Copyright © 2012 Dag Lukkassen and Annette Meidell. This is an open access article distributed under the   Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
        
     
Abstract
We consider generalized chessboard structures where the local conductivity takes two values  and . All integer combinations of  and  which make the components of effective conductivity matrix integer valued are found. Moreover, we discuss the problem of estimating the effective conductivity matrix by using the finite-element method.