1. Ph.D. Candidate, Dept. of Mechanical and Materials Engineering, Portland State Univ., Portland, OR 97207-0751.
2. Associate Professor, Dept. of Mechanical and Materials Engineering, Portland State Univ., Portland, OR 97207-0751.
3. Principal Researcher, Center for Aviation Technology, Korea Institute of Industrial Technology, 7-47 Songdo-dong, Incheon 406-840, Korea.
4. Director, Center for Aviation Technology, 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 97207-0751 (corresponding author).