Location and service mix decisions for a managed health care network

For managers of managed health care organizations, the problem of designing a competitive multiple facility network cannot be solved by existing mathematical models. This paper thus presents a nonlinear integer model for determining a facilities design strategy that embodies the economic tradeoffs encompassed in a competitive strategy: minimizing cost and maximizing market share. The integrated location and service mix model determines the number, location and service offerings of facilities that maximize profitability in a two-level hierarchical referral delivery network where an organization's market share is represented by a multiplicative competitive interaction model. To demonstrate the usefulness of the proposed integrated model, a series of problems is solved by an interchange heuristic and compared to the solutions derived by a simpler approach that ignores market competition.     

Feasibility on the integration of passenger and freight transportation in rural areas: A service mode and an optimization model

Public transport operators in rural areas have been under pressure from weak profitability and emission issues. At the same time, scattered demand for transport has been preventing logistics systems from reaching the last mile in residential areas. Multimodal transport can synergistically integrate passenger and freight demand, increase transportation network coverage, and reduce the cost of transportation, while demand-driven services improve the flexibility and reliability of operational decisions. Therefore, this paper proposes a demand-driven passenger-and-freight-integration service (DDPFIS) mode. From the perspective of routing decisions, a new mixed-integer linear programming model based on the green vehicle routing problem is formulated to assist public transport operator’s complex decision-making. In the proposed model, vehicle capacity is fully utilized through a combination of passenger and freight demand so that optimal decisions are made about vehicle routing. Numerical experiments are designed and conducted based on realistic instances with the results indicating that: the DDPFIS mode enables effective integration of different demands, leading to high-level vehicle capacity utilization and cost reduction; and compared with two conventional models of vehicle routing problems, the proposed model achieves lower fuel consumption and cost for all problem sizes. In addition, some important management insights are provided, e.g., a greater proportion of integrated service nodes is not necessarily better; and it is more suitable to provide a service for rural residents who are relatively insensitive to time.     

湛江港拓宽腹地、提升服务功能对策分析

拓宽腹地、提升服务功能是现代港口保持市场竞争优势的关键.作为西南港口群主体港和广东枢纽港的湛江港面临周边港口激烈竞争的挑战.湛江港需要从建立"无水港"打造供应链、打造区域性国际航运中心、加快交通基础设施综合化网络化建设、港城互动、建设大型分销中心、构建组合港、建立保税港或保税务流区区方面谋求突破.     

Vehicle flow formulation for two-echelon time-constrained vehicle routing problem

Two-echelon routing problems, including variants such as the two-echelon vehicle routing problem (2E-VRP) and the two-echelon location routing problem (2E-LRP), involve assignment and location decisions. However, the two-echelon time-constrained vehicle routing problem (2E-TVRP) that caters to from-linehaul-to-delivery practices does not involve assignment decisions. This routing problem variant for networks with two echelons has not yet attracted enough research interest. Localized or long-distance services suffer from the lack of the assignment decisions between satellites and customers. Therefore, the 2E-TVRP, rather than using assignment decisions, adopts time constraints to decide the routes on each of the two interacting echelons: large-capacity vehicles transport cargoes among satellites on the first echelon, and small-capacity vehicles deliver cargoes from satellites to customers on the second echelon. This study introduces a mixed integer linear programming model for the 2E-TVRP and proposes a heuristic algorithm that incorporates the savings algorithm followed by a variable neighborhood search phase. Illustrative examples are used to test the mathematical formulation and the heuristic and a case study is used to demonstrate that the heuristic can effectively solve realistic-size instances of the 2E-TVRP.     

