power - off的用法和樣例：
例句
- Three-phase UPS systems are used in most large data centers for power conditioning and battery back-up in the event of mains power failure.
當數據中心一旦發(fā)生主電源掉電的時(shí)候，三相不間斷電源系統是應用最廣泛的后備電池和供電條件。 - It performs file recovery after power failure, system crash, virus infection or partition reformation.It also has unformatand unerase tools.
在掉電，系統失效，病毒傳染或者隔離物革新以后表演文件恢復。
