1. Assistant Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology, 790 Atlantic Dr. N.W., Atlanta, GA 30332-0355 (corresponding author).
2. Ph.D. Student, School of Civil and Environmental Engineering, Georgia Institute of Technology, 790 Atlantic Dr. N.W., Atlanta, GA 30332-0355.
3. Associate Professor, Dept. of Physics, Texas A&M Univ., College Station, TX 77843-4242; presently, Foreign Principal Investigator and Visiting Professor, WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
4. Ph.D. Student, Dept. of Mechanical Engineering, Univ. of Texas at Austin, Austin, TX 78712.