9704099 Day This is a theoretical research grant to Professor Day at Marquette and Professor Thorpe at Michigan State. The work involves using a spectral function approach to calculate the effective conductivity of composites. The spectral function is essentially a density of the singularities of the effective conductivity of a two-component composite and contains all of the information about the geometry of the composite. Consequently, knowing the spectral function for a wide range of geometries, and seeing how it varies with a change in geometry, will provide a powerful new tool for understanding the relationship between microstructure and material properties. %%% This theoretical research will be done at both Marquette University and Michigan State University. The work involves a new way of determining the properties of materials comprised of two components, i.e., composite materials. These materials are used quite commonly and the results of this research should aid in the design of these useful materials. On a more fundamental basis, this research will aid in relating microstructure of materials to their macroscopic properties. ***