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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.
451

Prototipação de dispositivos com laser de fermtosegundos

Costa, Larissa Nunes da 28 March 2014 (has links)
Este trabalho descreve a produção de dispositivos protótipos em vidro e fibras óticas utilizando exposição a um laser de femtosegundos. As estruturas são caracterizadas utilizando microscopia convencional e confocal. A capacidade de guiamento de luz é investigada acoplando uma fonte de laser na entrada da estrutura e medindo o perfil de campo próximo. Foram ainda fabricadas redes de Bragg em fibras óticas submetidas à tratamento térmico após a gravação, para obter redes regeneradas. Micro-usinagem em vidro seguido de ataque químico resultou em uma estrutura 3D formada por uma matriz interconectada. / This work describes the device prototiping with a femtosecond laser. The obtained structures are characterized by conventional and confocal microscopy. Hight guiding is verified by launching light and measuring the near field profile at the exit facet. Fiber Bragg grating where also recorded and heated to obtain regenerated gratings. Glass micromachining followed bt chemical etching resulted in a 3D structure made by an interconnected array of microchannels.
452

Controle para protótipos registrados com laser de femtosegundos

Fiorin, Rodrigo 15 August 2013 (has links)
Um dos problemas da fabricação de protótipos de dispositivos fotônicos esta no controle dos vários parâmetros de construção. A utilização do laser de femtosegundo para a fabricação de dispositivos óticos esta cada vez mais comum devido as suas qualidades e propriedades. Com a utilizaçãao das instruções de programação e do laser de femtosegundo foi possível a alteração do índice de refração dos substratos de sodocálcico e de sílica fundida, tornando viável o guiamento em estruturas planas. Com estas estruturas de guiamento devidamente produzidas e caracterizadas, permitiu construir um acoplador direcional, mostrando a possibilidade de controle para fabricação de diversos dispositivos. / One of the problems of manufacturing prototypes of photonic devices that control the various parameters of construction. The utilization of the femtosecond laser for the fabrication of optical devices is increasingly common due to their qualities and properties. With the utilization of the instructions for programming and femtosecond laser was possible alteration of the index of refraction of the substrates of soda-lime and fused silica, making viable guiding in planar structures. With these guiding structures properly produced and characterized, it was possible to build a directional coupler, showing the possibility of control for the manufacture of various devices.
453

Prototipação de dispositivos com laser de fermtosegundos

Costa, Larissa Nunes da 28 March 2014 (has links)
Este trabalho descreve a produção de dispositivos protótipos em vidro e fibras óticas utilizando exposição a um laser de femtosegundos. As estruturas são caracterizadas utilizando microscopia convencional e confocal. A capacidade de guiamento de luz é investigada acoplando uma fonte de laser na entrada da estrutura e medindo o perfil de campo próximo. Foram ainda fabricadas redes de Bragg em fibras óticas submetidas à tratamento térmico após a gravação, para obter redes regeneradas. Micro-usinagem em vidro seguido de ataque químico resultou em uma estrutura 3D formada por uma matriz interconectada. / This work describes the device prototiping with a femtosecond laser. The obtained structures are characterized by conventional and confocal microscopy. Hight guiding is verified by launching light and measuring the near field profile at the exit facet. Fiber Bragg grating where also recorded and heated to obtain regenerated gratings. Glass micromachining followed bt chemical etching resulted in a 3D structure made by an interconnected array of microchannels.
454

Pollinator Power: Supporting Bees Through Ecoregion Specific Planting Guides

Thomas, Maya 01 January 2018 (has links)
The pollination of flowering crops by bees is an invaluable ecosystem service that supports biodiversity and much of the global agricultural system. Pollinators move pollen between the male structures of a plant to the female structures of a plant of the same species. This fertilizes the female plant, which then produces the next generation. This process also provides the pollinator with the nectar or pollen it needs to survive. While some plants transfer pollen through different means, the majority of plants need help from pollinators to reproduce. Depending on the means of pollination, pollination can be classified as abiotic or biotic. Abiotic pollination occurs without the assistance of living organisms, through agents like wind or water. Around 80% of pollination is biotic-- at least 100,000 different species of animals pollinate the estimated 250,000 species of flowering plants in the world (Penn State). Pollinators promote local biodiversity in their ecoregions and are vital to many of the essential crops used for human consumption. Klein et al. found that 87 crops, 70% of the 124 most important food crops used for human consumption globally, are dependent on pollinators (Klein, 2007). Insect pollination is a production practice used extensively by farmers all over the world for producing crops (Kearns, 1998). Widespread pesticide usage, climate change, and destroyed habitats are leading to a loss in biodiversity and a considerable decline in pollinator communities. It is imperative for us to increase education around the significance of pollinators, and work to reverse the anthropogenic causes of dwindling pollinator populations. While bees have long been a vital part of preserving biodiversity and sustaining human agricultural systems, the plight to save the bees has generated considerable buzz in the last few years related to the recent phenomenon of Colony Collapse Disorder. During the winter of 2006-2007, beekeepers began to report unusually high losses of 30-90 percent of their hives. As many as half of affected colonies demonstrated symptoms inconsistent with any known causes of honeybee death (EPA, 2017). The problem is clear--the bees are disappearing. The question becomes what does that mean, and how do we fix it? The large scale answer must include a careful consideration of current agricultural practices and the factors that are contributing to losses in biodiversity. But on a small scale, everyone can help support local pollinator populations-- as long as they have access to the right media to guide them. For my thesis project, I decided to build a website that allows users to input their zip code in order to receive information on which types of native pollinator-friendly plants are best suited to grow in their specific ecoregion.
455

