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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.
291

A Gameful Quest to Make Second Language Acquisition Fun

Andersson, Erik Olov Mårten January 2015 (has links)
This study explores the application of principles from game design, and the motivational psychology it is founded upon, to the domain of second language acquisition. A gameful design process based on playtesting andanalysis with design lenses is adapted and used to iteratively design and develop a system for conversation practice with the goal of creating a motivating and engaging experience.The results indicate effectiveness of the process, but generalizing the results would require further research with bigger sample sizes and studies with varied core activities.
292

A Content-Aware Design Approach to Multiscale Navigation

Pindat, Cyprien 20 December 2013 (has links) (PDF)
Computer screens are very small compared to the size of large information spaces that arise in many domains. The visualization of such datasets requires multiscale navigation capabilities, enabling users to switch between zoomed-in detailed views and zoomed-out contextual views of the data. Designing interfaces that allow users to quickly identify objects of interest, get detailed views of those objects, relate them and put them in a broader spatial context, raise challenging issues. Multi-scale interfaces have been the focus of much research effort over the last twenty years.There are several design approaches to address multiscale navigation issues. In this thesis, we review and categorize these approaches according to their level of content awareness. We identify two main approaches: content-driven, which optimizes interfaces for navigation in specific content; and content-agnostic, that applies to any type of data. We introduce the content-aware design approach, which dynamically adapts the interface to the content. The latter design approach can be used to design multiscale navigation techniques both in 2D or 3D spaces. We introduce Arealens and Pathlens, two content-aware fisheye lenses that dynamically adapt their shape to the underlying content to better preserve the visual aspect of objects of interest. We describe the techniques and their implementation, and report on a controlled experiment that evaluates the usability of Arealens compared to regular fisheye lenses, showing clear performance improvements with the new technique for a multiscale visual search task. We introduce a new distortion-oriented presentation library enabling the design of fisheye lenses featuring several foci of arbitrary shapes. Then, we introduce Gimlens, a multi-view detail-in-context visualization technique that enables users to navigate complex 3D models by drilling holes into their outer layers to reveal objects that are buried into the scene. Gimlens adapts to the geometry of objects of interest so as to better manage visual occlusion problems, selection mechanism and coordination of lenses.
293

Cosmic applications of gravitational lens assisted spectroscopy (GLAS)

Thanjavur, Karunananth G. 19 November 2008 (has links)
The principal observational contribution of this thesis is an innovative technique, using spatially resolved spectroscopy of highly magnified, gravitationally lensed galaxies, to study their internal structure and kinematics at redshift, z≥1 on sub-galactic scales. The scientific objective is to measure the important, but poorly understood, role of star formation and associated feedback on galaxy evolution. With Gemini GMOS-IFU observations of CFRS03+1077, a lensed galaxy at z=2.94, we determined surface brightness and integration time requirements for spatially resolved kinematics with spectra in the visible region (< 1 micron). For reasonable exposure times the presence of a strong emission line is key, limiting the redshift range to < 1.5 for [OII]3727Å. To tackle the lack of suitable lenses for such studies, we designed a lens search algorithm suitable for multi-color photometric data (with a minimum of 2 colors). Our method uses a two-step approach, first automatically identifying galaxy clusters and groups as high likelihood lensing regions, followed by a dedicated visual search for lensed arcs in pseudo-color images of sub-regions centered on these candidates. By using the color-position clustering of elliptical galaxies in high density environments, the algorithm efficiently isolates candidates with a completeness ≥ 80% for z ≤ 0.6 in Monte-Carlo simulations. Implemented on the CFHT Legacy Survey-Wide fields with available g, r and i photometry, the present yield is 9 lenses (8 new and 1 previously known) from 104 deg². With Gemini GMOS, we confirmed two lensed galaxies with strong [OII]3727Å emission suitable for IFU spectroscopy. The follow-up of both systems, the confirmation of remaining lenses and the application of the lens detector to the remaining 91 square degrees of CFHTLS-Wide are ongoing. In a complementary project, we aim to understand non-linear structure formation within the Λ-CDM framework by characterizing the mass distributions and mass/light ratios of galaxy groups; these structures (where 60% of all galaxies reside), have masses representative of the critical break between cluster and field galaxy mass scales. We use strong gravitational lensing to constrain the mass in the inner core, with velocity dispersion measurements from MOS spectroscopy to map the mass distribution up to the scale of the virial radius. The formalism supporting this approach as well as the tools for analysis (including an efficient B-spline based method for flat fielding and sky subtraction of sky limited spectra) are presented in this thesis. The deflectors of 6 lenses in our catalog resemble galaxy groups suitable for this study. One group, for which the observations are complete, is compatible with either NFW or Hernquist profile; these results will be corroborated with observations of other candidates in forthcoming observing programs. The objective is to amalgamate our results with mass measurements from weak lensing and X-ray observations from our Strong Lensing Legacy Survey (SL2S) collaborators to build a comprehensive picture of the dark matter profile and thus constrain theoretical predictions of mass assembly in galaxy groups.
294

