Spectral Factorization

Nous présentons dans ce papier deux nouveaux modèles de texture orientée, basés sur une nouvelle classe de champs gaussiens, appelés champs browniens fractionnaires localement anisotropes, à orientation locale prescrite en chaque point. Ces champs aléatoires sont une version locale d'une classe spécifique de champs anisotropes autosimilaires à incréments stationnaires. La simulation de telles textures s'appuie sur un nouvel algorithme couplant l'utilisation de la notion de champs tangents à la méthode de Cholesky ou plus récemment la méthode des bandes tournantes, cette dernière ayant prouvé son efficacité à générer des textures stationnaires anisotropes. Des applications numériques illustrent la faculté de la méthode à synthétiser des textures à orientation locale prescrite.

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n premier lieu j'exprime mes sincères remerciements envers M. le Professeur Jean-Pierre Delmas pour avoir accepté de présider le jury de cette thèse. Je souhaite exprimer toute ma reconnaissance envers M. le Professeur Pascal Larzabal dont les remarques m'ont été très précieuses et réellement constructives ainsi que pour la tâche de rapporteur qu'il a bien voulu assumer. Je remercie aussi vivement M. le Professeur Jean-Yves Tourneret pour l'honneur qu'il m'a fait d'accepter de rapporter ce travail et l'intérêt qu'il y a porté. Je tiens à remercier Mme. Sylvie Marcos, directrice de recherche, pour l'intérêt qu'elle a porté aux travaux de cette thèse. Je remercie enfin très vivement MM. Roland Badeau et Mohamed El Badaoui, maître de conférences, pour le crédit qu'ils ont bien voulu accorder à mon travail en participant au jury de cette thèse. Viennent maintenant deux personnes sans qui rien de tout ceci n'aurait pu exister. La première, M. Rémy Boyer, maître de conférences qui m'a lancé et fortement encadré pour que cette thèse puisse débuter et se terminer convenablement. La deuxième est M. le professeur François Guillet, directeur du LASPI (Laboratoire d'Analyse des Signaux et des Processus Industriels) qui s'est toujours démené pour que je puisse travailler, vivre et me développer dans les meilleures conditions. Sans toi ma vie et ma carrière seraient incontestablement différentes, c'est plus qu'un merci que je t'adresse c'est une réelle reconnaissance. Plus que d'autres tu m'as, à ta manière et de façon directe ou indirecte, apporté : es années ont vraiment été différentes, les années parisiennes ont été plutôt classiques, bien que très prenantes psychologiquement et difficiles à vivre, j'aimerais simplement parler de Kun et Titi à qui j'ai du contre mon gré mettre des fessés à PES, les gars je n'ai plus l'entraînement mais vous êtes tellement mauvais qu'il n'y a plus rien à faire pour vous ! ! ! Parler des Bretons et Bretonnes, Seb et son appart, ses cocktails à base de Chartreuse orangina et vodka, la mule pour avoir tiré la carriole tous les jours en suède, Erwan, ya trop à dire, tu es la personne qui a éduqué mon palet à ce doux breuvage des pays du nord ouest, Kev, Dylan les Lyonnais, Marine et Nelly qui adorent ma voix "Guigui White" et tous ceux que j'ai pu croiser lors des soirées de Malakof. Biensûr, je ne peux oublier les petits jeunes, Damibou, Bubu, Mommon et Max, Steph, t'inquiète chaussette Europapark et les Six Flags nous attendent et puis Dago et Vaness complètement dans l'excès. P uis il y a eu le changement complet en arrivant à Roanne. J'ai pu y vivre mes plus fortes émotions jusqu'à présent. Tout d'abord merci à ces femmes qui s'occupent de nous (gentils thésards et jeunes enseignants contractuels), merci à Mylène et Nezha. Merci à Raph pour m'avoir fait pleurer de rire avec son bonnet rouge...et pour son dynamisme quotidien et puis à Pascal, Pierre, Nabih pour leurs conseils et soutien moral. Merci à M. Khalid Sabri, Frédéric Albert et Mounir Lahlimi compagnons de bureau pour les bons moments passés ensemble, même si parfois il y eu quelques tensions et énervement.... Je ne peux oublier Khalid, Ali, Nat Anh, Aissam, Said pour les quelques heures passées à leur apprendre l'art du Baby-foot et puis merci à Mathieu pour son