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Park, Jae H. "Chebyshev Approximation of Discrete polynomials and Splines." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/30195.
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The recent development of the impulse/summation approach for efficient B-spline computation in the discrete domain should increase the use of B-splines in many applications. Because we show here how the impulse/summation approach can also be used for constructing polynomials, the approach with a search table approach for the inverse square root operation allows an efficient shading algorithm for rendering an image in a computer graphics system. The approach reduces the number of multiplies and makes it possible for the entire rendering process to be implemented using an integer processor.
In many applications, Chebyshev approximation with polynomials and splines is useful in representing a stream of data or a function. Because the impulse/summation approach is developed for discrete systems, some aspects of traditional continuous approximation are not applicable. For example, the lack of the continuity concept in the discrete domain affects the definition of the local extrema of a function. Thus, the method of finding the extrema must be changed. Both forward differences and backward differences must be checked to find extrema instead of using the first derivative in the continuous domain approximation. Polynomial Chebyshev approximation in the discrete domain, just as in the continuous domain, forms a Chebyshev system. Therefore, the Chebyshev approximation process always produces a unique best approximation. Because of the non-linearity of free knot polynomial spline systems, there may be more than one best solution and the convexity of the solution space cannot be guaranteed. Thus, a Remez Exchange Algorithm may not produce an optimal approximation. However, we show that the discrete polynomial splines approximate a function using a smaller number of parameters (for a similar minimax error) than the discrete polynomials do. Also, the discrete polynomial spline requires much less computation and hardware than the discrete polynomial for curve generation when we use the impulse/summation approach. This is demonstrated using two approximated FIR filter implementations.Ph. D.
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Chit, Nassim N. "Weighted Chebyshev complex-valued approximation for FIR digital filters." Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278340.
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Taylor, Barbara J. "Chebyshev centers and best simultaneous approximation in normed linear spaces." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63872.
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Pachon, Ricardo. "Algorithms for polynomial and rational approximation." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:f268a835-46ef-45ea-8610-77bf654b9442.
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Robust algorithms for the approximation of functions are studied and developed in this thesis. Novel results and algorithms on piecewise polynomial interpolation, rational interpolation and best polynomial and rational approximations are presented. Algorithms for the extension of Chebfun, a software system for the numerical computation with functions, are described. These algorithms allow the construction and manipulation of piecewise smooth functions numerically with machine precision. Breakpoints delimiting subintervals are introduced explicitly, implicitly or automatically, the latter method combining recursive subdivision and edge detection techniques. For interpolation by rational functions with free poles, a novel method is presented. When the interpolation nodes are roots of unity or Chebyshev points the algorithm is particularly simple and relies on discrete Fourier transform matrices, which results in a fast implementation using the Fast Fourier Transform. The method is generalised for arbitrary grids, which requires the construction of polynomials orthogonal on the set of interpolation nodes. The new algorithm has connections with other methods, particularly the work of Jacobi and Kronecker, Berrut and Mittelmann, and Egecioglu and Koc. Computed rational interpolants are compared with the behaviour expected from the theory of convergence of these approximants, and the difficulties due to truncated arithmetic are explained. The appearance of common factors in the numerator and denominator due to finite precision arithmetic is characterised by the behaviour of the singular values of the linear system associated with the rational interpolation problem. Finally, new Remez algorithms for the computation of best polynomial and rational approximations are presented. These algorithms rely on interpolation, for the computation of trial functions, and on Chebfun, for the location of trial references. For polynomials, the algorithm is particularly robust and efficient, and we report experiments with degrees in the thousands. For rational functions, we clarify the numerical issues that affect its application.
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Filip, Silviu-Ioan. "Robust tools for weighted Chebyshev approximation and applications to digital filter design." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEN063/document.
