Classical sieving theory

In the previous classical modelling, the elements mentioned above were supposed to be independent. At present, it is obvious that this assumption leads to a distortion in description of various processes occurring in porous solids, such as desorption of sorbate, intrusion of mercury, filtration, molecular-sieve adsorption. Por this reason, modelling of the primary elements may be considered as the first step, which is necessary though insufficient. The second step must be the modelling of interconnection between the elements. At present, it is conducted by the network models, and processes in them — by percolation theory (refs.4-7) ... 

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