1. Division of System Research, Faculty of Engineering, Yokohama National University, Tokiwadai 79-5, Hodogaya-ku, Yokohama, 240-8501, Japan
2. Department of Civil and Environmental Engineering, Ritsumeikan University, Noji-Higashi 1-1-1, Kusatsu, Shiga, 525-8577, Japan
3. Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA