1. School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-744, Republic of Korea
2. Mechanical, Aerospace, and Biomedical Engineering, The University of Tennessee, Knoxville, Tennessee 37996, USA
3. Department of Mechanical Design, Chosun College of Science and Technology, Gwangju 61453, Republic of Korea
4. Institute of Advanced Machinery and Design (SNU-IAMD), Seoul National University, Seoul 151-744, Republic of Korea
5. Institute of Engineering Research, Seoul National University, Seoul 151-744, Republic of Korea