Precise description of the different far fields encountered in the problem of diffraction of acoustic waves by a quarter-plane

This paper provides a review of important results concerning the Geometrical Theory of Diffraction and Geometrical Optics. It also reviews the properties of the existing solution for the problem of diffraction of a time harmonic plane wave by a half-plane. New mathematical expressions are derived for the wave fields involved in the problem of diffraction of a time harmonic plane wave by a quarter-plane, including the secondary radiated waves. This leads to a precise representation of the diffraction coefficient describing the diffraction occurring at the corner of the quarter-plane. Our results for the secondary radiated waves are an important step towards finding a formula giving the corner diffraction coefficient everywhere. © 2012 The authors.

Distortion of Dimension under Quasiconformal Mappings

Quasiconformal mappings are natural generalizations of conformal mappings. They are homeomorphisms with 'bounded distortion' of which there exist several approaches. In this work we study dimension distortion properties of quasiconformal mappings both in the plane and in higher dimensional Euclidean setting. The thesis consists of a summary and three research articles. A basic property of quasiconformal mappings is the local Hölder continuity. It has long been conjectured that this regularity holds at the Sobolev level (Gehring's higher integrabilty conjecture). Optimal regularity would also provide sharp bounds for the distortion of Hausdorff dimension. The higher integrability conjecture was solved in the plane by Astala in 1994 and it is still open in higher dimensions. Thus in the plane we have a precise description how Hausdorff dimension changes under quasiconformal deformations for general sets. The first two articles contribute to two remaining issues in the planar theory. The first one concerns distortion of more special sets, for rectifiable sets we expect improved bounds to hold. The second issue consists of understanding distortion of dimension on a finer level, namely on the level of Hausdorff measures. In the third article we study flatness properties of quasiconformal images of spheres in a quantitative way. These also lead to nontrivial bounds for their Hausdorff dimension even in the n-dimensional case.

Model independent bounds on the modulus of the pion form factor on the unitarity cut below the omega pi threshold

We calculate upper and lower bounds on the modulus of the pion electromagnetic form factor on the unitarity cut below the omega pi inelastic threshold, using as input the phase in the elastic region known via the Fermi-Watson theorem from the pi pi P-wave phase shift, and a suitably weighted integral of the modulus squared above the inelastic threshold. The normalization at t = 0, the pion charge radius and experimental values at spacelike momenta are used as additional input information. The bounds are model independent, in the sense that they do not rely on specific parametrizations and do not require assumptions on the phase of the form factor above the inelastic threshold. The results provide nontrivial consistency checks on the recent experimental data on the modulus available below the omega pi threshold from e(+)e(-) annihilation and tau-decay experiments. In particular, at low energies the calculated bounds offer a more precise description of the modulus than the experimental data.

Parametrisation-free determination of the shape parameters for the pion electromagnetic form factor

Recent data from high-statistics experiments that have measured the modulus of the pion electromagnetic form factor from threshold to relatively high energies are used as input in a suitable mathematical framework of analytic continuation to find stringent constraints on the shape parameters of the form factor at t = 0. The method uses also as input a precise description of the phase of the form factor in the elastic region based on Fermi-Watson theorem and the analysis of the pi pi scattering amplitude with dispersive Roy equations, and some information on the spacelike region coming from recent high precision experiments. Our analysis confirms the inconsistencies of several data on the modulus, especially from low energies, with analyticity and the input phase, noted in our earlier work. Using the data on the modulus from energies above 0.65 GeV, we obtain, with no specific parametrisation, the prediction < r(pi)(2)> is an element of (0.42, 0.44) fm(2) for the charge radius. The same formalism leads also to very narrow allowed ranges for the higher-order shape parameters at t = 0, with a strong correlation among them.

The Complexity of Approximately Solving Influence Diagrams

Influence diagrams allow for intuitive and yet precise description of complex situations involving decision making under uncertainty. Unfortunately, most of the problems described by influence diagrams are hard to solve. In this paper we discuss the complexity of approximately solving influence diagrams. We do not assume no-forgetting or regularity, which makes the class of problems we address very broad. Remarkably, we show that when both the treewidth and the cardinality of the variables are bounded the problem admits a fully polynomial-time approximation scheme.

