1. Department of Mathematics and Computer Science, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600 MB, The Netherlands e-mail:
2. School of Computer Science and Technology, State Key Laboratory of Hydraulic Engineering, Simulation and Safety, Tianjin University, Tianjin 300072, China e-mail:
3. Hydromechanics Laboratory, Department of Civil Engineering, Middle East Technical University, Ankara 06800, Turkey e-mail:
4. Department of Mechanics, Tallinn University of Technology, Tallinn 19086, Estonia e-mail: