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571.
空间分析方法在航线设计和航路监视中的应用 总被引:3,自引:0,他引:3
探讨在电子海图中,使用GIS空间分析函数自动判断计划航线的偏航极限范围内是否存在危险点、线、面的方法,为航线设计起决策参考,在航行过程中,起实时航路监视作用。 相似文献
572.
Preparing highway emissions inventories for urban scale modeling: A case study in Philadelphia 总被引:1,自引:0,他引:1
R. Cook J.S. Touma A. Beidler M. Strum 《Transportation Research Part D: Transport and Environment》2006,11(6):396-407
Highway emissions represent a major source of many pollutants. Use of local data to model these emissions can have a large impact on the magnitude and distribution of emissions predicted and can significantly improve the accuracy of local scale air quality modeling assessments. This paper provides a comparison of top–down and bottom–up approaches for developing emission inventories for modeling in one urban area, Philadelphia, in calendar year 1999. A bottom–up approach relies on combining motor vehicle emission factors and vehicle activity data from a travel demand model estimated at the road link level to generate hourly emissions data. This approach can result in better estimates of levels and spatial distribution of on-road motor vehicle emissions than a top–down approach that relies on more aggregated information and default modeling inputs. 相似文献
573.
Spatial and temporal variation of bacterioplankton in a sub-Antarctic coastal area (Kerguelen Archipelago) 总被引:1,自引:0,他引:1
Bacterial abundance and production were measured monthly for one year along cross-shore transects in 3 sub-Antarctic fjords of the Kerguelen Archipelago (seven stations each). Mean values of the 3 most coastal (inside) and most offshore (outside) stations were used to describe the relationship between temperature, phytoplankton biomass, bacterial abundance and bacterial production over a one year annual cycle. The entire sampling protocol was repeated twice during each cruise: once at noon and once at midnight. Over the whole sampling period, the temperature ranged from 2.1 to 7.4 °C, while chlorophyll a concentrations varied by a factor of 10, and bacterial abundance and production varied by factors of 12 and 30, respectively. Within one day, all of these parameters sometimes varied by a factor of 4 between noon and midnight. A clear seasonality was observed for all of the parameters. However, while variations of phytoplankton and bacterial production paralleled those of temperature, bacterial abundance was low in midsummer and maximum in autumn. While no general pattern could be observed from the total data set, spatial gradients could interfere strongly with temporal changes. 相似文献
574.
575.
《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
576.
577.
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
578.
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
579.
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
580.
Arne Kesting Martin Treiber Martin Schnhof Dirk Helbing 《Transportation Research Part C: Emerging Technologies》2008,16(6):668-683
We present an adaptive cruise control (ACC) strategy where the acceleration characteristics, that is, the driving style automatically adapts to different traffic situations. The three components of the concept are the ACC itself, implemented in the form of a car-following model, an algorithm for the automatic real-time detection of the traffic situation based on local information, and a strategy matrix to adapt the driving characteristics (that is, the parameters of the ACC controller) to the traffic conditions. Optionally, inter-vehicle and infrastructure-to-car communication can be used to improve the accuracy of determining the traffic states. Within a microscopic simulation framework, we have simulated the complete concept on a road section with an on-ramp bottleneck, using empirical loop-detector data for an afternoon rush-hour as input for the upstream boundary. We found that the ACC vehicles improve the traffic stability and the dynamic road capacity. While traffic congestion in the reference scenario was completely eliminated when simulating a proportion of 25% ACC vehicles, travel times were already significantly reduced for much lower penetration rates. The efficiency of the proposed driving strategy even for low market penetrations is a promising result for a successful application in future driver assistance systems. 相似文献