annular boundary的用法和样例：
例句
- The boundary condition on the body is transfered to body axis.
物面边界条件被转移到物体轴上。 - Moreover, the sound pressure and velocity on the virtual boundaries can be get simultaneity by using this method, which cannot be done by conventional boundary element method.
同时采用文中的方法还可以同时得到声场中非物面边界上质点的振动速度和压力，这是常规边界元法无法做到的。
