共查询到20条相似文献,搜索用时 818 毫秒
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(接上期) 4.1开孔 在对施工作业的管段两端分别开出一个孔是为封堵头塞入管道内进行截堵介质和介质通过这个孔从设置的临时旁路上流通之用. 安装开孔机,开孔机的连接盘与支架上的连接器连接并密封,开启支架上扇形阀,操纵开孔机将开孔刀上的中心钻伸抵管顶就可开始开孔.开孔时,顺时针转动操纵手柄,驱动钻杆旋转,钻杆上装有一对差动内外齿轮,外齿轮的内孔上车有T型螺牙,螺牙又与固定在钻杆上的螺套啮合.带T牙的外齿轮置放在机壳内只作旋转运动,钻杆旋转时通过差动齿轮驱动固定在钻杆上的螺套,从而使钻杆在旋转的同时又作轴向差动移动,开孔刀实现切削开孔.钻杆旋转一周刀具切削进给Xmm,当更换差动齿轮的齿数比时可实现不同的差动进给量. 相似文献
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燃气管道不停输带压开孔封堵技术的特点为作业全程都在密封状态下进行,安全可靠,能保证正常供气,无资源浪费。该技术的核心设备有:开孔机、封堵器、下堵器、夹板阀、管件。文中着重介绍该技术在钢管型燃气管道的应用原理及实际作业中的操作规程,并介绍了其在实际应用中的不足。 相似文献
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埋地管道铺建时预留的分支管道接口不合适,需要在管道带压正常运行的状态下进行开孔施工.介绍了埋地燃气管道带压开孔技术的专用设备组成、操作方法、步骤和技术要点.实践证明:这项带压开孔技术的应用会更加广泛. 相似文献
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气囊式封堵是管道不停输封堵技术中的一种新的方式,它适用于城市低压燃气管网管线和供水管道的带压开孔封堵作业。橡胶气囊式封堵的关键技术是气囊的结构形式和被封管道内部气囊所处位置的预先清理,即开孔切削时铁屑散落于管道内腔底部和管道内部原有的沉积物的清理。文中介绍了气囊式封堵的基本原理,设备的构造特点和应用方法。 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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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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介绍了城市轨道交通工程中杂散电流不同的监测系统的构成,分析了集中式、分散式和智能型等监测系统的配置和功能,以及智能型实时在线监测系统的重要意义,为轨道交通工程杂散电流监测系统的选择与应用提供参考。 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
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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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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