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1、Facility location models for distribution system design物流系统设计的选址模型1 1IntroductionTypes of modelsGeneral methods2 2 The design of the distribution system is a strategic issue for almost every company. The problem of locating facilities and allocating customers covers the core topics of distribution s
2、ystem design. Introduction3 3 Industrial firms must locate fabrication(制造厂) and assembly plants(组装厂) as well as warehouses(仓库). Stores have to be located by retail outlets(零售网点). The ability to manufacture and market its products is dependent in part on the location of the facilities. Similarly, gov
3、ernment agencies have to decide about the location of offices, schools, hospitals, fire stations, etc. In every case, the quality of the services depends on the location of the facilities in relation to other facilities.4 4Types of models The The problem problem of of locating locating facilities fa
4、cilities is is not not new new to to the the operations operations research research community(community(运运 筹筹 学学 ); ); the the challenge challenge of of where where to to best best site site facilities facilities has has inspired inspired a a rich, colorful and ever growing body of literature. rich
5、, colorful and ever growing body of literature. To To cope cope with with the the multitude multitude of of applications(applications(众众多多应应用用) ) encountered encountered in in the the business business world world and and in in the the public public sector, sector, an an ever ever expanding expandin
6、g family family of of models models has has emerged.emerged.5 5Facility location models can be broadly classified as follows:The shape or topography of the set of potential plants yields models in the plane, network location models(网络选址模型), and discrete location(离散选址) or mixed-integer programming mo
7、dels(混合正数规划模型), respectively.6 6Objectives(目 标 函 数 ) may be either of the minsum or the minmax type. Minsum models are designed to minimize average distances while minmax models have to minimize maximum distances. Predominantly(此外), minsum models embrace location problems of private companies while
8、minmax models focus on location problems arising in the public sector.7 7Models without capacity constraints do not restrict(限制) demand allocation. If capacity constraints for the potential sites have to be obeyed demand has to be allocated carefully. In the latter case we have to examine whether si
9、ngle-sourcing(单来源) or multiple-sourcing(多来源) is essential.8 8Single-stage models(单阶段模型) focus on distribution systems covering only one stage explicitly. In multi-stage models(多阶段模型) the flow of goods comprising several hierarchical(层次) stages has to be examined.9 9Single-product models(单产品模型) are c
10、haracterized by the fact that demand, cost and capacity for several products can be aggregated to a single homogeneous product. If products are inhomogeneous their effect on the design of the distribution system has to be analyzed, viz. multi-product models(多产品模型) have to be studied.1010Location mod
11、els base on the assumption that demand is inelastic(无弹性的), that is, demand is independent of spatial decisions. If demand is elastic(弹性的) the relationship between, e.g., distance and demand has to be taken into account explicitly. In the latter case cost minimization (成本最小)has to be replaced through
12、, for example, revenue maximization(收益最大).1111Static models (静态模型)try to optimize system performance(性 能 ) for one representative(代表) period. By contrast dynamic models(动 态 模 型 ) reflect data (cost, demand, capacities, etc.) varying over time within a given planning horizon.1212In practice model(实践模
13、型) input is usually not known with certainty. Data are based on forecasts and, hence, are likely to be uncertain. As a consequence, we have either deterministic models (确定模型)if input is (assumed to be) known with certainty or probabilistic models (概率模型) if input is subject to uncertainty.1313In clas
14、sical models the quality of demand allocation is measured on isolation for each pair of supply and demand points. Unfortunately, if demand is satisfied through delivery tours(运输,投递) then, for instance, delivery cost cannot be calculated for each pair of supply and demand points separately. Combined
15、location/routing models(选 址 /路 线 模 型 ) elaborate on this interrelationship.1414General methodsAHP (Analytic Hierarchy Process) 层次分析法Fuzzy Clustering 模糊聚类法Cross-median method交叉中值法gravity method重心法P-median method P-中值法Systemic arithmetic 系统模拟法Genetic algorithm (GA) 遗传算法The shortest path method最短路径法Simulated Annealing (SA) 模拟退火算法1515Thank you !3030
