Funding for this research was provided by:
National Natural Science Foundation of China (No. 61873221, No. 61672447)
Natural Science Foundation of Hunan Province (No. 2018JJ4058, No. 2017JJ5036)
Hunan Provincial Science and Technology Department (No. 2018TP1036)
the CERNET Next Generation Internet Technology Innovation Project (No. NGII20160305, No. NGII20170109)
Article History
Received: 18 December 2018
Accepted: 3 July 2019
First Online: 17 July 2019
Ethics approval and consent to participate
: Not applicable.
: Not applicable.
: The authors declare that there are no competing interests regarding the publication of this paper.