1. Graduate School of Science and Technology, Gunma University, Maebashi 376-8515, Japan
2. Faculty of Engineering, Thai-Nichi Institute of Technology, 1771/1 Pattanakarn Rd. Suanluang, Bangkok 10250, Thailand
3. Department of Electrical and Electronic 1, Posts and Telecommunications Institute of Technology, Hanoi 100000, Vietnam
4. Division of Mechanical Science and Technology, Gunma University, Maebashi 376-8515, Japan