1. Senior Researcher, Research Institute of Industrial Science and Technology, 79-5 Youngcheon-ri, Dongtan-myeon, Hwaseong-si, Kyounggi-do 445-813, South Korea.
2. Professor, Dept. of Architecture, Seoul National Univ., Gwanak 599, Gwanak-ro, Gwanak-gu, Seoul 151-744, South Korea (corresponding author).