Interfacility Interaction in Models of Hub and Spoke Networks

Providers of transportation services may reduce their average unit costs by bundling flows and channeling them between hubs (also known as concentrators or routers). The resulting facility locations are interdependent because of the flows between them. This paper analyzes mathematical models of hub systems in an effort to enhance understanding of the optimal location of interactive facilities. The paper examines the behavior of solutions to several alternative models that require the location of a hub at either of two similar locations. A model employing a concave cost function favors the assembly of flows, penalizes fractional facility locations, and produces local minima that have integer facilities.     

Reliable p-Hub Location Problems in Telecommunication Networks

Hubs are critical elements of telecommunication and transportation networks because they play a vital role in mass traffic movement. The design of more reliable networks in hub-and-spoke systems is a critical issue because current networks, particularly many commercial Internet backbones, are quite vulnerable. In hub-and-spoke-type topologies, any malfunction at a hub may cause degradation of the entire network's ability to transfer flows. This article presents a new hub location problem, termed the reliable p-hub location problem , which focuses on maximizing network performance in terms of reliability by locating hubs for delivering flows among city nodes. Two submodels, the p-hub maximum reliability model and the p-hub mandatory dispersion model, are formulated. Based on hypothetical and empirical analyses using telecommunication networks in the United States, the relationship between network performance and hub facility locations is explored. The results from these models could give useful insights into telecommunication network design.     

Extensions to the Hub Location Problem: Formulations and Numerical Examples

Although a tremendous amount of analytical research is being conducted on the hub location problem, few models exist that extend the number of characteristics found in actual hub-and-spoke networks. Four extensions are presented in this paper: (1) a capacitated network model; (2) a minimum threshold model; (3) a model that endogenously determines the number of open hubs for the network; and (4) a model that incorporates a flow-dependent cost function for the spokes as well as the interhub links. Both the capacitated and the minimum threshold models drop the assumption of a completely interconnected network commonly found in hub location models. Numerical results show that total network costs are often minimized by closing a few interhub links. The third extension is the first known hub location model to determine the optimal number of hubs based on the needs of the network. In this model, the number of open hubs depends on the distribution of flows in the network and how cost effectively the flows can be moved across the network. Previous models that endogenously determined the number of open hubs utilized a fixed cost for establishing each hub in order to limit the number of hubs in the network. The final extension recognizes the potential of all links to amalgamate flows and includes a separate flow-dependent cost function for the spokes in addition to the one for the interhub links. Numerical results are shown for all four models.     

LOCATION AND SPATIAL PRICING FOR PUBLIC FACILITIES

ABSTRACT. Past analysis of public facility location has generally assumed a single goal, such as cost minimization or welfare maximization, and exogenous spatial pricing. This paper considers optimal facility location under a variety of goals. Furthermore, the facility manager is allowed to engage in freight absorption so that the delivered price to consumers need not reflect actual transportation costs. A systematic interaction among management goals, freight absorption, and the optimal size and spacing of public facilities is found.     

火车客运站综合流通空间规划探索——以广州市铁路新客站地区规划为例

本文简要回顾了火车客运站地区规划研究的发展。提出火车客运站具有增长极的性质,各种经济流通空间集聚在火车客运站周边,形成了综合流通空间。分析了综合流通空间的内涵与特点。指出综合流通空间由核心功能区、衍生功能区、外围功能区三个层次构成,分析了各个层次的功能构成、服务设施与布局模型。对综合流通空间与其他城市功能空间的关系进行了探讨。以广州铁路新客站地区规划为例,从集聚作用、功能结构与布局、与其他城市功能区的联系三方面对综合流通空间进行了实证分析。     

Multiple Allocation Hub Location Model with Fixed Arc Costs

This article formulates a model to analyze the role of fixed costs in the design of optimal transportation hub networks. The primary purpose of this article is to better model costs in hub networks, an issue that has attracted considerable attention. This article allows particular versions of hub networks to emerge from the cost structure, rather than by imposing a rigid predefined connectivity protocol. The article integrates modeling approaches from an environmental hub location model with the three‐index formulation of Ernst and Krishnamoorthy to produce a hub location model with fixed and variable costs for all arcs. Our goal is to demonstrate how the inclusion of a richer cost model in transportation hub location can generate a wide range of different network types, depending on the relative magnitudes of the cost elements. While the existence of special case network solutions is well known and has been exploited in optimization, the current research provides added insight to the cost of flow in a more, or less, connected hub network. Eight fundamental prototype networks are derived as special cases, and some additional unanticipated network types also emerge. The results are illustrated with a standard CAB25 data set.     

