铁路防灾安全监控系统分布式实时监测单元的设计与实现

设计一种基于AVR单片机的铁路防灾安全监控系统的现场新型数据采集平台,采用分布式结构及组网方式,实现对铁路现场风速、雨量、雪量和地震等数据的实时监测.重点研究了分布式实时监测单元的架构、功能、扩展功能、接口传输及其软硬件实现.     

吸盘挖泥船采用全电力驱动系统设计论证

通过对定距桨推进器与调距桨推进器的比较,以及针对该吸盘挖泥船全电力驱动配置方案和一拖二(柴油机拖动螺旋桨和轴带发电机)动力配置方案的主要性能与参数进行论证分析比较,得出推荐采用全电力驱动配置方案的结论,并对全电力驱动配置方案中采用何种电力驱动方式及配电系统进行简单论证,为船东选择采用全电力驱动配置方案提供技术支持。     

三维近自由表面水翼升力线理论

文章将普朗特的升力线理论扩展到自由表面下的三维水翼升力分析问题。二维水翼升力计算采用奇点分布法,三维水翼升力采用普朗特的马蹄涡叠加法,得到了三维水翼升力线计算理论。并且都考虑了自由表面的影响。在算例中,针对不同的潜深和翼弦长度,给出了升力系数和潜深弗汝德数的关系。其计算结果与其他文献所给的结果相比吻合得很好。     

某高速公路岔道口桥梁有限元分析及配筋研究

结合某高速公路岔道口桥梁的实际情况,应用大型有限元MIDAS软件建立岔道口桥梁的梁格空间模型对岔道口受力进行仿真分析,并运用ANSYS软件建立实体模型与梁格模型在自重情况下的结果进行对比,根据应力分布特点对结构进行配筋研究,取得了传统平面计算无法获得的结果。     

Modelling waiting time for passengers transferring from rail to buses

This paper develops a mathematical model to calculate the average waiting time for passengers transferring from rail transit to buses based on the statistical analysis of primary data collected in Beijing. An important part of the average waiting time modelling is to analyse the distributions of passenger arrival rates. It is shown that the lognormal and gamma distributions have the best fit for direct transfer and non-direct transfer passengers, respectively. Subsequently, an average waiting time model for transferring passengers is developed based on passenger arrival rate distributions. Furthermore, case studies are conducted for two scenarios with real and estimated data, resulting in relative errors of ?3.69% and ?3.77%, respectively. Finally, the paper analyses the impacts of bus headway, the headway of rail cars, and the proportion of direct transfer passengers on average waiting time.     

Modeling Capacity Reliability of Minor Roads at At-Grade Un-Signalized Intersections for Potential Performance Evaluation

Abstract

Given stochastic features of the demands on both the major road and the minor road at an at-grade un-signalized intersection, the capacity of the minor road is viewed as the vulnerable and critical part impacting on the overall capacity of the intersection. To facilitate the analysis of intersection performance reliability, the capacity reliability of the minor road is defined as the probability that the capacity of the minor road can accommodate a certain traffic demand at a certain degree of saturation. The headway distribution of traffic stream on major road is reflected by three types of distributions, namely, exponential distribution, shifted exponential distribution, and Cowan's M3 distribution. Based on field observations, the volumes on both major roads and minor roads are treated as correlated normal random variables. This paper presents the methods for modeling capacity reliability of the minor road at an at-grade un-signalized priority intersection. A method based on first-order reliability method is used to model the capacity reliability index. As important associated factors of capacity reliability analysis, the methods for modeling and analyzing capacity sensitivity of the minor road and reserve capacity of the priority intersection are also presented. A procedure for evaluating the intersection potential performance using capacity reliability, sensitivity and reserve capacity is developed and demonstrated with a numerical example. Finally, some new findings from the case studies are summarized.     

车用重型柴油机二级增压系统模拟及试验研究

针对某车用重型柴油机进行了二级增压系统匹配研究,根据产品开发目标要求选择了高、低二级增压器。采用GT-Power软件建立了二级增压柴油机仿真模型,并对柴油机外特性稳态工况性能进行了模拟计算,分析了二级增压系统能量分配对柴油机性能的影响规律。建立了二级增压柴油机测试平台,并进行了外特性、万有特性及排放特性试验。模拟及试验结果表明,二级增压系统可以大幅提高柴油机低速扭矩,改善燃油经济性,拓宽柴油机燃油经济性运行区域,大幅降低柴油机PM排放。     

沥青分子聚集状态变化特征研究

为研究沥青的化学结构特征,根据沥青组分溶解度参数和极性的不同,将沥青分为沥青质、胶质、油分3个组分,分别采用一个典型分子模型代表沥青的每一个组分,构建2种沥青分子模型,采用分子动力学模拟方法对沥青分子聚集状态变化特征进行分析.结果表明:由于π-π效应,沥青质分子之间形成层状堆积现象,但较长烷烃链造成芳环间扭转角增大,阻碍层状堆积现象的形成;随着温度升高,芳环间扭转角增大,沥青质分子之间的层状堆积结构被破坏,形成穿插或垂直排列结构;在沥青分子模型中,胶质和油分分子的存在使沥青质分子间的距离大于沥青质分子模型中的距离,也使沥青质分子间形成的聚集结构趋于稳定;沥青质与胶质分子形成聚集结构,分散在油分中,沥青质分子结构对沥青能否形成稳定胶体结构具有重要影响.     

基于混合进化算法的甩挂配送问题

甩挂配送问题考虑甩挂运输的交通限制,将客户区分为是否为单箱卡车客户,建立单箱卡车配送和双箱甩挂车配送的混合线路,是带有子回路的新型路径优化问题.采用2-opt局部优化算法对线路进行了优化.然后,建立了0/1整数规划模型,对线路进行了分段,以最小化子回路新增成本为目标优化子回路组合.在此基础上建立了混合进化算法,搜索最优混合线路.通过算例研究演示了甩挂配送问题的新特征,通过仿真分析了子回路组合优化模型的性能,以及算法在集成2-opt与否时适应度的演化,结果表明了该方法的有效性.     

基于判别分析法室内悬浮颗粒物浓度与粒径分布测量

基于数学形态学对室内悬浮颗粒物图像进行图像处理,检测了颗粒物粒径,分形维数和形状系数等重要形态学参数.通过显微观察法,将颗粒物近似分为几个标准的类,以形状系数和分形维数为每一类的观测数据,提出了一种颗粒物判别分析归类的方法,将待测颗粒物归类,实现颗粒物的粒形、体积和表面积的按类近似估计;分析颗粒物的来源,估算颗粒物的密度,计算得出室内悬浮颗粒物浓度和粒径分布的实验数据.这种测量方法可以同时获取颗粒物的质量浓度、总表面积和体积浓度与粒径分布情况.