1. Department of Mechatronics Engineering, Chosun University, 375 Seosuk-dong, Dong-gu, Gwangju 501-759, Korea
2. Department of Advanced Parts and Materials Engineering, Chosun University, 375 Seosuk-dong, Dong-gu, Gwangju 501-759, Korea
3. Department of Naval Architecture and Mechanical Engineering, Jeonnam Provincial College, 262 Hyanggyo-ri, Damyang-eup, Damyang-gun, Jeonnam-Province 517-802, Korea