[1] Kobe Univ, Dept Elect & Elect Engn, Kobe, Hyogo 6578501, Japan
[2] Univ London Queen Mary & Westfield Coll, London E1 4NS, England
[3] Univ Electrocommun, Dept Elect Engn, Chofu, Tokyo 1828585, Japan
[4] Hokkaido Univ, Grad Sch Sci, Div Phys, Sapporo, Hokkaido 0600812, Japan