1. Department of Mechanical Systems and Design Engineering, Iwaki Meisei University, Iino 5-5-1, Chuohdai, Iwaki 970-8551, Japan,
2. Department of Machine Intelligence and Systems Engineering, Akita Prefectural University, Ebinokuchi 84-4 Tsuchiya, Yurihonjo 015-0055, Japan
3. Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan