1. Graduate Research Assistant, Northwestern Univ., 2145 Sheridan Rd., CEE/A123, Evanston, IL 60208.
2. McCormick Institute Professor and W.P. Murphy Professor, Dept. of Civil and Mechanical Engineering, and Materials Science, Northwestern Univ., 2145 Sheridan Rd., CEE/A123, Evanston, IL 60208 (corresponding author).
3. Associate Professor, Energy Technologies (INTE/ETSEIB), Universitat Politécnica de Catalunya, Avinguda Diagonal No. 647, 08028 Barcelona, Spain.