1. Department of Applied Chemistry, Sejong University, 98 Gunja, Gwangjin, Seoul, 143-747, Korea; Korea Institute of Science and Technology, P.O. Box 131 Cheongryang, Seoul 130-650 Korea; and Department of Chemical Engineering, Kangwon National University, 192-1, Hyoja2, Chunchon, Kangwon, 200-701, Korea