1. Faculty of Engineering, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
2. Department of Electrical Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan
3. Department of Nuclear System Safety Engineering, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan