The concept of intelligent CAD systems to assist a designer in automating the design process has been discussed for years. It has been recognized that knowledge engineering techniques and the study of design theory can provide certain solutions to this approach. A major issue in developing intelligent CAD systems for geometric modeling is the integration of the design geometry with the representation of the design constraints. Current commercial computer aided design (CAD) systems are used primarily for recording the results of the design process. Using conventional CAD systems, a design engineer either must create the geometry of the design object with precise coordinates and dimensions, or start his design from an existing geometry of a previous design. It is difficult to propagate a dimensional change throughout an entire model -- especially solid models. This rigidity imposed by conventional CAD systems discourages a designer from exploring different approaches in creating a novel product. / Ph. D.

In an integrated design environment, the common thread between the different design stages is usually the geometric model of the part. However, the requirements for the geometric definition of the design is usually different for each stage. The transformation of data between these different stages is essential for the success of the integrated design environment. For example, conceptual design systems usually deal with geometric dimensional parameters (e.g. length, radius, etc.) whereas preliminary design systems frequently require the geometry definition to be in the form of surface models. This dissertation presents the necessity and scope of creating and implementing methodologies to obtain dimensional geometric parameters from the surface description of an object. Since the study of geometric modeling and parametric surfaces is a new field, few classical methods are applicable. Methods and algorithms for the extraction of various geometry parameters are created. A few methods to pre-process and manipulate these surfaces before the parameter extraction methods can be applied are outlined. One of the most important applications of parameter extraction is in the field of aircraft design. There are two important aspects of geometry data conversion in the design cycle. The first is the conversion from conceptual CAD models to CFD compatible models. The second is the conversion from surface representations of CFD models to obtain component parameters (e.g. wing span, fuselage fineness ratio, moments of inertia, etc.). The methods created in this dissertation are used to extract geometric parameters of importance in aircraft design. This enables the design cycle to be complete and promotes integrated design. These methods have been implemented in the aircraft design software, ACSYNT. Examples of the conversion of data from B-spline surface models to dimensional geometric parameters using these methods are included. The emphasis of this dissertation is on non-uniform B-spline surfaces. Methods for obtaining geometric parameters from aircraft models described by characteristic points are also considered briefly. / Ph. D.

Prediction of the sound field in large urban environments has been limited thus far by the heavy computational requirements of conventional numerical methods such as boundary element (BE), finite-difference time-domain (FDTD), or ray-tracing methods. Recently, a considerable amount of work has been devoted to developing energy-based methods for this application, and results have shown the potential to compete with conventional methods. However, these developments have been limited to two-dimensional (2-D) studies (along street axes), and no real description of the phenomena at issue has been exposed (e.g., diffraction effects on the predictions). The main objectives of the present work were (i) to evaluate the feasibility of an energy-based method, the diffusion model (DM), for sound-field predictions in large, 3-D complex urban environments, (ii) to propose a numerical hybrid method that could improve the accuracy and computational time of these predictions, and (iii) to verify the proposed hybrid method against conventional numerical methods. The proposed numerical hybrid method consists of a full-wave model coupled with an energy-based model. The full-wave model is used for predicting sound propagation (i) near the source, where constructive and destructive interactions between waves are substantial, and (ii) outside the cluttered environment, where free-field-like conditions apply. The energy-based model is used in regions where diffusion conditions are met. The hybrid approach, as implemented in this work, is a combination of FDTD and DM models. Results from this work show the role played by diffraction near buildings edges close to the source and near the exterior boundaries of the computational domain, and its impact on the predictions. A wrong modeling of the diffraction effects in the environment leads to significant under or overpredictions of the sound levels in some regions, as compared to conventional numerical methods (in these regions, some differences are as high as 10 dB). The implementation of the hybrid method, verified against a full FDTD model, shows a significant improvement of the predictions. The mean error thus obtained inside the cluttered region of the environment is 1.5 dB. / Master of Science

Fewer geometrical analyses have been made of paintings than of any other group of works of art. For this reason ten paintings by a typical Florentine painter, Botticelli, were chosen by the author in order to find out; first, the extent to which geometrical divisions were used in determining the enclosing rectangles and the main lines of the composition; second, whether or not the same geometrically determined relationships were used by Botticelli frequently enough to be considered an important determinant of his style.

