The Location of Hubs in Networks

这项研究将整合和概括关于设施间流动在选址问题中的作用的相互矛盾的观点。一个最重要的问题是，为什么构建一个模型来代表现实中如此频繁发生的现象如此困难？许多研究工作都致力于开发相互依赖的枢纽设施选址的模型。在这些问题中，由于不了解的原因，有时会遇到非整数解。一些程序产生了高度分数的解决方案，尽管另一些程序表现得更好。回答这个问题很重要，因为出于理论和实践的目的，设施之间的相互依存是空间经济中集聚/集聚的重要来源。这项研究将完善枢纽系统的数学模型，从而整合大量的最新文献，以努力提高对经济地理学中一个基本问题的科学理解，即互动设施的最优选址。所采用的方法包括优化、数学规划和网络分析。对推动知识进步的潜在影响如下。对于相互依赖的活动的情况，区位模型的失败是理论家的一个主要难题：实际上，通过仔细地、创造性地研究这些问题在中心星型网络中的表现方式，这一问题可能会得到修复。集线器充当地理上分散的节点之间交互的管道。在飞机、卡车、管道或网络连接的容量限制内，额外单位流量的边际成本很小(可能接近于零)。此外，在由容量更高的基础设施处理更大流量的情况下，可变成本更低。因此，运输服务提供商通过捆绑流量来降低其平均单位成本。

This research will integrate and generalize conflicting views of the role of inter-facility flow in location problems. An over-riding question is 'why is it so difficult to construct a model to represent a phenomenon that occurs so frequently in reality?' Much research effort has been devoted to developing models for the location of interdependent hub facilities. In these problems, for reasons that are not understood, non-integer solutions are sometimes encountered. Some procedures have produced highly fractional solutions, although others have fared better. It is important to answer this question because, for theoretical and practical purposes, interdependence between facilities is a crucial source of clustering/agglomeration in the space economy. The research will refine mathematical models of hub systems, thereby integrating a wide range of recent literature in an effort to enhance scientific understanding of a fundamental problem in economic geography, namely the optimal location of interactive facilities.Methods to be employed include optimization, mathematical programming, and network analysis. The potential impact on advancing knowledge is as follows. The failure of location models for the case of interdependent activities is a major puzzle for theorists: this may in fact be repaired as a result of a careful, creative examination of the way in which these issues play out in the case of hub and spoke networks. Hubs serve as conduits for interactions between geographically dispersed nodes. Within the capacity limits of aircraft, trucks, pipelines, or network links, the marginal cost of an extra unit of flow is small (perhaps close to zero). Furthermore, there are lower variable costs where greater flows are handled by higher capacity infrastructure. Thus, providers of transportation services reduce their average unit costs by bundling flows.