基于GIS和MDVRP的成都市城乡配送网络仿真

本文应用ArcGIS构建了包含4个物流中心和151个乡镇需求点的成都市二级城乡配送网络,并利用ArcMap分析工具得到了155×155的最短距离对称矩阵;以配送总距离最小化为目标函数,考虑车容量限制、车辆数限制、车流量限制等约束条件,建立了多车场车辆路径问题(MDVRP)的0-1整数规划模型;采用基于客户编码方式,应用稳态繁殖选择策略,设计了遗传算法进行求解。在不同需求分布和不同车容量的条件下对算法收敛效果、配送行驶总距离、配送使用车辆数、平均车辆满载率进行了对比分析。结果表明:配送距离、配送车辆数与需求规模成正比;平均车辆满载率差异较大,20t车型满载率较稳定,适合小批量需求配送;建议成都市城乡配送以20t和25t车辆为主力车型,并重点关注崇州物流中心的建设。     

订单生成时间不确定的货物配送路径优化

针对各个配送点订单生成时间不确定，且未来生成订单现阶段配送方案制定有影响，本文提出了动态订单匹配策略，将已生成和未生成的订单信息综合考虑，提高匹配效果。然后，本文建立了以最小化运能浪费和订单等待处理时间为目标的二阶段随机规划模型来编制当前和下一阶段的配送方案，并设计了自适应遗传算法进行求解。最后，本文利用某地25个配送点数据信息进行二阶段配送路径规划。与蚁群算法相比，本文算法对两个阶段的运能浪费成本和时间浪费成本求解过程收敛时间分别为：112.3s、102.4s、98.5s、114.7s，均小于蚁群算法收敛时间：117.3s、115.4s、109.6s、118.2s。且本文算法求得的两个阶段总运能浪费成本和时间浪费成本分别为62000t.km、644t.h，远小于传统启发式算法的72400t.km、816t.h。     

基于遗传算法的地面常规公交与城市轨道交通接驳研究

为了研究地面常规公交与城市轨道接驳问题,构建了基于乘客交通出行时间最短优化模型,采用遗传算法进行求解,并通过具体案例进行了模型验证。结果表明建立的优化模型及遗传算法适用于接驳问题。     

昆明掌鸠河引水隧洞工程

昆明是位于中国西南部的云南省的政治和经济中心,是中国最美丽的历史文化名城之一.昆明也是中国14个严重缺水的城市之一,为了解决当地的供水问题,"昆明市掌鸠河引水供水工程"现已付诸实施.工程的总投资约为4.76亿美元.工程的目标是建设一座每日供水量为60万吨的供水系统.项目的主要组成部分有·云龙水库大坝,总的贮水能力为4.42亿立方米,年供水量为2.45亿立方米;·小型电站;·长97.72 km的引水线(大多为隧洞,少量为倒虹管);水处理场(初期供水能力为4×105 t/d,全部建成后的供水能力为6×105t/d);·输配水管网,总长为93.43 km;11 756名农村人口的迁移.工程计划于2006年年底竣工.     

马井气田增压系统运行优化研究

马井气田目前采用气田内部集中增压为主、边远井小型撬装增压为补充的互补型增压模式,其中MP53D增压机组的实际处理量为12.49万m~3/d,远小于其设计处理量(35万m~3/d),机组只能低负荷运转,运行稳定性较差;同时,部分未增压气井受管网压力制约严重,气田产量递减迅速,采输矛盾日益突出。为维持气田正常平稳生产,采用Reo软件建立了马井气田集输管网模型,并设计了11种增压开采方案进行优化模拟。研究结果表明,方案5为最佳增压开采方案,此时气田的总产量最高,增压机组消耗的功率低,机组运行稳定性好。优化后气田的总产量增加12.07万m~3/d,压缩机站总功率降低26 k W,MP53D压缩机组处理量增大6.92万m~3/d,机组运行稳定性提高。     

天然气管网的初始流量分配

在对天然气管网进行离线数值模拟计算时,需要给各管段分配初始流量,作为迭代计算的初始值。根据管道的流动状态多在阻力平方区的特点,建立初始流量分配的数学模型,用C 语言编制出计算程序。对实例进行计算和分析,表明用最小平方和法求解各管段初始流量时,不需手工预分初始流量,也不需预先确定各管段流体流动方向,求解所得初始值接近真实值,使数值计算的收敛速度大大提高。     