calme, sa sérénité, sa passion du blues et du rock, merci pour m'avoir fait découvrir Harvest, merci aussi pour m'avoir laissé gagner 2 matchs de squash en 35682 rencontres... Un énorme merci pour leur monstrueuse patience, parce que pour me supporter il en faut, leur gentillesse intarissable, leur attention, merci d'avoir et de vivre mes émotions, merci pour votre oreille et vos paroles...Salma et Widian, MERCI pour avoir été là .... Encore plus difficile de dire simplement merci puisque Manue, Arnaud et Arnaud, Damien et Vaness et enfin Antoine partagent depuis quelques années maintenant ma vie. C'est une chance immense que d'avoir des amis comme vous, toujours présent, toujours là quelque soit la distance et le temps. C'est de tout mon coeur que je souhaite parler de Patricia, Christian et Armelle, Odile, Florence et enfin Gérard mes oncles et tantes qui malgré la distance et nos réunions sporadiques sont toujours présents dans mon coeur et mon esprit. Je souhaite dire à mes parents, Annick et Richard, que malgré ma dureté apparente, je tiens énormément à vous. Sans votre apport et votre dure responsabilité de parents ma vie serait différente. Si je commence à voir le bout du tunnel aujourd'hui c'est grace à vous, à vos efforts et parfois même à vos sacrifices. Vous êtes toujours avec moi, près de moi. Je souhaiterais quoi qu'il advienne demain, dédier tout ce mémoire à la personne qui m'a absolument transfiguré, changé, chamboulé, à la personne qui m'a apporté tout ce que je pouvais espérer, tout ce qui me faisait rêver et que je désespérais de ne pas voir arriver. Pour toutes les émotions que tu m'as procurées, ton soutien, pour tes encouragements, pour ton attention quasi-permanente ou encore pour ton affection... pour être là ..., Lorraine...merci... i m : matrice de projection sur R(A m ) ⊥ à la m ième itération de l'algorithme ZF-MUSIC F (Lz) m (ω) : fonction de pondération f MUSIC (ω) : fonctionnelle MUSIC z : racine des polynômes Fct. : en fonction de L : fonction de vraisemblance II Les algorithmes introduits. Compte tenu des résultats obtenus sur les CRB (dans le cas où le sous-espace associé à l'interférence structurée est exacte), nous avons opté pour l'établissement d'algorithmes basés non plus sur une déflation orthogonale mais plutÙt sur une déflation oblique du sous-espace signal. Ces algorithmes de types prior MUSIC et MinNorm montrent leur supériorité dans l'estimation des paramètres d'intérêts quand les DDA des sources sont proches et ce comparativement aux algorithmes à déflation orthogonale du sous-espace signal. Nous donnons, de Organisation du document L'introduction d'un a priori sous sa forme d'interférence structurée, dans les méthodes à Hautes Résolution peut naturellement être pensée et classifiée selon deux catégories. Nous proposons une classification simple, reposant sur les hypothèses suivantes soit (i) : la connaissance de l'a priori est certaine soit (ii) : la connaissance de l'a priori est incertaine. Le chapitre 2 de ce document adopte l'hypothèse (i), alors que le chapitre 3 est exclusivement consacré aux méthodes et analyses sous l'hypothèse (ii). Dans cette partie, nous introduisons le formalisme matriciel classique pour l'estimation des DDA dans le cadre d'une Antenne Linéaire et Uniforme (ALU).

We construct a globally invertible analytic model for functions in the Hardy space H 2 (C +) [6, 17] via an explicit atomic system {Φn}, where each atom is defined to satisfy analyticity, completeness, stability, and modulator regularity [7, 4] by construction. No external hypotheses are required; all structural properties are encoded directly. The family {Φn} forms a Riesz basis of H 2 (C +) [3], yielding a unique and stable expansion f (s) = ∞ n=1 cnΦn(s), f ∈ H 2 (C +), which is globally invertible: coefficients can be recovered from analytic data, and synthesis reconstructs the function uniformly on compact subsets [14]. This construction provides a fully explicit, logically self-contained framework for analyzing analytic functions with growth and symmetry constraints, and suggests applications to L-functions and other areas of analytic number theory [15, 1, 5].

