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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
171

Vetenskaplig grund och forskning : En enkätstudie om vetenskaplig grund i förskolan

Berglund, Sara January 2015 (has links)
Purpose and questions: The Swedish School Law states that education in preschools and schools shall rest on a scientific base. The aim of this study is to examine to what extent and in what ways that preschool teachers are acquiring and getting information about research. It also aims to investigate the possibilities and the problems that may arise due to the requirement that education in preschools should have a scientific base. In what extent does preschool teachers believe that scientific basis and new research has significance for their work? How does preschool teachers get information about research and in what extent? What are the opportunities and problems that preschool teacher faces when it comes to new research? Theory: The theory that are used is Illeris learning theory. Also the postmodern view of the world, with its perspective on knowledge and the reflexive term is used. Method: The research is done with a quantitative method, web survey. The analysis is done with more of a mix between quantitative and qualitative analysis method. The response rate is 30,5 % for the survey, which is 25 preschool teachers. Conclusion: The preschool teachers in this study states that they comes in contact with research mainly by seeking it out themselves. They overall states that it's interesting to read these texts and they understand them. Furthermore the majority of the teachers states that research has relevance to their professional practice and that the research they have read has changed their preschool. The majority of the teachers also states that it's important that the preschool education is resting on a scientific base. Generally the preschool teachers in this study have the skills and motivation they need to read, get information and knowledge through research and to use the acquired knowledge in their preschools. The biggest problem for them to use more research is lack of time.
172

Empirical Bayesian Smoothing Splines for Signals with Correlated Errors: Methods and Applications

Rosales Marticorena, Luis Francisco 22 June 2016 (has links)
No description available.
173

Recognising three-dimensional objects using parameterized volumetric models

Borges, Dibio Leandro January 1996 (has links)
This thesis addressed the problem of recognizing 3-D objects, using shape information extracted from range images, and parameterized volumetric models. The domains of the geometric shapes explored is that of complex curved objects with articulated parts, and a great deal of similarity between some of the parts. These objects are exemplified by animal shapes, however the general characteristics and complexity of these shapes are present in a wide range of other natural and man-made objects. In model-based object recognition three main issues constrain the design of a complete solution: representation, feature extraction, and interpretation. this thesis develops an integrated approach that addresses these three issues in the context of the above mentioned domain of objects. For representation I propose a composite description using globally deformable superquadratics and a set of volumetric primitives called geons: this description is shown to have representational and discriminative properties suitable for recognition. Feature extraction comprises a segmentation process which develops a method to extract a parts-based description of the objects as assemblies of defoemable superquadratics. Discontinuity points detected from the images are linked using 'active contour' minimization technique, and deformable superquadratic models are fitted to the resulting regions afterwards. Interpretation is split into three components: classification of parts, matching, and pose estimation. A Radical Basis Function [RBF] classifier algoritm is presented in order to classify the superquadratics shapes derived from the segmentation into one of twelve geon classes. The matching component is decomposed into two stages: first, an indexing scheme which makes effective use of the output of the [RBF] classifier in order to direct the search to the models which contain the parts identified. this makes the search more efficient, and with a model library that is organised in a meaningful and robust way, permits growth without compromising performance. Second, a method is proposed where the hypotheses picked from the index are searched using an Interpretation Tree algorithm combined with a quality measure to evaluate the bindings and the final valid hypotheses based on Possibility Theory, or Theory of Fuzzy Sets. The valid hypotheses ranked by the matching process are then passed to the pose estimation module. This module uses a Kalman Filter technique that includes the constraints on the articulations as perfect measurements, and as such provides a robust and generic way to estimate pose in object domains such as the one approached here. These techniques are then combined to produce an integrated approach to the object recognition task. The thesis develops such an integrated approach, and evaluates its perfomance inthe sample domain. Future extensions of each technique and the overall integration strategy are discussed.
174

Contributions mathématiques aux calculs de structures électroniques / Mathematical contributions to the calculations of electronic structures

