Funding for this research was provided by:
National Natural Science Foundation of China (61603275)
Natural Science Foundation of Tianjin City (15JCYBJC51500)
Tianjin Normal University (043-135202XB1602)
Tianjin Normal University (52XB1505)
Received: 2 January 2018
Accepted: 11 March 2018
First Online: 20 March 2018
: The authors declare that they have no competing interests.
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