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。
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。
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.
这一款耳塞导线上有回放控制和像个农贸市场般齐全的耳塞头：三椎体的，黄色泡沫圆柱体，以及五种尺寸的黑色硅胶。
They include playback controls on the cord and a whole farmer’s market of tips: triple-cone, yellow foam cylinders, and five sizes of black silicone.
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