[1] Univ Bourgogne Franche Comte, Inst Math Bourgogne, F-21078 Dijon, France
[2] Univ Paris Est, CERMICS, ENPC, F-77455 Marne La Vallee 2, France
[3] INRIA Paris, F-75589 Paris, France
[4] EDF, R&D ERMES, Palaiseau, France
[5] UMR EDF CNRS CEA ENSTA 9219, IMSIA, Palaiseau, France
[6] Univ Paris Est, CERMICS ENPC, F-77455 Marne La Vallee 2, France