基于交换式以太网的列车通信网络的交换机排队时延分析

传统列车通信网络的带宽难以满足现代列车数据传输的要求.本文提出了一种基于交换式以太网的列车通信网络解决方案,为了降低列车实时数据的传输时延,为交换机设计了具有优先级的队列调度策略,并采用G/D/1排队论分析了列车实时数据和非实时数据的排队时延,计算证实了该策略可以将实时数据在交换机的平均排队时延降低到70 μs以下.最后,通过网络仿真研究证实了实时周期数据的平均排队时延从无优先级时的91 μs降低到了有优先级时的61 μs.     

城市信号控制交叉口仿真研究与优化设计

文章分析了西安市翠华路-育才路道路交叉口拥堵的原因,研究了从改善信号配时方案角度对交叉口进行优化的可行性,并相应地进行仿真评估,以出行时间、平均排队长度为指标对现状配时方案比较,说明优化效果。     

防空作战中的信息传输时间迟延问题及解决方法分析

针对数据链系统中信息传输时间迟延问题,阐述了数据链系统信息传输的方式,分析了数据链系统信息传输过程,利用排队论方法得出信息传输时间延迟模型并以JTIDS为例求得信息传输延迟时间,同时分析了防空作战中信息传输时间延迟带来的影响,并提出了解决方法。     

基于复式伸缩窗的车辆排队与消散快速检测算法

基于视频图像处理方法,提出了一种复式伸缩窗来实时跟踪交叉口排队车辆队尾和队头的位置变化,从而准确描述交叉口车辆排队形成和消散过程。通过检测指定区域内车辆是否存在和是否运动,分别构建跟踪排队队尾和队头的队尾伸缩窗和队头伸缩窗。描述排队首尾伸缩变化的复式伸缩窗则由这两个伸缩窗相互协作所构成。根据跟踪队尾和队头的结果,车辆排队长度和停车延迟时间等重要参数就可以轻易得到。试验结果表明本文算法能实时准确地跟踪队尾和队头的位置,能适应不同天气环境和光照变化,其准确率达到92%以上,较好地满足车辆堵塞监控和交通信号灯控制的需要。     

动态交通分配中一种多模式动态决定式点排队模型及其特性分析

提出了一个可应用于动态交通分配中的多模式决定式点排队模型。模型中不同的交通模式(如小汽车、卡车和公交车等)由于车辆特性以及长度的差异在路网中将分别具有不同的行驶特性。为了能够反映不同模式车辆在路段上的相互作用,将单模式点排队模型扩展为多模式点排队模式。并对这个模型的相关特性进行了研究,如:反映不同模式车辆在路段上的速度收敛特性,在路段上每一模式车辆的先入先出特性(FIFO)以及路段上不同模式车辆的因果特性。     

信号交叉口红绿灯配时优化的休假排队模型

通过深入分析机动车辆在十字型信号交叉口的排队现象,建立了休假排队模型,求出该系统处于稳态时的各项指标,通过对系统稳态指标的分析建立对于信号交叉口的配时优化与评价的方法。     

ETC系统缴费方式随机选择模型

针对组合式收费系统中驾驶员缴费方式的随机选择行为,以排队论与非集计理论为基础,建立电子收费(Electronic Toll Collection,ETC)系统缴费方式随机选择模型及均衡状态求解算法。通过均衡分析与灵敏度分析探讨了ETC技术的采用对道路使用者的技术选择与车道选择行为所产生的影响,所得结果可为ETC系统的规划和管理提供帮助。     

Queue discharge patterns at signalized intersections with green signal countdown device and long cycle length

Two apparent features that prevail at signalized intersections in China are green signal countdown device and long cycle lengths. The objective of this study is to investigate the impacts of green signal countdown device and long cycle length on queue discharge patterns and to discuss its implications on capacity estimation in the context of China's traffic. At five typical large intersections in Shanghai and Tianjin, 11 through lanes were observed, and 9251 saturation headways were obtained as valid samples. Statistical analyses indicate that the discharge process of queuing vehicles can be divided into three distinct stages according to the discharge flow rate: a start‐up stage, a steady stage, and a rush stage. The average time for queuing vehicles to reach a stationary saturation flow rate, that is, the start‐up stage, was found to be approximately 20–30 seconds; the rush stage usually occurs during the phase transition period. The finding is contrary to the conventional assumption that the discharge rate reaches a maximum value after the fourth vehicle is discharged and then remains constant during the green time until the queue is completely dissolved. The capacity estimation errors that might arise from the conventional methods are discussed through a comparative study and a sensitivity analysis that are based on the identified queue discharge patterns. In addition, a piecewise linear regression method was proposed in order to reduce such errors. The proposed method can be used for capacity estimation at signalized intersections with the identified queue discharge patterns. Copyright © 2017 John Wiley & Sons, Ltd.     

实时信息交换技术在地铁清分系统中的研究与实现

基于TCP/IP协议,从逻辑架构、处理流程、技术特点、数据结构定义、模块功能、业务逻辑和数据库的实现等方面,对采用多层体系结构的实时信息交换系统作了详细的阐述。给出了它作为轨道交通清分系统的重要子系统的一个应用实例。实践表明,该技术的实际应用提高了整个清分系统的可靠性、可扩展性、可管理性和安全性。     

New Approach to Measuring Traffic Queue at Intersections

To measure the length of traffic queue, a vehicle motion model at intersections was built, and based on it the effective traffic queue was defined. Color images segmentation and frame differencing technique were used to detect the foreground and the moving vehicles by detecting regions of the images, and then measure the length of effective traffic queue. By processing the image sequence acquired at certain intersection, the results prove that it is able to work out the traffic queue effectively by using the two techniques.