Avaliação dos métodos biométricos do olho humano empregados no cálculo do poder dióptrico da lente intra-ocular / Evaluation of the biometric methods used for the human eye axial measurements on intraocular lens calculation

Oliveira, Filipe de [UNIFESP] 27 January 2010 (has links) (PDF)
Made available in DSpace on 2015-07-22T20:49:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-01-27 / Objetivo: Avaliar os métodos biométricos do olho humano em pacientes portadores de catarata e com indicação de implante de lente intra-ocular. Métodos: Oitenta e quatro pacientes com média de idade de 58,82 ± 10,03 anos foram submetidos às biometrias óptica e ultra-sônica (imersão e contato) em ambos os olhos (n = 168). Os dados do comprimento axial, profundidade da câmara anterior, espessura do cristalino, profundidade da câmara vítrea e curvatura da córnea foram analisados. Foi avaliada a diferença das médias de cada método biométrico usado e a concordância foi investigada pela análise gráfica intra-individual de Bland-Altman de um método em relação ao outro. Resultados: Não houve diferença estatisticamente significante para as médias do comprimento axial (P=0,245), profundidade da câmara anterior (P=0,073), espessura do cristalino (P=0,8794) e profundidade da câmara vítrea (P=0,7640) entre os métodos usados. A diferença das médias da curvatura da córnea entre o IOLMaster® e o ceratômetro manual OM-4® foi estatisticamente significante (P<0,0001). Apesar da boa reprodutibilidade dos resultados, os gráficos de Bland- Altman mostraram algumas medidas fora dos limites de concordância estabelecidos em todas as variáveis analisadas. Houve menor concordância das medidas ceratométricas na comparação entre o IOLMaster® e o ceratômetro OM- 4®. Conclusões: Não houve diferença das médias dos métodos biométricos usados nesse estudo, exceto a curvatura da córnea que apresentou uma diferença estatisticamente significante entre as médias apresentadas. Os métodos demonstraram boa concordância, entretanto algumas medidas se apresentaram discordantes e podem ocasionar erros no cálculo do poder dióptrico da lente intraocular. / TEDE / BV UNIFESP: Teses e dissertações
295

Desenvolvimento de processos de deposição de filmes filmes sobre substratos polimericos fotopolimerizdos / Development of process of deposition of thin films on photopolymerization polymeric substrats

