Porosity is defined as the ratio of the void space in a rock to the bulk volume of that rock multiplied by 100 to express in percent.

孔隙度定义为岩石内的孔隙体积占岩石总体积的百分率。

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Psychologically, however, it might fill a different kind of void: According to the Institute for Policy Studies, the top 10 percent of all citizens here own 80 percent of all stock market wealth.

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