Free convection has been defined as a flow driven by density variations.

自由对流是一种由于流体的密度变化而产生的流体的运动。

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The density variations of deformed powder metallurgical molybdenum bars were tested by using suspending weight method.

通过悬重法测量热变形后粉末冶金钼坯致密度的变化情况。

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Such expansion would stretch space and smooth matter, while leaving small density variations that show up in the CMB.

BBC: The observable Universe and beyond

Introduce variations in density into the gas, however, and the waves will be bent and scattered, just as they would be by irregularities in a pane of glass.

ECONOMIST: Pulsars: In a wink | The