Horst W. Hamacher

Bio: Horst W. Hamacher is an academic researcher from Kaiserslautern University of Technology. The author has contributed to research in topics: Flow network & Facility location problem. The author has an hindex of 37, co-authored 162 publications receiving 5479 citations. Previous affiliations of Horst W. Hamacher include Saarland University & Siemens.

Facility location : applications and theory

Abstract: 1 The Weber Problem.- 2 Continuous Covering Location Problems.- 3 Discrete Network Location Models.- 4 Location Problems in the Public Sector.- 5 Consumers in Competitive Location Models.- 6 An Efficient Genetic Algorithm for the p-Median Problem.- 7 Demand Point Aggregation for Location Models.- 8 Location Software and Interface with GIS and Supply Chain Management.- 9 Telecommunication and Location.- 10 Reserve Design and Facility Siting.- 11 Facility Location Problems with Stochastic Demands and Congestion.- 12 Hub Location Problems.- 13 Location and Robotics.- 14 The Quadratic Assignment Problem.

Mathematical Modelling of Evacuation Problems: A State of Art

Abstract: This paper details models and algorithms which can be applied to evacuation problems. While it concentrates on building evacuation many of the results are applicable also to regional evacuation. All models consider the time as main parameter, where the travel time between components of the building is part of the input and the overall evacuation time is the output. The paper distinguishes between macroscopic and microscopic evacuation models both of which are able to capture the evacuees' movement over time. Macroscopic models are mainly used to produce good lower bounds for the evacuation time and do not consider any individual behavior during the emergency situation. These bounds can be used to analyze existing buildings or help in the design phase of planning a building. Macroscopic approaches which are based on dynamic network flow models (minimum cost dynamic flow, maximum dynamic flow, universal maximum flow, quickest path and quickest flow) are described. A special feature of the presented approach is the fact, that travel times of evacuees are not restricted to be constant, but may be density dependent. Using multicriteria optimization priority regions and blockage due to fire or smoke may be considered. It is shown how the modelling can be done using time parameter either as discrete or continuous parameter. Microscopic models are able to model the individual evacuee's characteristics and the interaction among evacuees which influence their movement. Due to the corresponding huge amount of data one uses simulation approaches. Some probabilistic laws for individual evacuee's movement are presented. Moreover ideas to model the evacuee's movement using cellular automata (CA) and resulting software are presented. In this paper we will focus on macroscopic models and only summarize some of the results of the microscopic approach. While most of the results are applicable to general evacuation situations, we concentrate on building evacuation.

On spanning tree problems with multiple objectives

Abstract: We investigate two versions of multiple objective minimum spanning tree problems defined on a network with vectorial weights. First, we want to minimize the maximum ofQ linear objective functions taken over the set of all spanning trees (max-linear spanning tree problem, ML-ST). Secondly, we look for efficient spanning trees (multi-criteria spanning tree problem, MC-ST). Problem ML-ST is shown to be NP-complete. An exact algorithm which is based on ranking is presented. The procedure can also be used as an approximation scheme. For solving the bicriterion MC-ST, which in the worst case may have an exponential number of efficient trees, a two-phase procedure is presented. Based on the computation of extremal efficient spanning trees we use neighbourhood search to determine a sequence of solutions with the property that the distance between two consecutive solutions is less than a given accuracy.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …