1. Department of Chemical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Kusong, Yusong, Taejon, Korea 305-701, and Nanokor Co. Ltd., Room 911, Technology Business Incubator Center, University of Suwon, Wawoo-ri, Bongdam-eub, Hwasung-gun, Kyunggi-do, Korea 455-743