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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.
181

Liquid crystals with novel terminal chains as ferroelectric liquid crystal hosts

Cosquer, Guirec Yann January 2000 (has links)
No description available.
182

Rhythms Of Times And Places

Pope, Bettye 10 March 2012 (has links)
Artist Statement I am inspired by living in multiple environments and experiencing many regions of the United States. My imagery varies from references to landscapes to geometric abstractions of quilt patterns. My media consists of acrylics, oils, and pastels on supports including fabric, canvas, or paper. Mixed media allows me to add multiple layers in creating visual textures, depth, and energy to draw in my viewers. The media is glazed, flowed, dripped, sprayed, rolled, scraped, and scrubbed into my interpretations of natural elements and geometric patterns. My landscape paintings are of observations of nature, and I attempt to capture the power, motion, and energy of a moment in time. I paint from memory and purposely filter the images, simplifying and strengthening the focus of the captured moment. Rhythmic patterns in nature and seasonal light on the land are sources of my visual stimulation. My affinity for geometric shapes and patterns is sometimes expressed in abstract paintings of quilt patterns. I form rhythmic compositions and enhance the patterns with delicate brushwork and several glazed layers for added surface interest. These patterns of quilts are also reminiscent of landscapes from a bird’s eye view.
183

Preparation and characterisation of thin film CdS/CdTe solar cells produced by close space sublimation

Alamri, Saleh Naeeman O. January 1999 (has links)
No description available.
184

Synthèse de nanoparticules de forme, taille et dispersion contrôlées pour l'élaboration de couches composites aux propriétés optiques modulables / Synthesis of nanocrystals with tunable shape, size and dispersion for the elaboration of composite films with tunable optical properties

Pourcin, Florent 08 November 2018 (has links)
Les nanoparticules de métaux nobles possèdent des propriétés optiques étonnantes. Sous l’effet de la lumière, elles sont capables de résonner pour générer des plasmons de surface localisés. Ces plasmons absorbent ou diffusent la lumière aux longueurs d’ondes de ces résonnances et sont fortement dépendants de la forme, de la taille et de l’environnement des nanoparticules. Dans ce manuscrit, elles sont impliquées dans la conception de matériaux furtifs à des fins militaires.Des nanoparticules d’argent de formes contrôlées ont été associées à un polymère pour élaborer de nouveaux matériaux hybrides déposables par voie liquide sous la forme de couches minces.Un absorbeur quasi-parfait (98,8%) sur une gamme étroite de longueur d’onde a été obtenu en maintenant une très bonne dispersion des nanoparticules dans la couche, alors qu’un absorbeur large bande efficace (~90%) sur toute la gamme spectrale du visible a été réalisé en provoquant l’agrégation des nanoparticules. Une étude qualitative par microscopie et spectroscopie sur la densité et l’organisation des nanoparticules au sein de la couche mince a mis en évidence la présence de couplages plasmoniques de natures et d’intensités différentes en fonction de l’espacement entre les cubes. Il a été montré que les propriétés optiques mesurées étaient indépendantes de la nature du substrat utilisé, mais aussi indépendantes de l’angle de la lumière incidente sur une large gamme angulaire. Enfin, des systèmes multicouches déposés par voie liquide ont été explorés afin d’étendre l’absorption des couches jusqu’au proche infrarouge par l’ajout de matériaux tel que le l’oxyde de tungstène. / Nanoparticles of noble metals have unexpected optical properties. Under the effect of light, they are able to resonate, generating localized surface plasmon resonances that are used in many applications. These plasmons absorb and scatter the light at the wavelengths of these resonances and are highly dependent on the shape, the size and the environment of the nanoparticles. In this thesis, they are applied for the design of stealth materials for military purposes. For this, controlled shapes of silver nanoparticles were blended within a polymer to develop new hybrid materials that are solution-processed as thin layers. A quasi-perfect absorber (98,8%) in a precise range of wavelengths has been obtained by maintaining well-dispersed nanoparticles in the layer, while an effective broadband absorber (~90%) over the entire visible range has been achieved by triggering the aggregation of the nanoparticles. Microscopy and spectroscopy qualitative studies performed on the density and organization of the nanoparticles within the thin layers revealed the presence of plasmonic couplings of different natures and intensities as a function of the spacing between the cubes. It has been shown that the optical properties measured are independent of the nature of the substrates used and independent of the angle of the incident light on a wide angular range. Finally, solution-processing of multilayers systems was explored to extend the absorption of the layers to the near infrared by the addition of other materials such as tungsten oxide.
185

