Towards improving resilience of cities: an optimisation approach to minimising vulnerability to disruption due to natural disasters under budgetary constraints

Transportation - In recent years, climate change emerged as a dominant concern to many parts of the world bringing in huge economic losses disturbing normal business/life. In particular cities are...     

柴油发动机的最新排放控制技术

应用了电子学最新发展成果的新型柴油发动机和柴油燃料将会颠覆你以前对柴油车的所有偏见。不仅如此,它还将为汽车维修行业提供新的赢利机会。     

先进的发动机气门电子控制技术

<正>本文译自美国MOTOR杂志。当我们期待着实用化的车用动力装置取代传统的汽油内燃机之时,汽车工程师们也仍在继续努力探索提高传统汽车发动机性能的方法。菲亚特公司的多气门电子控制系统算得上是最新成果的实例。     

北美铁路货车转向架的发展(续一)

9 一系悬挂转向架 一系悬挂转向架也叫做轴箱弹簧转向架，通常是作为提供给特种运用服务的优质转向架。在这种型式转向架上，其主弹簧和阻尼是装在轮轴系统与转向架构架之间的，因而垂向和横向弹簧挠度和阻尼与最小的簧下重量一起就直接作用于转向架轮对运动。随之带来优良的垂向和横向运行品质，以及高速蛇行稳定性和良好的曲线通过性能。 提供的这种基本结构是在运用于欧洲的转向架系列结构基础上设计的，在最新专门设计中，还结合了摆吊式横动和迫导向功能。图18为一种迫导向径向转向架。     

Logistical restructuring and road freight traffic growth

The forecasting of road freight traffic has relied heavily on the close correlation between GDP and road tonne-kilometers. It has not been rooted in an understanding of the causes of freight traffic growth. The research reported in this paper has investigated this process of traffic growth in two ways: first, by analysing official data on the production, consumption and movement of food and drink products, and second, by conducting a survey of the changing freight transport requirements of 88 large British-based manufacturers.The analysis of secondary data shows how, in the food and drink sector, the relationship between the real value of output and road vehicle-kms hinges on four key parameters: value density, handling factor, average length of haul and consignment size. An attempt is made to explain variations in these parameters.The survey of manufacturers suggests that the growth of lorry traffic is the net result of a complex interaction between factors operating at four levels of logistical management: strategic planning of logistical systems, choice of suppliers and distributors, scheduling of product flow and the management of transport resources. Changes in the frequency and scheduling of freight deliveries in response to tightening customer service requirements and just-in-time management appear to have become a more prevalent cause of freight traffic growth than the physical restructuring of logistical systems. Manufacturers anticipate that their road freight demand will broadly increase in line with sales and be largely unaffected by road transport cost increases at the levels currently proposed. The paper concludes by examining their likely reactions to a much sharper increase in the cost of road freight movement.     

Optimal Control of the Tractor-Semitrailer Truck

This paper is concerned with the braking performance and the handling behavior of the tractor-semitrailer truck under optimal braking. Optimal control theory is used in order to deal with the problem and a combination of the steepest descent method and the Davidon Fletcher Powell method is used to solve it numerically. Results for some chosen braking maneuvers are obtained for a nonlinear truck model which has 14 degrees of freedom. These results show that, for the chosen maneuvers an idealized anti-skid braking is close to being optimal in the sense defined in this paper. Implementation of an idealized anti-skid braking on the tractor-semitrailer truck, however, may be not desirable.     

车载多路传输网络的结构特点与协议

在我们开始了解数据网络的结构和协议时,是躲不过总线网络的,因为下一代网络可能就是快速传递数据的时代。     

Accelerated Service Life Testing of Automotive Vehicles on a Test Course

The accelerated service life testing of automotive vehicles for durability to road roughness induced dynamic loads is often accomplished in the laboratory using road roughness simulation facilities [1-5]. However, such tests can also be accomplished by a carefully designed field operation on a test course [6], where both the speed of the vehicle and the roughness of die test course become variables that control the degree of the test acceleration. Field tests are generally harder to control than laboratory tests, but offer a greater degree of realism since the vehicle is fully operational during the test exactly as it will be in service. This paper formulates the criteria for accelerated service life tests on a test course, evaluates the assumptions that must be enforced to obtain valid results, and explores the sensitivity of the results to the critical test parameters, namely, the vehicle speed and the road roughness severity of the test course relative to the service environment.     

水平连铸QCr0.5铜合金线电磨损性能研究

对水平连铸工艺制备的QCr0.5铬青铜合金接触导线坯料经过固溶、时效、冷轧处理后,研究接触导线的微观摩擦性能与受流滑动磨损行为,分析不同电流作用下接触导线的磨损形貌及磨损特征。微观划擦测试表明:通过加入合金元素Cr,改变了接触导线合金材料的微观组织,提高了合金材料的强度、抗软化性能和抗变形能力,改善了合金的磨损性能,降低了摩擦系数;水平连铸QCr0.5铬青铜合金接触导线的硬度为165.5HV,最大摩擦系数为0.155,最大压入深度为2.68μm。电磨损测试表明:水平连铸QCr0.5铬青铜合金接触导线未加载电流时的磨损主要以磨粒磨损和黏着磨损为主,载流条件下的磨损主要是黏着磨损、磨粒磨损和电侵蚀磨损。磨损率测试结果显示,水平连铸QCr0.5铬青铜合金接触导线磨损性能明显优于商用Cu-Ag接触导线。