Determinants of modal choice in freight transport

In the next few years, exciting developments in the field of freight transport are likely to occur. The Channel Tunnel will be perceived as giving railways much greater distance of operation, compared to the current train ferry to/from Great Britain. The further development of swap-body technology will allow easier modal transfer and the creation, in 1992, of a single market in Europe will transform the pattern of trade. All of these are likely to have significant impacts on modal choice, and hence modal split, in freight transport. Reappraisal by many firms of the modes of transport used is likely but will it result in a net transfer of freight from road to rail and, if so, to what extent? To answer such questions, an accurate and reliable method of predicting modal split is required. Research in the past has concentrated on the development of modal split models based on generalised costs. These fail to explain adequately the prevalence of road freight in the UK. From surveys of freight managers within industry, it is clear that models to date rely too heavily on the economic cost factor and too little on behavioural factors (Jeffs 1985). This paper derives from a recent study of freight transport modal choice from the standpoint of the transport decision-maker within the firm. It attempts to shed light on the actual parameters which should be incorporated into a modal split model. Many variables appear to exert an influence on modal choice decision-making process. However, it is possible to categorise them into six main groups, namely: customer-requirements; product-characteristics; company structure/organisation; government interventions; available transport facilities; and perceptions of the decision-maker him/herself. It is the interactions and inter-relationships between these which ultimately determine freight modal split. This study has shown that the relationship between the outcome of the transport decision process and the values of particular determinants of modal split is not straight-forward, due to the complexity and variety of interactions involved. Perhaps one of the main reasons for researchers' failure hitherto to develop a successful modal-split model has been the preoccupation with techniques that rely on the development of common metric (e.g. generalised cost), which has led to the exclusion of some important explanatory variables along quite different dimensions. Another important issue concerns the appropriate level of aggregation. In order not to reduce the explanatory power of the key variables, it is important to work at a disaggregate level, although this does make substantial demands on data. The use of factor analysis enables both the aggregation of information without loss of behavioural reality and the specification of variables in terms of a common metric. In conclusion, freight transport has usually been examined within too narrow a framework. It must be placed firmly within the context of the total industrial process. The demand for freight transport is directly influenced by the level, composition and geographical distribution of production and consumption activities. Freight flows are complex and so it is highly unlikely that a universal mode-choice model can ever be developed. Future research should, therefore, be directed towards developing partial models in response to specific needs of those involved in decision-taking in the freight sector.     

小波变换检测铁路交流计数信号的研究

傅氏变换在频域能对信号整体作频谱分析,很难直接分析交流计数信号。近年来兴起的子波变换可对信号进行多尺度分析,容易提取信号特征。本文是用子波变换方法分析铁路交流计数信号。并且通过采用不同的小波基对铁路交流计数信号进行仿真,通过分析比较找到合适的小波基,结合频谱分析的方法得到铁路交流计数信号的有关参数。最后给出仿真的例子。     

论三与四显示自动闭塞制式的选择

本文论述了在列车运行最高速度120km/h 的线路上,采用三或四显示自动闭塞制式的条件, 提出了应该优先考虑四显示自动闭塞制式的论点。     

Bragg光栅辅助非对称双芯光纤耦合器的研究

利用耦合模理论,推导出了其中一个纤芯写有Bragg光栅的双芯光纤耦合器的完整的耦合模方程。并通过打靶法和Broyden叠代数值解此耦合模微分方程组,分析了在不同失配条件下,双芯光纤耦合器各个端口的输出特性。得到了双芯光纤最佳的失配条件,在此条件下,光栅谐振波长处信号具有优异的反射特性,其他波长的信号则基本不发生耦合,接近无损地通过,此种耦合器具有非常小的插入损耗,是WDM系统中分插复用器的极佳选择。     

隧道内接触网悬挂固定方式研究

研究目的:隧道内接触网悬挂固定方式从高铁建设开始就一直存在争论,分析明确两种固定方式的各种性能,合理选用悬挂固定方式是高速铁路接触网设计的关键。研究结论:本文通过对预埋滑槽和后置锚栓两种接触悬挂固定方式的受力情况、零件性能、对隧道的影响、工程造价、施工方式、运营维护等多个方面的对比分析,得出:(1)预埋滑槽具有受力均匀、后期施工方便、接地可靠等优点,但工程造价高,且站前施工单位预留精度较差;(2)化学锚栓需要单独增加接地端子、调整余量小,但不受模板限制、定位灵活、施工精度可控和工程造价低;(3)结合国内的施工建设情况,建议优先采用后置锚栓的悬挂固定方式。     

城市轨道交通信号系统冗余技术分析

冗余技术是提高计算机系统安全可靠性的有效手段。介绍了城市轨道交通信号系统软件冗余与硬件冗余的原理,对采用的冗余技术进行了对比分析。分析了现代城市轨道交通信号系统中的冗余技术方案。以URBALISTM系统为例,从设备冗余与通信冗余两方面分析,指出冗余技术的合理设计对提高城市轨道交通信号系统的安全可靠性会产生重要影响。     

城市轨道交通信号电源系统配置方案研究

信号系统是保障列车运行安全、提高运输效率的关键设备,因此其电源系统必须稳定可靠。针对城市轨道交通土建造价高昂的现状和信号设备安全供电的重要性,有三种可供选择的信号电源配置方案。根据实际工程和后期运营维护中所遇到的问题,从安全性、可靠性及占地面积等方面,对三种方案分别进行了深入的探讨和分析。其中的信号集中式独立供电方案是目前最优的供电方案。     

基于无线通信的列车控制系统下后备模式的选择与应用

后备模式是城市轨道交通信号系统在设备故障时降级运行、保持一定运营秩序的一种手段,是保证故障列车安全退出运营的一种设备技术保障。介绍了基于无线通信的列车控制系统下不同制式的后备模式的构成、特点,阐述了后备模式的作用,并从系统设计和标准适用的角度,提出了选用后备模式的关键条件及应用效果。     

城市轨道交通基于通信的列车控制系统后备模式方案

对基于通信的列车控制(CBTC)系统在中央ATS(列车自动监控)或中央至车站的信息传输通道完全故障、轨旁设备故障、车-地通信设备故障、车载系统出现故障等各种可能故障情况下的后备控制模式做了分析。在后备模式下列车的运营能力和运行速度都不可能与正常进行状态相题并论,但能够确保信号系统在最少的人工参与条件下最大限度地实现列车安全与自动控制,这才是后备模式的意义所在。     

广州地铁5号线列车自动报站广播的实现与改进

介绍了广州地铁5号线列车自动报站广播功能的实现逻辑,对自动报站广播存在的问题进行了分析,提出了改进措施。经过改进,5号线列车具备了较为完善和稳定的自动报站广播功能。