Desempenho de camadas de proteção para geomembranas / Performance of protective layers for geomembranes

Geroto, Regis Eduardo 17 October 2008 (has links)
A eficiência das geomembranas como barreiras para controle e desvio de fluxo está diretamente relacionada com a integridade de sua superfície. Nos sistemas de impermeabilização basal, como utilizados em aterros sanitários, as geomembranas podem entrar em contato com materiais perfurantes e cortantes, como a brita do sistema de drenagem. Para prevenir perfurações e outros danos em geomembranas, são empregadas camadas de proteção, como geotêxteis não-tecidos e areia. Este estudo avalia o desempenho de geotêxteis não-tecidos de fibras curtas de poliéster (PET) e de polipropileno (PP), além de uma configuração com areia, como camadas de proteção para geomembranas de policloreto de vinila (PVC) e de polietileno de alta densidade (PEAD). Foram realizados ensaios índices, ensaios de puncionamento hidrostático e ensaios de carregamento estático em grande escala, para verificar os mecanismos de ruptura das geomembranas e o comportamento da resistência ao puncionamento com a adoção de camadas de proteção. Os resultados demonstraram desempenho superior, como elemento de proteção, dos geotêxteis de maior resistência mecânica e mecanismos de rupturas diferenciados entre geomembranas de PEAD e de PVC. / The efficiency of geomembranes as barriers for flow diversion is directly related to its integrity. In basal lining systems, such as those used in landfills and waste disposal lagoon, geomembranes can get into contact with sharp materials, such as gravel from the drainage system, which can induce excessive deformation and holes. To prevent geomembrane damage, nonwoven geotextiles and sand are usually employed as protective layers. This paper deals with the performance of polyester (PET) and polypropylene (PP) nonwoven geotextiles and a sand layer, as protective layers for polyvinyl chloride (PVC) and high density polyethylene (HDPE) geomembranes. Index, hydrostatic puncture and large-scale uniaxial compression tests were performed and have allowed understanding the geomembrane damage mechanism and the influence of protective layers properties in increasing the geomembrane performance against puncture. The test results have shown that the behavior in puncture protection is related to the mechanical resistance of geotextile and that the rupture mechanism is different for the different types of geomembrane used in the study.
186

A irmandade fraturada: a relação entre os intelectuais de esquerda e as camadas populares no filme Quase dois irmãos (Lúcia Murat, 2005) / The fractured brotherhood: the relationship between the left intellectuals and the popular layers in the film Almost two brothers (Lúcia Murat, 2005)

Batista, Grazieli Chirosse 18 October 2017 (has links)
Esta dissertação visa analisar a representação do relacionamento entre os intelectuais de esquerda e as camadas populares na obra cinematográfica Quase dois irmãos (Lúcia Murat, 2005). O filme representa, a partir de uma narrativa dramática, aspectos fundamentais das relações entre a classe média e as camadas populares. Através de três espaços temporais, década de 1950, 1970 e anos 2000, o contato entre a classe média e o morro carioca, são representadas as perspectivas dos intelectuais de esquerda referente a aproximação com o povo entre décadas de 1950 e 1970. O golpe militar de 1964 interromperia o momento de construção de projeto cultural de revolução social engendrado pelos intelectuais de esquerda, acirrando as tensões existentes entre os dois ethos sociais. Esta pesquisa busca compreender como essa construção ficcional, enquanto criação artística da diretora Lucia Murat, sedimenta na forma cinematográfica determinada compreensão do mundo, conectada à memória da ditadura militar de setores da esquerda brasileira. Configura-se uma fonte documental importante pela experiência histórica que está condensada em sua narrativa, assim como em sua estrutura estética que ratifica os movimentos históricos de permanência e cisão expostos no filme e possibilita reflexões sobre relações e problemas sociais e raciais no Brasil. / This dissertation aims to analyze the representation of the relationship between the left intellectuals and the popular strata in the cinematographic \"Almost brothers\" (Lúcia Murat, 2005). The film represents, from a dramatic narrative, fundamental aspects of the relationships between the middle class and the popular strata. Through three timelines, the 1950, 1970 and 2000 years, the contact between the middle class and the carioca Hill, are represented the perspectives of left-wing intellectuals for rapprochement with the people between 1950 and 1970 decades. The military coup of 1964 would interrupt the moment of construction of cultural project of social revolution engendered by leftist intellectuals, intensify existing tensions between the two social ethos. This research seeks to understand how this fictional construct, while artistic creation of director Lucia Murat, forms a sediment in cinematic form determined understanding of the world, connected to the memory of the military dictatorship of sectors of the brazilian left. Configures a document source important for historical experience that is condensed into your narrative, as well as in your aesthetic structure that ratifies the historical movements of permanence and spin-off exposed in the film and provides reflections on relationships and problems racial and social in Brazil.
187

