Experimental characterization of vibrated granular rings
  We report an experimental study of the statistical properties of vibrated granular rings. In this system, a linked rod and bead metallic chain in the form of a ring is collisionally excited by a vertically oscillating plate. The dynamics are driven primarily by inelastic bead-plate collisions and are simultaneously constrained by the rings' physical connectedness. By imaging many instances of the ring configurations, we measure the ensemble averages and distributions of several physical characteristics on the scale of individual beads and composite ring. We study local properties such as inter-bead seperation and inter-bonds angles, and global properties such as the radius of gyration and center of mass motion. We characterize scaling with respect to the size of the chain. 
Z.A. Daya, E. Ben-Naim, R.E. Ecke