Funding for this research was provided by:
the National Natural Science Foundation of China (51403033)
Fundamental Research Funds for the Central Universities from China (No.14D310106 and NO. 2232014D3-15)
Article History
Received: 25 May 2018
Accepted: 3 September 2018
First Online: 12 September 2018
Competing Interests
: The authors declare that they have no competing interests.
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