Since normal plastic theory is too complex, the membrane theory and the semi-membrane theory are adopted to establish the equilibrlm equations in plastic limit analysis.
The conventional method involves boiling and then distilling water. An alternative works by reverse osmosis, in which water is forced through a semi-permeable membrane.
传统技术用的是蒸馏，新兴的替代技术是通过迫使咸水通过一个反渗透薄膜以达到过滤。
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This involves tapping both freshwater and seawater at the mouths of Norway’s many rivers and fjords, and diverting it to tanks on either side of a semi-permeable membrane.