1. School of Advanced Materials Science & Engineering, Sungkyunkwan University, Suwon 440-746, Korea
2. Department of Mechanical
Engineering and Materials Science, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
3. Department of Materials Science & Engineering and Energy Systems Research, Ajou University, Suwon 443-749, Korea
4. School of Mechanical Engineering, Hanyang University, Seoul 133-791, Korea