4 gases down to concentrations of less 

than 5 ppm, which are both gases relevant for 

safety and environmental issues. 


Triggered by various applications like industrial 

process control, safety systems, environmental monitoring 

or disease diagnostics in medicine, there is an 

increasing demand for high sensitive gas detecting 

devices. Over the last decades, especially metal oxides 

have become established gas sensing materials 

for a number of applications [1-4]. The most prominent 

candidate among all sensing materials is SnO2, 

and many SnO2 based sensing devices have been 

realized so far [5-7]. A most powerful strategy for the 

improvement of sensor performance is the implementation 

of nanostructures as gas sensing components 

due to their high surface to volume ratio which 

allows a strong interaction between the ambient 

gases and the material. Several sensors based on 

nanocrystalline metal oxide films [8-10] or single 

crystalline nanowires [11, 12] have been realized so 

far. 

II. SENSORS BASED ON TIN OXIDE 

NANOCRYSTALLINE FILMS 

The thin film gas sensors are fabricated by a spray 

pyrolysis process on silicon substrates. A solution of 

tin chloride pentahydrate and ethyl acetate is sprayed 

on Si-substrates with a 750 nm thick SiO2 layer on 

top, which are heated to a temperature of 500°C in 

ambient atmosphere. Produced film thickness is 20- 

100 nm. Subsequently the SnO2-films are mesastructured 

by means of photolithography and reactive 

Email: alexandra.tischner@arcs.ac.at 

anton.koeck@arcs.ac.at 

145 

CO flow [sccm] 

Fig. 1: Nanocrystalline sensor element with 

SnO2-bars on SiO2/Si-substrate. 

10 

9 

5,80E+03 

8 

7 

5,64E+03 

6 

5 

5,48E+03 

4 

3 

5,32E+03 

2 

1 

CO flow [sccm] 

Sensor R [Ω] 

5,16E+03 

0 

5,00E+03 

0 500 1000 1500 2000 

Time [s] 

Fig. 2: Nanocrystalline sensor response to 4ppm 

CO 

ion etching; sensors are accomplished by evaporation 

of Ti/Au-contacts (Fig. 1). 

Gas sensing performance is investigated in an automated 

measurement setup, which allows precise 

adjustment of the gaseous environment with synthetic 

air as background gas. The following results 

have been found: The sensors, which are operated at 

temperatures of 250–400°C, are able to detect CO 

and CH4 down to a concentration of less than 5 ppm 

[13]. Fig. 2 shows the response of the nanocrystalline 

sensor to CO gas pulses with a concentration of only 

4 ppm at an operating temperature of 350°C. 

Sensor Resistance [Ω]

Despite the excellent sensitivity performance, stability 

and selectivity to specific gas species are a problem 

for the presented ultrathin SnO2-gassensor: as 

can be seen from Fig. 2 the sensor signal drifts In 

addition the sensor shows cross sensitivity with water. 

III. STABILITY AND SELECTIVITY 

A. NANOWIRES 

With respect to sensor stability single crystalline 

nanowires are basically superior to nanocrystalline 

sensing layers. Thus SnO2 nanowires have been 

fabricated and implemented as sensing elements. 

The SnO2-nanowires are realized in a two-stage 

procedure: First of all nanocrystalline SnO2-films 

are fabricated by the spray pyrolysis process described 

above. A tempering process in Aratmosphere 

(800-1100°C) leads to growth of single 

crystalline SnO2-nanowires. Fig. 3 shows the 

SEM-photograph of a single SnO2-nanowire sensor 

with diameter of ~ 85 nm and a length of 

~ 55 μm. Fig. 4 represents the response of the 

SnO2-nanowire sensor at an operating temperature 

of 200°C when exposed to CH4-gas pulses with a 

concentration of only 3 ppm. The nanowire sensors 

show extremely high sensitivity towards CO 

and CH4, have very short response and recovery 

times and can be operated at lower temperatures 

than the nanocrystalline sensors. 

CH4 Flow [sccm] 

Fig. 3: SEM-photograph of a single SnO2nanowire 

sensor 

1,0 

3,00E+06 

0,9 

2,98E+06 

0,8 

2,96E+06 

0,7 

2,94E+06 

0,6 

2,92E+06 

0,5 

2,90E+06 

0,4 

2,88E+06 

0,3 

2,86E+06 

0,2 

2,84E+06 

0,1 

CH4 flow 

Sensor R [Ω] 

2,82E+06 

0,0 

2,80E+06 

300 600 900 1200 1500 1800 2100 2400 

Time [s] 

Fig. 4: Nanowire sensor response to 3ppm CH 4. 

Sensor Resistance [Ω] 

146 

B. SURFACE DOPING 

With respect to selectivity issues, additional surface 

doping by sputter deposition of a few monolayers of 

functional layers is a powerful strategy both for ultrathin 

sensing layers as well as for nanowires. First Ptdoping 

results demonstrate improved drift behaviour 

and very high sensitivity as well as lower cross sensitivity 

towards humidity in comparison with undoped 

sensor devices. 


The high sensitivity as well as the low cost production 

process, the small size and excellent response 

and recovery times show the high potential of the 

presented nanosensor devices for gas detection applications. 

REFERENCES 

[1] H. Meixner, J.Gerblinger, U.Lampe, M.Fleischer, 

Sens. Act. B 23 (1995) 119-125. 

[2] M. Fleischer, H. Meixner, Sens. Act. B 43 (1997) 

1-10. 

[3] G. Korotcenkov, Sens. Act. B 107 (2005) 209- 

232. 

[4] G. Korotcenkov, Mater. Sci. Eng. B 139 (2007) 

1-23. 

[5] W. Göpel, K.D. Schierbaum, Sens. Act. B 26-27 

(1995) 1-12. 

[6] J. Kappler, A. Tomescu, N. Barsan, U. Weimar, 

Thin Solid Films 391 (2001) 186-191. 

[7] G. Korotcenkov, V. Brynzari, S. Dmitriev, Mater. 

Sci. Eng. B 56 (1999) 195-204. 

[8] B. Schumacher, D. Szaboó, S. Schlabach, R. 

Ochs, H. Müller, M. Bruns, Mater. Res. Soc. 

Symp. Proc. 900E (2006) 6.1-6.6. 

[9] V. Malyshev, A. Pislyakov, Sens. Act. B 123 

(2007) 71-81. 

[10] E. Comini, Analytica Chimica Acta 568 (1-2) 

(2006) 28-40. 

[11] F. Patolsky, C.M. Lieber, Mat. Today 8 (2005) 

20-28. 

[12] C. Li, D. Zhang, X. Liu, S. Han, T. Tang, J. 

Han, C. Zhou, Appl. Phys Lett. 81 (10) (2002) 

1869-1871. 

[13] A. Tischner, T. Maier, C. Stepper, A. Köck, 

Sens. Act. B 134 (2008) 796-802.

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Electron microscopy of LiAlO2 - 

a promising substrate for opto-electronic devices 

Walid Hetaba and Peter Schattschneider (Faculty Mentor) 

Institute for Solid State Physics 



Email: walid.hetaba@student.tuwien.ac.at 

Abstract — γ-LiAlO2 is a promising substrate for GaN epitaxy. 

Inclusions in γ-LiAlO2-specimen were analysed using 

energy loss near edge structure (ELNES) of O K-edge. The 

ELNES spectra were simulated for different materials using 

WIEN97 program. It is shown that the inclusions can be assigned 

to LiAl5O8. As an effect of electron beam radiation damage 

it can be seen that γ-LiAlO2 undergoes a transformation to 

Al2O3. Experimental O K-edge spectra contain an additional 

peak at 531 eV, which can be attributed to molecular oxygen 

O2. This result suggests that the electron beam induced LiAlO2 

decomposition occurs through the loss of O2. 


(100)γ-LiAlO2 is considered to be a promising substrate 

which allows for growth of both c- and m-plane oriented 

GaN layers [1]. In contrast to conventional substrates 

like SiC the advantage of (100)γ-LiAlO2 is the very 

small lattice mismatch of about 1.4%. Thus, the GaN 

layers grown on this substrate show a low defect density. 

Also, it allows the growing of non-polar m-plane GaN 

which shows absence of internal electrostatic fields along 

the growing direction. This makes it possible to generate 

new efficient white light-emitting diodes (LEDs) [2]. 

At certain growth conditions the LiAlO2-single crystalls 

contain a core of inclusions. Also at the GaN/LiAlO2 interface 

there are inclusions which are partly surrounded 

by cavities in the LiAlO2-matrix. These inclusions at 

the interface are suspected to be the cause of a spontaneous 

separation of thick GaN layers. This effect may be 

used in the future to generate GaN layers for homoepitaxy 

which would allow to produce almost defect free 

GaN wafers. 

Preliminary transmission electron microscopy (TEM) 

analysis using electron diffraction showed that the inclusions 

mentioned above consist of LiAl5O8 [3]. But also 

the formation of Al2O3 can occur. The aim of this research 

project was to see if these materials can be clearly 

distinguished using Oxygen K-edge ELNES spectra. 

II. SIMULATIONS AND EXPERIMENTS 

Simulations were carried out using the full potential linear 

augmented plane wave code WIEN97. The unit cells 

of the three materials are of different size resulting in dif- 

149 

ferent simulation parameters and time consumption for 

simulation. The used parameters are then verified by 

analysing monople-, dipole- and quadrupole-transition 

terms. 

TEM analysis comprising scanning transmission electron 

microscopy (STEM) and EELS was carried out on 

a 200 kV JEOL JEM2200FS microscope at Humboldt- 

University Berlin. In Figure 1 the simulated and experimental 

spectra are compared. Considering the known 

limitations of the simulation program, the very good 

agreement of simulation and experimental spectra is visible. 

Intensity [a.u.] 

14000 

12000 

10000 

8000 

6000 

4000 

2000 

O-K ELNES Simulation vs. Experiment 

LiAlO2 Experiment 

LiAlO2 Simulation 

LiAl5O8 Experiment 

LiAl5O8 Simulation 

Al2O3 Experiment 

Al2O3 Simulation 

0 

520 530 540 550 560 

Energy Loss [eV] 

570 580 590 600 

Figure 1: Comparison of simulated and experimental 

ELNES spectra of oxygen K-edge. From top to bottom 

LiAlO2, LiAl5O8 and Al2O3. 

III. RESULTS 

The simulations show that the materials γ-LiAlO2, 

LiAl5O8 and α-Al2O3 can be clearly distinguished using 

O K-edge ELNES. The investigations showed that the 

inclusions in γ-LiAlO2 consist of LiAl5O8. It was also 

found that the specimen is damaged due to electron beam 

irradiation. Comparison of ELNES simulations and experimental 

spectra did not only show the already known 

transformation of LiAlO2 into LiAl5O8 [4] but also an 

unexpected transition to Al2O3 which is shown in Figure 

2. At the beginning the two peaks of LiAlO2 can

Intensity [a.u.] 

10000 

9000 

8000 

7000 

6000 

5000 

4000 

O-K ELNES 

3000 

500 520 540 560 580 600 

Energy Loss [eV] 

5s 

10s 

15s 

20s 

25s 

Figure 2: Spectra acquired at intervals of five seconds. 

The transformation of LiAlO2 to Al2O3 is clearly visible. 

The π ∗ -resonance peak of molecular oxygen at 531 eV is 

marked with an arrow. 

be clearly identified, while the intensity of the first peak 

is decreasing until the peak is transformed to the shoulder 

in the rising edge of Al2O3. These changes can be 

attributed to the following reactions: 

5 LiAlO2 −→ 2 Li2O ↑ + LiAl5O8 (1) 

2 LiAl5O8 −→ Li2O ↑ +5Al2O3. (2) 

The spectra contain an additional peak at 531 eV which is 

marked with an arrow in Figure 2. This peak is observed 

as long as the transformation from LiAlO2 to Al2O3 

takes place. This suggests that it can be associated with 

the loss of Li2O. The peak can be attributed to a so-called 

π ∗ -resonance which occurs when an electron is excited 

from a σ-molecular orbital to a π ∗ -orbital [5]. Li2O has 

a similar structure as H2O which means that there are 

only σ-bondings and no π ∗ -resonance can occur. Thus, 

the peak at 531 eV has to be attributed to molecular oxygen. 

The molecular orbital structure of O2 is shown in 

Figure 3. All this means that in the local environment of 

the beam cross-section O2 is set free due to heating of 

the sample. This causes a change in the chemical composition 

of the sample so that it becomes more Al-rich. 


For the first time the inclusions in γ-LiAlO2 are investigated 

using oxygen K-edge ELNES spectra. It is 

suggested that the inclusions at the GaN/LiAlO2 interface 

cause the spontaneous separation of thick GaN layers 

which in the future may be used to generate GaN 

wafers for homoepitaxy. An unexpected transfomation 

of LiAlO2 into Al2O3 was observed. The ocurrence of 

an additional peak at 531 eV which can be attributed to 

a π ∗ -resonance allows a better understandig of this transition. 

Further investigation of the LiAlO2 transforma- 

150 

Figure 3: Molecular orbitals of O2. An electron can be 

excited from a σ-orbital into a partly occupied π ∗ -orbital. 

tion would allow an adaption of the production paramters 

for fabrication of defect-free LiAlO2 for subsequent GaN 

epitaxy. With this substrate a new generation of high 

quality LEDs could be produced. 


The Author wants to thank W. Neumann and the 

members of his workgroup for crystallography at the 

Humboldt-University Berlin for their support with the 

experimental part of this work. 

REFERENCES 

[1] H.P. Maruska, D.W. Hill, M.C. Chou, J.J. Gallagher, 

and B.H. Chai. Free-standing non-polar gallium nitride 

substrates. Opto-Electronics Review, 11(1):7– 

17, 2003. 

[2] P. Waltereit, O. Brandt, A. Trampert, H.T. Grahn, 

J. Menniger, M. Ramsteiner, M. Reiche, and K.H. 

Ploog. Nitride semiconductors free of electrostatic 

fields for efficient white light-emitting diodes. Nature, 

406:865–868, 2000. 

[3] A. Mogilatenko, W. Neumann, E. Richter, M. Weyers, 

B. Veličkov, and R. Uecker. Mechanism 

of LiAlO2 decomposition during the GaN growth 

on (100)γ-LiAlO2. Journal of Applied Physics, 

102:023519, 2007. 

[4] M.H. Auvrey-Gély, A. Dunlop, and L.W. Hobbs. Irradiation 

damage in lithium ceramics. Journal of Nuclear 

Materials, 133&134:230–233, 1985. 

[5] J. Stöhr. NEXAFS Spectroscopy. Springer Verlag, 

Berlin, 1996.

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Silver plated tungsten carbide powders for 

electrical contact materials with improved homogeneity 

Robert Christian Hula and Christian Edtmaier (Faculty Mentor) 




Email: robert.hula@tuwien.ac.at 

Abstract — Electrical contact materials based on 

tungsten carbide and silver (WCAg) are most commonly 

produced by infiltration techniques as they 

are superior to mixing-pressing-sintering. Nevertheless, 

infiltrated WCAg shows inhomogeneity and 

more or less porosity. Moreover, the process is not 

suitable for high volume fractions of silver or submicron 

tungsten carbide powders. A new technique 

using chemical silver plating of tungsten carbide 

was investigated. The coated composite powders 

were consolidated using uniaxial cold pressing 

followed by liquid phase sintering. Products obtained, 

showed distinct higher homogeneity than 

industrial infiltrated products. 


Tungsten carbide–silver composites (WCAg) are 

common electrical contact materials e.g. for heavyduty 

circuit breakers and vacuum contactors [1]. The 

combination of high thermal and electrical conductivity 

(Ag) with hardness and refractory properties 

(WC) leads to high arc resistance and low chopping 

currents [2]. Typically, the silver fraction is in the 

range of 38 to 67 w%, most likely around 40 w%. 

Properties of WCAg contact materials are standardized 

in ASTM B 663-89. 

Industrial production mostly uses infiltration techniques 

of tungsten carbide preforms with liquid silver. 

As the green body has to have distinct 

cohesiveness, complete infiltration is not possible. 

Therefore the products show residual pores and also 

poor homogeneity on a microscopic level. Beside 

that, it is not possible to use submicron tungsten 

carbide and also high volume fractions of silver are 

not achievable using infiltration techniques. 

Chemical plating methods offer a new approach 

for improved homogeneity of WCAg [3]. By covering 

single tungsten carbide particles with silver by 

wet chemical deposition, idealized dispersion of the 

components can be expected. 

153 


The substrate was tungsten carbide powder of 3 μm 

average particle diameter and an oxygen concentration 

of 550 μg/g (delivered by H.C.Starck). The 

powder was chemically plated, pressed and sintered 

as described beneath. 

A. CHEMICAL PLATING 

In order to minimize impurities, a method using 

hydrazine hydrate as the reducing agent was used. 

Following equation 1, hydrazine completely dissipates 

during reaction with silver. 

Ag + + N2H4 + 4OH - --> Ag + N2 + 4H2O (1) 

To maximize yield and reduction strength, a high pH 

value is preferable. Therefore alkaline solutions of 

ammonia and ammonium bicarbonate have been 

applied [4]. Ammonia also has the advantage to 

stabilize silver containing solutions due to formation 

of silver diamine complex. 

The reaction was performed in a flat flange glass 

reaction vessel with PTFE stirrer at room temperature. 

While stirring, the silver nitrate (99,97 %, Umicore) 

containing ammonia solution was added dropwise 

to the suspension of tungsten carbide in alkaline 

hydrazine hydrate solution. Table 1 shows the composition 

of the used solutions. The plated powders 

were separated by filtration, washed with water and 

ethanol and were dried in a desiccator under vacuum 

at 50 °C. 

Component Solution A 

mol/L 

AgNO3 

N2H4.H2O 

NH4HCO3 

NH4OH 

WC 

0.127 

- 

1.897 

3.340 

- 

Solution B 

mol/L 

- 

0.082 

- 

- 

0.105 

Table 1: Composition of the chemical plating 

solutions

Figure 1: Silver plated tungsten carbide 

(SEM, 200x (top) and 5000x (bottom)) 

Characterisation was done by SEM (Philips 

XL30, 20kV), the silver concentration was 

checked by volumetric method (Volhard) and the 

oxygen content was measured by N/O/H-analyzer 

(LECO TCH 600). 

B. CONSOLIDATION 

The plated powders were cold pressed (300 MPa) 

and liquid phase sintered under flowing hydrogen (1- 

2 L/min) at 1100 °C (dwell time: 30 minutes). The 

samples were characterized by light optical microscopy 

(LOM) and density measurements. 

III. RESULTS 

The plated WCAg powder is shown in Fig. 1. Silver 

was deposited homogeneous forming smooth surfaces 

and showing no detachment. The silver concentration 

of 40,2 w% was within the desired range and 

the oxygen concentration was 1808 μg/g. 

After consolidation, the composite had some porosity 

on the surface and a density of 10,5 g/cm 3 

(80 % of theoretical value). Nevertheless, the samples 

had much higher density inside. The microstruc 

ture was highly homogeneous without any substantial 

silver or tungsten carbide culmination. 

154 

Figure 2: Comparison of microstructure: Sintered 

product from plated WCAg (left) and industrial 

infiltrated WCAg (right) with same composition. 

(LOM, 200x (top), 500x (middle) 1000x (bottom)) 

In Fig. 2, consolidated WCAg, made from silver 

plated tungsten carbide is shown next to industrial 

infiltrated WCAg, made out of the same tungsten 

carbide powder and with the same silver concentration 

like the plated one. A significant improvement 

of homogeneity due to the use of silver plated tungsten 

carbide is distinguishable. Therefore a positive 

effect on the arc erosion resistance may be expected 

but have not been measured yet. 

REFERENCES 

[1] J. R. Davis (Ed.). Metals Handbook, volume 3. 

ASM International, Metals Park, Ohio, USA, 

10th edition, 1990 

[2] S. Temborius and M. Lindmayer. Stromnullverhalten 

unter Vakuum-Lastschalter-Bedingungen. 

In 15. Fachtagung Kontaktverhalten und Schalten, 

pages 1–10, Karlsruhe, Germany, 1999. 

[3] R. C. Hula. Silberbeschichtung von Wolframcarbidpulvern 

zur Anwendung in elektrischen Kontaktwerkstoffen. 

Diploma Thesis, TU Wien, Vienna, 

Austria, February 2007. 

[4] A. S. Kozlov and T. Palanisamy and D. Narasimhan. 

Electroless silver plating, Patent 

WO02/04711A2, Honeywell, 2002.

Investigation of mechanical properties of polymer-derived 

Si-C-N/Al2O3-composites with low shrinkage 

Thomas Konegger and Antje Liersch (Faculty Mentor) 




Email: konegger@mail.tuwien.ac.at 

Abstract — The mechanical characteristics of a 

ceramic composite material using a polysilazanederived 

binder phase and alumina filler were investigated. 

Green bodies with high stability and good 

machinability were manufactured by warm-pressing 

of the polysilazane-coated filler powder, thereby 

thermally cross-linking the polymer which was used 

in a volume fraction of 20 to 40 Vol.%. Shrinkage 

during pyrolysis was very low, reaching a maximum 

of 2.3 % at 1200 °C. 


An inherent problem of ceramic materials is the need 

for high process temperatures during sintering, for 

Si3N4 usually exceeding 1700 °C. For Si-based ceramic 

compounds, the thermal conversion of Sicontaining 

polymeric precursors, for example polysilanes, 

polycarbosilanes of polysilazanes, is an alternative, 

resulting in covalent ceramics in amorphous 

state [1]. A disadvantage is the high shrinkage rate 

resulting in cracks, which can be reduced by an application 

of inert ceramic fillers like B4C or Si3N4 [2]. 

Due to the polymeric nature of the material after 

cross-linking, a good machinability in green state is 

given. A possible method of forming of said materials 

is the precoating of the filler powder with the 

polymer and subsequent cross-linking of the polymeric 

contents by warm-pressing, followed by a 

pyrolytic conversion of the polymeric precursor [3]. 

The combination of a polysilazane precursor with 

zirconia or alumina/zirconia powders led to specimens 

with high green strength and a microhardness 

of up to 1080 HV0.5 after pyrolysis at 1400 °C. The 

application of zirconia/alumina resulted in a decrease 

in shrinkage but also in lower material strength [4]. 

The aim of this study is the examination of ceramic 

composites with low shrinkage and good machinability 

in green state, enabling a near-net-shape 

production of ceramic parts. This particular investigation 

focuses on the determination of mechanical 

properties of polysilazane-alumina-composites that 

can be achieved by the variation of process parameters 

including polymer volume fraction, curing 

conditions and pyrolysis temperature. 

155 


A. MATERIALS 

A commercially available liquid poly(vinyl)silazane 

(KiON HTT 1800, Clariant) was used as preceramic 

polymer binder. As ceramic filler, Al2O3 powder 

(Almatis CT 3000 SG) with a median particle size 

(D50) of 0.8 μm was used. 

B. FABRICATION OF SPECIMENS 

The alumina powder was attrition milled for 2 h, 

dried and sieved. The prepared powder was dispersed 

in dried acetone, mixed with the polysilazane and 

stirred for one hour. The amount of polysilazane was 

calculated to yield between 20 and 40 Vol.% after the 

cross-linking step. After removal of the solvent under 

reduced pressure, the particulate mixture was ground 

and sieved through a 200 μm sieve. 

The cross-linking of the specimens was accomplished 

by warm-pressing of the polymer-coated 

powders at pressures between 25 and 55 MPa at 

200 °C for 4 h, resulting in cylindrical specimens 

with a diameter of 40 mm. 

Pyrolytic conversion was carried out in a tube furnace 

under nitrogen at temperatures of 1000 and 

1200 °C for 4 hours, with a heating rate of 36 K/h. 

C. CHARACTERIZATION 

The density of the specimens was determined by the 

Archimedes method. A helium pycnometer (Quantachrome 

Ultrapycnometer 1000) was used to determine 

the open porosity of selected samples. 

The samples were cut and embedded in epoxy 

resin before grinding and polishing to 1 μm. Examination 

of the microstructure was carried out by light 

optical microscopy (Olympus GX51). 

Four point bending strength was determined with 

polished samples on the basis of DIN EN 843-1 on a 

universal testing machine (Zwick 1474). 

The hardness of the material was determined by 

the Vickers method with a load of 0.5 kg (Leco LM- 

100).


By the described method of production, specimens 

with a high stability in green state could be manufactured. 

Ceramography showed a homogeneous distribution 

of components in the ceramic/ceramiccomposite. 

The observed shrinkage of the specimens during 

thermal transformation was very low, rising with 

volume fraction and process temperature to a maximum 

of 2.3 % at a polymer content of 40 Vol.% and 

a pyrolysis temperature of 1200 °C. 

By helium pycnometry and calculation of the theoretical 

density of the material, an open porosity between 

21 and 43 % could be determined for polysilazane 

contents of 40 Vol.% and 20 Vol.%, respectively. 

These values are in accordance to the relative 

density of the material determined by the Archimedes 

method. 

It could be shown that a good compaction of the 

specimens during cross-linking is crucial in obtaining 

high flexural strength values. Figure 1 shows the 

determined flexural strength of the material as a 

function of the polymer binder volume fraction. As 

can be seen, a high increase in material strength can 

be accomplished by an increase in binder content. 

Due to the polymeric nature of the polysilazane, the 

mechanism of compaction includes viscous flow of 

the material during warm-pressing. An increase in 

polymer content leads to an improved compaction, 

thus leading to a reduction of porosity of the pyrolyzed 

product and a higher structural integrity of the 

material. 

Figure 1: Flexural strength of specimens as function 

of polysilazane volume fraction 

Figure 2 shows the influence of the pressure applied 

during thermal cross-linking by warm-pressing 

on the material’s flexural strength. An increase in 

pressure leads to an increase in flexural strength, 

caused by the aforementioned improvement of densification 

which remains present through the course of 

pyrolytic transformation and sintering. 

156 

Figure 2: Flexural strength of specimens as function 

of pressure during thermal cross-linking 

The hardness of the material increased with process 

temperature and polymer content, averaging at 

385 HV0.5 for specimens with 40 Vol.% of polysilazane 

pyrolyzed at 1200 °C. Significant differences 

by a variation of cross-linking pressure could not be 

observed in the investigated range. 

It could be shown that a good compaction of 

specimens during thermal cross-linking is crucial to a 

high mechanical stability of the investigated composite 

material. By careful variation of process parameters, 

a material could be produced that combines a 

high green stability with a very low shrinkage during 

thermal consolidation and mechanical characteristics 

that can be tailored to specific applications in the 

field of structural ceramics. 

REFERENCES 

[1] P. Greil. Active-filler controlled pyrolysis of 

preceramic polymers. Journal of the American 

Ceramic Society, 78(4):835-848, 1995. 

[2] H.J. Kleebe. Microstructure and stability of 

polymer-derived ceramics; the Si-C-N system. 

physica status solidi (a), 166(1):297- 

313, 1998. 

[3] D. Galusek, J. Sedlacek and R. Riedel. 

Al2O3-SiC composites prepared by warm 

pressing and sintering of an organosilicon 

polymer-coated alumina powder. Journal of 

the European Ceramic Society, 27(6):2385- 

2392, 2007. 

[4] T. Konegger, A. Liersch and R. Felzmann. 

Influence of oxide ceramic fillers on mechanical 

characteristics of polysilazanederived 

ceramic materials. In 2 nd International 

Congress on Ceramics – Global 

Roadmap for Ceramics & ICC2 Proceedings, 

Paper 3-P-10, Verona, Italy, July 2008.

Preparation of Alkyne and Azide modified Spherosilicates 

Angelika Bachinger and Guido Kickelbick 




Email: angelika.bachinger+e165@tuwien.ac.at 

Abstract — The aim of this work is the use of 

Huisgen 1,3-dipolar cycloaddition reaction for the 

eight corner functionalization of spherosilicates in 

order to prepare new nanocomposites or literature 

known nanocomposites by a simple and efficient 

reaction, that is based on the building block system. 


Their small and defined sizes as well as the high 

density of functional groups and their rigid framework 

make silica cages very popular in materials 

chemistry. Many different synthetic techniques 

have been used for their functionalization, such as 

silylation 1-6 , hydrosilation 6-11 , substitution reactions 

12,13 and a lot more. However, all of these 

reactions require the absence of specific functional 

groups, a fact that constricts their applicability. 

Thus, the well-established and insensitive click 

reactions were applied on such systems by Binder 

et al 14 . These reactions are characterized by their 

high efficiency, simplicity, modularity and especially 

their broad applicability – due to their insensitivity 

towards most organic functionalities and 

selectivity 15 . Binder and his co-workers applied 

one of the most versatile click reactions – the Huisgen 

1,3-dipolar cycloaddition reaction – for the 

one-corner functionalization of POSS cages 14 . 

Considering that this reaction has been shown to 

allow reactions also in sterically hindered environments 

16 , we assumed that the eight corner 

modification of spherosilicates and POSS cages 

might be possible by this approach. 

II. RESULTS AND DISCUSSION 

For the preparation of eight corner modified 

spherosilicates it was assumed that highly efficient 

functionalization reactions are required. Thus, a 

literature known spherosilicate having the instable 

silicon-chlorine bond on all eight corners was prepared 

and a substitution reaction with ethinyl magne- 

157 

siumbromide yielded the corresponding alkyne modified 

spherosilicate. 

The product was characterized by spectroscopic 

techniques such as 1 H NMR (Figure 1), 13 C NMR, 

29 Si NMR and FT-IR. 

Figure 1: 1 H NMR of alkyne modified spherosilicate 

Synthesis of a spherosilicate with azide groups 

was conducted via tosylation of a literature known 

OH modified spherosilicate and subsequent substitution 

reaction with sodium azide. 

The product was characterized by 1 H NMR 

(Figure 2), 13 C NMR (Figure 2), 29 Si NMR and 

FT-IR. 

Figure 2: 1 H NMR (top) and 13 C NMR (bottom) of 

azide modified spherosilicate

Click reaction of the alkyne modified spherosilicate 

with a model azide compound revealed partial 

success. 


We thank Dr. Sorin Ivanovici for providing good 

ideas and Dr. Michael Puchberger for NMR measurements. 

REFERENCES 

(1) Hoebbel, D.; Wieker, W. 

Zeitschrift fuer Anorganische und Allgemeine 

Chemie 1971, 384, 43-52. 

(2) Hasegawa, I.; Kuroda, K.; Kato, C. 

Bulletin of the Chemical Society of Japan 1986, 59, 

2279-83. 

(3) Hoebbel, D.; Weber, C.; Schmidt, 

H.; Krueger, R.-P. Journal of Sol-Gel Science and 

Technology 2002, 24, 121-129. 

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15-54.

Learning more about the Gene Regulation of Hydrolytic enzymeencoding 

Genes in an industrial relevant Fungus 

Matthias G. Steiger, Marion E. Pucher, Astrid R. Mach-Aigner and Robert L. Mach 

Institute of Chemical Engineering 



Email: msteiger@mail.tuwien.ac.at 

Abstract — Hydrolytic enzymes are needed for 

plant biomass degradation in order to make these 

renewable resources available for industrial purposes. 

The filamentous fungus Trichoderma reesei 

has a high secretory capacity of those enzymes. 

With Xyr1 (Xylanase regulator 1) a very potent 

genetic regulator of the xylanolytic and cellulolytic 

enzyme system was found. This study reports the 

action of transcription factors, namely Ace1 and 

Cre1, on the transcription of xyr1. Independent of 

the carbon source xyr1 transcription is repressed 

by Ace1 and subject to carbon catabolite repression 

mediated by Cre1. 


Trichoderma reesei is a filamentous ascomycete 

which degrades plant biomass and frequently occurs 

in soil. With high effectivity polyssacharides are 

metabolized by the hydrolytic enzyme system of 

Trichoderma [1]. Due to the high secretion capacity 

of hydrolytic enzymes (up to 100 g/L [2]) this fungus 

is often used in industrial applications in a broad 

range of industries (e.g. textile, food and feed or 

paper industries). Today this fungus is also considered 

as a powerful organism for the production of 

biofuels (like ethanol) [3] and biochemical building 

blocks (e.g. succinate, aspartic acid, itaconic acid, 

glycerol, xylitol). Understanding the genetic regulation 

of his fungus is crucial for any further targeted 

strain improvement. With Xyr1 (Xylanase regulator 

1) an important genetic regulator was found [3]. This 

regulator is responsible for the activation of more 

than 10 genes involved in xylan and cellulose degradation 

and has also a regulatory impact on D-xylose 

metabolism. Ace1 another transcription factor (Activator 

of Cellulase expression) has a misleading name 

because its impact on cellulase and xylanase expression 

was shown to be repressing instead of activating 

[4]. The consensus binding sequence of Ace1 was 

found to be AGGCA. Another important regulator is 

the carbon catabolite repressor Cre1 which can be 

described as a wide domain repressor of particular 

hydrolase-encoding genes [5]. Sugars easy to metabolize, 

like glucose, repress the transcription of 

159 

genes which encode enzymes needed for the utilization 

of alternative carbon sources, this process is 

known as carbon catabolite repression. Cre1 consensus 

binding sequence to DNA is SYGGRG. In this 

report we describe the influence of Ace1 and Cre1 on 

the transcription of Trichoderma reesei xyr1 gene. 

II. RESULTS AND DISCUSSION [6] 

A. PROMOTER ANALYSIS OF XYR1 GENE 

In order to get an idea which transcriptional regulators 

could have an influence on the transcription of 

xyr1 gene a promoter analysis was carried out. The 

genome of Trichoderma reesei is sequenced and the 

structure gene of xyr1 can be found on scaffold 11 

(sc11) in reverse orientation between positions 

204723 and 201774. The region 1400 bp (sc11: 

201774 - 200374) upstream of the structural gene 

was investigated for binding sites of transcription 

regulators. 

Figure 1: In silico analysis of the xyr1 promoter 

(-1400 to -1 bp upstream the structural gene) for 

binding sites of transcriptional regulators; Cre1 

(black vertical bars), Ace1 (white vertical bars) 

As can be seen in Figure 1 two potential binding sites 

of Ace1 and ten of Cre1 were found in the promoter 

region. 

B. ACE1 A REPRESSOR OF XYR1 TRANSCRIPTION 

To prove the influence of Ace1 on the xyr1 mRNA 

formation the transcription level of xyr1 was studied 

in an ace1 ��ace1) compared 

to the parental strain (Table 1). Results reveal that a 

�ace1 strain has always 4 to 6 times higher transcription 

levels compared to the parental strain. This effect 

was found on all carbon sources tested. This fact 

provides evidence that Ace1 has a negative influence 

on the transcriptional regulation of xyr1 independent

of the carbon source. This finding is consistent with 

the presence of two Ace1 binding sites in the promoter 

sequence of xyr1 gene and the so far known repressing 

action of Ace1 on hydrolase expression in 

Trichoderma reesei. 

carbon source 

multiple amounts of 

xyr1 mRNA 

Xylose 4,1 ± 0,4 

Glucose 6,2 ± 0,4 

Sophorose 5,1 ± 0,4 

Xylobiose 6,0 ± 0,5 

no carbon source 4,0 ± 0,3 

Table 1: Increase of xyr1 transcription level in a 

�ace1 mutant strain compared to parental strain on 

various carbon sources 

C. TRANSCRIPTION OF XYR1 IS REGULATED VIA 

CRE1-MEDIATED CARBON CATABOLITE 

REPRESSION 

Investigating whether Cre1 has also an impact on 

xyr1 transcription, transcription levels obtained on 

glucose, a sugar mediating carbon catabolite repression 

(CCR), were compared to the levels received on 

no carbon source, xylobiose and xylose, two sugars 

inducing xylanase formation. 

Figure 2: xyr1 transcript formation on no carbon 

source (NC), glucose (G), xylose (XO) and xylobiose 

(XB) 

Results show decreased xyr1 transcription on glucose 

compared to inducing substances (Figure 2). To 

investigate whether the reduced transcript level of 

xyr1 on glucose is due to Cre1-mediated CCR, we 

cultured a Cre1 negative strain (Rut-C30) on the 

same carbon sources as the parental strain. A transcript 

analysis of xyr1 in RutC-30 revealed similar 

levels for all conditions tested (data not shown), 

indicating a general release from Cre1- dependent 

CCR (i.e. de-repression). 

160 

Summing up, Ace1 acts as a repressor of the xyr1 

transcription. xyr1 is subject to CCR mediated by 

Cre1. A Cre1-dependent regulation of the Xyr1 expression 

can now also explain the Cre1-related expression 

of hydrolytic enzyme-encoding genes in 

Trichoderma, which do not bear functional Cre1 

binding sites in their own promoters. These aspects 

help to gain further insight into the regulatory enigma 

of hydrolase production in Trichoderma. 


This study was supported by a grant from the Austrian 

Fonds zur Förderung Wissenschaftlicher Forschung 

(P20192-B03) given to R.L. Mach which is 


REFERENCES 

[1] B. Nidetzky, W. Steiner and M. Claeyssens. Cellulose 

hydrolysis by the cellulases from Trichoderma 

reesei: Adsorptions of two cellobiohydrolases, 

two endocellulases and their core proteins 

on filter paper and their relation to hydrolysis. 

(303): 817-823, November 1994. 

[2] J. R. Cherry and A. L. Fidantsef. Directed evolution 

of industrial enzymes: an update. (14): 438- 

443, July 2003. 

[3] B. Hahn-Hagerdal, M. Galbe, M. F. Gorwa- 

Grauslund, G. Liden and G. Zacchi. Bio-ethanol- 

-the fuel of tomorrow from the residues of today. 

(24): 549-56, December 2006. 

[4] A. R. Stricker, K. Grosstessner-Hain, E. Würleitner, 

and R. L.Mach. Xyr1 (Xylanase regulator 1) 

regulates both the hydrolytic enzyme system and 

D-xylose metabolism in Hypocrea jecorina. Eukaryot 

Cell, 5:2128-2137, December 2006. 

[5] N. Aro, M. Ilmen, A. Saloheimo and M. Penttila. 

ACEI of Trichoderma reesei Is a Repressor of 

Cellulase and Xylanase Expression. (69): 56-65, 

January 2003. 

[6] R. L. Mach, J. Strauss, S. Zeilinger, M. Schindler 

and C. P. Kubicek. Carbon catabolite repression 

of xylanase I (xyn1) gene expression in Trichoderma 

reesei. (21): 1273-1281, July 1996. 

[7] A. R. Mach-Aigner, M. E. Pucher, M. G. Steiger, 

G. E. Bauer, S. J. Preis and R. L. Mach. Transcriptional 

regulation of xyr1, encoding the main 

regulator of the xylanolytic and cellulolytic enzyme 

system in Hypocrea jecorina. AEM.01143- 

08, September 2008.

Investigations of Xyr1 (Xylanase regulator 1), the main transcriptional 

regulator of the xylanolytic and cellulolytic enzymes in 

Hypocrea jecorina (Trichoderma reesei) 

Marion E. Pucher, Gudrun E. Bauer, Matthias G. Steiger, Robert L. Mach and Astrid R. Mach- 

Aigner 

Department of Gene Technology and Applied Biochemistry, Institute of Chemical Engineering 


A-1060 Vienna, Austria 

Email: mpucher@mail.zserv.tuwien.ac.at 

Abstract — In Trichoderma reesei (teleomorph 

Hypocrea jecorina), Xyr1 (Xylanase regulator 1) is 

the main transcription activator of hydrolaseencoding 

genes, such as xyn1, xyn2, bxl1, cbh1, 

cbh2, egl1, and bgl1. We showed that Xyr1 is permanently 

available in the cell, and no de novo synthesis 

of this factor is needed for a first induction of 

xyn1 transcription. The constitutive expression of 

the transcription factor leads to clearly elevated 

xylanolytic enzyme activities compared to the parental 

strain QM9414. These hydrolytic enzymes 

may be used for the efficient hydrolysis of plant 

biomass waste into monomeric compounds which 

have an attractive potential as renewable source of 

energy and basic chemicals. 


Xylans are heteropolysaccarides with a backbone 

�� -1,4-linked xylopyranosyl units, which compose 

20 – 35 % of the approximate 830 Gt of annually 

formed renewable plant biomass. Filamentous 

ascomycetes of the genus Trichoderma 

mainly act as saprophytes thereby degrading a 

wide range of bio-polymeric substrates. A large 

number of hydrolytic enzymes secreted by Trichoderma 

reesei (teleomorph Hypocrea jecorina) 

have received broad industrial interest. Within the 

last 20 years a large number of hydrolytic enzymes 

have been cloned from T. reesei and other Trichoderma 

spp., but only few of them, namely xyn1 

and xyn2 (encoding the two main Endo-�-1,4xylanases 

I and II), have received detailed attention 

concerning their regulation of expression (e.g. 

[1], [2]). Whereas in Aspergillus the xylanolytic 

and cellulolytic system is strictly co-regulated via 

the inducer D-xylose (e.g. [3]), the hydrolytic 

enzymes of T. reesei are not. Their differential 

expression has been reported in several studies 

(e.g. [4]). In contrast to the diversity of inducers 

and induction mechanisms, it was recently shown 

that transcriptional regulation of the major hydro- 

161 

lytic enzyme-encoding genes XYNI and XYNII, 

as well as cellobiohydrolases CBHI, CBHII, and 

EGLI are strictly dependent on Xyr1 (Xylanase 

regulator 1). Furthermore, it was demonstrated that 

Xyr1 plays an essential role in the regulation of 

the D-xylose reductase expression. Altogether, it 

can be summarized that Xyr1 is the main transcription 

activator of the hydrolase system in T. 

reesei [5]. 

II. RESULTS [7] 

A. NO DE NOVO SYNTHESIS OF XYR1 IS NEEDED 

FOR A FIRST INDUCTION OF XYN1 

We questioned if de novo synthesis of Xyr1 is 

necessary for an initial induction of xyn1 transcription. 

To answer this, the parental strain was replaced 

to D-xylose or glucose, with or without the 

translation inhibitor cycloheximide. Transcriptional 

analysis showed that xyn1 transcription 

levels are not significantly altered, independent of 

cycloheximide supplementation. This is remarkable 

because xyn1 transcription, which is strictly 

dependent on Xyr1, is induced although the addition 

of a translation inhibitor prevents de novo 

synthesis of Xyr1. We assume that a low constitutive 

level of Xyr1 is present in the cell under all 

growth conditions. 

B. CONSTITUTIVE ACTIVATION OF XYR1 

To investigate the effect of a constitutive activated 

Xylanase regulator 1, the structural gene xyr1 (Gen- 

Bank accession no. AF479644) was put under the 

control of the nag1 promotor of H. atroviridis. This 

nag1::xyr1 fusion and the vector pAN7 [6], conferring 

hygromycin B resistance, were transformed into 

the genome of H. jecorina �xyr1 strain [5]. The 

resulting nx transformant strains showed similar 

growth rates on malt extract medium compared to the 

QM9414 pa�� xyr1 strain. The

conidiospores are white to brownish instead of dark 

green and conidiation is slightly delayed in the nx 

strains compared with the parental strain. 

C. MODIFIED XYLANASE EXPRESSION DUE TO 

THE CONSTITUTIVE ACTIVATED XYR1 

The parental and the nx strain were cultivated in 

medium containing xylan. We observed endo-�-1,4xylanase 

activity at an earlier culture stage (Fig. 1A) 

�� -xylosidase activity was clearly elevated (Fig. 

1B) in the nx transformant strain. NaOH-soluble 

protein measurements showed that growth characteristics 

slightly differed in the strains tested (Fig. 1C), 

most likely due to the delayed xylanase production in 

the parental strain. Complete clearing (i.e., enzymatic 

degradation of the insoluble xylan compounds) of the 

xylan-containing medium by the nx transformant 

strain was visible after approximately 50 h of cultivation, 

whereas the parental strain could not clear the 

medium during the duration of the experiment. 

Figure 1: Analysis of xylanase enzyme activity 

formation. Endo-�-�� xylosidase 

(B) activities in culture supernatants of 

the QM9414 parental strain (grey diamonds) and 

the nx mutant strain (black squares) (A to C). Detection 

of enzyme activity formation in both 

strains was accomplished after 0, 12, 24, 36, 48, 

60, and 72 h of cultivation in shake flasks on 1% 

(wt/vol) xylan after inoculation with spores. One 

unit of activity is defined as the amount of enzyme 

required to release 1 micromole of xylose reducing 

sugar equivalents or 4-nitrophenyl residues per 

minute under the defined assay conditions. (C) 

162 

Determination of biomass formation in medium 

containing insoluble xylan by measurement of 

NaOH-soluble protein. All data are means of results 

from three independent biological replicates. 

Error bars indicated standard deviations. 


This study was supported by a grant from the Austrian 

Fond zur Förderung Wissenschaftlicher Forschung 

(P 20192-B03) given to R.L.M., which is 

gratefully acknowledged. I want to thank Astrid R. 

Mach-Aigner and Robert L. Mach for supporting my 

work. 

REFERENCES 

[1] R. L. Mach, J. Strauss, S. Zeilinger, M. Schindler, 

C. P. Kubicek. Carbon catabolite repression of 

xylanase I (xyn1) gene expression in Trichoderma 

reesei. Mol Microbiol, 21(6):1273-1281, 

September 1996. 

[2] E. Würleitner, L. Pera, C. Wacenovsky, A. Czifersky, 

S. Zeilinger, C. P. Kubicek, and R. L. 

Mach. Transcriptional regulation of xyn2 in Hypocrea 

jecorina. Eukaryot Cell, 2(1):150-158, 

February 2003. 

[3] M. M. Gielkens, E. Dekkers, J. Visser, and L. H. 

de Graaff. Two cellobiohydrolase-encoding 

genes from Aspergillus niger require D-xylose 

and the xylanolytic transcriptional activator XlnR 

for their expression. Appl Environ Microbiol, 

65(10):4340-4345, October 1999. 

[4] S. Zeilinger, R. L. Mach, M. Schindler, P. Herzog 

and C. P. Kubicek. Different inducibility of expression 

of the two xylanase genes xyn1 and 

xyn2 in Trichoderma reesei. J Biol Chem, 

271(41):25624-25629, October 1996. 

[5] A. R. Stricker, K. Grosstessner-Hain, E. Würleitner, 

and R. L.Mach. Xyr1 (Xylanase regulator 1 

regulates both the hydrolytic enzyme system and 

D-xylose metabolism in Hypocrea jecorina. Eukaryot 

Cell, 5(12):2128-2137, December 2006. 

[6] P. J. Punt, R. P. Oliver, M.A. Dingemanse, P. H. 

Pouwels, and C. A. van den Hondel. Transformation 

of Aspergillus based on the hygromycin B 

resistance marker from Escherichia coli. Gene, 

56(1):117-124, May 1987. 

[7] A. R. Mach-Aigner, M. E. Pucher, M. G. Steiger, 

G. E. Bauer, S. J. Preis, and R. L. Mach. Transcriptional 

regulation of xyr1, encoding the main 

regulator of the xylanolytic and cellulolytic enzyme 

system in Hypocrea jecorina. Appl Environ 

Microbiol, 74(21):AEM.01143-08v1, November 


Using Confocal Microscopy to Study Mechanotransduction 

in Renal Epithelial Cells 

Yi Duan and Sheldon Weinbaum 

Department of Biomedical Engineering 

The City College and Graduate Center of the City University of New York 


Email: yduan@ccny.cuny.edu 

Abstract — The study of mechanotransduction in 

renal epithelial cells (REC) is critical in understanding 

the coupling between mechanical forces 

and biochemical reactions. In the current study, we 

used confocal microscopy to study the dynamic 

cytoskeletal responses of RECs to a laminar fluid 

shear stress (FSS). Confluent RECs were exposed to 

a FSS of 1 dyne/cm 2 for 5h. Immunofluorescence 

images demonstrated a reinforcement of peripheral 

actin networks, a disappearance of stress fibers, 

and an enhanced linearly distributed ZO-1. In addition, 

FSS caused an accumulation of paxillin at the 

cell base. Our results showed that FSS-induced 

cytoskeletal reorganization of RECs is, surprisingly, 

exactly opposite that observed in endothelial cells. 


The most important unresolved mystery in kidney 

proximal tubule is that the fractional reabsorption of 

water is reliably at 65% despite the large variation 

of the glomerular filtration rate. Guo et al. [1] proposed 

that the brush border microvilli, which are 

composed of a bundle of actin filaments, serve a 

mechanosensory function and proposed that the 

torque (bending moment) on the microvilli modulated 

transport activities. Clearly this hypothesis 

demonstrated that an intact actin cytoskeleton was 

essential to this transport activity. However, in 

marked contrast to endothelial cells (EC), there are 

very few studies on cultured epithelial cells in 

which cytoskeletal reorganization has been examined 

in response to laminar FSS under carefully 

monitored flow conditions. In the present study, we 

exposed REC to defined laminar FSS for 5hs and 

investigated the structural responses of RECs to 

FSS by examining the localization of F-actin (cytoskeleton), 

tight junction (TJ) protein ZO-1 and 

focal adhesion (FA) protein paxillin. 

II. EXPERIMENTAL METHODS 

Cell cultures and flow experiments: Mouse RECs 

were grown to confluence on glass coverslips for 5 

163 

days and were exposed to a FSS of 1 dyne/cm 2 for 

5h. The system was kept in 37 o C. 

Immunofluorescence and confocal microscopy: 

After exposed to FSS, cells were stained with the 

following monoclonal antibodies: 1) ZO-1, 2) Ecadherin, 

and 3) paxillin. F-actin was labelled by 

phalloidin. Fluorescence images were captured using 

a confocal microscope (Zeiss, LSM510). 

III. KEY RESULTS 

Cytoskeleton Reorganization: To study actin cytoskeleton 

reorganization after application of FSS, 

distribution of F-actin stress fibers was examined 

in REC and compared with no-flow controls. We 

witnessed a marked change of F-actin organization. 

In control, numerous long, thick cytosolic 

stress fibers were found regularly at the basal aspect 

of REC (Figure 1C) and a relatively thin 

circumferential actin network at cell-cell contacts 

at the basal surface (Figure 1A). Gaps were often 

found in between the cells. Exposure of RECs to 

5h FSS causes dramatically diminished stress fibers 

at the basal surface (Figure 1D) and a reinforcement 

of actin filaments at peripheral cell borders 

near the apical surface (Figure 1B). 

TJ: To investigate FSS-stimulated TJ distribution in 

epithelial cells, TJ-associated protein ZO-1 was 

analyzed. In static control, ZO-1 does not even 

form a cell-cell contact structure but appears as 

isolated rings surrounding individual cells (Figure 

2A), though these cells are cultured until fully confluent. 

A continuous distribution with dramatically 

reinforced junction staining pattern of ZO-1 was 

observed after exposure to 5h FSS (Figure 2B). 

FAs: Paxillin, an adaptor protein at FAs was examined 

to study the effect of FSS in the modulation of 

FAs. Under static conditions, paxillin appears either 

weak or absent in the basement membrane 

(Figure 3A). After 5h FSS, a predominant upregulation 

of paxillin was found at both cell periphery 

and inside of the cells (Figure 3B).

Apical 

Basal 

CTL 

A B 

C 

Figure 1: Confocal images of F-actin showing actin 

reorganization of REC exposed to 5h FSS. CTL, 

control; FSS, fluid shear stress. Bar, 10μ. 

Figure 2: Reorganization of TJs in response to FSS. 

CTL, control; FSS, fluid shear stress. Bar, 10μ. 

Figure 3. Confocal fluorescence images for antipaxillin 

binding before (A) and after (B) 5h FSS. 

CTL, control; FSS, fluid shear stress. Bar, 10μ. 


FSS 

The experiments in this paper have led to two important 

and unexpected observations. First, the 

cytoskeletal reorganization in response to FSS in 

cultured confluent epithelial cells is nearly diametrically 

opposite to that observed in [2] for ECs 

which were also subjected to FSS for 5h. In the 

D 

CTL FSS 

A B 

CTL FSS 

A B 

164 

latter paper, provided an intact glycocalyx is present, 

there was a dense peripheral actin band, few 

basal stress fibers, a dispersed distribution of vinculin 

and clearly defined continuous TJs in the control 

state as indicated by the localization of ZO-1. This 

organization was greatly altered after FSS with a 

breakdown of peripheral actin bands, a formation of 

stress fibers, a movement of vinculin to cell borders 

and a disruption of TJs. These observations are just 

opposite that observed in the present study. Second, 

culture RECs, though confluent, do not form TJ in 

their control state. Quite remarkably, a FSS of only 

1 dyne/cm 2 appears to be a critical precondition for 

the formation of TJs. This FSS is only one tenth that 

applied in the EC studies of [2]. 

Why do confluent EC and REC respond in such a 

different manner to FSS? The most important clue 

is the fact that, the cells, though, confluent and 

touching at their base, do not have TJ as indicated 

by the distribution of ZO-1. There is a strong expression 

of stress fibers at the base of the cell, as 

indicated by Figure 1B, which causes a firm adhesion 

of the cell to its substrate. This creates a tension 

in the cell membrane, due to the compressive 

resistance of the internal cytoskeleton, which in turn 

produces a rounding of the apical surface and a 

pulling away of a cell from its neighbor at its basolateral 

surface. The cells have the appearance of tall 

columnar domes. Cell junctions can not form until 

there is a disruption of the stress fibers at the basal 

surface and a release of this membrane tension. 

Even a small FSS will cause these tall columnar 

cells to tilt and their basolateral surfaces to come in 

contact. This also causes a release of actin stress 

fibers at the basal surface and the formation of a 

DAPB as part of AJ assembly as shown in Figure 1. 

The present study demonstrated for the first time 

the importance of FSS in the formation of TJ in 

RECs in comparison with the cytoskeleton reorganization 

of ECs under the same duration of flow. 

Whether this dramatic structural change participates 

in the process of FSS-induced transporter activation 

or translocation will be examined in the future. 

REFERENCES 

[1] Guo P, Weinstein AM, Weinbaum S. A hydrodynamic 

mechanosensory hypothesis for brush border 

microvilli. Am J. Physiol Renal Physiol. 

279(4): F698-712, 2000. 

[2] Thi MM, Tarbell JM, Weinbaum S, Spray DC. 

The role of glycocalyx in reorganization of the 

actin cytoskeleton under fluid shear stress: a 

“bumper-car” model. Proc. Natl Acad Sci USA. 

101 (47): 16483-8, 2004.

Low-energy School in Indian Himalayas 

Jan Tilinger (mentor: Ing. Frantisek Kulhanek, CSc. - kulhanek@fsv.cvut.cz) 

Faculty of Civil Engineering 

Czech Technical University in Prague, www.cvut.cz 


Email: jan.tilinger@suryaschool.org 

www.suryaschool.org 

Abstract — We have build low-energy solar school 

in village Kargyak in northern part of Indian Himalayas 

as a main part of Project Surya. Construction 

was made by local materials and with use of traditional 

building techniques with respect to harmonious 

proportions and adaptation to the landscape 

typical for local structures. The project responds to 

the existing socio-demographic situation in this 

remote region. Literacy is far below average in 

India; only few local people out of hundreds can 

read and write. The current situation leads to migration 

out of the region which dramatically disrupts 

not only the local culture but also traditional 

family relations. 

Village Kargyak is located in Zanskar mountain 

range at altitude of 4200 metres; it is a village in the 

highest location within this very isolated region. 

Kargyak is located 80 kilometres (3 days walk) from 

Padum, administrative centre of the region, where the 

regular road ends. 

Climatic conditions are quite uncommon in 

Kargyak. Village is located in rain shadow of nearby 

mountains in extremely dry climate with substantial 

proportion of sunshine – more than 300 days a year 

are classified as sunny. The landscape has character 

of mountain desert: ridges, rubble and sand mountainsides; 

sporadic green vegetation is only alongside 

water courses or on artificially irrigated fields. There 

was not any systematic monitoring of the local climate 

carried out yet (project carries out limited 

measurements). 

The building is designed in compliance 

with the local architectonic principles, with emphasis 

on usage of local natural materials and traditional 

building technologies as part of doctoral research on 

CTU. Detail research of local procedures, material 

properties and traditional architecture was done. In 

the region is still tradition of making and using clay 

bricks and other natural materials like stone, poplar 

and willow wood, low bushes, straw and yak, sheep 

and goat dunk. Other imported materials like glass 

and timber species for assembly construction are also 

used for the construction. 

165 

Due to the use of solar energy will be possible 

to teach in the school almost all year round which 

would not be possible otherwise. In summer 2006 

realization team made an agreement with Kargyak 

village, chosen in previous years. Cooperation was 

based on the fact that the village itself as well as 

neighbouring villages lacked school education and 

only few children had the opportunity to study in 

boarding schools in lowlands. In autumn 2006 was 

built a greenhouse in order to test cooperation with 

the villagers and also in order to verify the possibility 

of the use of solar energy, research of quality of local 

building materials and building technologies and last 

but not least in order to obtain fresh vegetable during 

Zanskar winter. Data logger was placed in the greenhouse 

to record inside and outside temperature as 

well as air humidity. The temperature in the greenhouse 

reached 20�� 

on average and vegetable was grown in the greenhouse 

during all winter season, even though the temperature 

in surroundings was up to 27�� 

The lowest air temperature measured in the greenhouse 

was only 3.6�� 

In February 2007 realisation team travelled 

to the construction site to ensure delivery of timber 

on frozen river from village of Ichar to Kargyak as 

well as to document functionality of the greenhouse, 

assemble temperature. In spring 2007 continued 

transport of building tools, timber and provisions for 

workers living in the village. All the work was due to 

inaccessibility of any machinery done manually or by 

simple hand tools. In spring and during summer 2007 

were dug trenches in the volume of 1600 cubic metres 

of stony soil, built three abutment walls of total 

length 120 metres and done other groundwork. 

Foundations were surveyed, dug and lined and on the 

edge of the site was built a toilet for workers. 

During the summer 2007 production of clay 

bricks sized 20x20x40 centimetres was optimized. 

Intensity of labour on clay bricks production: four 

workers produce about 50 clay bricks a day/ 28 kilos 

each brick. Bricks are dried at the place of production, 

three weeks later piled into pyramids and a 

month after the production transported on a horse or

yak back approximately 1500 metres to the building 

site. Samples of clay bricks were at the end of year 

2007 tested in the laboratories of Faculty of Civil 

Engineering in Prague; obtained basic engineering 

characteristics of the bricks are: heat conductivity 

coefficient - � = 0,317 W/mK, specific thermal 

capacitance - cp = 1,39 106 J/m3K, specific gravity - 

� = 2054.32 kg/m3, dynamic modulus of elasticity - 

E = 1.37 GPa. 

Volume solution of the school building is 

based on the shape of bevelled ashlar, partially embedded 

in the ground. Faced wall which is substantially 

glassed-in south-facing (azimuth 195�� 

west from south) allows direct use of solar energy. 

Ground floor of the house is centrally symmetric 

with the entrance area in west-facing wall. 

The school building consists of three classrooms, 

corridor, lobby and two toilets. Strip foundations of 

the building are made of shaped stone. Vertical 

framework consists of timber poles and stone wall. 

Cladding is filled with adobe bricks. Thermal insulation 

is ensured by a layer of straw between the stone 

and adobe walls, which runs around the building 

periphery. 

Figure 1: Section 

The roof structure was made entirely according 

to local traditions and its construction is 

based on low incidence of rainfall in the area. Horizontal 

supporting structure is made of poplar wood, 

heat insulation layer is made of straw mixed with yak 

dirt and branches tabulated with soil and covered 

with clay (hydro insulation layer) with mound of 

sandy soil. 

Because the characteristics of indoor climate 

are determined by the local customs the anticipated 

use of the building is non-standard (by European 

norms); as a result it is difficult to carry out 

classification of energy intensity of the building 

according to established European conventions. It is 

assumed that major part of the heat loss will be cov- 

166 

ered by solar acquisition and heat acquisition from 

indoor sources. The main effort is to use the solar 

energy at the most: air heated by the sun will be 

distributed around the building by especially designed 

system of air circulation. 

Project Surya will follow in long term observations 

of indoor environment characteristics in 

the school building and observation of efficiency of 

solar system. 


The school construction was supported by donation 

of private donors. The project was run by Czech 

Civic Association Surya and the construction part of 

the project was finished in September 2008 with 

great help of volunteers from more then 20 different 

countries. 

REFERENCES 

[1] ŠUBRT, R., TILINGER, J.: Pasivní stavba 

školy v Himalájích, Energie kolem nás, 

6/2006 

[2] TILINGER, J.: Solární škola v Kargyaku, 

�� 

[3] TILINGER, J., KULHÁNEK, F.: 

Nízkoenergetická solární škola v indickém 

Himaláji, In: Tepelná ochrana budov 2006, 

sborník mezinárodní konference, Praha 2006 

[4] Stavebníctvo a bývanie, pr�� 

�� 

2279/2000, vydává MEDIA/ST, s.r.o., Žilina 

�� 

Pasívna stavba školy v �� 

80, text+foto: Ing. Roman Šubrt, Ing. Jan 

Tilinger 

[5] Stavebníctvo a b�� 

146 stran, �� 

2279/2000, vydává MEDIA/ST, s.r.o., Žilina 

�� 

Pasívna stavba školy v �� 

82, 83, text: Ing. Roman Šubrt, foto Daniel 

Šubrt 

[6] TILINGER, J.: Realizace nízkoenergetické 

solární školy v indickém Himaláji, Tepelná 

ochrana budov 2007, sborník mezinárodní 

konference, Podbánské 2007 

[7] ��-��– ERA - 

Brno 2002 - ISBN:80-86517-21-7 

[8] Minke, Gernot - Earth Construction 

Handbook: The Building Material Earth in 

Modern Architecture - 2000 - 

80.237.211.43

ALGORITHM OF SIMULATION AND OPTIMALIZATION OF 

CONVENTIONAL MECHANICAL PRODUCTION 

Robert Jurcisin, and Dusan Sebo (Faculty Mentor) 

Faculty of Mechanical Engineering 

Technical University in Kosice 

Kosice, Slovakia 

Email: {robert.jurcisin,dusan.sebo}@tuke.sk 

Abstract — The main idea of the article is the 

assignment of components to machines by 

mathematical algorithm. Algorithm is able to 

calculate each queue which is arranged to 

production and calculate continuous period of 

production of each component. Mentioned 

algorithm is able to determine structure of 

machining time needs for fulfilled order according 

to individual components and machines or separately 

for each component. There are also other 

given information for farther technical - economic 

analyses in global aspect. 


Following article deals with problems of engineering 

and production scheduling in conventional machineindustry 

production. For filling of production was 

used method FIFO (First in First Out) which is suitable 

for conventional machine-industry production. 

In this algorithm, we were looking for an optimal 

solution with the shortest technological times of 

production. This thesis has also wide possibilities to 

use in technical-economic analysis and also pricing 

of machinery products, technical preparation of 

production using expert methods and so on. 

II. SIMULATION AND OPTIMALIZATION 

OF CHARGING OF CONVENTIONAL 

MECHANICAL PRODUCTION 

The entrance for simulation algorithm is a matrix of 

assignment tij, which sets how much time is needed 

for proceeding the operations of i –part of component 

on j – part of machine. 

The second entrance for initialization formula of 

algorithm is the matrix iBiv, which determines how 

many components of the kind of i – part is in v – 

part of product (number of components is taken over 

from bill of material of composition drawing of 

product). 

The third entrance is matrix uBuv (number of components 

of product A1....v, which is necessary to 

produce for the certain order DvQ). 

167 

We will still follow interval of time jump of finishing 

work Tk find from initialization formula, 

where for minus item hold the rule of counting off 

for ƒ k ksi VZj, if in the last step the component 

was on the same machine. 

Production system in which 5 production equipments 

are situated has a right to manage and charge production 

by computer even if its processes are simply 

controlled and dispatching control does not exceed 

human abilities. 

It would be more complicated if there were tenths of 

machines and equipments and thousands of components 

in production system and conventional small 

batch production for which mentioned algorithm is 

suitable for. 

III. CASE STUDY 

We will illustrate the case study of production 

scheduling in conventional mechanical production on 

virtual company in which there are situated four 

following machines: 

VZ1: Centre lathe SV 18RA 

VZ2: Table milling FC 50V with system NS 350 

VZ3: Centre lathe SU 80A 

VZ4: Grinding machine BP1/600 

Figure 2: Disposition of production system

We are concerned with conventional mechanical 

production in which machines do not have NC or 

CNC control but are controlled by human factor. 

Mathematically we try to find optimal solution with 

the shortest time of production. According to 

combinatory analysis we have n! possibilities for 

choosing the order of components. In our case we 

have exactly 120 possibilities. Therefore we showed 

the principle of algorithm only for illustration on 

three examples. 

Si/VZj Vz1 Vz2 Vz3 Vz4 A1 A2 

S1 38,6 6,9 3,6 3,8 16 16 

S2 77,6 16,3 8,3 14,3 8 8 

S3 27,5 5,3 - - 20 20 

S4 10,3 - 3,4 5,3 70 70 

S5 6,7 - 5,7 - 10 10 

Q1=5 Q2=5 

Table 1: Table with input data 

IV. EXAMPLE OF CALCULATIONS 

T0 = 0 

F1 = S2, S3 ,S4,S5 

Vz1 = S1 T1S1 = 38,6. (16.5+16.5) = 6 176 

F2 = 0 Vz2 = 0 

F3 = 0 Vz3 = 0 

F4 = 0 Vz4 = 0 

T1 = 6 176 

F1 = S3, S4, S5 Vz1 = S2 T2S2 = 77,6. (8.5+8.5) = 6 208 

F2 = 0 Vz2 = S1 T2S1 = 6, 9. (16.5+16.5) = 1 104 

F3 = 0 Vz3 = 0 

F4 = 0 Vz4 = 0 

T2 = 1 104 

F1 = S3, S4, S5 Vz1 = S2 T3S2 = 6 208 – 1 104 = 5 104 

F2 = 0 Vz2 = 0 

F3 = 0 Vz3 = S1 T3S1 = 3, 6. (16.5+16.5) = 347, 4 

F4 = 0 Vz4 = 0 

….., 

∑T = T1+T2+T3+T4+....+T15 = 6 176 + 1 104 + 347, 4 + 

608 + 4 148, 6 + 1 304 + 664 + 1 144 + 2 388 + 1 060 + 

6 150 + 670 + 1 710 + 570 + 3140 = 31 184 norm 

minutes 

Total machine time by setting of components from 

S1 – S5 is 31 184 norm minutes, what equally 

rounded is 520 norm hours. 

1.Example 31 184 norm min 520 norm hour 

2. Example 26 624 norm min 444 norm hour 

3. Example 28 052 norm min 467 norm hour 

Table 2: Table with results of calculations 

168 

V. CONCLUSION 

The best combination of charging the system by 

FIFO method requires 444 norm hours for 

machining both orders. As we sad it is three 

examples of 120 possibilities. Selected algorithms 

show how important it is for mechanical companies 

with conventional machines and also it can be a 

feedback for own technological preparation of 

production. 

This project will be programmed into integrated 

software package, where the whole program will be 

synergically built on three autonomous programs. 

The first program will ensure expert calculations of 

technological times for machining based on method 

of primitives. The second program will ensure 

managing of stocks from production point of view. 

The third program will ensure algorithm which on 

the basis of initialization formula calculates the 

shortest time for machining production batch or 

whole order. This software package will work with 

the help of interface such as autonomous universal 

system on existing systems and will be tested in real 

mechanical production. 


I would like to acknowledge my professor 

Dusan Sebo for his support and his advice. 

REFERENCES 

[1] Šebo, D.: LOGISTIKA AKO NÁSTROJ 

MANAŽERSKEJ ČINNOSTI, Edícia vedeckej 

a odbornej literatúry – Strojnícka fakulta, ISBN 

978-80-8073-776-4, Košice, 2007. 

[2] Malindžák, D.: VÝROBNÁ LOGISTIKA I., 

Vydavateľstvo ŠTROFFEK KOŠICE, ISBN 80- 

967636-6-0, Košice, 1997. 

[3] Leščišin, M, Stern, J, Dupaľ, A.: 

MANAŽMENT VÝROBY, 1. Vydanie EU v 

Bratislave, ISBN 80-968881-0-2, Bratislava, 

2002. 

[4] TER-Manuelliac, A.: Matematické modely teórie 

zásob, In., Matematicko – ekonomický obzor č. 

2, Praha, 1972. 

[5] Leščišín, M, Stern, J, Dupaľ, A.: 

MANAŽMENT VÝROBY, SPRINT –vfra Bratislava, 

ISBN 80-89085-00-6, Bratislava, 2008.

A Computer-Controlled Joint Loading System 

for Quantitative Analysis of Mechanoresponsiveness in Articular Cartilage 

Xiang Gu1,2,3, Daniel Leong1,2,3, Yong Hui Li2, Francisco Guzman1, Hui Bin Sun2,3 , and 

Luis Cardoso1,2 

1 Dept. of Biomedical Engineering, City College of New York, New York, U.S.A 

2 The Graduate Center, City University of New York, New York, U.S.A 

3 Mount Sinai School of Medicine, New York, U.S.A 

Email: cardoso@engr.ccny.cuny.edu 

Abstract —Motion and mechanical load of the joint 

have been associated with complex beneficial and 

detrimental effects on cartilage during the progression 

of degenerative joint diseases. The development of in 

vivo computer-controlled joint loading system is 

critical to studying how motion and load regulate 

cartilage homeostasis. The goal of this study was to 

develop a joint loading system to assess the biological 

response of cartilage due to well quantified 

underloading, physiological, and overloading 

conditions. A computer-controlled joint loading 

system was designed to apply precisely controlled 

cyclic motion and compressive loading protocols to 

the rat’s right knee, and under-, physiological, and 

over-loading conditions were created to test the 

mechanoresponsiveness of the cartilage. In contrast, 

continuous passive motion suppressed catabolic 

effects induced by immobilization, while the overload 

led to the catabolic responses similar to those caused 

by immobilization. The current data was consistent 

with our previous in vitro studies where moderate load 

had anticatabolic effects, while underloading or 

overloading conditions may lead to cartilage 

degeneration. 

I. INTRODUCTION: Joint diseases such as 

Osteoarthritis (OA) are common cause of disability 

worldwide. Physical activity and weight bearing 

condition play an important role in the regulation of 

joint homeostasis throughout life. Quantitative 

assessment of physiological dosage of mechanical load 

necessary to preserve the homeostasis of articular 

cartilage, and parametric characterization of 

deleterious and beneficial joint loading regimens are 

of great interest from both a basic research and clinical 

practice point of view. Prevention and treatment of 

OA depend on understanding the onset, progression of 

cartilage degeneration associated with joint loading 

abnormalities, and the wide use of motion-based 

physical therapies such as continuous passive motion 

(CPM) requires more scientific guidelines for optimal 

protocols (frequency, intensity, and duration, etc). 

The development of in vivo animal models is critical 

to studying how motion and load regulate cartilage 

homeostasis, by revealing underlying mechanisms 

mediating the biomorphological effects in articular 

joints in response to external mechanical stimuli. To 

date, few experimental devices offer a non-invasive 

approach to providing precise control of joint loading 

169 

parameters, or wide range of well-quantified loading 

environments on small animal models such as rats. In 

the present work, we introduced a novel computercontrolled 

loading system capable of applying cyclic 

motions on a single anesthetized rat’s knee joint under 

axial compressive load. The system fulfills the control 

requirements of 1) Knee joint position and angular 

displacement (Initial/Final angle, Flexion); 2) Cyclic 

motion frequency; 3) Magnitude of the axial 

compressive loading force along the tibia; 4) Realtime 

monitoring of the system operation. We loaded 

the rats with under-, physiological, and overloading 

conditions to determine the ability of the system in 

implementing defined joint loading protocols. 

II. MATERIALS AND METHODS: Motion 

Design. The animal is anesthetized using a mask on a 

custom built flat bed plane, the hip is maintained at a 

fixed height and the right hind femur is stabilized by a 

clamp coupled on the bed plane. The cyclic motion of 

the right knee is implemented by a computer-controlled 

linear actuator. An adaptor attached to the shaft of the 

linear actuator translates the linear motion of the 

actuator into the rotational motion experienced by the 

animal’s knee. The user defines the loading parameters 

by inputting the initial and final angles (in deg) and the 

cyclic frequency (in cycle/min) on the LabView control 

panel. By adjusting the extension of two springs on 

each side of the tibia, the axial compressive force is 

applied on the knee. In vivo animal study. Five 

months old male Sprage Dawley rats (n=5/group) were 

randomly assigned to five testing groups of animals by 

analyzing the gene expression of selected proinflamatory 

and anti-inflamatory proteins due to 

different motion conditions. For the immobilization 

group (IM), animals were immobilized for six hours 

using a cast made of cotton and steel mesh as described 

in Coutinho et al. (2002) [1]. A second group of 

animals (CPM) was immobilized for 2.5 hours, 

remobilized using CPM (70° flexion, 30 sec/cycle) for 

one hour, and immobilized again for 2.5 more hours. 

The third group was treated similar to the CPM group, 

while the joints were overloaded (OVL) during the one 

hour motion treatment by applying an axial load 

equivalent to ~ 2X body weight. A fourth group of 

animals (SHAM) was treated exactly the same way as 

those in the CPM group except that the animals on the 

device did not received any motion or loading. A fifth

group not subjected to any treatment was used as naïve 

controls (NAI). Real-time PCR. After each rat’s 

respective experiment endpoint, the lateral and femoral 

condyles were dissected, rinsed in 1X PBS/DEPCtreated 

water, and frozen in liquid nitrogen. The 

isolation of total RNA was conducted using the Rneasy 

mini protocol. The RNA was then reverse transcribed 

(RT) with reverse transcriptase using Oligo(dT), and 

the RT products were amplified with real-time PCR, 

using GAPDH for normalization. The primers used 

were: MMP-3, MMP-13, Collagen II. 

III. RESULTS: Figure 1 shows the schematic 

system design. It consists of a linear actuator with 

micro-step drive and encoder, a knee joint loading 

apparatus for controlled movement and adjustable 

compressive force on the rat’s knee joint, a magnetic 

encoder for real-time joint angle readout, a load cell for 

real-time compressive force monitoring, a USB port 

analog/digital data acquisition module, and an 

anesthesia machine (not shown). Figure 2 shows the 

experimental settings, the system covers the 

physiological range of motion (ROM) from 55° to 

125°, offers up to 4 cycles/min speed for 70° and up to 

5X body weight axial compressive load. Figure 3 

shows the LabView software interface with user inputs 

and three channels of real-time measurement. Figure 4 

shows gene expressions of Pro-inflammatory mediators 

(MMP-3 and MMP-13) and anti-inflammatory 

mediator Collagen II in response to immobilization, 

physiological, and overloading conditions. In contrast, 

overload resulted in catabolic responses (increased 

MMP, decreased collagen II) similar to those caused by 

immobilization, while CPM reversed the catabolic 

responses caused by immobilization. 

IV. DISCUSSION: The development of the 

animal model incorporated with the novel joint loading 

system addresses the quantification of the motion and 

load in the characterization of the consequential tissue 

responses. The flexibility of the system allows for test 

or evaluation of a broad range of clinically relevant 

protocols and motion-based hypotheses. The outcome 

from the animal study provided supporting evidence 

for validation of the system designed for extensive 

experiments in biomechanics research. The expression 

of MMP-3, MMP-13, and Collagen II were found 

similar during immobilization and overloading, and 

they had the opposite behavior compared to the results 

of passive motion, suggesting continuous excessive 

stress on the joint in motion can result in degeneration 

of articular cartilage. The current data was consistent 

with our previous in vitro studies [2] where moderate 

load had anticatabolic effects, while underloading [3] 

or overloading conditions may lead to cartilage 

degeneration. This novel loading system can contribute 

to quantitative investigations of mechanoresponsiveness 

in joint tissues, and can help better 

understand the effects of physical activity and weight 

bearing condition on joint homeostasis, in particular, 

170 

the role of important pro- and anti- inflammatory 

effectors in cartilage in regard of the mechanical 

loading environment. 

1. 

2. 

3. 

4. 

REFERENCES 

[1] Coutinho E.L., Gomes A.R., Franca C.N., and 

Salvini T.F.. A new model for the immobilization 

of the rat hind limb. Braz J Med Biol Res; 35: 

1329-1332, 2002 

[2] Sun HB, and Yokota H. CITED2-mediated 

Regulation of MMP-1 and MMP-13 in Human 

Chondrocytes under Flow Shear.J. Biol. Chem., 

278(47): 47275-47280, November 21 2003 

[3] Gu, X; Leong, D; Li, Y.H.; Guzman, F; Sun 

H. B; and Cardoso, L. Computer-Controlled Joint 

Loading System For Biomechanics Research In A 

Rat Model. In Proceedings of the 2007 Annual 

Biomedical Engineering Society Meeting, Los 

Angeles, California, September 2007

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Colloidal gel formation dynamics: 

light scattering, rheometry and simulation 

Xiujuan Cao, Herman Z. Cummins and Jeffrey Morris 

Levich Institute 

The City College of New York, Graduate Center, CUNY 


Email: xcao@che.ccny.cuny.edu 

Abstract — Effects of particle concentration and ionic 

strength on the gelation of colloidal silica particles are studied 

by dynamic and static light scattering (DLS, SLS) and rheological 

measurements. The combination of these experimental 

approaches gives us a simultaneous observation of microstructure 

and macroscopic rheology. The hydrodynamic radius Rh, 

measured through DLS, was found to grow exponentially. Approaching 

the gel point, the fractal dimension Df was determined 

to be 1.8 by SLS. The storage modulus G ′ and loss modulus 

G ′′ become measurable and increase as the gel forms. 

Stokesian and Brownian Dynamics simulation techniques are 

applied to study the evolution of particle aggregation and gelation, 

with a focus on understanding the role of hydrodynamics. 


In an aqueous colloidal silica suspension, there is negative 

charge on the surface of the particles, which stabilizes 

the dispersion against flocculation by inducing electrostatic 

repulsion. The addition of salt solution reduces 

the repulsive barrier of potential energy, destabilizing the 

kinetically stable system. The resulting aggregation of 

the particles leads to gelation: the dynamics of this process 

in general and the specific role of hydrodynamic interactions 

are of primary interest in this study. 


We used the aqueous colloidal silica suspension Ludox− 

SM (pH = 10.47) with radius 7.0 nm and 32 mass% SiO2 

(corresponding to a volume fraction ϕ =18.4%) from 

Grave Davison. The aggregation is initiated by the addition 

of aqueous NaCl under stirring. 

A. DYNAMIC LIGHT SCATTERING 

Dynamic light scattering, which probes the aggregation 

kinetics, measures the time-averaged time correlation 

function of the intensity I(q,t) of light scattered by the 

sample in the direction described by the scattering vector 

q, |q| =(4πn/λ)sin(θ/2) (n is the refractive index). In 

our experiment, the samples are tested with λ = 488 nm, 

n = 1.33, and with scattering angle θ =90 o . Normalization 

of the intensity correlation function g2(t) is 

g2(t) =/ 2 . (1) 

173 

For a polydisperse system, g2(t) can be expressed as 

|g2(t)| =1+aexp[−(2t/τ) β ], (2) 

where 1/τ = Dq2 , and D = kT/6πηRh. Equation (2) 

can be used to fit the intensity correlation function data 

in order to obtain a first estimate of Rh. 

After destabilization of the system, hydrodynamic radius 

Rh was measured through DLS, and found to grow 

exponentially (Figure 1). Approaching the gel point, Rh 

diverges, apparently because the particles form a spacefilling 

network. The initial aggregation rate is very slow 

and the rate increases as the size of the cluster increases; 

large clusters have more possibilities to connect to particles 

and clusters [1]. 

Figure 1: Evolution of hydrodynamic radius Rh 

B. STATIC LIGHT SCATTERING 

Static light scattering averages the scattering intensities 

detected and observed at one specific scattering angle. It 

is applied to determine the fractal dimension Df (Figure 

2). At the beginning of aggregation, the I(q) curves 

do not demonstrate power-law behavior. As the clusters 

grow, the power-law dependence of I(q) is seen over 

most of the observation regime and the slope is then determined 

to be the fractal dimension Df =1.8 [2]. 

C. RHEOLOGICAL APPROACH 

Rheological measurements are a measure of the mechanical 

properties of the colloidal network. As gel forms,

Figure 2: Structure evolution by SLS 

the storage (G ′ ) and loss (G ′′ ) modulus were measured 

as function of the time at fixed frequency 1.0 rad/s, as 

shown in (Figure 3). After gel formation, dynamics are 

largely due to the unconnected particles, particle chains 

and particle clusters among the network, which continue 

to make contributions to the stiffness of system as they 

attach to the space-filling network (the increase in storage 

modulus G ′ ). Finally, each particles is trapped in a 

small region and cannot move any further. The increase 

in the storage modulus becomes very slow and ultimately 

reaches to a constant value [3]. 

Figure 3: Storage and loss modulus evolution 

D. SIMULATION RESULTS 

Stokesian and Brownian Dynamics simulation techniques 

[4] are applied to study the relationship between 

microstructure and mechanical properties of the colloidal 

gel. At a solid volume fraction of φ = 10%, the system 

forms compact structures; for lower φ =1%, the 

particles evolve into small clusters (Figure 4 and Figure 

5). The fractal structure of colloidal gel is predicted 

depending on the balance of long-range repulsive forces 

and short-range attractive forces with the force form 

F = −∇V, (3) 

174 

where 

V = 40[( 2 

r )12 − ( 2 

r )6 ]+40 e−r/2 

r 

. (4) 

Figure 4: Cluster aggregation for φ = 10%,t= 100. 

Figure 5: Cluster aggregation for φ =1%,t= 100. 


I would like to thank my advisor Professor Jeffrey Morris, 

who is very supportive and knowledgable. I would 

like to thank Dr. Xiangnan (Allen) Ye for his patient 

guidance on the experimental work. 

REFERENCES 

[1] M. Y. Lin, H. M. Lindsay, D. A. Weitz, R. C. Ball, 

R. Klein, and P. Meakin. Universal reaction-limited 

colloid aggregation. Phys. Rev. A., 41(4):2005–2020, 

1990. 

[2] D. W. Schaefer and J. E. Martin. Fractal geometry of 

collodal aggregates. Phys. Rev. Lett., 52(26):2371– 

2374, 1984. 

[3] V. Prasad, V. Trappe, A. D. Dinsmore, P. N. Segre, 

L. Cipelletti, and D. A. Weitz. Universal features 

of the fluid to solid transition for attractive colloidal 

particles. Faraday Discuss., 123:1–12, 2002. 

[4] J. F. Brady and G. Bossis. Stokesian dynamics. Ann. 

Rev. Fluid Mech., 20:111–157, 1988.

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176

Site-Selective Time Resolved Laser Fluorescence Spectroscopy on 

Ca 2+ -Bearing Mineral Phases Doped with Europium 

Moritz Schmidt a , Thorsten Stumpf a,b , Clemens Walther a , Horst Geckeis a , Thomas Fanghänel b,c 

a) 

Institut für Nukleare Entsorgung, Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 

Karlsruhe (Germany) 

b) 

Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer 

Feld 253, 69120 Heidelberg (Germany) 

c) 

European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 

2340, 76125 Karlsruhe (Germany) 

Email: moritz.schmidt@ine.fzk.de 

Abstract — The aim of the presented work is to 

understand the interaction behaviour of trivalent 

actinides with Ca 2+ -bearing mineral phases on a 

molecular level. A comparison of the sorption behaviour 

of Eu 3+ (as an inactive homologue of the 

trivalent actinides with convenient fluorescence 

properties) with aragonite and gypsum is presented. 

Results from time resolved laser fluorescence spectroscopy 

show a significantly different mode of 

interaction in the two cases. While in aragonite only 

structural incorporation is observed, on gypsum 

nothing but inner-sphere sorption complexes can be 

found. 


Assessing the geochemical long-term safety of a 

nuclear waste repository requires a molecular level 

understanding of radionuclide behavior in the geosphere. 

In particular, the interaction of radionuclides 

with mineral phases (adsorption, solid solution formation) 

strongly affects their mobility and sequestration. 

The retardation capabilities of the mineral 

phases in the geotechnical and geological barrier are 

a key component of the safety assessment of every 

nuclear waste repository in deep geological formations[1]. 

The actual mode of interaction (e.g. formation 

of inner and outer sphere complexes and structural 

incorporation) is a major controlling factor of 

this retardation capability. Recent results on the interaction 

of Eu 3+ and Cm 3+ with calcite show the 

formation of solid solutions by exchange of 

Eu 3+ /Cm 3+ for Ca 2+ [2, 3]. Thus the question arose if 

this mechanism is generally applicable for Ca 2+ - 

bearing mineral phases. 

177 

II. RESULTS 

In order to shed light on this question, Ca 2+ - 

bearing mineral phases homogeneously doped with 

Eu 3+ were synthesized in a mixed-flow-reactor. The 

investigated mineral phases are aragonite, a metastable 

CaCO3 modification, and gypsum CaSO4·2H2O. 

Europium fluorescence spectroscopy is a versatile 

tool for the elucidation of the local structure, hydration 

state and substitution mechanism in crystalline 

and non-crystalline systems (e.g. [2, 4-6]). The applied 

site-selective excitation of the 7 F0 � 5 D0 transition 

at low temperatures (

Figure 1: Excitation spectra of the 7 F0 --> 5 D0 

transition in Eu 3+ doped aragonite (circles) and gypsum 

(crosses). 

Time resolved laser fluorescence spectroscopy results 

clearly show that Eu 3+ exhibits completely opposed 

sorption behavior on both investigated Ca 2+ 

mineral phases. In the aragonite system formation of 

solid solutions by substitution for Ca 2+ is the only 

observed form of interaction, which is evident by the 

corresponding emission spectrum and fluorescence 

lifetime. However, in the gypsum system no incorporation 

occurs, but only one inner-sphere sorption 

species can be found. On macroscopic level ICP-MS 

results show a significantly weaker Eu 3+ uptake by 

gypsum compared to aragonite. 

These results clearly show that the exchange 

mechanism observed for calcite and aragonite is not 

generally applicable to other Ca 2+ -bearing mineral 

phases. Apparently other parameters such as the 

binding strength of the anion have to be taken into 

consideration. It is, however, evident that radically 

different modes of interaction as observed for these 

two mineral phases will have a considerable impact 

on their retardation capabilities, and thus on their 

desirability in the near and far field of a potential 

waste repository. 


This work was co-financed by the Helmholtz Gemeinschaft 

Deutscher Forschungszentren (HGF) by 

supporting the Helmholtz-Hochschul-Nachwuchsgruppe 

"Aufklärung geochemischer Reaktionsmechanismen 

an der Wasser/Mineralphasen Grenzfläche". 

REFERENCES 

[1] N. M. Edelstein, R. Klenze, T. Fanghänel, 

and S. Hubert, "Optical properties of 

Cm(III) in crystals and solutions and their 

178 

application to Cm(III) speciation," Coordination 

Chemistry Reviews, vol. 250, pp. 

948-973, 2006. 

[2] M. Schmidt, T. Stumpf, M. M. Fernandes, 

C. Walther, and T. Fanghaenel, "Charge 

compensation in solid solutions," Angewandte 

Chemie Int. Ed., vol. 47, pp. 5846- 

5850, 2008. 

[3] M. M. Fernandes, M. Schmidt, T. Stumpf, 

C. Walther, D. Bosbach, R. Klenze, and T. 

Fanghaenel, "Site-selective time resolved 

laser fluorescence spectroscopy of Eu 3+ 

doped calcite," Journal of Colloid and Interface 

Science, vol. 321, pp. 323-332, 


[4] K. Binnemans and C. Görller-Walrand, 

"Crystal field analysis of EuCl3·6H2O," 

Journal of Alloys and Compounds, vol. 250, 

pp. 326-331, 1997. 

[5] B. Piriou, M. Fedoroff, J. Jeanjean, and L. 

Bercis, "Characterization of the sorption of 

europium(lll) on calcite by site-selective 

and time-resolved luminescence spectroscopy," 

Journal of Colloid and Interface Science, 

vol. 194, pp. 440-447, 1997. 

[6] T. Stumpf and T. Fanghänel, "A timeresolved 

laser fluorescence spectroscopy 

(TRLFS) study of the interaction of trivalent 

actinides (Cm(III)) with calcite," Journal of 

Colloid and Interface Sciences, vol. 249, pp. 

119-122, 2002.

Nanofeatured carbon-copper metal matrix composites 

Michael Kitzmantel, Christoph Eisenmenger-Sittner (Faculty Mentor) and Dan Cunningham * 

Institute for Solid State Physics, Vienna University of Technology, Austria 

* Department of Engineering Mechanics, The Pennsylvania State University, USA 

Email: michael.kitzmantel@student.tuwien.ac.at 

Abstract — In electronic devices materials with a 

high thermal conductivity and a coefficient of thermal 

expansion matching to the ones of Si, GaAs or 

alumina are used as heat sinks, heat spreaders and 

substrates. Besides the high thermal conductivity a 

low coefficient of thermal expansion (CTE) is a 

crucial property for the long-term stability and 

reliability of the products. Today commonly used 

materials such as Mo-Cu, W-Cu, Kovar, Al/SiC, 

AlN or diamond exhibit several limitations in respect 

to limited thermal conductivity (Kovar), high 

density (Mo-Cu, W-Cu), bad machinability (Al/SiC, 

AlN) or high price (diamond). 

The wetting and infiltration behavior of copper 

and some copper alloys containing carbide forming 

elements such as Ti, Mo, Cr or B on carbon nanofibers 

was investigated. These additives promote 

wetting on the carbon surface. It is shown how 

carbon nanofibers (CNF) and nanotubes (CNT) 

can be used to reinforce a copper matrix. Several 

ways of producing metal matrix composites (MMC) 

with carbon nanoparticles as building blocks were 

investigated, including liquid metal infiltration, 

powder metallurgical approaches and chemical 

coating of the nanofibers. 


As the building elements of micorelectronics get 

smaller and have to cope with growing power density, 

more efficient cooling are a hot topic. Suitability 

for cycling temperatures as well as long-term 

stability is also crucial for future materials. 

However, it is difficult to fabricate carbon/metal 

composites because of the poor wettability between 

carbon and molten metal alloys [1]. 

Miscellaneous investigations with graphite flakes 

and regular carbon fibers have been reported to show 

promising results [2]. Due to the lack of chemical 

interactions between carbon and the matrix metal, the 

manipulation and investigation of the interface plays 

an essential role. 

Several potentially interesting matrices degrade 

the fibers [3] at high temperatures and therefore 

179 

development has concentrated on matrices chemically 

inert towards carbon, such as copper. 

The non-wetting behavior of the C/Cu system [4], 

leads to several problems to be addressed in the production 

of MMCs. How can the wetting behavior be 

promoted, and how to infiltrate carbon fiber preforms 

with these metals? One approach is to alloy the liquid 

metal with an element that will react with the carbon 

fibers to change their wettability but that will not 

produce serious degradation. To investigate the wetting 

behavior, the sessile drop technique was successfully 

used in various studies [5]. Another way is to 

functionalize the� carbon fibers themself to build a 

catalytically-active surface and then deposit the metal 

chemically on the carbon [6]. 


A. INFILTRATING CARBON SKELETONS 

Clustering of the nanoparticles is a mayor problem 

when using a high volume percent (>20%) of 

CNT/CNF as a filler material in the composite. This 

can be overcome by using carbon preforms and infiltrate 

these skeletons by the copper matrix. Wetting 

and infiltration experiments were performed in a high 

temperature sessile drop device (HTSDD) [7] and a 

high vacuum sintering furnace (ASTRO APF-0716- 

MM) at 10 -3 Pa. 

Figure 1: Setup HTSDD (left) and ASTRO (right) 

Figure 1 shows the setups were the preform is topped 

with the metal and heated up to the metal melting 

temperature. In the sintering furnace external 

mechanical pressure (up to 80kPa) was applied to 

enhance the infiltration.

B. COPPER PLATING OF CNF 

Coating the CNF with copper with subsequent hot 

pressing is another successful way to receive a 

composite with homogeneous dispersed filler 

material. The technique chosen is electroless 

chemical copper plating depositing copper from a 

CuSO4 solution [6]. Pretreatment including activation 

and sensitization of the CNF was studied. The plating 

process was enhanced by ultrasonic agitation in a 

conventional cleaning device (Branson 5510). 


The preforms investigated were produced by Future 

Carbon GmbH [9] in form of CNT foams, CNF felts 

and CNT papers (BuckyPaper). 

Infiltration depths up to 200 m were observed for 

alloys containing carbide forming elements like Ti, 

Cr, B and Mo. No conclusive differences between 

various pre-treatments (thermal annealing, surface 

modification in Boric acid) of the skeletons were 

found. In the infiltration zone the carbon particles are 

gradual consumed by carbide formation during the 

process. Figure 2 shows the infiltration zone of an 

infiltrated CNF felt with clearly visible carbon nanofiber 

structures. 

Figure 2: CNF infiltrated by a Cu-Ti alloy. The arrow 

indicates the gradient of carbide formation. 

Good infiltration results were also obtained for CNT 

skeletons, both foams and BuckyPaper, when 

infiltrating with Cu-Ti and Cu-B alloys. The 

significantly tinier structures of nanotubes seem not 

to hold very stable positions within the skeleton 

during the infiltration process. 

Goal 

Figure 3: Cu-B infiltrated CNT foam, microstructure. 

180 

The metal meanders through the preform, but tiny 

CNT clews remain within the infiltration zone of 

several hundred m. 

The future goal is a complete infiltration also of these 

agglomerates. Figure 3 shows the successful CNT 

foam infiltration by a Cu-B alloy and a sketch of the 

CNT microstructure still to be infiltrated. 

Figure 4: Copper coated CNF, SEM image. 

The other approach followed is copper coating of the 

CNFs and subsequent hot pressing. The deposited Cu 

keeps the CNF in distance which improves the particle 

dispersion in the composite. Homogeneous coating 

for a composite with 40 vol.% CNF succeeded. 

Figure 4 shows a SEM image of Cu coated CNF. 

IV. OUTLOOK 

Future investigations will include optimization of the 

carbide interlayer to exploit the theoretically 

predicted composite limitations. 


This work was supported by the Austrian Research 

Centers Seibersdorf and the Center for Innovative 

Products at the Pennsylvania State University. 

Dr. Neubauer and Prof. Smid are kindly acknowledged 

REFERENCES 

[1] N. Eustathopoulos: Acta Metallurgica Vol.46, 

No.7 (1998) 2319-2327 

[2] H. Weidmueller, T. Weissgarber et al.: Materials 

Science Forum Vols. 534–536 (2007) 853–856 

[3] R.B. Barclay: Journal of Mat. Sci. 6 (1971) 1076 

[4] Naidich, Yu and Kolesnichenko G.A.: Russian 

Metallurgy (Metally) No.4 (1968) 141 

[5] R. Voitovitch, A. Mortensen and F. Hodaj: Acta 

Metallurgica Vol.47, No.4 (1999) 1117-1128 

[6] L.M. Ang et al.: Carbon 38 (2000) 363-372 

[7] B. Schwarz, C. Eisenmenger-Sittner, H. Steiner: 

Vacuum, vol 82 issue 2 (2008) 186-188 

[8] Future Carbon GmbH, Bayreuth, Germany

Substitution of fossil fuels by using low temperature pyrolysis of 

agricultural residues in a thermal power plant 

Michael Halwachs and Hermann Hofbauer (Faculty Mentor) 

Institute of Chemical Engineering 



Email: halwachs@mail.zserv.tuwien.ac.at 

Abstract — Externally heated rotary kiln pyrolysis 

reactor is used as a new process technology for the 

conversion of biomass into useful primary energy 

products. A 3 MW pyrolysis pilot plant is presently 

being investigated using agricultural residues 

(straw as the primary feedstock). Several analytical 

methods are applied to provide an insight into the 

complex process of pyrolysis. Fundamentals for an 

advanced pyrolysis model approach will be obtained 

by the results of the pilot plant. 


The global warming due to the increasing CO2 emission 

and dependency on fossil fuels, as well as the 

high-energy price level have resulted in an increasing 

demand in renewable energy source. Biomass, as a 

renewable energy sources, has the potential to contribute 

to the future energy mix in many countries. 

The desire of the conversion of biomass is to generate 

useful primary products. The choice of the conversion 

process depends upon the type and quantity 

of biomass feedstock, the desired form of energy, end 

use requirements, environmental standards and economic 

conditions. The two main processes to convert 

biomass into useful products are thermo-chemical 

processes and bio-chemical processes. Thermochemical 

processes include combustion, gasification, 

liquefaction, hydrogenation and pyrolysis. Biochemical 

processes are aerobe and anaerobe decomposition, 

which include the alcoholic and methane 

fermentation. 

II. PRINCIPLE OF PYROLYSIS 

A. GENERAL ASPECTS 

Pyrolysis is a process to convert biomass directly into 

solid, liquid and gaseous products by thermal decomposition 

in absence of oxygen. Pyrolysis is a 

very complex process. Many different reactions take 

place and can be influenced by numerous factors. 

The influencing parameters are chemical or physical 

pretreatment of raw material, heating rate, reactor 

type, pyrolysis temperature, residence time, pyrolysis 

181 

atmosphere and particle size [1]. Biomass pyrolysis 

can be divided into four different stages: moisture 

evolution, hemicellulose decomposition, cellulose 

decomposition and lignin decomposition. [2] Pyrolysis 

is always a step in combustion and gasification 

processes where it is followed by total or partial 

oxidation of the primary products. An advantage of 

the pyrolysis process is that pyrolysis products are 

easily storable and transportable. 

Figure 1: Typical yields of organic liquid, reaction 

water, gas and char from fast pyrolysis of wood, 

wt% on dry feed basis [3] 

B. REACTION KINETICS 

Pyrolysis of ligno-cellulosic biomass is a very complex 

process of interdependent reactions. Nevertheless, 

it can be reduced to a simple kinetic model, 

which is shown in Figure 2. 

Figure 2: Simple kinetic model for biomass pyrolysis 

[4]

The yield of main products: liquid, char and gas 

depends especially on the pyrolysis temperature. At 

high temperatures liquid products are obtained, lower 

temperatures favour high char yields (see Figure 1). 

III. PILOT PLANT AND EXPERIMENTAL 

WORK 

The externally heated rotary kiln pyrolysis reactor in 

Dürnrohr is an innovative process technology which 

can also be used for high capacities. The design fuel 

power is about 3 MW, the pyrolyis gas capacity is 

about 1.5 MW. Approximately 0.6 t/h straw can be 

processed in the rotary kiln. The combustible straw is 

characterized by a high ash fraction and his culm 

shape. The process is operated at low temperatures 

(350 to 630 °C) to prevent an entry of corrosive ash 

elements (K,Cl,S, etc.) and additional emissons in the 

steam boiler of the coal fired power plant. An energetic 

use of the pyrolysis-charcoal (approximately 

40-50% of the original heating value) occurs separately 

in a fluidised bed reactor. Several analytical 

methods are used to get more insight about the behaviour 

during pyrolysis. The main compounds of 

the pyrolysis gas are measured with a permanent gas 

measurement system. For the analytical determination 

of water and organic liquids in the pyrolysis gas 

phase two complementary methods are used: Gravimetric 

determination and GC-MS determination. 

First test runs were carried out at pyrolysis gas temperatures 

ranging from 600 to 630 °C. 

IV. RESULTS AND DISCUSSION 

Organic liquids can be classified due to the viscosity. 

Thereby liquids differ in low viscous pyrolysis oils 

and high viscous tar. 

Figure 3: Typical chromatogram (GC-MS) from 

the pyrolysis gas 

182 

The components are a mixture of alcohols, furans, 

aldehydes, esters, phenols, organic acids and oligomer 

carbohydrate and lignin products. The composition 

depends on the raw material and the pyrolysis 

process. The pyrolysis gas mainly contains H2, CO2, 

CO, CH4, trace amounts of larger gaseous organics 

compounds and water vapor. The water content results 

from the biomass humidity, about 10 %, and 

from the reaction water. To control the water content, 

the water content of the used biomass should be 

lower than 10 wt.%. The charcoal consists of carbon, 

volatile components, ash and partly tar. The content 

of carbon is one of the most important parameter for 

the quality of the charcoal, as well as the water content, 

ash content, elemental analysis, particle size, 

and energy density. All of the quality characteristics 

depend on the used biomass and the pyrolysis process 

as well as the purpose of use. 

Straw Charcoal 

C 42.85 68.80 

H 5.30 1.93 

N 0.44 0.73 

Natrium (water soluble) 0.005 0.090 

Kalium (water soluble) 1.07 3.75 

Volatile Compounds 70.97 15.25 

Gross Heating Value (Ho) 17111 25332 

Table 1: Typical straw and charcoal composition 

V. CONCLUSION 

The findings of the pilot plant will deliver fundamentals 

for the development of an advanced pyrolysis 

model. Furthermore, the results will be the basis for a 

scale up to a 30 MW capacity. For an improved description 

of this highly complex process it is necessary 

to carry out more runs in the pilot plant in the 

future. 

REFERENCES 

[1] Pütün, A. E. (2007). Comparision between the 

"slow" and the "fast" pyrolysis of tabacco 

residue. Industrial Crops and Products (26), 

307-314. 

[2] Yang, H., et al. (2007). Charateristics of 

hemicellulose, cellulose and lignin pyrolysis. 

Fuel (86), 1781-1788. 

[3] Toft A.J. (1996) A Comparison of Integrated 

Biomass to Electricity Systems, PhD Thesis, 

Aston University, Birmingham, UK 

[4] Kaltschmitt, M., & Hartmann, H. (2001). Energie 

aus Biomasse. Springer Verlag

Long Wave Instabilities in Periodic Structures 

Melanie Todt and Thomas Daxner (Faculty Mentor) 

Institute of Lightweight Design and Structural Biomechanics 



Email: mt@ilsb.tuwien.ac.at 

Abstract — The aim of the present work is the implementation 

of an efficient method for detecting the onset of buckling in spatially 

periodic structures loaded under compression. All calculations 

made are based on the Bloch Wave method which allows 

for detecting the critical state of the structure by using a single, 

geometrically representative cell. The Bloch Wave method is 

applied to different periodic structures, viz., an open cell foam, 

a closed cell foam, and a two-dimensional periodic lattice. 


Materials with a periodic microstructure, like composite 

materials or cellular solids, are widely used in engineering 

applications. Loaded under compression the onset 

of instability of these solids may be related to a buckling 

type instability. For large structures the evaluation 

of the critical load and the prediction of the corresponding 

buckling mode can be a numerically expensive task. 

Exploiting the periodicity of the structure can reduce the 

numerical requirements significantly. 

II. STABILITY CRITERIA 

Two different criteria are used for evaluating the critical 

state of periodic structures, namely a microscopic stability 

criterion and a macroscopic stability criterion. In both 

cases only a single unit cell, which can be as small as the 

smallest periodic unit of the structure, is used for predicting 

the critical state. The general theory for both concepts 

can be found in [1]. 

A. MICROSCOPIC STABILITY CRITERION 

The microscopic stability criterion is based on the fact 

that the buckling eigenmode of a periodic structure can 

be expressed in terms of the displacement field: 

δu ∼ (X ∼ )=U ∼ (X ∼ )exp[i( m1 

h1 

X + m2 

h2 

Y + m3 

Z)], (1) 

h3 

where hi are the unit cell dimensions, and U is a peri- 

∼ 

odic function with the same periodicity as the unit cell. 

Equation (1) is the so called Bloch Wave representation 

of the buckling eigenmode. The incremental equilibrium 

condition can be written as: 

⎡ 

⎣ 

K ≈ 11 K ≈ 12 K ≈ 1I 

K ≈ 21 K ≈ 22 K ≈ 2I 

K ≈ I1 K ≈ I2 K ≈ II 

⎤ ⎛ 

⎦ ⎝ 

Δu ∼ 1 

Δu ∼ 2 

Δu ∼ I 

⎞ ⎛ 

⎠ = ⎝ 

ΔF ∼ 1 

ΔF ∼ 2 

ΔF ∼ I 

⎞ 

⎠ 

(2) 

183 

with Δu ∼ 1 and Δu ∼ 2 being the increments of the nodal displacement 

vectors of the Bloch Wave (BW) master nodes 

and of the BW slave nodes, respectively. The BW master 

and slave nodes are located on the outer boundaries of the 

cell and sit on opposite sides of the cell. Δu ∼ I is the increment 

of the nodal displacement vector of the internal 

nodes of the cell. The partition of the tangent stiffness 

matrix K ≈ is implied by the partition of the increment Δu ∼ 

of the nodal displacement vector. The internal degrees of 

freedom can be condensed out and Δu ∼ 1 and Δu ∼ 2 can be 

coupled using Equation (2). The static stability criterion 

can now be expressed as: 

˚K ≈ δu ∼ 1 = 0 ∼ 

(3) 

involving only the part of the buckling eigenmode corresponding 

to the BW master nodes δu ∼ 1. ˚ K ≈ is the reduced 

stiffness matrix. For details see, e.g., [1], [2], or [3]. 

B. MACROSCOPIC STABILITY CRITERION 

The macroscopic loss of stability is indicated by the loss 

of rank one convexity of the homogenized tangent moduli 

tensor LH ijkl of the single unit cell: 

with 

det|L H ijkl(Λ)njnl| =0 (4) 

n ∼ = {cos(ϕ), sin(ϕ)cos(ψ), sin(ϕ)sin(ψ)} T 

0 ≤ ϕ ≤ π 0 ≤ ψ ≤ 2π (5) 

for the 3D case. The buckling eigenmode has infinite 

wavelength and its band direction is given by n ∼ see, e.g., 

[4]. 

III. OPEN CELL AND CLOSED CELL FOAM 

The open cell foam is modeled on the basis of the spacefilling 

Kelvin cell depicted in Figure 1 (left) which is 

assigned geometric properties reported in the literature, 

e.g., [2], [5], and [6]. The cell is elongated in x-direction 

(rise direction), see Figure 1, and subjected to uniaxial 

loading and a set of triaxial loading cases. 

The critical stresses and the corresponding buckling 

modes depend on the number of base cells that form 

the periodic structure and the multiaxiality of the loading 

case. For triaxial loading cases close to pure hydrostatic 

pressure the corresponding buckling mode is independent 

of the number of base cells and corresponds to a buckling

Figure 1: Unit cells representing a open cell foam (left) and a 

closed cell foam (right). 

mode local to a single unit cell. The results obtained for 

the Kelvin cell are in good agreement with the results reported 

in [2]. 

Specifically, the results received for uniaxial loading 

in transverse direction (y-direction) are depicted in Figure 

2. Both stability criteria are used to predict the critical 

stress and the corresponding buckling mode. For 

columns consisting of up to 60 base cells the critical 

stress and the corresponding buckling mode, which is 

local to a single cell, are independent of the number of 

base cells. For configurations consisting of more than 60 

cells the critical stress drops asymptotically towards the 

critical stress σ H 1c predicted by the macroscopic stability 

criterion as the mode wavelength tends towards infinity. 

Figure 2: Results of the micro- and macroscopic stability criteria 

in transverse direction (y- orz-direction). 

The closed cell model is based on the space-filling 

Weaire-Phelan cell shown in Figure 1 (right), see, e.g., 

[7]. The cell was subjected to uniaxial loading and pure 

hydrostatic pressure. For both cases the critical buckling 

mode is local to a single unit cell and, like the critical 

stress, independent of the number of base cells that form 

the periodic structure. For multi-cell models consisting 

of up to 4 × 4 × 4 base cells it is possible to show that 

local cell wall buckling is the dominant buckling mode, 

as predicted by the Bloch Wave method. 

IV. TWO-DIMENSIONAL PERIODIC LATTICE 

A square two-dimensional periodic lattice is modeled using 

four different unit cells. These four unit cells are sub- 

184 

jected to uniaxial and bi-axial compressive loads. The 

critical stresses and the corresponding buckling modes 

depend on the size of the structure (number of base cells 

in each direction) and on the multiaxiality of the loading. 

The results received for all four unit cells are in good 

agreement with and confirmed by accompanying eigenvalue 

analyses of Finite Element models containing multiple 

base cells. 

V. SUMMARY 

By analyzing various regular periodic structures, it was 

possible to demonstrate how the Bloch Wave method 

helps to reduce significantly the numerical effort for predicting 

buckling in periodic structures. While opencell 

topologies showed buckling modes of infinite wavelength, 

the examined closed-cell Weaire-Phelan structure 

showed no signs of long-wavelength buckling. 

REFERENCES 

[1] N. Triantafyllidis, M. D. Nestorović, and M. W. 

Schraad. Failure surfaces for finitely strained twophase 

periodic solids under general in-plane loading. 

Journal of Applied Mechanics, 73(3):505–515, May 

2006. 

[2] L. Gong, S. Kyriakides, and N. Triantafyllidis. On 

the stability of Kelvin cell foams under compressive 

loads. Journal of the Mechanics and Physics 

of Solids, 53(4):771–794, April 2005. 

[3] M. Todt. Long wave instabilities in periodic structures. 

Diploma thesis, Vienna University of Technology, 

Vienna, 2008. 

[4] G. Geymonat, S. Müller, and N. Triantafyllidis. Homogenization 

of nonlinearly elastic materials, microscopic 

bifurcation and macroscopic loss of rank-one 

convexity. Archive for Rational Mechanics and Analysis, 

122:231–290, 1993. 

[5] L. Gong, S. Kyriakides, and W.-Y. Jang. Compressive 

response of open cell foams. Part I: Morphology 

and elastic properties. International Journal of Solids 

and Structures, 42(5-6):1355–1379, March 2005. 

[6] L. Gong and S. Kyriakides. Compressive response of 

open cell foams. Part II: Initiation and evolution of 

crushing. International Journal of Solids and Structures, 

42(5-6):1381–1399, March 2005. 

[7] T. Daxner, R.D. Bitsche, and H.J. Böhm. Spacefilling 

polyhedra as mechanical models for solidified 

dry foams. Materials Transactions, 47(9):2213– 

2218, 2006.

Determination of the stoichiometry of complexes of trivalent 

lanthanides and extraction-relevant ligands with nanoelectrospray 

ionization time-of-flight mass-spectrometry 

Michael Steppert, Clemens Walther, Andreas Geist, Horst Geckeis, Thomas Fanghänel 

Institute for Nuclear Waste Disposal 

Forschungszentrum Karlsruhe 

76021 Karlsruhe, Germany 

Email: michael.steppert@ine.fzk.de 

Abstract — The minor actinides (neptunium, americium 

and curium) and plutonium control the 

long-term radiotoxicity of spent nuclear fuel. While 

direct disposal of this waste requires repositories 

which are save for >100.000 years, partitioning of 

the long lived products and their subsequent transmutation 

to short lived or stable nuclides reduces 

storage time scales to only some hundreds of year: 

plutonium separation is already performed on the 

industrial scale by the PUREX process. However, 

efficient transmutation requires also partitioning of 

the trivalent actinides Am and Cm from lanthanide 

fission products, which is not yet feasible in large 

scale. The present work focuses investigations on a 

possible candidate for An(III)/Ln(III) separation: 

bis-triazinyl-pyridine (BTP). By means of nanoelectrospray 

mass-spectrometry complex formation of 

BTP with selected elements of the lanthanide series 

is investigated 


Besides uranium, spent nuclear fuel contains plutonium, 

minor actinides (MA, neptunium, americium, 

curium), and fission products (FP). While 

most of the fission products decay within the first 

100 years, the radiotoxicity of spent nuclear fuel is 

dominated by the contributions of Pu and the MA 

at time scales exceeding 300y (see Fig. 1). Uranium 

and plutonium are separated from the spent 

fuel by liquid-liquid extraction in the PUREX 

process. In the subsequent DIAMEX process trivalent 

lanthanides and actinides [1] are coextracted. 

However, for an efficient transmutation the lanthanides 

must be separated from the chemically 

very similar trivalent actinides Am and Cm. To 

these ends, the organic complexing agent bistriazinyl-pyridine 

(BTP) was developed [2]. Distribution 

ratios between organic and aqueous 

phase using this highly selective ligand are depicted 

in Figure 2. Though BTP works well in the 

laboratory and has passed already first upscaling 

tests [3] the origin of its exceptionally high 

185 

Figure 1: Radiotoxicity, i.e. the measure of the 

cumulative negative health effects of radionuclides 

due to ionizing radiation after ingestion, of 1t of 

spent nuclear fuel after discharge from a pressurized 

light water reactor (40GW/t) 

selectivity towards trivalent actinides is not yet 

understood. 

For a better understanding, the interaction of BTP 

with trivalent lanthanides was studied with nanoelectrospray-ionization 

mass spectrometry. 

Figure 2: Distribution coefficients for extraction to 

the organic phase with BTP-ligand

With the nano-electrospray method, ions that are 

present in a solution can be transferred to the gas 

phase almost non invasively (so called “soft ionisation”) 

[4][5] avoiding fragmentation reactions of the 

ions. These soft ionization conditions make the nanoelectrospray 

ionization mass spectrometry the ideal 

method to determine the stoichiometry of complexes. 

The low invasiveness of measurements with the used 

ALBATROS ESI-TOF spectrometer could be shown 

in the investigation of polynuclear Zr(IV) hydroxide 

complexes in [6]. 


Solutions of lanthanide nitrates (5 x 10 -5 M) and 

BTP with ligand-to-metal ratios of 2 in octanol 

were prepared for each ESI-measurement with the 

ALBATROS ESI-TOF mass spectrometer [7]-[9]. 

III. RESULTS 

The ESI measurements for the interaction of the 

lanthanide nitrates with BTP in octanol show that the 

relative abundances of the complexes [Ln(BTP)- 

(NO3)2 1+ ], [Ln(BTP)2(NO3)2 + ] and [Ln(BTP)3- 

(NO3) 2+ ] are very different for Ln= La, Pr, Eu, Tb 

and Lu, respectively. Figure 3 shows the ratios of the 

different detected species of the observed lanthanides 

normalized to 100% for [Ln(BTP)(NO3)2 1+ ], 

[Ln(BTP)2(NO3)2 + ] and [Ln(BTP)3(NO3) 2+ ]. 


The complexation of lanthanide ions by BTP was 

studied before by ESI-TOF [10]. However, while 

these investigations were perfomed in water/methanol, 

mixtures the present work focuses on the diluent 

octanol. Since the diluent has a drastic influence on 

the speciation of the metal ligand complexes investigations 

must be performed in a diluent relevant to the 

actual extraction process, in this case octanol. The 

relative abundances of the Ln(BTP)3-complexes of 

the different lanthanides (Figure 3) correlate with the 

distribution ratios (Figure 2): We found that a high 

distribution ratios, i.e. an efficient extraction from the 

aqueous into the organic phase correlates with a high 

abundance of the respective Ln(BTP)3-complex (e.g. 

for the case of Tb). In contrast, formation of 

Ln(BTP)(1-2)-complexes result in lower distribution 

ratios and high separation factors from the actinides 

Cm and Am. Both, electrostatic and steric effects 

seem to play a role in the formation of the different 

complexes: For the lanthanides La through Tb the 

decreasing ionic radius causes an increasing electrostatic 

attraction and a stabilization of the 1:3 complex. 

Further contraction of the ions from Tb through 

186 

Lu favours formation of 1:2 and 1;1 complexes, most 

likely due to steric hindrance. 

Similar results as for the 1:2 metal to ligand ratio 

were obtained for the ligand-to-metal ratio 10. The 

better the lanthanide is extracted to the organic phase 

by BTP, the more Ln(BTP)3-complexes are detected. 

Figure 3: Ratios of the different detected species of 

the observed lanthanides normalized to 100%. Top 

left: Structure of Ln(BTP)3-complexes. 


I would like to thank Prof. Thomas Fanhänel for the 

opportunity to work on this exciting topic. I thank 

Clemens Walther and Andreas Geist for supervising 

my work and for the helpful discussions. I am grateful 

for the technical support of Sebastian Büchner 

and the help of Markus Fuß through the first steps 

with the ESI device. 

REFERENCES 

[1] C. Madic et al. J. All. Com., 444-445, 23-27, 

2007. 

[2] Z. Kolarik et. al. Solvent. Extr. Ion. Exch., 17, 

5, 1155-1170, 1999. 

[4] J. Fenn. J. Biomol. Tech., 13,101–118, 2002. 

[3] C. Hill et al., J. Nucl. Sci. Technol., 3, 309-312, 

2002. 

[5] M.Wilm, M. Mann. Anal. Chem., 68, 1–8, 

1996. 

[6] C. Walther et al. Anal. Bioanal. Chem., 388, 409- 

431, April 2007. 

[7] T. Bergmann, T.P. Martin, H. Schaber. Rev. Sci. 

Instrum., 60, 347–349, 1989. 

[8] T. Bergmann, T.P. Martin, H. Schaber. Rev. Sci. 

Instrum., 61, 2592–2600, 1990. 

[9] T. Bergmann, et. al. Rev. Sci. Instrum., 61, 

2585–2591, 1990 

[10] S. Colette, et al. Inorg. Chem., 42, 2215-2226, 

2003.

Quantum Optical Coherence Tomography 

Abstract- Quantum entanglement, which is a 

unique phenomenon of Quantum Mechanics, is 

being used in many areas like Quantum cryptography, 

imaging and computing. In this project, 

which is the preliminary work for Quantum Optical 

Coherence Tomography (QOCT), we have used the 

process of spontaneous parametric down conversion 

(SPDC) to generate entangled photon 

pairs. These newly created photons, separated by a 

polarizing beam splitter (PBS), are then sent 

separately to a single photon detector via different 

paths. Using a LabView user interface software, we 

recorded the amount of photons entering each 

detector over a period of time, along with a 

coincidence count between the two detectors. Using 

those data, we obtained a visibility curve, which 

indicates the degree of correlation between the 

entangled photons. We have achieved a visibility of 

94%, which allowed us to move on to the next step: 

QOCT. 


The field of Quantum Cryptography has 

received renewed interest during the past 

decade due to the advent of a new source 

of light. This source, made of entangled 

photon pairs allows for enhanced security 

and robustness of the system. 

This project is divided into two parts. First, 

we generate and characterize entangled 

photon pairs through parametric down 

conversion. Then we move on to QOCT. 


The diagram below is a simplified version 

of the actual experimental setup. The idea 

is to generate two beams and let them 

propagate on different paths. A sample is 

PIERRE BOUZI 

Dr. ROGER DORSINVILLE 

Department of Electrical Engineering 


New York, USA 

Email: pbouzi00@ccny.cuny.edu 

187 

placed in a fixed arm while the other path 

is varied over a small distance. When the 

two path lengths are equal, we obtain an 

interference pattern which reveals the 

image inside the sample. 

Figure1. Simplified QOCT setup 

The results we have obtained so far are 

show next. 

III. RESULTS 

We have obtained a visibility of 94%, as 

shown in the figure below. 

Coincidence counts in 30 sec 

laser 

source 

Prism 

Mirror 

PBS 

KTP 

V isib ility (~94 % ) 

160 

140 

120 

100 

80 

60 

40 

20 

0 

0 50 100 150 200 250 300 350 400 

QWP angles in degree 

Detector 

Figure2. Degree of correlation between the 

entangled photons 

Mirror

Such a curve, which indicates the degree 

of correlation between the photons, was 

obtained using the following formula: 

V= max c min c 

max c min c 

100 ,where the subscript 

c stands for coincidence count. 

With such a high visibility, we are ready to 

move on to the other part of the 

experiment: QOCT. 


We have completed the first part of the 

project successfully, as indicated by the 

visibility plot. Now we are working on the 

QOCT part, where we hope to match a 

simulation obtained at Boston University 

[1]. A similar technique already exists in 

188 

imaging, but by using entangled photon 

pairs it is possible to achieve a two fold 

increase in resolution. 

V. ACKNOWLEDGMENTS 

I would like to thank our sponsors at Corning 

Incorporated for their support, as well as my 

colleagues and my supervisor. 

VI. REFERENCES 

[1] Mark C. Booth, Giovanni Di Giuseppe, 

Bahaa E. A. Saleh, Alexander V. 

Sergienko, and Mavin C. Teich, 

“Polarization-sensitive quantum-optical 

coherence tomography”

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Functionalized Cadmium Sulfide Clusters as Nanosized Building 

Blocks for Hybrid Materials – Investigation of the 

“[Cd10S4(SPh)12]” Cluster Structure 

Maria Bendova, Michael Puchberger and Ulrich Schubert (Faculty Mentor) 




Email: mbendova@mail.zserv.tuwien.ac.at 

Abstract — The goal of our work is to synthesize 

molecular CdS clusters with polymerizable ligands 

(“functional” clusters) in order to use them as comonomers 

in polymerization reactions. In this way, 

cluster-crosslinked polymers might be formed which 

possess special physical, e.g. optoelectronic, properties. 

In this contribution, we present our results on the 

investigation of “[Cd10S4(SPh)12]” (1) which is 

formed by thermal treatment of the precursor 

(Me4N)4[Cd10S4(SPh)16] cluster. According to previous 

literature studies, it should have four free Cd 

coordination sites available for further functionalization. 

However, we proved now that the core 

structure of the cluster is not maintained during the 

pyrolysis reaction and that it grows unspecifically. 

Thus, it is not suitable for further functionalization. 


Molecular semiconductor clusters with a defined 

number of atoms and a defined molecular structure 

are of particular interest for investigations on the 

variation of properties related to the change in size. 

There is a series of defined molecular CdS clusters 

with increasing size. The two smallest clusters 

([Cd10S4(SPh)16] 4- [1] and [Cd17S4(SPh)28] 2- [2]) are 

synthesized via kinetic trapping method, using powdered 

S or a S 2- salt as the sulfur source. The cluster 

with 32 Cd atoms ([Cd32S14(SPh)40] 4- ) can be prepared 

in different ways: (i) by solvothermal synthesis 

with thiourea as the sulfur source [3], or (ii) by solidstate 

formation of “[Cd10S4(SPh)12]” (1) from 

[Cd10S4(SPh)16] 4- and subsequent crystallization from 

pyridine/DMF solution [4]. The currently biggest 

cluster, which could be characterized by X-ray diffraction, 

has 54 Cd atoms ([Cd54S32(SPh)48(H2O)4] 4- ) 

and was synthesized by the solvothermal method 

using thiourea as sulfur source [5]. 

Few contributions were published concerning the 

structure of 1. The early one [6] concludes from 

different measurements (thermogravitmetric, X-ray 

powder diffraction, luminescence and absorption 

191 

spectra, 113 Cd and 1 H NMR) that 1 consists of charge 

neutral cluster [Cd10S4(SPh)12] that tends to aggregate 

to different degrees in the solid and solution. This 

observation was used by Hiratani et al. [7], who 

reacted 1 with ionic organic bromides with long alkyl 

chains and studied intercalative cation accumulation. 

He states to have a cluster with Cd10 core. Herron et 

al. [4] synthesized the [Cd32S14(SPh)36.DMF4] cluster 

from the solution of 1 in pyridine by addition of 

DMF. This claims that both 1 and 

[Cd32S14(SPh)36.DMF4] undergo a rearrangement in 

pyridine solution caused by rapid fracture of the 

cluster cores which leads to a dynamic mixture of 

species with lower nuclearities. 

We used mostly different NMR measurements and 

crystallization experiments to characterize the intermediate 

product 1. 


A. NMR MEASUREMENTS 

1. 1 in d5-pyridine, which showed one set of PhS 

and one set of pyridine signals, and no H correlation 

to Cd, probably due to fast ligand exchange. 

2. The pyridine solution of 1 in d-pyridine was 

evaporated and dissolved again in CD2Cl2. 

Two sets of PhS signals were observed, one of 

them showed correlation to Cd. NMR spectra 

changed its pattern after 2 weeks and crystals 

were formed (Cd17 cluster connected via PhS 

bridges, building a 1D polymer). 

3. 1 in d-DMSO after heating at 80 °C shows 3 

different PhS ligands and 3 Cd signals. Maybe 

[Cd32S14(SPh)36.DMSO4] was formed. 

4. Backward reactions with 4 equivalents of 

PhSH/Et3N or NaSPh/Me4NCl or Me4NSPh in 

d-acetonitrile or d-DMSO showed no explicit 

results, but there was a certain similarity with 

expected spectra (Figure 1).

5. Solid-state 113 Cd NMR showed only one intense 

broad and several small signals, although 

the spectra of [Cd10S4(SPh)16] 4- revealed 

sharp peaks. 

Figure 1: 1 H NMR spectra of a backward reaction of 

1 with NaSPh (up) and of the starting cluster 

[Cd10S4(SPh)16] 4- (down). 

These measurements allowed the conclusion that 

the substance 1 has not a defined core structure. In 

coordinating solvents (like pyridine, DMF, DMSO), 

some rearrangement of the clusters takes place which 

was also observed earlier [4]. Reactions in noncoordinating 

solvents (CH2Cl2) did not lead to the 

formation of one defined cluster species which supports 

our conclusion. 

B. CRYSTALLIZATION EXPERIMENTS 

We could successfully crystallize different clusters 

from different solutions of 1. The results from singlecrystal 

XRD are summarized in Table 1. 

Preparation Cluster core 

1 + 1:4 PhSH/Et3N in acetonitrile, 

filtration, cooling to -20 °C 

Cd10 

1 + excess pyridine, evaporation, 

dissolution in CH2Cl2 

Cd17 

1 in pyridine, addition of DMF Cd32 [4] 

1 in pyridine, addition of toluene Cd54 

1 in DMF, heating to 70 °C, filtration, 

addition of acetone 

Cd54 

Table 1: Summary of crystallization experiments. 

The first experiment (addition of 1:4 PhSH/Et3N in 

acetonitrile) clearly shows that part of the starting 

cluster [Cd10S4(SPh)16] 4- retains its core structure 

during the thermal decomposition, while the rest 

forms aggregates or clusters with other cores, which 

are not soluble in acetonitrile after addition of 

PhSH/Et3N and thus could not be obtained in this 

way. 

The latter experiments can be explained by two 

different effects: (i) different species are present in 1 

immediately after the thermal decomposition, and (ii) 

they rearrange to other stable species in solutions of 

coordinating solvents [4]. 

192 

In conclusion, the core structure of 1 is not uniform. 

Different clusters can be obtained from its 

solutions. So, the assumed four free coordination 

sites cannot be used for further functionalization. 


The authors thank the Austrian Science Fund (FWF) 

for financial support and Prof. Kurt Mereiter from 

Vienna University of Technology for help with single-crystal 

XRD. 

REFERENCES 

[1] I. G. Dance, A. Choy and M. L. Scudder. J. Am. 

Chem. Soc., 106: 6285-95, 1984. 

[2] G. S. H. Lee, D. C. Craig, I. Ma, M. L. Scudder, 

T. D. Bailey and I. G. Dance. J. Am. Chem. Soc., 

110: 4863-4, 1988. 

[3] N. Zheng, X. Bu, J. Lauda and P. Feng. Chem. 

Mater., 18: 4307-11, 2006. 

[4] N. Herron, J. C. Calabrese, W. E. Farneth and Y. 

Wang. Science, 259(5100): 1426-8, 1993. 

[5] N. Zheng, X. Bu, H. Lu, Q. Zhang and P. Feng. 

J. Am. Chem. Soc., 127: 11963-5, 2005. 

[6] W. E. Farneth, N. Herron and Y. Wang. Chem. 

Mater., 4: 916-22, 1992. 

[7] T. Hiratani and T. Konishi. Angew. Chem. Int. 

Ed., 43: 5943-6, 2004.

Creating building blocks for Hybrid Materials: 

Investigation of Adhesives for Zirconia Substrates 

Christoph Lomoschitz and Guido Kickelbick 




Email: chlomo@mail.zserv.tuwien.ac.at 

Abstract — Phosphorus based coupling agents 

(P-CAs) comprising different chain lengths were 

prepared via a multistep synthesis approach. P-CAs 

were used for modification of zirconia nanometer 

sized particles and investigated towards bonding 

(IR and 31 P MAS NMR), surface coverage (TGA) 

and surface properties (nitrogen sorption at 77 K). 

Results suggest that bonding of P-CAs is of covalent 

character. Furthemore it was found that different 

chain lengths influence the surface properties 

significantly. 


Transition metal oxides are a widespread class of 

substances offering a variety of properties such as 

reasonable hardness, magnetism or photo-catalytical 

activity. However homogeneous incorporation of 

such advanced ceramics into a polymeric matrix, 

thus creating hybrid materials, is often rather 

delicate and governed by phase separation. This 

problem can be overcome by introducing molecular 

layers of adhesives, so called coupling agents. Very 

prominent systems comprise alkyl thiol films on 

gold or noble metals as well as alkylsilicon based 

films on metal oxides. 1 The affinity of phosphates 

and/or phosphonates to transition metal oxides was 

also subject for several studies in literature. 2-4 

However, fundamental studies concerning P-CAs 

are only limited. 

In this paper we present a convenient multistep 

synthesis approach to obtain methacryl based P- 

CAs of convenient purity with reasonable yields. 

The prepared linkers were grafted onto zirconia 

surfaces, observing rather high reactivity of P-CAs 

towards zirconia. The surface properties of 

modified zirconia were significantly changed. 

Evaluation of analytical data suggested reasonably 

high grafting densities of P-CAs thus resulting 

partially in self-assembled monolayer like systems. 

193 


Two different classes of P-CAs were synthesized 

being methacryloyloxy alkyl phosphates and 

methacryloyloxy alkyl phosphonates (Figure 1). 

Phosphates were synthesized via a simple 

condensation reaction of the corresponding �methacryloyloxy-�-alkanol 

with POCl3 followed by 

hydrolysis. Phosphonate homologues were 

synthesized using a multistep approach comprising 

the Arbuzov reaction followed by deprotection, 

functionalization and mild hydrolysis via 

trimethylsilyl bromide. 

O 

O 

Br 

n 

O 

O 

P(OEt) 3 O P KOH/MeOH HO P 

n O 

n O 

150°C 

O 

O 

O 

O 

HO n O 

O 

O 

O 

P 

n OH 

OH 

1. TMSBr 

2. MeOH 

+ 

CH 2 Cl 2 

1. POCl3/NEt3 

O 

O 

2. H2O 

HO 

P 

O 

OH 

n O 

O 

O 

O 

NEt CH 3 2Cl Cl 

2 

O 

P 

n O 

O 

Figure 1: Synthesis of P-CAs; up: phosphonic acid 

bottom: phosphoric acid mono ester 

Mono alkyl phosphoric acids as well as 

phosphonic acids offer the possibility of tridentate 

bonding to a substrate caused by two possible 

condensation sites (P-OH) and an electron donating 

site (P=O). 5 In literature bonding states of P-CAs on 

metal oxides are intensely debated. Typical results of 

modified metal oxide surfaces suggest a variety of 

different bonding modes present. 6 

Zirconia particles (Aldrich,

CH 2 

3000 

CH 2 

3000 

MUPnA 

MHPnA 

MPPnA 

MEPnA 

2500 

2500 

MDPA 

MEPA 

C=O 

C=C 

2000 1500 

Wavenumber cm-1 2000 1500 


Wavenumber cm-1 C=O 

C=C 

2000 1500 




Wavenumber cm-1 P=O / C-O-C 

P-O 

P-OH 

CH 2 

1000 3000 

P=O / C-O-C 

P-O 

P-OH 

1000 

CH 2 

3000 

MUPnA@ZrO 2 

MHPnA@ZrO 2 

MPPnA@ZrO 2 

MEPnA@ZrO 2 

C=O 

C=C 

2500 2000 1500 

Wavenumber cm-1 2500 2000 1500 

Wavenumber cm-1 2500 2000 1500 

Wavenumber cm-1 MDPA@ZrO 2 

MEPA@ZrO 2 

2500 

C=O 

C=C 

2000 1500 




Wavenumber cm-1 P=O / C-O-C 

P-O 

P-OH 

1000 

P=O / C-O-C 

P-O 

P-OH 

1000 

Figure 2: IR Spectra of synthesized phosphonic acids 

(top) and mono alkyl phosphates (bottom); right: 

pure left: grafted on zirconia 

From the IR spectra of P-CAs, pure and grafted on 

zirconia, it is clearly visible that the methacrylic 

moiety, crucial for attachment to a polymer matrix, 

did not change after the grafting process, as 

evidenced by the C=O (1720 cm -1 ) and C=C (1630 

cm -1 ) stretching vibrations. Changes in the P-O 

region 950-1200 cm -1 (decrease of P-OH and P=O 

band) indicate covalent multidentate bonding of P- 

CA on the zirconia surface featuring a variety of 

different bonding modes according to published 

results. 2, 3 The results obtained could be confirmed 

using 31 P solid state NMR (data not shown) where an 

upfield shift of the main resonance could be detected. 

TG /% 

100.0 

99.0 

98.0 

97.0 

96.0 

95.0 

94.0 

93.0 

Phosphonate 

C2 

C3 

C6 

C11 

Phosphate 

C2 

C10 

100 200 300 400 500 600 700 

Temperature /°C 

Figure 4: TGA graphs of modified zirconia powder 

Thermogravimetric measurements were carried out 

in order to investigate grafting densities of modified 

zirconia particles (Figure 4). It could be observed that 

coverages range from 55 to 85 % for phosphonates 

and from 35 to 45 % of a theoretically dense 

194 

monolayer for phosphates assuming a theoretical 

bonding area of 24 Å 2 per phosphonate or phosphate 

headgroup respectively. 3 These results suggest that 

phosphonates possess a higher affinity to zirconia 

than phosphates under the conditions used for 

grafting process. In addition it was observed that 

longer alkyl spacers favour higher grafting densities. 

This effect can be ascribed to van-der-Waals 

interactions between the alkyl chains similar as 

known from self assembled monolayers. 1 

Nitrogen sorption measurements at 77 K show a 

significant change in surface properties. It can be 

clearly observed that CBET constants decrease with 

increasing chain length of P-CA which is equivalent 

to an increasing hydrophobicity of the surface, as 

CBET is proportional to the adsorption enthalpy of 

nitrogen (Figure 5). 

CBET 

70 

65 

60 

55 

50 

45 

40 

35 

30 

0 2 4 6 8 1012 No. Methylene 

Phosphonate 

Phosphate 

Unmodified 

Figure 5: CBET constants of modified zirconia 

powders 


This work was financed by IvoclarVivadent AG. We 

thank Dr. Burtscher, Dr. Moszner and Dr. Salz for 

encouragement and scientific support. 

REFERENCES 

[1] A. Ulman, Chem. Rev. 1996, 96, 1533-1554. 

[2] W. Gao, L. Dickinson, C. Grozinger, F. G. Morin 

and L. Reven, Langmuir 1996, 12, 6429- 

6435. 

[3] G. Guerrero, P. H. Mutin and A. Vioux, Chem. 

Mater. 2001, 13, 4367-4373. 

[4] J. T. Woodward, A. Ulman and D. K. Schwartz, 

Langmuir 1996, 12, 3626-3629. 

[5] P. H. Mutin, G. Guerrero and A. Vioux, J. Mater. 

Chem. 2005, 15, 3761-3768. 

[6] F. Brodard-Severac, G. Guerrero, J. Maquet, P. 

Florian, C. Gervais and P. H. Mutin, Chem. 

Mater. 2008, 20, 5191-5196.

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Realization of Inversion-type GaN MOSFETs with Ar Implantation 

for Device Isolation 

Clemens Ostermaier a,c , Sang-Il Ahn a , Kay Potzger b , Manfred Helm b , Stefan Kalchmair c , 

Dionyz Pogany c (Faculty Mentor), Jong-Ho Lee a , Sung-Ho Hahm a , and Jung-Hee Lee a 

a 

School of Electrical Engineering & Computer Science, Kyungpook National University, Daegu, 

Republic of Korea 

b 

Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, 

Dresden, Germany 

c 

Institute for Solid State Electronics, Vienna University of Technology, Vienna, Austria 

Email: Clemens.Ostermaier@TUWien.ac.at 

Abstract — We report an inversion-type metaloxide-semiconductor 

field-effective transistor 

(MOSFET) on MOCVD-grown p-type GaN with 

silicon - implanted source/drain regions and device 

isolation by argon implantation. This isolation 

technique allows a planar process without 

surface leakage current caused by loss of nitrogen 

at the surface during the high-temperature annealing 

required for the activation of silicon dopant. 

The maximum measured drain output current was 

100 �A/mm while the device isolation current was 

below 10 nA/mm over the whole range of device 

operation. 


GaN is known for its high power device capability 

due to the high saturation velocity, high mobility 

in the two-dimensional electron gas layer, large 

bandgap and high thermal conductivity. Therefore 

heterostructure devices with nitride-compounds 

showed incredible performances during the last 

years. Those devices are usually depletion mode 

devices and need therefore a higher implementation 

to be used in electronic circuits. On the other 

hand, inversion-type GaN metal-oxidesemiconductor 

field-effect transistors (MOSFET) 

are usually normally off and further have the advantage 

that the off-state drain current is reduced 

by the large band gap [1,2]. This could lead to a 

competitive on/off current ratio, which is the determining 

factor of a power switch. On the other 

side, source/drain implantation is very difficult in 

GaN with its strong atomic binding energy and its 

high melting point. Hence, the annealing temperature 

for a full crystal recovery should be around 

1800°C and requires high nitrogen partial pressure. 

Usually used annealing processes with temperatures 

around 1000°C at normal ambient pressure 

lead to outdiffusion of nitrogen, which is 

known to create donor like vacancies causing n+ 

197 

doping in the surface region [3,4]. In this paper we 

present the fabrication of GaN MOSFET devices 

with Ar+ device isolation as shown schematically 

in Fig. 1. The high fluence of argon atoms prevents 

the current flow in the implanted surface 

layer [5]. 

Figure 1: Schematic of the structure 

II. DEVICE FABRICATION 

For device fabrication we grew by metal-organic 

chemical vapour deposition (MOCVD) a 1 �m 

Mg-doped p-type GaN layer on a 2 �m GaN buffer 

grown on sapphire substrate. Silicon implantation 

[6,7] was performed at 45 keV and 100 keV with 

an overall fluence of 1x10 16 cm -2 into a 300 nm 

thick SiO2 channel mask making a 2 �m channel 

length. The silicon atoms were activated during a 5 

minutes annealing process at 1100°C under N2 and 

Ar ambient and different capping modes. The 

summary of the secondary mass ion spectroscopy 

(SIMS) profiles for different annealing techniques 

are shown in Fig. 2. After wet removal of the mask 

and cleaning the surface in H2SO4:H2O2, a 60 nmthick 

PECVD-SiO2 film was deposited as gate 

oxide. The interface characteristic of such an interface 

was known to have an interface and fixed 

charge density below 3x10 12 cm -2 and an interface 

trap density of around 10 11 cm -2 eV -1 close to band 

edge. The characterization of the interface was 

performed by UV-induced capacitance-voltage

(CV) measurements and the CV conduction 

method [8,9]. Source and drain contacts were 

provided by dry-etching, Ti/Al/Ni/Au deposition 

by electron-beam evaporator and annealing in an 

rapid thermal annealing process at 700°C. In order 

to isolate the MOSFET devices, Ar + with a fluence 

of 5x10 14 cm -2 was implanted at 40 keV and 140 

keV. The average implantation depth of the argon 

atoms exceeded that one of silicon to guarantee a 

sufficient isolation for all tested annealing methods, 

as shown in Fig. 2. 

Source-Drain implanted Si atoms (cm -3 ) 

1E21 

1E20 

0 100 200 300 400 

Depth (nm) 

not annealed 

SiO capping in N 2 2 

no capping in Ar 

GaN wafer capping in N2 simulated Ar profil 

1E19 

1E18 

Figure 2: Measured Si and simulated Ar SIMS 

profiles for different ambients and capping 

Finally, a Ni/Au gate film was deposited with a 3 

�m gate overlapping on each side over the nonimplanted 

channel area to ensure sufficient channel 

modulation. 