生态旅游区废弃物回收的逆向物流选址-路径问题

研究了生态旅游区废弃物逆向物流网络设计问题,包括中转站选址和车辆路径问题,并建立了最小化选址费用和运输费用的模型。选址路径问题为NP困难问题,本文采用了四叉树原理划分满足车辆容量限制的收集区,将问题化为小型的TSP问题。     

装卸混合的软时间窗VRP问题混合算法研究

考虑了配送车辆在客户点会同时发生卸货和装货的情况,构建了装卸混合的软时间窗VRP模型,并通过遗传禁忌混合算法求解。通过实例说明,该混合遗传算法能很好地解决装卸货混合VRPTW问题,获得较好的优化效果。     

洛阳市公交线路优化模型的构建

随着个人用车数量的增多,交通拥堵问题在各个城市显现的更加严峻,发展公交事业是缓解交通问题的有效途径之一。为了对现有公交线网进行优化,有效利用现有交通资源,解决城市交通问题,本文分析了公交路线的优化目标及约束条件,建立了公交线网的线性优化模型。针对洛阳市公共交通存在的问题,文中又建立了公交线网优化的直达乘客密度模型。     

Managing returnable transport items in a vendor managed inventory system

This paper addresses a closed-loop inventory routing problem with demand uncertainty, which manages the delivery operations to customers and pick-up operations of empty returnable transport items (RTIs) from customers. The problem involves decisions regarding forward and backward vehicle routes, the delivery and collection quantities, the amount of production in terms of the number of filled RTIs, and the number of RTIs produced/ bought by the vendor during the defined planning horizon. The problem considers the holding costs, fixed cost of operating vehicles, fuel consumption cost, producing/buying costs, cleaning costs of RTIs, and loading and unloading costs. We formulate the problem as a mixed integer linear programming model and propose a Relax and Fix based solution approach to solve large instances. We conduct extensive analyses on a case study derived from a fruit and vegetable distribution network and several hypothetical instances. Our analyses investigate the effects of several problem parameter changes (i.e., average collection rate, customer service level, cost of buying crate and handling cost) on the total logistics cost. Additional numerical analyses are performed to demonstrate the usage of the model for evaluating the cost of being more green and environmental-friendly. Moreover, experiments on relatively large-scaled problems allow us to demonstrate the potential benefits of the proposed heuristic     

面向对象的车辆路径问题仿真研究

针对车辆路径问题的复杂性和随机性,采用离散事件仿真的方法对车辆配送过程建模,并用面向对象技术实现了仿真模型。通过对象识别和层次划分,将模型分为实体建模和仿真控制建模两部分,构建了面向对象的车辆路径问题的仿真框架。这种方法克服了精确算法和智能启发式算法较难解决具有NP—hard性质的多约束车辆路径问题的弊端,实验结果验证了新方法的有效性和可行性。     

我国航海教育的历史现状和发展方向演进

随着我国航运业的发展,优秀航海人才的需求量也越来越多。航海教育作为培养航海人才的基础,其发展情况直接关系到航海人才的培养。为了培养更多航海人才,尤其是高端航海人才,文中在研究以往资料的基础上,分析了航海教育的历史和发展现状,并预测了航海教育的发展方向。通过对历史的总结,解决当前航海教育中存在的问题,使航海教育朝着素质化、国际化、网络化、绿色化方向发展,培养符合STCW78/10公约要求的高素质航海人才,以实现我国“海洋强国”战略目标。     

基于真实路网的车辆路径问题研究

车辆路径问题(VRP)是广泛应用于物流配送的组合优化问题。在实际应用中,传统的处理方法是先利用路网信息求出任意两点间最短路,生成完全连通图,然后进行VRP的优化求解,这样会浪费时间和空间,降低求解效率。因此,提出了一种基于真实路网的VRP建模方法,把任意两点间最短路的求解与VRP联合起来,通过仿真实验与传统的处理方法进行了比较,两种方法得到了相同的最优解,但基于真实路网的VRP建模方法在计算时间方面占优。     

动态自适应混合智能算法在VRP问题中的应用

货物配置和车辆路径安排是个典型的NP难题。文中在建立VRP问题数学模型的基础上,构造了求解该问题的混合智能算法。在如何确定车辆数的问题上提出一种新的算法思路——动态自适应确定车辆数;同时文中提出了一种新的编码思维,将车辆信息引入染色体中;在遗传算法终止后,利用模拟退火对每一辆车的路线分别进行优化。最后,对具体案例进行仿真实验,证明了文中算法是有效的。     

