1. Visiting Student, Smart Sensors and NDT Laboratory, Dept. of Civil and Materials Engineering, Univ. of Illinois at Chicago, Chicago, IL 60607.
2. Ph.D. Student, Smart Sensors and NDT Laboratory, Dept. of Civil and Materials Engineering, Univ. of Illinois at Chicago, Chicago, IL 60607.
3. Professor Emeritus, Politecnico di Torino, 10129 Torino, Italy.
4. Distinguished Professor, Smart Sensors and NDT Laboratory, Dept. of Civil and Materials Engineering, Univ. of Illinois at Chicago, Chicago, IL 60607 (corresponding author).