And the sand ripples on the surface arise obviously with the increasing silt mass fraction and wind speed, but disappear as silt mass fraction exceeds 15%.

实验中沙波纹的高度和波长随风速及粉粒的质量分数的增大而增大，而当粉粒的质量分数超过15%时沙波纹消失。

youdao

The cassiterite makes up some fraction of the standard sand and river silt there.

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