It is presented that the locus of a line crossed with each of two guide line and a guide conic not being on a common plane is a ruled surface of fourth order.

本文提出了由一条二次曲线和与该二次曲线不共面的两条异面直线为导线，与该三导线均相交的直线轨迹是一个直纹四次曲面，并讨论了二次曲线分别为椭圆、双曲线和抛物线时，形成的曲面的形状特征。

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In this paper, it is presented that the locus of a line crossedwith each of two guide lines and a guide conic not being on a commonplane is a ruled surface of fourth order.

本文提出了由一条二次曲线和与该二次曲线不共面的两条异面直线为导线，与该三导线均相交的直线轨迹是一个直纹四次曲面，并讨论了二次曲线分别为椭圆、双曲线和抛物线时，形成的曲面的形状特征。

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Study a class of fourth-order nonlinear systems, decouple the whole system into two second-order systems, and design their separate sliding surface of each subsystems.

然后将一个子系统的控制目标嵌入到另一个子系统的控制目标中，用一个控制量使两个子系统同时向各自的滑模面趋近，使该四阶系统稳定。

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