Made available in DSpace on 2016-03-15T19:37:51Z (GMT). No. of bitstreams: 1 Andre Brasiliano da Silva.pdf: 4815626 bytes, checksum: e53fa837ff6a7eb3cff0f55f4b3b26ac (MD5) Previous issue date: 2014-08-21 / Eye tracking is an important issue for Human Computer interaction, mainly for users with hand-eye coordination problems. The work presented here shows a low cost and robust eye tracking system capable to work with an HD stream. The implementations used in this work over the base system present diferent techniques in all stages, from face detection to iris detection. Local processing is used in most stages in this implementation, delimiting the region of interest (ROI) for face detection, eye detection and iris detection. The system robustness allow the eye tracking system to control the mouse using eye movements allowing disable users to communicate through a communication interface. The hardware required is simple and based in an high definition webcam. The face detection and eye detection processes are based on the Viola Jones technique; iris detection and tracking are based on the Hough Transform. The usage of local processing reduces the computational cost and even working with high definition stream leads to a performance 33% better than the base system. The system presented here was compared with a commercial system and a set of equipment were tested in order to dene the best set up for the eye tracking system and to validate the work presented here. Future work is presented at the end in order to allow the project continuity. / O rastreamento ocular para usuários com problemas motores é um estudo importante na área de Interface Humano-Computador (IHC). Com o objetivo de fornecer um sistema de rastreamento ocular de baixo custo, este trabalho apresenta uma nova abordagem para um sistema robusto e com alto desempenho. Com relação ao trabalho base para esta pesquisa, a implementação proposta contém inovações em todas as etapas do processo envolvendo o rastreamento ocular, desde a detecção da região da face e dos olhos até a detecção da íris. Neste trabalho, foi utilizado o conceito de processamento local, delimitando as regiões de interesse em todas as etapas do processo: detecção da região da face, região dos olhos e região da íris. Este trabalho permite que pessoas possam efetuar ações controlando o mouse através do movimento dos olhos em uma interface de rastreamento ocular, utilizando apenas equipamentos de uso comum, como, por exemplo, uma webcam. O processo de detecção da face e detecção ocular foi feito através da técnica de Viola e Jones. Para a detecção e rastreamento da íris foi utilizada a Transformada de Hough, e utilização de regiões de interesse com o objetivo de limitar a área de processamento da imagem, e consequentemente, o custo computacional, resultando em uma aplicação com um melhor desempenho e robustez em todas as etapas. Obteve-se um ganho de até 33% em relação ao tempo de processamento do sistema, quando comparado com o sistema base, porém, operando com imagens em alta definição. Foi realizada ainda uma comparação com sistemas de rastreamento ocular de uso comercial e diferentes tipos de equipamentos para validar as técnicas estudadas neste trabalho.

This study presents mathematical surrogate models, derived from finite element kinematic response data, to predict car crash-induced occupant head and neck injury risk for a broad range of impact velocities (10 – 45 mph), impact locations, and angles of impact (-45° to 45°). The development of these models allowed for wide-scale injury prediction while significantly reducing the overall required number of impact test cases. From these, increases in both the impact velocity and the impact’s locational proximity to the occupant were determined to result in the greatest head and neck injury risks. Additionally, strong interactions between the impact orientation variables (location and angle) produced significant changes in the head injury risk, while the neck injury risk was relatively insensitive to these interactions; likely due to the uniaxiality of the current standard neck injury risk metrics. Overall, this methodology showed potential for future applications in wide-scale injury prediction or vehicular design optimization.

