易腐货物运输损耗的探讨

根据铁路和公路各自运输特点,分析铁路和公路易腐货物联合运输途中各种影响货物腐败速率的因素,提出缩短运输时间减少易腐货物损耗的方法,最后通过实例说明.     

易腐货物损耗的影响因素分析

基于铁路与公路货物联合运输的时间影响因素,分析易腐货物运输途中的损耗问题。分别根据铁路运输时间、公路运输时间、装卸作业时间、货物滞留时间等四部分的时间构成因素及其对货物运输时间的影响,提出了缩短货物运输时间以减少易腐货物损耗的对策并给出算例。     

拥挤条件下的铁路随机用户平衡配流模型

在对铁路客流分配问题进行概述的基础上,结合铁路旅客运输组织的特点,采用平衡分配法对铁路客流分配问题进行研究,建立了拥挤条件下的铁路随机用户平衡配流模型,并给出了求解算法和算例。     

运用学习规则求解编组站静态配流问题的研究

编组站静态配流问题需要制定配流方案,明确出发列车的编组内容和车流来源。算法的思路是通过构建网络模型,将静态配流问题转化为固定费用的产销平衡运输问题,并将目标函数转化为求最小虚拟到达列车车辆数。首先设定虚拟到达列车并对其赋初值,把出发列车分为可欠轴与不可欠轴两类,在计算过程中调用学习规则保证出发列车满轴,最后求出虚拟到达列车的最小值,得到配流方案。通过简单的算例验证表明,该算法能够在有效的时间内求解大规模的静态配流问题,为静态配流问题提供一种新的方法。     

与时间赛跑 与温度抗争

为满足日益增长的易腐产品运输要求,货物承运人开始采用新型集装箱和先进技术。     

考虑货物到达与列车出发时间接续的货物列车编成辆数研究

铁路货物列车适当欠轴发车能够加速货车周转,保障货物运到时限。阐述货物到达情况与列车图定发车时刻间的接续关系,以铁路运输企业经济效益最大化为目标,建立基于接续时间的货物列车编成辆数波动模型,利用软件对算例进行列车编成辆数波动下的货物列车配流,同时分析最大、最小编成辆数与技术作业时间波动率对发送货车数量和货物运输收益的影响。结果表明,货物到达与列车编组的接续时间关系会直接影响列车编成辆数和货物列车配流方案的确定,发送货车数量和货物运输收益依不同的最大、最小编成辆数和技术作业时间波动率而有所变化。     

航空货运产品的实质与构建

一、什么是航空货运产品？ 除航线产品以外，目前航空公司在划分和定义航空货运产品时，主要的标准是货物要求的运输时效性和货物要求的运输环境。按照货物要求的运输时效性，产品被分为优先运输货物（例如快件）、普通货物和候补运输货物（例如大部分按特殊比例分摊协议执行的货物）。按照货物要求的运输环境，可以分为鲜活易腐货物、尸体骨灰、活动物、贵重物品、危险品、超大超重货物等。     

基于运到期限的技术站动态配流优化研究

技术站配流作为货物运输的重要环节，影响着货物运输的时间和效率。为实现运到期限的兑现，以考虑运到期限的技术站动态配流为研究对象，将运到期限利用蒙特卡洛法分配到技术站转化为最大在站停留时间约束，引入优先级来评价货物的紧急程度，以优先级加权的货物总在站停留时间最小和发出总车辆数最多为双目标，为避免列车不合理停运，考虑不同满轴约束条件及摘挂、小运转列车可欠轴发出等车站实际，构建了混合整数规划模型，设计遗传模拟退火算法并采用软件求解。算例表明：与既有方法相比，研究的模型与算法能充分配流使得所有出发列车正点发出，优先处理优先级高的货物以减少其在站停留时间，且能保障所有货物不同运到期限的要求。     

