1. Department of Aeronautics and Astronautics, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
2. Department of Aerospace Engineering, Tohoku University , 6-6-01 Aoba-yama, Aoba-ku, Sendai, Miyagi 980-8579, Japan
3. Department of Materials Science and Engineering, University of Washington , 302 Roberts Hall, Seattle, WA 98195, USA