Systems and Software Engineering Laboratory, Research and Development Center, Toshiba Corporation, 70 Yanagi-cho, Saiwai-ku, Kawasaki-shi, Kanagawa, Japan;Systems and Software Engineering Laboratory, Research and Development Center, Toshiba Corporation, 70 Yanagi-cho, Saiwai-ku, Kawasaki-shi, Kanagawa, Japan;Systems and Software Engineering Laboratory, Research and Development Center, Toshiba Corporation, 70 Yanagi-cho, Saiwai-ku, Kawasaki-shi, Kanagawa, Japan