Dissertations / Theses: 'Fibers'

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Santos, Eliane Moura dos. "Processos relacionados a inserção de fluidos para sensoriamento com fibras de cristal fotônico." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278251.

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Orientadores: Luiz Carlos Barbosa, Cristiano Monteiro de Barros Cordeiro
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Este trabalho apresenta estudos de como inserir fluidos (líquidos e gases) em fibras ópticas microestruturadas, especialmente fibras de cristal fotônico, também conhecidas como PCF¿s (do inglês Photonic Crystal Fibers). Estas fibras possuem buracos de ar que percorrem todo seu comprimento. Elas podem ser divididas em dois grandes grupos: as de núcleo sólido que guiam luz por reflexão interna total e as de núcleo oco que guiam luz por um mecanismo conhecido como photonic bandgap. Ambos os tipos de fibras permitem várias aplicações em áreas como óptica e fotônica e nos dedicamos aqui à área de sensoriamento a fibra. Nesta área, usamos os microburacos para inserir fluido e dessa maneira manipular as propriedades de guiamento (em fibras de núcleo líquido), deixar a fibra mais sensível a algum parâmetro externo ou para sensoriar o fluido em questão. Nos três casos, precisamos estudar os processos de preenchimentos de fibras microestruturadas. Para este fim, estudamos e desenvolvemos maneiras de inserir fluidos em fibras de núcleos sólidos ou ocos. Usando preenchimento seletivo, produzimos fibras com núcleo líquido, criando uma região de alta interação entre luz e material. Neste trabalho, estudamos diferentes técnicas de preenchimento. A primeira, para fibras de núcleo líquido, é um preenchimento seletivo que pode ser feito usando uma máquina de emendas (splicer) ou um polímero para bloquear os microburacos. O outro consiste em manter as pontas das fibras livres (para medidas ópticas) enquanto o preenchimento é feito. Por fim, usamos o conhecimento desses processos em aplicações como sensoriamento de fluidos ou parâmetros externos e manipulação de propriedades de guiamento da luz
Abstract: This work presents studies of how to insert fluids (liquid and gas) into microstructured optical fibers, especially photonic crystal fibers, also known as PCF¿s. These optical fibers possess air holes that run along its entire length. They can be divided into two major groups: solid core fibers that guide light by total internal reflection and hollow core fibers that guide light by photonic bandgap. Both types of fibers allow several applications in areas such as optics and photonics and we dedicated this work to the fiber-sensing field. In this area we use the micro holes to insert fluids and in this way to manipulate the guidance properties in liquid core fibers, to leave the fiber more sensitive to some external parameter or to sensing the fluid. In these three cases we need to study the filling procedures in microstructured fibers. For this purpose, we studied and developed ways of inserting fluids in hollow and solid core fibers. We produced liquid core fibers, creating a high light-material overlap, using a selective filling technique. In this work we studied different filling techniques. The first one, for liquid core fibers, is a selective filling, which can be done by using a splicer machine or a polymer to block the fiber micro holes. The last one consists of keeping the fiber tips free (for optical measurements) while the filling is done. And finally we used the filling process knowledge in applications like sensing of fluids or external parameters and manipulation of guidance properties
Mestrado
Física Geral
Mestre em Física

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MURA, EMANUELE. "PHOPSHATE OPTICAL FIBERS FOR IR FIBER LASERS." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2544536.

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Paye, Corey. "An Analysis of W-fibers and W-type Fiber Polarizers." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32474.

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Optical fibers provide the means for transmitting large amounts of data from one place to another and are used in high precision sensors. It is important to have a good understanding of the fundamental properties of these devices to continue to improve their applications. A specially type of optical fiber known as a W-fiber has some desirable properties and unique characteristics not found in matched-cladding fibers. A properly designed W- fiber supports a fundamental mode with a finite cutoff wavelength. At discrete wavelengths longer than cutoff, the fundamental mode experiences large amounts of loss. The mechanism for loss can be described in terms of interaction between the fiberâ ¢s supermodes and the lossy interface at the fiberâ ¢s surface. Experiments and computer simulations support this model of W-fibers. The property of a finite cutoff wavelength can be used to develop various fiber devices. Under consideration here is the fiber polarizer. The fiber polarizer produces an output that is linearly polarized along one of the fiberâ ¢s principal axes. Some of the polarizer properties can be understood from the study of W-fibers.
Master of Science

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Washburn, Brian Richard. "Dispersion and nonlinearities associated with supercontinuum generation in microstructure fibers." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/30964.

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Polley, Arup. "High performance multimode fiber systems a comprehensive approach /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31699.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Ralph, Stephen; Committee Member: Barry, John; Committee Member: Chang, G. K.; Committee Member: Cressler, John D.; Committee Member: Trebino. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Rugeland, Patrik. "Applications of monolithic fiber interferometers and actively controlled fibers." Doctoral thesis, KTH, Laserfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118750.

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The objective of this thesis was to develop applications of monolithic fiber devices and actively controlled fibers. A special twin-core fiber known as a ‘Gemini’ fiber was used to construct equal arm-length fiber interferometers, impervious to temperature and mechanical perturbations. A broadband add/drop multiplexer was constructed by inscribing fiber Bragg gratings in the arms of a Gemini Mach-Zehnder interferometer. A broadband interferometric nanosecond switch was constructed from a micro-structured Gemini fiber with incorporated metal electrodes. Additionally, a Michelson fiber interferometer was built from an asymmetric twin-core fiber and used as a high-temperature sensor. While the device could be readily used to measure temperatures below 300 °C, an annealing process was required to extend the range up to 700 °C. The work included development, construction and evaluation of the components along with numerical simulations to estimate their behaviors and to understand the underlying processes. The thesis also explored the use of electrically controlled fibers for filtering in the microwave domain. An ultra-narrow phase-shifted fiber Bragg grating inscribed in a fiber with internal electrodes was used as a scanning filter to measure modulation frequencies applied to an optical carrier. A similar grating was used inside a dual-wavelength fiber laser cavity, to generated tunable microwave beat frequencies. The studied monolithic fiber interferometers and actively controlled fibers provide excellent building blocks in such varied field as in microwave photonics, telecommunications, sensors, and high-speed switching, and will allow for further applications in the future.
Syftet med denna avhandling var att utveckla tillämpningar av monolitiska fiber komponenter samt aktivt kontrollerbara fiber. En speciell tvillingkärnefiber, även kallad ’Geminifiber’ användes för att konstruera fiber interferometrar med identisk armlängd som ej påverkas av termiska och mekaniska variationer. En bredbanding utbytarmultiplexor konstruerades genom att skriva in fiber Bragg gitter inuti grenarna på en Gemini Mach-Zehnder interferometer. Geminifibrer med interna metallelektroder användes för att konstruera en bredbandig nanosekundsnabb interferometrisk fiberomkopplare. Därtill användes en tvillingkärnefiber som en hög-temperatursensor. Även om komponenten direkt kan användas upp till 300 °C, måste den värmebehandlas för att kunna användas upp till 700 °C. Arbetet har innefattat utveckling, konstruktion och utvärdering av komponenterna parallellt med numeriska simuleringar för att analysera deras beteenden samt få insikt om de underliggande fysikaliska processerna. Avhandlingen behandlar även tillämpningar av en elektriskt styrbar fiber för att filtrera radiofrekvenser. Ett ultrasmalt fasskiftat fiber Bragg gitter skrevs in i en fiber med interna elektroder och användes som ett svepande filter för att mäta modulationsfrekvensen på en optisk bärfrekvens. Ett liknande gitter användes inuti en laserkavitet för att generera två olika våglängder samtidigt. Dessa två våglängder användes sedan för att generera en svävningsfrekvens i mikrovågsbandet. De undersökta monolitiska fiberinterferometrarna och de aktivt styrbara fibrerna erbjuder en utmärkt byggsten inom så pass skiljda områden som Mikrovågsfotonik, Telekommunikation, Sensorer samt Höghastighets-omkopplare och bör kunna användas inom många olika tillämpningar i framtiden.

QC 20130226

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Kominsky, Daniel. "Development of Random Hole Optical Fiber and Crucible Technique Optical Fibers." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28949.

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This dissertation reports the development of two new categories of optical fibers. These are the Random Hole Optical Fiber (RHOF) and the Crucible Technique Hybrid Fiber (CTF). The RHOF is a new class of microstructure fiber which possesses air holes which vary in diameter and location along the length of the fiber. Unlike all prior microstructure fibers, these RHOF do not have continuous air holes which extend throughout the fiber. The CTF is a method for incorporating glasses with vastly differing thermal properties into a single optical fiber. Each of these two classes of fiber brings a new set of optical characteristics into being. The RHOF exhibit many of the same guidance properties as the previously researched microstructure fibers, such as reduced mode counts in a large area core. CTF fibers show great promise for integrating core materials with extremely high levels of nonlinearity or gain. The initial goal of this work was to combine the two techniques to form a fiber with exceedingly high efficiency of nonlinear interactions. Numerous methods have been endeavored in the attempt to achieve the fabrication of the RHOF. Some of the methods include the use of sol-gel glass, microbubbles, various silica powders, and silica powders with the incorporation of gas producing agents. Through careful balancing of the competing forces of surface tension and internal pressure it has been possible to produce an optical fiber which guides light successfully. The optical loss of these fibers depends strongly on the geometrical arrangement of the air holes. Fibers with a higher number of smaller holes possess a markedly lower attenuation. RHOF also possess, to at least some degree the reduced mode number which has been extensively reported in the past for ordered hole fibers. Remarkably, the RHOF are also inherently pressure sensitive. When force is applied to an RHOF either isotropically, or on an axis perpendicular to the length of the fiber, a wavelength dependent loss is observed. This loss does not come with a corresponding response to temperature, rendering the RHOF highly anomalous in the area of fiber optic sensing techniques. Furthermore an ordered hole fiber was also tested to determine that this was not merely a hitherto undisclosed property of all microstructure fibers. Crucible technique fibers have also been fabricated by constructing an extremely thick walled silica tube, which is sealed at the bottom. A piece of the glass that is desired for the core (such as Lead Indium Phosphate) is inserted into the hole which is in the center of the tube. The preform is then drawn on an fiber draw tower, resulting in a fiber with a core consisting of a material which has a coefficient of thermal expansion (CTE) or a melting temperature (Tm) which is not commonly compatible with those of silica.
Ph. D.

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Richmond, Eric William. "Birefringent single-arm fiber optic enthalpimeter for catalytic reaction monitoring." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07282008-135248/.

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Acera, Fernandez José. "Modification of flax fibres for the development of epoxy-based biocomposites : Role of cell wall components and surface treatments on the microstructure and mechanical properties." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS218.

