A exploração de fenômenos aeroelásticos dinâmicos visando à conversão de energia do escoamento em eletricidade tem recebido crescente atenção nos últimos anos. As aplicações se estendem desde estruturas aeroespaciais até a alimentação de sistemas eletrônicos sem fio e diferentes mecanismos de transdução têm sido utilizados. O uso de um aerofólio é uma abordagem conveniente e escalável para criar instabilidades e oscilações persistentes para coleta aeroelástica de energia. Este trabalho tem por objetivo avaliar configurações alternativas de aerofólio para a coleta de energia do escoamento. As análises abrangem as versões lineares e não lineares de geradores aeroelásticos de energia baseados em aerofólio com dois (2GDL) e com três graus de liberdade (3GDL) que utilizam transdução piezelétrica e eletromagnética separadamente e também simultaneamente. Em todos os casos o acoplamento eletroaeroelástico é adicionado ao grau de liberdade de flexão do aerofólio e um circuito elétrico externo utilizado para cada tipo de mecanismo de transdução. As equações adimensionais que governam o sistema eletroaeroelástico são apresentadas para cada caso e uma carga resistiva é considerada no domínio elétrico para a previsão da potência gerada. Inicialmente, as previsões do modelo piezoaeroelástico linear com 2GDL são verificadas a partir de resultados experimentais obtidos em ensaios em túnel de vento na condição de flutter. Posteriormente, no primeiro estudo de caso, o comportamento eletroaeroelástico da seção típica com 2GDL é investigado, na velocidade de flutter, variando-se parâmetros aeroelásticos e eletromecânicos. No segundo estudo de caso, uma não linearidade do tipo freeplay é adicionada ao grau de liberdade de rotação da seção típica de 2GDL. Neste caso, a seção típica é estudada na velocidade mais baixa na qual o sistema apresenta oscilações em ciclo limite para diversas configurações de parâmetros aeroelásticos e eletromecânicos. As oscilações não lineares em ciclo limite podem ser obtidas abaixo da velocidade linear de flutter. Finalmente, o comportamento eletroaeroelástico de uma seção típica linear com 3GDL é estudado segundo a variação de diferentes parâmetros. Em todos os estudos de caso, a potência gerada e a amplitude dos GDLs mecânicos são investigadas. Com o estudo, é possível localizar regiões ótimas de parâmetros adimensionais as quais propiciam um aumento da potência elétrica de saída com velocidades de escoamento aceitáveis. Uma vez escalável, é possível redimensionalizar o modelo e manufaturá-lo. / The exploration of dynamic aeroelastic phenomena for converting wind energy into low-power electricity has received growing attention in the last years. Applications extend from aerospace structures to wireless electronic systems. The use of an airfoil is a convenient approach to create instabilities and persistent oscillations for flow energy harvesting. In this work, the goal is to establish alternative configurations of the airfoil for flow energy harvesting. The analysis presented here covers linear and nonlinear versions of aeroelastic energy generators based on an airfoil with two degrees of freedom and three degrees of freedom using piezoelectric and electromagnetic transduction separately and simultaneously. Both forms of coupling are added to the plunge degree of freedom in the presence of a separate electrical load for each type of transduction. The governing coupled dimensionless electroaeroelastic equations are given with a resistive load in each electrical domain to predict system behavior. First, the model predictions are compared with experimental data obtained in wind tunnel tests under flutter condition validating the model for the case of two degrees of freedom and piezoelectric coupling. After, in the first case study the typical section with two and three degrees of freedom is studied at the linear flutter speed for several aeroelastic and electromechanical parameters configurations. In the second case of study a freeplay non-linearity is added to the rotational degree of freedom of the two degree of freedom typical section. In this case, the typical section is studied at the lowest flow speed at which the system presents limit cycle oscillations for different aeroelastic and electromechanical system parameters. The non-linear limit cycle oscillations may be obtained below the linear flutter speed. In both cases, the power generation is analyzed as well as the maximum displacements of the mechanical degrees of freedom. With this study, it is possible to locate the favorable dimensionless parameter regions that give maximum electrical power output as well as reasonable airflow speeds. In this scalable problem, the results can be used for design and fabrication of optimal airfoil-based flow energy harvesters.

This dissertation consists of three projects utilizing electric and electromagnetic (EM) methods to better understand critical-zone hydrogeologic conditions in select Florida wetlands and waters. First, a time-lapse electrical resistivity (ER) survey was conducted in section of mangrove forest on a barrier island in southeast Florida to image changes in pore-water salinity in the root zone. ER data show the most variability in the root zone over a 24-hour period, and, generally, the ground is more resistive during the day than overnight. Second, a suite of three-dimensional forward models, based on varying lateral boundaries and conductivities typical of a coastal wetland, were run to simulate the EM response of a commerical electromagnetic induction instrument crossing over said boundaries. Normalized profiles show the transition is sharper in a hypersaline regime than one where freshwater and clay are present. Furthermore, enough variability exists in hypersaline regimes to justify collecting profile measurements in multiple coil configurations to constrain the nature of a lateral boundary. Also, under certain circumstances, there are kinks in the EMI response even across abrupt boundaries due to concentrated current density at a layer's edge. Lastly, geophysical surveys were conducted at six wetlands in west-central Florida to characterize potential hydrostratigraphic units and compare/contrast them to the current conceptual model for cypress dome wetlands. ER was used to image the geometry of the top of limestone; ground penetrating radar (GPR) was used to image stratigraphy beneath and surrounding wetlands. These wetlands can be grouped into two models. Topographic highs surrounding wetlands are controlled by the undulating top of limestone at sites where the region is characterized by limestone ridges. In contrast, topographic highs are controlled by thick sand packages at sites regionally characterized by sand dunes over scoured limestone.

This thesis presents a robust method for estimating the relaxations of a metallic object from its electromagnetic induction (EMI) response. The EMI response of a metallic object can be accurately modeled by a sum of real decaying exponentials. However, it is difficult to obtain the model parameters from measurements when the number of exponentials in the sum is unknown or the terms are strongly correlated. Traditionally, the relaxation constants are estimated by nonlinear iterative search that often leads to unsatisfactory results. An effective EMI modeling technique is developed by first linearizing the problem through enumeration and then solving the linearized model using a sparsity-regularized minimization. This approach overcomes several long-standing challenges in EMI signal modeling, including finding the unknown model order as well as handling the ill-posed nature of the problem. The resulting algorithm does not require a good initial guess to converge to a satisfactory solution. This new modeling technique is extended to incorporate multiple measurements in a single parameter estimation step. More accurate estimates are obtained by exploiting an invariance property of the EMI response, which states that the relaxation frequencies do not change for different locations and orientations of a metallic object. Using tests on synthetic data and laboratory measurement of known targets, the proposed multiple-measurement method is shown to provide accurate and stable estimates of the model parameters. The ability to estimate the relaxation constants of targets enables more robust subsurface target discrimination using the relaxations. A simple relaxation-based subsurface target detection algorithm is developed to demonstrate the potential of the estimated relaxations.

The response of geological materials at the scale of meters and the response of buried targets of different shapes and sizes using controlled-source electromagnetic induction (CSEM) is investigated. This dissertation focuses on three topics; i) frac- tal properties on electric conductivity data from near-surface geology and processing techniques for enhancing man-made target responses, ii) non-linear inversion of spa- tiotemporal data using continuation method, and iii) classification of CSEM transient and spatiotemporal data. In the first topic, apparent conductivity profiles and maps were studied to de- termine self-affine properties of the geological noise and the effects of man-made con- ductive metal targets. 2-D Fourier transform and omnidirectional variograms showed that variations in apparent conductivity exhibit self-affinity, corresponding to frac- tional Brownian motion. Self-affinity no longer holds when targets are buried in the near-surface, making feasible the use of spectral methods to determine their pres- ence. The difference between the geology and target responses can be exploited using wavelet decomposition. A series of experiments showed that wavelet filtering is able to separate target responses from the geological background. In the second topic, a continuation-based inversion method approach is adopted, based on path-tracking in model space, to solve the non-linear least squares prob- lem for unexploded ordnance (UXO) data. The model corresponds to a stretched- exponential decay of eddy currents induced in a magnetic spheroid. The fast inversion of actual field multi-receiver CSEM responses of inert, buried ordnance is also shown. Software based on the continuation method could be installed within a multi-receiver CSEM sensor and used for near-real-time UXO decision. In the third topic, unsupervised self-organizing maps (SOM) were adapted for data clustering and classification. The use of self-organizing maps (SOM) for central- loop CSEM transients shows potential capability to perform classification, discrimi- nating background and non-dangerous items (clutter) data from, for instance, unex- ploded ordnance. Implementation of a merge SOM algorithm showed that clustering and classification of spatiotemporal CSEM data is possible. The ability to extract tar- get signals from a background-contaminated pattern is desired to avoid dealing with forward models containing subsurface response or to implement processing algorithm to remove, to some degree, the effects of background response and the target-host interactions.

