老化沥青胶结料的疲劳特性研究

采用动态剪切流变仪(DSR)研究了短期老化与长期老化的沥青胶结料在应变模式,应力模式下的抗疲劳性能.实验中,采用了旋转薄膜烘箱实验(RTFOT)及压力老化(PAV)来模拟沥青胶结料的短期及长期老化.沥青胶结料的应变疲劳实验中选取1.0％,1.5％,2.0％以及2.5％四个应变值,应力疲劳实验中选取了0.25,0.35,0.45,0.55 MPa 4个应力值.实验结果表明,采用应变疲劳实验能够区别老化对沥青抗疲劳性能的影响,而应力疲劳并不能很好的显示老化对沥青抗疲劳性能的影响.因此,应变模式下的疲劳实验更适合用来评价老化沥青胶结料的抗疲劳性能.     

The Circumferential Contact Problem for the Belted Radial Passenger Car Tire

The belted radial passenger car tire is idealized as a prestressed circular ring connected to a hub through a distribution of linear springs modeling the sidewall. A second distribution of such springs exterior to the ring represents the tread rubber. The tire is supposed to be at rest, loaded at its hub, and pressed onto a flat, rigid, frictiontess roadway. In this situation the linear differential equations of the model are solved using a singular perturbation technique. Given the load at the hub, the solutions furnish the length of tread in contact with the road, the radial and circumferential displacement of all points on the ring, and the distribution of pressure over the region of contact.     

结构自诊断沥青混凝土路用性能评价研究

通过马歇尔稳定度、冻融劈裂、车辙以及四点弯曲疲劳试验,对比分析评价了结构自诊断沥青混凝土水稳定性、高温稳定性和疲劳特性等路用性能.结果表明:石墨的掺入会在一定程度上降低结构自诊断沥青混凝土水稳定性能,但是由于同时降低了沥青胶浆的温度敏感性,因而对其高温稳定性具有改善作用;与普通沥青混凝土相比,结构自诊断沥青混凝土的疲劳寿命更短;并且疲劳破坏速率呈现出温度依赖性,在同一应变水平下,温度下降时,传导型沥青混凝土的破坏速率加快,疲劳寿命缩短.     

On modeling telecommuting behavior: option, choice, and frequency

The current study contributes to the already substantial scholarly literature on telecommuting by estimating a joint model of three dimensions—option, choice and frequency of telecommuting. In doing so, we focus on workers who are not self-employed workers and who have a primary work place that is outside their homes. The unique methodological features of this study include the use of a general and flexible generalized hurdle count model to analyze the precise count of telecommuting days per month, and the formulation and estimation of a model system that embeds the count model within a larger multivariate choice framework. The unique substantive aspects of this study include the consideration of the “option to telecommute” dimension and the consideration of a host of residential neighborhood built environment variables. The 2009 NHTS data is used for the analysis, and allows us to develop a current perspective of the process driving telecommuting decisions. This data set is supplemented with a built environment data base to capture the effects of demographic, work-related, and built environment measures on the telecommuting-related dimensions. In addition to providing important insights for policy analysis, the results in this paper indicate that ignoring the “option” dimension of telecommuting can, and generally will, lead to incorrect conclusions regarding the behavioral processes governing telecommuting decisions. The empirical results have implications for transportation planning analysis as well as for the worker recruitment/retention and productivity literature.     

自动化实时监测系统在中国台湾高速铁路浅埋隧道的应用

中国台湾高速铁路新竹二高隧道以覆土深度9～12m穿越台湾北部第二高速公路。为了考虑高速公路下方隧道穿越施工时的行车安全,采用自动化监测系统,监控隧道施工产生之顶部路面沉降与隧道侧墙土层之变位。监测系统采用捷仪工程科技公司GeoAuto自动化实时监测软件系统,该系统分前端、中端、后端三部分。前端部分在隧道顶部沿隧道方向安装有自动量测水平倾斜计、在隧道两侧各安装有自动量测垂直倾斜计与伸张仪,另沿高速公路方向安装3排路面沉降点以全站仪自动监测,前述各类仪器皆连接至资料集录器;中端部分为ADSL、直接联机与无线传输等方式进行数据传输;后端部分为GeoAuto自动监测软件系统,所有路面沉降、土层变位等现场数据,皆由前端仪器量测、经中端传输,最后将所有现场有关沉降、变位等数据,皆显现于后端电脑显示器上。在自动监测系统配合下,有效协助浅埋隧道凿进,顺利完成隧道施工。     

Urban public transport in Japan

This article describes some general features of public transport provision in the urban areas of Japan (especially the large urban areas), and some specific features of an integrated transport system currently being developed in one such area. Although there are a number of important differences between Japan and the United Kingdom — such as the degree of urbanisation, level of car ownership, the responsibilities of government organisations and the existence of private railways in Japan — there are many similarities in the role that public transport plays and the factors which influence the efficiency of public transport.The success or otherwise of the developments in urban public transport systems in Japan would seem to have important implications for the design of transport systems in the similarly dense and compact conurbations of the United Kingdom and other European countries.