You'll see why very soon, in such a way that the derivative is this given unit vector u hat.
你很快就会明白为什么,导数dr/ds等于给定的单位u向量。
2
We obtain two formulas about the covariant derivative of the coordinate functions on the unit sphere in Eucdidean space.
得到了欧氏空间中，单位球面上坐标函数关于某一特定标架场的协变微分的两个等式。
3
When the second derivative of the bubble number in unit bed volume with respect to gas velocity equals zero, the flow regime transition occurs. The model fits fairly well with the experimental data.