A genetic algorithm for the uncapacitated single allocation planar hub location problem

Given a set of n interacting points in a network, the hub location problem determines location of the hubs (transfer points) and assigns spokes (origin and destination points) to hubs so as to minimize the total transportation cost. In this study, we deal with the uncapacitated single allocation planar hub location problem (PHLP). In this problem, all flow between pairs of spokes goes through hubs, capacities of hubs are infinite, they can be located anywhere on the plane and are fully connected, and each spoke must be assigned to only one hub. We propose a mathematical formulation and a genetic algorithm (PHLGA) to solve PHLP in reasonable time. We test PHLGA on simulated and real life data sets. We compare our results with optimal solution and analyze results for special cases of PHLP for which the solution behavior can be predicted. Moreover, PHLGA results for the AP and CAB data set are compared with other heuristics.     

LTL logistics networks with differentiated services

This research addresses the problem of designing a LTL logistics network over individual lanes by offering different delivery services (1-day, 2-day, 3-day). A network design is proposed which links lane-specific delivery service choices and service profitability to the hub location-allocation decisions. A hybrid-heuristic is developed which uses a search interval reduction technique with a meta-heuristic. The performance of the hybrid-heuristic is evaluated in a computational study. A factorial experiment design with real world data is used to analyze the network structure, service choices and shipment flows, which results in managerial insights about the design and operation of a LTL logistics network with differentiated services.     

Gas and LNG trading hubs,hub indexation and destination flexibility in East Asia

In the East Asian gas markets, issues like gas trading hubs, hub indexed pricing, and destination flexibility are being debated. This paper examines the impact of a change in East Asia's pricing benchmark and contract flexibility on the regional and global gas markets. The paper uses the Nexant World Gas Model, a linear program with global cost minimization as the objective. To our knowledge, this study on hub competition, price benchmark change and contract flexibility improvement in East Asia will be the first in the literature and have real policy relevance. The results show that both price benchmark change and contract flexibility improvements will create an overall benefit for the world and East Asia importers, but the impacts are different among exporters and importers. However, there is no evidence of competition among different benchmark hubs and no evidence that destination restrictions cause the “Asia Premium”. It implies that removal of destination clauses has higher priority than the change to hub indexation for Japan, Korea and Chinese Taipei, but both should be treated equally in China. The study also suggests that East Asian importers should cooperate among themselves and with exporters to facilitate the hub creation and contract changes in East Asia.     

POE理论在快速公交枢纽站设计中的应用初探——以厦门快速公交第一码头站为例

本文以厦门快速公交第一码头枢纽站为例,运用POE理论,通过现场调研和数据分析,对其周边环境空间、建筑主体空间和交通流线进行建成环境使用后评估,以期对相关的枢纽站设计提供借鉴和参考。     

The uncapacitated hub location problem in networks under decentralized management

We propose a new hub location model defined by the minimization of costs. The main contribution of this work is to permit the analysis of a hub-and-spoke network operated under “decentralized management”. In this type of network, various transport companies act independently, and each makes its route choices according to its own criteria, which can include cost, time, frequency, security and other factors, including subjective ones. Therefore, due to the diversity of the various companies’ criteria, one can expect that between each origin–destination pair, a fraction of the flow will be carried through hubs and a fraction will be carried by the direct route. to resolve this problem, it becomes necessary to determine the probability that any network user will choose the hub route for each trip to be made (or for each load to be carried). We present an integer programming formulation, subject the new model to experiments with an intermodal general cargo network in Brazil and address questions regarding the solution of the problem in practice.     

Analysis of factors influencing the Henry Hub natural gas price based on factor analysis

Henry Hub as an important transaction hub for natural gas sets the gas price standard in the USA. In this paper, the factors influencing Henry Hub natural gas prices are analyzed, and the major factors determining the price levels in the period between January 1997 and December 2016 are studied. It is found that economic conditions, total energy demand, US dollar exchange rate and gas consumption are the major factors. The mechanism of each factor influencing the Henry Hub natural gas price is also explored in the paper.     

汽车轮毂加工和气密性检测工作站的设计

针对汽车轮毂机加工过程中定位困难、生产工序衔接不顺畅等问题,基于工业机器人设计了一种汽车轮毂加工和气密性检测工作站。根据轮毂生产工艺流程,构建适应生产节拍的工作站空间布局。通过SolidWorks软件创建工业机器人专用夹具,在仿真软件中创建相应组件,添加输入输出信号,并对信号属性进行连接,实现了这一工作站的仿真和优化。仿真结果表明,这一工作站能够优化汽车轮毂加工工序,提高生产效率。通过路径规划和碰撞监测,这一工作站还可以得到准确的工业机器人作业速度、电机功率、能耗等数据,进而提高生产过程的稳定性。     

飞来峡水利枢纽通信系统

介绍了飞来峡水利枢纽通信系统,对系统存在的问题进行了初步的分析,并提出了处理办法.     

轨交枢纽站域步行系统发展的模式、逻辑与机制--基于三个亚洲案例的比较研究

在中国城市轨道交通快速发展背景下,轨交枢纽站域步行系统面临转型重构问题,一些亚洲高密度城市的发展模式可资借鉴。大阪梅田枢纽、香港中环枢纽和新加坡政府大厦枢纽分别代表了站城一体、广域互联和活力导向的步行系统发展模式。通过系统归纳与比较分析,它们在结构、功能和品质层面上体现出层化与网络、内化与关联、包容与持续的共性特征,而在具体的建构方式上又呼应了不同建成环境的有机差异。这些发展模式的成功实践依赖于有效的城市设计运作与导控机制,三个案例在持续推进、协同组织、精细导控等方面的经验对于我国现代城市设计实践与制度创新具有启发意义。     

Solving the hub location problem with modular link capacities

This paper deals with a capacitated hub location problem arising in the design of telecommunications networks. The problem is different from the classical hub location problem in two ways: the cost of using an edge is not linear but stepwise and the capacity of a hub restricts the amount of traffic transiting through the hub rather than the incoming traffic. In this paper both an exact and a heuristic method are presented. They are compared and combined in a heuristic concentration approach to investigate whether it is possible to improve the results within limited computational times.