Made available in DSpace on 2014-10-09T12:46:31Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:22Z (GMT). No. of bitstreams: 1 07977.pdf: 2200288 bytes, checksum: 75fcd64975e2719bf0f41d38ec387c77 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

High intensity proton synchrotrons provide beams for several types of facility around the world, including spallation neutron sources and high energy physics experiments. The defining feature of these particle accelerators, that of intense beams, is tightly coupled to what limits the intensity, which is the controlled loss of beam particles. Many different factors contribute to beam loss. Beam will be lost on injection to a synchrotron and may be lost on extraction or in transfer lines. Non-linearities in the accelerator lattice can introduce driving terms for resonant beam behaviour. Collective effects between the beam particles and with the beam environment modify the single particle behaviour considerably. High intensity loss that occurs in the transverse plane, due to space charge and image fields, was investigated. The rapid cycling synchrotron at the ISIS Spallation Neutron Source in the UK was the focus for all of the work. The ISIS Synchrotron has many particular features which were described. One such feature is the conformal rectangular vacuum vessel, which takes the shape of the design beam envelope with certain modifications. This vacuum vessel has a complex effect on beam image fields. Numerical tools to study the space charge and image fields at ISIS were created and reported. The tools included two Poisson solvers to study space charge and images which were benchmarked against commercially available algorithms. A two dimensional particle-in-cell tracking code was created using the space charge solvers in combination with either a smooth focusing lattice model or one which generated Twiss matrices. A variety of diagnostic tools were available. A survey of existing analyses for pencil beams in parallel plate and rectangular geometry was made. Results from the analysis were then compared with two dimensional simulations with round uniform beams in rectangular geometry. Differences and extensions to the analysis were summarised. Coefficients for higher order image terms were defined and tabulated. The two dimensional nature of the image field was discussed and values for the coefficients for certain higher order terms identified in the plane orthogonal to the beam offset. Solutions for closed orbits produced with single and harmonic kicks at low and high intensity were discussed and simulated. A model was proposed which included the higher order image coefficients produced by the closed orbits. A single particle model was then explored which obtained resonance conditions from the closed orbits and image coefficients. The effect of self-consistent coherent motion on the results was discussed. Particle-in-cell beam tracking simulations were used to explore the results of this analysis numerically. Image resonances were found and described for a variety of simulation parameters starting with a smooth focusing lattice and uniform density beam, then progressing to more realistic cases including waterbag beams, alternating gradient lattices and conformal vacuum vessels. Image resonances described by the models were reported as were others that needed further explanation. Their possible impact for ISIS was discussed. New experiments with coasting beams at ISIS were carried out to explore the relationship between tune and beam loss at low intensity. Such experiments are a vital first step to understanding high intensity behaviour. It was shown that ISIS has existing lattice nonlinearities (some known, some unknown) which will need to be taken into account for high intensity experiments and simulations. Finally this work was put into context by examing specific transverse space charge effects for a proposed ISIS upgrade and including ideas developed throughout the thesis. Estimates were made of the strength of space charge effects and emittance scaling using conventional methods. The particle tracking tools developed for the thesis were then used to study beam behaviour with lattice gradient errors, the effects of closed orbits and changes to the working point. The transverse calculations and simulations suggested that the upgrade was feasible.

Background: Worry is theorised to function as a form of cognitive or experiential avoidance wherein an individual uses repetitive thinking in an attempt to avoid a future event or an aversive internal experience. There is evidence of a closer link between non-verbal thought (e.g. mental images) and emotion, physiology and behaviour than with verbal thought. Based on findings that worry is predominantly a verbal-linguistic activity, with less imagery occurring during worry episodes than during relaxation; it is theorised that worriers may move from non-verbal to verbal thought in order to avoid the greater arousal associated with non-verbal thought intrusions. This carries with it the unintended consequence of reducing emotional processing, leading to a subsequent increase in intrusive thoughts. Whilst cognitive science has emphasised the content of cognition and how this links to emotion, the psychological flexibility model suggests that content is less important than how we relate to our cognitive events. The degree to which we get entangled in our thinking, lack perspective on our thoughts and the degree to which cognition comes to regulate our behaviour over other sources is known as cognitive fusion. It is postulated that some individuals may be more prone to avoiding internal experiences due to the stance they take toward these experiences. In the long-term, worry should lead to a reduction in the experience of intrusive images and memories and an increase in intrusive thoughts; and this relationship should vary depending on an individual’s stance in relation to their internal experiences. The purpose of the current study is to explore the experience of intrusive memories, images and thoughts in an older adult sample, and the relationship of these experiences to level of worry, cognitive fusion and psychological inflexibility. Method: Sixty-two community dwelling older adults were involved in the study. Each completed questionnaire measures to assess level of trait worry, depression, cognitive fusion and psychological inflexibility, as well as an interview to determine whether diagnostic criteria were met for any mood or anxiety disorder and to complete an interview exploring the experience of intrusive memories, thoughts and images. Findings: Higher levels of trait worry were strongly associated with higher levels of cognitive fusion and psychological inflexibility. Intrusive memories, images and thoughts were all reported in low levels across the sample. Level of worry was positively associated with the severity but not the occurrence of intrusive memories and thoughts. Higher levels of psychological inflexibility were associated with less occurrence of intrusive memories and images; whereas higher levels of cognitive fusion were associated with the increased occurrence of intrusive images. Higher levels of worry, cognitive fusion and psychological inflexibility were all associated with increased severity of intrusive thoughts. The findings are discussed in relation to previous research and to the Avoidance Theory and Acceptance Model of GAD. Implications are considered for further research and clinical applications.

