1. National Institute of Information and Communications Technology, 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795, Japan
2. Department of Electrical and Computer Engineering, University of Massachusetts Lowell, 1 University Ave., Lowell, Massachusetts 01854, USA
3. Department of Applied Chemistry, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan