混凝土简支梁的预设变形值探讨

钢筋混凝土与预应力混凝土简支梁在预制时,依据其结构变形特点,应分别把预制底模做成上拱与下挠的曲线,以期全桥完成以后,尽量减少大梁变形造成的不良影响。     

汽车动力总成悬置系统的非线性刚度设计方法

以某一微型车动力总成3点悬置系统为例,针对汽车的28种载荷工况,对动力总成的质心位移和各悬置点的位移与反力进行了计算,并论述了动力总成悬置系统非线性刚度的设计思想和计算方法.     

立姿假人实车碰撞试验的研究

在指出目前采用人体模块的行人保护法规试验方法的局限性之后,对立姿假人及其试验方法与装置进行了全面介绍.采用Polar立姿假人进行其实车碰撞试验,并根据试验结果进行假人的运动和伤害分析.结果表明,采用立姿假人的实车碰撞试验,可获得假人的整个运动过程,包括其轨迹、速度和加速度等运动参数,以及伤害程度,因而可为人体模块试验方...     

Meta-analysis of UK values of travel time: An update

Numerous travel demand studies have been carried out over the past five decades, many of which produce estimates of the value of travel time. This includes a rich body of largely unpublished evidence, which can provide valuable insights into the impact of variables such as GDP, travel distance, purpose and mode on this critical parameter for transport modelling and appraisal. The work reported in this paper updates and extends our previous meta-analyses of UK values of time ( [Wardman, 1998], [Wardman, 2001a] and [Wardman, 2004]) by adding recent studies and widening the range of explanatory variables included. Our current research covers 226 studies carried out between 1960 and 2008, yielding a total of 1749 valuations (a 50% increase relative to our previous work) and making this the largest data set of its kind to the best of our knowledge. This is also the most comprehensive study to date of parameters other than in-vehicle time and includes valuations of walk, wait, headway, congested, free flow, late, departure time shift and search time. Exploratory analysis of the data set provides interesting insights into methodological trends in travel demand modelling.For each valuation, over thirty quantitative and categorical variables were recorded and then included in a multivariate regression model to explain variations in the value of time. A large number of statistically significant effects were obtained from this meta-analysis, some of which are in marked contrast with, or not present in, our previous work. One finding that stands out is that the estimated elasticity of the value of time with respect to GDP per capita is 0.9 and highly significant, a much closer correspondence to the widely used convention of a unit income elasticity over time than we have previously obtained. The ratio between walk and wait time and in-vehicle time was found to be substantially lower than the commonly used value of two. We also found large and significant differences between the results from studies based on different types of Stated Preference survey presentation. Other important effects include variations by mode used, mode valued, travel purpose, attribute type and distance. It is envisaged that the results are of direct relevance in the British context, as inputs to appraisal or for benchmarking, whilst the methodological implications are of broader interest and the results, in terms of time equivalents and variations in values of time, can be transferred to other contexts.     

Mixité sociale et choix modal : importance des dimensions symboliques dans l’attrait des transports collectives

Our understanding of transport mode choice is largely based upon functional attributes, such as travel time, cost or accessibility. It is important, however, to also look at symbolic and affective attributes. Indeed, one of the main differences between mass transit and private car use is strongly symbolic: public transport compels users to confront social diversity. Given a hypothetical choice between those modes, 200 residents of the Parisian region were asked five times to evaluate (measuring usage intention on a six point scale: ?3 meaning never and +3 meaning always, with no neutral point) the attractiveness of bus versus car-based transport, according to relative travel time and bus users’ population type. The results show that the symbolic dimension (the social mix) strongly contributes to the desirability of a transport mode, as does the functional dimension (travel time).     

基于三角模糊数的高铁天窗施工实施效果评价

为提升高速铁路施工维修水平,减少列车运行延误,对施工计划的具体内容进行效果评价,能找出检修内容的薄弱环节,从而保证高铁设施设备质量状态及列车安全稳定的运行.以实际施工计划数据为基础,对现场施工计划进行影响因子提取,建立基于供电、控制设备、车站及线路及信号及通信设备等重点检修项目内容的评价体系;引入三角模糊数和模糊评价模型,建立施工项目内容的重要度判别矩阵,判断各因子在天窗施工计划中受到重视的程度;分析实际列车延误数据,提取合并与设备故障相关的延误致因,并证明了合并后因子间的独立性;以施工计划实施后仍产生的各类型设备故障及其导致的延误列车数为指标,评价施工计划项目实施效果;最后,以某铁路局实际天窗施工计划内容、列车延误数据为实例.研究结果表明:施工维修项目重视度与设备故障导致的列车运行延误数量、晚点程度成反比;对控制设备和供电设备的检修较为薄弱,这类设备的故障是列车运行延误和晚点多发源.      

Reliability Analysis of Systems with Common Cause Failure Based on Stress-Strength Interference Model

Many mechanical systems have the characteristics of multiple failure modes and complex failure mechanisms. On the basis of stress-strength interference (SSI) model, this paper takes the mechanical system with common cause failure (CCF) as the research object. The relationship between the stress distribution and the strength distribution is studied, and the failures of components are independent of each other under the deterministic stress. Then, the concept of conditional reliability is introduced to build the system reliability models under the action of one-stress and multi-stress for both series and parallel systems. Finally, the corresponding properties of the proposed methods are discussed to show their advantages.     

CD_4~( ) EFFECTOR CELLS DEFAULT TO THE TH2 PATHWAY IN INTERFERONγ-DEFICIENT

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Modal split and urban public transport management in an Eastern European country

When public transport is the main means of travel in urban areas, management and planning are easy and the main objective can be to minimise costs for the demand available, i.e. maximise profit. However when public transport faces competition from other modes of transport, and activities can be undertaken in a variety of locations, then the management and planning of public transport services is considerably more difficult.This paper examines a methodology for representing consumer behaviour when faced with alternative travel decisions, in order to identify the demand for public transport and to help operators adjust services and prices to maximise demand, when considering people's disposable income, the alternative modes and activity locations available. From this it is possible to devise criteria for maximising consumer surplus in a city, taking into account social benefits.