Análise de guias culturais da Área de negociação à luz da teoria da Inteligência Cultural: o caso da cultura árabe / Analysis of cultural guides from the area of negotiation under the light of Cultural Intelligence\'s theory: the case of arab culture

Andréia Lopes da Costa 14 September 2009 (has links)
Este trabalho traz um exame dos guias classificados como culturais, e elaborados especificamente para a área de comércio internacional. Procura verificar a qualidade das informações neles contida a respeito da cultura em geral e da cultura árabe em particular, e também sua eficácia no processo de contato intercultural, verificando se de fato cumprem seu papel de guiar o leitor rumo ao conhecimento das características culturais do país alvo, com a intenção de possibilitar e facilitar o contato entre diferentes culturas. O exame desses guias é feito a luz da Inteligência Cultural, conceito relativamente novo que propõe o desenvolvimento de habilidades e de flexibilidade para aprender e assimilar aspectos de uma cultura. / This work brings an examination of the guides classified as cultural guides, elaborated specifically for the area of international commerce. Its aim is to verify the quality of the information contained in them about culture in general and, the Arab culture particularly; and so its efficiency in the process of intercultural contact, verifying whether in fact they fulfill the role of guiding the reader onto the path of knowledge of cultural characteristics about a particular country, with the intention of making contact possible and facilitating the contact between different cultures. The examination of these guides is made through the theory of Cultural Intelligence, a concept relatively new which is centered on the development of skills and flexibility to learn and assimilate aspects of a new culture.
456

Revisão dos modos espúrios na análise modal de guias de onda por elementos finitos / Review of spurious modes in the modal analysis of waveguides using finite elements

Peternella, Fellipe Grillo 20 August 2018 (has links)
Orientador: Hugo Enrique Hernandez Figueroa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-20T11:52:35Z (GMT). No. of bitstreams: 1 Peternella_FellipeGrillo_M.pdf: 1154928 bytes, checksum: 3baba2c7d322af524dd1a6e07ee0e918 (MD5) Previous issue date: 2012 / Resumo: Desde as primeiras formulações em elementos finitos para o eletromagnetismo, os modos espúrios sempre foram um empecilho para a analise modal. Inicialmente, elementos nodais foram utilizados a fim de resolver a equação vetorial de onda no domínio da frequência. Naquele momento, os modos espúrios eram encontrados espalhados pelo espectro, o que dificultava a distinção entre soluções físicas e soluções espúrias. Anos mais tarde, o problema foi aparentemente resolvido pelo uso de elementos de aresta na equação vetorial de onda. Essa nova aproximação não eliminava por completo as soluções não físicas, apenas as confinava em torno do autovalor zero, o que não era problema na maioria das situações na analise modal. Recentemente, novas aplicações de elementos finitos no domínio do tempo resultaram em soluções instáveis, devido a presença dos modos espúrios em baixas frequências. Na década de 1990, Demkowicz[1], propôs uma formulação diferente em elementos finitos usando uma combinação da equação vetorial de onda com a condição do divergente de Gauss, que eliminou por completo os modos espúrios. O objetivo deste trabalho e analisar o impacto da condição de Gauss no FEM e entender como a mesma elimina os modos espúrios / Abstract: Since the earlier finite elements formulation for electromagnetics, spurious solutions have always plagued the modal analysis. Initially, nodal elements were employed to solve the vectorial wave equation in frequency domain. At that moment, the spurious modes could be found spread in frequency spectrum, and it was hard to distinguish between physical solutions and spurious ones. Some years later, this issue was apparently solved by using in the edge elements. This new approach does not completely eliminate non-physical solutions, but only confine them around to zero eigenvalue, which is not a problem in most of the situations in modal analysis. Recently, new applications of finite elements in time domain resulted to instable solution behavior, due to spurious modes at low frequencies. In the nineties, Demkowicz [1] proposed a different FEM formulation using a combination of vectorial wave equation and Gauss divergent equation, which definitely eliminates the spurious modes. The goal of this work is to analyze the impact of the Gauss condition in FEM and understand how it can eliminate spurious modes / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica
457

