车用柴油机微粒捕集器热再生的一维数值模拟

以壁流式蜂窝陶瓷微粒捕集器(DPF)为研究对象,建立了DPF一维热再生过程的数学模型。对陶瓷孔道内微粒(PM)的燃烧过程及其温度分布进行了模拟,结果表明,再生过程进行到一半时,DPF载体的温度达到最大值。设计时必须保证在此温度下DPF的载体壁面不会发生破裂,以免影响其正常工作。     

高速公路长寿命沥青路面结构研究

介绍长寿命路面在国内外的发展状况,阐述其结构特点,从设计理念、设计指标和设计要求上对其设计进行探讨,最后进行经济效益分析.     

寓于语境的英语词汇教学

针对当前大学生的英语词汇学习存在弊端这一问题,提出英语词汇教学应分为直接词汇教学和间接词汇教学,间接词汇教学应结合语境来进行。并结合话语语境、情景语境、文化语境与词汇外延意义和内涵意义的关系,分析语境对词汇教学的影响及实际意义。     

Vehicle modeling with nonlinear tires for vehicle stability analysis

The dynamic stability of a vehicle depends on various maneuvering features, such as traction, braking, and cornering. This study presents nonlinear vehicle models for estimating the stability region and simulating the dynamic behavior of a vehicle. Two types of vehicle models were found by considering the degrees of freedom and linearity. A simple model with nonlinear tire dynamics is useful for determining the stability region, while a complex model (a multi-body dynamic model in MSC.ADAMS) is appropriate for carrying out accurate simulations. Actual data for a mid-sized passenger car were used, and the models were validated by comparison with test results.     

Risk analysis of vessel traffic systems

A risk analysis approach to the capital planning of vessel traffic services (VTS) is embedded within the benefit-cost methodology. The method is discussed in the Canadian context, but has already been used to plan the Hong Kong VTS system. Recently, in response to the Exxon Valdez oil spill, the US Congress asked for a study of the requirements for VTS systems in American ports and waterways, and the US Coast Guard chose to apply our risk analysis approach to their study.     

Decision making processes governing federal expenditures within the transportation sector of the United States

The current process for allocating federal funds within the transportation sector of the U. S. is dominated by concerns for territorial equity, administrative feasibility, technical feasibility, and national defense. Economic efficiency as a long range objective is conspicuous by its absence except insofar as it is embodied in the desire to E" BORDER="0">promote the commerceE" BORDER="0"> of the nation.Federal allocations for highways, waterways, and maritime subsidies are declining relative to urban public transit, and Coast Guard navigation related expenditures. Environmental considerations and obvious failure in the case of maritime subsidies appear to be the major reasons. Airport and airway allocations will be subject to the same negative forces.The next massive transportation program to appear in the federal budget other than urban public transit is likely to involve the national railway system. The big question here is how the money will be handed out. Economists and planners so far appear to have had little interest or impact in this difficult and crucial area of public decision making.Former Senior Economist, Policy and Plans Development, Office of the Assistant Secretary for Policy and International Affairs, U. S. Department of Transportation. Presently Advisor to the Government of Ethiopia with the Harvard University Development Advisory Service.     

Port investment appraisals for the 1990s

A major challenge facing port managers is how to remain competitive in the tough economic climate of the 1990s. More than ever, they will have to pay close attention to the type of investments they choose. This article provides some practical advice on port investment appraisals. It covers three critical areas of concern: the scope of the appraisal, appraisal methods and where the appraisal process fits into the port's overall strategy.     

Running for the 7:45: The effects of public transit improvements on commuter stress

This research project took advantage of the implementation of a major mass transit improvement by New Jersey Transit which provided a "one-seat ride" into New York City for many commuters who previously had to transfer in Hoboken in order to take Port Authority Trans Hudson (PATH) trains into New York City. The creation of this new service provided a natural experiment in which some riders switched to the new route, while others continued to use their previous route. We studied psychological and psychophysiological responses to these commuting options, using a quasi-experimental, pre-post change, field research design.We found that riders on this new line had lower levels of stress, as multiply measured, than they had earlier, before the advent of this new train, or than did other riders currently using the Hoboken-PATH option. The stress effects seemed to be mediated by the time of the trip – that is, the reduced trip time of the new, direct service seemed to be a primary factor in the reduced stress to riders. Predictability of the trip was also inversely correlated with stress, but did not distinguish between the commuter groups. These results were largely replicated with a student group who rode the same lines acting as simulated commuters.     

An evaluation of web site services in liner shipping in Taiwan

This paper empirically evaluates web site services in the liner shipping industry based on the service requirements of the user firms, i.e., shippers. The results suggest that shippers perceive tracing to be the most important service attribute of a web site, followed by customs response, vessel schedules, and electronic document service. Based on the concept of market segmentation, we employed cluster analysis to classify users (shippers) of web site services provided by liner shipping companies into four segments, namely support and performance services oriented firms, equipment information oriented firms, performance information oriented firms, and transaction services oriented firms. Theoretical and practical implications of the research findings are discussed.