1. Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education Harbin University of Science and Technology 52 Xuefu Road Harbin Heilongjiang 150080 People's Republic of China
2. School of Electrical and Electronic Engineering Harbin University of Science and Technology 52 Xuefu Road Harbin Heilongjiang 150080 People's Republic of China
3. Department of Electrical Engineering and Applied Electronics Tsinghua University 30 Shuangqing Road, Haidian District Beijing 100084 People's Republic of China