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De nombreuses méthodes de traitement du signal reposent sur des résultats puissants d'approximation numérique. Un exemple significatif en est l'utilisation de l'approximation de type Chebyshev pour l'élaboration de filtres numériques.En pratique, le caractère fini des formats numériques utilisés en machine entraîne des difficultés supplémentaires pour la conception de filtres numériques (le traitement audio et le traitement d'images sont deux domaines qui utilisent beaucoup le filtrage). La majorité des outils actuels de conception de filtres ne sont pas optimisés et ne certifient pas non plus la correction de leurs résultats. Notre travail se veut un premier pas vers un changement de cette situation.La première partie de la thèse traite de l'étude et du développement de méthodes relevant de la famille Remez/Parks-McClellan pour la résolution de problèmes d'approximation polynomiale de type Chebyshev, en utilisant l'arithmétique virgule-flottante.Ces approches sont très robustes, tant du point de vue du passage à l'échelle que de la qualité numérique, pour l'élaboration de filtres à réponse impulsionnelle finie (RIF).Cela dit, dans le cas des systèmes embarqués par exemple, le format des coefficients du filtre qu'on utilise en pratique est beaucoup plus petit que les formats virgule flottante standard et d'autres approches deviennent nécessaires.Nous proposons une méthode (quasi-)optimale pour traîter ce cas. Elle s'appuie sur l'algorithme LLL et permet de traiter des problèmes de taille bien supérieure à ceux que peuvent traiter les approches exactes. Le résultat est ensuite utilisé dans une couche logicielle qui permet la synthèse de filtres RIF pour des circuits de type FPGA.Les résultats que nous obtenons en sortie sont efficaces en termes de consommation d'énergie et précis. Nous terminons en présentant une étude en cours sur les algorithmes de type Remez pour l'approximation rationnelle. Ce type d'approches peut être utilisé pour construire des filtres à réponse impulsionnelle infinie (RII) par exemple. Nous examinons les difficultés qui limitent leur utilisation en pratiqueThe field of signal processing methods and applications frequentlyrelies on powerful results from numerical approximation. One suchexample, at the core of this thesis, is the use of Chebyshev approximationmethods for designing digital filters.In practice, the finite nature of numerical representations adds an extralayer of difficulty to the design problems we wish to address using digitalfilters (audio and image processing being two domains which rely heavilyon filtering operations). Most of the current mainstream tools for thisjob are neither optimized, nor do they provide certificates of correctness.We wish to change this, with some of the groundwork being laid by thepresent work.The first part of the thesis deals with the study and development ofRemez/Parks-McClellan-type methods for solving weighted polynomialapproximation problems in floating-point arithmetic. They are veryscalable and numerically accurate in addressing finite impulse response(FIR) design problems. However, in embedded and power hungry settings,the format of the filter coefficients uses a small number of bits andother methods are needed. We propose a (quasi-)optimal approach basedon the LLL algorithm which is more tractable than exact approaches.We then proceed to integrate these aforementioned tools in a softwarestack for FIR filter synthesis on FPGA targets. The results obtainedare both resource consumption efficient and possess guaranteed accuracyproperties. In the end, we present an ongoing study on Remez-type algorithmsfor rational approximation problems (which can be used for infinite impulseresponse (IIR) filter design) and the difficulties hindering their robustness
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Melkemi, Khaled. "Orthogonalité des B-splines de Chebyshev cardinales dans un espace de Sobolev pondéré." Phd thesis, Université Joseph Fourier (Grenoble), 1999. http://tel.archives-ouvertes.fr/tel-00004843.
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Ce travail porte sur l'étude théorique et numérique des splines de Chebyshev. Ces fonctions généralisent les splines polynomiales tout en préservant l'essentiel de leurs propriétés. Elles offrent de plus un intérêt particulier pour le design géométrique grâce aux paramètres de forme qu'elles fournissent. Dans un premier temps, nous étudions les splines basées sur un espace de Chebyshev invariant par translations, et les propriétés de la B-spline correspondante. Dans un deuxième temps, nous montrons, sous certaines hypothèses, que la base des B-splines de Chebyshev est orthonormale dans un espace de Sobolev pondéré par une suite unique de nombres positifs. La meilleure approximation dans l'espace de splines de Chebyshev au sens de la norme associé au produit scalaire précédent est alors un projecteur local. Enfin, pour l'implémentation numérique des résultats précédents, nous utilisons une méthode de quadratures adaptées. Quelques exemples illustrant les effets de forme obtenus sont présentés. Ces résultats généralisent un résultat prouvé récemment par Ulrich Reif dans le cas particulier des splines polynomiales.
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Johnson, William Joel Dietmar. "Rational fraction approximations for passive network functions." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001083.
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Masson, Yannick. "Existence et construction de réseaux de Chebyshev avec singularités et application aux gridshells." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1144/document.