旅游集散地研究初探:整体性、转换机制、自身调节性——以结构主义地理学方法为研究视角

旅游集散地正随着区域旅游的发展,重要程度日益显现。文章基于结构主义人文地理学的研究方法,认为结构是决定区域旅游发展的关键因素,决定内核的是机制,而决定机制的是结构,文章在围绕皮亚杰认为的结构三特性:整体性、转换机制、自身调节性对一直以来关注较少的旅游集散地的形成和功能进行了分析后,提出了旅游集散地地位不应低于旅游目的地,越是高层次的区域,越发体现出旅游开发的结构效益。旅游集散地的建设要强调休闲功能,而不是观光功能,要强调服务价值,而不是资源价值。     

On Covering Problems and the Central Facilities Location Problem

A number of variations of facilities location problems have appeared in the research literature in the past decade. Among these are problems involving the location of multiple new facilities in a discrete solution space, with the new facilities located relative to a set of existing facilities having known locations. In this paper a number of discrete solution space location problems are treated. Specifically, the covering problem and the central facilities location problem are shown to be related. The covering problem involves the location of the minimum number of new facilities among a finite number of sites such that all existing facilities (customers) are covered by at least one new facility. The central facilities location problem consists of the location of a given number of new facilities among a finite number of sites such that the sum of the weighted distances between existing facilities and new facilities is minimized. Computational experience in using the same heuristic solution procedure to solve both problems is provided and compared with other existing solution procedures.     

我国北方沿海地区和京、津两市的发展

环渤海省、市规划区是京、津两市发展的主要区域经济基地。本文在分析该区资源、经济和区位的基础上论证了两市在我国的重要职能、发展基础和条件,以及彼此的比较优、劣势。
环渤海地区资源丰富,重工业基础好,交通运输地位重要,土地和劳动力价格便宜,投资环境改善,在下世纪初将可成为我国开放发展的重要地区。
京、津两市相距很近,可以发展成为集合城市。其经济和人口规模将超过我国最大城市上海。为此,两市应协调发展,合作建设,共同形成我国北方的国际经济活动中心城市。当前的主要发展途径是调整产业结构,发展高新技术产业和第三产业;发展节水型产业,建设节水型城市;合作建设京津高速公路沿线高新技术产业带;共同开发塘沽滨海区。     

Identifying Critical Facilities in Hub‐and‐Spoke Networks: A Hub Interdiction Median Problem

The hub location problem has been widely used in analyzing hub‐and‐spoke systems. The basic assumption is that a large number of demands exist to travel from origins to destinations via a set of intermediate transshipment nodes. These intermediate nodes can be lost, due to reasons such as natural disasters, outbreaks of disease, labor strikes, and intentional attacks. This article presents a hub interdiction median (HIM) problem. It can be used to identify the set of critical facilities in a hub‐and‐spoke system that, if lost, leads to the maximal disruption of the system's service. The new model is formulated using integer linear programming. Special constraints are constructed to account for origin‐to‐destination demand following the least‐cost route via the remaining hubs. Based on the HIM problem, two hub protection problems are defined that aim to minimize the system cost associated with the worst‐case facility loss. Computational experiment results are presented along with a discussion of possible future work. El problema de la ubicación de la central (hub) ha sido ampliamente analizado para el caso de los sistemas de sistemas radiales (hub‐and‐spoke). La presunción inicial es que existe un gran número de demandas que viajan desde puntos de origen hasta sus puntos de destino a través de un set de nodos intermedios de trasbordo. Estos nodos intermedios pueden perderse por diferentes motivos, como desastres naturales, brotes de enfermedades, huelgas de trabajadores, o ataques intencionales. Este artículo presenta un problema de tipo mediana de interdicción de hub, conocido como hub interdiction median‐HIM. Puede usarse para identificar un set de instalaciones críticas de un sistema tipo hub‐and‐spoke que, si se pierde, conduce a la máxima interrupción del servicio del sistema. El nuevo modelo se ha formulado utilizando programación entera lineal, (integer linear programming‐ILP). El modelo construye restricciones especiales para dar cuenta de la demanda de “origen‐a‐destino” (O‐D), siguiendo la ruta de menor costo, a través de los hubs restantes. Basándonos en el problema de HIM, se definen dos problemas de protección de hub que buscan minimizar el costo asociado al peor caso posible de pérdida de instalaciones. Se presentan además, resultados de experimentos computacionales, así como a una discusión sobre posibles futuros trabajos en la materia. 枢纽区位研究已广泛应用于中枢辐射型系统分析,其基本假设条件为起始点到目的地之间存在大量旅行需求的中间转运节点。但自然灾害、突发疾病、劳务罢工和蓄意攻击等因素可能导致中间转运节点的丧失。本文提出了一种枢纽封闭中心模型（HIM）,可用于识别中枢辐射型系统的重要节点,一旦这些节点丧失,将导致整个系统服务最大程度的瓦解。新模型通过整数线性规划公式建立。模型特殊约束条件的建立基于最小成本路径通过余下枢纽的花费来解释始发到目的地（ origin‐to‐destination）需求量。基于HIM问题,双枢纽保护问题被定义为旨在最小化系统花费及其与之关联的最坏情况下节点丢失问题。最后,根据计算的经验结果讨论未来可能深入的研究。     