In this paper, an economic parameterization for positive parahermitian matrix functions is introduced and applied to the µ-analysis framework wherein we propose a new state-space optimization problem for finding the required D-scales. Among the four state-space matrices to be used to realize the optimal D-scale, A and B are chosen via a Laguerre parameterization whereas the other two state-space matrices, C and D are obtained by spectral factorization after solving a convex optimization problem formulated in an LMI framework. The obtained D-scale satisfies the commuting property with the uncertainty structure. The proposed economic parameterization yields advantages in terms of less computational time and less number of decision variables and also, the proposed state-space optimization framework gives a frequency independent solution algorithm in state-space variables for the required D-scales. Two numerical examples are used to demonstrate the effectiveness of the proposed algorithm.

In this paper we show how the zero dynamics of (not necessarily square) spectral factors relate to the splitting subspace geometry of stationary stochastic models and to the corresponding algebraic Riccati inequality. We introduce the notion of output-induced subspace of a minimal Markovian splitting subspace, which is the stochastic analogue of the supremal output-nulling subspace in geometric control theory. Through this concept the analysis can be made coordinatefree, and straightforward geometric methods can be applied. We show how the zero structure of the family of spectral factors relates to the geometric structure of the family of minimal Markovian splitting subspaces in the sense that the relationship between the zeros of different spectral factors is reflected in the partial ordering of minimal splitting subspaces. Finally, we generalize the wellknown characterization of the the solutions of the algebraic Riccati equation in terms of Lagrangian subspaces invariant under the corresponding Hamiltonian to the larger solution set of the algebraic Riccati inequality.

In this paper, we introduce a special type of SOC-functions which is a vectorvalued function associated with second-order cone. By using it, we construct a type of smoothing functions which converges to the projection function onto second-order cone. Then, we reformulate the system of equalities and inequalities under the order induced by second-order cone as a system of parameterized smooth equations. Accordingly, we propose a smoothing-type Newton algorithm to solve the reformulation, and show that the proposed algorithm is globally convergent and locally quadratically convergent under suitable assumptions. Preliminary numerical results demonstrate that the approach is effective. Numerical comparison based on various smoothing functions is reported as well.

This paper presents an efficient method for the design of M -channel oversampled warped cosine-modulated filter banks. The method consists in filter prototype design for synthesis filter bank using optimization procedure, which minimizes filter bank overall distortion transfer function. Optimization takes into account channel subsampling factors as well.

In this paper we consider a problem (that follows directly from realization problem): how to find a possible states (even minimal) of a stochastic dynamic system S1 with known outputs, provided it is in a certain causality relationship with another stochastic dynamic system S2 whose states (or some information about them) are given. This paper is continuation of the papers (Gill and Petrović 1987), (Petrović 1996) and (Petrović 2005). Keywords— Causality, Hilbert space, realization, stochastic dynamic system.

In this paper, a scheme for perfect reconstruction in M channel, maximally decimated QMF banks is first presented, for arbitrary M . The solutions are such that the analysis and synthesis filters are FIR and of the same length. Based on the theory, lattice structures for the two-channel case are derived, which offer an efficient design as well as implementation procedure for two-channel perfect reconstruction systems. Such lattice implementations are robust in the sense that the perfect-reconstruction property is preserved inspite of coefficient quantization.

