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581.
582.
《铁道标准设计通讯》2015,(11):68-73
京沪高速铁路(京徐段)多次跨越既有铁路,跨越既有线桥涵设计是京沪高速铁路桥梁设计的重要节点。通过对上跨大李联络线及预留复线、京山四线及西黄左线、两个津浦单线、津浦双线等四处跨线桥梁工点介绍,针对不同的既有线现状情况,总结出跨越既有线桥涵设计的常用结构形式为:空间刚架、悬浇连续梁、基础斜置简支梁及转体施工连续梁。 相似文献
583.
584.
Future aspects in marine ecosystem modelling 总被引:1,自引:0,他引:1
Existing ecosystem models are briefly presented and summarised. The problem of coupling physical and biological models as well as aspects of prediction and predictability are discussed. The general perception that marine ecosystems are inherently unpredictable due to non-linearity becomes questionable if the response of climate variability in marine ecosystems is analysed. Many authors have shown correlations between climate variability and the variability of abundance or biomass of marine organisms such as phytoplankton, zooplankton, benthos or fish recruitment in different parts of the world ocean. In the northern hemisphere, certain species show a linear response to climate variability mainly during winter and spring. However, the underlying mechanisms are not well understood. Often, a phase lag can be observed between climate variability and the reaction of organisms. The identification of a plausible mediator between climate and biology is difficult, since all possible physicochemical mechanisms having a direct or indirect influence on the variability of abundance or biomass of marine organisms have to be considered as mediator.The understanding of the reason of the phase lag, which possibly implies a “biological memory”, and the identification of all possible mediators are necessary to predict the response of marine organisms to climate variability. The identification of mediators will result in an improvement of coupled models, a deeper understanding of physical–biological interaction and the improvement of predictive capability of marine ecosystem models. 相似文献
585.
马英驹 《大连铁道学院学报》1994,15(3):24-29
提出了采用完整的短幅外摆线的等距曲线作为摆线轮齿廓,来等效代换针摆行星传动中复合齿形摆线轮齿廓的理论,并给出了求解等效齿廓参数的数学模型、计算方法和求解实例。 相似文献
586.
空间数据的多尺度表达研究 总被引:1,自引:0,他引:1
多尺度是空间数据的重要特征之一,研究空间数据在不同尺度条件下的表达特征和方式具有极其重要的现实意义.在参考相关资料和同类研究的基础上,阐述了空间数据多尺度表达的特征和数据模型以及表达中可能出现的问题,并给出了试验结果. 相似文献
587.
城市交通需求预测组合模型的研究 总被引:10,自引:1,他引:10
分析了交通需求预测组合模型的应用,重点研究了适用于城市交通需求预测的两种组合模型。给出了基于熵最大化原理的交通分布与交通分配组合模型的求解算例,并且构造了各种客运交通方式的广义出行费用模型,提出了基于广义出行费用和动脉多路径概率分配的交通方式划分和交通分配组合模型。 相似文献
588.
Featured in this pilot experimental study is the construction and design of an instrumented vehicle that is able to capture vehicle trajectory data with an extremely high level of accuracy and time resolution. Once constructed and properly instrumented, the various data collection systems were integrated with one another and a driving experiment was conducted on northern Virginia roadways with 18 participants taking part in the study. Trajectory data were collected for each of the drivers as they traversed a predefined loop of four roadway segments with varying numbers of lanes and varying shoulder widths. Data collected from the experiment were then used to calibrate the parameters of the prospect theory car-following model through a genetic algorithm calibration procedure. Once all model parameters were successfully calibrated, significance testing was carried out to determine the impacts that the varying roadway infrastructure had on driving behavior. Results indicated that there were significant changes in behavior when comparing one lane roadways to their two lane counterparts—specifically in cases where the roadway featured a wide shoulder. Additional testing was conducted to ensure that there was no variation based on gender, as nine study participants were female and nine were male. The successfulness of this first study conducted with the newly constructed instrumented vehicle creates the opportunity for a variety of additional studies to be conducted in the future. 相似文献
589.
Transport models, philosophy and language 总被引:1,自引:0,他引:1
Paul Timms 《Transportation》2008,35(3):395-410
The aim of this paper is to encourage debate about the nature of transport modelling. It does so firstly by considering the
underlying philosophies of science (apparently) adopted by transport modellers, over a period of more than 50 years, from
the 1950s until the present day. The conclusion is that a new philosophy of science needs to be developed, which is more in
tune with how transport modelling is actually carried out (as opposed to how early transport modellers thought it ought to
be carried out). It is recommended that such a new philosophy perceives transport modelling as a linguistic activity within
the overall context of transport planning, which is in turn considered as a communication process. The paper outlines three
main approaches that could be taken in this respect, analysing transport models from metaphorical, narrative and aesthetic
perspectives. Conclusions are drawn upon the possible future research directions that might follow from the analysis provided
in the paper, emphasising the importance of bringing formal philosophical thinking into transport modelling research and practice.
Paul Timms is a Senior Research Fellow at the Institute for Transport Studies, University of Leeds. He has been involved for 20 years in research covering a wide range of transport modelling (from traffic signals to world futures), applied to various locations in Europe, Asia and Latin America. 相似文献
Paul TimmsEmail: |
Paul Timms is a Senior Research Fellow at the Institute for Transport Studies, University of Leeds. He has been involved for 20 years in research covering a wide range of transport modelling (from traffic signals to world futures), applied to various locations in Europe, Asia and Latin America. 相似文献
590.
Traffic microsimulation models normally include a large number of parameters that must be calibrated before the model can
be used as a tool for prediction. A wave of methodologies for calibrating such models has been recently proposed in the literature,
but there have been no attempts to identify general calibration principles based on their collective experience. The current
paper attempts to guide traffic analysts through the basic requirements of the calibration of microsimulation models. Among
the issues discussed here are underlying assumptions of the calibration process, the scope of the calibration problem, formulation
and automation, measuring goodness-of-fit, and the need for repeated model runs.
Yaron Hollander is a transport analyst, working for Steer Davies Gleave in London. His work combines advanced demand modelling, Stated Preference, appraisal, design of public transport systems, transport policy and network modelling. He completed his PhD at the Institute for Transport Studies in Leeds, and previously worked for the Technion – Israel Institute for Technology; for the Israeli Institute for Transportation Planning and Research; and for the public transport department at Ayalon Highways Co. Ronghui Liu is a Senior Research Fellow at the Institute for Transport Studies, University of Leeds. Her main research interests are modelling of traffic and microsimulation of driver behaviour and dynamical systems. She develops and applies network microsimulation models to a wide range of areas from transport policy instruments such as road pricing, to public transport operations and traffic signal controls. 相似文献
Ronghui LiuEmail: |
Yaron Hollander is a transport analyst, working for Steer Davies Gleave in London. His work combines advanced demand modelling, Stated Preference, appraisal, design of public transport systems, transport policy and network modelling. He completed his PhD at the Institute for Transport Studies in Leeds, and previously worked for the Technion – Israel Institute for Technology; for the Israeli Institute for Transportation Planning and Research; and for the public transport department at Ayalon Highways Co. Ronghui Liu is a Senior Research Fellow at the Institute for Transport Studies, University of Leeds. Her main research interests are modelling of traffic and microsimulation of driver behaviour and dynamical systems. She develops and applies network microsimulation models to a wide range of areas from transport policy instruments such as road pricing, to public transport operations and traffic signal controls. 相似文献