We show that a model proposed by Rubin, Rosenau, and Gottlieb [J. Appl. Phys. 77, 4054 (1995)] for dispersion caused by an inherent material characteristic length belongs to the class of simple materials. Therefore, it is possible to generalize the idea of Rubin, Rosenau, and Gottlieb to include a wide range of material models, from nonlinear elasticity to turbulence. Using this insight, we are...
