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Published: 10 December 2022
Last updated: 28 January 2023

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1

Lozano, Flavien. "Elaboration de matelas à base de fibres de verre par voie humide." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI001.

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Les matelas fibreux à base de fibres de verre produits par voie humide ont des applications industrielles en tant que séparateur de batterie et matériaux d’isolation (cœur de panneaux d’isolation sous vide). Ces matériaux utilisent principalement des fibres submicroniques, relativement chères et pouvant présenter des risques pour la santé. Ce projet est une contribution à l'élaboration d'un procédé de fabrication par voie humide de matelas de fibres de verre visant à valoriser des fibres plus grossières, le produit final devant respecter un cahier des charges précis. Nous avons été amenés à étudier le comportement des fibres de verre dans les différentes étapes du procédé et à caractériser les matelas résultants. Nous nous sommes intéressés en particulier au comportement physico-chimique des suspensions aqueuses de fibres de verre. Nous avons caractérisé les propriétés de contexture, la résistance mécanique en traction, la compressibilité et la conductivité thermique des matelas fibreux. Les travaux expérimentaux nous ont permis de proposer une formulation de la composition optimisée et des conditions opératoires du procédé afin que le matelas final soit conforme au cahier des charges. Cette nouvelle composition intègre des fibres de renfort en faible quantité. Elle permet d’améliorer les caractéristiques mécaniques sans affecter les autres propriétés.Enfin, nous avons quantifié les coûts de production et les avons comparés à ceux du procédé actuellement utilisé avec des fibres grossières (production par voie sèche).Mots-clés : Génie papetier, physico-chimie, milieu poreux, fibres de verre, caractérisation
Glass fibre - based mats produced by a wetlaid process have industrial applications as a battery separator and insulation materials (core of vacuum insulation panels). These materials are mainly made with sub-micron fibres which relatively expensive and can present a risk to health. This project is a contribution to the production of glass fibre-based mats by a wet-laid process to add value to coarser fibres, the final product should respect precise specifications. We have been led to study the behavior of glass fibers in different stages of the process and to characterize the resulting mats. We investigated especially the physico-chemical behavior of aqueous suspensions of glass fiber. We have characterized structure properties, the mechanical resistance to traction, the compressibility and the thermal conductivity of fibrous mats. The experimental work has allowed us to give a formulation of the optimized composition and operational conditions of the process so that the final mattress conforms to the specifications. This new composition includes reinforcement fibres in small quantities. It allows improving the mechanical characteristics without affecting the other properties. Finally, we quantified the production costs and compared them to those of the process currently used with coarse fiber (dry-laid production).Keywords: Paper engineering, physical chemistry, porous media, glass fibre, characterization
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2

Forsström, Jennie. "Fundamental Aspects on the Re-use of Wood Based Fibres : Porous Structure of Fibres and Ink Detachment." Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-84.

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In this work, different aspects on the re-use of wood based fibres have been studied, focusing on ink detachment of flexographic ink from model cellulose surfaces and changes in porous structure of kraft fibres following different treatments. New model systems for evaluation of ink detachment and ink-cellulose interactions were used. Ink detachment was studied using Impinging jet cell equipment, taking into consideration the influence of storage conditions, surface roughness and surface energy of the cellulose substrate. A micro adhesion measurement apparatus (MAMA) was used to directly study ink-cellulose interactions, from which the adhesive properties between ink and cellulose, having various surface energies, could be derived. UV-light, elevated temperatures, longer storage time, decreased surface energy, i.e. making the cellulose surface more hydrophobic, and high surface roughness all negatively affected ink detachment. Attenuated total reflectance - fourier transform infra red (ATR-FTIR) and atomic force microscopy (AFM) was used to evaluate structural and chemical changes of ink and cellulose upon storage at elevated temperature or under UV-light. After storage at elevated temperatures, ATR-FTIR spectra indicated that a hydrolysis or an oxidative reaction took place as a peak at 1710 cm-1 appeared. AFM revealed that storage at elevated temperatures caused the latex particles present in the ink to form a film, most likely due to annealing. Less ink detached from hydrophobic cellulose surfaces. Ink detachment decreased for rougher cellulose substrates due to an increased molecular contact area.

Fibre pore structure and water retaining ability influenced fibre/fibre joint strength and different paper strength properties. Investigations took into account the effect of pulp yield, counter-ion types, pH, salt, hornification and strength enhancing additives. Nuclear magnetic resonance relaxation (NMR), inverse size exclusion chromatography (ISEC) and water retention value (WRV) measured the changes that occur in the fibre wall upon varying the conditions. Each different measuring technique contained unique information such that a combination of the techniques was necessary to give as complete a picture as possible over the changes that occurred in the fibre wall upon varying the conditions for the fibre. A correlation between fibre pore radius and sheet strength properties was found, suggesting that fibres with larger pores allow for a larger molecular contact area between fibres to be formed during drying and consolidation of the paper. Fibre/fibre joint strength, fibre flexibility, and the number of efficient fibre/fibre contacts also controlled sheet strength. The effect of different strength enhancing additives on fibre pore structure and paper strength was investigated. Larger pores in the fibres allowed for additives to penetrate into the fibre wall. Additives with low molecular mass (Mw) penetrated into the fibre wall to a larger extent than additives with a high Mw, causing an embrittlement of the fibre. However, low Mw additives gave higher sheet tensile strength despite a leveling out in strength at high additions, indicating that the fibre wall can only adsorb a limited amount of chemical. Polyallylamine hydrochloride (PAH) and polyelectrolyte complexes (PEC) of PAH and polyacrylic acid (PAA) were added separately to the pulp. PEC significantly improved both tensile strength and Z-strength, whereas PAH alone did not increase the strength properties to the same extent unless the sheets were heated to 150°C for 10 minutes. The results suggested that the effect of PEC was dominated by an improvement in fibre/fibre joint strength, whereas the effect of PAH was significantly affected by an improvement of the intra-fibre bond strength

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3

Forsström, Jennie. "Fundamental aspects on the re-use of wood based fibres : porous structure of fibres and ink detachment /." Stockholm, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-84.

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4

Katsogiannis, Konstantinos A. G. "Single step production of nanoporous electrospun poly(ε-caprolactone) fibres." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/22929.

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Nanoporous polymer fibres are currently attracting increasing interest due to their unique characteristics. Increased specific surface area, improved mechanical properties and improved cellular growth are amongst the advantages that set porous fibres as ideal candidates in applications like catalysis, separation and tissue engineering. This work explores the single step production of porous poly(ε-caprolactone) (PCL) fibres through combinative electrospinning and Non-solvent Induced Phase Separation (NIPS) technique. Theoretical models, based on three different contact models (Hertzian, DMT, JKR), correlating the fibrous network specific surface area to material properties (density, surface tension, Young s modulus, Poisson s ratio) and network physical properties (density) and geometrical characteristics (fibre radius, fibre aspect ratio, network thickness) were developed in order to calculate the surface area increase caused by pore induction. Experimental results proved that a specific surface area increase of up to 56% could be achieved, compared to networks composed of smooth surfaced fibres. The good solvent effect on electrospun fibre surface morphology and size was examined through experimental investigation of four different good solvent (chloroform, dichloromethane, tetrahydrofuran and formic acid) based solutions at various good/poor solvent ratios. Chloroform was proven to be the most suitable solvent for good /poor solvent ratios varying from 75-90% v/v, whereas alternative mechanisms leading to different fibre morphologies were identified, interpreted and discussed. Evaporation rate of the good solvent was identified as the key parameter of the process. Second order polynomial equations, derived from the experimental data, correlating the feed solution physical parameters (viscosity, conductivity, surface tension) to the fibre average diameter produced were developed and validated. Response surface methodology was implemented for the design and conduction of electrospinning experiments on a 12.5 % w/v Chloroform/DMSO solution 90/10 % v/v in order to determine the individual process parameters (spinning distance, applied voltage, solution flow rate) effect in fibre surface morphology and size. The increase in any of these parameters results in increase of both the fibre size and the tendency for pore generation, whereas applied voltage was the parameter with the strongest effect. Findings from this thesis expand the knowledge about both phenomena occurring during the production process and end product properties, and can be used for the production of controlled morphology and size porous poly(ε-caprolactone) (PCL) fibres.
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5

Collignon, Brice. "Séchage des bétons réfractaires : expérimentation, modélisation et influence d'un ajout de fibres polymère." Thesis, Vandoeuvre-les-Nancy, INPL, 2009. http://www.theses.fr/2009INPL051N/document.

