1. a School of Electronics Engineering, College of IT Engineering, Kyungpook National University , Daegu , Korea
2. b Department of Electrical and Computer Engineering , University of Minnesota , Minneapolis , MN , 55455 , USA
3. c School of Technology Management, Ulsan National Institute of Science and Technology (UNIST) , Ulsan , Korea
4. d Department of Biomedical Engineering , School of Electrical Engineering, University of Ulsan , Ulsan , Korea