The wavelet transform has been used for several decades and it is still an object of research - especially its recent modifications which are using the so-called second generation wavelets. It has several advantages over other integral transformations. The most important of them are the ability to localize both in time and frequency and an ability to decorrelate some real non-stationary signals such as images. For this reasons, the wavelet transform became an often used tool in many image processing tasks, for example in image compression, edge detection or contrast enhancement. In this thesis, the wavelet transform is explained, including the theoretical foundation and implementation for use with two-dimensional discrete signals. Some of the applications of the wavelet transform are presented and described. The wavelet transform showed to be suitable tool for edge detection, noise reduction, contrast enhancement and HDR compression.

This thesis deals with recognition by retina (identification, verification). In introduction we describe information about human eye, its diseases with focus on retina impact. Further (in main part) we conduct SW analyses based on biometry retina requirements and design of SW application for retina recognition. It is based on processing pipeline design (sequential application of image filters). This pipeline mostly contains filters focused on edge detection, adaptive threshold and skeletonisation. Finally, basic SW functions includes users registration (enroll), identification, verification. In conclusion we discuss experimental results and success of designed SW in practical application.

Orientador: Denis Henrique Pinheiro Salvadeo / Resumo: Tomossíntese Mamária Digital (DBT) é uma técnica de imageamento radiográfico, com aquisição de projeções em ângulos limitados utilizando dose reduzida de radiação. Ela tem por objetivo reconstruir fatias tomográficas do interior da mama, possibilitando o diagnóstico precoce de possíveis lesões e aumentando, consequentemente, a probabilidade de cura do paciente. Contudo, devido ao fato de que DBT utiliza doses baixas de radiação, a imagem gerada contém mais ruído que a mamografia digital. Embora a qualidade do exame esteja diretamente relacionada com a dose utilizada, espera-se que a dose de radiação empregada no exame seja a mais baixa possível, mas ainda com qualidade suficiente para que o diagnóstico possa ser realizado, conforme o princípio As Low As Reasonably Achievable (ALARA). Uma das etapas importantes para se buscar o princípio ALARA é a reconstrução tomográfica, que consiste em um software que gera as fatias do interior da mama a partir de um conjunto de projeções 2D de DBT adquiridas. Por outro lado, técnicas de Aprendizado de Máquina, especialmente redes neurais com aprendizado profundo, que recentemente tem evoluído consideravelmente o estado da arte em diversos problemas de Visão Computacional e Processamento de Imagens, tem características adequadas para serem aplicadas também na etapa de reconstrução. Deste modo, este trabalho investigou uma arquitetura básica de rede neural artificial com aprendizado profundo que seja capaz de reconstruir imagens de DBT, espe... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Digital Breast Tomosynthesis (DBT) is a technique of radiographic imaging, with acquisition of projections at limited angles using reduced dose of radiation. It aims to reconstruct tomographic slices inside the breast, making possible the early diagnosis of possible lesions and, consequently, increasing the probability of cure of the patient. However, due to the fact that DBT uses low doses of radiation, the generated image contains more noise than digital mammography. Although the quality of the exam is directly related to the dose applied, the radiation dose used in the examination is expected to be as low as possible, but still keeping enough quality for the diagnosis to be made, as determined by the As Low As Reasonably Achievable (ALARA) principle. One of the important steps to achieve the ALARA principle is the tomographic reconstruction, which consists of a software that generates slices inside the breast from an acquired set of 2D DBT projections. On the other hand, Machine Learning techniques, especially neural networks with deep learning, that have recently evolved considerably the state-of-the-art in several problems in Computer Vision and Image Processing areas, it has suitable characteristics to be applied also in the reconstruction step. Thus, this work investigated a basic architecture of artificial neural network with deep learning that is capable to reconstruct DBT images, especially focused on noise reduction. Furthermore, considering an additional filtering... (Complete abstract click electronic access below) / Mestre

