1. Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
2. Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2, Asashiro-Nishi, Kumatori, Sennan-gun, Osaka 590-0494, Japan
3. SAKURA Internet Research Center, SAKURA Internet Inc., Grand Front Osaka Tower A 35F, 4-20 Ofukacho, Kita-ku, Osaka 530-0011, Japan
4. Research Institute of Nuclear Engineering, University of Fukui, 1-2-4 Kanawa-cho, Tsuruga, Fukui 914-0055, Japan