1. Department of Chemical Engineering, Kyungpook National University, Daegu, 702-701, Korea, GS Fuel Cell Co., Ltd., 289-15, Daehwa-Dong, Daedeok-Gu, Daejeon, 306-801, Korea, School of Chemical Engineering and Technology, Yeungnam University, Kyongsan, 712-749, Korea, and Korea Electric Power Research Institute, Daejon, 305-380, Korea