<p>Hydraulic systems have many applications in the construction, transportation, and manufacturing sectors. Recent design trends involve systems with higher working pressures and more compact systems, which are advantageous because of power density increase. However, these trends imply higher forces and larger vibration amplitudes while having lesser mass and damping, leading to higher noise levels. Meanwhile, hydraulic machinery started prospecting new applications with tighter noise regulations, a trend which was also pushed by the electrification tendency in several fields of transportation and agriculture. One method to attain noise mitigation is passive-noise canceling techniques have the advantage of not introducing energy to the system. This approach arranges pressure ripple waves in a destructive pattern by projecting a hydraulic circuit's geometry, configuration, and features.</p> <p> </p> <p>This dissertation aims to predict fluid-borne noise sources and investigate passive noise-canceling solutions for multiple operations conditions targeting to impact many hydraulic systems and a broad range of operating conditions. Primarily a coupled system model strategy that includes a one-dimensional line finite element model is developed. The line model predicts pressure wave generation and propagation. The model features versatility since parameters like line diameter and material can be discretized node by node. Simulations are compared to measured data in a realistic novel hydraulic hybrid transmission for validation. </p> <p> </p> <p>Subsequently, an extensive numerical investigation is performed by setting fixed parameters along the hydraulic lines' length and comparing several isolated geometric properties in simulation. The developed line model is also used to study the influence of line features such as diameter and extent of the conduit. Cost-effective and simple passive solution solutions such as Quincke tubes (parallel lines), expansion chambers, and closed branches are selected and investigated on simulation. Four target pressure ripples are chosen as indicators for summarizing passive line elements behavior. The frequency-domain behavior of the pressure ripple peaks regarding the line's length is identified and isolated in simulation at the 50-5000Hz frequency spectrum. An experiment test rig is designed to implement these solutions and the experiments show three developed passive elements as practical and effective solutions for reducing fluid borne noise sources. The selected designs yielded noise source attenuation over most of the frequency spectrum measured with piezoelectric pressure variation sensors and accelerometers in different positions in the hydraulic circuit. Sound pressure measurements detected reductions over 3dB in the best cases. </p> <p> </p> <p>Also, a passive interference approach based on the principle of secondary source flow ripple cancellation was conceptualized, modeled, and implemented in a tandem axial-piston unit. The strategy consists of setting the phase between the two synchronous units to accomplish destructive interference in targeted unit harmonics. Two indexing strategies are investigated first analytically and then on simulation. One of the indexing strategies was implemented in a pre-existent commercial axial-piston tandem unit. Experiment results confirmed effectiveness for the first and third unit’s harmonics, where reductions over 15dB on pressure ripple were measured.</p> <p> </p> <p>Finally, a fluid-structure interaction based on the poison coupling principle is developed using the method of characteristics. Transfer functions of the pipeline accelerations versus the pressure ripples on lines calculated on simulation and later obtained experimentally to highlight ta critical vibration band from 2000Hz to 3000Hz with high acceleration response.</p> <p> </p><br>

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Over the past ten years, there has been increased use of electronic power processing in alternative, sustainable, and distributed energy sources, as well as energy storage systems, transportation systems, and the power grid. Three-phase voltage source converters (VSCs) have become the converter of choice in many ac medium- and high-power applications due to their many advantages, such as high efficiency and fast response. For transportation applications, high power density is the key design target, since increasing power density can reduce fuel consumption and increase the total system efficiency. While power electronics devices have greatly improved the efficiency, overall performance and power density of power converters, using power electronic devices also introduces EMI issues to the system, which means filters are inevitable in those systems, and they make up a significant portion of the total system size and cost. Thus, designing for high power density for both power converters and passive components, especially filters, becomes the key issue for three-phase converters. This dissertation explores two different approaches to reducing the EMI filter size. One approach focuses on the EMI filters itself, including using advanced EMI filter structures to improve filter performance and modifying the EMI filter design method to avoid overdesign. The second approach focuses on reducing the EMI noise generated from the converter using a three-level and/or interleaving topology and changing the modulation and control methods to reduce the noise source and reduce the weight and size of the filters. This dissertation is divided into five chapters. Chapter 1 describes the motivations and objectives of this research. After an examination of the surveyed results from the literature, the challenges in this research area are addressed. Chapter 2 studies system-level EMI modeling and EMI filter design methods for voltage source converters. Filter-design-oriented EMI modeling methods are proposed to predict the EMI noise analytically. Based on these models, filter design procedures are improved to avoid overdesign using in-circuit attenuation (ICA) of the filters. The noise propagation path impedance is taken into consideration