1. Technical Staff, MIT Lincoln Laboratory, 244 Wood St., Lexington, MA 02420.
2. Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Illinois, Urbana–Champaign, 205 N. Mathews Ave., Urbana, IL 61801.
3. Associate Professor, Dept. of Electrical and Computer Engineering, Univ. of Illinois, Urbana–Champaign, 1406 W. Green St., Urbana, IL 61801.
4. Professor, Dept. of Industrial and Enterprise Systems Engineering, Univ. of Illinois, Urbana–Champaign, 104 S. Mathews Ave., Urbana, IL 61801 (corresponding author).