1. De´partment de Mathe´matiques et de Ge´nie Industriel, E´cole Polytechnique de Montre´al, C.P. 6079, succ. Centre-ville, Montre´al (Que´bec), H3C3A7, Canada
2. Intelligent Systems Laboratory, 2139 Seamans Center, Department of Mechanical and Industrial Engineering, The University of Iowa, IA 52242-1527