1. a Department of Mechanical and Materials Engineering , Portland State University , Portland, OR, 97207, USA
2. b Department of Mechanical Engineering , The Johns Hopkins University , Baltimore, MD, 21218, USA
3. c Department of Mechanical, Aerospace and Nuclear Engineering , Rensselaer Polytechnic Institute , Troy, NY, 12180, USA
4. d Department of Applied Mechanics , Chalmers University of Technology , SE-41296, Gothenburg, Sweden