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In Operations Enduring Freedom and Iraqi Freedom, explosions accounted for 81% of all injuries; this is a higher casualty percentage than in any previous wars. Blast wave overpressure has recently been associated with varying levels of traumatic brain injury in soldiers exposed to blast loading. Presently, the injury mechanism behind primary blast brain injury is not well understood due to the complex interactions between the blast wave and the human body. Despite these limitations in the understanding of head injury thresholds, head kinematics are often used to predict the overall potential for head injury. The purpose of this study was to investigate head kinematics, and predict injury from a range of simulated blast loads at varying standoff distances and differing heights of bursts. The validated Generator of body data multi-body human surrogate model allows for numerical kinematic data simulation in explicit finite element method fluid structure interaction blast modeling. Two finite element methods were investigated to simulate blast interaction with humans, an enhanced blast uncoupled method, and an Arbitrary Lagrangian Eularian fully coupled method. The enhanced blast method defines an air blast function through the application of a blast pressure wave, including ground reflections, based on the explosives relative location to a target; the pressures curves are based on the Convention Weapons databases. LBE model is efficient for parametric numerical studies of blast interaction where the target response is the only necessary result. The ALE model, unlike classical Lagrangian methods, has a fixed finite element mesh that allows material to flow through it; this enables simulation of large deformation problems such as blast in an air medium and its subsequent interaction with structures. The ALE model should be used when research into a specific blast scenario is of interest, since this method is more computationally expensive. The ALE method can evaluate a blast scenario in more detail including: explosive detonation, blast wave development and propagation, near-field fireball effects, blast wave reflection, as well as 3D blast wave interaction, reflection and refraction with a target. Both approaches were validated against experimental blast tests performed by Defense Research and Development Valcartier and ConWep databases for peak pressure, arrival time, impulse, and curve shape. The models were in good agreement with one another and follow the experimental data trend showing an exponential reduction in peak acceleration with increasing standoff distance until the Mach stem effect reached head height. The Mach stem phenomenon is a shock front formed by the merging of the incident and reflected shock waves; it increases the applied peak pressure and duration of a blast wave thus expanding the potential head injury zone surrounding a raised explosive. The enhanced blast model was in good agreement with experimental data in the near-field, and mid-field; however, overestimated the peak acceleration, and head injury criteria values in the far-field due to an over predicted pressure impulse force. The ALE model also over predicted the response based on the head injury criteria at an increased standoff distance due to smearing of the blast wave over several finite elements leading to an increased duration loading. According to the Abbreviated Injury Scale, the models predicted a maximal level 6 injury for all explosive sizes in the near-field, with a rapid acceleration of the head over approximately 1 ms. There is a drastic exponential reduction in the insult force and potential injury received with increasing standoff distance outside of the near-field region of an explosive charge.

Les viroles en acier microallié 18MND5, destinées aux générateurs de vapeur, présentent une composition hétérogène à plusieurs échelles. Un écart au procédé de fabrication ou une teneur en hydrogène excessive, peuvent conduire à la formation des Décohésions Dues à l’Hydrogène. Ces DDH résultent de la désorption de l’hydrogène interne lors du refroidissement jusqu’à température ambiante. La pression interne n’étant pas mesurables expérimentalement, une modélisation du phénomène est requise. Afin de préciser les mécanismes sous-jacents, il est proposé un scénario de formation de ces défauts s’appuyant conjointement sur une expertise et la modélisation des processus de diffusion-désorption-propagation. Les observations ont révélé une corrélation entre les DDH, les zones ségrégées et les amas de MnS (sites préférentiels d’initiation). Un modèle de diffusion dans un milieu hétérogène a été proposé afin d’évaluer la pression interne associée. La pression maximale excède ainsi 8600 bar en considérant une loi d’Abel-Noble optimisée du gaz réel. Le couplage de ce modèle avec la mécanique de la rupture a permis de quantifier l’évolution des paramètres relatifs à la propagation (pression interne, taille finale, vitesse, …). Un scénario de formation des DDH industriel a ainsi pu être formulé sur la base d’une étude paramétrique. Bien que les simulations préliminaires corroborent le retour d’expérience, le modèle raffiné et la prise en compte du gonflement de la DDH semblent sous-estimer la cinétique. Le caractère multi-fissuré des amas de MnS (homogénéisation des propriétés mécaniques) associé à un critère de rupture à l’échelle locale permettrait d’ajuster ce modèle. / Heat generators are manufactured from ingots of 18MND5 (A508cl3) low alloy steel and present composition heterogeneities at different scales. Under specific conditions (non-respect of guidelines or high initial content of H), Hydrogen Induced Cracks (HIC) may result from diffusion-desorption of internal hydrogen during cooling down to room temperature. Since neither hydrogen redistribution nor its internal pressure within cavities could be measured by experimental techniques, quantitative investigation is based on the modelling of related physical phenomena. A scenario of HIC formation, based on industrial feedback and modelling, has been proposed. A correlation between these defects, segregated areas and clusters of MnS (preferred initiation sites) has been revealed by expertise of HIC. A model of diffusion in heterogeneous alloys has then been proposed to assess the maximal pressure of H2 in such HIC. Simulation has shown that internal pressures above 860MPa are reached by considering an optimized Abel-Noble real gas behavior. The previous model has then been coupled to a failure mechanics procedure to characterize and quantify the crack growth parameters. Based on a parametric study, a scenario of HIC formation during the cooling has been proposed regarding process. Although results from preliminary simulations matched with feedback, the refined model based on the pressure induced elastic deformation of HIC has been developed but provided an underestimated kinetic of crack growth. Consequently, the multi-cracked nature of MnS clusters (homogenization of mechanical properties) and the updated local failure criterion appear to be a viable path to adjust predictions.

