And, if you take a vector field where maybe everything is rotating, a flow that's just rotating about some axis, then you'll find that its divergence is zero.
如果取一个有旋的向量场，流体流动方向是环绕某个坐标轴的，那么就会发现它的散度是零。
2
When an electric field is applied to the electrodes the piezoelectric material translates this into a mechanical strain along its radial axis, causing it to vibrate.
当两个电极之间形成电场时，压电性物质便将电场转化为沿径向轴的机械压力，使纤维震动。
3
When the visitors type in the data their eyes are fixed across the vertical axis at the left to the input field.