Dynamic textile patterns : using Smart textile

Worbin, Linda January 2004 (has links)
It is the possibilities to create dynamic textile patterns in Smart Textiles that isin focus in this report. The result will be presented in form of different materialand pattern samples. The samples show both different technical solutions andinteractions needed to develop a dynamic textile pattern.My intention with this work is to enlarge the use of a decoration, as somethingmore than a static extra value. We do have a need for beautiful things in oursurrounding and I want to explore how dynamic patterns could give decorationan extended use. Where new kinds of values can be included, interaction and theinformation. The result can be applied in further research concerning bothwearables, fashion, soft furnishing as well as for public environment forcommunications. / <p>Program: Designteknikerutbildningen</p><p>Uppsatsnivå: D</p>
188

On pulsatile jets and related flows

Livesey, Daniel January 2017 (has links)
An overview of unsteady incompressible jet flows is presented, with the primary interest being radially developing jets in cylindrical polar coordinates. The radial free jet emanates from some orifice, being axisymmetric about the transverse (z) axis and possessing reflectional symmetry across its z=0 centreline. The radial wall jet is also axisymmetric about the transverse axis, however in this case impermeability and no-slip conditions are imposed at the wall, which is situated at z=0. The numerical solution of a linear perturbation superposed on the free jet, whose temporal form is assumed to be driven by a periodic source pulsation, gives rise to a wave-like disturbance whose amplitude grows downstream as its local wavelength decreases. An asymptotic analysis of this linear perturbation, which applies to the wall jet as well with some minor changes, captures the exact nature of the exponential spatial growth, and also algebraic attenuation of the growth. The linear theory is only valid for a small amplitude pulsation (|ε| << 1, where ε is the perturbation amplitude). When a nonlinear pulsation (ε = O(1)) is applied to the radial free jet, any linear theory must be dropped. Solving the full nonlinear system of equations reveals singular behaviour at a critical downstream location, which corresponds to the presence of an infinitely steep downstream gradient. The replacement of molecular diffusivity with a larger-scale eddy viscosity does little to affect the qualitative growth of the linear perturbation. In order for an experimental study to reproduce any of the discussed boundary-layer results, we must consider the behaviour of jet-type flows at finite Reynolds number. This involves solving the full Navier-Stokes equations numerically, to determine the Reynolds number at which we should expect to qualitatively recover boundary-layer behaviour. The steady solution for the radial free jet and its linear pulsation are studied in this way, as is the linear pulsatile planar free jet. We may enhance the streamwise velocity of a radial jet by applying swirl around the z axis. Modulating this swirl is looked at as a possible mechanism to induce the previously discussed pulsation, which then motivates the introduction of a finite spinning disk problem. In this case the system may be completely confined within an enclosed cylinder, making a hypothetical experimental approach somewhat more approachable.
189

Fabricação e caracterização de dispositivos poliméricos emissores de luz com camada ativa de poli(2-metóxi, 5-(2\'-etil-hexilóxi)-1,4-fenileno vinileno) (MEH-PPV) / Fabrication and characterization of polymer light-emitting diodes with active layer composed by poly(2-methoxy, 5-(2\'-etil-hexilhoxy)-1,4-phenilene vinilene) (MEH-PPV).