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Les matériaux réfractaires non façonnés dense (MRNF) prennent une part de plus en plus importante aussi bien en cimenterie, fonderie, sidérurgie, ... Principalement constitués d’agrégats à base d’alumine, de magnésie, de spinelle, … ils constituent des matériaux de faible perméabilité contenant une teneur résiduelle en eau de 4 à 6 %. Leur séchage avant leur première utilisation est une opération critique qui conditionne leur durée de vie. D’une part, mal conduit, il peut du fait des endommagements occasionnés, réduire considérablement la durée de vie des installations. D’autre part, certaines conditions de séchage conduisent à une véritable destruction de nature explosive du matériau correspondant à une élévation brutale de la pression interne (accompagnant l’élévation de la pression de vapeur saturante de l’eau avec la température). Le travail a permis de se familiariser avec les matériaux réfractaires non-façonnés à l’aide d’une caractérisation thermomécanique complète menée entre la température ambiante et 500 °C, de comprendre les mécanismes mis en jeu lors de leur séchage, d’une part, par une expérimentation et, d’autre part, en les reproduisant en s’appuyant sur un transfert simultané de chaleur et de masse en milieu poreux. Et enfin, il a permis d’étudier l’impact d’un ajout de fibres polymère sur une caractéristique qui gère l’évacuation de l’eau, la perméabilité, et plus généralement sur le séchage
Castable refractories take a more and more important place in various industries: cement factory, casting, iron and steel making. They consist mainly of aggregates of high-alumina and ultra-low cement. Their permeability is very low and they contain before the first heat-up a residual water content of 4 to 6 % (dry basis). Drying during the first heat-up is a crucial step which sharply influence the refractory in-service performances. On one hand, damaging can occur, and as a consequence will reduce drastically the life time of the plants. On the other hand, particular drying conditions can lead to an explosive spalling of the refractory corresponding to an internal gas pressure steep raise linked to the water saturated vapour pressure raise with temperature. First, a complete thermomechanical characterization between ambient temperature and 500 °C of the unshaped refractory materials has been conducted. Then the mechanisms involved during their drying, on one hand, by an experiment and, on the other hand, by using a simultaneous heat and mass transfer model in porous media have been studied. And last, the impact of adding polymer fibers has been analysed both on the concrete permeability as well as their influence on drying
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6

Loffler, Steven Marc. "Dyeing of cellulose fibres : a case study in structure-transport relationships in heterogeneous porous media." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627033.

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7

Shukla, Sushumna. "Membrane distillation with porous metal hollow fibers for the concentration of thermo-sensitive solutions." Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20215/document.

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Cette thèse présente une approche originale du procédé de distillation membranaire avec balayage gazeux pour la concentration des solutions thermosensibles (SGMD). Pour ce faire, un nouveau contacteur membranaire avec des fibres creuses métalliques a été conçu afin réaliser le procédé de distillation à basse température. La chaleur nécessaire au procédé est produite au niveau des fibres par effet Joule, plutôt qu'à partir de chaleur latente de la phase aqueuse. La génération localisée de la chaleur a comme conséquence une réduction du phénomène de polarisation de la température. Des fibres creuses en acier inoxydable ont été synthétisées avec les propriétés structurales appropriées et une bonne résistance mécanique. La surface des pores des fibres a été rendue hydrophobe par le dépôt d'une fine couche d'un élastomère. En outre, une nouvelle méthode « verte » a été développée pour fabriquer des fibres creuses en alumine et acier inoxydable. Cette méthode est basée sur la gélification ionique des bio-polymères et ne n'utilise pas des solvants nocifs. L'étude expérimentale détaillée du SGMD a permis de déterminer l'influence de différents paramètres opérationnels sur les performances du procédé. Il a été démontré que l'effet Joule permet d'améliorer le flux et l'efficacité de la séparation non seulement pour le SGMD mais aussi pour la pervaporation
This thesis presents an original approach for the concentration of thermo-sensitive solutions: the Sweep Gas Membrane Distillation (SGMD) process. A new membrane contactor with metallic hollow fibers has been designed and allows the distillation process to be operational at low temperature. Heat is generated in the fibers by the Joule effect, rather than being supplied as latent heat in the liquid bulk. The localized generation of heat results in a reduction of temperature polarization phenomena. The stainless-steel hollow fiber membranes have been synthetized with appropriate structural properties and sufficient mechanical strength. The pore surface of the fibers has been made hydrophobic by the deposition of a thin layer of an elastomer. Moreover, a novel and green method is presented to fabricate alumina and stainless-steel hollow fibers. This method is based on ionic gelation of a biopolymer and completely avoids the use of harmful solvents. By a detailed experimental study of the SGMD the influence of different operational parameters on the process performance has been investigated. The improvements in the flux and the separation efficiency using Joule effect have been successfully demonstrated, even in the case of pervaporation
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8

Salinas-Torres, David. "Tailoring of carbon materials for their use as electrodes in electrochemical capacitors." Doctoral thesis, Universidad de Alicante, 2014. http://hdl.handle.net/10045/45286.

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9

Biasi, Valentin. "Modélisation thermique de la dégradation d’un matériau composite soumis au feu." Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0034/document.

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L’utilisation des matériaux composites devient de plus en plus importante dans les structures aéronautiques de nouvelle génération. Le gain de masse engendré, et donc de carburant, pousse les constructeurs aéronautiques à les employer de façon optimale. Néanmoins, ces matériaux se dégradent rapidement lorsqu’ils sont soumis à des flux de chaleur importants, entraînant une perte de leur résistance mécanique. Ce problème peut être dramatique pour la sécurité des passagers car la tenue de ces nouvelles structures peut ne plus être assurée dans le cas d’un incendie. Les méthodes actuelles de certification de la tenue au feu des matériaux composites aéronautiques reposent principalement sur l’utilisation de moyens expérimentaux, dont les résultats ne sont représentatifs que des conditions particulières dans lesquelles les essais ont été réalisés. La compréhension des différents phénomènes thermiques, chimiques et mécaniques intervenant lors de la dégradation de ces matériaux, avec l’appui de simulations numériques et d’expériences, peut permettre d’améliorer les méthodes existantes et donc d’optimiser les futures structures aéronautiques dès la phase de conception.Cette étude s’est attachée à développer et valider un modèle thermo-chimique de dégradation des matériaux composites multi-dimensionnel et multi-constituants. Ce modèle permet de traiter des cinétiques de dégradation complexes suivant plusieurs réactions de décompositions et de prendre en compte le transport des gaz produits depuis leur formation jusqu’à leur évacuation hors du matériau. L’utilisation de lois d’homogénéisation avancées est proposée afin de rendre compte des effets des transformations sur les transferts de chaleur et de masse se produisant au sein du matériau. L’application du modèle thermo-chimique à un cas de dégradation sous flux thermique connu mais non-uniforme dans un environnement contrôlé permet de confronter les résultats de simulation aux mesures expérimentales et ainsi de valider l’approche multi-constituants adoptée. Enfin, l’étude numérique de la dégradation d’un composite soumis à une flamme met en avant l’effet des gaz de décomposition éjectés à l’interface sur le flux thermique pariétal échangé
Composite materials are increasingly used in new generation aircraft structures. Mass and as a consequence fuel savingsencourage aircraft manufacturers to use them optimally. However, these materials can degrade quickly when exposed tosignificant heat fluxes, resulting in a loss of mechanical strength. This problem can be dramatic for passenger safety asmechanical resistance of such innovative structures can not be ensured in case of fire events. Current certification methodsof fire resistance of aeronautical composite materials are mainly based on experiments, that are only representative of thespecific conditions under which they were carried out. The understanding of thermal, chemical and mechanical phenomenaoccurring during the decomposition of these materials, with the support of numerical simulations and experiments, can helpimproving existing methods and optimizing the future aeronautical structures from the design chain. This study deals withthe development and validation of a multi-components and multi-dimensional thermo-chemical model of decomposing compositematerials. It can deal with complex degradations following several decomposition reactions as well as transport ofpyrolysis gases from their formation up to their ejection out of the material. The use of advanced homogenization laws isproposed to account for the chemical transformations on heat and mass transfers occurring in the material. The applicationof the thermo-chemical model to a laser degradation study under known but non-uniform heat flux in a controlled environmentallows to confront the simulation results with experimental measurements and thus validate the multi-componentsapproach. Finally, the numerical analysis of a decomposing composite material submitted to a flame highlights the effectof emitted decomposition gases on the exchanged parietal heat flux
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10

Novotná, Aneta. "Možnosti využití rozptýlené výztuže pro lehké konstrukční betony." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226093.

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Master´s thesis deals with some problems associated with utilisation of lightweight concrete from the porous aggregates in the load – carrying structures. The thesis focuses on the possibilities of the increase of the cement composites toughness using dispersed reinforcement. Lightweight concretes were reinforced with a combination of different lengths of polypropylene fibers Forta Ferro. There were used polypropylene fibers of three lengths 19, 38, 54 mm. The thesis is divided into theoretical, experimental and static part.
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11

Nam, Gi-moon. "Dynamics of confined biofilaments." Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAE048/document.

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Cette thèse est consacrée à la mécanique et à la mécanique statistique de biofilaments/biopolymères et de leur modèle le plus répandu le Worm-Like Chain (WLC) qu’il s’avère nécessaire d’étendre. Nous étudions WLC à 2-d en présence d’obstacles plus proches que la longueur de persistance. Nous caractérisons le mouvement aux temps courts par des simulations numériques complétées par des calculs analytiques. Des concepts similaires servent à décrire des ADN greffés balayés par le front d’une vésicule en cours d’étalement, l’adhésion de la vésicule est promue par des paires biotine/streptavidine qui contraignent les molécules d'ADN sur des chemins étroits où ils peuvent être imagés. Les microtubules (MT) ici stabilisés au taxol, présentent par contre certains comportements qui échappent au WLC et doivent être ramenés à leur structure interne : i)les déflexions latérales d’un MT attaché par un bout correspondent à une longueur de persistance apparente qui augmente avec la longueur ii) les MT adoptent des formes super-hélicoïdales. Ces deux points sont établis au moyen d’analyses de forme des MT. Des transitions de forme corrélées le long du MT mises en évidence sont compatibles avec un modèle basé sur la bistabilité du dimère de tubuline. Finalement un modèle de chaîne super-hélicoïdale comprenant une courbure et une torsion spontanées élargi le WLC. Confiné à 2-d, HWLC peut adopter un état fondamental circulaire ou sinueux caractérisé par le nombre de points d’inflexion où se concentre la torsion (twist-kink). Dans le cas circulaire, il existe des états métastables proches, à petit nombre de twist-kinks, hyperflexibles
This PhD is devoted to the mechanics and statistical mechanics of biofilaments and their most widespread model, the Worm-Like Chain (WLC) model, which, as it turns out, needs to be extended. We study the WLC in 2-d in the presence of obstacles closer than their persistence length. We characterize the short time motion by numerical simulations complemented by analytical calculations. Similar concepts serve to describe grafted DNAs swept by the front of a spreading vesicle whose adhesion is promoted by biotin/streptavidin bonds, which constrain the DNAs on narrow paths where they can be imaged. Microtubules (MT), here stabilized by taxol, show features which cannot be rationalized by the WLC and shall be related to their internal structure : i)lateral deflections of a clamped MT correspond to an effective persistence length growing with the MT size ii) MT adopt super-helical shapes. These two points are proven by refined image analysis. We analyze shape transitions correlated along the MT which are compatible with a model based on dimer bi-stability. Finally, a super helical chain model (HWLC) allowing for spontaneous curvature and twist is developed which extends the WLC. When confined to 2-d, the HWLC can adopt a ground state which is circular or wavy with inflection points where twist accumulates, so-called twist-kinks. In the circular case there exist close metastable states, with a small number of twist-kinks, which are hyperflexible
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12

Luminari, Nicola. "Modeling and simulation of flows over and through fibrous porous media." Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/20132/1/LUMINARI_Nicola.pdf.

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Any natural surface is in essence non-smooth, consisting of more or less regular roughness and/or mobile structures of different scales. From a fluid mechanics point of view, these natural surfaces offer better aerodynamic performances when they cover moving bodies, in terms of drag reduction, lift enhancement or control of boundary layer separation; this has been shown for boundary layer or wake flows around thick bodies. The numerical simulation of microscopic flows around "natural" surfaces is still out of reach today. Therefore, the goal of this thesis is to study the modeling of the apparent flow slip occurring on this kind of surfaces, modeled as a porous medium, applying Whitaker's volume averaging theory. This mathematical model makes it possible to capture details of the microstructure while preserving a satisfactory description of the physical phenomena which occur. The first chapter of this manuscript provides an overview of previous efforts to model these surfaces, detailing the most important results from the literature. The second chapter presents the mathematical derivation of the volume-averaged Navier-Stokes equations (VANS) in a porous medium. In the third chapter the flow stability at the interface between a free fluid and a porous medium, formed by a series of rigid cylinders, is studied. The presence of this porous layer is treated by including a drag term in the fluid equations. It is shown that the presence of this term reduces the rates of amplification of the Kelvin-Helmholtz instability over the whole range of wavenumbers, thus leading to an increase of the wavelength of the most amplified mode. In this same context, the difference between the isotropic model and a tensorial approach for the drag term has been evaluated, to determine the most consistent approach to study these flow instabilities. This has led to the conclusion that the model that uses the apparent permeability tensor is the most relevant one. In the following chapter, based on this last result, the apparent permeability tensor, based on over one hundred direct numerical simulations carried out over microscopic unit cells, has been identified for a three-dimensional porous medium consisting of rigid cylinders. In these configurations the tensor varies according to four parameters: the Reynolds number, the porosity and the direction of the average pressure gradient, defined by two Euler angles. This parameterization makes it possible to capture local three-dimensional effects. This database has been set up to create, based on a kriging-type approach, a behavioral metamodel for estimating all the components of the apparent permeability tensor. In the fifth chapter, simulations of the VANS equations are carried out on a macroscopic scale after the implementation of the metamodel, to get reasonable computing times. The validation of the macroscopic approach is performed on a closed cavity flow covered with a porous layer and a comparison with the results of a very accurate DNS, homogenized a posteriori, has shown a very good agreement and has demonstrated the relevance of the approach. The next step has been the study of the passive control of the separation of the flow past a hump which is placed on a porous wall, by the same macroscopic VANS approach. Finally, general conclusions and possible directions of research in the field are presented in the last chapter.
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MENESES, J. P. C. "ESTUDO Experimental de Parâmetros de Dosagem e Desempenho de Concreto Asfáltico Poroso Com Adição de Fibras de Bagaço de Cana-de-açúcar." Universidade Federal do Espírito Santo, 2017. http://repositorio.ufes.br/handle/10/9493.

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Made available in DSpace on 2018-08-01T23:58:55Z (GMT). No. of bitstreams: 1 tese_11462_João Paulo.pdf: 449446 bytes, checksum: a7d43e3f0e06777c60f60abd18c547cb (MD5) Previous issue date: 2017-09-18
Revestimentos asfálticos porosos, conhecidos como camada porosa de atrito (CPA), são uma técnica bastante difundida internacionalmente, visto suas vantagens sobre pavimentos comuns, principalmente em condições chuvosas, como redução de spray e risco de aquaplanagem, aumento da aderência pneu-pavimento e redução do fenômeno de espelhamento noturno. Em contraponto, um dos problemas da mistura é sua maior susceptibilidade ao escorrimento de ligante, e uma das formas de se minimizar o fenômeno é a utilização de fibras na dosagem. As fibras de bagaço de cana-de-açúcar são uma das opções de fibras, e seu emprego é motivado por questões ambientais, pois as fibras são de origem do resíduo da indústria sucroalcooleira. O Brasil, devido ao seu posicionamento geográfico, apresenta períodos intensamente chuvosos e, dessa forma, o emprego de revestimentos asfálticos porosos se mostra bastante adequado. Todavia, os estudos e aplicações de CPA no país ainda são incipientes, seja por questões de custo e/ou ausência de normas específicas nacionais para dosagem desse tipo de mistura. Deste modo, buscou-se avaliar o comportamento físico e mecânico de CPAs com adição de fibras de celulose (CEL), comumente empregadas para minimizar o escorrimento em CPAs, mas também com fibras de bagaço de cana-de-açúcar (BCA). Devido à ausência de regulamentação nacional, empregou-se para a dosagem a ASTM D7064-13. Além de resistência à abrasão (Los Angeles) e escorrimento de ligante, ensaios mínimos estabelecidos por norma para dosagem de CPA, foram verificados módulo de resiliência (MR), resistência à tração (RT) e permeabilidade, para avaliar o desempenho das misturas. As misturas BCA apresentaram maior valor de escorrimento de ligante, embora o BCA tenha reduzido o escorrimento comparando-se a uma mistura referência (sem fibras). Ainda, menores valores obtidos para relação MR/RT para as misturas BCA, indicaram melhor comportamento de vida de fadiga. Ainda que os resultados de permeabilidade obtidos tenham sido baixos, foi possível concluir que a presença de fibras pode reduzir significativamente o coeficiente de permeabilidade de CPAs. Palavras-chave: asfalto poroso (AP); camada porosa de atrito (CPA); fibras; celulose; bagaço de cana-de-açúcar (BCA); durabilidade; fadiga; drenabilidade.
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14

Cadet, Marine. "Vers la conception d’une biopile enzymatique à glucose/oxygène efficace en milieu biologique." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0260/document.

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La première partie du travail présenté ici se concentre sur l’optimisation d’une cathode à oxygène. Tout d’abord, l’utilisation d’une nouvelle enzyme (la BOD de Magnaporthe oryzae) permet de multiplier le courant de réduction de l’oxygène en eau jusqu’à neuf fois. Ensuite la synthèse d’un polymère rédox adapté a permis d’améliorer le coefficient de diffusion des électrons dans l’hydrogel résultant en l’augmentation de la densité de courant générée. Enfin nous sommes passés d’uneélectrode de carbone en 2 dimensions à une fibre d’or poreuse tridimensionnelle. Après modification de cette fibre avec l’hydrogel rédox à base de BOD de M. oryzaenous avons évalué sa biocompatibilité : in vitro les tests ont montré l’absence totale de cytotoxicité et seule une très faible réponse inflammatoire ; in vivo aucune infection ne s’est déclarée pendant les 8 semaines d’implantation dans les souris etla formation d’une capsule fibrotique autour de l’électrode traduit sa bonne intégration dans les tissus de l’animal. La seconde partie concerne la biopile dans son intégralité, construite à partir de la cathode optimisée et d’une anode adaptée à base de GDH. Elle permet de générer jusqu’à 240 μW.cm-2 dans du tampon Pipes/CaCl2 à 5mM de glucose. La biopile a ensuite été testée dans du sang humain total. Un maximum de 129 μW.cm-2 a été obtenu dans un échantillon avec une glycémie de 8,2 mM sous air. De plus nous avons constaté que la densité de puissance délivrée augmente proportionnellement avec la glycémie des différents échantillons de sang testés, faisant de la biopile à la fois une source d’électricité et un biocapteur à glucose ce qui n’avait jamais été démontré auparavant
The first part of the work presented here focuses on the optimization of an oxygen cathode. First, the use of a new enzyme (BOD from Magnaporthe oryzae) permit to increase the current of reduction of oxygen into water by a factor nine. Then the synthesis of a suitable redox polymer greatly improved the diffusion coefficient of electrons in the hydrogel, resulting in an increase of the current density. Finally we switched from a two-dimensional carbon electrode to a three-dimensional porous gold fiber. After modification of the fiber with the redox hydrogel based on BOD from M. oryzae, we assessed its biocompatibility: in vitro the tests showed the total absence of cytotoxicity and only a very low inflammatory response; in vivo noinfection appeared during the 8 weeks of implantation in mice and the formation of afibrotic capsule around the device reflects its successful integration into the animal tissues.The second part concerns the full biofuel cell, elaborated from the optimized cathode and an adapted GDH-based anode. It could generate up to 240 μW.cm-2 at 5mMglucose in Pipes/CaCl2 buffer. The biofuel cell was then tested in whole human blood. A maximum of 129 μW.cm-2 was obtained in a sample with 8,2 mM glycaemiaunder air. In addition we observed that the delivered power density increased proportionally with the glycaemia of the different blood samples tested, making the biofuel cell both a power source and a glucose biosensor at the same time which had never been shown before
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15

Chaves, Vieira Lins Luanda. "Study and development of electrospun fibers for biotechnology application." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI073.

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Actuellement, le procédé d’électrofilage également appelé electrospinning est une des voies les plus prometteuses permettant le design et le développement de nanofibres polymères poreuses. En effet, cette technique est simple d’utilisation, unique, modulable, à faible coût et est déjà couramment utilisée dans le milieu industriel. De part ces avantages, l’electrospinning fait l’objet d’un engouement grandissant de la recherche académique et industrielle dans plusieurs domaines d’applications tels que ceux de la filtration, la cosmétique, du textile, de l’ingénierie tissulaire et du domaine médical, notamment pour le relargage de molécules actives. De plus, cette technique est applicable sur de nombreux polymères synthétiques ou naturels et il est possible de contrôler de nombreux paramètres tels que la porosité, le diamètre des fibres ou encore la surface accessible. Un des premiers objectifs de cette thèse a été de développer des scaffolds pour le domaine de l’ingénierie des tissus neuronaux afin d’imiter les propriétés biologiques, physiques et mécaniques de la matrice extracellulaire native. Dans un premier temps, l’effet de l’alignement des fibres d’une matrice fluorée (PVDF) biocompatible a été étudié sur le comportement de cellules souches neurales de singe, en particulier les morphologies, l’adhésion cellulaire ainsi que leurs différentiations en cellules gliales ou neuronales. Dans un second temps, des scaffolds bioabsorbables composés de PLA et de PEG ont été synthétisés afin d’étudier l’influence de l’équilibre hydrophile-hydrophobe sur la culture de cellules souches neurales. Et dans une dernière partie, une véritable étude exploratoire a été réalisée afin de développer des textiles intelligents à base de PBAT contenant des curli, protéine bien connue pour sa capacité à chélater des métaux
Currently, the electrospinning process is also one of the most promising routes for the design and development of polymer fibers. This technique is easy to use, unique, versatile, and low cost, which can be used to create fibers from a variety of starting materials. The structure, chemical and mechanical stability, functionality, and other properties of the fibers can be modified to match end applications. The first goal of this thesis was to develop scaffolds for the field of neural tissue engineering in order to mimic the biological, physical and mechanical properties of the native extracellular matrix. In the first time, the effect of fiber alignment of a biocompatible and fluorinated matrix denoted polyvinylidene fluoride (PVDF) was studied on the behavior of monkey neural stem cells particularly the morphology, cell adhesion and their differentiation in glial or neuronal cells. Secondly, bioabsorbable scaffolds composed of polylactide (PLA) and polyethylene glycol (PEG) polymers were synthesized to investigate the influence of the hydrophilic-hydrophobic balance on the culture of neural stem cells. Finally, an exploratory work was conducted to develop smart textiles based on poly(butylene adipate-co-terephthalate) (PBAT) containing curli as protein, well-known for its ability to chelate metals
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16

Manning, John Peter. "Modèle acoustique d'une couche absorbante composée de fibres Shoddy." Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/5515.

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Shoddy fibres or"Shoddies" are a mixture of post-consumer and post-industrial fibres diverted from textile waste streams and recycled into their raw fibre form. They have found widespread use as a raw material for manufacturing sound absorbers that include, but are not limited to: automotive, architectural and home appliance applications. The purpose of this project is to develop a simple acoustic model to describe the acoustic behaviour of sound absorbers composed primarily of Shoddy fibres. The model requires knowledge of the material's bulk density only. To date, these materials have not been the focus of much published research and acoustical designers must rely on models that were developed for other materials or are overly complex. For modelling purposes, an equivalent fluid approach is chosen to balance complexity and accuracy. In deriving the proposed model, several popular equivalent fluid models are selected and the required input parameters for each model identified. The models are: the model of Delaney and Bazley, two models by Miki, the model of Johnson in conjunction with the model of Champoux and Allard and the model of Johnson in conjunction with the model of Lafarge. Characterization testing is carried out on sets of Shoddy absorbers produced using three different manufacturing methods. The measured properties are open porosity, tortuosity, airflow resistivity, the viscous and thermal characteristic lengths and the static thermal permeability. Empirical relationships between model parameters and bulk density are then derived and used to populate the selected models. This yields several"simplified" models with bulk density as the only parameter. The most accurate model is then selected by comparing each model's prediction to the results of normal incidence sound absorption tests. The model of Johnson-Lafarge populated with the empirical relations is the most accurate model over the range of frequencies considered (approx. 300 Hz - 4000 Hz) Characterization testing yields specific values for intrinsic material parameters that allow for comparison to other porous materials. Individual parameter relations allow users to substitute measured or theoretical values as needed. A new empirical acoustical model is proposed to describe the behaviour of Shoddy-based fibre absorbers. The model requires knowledge of the bulk density only. This parameter is easily measured making application of the model elementary.
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17

Bijeljic, Branko. "Flow and mass transfer in fibrous and granular porous media." Thesis, Imperial College London, 2000. http://hdl.handle.net/10044/1/8005.

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18

Vallabh, Rahul. "Modeling Tortuosity in Fibrous Porous Media using Computational Fluid Dynamics." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-08062009-153236/.

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Tortuosity factor is often used to characterize the structure of the pore volume in fibrous porous media. This work involves the determination of tortuosity using computational fluid dynamic (CFD) simulation and particle tracking analysis. A new method has been adopted to generate 3-D geometry for modeling fibrous porous structures using ANSYS® Parametric Design Language (APDL). Computation fluid dynamics has been used to simulate permeability of modeled 3-D fiberweb structures. The simulated permeability results are in good agreement with the models proposed by other authors. The experimental results were found to be slightly higher compared to simulated results and existing models due to the layered configuration of the samples. Permeability is found to be significantly influenced by fiber diameter, and porosity as well as fiberweb thickness. The relationship between air permeability and fiberweb thickness has been used to develop an indirect method for determination of tortuosity factor. Tortuosity factor has also been determined using a more direct method involving CFD simulation and Particle Tracking analysis. Different models established using the direct and indirect methods of determination show that tortuosity is significantly influenced by porosity, fiber diameter and fiberweb thickness, whereas the models available in the literature express tortuosity as a function of porosity only.
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19

Palakurthi, Nikhil Kumar. "Direct Numerical Simulation of Liquid Transport Through Fibrous Porous Media." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406881191.

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20

Williams, Edward McRae. "A model of the formation of a porous fibrous cake." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06162009-063510/.

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21

Van, Heyningen Martha Catharina. "Investigating the effect of compression on the permeability of fibrous porous media." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86245.

