1. Department of Automotive Engineering, Keimyung University, Shindangdong 1000, Dalseogu, Daegu704-701, Korea
2. Department of Automobile, Cheonan National Technical College, Boodaedong 275, Cheonan, Chungnam 330-717, Korea
3. Department of Mechanical Engineering, Inha University, 253 Yonghyun-dong, Nam-gu, Inchon 402-751, Korea