smoothing circuit

例句：

1. 1.The surface of the metal is smooth and shiny.
   金属的表面光滑且有光泽。
2. 2. The road was smooth as glass.
   道路像玻璃一样光滑。
3. 3.The paint was smooth enough to prevent scratches.
   油漆足够平滑，可以防止刮伤。