861 resultados para Orientation tensor
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Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Geospatial Technologies.
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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics
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A simulação dinâmica de reservatórios de petróleo requer a alocação de permeabilidades equivalentes para todos os blocos. A determinação da permeabilidade equivalente em reservatórios fraturados é uma questão complexa e crítica no fluxograma de modelação, porque é totalmente dependente da geometria 3D sistema de fraturas, e respetivas aberturas, que muitas vezes são mal conhecidos. Para avaliar a permeabilidade equivalente de blocos fraturados, o método do tensor ou de Oda é um dos mais utilizados. É expedito e eficiente mesmo para a sistemas com vários milhões de fraturas. Todavia, na literatura são apontadas algumas críticas, por exemplo, sobrestima a permeabilidade em blocos pouco fraturados e subestima-a em blocos muito fraturados. Este trabalho tem como objetivos, revisitar a problemática da caracterização da permeabilidade equivalente em blocos de reservatórios fraturados. Recorreu-se a um pacote de programas informáticos FROM3D-K (fractures object model – permeability evaluation) desenvolvidos e/ ou adaptados no contexto deste trabalho e que permitem as funcionalidades: (1) simulação estocástica 3D de fraturas; (2) determinação da permeabilidade equivalente pelo método do tensor; (3) determinação da permeabilidade equivalente pelo método de upscaling de microblocos. Estas funções permitem que a mesma rede de fraturas seja avaliada pelos dois métodos. Para a demonstração de resultados mostram-se dois exemplos, o primeiro onde são simuladas fraturas condicionadas a estatísticas sintéticas de orientação, intensidade e abertura e o segundo onde se utilizam dados FMI de poço de um reservatório fraturado.
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A Doença de Parkinson (PD) e o Tremor Essencial (ET) são duas doenças neurológicas, crónicas e progressivas. Mundialmente, estima-se que a PD afete cerca de 1% da populaçãom com mais de 65 anos e que o ET afete até 5% da população com mais de 40 anos. A PD é o principal diagnóstico diferencial do ET, sendo que o diagnóstico se baseia em critérios clínicos cuja sensibilidade e especificidade em fase precoce da doença pode ser baixa. Como tal, é necessário descobrir biomarcadores que auxiliem o diagnóstico destas doenças e a sua diferenciação. Com recurso à técnica de imagem de RM com tensores de difusão (DTI) e à análise com regiões de interesse, este estudo teve como principal objetivo avaliar se os valores de anisotropia fracional (FA) e de difusibilidade média (MD) medidos em 11 regiões neuroanatómicas, podem ser biomarcadores precoces da PD e do ET. Teve também como objetivos estudar a reprodutibilidade destas medições, a sua evolução no espaço de 1 ano e se nos doentes com diagnóstico inicial de PD esses valores eram influenciados pela medicação anti-parkinsónica. Como resultado deste estudo foram encontradas alterações nos valores de FA ao nível do pedúnculo cerebeloso médio e nos valores de MD ao nível do núcleo lenticular (NL), pedúnculo cerebeloso superior e núcleo dentado. Foi também verificado que na substantia nigra, núcleo caudado e NL, os valores de FA e MD são satisfatoriamente reprodutíveis, não se alteram com o início da medicação anti-parkinsónica e que de uma forma geral não variam significativamente no espaço de 1 ano. Estes resultados comprovam que os valores de FA e MD medidos nas referidas regiões neuroanatómicas podem constituir potenciais biomarcadores que auxiliem os clínicos no diagnóstico precoce e diferencial da PD e do ET, bem como na monitorização da progressão destas doenças.
