Control of flow separation in magnetohydrodynamics

The control of separation in a flow can be effected by specifying the surface vorticity. If one specifies the surface vorticity, then one can enforce the usual boundary conditions by optimizing with respect to the boundary. If there are no net magnetic surface stresses, then the computation of the shape derivative decouples from the magnetic field

Control of the wave equation at a rational point

The wave equation is controlled by a force at one point, which is a rational point of the interval [-1, 1]: geometric interpretations are given of the controllable subclasses. © 1992

Modeling and computation of pulsed laser materials processing

Pulsed laser materials processing incorporates many physical processes, the modeling of which requires disparate techniques. We focus on two closely related topics that arise in laser processing. First, we illustrate by use of numerical simulation the distinction between metals and ceramics in their response to laser fluence. Second we explain recent experiments that indicate that the substrate heater is a strong control parameter in laser processing, and this can be understood from the point of view of shock dynamics. © 2007 Institute for Scientific Computing and Information

Modeling and computation of pulsed laser materials processing

Pulsed laser materials processing incorporates many physical processes, the modeling of which requires disparate techniques. We focus on two closely related topics that arise in laser processing. First, we illustrate by use of numerical simulation the distinction between metals and ceramics in their response to laser fluence. Second we explain recent experiments that indicate that the substrate heater is a strong control parameter in laser processing, and this can be understood from the point of view of shock dynamics. © 2007 Institute for Scientific Computing and Information

Control of flow separation in magnetohydrodynamics

The control of separation in a flow can be effected by specifying the surface vorticity. If one specifies the surface vorticity, then one can enforce the usual boundary conditions by optimizing with respect to the boundary. If there are no net magnetic surface stresses, then the computation of the shape derivative decouples from the magnetic field

Control of the wave equation at a rational point

The wave equation is controlled by a force at one point, which is a rational point of the interval [-1, 1]: geometric interpretations are given of the controllable subclasses. © 1992

Magnetocaloric effect in ferromagnetic and superconducting materials

Computer studies are made illustrating the similarities of the interesting change of sign in the magnetocaloric effect between the vortex lattice in superconductors and a system of interacting magnons and phonons in ferromagnetic materials. This change happens in the superconducting system when the external magnetic field approaches a critical value, while the critical point in the ferromagnetic system is where the external magnetic field turns the direction of magnetization from the easy to the hard direction. The usefulness for the study of high-temperature superconductors is suggested

Reacting dynamics of the laser ablation plume

Pulsed laser ablation of metals and oxides have been carried out under controlled conditions. Process control parameters such as laser power, laser excitation voltage, beam focus, chamber pressure, substrate temperature, pulse repetition rate, and target rotation rate were changed and the outputs analyzed. The real-time signature of the plume has been studied and characterized. These experimental results are compared with mathematical models of the ablation process and the supersonic plume propagation wave. We can explain with reference to the correlation of real-time spectroscopy some anomalies present in the ablation process involving the non-equilibrium production of oxides. In the computational model for the reacting pulsed-laser ablation plume, the stoichiometry depends on input energy via a prescribed inlet velocity, density, and temperature, which are calculated at the edge of a Knudsen layer. We conclude that a sharp reaction front promotes a quick rise to desired stoichiometry, which can be important in applications involving deposition onto substrates. © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved

Reacting dynamics of the laser ablation plume

Pulsed laser ablation of metals and oxides have been carried out under controlled conditions. Process control parameters such as laser power, laser excitation voltage, beam focus, chamber pressure, substrate temperature, pulse repetition rate, and target rotation rate were changed and the outputs analyzed. The real-time signature of the plume has been studied and characterized. These experimental results are compared with mathematical models of the ablation process and the supersonic plume propagation wave. We can explain with reference to the correlation of real-time spectroscopy some anomalies present in the ablation process involving the non-equilibrium production of oxides. In the computational model for the reacting pulsed-laser ablation plume, the stoichiometry depends on input energy via a prescribed inlet velocity, density, and temperature, which are calculated at the edge of a Knudsen layer. We conclude that a sharp reaction front promotes a quick rise to desired stoichiometry, which can be important in applications involving deposition onto substrates. © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved