Funding for this research was provided by:
National Natural Science Foundation of China (51475039, 51105028)
Article History
Received: 6 March 2018
Accepted: 27 April 2018
First Online: 8 May 2018
Authors’ Information
: Rui Li is an associate professor in the University of Science and Technology Beijing; Shiwei Wang is a graduate student in the University of Science and Technology Beijing; Qing Peng is a research fellow in University of Michigan, Ann Arbor.
: The authors declare that they have no competing interests.
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