A exploração de fenômenos aeroelásticos dinâmicos visando à conversão de energia do escoamento em eletricidade tem recebido crescente atenção nos últimos anos. As aplicações se estendem desde estruturas aeroespaciais até a alimentação de sistemas eletrônicos sem fio e diferentes mecanismos de transdução têm sido utilizados. O uso de um aerofólio é uma abordagem conveniente e escalável para criar instabilidades e oscilações persistentes para coleta aeroelástica de energia. Este trabalho tem por objetivo avaliar configurações alternativas de aerofólio para a coleta de energia do escoamento. As análises abrangem as versões lineares e não lineares de geradores aeroelásticos de energia baseados em aerofólio com dois (2GDL) e com três graus de liberdade (3GDL) que utilizam transdução piezelétrica e eletromagnética separadamente e também simultaneamente. Em todos os casos o acoplamento eletroaeroelástico é adicionado ao grau de liberdade de flexão do aerofólio e um circuito elétrico externo utilizado para cada tipo de mecanismo de transdução. As equações adimensionais que governam o sistema eletroaeroelástico são apresentadas para cada caso e uma carga resistiva é considerada no domínio elétrico para a previsão da potência gerada. Inicialmente, as previsões do modelo piezoaeroelástico linear com 2GDL são verificadas a partir de resultados experimentais obtidos em ensaios em túnel de vento na condição de flutter. Posteriormente, no primeiro estudo de caso, o comportamento eletroaeroelástico da seção típica com 2GDL é investigado, na velocidade de flutter, variando-se parâmetros aeroelásticos e eletromecânicos. No segundo estudo de caso, uma não linearidade do tipo freeplay é adicionada ao grau de liberdade de rotação da seção típica de 2GDL. Neste caso, a seção típica é estudada na velocidade mais baixa na qual o sistema apresenta oscilações em ciclo limite para diversas configurações de parâmetros aeroelásticos e eletromecânicos. As oscilações não lineares em ciclo limite podem ser obtidas abaixo da velocidade linear de flutter. Finalmente, o comportamento eletroaeroelástico de uma seção típica linear com 3GDL é estudado segundo a variação de diferentes parâmetros. Em todos os estudos de caso, a potência gerada e a amplitude dos GDLs mecânicos são investigadas. Com o estudo, é possível localizar regiões ótimas de parâmetros adimensionais as quais propiciam um aumento da potência elétrica de saída com velocidades de escoamento aceitáveis. Uma vez escalável, é possível redimensionalizar o modelo e manufaturá-lo. / The exploration of dynamic aeroelastic phenomena for converting wind energy into low-power electricity has received growing attention in the last years. Applications extend from aerospace structures to wireless electronic systems. The use of an airfoil is a convenient approach to create instabilities and persistent oscillations for flow energy harvesting. In this work, the goal is to establish alternative configurations of the airfoil for flow energy harvesting. The analysis presented here covers linear and nonlinear versions of aeroelastic energy generators based on an airfoil with two degrees of freedom and three degrees of freedom using piezoelectric and electromagnetic transduction separately and simultaneously. Both forms of coupling are added to the plunge degree of freedom in the presence of a separate electrical load for each type of transduction. The governing coupled dimensionless electroaeroelastic equations are given with a resistive load in each electrical domain to predict system behavior. First, the model predictions are compared with experimental data obtained in wind tunnel tests under flutter condition validating the model for the case of two degrees of freedom and piezoelectric coupling. After, in the first case study the typical section with two and three degrees of freedom is studied at the linear flutter speed for several aeroelastic and electromechanical parameters configurations. In the second case of study a freeplay non-linearity is added to the rotational degree of freedom of the two degree of freedom typical section. In this case, the typical section is studied at the lowest flow speed at which the system presents limit cycle oscillations for different aeroelastic and electromechanical system parameters. The non-linear limit cycle oscillations may be obtained below the linear flutter speed. In both cases, the power generation is analyzed as well as the maximum displacements of the mechanical degrees of freedom. With this study, it is possible to locate the favorable dimensionless parameter regions that give maximum electrical power output as well as reasonable airflow speeds. In this scalable problem, the results can be used for design and fabrication of optimal airfoil-based flow energy harvesters.