Gontier, David 28 September 2015 (has links)
Cette thèse comprend trois sujets différents, tous en rapport à des problèmes de structures électroniques. Ces trois sujets sont présentés dans trois parties indépendantes.Cette thèse commence par une introduction générale présentant les problématiques et les principaux résultats.La première partie traite de la théorie de la fonctionnelle de la densité lorsqu'elle est appliquée aux modèles d'électrons avec spins polarisés. Cette partie est divisée en deux chapitres. Dans le premier de ces chapitres, nous introduisons la notion de N-représentabilité, et nous caractérisons les ensembles de matrices de densité de spin représentables. Dans le second chapitre, nous montrons comment traiter mathématiquement le terme de Zeeman qui apparaît dans les modèles comprenant une polarisation de spin. Le résultat d'existence qui est démontré dans (Anantharaman, Cancès 2009) pour des systèmes de Kohn-Sham sans polarisation de spin est étendu au cas des systèmes avec polarisation de spin.Dans la seconde partie, nous étudions l'approximation GW. Dans un premier temps, nous donnons une définition mathématique de la fonction de Green à un corps, et nous expliquons comment les énergies d'excitation des molécules peuvent être obtenues à partir de cette fonction de Green. La fonction de Green peut être numériquement approchée par la résolution des équations GW. Nous discutons du caractère bien posé de ces équations, et nous démontrons que les équations GW0 sont bien posées dans un régime perturbatif. Ce travail a été effectué en collaboration avec Eric Cancès et Gabriel Stoltz.Dans le troisième et dernière partie, nous analysons des méthodes numériques pour calculer les diagrammes de bandes de structures cristallines. Cette partie est divisée en deux chapitres. Dans le premier, nous nous intéressons à l'approximation de Hartree-Fock réduite (voir (Cances, Deleurence, Lewin 2008)). Nous prouvons que si le cristal est un insolant ou un semi-conducteur, alors les calculs réalisés dans des supercellules convergent exponentiellement vite vers la solution exacte lorsque la taille de la supercellule tend vers l'infini. Ce travail a été réalisé en collaboration avec Salma Lahbabi. Dans le dernier chapitre, nous présentons une nouvelle méthode numérique pour le calcul des diagrammes de bandes de cristaux (qui peuvent être aussi bien isolants que conducteurs). Cette méthode utilise la technique des bases réduites, et accélère les méthodes traditionnelles. Ce travail a été fait en collaboration avec Eric Cancès, Virginie Ehrlacher et Damiano Lombardi / This thesis contains three different topics, all related to electronic structure problems. These three topics are presented in three independent parts.This thesis begins with a general introduction presenting the problematics and main results.The first part is concerned with Density Functional Theory (DFT), for spin-polarized models. This part is divided in two chapters. In the first of these chapters, the notion of N-representability is introduced and the characterizations of the N-representable sets of spin-density 2X2 matrices are given. In the second chapter, we show how to mathematically treat the Zeeman term in spin-polarized DFT models. The existence of minimizers that was proved in (Anantharaman, Cancès 2009) for spin-unpolarized Kohn-Sham models within the local density approximation is extended to spin-polarized models.The second part of this thesis focuses on the GW approximation. We first give a mathematical definition of the one-body Green's function, and explain why methods based on Green's functions can be used to calculate electronic-excited energies of molecules. One way to compute an approximation of the Green's function is through the self-consistent GW equations. The well-posedness of these equations is discussed, and proved in the GW0 case in a perturbative regime. This is joint work with Eric Cancès and Gabriel Stoltz.In the third and final part, numerical methods to compute band-diagrams of crystalline structure are analyzed. This part is divided in two chapters.In the first one, we consider a perfect crystal in the reduced Hartree-Fock approximation (see (Cances, Deleurence, Lewin 2008)). We prove that, if the crystal is an insulator or a semi-conductor, then supercell calculations converge to the exact solution with an exponential rate of convergence with respect to the size of the supercell. This is joint work with Salma Lahbabi. In the last chapter, we provide a new numerical method to calculate the band diagram of a crystal (which can be either an insulator or a conductor). This method, based on reduced basis techniques, speeds up traditional calculations. This is joint work with Eric Cancès, Virginie Ehrlacher, and Damiano Lombardi
175

Bayesian numerical analysis : global optimization and other applications

Fowkes, Jaroslav Mrazek January 2011 (has links)
We present a unifying framework for the global optimization of functions which are expensive to evaluate. The framework is based on a Bayesian interpretation of radial basis function interpolation which incorporates existing methods such as Kriging, Gaussian process regression and neural networks. This viewpoint enables the application of Bayesian decision theory to derive a sequential global optimization algorithm which can be extended to include existing algorithms of this type in the literature. By posing the optimization problem as a sequence of sampling decisions, we optimize a general cost function at each stage of the algorithm. An extension to multi-stage decision processes is also discussed. The key idea of the framework is to replace the underlying expensive function by a cheap surrogate approximation. This enables the use of existing branch and bound techniques to globally optimize the cost function. We present a rigorous analysis of the canonical branch and bound algorithm in this setting as well as newly developed algorithms for other domains including convex sets. In particular, by making use of Lipschitz continuity of the surrogate approximation, we develop an entirely new algorithm based on overlapping balls. An application of the framework to the integration of expensive functions over rectangular domains and spherical surfaces in low dimensions is also considered. To assess performance of the framework, we apply it to canonical examples from the literature as well as an industrial model problem from oil reservoir simulation.
176

Seeking the "C" in the "Y" : discerning the meaning of the Christian basis in the English YMCA

