About the Authors

Jun Tang

tjuns1979@126.com

Affiliation College of Science, China University of Mining and Technology, Xuzhou, China

Jin-Ming Luo

Affiliation College of Science, China University of Mining and Technology, Xuzhou, China

Jun Ma

Affiliation Department of Physics, Lanzhou University of Technology, Lanzhou, China

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: JT. Performed the experiments: JT JL JM. Analyzed the data: JT JL JM. Wrote the paper: JT.