The heat accumulation plays key role in coal self-ignition.

热量的积聚在煤自燃过程中起着关键的作用。

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In fact, it's also an accumulation of self-confidence.

事实上，这也是一种信心的积累。

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In fact, it's also an accumulation of self-confidence.

事实上，这也是一种信心的积累。

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