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231.
232.
反求工程中对测量数据进行优化的研究 总被引:4,自引:0,他引:4
由三坐标测量机测量获得的数据具有一定的杂乱性,难以直接用于通用CAD软件的反求工程设计中。采用参数样条方法对测量数据进行优化,生成利于反求曲面重构需要的数据点,可达到提高曲面反求速度和光顺效果的目的。 相似文献
233.
234.
介绍了地铁无线TETRA系统覆盖应考虑的因素、模型、设计步骤等,并以深圳地铁为实例进行了场强覆盖的计算;浅析了地铁线路之间的覆盖规划,场强覆盖的优化以及干扰问题。 相似文献
235.
水面舰船多学科设计优化 总被引:1,自引:0,他引:1
多学科设计优化(MDO)被认为是目前处理海洋结构物设计的有效方法.中国船舶科学研究中心也开展了将多学科设计优化应用于船舶设计的研究.上一篇文章从船舶设计研究人员的角度出发对多学科设计优化的理论进行了介绍并且对一条发表了的国外舰船的模型进行了优化.在本文中,作者对国内的一艘实船的概念设计建立了多学科设计优化模型,该模型包括快速性、操纵性和船中剖面的总纵强度分析,它有37个设计变量,9个约束和两个目标.iSIGHT9.O被用来集成这些模块并执行优化,最终找到的优化设计不仅提高了该船的快速性,同时减小了船中剖面的截面积. 相似文献
236.
David Watling David MilneStephen Clark 《Transportation Research Part A: Policy and Practice》2012,46(1):167-189
In spite of their widespread use in policy design and evaluation, relatively little evidence has been reported on how well traffic equilibrium models predict real network impacts. Here we present what we believe to be the first paper that together analyses the explicit impacts on observed route choice of an actual network intervention and compares this with the before-and-after predictions of a network equilibrium model. The analysis is based on the findings of an empirical study of the travel time and route choice impacts of a road capacity reduction. Time-stamped, partial licence plates were recorded across a series of locations, over a period of days both with and without the capacity reduction, and the data were ‘matched’ between locations using special-purpose statistical methods. Hypothesis tests were used to identify statistically significant changes in travel times and route choice, between the periods of days with and without the capacity reduction. A traffic network equilibrium model was then independently applied to the same scenarios, and its predictions compared with the empirical findings. From a comparison of route choice patterns, a particularly influential spatial effect was revealed of the parameter specifying the relative values of distance and travel time assumed in the generalised cost equations. When this parameter was ‘fitted’ to the data without the capacity reduction, the network model broadly predicted the route choice impacts of the capacity reduction, but with other values it was seen to perform poorly. The paper concludes by discussing the wider practical and research implications of the study’s findings. 相似文献
237.
针对客专ZPW-2000A轨道电路故障处理时,仅靠监测手段不能准确区分室内外故障,需要人工测量,处理时间普遍较长的问题,通过分析信号集中监测系统及轨道电路原理,提出在既有监测系统基础上,增设接收电缆模拟网络监测点的优化措施;同时对轨道电路故障进行模拟试验,分析发生故障时各监测点的数据,总结不同种类故障发生时的规律;最后以2个实际案例验证了优化措施的效果。 相似文献
238.
调度通信系统是铁路行车调度指挥的重要组成部分,论述了铁路专用调度通信设备的技术发展历程,针对高铁客专、干线、支线等不同线路主要运用模式和技术特点,提出调度通信系统适应性的发展趋势及技术实现方案。 相似文献
239.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(2):154-178
Tyre models are a prerequisite for any vehicle dynamics simulation. Tyre models range from the simplest mathematical models that consider only the cornering stiffness to a complex set of formulae. Among all the steady-state tyre models that are in use today, the Magic Formula tyre model is unique and most popular. Though the Magic Formula tyre model is widely used, obtaining the model coefficients from either the experimental or the simulation data is not straightforward due to its nonlinear nature and the presence of a large number of coefficients. A common procedure used for this extraction is the least-squares minimisation that requires considerable experience for initial guesses. Various researchers have tried different algorithms, namely, gradient and Newton-based methods, differential evolution, artificial neural networks, etc. The issues involved in all these algorithms are setting bounds or constraints, sensitivity of the parameters, the features of the input data such as the number of points, noisy data, experimental procedure used such as slip angle sweep or tyre measurement (TIME) procedure, etc. The extracted Magic Formula coefficients are affected by these variants. This paper highlights the issues that are commonly encountered in obtaining these coefficients with different algorithms, namely, least-squares minimisation using trust region algorithms, Nelder–Mead simplex, pattern search, differential evolution, particle swarm optimisation, cuckoo search, etc. A key observation is that not all the algorithms give the same Magic Formula coefficients for a given data. The nature of the input data and the type of the algorithm decide the set of the Magic Formula tyre model coefficients. 相似文献
240.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(11):981-999
A comparative study of the performance of three rheological automotive shock absorber models as well as of an extended force–velocity relation in full vehicle simulation is performed. Simulation results for both the shock absorber test rig and a full vehicle crossing a single obstacle are compared with measured data. While the gain of accuracy by the extended force–velocity relation is marginal, the rheological models in general yield a noticeable improvement, which, however, in full vehicle simulation is less significant than in test rig simulation. Among the rheological models studied here, the one consisting of a nonlinear spring–dashpot element with an element modelling friction by a continuous transition from the compression to the extension range in parallel and a quadratic approximation of the static gas force exhibits the best global performance. 相似文献