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输气管道试压是对管道施工质量、管材性能及管道整体质量的一次综合检验,也是投产前对管道系统能否在设计压力下安全运行的最后一次检验。因此,基于管道试压在管道工程建设和运行中的重要意义,从试压介质、试压管段划分和强度试验压力等方面对试压工作进行了论述,并介绍了国内外输气管道试压标准在以上方面的相关规定,分析了不同标准之间的差异,通过对比指出了目前国内管道试压水平与国外的差距及今后的发展方向。 相似文献
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在管道安装等工程中,准确地估算试压装水时间对工程很重要。文中利用流体力学理论对压力管道的装水过程进行模型化,从而选取适当的理论计算公式,并根据流动状态选取适当的计算参数,对沿程阻力损失等还需要采取迭代的方法进行计算,从而得到了较准确的结果。通过计算发现,计算结果的准确性取决于建立适当的水力学模型以及合理边界条件的设置。 相似文献
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文中研究了天然气长输管道高强度试压在国内的可行性。通过对国外天然气长输管道普遍采用高强度试压的现状分析,结合国内的标准规范及试压现状,提出了国内天然气长输管道高强度试压具备发展潜力。重点分析了高强度试压时管道缺陷的暴露、管材的质量要求、管道的塑性变形、管道承压能力逆转4个关键问题,证明了高强度试压在国内是可行的。 相似文献
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天然气管道试压过程中可能发生泄漏,及时、准确地确定管道的漏失位置并进行修复,确保管道按时投产运行,是管道试压阶段的一项十分重要的工作.文中从管输天然气理论出发,结合管道试压过程的工艺特点,给出了描述输气管道泄漏的一个数学模型;应用偏微分方程数值反演方法,给出了确定泄漏位置、漏失函数的数学表达式;并给出了数值模拟的方法和步骤.文中提供的理论方法不仅适用于输气管道试压阶段的泄漏检测,而且可以推广到运行中的输气和输油管道的泄漏检测中去. 相似文献
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当已建碳钢管海底管道因为延寿、使用功能变化或者其他原因导致设计基础发生变化时,为确保碳钢管海底管道继续安全可靠的运行,需要对其结构强度进行评估。对于已建碳钢管海底管道结构强度的评估方法,国际上相关设计标准仅给出了指导意见。文中根据评估时间的不同,将已建碳钢管海底管道结构强度评估分为寿命期内评估和超过寿命期评估两大类,并系统总结了这两类结构强度评估的工作内容和评估方法。 相似文献
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Pedestrians as compared to vehicular traffic enjoy a high degree freedom of movement even in heavily congested areas. Consequently, there are more alternative links available to pedestrians between a given origin‐destination (O‐D) pair. This paper describes a study done by the University of Calgary to evaluate the factors affecting the choice of route on intra‐CBD trips or trips within the Central Business District (CBD). An origin destination survey conducted in downtown Calgary, Alberta enabled the identification of the most significant factors influencing the choice. These factors were analyzed in relation to the physical characteristics of the location, personal characteristics of the trip maker and the type of the trip. It appears that most people chose the shortest link and factors such as the level of congestion, safety or visual attractions were only secondary. This suggests that the length should be made a major consideration when planning and designing pedestrian links. 相似文献
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Joseph N. Prashker 《Transportation》1979,8(4):329-346
Reliability of travel modes was found to be the most important characteristic of transportation systems in several attitudinal investigations of individual travel behavior. This paper represents the first part of a research effort aimed at gaining a better understanding of the characteristics of reliability of transportation modes in urban travel. In this research, reliability characteristics are identified; their importance relative to each other is assessed, and an insight into possible structure of an objective reliability index is discussed. The research is based on perceived values of reliability, which were identified through a large attitudinal survey conducted in the Chicago metropolitan area. 相似文献
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本文阐述了混合动力列车的技术特点及其相应优势与劣势,同时介绍了其在国内外的研究动向,并对其应用前景进行了展望。尽管该类新型铁道车辆的续航能力、电池寿命以及成本等相关问题目前仍有待改善,但以其对城市环境的美化作用与优越的舒适驾乘性能,以及高效节能、绿色环保的显著优势,依然不失为一类充满前景的新型轨道交通运输方式。 相似文献
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天然气自动计量系统有多种组态软件,由于软件的不相通性,造成了计量系统数据采集的通用性差、数据传输与入库的时效性差、数据利用的可靠性低.结合各组态软件的实际情况,从设计上充分利用Oracle大数据处理能力以及Partition(分区表)的特性,实现历史数据的存储,应用WebService与COM+数据访问组件提供多层数据访问架构,采用OPC与DDE工业数据交换协议,实现了各站场计量数据的实时上传,为连续数据采集和实时监控提供了可能,节约了改造成本. 相似文献
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This paper estimates the efficiencies and productivity changes of 12 international airports in the Asia-Pacific region based on data from 1998 to 2006. We apply stochastic frontier analysis (SFA) to compute efficiency estimates and use the Malmquist productivity index (MPI) to analyze productivity changes. We use the SFA model with a translog-type production function after testing the statistical hypotheses. According to the results of the SFA hypothesis tests, airports have experienced a technological regression; the deviations from the efficiency frontier are caused more by technical inefficiency than random noise. However, the inefficiency was found to decrease. The MPI reveals a declining trend resulting more from technological change than from efficiency change, with a decrease in inefficiency. Taken together, both the hypothesis tests and the MPI not only provide consistent conclusions, but also suggest that airports should concentrate on technological progress. 相似文献
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明确埋地管道防腐保温层的技术评价标准,对埋地钢质管道的安全运行,延长管道使用寿命具有重要意义。为了对埋地管道防腐保温层做出有效评价,从间接检测与开挖检测2个方面,结合现场检测数据,提出了基于防腐保温层的电流衰减率、绝缘电阻率、质量状况与厚度的分级评价标准及基于4种评价指标的综合评判方法。工程实践表明,该评价标准对防腐保温层是否存在失效能做出有效判断。 相似文献