基于行程时间可靠性的弹性需求SUE配流模型

从路段通行能力和路段行程时间关系的角度,提出行程时间可靠性和广义出行费用的概念,基于出行者根据行程时间和行程时间可靠性选择路径,以及路径上的交通流量满足Logit模型,建立弹性需求交通网络随机用户平衡(SUE)配流模型,并将其转化成等价的变分不等式形式,给出模型解的等价性和唯一性证明,最后对模型进行算法分析。     

内陆集装箱多式联运经济运距研究

发展内陆集装箱多式联运有利于实现各种运输方式无缝衔接,加快构建综合运输体系,实现物流降本增效。基于货物时间价值的综合费用计算方法,计算铁路、公路、内河水运3种运输方式下装载不同时间价值货物的20ft与40ft集装箱"门到门"运输综合费用。对高、中、低时间价值货物,分别计算各运输方式"门到门"运输的经济运距,分析货物时间价值对"门到门"运输经济运距的影响。计算结果表明,货物时间价值对公路与铁路综合费用影响较小,而对内河水路运输影响显著。最后,针对影响"门到门"运输经济运距的关键因素,提出发展内陆集装箱多式联运若干建议。     

An origin–destination based road pricing model for static and multi-period traffic assignment problems

To mitigate traffic externalities, we propose an origin–destination (OD) based road pricing model for traffic assignment problems. For elastic demand, we derive explicit optimal tolls for the OD-based pricing scheme. We also extend the model to a multi-period static traffic assignment (MSTA) where we derive analytically the route and OD-dependent tolls based on equilibrium conditions. We present some examples to show that the OD-based tolling scheme could improve the system welfare significantly, compared to the no-toll scenario (user equilibrium – UE).     

The impact of environmental variables on the efficiency of Chinese and other non-Chinese airlines

This paper explores the impact of an international focus, the proportion of cargo traffic, and the level of salaries on the operational efficiency of Chinese airlines and other non-Chinese airlines. Data envelopment analysis (DEA) is employed to evaluate the operational efficiency and a bootstrapped truncated regression is applied to explore the impact of environmental variables on efficiency. The results show that an international focus has a negative impact, while the level of salaries has a positive impact. Also, we demonstrate that there is an inverted U-shaped relationship between efficiency and the proportion of cargo traffic.     

A matheuristic approach to the air-cargo recovery problem under demand disruption

Air cargo transport is subject to unpredictable changes in expected demand, necessitating adjustments to itinerary planning to recover from such disruptions. We study a flight rescheduling problem to react to cargo demand disruptions in the short run. To increase flexibility, we consider two different cargo assignment policies. We propose a matheuristic approach to solve the problem that provides high-quality solutions in a short computational time, based on column generation in which each subproblem is solved using an ad-hoc heuristic. The approach is tested on demand disruption instances containing up to 75 air cargo orders with different penalty levels. The results show that the proposed method improves profit by 54% over the solution generated by a commercial MIP solver within a 1-h time limit, and by 15% over the solution with the routes fixed as in the original flight planning that only allows cargo to be re-routed. We also show that there exist incremental benefits in the range of 3–5% by allowing cargo for a given order to be transported by various aircraft.     

Exploring multiple eco-routing guidance strategies in a commuting corridor

The introduction of eco-routing systems has been suggested as a promising strategy to reduce carbon dioxide emissions and criteria pollutants. The objective of this study is to scrutinize the impacts of an eco-routing guidance system on emissions through the use of a case study in a commuting corridor. This research aims at assessing the potential environmental benefits in terms of different pollutant emissions. Simultaneously, it addresses the extent of variations in system travel time (S_TT) that each eco-routing strategy implies. The methodology consists of three distinct phases. The first phase corresponds to the adjustment of a microsimulation platform of traffic and emissions with empirical data previously collected. Second, to volume-emission-functions (VEF), developed based on the integrated modeling structure. Final, to different scenarios of traffic flow optimization performed at the network level based on a simplified assignment procedure. The results show that if the traffic assignment is performed with the objective to minimize overall impacts, then the total system environmental damage costs can be reduced up to 9% with marginal oscillations in total S_TT. However, if drivers are advised based on their own emissions minimization, total system emissions may be higher than under the standard user equilibrium flow pattern. Specifically, environmentally friendly navigation algorithms focused on individual goals may tend to divert traffic to roads with less capacity affecting the performance of the remaining traffic. This case study brings new insights about the difficulties and potentials of implementing such systems.     