大规模突发事件应急物资调度中的车辆路径问题

研究了n台应急车辆将应急物资从应急服务中心如机场、火车站运送到m个应急需求点,最后返回到应急服务中心的车辆路径问题,并以所花费的总时间最短且各辆车花费时间尽可能均衡为目标建立了模型,给出了改进的"最近搜索法",并用算例验证了模型的有效性。     

浅谈海船船员的违法行为

海船船员是海上运输活动的直接参与者,他们的行为的合法性直接关系着海上运输安全,对我国海运事业的有序发展起着至关重要的作用。船员的违法行为会对船舶的安全航行造成直接的影响,对船员违法行为进行分析和研究具有重要的理论和实践意义。文中通过对海船船员违法行为概念、种类以及成因的进行分析,并在这个基础上提出相关的对策和建议。     

对立交桥选址建模的初步探讨

本文提出了立交桥选址问题的0－1规划模型。该模型以平均车速和对路网交通均衡的作用为目标函数，考虑了立交桥选址的各项约束条件。考虑由计算机实现隐枚举法求解。在解的过程中该规模规划与交通流量分配模型不断相互作用。     

基于PDDL智能规划的车辆路径问题研究

针对车辆路径问题和多种扩展问题,文章提出一种基于PDDL智能规划的建模和求解方法,给出了多种车辆路径问题的PDDL模型,并利用SGPlan6和DaeYa规划器对PDDL模型进行了求解。实验结果表明,该算法能够在较短时间内给出高质量的车辆路径安排方案,并具备很好的扩展能力。     

加快建设福建省湄洲湾港口航运市场服务体系

文章分析了湄洲湾港在港口航运体系建设中存在的主要问题,并针对存在的问题,提出应该从提高港航等企业的服务水平、加快集疏运系统的建设、加快信息化建设、加强船舶融资、海事保险等航运高端服务业建设等策略来建设湄洲湾港航运市场服务体系。     

基于多智能体的公交线网动态优化系统阐述

随着我国城市化建设不断加快,道路交通拥堵问题也日益严重。为解决城市交通问题,国家加大了城市公共交通发展力度。城市公交的快速发展虽在一定程度上缓解了交通压力,但也带来了多线路公交车运行区间重叠等问题。多线路公交车运行区间重叠易造成交通资源的浪费,也会使车辆碰撞等安全事故的发生几率上升。因此,在加大力度发展城市公共交通的同时,还需要寻求科学合理的公交线路调度方法,通过对相关技术手段与科技产品的运用提高公交车到站的准点率,有效降低重叠运行区间车辆串车率,为市民的出行提供方便。论文基于相关的理论、技术与经验提出一种基于多智能体的公交线网动态优化系统,对系统的原理、构成、功能等进行分析论述,以供参考。     

基于SPFA的整车物流运输线路及运输方式的优化及求解

运输成本对物流企业的作用至关重要,而运用计算机辅助技术来解决整车运输线路优化的问题也一直是物流企业关注的重点。文中以安吉整车物流现有的运输网络为研究对象,以运输成本最低为目标,建立运输线路及运输方式的优化模型,并运用改进后的SPFA算法编程进行求解,从而解决运输线路及运输方式的选择问题。希望通过研究在降低物流运输成本方面做出一些有益的探索。     

混合柔性充电策略支持下的电动汽车配送路径优化

针对电动汽车在市区配送中应用越来越广泛的现象,提出了混合充电策略支持下带时间窗的电动汽车路径规划问题。在充电站,电动汽车可以选择快速充电方式充满电池或充一部分必须的电量,也可以选择直接更换满电状态的电池,这种柔性的充电策略为电动汽车提供了更灵活的运作方式,降低配送的时间和成本。通过引入充电策略相关的决策变量,在车辆路径问题的基础上,建立了混合充电策略的电动汽车路径优化的非线性混合整数规划模型。设计了一种改进的蚁群算法,通过集成局部搜索算法,提高了问题求解的效率。最后通过三个具有不同客户点分布特征的实例验证了算法的有效性,并分析了混合充电策略的影响。