Masashi Aiko
   National Institute of Technology, Miyakonojo College, Miyakonojo, Miyazaki 885-8567, Japan
   m-aiko@miyakonojo.kosen-ac.jp

Shinya Kanemura
   Department of Physics, University of Osaka, Toyonaka, Osaka 560-0043, Japan
   kanemu@phys.sci.osaka-u.ac.jp

Mariko Kikuchi
   Department of Physics, Saga University, 1 Honjomachi, Saga 840-8502, Japan
   mkikuchi@cc.saga-u.ac.jp

Kodai Sakurai
   National Institute of Technology, Tsuruoka College, Tsuruoka, Yamagata 997-0842, Japan
   kodai.sakurai@tsuruoka-nct.ac.jp

Kei Yagyu
   Department of Physics, Tokyo University of Science, 1-3, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
   yagyu@rs.tus.ac.jp