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Natural frequency characteristics of a thin-walled multiple layered cylindrical shell under lateral pressure are studied.The multiple layered cylindrical shell configuration is formed by three layers of isotropic material where the inner and outer layers are stainless steel and the middle layer is aluminum.The multiple layered shell equations with lateral pressure are established based on Love's shell theory.The governing equations of motion with lateral pressure are employed by using energy functional and applying the Ritz method.The boundary conditions represented by end conditions of the multiple layered cylindrical shell are simply supported-clamped(SS-C),free-clamped(F-C)and simply supported-free(SS-F).The influence of different lateral pressures,different thickness to radius ratios,different length to radius ratios and effect of the asymmetric boundary conditions on natural frequency characteristics are studied.It is shown that the lateral pressure has effect on the natural frequency of multiple layered cylindrical shell and causes the natural frequency to increase.The natural frequency of the developed multilayered cylindrical shell is validated by comparing with those in the literature.The proposed research provides an effective approach for vibration analysis shell structures subjected to lateral pressure with an energy method.- 中国机械工程学报文章来源： 万方数据
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龙门以上流域下垫面变化对洪水影响分析
以海河流域龙门水库以上流域为研究对象,在对流域下垫面条件进行调查分析的基础上,分析了下垫面条件对流域产汇流特征变化的影响,龙门以上流域降雨产汇流规律在1980年左右发生明显变化,龙门以上流域的土壤含水量消退系数1980年均值为0.91,1980年后均值为0.94,1980年均值后较1980年前均值略增3.3%.对流域下垫面条件变化影响下的洪水变化规律进行了分析和探讨,为流域洪水系列一致性修正奠定了基础,为流域防洪规划和管理提供了技术支撑,为洪水预报方案编制提供了第一手资料.于广英,胡春景 - 南水北调与水利科技文章来源： 万方数据
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