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降雨作为一种常见的气象条件,对高速公路网行程时间的稳定性有着直接的影响.本文针对雨天能见度降低、路面摩擦系数变小的特征,通过分析降雨的空间分布模式,建立了雨天路段单元自由流车速、通行能力以及公路网需求水平的修正模型,进而提出了雨天路段单元的广义行程时间函数.结合用户最优平衡分配模型,以及系统工程中的串并联理论,建立了雨天高速公路路段单元、路径、OD对和公路网的行程时间可靠度评价模型.应用Matlab工具箱模拟公路网上的降雨分布,设计了基于Monte Carlo方法的评价模型求解思路.最后以算例验证了该方法在行程时间可靠性评价中的应用.结果表明,能藉此有效地找出雨天公路网中行程时间敏感性最大的关键路段.     

船用绞车230kW变频调速异步电动机设计

230 kW变频调速异步电动机是专门为逆变器供电、船用100吨绞车而设计的新型电机.针对该电机的特殊设计要求和非正弦电源供电的特点,本文主要介绍了电机的电磁方案、IP56防护等级结构及其它结构设计和采取的措施.最后通过试验结果分析表明该电机满足船用100吨绞车的要求,验证了其设计的可行性和有效性.     

C^4ISR系统能力需求模型综合效能分析与评估方法

系统综合效能是判断C4ISR系统体系结构设计优劣的一个重要依据。对C4ISR系统能力需求模型的综合效能评估进行了研究,在定量分析系统信息优势能力和决策优势能力的基础上,提出了基于信息优势的系统综合效能分析方法和基于决策优势的系统综合效能分析方法。利用这两种分析方法可以寻找到C4ISR系统中对系统信息优势能力和决策优势能力影响最大的节点或节点集合,为网络中心系统体系设计提供指导。最后通过案例验证了方法的有效性。     

A random utility maximization (RUM) based dynamic activity scheduling model: Application in weekend activity scheduling

The paper presents a modeling framework for dynamic activity scheduling. The modeling framework considers random utility maximization (RUM) assumption for its components in order to capture the joint activity type, location and continuous time expenditure choice tradeoffs over the course of the day. The dynamics of activity scheduling process are modeled by considering the history of activity participation as well as changes in time budget availability over the day. For empirical application, the model is estimated for weekend activity scheduling using a dataset (CHASE) collected in Toronto in 2002–2003. The data set classifies activities into nine general categories. For the empirical model of a 24-h weekend activity scheduling, only activity type and time expenditure choices are considered. The estimated empirical model captures many behavioral details and gives a high degree of fit to the observed weekend scheduling patterns. Some examples of such behavioral details are the effects of time of the day on activity type choice for scheduling and on the corresponding time expenditure; the effects of travel time requirements on activity type choice for scheduling and on the corresponding time expenditure, etc. Among many other findings, the empirical model reveals that on the weekend the utility of scheduling Recreational activities for later in the day and over a longer duration of time is high. It also reveals that on the weekend, Social activity scheduling is not affected by travel time requirements, but longer travel time requirements typically lead to longer-duration social activities.     

A mixed-integer linear program for optimizing sensor locations along freeway corridors

How to optimally allocate limited freeway sensor resources is of great interest to transportation engineers. In this paper, we focus on the optimal allocation of point sensors, such as loop detectors, to minimize performance measurement errors. Although it has been shown that the minimization problem can be intuitively formulated as a nonlinear program, the formulation is so complex that only heuristic approaches can be used to solve the problem. In this paper, we transform the nonlinear program into an equivalent mixed-integer linear model. The linearized model is shown to have a graphical interpretation and can be solved using resource constrained shortest path algorithms. A customized Branch-and-Bound technique is then proposed to solve the resource constrained shortest path problem. Numerical experiments along an urban freeway corridor demonstrate that this sensor location model is successful in allocating loop detectors to improve the accuracy of travel time estimation.     

天津港北港池新建滚装码头工程的基桩设计

天津港北港池新建滚装码头距离既有港区较远,工程地质条件差异较大,既有码头设计中采用的基桩竖向承载力的参考值已不再适用.结合具体工程实例,提出在持力层埋藏较深的条件下高桩码头基桩的设计原则、设计方案和沉桩施工中的相关控制标准.     

基于SVPWM五相三电平H桥逆变器中点电位控制研究

针对多相三电平H桥逆变器的电压矢量数量多,难以应用传统的空间矢量PWM算法的问题,提出了一种简化的五相三电平H桥逆变器空间矢量PWM算法。该方法采用相移SPWM思想,将五相三电平H桥逆变器作为两个由单桥臂组成的五相分别予以控制。分析选择合理的工作电压矢量及开关作用顺序,计算了开关周期内的各工作电压矢量的作用时间;不同开关状态下,针对中点电位分析的基础上,提出利用冗余矢量对中点电位进行控制,实现了电容电压的平衡。     

城市快速路互通立交选型思路探讨——以长春市快速路系统互通立交为例

互通立交在城市快速路交通系统中起着举足轻重的作用,城市快速路互通立交的选型对整个立交的交通功能、投资、占地、景观及社会和经济效益等起较为重要的作用。我国各个大中城市相继修建快速路,通过对长春快速路上的互通立交选型进行总结分析,提出一些互通立交选型思路,可供相关专业人员参考。