spherical shell的用法和樣例：
例句
- The compatible boundary conditions are evidently uniform tractions applied on the inner and outer surfaces of the shell.
可相容的邊值條件顯然是作用在球殼的內表面和外表面上的均勻曳力。 - Light emitted from the inner surface of a spherical shell, for instance, satisfies that requirement.
唯一的條件是，這道想像的光束一開始是會聚的，例如從球殼內層表面發出的光就滿足這個條件。
