从车流运动过程分析交通流中流量陡降现象

针对交通流流量密度模型中当密度达到最佳密度Km 附近时流量值出现突然下降的现象,从车流运动过程分析移动车流群在最佳密度附近的流量-时间变化规律和密度-时间变化规律,发现车流群所产生的回波速度是影响流量陡降现象的主要因素。在分析格林希尔治模型缺陷本质的基础上,指出交通流模型采用二阶段模型的必然性,并建立了相应模型。     

车载网络入侵检测技术综述

智能网联汽车促进了交通运输的革新与发展,同时也伴生了网络安全问题,给用户的生命、财产造成了巨大的威胁。入侵检测技术作为一种轻量化的防御技术,能够通过建立的特征对攻击进行有效检测,从而完成对攻击的进一步分析与防御。从广泛使用的车载网络出发,调研了近年来针对常见攻击所提出的入侵检测技术,并对这些技术的特征与方法进行了划分,体现了不同技术之间的先进性与局限性,为车载网络入侵检测技术的研发提供了借鉴。     

重点营运车辆安全监管平台设计与实践

重点营运车辆的统一安全监管历来是各个城市交通运输安全保障的重点.采用信息化手段实时掌握车辆运行状况,全面记录和统计车辆的数据信息,实现对重点营运车辆的统一安全监管已成为亟待解决的重要问题.文中基于广州市重点营运车辆安全监管工作的实际需要,提出了一种车辆安全监管平台的设计思路,进行了平台的架构设计、功能设计,并介绍了平台设计的特色之处.目前该平台在广州市运行状态良好,已接入重点营运车辆38 798辆,并在2010年广州亚运会期间接入亚运专用车辆,实践表明效果良好,有效预防了交通事故的发生.     

A model for vehicle–track random interactions on effects of crosswinds and track irregularities

A stochastic mathematical model is developed to evaluate the dynamic behaviours and statistical responses of vehicle–track systems when random system excitations including crosswinds and track irregularities are imposed. In this model, the railway vehicle is regarded as a multi-rigid-body system, the track system is modelled by finite element theory. These two systems are spatially coupled by the nonlinear wheel–rail contact forces and unsteady aerodynamic forces. The high efficiency and accuracy of this stochastic model are validated by comparing to the robust Monte-Carlo method. Numerical studies show that crosswinds have a great influence on the dynamic performance of vehicle–track systems, especially on transverse vibrations. When the railway vehicle initially runs into the wind field, it will experience a severe vibration stage, and then stepping into a relatively steady state where the fluctuating winds and track irregularities will play deterministic roles in the deviations of system responses. Moreover, it is found that track irregularities should be properly considered in the safety assessment of the vehicle even in strong crosswinds.     

Optimal motion control for collision avoidance at Left Turn Across Path/Opposite Direction intersection scenarios using electric propulsion

Collision avoidance at intersections involving a host vehicle turning left across the path of an oncoming vehicle (Left Turn Across Path/Opposite Direction) have been studied in the past, but mostly using simplified interventions and rarely considering the possibility of crossing the intersection ahead of a bullet vehicle. Such a scenario where the driver preference is to avoid a collision by crossing the intersection ahead of a bullet vehicle is considered in this work. The optimal vehicle motion for collision avoidance in this scenario is determined analytically using a particle model within an optimal control framework. The optimal manoeuvres are then verified through numerical optimisations using a two-track vehicle model, where it was seen that the wheel forces followed the analytical global force angle result independently of the other wheels. A Modified Hamiltonian Algorithm controller for collision avoidance that uses the analytical optimal control solution is then implemented and tested in CarMaker simulations using a validated Volvo XC90 vehicle model. Simulation results showed that collision risk can be significantly reduced in this scenario using the proposed controller, and that more benefit can be expected in scenarios that require larger speed changes.     

