Funding for this research was provided by:
the National Natural Science Foundation of China (61573299)
the Science and Technology Plan Project of Hunan Province (2016TP1020)
the Open Fund Project of Hunan Provincial Key Laboratory of Intelligent Information Processing and Application for Hengyang Normal University (2017IIPAYB04)
the Natural Science Foundation of Hunan Province (2017JJ2011)
the Research Project of the Education Department of Hunan Province (17A031)
Article History
First Online: 6 September 2018
Compliance with Ethical Standards
:
: The authors declare that they have no conflicts of interest.