901 resultados para residual variance classes


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Many marine organisms have pelagic larval stages that settle into benthic habitats occupied by older individuals; however, a mechanistic understanding of inter cohort interactions remains elusive for most species. Patterns of spatial covariation in the densities of juvenile and adult age classes of a small temperate reef fish, the common triplefin (Forsterygion lapillum), were evaluated during the recruitment season (Feb–Mar, 2011) in Wellington, New Zealand (41°17′S, 174°46′E). The relationship between juvenile and adult density among sites was best approximated by a dome-shaped curve, with a negative correlation between densities of juveniles and adults at higher adult densities. The curve shape was temporally variable, but was unaffected by settlement habitat type (algal species). A laboratory experiment using a “multiple-predator effects”design tested the hypothesis that increased settler mortality in the presence of adults (via enhanced predation risk or cannibalism) contributed to the observed negative relationship between juveniles and adults. Settler mortality did not differ between controls and treatments that contained either one (p = 0.08) or two (p = 0.09) adults. However, post hoca analyses revealed a significant positive correlation between the mean length of juveniles used in experimental trials and survival of juveniles in these treatments, suggesting that smaller juveniles may be vulnerable to cannibalism. There was no evidence for risk enhancement or predator interference when adults were present alongside a hetero specific predator (F. varium). These results highlight the complex nature of intercohort relationships in shaping recruitment patterns and add to the growing body of literature recognizing the importance of age class interactions.

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The development of the latest generation of wide-body carbon-fibre composite passenger aircraft has heralded a new era in the utilisation of these materials. The premise of superior specific strength and stiffness, corrosion and fatigue resistance, is tempered by high development costs, slow production rates and lengthy and expensive certification programmes. Substantial effort is currently being directed towards the development of new modelling and simulation tools, at all levels of the development cycle, to mitigate these shortcomings. One of the primary challenges is to reduce the extent of physical testing, in the certification process, by adopting a ‘certification by simulation’ approach. In essence, this aspirational objective requires the ability to reliably predict the evolution and progression of damage in composites. The aerospace industry has been at the forefront of developing advanced composites modelling tools. As the automotive industry transitions towards the increased use of composites in mass-produced vehicles, similar challenges in the modelling of composites will need to be addressed, particularly in the reliable prediction of crashworthiness. While thermoset composites have dominated the aerospace industry, thermoplastics composites are likely to emerge as the preferred solution for meeting the high-volume production demands of passenger road vehicles. This keynote presentation will outline recent progress and current challenges in the development of finite-element-based predictive modelling tools for capturing impact damage, residual strength and energy absorption capacity of thermoset and thermoplastic composites for crashworthiness assessments.

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In this thesis, we study the existence and multiplicity of solutions of the following class of Schr odinger-Poisson systems: u + u + l(x) u = (x; u) in R3; = l(x)u2 in R3; where l 2 L2(R3) or l 2 L1(R3). And we consider that the nonlinearity satis es the following three kinds of cases: (i) a subcritical exponent with (x; u) = k(x)jujp 2u + h(x)u (4 p < 2 ) under an inde nite case; (ii) a general inde nite nonlinearity with (x; u) = k(x)g(u) + h(x)u; (iii) a critical growth exponent with (x; u) = k(x)juj2 2u + h(x)jujq 2u (2 q < 2 ). It is worth mentioning that the thesis contains three main innovations except overcoming several di culties, which are generated by the systems themselves. First, as an unknown referee said in his report, we are the rst authors concerning the existence of multiple positive solutions for Schr odinger- Poisson systems with an inde nite nonlinearity. Second, we nd an interesting phenomenon in Chapter 2 and Chapter 3 that we do not need the condition R R3 k(x)ep 1dx < 0 with an inde nite noncoercive case, where e1 is the rst eigenfunction of +id in H1(R3) with weight function h. A similar condition has been shown to be a su cient and necessary condition to the existence of positive solutions for semilinear elliptic equations with inde nite nonlinearity for a bounded domain (see e.g. Alama-Tarantello, Calc. Var. PDE 1 (1993), 439{475), or to be a su cient condition to the existence of positive solutions for semilinear elliptic equations with inde nite nonlinearity in RN (see e.g. Costa-Tehrani, Calc. Var. PDE 13 (2001), 159{189). Moreover, the process used in this case can be applied to study other aspects of the Schr odinger-Poisson systems and it gives a way to study the Kirchho system and quasilinear Schr odinger system. Finally, to get sign changing solutions in Chapter 5, we follow the spirit of Hirano-Shioji, Proc. Roy. Soc. Edinburgh Sect. A 137 (2007), 333, but the procedure is simpler than that they have proposed in their paper.

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The main objective of this work was to monitor a set of physical-chemical properties of heavy oil procedural streams through nuclear magnetic resonance spectroscopy, in order to propose an analysis procedure and online data processing for process control. Different statistical methods which allow to relate the results obtained by nuclear magnetic resonance spectroscopy with the results obtained by the conventional standard methods during the characterization of the different streams, have been implemented in order to develop models for predicting these same properties. The real-time knowledge of these physical-chemical properties of petroleum fractions is very important for enhancing refinery operations, ensuring technically, economically and environmentally proper refinery operations. The first part of this work involved the determination of many physical-chemical properties, at Matosinhos refinery, by following some standard methods important to evaluate and characterize light vacuum gas oil, heavy vacuum gas oil and fuel oil fractions. Kinematic viscosity, density, sulfur content, flash point, carbon residue, P-value and atmospheric and vacuum distillations were the properties analysed. Besides the analysis by using the standard methods, the same samples were analysed by nuclear magnetic resonance spectroscopy. The second part of this work was related to the application of multivariate statistical methods, which correlate the physical-chemical properties with the quantitative information acquired by nuclear magnetic resonance spectroscopy. Several methods were applied, including principal component analysis, principal component regression, partial least squares and artificial neural networks. Principal component analysis was used to reduce the number of predictive variables and to transform them into new variables, the principal components. These principal components were used as inputs of the principal component regression and artificial neural networks models. For the partial least squares model, the original data was used as input. Taking into account the performance of the develop models, by analysing selected statistical performance indexes, it was possible to conclude that principal component regression lead to worse performances. When applying the partial least squares and artificial neural networks models better results were achieved. However, it was with the artificial neural networks model that better predictions were obtained for almost of the properties analysed. With reference to the results obtained, it was possible to conclude that nuclear magnetic resonance spectroscopy combined with multivariate statistical methods can be used to predict physical-chemical properties of petroleum fractions. It has been shown that this technique can be considered a potential alternative to the conventional standard methods having obtained very promising results.

