Submitted by Guilherme Priólli Daniel (gui.computacao@yahoo.com.br) on 2016-09-06T13:30:29Z No. of bitstreams: 1 Dissertação_final.pdf: 2456534 bytes, checksum: 4d2279141f7c034de1e4e4e261805db8 (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-09-09T17:54:56Z (GMT) No. of bitstreams: 1 daniel_gp_me_sjrp.pdf: 2456534 bytes, checksum: 4d2279141f7c034de1e4e4e261805db8 (MD5) / Made available in DSpace on 2016-09-09T17:54:56Z (GMT). No. of bitstreams: 1 daniel_gp_me_sjrp.pdf: 2456534 bytes, checksum: 4d2279141f7c034de1e4e4e261805db8 (MD5) Previous issue date: 2016-08-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A quantidade de dados gerenciados por serviços Web de grande escala tem crescido significantemente e passaram a ser chamados de Big Data. Esses conjuntos de dados podem ser definidos como um grande volume de dados complexos provenientes de múltiplas fontes que ultrapassam a capacidade de armazenamento e processamento dos computadores atuais. Dentro desses conjuntos, estima-se que 80% dos dados possuem associação com alguma posição espacial. Os dados espaciais são mais complexos e demandam mais tempo de processamento que os dados alfanuméricos. Nesse sentido, as técnicas de MapReduce e sua implementação têm sido utilizadas a fim de retornar resultados em tempo hábil com a paralelização dos algoritmos de prospecção de dados. Portanto, o presente trabalho propõe dois algoritmos de agrupamento espacial baseado em densidade: o VDBSCAN-MR e o OVDBSCAN-MR. Ambos os algoritmos utilizam técnicas de processamento distribuído e escalável baseadas no modelo de programação MapReduce com intuito de otimizar o desempenho e permitir a análise em conjuntos Big Data. Por meio dos experimentos realizados foi possível verificar que os algoritmos desenvolvidos apresentaram melhor qualidade nos agrupamentos encontrados em comparação com os algoritmos tomados como base. Além disso, o VDBSCAN-MR obteve um melhor desempenho que o algoritmo sequencial e suportou a aplicação em grandes conjuntos de dados espaciais. / The amount of data managed by large-scale Web services has increased significantly and it arise to the status of Big Data. These data sets can be defined as a large volume of complex data from multiple data sources exceeding the storage and processing capacity of current computers. In such data sets, about 80% of the data is associated with some spatial position. Spatial data is even more complex and require more processing time than what would be required for alphanumeric data. In that sense, MapReduce techniques and their implementation have returned results timely with parallelization of data mining algorithms and could apply for Big Data sets. Therefore, this work develops two density-based spatial clustering algorithms: VDBSCAN-MR and OVDBSCAN-MR. Both algorithms use distributed and scalable processing techniques based on the MapReduce programming model in order to optimize performance and enable Big Data analysis. Throughout experimentation, we observed that the developed algorithms have better quality clusters compared to the base algorithms. Furthermore, VDBSCAN-MR achieved a better performance than the original sequential algorithm and it supported the application on large spatial data sets.