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Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Fluid flow through porous media plays an important role in a variety of contexts of which filtration is one. Filtration efficiency of fibrous filters depends on the micro-structural characterization of these porous materials and is reflected in the permeability there-of. Compression of fibrous porous media has a significant effect on the permeability. Experimental data indicate that the permeability varies generally with more than an order of magnitude over the narrow porosity range in which the compression takes place. Relative to the amount of experimental studies regarding this phenomenon, there is a scarcity of geometric models in the literature that can account for the effect of compression on the permeability of a fibrous porous medium. Within the context of existing geometric porescale models based on rectangular geometry, a new model is presented and an existing model improved to predict the effect of one-dimensional compression in the streamwise direction. In addition, without compromising on a commitment to mathematical simplicity, empirical data of a non-woven fibrous porous medium was used to highlight the effect of model geometry on its predictive capability. Different mathematical expressions for the relationship between compression and porosity were considered. The permeability is expressed explicitly in terms of the fibre diameter and the compression fraction and implicitly in terms of the porosity. The porosity is incorporated through the relationship between the linear dimensions of the geometric model. The general applicability of the model(s) was validated by making use of data on airflow through a soft fibrous porous material as well as through glass and nylon fibres. The permeability predictions fall within the same order of magnitude as the experimental data. Given the mathematical simplicity of the model(s), the prediction capability is satisfactory. Attention is drawn to assumptions made and model restrictions within the analytical modelling procedure. A general predictive equation is presented for the permeability prediction in which a solid distribution factor is introduced. The proposed models serve as basis for further adaptation and refinement towards prediction capability.
AFRIKAANSE OPSOMMING: Vloei van vloeistowwe deur poreuse media speel ’n belangrike rol in ’n verskeidenheid kontekste waarvan filtrasie een is. Die filtrasie doeltreffendheid van vesel filters hang af van die mikro-strukturele karakterisering van hierdie poreuse materiale en word gereflekteer in die permeabiliteit. Kompressie van veselagtige poreuse media het ’n beduidende effek op die permeabiliteit. Eksperimentele data dui aan dat die verandering in permeabiliteit gewoonlik oor meer as ’n orde grootte strek oor die klein porositeitsinterval waarin die kompressie plaasvind. Relatief tot die aantal eksperimentele studies rakende hierdie verskynsel, is daar ’n tekort aan geometriese modelle in die literatuur wat die effek van kompressie op die permeabiliteit van veselagtige poreuse media in ag kan neem. Binne die konteks van bestaande geometriese kanaal-skaal modelle gebasseer op reghoekige geometrie, is ’n nuwe model voorgestel en ’n bestaande model verbeter om die effek van een-dimensionele kompressie in die stroomsgewyse rigting te voorspel. Sonder om die verbintenis tot wiskundige eenvoud prys te gee, is empiriese data van ’n nie-geweefde veselagtige poreuse medium gebruik om die effek van die geometrie van ’n model op sy voorspellingsvermo¨e uit te lig. Verskillende wiskundige uitdrukkings is oorweeg vir die verband tussen kompressie en porositeit. Die permeabiliteit is eksplisiet uitgedruk in terme van die veseldiameter en die kompressie breukdeel en implisiet in terme van die porositeit. Die porositeit is ge-inkorporeer deur die verhouding tussen die lineêre dimensies van die geometriese model. Die algemene toepaslikheid van die model(le) is gestaaf deur gebruik te maak van data oor lugvloei deur ’n sagte veselagtige poreuse materiaal sowel as deur glas en nylon vesels. Die voorspellings van die permeabiliteit val binne dieselfde groote orde as die eksperimentele data. Gegee die wiskundige eenvoud van die model(le), is die voorspellingsvermoë bevredigend. Aandag is gevestig op aannames wat gemaak is en modelbeperkings binne die analitiese modellerings prosedure. ’n Algemene voorspellingsvergelyking is voorgestel vir die voorspelling van die permeabiliteit waarin ’n vaste stof distribusie faktor geinkorporeer is. Die voorgestelde modelle dien as basis vir verdere aanpassing en verfyning van voorspellingsvermoë.
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22

Badini, G. E. "Investigation of porous glass-like substrates for use in fibre-optic chemical sensors." Thesis, City University London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281842.

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23

Novellani, Marc. "Etude expérimentale et numérique des empilements de fibres : structure et propriétés thermiques." Aix-Marseille 1, 2000. http://www.theses.fr/2000AIX11058.

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La caractérisation et la compréhension des transferts de chaleur et de masse au sein de milieux poreux est un enjeu majeur dans des domaines aussi variés que le génie thermique, mécanique, chimique, Un des objectifs principaux consiste à faire le lien entre la structure des milieux poreux et leurs propriétés de transfert. Pour ce faire, l'utilisation de milieux poreux modèles moins complexes structurellement s'avère nécessaire. Ainsi, cette étude va focaliser son attention sur les empilements désordonnés de fibres rigides monodisperses. La première partie concerne l'étude structurale d'empilements de fibres bidimensionnels dont la structure est plus facile à appréhender que les empilements 3D. Différentes approches ont été utilisées. Dans un premier temps, une étude expérimentale faisant notamment appel à l'analyse d'images met en évidence l'influence de la longueur des fibres (à diamètre fixé) sur la structure du milieu ainsi que dans sa complexité. L'approche théorique fournit des lois simples de variation de la porosité en fonction du rapport d'aspect (longueur/diamètre) des fibres en bon accord avec les mesures expérimentales. Enfin, une simulation numérique d'empilements 2D de fibres a été conçue et a permis de montrer le rôle prépondérant joué par la gravité sur les variations de structure en fonction du rapport d'aspect. La seconde partie concerne l'étude des transferts de chaleur dans un empilement 3D de fibres traversé par un fluide en écoulement. Ils ont été caractérisés grâce à la mise en place d'un dispositif expérimental. La démarche numérique a été utilisée afin de mieux comprendre les résultats observés. Ce travail a notamment permis de mettre en évidence la très grande influence de la morphologie des fibres sur la conductivité thermique équivalente du milieu ce qui ouvre des perspectives intéressantes dans la conception de milieux qui soient à la fois poreux et bons conducteurs thermiques.
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24

Barančíková, Miriama. "Vysoce porézní keramické materiály připravené metodou Spark Plasma Sintering." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-442603.

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Porous ceramic materials are an interesting group of materials due to a wide range of physical properties, low density, and good permeability. Production of a monolith with a shape stability that would also have a high specific surface area and high porosity is a common problem with porous ceramics. The goal of this work was to maintain the high specific surface area and to produce a monolith with a shape stability. Two forms of porous silica nanofibers (as prepared and milled) were used and partially sintered using the Spark Plasma Sintering method (SPS). Different sintering times and temperatures for SPS were tested. The findings revealed that the best SPS conditions were as follows: temperature: 600 °C, sintering time: 5 minutes, pressure: 3 MPa, and the heating rate: 144 °C/min. These sintering conditions resulted in a stable silica based machinable monolith made from fibers or milled fibers. The monoliths have the specific surface area of up to 470 m^2/g and porosity of 72 %, or the specific surface area of up to 422 m^2/g and porosity of 69 % for as prepared fibers and milled fibers, respectively.
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25

Grena, Benjamin (Benjamin Jean-Baptiste). "Phase separation in thermally-drawn fibers: From porous domains to structured Si-Ge spheres." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111324.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 149-160).
The preform-to-fiber thermal drawing method is a versatile process that allows the fabrication of polymer or glass-based fibers with complex multimaterial internal structures, which grant them functions ranging from optical transmission to chemical detection. However, while a wide range of materials have been successfully drawn in various phases - such as metals, semiconductors, and ferroelectric polymers - the overall structure of the fiber is typically axially-invariant and the incorporation of heterogeneous materials with isotropic microstructures such as porous domains has remained elusive thus far. In this thesis we investigate the use of in-fiber phase separation as a means to control the microstructure of different components within thermally-drawn fibers. In particular we propose a novel method based on controlled phase separation of a polymer solution that we use to embed isotropically porous polymeric domains inside multimaterial fibers. We achieve this by thermal-drawing a hollow polymer preform filled with a liquid polymer solution in its core. We later apply this method to the fabrication and characterization of scaffolds for neural regeneration. In addition, we show that the same principle can also be used to draw a functional lithium-ion fiber battery; a fiber device capable of electrochemical energy storage. Finally, we demonstrate how to produce structured Si-Ge spheres encapsulated within a silica cladding by inducing capillary breakup of a continuous Si-Ge core fiber in a strong axial thermal gradient. The thermal gradient causes a "kinetic phase separation" of the alloy, leading to structured Janus particles.
by Benjamin Grena.
Ph. D.
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26

Klein, Christian. "Etude du procédé de densification par caléfaction de composites C/C, modélisation, optimatisation du contrôle et du bilan énergétique." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0231.

