1. Laboratorie d’Analyse et de Mathématiques Appliquées, UMR 8050 CNRS; Université Paris-Est; 5 boulevard Descartes, Cité Descartes Champs-sur-Marne Marne-la-Vallée, Cedex 2 77454 France
2. Institute of Applied Physics and Computational Mathematics; PO Box 8009 Beijing 100088 PR China
3. The Graduate School of China Academy of Engineering Physics; PO Box 2101 Beijing 100088 PR China