Funding for this research was provided by:
the National Natural Science Foundation of China (No. 61363006)
the Open Projects of State Key Laboratory of Integrated Service Networks (ISN) of Xidian University (No. ISN19-13)
the National Natural Science Foundation of Guangxi (No. 2016GXNSFAA380098)
the Science and Technology Program of Guangxi (No. AB17195045)
Article History
Received: 20 August 2018
Accepted: 22 November 2018
First Online: 22 December 2018
Competing interests
: The authors declare that they have no competing interests.
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