1. Department of Computer and Radio Communications Engineering, Korea University, Anam-dong 1, 5-ga, Seongbuk-gu, Seoul 136-701, Republic of Korea
2. Department of Statistics and Computer Science, Kunsan National University, 558 Daehangno, Gunsan, Jeollabuk-do 573-701, Republic of Korea
3. Department of Computer Intelligence Research, Korea Institute of Science and Technology Information (KISTI), 245 Daehak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea
4. Graduate School of Convergence IT, Korea University, Anam-dong 1, 5-ga, Seongbuk-gu, Seoul 136-701, Republic of Korea