下位叶比上位叶对土壤氮的供应状况更为敏感，随着施氮量的增加，水稻叶片氮素含量、叶绿素含量、SPAD值相应的增加，而下位叶的增幅更明显。
Leaf N/ chlorophyll content and SPAD value increased with the increasing N fertilizer, and the lower leaves were more sensitive to the soil N supply than the upper leaves.
首先利用付里叶变换，使问题的求解转换成对一对变量为裂纹面上位移差的对偶积分方程的求解。
By using the Fourier transform, the problem can be solved with a pair of dual integral equations in which the unknown variable is the jump of displacements across the crack surfaces.
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