First Author:   Masao Kumamoto Hitotsubashi University masao.kumamoto@r.hit-u.ac.jp   2-1, Naka Kunitachi-shi, 1868601, Japan   +81-42-580-8252(Phone) +81-42-580-8252(Fax) Second Author: Juanjuan Zhuo Kochi University zhuojj@kochi-u.ac.jp   Kochi-shi, 7808520, Japan   +81-88-844-8235(Phone)