The output characteristics of the GaN MOSFET 

(Fig. 3) show a transistor behavior with a positive 

ID (VD) slope until 10 V. The low current value is 

determined by the large amount of interface states 

at the dielectric/channel interface. The maximum 

applied gate voltage is around 13 V, since the gate 

leakage current of the device becomes dominant 

for higher voltages. However, the drain current 

increases to 104 mA/mm for higher drain voltage 

up to 40 V, due to drain induced barrier lowering 

(DIBL). Below the threshold voltage, the device 

showed a wide dynamic range over four orders of 

magnitude. The off-state breakdown voltage of the 

MOSFET is 38 V. 

The argon implantation was tested between active 

areas with a pitch of 100 �m. Since the mask for 

the silicon implantation included only the gate 

finger regions, the whole other area was implanted 

by silicon and then isolated by argon atoms. The 

Ar + isolation showed extremely low leakage current 

values around 10 nA/mm at 40 V as shown in 

Isolation implanted Ar atoms (cm -3 ) 

198 

the inset of Fig. 3. It is therefore an easy-to-apply 

and efficient isolation method for GaN MOSFET 

devices in comparison to non-planar MESA etching 

isolation. In comparison to source/drain island 

isolation, the leakage is lowered and surface leakage 

current is prevented by a shallow implantation. 

However, no additional annealing steps can be 

applied after the argon isolation, since this would 

cause most argon atoms to escape from GaN resulting 

in an ineffective isolation. 

Drain Current I D (�A/ mm) 

125 

100 

75 

50 

25 

Buffer current (A/mm) 

1E-9 

1E-10 

-40 -20 0 20 40 

Voltage (V) 

�V G = -1 V 

0 

0 2 4 6 8 

Drain Voltage V D (V) 

V G = 13 V 

Figure 3: Output IV characteristic and buffer leakage 

current. 


This research was supported by 2008 Brain Korea 

21 (BK21) and the Korea Science and Engineering 

Foundation (KOSEF) grant funded by the Korea 

government (MEST) (No.M10600000273-06J0000- 

27310). 

REFERENCES 

[1] H.-B. Lee et al., IEEE Electronic Device Letters 

27(2): 81-83, February 2006 

[2] W. Huang, et al., Journal of Electronic Materials 

35(4):726-732, 2006 

[3] J.C. Zolper et al., Journal of Crystal Growth 

178:157–167, 1997 

[4] B. Boudart, Journal of Raman Spectroscopy, 

33:283–286, 2002 

[5] H. Boudinov et al., Applied Physic Letters 

78(7):943-945, February 2001 

[6] D.W. Jenkins et al., Physical Review B 

39(5):3317-3329, February 1989 

[7] C.J. Sun et al., Joural of Applied Physics 76(1): 

236-241, July 1994 

[8] C. Ostermaier et al., Physica Status Solidi (c) 5 

(6):1992-1994, May 2008 

[9] E.H. Nicollian et al., MOS Physics and Technology, 

Wiley, New York, 1982

Solution Stability of Trinuclear Iron Oxo Clusters 

Robert Potzmann, Stefan O. Baumann, Maria Bendova, Michael Puchberger, 

Ulrich Schubert 

Institute of Materials Chemistry, Vienna University of Technology, 

1060 Vienna, Austria 

e-mail: rpotzman@mail.zserv.tuwien.ac.at 

Abstract — A large number of clusters with a Fe3O 

core was synthesised varying the ligands and anions. 

Detailed investigation in solid state and solution 

elucidate the close relation between the different 

coordination compounds and show a complex 

equilibrium between them. 


Iron oxide clusters with bridging carboxylates of 

the general formula [Fe3O(OOCR)6(L)3]X (figure 

1) also named “basic iron acetate” are well known 

for more than three centuries. A huge number of 

publications has been published in the field of 

electron transfer effects, intramolecular spin coupling, 

magnetic behavior, model compounds for 

iron storage proteins and the use as oxidation catalyst 

for aliphates. [1] Due to these wide spread applications 

and the simple synthesis numerous clusters 

have been prepared. Clusters with a wide 

variety of different coordinating ligands and diverse 

acids to a serious of anions. [2][3][4] This work 

focuses on the stability of methacrylate-modified 

basic iron acetate in solution and opens new insights 

in the behavior of three membered iron oxo 

clusters when the anion or the coordinating ligands 

are modified. 

Figure 1: [Fe3O(OOCCH3CCH2)6(H2O)3]NO3 

199 

II. RESULTS 

Although basic iron acetate is well known for over 

hundred years little is known about the stability in 

solution and the influence of the coordinating 

ligands on the cluster behavior. We systematically 

synthesized a large number of methacrylatesubstituted 

clusters with pyridine, methanol, ethanol 

and water as co-ligends and nitrate, chloride 

and methacrylate as counter-anions. Furthermore, 

detailed analysies were carried out to investigate 

interactions of the cluster with the solvent. 

A. SYNTHESIS AND CRYSTAL STRUCTURE 

Water-substituted derivatives were easily prepared 

by combining the iron salt with sodium methacrylate 

in water. Other derivatives were synthesised 

by exchanging the ligand in chloroform by common 

synthetic techniques. 

B. SOLUTION BEHAVIOUR 

The stability and behaviour of the clusters in solution 

was investigated by solution NMR and IR in different 

solvents. Coordinating solvents led to spontaneous 

exchange of the coordinated ligand against solvent 

molecules while in non-coordinating solvents 

the counter-anion partly coordinates to the cluster 

core (figure 2). By varying the ligands, the exchange 

against the anion could be suppressed accompanied 

by a tremendous change of the solubility and reactivity.

Figure 2: Solvent effect on trinuclear iron oxo 

clusters a) using a coordinating solvent b) using a 

coordinating anion 

C. SELF ORGANISATION 

Dynamic light scattering (DLS) proved the existance 

of agglomerates in the size between 100 and 500 nm. 

These agglomerates were investigated by solution 

small angle X-ray diffraction (SAXS) and it turned 

out that they show the ordering in the nanometer 

regime. 


In this abstract we have described the synthesis of 

methacrylate, modified trinuclear iron oxo clusters, a 

new class of basic iron acetates. The stability of such 

compounds in different solvents was investigated 

resulting in a detailed knowledge about the influence 

of the coordinating ligand and the anion. Finally, the 

self organisation tendencies of these molecules were 

described. 


Thank to the Fonds zur Förderung der wissenschaftlichen 

Forschung (FWF) for funding this project. 

REFERENCES 

[1]F. E. Sowrey, C. J. McDonald and R. D. Cannon; 

J. Chem. Soc. Faraday Trans. 94 (1998) 1571-74 

[2] M.Losalda, M. A. Mendiola and M. T. Sevilla; 

Inorganic Chimica Acta 255 (1997) 125-31 

[3] M. A. Kiskin, F. A. Fomina and I. I. Moiseev; 

Russian Chemical Bulletin Int. Ed. 53 (2004) 

2508-18 

200 

[4] A. M. Bond, R. J. H. Clark and A. H. White; J. 

Chem. Soc. Dalton Trans. (1998) 1845-52

Olefinic Bioreduction 

Naseem Iqbal, Marko D. Mihovilovic. 


Institute of Applied Synthetic Chemistry, Getreidemarkt 9/163-OC, 1060 Wien (Austria) 

Phone (+43) 1 58801-15451 

E-mail: naseem.iqbal@ias.tuwien.ac.at 

Enzyme mediated reactions have become a powerful methodology in asymmetric synthesis and this area 

has received considerable attention within the past decade. 1 Currently, biocatalysis offers complementary 

solutions to metal-assisted transformations in chiral catalysis and is considered one of the important 

strategies of “green chemistry”. In particular the high sustainability of protein based catalytic entities 

represents a major advantage. Recent trend studies indicate a significant potential for growth of the 

contribution by “white biotechnology” to the industrial scale synthesis of chiral compounds via 

biotransformations at the expense of classical chiral auxiliary strategies (with recently re-discovered 

“organocatalysis” as yet to be adopted methodology for industrial applications). 2 A particularly appealing 

target for application of the outlined strategy in the area of bioreductions is the emerging field of formal 

biocatalytic olefin hydrogenation. This biotransformation is merely a nucleophilic attack by hydride 

originating from NAD(P)H across an activated C=C double bond via a Michael-type reaction. Enzymes 

involved are referred to as olefin reductases (OREDs). Recently, old yellow enzyme (OYE) from 

Saccharomyces carlsbergensis was re-discovered for the chemo- and stereoselective conversion of enones 

and nitroolefins into saturated compounds. 3 Homologs of this enzyme from Shewanella oneidensis 

(SYEs) were shown to be catalytically active when recombinantly expressed as GST fusion proteins. 4 

Whole cell and crude protein extract biotransformation with different substrates (unsaturated cyclic 

ketones, unsaturated diesters, substituted imides) for SYE-3(BL21 DE3) and SYE-4(BL21 DE3) 

(Shewanella Yellow Enzyme) were performed. The results (conversion and ee) were rationalized by 

chiral GC. 

�� 

1 

Biocatalysis in the Pharmaceutical and Biotechnology Industries, Patle, R.N. (ed.) CRC Press, Boca 

Raton, 2007. Enzyme Catalysis in Organic Synthesis, Drauz, K.; Waldmann, H. (eds.) Wiley-VCH, 

Weinheim 2002. 

2 

Business assessment by Frost&Sullivan, Chem. Eng. News 2003, 81. 

3 

Swiderska, M.A.; Stewart, J.D. J. Mol. Catal. B: Enzym. 2006, 42, 52. Swiderska, M.A.; Stewart, J.D. 

Org. Lett. 2006, 8, 6131. 

4 

Brige, A.; van den Hemel, D.; Carpentier, W.; de Smet, L.; van Beeumen, J.J. Biochem. J. 2006, 394, 

335. 

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204

Effect of Various Composition and Dosage of Potassium 

Activator on the Properties of Alkali Activated Slag Mortar 

Iva Frýbortová and Pavel Rovnaník (Faculty Mentor) 

Institute of Chemistry 

Brno University of Technology, Faculty of Civil Engineering 


frybortova.i@fce.vutbr.cz 

Abstract — Alkali activated slag is a clinker-free 

binding material capable of replacing Portland 

cement in concrete production. In this paper properties 

of alkali activated blast furnace slag mortars 

were studied. Potassium silicate and hydroxide 

solution of various silicate moduli (Sio2/K2O) was 

used as an activator. Activator dosage was 4, 8, 10 

and 20 % with respect to the mass of slag. Compressive 

strength of the mortar samples was measured 

28 days after casting. It was found that increasing 

amount of activator added to the mixture 

leads to an increase in compressive strength. No or 

very little efflorescence was observed on the samples. 


Utilization of waste materials is an issue that has 

been paid increasing attention to not only for economical 

but also environmental reasons. Portland 

cement plants are responsible for 5 % of worldwide 

CO2 emissions; with every 1 ton of cement 

produced 0.66 ton of CO2 is released to the atmosphere 

[1]. Alkali activated aluminosilicates, such 

as metallurgical slags, fly ash and other industrial 

by-products can be used as binding materials substituting 

Portland cement in concrete. Latent hydraulic 

properties of these materials are activated 

by addition of alkaline substances, such as sodium 

or potassium hydroxides, silicates, carbonates etc. 

Alkali activated blast furnace slag shows very 

good mechanical properties, high resistance to 

chemical attack, freezing and thawing, high temperatures 

and alkali-aggregate reaction [2–5]. 

Properties of the final product are determined by 

many factors, such as chemical and phase composition 

of the slag, slag fineness, type and concentration 

of activator, water to slag ratio, curing conditions 

etc [6]. 

Properties of blast furnace slag mortars activated 

by potassium activator of various composition and 

dosage were studied in this paper. 

205 


A ground blast furnace slag (Kotouc, Czech Republic) 

with specific surface 380 m 2 /kg was used. 

Chemical composition of the slag is in Table 1. 

Component Content [%] 

SiO2 34.74 

Al2O3 5.91 

Fe2O3 0.39 

CaO 40.27 

MgO 9.60 

MnO 0.36 

Stotal 

0.39 

Na2O 0.29 

K2O 0.41 

Table 1: Chemical composition of blast furnace slag. 

Water solution of anhydrous potassium silicate 

Portil K (Henkel, Germany) and potassium hydroxide 

was used as an alkaline activator. Silicate 

modulus MS of the activator, i.e. molar ratio of 

SiO2 to K2O, was 0.8; 1.0 and 1.2. The amount of 

activator in solid state added to the mixture was 4, 

8, 10 and 20 % with respect to the mass of slag. 

Standard silica sand was used as an aggregate. 

Mortar samples of 40×40×160 mm dimensions 

were cast and 24 hours after demoulding immersed in 

water. 28 days after casting the samples were subjected 

to compressive strength test. Pieces of samples 

left after strength testing were partly immersed in 

water due to efflorescence observation. 

III. RESULTS 

Table 2 and Figure 1 show 28 day compressive 

strengths of the specimens. It can be seen that for all 

silicate moduli increasing amount of alkaline activator 

results in the strength growth. Therefore, it can be 

stated that the required ultimate strength of the mixture 

can be adjusted by the amount of activator, 

which also works partly as a plasticizer. On the other

hand, the activator concentration should be kept as 

low as possible due to several reasons: 

− alkaline activator solution is very corrosive to 

the material of storing and mixing equipment, 

− alkaline activator is the most expensive constituent 

of the mixture, 

− alkalis represent ecological load when occur in 

waste water, 

− excessive amount of alkalis in the mixture can 

lead to efflorescence. 

% of 

MS = SiO2/K2O 

activator 0.8 1.0 1.2 

4 41.0 48.9 58.2 

8 77.2 66.8 60.7 

10 84.1 84.3 77.7 

20 90.1 90.4 86.3 

Table 2: Compressive strength (28 day) of alkali 

activated slag mortar samples in MPa. 

Table 2 shows that even with only 4 % of alkaline 

activator, based on the mass of slag, the compressive 

strength can reach 58.2 MPa (for MS = 1.2). The 

mixtures with 20 % of activator had the highest compressive 

strength, i.e. 90.1; 90.4 and 86.3 MPa, for 

silica modulus equal to 0.8; 1.0 and 1.2, respectively. 

However, the compressive strength difference between 

the mixtures with 10 % and 20 % of the alkaline 

activator is not substantial. 

For mixtures with low amount of activator the 

strength is rather variable for different silica moduli 

contrary to the mixtures with 10 or 20 % of activator, 

see Figure 1. 

Efflorescence occurred, to a very small extent, only 

on samples with 20 % of activator. 

Compressive strength [MPa] 

100 

90 

80 

70 

60 

50 

40 

30 

0,8 1,0 1,2 

Ms = SiO2/K2O 

4 % 

8 % 

10 % 

20 % 

Figure 1 Compressive strength (28 day) of blast furnace 

slag activated by 4, 8, 10 and 20 % of activator 

(with respect to the mass of slag) with silicate 

modulus 0.8; 1.0 and 1.2. 

206 


Properties of alkali activated blast furnace slag depend 

on several factors; one of them is type and dosage 

of alkaline activator. In this study anhydrous 

potassium silicate and potassium hydroxide in 

amount 4, 8, 10 and 20 %, based on the mass of slag, 

was used as an activator. Silicate moduli of the prepared 

solutions were 0.8; 1.0 and 1.2. 

It was found that it is possible to reach rather high 

compressive strength after 28 days with only 4 % of 

alkaline activator, i.e. 58.2 MPa for silicate modulus 

1.2. The higher amount of activator was added to the 

mixture the higher compressive strength was obtained 

for all silicate moduli. Maximum strength measured 

was 90.4 MPa for samples with 20 % of activator and 

silicate modulus 1.0. Very small difference in 

strengths between the mixtures with 10 and 20 % of 

activator has been observed. 

Excessive amount of alkalis causes efflorescence, 

especially when sodium activators are used. Larger 

ionic radius of potassium does not allow it to crystallize 

on the surface to such an extent. Therefore, very 

little marks of efflorescence occurred only on the 

surface of specimens with 20 % of activator. 


This paper was elaborated with the financial support 

of the project granted by Ministry of Education, 

Youth and Sport (MSM 0021630519). 

REFERENCES 

[1] J. Davidovits, High-Alkali Cements for 21st Century 

Concretes, American Concrete Institute, SP- 

144 (Concrete Technology): 383-97, 1994. 

[2] P. Rovnanikova, P. Bayer, Corrosion Resistance 

of Alkali-activated Aluminosilicate Materials, 

Innovations and Developments in Concrete Materials 

and Construction, 373-381, 2002. 

[3] T. Bakharev, J. G. Sanjayan, Y. B. Cheng, Sulfate 

attack on alkali-activated slag concrete, Cement 

and Concrete Research, 32: 211-216, 2003. 

[4] T. W. Cheng, J. P. Chiu, Fire-resistant geopolymer 

produced by granulated blast furnace slag, 

Minerals Engineering, 16:, 205-210, 2003. 

[5] A. Fenandez-Jimenez, F. Puertas, The alkali-silica 

reaction in alkali activated granulated slag mortars 

with reactive aggregate, Cement and Concrete 

Research, 32(7): 1019-1024, 2002. 

[6] Talling B., Krivenko P., Blast Furnace Slag – The 

Ultimate Binder, Waste Materials Used in Concrete 

Manufacturing, 235-289 1997.

Impact of Mineral Dust on PM10 Levels in Austria – 

Seasonal and local variations of carbonate carbon in ambient 

PM10 and source samples 

Nicole Jankowski and Hans Puxbaum 




Email: Nicole.Jankowski@tuwien.ac.at 

Abstract — Mineral dust contributing to PM10 

levels in Austria arises from different sources. The 

aim of this study was to identify these sources and 

characterise them chemically. Paved and unpaved 

street dust, bare soil samples, dust from construction 

sites and gritting material were considered as 

main contributors of mineral dust to ambient air 

concentrations. The grab samples were resuspended 

and the PM10 fractions were collected on 

two different filter materials. Metals, soluble ions 

and various carbonaceous constituents were determined. 

The chemical mass balance (CMB) model 

and a macrotracer concept were used to estimate 

the contribution to ambient PM10 levels. 


Exceedings of the short term air quality standard 

of particulate matter smaller than an aerodynamic 

diameter of 10μm (PM10), set by the Commission 

of the European Communities [1], has been reported 

for many urban settlements in Europe [2]. 

To develop effective reduction measures, more 

information about the sources and their contribution 

to ambient particle concentration is required. 

Various programs have been launched (e.g. CAFE 

program – Clean Air for Europe [3]), to find the 

sources responsible for the exceedings. Generally, 

the sources of fine particulate matter can either be 

natural or man-made; for mineral dust both origins 

are possible. Important sources for mineral dust 

are: natural soil dust, paved and unpaved street 

dust, fugitative dust from construction activities 

and gritting materials used in winter. 


Sufficient sample material was collected around the 

stations for ambient air monitoring. The dried material 

was then resuspended in a therefore constructed 

apparatus, and the PM10 fraction was collected with 

PM10 sampling heads on two filters in parallel. For 

the analysis of metals a cellulose membrane filter 

207 

was used, for the determination of ions and carbonaceous 

constituents quartz fibre filters were applied. 

Gravimetric analysis was performed prior and after 

the sampling after 48h of equilibration in a room 

with 20±1°C and 50±5% RH, according to EN 12341 

[4]. 

Samples were analysed by X-Ray fluorescence 

for Al and Si, after digestion of 1 up to 3 filters 

with aqua regia ICP-HRMS and GF-AAS were 

applied to determine Mg, Ca, Ti, V, Cr, Mn, Fe, 

Co, Ni, Cu, Zn, Sr, Cd, Sn, Ba, Pb and As. The 

soluble ions Na + , K + , NH4 + , Cl - , NO3 - , SO4 2- were 

determined by anion and cation chromatography. 

The composite parameters total carbon and its 

fractions organic carbon, elemental carbon and 

carbonate carbon were determined with different 

combustion methods and the subsequent determination 

of the evolved CO2 [5, 6]. The anhydrosugar 

levoglucosan (a tracer for wood smoke) and 

the sugar alcohol arabitol (a tracer for fungal 

spores) were analysed with HPLC [7]. Cellulose 

was determined with a photometric method [8], 

HULIS (humic like substances) were separated by 

solid phase extraction (SPE) and analysed as dissolved 

organic carbon [9]. 

III. RESULTS 

The analysis of street dust samples taken in March 

at the sampling stations revealed high levels of carbonate 

carbon (CC). Figure 1 shows a TLT-plot 

(thermo-optical method with laser correction) of a 

street dust sample highly burdened with CC in comparison 

to the ambient air sample taken at the same 

day and station “Kendlerstraße” in Vienna, Austria. 

The laser signal indicates increasing transmission and 

the burn off of elemental carbon, mainly to be found 

in the ambient PM10 sample. Organic carbon burns 

off at lower temperatures (below 350°C), a charring 

artefact could also be corrected with the laser signal. 

The quantification of CC results in 8% of total mass 

in street dust samples; calculated as CO3 2- the mass 

fraction in street dust 41%.

dCO 2/dT Street Dust 

dCO2/dT PM10 

1.1 

1.0 

0.9 

0.8 

0.7 

0.6 

Vienna, Kendlerstraße March 

Organic Carbon 

Elemental Carbon 

Carbonate Carbon 

50 100 150 200 250 300 350 400 450 500 550 600 650 

0 

700 

Temperature [°C] 

Figure 1: TLT-plot of street dust sample and ambient 

air sample taken at the sampling site “Kendlerstraße” 

An investigation of the samples revealed, that the 

sampled street dust material taken at “Kendlerstraße” 

mostly consists of dolomite (Ca- and MgCO3), which 

was used as gritting material during winter in the 

sampling period. 

The source contribution of fine particulate matter 

arising from street dust to the ambient air concentration 

at that day results in about 70% (calculated from 

the slope between the correlation of the CO3 2- , Ca 2+ 

and Mg 2+ content of the street dust and ambient air 

sample). These results were confirmed with the CMB 

model as well. 

Figure 2 shows the local and seasonal variation of 

carbonates at two sampling sites in Vienna. The 

traffic related site was obviously more affected by 

the use of gritting materials than the urban background 

site. 

2- in PM10 

% CO 3 

40 

35 

30 

25 

20 

15 

10 

5 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

12123412121212121212345678912345123456 

Comparison of Carbonate Content at 2 sampling sites 

Jan Feb Mar AprMayJun JulAugSep Oct Nov Dec 

Urban traffic related Vienna Urban background Vienna 

Figure 2: Comparison of CO3 2- content at a traffic 

related and an urban background site in Vienna 

Figure 2 demonstrates that some single events 

(point 8 in January and point 2 in March) can amount 

in about 35% CO3 2- of total PM10 mass (about 55% 

calculated as Ca- and MgCO3). 

The mean contribution of all mineral dust sources 

to ambient PM10 samples estimated by the macrotracer 

concept and the CMB model was in the range 

of 10 up to 70%, showing the high variation of this 

source due to special occurrences like gritting and 

construction sites. 

4 

3 

2 

1 

Laser [V] 

208 


This work was part of the AQUELLIS IGL – project 

(Emissions of industry, craft and agriculture) 

funded by the Austrian Federal Ministry of Agriculture, 

Forestry, Environment and Water Management 

and the AQUELLA Vienna, AQUELLA 

Graz, AQUELLA Salzburg and AQUELLA Linz 

projects. Special thanks to all members of the 


at the Vienna University of Technology for doing 

parts of the analysis work. 

REFERENCES 

[1] European Air Qualitative Directive 199/30/EC 

[2] X. Querol, A. Alastuey, C.R. Ruiz, B. Artinano, 

H.C. Hansson, R.M. Harrison, E. Buringh, H.M. 

ten Brink, M. Lutz, P. Bruckmann, P. Straehl, J. 

Schneider. Speciation and origin of PM10 and 

PM2.5 in selected European cities. Atmospheric 

Environment 38, pages 6547-6555, 2004. 

[3] J.-G. Bartaire. Clean Air for Europe. Pollution 

Atmospherique 172, pages 493-497, 2001. 

[4] EN12341, Air Quality – Determination of the 

PM10 fraction of suspended particulate matter – 

Reference method and field testing procedure to 

demonstrate reference equivalence of measurement 

methods, 1998. 

[5] H. Puxbaum, Thermo-Gasanalysator zur Charakterisierung 

von Kohlenstoff- und Schwefelverbindungen 

in Luftgetragenen Stäuben. 

Fresenius Zeitschrift für Analytische Chemie 

298, 250-259, 1979. 

[6] H. Puxbaum, J. Rendl., Ein automatisches 

Analysatorensystem zur Bestimmung von 

Kohlenstoff und Schwefel in Luftgetragenen 

Stäuben. Microchemia Acta, 263-272, 1983. 

[7] A. Caseiro, I.L. Marr, M. Claeys, A. Kasper- 

Giebl, H. Puxbaum, C.A. Pio, Determination 

of saccharides in atmospheric aerosol using 

anion-exchange high-performance liquid 

chromatography and pulsed-amperometric detection. 

Journal of Chromatography A. 1171 

(1-2), 37-45, 2007. 

[8] H. Puxbaum, M. Tenze-Kunit, Size distribution 

and seasonal variation of atmospheric cellulose. 

Atmospheric Environment 37, 3693- 

3699, 2003. 

[9] A. Limbeck, M. Handler, B. Neuberger, B. 

Klatzer, H. Puxbaum, Carbon-Specific- 

Analysis of Humic like Substances in Atmospheric 

Aerosol and Precipitation Samples. 

Analytical Chemistry 77 (22), 7288-7293, 

2005.

PE-UHMW in hip implants: The influence of crosslinking on 

structural parameters and micro-mechanical properties 

R. Markut-Kohl, T. Koch, V.-M. Archodoulaki, S. Seidler 

Institute of Materials Science and Technology 



Email: rmarkut@mail.tuwien.ac.at 

Abstract - Ultra-high molecular weight polyethylene 

(PE-UHMW), commonly used in hip implants, 

is the limiting factor within the prosthesis 

due body reactions on wear debris [1]. With the 

objective of prolonging the durability of the hip 

replacement, radiation-crosslinking of the PE- 

UHMW hip component is more and more applied. 

In this way the amount of wear in the prosthesis is 

reduced [2]. Influences of chemical constitution 

and morphology on the micro-mechanical properties 

of PE-UHMW hip components due to in vivo 

use and in vitro testing are discussed. Furthermore 

influences of manufacturing and sterilization 

processes on the material properties are investigated. 


The most important medical application of PE- 

UHMW is the replacement of damaged cartilage in 

total joint replacement surgery. Since 1998 radiation 

crosslinked PE-UHMW, developed to optimize 

the wear behavior in the prosthesis, replaces 

conventional non-crosslinked PE-UHMW in hip 

joint replacement [1]. Manufacturing, irradiation 

(sterilization as well as crosslinking procedures) 

and subsequent thermal treatment (in order to 

reduce the oxidation tendency of the material [3]) 

significantly alter the microstructure [4]. This 

results in changes of the mechanical properties of 

the material [5]. During the life cycle of the implant 

shelf aging and in vivo use influence the 

properties of the material additionally. 

The investigations are part of a PhD-project which 

aims to correlate structural parameters at molecular 

level and at nanometer scale to the micro- and 

macro-mechanical behavior of orthopedic grade 

PE-UHMW. Assuming that surrounding medium 

and elevated temperature in the artificial joint are 

involved in changes of the material, the influences 

of time, temperature, surrounding medium and 

mechanical load on the properties of PE-UHMW 

will be figured out. In this contribution, influences 

of chemical constitution and morphology on the 

209 

microhardness will be shown. A depth profile of 

the micro-hardness was taken over the crosssection 

of the PE-UHMW hip implants revealing 

local variations within the components which can 

be attributed to changes in the degree of crystallinity 

and the oxidative degradation state. 


The physical and mechanical properties of three 

highly crosslinked PE-UHMW hip components at 

different states (shelf aged, after in vitro testing 

and after two years in vivo) are compared. As a 

reference, medical grade PE-UHMW and a noncrosslinked 

retrieved hip implant were investigated. 

Fourier Transformed Infrared Spectroscopy 

(FTIR) was used to analyze oxidized species, 

molecules diffused into the material and to evaluate 

irradiation conditions. The characterization of 

the morphology was carried out via Differential 

Scanning Calorimetry (DSC). Instrumented 

Nanoindentation technique was used for micro 

mechanical characterization. 

III. RESULTS AND CONCLUSIONS 

Crosslinking and oxidative degradation influence 

the degree of crystallinity and the melting behavior 

of the polymer, thus reflecting manufacturing 

processes and in vivo use. Oxidative degradation 

leads to chain scission and recrystallization. The 

resulting higher degree of crystallinity can be 

correlated to higher hardness values. These dependencies 

are shown in non-crosslinked and 

highly crosslinked materials. 

The depth profile of the non-crosslinked explant 

reveals a maximum in microhardness, which can 

be correlated to a greater extend of oxidation and a 

higher degree of crystallinity. 

The shelf aged highly crosslinked PE-UHMW 

implant and the in vivo used one show no changes 

in hardness, crystallinity and indication of oxidative 

degradation in their depth profiles. The in

vitro tested implant shows oxidative degradation 

and a higher degree of crystallinity in a region of 

elevated micro-hardness. Such characteristics have 

not been reported in the field of highly crosslinked 

PE-UHMW used for implants jet. 

The formation of crosslinks hinders the crystallization 

and leads to a reduced degree of crystallinity. 

Beside this, the in vitro tested implant shows a 

different melting behavior as shown in Figure 1. 

Heat Flow [W/g] (endo up) 

Heat Flow [W/g] (endo up) 

3,0 

2,5 

2,0 

1,5 

1,0 

0,5 

0,0 

3,0 

2,5 

2,0 

1,5 

1,0 

0,5 

0,0 

1st Heating Run (10 K/min) 

100 120 140 


Shelf aged (surface) Shelf aged (back) 

In vivo (surface) In vivo (back) 

In vitro (2 mm sub-surface) In vitro (back) 

non-sterilized PE-UHMW 

2nd Heating Run (10 K/min) 

100 120 140 


Figure 1: DCS results of all material conditions 

The different properties of the in vitro tested 

highly crosslinked implant can be attributed to 

severe chemical degradation, a different crosslinking 

state, different manufacturing processes and/or 

lot to lot variations. 

Although adsorbed and diffused chemical compounds 

from the surrounding media are observed 

in the in vivo used samples and the in vitro tested 

one, no plasticizer effect as hypothesize in [6], was 

found. Obviously 2a in vivo and the duration of in 

vitro testing are too short that a sufficient amount 

of molecules can diffuse in these crosslinked hip 

components. One other explanation could be, that 

since the oxidation level in the non-crosslinked 

210 

explant after 10a in vivo is high, plasticizing effects 

interfere with oxidation peaks. For the time 

being no further verifications are possible because 

only one material in this state is available. 

REFERENCES 

[1] S. M. Kurtz; The UHMWPE Handbook: Ultra 

High Molecular Weight Polyethylene in Total 

Joint Replacement; Elsevier Academic Press 

2004 

[2] D.W. Manning, P. P. Chiang, J. M. Martell, 

J. O. Galante, W. H. Harris; In Vivo Comparative 

Wear Study of Traditional and 

Highly Cross-linked Polyethylene in Total 

Hip Arthoplasty; The Journal of Arthoplasty 

Vol. 20 No. 7 (2005) 880-886 

[3] G. Lewis; Properties of crosslinked ultrahigh-molecular-weight 

polyethylene; Biomaterials 

22 (2001) 371-401 

[4] S. M. Lee, S. W. Choi, Y. C. Nho, H. H. 

Song; Modification of Microstructures and 

physical Properties of Ultra High Molecular 

Weight Polyethylene by Electron Beam Irradiation; 

Journal of Polymer Science: Part 

B: Polymer Physics 43 (2005) 3019-3029 

[5] L. A. Pruitt; Deformation, yielding, fracture 

and fatigue behaviour of conventional and 

highly cross-linked ultra high molecular 

weight polyethylene; Biomaterials 26 (2005) 

905-915 

[6] L. Costa, P. Bracco, E. Brach del Prever, M. 

P. Luda, L. Trossarelli; Analysis of products 

diffused into UHMWPE prosthetic components 

in vivo; Biomaterials 22 (2001) 307- 

315

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212

Shadowgrahic Imaging of Femto Second Laser 

Induced Ablation of Al 

Shazia Bashir, M.Shahid Rafique and Wolfgang Husinsky 

Institut für Allgemeine Physik, Vienna University of Technology, 

Abstract- Shadowgraphy technique is used to 

investigate the ablation of Al as a function of the 

laser fluence. Ablation is done with an 800 nm, 25fs 

Ti: Sapphire laser. The shadowgraphs of ablation 

are captured by CCD and imaging is done by the 

probe beam having wavelength 400 nm (produced 

by frequency doubling of Ti: Sapphire laser).The 

experimental data shows that the phenomenological 

development of the ablation dynamics is dependent 

on the number of pulses and laser fluence. The 

phenomenon of particles emission, nucleation 

growth, bursting of bubbles and droplets at the 

target surface can be attributed to hydrodynamic 

instability. 

I. Introduction 

Ultra fast time-resolved optical shadowgraphy with 

pump-probe technique allowing time- and spaceresolved 

measurements of the changes in the 

expansion dynamics of the femtosecond laser 

ablation is very useful in picoseconds to 

nanosecond time scale. This imaging analysis can 

provide information about the ablation efficiency as 

a function of the laser fluence .Then this 

information about the ejected species can be 

correlated with Raman spectroscopy, time of flight 

mass spectrometry, SEM and AFM analysis. This 

ultrafast shadow graphic imaging can be used to 

investigate femtosecond laser ablation of variety of 

materials like CaF2, 

Si, Al, Au, CR-39 etc 

A-1040 Wien, Austria 

Email: bashir@iap.iap.tuwien.ac.at 

213 

II. Layout 

Schematic of shadowgraphy setup is shown in 

“Figure 1”. A Ti: saphire 800 nm 25 fs laser 

operated at 1 KHz repetition rate has been used in 

the experiment. Beam was split into two parts with 

the help of a beam splitter. First part (pump beam) 

was focused to a spot size of 50 �m in diameter 

onto a target using 36 cm focal-length lens to 

produce ablation. Second part is converted into 400 

nm with a BBO crystal and is used as a probe beam. 

A fast response CCD along with fly capture 

software has been used to grab the image made by 

the probe beam. 

III. Results 

Figure 2 is a sequence of frames of ablated Al with 

2 

laser fluence 3.6 J/cm for different number of 

pulses. These frames are taken from an 80 second 

movie which recorded the real time ablation of Al 

when irradiated with femtosecond pump beam 

operated at a repetition rate of 1 kHz. The sequence 

shows a gradual appearance of the ablated material 

with the increased number of pulses or exposure 

time. The sequences clearly indicate the liquid– 

phase expulsion, and vaporization .increases with 

increasing number of pulses There seems to be a 

nucleation growth and bursting of bubbles and 

droplets which can be attributed to hydrodynamic 

instability. One of the basic quantities in laser 

ablation is temperature rise induced by 

the absorbed laser radiation on material surface.

This localized temperature rise can be calculated by 

solving three dimensional heat equations. In the 

liquid-phase expulsion technique, high pressure 

gas-jet is formed which expels the liquefied 

material as clear from “Figure.2.”Molten material 

accumulates near the target surface due to surface 

tension. Melting and evaporation are widely 

exploited in the treatment of materials by laser 

pulses. It has been recognized that shorter laser 

pulses may strongly superheat the melt, causing a 

homogeneous nucleation of gas bubbles. Their rate 

rises near the critical temperature. In the end, the 

liquid is believed to disrupt into a mixture of gas 

and droplets by this phase explosion. The 

development of these melt ejections are 

complicated depending upon the energy deposition 

and material ejection mechanism. 

REFERENCES 

Femto second 

laser 

CCD 

Interference 

filter 

HR mirror 

Imaging lens 

[1] X. Zeng, X.L. Mao, R. Greif, R.E. Russo 

Appl. Phys. A 80, 237–241 (2005) 

[2] H-.Dachraoui W. Husinsky Applied Phys 

Lett. 89, 104102(2006) 

[3] N. Zhang, X. Zhu, J. Yang, X. Wang, 

Phys. Rev. Lett. 99, 167602 (2007) 

800nm 

Beam 

splitter 

Ablated 

material 

Target 

Unexpose 

BBO 

crystal 

Focussing 

lens 

Probe beam 

400nm 

Figure 1 : A Schematic of shadowgraphy experimental 

set up 

214 

5000 

5500 5600 

5000 

7500 9500 9800 11000 

7500 12000 15000 9500 30000 300 

66000 80000 

30000 57000 

100 μm 

Figure 2: An ablation sequence at fluence of 3.6 J/cm 2 .

3D-analysis of neuronal and vascular networks by ultramicroscopy 

Nina Jährling 1,2,3 , Stefan Kalchmair 1,2 , Klaus Becker 1,2 , Andreas Gewies 4 , 

Edgar R. Kramer 5 and Hans-Ulrich Dodt 1,2 

1 FKE, Dept. of Bioelectronics, TU Vienna, Vienna, Austria 

2 Center of Brain Research, Medical Univ. of Vienna, Vienna, Austria 

3 University of Oldenburg, Dept. of Neurobiology, Oldenburg, Germany 

4 TU Munich, Klinikum rechts der Isar, 3. Med. Dept., Munich, Germany 

5 ZMNH, Dept. of Molecular Neurobiology, Hamburg, Germany 

Email: nina.jaehrling@meduniwien.ac.at 

Abstract — Ultramicroscopy has recently been shown as a 

useful imaging technique for three-dimensional visualization 

of biological specimens. It allows 3D-reconstructions of up 

to cm-sized samples with μm resolution. We present ultramicroscopic 

3D reconstructions of whole immunhistochemically 

labelled mouse embryos, giving detailed insight into their neuronal 

and vascular networks. We further obtained reconstructions 

of parts of the blood vessel network. For analysis images 

were vectorized parts. Generally, ultramicroscopy is especially 

suitable for investigations of biological networks, because mechanical 

slicing aretfacts are avoided. 


In the last decade a lot of innovative imaging techniques 

were developed, giving new impulses in biological sciences. 

One of these techniques is ultramicroscopy, which 

allows three-dimensional reconstructions of cm-sized 

objects with micrometer resolution [1, 2, 3]. Thus, ultramicroscopy 

bridges a gap between confocalmicroscopy 

and macroscopic imaging techniques, like computer tomography 

and optical resonance tomography [4]. 

II. ULTRAMICROSCOPY 

Ultramicroscopy is based on the principle of light sheet 

illumination, i.e. the specimen is illuminated perpendicular 

to the imaging pathway by a fine sheet of laserlight, 

formed by clinderical lenses (Fig. 1). Thus, out of focus 

parts of the specimen are not illuminated, so that they 

cannot contribute to image blurring or stray light generation. 

Therefore, many drawbacks of histology, like 

mechanical distortions and misalignments of slices are 

avoided. 

Since ultramicroscopy requires specimens to be transparent, 

most specimens have to be chemically cleared before. 

To render the specimens transparent, they are incubated 

in a medium, having approximatley the same 

refractive index as protein. Thus, light scattering is 

strongly reduced, and the specimens appear translucent. 

This clearing procedure was invented 1914 by the German 

anatomist W. Spalteholz [5]. 

215 

Figure 1: The sample is illuminated from side by a laser 

forming a thin sheet of light. A 488 nm diode laser with 

500 mW power (Coherent, Germany) was used for excitation. 

Fluorescent light is therefore only emitted from 

a thin plane. The light is then collected by an objective 

lens and projected onto a camera target. The excitation 

light was blocked by an optical filter (525/50nm). Fig. 

from [3]. 

We immunhistochemically labelled mouse embryos with 

a conjugated secondary fluorescent antibody before 

clearing. For imaging, an Olympus XL 4x objective with 

a N.A. of 0.28 was used. Images were recorded with 

CoolSnap K4 CCD-camera. 3D image reconstruction 

was done with 3D reconstruction software (Amira 4.1, 

Mercury Computer Systems, Germany). 


A. PROJECT: NERVE GROWTH 

In an ongoing study we applied ultramicroscopy to investgations 

of nerve growth in mouse embryos, labelled

with neurofilament-160 antibody, conjugated with the 

fluorescent dye Alexa488 (Fig. 2). By detecting the fluorescence 

signal, neuronal structures can be precisley localized 

in three dimensions. 

Figure 2: 3D-reconstruction of limb-innervating nerves 

of a mouse embryo E12.5 (PN:peroneal nerve, TN: tibial 

nerve). Size of scale bar 100 μm. 

B. PROJECT: VASCULAR NETWORKS 

Furthermore, we obtained reconstructions of blood vessel 

networks (Fig. 3). In this ongoing project, we plan to 

investigate the complexity of vascular networks in mouse 

embryos. Therefore the data are vectorized (Fig. 3). 

Figure 3: Blood vessel network in a mouse embyro 

E12.5. Parts of the network were vectorized for further 

analysis. Size of scale bar 100 μm. 


Ultramicroscopy has been validated as a valuable tool 

for the three-dimensional analysis of complex anatomical 

structures. As in ultramicroscopy mechanical artefacts 

are avoided, even large specimen can be threedimensonally 

reconstructed with outstanding resolution. 

216 


The study was supported by SFB 391 and the Hertie 

Foundation. 

REFERENCES 

[1] H.U. Dodt, U. Leischner, A.Schierloh, 

N. Jährling, C.P. Mauch, J.M. Deussing, M. Eder, 

W. Zieglgänsberger, and K. Becker. Ultramicroscopy: 

three-dimensional visualization of 

neuronal networks in the whole mouse brain. Nature 

Methods, 4(4):331–336, April 2007. 

[2] K. Becker, N. Jährling, E.R. Kramer, F. Schnorrer, 

J.M. Deussing, and H.U. Dodt. Ultramicroscopy: 

3D reconstruction of large microscopic specimens. 

Journal of Biophotonics, 1(1):36–42, January 2008. 

[3] N. Jährling, K. Becker, E.R. Kramer, and H.U. Dodt. 

3D-Visualization of nerve fiber bundles by ultramicroscopy. 

Medical Laser Application, 2008 in press. 

[4] J.R. Walls, L. Coultas, J. Rossant, and R.M. Henkelmann. 

Three-dimensional analysis of vascular development 

in the mouse embryo. PLoS one, 1(1):1, 

August 2008. 

[5] W. Spalteholz. Über das Durchsichtigmachen von 

menschlichen und tierischen Präparaten. S.Hierzel, 

Leipzig, Germany, 1914.

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Optimisation of the incoupling geometry of a pulsed 

solid-state laser 

E. Schwarz, J. Tauer, H. Kofler and E. Wintner 

Institut für Photonik 



Email: e9925266@student.tuwien.ac.at, 

ernst.wintner+e387@tuwien.ac.at 

Abstract — The topic of this work is the analysis of 

the incoupling geometry for an ignition laser 

concept. The ignition laser is a compact high peak 

power, passively Q-switched, longitudinally diodepumped 

solid-state laser. The incoupling optic 

consists of the pump fiber and an aspheric 

collimating lens. For optimal operation of a pulsed 

solid-state laser not only the usual parameters 

(pump power, OC mirror and absorber) should be 

taken into account, also the incoupling geometry 

has to be adapted to the structural conditions. 


A fully functional laser ignition concept for gas 

engines was developed in seven years by the “Laser 

Ignition Group” [1-4] at the “Institut für Photonik”. 

The outcome was a compact high peak power, 

passively Q-switched, longitudinally diode-pumped 

solid-state laser. One day this “laser spark plug” 

should replace conventional spark plugs because of 

the fact that conventional ignition has reached it limit 

in terms of efficiency and reduction of pollutant 

emissions 


The components of the laser system used in this work 

are the pump fiber, an aspheric incoupling lens, the 

active medium, a passive saturable absorber and the 

output mirror (see Figure 1). 

Figure 1: Experimental setup 

219 

The reflectivity of the output mirror should be about 

50% whereas the initial transmission of the absorber 

should approximately be 40%. As active medium a 

Nd:YAG crystal with a diameter of 4 mm and a 

length of 15 mm was used and Cr 4+ :YAG as 

saturable absorber medium. 

For pumping, a laser diode emitting at 808 nm with 

an output power of up to 400 W and a pulse duration 

of up to 300 μs was employed. The length of a laser 

pulse is about 1 ns. 

The incoupling geometry consists of the pump fiber 

and an aspheric collimating lens with a focal length 

of 8 mm. Furthermore, the distance between pump 

fiber and collimating lens was continuously variable. 

III. EXPERIMENTAL RESULTS 

By changing the distance between fiber and lens the 

dependency of the pulse energy and the temporal 

pulse position of the laser pulse on the configuration 

of the incoupling optic was analysed. The distance 

between fiber and lens primarily is related to the 

diameter of the pump beam. 

Figure 2: Pulse energy as a function of distance V.

That means, for increasing distance between fiber 

and lens the pump beam diameter is decreasing, 

consequently the pump volume becomes smaller and 

less energy is deposited in the crystal. 

In the case of decreasing distance between fiber and 

lens, the pump beam diameter becomes smaller. 

Hence the pump volume enlarges, more energy can 

be deposited in the crystal and consequently the pulse 

energy is higher (see Figure 2). 

For optimal operation of a pulsed solid-state laser not 

only the usual parameters (pump power, OC mirror 

and absorber) should be taken into account, also the 

incoupling geometry has to be adapted to the 

structural conditions. 

REFERENCES 

[1] H. Kofler, J. Tauer, G. Tartar, K. Iskra, J. 

Klausner, G. Herding and E. Wintner, An 

innovative solid-state laser for engine ignition. 

Laser Phys. Lett. 4, 2007. No. 4: p. 322-327. 

[2] Tauer, Johannes, Development of an Ignition 

Laser. 2006, TU-Wien. 

[3] Weinrotter, M., Laser Ignition of Internal 

Combustion Engines- Basic Laser and Ignition 

Optics Developments, Engine Application and 

Optical Diagnostics. 2006, TU Wien. 

[4] Kopecek, H., "Laser Ignition of Gas Engines". 

2004, Vienna University of Technology. 

220

Enhancement Mode HEMTs: Evaluation of Two Approaches by 

Numerical Simulation 

Stanislav Vitanov and Vassil Palankovski (Faculty Mentor) 

Advanced Material and Device Analysis Group 

Institute for Microelectronics, TU Wien 


Email: {vitanov,palankovski}@iue.tuwien.ac.at 

Abstract — Normally-off operation of high electron mobility 

transistors is desired for many reasons, however proved to 

be difficult to achieve, despite the rapid development of the depletion 

mode devices. Amongst the few approaches proposed so 

far, we focus on two, which promise high performance. The first 

device features an InGaN cap layer, while the later relies on 

gate recess technology. We perform DC and AC analyses, using 

our device simulator calibrated against experimental data, 

and compare the performance of the devices based on simulation 

results. 


The transport and material properties of GaN and AlN 

and their heterostructures have encouraged the research 

of AlGaN/GaN based transistors for various applications 

in the last decade. Consequently, outstanding results 

have been reported for the depletion mode (D-mode) 

high electron mobility transistors (HEMTs). However, 

for several applications enhancement mode (E-mode) devices 

are essential. In analog electronics they supersede 

the negative voltage supply and also assure a safe state 

in case of power loss. In digital electronics, they allow 

complementary logic. 

Despite the interest in E-mode operation, the excellent 

results as in D-mode devices remain to be seen. The first 

E-mode transistor was reported back in 1996 by Khan et 

al. [1], and several other refinements followed. In this 

paper we focus on two recently proposed approaches. 

The first relies on gate recess combined with fluorine 

based surface treatment, while the second incorporates 

a thin InGaN layer, which raises the conduction band. 

For the study of the devices we use our two-dimensional 

device simulator MINIMOS-NT. 

II. DEVICE STRUCTURE WITH INGAN-CAP 

The InGaN/AlGaN/GaN device structure was proposed 

by Mizutani et al. [2]. A 3 μm thick GaN layer is grown 

on sapphire substrate. A 20 nm thick Al0.25Ga0.75N supply 

layer follows (5 nm undoped, 10 nm highly-doped, 

and 5 nm undoped). A 5 nm non-intentionally doped 

In0.2Ga0.8N layer is deposited next. The gate length 

lg=1.9 μm, source-gate distance is 1.5 μm, and gatedrain 

distance is 2.4 μm. 

221 

III. DEVICE STRUCTURE WITH RECESSED 

GATE 

The gate recess structure and its fabrication is reported 

by Palacios et al. [3]. The 11 nm thick GaN channel is 

grown on-top of a 1 nm thick In0.1Ga0.9N back-barrier. 

A 1 nm thick AlN layer between the channel and the 

25 nm Al0.33Ga0.67N is grown in order to improve the 

electron mobility. After the AlGaN surface treatment a 

12 nm gate recess is performed, resulting in a gate-tochannel 

distance of 13 nm. The gate length lg is 160 nm, 

source-gate distance is 0.6 μm, and gate-drain distance is 

0.9 μm. 

IV. SIMULATION SETUP 

ThedevicesimulatorMINIMOS-NT has proven to be a 

suitable tool for the analysis of heterostructure devices 

[4]. Recently, it has been used for the study of a whole 

generation of AlGaN/GaN HEMTs [5]. Since the longitudinal 

electric field in the channel reaches peak values 

of above 500 kV/cm, the hydrodynamic transport model 

is used to properly model electron transport and energy 

relaxation. Self-heating effects are accounted for by using 

a global self-heating model, which calculates a spatially 

constant lattice temperature. The value of the sheet 

charge at the AlGaN/GaN interface induced by the polarization 

effects is derived from the DC characteristics. 

Additional charges at the InGaN and AlGaN interfaces 

are accounted for [6]. 

V. SIMULATION RESULTS 

Figure 1 shows the results for the transfer characteristics 

of both devices. After a calibration of the sheet charges 

a good agreement is achieved. The InGaN/GaN device 

exhibits lower current, however a higher threshold voltage 

is achievable, without recessing the InGaN cap layer 

[2]. The threshold voltage of the recess device can be 

increased too (Figure 2) by increasing the recess depth. 

Figure 3 compares the DC transconductance gm for 

both devices. The decrease in the measured gm of the 

InGaN/AlGaN/GaN transistor at higher gate bias, might 

be due to non-idealities in the source and drain ohmic 

contacts, which are not considered in the simulation.

I D [A/mm] 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

exp. data 

simulation 

0.0 

−1.0 −0.5 0.0 0.5 1.0 1.5 2.0 

V GS [V] 

gate recess 

InGaN cap 

Figure 1: Comparison of the measured (symbols) and 

simulated (lines) transfer characteristics at Vds=5 V. 

As expected, the recessed gate device exhibits a higher 

gm due to the much shorter gate length lg and the reduced 

gate-to-channel separation. 

We also perform an AC analysis of the transistors. 

The recessed gate structure (lg=0.16 μm) exhibits transit 

cut-off frequency fT=85 GHz, while our simulation 

gives fT=10 GHz for the InGaN/AlGaN/GaN device 

(lg=1.9 μm). Note, that the product fT×lg=19 GHz·μm 

is higher than 14.4 GHz·μm of the recessed-gate device. 

Our simulation of an InGaN cap structure with lg=0.8 μm 

shows that fT=30 GHz can be achieved. 


After a calibration against experimental data our device 

simulator provides reliable results for the DC and AC 

performance of the investigated novel HEMTs. This allows 

us to perform further device optimization, e.g. for 

higher current capability, higher threshold voltage, and 

better AC performance. 


The authors acknowledge support from the Austrian Science 

Fund (FWF), Project START Y247-N13. 

REFERENCES 

[1] M. Khan, Q. Chen, C. Sun, J. Yang, M. Blasingame, 

M. Shur, and H. Park. Enhancement and depletion 

mode GaN/AlGaN heterostructure field effect transistors. 

Appl.Phys.Lett. 68(4):514–516, Jan. 1996. 

[2] T. Mizutani, M. Ito, S. Kishimoto, and F. Nakamura. 

AlGaN/GaN HEMTs with thin InGaN cap layer for 

normally off operation. IEEE Electron Device Lett. 

28(7):549–551, July 2007. 

222 

I D [A/mm] 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

12 nm gate recess depth 



0.0 

−0.5 0.0 0.5 

V [V] GS 

1.0 1.5 2.0 

Figure 2: Simulated transfer characteristics at Vds=5 V 

for HEMTs with different gate recess depths. 

DC g m [S/mm] 

0.5 

0.4 

0.3 

0.2 

0.1 

exp. data 

simulation 

gate recess 

InGaN cap 

0.0 

−1.0 −0.5 0.0 0.5 

V [V] GS 

1.0 1.5 2.0 

Figure 3: Comparison of the measured (symbols) and 

simulated (lines) DC transconductance gm at Vds=5 V. 

[3] T. Palacios, C. Suh, A. Chakraborty, S. Keller, 

S. DenBaars, and U. Mishra. High-performance Emode 

AlGaN/GaN HEMTs. IEEE Electron Device 

Lett. 27(6):428–430, June 2006. 

[4] V. Palankovski and R. Quay. Analysis and Simulation 

of Heterostructure Devices. Wien – New York, 

Springer, 2004. 

[5] S. Vitanov, V. Palankovski, S. Murad, T. Rödle, 

R. Quay, and S. Selberherr. Predictive Simulation 

of AlGaN/GaN HEMTs. Tech.Dig. IEEE Compound 

Semiconductor IC Symp. pp. 131–134, Nov. 2007. 

[6] S. Vitanov and V. Palankovski. Normally-off Al- 

GaN/GaN HEMTs with InGaN cap layer: A simulation 

study. Solid-State Electron. 2008, (in press).

Simulation of Q-switched solid-state laser ignition 

F. Trawniczek, J. Tauer, H. Kofler, M. Deneva and E. Wintner 

Institut für Photonik 



Email: franz.trawniczek@gmx.at 

ernst.wintner+e387@tuwien.ac.at 

Abstract — The main topic of this work covers the 

analysis and the simulation of a Q-switched laser 

system. The calculations including all relevant 

parameters are based on the rate equations for a 

4-level laser system. 

The approximation of the pump function, the 

analysis of the Q-modulator and the detailed 

overview of one single roundtrip in the laser system 

are indispensable to obtain all important values of 

the laser system. 

Using an established code, the optimal performance 

of the high peak power Q-switched ignition laser is 

obtained by the application of numerical 

procedures (Runge-Kutta) and the adaption of 

several important parameters (reflectivities of the 

two used mirrors, best time for opening of the Qmodulator, 

...). 


The exact analysis of the system of rate equations 

and the four level laser system in combination with 

the attributes of the used active medium Nd:YAG 

(neodymium-doped yttrium aluminium garnet) are 

the background for understanding the laser system. 

The approximation of the actual pump function as a 

trapezoid function is essential for obtaining significant 

results. It is important to analyze all the parameters 

of a Q-switched laser system for the simulation. 

II. CALCULATION 

In this diploma thesis a certain system of rate equations 

is used to describe to processes in the ignition 

laser system is: 

dN 

dt 

2 � Rp( 

t) 

� BqN 

2 

N2 

� 

� 

(1) 

223 

dq 

dt 

q 

BqN Va � 

� 

� 2 

c 

(2) 

Equations (1) and (2) describe the effects in the laser 

system due to stimulated and spontaneous emission, 

the influence of the pump function and the active 

volume. By the help of these equations it is possible 

to calculate one single roundtrip in the laser system 

to obtain values for the gain and the losses in the 

therein. 

Furthermore, they are necessary to define the threshold 

conditions. There are some more calculations 

needed like the function that describes the opening of 

the Q-modulator being responsible for the differences 

between active and passive Q-switched systems. 

The additional losses in the system are considered by 

the introduction of logarithmic losses in the calculation 

of one single roundtrip. 

III. SIMULATION 

Applying a code, written in Borland PASCAL, the 

main behavior of the laser ignition system is simulated 

to find the conditions for optimal performance of 

the high peak power laser. 

Numerical procedures (Runge- Kutta) are needed to 

solve the coupled nonlinear differential equations. It 

is necessary to diversify several important parameters 

in the program (reflectivities of the two mirrors, best 

time for opening of the Q-modulator, pumping energy, 

opening time of the Q-modulator, ...) to obtain 

only one single pulse with high peak power (MW) 

and a very short duration (~ 1ns). 

A Q-modulator is introduced to meet demands of the 

ignition laser. It is an active Q-switched system, 

where it is possible to choose the time for opening of 

the Q-modulator to obtain only one single high peak 

pulse.

starting time of pulses, 

�s 

90 

80 

70 

60 

50 

40 

30 

20 

10 

0 

60% 

70 

80% 

90% 

0 10 20 30 40 50 60 70 

60% 

70% 

80% 

90% 

E pump, mJ 

Figure 1: Starting times of pulses without Q-switch 

as a function of pump energy 

Figure 1 shows the starting times of the pulses in a 

system without Q-modulator (free lasing) as a function 

of the pump energy that is applied. In this 

graphic the dependence is shown for four different 

reflectivities of the outcoupling mirror. 

In the case of active Q-switching, one important 

question is to find the optimal time for switching to 

obtain maximum output power. 

P out, W 

800000 

600000 

400000 

200000 

P out, W 

0 

289 291 293 295 297 299 301 303 

t_Q, �s 

Figure 2: Peak power as a function of time for 

switching the Q-Modulator 

Figure 2 shows the best time for switching the Q-modulator 

to obtain maximum power. It is necessary to 

lock one parameter in position and slightly change 

some others to reach finally the best conditions of the 

whole system. 

REFERENCES 

[1] Orazio Svelto. Principles of Lasers. Plenum 

Press New York, USA, Fourth Edition, 1998 

[2] Wulfhard Lange. Einführung in die Laserphysik. 

Wissenschaftliche Buchgesellschaft, 

Deutschland, zweite Auflage, April 2002 

224

Priorities in Improving of Railway Infrastructure 

Jiří Pospíšil(Karel Baudyš) 

Faculty of Transportation Sciences 


Prague, Czech Republic 

Email: {xjpospisil,baudys}@fd.cvut.cz 

Abstract — Article brings new point of view on 

problems of public transport systems improving. 

New solution is based on some ideal supply in ideal 

infrastructure net. Introduced method assesses 

priorities to arcs, junctions or rolling stock to 

enabled efficient improving of whole system of 

public transport stepwise. One time made 

improvements are useful later, they are according 

to final ideal system. It enables efficient investment, 

fastest supply improvements on beginning of 

process and goal-directed approach to ideal system. 


Railway has potential to support a device to main 

traffic flows. But can be ecological and efficient only 

if will be competitive. Public transport must offer 

frequent, fast connection between all spots in 

network. Such supply can be created thanks to 

periodic timetables. Temporal availability is 

guaranteed by appropriate period between trains. 

Spatial availability is guaranteed by suitable 

coordination of train time positions (time slots) on 

tracks and in junctions. Based on Integrated Periodic 

Timetable (IPT), lines in particular area are 

interconnected so that there are realised optimal 

changing connections, i.e. without waiting times. 

II. INTEGRATED PERIODIC TIMETABLE 

IPT is based on principle „in each hour – the same 

minute – in each junction – in each direction“. 

Figure 1 – Principle of Integrated Periodic Timetable 

Optimal connections between particular lines in IPT 

junctions need system travelling times between 

225 

junctions. System travelling time includes regular 

travelling time + stop-times in stations between 

junctions + proportionate part of changing times in 

junctions + time allowance. To build a net-supply 

with synergic effect basic condition must be fulfilled: 

- System travelling time = half of multiple period 

- In addition, IPT edge condition must be fulfilled: 

Arc equation tH = n . ½ tT forn=1,2,3,…(1) 

Circle equation ∑ tH = n .tT forn=1,2,3,…(2) 

tH = Arc length (system travelling time) and 

tT =Period 

To enable equal connection in both directions all 

lines must have unified symmetry axis, i.e. time, in 

which trains of one line are crossing each other. In 

long-distance transport in Europe this axis is usually 

set to minute 00, eventually according to period 30. 

For suburban trains is used symmetry axis 00 and 30 

eventually also 15 and 45. 

Concept of periodic transport consists in relevant 

location of IPT-junctions in net, in achieving system 

travelling times on arcs and unified symmetry axis on 

all lines. Transport chains are attractive supply in net. 

Supply of long-distance trains in Czech Republic 

bases on IPT-principle, passenger count increases. In 

infrastructure area we first build and than we make 

some proposal for transport conceptions. It’s not 

optimal. Due to life-cycle of infrastructure and its 

high costs could be better first plan “ideal” supply of 

public transport system (problem of transport 

planning) and than determine requirements for 

infrastructure and rolling stock. 

In praxis (with actual infrastructure and rolling 

stock) is not easy to realise ideal supply, very often is 

it impossible. High investment is necessary. But 

often is invested uncoordinatedly without net synergy 

effects. There are some political wishes witch evoke 

direct technical requirement for process of improving 

of public transport system: 

- Minimize total passenger time in system 

- Have a circles corresponding to circle equation as 

soon as possible and ideal arcs IPT (net bindings) 

- During improving maximize relationship between 

contributions and cost (first contributions for lower 

costs, high costs and their contributions later) 

- High stability of timetable (supply) during process 

– It’s impossible to change timetable all the time

III. ASSESSMENT OF PRIORITIES IN RAILWAY 

INFRASTRUCTURE IMPROVING 

Method assesses priorities in railway infrastructure 

improving has two inputs: contemporary and ideal 

net. By simple table adjustment with all circles and 

arcs of net(s) is possible to go from contemporary 

(actual) to ideal net. Each step represents next 

priority. It’s necessary to choose right arc from right 

circle and this one improve – shorten for needed 

length to make possible to travel in circles without 

waiting times. It’s not necessary to shorten arc to 

ideal (shortest) length. So is possible leave the most 

expensive parts of arcs (e.g. new tunnels) and make 

them later. 

Method takes into account system travelling times 

(arc length), investment needs (infrastructure, rolling 

stock) and a passenger flows. Most important value 

is time. Passengers and costs are only significant. 

Method give priority to low-cost improvements, 

witch enable faster transition to ideal net with ideal 

change possibilities in railway junction, but not with 

ideal length of arcs. It isn’t problem. Improvements 

shorten arc length anyway and also passengers 

travelling on arcs go shorter time. Final lifetime and 

costs of improvements are by any priorities the same. 

IV. FIRST RESULTS 

I have tested simplified method (unitary valuation of 

costs and traffic flows) on chosen net of longdistance 

railway lines in west Bohemia and in 

Moravia. In both cases give method successful 

outputs how show tables. For confrontation I used 

chooses with biggest timesavings on arcs, 

lowest/highest investment and randomised chooses. 

“K1-K6” represents all available circles in net. “x” 

indicates circle with null waiting times in all junction 

on this circle. 

Steps Travel. time Waiting t. Timesavings Price k1 k2 k3 k4 k5 k6 

1 2680 80 120 20 x x x x 

2 2640 120 120 30 x x 

3 2610 30 240 40 x x x 

4 2520 30 330 70 x x x 

5 2460 0 420 90 x x x x x x 

6 2370 0 510 120 x x x x x x 

7 2280 30 570 150 x x x x x 

8 2190 0 690 180 x x x x x x 

Table 1: Method for priorities assessment 

Steps Travel. time Waiting t. Timesavings Price k1 k2 k3 k4 k5 k6 

1 2680 80 120 20 x x x x 

2 2650 110 120 30 x x 

3 2530 50 300 70 x x 

4 2440 50 390 100 x x 

5 2380 80 420 120 x x x 

6 2320 110 450 140 x 

7 2280 30 570 150 x x x x x 

8 2190 0 690 180 x x x x x x 

Table 2: Political priority for TEN-corridors 

226 

In table 1 have good connections on circles longest 

continuity. After 5th step we have net with system 

travelling times, without waiting times in junctions. 

Some arcs are still longer then ideal length. These 

arcs need higher investment and bigger infrastructure 

adjustments. There can’t be compared appropriate 

steps, but timesaving for accordant costs. Travelling 

time + waiting time correspond to total time of 

passengers in public transport system. 

There are some opened questions in method still: 

- Efficient choose of junctions and arcs IPT 

- Determination of all circles in net 

- Traffic flows (net lay-out) 

- Efficient valuation of improvements 

- Problem of arc elongation, withdrawal or insertion 

Introduced method enables manual intervention 

(political choose) providing misalignment from ideal 

path of improvements. But there is enabled also 

limitation on total investment level or investment 

level for saved time value. 

V. CONCLUSION 

In method are included not only infrastructure but 

rolling stock improvements too. It’s about 

improvement of whole public transport system. 

Regional transport systems (including Buses) could 

be included or solved separately. 

Impartial assessment of priorities (in the sense first 

contributions for lower costs, high costs and their 

contributions later) could bring more efficiency to 

whole public transport system, better competitive 

advantage of service (net connections) and enable its 

sustainable development. Supply of service will be 

better thanks investment to infrastructure and 

according to this to rolling stock too. Method 

assesses time horizons of realization respective of 

introduction of new supply according to investment 

budget. Introduced method could be suitable for 

employers of public transport service or for managers 

of transport infrastructure. 

REFERENCES 

[1] M. Bär. Merkblatt zum integralen Taktfahrplan. 

TU Dresden, 2001. 

[2] K. Baudyš, V. Janoš. Optimalizační metody 

používané při sestavě integrálního taktového 

grafikonu. Konference “Věda o dopravě”, FD 

ČVUT Praha, 2001. 

[3] O. Pastor, A. Tuzar. Teorie dopravních 

systémů. Praha ASPI, 2007. 

[4] Z. Michl, J. Pospíšil. Is railway ecological? 

Summer school „Transportation and Climate 

Change“, Ostritz, Germany, 2007.

Raman and Surface Enhanced Raman Spectra of Apigenin and Luteolin 

Charlie Corredor and John R. Lombardi (Faculty Mentor) 

Department of Chemistry and Center for Study of Structures and Interfaces (CASI), 


New York, N.Y. 10031 

Email: Ccorred00@ccny.cuny.edu 

Abstract — The FT-Raman and surfaceenhanced 

Raman (SER) spectra of three flavonoids, 

namely chrysin, apigenin and luteolin, have been 

obtained. The SERS spectra were obtained on citrate 

reduced Ag colloids. Assignments of the experimentally 

obtained normal vibrational modes were aided 

by density fuctional theory (DFT) calculations using 

the B3LYP functional and the 6-31+G* basis set. 

Excellent fits were obtained for the observed spectra 

with little or no scaling. The most intense lines in 

the three flavonoids are those in the C=O stretching 

region and around 1250cm -1 . The first ones are often 

weakened by proximity of the metal surface, while 

the latter are not affected by the Ag. On the other 

hand, the lines at lower wavenumbers, assigned to inplane 

ring deformation, are strongly enhanced by the 

surface, indicating a perpendicular orientation of the 

flavonoids on the Ag surface. The spectra of the 

flavonoids are compared, and a case study of application 

to detect weld, a mixture of apigenin and luteolin, 

in a textile is presented. 


Phenolic derivatives of flavone are responsible 

for the brightly colored pigments of many fruits 

and vegetables. Polyphenols are found in high concentrations 

in wine, tea, grapes and in a wide variety 

of other plants and have been associated with prevention 

of heart disease and cancer i . Due to their polyphenolic 

nature, flavonoids exhibit strong antioxidant 

properties and have been widely used as ingredients 

in pharmaceutical products. They can be subdivided 

into: flavonols (e.g. quercetin), flavones (e.g. 

apigenin, luteotin), flavanols (e.g. catechin) and 

isoflavones (e.g. genistein). Flavones are also the 

main components of various natural dyes (e.g. weld, 

fustic, quercitron), mainly yellow but ranging from 

brown to green and olive-green, used in textile industries 

since ancient times ii,iii . Present in plants as 

glycosides, 

they can be used as mordant dyes by hydrolysis of 

glycoside bonds and chelating with metals such as 

aluminum or copper iv . 

227 

Figure 1 shows the structure of chrysin (5, 

7-dihydroxyflavone), apigenin (5, 7, 4’trihydroxyflavone) 

and luteolin (5, 7, 3’, 4’tetrahydroxyflavone). 

They differ only in that apegenin 

and luteolin have a 4’ or 3’ and 4’ OH group on 

the bezene ring. Among those, chrysin has been 

studied least by spectroscopic techniques. Even 

though it contains two hydroxyl groups, this molecule 

is relatively insoluble in water, making the preparation 

of the samples difficult. Chrysin and its complexes 

with Al 3+ , Ga 3+ and In 3+ have been studied by 

IR, UV-vis and NMR v . The IR spectra shows (OH) 

bands at 3600-2400 cm -1 , (C=O) at 1655 cm -1 , aromatic 

(C=C) at 1505 cm -1 , other bands at 1460 cm -1 , 

1168 cm -1 , (CH) at 850 cm -1 and 815 cm -1 . Only the 

UV resonance Raman (UVRR) spectrum of chrysin 

has been reported in the study on extractable compounds 

in Scots pine wood, where the flavonoid was 

used as a reference vi . The reported Raman bands are 

the symmetric aromatic ring stretching at 1605 cm -1 , 

the C=C ring stretching at 1649 cm -1 , and the asymmetric 

ring vibration at ~1500 cm -1 . 

On the other hand, apigenin and luteolin are 

the main coloring matters of the natural dyestuff 

weld. It originates from the leaves and stem of Reseda 

luteola L. found in Central Europe, India and 

China. Before the discovery of America, weld was 

the dyestuff most used in Western Europe. In 1775, 

quercitron became available in large quantities and 

superseded weld and fustic as the principal yellow 

dye vii . Apigenin and luteolin are very abundant in 

textile dyes from various samples and HPLC, GCMS, 

IR, Raman and SERS on silver colloid data have 

been reported viii,ix,x,xi . Their structure differs by only 

one hydroxyl group, so they exhibit similar structural 

properties. Luteolin shows (O-H) vibrations around 

3220 cm -1 and (C=O) at 1655 cm -1 in IR. FT-Raman 

spectra of luteolin and apigenin in solid state show 

similar trend of the region corresponding to (C=O) 

and (C=C) vibrations at 1660-1550 cm -1 , but differences 

in the 1400-1000 cm -1 region. This is explained 

by appearance of different (O-H) and (C-O) 

motions due to the different number of hydroxyl 

groups. SERS of luteolin on silver colloid showed a 

strong downward shift of the aromatic (C=C) vibra-

tion at 1608 cm -1 in solid to 1577 cm -1 in colloid. 

