基于费用流的废纸动态回收网络优化设计

通过建立基于费用流的废纸动态回收网络模型并求解,解决废纸在运输网络中流动的路径问题,避免了经典运输问题无法直接体现转运和路径选择的问题,最后通过一个模拟算例验证了模型的优越性。     

基于多种运输方式的第四方物流路径问题研究

建立了基于多种运输方式的第四方物流路径优化模型,通过虚拟运输网络,将第四方物流路径问题转化为一个带时间约束和能力约束的最短路径问题,并给出了基于Dijkstra的启发式算法。算例显示,该算法能方便有效地求解基于多种运输方式的第四方物流路径问题。     

基于多种运输方式的行包快捷货物运输网络模型的设计与研究

分析了快捷运输网络的结构，建立基于多种运输方式的综合快运换装网络模型，并进一步探讨求解算法。通过对换装网络结构特点的分析，将行包快捷货物运输方案的编制分解为最优径路选择和运输网络优化两部分，并提出了具体的解决方法。     

客货分线条件下的铁路快捷运输产品设计方法研究

运用图论构建铁路快捷运输网络,并设计基于网络流方法的数学模型求解快捷运输产品设计方法,通过给定运输预算,最大限度满足货运需求,并有效降低货物的运达时间。运用成熟数学规划软件求解该模型,并设计算例证明模型与算法的有效性。     

面向支线港腹地的集装箱卡车运输网络成本模型研究——直接装运策略下

本文研究了由一个集装箱支线港码头和若干收货人组成的面向港口腹地的集装箱卡车运输网络。着眼于运输网络的总成本,该网络涉及到两种类型的决策者:集装箱码头货运站经营人和收货人,前者负责提供运输服务,而收货人负责租赁集装箱并与货运站签订运输合同。本文建立直接装运运输策略下,面向支线港腹地的集装箱卡车运输网络的总成本模型。     

集装箱多式联运系统中各种运输方式最优组合模式研究

针对集装箱多式联运系统中各运输方式的最优组合模式进行了研究。首先,通过对集装箱多式联运网络的描述和相应变形,建立了多式联运虚拟运输网络,然后以多式联运网络系统性能指标(PI)最优为目标建立了模型,并采用改进的遗传算法作为求解算法。系统性能指标(PI)定义为各运输方式运输费用和运输时间的线性加权之和,针对不同货物可分别赋予不同的权重系数。最后,通过对一个实例问题的求解验证表明,本文方法有效地从定量角度分析了集装箱多式联运过程中各种运输方式的最优组合模式,为集装箱多式联运的相关研究工作提供了理论基础。     

面向支线港腹地的集装箱卡车运输网络G_1的成本模型研究——巡回装运策略下

本文研究了由一个集装箱支线港码头和偶数个收货人组成的面向港口腹地的集装箱卡车运输网络G_1。着眼于运输网络的总成本,该网络涉及到两种类型的决策者:集装箱码头货运站经营人和收货人,前者负责提供运输服务,而收货人负责租赁集装箱并与货运站签订运输合同。本文建立巡回装运运输策略下,面向支线港腹地的集装箱卡车运输网络G_1的总成本模型。     

多式联运路径优化模型与方法研究

考虑到多式联运路径的选择受到运输成本、运输时间、运输质量和服务水平等相关因素的影响,将多式联运的路径优化问题转化成为一个广义最短路径问题,以成本和时间为优化目标建立了适应运量变化情况下的多式联运路径优化数学模型,并选择蚁群算法对实际问题进行了求解验证。     

多式联运路径优化模型与方法研究

考虑到多式联运路径的选择受到运输成本、运输时间、运输质量和服务水平等相关因素的影响,将多式联运的路径优化问题转化成为一个广义最短路径问题.以成本和时间为优化目标建立了适应运量变化情况下的多式联运路径优化数学模型,并选择蚁群算法对实际问题进行了求解验证.     

危险品转运运输路径问题研究

研究了危险品转运运输问题,在对危险品转运运输网络中的运输风险、运输成本等进行分析的基础上,确定了危险品转运问题的目标函数,并构造了该问题的混合目标函数,进一步采用Dijkstra算法确定出转运运输路径,最后结合实例进行了分析求解。     

Improving accessibility to rural health services: The maximal covering network improvement problem

Accessibility to health facilities is a critical factor in effective health treatment for people in rural areas of lesser-developed countries. In many areas accessibility is diminished by the lack of all-weather roads, making access subject to weather conditions. Location-allocation models have been used to prescribe optimal configurations of health facilities in order to maximize accessibility, but these models are based on the assumption that the underlying transport network is static and always available. Essentially, past work has ignored the potential impacts of improvements to the transport system in modeling access. In this paper we propose a model that treats the opposite side of the location/transport equation; that is, a model that treats existing facility locations as fixed and improves health service accessibility by upgrading links of the transport network to all-weather roads. This new model, called the Maximal Covering Network Improvement Problem (MC-NIP) is formulated as an integer-linear programming problem. An application of the MC-NIP model to the Suhum District of Ghana is presented, which shows that even a modest level of road improvement can lead to substantial increases in all-season access to health service.     

基于道路网络分析的省际粮食运输成本研究

借助GIS软件平台,结合铁路、水运航线、运费、转运费等数据,建立了道路网络数据模型,利用网络分析工具,分别获取了基于最低成本和最短运距下的两种运输路径及成本数据。对比分析发现:水路和铁路运输凭借其成本较低的优势在我国省际粮食运输中占据主要地位。在最低成本条件下,运输优路径经沿海和长江中下游航线频次最高,公路运输因其成本较高主要集中于省内或短途运输;省际粮食运输最高运费段为哈尔滨—拉萨段,总里程5 133km,经铁路一次性运输,运费为770元/吨;最低运费段为上海—南京段,总航程350km,经水路一次性运输,运费仅6元/吨。     

Time-varying road network design for urban hazmat transportation

Hazmat transportation in cities faces significant risks that may cause catastrophic losses to humans. From the perspective of the regulator, the main responsibility is to mitigate hazmat transport risk by determining the availability of road networks to hazmat carriers. Based on the time-variant population distribution, the hazmat transport risk was assessed via the total population exposure associated with the resident and variable populations at different times. We propose a risk-minimizing urban hazmat road network design model for multiple types of hazmats, considering time-varying traffic. The model was applied to a realistic case study of hazmat transportation in a densely populated urban area with complex traffic in Shanghai, China.     

Portfolio diversification and systemic risk in interbank networks

This paper contributes to a growing literature on the ambiguous effects of risk diversification. In our model, banks hold claims on each other’s liabilities that are marked-to-market on the individual financial leverage of the obligor. The probability of systemic default is determined using a passage-problem approach in a network context and banks are able to internalize the network externalities of contagion through their holdings. Banks do not internalize the social costs to the real economy of a systemic default of the banking system. We investigate the optimal diversification strategy of banks in the face of opposite and persistent economic trends that are ex-ante unknown to banks. We find that the optimal level of risk diversification may be interior or extremal depending on banks exposure the external assets and that a tension arises whereby individual incentives favor a banking system that is over-diversified with respect to the level of diversification that is desirable in the social optimum.     

基于空间扩展的物流保障网络建模与分析方法

分析保障实体、交通道路基本属性,采用基于空间扩展的建模方法,实现不同运输网络之间无缝连接,建立可计算用的物流保障网络模型,作为综合调度、网络优化的基本工具。     

An optimal inventory model where resupply is possible but uncertain

A model is formulated for computing the optimal stock quantity of an item when resupply is possible but uncertain. The distinguishing feature of the model is that the optimal stock quantity calculation takes into account the cost of resupply and the probability of stock arriving by a specified mode of transport in time for issue to customers. The model is then applied to the problem of determining a preferred mode of transport for an assumed set of parameters.     

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.     

Interaction of maritime shipping and hinterland traffic using a two-level hierarchical transport network

A transport scenario based on a two-level network is developed in order to model operations in maritime transport. To enhance competitiveness and sustainability of shipping companies, the interaction between maritime shipping and hinterland traffic is considered in the novel two-level hierarchical transport network. Demand occurs on the second level, the hinterland, whereas the first level, the sea transport, acts as a pure distribution network. The two-level hierarchical transport model allows regulating the degree of interaction a liner operator has regarding the hinterland traffic. Moreover, access of vehicles to nodes or edges is given subject to feasibility constraints, relating to the size of a vehicle. In this work, the relation to existing routing models, such as the travelling salesman problem, the vehicle routing problem, or the travelling purchaser problem, is illustrated. Moreover, through the definition of a proper set of assumptions, it is possible to reduce the considered two-level hierarchical transport network to different standard routing models. These new insights allow the application of existing solution methods. Numerical experiments are conducted for a particular case and illustrate the influence of node costs on the distribution of workload to the vehicles.