Funding for this research was provided by:
National Natural Science Foundation of China (11201128)
Natural Science Foundation of Heilongjiang Province (A201414)
Natural Science Foundation of Heilongjiang Province (QC2016005)
Directorate for Mathematical and Physical Sciences (1313243)
Article History
Received: 25 February 2017
Revised: 25 June 2017
First Online: 1 August 2017