Cílem předkládané diplomové práce je pomocí lícování obrazů přesně popsat distorzní pole pro následné odstranění geometrické distorze. Snímky zkreslené geometrickou distorzí pochází z prozařovacího elektronového mikroskopu. První část práce se zabývá zejména teorií spojenou s elektronovou mikroskopií, vznikem geometrické distorze a samotnou obrazovou registrací s důrazem na intenzitní flexibilní metody lícování. Ve druhé části je pak představena vytvořená metoda pro modelování geometrické distorze a lícování obrazů postižených slabou geometrickou distorzí. Vyvinutá metoda je následně otestována na testovacích i reálných datech a srovnána s existujícími popsanými metodami pro obrazovou registraci (například open-source softwarem Elastix).

A way to obtain materials that show novel phenomena is to explore the interplay between geometry and interactions. When it is not geometrically possible to satisfy all the interactions by a given configuration, then to find the ground state becomes very complicated. This interplay between geometry and interactions defines geometrical frustration. One of the most popular examples of geometrical frustration in magnetism is spin ice. In this system, nearest neighbour ferromagnetic interactions between Ising spins in a pyrochlore structure emulate water ice by showing the same degree of frustration. This is manifested by the same ground state residual entropy. Although the clearest example of spin ice among magnets is shown by Dy₂Ti₂O₇, the behaviour of this material is richer than that of pure spin ice. The large magnetic moments of the rare earth Dy form a spin ice that also interacts via dipolar interactions. These long range interactions give rise to monopolar excitations which dramatically affect the dynamics of the system with respect to the pure spin ice case. In this thesis magnetisation experiments and numerical methods are used to explore the properties of the magnetic insulator Dy₂Ti₂O₇. We study its excitations at low temperature and describe the out-of-equilibrium characteristics of the magnetisation processes, below a temperature where the system freezes out. For temperatures above the freezing temperature, we describe and measure a 3D Kasteleyn transition and the concomitant Dirac strings associated to it, for the field in the [100] crystallographic direction. For temperatures below the freezing temperature, we find new out-of-equilibrium phenomena. Magnetic jumps are measured and their sweep rate dependence analysed. A deflagration theory is proposed and supported by simultaneous magnetisation and sample temperature measurements obtained by a new design of a Faraday magnetometer.

Det här examensarbetet kretsar kring mina experiment med parkettläggningstekniker, och mina försök att bygga en möbel som ser ut som att den har tagits över av ett mönster eller en struktur. En övergång till någonting mer skulpturalt. Jag använder träbitar som blivit över från andra projekt för att tillverka dessa dekorationer. Min utgångspunkt är traditionella parkettläggningstekniker, men jag arbetar också med en slags mer tredimensionell parkettläggning, med tjockare, vinklade bitar, för att skapa djup och ett intryck av växande. / This thesis work revolves around my experiments with parquetry and my attempts to build a piece of furniture that appears to have been taken over by a pattern or structure. A transition into something more sculptural. I use pieces of wood left over from other projects to create these decorations. My basis is traditional parquetry techniques, but I also work with a type of more three dimensional parquetry, with thicker, angled pieces, to create depth and an impression of growing.

Cette recherche, réalisée en milieu scolaire québécois, concerne l’enseignement et l’apprentissage de la géométrie à l’entrée au secondaire. Ce contexte est caractérisé par une géométrie non clairement définie d’un point de vue épistémologique, tant dans le programme d’études du premier cycle que dans les manuels scolaires. Ainsi, nous avons cherché à voir d’une part, l’activité géométrique souhaitée et actualisée par des enseignants incluant les problèmes proposés et, d’autre part, les conceptions d’élèves développées par ces problèmes. À partir de données recueillies auprès de quatre classes, nous avons déterminé cette activité géométrique et répertorié six types de problèmes dont quatre sont dominants ainsi que des conceptions d’élèves. L’activité géométrique en classe a donné lieu à des moments d’hésitation épistémologique, lesquels ne sont pas sans effet dans le développement des conceptions des élèves. / This research was conducted in a Quebec classroom environment. It pertains to the teaching and learning of geometry at the outset of secondary school. This context is characterized by a geometry that is not clearly defined from the epistemological point of view in either the secondary cycle one program or in textbooks. We attempted to find firstly, the desired geometric activity and updated by teachers with the proposed problems and, secondly, students conceptions developed by these problems. Using data collected from four classes, we then determined this geometric activity and identified six types of problems from which four were predominant. We also observed students conceptions. The classroom activity gave birth to moments of epistemological hesitance that may have had a certain effect on the development of the students’conceptions.

