1. Department of Electrical Engineering, Hanyang University, Haengdang 1-dong, Seongdong-gu, Seoul 133-791 Korea. Tel.: +82 2 2290 0349; Fax: +82 2 2295 7111; E-mail: julee@hanyang.ac.kr
2. Department of Electrical Engineering, Hanbat National University, Daejeon, 305-719 Korea. Tel.: +82 41 821 1099; E-mail: yhyunk@hanbat.ac.kr