基于梁格法的某斜交变宽连续箱梁桥荷载试验分析

基于梁格理论建立某斜交变宽连续箱梁桥的空间梁格模型,计算分析设计活载及试验荷载作用下结构的静动力响应,基于模型计算结果指导该桥的现场荷载试验,并据现场试验结果评价箱梁结构的工作状态。     

修建高速铁路的环境保护问题

自从1964年日本建成世界上第一条高速铁路以来,高速铁路为世界经济的发展及人民生活创造了良好的效益.我国铁路为了适应经济发展的要求,已逐步对既有铁路进行提速、开通运营了广深准高速铁路,并计划修建京沪高速铁路.高速铁路在国内外、都呈现出良好的发展势态.但是,不可忽视的环境污染问题也随之而来.高速铁路的环境污染主要有振动、噪声和电波干扰等,其中振动和噪声干扰对社会影响最大.     

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。     

“大思政”背景下《汽车工程概论》教学改革与实践

为贯彻落实党中央关于高校思政教育工作新要求,逐步构建"大思政"教育新格局,着力推进高校课程思政教学改革势在必行。本文以重庆理工大学通识教育核心课《汽车工程概论》为例,剖析其以往教学实践存在不足,从改革教学目标、优化教学内容、改进教学方式及改善教学评价四个维度探讨其"大思政"背景下教学改革路径。改革实践表明,学生学习积极、主动性明显增强,专业知识、综合能力、品格素质、道德涵养得到协同有效提升。     

对《三相异步电动机缺相保护电路的改进》一文探讨

《铁道通信信号》期刊在2004年第2期刊登的《三相异步电动机缺相保护电路的改进》一文，介绍的方法简单、易行，很贴合实际，但在应用过程中发现经常出现拒动现象。经过分析认为该电路（如图1）有几点值得商榷。     

容差分配技术在轿车车身设计中的应用研究

阐明了容差分配理论,论述了容差分配技术在轿车车身设计中的应用,并将其应用到某车型开发的工程实例中.在满足产品装配精度和技术要求的前提下,制定出了较宽松的公差,从而降低了开发成本,减少了整改次数,缩短了产品开发周期.     

钢轨打磨车打磨作业后轨顶不平顺度的研究

PGM-48型钢轨打磨车打磨作业一定遍数后,如继续打磨,波磨深度反而越大,通过分析打磨车作业控制原理,标定相关系统,找出打磨后波磨深度变化的临界值,即打磨到平均波磨深度为0.17 mm左右时,已经达到其最佳效果,没有必要再增加打磨作业遍数.     

Prenatal assessment of normal fetal pulmonary grey-scale and lung volume by three-dimensional ultrasonography

Objective To quantitatively analyze the fetal lung echo and right lung volume in the third trimester by real-time three-dimensional ultrasound (3-D US) and evaluate the feasibility of fetal lung maturity. Methods A total of 732 women with normal singleton pregnancies between 28 and 42 weeks of gestation underwent ultrasound examination. The 3-D US equipment with a 3.5-5MHz transabdominal transducer was used for the fetal biometric measurement. The echogenicity ratio between fetal lung and liver was compared. The fetal lung volume was calculated by the rotational multiplanar technique for volume measurement (VOCAL). Results The right fetal lung volume increased with the increase of gestational age with a linear positive correlation (r=0.884, P<0.01). After 34 weeks, the echogenicity ratio of fetal lung to liver was more than 1.1. Conclusion The echogenicity of lung/liver and fetal lung volume could be used as normal fetal predictable indicators for fetal lung maturity.     

温州市域铁路线路敷设方式比选研究

市域铁路线路敷设方式比选是市域铁路设计重点之一。本文结合市域铁路建设条件和工程特点，以温州市域铁路南洋大道段线路为例，对地下线和高架线路敷设方式进行了综合比选研究，总结市域铁路线路敷设控制要点，为类似工程设计提供借鉴。     

Analyzing travel time reliability and its influential factors of emergency vehicles with generalized extreme value theory

Travel time reliability is very critical for emergency vehicle (EV) service and operation. The travel time characteristics of EVs are quite different from those of ordinary vehicles (OVs). Although EVs own highest road privilege, they may still experience unexpected delay that results in massive loss to the society. In this study, we employ the generalized extreme value (GEV) theory to measure extremely prolonged travel time and analyze the potential influential factors. First, among three GEV distributions, Weibull distributions are found to be the best distribution model according to several goodness-of-fit tests; a new reliability index is derived to measure travel time reliability. Numerical examples demonstrate the advantages of GEV-based reliability index over variance and percentile value in the applications of EV. This index will be of great practicability in the EV operation performance and reliable route choices. Second, we further investigate the potentially influential factors of EV travel time reliability. Results show that link length and left-turn traffic volume may have an adverse impact on the link reliability while more left-turn lanes may increase the travel time reliability. The influential factor study will help us understand the causes of the EV travel time delay and the differences of travel time reliability between OVs and EVs.