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《铁道标准设计通讯》2017,(10)
针对高速铁路常用的CRTSⅡ型板式无砟轨道结构,根据其特点,建立二维模型时,可将钢轨与底座板模拟为无限长Euler-Bernoulli梁。根据动力学基本原理,首先建立无限长Euler-Bernoulli梁在简谐荷载作用下的运动微分方程,通过稳态响应求解和积分变换,求出梁体的位移、速度和加速度频率响应函数。利用所推导的频响函数,探讨CHN 60型钢轨的位移、速度和加速度频率响应的频谱特性和频响衰减率。通过分析可知,钢轨的位移和速度频率响应随频率增加而降低,而加速度频率响应随频率增加而增大;位移频响衰减率随频率增加而显著降低,速度频响衰减率在10~100 Hz频段较大,加速度频响衰减率随频率增加而显著增大。 相似文献
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Unmet travel needs can be defined as trips and activities that people need or would like to do more, but for a variety of reasons they are prevented from doing so. This paper provides a critical evaluation of the literature focused on unmet travel needs, with the aim of assessing the scope of existing studies on this topic and better understanding the full context of older people’s mobility. This narrative review identifies how travel needs in later life have been assessed, and the barriers that affect the ability of older people to fulfil these needs. Due to the heterogeneity of older people and differences in research approaches, the analysis of the literature is not conclusive in terms of identifying the real impact of the analysed variables and measures on unrealised mobility. Nevertheless, of the studies analysed, on average at least one-third of older people report unmet travel needs. This situation was found to worsen with age, and women were reported to be more affected than men. The pursuit of leisure, and in particular visiting friends and family, was found to be the activity most associated with unmet travel needs. 相似文献
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A moving sidewalk system installed at an airport pier finger is analyzed. The optimal length of the moving sidewalk and the optimal spacing between the access points which minimize the total cost of the system are obtained using methods of calculus, for a number of cases based on the different proportions of arriving, departing and transferring passengers and for two different types of moving sidewalks: elevated, at‐grade. The optimal length of the moving sidewalk is shown to be linearly related to the length of the concourse, and to the total passenger demand. The effect due to preticketed transferees is insignificant. The optimal spacing between access points is shown to be proportional to the square‐root of either the cost of an access escalator or the cost of inconvenience to a passenger due to an intermediate gap, depending on the moving sidewalk system under consideration. It also changes with the percentage of preticketed transferees. 相似文献
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轿车碰撞安全性的评价及车身碰撞安全性设计 总被引:3,自引:1,他引:3
汽车的安全越来越受到重视,各国各地区都加强了对安全法规的制定工作,尤其是碰撞安全性更是得到关注。目前,在美国、日本、欧洲及澳洲都有称为NCAP的组织机构,对不同车型进行汽车碰撞安全性评估。汽车碰撞安全性评估主要包括正面碰撞、侧面碰撞、儿童保护和行人保护4个方面。防正面碰撞的车身结构设计已经成熟,由刚性的乘员舱与前后的吸能区组成,并注意吸能后撞击力的分流;防侧面碰撞的车身结构设计也正趋完善,重点是放在加强车身刚性和冲击力分流2个方面;为满足保护行人法规要求,整车的造型和汽车前部结构发生了很大的变化。 相似文献
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以桥梁美学设计为出发点,主要阐述桥梁美学设计的基本观点、美学标准、美学设计的三要素及其实现方法;以此美学原理为基础分析孟克河人行桥的美学设计过程和特点。阐明设计时,如何使人行桥造型与形式、功能、环境相一致。 相似文献
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ABSTRACTRidesourcing services such as Uber are nowadays a common feature within available transport options of many cities around the world (E.g. London & San Francisco). There has been much publicity about the potential impacts of ridesourcing services and how (or if) they should be managed or regulated without an objective understanding of who uses these services and why, as well as its current and future implications for public transport (PT).Ridesourcing is part of a broader tech-driven, mobile app-based sharing phenomenon – the ‘sharing economy’ – which has disrupted traditional market models and industries, for example, the transport industry, where new players such as Uber have emerged and have quickly become part of the urban transport landscape. Uber has been at the forefront in disrupting the transport sector since its first launch in 2010 (San Francisco, USA). Since its launch, Uber has generated extensive media coverage and debate among policymakers, transport planners and transport authorities on how these services are affecting traditional transport modes such as buses and taxis. However, without objective empirical data – in terms of impacts on trip making characteristics, PT ridership and congestion – policymakers and transport regulators are yet to fully understand the real impacts ridesourcing services are having on the transport network.This paper is part of broader research that aims to provide insights and empirical-based evidence on how Uber services are used (UberX and Uberpool) in London. A comprehensive survey was undertaken using a detailed questionnaire, issued to UberX and Uberpool users in London to gather detailed data on who uses the Uber services, why they use it and what are the trip purposes, in order to understand Uber user demographics and what effects (if any) Uber services are having on PT usage and trip making characteristics in London. The final findings provide important insights on Uber user demographics, trip purposes, types of trips replaced, impact on car ownership and why travellers use Uber services. 相似文献
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应用有限元法对加筋复合材料层合板结构进行固有振动特性和导纳特性分析。基于一阶剪切理论的复合材料层合板理论,采用4节点Mindlin壳单元进行结构离散,通过动力学原理建立结构动力学有限元方程,并编制出相应的计算机程序。针对双向加筋复合材料结构进行分析,讨论不同结构模态阻尼系数、不同激励位置、不同边界条件和加筋的疏密程度对结构原点导纳及跨点导纳的影响。依据计算结果,可以进一步研究舰船复杂结构振动能量的传递和隔振效果,为追求最佳振动和声学设计提供分析方法。 相似文献