Modeling techniques for periodic vehicle routing problems

This paper presents a continuous approximation model for the period vehicle routing problem with service choice (PVRP-SC). The PVRP-SC is a variant of the period vehicle routing problem in which the visit frequency to nodes is a decision of the model. This variation can result in more efficient vehicle tours and/or greater service benefit to customers. We present a continuous approximation model to facilitate strategic and tactical planning of periodic distribution systems and evaluate the value of service choice. Further, results from the continuous model can provide guidelines for constructing solutions to the discrete PVRP-SC.     

A Hybrid TCNN Optimization Approach for the Capacity Vehicle Routing Problem

Introduction The vehicle routing problem(VRP)is one ofthe well-known NP-hard optimization problems[1]occurring in many transport logistics and distribu-tion systems of considerable economic significance.The capacity vehicle routing problem(CVRP)likeVRP with the additional constraint that every vehi-cle must have a capacity,so it is also an NP-hardoptimization problems.It involves minimizing costvehicle schedules for a fleet of vehicles originatingand terminating from a central depot.The …     

Matlab在航线配船中的应用

利用OLE自动化技术实现Visual Basic调用Matlab函数进行航线配船,应用于赤水河机动驳船队配船,证明该方法的有效性,将Visual Basic的可视化界面与Matlab强大的数值计算相结合,为航线配船提供了一种有效的解决手段。     

不固定牵引方式双肩回交路机车最优配置的遗传算法

机车周转图的编制是多约束条件的组合优化问题。针对不固定牵引方式双肩回交路机车周转图编制建立数学模型,并以机车在2个折返段(站)和基本段(站)总停留时间最少为目标,设计不固定牵引方式双肩回交路机车运转制下求解机车最优配置的遗传算法。基于知识的变异方法和采用交叉概率、变异概率随个体优劣程度自适应的调整策略,提高算法的局部搜索能力以及收敛和优化性能。以某实际列车运行图为例进行仿真计算,结果表明:运用该算法可使机车的段内总停留时间和需要的牵引机车台数较实际的机车周转图分别减少约21%和8.6%。     

带时间窗车辆路径问题的启发式遗传算法

为了在运输生产中按时间要求合理安排车辆路径,建立了带时间窗车辆路径问题数学模型,用启发式遗传算法进行求解。先构造染色体,产生初始群,再对其进行优化,根据个体生存能力的体现进行性能估计,并计算优化值。运用VisualBasic编写相应计算程序,设定迭代代数为100,运算次数为10次,对有时间窗限制的有1个中心仓库与8个分仓库的实际问题进行求解。模拟结果显示需要3辆车按照3条运输线路进行物流配送服务,总运行距离为483km,总运行时间为15.55h,车辆未出现闲置时间,且全部仓库得到及时服务。可见启发式遗传算法有效、可行。     

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创新性地考虑了多车型车辆路径问题中不同车型具有不同的边际费用和行驶费用的问题,并同时考虑车型与任务的相容性,对带时间窗约束的多车型多费用非满载车辆路径问题,以最小化总费用为目标建立了数学模型。由于该模型的NP-hard性质,基于高费用车型的边际费用和单位行驶费用比低费用车型的相应费用都要高以及低费用车型的边际费用远大于高费用车型的单位行驶费用的思想,对该模型设计了一个启发式算法。     

A decision support system for integrated hazardous materials routing and emergency response decisions

Hazardous materials routing constitutes a critical decision in mitigating the associated transportation risk. This paper presents a decision support system for assessing alternative distribution routes in terms of travel time, risk and evacuation implications while coordinating the emergency response deployment decisions with the hazardous materials routes. The proposed system provides the following functionalities: (i) determination of alternative non-dominated hazardous materials distribution routes in terms of cost and risk minimization, (ii) specification of the hazardous materials first-response emergency service units locations in order to achieve timely response to an accident, and (iii) determination of evacuation paths from the impacted area to designated shelters and estimation of the associated evacuation time. The proposed system has been implemented, used and evaluated for assessing alternative hazardous materials routing decisions within the heavily industrialized area of Thriasion Pedion of Attica, Greece. The implementation of the aforementioned functionalities is based on two new integer programming models for the hazardous materials routing and the emergency response units location problems, respectively. A simplified version of the routing model is solved by an existing heuristic algorithm developed by the authors. A new Lagrangean relaxation heuristic algorithm has been developed for solving the emergency response units location problem. The focus of this paper is on the exposition of the proposed decision support system components and functionalities. Special emphasis is placed on the presentation of the two new mathematical models and the new solution method for the location model.     

一种支持多层次MPLS网络的标签设计

提出了一种支持多层次MPI。S网络的标签改进方法以及这种改进后的标签的工作原理，文章主要介绍了MPLS的优势以及现有的MPLS标签结构和工作原理，同时提出一种多层次MPLS网络模型，以及改进的MPLS标签的结构，多层次MPLS工作过程并给出了一个模拟，最后指出了多层次和单层次MPLS之间明显的不同之处。     

A systematic review of route optimisation and pre-emption methods for emergency vehicles

ABSTRACT

Reducing the travel time of emergency vehicles (EVs) is an effective way to improve critical services such as ambulance, fire, and police. Route optimisation and pre-emption are powerful techniques used to reduce EV travel time. This paper presents a systematic literature review of optimisation and pre-emption techniques for routing EVs. A detailed classification of existing techniques is presented along with critical analysis and discussion. The study observes the limitations of existing routing systems and lack of real-world applications of the proposed pre-emption systems, leading to several interesting and important knowledge and implementation gaps that require further investigation. These gaps include optimisations using real-time dynamic traffic data, considering time to travel as a critical parameter within dynamic route planning algorithms, considering advanced algorithms, assessing and minimising the effects of EV routing on other traffic, and addressing safety concerns in traffic networks containing multiple EVs at the same time.     

电力机车新型电器屏柜设计分析

文章以新开发的电力机车的屏柜设计为例,着重从电器屏柜的柜体设计和柜内设计两个方面对屏柜的设计方法和设计原则进行了分析说明。