timed annular balance with brequet hairspring

例句：

1. 1.The planet is annular in shape.
   这个行星是圆形的。
2. 2. Themoon has annularcraters on its surface.
   月球表面有环形的陨石坑。
3. 3.The ring of fire is annularand glows with a reddishhue.
   火环是环形的，呈现出红色的光芒。