power - off的用法和样例：
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.
当数据中心一旦发生主电源掉电的时候，三相不间断电源系统是应用最广泛的后备电池和供电条件。 - It performs file recovery after power failure, system crash, virus infection or partition reformation.It also has unformatand unerase tools.
在掉电，系统失效，病毒传染或者隔离物革新以后表演文件恢复。