Échantillonnage et modélisation de l’habitat des communautés de poissons de rivière des basses Laurentides

Plusieurs études à grande échelle ont identifié la modification ou la perte d’habitats comme menace principale à la conservation des communautés de poissons d’eau douce. Au Canada, « aucune perte nette dans la capacité productive des habitats » (NNL) est le principe directeur de la politique de gestion des habitats du ministère des Pêches et Océans. Le respect du NNL implique l’avancement des connaissances au niveau des relations entre les poissons et leurs habitats, de même que des outils pour quantifier l’impact de la modification des habitats sur les poissons. Les modèles d’utilisation de l’habitat des poissons (FHUM) sont des outils qui permettent d’améliorer nos connaissances des relations poissons – habitat, de prédire la distribution des espèces, mais aussi leurs densités, biomasses ou abondances, sur la base des caractéristiques de l’environnement. L’objectif général de mon mémoire est d’améliorer la performance des FHUM pour les rivières des basses Laurentides, en suggérant des perfectionnements au niveau de 2 aspects cruciaux de l’élaboration de tels modèles : la description précise de la communauté de poissons et l’utilisation de modèles statistiques efficaces. Dans un premier chapitre, j’évalue la performance relative de la pêcheuse électrique et de l’échantillonnage en visuel (plongée de surface) pour estimer les abondances des combinaisons d’espèces et de classes de taille des poissons en rivière. J’évalue aussi l’effet des conditions environnementales sur les différences potentielles entre les communautés observées par ces 2 méthodes d’échantillonnage. Pour ce faire, 10 sections de rivière de 20 m de longueur ont été échantillonnées à l’aide de ces 2 méthodes alors qu’elles étaient fermées par des filets de blocage. 3 plongeurs performèrent l’échantillonnage en visuel en se déplaçant de l’aval vers l’amont des sections, tout en dénombrant les espèces et classes de taille. Par la suite, nous avons fait 3 passages de pêcheuse électrique et les abondances furent estimées grâce à un modèle restreint de maximum de vraisemblance, basé sur la diminution des abondances observées. De plus grandes abondances de poissons furent observées en visuel qu’avec la pêcheuse électrique à tous les sites. La richesse spécifique observée en visuel était plus élevée (6/10) ou égale (4/10) à celle observée avec la pêcheuse électrique. Les différences entre les communautés de poissons observées à l’aide de ces 2 méthodes ne purent être reliées aux conditions environnementales. Les résultats de cette expérience sont contraires à ceux de toutes les études comparant ces 2 méthodes d’échantillonnage, lesquels suggèrent une supériorité de la pêcheuse électrique. Les conditions environnementales de notre expérience étaient distinctes de celles observées dans les autres études (absence d’arbres tombés dans l’eau, très peu de substrats grossiers), mais la différence la plus marquante était en terme de communauté de poissons observée (dominance des cyprinidés et des centrarchidés plutôt que des salmonidés). Je termine ce chapitre en suggérant que les caractéristiques comportementales favorisant l’évitement de la capture (formation de bancs) et facilitant l’observation en visuel (curiosité) sont responsables de la supériorité de la plongée de surface pour échantillonner les communautés dans les rivières des basses Laurentides. Dans un deuxième chapitre, je développe des FHUM pour des communautés de poissons de rivière ayant plusieurs espèces. Dans le but de simplifier la modélisation de telles communautés et d’améliorer notre compréhension des relations poissons – habitat, j’utilise les concepts de guilde écologique et de filtre environnemental pour explorer les relations entre les guildes formées sur la bases de différents types de traits (reproducteurs, taxonomiques, éco-morphologiques et alimentaires) et les conditions environnementales locales à l’échelle du méso-habitat. Les modèles d’habitats basés sur les guildes reproductrices ont clairement surpassé les autres modèles, parce que l’habitat de fraie reflète l’habitat de préférence en dehors de la période de reproduction. J’ai également utilisé l’approche inverse, c’est à dire définir des guildes d’utilisation de l’habitat et les mettre en relation avec les traits des espèces. Les traits reliés à l’alimentation des poissons ont semblés être les meilleurs pour expliquer l’appartenance aux groupes d’utilisation de l’habitat, mais le modèle utilisé ne représentait pas bien la relation entre les groupes. La validation de notre modèle basé sur les guildes reproductrices avec un jeu de données indépendant pourrait confirmer notre découverte, laquelle représente une manière prometteuse de modéliser les relations poissons – environnement dans des communautés de poissons complexes. En conclusion, mon mémoire suggère d’importantes améliorations aux FHUM pour les communautés de poissons des basses Laurentides, en suggérant de prendre en compte les caractéristiques biologiques des cours d’eau dans le choix d’une méthode d’échantillonnage, et également en utilisant une méthode prometteuse pour simplifier les FHUM de communautés de poissons complexes : les guildes reproductrices.

