This difference seems to be applied to explain the cause why the squeal only occurs in the end of the upward-stroke under reciprocating sliding.

这为解释往复滑动摩擦噪声只在向上行程末期发生的原因拓宽了视野。

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The bright return stroke travels upward at around half the speed of light, and is too fast to capture in more than one image.

闪亮的回击以光速的一半速度上行传播，由于它的速度太快，在一张图象中不能捕捉到这一过程。

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This upward leader connects with the downward leader and a return stroke occurs. Five more dart leader-return strokes follow.

上行先导与下行先导连接，于是产生了一次回击，随后又是五次以上的直窜先导型回击。

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