This was explained by the effect of polymerization of 

the catechol-like moiety on the Ag nanoparticles. 

Apigenin was reported to have fewer differences 

between the Raman spectrum of the solid and the 

SERS on the colloid 11 . 

The limited number of studies on chrysin by 

Raman and SERS spectroscopy may be due to its 

poor solubility in water as well as the strong fluorescence 

upon excitation, which obscure regularly weak 

Raman spectra. Our recent study on other flavonoid 

molecules including pentahydroxyflavone quercitin 

has shown effectiveness of SERS in quenching the 

fluorescence and inducing spectra intensity by the 

few orders of magnitude xii,xiii . This method also allows 

using very little sampling which is crucially 

important in art painting and textile conservation xiv as 

well as in bioresearch and forensic science xv . 

In this article we report FTR and SERS on Ag 

colloid of all three molecules as well as Ag electrode 

SERS spectra of luteolin. These studies are aided in 

their interpretation by DFT calculations. We provide 

comparative analysis of the spectra of molecules with 

relation to each other. Our objective is to apply techniques 

similar to our past studies to obtain spectra of 

flavonoids and to further study their structures and 

possibly seek better methods of analysis suitable for art 

preservation and other fields. In order the better 

interpret the results, we have also conducted studies of 

the related compounds 7-hydroxyflavone, and 3’,4’- 

Dihydroxyflavone. These are presented in the supplementary 

materials, and referred to when needed. 

II. FIGURES 

Figure 1. 

(a) Chrysin 

(b) Apigenin 

(c) Luteotin 

REFERENCES 

i 

Oliveira Brett, A.M., Ghica, M-E., Electroanalysis 15, 

22 (2003). 

228 

ii Joosten, I., Boomel, M., R., Keijzer, R., H., Reschreiter, 

H.; Micro Analysis on Hallstatt Textules: Colour and 

Condition; J. Microchim. Acta. 155, 169-174 (2006) 

iii Zhang, X., Boytner, R., Cabrera, J., L., Laurson, R.; 

Identification of Yellow Dye Types in Pre-Columbian 

Andean Textiles; J. Anal. Chem. 2007, 79, 1575-1582 

iv Ferreira ESB, Hulme AN, McNab H, Quye A; The 

Natural Constituents of Historical Textile Dyes; Advance 

Article, www.rsc.org, 2004 

v Pusz, J., Nitka, B., Zielinska, A., Wawer, I.; Synthesis 

and physicochemical properties of the Al(III), Ga(III) and 

In(III) complexes with chrysin; Microchem. J. 65 (2000) 

245-253 

vi Nuopponen, M., Willfor, S., Jaaskelainen, A. S., 

Vuorinen, T.; A UV resonance Raman (UVRR) spectroscopic 

study on the extractable compounds in Scots pine 

(Pinus sylvestris) wood Part II. Hydrophilic compounds; 

Spectrochimica Acta Part A 60 (2004) 2963-2968 

vii Judith H. Hofenk de Graaff , The Colorful Past, 165- 

231, Abegg-Stiftung and Archetype Publications, Riggisberg 

and London, 2004. 

viii Chen K, Leona M, Vo-Dinh KC, Yan F, Wabuyele 

MB, Vo-Dinh T. Application of surface-enhanced Raman 

scattering (SERS) for the identification of athranquinone 

dyes used in works of art. Journal of Raman Spectroscopy, 

2006; 37: 520-527 

ix Colombini, M. P., Andreotti, A., Baraldi, C., Degano, 

I., Lucejko, J. J; Colour fading in textiles: A model study 

on the decomposition of natural dyes; Microchem. J. 85 

(2007) 174-182 

x Inglett, G. E.; Infrared spectra of naturally occurring 

flavonoids; J. Org. Chem (1958), 23, 93-94 

xi Jurasekova, Z., Garcia-Ramos, J. V., Dominigo, C., 

Sanchez-Cortes, S.; Surface-Enhanced Raman scattering 

of flavonoids; J. Raman. Spectrosc. 2006; 37: 1239-1241 

xii Wang, M., Teslova, T., Xu, F., Spataru, T., Lombardi, 

J. R., Birke, R. L; Raman and Surface Enhanced Raman 

Scattering of 3-Hydroxyflavone; . Phys. Chem. C, 111 

(7), 3038 -3043, 2007 

xiii Teslova , T.; Corredor , C.; Livingstone , R.; Spataru 

T.; Birke R.L.; Lombardi ,J.R.; M. V. Cañamares, 

M.V.; Leona, M.; Raman and surface-enhanced Raman 

spectra of flavone and several hydroxy derivatives; J. 

Ram. Spectrosc. 38, 802 (2007). 

xiv Z, Wiggins K, Russell C, Chabli S, Rosengarten A. 

Evaluation of Raman Spectroscopy for the analysis of 

colored fibers: a collaborative study. J. Forensic Sci. 

2005, 50(5) 1028-1038 

xv Review Papers, 14 th International Forensic Science 

Symposium, Interpol- Lyon, 19-22 October 2004, (N. N. 

Daeid Editor)

A Sustainable Approach in Hybrid Materials Development: 

Metal Nanoparticles Synthesis in Biobased Polymeric Systems 

Colleen Achong, Praveen Kumar Vemula, Kareem Douglas, and George John * 

Department of Chemistry, City College of the City University of New York, 160 Convent Avenue, 

New York, NY 10031 USA. Fax: +1-212-650-6107; Tel:+1-212-650-8353 

* Corresponding author Email: john@sci.ccny.cuny.edu 

Abstract —In situ synthesis of metal nanoparticles 

using various forms of self-assembled organic soft 

materials such as molecular gels and liquid crystals 

proved to be an efficient approach in preparing 

hybrid materials. The present study shows the successful 

extension of our previous strategies to generate 

metal nanoparticles (MNPs) in polymeric 

systems, another form of soft matter. We have synthesized 

a biobased polymer, poly(cardanyl acrylate) 

(PCA) from cardanol (byproduct of cashew 

industry) equipped with usaturated side chains 

suitable for oxidative drying. Autoxidation (crosslinking) 

of PCA produced various free-radicals 

which were used as a tool to reduce metal salts for 

preparing and stabilizing the gold and silver 

nanoparticles in situ. This sustainable approach 

enabled us to avoid external hazardous reducing 

and stabilizing agents. 


Design and synthesis of organic-inorganic hybrid 

materials from biobased monomers/polymers have a 

tremendous impact on industry and the environment. 

Strategic utilization of renewable resources as starting 

material for generating value-added products and 

building blocks in chemistry will have broad impact 

in industrial economy as well as in sustainable development. 

We 1-4 and others 5-6 have shown the efficient 

use of renewable resources for developing novel 

monomers, polymers and hierarchically assembled 

soft nanomaterials. Polymers are one among the most 

important products of the chemical industry used for 

versatile applications in everyday life. Herein we 

report the synthesis and stabilization of AuNPs and 

AgNPs in biobased poly(cardanyl acrylate), PCA. 

Focal point of present study is, naturally occurring 

cross-linking of unsaturated alkyl chains which is 

known as autoxidation or drying process produces 

free-radicals in situ; such free-radicals were used as a 

tool to reduce metal salts to generate MNPs in situ, 

which allowed us to avoid using external hazardous 

reducing and stabilizing agents. 

229 


Cardanol [obtained from thermal treatment of 

cashew nut shell liquid] is well known to exist as a 

mixture of four components differing in the degree of 

unsaturation in the side chain: 5% of 3-(pentadecyl)phenol, 

49% of 3-(8Z-pentadecenyl)-phenol, 17% of 

3-(8Z,11Z-pentadecadienyl)-phenol, and 29% of 3- 

(8Z,11Z,14-pentadecatrienyl)-phenol (Figure 1). 

Figure 1. Chemical structures and synthetic 

scheme of a) PCA and b) PPDA. i) acryloyl chloride, 

NaOH, toluene, 8 hr; ii) azobisisobutyronitrile, 

toluene, 60ºC. c) General mechanism for 

free-radical mediated cross-linking of cardanyl 

polymer side chains. 

Cardanyl acrylate (CA) was synthesized using a 

reported procedure. Subsequently, solution polymerization 

was achieved using azobisisobutyronitrile 

(AIBN) in toluene to obtain PCA (Figure 1a). The 

PCA was dissolved in chloroform and could easily 

be cast into a thin transparent and sticky film by the 

solution-casting technique. On heating to 65ºC for 30 

min or upon exposure to the air (ambient conditions) 

for 10 hours the sticky film converted into non-sticky 

(scratch-free) transparent insoluble film. The crosslinking 

of PCA unsaturated hydrocarbon chains 

possibly occurred through the hydrogen abstraction 

(at allylic carbon center) proceeded by a cascade of

eactions with bond breaking and forming to generate 

an insoluble polymer network (Figure 1c). This was 

thoroughly characterized using various techniques 

such as infra-red spectroscopy, 1 H-NMR and differential 

scanning calorimeter as reported earlier. It is 

proposed that cross-linking was occurred through 

hydroperoxidation of allylic radical centers of cardanol 

alkyl chain, during this process various freeradicals 

were generated in situ (Figure 1c). In case of 

PCA, the side chains are brought close to each other 

by the acrylate polymer backbone and precisely align 

the allylic side chains for further cross-linking process 

as shown schematically in Figure 1a. 

Figure 2. a) Images of glass slides coated with 

PCA containing AuNPs (left), AgNPs (middle) 

and un-reduced metal salts (right). b) Absorption 

spectra of PCA (i) after addition of chloroauric 

acid, (ii) after AuNPs formed. Similarly, (iii) after 

addition of silver benzoate and (iv) after AgNPs 

formed. 

Polymer films which contained in situ prepared 

MNPs were characterized using different techniques 

such as ultraviolet-visible (UV-vis) spectrophotometer, 

transmission (TEM) and scanning electron microscopy 

(SEM). The absorption spectra were recorded 

for metal salts contained polymer films before 

and after drying process (Figure 2b). Absorption 

spectrum of AuNPs contained polymer was showed 

characteristic surface plasmon resonance band at 555 

nm, whereas such peak was absent when we immediately 

measured after the addition of metal salts 

(before drying process occurs, Fig. 2b: i & ii). This is 

clearly suggesting the formation of AuNPs during the 

cross-linking process. Similarly, absorption spectra 

of in situ synthesized AgNPs in polymer have shown 

peak at 460 nm, and this peak is noticed for the 

AgNPs due to the characteristic surface plasmon 

230 

resonance effect originating from the quantum size 

effect of AgNPs. In this instance also prior to autoxidation 

(cross-linking) process such absorption band 

in UV was absent (Figure 2b: iii &iv) which is 

clearly suggesting that indeed MNPs are generated 

during the oxidative drying of the polymer film. The 

absorbance maximum does not change over a long 

period which indicates that MNPs are prevented from 

coagulation due to the stabilization of NPs in the 

polymer matrix. The SEM and TEM analysis of the 

in situ synthesized AuNPs and AgNPs in PCA indicated 

that the synthesized MNPs were nearly monodispersed 

with the average size of 18 nm for AuNPs, 

and 13 nm for AgNPs. Polydispersity of the particles 

were calculated from TEM data. 

III. CONCLUSIONS 

In conclusion, renewable resources based monomer 

(cardanol from cashew nut shell liquid) was used 

to prepare a biobased polymer. In situ synthesis of 

MNPs has been achieved with this polymer without 

using any external reducing and stabilizing agents. 

Free-radicals which were generated during oxidative 

drying of cardanol unsaturated chains have been used 

as a tool for MNPs synthesis, such hypothesis was 

confirmed by synthesizing saturated analogue polymer 

which failed to generate MNPs. MNPs embedded 

polymers films were stable at ambient conditions 

for a longer period. The preparation of organicinorganic 

hybrid materials would have applications 

in developing materials with tunable optical, electrical, 

and catalytic properties. Potential antibacterial 

activity of AgNPs embedded biobased polymers are 

currently under investigation in our laboratory. 


We thank Science Interdepartmental Electron Microscope 

and Imaging Center at CCNY. 

REFERENCES 

[1] P. K. Vemula, and G. John, Chem. Commun. 

2218 (2006). 

[2] P. K. Vemula, U. Aslam, V. A. Mallia, and G. 

John, Chem. Mater. 19, 138 (2007). 

[3] V. A. Mallia, P. K. Vemula, G. John, A. Kumar, 

and P. M. Ajayan, Angew. Chem. Int. Ed. 46, 

3269 (2007). 

[4] P. K. Vemula, V. A. Mallia, K. Bizati, and G. 

John, Chem. Mater. 19, 5203 (2007). 

[5] F. W. Lichtenthaler, Acc. Chem. Res. 35, 728 

(2002). 

[6] A. Corma, S. Iborra, and A. Velty, Chem. Rev. 

107, 2411 (2007).

Micro-lenses Fabrication by Solvent-Casting of Chalcogenide 

Glass 

Eric Sanchez 1 and Craig Arnold 2 

1 The City College of New York, New York, NY 10031, USA 

2 Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 

08540, USA 

Email: esanche05@ccny.cuny.edu 

Abstract — A solution-based method for the fabrication 

of chalcogenide glass optical elements is 

described. A micro-syringe system using manual 

disposition has been applied to the fabrication of 

micro-lenses that range from 7μm to 350 μm. The 

micro-lenses are made As2S3 which has demonstrated 

important optical properties for mid infrared 

wavelengths of light. The method itself can be 

divided in two steps: disposition of chalcogenide 

solution, and heat treatment. The produced microlenses 

are measured by profilometry and photographed 

using a light microscope. 


Quantum Cascade Lasers (QCLs) have emerged as a 

leading method to produce mid-infrared (Mid-IR) 

laser light for sensing applications for health and the 

environment [1]. Due to the small size of QCLs, they 

have the potential to significantly reduce overall 

device size and even to be directly integrated for onchip 

sensing. However, in order to successfully implement 

this technology, corresponding optics must 

be scaled down creating a need for micro-lenses and 

waveguides at these frequencies. Chalcogenide 

glasses have become an important material for Mid- 

IR technology due to their favorable physical and 

optical properties [2]. Through novel processing 

approaches, these materials promise a path for developing 

micro-lenses for Mid-IR technology. 

In developing optical elements, the method used 

plays a critical role in reaching the small feature 

sizes. In this presentation, we describe a solutionbased 

method for the fabrication of chalcogenide 

glass micro-lenses. This particular method consists of 

two components: micro-syringe dispensing and heat 

treatment. The micro-syringe is an attractive technique 

due to its low cost and relative ease of implementation. 

II. METHOD 

Chalcogenide glasses are amorphous compounds 

containing sulfur, selenium, or tellurium, and are 

231 

known to be low-loss mid-infrared materials [3]. 

Chalcogenide glasses micro-lenses are fabricated by 

disposing As2S3 on a hydrophobic surface in controlled 

conditions. In this case, we use InP, which is 

one of the mid-IR technology semi-conductor materials 

used as substrate for QCL’s and other devices. 

This solution-based method for fabrication of 

chalcogenide glass micro-lenses is divided into four 

parts: 

- Solution preparation 

- Surface conditioning 

- Dispensing 

- Heat treatment 

The chalcogenide solution is produced by grinding 

bulk As2S3 (typically 99.9% pure) into a fine powder 

using a ceramic mortar and pestle; 2.50±0.03 g of the 

powder is combined with 10±0.1 ml of butylamine 

and allowed to dissolve for four days. An ultrasonic 

homogenizer is used to expedite this dissolving 

process. The solution is then centrifuged at 3000 rpm 

for 3 minute to remove any suspended particulates or 

impurities. Exposure of solution or samples to ambient 

light and atmospheric moisture is kept to a 

minimum throughout the preparation procedure [3]. 

After this, the As2S3 solution is ready for use in the 

micro-lenses fabrication. 

The method described is only effective in a hydrophobic 

surface. Because of the InP hydrophilic nature, 

this must be treated first with 10% hydrofluoric 

acid (HF) for 10 seconds to remove surface native 

oxide thus becoming hydrophobic [4]. 

In the dispensation process, 30μl of As2S3 solution 

are placed in a pneumatic micro-syringe dispensator 

(EFD 1500XL) with a tip of aperture of 25.4μm. The 

tip is placed at 0.25mm above the InP surface in a 

semi dust-free atmosphere. Next, As2S3 solution is 

dispensed on the InP surface with a positive pressure 

of 0.5 psi for 1μs. this is continually performed manually 

displacing the InP surface about a 1mm in the 

x-axis and recording the micro-drops’ position. 

In the heat treatment phase, the micro-droplets are 

introduced in a vacuum oven and baked under vacuum 

at 50°C for 45 minutes in dark due to the pho-

tosensitivity of chalcogenide glasses. After this, the 

micro-droplets become plano-convex micro-lenses. 

Following deposition and treatment, the micro-lenses 

are analyzed with a light microscope to estimate size, 

shape and quality of the droplets. After this is complete, 

the best samples undergo profilometry to determine 

their specific dimensions and focal length. 

III. RESULTS 

The micro-lenses fabricated can be divided in two 

categories. The first one range in from 120μm to 

350μm in diameter. The yield of successful lenses 

from this group is approximately 85%. The second 

category is micro-lenses that range from 7μm to 

30μm in diameter. However, the yield of successful 

lenses from this latter group is only about 10% due to 

the presence of dust and other contamination. Thus 

further study must be performed to increase the yield 

and improve the technique. 

Table 1 shows measurements obtained through 

profilometry of four lenses in two different InP substrates. 

Figure 1 shows plot of data obtained through 

superficial profiling of the C2 micro-lens. 

Figure 2 shows a microscopic picture at 100x 

magnification of a lens in this range. Although profilometry 

on this have not been done yet, though calibrated 

images, we estimate its diameter is about 8 

μm, with a height of about 0.6 μm corresponding to a 

focal length of about 20μm. As it mentioned before, 

further improvement on the technique is necessary to 

fabricate lens in the range of 7-30 μm. 

Lens Diameter 

(μm) 

Height 

(μm) 

Focal 

Length 

(μm) 

C2 147 8.1 337 

C3 137 7.6 312 

A4 203 8.6 617 

A5 331 22 644 

Table 1: Micro-lenses’ dimensions 

232 

Profile (μm) 

10 

8 

6 

4 

2 

0 

-2 

100 150 200 250 300 

Distance (μm) 

Figure 1: Profilometry of C2 Micro-lens 

Figure 2: Micro-lens at 100x magnification 


The authors acknowledge partial financial support of 

Mid-Infrared Technologies for Health and the Environment 

(MIRTHE). The authors also acknowledge 

assistance form Shanshan Song and Candice Tsay. 

REFERENCES 

[1] C. Gmachl, F. Capasso, D. L. Sivco, and A. Cho. 

Recent progress in quantum cascade lasers and 

Applications. Reports on Progress in Physics. 64, 

1533–1601 October 2001. 

[2] H. Hisakuni and K. Tanaka Optical fabrication of 

microlenses in chalcogenide glasses. Optics letters, 

Vol. 20, No. 9, May 1995. 

[3] S. Song, S. Howard, Z. Liu, A. Dirisu, C. 

Gmachl, C. Arnold. Mode tuning of quantum 

cascade lasers through optical processing of 

chalcogenide glass claddings. Optics letters. Applied 

Physics Letters, 89, 041115, July 2006. 

[4] H. Zhao, L. Yu, Y. Huang. Investigation of a 

chemically treated InP(1 0 0) surface during hydrophilic 

wafer bonding process. Materials 

Science and Engineering B, 128 (2006) 93–97, 

January 2006.

Abstract 

Structure and Dynamics of the Protein P7 from 

Bacteriophage 12 

Towards attaining the complete structural 

and functional characterization of all proteins 

of the cystoviral PX we have obtained the 

crystal structure of the P7 protein (from the 

12 cystovirus) at 1.8 Å resolution. We find 

that both the N-terminal core and the 

dynamic C-terminus tail of P7 play a role in 

RNA recognition leading to a significant 

reduction of the degree of disorder in the Cterminal 

tail [1]. 


The cystoviruses ( 6-14)[2] constitute an 

unique group of enveloped bacteriophages 

that utilize a three-segmented doublestranded 

RNA genome, infect strains of the 

plant pathogen, Pseudomonas phaseolicola 

and share an overall organization and 

replicative mechanism analogous to the 

reoviruses[3]. The innermost layer of the 

cystoviral virion consists of an arrangement 

of four proteins: P1 (major capsid protein), 

P2 (RNA-directed RNA polymerase), P4 

(packaging ATPase) and P7 (putative 

assembly co-factor) (Figure 1). 

Figure 1: Organization of cystoviruses. 

These proteins that are encoded by the Lsegment 

of viral genome constitute the 

polymerase complex (PX) that is responsible 

for genome replication and transcription. Of 

the four PX proteins (Figure 1), highresolution 

structures are available for the 

RNA-directed RNA polymerase (RdRp) P2 

Ertan Eryilmaz, Ranajeet Ghose 


New York, USA 

{eertan,rghose}@sci.ccny.cuny.edu 

233 

from 6 and the hexameric ATPase motor 

P4 from 12. The least characterized of the 

PX proteins is the protein P7. Little is known 

about its structure except that it exists in 

solution as an elongated dimer[4]. We solved 

the structure of N-terminal core of P7 from 

12, characterized the dynamics of the Cterminal 

tail and the core, and provided 

insight into its possible role in RNA 

recognition [1]. 

II. RESULTS 

The Highly Flexible C-terminal Tail of P7 

Interacts Minimally with the Protein 

Core[1] 

The 15 N, 1 H HSQC spectrum of fullyprotonated 

full-length P7 (1-169, P7fl) from 

12 revealed a set of highly intense peaks in 

a background of broad resonances indicative 

of a highly unstructured region in the protein. 

These intense resonances were not seen in 

a construct of P7 (P7 C, 1-129) lacking the 

last 40 residues from the C-terminal tail 

(Figure 2). 

Figure 2. The flexible C-terminal tail of P7 interacts 

minimally with the protein core. (a) Overlay of 15 N, 1 H 

TROSY spectra (800 MHz) of 15 N,REDPRO- 2 H-labeled 

P7fl (black) and P7 C (red). Also shown are the intense 

resonances corresponding to the C-terminal tail 

residues in a 15N,1H HSQC spectrum (600 MHz, cyan) 

of fully-protonated P7fl. (b) Resonance assignments of 

the flexible C-terminal tail resonances in fully-protonated 

full-length P7 (p7fl).

Structure of P7 Core 

P7 forms a novel / -fold[1]. The 

dimerization surface consists of interactions 

involving helices 2 and 3 on each 

monomer (Figure 3) and is composed of the 

largely hydrophobic residues. 

Figure 3. Structure of the P7 C biological unit. (a) 

P7 C forms a symmetric homodimer in solution. The 

monomers are colored blue and red. 

Residual Structure of P7 Tail and RNA 

Interactions 

Although the 15 N-{ 1 H} NOE values for the Cterminal 

tail resonances were very low 

indicative of extensive disorder on the ps-ns 

timescale, the values for the residues 

comprising the stretch between Leu136 and 

Gln145 on the N-terminal end of the tail were 

significantly higher indicating a higher 

degree of local order. (see Figure 4(a)). 

Figure 4. (a) Steady-state 15 N- { 1 H} NOE data at 

600MHz for the 41 C-terminal tail residues in fully 

protonated full-length P7. (b) The difference in the 

deviation of the C and C chemical shifts from the 

corresponding random coil values for the 41 C-terminal 

residues in fully-protonated full-length P7 (P7fl). 

234 

Given the requirement of P7 in maintaining 

genome packaging efficiency and 

transcriptional fidelity we wanted to test the 

possible role of P7 in RNA recognition; we 

have recorded a series of 15 N, 1 H HSQC 

experiments with varying amounts of a 5-nt 

RNA constructs corresponding to the 5’-ends 

of the plus-strands of the 12 genome. Both 

the core and the tail resonances showed 

significant chemical shift changes. Majority 

of the residues of the tail were located near 

the C-terminal end of the protein (159-163) 

(Figure 5(a)), and the moving residues of the 

core domain make continuous surfaces 

(Figure 5(b)). 

Figure 5. Interactions of the C-terminal tail and Nterminal 

core with RNA. (a) 15 N, 1 H HSQC spectrum of 

fully protonated 15 N-labeled P7fl with varying RNA 

concentrations. Resonances showing significant 

chemical shiftchanges are shown. (b) The surface maps 

of N-terminal core; two specific surfaces display large 

chemical shift changes in the presence of RNA – key 

residues are labeled and the color 

REFERENCES 

[1] Eryilmaz, E., Benach, J., Su, M., Seetharaman, J., 

Dutta, K., Wei, H., Gottlieb, P., Hunt, J.F., and 

Ghose, R. (2008). Structure and dynamics of the 

P7 protein from the bacteriophage f12. J. Mol. Biol. 

382, 402-422. 

[2] Mindich, L., Qiao, X., Qiao, J., Onodera, S., 

Romantschuk, M. & Hoogstraten, D. (1999). 

Isolation of additional bacteriophages with 

genomes of segmented double-stranded RNA. J. 

Bacteriol. 181, 4505-8. 

[3] Mertens, P. (2004). The dsRNA viruses. Virus Res. 

101, 3-13. 

[4] Huiskonen, J. T., de Haas, F., Bubeck, D., 

Bamford, D. H., Fuller, S. D. & Butcher, S. 

J.(2006). Structure of the bacteriophage f6 

nucleocapsid suggests a mechanism for sequential 

RNA packaging. Structure 14, 1039-48.

Dsh is required for the phosphorylation of Dpr1a by 

CKIδ 

Evelyn Teran, and Joni M. Seeling 

Queens College 


New York,United States of America 

Abstract 

Colon cancer is the third most common form of 

cancer and the second leading cause of cancerrelated 

death in the Western world causing 

655,000 deaths worldwide per year [1]. The Wnt 

signaling pathway plays an important role during 

embryonic development and colon cancer. The 

PDZ-Binding domain of protein XDpr1a interacts 

with the PDZ domain of protein Dsh to inhibit the 

Wnt signaling pathway. β-catenin, a protein found 

in abundance in colorectal cancerous cells is reduced 

in abundance by XDpr1a which also decreases 

activation of Wnt responsive genes. We 

have found that XDpr1a is phosphorylated by 

CKIδ, an activator of Wnt signaling, in the presence 

of Dsh. PDZ-binding mutants of XDpr1a 

which do not bind Dsh are not phosphorylated by 

CK1δ in the presence of Dsh. Mutation of the PDZ- 

B binding loop of the Dsh PDZ domain prevents 

Dsh from promoting XDpr1a phosphorylation, 

whereas mutation within the PDZ domain but outside 

of the PDZ-B binding loop does not. 

Introduction 

The Wnt signaling pathway is involved in 

a large range of embryonic patterning events and 

cancer. One of the most distinctive effects of the 

Wnt proteins is their ability to induce formation of 

the dorsoventral body axis in the model organism 

Xenopus laevis. It has been shown that activation of 

the Wnt/�-catenin signaling pathway is commonly 

associated with the development of colorectal cancer 

and various types of cancers [2]. In the absence 

of the Wnt ligand, glycogen synthase kinase 3� 

(GSK-3�) phosphorylates �-catenin in the �catenin 

degradation complex. This leads to the 

ubiquitination and degradation of �-catenin. Hence, 

�-catenin levels are maintained low. However, 

when a Wnt ligand is present, the ligand binds to 

the seven pass transmembrane receptor Frizzled 

(Fz), and the signal activates the protein Dishevelled 

(XDsh) by phosphorylation. Activated XDsh 

destabilizes the �-catenin degradation complex, and 

�-catenin therefore accumulates in the cytoplasm. 

As a result, �-catenin enters the nucleus, where it 

forms a complex with members of T-cell factor/lymphoid-enhancing 

factor (TCF/LEF) and 

upregulates TCF/LEF-dependent transcription of 

target genes such as c-Myc and siamois. 

Email: Evelyn0021@aol.com 

235 

Regulatory subunit B56 of protein phosphatase 

2A(PP2A), interacts with APC in the Wnt 

pathway [3], PP2A is a heterotrimeric intracellular 

serine-threonine phosphatase. PP2A contains a 

conserved catalytic (C), structural (A), and a variable 

regulatory (B) subunit [3]. There are three 

families of B subunits; B55, B56 and B72. Each 

family subunit has multiple isoforms, leading to 

many distinct holoenzymes, which explains the 

diversity and multiple functions of PP2A. The B 

subunit provides substrate specificity to PP2A and 

subcellular localization. Furthermore, it found that 

casein kinase I (CKI), more specifically CKI� and 

CKI�, phosphorylate and destabilize the �-catenin 

degradation complex through the dissociation of 

PP2A [4]. 

Dishevelled (XDsh) is a key activator of 

the Wnt pathway that destabilizes the �-catenin 

degradation complex. XDsh contains a central Post 

synaptic density-95, Discs-large, Zonula occludens-1 

(PDZ) domain. The PDZ domain is involved 

in protein-protein interaction which usually 

binds to the extreme C-terminus of transmembrane 

proteins containing PDZ-binding motifs (PDZ-B) 

[4]. Each domain of XDsh binds to specific proteins 

that transduce Wnt signaling to different 

downstream pathways. Dapper (XDpr1a), functions 

as an inhibitory protein in the pathway by 

inhibiting XDsh functions during Xenopus embryogenesis. 

XDpr1a also downregulates levels of 

�-catenin accumulation in the cytoplasm and therefore 

also downregulates Wnt ligand mediated transcription. 

XDpr1a contains a PDZ-binding domain 

at its C-terminal end which binds to the PDZ domain 

of XDsh. 

Materials and Methods 

Transcription /Translation 

In vitro transcription and translation was 

performed with [ 35 S]methionine (Amersham Biosciences 

Corp., Piscataway, NJ) using TNT SP6 

Quick Coupled Transcription/Translation System 

(Promega, Madison, WI) according to the manufacturer’s 

instructions. Unlabeled XDsh was prepared 

with the TNT SP6 Quick Coupled kit using cold 

methionine. 

In Vitro phosphorylation assay 

[ 35 S]methionine labeled XDpr1a and either 

[ 35 S]methionine labeled or unlabeled XDsh 

were mixed also containing MgCl2 and ATP. Rat

CKIδ lacking its autoinhibitory carboxy-terminal 

domain (New England Biolabs, Beverly, MA) was 

added to a final concentration. Samples were resolved 

using SDS-PAGE and visualized by autoradiography 

Results We have found that Dapper is phosphorylated 

by CK1 in the presence of Disheveled. PDZbinding 

mutants of Dapper are not phosphorylated 

by CK1 in the presence of Disheveled and the Disheveled 

mutation of the PDZ domain is still able 

to promote dapper phosphorylation, but a mutation 

N-terminal to the PDZ domain is unable. 

Mutant XDpr1a and XDsh constructs were obtained 

from Randall Moon’s lab. We analyzed 

three XDpr1a mutants. The first mutant, DprΔLZ, 

lacks the 36 amino acid leucine zipper region, the 

second mutant XDpr1aMNTV contains a 

Thr822Asn point mutation in the PDZ-B domain, 

and the third mutant XDpr1aΔMTTV lacks the 

PDZ-B domain. 

The results in Figure 1 show that DprΔLZ protein 

behaved similar to wild-type XDpr1a and underwent 

a gel-shift of hyperphosphorylation in the 

presence of CKIδ. XDpr1aΔMTTV did not undergo 

a mobility shift in the presence of CKIδ, suggesting 

that it is not phosphorylated by CKIδ. 

XDprMNTV behaved similar to XDpr1aΔMTTV, 

and did not exhibit a mobility shift as well. Therefore, 

these data suggest that unmodified PDZ-B 

domain in XDpr1a is required for the XDshdependent 

phosphorylation of XDpr1a by CK1δ. 

In addition, we examined mutations in 

XDsh that prevent its interaction with XDpr1a, to 

determine if they had any effects on the phosphorylation 

of XDpr1a by CKI. In a paper by Cheyette 

(et al., 2002), it was found that an N317T point 

mutation in Dsh’s PDZ-B binding domain 

(XDsh*α) (Figure.2), disrupts its interaction with 

XDpr1a. On the other hand, a triple mutation in a 

PDZ domain loop upstream of XDsh’s PDZ-B 

binding domain (XDsh***β-β) does not. We 

wanted to find out whether a mutation of the PDZ 

domain of XDsh could prevent XDsh from promoting 

a mobility shift and hyperphosphorylation of 

XDpr1a in the presence of CK1δ. Our results show 

that XDpr1a did not exhibit a mobility shift in the 

presence of XDsh*α but in fact XDpr1a exhibited a 

mobility shift in the presence of wild type XDsh 

and XDsh***β-β. The inability of a XDsh*� to 

promote the phosphorylation of XDpr1a by CKI 

due to its point mutation in the PDZ-B binding 

domain of its PDZ domain, suggests that Dsh must 

bind to XDpr1a to promote its phosphorylation. 

236 

Figure 1: XDpr1a lacking PDZ-B is not phosphor 

ylated by CKI� 

Figure 2: Mutation of the Dsh PDZ-B binding loop 

abrogates XDpr1a phosphorylation by CKI�. 

Conclusion 

We have found that an interaction of PDZ 

domain of Dsh and the PDZ-binding domain of 

XDpr1a are required for gel-shift, indicating phosphorylation. 

When the domains were mutated or 

deleted, XDpr1a’s phosphorylation by CKI� was 

not functional. By doing TNT assays, we have 

shown that a deletion (� MTTV) and point mutation 

(MNTV) of the PDZ-binding domain in dapper 

prevents it from binding to Dsh. Conversely, we 

have shown that a triple mutation (***β-β) outside 

the binding pocket of Dsh appears to affect gel shift 

to XDpr1a, whereas a point mutation (α) within the 

PDZ domain of Dsh does not inhibit its gel shift. 

Acknowledgements 

I’d like to thank my mentor Dr.Joni 

Seeling as well as my funding programs 

LSAmp and Bridges to Doctorate. 

References 

[1] World Health Organization, February 

2006. 

[2] X.Li, H.Yost, D.Virshup and J.Seeling 

(2001) The EMBO Journal, 4122-4131 

[3] Z.Gao, J.Seeling, V.Hill, A.Yochum and 

D.Virshup (2002) PNAS, 1182-1187 

[4]Cheyette, B.N., J. S. Waxman, et al. (2002). 

Dev Cell 2(4): 449-61

Momentum of Optical Airy Beams 

H. I. Sztul and R. R. Alfano (Faculty Mentor) 

Institute of Ultrafast Spectroscopy and Lasers 

The Graduate Center and City College of the City University of New York 

New York, USA 

Email: hsztul@gc.cuny.edu 

Abstract — The optical Airy beam is a unique solution to 

the wave equation that curves as it travels through space. We 

analyze and describe the evolution of the Poynting vector and 

angular momentum of the optical Airy beam as it propagates 

through space. We show that while the total angular momentum 

of the Airy beam is zero, the angular momentum of the main 

intensity peak and the Airy “tail” are non-zero. 


Until recent laser beams have been known to travel along 

straight paths. A new class of laser beam known as 

the Airy beam, that is a solution to the paraxial wave 

equation, follows a parabolic trajectory, curving through 

space [1, 2, 3]. These beams of light are diffraction-free 

accelerating beams of light that have the spatial profile 

of the Airy function. The 1-D and 2-D Airy solution was 

most recently shown experimentally in optical beams of 

light [2]. The Airy beam is said to be free of diffractive 

spreading and freely accelerating in the absence of any 

external potential [1, 4]. 

In this paper the Poynting vector and angular momentum 

of the Airy beam as it propagates through space is 

explored. 

Figure 1: The numerically calculated Poynting vector in 

the sx − sy plane, of the finite-energy Airy wave with 

a = 0.15 at ξ =0(a), ξ =0.025 (b), ξ =0.050 (c), 

ξ =0.075 (d). The intensity of the Airy field is shown in 

the background of each frame. 

II. POYNTING VECTOR OF AIRY BEAMS 

The (2 + 1)D paraxial wave equation has the nondispersive 

solution that limits infinite energy flow of the 

form [1, 3, 4], 

φ(sx,sy,ξ) = 

� 

Ai sx − (ξ/2) 2 � 

+ iaξ 

� 

Ai sy − (ξ/2) 2 � 

+ iaξ 

� 

× exp asx + asy − (aξ 2 /2) − i(ξ 3 /12) 

−i(a 2 electrodynamics [5, 6]. This vector is routinely examined 

for plane waves but has received considerable attention in 

the literature with regard to Laguerre-Gaussian beams of 

light that have helical wavefronts [7, 9]. 

The Poynting vector is defined as [6]: 

�S =(c/4π) 

� 

ξ/2) + iξ(sx + sy)/2 . (1) 

where sx = x/x0 and sy = y/y0 are normalized transverse 

coordinates, ξ = z/k(x0 + y0) is a normalized 

propagation distance, x0 and y0 are normalization constants, 

and k =2πn/λ0. The background of Figure 1(ad) 

shows the intensity in the transverse plane at various 

ξ-positions when a =0.15 and xo = yo =0.1. 

The rate of electromagnetic energy flow per unit area, 

or the Poynting vector, is a commonly known quantity in 

� E × � B, (2) 

where c is the speed of light. Given a vector potential 

�A =ˆɛu(sx,sy,ξ)exp[ik2ξ(x0 + y0)], where ˆɛ is an arbitrary 

polarization and u(sx,sy,ξ) is the Airy field amplitude 

given by Eq. (1), we can use the � E and � B-fields 

in the Lorenz gauge, as given by Ref. [8], to calculate the 

time-averaged Poynting vector, < � S>, numerically. 

Figure 1 (a-d) shows the numerically computed ˆsxand 

ˆsy-components of the Poynting vector for a =0.15 

at ξ =0.025, 0.050, 0.075, and 0.1, respectively. The direction 

and magnitude of the arrows (shown in red) correspond 

to the direction and magnitude of the energy flow 

in the transverse plane. The intensity of the Airy field is 

shown in the background of each frame to show the direction 

of the energy flow in relation to the peaks of the 

237

Figure 2: The numerically calculated angular momentum 

in the ˆ ξ-direction of the finite-energy Airy wave given by 

eq. (3) with a = 0.15 at ξ =0.025 (a), ξ =0.050 (b), 

ξ =0.075 (c), ξ =0.100 (d). Reds are positive values, 

blues are negative values, and green is zero. 

Airy beam. The flow of energy of the main peak at ξ>0 

is consistently pointed at 45 o relative to the sx −sy plane 

at all ξ-locations. In contrast, the direction of the energy 

flow for the Airy tails, or the peaks oriented along the 

horizontal or vertical axis approaches a direction perpendicular 

to that axis. The net energy flow is measured, 

however, to be constant and pointed in the direction that 

the main peak moves, i.e 45 o or along the line sx = sy. 

III. ANGULAR MOMENTUM OF AIRY 

BEAMS 

It is well known that as �p ∝ � E × � B from which follows 

that angular momentum density about the ˆ ξ-direction is 

jξ(sx,sy,ξ) = 

� � 

�r × �E × B� 

ξ 

= sx · Ssy + sy · Ssx. (3) 

The numerically computed < � S > shown in Figure 

1 is used to calculate the angular momentum in the ˆ ξdirection. 

Figure 2 (a-d) shows the ˆ ξ-component of the 

angular momentum density with a =0.15 at ξ =0.025, 

0.050, 0.075, and 0.100, respectively. At ξ =0the computed 

angular momentum is zero so it is not shown. In 

Figure 2 reds are positive values (clockwise), blues are 

negative values (counter-clockwise), and green is zero. 

As the beam propagates, the net angular momentum in 

the ξ-direction is always zero. The spatial distribution of 

the angular momentum is changing however, and locally 

has non-zero values of angular momentum. Not only is 

the angular momentum changing in the Airy tails, but 

238 

there are also changes to the angular momentum in the 

main Airy peak. This change of angular momentum is 

a torque that corresponds to the force present due to the 

changing linear momentum. 


In this paper we analyze the spatial evolution of the Airy 

solution to the paraxial wave equation and show that 

while momentum is changing, energy and momentum 

are conserved. We point out that the linear and angular 

momenta are changing as the Airy beam propagate in 

the ξ-direction which should implications when analyzing 

the velocity of this field. Some form of the velocity, 

be it phase, energy, or signal velocity, should be changing 

as the beam propagates and should be investigated in future 

studies. These beams have promise for applications 

in optical trapping, imaging, and spectroscopy where a 

sample might interact with a changing momentum and 

spatially varying angular momentum. 


This work was supported in part by organized research 

at CCNY, NASA URC - Center for Optical Sensing and 

Imaging (COSI) at CCNY (NASA Grant No.: NCC- 

1-03009), and DOD Center of Nanoscale Photonics at 

CCNY. 

REFERENCES 

[1] M.V. Berry and N.L. Balazs, “Nonspreading wave 

packets,” Am. J. Phys. 47, 264 (1979). 

[2] G.A. Siviloglou, J. Broky, A. Dogariu, and D. N. 

Christodoulides, “Observation of Accelerating Airy 

Beams,” Phys. Rev. Lett. 99, 213901 (2007). 

[3] G. A. Siviloglou and D. N. Chistodoulides, “Accelerating 

finite energy Airy beams,” Opt. Lett. 32, 979 

(2007). 

[4] D. M. Greenberger, “Comment on ’Non-Spreading 

Wave Packets’, ” Am. J. Phys. 48, 256 (1980). 

[5] J.D. Jackson, Classical Electrodynamics, Wiley, 

New York, 1962. 

[6] Max Born and Emil Wolf, Principles of Optics, 

7th Ed., Cambridge University Press, Cambridge, 

1999. 

[7] L. Allen and M.J. Padgett, “The Poynting vector 

in Laguerre-Gaussian beams and the interpretation 

of their angular momentum desnity,” Opt. Comm. 

184, 67-71 (2000). 

[8] L. Allen, M. J. Padgett, and M. Babiker, Progress 

in Optics XXXIX, pp. 291-372 (1999). 

[9] H.I. Sztul and R. R. Alfano, “Double-slit interference 

with Laguerre-Gaussian beams,” Opt. Lett. 31, 

999-1001 (2006).

Electrochemistry, Optical Spectroscopy and DFT Calculations of 

Glutathionylcobalamin 

Iya Likhtina and Ronald L. Birke (Faculty Mentor) 

Department of Chemistry and Center for Analysis of Structures and Interfaces (CASI), The City 

College and The Graduate School and University Center of City University of New York 

Email: ilikhtina@gc.cuny.edu 

Abstract - The bioinorganic chemistry of vitamin 

B12 is an active area of research [1]. Forms of 

vitamin B12 in the reduced state are powerful reducing 

agents which have been used for dehalogenation 

of organic halide compounds in aqueous 

solution such as the reductive dehalogenation of 

bromoform for environmental remediation [2]. In 

this work we studied the cyclic voltammetry (CV), 

UV-Visible spectroscopy, and circular dichroism 

(CD) of GSCbl in solution. Also, DFT calculations 

(B3LYP/6-311G*) have been used to calculate the 

properties of glutathionylcobalamin, GS-Cbl. UV- 

Vis spectroscopy was employed to monitor the formation 

of GSCbl which showed well-defined 

isosbestic points. Time dependent (TD) DFT calculations 

were again used to calculated the electronic 

excitation energies found in the electronic spectra. 


A corrin macrocyclic ring is the base ligand 

for the structure of glutathionylcob(III)alamin 

which contains a Co3+ ion. The ring resembles 

the porphyrin ring but has one less carbon. With 

side chains and Co ion in the center of the corrin 

ring , the molecules are called cobalamins. Four of 

the six coordination sites are occupied by 

equatorial nitrogens of the corrin ring, and there 

are two axial ligands above and below the ring. 

The lower ligand is a dimethylbenzimidazole 

group in cobalamins. The sixth coordination site 

which is above the corrin can be substituted by 

many groups such as a cyano group, a hydroxyl 

group, a methyl group, a 5’-deoxyadenozyl group 

and in our case a glutathionyl group giving 

glutathionylcobalamin, GS-Cbl. 

In biological tissues glutathione, GSH, is a 

major intracellular reducing agent and GS-Cbl(III) 

is one of the major forms of B12 in mammalian 

cells. This species appears to be the natural 

precursor of the cobalamin coenzymes. All of 

above evidence suggests that GS-Cbl(III) is an 

important intermediate for biological processes 

involving vitamin B12 species. 

239 

Electrochemistry has proven to be a valuable 

tool for investigating the electron-transfer steps of 

the three oxidation states of cobalt and their 

coupling with ligand exchange reactions in the 

oxidoreduction chemistry of various vitamin B12 

derivatives. There is only one paper on the 

electrochemistry of GSCbl and this is from the 

absorbed state [3]. We studied the cyclic 

voltammetry (CV ) on glassy carbon and mercury 

electrodes as a function of potential scan rate, pH 

and concentration of GSCbl. Digital simulation of 

the electrode process was investigated for possible 

mechanisms. The CVSIM program was utilized to 

perform the simulation of the CV curves. The 

shape of a cyclic voltammetric curve reflects both 

electron transfer at the electrode and solution 

chemical reaction that are coupled to the electron 

transfer. Both UV-Vis and circular dichroism (CD) 

electronic spectroscopic techniques were used to 

elucidate the electronic transitions in the visible 

and ultraviolet regions of the spectrum. 


A. RESULTS 

The CV experiments were performed with the 

CH 660A workstation. A three electrodes 

configuraton was used in all experiments. The 

working electrodes were a mercury drop from a 

BAS controlled growth Hg electrode (CGME) or a 

glassy carbon electrode. A Ag/AgCl/Cl (3M) 

electrode was used as the reference electrode and a 

platinum electrode was used as the counter 

electrode. The electrode process found on glassy 

carbon and mercury electrodes at pH 4 indicates a 

one-electron reduction after which the Co(II)-S 

bond breaks. The one-electron reduction 

mechanism has been confirmed by digital 

simulation at pH 4. Figure 1 shows a good fit 

between the simulation of the one-electron 

reduction, dotted line, and the experimental 

results. The reduction potential of GS-Cbl(III) at 

pH 4 is at ca. -0.9V vs. the reference electrode.

This shows that the glutathionyl ligand is a better σ 

-donating ligand than water but poorer than 

cyanide or alkyl carbanions. We also studied the 

equilbrium reaction between GSH and Cbl(III) 

between pH 3 and 5 by Uv-Vis spectrocopy. 

Finally the structure and excited states of GS- 

Cbl(III) was investiagted by DFT calculations. 

B. COMPUTATIONAL DETAILS 

We have made DFT electronic structure calculations 

on the glutathionylcobalamin. The model of GS- 

Cbl(III) that we used includes the full corrin ring 

with all side-chain groups replaced by hydrogen 

atoms and with the dimethylbenzimidazole base 

ligand replaced by imidazole. Since the model does 

not include the negative phosphate-containing side 

chain, the GS-Cbl(III) model is a singly plus charged 

species. The calculations were made with the 

Gaussian 03 package of programs using the B3LYP 

hybrid functional level of theory and the 6-311G** 

basis set. 

The geometric optimization of the model shows a 

very good fit with the XAFS [4] and X-ray 

diffraction [5] results for Co-S, Co-N(equatorial) and 

Co-N(axial) bond distances as indicated in Table 1. 

TD-DFT TD-DFT GS-Cbl (III) RS-Cbl (III) 

R GS-Cbl GS-Cbl EXAFS, Å X-ray Diff, 

(III) z = (II) z = 0, 

Å 

+1, Å Å 

Co - S 2.2958 2.31460 2.28±0.05 2.267 

Co - Nax 2.0685 2.05710 2.15±0.03 2.049 

Co - Neq 

(5-mem) 

Co - Neq 

(5-mem) 

Co - Neq 

(6-mem) 

Co - Neq 

(6-mem) 

1.9020 1.90490 1.89±0.01 1.885 

1.8880 1.90582 1.891 

1.93645 1.95293 1.902 

1.93645 1.95160 1.914 

Table1. Comparison of Co-X bond distances in 

GS-Cobalamin. There are two sets (5-mem and 6mem) 

of equatorial Co-N bonds in the molecule. 

The excited state transitions calculated by TD- 

DFT show a good fit with the experimental results 

from the UV-Vis and CD optical experiments. The 

vertical excitations are depicted by the transitions 

between molecular orbitals. 

240 

CONCLUSION 

The GC-Cbl(III) molecule has 

electrochemistry, optical spectroscopy, and electron 

structure which is very similar to the biologically 

active vitamin B12 coenzymes, methylcobalamin and 

5’-deoxyadenozylcobalamin. This is consistent with 

the supposition that it is the storage form of the 

vitamin in the human body . 

Current, mkAmp 

1 0 

8 

6 

4 

2 

0 

-2 

- 4 

-0.6 -0.7 -0.8 -0.9 -1 .0 -1 .1 - 1 .2 

P otent ia l, V 

Figure1. Simulated and experimental CV of GS- 

Cbl on mercury electrode. Solid line: experimental 

CV, dotted line: simulated CV. 

REFERENCES 

[1] J. M. Pratt, In: R. Banerjee (Ed) , Chemistry and 

Biochemistry of B12., John Wiley & Sons, 

New York , 1999, p. 104 

[2] Eric A. Betterton, Robert G. Arnold, Ronald J. 

Kuhler and Gregory A. Santo Environmental 

Health Perspectives, Vol. 103, Supplement 5: 

Biodegradation (Jun., 1995), pp. 89-91. 

[3] L. Xia, A. G. Cregan, L. A. Berben, N. Brash, 

Inorg. Chem. 43 (2004) 6848-6857. 

[4] Eva M. Scheuring, Irit Sagi and Mark R. 

Chance, Biochem (1994) 33, 6310-6315. 

[5] Robert K. Suto et al., Inorg. Chem., 2001, 40, 

2686-2692.

Surface Enhanced Raman Spectroscopy of 

Flavanthrone 

Jingjing Chang 1,2 , Maria Vega Cañamares 1 , John R. Lombardi 1 

1 Department of Chemistry, City College of New York 

N.Y., N.Y. 10031 

2 State Key Laboratory of Supramolecular Structure and Materials, Jilin University 

Changchun, P. R. China, 130012 

Email: changjj@sci.ccny.cuny.edu 

Abstract —Flavanthrone is among the oldest 

synthetic vat dyes. It is of considerable interest 

due to its high symmetry. As it has a point of inversion, 

no spectral lines are common to the infrared 

and Raman spectrum. In this work, flavanthrone 

has been studied by FT-Raman and Surface-enhanced 

Raman scattering (SERS) spectroscopy. 

The SERS spectra were recorded at 633 and 

785 nm on Ag nanoparticles. The SERS spectra 

show lines which are forbidden in normal Raman 

spectra. This is due to the reduction in symmetry 

originated by the interaction of the molecules with 

the metallic surface. The B3LYP method of the 

Density Functional Theory (DFT) was used to 

identify those new lines and determine their origin. 


Flavanthrone is one of the oldest synthetic vat dyes. 

It was synthesized by Rene Bohn in 1901 [1]. Due to 

its high light fastness, flavanthrone is especially 

favoured as an artists’ color [2]. As shown in Figure 

1, we illustrate a recent installation in which flavanthrone 

has been infused into a wax sculpture to produce 

a luminescent orange glow. 

This yellow dye is of considerable interest in spectroscopy 

due to its high symmetry. As it has a point 

of inversion, no spectral lines are common to both 

the infrared and Raman spectrum. 

Most organic dyes exhibit an intense fluorescence 

emission. This makes their analysis by normal 

Raman spectroscopy difficult, as the fluorescence 

background can overwhelm the Raman bands. The 

use of surface-enhanced Raman spectroscopy 

(SERS), however, allows the analysis of organic 

dyes. The great advantage of this technique is the 

combination of a highly increased Raman sensitivity 

with the fluorescence quenching that occurs on rough 

metallic surfaces [3, 4]. 

In this work, we present the first SERS analysis of 

one of the oldest synthetic vat dyes, flavanthrone, 

241 

together with the DFT analysis of its vibrational 

normal modes. 

Figure 1: Contemporary Art with Flavanthrone. 

Title: "In Front of the Plane, No. 8". Artist: Johannes 

Girardoni, 2007/2008, Installed at: Lukas Feichtner 

Gallery, Vienna 

II. EXPERIMENT 

Ag colloid was prepared following the method of 

Lee and Meisel [5] by reduction of silver nitrate with 

sodium citrate. To further concentrate the colloid for 

use, a volume of 1 ml of the original colloid was 

centrifuged at 8000 rpm for 5 minutes. Then, 900 μl 

of the supernatant was discarded and the settled 

portion was resuspended in 900 μl of original colloid. 

This process was repeated 5 times. SERS 

measurements were made simply by adding a 1 �l 

drop of the colloid and 2 �l drop of a 10 -4 M 

flavanthrone solution, followed by the addition of 1 

�l of a 0.5 M KNO3 solution. The potassium nitrate 

was used for aggregating the colloid so it would 

become active in SERS [6]. The SERS 

measurements were taken directly from the drop 

focusing by a microscope . 


The SERS spectra of flavanthrone obtained by using 

the excitation of 633 and 785 nm are displayed in 

Figure 2 in comparison with the FT-Raman spectrum.

Raman Intensity 

477 

509 

N 

O 

637 

O 

N 

1296 

1322 

1425 

* * 

* 

* 

* * 

817 

926 

1018 

1042 

1160 

400 600 800 1000 1200 1400 1600 

a 

1800 

Wavenumber (cm -1 ) 

1560 

1601 

Figure 2: Comparison of the FT-Raman spectrum 

of flavanthrone (a) and SERS spectra of Flavanthrone 

(10 -4 M) with excitation at 785nm (b) and 

633nm (c) in the region 400-1800 cm -1 . Some forbidden 

lines are marked with *. Inset: the structure of 

the flavanthrone molecule 

The DFT wavenumbers have been scaled by a factor 

of 0.98 (table 1). As can be seen, the fit of the 

DFT wavenumbers and the FT-Raman wavenumbers 

is excellent, and we may therefore have great confidence 

in the assignments. 

The position of the bands and the normal modes 

assigned to the corresponding vibrations are compared 

in table 1. The most intense bands in the FT- 

Raman spectrum (Fig. 2a) are at 1183, 1384 and 

1596 cm -1 , which involve the �(C=C), �(C=N) and 

�(CH) vibrations. Other important bands appear at 

1160, 1260, 1419, 1596 and 1619 cm -1 . The first two 

bands are assigned to �(CH) motions. The third one 

is due to a �(C=N) motion, and the last two bands 

correspond to �(C=C) vibrations. It is also shown 

that the majority of the most intense bands in the FT- 

Raman spectrum are totally symmetric modes (ag). 

Both of the SERS spectra of 633 (Fig. 2c) and 

785nm (Fig. 2b) excitation are shown in Fig. 2 in 

comparison with the FT-Raman spectrum (Fig. 2c). 

Several of the prominent bands, such as 1619, 1596, 

1419, 1384, 1260, 1183 and 1160 cm -1 are present in 

both (giving the FT-Raman measurements). All of 

them are assigned to ag modes, with the exception of 

the last one. The relative intensities of many bands 

have been drastically changed. The intensities of the 

bands at 1619, 1596, 1384 and 1183 cm -1 are 

distinctly decreased. On the other hand, the bands 

located at 1419, 1355, 1312, 1287, 1260 and 1160 

cm -1 are strongly enhanced on the Ag nanoparticles 

surface. Moreover, the bands at 1502, 1456, 1208, 

951, 926 and 902 cm -1 appear in the SERS spectra of 

flavanthrone but are not shown in FT-Raman spectrum. 

Only the first one involves the totally symmetric 

mode (ag) all others are due to the non-totally 

symmetric modes bu or bg. 

c 

b 

242 

Descrip 

tion 

�(CC) 

�(CC) 

�(CC) 

�(CN) 

�(CN) 

�(CN) 

�(CC) 

�(CC) 

�(CN) 

�(CH) 

�(CH) 

�(CH) 

�(CH) 

�(C=O) 

�(CH) 

�(CNC) 

Sym DFT 

ag 

ag 

ag 

bu 

ag 

ag 

ag 

ag 

bu 

ag 

bu 

ag 

bu 

bu 

bg 

bu 

1609 

1595 

1497 

1447 

1417 

1383 

1358 

1325 

1285 

1278 

1193 

1177 

1166 

940 

923 

902 

FTR SERS 

633 

1619 

1596 

1419 

1384 

1355 

1312 

1287 

1260 

1183 

1160 

1628 

1601 

1502 

1456 

1425 

1405 

1371 

1322 

1296 

1273 

1208 

1188 

1160 

951 

926 

902 

SERS 

785 

1621 

1598 

1498 

1455 

1418 

1401 

1368 

1318 

1285 

1270 

1207 

1186 

1159 

949 

927 

901 

Table 1: Wavenumbers (in cm -1 ) and assignments 

of some forbidden lines and the most intense lines 

in the FT-Raman and SERS spectra of flavanthrone. 

The DFT wavenumbers are scaled by a 

factor of 0.98 


We gratefully acknowledge Marco Leona for 

possibility to use the SERS instrument, and Manfred 

Schreiner, Wilfreid Vetter, Johannes Giradoni, for 

providing samples and photographs of the art work. 

We are indebted to the National Institute of Justice 

(Department of Justice Award #2006-DN-BX-K034) 

REFERENCES 

[1] E.R. Riegel, J.A. Kent, Riegel’s Handbook of 

Industrial Chemistry, J.A. Kent, Ed, 10th Edition, 

Springer, 2003. 

[2] W. Herbst, K. Hunger, Industrial Organic Pigments. 

Production, Properties, Applications. 

Third, Completely Revised Edition. Wiley-VCH 

Verlag GmbH & Co. KGaA , Weinheim, Germany, 

2004. 

[3] Birke, R.L., Lombardi, J.R. Surface Enhanced 

Raman Scattering. In Spectroelectrochemistry: 

Theory and Practice, Gale RJ (ed). Plenum:New 

York, 1988; 263–348. 

[4] Moskovits M. Rev. Mod. Phys 1985; 57: 783. 

[5] Lee PC, Meisel D. J.Phys.Chem. 1982; 86: 3391. 

[6] M.V. Cañamares, J.V. Garcia-Ramos, J.D. Gomez-Varga, 

C. Domingo, S. Sanchez-Cortes, 

Langmuir 2005; 21: 8546.

Nonlinear resistance of 2D electrons in crossed electric and 

magnetic fields 

JingQiao Zhang and Sergey Vitkalov (Faculty Mentor) 

Physics Department 



Email: {phyzjqk,vitkalov}@sci.ccny.cuny.edu 

Abstract — Electric field induced, dramatic reduction of 

longitudinal resistivity of two dimensional electrons placed in 

strong magnetic field is studied in broad range of magnetic 

fields B and temperatures T . The data are found to be in good 

agreement with theory, considering the strong nonlinearity of 

the resistivity as result of non-uniform spectral electron diffusion 

induced by the electric field. Comparison with the theory 

gives inelastic scattering time τin of the 2D electrons. In temperature 

range T =2− 20K for overlapping Landau levels, 

the inelastic scattering rate 1/τin is found to be proportional 

to T 2 , indicating dominant contribution of the electron-electron 

interaction to the inelastic electron relaxation. 


In this report we study and discuss in details effect of 

a small electric field Edc on longitudinal resistance of 

two-dimensional electrons placed in a strong magnetic 

field. At the magnetic field the density of states of the 

2D electrons is modulated due to Landau quantization of 

the electron motion. Strong reduction of the longitudinal 

resistance of the 2D electrons in response to the dc electric 

field has been observed recently [1, 2]. The effect is 

attributed [2] to a spectral diffusion of the electrons induced 

by the electric field [3]. The diffusion is limited 

by an electron inelastic relaxation, which moves the system 

back to the thermal equilibrium. A reasonable agreement 

between the theory [3] and the experiment has been 

found[2]. The finding opens new possibilities to study inelastic 

electron processes and nonlinear electron kinetics 

of the low dimensional systems. 


Our samples are cleaved from a wafer of a high-mobility 

GaAs quantum well grown by molecular beam epitaxy 

on semi-insulating (001) GaAs substrates. The width of 

the GaAs quantum well is 13 nm. Two AlAs/GaAs type- 

II superlattices grown on both sides of the well served 

as barriers, providing a high mobility of the 2D electrons 

inside the well at a high electron density. Two samples 

(N1 and N2) were studied with electron density n1 = 12.2 

×10 15 m −2 , n2=8.2 ×10 15 (m −2 ) and mobility μ1= 93 

m 2 /Vs, μ2=85 (m 2 /Vs) at T=2.7K. 

Measurements were carried out between T=0.3K and 

243 

Figure 1: Schematic view of experimental setup. 

T=20 K in a He-3 insert in a superconducting solenoid. 

Magnetic field up to 1 T was applied perpendicular to the 

2D electron layers patterned in a form of d=50 μm wide 

Hall bars with a distance of 250 μm between potential 

contacts. The shape of the samples and the experimental 

setup are shown in Fig.1. The differential longitudinal 

resistance rxx is measured at a frequency of 77 Hz in the 

linear regime. 

III. THEORY AND NUMERICAL SIMULA- 

TIONS 

The net longitudinal conductivity of the 2D electrons σnl 

is a sum of conductivities σ(ɛ) of the levels with energy ɛ 

over all possible energies, weighted with the first derivative 

of the distribution function ∂f/∂ɛ [?]: 

� 

σnl = σ(ɛ)(−∂f/∂ɛ)dɛ, (1) 

In the leading approximation for a classically strong 

magnetic field (ωcτtr ≫ 1) the longitudinal conductivity 

σ(ɛ) at an energy ɛ reads [3]:

σ(ɛ) =σD ˜ν 2 (ɛ), (2) 

where σD = e 2 ν0v 2 F /2ω2 cτtr is the dc Drude conductivity 

in strong magnetic field B, ˜ν(ɛ) =ν(ɛ)/ν0 is dimensionless 

density of states (DOS), τtr and ν0 = m/π¯h 2 

are transport scattering time and the density of states at 

zero magnetic field. 

As a result of the energy conservation, the diffusion 

motion of the electron in real space originates a spectral 

diffusion of the electron kinetic energy in the energy 

space. The spectral diffusion is described by the Fokker- 

Plank type equation [3]: 

− ∂f 

∂t + E2 σD dc 

ν0˜ν(ɛ) ∂ɛ 

� 2 

˜ν (ɛ)∂ɛf(ɛ) � = f(ɛ) − fT (ɛ) 

τin 

(3) 

The left side of the equation describes the spectral diffusion 

of a spherical part of the electron distribution function 

f induced by the electric field E in the presence of 

the elastic impurity scattering. 

The numerical calculations are done in several steps. 

The first step is to find the density of electron states ν(ɛ), 

which are obtained using a Gaussian form of the DOS. 

In the second step we use the DOS to calculate numerically 

the distribution function f(ɛ) using the eq.3 in the 

limit t ≫ τin. In the third step the normalized nonlinear 

conductivity σnl/σD is calculated using the eq.1 for 

different electric field. The results is compared with the 

normalized resistance Rxx/R0. The inelastic scattering 

time τin is found from the best fit between the normalized 

resistance Rxx/R0 and the calculated normalized 

conductivity σnl/σD. 

IV. RESULTS AND DISCUSSION 

At small magnetic fields the separation between Landau 

levels ¯hωc is less than the effective width of the levels 

Γ = ¯h/τq. At low temperatures the width Γ is predominantly 

determined by the elastic impurity scattering 

of the 2D electrons. At the small magnetic field the 

density of states ν(ɛ) is weakly oscillating with the energy 

ɛ, making the spectral diffusion to be also a weakly 

modulated function of the energy. We consider a regime 

of high temperatures: kT ≫ ¯hωc. In this regime the 

electron-electron interaction is proposed to be the dominant 

mechanism of the inelastic electron relaxation at 

relatively low T[3]. The theory predicts the temperature 

dependence of the inelastic scattering rate 1/τin to be 

proportional to square of the temperature T 2 . 

Figure 2 shows the comparision between the experimental 

results and numerical simulation of theory. The 

results are in good agreement with the theory. 

244 

Figure 2: (Color online), (a) Dependence of normalized 

longitudinal resistance Rxx/R0 on electric current at different 

temperatures as labeled. Solid lines are experimental 

curves. Symbols present result of numerical calculations 

of the resistance. (b) Dependencies of normalized 

density of states ˜ν(ɛ) =ν(ɛ)/ν0 and electron distribution 

function f on electron energy ɛ counted with 

respect to Fermi energy μ. The quantum scattering time 

τq=3.42 (ps) is obtained from comparison of the resistance 

at magnetic field B=0.2 (T) with eq.(1). The distribution 

function is solution of eq.(3) using the DOS, 

the temperature and the electric current shown in the figure. 

(c) Dependence of inelastic scattering time τin and 

quantum scattering time τq on temperature. B=0.2 (T); 

sample N2. 


This work was supported by National Science Foundation: 

DMR 0349049 and by Russian Fund for Basic Research, 

project No.08-02-01051 

REFERENCES 

[1] A. A. Bykov, Jing qiao Zhang, Sergey Vitkalov, 

A. K. Kalagin and A. K. Bakarov. Phys.Rev.B, 

72:245307, 2005. 

[2] Jing qiao Zhang, Sergey Vitkalov, A. A. Bykov, 

A. K. Kalagin and A. K. Bakarov. Phys.Rev.B, 

75:081305(R), 2007. 

[3] I. A. Dmitriev, M.G. Vavilov, I. L. Aleiner, A. D. 

MirlinandD.G.Polyakov.Phys.Rev.B, 71:115316, 

2005.

Understanding the Effects of Aerosols in Cloud Microphysics in 

Coastal Urban Environments 

Nathan Hosannah and Jorge E. Gonzalez (Faculty Mentor) 

Mechanical Engineering Department 

City College / The City University of New York Graduate Center 

New York, United States of America 

Email: nhosannah@gmail.com , gonzalez@me.ccny.cuny.edu 

Abstract — Several studies have found evidence of 

warm-season rainfall increases over and downwind 

of cities. This induced precipitation (PCP) has been 

attributed mostly to induced updraft of warm air 

masses. Aerosols are abundant in urban environments 

and it has been hypothesized that they play a 

role in the water balance of cities. High concentrations 

of cloud condensation nuclei (CCN) may induce 

precipitation in humid urban environments. 

However precipitation may be reduced due to excess 

CCN’s or by large aerosols. The objective of 

the present research is to improve our understanding 

of the role of aerosols in cloud processes of 

complex coastal urban environments. 


There is increasing evidence that anthropogenic 

activities can significantly alter precipitation processes. 

Urbanization is an example of anthropogenic 

forcing. Recent studies [1] provide evidence that 

urban environments can modify or induce precipitation 

under a specific set of conditions. In the past 30 

years, several observational and climatological studies 

have found evidence of warm-season rainfall 

increases of 9%–17% over and downwind of major 

urban cities [2]. This work shows that historical 

records indicate an increase in the frequency of intense 

rain showers in recent decades in correlation 

with the population growth. 

A. AEROSOLS 

Aerosols may play an important role in precipitation 

increase. Our research is aimed to understand how 

aerosols may impact precipitation in NYC. Aerosols 

in the atmosphere have direct and indirect effects on 

the Earth's climate (Figure 1). The direct effect is 

related to their optical properties. Aerosols scatter 

and/or absorb solar and terrestrial radiation. The level 

of scattering and absorption depends on their physical 

and chemical characteristics. Consequently, aerosols 

act to modify the Earth's radiation budget and 

thus influence the warming/cooling of the planet. 

245 

B. MICROPHYSICS AND IMPACTS ON PCP 

Microphysical processes are cloud processes 

(growth, evaporation, etc.) which take place on the 

scale of the individual aerosol (polluted particle) or 

precipitation particle as opposed to the scale of the 

visual cloud. These processes include collision, coalescence, 

and droplet growth. Aerosols may either 

enhance or reduce urban precipitation, depending on 

their composition and particle size. Cloud microphysics 

is affected by changes in the aerosol concentration. 

High concentrations yield more cloud water, 

but less rainwater in the atmosphere. 

Figure 1: Effects of aerosols on clouds, and 

microphysical processes (Image by Dr. S. N. Tripathi: 

Department of Civil Engineering Indian Institute 

of Technology)

II. HYPOTHESIS 

Based on analysis of background information, it can 

be inferred that aerosols may influence (enhance or 

decrease) precipitation in urban environments without 

added convection. To test this hypothesis, data of 

particle size distributions and precipitation levels 

from ground and satellite observations can be analyzed, 

and be ingested into refined mesoscale models 

with improved microphysics model (i.e. RAMS or 

WRF). 

III. MODELLING 

Mesoscale models can be used to interpret data 

from observations and to improve our understanding 

of microphysical processes. Through modeling, 

optimum conditions for precipitation to occur 

can be inferred with simulated or observed in-situ 

data particle size distribution and composition 

obtained from satellite and ground observations. 

The Regional Atmospheric Modeling System 

(RAMS), for example, contains a cloud microphysics 

component that will be used to simulate 

precipitation in a coastal urban environment [3]. 

Idealized simulations utilize the extreme effects of 

the microphysical parameterizations to expose the 

impacts. The results suggest that cloud microphysics 

impact quasi-equilibrium temperature and moisture 

profiles substantially, but the relative humidity 

is only weakly affected [4]. Figure 2 shows how 

CCN size distribution may vary during clear skies 

(straight line), and cloudy skies (single dash curve, 

and bold solid curve). 

Figure 2: Variation of particle size distribution [5]. 

Figure 3 shows results from a RAMS PCP simulation 

using the data from Figure 2. This work is expanding 

upon the work by Comarazamy et al. for the case of 

New York City to investigate the role of aerosols in 

PCP in complex urban coastal environments. 

246 

Figure 3: Simulation of PCP in polluted (right) and 

non-polluted air (left). Rainwater mixing ratio in 

polluted air is less than a third of that in clear air [5]. 


This work was financially supported by the 

NASA COSI and NOAA CREST programs at 

the City College of New York. 