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Les fibres végétales peuvent être considérées comme une alternative intéressante aux fibres de verre pour la fabrication de matériaux composites. En effet, elles présentent des caractéristiques physiques intéressantes, telles que leur faible densité et leurs bonnes propriétés mécaniques spécifiques, qui peuvent rivaliser avec les composites renforcés de fibres de verre. En outre, les fibres végétales sont obtenues à partir de ressources renouvelables, et présentent généralement moins d'impacts environnementaux lors de leurs phases de production, d’utilisation et en fin de vie. Contrairement aux fibres de verre, les fibres végétales, telles que des fibres de lin, présentent des structures hiérarchiques complexes composées essentiellement de cellulose, hémicellulose, lignine, ciments peptiques et extractibles lipophiliques (cires, acides gras, etc.). Cette composition varie selon les espèces, le lieu et les conditions de croissance, la maturité de la plante, etc. De la même façon, la composition biochimique et la structure des produits et des sous-produits issus du lin sont soumis à de grandes variations selon les étapes successives de transformation réalisées à partir des tiges de lin jusqu’aux fils et tissus. Cela influence fortement les propriétés finales des fibres de lin et de leurs biocomposites. La première partie de cette étude se concentre sur la caractérisation de fibres de lin au cours de leurs étapes successives de transformation. Une homogénéisation de la composition chimique est observée dans les étapes finales de transformation, ainsi qu’une augmentation des propriétés en traction longitudinale des mèches de fibres de lin. La deuxième partie traite de l'utilisation de différents traitements de lavage appliqués sur des tissus d’étoupes de lin et leur influence sur l'extraction des composants de la paroi cellulaire des fibres, ainsi que sur la microstructure et les propriétés mécaniques de biocomposites époxy/lin. Il est montré que les composants de la paroi cellulaire jouent un rôle clé dans la dispersion des mèches et des fibres élémentaires de lin et sur le comportement mécanique transversal de leurs biocomposites. Enfin, l'application de différents traitements de fonctionnalisation sur des tissus de fibre de lin est étudiée afin d'améliorer l'adhérence interfaciale entre les fibres et la matrice. L'utilisation de molécules de type organosilanes (aminosilane, époxysilanes) et de molécules biosourcés (acides aminés et polysaccharides) est étudiée. Une augmentation de la rigidité en traction longitudinale et de la rigidité et de la contrainte maximale en traction transverse est observée en raison de l'amélioration de l'adhésion interfaciale par la fonctionnalisation de surface des fibres avec des molécules d'origine biosourcé et non-biosourcé
Natural fibres can be considered as a relevant alternative to glass fibres in the manufacture of composite materials. Indeed, they present interesting physical characteristics, such as low density and good specific mechanical properties, which can compete with glass fibre reinforced composites. Moreover, natural fibres are obtained from renewable resources, and generally present lower environmental impacts during their production and use phases and their end of life. Unlike glass fibres, natural fibres, such as flax fibres, are complex hierarchical materials composed essentially of cellulose, hemicellulose, lignin, peptics cements and lipophilic extractives (waxes, fatty acids, etc.). This composition varies among species, collection site, plant maturity, batches, etc. Besides, the biochemical composition and structure of flax products and sub-products undergo wide variations according to the transformation steps from stems to yarns and fabrics. This influences greatly the final properties of flax fibres and their biocomposites. The first part of this study is focused on the characterization of flax fibres during their successive transformation steps. A homogenization of the chemical composition is observed at the final transformation steps, as well as an increment of the longitudinal tensile properties of flax yarns. The second part deals with the use of different washing treatments applied on flax tow fabrics and their influence on the extraction of flax cell wall components and the resulting microstructure and mechanical properties of epoxy/flax fibres reinforced biocomposites. It is shown that cell wall components play a key role in the flax yarns and elementary fibres dispersion and transverse mechanical behaviour of biocomposites. Finally, the application of different functionalization treatments onto flax fibres fabrics is investigated in order to improve the interfacial adhesion between fibres and matrix. The use of non-bio-based organosilane molecules (aminosilane, epoxysilane) and bio-based molecules (amino-acids and polysaccharides) is studied. Improvedstiffness in longitudinal tension test and stiffness and tensile strength in transverse tension test are observed due to the improvement of interfacial adhesion by surface functionalization of the fibres with both bio-based and non-bio-based molecules

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Osório, Jonas Henrique 1989. "Specialty optical fibers for sensing = Fibras ópticas especiais para sensoriamento." [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/330348.

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Orientador: Cristiano Monteiro de Barros Cordeiro
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Nesta tese, fibras ópticas especiais são estudadas para fins de sensoriamento. Primei-ramente, propomos a estrutura denominada fibra capilar com núcleo embutido (embedded-core capillary fibers) para realização de sensoriamento de pressão. Estudos numéricos e analíticos foram realizados e mostraram que altas sensibilidades a variações de pressão poderiam ser al-cançadas com esta estrutura simplificada, que consiste de um capilar dotado de um núcleo, dopado com germânio, em sua parede. Experimentos permitiram medir uma sensibilidade de (1.04 ± 0.01) nm/bar, que é um valor alto quando comparado a outros sensores de pressão ba-seados em fibras microestruturadas. Ademais, estudamos fibras do tipo surface-core, que são fibras cujos núcleos são colocados na superfície externa da fibra. Nesta abordagem, redes de Bragg foram utilizadas para obter sensores de índice de refração ¿ fazendo-se uso da interação entre o campo evanescente do modo guiado no núcleo e o ambiente externo à fibra ¿ e de cur-vatura ¿ ao se explorar o fato de que, nestas fibras, o núcleo se encontra fora do centro geomé-trico da mesma. As sensibilidades a variações de índice de refração e curvatura medidas, 40 nm/RIU em torno de 1.41 e 202 pm/m-1 comparam-se bem a outros sensores baseados em redes de Bragg. Outrossim, fibras capilares poliméricas foram investigadas como sensores de temperatura e pressão. Para a descrição do sensor de temperatura, usou-se um modelo analítico para simular o espectro de transmissão dos capilares e a sua dependência com as variações de temperatura. No que tange à aplicação de sensoriamento de pressão, variações nas espessuras dos capilares devido à ação da pressão foram calculadas e relacionadas à sensibilidade da me-dida de monitoramento. Nestas duas aplicações, realizações experimentais também são repor-tadas. Finalmente, oportunidades adicionais de sensoriamento ao se utilizar fibras ópticas es-peciais são apresentadas, a saber, um sensor de pressão para dois ambientes baseados em fibras de cristal fotônico, um sensor de três parâmetros baseado em redes de Bragg, fibras afinadas e interferência multimodal, um sensor de nível de líquido baseado em redes de Bragg e interfe-rência multimodal e um sensor de temperatura baseado em fibras embedded-core preenchidas com índio. Os resultados aqui reportados demonstram o potencial das fibras ópticas em forne-cerem plataformas de sensoriamento para alcançar medidas de diferentes tipos de parâmetros com alta sensibilidade e resolução adequada
Abstract: In this thesis, specialty optical fibers for sensing applications are investigating. Firstly, we propose the embedded-core capillary fiber structure for acting as a pressure sensor. Analyt-ical and numerical studies were performed and showed that high pressure sensitivity could be achieved with this simplified fiber structure, which consists of a capillary structure with a germanium-doped core placed within the capillary wall. Experiments allowed measuring a sensitivity of (1.04 ± 0.01) nm/bar, which is high when compared to other microstructured optical fiber-based pressure sensors. Moreover, we studied the so-called surface-core optical fibers, which are fibers whose cores are placed at the external boundary of the fiber. In this approach, Bragg gratings were used to obtain refractive index ¿ making use of the interaction between the guided mode evanescent field and the external medium ¿ and directional curva-ture sensors ¿ by exploring the off-center core position. The measured refractive index and the curvature sensitivities, respectively 40 nm/RIU around 1.41 and 202 pm/m-1, compares well to other fiber Bragg grating-based sensors. Additionally, antiresonant polymer capillary fibers were investigated as temperature and pressure sensors. For the temperature sensing descrip-tion, one used an analytical model to simulate the transmission spectra of such fibers and the dependence on temperature variations. Regarding the pressure sensing application, pressure-induced capillary wall thickness variations were analytically accounted and related to the sys-tem pressure sensitivity. In both these applications, experimental data were presented. Finally, additional opportunities using specialty optical fibers were presented, namely, a photonic-crystal fiber-based dual-environment pressure sensor, a three parameters sensor using Bragg gratings, tapered fibers and multimode interference, a liquid-level sensor based on Bragg grat-ings and multimode interference, and a temperature sensor based in an embedded-core fiber filled with indium. The results reported herein demonstrates the potential of optical fibers for providing sensing platforms to attain measurements of different sort of parameters with highly sensitivity and improved resolutions
Doutorado
Física
Doutor em Ciências
152993/2013-4
CNPQ

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Sousa, Carlos MaurÃcio de. "Estudo numÃrico do acoplador duplo simÃtrico nÃo linear de fibras de cristais fotÃnicos sob modulaÃÃo ppm." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9383.

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Neste trabalho, apresentamos uma anÃlise numÃrica para a obtenÃÃo de portas lÃgicas totalmente Ãpticas, baseadas em um Acoplador Direcional NÃo-Linear Duplo SimÃtrico (NLDC) em fibras de cristais fotÃnicos (PCF) sem perda, trabalhando com pulsos ultracurtos de 100 fs(femtosegundos), para a obtenÃÃo de portas lÃgicas E/OU, sob ModulaÃÃo por PosiÃÃo de Pulsos (PPM). A investigaÃÃo Ã realizada atravÃs de simulaÃÃes numÃricas, utilizando-se o mÃtodo de Runge-Kutta de quarta ordem. Considerando a operaÃÃo das portas lÃgicas, foram utilizadas as quatro possÃveis combinaÃÃes para dois pulsos nas entradas das fibras 1 e 2, modulados pela posiÃÃo temporal (PPM) nos nÃveis lÃgicos 0 ou 1. Foram investigados, inicialmente, os efeitos de uma variaÃÃo no parÃmetro de ajuste PMM (ε) no deslocamento do pulso de saÃda em cada uma das fibras; em seguida, foram investigados os efeitos da diferenÃa de fase(ΔФ) entre os pulsos sÃlitons fundamentais de entrada, devidamente modulados, no deslocamento do pulso de saÃda em cada uma das fibras. Nas duas aplicaÃÃes, foram levados em consideraÃÃo a dispersÃo de velocidade anÃmala de grupo (GVD), a dispersÃo de segunda ordem (β2), a dispersÃo de terceira ordem (β3) e os efeitos nÃo-lineares SPM, SS e IRS. Os resultados indicam que Ã possÃvel a obteÃÃo de portas lÃgicas OU utilizando um controle de fase para um pulso de entrada.
In this work, we present a numerical analysis for obtaining all-optical logic gates based on a Directional Coupler Nonlinear Symmetric Double (NLDC) in photonic crystal fibers (PCF) without loss, working with ultrashort pulses of 100 fs (femtoseconds) , to obtain gates AND / OR under Pulse Position Modulation (PPM). Research is conducted through numerical simulations, using the Runge-Kutta fourth order. Considering the operation of logic gates were used the four possible combinations to the inputs of two pulses fibers 1 and 2, the temporal position modulated (PPM) in the logic levels 0 or 1. Were investigated initially, the effects of a change in tuning parameter PMM (ε) in the displacement of the output pulse in each fiber, then we investigated the effects of the phase difference (ΔФ) between pulses of fundamental solitons input, suitably modulated, at offset output pulse in each fiber. In both applications, were considered anomalous dispersion of group velocity (GVD), second order dispersion (β2), the third-order dispersion (β3) and nonlinear effects SPM, SS and IRS. The results indicate that it is possible to achievement OR logic gate using phase control to an input pulse.

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Kuhlmey, Boris T. "Theoretical and numerical investigation of the physics of microstructured optical fibres." Connect to full text, 2004. http://setis.library.usyd.edu.au/adt/public_html/adt-NU/public/adt-NU20040715.171105.