Made available in DSpace on 2017-07-10T17:55:39Z (GMT). No. of bitstreams: 1 Thomaz_Joezer_Herler.pdf: 2198063 bytes, checksum: 935518ce2a15c6470da052d2b9280865 (MD5) Previous issue date: 2015-05-27 / This master‟s thesis deals with the formation and trajectory of the first MR-8 (Movimento Revolucionário 8 de Outubro), an armed group that was formed in order to confront the dictatorship established by the Coup of 64, attempting its overthrow and the construction of socialism in Brazil. Beginning as a PCB Dissent in Rio de Janeiro (DI-RJ) in 1964, at a time when the party was suffering cracks in many states of Brazil, its members rallied several frames of other organizations, such as Dissent of Paraná (DI-PR), Polop, Ação Popular (AP) and the Ligas Camponesas, proposing constitute a "revolutionary front". Having the break from the PCB been motivated by differences not only with the concept of "revolution through peaceful means" adopted by the party, as well as the paradigm of "revolution by stages", the MR-8, which advocated direct transition to socialismo, sought inspiration in several international revolutionary experiences. Being attracted by the recent success of the Cuban Revolution, members of the movement sought in the "theory of guerrilla focus", developed by Ernesto Guevara and Régis Debray, a starting point for building a revolutionary vanguard in a country ravaged by a Corporate-Military Dictatorship, as was the case in Brazil. However, during the development of their actions, the militants of the MR-8, due to the difficulties and limitations found in concrete experiences, would adapt the theory of guerrilla focus the possibilities afforded at that historic moment. Having its downfall in August 1969, Movimento Revolucionário 8 de Outubro was one of the first Brazilian armed Marxist organizations to fight the Corporate-Military Dictatorship, as well as one of the first to be destroyed by repression. To better understand the theoretical discussions taking place among its members, we will articulate the discussion of "party" developed by Lenin with the "theory of guerrilla focus", from the perspective of Ernesto Guevara and Régis Debray. To rebuild his career, we use a number of historical sources, some produced by the organization, by other law enforcement agencies as well as books written by people who took part or had contact with the group in question / Esta dissertação aborda a formação e trajetória do primeiro MR-8 (Movimento Revolucionário 8 de Outubro), grupo armado que foi formado visando o enfrentamento à Ditadura instaurada pelo Golpe de 64, intentando a derrubada da mesma e a construção do socialismo no Brasil. Tendo seu início enquanto Dissidência do PCB no Rio de Janeiro (DI-RJ) no ano de 1964, num momento em que o partido estava sofrendo rachas em vários estados, seus membros arregimentaram diversos quadros de outras organizações, tais como a Dissidência do Paraná (DI-PR), Polop, Ação Popular (AP) e Ligas Camponesas, propondo constituir uma frente revolucionária . Tendo a ruptura com o PCB sido motivada por divergências não apenas com o paradigma de revolução por via pacífica adotado pelo partido, como também pela concepção de revolução por etapas , o MR-8, que pregava a transição direta ao socialismo, buscou inspiração em diversas experiências revolucionárias internacionais. Sendo atraídos pelo recente sucesso da Revolução Cubana, os quadros do movimento buscaram na teoria do foco guerrilheiro , desenvolvida por Ernesto Guevara e Régis Debray, um ponto de partida para a construção de uma vanguarda revolucionária em um país assolado por uma Ditadura Empresarial-Militar, como era o caso do Brasil. Contudo, durante o período de desenvolvimento de suas ações, os militantes do MR-8, a devido às dificuldades e limites encontrados nas experiências concretas, adaptariam a teoria do foco guerrilheiro às possibilidades propiciadas naquele momento histórico. Tendo sua derrocada em agosto de 1969, o Movimento Revolucionário 8 de Outubro foi uma das primeiras organizações armadas brasileiras de inspiração marxista a lutar contra a Ditadura Empresarial-Militar, bem como uma das primeiras a serem destruídas pela repressão. Para melhor compreender as discussões teóricas que ocorriam entre seus membros, articularemos a discussão de partido desenvolvida por Lenin com a teoria do foco guerrilheiro , partindo da percepção de Ernesto Guevara e Régis Debray. Para reconstituir sua trajetória, utilizaremos uma série de fontes históricas, algumas produzidas pela organização, outras pelos órgãos repressivos, bem como livros escritos por pessoas que fizeram parte ou tiveram contato com o grupo em questão