Vieira, Adalena Kennedy 29 November 2007 (has links)
Orientador: Edison Bittencourt / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-09T15:54:46Z (GMT). No. of bitstreams: 1 Vieira_AdalenaKennedy_D.pdf: 3876527 bytes, checksum: 24d0e24d715ff4f8fefc97ffd5a4e1b9 (MD5) Previous issue date: 2007 / Resumo: Em todo o mundo inicia-se uma nova era. A qualidade de vida e segurança dependem cada vez mais da capacidade de toda humanidade em resolver problemas cada dia mais complexos e demorados. Com o advento da comunicação e a globalização o tempo cada vez mais torna-se um bem escasso e precioso. Os materiais semicondutores usados para desempenhar as funções lógicas e de memória de alta velocidade utilizados no processamento de informação e hardware de armazenagem são os materiais mais difíceis de serem produzidos. Com relação a estes materiais nesta indústria, a capacidade de transformação é enorme, pois o que era o equipamento mais moderno num piscar de olhos passa a ser obsoleto. Assim, avanços nas áreas de tecnologias de informação estão relacionados a avanços em semicondutores e conseqüentemente em materiais. Conforme aumenta a funcionalidade dos chips, aumentam também substancialmente as alternativas para melhorá-los, porque a demanda por este produto não para de crescer e aumenta exponencialmente com relação à população que os consome. Para satisfazer à demanda por densidades mais elevadas nos chips, serão necessárias novas tecnologias de empacotamento e interconexão e a integração destas com toda a tecnologia microeletrônica. É, pois, neste contexto que se insere o presente trabalho. Um dos objetivos principais foi a obtenção de uma cobertura que pode ser um início de uma nova tecnologia para o desenvolvimento de um ¿microchip¿ sobre materiais poliméricos. É o nascer de uma nova era na área de materiais e dispositivos eletro-eletrônicos. Para a indústria nacional e para o Pólo Industrial de Manaus, talvez seja uma tecnologia de ponta com um material mais barato e acessível a todos. Para a execução deste trabalho foram feitos planejamentos experimentais visando melhorar as condições ¿ótimas¿ para o recobrimento por spin coating. Através da deposição de filmes de óxido de silício sobre lentes oftálmicas produziu-se os filmes de óxido de sílicio que foram depositados através de um reator de Microwave Electron Cyclotron Resonance, com o auxílio de um campo magnético em um plasma constituído por uma mistura de argônio, oxigênio e silana. Esse método de deposição é conhecido como ¿ECR¿. A estrutura dos filmes de óxidos de silício depositados foi estudada através de transmitância na região do visível. A morfologia das superfícies recobertas com os filmes foi analisada por Microscopia Óptica e também através de Microscopia de Varredura Eletrônica (MEV). Os resultados de transmitância para os filmes mostram que na medida em que a camada é depositada são formadas estruturas que melhoram a proteção oferecida pela cobertura. As micrografias ópticas revelaram que as lentes sofrem um ¿stress¿ em razão da diferença do coeficiente de expansão entre os dois materiais. As micrografias de MEV mostraram, também, que as superfícies melhores protegidas pelo óxido de silício são as obtidas através de fabricação e moldagem feita com resina acrílica, como comprovam os testes anti-risco. A análise de ângulo de contato do filme mostrou que a cobertura serve como camada aderente ao polímero, mas não como camada hidrofóbica, pois o polímero ainda assim absorve água. As medidas de parâmetros S encontradas foram tiradas com base nas características dos protótipos ensaiados e de acordo com as limitações da resposta em frequência do equipamento utilizado para o ensaio. O resultado dos ensaios também não pode ser melhor detalhado, pois o material foi depositado sem a expectativa dessa finalidade inicialmente. Podemos, entretanto, comprovar que a metodologia é viável e a partir do mesmo principio poderão ser desenvolvidas diversas utilidades para essa técnica inovadora / Abstract: A new era has begun all around the world. The quality of life and health depends more and more on the human capacity of resolving problems that are becoming longer and more complex day by day. As communication and globalization advance, time becomes scarcer and more precious. The semiconductor materials which are used to activate the logical functions, the high velocity memory used in processing information and the storage ¿hardware¿ are the most difficult materials produced in this area. The ability to change is enormous, due to the fact that what was considered the most modern equipment has become obsolete in the blink of an eye. Consequently, the advances in the areas of technological information are related to the advances in those in semiconductors and as result in materials. As the use of the ¿chip¿ increases, the alternatives also become varied, with the objective of improving the chip¿s functions, this is because the demand for the product is getting stronger, increasing, when referring to the population, the search for these products. This study has achieved a covering which can be perceived as a beginning to New Technology, in order to create a ¿microchip¿ with polymeric materials. It¿s the start of a new era when dealing with the area of electro-electronic materials and models. For the National Industry and for Manaus¿ Industry Pole, it might be viewed as cheaper and more accessible technology for all. An adaptation of a reactor has become full filled that produces electronic components for a deposition on a polymer substratum (ophtalmic lenses) for the attainment of a treatment of alternative anti-reflexive. This methodology is used in the industry of electronic components, more known as "chip". In this work they had been experiment design facts to optimize the excellent conditions for the covering for spin coating. Through the deposition of silicon oxide films on ophtalmic lenses one produced the silicon oxide films that had been deposited through a reactor of Microwave Electron Cyclotron Resonance, with aid of a magnetic field, a plasma constituted by a mixture of argon, oxygen and silane.This method of deposition is known as "ECR". The structure of deposited the silicon oxide films was studied through transmittance in the region of the visible light. The morphology of the surfaces re-covered with the films was analyzed by Optic Microscopy and also through Scanning Electron Microscopy Analysis (MEV). The results of transmittance for the films show that the measure where the layer is deposited form structures that improve the protection offered for the covering. The MEV micrographs had shown, also, that the surfaces best protection for silicon oxide are the gotten ones through acrylic resin, as they prove the anti-risk tests. The analysis of angle of contact of the film showed that the covering does not serve as hydrophobic layer. The measurements of parameter S which were found, were based on characteristics of the resulted prototypes and the answer limitations regarding the frequency of the equipment used for these readings. Moreover, the overall results can¿t be better detailed due to the fact that the material wasn¿t deposited with this objective. The methodology is viable, and based on the same principles it can develop diverse utilities to this innovate technique / Doutorado / Ciencia e Tecnologia de Materiais / Doutor em Engenharia Química
296