大都市区居民对新兴边缘城市的认知与迁居意向——以天津大都市区为例

目前天津经济技术开发区(TEDA)已发展成为天津大都市区的新兴边缘城市。本文以居民问卷调查的第一手资料为基础,分析天津大都市区内各地区居民对TEDA的认知程度与迁居意向以及地域选择性特征,为以TEDA为核心的人口反磁力中心建设为主导的天津大都市区人口调整对策提供科学依据。     

Pursuing the Peripheral Path? A Path-Dependent Analysis of the Frankfurt and Munich Fairs

As a result of increasing competition and internationalization, many Western European cities have invested in exhibition facilities. Surprisingly, many new exhibition centres emerge in the urban periphery. An assessment of the 34 largest exhibition centres in Western Europe shows that only 16 are still centrally located while 18 now have a peripheral location. This is a drastic break from the traditional location of these centres in inner city cores. Behind this observation of spatial change is a complex set of dilemmas about investments in current or new locations. A fresh analytical model (based on assumptions of path dependency) is constructed and employed to analyse time and place specific determinants and opportunities. Two contrasting cases are selected in comparable German cities. Frankfurt decided to renew its facilities in the centre of the city, whereas Munich opened a relocated exhibition centre in 1998. Based on these case studies, the paper concludes that there is no autonomous force pulling exhibition centres towards the periphery, but it is rather a misfit between the central location and new physical, functional, spatial, and institutional demands that causes a facility to move.     

Institutional contradictions and attempts at innovation. Evidence from the Italian urban facility planning

Spatial planning affects the way in which cities are created and developed, as well as their economics and welfare. It does so by constructing institutional frameworks that frequently undergo states of contradiction and demands for adjustment and revision. This situation is particularly evident by looking at the way in which urban facilities have been planned during the twentieth century. The article explores the issue of urban facility planning in Italy by taking into account the adaptations of the institutional framework governing and regulating their supply. In particular, it explores the central contradictions which guided reforms and revisions of urban facility planning in Italy, starting from the post-war period until now, and the main problems left unsolved after years of attempts at innovation aiming at a more flexible and quality-oriented approach. In order to contribute to this debate, specific policy implications and devices are presented.     

Mode Choice in a Hub-and-Spoke Network: A Zero-One Linear Programming Approach

While research has tackled the hub-and-spoke network design problem, that research has overlooked the air-truck modal integration issue which is a common feature of real express delivery systems. This paper devises integer linear programs to represent the mode and route assignment aspects of the operational problem. The model is solved under four different levels of delivery schedule, and the results show that as the promised delivery schedule is relaxed, not only does the use of truck routes become more desirable, but also interesting adjustments in mode and hub assignment occur. Consider the case of hubs in Los Angeles and Dayton. As the time constraints are relaxed, cities such as Minneapolis and New Orleans originally linked by air to Los Angeles, switch to Dayton because cheaper truck routes become feasible.     

空铁型综合交通枢纽地区空间演化特征——以上海虹桥枢纽为例

空铁型综合交通枢纽是将航空枢纽和高铁枢纽有机整合而形成的航空高铁一体化综合交通枢纽,具有较强的经济社会带动作用,对区域空间演化产生重要影响。根据复杂适应系统理论,选取上海虹桥综合交通枢纽地区为案例地,分析了空铁型综合交通枢纽地区地域空间演化阶段性特征。结果表明：交通枢纽地区地域系统通过多个适应性主体之间非线性相互作用形成复杂适应系统,该地域系统演化过程可划分为枢纽地区空间形成阶段、枢纽地区空间生长阶段和枢纽地区空间涌现阶段。上海虹桥综合交通枢纽地区在三个阶段特征不同,配套设施建设、要素集聚与流动、城市功能形成与发展、区域品牌形成等方面不断深化。研究有助于认知综合交通枢纽地域系统空间演化规律,为深化研究和实践发展提供科学借鉴。     

