In today’s extremely competitive marketplace, firms are facing the need to meet or exceed increasing customer expectations while cutting costs to stay competitive in a global market. To develop competitive advantage in this business climate, companies must make informed decisions regarding their supply chain. In recent years, supply chain networks have received increasing attention among companies. The decision makers confront the network design problem in different situations. In order to make decisions, especially in strategic supply chain management, decision makers must have a holistic view of all the components. Supply chain network design, particular facility location problems, is one of the most complex strategic decision problems in supply chain management The aim of this dissertation is to make an inquiry about the facility location problems and related issues in supply chain and logistics management, and the use of modelling approaches to solve these problems. The methodology is to construct a review protocol by forming a review panel, and developing a detailed search strategy with clear inclusion and exclusion criteria. In addition, the measurement for evaluating the quality of studies is presented with a strategy for extracting data and synthesising the methodologies. The search results show the background of the facility location problems, the importance and the basic questions of these problems. The taxonomy of facility location problems with eighteen factors is presented. The basic static and deterministic problems in facility location including the covering, centre, median and fixed charge problems are discussed. Also, the extension of facility location problems comprises of location-allocation, multi-objective, hierarchical, hub, undesirable and competitive problems. In terms of uncertainty, dynamic, stochastic and robust facility location problems are presented. Finally, strengths and weaknesses of different modelling approaches are discussed; importantly, gaps from the review process are indentified. Recommendations of future research are described; and the facility location problem to be addressed by the proposed research is shown. In addition, contributions of the proposed facility location problem are illustrated.

This dissertation studies models for locating facilities in time varying demand environments. We describe the characteristics of the time varying demand that motivate the analysis of our location models in terms of total demand and the change in value and location of the demand of each customer. The first part of the dissertation is devoted to the dynamic location model, which determines the optimal time and location for establishing capacitated facilities when demand and cost parameters are time varying. This model minimizes the total cost over a discrete and finite time horizon for establishing, operating, and closing facilities, including the transportation costs for shipping demand from facilities to customers. The model is solved using Lagrangian relaxation and Benders? decomposition. Computational results from different time varying total demand structures demonstrate, empirically, the performance of these solution methods. The second part of the dissertation studies two location models where relocation of facilities is not allowed and the objective is to determine the optimal location of capacitated facilities that will have a good performance when demand and cost parameters are time varying. The first model minimizes the total cost for opening and operating facilities and the associated transportation costs when demand and cost parameters are time varying. The model is solved using Benders? decomposition. We show that in the presence of high relocation costs of facilities (opening and closing costs), this model can be solved as a special case by the dynamic location model. The second model minimizes the maximum regret or opportunity loss between a robust configuration of facilities and the optimal configuration for each time period. We implement local search and simulated annealing metaheuristics to efficiently obtain near optimal solutions for this model.

A destructive earthquake is anticipated to occur in Istanbul in the near future. The effects of this earthquake on human, infrastructure and economy are anticipated to be enormous. The Metropolitan Municipality of Istanbul has initiated a disaster plan to mitigate the effects of the disaster. Locating disaster response facilities to execute post-disaster activities and relief operations is a part of this plan. In this study, we address the disaster response and relief facility location problem for Istanbul. Our aim is to study the situation and provide insights on the effects of the number of facilities and their locations. We propose a two-stage distribution system that utilizes existing public facilities as well as the new facilities to be established. We develop a mathematical model that tries to minimize the average distance to the population who need relief services while opening a small number of facilities. We analyze the trade-offs between these two objectives under various circumstances and present the results.

This report presents an optimization of the allocation of maintenance resources for Air Navigation Service (ANS) equipment of which LFV is responsible for the maintenance. The purpose the authors have worked after is to research ways of minimizing travelling time linked to maintenance visits for ANS equipment, this report includes the suggestions where the maintenance facilities should be placed in order to minimize the total travelling time. The report describes the problem background and presents the customer, LFV. It includes a chapter on some of the theories used for facility location and routing, and also presents methods for reducing the total travelling time used for maintenance visits annually. The authors have worked with a given set of airports in Sweden. Information about the general work with maintenance as well as the annual demand of maintenance, including the frequency of visits, for each airport included in this project was received by Pär Oberger, the task expert and contact at LFV for this report. A model for facility location based on the p-median model have been created and used when solving the problem, it was written in AMPL and solved with the CPLEX solver. The model was modified with two additional constraints regulating the minimum annual working time and the maximum distance for one-way travelling. The authors deems that a solution with five facilities is better since the benefit of additional facilities, in term of lower total distance, do not compensate for the assumed cost of establishing them.

Discrete location analysis is one of the most widely studied branches of operations research, whose applications arise in a wide variety of settings. This thesis describes a powerful new approach to facility location problems - that of message passing inference in probabilistic graphical models. Using this framework, we develop new heuristic algorithms, as well as a new approximation algorithm for a particular problem type. In machine learning applications, facility location can be seen a discrete formulation of clustering and mixture modeling problems. We apply the developed algorithms to such problems in computer vision. We tackle the problem of motion segmentation in video sequences by formulating it as a facility location instance and demonstrate the advantages of message passing algorithms over current segmentation methods.

