Easy capacitated facility location problems,with connections to lot-sizing

In this note, we consider the capacitated facility location problem when the transportation costs of the instance satisfy the Monge property. We show that a straightforward dynamic program finds the optimal solution when the demands are polynomially bounded. When demands are not polynomially bounded, we give a fully polynomial-time approximation scheme by adapting an algorithm and analysis of Van Hoesel and Wagelmans (2001).     

Accelerating Benders' decomposition for the capacitated facility location problem

Discrete facility location problems are attractive candidates for decomposition procedures since two types of decisions have to be performed: on the one hand the yes/no-decision where to locate the facilities, on the other hand the decision how to allocate the demand to the selected facilities. Nevertheless, Benders' decomposition seems to have a rather slow convergence behaviour when applied for solving location problems. In the following, a procedure will be presented for strengthening the Benders' cuts for the capacitated facility location problem. Computational results show the efficiency of the modified Benders' decomposition algorithm. Furthermore, the paretooptimality of the strengthened Benders' cuts in the sense of [Magnanti and Wong 1990] is shown under a weak assumption.This paper was written when the author was at the Institute for Operations Research, University of St. Gallen, Switzerland, and partly supported by Schweizerischer Nationalfond zur Förderung der wissenschaftlichen Forschung (Grant 12-30140.90).     

Reverse 2-median problem on trees

This paper concerns the reverse 2-median problem on trees and the reverse 1-median problem on graphs that contain exactly one cycle. It is shown that both models under investigation can be transformed to an equivalent reverse 2-median problem on a path. For this new problem an algorithm is proposed, where n is the number of vertices of the path. It is also shown that there exists an integral solution if the input data are integral.     

Simulation of Oxford University Gun Tunnel performance using a quasi-one-dimensional model

The performance of the Oxford University Gun Tunnel has been estimated using a quasi-one-dimensional simulation of the facility gas dynamics. The modelling of the actual facility area variations so as to adequately simulate both shock reflection and flow discharge processes has been considered in some detail. Test gas stagnation pressure and temperature histories are compared with measurements at two different operating conditions – one with nitrogen and the other with carbon dioxide as the test gas. It is demonstrated that both the simulated pressures and temperatures are typically within 3% of the experimental measurements. Received 18 June 2001 / Accepted 15 January 2002     

气体放电装置中的中子能谱测量

通过气体放电法研究常温核聚变现象时，用ＮＥ－２１３有机液体闪烁中子谱仪测量了气体放电装置中的中子能谱。验证了气体放电装置中中子的存在。在不同高压下，中子能谱中的峰能量均为２．３８ＭｅＶ。没有能量大于３ＭｅＶ的中子。并与加速器Ｄ—Ｄ中子源的中子能谱进行了比较。中子能谱的测量误差为±６％。     

SFC的改进

根据兰州重离子加速器的注入器SFC运行20年来所发现的问题, 近几年进行了一次大的改造, 使其真空度、 磁场分布以及高频系统的状态都得到了明显的改善。 半年多的调束和运行实践表明这次改造是十分成功的。     

An aggressive reduction scheme for the simple plant location problem

Pisinger et al. introduced the concept of ‘aggressive reduction’ for large-scale combinatorial optimization problems. The idea is to spend much time and effort in reducing the size of the instance, in the hope that the reduced instance will then be small enough to be solved by an exact algorithm.     

Soft-capacitated facility location game

We study the soft-capacitated facility location game which is an extension of the facility location game of Pa1 and Tardos. We propose a 6-approximate cross-monotonic cost-sharing method. Numerical tests indicate that the method is effective.     

An Improved IP Formulation for the Uncapacitated Facility Location Problem: Capitalizing on Objective Function Structure

In this paper we examine the Uncapacitated Facility Location Problem (UFLP) with a special structure of the objective function coefficients. For each customer the set of potential locations can be partitioned into subsets such that the objective function coefficients in each are identical. This structure exists in many applications, including the Maximum Cover Location Problem. For the problems possessing this structure, we develop a new integer programming formulation that has all the desirable properties of the standard formulation, but with substantially smaller dimensionality, leading to significant improvement in computational times. While our formulation applies to any instance of the UFLP, the reduction in dimensionality depends on the degree to which this special structure is present. This work was supported by grants from NSERC.