基于弱势群体需求的北京服务设施可达性集成研究

关注人群属性和需求,探讨服务设施供给的社会公平是新时代服务设施研究的重要议题,对于人口总量巨大、社会构成多元、社会空间分异凸显的大城市尤其如此。尽管研究某一弱势群体对单项服务设施需求的文献不断涌现,但是结合居民主观的服务设施需求偏好的可达性集成研究尚不多见。本文以北京作为案例城市,首先采用居民主观调查数据分析四类弱势群体对于公共服务设施的需求结构,然后基于POI数据,借助GIS分析这四类弱势群体服务设施需求偏好下的北京市公共服务设施综合可达性情况,且对综合可达性较差的区域进行了空间识别。本研究综合定性与定量方法,探讨主观与客观数据相匹配的可达性集成方法,可以为今后的相关研究提供借鉴,并能够对北京建设国际一流和谐宜居之都提供理论支撑。     

空间扩容背景下长三角城市群陆路交通联系时空演化

城市群空间扩容有赖于城市间交通联系的强化。文章以县域为研究单元,探讨长三角城市群由16个设区市扩容至26个设区市,各单元经由陆路交通与中心城市及设区市市区的交通联系时空演化。结果显示：(1)空间扩容引致公路通达时间有所增长,但趋于均衡化发展。(2)扩容后普速铁路网络通达时间明显增加,尽管连通度有所提升,但连通强度明显下降;高铁网络通达时间显著低于普铁网络,且连接指数显著高于普铁网络,中心城市在高铁网络中优势突出。(3)主要得益于高速铁路发展,扩容后陆路可达性及其均衡性均有所提升,交通发展很好地支撑了城市群扩容;受城市群扩容及陆路交通发展的共同作用,可达性格局发生了明显变化,长江的阻隔效应更为明显。     

枢纽经济及其发展机制——以中国交通枢纽经济为例

枢纽经济是当前很多省份的重要区域发展战略，但是对枢纽经济内涵、发展机制等核心问题的讨论还不足以指导现实枢纽经济发展。文章构建并检验枢纽经济的发展机制，一方面界定枢纽经济内涵，从系统论的自组织和他组织视角使用区域循环累积因果模型推演出枢纽经济发展的四个阶段；另一方面以交通枢纽经济为例使用省级2007-2017面板数据检验主要变量的定量影响，并判断我国枢纽经济的当前所处阶段。主要结论：枢纽经济发展受经济系统自组织和政府他组织影响，是由初始变化形成阶段、次级强化形成阶段、产业竞合上升发展阶段、成熟阶段组成的循环累积因果过程；经验检验表明劳动力数量、公共基础设施配套、制度创新和技术水平显著影响枢纽经济；当前我国枢纽经济发展处于初始形成阶段，政府政策是触发关键；提高丝绸之路经济带沿线西部省份的枢纽数量和质量能有效拉动枢纽经济发展。     

港口、铁路与近代青岛城市变动:1898-1937

19世纪末20世纪初,随着近代中国社会与经济的现代转型,铁路、轮船等新型交通运输方式应运而生,一批新兴交通型城市逐渐形成,青岛便是其中之一。作为青岛港所在地和胶济铁路起点,青岛市在1898至1937年间的变动与港路休戚相关:港路运输体系的构建,极大改善了当地的交通运输条件,使青岛成为陆上交通枢纽并跃居山东省沿海第一大港;凭借路港联动,物流与人流均以前所未有的速度和规模在内陆—青岛—海外地区间流动,带动了青岛工商经济的飞速发展,也为青岛集聚了人气,大批务工、经商人员移居青岛,青岛市人口规模增大,街市不断扩展。在青岛港和胶济铁路的作用下,青岛完成了由小渔村到现代化城市的嬗变,并由此带动了山东省乃至近代华北地区交通和经济格局的变动。     

沪宁杭城市群区发展趋势探讨

沪宁杭城市群区发展趋势探讨姚士谋Ｊ．Ｎｉｐｐｅｒ（中国科学院南京地理与湖泊研究所）（德国科隆大学地理所）关键词城市群区,集聚功能,基础设施建设,外向型经济,国际化城市沪宁杭地区位于中国东部沿海居中的地理位置,历史上也是属于经济比较发达与城镇密集的区域...