First Author:   Franck Martin University of Rennes 1 and Crem franck.martin@univ-rennes1.fr   7, place Hoche Rennes, 35065, France   33(0)223233577(Phone) 33(0)223233577(Fax) http://perso.univ-rennes1.fr/franck.martin/ Second Author: Jiangxingyun Zhang University of Rennes 1 and Crem zhangjxy@gmail.com   Rennes, 35065, France   33(0)659158374(Phone) 33(0)223233599(Fax)