as part of a detailed discussion of the interaction between EMI filters, and the key design constraints of inductor implementation are presented. Based on the modeling, design and implementation methods, the impact of the switching frequency on EMI filter weight design is also examined. A two-level dc-fed motor drive system is used as an example, but the modeling and design methods can also be applied to other power converter systems. Chapter 3 presents the impact of the interleaving technique on reducing the system passive weight. Taking into consideration the system propagation path impedance, small-angle interleaving is studied, and an analytical calculation method is proposed to minimize the inductor value for interleaved systems. The design and integration of interphase inductors are also analyzed, and the analysis and design methods are verified on a 2 kW interleaved two-level (2L) motor drive system. Chapter 4 studies noise reduction techniques in multi-level converters. Nearest three space vector (NTSV) modulation, common-mode reduction (CMR) modulation, and common-mode elimination (CME) modulation are studied and compared in terms of EMI performance, neutral point voltage balancing, and semiconductor losses. In order to reduce the impact of dead time on CME modulation, the two solutions of improving CME modulation and compensating dead time are proposed. To verify the validity of the proposed methods for high-power applications, a 100 kW dc-fed motor drive system with EMI filters for both the AC and DC sides is designed, implemented and tested. This topology gains benefits from both interleaving and multilevel topologies, which can reduce the noise and filter size significantly. The trade-offs of system passive component design are discussed, and a detailed implementation method and real system full-power test results are presented to verify the validity of this study in higher-power converter systems. Finally, Chapter 5 summarizes the contributions of this dissertation and discusses some potential improvements for future work. / Ph. D.

The study of the flow of a fan blade was conducted to improve tonal fan noise reduction by optimizing an existing flow control configuration. The current configuration consisted of a trailing edge Slot with a flow control area of 0.045 in² per inch span with an exit angle of -3.3° with respect to the blade exit angle. Two other flow control configurations containing discrete jets were investigated. For the first configuration, the trailing edge jets (TEJ), the fan blade was modified with discrete jets spaced 0.3 inches apart with a flow control area of 0.01 in² per inch span positioned on the trailing edge aimed at -3.3° with respect to the blade exit angle. Similarly, discrete jets were also placed on the suction surface at 95.5% chord aimed at 15° with respect to the local blade surface. This configuration is referred to as the suction surface jet (SSJ). The discrete jets for both configurations were designed to be choked while injecting a mass flow rate of 1.00% of the fan through-flow. Computational Fluid Dynamics (CFD) was used to model new configurations and study subsequent changes in total pressure deficit using a blade design inlet Mach number of 0.73, Reynolds number based on chord length of 1.67 à 106, and design incidence angle of 0°. Experimental testing was later conducted in a 2D cascade tunnel. The TEJ and SSJ were tested at design blowing of 1.00% and at off-design conditions of 0.50%, 0.75%, and 1.25% fan through-flow. Results between the different flow control configurations were compared using a blowing coefficient. CFD showed the TEJ and SSJ offered aerodynamic improvement over the Slot configuration. Testing showed the SSJ outperformed the TEJ, as validated in CFD, producing wider and shallower wakes. SSJ area-averaged pressure losses were 25% less than TEJ at design. Noise predictions based on CFD findings showed that both TEJ and SSJ provided additional tonal sound power level attenuation over the Slot configuration at similar blowing coefficients, with the SSJ providing the most attenuation. Noise prediction based on experimental results concurred that the SSJ provided more total attenuation than the TEJ. Experimental results showed that the SSJ performed better aerodynamically and, based on analytical prediction, provided 2 dB more total attenuation than the TEJ. / Master of Science

Microscope cameras possess high zoom capabilities and are frequently used for quality control in various industries. Visus Technology is a company that manufactures and sells these cameras, along with control software. The problem is that these cameras can only be set to one focus depth at a time. Therefore, we were tasked with implementing a fast focus stacking algorithm that combines multiple input images with different focus depths, resulting in a composite image with consistent focus throughout. This will later be integrated into the control software. We initially approached the problem by choosing pixels with the highest Laplacian intensity. This resulted in very noisy output images since the blurry images could sometimes produce high-intensity pixels where they were not supposed to be. To address this, we implemented a grid-based focus stacking algorithm. The algorithm divides the input images into tiles, filtering out the blurriest tiles to exclude them from the stacking process. The result is a composite image with significantly reduced blur.

