A fuzzy programming approach for dynamic virtual hub location problem

Hub location problem has been used in transportation network to exploit economies of scale. For example, a controversial issue in the planning of air transportation networks is inclement weather or emergency conditions. In this situation, hub facilities would not be able to provide a good service to their spoke nodes temporarily. Thus, some other kinds of predetermined underutilized facilities in the network are used as virtual hubs to host some or all connections of original hubs to recover the incurred incapacitation and increase network flexibility and demand flow. In such an unexpected situation, it is not unreasonable to expect that some information be imprecise or vague. To deal with this issue, fuzzy concept is used to pose a more realistic problem. Here, we present a fuzzy integer liner programming approach to propose a dynamic virtual hub location problem with the aim of minimizing transportation cost in the network. We examine the effectiveness of our model using the well-known CAB data set.     

The transfer point location problem

In this paper, we introduce the transfer point location problem. Demand for emergency service is generated at a set of demand points who need the services of a central facility (such as a hospital). Patients are transferred to a helicopter pad (transfer point) at normal speed, and from there they are transferred to the facility at increased speed. The general model involves the location of p helicopter pads and one facility. In this paper, we solve the special case where the location of the facility is known and the best location of one transfer point that serves a set of demand points is sought. Both minisum and minimax versions of the models are investigated. In follow up papers we investigate the general model using the results obtained in this paper.     

Web结构挖掘算法探讨

在分析Web结构挖掘现有算法的基础上，重点研究了HITS(Hyperlink—InducedTopic Search)算法。Hub页面的多主题性、无关页面和无关链接等对于HITS算法有较大影响。针对这些问题，提出了HITS算法的改进算法。     

The p-hub center allocation problem

The p-hub center problem is to locate p hubs and to allocate non-hub nodes to hub nodes such that the maximum travel time (or distance) between any origin–destination pair is minimized. We address the p-hub center allocation problem, a subproblem of the location problem, where hub locations are given. We present complexity results and IP formulations for several versions of the problem. We establish that some special cases are polynomially solvable.     

Strategic planning in LTL logistics – increasing the capacity utilization of trucks

A “less than truckload” (LTL) network organises the transport of small shipping volumes by truck between given depots. To be cost-efficient it is necessary to bundle and unbundle goods on their way, using depots as so-called hubs. Our aim is to develop a strategic plan which is cost-optimal for given average shipping volumes. We consider transshipment and transport costs; to give a realistic estimate of the economies of scale, we charge each truck on a specific route equally, whether it is full or (nearly) empty.Real-sized problems become too hard for standard solvers so that we develop a combination of heuristic strategies (which can, in the end, be combined with solvers like CPLEX). We consider the problem in two flavours: MAPIT requires to transport unsplit goods from one depot to another, using at most two intermediate depots as hubs. IO-MAPIT furthermore considers the circulation of trucks.     

Solving a new stochastic multi-mode p-hub covering location problem considering risk by a novel multi-objective algorithm

In this paper, we develop a novel stochastic multi-objective multi-mode transportation model for hub covering location problem under uncertainty. The transportation time between each pair of nodes is an uncertain parameter and also is influenced by a risk factor in the network. We extend the traditional comprehensive hub location problem by considering two new objective functions. So, our multi-objective model includes (i) minimization of total current investment costs and (ii) minimization of maximum transportation time between each origin–destination pair in the network. Besides, a novel multi-objective imperialist competitive algorithm (MOICA) is proposed to obtain the Pareto-optimal solutions of the problem. The performance of the proposed solution algorithm is compared with two well-known meta-heuristics, namely, non-dominated sorting genetic algorithm (NSGA-II) and Pareto archive evolution strategy (PAES). Computational results show that MOICA outperforms the other meta-heuristics.     

多层次的数据仓库系统总体框架的研究

数据仓库作为一项数据管理领域的新技术,到目前为止还没有成熟、可靠且能被广泛接受的系统构建标准.为此文章提出了多层次的数据仓库系统总体框架,以及基于该框架的数据仓库的体系结构、数据仓库系统的标准开发过程及数据仓库平台的测试指标.以此为基础,并结合已有的业务系统,企业可以逐步构建完整的、健壮的数据仓库系统.     

Do larger firms have more interfirm relationships?

In this study, we investigate interfirm networks by employing a unique data set containing information on more than 800,000 Japanese firms, about half of all corporate firms currently operating in Japan. First, we find that the number of relationships, measured by the indegree, has a fat-tail distribution, implying that there exist “hub” firms with a large number of relationships. Moreover, the indegree distribution for those hub firms also exhibits a fat tail, suggesting the existence of “super-hub” firms. Second, we find that larger firms tend to have more counterparts, but the relationship between firms’ size and the number of their counterparts is not necessarily proportional; firms that already have a large number of counterparts tend to grow without proportionately expanding it.     

厦门BRT枢纽站设计对策及技术探讨

本文详细介绍了厦门BRT枢纽站的结构设计,包括桩基础、结构体系与计算分析以及关键技术的解决方案,针对结构超长、楼板大开洞、停车场动荷载作用和大跨度的设计难点,结构设计时采用计算温度应力、设置诱导缝,对楼板采取加强措施,考虑车辆的动荷载作用及采用预应力技术,满足建筑功能的要求。     

工会组织加强和创新社会管理的路径探析

加强和创新社会管理,是党和政府应对社会矛盾凸显期而做出的战略部署。工会组织如何参与社会管理及其创新,需要进行顶层设计,解决工会组织参与路径中的协同意识、职能定位、治理结构、工作制度、管理机制等问题。