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Les réseaux de Chebyshev sont des systèmes de coordonnées sur les surfaces que l'on obtient par cisaillement d'un domaine du plan. Ceux-ci sont utilisés en particulier pour modéliser les gridshells qui constituent une construction architecturale notamment reconnue pour son faible coût environnemental. La difficulté principale dans la conception des gridshells est le manque de diversité des formes accessibles. En effet, bien que toute surface admette localement en tout point un réseau de Chebyshev, l'existence globale de ce type de coordonnées n'est possible que sur un ensemble restreint de surfaces. La recherche de conditions suffisantes pour l'existence globale de réseaux de Chebyshev est toujours d'actualité. Un des résultats de cette thèse est l'amélioration de ces conditions. Les possibilités d'améliorations en ce sens étant néanmoins limitées, nous élargissons la perspective en considérant des réseaux de Chebyshev avec singularités. Notre résultat principal est l'existence de réseaux de Chebyshev avec singularités coniques, lisses par morceaux, sur toute surface dont la courbure totale positive est inférieure à $2pi$ et dont la courbure totale négative est finie. Notre preuve est constructive, ce qui permet de déterminer ces réseaux dans des cas pratiques. Nous avons implémenté un cas particulier de notre algorithme dans le logiciel Rhinoceros et nous présentons des exemples de réseaux construits par cette méthodeChebyshev nets are coordinate systems on surfaces obtained by pure shearing of a planar domain.These nets are used in particular to model gridshells, an architectural construction which is well-known for its low environmental impact. The main issue when designing a gridshell is the lack of diversityof the accessible shapes. Indeed, although any surface admits locally a Chebyshev net at any point, the global existence for these coordinate systems is only possible for a restricted set of surfaces. The research for sufficient conditions ensuring the global existence of Chebyshev nets is still ongoing. A result achieved in this thesis is an improvement on these conditions. Since the improvement in this direction seems to be rather limited, we broaden the perspective by introducing Chebyshev nets with singularities. Our main result is the existence of a global Chebyshev net with conical singularities on any surface with total positive curvature less than $2pi$ and with finite total negative curvature. Our proof is constructive, so that this method can be applied to practical cases. We have implemented a special instance of this algorithm in the software Rhinoceros and some discrete Chebyshev nets constructed using this method are presented
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Essakhi, Brahim. "Modélisation électromagnétique 3D sur une large bande de fréquences par combinaison d'une méthode d'éléments finis et d'une approximation par fractions rationnelles : application aux structures rayonnantes." Paris 11, 2005. http://www.theses.fr/2005PA112151.
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Les outils de simulation numérique connaissent une utilisation intensive dans la résolution des problèmes de CEM. L'une des raisons est que la complexité croissante des problèmes à étudier rend l'expérimentation difficile à réaliser. De plus, les mesures ne peuvent être faites qu'en un nombre restreint de points de l'espace. La méthode des éléments finis a pour avantages de pouvoir aisément prendre en compte des géométries complexes et des milieux hétérogènes. Elle utilise un maillage conforme, qui s'adapte à la géométrie de la structure analysée et qui permet des raffinements locaux dans les régions où les variations des propriétés physiques, géométriques ou des champs sont plus importantes. Une formulation temporelle permet l'analyse de problèmes directement dans le domaine du temps. Une formulation fréquentielle conduit à résoudre un système linéaire pour chaque fréquence d'étude. Dans de nombreuses applications, les quantités électromagnétiques doivent être déterminées sur une large bande de fréquences et le système linéaire doit être résolu pour chaque fréquence d'intérêt. Ceci entraîne un coût de calcul important. Une alternative consiste à rechercher une approximation de la solution sous forme d'un développement en série ou d'une fraction rationnelle. Une approche possible consiste à développer la solution en série de Taylor autour d'une fréquence centrale. Le rayon de convergence de la série est limité mais il est possible d'étendre cet intervalle de validité en recourant à une approximation rationnelle de Padé. Une autre méthode consiste à rechercher une interpolation de la solution par fractions rationnelles, il s'agit de l'approximation de ChebyshevThe tools for digital simulation know an intensive use in the resolution of the problems of CEM. One of the reasons is that the increasing complexity of the problems to be studied makes the experimentation difficult to realize. Moreover, measurements cannot be made that in a restricted number of points of space. The finite element method has the advantages of easily being able to take into account complex geometries and heterogeneous mediums. It uses a grid in conformity, which adapts to the geometry of the analyzed structure and which allows local refinements in the areas where variations of the physical properties, geometrical or of the fields are more significant. A temporal formulation allows the analysis of problems directly in the field of time. A frequential formulation results in solving a linear system for each frequency of study. In many applications, the electromagnetic quantities must be given on a broad frequency band and the linear system must be solved for each frequency of interest. This involves a cost of significant calculation. An alternative consists in seeking an approximation of the solution in the form of a development in series or of a rational fraction. A possible approach consists in developing the solution in Taylor series around a centre frequency. The interval of convergence of the series is limited but it is possible to extend this interval of validity while resorting to a rational approximation of Padé. The approximation of Chebyshev is an other method based on rational approximation, it consists in seeking an interpolation of the solution
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Midgley, Stuart. "Quantum waveguide theory." University of Western Australia. School of Physics, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0036.
