Funding for this research was provided by:
National Nature Science Foundation of China (Grant No. 91746111, Grant No.71702143)
Ministry of Education & China Mobile Joint Research Fund Program (No. MCM20160302)
Shaanxi provincial development and Reform Commission (No. SFG2016789)
Xi’an Municipal Science & Technology Commission (No. 2017111SF/RK005-(7))
Natural Science Foundation of Shaanxi Province (NO. 2017JQ7004)
China Postdoctoral Science Fund (No. 2016M602840)
Article History
Received: 1 June 2017
Revised: 3 February 2018
Accepted: 9 April 2018
First Online: 11 May 2018