MRI is a very useful imaging modality in medical imaging for both diagnostic as well as functional studies. It provides excellent soft tissue contrast in several diagnostic studies. It is widely used to study the functional aspects of brain and to study the diffusion of water molecules across tissues. Image acquisition in MR is slow due to longer data acquisition time, gradient ramp-up and stabilization delays. Repetitive scans are also needed to overcome any artefacts due to patient motion, field inhomogeneity and to improve signal to noise ratio (SNR). Scanning becomes di cult in case of claustrophobic patients, and in younger/older patients who are unable to cooperate and prone to uncontrollable motions inside the scanner. New MR procedures, advanced research in neuro and functional imaging are demanding better resolutions and scan speeds which implies there is need to acquire more data in a shorter time frame. The hardware approach to faster k-space scanning methods involves efficient pulse sequence and gradient waveform design methods. Such methods have reached a physical and physiological limit. Alternately, methods have been proposed to reduce the scan time by under sampling the k-space data. Since the advent of Compressive Sensing (CS), there has been a tremendous interest in developing under sampling matrices for MRI. Mathematical assumptions on the probability distribution function (pdf) of k-space have led researchers to come up with efficient under sampling matrices for sampling MR k-space data. The recent approaches adaptively sample the k-space, based on the k-space of reference image as the probability distribution instead of a mathematical distribution, to come with an efficient under sampling scheme. In general, the methods use a deterministic central circular/square region and probabilistic sampling of the rest of the k-space. In these methods, the sampling distribution may not follow the selected pdf and viii Adaptive Sampling Pattern Design Methods for MR Images the selection of deterministic and probabilistic sampling distribution parameters are heuristic in nature. Two novel adaptive Variable Density Sampling (VDS) methods are proposed to address the heuristic nature of the sampling k-space such that the selected pdf matches the k-space energy distribution of a given fully sampled reference k-space or the MR image. The proposed methods use a novel approach of binning the pdf derived from the fully sampled k-space energy distribution of a reference image. The normalized k-space magnitude spectrum of the reference image is taken as a 2D probability distribution function which is divided in to number of exponentially weighted magnitude bins obtained from the corresponding histogram of the k-space magnitude spectrum. In the first method, the normalized k-space histogram is binned exponentially, and the resulting exponentially binned 2D pdf is used with a suitable control parameter to obtain a sampling pattern of desired under sampling ratio. The resulting sampling pattern is an adaptive VDS pattern mimicking the energy distribution of the original k-space. In the second method, the binning of the magnitude spectrum of k-space is followed by ranking of the bins by its spectral energy content. A cost function is de ned to evaluate the k-space energy being captured by the bin. The samples are selected from the energy rank ordered bins using a Knapsack constraint. The energy ranking and the Knapsack criterion result in the selection of sampling points from the highly relevant bins and gives a very robust sampling grid with well defined sparsity level. Finally, the feasibility of developing a single adaptive VDS sampling pattern for a organ specific or multi-slice MR imaging, using the concept of binning of magnitude spectrum of the k-space, is investigated. Based on the premise that k-space of different organs have a different energy distribution structure to one another, the MR images of organs can be classified based on their spectral content and develop a single adaptive VDS sampling pattern for imaging an organ or multiple slices of the same. The classification is done using the k-space bin histogram as feature vectors and k-means clustering. Based on the nearest distance to the centroid of the organ cluster, a template image is selected to generate the sampling grid for the organ under consideration. Using the state of the art MR reconstruction algorithms, the performance of the proposed novel adaptive Variable Density Sampling (VDS) methods using image quality measures is evaluated and compared with other VDS methods. The reconstructions show significant improvement in image quality parameters quantitatively and visual reduction in artefacts at 20% 15%, 10% and 5% under sampling

The thesis deals with addition of pixels outside the image. Lists some methods for inpainting using computers and highlights the pitfalls that appear here. Examines methods for interpolation and approximation of functions in order to find the best method for extrapolating the image beyond its borders. Describes the basics of Wavelet transformation and Multiresolution analysis. It is proposed several methods for replenishment of pixels outside the image. PSNR and SSIM are used to compare achieved results. These methods are explained and compared. Briefly discusses the algorithm OMP, falling within the sparse representation of signals, and used in one of the methods. Also discussed is the development environment of MATLAB as a tool for the implementation of algorithms that practically solves the given problem. The practical part describes the implemented methods for adding pixels outside the image.