Micro-concentrateurs de lumière à base de métamatériaux polymères pour la détection infrarouge / Wavelength-scale light concentrators made of polymer metamaterials for infrared applications

Moughames, Johnny 13 July 2016 (has links)
Dans cette thèse, nous développons des micro-concentrateurs de lumière en vue d’applications dans l’infrarouge. Les optiques, plates, de dimensions comparables à la longueur d’onde, sont formées d’une couche micronique de métamatériau, constituée de polymère structuré par des trous d’air. Une focalisation dans la zone de Fresnel des structures est recherchée en réalisant un gradient d’indice, obtenu en variant le diamètre des inclusions d’air (de λ//20 à λ/8). Des simulations électromagnétiques sont d’abord effectuées pour valider un design. La fabrication de ces concentrateurs repose sur la structuration d’une couche de photorésine à l’aide d’une technique de lithographie optique 3D à deux photons. Les mesures obtenues par l’imagerie infrarouge des structures montrent l’obtention d’une focalisation en accord avec les simulations pour un volume de concentrateur de 1,5 λ³, en dépit de l’absorption résiduelle de la résine choisie. Les structures proposées sont invariantes dans la direction axiale et peu épaisses, et peuvent donc être transférées dans d’autres types de matériaux ayant des indices de réfraction plus importants, comme le silicium. Les structures proposées peuvent également servir de plateforme pour réaliser un confinement sub-longueur d’onde par l’ajout d’antennes plasmoniques / In this thesis, we develop flat light concentrators for infrared applications. The structures have dimensions comparable with the wavelength and are made of a metamaterial layer (few microns) made of polymer with air holes inclusions. Light focusing in the Fresnel zone of the structures is achieved by a gradient index profile obained by chirping the holes diameter (from λ//20 to λ/8). Electromagnetic simulations are first performed to validate a design. The fabrication of these concentrators is then made by direct laser writing using a 3D two-photon lithography technique. Infrared imaging of the structures reveals a clear focusing of the infrared light for concentrators volume as small as 1,5 λ³, in agreement with the electromagnetic simulations. Considering that the metamaterial concentrator slabs are invariant in the axial direction and not too thick, similar structures can be transferred in transparent substrates such as silicon using deep reactive ion etching. A subwavelength light confinement can also be exploited by adding plasmonic antenna on the top surface of the flat concentrators
297