Sargent, David Ian January 2013 (has links)
This research has identified meanings attached by participants to the YMCA’s Christian basis within the context of volatile environments by engaging with voices in a qualitative, inductive, small-scale research project within the English YMCA. My proposition was that people working in the YMCA were appointed on the understanding that it was Christian-based, that the corporate and collective agreed means of association were located primarily in the Christian basis and that the YMCA attached significant meaning to its Christian basis whilst operating within an inclusive environment. Thematic descriptions of voices in communication were identified using a mixed set of research methods. The data were analysed in a between-method triangulation to produce adialectic towards meaning. Methods included: a literature review, interviews in a pilot study, a comparative historical review, facilitated groups, field visits and website surveys. I engaged various literary sources for interpretative perspectives on voices to differentiate participant’s relationships with the Christian basis in terms of audibility, affinity and attitude. The majority of participants felt that they had been appointed on the understanding that the YMCA is Christian-based, but very few had actually been given an opportunity, or felt it necessary, to make sense of it in their work. The Christian basis did not command a universally accepted meaning amongst participants. Instead, it was often perceived to have limited meaning, but with a degree of historical status attached to it. For the majority of participants, the actual corporate and collective agreed means of motivation was defined as care for young people within an inclusive environment and without any overt reference to the Christian basis and its meaning. However, where the Christian basis did feature locally it elicited communication that was complex, layered and variable in its nature. In these circumstances it produced powerful models of inclusive Christian service. The research identified three implications for further consideration: (a) ineffective communication between member YMCAs resulting in; (b) the creation of disjointed and remote islands of understanding about the Christian basis; and (c) in turn generating informal disassociations as a key factor in diminishing the value of the Christian basis within local member YMCAs.
177

Fundamental Issues in Support Vector Machines

McWhorter, Samuel P. 05 1900 (has links)
This dissertation considers certain issues in support vector machines (SVMs), including a description of their construction, aspects of certain exponential kernels used in some SVMs, and a presentation of an algorithm that computes the necessary elements of their operation with proof of convergence. In its first section, this dissertation provides a reasonably complete description of SVMs and their theoretical basis, along with a few motivating examples and counterexamples. This section may be used as an accessible, stand-alone introduction to the subject of SVMs for the advanced undergraduate. Its second section provides a proof of the positive-definiteness of a certain useful function here called E and dened as follows: Let V be a complex inner product space. Let N be a function that maps a vector from V to its norm. Let p be a real number between 0 and 2 inclusive and for any in V , let ( be N() raised to the p-th power. Finally, let a be a positive real number. Then E() is exp(()). Although the result is not new (other proofs are known but involve deep properties of stochastic processes) this proof is accessible to advanced undergraduates with a decent grasp of linear algebra. Its final section presents an algorithm by Dr. Kallman (preprint), based on earlier Russian work by B.F. Mitchell, V.F Demyanov, and V.N. Malozemov, and proves its convergence. The section also discusses briefly architectural features of the algorithm expected to result in practical speed increases.
178

Corn storage and marketing feasibility in northern Mississippi

Milstead, Andrew January 1900 (has links)
Master of Agribusiness / Department of Agricultural Economics / Daniel M. O'Brien / On-farm grain storage plays a key role in the production and distribution of corn in the United States. It can have economic impacts on a farm’s profitability and production efficiency over time. With the free market system of the United States, market fundamentals are a key component of decisions made on the farm regarding construction of grain storage facilities and how they are used in marketing decisions throughout a given production and marketing year. This analysis researches how grain storage decisions in the Northern Mississippi area are effected by corn basis differentials between the Memphis, TN river market and the Northern Alabama corn market. Corn basis differentials are considered along with annual changes in corn futures market carry in response to variations in grain market fundamentals. The profitability of constructing, maintaining, and operating on-farm grain storage is analyzed based on the local history of the local corn market basis patterns and the carry priced into the corn futures market. Through this analysis it was found that the biggest obstacle affecting the profitability of on-farm grain storage was the upfront cost of the facility. As costs of the facility were incurred, grain had to be stored for longer periods of time in order to be profitable based on history of improved basis and market carry over time. On-farm storage became profitable over a shorter storage period once the upfront costs of grain storage and handling facilities were paid based on the operating costs and market conditions within the analysis. On-farm storage can be a useful tool for a farm to increase profitability over time, beyond the scope of this analysis. This analysis proves that in the Northern Mississippi area over time, grain storage can be profitable based on improved cash basis and futures market carry. However, due to ever-changing market conditions, on-farm grain storage does not replace the need for the development of grain marketing plans in order to increase the likelihood of profitability.
179