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-11-12T14:11:44Z No. of bitstreams: 1 luizarthurrodriguesdemello.pdf: 3984461 bytes, checksum: 78cfb143fdfb4f0c949412a0b1fc9d0c (MD5) / Approved for entry into archive by Renata Lopes (renatasil82@gmail.com) on 2018-11-13T13:27:27Z (GMT) No. of bitstreams: 1 luizarthurrodriguesdemello.pdf: 3984461 bytes, checksum: 78cfb143fdfb4f0c949412a0b1fc9d0c (MD5) / Made available in DSpace on 2018-11-13T13:27:27Z (GMT). No. of bitstreams: 1 luizarthurrodriguesdemello.pdf: 3984461 bytes, checksum: 78cfb143fdfb4f0c949412a0b1fc9d0c (MD5) Previous issue date: 2018-08-24 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo dessa dissertação é apresentar a educadores de escolas da rede pública e particular alternativas para a produção de equipamentos para laboratório de indução eletromagnética de custo reduzido e com qualidade comparável aos equipamentos disponíveis no mercado, além de apresentar uma metodologia para aproveitar esse material. O docente é desafiado a mudar do método tradicional, mecanizado, para um formato onde o aluno é levado a interagir com os equipamentos de laboratório, levantar hipóteses para fenômenos observados, discutir essas hipóteses com colegas e apresentar resultados. Apresentamos um planejamento com atividades de Ensino por Investigação, transferindo o foco da aprendizagem para o aluno e possibilitando a sua participação ativa no processo de aquisição do conhecimento. Docentes e discentes dialogam e constroem o conhecimento a partir dessa interação. O produto dessa dissertação inclui um passo-a-passo para construção de uma Mini-bobina de Tesla, uma bobina com quatro mil espiras ligada a diodos LED, um tubo de Foucault e uma bobina chata, além de propor experimentos para utilizar esses equipamentos. Utilizamos a metodologia POE (prever, observar, explicar) na atividade com a Mini-bobina de Tesla e atividades voltadas ao Ensino por Investigação para os demais experimentos. Ao aplicar o produto nas escolas onde o autor trabalha foi possível perceber que os resultados foram positivos, com aumento do interesse dos alunos, melhora na relação com o docente e facilidade para formalizar os conceitos nas aulas teóricas. / The objective of this dissertation is to present educators at schools in the public and private sectors alternatives to produce low-cost electromagnetic induction laboratory equipment with comparable quality to the equipment available in the market, as well as presenting a methodology to take advantage of this material. The teacher is challenged to change from the mechanized traditional method to a format where the student is led to interact with the equipment of the laboratory, to formulate hypotheses about the observed phenomena, to discuss these hypotheses with colleagues and to present results. We present a planning with activities of inquirybased science education, transferring the focus of the learning to the student and enabling their active participation in the process of learning. Teachers and students dialogue and build knowledge from this interaction. The product of this dissertation includes a step-by-step construction of a Tesla Mini-coil, a coil with four thousand wire loops connected to LEDs, a Foucault tube and a flat coil, and propose experiments to use such equipment. We used the POE methodology (predict, observe, explain) in the activity with the Tesla Mini-coil and activities focused on investigation for the other experiments. When applying the product in the schools where the author works, it was possible to perceive that the results were positive, with an increase in student interest, improvement in the relation with the teacher and ease of formalizing the concepts in the theoretical classes.

Submitted by Larissa Vitoria Cardoso Cusielo (larissavitoria@id.uff.br) on 2017-05-11T16:19:16Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Antonio Cezar Ramos - Dissertação Final.pdf: 4550651 bytes, checksum: 52ee77e5f3cb85c60a138229dfce60e4 (MD5) / Rejected by Biblioteca do Aterrado BAVR (bavr@ndc.uff.br), reason: oi on 2017-05-22T16:24:26Z (GMT) / Submitted by Larissa Vitoria Cardoso Cusielo (larissavitoria@id.uff.br) on 2017-05-22T17:09:37Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Antonio Cezar Ramos - Dissertação Final.pdf: 4550651 bytes, checksum: 52ee77e5f3cb85c60a138229dfce60e4 (MD5) / Approved for entry into archive by Biblioteca do Aterrado BAVR (bavr@ndc.uff.br) on 2017-08-21T16:03:21Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Antonio Cezar Ramos - Dissertação Final.pdf: 4550651 bytes, checksum: 52ee77e5f3cb85c60a138229dfce60e4 (MD5) / Made available in DSpace on 2017-08-21T16:03:21Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Antonio Cezar Ramos - Dissertação Final.pdf: 4550651 bytes, checksum: 52ee77e5f3cb85c60a138229dfce60e4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Ciências Exatas. Programa de Pós-Graduação em Ensino de Física. Volta Redonda,RJ / O uso de tecnologia da informação e da comunicação em sala de aula tornou-se uma realidade em poucas escolas desse país. Nossos alunos possuem em suas mãos aparelhos, como tablets e celulares, com alta tecnologia que são ferramentas essenciais para atraírmos os jovens na busca da melhoria do conhecimento. Fica evidente a insatisfação dos alunos que recebem aulas