A method to improve the effective medium theory towards percolation problem

The effective medium theory is an excellent theory for the effective conductivity of random media, but when the theory is applied to percolation problems the result shows a somewhat unrealistic behaviour, because the effective conductivity by the theory increases exactly linearly from the percolation threshold against the volume fraction of the conductive component. To remove the defect for the theory a simple method to improve the effective medium theory is proposed. The effective conductivity by the improved method increases less than linearly from the percolation threshold and agrees well with the result by computer simulation, both for three and for two dimensions.