Two questions concerning the boundary control of certain elastic systems

We present two questions connected with the stabilization of certain hyperbolic partial differential equations which are controlled on their boundaries. The uncontrolled versions of these systems are conservative and therefore represent only approximate realizations of the physical phenomena. The first question concerns the qualitative behavior of a given stabilizing feedback for such a system vis à vis that of an appropriately damped realization using the same feedback. The second question concerns the robustness of both the original system and a damped version when time delays occur in a given feedback stabilization scheme.