The thesis deals with addition of pixels outside the image. Lists some methods for inpainting using computers and highlights the pitfalls that appear here. Examines methods for interpolation and approximation of functions in order to find the best method for extrapolating the image beyond its borders. Describes the basics of Wavelet transformation and Multiresolution analysis and briefly discusses about spatial filtering, edge detection and the algorithm OMP, falling within the sparse representation of signals. Theoretical knowledge of these areas are used in the design of several methods for adding pixels outside the image. PSNR and SSIM are used to compare achieved results. Also discussed is the development environment of MATLAB as a tool for the implementation of algorithms that practically solves the given problem.

This master's thesis deals with an engineering design of an external reservoir for hydraulic shock absorbers with combined filling of oil and magnetorheological fluid. The first part describes existing designes of magnetorheological shock absorbers and characteristics of magnetorheological fluid. Next part describes a design of an experimental external reservoir and a test of its functionality on a prototype. This is followed by an optimalized engineering design of the experimental external reservoir.

This work deals with the usage of magneto-rheological (MR) damper in the semi-active car suspension. Semi-active suspension can improve ride comfort or tyre grip to the level, which cannot be achieved with the common passive setting of the damper. MR damper has however features, like time response of the controller with MR damper and the control range of the MR damper, which limit area of application. It was found out that especially the time response of the damper significantly influences the efficiency of semi-active algorithms. Current MR dampers with controllers are not capable of efficient control of the semi-active suspension. For proper design of semi-active suspension with MR dampers, the time response must be decreased. Therefore, a new PWM current controller was designed and verified. Also changes in MR damper design which eliminate eddy-currents in the magnetic circuit were proposed. The results of this work should contribute to the better design of semi-active suspension systems with MR damper.

Les modèles d’aptitude et maturité de processus logiciel (AMPL) sont actuellement largement utilisés dans l’industrie. Pour exécuter les pratiques définies dans ces modèles, des approches d’ingénierie logicielle sont appliquées. On constate également une grande définition en termes de méthodes, techniques, patrons et normes pour l’analyse, la conception, la mise en œuvre et l’évaluation de systèmes interactifs, axés sur les questions d’Interaction Homme-Machine (IHM). Néanmoins, il est bien connu que les approches d’IHM ne sont pas largement utilisées dans l’industrie. Afin de profiter de l’utilisation des modèles AMPL, cette thèse propose d’intégrer les questions d’IHM (concepts de conception, mise en œuvre et évaluation de systèmes interactifs) dans le modèle international le plus connu (CMMI-DEV – Capability Maturity Model Integration for Development) et dans le modèle brésilien (MR-MPS-SW – MPS for Software reference model). À cette fin, nous avons travaillé sur (i) l’identification des approches de l’IHM appropriées pour chaque pratique de l’ingénierie préconisée par ces modèles, (ii) l’évaluation et l’amélioration des approches de l’IHM identifiées avec des experts en IHM, (iii) la validation de la proposition dans un environnement académique, et (iv) la réalisation de deux études empiriques sur la perception de la connaissance et l’utilisation des approches de l’IHM dans l’industrie. En conséquence, nous avons obtenu 14 catégories d’approches de l’IHM avec des exemples de méthodes, techniques, patrons et normes propres à réaliser chaque pratique des activités d’ingénierie des deux modèles lors du développement de systèmes interactifs. De plus, l’étude empirique avec l’industrie brésilienne a confirmé statistiquement que les consultants de ces modèles AMPL ne connaissent et n’utilisent pas ou peu les approches de l’IHM, comme ils connaissent et utilisent des approches d’ingénierie logicielle. / Software process capability maturity (SPCM) models are currently widely used in industry. To perform the practices defined in these models, software engineering approaches are applied. We also have experienced a large definition of methods, techniques, patterns, and standards for the analysis, design, implementation, and evaluation of interactive systems focusing on Human-Computer Interaction (HCI) issues. Nevertheless, it is well known that HCI approaches are not largely used in industry. In order to take advantage of the widespread use of SPCM models, this thesis proposes to integrate HCI issues (concepts of design, implementation, and evaluation of interactive systems) in the most known international SPCM model (CMMI-DEV – Capability Maturity Model Integration for Development) and in the Brazilian SPCM model (MR-MPS-SW – MPS for Software reference model). To that end, we have worked on (i) the identification of appropriate HCI approaches for each practice of the engineering advocated by these models, (ii) the evaluation and improvement of the identified HCI approaches with HCI experts, (iii) the validation of the proposition in an academic environment, and (iv) the conduction of two empirical studies about the perception of knowledge and use of HCI approaches in the industry. As a result, we got 14 categories of HCI approaches with examples of methods, techniques, patterns, and standards adequate to perform each practice of engineering activities of the both models when developing interactive systems. Moreover, the empirical study, in Brazilian industry, confirmed statistically that consultants of those SPCM models do not know and do not use HCI approaches as well as they know and use software engineering approaches.

