Funding for this research was provided by:
the National Natural Science Foundations of China (61471310)
the Natural Science Foundations of Hunan Province, China (2015JJ2142)
the Research Foundation of Education Bureau of Hunan Province, China and the Natural Science Foundation of Xiangtan University, China (17C1530 15XZX33)
Article History
Received: 19 September 2017
Revised: 1 December 2017
Accepted: 6 December 2017
First Online: 12 April 2018