用比较直接的方法证明幂级数的和函数在收敛域内可以逐项微分的公式；并得到了计算傅立叶系数的一种简便方法。

A relatively direct method is expounded in this paper to prove the termwise differentiation of power series, and a simple method is expressed to calculate the Fourier coefficient.

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研究了西红柿、叶子、枝干的形状特征，通过傅立叶描绘子，提取基于傅立叶系数导出的如圆形度、细长度、凹度、密集度等形状特征。

On the basis of analyzing shape features of tomatoes, leaves and branches, we extract features of roundness, slightness, concavity degree and denseness depending on Fourier description.

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文中提出应用傅立叶级数系数的电流控制算法，能明显减少转矩波动。

In this paper, a current control algorithm using Fourier series coefficients is proposed. This algorithm can minimize torque ripple obviously.

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