直纹[曲]面的平稳母线
stationary generator of a ruled surface
直纹面的奇异母线
singular generator of a ruled surface
直纹面的
director cone of a ruled surface
曲面的母线
generating line of surface
generator of a surface
ruling on a surface
垂直面直接曝辐量
direct solar radiation on perpendicular plane
带回流线的直接供电方式
direct feeding system with return wire
光的直线传播
the light straight propagation