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.

The main purpose of this study was to develop and administer a four-tier test for assessing Turkish pre-service physics teachers&rsquo / misconceptions about geometrical optics. Sixteen pre-service physics teachers, who were selected by maximum variation and convenience sampling methods from three state universities in Ankara, were interviewed in the contexts of plane mirrors, spherical mirrors, and lenses. From these interviews and the studies in the literature, the Open-Ended Geometrical Optics Test was developed. It was administered to 52 pre-service physics teachers from three state universities selected by purposive and convenience sampling. The responses of each subject for each item were categorized in order to determine the alternatives of the multiple-tier multiple-choice misconception test. The initial form of the test, the Three-Tier Geometrical Optics Test (TTGOT), was administered to 53 pre-service physics teachers from three state universities selected by purposive and convenience sampling as a pilot study. The analysis of the results of the TTGOT was used to revise the test items. Finally, the Four-Tier Geometrical Optics Test (FTGOT) was developed and administered to 243 pre-service physics teachers from 12 state universities in Turkey. The validity of the FTGOT scores was established by means of some qualitative and quantitative methods. The Cronbach alpha reliability coefficients were calculated for different test scores. Those for the total correct scores and standardized misconception scores (SUMM4) were found to be .59 and .42, respectively. Some misconceptions, which were held by more than 10 % of the pre-service teachers, were identified and considered to be significant.

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.

The potential for high spatio-temporal resolution microwave measurements has urged the adoption of the signals of opportunity (SoOp) passive radar technique for use in remote sensing. Recent trends in particular target highly complex remote sensing problems such as root-zone soil moisture and snow water equivalent. This dissertation explores the continued open-sourcing of the SoOp coherent bistatic scattering model (SCoBi) and its use in soil moisture sensing applications. Starting from ground-based applications, the feasibility of root-zone soil moisture remote sensing is assessed using available SoOp resources below L-band. A modularized, spaceborne model is then developed to simulate land-surface scattering and delay-Doppler maps over the available spectrum of SoOp resources. The simulation tools are intended to provide insights for future spaceborne modeling pursuits.

No description available.

[pt] Este trabalho aborda o projeto de antenas omnidirecionais de duplorefletores, onde o refletor principal é obtido a partir de uma geratriz circular. A antena é composta de refletores circularmente simétricos e concêntricos que são alimentados por uma corneta cônica coaxial excitada pelo modo TEM para a produção de polarização vertical. Para realizar este estudo são utilizadas técnicas de síntese e de análise eletromagnética rigorosa. A técnica de análise eletromagnética rigorosa é baseada na associação do Método de Casamento de Modos para representar os campos no interior do alimentador e do Método dos Momentos para solucionar as equações integrais para o campo elétrico e para o campo magnético e determinar a corrente elétrica induzidas sobre as paredes metálicas externas e a amplitude dos modos sobre a abertura da corneta. A técnica de síntese destas antenas é baseada na aplicação dos princípios da Ótica Geométrica para modelar o subrefletor que irá produzir uma distribuição de fase uniforme em uma abertura cônica colocada em frente ao refletor principal com geratriz circular. O estudo exploratório sobre o desempenho destas antenas é dividido em três partes. Na primeira, as soluções fornecidas pela síntese ótica e aproximações para os campos na abertura são utilizadas para identificar configurações de antenas compactas ou que maximizem o ganho ao longo do plano horizontal. Entretanto, pode-se obter uma melhor iluminação da área de cobertura através da inclinação do lobo principal (down tilt). Para reduzir o custo de fabricação de um conjunto de antenas que atendam diferentes áreas de cobertura, pode-se utilizar o mesmo refletor principal e modelar os subrefletores para deslocar a direção de máximo do diagrama. Assim, em uma segunda etapa do estudo paramétrico, são considerados alguns refletores principais, e, para cada um deles, é obtida uma família de subrefletores modelados para deslocar o máximo do diagrama no plano vertical. Esta estratégia se torna efetiva na medida em que o custo de fabricação do subrefletor é menor do que o do refletor principal. Na terceira parte, utilizando o método híbrido composto pelo Método do Casamento de Modos e pelo Método dos Momentos, é feito o modelamento da corneta coaxial TEM com o objetivo de reduzir sua perda de retorno e estender sua banda de operação. Por fim, ainda utilizando este método híbrido, é feita uma análise rigorosa das antenas duplo-refletoras propostas neste trabalho, procurando otimizar o desempenho destas antenas em termos do diagrama de radiação e da perda de retorno. / [en] This work presents a design study of omnidirectional dual-reflector antennas, where the main reflector is obtained from a circular generatrix. The antenna is composed of two concentric circularly symmetric reflectors and it is fed by a coaxial conical horn excited by TEM mode to produce vertical polarization. To obtain the subreflector surface, the study employs a GO synthesis technique to shape the subreflector in order to produce a uniform phase distribution in a conical aperture placed in front of the main reflector. To validate the results, it is employed a rigorous electromagnetic analysis technique based on the association of Mode Matching Technique to represent the fields inside the horn and Method of Moments to solve the integral equations of electric and magnetic fields. The solution of Method of Moments yields the induced electric current on the outer surface of the horn and the amplitude of the modes on the aperture of the horn. The exploratory study is divided in three parts. First, by using the GO approximations for the aperture fields, the geometry parameters are explored to identify compact antenna configurations that maximize the gain along the horizontal plane. However, a more uniform coverage of the ground can be obtained by tilting the main lobe. Thus, in a second step of the parametric study, it is considered a family of designs with the same main reflector and a set of subreflectors that are designed for different tilt angle of main lobe. This strategy is effective to reduce the manufacturing costs of a family of antennas designed to provide different coverage. Third, by using the hybrid method, the TEM coaxial horn is shaped to reduce the return loss and extend its operating band, and, finally, the overall antennas performance is optimized by controlling radiation pattern and return loss.