Gozzi, Giovani 20 February 2008 (has links)
Dispositivos poliméricos emissores de luz (Polymer Light Emitting Diodes - PLEDs) têm sido amplamente investigados devido à sua possibilidade de aplicação na fabricação de telas de projeção e displays. As principais vantagens dos materiais poliméricos, nesses casos, são o baixo custo e a possibilidade de processamento em superfícies de grande área, ao contrário do que ocorre para dispositivos contendo cristais líquidos (Liquid Crystal Display - LCD\'s). Apesar de amplamente investigados nos últimos anos, alguns aspectos fundamentais acerca dos mecanismos de injeção de carga nos PLEDs ainda não estão completamente elucidados. Nesta dissertação estudamos as propriedades ópticas, morfológicas e elétricas de dispositivos poliméricos emissores de luz contendo poli(2-metóxi, 5-(2\'-etil-hexilóxi)-1,4-fenileno vinileno) (MEH-PPV) como camada ativa. Inicialmente foi investigada a influência de camadas transportadoras de lacunas (Hole Transport Layer - HTL) e/ou elétrons (Electron Transport Layer - ETL) na eficiência dos dispositivos. As camadas HTL e ETL foram compostas de poli(3,4-etilenodioxithiofeno):poliestireno sulfonado (PEDOT:PSS), e poli(estireno-co-p-estireno sulfonado-co-metaacrilato de metila) (PS-co-SS-co-MMA), respectivamente. Os filmes de PEDOT:PSS foram depositados por centrifugação. Devido ao seu caráter isolante (condutividade elétrica 10-5 S/cm), e por ter nível energético HOMO (Highest Occupied Molecular Orbital) próximo ao nível de Fermi do ITO (Indium Thin Oxide), a utilização do PEDOT:PSS como camada reguladora da injeção de lacunas resultou num aumento do tempo de meia vida do dispositivo em cerca de 10 vezes. No caso de dispositivos contendo a camada de ETL, foi identificada a formação de estados localizados gerados pela sulfonação do poliestireno. Estes estados auxiliam no processo de tunelamento através da camada polimérica. Na segunda parte do trabalho, apresentada no capítulo 4, desenvolvemos um modelo teórico para descrever as regiões das curvas da densidade de corrente elétrica (J) vs. campo elétrico aplicado (F) (dependentes e independentes da temperatura). Este modelo é uma extensão do modelo de Arkhipov, onde inserimos um termo de injeção de carga via tunelamento Fowler-Nordhein através de uma distribuição gaussiana de barreiras de potencial de interface, além do termo de injeção via hopping, já tratado por Arkhipov. O modelo proposto ajustou satisfatoriamente as curvas de J vs. F tanto nos modo de polarização direta, quanto reversa. / Polymer light emitting diodes (PLEDs) have been widely investigated as candidate materials for display fabrication. The main advantages exhibited by PLEDs are the low-cost processing and possibility of large-area display fabrication, in comparison to the conventional liquid crystal displays (LCD\'s). Although the engineering aspects concerning device fabrication and characterization are well understood, some specific points regarding the electrical transport in the bulk and at the interfaces of the devices are not fully explained. In this study, we present a morphological, optical and electrical characterization of PLEDs containing poly(2-methoxi, 5-(2\'-etyl-hexiloxy)-1,4-phenilene vinilene) (MEH-PPV) as the emissive layer. We investigated the influence of hole transport layers (HTL) and/or electron transport layers (ETL) on the efficiency of the devices. The HTL and ETL comprised thin polymeric films of poly(3,4-etylenedioxythiphene):sulfonated polystyrene (PEDOT:PSS) and poly(estyrene-co-p-sulfonated styrene-co-metyl metacrylate) (PS-co-SS-co-MMA), respectively. Devices containing the PEDOT:PSS exhibited a life-time 10 times higher than the devices not containing the HTL material, which is probably due to the controlled hole injection that may be achieved in former devices. In the second set of devices, in which an ETL was incorporated, we observed the formation of localized states in the polymeric ETL layer, which was responsible for improving the tunneling process of charges injected from cathode. A theoretical model concerning the charge injection mechanisms in the PLEDs containing MEH-PPV is presented in chapter 4. The final device architecture was ITO/MEH-PPV/Al, and the J vs. F measurements were taken at temperatures between 120 K and 270 K. The model proposed here is a combination of the Arkhipov´s and Fowler-Nordhein tunneling models, considering a Gaussian distribution of triangular potential barriers. The model takes into account the charge carrier/image charge recombination probability at the interface of the electrode, being very appropriate to explain the dependence of the electric current on the temperature and applied electric field.
190

The Use of encapsulation techniques as an alternative to employment of soil contaminated by petroleum products in base and sub-base of pavement layers / O Uso da tÃcnica de encapsulamento como alternativa para o emprego de solo contaminado por derivados de petrÃleo em camadas de base e sub-base de pavimentos

