K-Median Problem on Graph

In past decades there has been a tremendous growth in the literature on location problems. However, among the myriad of formulations provided, the simple plant location problem and the k-median problem have played a central role. This phenomenon is due to the fact that both problems have a wide range of real-world applications, and a mathematical formulation of these problems as an integer program has proven very fruitful in the derivation of solution methods. In this paper we investigate the k-median problem defined on a graph. That is, each point represents a vertex of a graph

Reducing rail-truck freight intermodal drayage costs

In rail-truck intermodal transport, a highway truck-trailer or container is moved by truck from a shipper to a rail terminal in the shipper\u27s vicinity, and by rail in line haul between rail terminals. Upon being unloaded at the destination rail terminal, the container is delivered to a receiver (consignee) by truck. The highway portion of the move, or drayage, accounts for a relatively high percentage of total origin to destination cost, and it limits severely the competitiveness of intermodal service with door-to-door truck service. The approach used in this thesis is to examine in detail the current costs and potential for improvement at one intermodal terminal for a pre-determined analysis period. The analysis is conducted by first determining the actual cost of container movements and comparing it with the costs of an operation in which movements are scheduled using a proposed heuristic model that reduces the movements of empty containers. The model results indicate a 7.79% reduction in the overall cost of drayage. This reduction is achieved by repositioning and reloading containers, after they have been unloaded at consignees

A Survey on Approximation in Parameterized Complexity: Hardness and Algorithms

Parameterization and approximation are two popular ways of coping with NP-hard problems. More recently, the two have also been combined to derive many interesting results. We survey developments in the area both from the algorithmic and hardness perspectives, with emphasis on new techniques and potential future research directions