Affiliation: | a Kure National College of Technology, 2-2-11 Aga-Minami Kure-shi Hiroshima 737-8506, Japan b Hiroshima Institute of Technology, 2-1-1 Miyake Saeki-ku Hiroshima 731-5193, Japan c Miyakonojo National College of Technology, 473-1 Yoshio-cho Miyakonojoshi Miyazaki 885-8567, Japan |