大直径深嵌岩桩的承载特性与桩长设计研究

基于自平衡桩基测试技术,根据荆岳长江公路大桥一桩的静载荷试验,对其泥质岩地区大直径钻孔嵌岩桩,在嵌岩深度较大情况下的承载特性进行了研究。结果表明:大直径深长嵌岩桩桩顶的Q-S曲线主要是缓变型为主,属摩擦型桩。根据实测的桩侧荷载位移曲线,利用荷载传递法,研究了桩端缩短5,10m两种情况下桩顶的荷载大小及其相应的位移情况,为桩长的设计提供了依据。     

非饱和土基质吸力量测试验研究与探讨

土-水特征曲线能够解释非饱和土力学的许多力学特性。土-水特征曲线的获取依赖于试验设备、试验技术、试验方法,土-水特征曲线的准确获取能够促进非饱和土力学的发展。结合目前的非饱和土力学研究,对现有主要非饱和基质吸力量测试验进行了归纳总结。     

泡沫沥青发泡特性的试验研究

泡沫沥青作为泡沫沥青冷再生施工中的主要黏结剂和稳定材料,研究其发泡特性具有很重要的意义。文章介绍了泡沫沥青的发泡机理和评价方法,并对泰普克70#沥青进行室内发泡试验,通过对发泡特性曲线的分析,得到最佳发泡条件。     

XML5163XLJ13型旅居客车开发

介绍XML5163XLJ13型旅居车的总体布置、结构特点,以及开发旅居客车的前景.     

大功率船用齿轮箱传动系统和结构系统耦合特性分析

船用齿轮箱是船舶轮机系统的重要组成部分,其动态性能的好坏直接影响系统的性能,因而开展船用齿轮箱动态特性研究具有重要的意义。文章对某大型船用齿轮箱的固有特性进行分析,通过轴承支撑把传动子系统和结构子系统两者耦合起来,建立齿轮—转子—轴承—箱体耦合系统动力学模型。采用有限元软件中的Lanczos方法对齿轮箱系统固有特性进行了计算,得到固有频率及其振型,通过分析齿轮系统的激励频率,得出传动级离合器齿轮在工作过程中造成了较大的振动和噪音,与实际相符。     

Experimental design influences on stated choice outputs: An empirical study in air travel choice

Discrete choice experiments are conducted in the transport field to obtain data for investigating travel behaviour and derived measures such as the value of travel time savings. The multinomial logit (MNL) and other more advanced discrete choice models (e.g., the mixed MNL model) have often been estimated on data from stated choice experiments and applied for planning and policy purposes. Determining efficient underlying experimental designs for these studies has become an increasingly important stream of research, in which the objective is to generate stated choice tasks that maximize the collected information, yielding more reliable parameter estimates. These theoretical advances have not been rigorously tested in practice, such that claims on whether the theoretical efficiency gains translate into practice cannot be made. Using an extensive empirical study of air travel choice behaviour, this paper presents for the first time results of different stated choice experimental design approaches, in which respective estimation results are compared. We show that D-efficient designs keep their promise in lowering standard errors in estimating, thereby requiring smaller sample sizes, ceteris paribus, compared to a more traditional orthogonal design. The parameter estimates found using an orthogonal design or an efficient design turn out to be statistically different in several cases, mainly attributed to more or less dominant alternatives existing in the orthogonal design. Furthermore, we found that small designs with a limited number of choice tasks performs just as good (or even better) than a large design. Finally, we show that theoretically predicted sample sizes using the so-called S-estimates provide a good lower bound. This paper will enable practitioners in better understanding the potential benefits of efficient designs, and enables policy makers to make decisions based on more reliable parameter estimates.     

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城市公共交通乘客出行成本的量化研究,对于科学合理地评价公共交通系统的社会效益意义重大,而出行时间价值是进行乘客出行成本估计的一个重要环节. 本文以北京市市区居民SP调查数据为依托,通过分析公共交通出行时间价值的影响因素,选取Logit模型为基础模型,引入“出行者收入”作为模型新增变量,并针对工作商务、社会娱乐两种出行目的在不同换乘情况下出行时间价值模型进行参数标定,建立了基于SP调查数据的改进型时间价值求解模型,并计算得到北京市公共交通出行者在不同出行目的和有无换乘情况下的换乘时间价值、候车时间价值以及运行时间价值. 研究发现,工作商务出行目的出行时间价值普遍高于社会娱乐的出行时间价值,出行者在不同出行目的和有无换乘情况下的候车时间价值,大于换乘时间价值以及运行时间价值,并且有换乘情况下的候车时间价值大于无换乘情况下的候车时间价值.     

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在城市轨道交通的线路网络形成、实行一票换乘并伴随投资主体多元化时,需要建立公平公正的票务清分机制,本文提出一个基于乘客旅行实际时间分布计算各路径上乘客比例的新方法.根据交通卡中的进出站的时间记录,计算出在一段时间内在一对出入站之间完成旅行的所有乘客的时间分布,以这个分布为依据计算在这段时间里各路径上的乘客比例.采用数值模拟的方法在一对有两条有效路径的出入站间产生乘客旅行时间的数据,然后根据这些数据进行客流比例计算.结果表明,即使两条路径的运营时间差异很小也能实现较准确的比例划分,这种动态计算客流分布的方法能更准确地反映实际客流分布.     

温拌沥青混合料马歇尔变温变击实功设计方法

为了建立温拌沥青混合料组成设计方法,在不同温度和击实次数下进行了AC-13C温拌沥青混合料的马歇尔击实试验,分析了温拌沥青混合料体积特性。分析结果表明：随着击实温度的降低和击实次数的减少,温拌沥青混合料的空隙率和矿料间隙率增大,沥青饱和度降低;与热拌沥青混合料相比,温拌沥青混合料中沥青被集料吸收的含量（质量分数）、有效...     

Modeling Correlation of Family Holiday Activities Based on Structural Equation Model

Previous researches in activities-decision have more in-depth study in context of individuals, while less work has been done within household activity decisions. The structural equation model is applied to analyze the relationship of three household activity categories on holiday using data from 2009 Jinan travel survey. Six attributes were first chosen as exogenous variables for the structural equation model. Meanwhile, six activity characteristic indexes were selected as endogenous variables including activity duration time and activity times in three kinds of activity, hereby Subsistence activity, maintenance activity and discretionary activity. respectively. Then, the paper attempted to discuss the correlation of all types of activities behavior through analyzing not only the influence of household economics and family members factors on activity but the correlation of holiday activities. The research shows that complex relationships among composition of the family, economic status, and activities-decision can be captured by the structural equation model structure. Specifically, the results show that flexibility of three categories activities will affect the activities of decision-making.