A new approach to solving a class of rankconstrained semi-definite programming (SDP) problems, which appear in many signal processing applications such as transmit beamspace design in multiple-input multiple-output (MIMO) radar, downlink beamforming design in MIMO communications, generalized sidelobe canceller design, phase retrieval, etc., is presented. The essence of the approach is the use of underlying algebraic structure enforced in such problems by other practical constraints such as, for example, null shaping constraint. According to this approach, instead of relaxing the non-convex rankconstrained SDP problem to a feasible set of positive semidefinite matrices, we restrict it to a space of polynomials whose dimension is equal to the desired rank. The resulting optimization problem is then convex as its solution is required to be full rank, and can be efficiently and exactly solved. A simple matrix decomposition is needed to recover the solution of the original problem from the solution of the restricted one. We show how this approach can be applied to solving some important signal processing problems that contain null-shaping constraints. As a byproduct of our study, the conjugacy of beamfoming and parameter estimation problems leads us to formulation of a new and rigorous criterion for signal/noise subspace identification. Simulation results are performed for the problem of rank-constrained beamforming design and show an exact agreement of the solution with the proposed algebraic structure, as well as significant performance improvements in terms of sidelobe suppression compared to the existing methods.

We consider three different ways of algorithmization of the Janashia-Lagvilava spectral factorization method. The first algorithm is faster than the second one, however, it is only suitable for matrices of low dimension. The second algorithm, on the other hand, can be applied to matrices of substantially larger dimension. The third algorithm is a superfast implementation of the method, but only works in the polynomial case under the additional restriction that the zeros of the determinant are not too close to the boundary. All three algorithms fully utilize the advantage of the method which carries out spectral factorization of leading principal submatrices step-by-step. The corresponding results of numerical simulations are reported in order to describe the characteristic features of each algorithm and compare them to other existing algorithms.

It is shown how with analogy to analogue control theory, that the problem of polynomialmatrix spectral factorization can be solved using negative feedback. This recursive method is particularly simple to implement as compared with other approaches. The algorithm in its basic form requires no matrix inversions or special matrix decompositions. 1.Introduction The multivariable spectral factorization problem can be mathematically defined as follows: Given a finite matrix Laurent-series z L() in the z-domain of degree n,

A kepstrum (or complex-cepstrum) approach to minimum-phase Wiener filtering of stationary scalar processes is proposed and solved for the case of signal plus coloured noise, where the noise possibly includes a white-noise component. A general solution is found in an innovations form. The spectral factorization of the noise model and of the signal-plus-noise model required for the solution are determined from data using the kepstrum technique with the fast Fourier transform. This approach avoids dependence on any form of multidimensional state-space or polynomial-based model and so avoids use of recursive parameter estimation or of Diophantine equations.

Nonsymmetric cone program and its corresponding complementarity problem have long been mysterious to optimization researchers because of no unified analysis technique to handle these cones. Nonetheless, merit function approach is a popular method to deal with general conic complementarity problem, for which the key lies on constructing appropriate merit functions. In this paper, we focus on a special class of nonsymmetric cone complementarity problem, that is, the ellipsoidal cone complementarity problem (ECCP). We not only show the readers how to construct merit functions for solving the ellipsoidal cone complementarity problem, but also we study the conditions under which the level sets of the corresponding merit functions are bounded. In addition, we assert that these merit functions provide an error bound for the ellipsoidal cone complementarity problem. All these results build up a theoretical basis for the merit function method for solving ellipsoidal cone complementarity prob...

Through this research the following research objectives should be met: * Present spectral factorization of invertible non-scalar matrices ([24] and ) in order to place the current investigation concerning factorization in a broader context. * Present a unified and coherent treatment of the factorization of singular matrices as contained in the works by Wu [29], Laffey [17] and Sourour [26]. * Investigate applications of spectral factorization to invertible matrices i.e. unipotent, positive-definite, commutator, involutory and Hermitian factorization as found in [24], [17], [18] and [26]. * Investigate the conditions under which an invertible matrix can be expressed as a product of two involutions as found in [13]. * Investigate applications of spectral factorization on singular matrices i.e. positive-semidefinite factorization as found in [26]. * The UNISA library catalogue * E-journals * MathSciNet * arXiv () * Wikipedia * JSTOR * Cambridge Journal Online * ScienceDirect

The weak structure at infinity of time-delay system of neutraln type is used to solve the disturbance rejection and the row-by-row decoupling problems. Delayed derivative of the disturbance or of the new control must be used in a general case. This is the counterpart of the generality. For practical use this means that if the disturbance or the new control are not smooth enough, we need in fact very high gain in approximation.