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Thesis (Ph. D.)--School of Physics, Faculty of Science, University of Sydney, 2004. (In conjunction with: Université de Droit, d'Économie et des Sciences d'Aix-Marseille (Aix Marseille III)).
Bibliography: leaves 196-204.

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Snyder, Heidi Ghent. "Fiber type-specific desmin content in human single muscle fibers /." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1253.pdf.

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Ghent, Heidi. "Fiber Type-specific Desmin Content in Human Single Muscle Fibers." BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/381.

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Contractile and cytoskeletal protein concentrations have been shown to differ on the basis of fiber type in whole muscle homogenates. The purpose of this study was to compare the content of the intermediate filament protein, desmin, between type I and type IIa single muscle fibers from a mixed muscle in human subjects. Biopsies were taken from the vastus lateralis of six recreationally active males. Approximately 150 single muscle fibers were dissected from each sample and analyzed using SDS-PAGE to determine myosin heavy chain (MHC) composition. Following identification, muscle fibers were pooled into two groups (MHC I and MHC IIa). Desmin and actin content within the pooled samples was determined via immunoblotting. On average, muscle samples were composed of 51 ± 7 % type I, 2 ± 1% type I/IIa, 27 ± 5% type IIa, 19 ± 4% type IIa/IIx and 1 ± 1% type IIx MHC single fibers. Desmin and actin contents were 40% and 34% higher in type I fibers compared to type IIa fibers, respectively (P < 0.05). However the desmin to actin ratio was similar between pooled type I and IIa single muscle fibers within the vastus lateralis. These data suggest that desmin and actin content is a function of muscle fiber type. These differences in cytoskeletal protein content may have implications for differences in contractile function and eccentric damage characteristics between fiber types.

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Ma, Hongming. "Structure-property relationships in copolyester fibers and composite fibers." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04112004-150623/unrestricted/Ma%5FHongming%5F200405%5Fphd.pdf.

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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2004.
Collard, David, Committee Co-Chair ; Schiraldi, David, Committee Member ; Liotta, Charles, Committee Member ; Weck, Marcus, Committee Member ; Srinivasarao, Mohan, Committee Member ; Kumar, Satish, Committee Co-Chair. Vita. Includes bibliographical references.

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Apriyanto, Haris. "Study, analysis and experimental validation of fiber refractometers based on single-mode, multimode and photonic crystal fibers for refractive index measurements with application for the detection of methane." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0022.

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La mesure de l'indice de réfraction a été étudiée depuis qu'Ernest Abbé aie initialement conçu un réfractomètre en 1869, appelé le réfractomètre d'Abbé. Depuis lors, de nombreux réfractomètres ont été développés tels que le réfractomètre à prisme optique ainsi que le réfractomètre à fibre optique, en raison de leurs applications étendues pour la détection de divers paramètres physiques, biologiques et chimiques. Récemment, un grand nombre de chercheurs ont mis au point des réfractomètres basés sur des fibres optiques, exploitant des mécanismes tels que la résonance des plasmons de surface (SPR), les interférences multimodes, les fibres à réseaux de Bragg (FBG), les fibres à réseaux à longues périodes (LPG), les fibres optiques coniques et la fibre multimode à gaine dénudée. Les capteurs fibrés sont avantageux grâce à leur immunité contre les interférences électromagnétiques, passivité électrique au niveau de la sonde de détection et potentiel de mesure in situ à long terme. Cette thèse concerne le développement de modèles complets fonctionnels et précis pour les réfractomètres à fibres optiques basés sur la modulation d'intensité optique, en particulier la réfractométrie à fibre multimode à gaine dénudée ainsi que les systèmes hybrides associant fibres monomode et multimode, et un réfractomètre hybride tout fibré utilisant des fibres à cristaux photoniques. L'objectif clé de ce travail est de caractériser les performances de ces réfractomètres à fibres optiques basés sur la modulation d'intensité en termes de réponse en puissance, de sensibilité, de résolution et de dynamique de mesure. Les résultats de simulation qui sont corroborés expérimentalement démontrent que la très grande sensibilité obtenue dans la zone II (c'est-à-dire le régime de détection typiquement utilisé pour mesurer l'indice du milieu supérieur à l'indice de gaine mais inférieur ou égal à l'indice du coeur) pour tous les trois réfractomètres. Cependant, la sensibilité dans la Zone (c’est-à-dire le régime de détection pour lequel l’indice du milieu à mesurer est supérieur à celui du coeur) est très faible. Ainsi, un refractomètre fibré hybride monomode-multimode est utilisé pour améliorer la sensibilité dans la Zone III. D'autre part, la sensibilité pour la zone I (c'est-à-dire le régime de détection pour mesurer l’indice du milieu inférieur à l'indice de la gaine) a été améliorée en augmentant l'absorption des ondes évanescentes à l'aide du réfractomètre hybride tout fibré à base de fibres à cristaux photoniques à coeur solide. En termes d'application réelle du réfractomètre à fibre pour la détection biochimique, une preuve de concept pour un capteur du gaz méthane a été démontrée en utilisant les supramolécules de cryptophane-A qui permettent de piéger les molécules du méthane. Le cryptophane-A incorporé dans un film hôte à base de styrène acrylonitrile (SAN) est appliqué sur la zone dénudée du capteur comme une région fonctionnalisée. L'indice de réfraction de cette couche sensible augmente proportionnellement avec l'augmentation de la concentration du méthane, ce qui induit une variation de la puissance optique transmise dans le capteur fibré
Refractive index measurement has been studied since Ernest Abbé initially designed a refractometer in 1869, which is named the Abbé refractometer. Since then, numerous types of refractometers have been developed by employing either the optical prism-based refractometer or the optical fiber-based refractometer, due to their wide-ranging applications such as for sensingvarious physical, biological and chemical parameters. Recently, a large number of researchers have been developing refractometers based on optical fibers, exploiting mechanisms such as surface plasmon resonance (SPR), multimode interference, fiber Bragg gratings (FBG), long period gratings (LPG), tapered optical fibers, and striped-cladding multimode fibers (MMF), for their advantages in immunity against electromagnetic interference, electrical passivity at the sensing probe, and capability to long term in-situ measurement. This thesis concerns the development of comprehensively functional and accurate models for optical fiber refractometers based on optical intensity modulation, in particular for stripped-cladding MMF refractometry as well as hybrid systems involving a combination of single-mode-multimode fiber refractometery and the all-fiber hybrid refractometer using photonic crystal fibers. A key objective of this work is to characterize the performance of these intensity-based optical fiber refractometers in terms of their power response, sensitivity, resolution, and dynamic range. The simulation results which are corroborated experimentally demonstrate very high sensitivity being obtained in Zone II (i.e. the sensing regime typically employed for measuring a sensing medium index higher than the cladding index but less than or equal to the core index) for all three types of refractometers. However, the sensitivity in Zone III (i.e. the sensing regime for which the sensing medium index is higher than the core index) is very low. A hybrid single-mode fiber - multimode fiber configuration is used to improve the sensitivity in Zone III. On other hand, the sensitivity for Zone I (i.e. the sensing regime typically employed for measuring a sensing medium index lower than the cladding index) has been improved by increasing evanescent wave absorption using the all-fiber hybrid refractometer based on solid-core photonic crystal fibers. As a further potential of the fiber refractometer for applications in biochemical sensing, the proof-of-concept for a methane gas sensor has been demonstrated using supramolecular cryptophane-A which enables to trap the methane molecules. Cryptophane-A incorporated into a functionalized film of StyreneAcrylonitrile (SAN) host is applied to a de-cladded region of the sensor as the sensitive region. The refractive index of this functionalized layer increases proportionally with increasing methane concentration, subsequently inducing variations in the transmitted optical power along the fiber sensor

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17

Haakestad, Magnus W. "Optical fibers with periodic structures." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1494.

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This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated.

The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied.

In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated.

The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings.

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18

Shaikh, Saif. "Dynamics and rheology of concentrated suspensions of rigid fibers." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0495.

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Une étude combinant expériences et analyses est menée afin de rationaliser la dynamique et la rhéologie des suspensions très concentrées de fibres rigides, non colloïdales dans un fluide newtonien. Des mesures rhéologiques couplées à des mesures de la microstructure sont réalisées à l’aide de plusieurs dispositifs expérimentaux permettant d’analyser différents types de géométries et d’écoulements. Des expériences de rhéologie standards (rhéologie à volume contrôlé), ainsi qu’une méthode de rhéologie non-conventionnelle (rhéologie à pression contrôlée) sont associées afin de mesurer la contrainte de cisaillement, la pression de la phase particulaire et la fraction volumique des suspensions très concentrées. Un autre dispositif expérimental a été conçu dans le but d’étudier la microstructure (distribution spatiale et distribution d’orientations) d’une suspension de fibres rigides dans un écoulement de Poiseuille oscillant. Alors que ce type d’écoulement est réversible pour un liquide newtonien, dans le cas d’une suspension concentrée, les interactions entre particules introduisent des changements irréversibles de microstructure. Cette microstructure est affectée et a un effet sur l’écoulement imposé, cette dépendance non-linéaire incluant les interactions hydrodynamiques. L’objectif de ces expériences est d’apporter un éclairage sur des effets tels que la rhéofluidification observée à fort taux de cisaillement et sur le démixage dû à la migration induite par cisaillement
A combined work of experiments and data analyses is proposed to investigate the dynamics and rheology of highly concentrated suspensions of non-colloidal rigid rods in a Newtonian fluid. Detailed measurements of the rheology and the microstructure are made using a variety of experimental devices with different geometries and imposed flows. Standard rheology experiments (volume-controlled rheology), as well as a novel method of rheometry, are carried out to measure torques, particle pressures, and volume fractions at high concentration (pressure-controlled rheology). Another experiment has been designed and constructed to study the microstructure (spatial and orientation distribution) of a suspension of rigid rods in an oscillatory parabolic flow. Though the flow is reversible in these systems, the changes in the microstructure are irreversibile in the case of concentrated suspensions due to particle interactions. The microstructure is affected by, and has an effect, on the imposed flows; this non-linear dependency includes hydrodynamic interactions. The purpose of these experiments is to gain insight into phenomena such as apparent shear-thinning at high shear rates and demixing due to shear-induced migration

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19

Robinson, Risa J. "Polarization modulation and splicing techniques for stressed birefringent fiber /." Online version of thesis, 1995. http://hdl.handle.net/1850/12228.

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Chesini, Giancarlo. "Dispositivos óticos baseados em fibras de cristal fotônico com eletrodos integrados." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277529.

