1. School of Mechatronics, Gwangju Institute of Science and Technology, 123 Cheomdangwagiro, Bukgu, Gwangju, 500-712, Korea
2. Korea Culture Technology Institute, Gwangju Institute of Science and Technology, 123 Cheomdangwagiro, Bukgu, Gwangju, 500-712, Korea
3. Department of Science, Agricultural University of Athens, Athens, 118 55, Greece