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Le présent travail est réalisé dans le cadre de l’étude d’un procédé industriel de densification de matériaux composites carbone/carbone (C/C) destinés aux freins d’avion. Une préforme poreuse de fibres de carbone baigne dans un précurseur liquide et elle est chauffée par induction électromagnétique radio-fréquence. Le précurseur porté à ébullition dans l’espace poral crée un dépôt de carbone dans les zones les plus chaudes ; ce dépôt constitue la matrice du composite. On propose une modélisation physico-chimique de ce procédé afin d’en assurer le contrôle et l’optimisation. Le travail a consisté à développer un solveur couplant l’induction électromagnétique avec les transferts de masse, de chaleur, de mouvement et d’espèces chimiques, en incluant l’ébullition et le dépôt chimique. Le modèle inclut le circuit électrique complet permettant d’effectuer le chauffage : il permet donc de suivre en temps réel et de façon non destructive l’avancement de la densification par l’évolution des grandeurs électriques. Une formulation originale adaptée à la représentation simultanée du liquide, du gaz et de la zone en ébullition a été développée et implémentée avec succès dans un logiciel commercial d’éléments finis. Les résultats de la simulation sont comparés avec les données obtenues sur le moyen expérimental, avec un bon accord. Enfin, la simulation est utilisée pour proposer des pistes d’amélioration du procédé, en altérant la géométrie du dispositif de chauffage par induction et en modifiant la stratégie de pilotage en puissance
This work has been carried out in the frame of the study of an industrial process for the manufacturing of carbon/carbon (C/C) composite aircraft brake discs. A porous preform made of carbon fibres is immersed in a liquid precursor and is heated by Radio-Frequency electromagnetic induction. The boiling precursor enters the porous preform and yields a carbon deposit in the hottest zones; this deposit will be the carbon matrix of the composite. A physico-chemical process model is proposed in the aim of ensuring its control and optimisation. The work consisted in developing a numerical solver coupling electromagnetic induction heating with heat, mass and species balances accounting for boiling, diffusion and chemical deposition reactions. The model includes the complete electrical circuit of the heating device: it therefore allows real-time, non-destructive monitoring of the infiltration progress through the evolution of the electrical properties. An original formulation has been designed to simultaneously describe the liquid, the gas and the boiling zone; it has been implemented in a commercial Finite Element software package and validated physically with respect to experimental data, with a good agreement. Finally, the simulation software has been used to propose directions for process improvements, through alterations of the inductive heating device geometry or of the heating power supply program
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27

Serrat, Pierre J. L. "Numerical study of a stokes flow through a fibrous porous medium." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17926.

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28

Timnak, Azadeh. "GRADIENT POROUS FIBROUS SCAFFOLDS AS A PARADIGM FOR IMMUNOMODULATORY WOUND DRESSINGS." Diss., Temple University Libraries, 2017. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/474843.

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Bioengineering
Ph.D.
Engineering therapeutic approaches to wound healing can be divided into two major categories of fibrous and non-fibrous approaches. There has been significant progress in designing artificial skin products to replace autografting. For patients with non-healing/hard-to-heal wounds, there is an unmet clinical need for inexpensive skin substitutes to be transplanted. In skin regeneration area of research, electrospinning is a very commonly used method of production of grafts for wound healing applications, owing its popularity to the fibrous nature of the resultant product, which mimics the extracellular matrix of the native skin. Despite the high degree of porosity in conventional electrospun scaffolds, the small pore size effectively limits the penetration of cells into the scaffold. Transplantation of such scaffolds with poor cell infiltration abilities may lead to a range of negative consequences, from prolongation of the first/destructive phase of inflammation to rejection of the scaffolds. Several experimental approaches have been developed to generate interfibrillar space in the electrospun scaffolds, including but not limited to modifications of the electrospinning set-up and inclusion of sacrificial components. It has been reported that scaffolds with larger pore diameters in the range of ~ 40-100 μm can modulate, moderate and reduce acute inflammatory responses of the body, by influencing macrophages biological behavior, and direct the course of the wound healing process to the tissue remodeling phase. Macrophages are the major cell component of innate immune system and play critical roles in clearance of pathogens, resolution of inflammation and wound healing following an injury. Macrophages are characterized by their diversity and plasticity. In response to environmental stimuli, they acquire different functional phenotypes of pro-inflammatory (M1) or anti-inflammatory (M2). In this thesis, we developed a novel unique gradient porous structure from a plant-based “green” soy protein isolate (SPI) with improved pore size for macrophages to infiltrate. We further showed the ability of the scaffold to modulate phenotype switch in macrophages in vitro and in vivo. The proposed scaffold, moreover, appeared to support transition of the inflammation process from the destructive to the constructive phase in vivo. Based on the promising results of this thesis, we propose our newly developed scaffold has the ability to be used as a new therapeutic modality for treatment of non-healing chronic wounds.
Temple University--Theses
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29

Powell, Sean K. "A quantitative study of diffusion in quasi-periodic fibre networks and complex porous media." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/92506/12/92506%28thesis%29.pdf.

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Diffusion is the fundamental process behind many molecular phenomena such as the mixing of substances. Its physical basis is the random motion of particles in a fluid. In complex porous media, diffusion is restricted by interactions with internal structures. In this work, we present studies of restricted diffusion that aim to efficiently produce quantitative models for obtaining detailed information about the morphology of biological porous media from diffusion tensor imaging experiments. We achieved this by developing a Langevin dynamics algorithm to provide physically realistic modelling of water/barrier interactions and the Lattice-Path Count algorithm to enumerate all available particle trajectories to evaluate molecular transport properties. We also performed diffusion tensor imaging experiments of the fibre networks of tissue engineering scaffolds. The findings of this thesis provide further insight into the physics underlying restricted diffusion.
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Duan, Gaigai [Verfasser], and Andreas [Akademischer Betreuer] Greiner. "3D porous sponges from electrospun polymer fibers and their applications / Gaigai Duan ; Betreuer: Andreas Greiner." Bayreuth : Universität Bayreuth, 2017. http://d-nb.info/1139358235/34.

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31

Bezik, Cody. "Poly(High Internal Phase Emulsion) Foams and Fibers: Structure-Property Relationships." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1436458970.

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32

Yu, Li. "Multi-Material Fiber Fabrication and Applications in Distributed Sensing." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/99380.

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Distributed sensing has been an attractive alternative to the traditional single-point sensing technology when measurement at multiple locations is required. Traditional distributed sensing methods based on silica optical fiber and electric coaxial cables have some limitations for specific applications, such as in smart textiles and wearable sensors. By adopting the fiber thermal drawing technique, we have designed and fabricated multi-material electrode-embedded polymer fibers with distributed sensing capabilities. Polymers sensitive to temperature and pressure have been incorporated into the fiber structure, and thin metal electrodes placed inside fiber by convergence drawing have enabled detection of local impedance change with electrical reflectometry. We have demonstrated that these fibers can detect temperature and pressure change with high spatial resolution. We have also explored the possibility of using polymer optical fiber in a Raman scattering based distributed temperature sensing system. Stokes and Anti-Stokes signals of a PMMA fiber illuminated by a 532 nm pulsed laser was recorded, and the ratio was used to indicate local temperature change. We have also developed a unique way to fabricate porous polymer by thermal drawing polymer materials with controlled water content in the polymer. The porous fibers were loaded with a fluorescent dye, and its release in tissue phantoms and murine tumors was observed. The work has broadened the scope of multi-material, multi-functional fiber and may shed light on the development of novel smart textile devices.
PHD
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33

Langeard, Olivier. "Numerical study of a Navier-Stokes flow through a fibrous porous medium." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/15944.

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34

Ashari, Alireza. "Dual-Scale Modeling of Two-Phase Fluid Transport in Fibrous Porous Media." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2326.

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The primary objective of this research is to develop a mathematical framework that could be used to model or predict the rate of fluid absorption and release in fibrous sheets made up of solid or porous fibers. In the first step, a two-scale two-phase modeling methodology is developed for studying fluid release from saturated/unsaturated thin fibrous media made up of solid fibers when brought in contact with a moving solid surface. Our macroscale model is based on the Richards’ equation for two-phase fluid transport in porous media. The required constitutive relationships, capillary pressure and relative permeability as functions of the medium’s saturation, are obtained through microscale modeling. Here, a mass convection boundary condition is considered to model the fluid transport at the boundary in contact with the target surface. The mass convection coefficient plays a significant role in determining the release rate of fluid. Moreover the release rate depends on the properties of the fluid, fibrous sheet, the target surface as well as the speed of the relative motion, and remains to be determined experimentally. Obtaining functional relationships for relative permeability and capillary pressure is only possible through experimentation or expensive microscale simulations, and needs to be repeated for different media having different fiber diameters, thicknesses, or porosities. In this concern, we conducted series of 3-D microscale simulations in order to investigate the effect of the aforementioned parameters on the relative permeability and capillary pressure of fibrous porous sheets. The results of our parameter study are utilized to develop general expressions for kr(S) and Pc(S). Furthermore, these general expressions can be easily included in macroscale fluid transport equations to predict the rate of fluid release from partially saturated fibrous sheets in a time and cost-effective manner. Moreover, the ability of the model has been extended to simulate the radial spreading of liquids in thin fibrous sheets. By simulating different fibrous sheets with identical parameters but different in-plane fiber orientations has revealed that the rate of fluid spread increases with increasing the in-plane alignment of the fibers. Additionally, we have developed a semi-analytical modeling approach that can be used to predict the fluid absorption and release characteristics of multi-layered composite fabric made up of porous (swelling) and soild (non-swelling) fibrous sheets. The sheets capillary pressure and relative permeability are obtained via a combination of numerical simulations and experiment. In particular, the capillary pressure for swelling media is obtained via height rise experiments. The relative permeability expressions are obtained from the analytical expressions previously developed with the 3-D microscale simulations, which are also in agreement with experimental correlations from the literature. To extend the ability of the model, we have developed a diffusion-controlled boundary treatment to simulate fluid release from partially-saturated fabrics onto surfaces with different hydrophilicy. Using a custom made test rig, experimental data is obtained for the release of liquid from partially saturated PET and Rayon nonwoven sheets at different speeds, and on two different surfaces. It is demonstrated that the new semi-empirical model redeveloped in this work can predict the rate of fluid release from wet nonwoven sheets as a function of time.
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Amico, Sandro Campos. "Permeability and capillary pressure in the infiltration of fibrous porous media in resin transfer moulding." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/1011/.

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36

Wooddell, Michael Gary. "Increased Functionality Porous Optical Fiber Structures." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/35324.

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A novel fiber optic structure, termed stochastic ordered hole fibers, has been developed that contains an ordered array of six hollow tubes surrounding a hollow core, combined with a nanoporous glass creating a unique fully three dimensional pore/fiber configuration. The objective of this study is to increase the functionality of these stochastic ordered hole fibers, as well as porous clad fibers, by integrating electronic device components such as conductors, and semiconductors, and optically active materials on and in the optical fiber pore structures. Conductive copper pathways were created on/in the solid core fibers using an electroless deposition technique. A chemical vapor deposition system was built in order to attempt the deposition of silicon in on the porous clad fibers. Additionally, conductive poly(3,4-ethylenedioxythiophene)- poly(styrene sulfonate) (PEDOT:PSS) and photoactive polymer blend poly(3- hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-)6,6)C61 (P3HT: PCBM) were deposited on the fibers using dip coating techniques. Quantum dots of Cadmium Selenide (CdSe) with particle sizes of ranging from 2- 10 nm were deposited in the stochastic ordered hole fibers. SEM and EDS analysis confirm that copper, polymer materials, and quantum dots were deposited in the pore structure and on the surface of the fibers. Finally, resistance measurements indicate that the electrolessly deposited copper coatings have sufficient conductivity to be used as metallic contacts or resistive heating elements.
Master of Science
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37

Nam, Gi-Moon. "Dynamics of confined biofilaments." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00976029.

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This PhD is devoted to the mechanics and statistical mechanics of biofilaments and their most widespread model, the Worm-Like Chain (WLC) model, which, as it turns out, needs to be extended. We study the WLC in 2-d in the presence of obstacles closer than their persistence length. We characterize the short time motion by numerical simulations complemented by analytical calculations. Similar concepts serve to describe grafted DNAs swept by the front of a spreading vesicle whose adhesion is promoted by biotin/streptavidin bonds, which constrain the DNAs on narrow paths where they can be imaged. Microtubules (MT), here stabilized by taxol, show features which cannot be rationalized by the WLC and shall be related to their internal structure : i)lateral deflections of a clamped MT correspond to an effective persistence length growing with the MT size ii) MT adopt super-helical shapes. These two points are proven by refined image analysis. We analyze shape transitions correlated along the MT which are compatible with a model based on dimer bi-stability. Finally, a super helical chain model (HWLC) allowing for spontaneous curvature and twist is developed which extends the WLC. When confined to 2-d, the HWLC can adopt a ground state which is circular or wavy with inflection points where twist accumulates, so-called twist-kinks. In the circular case there exist close metastable states, with a small number of twist-kinks, which are hyperflexible.
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38

Bauer, Alexander Günter. "Direct methanol fuel cell with extended reaction zone anode : PtRu and PtRuMo supported on fibrous carbon." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/913.

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The direct methanol fuel cell (DMFC) is considered to be a promising power source for portable electronic applications and transportation. At present there are several challenges that need to be addressed before the widespread commercialization of the DMFC technology can be implemented. The methanol electro oxidation reaction is sluggish, mainly due to the strong adsorption of the reaction intermediate carbon monoxide on platinum. Further, methanol crosses over to the cathode, which decreases the fuel utilization and causes cathode catalyst poisoning. Another issue is the accumulation of the reaction product CO₂ (g) in the anode, which increases the Ohmic resistance and blocks reactant mass transfer pathways. A novel anode configuration is proposed to address the aforementioned challenges. An extended reaction zone (thickness = ∼100-300 µm) is designed to facilitate the oxidation of methanol on sites that are not close to the membrane-electrode interface. Thus, the fuel concentration near the membrane may decrease significantly, which may mitigate adverse effects caused by methanol cross-over. The structure of the fibrous electrode, with its high void space, is believed to aid the disengagement of CO₂ gas. In this thesis the first objective was to deposit dispersed nanoparticle PtRu(Mo) catalysts onto graphite felt substrates by surfactant mediated electrodeposition. Experiments, in which the surfactant concentration, current density, time and temperature were varied, were conducted with the objective of increasing the active surface area and thus improving the reactivity of the electrodes with respect to methanol electro-oxidation. The three-dimensional electrodes were characterized with respect to their deposit morphology, surface area, composition and catalytic activity. The second objective of this work was to utilize the catalyzed electrodes as anodes for direct methanol fuel cell operation. The fuel cell performance was studied as a function of methanol concentration, flow rate and temperature by using a single cell with a geometric area of 5 cm². Increased power densities were obtained with an in-house prepared 3D PtRu anode compared to a conventional PtRu catalyst coated membrane. Coating graphite felt substrates with catalytically active nanoparticles and the utilization of these materials, is a new approach to improve the performance of direct fuel cells.
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39

Wang, Xiaokun. "Fabrication of electrospun fibrous meshes and 3D porous titanium scaffolds for tissue engineering." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/51724.

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Tissue engineering is a multidisciplinary field that is rapidly emerging as a promising approach for tissue repair and regeneration. In this approach, scaffolds which allow cells to invade the construct and guide the cells grow into specific tissue play a pivotal role. Electrospinning has gained popularity recently as a simple and versatile method to produce fibrous structures with nano- to microscale dimensions. These electrospun fibers have been extensively applied to create nanofiber scaffolds for tissue engineering applications. Specifically for bone and cartilage tissue engineering, polymeric materials have some attractive properties such as the biodegradability. Ceramic scaffolds and implant coatings, such as hydroxyapatite and silica-based bioglass have also been considered as bone graft substitutes for bone repair because of their bioactivity and, in some cases, tunable resorbability. Besides tissue engineering scaffolds, for clinical application, especially for load-bearing artificial implants, metallic materials such as titanium are the most commonly used material. Osseointegration between bone and implants is very essential for implant success. To achieve better osseointegration between bone and the implant surface, three dimensional porous structures can provide enhanced fixation with bone by allowing tissue to grow into the pores. In this study, pre-3D electrospun polymer and ceramic scaffolds with peptide conjugation and 3D titanium scaffolds with different surface morphology were fabricated to testify the osteoblast and mensechymal stem cell attachment and differentiation. The overall goal of this thesis is to determine if the peptide functionalization of polymeric scaffolds and physical parameters of ceramic and metallic scaffold can promote osteoblast maturation and mesenchymal stem cell differentiation in vitro to achieve an optimal scaffold design for greater osseointegration. The results of the studies showed with functionalization of MSC- specific peptide, polymer scaffolds behaved with higher biocompatibility and MSC affinity. For the ceramic and metallic scaffolds, microstructures and nanostructures can synergistically promote osteoblast maturation and 3D micro-environment with micro-roughness is a promising design for osteoblast maturation and MSC differentiation in vitro compared to 2D surfaces.
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40

Gondy, Dominique. "Développement de la texture poreuse et variation dimensionnelle des fibres de carbone au cours de leur activation." Mulhouse, 1996. http://www.theses.fr/1996MULH0447.

