研究了采用二阶抽样对水路运输量进行抽样调查时的第二阶抽样方法。

This paper studies the second stage sampling methods used in the two stage sampling survey for waterway transportation volume.

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数值分析结果表明：在水平地震作用下，地震波频率与边坡的第二阶固有频率一致时，才会发生共振。

Numerical results show that under the influence of horizontal seismic action, resonance will occur when the seismic wave frequency is identical to the second-order natural frequency of slope.

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为使第二阶模态频率避开发动机一阶惯性力频率，文中对扶手架的质量、刚度进行局部修改，结果使手把振动有较大幅度的下降。

To separate these frequencies, we make a local modification to mass and stiffness of the handle and results in the vibration on the handle of walking tractor to reduce considerably.

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