tradicionalistas, realizadas apenas pelo diálogo com o professor, usando, ainda hoje, quadro e giz. No estado do Rio de Janeiro os professores fazem o uso do computador e da internet para tornar suas avaliações mais interessantes, lançando notas em uma plataforma exigida pelo governo , mas em sala de aula encontramos alunos com pouco interesse, o que torna a escola uma instituição ultrapassada e desinteressante. Utilizar o computador de forma a tornar as aulas mais envolventes, interativas , criativas e inteligentes, usando uma metodologia já pensada anteriormente, com os recursos tecnológicos que nosso aluno domina, é o grande desafio de quem está comprometido com a educação. Com esse intuito criamos um roteiro visando o ensino de indução eletromagnética utilizando o simulador Phet, que trabalha desde as propriedades dos imãs até a produção de energia elétrica, um grande impulsionador de nossa economia. Nosso trabalho consiste num roteiro didático que orienta o professor na aplicação do simulador, mostrando o passo a passo de seu funcionamento; possui também um roteiro de atividades a serem realizadas pelos alunos, através da interação com o professor, que irá facilitar a compreensão de cada conteúdo abordado. Nosso produto está fundamentado segundo a teoria de aprendizagem significativa do americano David Auzubel. O produto foi aplicado em 2 ( duas ) turmas do 3o ano do ensino médio, sendo a intervenção didática realizada em 2 ( dois ) encontros de 100 minutos cada. Para execução da intervenção usamos um roteiro que os alunos deveriam responder antes e após a demonstração de cada simulação. Foi feito um questionário avaliativo sobre o uso do simulador. Os resultados nos indicaram que o uso da simulação é uma boa forma de se expor o conteúdo. Para concretizar o aprendizado foi feita uma visita a usina de Funil, pertencente a estatal Furnas, em Itatiaia/RJ. / The use of information and communication technology in the classroom has become a reality in a few schools that country. Our students have in their hands devices such as tablets and mobile phones at high tecnologiaque are essential tools for we attract young people in the pursuit of improving knowledge. It is evident dissatisfaction of students who receive traditionalist classes held only by the dialogue with the teacher using today, and chalk. In Rio de Janeiro teachers of the state make use of computers and the internet to make your most interesting reviews, releasing notes on a required government platform, but in the classroom we find students with little interest, which makes the school an institution outdated and uninteresting. Using the computer to make the most immersive, interactive, creative and intelligent classes, using a methodology as previously thought, with the technological resources that our student dominates, it is the great challenge of those who are committed to education. To that end we have created a road map aimed at electromagnetic induction teaching Phet using the simulator, working from the properties of magnets to the production of electrical power, a major driver of our economy. Our work is a didactic script that guides the teacher in implementing the simulator, showing step by step of its operation; has also an activity guide to be performed by the students, through interaction with the teacher, which will facilitate the understanding of each addressed content. Our product is based according to the meaningful learning theory of American David Auzubel. The product was applied in two (2) classes of the third year of high school, and the teaching intervention carried out in two (2) meetings of 100 minutes each. For intervention of execution used a script that students should respond before and after the demonstration of each simulation. An evaluation questionnaire on the use of the simulator was made. The results showed us that the use of simulation is a good way to expose the contents. To realize the learning was made a visit to funnel plant, owned by Furnas, in Itatiaia / RJ.

The thesis deals with surface quenching of steel 42CrMo4 by electron beam. Influence of technologic parameters and beam deflection on properties and structure of prepared layers is studied. Electron beam surface quenching was applicated with and without melting of the surface. Structures of layers made by electron beam quenching were compared with structures made by laser and electromagnetic induction. Structures and phases were analysed by optical microscopy, SEM and roentgen diffraction. Hardness was measured on hardened layers.

This work is aimed to creating a system for presentation of oscilations. The main part consist of electromagnetic damper, which properties are suitable for use in this system. In the first part are some conditions for design of damper body . In he second part are selected next parameters for electromagnetic damper and of the whole system by MATLAB / Simulink with iterative method. In last part is whole system analyzed and the results indicate next changes in the structure of the system.

No description available.