从理论上讲，通过坐标轴旋转将二次方程化简为规范形式，从而讨论其曲线的形状，这已是讨论得相当明了的课题。

Theoretically speaking, it is a rather-clearly discussed subject to standardize the quadratic equation into the normal forms by spinning the coordinate axis so as to approach the shapes of its curves.

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本文分析了普通十字轴万向节内二次力矩产生的原因。

In this paper, why the second couple in the ring-fork U-joint occurs is analyzed.

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为了成形大断面收缩率轴类零件，进行了楔横轧二次楔入试验。

For the sake of the axis accessory's figuration, the experiment of second wedge heavy section shrinkage was carried out.

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