The pipe must be cut perpendicularly to its axis and its external surface deburred. 管件必须根据坐标轴纵切割且外表面去毛刺处理。
The position of a moving particle is determined by measuring the displacement along its path from a reference point. 以点的轨迹作为一条曲线形式的坐标轴来确定动点的位置的方法叫自然坐标法。