This paper develops a n improved technique for the design of analysis filters in a n M channel maximally decimated FIR perfect reconstruction QMF bank, having a lossless polyphase-component matrix E (z). As in earlier work, the aim is to optimize the parameters characterizing E (z) until the sum of the stopband energies of the analysis filters is minimized. There a r e four new ingredients in the procedure reported here. The first is a technique for efficient initialization of one of the M analysis filters, as a spectral factor of a n Mth band filter. This factorization itself is done without root-finding techniques, in a n efficient manner using the eigenjlters approach. The second component is the initialization of the internal parameters which characterize E (z) , based on the above spectral factor. In earlier work, the parameters characterizing the lossless E (z) were rotation angles, which resulted in slow convergence of the above-mentioned optimization. The third ingredient of the improved approach is a modified characterization, mostly free from rotation angles, of the lossless FIR E (z). The fourth component of improvement is the incorporation of symmetry among the analysis filters, so as to minimize the number of unknown parameters being optimized. The resulting design procedure always gives better filter responses than earlier ones (for a given filter length), and converges much faster.

Spectral factorization (SF) has been well developed for a uniformly sampled sequence (USS). Our recent study found important applications of SF for a non-uniformly sampled sequence (NUSS) in array processing, especially considering arbitrary arrays. Since SF for an arbitrarily sampled sequence is intractable, in this paper, we propose a new SF method for an integer-interval sampled sequence (IISS). Its applications in robust adaptive beamforming and array pattern synthesis for a non-uniform linear array (NULA) are studied. Simulation results show the outstanding performance of the proposed method.

Earth Radiation Budget Experiment (ERBE) wide-field-of-view (WFOV) nonscanners aboard ERBS and NOAA- 9/NOAA-10 provided broadband shortwave and longwave irradiances from 1985 to 1999. The previous analysis showed dome degradation in the shortwave nonscanner instruments. The correction was performed with a constant spectral (gray assumption) degradation. We suspect that the gray assumption affected daytime longwave irradiance and led to a day-minus-night longwave flux differences (little change in night time longwave) increase over time. Based on knowledge from the CERES process, we will reprocess entire ERBE nonscanner radiation dataset by characterizing shortwave dome transmissivity with spectral dependent degradation using the solar data observed by these instruments. Once spectral dependent degradation is derived, imager derived cloud fraction and the cloud phase as well as surface type over the FOV of nonscanner instruments will be used to model unfiltering coefficients. This po...

We give a relation between the exponential stability of C 0 −semigroup T = {T (t)} t≥0 and the solutions of Lyapunov inequality QAx, x + Qx, Ax ≤ −||x|| 2 , in B + (X, X *), with X is a Banach space. The solutions of this inequality characterizes, the boundedness of the resolvent R(λ, A) inside and outside of the left half-plane ℜλ ≥ 0, and also the left invertibility of the C 0 −semigroup T.

We provide an analysis of the algorithms necessary for the optimal use of multidimensional signal reconstruction from multichannel acquisition. Firstly, we provide computable conditions to test the matrix invertibility and propose algorithms to find a particular inverse. Secondly, we determine the existence of perfect reconstruction systems for given FIR analysis filters with some sampling matrices and some FIR synthesis polyphase matrices. Then, we present the development of an efficient algorithm designed to find a sampling matrix with maximum sampling rate and FIR synthesis polyphase matrix for given FIR analysis filters so that the system provides a perfect reconstruction. Once a particular synthesis matrix is found, we can characterize all synthesis matrices and find an optimal one according to a design criterion.

In this letter, construction of analytic functions from evaluations of real or imaginary parts on finite subsets of the unit circle is studied. The points in the subsets are not necessarily uniformly spaced as in the most existing works. An algorithm exactly retrieving finite-dimensional systems from noise-free data is presented. This algorithm is based on a recent frequency-domain subspace algorithm to identify discrete-time power spectra from nonuniformly spaced measurements and inherits consistency and robustness properties of the latter with respect to inaccuracies in data.