Hintergrund: Patienten mit Bauchspeicheldrüsenkrebs könnten von der Protonentherapie (PT) profitieren, aufgrund ihres Potentials der Schonung von Risikoorganen. Jedoch führen die inter- und intrafraktionelle Beweglichkeit der Bauchspeicheldrüse zu hohen Unsicherheiten bei der Dosisapplikation und erfordern daher große Sicherheitssäume. Aufgrund des hohen Weichgewebskontrastes in der MRT und der Möglichkeit der Echtzeitbildgebung gewinnt die Unterstützung der Strahlentherapie durch die MRT stetig höheres Interesse. In der Translation von konventioneller Röntgen-geführter XT zur MR-geführten PT müssen Methoden zur Kontrolle der inter- und intrafraktionellen Organbeweglichkeit re-evaluiert, adaptiert oder neu entwickelt werden. Fragestellung/Hypothese: Für die interfraktionelle Bewegungskontrolle wurde die Hypothese aufgestellt, dass der neu entwickelte Flüssigmarker BioXmark®, injiziert in Pankreasgewebe, sichtbar in der MR-Bildgebung ist und verglichen zu üblich verwendeten soliden Markern die Bildartefakte reduziert. Für die intrafraktionelle Bewegungskontrolle wurde erwartet, dass ein Patienten-individuelles MR-kompatibles Korsett die atmungs-induzierte Pankreasbeweglichkeit reduziert, von Patienten mit Tumoren im Oberbauch gut vertragen wird und in die PT implementiert werden kann. Ein 4D MR-Linac Bewegungsphantom wurde für die Evaluierung der Geometrietreue und der Genauigkeit der Bewegungswiedergabe des genutzten diagnostischen 3.0 T MR Scanners verwendet. Es wurde erwartet, dass dieses Phantom für die Verwendung am diagnostischen MR Scanner implementiert werden kann und für die Qualitätssicherung von bewegungscharakterisierenden MR Pulssequenzen genutzt werden kann. Material und Methode: Die MR Eigenschaften von BioXmark® wurden in einer Phantomstudie durch MR Relaxometrie quantitativ analysiert und verglichen mit zwei Arten von soliden Marker. Des weiteren wurde die MR-Sichtbarkeit von BioXmark® das erste mal in ex vivo tumorösem Pankreasgewebe getestet für Markern dreier Größenkategorien (20/25 µL, 50/60 µL, 100 µL), injeziert mit jeweils drei verschiedenen Nadelgrößen (18 G, 22 G, 25 G). Ein 4D MR-Linac Bewegungsphantom wurde für den diagnostischen 3.0 T MR Scanner unserer Klinik kommissioniert und Programme für die automatische Evaluierung der 3D Geometrietreue und Genauigkeit der Bewegungscharakterisierung entwickelt. Drei Korsetts aus verschiedenen Materialien (PU, PE, 3DPE) wurden in Bezug auf die Verwendbarkeit in der PT untersucht. Des weiteren wurde der Effekt der Korsetts auf die Reduzierung der Pankreasbeweglichkeit bei einem gesunden Freiwilligen analysiert, mittels zeitaufgelöster 2D-cine MRT und respirationskorrelierter 4D-MRT in einem 1.5 T MR Scanner. Daraufhin wurde eine klinische Studie durchgeführt, die 13 Patienten mit Tumor im Oberbauch einschloss. Im Rahmen der Studie wurde der Effekt des verwendeten 3DPE Korsetts auf die Reduktion der Pankreasbeweglichkeit analysiert, mittels 2D-cine MRT und 4D-MRT in einem 3.0 T MR Scanner. Abschließend wurde die Patienten-Verträglichkeit bei Anwendung des Korsetts analysiert. Ergebnisse: Für BioXmark® wurde keine Korrelation zwischen der Intensität der Sichtbarkeit und Artefakte gefunden (RS = 0.0) und nur eine schwache Korrelation zwischen der Größe der Sichtbarkeit und Artefakte (RS = 0.4). Im Gegensatz dazu wurde für die soliden Marker eine lineare Abhängigkeit der Größe der Sichtbarkeit und Artefakte (RS = 0.99) und eine nicht-lineare Abhängigkeit zwischen der Intensität der Sichtbarkeit und Artefakte gefunden (RS = 0.964). Nach