1. Ph.D. Candidate, Dept. of Mechanical and Materials Engineering, Portland State Univ., Portland, OR 97201.
2. Associate Professor, Dept. of Mechanical and Materials Engineering, Portland State Univ., Portland, OR 97201.
3. Principal Researcher, R&D Center, Korea Institute of Industrial Technology, 7-47 Songdo-dong, Incheon 406-840, Korea.
4. Director, R&D Center, Korea Institute of Industrial Technology, 7-47 Songdo-dong, Incheon 406-840, Korea.
5. Professor, Dept. of Mechanical and Materials Engineering, Portland State Univ., Portland, OR 97201 (corresponding author).