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A imagem por tensor difusão (DTI) é uma extensão da imagem por ressonância magnética que permite a caraterização microestrutural dos tecidos, sendo um destes, os músculos esqueléticos. No entanto, dadas as grandes dimensões dos mesmos, a aquisição de volumes DTI deste tipo de tecidos é comumente realizada em mais que uma sessão. A não linearidade dos gradientes de codificação espacial e a presença de magnetizações parasitas levam a que ocorram distorções que impossibilitam, quando unidos, a continuação de volumes na sua transição. No mercado já existem sotwares que permitem estas correções, no entanto, o seu objetivo tem como fim estudos populacionais aplicados na neurologia, não estando preparados para o alinhamento e união de volumes contíguos. Ao recorrer a algoritmos aplicados nestes softwares, com a devida preparação, é possível garantir a continuidade de volumes. Um desses algoritmos, demons, foi aplicado em pontos de sobreposição de imagens de volumes contíguos. A transformada resultante deste algoritmo foi aplicado ao volume considerado a transformar e unido ao volume de referência. Mostra-se ser possível a aplicação destes algoritmos para a continuação de volumes, sendo observada a preservação da coerência anatómica das fibras quando comparadas aos grupos de controlo. Numa versão futura, recomenda-se a utilização de algoritmos mais robustos, que tomam partido da informação direcional que a imagem por tensor de difusão fornece.
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Adding fibres to concrete provides several advantages, especially in terms of controlling the crack opening width and propagation after the cracking onset. However, distribution and orientation of the fibres toward the active crack plane are significantly important in order to maximize its benefits. Therefore, in this study, the effect of the fibre distribution and orientation on the post-cracking tensile behaviour of the steel fibre reinforced self-compacting concrete (SFRSCC) specimens is investigated. For this purpose, several cores were extracted from distinct locations of a panel and were subjected to indirect (splitting) and direct tensile tests. The local stress-crack opening relationship (σ-w) was obtained by modelling the splitting tensile test under the finite element framework and by performing an Inverse Analysis (IA) procedure. Afterwards the σ-w law obtained from IA is then compared with the one ascertained directly from the uniaxial tensile tests. Finally, the fibre distribution/orientation parameters were determined adopting an image analysis technique.
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Conformally flat spacetimes with an elastic stress energy tensor having diagonal trace-free anisotropic pressure are investigated using 1+3 formalism. The 1+3 Bianchi and Jacobi identities and Einstein field equations are written for a particular case with a conformal factor dependent on only one spatial coordinate. Solutions with non null anisotropic pressure are obtained.
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Dissertação de mestrado em Psicologia Aplicada
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The Rufous Hornero (Furnarius rufus) is one of the most common bird species in Brazil. Anecdotal information indicates that nest opening orientation in this species is contrary to wind or rainfall direction. To check for the existence of such a pattern, F. rufus nests were randomly sampled within an urban area in central Brazil to assess whether factors such as wind and vegetation cover influence nest opening orientation. Using circular statistics, no evidence was found that nest-opening orientation was important for the species. These results refuse the expected pattern for tree hollow or enclosed nests. The results suggest that factors such as nesting architecture, nest material, nest microclimate or a combination of these, instead of local climate, must be conditioning nesting behavior in this species.
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Does shareholder value orientation lead to shareholder value creation? This article proposes methods to quantify both, shareholder value orientation and shareholder value creation. Through the application of these models it is possible to quantify both dimensions and examine statistically in how far shareholder value orientation explains shareholder value creation. The scoring model developed in this paper allows quantifying the orientation of managers towards the objective to maximize wealth of shareholders. The method evaluates information that comes from the companies and scores the value orientation in a scale from 0 to 10 points. Analytically the variable value orientation is operationalized expressing it as the general attitude of managers toward the objective of value creation, investment policy and behavior, flexibility and further eight value drivers. The value creation model works with market data such as stock prices and dividend payments. Both methods where applied to a sample of 38 blue chip companies: 32 firms belonged to the share index IBEX 35 on July 1st, 1999, one company represents the “new economy” listed in the Spanish New Market as per July 1st, 2001, and 5 European multinational groups formed part of the EuroStoxx 50 index also on July 1st, 2001. The research period comprised the financial years 1998, 1999, and 2000. A regression analysis showed that between 15.9% and 23.4% of shareholder value creation can be explained by shareholder value orientation.