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Orientador: Cristiano Monteiro de Barros Cordeiro
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"
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Resumo: Neste trabalho de mestrado apresentamos o estudo e desenvolvimento de dispositivos óticos totalmente à fibra. Para isso, exploramos as novas possibilidades trazidas pelo advento das fibras de cristal fotônico (PCF's, do inglês Photonic Crystal Fibers). As PCF's são uma classe especial de fibras óticas que apresentam uma estrutura regular de buracos de ar na sua seção transversal, semelhante a um cristal fotônico. As fibras de cristal fotônico, além de apresentarem as vantagens inerentes às fibras óticas tradicionais, possuem novos graus de liberdade intrínsecos. Entre eles, o mais importante é a possibilidade de alterar fortemente as características da fibra através, apenas, do arranjo de buracos. Aqui, desenvolvemos uma fibra de cristal fotônico com dois buracos externos à microestrutura para integração de eletrodos. Posteriormente, um desses eletrodos foi exposto, polindo-se a lateral da fibra, e contato elétrico foi realizado. O elemento de controle do dispositivo ótico é a corrente elétrica que, aplicada ao eletrodo, o esquenta e o faz expandir via efeito Joule. O aumento de temperatura e a compressão causada pela expansão do eletrodo alteram o índice de refração e, portanto, a birrefringência da fibra. Foram realizadas, ainda, simulações utilizando o software comercial Comsol Multiphysics com o objetivo de entender a influência da temperatura e da compressão mecânica no modo ótico guiado pela fibra, bem como encontrar maneiras de otimizar o dispositivo em questã
Abstract: In this work we present a study and the development of all-fiber optical devices. For this purpose we exploited the new possibilities brought by the development of Photonic Crystal Fibers. PCF's are special kind of optical fibers with a regular pattern of air holes in their transverse section, resembling a photonic crystal. Photonic Crystal Fibers not only have the inherent advantages of traditional optical fibers but they have new intrinsic degrees of freedom. Among them, we can quote the possibility of strongly altering the fiber characteristics through the design of the air holes pattern. Here, we developed a photonic crystal fiber with two extra holes for electrode integration. One of these electrodes was exposed by side polishing the fiber and electrical contact to an external circuit was made. The contrai element of the optical device is the electrical current which, when applied to the electrode, heats it up and make it expand by Joule effect. The temperature increase and the compression caused by the electrode expansion alter the refractive index and, consequently, the fiber birefringence. We algo numerically studied the problem through Com sol software. The objective here was to understand the influence of temperature and stress on the light guided mode. In conclusion, we demonstrated in this work the creation of an all-fiber device based on the integration of electrodes to photonic crystal fibers where the element of contrai is the electrical current applied to the electrodes. We algo studied how to improve the parameters concerning the device operation
Mestrado
Física Geral
Mestre em Física

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Santos, Alexandre Bozolan dos. "Geração de supercontínuo em fibra óptica de cristal fotônico com núcleo de água." Universidade Presbiteriana Mackenzie, 2008. http://tede.mackenzie.br/jspui/handle/tede/1484.

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Photonic crystal fibers (PCFs) are optical fibers whose core is surrounded by a regular matrix of holes that is responsible for light confinement and guidance. This new architecture opens new perspectives in the development of nonlinear applications, many of which are based upon the high efficiency with which nonlinearity-driven spectral broadening known supercontinuum generation is obtained in solid-core PCFs. Another asset of PCFs is that their structure can be filled with liquids or gases, which then efficiently interact with the guided light. The possibility of obtaining supercontinuum generation in a PCF whose core is filled with highly nonlinear liquids has been recently theoretically studied. The insertion of liquids in PCFs introduces a new degree of freedom with which the efficiency of nonlinear effects can be maximized. This dissertation describes experimental work, in which the generation of a supercontinuum spectrum is demonstrated in a PCF whose hollow core was selectively filled with distilled water. A maximum broadening of 503nm, measured at -20dB, was obtained with femtosecond pulse pumping at λ=976nm. The comparison with spectra obtained with a 800nm pump and with bulk samples demonstrate that both a low dispersion at the pump wavelength and pump guidance are crucial for the broad output spectrum obtained. Numerical simulations and analyses were also undertaken to complement the study.
Fibras de cristal fotônico (PCF s) são fibras ópticas cujo núcleo é cercado por uma matriz regular de buracos, responsável pelo confinamento e guiamento da luz. Esta nova arquitetura abre novas perspectivas no desenvolvimento de aplicações não-lineares, muitas das quais são baseadas na alta eficiência com que o alargamento espectral não-linear conhecido como geração de supercontínuo é obtido em PCF s de núcleo sólido. Outra característica das fibras de cristal fotônico é que sua estrutura pode ser preenchida com líquidos e gases, que então interagem eficientemente com a luz guiada. A possibilidade de se obter a geração de supercontínuo em uma fibra de cristal fotônico cujo núcleo é preenchido com líquidos altamente não-lineares foi teoricamente estudado recentemente. A inserção de líquidos nas PCF s introduz um novo grau de liberdade, aumentando a eficiência com que os efeitos não-lineares podem ser gerados. Esta dissertação descreve um trabalho experimental no qual é demonstrada a geração de supercontínuo em uma PCF cujo núcleo foi preenchido seletivamente com água destilada. Obteve-se um alargamento máximo de 503nm medido, a -20dB, com o bombeio de pulsos de femtossegundos em 976nm. A comparação com o espectro obtido com o bombeio em 800nm e em amostras volumétricas demonstram que tanto a baixa dispersão no comprimento de onda de bombeio quanto o guiamento dos pulsos são cruciais para a obtenção do largo espectro observado. Simulações e análises numéricas foram também realizadas para complementar o estudo.

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22

Thomson, Cameron Ian. "Probing the Nature of Cellulosic Fibre Interfaces with Fluorescence Resonance Energy Transfer." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16277.

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The material properties of fibre networks and fibre reinforced composites are strongly influenced by fibre-fibre interactions. Stress transfer between load bearing elements in such materials is often dictated by the nature of the fibre-fibre interface. Inter-fibre bonding is solely responsible for internal cohesion in paper, because all stresses transferred between fibres operate through fibre-fibre bonds. . The future development of cellulosic fibre materials will require an improved understanding of the fibre-fibre interface. Fluorescence resonance energy transfer (FRET) was proposed as a new tool for the study of fibre interfaces. A protocol for covalent linkage of fluorophores to natural and regenerated cellulosic fibres was developed and the absorptive and emissive properties of these dyes were characterized. The fluorescent response of these dyed fibres in paper sheets was studied using steady-state fluorescence spectroscopy. Fluorescence micrographs of fibre crossings on glass slides were analyzed using the FRETN correction algorithm. Energy transfer from coumarin dyed fibres to fluorescein dyed fibres at the interface was observed. The FRETN surfaces for spruce and viscose rayon fibre crossings were distinctly different. The FRET microscopy method was able to detect statistically significant differences in spruce fibre interface development when fibre fraction and wet pressing were varied. The coalescence of natural cellulosic fibre interfaces during drying was also observed with the technique. Polysaccharide films were employed as model systems for the natural and regenerated cellulose fibre interfaces. It was found that pressing cellulose films did not result in significantly increased FRETN either due to resistance to deformation or the inability to participate in interdiffusion. Conversely, xylan films demonstrated a drastic increase in the FRETN signal with increased wet pressing. These results support the previously observed differences between regenerated cellulose fibres and natural wood fibres. The results of the FRETN analysis of the polysaccharide film model systems suggest that lower molecular weight amorphous carbohydrates are likely to be significant contributors to fibre interface development.

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23

Issa, Nader. "Modes and propagation in microstructured optical fibres." University of Sydney. Physics and Optical Fibre Technology Centre, 2005. http://hdl.handle.net/2123/613.

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Microstructured optical fibres (MOFs), also commonly called photonic crystal fibres or holey fibres, describe a type of optical fibre in which continuous channels of (typically) air run their entire length. These `holes' serve to both confine electromagnetic waves within the core of the fibre and to tailor its transmission properties. In order to understand and quantify both of these functions, a new computational algorithm was developed and implemented. It solves for the eigenvalues of Maxwell's wave equations in the two-dimensional waveguide cross-section, with radiating boundary conditions imposed outside the microstructure. This yields the leaky modes supported by the fibre. The boundary conditions are achieved exactly using a novel refinement scheme called the Adjustable Boundary Condition (ABC) method. Two implementations are programmed and their computational efficiencies are compared. Both use an azimuthal Fourier decomposition, but radially, a finite difference scheme is shown to be more efficient than a basis function expansion. The properties of the ABC method are then predicted theoretically using an original approach. It shows that the method is highly efficient, robust, automated and generally applicable to any implementation or to other radiating problems. A theoretical framework for the properties of modes in MOFs is also presented. It includes the use of the Bloch-Floquet theorem to provide a simpler and more efficient way to exploit microstructure symmetry. A new, but brief study of the modal birefringence properties in straight and spun fibres is also included. The theoretical and numerical tools are then applied to the study of polymer MOFs. Three types of fibres are numerically studied, fabricated and characterised. Each is of contemporary interest. Firstly, fabrication of the first MOFs with uniformly oriented elliptical holes is presented. A high degree of hole ellipticity is achieved using a simple technique relying on hole deformation during fibre draw. Both form and stress-optic birefringence are characterized over a broad scaled-wavelength range, which shows excellent agreement with numerical modelling. Secondly, an analysis of leaky modes in real air core MOFs, fabricated specifically for photonic band gap guidance, is then used to identify alternative guiding mechanisms. The supported leaky modes exhibit properties closely matching a simple hollow waveguide, weakly influenced by the surrounding microstructure. The analysis gives a quantitative determination of the wavelength dependent confinement loss of these modes and illustrates a mechanism not photonic band gap in origin by which colouration can be observed in such fibres. Finally, highly multimode MOFs (also called `air-clad' fibres) that have much wider light acceptance angles than conventional fibres are studied. An original and accurate method is presented for determining the numerical aperture of such fibres using leaky modes. The dependence on length, wavelength and various microstructure dimensions are evaluated for the first time for a class of fibres. These results show excellent agreement with published measurements on similar fibres and verify that bridge thicknesses much smaller than the wavelength are required for exceptionally high numerical apertures. The influence of multiple layers of holes on the numerical aperture and capture efficiency are then presented. It shows that a substantial increase in both these parameters can be achieved for some bridge thicknesses. Simple heuristic expressions for these quantities are given, which are based on the physical insight provided by the full numerical models. The work is then supported by the first fabrication attempts of large-core polymer MOFs with thin supporting bridges. These fibres exhibit relatively high numerical apertures and show good agreement with theoretical expectations over a very wide scaled-wavelength range.

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Nunes, Nelson Lúcio. "Contribuição para a aplicação do concreto reforçado com fibras de aço em elementos de superfície restringidos." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3146/tde-04052006-170328/.

