1. Assistant Manager, Samsung Construction & Trading Corporation, 1321-20 Seocho2-Dong, Seocho-gu, Seoul 137-956, South Korea; and Instructor, Chung-Ang Univ., 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756, South Korea.
2. Adjunct Professor, Colorado State Univ., Fort Collins, CO 80523.
3. Professor, Chung-Ang Univ., 221 Heuksuk-Dong, Dongjak-Ku, Seoul 156-756, South Korea, (corresponding author).