Stochastic control problems with delay

We consider optimal control problems for systems described by stochastic differential equations with delay. We state conditions for certain classes of such systems under which the stochastic control problems become finite-dimensional. These conditions are illustrated with three applications. First, we solve some linear quadratic problems with delay. Then we find the optimal consumption rate in a financial market with delay. Finally, we solve explicitly a deterministic fluid problem with delay which arises from admission control in ATM communication networks.     

Self-organized minimum-energy structures for dielectric elastomer actuators

When a stretched elastomer is laminated to a flat plastic frame, a complex shape is formed, which is termed a minimum-energy structure. It is shown how self-organized structures can be applied in the development of actuators with complex, out-of-plane actuationmodes. This unusual concept is then demonstrated in the case of dielectric elastomer actuators. Among advantages of this approach are the simplicity in manufacturing, the potential complexity and sophistication of the manufactured structures, and the general benefits of the concept when applied to other electro-mechanically active materials. PACS 46.32.+x; 77.65.-j; 83.80.Va     

Morphological modifications of Ag/Cu(111) probed by photoemission spectroscopy of quantum well states and the Shockley surface state

Epitaxial ultra-thin Ag films grown on Cu(111) have been investigated by angle-resolved photoemission spectroscopy. The thickness dependence of the binding energy for the Shockley surface state at 300 K could be determined accurately in films up to 5 ML thick. Furthermore, we observe drastic changes in the film morphology after annealing to 450 K. Spectral modifications in the shape of the quantum-well states (QWS), characteristic for these ultra-thin silver films, prove that the surface morphology is homogeneous. The photoemission spectra also indicate that the silver film bifurcates to form a film exhibiting two distinct film thicknesses. For all levels of silver coverage, we identify surface regions that are 2 ML thick, while the thickness of the remaining surface depends on the amount of deposited silver. The almost purely Lorentzian line-shape of the spectral features corresponding to the two different surface regions show that both surface areas are atomically flat. PACS 68.55.Jk; 73.20.At; 73.21.Fg; 79.60.Dp