REFERENCES 

[1] J. Sheperd, H. Peirce, & A. Negri. Rainfall 

Modification by Major Urban Areas: Observations 

from Space Bourne Rain Radar on 

the TRMM Satellite. Journal of Applied Meteorology, 

Volume 41 pages 689–701, 2002. 

[2] F. Huff and S. Changnon. Precipitation modification 

by major urban areas. Bulletin 

American Meteoroligcal Society, Volume 

54, 1220 – 1232, 1973. 

[3] S. Saleeby and W. Cotton. A Large-Droplet 

Mode and Prognostic Number Concentration 

of Cloud Droplets in the Colorado State 

University Regional Atmospheric Modeling 

System (RAMS). Part I: Module Descriptions 

and Supercell Test Simulations. Journal 

of Applied Meteorology, Volume 43 

pages 182–195, 2004. 

[4] W. Grabowski. Cloud Microphysics and the 

Tropical Climate: Cloud-Resolving Model 

Perspective. Journal of Climate, Volume 13 

pages 2306 – 2322, 1999. 

[5] D. Comarazamy, J. Gonzalez, C. Tepley, S. 

Raizada, and V. Pandya. The effects of Atmospheric 

particle Concentration on Cloud 

Microphysics over Arecibo. 2006.

Derivation of a Water Potential that Parameterizes Cooperative Effects 

Abstract - We propose a method for keeping track of 

positions, distances and angles of water molecules 

during a simulation. Using FORTRAN 90, we have 

produced a program that keeps track of atoms by 

listing them in terms of adjacency matrices. We read 

in coordinates from an xyz data file. Molecules are 

rotated using Euler angles and translated using a 

displacement vector. At the current stage the 

program calculates distances of relative atomic 

positions, creates adjacency relationships of 

molecules, outputs a graph of radial and angular 

distributions of molecules and an adjacency matrix 

for each atom. We also have a Monte Carlo 

algorithm. We find that it is necessary to devise new 

potentials for water that include parameterization of 

cooperative effects. It has been observed that the 

potential for hydrogen bonding varies with number of 

donor/acceptor neighbors to a given central pair of 

water molecules. The final program will allow us to 

simulate extended systems at nearly quantum 

mechanical accuracy. 

INTRODUCTION 

Philipa A. Njau and Michael E. Green 

City College of New York of the 


New York, USA 

phnjau@gmail.com 

Water models are necessary as water surrounds other 

molecules in biological chemistry. In heterogeneous 

solutions one cannot use the dielectric of water for 

simulations. There are about fifty potentials in the 

literature for modeling water. Which is used depends 

on the kind of accuracy you are looking for and the 

available computer resources. For studying 

molecular clefts and surfaces and therefore for the 

most important applications in biophysics, there is a 

need for a potential that parameterizes cooperative 

effects. Previous studies by Green and Znamenskiy 

in our group showed that hydrogen bond strength 

varies with the number of neighbors a given central 

pair of water molecules has [1,2,3,4] . Green and 

Znamenskiy have already started the work of 

producing such a potential. The idea is that “the 

potential of interaction of two water molecules is a 

function of the number of donor and acceptor 

neighbors” [1,2] . In this work, lengths and angles for 

36 different clusters were ‘scanned’ using density 

functional theory for each possible arrangement of 

donor acceptor hydrogen bonds to a given central 

hydrogen bonding pair. Four numbers (defined 

247 

below), K1K2K3K4, where K1 and K4 can be 1 or 2 

and K2 and K3 can be 0, 1 or 2 defined a cluster. As a 

result there is a possibility of 2x3x3x2=36 distinct 

clusters (not sixty-four), due to symmetry (see figure 

1). K1= the number of times the central 

Figure 1: A 2222 cluster. Reprinted from 

Znamenskiy and Green 1 

donor acts as a donor; K1 can donate one more time. 

Hence it 

has values of 1 and 2, not 0, since it is already the 

central donor, K2=number of times the central donor 

water molecule is an acceptor, for 0, 1, or 2 bonds. 

The central acceptor K3 can be a donor for 0, 1, or 2 

bonds and the acceptor K4 can accept 1 or 2 bonds but 

not 0. For example, an isolated pair has 1001 where 

the central donor donates once and the acceptor 

accepts once; the cluster with the maximum number 

of neighbors is 2222 (figure 1). A graph (figure 2) of 

energy versus O-O distance was generated; let K1 - K2 

– K3 + K4 = KN; KN shows the different distanceenergy 

graphs that are found 1 . This turns out to be a 

key index, giving a first order correction (up to ±3kT 

from the TIP3P curve) to the potential. The task is to 

somehow include this parameter in a derivation of a 

potential; this way cooperative effects will be 

included. A second order effect would allow the 

potential to vary with an angle: this has yet to be 

included. However, so far there is enough data to 

know that we can ignore the angles, as the 

computational time will be greatly extended, with 

little effect on the results, as the energy involved is 

less than thermal energy. The graph shows that

increase in KN correlates with decrease in electron 

density in the bond. Moreover, the energy ratio of 

variation with KN to thermal energy, a total range of 

6kT, suggests that it is worth pursuing this potential. 

We want a set of parameters that describes the 

number of types of neighbors. From the energydistance 

curve we can describe a potential for a given 

KN . 

Figure 2: Graph of Energy of H-bond versus O-O 

distant for all 36 clusters. Reprinted from 

Znamenskiy and Green 1 

METHODS 

FORTRAN 90 has been used for the program. The 

Cartesian coordinates of atoms are read from a data 

file. Adjacency relationships are inferred by 

functions that perform standard calculations of inner 

product vector operations. Adjacency relationships 

are established and a table of adjacency is output. We 

also have a Monte Carlo algorithm set up for a 

simulation employing a dummy potential for the time 

being. 

RESULTS 

We have set up a framework for a simulation. 

The program now runs, and we are proceeding to 

insert the new potential for tests on standard 

systems, so far water. We will soon add other 

potentials that include proton transfer so that we 

can track, for example, pKa values. 

CONCLUSIONS 

We have created a program that keeps track of 

adjacent atoms in a given simulation. Once we insert 

the potential we will incorporate it into the program. 

In the meantime we use a dummy potential to test our 

program. If these routines work well in a standard 

248 

molecular dynamics or Monte Carlo simulation then 

we will add proton transfer and salt bridge potentials, 

now under development, prior to applying it to some 

interesting system such as an ion channel or other 

large scale simulation. We are in the process of 

getting this program to read data generated from 

studies done by Znamenskiy and Green. The data are 

the points on the graph (figure 2). This program 

should be able to read the data and, as its output, 

produce a simulation. If we have a good potential, our 

simulations should be able to reproduce 

experimentally observed thermodynamic properties 

of water. If we calculate accurately the heat capacity 

of water, that will be a severe test, as it is a second 

derivative of the partition function. 


We thank Vasiliy Znamenskiy for useful 

scientific discussions. This work has been 

supported in part by PSC-CUNY grants, and by 

a grant of computer time from the 

Environmental Molecular Science Laboratory of 

Pacific Northwest National Laboratory, a DOE 

facility. 

REFERENCES 

[1] Green M.E., Znamenskiy V. Quantum 

Calculations on Hydrogen Bonds in Certain 

Water Clusters Show Cooperative Effects. J 

Chem Theory Comp. (2006).3, 103-114 

[2] V.S. Znamenskiy and M.E. Green, 

Topological changes of hydrogen bonding of 

water with acetic acid: AIM and NBO studies. J. 

Phys. Chem. A 108, 6543-6553 (2004) 

[3] J. Lu, J. Yin, and M.E. Green, A model for 

ion channel voltage gating with static S4 

segments, Ferroelectrics, 220, 249-271 (1999) 

[4] J. Lu and M.E. Green, Simulation of water in 

a small pore: Effect of Electric field and density 

II: Immobilized Molecules, J. Phys. Chem. B 

103, 2776-2780 (1999)

REAL-TIME VISUALIZATION AND 

QUANTIFICATION OF GLIAL PROGENITOR 

AND GLIOMA CHEMOTACTIC MIGRATION 

Richard A. Able Jr. 1 and Dr. Maribel Vazquez 2 

1 Department of Biochemistry, the Graduate Center CUNY 2 

2 Department of Biomedical Engineering, the City College of New York 

New York, NY, USA 

Rable00@ccny.cuny.edu 

Abstract - 

Previous research has indicated that progenitor 

precursor cells have distinct migration patterns 

in brain tissue, which may be induced mainly by 

specific cytokines. Our experiments analyzed and 

quantified the preferential migration of tumor 

cells towards four specific growth factors 

concentrations. Using transwell assays, the 

chemotactic migration of the Ntva-mouse 

derived glial progenitor cells was compared to 

the migration of cells derived from a Human 

Glioblastoma multiforme cell line (U-87MG). 

This investigation illustrated that glial 

progenitor motility approached zero at higher 

ligand concentrations, while gliomas remained 

motile. In order to further investigate the 

directionality of migration, a new set of 

experiments made use of a microfluidic system in 

which to monitor chemotaxis of individual cells. 

Introduction 

Brain tumors can be highly aggressive and 

debilitating for many patients and lead to an 

untimely death in just a few months. 

Unfortunately, due to the location of many brain 

tumors, therapy with ionizing radiation, 

chemotherapeutic agents and surgery has limited 

rewards (1). Furthermore, the ability of cancer 

cells to undergo metastasis- invasion and 

migration of new tissue- makes them even more 

illusive and difficult to treat. 

Here, glial progenitor cells (PDGF, Ras, 

LacZ), have been engineered to perform special 

functions. RCAS-PDGF infected cells are driven 

by a PDGF autocrine loop and can not detect any 

exogenous PDGF gradients. The RCAS-Ras 

infected cells’ downstream Ras pathways are 

activated independently of its receptors. And, the 

RCAS-LacZ cells, which express markers for the 

transgenic �-galactosidase gene, do not actually 

249 

have any experimentally-induced mutations to its 

growth factor receptors, and is used as the 

control cell line. The U87 Malignant Glioma cell 

line is a human glioblastoma; astrocytoma type 

of epithelial morphology. This grade III tumor 

was purchased from ATCC and was used for 

comparative purposes. 

Methods 

Boyden Migration Assay 

The migration of cells in response to signaling 

from different concentrations of growth factors 

was analyzed via transwell assay as described 

previously (2). Growth factors were added to the 

lower well of the 24-well Boyden chamber 

Falcon Companion TC Plate (BD Bioscience, 

MA). An incubation time of 12 hours at 37 0 C 

was used for every assay. The nuclei of cells that 

migrated to the underside of the filter were 

counted using an inverted light microscope under 

20x magnification (Nikon TE300, Morrell 

Instruments, NY). 

Channels used for this study were 1.5cm in 

length, and approximately 100�m by 100�m in 

cross-section. Channels were filled with a 

solution of 2�g/mL of Matrigel® (BD 

Bioscience, MA) containing a desired cytokine 

concentration. A 10�L volume of Matrigel was 

pipetted into the loading reservoir, termed the 

Northpole, until the entire volume was seen 

exiting the opposite reservoir, designated the 

Southpole. Systems were then incubated at 37 o C 

for one hour to allow polymerization. Afterwards, 

a rectangular section of PDMS was cut out 

around the Southpole to generate a larger 

reservoir. A cell solution having a density of 

10 6 /mL was pipetted into this reservoir.

Immediately, the system was imaged using an 

inverted microscope to verify the locations of 

viable cells at the reservoir-�Lane interface and 

then incubated at 37 o C. 

Results 

Boyden experiments show all three progenitor 

cell lines to have single digit migrating cells at 

the 12hr time point accompanied by a 

progressive increase in the number of migrating 

cells and an increase in distance traveled, as time 

increases. GPC-Lacz, after a 36hrs incubation 

time had ~59 cells invade the matrix. Of the 59 

cells to penetrate the matrix 55/59 migrated a 

distance found between the interface and 200�m. 

The other 4/59 was found between 200�m and 

400�m having a maximum extension at ~256�m. 

GPC-PDGF, after a 36hrs incubation time had 

~53 cells invade the matrix. Of the 53 cells to 

penetrate the matrix 47/53 migrated a distance 

found between the interface and 200�m. The 

other 5/53 was found between 200�m and 


GPC-Ras, after a 36hrs incubation time had ~50 

cells invade the matrix. Of the 50 cells to 

penetrate the matrix 42/50 migrated a distance 

found between the interface and 200�m. The 

other 8/50 was found between 200�m and 


Further, cells were exposed to 10pM 

TGF-�. GPC-PDGF had ~125 cells invade the 

matrix in response to 10pM TGF-� after 45hrs. 

100/125 was in the

Surface Enhanced Raman Spectroscopy of Pyridine on 

CdSe/ZnBeSe Quantum Dots Grown by Molecular Beam Epitaxy 

Abstract — Using Surface Enhanced Raman 

Spectroscopy (SERS), we observed large Raman 

5 6 

enhancements (10 -10 ) for pyridine molecules 

adsorbed on a II-VI semiconductor CdSe/ZnBeSe 

sample of uncapped self-assembled quantum dots 

produced by molecular beam epitaxy. When a 

monolayer of pyridine is adsorbed on these structures, 

excitation at 488 nm produces intense Raman 

spectra a very large enhancement of the A 1 and B2 

modes. Examination of individual Raman frequencies 

provides information as to the mode of attachment 

of the molecules to the CdSe surface. These 

results demonstrate that the CdSe quantum dot 

system provides a high degree of molecular specificity 

and large Raman enhancement factor, enabling 

sensitive detection and identification of SERS 

active molecules. 


Surface enhanced Raman scattering (SERS) has been 

found to be of value in surface and interface Raman 

studies in metals. The SERS effect is characterized 

by an enormous increase in the Raman intensity by 

many orders of magnitude for species adsorbed on 

rough metal surfaces, and the technique displays a 

number of important advantages: sensitivity, selectivity, 

non-destructive detection, and feasibility for insitu 

studies and on metal substrates. The SERS effect 

has been shown to arise from a product of surface 

plasmon and charge transfer resonances 1 . 

In recent work we have observed SERS from III-V 

(InAs/GaAs) semiconductor quantum dots 2 . This 

suggests a technique for sensitive, high-resolution 

study of the interaction of adsorbate molecules with 

quantum dot surfaces. Furthermore, the technique of 

molecular beam epitaxy (MBE) is useful in constructing 

and testing of solid state surface, made 

under controlled conditions. In this work, we report 

on the observation of surface enhancement of a Raman 

signal from pyridine molecules adsorbed on a 

self-assembled CdSe quantum dot array produced by 

molecular beam epitaxy (MBE). The high degree of 

spectral selectivity, coupled with the high sensitivity 

Richard Livingstone and John Lombardi 


New York, New York, 10031 USA 

Email: livingstonerm@aol.com 

251 

afforded by the rather large enhancement factors, 

makes such systems good candidates for possible use 

in detecting and identifying SERS active molecules. 


The quantum dot (QDs) assemblies were grown by 

MBE on GaAs (001) substrates in an ultrahigh 

vacuum (UHV) Riber system. This was followed 

by the growth of a ZnBeSe epilayer on which the 

CdSe quantum dots were deposited. The entire 

growth process was monitored in situ by reflection 

high-energy electron diffraction (RHEED). 

Samples were removed from the MBE growth 

chamber, cut into smaller rectangles 

(approximately 3mm) and stored in liquid nitrogen 

to prevent possible ripening until used. One of the 

cut pieces of the quantum dot samples would then 

be removed allowed to attain room temperature 

conditions, and then immersed in a small portion 

(10ml) of the liquid organic substance for 20 

minutes. The sample was sonicated in commercial 

acetonitrile solution for 5 minutes to remove 

excess liquid and mounted near the entrance slit of 

a SPEX (0.75 meter) model 1401 double 

monochromator and slit width 200 nm. Light from 

a Spectra Physics Model 2560 argon ion laser was 

focused on to the sample. All spectra reported 

below were taken at 488 nm. Typical power levels 

at the sample were measured to be approximately 

30 mW. 

III. RESULTS 

Figure 1 shows the SERS spectrum of the pyridine 

molecules adsorbed on the CdSe quantum dots, together 

with the Raman spectrum of the quantum dots 

sample before the deposition of the molecule and the 

Raman spectrum of the pyridine solution. Numerous 

lines characteristic of pyridine appear, as can be seen 

by comparison with the normal Raman spectrum of 

pyridine liquid. These are listed in the table, along 

with the lines observed on Ag. We also present a 

brief summary of the assignment of the normal modes 

3 of pyridine, including their Wilson number and 

symmetry in C2v. On the quantum dot surface most of

the lines correspond to lines previously observed 

either in the liquid or on a Ag surface. Note that in 

addition to the expected enhancement of several a1 

modes, the bands at 665 (b2), 728 (b1) and 946 (b1) 

cm -1 are also considerably enhanced relative to the 

liquid spectrum. The line at 728 cm -1 suffers from 

interference from the bare quantum dot line at 742 

cm -1 , and should therefore be considered questionable. 

The same is true for the a1 line at 897 cm -1 , 

while the line at 1221 cm -1 is sufficiently distinct 

from the QD line at 1203 cm -1 to be acceptable. The 

observation of relatively intense non-totally symmetric 

modes is usually diagnostic of a charge-transfer 

contribution to the observed enhancement, most 

probably from the quantum dots to the molecule. 

Intensity (Arbitrary Units) 

605 

Raman of CdSe Quantum Dots 

SERS of Pyridine adsorbed on CdSe Quantum Dots 

Raman of Pyridine 

653 

665 

728 

708 753 812 

742 

809 897 

993 

923 

946 

887 

945 

887 

1004 

1236 

1069 

1150 

1192 

600 700 800 900 1000 1100 1200 

Wavenumbers (cm-1) 

1202 

1203 

1219 

1221 

Fig 1: Normal Raman and SERS spectrum of 

pyridine on Ag and CdSe quantum dots 

excited at 488 nm. 

Wilson # 

C2v 

Symm 

SERS 

Pyridine 

on Ag 

SERS 

Pyridine on 

CdSe QDs 

6a a1 623(mw) 616(w) 

6b b2 649 (w) 665(m) 

698 715(w) 

4, QD b1 753(w) 728(m) 

809(m) 

10a, QD a1 877(vw) 897 (s) 

923(w) 

17b b1 940 (w) 946 (w) 

1 a1 1005(vs) 1004(vs) 

12 a1 1034(s) 

18a,18b a1,b2 1063(w) 

15 b2 1148(vw) 

QD 1202 

9a a1 1214(m) 1221(s) 

252 

Table showing Pyridine lines as observed in Normal 

Raman, SERS on a Ag surface and on CdSe/ZnBeSe 

self-assembled quantum dots. 


The observed Raman spectrum shows several 

differences from the normal Raman spectrum, and 

is closer in some ways to the SERS observed on 

Ag nanoparticles. Among other things, the 

prominence of non-totally symmetric lines 

indicates the importance of charge-transfer 

contributions to the overall enhancement. These 

enhancements are far from the region of surface 

plasmon resonance for CdSe and so the magnitude 

of enhancement must be attributed to some other 

resonance. We suggest that this is likely charge 

transfer resonance between the molecule and the 

quantum dot. 


This work was supported by the MARC/RISE 

Fellowship, National Science Foundation under 

Cooperative Agreement No. RII-9353488, grant 

No. CHE-0091362, CHE-0345987. We are also 

indebted to the National Institute of Justice 

(Department of Justice award No. 2006-DN-BX- 

K034) 

REFERENCES 

[1] Lombardi, J. R.; Birke, R.L.; Lu, T.; Xu, J., J. 

Chem. Phys.. 1986, 84, 4357. 

[2] Quagliano, L., J.Am.Chem.Soc., 2004, 126, 7393- 

7398.. 

[3] Lombardi, J.R.; Birke, R.L Foucault R; Vivoni A, 

J.Phys.Chem. B, 2003, 107, 5547-5557.

Chapter 3 

Environmental Science and Energy

Using RFID Technology in Pedestrian Navigation 

for Information Transmission and 

Data Communication Recording 

Qing Fu and Guenther Retscher (Faculty Mentor) 

Institute of Geodesy and Geophysics 



Email: fu@mail.tuwien.ac.at 

or gretsch@pop.tuwien.ac.at 

Abstract — The development of pedestrian 

navigation and guidance services are 

challenging research topics and have been 

investigated by several researchers worldwide. 

Most of the developed systems thereby rely on 

the use of satellite positioning (GNSS), 

sometimes also in combination with other 

sensors and positioning methods. In our 

approach in the project UCPNAVI (Ubiquitous 

Carthograpy for Pedestrian Navigation) active 

RFID (Radio Frequency Identification) in 

combination with GNSS and INS (Inertial 

Navigation Systems) are employed for 

positioning. RFID can be employed in areas 

where no satellite positioning is possible due to 

obstructions, e.g. in urban canyons and indoor 

environments. This paper presents our approach 

for positioning of a pedestrian by using RFID. 


Radio-frequency identification, or RFID for 

short, is a technology for data transmission via 

radio waves without line of sight contact. 

Nowadays, the technology of RFID is also used 

for positioning, because the location estimation 

can be based on RSSI (short for received signal 

strength indication) which is a measurement of 

the power present in a received radio signal. The 

receiver can compute its position using various 

methods based on RSSI (e.g. a range-based 

positioning system based on trilateration, 

modeling of indoor positioning systems based on 

location fingerprinting). Totally, three different 

methods have been employed, i.e., cell-based 

positioning, trilateration using ranges to the 

surrounding RFID tags deduced from received 

signal strength measurements and RFID location 

fingerprinting. In our experiment for the 

positioning of a pedestrian from the underground 

255 

station “Karlsplatz” to one of the offices in the 

building of the Vienna University of Technology 

on Gusshausstrasse 27-29 these three methods 

have been combined. The results showed that 

these approaches using RFID are suitable to 

navigate the user (see [1]). In the following the 

principles and methods of the positioning using 

active RFID would be described briefly. 

II. POSITIONING USING ACTIVE RFID 

Thanks to the RFID technology, data can be 

transmitted from RFID tags to a reader via 

radio waves without line of sight contact. The 

transmitted data might include the ID and the 

information of the position of the RFID tags. In 

the presented work only one reader and a large 

number of active tags are used. The moving 

object is equipped with a RFID reader and the 

unmoving objects in the surrounding 

environment are equipped with RFID tags. The 

user is equipped with a portable RFID reader 

(e.g. a reader in form of a PCMCIA card that 

can be plugged into a laptop). If the user moves 

inside the surrounding of the RFID tags, the 

tags’ ID, signal strength RSSI, known location 

and time can be obtained. The position is a 

function f as shown in (1): 

position = f (ID, RSSI, known location) (1) 

at a certain time t. Then the position of the user 

can be calculated by using various methods 

based on RSSI and known location of the tag 

with a certain ID. The measured data is 

recorded in a database. Three methods, i.e., 

cell-based positioning, trilateration and RFID 

location fingerprinting, are employed 

depending on the current enviroment of the user 

(see Figure 1).

Figure 1: Information transmission and data 

communication recording for the active RFID 

positioning system 

1. CELL-BASED POSITIONING 

Cell-based positioning is an algorithm to 

determine the location of the user in a cell 

around the RFID tag with a size defined by the 

maximum range of the RFID signals. The 

achievable positioning accuracies depend on 

the size of the cell, i.e., up to 20 m using our 

long range RFID equipment. Therefore this 

method is only well suited for areas where 

accuracy is not that import, such as urban 

outdoor environment. 

2. TRILATERATION 

Trilateration is a method of determining the 

absolute positions of moving objects (e.g. a 

user with a portable RFID reader) using the 

know location of two or more unmoving 

objects (i.e., tags), and the range between the 

moving object and the unmoving objects. To 

accurately and uniquely determine the 

absolute position of a RFID reader on a 2D 

plane two ranges are necessary. Trilateration 

achieves a positioning accuracy of � 2-3 m 

and can be employed in the transition zone 

between outdoor to indoor (e.g. at the entrance 

of a building). 

3. RFID LOCATION FINGERPRINTING 

The principle of operation of RFID location 

fingerprinting is similar to that used in WiFi 

networks. Here the signal strength is used 

directly to obtain the location of the user. 

Positioning accuracies on the 1 to 2 m level 

can be achieved. Fingerprinting can therefore 

be used in indoor environments as it provides 

the highest level of positioning accuracy. 

256 

4. INTELLIGENT INTEGRATION 

The most challenging task is the selection of one 

of the positioning methods in the current 

environment of the user by using an intelligent 

software package. For this purpose, the use of 

knowledge-based systems will be investigated. 

III. COMPARISON OF THE METHODS 

As mentioned in the introduction all the three 

methods of positioning were used for the 

positioning in a complex urban and indoor 

environment. Table 1 shows a comparison of 

the methods with their suitable enviroment 

and achievable positioning accuracy. 

Method Environment Accuracy 

Cell-based 

positioning 

Trilateration 

Location 

fingerprinting 

Outdoor � 20 m 

Transition 

zone 

� 2-3 m 

Indoor � 1-2 m 

Table 1: Comparison of the three methods. 


RFID tags transmit useful information such as 

ID, position and signal strength to the RFID 

reader. This information is recorded in a 

database and can be used for determination of 

the position of the RFID reader. Based on the 

principle of RSSI measurement three approaches 

could be employed for the positioning, i.e., cellbased 

positioning, trilateration and location 

fingerprinting. The test results showed that with 

a combination of these three methods and a 

knowledge-based selection it is possible to 

navigate a pedestrian in a complex urban and 

indoor environment. 


This research is supported by the research 

project P19210-N15 “UCPNAVI” founded by 

the Austrian Science Fund (FWF). 

REFERENCES 

[1] Fu Q., 2008. Active RFID for Positioning 

Using Trilateration and Location 

Fingerprinting Based on RSSI, in: Papers 

presented at the ION GNSS Conference, 

September 16-19, 2008, Savannah, Georgia, 

USA, CD-Rom Proceedings, 14 pgs.

Adaptive Boundary Element Methods Based on 

Accurate A Posteriori Error Estimation 

Samuel Ferraz-Leite and Dirk Praetorius (Faculty Mentor) 

Institute for Analysis and Scientific Computing 



Email: {Samuel.Ferraz-Leite,Dirk.Praetorius}@tuwien.ac.at 

Abstract — The boundary element method is one strategy to 

solve partial differential equations of elliptic type. As model 

problem, we consider the computation of the charge density φ 

and the capacitance C of a thin electrified plate. We introduce 

an intelligent algorithm based on certain error estimators. The 

mesh-refinement is steered automatically in the sense that the 

mesh is locally refined, where the error appears to be large. Numerical 

experiments show that the new method reveals the optimal 

order of convergence and is therefore significantly faster 

than a standard uniform approach. All mathematical results are 

valid in a quite general framework and thus apply to a large 

problem class, including, e.g., the Laplace problem, the Stokes 

system, and the Lamé equation. 


Computer aided simulations – and therefore usually the 

solution of partial differential equations (PDEs) – have 

established themselves as cost and time efficient methods 

in research and development. 

Certain PDEs of elliptic type can be solved by the socalled 

boundary element method (BEM). Compared to 

the more popular finite element method (FEM), the essential 

disadvantage of BEM is that it leads to large dense 

matrices. Mathematical strategies to overcome this disadvantage, 

e.g. fast multipole methods, have been developed 

and are usually employed by engineers nowadays. 

Besides the fact that one only has to discretize the boundary 

of the simulation domain, one key advantage of BEM 

is its generically higher order of convergence when compared 

to FEM. With respect to the mesh-size h of the 

discretization Th of the simulation domain optimal convergence 

for lowest-order approximations reads: 

– FEM: O(h) as h → 0, 

– BEM: O(h3/2 ) as h → 0. 

However, these convergence rates are only observed 

if the unknown solution is sufficiently smooth. This is 

generically not the case in practice. One possibility to recover 

the optimal order of convergence is to estimate the 

simulation error, and to refine the spatial discretization 

only locally, where the error appears to be large. 

In the context of BEM, only few a posteriori error estimators 

and adaptive strategies have been proposed in 

the literature. All of them imply a significant implementational 

and computational overhead. In the following, 

257 

we introduce a simple and efficient approach of practical 

relevance. 

II. MODEL PROBLEM 

We consider the Dirichlet screen problem 

Δu =0 in R 3 \ Γ, 

u = f on Γ ⊆ R 2 ×{0}, 

u = O(�x� −1 (1) 

) as x →∞, 

which describes the potential u away from an electrified 

thin plate Γ loaded with potential f, see [1]. This problem 

is equivalent to Symm’s integral equation 

Vφ(x) :=− 1 

� 

1 

4π Γ �x − y� φ(y) dsy = f(x). (2) 

Then, φ is the charge density on the plate Γ which 

is known to show singularities along the edges. Of 

special interest in physics is the so-called capacitance 

C = − 1 

� 

4π Γ φds, where the charge density φ now 

solves Symm’s integral equation (2) with f =1. 

III. MAIN RESULTS 

A. A POSTERIORI ERROR ESTIMATION 

The h-h/2-strategy is a basic technique for the a posteriori 

error estimation, well-known from the context of 

ordinary differential equations. In [2], this approach is 

proposed in the context of BEM. Let φ denote the exact 

(but in general unknown) solution of (2). One then considers 

ηH := �φh − φh/2� (3) 

to estimate the error �φ − φh�,whereφh is the Galerkin 

solution with respect to a mesh Th and φ h/2 is the 

Galerkin solution for a mesh T h/2 obtained from a uniform 

refinement of Th. We stress that ηH is always a 

lower bound 

ηH ≤�φ− φh�, (4) 

even with known constant 1. Under the saturation assumption 

�φ − φh/2� ≤σ �φ − φh� with some constant 

σ ∈ (0, 1), there holds 

�φ − φh� ≤ 

1 

√ 1 − σ 2 ηH. (5)

This means, ηH also gives an upper bound for the error. 

However, for boundary element methods, the energy 

norm �·�is non-local and thus the error estimator ηH 

does not provide information about the local error. Recent 

localization techniques from [3] allow to replace the 

energy norm by mesh-size weighted L 2 -norms. For instance, 

the estimator μH defined by 

μ 2 H 

= � 

T ∈Th 

μ 2 H,T 

:= � 

T ∈Th 

hT �φh − φh/2� 2 L2 (T ) , (6) 

where hT denotes the diameter of an element T ∈Th, is 

equivalent to ηH, see [4]. 

B. ADAPTIVE ALGORITHM 

Based on the error estimators ηH and μH from the previous 

section, we now introduce an adaptive algorithm. 

With a fixed parameter θ ∈ (0, 1) as well as an initial 

mesh Th, our strategy reads as follows: Until ηH is sufficiently 

small, do: 

1. Refine Th uniformly to obtain Th/2. 2. Compute discrete solutions φh and φh/2 as well as 

corresponding error estimators ηH and μH. 

3. Find minimal set M⊆Th such that 

θμ 2 H = θ � 

μ 

T ∈Th 

2 H,T ≤ � 

μ 

T ∈M 

2 H,T (7) 

4. Refine T ∈Mto obtain new mesh Th. 

IV. NUMERICAL EXPERIMENTS 

Figure 1 shows the discrete charge density φh computed 

over an adaptively generated mesh Th which discretizes 

an L-shaped plate. The solution shows strong singularities, 

i.e. peaks, at all edges and the convex corners of the 

simulation domain. Our algorithm leads to a well aligned 

mesh showing refinements towards the edges, thus resolving 

the singularities efficiently. 

Figure 2 shows the true error �φ − φh� as well as the 

error estimators ηH and μH in the uniform and adaptive 

case. All quantities are plotted over the number of boundary 

elements N. In the double logarithmic plot the convergence 

rate is the slope of a straight line. We stress 

that for uniform meshes the equivalence h ∼ N −1/2 implies 

that the optimal order of convergence is O(N −3/4 ). 

A uniform approach only reveals a convergence order of 

O(N −1/4 ) due to the singularities of the unknown solution 

φ. Our proposed adaptive algorithm, however, recovers 

the optimal order of convergence O(N −3/4 ). 

REFERENCES 

[1] V. J. Ervin, E. P. Stephan, and S. Abou El-Seoud. An 

improved boundary element method for the charge 

density of a thin electrified plate in R 3 . Mathematical 

Methods in the Applied Sciences, 13(4):291–303, 

1990. 

258 

Figure 1: Discrete charge density φh on L-shaped plate 

and enlargement of the solution at the lower left corner. 

error and estimators 

10 0 

10 −1 

10 −2 

10 1 

error (unif.) 

η H (unif.) 

μ H (unif.) 

error (adap.) 

η H (adap.) 

μ H (adap.) 

3/4 

10 2 

1 

number of elements 

Figure 2: Error and error estimators plotted over the number 

of boundary elements used. 

[2] S. Ferraz-Leite. A Posteriori Fehlerschätzer für die 

Symmsche Integralgleichung in 3D. Diploma Thesis 

(in German), Institute for Analysis and Scientific 

Computing, Vienna University of Technology, 

Vienna, Austria, October 2007. 

[3] C. Carstensen and D. Praetorius. Averaging 

techniques for the effective numerical solution of 

Symm’s integral equation of the first kind. SIAM 

Journal on Scientific Computing, 27(4):1226–1260 

(electronic), 2006. 

[4] S. Ferraz-Leite and D. Praetorius. Simple a posteriori 

error estimators for the h-version of the boundary 

element method. Technical report, ASC Report 

01/2007, July 2007. 

1 

10 3 

1/4 

10 4

Risk Habitat Megacity - Recycling Systems in Santiago 

de Chile 

Tahnee González, Klaus-Rainer Bräutigam, Helmut Seifert 

Forschungszentrum Karlsruhe, POB 3640, D-76021 

Karlsruhe, Germany 

Email: Tahnee.gonzalez@itc-tab.fzk.de 

Helmut.seifert@itc-tab.fzk.de 

Klaus-Rainer.Braeutigam@itas.fzk.de 

Abstract — Within the research initiative “Risk 

Habitat Megacity” a study about sustainability 

within the field of waste management for the city of 

Santiago de Chile will be work out. A flow chart of 

the current waste flows in Santiago is presented and 

recycling systems are briefly described, including 

the contribution of the informal primary collectors, 

who supply more than 90% of the total materials 

recycled in the city. 


Megacities are centres of complex and highly dynamic 

processes, such as population growth and 

density, change of land use, informal and formal 

economies, etc. However, their real impact on global 

environmental change is currently not well understood. 

How are interactions between these processes? 

How could the risks associated with megacities be 

turned into opportunities for a sustainable development? 

These are some of the questions that the research 

initiative “Risk Habitat Megacity” of the 

German Helmholtz-Association intended to answer. 

The initiative is interdisciplinary and integrative 

and it means to establish a conceptual framework 

based on three theoretical concepts: 

1. The concept of sustainable development: defines 

criteria towards basic sustainability 

goals. 

2. The risk concept: focus on extend and severity 

of the problems and their threat for future sustainability. 

3. The governance concept: focus on stakeholders 

and policy makers that are important 

for implementation of strategies. 

The initiative applies these three concepts, to several 

typical megacity issues, such as land use management, 

socio-spatial differentiation, energy system, 

transportation, air quality and health, water resources 

and services, and waste management. 

This research focuses on the Latin America Region, 

which is characterized by being the developing 

region more urbanized and with more wealth distri- 

259 

bution inequalities [1]. The pilot city chosen for the 

study is Santiago de Chile because it shows the main 

problems of large cities in the region, additionally 

international institutions like the Economic Commission 

for Latin America and the Caribbean 

(ECLAC/CEPAL) are located in Santiago and with 

cooperation of the diverse Chilean partners it would 

be feasible to transfer the developed conceptual 

framework to other large cities in this geographical 

area. 

II. OBJECTIVES 

As a part of the “Risk Habitat Megacity” study, a 

doctoral work has being proposed in the waste management 

application field. 

The general objective of this research is to develop 

a waste management concept in the Metropolitan 

Region of Santiago (MRS), based on the Integrative 

Helmholtz Sustainability Concept [2] considering the 

integration of the informal sector. 

This study is searching for answers to the following 

questions: 

1. Which is the role of the informal sector in the 

current waste management system? 

2. How sustainable is the current waste management 

situation in the MRS? 

3. Which technical systems will guarantee a 

more sustainable management of municipal 

solid waste? 

4. How can the informal sector be integrated into 

the formal waste labour market and technical 

systems? 

This paper focuses on the investigation of question 

number 1. 

III. METHODOLOGY 

In order to obtain information related with recycling 

systems and to understand the current situation of the 

informal sector, field research was carried out in 

Santiago de Chile. This research included technical 

interviews and visits to the most important stakeholders 

in waste management, such as municipalities

with recycling programs, industries, non governmental 

organizations and leaders of scavengers associations. 

IV. WASTE RECYCLING IN MRS 

A. BACKGROUND 

Recycling has taken place in Chile since 1970 [3], 

but more as an informal activity carried out by primary 

collectors (known in Chile as cartoneros) who 

collect valuable materials on the streets, than a formal 

organized action. 

B. RECYCLING SYSTEMS 

Figure 1 shows the diagram for the mass flow from 

the municipal solid waste in Santiago. About 90 % of 

this waste is correctly disposed of in one of the three 

landfills in the area (2.5 Million tonnes per year) (see 

flow 1). 

According to official data the recycling rate in 

2004 in the Metropolitan Region was 9% [4]. Currently 

formal recycling actions are developed only in 

five municipalities (MRS in total consists of 52 

municipalities), consisting basically on segregated 

collection of valuable materials which are separated, 

classified and given to production companies of 

paper and cardboard, plastics, glass and scrap, as 

most important ones. The contribution of these initiatives 

corresponds only to 1% of the total recycled 

(3,100 tons per year – flow 9 in Figure 4). 

Another formal initiative consists on several containers 

located in public places such as supermarkets, 

churches, parks, etc. where people can bring their 

materials and drop them off directly into the containers. 

It has been estimated that the contribution of 

these recycling scheme is 6.7% (19,000 tons per year 

– flow 3 in Figure 1) being glass the material mostly 

collected. 

Municipal 

Solid 

Waste 

2,8 

Mio. Ton 

pro year 

Bins 

Bags 

Drop off 

Systems 

Formal 

Collection 

1 

Landfills 

Informal 

Collection 

Paper 

Figure 1: Diagram Flow of Municipal Solid Waste 

in the Metropolitan Region of Santiago 

On the other hand, the largest contribution to recycling 

(92.3%) is carried out by the informal sector, 

with a total of 260,000 tons per year (flow 2 in Figure 

1). Figure 2 compares the contributions of the 

3 

4 

2 

260 

three recycling schemes in MRS. The importance of 

informal collectors is evident. 

100% 

90% 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 

Paper / 

cardboard 

Figure 2: Materials recycled in RMS with three 

different recycling systems 

V. CONCLUSIONS 

� Informal sector contributes with more than 

90% of the total recycling in MRS. 

� Integration of informal sector into formal 

waste management schemes can contribute to 

achieve higher recycling rates. 


I would like to acknowledge funding of the 

present PhD thesis given by the Initiative and 

Networking Fund of the Helmholtz Association. 

Additionally funding for the foreign stay in 

Santiago de Chile was given by the Karlsruhe 

House of Young Scientists. 

REFERENCES 

Municipal Program 

Charity 

Informal Sector 

Glass Metals Plastics 

[1] United Nation. The millennium development 

goals: A Latin America and Caribbean perspective. 

United Nation Publications, pages 41, 61, 

Santiago de Chile, Chile, August 2005. 

[2] Kopfmüller, J. et al. 2001 Nachhaltige Entwicklung 

integrativ betrachtet. Konstitutive Elemente, 

Regeln, Indikatoren. Berlin, Germany, 2001. 

[3] Szantó Marcel. Gestión de Residuos Sólidos 

Domiciliarios en Santiago de Chile. Pontifica 

Universidad Católica de Valparaíso, Grupo de 

Residuos Sólidos, p. 21, Valparaíso, Chile, July 

2006. 

[4] Szantó Marcel. Caracterización de residuos sólidos 

domiciliarios en la Región Metropolitana. 

Pontifica Universidad Católica de Valparaíso, 

Grupo de Residuos Sólidos, p. 93, Valparaíso, 

March 2006.

Slurry sampling ICP-AES procedure for fast and accurate 

measurement of crustal elements in airborne particulate matter 

Azam Mukhtar and Andreas Limbeck 




Email: amukhtar@mail.zserv.tuwien.ac.at 

Abstract — Slurry sampling ICP-AES method for 

fast and accurate determination of crustal elements 

(Ca, Si, Fe, Mg, Ti, Al) in airborne particulate 

matter is presented. Decomposition and mineralization 

of the filter material including deposited 

particulate matter was obtained by treatment of the 

samples with a mixture of nitric acid and perchloric 

acid. The prepared slurry solutions were comprised 

of the dissolved part of the sample as well as the 

suspended insoluble material (such as Si oxides), 

and were measured by ICP-AES using La as internal 

standard. Quantification was performed using 

aqueous standards. Analysis of the certified reference 

material 2709 ® (San Joaquin soil) revealed a 

good agreement for the elements Ca, Mg, Fe and T. 

The contents of Al and Si were underestimated 

which might be due to loss of volatile species during 

sample preparation and/or influences of the matrix. 


The short term standard for particulate matter PM10 is 

violated in many European cities [1] , therefore the 

current air quality status of PM10 is under investigation 

in many countries in particular to understand the 

source terms of the particulate matter and to propose 

a catalogue of measures to avoid further exceeding of 

the limiting value. 

The crustal elements Si, Al, Fe, Ca, Mg and Ti have 

been shown to be important constituents of airborne 

particulate matter. For measurement of these elements 

in atmospheric samples, preferably nondestructive 

multi-elemental techniques, such as X-ray 

fluorescence (XRF), particle induced x-ray emission 

(PIXE) or instrumental neutron activation analysis 

(INAA) were used [2,3] . However although frequently 

applied, all of these methods suffer from distinct 

limitations. X-ray fluorescence does not allow the 

quantitative determination at the lowest level of 

μg g -1 and requires a sophisticated calibration. 

Similarly neutron activation analysis encounters with 

matrix problems. So the application of these techniques 

for routine analysis of aerosol samples is 

difficult. However, the use of inductively coupled 

261 

plasma atomic emission spectroscopy (ICP-AES) in 

comparison to above mentioned techniques, yield 

enhanced selectivity, reproducibility and in some 

cases also sensitivity, but these improvements are 

always associated with distinctly increased efforts in 

sample pretreatment and measurement 

[4,5] . The 

present study describes the development of a slurry 

ICP-AES procedure for fast and accurate multielement 

measurement of Si, Al, Fe, Ca, Mg and Ti in 

solid environmental samples. 


A. INSTRUMENTATION 

ICP-AES measurement of slurry samples was performed 

using a Spectroflame P optical emission 

spectrometer (Spectro, Germany). The instrument 

was equipped with a pneumatic nebulizer and a 

cyclonic spray chamber and was controlled by 

Spectro Smart Analyzer Software. 

B. REAGENTS ANS SAMPLES 

Nitric acid, perchloric acid and all other reagents 

used were of analytical grade. For method development 

a certified multi-element solution (Ca, Fe, Mg, 

Ti, 100 mg/L) and stock solutions of Al and Si (1000 

mg/L) procured from Merck (Germany) were used. 

Working solutions were prepared by dilution with 

metal free water. Certified reference material 2709 ® 

(CRM, San Joaquin Soil) from NIST (National Institute 

of Standards and Technology, Gaithersburg, 

MD, USA) was used to verify the accuracy of the 

method for multi-element determination. PM10 samples 

were collected in Vienna using standard procedures 

and GN4-Matricel filter as sampling substrate. 

C. PRE-TREATMENT PROCEDURE 

Slurry solutions of PM10 test samples were prepared 

by treatment of PM10 samples with a mixture of conc. 

nitric acid and perchloric acid in bernas type Teflonlined 

bomb heated in refractory oven at 110 o C for 1 

hr and subsequently temperature was increased to 

150 o C for 1 hr ensuring an enhanced decomposition

of carbonaceous material, and simultaneously the 

excess of nitric acid was evaporated. After cooling 

the samples to room temperature, derived solution of 

perchloric acid including undissolved particles was 

completely transferred to 20 mL polypropylene tubes 

and diluted to a final volume of 20 mL with 2.5% 

(v/v) HNO3 in bi-distilled water. 

III. RESULTS 

A- METHOD OPTIMIZATION 

The slurry method demands the complete mineralization 

of organic material, dissolution of soluble sample 

constituents and the homogeneous suspension of 

insoluble material (e.g. Si and Al oxides) [6] . To 

achieve this condition, various concentrations of 

nitric acid and perchloric acid at various temperatures 

were used. Finally, treatment of PM10 samples with 2 

mL of nitric acid and 500 μL of perchloric acid at 

110 o C for 1 hr and subsequently increasing temperature 

to 150 o C for 1 hr were found to give slurry solutions 

with comparable characteristics to aqueous 

solutions, enabling the use of aqueous standards for 

quantification. 

Instrumental parameters with respect to flow rate, 

gas pressure and RF power were also optimized to 

get maximum signal intensity, minimum background 

signal, high reproducibility and to overcome 

matrix and spectral interferences. Lanthanum 

was used as internal standard for correction 

of changing conditions during measurement. 

B- ANALYSIS OF REAL SAMPLES 

Prior to the application of the method to real sample 

the accuracy of the procedure was tested by the 

analysis of the CRM. For this purpose 20 mg of 

the CRM was analyzed using proposed method 

and the quantification was performed using aqueous 

standards. The results derived for the investigated 

elements were in good agreement with certified 

contents except for Al and Si (Table 1). The 

insufficient results for Al and Si were probably 

due to loss of volatile species during sample pretreatment 

and/or influences of remaining matrix 

during measurement. 

Finally the developed procedure was applied to the 

analysis of PM10 samples from Vienna, confirming 

that the investigated crustal elements were major 

constituents of urban aerosol samples. 

262 

Mg 

Al 

Si 

Ca 

Fe 

Ti 

Elements Content (%) 

Measured 

1.52±0.032 

5.90±0.6 

24.8±7 

1.85±0.04 

3.46±0.12 

0.328±0.05 

Content (%) 

Certified 

1.51±0.05 

7.50±0.06 

29.66±0.23 

1.89±0.05 

3.50±0.11 

0.342±0.024 

Table 1: Comparison of measured and certified 

values of standard reference material 

IV- CONCLUSION 

The presented slurry sampling method enables fast 

and accurate analysis of Ca, Mg, Fe and Ti in airborne 

particulate matter and can widely be employed 

to other solid and environmental samples. Future 

work will be dedicated to the problems associated 

with measurement of Al and Si, so that this method 

can also be applied to for accurate determination of 

these elements. 

REFERENCES 

[1] Querol et al, Speciation and origin of PM10 and 

PM2.5 in selected European cities, Atmos. Envor. 38: 

6547-6555, 2004. 

[2] V. Ariola , et al, Elemental characterization of 

PM10, PM2.5 and PM1 in the town of Genoa 

(Italy), chemosphere, 62: 226-232, 2006. 

[3] A. Najat, Saliba, H. Kouyoumdjian, M. Roumie, 

Effect of local and long-range transport emissions 

on the elemental composition of PM10–2.5 

and PM2.5 in Beirut, Atmospheric Environment, 

41: 6497–6509, 2007. 

[4] A.P. Krushevska, R.M. Barnes, Determination 

of low silicon concentration in food and coral soil 

by inductively coupled plasma atomic emission 

spectrometry, J. Anal. At. Spectrum. 9: 981-984, 

1994. 

[5] P. Klemens, K.G. Heumann, Development of 

an ICP-HRIDMS method for accurate determination 

of traces of silicon in biological and clinical 

samples, Fresenius J. anal. Chem. 371: 758-763, 

2001. 

[6] M.J. Cal-Prieto et al, Slurry sampling for direct 

analysis of solid materials by electrothermal atomic 

absorption spectrometry (ETAAS), a literature 

review from 1990 to 2000, Talanta, 56: 1-51,2002.

Effects of Environmental Degradation on the Response of Reinforced 

Concrete Structures 

Paola Simioni and Anna Saetta (Faculty Mentor) 

Department of Architectural Construction 

University IUAV of Venice 

Venice, Italy 

Email: paolasim@dipolo.dicea.unifi.it; saetta@iuav.it 

Abstract — Durable design and maintenance of 

r.c. structures have become a great societal concern, 

especially in the last decades, considering the 

extensive use of concrete for infrastructure facilities. 

Significant efforts have been made by the scientific 

community in order to enhance an efficient 

distribution of resources for the assessment and 

prevention of the environmental degradation which 

a structure may suffer during its service life. 

In this paper, the major effects of aggressive environments 

on the structural response of r.c. members 

are analysed. Particular attention is paid to reinforcement 

corrosion that may increase the vulnerability 

of the structural elements to natural hazards. 


The safety and serviceability assessment of r.c. structures 

is strongly related to their time-variant degradation, 

which may produce significant changes in the 

safety coefficients, with respect to both the ultimate 

and service limit states. These degradation processes 

may be ascribed to the diffusive attack of environmental 

aggressive agents, such as chloride and sulphate 

ions, or to carbonation, alkali-aggregate reaction, 

freeze-thaw cycles, etc. In reinforced concrete, 

the most detrimental deterioration mechanisms are 

those leading to reinforcement corrosion. 

Experimental tests performed on corroded r.c. 

members have shown the reduction of their load 

carrying capacity and ductility as the level of corrosion 

increases, e.g. [1]. Such effects are herein considered 

in the framework of the Risk Management, 

and both the static (at a “micro-level”) and dynamic 

(at a “macro-level”) behaviours of r.c. elements suffering 

from corrosion attacks have been modelled. 

II. CORROSION RISK MANAGEMENT 

Combining the general Risk Management procedure 

developed within the International Graduate College 

802, e.g. [2], with the methodology proposed in [1] 

for assessing the residual service life of corrosionaffected 

r.c. structures, a proposal for a Corrosion 

Risk Management Process is herein presented. 

263 

The procedure consists of three main parts, Figure 

1. First, the Corrosion Detection phase is performed 

through inspections, if necessary repeated at certain 

time intervals. Preliminary visual inspection allows 

the identification of the deterioration mechanisms, 

mapping damage and selecting the sites for testing. 

Afterwards the exposure class is recognized and insitu 

testing is carried out. When corrosion is definitely 

detected, the Corrosion Assessment phase 

starts. After the estimate of the time for corrosion 

initiation, the main effects of corrosion are evaluated, 

i.e. loss of steel section, reduction of steel-concrete 

bond strength and degradation of concrete cover. 

Then the analyses on the corroded structure are carried 

on, resulting in the diagnosis and prognosis on 

its safety condition, which are the input data for the 

final phase of Corrosion Treatment. 

CORROSION DETECTION 

yes no 

CORROSION ASSESSMENT 

Initiation time 

ANALYSIS 

DIAGNOSIS 

PROGNOSIS 

CORROSION TREATMENT 

Inspection 

time 

Residual steel section 

Residual bond strength 

Residual concrete section 

Management 

strategy 

Figure 1: Corrosion Risk Management Process 

In the present work, the Corrosion Risk Assessment 

phase is considered, at two different levels: a 

micro-level, consisting on the improvement of a 

durability model which accounts for the main effects 

of corrosion and is able to predict the structural response 

of corroded r.c. members; a macro-level, 

aiming at the safety assessment of existing structures 

under seismic excitations. The major results are 

briefly discussed in the following sub-sections.

A. MICRO-LEVEL ANALYSIS 

A model representing the loss of steel-concrete bond 

as a function of the corrosion degree has been formulated 

and implemented in a research code enclosing 

the coupled mechanical-environmental damage 

model developed in [3]. In particular, a bond damage 

parameter has been introduced, [4], being a simple 

tool for describing bond degradation phenomena. 

The model reliability has been assessed by simulating 

experimental pull-out tests and beam tests, 

performed at different levels of corrosion, obtaining a 

good agreement with the numerical results, e.g. [4]. 

B. MACRO-LEVEL ANALYSIS 

Corrosion may also induce the shift of the failure 

mechanism from ductile to a more brittle type. This 

effect becomes of great concern especially in seismic 

areas, where ductility and the actual collapse mechanism 

are key issues in safety assessment. 

Pushover analyses have been performed in the 

framework of lumped plasticity. By means of theoretical 

as well as experimental relationships, the 

effects of corrosion have been considered by modifying 

the moment-rotation relationships of the plastic 

hinges including steel section loss, reduction of steel 

ultimate deformation and concrete cover degradation. 

An applicative example of the variation, respect to 

the pristine state, of the seismic behaviour of r.c. 

structures affected by a moderate level of corrosion 

due to a carbonation attack, is proposed in [5]. Moreover, 

the case of a non-symmetric corrosion attack 

may result in detrimental torsional effects, [6]. 

III. PROBABILISTIC MODELLING 

It is well-known that, due to the high level of uncertainty 

affecting the performance of deteriorating 

structures, the time-variant structural safety can be 

realistically assured only in probabilistic terms. 

In the present research, the durability model, [3], 

has been adopted to evaluate the probability of corrosion 

initiation including statistical uncertainties in the 

most influencing material and environmental parameters 

(identified by a preliminary sensitivity 

analysis). In particular, it is assumed that corrosion 

starts when the carbonation coefficient at the depth of 

the concrete cover exceeds the threshold value 0.1. 

Figure 2 shows the results for different w/c ratios and 

a mean value of relative humidity of 70%. 

IV. CONCLUDING REMARKS 

The assessment of existing r.c. structures affected by 

environmental degradation is a complex issue due to 

the large numbers of factors coming into play. Considerable 

progress has been made in the attempt of a 

durable design and efficient maintenance planning 

264 

and repair, e.g. [7]. However further research is necessary, 

in particular concerning a realistic model of 

loss of bond, [8]. Future work will be devoted to the 

improvement of the suggested bond model and to the 

merger of the micro and macro-level analyses for a 

detailed analysis of plastic hinge zones. 

probability of corrosion initiation 

1.0 

0.8 

0.6 

0.4 

w/c = 0.6 

0.2 

0.0 

w/c = 0.5 

w/c = 0.4 

0 10 20 30 40 50 60 70 80 

initiation time [yr] 

Figure 2: Probability of corrosion initiation 


The present research is carried on in the framework 

of the IGC 802 on “Risk Management of Natural and 

Civilization Hazards on Buildings and Infrastructure”, 

with a partnership between the University of 

Florence and the TU of Braunschweig. 

REFERENCES 

[1] J. Rodriguez and C. Andrade. A validated users 

manual for assessing the residual service life of 

concrete structures. GEOCISA, Madrid, 2001. 

[2] T. Pliefke, S. Sperbeck, M. Urban, U. Peil, H. 

Budelmann. A standardized methodology for 

managing disaster risk - An attempt to remove 

ambiguity. 5 th Int. Prob. Workshop, Ghent, 2007. 

[3] A. Saetta, R. Scotta, R. Vitaliani. Coupled Environmental-Mechanical 

Damage Model of RC 

Structures. J. Eng. Mech., 125(8):930-940, 1999. 

[4] L. Berto, P. Simioni, A. Saetta. Numerical modelling 

of bond behaviour in RC structures affected 

by reinforcement corrosion. Eng. Struct, 

30:1375–1385, 2007. 

[5] A. Saetta, P. Simioni, L. Berto, R. Vitaliani. Seismic 

response of corroded r.c. structures. Int. fib 

Symp. 2008, Amsterdam, the Netherlands. 

[6] L. Berto, R. Vitaliani, A. Saetta, P. Simioni. Seismic 

assessment of existing RC structures affected 

by degradation phenomena. Submitted, 2008. 

[7] Model Code for Service Life Design. Fib Bulletin 

34, CEB-FIP; 2006. 

[8] M. Faber, D. Straub, M. Maes. A computational 

framework for risk assessment of RC structures 

using indicators. Computer-Aided Civil and Infr. 

Eng., 21:216–230, 2006.

Usage of the Global Positioning System GPS in the fields of 

weather forecast and fleet navigation 

Ana Karabatic, Gottfried Thaler and Robert Weber 


Technical University of Vienna 


Email: {anna,gthaler,rweber}@mars.hg.tuwien.ac.at 

Abstract — The Global Navigation Satellite System 

GPS, which was established by the US military 

in the early 1970´s, has become very important for 

civil navigation and also for geosciences. Nowadays 

a huge number of applications make use of the 

GPS. 

In this paper we will present results of two basically 

different applications, carried out at our institute. 

The first one deals with the topic weather forecast 

based on the atmospheric influences on microwave 

signals. The second application is about using GPS 

in the field of fleet navigation in urban areas. 


Since the invention of the Global Positioning System 

GPS by the US military in the early 1970´s, the importance 

of this system has also grown for civil usage. 

The Russians established their own system 

GLONASS and further systems like Galileo (Europe) 

and COMPASS (China) will come. All together 

these systems are called Global Navigation Satellite 

Systems or GNSS. The fundamental observation 

equations for code and phase measurements are equal 

to all systems and read as follows 

and 

(1) 

(2) 

is the Pseudorange, the real 

distance, the clock error of the receiver, the 

clock error of the satellite, c the speed of light, the 

wavelength of the signal and the unknown ambiguity 

factor. All GNSS applications are based on 

these two observation equations for Code and Phase. 

Below we present two different applications for 

GNSS carried out at our institute. 

II. GNSS FOR WEATHER FORECAST 

One of many applications of the Global Positioning 

System is the investigation of atmospheric influences 

on microwave signals. The availability of real-time 

265 

or near real-time tropospheric data derived from GPS 

measurements to be assimilated in existing meteorological 

models represents an important issue. While 

the zenith hydrostatic delay of GPS microwave signals 

is usually well sizeable, the wet component, 

describing the rapid variable water vapour content of 

the troposphere has to be estimated from the observation 

data. High resolution meteorological analysis of 

the humidity field is an important precondition for a 

better monitoring of local and regional extreme precipitation 

events and for forecasts with improved 

spatial resolution. 

Figure 1: Hourly ZWD estimates 

In this presentation we present the results of continuous 

measurements of a regional network consisting 

of 8 GPS reference stations, located in Carinthia, 

Austria. The network has been extended with surrounding 

stations of the IGS and EUREF-network. 

The aim is to provide GNSS based measurements of 

the tropospheric water vapour content with a temporal 

resolution of one hour and a temporal delay of 

less than one hour (Fig. 1) to use them within the 

INCA (Integrated Nowcasting through Comprehensive 

Analysis) system, operated by the Austrian Meteorological 

Service (ZAMG). 

III. GNSS FOR FLEET-NAVIGATION 

Another application for GNSS, which was carried 

out within the project called PPos – Taxi [1] at our 

institute, can be assigned to the field of fleet navigation. 

This time GNSS-Signals are used to compute 

the positions of hundreds of GPS receivers, in this

special case the positions of taxis from a taxi fleet in 

Vienna. 

To perform this task we need the positions and 

clock errors of the GPS satellites, as well as at least 

four Pseudorange measurements to four GPS satellites. 

If the Code observation equation in (1) is used position 

accuracies of about ± 5-8 m can be achieved. 

In the case of using the Phase observation equation in 

(2) positioning on the cm-level is possible. However, 

solving the integer ambiguities in (2) is not possible 

in real-time approaches like fleet navigation. It is 

possible to improve the positioning accuracy with 

Code measurements by using Differential GNSS 

approaches. In this case correction terms, so called 

Pseudorange-corrections PRCs, are transmitted to the 

user by reference station networks. This approach 

allows for accuracies of 1 – 2 meters. Figure 2 shows 

the results of a test drive as differences to a reference 

trajectory. 

Figure 2: Position differences of test drive 

Another problem concerning positioning accuracy 

is the so called Multipath-effect, especially in urban 

areas like Vienna. Multipath occurs, when the satellite 

signal is reflected at glass, facades, trees, water 

surfaces etc. The travel time of the reflected signal is 

longer than the travel time of the direct signal. This 

results in an increased Pseudorange which again 

results in a position error. Errors due to Multipath 

can reach up to 50 – 100 meters [2]. 

Nowadays there are many different ways to mitigate 

Multipath-effects [3]. One way, which was 

examined in detail in this application, is the analysis 

of the Signal-to-Noise-Ratio SNR of the received 

Signal. Reflection or diffraction of the signal usually 

leads to a decrease in the SNR. The SNR of the signal 

is also related to the elevation (angle of the satellite 

above the horizon) of the satellite. Due to the 

longer travel path through the atmosphere signals 

from lower elevations have lower SNR-values too. 

These two facts can be used to detect Multipath and 

further on to mitigate it [2]. Figure 3 shows an exam- 

266 

ple of the relationship between SNR and elevation 

and candidates for Multipath-signals. 

Figure 3: Relationship SNR and Multipath 

Finally Figure 4 shows the results of a test drive in 

Vienna using DGNSS corrections and Multipath 

mitigation. 

Figure 4: Corrected car path of test ride 

REFERENCES 

[1] M. Haberler-Weber, G. Thaler, R. Weber: Efficient 

Taxi Allocation based on SISNet and 

DGPS-corrected Vehicle Positioning, Toulouse 

Space Show 08, Toulouse, 22.-25.04.2008 

[2] G. Thaler, Mltipathreduktion bei der 

Fahrzeugpositionierung im innerstädtischen 

Bereich, Diplomarbeit, TU Wien, Institut für 

Geodäsie und Geophysik, 2007 

[3] B. Hofmann-Wellenhof, H. Lichtenegger, J. 

Collins, GPS Theory and Practice, Springer 

Wien New York, Fünfte überarbeitete Auflage, 

2001

Organically Modified Mixed-Oxide Sol-Gel Films with Macro 

Meso and Micro Porosity 

Marina Lomoschitz, Ulrich Schubert 


Vienna University of Technology, 


Email: mjosip@mail.tuwien.ac.at 

Abstract — Highly porous mixed oxide sol-gel films 

with multiple organic functionality and different 

pore-size regimes were manufactured by a simple 

dip coating method using different metal precur- 

sors, different organic groups and combinations of 

several porogens. Post-synthesis modification with 

phosphonic acids allows introduction of a further 

organic functionality. Spectroscopic methods like 

NMR and IR were used for qualitative analysis of 

the organic functionalities. Macro- and mesoporos- 

ity were verified using transmission electron mi- 

croscopy (TEM) and atomic force microscopy 

(AFM). Nitrogen sorption measurements at 77 K 

were used for quantification of the micro- meso 

pore surface area. For investigation and better 

understanding of material formation, small angle X- 

ray scattering (SAXS) measurements were per- 

formed. The degree of post-functionalization was 

determined by thermogravimetric analysis (TGA). 


Surfactant templated mesoporous sol-gel materials 

have potential applications in catalysis, separation 

and sensing because of their high surface area, 

controllable pore size and narrow pore size distri- 

bution. Adsorption applications may require ex- 

traordinary materials properties such as combina- 

tion of different adsorption sites. Different metal 

sites and different organic functionalities may 

increase the interactions of adsorbate mixtures in 

one material. Another very important criterion for 

adsorption is high mass transport which can be 

achieved by macropores. 

In the current work we present the combina- 

tion of approaches for creating films with polymo- 

dal (macro-, meso- and micropores) porosity as 

well as complex materials compositions (different 

metals, different organic groups) 1 in one material. 

Thus, a combination of (i) several porogens, (ii) 

co-condensation of different metal alkoxide pre- 

cursors (Fig.1) and (iii) post-synthesis modifica- 

tion was used to obtain highly porous mixed oxide 

films with multiple organic functionality and dif- 

ferent pore-size regimes. 

Fig. 1 Sol-gel precursors and templates 


For creating macro porosity polystyrene (PS) 

spheres of 100 nm diameter were deposited onto 

cleaned glass slides from a dispersion in water by 

dip coating. This is a simple and convenient 

method which allows formation of densely packed 

layers of polymer spheres by self-assembly. 2 In a 

subsequent step the slides were immersed in a sol 

PS + H 2O 

sol 

toluene 

ΔT post-functionallized 

micro-meso-macro 

porous material 

P OH 

OH 

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micro porous 

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meso pore 

inorganic precursor 

+ template 

polystyrene 

sphere dispersion 

removal of 

polystyrene 


porous hybrid material 

macro pore 

Fig. 2 Schematic illustration of the film preparation procedure 

Si 

O 

O O 

O 

Si 

O 

O CH 3 

O 

Si 

O 

O 

O 

Zr 

O 

O O 

O 

Ti 

O 

O O 

O 

O 

O 

O 

O 

OH 

n 

TEOS MTES PTES Zr(OPr) 4 Ti(OiPr) 4 

Brij 56 

267

of hydrolyzed alkoxide precursors. During this 

step the PS spheres are coated with an organically 

modified mixed oxide gel network. 

After sol-gel network stabilization by drying, 

PS porogen was removed by extraction. The 

calcination at adequate temperature allowed removal 

of residual PS and surfactant without removing the 

organic groups covalently bonded to the silicon atoms 

of the gel network. All steps of film manufacturing 

are schematically shown in Fig. 2. 

The formation of uniform macropores was 

demonstrated using TEM. Figure 3 shows that the 

films had uniform ellipsoidal macropores after calcination. 

The anisotropic shrinkage during calcination, 

from originally 100 nm to 70 nm in the present case, 

is a common effect during heat treatment of porous 

films, where a higher tendency of film pore shrinking 

perpendicular to surface was noticed. 3 

Fig. 3 TEM image of macro pores 

The stability of organic groups covalently bonded 

to silica matrix during calcination was monitored by 

IR spectroscopy (Fig. 4). 

ν OH 

ν CH template 

ν C-O-C 

ν Si-CH 3 

4000 3500 3000 2500 2000 1500 1000 500 

Wavenumber / cm -1 

ν Zr-O-Si 

ν Si-O-Si 

Si-CH 3 

130°C 

200°C 

300°C 

400°C 

Fig. 4 IR spectra of a film deposited onto a KBr 

disk, during temperature treatment 

To quantify the surface area of the porous films, 

meso and microporosity was investigated by N2 

sorption measurements at 77K (Fig. 5). The Brun- 

268 

auer-Emmett-Teller (BET) method was applied to 

calculate the total surface area, while the t-plot 

method was used to determine microporosity. The 

average mesopore sizes were calculated according to 

the BJH model 5 and NLDFT was applied on adsorption 

isotherms to evaluate the size of the micropores. 

Volume Adsorbed / g/cm³ 

120 

100 

80 

60 

40 

0,0 0,2 0,4 0,6 0,8 1,0 

Fig. 5 N2 sorption isotherm and pore size distribution 

Phosphonic acids are known to coordinate tightly 

to titanium and zirconium and selective modification 

of the metal sites in MO2 (M = Ti, Zr)/SiO2 composites 

could be accomplished in aqueous solution. 6 The 

post-functionalization of the calcined samples with 

phosphonic acids, was verified by IR spectroscopy 

and thermogravimetric analysis (TGA). 


This work was supported by the European Space 

Agency (ESA) and the Austrian Forschungsförderungsgesellschaft 

(FFG) in the framework of the 

Austrian Space Application Programme (ASAP). 

REFERENCES 

dV / d log (d) 

0,06 

0,05 

0,04 

0,03 

0,02 

0,01 

0,00 

0 5 10 15 20 25 30 35 40 

Pore diameter / nm 

p/p° 

[1] P. C. Angelome and G. J. d. A. A. Soler-Illia, J. 

Mater. Chem. 2005, 15, 3903-3912. 

[2] M. Sakurai, A. Shimojima, M. Heishi and K. 

Kuroda, Langmuir 2007, 23, 10788-10792. 

[3] R. A. Farrell, N. Petkov, H. Amenitsch, J. D. 

Holmes and M. A. Morris, J. Mater. Chem. 2008, 18, 

2213-2220. 

[4] K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. 

Moscou, R. A. Pierotti, J. Rouquerol and T. Siemieniewska, 

Pure Appl. Chem. 1985, 57, 603-619. 

[5] J. C. Groen, L. A. A. Peffer and J. Perez-Ramirez, 

Microporous and Mesoporous Materials 2003, 60, 1- 

17. 

[6] P. H. Mutin, V. Lafond, A. F. Popa, M. Granier, 

L. Markey and A. Dereux, Chem. Mater. 2004, 16, 

5670-5675.

Development of a New High Frequency Fatigue Testing Method 

for Concrete Bridges 

V 

Dyn 

Johannes Berger and Johann Kollegger (Faculty Mentor) 

Institute for Structural Engineering 



Email: johannes.berger+e212@tuwien.ac.at 

Abstract — This paper describes a new method 

for high frequency fatigue testing, based on the 

resonance effect. Because of the stiffness, mass 

and damping features, the test specimen itself 

becomes the major element of the testing facility. 

The aim was to increase the test frequency from 

1 Hz to 10 Hz with an energy consumption which 

is a fractional amount compared to conventional 

methods (servo-hydraulic facilities). 

Furthermore, an analytical and numerical 

analysis for a fatigue testing facility was carried 

out, to analyse the material behaviour of a new 

bridge restoration method. 


Fatigue is one of the main reasons of failure in 

mechanical components and structures subjected to 

cycling loading. The testing of structural components 

under cyclic loading constitutes one of the most 

important fields of experimental mechanics [1]. At 

the Institute for Structural Engineering at Vienna 

University of Technology, a new method for 

dynamic fatigue tests for tendons has been developed 

and patented [2]. The new method is based on the 

physical principle of the resonance effect, and is now 

also being used for reinforced concrete. For the 

development of a new bridge restoration method, by 

concrete overlay in compound with the structure, it is 

necessary to carry out dynamic fatigue tests for the 

fatigue verification, in order to gain information 

about the long-term behaviour of the compound. 

II. PRINCIPLE OF OPERATION 

The basic concept of the test arrangement is to 

choose an excitation frequency (e.g. vibration 

generator) which correlates to the resonance 

frequency of the testing facility. Then the applied 

force is multiplied due to resonance, whereas the 

dynamic magnification factor (VDyn) depends on 

the damping ratio (x), as in Eq. (1). 

1 

� 

�� 

2 

2 (1 ) 

(1) 

269 

K 

M 

x 

Figure 1: (a) SDOF-System, (b) Model of the 

testing facility 

The testing facility is designed as a single degree 

of freedom system (SDOF), shown in Figure 1(a). 