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Tese dout., Matemática, Universidade do Algarve, 2007,

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Dissertação de mest., Energias Renováveis e Gestão de Energia, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 2011

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Cette étude qualitative a pour objectif de comprendre comment les interventions verbales des apprenantes et apprenants contribuent à la résolution effective des tâches linguistiques orales dans une classe d'anglais langue seconde selon la théorie Vygotskienne. La recherche a montré que les apprenantes et apprenants passent un temps considérable à discuter les énoncés ainsi que de la meilleure façon de résoudre les tâches linguistiques orales. Or, la recension des écrits a révélé que peu d'études ont tenté de comprendre ce que font les apprenantes et apprenants quand ils sont appelés à résoudre des tâches orales. Dans notre étude nous avons donc essayé de jeter la lumière sur ce phénomène. Les interactions verbales de 10 apprenantes et apprenants ont été enregistrées pendant la résolution de tâches linguistiques orales dans une classe d'anglais langue seconde de l'université de Sherbrooke. Pour analyser les données, nous avons utilisé des éléments de trois méthodes d'analyse, notamment la méthode microgénétique de Vygotsky, l'analyse interactionnelle et l'analyse des conversations. Les résultats ont révélé que les apprenantes et apprenants utilisent un nombre important de stratégies afin de mieux comprendre et résoudre les tâches linguistiques orales de façon efficace. Ils recourent notamment à leur langue maternelle, la répétition et la co-construction de phrases. La discussion de ces résultats a montré que la meilleure compréhension des stratégies utilisées par les apprenantes et apprenants ainsi que comment celle-ci [i.e. celles-ci] sont utilisées pourrait contribuer positivement à l'amélioration des techniques d'enseignement par tâches des langues secondes.

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Le gouvernement québécois souhaite intégrer ses immigrants afin d'en faire une tranche active de la population. Cette intégration passe à la fois par l'apprentissage de la langue et par la connaissance et l'appartenance à notre culture. Les classes de français langue seconde, où transitent chaque année un bon nombre d'immigrants, sont un vecteur de choix pour la transmission des valeurs québécoises et des éléments qui fondent la culture du Québec. Or, pour permettre aux enseignants de transmettre des éléments culturels en classe, il faut un consensus, relayé sous forme de programme pédagogique ou de guides d'enseignement. Au milieu des années 1990, le ministère de l'Immigration et des Communautés culturelles du Québec a justement élaboré une vaste collection, Québec Atout, qui vise à la fois l'apprentissage du français et l'apprentissage de diverses composantes culturelles. Quinze ans plus tard, cette collection est délaissée par les intervenants en francisation, faute de mises à jour de son contenu et de son approche pédagogique. La pertinence de ce matériel n'est pas à remettre en cause. Pour actualiser Québec Atout, il faudrait cependant revoir certaines dimensions, dont les valeurs et les codes communicationnels et y intégrer une approche actionnelle. Il faudrait surtout tirer profit des technologies émergentes, qui se doivent d'être intégrées en salle de classe et qui peuvent, lorsqu'elles sont bien utilisées, devenir un puissant véhicule d'intégration.

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It is now well established that some patients who are diagnosed as being in a vegetative state or a minimally conscious state show reliable signs of volition that may only be detected by measuring neural responses. A pertinent question is whether these patients are also capable of logical thought. Here, we validate an fMRI paradigm that can detect the neural fingerprint of reasoning processes and moreover, can confirm whether a participant derives logical answers. We demonstrate the efficacy of this approach in a physically non-communicative patient who had been shown to engage in mental imagery in response to simple audi- tory instructions. Our results demonstrate that this individual retains a remarkable capacity for higher cogni- tion, engaging in the reasoning task and deducing logical answers. We suggest that this approach is suitable for detecting residual reasoning ability using neural responses and could readily be adapted to assess other aspects of cognition.

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Os solos residuais mostram divergências em relação aos solos transportados modelados pelas teorias da Mecânica dos Solos. Estas divergências são em grande parte devido a uma estrutura de cimentação herdada da rocha mãe. Este estudo foi baseado nos resultados obtidos em sondagens mecânicas e ensaios de penetração dinâmica, estática e laboratoriais e consistiu na avaliação e correlação dos parâmetros que determinam o comportamento geomecânico do terreno, como a resistência e a deformabilidade.

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This paper proposes a dynamic scheduler that supports the coexistence of guaranteed and non-guaranteed bandwidth servers to efficiently handle soft-tasks’ overloads by making additional capacity available from two sources: (i) residual capacity allocated but unused when jobs complete in less than their budgeted execution time; (ii) stealing capacity from inactive non-isolated servers used to schedule best-effort jobs. The effectiveness of the proposed approach in reducing the mean tardiness of periodic jobs is demonstrated through extensive simulations. The achieved results become even more significant when tasks’ computation times have a large variance.