Injektion in drei ex vivo Pankreas-Resektionspräparate war BioXmark® als Hypointensität in sowohl T1- als auch T2- gewichteten MR Bildgebung sichtbar. Marker aller drei getesteten Größenkategorien waren in klinisch verwendeten MR Sequenzen detektierbar. Jedoch führte eine diffuse Gelierung oder Injektion zu nah am Geweberand zur Minderung der Detektierbarkeit. Dies hatte zur Folge hatte, dass 4 von in Summe 17 Markern in der MR-Bildgebung nicht erkennbar waren. Das MR-Linac Bewegungsphantom wurde erfolgreich am diagnostischen 3.0 T MR Scanner kommissioniert. Eine Fixierungs- und Positionierungshilfe wurde entwickelt und konstruiert, die eine sichere und reproduzierbare Positionierung des Aktuators und des Phantoms (< 0.4mm) ermöglichte. Ein Programm zur automatischen Verzerrungsanalyse wurde entwickelt, basierend auf einer Referenz-CT Aufnahme. Die Auswertung einer klinisch verwendeten 3D GRE Sequenz offenbarte eine maximale Verzerrung von 1.3mm in einem elliptischen Zylindervolumen von 15×23×6 cm³. Das Referenz-CT offenbarte zusätzlich einen Abweichung der eingestellten Targetbeweglichkeit in AP/LR Richtung. Kontrastreiche und geometrisch korrekte 2D-cine MR Bilder des sich bewegenden Phantom-Targets konnten aufgenommen werden. Ein Programm für ein automatisiertes Target-Tracking wurde entwickelt, welches eine hohe Genauigkeit der bewegungscharakterisierenden Sequenzen bestätigte (< 0.2mm in 2D-cine MRT, < 0.3mm in 4D-MRT). Eine vergleichbare Reduzierung der respirationsbedingten Pankreas-Bewegung von 46%–56% (7.7mm – 9.4 mm) wurde für die drei getesteten Korsetts gefunden. Die Materialanalyse führte jedoch zum Ausschluss des PU Korsetts für die Verwendung in der PT, aufgrund der gravierenden Heterogenität des Korsettmaterials. Das 3DPE Korsett wurde als für die PT implementierbar bewertet, wobei eine direkte Integration in der PT Planung mit der klinisch verwendeten Hounsfield-SPR Übersetzungstabelle möglich war. Das 3DPE Korsett wurde für 13 Patienten mit Tumor im Oberbauch in den PT Arbeitsablauf integriert, in welchem das Korsett von den Patienten gut toleriert wurde. Die MR-basierte Analyse der respirationsbedingten Pankreasbewegung in 9 Patienten mit und ohne Korsett ergab eine Reduzierung der Beweglichkeit um 37% (~3.3 mm). Schlussfolgerungen: BioXmark® und das entwickelte 3DPE Korsett wurden als verwendbar für die MR geführte PT bewertet. BioXmark® war in der MR-Bildgebung als Hypointensität sichtbar, unabhängig von der verwendeten MR Pulssequenz, solange die Markergröße die Voxelauflösung überschritt. Die MR-Sichtbarkeit von BioXmark® sollte jedoch in vivo getestet werden, da sich dort die Gelierung unterscheiden könnte und dementsprechend die Sichtbarkeit beeinflussen könnte. Das MR-Linac Bewegungsphantom kann in Zukunft für QA von bewegungscharakterisierenden Pulssequenzen des diagnostischen MR Scanners verwendet werden. Dies ist empfohlen, wann immer neue Pulssequenzen implementiert werden. Das entwickelte Korsett reduziert die respirationsbedingte Pankreas-Beweglichkeit in Patienten mit Tumor im Oberbauch um ~37% und kann in Zukunft für die MR geführte PT verwendet werden. Die Studie offenbarte jedoch auch, dass eine erhebliche Anzahl an Patienten nicht von der Verwendung eines Korsetts profitiert, aufgrund ihrer initial geringen Beweglichkeit bei freier Atmung (< 6 mm). Schlussfolgernd ist eine vorherige Einschätzung der Beweglichkeit jedes individuellen Patienten bei freier Atmung zu empfehlen, bevor eine Entscheidung über die Implementierung des Korsetts in der PT getroffen wird.

