1. SUMCO Corporation, 1-52 Kubara, Yamashiro-cho, Imari-shi 849-4256, Saga, Japan
2. Graduate School of System Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi 719-1197, Okayama, Japan
3. Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi 719-1197, Okayama, Japan