Empirics of multi-modal traffic networks – Using the 3D macroscopic fundamental diagram

Traffic is multi-modal in most cities. However, the impacts of different transport modes on traffic performance and on each other are unclear – especially at the network level. The recent extension of the macroscopic fundamental diagram (MFD) into the 3D-MFD offers a novel framework to address this gap at the urban scale. The 3D-MFD relates the network accumulation of cars and public transport vehicles to the network travel production, for either vehicles or passengers. No empirical 3D-MFD has been reported so far.In this paper, we present the first empirical estimate of a 3D-MFD at the urban scale. To this end, we use data from loop detectors and automatic vehicle location devices (AVL) of the public transport vehicles in the city of Zurich, Switzerland. We compare two different areas within the city, that differ in their topology and share of dedicated lanes for public transport. We propose a statistical model of the 3D-MFD, which estimates the effects of the vehicle accumulation on car and public transport speeds under multi-modal traffic conditions. The results quantify the effects of both, vehicles and passengers, and confirm that a greater share of dedicated lanes reduces the marginal effects of public transport vehicles on car speeds. Lastly, we derive a new application of the 3D-MFD by identifying the share of public transport users that maximizes the journey speeds in an urban network accounting for all motorized transport modes.     

Energy use in passenger transport in OECD countries: Changes since 1970

This paper analyzes some of the changes that took place in the structure of energy use for passenger travel in industrialized countries. Data is presented on energy use and travel activity for the four major modes of travel — automobile, bus, rail and air — for eight OECD countries: the United States, Japan, the United Kingdom, West Germany, France, Italy, Sweden, and Norway. We use the Laspeyres and Divisia indices to analyze the causes of the change in energy use between 1970 and 1987. The total change in energy use for travel is explained by changes in domestic passenger transport volumes, the mix of modes of travel, and the energy intensities of each mode. We have found two important effects that have a fundamental impact on energy use for travel since 1970. First, shifts among modes of transport towards more energy-intensive ones and large increases in volumes of travel (measured in passenger-kilometers) increased energy use for travel in many OECD countries, often more rapidly than the overall growth in GDP. Second, energy intensities, measured in mJ/passenger-kilometer, of passenger transport fell only in a few countries between 1970 and 1987. Even though individual automobiles have become more energy-efficient, greater size, power, and weight, worsening traffic conditions in Japan and Europe, and fewer people in cars restrained or even offset efficiency improvements. Particularly notable are the increases in intensities in Japan and Germany. The most important exception to this trend was the United States, but the intensities of land-based travel remain higher there than in most other countries. These findings lead to a pessimistic outlook for future energy use for travel. After all, if little or no energy was saved during the decades of high fuel prices, what can be expected in the 1990s?     

基于两车模型的地铁隧道活塞风对屏蔽门影响研究

为研究隧道活塞风对地铁屏蔽门的影响,通过分析活塞风形成机理,构建两车、两车站、三区间隧道的地铁隧道模型,利用滑移网格技术仿真模拟列车在隧道运行时引起的活塞风速度与压力,并提取所研究车站屏蔽门区域所受活塞风的压力值。通过对屏蔽门进行静力学分析,利用屏蔽门所受最大阻力来衡量屏蔽门开关能力。将仿真结果与南宁地铁1号线的实际故障进行对比分析,研究不同工况下活塞风对屏蔽门的影响。研究结果表明:所建仿真模型有效、合理,屏蔽门所受最大风压受列车运行速度、屏蔽门位置及风井布置模式的综合影响。研究成果可为屏蔽门故障诊断和智能运维提供理论参考。     

杭州南站幕墙受过站列车风影响的数值模拟分析

分析高速列车过站时列车风对站台上方幕墙的影响,采用CFD数值模拟方法,结合"动网格"技术,对列车高速过站风环境进行数值模拟,给出高速列车开始驶入、完全驶入和驶离车站时,站台区域幕墙受列车风影响的变化情况。对列车风的影响进行定量评估,研究结果表明:过站列车通过产生的流场对站内风速影响较小,不会对乘客造成安全问题,但该流场对幕墙产生一定的力作用。结论为列车风侧向影响范围最大处出现在头部顶端;列车经行的最不利工况为单线同时对开。     

基于动网格的铁路沿线孔板式沙障流固耦合数值模拟

孔板式沙障是新型多孔的阻风沙构筑物,具有很好的阻风沙功效,但孔板式沙障的应用必须考虑其在风荷载作用下的流场特征以及力学特性。对孔板式沙障进行三维流固耦合数值模拟,分析其在固定孔隙率不变的情况下,孔径变化时沙障周围流场特性以及孔隙率不变孔径变化对沙障位移、应力特征的影响,并总结相关规律特征。研究结果和结论:不同孔径沙障在障后均无涡流区仅有大面积减速区,且减速区随孔径减小而增大,减速效果也随之增强;孔径的变化对沙障的受力特征和变形位移分布无影响,仅对其量值有影响;沙障立柱受力最大位置在距柱底(4.5±0.025)cm,且孔径越小其最大值越大;来流首次接触沙障时会产生"冲击效应",其"冲击效应"最大值为沙障变形的最大值即最危险值,孔径越小,其"冲击效应"最大值越大,稳定状态下的位移值也越大。     

基于移动网格技术的微型客车会车外流场仿真研究

本文采用计算流体力学CFD软件,对微型面包车与大型客车相会进行了会车多工况仿真计算,给出了处于会车特征位置的小车侧面压力值及压力场分布图,为我国实现汽车外形自主研发提供方法借鉴。     

水资源开发事业（项目）费用分配的理论研究

在对传统的费用分配方法分析研究的基础上,探讨了以Gam e理论为基础的费用分配方法及其适用条件,并以水资源开发中的多目的大坝建设为例,分析研究了项目开发费用在不同建设主体间的分配,提出了适用多种条件费用分配的计算方法.     

钢筋网在土中极限抗拔力的理论计算探讨

结合钢筋网在土体内的极限抗拔力试验,运用现有的几种极限抗拔力理论计算公式,算出每个测点的钢筋网的极限抗拔力,通过对理论计算值与试验值的比较,推荐适合于粘性土和砂性土的钢筋网极限抗拔力理论计算公式,为该类拉筋的加筋挡土墙的内部稳定验算提供较为合理的理论计算依据。     

水下机器人进行逆向运动时导管螺旋桨推力特性的模拟*

采用动网格与滑移网格混合技术,运用弹簧光顺与局部网格重构的组合式网格更新方式,在水下机器人系统所处流域以计算流体力学方法求解其N—S方程。数值计算结果表明：采用动网格与滑移网格混合技术在模拟水下机器人系统水动力上是可以获得正确结果的；水下机器人系统在逆向运动、螺旋桨反转时,由于主体对水流的阻塞作用和外扩作用,使得后桨、左桨、右桨所处区域的水流轴向速度偏小,造成后桨、左桨、右桨所发出的推力都较单桨大。     

编组站作业大表自动生成系统的设计与实现

探讨了编组站作业大表自动生成系统的工作原理,数据来源,网络构成及实现方法等.