什麼是shape呢？二維的話就是看兩個方向是否相同。可是曲面有很多方向啊，於是考慮是principle curvature. det(Shape_x)>0 就是有凹凸的，det(Shape_x)<0就是馬鞍的，然後eigenvalue反映了主方向的曲率（最大最小normal 變化方向）。

operating voltage工作電壓; 例句:

1.At first glance 1 this may appear to be a simple matter once the operating voltage of the system is decided, but unfortunately this is far from so. 初看起來，一旦系統工作電壓確定後這是一件很簡單的事件，但遺憾的是遠非如此。

2.The recently rapid growth in demand for wireless communications services has been a strong motivation for designing more highly integrated rfics with low operating voltage, power, and cost. 現今對無線通訊服務的需求急速成長，使得射頻晶片朝向無線系統所要求的低功率、低成本以及高整合性能邁進。