retarder in closed state

例句：

1. 1. The engineer designed a new retarder to improve the efficiency of the machine.
   工程师设计了一种新的减速器，以提高机器的效率。
2. 2. The car's engine is retarded by a special device to reduceits speed.
   汽车的发动机通过一种特殊的装置来减速，以降低其速度。
3. 3. The scientistused a retarder to slow downthe projectile before it hit the target.
   科学家使用减速器来减缓弹丸在撞击目标前的速度。