1. Dept. of Mechanical & Automotive Engineering, Junju University, 1200 Hyoja-Dongs, Wansan-Gu, Junju, 560 - 759, Korea
2. Dept. of Precision Mechanical Engineering, Chosun University Graduate School, 375 Seosuk-Dongs, Dong-Gu, Gwangju, 501 - 759, Korea