Moduly s minimální množinou generátorů / Moduly s minimální množinou generátorů

Hrbek, Michal January 2013 (has links)
Title: Modules with a minimal generating set Author: Michal Hrbek Department: Department of Algebra Supervisor: Mgr. Pavel Růžička, Ph.D., Department of Algebra Abstract: By a minimal generating set of a module we mean a subset which generates the module but any of its proper subsets does not. If the module is not finitely generated, an existence of a minimal generating set is not guaranteed. We say that a module is weakly based if it has a minimal generating set. In the presented thesis, we provide a characterization of weakly based modules over Dedekind domains. As an application of this, we show that the class of weakly based modules is not closed under extensions and the complement of this class is not closed under finite direct sums. Also, we show an example of an abelian group which is weakly based if and only if CH holds. Then we treat rings such that all modules are weakly based. We prove that a Baer regular ring has this property if and only if it is semisimple, and we show that any ℵ0-noetherian commutative semiartinian ring has this property. Final part of the text concerns the problem of Nashier and Nichols - does any generating set of any module over a perfect ring contain a minimal generating set? Keywords: module, minimal generating set, weak basis 1
180

Modes de représentation pour l'éclairage en synthèse d'images

Pacanowski, Romain 25 September 2009 (has links)
En synthèse d'images, le principal calcul à effectuer pour générer une image a été formalisé dans une équation appelée équation du rendu [Kajiya1986]. Cette équation est la intègre la conservation de l'énergie dans le transport de la lumière. Elle stipule que l'énergie lumineuse renvoyée, par les objets d'une scène, dans une direction donnée est égale à la somme de l'énergie émise et réfléchie par ceux-ci. De plus, l'énergie réfléchie par un élément de surface est définie comme la convolution de l'éclairement incident avec une fonction de réflectance. Cette dernière modélise le matériau (au sens physique) de l'objet et joue le rôle d'un filtre directionnel et énergétique dans l'équation du rendu, simulant ainsi la manière dont la surface se comporte vis-à-vis d'une réflexion. Dans ce mémoire de thèse, nous introduisons de nouvelles représentations pour la fonction de réflectance ainsi que pour la représentation de l'éclairement incident. Dans la première partie de ce mémoire, nous proposons deux nouveaux modèles pour représenter la fonction de réflectance. Le premier modèle s'inscrit dans une démarche artistique et est destiné à faciliter la création et l'édition des reflets spéculaires. Son principe est de laisser l'utilisateur peindre et esquisser les caractéristiques (forme, couleur, gradient et texture) du reflet spéculaire dans un plan de dessin paramétrisé en fonction de la direction de la réflexion miroir de la lumière. Le but du second modèle est de représenter de manière compacte et efficace les mesures des matériaux isotropes. Pour ce faire, nous introduisons une nouvelle représentation à base de polynômes rationnels. Les coefficients de ces derniers sont obtenus à l'aide d'un processus d'approximation qui garantit une solution optimale au sens de la convergence. Dans la seconde partie de ce mémoire, nous introduisons une nouvelle représentation volumétrique pour l'éclairement indirect représenté directionnellement à l'aide de vecteurs d'irradiance. Nous montrons que notre représentation est compacte et robuste aux variations géométriques et qu'elle peut être utilisée comme système de cache pour du rendu temps réel ou non, ainsi que dans le cadre de la transmission progressive des données (\textit{streaming}). Enfin, nous proposons deux types de modifications de l'éclairement incident afin de mettre en valeur les détails et les formes d'une surface. Le première modification consiste à perturber les directions de l'éclairement incident tandis que la seconde consiste à en modifier l'intensité. / In image synthesis, the main computation involved to generate an image is characterized by an equation named rendering equation [Kajiya1986]. This equation represents the law of energy conservation. It stipulates that the light emanating from the scene objects is the sum of the emitted energy and the reflected energy. Moreover, the reflected energy at a surface point is defined as the convolution of the incoming lighting with a reflectance function. The reflectance function models the object material and represents, in the rendering equation, a directional and energetic filter that describes the surface behavior regarding the reflection. In this thesis, we introduce new representations for the reflectance function and the incoming lighting. In the first part of this thesis, we propose two new models for the reflectance function. The first model is targeted for artists to help them create and edit highlights. Our main idea is to let the user paint and sketch highlight characteristics (shape, color, gradient and texture) in a plane parametrized by the incident lighting direction. The second model is designed to represent efficiently isotropic material data. To achieve this result, we introduce a new representation of the reflectance function that uses rational polynomials. Their coefficients are computed using a fitting process that guarantees an optimal solution regarding convergence. In the second part of this thesis, we introduce a new volumetric structure for indirect illumination that is directionally represented with irradiance vector. We show that our representation is compact and robust to geometric variations, that it can be used as caching system for interactive and offline rendering and that it can also be transmitted with streaming techniques. Finally, we introduce two modifications of the incoming lighting to improve the shape depiction of a surface. The first modification consists in warping the incoming light directions whereas the second one consists in scaling the intensity of each light source.

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