A Variable Time-Discretization Strategies-Based,Time-Dependent Shortest Path Algorithm for Dynamic Traffic Assignment

Within the simulation-based dynamic traffic assignment (SBDTA) model, the time-dependent shortest path (TDSP) algorithm plays a crucial role in the path-set update procedure by solving for the current optimal auxiliary solution (shortest path). Common types of TDSP algorithms require temporal discretization of link/node time/cost data, and the discretization could affect the solution quality of TDSP and of the overall SBDTA as well. This article introduces two variable time-discretization strategies applicable to TDSP algorithms. The strategies are aimed at determining the optimal time discretization for time-dependent links/nodes travel time data. The first proposed strategy produces a specific discretization interval for each link. The second proposed strategy generates time-varying intervals for the same link over the analysis period. The proposed strategies are implemented in a link-based time-dependent A* algorithm in a SBDTA model DynusT and tested with two numerical experiments on two traffic networks. The results show that the proposed discretization methods achieve the research goal—to flexibly and scalably balance the memory usage and run time for SBDTA without degrading the convergence. This property is rather important when dealing with a large real-world network with a long analysis period.     

汽车挡风玻璃除霜性能数值模拟分析

本文采用计算流体力学软件STAR-CCM+对某新开发汽车除霜风道进行数值模拟。通过稳态计算来预测汽车的除霜性能,对除霜效果进行了探讨,并进行了试验。对比模拟结果和试验结果总体比较接近,验证了CFD模拟的的可靠性,为汽车挡风玻璃除霜效果模拟工程提供了参考。     

地面出入式盾构隧道稳定性控制措施有效性研究

文章以南京地面出入式盾构工程为背景,采用三维有限元模拟了地面出入式盾构隧道的整个施工过程,通过在模型中施加隧道内部压重与地表堆载,研究了两者对控制隧道上浮量、提高隧道稳定性的有效性。分析计算结果与现场监测数据表明:内部压重能够明显地提高隧道的稳定性,且效果比较明显;地表堆载也能在一定程度上减小隧道的上浮量,但其效果没有内部压重明显;施工中应结合现场实际条件,综合采用两者来实现最佳的稳定隧道效果。     

TN系统杂散电流的产生机理及其危害研究

配电系统的工作电流从不期望的回路返回电源时会产生杂散电流。以常用的单电源TN—S配电系统为分析对象,从电源、线路、负载三个方面分析了电路参数不平衡产生杂散电流的机理。分析结果表明,电路中任意参数的不平衡将造成中性点电位漂移,是导致TN配电系统中产生杂散电流的根本原因,并带来电磁干扰、电化学腐蚀等一系列问题;合理地设置TN配电系统的工作接地与重复接地能够有效防止杂散电流对信息设备的干扰。而改用IT系统配电方式则可以从根本上减小甚至消除杂散电流。本文提出基于MATLAB的杂散电流电路模型,对系统杂散电流进行仿真分析,验证了理论推导。     

零序电压综合不平衡度探讨

阐述了现行标准对电压不平衡度定义存在的问题,分析了现有谐波电压不平衡度算法不足,提出了非线性负载情况下零序电压不平衡度的计算方法,实验表明了零序综合电压不平衡度定义的必要性与正确性。     

谈自动化集装箱码头

概括自动化集装箱码头的主要特点,介绍世界上几处新近建设、具有一定代表性的自动化集装箱码头。     

Leave the expressway or not？ Impact of dynamic information

This study investigates drivers＇ diversion decision behavior under expressway variable message signs that provide travel time of both an expressway route and a local street route. Both a conventional cross-sectional logit model and a mixed logit model are developed to model drivers＇ response to travel time information. It is based on the data collected from a stated preference survey in Shanghai, China. The mixed logit model captures the heterogeneity in the value of ＂travel time＂ and ＂number of traffic lights＂ and accounts for correlations among repeated choices of the same respondent. Results show that travel time saving and driving experience serve as positive factors, while the number of traffic lights on the arterial road, expressway use frequency, being a middle-aged driver, and being a driver of an employer-provided car serve as negative factors in diversion. The mixed logit model obviously outperforms the cross-sectional model in dealing with repeated choices and capturing heterogeneity regarding the goodness-of-fit criterion. The significance of standard deviations of random coefficients for travel time and number of traffic lights evidences the existence of hetero- geneity in the driver population. The findings of this study have implications for future efforts in driver behaviormodeling and advanced traveler information system assessment.     

FRP布加固RC梁弯曲疲劳性能研究现状与建议

FRP作为一种新兴材料,其在实际结构疲劳加固中的应用随着价格的降低而飞速发展。主要介绍了国内外关于不同 FRP布加固钢筋混凝土梁弯曲疲劳性能的试验研究与理论分析,结合课题组进行的玄武岩纤维布（BFRP）加固 RC梁试验情况,为今后FRP布加固RC梁弯曲疲劳性能的研究方向提出几点建议,有利于该学科的发展。     

保障基本机动性的中央财政公交投入机理

中央财政公交投入不到位是中国城市公交优先发展面临的重要问题,加强中央财政资金投入、完善公交财政保障体系才能确保未来城市公交发展的可持续动力。提出保障公民基本机动性平等是中央政府支持城市公交发展的重要价值基准,从法理上为中央财政承担城市公交支出责任提供依据。从基本公共服务供给最低水平均等化的角度出发,提出中央财政公交投入资金额度的测算方法,为中央财政公交投入的科学决策提供了参考依据。以2010年为目标年进行案例分析,测算得到全国保障基本机动性的中央财政公交投入总额为150.1亿元。     

DC/DC级联系统电压稳定性分析

本文通过介绍新能源供电系统的主体结构,引出在直流并网过程中母线电压稳定性问题,建立了Boost电路和Buck电路的小信号模型,计算得到Boost电路的输出阻抗以及Buck电路的输入阻抗,画出该级联系统的阻抗Bode图和阻抗比Nyquist图。通过Middlebrook稳定性判据判断该系统的稳定性。