The result indicates that the discharge per unit width, the sediment concentration, the grain size of sand influences the depth of scour hole.

试验结果表明：浑水水流的单宽流量大小、含沙量的多少以及含沙粒径的变化都对冲刷坑深度有一定的影响。

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As these rise, they latch on to dust in the air and become particulates, a quarter the size of a grain of sand.

上升过程中，这些元素附着在空气中的尘埃上，变成微粒，大小相当于一粒砂子的四分之一。

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“Sometimes more than a thousand, ” he wrote, “in anamount of material the size of a grain of sand.”

他写道，“有时一粒沙子大小的样本中就有超过一千的微生物。”

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Such nanotechnology involves engineering carbon-based polymer molecules, one-millionth the size of a grain of sand, that attach to fibers to wick away moisture and resist stains, water and static.

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