1. School of Physical Science and Technology Lanzhou University Lanzhou Gansu 730000 China
2. School of Stomatology Lanzhou University Lanzhou Gansu 730000 China
3. Department of Biomedical Engineering University of Houston Houston TX 77204 USA
4. Departments of Mechanical Engineering and Electrical and Computer Engineering Texas Center for Superconductivity University of Houston Houston TX 77204 USA