International Telemetering Conference Proceedings / October 17-20, 1994 / Town & Country Hotel and Conference Center, San Diego, California / In this paper, by using computer simulations, the interference of channel data in the SDM telemetry system is investigated, the performance of the copy demultiplexing is examined, and finally the selection rule of Walsh functions is recommended.

International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, Nevada / In most transmission channels, bandwidth is at a premium and an important attribute of any good digital signalling scheme is to optimally utilise the bandwidth for transmitting the information. The Data Compression System in this way plays a significant role in the transmission of picture data from any Remote Sensing Satellite by exploiting the statistical properties of the imagery. The data rate required for transmission to ground can be reduced by using suitable compression technique. A data compression algorithm has been developed for processing the images of Indian Remote Sensing Satellite. Sample LANDSAT imagery and also a reference photo are used for evaluating the performance of the system. The reconstructed images are obtained after compression for 1.5 bits per pixel and 2 bits per pixel as against the original of 7 bits per pixel. The technique used is uni-dimensional Hadamard Transform Technique. The Histograms are computed for various pictures which are used as samples. This paper describes the development of such a hardware and software system and also indicates how hardware can be adopted for a two dimensional Hadamard Transform Technique.

Les méthodes de projection sur des espaces de Krylov ont été employées avec grand succès pour diverses tâches en calcul scientifique, par exemple la résolution de grands systèmes d’équations linéaires, le calcul approché de valeurs propres, ou encore le calcul approché des fonctions de matrices fois un vecteur. L’objectif majeur de cette thèse est d’étudier et d’expliquer la convergence superlinéaire des méthodes de Krylov. La plupart des résultats existants sont asymptotiques avec passage à la racine n-ième et considèrent des suites de matrices. Dans un premier temps, nous généralisons une formule de Ipsen et al. concernant la convergence superlinéaire des méthodes MR valable pour des disques, à l’aide des opérateurs de Hankel et de la théorie AAK. Notre analyse permet aussi d’obtenir des bornes supérieures pour des ensembles convexes en utilisant la transformée de Faber. Ensuite nous énonçons notre principal résultat qui est un théorème d’optimalité en théorie du potentiel logarithmique. Nous montrons, à l’aide d’une nouvelle technique de discrétisation d’un potentiel, que l’inégalité de Bernstein-Walsh à poids sur un intervalle réel est optimale, à un facteur universel près, dans le cas où le champs extérieur est un potentiel d’une mesure à support réel à gauche de l’intervalle, ce qui inclut le cas des poids polynômiaux. Via un lien avec un problème sous contrainte, l’inégalité précédente s’applique à l’analyse de la convergence des méthodes de Krylov, et permet de prédire analytiquement un taux de convergence superlinéaire de la méthode du gradient conjugué et des approximations de Rayleigh-Ritz pour des fonctions de Markov, à chaque étape et pour une seule matrice. / Projection methods on Krylov spaces were used with great success for various tasks in scientific computing, for example the resolution of large systems of linear equations, the approximate computation of eigenvalues, or the approximate computation of matrix functions times a vector. The main goal in this thesis is to study and explain superlinear convergence of Krylov methods. Most of the existing formulas provide asymptotic results for the n-th root considering an increasing sequence of matrices. Firstly, we generalize a formula of Ipsen et al. concerning superlinear convergence of MR methods valid for disks using Hankel operators and AAK theory, our analysis also allows to obtain upper bounds for convex sets using the Faber transform. Then we state our main theorem which is a sharpness result in logarithmic potential theory using a new technique of discretization of a logarithmic potential. We prove that the weighted Bernstein-Walsh inequality on a real interval is sharp up to some universal constant, when the external field is given by a potential of a real measure supported at the left of the interval. As a special case this result includes the case of weights given by polynomials. Via a link with a constrained extremal problem our inequality applies to the analysis of the convergence of Krylov methods, and allows us to predict analytically the superlinear convergence of the conjugate gradient method and of the error for Rayleigh-Ritz approximations for Markov functions. Our results apply to a simple matrix, without taking the limit and without n-th root.

This dissertation is devoted to theories of processes we call ``Walsh semimartingales" and ``Walsh diffusions", as well as to related optimization problems of control and stopping. These processes move on the plane along rays emanating from the origin; and when at the origin, the processes choose the rays of their subsequent voyage according to a fixed probability measure---in a manner described by Walsh (1978) as a direct generalization of the skew Brownian motion. We first review in Chapter 1 some key results regarding the celebrated skew Brownian motions and Walsh Brownian motions. These results include the characterization of skew Brownian motions via stochastic equations in Harrison & Shepp (1981), the construction of Walsh Brownian motions in Barlow, Pitman & Yor (1989), and the important result of Tsirel'son (1997) regarding the nature of the filtration generated by the Walsh Brownian motion. Various generalizations of Walsh Brownian motions are described in detail in Chapter 2. We formally define there Walsh semimartingales as a subclass of planar processes we call ``semimartingales on rays". We derive for such processes Freidlin-Sheu-type change-of-variable formulas, as well as two-dimensional versions of the Harrison-Shepp equations. The actual construction of Walsh semimartingales is given next. Walsh diffusions are then defined as a subclass of Walsh semimartingales, described by stochastic equations which involve local drift and dispersion characteristics. The associated local submartingale problems, strong Markov properties, existence, uniqueness, asymptotic behavior, and tests for explosions in finite time, are studied in turn. Finally, with Walsh semimartingales as state-processes, we study in Chapter 3 succesively a pure optimal stopping problem, a stochastic control problem with discretionary stopping, and a stochastic game between a controller and a stopper. We derive for these problems optimal strategies in surprisingly explicit from. Crucial for the analysis underpinning these results, are the change-of-variable formulas derived in Chapter 2. Most of the results in Chapters 2 and 3 are based on two papers, [21] and [31], both cowritten by the author of this dissertation. Some results and proofs are rearranged and rewritten here.