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Este trabalho apresenta um estudo para a previsão de comportamento quanto à fissuração e seu controle pelo uso das fibras de aço, em elementos de superfície de concreto restringidos, ou seja, submetidos às tensões de tração induzidas pela retração restringida. Neste estudo, foi desenvolvido um método analítico para calcular o consumo de um determinado tipo de fibra de aço em função do potencial de retração da matriz de concreto e da máxima abertura de fissura, determinada em função de parâmetros de durabilidade e aceitabilidade sensorial. Posteriormente, foram realizados ensaios para caracterização do potencial de fissuração de matrizes de concreto utilizadas em obras de elementos de superfície, onde testou-se um método de estimativa das tensões induzidas por retração restringida no concreto, no momento da primeira fissura. Na etapa final do trabalho, foi realizado um programa experimental, com a construção de pistas de concreto reforçado com fibras de aço (CRFA), com consumos de fibras de 10 kg/m3, 30 kg/m3 e 60 kg/m3, construídas sobre bases com duas condições de restrição: superfície desempenada e superfície jateada com exposição dos agregados. A fissuração destas pistas, nas primeiras idades, foi monitorada através da medida da abertura e do comprimento das fissuras. Com os resultados desta etapa experimental, foi realizada uma retroanálise do método onde concluiu-se que a consideração de valores característicos na previsão da resistência à tração do concreto era um ajuste necessário e coerente com a observação prática. Com o ajuste, os resultados experimentais de abertura de fissura ficaram dentro da faixa de previsibilidade do método, considerando um intervalo de confiança de 90%. Com o desenvolvimento deste método, buscou-se contribuir para a aplicação do CRFA no controle da fissuração por retração restringida de elementos de superfície, ampliando a fronteira do conhecimento no aspecto da escolha e dosagem da fibra para um determinado desempenho esperado quanto à fissuração.
This work presents a study for crack prediction and use of steel fibers to crack control in concrete surface elements submitted to tension stress induced by restrained shrinkage. In this study, a method was developed where a certain steel fiber type could be quantified, as function of concrete matrix shrinkage potential and maximum crack width, determined from human sensorial and durability criteria. Afterwards, an experimental program was done in order to characterize the crack potential of concrete matrices commonly used in surface elements. In this program, a method to predict tension stress induced by restrained shrinkage, at first crack moment, was tested. In the final step of this work, another experimental program was done, where steel fiber reinforced concrete (SFRC) tracks were built, with fiber contents of 10 kg/m3, 30 kg/m3 and 60 kg/m3, over substrates with two restriction conditions: smooth surface and rough surface, with exposition of surface aggregates. Lengths and widths of the early age shrinkage cracks in the tracks were monitored. The results obtained in this program were useful to analyze the method, adjusting it with the consideration of characteristic values in prediction of tension strength. With this adjust, experimental crack width results were more compatible with 90% confidence interval for crack width values predicted by the method. With this study, the goal was the contribution to use SFRC in the control of restrained shrinkage cracks in surface elements, amplifying the knowledge border in the aspect of fiber selection and proportioning, for a determined and expected performance in terms of crack width.

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25

Chocat, Noémie. "Multimaterial acoustic fibers." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/79552.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 141-150).
The emergence of multimaterial fibers that combine a multiplicity of solid materials with disparate electrical, optical, and mechanical properties into a single fiber presents new opportunities for extending fiber applications well beyond optical transmission. Fiber reflectors, thermal detectors, photodetectors, chemical sensors, surface-emitting fiber lasers, fiber diodes, and other functional fiber devices have been demonstrated with this approach. Yet, throughout this development and indeed the development of fibers in general, a key premise has remained unchanged : that fibers are essentially static devices incapable of controllably changing their properties at high frequencies. Unique opportunities would arise if a rapid, electrically-driven mechanism for changing fiber properties existed. A wide spectrum of hitherto passive fiber devices could at once become active with applications spanning electronics, mechanics, acoustics, and optics, with the benefits of large surface-area, structural robustness, and mechanical flexibility. This thesis addresses the challenges and opportunities associated with the realization of electromechanical transduction in fibers through the integration of internal piezoelectric and electrostrictive domains. The fundamental challenges related to the fabrication of piezoelectric devices in fiber form are analyzed from a materials perspective, and candidate materials and geometries are selected that are compatible with the thermal drawing process. The first realization of a thermally drawn piezoelectric fiber device is reported and its piezoelectric response is established over a wide range of frequencies. The acoustic properties of piezoelectric fiber devices are characterized and related to their mechanical and geometric properties. Collective effects in multi-fiber constructs are discussed and demonstrated by the realization of a linear phased array of piezoelectric fibers capable of acoustic beam steering. High strain actuation capabilities in a fiber are demonstrated based on the integration of a highly electrostrictive relaxor ferroelectric polymer. The potential of this approach to realize integrated microelectromechanical systems in fibers is illustrated by the fabrication of a hybrid fiber comprising an electrostrictive device and an adjacent Fabry-Perot optical filter. Amplitude modulation of the light reflected from the Fabry-Perot cavity is demonstrated through electric field induced tuning of the cavity resonance.
by Noémie Chocat.
Ph.D.

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Lin, Zhiyuan. "Nanocomposite-based Lignocellulosic Fibers." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/40488.

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The formation of layered nanoparticle films on the surface of wood fibers is reported in this study. The layer-by-layer (LbL) assembly technique was comprehensively investigated as a non-covalent surface modification method for lignocellulosic fiber. Nanocomposite-based lignocellulosic fibers were successfully fabricated by sequential adsorption of oppositely charged poly(diallydimethylammonium) chloride (PDDA) and clay nanoparticles in a number of repeated deposition cycles. Nanocomposite fibers displayed layered structure as indicated by the electrokinetic potential studies and scanning electron microscopy (SEM) analysis. Layer-by-layer films of PDDA and clay impacted the thermal stability of wood fibers. Average degradation temperature at 5 and 10% weight loss for modified fibers with 4 bi-layers increased by up to ~24 and ~15Â°C, respectively. Significant char residue formed for the LbL modified fibers after heating to 800Â°C, indicating that the clay-based coating may serve as a barrier, creating an insulating layer to prevent further decomposition of the material. Layer-by-layer film formation on wood fibers was investigated as a function of parameters related to fiber composition and solution conditions (ie. presence of lignin, salt concentration and pH). Elemental analysis of modified fibers revealed that PDDA adsorption to the fibers was reduced for all solution conditions for the samples with the highest content of lignin. Upon extracting the non-covalently attached lignin, the samples showed the greatest amount of PDDA adsorption, reaching to 1.5% of total mass, under neutral solution conditions without the presence of added electrolyte. Furthermore, the influence of both the amount of PDDA adsorbed onto the fiber surface and electrokinetic potential of modified fibers on subsequent multilayer formation was quantified. Under select fiber treatments, great amount of PDDA/clay (up to ~75% total mass for only 4 bi-layers) was adsorbed onto wood fibers through the LbL process, giving these high surface area fibers nanocomposite coatings. LbL modified fibers were melt compounded with isotactic polypropylene (PP) and compression molded into test specimens. The effect of LbL modification as a function of the number of bi-layers on composite performance was tested using the tensile, flexural, dynamic mechanical and thermal properties of fiber reinforced thermoplastic composites. LbL modified fiber composites had similar modulus values but significantly lower strength values than those of unmodified fiber composites. However, composites composed of LbL modified fibers displayed increased elongation at break, increasing by more than 50%, to those of unmodified samples. DSC results indicated that crystallization behavior of PP is promoted in the presence of wood fibers. Both unmodified and LbL modified fibers are able to acts as nucleating agents, which cause an increase of the crystallinity of PP. Moreover, results from tensile and flexural strength, dynamic mechanical analysis and water absorption tests revealed that the material (PDDA or clay) at the terminal (outer) layer of LbL modified fiber influences the performance of the composites. These findings demonstrate control over the deposition of nanoparticles onto lignocellulosic fibers influencing terminal surface chemistry of the fiber. Further investigation into using renewable fibers as carriers of nanoparticle films to improve fiber durability, compounding with thermoplastics that have higher melt processing temperatures, and tailoring terminal surface chemistry to enhance adhesion is justified by this research.
Ph. D.

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27

Qiu, Tong. "Adaptive Mode Control in Few-Mode and Highly Multimode Fibers." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/82067.

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Few-mode fibers (FMFs) and multimode fibers (MMFs) can provide much higher data-carrying capacities compared with single-mode fibers. But in order to achieve this goal, one must address the challenge of intermodal coupling and dispersion. Therefore the ability to accurately control the optical signal propagation in FMFs/MMFs can play a pivotal role in FMF/MMF applications. This thesis demonstrates the ability to excite, in FMFs and MMFs, the desired linearly polarized (LP) modes as well as their superpositions through adaptive optics (AO). Specifically, in the case of step-index FMFs, a phase-only spatial light modulator (SLM) is employed to manipulate the light at the fiber input end, driven by the feedback signal provided by the correlation between the charge coupled device (CCD) camera captured images at the fiber output end and the target light intensity profile. Through such an adaptive optical system, any arbitrarily selected LP modes can be excited at the distal end of the four-mode and seventeen-mode fibers, respectively. For a graded-index MMF with a uniform Bragg grating, we use a deformable mirror (DM) to perform the wavefront modulation at the fiber input end, where the feedback is based on the ratio of the grating-reflected signal power to the transmitted signal power. At the Bragg grating position of this highly multimode fiber, any desired principal mode groups can be successfully chosen. These experimental results suggest that adaptive control of optical wavefront in FMFs/MMFs is indeed feasible.
Master of Science
Optical fibers, in terms of the number of modes they support, can be generally divided into single-mode fibers (SMFs), and few-mode fibers/multimode fibers (FMFs/MMFs). FMFs/MMFs can provide much higher data-carrying capacities than SMFs. For example, an FMF/MMF that supports M modes can ideally increase the data transmission rate by a factor of M, where each mode can serve as a distinct communication channel. However, in order to achieve good performance, one must accurately control signal propagation in FMFs/MMFs, which are often degraded due to the multiple-mode nature. This thesis demonstrates the ability, using adaptive optics (AO), to control signal propagation in FMFs and a highly MMF, respectively. Specifically, in the case of FMFs, a phase-only spatial light modulator (SLM) is employed to manipulate the light at the fiber input, driven by AO feedback signal provided by the similarity between the real-time fiber output image and the target mode profile. Through such an adaptive optical system, any desired linearly-polarized (LP) modes can be excited at the output of the four-mode and seventeen-mode fibers, respectively. For the highly MMF with uniform Bragg grating, we use a deformable mirror (DM) to perform the wavefront modulation at the fiber input, where AO feedback is provided by the fiber Bragg grating (FBG) reflectivity. At the FBG position, any desired principal mode groups can be successfully chosen. These experimental results suggest that adaptive control of optical wavefront in FMFs/MMFs is indeed feasible, and may find a large number of applications in optical communication, sensing, and imaging.

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Lyyttkäinen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing /." Connect to full text, 2004. http://setis.library.usyd.edu.au/adt/public_html/adt-NU/public/adt-NU20041011.120247.

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Greaves, James David. "Numerical analysis of the outside vapor deposition process." Ohio : Ohio University, 1990. http://www.ohiolink.edu/etd/view.cgi?ohiou1183491109.

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30

Scott, David Edward. "Characterization of fibrillated polypropylene and recycled waste fiber reinforced concrete." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19543.

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Lyytikäinen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing." Connect to full text, 2004. http://hdl.handle.net/2123/597.

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Thesis (Ph. D.)--University of Sydney, 2004.
Title from title screen (viewed 14 May 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Includes bibliographical references. Also available in print form.

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32

Kneis, Christian. "Investigation of mid-infrared supercontinuum generation in soft-glass fibers from a Q-switched mode-locked 2 mm fiber laser." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0135/document.

