1. Department of Civil Engineering, University of Salerno, Via G. Paolo II, No. 132, 84084 Fisciano, Salerno, Italy
2. Mechanical and Aerospace Engineering Department, University of California, San Diego, 9500 Gilman Dr., La Jolla, California 92093-0418, USA
3. Materials Science and Engineering Program, University of California, San Diego, 9500 Gilman Dr., La Jolla, California 92093-0418, USA