Funding for this research was provided by:
National Natural Science Foundation of China (61801363)
Basic Scientific Research Foundation of Xidian University (8002/20101166309, 8002/20103166309)
Natural Science Foundation of Shaanxi Province (2017JM6039)
National Natural Science Fundation of China (61271299, 61501348)
Article History
Received: 14 July 2017
Revised: 8 October 2018
Accepted: 9 October 2018
First Online: 16 October 2018