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Cette thèse est dédiée à l’étude de la génération de supercontinuum (SCG) deforte puissance moyenne dans le domaine spectral entre 2 mm et 5,5 mm. Un laser à fibredopée thulium (Tm3+) opérant dans un régime simultanément déclenché et à verrouillage demodes (QML) a été développé. En régime continu ce laser a délivré 70 W et en régime QML,26Wmoyens ont été obtenus pour des taux de répétition en QS de 180 kHz ou plus. L’énergiela plus élevée contenue dans une enveloppe QS a été évaluée à 166 mJ avec 66 mJ contenuedans la sous-impulsion à verrouillage de mode la plus énergétique. L’émission du laser àfibre correspondait toujours à un facteur de qualité M2 excellent, entre 1,1 et 1,2. La SCGcouvrant la plage spectrale de 2 mm à 5,5 mm a été réalisée en implémentant différentes fibresen cascade. Des supercontinua jusqu’à environ 4 mm ont été générés dans des fibres en fluorurepuis pour la plage spectrale complémentaire entre 4 mm et 5,5 mm, des fibres en chalcogénureont été utilisées.La puissance moyenne maximale de 7,8 W a été démontrée pour un supercontinuum dans unefibre en ZBLAN. Le spectre s’étend jusqu’à 4,2 mm. Au total, 69%/43%/30%/16,5% de lapuissance totale ont été mesurés au-delà de 2,15 mm/2,65 mm/3,1 mm/3,5 mm respectivement.La fibre en InF3 a permis d’atteindre une puissance moyenne de 0,8 W et le supercontinuums’étend jusqu’à 2,95 mm.Pour les essais d’élargissement spectral complémentaire, trois fibres en chalcogénure ont étéutilisées. L’élargissement spectral a été démontré pour toutes les fibres en chalcogénure.Jusqu’à 20 mW de puissance ont été obtenus avec une fibre As2Se3. Le spectre a été étendujusqu’à 4,9 mm
This thesis reports about the investigation of high power supercontinuum (SC)generation between 2 mm and 5.5 mm. A Q-switched mode-locked (QML) thulium (Tm3+)-doped fiber laser has been developped to pump different nonlinear fibers. The fiber laserprovided in continuous wave regime an output power of 70 W. In QML operation, 26 W havebeen obtained with Q-switched repetition rates of 180 kHz or higher. The highest energy of theQS envelopes has been 166 mJ with 66 mJ contained in the most-energetic ML pulses, whichhave been surrounded by Gaussian-like pedestals with temporal widths around 2.5 ns. On topof these pedestals, very short temporal peaks with pulse durations around 15 ps appeared. Thehighest achieved peak power of a pedestal has been 25 kW. The beam parameter product M2of the fiber laser has been measured in different operational regimes and resulted always in anexcellent value around 1.2.The highest SC output power level from a ZBLAN fiber has been 7.8 W. In total, 69%/43%/30%/16.5% of the transmitted SC output radiation could be converted beyond the wavelengthof 2.15 mm/2.65 mm/3.1 mm/3.5 mm, respectively, with the broadest output spectrum from theZBLAN fiber exceeding 4.2 mm. The InF3 fiber provided a total output power of 0.8 W withan output spectrum up to 2.95 mm.Successful broadening of the wavelength-limited SC output from the ZBLAN fibers has beenachieved with all three investigated chalcogenide fibers with as much as 20 mW of outputpower by using an arsenic selenide fiber. The output spectrum exceeded 4.9 mm

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Ruys, David Julian Materials Science &amp Engineering Faculty of Science UNSW. "The influence of bast fibre structure on the mechanical properties of natural fibre composites." Awarded by:University of New South Wales. Materials Science & Engineering, 2007. http://handle.unsw.edu.au/1959.4/40688.

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Composite materials based on natural bast fibres offer potential commercial and environmental benefits due to the low cost, availiability, and biodegradability of the fibres. However, such benefits cannot be realised without a comprehensive evaluation of processing and properties. This thesis involved a comprehensive evaluation of composites based on two types of natural bast fibre (hemp and flax), and two types of matrix - synthetic (epoxy), and biodegradable (Novamont Mater-Si). The experimental work involved four strands: the effects of growing conditions and fibre processing on the properties of raw bast fibres; the optimisation of a pultrusion process for epoxy-matrix composites; development of a film stacking process for Mater-Bi composites, and a detailed evaluation of the mechanical properties of the composites themselves. Fibre bundles and individual fibre cells were investigated to characterise their structure, with particular focus on compressive kink defects. The kink bands were sectioned using a novel technique of focused ion beam milling, and kinking was found to induce delamination and voiding of the lamellar fibre structure. The defect concentration per unit length was assessed for conventionally-processed fibres and for hemp fibres from plants grown under controlled conditions to assess the effect of wind shear and stem flexure on fibre defect concentration. No effect was found for plant flexure, while industrially processed fibre was found to have increased defect concentration. The loading behaviour of both types of composite was seen to be initially linear with a yield point at 20 - 30 MPa and a transition to nonlinear deformation dominated by damage mechanisms as a result of fibre kinks. Epoxy composites possessed an inital modulus of 30 GPa with a 30 - 60% reduction in modulus after yield. Flax reinforcement was found to increase the modulus of Mater-Bi from 0.1 to 20 GPa and strength from 24 to 169 MPa. Fibre addition was also found to significantly embrittle the polymers.

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Kim, Jeong I. "Analysis and Applications of Microstructure and Holey Optical Fibers." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/29089.

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Microstructure and photonic crystal fibers with periodic as well as random refractive-index distributions are investigated. Two cases corresponding to fibers with one-dimensional (1D) radial index distributions and two-dimensional (2D) transverse index distributions are considered. For 1D geometries with an arbitrary number of cladding layers, exact analytical solutions of guided modes are obtained using a matrix approach. In this part, for random index distributions, the average transmission properties are calculated and the influence of glass/air ratio on these properties is assessed. Important transmission properties of the fundamental mode, including normalized propagation constant, chromatic dispersion, field distributions, and effective area, are evaluated. For 2D geometries, the numerical techniques, FDTD (Finite-Difference Time-Domain) method and FDM (Finite Difference Method), are utilized. First, structures with periodic index distributions are examined. The investigation is then extended to microstructure optical fibers with random index distributions. Design of 2D microstructure fibers with random air-hole distributions is undertaken with the aim of achieving single-mode guiding property and small effective area. The former is a unique feature of the holey fiber with periodic air-hole arrangement and the latter is a suitable property for nonlinear fiber devices. Measurements of holey fibers with random air-hole distributions constitute an important experimental task of this research. Using a section of a holey fiber fabricated in the draw tower facility at Virginia Tech, measurements of transmission spectra and fiber attenuation are performed. Also, test results for far-field pattern measurements are presented. Another objective of this dissertation is to explore new applications for holey fibers with random or periodic hole distributions. In the course of measuring the holey fibers, it was noticed that robust temperature-insensitive pressure sensors can be made with these fibers. This offers an opportunity for new low-cost and reliable pressure fiber-optic sensors. Incorporating gratings into holey fibers in conjunction with the possibility of dynamic tuning offers desirable characteristics with potential applications in communications and sensing. Injecting gases or liquids in holey fibers with gratings changes their transmission characteristics. These changes may be exploited in designing tunable optical filters for communication applications or making gas/liquid sensor devices.
Ph. D.

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35

Karakaya, Yeliz. "Instrumentation for microscale measurement and characterization of bio-fibers." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.65 Mb., 112 p, 2006. http://proquest.umi.com/pqdlink?did=1037889801&Fmt=7&clientId=8331&RQT=309&VName=PQD.

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36

Kosappallyillom, Muraleedharan Praveen. "Studies on O2 plasma modification and fluoroalkyl functional siloxane (FAS) coating effects on natural lignocellulosic coir fibers and development of coir based polypropylene (PP)/ethylene-propylene-diene rubber (EPDM) composites." Thesis, Lorient, 2018. http://www.theses.fr/2018LORIS495/document.

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Au cours des dernières années, le développement de matériaux composites avancés fabriqués à partir de fibres naturelles a été principalement axé sur l'obtention de matériaux à haut module et à haute résistance. Cependant, la résistance élevée n'est pas suffisante, car certains des matériaux possèdent une nature fragile (l'allongement à la rupture est faible), et l'un des critères de performance les plus importants devrait être la capacité à absorber l'énergie et à résister aux chocs. La manière dont un matériau composite se déforme et subit des endommagements dépend à la fois des propriétés chimiques et mécaniques de trois constituants de base : les fibres, la matrice et une fine région d'interphase (parfois appelée interface) chargée d'assurer le lien entre matrice et fibre. En raison de leurs propriétés uniques et de leur nature abondante, les fibres à base de cellulose émergent comme un choix privilégié pour les communautés scientifiques, techniques et commerciales qui recherchaient des matériaux durables dans diverses applications. Bien que ces fibres possèdent plusieurs avantages par rapport aux charges synthétiques, l'adhérence entre la fibre et la matrice, la sensibilité à l'humidité et les propriétés au feu restent des domaines difficiles à traiter. Dans ce contexte, une nouvelle technique basée sur la méthode par pulvérisation-séchage-durcissement a permis de fabriquer un revêtement sol-gel hydrophobe sur la surface de la fibre de coco lignocellulosique. La modification de surface des fibres de coco a été effectuée à l'aide d'un plasma oxygène à basse pression suivi d'un enduit sol-gel polymérisable à sec avec un siloxane à fonction fluoroalkyle (FAS). Le prétraitement par plasma a augmenté la concentration effective du réseau FAS sur les fibres de fibre de coco dans le but de créer la surface extrêmement hydrophobe. L'efficacité du traitement plasma et du sol gel FAS sur fibre de coco a été étudiée en utilisant différentes techniques de caractérisation telles que l'analyse de l'angle de contact, l'absorption d'eau, la microscopie électronique à balayage, la microscopie à force atomique et la spectroscopie photoélectronique. Les propriétés mécaniques, morphologiques, rhéologiques et thermiques de différentes formulations de mélanges PP/EPDM ont été étudiées pour trouver la composition optimale du mélange pour la préparation de composites. Les composites résultants à base de polypropylène, d'EPDM et de fibre de coco possèdent des propriétés de résistance aux chocs élevées et des propriétés de traction et de flexion comparables. Les propriétés mécaniques, morphologiques, rhéologiques et thermiques des composites PP/EPDM/Coir ont été étudiées en détail pour examiner la stabilité des composites
In recent years, the development of advanced high performance composite materials made from natural fibers was mainly focussed on achieving high modulus and strength materials. However, the high strength is not sufficient, as some of the materials possess brittle nature (the overall elongation to fracture is small), and one of the more important performance criterion should be the ability to absorb energy and resist impact loadings. The manner in which a composite material deforms and subjected to fractures depends upon both the chemical and mechanical properties of three basic constituents: the fibers, the matrix and a fine interphase region (sometimes referred to as the interface) responsible for assuring the bond between the matrix and fiber. Due to its unique properties and abundant in nature, lignocellulose based fibers are emerging as a preferred choice for scientific, engineering and commercial communities who were looking for sustainable materials in various applications. Though these fibers possess several advantages over synthetic fillers, adhesion between the fiber and matrix, moisture repellence, flame retardant properties etc are still challenging areas to be addressed. In this context a novel technique based on spray-dry- cure method to establish a hydrophobic sol-gel coating on the lignocellulosic coir fiber surface. The surface modification of lignocellulosic coir fibers was done with the use of low-pressure oxygen plasma, followed by the application of a spray-dry-cure sol–gel coating with the water and oil repellent organic–inorganic hybrid precursor fluoroalkyl-functional siloxane (FAS), with the aim of creating the extremely hydrophobic coir fiber surface. The plasma pre-treatment increased the effective concentration of the FAS network on the lignocellulosic coir fibers. The effectiveness of plasma treatment and FAS sol gel coating on the coir fiber was studied using different characterisation techniques such as contact angle analysis, water absorption studies, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The mechanical, morphological, rheological and thermal properties of different PP/EPDM blend formulations were carried out to find out optimum blend composition for composite preparation. The resulting composites based on polypropylene, EPDM and coir possess high impact strength properties and comparable tensile and flexural properties. The mechanical, morphological, rheological and thermal properties of PP/EPDM/Coir composites were studied in detail to examine the stability of the composites

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Schneider, Diego. "Desenvolvimento de fibras metálicas espaciais e avaliação experimental do comportamento de compósitos de concretos com adições híbridas de fibras." Universidade do Vale do Rio dos Sinos, 2016. http://www.repositorio.jesuita.org.br/handle/UNISINOS/6268.

