宝石即使落入泥潭里，仍是一样珍贵；尘土纵然扬到天上，还是没有价值。
If a jewel falls into the mire, it remains as precious as before; dust should ascend to heaven, its former worthlessness will not be altered.
将皮带轮置于皮带槽内，可以防止尘土落入皮带轮上，影响正常工作。
The belt pulley is arranged in the belt groove, and therefore the dust can be prevented form falling on the belt pulley to influence the normal working.
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