Cette thèse s'inscrit dans le cadre de la recherche des moyens de réduction du bruit. Le but est d’analyser et de créer par une méthode passive, le confinement d’énergie acoustique dans les irrégularités géométriques via le phénomène de localisation pour ensuite la dissiper. En prélude à l'atténuation du bruit par les géométries irrégulières, les mécanismes de la dissipation acoustique sont rappelés et illustrés par quelques exemples de réseaux de résonateurs quart-d'onde. Le phénomène de localisation est ensuite étudié par une analyse modale. Le caractère localisé d'un mode est quantifié par son volume d'existence relatif (VER) qui donne, en fraction du volume total du domaine, le volume effectif concerné par l'énergie du mode. Il ressort de cette étude que seules les cavités irrégulières ayant des irrégularités en forme de sous-cavités couplées à une cavité principale sont « localisantes ». La fréquence d'un mode localisé est liée aux dimensions de la zone irrégulière de localisation. Le lien entre les irrégularités géométriques et la dissipation acoustique est ensuite analysé au moyen des indicateurs tels que le facteur de qualité, le coefficient d'absorption ou le taux d'amortissement de l'énergie. Cette étude montre que les cavités irrégulières amortissement mieux une onde acoustique comparativement aux cavités à géométrie régulière. Toutefois, la dissipation de l'énergie acoustique des cavités irrégulières n'est pas uniquement liée à la localisation. Elle dépend également d'autres paramètres (porosité, résistivité, etc.). Lorsque les irrégularités des parois rigides ne permettent pas de réaliser une dissipation suffisante, elles peuvent être réalisées dans les matériaux poroélastiques à performance acoustique moyenne pour augmenter leur capacité dissipative. Enfin, des études expérimentales menées ont permis de valider l'existence du phénomène de localisation et de confirmer la tendance plus dissipative des géométries irrégulières par rapport aux géométries régulières. De même, des mesures du coefficient d'absorption d'un échantillon de forme préfractale d'un béton de chanvre (matériau ayant une performance acoustique moyenne) montrent une augmentation de la dissipation de plus de 40% induite par la forme irrégulière. La contribution majeure de cette thèse est d’avoir répondu à un défi technologique important consistant à effectuer une mise en évidence expérimentale du phénomène de localisation jusque-là difficile à réaliser avec des microphones. Pour y parvenir, un outil optique peu conventionnel dans la métrologie acoustique est adopté; il s'agit de la réfracto-vibrométrie qui consiste à utiliser, sous certaines conditions, le vibromètre laser pour mesurer un champ acoustique (pression acoustique). Bien que contraignante, cette technique présente l'avantage d'être non intrusive et donc moins encombrante même pour de petites cavités comparativement aux microphones. / In this thesis, the acoustical behavior of irregular cavities leading to localization phenomenon is investigated for noise reduction applications. The aim of this work is to study and create by means of passive method, an accumulation of acoustical energy and dissipate it. Before addressing geometrical irregularities effects on the sound field, viscothermal dissipation mechanisms of sound are recalled and illustrated through few networks of quarter-wave resonators. In a second part, a study of the localization phenomenon is carried out by a modal analysis approach. The localization is quantified by the relative existence volume (VER), an indicator which gives a measure of the volume of the region in which a mode is localized as a fraction of the total cavity volume. The localization analysis is conducted using both regular and irregular cavities. It has been shown that only cavities with irregular geometry, such that sub-cavities are formed, can localize some acoustical modes. Moreover, the frequency of a localized mode is related to the dimensions of the localization region. Following the investigation of the localization phenomenon, the relation between cavities geometry and sound energy dissipation has been studied by the estimation of damping indicators, such as the quality factor, the sound absorption coefficient or