官员表示，没有迹象表明，飞机在坠毁前遭到了地面火力袭击。因为飞机在失事前是断路器着地的，很可能是机械故障。

There was no indication of hostile fire, officials said, saying it appeared the chopper went down because of some other problem, possibly mechanical.

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主要介绍了高压真空断路器机械特性测试仪的硬件电路设计和软件程序的编程。

It mainly introduced hardware circuit design and software program programming for high-voltage circuit breaker mechanical characteristic tester.

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介绍了一种断路器机械状态在线监测与诊断的方法。

This paper introduces a method that the mechanical condition of circuit breaker can be monitored and diagnosed on-line.

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