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Nenhuma
A adição de fibras a uma matriz cimentícia proporciona vários benefícios para o desempenho do compósito, podendo-se citar o controle da fissuração, ganho de tenacidade, aumento da resistência à tração, entre outros. Diante disto, busca-se uma distribuição aleatória e mais homogênea possível das fibras ao longo da matriz. É esperado que a proposição de um elemento de reforço definido a partir da união ortogonal de filamentos – fibra espacial – venha contribuir para uma distribuição mais uniforme e homogênea do reforço da matriz, evitando imperfeições no compósito e maximizando a eficiência do reforço. Este trabalho tem por objetivo criar um modelo de fibra espacial e adicioná-la em uma matriz de concreto convencional, tanto isoladamente como combinada com macrofibras monofilamentos de aço e microfibras de polipropileno, avaliando o desempenho dos compósitos resultantes em termos de trabalhabilidade, resistência à compressão, resistência à tração indireta e tenacidade. Ademais, avaliou-se a distribuição das fibras no interior da matriz de concreto e sua influência no desempenho final do compósito. Para tal, foi realizado um programa experimental com 18 compósitos, cada um com uma combinação diferente de fibras espaciais, fibras de aço monofilamento e microfibras de polipropileno. Foram executados ensaios de compressão axial, segundo a ABNT NBR 5739:2007, resistência à tração na flexão, conforme a norma JSCE-SF4 (1984) e ABNT NBR 12142:2010, e tenacidade, de acordo com a JSCE-SF4 (1984). Em virtude dos resultados obtidos, concluiu-se que as fibras espaciais apresentaram desempenho satisfatório, tanto isoladamente como hibridizada pois, além de não afetar a resistência à compressão, melhorou o comportamento à tração em 37,6% e atingiu um Fator de Tenacidade de 3,4 MPa . Ainda, observou-se que a trabalhabilidade diminuiu em relação ao concreto sem fibras, mas a capacidade de compactação não foi prejudicada.
The addition of fibers to a cementitious matrix provides several benefits to the performance of the composite, including the control of cracking, tenacity gain, increased tensile strength, among others. In view of this, a random and more homogeneous distribution of the fibers along the matrix is sought. It's expected that the proposition of a reinforcement element defined from the orthogonal union of filaments - spatial fiber - will contribute to a more uniform and homogeneous distribution of the matrix reinforcement, avoiding imperfections in the composite and maximizing the reinforcement efficiency. This dissertation aims to create a spatial fiber model and add it in a conventional concrete matrix, either alone or in combination with steel macro fibers monofilaments and polypropylene microfibers, evaluating the performance of the resulting composites in terms of workability, compressive strength, indirect tensile strength and tenacity. In addition, the distribution of the fibers inside the concrete matrix and their influence in the final performance of the composite were evaluated. For this, an experimental program was carried out with 18 composites, each with a different combination of spatial fibers, steel macro fibers monofilaments and polypropylene microfibers. It was performed the axial compression tests according to ABNT NBR 5739: 2007, the flexural tensile strength tests according JSCE-SF4 (1984) and ABNT NBR 12142:2010, and the tenacity tests according to JSCE-SF4 (1984). Based on the results obtained, it was concluded that the spatial fibers presented satisfactory performance, both alone and hybridization, because they didn't affect the compressive strength, improved the tensile behavior in 37,6% and reached a tenacity factor of 3,4 MPa. Also, it was observed that the workability decreased in relation to the concrete without fibers, but the capacity of compaction was not impaired.

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38

Lima, Vanessa Morais. "Efeitos da penicilina G na pelve renal de ratos Wistar (Rattus norvegicus albinus) normais e diabéticos." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/10/10132/tde-09102013-180434/.

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A penicilina G é um dos antibióticos mais importantes. Além de possuir um baixo preço e comprovada eficácia de tratamento, mostra inúmeras possibilidades para a redução da morbidade e mortalidade por doenças infecciosas em todo o mundo. Como eventualmente este medicamento causa sequelas no parênquima renal e estruturas associadas, e sendo que a secreção da rede tubular renal contribui para a excreção da penicilina G, onde cerca de 60% do antibiótico é eliminado pela urina, nos propomos a fazer um estudo das principais alterações que possam ocorrer na pelve renal de ratos normais e ratos induzidos à diabetes. Este projeto tem o propósito de descrever e analisar as fibras colágenas, musculares lisas e elásticas da pelve renal de ratos wistar observando alterações estruturais e ultraestruturais dos grupos experimentais quando comparados ao grupo controle com relação ao uso da penicilina G. Os ratos foram divididos em 4 grupos, ratos Wistar normais (N); ratos Wistar tratados com penicilina G (NP); ratos Wistar induzidos à diabetes (D); ratos Wistar diabéticos com penicilina G (DP). Os ratos dos grupos D e DP foram induzidos ao diabetes por aloxano. A região da pelve renal com representação das fibras foi coletada e reduzida em pequenos fragmentos. Os cortes obtidos foram utilizados para Microscopia Eletrônica de Transmissão e corados pelos seguintes métodos para Microscopia Óptica: Hematoxilina Férrica para evidenciação de fibras elásticas; Resorcina fucsina para evidenciação de fibras elásticas e elaunínicas; Resorcina fucsina após oxidação com solução aquosa a 1% de oxona para evidenciação de fibras elásticas, elaunínicas e oxitalânicas; Azan para evidenciação do componente colágeno e muscular lisa; Picrosírius para observação do componente colágeno (especificamente tipo I e III); e Hematoxilina e Eosina, para evidenciação do componente celular. A análise microscópica e a histomorfometria mostraram que a Penicilina G altera os componentes fibrosos da pelve renal, fazendo com que as áreas de fibras musculares lisas e de colágeno tipo III fossem aumentadas e as fibras elásticas maduras diminuídas (neste caso, apenas entre N e NP). O Diabetes mellitus mostrou-se como uma doença metabólica também capaz de alterar a morfologia da pelve, fazendo com que a área de fibras musculares lisas aumentasse, a área de colágeno tipo I e a quantidade de fibras elásticas maduras e elaunínicas diminuísse e as oxitalânicas aumentassem, além de um notável aumento na quantidade de mitocôndrias. Podemos inferir que a antibioticoterapia feita pela penicilina G e o diabetes, provocam diferenças estruturais e ultraestruturais na pelve renal dos ratos Wistar, principalmente na organização dos componentes fibrosos elástico, muscular e colágeno.
Penicillin G is the most important antibiotics. Besides having a low cost and proven effectiveness of treatment, it shows great possibilities for reducing morbidity and mortality from infectious diseases worldwide. As this medicine may cause sequelae in the renal parenchyma and associated structures, and since the net renal tubular secretion contributes to the excretion of penicillin G, where about 60% of the antibiotic is eliminated in urine, this study aims to investigate the main structural and ultrastructural changes occurring in the kidney of normal and diabetes rats. Thus, this project aims to describe and analyze the collagen fibers, smooth muscle and elastic fibers of the renal pelvis of Wistar rats, comparing control and penicillin G-treated animals. The animals were divided into 4 groups, normal rats (N), Wistar rats treated with penicillin G (NP); rats induced diabetes (D), diabetic Wistar rats with penicillin G (DP). The diabetes was induced in groups D and DP by alloxan. The fibrotic region of the renal pelvis was collected and reduced into small fragments. The sections were used for the transmission electron microscopy and stained by the following methods for optic microscopic: Iron Hematoxylin for disclosure of elastic fibers; Resorcin fuchsin for disclosure of elastic and elauninic fibers; Resorcin fuchsin after oxidation with 1% aqueous solution of oxone for disclosure of elastic, elauninic and oxytalan fibers; Azan evidencing the collagen and smooth muscle components; Picrosirius for observation of the collagen component (specifically type I and III); and Hematoxylin and Eosin, to show the cellular component. Microscopic and histomorphometry analysis showed that penicillin G alters the fibrous components of the renal pelvis, increasing areas of smooth muscle fibers and collagen type III deposition and decreasing mature elastic fibers (in this case, only between N and NP). Diabetes mellitus proved to be a metabolic disease also able to alter the morphology of the pelvis, leading to the augmentation of smooth muscle fiber area. Moreover, the area of type I collagen and the amount of mature elastic and elauninic fibers were diminished, while oxytalan fibers increased, together with a remarkable increase in the number of mitochondria. We can infer that the antibiotic therapy made by penicillin G and the diabetes, cause structural and ultrastructural differences in the renal pelvis of rats, mainly in the organization of elastic fiber, muscular and collagen components.

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39

Zhang, Rui. "Propagation of ultrashort light pulses in tapered fibers and photonic crystal fibers." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981255191.

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Kleinhans, Henrik. "Evaluation of the Carbonization of Thermo-Stabilized Lignin Fibers into Carbon Fibers." Thesis, Linköpings universitet, Kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-120519.

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Thermo-stabilized lignin fibers from pH-fractionated softwood kraft lignin were carbonized to various temperatures during thermomechanical analysis (TMA) under static and increasing load and different rates of heating. The aim was to optimize the carbonization process to obtain suitable carbon fiber material with good mechanical strength potential (high tensile strength and high E-modulus). The carbon fibers were therefore mainly evaluated of mechanical strength in Dia-Stron uniaxial tensile testing. In addition, chemical composition, in terms of functional groups, and elemental (atomic) composition was studied in Fourier transform infrared spectroscopy (FTIR) and in energy-dispersive X-ray spectroscopy (EDS), respectively. The structure of carbon fibers was imaged in scanning electron microscope (SEM) and light microscopy. Thermogravimetrical analysis was performed on thermo-stabilized lignin fibers to evaluate the loss of mass and to calculate the stress-changes and diameter-changes that occur during carbonization. The TMA-analysis of the deformation showed, for thermo-stabilized lignin fibers, a characteristic behavior of contraction during carbonization. Carbonization temperatures above 1000°C seemed most efficient in terms of E-modulus and tensile strength whereas rate of heating did not matter considerably. The E-modulus for the fibers was improved significantly by slowly increasing the load during the carbonization. The tensile strength remained however unchanged. The FTIR-analysis indicated that many functional groups, mainly oxygen containing, dissociate from the lignin polymers during carbonization. The EDS supported this by showing that the oxygen content decreased. Accordingly, the relative carbon content increased passively to around 90% at 1000°C. Aromatic structures in the carbon fibers are thought to contribute to the mechanical strength and are likely formed during the carbonization. However, the FTIR result showed no evident signs that aromatic structures had been formed, possible due to some difficulties with the KBr-method. In the SEM and light microscopy imaging one could observe that porous formations on the surface of the fibers increased as the temperature increased in the carbonization. These formations may have affected the mechanical strength of the carbon fibers, mainly tensile strength. The carbonization process was optimized in the sense that any heating rate can be used. No restriction in production speed exists. The carbonization should be run to at least 1000°C to achieve maximum mechanical strength, both in E-modulus and tensile strength. To improve the E-modulus further, a slowly increasing load can be applied to the lignin fibers during carbonization. The earlier the force is applied, to counteract the lignin fiber contraction that occurs (namely around 300°C), the better. However, in terms of mechanical performance, the lignin carbon fibers are still far from practical use in the industry.

