铁路信息化建设的战略思考

回顾我国铁路信息化历程,介绍铁路信息化的总体目标、思路.分析铁路信息化的特点、瓶颈和阻力,提出加快铁路信息化建设的建议.     

基于UML技术的精益船舶生产计划系统的设计

摘 要：精益船舶生产计划是船厂组织精益生产活动的直接依据,其系统开发与应用有迫切需求。由于精益船舶生产计划管理流程复杂,传统的结构化设计方法难以完成系统的分析与设计。本文介绍应用UML技术进行复杂的船舶生产计划系统分析与设计。首先,分析精益船舶生产计划的特征,提炼系统的功能需求;然后,结合精益船舶生产计划管理的业务流程,划分系统功能模块并理清系统工作流;最后,对系统进行静态建模和动态建模,完成整个系统的设计。     

Carbon dioxide emissions from diesel and compressed natural gas buses during acceleration

Motor vehicle emission factors are generally derived from driving tests mimicking steady state conditions or transient drive cycles. Neither of these test conditions, however, completely represents real world driving conditions. In particular, they fail to determine emissions generated during the accelerating phase – a condition in which urban buses spend much of their time. We analyse and compare the results of time-dependant emission measurements conducted on diesel and compressed natural gas buses during an urban driving cycle on a chassis dynamometer and we derive power-law expressions relating carbon dioxide emission factors to the instantaneous speed while accelerating from rest. Emissions during acceleration are compared with that during steady speed operation.     

Increase in particle number emissions from motor vehicles due to interruption of steady traffic flow

We assess the increase in particle number emissions from motor vehicles driving at steady speed when forced to stop and accelerate from rest. Considering the example of a signalized pedestrian crossing on a two-way single-lane urban road, we use a complex line source method to calculate the total emissions produced by a specific number and mix of light petrol cars and diesel passenger buses and show that the total emissions during a red light is significantly higher than during the time when the light remains green. Replacing two cars with one bus increased the emissions by over an order of magnitude.