1. School of Mechanical Engineering, Sungkyunkwan University; Suwon 440-746 Republic of Korea
2. Xidex Corporation; Austin, Texas 78754 USA
3. Department of Mechanical Engineering and the Materials Science and Engineering Program; The University of Texas at Austin; Austin, Texas 78712 USA
4. Department of Aerospace Engineering and Engineering Mechanics; The University of Texas at Austin; Austin, Texas 78712 USA
5. Institute of Basic Sciences Center for Multidimensional Carbon Materials &Department of Chemistry and School of Materials Science and Engineering, Ulsan National Institute of Science and Technology; Ulsan 689-798 Republic of Korea