| 1. |
- Gunnarsson, Svante, et al.
(författare)
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Some asymptotic results in recursive identification using Laguerre models
- 1990
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Ingår i: Proceedings of the IEEE Conference on Decision and Control. - Honolulu, HI, USA : Linköping University. ; , s. 1068-1073
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Konferensbidrag (refereegranskat)abstract
- Frequency domain expressions for the quality of recursively identified Laguerre models are presented. These models generalize finite impulse response (FIR) models by using a priori information about the dominating time constants of the system to be identified. Expressions for the model quality are derived under the assumptions that the system varies slowly, that the model is updated slowly, and that the model order is high. The model quality is evaluated by investigating the properties of the estimated transfer function, and explicit expressions for the mean square error (MSE) of the transfer function, and explicit expressions for the mean square error of the transfer function estimate are derived.
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| 2. |
- Ottersten, Björn, 1961-, et al.
(författare)
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Asymptotic Robustness of Sensor Arrary Processing Methods
- 1990
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Ingår i: Proceedings of the 1990 International Conference on Acoustics, Speech and Signal Processing. - Linköping : IEEE Signal Processing Society. ; , s. 2635-2638
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Konferensbidrag (refereegranskat)abstract
- Methods for estimating the parameters of narrowband signals arriving at an array of sensors are analyzed. Asymptotic results for several estimators have recently appeared in the literature. With few exceptions, the previous analysis requires the incident signal waveforms to be Gaussian random variables. These results are shown to be valid under much more general conditions, i.e. the actual distribution of the signal waveforms does not affect the asymptotic properties of the parameter.
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| 3. |
- Hansbo, Peter F G, 1959, et al.
(författare)
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A velocity-pressure streamline diffusion finite element method for the incompressible Navier-Stokes equations
- 1990
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Ingår i: Computer Methods in Applied Mechanics and Engineering. - LAUSANNE : Elsevier BV. ; 84:2, s. 175-192
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a streamline diffusion finite element method is introduced for the time-dependent incompressible Navier-Stokes equations in a bounded domnain in R^2 and R^3 in the case of high Reynolds number flow. An error estimate is proved and numerical results are given. The method is based on a mixed velocity-pressure formulation using the same finite element discretization of space-time for the velocity and the pressure spaces, which consists of piecewise linear functions, together with certain least-squares modifications of the Galerkin variational formulation giving added stability without sacrificing accuracy.
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| 4. |
- Johnson, Claes, et al.
(författare)
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On the convergence of shock-capturing streamline diffusion finite element methods for hyperbolic conservation laws
- 1990
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Ingår i: Mathematics of Computation. - PROVIDENCE : American Mathematical Society (AMS). - 0025-5718 .- 1088-6842. ; 54:189, s. 107-129
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Tidskriftsartikel (refereegranskat)abstract
- We extend our previous analysis of streamline diffusion finite element methods for hyperbolic systems of conservation laws to include a shock-capturing term adding artificial viscosity depending on the local absolute value of the residual of the finite element solution and the meh size. With this term present, we prove a maximum norm bound for finite element solutionsof Burgers' equation an thus complete an earlier convergence proof for this equation. We further prove, using entropy variables, that a strong limit of finite element solutions is a weak solution of the system of conservation laws and satisfies the entropy inequality asociated with the entropy variables. Results of some numerical experiments for the time-dependent compressible Euler equations in two dimensions are also reported.
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| 5. |
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| 6. |
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| 7. |
- Brunnström, Kjell, et al.
(författare)
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Scale and Resolution in Active Analysis of Local Image Structure
- 1990
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Ingår i: Image and Vision Computing. - : Elsevier. ; 8:4, s. 289-296
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Tidskriftsartikel (refereegranskat)abstract
- Focus-of-attention is extremely important in human visual perception. If computer vision systems are to perform tasks in a complex, dynamic world they will have to be able to control processing in a way that is analogous to visual attention in humans. Problems connected to foveation (examination of selected regions of the world at high resolution) are examined. In particular, the problem of finding and classifying junctions from this aspect is considered. It is shown that foveation as simulated by controlled, active zooming in conjunction with scale-space techniques allows for robust detection and classification of junctions.
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| 8. |
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| 9. |
- Krishnamurthy, Vikram, et al.
(författare)
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Factorizations that relax the positive real condition in continuous-time and fast-sampled ELS schemes
- 1990
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Ingår i: International journal of adaptive control and signal processing (Print). - : Wiley. - 0890-6327 .- 1099-1115. ; 4:5, s. 389-414
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes extended least-squares (ELS) for ARMAX model identification of continuous-time and certain discrete-time systems. The schemes have a relaxed strictly positive real (SPR) condition for global convergence. The relaxed SPR scheme is achieved by introducing overparametrization and prefiltering but without introducing ill-conditioning. The schemes presented are the first such proposed for continuous-time systems. The concepts developed in continuous time carry through to fast-sampled continuous-time systems and associated discrete-time ELS algorithms. For such situations, in comparison with previously proposed discrete-time schemes, the degree of overparametrization required in the proposed scheme of this paper is significantly lower. The reduction is achieved by using more suitable prefiltering and overparametrization techniques than previously proposed. We also establish the persistence of excitation (PE) of the regression vectors in the proposed ELS schemes to assure strong consistency, obtain convergence rates and provide robustness to unmodelled dynamics. To prove the PE of continuous-time regression vectors, we develop output reachability characterization for MIMO linear continuous-time systems.
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| 10. |
- Ottersten, Björn, 1961-, et al.
(författare)
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Direction-of-Arrival Estimation for Wideband Signals using the ESPRIT Algorithm
- 1990
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Ingår i: IEEE Transactions on Acoustics, Speech and Signal Processing. - : IEEE Signal Processing Society. - 0096-3518. ; 38:2, s. 317-327
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Tidskriftsartikel (refereegranskat)abstract
- A novel direction-of-arrival estimation algorithm is proposed that applies to wideband emitter signals. A sensor array with a translation invariance structure is assumed, and an extension of the ESPRIT algorithm for narrowband emitter signals is obtained. The emitter signals are modeled as the stationary output of a finite-dimensional linear system driven by white noise. The array response to a unit impulse from a given direction is represented as the impulse response of a linear system. The measured data from the sensor array can then be seen as the output of a multidimensional linear system driven by white noise sources and corrupted by additive noise. The emitter signals and the array output are characterized by the modes of the linear system. The ESPRIT algorithm is applied at the poles of the system, the power of the signals sharing the pole is captured, and the effect of noise is reduced. The algorithm requires no knowledge, storage, or search of the array manifold, as opposed to wideband extensions of the MUSIC algorithm. This results in a computationally efficient algorithm that is insensitive to array perturbations. Simulations are presented comparing the wideband and ESPRIT algorithm to the modal signal subspace method and the coherent signal subspace method.
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