1. Materials and Engineering Program, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
2. Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
3. Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003, USA
4. Department of Mathematical Sciences, University of Delaware, Newark, Delaware 19702, USA
5. Department of Energy Resources Engineering, Stanford University, 367 Panama Street, Stanford, California 94305, USA