1. Department of Automotive Engineering, Seoul National University of Technology, 172 Kongnung-dong, Nowon-ku, Seoul 139-743 E-Mail:
2. Department of Structural Engineering, Seoul National University of Technology 172 Kongnung-dong, Nowon-ku, Seoul Korea, 139-743
3. Department of Materials Science and Engineering, Seoul National University of Technology 172 Kongnung-dong, Nowon-ku, Seoul 139-743