Made available in DSpace on 2015-05-08T14:53:16Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1804871 bytes, checksum: 3742cf56fa1697798272feaab03570e7 (MD5) Previous issue date: 2011-03-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work presents a computational system that integrated with a WebGIS system, has the function to optimize the problems of facility location. System access is via a web browser and Internet connection, and aims to generate the array of actual distances between clients and facilitators. The system was applied to the problem of fnding points of collection and transmission, faced by the Brazilian electoral system in order to assist in decision making about the best locations for installation of such points. The order of the court is to minimize the sum of the total distances traveled, and also have the option to minimize the maximum distance. In this example of applicability of the treaty system was the P-median problem with GRASP. / Este trabalho apresenta um sistema computacional que, integrado com um sistema WebGIS, tem a função de otimizar os problemas de localização de medianas e cobertura. O acesso ao sistema se dá através de um navegador web e conexão com a internet e, se propõe a gerar a matriz de distâncias reais entre clientes e facilitadores. O Sistema foi aplicado ao problema de localização de pontos de coleta e transmissão, enfrentado pelo sistema eleitoral brasileiro, a fim de auxiliá-lo na tomada de decisão acerca dos melhores locais para instalação de tais pontos. O intuito do tribunal é minimizar o somatório das distâncias totais percorridas, bem como também ter a opção de minimizar a máxima distância percorrida. Para ilustrar a utilização do Sistema foi feita uma aplicação do mesmo no Tribunal Regional Eleitoral da Paraíba onde o mesmo conseguiu diminuir em, no mínimo, 23% o somatório da distância total percorrida dos locais de votação até os pontos de coleta e transmissão de votos e diminuir em 70% a distância máxima percorrida entre o local de votação e seu respectivo PCT. Neste exemplo de aplicabilidade do sistema foi tratado o problema P-mediana com a metaheurística GRASP que também foi testada em instâncias da biblioteca OR-Library e atingiu a solução ótima em mais de 62% dos casos.

The focus of this thesis is the development and solution of problems that simultaneously involve the planning of the location of facilities and transportation decisions from such facilities to consumers. This has been termed integrated distribution planning problems with practical application in logistics and manufacturing. In this integration, different planning horizons of short, medium and long terms are involved with the possibility of reaching sub-optimal decisions being likely when the planning horizons are considered separately. Two categories of problems were considered under the integrated distribution models. The first is referred to as the Step-Fixed Charge Location and Transportation Problem (SFCLTP). The second is termed the Fixed Charge Solid Location and Transportation Problem (FCSLTP). In these models, the facility location problem is considered to be a strategic or long term decision. The short to medium-term decisions considered are the Step-Fixed Charge Transportation Problem (SFCTP) and the Fixed Charge Solid Transportation Problem (FCSTP). Both SFCTP and FCSTP are different extensions to the classical transportation problem, requiring a trade-off between fixed and variable costs along the transportation routes to minimize total transportation costs. Linearization and subsequent local improvement search techniques were developed to solve the SFCLTP. The first search technique involved the development of a hands-on solution including a numerical example. In this solution technique, linearization was employed as the primal solution, following which structured perturbation logic was developed to improve on the initial solution. The second search technique proposed also utilized the linearization principle as a base solution in addition to some heuristics to construct transportation problems. The resulting transportation problems were solved to arrive at a competitive solution as regards effectiveness (solution value) compared to those obtainable from standard solvers such as CPLEX. The FCSLTP is formulated and solved using the CPLEX commercial optimization suite. A Lagrange Relaxation Heuristic (LRH) and a Hybrid Genetic Algorithm (GA) solution of the FCSLTP are presented as alternative solutions. Comparative studies between the FCSTP and the FCSLTP formulation are also presented. The LRH is demonstrated with a numerical example and also extended to hopefully generate improved upper bounds. The CPLEX solution generated better lower bounds and upper bound when compared with the extended LRH. However, it was observed that as problem size increased, the solution time of CPLEX increased exponentially. The FCSTP was recommended as a possible starting solution for solving the FCSLTP. This is due to a lower solution time and its feasible solution generation illustrated through experimentation. The Hybrid Genetic Algorithm (HGA) developed integrates cost relaxation, greedy heuristic and a modified stepping stone method into the GA framework to further explore the solution search space. Comparative studies were also conducted to test the performance of the HGA solution with the classical Lagrange heuristics developed and CPLEX. Results obtained suggests that the performance of HGA is competitive with that obtainable from a commercial solver such as CPLEX. / Thesis (PhD)--University of Pretoria, 2019. / Industrial and Systems Engineering / PhD / Unrestricted

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<p> This dissertation examines the facility location problems in the presence of barrier regions and consists basically of four essays exploring new problems. Despite the fact that the facility location problems considering barriers to travel are more realistic than their unrestricted counterparts, research in the area is relatively limited. This is due to the computational complexity associated with them. </p> <p> The first essay analyzes the problem of locating a facility in a region in the presence of a probabilistic line barrier. The objective is to locate the facility such that the sum of the volume times distances between the facility and demand points is minimized. Some convexity results are presented and a solution algorithm is proposed. </p> <p> Another interrelated problem is locating a facility in a region where a fixed line barrier such as a borderline divides the region into two. The regions communicate with each other through a number of passage points located on the line barrier. A version of this problem with minisum objective has been studied in the literature where the locations of the passage points are known. The second essay considers a number of extensions to this problem and proposes an efficient solution methodology based on the Outer Approximation algorithm. </p> <p> The third essay discusses the problem of locating a rectangular barrier facility m an area where interactions among existing facilities are present. The problem has two objectives. The first objective is to minimize the interference of the barrier facility to the interactions among the existing facilities. The second objective is to find a center (minimax) location for the barrier facility. The problem is formulated as a bi-objective problem and a mixed integer program is proposed as a solution methodology. A Simulated Annealing algorithm is presented for an extension of the problem where expropriation of existing facilities is also possible. </p> <p> Finally, the last essay suggests a practical analog approach for facility location problems in the presence of barriers. The use of the analog for certain problems is justified through some analytical results and a number of problems that appeared in the literature are solved efficiently. </p> / Thesis / Doctor of Philosophy (PhD)

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