Neste trabalho são discutidos os aspectos inerentes à análise não-linear física (NLF) e geométrica (NLG) das estruturas de contraventamento em concreto armado. O estudo proposto tem como base a análise estrutural de pórticos planos de concreto armado, desenvolvendo-se uma ferramenta rigorosa capaz de analisar essas estruturas de forma elaborada e consistente. Com essa ferramenta serão avaliadas as reduções de inércia que ocorrem em pórticos planos de concreto armado, submetidos a diferentes condições de carregamento e a diferentes taxas de armadura, contribuindo para o estabelecimento de estimativas confiáveis dos efeitos da NLF nessas estruturas. Estes resultados, combinados com os parâmetros de estabilidade &#945 e &#947z - capazes de estimar com bastante precisão os efeitos devidos à NLG - permitem o estabelecimento de métodos simplificados para a análise não-linear física e geométrica das estruturas de contraventamento de edifícios em concreto armado, de grande utilidade para os projetistas. / In this work the inherent aspects to the physical nonlinear analysis (PNL) and geometric nonlinear analysis (GNL) of reinforced concrete bracing structures are argued. The considered study is based in the structural analysis of in reinforced concrete plane frames, developing a rigorous tool capable to analyze these structures of elaborated and consistent form. Using this tool, inertia reductions that occurs in reinforced concrete plane frames, submitted the different loading conditions and the different levels of reinforcement will be evaluated, contributing for the establishment of trustworthy estimates to the effects of PNL in these structures. These results, matched with the stability parameters &#945 e &#947z - capable to estimate with sufficient accuracy the effects of GNL - allow the establishment of simplified methods for physical and geometrical non-linear analysis of reinforced concrete buildings bracing structures, of great utility for the designers.

Atualmente existe, praticamente, um consenso entre os pesquisadores de Ensino de Física, de que a metodologia tradicional não é a mais efetiva por não promover um real engajamento dos estudantes durante o processo de ensino/aprendizagem. Muitos pesquisadores denominam Aprendizagem Ativa (AA), os métodos que requerem tal engajamento e as pesquisas indicam que esta abordagem é mais efetiva. Ou seja, verifica-se um aumento da compreensão dos conceitos básicos de Física. Entretanto, ainda há pouca aplicação de novas metodologias em sala de aula, tanto no ensino médio quanto no superior. No nosso entender, as atividades experimentais (de laboratório ou demonstração) são as mais adequadas para a aplicação de metodologias de AA. Entretanto, particularmente no Brasil, existe pouco material didático experimental disponível que utilize essa metodologia. Este trabalho visa sanar tal necessidade no campo da Ótica Geométrica, oferecendo uma série de roteiros comentados para experimentos e demonstrações interativas. Estes roteiros usam a idéia de investigação orientada onde se pretende que os conhecimentos prévios dos alunos sejam expostos e confrontados com os conceitos científicos. Este material foi aplicado a estudantes do ensino médio (escolas públicas) e do curso de Licenciatura em Ciências Exatas do IFSC. Para a avaliação do mesmo foram realizados testes escritos e monitoramentos em sala de aula. / There is nowadays consensus among the physics education researchers that the traditional teaching methods are not the most effective in promoting real engagement of the students in the teaching/learning process. Several researchers named Active Learning (AL), methods that require this engagement and research evidences indicate that this approach is the most effective, a better comprehension of the basic physics concepts is verified. However, particularly in Brazil, there are few didactic materials available using AL approaches. This works aims to fulfill this need in the field of Geometrical Optics, offering a series of tutorials (guides) for experiments and interactive demonstrations. These tutorials are based in the idea of guided investigation where the students previous beliefs are exposed and confronted with the scientific concepts. This material was applied to high school students (in public schools) and college students (science teacher preparation course of IFSC). In order to evaluate this material, written tests were performed as well as observation of classrooms.