1. NEC Corporation, 7-1 Shiba 5-chome, Minato-ku, Tokyo, Japan, Tokyo Metropolitan University, Graduate School of Engineering, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397, Japan, and The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan