阴极保护技术及其在埋地钢质管道中的应用

介绍了阴极保护技术的原理与常用方法.介绍了阴极保护技术在国内油气管道中的重要作用.并对3个实例的防蚀效果进行评价,验证了阴极保护技术显著的经济技术优势.建议在埋地钢质管道中大力推广应用.     

并行敷设旧管道的防腐蚀维护

对某并行敷设旧管道防腐层绝缘性、阴极保护技术水平、均压线分布状况进行了分析，举例阐述了并行敷设旧管道在后期维护中存在的防腐蚀技术不均衡、防腐层大修不均衡等维护措施不利的问题，探讨了防蚀保护效果不佳的基本原因，并简要论述了提高并行敷设管道防腐蚀效果的措施。     

石油储罐防腐蚀技术现状

地上钢质石油储罐因采用防蚀技术不当,腐蚀泄漏事故时有发生。为了解国内外石油储罐现有的防蚀技术水平,本文较为详细论述了储罐防蚀技术中常用覆盖层保护和阴极保护技术现状,分析了国内石油储罐现有防蚀技术存在问题,并提出了一些发实可行的建议。     

基于检查片的埋地管道阴极保护检测与评估

阴极保护作为埋地管道的主要防护措施,在管道保护方面起到重要作用。为了准确地评估管道阴极保护效果,文中介绍了管道阴极保护检查片检测技术,重点阐述了国内外发展状况以及利用检查片检测管道阴极保护效果的优势,分析了目前国外对检查片检测技术的改进方式和评价准则,对埋地管道阴极保护检查片检测评估技术提出了展望,并成功应用于某长输管道阴极保护的检测与评估。     

基于防腐层质量和土壤对埋地管道阴极保护的研究

为了确保东黄复线输油管道的安全运行,对该埋地管道进行了完整性检测与评价,并对管道的阴极保护情况做了分析和研究。基于管道敷设环境的调查和埋地管道防腐层整体状况的检测,对管道防腐层整体质量和IR降对管道阴极保护的影响进行了研究分析,发现管道防腐层质量和IR降对管道阴极保护具有很重要的作用,为进一步提高和改善在用埋地管道的阴极保护效果提供参考。     

长输管道站场埋地管网区域阴极保护技术的应用

为了促进油气管道站场区域性阴极保护实施达到预期效果,文中采用综合归纳总结的方式分析了区域阴极保护设计应用的技术特点,介绍了区域阴极保护技术的设计原则和计算内容,提出了区域阴极保护技术实施中需要关注的问题和技术对策,对于站场区域阴极保护技术的开展具有一定的借鉴作用。     

城镇燃气管道腐蚀防护对策研究

文中研究了城镇燃气管道腐蚀防护的现状,发现防腐层保护、阴极保护等方面存在问题。防腐层损伤多发生在管道安装施工过程中,且质量较差防腐层因使用时间较长而存在安全隐患。存在阴极保护效果测试不准确以及附属设施安装和维护不到位等问题。基于腐蚀防护措施问题,从防腐层保护、阴极保护和杂散电流防护方面提出对策建议。     

管桥油漆防蚀浅论

油气长输管道的跨越部分，为干线管道的关键结构之一。管桥的防蚀是一个重要课题。本文简述了国外桥梁用油漆以及国内在管桥防蚀涂料选材等方面存在的问题。最后，结合生产实际提出油漆防蚀中涉及的多层涂层、正确判断油漆失效程度、严格施工程序、控制施工质量等方面的建议。     

应用阴极保护电流密度评价阴极保护的有效性

管道阴极保护的参数主要有自然腐蚀电位、阴极保护电位、保护电流密度等.正确选择和控制这些参数是决定管道阴极保护效果的关键.文中结合相关标准,通过不同防腐层电流密度值大小对防腐层进行分级,对电流密度异常进行分析,从而判断防腐层有效性,结果发现阴极保护电流密度在评价防腐层性能与阴极保护有效性方面具有很强的指导意义,但关于阴极...     

站内埋地管道阴极保护实施中的几个问题

简单介绍了我国管道企业站（库）内埋地管道阴极保护技术现状，对站（库）内管道阴极保护实施过程中的绝缘、阳极分布、调试、安全等问题提出了解决、处理措施。     

Survey of R&D in PRT systems

A survey of research and development in advanced transit has been made by Chalmers University of Technology in Gothenburg in cooperation with Trans21 in Boston. Summary findings are reported for fourteen academic research programs and ten development programs for PRT. An earlier version of this paper was presented at the International Conference of PRT and other Emerging Systems held in Minneapolis in 1996.     

管道风险分析指数评分法中分值调整初探

管道风险分析指数评分法中重要步骤之一就是确定影响管道事故因素的权重,各个管道风险因素在整个管道事故中所占的权重是不相同的。针对目前管道风险分析指数评分法基本假设之一（各因素的分值范围都是0～100分）,为了更加客观、准确、合理地反映各个风险因素对于管道事故的影响程度,提出并论述了依据层次分析法的数学逻辑性进行综合计算得出管道风险因素的权重,然后对评分法中各个因素的最高分值,根据其权重不同进行相应调整,从而增强评价者对风险因素的认识和评判能力,提高管道风险评价结果的准确性。     

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.     

A century of evolution of the accessibility concept

The concept of accessibility has acquired numerous meanings along multiple dimensions during the century of its evolution. This essay argues for the salience of two dimensions: application-based and definition-based. In its application, accessibility has incorporated positive and normative dimensions which have varied in prominence over time. In its definition, accessibility has varied between a mode of evaluation incorporating measured mobility and proximity, on the one hand, and a predefined market basket of urbanist improvements to transportation and land use systems, on the other. Advocates of the accessibility shift should emphasize both the measured approach to accessibility and accessibility’s normative side.     

天然气站往复式压缩机活塞失效分析

针对天然气站往复式压缩机活塞的断裂事故,运用失效分析方法,开展了活塞断口扫描电镜分析、能谱和金相分析。根据断口形貌的电镜和金相观察结果,结合理论知识,分析确定了该活塞发生断裂事故的主要原因,即在特定工况下该活塞的材料缺陷是造成断裂的主要因素。     

中国城市道路规划方位性问题研究

文章结合中国的传统建筑文化理念和现代科学原理,从历史文化、能源节约、环境保护、房地产定价、交通安全等多方面分析研究了城市道路在规划和设计时所应遵从的定向规则。     

Predicting queue variability to enable analysis of overload risk

ABSTRACT

Predicting the risk of traffic demands and delays exceeding critical limits at road junctions, airports, hospitals, etc., requires knowing how both mean and variance of queue size vary over time. Microscopic simulation can explore variability but is computationally demanding and gives only sample results. A computationally efficient approximation to the mean is used in many modelling tools, but only empirical extensions for variance in particular situations have been available. The paper derives theoretical formulae for time-dependent and equilibrium variance, believed to be novel and to apply generally to queues covered by the Pollaczek–Khinchin mean formula, and offering possible structural insights. These are applied in an extended approximation giving mutually consistent mean and variance estimates with improved accuracy. Tests on oversaturated peak demand cases are compared with Markov probabilistic simulation, demonstrating accuracy (R^2?>?0.99) for typical random, priority-like (M/M/1) and traffic-signal-like (M/D/1) queues. Implications for risk analysis, planning and policy are considered.     

Planning guidelines for metro–bus interchanges by means of a pedestrian microsimulation model

The big paradigm for cities nowadays is to study the movement of pedestrians at the interface between metro and bus systems – metro–bus interchanges. When these interchanges are not well designed, walking is inefficient and can be unsafe for pedestrians. This paper analyses, by means of a pedestrian microsimulation model, metro–bus interchange spaces in order to propose planning guidelines for the city of Santiago de Chile. Specific objectives are (1) to identify the variables that provide efficiency and safety in those spaces; (2) to simulate different scenarios using the pedestrian simulation model LEGION; (3) to propose planning and design guidelines for pedestrian spaces at metro–bus interchanges; and (4) to contrast the recommendations in the recently opened terminal station on Line 1 of Metro de Santiago: Los Dominicos Station.     

生命大过天

文章介绍了广西壮族自治区公路管理局开展专项行动,治理以桥梁为重点的交通基础设施安全隐患的情况,针对在役桥梁、在建桥梁和农村公路桥梁存在的安全隐患提出了相应的治理措施。