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71.
结合工程实践,介绍二级公路中超大粒径的水稳砂砾作为基层材料在施工中的质量弊端,分析平整度、压实度的控制技术,对工程实践具有借鉴意义。 相似文献
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Chih-Ching Yang 《运输规划与技术》2013,36(8):769-789
Abstract This paper evaluates the productivity changes in Taiwan's port industry for the period 2003–2007. Based on a ‘three-year-window’ data envelopment analysis method, Luenberger productivity indicators are employed to estimate the productivity changes that account for the success of attempts by port agents to control harbor water quality. This is one of the typical environmental concerns in port operations that prior studies on port productivity changes over time have not considered. The results show that the productivity of Taiwan's port industry has experienced growth over the study period, regardless of whether water quality has been considered or not. At a disaggregated level, however, if a port agent has succeeded in controlling water quality, but we do not consider it, the results will misclassify the agent by understating the port's productivity. 相似文献
74.
In response to increasing demand, airlines may increase capacity by increasing the frequency of flights or they may choose to increase aircraft size. This may yield operating cost economies. If the airports they operate from are capacity constrained, they will be limited in the extent that they can change frequency which will limit their ability to compete with the number of frequencies offered. This article focuses on this trade-off and pays particular attention to the practices of a specific airline. Conclusions are offered on the impact of inter alia competition, changes in aircraft technology, 9/11 and the impact of slot constraints. It appears that changes in size are more important than frequency, which is consistent with the presence of slot constraints and there is a significant impact of competition. As the concentration of carriers increases, so aircraft size falls. 9/11 also has a significant impact on traffic whereas the introduction of the Boeing 777, as an illustration of a change in technology, does not. 相似文献
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为了研究不同开挖尺寸和围岩节理组倾角对隧道开挖变形稳定的影响,应用UDEC程序,通过一些假设,设定计算域内包含有水平垂直节理组(0°-90°)和倾斜节理组(45°-135°)2种计算情况,对硐室不同开挖尺寸下围岩的变形稳定情况进行数值模拟。结果表明:1)水平垂直节理组岩体中围岩变形随硐室开挖尺寸增大先缓慢增加,后呈指数形式急剧增加且失稳,围岩失稳表现为贯穿地表的拱部上方岩体整体塌落;2)倾斜节理组岩体中围岩变形随硐室开挖尺寸增大先缓慢增加,后急剧增大且失稳,围岩失稳表现为拱部围岩局部塌落;3)倾斜节理组岩体中硐室开挖后变形比相应水平垂直节理组的要大。 相似文献
77.
为克服工作空间受限的箱式结构不易清扫的问题,以实验室现有的气箱为清扫对象,设计了一种箱式结构清扫臂,并依据优化设计的思想,以箱式结构清扫臂的工作空间最小为优化目标,确定了基杆的最优长度和基杆与箱体壁的最优夹角;同理,在各臂转到同一条线上时,以清扫臂对各个关节的转动惯量最小为优化目标,得出各臂的最优臂长;最后,根据箱体的尺寸和结构规划了一条清扫路径,并基于路径各个部分的特点分别在关节空间和笛卡尔空间进行了轨迹规划,最终导出整条轨迹的运动学方程,以此进行运动学验证和仿真. 相似文献
78.
纪延涛 《船舶标准化工程师》2014,(6):17-19
结合钢制导管架建造的特点,重点总结和介绍了海洋钢制平台导管架建造阶段所使用的测量技术及其精度控制中应该注意的事项,以期达到相互学习和交流的目的。 相似文献
79.
Assessment system of implicit environmental impacts was established including environmental impact indicator, resources consumption indicator and energy consumption indicator. The quantification of environmental impact indicators is based on the life cycle assessment system of the Society of Environmental Toxicology and Chemistry (SETAC) and the evaluation software BEES. Normalization reference values and weights of 12 categories of environmental impacts were identified, and the environmental impact indicators in the phases of raw material extraction, transportation, manufacturing, use and end of life were analyzed. By analyzing the environmental performance of a university refectory as a case study, it is demonstrated that human health, global warming and acidification are the first three environmental impacts in 12 categories. The total implicit environmental impact load per square meter of this project is 18.448×10~(-2) standard human equivalent weight. Moreover, 97.3% of total environmental impacts occur in the phase of raw material extraction. 相似文献
80.
在役的钢筋混凝土桥梁的可靠度分析是根据桥梁结构的现有状况及已有信息,并每考同类或类似结构的信息资料,采用适当的分析方法对其在服役基准期内的可靠度或失效慨率进行评估,为合理利用桥梁提供依据:对已不满足现有需求的桥梁,应做出维修加固或拆除的决策,以避免重大事故的发生。 相似文献