1. Department of Civil Engineering, Graduate School of Engineering, Tohoku University Aoba, Sendai 980-8579, Japan
2. Taejin Engineering, Inc., 375-17, Dongbu-ri, Gijang-gun, Busan 619-905, Korea
3. Nishihara Environmental Sanitation Research Corporation, Ltd., 3-6-18, Shibaura, Minato-ku, Tokyo 108-0023, Japan
4. Department of System Engineering, Faculty of Engineering, Shizuoka University, 3-5-1, Jouhoku, Shizuoka 432-8561, Japan