Horst W. Hamacher (University of Kaiserslautern, Germany)

Short Biography

Horst W. Hamacher got his Diploma (1977) and Dr. rer. nat (1980) degrees from the University of Cologne , where he studied Mathematics, Physics and Management Sciences. Between 1981 and 1988 he was Assistant and Associate Professor at the the Department of Industrial and Systems Engineering of the University of Florida . He was the founder of the Center for Optimization and Combinatorics (COCO) which he directed from 1986 to 1992. Since 1988 he is Professor for Management Mathematics at the University of Kaiserslautern , where he was also Vice President (1994 -1997). Since 2004 he is Honorary Professor of the Department of Engineerig, University of Auckland , New Zealand .

His main interest is in integer and network optimization, location theory, and applications of these areas to real-world problems. He has authored and co-authored 18 books and some 100 articles in professional journals. He is member of several editorial and advisory boards of professional journals and one of four board members of the German Operations Research Society (GOR). In 2004 he was the inaugural recipient of the Julius-von-Haast Award of the New Zealand Government.

Lecture to be presented in EWI 2007  

Title

Center Hub Location Problems and Multicriteria Optimization

Abstract

The location of hubs is of crucial importance in transportation networks. Corresponding models are used in many common processes including air transportation, the distribution of mail, the design of computer networks, etc.
Formally, a hub location problem can be described as a two-phase process. In the first phase, a subset of network nodes is selected (the hubs) among which communication is accelerated. In this talk we restrict ourselves to the case of single allocation problems in which traffic between any pair of nodes has to go through these hubs. Hence, in the second phase, the remaining network nodes (the spokes) are allocated to the hubs. We concentrate in this talk on hub center problems in which the largest distance between any pair of nodes is to be minimized.
After establishing the NP completeness for both phases of the problem, we report on some heuristics. We then turn to integer programming formulations and present a radius formulation which improves previous formulations. We show some of the properties of the corresponding feasability polyhedron and demonstrate, how the formulation can be used in combination with a hub covering model to compute optimal solutions in reasonable computation times.
In order to apply the model in practice, we embed the hub model in a multicriteria environment. For the latter we propose methods to find representative systems of all Pareto solutions using the sandwich and box method for continous and discrete problems, respectively.
The presentation is based on joint work with Silke Baumgartner, Andreas Ernst, Houyuan Jiang, Mohan Krishnamoorthy, Tanja Meyer, Christian Petersen, and Stefan Ruzika, and Gerhard Woeginger.

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