Made available in DSpace on 2016-04-28T14:16:43Z (GMT). No. of bitstreams: 1 Midori Hijioka Camelo.pdf: 3378645 bytes, checksum: d5a844d84ac1ae690e2ae66fd45c6c79 (MD5) Previous issue date: 2009-10-16 / This work tried to identify the contributions of Filippo Brunelleschi and Leon Battista Alberti to the geometrical optics study. Tradicinally, seen by the history of arts and architecture study as inventors of the perspective, in this history of science study, the issue of genealogy was left behind, so they could find in the investigations about costruzione legittima , contributions for the geometrical optics. The period lived by Brunelleschi and Albert, the Renaissance one, shows many changing elements that made the transition from the Medieval and the Modern History. Specially about the perspective study, it s an incorporating moment, with a different meaning to the word. What used to be the synonym of optics throughout Middle Age, thanks largely to the investigations of architects and painters started then, has now the idea of the representation way , keeping it though the time, like we understand it today. Along with the complex movement of approaching of the heavenly thing to the ones here on Earth, witch in canvas mean the introduction of elements of the real world in representations, we can also see an approach of mathematics to the useful things of life, and geometry becomes equally important to the costruzione legittima of visual reality. In the arts and science knowledge and duties meetings, brought to you by the humanism, the spirit of modern science blends together, In the history of geometrical and experimental optics, the art of painting is show more present than it was traditionally thought to. At the time of seeing, the birth of modern science, the connections of Brunellesch and Alberti revealed how artificial the limit of art and science, the duties and the knowledge / Esta pesquisa buscou identificar as contribuições de Filippo Brunelleschi e Leon Battista Alberti para o estudo da óptica geométrica. Tradicionalmente, disputados pelos estudiosos da história da arte e arquitetura como inventores da perspectiva, neste estudo em história da ciência, deixaram-se de lado a questão de genealogia para encontrar, no interior das investigações para a costruzione legittima , contribuições para a óptica geométrica. O período vivido por Brunelleschi e Alberti, o Renascimento, apresenta muitos elementos de transformações que marcaram historicamente a transição entre o Medieval e o Moderno. Particularmente para o estudo da perspectiva, trata-se de um momento de formação de um novo significado para o termo. O que era sinônimo de óptica durante toda Idade Média, passa a incorporar, graças às investigações dos pintores e arquitetos iniciada ali, a idéia de modo de representação , ficando no decorrer do tempo somente com esta última, tal como entendemos hoje. Juntamente com o complexo movimento de aproximação de elementos do mundo real para a pintura, vemos ocorrer uma aproximação da geometria à forma de representação. No encontro de saberes e fazeres, de arte e ciência, plasma-se o espírito da ciência moderna. Na história da óptica geométrica e experimental, a arte da pintura mostra-se mais presente que tradicionalmente se pensa. Ao vislumbrar, no alvorecer da ciência moderna, as conexões entre Brunelleschi e Alberti revelou-se a artificialidade da fronteira entre a arte e a ciência, o fazer e o saber

In ground based high frequency (HF) radio pumping experiments, absorption of ordinary (O) mode pump waves energises the ionospheric plasma, producing optical emissions and other effects. Pump-induced or natural kilometre-scale field-aligned density depletions are believed to play a role in self-focussing phenomena such as the magnetic zenith (MZ) effect, i.e., the increased plasma response observed in the direction of Earth's magnetic field. Using ray tracing, we study the propagation of ordinary (O) mode HF radio waves in an ionosphere modified by density depletions, with special attention to transmission through the radio window (RW), where O mode waves convert into the extraordinary (X, or Z) mode. The depletions are shown to shift the position of the RW, or to introduce RWs at new locations. In a simplified model neglecting absorption, we estimate the wave electric field strength perpendicular to the magnetic field at altitudes normally inaccessible. This field could excite upper hybrid waves on small scale density perturbations. We also show how transmission and focussing combine to give stronger fields in some directions, notably at angles close to the MZ, with possible implications for the MZ effect. In a separate study, we consider electromagnetic (e-m) beams with helical wavefronts (i.e., twisted beams), which are associated with orbital angular momentum (OAM). By applying geometrical optics to each plane wave component of a twisted nonparaxial e-m Bessel beam, we calculate analytically the shift of the beam's centre of gravity during propagation perpendicularly and obliquely to a weak refractive index gradient in an isotropic medium. In addition to the so-called Hall shifts expected from paraxial theory, the nonparaxial treatment reveals new shifts in both the transverse and lateral directions. In some situations, the new shifts should be significant also for nearly paraxial beams.