[pt] A tese pretende acompanhar como, em seu livro Homens em tempos sombrios, Hannah Arendt construiu uma narrativa para falar da aparição de determinadas pessoas a partir de quem elas foram e não do que eram. Com isso pretende elucidar o que seriam os tempos sombrios, além de mostrar o motivo de Hannah Arendt precisar formular seus textos aludindo a imagens. / [en] The study aims to follow Hannah Arendt s developping of a narrative that illuminates the disclosure of certain people taking into account who and not what they where. Through this it also intends to elucidate what would be the dark times and show why Hannah Arendt needed to build on images to make up her texts.

This thesis addresses the problem of cell loss when transmitting video data over an ATM network. Cell loss causes sections of an image to be lost or discarded in the interconnecting nodes between the transmitting and receiving locations. The method used to combat this problem is to use a technique called Error Concealment, where the lost sections of an image are replaced with approximations derived from the information in the surrounding areas to the error. This technique does not require any additional encoding, as used by Error Correction. Conventional techniques conceal from within the pixel domain, but require a large amount of processing (2N2 up to 20N2) where N is the dimension of an N×N square block. Also, previous work at Loughborough used Linear Interpolation in the transform domain, which required much less processing, to conceal the error.

Orientador: Edson Antonio Capello Sousa / Banca: José Eduardo Cogo Castanho / Banca: Cleudmar Amaral de Araujo / Resumo: Na biomecânica, a computação tem se tornado uma forte aliada no estudo utilizando-se imagens, pois avanços significativos têm sido verificados devido à evolução das técnicas de aquisição de imagens médicas. Em estruturas ósseas, devido à complexidade das formas geométricas, a obtenção de modelos precisos torna-se um processo difícil, exigindo métodos computacionais igualmente complexos. Por outro lado, a computação gráfica oferece técnicas que possibilitam a adequada manipulação destas imagnes. Entre os diversos métodos existentes, o modelo de contornos ativos, também conhecido como snakes, vem sendo amplamente difundido no processo dd segmentação para extração de estruturas de interesse no contexto médico. Este trabalho utiliza o método de contornos ativos por Fluxo do Vetor Gradiente (GVF) para obtenção das matrizes do contorno de estruturas com geometrias côncavas, neste representado por seções transversais obtidas da tomografia de uma mandíbula humana. Utilizando-se as matrizes obtidas, é gerado um modelo da mandíbula em 3D aplicando-se o método de triangulação foi utilizado o pacote MATLAB®, e para obtenção do modelo tridimensional, foi utilizado o pacote ANSYS®. / Abstract: In biomechanics, the computer has become a strong ally to study using the images, as significant advances have been recorded owing to technical progress of the acquisition of medical images. In bone structures due to the complexity of geometric shapes, to obtain accurate models becomes a difficult processes, requiring equally complex computational methods. On the other hand, offers computer graphics techniques that enable the appropriate handling of these images. Among the various existing methods, the model of active contours, also known as snakes, have been widely disseminated in hte process of segmentation to extract structures of interest medical. This work uses the method of active contours for Gradient Vector Flow (GVF) to obtain the matrices of the outline of structures with concave geometries, this represented by cross sections obtained from the tomography of a human jaw. Using the matrices obtained, it generated a 3D model of the jaw by applying the method of triangulation between adjacent contours. For the process of segmentation and triangulation was performed using MATLAB® application, and for obtaining three-dimensional model was performed using ANSYS® application. / Mestre

The interpretation of medical images is one of the most difficult tasks in computer vision, largely because of the high degree of variability associated with normal and abnormal appearances. This thesis introduces a systematic method for the detection of microcalcifications as one of the most important signs of early breast cancer. It involves a four step procedure. The first step is blob detection to detect regions of microcalcification size range. The second step involves a specially designed directional region growing method to find the best fitting boundaries for each blob region. A newly developed combination of classifiers is then applied to label each region as a microcalcification or background. The final processing step involves a search for the existence of clusters of microcalcifications using a hierarchical nearest mean clustering method. The contributions of the work to the field of image processing are; a new blob detection system; a novel region growing method and a theoretical framework for combining classifiers which use a combination of shared and distinct representations. Here specifically, we present a blob detection method with the capability of detecting any suspected blob of specific size range. Then a new region growing method is developed based on a unique directional growing process providing predictable behaviour for the method. The application of two discontinuity measures is considered for the extraction of two fitting boundaries representing information about the region and its local background. The information conveyed by the boundaries and their associated regions is used to compute reliable representations for labelling each blob region. The robustness of the region growing method to the choice of a starting point and to Gaussian noise is examined on real images. We demonstrate that commonly used classifiers provide reliable results in labelling the suspected regions. In spite of achieving an acceptable performance using different individual classifiers, a decision fusion rule involving a weighted combination of classifiers is developed and its performance on the problem is investigated. The combination rule is applicable when mixed mode representations (some shared and some individual features) are used. A comparative study of the individtial classifiers and also of conventional classifier combination techniques with the weighted combiner is performed on independent test sets. The results achieved with the presented algorithm are very promising and approaching a level where a clinical pilot evaluation for screening purposes would be warranted.

