About the Authors

Yan Xu

xuyan@ustb.edu.cn

Affiliation Department of Information and Computer Science, University of Science and Technology Beijing, Beijing 100083, China

Jun Ding

Affiliation Department of Information and Computer Science, University of Science and Technology Beijing, Beijing 100083, China

Ling-Yun Wu

Affiliation Institute of Applied Mathematics, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100190, China

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: YX. Performed the experiments: YX JD. Analyzed the data: JD. Contributed reagents/materials/analysis tools: LYW. Wrote the paper: YX JD.