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EVENTS ON June 11, 2013

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2:00 PM - 3:00 PM

NUTC Seminar: "A Reformulation-based Exact Algorithm for Solving a Recycling Districting Problem" - Roger Rios, University of Texas, Austin

“A Reformulation-based Exact Algorithm for Solving a Recycling Districting Problem”


Roger Z. Ríos
Fulbright Visiting Scholar in the Graduate Program in Operations Research and Industrial Engineering; Professor, Operations Research
University of Texas at Austin; Universidad Autonoma de Nuevo Leon, Mexico

Territory design problems consist of grouping small geographic areas into larger geographic clusters called territories such that the latter fulfill relevant planning criteria. The decision-making problem addressed in this work is motivated by a real-world case arising in the recollection and recycling of waste electric and electronic equipment (WEEE) in Europe. The WEEE Directive establishes that each company that sells electronic products in an European country has the obligation to recollect and recycle an amount of returned items proportional to the market share of the company. The decision making process involves assigning recollection units to companies subject to some planning requirements. In addition, the core of the law dictates that a regional monopoly by any company has to be avoided, that is, all basic areas allocated to the same corporation should be as geographically dispersed as possible. An integer programming modeling framework for this territory design problem is presented. From the computational standpoint, this discrete optimization problem is very hard to solve. Thus, several algorithmic strategies and model enhancements that effectively exploit the underlying mathematical structure of the problem are developed. Particularly, a dual bounding scheme and an improved problem reformulation based on a coverage location problem using a significantly fewer number of binary variables are proposed. An exact optimization  algorithm based on the problem reformulation is developed. Empirical evidence over a wide set of problem  instances illustrate the usefulness and positive impact of the proposed strategies resulting in dramatic speed-up of  solution times when compared to existing approaches and commercial methods.

Contact Info: Diana Marek

Location: Chambers Hall 600 Foster St Ruan Conference Center Evanston IL 60208

Event URL: http://www.transportation.northwestern.edu/news_ev...