The differential equation of this system is 

described in Equation (2), where M is the mass 

and K is the stiffness. The eigenvalue (w) and the 

natural frequency (f) can be determined easily, see 

Eq. (3) and Eq. (4). 

2 

� x(t) 

M �K�x 2 

(t) �0 

�t 

�� 

f 

K2 

K 

M 

� 

� 

2 �� 

(2) 

(3) 

(4) 

III. DESIGN OF THE TESTING FACILITY 

To obtain practical values of dynamic fatigue tests of 

bridges, experiments which have already been 

performed at the Technical University of Graz and 

the University of Innsbruck, were analysed. In 

addition, a bridge restoration with concrete overlay 

has been analysed for the fatigue verification. Based 

on this experience and on the basis of the fatigue 

verification according to EN 1992-1-1 [3], the 

specimen has been designed. 

In order to design the load-bearing of a bridge as 

good as possible, the cantilever and field area are 

modelled for the specimen as a tension and a 

compression area supplement. 

M 

K1 

K2 

K3 K3 

K4 K4 

(a) (b)

IV. ANALYTICAL AND NON-LINEAR 

NUMERICAL SIMULATION 

To obtain high efficiency the testing facility, shown 

in Figure (2), was designed in such a way that the 

resonance effect will set in at a frequency of about 10 

Hz. The first investigations revealed, that regarding 

the resonance frequency state I (concrete without 

cracks) and state II (concrete with cracks) show 

considerable differences. The frequency ranges 

between 26,21 Hz in state I and 13,52 Hz at the 

compression area supplement and 8,65 Hz at the 

tension area supplement in state II. These frequencies 

were determined by analytical methods. 

Figure 2: Experimental set-up 

However, since there will be no pure state II 

condition, the calculations need to be done with a 

realistic model. This is necessary to avoid resonance 

overlapping of the specimen with other parts of the 

testing facility. These calculations are made by using 

a finite element program, taking into account a 

nonlinear material behaviour and a concrete cracking 

model, see Figure (3). With the previously 

determined stiffness, the resonance frequency was 

determined analytically and numerically by using the 

finite element method in a 3D- model. 

Furthermore, it was essential to determine the 

magnification factor of the system, whether the 

capacity of the vibration generator is sufficient or 

not. 

270 

Figure 3: Material behaviour, nonlinear 2D FE- 

Analysis 

V. ACHIEVEMENT 

Finally seven specimens with the following 

dimensions were built: 

� Length: 5,0m 

� Width: 1,0m 

� Thickness: 0,4m (including 16cm of top 

concrete as decking) 

Four million load cycles for each specimen were 

carried out for the fatigue test. This means that with a 

frequency of 10 Hz, it takes 111 hours to finish one 

test. 


High frequency fatigue tests, based on the resonance 

effect, can be carried out for reinforced concrete 

(RC) structures. As a result of the variable stiffness 

of RC in state II, there is a big range of 

eigenfrequencies of the testing facility. The limits are 

given by state I and state II conditions. The tests can 

be performed 8 to 26 times faster by using the new 

developed test set-up, compared to the servo 

hydraulic testing procedure. 

REFERENCES 

[1] B. Koeberl and J. Kollegger. High frequency 

testing facility for stay cables and tendons. 

Structural Engineering International, August 


[2] Kollegger J, Koeberl B, Pardatscher H, Vill M. 

Verfahren zur Durchführung von Dauerschwingversuchen 

an einem Prüfkörper sowie eine Vorrichtung 

zur Durchführung des Verfahrens. 

Austrian Patent AT 501 168 B1, 2006. 

[3] EN 1992-1-1. Eurocode 2: Bemessung und Konstruktion 

von Stahlbeton und Spannbetontragwerken, 

Teil 1-1: Allgemeine Bemessungsregeln 

und Regeln für den Hochbau, Dezember 2004.

Antenna far-fields determination from phaseless 

measurement using the real-valued GA 

Jan Puskely and Zden�k Nová�ek (Faculty Mentor) 

Departure of Radio Electronics 



Email: xpuske01@stud.feec.vutbr.cz, novacek@feec.vutbr.cz 

Abstract — In this paper, we present an 

optimization procedure exploiting in a functional 

minimization method that utilizes the phaseless 

electric field data over two plane surfaces for the 

reconstruction of the phase distribution on the 

aperture of the measured antenna. The 

performance of a real-valued genetic algorithm 

applied to the functional minimization is presented. 

Analyses of the different pairing and mating 

methods which influence the GA behavior are 

included. 


When dealing with a near-field to far-field (NF- 

FF) transformation for an antenna measurement, 

traditional techniques require not only the amplitude 

but also the phase information of the NF data in order 

to calculate accurately the far-field pattern of the 

antenna under test (AUT). However, it is difficult to 

obtain the complex (amplitude and phase) 

measurement at millimeter-wave frequencies. Also, 

at low frequencies, the amplitude-only measurement 

techniques are economical to employ. 

Thus, this work is focused on calculating the fields 

on the antenna aperture that characterize the AUT or 

generate the FF information using amplitude-only 

information of the electric field collected over two 

plane surfaces in the near field. In this work, a realvalued 

genetic algorithm (R-VGA) [3] has been 

developed and tuned to predict the radiation pattern 

of the AUT. 

II. PRINCIPLE OF THE METHOD 

The reconstruction method using the amplitudeonly 

data on two planes is based on the phaseretrieval 

techniques. Reconstructing the phase of the 

NF data is the main goal in those techniques. This 

usually leads to an iterative scheme in which the 

phase of the known amplitude near-field data on two 

different planes is reconstructed in a forward– 

backward fashion. The presented method exploits 

two known principles, the functional minimization 

[2] and the Fourier iterative algorithm (FIA) [1]. 

271 

In the functional minimization scheme using GA 

for finding the global minimum, the random guess is 

refined in each step by the minimization difference 

between the calculated amplitudes and measured 

ones. Since the GA can slow down the convergence, 

we use it to find an initial estimation only. In order to 

improve the initial estimation, the FIA is applied, 

which minimizes the functional also. The process 

continues until some stopping criteria are satisfied. 

By the Fast Fourier Transform (FFT), coefficients 

of the plane wave spectrum (PWS) are calculated and 

the far-field pattern can be obtained consequently. 

A. REAL-VALUED GENETIC ALGORITHM 

Genetic Algorithm (GA) is a stochastic search 

method widely used in electromagnetism to find the 

global minimum in a multidimensional domain. The 

set of the parameters forms the population, which is 

evolved by means of the selection, the crossover, and 

the mutation genetic operators [3]. The fitness 

function F to be minimized is of the following form: 

N 

N 

2 ~ 2 

�E1�i, j� 

� M 1�i, 

j� 

� 

~ 2 

M �i, j� 

F � �� 

� ... (1) 

i�1 

j�1 

1 

In (1), E1(i, j) is the computed complex intensity and 

M ~ 1(i, j) is the measured amplitude in the point i, j on 

the first scanning plane. For the second scanning 

plane, a similar scheme is applied. 

Case 

#1 

#2 

#3 

#4 

#5 

#6 

#7 

Selection Crossover Mutation 

strategy strategy Pc (%) Pm (%) 

Random 

Rank weight 

Cost weight 

Tournament 

Tournament 

Tournament 

Tournament 

Blending 

Blending 

Blending 

Blending 

Linear 

Heuristic 

Extrapolation 

2 

70 10-30 

Table 1: The strategies and parameters considered 

to tune up the real-valued GA [3] 

For the proposed problem, the influence of the 

selection and crossover strategies and the influence 

of the population size on the accuracy of the results

are investigated. The chosen strategies are 

summarized in Table 1. The optimizations were 

repeated 10 times and were stopped in the 3000 th 

iteration. 

III.RESULTS 

The radiation pattern reconstruction was 

performed for the horn antenna T1-R100. The 

antenna was analyzed at the working frequency of 

12.4 GHz. 

With regard to the fact that the tournament 

selection and the linear crossover offer the most 

accurate results, they were chosen (shown in Fig. 1). 

Since the computational cost depends on the 

population size, we try to find out the optimal 

population size to achieve the accurate solutions 

saving CPU time. The population sizes were chosen 

12, 24, 48 and 96 individuals. 

Figure 1: The analysis of the influence of the 

different crossover operators: #4, #5, #6, #7. 

Figure 2: The performance of the R-VGA as a 

function of the population size; results for case #5. 

As shown in Fig. 2, larger population offers the 

fast convergence but only for a cost of the higher 

expense of the CPU time. The population size of 24 

individuals was chosen as an optimum since 

providing the best performance ratio. 

The far-field results of the E plane obtained by the 

R-VGA and the FIA are shown in Fig. 3. The 

272 

radiation pattern achieved by the direct 

transformation of the complex electric field intensity 

is represented by the dotted line. The radiation 

pattern calculated from the initial estimation 

(achieved by the R-VGA) is represented by the 

dashed line, and the radiation pattern achieved by 

applying the FIA is represented by the solid line. 

Figure 3: Reconstructed far-field pattern; E-plane 


Method for the reconstruction of the radiation 

pattern based on the functional minimization using 

GA for finding the initial estimation has been 

presented. The behaviour of the R-VGA has been 

analyzed. The confrontation of the R-VGA and 

particle swarm optimization (PSO), which showed 

the best performance till now, shows that the R- 

VGA exhibits comparable convergence properties. 


Research described in this contribution was 

financially supported by the Czech Grant Agency 

under the grants no. 102/07/1084 and 

102/08/H018, and by the research program MSM 

0021630513. 

REFERENCES 

[1] R. G. Yaccarino and Y. R. Samii, “Phase-less bipolar 

planar near-field measurements and 

diagnostics of array antennas,” IEEE Trans. 

Antennas Propagat., vol. 47, pp. 574–583, Mar. 

1999. 

[2] Bucci, O. M., D’elia, G., Leone, G., Pierri, R. 

Far-field pattern determination from the nearfield 

amplitude on two surfaces. IEEE 

Transaction on Antennas and Propagation. 

1990, vol. 38, no. 11, p. 1772–1779. 

[3] Haupt, R. L., Haupt, S. E. Practical genetic 

algorithm. A Wiley-Interscience Publication, 

1998, ISBN 0-471-18873-5

Catalyst loaded porous membranes for 

environmental applications - Smart Membranes 

Abstract —This project involves the fabrication 

and testing of microporous, polymer membranes 

designed to remove minute amounts of toxic air 

pollutants such as formaldehyde from air streams. 

The hypothesis to be tested is that active silver 

contained within the porous polymer membranes 

results in high formaldehyde retention. The silver 

caps in the porous membrane absorb formaldehyde 

from the air, while in fact at the same time the silver 

caps are oxidized and become Ag2O, which will 

initiate a gas-phase/solid reaction with 

formaldehyde. 


Porous materials are useful in a wide range of 

applications,, for example, as membranes for 

separation and purification, as high surface area 

adsorbents, as solid supports for sensors and catalysts, 

as scaffolds for tissue engineering, and as lowdielectric 

constant materials for microelectronic 

devices. These materials have also been actively 

explored as photonic band gap (PBG) materials for 

use in optoelectronics and as new types of 

mechanical materials that may exhibit negative 

Poisson ratios. 

Generally, colloidal crystals have been used as 

templates to form organic, inorganic, or metallic 

porous structures depending on the nature of the 

applications. Unlike lithography based techniques 

that have shown mostly two-dimensional features, a 

colloidal self-assembly approach can produce 

complex and regular three-dimensional structures 

including channel-like, spherical, ellipsoidal, and 

rectangular shapes as well as more complex forms 

such as star shaped assemblies. 

This project involves the fabrication of ordered 

microporous cylinders by colloidal self-assembly[1] 

in microcapillaries. Microporous structures can 

enhance mass transport to and efficiency of catalysts. 

Such shape-controlled colloidal crystals are of 

critical importance for practical use of bulk colloidal 

crystals. 

Bin Ren and Prof. Ilona Kretzschmar 

Department of Chemical Enigneering 


New York, USA 

Email: renbin83@gmail.com 

273 


The fabrication of the porous membranes in our work 

consists of four parts: monolayer assembly, silver 

coating deposition, cylindrical colloidal crystal 

assembly, and porous membrane fabrication. The 

first two steps are the preparation work for the last 

one, which provide half capped silver coatings on 

each of the spherical particle templates. 

A. MONOLAYER ASSEMBLY 

The monolayer of closed packed polystyrene(PS) 

particles is obtained on a glass slide by dragging a 

glass slide with a syringe pump from New Era 

Systems. Inc. The proper dragging speed is set 

according to the humidity and the size of PS 

particles. The deposiiton process only takes a few 

minutes. 

B. SILVER COATING DEPOSITION 

A bench top metal evaporator 308R system from Ted 

Pella Inc. is used in which the source materials 

(silver and titanium) are evaporated in a vacuum, and 

the vacuum allows vapor particles to travel directly 

to the target object (monolayers), where they 

condense back to a solid state. The thickness of 

coating is controlled by the deposition time. 

C. COLLOIDAL CRYSTAL ASSEMBLY 

This process is carried out in a 100 �m OD/50 �m ID 

microcapillary template. The PS particles are washed 

off from the glass slide by sonication in deionized 

water. Uniform cylindrical colloidal crystals of 

modified PS spheres are self-assembled inside the 

microcapillary by capillary force. The water is 

evaporated from the open end of the capillary. 

D. FABRICATION OF POROUS MEMBRANE 

A polyurethane prepolymer is infiltrated into the asprepared 

PS colloidal crystals. The prepolymer is 

cured by UV exposure. The PS particles are removed 

from the particle polymer membrane by treatment

with organic solvents resulting in the formation of 

inverse opal structures. Silver does not dissolve in the 

organic solvents and cannot leave the pores due to 

the small size of connecting holes in an inverse opal. 

III. RESULTS 

The monolayer is easy to obtain, which is shown in 

Figure 1(left). Figure 1 (right) shows the surface of 

silver capped particles as smooth right after silver 

deposition. However, the surface becomes rough 

shortly after because of silver cap oxidation. 

Figure 1: Optical microscope image of 2.5 �m PS 

monolayer (left), SEM image of 2.5 �m silver 

capped PS particle(right). 

Fierce vibration is employed when the silver 

capped particles are assembled. Because the silver 

capped particles are much heavier than the 

uncapped sPS particles. The shinning parts in 

Figure 2 are the silver capped particles. 

Figure 2: Optical microscope image of sectioned 

cylindrical colloidal crystals with silver capped 

particles (a). Interface (b). 

Theoretically, in an evaporation-induced colloidal 

self-assembly, the thickness (or the number of layers) 

of deposited colloidal crystals on a substrate is 

proportional to the meniscus height, which is mainly 

related to the lateral capillary force. The lateral 

capillary force is given by the derivative: 

F ��d�W / dL 

(1) 

which yields: 

F �� 2 ��Q1Q2qK1( 

qL) 

( rk�L) (2) 

K1 is the modified Bessel function. 

In Figure 3 the interface between different sizes of 

pores and the uniform close packing of pores are 

clearly visible in the SEM images. The dark lines 

274 

next to the porous membranes are PMMA 

microcapillary and PS template residues. 

Figure 3: SEM images of the polymeric inverted 

replica after the PS particles and microcapillaries 

have been removed by THF. All the images show the 

interface between 10 �m and 2.5 �m sPS particles. 

In Figure 4, the inner part of the cylindrical colloidal 

crystal is visible and shows that the pores are 

arranged uniformly. This further confirms that the PS 

particles with silver caps arranged into a closed 

packed fcc lattice throughout the capillary without 

forming a hollow core. 

Figure 4: SEM image of porous membrane 

containing silver caps. 

Future studies will explore the use of mixed 

TiO2/silver caps as catalyst material and study the 

retention of formaldehyde in the membranes. 


This work was supported by the National Science 

Foundation under Award Number #0625753. 

REFERENCES 

[1] Moon, J. H.; Kim, S.; Yi, G-R.; Lee, Y-H.; Yang, 

S-M.; Langmuir 2004, 20, 2033-2035.

Presence of the Bacteria Legionella in Hot Water Distribution 

Systems 

Daniela Ocipova and Zuzana Vranayova 

Institute of Building and Environmental Engineering 



Email: daniela.ocipova@tuke.sk, zuzana.vranayova@tuke.sk 

Abstract — The presence of the bacteria Legionella 

in water systems, especially in the hot water 

distribution system, represents in terms of health 

protection of inhabitants the crucial problem which 

can not be overlooked. The aim of my thesis is the 

research focused on theoretical and experimental 

analysis of hot water distribution systems from the 

point of view of microbiological risk on the basis of 

confrontation between the theoretical analysis and 

synthesis of gathered information in conditions of 

the Slovak Republic. There are a lot of guidelines 

and regulations developed in many individual 

countries for the design, operation, and 

maintenance of tap water systems to avoid the 

growth of bacteria Legionella. The core of the 

article consists in my investigation of Legionella 

contamination of hot water in a cross-sectional 

survey in Kosice, the Slovak Republic. 


Legionellosis is a collection of infections that 

emerged in the second half of the 20th century, and 

that are caused by Legionella pneumophila and 

related Legionella bacteria. Water is the major 

natural reservoir for legionella, and the bacteria are 

found worldwide in many different natural and 

artificial aquatic environments, such as cooling 

towers; water systems in hotels, homes, ships and 

factories; respiratory therapy equipment; fountains; 

misting devices; and spa pools. About 20% of the 

cases of legionellosis detected in Europe are 

considered to be travel-related; these cases present a 

particular set of problems because of difficulties in 

identifying the source of infection. The severity of 

legionellosis varies from mild febrile illness (Pontiac 

fever) to a potentially fatal form of pneumonia 

(Legionnaires’ disease) that can affect anyone, but 

principally affects those who are susceptible due to 

age, illness, immunosuppression or other risk factors, 

such as smoking [1].Outbreaks of disease have 

generally occurred when the concentrations in water 

systems have been high and aerosol has been 

produced. The aim therefore is to minimise the 

possibility for infectious doses to be produced as a 

275 

result of operation of water systems. It is important 

that appropriate measures are taken to guard against 

conditions which may encourage Legionella 

multiplication. 

II. LEGISLATION 

In the last years particular parts of the ‘STN EN 

806 Specifications for installations inside 

buildings conveying water for human 

consumption’ have been accepted by the Slovak 

Republic. Installations have to be operated and 

maintained without having an adverse effect on 

conveying water for human consumption and 

water quality. Safety quality and suitability of 

procedures accepted for safeguarding of system 

performance according to EN 806 and EN 1717 

should be regularly controlled. Conditions of 

installations operation have to be compared with 

conditions of design and assembly in order to 

insure their functionality. 

Potable water is safeguarded by basic formula: 

� Cold water must remain cold 

� Hot water must remain hot 

� Water must not stagnate in water pipes 

longer than it is necessary 

III. AIMS AND METHODS 

To assess the potential public health impact of 

Legionella colonization at domestic level, as well as 

public level, a descriptive multicentric study was 

undertaken to identify and qualify the levels of the 

microorganism in a substantial number of Slovak 

domestic and public hot water samples. 

We addressed three specific aims: 

1. to estimate the frequency of Legionella 

colonization and severity of contamination at 

different levels 

2. to identify the potential risk factors for 

contamination relative to distribution systems 

and water characteristics 

3. to define relative role of each risk factor and 

suggest possible remediation.

Lastly, risk for legionellosis will be retrospectively 

evaluated by collecting information about pneumonia 

symptoms recorded by residents at buildings [2]. 

A. SAMPLE COLLECTION 

From February to October 2006, a total of 46 water 

samples were collected from private homes, hospitals 

and boiler houses of Kosice, representative samples 

of Eastern Slovakia.The selection was made on the 

basis of the water distribution systems inside the 

town and buildings and heater types in each area. 

After we identified each building, we asked a random 

family, or a work collective to participate in the 

study, i.e. to complete our questionnaire and give 

informed consensus for water collection. Laboratory 

examinations and Legionella analysis were made by 

the Regional Health Office – referential centre for 

potable water in Kosice. The hot water samples were 

drawn from the bathroom outlets in the case of 

residential houses (shower heads or bathroom taps) 

in the sterile 1-L glass bottles after a short flow time 

(to eliminate cold water inside the tap or flexible 

shower pipe). To neutralize residual free chlorine, 

sodium thiuosulphate was added into sterile bottles 

for bacteriological analysis, whereas acid-preserved 

glass bottles were used for chemical determinations. 

The collection bottles were returned to the laboratory 

immediately after sampling for bacteriological 

examination by a Membrane filtration. Filters 

Millipore were used for 10 ml sample volumes. Adjusted 

samples were inoculated on the medium 

GVPC surface [3]. 

B. POSITIVE SAMPLES 

Legionellas presence was detected in 8 samples out 

of analysed drinking water samples. Positive findings 

were recorded in 8 samples of PWH (potable water 

hot)In waters for human consumption (potable water 

cold - PWC) volume of legionellas were detected, 

from sporadic colonies of 20 CCU/100ml up to 

massive colonizations in the quantity 6700 

CCU/100ml per a sample. In water for human 

consumption (PWH) volume of legionellas were 

detected, from sporadic colonies of 200CCU/100ml 

up to massive colonizations in the quantity 14600 

CCU/100ml per a sample. Legionellas presence was 

detected in 8 samples of analysed PWH samples, i.e. 

in 17,4 %. 

C. RESULTS 

We repeated sampling after thermal disinfection in 

contaminated places. After 12 days the level of 

legionella colonies was almost the same as before 

this measure (Figure 1). 

276 

Figure 1: Legionella results – positive samples 

Much worse results were obtained in similar survey 

in Italy or Germany �2]. In this case 36 - 68 % of 

samples were positive. In case the thermal 

disinfection in contaminated places was not done the 

concentration of bacterias will have an exponential 

character. The measures have proved that the thermal 

disinfection is not a suitable system treatment. New 

strategies are tend to permanent disinfection due to 

the fact that spasmodic disinfection is not enough 

reliable to ensure the required standard. 


By collecting the samples we verify that thermal 

disinfection is not the systematic solution and it is 

inevitable to find a new complex solution. Expenses 

on the elimination of Legionella from the water 

distribution systems are very high and the results are 

not often sufficient. Our control preventive measures 

have been in progress in order to find an effective 

way to suppress the spread of the Legionella bacteria 

in water systems. Nevertheless, it should be the 

common goal of designers and operators to reduce 

the risk of Legionella bacteria in the installation 

inside buildings. To prevent tragic events it is 

obviously necessary to monitor the issue in the world 

and pay attention to precautionary regulations. 


This work was funded by NATO ESP.NUKR.CLG 

982978. 

REFERENCES 

[1] P. Borella et al. Environmental diffusion of 

Legionella spp. and legionellosis frequency 

among patients with pneumonia: results of a 

multicentric Italian survey, 15;.493–503, 2003 

[2] F. J. Bartram et al.: LEGIONELLA and the 

prevention of legionellosis, EWGLI,2007. 

[3] Z. Vranayová: Stav kontaminácie legionellou 

v rozvodoch teplej vody. Sanhyga, Bratislava 

SSTP st: 43 -52, October 2007

Development and Processing of a Multi-Filter Rotating Shadowband Radiometer 

Network for Distributed Monitoring of Aerosol Optical Depth: Comparisons Between 

Conventional Langley Regression and a Novel NASA-GISS Algorithm 

Miguel Bustamante, Fred Moshary, Barry Gross and Sam Ahmed 

NOAA-CREST Optical Remote Sensing Laboratory, The City College of New York, NY 

10031 and CUNY Graduate Center 365 Fifth Ave. NY, NY 10016 

Email: mbustamante@cuny.ccny.edu 

ABSTRACT 

Information about global distributions of aerosol 

optical thickness (AOT) is necessary to quantify the 

aerosol radiative forcing. The development and 

processing of suitable radiometer networks is central 

to this effort. Modern robotic solar instruments for 

retrievals of aerosols optical depth and other 

microphysical parameter retrievals, such as the 

CIMEL Sky Scanning Radiometers part of the 

Aeronet Network are crucial to this effort but are 

unfortunately quite sparse and expensive. It has been 

proposed that the use of more cost effective devices 

likes the Multi-Filter Rotating Shadow-band 

Radiometer in a network might prove sufficient. 

Therefore it is crucial to develop appropriate 

algorithms that can be used in unattended processing 

which allows us to assess satellite retrieval 

performance. 

1 INTRODUCTION 

Atmospheric aerosols play an important role in the 

Earth’s radiative budget [1] and affect the global 

climate through radiative forcing and chemical 

perturbations. Information about global distributions 

of aerosol optical thickness (AOT) is necessary to 

quantify the aerosol radiative forcing and can play an 

important role in improving atmosphere correction for 

land and ocean products. The used of modern robotic 

solar instruments for retrievals of aerosols optical 

depth, such as the Multi-Filter Rotating Shadow-band 

Radiometer [2] is crucial in the assessment of aerosol 

retrievals from satellites. As an example of the 

usefulness of the MFRSR network we are developing, 

we plot in figure 1 a comparison of the MFRSR 

radiometer retrievals against the operational retrieval. 

We observe MODIS under-estimates AOD for 

Princeton (rural) and over-estimates for urban sites 

like NYC and MECC Brooklyn. We find that over 

urban areas there is a strong bias in the retrieval of 

277 

AOD from satellite instruments due to poor 

estimation due to surface reflection. This observation 

was crucial in trying to develop a better surface 

model of urban areas for better aerosol retrieval. For 

example, an overestimate of the aerosol retrieval 

points to an underestimate in the ground reflection If 

we only had available the CIMEL site at CCNY, we 

could not confirm our hypothesis. However, our 

ground measurements at Princeton and MECC were 

performed with relatively inexpensive and portable 

MFRSR and the development of a suitable MFRSR 

network would be very advantageous. However, 

processing MFRSR data using calibrations method 

which are not robust affects the accuracy of the 

measurements which are not at the level of Aeronet. 

Some calibration approach assumes stability in the 

aerosol loading over the entire day. Evidently, the 

operational method of calibration of these instruments 

by Langley Regression is extremely difficult in 

regions where the aerosol loading varies significantly. 

However, a new processing technique which 

combines the use of both the direct and the diffuse 

components should lead to improved results. This 

method only assume that the aerosol spectral ratios 

(i.e. aerosol type) be uniform. To this end, we have 

� MODIS 

1 

0.8 

0.6 

0.4 

0.2 

0 

ME 

PR 

NYC 

0 0.2 0.4 

� 

aer 

0.6 0.8 1 

Figure 1 Comparison of MFRSR AOD vs. MODIS AOD 

between Sites: Princeton, Medgar Evers and CCNY for Sep- 

Oct 2007 period. Princeton is under estimated compared to 

CCNY and MECC.

Error 

begun a massive effort to outfit the metropolitan area 

with these instruments and explore the processing 

performance of the GISS algorithm against the more 

traditional Langley Regression approach. We are 

interested in assessing the performance of the 

MFRSR retrievals against the Aeronet CIMEL 

instrument and embark on using the network data to 

assess the diversity of aerosols over the New York 

Metropolitan area. At present, the network includes 

5 sites which will ultimately be extended to form 

both an urban and suburban ring which will allow us 

to look at transport between these two rings for a 

better determination of aerosol sources. 

2. DATA ANALYSIS 

A new regression technique similar to the Langley 

approach but relying on the spectral stability of 

aerosol extinction instead of optical depth stability 

was developed at NASA GISS [1,2]. The main 

point in the new scheme is the fact that the 

calibration is based on the stability of aerosol type 

0.5 

0.4 

0.3 

0.2 

0.1 

Fractional Error 

0 

0 50 100 150 200 250 300 350 

Julian Date 

and not aerosol loading. That this is in general an 

improvement is seen in figure 2 which shows that the 

normalized optical depth variability approximately 

three times larger than the optical depth ratio 

variability. 

3. INTERCOMPARISONS 

tau 8 70 

Ratio 8 70 

Figure 2 calculating the fractional error between AOD at 870 nm 

channel vs. the AOD ratios of Diffuse/Direct clearly shows an 

improvement of AOD. 

The most important parameter to assess is the aerosol 

optical depth retrieval in the visible channel. In figure 

3, we plot the retrieved AOD at 500 nm for both the 

GISS processing (left panel) and the normal Langley 

regression approach. We note in that the GISS 

approach leads to less variance from the Aeronet 

baseline but there is persistence over bias. This is 

symptomatic of the need to compensate for the optical 

278 

opacity [2] factor which seems to difficult over urban 

scenes. On the other hand, the Langley approach does 

not show bias but clearly produces larger errors. 

AOT500 

0.35 

0.3 

0.25 

0.2 

0.15 

0.1 

0.05 

0 

-0.05 

-0.1 

Giss - CIMEL tau 

100 200 

Julian Day 

300 

4. CONCLUSIONS 

The processing of MFRSR data with the improved 

algorithm processing method based on calibration of 

the long channel (870) using a combination of direct 

and diffuse radiation does not require good stability 

in the optical depth during the calibration stage. 

Instead, the calibration assumes only that the optical 

depth ratios are stable which we showed is a more 

robust assumption. 

5. AKNOWLEDGMENTS 

This work is supported by grants from NOAA 

#NA17AE1625 and NASA #NCC-1-03009. The views, 

opinions, and findings contained in this report are those of 

the author(s) and should not be construed as an official 

NOAA, NASA or U.S. Government position, policy, or 

decision. 

6. REFERENCES 

AOT500 

0.35 

0.25 

0.15 

0.05 

-0.05 

-0.15 

0 200 

Julian Day 

400 

[1] Alexandrov M., et al. “Remote Sensing of 

Atmospheric Aerosols and Trace Gases by Means of 

Multifilter Rotating Shadowband Radiometer”. Part 

I,II: J. Atmos. Sci., 59, pp524-542, pp544-566, 2002. 

[2] Alexandrov et. al.: ”Separation of fine and coarse 

aerosol modes in MFRSR data sets”. J.Geophys. Res. 

110, D13204, doi:10.1029/2004JD005226, 2005. 

0.3 

0.2 

0.1 

0 

-0.1 

Lang - CIMEL ave 

Figure 3 Inter-comparison of AOD retrieval at 500nm using a) novel GISS 

algorithm b) current Langley algorithm

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280

Random Bipartite Graphs and their Application to Cuckoo Hashing 

Reinhard Kutzelnigg and Michael Drmota (FacultyMentor) 

Institute of Discrete Mathematics and Geometry 



Email: {reinhard.kutzelnigg,michael.drmota}@tuwien.ac.at 

Abstract — Cuckoo hashing is a hash table data structure 

introduced in [1], that offers constant worst case search time. 

This paper presents a precise average case analysis of Cuckoo 

hashing, and extends the analysis of [2]. In particular we determine 

the probability that the construction of a cuckoo hash table 

succeeds and give an upper bound for the construction time 

that is linear in the size of the table. As a further contribution, 

we analyse modified versions of this algorithm with improved 

performance. Finally, we provide an asymptotic analysis of the 

search costs of all this variants of cuckoo hashing and compare 

this results with the well known properties of double hashing 

and linear probing. 


Cuckoo hashing introduced in [1] uses two tables of size 

m to store n = m(1 − ε) keys, where ε ∈ (0, 1) holds. 

The algorithm is based on two hash functions h1 and h2, 

both map a key to a unique position in the first resp. second 

table. These are the only allowed storage locations 

of this key and, hence search operations need at most 

two look-ups. To insert a key x, we put it into its primary 

storage cell h1(x) of the first table. If this cell was 

empty, the insertion is complete. Otherwise, there exists 

akeyy such that h1(x) =h1(y). We move this key to 

its secondary position h2(y) in the second table. If this 

cell was previously occupied too, we proceed with rearranging 

keys in the same way until we hit an empty cell. 

Obviously, there are of course situations where we might 

enter an endless loop because the same keys are moved 

again and again. In such a case, the whole data structure 

is rebuild by using two new hash functions. As a strong 

point, this is a rare event [2, 3]. 

Our analysis is based on the assumption, that the storage 

locations of the keys form a sequence of pairs of independent 

uniform random integers. If a rehash is necessary, 

we assume that all new hash values are independent 

from all previous attempts. 

Consider the bipartite graph possessing m labelled 

nodes of each type and n labelled edges, where each edge 

connects the two possible storage locations of a fixed key. 

This graph is called the cuckoo graph. The shape of it determines, 

whether the construction of the data structure 

is successful or not, since we enter an endless loop iff 

there is a connected component with more than one cycle 

[2]. The further analysis rests on a generating function 

approach to the cuckoo graph. We than apply a double 

saddle point method to obtain asymptotic results. 

281 

II. SUCCESS 

Theorem 1 ([3, 4]) Suppose that ε ∈ (0, 1) is fixed. 

Then the probability that a cuckoo hash of n = ⌊(1 − 

ε)m⌋ data points into two tables of size m succeeds, is 

equal to 

1 − (2ε2 − 5ε + 5)(1 − ε) 3 

12(2 − ε) 2ε3 � 

1 1 

+ O 

m m2 � 

. (1) 

� 

2 

This probability decreases to 3 + o(1), ifn equals m. 

III. ASYMMETRIC CUCKOO HASHING 

Assume that we choose the tables in such a way, that the 

first table holds more memory cells than the second one 

(cp. [1]). Thus, we expect that the number of keys actually 

stored in the first table increases, what leads to improved 

search and insertion performance. 

Theorem 2 ([5]) Suppose that c ∈ [0, 1) and ε ∈ (1 − 

√ 1 − c 2 , 1) are fixed. Then, the probability that an asymmetric 

cuckoo hash of n = ⌊(1 − ε)m⌋ data points 

into two tables of size m1 = ⌊m(1 + c)⌋ respectively 

m2 =2m − m1 succeeds, is equal to 

1 − 

h(c, ε) 

m 

+ O 

� 1 

m 2 

� 

. (2) 

Note that it is possible to calculate the function h(c, ε), 

see [5]. The analysis reveals a major drawback of this 

modification. The algorithm requires a load factor less 

than √ 1 − c 2 /2 and this bound decreases if the asymmetry 

increases. 

IV. SIMPLIFIED CUCKOO HASHING 

Instead of using two separate tables, it is straightforward 

to “glue” them together and use one table of double size 

only (cp. [1]). Further, both hash functions address the 

whole table. As a result of this change, the probability 

that the first hash function hits an empty cell increases, 

hence we expect a better performance for search and insertion 

operations. 

Theorem 3 ([5]) Suppose that ε ∈ (0, 1) is fixed. Then, 

the probability that a simplified cuckoo hash of n = 

⌊(1 − ε)m⌋ data points into a table of size 2m succeeds, 

is equal to 

(5 − 2ε)(1 − ε)2 

1 − 

48ε3 � 

1 1 

+ O 

m m2 � 

. (3)

We now conclude that the success probability of simplified 

cuckoo hashing is slightly decreased compared to 

the standard algorithm, but the practical behaviour is almost 

identical in this aspect. 

V. SEARCH 

Similar to the analysis of linear probing and uniform 

probing in [6], we consider hashing without deletions. 

Theorem 4 ([5]) Under the assumptions of Theorem 2, 

assume that an asymmetric (resp. standard) cuckoo hash 

table has been constructed successfully. Then, the expected 

number of inspected cells of an successful search 

is asymptotically given by 

2 − 1+c 

2α 

� 

1 − e −2α/(1+c)� 

+ O � m −1� , (4) 

where α = n/(2m) denotes the load factor of the table. 

Furthermore, the expected number of steps of an unsuccessful 

search is asymptotically given by 

2 − e −2α/(1+c) + O � m −1� . (5) 

Theorem 5 ([5]) Under the assumptions of Theorem 3, 

consider a simplified cuckoo hash data structure. Then 

the expected number of inspected cells of an successful 

search is bounded between 

2− 

1 − e−α 

α 

+O � m −1� 1 − e−2α 

and 2− 

2α +O � m −1� , 

(6) 

where α = n/(2m) denotes the load factor of the table. 

Furthermore, the expected number of steps of an unsuccessful 

search is given by 1+α. 

Figure 1 displays the asymptotic behaviour of a successful 

search, depending on the load factor α. For simplified 

cuckoo hashing, the grey area shows the span between 

the upper and lower bound. The corresponding 

curve is obtained experimentally. Further, Figure 2 shows 

a plot according to an unsuccessful search. We conclude 

that simplified cuckoo hashing offers the best average 

performance over all algorithms considered here, for all 

feasible load factors. 

VI. INSERTION 

Until now, no exact analysis of the insertion cost of 

cuckoo hashing is known. However, it is possible to establish 

an upper bound. 

Theorem 6 ([4]) Under the assumptions of Theorem 2 

resp. 3, an upper bound of the number of expected memory 

accesses during the construction of a standard resp. 

simplified cuckoo hash table is given by 

min 

� 

4, 

− log(1 − 2α) 

2α 

� 

n + O(1), (7) 

where α =(1− ε)/2 denotes the load factor and the 

constant implied by O(1) depends on α. 

282 

steps 

1.4 

1.3 

1.2 

1.1 

1 

� 

stand. cuckoo 

� 

� 

double hashing 

� 

simpl. cuckoo 

0 0.1 0.2 0.3 0.4 

� 

� 

� 

lin. probing 

asymm. cuckoo, c =0.3 

Figure 1: Comparison of successful search. 

steps lin. probing 

1.8 

1.6 

1.4 

1.2 

1 

stand. cuckoo 

double hashing 

asymm. cuckoo, c =0.3 

simpl. cuckoo 

0 0.1 0.2 0.3 0.4 

Figure 2: Comparison of unsuccessful search. 

Numerical results show that the expected performance is 

by far below this upper bound. Further, we notice that 

the simplified version offers better average performance 

for all investigated settings compared to other variants of 

cuckoo hashing. 


Research supported by the Austrian Science Foundation 

FWF, project S9604 and by the EU FP6-NEST- 

Adventure Programme, Contract number 028875. 

REFERENCES 

[1] R. Pagh and F. F. Rodler. Cuckoo hashing. Journal 

of Algorithms, 51(2):122–144, 2004. 

[2] L. Devroye and P. Morin. Cuckoo hashing: Further 

analysis. Information Processing Letters, 86(4):215– 

219, 2003. 

[3] R. Kutzelnigg. Bipartite random graphs and cuckoo 

hashing. In Proceedings of the 4th Colloquium on 

Mathematics and Computer Science, DMTCS, pages 

403–406, 2006. 

[4] Michael Drmota and Reinhard Kutzelnigg. A precise 

analysis of cuckoo hashing. preprint, 2008. 

[5] R. Kutzelnigg. An improved version of cuckoo hashing: 

Average case analysis of construction cost and 

search operations. In Proceedings of the 19th internatinal 

workshop on combinatorial algoritms, pages 

253–266, 2008. 

[6] Donald E. Knuth. The Art of Computer Programming, 

Volume III: Sorting and Searching. Addison- 

Wesley, Boston, second edition, 1998. 

� 

� 

α 

α 

�

Adaptive hp-Finite Element Methods for Two-Dimensional 

Elasticity with Tresca Friction 

Philipp Dörsek and Jens Markus Melenk (Faculty Mentor) 




Email: philipp.doersek@tuwien.ac.at 

Abstract — We consider a frictional contact problem, given 

as a variational inequality of the second kind. Using a primaldual 

variational formulation, we analyse its discretisation by 

the hp-version of the finite element method (hp-FEM). With 

the aid of a novel hp-mortar projection operator, we obtain 

a priori error estimates for this discretisation that are explicit 

in the mesh width h and the approximation order p. We extend 

residual error indicators, which are known from the classical 

h-version FEM, to the hp-FEM and prove their reliability. 

These indicators are employed to steer an hp-adaptive algorithm. 

Numerical experiments for a 2D elasticity problem 

with Tresca friction demonstrate exponential convergence of 

the hp-FEM, i. e., highly accurate solutions are obtained with 

very small computational effort. 


Mathematical models and numerical simulations are an 

indispensable tool in science and engineering. In engineering, 

for example, they can contribute tremendously 

to cost reduction in product design since the manufacture 

and the testing of costly prototypes can be limited to 

those that proved successful in the simulation. 

Typically, the mathematical models employed are very 

complex and can therefore be tackled only numerically. 

The key to obtaining highly accurate and reliable numerical 

results are adaptive algorithms. The purpose of the 

thesis [1] is the development of such an algorithm for 

a class of problems that arise in technical applications, 

namely, a friction problem. 

II. THE FRICTION PROBLEM 

We want to simulate an elastic body that has frictional 

contact with a fixed object. While the behaviour of elastic 

bodies can be described by partial difference equations, 

the presence of frictional contact leads to a partial 

differential inequality, more precisely, a variational inequality 

of the second kind. The transition from an equation 

to an inequality leads to several difficulties in the numerical 

simulation. For example, while the Newton algorithm 

is the standard and well-established tool for solving 

nonlinear system of equations, the presence of a nondifferentiable 

functional in the variational inequalities considered 

here necessitates very different algorithms. One 

283 

approach is the primal “energy minimising” method described 

in detail in [2]. We focus, however, on a different 

idea: The special structure of the nondifferentiable functional 

allows one to derive a so-called primal-dual formulation 

leading to a saddle point problem as described 

in [3]. This is numerically attractive, as, by first solving 

a linear problem in the interior of the elastic body to construct 

the Schur complement of the system matrix, we 

only have to solve a single variational inequality of the 

first kind on the contact boundary, which is a relatively 

small problem. 

III. CONVERGENCE 

In linear FEM, high order methods, that is, polynomials 

of high degree, have been successfully used to obtain 

accurate solutions with small computational effort. 

The standard approach in finite element methods is to 

use conforming methods, that is, the discrete solutions 

are required to be admissible for the continuous problem. 

In contrast to h-version methods, which have been 

in use since the 1980s (see [4]), it is not clear how to 

achieve this for polynomials of higher degree, which are 

used in hp-finite element methods, as we have to discretise 

a pointwise constraint. This can be explained as follows: 

Let K be the set of functions defined on the interval 

(0, 1) that are bounded pointwise by 1. It is easy to check 

whether a piecewise affine function is an element of K – 

it suffices to check the constraint in the nodes. But already 

for piecewise quadratic functions, it is not possible 

to ascertain membership in K by checking the pointwise 

constraint in a few a priori known points. Thus, if one 

wishes to use higher order methods, one has to consider 

non-conforming approximations, that is, the discrete set 

ˆK is no longer a subset of the continuous set K. 

This raises the question of how to define ˆ K. In [5], 

it was shown that an effective approach is to relax the 

pointwise constraint by requiring the boundedness only 

at certain quadrature points. Using a theorem due to 

Glowinski (see [4]), it is then possible to show convergence. 

In addition to the abstract convergence obtained by the 

theorem cited above, it is essential to give estimates of 

the rate of convergence, assuming that the solution of

the continuous problem is sufficiently regular. A result 

due to Haslinger (see [3]) shows that, as is typical for 

mixed finite element methods, such an estimate has to 

be based on an inf-sup condition. Using methods from 

functional analysis and Sobolev spaces, we were able to 

derive a non-uniform inf-sup condition in [1, Theorem 

3.33], which gives a better bound than a corresponding 

result in [6]. Finally, we obtain an error estimate which 

shows that, assuming that the meshes resolve all singularities, 

we can expect exponential convergence rates. 

IV. ADAPTIVITY 

For the successful application of hp-finite element methods, 

it is essential to have a mesh resolving all features 

of the solution such as singularities arising, for example, 

at the transition from sliding to sticking on the contact 

boundary. Since these transition points are unknown, 

adaptivity is essential. Adaptive algorithms are steered 

by local error indicators. The error indicator employed 

error estimate 

1000 

100 

10 

1 

100 1000 

displacement degrees of freedom 

10000 

uniform h-FEM 

adaptive h-FEM 

uniform p-FEM 

adaptive hp-FEM 

Figure 1: Error plot for a model friction problem 

in this work is of residual type, generalised appropriately 

from the version for the h-FEM as given in [7] to the 

present hp-context. 

The key issue in hp-adaptivity, to decide whether to 

do an h-refinement, more appropriate for a singular, or 

a p-refinement, more appropriate for a regular solution. 

This decision is realised as follows: We estimate the 

local smoothness of the solution by expanding the approximate 

solution into a Legendre series. Depending 

on the decay rate of the coefficients in this expansion, 

calculated by a least squares method, we do an h- or 

a p-refinement. This method, analysed in [8], yields 

very good empiric convergence rates in our numerical 

experiments, and can thus be recommended for practical 

computations: In particular, as can be seen in Figure 1, 

the hp-adaptive method delivers much more accurate results 

for comparable problem sizes than uniform and hadaptive 

methods, and yields exponential convergence. 

284 

Figure 2: Deformation for a model friction problem 

REFERENCES 

[1] Philipp Dörsek. hp-Finite Element Methods for Variational 

Inequalities. Master’s thesis, Vienna University 

of Technology, Sep 2008. 

[2] Ralf Kornhuber. Adaptive monotone multigrid methods 

for nonlinear variational problems. Advances 

in Numerical Mathematics. B. G. Teubner, Stuttgart, 

1997. 

[3] I. Hlaváček, J. Haslinger, J. Nečas, and J. Lovíˇsek. 

Solution of variational inequalities in mechanics, 

volume 66 of Applied Mathematical Sciences. 

Springer-Verlag, New York, 1988. Translated from 

the Slovak by J. Jarník. 

[4] Roland Glowinski. Numerical methods for nonlinear 

variational problems. Springer Series in Computational 

Physics. Springer-Verlag, New York, 1984. 

[5] Matthias Maischak and Ernst P. Stephan. Adaptive 

hp-versions of BEM for Signorini problems. Appl. 

Numer. Math., 54(3-4):425–449, 2005. 

[6] Padmanabhan Seshaiyer and Manil Suri. Uniform 

hp convergence results for the mortar finite element 

method. Math. Comp., 69(230):521–546, 2000. 

[7] Weimin Han. A posteriori error analysis via duality 

theory, volume 8 of Advances in Mechanics 

and Mathematics. Springer-Verlag, New York, 2005. 

With applications in modeling and numerical approximations. 

[8] T. Eibner and J. M. Melenk. An adaptive strategy for 

hp-FEM based on testing for analyticity. Comput. 

Mech., 39(5):575–595, 2007.

Thermal Bridge in Detail of a Gully in a Warm Flat Roof 

Petr Zahradník and František Kulhánek (Faculty Mentor) 

Department of Building Structures 


Prague, The Czech Republic 

Email:petr.zahradnik@fsv.cvut.cz and Frantisek.kulhanek@fsv.cvut.cz 

Abstract — Details are the most problematic parts 

of car park roofs. These details cause thermal 

bridges – anchoring, perforating elements, dilatation 

etc. In this document, there are two different 

solutions of a gully described. Both badly and well 

designed details from a thermal-bridge-solutionviewpoint. 

Linear isotherms show the risk of condensation 

on surfaces of the details. Final calculation 

is compared to the Czech Standard �SN 73 

0540 Thermal protection of buildings and is evaluated 

in relation to durability and reliability. 


Almost all problems with durability in roofs are 

located in details of it. One of the biggest problem 

besides leakage is condensation and, as a result, fungi 

growth. Mostly we can see it around details. In following 

article, differences between two solutions are 

described (both, however, quite usual). 

II. OBJECTIVENESS OF AN ANALYSIS 

Due to objectivness reasons, both variants of a solution 

of a gully are calculated with the same roof 

layer-composition. Roof with foamglass thermal 

insulation has been used as one of the most safe types 

of roof construction [1], suitable for example for 

traffic public use. 220 mm of foamglass has been 

used (corresponds to recommended U-value in the 

Czech Republic [2], values in Table 1). 

Basic requirements of �SN 73 0540 [2] value 

U-value required 0,24 W/(m 2 .K) 

U-value recommended 0,16 W/(m 2 minimal internal surface temperature (at 

.K) 

this temperature, max.80% relative 

humidity is guaranteed) 

13,57 o C 

Table 1: Basic Standard [2] requirements 

Other conditions used in the calculation are described 

in Table 2. 

285 

Conditions used in a calculation value 

external design temperature �e o 

-15 C 

internal design air-temperature �ai o 

21 C 

external design relative air-humidity �e 84% 

internal design air-temperature �i 50% 

Table 2: Conditions used in calculation based on [2] 

III. NUMERIC ANALYSIS OF TWO VARI- 

ANTS OF A GULLY DETAIL 

Numeric analysis of this thermal bridge has been 

done with use of Czech calculation tool Cube 3D [3]. 

Three-dimensional analysis is necessary in this case 

due to non-linearity of such a bridge. 

Analysis shows linear isotherm as a graphic result. 

Important value in this case is temperature of 

13,57 o C, which is border-value for risk of vapour 

condensation and fungi growth. 

A. UNSUITABLE, BUT USUAL SOLUTION OF A 

GULLY DETAIL 

Results of this detail solution will be compared to 

another, more sophisticated, solution. 

There are two main mistakes in this solution: 

1. there is no additional thermal insulation layer 

around the pipe; 

2. the gully and a part of the pipe have been directly 

buried in concrete. 

Figure 1: Unsuitable, but usual detail of a gully

Figure 2: Linear Isotherm of a gully 

Main problem of this solution is very low internal 

surface temperature, which is 9,96 ºC. It causes water 

vapour condensation and supports expectable fungi 

growth. This solution does not dramatically fulfil 

Standard [1] requirement. Due to missing dilatation 

between pipe and the concrete ceiling, we can expect 

cracking and crumbling of the concrete and deformation 

of the pipe. 

This solution is unacceptable from both energetic 

and hygienic viewpoint. 

B. SUITABLE SOLUTION OF A GULLY DETAIL 

Thanks to well done, continuous thermal insulation 

layer we can expect much higher surface temperature. 

1. we calculate 60mm thick insulation around 

the pipe. The insulation makes (1) dilatation 

space for any volume changes in construction 

and (2) acoustic barrier. There should be at 

least 0,5m of an insulation on the pipe. 

2. the gully is located to an insulation “ring”, 

which is made of foamglass; 

3. load-bearing part of the detail – covering grid 

– is embedded to the concrete, which eliminates 

any external forces by the traffic on the 

gully. 

Figure 3: Suitable detail of a gully 

286 

Figure 4: Linear Isotherm of a gully 

This variant of the detail already fulfils Standard [1] 

requirements according to internal surface temperature 

and risk of fungi growth. The lowest surface 

temperature (in area of connection of a pipe to a 

ceiling) is calculated at 18,36 ºC which is higher than 

required (13,57 ºC). 


Due to badly designed or made detail, we can expect 

not only unreasonable energy losses, but risk of illnesses 

in case of low internal surface temperature 

that can cause fungi growth, as well. Degradation of 

construction and decrease of its durability is additional 

negative effect. 

At commonly made details like gully, described in 

previous text, we can find serious thermal bridges. 

Some of those solutions are unacceptable from both 

energetic and hygienic viewpoint. Obviously, it has 

big influence on durability and reliability of a construction. 

Well designed detail and its correct application, influence 

energy performance more, the better insulation 

the building has. 


This article has been made with support of Research 

Project MSM 6840770001 Reliability, Optimalisation 

and Durability of Building Materials and Construction. 

REFERENCES 

[1] Erfahrungen mit Foamglas an wärmegedämmten 

Parkdächern und Verkehrsflächen in Neubau und 

Sanierung, Pittsburgh Corning Europe, 2004; 

[2] Standard �SN 73 0540 Thermal Protection of 

Buildings (April 2007); 

[3] Software Cube 3D, Svoboda Software, Kladno, 

The Czech Republic.

Development of Novel Flow Sensors using SPICE Simulations 

Samir �erimovi� 1,2 , Almir Tali� 1,2 , Franz Keplinger 2 

1 FISS, Austrian Academy of Sciences, Wiener Neustadt, Austria 

2 ISAS, Vienna University of Technology, Vienna, Austria 

Email: {samir.cerimovic,almir.talic,franz.keplinger}@tuwien.ac.at 

Abstract — A novel control loop scheme for calorimetric 

flow sensors combining an electronic twostate 

controller with the electro-thermal transduction 

system is presented. For a convenient controller 

design, we developed a comprehensive SPICE 

model of the thermal system able to fully cover its 

static and dynamic behavior. Such on-off control 

schemes can be optimized for a specified flow range 

and by that outperform classical analogue controllers. 

Experiments confirm that this approach is a 

convenient method for the development of optimized 

controllers for any calorimetric flow transducer 

and specific measurement tasks. 


A typical calorimetric flow sensor consists of a 

miniaturized heat source and spatially separated 

temperature sensors (thermistors), all embedded in a 

thin membrane (Figure 1). The sensor relies on flow 

dependent heat transfer altering the temperature 

distribution near the heater [1]. Operating it with 

constant heating power, a high sensitivity is feasible 

only within a limited flow range. Due to efficient 

convective cooling at higher flow rates the output 

characteristic becomes ambiguous. In order to avoid 

this ambiguity a constant temperature difference 

between the membrane and the fluid is necessary. 

This can be achieved by controlling the heater voltage 

with an electronic controller [2]. Figure 2 shows 

the measured sensor output characteristic for both 

operational modes. The output signal is proportional 

to the temperature difference of the thermistors. In 

the constant over-temperature mode a standard PI 

controller was applied, resulting in an extended 

measurement range but poorer sensitivity at higher 

flow rates. In order to achieve better sensitivity, we 

Figure 1: Sensor layout with two temperature 

sensors (MT1, MT2) and a heater (H). 

287 

investigated the application of a two-state controller. 

For this purpose a SPICE model of the sensor was 

developed using PSpice as simulation tool [3]. 

II. SPICE MODELING 

In order to obtain the model parameters the dependence 

of stationary and dynamic sensor properties on 

flow velocity was experimentally analyzed. Figure 3 

depicts the SPICE model diagram of the sensor electro-thermal 

transduction system. The input variables 

are the heater voltage UH, the ambient temperature 

�LAB B and the flow velocity v. After the steady state 

value is calculated the transient behavior is approximated 

using the sequence of low pass filters. The 

time constants of the last two of them depend on the 

flow velocity. Two additional thermistors (ST1, ST2) 

measure the ambient temperature. The output variables 

are the thermistor resistances. Using this SPICE 

model, it is possible to investigate the interaction of 

sensor and its evaluation and controlling circuit in 

order to find the best controller parameters. Figure 4 

shows the scheme of a novel operational mode using 

two-state closed loop controller which keeps the 

average excess temperature (��) of the membrane 

constant. The on-off-controller establishes a train of 

voltage pulses at the heater. This approach offers the 

quotient of high to low pulse duration (TH/TL) 

as 

output quantity, in addition to the temperature difference 

signal (Uout). 

III. RESULTS 

The simulation results are depicted in Figure 5. Due 

to convective cooling, the pulse duration increases 

Figure 2: Relative output signal of the flow sensor 

with and without analogue controller.

U H 

v 

f ( U , � , v) 

H LAB 

steady state 

� LAB 

f ( U , � , v) 

H LAB 

steady state 

v 

and the pulse gap becomes smaller with increasing 

flow velocity. On the other hand, reducing the amplitude 

of the heating pulse (Uh) at constant velocity 

evokes the same effect. In order to keep the average 

excess temperature (��) of the membrane constant, 

the controller must increase the average heating 

power and hence the quotient of high to low pulse 

duration (TH/TL) increases too. Thus, altering the 

amplitude of the heating pulse one can influence the 

slope of the output characteristic in order to achieve 

better sensitivity. 

The measurement results for different amplitudes of 

the heating pulses (Uh) are presented in Figure 6. The 

course of the output characteristic is in good agreement 

with simulated results. The slight difference in 

absolute values of the heating pulse amplitude results 

from non-ideal circuit components. 

In addition to the ratio of high to low pulse duration 

(TH/TL), the temperature difference signal can be 

used too, yielding the similar output characteristic as 

obtained with PI-Controller (Figure 2). For low flow 

velocities, this signal provides the highest sensitivity 

whereas the ratio TH/TL becomes the preferable output 

quantity at higher flow rates. 


TP TP TP 

v v 

TP TP TP TP 

v v 

We presented a novel control loop scheme combining 

an electronic two-state controller with the electrothermal 

transduction system of the micromachined 

calorimetric flow sensors. Closed loop control of the 

sensor membrane excess temperature with the twostate 

controller results in a pulse form of the heater 

� th2 

� LAB 

flow direction 

� LAB 

Figure 3: Block diagram of the SPICE model of 

the sensor electro-thermal transduction system. 

~�� ref 

~�� 

- 

Comparator Amplifier 

G 

Transducer 

membrane 

Heater 

Flow velocity 

Figure 4: Scheme of a novel operational mode 

using two-state closed loop controller. 

� th1 

Thermistors 

ST2 

MT2 

MT1 

ST1 

Output quantities: 

Uout ~ �th2 - �th1 

288 

Figure 5: Simulated output characteristic. 

Figure 6: Measured output characteristic. 

voltage. This approach offers the quotient of high to 

low pulse duration (TH/TL) as output quantity in 

addition to the temperature difference signal. The 

slope of output characteristic and hence the flow 

sensitivity can be optimized for a certain flow range 

through suitable selection of the heating voltage 

amplitude. 


We gratefully acknowledge partial financial 

support by the Austrian Science Fund FWF 

(research grant L234-N07). 

REFERENCES 

[1] N. Sabaté, J. Santander, L. Fonseca, I. Gràcia, C. 

Cané, Multi-range silicon micromachined flow 

sensor, Sensors and Actuators A 110 (2004) 

282–288. 

[2] A. Glaninger, A. Jachimowicz, F. Kohl, R. 

Chabicovsky, G. Urban, Wide range semiconductor 

flow sensors, Sensors and Actuators A 85 

(2000) 139–146. 

[3] PSpice (Cadence) is based on SPICE circuit 

simulation software developed by UC Berkeley.

Pre-heating Vegetable Oil as a Sustainable Energy 

Development Solution : A Biofuel-Engine 

Longevity Test 

Amir Hossein Nosrat, Mostafa Morovati, Martin Nolan, and Paul A.West (Faculty Mentor) 

Grove School of Engineering 


New York, USA 

Email: sase@ccny.cuny.edu 

Abstract — In many parts of the world, 

including Africa and India, diesel engines are 

relied on heavily for mechanical power, which 

is used to grind grain, pump water, and 

generate electricity. In these parts of the 

world, single cylinder engines like the Listertype 

engine are popular for their reliability 

and longevity. These communities, however, 

often have limited access to diesel, driving up 

the costs and burden of running these engines. 

The Biofuel-Engine Longevity Test (BELT) 

investigates Jatropha oil as a sustainable 

energy solution for these rural communities.. 


The most common stationary diesel engines in 

rural Africa and India are single-cylinder, low- 

RPM designs similar to the British Lister 

engine. They are older, purely mechanical 

designs popular for their reliability, longevity 

and inexpensive price. Common engine sizes 

are between 5 and 16 horsepower, which can 

provide a community of 300 to 1500 people 

all of its agricultural processing and potable 

water pumping. [1] 

The most important setback related to the 

use of Jatropha Oil is its viscosity. If the fuel is 

fed to the engine at room temperatures, the 

engine can bear critical amounts of wear in 

vital components such as its fuel line and 

cylinder. This problem can be potentially fixed 

by pre-heating the Jatropha Oil to an ideal 

temperature of 110 o C. Jatropha Oil is known 

to have viscosity levels matching that of 

regular diesel at this designated range. 

II. OBJECTIVE 

Accordingly, the objective of the BELT 

program is to devise an economical and 

practical pre-heating kit capable of fueling the 

engine on Jatropha Oil at the desired 

temperature. The project includes three 

different teams located at CCNY, Manhattan 

College and Columbia Universities. Each team 

is charged with the task of devising their own 

289 

Viscosity (cS) 

70 

60 

50 

40 

30 

20 

10 

Viscosity vs. Temperature 

Jatropha 

Canola 

Diesel 

0 

20.0 60.0 100.0 

Temperature (C) 

140.0 

Figure 1: Viscosity as a function of 

temperature 

pre-heating kit and providing experimental 

data on the practicality of the design during a 

500-hour test using waste vegetable oil 

(WVO), a fluid with similar characteristics as 

Jatropha Oil. The apparatus is then to be 

modified into a 'field kit' that is intended for 

use at a pilot site in Uganda. 

III. METHOD 

The experiment consists of mechanical, 

electrical and data acquisition components. 

The Listeroid engine itself is attached to an ST 

generator by a groove belt. The generator is 

then wired to an electric board consisting of 

ten 300-Watt bulbs which act as a variable 

engine load. This composition mimics a field 

setup of the Listeroid engine where it is 

usually loaded by a pump, mill, or generator. 

The innovative portion of the experiment 

lies within the pre-heating kit. The CCNY 

BELT team is designing a dual stage preheating 

kit where the vegetable fuel is preheated 

to 110 C before the fuel pump as well 

as before the fuel injector, which is 

approximately 2 feet of fuel line away from 

the fuel pump. 

This approach willdecrease the load on the 

pump cycle and improve the efficiency of the 

engine's thermodynamic cycle.

A). CONTROLS AND PRE-HEATING 

SYSTEM 

The process of pre-heating the biofuel before 

it is injected into the engine is a vital part of 

the BELT project. The first heating element, 

the VOW2, which is installed before the 

pump, serves as a “ball-park” pre-heater, 

effectively increasing the temperature of the 

biofuel from ambient conditions to about 

90�C�95� C , so that the fuel pump does 

less work transporting the warmer biofuel 

(with lower viscosity and therefore, less 

energy loss). 

The biofuel then travels through the pump 

until it reaches second heating element, the 

cartridge heater, which is installed right before 

the fuel is injected into the engine. The 

cartridge heater will then serve as a precision 

heating device, raising the temperature of the 

pre-heated fuel to the desired range of 

110�C�115� C . The purpose of the control 

system, as the name suggests, is to control the 

fuel heating process. If left unattended, the 

two heating elements may raise the biofuel 

temperature to undesirable values which 

undermines the energy efficiency purpose of 

this project. This mechanism will result in a 

double-loop. A theoretical PID analysis of an 

impulse response reveals that the system is 

stable and can reach the target temperature 

within approximately 5 seconds. [2] 

The temperature output of an individual 

heating element was calculated to be 

T mi 

0 

x 

q s '' 

(1) 

T m (x) 

Figure 2: Theoretical illustration of preheating 

element 

where Tme is the exit temperature, Tmi is the 

inlet temperature, qs” is the heat flux, P is the 

perimeter of the fuel line, L is the pre-heater 

length, m� is the mass flow rate and cp is the 

specific heat of the Jatropha oil. [3] 

B). TESTING PARAMETERS 

In order to ensure compatible data sets 

between the three BELT teams, the following 

290 

general categories will be used as various 

testing parameters: 

1. Emissions 

2. Lubricating oil 

3. Fuel 

4. Engine Loading 

5. Thermal/Pressure 

IV. DISCUSSION AND FUTURE WORK 

The CCNY team has to collect sufficient data 

that will provide accurate information on the 

viability of using pre-heated Jatropha oil for 

third world communities. Even collecting data 

from the current pre-heating mechanism has to 

be used to refine the design into a much more 

robust device that can be implemented outside 

of the laboratory and in remote environments. 

The team is also expected to participate in the 

expansion of a BELT pilot site in Uganda that 

has been constructed at a secondary school 

through collaboration between Columbia 

University, and Pilgrim (a Ugandan NGO). 

Additionally, the team looks to expand such 

that another Listeroid engine may be installed 

by the end of the 2008-2009 academic year. 

Future pre-heating designs with additional 

data will further serve the BELT project's 

objectives. 


The authors would like to thank Matt 

Basinger, PhD student at Columbia University, 

for project mentoring and data findings. 

REFERENCES 

[1]Nate Beckett, Manuel Donnay, Seth 

Karpkinski, S. Carl Nolen, and Rena 

Rudavsky. Straight Vegetable Oil 

(SVO) Engine Modification Kit. 

Columbia University Department of 

Mechanical Engineering, pp. 7-12, 

June 2006 

[2] Jiji, Latif M. Heat Convection. 

New 

York: Springer, 2006. 

[3] Ogata, Katsuhiko. System Dynamics. 

4 th edition. New Jersey: Pearson 

Prentice Hall, 2004.

The “G” Ring Laser in Wettzell, Germany, as an Indicator for Astronomical 

and Geophysical Disturbances of the Planet Earth 

Lucia Plank and Paulo Jorge Mendes Cerveira (Faculty Mentor) 




Email: luciplank@hotmail.com 

Abstract — In the last years, the absolute measurement 

of Earth’s rotation using inertial sensors 

has become reality. Laser gyroscopes, e.g. the “G” 

Wettzell ring laser, use the Sagnac effect to sense 

the instantaneous spin and orientation of the Earth. 

Variations in the latter are of astronomical and 

geophysical origin. The astronomical part, e.g. the 

Oppolzer terms, is detected from a dynamical approach 

and supports current theories up to a very 

high accuracy (

III. RESULTS 

A. DIURNAL POLAR MOTION 

The lunisolar and planetary torques on an heterogeneous, 

quasi-ellipsoidal and tilted Earth cause a 

nearly circular motion of the instantaneous rotation 

pole (IRP) in an Earth-fixed frame (see figure 2), also 

known as Oppolzer terms. Space geodetic techniques 

are basically not able to distinguish between spacerelated 

(nutation terms) and Earth-related (Oppolzer 

terms) components. Ring lasers have direct access to 

the Earth-related motions and are therefore sensitive 

to diurnal polar motion [3]. Detailed theoretical investigations 

of diurnal polar motion for an elastically 

and anelastically deformable Earth with a liquid outer 

core are available. Differences between theory and 

measurement are small. 

Figure 2: Oppolzer terms for the period 22.9.2006- 

13.2.2007, derived from space geodetic techniques. 

CIP stands for Celestial Intermediate Pole. 

B. LOCAL ORIENTATION CHANGES 

The “G” ring laser works also as a north-south tiltmeter 

[2], i.e. it divulges small angular variations 

arising from local tilts due to ground deformation. 

As is shown in figures 3 and 4, the solid Earth tides 

in north-south direction can be nicely monitored. A 

big difference of the ring laser versus some tiltmeter 

is that the former is only sensitive to the geometrical 

deformation and does not respond to attractional 

variations. 

292 

Figure 3: theoretical scalograms of the relative 

Sagnac frequency (units of mas) for the Oppolzer 

terms (left) and solid Earth tides (right). 

Figure 4: relative Sagnac frequency (units of mas) 

from the original ring laser data (left), and residual 

of relative Sagnac frequency, after removal of 

Oppozer terms and solid Earth tides (right). 


The author is indebted to the Bundesamt für Kartographie 

und Geodäsie (BKG), and in particular to 

Prof. U. Schreiber and Dr. T. Klügel for giving access 

to the ring laser data from the Geodätisches 

Observatorium Wettzell, Germany. 

REFERENCES 

[1] E.J. Post, Sagnac Effect, Reviews of Modern 

Physics, Vol. 39 (2), pp. 475-493 (1967) 

[2] V. Rautenberg, H.P. Plag, M. Burns, G.E. Stedman 

and H.U. Jüttner, Tidally induced Sagnac 

signal in a ring laser, Geophys. Res. Lett., Vol. 

24 (8), pp. 893-896 (1997) 

[3] K.U. Schreiber, T. Klügel, A. Velikoseltsev, W. 

Schlüter and G.E. Stedman, The Large ring laser 

G for Continuous Earth Rotation Monitoring, 

submitted to PAGEOPH (2008)

Occurrence and Possible Origin of 

Humic-like substances in 

Vienna Airborne Particulate Matter 

BARBARA KLATZER, Alex Caseiro, Heidi Bauer, Hans Puxbaum. 




Email: bklatzer@mail.tuwien.ac.at 

The presence of Humic-like substances (HULIS), 

also referred to as organic macromolecules and 

polyacids, in airborne particulate matter was reported 

as early as 1980 [1]. Since then, numerous 

studies have been conducted to shed light on 

chemical structure, physical properties and formation 

pathways of these macromolecular compounds 

that contribute to atmospheric organic 

carbon with up to 50 %. Figure 1 visualises the 

increasing interest since the term HULIS was 

coined [2] in 1998. 

20 

10 

0 

2 

0 

1998 

1999 

number of 

publications 

containing the term 

"HULIS" in title or 

keywords 

1 

0 

2 

2000 

2001 

2002 

4 

2 

9 

11 

2003 

2004 

2005 

2006 

Figure 1: Histogram of publications 

18 

11 

2007 

2008 

Atmospheric HULIS levels have been quantified 

by using a two step separation technique with 

subsequent carbon-specific detection [3] and contributions 

of HULIS to organic carbon between 6 

and 40 % have been revealed for background sites 

in a European west east transect and for intra urban 

and remote sites, respectively [4, 5]. For urban 

and suburban sampling sites in Eastern Austria 

2004 seasonal behaviour of HULIS levels were 

investigated in airborne particulate matter (PM10) 

by quantification with the TU Vienna HULIS 

Analyser [3]. The first separation step assures the 

removal of inorganic ions and organic hydrophilic 

compounds, while an ion-exchange step removes 

mono- and dicarboxylic acids. Aerosol samples on 

quartz fibre filters are extracted first with ultrapure 

293 

water and dilute alkali. Monthly averaged HULIS 

levels are depicted in figure 2. 

µg HULIS C/m³ 

2,5 

2,0 

1,5 

1,0 

0,5 

0,0 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov 

Urban fringe Intra urban 

Figure 2: Monthly averaged HULIS C concentration 

(n=2-14) 

Lowest concentration levels were found during 

summer season with 0.2 μg HULIS C/m³. The 

highest monthly mean occurred in December at the 

urban fringe site with 2.2 μg C/m³. Seasonal averaged 

winter enrichment factors of 2 and 4, have 

been found for the intra urban and the urban fringe 

site, respectively. 

