A proton contains three charged quarks bound by the strong force and its radius is defined as the distance at which the charge density drops below a certain value.

一个质子由三个带电的夸克通过强相互作用力结合而形成，它的半径是由电荷密度降到某一确定值的距离来确定的。

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The value of the critical density is very small: it corresponds to roughly 6 hydrogen atoms per cubic meter, an astonishingly good vacuum by terrestrial standards!

临界密度的值非常小：它相当于每立方米约6个氢原子，从地球上的标准来看这简直是真空！

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The value of density of NaOH liquor is measured by CCD, and the quality fraction of NaOH liquor is got by table.

通过CCD读取碱溶液的密度值，查表获取碱溶液的质量分数。

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And one common way to think about it, is to think about the value of r, or the radius, below which 90% of that electron density is going to be contained.

而通常的想法，是想象，r，的值，也就是半径的值，即有百分之九十的电子密度,都落在这个范围之内。

麻省理工公开课 - 化学原理课程节选

The lost amenities and added population density, they said, would cut their property value by a third, and they were not going to take it lying down.

ECONOMIST: The well-off stand up for their rights