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The study of nano-electronic devices is fundamental to the advancement of the semiconductor industry. As electronic devices become increasingly smaller, they will eventually move into a regime where the classical nature of the electrons no longer applies. As the quantum nature of the electrons becomes increasingly important, classical or semiclassical theories and methods will no longer serve their purpose. For example, the simplest non-classical effect that will occur is the tunnelling of electrons through the potential barriers that form wires and transistors. This results in an increase in noise and a reduction in the device?s ability to function correctly. Other quantum effects include coulomb blockade, resonant tunnelling, interference and diffraction, coulomb drag, resonant blockade and the list goes on. This thesis develops both a theoretical model and computational method to allow nanoelectronic devices to be studied in detail. Through the use of computer code and an appropriate model description, potential problems and new novel devices may be identified and studied. The model is as accurate to the physical realisation of the devices as possible to allow direct comparison with experimental outcomes. Using simple geometric shapes of varying potential heights, simple devices are readily accessible: quantum wires; quantum transistors; resonant cavities; and coupled quantum wires. Such devices will form the building blocks of future complex devices and thus need to be fully understood. Results obtained studying the connection of a quantum wire with its surroundings demonstrate non-intuitive behaviour and the importance of device geometry to electrical characteristics. The application of magnetic fields to various nano-devices produced a range of interesting phenomenon with promising novel applications. The magnetic field can be used to alter the phase of the electron, modifying the interaction between the electronic potential and the transport electrons. This thesis studies in detail the Aharonov-Bohm oscillation and impurity characterisation in quantum wires. By studying various devices considerable information can be added to the knowledge base of nano-electronic devices and provide a basis to further research. The computational algorithms developed in this thesis are highly accurate, numerically efficient and unconditionally stable, which can also be used to study many other physical phenomena in the quantum world. As an example, the computational algorithms were applied to positron-hydrogen scattering with the results indicating positronium formation.
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Volkmer, Toni. "Multivariate Approximation and High-Dimensional Sparse FFT Based on Rank-1 Lattice Sampling." Doctoral thesis, Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-222820.