Dual retrieval in conceptual information systems

Conceptual Information Systems provide a multi-dimensional conceptually structured view on data stored in relational databases. On restricting the expressiveness of the retrieval language, they allow the visualization of sets of realted queries in conceptual hierarchies, hence supporting the search of something one does not have a precise description, but only a vague idea of. Information Retrieval is considered as the process of finding specific objects (documents etc.) out of a large set of objects which fit to some description. In some data analysis and knowledge discovery applications, the dual task is of interest: The analyst needs to determine, for a subset of objects, a description for this subset. In this paper we discuss how Conceptual Information Systems can be extended to support also the second task.

ExtSym: a program to aid space-group determination from powder diffraction data

Once unit-cell dimensions have been determined from a powder diffraction data set and therefore the crystal system is known (e.g. orthorhombic), the method presented by Markvardsen, David, Johnson & Shankland [Acta Cryst. (2001), A57, 47-54] can be used to generate a table ranking the extinction symbols of the given crystal system according to probability. Markvardsen et al. tested a computer program (ExtSym) implementing the method against Pawley refinement outputs generated using the TF12LS program [David, Ibberson & Matthewman (1992). Report RAL-92-032. Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, UK]. Here, it is shown that ExtSym can be used successfully with many well known powder diffraction analysis packages, namely DASH [David, Shankland, van de Streek, Pidcock, Motherwell & Cole (2006). J. Appl. Cryst. 39, 910-915], FullProf [Rodriguez-Carvajal (1993). Physica B, 192, 55-69], GSAS [Larson & Von Dreele (1994). Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA], PRODD [Wright (2004). Z. Kristallogr. 219, 1-11] and TOPAS [Coelho (2003). Bruker AXS GmbH, Karlsruhe, Germany]. In addition, a precise description of the optimal input for ExtSym is given to enable other software packages to interface with ExtSym and to allow the improvement/modification of existing interfacing scripts. ExtSym takes as input the powder data in the form of integrated intensities and error estimates for these intensities. The output returned by ExtSym is demonstrated to be strongly dependent on the accuracy of these error estimates and the reason for this is explained. ExtSym is tested against a wide range of data sets, confirming the algorithm to be very successful at ranking the published extinction symbol as the most likely. (C) 2008 International Union of Crystallography Printed in Singapore - all rights reserved.

Políticas de recursos humanos, do discurso oficial à prática : estudo realizado na administração direta do estado do Espírito Santo

O distanciamento entre discurso oficial prática das políticas de Recursos Humanos definidas para os servidores da Administração Direta do Poder Executivo do Estado do Espirito Santo no período de 1971/1991, neste estudo de caso, foi analisado tomando-se como base conceituai teoria de Análise de Políticas Públicas Recursos Humanos. Verificou-se as Diretrizes programadas as ações que foram implementadas, utilizando-se documentos oficiais, Planos de Governos, Mensagens Legislativas, Leis, Decretos outros documentos abrangendo cinco períodos diferentes de governo, compreendendo um espaço histórico de vinte anos da Administração Pública Estadual Capixaba, englobando parte do período de "Regime Militar Autoritário", "Abertura Política" "Nova República". Buscando-se ressaltar aspectos importantes conseguir descrição mais precisa da situação em estudo, realizou-se pesquisa de campo, utilizando-se instrumento da entrevista semi-estruturada. Foram selecionados entrevistados Dirigentes Assessores Públicos, bem como Secretários de Estado que atuaram no cenário em investigação. No período 1971/91, as diretrizes propostas seguiram procedimentos racionais as ações foram implementadas de forma isolada, distanciando-se das diretrizes propostas nos planos dos Governos. distanciamento entre discurso e a prática, chega ser considerado como um procedimento natural, haja vista, que pesquisa permeou cinco períodos de governos, cujo cenário político foi bastante diferente, entretanto, prática adotada pelos diversos governantes administradores públicos, em relação Administração Pública especialmente ao tratamento dispensado aos Recursos Humanos, foi desenvolvida com mesma desconsideração. De onde se conclui que no período 1971/91, as diretrizes da política de Recursos Humanos para os servidores da Administração Direta do poder Executivo do Estado do Espirito Santo permaneceram apenas na retórica do discurso governamental, e, em nenhum momento na prática elas foram implementadas nível de Governo.

