30,923 research outputs found
A numerical algorithm for optimal feedback gains in high dimensional LQR problems
A hybrid method for computing the feedback gains in linear quadratic regulator problems is proposed. The method, which combines the use of a Chandrasekhar type system with an iteration of the Newton-Kleinman form with variable acceleration parameter Smith schemes, is formulated so as to efficiently compute directly the feedback gains rather than solutions of an associated Riccati equation. The hybrid method is particularly appropriate when used with large dimensional systems such as those arising in approximating infinite dimensional (distributed parameter) control systems (e.g., those governed by delay-differential and partial differential equations). Computational advantage of the proposed algorithm over the standard eigenvector (Potter, Laub-Schur) based techniques are discussed and numerical evidence of the efficacy of our ideas presented
A unified framework for approximation in inverse problems for distributed parameter systems
A theoretical framework is presented that can be used to treat approximation techniques for very general classes of parameter estimation problems involving distributed systems that are either first or second order in time. Using the approach developed, one can obtain both convergence and stability (continuous dependence of parameter estimates with respect to the observations) under very weak regularity and compactness assumptions on the set of admissible parameters. This unified theory can be used for many problems found in the recent literature and in many cases offers significant improvements to existing results
Computational methods for estimation of parameters in hyperbolic systems
Approximation techniques for estimating spatially varying coefficients and unknown boundary parameters in second order hyperbolic systems are discussed. Methods for state approximation (cubic splines, tau-Legendre) and approximation of function space parameters (interpolatory splines) are outlined and numerical findings for use of the resulting schemes in model "one dimensional seismic inversion' problems are summarized
Observations of solar energetic particles at a synchronous orbit
The Space Environment Monitors (SEM) on board the Japanese geostationary meteorological satellites (GMS-1 and GMS-2) observed energetic protons, alpha particles and electrons continuously for February 1978 to September 1984. The satellites were at 6.6 Earth radii above 140 deg E equator
Instanton Calculus in R-R 3-form Background and Deformed N=2 Super Yang-Mills Theory
We study the ADHM construction of instantons in N=2 supersymmetric Yang-Mills
theory deformed in constant Ramond-Ramond (R-R) 3-form field strength
background in type IIB superstrings. We compare the deformed instanton
effective action with the effective action of fractional D3/D(-1) branes at the
orbifold singularity of C^2/Z_2 in the same R-R background. We find discrepancy
between them at the second order in deformation parameters, which comes from
the coupling of the translational zero modes of the D(-1)-branes to the R-R
background. We improve the deformed action by adding a term with space-time
dependent gauge coupling. Although the space-time action differs from the
action in the omega-background, both actions lead to the same instanton
equations of motion at the lowest order in gauge coupling.Comment: 27 pages, version to appear in JHE
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