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441.
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ABSTRACTIn current urban planning practice, macroscopic transport demand and assignment models are essential for the evaluation of mid- and long-term land use developments and infrastructure investments. The credibility of their projections strongly depends on their ability to reproduce present day traffic volumes. Obviously, a simplified model of reality will display some shortcomings, and the effect of these is asserted by quality measures that quantify the divergence from observed traffic volumes. There is, however, only rough guidance regarding acceptable ranges of these measures. Most of the literature on this subject approach these ranges from below, by discussing measures attained by operational models and using these as a benchmark, or by using the adverse effects of modelling errors to derive a minimum quality level. On the contrary, this study suggests upper limits for quality measures by analysing year-on-year variations in traffic volumes that result from changing land use and infrastructure. 相似文献
443.
Abstract To understand fully passengers’ perceptions and expectations of the bus service quality in Taipei, business managers and governmental agencies must seek a proper scale that can reflect passengers’ opinions accurately. This study develops and tests a service quality scale designed for a city bus transit system in Taipei. Churchill’s paradigm and a focus group interview were combined into a multistage scale development procedure. Based on the procedure, Taipei city buses were selected as the example, for which a service quality scale was developed. The final scale contains four dimensions and 20 items. These four dimensions are ‘interaction with passengers’, ‘tangible service equipment’, ‘convenience of service’ and ‘operating management support’. Finally, the results of scale development and the managerial applications of the service quality scale for the city transit system are discussed. 相似文献
444.
简单的结构可通过数学方法获得比较准确的模态结果,较复杂的结构很难用数学方法直接进行分析,需要将模型简化,不合理的简化会导致分析结果的错误,使用有限元软件分析可以获得比较理想的结果。划分网格是有限元分析的关键一步,文中以大拉杆为例,进行了数学计算、有限元软件ANSYS与ADINA模态分析,通过对比模态结果,对这两款不同有限元分析软件的计算特点进行了总结,得出并不是网格密度越密计算精度越高的结论。 相似文献
445.
文章阐明了PBL教学法在“船舶强度与结构设计”课程教学中的应用,介绍了其具体实施步骤。实施效果显示,该方法取得了良好的教学效果,具有一定的参考意义。 相似文献
446.
447.
铁道车辆液压锚定机械手 总被引:1,自引:0,他引:1
针对铁道车辆在港口、厂矿等装卸时需要固定的要求,研制出铁道车辆液压锚定机械手。机械手最大锚定力为450 kN,在非工作状态时设备最高点不高出轨面。机械手采用液压驱动,由升降臂、伸缩臂和末端手爪组成。升降臂采用双杆结构的四连杆机构,并对伸缩缸、支撑杆等关键部件进行强度校核。液压系统采用节能设计,并利用液压锁实现机械手的位置锁定。采用程序互锁和行程时间联合冗余控制,以保障系统的可靠性。现场使用表明,机械手在1.5 m水平距离内可实现车辆空间位置自动寻找、自动摘挂车钩、定位和位置锁定,达到设计目标,可实现安全高效生产。 相似文献
448.
为减小列车由直线进入曲线时车轮对轨道产生的横向冲击力,对曲线入口的结构性晃车问题进行了分析,进而对轮轨游间及相关技术标准进行了讨论,从机车车辆和线路2个方面提出了建议。 相似文献
449.
450.
Yusuke Tahara Robert V. Wilson Pablo M. Carrica Frederick Stern 《Journal of Marine Science and Technology》2006,11(4):209-228
Steady flow simulations for the Korean Research Institute for Ships and Ocean Engineering (KRISO) container ship (KCS) were
performed for towing and self-propulsion. The main focus in the present article is on the evaluation of computational fluid
dynamics (CFD) as a tool for hull form design along with application of state-of-the-art technology in the flow simulations.
Two Reynolds-averaged Navier-Stokes (RANS) equation solvers were employed, namely CFDShip-Iowa version 4 and Flowpack version
2004e, for the towing and self-propulsion cases, respectively. The new features of CFDShip-Iowa version 4 include a single-phase
level-set method to model the free surface and an overset gridding capability to increase resolution in the flow and wave
fields. The new features of Flowpack version 2004e are related to a self-propulsion scheme in which the RANS solver is coupled
with a propeller performance program based on the infinitely bladed propeller theory. The present work is based on a close
interaction between IIHR-Hydroscience and Engineering of the University of Iowa and Osaka Prefecture University. In the following
article, overviews are given of the present numerical methods and results are presented and discussed for the KCS in towing
and self-propulsion modes, including comparison with available experimental fluid dynamics (EFD) data. Additional evaluation
is provided through discussion of the recent CFD Workshop Tokyo 2005, where both methods appeared to yield very promising
results. 相似文献