Francisco das Chagas Isael Teixeira Cavalcante 13 December 2013 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / The petrochemical industry or petroleum deserves special attention because, in practically all stages (drilling, refining, storage and distribution), residues that harm the environment and is a challenge to those responsible for their management are generated. Among the various wastes generated by the oil industry, are the Soils Contaminated by Petroleum Products (SCPD). In Cearà state, the generation of this type of waste is coming from a refinery that is located in Fortaleza city. During maintenance performed on the steps of refining and storage of petroleum, can occur contact derivatives with soil, contaminating it, thus generating SCPD which finishes stored in drums, requiring alternative for correct final disposal. Given the above, was decided to study the incorporation of SCDP in the granular layers of the floor so that it ensures no damage to the environment. A new methodology was developed allowing the assessment of the technical feasibility of using SCDP (natural or stabilized) in Road Paving, using the encapsulation technique with cement. In the experimental program developed, the characterization tests, compaction, California Bearing Ratio (CBR), Simple Compression Strength (RCS), Diametrical Compression (RTCD), Resilience Modulus (MR), durability were executed, thus as the achievement of the environmental tests of leaching and solubilization. Observed after conducting of the experimental program, there are technical possibility for the incorporation of SCDP in granular pavement layers. The results shown an incorporation of residue to the natural ground, in other words, a particle size stabilization already has considerable gains, since it increases the index support. By adding cement, significant gains were obtained from CBR, MR, RCS and RT, and a condition of reasonable durability. However, environmentally, in an initial assessment, the feasibility of using the SCDP on pavements was not possible, because the mix without cement and mixing with cement evaluated, obtained concentrations of the parameters analyzed in the assay solubilization above permitted. However, it is important to note that the current method of assessing contaminant parameters does not take into consideration conditions that might be encountered in the field, thus there is a need to design of a model to evaluate the mechanical and environmental properties for waste that may be incorporated in the pavement construction process. Thus, the encapsulation technique contaminants cannot be ignored as an alternative to incorporating SCDP granular layers of paving. / A indÃstria petroquÃmica ou do petrÃleo merece atenÃÃo especial. Em praticamente todas as etapas (perfuraÃÃo, refino, armazenamento e distribuiÃÃo) sÃo gerados resÃduos nocivos ao ambiente que representam um desafio para os responsÃveis pelo seu gerenciamento. Dentre os diversos resÃduos gerados pela indÃstria petrolÃfera, estÃo os Solos Contaminados por Derivados de PetrÃleo (SCPD). No estado do CearÃ, a geraÃÃo desse tipo de resÃduo à proveniente de uma refinaria que fica localizada na cidade de Fortaleza. Durante as manutenÃÃes realizadas nas etapas de refino e armazenamento do petrÃleo, pode ocorrer o contato de derivados com o solo, contaminando-o, gerando assim, o SCPD. Esse resÃduo acaba estocado em tambores, necessitando de alternativas para uma disposiÃÃo final correta. Diante do exposto, resolveu-se estudar a incorporaÃÃo do SCDP nas camadas granulares dos pavimentos de forma que se garanta a ausÃncia de danos ao meio ambiente. Elaborou-se uma metodologia que permitiu avaliar a viabilidade tÃcnica do uso do SCDP (natural ou estabilizado) na PavimentaÃÃo RodoviÃria, usando a tÃcnica de encapsulamento com cimento. No programa experimental desenvolvido foram executados os ensaios de caracterizaÃÃo, compactaÃÃo, Ãndice de Suporte CalifÃrnia (CBR), ResistÃncia à CompressÃo Simples (RCS), ResistÃncia à TraÃÃo por CompressÃo Diametral (RTCD), MÃdulo de ResiliÃncia (MR), durabilidade, bem como a realizaÃÃo dos ensaios ambientais de lixiviaÃÃo e solubilizaÃÃo. Observou-se, apÃs a realizaÃÃo do programa experimental, que hà possibilidade tÃcnica para a incorporaÃÃo do SCDP em camadas granulares de pavimentos. Os resultados mostram que a incorporaÃÃo de resÃduo ao solo natural, ou seja, uma estabilizaÃÃo granulomÃtrica, jà traz bons ganhos, uma vez que eleva o Ãndice de suporte das misturas. Ao se adicionar cimento, foram obtidos ganhos significativos para CBR, MR, RCS e RTCD, bem como uma razoÃvel condiÃÃo de durabilidade. PorÃm, ambientalmente, em uma primeira avaliaÃÃo, as concentraÃÃes dos parÃmetros analisados no ensaio de solubilizaÃÃo ficaram acima do permitido. No entanto, à importante ressaltar que o mÃtodo atual de avaliaÃÃo dos parÃmetros contaminantes nÃo leva em consideraÃÃo as condiÃÃes que poderÃo ser encontradas em campo. Logo hà a necessidade da concepÃÃo de um modelo de avaliaÃÃo das propriedades mecÃnicas e ambientais para resÃduos que venham a ser incorporados no processo de construÃÃo de pavimentos. Assim, a tÃcnica de encapsulamento de contaminantes nÃo pode ser desconsiderada como alternativa à incorporaÃÃo do SCDP em camadas granulares de pavimentos.

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