Funding for this research was provided by:
China Postdoctoral Science Foundation (2016M600190)
Key Project of Science & Technology Research of Higher Education Institutions of Hebei Province (ZD2018059)
Innovation & Entrepreneurship Training Program of Hebei University of Technology (201710080052)
Guangdong Provincial Science and Technology Project (2017A050506009)
Received: 14 May 2018
Accepted: 14 October 2018
First Online: 30 October 2018
: The authors declare that they have no competing interests.
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