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双组分速凝剂兼顾了有碱液体速凝剂和无碱液体速凝剂两种产品的优点.文章从改善水泥特性着手,在拌和中加入双组分速凝剂,经现场对比及试用,发现添加了双组分速凝剂的混凝土具有性能稳定、质量好、综合价格低廉等特点,为隧道高效施工提供了参考. 相似文献
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水泥是工业生产中最重要的原材料之一.水泥的水化反应过程是水泥发挥其各项性能的基础,正确地理解水泥的水化反应对于充分发挥水泥效能,选择合适的水泥使用条件,解决其在生产使用中各种问题具有重要意义.主要从水泥的水化反应过程出发,介绍水泥各矿物相的水化反应特性和影响因素,以及水化反应的产物及其特性,并分析其对水泥强度及混凝土特性的影响. 相似文献
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硅粉混凝土的抗渗透性机理分析 总被引:2,自引:0,他引:2
分析了硅粉混凝土的微观结构和孔结构,硅粉对于水泥浆体-骨料界面区的微结构的影响及硅粉混凝土的渗透性.硅粉能降低混凝土的渗透性,提高混凝土的抗冻性. 相似文献
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本文研究不种微胶囊相变材料(MPCM)对地聚合物混凝土(GPC)和硅酸盐水泥混凝土(PCC)凝结时间的影响.试验结果表明:当温度降低到0℃时,由于低温和高粘度,硅酸盐水泥浆体的初凝时间变长;对于地聚合物浆体,由于低温下碱性溶液的相分离,初凝时间变短;提高MPCM浓度可缩短硅酸盐水泥和地聚合物浆体的终凝时间. 相似文献
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钢纤维喷混凝土是一种新型复合材料,与普通喷混凝土相比,它显著改善了混凝土的抗拉、抗剪、抗弯、抗磨、抗裂性能,而且可以大大增强断裂韧性和抗冲击性,提高结构的抗疲劳性能和耐久性.由于钢纤维喷混凝土施工简便、施工速度快、工程总造价低,在土建工程中得到了广泛应用. 相似文献
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水泥混凝土施工过程产生的收缩裂缝,影响混凝土的性能,降低结构耐久性,文章通过从水泥混凝土收缩裂缝类型和产生机理进行分析,指出了收缩裂缝形成的原因,提出了混凝土收缩裂缝防治措施。 相似文献
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北京地铁五号线预制盾构管片的高性能混凝土研究 总被引:1,自引:0,他引:1
文章通过利用2次正交试验,对内掺4种掺合料的高性能混凝土配合比的多指标进行了评价和筛选,确定了理论配合比.与国内其他地铁管片厂家的混凝土配合比相比,该配合比的突出特点是总胶凝材料用量较低、大量使用了矿碴掺合料、水胶比和砂率较低.依据该配合比配制的混凝土试验结果表明混凝土强度达到了C50、拌合物易于浇捣、28天收缩值较纯水泥降低一半、抗渗等级为P30、碱含量仅2.4 kg/m3,满足用于潮湿条件等耐久性要求.目前用该配合比生产的预制盾构管片已在北京地铁五号线中累计使用超过1 000环,满足工程无结构缺陷、无外形缺陷、无外表缺陷和无外表油污的四无质量要求. 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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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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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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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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《Transportation Research Part A: General》1991,25(6):407-418
The main deficiency of most current modeling approaches to transportation can be identified as neglect of the integration of existing geographical knowledge in regard to the ex ante transport/land use modeling approaches, with its focus on territorial dynamics and theory development. This paper addresses this aspect of the problem by introducing a theoretical and methodological framework for the analysis of the interrelationship between land uses. The analysis attempts to determine to what extent the functional land use in a city can be considered an ordered pattern. The order sought does not rely on purely spatial configurations, but on the correlation of transportation and land use. The first section of this paper focuses on theoretical considerations. It stresses the fact that conventional approaches do not apply in the present context. It then suggests an alternative based on areas of influence and measured in terms of level of attractance of land uses. The second describes a procedure based on this alternative following the remarkable contribution of Hanjoul, Beguin and Thill. An application of this procedure to the analysis of Shanghai is then examined. Finally, an evaluation of the strategies for optimizing the interrelationship between land uses is presented. The paper concludes with a possible research agenda. 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