In this letter, construction of analytic functions from evaluations of real or imaginary parts on finite subsets of the unit circle is studied. The points in the subsets are not necessarily uniformly spaced as in the most existing works. An algorithm exactly retrieving finite-dimensional systems from noise-free data is presented. This algorithm is based on a recent frequency-domain subspace algorithm to identify discrete-time power spectra from nonuniformly spaced measurements and inherits consistency and robustness properties of the latter with respect to inaccuracies in data.

In many inverse problems it is essential to use regularization methods that preserve edges in the reconstructions, and many reconstruction models have been developed for this task, such as the Total Variation (TV) approach. The associated algorithms are complex and require a good knowledge of large-scale optimization algorithms, and they involve certain tolerances that the user must choose. We present a simpler approach that relies only on standard computational building blocks in matrix computations, such as orthogonal transformations, preconditioned iterative solvers, Kronecker products, and the discrete cosine transform-hence the term "plug-andplay." We do not attempt to improve on TV reconstructions, but rather provide an easy-to-use approach to computing reconstructions with similar properties.

It is shown that infinite-dimensional positive real systems can be robustly stabilized with respect to coprime factor perturbations with a robustness margin of a t least l/m. This result is applied to dissipative colocated systems which arise in p.d.e. models of flexible structures.

This study describes a method for determining the reflection of sunlight to space and absorption by the earth and atmosphere, using low-resolution radiometer data from earth satellites. The method has been used with TIROS ISi data together with radiation measurements a t the ground to determine the reflection and absorption of sunlight over the United States during the spring of 1962.

Sensors carried on the first and second generation meteorological satellites (TIROS, NIMBUS, ESSA) during the 1960's were designed to measure solar energy reflected and scattered by the earth and its atmosphere. From many months of data, a global planetary albedo of 30 per cent has been measured. Only small seasonal variations are detected on the global scale. However, much more solar energy is apparently absorbed in tropical regions than was previously believed. Application of these measurements to the total radiation and energy budgets provides a new insight into atmospheric energetics. In addition, the measurements allow quantitative study of the mean solar energy input at geographical locations, as well as temporal variations from that mean. R~mum~-Des dipositifs install~s a bord des satellites m~t~orologlques de leet 2e gc~nSration (TIROS, NIMBUS, ESSA) au cours des ann6es 1960 ~taient destinc~s a mesurer I'¢~nergie solaire r~fl~chie et dispers~e par la terre et par son atmosphere. A partir de mesures faltes pendant plusieurs mois un alb~do plan~taire global de 30% a ¢~t~ mesur~. Seules quelques falbles variations saisonni/~res oat pu ~tre d6tect6es a I'¢~chelle globale. Cependant, bien plus d'$nergle solalre est absorb6e dans les r~gions tropicales que I'on imaginalt auparavant. L'application de ces mesures a la radiation totale et aux budgets d'6nergie offre un nouvel aspect de r~nergle atmosph~rique. De plus, les mesures perrnettent l'~tude quantitative de la puissance moyenne de r~nergie solaire dans les r~glons g6ographiques et des variations avec le temps de cette moyenne. Resumen-Los sensores que viajaron en los sat~lites meteorol6glcos de primera y segunda generaci6n (TIROS, NIMBUS, ESSA) durante los afios 1960 estaban destinados a medir la energla solar reflejada y dispersada por la Tierra y su atm6sfera. A partir de los datos correspondientes a muchos meses de investi-gaci6n, se ha determinado un albedo planetario global del 30~. S61o se detectan pequefias variaciones estacionales en la escala global. Sin embargo, parece ser que ia absorci6n de energla solar en ias reglones tropicales es mucho mayor de lo que se creia ser antignamente. La aplicaci6n de estas medidas a la radiaci6n total y a los presupuestos de energla presenta un nuevo concepto de la energC~tica atmosf~rica. Adem~s, las medidas permiten el estudio cuantitativo de la admisi6n media de energla solar en iugnres geogn~ficos, asi como variaciones temporales a partir de dicha media.