HULIS C 

2,5 

2,0 

1,5 

1,0 

0,5 

R 2 = 0,82 

R 2 = 0,78 

0,0 

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50 

levoglucosan 

Schafbergbad (urban fringe) Rinnböckstrasse 

Linear (Schafbergbad (urban fringe)) Linear (Rinnböckstrasse) 

Figure 3: Correlation between HULIS C and 

levoglucosan for intra urban and urban fringe site 

Monthly HULIS averages strongly correlated with 

levels of the biomass combustion tracer levoglucosan 

for both sites (R²~0.8), shown in figure 3, what 

indicates biomass combustion products to be a 

source for HULIS formation. 

Dec

REFERENCES 

[1] Simoneit, B.R.T., 1980.Eolian particulates 

from oceanic and rural areas - their 

lipids, fulvic and humic acids and residual 

carbon. Physics and Chemistry of the Earth 

(1956-1998) 12 (Adv. Org. Geochem. 1979), 

343-52. 

[2] Havers, N., Burba, P., Lambert, J., 

Klockow, D., 1998. Spectroscopic characterization 

of humic-like substances in airborne 

particulate matter. Journal of Atmospheric 

Chemistry, 29(1), 45-54. 

[3] Limbeck, A., Handler, M., Neuberger, B., 

Klatzer, B., Puxbaum, H., 2005.Carbon- 

Specific Analysis of Humic-like Substances in 

Atmospheric Aerosol and Precipitation Samples. 

Analytical Chemistry 77(22), 7288- 

7293. 

[4] Feczko, T., Puxbaum, H., Kasper-Giebl, 

A., Handler, M., Limbeck, A., Gelencser, A., 

Pio, C., Preunkert, S., Legrand, M. 2007. 

Determination of water and alkaline extractable 

atmospheric humic-like substances with 

the TU Vienna HULIS analyzer in samples 

from six background sites in Europe. Journal 

of Geophysical Research, [Atmospheres] 

112(D23), D23S10/1-D23S10/9. 

[5] Wonaschütz, A., Hitzenberger, R.,Bauer 

H., Klatzer, B., Puxbaum, H., 2008. Separation 

of „brown“and black carbon in wood 

smoke impacted atmospheric aerosol with the 

integrated sphere technique, Environmental 

Science & Technology, submitted. 

294 


Financial funding of the AQUELLA Wien project, 

which the work presented here was part of, by the 

municipal government of Vienna is greatly appreciated.

Communication Specialties between Ear and Brain: 

Analysis of the Cluster Functions in the Human Cochlea 

Abstract — Although the somatic region of afferent human 

cochlear neurons is quite unique, our contemporary knowledge 

on the neural coding principles in mammalian cochlear neurons 

is primarily based on animal experiments. However two 

outstanding human particularities are expected to essentially 

affect the neural code resulting in a specific human physiologic 

hearing performance. 

Two mathematical models are presented to account for the 

anatomical differences which are of major relevance for the 

propagation of an action potential. 


The somatic region of afferent human cochlear neurons 

is quite unique. Firstly many of the cochlear neurons are 

gathered to clusters with 2-4 [1] neurons having a common 

insulation by myelin (B in Figure 1). Secondly 94% 

of human spiral ganglion cells are mostly surrounded by 

only one to several layers of satellite cells [2], whereas 

in cats 95% of spiral ganglion cells are firmly myelinated 

[3], which represents almost a reverse proportion 

between man and cat (A in Figure 1). 

Figure 1: (A) Schema of the cochlear neurons in cat 

and man; myelinated (grey) and nonmyelinated (white). 

(B) Scanning electron microscopy of the 2kHz (left) and 

1kHz (right) region. [4] 

Nerve fiber model analysis and computer simulations 

are valuable tools to enlighten the functional relevance 

of the particular human case which is not accesible to 

neurophysiologic experiments as used in animals. Based 

Cornelia Wenger and Frank Rattay 


Technical University of Vienna 


corneliawenger@hotmail.com 

295 

on [5] a mathematical model of the neuron clusters is developed 

to study their influence on the spiking behavior 

of the involved neurons. 

II. METHODS 

In our compartment model the processes are split up in 

nodes and internodes. Furthermore the presomatic region 

represents three compartments whereas the soma 

and its postsomatic region are single units. All compartments 

are cylindrically approximated beside the spherical 

soma. Neurons which share a cluster are similarly 

spatially arranged and are assumed to have the same geometrical 

and electrical properties. The surrounding passive 

cluster membrane enwraps the whole nonmyelinated 

soma region from the pre- to the postsomatic compartment. 

To simulate the reduced transmembrane voltage of the 

n-th compartment of a neuron Vn = Vi,n −Ve,n −Vrest,n 

the Hodgkin-Huxley equations were adapted [5]. For 

analyzing the neuron cluster the electrical circuit is en- 

hanced to obtain the differential equations for the trans- 

membrane potential of the cluster V Cl 

n , presented in (1), 

and the enclosed neurons V k n ,k=1..4 in (2). For more 

details see [6]. 

dV k n 

dt = 

� 

− I k ion,n + 

V k n+1 − V k n 

Rk n+1 /2+Rk n/2 + 

V k n−1 − V k n 

Rk n−1 /2+Rk n/2 + 

V Cl 

n+1 − V Cl 

n 

Rk n+1 /2+Rk V Cl 

n−1 − V Cl 

n 

+ 

n/2 Rk n−1 /2+Rk � 

/C 

n/2 

k n 

(1) 

dV Cl 

n 

dt = 

� 

− I Cl 

ion − 

j� 

[I 

k=1 

k ion + Ik c ]+ 

V Cl 

n−1 − V Cl 

n 

RCl n−1 /2+RCl 

+ 

n /2 

V Cl 

n+1 − V Cl 

n 

RCl n+1 /2+RCl n /2 ] 

� 

/ cCl n 

nmCl n 

(2) 

III. RESULTS 

A first model of a single human cochlear neuron showed 

strong effects on the excitation patterns of the neuron by 

small changes in certain sensitive geometrical and electrical 

parameters. The second extended model demonstrated 

the influence of the cluster on the spiking behavior 

of the enclosed cochlear neurons.

A. NONMYELINATED SOMA REGION 

Five parameters have been tested: the intracellular resistivity 

ρi, the number of myelin sheets at the soma 

nmsoma, the diameter of the peripheral process d(1), the 

length of the last peripheral internode li(6) and that of 

the presomatic region lsomap. To analyze the influence 

of changes in these parameters standard values have been 

defined. As an example Figure 2 presents the transmembrane 

voltage of the last peripheral internode at the left, 

the first presomatic region in the middle and the soma at 

the right. 

Figure 2: Variation of d(1). The thinnest diameter fails 

to excite the soma. 

The simulation starts with a thinner peripheral process 

with a diameter of 0.2 μm which is also the stepsize leading 

to five different cases up to the standard value for 

d(1) of 1 μm. 

The excitation with the thinnest diameter is the fastest 

and strongest but leaks the second rising phase after a 

short fall of Vn (Figure 2 left). Although it seems that 

at the first presomatic soma compartment all cases lead 

to an ongoing propagation, the thinnest diameter fails 

to excite the soma. Even if it looks like the velocity 

and strength increases from thinnest to thickest diameter 

as detected in the middle subframe it turns out that 

the strongest excitation is provided by the thickest diameter. 

Nevertheless two cases have increased velocity 

compared to the standard case value. 

B. NEURON CLUSTER 

At first the theoretical case of a single neuron with a 

soma ensheathing cluster has been tested, in order to see 

whether the cluster sheets support or hinder the spiking 

behavior. Altered cluster diameters revealed a decreased 

influence of the cluster on the neuron with increasing 

size. Increasing the myelin layers of the cluster and the 

neuron show that in most cases the neuron is positively 

effected, resulting in an increased and accelerated excitation. 

Furthermore multiple neuron clusters have been analyzed 

with the goal to examine the influence of the nerve 

cells on each other and to elucidate if one neuron could 

be triggered to produce a nerve impulse under subthreshold 

conditions when it is supported by properly stimu- 

296 

lated other neurons within the same cluster (Figure 3). 

Figure 3: Voltages in a four neuron cluster at the soma for 

properly excited neurons at the left. One graph represents 

a neuron under subthreshold condition in the middle and 

right. 

On the left all four neurons are properly stimulated 

with identical strengths, i1a-i1d, but different onsets, t1at1d. 

Observing the maximum values V k max the effect of 

the neurons on each other can be verified, especially the 

fourth is profiting from the excitation of the others. 

The other subframes show three properly stimulated 

neurons and one with a subthreshold stimulus with different 

stimulus onsets. Although the influence on the excitation 

of the fourth neuron can be clearly observed the 

other neurons are still not able to produce a nerve impulse 

at an adjacent one under subthreshold conditions. 

REFERENCES 

[1] S. Tylstedt, A. Kinnefors, and H. Rask-Anderson. 

Neural interaction in the human spiral ganglion: A 

tem study. Acta oto-laryngologica, 117:505–512, 

1997. 

[2] C.Y. Ota and R.S. Kimura. Ultrastructural study of 

the human spiral ganglion. Acta oto-laryngologica, 

89:53–62, 1980. 

[3] H. Spoendlin. Degeneration behaviour of the 

cochlear nerve. Arch. Klin. Exp. Ohren Nasen 

Kehlkopfheilkd., 200:275–291, 1971. 

[4] R. Glueckert, K. Pfaller, A. Kinnefors, H. Rask- 

Anderson, and A. Schrott-Fischer. The human spiral 

ganglion: New insights into ultrastructure, survival 

rate and implications for cochlear implants. Audio 

Neurothology, 10:258–273, 2005. 

[5] F. Rattay, P. Lutter, and H. Felix. A model of 

the electrically excited human cochlear neuron: I. 

contribution of neural substructures to the generation 

and propagation of spikes. Hearing Research, 

153:43–63, 2001. 

[6] C. Wenger. Analysis of the cluster functions in the 

human cochlea. Master’s thesis, Technical University 

of Vienna, 2008.

Spatial potentials for renewable energies 

Study results concerning 3 federal states in eastern Austria 

A. Dillinger, H. Dumke, S. Plha, H. Schaffer and 

Vicerektor Hon. Prof. Dipl.-Ing. Dr.techn. Gerhard Schimak 

Department of Spatial Development, Infrastructure & Environmental Planning 

Center Regional Planning and Regional Development 



e0025325@mail.student.tuwien.ac.at 

Abstract — The study “Spatial potentials for renewable 

energies” analysed the distribution and 

amounts of renewable energy production in 3 federal 

states in eastern Austria with main focus on 

biomass, geothermal energy and wind power potentials. 

As many EU guidelines, policy papers, national 

laws, local mission statements demand an 

enormous increase in the production of renewable 

energy and biofuel, accurate data on their spatial 

distribution and dimension is urgently needed. 

Therefore all results were visualised in maps down 

to the level of the communities, which represents an 

innovative approach since most previous studies 

included only figure calculations. The main aims 

were to find “potential focus regions” and to assess 

the possible additional energy output especially out 

of local resources in these areas. 

I. MAIN IMPORTANT RESULTS -BIOMASS 

The future of biomass-related energy production lies 

within a vast pool of rather small-scaled decentralised 

facilities, using local resources from the 

nearby environment. The aggregation of forest, agriculture 

(including derelict areas), grassland and reed 

indicated clearly the respective focus areas, representing 

typical landscape units on the one hand and 

the per-capita (hectares per person) distribution on 

the other. Using a simple model showing the probable 

share of potential energetic use in total (in competition 

to industrial use or food production) the 

energy output of 38 Petajoule seems possible in a 

short-time period. This amount represents a heat 

capacity for about 1.8 million people. In order to 

increase efficient biomass energy production without 

huge transport costs, rural communities with large 

areas, but low population densities have the best 

endogenous preconditions, whereas urban regions 

will always be bound to immense imports of resources. 

297 

The aggregation of the different potential biomass 

areas showed that the most promising regions are the 

northern and southern (Figure 1) parts of Lower 

Austria. The eastern part of Lower Austria and the 

northern part of the Burgenland (close to the Neusiedler 

Lake) can rather benefit from agricultural 

Biomass. The east shore of the lake also provides a 

very specific resource - large reed fields - which are 

ecologically very valuable, but can also provide heat 

production. 

Figure 1: Extract of potential energy 

output per person 

II. MAIN IMPORTANT RESULTS -WIND 

POWER 

Due to the massive enlargements of wind parks in the 

recent years the three federal states already produce 

electricity for about 560.000 households. This equals 

90% of the total Austrian production. The study 

mapped all existing single wind engines and supporting 

and hindering factors were added. A consistent 

and complete GIS model was created to maintain 

ongoing surveys. Buffers have been introduced to 

show hindering or prohibiting factors for new wind

mills like existing (or zoned) building land, nature 

reserves of all kinds or aircraft fields. Supporting 

factors are zoned wind enlargement areas (only in the 

Burgenland zoned by law) and a strong average wind 

power. Suitable areas for new wind parks are visualised 

in dark blue colour on the map (Figure 2). 

Figure 2: Extract of suitable areas for wind power 

This remaining space for additional engines is rather 

limited, but still about 440 new wind mills – which 

can conduct electricity for another 500.000 households 

- are possible here. This amount of energy is 

comparable with the output of three large water 

power plants along the Danube. The most appropriate 

areas for new wind plants are the northern and 

eastern parts of Lower Austria and the northern part 

of the Burgenland. 

III. MAIN IMPORTANT RESULTS -GEO- 

THERMAL HEAT 

Geothermal energy is often underestimated or even 

not existent in the current energy debate. In Austria 

there are only 12 geothermal plants, two of them 

producing electricity, the others heat. But the future 

potentials are very promising. A single geothermal 

plant could cover the demand of over 1.000 households 

producing a constant heat flow without any 

emissions. But the land use patterns have to fit accurately 

to use geothermal energy efficiently: a specific 

structure of consumption, a needed density of buildings 

in combination with existing or newly constructed 

heating systems (pipes, single connections 

and steering logistics) are crucial. In the study area 

there exist four geological regions with good geological 

preconditions: the both in the North also offer 

the above mentioned specifics concerning consumption. 

The raster analysis (Figure 3) layered the existing 

average local heat connections (orange to red 

298 

squares) and the geologically promising areas (blue 

grid). This model allows a realistic estimation on the 

number of household that could be served by geothermal 

heat soon. These approximately 60.000 

households are mostly located in the northern and 

eastern parts of the city of Vienna and the adjacent 

areas. At the moment the largest petrol company in 

Austria (OMV) is checking if its closed oil wells 

could be used for geothermal matters. As geothermal 

energy suffers from enormous investment (drilling) 

costs and misses economic efficiency especially in 

the OCR electricity production, this re-use of closed 

oil wells would be a sustainable and reasonable solution. 

Still geothermal energy seems to be rather suitable 

for urban areas. Additionally new technologies 

are very often underrated – as the very first experiences 

with solar energy showed. 

Figure 3: Extrakt of geothermal potentials meet 

urban structures 

Further information: www.pgo.wien.at/pgo_d.html 


This study was done by order of 

Planungsgemeinschaft Ost | DI Walter Pozarek, 

DI Hans Schulz, Eva Maria Danzer-Horvath 

www.pgo.wien.at 

was conducted by 

mecca - Technisches Büro für Raum- und Landschaftsplanung 

| DI Hartmut Dumke, Mag. 

Stefan Plha, Dr. Hannes Schaffer, DI Andreas 

Dillinger, DI Beate Schaffer 

www.mecca-consulting.at 

and kindly supported by 

more than 30 different institutions and organisations

Silica nanoparticles connected 

through ionic linkers 

Marco Litschauer, Marie-Alexandra Neouze 




Email: malitsch@mail.zserv.tuwien.ac.at 

Abstract — To obtain networks build up by silica 

nanoparticles, connected through ionic linkers, two 

different synthetic approaches were investigated. 

First, a bissilylated functional ionic compound was 

synthesized and afterwards linked to silica 

nanoparticles. In the second approach, silica 

nanoparticles were modified with either 3chloropropyltrimethoxysilane 

or N-(3trimethoxysilylpropyl)imidazol 

before being connected 

via nucleophilic substitution. Both strategies 

are compared in order to determine the most efficient 

method to get large networks. 


The development and introduction of nanoparticles 

on the one hand and functionalized ionic linkers on 

the other hand provided materials chemistry two new 

versatile compounds. 

Functionalized ionic linkers, were intensively studied 

when connected to an inorganic matrix, e.g. silica 

[1]. Many different applications were pointed out for 

such composites or hybrid materials, among others 

catalytic properties, e.g. for Mizoroki-Heck reactions 

[2]. For metal oxide nanoparticles, the synthesis 

routes, mainly sol-gel reactions [3], are well established. 

These particles in the nanometer range offer, 

in contrast to the bulk material, interesting electronic 

or magnetic properties [4]. Combination of ionic 

species with nanoparticles drove to powerful synergies 

[5]. 

The aim of this work is to synthesise 3-dimensional 

silica nanoparticles networks with ionic linkers by 

combining these two interesting materials. The originality 

of this new compound lies in the covalent 

bonding. The two different synthetic pathways to 

obtain these networks are further named strategy A 

and B. 

In strategy A (Scheme 1) the fist step was to synthesize 

the functionalized ionic bridging agent, 

1,3-di(propyltrimethoxysilyl)imidazolium iodid, via 

a nucleophilic substitution reaction. This reaction 

occurs without solvent at room temperature quanti- 

299 

tatevely [6]. Afterwards this bissilylated compound 

was condensed on silica nanoparticles. The nanoparticles 

were prepared through a Stöber process, where 

the size of the particles can easily be controlled by 

the synthesis parameters, like pH or concentration of 

the precursor. 

O 

O 

Si 

O 

SiO 2 

O 

N 

+ 

N 

Si 

O 

I O 

- 

N 

+ 

I - 

N 

+ 

SiO 2 

Scheme 1: Strategy A. 

Strategy B (Scheme 2) is the inversive equivalent 

of strategy A. Here, previously synthesized silica 

nanoparticles are separately modified, through a 

condensation reaction, with either 

3-chloropropyltrimethoxysilane or N-(3trimethoxysilylpropyl)imidazol 

[7]. Afterwards 

these two different nanoparticles suspensions are 

mixed together for the nucleophilic substitution to 

take place. 

O 

O 

Si 

O 

SiO2 

SiO 2 

+ + 

N 

Cl N 

Cl 

+ 

N 

Scheme 2: Strategy B. 

N 

SiO2 

SiO 2 

O 

O 

Si 

O 

SiO 2

II. RESULT AND DISCUSSION 

To prove the formation of the imidazolium linker 

TGA measurements were carried out. Indeed the 

thermal stability of imidazolium species are remarkably 

high, e.g. around 300 °C [8, 9]. For strategy 

B, it proves the occurrence of the nucleophilic 

substitution, as the thermal stability of the product is 

higher as the one of the reactants (Figure 1). The 

mass loss appearing around 100 °C are due to water 

desorption and SiO2-dehydration phenomena. 

Remaining mass / weight% 

100 

80 

60 

40 

20 

0 

100 200 300 400 500 600 700 800 

Temperature / °C 

Figure 1: TGA analysis; dotted lines: silica 

nanoparticles modified with either chloropropyl or 

propyimidazole; solid line: product of strategy A. 

Solid state 29 Si CP MAS NMR confirmed that a 

condensation reaction between the linker and the 

silica nanoparticles took place, formation of Si-O-Si 

bonds. The characteristic signals for the material are 

around -115 ppm, quaternary units issued from the 

condensation of the nanoparticles precursor, and -70 

ppm, tertiary units originating from the condensation 

of the Si(OR) units of the bissilylated compound. 

As the condensation on the nanoparticles was already 

performed, for strategy B, the appropriate experiment 

is 13 C CP MAS NMR that confirmed the formation 

of the imidazolium bridge, via creation of an N + -C 

bond. 

Figure 2: TEM of silica nanoparticles linked via 

strategy A (left) and strategy B (right) [10]. 

By looking at the TEM pictures, which were recorded 

for both strategies (Figure 2), one can see, 

300 

that for strategy A small “island-like” systems (50 – 

100 nm) were observed. The micrograph of strategy 

B indicated that much more nanoparticles are linked, 

leading to bigger domains. Thus strategy B seems to 

be more efficient. 

This is confirmed by SAXS experiments, comparing 

both methods. Fitting of the diffraction curves demonstrated 

a short-range ordering of the nanoparticles 

in the case of method B. 


The formation of a 3D network consisting of silica 

nanoparticles and imidazolium based ionic linkers 

was described. For the creation of these hybrids two 

strategies were developed. Strategy B was examined 

to be the more efficient leading to a more extended, 

short-range ordered, network. 


The authors are thanking Prof. Schubert for his 

support and the Hochschuljubiläumstiftung der 

Stadt Wien for financial support. 

REFERENCES 

[1] M.-A. Neouze, J. Le Bideau, P. Gaveau, et 

al., Chemistry of Materials, 18, 3931-3936, 

2006. 

[2] V. Polshettiwar, P. Hesemann, and J.J.E. 

Moreau, Tetrahedron Letters, 48, 5363- 

5366, 2007. 

[3] W. Stoeber, A. Fink, and E. Bohn, Journal 

of Colloid and Interface Science, 26, 62-9, 

1968. 

[4] C.P. Collier, R.J. Saykally, J.J. Shiang, et 

al., Science (Washington, D. C.), 277, 1978- 

1981, 1997. 

[5] A. Taubert and Z. Li, Dalton Transactions, 

723-727, 2007. 

[6] G. Cerveau, R.J.P. Corriu, E. Framery, et 

al., Journal of Materials Chemistry, 12, 

3021-3026, 2002. 

[7] C.S.J. Cazin, M. Veith, P. Braunstein, et al., 

Synthesis, 622-626, 2005. 

[8] P. Migowski and J. Dupont, Chemistry--A 

European Journal, 13, 32-39, 2006. 

[9] P. Wasserscheid and T. Welton, Ionic Liquids 

in Synthesis. 2003. 364 pp. 

[10] M. Litschauer and M.-A. Neouze, Journal 

of Materials Chemistry, 18, 640-646, 2008.

An Adaptive Solver for Parabolic Partial Differential Equations 

Abstract — TIMETRAVELLER is a numerical solver for the 

solution of initial/boundary value problems (IBVPs) of partial 

differential equations (PDEs). The transverse method of 

lines generates a sequence of boundary value problems in 

ordinary differential equations (ODEs) resulting from semidiscretization 

in time. To these it is possible to apply a code 

for boundary value problems (BVPs) to find the numerical solution 

in both, space and time adaptively. The BVPs are solved 

using BVPSUITE which has already been successfully applied 

to a variety of problems, see for example [1], [2], and [3]. 

In the following an adaptive technique for mesh generation in 

two-point BVPs (2pBVPs) is presented, which tries to find a 

suitable mesh density function on a coarse mesh before increasing 

the number of mesh points to satisfy the tolerance requirements. 


Based on the encouraging results for the collocation code 

SBVP 2.0 [4], the first part of this study is concerned 

with the solution of IBVPs of parabolic partial differential 

equations. The idea is to design a solver which is 

adaptive in both, time and space. In the second part, an 

algorithm for mesh adaptation for 2pBVPs is presented 

which follows the idea of first refining the mesh density 

function φ and estimating the number of points once the 

density has stabilized. 

II. THE TRANSVERSE METHOD OF LINES 

Consider partial differential equations of the following 

type: 

� � 

2 ∂u 

∂ u ∂u 

(x, t) =F (x, t), (x, t),u(x, t) (1) 

∂t ∂x2 ∂x 

The main interest lies in the solution of initial/boundary 

value problems of partial differential equations (1) with 

initial and boundary conditions 

Dipl.-Ing. Gernot Pulverer 

Advisor: Ao. Univ. Prof. Dr. Ewa B. Weinmüller 




Email: gernotpulverer@gmail.com 

u(x, 0) = u0(x), (2) 

B(u(a, t),u(b, t)) = 0, (3) 

with a ≤ x ≤ b. In order to solve Problem (1) – (3), 

the transverse method of lines approach is used. The 

idea behind the transverse method of lines is to use a 

discretization in time such that each timestep of the 

301 

resulting procedure implies a boundary value problem 

for an ordinary differential equation which can be solved 

using a solver designed for this class. Therefore, the 

well established BVP-solver BVPSUITE is very suitable. 

BVPSUITE is capable of solving fully implicit systems 

of singular and regular boundary value problems for 

ordinary differential equations of arbitrary, mixed order. 

For the discretization in time the implicit Euler 

method is used, yielding 

u(x, tn+1) − u(x, tn) 

= 

Δtn 

� 2 ∂ u 

F 

∂u 

(x, tn+1), 

∂x2 ∂x (x, tn+1), u(x, tn+1) 

with initial/boundary conditions 

u(x, 0) = u0(x), 

B(u(a, tn+1),u(b, tn+1)) = 0. 

� 

, 

Setting vn(x) :=u(x, tn), it is easy to find that each 

time step corresponds to an ordinary differential equation 

of second order in vn+1: 

0=G(v ′′ 

n+1(x), v ′ n+1(x), vn+1(x), vn(x)) (4) 

with boundary conditions 

B(vn+1(a), vn+1(b)) = 0. (5) 

As an example consider the imaginary time 

Schrödinger equation: 

∂u 

∂t − ∂2u + Vu=0, 

∂x2 x ∈ [−π, π], t>0. (6) 

Here V : Rm → R is a smooth potential that is 2πperiodic. 

The following initial/boundary conditions are 

used for the calculations: 

u(x, 0) = u0(x), −π ≤ x ≤ π (7) 

u(−π, t) = 0, 0 ≤ t ≤ b (8) 

u(π, t) = 0, 0 ≤ t ≤ b (9)

For numerical calculations Vu = (1 − cos x)u and 

u0(x) = sin(4x) +cos(x) +1. Results are shown in 

Figures 1 and 2. 

u(x,t) 

2 

1 

0 

−1 

−2 

0 

x 

2 

Figure 1: The evolution in time for the imaginary 

time Schrödinger equation with initial profile sin(4x) + 

cos(x) +1. The numerical solution was calculated using 

time tolerance Tt = 10 −3 and spatial tolerance 

Ts =10 −5 . 

0 

0.1 

t 

0.2 

0 0.05 0.1 0.15 0.2 0.25 

t 

Figure 2: The values for t where the corresponding 

boundary value problems had to be solved to satisfy the 

tolerance requirement Tt =10 −3 . 

For difficult problems the number of time steps is very 

large. As every time step requires the solution of a full 

two point ODE boundary value problem, an efficient 

mesh adaptation algorithm is necessary. 

III. AN ADAPTIVE MESH SELECTION AL- 

GORITHM 

The efficient solution of the sub-problem (4), (5) implies 

the implementation of an adaptive algorithm for the numerical 

solution of 2pBVPs for ODEs, a well explored 

area in which some well established standard codes exist, 

see for instance [5] and references therein. Nevertheless, 

most codes are using a technique for the equidistribution 

of the error function that changes the grid density function 

and the number of mesh points in the same step. But 

the estimation of the number of mesh points which is necessary 

to solve the BVP to the desired tolerance requirement 

is based on the density function of the last step and 

not on the updated one. So one is at great risk to solve to 

a much higher accuracy than requested, yielding longer 

302 

runtimes and much denser meshes than necessary. 

As a remedy for this difficulty an algorithm is designed 

to first adapt the mesh density φ on a coarse mesh and 

then determine the number of points to satisfy the tolerance 

requirements. 

To ensure that this method works, it is necessary that the 

mesh density φ stabilizes rather quickly. In Figure 3 the 

evolutions of φ and N are shown for 12 iterations for a 

typical BVP. Note that after the sixth iteration the algorithm 

could have been stopped since the tolerance was 

satisfied. 

φ 

3 

2 

1 

12 

10 

8 

6 

Iteration 

4 

2 

Evolution of φ 

0 

x 

0.5 

1 

N 

200 

150 

100 

50 

Evolution of N 

2 4 6 8 10 12 

Iteration 

Figure 3: Evolution of the density function φ (left) and 

the number of mesh points N (right). Both are stable 

after eight iterations. 


This work was supported by the project ”Development 

of adaptive software for singular boundary value problems” 

of the Austrian Science Fund (FWF) under grant 

no. P17253-N12, project leader: A.o. Univ. Prof. Dr. 

Ewa B. Weinmüller. 

REFERENCES 

[1] I. Rach˚unková, O. Koch, G. Pulverer, and 

E. Weinmüller. On a singular boundary value problem 

arising in the theory of shallow membrane caps. 

Math. Anal. and Appl., 332:523–541, 2007. 

[2] S. Stanek, G. Pulverer, and E. Weinmüller. Analysis 

and numerical solution of positive and dead core 

solutions of singular two-point boundary value problems. 

Comp. Math. Appl., 56:1820–1837, 2008. 

[3] G. Kitzhofer, O. Koch, P. Lima, and E. Weinmüller. 

Efficient numerical solution of the density profile 

equation in hydrodynamics. J. Sci. Comput., 32:411– 

424, 2006. 

[4] W. Auzinger, O. Koch, D. Praetorius, G. Pulverer, 

and E. Weinmüller. Performance of collocation 

software for singular boundary value problems. 

Techn. Rep. Nr. 4/04, Inst. for Analysis and Scientific 

Computing, Vienna Univ. of Technology, Austria, 

2004. 

[5] W. Auzinger, G. Kneisl, O. Koch, and E. Weinmüller. 

A collocation code for boundary value problems in 

ordinary differential equations. Numer. Algorithms, 

33:27, 2003.

ICT – The Big Picture: 

Intertwined Driving Potentials: 

Innovation, Technology Penetration and the Global Economy 

DI Ranja Reda 


Institute for Mathematical Methods in Economics 


Email: ranja.reda@fam.tuwien.ac.at 

Abstract — The goal of this paper is to provide a 

novel analytical study of the Information Communication 

Technologies (ICT) sector. Future trends and 

the impact of this sector on the Global Economy are 

presented. Subsequently, the intertwined ICT driving 

potentials Innovation, Technology Penetration 

and the Global Economy are analyzed under the 

spotlight of the recent subprime crisis. 

Recent studies showed that the global economy in 

2007 was not in a recession phase. Furthermore, 

for 2008 there is no recession phase to be expected 

either. Some sectors, e.g. Information Communication 

Technology, even exhibit a promising growth 

rate. However, in some sectors, especially industrial 

and infrastructure sector, the subprime crisis 

started to turn the global economy the other way 

around. This work presents an analytical study of 

the Information Communication sector, which is 

considered to be the main driving potential of the 

global economy. On the other hand, a healthy 

economy will boost the technology penetration 

which in turn will enhance economic growth. The 

intertwining of the global economy and technological 

progress in the communication sector is analyzed. 

Finally, the impact of the subprime crisis on the 

global economy, and subsequently its connection to 

the communication technology sector is discussed. 


With the beginning of the third millennium, we experienced 

a unique technological progress rate, accompanied 

by a big transformation from the old 

economy to the new economy to the current agile 

economy, where technology and economy are more 

and more intertwined. 

From the service point of view, the advance from 

peer to peer VoIP, to triple play and finally to quadruple 

play enabled everyone using the appropriate 

access technology to be online, any time, everywhere. 

This was supported by the progress of wire- 

303 

less broadband technologies. Accordingly, more than 

70% of the global business turned to be online business, 

making use of the available advanced communication 

technologies. 

II. ICT, THE BIG PICTURE 

Figure 1: ICT, Technological Penetration and the 

Global Economy [ 1 ] 

(Analysis to be provided in the full paper) 

III. INFORMATION TECHNOLOGY AND 

COMMUNICATION: THE MARKET 

POINT OF VIEW 

Information Communication Technology is considered 

as the motivator and facilitator for the global 

economy. 

The world entered the 21st century on a wave of 

technological optimism, far from bringing the world 

to a halt during the economic difficulties. Information 

and Communication Technologies (ICT) and 

especially the Communication part, seem capable of 

generating a new level of global prosperity. 

The progress of the world ICT Market is illustrated 

in Fig. 3.

Fig. 3: Worldwide ICT Market 

Convergence between the IT and telecom markets 

will be analyzed in the full paper. 

IV. COMMUNICATION MARKET 

The global communication market reached a record 

of over 1100 Billion € (see Fig.4). It showed the 

following break down according to the main global 

economical domains [ 2 ], [ 3 ]: 

Fig. 4: Global Communication Market 

by Region 

From the growth rate point of view, BRIC are sustaining 

an amazing growth rate of 7,8 % p.a., 

whereas the 4 Tigers are moving into the future with 

speed and skill, showing a remarkable growth rate of 

more than 6%. 

Economical Domain Billion € % 

Europe 346 30,7 

US 243 21,6 

304 

Japan 164 14,68 

BRIC 97 9 

4 Tigers 11 1 

RoW 264 23 

BRIC: Brazil, Russia, India and China 

4 Tigers: Hong Kong, Singapore, S. Korea and Taiwan 

RoW: Rest of the World 

V. SUBPRIME CRISIS 

With the US as its epicentre, in late 2006 the subprime 

mortgage crisis triggered a global liquidity 

crunch putting downward pressure on economic 

growth. As the International Monetary Fund stated, 

the worldwide losses stemming from the US subprime 

mortgage crisis could hit 945 billion dollars as 

the impact spreads in the global economy. 

Today, trading strategies involve complex structures, 

high volumes of securities, enormous trading frequencies 

and high-level quantitative methods. Therefore, 

sophisticated technological tools like pricing 

software and trading platforms are absolutely necessary 

to make faster, more accurate trading decisions. 

These technological tools played a fundamental role 

in the early stages of the US subprime mortgage 

crisis which now quickly spreads all over the world 

having a great impact on global economy. As early as 

2003, US investment guru Warren Buffet referred to 

quantitative instruments as “financial weapons of 

mass destruction”. 

(Further analysis, conclusion and references: to be 

provided in the full paper) 

VI. REFERENCES 

[1] R. Reda, ICT, e-Business, e-Commerce and 

Online Services. Technological Evolution, Future 

Trends and Impact to the Global Economy, 

Proceedings of the Networking and Electronic 

Commerce Research Conference 2008 (NAEC 

2008), Lake Garda, Italy, Sept. 2008 

[2] European Information Technology Observatory 

2007, EITO, Published by European Economic 

Interest Grouping (EEIG) , ISSN 0947-4862 

[3] R. Reda & N. Jordan, “Signpots for the Future 

of Mobile Communication” , e&I, elektronik 

und informationstechnik, heft 9.2006,published 

by Springer Wien New York, ISSN: 0932-383X 

EIEIEE 123(9) 361-408, a1-a44(2006)

Activation of Neural Networks in the Human Spinal Cord with 

Implanted and Surface Electrodes: 

Conclusions from Finite Element Simulations 

Josef Ladenbauer, Ursula S. Hofstoetter, Karen Minassian, 

Milan R. Dimitrijevic and Frank Rattay 




josef.ladenbauer@gmail.com 

Abstract — Using surface electrodes it is possible 

to communicate with neural networks in the human 

spinal cord in a similar way as with a small single 

implanted electrode, which is essentially closer to 

the neural elements. This surprising result is promising 

to become of great importance for paralyzed 

people because with the new non-invasive method 

some inherent functions of the spinal cord (neural 

circuits called pattern generators) controlling stepping 

and standing can be activated. With the help of 

the activating function, a mathematical concept 

derived from nerve fiber models, the presented 

computer simulations show a quite similar excitation 

situation for both stimulation methods. 


Since 1998 there is an increasing hope to find a new 

clinical method for people which are paralyzed as a 

consequence of spinal cord injury. This hope is based 

on the observation that a train of constant pulses (e.g. 

7 Volt, 30 Hz) from a single active electrode, implanted 

close to the spinal cord, can result in stepping 

like movements in paralyzed patients, even when 

their lower spinal cord is completely separated from 

the brain [1]. 

Based on previous work it can be assumed that this 

surprising phenomenon is caused by neural networks 

in the lumbar spinal cord, which are indirectly activated 

by artificially generated neural impulses from 

the largest diameter nerve fibers originating in the 

lower limbs [2,3]. These fibers enter the spinal cord 

in the vicinity of the active electrode within the socalled 

posterior roots. Every action potential (AP) in 

the population of the stimulated nerve fibers operates 

as input to the neural network. In case of proper input 

sequences for walking, the network sends patterned 

signals to the muscles of the legs, leading to rhythmic 

contraction and relaxation phases. 

Nobody could believe that this principle of artificial 

pattern generator activation would be possible with 

305 

surface electrodes, because such electrodes are much 

further away from the target neurons and additionally 

they are essentially bigger in size. These two properties 

are assumed not to allow the focused stimulating 

effects needed to activate the pattern generator. 

Motivated by some experimental successes (Fig. 1), 

[4], we demonstrate with the presented simulation 

study that the general concerns are wrong and focusing 

is strong enough to activate the neural pattern 

generators by the same principle using surface electrodes 

instead of implanted ones. 

Figure 1: Changes of the Hoffmann reflex during 

stimulation of the spinal cord with surface electrodes. 

II. METHOD AND RESULTS 

The artificial activation of the pattern generators in 

the human lumbar spinal cord is caused by fiber 

excitation in the vicinity of the stimulating electrode. 

A single target fiber can be simulated as a compartment 

model, where the transmembrane voltage Vn of 

the n-th compartment in response to an external potential 

Ve can be calculated as 

dVn 

Vn 

� 1 �Vn 

Vn 

� 1 �Vn 

�[ 

�Iion, 

n � 

� 

dt 

Rn 

� 1/ 

2 � Rn 

/ 2 Rn 

� 1/ 

2 � Rn 

/ 2 (1) 

Ve, 

n � 1 �Ve, 

n Ve, 

n � 1� 

Ve, 

n 

+ 

� ] / Cn 

Rn 

� 1/ 

2 � Rn 

/ 2 Rn 

� 1/ 

2 � Rn 

/ 2 

where C is the membrane capacitance and R/2 the 

internal resistance between the center and the border

Figure 2: A-D describe the situation of an implanted dipole, where the lower electrode contact in (A) 

stimulates a sensory nerve fiber which enters the spinal cord at a position marked by arrow. At this position, 

which is marked also by a dotted line in (B) and (C) the activating function is quite large and initiates 

an AP that propagates in both directions (D). The 2 diagrams at the left side describe the same target 

fiber in the same region when stimulated with surface electrodes. The electrical potential profile is similar 

to case B, and the activating function is comparable with (C) in the region of interest. 

of the compartment. Ion membrane current Iion,n is 

assumed to be proportional to Vn (linear analysis) or 

can be calculated with a model of the Hodgkin- 

Huxley type. The term 

Ve, 

n � 1 �Ve 

, n Ve, 

n � 1 �Ve 

, n 

f n �[ 

� ] / Cn 

(2) 

Rn � 1 / 2 � Rn / 2 Rn � 1 / 2 � Rn 

/ 2 

is called the generalized activating function [5]. f is 

the driving force for every compartment and an AP is 

expected to be generated in a region where f>0. 

The excitation of selected target fibers is simulated in 

a two step procedure. First the potential distribution 

is calculated with the finite element software COM- 

SOL Multiphysics for implanted or surface electrodes. 

In the second step, the potential distribution 

along the pathway of a specific fiber is used as input 

data for the compartment model, where the ion currents 

in the active membrane are calculated with the 

CRRSS model [6]. 

The potential distribution along a typical nerve fiber 

pathway of a sensory neuron is shown in the leftmost 

part of Fig. 2 for surface stimulation with a pair of 

small active electrodes, see [4] for stimulation details. 

For the same neuron geometry (Fig. 2A) the 

potential distribution was calculated again with finite 

elements and found a rather similar relation. The 

stimulation is focused within a region of strong curvature 

and spike initiation is also supported by the 

change of extracellular conductance at the entry point 

of the fiber into the spinal cord (arrow in Fig. 2A). 


With appropriate positions for surface and implanted 

electrodes, similar characteristic shapes of the acti- 

306 

vating functions for the same sensory target neurons 

are obtained. The shapes of the activating functions 

predict corresponding spike initiation regions and 

thereby a comparable neural input for the pattern 

generator networks within the spinal cord. Thus, 

similar effects can be expected in both stimulation 

strategies, either using surface electrodes or implants. 

REFERENCES 

[1] M. R. Dimitrijevic, Y. Gerasimenko, and M. M. 

Pinter. Evidence for a spinal central pattern generator 

in humans. Annals of the New York Academy 

of Sciences, 860: 360–376, 1998. 

[2] F. Rattay, K. Minassian and M. R. Dimitrijevic. 

Epidural electrical stimulation of posterior structures 

of the human lumbosacral cord: 2. Quantitative 

analysis by computer modeling. Spinal 

Cord, 38: 473–489, 2000. 

[3] K. Minassian. Modeling of a human spinal pattern 

generator for locomotion and its activation 

by electrical epidural stimulation. PhD Thesis. 

TU Vienna, 2004 

[4] U.S. Hofstoetter, K. Minassian, C. Hofer, W. 

Mayr, F. Rattay and M.R. Dimitrijevic. Modification 

of reflex responses to lumbar posterior 

root stimulation by motor tasks in healthy subjects. 

Artificial Organs 32(8):644–648, 2008. 

[5] F. Rattay. The basic mechanism for the electrical 

stimulation of the nervous system. Neuroscience 

89, 335-346, 1999. 

[6] F. Rattay, R. J. Greenberg and S. Resatz. Neuron 

Modeling. In Handbook of Neuroprosthetic Methods. 

Eds. W.E. Finn and P.G. LoPresti. CRC 

Press, 39-71, 2003.

Characterisation of biomass smoke particle emissions and its 

application to source receptor analysis 

Christoph Schmidl and Hans Puxbaum 




Email: Christoph.schmidl@tuwien.ac.at 

Abstract — An extensive study testing various 

biomass combustion systems and biomass fuel types 

was performed in order to investigate particulate 

matter emissions. Detailed chemical profiles were 

developed and applied in PM10 source apportionment 

studies using a chemical mass balance approach. 

Chemical species were identified that enable 

the differentiation between smoke of hard- and 

softwood types. Furthermore it could be shown that 

the use of two different biomass combustion profiles, 

one for manually and one for automatically 

fired systems, brings a significant improvement to 

source apportionment results. 


Wood smoke is increasingly being seen as an important 

component of airborne particulate matter 

(PM). Recent source apportionment studies in 

Austria (AQUELLA) and Europe (CARBOSOL) 

showed that wood smoke is the main primary 

particle source during the winter half year [1]. 

Emissions of this source are dominated by organic 

and elemental carbon, together constituting around 

70% of total particle emissions. Therefore it is 

obvious that wood combustion is one of the major 

primary sources of carbonaceous particles in the 

atmosphere as well. The source apportionment 

studies mentioned above applied a macrotracer 

concept using levoglucosan as single tracer for 

wood combustion [2]. Additionally the Austrian 

ambient dataset was analysed with a CMB model 

[3,4] approach to evaluate the macrotracer results. 

However experience with CMB showed problems 

with micro components, i.e. organic micro tracers, 

probably due to low concentrations and partly 

limited stability in the atmosphere and resulting 

difficulties in analysis. 


To make use of the advantages of macrotracer and 

CMB model we developed a combination of the 

two approaches. The number of species was reduced 

so that we are running the CMB model on a 

307 

number of 14 macro-compounds omitting organic 

micro tracers. This gave good correlations for 

most compounds except potassium where the 

measured values were consistently around one 

order of magnitude higher than the calculated (see 

marking in figure 1a). 

Figure 1: Measured/Calculated comparison (CMB); 

Original model result(a); with wood boiler profile(b). 

Hence, further improvement of source profiles was 

necessary. We therefore investigated a number of 

wood combustions facilities – reaching from smallscale 

stoves in the power range of some kilowatts 

(kW) to mid-scale boilers (50kW) – regarding to 

their particle emissions. A sampling system was 

designed, that allows PM samples to be collected 

directly out of the chimney of wood combustion 

appliances. The exhaust gas was diluted with precleaned 

air to simulate ambient conditions. For size 

segregation an impactor – type low volume sampling 

head (Digitel) was used. PM10 samples were collected 

afterwards on 8 filters, 6 quartz fibre and 2 

cellulose filters, in parallel at room temperature. All 

samples were analysed for a number of organic and 

inorganic compounds. From the obtained dataset 

source profiles for different wood and application 

types were developed and analysed with respect to

differences and similarities. Figure 2 gives an overview 

of the sampling equipment. 

Exhaust 

gas 

Dilution 

Dilution air 

(filtered, dried) 

Figure 2: Scheme of PM10 sampling system. 

III. RESULTS 

Mixing 

Cooling 

Condensation 

Separation 

PM10/PM2.5 

Collection 

8 Filters parallel 

Results showed that almost all differences in emission 

profiles within the group of manually fired small 

scale combustion units are rendered insignificant, 

mainly due to the high variability of the combustion 

process, which is in good agreement with previous 

studies [5]. Therefore it was decided to use one 

source profile for this group. Nevertheless specific 

compounds were identified that allow a distinction of 

smoke from hardwood- and softwoods. Levoglucosan 

and mannosan, both anhydrosugars originating 

from pyrolysis of cellulose and hemicelluloses, were 

found to differ significantly between wood types. 

Expressed as ratio the difference becomes even more 

marked, with higher ratios of around 15 found in 

hardwoods and lower ratios of around 3 in softwoods. 

Figure 3 gives a scatter plot of levoglucosan 

and mannosan results from tested appliance and 

wood types displaying this difference. 

Figure 3: Scatter plot of levoglucosan/mannosan 

ratios for different wood and appliance types 

Combustion conditions in automatically fired systems, 

however, are pretty stable after a short start-up 

phase and therefore also emissions are more constant. 

As the efficiency of combustion is much higher, the 

chemical composition of emissions differs significantly 

to manually fired appliances. Emissions from 

wood stoves are dominated by carbonaceous fractions 

(total carbon ~ 70%) while wood boilers mainly 

emit inorganic material (sum of ions ~ 60%). 

We therefore decided to use two different wood 

combustion profiles in CMB modelling, one for 

308 

small scale manually fired wood stoves, and the other 

for automatically fired systems (wood boilers). The 

enhanced model gave similar results for most compounds 

and a much better fit for potassium which can 

be explained by the high emission concentration of 

potassium in the new source profile (see figure 1b). 

Wood smoke source profiles and results from CMBbased 

source apportionment for Austrian PM10 data 

are presented. 


This study was funded by the European Union Interreg 

III Programme, the Austrian Federal Ministry of 

Agriculture, Forestry, Environment and Water Management, 

the government of Lower Austria and klimaaktiv 

– Holzwärme. 

The authors want to thank all members of the 

AQUELLA working group at the Institute of Chemical 

Technologies and Analytics at the Vienna University 

of Technology for doing analysis work. A 

special thanks goes to the institutions providing the 

test stands equipment: the Institute of Chemical Engineering, 

Vienna University of Technology, the 

Austrian Bioenergy Centre and the BLT Wieselburg. 

REFERENCES 

[1] H. Puxbaum, A. Caseiro, A. Sánchez-Ochoa, A. 

Kasper-Giebl, M. Claeys, A. Gelencsér, M. Legrand, 

S. Preunkert. C. Pio. Levoglucosan levels 

at background sites in Europe for assessing the 

impact of biomass combustion on the European 

aerosol background. Journal of Geophysical Research 

112(D23), D23S05/1-D23S05/11, 2007. 

[2] B.R.T. Simoneit, J.J. Schauer, C.G. Nolte, D.R. 

Oros, V.O. Elias, M.P. Fraser, W.F. Rogge, G.R. 

Cass. Levoglucosan, a tracer for cellulose in 

biomass burning and atmospheric particles. Atmospheric 

Environment 33, 173 – 182, 1999. 

[3] J.G. Watson. Overview of receptor model principles. 

Journal of Air Pollution Control Association 

34, 619-623, 1984. 

[4] J.J Schauer, W.F. Rogge, L.M. Hildemann, M.A. 

Mazurek, G.R. Cass, B.R.T. Simoneit. Source 

apportionment of airborne particulate matter using 

organic compounds as tracers. Atmospheric 

Environment, 30, 3837-3855, 1996. 

[5] C. Schmidl, I.L. Marr, A. Caseiro, P. Kotianova, 

A. Berner, H. Bauer, A. Kasper-Giebl, H. Puxbaum. 

Chemical characterization of fine particle 

emissions from wood stove combustion of common 

woods growing in mid-European Alpine regions. 

Atmospheric Environment 42, 126-141, 


Observations of the surface evolution of Pinka-plain: 

mass movements and neotectonics 

Gábor Kovács, Dr. Balázs Székely (Faculty Mentor), Dr. Sándor Papp (Faculty Mentor) 

Institute of Geography and Earth Sciences 

Eötvös Loránd University 

Budapest, Hungary 

Email: s_kovacs_gabor@hotmail.com 

Abstract — Pinka Plain is located at the western 

part of the Pannonian Basin. The margin of the 

plateau on north is a scarp surface of the valley of 

Arany Creek. In the first half of the 1990’s a 

landslide arose on a ski-track situated 1 km west 

from the city of Szombathely. Our goal was to 

investigate this phenomenon, especially the inner 

structure of the moved mass by shallow boreholes, 

and to measure recent velocity of movement with 

fixed points. In the period of investigation this the 

toe of the landslide didn’t move, but other 

landforms in the vicinity reveal that the scarp 

surface is still active. Comparison of our results 

with tectonic data and the crystalline basement 

structure reveal the neotectonic origin of 

movements in the study area. Therefore the scarp is 

expected to be active for long term. 


The surface evolution of western part of Pannonian 

Basin is largely determined by the uplift of the 

Eastern Alps and the tectono-geomorphic processes 

of the basin. The reason to examine this area was 

the abundant occurrence of mass movements and 

gullies on the northern scarp. Our assumption was 

that the above processes are, at least partly, of 

neotectonic origin. 

The general morphology south from the K�szegi 

Mountains shows typical SSE slopes with low relief 

cut off by 30–60 meter high scarps followed by 

streams. We examined the surface development 

processes on the steep scarp of the northern border 

of Pinka Plain. Previous studies examined 

individual mass movements [1], general 

morphology, and general the tectonic setting of the 

area [2] but the relation of these to the surface 

evolution has not been examined yet. Our goal was 

to investigate this relationship. 

An old ski-track is situated between 

Szombathely, and village of Sé. In the 1990’s, a 

landslide happened that hampered its further use. 

The understanding of this mass movement was the 

main reason for our investigation. 

309 

II. THE INVESTIGATION OF THE LANDSLIDE 

The slope became sensitive to the erosion due to the 

wood cutting on the ski-track. In the literature [3] 

authors consider the steep, surface parallel layering 

of the sediments as the most important reason for 

the previously occurred mass movements in our 

study area. 

A. SHALLOW BOREHOLES 

We drilled shallow boreholes along the landslide to 

check this assumed parallel structure. The clay and 

sand layers alternating almost parallel to the 

surface, and the straight oxidated clay layer as the 

margin between the wet and dry sediments verified 

this assumption. 

We couldn’t analyze the role of variation in 

precipitation, because the exact time of the 

landslide, being far away from urban area, is not 

known. According to different maps about this area, 

the landslide occurred in the first half of the 1990’s. 

B. OTHER PHENOMENA 

Breakdowns and ruptures also indicate the slope 

instability, but haven’t been investigated due to the 

possible artificial influence. The evidences of creep 

are deformed artificial structures, for example tilted 

fences or ruptures on walls. We tried to measure the 

velocity of movement with fixed checkpoints, but 

the moderate weather in winter 2006-2007 and 

2007-2008 retarded this. 

On the steep slope a lot of similar gullies with 

different state of development can be find, too. The 

investigated gully is conspicuously characterized by 

high erosive power: there are no sediment or even a 

layer of death fallen leaves on the valley floor after 

low amount of precipitation. The gully represents 

cascade long profile with numerous knickpoints due 

to the alternating erodibility of sediments in base 

rock. Visible layers in the valley side also show the 

near parallelism to the surface.

III. THE DISTRIBUTION OF PHENOMENA 

The geomorphologic features occur on the entire 6 

km long northern steep margin of the Pinka-plain. 

The apparent distribution of the mass movements is 

strongly correlates with the area of clear-cuts, 

especially where the base rock is the upper 

Pannonian sediment with the aforementioned 

alternating stratification. We investigated also the 

spatial distribution of the gullies. 

Where the base rock is the Pleistocene gravel, 

there the relief is low, and the surface is less 

dissected. However, if the base rock is of upper 

Pannonian strata of alternating sediments, the 

Tihany Formation, the relief is higher, and the 

appearance of gullies is more frequent. The reason 

for that is, that the precipitation immediately 

infiltrate into the gravel sediment without relevant 

erosion, contrary to the Pannonian base rock that 

include compact impermeable clay and sand layers 

with higher erodibility. 

IV. RELATION TO THE STRUCTURAL 

LINEAMENTS 

A conclusion of our investigation of the surface 

development is that the steep slope is a result of 

neotectonic uplifting or an asymmetric incision. 

The topography pretends like tilted platforms with 

stream pattern with two main directions. This form 

repeats between the different gravel platforms and 

also inside them. The neotectonic structure was 

already considered in previous investigations [4] 

just like the incision theory [5]. These contrasting 

theories and the active northern slope of Pinkaplain 

motivated us to investigate the area by GIS 

technology. 

The asymmetrical valley was analyzed using data 

of the densely spaced exploration wells by 

geostatistical evaluation of methods [6]. Data for 

three bedding plane and the surface was used for 

generating 3D DTMs. All models shows the scarp, 

less and less steep but situated more and more 

towards N. 

Based on the results outlined above, we assume 

that the investigated scarp is related to a listric fault. 

V. SUMMARY AND OUTLOOK 

The steep scarp of the Pinka plain is found to be an 

actively forming slope. Our observations endorse 

the concept of the neotectonic origin of the 

movements. Accordingly, the instability of the 

slope is expected to be present in the future, 

therefore surface development phenomena are 

310 

going to happen. Geophysical measurements would 

be useful to get more detailed insights of the 

faulting. 

It would be interesting to study the structural 

movements, the impact the recent surface 

morphology, and also the effects of the differential 

uplift: 0 mm/yr vertical movement marker isoline is 

assumed to cross our study area [7]. A further 

interesting question: Are there any relation between 

the general morphology and the similar structure of 

the pre-Tertiary basement [8]? We also plan to 

investigate the active periods of the surface 

development phenomenon. 


The study has been carried out in the framework of 

No. T47104 project of the Hungarian National 

Research Fund OTKA. We thank the assistance in 

fieldwork of ZS. CSÁKÁNY, P. GADÁNYI, A. 

HORVÁTH, GY. ISZTIN, P. KOVÁCS, Z. MAGYAR, A. 

NAGY, G. ORBÁN, É. SPANNER, B. TÓTH. In the 

evaluation of the data B. KOHÁN, DR. J. KOVÁCS 

and A. ZÁMOLYI gave useful advices. All help is 


REFERENCES 

[1] SZILÁGYI E. 1989. Vas megye 

felszínmozgásainak katasztere. Földr. Ért. 38. 

1-2. pp. 33–54. 

[2] HORVÁTH, F. et al. 2006. A Pannon-medence 

jelenkori geodinamikájának atlasza: Eurokonform 

térképsorozat és magyarázó. Magyar 

Geofizika, 47, 133-137. 

[3] KECSKÉS T. 1968. A szombathelyi 

dombcsúszás. Vasi Szemle 22. 4. pp. 557–566 

[4] ÁDÁM L. 1962. A Rábántúli kavicstakaró. In: 

ÁDÁM L. et al.: Néhány dunántúli 

geomorfológiai körzet jellemzése. Földr. Ért. 

11. 1. pp. 41–52. 

[5] JASKÓ S. 1964. A nyugat-vas megyei 

barnak�szénterület. Földt. Kut. 7. 2–3 pp. 24– 

48. 

[6] FÜST A. 1997. Geostatisztika. Eötvös Kiadó. 

Budapest. pp. 18-69. 

[7] JOÓ, I. 1992. Recent vertical surface 

movements in the Carpathian Basin. – 

Tectonophysics. 202. pp. 129–134. 

[8] KILÉNYI, É. and ŠEFARA, J. (ed.) 1989. Pre- 

Tertiary basement contour map of the 

Carpathian basin beneath Austria, 

Czechoslovakia and Hungary. 1: 500 000. 

ELGI Budapest, Geofyzika Brno, Bratislava 

Branch

Spray Can Geometry 

Gwen Wilke and Andrew U. Frank (Faculty Mentor) 




Email: {wilke,frank}@geoinfo.tuwien.ac.at 

Abstract — A model of axiomatic projective geometry for geographic 

information systems (GIS) is proposed that incorporates 

positional uncertainty. We define mathematical models of 

extended points and lines that reflect the extended and uncertain 

character of geographic features. Geometric operations 

in this model exhibit tolerance for positional uncertainty. The 

axiomatic approach ensures the consistency of geometric reasoning 

despite the uncertainties in the locations. 


Geometric functionality in current vector based geographic 

information systems (GIS) is based on infinitely 

small points and infinitely thin lines. This is in contrast 

to the fact that geographic features and their representation 

are extended and uncertain in location. Object representation 

in GIS is discrete and of limited computational 

accuracy and often destroys the consistency of geometric 

reasoning. A more realistic model of geometry is needed. 

The present approach is based on Menger’s axiomatic 

system for projective geometry [1]. We refer to a geometry 

as an algebra, consisting of a set of primitive objects 

and operations and a set of axioms. Every interpretation 

of primitives that complies with the axioms is considered 

to be a model for the geometry. In the proposed work 

interpretations of the primitive objects point and line are 

extended in all dimensions. Interpretations of the primitive 

operations connection and intersection exhibit tolerance 

for positional uncertainty in their input. 

The advantage of the axiomatic approach over other 

more pragmatic efforts in the past is that the implementation 

of basic operations is sufficient to derive compound 

objects and operations, analytical functions, and tests for 

relations. It guarantees concistency in geometric reasoning. 

II. MOTIVATION 

The idea for the proposed research emerged from a 

keynote speech given by Lotfi Zadeh: The name Spray 

Can Geometry refers to “a primitive world in which figures 

are drawn with a spray can, with no ruler or compass 

available” [2]. Many conventional approaches to 

geometric uncertainty modeling for GIS are built upon 

underlying exact operations and idealized object representation. 

By contrast, the present work aims at a flexible 

311 

representation that tolerates uncertainty in location while 

preserving the consistency of the axiomatic system. 

The Spray Can Geometry for GIS assumes interpretations 

of geometric primitives that reflect the extended 

character of geographic features and the positional uncertainty 

in their representation. These Spray Can primitives 

must meet a number of requirements in order to be viable 

for practical application in GIS. The most important requirement 

for the processing in a computer is closedness 

of operations. This is ensured by the axiomatic approach: 

Every set of interpretations that complies with geometric 

axioms automatically is operationally closed. Apart from 

this, two main criteria have been identified: 

1. Spray Can Points and Spray Can Lines are uncertain 

in all dimensions. 

2. Spray Can Operations exhibit tolerance for positional 

uncertainty in their input. 

A model that violates criterion 1 does not account for 

the real character of geographic features. A model that 

violates criterion 2 is isomorphic to the exact model; the 

resulting geometric reasoning equals exact reasoning and 

produces similar problems in a descete representation. 

III. HYPOTHESIS 

Our hypothesis is that an axiomatic model of 2D projective 

geometry can be defined that incorporates geometric 

operations with tolerance for positional uncertainty. 

These operations apply to objects that reflect the 

extended character of geographic features and the positional 

uncertainty in their representation in GIS. 

IV. BUILDING A MODEL 

The proposed approach is based on Mengers axiomatic 

system for projective geometry [1]. Projective geometry 

provides a workable research domain for geometric uncertainty 

modeling and is preferable for GIS: Euclidean 

geometry can be naturally embedded in projective geometry; 

Menger’s axiomatization is smaller and formulated 

in simple algebraic terms; It does not depend on dimension 

and can easily be extended to 3D. 

In a first step of the modeling process, existing mathematical 

tools for geometric uncertainty modeling are inspected 

and tested for compliance with the criteria listed 

in chapter 2. Among these models are Rosenfeld’s fuzzy

geometry [3], fuzzy plane geometry introduced by Buckley 

and Eslami [3], fuzzy rough sets [4], probability metrics, 

and Poston’s fuzzy geometry [5]. 

In a second step interpretations of primitive geometric 

objects and operations are defined based on the findings 

of step one. The primitive geometric objects of projective 

plane geometry are points, lines, universe (“everything“), 

and vacuum (”nothing”). Primitive operations comprise 

intersection (∧) and connection (∨). In Menger’s system 

the behavior of projective primitives is axiomized by two 

projective laws that are dual to each other: 

X ∨ ((X ∨ Y ) ∧ Z) = X ∨ ((X ∨ Z) ∧ Y ) (1) 

X ∧ ((X ∧ Y ) ∨ Z) = X ∧ ((X ∧ Z) ∨ Y ) (2) 

where X, Y, Z are primitive objects. The special role of 

universe U and vacuum V is determined by four axioms: 

U ∨ X = U, U ∧ X = X (3) 

V ∧ X = V, V ∨ X = X (4) 

for all primitive objects X. Initially three of the six primitives 

are defined. The remaining primitives must be chosen 

appropriately to ensure consistency of the axioms. 

Additionally, an approximate version of equality is defined. 

The set of interpretations is acceptable as a projective 

model, if Menger’s axioms can be verified. As a 

result, consistency and operational closedness is ensured. 

We applied the proposed procedure to a statistical interpretation 

of Spray Can Objects [6]. In the following 

section this interpretation is discussed to show the 

methodology of the research. The presented example 

complies with Menger’s axioms. Primitive objects are 

uncertain in all dimensions, but primitive operations do 

not exhibit tolerance for positional uncertainty. Consequently, 

the model is not satisfactory for GIS applications. 

It is subject of ongoing research to prove or disprove 

the existence of a model that satisfies all criteria. It 

is expected that additionally a degree of uncertainty has 

to be assigned to the axioms in order to define a working 

model. 

V. EXAMPLE 

For a given exact projective point p the Spray Can Point 

˜p is defined by the probability density function (pdf) 

of a Gaussian normal distribution on the homogeneous 

plane Hp in p (cf. Figure 1). The Spray Can Dual 

scd of ˜p is defined by scd.˜p = ˜p.d, where d denotes 

the duality operation in the exact model and . denotes 

the composition of functions. The Spray Can Connection 

˜∨ of two Spray Can Points ˜p and ˜q is specified by 

˜p˜∨˜q = scd. � d(p ∨ q) � ∼ , where ∨ denotes the connection 

operation in the exact model and p and q are the corresponding 

exact points. The definition of these primitives 

is sufficient to derive all remaining primitives. As we 

312 

have proven in [6] the proposed set of interpretations of 

projective primitives complies with Mengers axioms. 

Figure 1: The projective plane is isomorphic to the unit 

sphere S 2 modulo opposite points. (a) The homogeneous 

plane Hp in p ∈ S 2 . (b) A Spray Can Point ˜p in p. 

VI. FUTURE RESEARCH 

The main types of positional uncertainty in GIS are measurement 

errors and vaguely defined locations. Uncertain 

geometric primitives showing these types of uncertainty 

can be expressed in terms of probabilistic and possibilistic 

constraints [7]. The proposed work contributes to the 

long term goal of describing geometric constructions of 

objects under different types of uncertainty by generalized 

constraint propagation rules. 

REFERENCES 

[1] Leonard Blumenthal and Karl Menger. Studies in 

Geometry. W. h. Freeman and Company, 1970. 

[2] Lotfi A. Zadeh. From fuzzy logic to extended 

fuzzy logic - the concept of f-validity 

and the impossibility principle. In FUZZ- 

IEEE 07, www.fuzzieee2007.org/ZadehFUZZ- 

IEEE2007London.pdf, 2007. 

[3] John N. Mordeson and Premchand S. Nair. Fuzzy 

Mathematics - An Introduction for Engineers and 

Scientists. Physica-Verlag. A Springer-Verlag Conpany., 

1998. 

[4] Didier Dubois and Henri Prade. Rough fuzzy sets 

and fuzzy rough sets. International Journal of General 

Systems, 17(2-3):191–209, 1990. 

[5] Tim Poston. Fuzzy Geometry. PhD thesis, University 

of Warwick, 1971. 

[6] Gwen Wilke and Andrew U. Frank. Projective spray 

can geometry - towards an axiomatic approach to error 

modelling for vector based geographic information 

systems. GEOWS 2009, accepted for publication. 

[7] Lotfi A. Zadeh. Generalized theory of uncertainty 

(gtu) - principal concepts and ideas. Computational 

Statistics & Data Analysis, 51:15–46, 2006.

Anammox Studies Using New York City Centrate to Correlate 

Performance, Population Dynamics and Impact of Toxins 

Alex Rosenthal, Krish Ramalingam, and John Fillos (Faculty Mentor) 

Department of Civil Engineering 


New York, The United States of America 

Email: arosent00@ccny.cuny.edu 

Abstract — Anaerobic ammonium oxidation 

(Anammox) is a promising new technology for the 

removal of nitrogen from wastewater. The City 

College of New York has been operating a bench 

scale Anammox sequencing batch reactor since 

January 2008 with the objective to enrich Anammox 

biomass in anaerobic digester centrate and to assess 

the impact of various environmental factors on 

Anammox performance. Also, with the data from 

batch activity tests it may be possible to correlate 

specific Anammox activity with the microbial dynamics 

of the reactor. These data will help the City 

of New York design a process that can be used to 

alleviate their nitrogen loading problem. 


Wastewater flows are a major source of nitrogen 

pollution to coastal ecosystems. In order to comply 

with current environmental regulations, The New 

York City Department of Environmental Protection 

(NYCDEP) is in the process of upgrading its water 

pollution control plants (WPCPs) from the conventional 

step-feed activated sludge process to biological 

nitrogen removal (BNR) processes. One promising 

technology under consideration is the use of anaerobic 

ammonia oxidation (Anammox) to remove nitrogen 

from the high strength centrate produced from 

the dewatering of anaerobic digested sludge. The 

Anammox process, i.e. the microbiological conversion 

of ammonium and nitrite to dinitrogen gas, is a 

very recent addition to our understanding of the biological 

nitrogen cycle. Compared to conventional 

BNR processes, the Anammox process requires no 

organic carbon addition and has decreased oxygen 

and alkalinity requirements. By some estimates, 

Anammox results in a 90% operating cost reduction 

compared to existing removal technologies [1]. 

II. AIMS 

The evaluation of the Anammox process was first 

initiated in New York City on December 2005 

through January 2008 at a pilot facility at the 26th 

313 

Ward Nutrient Research Facility using inoculum 

from the DEMON reactor in Strass, Austria. 

Though the applicability of the process was demonstrated, 

the present study is designed to address 

and elucidate inhibitory concerns that became 

evident during the pilot study and thus further 

demonstrate its viability to treat centrate at New 

York City wastewater treatment plants. This study 

began on January 2008 and is being conducted at 

the City College of New York (CCNY) using a 

bench scale continuous flow sequencing batch 

reactor (SBR) as an enrichment reactor for kinetic 

tests on Anammox biomass. The seed for the SBR 

was obtained from the previously operated pilot 

facility. 

An additional aspect of this research effort is to 

correlate the observed gross activities within the 

SBR to the active biology present. Using molecular 

analyses, changes in activity will be related to 

changes in microbial composition and may serve 

as a predictor for major process upsets. 

III. FINDINGS 

The CCNY SBR operates anoxically from a decanted 

volume of 10 liters up to a fill volume of 20 

liters, a 20 day solids retention time (SRT), 35˚C, 

and a pH controlled between 7.5-7.8. The feed to 

the SBR is anaerobic digester centrate from the 

Wards Island Wastewater Treatment Plant that is 

previously treated partially in a separate bench 

scale nitritation reactor. The nitritation reactor 

operates at a 42 hour SRT, 21˚C, and dissolved 

oxygen (DO) concentration of 2 mg/L, producing 

an effluent with a NO2-N concentration of 150-200 

mg/L and effluent NH3-N depending on the influent 

NH3-N concentration. To maintain the 

stoichiometry required to support the Anammox 

process, nitrite is added to the effluent as needed. 

The Anammox reactor currently operates at a 

nitrogen loading rate of 0.75 g/L*day and a nitrogen 

removal efficiency of 88% which is comparable 

to previously studied bench scale SBRs reported 

in the literature[2]. Average stoichiometry

of the main reactor has been 1.00 NH3 : 1.21 NO2 - 

: -0.13 NO3 - , a slight deviation from the published 

stoichiometry of 1.00 NH3 : 1.32 NO2 - : -0.26 NO3 - 

which is most likely due to the complex matrix of 

the feed that supports a complex ecology [3]. 

Parallel to the SBR study, short duration batch 

tests are being conducted to assess the impact of 

different environmental factors such as pH, DO, 

NO2 - , and Cl - toxicity. The seed for these batch 

tests is the waste solids required to sustain the 

SRT selected for the SBR. Figure 1 shows typical 

results from a batch study confirming the 

stoichiometry expected from the Anammox process. 

Figures 2 and 3 display preliminary results of 

the impact of pH and Cl - on Anammox activity. 

Phylogenetic analysis using the planctomycetales 

primer set (Pla46F, 1492R) and the 

Anammox target primer set (Pla46F, 820R) both 

detected the presence of the Anammox bacteria, 

Candidatus Brocadia sp. 40. This was followed by 

community analysis using Denaturing Gradient 

Gel Electrophoresis (DGGE) which confirmed that 

Candidatus Brocadia sp. 40 was the dominant 

Anammox performing species in the reactor. 

However, the dominant clone found in the inoculating 

culture from Strass was Kuenenia Stuttgartiensis 

and the dominant species at the New York 

pilot plant was Brocadia Fulgida. This observation 

has been found in other inoculation/reactor pairs 

and suggests varied selective pressures between 

one wastewater environment and another [4]. 

Weekly samples from the Anammox reactor 

have been extracted since May 2008 and are being 

analyzed using qPCR. This time interval includes 

two major process upsets and extended periods of 

progressively increased loading. It is hypothesized 

that variations in reactor performance may 

be related to temporal variations in microbial 

composition and activity. It may be possible to 

detect those changes using qPCR of mRNA. 