[en] ANALYSIS OF IRIS TYPE WAVEGUIDE DISCONTINUITIES / [pt] ANÁLISE DE DESCONTINUIDADES DO TIPO ÍRIS EM GUIAS DE ONDA

MARIA APARECIDA GONCALVES MARTINEZ 16 January 2007 (has links)
[pt] No presente trabalho, diversos métodos de análise são aplicados ao problema de íris em guias de onda. É feita, inicialmente, uma análise da teoria de pequenas aberturas. Uma verificação, através de comparação de resultados teóricos com experimentais, determina a faixa de validade e precisão da teoria. A seguir, aplica-se o método dos momentos, em particular para íris circulares em guias circulares e íris retangulares em guias retangulares. Para o caso da íris retangular em guia retangular, problemas de convergência relativa e séries lentas, típicos do método dos momentos, são contornados pela escolha adequada das funções de base e pela transformação de séries auxiliares de correção. Resultados experimentais mostram boa concordância com valores teóricos, para diversos valores de freqüência e dimensões de íris considerados. / [en] In this work, different methods are applied to iris - type discontinuity problems in waveguides. At first, the diffraction theory by small holes is considered. Theoretical results are compared with experimental ones and the accuracy and application range of the theory are verified. Further, the moment method is applied particularly to circular irises in circular waveguides and retangular irises in retangular waveguides. In the case of retangular irises in retangular waveguides, an acceleration procedure besides an special kind of basis functions is used to circumvent problems associated with relative convergence problem and slow convergent series. Experimental results are compared with theoretical ones and good accuracy is achieved for different frequencies and irises dimensions.
458

The mastering of life skills by disadvantaged black pupils in a dominantly white school

Harmer, Lawrence Peter 23 July 2014 (has links)
D. Ed. (Multiculturalism and Education) / This research will look at specific problem areas specifically pertaining to life skills which hamper the disadvantaged pupil in his development in the formal and non-formal educational sector of the school. with these identified factors, I aim to develop an acceptable information base for staff who have no in-service training as to how to assist, handle and participate with the sudden influx of disadvantaged pupils. This study is therefore aimed at gaining information to assist the teacher as well as the pupil. Reasons for the non-performance and thus the high failure rate, will also be noted in this study. One of the aims is to use pupil feedback extensively for the required information. My final aim is to illicit future research in this direction, thus assisting all parties.
459

Controlled Languages in Software User Documentation

Steensland, Henrik, Dervisevic, Dina January 2005 (has links)
In order to facilitate comprehensibility and translation, the language used in software user documentation must be standardized. If the terminology and language rules are standardized and consistent, the time and cost of translation will be reduced. For this reason, controlled languages have been developed. Controlled languages are subsets of other languages, purposely limited by restricting the terminology and grammar that is allowed. The purpose and goal of this thesis is to investigate how using a controlled language can improve comprehensibility and translatability of software user documentation written in English. In order to reach our goal, we have performed a case study at IFS AB. We specify a number of research questions that help satisfy some of the goals of IFS and, when generalized, fulfill the goal of this thesis. A major result of our case study is a list of sixteen controlled language rules. Some examples of these rules are control of the maximum allowed number of words in a sentence, and control of when the author is allowed to use past participles. We have based our controlled language rules on existing controlled languages, style guides, research reports, and the opinions of technical writers at IFS. When we applied these rules to different user documentation texts at IFS, we managed to increase the readability score for each of the texts. Also, during an assessment test of readability and translatability, the rewritten versions were chosen in 85 % of the cases by experienced technical writers at IFS. Another result of our case study is a prototype application that shows that it is possible to develop and use a software checker for helping the authors when writing documentation according to our suggested controlled language rules.
460

Design of substrate integrated waveguide H-plane horn antenna with symmetric beamwidths

Iqbal, Farzeen 16 August 2017 (has links)
Millimeter-wave Substrate Integrated Waveguide (SIW) technology presents itself as the most viable solution for the development of RF systems. It is a cost-e ective solution, suitable for mass production of such systems. Like planar circuits, SIW structures are compact, light weight and easy to fabricate. They also preserve some of the major advantages of metallic waveguides, namely, low loss, high quality factor and high power handling capabilities. In RF systems, rectangular waveguide horns have found various applications due to their exceptional radiation properties. From their simple construction, ease of ex- citation, usefulness and high gain, they are readily used as feed component in various RF systems, they also aid as the standardization for calibration and gain measure- ments of other high gain antennas. We are aware that, in an H-plane horn antenna, the rectangular waveguide is flared in the direction of the H-field. A large aperture in the H-plane presents the narrower half power beamwidth whereas a small aperture in the E-plane gives a wider beamwidth. In this research, the design of a SIW H- plane horn antenna with approximately symmetric half power beamwidths in both the E- and H-planes is proposed, using the commercially available electromagnetic field solver CST Microwave Studio to design and simulate proposed antenna characteristics and performance. Also, radiation patterns are analyzed and in order to validate the simulation results, measurements are performed on a fabricated prototype antenna. / Graduate

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