“…The coefficient of restitution for nanoparticles is not unity, and the absolute value is unknown for nanosized particles (Ayesh et al, 2010;Givehchi & Tan, 2014;Sato, Chen, & Pui, 2007;Wall, John, & Wang, 1990). The coefficient of restitution varies with the material of the nanoparticles, the filter media, and the impact velocity of the nanoparticles.…”