Funding for this research was provided by:
National Natural Science Foundation of China (51707159)
Natural Science Foundation of Shaanxi Province (2017JM5073)
State Key Laboratory of Electrical Insulation and Power Equipment (EIPE17205)
Fundamental Research Funds for the Central Universities (3102017zy047)
Article History
Received: 7 January 2019
Revised: 17 January 2019
Accepted: 21 January 2019
First Online: 1 February 2019
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.