Zugl.: Berlin, Humboldt-Univ., Diss., 2004

Thesis (M.S. in Engineering Science)--Naval Postgraduate School, December 1990. / Thesis Advisor(s): Davis, David S. Second Reader: Walters, D.L. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Infrared Images, Multiplexing, Spectroscopy, Applied Mathematics. Author(s) subject terms: Spectroscopy, Walsh Functions, Sequency Theory, Infrared Imaging. Includes bibliographical references (p. 120-121). Also available in print.

Thesis (M.S.)--Rochester Institute of Technology, 1994. / Typescript. Bibliography: leaves 57-58.

Optimisation heuristics rely on implicit or explicit assumptions about the structure of the black-box fitness function they optimise. A review of the literature shows that understanding of structure and linkage is helpful to the design and analysis of heuristics. The aim of this thesis is to investigate the role that problem structure plays in heuristic optimisation. Many heuristics use ordinal operators; which are those that are invariant under monotonic transformations of the fitness function. In this thesis we develop a classification of pseudo-Boolean functions based on rank-invariance. This approach classifies functions which are monotonic transformations of one another as equivalent, and so partitions an infinite set of functions into a finite set of classes. Reasoning about heuristics composed of ordinal operators is, by construction, invariant over these classes. We perform a complete analysis of 2-bit and 3-bit pseudo-Boolean functions. We use Walsh analysis to define concepts of necessary, unnecessary, and conditionally necessary interactions, and of Walsh families. This helps to make precise some existing ideas in the literature such as benign interactions. Many algorithms are invariant under the classes we define, which allows us to examine the difficulty of pseudo-Boolean functions in terms of function classes. We analyse a range of ordinal selection operators for an EDA. Using a concept of directed ordinal linkage, we define precedence networks and precedence profiles to represent key algorithmic steps and their interdependency in terms of problem structure. The precedence profiles provide a measure of problem difficulty. This corresponds to problem difficulty and algorithmic steps for optimisation. This work develops insight into the relationship between function structure and problem difficulty for optimisation, which may be used to direct the development of novel algorithms. Concepts of structure are also used to construct easy and hard problems for a hill-climber.

Fourier analysis, Walsh-Fourier analysis, and wavelet analysis have often been used in time series analysis. Fourier analysis can be used to detect periodic components that have sinusoidal shape; however, it might be misleading when the periodic components are not sinusoidal. Walsh-Fourier analysis is suitable for revealing the rectangular trends of time series. The flaw of the Walsh-Fourier analysis is that Walsh functions are not periodic. The resulting Walsh-Fourier analysis is more difficult to interpret than classical Fourier analysis. Wavelet analysis is very useful in analyzing and describing time series with gradual frequency changes. Wavelet analysis also has a shortcoming by giving no exact meaning to the concept of frequency because wavelets are not periodic functions. In addition, all three analysis methods above require equally-spaced time series observations. In this dissertation, by using a sequence of periodic step functions, a new analysis method, adaptive Fourier analysis, and its theory are developed. These can be applied to time series data where patterns may take general periodic shapes that include sinusoids as special cases. Most importantly, the resulting adaptive Fourier analysis does not require equally-spaced time series observations. / Ph. D.

O presente trabalho é um estudo da poética do escritor, jornalista e militante argentino Rodolfo Jorge Walsh. Tradutor, editor e autor de relatos policiais, soube fazer da atividade literária um ato de reflexão sobre a história do seu país e da própria ação militante. Os procedimentos de escrita utilizados dentro da sua obra procuravam a eficiência persuasiva, mas também a eficiência na representação dos problemas que estavam colocados para o escritor na sua ação política. São objeto de estudo deste trabalho: a passagem do policial de enigma para o hard-boiled e o posterior abandono do subgênero; a opção pela forma breve do conto e não do romance; o abandono da escrita estritamente literária que seria retomada só nos últimos meses da sua vida -processos que coincidiram com o desenvolvimento de investigações sobre crimes de Estado e seu ingresso na militância- e a retomada da autoria, pouco antes de morrer, para a produção de uma série de cartas pessoais no contexto da ditadura que se iniciou em 1976 e da polêmica do autor com a direção da organização Montoneros, na qual militava. / The present work is a study of Rodolfo Jorge Walsh\'s poetry. He was an author, a journalist and an activist. Also a translator, editor an author of police short stories. He knew how to transform the literary activity into an act of reflexion about the history of his country and the activist action itself. The writing procedures used inside his works searched not only for a persuasive efficiency, but also the efficiency in representing the problems faced by the author in his political action. They are object of study: the passage from police enigma to hard-boiled and the following desertion of the sub gender; the option for the brief form of the short story and not the novel; desertion of the writing strictly literary that would be taken up again in the last months of his life - processes that coincided with the development of State crime investigations and his participation in an activist life - and getting back the authorship, shortly before his death, into a production of personal letters in a dictatorship context that began in 1976 and the controversy of the author in relation to the direction of the Montoneros organization, for which he was an activist.