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排序方式: 共有1113条查询结果,搜索用时 468 毫秒
991.
用Saber作交直交系统仿真   总被引:1,自引:0,他引:1  
用Saber仿真一个典型的交直交系统,介绍了其调试过程,给出了部分仿真结果,通过Saber仿真可使一个理想化的系统向接近实际的系统过渡。  相似文献   
992.
强调了机车电子制控装置热设计的重要性,从热设计的基本原理出发,探讨了在机车电子控制装置元件级、插件级、插箱极和机柜级热设计中减小热阻,提高散热特性的方法和冷却方式的选择原则及应用。  相似文献   
993.
994.
As urban systems increase in size and diversity, the factors which influence spatial change increase in number and their interactions become more complex. Increasing emphasis is thus being placed by some governments and agencies on regular reviews of policies and programs, to ensure that they are consistent with and facilitate the evolving urban form. Consequently, the monitoring of urban transport and activity systems is of increasing importance, to aid the review processes. This paper considers the progress which has been made in and use of procedures for monitoring urban, transport-related spatial changes. The specification, estimation and presentation of appropriate indicators is briefly discussed. Experience with the use of spatial monitoring procedures on data for two Australian cities has revealed several possible implications for transport investment practice and the development of monitoring and modelling procedures. These are discussed and the paper then indicates the approach which is currently being taken at ARRB towards developing a monitoring system.  相似文献   
995.
Earlier work by the Transport Studies Group of the Polytechnic of Central London on minibus development in Britain for the Transport and Road Research Laboratory provided a financial analysis of intensive urban minibus operation. This is taken as the basis for the application of cost-benefit analysis. Unit operating cost savings and passenger benefits are taken into account, using typical demand elasticities derived from earlier work. Particular attention is paid to the problem of evaluating passenger benefits for which waiting time at the roadside is not necessarily an adequate proxy. A direct survey of passenger waiting times indicates that these do not necessarily decrease when a higher-frequency minibus service replaces a conventional bus service but the improved convenience produces an increase in ridership which may be assessed in terms of a demand curve shift to estimate benefits obtained.  相似文献   
996.
In this paper, the author focuses attentioon on the so-called Melbourne Dockers War of 1971-3. Having descrided its mains events, he goes on to analyse of the unprecedented level of violence in the milieuof trade union elections. He traces this in part to the influx of criminal elements into the Federated Ship-Painters and Dockers Union of Australia (FSPDU) during the Second World War, and to the more immediate disagreement between rival factors concerning the direction which union activities, legal or othewise, should follow. He then assesses the implications of the episode for Australian politics, law and public administration in general.  相似文献   
997.
调查了铁路特有体力劳动工种13个,共209名,其中男工171名女工38名,按照GB3869—83体力劳动强度分级标准的要求进行。被调查人员年龄在18~55岁之间,平均30岁,平均身高1.6802m,平均体重61.62kg,平均体表面积为1.6727m~2。调查指标为劳动时间率与平均能量代谢率。求出各工种的劳动时间率T值与能量代谢率M值。然后求出劳动强度指数Ⅰ值。调查结果是6个工种为Ⅲ级,3个工种为Ⅱ级,4个工种为Ⅰ级。  相似文献   
998.
This paper models traffic congestion formation on highways and roads by recognizing the centrality of dynamical systems and using concepts from complexity theory as imbedded in the spin glasses analogue. Further, it explores the concept of how an increase in air pollution caused by vehicle exhaust emission can be traced to traffic congestion, specifically to the acceleration/deceleration of vehicles on the roads. First, spin glass is introduced and then by applying the two-dimensional xy Ising model and defining a Hamiltonian (based on Edwards-Anderson and Mattis models of spin glass systems) for a system of vehicles on the road, derivations are made of the specific friction of congestion and the bulk modulus of congestion using the Gibbs-Boltzmann statistic. Similarly using the interactions of vehicles with each other and the resulting accelerations and decelerations of vehicles as the basis for exhaust emissions, derivations are made of a specificity of exhaust emissions. These are analogues to the entropy models of thermodynamics. This series of derivations serves as an analytical model for detecting incidents of congestion and increase in air pollution due to exhaust emissions in transportation systems.  相似文献   
999.
The paper examines an international service sector (passenger sea ferry services between the U.K. and continental Europe) from the perspective of its competitive environment. Porter's five forces model forms the basis of the analysis of the market illustrated by recent develoments. Within this context the barriers to entry into and exit from the market are considered in detail. Recently, there have been many changes in market structure, and with increased competition, including that from the Channel Tunnel, it may be necessary to pool services. This will improve ferry competition with other forms of transport, but will require the brand awareness of ferries to shift from the ferry company to the ferry service offer. The service offer will need to be more clearly defined.  相似文献   
1000.
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