Les fluides Magnéto-Rhéologiques (MR) de par leurs caractéristiques variant avec le champ magnétique qui leur est appliqué, sont utilisés dans la dissipation d’énergie mécanique. Ainsi, il existe de nombreux dispositifs utilisant ces fluides, par exemple des amortisseurs ou des freins, permettant de contrôler aisément leurs performances. Cependant ces dissipateurs d’énergie mécanique sont amenés à opérer dans des milieux soumis à des perturbations externes notamment des vibrations. Dans le cadre de cette thèse, nous étudions la stabilité des propriétés des fluides magnéto-rhéologiques lorsqu’ils sont perturbés par une stimulation de type vibratoire.Une comparaison analytique de l’ordre de grandeur des efforts vibratoires relativement aux efforts de cohésion magnétique ayant lieu dans le fluide laisse apparaître une possible perturbation du fluide par des vibrations.Nous avons mis en place un banc de test permettant à la fois d’injecter des perturbations vibratoires et de mesurer leur impact sur le fluide utilisé dans un mode classique de cisaillement.Dans certaines conditions, nous avons pu mesurer une diminution de la contrainte de cisaillement du fluide. La variation observée est liée à l’amplitude du mode de déformation de l’élément cisaillant. Trois directions de propagation de vibration selon un repère cylindrique sont étudiées et leurs impacts discutés. La direction normale à la surface est celle qui présente le plus d’effet. La variation maximale de la contrainte de cisaillement observée peut atteindre 40 %. Ce phénomène intervient pour des champs magnétiques faibles, inférieurs à 250 mT, et pour une vitesse de cisaillement faible, inférieure à 100 s-1.Enfin l’effet des vibrations est étudié sur des fluides de différentes viscosités et concentrations de particules, afin d’évaluer l’impact de ces derniers sur la stabilité du fluide / When subjected to a magnetic field, the Magneto-Rheological (MR) fluid increases its apparent viscosity and becomes a viscoelastic solid. They are used in applications requiring dissipation of mechanical energy such as shock absorbers or brakes. These devices operate in environments subject to external disturbances. In this thesis, we study the stability of magneto-rheological fluid properties when they are subjected to vibrations.When comparing the magnitude of the applied forces generated by the vibrations to the magnetic force between the particules it appears that these forces are of the same order. This implies a modification of the fluid behaviour.We developed a dedicated test bench allowing to induce vibration disturbances and to measure their impact on the fluid used in a shear mode configuration.We observed experimentally a decrease in the shear stress of the fluid. This variation depends on the modal deformation of the shearing element. Three propagation directions of vibration according to a cylindrical coordinate are studied and compared. The normal direction to the surface is the one with the most significant effect. The maximum shear stress variation reached was 40%. This phenomenon occurs for low magnetic fields, less than 250 mT, and low shear rate, less than 100 s-1.Finally, the vibration effect is studied on fluids with different viscosities and particle concentrations in order to assess their impact on the fluid’s stability.