Birmingham Environment for Academic Research - University of ...

More documents

Recommendations

Info

Parallel Computation of Braid Orbits with GAP and SCSCPIn algebra, the Inverse Galois Problem concerns whether or not every finite group G can be realized as aGalois group over the rational numbers. The case where G is soluble was resolved by Shafarevich in the1950s, but the general case remains open. One approach to the realization of a group as a Galois group isvia classification of Hurwitz loci of complex curves admitting G. These loci are indexed by the orbits of asuitable surface braid group acting on the generating tuples of G. When the genus of the curve is low, thebraid orbits can be enumerated explicitly using GAP (Groups, Algorithm, Programming) computer algebrasystem and the BRAID package by Magaard, Shpectorov and Völklein. The length of the orbits dramaticallyincreases with the size of G and genus of the curve. In order to handle larger orbits, we propose to useparallel computing in GAP via the package SCSCP (Konovalov and Linton).Using parallel computation, we have successfully computed an orbit of size approximately 1.2 million using 15 processors in theserver babbage2 in the School of Mathematics, where we set one master worker, eight applicator workers and six storage workersto do the parallel computation. We also repeated this computation in BlueBEAR.The communication in the SCSCP package and queuing takes a lot of time. It turns out that almost two-thirds of the duration time arefor waiting, encoding, decoding and so on. This needs to be improved. We want to use hundreds of processors at the same time forthe cases of orbit length up to 10 million or more, and we want to use them for several hours. While we consider using more resourcesto handle the large orbits, we are also thinking about reducing the size of each computing task. This requires more workaround the algorithm.Gehao WangSchool of MathematicsPage 14
Optimizing the Centrifugal Casting of Gamma Titanium AluminidesThe aim of the study is to investigate the effect of rotational velocity in the filling process ofmould designs during the centrifugal casting process and also to investigate the effect of thecentrifugal casting on the quality and reliability of TiAl-based alloy castings.TiAl alloys have great potential as a substitute for heavier Ni superalloys for a range of high temperaturecomponents, including aerospace gas turbine blades.Ti alloys are normally melted in an Induction Skull Melting furnace prior to casting into ceramicshell moulds but the low superheat makes it difficult to fill moulds completely using traditionalgravity casting. Centrifugal casting is used to fill thin section castings in a variety of conventionalalloys, but little research has been carried out to establish a scientific understanding which would allow the process to be appliedto more difficult alloys such as TiAl. The high g-force assists in mould filling and may also help to feed the shrinkage during solidification,but these benefits may be partly offset by the surface turbulence during mould filling which may entrain various defectssuch as bubbles.The aim is to establish means of controlling the flow in order to minimise entrainment defects. This will be subsequently complementedby a study of the effect of centrifugal casting on the quality and reliability of TiAl investment castings.Using the indirect gating system offers a non turbulent and stable filling process. However, it is necessary to analyse the cast flat barsby X-ray test in order to determine their quality and reliability.Eduardo TrejoDepartment of Metallurgy and MaterialsPage 15
Page 3: Copyright © The University of Birm
Page 6: ContentsAbstractiiPreface 5Peter Wi
Page 10 and 11: Computational model of affordance-b
Page 12 and 13: Medieval Warfare on the GridThis pr
Page 14 and 15: Chunk Learning and Move Prompting M
Page 18 and 19: Three-dimensional Numerical Modelli
Page 20 and 21: Micro- and Macromixing Studies in T
Page 22 and 23: Theoretical Studies of the Optical
Page 24 and 25: Evaluation of deformation mechanism
Page 26 and 27: High shear rotor-stator mixersA rot

Birmingham Environment for Academic Research - University of ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?