Funding for this research was provided by:
the National Natural Science Foundation of China (No.11501125)
the Science and Technology Project of Jiangxi Provincial Education Department (No.GJJ170821)
the Natural Science Foundation of Gannan Normal University (No.201605)
Received: 23 February 2018
Accepted: 15 June 2018
First Online: 27 July 2018
: The authors declare that they have no competing interests.