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In this work, the fast evaluation and reconstruction of multivariate trigonometric polynomials with frequencies supported on arbitrary index sets of finite cardinality is considered, where rank-1 lattices are used as spatial discretizations. The approximation of multivariate smooth periodic functions by trigonometric polynomials is studied, based on a one-dimensional FFT applied to function samples. The smoothness of the functions is characterized via the decay of their Fourier coefficients, and various estimates for sampling errors are shown, complemented by numerical tests for up to 25 dimensions. In addition, the special case of perturbed rank-1 lattice nodes is considered, and a fast Taylor expansion based approximation method is developed. One main contribution is the transfer of the methods to the non-periodic case. Multivariate algebraic polynomials in Chebyshev form are used as ansatz functions and rank-1 Chebyshev lattices as spatial discretizations. This strategy allows for using fast algorithms based on a one-dimensional DCT. The smoothness of a function can be characterized via the decay of its Chebyshev coefficients. From this point of view, estimates for sampling errors are shown as well as numerical tests for up to 25 dimensions. A further main contribution is the development of a high-dimensional sparse FFT method based on rank-1 lattice sampling, which allows for determining unknown frequency locations belonging to the approximately largest Fourier or Chebyshev coefficients of a functionIn dieser Arbeit wird die schnelle Auswertung und Rekonstruktion multivariater trigonometrischer Polynome mit Frequenzen aus beliebigen Indexmengen endlicher Kardinalität betrachtet, wobei Rang-1-Gitter (rank-1 lattices) als Diskretisierung im Ortsbereich verwendet werden. Die Approximation multivariater glatter periodischer Funktionen durch trigonometrische Polynome wird untersucht, wobei Approximanten mittels einer eindimensionalen FFT (schnellen Fourier-Transformation) angewandt auf Funktionswerte ermittelt werden. Die Glattheit von Funktionen wird durch den Abfall ihrer Fourier-Koeffizienten charakterisiert und mehrere Abschätzungen für den Abtastfehler werden gezeigt, ergänzt durch numerische Tests für bis zu 25 Raumdimensionen. Zusätzlich wird der Spezialfall gestörter Rang-1-Gitter-Knoten betrachtet, und es wird eine schnelle Approximationsmethode basierend auf Taylorentwicklung vorgestellt. Ein wichtiger Beitrag dieser Arbeit ist die Übertragung der Methoden vom periodischen auf den nicht-periodischen Fall. Multivariate algebraische Polynome in Chebyshev-Form werden als Ansatzfunktionen verwendet und sogenannte Rang-1-Chebyshev-Gitter als Diskretisierungen im Ortsbereich. Diese Strategie ermöglicht die Verwendung schneller Algorithmen basierend auf einer eindimensionalen DCT (diskreten Kosinustransformation). Die Glattheit von Funktionen kann durch den Abfall ihrer Chebyshev-Koeffizienten charakterisiert werden. Unter diesem Gesichtspunkt werden Abschätzungen für Abtastfehler gezeigt sowie numerische Tests für bis zu 25 Raumdimensionen. Ein weiterer wichtiger Beitrag ist die Entwicklung einer Methode zur Berechnung einer hochdimensionalen dünnbesetzten FFT basierend auf Abtastwerten an Rang-1-Gittern, wobei diese Methode die Bestimmung unbekannter Frequenzen ermöglicht, welche zu den näherungsweise größten Fourier- oder Chebyshev-Koeffizienten einer Funktion gehören
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Joldes, Mioara Maria. "Approximations polynomiales rigoureuses et applications." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2011. http://tel.archives-ouvertes.fr/tel-00657843.
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Quand on veut évaluer ou manipuler une fonction mathématique f, il est fréquent de la remplacer par une approximation polynomiale p. On le fait, par exemple, pour implanter des fonctions élémentaires en machine, pour la quadrature ou la résolution d'équations différentielles ordinaires (ODE). De nombreuses méthodes numériques existent pour l'ensemble de ces questions et nous nous proposons de les aborder dans le cadre du calcul rigoureux, au sein duquel on exige des garanties sur la précision des résultats, tant pour l'erreur de méthode que l'erreur d'arrondi.Une approximation polynomiale rigoureuse (RPA) pour une fonction f définie sur un intervalle [a,b], est un couple (P, Delta) formé par un polynôme P et un intervalle Delta, tel que f(x)-P(x) appartienne à Delta pour tout x dans [a,b].Dans ce travail, nous analysons et introduisons plusieurs procédés de calcul de RPAs dans le cas de fonctions univariées. Nous analysons et raffinons une approche existante à base de développements de Taylor.Puis nous les remplaçons par des approximants plus fins, tels que les polynômes minimax, les séries tronquées de Chebyshev ou les interpolants de Chebyshev.Nous présentons aussi plusieurs applications: une relative à l'implantation de fonctions standard dans une bibliothèque mathématique (libm), une portant sur le calcul de développements tronqués en séries de Chebyshev de solutions d'ODE linéaires à coefficients polynômiaux et, enfin, un processus automatique d'évaluation de fonction à précision garantie sur une puce reconfigurable.
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Le, Quéré Patrick. "Etude de la transition à l'instationnarité des écoulements de convection naturelle en cavité verticale différentiellement chauffée par méthodes spectrales chebyshev." Poitiers, 1987. http://www.theses.fr/1987POIT2003.
