Affiliation: | (1) Electronics and Telecommunications Research Institute, 138, Gajeongno, Yueseong-gu, Daejeon, Republic of Korea;(2) Department of Computer and Information Science, Korea University, 208, Seochang-Ri, Chochiwon, Chungnam, 339-700, South Korea;(3) Department of Computer Science Education, Catholic University of Daegu, 330 Geumnak, Hayang-eup, Gyeongsan-si, Gyeongbuk, 712-702, South Korea |