Funding for this research was provided by:
National Natural Science Foundation of China (61701067, 61671095)
Research Project of Chongqing Educational Commission (KJ1600427)
National Natural Science Foundation of China (61771085)
Research Project of Chongqing Educational Commission (KJ1600429)
Article History
Received: 2 December 2017
Accepted: 31 May 2018
First Online: 14 June 2018
Competing interests
: The authors declared that they have no competing interests.
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