1. Associate Professor, Institute of Energy Technologies, School of Industrial Engineering, Univ. Politecnica de Catalunya, Campus Sud, 08028 Barcelona, Spain; presently, Visiting Scholar, Dept. of Civil and Environmental Engineering, Northwestern Univ., Evanston, IL 60208.
2. Distinguished McCormick Institute Professor and W. P. Murphy Professor of Civil Engineering, Mechanical Engineering, and Materials Science, Northwestern Univ., Evanston, IL 60208 (corresponding author).