Research on Damage in Trabecular Bone of the Healthy Human Acetabulum at Small Strains Using Nonlinear Micro-finite Element Analysis

The mechanical properties of the pelvic trabecular bone have been studied at the continuum level. However, nothing is known about the tissue-level damage in the trabecular bone of the healthy human acetabulum at apparent small strains characteristic of habitual. By a DAWING 4000 A supercomputer, nonlinear micro-finite element （μFE） analysis was performed to quantify tissue-level damage accumulation in trabecular bone at small strains. The data indicate that damage in trabecular bone commence at 0.2% apparent strain. The findings imply that tissue yielding can initiate at very low strains in the trabecular bone of the healthy acetabulum and that this local failure has negative consequences on the apparent mechanical properties of trabecular bone.     

软弱地层大跨度暗挖地铁车站柱洞逆筑施工方法

柱洞逆筑法是近几年发展起来的一种新的施工方法,适用于城市暗挖地铁大跨度双层岛式站台车站的施工,以北京地铁10号线劲松站为工程实例,系统介绍软弱地层大跨度浅埋暗挖地铁岛式车站柱洞逆筑施工方法及工艺要点。     

超宽带安全性的研究

超宽带是一种新兴的高速率,低功耗的无线通信技术.根据超宽带的特性,选择性地分析了无线通信协议栈中的物理层和数据链路层的安全问题,对其相应的安全措施做出分析和研究.     

Bus travel time modelling using GPS probe and smart card data: A probabilistic approach considering link travel time and station dwell time

Abstract

Path travel time estimation for buses is critical to public transit operation and passenger information system. State-of-the-art methods for estimating path travel time are usually focused on single vehicle with a limited number of road segments, thereby neglecting the interaction among multiple buses, boarding behavior, and traffic flow. This study models path travel time for buses considering link travel time and station dwell time. First, we fit link travel time to shifted lognormal distributions as in previous studies. Then, we propose a probabilistic model to capture interactions among buses in the bus bay as a first-in-first-out queue, with every bus sharing the same set of behaviors: queuing to enter the bus bay, loading/unloading passengers, and merging into traffic flow on the main road. Finally, path travel time distribution is estimated by statistically summarizing link travel time distributions and station dwell time distributions. The path travel time of a bus line in Hangzhou is analyzed to validate the effectiveness of the proposed model. Results show that the model-based estimated path travel time distribution resembles the observed distribution well. Based on the calculation of path travel time, link travel time reliability is identified as the main factor affecting path travel time reliability.     

基于电化学热耦合模型的电动汽车电池模组热特性研究

为研究电池组的排列与布置方式对电池热特性的影响,本文中以18650锂离子电池为研究对象,建立了单体电池的电化学热力学耦合模型。利用模型仿真和实验测量获得了不同放电倍率时的电池表面温度随放电容量的变化关系,实验数据与仿真数据基本吻合,模型准确。基于单体耦合模型,分析了6×5动力电池模组的不同排列与布置方式下的热特性。结果表明:间距太小或太大均会使平均温度增加,本案例电池间距24 mm时平均温度最低;间距越大,温差越小,温度分布均匀性越好;间距一定,交叉排列散热效果优于对齐排列,且空间利用率更高。电池的排列和间距对电池散热有重要影响,锂离子动力电池组设计过程中应充分考虑。     

无车日与城市轨道交通

本文通过对无车日产生的背景介绍及其引发的思考，议论城市未来交通的发展，比较轨道交通的优势和发展潜力，得出大城市必须大力发展轨道交通的结论。     

整孔双线简支箱梁运输控制因素及工程措施和工期计算

结合京沪高速铁路制梁场设计以及京津、武广客运专线等先后开工建设的实践经验，较为系统地阐述了整孔双线简支箱梁在运输通道上的控制因素和解决的工程措施，并且提出了运梁工期的计算方法。此文论述的内容可对高速铁路及客运专线施工组织设计提供经验和指导。     

平稳性指标W和加权加速度Aw不能相互换算的分析

对TB/T2360—93《铁道机车动力学性能试验鉴定方法及评定标准》附录C3中平稳性指标W和加权加速度Aw的换算公式进行了分析，从平稳性指标W和加权加速度有效值Aw定义分析了二者的关系，结果表明平稳性指标W和加权加速度Aw不能相互换算，W和Aw没有相关性，需分别通过计算获得。     

基于分形理论的同步器接触磨损模型

基于磨合磨损的分形理论,结合粘着磨损理论和Majumdar-Bhushan分形接触模型,建立了换挡同步器接触磨损的数学模型.研究了AMT、DCT快速平稳换挡过程中换挡力对同步器磨损的影响,仿真结果表明.相对于低挡位,高挡位时同步时间短.所需要的换挡力小,所带来的同步齿环磨损深度率小;适当增大换挡力可缩短磨合时间和同步时间,减少同步器磨损量.     

西安市浐灞河2号桥拱形钢塔竖转施工方案

该文结合西安市浐灞河2号桥工程,介绍了拱形钢塔竖转施工方案,可供类似工程参考借鉴。