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The process of light orientation by the snail Biomphalaria glabrata was studied using the selection technique in a Y-shaped aquarium under vertical or horizontal lighting schemes. Snail behavior was measured on the basis of distance (cm) covered per hour, direction of locomotion, and localization of the animal in the aquarium. A comparison was made of the action of the light stimulus on young and adult animals of albino populations from Santa Luzia (State of Minas Gerais, Brazil) and of a melanic population from Touros (State of Rio Grande do Norte) studied in groups and separately. All groups studied were attracted to light. Analysis of the data suggests the exitence of two orientation mechanisms with respect to light in these animals, i.e. high photo-orthokinesia and positive phototaxis, which influence their motion in the environment. This evidence permitted us to discuss features of the distribution dynamics of these mollusks in the environment and their relationship with the larval phases of Schistosoma mansoni, for which they act as intermediated hosts.
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The behavioral response of Biomphalaria straminea to light was evaluted in terms of location of the snail in a Y-shaped aquarium in a situation of selection and of the rate (cm/hour) and direction of locomotion under homogeneous 9vertical) or differential (horizontal) lighting upon only one arm of the aquarium. The light source consisted of daylight fluorescent lamps with a spectrum close to that of natural light, with illumination varying from 28 to 350 lux. Analysis of the data showed that all animals, whether in groups or isolated, were attracted to light, although the time needed to approach the light source was 50% shorter for the former than for the latter. The rate of locomotion of B. straminea was 35% higher than observed in B. glabrata and 51% higher than that observed in B. tenagophila studied under similar conditions. The results are discussed in terms of social factors and geographical distribution of the three species.
PHYTOCHROME KINASE SUBSTRATE4 modulates phytochrome-mediated control of hypocotyl growth orientation
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Gravity and light are major factors shaping plant growth. Light perceived by phytochromes leads to seedling deetiolation, which includes the deviation from vertical hypocotyl growth and promotes hypocotyl phototropism. These light responses enhance survival of young seedlings during their emergence from the soil. The PHYTOCHROME KINASE SUBSTRATE (PKS) family is composed of four members in Arabidopsis (Arabidopsis thaliana): PKS1 to PKS4. Here we show that PKS4 is a negative regulator of both phytochrome A- and B-mediated inhibition of hypocotyl growth and promotion of cotyledon unfolding. Most prominently, pks4 mutants show abnormal phytochrome-modulated hypocotyl growth orientation. In dark-grown seedlings hypocotyls change from the original orientation defined by seed position to the upright orientation defined by gravity and light reduces the magnitude of this shift. In older seedlings with the hypocotyls already oriented by gravity, light promotes the deviation from vertical orientation. Based on the characterization of pks4 mutants we propose that PKS4 inhibits changes in growth orientation under red or far-red light. Our data suggest that in these light conditions PKS4 acts as an inhibitor of asymmetric growth. This hypothesis is supported by the phenotype of PKS4 overexpressers. Together with previous findings, these results indicate that the PKS family plays important functions during light-regulated tropic growth responses
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This paper has three contributions. First, it shows how field work within small firms in PR Chinese has provided new evidence which enables us to measure and calibrate Entrepreneurial Orientation (EO), as ‘spirit’, and Intangible Assets (IA), as ‘material’, for use in models of small firm growth. Second, it uses inter-item correlation analysis and both exploratory and confirmatory factor analysis to provide new measures of EO and IA, in index and in vector form, for use in econometric models of firm growth. Third, it estimates two new econometric models of small firm employment growth in PR China, under the null hypothesis of Gibrat’s Law, using our two new index-based and vector-based measures of EO and IA. Estimation is by OLS with adjustment for heteroscedasticity, and for sample selectivity. Broadly, it finds that EO attributes have had little significant impact on small firm growth, and indeed innovativeness and pro-activity paradoxically may even dampen growth. However, IA attributes have had a positive and significant impact on growth, with networking, and technological knowledge being of prime importance, and intellectual property and human capital being of lesser but still significant importance. In the light of these results, Gibrat’s Law is generalized, and Jovanovic’s learning theory is extended, to emphasise the importance of IA to growth. These findings cast new empirical light on the oft-quoted national slogan in PR China of “spirit and material”. So far as small firms are concerned, this paper suggests that their contribution to PR China’s remarkable economic growth is not so much attributable to the ‘spirit’ of enterprise (as suggested by propaganda) as, more prosaically, to the pursuit of the ‘material’.