Metamaterials for surface plasmons / Métamatériaux pour les plasmons de surface

Kadic, Muamer 29 November 2011 (has links)
Le travail présenté dans cette thèse comporte différents attrayant sujetsde l'optique comme les métamatériaux, l’optique transformationnelle, lescristaux photoniques, la réfraction négative et les interactions thermoplasmoniques.Nous avons développé plusieurs métamatériaux pour les plasmons desurface basés sur l'optique de transformation. Tout d'abord, nous avonsdémontré théoriquement, numériquement et expérimentalement certainsdispositifs mettant en scène le phénomène d’invisibilité.Deuxièmement, nous avons démontré la réfraction négative des plasmonsde surface en utilisant le concept d'espace de pliage (space folding) pourdes lentilles plates et anisotropes et enfin avec seulement desmétamatériaux diélectriques. Additionnellement, nous avons démontréqu’un damier structuré de films d'or peut exhiber une transmission extraordinairesur toute la gamme de fréquences visible.Enfin, nous avons étudié un problème multiphysique en mixant l'optiqueet thermique et leurs effets induits. Nous avons pu montrer que joueravec l'amplitude d'une onde électromagnétique ou une impulsion, peutinduire un gradient de température et le contrôle parfait d’un tel dispositifthermo-plasmonique. / The work which has been presented in this thesis includes differentappealing subjects of optics such as metamaterials, transformationaloptics, photonic crystals, negative refraction and thermo-plasmonicinteractions. In this manuscript we have developed several metamaterialsfor Surface Plasmon Polaritons based on the transformational optics.Firstly we have demonstrated theoretically, numerically andexperimentally some SPP cloaking devices. Secondly, we havedemonstrated SPP negative refraction using the concept of space foldingthen with some dielectric metamaterial, flat and anisotropic SPP lenses.Additionaly we have demonstrated that subwavelength checkerboardstructured thick gold films have demonstrated an extra-ordinarytransmission over the visble range of frequencies.Finally, we have investigated a general multiphysics problem to mix opticsand thermally induced effects. We have been able to show that playingwith the amplitude of an electromagnetic wave or a pulse, we can inducea gradient of temperature and control heat of a plasmonic device.
298

Étude des propriétés du moment angulaire orbital des ondes EM : développement de capteurs, transfert de moment et applications / Study of the properties of the orbital angular momentum of EM waves : development of sensors, transfer of moment and applications