[pt] Este trabalho tem como objetivo aplicar uma técnica de síntese ótica de lentes dielétricas circularmente simétricas, que são iluminadas por uma fonte pontual com diagrama circularmente simétrico. A interface da lente (interface do dielétrico-ar) será modelada utilizando as aproximações da Ótica Geométrica e da Física Ótica. Da Ótica Geométrica, o controle da densidade de potência em campo distante é obtido pela aplicação de conservação de energia no interior dos tubos de raios que emergem do centro de fase da fonte e a determinação da direção dos raios que emergem da superfície do dielétrico é obtida através da aplicação da Lei de Snell para os raios incidentes na interface. Da Física Ótica, é possível obter as correntes elétrica e magnética na superfície externa da lente para determinar o campo radiado na integração dessas correntes pela superfície a partir da suposição de que as dimensões da lente e da curvatura da interface sejam muito maiores que um comprimento de onda no espaço livre. Devido a simetria circular, simplificações na formulação e nos esquemas numéricos para a solução serão apresentadas, resultando em técnica de projeto mais eficientes. A descrição da superfície da interface da lente é obtida através de técnica numérica. / [en] This work aims to apply a technique of optical synthesis of symmetrically circular dielectric lenses, which are illuminated by a point source with a symmetrically circular diagram. The lens interface (dielectric-air interface) will be modeled using the approximations of Geometric Optics and Physical Optics. From Geometric Optics, control of the power density in the far field is obtained by applying energy conservation inside the ray tubes that emerge from the phase center of the source and the determination of the direction of the rays emerging from the dielectric surface is obtained through the application of Snell’s law for the incident rays at the interface. From Physical Optics, it is possible to obtain the electric and magnetic currents on the external surface of the lens to determine the radiated field in the integration of these currents along the surface assuming that the lens dimensions and interface curvature are much larger than a wavelength in free space. Due to circular symmetry, simplifications in formulation and numerical schemes for the solution will be presented, resulting in a more efficient design technique. The description of the lens interface surface is obtained through numerical technique.

Les travaux présentés dans cette thèse portent sur l’étude et la conception de lentilles continues en guide d’ondes à plans parallèles (PPW) pour des applications multi-faisceaux. La conversion du front d'onde est assurée par une lentille formée d’une lame et d'une cavité transversale. Ce concept, proposant une approche mécanique simplifiée et possiblement purement métallique, est particulièrement attractif pour les futurs systèmes de communications par satellites (GEO/LEO) requérants des solutions à moindre coût tout en maintenant de hautes performances. La première partie de cette thèse présente la réalisation d’un outil d’analyse numérique basée sur l’optique géométrique (GO). Une prédiction rapide et précise des performances en rayonnement est obtenue. En combinant cet outil avec des processus d’optimisation, des performances en dépointage sur un large secteur angulaire sont ensuite démontrées, incluant une stabilité des diagrammes en rayonnement (ouverture à mi-puissance, niveaux de lobes secondaires et pertes en dépointage). Un prototype fonctionnant dans la bande Ka est réalisé, validant les performances précédemment obtenues. De hautes efficacités de rayonnement sont également mises en avant sur l’ensemble de la plage de fréquence. Enfin un second prototype plus compact basé sur de multiples lentilles est proposé et étudié, démontrant des performances similaires à la première solution fabriquée et mesurée. / The activities presented in this PhD focus on the study and development of continuous parallel plate waveguide (PPW) lenses for multiple beam applications. The wave front conversion is ensured by a PPW transversal ridge and cavity. The proposed concept, based on a simplified mechanical approach and possibly full-metal, is particularly suitable for future satellite communication systems (GO/LEO) requiring low-cost antennas while maintaining high performances. The first part of the thesis deals with the development of a numerical analysis tool based on geometrical optics (GO). A fast and accurate prediction of the radiation performance is provided.Combining the tool with optimization processes, large scanning performances have been demonstrated, including a stability of the radiation pattern performance (HPBW, SLL, scan loss). A prototype working at Ka band has been manufactured, validating the performances demonstrated previously. High radiation efficiencies are also proved over the entire frequency range. Finally, a second prototype targeting performances in compactness and based on multiple lenses is proposed and studied, showing similar performances as the first solution fabricated and measured.