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On developpe un algorithme d'integration des equations bidimensionnelles instationnaires de navier-stokes d'un fluide de bomussinesq qui couple une discretisation spatiale des variables dependantes par approximation spectrale de chebyshev a une discretisation temporelle de type differences-finies du second ordre. Les cavites etudiees ont des rapports de forme de 1 a 10. Suivant le rapport de forme et les conditions aux limites thermiques, il existe trois mecanismes differents de transition a l'instationnarite qui correspondent a des bifurcations de hopf supercritiques
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Mason, J. C. "Near-best approximations by Chebyshev polynomials with applications." Thesis, University of Huddersfield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411894.
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Mace, Rob-Roy L. "Reduction of the Gibbs Phenomenon via interpolation using Chebyshev polynomials, filterying, and chebyshev-padé approximations." Huntington, WV : [Marshall University Libraries], 2005. http://www.marshall.edu/etd/descript.asp?ref=.
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Bhikkaji, Bharath. "Model Reduction and Parameter Estimation for Diffusion Systems." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4252.
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Minsker, Stanislav. "Non-asymptotic bounds for prediction problems and density estimation." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44808.
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This dissertation investigates the learning scenarios where a high-dimensional parameter has to be estimated from a given sample of fixed size, often smaller than the dimension of the problem. The first part answers some open questions for the binary classification problem in the framework of active learning.
Given a random couple (X,Y) with unknown distribution P, the goal of binary classification is to predict a label Y based on the observation X. Prediction rule is constructed from a sequence of observations sampled from P. The concept of active learning can be informally characterized as follows: on every iteration, the algorithm is allowed to request a label Y for any instance X which it considers to be the most informative. The contribution of this work consists of two parts: first, we provide the minimax lower bounds for the performance of active learning methods. Second, we propose an active learning algorithm which attains nearly optimal rates over a broad class of underlying distributions and is adaptive with respect to the unknown parameters of the problem.
The second part of this thesis is related to sparse recovery in the framework of dictionary learning. Let (X,Y) be a random couple with unknown distribution P. Given a collection of functions H, the goal of dictionary learning is to construct a prediction rule for Y given by a linear combination of the elements of H. The problem is sparse if there exists a good prediction rule that depends on a small number of functions from H. We propose an estimator of the unknown optimal prediction rule based on penalized empirical risk minimization algorithm. We show that the proposed estimator is able to take advantage of the possible sparse structure of the problem by providing probabilistic bounds for its performance.
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Levesley, Jeremy. "A study of Chebyshev weighted approximations to the solution of Symm's integral equation for numerical conformal mapping." Thesis, Coventry University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304879.
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Urban, Lukáš. "Laboratorní úloha zaměřená na obvody se spínanými kapacitory." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217788.
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This Master`s thesis is focused on through acquaintance of principles of the function circuits with switched capaticors and posibility of their application mainly in frequency filters or signal generators. The origin of the switched capacitor circuits is mentioned at the beginning of the work. There are references to the first scientific work and scientists who have dealt with this issue. Maxwell`s idea: lossy element (resistor) replace with lossless element (switched capacitor) in electric circuit, is further described. In the next chapter of this work are listed types of switching capacitors and their use in simple RC filters and in structures of inverted or noninverted integrators and their application in more complex higher order filters. The advantages and disadvantages of SC circuits versus circuit composed of discrete components are shown. It is also listed a simple low-pass switched RC filter implemented with analogue multiplexer 4053. Using the LTC1043 integrated circuit, which structure and properties are described and analyzed in detail in the work, the 1st order aktive or pasive low and high pass filters were designed and subsequently simulated in the computer simulator OrCAD PSpice v.10. Another chapter deals with the integrated circuits higher order filters, structure and properties of the integrated filter LTC1060 are further analyzed here. Except this IC there are mentioned integrated filters commercially less available from the corporations Linear Technology and Maxim. The main objective of thesis was to propose and establish laboratory device and laboratory measurment focused on the switched capacitor circuits. The laboratory device has been designed with integrated circuits LTC1043 and LTC1060, which is demonstrated by using passive and active integrator, 2nd order band-pass and 4th order band-pass with Chebyshevovou approximation.
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LING, MING-XING, and 林明興. "Quadrature mirror filter design by Chebyshev approximation." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/49760218487555791989.
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Liu, Yu-Chen, and 劉育成. "Rational Chebyshev Approximation and Generalized Fractional Programs." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/62033766952873260845.
