1. CRIStAL, UMR CNRS 9189, Ecole Centrale de Lille , Villeneuve d’Ascq, France
2. School of Transportation Science and Engineering, Beihang University , Beijing, P.R. China
3. Beijing Engineering Center for Clean Energy & High Efficient Power, Beihang University , Beijing, P.R. China
4. Department of Mathematics, Beijing Jiaotong University , Beijing, P.R. China