Niemiec, Ronan 08 December 2014 (has links)
Une onde électromagnétique est définie par son amplitude, son vecteur d'onde, sa fréquence et son moment angulaire. Ce dernier peut être séparé en deux parties : la polarisation (associée au moment angulaire de spin), et le moment angulaire orbital. Ce dernier n'a vraiment été étudié qu'à partir de ces dernières années. Cette thèse a pour but d'approfondir les connaissances sur ce moment angulaire orbital. Des prototypes ont ainsi été réalisés, et des outils d'analyse ont été développés. Dans un premier temps, une étude du transfert de ce moment angulaire orbital à un objet macroscopique, à la fréquence de 870 MHz, est présentée. Une interprétation du mécanisme de transfert est ensuite proposée, supportée par le calcul des équations de champs et des simulations électromagnétiques. Dans un second temps, la conception et la réalisation de deux antennes, pouvant générer une onde possédant un moment angulaire orbital, sont présentées. Ces deux antennes utilisent une lame de phase avec une loi à dépendance angulaire. La première est une lame de phase dite « spirale », à permittivité constante et à hauteur variable. La seconde est une lame à gradient d'indice, à permittivité variable et à hauteur constante. Ces deux antennes ont été simulées, puis mesurées au sein de la chambre anéchoïque CHEOPS (DGA-MI, Bruz). Des cartographies sur un plan du champ ont ainsi été obtenues. Dans un dernier temps, la réflexion sur des surfaces courbes et planes, et l'influence de l'échantillonnage sur l'estimation des modes d'OAM, ont été étudiées. En ce qui concerne la réflexion, les résultats de simulations sont prometteurs, et semblent indiquer l'existence d'une relation entre les déformations du faisceau réfléchi et le type de surface. Pour l'estimation des modes d'OAM, les valeurs de champs sont extraites sur un cercle. Différents paramètres (positionnement et rayon du cercle) ont été considérés, et une méthode d'estimation des modes d'OAM sur une large bande de fréquence est proposée. / An electromagnetic wave is defined by its amplitude, its wave vector, its frequency and its angular momentum. This momentum can be decomposed into two components: polarization (associated to spin angular momentum), and orbital angular momentum. The later has not been investigated thoroughly until the last few years. To deepen the knowledge on orbital angular momentum, both prototypes and analysis tools have been developed in this thesis. First, study of orbital angular momentum transfer to a macroscopic object, at a frequency of 870 MHz, is presented. An interpretation of the transfer mechanism is then proposed, supported by the calculation of field equations and electromagnetic simulations. Secondly, the conception and the realization of two antennas able to generate an EM wave with orbital angular momentum are presented. These antennas use phase plates with an angular dependent law. The first one is a “spiral” phase plate, with constant permittivity and variable height. The second one has variable permittivity and constant height. Both have been simulated and characterized in CHEOPS anechoic chamber (DGA-MI, Bruz). Measurements of magnitude and phase, on a plane, have been obtained. Lastly, total reflection on planar and curved surfaces and influence of sampling on OAM modes estimation were investigated. Simulation results of reflected waves are promising and show a relationship between the induced deformations and the object reflected on. As for OAM modes estimation, study has been performed using an extraction circle on the wave front. Several parameters (center of the circle, radius) have been considered, and a method for OAM modes estimation on a large bandwidth is proposed.
299

Axial scanning and spherical aberration correction in confocal microscopy employing an adaptive lens

Philipp, Katrin, Lemke, Florian, Wapler, Matthias C., Koukourakis, Nektarios, Wallrabe, Ulrike, Czarske, Jürgen W. 13 August 2020 (has links)
We present a fluid-membrane lens with two piezoelectric actuators that offer versatile, circular symmetric lens surface shaping. A wavefront-measurement-based control system ensures robustness against creeping and hysteresis effects of the piezoelectric actuators. We apply the adaptive lens to correct synthetic aberrations induced by a deformable mirror. The results suggest that the lens is able to correct spherical aberrations with standard Zernike coefficients between 0 μm and 1 μm, while operating at refractive powers up to about 4m-1. We apply the adaptive lens in a custom-built confocal microscope to allow simultaneous axial scanning and spherical aberration tuning. The confocal microscope is extended by an additional phase measurement system to include the control algorithm. To verify our approach, we use the maximum intensity and the axial FWHM of the overall confocal point spread function as figures of merit. We further discuss the ability of the adaptive lens to correct specimen-induced aberrations in a confocal microscope.
300

Mapování akrečního disku kvasaru gravitačním mikročočkováním / Quasar accretion disk mapping by gravitational microlensing

Ledvina, Lukáš January 2014 (has links)
Quasar microlensing is a relatively newly explored phenomenon, which is ideally suited for studying the spatial distribution of emission from the innermost accretion disc. By now we know many macrolensed quasars, in which we can observe multiple images formed by the deflection of light in the gravitational field of an intervening galaxy. In case one of these images passes directly through the stellar population of the galaxy, it can be additionally microlensed by individual stars. The gravitational field of these stars forms a caustic network for light passing by. When a quasar accretion disc crosses behind this network, induced changes can be observed in the light curve as well as in the spectrum. In the first part of this thesis we study the statistics of the time intervals between successive caustic crossings. In the second part we use a fully relativistic Kerr-metric thin-disc model for studying the light curve of a fold-caustic crossing and its dependence on the accretion- disc parameters. In the last part we simulate changes in the X-ray iron-line profile during a fold-caustic crossing. We find characteristic spectral features formed on the line, and derive their analytical description. Finally, we map the maximum strength of microlensing-generated peaks on the spectral line for different...

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