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碩士國立嘉義大學
應用數學系研究所
98
Rational Chebyshev approximation is used to find a rational function to approximate a given continuous function. Rational Chebyshev approximation is also an application of the generalized fractional programs which can be solved by Dinkelbach-type algorithm. Besides rational Chebyshev approximation, Pad'e fractional approximation also can produce a fractional function which approximate to the given continuous function. We implement Dinkelbach-type algorithm for solving rational Chebyshev approximation in Matlab and compare it with Pad'e approximation from numerical points of view.
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CHEN, XIANGKUN. "DESIGN OF OPTIMAL DIGITAL FILTERS (APPROXIMATION, CHEBYSHEV, LINEAR PHASE, MINIMUM PHASE, COMPLEX DOMAIN)." Thesis, 1986. http://hdl.handle.net/1911/15961.
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Four methods for designing digital filters optimal in the Chebyshev sense are developed. The properties of these filters are investigated and compared.
An analytic method for designing narrow-band FIR filters using Zolotarev polynomials, which are extensions of Chebyshev polynomials, is proposed. Bandpass and bandstop narrow-band filters as well as lowpass and highpass filters can be designed by this method. The design procedure, related formulae and examples are presented.
An improved method of designing optimal minimum phase FIR filters by directly finding zeros is proposed. The zeros off the unit circle are found by an efficient special purpose root-finding algorithm without deflation. The proposed algorithm utilizes the passband minimum ripple frequencies to establish the initial points, and employs a modified Newton's iteration to find the accurate initial points for a standard Newton's iteration. The proposed algorithm can be used to design very long filters (L = 325) with very high stopband attenuations.
The design of FIR digital filters in the complex domain is investigated. The complex approximation problem is converted into a near equivalent real approximation problem. A standard linear programming algorithm is used to solve the real approximation problem. Additional constraints are introduced which allow weighting of the phase and/or group delay of the approximation. Digital filters are designed which have nearly constant group delay in the passbands. The desired constant group delay which gives the minimum Chebyshev error is found to be smaller than that of a linear phase filter of the same length. These filters, in addition to having a smaller, approximately constant group delay, have better magnitude characteristics than exactly linear phase filters with the same length. The filters have nearly equiripple magnitude and group delay.
The problem of IIR digital filter design in the complex domain is formulated such that the existence of best approximation is guaranteed. An efficient and numerically stable algorithm for the design is proposed. The methods to establish a good initial point are investigated. Digital filters are designed which have nearly constant group delay in the passbands. The magnitudes of the filter poles near the passband edge are larger than of those far from the passband edge. A delay overshooting may occur in the transition band (don't care region), and it can be reduced by decreasing the maximum allowed pole magnitude of the design problem at the expense of increasing the approximation error.
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Chang, Hsin-Chih, and 張信志. "A New WLS Chebyshev Approximation Method for the Design of IIR Digital Filters." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/83373246513680110483.
Full textAbstract:
碩士國立清華大學
電機工程研究所
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This thesis proposes a new approximation method using the weighted least squares (WLS) algorithm for the design of IIR filters. The WLS algorithm used by Chi and Chiou's approxima- tion method for the design of FIR filters is modified for the designed of IIR filters. When the desired frequency response including magnitude and phase is specified, the designed IIR filter is nearly equiripple in absolute (complex) approxima- tion error, but it is not guaranteed to be stable. The pro- posed approximation method can also be used for the design of allpass filters by taking into account of some constraint in filter coefficients. The designed allpass filter is equiripple in phase and will be stable by adding an appropriate positive group delay to the desired group delay response. On the other hand, when only magnitude of the desired frequency response is specified, the designed IIR filter is minimum-phase. Six de- signed examples are provided to support the proposed approxi- mation method. Finally, we draw some conclusions.
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Bani, Younes Ahmad H. "Orthogonal Polynomial Approximation in Higher Dimensions: Applications in Astrodynamics." Thesis, 2013. http://hdl.handle.net/1969.1/151375.
