Funding for this research was provided by:
National Natural Science Foundation of China (No. 11671123)
Natural Science Foundation of Hunan Province (No. 14JJ1025)
Science Research Project of Hunan Province Education Office (No. 17C0467, No. 17C0468)
Article History
Received: 13 July 2017
Revised: 18 May 2018
First Online: 26 May 2018