Influência da variabilidade espacial de atributos químicos de um latossolo na aplicação de insumos para cultura de cana-de-acúcar

As técnicas de aplicação localizada e em taxas variadas de insumos agrícolas com auxílio da geoestatística têm sido umas das áreas de concentração de esforços recentes em pesquisas e desenvolvimento ligado à agricultura de precisão. Portanto, o trabalho teve como objetivo avaliar a necessidade de aplicação de calcário e fósforo com base no comportamento espacial de atributos químicos do solo. Foram feitas amostragens do solo a intervalos regulares de 50 m, em uma área de 42 ha, na profundidade de 0,0-0,2 m para determinação do pH, Ca, Mg, P, V% e cálculo da necessidade de calagem e superfosfato triplo. Os dados foram submetidos às análises da estatística descritiva, geoestatística e interpolação por krigagem. O uso da técnica de geoestatística possibilitou uma precisa descrição dos atributos do solo o que permitiu a definição de zonas de manejo, indicando os locais de ocorrência de déficit e excesso. A variabilidade espacial dos atributos químicos do solo, possibilita a recomendação de doses de calcário e fósforo com taxas variadas, proporcionando economia e maior eficiência na aplicação.

Control aspects in nonlinear Hill's equation

The Hill's equations-even in the linear original version are a describer of phenomenon having chaotic flavor, giving sometimes very unusual situations. The theory of the so called intervals of instability in the equation provides the precise description for most of these phenomena. Considerations on nonlinearities into the Hill's equation is a quite recent task. The linearized version for almost of these systems it reduces to the Hill's classical linear one. In this paper, some indicative facts are pointed out on the possibility of having the linear system stabilizable and/or exactly controllable. As consequence of such an approach we get results having strong classical aspects, like the one talking about location of parameters in intervals of stability. A result for nonlinear proper periodic controls, is considered too. (C) 2010 Elsevier B.V. All rights reserved.

Uma estratégia dirigida a modelos e baseada em linguagem de descrição arquitetural para linhas de produtos de software

Model-oriented strategies have been used to facilitate products customization in the software products lines (SPL) context and to generate the source code of these derived products through variability management. Most of these strategies use an UML (Unified Modeling Language)-based model specification. Despite its wide application, the UML-based model specification has some limitations such as the fact that it is essentially graphic, presents deficiencies regarding the precise description of the system architecture semantic representation, and generates a large model, thus hampering the visualization and comprehension of the system elements. In contrast, architecture description languages (ADLs) provide graphic and textual support for the structural representation of architectural elements, their constraints and interactions. This thesis introduces ArchSPL-MDD, a model-driven strategy in which models are specified and configured by using the LightPL-ACME ADL. Such strategy is associated to a generic process with systematic activities that enable to automatically generate customized source code from the product model. ArchSPLMDD strategy integrates aspect-oriented software development (AOSD), modeldriven development (MDD) and SPL, thus enabling the explicit modeling as well as the modularization of variabilities and crosscutting concerns. The process is instantiated by the ArchSPL-MDD tool, which supports the specification of domain models (the focus of the development) in LightPL-ACME. The ArchSPL-MDD uses the Ginga Digital TV middleware as case study. In order to evaluate the efficiency, applicability, expressiveness, and complexity of the ArchSPL-MDD strategy, a controlled experiment was carried out in order to evaluate and compare the ArchSPL-MDD tool with the GingaForAll tool, which instantiates the process that is part of the GingaForAll UML-based strategy. Both tools were used for configuring the products of Ginga SPL and generating the product source code

BRIDGE: uma ferramenta para o Design de Interfaces de Usuário baseada em especificações IMML

With hardware and software technologies advance, it s also happenning modifications in the development models of computational systems. New methodologies for user interface specification are being created with user interface description languages (UIDL). The UIDLs are a way to have a precise description in a language with more abstraction and independent of how will be implemented. A great problem is that even using these nowadays methodologies, we still have a big distance between the UIDLs and its design, what means, the distance between abstract and concrete. The tool BRIDGE (Interface Design Generator Environment) was created with the intention of being a linking bridge between a specification language (the Interactive Message Modeling Language IMML) and its implementation in Java, linking the abstract (specification) to the concrete (implementation). IMML is a language based on models, that allows the designer works in distinct abstraction levels, being each model a distinct abstraction level. IMML is a XML language, that uses the Semiotic Engineering concepts, that deals the computational system, with the user interface and its elements like a metacommunicative artifact, where these elements must to transmit a message to the user about what task must to be realized and the way to reach this goal. With BRIDGE, we intend to supply a lot of support to the design task, being the user interface prototipation the greater of them. BRIDGE allows the design becomes easier and more intuitive coming from an interface specification language

Biodegradação de derivados do petróleo com a aplicação de biossurfactante produzido por Bacillus subtilis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Formas do relevo e variabilidade espacial de atributos químicos e mineralógicos de um argissolo cultivado com cana-de-açúcar

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)