DirecTVn.(美国)卫星电视directadj.直接的；笔直的；坦白的v.对准；指挥；指示；命令directoscopy直接镜检查法direct costsn.直接成本direct shoot直接射门direct labor直接人工direct logic直接逻辑directinsertadj.直接插入的direct cross正交direct point直接点direct reuse直接复用direct match直接配血

1. Based on the geometry characteristics of Bertrand surfaces, the complicated surface conjugation issue can be discussed with their directrix line.
   基于白川德曲面的几何特征，将复杂的曲面共轭问题归结到准线上来讨论。
2. The surface generated by a straight line,the generator,passing through a fixed point,the vertex,and moving along a fixed curve,the directrix.
   锥面由一条直线，即母线，通过一固定点，即顶点，沿一给定曲线，即准线，连续移动而产生的平面。