Kepler went on to show that an elliptical orbit is sufficient to explain the movement of the other planets and to devise the laws of planetary motion that Newton built on.
He comes into my little story here because it was he, in explaining not how planetary motion worked but how light bent through lenses, it was Kepler who coined the term focus.
So, that researching on the flow of viscoelastic fluid in annulus with the inner cylinder executing a planetary motion has great significance in academic theory in the engineering.
因此研究粘弹性流体在内管做行星运动的环空中的流动具有学术理论意义和工程实际意义。
Reference efficiency of a pair of gear drive without planetary motion is the base to calculate efficiency of the whole planetary gear train.