the energy damping rate. According to this study, irregular cavities have higher capability to damp sound waves compared to regular cavities. However, for the case of irregular cavities only, the induced dissipation is not proportional to the localization. Nevertheless, when irregularities of rigid walls are not able to achieve sufficient dissipation, this can be obtained with slightly absorptive porous materials of irregular geometry. In fact, the dissipative properties of some porous materials can be optimized by giving them irregular interface. Finally, an experimental set-up has been designed to validate the localization phenomenon and to confirm the damping tendency of irregular geometries in comparison to regular ones. Moreover, measurements of the sound absorption coefficient of a hemp concrete reveal that the sample of irregular geometry achieves sound dissipation more than 40% higher than the one achieved by a regular plane sample. Finally, this thesis has addressed a technological challenge consisting of experimentally validating the localization phenomenon which is so far very difficult to obtain by the use of conventional pressure microphones. In the framework of this thesis, an optical non-conventional sound pressure measurement technique has been used. The used technique is the laser refracto-vibrometry which consists of using a laser vibrometer in some specific conditions to measure the acoustical field (sound pressure). This technique is difficult to conduct but it has the advantage of being contactless, thus less cumbersome for even very small cavities as compared to pressure microphones.

Les SPA sont des moteurs piézoélectriques inertiels amplifiés. Ils fonctionnent en convertissant des vibrations asymétriques en μ-déplacements par frottement, grâce au phénomène d’adhérence-glissement. Ces vibrations et ce frottement soulèvent des problématiques liées à l’usure et au bruit. Pour y répondre, ces travaux étudient les comportements tribologique et vibratoire de ces moteurs. Dans un premier temps, un tribomètre pion-plan, actionné par un SPA, a été développé. Il a permis d’observer, in-situ et en fonctionnement, les débits solides interfaciaux: le 3ème corps. Ces observations directes, couplées à des analyses post-mortem ont permis de décrypter les sollicitations tribologiques et de multiplier par dix la durée de vie des moteurs. Dans un second temps, des analyses numérique et expérimentale ont été proposées afin de mieux appréhender le comportement vibratoire des SPA. Le modèle existant, à constantes localisées, a été modifié en une version hybride, constantes localisées-FEM, plus versatile. Les tests expérimentaux ont permis de déterminer le principal contributeur acoustique et de réduire le niveau de bruit de seize dBA. Finalement, la double approche tribologie/mécanique vibratoire a permis de mieux saisir les subtilités des SPA. Elle a notamment mené au développement de structures innovantes tels qu’un moteur à trois degrés de liberté et deux moteurs rotatifs. / SPA are amplified piezoelectric inertia motors. They operate by converting asymmetrical vibrations into μ-displacements by means of friction through stick-slip. These vibrations and this friction raise issues related to wear and noise. So, the present work investigates both the tribological and vibratory behaviours of these motors. First, a pin-on-pad tribometer, actuated by a SPA, was developed. It led us to observe, in-situ and in operation, interfacial solid flows: the 3rd body. These direct observations carried out in conjunction with post-mortem analyses resulted in decrypting the tribological solicitations and in increasing by ten the lifetime of the motors. Second, numerical and experimental considerations have been proposed to better grasp the vibratory behaviour of SPA. The existing lumped model was modified to a more versatile hybrid lumped-FEM model. The experimental tests made it possible to determine the main acoustic contributor and to reduce the noise level by sixteen dBA. Finally, this dual - tribology/vibratory - approach provided a better understanding of the SPA intricacies. In particular, it led to develop innovative structures such as a motor with three degrees of freedom and two rotary motors.