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51.
通过对刚性悬挂的简化,在一些基本假设的基础上,建立了刚性悬挂的有限元模型。进行了静力分析和模态分析,得到了悬臂长度大小对汇流排整体变形的影响,合理选择可改善汇流排终端几跨的跨中挠度,并分析了悬臂的大小、之字值和悬挂刚度对刚性悬挂振动特性的影响。 相似文献
52.
A parameterized consideration set model for airport choice: an application to the San Francisco Bay Area 总被引:1,自引:0,他引:1
Airport choice is an important air travel-related decision in multiple airport regions. This paper proposes the use of a probabilistic choice set multinomial logit (PCMNL) model for airport choice that generalizes the multinomial logit model used in all earlier airport choice studies. The paper discusses the properties of the PCMNL model, and applies it to examine airport choice of business travelers residing in the San Francisco Bay Area. Substantive policy implications of the results are discussed. Overall, the results indicate that it is important to analyze the choice (consideration) set formation of travelers. Failure to recognize consideration effects of air travelers can lead to biased model parameters, misleading evaluation of the effects of policy action, and a diminished data fit. 相似文献
53.
美海军协同作战系统的组成与发展 总被引:1,自引:0,他引:1
协同作战系统是美国海军实现网络中心作战思想的关键环节,该系统的投入使用将有效提高航母战斗群的对空防御作战能力。本文对该系统的组成,功能及发展趋势进行介绍和分析。 相似文献
54.
车辆—轨道系统高中低频动力学模型的理论特征及其应用范围的研究 总被引:4,自引:1,他引:3
针对铁路在提速和高速发展中碰到的车辆—轨道系统的结构磨损加剧、关键部件疲劳破坏和噪声等问题,提出必须进行车辆—轨道系统高中低频范围的动力学模型研究。根据激扰的差异及其波长范围,针对车辆—轨道系统动力学在低频、中频和高频3个范围内存在问题的性质,建立符合研究要求的车辆模型、轨道模型和轮轨接触模型,并采用合理的数学方法求解。认为以车辆—轨道系统的频率特征为基础,进行完整的车辆—轨道系统动力学研究,可以有效研究车辆—轨道系统的短时动力学和长期行为之间的关系。 相似文献
55.
Prediction of fatigue life and estimation of its reliability on the parts of an air suspension system 总被引:1,自引:0,他引:1
K. J. Jun T. W. Park S. H. Lee S. P. Jung J. W. Yoon 《International Journal of Automotive Technology》2008,9(6):741-747
Air suspension systems have been implemented in various commercial vehicles, such as buses and special purpose trucks, because
of the comfortable ride and easy height control. An evaluation of the durability of vehicle parts has been required for service
life and safety starting in the early stages of design. The cyclic load applied to the vehicle can cause fatigue failure of
parts, such as the suspension frame. This paper presents a method to predict the fatigue life of the suspension frame at the
design stage of the air suspension system used in a heavy-duty vehicle. To estimate the fatigue life using the SN method,
the Dynamic Stress Time History (DSTH) is necessary for the part of interest. DSTH can be obtained from the results of the
flexible body dynamic analysis using the Belgian road simulation and the Modal Stress Recovery (MSR) method. Furthermore,
the reliability of the predicted fatigue life can be evaluated by considering the variations in material properties. The probability
and distribution of the expected life cycle can be obtained using experimental design with a minimum number of simulations.
The advantage of using statistical methods to evaluate the life cycle is the ability to predict replacement time and the probability
of failure of mass-produced parts. This paper proposes a rapid and simple method that can be effectively applied to the design
of vehicle parts. 相似文献
56.
Julie Wallace Pavlos Kanaroglou 《Transportation Research Part D: Transport and Environment》2008,13(5):323-333
This study characterizes the dispersion of emissions of oxides of nitrogen and nitrogen dioxide from traffic sources in the Hamilton census metropolitan area. The Integrated Model of Urban Landuse and Transportation for Environmental Analysis software was used to estimate emissions of oxides of nitrogen from traffic sources. The Air Pollution Model, was used to simulate dispersion of the traffic emissions over the city. The models account for the two primary wind directions in this region – the prevailing southwest and a secondary northeast direction. The results show a prominent triangle of high pollution defined by major roads and highways along the periphery of the Hamilton Harbour, at peak-hour. With southwest winds, residential areas along the northern shoreline of the Harbour are affected, while the western sections of the city are affected by northeast winds. High concentrations are persistent in some areas, for both wind directions. The resulting dispersion surfaces characterize the spatial distribution of traffic emissions and thus provide a means of assessing population exposure over the Hamilton area. 相似文献
57.
Forng-Chen Chiu Wen-Chuan Tiao Jenhwa Guo 《Journal of Marine Science and Technology》2007,12(4):203-217
It is well known that the hydrodynamic responses of a high-speed vessel traveling in regular head waves of even moderate wave
height can show significant nonlinear behavior, and so linear statistical techniques become insufficient for predicting the
statistics of responses in irregular waves. On the other hand, it has been shown that an approximate third-order Volterra
model is applicable to handling the statistics of some nonlinear seakeeping problems, such as motions and vertical hull girder
loads. In the present study, the focus is on the nonlinear behavior of the pressure responses of the hull surface, especially
on the pressures acting on alternately wet and dry areas near the waterline and on the bow zone with high deadrise angles
that may be subject to slight impact and water pile-up effects. To clarify the validity of applying Volterra modeling to this
problem, a series of experiments in regular and irregular head waves were carried out, and approximate third-order and fifth-order
Volterra models with the proposed algorithm for finding frequency response functions (FRFs) were applied as a means of validation.
In the present article, the first part of the validation was performed using experimental data in regular waves. It was confirmed
that the third-order Volterra model has adequate accuracy to simulate deterministically the variation of pressure responses
in regular waves of different wave steepness up to a wave amplitude to wavelength ratio of 0.01 even for the highly nonlinear
pressures acting on the above-mentioned areas of the hull surface. 相似文献
58.
59.
杭州湾大桥北航道桥结构优化研究 总被引:5,自引:1,他引:4
应用三维空间有限元模型,进行斜拉桥结构优化设计。利用有限元法进行结构分析,求出优化所需的状态变量,挠度、应力和频率。综合考虑设计变量、状态变量和目标函数的联系,应用混合罚函数建立优化模型。运用一阶优化计算方法和引入灵敏度分析进行算法优化,使结构在应力、变形和频率等约束条件下达到最小造价。以通用有限元软件ANSYS作为平台,编制相应程序,综合考虑斜拉桥结构静力性能和动力性能,用两种不同方案对杭州湾大桥北航道桥主桥进行结构优化设计,使全桥造价分别降低9 1%和5 5%。 相似文献
60.