通常，你只会在这两种情况下用替代法，或者这可以极大地简化被积函数，或者就是这可以简化，积分的上下限。

I mean, normally, you would only do this kind of substitution if either it simplifies a lot the function you are integrating, or it simplifies a lot the region on which you are integrating.

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本文提出了用优化连续法研究曲柄滑块机构的近似函数综合。

This article provides an optimizing series method to study the approximate function synthesis of the slider-crank mechanism.

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结论：用幂函数曲线法来提高眼底图像对比度的效果是比较好的。

CONCLUSION: It is better effect of exponential curve method on improving contrast of image of eye fundus.

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