M. Wang, F. Xu, D. Satpathi, and Z. Chen. Proc. SPIE Vol. 3671, p. 328-336, Smart Structures and Materials 1999: Smart Systems for Bridges, Structures, and Highways, Steve C. Liu; Ed., volume 3671 of Presented at the Society of Photo-Optical Instrumentation Engineers (SPIE) Conference, page 328-336. (May 1999)