排序方式: 共有159条查询结果,搜索用时 343 毫秒
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重庆是比较典型的山地城市,步行成为市民出行除机动车外的最重要方式.对重庆而言,进行城市行人交通安全保障的深入研究是必要而且紧迫的.从人、道路、交通流、管理控制等方面分析了重庆的城市交通特点,明确了重庆的城市行人交通系统运行规律和安全隐患,并进一步深入研究,针对设施薄弱、管理不善、安全意识差等问题提出了重庆城市行人安全工作的各项技术保障措施,对行人的交通安全具有指导意义. 相似文献
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This article presents an econometric analysis for the fluctuation of the container freight rate due to the interactions between the demand for container transportation services and the container fleet capacity. The demand is derived from international trade and is assumed to be exogenous, while the fleet capacity increases with new orders made two years before, proportional to the industrial profit. Assuming the market clears each year, the shipping freight rate will change with the relative magnitude of shifts in the demand and fleet capacity. This model is estimated using the world container shipping market statistics from 1980 to 2008, applying the three-stage least square method. The estimated parameters of the model have high statistical significance, and the overall explanatory power of the model is above 90%. The short-term in-sample prediction of the model can largely replicate the container shipping market fluctuation in terms of the fleet size dynamics and the freight rate fluctuation in the past 20 years. The prediction of the future market trend reveals that the container freight rate should continue to decrease in the coming three years if the demand for container transportation services grows at less than 8%. 相似文献
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铁磁构件缺陷参数对漏磁场的影响较复杂,磁荷模型在理论上可以定量分析该磁场问题,但只能适用于简单缺陷形状情况。因此,采用有限元数值计算技术更具灵活性。为了进一步分析油管缺陷参数对漏磁场的影响,建立了油管缺陷漏磁场仿真模型,研究了裂纹深度、裂纹宽度、裂纹深宽比、裂纹倾角对漏磁场的影响。分析结果表明:漏磁场强度随油管缺陷裂纹宽度的减小或裂纹深度、裂纹角度的增加而增强;对于深度比,相对于裂纹宽度,裂纹深度对漏磁场的影响更明显。仿真结果为缺陷检测系统设计和缺陷信号分析提供了参考。 相似文献
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分析了默会知识的内涵与表征,论述了默会知识在科学研究中的作用,进而提出基于默会知识培养学生科研能力的途径。 相似文献
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We examine lead–lag relationships between new-building and second-hand ship prices. Our analysis shows the existence of a one-directional lead–lag relationship between two ship prices. The direction of lead–lag relationship is not affected by the time evolution and age of second-hand ships, but is affected by the division of shipping sector. Particularly, directions of ship price movements in dry bulk and tanker shipping sectors are opposite. We argue that the opposite directional lead–lag relationships are caused by the difference in competition levels and the difference in the purposes of trading in the two shipping sectors. 相似文献
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考虑风险的桥梁防火措施选择 总被引:2,自引:0,他引:2
阐述了基于风险的桥梁防火措施的基本思想与基本内容,包括桥梁防火水准和防火性能之间的关系、桥梁防火等级划分以及防火性能目标;提出了考虑风险的桥梁防火措施选择方法,这只需简单改变等级参数即可;通过一个算例来说明该方法的应用过程. 相似文献
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