The underlying drivers and future development of air cargo

Air cargo plays a crucial role in the air transport chain and in the globalized economy. As for other modes of transport, the demand for air cargo is a derived demand. Previous studies showed that the main determinants of air cargo demand are merchandise trade and the share of manufactures in merchandise trade. This paper aims to fill a gap in the existing literature by additionally taking the influence of air freight yields and oil prices into account when modelling the global air cargo development. Furthermore, it provides an insight into the future development of air cargo. Forecasts until 2023 are made based on a number of scenarios for the main determinants of air cargo demand. Moreover, an insight is provided into the current air cargo market, including traffic levels and different types of actors and traffic flows. The results are useful not only for academics but also for industry stakeholders for which air cargo is an important contributor to profit and/or cash levels.     

从经济学角度探究公路货运超载原因

目前货运超载已成为公路运输发展中普遍存在的问题,它体现了经济发展的不均衡,也反映出社会各方面存在的问题。货物运输超载的原因是多方面的,从经济学的角度分析,有法制不健全、各项税费支出比例大、货运企业集中度低等客观原因,也有运输成本规模效应的驱使、货运联合成本上升的作用等主观原因。针对实际现状提出相关政策性建议,以使公路货运业良性循环发展。     

Air express network design based on express path choices – Chinese case study

Due to the shortage of cargo aircraft, Chinese express companies have to provide transportation services with a hybrid method that consists of “rented bellies and self-owned cargo aircraft”. Because the bellies are rented from air passenger companies and because the cargo aircraft are owned by the express companies, it is important for the express companies to use their cargo aircraft as effectively as possible. This paper constructs a bi-level model to optimize the flight transportation network of an express company. The upper model designs the network and allocates the transportation capacity with the objective of minimizing the total transportation cost, and the lower model calculates the link flows in user equilibrium. Data from ShunFeng (SF) Express Company (China) are used to conduct the case study. Using the model outputs, the flows on links and at nodes are analyzed to illustrate the transportation and transshipment situations.     

Concentration and the formation of multi-port gateway regions in the European container port system: an update

The European container port system features a unique blend of different port types and sizes combined with a vast economic hinterland. This paper provides an update of the detailed container traffic analysis developed by Notteboom (1997) by extending it to the period 1985–2008 and to 78 container ports. The paper also aims at identifying key trends and issues underlying recent developments in the European container port system. These trends include the formation of multi-port gateway regions, changes in the hinterland orientation of ports and port regionalization processes. While the local hinterland remains the backbone of ports’ traffic positions, a growing demand for routing flexibility fuels competition for distant hinterlands between multi-port gateway regions. The prevailing assumption that containerisation would lead to further port concentration is not a confirmed fact in Europe: the European port system and most of its multi-port gateway regions witness a gradual cargo deconcentration process. Still, the container handling market remains far more concentrated than other cargo handling segments in the European port system, as there are strong market-related factors supporting a relatively high cargo concentration level in the container sector.     

Evaluating airline efficiency: An application of Virtual Frontier Network SBM

In this paper, airline efficiency is divided into three stages: Operations Stage, Services Stage and Sales Stage. The new three-stage strategic operating framework of airline efficiency is a modification of existing models. A new model, Virtual Frontier Network SBM, is proposed to evaluate the efficiency of 22 international airlines from 2008 to 2012. The results demonstrate the following: 1. The new model can apply to a new benchmarking airline such as Scandinavian Airlines. 2. Although passenger traffic, cargo traffic and revenue decreased from 2008 to 2009, most airlines’ overall efficiency increased in the period.