基于粗糙集的铁路工程项目投标决策方法研究

铁建企业项目具有规模大、周期长、技术性强等特征,使工程投标项目评估更复杂、决策难度更大.本文将盈利与竞争力提升作为铁路建筑企业项目投标决策的直接影响因素,提出了基于波士顿矩阵原理的项目分类策略,从项目因素、环境因素、自身因素和业主因素等4个方面出发构建了项目类别判定的粗糙集模型,并利用SVM(支持向量机)对已建立的粗糙集模型进行改进,证明改进模型的计算结果更加准确.根据模型分析结果对项目投标提出了若干有意义的建议,为铁路建筑企业项目投标决策提供参考.     

Digging Deep: Managing Social and Policy Dimensions of Geoduck Aquaculture Conflict in Puget Sound,Washington

Shellfish aquaculture can result in conflicts among stakeholders who perceive impacts and tradeoffs regarding sense of place, aesthetic, recreational, economic, and ecological values. Pacific geoduck clams (Panopea generosa Gould 1850) are grown in intertidal plots using gear- and labor-intensive techniques that result in a high value export product. A confluence of issues has resulted in on-going social and legal tensions surrounding geoduck aquaculture in southern Puget Sound, Washington (WA), USA. Using interviews and document analysis, we explored stakeholder perspectives and policy issues related to geoduck aquaculture in southern Puget Sound. Twenty-three stakeholders were interviewed, including state agency employees, representatives of the aquaculture industry, nongovernmental organizations, landowners, a tribal member, and an academic. Nine state hearings board decisions on challenges to aquaculture permits were also analyzed. Stakeholders articulated a variety of perspectives regarding aesthetic, recreational, land-use, ecological, political, regulatory, and economic aspects of geoduck aquaculture activities. Hearings board cases addressed similar issues (aesthetic, ecological, and recreational), as well as challenges to restrictions on aquaculture. Potential strategies for managing this conflict include emphasizing best management practices, identifying and incorporating best available science, joint fact-finding approaches, and initiating and improving communication among all stakeholders.     

An agent‐based simulation model to assess the impacts of introducing a shared‐taxi system: an application to Lisbon (Portugal)

This paper presents a new concept of urban shared‐taxi services. The proposed system has a new organisational design and pricing scheme that aims to use the capacity in traditional taxi services in a more efficient way. In this system, a taxi acting in ‘sharing’ mode offers lower prices to its clients, in exchange for them to accept sharing the vehicle with other persons who have compatible trips (time and space). The paper proposes and tests an agent‐based simulation model in which a set of rules for space and time matching between a request of a client and the candidate shared taxis is identified. It considers that the client is only willing to accept a maximum deviation from his or her direct route and establishes an objective function for selecting the best candidate taxi. The function considers the minimum travel time combination of pickup and drop‐off of all the pool of clients sharing each taxi while allowing to establish a policy of bonuses to competing taxis with certain number of occupants. An experiment for the city of Lisbon is presented with the objectives of testing the proposed simulation conceptual model and showing the potential of sharing taxis for improving mobility management in urban areas. Results show that the proposed system may lead to significant fare and travel time savings to passengers, while not jeopardising that much the taxi revenues. Copyright © 2014 John Wiley & Sons, Ltd.     

系统仿真转移矩阵法的另一类算法

本文利用增广矩阵法的一些结果,将数值逼近原理运用于线性定常系统的数字仿真中,给出了 转移矩阵法的另一类算法。此类算法精度较高,计算量较小,且便于应用。      

基于相空间重构与LSSVM的交通流量预测

针对仅利用欧氏距离不能准确反映相空间中相点间的相似性大小,提出一种改进预测模型,该模型同时考虑相点间的欧氏距离和相似性来选取邻近点。在对交通流量时间序列进行相空间重构后,运用最小二乘支持向量机分别对不同方法得到的邻近点进行训练,并对未来时段的交通流量进行了多步预测。实际案例的预测结果表明,改进方法比一般方法具有更好的适应能力和预测精度。