1. Laboratory of Dielectric Polymer Materials and Devices, Department of Polymer Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People's Republic of China
2. Laboratoire de Mécanique des Sols, Structures et Matériaux, CNRS UMR8579, Ecole Centrale Paris, Grande Voie des Vignes, 92290 Châtenay-Malabry Cedex, France
3. State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, People's Republic of China