1. Research Fellow, Graduate Institute of Environmental Engineering, National Taiwan Univ., Taipei 106, Taiwan; formerly, Research Fellow, School of Civil & Environmental Engineering, Cornell Univ., Ithaca, NY 14853-3501.
2. Professor, School of Civil & Environmental Engineering, Cornell Univ., Ithaca, NY 14853-3501.
3. Senior Lecturer, School of Civil & Environmental Engineering, Cornell Univ., Ithaca, NY 14853-3501 (corresponding author).