Funding for this research was provided by:
Industrial Science and Technology Project of Shaanxi Province (2016GY-140)
Science Research Project of the Key Laboratory of Shaanxi Provincial Department of Education (15JS078)
National Natural Science Foundation of China (61502384)
Article History
Received: 7 March 2018
Accepted: 21 March 2018
First Online: 2 April 2018
Competing interests
: The authors declare that they have no competing interests.
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