Full textAbstract:
We propose novel methods to utilize orthogonal polynomial approximation in higher dimension spaces, which enable us to modify classical differential equation solvers to perform high precision, long-term orbit propagation. These methods have immediate application to efficient propagation of catalogs of Resident Space Objects (RSOs) and improved accounting for the uncertainty in the ephemeris of these objects. More fundamentally, the methodology promises to be of broad utility in solving initial and two point boundary value problems from a wide class of mathematical representations of problems arising in engineering, optimal control, physical sciences and applied mathematics. We unify and extend classical results from function approximation theory and consider their utility in astrodynamics. Least square approximation, using the classical Chebyshev polynomials as basis functions, is reviewed for discrete samples of the to-be-approximated function. We extend the orthogonal approximation ideas to n-dimensions in a novel way, through the use of array algebra and Kronecker operations. Approximation of test functions illustrates the resulting algorithms and provides insight into the errors of approximation, as well as the associated errors arising when the approximations are differentiated or integrated. Two sets of applications are considered that are challenges in astrodynamics. The first application addresses local approximation of high degree and order geopotential models, replacing the global spherical harmonic series by a family of locally precise orthogonal polynomial approximations for efficient computation. A method is introduced which adapts the approximation degree radially, compatible with the truth that the highest degree approximations (to ensure maximum acceleration error < 10^−9ms^−2, globally) are required near the Earths surface, whereas lower degree approximations are required as radius increases. We show that a four order of magnitude speedup is feasible, with both speed and storage efficiency op- timized using radial adaptation. The second class of problems addressed includes orbit propagation and solution of associated boundary value problems. The successive Chebyshev-Picard path approximation method is shown well-suited to solving these problems with over an order of magnitude speedup relative to known methods. Furthermore, the approach is parallel-structured so that it is suited for parallel implementation and further speedups. Used in conjunction with orthogonal Finite Element Model (FEM) gravity approximations, the Chebyshev-Picard path approximation enables truly revolutionary speedups in orbit propagation without accuracy loss.
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郭永田. "A new self-initated optimum WLS chebyshev approximation method for the design of linear phase fir digital filters." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/18215789495672715919.
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Wolfkill, Karlan Stephen. "Pseudo-spectral approximations of Rossby and gravity waves in a two-Layer fluid." Thesis, 2012. http://hdl.handle.net/1957/30138.
Full textAbstract:
The complexity of numerical ocean circulation models requires careful checking with
a variety of test problems. The purpose of this paper is to develop a test problem involving
Rossby and gravity waves in a two-layer
fluid in a channel. The goal is to compute very
accurate solutions to this test problem. These solutions can then be used as a part of the
checking process for numerical ocean circulation models.
Here, Chebychev pseudo-spectral methods are used to solve the governing equations
with a high degree of accuracy. Chebychev pseudo-spectral methods can be described in
the following way: For a given function, find the polynomial interpolant at a particular
non-uniform grid. The derivative of this polynomial serves as an approximation to the
derivative of the original function. This approximation can then be inserted to differential
equations to solve for approximate solutions. Here, the governing equations reduce to
an eigenvalue problem with eigenvectors and eigenvalues corresponding to the spatial
dependences of modal solutions and the frequencies of those solutions, respectively.
The results of this method are checked in two ways. First, the solutions using the
Chebychev pseudo-spectral methods are analyzed and are found to exhibit the properties
known to belong to physical Rossby and gravity waves. Second, in the special case
where the two-layer model degenerates to a one-layer system, some analytic solutions are
known. When the numerical solutions are compared to the analytic solutions, they show
an exponential rate of convergence.
The conclusion is that the solutions computed using the Chebychev pseudo-spectral
methods are highly accurate and could be used as a test problem to partially check numerical
ocean circulation models.Graduation date: 2012
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Dostalík, Mark. "Vliv materiálových parametrů na stabilitu termální konvekce." Master's thesis, 2016. http://www.nusl.cz/ntk/nusl-346943.
Full textAbstract:
The thesis is focused on the investigation of Rayleigh-Bénard problem in an extended setting approximating the conditions in the Earth's mantle. The aim is to evaluate the influence of depth- and temperature- dependent material parameters, dissipation, adiabatic heating/cooling and heat sources on the qualitative characteristics of thermal convection. We identify the critical values of dimensionless parameters that determine the onset of convection and characterize the dominating convection patterns in marginally supercritical states. These issues are addressed by the application of linear stability analysis and weakly non-linear analysis. It has been found that the character of convection differ substantially from the standard case of Rayleigh-Bénard convection. Powered by TCPDF (www.tcpdf.org)