[N] (mg/L) 

50 

40 

30 

20 

10 

Anammox Activity Test 

0 

0 15 30 45 60 

Time (min) 

NH3-N 

NO2-N 

NO3-N 

Figure 1. Typical results from Anammox batch 

activity tests 

314 

SUR (ug/mgVSS*hr) 

Figure 2. pH effect on Anammox activity. pH was 

adjusted from original values of 7.5-7.8 using CO2 

and NaCO3. 

SUR (ug/mgVSS*hour 

35 

30 

25 

20 

15 

10 

Figure 3. Cl - effect on Anammox activity. Cl - was 

added as NaCl. 


This research is funded by the New York City 

Department of Environmental Protection. Special 

thanks go to Alan Deur, Keith Beckmann, 

and Rolando Villacres for their continued 

guidance and support. 

REFERENCES 

pH effect on Anammox Activity 

5 

0 

7.00 8.00 

pH 

NH3-N 

NO2-N 

Cl - Effect on Anammox Activity 

15 

10 

5 

0 

0 mg/L 500 mg/L 1000 mg/L 2000 mg/L 

Additional Chloride 

NH3-N 

NO2-N 

[1] M. Jetten et al. Microbiology and application of 

the anaerobic ammonium oxidation (‘anammox‘) 

process. Current Opinion in Biotechnology, 

12:283-288, 2001. 

[2] A. Dapena-Mora et al. Stability of the ANAM- 

MOX process in a gas-lift reactor and a SBR. 

Journal of Biotechnology, 110:159-170, 2004. 

[3] M. Strous et al. The sequencing batch reactor as 

a powerful tool for the study of slowly growing 

anaerobic ammonium-oxidizing microorganisms. 

Appl Microbiol Biotechnol, 50:589-596, 1998. 

[4] W. van der Star et al. Startup of reactors for 

anoxic ammonium oxidation: Experiences from 

the first full-scale anammox reactor in Rotterdam. 

Water Research, 41:4149-4163, 2007.

Multi-Perspective Ultramicroscopy with Structured Illumination in 

Optically Dense Specimens 

Stefan Kalchmair, Klaus Becker, Nina Jährling and Hans-Ulrich Dodt (Faculty Mentor) 

Institute of Solid State Electronics, Dept. of Bioelectronics 



Email: stefan.kalchmair@tuwien.ac.at 

Abstract — Three-dimensional imaging of biological 

specimens allows visualization of the spatial 

structures in a relatively short amount of time. 

Structured illumination ultramicroscopy is a technique 

to obtain good 3D reconstruction even in 

optically dense specimens. However, in large samples 

scattering of the excitation beam and especially 

the illumination pattern ultimately limits the functionality 

of this method. We present a method for 

increasing the image quality by illuminating from 

multiple perspectives with a specially designed 

specimen rotator. For comparison of conventional 

and multi-perspective ultramicroscopy the central 

part of an entire mouse brain is imaged. Our results 

show significantly enhanced contrast and reduced 

artefacts. 


Imaging of fluorescence labelled specimens has 

become a standard tool in life sciences. A fluorescent 

dye is injected into the specimen or a fluorescent 

protein genetically expressed, excited with a laser 

and examined under a microscope. Ultramicroscopy 

(UM) is a technique which allows three-dimensional 

imaging of macroscopic samples with micrometer 

resolution [1, 2]. In ultramicroscopy, a cleared 

specimen is illuminated from the side with a thin 

sheet of laser light. Only the focal plane of the detection 

optics is illuminated, so that no out-of-focus 

light is generated and only structures from a thin slice 

of the specimen are recorded. 

We improved this technique by the introduction of 

structured illumination ultramicroscopy (SI-UM) [3]. 

The light sheet is spatially filtered to form single 

beams of light with large spaces in between. After 

recording each image, the illumination mask is 

shifted by a fraction of one single beam width and 

the next image is recorded (Figure 1). By processing 

the entire set of images, an improved image is calculated 

with reduced background fluorescence and 

enhanced contrast. 

However, in large samples or optically dense specimens, 

scattering of the structured light sheet limits 

315 

Figure 1: Optical setup of the multi-perspective 

SI-UM. The fluorescent sample is excited from the 

left side with a structured light beam. The sample 

is mounted on the magnetically coupled platform 

and rotated after each recorded SI-UM image. 

the functionality of the method. SI-UM depends on 

the clear visibility of the pattern in the focal plane of 

the detection optics. In a scattering sample, the structured 

light sheet is clearly visible in the outer area of 

the specimen, but appears strongly degraded deep 

inside the sample. Also shadowing effects become 

stronger as the beam propagates through the tissue. 

This paper describes a method to reduce the influence 

of light sheet degradation. By merging images 

from multiple perspectives, we can increase the final 

image quality. For this purpose we developed a computer 

controlled specimen rotator that allows precise 

sample movement inside the liquid filled specimen 

chamber. 


The fluorescent samples were excited by a solid state 

laser (Cyan Excelsior, Spectra Physics, � = 488 nm, 

50mW). The expanded beam was focused vertically 

by a cylindrical lens to form a thin light sheet. A 

mask was placed in the focus of the cylindrical lens 

to form the illumination pattern, which then was

projected into the specimen. The microscope (Zeiss) 

was equipped with a bandpass filter (pass band: 505- 

530nm, Zeiss) positioned above the objective. Images 

were recorded with a CCD Camera (CoolSnap 

K4, 2048x2048 pixels, 12bit, Roper Scientific). To 

achieve sufficient transparency for most biological 

specimens, chemical clearing is necessary. Clearing 

was done by incubation in benzylbenzoat/ benzylalcohol 

(BABB), which has the same refractive index 

as protein. 

The specimens were mounted on a custom made 

specimen rotator. To avoid image distortions after 

reconstruction, displacements along the optical axis 

had to be below the vertical resolution of the microscope, 

which was about 30 �m. To protect the motor 

chamber against fluid in the BABB filled specimen 

chamber, the rotating specimen platform was magnetically 

coupled to the motor (Figure 2). To ensure 

smooth movements a chemically resistant bearing 

was used. 

III. RESULTS 

We recorded images from the central region of a 

mouse brain by using tissue autofluorescence. If the 

sample is illuminated from only one direction, the 

illumination pattern appears dim and gradually degraded 

from top to bottom (Figure 3 a). This effect is 

mainly due to scattering caused by tissue outside the 

field of view. The processed image shows sharp 

edges at the surface of the specimen but blurred 

features deep inside the sample (Figure 3 b). After 

multi-perspective imaging, the single SI images are 

superimposed computationally (Figure 3 c). The 

processed image now appears sharp in most areas of 

the image (Figure 3 d). The white arrow in Figure 3 d 

marks a feature deep inside the sample, which was 

hardly noticeable in Figure 3 b and is now clearly 

visible. Further, artefacts from shadowing effects 

were significantly reduced. 

Figure 2: Schematic of the specimen rotator. 

316 

Figure 3: Comparison of conventional and multiperspective 

SI-UM. (a) Single-perspective image 

with structured illumination. (b) Result of post 

processing of 40 shifted SI images. (c) Multiperspective 

image. (d) Combination of two post 

processed multi-perspective SI-UM images. 

Future improvements are possible by computational 

analysis of the single SI images for automatic alignment 

of the superposition boarders. Optimization of 

the specimen rotator should also result in increased 

accuracy and recording speed. 


We have demonstrated that multi-perspective illumination 

improves image quality of SI-UM 

images in optically dense specimens. Artefacts 

from shadowing effects are also significantly reduced. 

Especially for large specimens this approach 

is advantageous. 

REFERENCES 

[1] H.-U. Dodt, U. Leischner, A. Schierloh, N. Jährling, 

C. P. Mauch, K. Deininger, J. M. Deussing, 

M. Eder, W. Zieglgänsberger, and K. Becker. Ultramicroscopy: 

three-dimensional visualization 

of neuronal networks in the whole mouse brain. 

Nat Meth, 4:331-336, April 2007. 

[2] K. Becker, N. Jährling, E. R. Kramer, F. Schnorrer 

and H.-U. Dodt. Ultramicroscopy: 3D reconstruction 

of large microscopical specimens. J. 

Biophoton. 1:36-42, January 2008. 

[3] S. Kalchmair. Image Improvement by Structured 

Illumination in Ultramicroscopy. MA thesis, 

Vienna University of Technology, June 2008.

Analytical technology for biogas production from 

straw by multivariate Near-infrared spectroscopy 

Chularat Krongtaew 1 , Karin Fackler 1 , Barbara Hinterstoisser 2 

and Kurt Messner 1 (Faculty Mentor) 

1 Institute of Chemical Engineering, Vienna University of Technology, Vienna, Austria 

2 Department of Material Sciences and Process Engineering, University of Natural Resources 

and Applied Life Sciences, Vienna, Austria 

Email: ckrongta@mail.zserv.tuwien.ac.at 

Abstract —An analytical procedure to evaluate 

the key process parameters of wheat (Triticum 

aestivum L.) and oat (Avena sativa L.) straw pretreatment 

as well as the biogas fermentation of 

treated straw using Fourier transform nearinfrared 

(FT-NIR) spectra in combination with 

chemometrics was developed. Not only weight 

loss, residual lignin content and hydrolysable 

polysaccharides in terms of reducing sugars of 

delignified straw, but also biogas productivity of 

pre-treated straw and the parameters, total solids 

and volatile solids, were accurately calculated 

based on substrate quality after pretreatment. The 

multivariate mathematical analysis was used as an 

efficient facility for spectral data processing. The 

findings in this work suggest FT-NIR spectroscopy 

as an alternative and low-budget analytical tool 

providing robust and validated prediction models 

for lignocellulose-to-energy conversion in biogas 

production. 


Owing to the world’s energy shortage, a bulk volume 

industry of new rapidly growing agricultural biomass-to-energy 

conversion is urgently required. 

These processes need a robust and low-budget process 

analytical chemistry (PAC) approach to come 

across all hindrances for efficiently industrial anaerobic 

digestion process analyses. Great advantages 

of process analytical chemistry will be accomplished 

if analyses can be done prior to bulk production in 

terms of both growing plants and building up the 

digester. As pretreatment step of lignocellulose was 

required to diminish the rate-limiting step of overall 

anaerobic digestion processes, in the present study 

the crucial parameters of both pretreatment and anaerobic 

digestion steps of wheat and oat straw were 

evaluated by means of Fourier transform nearinfrared 

(FT-NIR) analysis with mathematical treatment 

of spectral data. This led to achievement on 

evaluating biogas productivity based on substrate 

quality by practical and inexpensive means. 

317 


Delignifying pretreatment of wheat and oat straw 

performed in aqueous suspension (2 g/ 20ml) with 

different acidic and alkaline pre-treatment systems. 

Afterwards, straw particles were washed with deionized 

water and dried at 50°C before they were 

either milled with a Retsch ZM 1000 ultracentrifugal 

mill (80 �m) or enzymatically hydrolysed (Viscozyme®L, 

www.novozymes.com). After hydrolysis, 

the amount of reducing sugars in the supernatant 

was determined by means of a modified 

dinitrosalicylic acid (DNS) assay. Extraction and 

lignin analyses of milled sample were carried out 

according to TAPPI methods. 

For biogas potential test both solid and liquid 

parts after straw pretreatment was used as substrate 

and 150 ml digested sludge was added as inoculum. 

The anaerobic digestion performed at 37°C and 

accumulative biogas generation was recorded daily. 

Total solids and volatile solids of digested sludge 

were determined after the gas generation ceased. 

NIR spectroscopy of delignified straw (80 μm) 

was recorded by EQUINOX 55 (Bruker Optics 

Inc., Germany) using a fiber optic probe [1]. The 

appearance absorbance, log [1/ Reflectance], of 

treated straw samples was measured with 8 cm -1 

resolution, 100 scans, the wave number ranging 

from 10000 to 4000 cm -1 with four replication. 

The 17 smoothing points and 2 nd order polynomial 

fit of spectra were applied [2]. Statistical analyses 

of NIR spectra were performed using OPUS 6.0 

(www.brukeroptics.de) and Unscrambler 9.7 

(www.camo.com), the chemometric software. 


For the highly lignified and acetylated wheat straw 

samples (i.e. non-treated sample with 20.68 % total 

lignin content), the minima at 5980 cm -1 attributed 

to lignin, and at 5800 cm -1 attributed to lignin and 

xylan moieties [3] were intense as shown in Figure 

1A. The similar results and spectral features were 

obtained in oat straw samples (Figure 1B). Princi-

pally, there were two major characteristics of delignified 

straw samples found from the NIR 2 nd derivative: 

1) the lignin minimum near 5980 cm -1 and the 

overlapping of lignin and xylan minimum at 5800 

cm -1 were less intense due to the delignifying steps 

in which lignin and hemicellulose xylan were degraded, 

2) the minima at 5960 and 5990 cm -1 assigned 

to xylan disappeared due to the degradation 

or deacetylation. Therefore, the lignin and carbohydrate 

content within delignified straw after pretreatment 

were certainly analysed from the FT-NIR 

spectra by means of quantitative analysis through 

partial least-squares (PLS) regression models as 

shown in Table 1. 

As some of hemicelluloses, extractives, mineral 

salts in straw were solubilised after pretreatment, 

volatile solid content in treated straw increased and 

led to higher biogas yield for anaerobic digestion. 

Total solids and volatile solids of digested sludge 

that significantly influenced biogas yield were powerfully 

analysed by FT-NIR spectroscopy (Table 1). 

Component range 

Spectral processing 

No. of Sample 

Loading factors 

Calibration 

R 2 cal 

Figure 1: NIR 2 nd derivative of delignified straw: 

(A) wheat, and (B) oat straw samples. 

NIR Reducing sugars Total residual lignin Total solids Volatile solids Biogas 

Wave number [cm -1 ] 10001.1-6398.7 

5800.9-5199.2 

4601.3-3999.7 

115.80-704.20 mg/g 

First derivative + MSC 1 

10001.1-7598.2 10001.1-9399.4 10001.1-8199.9 

7000.4-4597.5 8801.6-8199.9 7602.1-7000.4 

7602.1-5797.0 5800.9-5199.2 

5.23-21.45 % 93.60-99.73 % 94.50-99.20 % 

First derivative Second derivative First derivative + MSC 

38 

38 

32 

5 

4 

5 

1 

10001.1-8199.9 

7000.4-6398.7 

5800.9-4597.5 

219.0-386.5 ml/g 

MSC 

38 

4 

1 

30 

2 

RMSEE 2 

Validation 

R 2 val 

0.96 

38.50 mg/g 

0.92 

0.98 

0.64 % 

0.97 

0.96 

0.47 % 

0.93 

0.27 % 

0.75 

20.9 ml/g 

RMSECV/RMSEP 3 

53.70 mg/g 

0.73 % 

0.80 % 

0.33 % 

1 2 3 

Multiplicative scattering correction, Root mean square error of estimation, Root mean square error of cross validation/Root mean square error of prediction 

0.85 

0.88 

0.65 

23.4 ml/g 

Table 1: Partial least-squares (PLS) regression models calculated from FT-NIR spectra 

It was obvious that the analytical procedure of the 

pre-treated substrate by means of NIR spectra combined 

with multivariate analysis could be applied to 

the entire process – from the pre-treatment of lignocellulose 

to anaerobic digestion. Mathematical 

spectral data processing (partial least squares regression 

– PLSR) together with derivatization, 

multiplicative scattering correction (MSC), minmax 

normalization, constant offset elimination as 

data pre-treatment was applied in order to achieve 

optimized, robust, and validated models. This study 

provided a potential analytical approach based on 

substrate quality which can be feasibly broadened to 

the large scale industrial application. 


The Technology Grants from the Austrian Federal 

Ministry for Science and Research is honourably 

acknowledged. 

318 

Lignin decrease 

5990 

5980 

5960 

5990 

5980 

5960 

REFERENCES 

5885 

5885 

5840 

5840 

Lignin decrease 5800 

5800 

5750 

Lignin 8.32% 

Lignin 11.29% 

Lignin 16.97% 

Lignin 20.68% 

4.E-06 

2.E-06 

0.E+00 

-2.E-06 

-4.E-06 

-6.E-06 

-8.E-06 

[1] K. Fackler, M. Schwanninger, C. Gradinger, 

B. Hinterstoisser and K. Messner. Fungal decay 

of spruce and beech wood assessed by 

near infrared spectroscopy in combination 

uni- and multivariate data analysis. Holzforschung 

61: 680-687, 2007. 

[2] A. Savitzky and M.J.E. Golay. Smoothing 

and differentiation of data by simplified 

least squares procedures. Analytical chemistry 

36(8):1627-1639, 1964. 

[3] J.S. Shenk, J.J. Workman and M.O. Westerhaus. 

Application of NIR Spectroscopy to 

Agricultural Products. Handbook of Near- 

Infrared Analysis. (D.A. Burns, E.W. Ciurczak, 

eds.). Dekker, New York pp. 419- 

474, 2001. 

5750 

5700 

5700 

Wave number [cm -1 ] 

(A) 

Lignin 8.83% 

Lignin 9.90% 

Lignin 15.64% 

Lignin 18.51% 

(B) 

4.E-06 

2.E-06 

0.E+00 

-2.E-06 

-4.E-06 

-6.E-06 

-8.E-06 

derivative 

NIR 2 nd 

NIR 2 nd derivative

PLAYING WITH MAPS: 

THE ROLE OF WEBCARTOGRAPHY IN EDUCATION 

Univ.Ass. MSc. Eszter Simonné-Dombóvári and 

Univ.Prof. Mag. Dr. Georg Gartner (Faculty Mentor) 




Email: eszter@cartography.tuwien.ac.at, 

georg.gartner@tuwien.ac.at 

Ass.Prof. MSc. Dr. José Jesús Reyes Nuñez (Faculty Mentor) 

Department of Cartography and Geoinformatics 

Eötvös Loránd University 

Budapest, Hungary 

Email: jesus@lundens.elte.hu 

Abstract — My PhD thesis is about developing 

map games in the geographic education for 4th, 6th 

and 8th grade of High Schools. It analyses 

geography and cartography education and their 

teaching and learning methods. It also researches 

possibilities of not traditional teaching tools in 

Austria, Hungary and in other countries of 

European Union. My aim is to make an interactive 

website with applications to learn cartographical 

skills. They can be used by pupils to practice map 

reading and geographical concepts. 


As far back as the history of geography teaching 

goes, conscientious teachers have sought new and 

better ways to facilitate and accelerate geography 

learning. We all know that people’s best learning 

experience comes when they are engaged in activities 

that they enjoy and care about [1]. 

Edutainment, the method of amusing teaching, can 

help practicing and enlarging the store of learning in 

particular by map reading and geographical concepts. 

The edutainment games have some basic elements, 

such as educational content, interactive components 

and attractive interface that can catch the attention of 

the users. But one of the most important rules of the 

map games is the interactivity which is possible with 

the special opportunities of the web environment like 

Flash, Java, JavaScript, SVG. This new techniques 

let the developers using interactive and multimedia 

elements to make dynamic websites [2]. 

These days we witness an unexpected 

development of Information and Communication 

Technology (ICT). Its rule and importance is 

determinative even in schoolwork [3]. Using 

319 

computer and online-medium in geography education 

was summarized by A. Koller. He expressed that 

more and newer means have to be used in education 

beside traditional tools. Certainly this brings a new 

situation for teachers and students as well [4]. 

Nowadays the number of geographical and 

cartographical websites – e.g. homepages of 

institutes, geography portals, lexicons, guides, 

methodological assistance, databases, map- and 

outline map catalogs – is continuously increasing. 

The main aim of these is to help the work of students 

and teachers in preparation for the lessons or to raise 

their attention. A website containing map games can 

be included to this category, because it is planned to 

entertain, but at the same time it is also able to 

develop the user’s cartographical skills. It is a great 

tool to practice what they have learnt previously, that 

is the curriculum itself. It is recommended to people 

of different ages, who prefer games and putting their 

memory and general knowledge into test. 

II. EXPERIENCES 

Nowadays not only the 3D, complicated, virtual 

reality games but also the amusing, simple, easy-touse, 

non-violent, short, intellectual type of 

entertainment games is popular. The main types of 

traditional cartographic edutainment are the 

following [5]: 

One: Outline map game. The users have to identify 

map features or to position them on a map. 

Two: Puzzle. The elements can be equal in size or 

administrative areas like countries or counties. 

Three: Cross-words. It is a combination of the 

normal cross-word and the outline map.

In the poster different educational software and 

websites are presented, including a website 

developed for schools. This application is the first 

result of my PhD research (Figure 1). It was 

originally prepared for Hungarian education, but my 

aim is to implement this program into German and 

other languages too. 

A. AIMS 

The aim was to make a program which can help 

learning, practising and exercising cartographical 

knowledge, an educational tool which is easily 

accessible on internet. If it is based on the 

requirement of the secondary school, it can help the 

teachers’ work in preparation for the lessons as well 

as to raise students’ attention. This develops spatial 

orientation which is a geographical competence in 

education. This is the ability to orientate oneself: 

topographical orientation skills, map-reading 

competence, orientation in real space and reflection 

upon spatial perception [6]. 

Figure 1: GeoLearn website, 

http://cartography.tuwien.ac.at/geolearn 

B. TECHNIQUES 

The interactive web applications will be developed 

with scripting languages (PHP and JavaScript) on the 

base of MySQL-database to be portable. The lists of 

topographic requirements are saved as tables in a 

MySQL-database with the same structure and PHP 

was used to implement the user management, to 

work with HTML-forms and to make database 

connection. The client-side JavaScript realizes the 

interactivity of the website. This technical 

environment can help making a dynamic website 

with cartographical contents and a cartographical 

information system [7]. 

C. PLANS 

According to the feedbacks, users would like to see 

more functions on the website, e.g. separate screen 

for teachers with the possibility to adjust, modify the 

pre-defined database. There will be a complete web 

application for using and learning geographical 

320 

names including these new functions. The further 

plans are to make other applications about 

cartographical skills to this website, e.g. tests, outline 

maps, puzzles. 

III. FEEDBACK 

Some teachers built the program into their geography 

class thematic. They made tests with this application. 

They found it helpful to memorize topographic 

information. Pupils and students used it for preparing 

for tests and final exams. Students outside school 

were also interested in it. The number of the visitors 

on the website shows it (more than 1400 visitors in 6 

months on Hungarian website). They found this 

website very useful and entertaining. Last but not 

least, we could compare the exam results of students 

who practised with our program or not. The results of 

the program users were 15% better on average. 

REFERENCES 

[1] M. Resnick. Edutainment? No Thanks. I Prefer 

Playful Learning. Retrieved March 08, 2008, 

from http://www.roboludens.net/Edut_Articoli/ 

Playful_Learning.pdf 

[2] L. Zentai, E. Dombóvári. Edutainment in 

cartography. In: Proceedings of International 

Cartographic Association (Eds.), Joint ICA 

Commissions Seminar, pages 60-65, Madrid- 

Budapest, July 2005. 

[3] Eurydice. Key Data on Information and 

Communication Technology in Schools in 

Europe. Retrieved February 03, 2008, from 

http://www.eurydice.org/ressources/Eurydice/pdf 

/0_integral/048EN.pdf 

[4] A. Koller. Computereinsatz und Online-Medien 

im GW-Unterricht. In: W. Sitte und H. 

Wohlschlägl (Eds.): Beiträge zur Didaktik des 

„Geographie und Wirtschaftskunde“-Unterrichts 

(= Materialien zur Didaktik der Geographie und 

Wirtschaftskunde, 16). Universität Wien, pp. 59- 

75, Wien, 2001. 

[5] E. Dombóvári. Master thesis. Interaktív 

térképrejtvények. Eötvös Loránd University, 

Budapest, Juni 2005. 

[6] Deutsche Gesellschaft für Kartographie (DGfK) 

(Eds.) Educational Standards in Geography for 

the Intermediate School Certificate. Retrieved 

February 10, 2008, from 

http://www.geographie.de/ 

[7] M. Gede, E. Simonné-Dombóvári. The blind 

mouse – mute map game. In: Proceedings of 5th 

International Conference on Geographic 

Information Systems (ICGIS2008), pages 461- 

466, Istanbul, July 2008.

Overtopping of Dams – A Model Approach 

Michael Pucher and Peter Tschernutter (Faculty Mentor) 

Institute of Hydraulic And Water Resources Engineering 



Email: michael.pucher@kw.tuwien.ac.at 

Abstract — The design of dams with full or partial 

overtoppable crests already has a long history. 

Since recently their number is increasing constantly, 

but there are still open questions concerning 

their design. Design formulas in the literature 

give different results. One of the reasons could be 

the underlying model test assumptions. Model test 

on two different sets were performed and their results 

compared to recommendations from literature. 


The problem of flood discharges in high dams is 

usually solved by means of a concrete spillway separated 

from the dam. But overflowable dams can be 

� less expensive – less “over-design” - especially 

when used during construction of diversion 

structures 

� aesthetically pleasing 

Figure 1: Types of failures of bank protections. 

Erosion of single stone (left) or the bank as a 

whole (right) [1] 

Of late, it has repeatedly been attempted to reduce 

the cost of higher dams of this type by admitting their 

overtopping. The design of dams with full or partial 

overtoppable crests has already a long history. This 

type of dam can be found on river dykes, with a 

sideways overflow section, or in the case of retention 

dams, with a vertical flow direction towards the crest. 

Because of the recent floods overtoppable dykes or 

retentions dams have undergone a revival. The main 

scientific questions are the: 

� flow characteristic on the overflow section 

� forces on the lining or single stone 

� location of overtopping section 

321 

� best and economic type of slope protection 

� design of special features (e.g. crest, dam base) 

To find answers for our questions a literature review 

and physical model tests have been undertaken. 

II. STATE OF THE ART 

In [1] the basic hydraulic mechanisms at and over a 

overflow section are discussed. A lot of formulas for 

overflow sections in terms of hydraulics and stability 

are based on research on ramps [2]. The mechanisms 

of failure and forces on the lining or single stone are 

well described in [1, 3, 4]. Recommendations on the 

location of the overflow section are given in (5). 

Usually the design of a well defined section is recommended. 

Due to differential settlements the discharge 

at preferred flow paths can exceed the design 

discharge. Thus often causing failures. 

Figure 2: Comparison of rip-rap formulas [4] 

For the design of over-flow dam sections a multitude 

of slope-protection methods can be found in the 

literature [1, 5]. 

� Placing of a lining (bank protection) like riprap, 

placed riprap, paver stones, open-stone asphalt 

and more 

� Consolidation with soil cement 

� Composite methods with geotextiles or gabions 

For most of the construction methods design formulas 

can be found in the literature [4, 5, 6, 7]. However, 

these design formulas (see for example “Figure 

2”give results in a wide range [4, 5]. This is not surprising 

since most of the formulas are based on 

model tests, where the settings and boundary condi-

tions are difficult to translate to any other test. For 

special design features individual project design and 

the literature often propose quite divergent solutions 

[4]. 

III. PHYSICAL MODEL TESTS 

Due to the differences in formulas and their underlying 

model tests it was decided that basic research in 

terms of an extended “model family” is needed to 

clarify the influence of the model type on results. The 

first two sets of physical model tests were performed 

by means of a sectional model with a slope of 2H:1V 

in a 50 cm wide flume of the Hydraulic Laboratory. 

For the first set (1) a box model substituted the 

dam body, while in the second (2) set a “half-dam” 

mode was used (see “Figue 3”) [8]. 

1 2 

Figure 3: Model sets 

Testing the first set we found that the failure mode 

was often a slip surface along the border of the lining 

and the filter. That means that the whole rip-rap 

slipped one to two centimeters. Thus opening a joint 

at the dam crest and destabilizing the single stones. 

By increasing the discharge the riprap was destroyed 

beginning from top down to bottom. Sometimes the 

slip would occur earlier but the rip rap would stay 

stable until a higher discharge (see “Figure 4”). By 

protecting the upper fourth of the riprap we could 

improve the performance reasonably. 

Figure 4: Results on a slope H2:V1 (tan�=0,5) 

In the series with 1V:2H slopes on the “half-dam” 

model, with a slightly different time-step of discharge 

increase, no slip surface occurred. Higher 

discharge levels than in the first set could be 

achieved. As the failure mode, the erosion of single 

stones could be determined. An interesting effect is 

322 

that during the erosion process temporarily a quasi 

stable system of “cascades”, before the final erosion, 

is formed. 

IV. CONCLUSION AND OUTLOOK 

The research indicates that the model test setup might 

have significant influence on the results. The “Halfdam” 

model setup, with a small discharge increase, 

results in higher critical discharge levels than in the 

box setup, while no slip surface occurred. Generally, 

the results are in range with to the ones found in the 

literature. It is not yet possible to recommend or 

discard any design formula. Since we found such 

variation in our results we will continue our efforts. 

An extended series will be run in a big flume to 

check on 3D effects (prefered flow patchs etc.). 

REFERENCES 

[1] M. Bosshard, Überflutbarkeit kleiner Dämme, 

Versuchsanstalt für Wasserbau, Hydrologie und 

Glaziologie der ETH Zürich, 1991 

[2] G. Platzer, Hydraulische Grundlagen für die 

Dimensionierung ebener und muldenförmiger 

Blocksteinrampen mit einer Neigung von 1 : 10, 

Dissertation an der Technischen Universität 

Wien, 1994 

[3] A.Biberstein, H. Wörschnig, J.Queißer, H.H. 

Bernahrt, Überströmbare Dämme – landschaftsverträgliche 

Ausführungsvarianten für den dezentralen 

Hochwasserschutz in Baden- 

Württemberg, Institut für Bodenmechanik und 

Felsmechanik, Universität Karlsruhe, Förderkennzeichen 

BWC 20005 und BWT 22004 Land 

Baden-Württemberg, 2004 

[4] S. Dornack, Überströmbare Dämme – Beitrag zur 

Bemessung von Deckwerken aus Bruchsteinen, 

Wasserbauliche Mitteilungen Heft 20, Inst. f. 

Wasserbau und Techn. Hydromechanik, 2001 

[5] Landesanstalt für Umweltschutz (LfU) Baden- 

Württemberg-Oberirdische Gewässer, Gewässerökologie 

90, Überströmbare Dämme, 2006 

[6] Rathgeb A., Hydrodynamische Bemessungsgrundlagen 

für Lockerdeckwerke an überströmbaren 

Erdämmen, Mitteilungen, Institut für Wasserbau, 

Universität Stuttgart, Heft 109, 2001 

[7] Queißer J., Entwicklung landschaftsverträglicher 

Bauweisen für überströmbare Dämme, Mitteilungen 

des Instituts für Wasser und Gewässerentwicklung 

– Bereich Wasserwirtschaft und 

Kulturtechnik – der Universität Karlsruhe (TH), 

Heft 233, 2006 

[8] A. Kainrath, C. Henzinger, Interdiszilpinäre Seminararbeit 

– Überströmbare Dämme, Institut für 

Wasserbau und Ingenieurhydrologie, 2008

Rediscovery of a Special Type of Separation Pier 

Michael Pucher and Peter Tschernutter (Faculty Mentor) 

Institute of Hydraulic and Water Resources Engineering 



Email: michael.pucher@kw.tuwien.ac.at 

Abstract — At low head river hydropower plants 

the optimal flow to the turbines is of great importance 

for maximum power production. In the case of 

the lateral arrangement of the power house, the 

flow must be redirected toward the turbine inlet. In 

order to achieve the flow around the separation 

pier as loss free as possible, great attention is put 

on its design. In the literature only a few design 

rules can be found. Optimal geometries are mainly 

found by model tests. In the course of full model 

tests of a projected bay power plant, a special pier 

type was rediscovered as the best design solution 

for inflow optimization. 


For thousands of years hydroelectric power plants 

have already been used for environmental friendly 

energy production. In order to reach an optimal energy 

output – i.e. minimize energy loss in “Figure 1” 

- a careful design and, usually, model tests are necessary. 

This work is concerned with the structural design 

of bay power plant intakes. Bay power plants 

“Figure 2” belong to the low head power plants and 

form a special type of run-of-river power plants 

where the power house is arranged besides the weir 

in a lateral bay. Because of the lateral arrangement of 

the power house, the current flow must be redirected 

toward the turbine inlet. In order to achieve the flow 

around the separation pier as loss-free as possible, 

great attention is put on its design. 

Figure 1: Magnitude of energy losses [1] 

First a literature review was undertaken to assess 

the state of the art in separation pier design. 

323 

In a further step existing structures were evaluated. 

The main part of this paper focuses on the full model 

tests of a projected bay power plant. 

Figure 2: Bay plant. Typical Setting and Flow [2] 

II. STATE OF THE ART 

In [2, 3] an overview of low head hydropower plant 

design can be found, while [4, 5] try to give more 

detailed insight into bay plant design, flow criteria 

and energy losses. Views from the point of a turbine 

maker concerning criteria for determining favourable 

flow conditions are given in [6], while the newest 

development in the trash rack design is shown in [7]. 

For one of the only detailed separation pier design 

rules, consult the still up to date [8], while in [9] 

computational fluid dynamics design with optimization 

algorithms are used to determine the optimal 

shape of the pier. In [2,5,8,9] different shapes of 

separation piers are discussed. After reviewing proposed 

and existing separation pier geometries it becomes 

apparent that since each hydropower plant is a 

prototype, favourable geometries are, in spite of basic 

rules and recommendations, mainly found by model 

tests. In [10, 11] a special type of “split”-separation 

pier (pier with a guidance wall) has been used successfully 

since the 1960s, although no design rules 

and support in the literature can be found. 

III. PHYSICAL MODEL TESTS 

The physical model tests were performed in a temporary 

flume of approximately 25 m length and 3,75 m 

width in the institute’s own laboratory. The chosen

model scale was 1 : 40 in accordance with Froud´s 

Law,whichresultedinamaximumdesignflowof 

20 l/s for two turbines. The projected hydro power 

plants performance in various fields like maximum 

flood discharge, energy dissipation, bed load transport 

and especially turbine inflow was tested. 

Figure 3: Fisher & Franke evaluation [2] 

The resulting inflow conditions were evaluated 

qualitatively using strings visualizing flow conditions. 

Qualitative performance evaluation could be 

achieved by examining velocity (v) distributions 

from a 10 x 10 raster at each turbine intake according 

to the Fisher & Franke (F&F) criteria [in 5]. By using 

different criteria it was possible to order the alternatives 

according to the quality of the inflow conditions 

(“Figure 3”,”Table 1”). 

Rank Geometry �-value F&F 

1 1,021 6,37 

7 1,046 1,51 

9 

Original 

1,077 -3,39 

Table 1: Ranking of Pier Geometries [4] 

The original design showed unfavourable inflow 

conditions into and at the turbine next to the weir. In 

a set of model tests first the intake shape was 

changed and then the separation pier geometry was 

varied. The width of the separation pier could not be 

increased, as calculated according to [8]; therefore 

only slight improvements could be obtained with 

standard pier geometries (see “Table 1” rank 7 and 

9). Finally, only special solutions with additional 

guidance walls [8, 10, 11] in front of separation piers 

resulted in acceptable inflow conditions to the turbines. 

Up to a point all guidance walls/split pier 

solutions resulted in similar performance. In further 

324 

tests it became apparent that the position of the guidance 

wall is the dominating factor. 

IV. OUTLOOK 

Further research based on 3D simulation and further 

physical model tests will be undertaken to clarify the 

underlying hydraulic processes. Through understanding 

the hydraulics, it will be possible to define design 

rules that can be used in small scale hydro projects 

were 3D and model tests are too expensive. 

REFERENCES 

[1] J. Erlach: Betrachtung der Gesamtenergiebilanz 

einer Wasserkraftanlage mit Aufschlüsselung der 

Einzelverluste, in: Beiträge zum 2. Seminar 

Kleinwasserkraft; Praxis und aktuelle Entwicklung, 

Stuttgart, 1.10.1999, (Mitteilungen des Inst. 

F. Strömungsm. und Hydr. Strömungsm. 

[2] H. Blind: Wasserbauten aus Beton, Berlin: Ernst, 

Verl. für Architektur und techn. Wiss., 1987 

[3] J. Giesecke & E. Monsony: Wasserkraftanlagen: 

Planung, Bau und Betrieb, Berlin: Springer, 4., 

aktual. u. erw. edition, 2005 

[4] T. Mayr: Bauliche und konstruktive Gestaltung 

von Buchtenkraftwerken, Diplomarbeit 2008, Institut 

für Wasserbau und Ingenieurhydrologie, 

Technische Universität Wien, 2008 

[5] D. Godde: Experimentelle Untersuchungen zur 

Anströmung von Rohrturbinen. Wasserbau und 

Wasserwirtschaft: Berichte der Versuchsanstalt 

Obernach und des Lehrstuhls für Wasserbau und 

Wassermengenwirtschaft der Technischen Universität 

München;75, 1994), ISSN 0947-7187. 

[6] A. Nichtawitz: Kriterien und Methoden zur Optimierung 

der Einlaufströmung von Wasserturbinen, 

in: Konstruktiver Wasserbau - Landschaftswasserbau, 

Band 18, Institut für konstruktiven 

Wasserbau, TU Wien, 2004 

[7] H. Meusburger, Energieverluste an Einlaufrechen 

von Flusskraftwerken, Zürich: Eidgen. 

Techn. Hochschule, 2002 (Diss. ETH;14891). 

[8] G. Rouvé: Der Krafthaustrennpfeiler; Strömungsverhältnisse 

an gekrümmten Wänden, 

Karlsruhe: Eigenverlag, 1958 (Arbeit aus dem 

Theodor- Rehbock- Flussbaulaboratorium; 145). 

[9] G. Demny: Erschließung der automatischen 

Strömungsoptimierung zur Lösung von Gestaltungsaufgaben 

im Wasserbau. Aachen: Rheinisch-Westfälische 

Techn. Hochsch., Diss. 2004 

[10] RWE, Hydro power design maps, Personal 

communication 

[11] e.on, Hydro power design maps, Personal communication

Possibilities of bentonite substitution – development of new 

progressive grouting materials and durability monitoring. 

Pavla Matulova, (Rostislav Drochytka) 

Institute of Technology of Building Materials and Components 



Email: matulova.p@fce.vutbr.cz 

Abstract — The cracks and caverns of different 

types belong to the most frequent failures within 

concrete, reinforced concrete and masonry 

structures. These can appear also in the bottom 

surface, in rocks and grounds under the structure. 

Very efficient method of these failures rehabilitation 

and repair is the grouting with a medium which has 

better physical properties than the original 

structure. Paper is focused on the monitoring 

durability of new progressive grouting mixtures. 

The paper describes the possibilities of grouting 

strategy and especially the development of new 

progressive materials. 


The grouting is the process of pumping the liquid 

with variable viscosity into the ground, into the 

fissured or loose ground, concrete or masonry in 

order to increase the density of these materials. The 

classical technology of grouting is well known for 

some centuries. The principle of this technology is 

the filling of pores and cavities by the grouting 

mixture. The mixing of the grouting mixture with the 

original material forms a composite which has new 

physical properties. This is most frequently the way 

to improve the strength and the imperviousness of the 

material. Another typical application is the 

waterproofing of cracks and gaps (to secure the water 

tightness of cracks and gaps). Basic characteristics of 

grouting are: good workability, volume stability, 

good penetration properties, good pump ability, great 

resistance against erosion, sufficient compression 

strength. And technological and technical variables 

are grouting material curing time of the material, way 

of fastening, fastening of spacing distance, grouting 

pressure, grouting time for one connecting opening, 

grouted volume for one connecting opening, 

sequence of works. The problem of building 

structures subsoil hardening, of filling the cavities 

and the formed caverns became to be a very topical 

subject in the Czech Republic, especially after the 

year 2002, when the Czech Republic suffered under 

extensive floods, which caused the significant 

disturbance of foundation subsoil. These problems 

325 

can be successfully solved by the utilization of 

grouting technologies. This concerns the application 

of large scale grouting and possibilities are looked 

for to decrease the final price under keeping the 

demanded parameters for the grout mixtures. 

Considering the fact, that the floods came also in 

year 2006, though they were not so great, the subject 

of large scale grouting is still very topical. The 

number of structures rehabilitated by grouting 

materials increases the demands on the research and 

development of new building materials. Large-scale 

grouting in the ground work is connected with 

increasing demand to solve the question of large 

scale utilization of industrial wastes in the largest 

possible extent. The utilization of wastes would not 

only partially solve the problem with wastes disposal 

but the wastes application would have positive effect 

on the price of the work. 

II. THE METHODICS OF REALIZED 

WORK 

The Institute of Technology of Building Materials 

and Components at the Faculty of Civil Engineering, 

Brno University of Technology in the Czech 

Republic is already years concerned with the solution 

of optimization problems connected with the 

selection of the material type and the dose of waste 

materials. The methodics of realized work were 

devided into three main parts. First of all the atention 

was paid on substitution of filler by 10% till 50% of 

waste material. We have performed the experimental 

erification of the partial substitution effect of filler 

by the grouting mixture. The second stage was 

focused on substitution of bending materials. And in 

the third stage of realized work was concerning to 

bentonite stage. The fresh mixtures of all selected 

formulae were tested by following basic tests: 

Consistency of the mixture, initial and final setting 

time, bending strength on test samples (40/40/160 

mm), compression strength on test samples 

(40/40/160 mm), volume mass, shrinkage during 

hardening on test samples (40/40/160 mm). And the 

most successful mixture were monitoring also by the 

durability view.

III. EXPERIMENTAL PART 

Aim of this paper is to describe the durability 

monitoring. The Attention was paid first of all 

physico-mechanical parameters of the hardened 

mixture after 180 days expoatation in corosive 

solution. 

corosive solution. concetration 

sulphate SO3 2- 10 000 mg/l 

chloride NaCl 1 000 mg/l 

cyclic action Chloride NaCl 1 000 mg/l 

CO2 

80 mg/l 

Table 1: expoation in corosive solution. 

RESULTS IN GRAPHS 

25 

20 

15 

10 

5 

0 

-5 

-10 

10 

5 

0 

-5 

-10 

-15 

-20 

22,2 

17,6 

10,5 

17,5 

12,8 

2,2 

5,9 

9,9 

9,4 

-0,7-1,2 

-3,2 -2,9 -3,1 

-5,1 -4,6 

-5,7 

-7,4 

sírany 2- 

sulphate NaCl NaCl cyklicky Agresivní CO2 

SO3 

NaCl cyclic action Chloride NaCl CO2 

S ref SP SS SP zeolit 75% SP sádra SS zeolit 75% 

Figure 1: Tensile strength change under the 

exploration of corrosive solution 

-7,5 

-9,6 

-5,4-5,3-5,7 

-9,8 

-7,9 

-9,4 

1,7 1,6 

-0,31 -0,3 -0,3 

-5,9 

-17 -17,3 

-4,3 

-5,3 

2,9 

-5,8 

5,4 

1,2 

8,8 

-10,7 -10,3 

2- 

sulphate SO3 

NaCl cyclic action Chloride NaCl CO2 

sírany NaCl NaCl cyklicky Agresivní CO2 

S ref SP SS SP zeolit 75% SP sádra SS zeolit 75% 

Figure 1: Compressive tensile strength change 

under the exploration of corrosive solution 

1,5 

-4 

-3,9 

4 

0,9 

326 

MICRO-STRUCTURAL ANALYSES IS ELECTRON MICROSCOPY 

Figure 1: Structure of grouting matrix – exploation 

of chloride NaCl 1 000 mg/l (enlarged -I.4000x 

II. 5000x), 200 days exploatation 


It was further proved that it is possible with the 

suitably selected substitution of the original filler 

bonding and bentonite part by waste materials to 

manufacture grouting materials for utilization in 

practice which fulfill the given conditions. Corrosive 

resistance of modifacated mixtures by by-product is 

comparable with the resistance of reference basic 

mixture, and in some case (see graphs were corrosive 

resistance by modificated mixture exceeded as 

well).The first stage shown very good results and in 

following research was provided that it is possible to 

substitute also bending material There were 40% of 

bonding material (cement) decreasing in the 

modificated mixture. The research describes the 

possibilities of development of new rehabilitation 

grouting materials containing different wastes (fly 

ash, washing wastes, etc.) under respecting the 

increase of quality. In praxis this research could case 

lower prices of large scale grouting works. 


The given problems are solved in the framework of 

the Grant Project no.103/05/H044 called: 

“Stimulation of Doctorands Scientific Development 

in the Branch of Building-Materials Engineering” 

and in the framework of the research project MSM 

0021630511 called: “Progressive Building Materials 

with Utilization of Secondary Raw Materials and 

their Effect on Service Life of Structures”. 

REFERENCES 

[1] EMMONS, P. H., DROCHYTKA, R., JE�ÁBEK 

Rehabilitation and Maintenance of Concrete in Pictures. Brno 

CERM 1999, ISBN 0-87629-286-4 (in Czech) 

[2] P ŠÍMA, J. Research and development of new progressive 

grouting system. Dissertation, 2007 (in Czech) Brno 2007

Combined Active/Passive Microwave Wavelet-Based Approach 

For Snowmelt Detection Over Antarctica Ice Shelves 

Nicholas Steiner and Marco Tedesco (Faculty Mentor) 

The Graduate Center of The City University of New York 

New York, USA 

Email: NSteiner@gc.cuny.edu 

Abstract — The presence of wet snow on Antarctica 

can be monitored using Earth orbiting active 

microwave sensors, such as QuickScat, using several 

threshold-based techniques. The goal of this 

study is to apply several signal thresholding techniques 

to microwave backscattering data and 

evaluates them based on comparison to passive 

sensors and ground measurements Since effects of 

climate change will be most evident in Polar Regions, 

monitoring changes in the cryosphere is 

imperative to understanding global climate change. 

The seasonal geographic extent of melted snow and 

the temporal persistence these melt areas are a 

direct indicator of the climactic conditions at the 

poles. Active microwave sensors give us the ability 

to measure these quantities with a high temporal 

and spatial resolution, compared to passive sensors. 

The SeaWinds scatterometer mounted on the 

QuickScat satellite provides daily, near global, 

coverage of Antarctica from 1999 to the present. 

This data will be compared with Special Sensor 

Microwave/Imager (SSM/I) passive microwave 

derived melting products and measurements taken 

at ground stations on Antarctica. 


Since effects of climate change will be most evident 

in Polar Regions [1], monitoring changes in the 

cryosphere is imperative to understanding global 

climate change. The seasonal geographic extent of 

melted snow and the temporal persistence these melt 

areas are a direct indicator of the climactic conditions 

at the poles. Active microwave sensors give us the 

ability to measure these quantities with a high temporal 

and spatial resolution, compared to passive sensors. 

The introduction, through a change of phase, of 

liquid water into a volume of snow will dramatically 

alter its microwave properties. The absorption of 

incoming microwave energy will dominate scattering, 

leading to a marked decrease in the observed 

backscatter signal. The SeaWinds scatterometer 

mounted on the QuickScat satellite provides daily, 

near global, coverage of Antarctica from 1999 to the 

present. This data is readily available from the 

NASA Scatterometer Climate Record Pathfinder 

(SCP) [2]. 

327 

II. METHODS 

Identifying the presence of wet snow is most often 

achieved by defining a threshold value for change in 

measured signal and assuming that all signals above 

that value represent wet snow. Methods for deriving 

a valid threshold have been put forth by various 

authors, and include a constant threshold, one based 

on wintertime signal statistics [3] as well as a novel 

technique based on the thresholding of wavelettransform 

melt onset detection [4]. To our knowledge, 

a wavelet-transform based edge detection approach 

has never been applied to active microwave 

observations of Antarctica. The application of all 

previously mentioned techniques will be performed 

on QuickScat data from 1999 to the present to obtain 

the spatial extent of Antarctic and the persistence of 

this melt, the melting index (MI). This dataset will 

be used to compare with ground based measurements 

as well as passive measurements over the same time 

period, to evaluate the effectiveness of each thresholding 

technique. 

III. RESULTS 

A constant threshold of 3 dB, based on an approximate 

of 8 standard deviations from the average winter 

signal is suggested in many approaches. This 

corresponds to layer of wet snow with a 3.8 cm 

depth. Results obtained with this threshold value 

leads to the detection of melt in areas where it is not. 

Patterns in these ‘false’ melting areas appear to be 

consistent to the local topography, so that these may 

be due to local elevation variations. The effects of 

these are most evident on the Wilkes ice shelf and 

may account for a 20% overestimation. These effects 

are removed by increasing the threshold value 

to 7 Db “Figure 1”.

Backscattering Coefficient (dB) 

0 

-10 

-20 

-30 

Winter 

150 200 250 300 350 400 450 500 

Day 

Average 

Thresh = 3 dB 

Thresh = 7 dB 

Figure 1: A single pixel record of backscattering 

measurements for 2000-2001 illustrating several 

melting thresholds 

Results for the melting index and extent calculated 

with a 7 dB threshold agree, to a large extent, to 

recently published SSMI results [5], although there 

does appear to be a discrepancy in defining the melt 

year ”Figure 2”. The melting index does not appear 

to be as well matched, and the absolute values do not 

have overlapping ranges. 

Figure 2: Melting Index and Extent calculated 

using a variable threshold based on wintertime 

values. 

REFERENCES 

[1] Stainforth, D.A., T. Aina, C. Christensen, M. 

Collins, N. Faull, D.J. Frame, J.A. Kettleborough, 

S. Knight, A. Martin, J.M. Murphy, C. Piani, 

D. Sexton, L.A. Smith, R.A. Spicer, A.J. 

Thorpe, and M.R. Allen, Uncertainty in predictions 

of the climate response to rising levels of 

greenhouse gases, Nature, 433, 403-406, 2005. 

[2] Brigham Young University Center for Remote 

Sensing; NASA Scatterometer Climate Record 

Pathfinder;http://www.scp.byu.edu/ 

328 

[3] Ashcraft, I. & Long, D. Comparison of methods 

for melt detection over Greenland using active 

and passive microwave measurements. Int. J. 

Remote Sens. 27, 2469-2488 (2006). 

[4] Liu, H., Wang, L. & Jezek, K. C. Wavelettransform 

based edge detection approach to derivation 

of snowmelt onset, end and duration from 

satellite passive microwave measurements. Int. J. 

Remote Sens. 26, 4639-4660 (2005). 

[5] Tedesco, M. Updated 2008 Surface Snowmelt 

Trends in Antarctica. Eos Trans.AGU 89, 126 

(2008).

Binary Quadratic Forms 

over the Modular Ring �/n� Clyde W. Lewis, Dr. Rony Gouraige 

Lehman College & 

Bronx Community College 

Dept. of Mathematics 


cwlewis777@aol.com rgouraige@yahoo.com 

Abstract � Given a binary quadratic form 

2 2 

ax +bxy+cy 

where a, b, c � �. 

then it is a known result of number 

theory that the reduction of Binary quadratic forms 

depends on the coefficients a, b, and c, while the 

equivalence of two Binary quadratic forms outwardly 

depends on the variables x and y. We now relate these 

two observations to the notion of binary quadratic 

forms over the modular ring �/ n�, 

and ask, how 

much of what is known about the reduction of these 

forms depend on a, b, and c being integers? At what 

point in establishing equivalence do we use the fact 

that x and y are integers? These are questions that if 

answered may explain the behavior of these forms not 

apparent to us over an integral domain. 

Elements in �� /n� 

of the form 

2 2 

x �� y 

Before we investigate the general equivalence and 

reduction results of binary quadratic forms over the 

modular ring �/ n�, 

we consider a classic result in 

number theory by Fermat, which states that an odd 

prime p may be written as a sum of two squares of 

integers, 

2 2 

p=x +y � p�1mod4. 

� � 

We may extend this fact and state that every prime 

in the factorization of a natural number a which is 

congruent to 3 modulo 4, i.e. 

p � 3 �mod4�, has to be occurring to an even power in order for a to 

be written as a sum of two squares. By generalizing 

this theorem over the modular ring �/ n�, 

we are 

asking, which elements in �/ n� 

can be written as a 

sum of two squares. And conveniently we begin with 

the basic binary quadratic form 

2 2 

Q(x, y) = x + y 

which is appropriately a sum of two squares. 

The first step in characterizing those n for which 

every element in �/ n� 

is a sum of two squares is to 

329 

compute n up to some considerable value and observe 

a pattern from which we may develop some function 

of n. 

“Table 1” lists the elements of �/ n� which are 

sums of two squares for 

n �� 2, 3, 4, 8,10,12, 25 

Modular ring 

� / n� 

Sums of squares in 

� / n� 

�/2� All elements are sums of squares 


�/4� �0� �1� �2� � � � � � � 

�/8� �0� �1� �2� �4� �5� � � � � � � � � � � 


�/12� �0� �1� �2� �4� �5� �6� �8� �9� �10� � � � � � � � � � � � � � � � � � � 


Table 1. 

Clearlywehavenotcomputednupto a value that 

would indicate a concrete pattern, but we may be able 

to include or exclude certain propositions that may or 

may not warrant investigation. For example one could 

ask, “for which n is it true that every element in 

�/ n� 

is a sum of two squares? “ And after an initial 

observation of “Table 1” one could conjecture, “If n 

is a product of distinct primes then every element in 

�/ n� 

can be written as a sum of two squares.” Now 

we have confirmed that this is true for all values of n, 

where 2 � n � 24, and we have also confirmed that 

for every n in �/ n�for 

n between 2 and 24 where 

the elements can be written as a sum of two squares, is 

a product of distinct primes. However this conjecture 

collapses at n= 25, 

since in �/25� all elements 

may be written as a sum of two squares but 25 is a 

2 

product of repeated primes i.e., 25 �� 5 .

Now a reasonable conjecture is, “If n is a prime, 

then every element in �/ n� 

is a sum of two 

squares”. Now we again have confirmed that every 

element in �/ n� 

in which n is a prime is indeed a 

sum of two squares for 2 � n � 25. This observation 

forces one to consider the “prime directive” in number 

theoretic investigations, and that is, we always begin 

with an exploration of the prime numbers. We do this 

for two reasons. First, patterns are generally easier to 

notice for primes numbers. Second, patterns for prime 

numbers are regularly used to figure out patterns for 

all numbers, since the Fundamental Theorem of 

Arithmetic says that the primes are the central 

building blocks for all numbers. So if we only look at 

n, when n is a prime p, then the conjecture holds for 

2 � p � 25, but until we are able to prove or disprove 

this conjecture for all primes p, in �/ p� 

we are only 

certain it is true for 2 � p � 25. A proof of this 

conjecture is pending. 

Binary Quadratic Forms over �� /n�. 

Let 

2 2 

f �x,y � = ax +bxy+cy 

then we denote the associated matrix of f 

�a �b � 2 

b 

2� 

=F 

c � 

� 

where the entries on the diagonal are the coefficients 

of the squared terms and whose entries off the 

diagonal are half the coefficients of the cross product 

term. In addition, since an associated matrix of G is 

uniquely determined by the coefficients of the binary 

quadratic form g, we may conclude that f is 

equivalent to g if there exist an element 

M SL � such that, 

� 2 

� � 

t 

M FM = G 

We now attempt to determine how much of the 

notion of equivalence of binary quadratic forms carry 

over in the modular ring �/ p�. 

keep in mind, if p, is 

prime then our conjecture, “If p is a prime, then every 

element in �/ p� 

is a sum of two squares”, will 

satisfy the squared terms of a binary quadratic form. 

We begin with an example of two forms we are 

familiar with. 

2 2 2 2 

f �x,y �= x + y and g�x,y �= 

x +2xy+2y 

we know the unimodular matrix M that takes f to g is 

of the form 

�1 1� 

M= � � 

�0 1� 

�1� 330 

and the matrix equation in (1) illustrates the 

equivalence between f and g. If we demonstrate this 

example over the modular ring �/2� we see that 

But 

t 

M F M G 

�1 0��1 0��1 1� �1 1� 

� 

� 

�1 1�� 0 1�� 0 1� � 

� 

�1 2� 

� 

�� 2 � �� 0 

in �/2� so the form associated G is 

but again 

therefore 

2 

� � � 2 

g x, y x + 2xy 

�� 2 � �� 0 

2 

� � � 2 

g x, y x 

and the equivalence between f and g is unfamiliar to 

us in �/2� since the desired form was not obtained. 

Preliminary results regarding the equivalence of 

binary quadratic forms over �/ p� 

looks promising 

but one simple case may not show the behavior of 

these forms over �/ p� 

for all p. However, based on 

our first few attempts it seems that if the greatest 

coefficient of the entire matrix equation in (1) is less 

than p in �/ p� 

then the equivalence amid two 

binary quadratic forms over the modular ring �/ p� 

is analogous to the equivalence of these forms over 

the integers �. And if the greatest coefficient of the 

entire matrix equation in (1) is equal to or greater than 

p in �/ p� 

then the matrix equation changes. 

REFERENCES 

[1] William J. Leveque, Topics in Number Theory. 

Dover Publications, Inc. Mineola, New York 

2002. 

[2] Stillwell, John. Elements of Number Theory. 

Springer. New York 2003. 

[3] Armenda’riz, E.P., & McAdam, S.J., Elementary 

Number Theory. Macmillan. New York 1980. 

[4] Buell, D.A., Binary Quadratic Forms: Classical 

Theory and Modern Computations. Springer- 

Verlag. New York. 1989.

Index of Authors 

Able, Richard, 249 

Achong, Colleen, 229 

Adam, Helmut, 47 

Adamec, Filip, 23 

Ahmed, Sam, 63, 277 

Ahn, Sang-Il, 197 

Alfano, Robert, 121, 237 

Amaya, Ronny, 171 

Amrhein, Wolfgang, 13 

Andrianova, Ekaterina, 57 

Angela, Ligorio, 189 

Anna Maria, DOnghia, 189 

Antonio, Ippolito, 189 

Archodoulaki, Vasiliki-Maria, 209 

Arnold, Craig, 231 

Arriaran, Vilma, 39 

Azar, Amir, 143 

Bünte, Sven, 115 

Babic, Frantisek, 15 

Bachinger, Angelika, 157 

Badurek, Gerald, 129 

Bashir, Shazia, 213 

Bauer, Gudrun E., 161 

Bauer, Heidi, 293 

Baumann, Stefan O., 137, 139, 199 

Becker, Klaus, 215, 315 

Bendova, Maria, 139, 191, 199 

Beneova, Anna, 33 

Benigni, Caterina, 211 

Berger, Johannes, 269 

Berghöfer, Thomas, 9 

Bikson, Marom, 171 

Birke, Ronald, 239 

Bleyer, Michael, 71 

331 

Bouzi, Pierre, 187 

Bräutigam, Klaus-Rainer, 259 

Brooks, Patricia, 123 

Brunthaler, Stefan, 41 

Bustamante, Miguel, 277 

Cao, Xiujuan, 173 

Cardoso, Luis, 169 

Carrion, Carmen, 123 

Caseiro, Alex, 293 

Cerimovic, Samir, 287 

Chang, Jingjing, 241 

Coppola, Antonio, 73 

Corredor, Charlie, 227 

Cummins, Herman, 173 

Cunningham, Dan, 179 

Dörsek, Philipp, 283 

Danninger, Herbert, 147 

DAO Tran, Minh, 83 

Datta, Abhisheck, 171 

Daxner, Thomas, 183 

Delvai, Martin, 85 

Deneva, Margarita, 223 

Despotovic, Vladimir, 75 

Diblík, Jan, 151 

Diechle, Dominic, 135 

Dillinger, Andreas, 297 

Dimitrijevic, Milan, 59 

Dimitrijevic, Milan R., 305 

Dodt, Hans-Ulrich, 215, 315 

Dorn, Jürgen, 57, 77 

Dorsinville, Roger, 187 

Dostal, Tomas, 17 

Douglas, Kareem, 229

Duan, Yi, 163 

Dumke, Hartmut, 297 

Dvorák, Radek, 27 

Dyer, Rushane, 63 

Edtmaier, Christian, 145, 153 

Eing, Christian, 9 

Eisenmenger-Sittner, Christoph, 179 

Eiter, Thomas, 29, 83 

El-Salloum, Christian, 95 

Elmenreich, Wilfried, 53, 61 

Eryilmaz, Ertan, 233 

Etienne, Michael, 187 

Fackler, Karin, 317 

Fanghänel, Thomas, 131, 133, 177 

Fanghänel, Thommas, 185 

Fehérvári, István, 53 

Fenz, Stefan, 69 

Ferraz-Leite, Samuel, 257 

Fertalj, Kresimir, 87 

Filipp, Stefan, 129 

Fillos, John, 313 

Fink, Michael, 29 

Flasik, Radoslav, 175 

Flickinger, Bianca, 9 

Fröhlich, Johannes, 195, 211, 217 

Franco, Nigro, 189 

Frank, Andrew U., 311 

Frey, Wolfgang, 9 

Fruhmann, Philipp, 217 

Frybortova, Iva, 205 

Fryza, Tomas, 23 

Fu, Qing, 255 

Göschka, Karl M., 113 

Gall, Michael, 37 

Gartner, Georg, 107 

Gayen, Swapan, 121 

Gebhard, Thomas, 203 

Geckeis, Horst, 177, 185 

Geist, Andreas, 131, 185 

Gelautz, Margrit, 71 

Gewies, Andreas, 215 

332 

Ghose, Ranajeet, 233 

Gierl, Christian, 147 

Gonzalez, Jorge, 245 

Gonzalez, Tahnee, 259 

Gouraige, Rony, 329 

Green, Michael, 247 

Gross, Barry, 277 

Gruber, Wolfgang, 13 

Gschwandtner, Theresia, 91 

Gspan, Christian, 145 

Gu, Xiang, 169 

Guadagini, Alberto, 73 

Guzman, Francisco, 169 

Hahm, Sung-Ho, 197 

Halwachs, Michael, 181 

Hametner, Christian, 195, 217 

Hasegawa, Yuji, 129 

Helm, Manfred, 197 

Hermany, Jirí, 67 

Hetaba, Walid, 149 

Heurix, Johannes, 79 

Hinterstoisser, Barbara, 317 

Hofstötter, Ursula S., 305 

Hofstoetter, Ursula, 59 

Horkel, Ernst, 211, 217 

Hosannah, Nathan, 245 

Hula, Robert Christian, 153 

Husinsky, Wolfgang, 213 

Iqbal, Naseem, 201 

Isabella, Pentimone, 189 

Jährling, Nina, 215, 315 

Jankowski, Nicole, 207 

Jaros, Jiri, 111 

Jerabek, Michal, 43 

Jilková, Jana, 99 

John, George, 229 

Jurcisin, Robert, 167 

Köck, Anton, 145 

Kadlec, Albrecht, 119 

Kaiser, Katharina, 91

Kalchmair, Stefan, 197, 215, 315 

Karabatic, Ana, 265 

Karl, Hans-Peter, 195 

Kassab, Mohamed, 73 

Kastil, Jan, 103 

Kellner, Gudrun, 93 

Keplinger, Franz, 287 

Khamis, Youssef, 189 

Khanbilvardi, Reza, 143 

Kickelbick, Guido, 157, 193 

Kirner, Raimund, 115, 117, 119 

Kitzmantel, Michael, 179 

Klösch, Bernhard, 195 

Klatzer, Barbara, 293 

Klenze, Reinhardt, 131, 133 

Klepp, Jürgen, 129 

Knoop, Jens, 41, 45, 113 

Kobierský, Petr, 109 

Koch, Thomas, 209 

Koeberl, Bernd, 269 

Kofler, Heinrich, 219, 223 

Kollegger, Johann, 269 

Konegger, Thomas, 155 

Korenek, Jan, 103 

Kothleitner, Gerhard, 145 

Kovács, Gábor, 309 

Kramer, Edgar R., 215 

Krcal, Jan, 43 

Krennwallner, Thomas, 29 

Krongtaew, Chularat, 317 

Krupa, Marek, 33 

Kutzelnigg, Reinhard, 281 

Labutov, Igor, 31 

Ladenbauer, Josef, 59, 305 

Lamaddalena, Nicola, 73 

Lambert, Tiffany, 125 

Lechner, Jakob, 85 

Lee, Jong-Ho, 197 

Leiste, Harald, 135 

Leong, Daniel, 169 

Lettner, Matthias, 129 

Lewis, Clyde, 329 

333 

Li, YongHui, 169 

Lichtenberger, Robert, 137 

Liersch, Antje, 155 

Likhtina, Iya, 239 

Limbeck, Andreas, 141, 261 

Litschauer, Marco, 299 

Livingstone, Richard, 251 

Lombardi, John, 227, 241, 251 

Lomoschitz, Christoph, 193 

Lomoschitz, Marina, 267 

Lopez, Veronica, 171 

Lumpi, Daniel, 211 

Mach, Robert L., 159, 161 

Mach-Aigner, Astrid R., 159, 161 

Maier, Thomas, 145 

Markut-Kohl, Ruth, 209 

Marsálek, Roman, 3 

Matulova, Pavla, 325 

Mecklenbrauker, Christoph F, 105 

Melenk, Jens Markus, 283 

Menghwar, Gordhan Das, 105 

Messner, Kurt, 317 

Mihovilovic., Marko., 201 

Miksch, Silvia, 91 

Mikula, Hannes, 195 

Minassian, Karen, 59, 305 

Mohsin, Ijaz Ul, 147 

Moore, Brandy, 123 

Morovati, Mostafa, 289 

Moshary, Fred, 277 

Mukhtar, Azam, 261 

Musliu, Nysret, 81 

Naz, Tabbasum, 77 

Neck, Volker, 133 

Neouze, Marie-Alexandra, 299 

Neubauer, Thomas, 79 

Nizetic, Ivana, 87 

Njau, Philipa, 247 

Nolan, Martin, 289 

Nosrat, Amir, 289 

Nothegger, Clemens, 97 

Novácek, Zdenek, 67, 271

Ocipova, Daniela, 275 

Offner, Mathias, 47 

Opelt, Aileen, 211 

Orság, Petr, 25 

Ortag, Felix, 107 

Ostermaier, Clemens, 197 

Palankovski, Vassil, 221 

Panak, Petra J., 131, 133 

Papp, Sándor, 309 

Paralic, Ján, 15 

Pfeifer, Norbert, 97 

Pichler, Reinhard, 89 

Plank, Lucia, 291 

Plha, Stefan, 297 

Podlubny, Igor, 75 

Pogany, Dionyz, 197 

Pokorný, Michal, 19 

Pospísil, Jirí, 225 

Potzger, Kay, 197 

Potzmann, Robert, 139, 199 

Povalac, Karel, 3 

Powell, Al, 143 

Praetorius, Dirk, 257 

Prantl, Adrian, 45 

Prescod, Andru, 187 

Puchberger, Michael, 137, 139, 191, 199 

Pucher, Marion E., 159, 161 

Pucher, Michael, 321, 323 

Puls, Christoph, 141 

Pulverer, Gernot, 301 

Pus, Viktor, 65 

Puschner, Peter, 101 

Puskely, Jan, 271 

Puxbaum, Hans, 207, 293, 307 

Rümmele, Stefan, 89 

Rabin, Laura, 123 

Rafique, M:Shahid, 213 

Raida, Zbynek, 11, 19, 21, 99 

Ramalingam, Krish, 313 

Raphan, Theodore, 31 

Rattay, Frank, 59, 295, 305 

Reda, DI Ranja, 303 

334 

Ren, Bin, 273 

Retscher, Guenther, 255 

Rieder, Bernhard, 101 

Riva, Monica, 73 

Rosenthal, Alex, 313 

Rovnanik, Pavel, 205 

Rupp, Markus, 35 

Sabo, Miroslav, 49 

Saetta, Anna, 263 

Sala, Pavel, 5 

Sanchez, Eric, 231 

Schaffer, Hannes, 297 

Schmidl, Christoph, 307 

Schmidt, Moritz, 177 

Schranz, Melanie, 61 

Schreiner, Dietmar, 113 

Schubert, Ulrich, 137, 139, 191, 199, 267 

Schwarz, Elisabeth, 219 

Schwarz, Josef, 111 

Sebo, Dusan, 167 

Seeling, Joni, 235 

Seidler, Sabine, 209 

Seifert, Helmut, 259 

Seitner, Florian, 71 

Semona, Sanzani, 189 

Seo, Dugwon, 143 

Shen, Lu, 279 

Sigmund, Milan, 5, 7 

Simioni, Paola, 263 

Simonné-Dombóvári, Eszter, 319 

Skerencak, Andrej, 133 

Skovranek, Tomas, 75 

Sotner, Roman, 17 

Sponar, Stephan, 129 

Stallinger, Thomas, 13 

Stanetty, Peter, 175 

Steiger, Matthias G., 159, 161 

Steiner, Nicholas, 327 

Steppert, Michael, 185 

Sterba, Christian, 37 

Stueber, Michael, 135 

Stumpf, Martin, 21

Stumpf, Thorsten, 177 

Suethanuwong, Ekarin, 95 

Sun, HuiBin, 169 

Székely, Balázs, 309 

Sztul, Henry, 237 

Talic, Almir, 287 

Tarbell, John, 171 

Tauer, Johannes, 219, 223 

Tedesco, Marco, 327 

Teran, Evelyn, 235 

Thaler, Gottfried, 265 

Tilinger, Jan, 165 

Tischner, Alexandra, 145 

Tjoa, A Min, 69 

Todt, Melanie, 183 

Trawniczek, Franz, 223 

Triska, Markus, 81 

Trumm, Sascha, 131 

Tschernutter, Peter, 321, 323 

Ulrich, Sven, 135 

Vasícek, Zdenek, 55 

Vazquez, Maribel, 249 

Vega Cañamares, Maria, 241 

Vemula, Praveen Kumar, 229 

Vitanov, Stanislav, 221 

Vitkalov, Sergey, 243 

Vranayova, Zuzana, 275 

Walther, Clemens, 177, 185 

Wang, Qi, 35 

Wassermann, Lubomir, 51 

Weber, Robert, 265 

Weinbaum, Sheldon, 163 

Wenger, Cornelia, 295 

Whitlock, Paula, 125 

Wilke, Gwen, 311 

Wintner, Ernst, 219, 223 

Wu, Binlin, 121 

Xiao, Jizhong, 31 

Zahradník, Petr, 285 

335 

Zelinka, Petr, 7 

Zhang, JingQiao, 243 

Zolda, Michael, 117 

Zvolensky, Tomas, 11

Proceedings of the Junior Scientist Conference 2008

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