地铁直流牵引供电系统故障测距研究

针对目前地铁线路日益增长,本文提出一种双端阻抗法,迅速、精准的判断出地铁直流牵引供电系统故障的方位,然后采取先进的同步设备确保通讯的同步性,与其他方法相比,大大提高了故障预测的精度和效率.     

基于非线性渗流模型的管道型岩溶隧道突水机理研究北大核心CSCD

管道型岩溶突水是一个复杂的多场耦合的非线性渗流问题,致灾具有突发性。为揭示管道型岩溶突水灾害的发生机理,文章基于多物理场耦合作用机理,开展了不同溶腔水压、岩溶管道内不同填充介质、不同岩溶管道宽度及岩溶管道长度条件下的多场耦合分析。得到以下结论:(1)管道型岩溶破坏模式下发生的突水灾害,根据填充介质透水性能的异同而表现不同;(2)流体从富水溶腔中流出时流速较小,流经岩溶管道后流速逐渐增加,进入隧道后达到最大值;(3)影响突水过程的因素主要有:富水溶腔水压、岩溶管道或断层裂隙带内填充介质的种类、岩溶管道的宽度、隧道与水源的距离,其中,岩溶管道宽度及岩溶管道内填充介质类型对突水影响大于其他因素。     

基于微信的地铁一码通支付系统

分析了地铁现有不同出行凭证方式的缺陷。运用lamp、ajax异步请求、二维码加解密、网页前端开发等技术,设计开发了利用手机微信二维码作为地铁通行凭证的一码通支付系统。重点介绍了该系统的工作原理。对系统进行模拟测试表明:此方案具有高可行性、可靠性和安全性。     

中小型船厂焊接工艺的认可与实施

随着我国船舶工业的快速发展,船舶建造向大型化、专业化方向发展;与此同时,民营中小型船厂也蓬勃发展并承担了大量的船舶建造任务.但在船舶建造过程中,这些船厂往往由于缺乏焊接工程技术人员,或对造船过程中焊接工艺的要求不太明确,严重影响到船舶的建造质量.作者从自身的实践经验出发,阐述了地方船舶检验部门对中小型船厂进行焊接工艺认...     

船舶伺服排缆Lebus滚筒多电机控制的研究

针对船舶伺服排缆Lebus滚筒多电机协同控制易受负载扰动和电机参数摄动影响的问题,本文提出了基于并行控制、相邻耦合控制、耦合误差同步控制的多电机动态协同控制系统,解决驱动电机动态偏差导致的准确性不足的问题;针对系统较强的非线性及不确定性,采用基于最小相关轴处理方法设计系统消除跟踪误差和同步误差控制器,将每一轴电机的跟踪误差和相邻轴电机的同步误差相结合,减少控制器数量。设计了船舶伺服排缆Lebus滚筒3轴协同控制系统,仿真结果表明,该方法具有较强的鲁棒性、动态快速性和同步精度。     

加强我国公共预算监督研究——把政府关进公共预算“笼子”里

公共预算是行政机构的生命之源,对于约束政府收支来说,公共预算就是最好的"笼子"。社会公众、立法机构与行政机构之间是一种委托代理关系,由于存在预算信息的不对称,行政机构的预算行为可能会具有机会主义倾向,从而损害社会公众的利益。要切实将政府装进公共预算"笼子"里,必须构建以立法机构监督为主导,预算部门监督和社会公众监督为辅助的全方位、立体式的预算监督体系。我国应打造涵盖政府全部收支和明细、公开透明且带把大锁的公共预算"笼子",预算改革可以作为我国行政管理体制改革乃至政治民主法治改革的一个突破口。     

汽车可靠性分析概述

汽车可靠性涉及汽车设计、试验、制造、运输、贮存、使用及车辆维护等内容,是汽车产品性能的重要指标之一。汽车可靠性分析在可靠性研究中扮演着重要角色[1],在此基础上,文章首先梳理了国内外汽车的可靠性发展历程;其次,对不同的可靠性分析方法进行了介绍;然后,对汽车可靠性设计进行了简要说明;最后,文章对我国汽车可靠性现状进行了总结与展望。     

Spectral and time‐frequency analyses of freeway traffic flow

This paper uses spectral and time‐frequency analyses to treat three macroscopic traffic characteristics, namely, time mean speed, volume and occupancy as stochastic processes. Spectral and time‐frequency analyses are performed to characterize power spectral density (PSD), cross‐PSD, autocorrelation and cross‐correlation of these characteristics using TransGuide traffic data collected from four different freeways. It is found that low‐frequency components dominate the PSDs of speed, volume and occupancy at all times. The magnitude of PSDs decreases dramatically as frequency increases and remains almost at a constant level in high‐frequency regimes. A power law is found to exist, which describes the relationship between the frequency and the PSD of traffic characteristics. It is also found that speed can be properly modeled by a narrowband low‐pass stochastic process in a low‐frequency regime and by a nonzero mean white noise in a high‐frequency regime. Strong periodicities and synchronization are both shown in traffic flow. A variety of frequencies can be excited by congestion, and there is no dominant frequency found in stop‐and‐go traffic. Copyright © 2013 John Wiley & Sons, Ltd.     

Vehicle stability control based on driver’s emergency alignment intention recognition

In this work, the reference model modification strategy for vehicle stability control based on driver's intention recognition under emergent obstacle avoidance situation was proposed. First the conflicts between the driver's emergency alignment (EA) intention and vehicle response characteristics were analyzed in critical emergent obstacle avoidance situation. Second combining steering wheel angle and its speed, the driver's EA intention was recognized. The reference model modification strategy based on steering operation index (SOI) was presented. Then a LQR model following controller with tire cornering stiffness adaption was used to generate direct yaw moment for tracking modified reference yaw rate and reference sideslip angle. Finally based on the four-in-wheel-motor-drive (FIWMD) electric vehicles (EV), double lane change and slalom tests were conducted to compare the results using modified reference model with the results using normal reference model. The experimental tests have proved the effectiveness of the reference model modification strategy based on driver's intention recognition.     

造型模板在桥梁建筑景观设计中的研究与运用

以上海市崇明东滩启动区市政道路(一期)工程为背景工程,简要介绍了造型模板在简欧风格桥梁建筑景观中的设计思路、运用要求及工程经济分析,为今后在其它类型桥梁中运用造型模板进行景观设计提供经验。