视频监控系统在港口的应用

在港口的货物仓库、堆场、各出入卡口、码头前沿等监控点安装视频监控探头,构建数字视频监控系统,可以使口岸监管部门实时监控现场情况,并可以通过数字化设备记录取证,从而大大减轻监管人员的劳动强度,提高口岸通关效率.     

Modeling traffic crash rates of road segments through a lognormal hurdle framework with flexible scale parameter

This study examines distributional characteristics of crash rates for road segments using observed accident data. The results indicate that the distribution of crash rates is mixed and right‐skewed, which motivates the consideration of non‐normal distributions. With the aid of Kolmogorov–Smirnov tests, kernel density plots, and Q–Q plots, the lognormal distribution is verified as an appropriate candidate for representing the positive domain of crash rates. Then, a lognormal hurdle model was developed and also compared with gamma and Weibull hurdle models. Further, the lognormal hurdle model was revised by allowing the scale parameter to vary with respect to explanatory variables. Such a modification enables the heterogeneous skewness of samples to be captured while enhancing the modeling flexibility. The proposed model was also compared with a Tobit model, an alternative approach that treats crash rates as censored data. Among all these models, the proposed lognormal hurdle model with flexible scale parameter presents the best modeling performance, and the analyses also reveal that several explanatory variables affect crash rates through not only the location parameter but also the scale parameter in the lognormal model. This study finally attempted to inspect crash rates through count models, and it discovered that the proposed hurdle model is superior because it is able to output the whole distribution form of crash rates, whereas the crash count model can only provide the expected value of crash rates, provided the exposure variable servers as an offset term in the link function of the mean parameter. Copyright © 2015 John Wiley & Sons, Ltd.     

09-3X型捣固装置结构原理分析

通过对09-3X型捣固装置的结构原理分析计算,并与09-32型对比,阐述09-3X型捣固装置满足3枕连续式捣固稳定车的作业需要,且结构合理,使用维护方便。     

磁浮线路轨道梁技术方案和特点

高速磁浮交通系统的线路轨道梁型式,是线路在穿越各种工况下的工程技术方案,以解决沿线不同路段线路轨道梁布置的技术难点.介绍了磁浮线路的主要轨道结构型式、误差指标和新型轨道梁梁型.在确保线路安全性和乘坐舒适性的条件下,研发的新型轨道梁梁型可以满足系统功能的特定要求.     

地铁列车可关断晶闸管牵引变流器综合测试技术研究

牵引变流器是地铁列车的关键部件,主要由牵引控制单元和变流模块构成,在牵引方式上有直流(斩波器)和交流(逆变器)之分。以上海轨道交通1、2号线列车的门极可关断晶闸管(GTO)牵引变流器为技术背景,基于虚拟仪器技术,对控制器和变流模块的测试方法进行了整合,提出了GTO牵引变流器的综合测试方案。该方法不仅能够对各部件实施分部测试,还可以对整体进行综合测试。测试方法方便有效,使部件在现场维修、测试过程中能够模拟在线工作状态,便于查找故障信息,为列车牵引系统的各种检修和部件国产化开发提供了必要的技术准备。     

去甲斑蝥素在体外对白血病细胞核酸和蛋白质合成的影响

应用细胞培养、放射性核素示踪技术研究了去甲斑蝥素对白血病细胞的作用。结果表明，去甲斑蝥素对人早幼粒白血病ＨＬ－６０细胞株ＤＮＡ和蛋白质合成有抑制作用，对ＲＮＡ合成未见明显影响；对正常人骨髓细胞ＤＮＡ合成无抑制相反有一定促进作用。     

Investigation of turbulent flows in a waterjet intake duct using stereoscopic PIV measurements

Stereoscopic particle image velocimetry measurements were made in a wind tunnel using a prototype waterjet model. The main wind tunnel provided the vehicle velocity and a secondary wind tunnel was set up as the waterjet propulsion model. Pressure distributions along the ramp and lip sides inside the duct were measured for three jet velocity to vehicle velocity ratios. Three-dimensional velocity fields were obtained at the intake entrance and the nozzle exit of the waterjet system. The flow into the duct was faster in the lip region than on the ramp side. Because of the variation in intake geometry from a rectangular to a circular section and because of the sudden curvature change on the lip side, a pair of counter-rotating vortices was observed in the mean velocity field at the nozzle exit. In addition, the turbulent kinetic energy correlated with the vortex pair was stronger on the lip side than in other areas. Dominant large-scale structures were extracted by using a snapshot proper orthogonal decomposition analysis. It was found that most of the turbulent kinetic energy was attributed to at least three vortices near the nozzle exit. This detailed three-dimensional velocity field will be useful for the verification of CFD simulations applied to the waterjet system.     

拉拔试验研究的现状与发展

加筋土界面的摩擦特性是现代加筋土技术研究的热点和难点,是彻底弄清加筋机理和建立加筋土理论体系的关键。许多学者做了大量的试验和理论研究工作,取得了一些成果,但由于影响筋土界面摩擦特性的因素多,情况复杂,加之目前由于实验设备及方法的限制,有许多问题还未能彻底搞清楚。本文介绍了目前国内外在此问题上的一些研究成果,着重分析了试验的影响因素、存在的问题及今后发展方向。     

An analysis of internal transit systems requirements for central cities

The deficient performance of existing downtown transit distribution systems may significantly affect the overall performance of the urban transportation system in many metropolitan areas. This paper has two principal objectives. First, it describes an approach entitled Performance Requirements Analysis for developing a set of requirements or standards that a downtown transit system should satisfy and structuring these requirements so as to generate a small set of alternative generic systems for detailed evaluation. Second, it provides a preliminary assessment of performance requirements for distribution systems in 19 of the largest cities in the United States.     

A three-stage decision-making model for selecting electric vehicle battery technology

This study proposes a three-stage decision-making model for the selection of electric vehicle battery technology. Data used for analysis include surveys completed by 45 technology experts from industry, academia, and research throughout Taiwan. A three-stage model that includes developing multiple-criteria during the first stage, integrating the importance of criteria assessment using the fuzzy analytical hierarchy process in the second stage, and using patent analysis tools to further identify the patent portfolio of the technology selected by experts in the third stage are employed. The empirical results indicate that power source management technology and battery module technology are the key technologies for development by the electric vehicle industry. Battery energy storage management and cooling technology are found to be the key for building patent portfolios. When faced with substantial technical and market uncertainty, multiple-criteria for research and development (R&D) selection and stage-wise integration of decision tool must be employed by battery firms to effectively allocate the resources for R&D decisions.