A kinematic wave approach to traffic statics and dynamics in a double-ring network

Recently there has been much interest in understanding macroscopic fundamental diagrams of stationary road networks. However, there lacks a systematic method to define and solve stationary states in a road network with complex junctions. In this study we propose a kinematic wave approach to defining, analyzing, and simulating static and dynamic traffic characteristics in a network of two ring roads connected by a 2 × 2 junction, which can be either an uninterrupted interchange or a signalized intersection. This study is enabled by recently developed macroscopic junction models of general junctions. With a junction model based on fair merging and first-in-first-out diverging rules, we first define and solve stationary states and then derive the macroscopic fundamental diagram (MFD) of a stationary uninterrupted network. We conclude that the flow-density relationship of the uninterrupted double-ring network is not unique for high average network densities (i.e., when one ring becomes congested) and unveil the existence of infinitely many stationary states that can arise with a zero-speed shockwave. From simulation results with a corresponding Cell Transmission Model, we verify that all stationary states in the MFD are stable and can be reached, but show that randomness in the retaining ratio of each ring drives the network to more symmetric traffic patterns and higher flow-rates. Furthermore we model a signalized intersection as two alternate diverge junctions and demonstrate that the signalized double-ring network can reach asymptotically periodic traffic patterns, which are therefore defined as “stationary” states in signalized networks. With simulations we show that the flow-density relation is well defined in such “stationary” states, and asymptotic traffic patterns can be impacted by signal cycle lengths and retaining ratios. But compared with uninterrupted interchanges, signalized intersections lead to more asymmetric traffic patterns, lower flow-rates, and even gridlocks when the average density is higher than half of the jam density. The results are consistent between this study and existing studies, but the network kinematic wave model, with appropriate junction models, is mathematically tractable and physically meaningful. It has offered a more complete picture regarding the number and type of stationary states, their stability, and MFD in freeway and signalized networks.     

基于静力试验的大跨钢管拱桥承载力的模糊神经网络评价

在深入研究现有桥梁结构承载力评价方法的基础上,把模糊理论与人工神经网络技术结合起来应用于大跨度钢管混凝土拱桥的承载力评价.建立了模糊神经网络评价模型,通过样本训练,获取评价专家的经验知识和直觉思维.经实际工程检验,评价结果直观简单,较好地反映了在役桥梁结构的承载力状况.     

突发事件下路网运行时间可靠性研究

对突发事件下的路网运行时间可靠性进行分析,从路段通行能力与运行时间关系的角度,对交通流量与运行时间关系进行讨论。在研究运行时间的均值、标准差等特征值在突发事件下变化的基础上,利用机会约束模型,建立异常状态下路网容量分析的非线性规划模型。实例分析结果表明,突发事件出现时路网运行时间可靠性与其承担的交通流量有直接的关系。     

基于多用户类型随机用户平衡的连续网络设计

用多用户类型随机用户平衡描述实际路网中出行者的路径选择行为。根据出行者对路网状况认识的不同程度,将出行者划分为具有相同特性的多个类型。将多用户类型随机用户平衡问题表示为一个无约束极小化问题,并提出了该问题的一种基于路段水平的灵敏度分析方法。建立了多用户类型随机用户平衡条件下的连续网络设计问题的双层规划模型,并给出了基于灵敏度分析的启发式算法。实例的结果表明模型具有一般性和适应性。     

地铁OTN传输系统的构成和可靠性分析

从开放式传输网络（OTN）的传输环路故障保护原理出发,结合地铁的实际情况,论述OTN传输系统的构成;分析端站光纤两种连接方式的可靠性,提出提高可靠性的建议。     

印尼铁路项目GSM-R系统核心网建设及互联互通研究

不同于中国铁路统一管理的模式,境外铁路项目需要根据当地的政治、经济制度制定不同的通信网络建设模式.通过对印尼高速铁路项目的分析,研究在境外铁路项目中可能出现的2种通信网络建设模式,即统一管理模式和独立管理模式.提出了2种模式下GSM-R系统核心网的可行性建设方案,以及有互联互通需求时可行的漫游方案,并分析了其他主要铁路...     

基于VR技术的多人协同船舶消防系统开发及应用

针对当前船舶消防培训的现状和不足,结合VR技术和网络通信技术,以Unity 3D为开发平台,基于典型船舶火灾处置流程,搭建多人协同船舶消防系统。借助VR设备捕捉人体运动数据,并将数据进行处理映射到虚拟角色的骨骼系统中,从而实现虚拟角色的动作跟随。以散货轮火灾为训练对象,借助三维建模技术,搭建消防训练虚拟火场环境,通过体感交互方式来对虚拟消防设备进行操作。通过网络通信技术搭建网络后台并开发客户端接口,实现多个客户端之间的交互数据同步,从而实现多个消防工位的协同消防演练。该系统能够提供一个安全的动态火灾训练环境,以实现提高学员的协同作战能力,降低船舶消防演习训练成本,提高学员训练效率的目的。实践表明,该系统的培训效果良好,可应用于消防培训。     

模糊理论在网络优化中的应用

随着网络应用范围的拓宽,应用中使用了大量的模糊语言,比如"费用高"、"距离远"和"代价低"等等,对于这类问题难以建立精确的数学模型.提出了运用模糊理论来解决网络优化中遇到的这类不确定的、模糊的问题,并结合一个具有模糊性的网络优化问题实例,建立数学模型,编写Java程序实现求解过程.最后通过对建模结果的验证,说明方法是有效的和可行的.     

Network impacts of a road capacity reduction: Empirical analysis and model predictions

In spite of their widespread use in policy design and evaluation, relatively little evidence has been reported on how well traffic equilibrium models predict real network impacts. Here we present what we believe to be the first paper that together analyses the explicit impacts on observed route choice of an actual network intervention and compares this with the before-and-after predictions of a network equilibrium model. The analysis is based on the findings of an empirical study of the travel time and route choice impacts of a road capacity reduction. Time-stamped, partial licence plates were recorded across a series of locations, over a period of days both with and without the capacity reduction, and the data were ‘matched’ between locations using special-purpose statistical methods. Hypothesis tests were used to identify statistically significant changes in travel times and route choice, between the periods of days with and without the capacity reduction. A traffic network equilibrium model was then independently applied to the same scenarios, and its predictions compared with the empirical findings. From a comparison of route choice patterns, a particularly influential spatial effect was revealed of the parameter specifying the relative values of distance and travel time assumed in the generalised cost equations. When this parameter was ‘fitted’ to the data without the capacity reduction, the network model broadly predicted the route choice impacts of the capacity reduction, but with other values it was seen to perform poorly. The paper concludes by discussing the wider practical and research implications of the study’s findings.     

列车无线定位方法初探

介绍了我国现有列车定位方法,简要阐述了基于网络的无线定位方法及其定位参数的测量与估计.结合铁路交通中的具体情况,分析适用我国铁路的列车无线定位技术以及确定定位点的图解方法,并分析了影响列车无线定位精度的因素,最后对列车无线定位的抗干扰措施进行了探讨.