这已经不是第一次有人指出这个现象。
This was not the first time that someone has pointed out this phenomenon.
在机械故障诊断领域，本文第一次注意到这一现象。
In the field of mechanical diagnosis, this phenomenon is noticed for the first time.
在机械故障诊断领域，本文第一次注意到这一现象。
In the field of mechanical diagnosis, this phenomenon is noticed for the first time.
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