基于列生成的城市轨道交通乘务排班计划优化

乘务排班计划是城市轨道交通运输计划的重要组成部分，高效的排班计划可以有效降低城市轨道交通运营成本。本文基于列生成算法，构建以班次数最小为目标的乘务排班模型。列生成算法的限制主问题采用集合覆盖模型，通过建立网络图模型，将定价子问题转化为带资源约束的最短路问题。提出了考虑复杂约束的改进的邻接矩阵构建方法，采用Floyed算法求得最短路径集合。在求解具有最小检验数的新班次时，提出了基于工作效率和工作时长综合惩罚的优化规则，以提高新班次集合的质量。最后求解0-1整数规划问题，即从可行班次集合中找到满足乘务片段全覆盖约束的最优子集，构成最终的排班方案。案例结果表明本文模型能够显著地减少乘务班次数，同时各项指标均有所改善。     

基于遗传算法的铁路技术站取送车计划研究

为了研究更切合实际的铁路技术站取送车计划的合理编制方案,文章在考虑调机牵引能力、装卸线容车限制的约束下,以取送照顾编组为前提,在取送控制时间窗内,对站存车组及陆续到达车组的取送优化建立了以调机取送成本最小为目标的概念模型,并采用改进的遗传算法求解。通过算例求解,验证了该模型的正确性和算法的有效性。     

基于混合整数线性规划的地下物流网络构建

城市地下物流系统作为一种新型的物流配送方式,可有效释放城市地面交通压力,减少环境污染。本文以最优化理论为基础,对如何构建地下物流网络问题进行了研究。首先考虑二级节点的容量和服务半径约束建立聚类模型,通过应用K-means算法求解模型,将地下物流需求点进行分类,即求得二级节点的数量与位置;其次,根据节点的固定建设成本和运输成本,在已求得的二级节点中选取部分作为一级节点,建立了混合整数线性规划模型,采用Lingo软件对其进行求解,以南京市仙林区为案例进行分析,最终得出综合成本最小的地下物流网络建设方案。     

电商环境下城市配送环状网络模型研究

电子商务环境下的物流城市配送具有小批量、多频次、进城难、客户位置分散等特点。为节约配送成本,本文基于先集货后配送的理念,以双层配送网络为基础设计了环状配送网络结构,并建立车辆路径问题模型。模型以城市配送网络总费用最小化为目标,建立了混合整数规划模型。为了验证模型的可行性,使用MATLAB调用CPLEX软件进行求解。并进行了算例计算,求解满足车辆容量,车距限制和配送中心处理能力的配送中心选用情况,环形网络上的流量,环内配送的线路以及车辆的使用情况。得到了正确有效的结果,验证了模型的可行性,为城市配送网络的建设及优化提供了理论基础。     

Survey of R&D in PRT systems

A survey of research and development in advanced transit has been made by Chalmers University of Technology in Gothenburg in cooperation with Trans21 in Boston. Summary findings are reported for fourteen academic research programs and ten development programs for PRT. An earlier version of this paper was presented at the International Conference of PRT and other Emerging Systems held in Minneapolis in 1996.     

管道风险分析指数评分法中分值调整初探

管道风险分析指数评分法中重要步骤之一就是确定影响管道事故因素的权重,各个管道风险因素在整个管道事故中所占的权重是不相同的。针对目前管道风险分析指数评分法基本假设之一（各因素的分值范围都是0～100分）,为了更加客观、准确、合理地反映各个风险因素对于管道事故的影响程度,提出并论述了依据层次分析法的数学逻辑性进行综合计算得出管道风险因素的权重,然后对评分法中各个因素的最高分值,根据其权重不同进行相应调整,从而增强评价者对风险因素的认识和评判能力,提高管道风险评价结果的准确性。     

A century of evolution of the accessibility concept

The concept of accessibility has acquired numerous meanings along multiple dimensions during the century of its evolution. This essay argues for the salience of two dimensions: application-based and definition-based. In its application, accessibility has incorporated positive and normative dimensions which have varied in prominence over time. In its definition, accessibility has varied between a mode of evaluation incorporating measured mobility and proximity, on the one hand, and a predefined market basket of urbanist improvements to transportation and land use systems, on the other. Advocates of the accessibility shift should emphasize both the measured approach to accessibility and accessibility’s normative side.     

Real-world gaseous and particle emissions of a Bi-fuel gasoline/CNG Euro 6 passenger car

The objective of the present study is the assessment of the environmental impact of a bivalent (bi-fuel) vehicle, running either on gasoline or compressed natural gas (CNG). To that aim, a Euro 6 passenger car was tested under various real-world driving conditions. In order to cover the full range of conventional powertrains currently in the market, the tests were also repeated on a Euro 6 diesel passenger car. Both cars were driven in two routes, the first complying with the regulation limits and the second going beyond them. Carbon monoxide (CO), nitrogen oxides (NO_x) and particle number (PN) emissions were recorded using a Portable Emissions Measurement System (PEMS). Apart from the aggregated emission levels, in g/km, the exact emission location along the route was also assessed. Natural gas proved beneficial for CO and PN emissions, the level of which always remained below the respective legislation limits. On the other hand, under the dynamic driving conditions with gasoline, the relevant limits were exceeded. Cold start, occurring at the beginning of the urban part, and motorway driving were identified as major contributors to total emissions, especially in gasoline mode. However, the application of natural gas was associated with a penalty in NO_x emissions, which were significantly increased as compared to gasoline. Local peaks within the urban part were identified in CNG mode. In any case, the diesel vehicle was by far the highest NO_x emitter.     