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Gapontsev, Denis Valentinovitch. "Fiber Raman lasers and amplifiers and their applications." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322403.

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Stolyarov, Alexander. "Integrated Optofluidic Multimaterial Fibers." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10080.

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The creation of integrated microphotonic devices requires a challenging assembly of optically and electrically disparate materials into complex geometries with nanometer-scale precision. These challenges are typically addressed by mature wafer-based fabrication methods, which while versatile, are limited to low-aspect-ratio structures and by the inherent complexity of sequential processing steps. Multimaterial preform-to-fiber drawing methods on the other hand present unique opportunities for realizing optical and optoelectronic devices of extended length. Importantly, these methods allow for monolithic integration of all the constituent device components into complex architectures. My research has focused on addressing the challenges and opportunities associated with microfluidic multimaterial fiber structures and devices. Specifically: (1) A photonic bandgap (PBG) fiber is demonstrated for single mode transmission at 1.55 µm with 4 dB/m losses. This fiber transmits laser pulses with peak powers of 13.5 MW. (Chapter 2) (2) A microfluidic fiber laser, characterized by purely radial emission is demonstrated. The laser cavity is formed by an axially invariant, 17-period annular PBG structure with a unit cell thickness of 160nm. This laser is distinct from traditional lasers with cylindrically symmetric emission, which rely almost exclusively on whispering gallery modes, characterized by tangential wavevectors. (Chapter 4)(3) An array of independently-controlled liquid-crystal microchannels flanked by viscous conductors is integrated in the fiber cladding and encircles the PBG laser cavity in (2). The interplay between the radially-emitting laser and these liquid-crystal modulators enables controlled directional emission around a full azimuthal angular range. (Chapter 4) (4) The electric potential profile along the length of the electrodes in (3) is characterized and found to depend on frequency. This frequency dependence presents a new means to tune the transversely-directed transmission at a given location along the fiber axis. (Chapter 5) (5) A chemical sensing system is created within a fiber. By integrating a chemiluminescent peroxide-sensing material into the hollow core of a PBG fiber, a limit-of-detection of 300 ppb for peroxide vapors is achieved. (Chapter 3)
Engineering and Applied Sciences

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Orf, Nicholas D. "Multimaterial rectifying device fibers." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53250.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Electronic and optoelectronic device processing is commonly thought to be incompatible with much simpler thermal drawing techniques used in optical fiber production. The incorporation of metals, polymer insulators, and chalcogenide semiconductors into structured fibers has reversed this paradigm and made it possible to realize optoelectronic device functionalities at fiber optic length scales and cost. In spite of the surprising robustness of this processing technique, the electronic performance and complexity of these optoelectronic fiber devices has been constrained by the small set of materials compatible with the fabrication method and the disordered nature of the semiconductor. Specifically, the high density of defects inherent to the amorphous chalcogenide semiconductors precludes the ability to create spatially extended internal electric fields necessary to create more sophisticated devices such as diodes and transistors. In this work, the design, fabrication, and characterization of the first fiber-integrated diode is described. The relevant optical, thermal, and electronic properties of candidate materials compatible with the thermal fiber drawing process are described and measured. Phase changing semiconductors are incorporated into the fiber having both amorphous properties amenable to thermal drawing and crystalline properties ideal for electronic devices. Combinations of metals and semiconductors that form both blocking and non-blocking contacts are identified and combined to form the first diode device that is compatible with the thermal drawing process. Techniques are developed to reduce the dimensions of the resulting devices by an order-of- magnitude compared to all previous multimaterial device fibers.
(cont.) A series of measurements of both compositional and potential spatial variation are used to determine that compound formation at specific metal semiconductor interfaces control the rectifying behavior of the fiber integrated rectifying junction. This work demonstrates the ability to synthesize compounds during fiber drawing to create complex electronic structures and combine them to form basic building blocks of circuits into arbitrary long fiber, paving the way to increasingly complex electronic structures and truly intelligent fibers and fabrics.
by Nicholas D. Orf.
Ph.D.

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Boivin, Luc. "Squeezing in optical fibers." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38373.

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Cholst, Beth (Beth Ellen). "Elastic stretchable optical fibers." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105710.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 23-24).
The utilization of soft materials in the design of optical systems provides opportunities for imparting these optical systems with completely unprecedented properties. This will enhance performance of systems, such as optical fibers, and enable new application scenarios. Here, we report the design, manufacture and characterization of elastic stretchable optical fibers. Analogous to conventional optical fibers, the elastic fibers consist of a high index core, made from a polystyrene-polyisoprene triblock copolymer, and a low refractive index cladding, formed by a fluorinated thermoplastic elastomer. The fibers are manufactured by co-extrusion of their constituent materials. They can be stretched to 300% strain repeatedly. Axial deformation of the fibers results in a variation of their light guiding properties. The fibers' attenuation coefficient was determined to be 0.021 ± 0.003 dB/mm, which is 2 orders of magnitude higher than for standard optical glass fibers. The high attenuation coefficient is likely due to scattering of light by air inclusions incorporated during manufacturing at the core-cladding interface. The fibers elastic modulus is 960 ± 280 kPA and their yield strength lies in the range of 2150 ± 480 kPA. The variation in intensity of guided light as a function of strain applied axially to the fibers was measured with a customized optical setup. Our experiments show that elastic optical fibers have properties that make them desirable as mechanical sensors and components in a range of other applications, provided current manufacturing shortcomings are addressed. The fibers could be used for light delivery to individual pixels of flexible deformable displays. They could be incorporated into clothing for delivery of light for display purposes or textile-integrated photonic circuits to create functional textiles. Because the fibers can stretch, the textiles or displays will be able to undergo deformation without damage or loss in performance.
by Beth Cholst.
S.B.

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Karlsson, Fredrik, and Erik Söderlöv. "Polymer-based conductive fibers." Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-10680.

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Conductive polymers, since from their discovery, have become a prominent area of research and found many useful applications in all fields of our daily life. Examples are light emitting diodes, heat generation, chemical sensors and electro-active membranes. Polymer coated textile substrates give flexible and lightweight materials. One well utilized and thoroughly explored conductive polymer is poly(3,4-ethylenedioxythiophene) also known as PEDOT. Although there are different ways to produce PEDOT one of the most common is the VPP technique. The typical procedure when using VPP is to introduce the monomer vapor to an oxidant coated substrate so that it polymerizes on the surface of the substrate. Throughout this study, the VPP technique has been used to produce PEDOT on different textile fibers. Aim was first of all optimizing the process gaining low electric resistance, i. e. high conductivity, of produced coated fibers but also multilayer coatings of fibers. Outcome indicates some parameters not having a clear influence over the results while others had a more distinct impact. A noteworthy result was obtained by coating a substrate, namely lyocell fiber, multiple times with layers deposited directly on each other. This decreased the resistance from 5.1 (± 1.6) kΩ/10 cm to 1.0 (± 0.1) kΩ/10 cm, for one layer and multiple layers respectively. Adding 15 wt. % of the copolymer PEG-PPG-PEG to the oxidant solution decreased the resistance from 6.8 (± 1.2) kΩ/10 cm to 3.9 (± 0.8) kΩ/10 cm. Final conclusion is that among the ways, to improve conductivity for PEDOT coated fibers, applied in this study are best results obtained by multi-layer coating.

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Nuzhna, A. A. "Morphology of nerve fibers." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/55336.

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Introduction. It is known that development of tooth begins approximately on the 6th week of pre-natal life. At this stage the epithelium of an oral cavity consists of two glowed, presented by different cages. After the 6th week reproduction of some cages of a basal layer is resulted by an epithelium thickening which received the name "tooth plate" and is a prototype of enamel body. On the 8th week of the period it is possible to observe the beginning of formation of a tooth nipple which represents a congestion of connecting fabric and in the future will turn into a tooth pulp. Work purpose. The purpose of our work is studying of century change of nerves of a pulp of second teeth.

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Azabi, Y. O. "Spiral photonic crystal fibers." Thesis, City, University of London, 2017. http://openaccess.city.ac.uk/19372/.

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This thesis is concerned with the study of special types of photonic crystal fibers (spiral) and their optical properties. The work is carried out using simulation techniques to obtain the modal field profile and properties for the designs. The method used in solving the Maxwell’s equations is the full vectorial finite element method with the implementation of penalty function and perfectly matched layer. The penalty function is used to eliminate nonphysical solutions. The perfectly matched layer is integrated to absorb rays of light traveling away from the core. These rays are absorbed by the layer and do not reflect back to negatively influence the results. The spiral shapes are implemented in the distribution of the holes in the cladding region of the photonic crystal fiber to determine the photonic crystal fiber properties. Three different spirals have been introduced which are equiangular, Archimedean and Fermat’s spiral. The study of the effective refractive index, effective area and dispersion with varying spiral parameters have been carried out and the results are analyzed to understand the effect of each parameter. The variation of similar parameters in the spirals leads to similar variation in the optical properties under consideration. Furthermore, the equiangular spiral photonic crystal fibers (ES-PCF) have been investigated in two different dimensional scales. The scales are in comparison with the wavelength of operation in the first case when core size is larger than the operating wavelength. In this case the total dispersion of the fiber has slightly higher values than the material dispersion but similar curve and slope. On the other hand, when the core size is comparable with the wavelength of operation, the dispersion is varying significantly with varying the spiral parameters. The effective area can be made very small and therefore the nonlinearity of the fiber very large to facilitate non-linear applications such as super continuum generation. The equiangular spiral photonic crystal fiber has been modified slightly where the position of holes in the third ring are shifted further from the center and their size is much bigger. This manipulation is proposed in an algorithm in this thesis to facilitate the fabrication of ES-PCF using an adaptive stack and draw technique. The design shows similar optical behavior to an ideal spiral and its dispersion has been tailored for supercontinuum generation.

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Hartley, William H. "High-Speed Imaging of Polymer Induced Fiber Flocculation." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14627.

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This study presents quantitative results on the effect on individual fiber length during fiber flocculation. Flocculation was induced by a cationic polyacrylamide (cPAM). A high speed camera recorded 25 second video clips. The videos were image-analyzed and the fiber length and the amount of fiber in each sample were measured. Prior to the flocculation process, fibers were fractionated into short and long fibers. Trials were conducted using the unfractionated fiber, short fiber, and long fiber. The short and long fibers were mixed in several trials to study the effect of fiber length. The concentration of cPAM was varied as well as the motor speed of the impeller (RPM). It was found that the average fiber length decreased more rapidly with increasing motor speed. Increasing the concentration of cPAM also led to a greater decrease in average fiber length. A key finding was that a plateau was reached where further increasing the amount of cPAM had no effect. Hence, fibers below a critical length resisted flocculation even if the chemical dose or shear was increased. This critical length was related to the initial length of the fiber.

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Srinivas, K. T. "Axial strain effects on optical fiber mode patterns." Thesis, This resource online, 1987. http://scholar.lib.vt.edu/theses/available/etd-04122010-083554/.

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Dissertations / Theses on the topic 'Fibers'

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