Funding for this research was provided by:
Research Foundation of Hunan Provincial Education Department, China (15A086)
Hunan Provincial Natural Science Foundation of China (2018JJ2177)
Postgraduate Research and Innovation Project of Hunan Province (CX2016B285 and CX2016B314)
Received: 17 October 2018
Accepted: 19 February 2019
First Online: 6 March 2019
Consent for publication
: Not applicable.
: The authors declare that they have no competing interests.
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