1. Department of Electrical Engineering, National University of Kaohsiung, Kaohsiung 81148, Taiwan
2. Department of Electronic Engineering, Minghsin University of Science and Technology, Hsinchu 30401, Taiwan
3. Department of Chemical and Materials Engineering, National University of Kaohsiung, Kaohsiung 811, Taiwan
4. Department of Aeronautical Engineering, Chaoyang University of Technology, Taichung 413, Taiwan