Spring of 2011
Welcome to the Management Science and Operations Management (MSOM) Seminar at the School of Business Administration at the University of Miami.
Here you will find details about the talks given during the Spring of 2011.
Past Talks
- April 29
Speaker: Tallys Yunes, Department of Management Science, University of Miami
Title: Valid Inequalities for the Cumulative Constraint and the Cumulative Job Shop Scheduling Problem
Abstract: In Constraint Programming, the cumulative global constraint is used to describe scheduling problems in which a machine can process more than one job at a time. We study the convex hull of feasible solutions to the cumulative constraint when (i) jobs are identical, and (ii) jobs differ in their resource utilization rates. In the first case, we revisit some of the previous work found in the literature; in the second case, we propose a new family of facet-defining inequalities. We also present computational results obtained with a branch-and-cut algorithm for cumulative scheduling, including a cumulative version of the well-known job shop scheduling problem. This is joint work with Dimitrios Magos and Ioannis Mourtos.
- March 11
Speaker: Christopher Tang, Anderson School of Management, University of California, Los Angeles
Title: Managing Opportunistic Supplier Product Adulteration: Deferred Payments, Inspection, and Combined Mechanisms
Abstract: Recent cases of product adulteration by foreign suppliers have compelled many manufacturers to re-think approaches to deterring suppliers from cutting corners, especially when manufacturers cannot fully monitor and control the suppliers' actions. Recognizing that process certification programs, such as ISO9000, do not guarantee unadulterated products and that product liability and product warranty with foreign suppliers are rarely enforceable, manufacturers turn to mechanisms that make payments to the suppliers contingent on no defects discovery. In this paper we study: (a) the deferred payment mechanism --- the buyer pays the supplier after the deferred payment period only if no adulteration has been discovered by the customers; (b) the inspection mechanism --- the buyer pays the supplier immediately, contingent on product passing the inspection; and (c) the combined mechanism --- a combination of the deferred payment and inspection mechanisms. We find the optimal contracts for each mechanism, and describe the Nash equilibria of inspection sub-games for the inspection and the combined mechanisms. The inspection mechanism cannot completely deter the suppliers from product adulteration, while the deferred payment mechanism can. Surprisingly, the combined mechanism is redundant: either the inspection or the deferred payment mechanisms perform just as well. Finally, the four factors that determine the dominance of deferred payment mechanism over the inspection mechanism are: (a) the inspection cost relative to inspection accuracy, (b) the buyer's liability for adulterated products, (c) the difference in financing rates for the buyer and the supplier relative to the defects discovery rate by customers, and (d) the difference in production costs for adulterated and unadulterated product. Joint work with Volodymyr Babich, Georgetown University
Speaker's Short Bio: Christopher Tang, a member of the faculty since 1985, served as Senior Associate Dean at the UCLA Anderson School from 1998 to 2002, and as Dean of the Business School at the National University of Singapore from 2002 to 2004. His research work deals with complex issues arising from production planning, supply chain management and the marketing/manufacturing interface. He has co-edited 4 books and published over 80 articles in journals such as Management Science, Operations Research, Manufacturing and Service Operations Management, Journal of Marketing Research, Production and Operations Management, and Sloan Management Review. Moreover, he has served on editorial boards for over 15 journals, including Management Science, Operations Research, Manufacturing, Service and Operations Management, and Production and Operations Management. In addition to his academic teaching experience at Hong Kong University of Science and Technology, National University of Singapore, Stanford University, and UCLA, he has various executive programs throughout Asia, Europe and Americas. He has advised over 20 multi-national firms such as Amgen, Hewlett Packard Company (world-wide locations), Honda America, Nestlé SA, IBM (world-wide locations). Chris received his BSc (First Class Honors) from King's College, University of London, M.A., MPhil and PhD from Yale University.
- March 11
Speaker: Jochen Könemann, Department of Combinatorics and Optimization, University of Waterloo, Canada
Title: Approximating Steiner Trees via Linear Programming
Abstract: This talk focuses on the classical Steiner tree problem, where one is given a weighted undirected graph G and a vertex subset R of so called terminals. The goal is to find the cheapest tree T that spans R, and may contain other, so called Steiner vertices. This problem has numerous applications, and is well known to be NP-hard to solve exactly. This talk focuses on finding fast approximation algorithms for the problem. Very recently, some very elegant new algorithms have been proposed; these are based on strong linear programming relaxations and random sampling. I will survey these LP relaxations, discuss some of their properties, and describe their algorithmic use. Some of the results presented are based on joint work with David Pritchard, and Deeparnab Chakrabarty.
Speaker's Short Bio: Jochen Könemann spent his undergraduate years in Saarbruecken, Germany, where he studied Computer Science in Kurt Mehlhorn's group at the Max-Planck Institute. He then moved on to Pittsburgh, where he became a student in the graduate program for Algorithms, Combinatorics & Optimization. After a postdoctoral year at University of Rome in Italy, he moved on to the University of Waterloo in Canada, where he is now an Associate Professor and Chair in the Department of Combinatorics & Optimization. Jochen's research focuses broadly on efficient algorithms for NP-hard optimization problems. He is particularly interested in problems arising in the areas of network design and in algorithmic game theory.
- February 18
Speaker: Jonas Baeklund, Department of Mathematical Sciences, University of Aarhus, Denmark
Title: Nurse Rostering in a Danish Hospital
Abstract: Nurse rostering is the complex scheduling problem of planning which shift each nurse should work over a number of consecutive of days. The problem we confront is a nurse rostering problem in a ward at a Danish hospital. The problem includes several special regulations that have to be fulfilled in this ward. This presentation will discuss the first results of the on-going work of my Ph.D. thesis project. It gives an overview on the solution approach we are currently working on. The overall method is a branch-and-price algorithm based on a linear master problem and a sub-problem handled with heuristics and constraint programming.
- January 31
Speaker: Yongtao Guan, Division of Biostatistics, Yale University
Title: Estimating Individual-Level Risk in Spatial Epidemiology Using Spatially Aggregated Information on the Population at Risk
Abstract: We propose a novel alternative to case-control sampling for the estimation of individual-level risk in spatial epidemiology. Our approach uses weighted estimating equations to estimate regression parameters in the intensity function of an inhomogeneous spatial point process, when information on risk-factors is available at the individual level for cases, but only at a spatially aggregated level for the population at risk. We develop data-driven methods to select the weights used in the estimating equations and show through simulation that the choice of weights can have a major impact on efficiency of estimation. We develop a formal test to detect non-Poisson behavior in the underlying point process and assess the performance of the test using simulations of Poisson and Poisson cluster point processes. We apply our methods to data on the spatial distribution of childhood meningococcal disease cases in Merseyside, U.K. between 1981 and 2007.