共查询到15条相似文献,搜索用时 109 毫秒
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用数控电子─液压振动台模拟整体大件产品的公路运输试验 总被引:1,自引:0,他引:1
本文简述运输环境和试验条件的制订。对模拟运输试验的各种方法作了简单评述 ,尤其是对利用电子─液压振动台对大型整体产品在悬臂梁状态的试验作了介绍。最后说明一种能模拟带有高峰值随机振动的试验技术 ,以改进现有数控设备的不足。 相似文献
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制定室内模拟运输试验条件的一种方法 总被引:4,自引:0,他引:4
介绍了制定室内模拟运输试验条件的一种技术方法。以运输距离、运输速度及路面等级给出的运输环境条件可以采用空间频率功率谱密度(PSD)描述,进而获得以时间频率PSD描述的室内模拟运输试验条件。文中还分析了确定的路面等级的空间频率PSD的波动以及运输速度对于室内模拟运输试验条件量级的影响,结果表明:相同的运输环境条件,其室内模拟运输试验条件振动量级可以具有的波动范围;相同的路面等级,运输速度与试验条件振动量级成正比。工程应用中可以针对不同产品的设计要求来剪裁使用。 相似文献
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通过HB5830.12-86(新航标)和HB6-71-76(老航标)霉菌试验方法的实际试验,重点对霉菌试验菌种,试验温湿度,试验箱风速,孢子悬液配制以及试验结果的等级评定等,作了探讨及对比分析。 相似文献
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Janie M. Chermak 《Resources Policy》1998,24(4):207-216
An intent of the U.S. Federal Regulatory Commission's Order 636, promulgated in April 1992, was to promote competition and efficiency in the transportation sector of the natural gas industry. Additionally, the Order altered the roles of the traditional players in the industry by increasing not only their options for purchase and sale of natural gas, but also their risks. Increased options have the potential of increasing competition and efficiency, not only in the transportation sector, but also in the distribution sector. This paper examines impacts of Order 636. Using annual, aggregate, U.S. price data, a Wilcox rank sum test is employed to test for statistically significant differences between the pre- and post-636 eras. Results indicate median revenues attributable to the transportation sector have declined since the implementation of Order 636.1 Although there are naturally a number of factors that may affect transportation revenues, the decline in median price can be attributed, at least in part, to increased competition, increased efficiency, or both. At this level of aggregation the effects can not be segregated. Results also indicate that although decreased costs of transportation have at least partially been passed on to final consumers, local distribution companies have not significantly altered their business practices when dealing with customers. 相似文献
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U. Oses E. Rojí I. Gurrutxaga M. Larrauri 《Journal of Environmental Planning and Management》2017,60(11):1891-1922
The management of urban transportation systems represents one of the most formidable challenges for local government that generates several problems related to the well-being and the comfort of the public that commute and travel in their daily life. Improvements to various policies and practical measures can move us closer to the ideal of sustainable urban areas with sustainable urban transportation systems. Nevertheless, these aspirations in no way ensure unanimity over the most effective actions to take and the extent of their benefits. In response, a mathematical model has been developed for decision-taking purposes using multi-criteria analysis adapted to urban transportation systems. This model not only takes account of environmental parameters, but also examines economic, social and urban models, the characteristics and condition of the transport fleet and freight distribution vehicles, in order to generate a sustainability index value for the transportation system of urban areas. 相似文献