Seaport performance analysis using robust non-parametric efficiency estimators

Abstract

Seaport services have been developing year on year, playing an increasingly important role in the economy and the transportation markets of each country. This increases interest in measuring their performance. This paper evaluates the performance of a set of European seaports by means of robust non-parametric approaches. Using order-m and bootstrap procedures, the major problems of traditional data envelopment analysis and free disposal hull methods – concerning noise, presence of outliers and the ‘curse of dimensionality’ – are overcome. With this study considerable levels of inefficiency were found in the European seaports sector.     

Bicycle parking: a systematic review of scientific literature on parking behaviour,parking preferences,and their influence on cycling and travel behaviour

ABSTRACT

Cycling is experiencing a revival in many cities. Research has focused on the determinants of cycling – in particular the role of the built environment and road infrastructure. Bicycle parking has received little attention – even though bicycles are parked most of the time. This article reviews the scientific literature on bicycle parking and identifies existing gaps in research and knowledge. The review analyses 94 peer-reviewed papers identified through a search in Scopus and Web of Science, in December 2017. The annual number of papers increased 15-fold between 1995 and 2017. Overall, the level of evidence on the importance of bicycle parking is limited. The majority of studies are based on cross-sectional data with the presence of parking as a binary independent variable. Most studies focus on bicycle parking at public transport stops and at work places. Few studies report on bicycle parking throughout cities, and hardly any on parking at residential locations. Bicycle parking supply and quality appears to be a determinant of cycling for current and potential cyclists. Our findings can serve as input for an evidence-based debate on the role of bicycle parking. For practitioners, our research supports investment in bicycle parking, but acknowledges that a proper evaluation of such initiatives needs to be conducted to increase the level of evidence.     

Multilevel analysis of daily time use and time allocation to activity types accounting for complex covariance structures using correlated random effects

In this paper multilevel analysis is used to study individual choices of time allocation to maintenance, subsistence, leisure, and travel time exploiting the nested data hierarchy of households, persons, and occasions of measurement. The multilevel models in this paper examine the joint and multivariate correlation structure of four dependent variables in a cross-sectional and longitudinal way. In this way, observed and unobserved heterogeneity are estimated using random effects at the household, person, and temporal levels. In addition, random coefficients associated with explanatory variables are also estimated and correlated with these random effects. Using the wide spectrum of options offered by multilevel models to account for individual and group heterogeneity, complex interdependencies among individuals within their households, within themselves over time, and within themselves but across different indicators of behavior, are analyzed. Findings in this analysis include large variance contribution by each level considered, clear evidence of non-linear dynamic behavior in time-allocation, different trajectories of change in time allocation for each of the four dependent variables used, and lack of symmetry in change over time characterized by different trajectories in the longitudinal evolution of each dependent variable. In addition, the multivariate correlation structure among the four dependent variables is different at each of the three levels of analysis.     

从"神经末梢"到"国际枢纽"——十六大以来广西交通发展综述

文章总结了党的十六大以来广西交通发展取得的成绩,指出广西交通正在从"神经末梢"发展为"国际枢纽",为广西经济社会发展提供了重要支撑。     

Increasing urban tram system efficiency,with battery storage and electric vehicle charging

This paper examines the possible placement of Energy Storage Systems (ESS) on an urban tram system for the purpose of exploring potential increases in operating efficiency through the examination of different locations for battery energy storage. Further, the paper suggests the utilisation of Electric Vehicle (EV) batteries at existing Park and Ride (P&R) sites as a means of achieving additional energy storage at these locations. The study achieves this through MATLAB modelling utilising captured GPS data and publically available information. This study examines the scenario of uni-directional substations with no interconnection between the overhead catenary for both directions of travel, and discusses the trade-offs between ESS size and required current limits.The results show the savings in both energy and basic CO₂ emissions alongside the discussion of Return on Investment (RoI) that can be achieved through the potential installation of ESS at identified ideal locations along the tram network. Moreover, this may be extended to the use of EVs as stationary ESS sited at the existing P&R facilities. Further, the model may also be used to inform future infrastructure upgrades and potential improvements to air quality within urban environments.