沥青混合料拌和生产技术管理中容易忽略的几个重要环节

以提高沥青混合料拌和生产质量为出发点,对沥青混合料拌和生产过程中容易忽略但又特别重要的几个技术管理环节进行阐述,提出＂加强目标配合比的现场控制、重视热料仓取样的代表性、做好油石比的对比和标定工作＂等细节控制措施,具有一定的理论和实际意义。     

交通事件持续时间预测及参数标定

有效的交通事件管理应基于精确的交通事件持续时间预测。交通事件持续时间包括4个部分:事件发现时间,事件响应时间,事件清除时间和交通恢复时间。提出了基于元胞传输模型的交通事件持续时间预测模型以及参数标定方法。实测数据和仿真数据对比结果表明,基于元胞传输模型的交通事件恢复时间预测方法具有较高的精度。     

发动机标定方法及性能预测的探讨

电控发动机性能开发是一项系统工程,包括性能设计、结构设计、标定数据优化以及整机性能优化。通过分析电控系统的标定方法、试验设计方法,认为标定方法不仅要做到优化电控系统与发动机的匹配,还应具备预测缺陷、性能和改进方向的功能。     

轨道几何状态检测数据里程校正算法研究

同一段铁路线路多次轨道几何状态检测数据间普遍存在一定的里程偏移,若直接使用存在里程偏差的数据参与计算或分析,结果有较大误差,无法保证现场养护维修的效果。文中提出了1种里程自动校正的优化模型,并结合轨道几何状态数据,按照数据预处理、建立校正基库、初步校正及精确校正4个步骤,编制软件实现了该优化方法,从而解决了轨道动态几何状态数据间的里程偏差问题。实例分析表明,该模型正确,效果良好。     

基于社会力的信号交叉口施工区交通流建模

由于施工区的存在,城市道路信号交叉口通行能力下降,车流运行混乱.本文为 了从微观层面研究信号交叉口施工区交通流运行特性,以初始社会力模型为基础,首次提 出一种新的适用于交叉口交通流的社会力模型;通过对影响岛式施工区通行能力的因素 进行分析,设计出一套数据采集方案;利用实测数据并结合遗传算法对提出的模型进行标 定,使用统计学指标对标定结果展开评价.结果表明,提出的新模型仿真得到的交通量与 实测值平均绝对相对误差仅为0.028,能为信号交叉口施工区交通流模拟提供参考.     

基于信号交叉口车头时距分布的VISSIM仿真参数校核研究

为了提高微观交通仿真评价分析的精度和可信度,需要根据实际交通情况对微观交通模型 关键参数进行校核。校核分析了VISSIM 微观交通仿真模型中关键驾驶行为参数和车辆动力性能 等参数,选取信号交叉口车头时距作为仿真校核目标参数,提出了信号交叉口仿真参数校核流 程。通过实际调查重庆市多个信号交叉口,统计得到车头时距分布关系,对仿真校核流程进行了 实例验证。实例验证结果表明,经过参数校核后构建的仿真场景与实际交通运行状态相吻合,以 此进行仿真评价分析具有较高的可信度。     

基于回归分析的龙泉港出海闸高淹没度下水位流量关系率定

龙泉港出海闸排水受外海潮汐影响显著,不适宜采用堰闸流量系数法进行推流。结合龙泉港出海闸水文过程试验的实测资料,以水力学公式为基础,采用回归分析法率定得到了高淹没度状态下的水位流量关系式,并对关系式进行了符号检验、适线检验、偏离检验和精度分析,结果表明：回归分析法率定得到的出海闸高淹没度状态下的水位流量关系成功通过了三项检验,定线精度能够达到一类精度标准,可以在受潮汐影响的出海闸水位流量关系率定中推广使用。     

Effectiveness of red light cameras on the right‐angle crash involvement of motorcycles

Red light cameras (RLCs) have been used to reduce right‐angle collisions at signalized intersections. However, the effect of RLCs on motorcycle crashes has not been well investigated. The objective of this study is to evaluate the effectiveness of RLCs on motorcycle safety in Singapore. This is done by comparing their exposure, proneness of at‐fault right‐angle crashes as well as the resulting right‐angle collisions at RLC with those at non‐RLC sites. Estimating the crash vulnerability from not‐at‐fault crash involvements, the study shows that with a RLC, the relative crash vulnerability (RCV) or crash‐involved exposure of motorcycles at right‐angle crashes is reduced. Furthermore, field investigation of motorcycle maneuvers reveal that at non‐RLC arms, motorcyclists usually queue beyond the stop line, facilitating an earlier discharge, and hence become more exposed to the conflicting stream. However at arms with a RLC, motorcyclists are more restrained to avoid activating the RLC and hence become less exposed to conflicting traffic during the initial period of the green. The study also shows that in right‐angle collisions, the proneness of at‐fault crashes of motorcycles is lowest among all vehicle types. Hence motorcycles are more likely to be victims than the responsible parties in right‐angle crashes. RLCs have also been found to be very effective in reducing at‐fault crash involvements of other vehicle types which may implicate exposed motorcycles in the conflicting stream. Taking all these into account, the presence of RLCs should significantly reduce the vulnerability of motorcycles at signalized intersections. Copyright © 2010 John Wiley & Sons, Ltd.     

Monitoring wildlife crossing structures along highways in Changbai Mountain,China

In China, the construction and monitoring of wildlife crossing structures is uncommon. Mountainous area occupies two-thirds area of China. A lot of tunnels (similar to overpasses in developed countries), bridges, and culverts (similar to underpasses) are constructed along highways. In general, these structures are multifunctional, including wildlife migration. However, studies on monitoring these potential crossing structures are almost vacant. Taking two highways in Changbai Mountain area as case studies, infra-red camera trapping and snow tracking were used to investigate the efficiency of tunnels, bridges and culverts on the highways. A total of 13 medium and large-sized wildlife species crossed highway through tunnels, bridges and culverts. One third of species were Chinese national protective species, and almost all species were present within 500 m from Ring Changbai Mountain Scenic highway used bridges and culverts to cross this highway. The tunnel along the expressway (length = 1000 m) and the bridges along the highway (width > 8 m) have been important passages for ungulates, Eurasian red squirrels (Sciurus vulgaris), yellow throated martens (Martes flavigula) and sables (Martes zibellina). Different species preferred to different types of structures, although most species preferred to bridges and tunnels. We suggest that short fences should be set around the bridges and culverts to guide animals to cross the passages, especially for ungulates. Monitoring programs of uses of crossing structures by wildlife should be conducted for at least 2 months to catch most species activity.     

Enhancing the performance of existing urban traffic light control through extremum-seeking

Urban traffic light controllers are responsible for maintaining good performance within the transport network. Most existing and proposed controllers have design parameters that require some degree of tuning, with the sensitivity of the performance measure to the parameter often high. To date, tuning has been largely treated as a manual calibration exercise but ignores the effects of changes in traffic condition, such as demand profile evolution due to urban population growth. To address this potential shortcoming, we seek to use a newly developed extremum-seeker to calibrate the parameters of existing urban traffic light controllers in real-time such that a certain performance measure is optimised. The results are demonstrated for three categories of traffic controllers on a microscopic urban traffic simulation. It is demonstrated that the extremum-seeking scheme is able to seek the optimal parameters, with respect to a certain performance measure, for each of these traffic light controllers in an urban, uni-modal traffic environment.