Effects of scale economies and production seasonality on optimal hub locations: the case of regional fresh produce aggregation

Interest in supporting local and regional food systems is rising and food hubs have attracted considerable attention among Federal, State, and local policymakers. This study explores the problem of endogenous hub location in fresh produce value chains in the Northeastern United States. To overcome limitations in the literature, we incorporate the effects of economies of scale and production seasonality into our models. Three experimental models are designed to examine the effects of alternatively applying yearly, quarterly, and monthly data on model solutions. We explicitly assess how interactions of scale economies and seasonality influence the structure and spatial attributes of an optimal regional produce aggregation hub system. The three models generate marketed different solutions and in many respects they lead to different conclusions about developing local/regional supply chains. The monthly model allows for production seasonality and actual hub operation cycle frequency and thus leads to more efficient hub solution with rich policy implications.     

Market microstructure in a global B2B network

On‐line marketplaces raise several interesting issues, among them the relevance of location when content is digitized, and the assessment of a supplier's capabilities when buyers worldwide only have electronic contact with sellers. In global B2B on‐line marketplaces, market microstructures, i.e. which firms compete for the same customers, are thus likely to be influenced by how customers value location and firm capabilities in their decisions to do business with different suppliers on‐line. We suggest that both these sets of attributes will continue to matter on‐line—firms possessing similar capabilities, as well as firms that are similar in location by country, time zones or clusters, will compete for business from the same customers. We model the similarity in competitive positions between pairs of firms based on the overlap in their customer networks, using data on actual interactions between supplier and customer banks on an electronic trading system. Using QAP network regression techniques on the 100 largest banks in this industry, we find that similarity in capabilities influences who competes with whom, and that location still matters in a global B2B exchange. Interestingly, location influences who a firm's competitors are, but not where its customers are from. Copyright © 2001 John Wiley & Sons, Ltd.     

服务业集聚与产业结构优化关系探究

随着全球化进程的不断加快，服务业集聚已经成为人们普遍关注的话题。产业集聚在获得规模效应的同时避免了垄断现象的产生，服务业集聚不但拥有这样的优势，而且还有自己独特的形成和发展特点。从产业结构的优化角度切入，借助区位商和专门化率等分析指标，以江苏省和上海市为例，对服务业集聚的形成进行理论和实证分析，提出产业结构的优化对于服务业集聚的形成和发展有着积极的作用。合理的产业结构能够为服务业集聚提供坚实的基础，各地区应该根据各自的产业特点积极的进行优化，催生服务业集聚，加快本地区经济的进一步发展。     

全国土壤污染状况调查中采样点定位方法初探

探讨了通过互联网利用Google Earth以及中文地图网页对全国土壤污染状况调查中的采样点进行定位的方法,阐述了必要的操作步骤及应用技巧,指出了这种方法的不足,提出应用此方法可大大提高土壤样品采集的工作效率。     

企业空间集聚的成因分析

企业空间集聚是当今世界区域经济发展的重要特色。本文从同行业和不同行业两个角度分别探讨了企业空间集聚的成困,并实例分析了徐州市金山桥开发区企业集聚体的形成与发展。     

Asymptotic expansion of S-estimators of location and covariance

By means of a straightforward application of empirical process theory, we show that S-estimators of multivariate location and covariance are asymptotically equivalent to a sum of independent vector and matrix valued random elements respectively. This provides an alternative proof of asymptotic normality of S-estimators and clearly explains the limiting covariance structure. It also leads to a relatively simple proof of asymptotic normality of the length of the shortest α-fraction.     

物流配送系统中的运筹学问题及方法研究

物流配送系统中包含诸多运筹学问题,如配送中心选址中的0-1规划问题,货物配载中的背包问题,配送路线优化中的动态规划问题等,通过建立数学模型,利用运筹学方法与信息技术的结合可对上述问题加以解决,为配送业务的进一步发展提供帮助.     

模型算法在企业的场址选择及其内部设施的平面布置中的应用

企业的场址选择及其内部设施的平面布置形式，对于企业的运输费用具有举足轻重的作用。本文对企业和内部设施的布置进行模型设计，并通过层次分析法对场址选择方案进行比选．采用对目标函数的优化对企业内部设施的平面布置形式进行优化。     

江西大型企业资本运作模式的现状及其改进对策研究

资本运作是一种有效配置资源、实现企业资本增殖的活动,其核心是产权制度创新。本文对江西大型企业资本运作模式的现状进行了分析,进而提出了一系列的合理的改进对策,以期提高起运作绩效。     

物流设施选址问题中时间满意度函数的定义及应用

建立了顾客对等待时间的满意度与物流设施和需求点间的距离之间的函数关系,描述了时间满意度函数的拟合方法并给出了函数的拟合原则,最后以集覆盖问题为例说明了时间满意度函数的应用。