Sensors carried on the first and second generation meteorological satellites (TIROS, NIMBUS, ESSA) during the 1960's were designed to measure solar energy reflected and scattered by the earth and its atmosphere. From many months of data, a global planetary albedo of 30 per cent has been measured. Only small seasonal variations are detected on the global scale. However, much more solar energy is apparently absorbed in tropical regions than was previously believed. Application of these measurements to the total radiation and energy budgets provides a new insight into atmospheric energetics. In addition, the measurements allow quantitative study of the mean solar energy input at geographical locations, as well as temporal variations from that mean. R~mum~-Des dipositifs install~s a bord des satellites m~t~orologlques de leet 2e gc~nSration (TIROS, NIMBUS, ESSA) au cours des ann6es 1960 ~taient destinc~s a mesurer I'¢~nergie solaire r~fl~chie et dispers~e par la terre et par son atmosphere. A partir de mesures faltes pendant plusieurs mois un alb~do plan~taire global de 30% a ¢~t~ mesur~. Seules quelques falbles variations saisonni/~res oat pu ~tre d6tect6es a I'¢~chelle globale. Cependant, bien plus d'$nergle solalre est absorb6e dans les r~gions tropicales que I'on imaginalt auparavant. L'application de ces mesures a la radiation totale et aux budgets d'6nergie offre un nouvel aspect de r~nergle atmosph~rique. De plus, les mesures perrnettent l'~tude quantitative de la puissance moyenne de r~nergie solaire dans les r~glons g6ographiques et des variations avec le temps de cette moyenne. Resumen-Los sensores que viajaron en los sat~lites meteorol6glcos de primera y segunda generaci6n (TIROS, NIMBUS, ESSA) durante los afios 1960 estaban destinados a medir la energla solar reflejada y dispersada por la Tierra y su atm6sfera. A partir de los datos correspondientes a muchos meses de investi-gaci6n, se ha determinado un albedo planetario global del 30~. S61o se detectan pequefias variaciones estacionales en la escala global. Sin embargo, parece ser que ia absorci6n de energla solar en ias reglones tropicales es mucho mayor de lo que se creia ser antignamente. La aplicaci6n de estas medidas a la radiaci6n total y a los presupuestos de energla presenta un nuevo concepto de la energC~tica atmosf~rica. Adem~s, las medidas permiten el estudio cuantitativo de la admisi6n media de energla solar en iugnres geogn~ficos, asi como variaciones temporales a partir de dicha media.

Some recent dereverberation approaches that have been effective for automatic speech recognition (ASR) applications, model reverberation as a linear convolution operation in the spectral domain, and derive a factorization to decompose spectra of reverberated speech in to those of clean speech and room-response filter. Typically, a general non-negative matrix factorization (NMF) framework is employed for this. In this work 1 we present an alternative to NMF and propose an iterative least-squares deconvolution technique for spectral factorization. We propose an efficient algorithm for this and experimentally demonstrate it's effectiveness in improving ASR performance. The new method results in 40-50% relative reduction in word error rates over standard baselines on artificially reverberated speech.

The diffraction of an incident plane wave by an isotropic penetrable wedge is studied using generalized Wiener-Hopf equations, and the solution is obtained using analytical and numerical-analytical approaches that reduce the Wiener-Hopf factorization to Fredholm integral equations of second kind. Mathematical aspects are described in a unified and consistent theory for angular region problems. The formulation is presented in the general case of skew incidence and several numerical tests at normal incidence are reported to validate the new technique. The solutions consider engineering applications in terms of GTD/UTD diffraction coefficients and total fields.

The diffraction of an incident plane wave by an isotropic penetrable wedge is studied using generalized Wiener-Hopf equations, and the solution is obtained using analytical and numerical-analytical approaches that reduce the Wiener-Hopf factorization to Fredholm integral equations of second kind. Mathematical aspects are described in a unified and consistent theory for angular region problems. The formulation is presented in the general case of skew incidence and several numerical tests at normal incidence are reported to validate the new technique. The solutions consider engineering applications in terms of GTD/UTD diffraction coefficients and total fields.