Dynamic user equilibrium with side constraints for a traffic network: Theoretical development and numerical solution algorithm

This paper investigates a traffic volume control scheme for a dynamic traffic network model which aims to ensure that traffic volumes on specified links do not exceed preferred levels. The problem is formulated as a dynamic user equilibrium problem with side constraints (DUE-SC) in which the side constraints represent the restrictions on the traffic volumes. Travelers choose their departure times and routes to minimize their generalized travel costs, which include early/late arrival penalties. An infinite-dimensional variational inequality (VI) is formulated to model the DUE-SC. Based on this VI formulation, we establish an existence result for the DUE-SC by showing that the VI admits at least one solution. To analyze the necessary condition for the DUE-SC, we restate the VI as an equivalent optimal control problem. The Lagrange multipliers associated with the side constraints as derived from the optimality condition of the DUE-SC provide the traffic volume control scheme. The control scheme can be interpreted as additional travel delays (either tolls or access delays) imposed upon drivers for using the controlled links. This additional delay term derived from the Lagrange multiplier is compared with its counterpart in a static user equilibrium assignment model. If the side constraint is chosen as the storage capacity of a link, the additional delay can be viewed as the effort needed to prevent the link from spillback. Under this circumstance, it is found that the flow is incompressible when the link traffic volume is equal to its storage capacity. An algorithm based on Euler’s discretization scheme and nonlinear programming is proposed to solve the DUE-SC. Numerical examples are presented to illustrate the mechanism of the proposed traffic volume control scheme.     

含坑点腐蚀的深海耐压球壳有限元分析

对于含坑点腐蚀等局部缺陷的球壳结构,由于结构的不连续性以及缺陷部位应力状态的三维特性,因此很难用传统的连续介质理论及板壳理论进行求解。为了对含坑点腐蚀的球壳的强度、稳定性进行精确分析,文中分别采用坑点腐蚀壳体单元(Pitting Corrosive Shell Element,PCSE)、基于多点约束(Multipoint Constraint,MPC)的壳体单元-实体单元集成以及实体单元三种方法进行对比计算,对比结果表明,采用PCSE方法的计算效率最高,且计算结果的精度满足工程应用要求。最后,基于PCSE方法并通过方差分析,讨论了坑点腐蚀对球壳强度及稳定性的影响。     

Principal components analysis and track quality index: A machine learning approach

Track geometry data exhibits classical big data attributes: value, volume, velocity, veracity and variety. Track Quality Indices-TQI are used to obtain average-based assessment of track segments and schedule track maintenance. TQI is expressed in terms of track parameters like gage, cross-level, etc. Though each of these parameters is objectively important but understanding what they collectively convey for a given track segment often becomes challenging. Several railways including passenger and freight have developed single indices that combines different track parameters to assess overall track quality. Some of these railways have selected certain parameters whilst dropping others. Using track geometry data from a sample mile track, we demonstrate how to combine track geometry parameters into a low dimensional form (TQI) that simplifies the track properties without losing much variability in the data. This led us to principal components. To validate the use of principal components as TQI, we employed a two-phase approach. First phase was to identify a classic machine learning technique that works well with track geometry data. The second step was to train the identified machine learning technique on the sample mile-track data using combined TQIs and principal components as defect predictors. The performance of the predictors were compared using true and false positive rates. The results show that three principal components were better at predicting defects and revealing salient characteristics in track geometry data than combined TQIs even though there were some correlations that are potentially useful for track maintenance.     

How much is too much for tolled road users: Toll saturation and the implications for car commuting value of travel time savings?

The current practice of forecasting the demand for new tolled roads typically assumes that car users are prepared to pay a higher toll for a shorter journey, and they will keep doing so as long as the toll cost is not higher than their current value of travel time savings. Practice ignores the possibility that there could be a point when motorists stop driving on toll roads due to a toll budget constraint. The unconstrained toll budget assumption may be valid in networks where the addition of a new toll road does not result in a binding budget constraint that car users may have for using toll roads (although it could also be invoked for existing tolled routes through a reduction in use of a tolled route). In a road network like Sydney which offers a growing number of (linked) tolled roads, the binding budget constraint may be invoked, and hence including additional toll links might in turn reduce the car users’ willingness to pay for toll roads to save the same amount of travel time. When this occurs, car users are said to reach a toll saturation point (or threshold) and begin to consider avoiding one or more toll roads. Whilst toll saturation has important implications for demand forecasting and planning of toll roads, this type of behaviour has not been explored in the literature. We investigate the influence that increasing toll outlays has on preferences of car commuters to use one or more tolled roads as the number of tolled roads increases. The Sydney metropolitan area offers a unique laboratory to test this phenomenon, with nine tolled roads currently in place and another five in planning. The evidence supports the hypothesis that the value of travel time savings decreases as a consequence of toll saturation.     

基于蚁群算法的舰载直升机维修资源优化调度研究*

针对舰载直升机远航时驻舰周期长、维修任务时间紧、资源有限的特殊性,合理构建舰载直升机驻舰维修模型,建立舰载直升机驻舰维修资源优化调度模型,采用改进蚁群算法进行仿真计算,通过计算验证表明：该算法较好的解决维修过程中出现的资源冲突问题,缩短舰载直升机维修工期。     

解决ZPW-2000A型无绝缘轨道电路对DX3型道口信号干扰问题

文章对叠加在ZPW-2000A型无绝缘轨道电路上的DX5型道口信号设备错误报警问题，提出了合理的解决方案。     

CBTC系统中的逻辑区段处理方案研究

介绍了CBTC系统中的列车位置检测方式,分析了当前联锁子系统对逻辑区段状态的处理方法,及其不合理之处,并提出了新的解决方案。     

基于响应面方法的车钩缓冲器特性曲线优化分析

为了更加真实地反映车钩缓冲器实际工作状态和进行缓冲器特性曲线优化,提出采用列车纵向动力学系统对缓冲器的特性曲线进行分析。在优化方面,从响应面方法的基本原理出发,建立响应面的子区域构造方法,运用凝聚函数和惩罚技术处理约束的遗传算法求解加约束条件的二次响应面最优解。以大秦线实际线路、列车编组以及列车纵向动力学性能为优化计算的条件,结合缓冲器数值模型建立缓冲器特性曲线的优化模型,运用所提出基于遗传算法的响应面方法对重载列车缓冲器特性曲线进行优化求解。结果说明所提方法对求解缓冲器特性曲线的优化问题非常有效。     

电气化牵引电流对信号轨道电路的干扰及防护措施

本文对电气化区段牵引电流对信号轨道电路产生的干扰进行分析,并提出防干扰措施。     

Matlab在轨道电路仿真计算中的应用

本文介绍了Matlab在轨道电路仿真计算中的应用。通过列举两个Matlab在计算中的实例,说明用Matlab完成轨道电路仿真计算,程序的可读性强,工作效率高。