La haute densité d’énergie atteinte au Large Hadron Collider (LHC) au CERN permet une production abondante de sondes dures, telles que quarkonia, jets à haute impulsion transverse (p_T) et bosons vecteurs (W, Z), qui sont produits lors de la collision partonique initiale. Les bosons vecteur se désintègrent avant la formation du Plasma de Quark et de Gluons (PQG), une phase déconfinée de la matière, qui peut être produite lors de collisions d’ions lourds ultra-relativistes. Les leptons issus de la désintégration des bosons électrofaibles ne sont pas sensibles à l’interaction forte avec le PQG. Pour ces raisons les bosons électrofaibles fournissent une référence pour l’étude des modifications induites par le milieu sur les sondes colorées.La production de bosons W en collisions pp à √s=8 TeV et en collisions p-Pb à √s_NN=5.02 TeV est mesurée dans le canal de désintégration muonique au LHC avec le détecteur ALICE. En collision pp, la gamme de rapidité couverte par la mesure est -4<y_cms<-2.5. En collision p-Pb, la différence d’énergie entre le proton et l’ ion plomb donne lieu à un décalage en rapidité. En inversant la direction des faisceaux, il est possible de couvrir les régions de rapidité -4.46<y_cms<-2.96 et 2.03<y_cms<3.53. Les résultats présentés dans cette thèse consistent dans la mesure de la section efficace de la production de muons avec pT>10GeV/c issus de la désintégration des bosons W+ et W-. La mesure de l’asymétrie de charge, définie comme la différence des taux de production des muons positifs et négatifs divisée par leur somme, est également effectuée. Les résultats sont comparés avec des calculs théoriques obtenus avec ou sans tenir compte des modifications des fonctions de distribution partonique dans les noyaux. La production du boson W est aussi étudiée en fonction de la centralité des collisions : nous observons que, dans les erreurs expérimentales, la section efficace des muons issus de la désintégration du boson W est proportionnelle aux nombre de collisions binaires entre les nucléons. / The high collision energies available at the LHC allow for an abundant production of hard probes, such as quarkonia, high-p_T jets and vector bosons (W, Z), which are produced in initial hard parton scattering processes. The latter decay before the formation of the Quark-Gluon Plasma (QGP), which is a deconfined phase of QCD matter produced in high-energy heavy-ion collisions. Their leptonic decay products do not interact strongly with the QGP. Thus electroweak bosons introduce a way for benchmarking in-medium modifications to coloured probes. The production of W-boson in pp collisions at √s=8 TeV and p-Pb collisions at √s_NN=5.02 TeV are measured via the muonic decay channel at the LHC with the ALICE detector. In pp collisions the rapidity covered by the measurement is -4<y_cms<-2.5. In p-Pb collisions, on the other hand, the different energies of the proton and lead ion give rise to a rapidity shift. By exchanging the direction of the beams, it is possible to cover the rapidity ranges -4.46<y_cms<-2.96 and 2.03<y_cms<3.53. The production cross section and charge asymmetry of muons from W-boson decays with p^μT>10 GeV/c are determined. The results are compared to theoretical calculations both with and without including the nPDFs. The W-boson production is also studied as a function of the collision centrality: the cross section of muons from W-boson decays is found to scale with the average number of binary nucleon-nucleon collisions with uncertainties.