Funding for this research was provided by:
Key Projects in the National Science & Technology Pillar Program during the Twelfth Five-year Plan Period (2014BAK12B00)
National Natural Science Foundation of China (61101186)
Article History
Received: 30 March 2017
Accepted: 22 August 2018
First Online: 17 September 2018
Competing interests
: The authors declare that they have no competing interests.
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