Este trabalho apresenta o memorial de composição, a partitura e a gravação do balé Mahavidyas para dois pianos, flauta, piccolo, timpani e orquestra de cordas. O balé é integrado por sete ciclos de peças livremente inspiradas em imagens das Mahavydias, deusas do hinduísmo. Cada um dos ciclos, agrupado em dois atos, contém três movimentos. O primeiro ato é composto pela abertura e pelos quatro primeiros ciclos; o segundo, por abertura, três ciclos e coda. O Memorial inclui breve descrição das referências estéticas que estimularam as atitudes composicionais, fundamentadas no pensamento de H. J. Koellreutter e Fernando Pessoa. O relato dos processos composicionais revela os critérios expressivos e estruturais para a escolha da instrumentação e a relação desta com materiais compostos e utilizados de forma espontânea e intuitiva. / The present study presents the score, the recording, and a compositional essay on Mahavidyas, a ballet for two pianos, flute, piccolo, timpani and string orchestra. The ballet consists of seven cycles freely inspired by images of Mahavydias, goddesses of Hinduism. Each cycle contains three movements, grouped into two acts. In the first act are presented an overture and the first four cycles, while the second act presents an overture, the remaining three cycles, and the coda. The Memorial includes a brief description of aesthetic references that have informed the composition, based on the ideas of H.J. Koellreutter and Fernando Pessoa. The description of the compositional process addresses the expressive and structural criteria for the choice of instrumentation and its relation to written materials, used spontaneously and intuitively.

This work describes a method based on three stages for reconstructing a model from a given set of scanned meshes obtained from 3D scanners. Meshes scanned from different scanner s view points have their representation in local coordinate systems. Therefore, for final model reconstruction, an alignment of the meshes is required. The most popular algorithm for cloud data registration is the ICP algorithm. However, ICP requires an initial estimate of mesh alignment, which is, many times, done manually. To automate this process, this work uses a surface representation called spin-images to identify overlap areas between the meshes and to estimate their alignment. After this initial registration, the alignment is refined by the ICP algorithm, and finally the model is reconstructed using a method called VRIP. / Fundação de Amparo a Pesquisa do Estado de Alagoas / Este trabalho descreve um método baseado em três etapas para reconstrução de modelos a partir de malhas capturadas de scanners 3D. Malhas obtidas a partir de diferentes pontos de visão de um scanner têm sua representação em sistemas de coordenadas local. Portanto, para a reconstrução final do modelo, é necessário realizar um alinhamento dessas malhas, ou registro. O algoritmo mais famoso para realizar registro de nuvens de pontos é o algoritmo ICP. Porém, um dos requisitos desse algoritmo é uma estimativa inicial do alinhamento das malhas, que muitas vezes é feita manualmente. Para automatizar esse processo, este trabalho utiliza descritores spin-image para identificar regiões de sobreposição entre as malhas e estimar seus alinhamentos. Após este registro inicial, o alinhamento é refinado através do algoritmo ICP, e finalmente o modelo é reconstruído usando uma técnica chamada VRIP.

Made available in DSpace on 2016-08-29T15:08:24Z (GMT). No. of bitstreams: 1 tese_5372_Imagem e imitação na Republica.pdf: 458238 bytes, checksum: 81ccd2881531646c674e3a31c21adbca (MD5) Previous issue date: 2012-02-24 / Pretendemos com nosso estudo propor uma aproximação entre a arte e o pensamento antigo a partir das considerações platônicas sobre a mímesis, presentes nos Livros II e III, do diálogo a República, mais especificamente, nas passagens sobre a parte inicial da educação dos guardiões. Abordaremos o princípio da proposta paidêutica platônica procurando assinalar o seu caráter estético, calcado na dimensão sensível da pólis. Analisaremos a importância atribuída aos mitos, enquanto imagens privilegiadas da formação, e o lugar da mímesis nesta etapa do processo, que visa em última instância o amor ao belo. / We pretend in our study to propose a link between art and the ancient thinking through Plato’s considerations about mimesis, which are described on the Books II and III of the Republic dialogue. We will approach the principle of the platonic paideutic proposal highlighting its esthetic features, based on the sensible dimension of the Polis. We will analyze the importance given to the myths, as privileged images of the formation, and the position of mimesis on this process, which aims ultimately the love to the beauty.