Optimization of quasi-normal eigenvalues for Krein-Nudelman strings
  The paper is devoted to optimization of resonances for Krein strings with total mass and statical moment constraints. The problem is to design for a given $\alpha \in \R$ a string that has a resonance on the line $\alpha + \i \R$ with a minimal possible modulus of the imaginary part. We find optimal resonances and strings explicitly. 
Illya M. Karabash
math.SP math.OC