1. Department of Chemical Engineering, Kyungpook National University, Daegu 702-701, Korea; GS Fuel Cell Company, 453-2 Seongnae-dong, Gangdong-gu, Seoul 134-848, Korea; School of Chemical Engineering and Technology, Yeungnam University, Gyongsan 712-749, Korea; and Korea Electric Power Research Institute, Daejon 305-380, Korea