Theoretical analysis shows that near field 3-d range migration imaging technique can reduce computational complexity in much degree by contrast with back propagation algorithm.

理论分析表明：近场三维距离偏移算法与后向投影算法相比，能在较大程度上减少运算量。

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The general elastic modulus of the dam is back analyzed by using the statistic model, hybrid model and the 3-D FEM analysis result.

应用统计模型、混合模型以及三维有限元的计算分析成果，反演了坝体的综合弹性模量；

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