汽车实验模态分析微机系统的开发及应用

本文介绍了自行开发的适用于汽车工程的实验模态分析微机系统。在阐述适合微机的模态分析理论基础上,展示了该系统的组成结构、软件开发及特点。最后介绍了应用该系统对SC-110汽车驾驶室和车架总成的实验模态分析。     

引气粉煤灰混凝土的氯离子扩散系数

基于盐碱寒冷地区的工程环境与混凝土的配制特点,模拟配制了SA溶液,采用正交方案试验研究了水灰比、含气量和粉煤灰掺量3个参数对引气粉煤灰混凝土氯离子扩散系数的影响,建立了氯离子扩散系数计算模型,并采用游程检验法对计算模型进行了检验,结果表明该模型表征的相关关系显著,预测值与实测值无显著差异。     

级配碎石裂缝缓解层防裂机理及足尺疲劳试验

反射裂缝是旧水泥混凝土路面沥青加铺层的主要病害之一,目前尚无理想的解决方法,针对这一问题,提出了采用级配碎石作为裂缝缓解层的方法。对级配碎石层的防裂机理进行了分析,采用大型反射裂缝试验台架进行了设置级配碎石层及其他对比结构层的加铺层疲劳破坏试验,模拟了沥青加铺层荷载型及温度型反射裂缝的产生、发展过程。结果表明,级配碎石防裂效果最好,玻纤格栅和土工布的防裂效果次之,普通沥青混凝土加铺层防裂效果最差。     

Effects of economic disincentives on private car use

A field experiment was conducted to investigate the effects of economic disincentives on private car use. Eighty two-adult households who were owners of at least one car were randomly assigned to three experimental groups and one control group. Both experimental and control groups logged their car trips during one week before, one week during, and one week after treatment. The treatment consisted of charging two of the experimental groups approximately 100% of normal cost per kilometer of driving during 2 weeks, and charging the third experimental group this amount per kilometer of driving during 4 weeks. With the purpose of investigating whether deliberate planning increases the effect of economic disincentives, the households in one of the former and in the latter group were asked to fill out a prospective car log for the following week. The control group was not charged or requested to fill out a prospective car log but was in other respects treated in the same way. Analyses of the car logs and odometer readings during and at the end of treatment showed a weak reduction of car use due to the economic disincentives that however were almost completely dependent on planning.     

砂砾地层盾构隧道受力光弹试验

为满足城市地下管廊、城际快速地下交通网的建设需求，中国隧道工程的应用率与日俱增。砂砾地层因黏聚力较低，与其他地质条件地层相比工程特性明显。在分析类似地质情况下的盾构隧道受力时，连续性介质假设已不能满足实际需求，应从非连续介质角度分析隧道及其周围岩石介质的受力分布。通过光弹试验观测砂砾地层中隧道-围岩系统内的力链强弱及其分布形式，并应用数字图像处理方法提取力链信息。在光弹颗粒中设置圆形管道以模拟盾构隧道，并通过改变内置管道的直径大小，改变上部及侧部载荷大小，以及在管道底部进行光弹颗粒释放，来分析砂砾地层中隧道直径、埋深变化及隧道底部的地层破坏、流动对隧道-围岩系统中力链分布的影响。利用颗粒元软件PFC对试验过程进行数值模拟，对比分析模拟结果与试验结果以验证试验的可靠性。结果表明：力链是砂砾地层与隧道之间载荷传递的主要方式，围岩与隧道间的接触力分布具有非对称性；隧道的椭圆化程度及其周围砂砾岩层中的力链密度，均随着隧道直径和埋深的增加而增大；当砂砾地层破坏、流动时，隧道-围岩系统内的力链也被破坏并重新分布，地层内维持系统稳定的“环状”强力链退化成为“拱形”强力链，系统自稳性产生破坏，此时应采取措施强化系统的稳定性。     

大跨度空腹式连续刚构桥设计理论与方法

为寻求常规连续刚构桥适用跨径和斜拉桥适用跨径之间的合理、经济桥型,在常规连续刚构桥的基础上结合拱桥的力学特点提出空腹式连续刚构桥型。该桥型在常规连续刚构桥的形式上加大箱梁根部高度,并对箱梁根部的腹板进行挖空,减轻自重,形成梁-拱组合力学效应,从而提高结构承载效率,增强桥梁跨越能力。空腹式连续刚构桥可布置为单主跨、多主跨以及单T的形式,也可与常规连续刚构组合,桥墩可采用双肢薄壁墩或箱形柱式墩。采用正交试验法对该桥型关键结构参数进行研究,并根据实际工程对总体结构参数取值提出建议。该桥型采用平衡悬臂方法施工,工程造价指标、运营维护技术要求及费用与常规连续刚构桥相当,适用跨径在200~400 m,可望填补常规连续刚构桥适用跨径和斜拉桥适用跨径之间的空白。     

Role of Bus‐Based Park and Ride in the UK: A Temporal and Evaluative Review

Abstract

The number of bus‐based Park and Ride (P&R) schemes in the UK has grown substantially over the past 40 years as a result of its encouragement by the Government as a tool to deal with increasing traffic congestion and traffic‐related pollution. The aim of this article is to analyse the degree to which P&R is effective in the contemporary policy context. The authors identify phases of development of P&R since its emergence as a local solution to transport capacity constraints in historic towns. Policy goals are identified against which a review of literature is used to highlight its effectiveness. It is concluded that P&R may increase the distance travelled by its users due to low load factors on dedicated buses, public transport abstraction and trip generation, although it is highlighted that there are areas in which further research is required to clarify its impacts.     

基于卷积型小波包变换的船用水位调节器故障辨识

以某型蒸汽船的主冷凝器水位调节器为研究对象,应用卷积型小波包变换提取各种故障信号分解后的相对小波包能量,建立水位调节器标准故障库,并引进Euclidean空间距离公式作为判据进行故障识别。实验结果表明,该方法可以对水位调节器的典型故障进行快速、正确分类,降低了其故障定位与维修的盲目性。     

水基型沥青清洗剂的研究

采用表面活性剂复配技术,经基质材料的性能对比及正交试验分析,开发出能在常温下迅速除去金属表面沥青且环保的水基型清洗剂;进一步,论文探讨了清洗方式、浸泡温度、清洗剂浓度以及浸泡时间等因素对金属表面清洗效果的影响,证实了该清洗剂良好的净洗力,验证了研发的清洗剂作为道路工程界传统沥青清洗剂替代品的可行性.