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SB19<br />

■ SB19<br />

19- West 211 A- CC<br />

Joint Session Healthcare Logistics/SPPSN: Routing<br />

Problems in Healthcare Operations I<br />

Cluster: Healthcare Logistics & Public Programs, Service and Needs<br />

Invited Session<br />

Chair: Burcu Keskin, University of Alabama, Alston Hall, Box: 870226,<br />

Tuscaloosa, AL, 3587-0226, United States of America,<br />

bkeskin@cba.ua.edu<br />

1 - A Sequential GRASP for the Therapist Routing and<br />

Scheduling Problem<br />

Yufen Shao, Research Engineer, ExxonMobil Upstream Research<br />

Company, 3120 Buffalo Speedway, Houston, TX, 77098, United<br />

States of America, yufen.shao@exxonmobil.com, Ahmad Jarrah,<br />

Jonathan Bard<br />

This talk presents a sequential GRASP for solving a weekly routing and<br />

scheduling problem for therapists. The problem contains both fixed and flexible<br />

patients with respect to appointment times, and two grades of therapists. In Phase<br />

I, feasible solutions are constructed one therapist and one day at a time. In Phase<br />

II, a high-level neighborhood search is proposed to obtain local optima.<br />

Performance is demonstrated using real and randomly generated data sets.<br />

2 - An Optimisation Model for Staff Planning in a<br />

Home Care Organization<br />

Pablo Andres Maya Duque, PhD, University of Antwerp/<br />

Universidad de Antioquia, Ottoveniusstrat 26, box 6, Antwerp,<br />

2000, Belgium, pmayaduque@gmail.com, Peter Goos,<br />

Kenneth Sörensen, Marco Castro<br />

In this talk, we present the core optimization component of a decision support<br />

system that Landelijke Thuiszorg, a non-profit organization that provides home<br />

care services for several provinces in Belgium, will implement in order to assist<br />

the regional service planning. The optimization model takes into account<br />

assignment, scheduling and routing decisions simultaneously, while considering<br />

two objectives, namely the service level and the travelled distance.<br />

3 - Incorporating Patient, Nurse, and Agency Considerations in<br />

Home Health Care Routing<br />

Ashlea Bennett Milburn, Assistant Professor, University of<br />

Arkansas, 4207 Bell Engineering Center, Fayetteville, AR,<br />

United States of America, ashlea@uark.edu, Jessica Spicer<br />

Home health routing and scheduling problems can be modeled as multi-objective<br />

optimization problems, as home health agencies are often interested in creating<br />

nurse routes that achieve a variety of goals. We use a multi-objective tabu search<br />

heuristic to study the relationship among travel cost, nurse consistency (a<br />

measure of patient satisfaction), and balanced workload (an indicator of nurse<br />

satisfaction) objectives. Computational results for a number of realistic scenarios<br />

are presented.<br />

4 - A Multi-period Home Care Scheduling Problem with<br />

Work Balance<br />

Burcu Keskin, University of Alabama, Alston Hall, Box: 870226,<br />

Tuscaloosa, AL, 3587-0226, United States of America,<br />

bkeskin@cba.ua.edu, Shirley (Rong) Li, Charles Schmidt<br />

We consider a home health care scheduling problem for a local hospital with<br />

multiple types of caregivers. We determine the assignment of caregivers to the<br />

patients visited at their homes so that the total routing costs are minimized and<br />

the workload of caregivers are balanced over a planning horizon while satisfying<br />

synchronization, precedence, loyalty, and other practical constraints. We present a<br />

MILP formulation and a branch-and-price solution approach based on Dantzig-<br />

Wolfe decomposition.<br />

■ SB20<br />

20- West 211B- CC<br />

Software Demonstration<br />

Invited Session<br />

1 - American Optimal Decisions - Portfolio Safeguard (PSG):<br />

Advanced Nonlinear Mixed-Integer Optimization Package<br />

Stan Uryasev,American Optimal Decisions, 5214 SW 91 Way, Ste.<br />

#130, Gainesville FL 32608, United States of America,<br />

uryasev@aorda.com<br />

Portfolio Safeguard is an advanced nonlinear mixed-integer optimization package<br />

used in risk management, financial engineering, military, medical and other<br />

applications. Design and solve complex optimization problems with built-in<br />

functions (maximum, StDev, variance, probability, VaR, CVaR, cardinality, fixedcharge,<br />

recourse etc.). See real-life case studies in Windows and MATLAB at<br />

www.aorda.com/aod/psg.action.<br />

INFORMS Phoenix – 2012<br />

86<br />

■ SB21<br />

21- West 212 A- CC<br />

Advances in Networks and Graphs<br />

Contributed Session<br />

Chair: Sivan Altinakar, École Polytechnique de Montréal, C.P. 6079,<br />

Succ. Centre-ville, Montreal, QC, H3C 3A7, Canada,<br />

sivan.altinakar@gerad.ca<br />

1 - Approximating Precedence Network Structure with<br />

Incomplete Information<br />

Adam Graunke, The Boeing Company, P.O. Box 3707, MC 13-98,<br />

Seattle, WA, 98124, United States of America,<br />

adam.a.graunke@boeing.com, Gabriel Burnett<br />

Accurate precedence networks are highly useful for planning and analysis, yet in<br />

large scale production systems, they are difficult, if not impossible, to define. In<br />

this research we investigate precedence networks in the presence of incomplete<br />

precedence information, with the goal of estimating production-critical properties<br />

of the network. Specifically, we investigate critical path analyses and the level of<br />

confidence associated with the results.<br />

2 - Shortest Path with Secure Multipary Computation<br />

Abdelrahaman Aly, Universite Catholique de Louvain, 34,<br />

Voie du Roman Pays, Louvain-la-Neuve, 1348, Belgium,<br />

abdelrahaman.aly@uclouvain.be, Mathieu Van Vyve<br />

In various applications, i.e. elections, auctions, the computation of a global<br />

optimum requires input data from competing parties. A trusted third party to<br />

perform these computations is not guaranteed. Secure Multiparty Computation<br />

(SMC) is an encryption method which does not rely on such third party. The<br />

present research expands SMC’s scenario to Shortest Path problem. We describe<br />

SMC variants of Bellman-Ford and Dijkstra algorithms and compare their<br />

performance with the traditional variants.<br />

3 - Reconstruction of Three Dimensional Objects from Three<br />

Orthogonal Cartesian Bi-plane Projections<br />

Siddhartha Sampath, Arizona State University,<br />

849 W Elna Rae, Tempe, AZ, United States of America,<br />

Siddhartha.Sampath@asu.edu, Pavithra Ramamoorthy,<br />

Pitu Mirchandani<br />

This application describes a network flow model for reconstructing the threedimensional<br />

shape of a three dimensional object from biplane x-ray readings for<br />

all three orthogonal Cartesian planes.Each two-dimensional cross-section consists<br />

of one region or view of the object whose image is to be reconstructed.We can use<br />

apriori information to constrain the number of solutions, and then to obtain most<br />

likely reconstruction.<br />

4 - Breaking Symmetry in Consecutive Edge-coloring<br />

Sivan Altinakar, École Polytechnique de Montreal, C.P. 6079,<br />

Succ. Centre-ville, Montreal, QC, H3C 3A7, Canada,<br />

sivan.altinakar@gerad.ca, Alain Hertz, Gilles Caporossi<br />

Consecutive edge-coloring, a special case of edge-coloring in graph theory, aims to<br />

minimize the sum of the span of colors (integers) incident to each node. This has<br />

applications in scheduling. It is also NP-hard, and may be difficult to solve exactly<br />

even for a very small number of vertices. We compare different modeling<br />

approaches in Mixed Integer Programming and Constraint Programming, with an<br />

emphasis on the latter, and subsets of Lex-Leader constraints for efficient<br />

symmetry breaking.<br />

■ SB22<br />

22- West 212 B- CC<br />

COIN-OR Multi-Threading Software<br />

Sponsor: Computing Society<br />

Sponsored Session<br />

Chair: Bradley Bell, Senior Research Scientist/Enginer, University of<br />

Washington, IHME, 2301 Fifth Ave., Suite 600, Seattle, WA, 98121,<br />

United States of America, bradbell@seanet.com<br />

1 - Could We Use a Million Cores to Solve a Single Integer<br />

Program?<br />

Ted Ralphs, Associate Professor, Lehigh University, 200 West<br />

Packer Avenue, Bethlehem, PA, 18015, United States of America,<br />

ted@lehigh.edu, Thorsten Koch, Yuji Shinano<br />

Given the steady increase in cores per CPU, it is only a matter of time before<br />

supercomputers will have a million or more cores. In this talk, we investigate the<br />

opportunities and challenges that will arise when trying to utilize the distributed<br />

multi-core architectures that have recently become pervasive to solve a single<br />

integer linear optimization problem. We raise the question whether best practices<br />

in sequential solution of ILPs will be effective in massively parallel environments.

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