1. Department of Physics and Astronomy San Francisco State University San Francisco CA 94132 USA
2. College of Electronic Engineering South China Agricultural University Guangzhou 510642 China
3. Guangxi Key Lab for Relativistic Astrophysics Center on Nanoenergy Research School of Physical Science and Technology Guangxi University Nanning Guangxi 530004 China
4. School of Electro-mechanical Engineering Guangdong University of Technology Guangzhou 510006 China