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1.
This paper uses observations from before and during the Stockkholm congestion charging trial in order to validate and improve a transportation model for Stockholm. The model overestimates the impact of the charges on traffic volumes while at the same time it substantially underestimates the impact on travel times. These forecast errors lead to considerable underestimation of economic benefits which are dominated by travel time savings. The source of error lies in the static assignment that is used in the model. Making the volume-delay functions (VDFs) steeper only marginally improves the quality of forecast but strongly impacts the result of benefit calculations. We therefore conclude that the dynamic assignment is crucial for an informed decision on introducing measures aimed at relieving congestion. However, in the absence of such a calibrated dynamic model for a city, we recommend that at least a sensitivity analysis with respect to the slope of VDFs is performed. 相似文献
2.
Dr Baha Bin Husein Azzee 《Maritime Policy and Management》2013,40(3):229-234
This paper discusses and assesses the complex process of change that has occurred in East Europe over thc last five years, and attempts to relate these changes to the shipping sector. Conventional mathematical methods are discussed as inappropriate in analysing economic, social and political developments and the technique of conceptual modelling is used, borrowed from other disciplines including those of environmental appraisal and computer sciences. The main linkages are discussed with particular reference to the Polish shipping sector, with specific analysis of the legal, managerial, spatial, economic, political, social and organizational contexts. The dominant themes of change are drawn out in an attempt to predict the impact on the Polish shipping industry in general and the three main State companies–Polish Ocean Lines (Liner Shipping); Polish Steamship Company (Bulk/Tramp) and Polish Baltic Ferries– that dominate the market. 相似文献
3.
Q-DAS CAMERA(R) Concept持柔性和模块化应用,既可以应用于单个工作场所,也可为部门级、工厂级或区域级的综合系统提供解决方案. 相似文献
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The transport demand in most major cities around the world can only be met with a high‐quality public transport system. The requirements on bus, rail, underground and tram systems are manifold with reliability and efficiency as the key factors. The service operating hours and the size of the network are often extended in order to serve the needs better. Further, most metropolitan areas are trying to provide more incentives for citizens to leave the car at home and use the local transit systems instead. The reasons are well known. Not only does a public transport system only make economical sense if it is well used, but most urban areas with a high car‐dependency face at least three major problems; safety, congestion, and pollution (noise and air pollution, land separation, etc.). It is generally recognised that to decrease car usage and to increase public transport usage a stick & carrot approach is needed. The London congestion‐charging scheme is an example since all revenues collected by the scheme are put into the improvement of bus and underground services. 相似文献
5.
EPBi系统使用了经市场验证的EPB系统的大部分部件,把所需的电子部件和软件集成在一个车辆现有的控制单元中,既实现系统效益,确保产品质量和稳定性,又减轻重量,进而节省燃油消耗。 相似文献
6.
Peter Mueller Mark Griffiths 《经济导报》2007,(2):82-87
尽管癌症治疗在过去的十多年取得了显著进展,但肿瘤学仍属于目前最不能满足临床需要的学科领域。在过去十多年里,临床药理学的进步和研发活动方面的巨大投资使得“癌症治疗”发展为“治疗过程研究”的数量急剧增加。但事实上,癌症和其他慢性疾病一样,治疗效果都很差,由此很多大型医药公司和生物制药公司都比以往更大力度的投入资金,用于肿瘤学和其他强效候选药物的研发上。[第一段] 相似文献
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8.
Dirk E. Smith Robert E. Benton 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1996,26(2):127-142
Advanced Vehicle Control Systems (AVCS), when realized, should substantially increase the convenience and safety of highway travel. Automated lateral control is an important step in the realization of AVCS. Much research has been concerned with lateral control during low-g maneuvers. However, before passengers' lives are in the hands of any automated laterally-controlled vehicle, the vehicle controller must be designed to respond to emergency situations where high-g maneuvers may be necessary.
This paper presents the development of a nonlinear-gain-optimized (NGO) controller for emergency automated lateral control of four wheel steered automobiles. Continuous gain equations (GE) are used to account for changes in the vehicle speed. The NGO controller uses a linear vehicle/tire model to define the state model. The response of a nonlinear vehicle/tire model is used to choose the performance index that optimizes the feedback gains for high-g emergency maneuvers at discrete speeds. Continuous gain equations are then derived as least-square approximations to each set of gains.
The performance of the four-wheel-steer continuous gain equations (4WS-GE) controller is compared to that of a two-wheel-steer continuous gain equations (2WS-GE) controller. Significant improvements in vehicle response are realized by using the 4WS-GE controller. The robustness of the controller's performance is examined with respect to changes in tire parameters and changes in vehicle mass. 相似文献
This paper presents the development of a nonlinear-gain-optimized (NGO) controller for emergency automated lateral control of four wheel steered automobiles. Continuous gain equations (GE) are used to account for changes in the vehicle speed. The NGO controller uses a linear vehicle/tire model to define the state model. The response of a nonlinear vehicle/tire model is used to choose the performance index that optimizes the feedback gains for high-g emergency maneuvers at discrete speeds. Continuous gain equations are then derived as least-square approximations to each set of gains.
The performance of the four-wheel-steer continuous gain equations (4WS-GE) controller is compared to that of a two-wheel-steer continuous gain equations (2WS-GE) controller. Significant improvements in vehicle response are realized by using the 4WS-GE controller. The robustness of the controller's performance is examined with respect to changes in tire parameters and changes in vehicle mass. 相似文献
9.
Dynamic modeling of an autonomous underwater vehicle 总被引:1,自引:0,他引:1
Chuanfeng Wang Fumin Zhang Dirk Schaefer 《Journal of Marine Science and Technology》2015,20(2):199-212
10.
Mohsen Babaei Jan‐Dirk Schmöcker Navid Khademi Ahmad‐Reza Ghaffari Ali Naderan 《先进运输杂志》2016,50(6):1252-1271
This paper introduces the taxi route network design problem (TXRNDP) for a fixed‐route taxi service operating in Iran and, in similar form, in various other developing countries. The service operates fairly similar to regular transit services in that vehicles are only permitted to follow a certain predetermined route on the network. The service is provided with small size vehicles and main features are that vehicles only depart if full and that there are no intermediate boarding stops. In Iran the service attracts a high modal share but requires better coordination which is the main motivation for the present study. We develop a mathematical programming model to minimize the total travel time experienced by passengers while constraining the number of taxi lines, the trip transfer ratio and the length of taxi lines. A number of assumptions are introduced in order to allow finding an exact rather than heuristic solution. We further develop a linear programming solution to minimize the number of taxis required to serve the previously found fixed‐route taxi network. Results of a case study with the city of Zanjan, Iran, illustrate the resulting taxi flows and suggest the capability of the proposed model to reduce the total travel time, the total waiting time and the number of taxi lines compared to the current taxi operation. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献