工字钢组合梁架空设备稳定性检算及应用

主要介绍了在营业线架空线路施工中常用的工字梁安全稳定性的检算依据、方法,并用实例进行了计算,对其应用条件、特点及改进措施作了阐述。     

中小城市自行车交通探讨

该文通过对洛阳市交通现状进行分析,提出了自行车交通存在的问题,并指出自行车交通不管是现在还是在将来相当长时期内仍将在我国中小城市交通构造中占据重要位置,如何认识和解决自行车交通问题对未来交通的发展有重要意义。     

铁路行车调度指挥仿真系统

铁路调度指挥仿真系统是一个分布式协同工作的递阶分散自律控制系统,由决策层、管理层、执行层和设备层组成,采用部分实物仿真的方式设计模拟系统的软硬件环境。仿真系统设计的关键技术包括:进路表的自动生成算法、控制命令自动生成算法、列车车次自动追踪运行算法、列车群自动追踪运行算法、计划自动调整算法、干扰源仿真模拟和仿真时空一致性控制等。通过选取铁路实际运营的计算机联锁系统和电气集中联锁系统、车站、自动闭塞区间和计轴半自动闭塞区间线路,构建近1∶1的仿真试验环境。按照铁路行车调度指挥实际需求、相关技术标准以及现场实际投入使用的行车调度指挥系统,对仿真系统进行了功能、性能测试。对实际应用中出现的故障进行了模拟分析。结果表明:仿真系统对于实际应用系统的研发、开通运营、日后的维护和系统升级具有不可替代的作用,它能够极大地缩短开通前的调试时间,方便故障分析和各种条件下调度指挥方式的模拟,特别适合特定条件下应急预案的演练。     

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.     

Induced traffic and economic appraisal

Economic appraisal of major roads in the UK is based on a set of standard procedures and conventions. A central assumption has been that the volume and pattern of traffic in any given year is independent of the quality of service offered by the network — the fixed trip matrix assumption. Failing to consider induced traffic can have serious consequences for the accuracy and robustness of the measured traffic benefits from road improvements. Assessment of the wider economic benefits of roads, which is an important political imperative for road investment, is also made more difficult. Two conclusions are reached. Variable trip matrix methods need to be introduced for the appraisal of major road schemes, and scheme appraisal needs to be complemented by a more strategic area-wide approach to evaluation. In responding to its advisory committee (SACTRA), the UK Department of Transport has accepted the first of these conclusions and is cautiously favourable to the second.     

珠江口水域航行安全现状分析与通航管理对策

随着海上运输的发展,大型船舶尤其是巨型油轮数量的增加,船舶航速的提高,珠江口水道越来越拥挤,使得加强船舶动态的监控管理、保障船舶航行安全、维护水域船舶通航秩序、预防和减少水上交通安全事故与水上环境污染等问题,越来越受到人们的关注。     

工业企业常用安全评价方法概述

安全评价是从事故发生的可能性、影响范围与损失程度等方面人手，运用系统工程理论去识别、分析和评价固有或潜在的危险因素。常用的安全评价方法按评价内容可分为过去状态的安全评价(如事故树分析、事件树分析、因果分析)、现有工艺过程和生产装置的综合安全评价(如按企业固有危险性和现实危险性两步评价、评价目标体系的数学模型计算法)以及系统设计阶段的安全评价。选择中应根据企业生产过程的不同阶段，要注意消化吸收国内外科学实用的方法，不一味的求新；要根据安全系统的复杂性考虑多种方法综合评估，或把不同方法结合起来；评价过程必须遵循科学性、公正性和针对性原则。     

实现速度控制的调车机车监控记录系统

调车机车无线信号安全监控系统将站场调车进路的开放、轨道电路的占用、道岔的位置、调车作业单、调车限制条件、平面调车的调车长控制命令等信息，通过无线信道传送到调车机车上，实现调车信号、调车进路及作业单等在机车上的实时显示，并由此产生联锁控制命令，控制作业机车实现对调车作业的安全防护和作业数据记录，可以有效地解决调车与机车监控装置联锁，保证站内调车作业的安全。该系统具备一次模式曲线无线传输的防护和列车自动控制的功能。     

基于滞回分配的VBR视频流量带宽管理方案

基于VBR视频流量预测提出了一种新的动态带宽分配算法———滞回算法。与Girish提出的门限算法和Youssef提出的基于GOP场景检测的带宽分配方案相比,对缓存尺寸的需求、信元丢失率等性能有明显提高。大量的仿真表明,该算法能够以较低的开销(带宽重分配次数百分比≤2%)同时兼顾了CLR和带宽利用率,而且只有在缓存队长超过迂回门限时才触发带宽重分配过程,有利于在线实现。     

大秦线开行2万t重载列车对湖东编组站到发场的影响

大秦线开行2万t重载列车,采用4台机车分散联挂的形式。湖东编组站重、空车到发场到发线的布置形式应为:2条重车线或2条空车线夹1条机走线为1束,每束到发线和机走线之间沿列车到达方向设置3处9号道岔,咽喉区至腰岔、每处腰岔和相邻的腰岔之间的有效长度为700m。以C76,C80及性能更好的适型车辆检算湖东站到发线有效长度,应达到2800m及以上。现有技术设备的特征、相邻线路技检作业分工方式、2万t重载列车的机车连挂方式、机车运用和组织方式、列车到达均衡程度、列检能力等是影响湖东站到发线通过能力的主要因素。应进一步优化和合理安排相关线路的行车组织方案,并对现行的技检作业分工方式和机车运用方案进行重新调整。采用重车方向列车在湖东站不换挂机车,各装车点到达湖东站的2万t、1万t列车均在装车地或集结地进行全面的技术检查方案。在此条件下,湖东站重车场到发线数量设置为6条基本可以适应远期大秦线运量的需求。