1. School of Civil and Environmental Engineering; Georgia Institute of Technology; Atlanta GA 30332-0355 USA
2. Department of Organic Material Science and Engineering; Pusan National University; Busan 609-735 Korea
3. Department of Energy Resources Engineering; Seoul National University; Seoul 151-742 Korea
4. Faculty of Liberal Education; Chonbuk National University; Jeonju Jeonbuk 561-756 Korea