Funding for this research was provided by:
National Natural Science Foundation of China (61673308, 61503292)
National Natural Science Foundation of China (61673014)
Fundamental Research Funds for the Central Universities (JB181305)
Science Foundation Project of Tianshui Normal University (ZD2017-01)
Innovition Fund of Xidian University
Article History
Received: 29 October 2017
Accepted: 27 July 2018
First Online: 3 August 2018
Compliance with ethical standards
:
: We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.