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Des fibres de carbone préparées à partir de brai isotrope ou de résine phénolique peuvent être utilisées comme matériau adsorbant. L'objet du présent travail est d'étudier les variations de microporosité et de morphologie des fibres activées par la vapeur d'eau et le dioxyde de carbone. La gazéification des fibres de carbone génère des volumes microporeux importants. Pour les fibres ex-brai, l'agent activant influe fortement sur la microporosité finale où le gaz carbonique produit une microporosité conséquente mais étroite. La vapeur d'eau entraîne plutôt un élargissement de la porosité existante. Pour les fibres ex-phénolique, l'influence de l'agent activant est peu marquée. L'étude du diamètre des fibres ex-brai au cours de l'activation par le dioxyde de carbone a mis en évidence un phénomène jusque-là inobservé : après une diminution du diamètre, un accroissement réel et significatif est mesuré. L'augmentation de diamètre n'est pas observée en utilisant la vapeur d'eau comme agent activant et les fibres phénoliques comme précurseur. L'ensemble des résultats suggère que le gonflement est dû à la présence au sein de la fibre de carbone ex-brai d'une fraction importante de composés organiques volatils qui vont se décomposer lors de la formation d'un réseau microporeux fortement interconnecté et affectant la totalité de la fibre. Avec la vapeur d'eau, la microporosité ne se développe que dans la partie externe de la fibre et une forte présence d'inhibiteurs empêche le gonflement. En conclusion, cette étude montre que les fibres de carbone possèdent après activation une grande capacité d'adsorption. De plus, il a été mis en évidence un phénomène nouveau, le gonflement des fibres de carbone issues d'un précurseur particulier, le brai. Ce phénomène est dû à la stabilisation et l'activation simultanée de la fraction de la fibre partiellement stabilisée
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41

Rahli, Ouamar. "Etude des milieux poreux constitués de fibres rigides : empilements, écoulements et transferts de chaleur." Aix-Marseille 1, 1997. http://www.theses.fr/1997AIX11064.

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Le sujet porte sur l'etude des empilements, des ecoulements et des transferts de chaleur dans les milieux fibreux. Le memoire comporte trois parties : la premiere partie traite des empilements desordonnes de fibres rigides. Suivant la dimension des fibres, on montre que la porosite de l'empilement varie dans une tres large gamme contrairement au cas d'empilements de particules spheriques. Une analyse systematique des variations de la porosite en fonction du rapport d'aspect des fibres longueur sur diametre (4 a 70) est realisee. La loi de porosite etablie est presentee sur la base du volume exclu propose par onsager. La deuxieme partie traite de l'ecoulement d'un fluide a travers les empilements desordonnes de fibres monodisperses rigides. Les lois de perte de charge en fonction de la vitesse du fluide sont determinees. L'influence de la direction de l'ecoulement sur les lois de perte de charge est aussi etudiee. La permeabilite et le parametre de kozeny carman kk sont deduits des resultats experimentaux et compares aux modeles proposes dans la litterature. La troisieme partie concerne l'analyse experimentale des phenomenes de transferts avec ou sans changement de phase liquide-vapeur dans un milieu poreux, compose de micro-billes de bronze, parcouru par un fluide en ecoulement force. Trois zones distinctes sont observees : liquide, diphasique et vapeur surchauffee. Les limites sont determinees a partir des champs de temperature. Une simulation bidimensionnelle par elements finis est utilisee pour calculer le champ de saturation a partir des limites de zone et des champs de temperature.
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Santos, Eduardo Pena dos. "Fibres et céramiques mésoporeuses de zircone préparées avec templates de cristaux liquides gonflés." Montpellier 2, 2005. http://www.theses.fr/2005MON20010.

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43

Hicks, David Cyprian. "Aligned Continuous Cylindrical Pores Derived from Electrospun Polymer Fibers in Titanium Diboride." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/99423.

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The use of electrospun polystyrene (PS) fibers to create continuous long range ordered multi-scale porous structures in titanium diboride (TiB2) is investigated in this work. The introduction of electrospun PS fibers as a sacrificial filler into a colloidal suspension of TiB2 allows for easy control over the pore size, porosity, and long range ordering of the porous structures of the sintered ceramic. Green bodies were formed by vacuum infiltrating an electrospun-fiber-filled mold with the colloidal TiB2 suspension. The size, volume, distribution, and dispersion of the pores were optimized by carefully selecting the sacrificial polymer, the fiber diameter, the solvent, and the solid content of TiB2. The green bodies were partially sintered at 2000 C in argon to form a multiscale porous structure via the removal of the PS fibers. Aligned continuous cylindrical pores were derived from the PS fibers in a range of ~5 - 20 μm and random porosity was revealed between the ceramic particles with the size of ~0.3 - 1 μm. TiB2 near-net-shaped parts with the multi-scale porosities (~50 to 70%) were successfully cast and sintered. The multi-scale porous structure produced from electrospun fibers was characterized both thermally and mechanically, at room temperature. The conductivity ranged from 12-31 W m^(-1) K^(-1) at room temperature and the compressive strength ranged from 2-30 MPa at room temperature. Analytical thermal and mechanical models were employed to understand and verify he processing-structure-properties relationship. Finally, a method was devised for estimating the effective thermal conductivity of candidate materials for UHTC applications at relevant temperatures using a finite difference model and a controlled sample environment. This low-cost processing technique facilitates the production of thermally and mechanically anisotropic structures into near-net shape parts, for extreme environment applications, such as ultra high temperature insulation and active cooling components.
MS
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44

Vennat, Elsa. "Étude expérimentale et numérique de l'infiltration de la dentine déminéralisée en surface par des résines composites." Phd thesis, Ecole Centrale Paris, 2009. http://tel.archives-ouvertes.fr/tel-00441341.

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Dans cette thèse, le problème de l'infiltration de bio-adhésifs résineux dans la dentine a été abordé par le biais de deux études, expérimentale et numérique. L'originalité de ces travaux réside dans le fait que l'échelle à laquelle nous nous sommes placés est nanoscopique. En effet, c'est l'infiltration d'un réseau de fibres de collagène de diamètre de l'ordre de 80nm qui pilote l'adhésion des composites résineux à la dentine. Une étude MEB a été menée pour confirmer et compléter la connaissance actuelle du milieu poreux. Cependant un paramètre manque dans la perspective d'une modélisation géométrique du réseau : la porosité n'est pas connue. Une étude complémentaire du substrat par porosimétrie à intrusion de mercure a donc été menée. La porosité volumique de la dentine déminéralisée est estimée à 55%. Deux tailles de pores sont révélées : la première correspond aux tubules et canalicules (autour de 1micron) et la seconde aux espaces interfibrillaires (autour de 50nm) jamais encore caractérisés de manière volumique. Cette étude permet aussi une investigation méthodologique. La lyophilisation, technique de séchage peu utilisée en odontologie, est évaluée et comparée à la technique de séchage utilisant l'HMDS. La lyophilisation semble être une technique de séchage fiable et convient parfaitement aux essais de porosimétrie. La modélisation géométrique du réseau fibreux est ensuite réalisée : les fibres sont considérées comme des zones à viscosité élevée. Cette modélisation est validée par comparaison des écoulements entre une fibre modélisée implicitement et une autre modélisée plus classiquement. L'orientation des fibres n'étant pas connue quantitativement, il a été choisi de construire trois types de réseau, le plus proche de la réalité (à la vue des images MEB) étant le réseau où les fibres sont disposées aléatoirement. Sa perméabilité a été estimée et validée par comparaison avec différentes études de réseaux fibreux ou non. Enfin, l'avancée du front est abordée de manière dynamique. Les équations d'avancée du front sont mises en place. Les équations de Navier Stokes sont couplées avec une méthode level set : l'interface correspondant au front d'infiltration n'est pas maillé (tout comme les fibres) mais correspond à une isovaleur d'une certaine fonction. Un attention particulière est portée aux conditions aux limites au niveau de la ligne triple et par le biais d'un terme ajouté à la formulation variationnelle, l'angle de contact est fixé. Ici, la principale difficulté est la prise ne compte des fibres qui ont été définies de manière implicite. Cette fois, les fibres sont uniquement le lieu de l'application de la condition aux limites fixant l'angle de contact et ne sont plus des zones de viscosité élevée car cela bloquerait le front. Le problème est résolu pour différentes géométries de réseaux fibreux. Tout d'abord, l'influence de certains paramètres sur des réseaux simples est sondée puis l'infiltration du modèle géométrique complet (réseau fibreux et tubules) est réalisée. Une conclusion cruciale pour les praticiens est mis en avant : augmenter le temps d'infiltration de la résine n'améliore pas l'infiltration. La simulation d'un essai de porosimétrie permet de distinguer deux tailles de pores distinctes et nécessite un ajustement car un décalage en pression par rapport à la courbe expérimentale est observée. L'outil construit permet une approche pédagogique de l'essai de porosimétrie et, après ajustement, pourra permettre la validation de diverses géométries.
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45

CARDOSO, Markos Paulo. "Estudo de fibras porosas com inclusões metálicas para guiamento em THz." Universidade Federal do Pará, 2017. http://repositorio.ufpa.br/jspui/handle/2011/9465.

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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
O guiamento de ondas THz tem se mostrado de grande importância na melhoria da performance das configurações de espectroscopia, imagem e sensoriamento. Um dos maiores desafios na concepção dessas estruturas é a mitigação das altas perdas apresentadas pelo meio dielétrico na faixa espectral THz (0.1 até 10 THz). Este trabalho realiza a modelagem numérica de fibras porosas com inclusões de ouro para guiamento em THz. O design dessas interfaces metal-dielétricas é capaz de confinar as ondas THz nas regiões de ar da fibra porosa através da excitação de plasmons de superfície, modos que resultam da interação ressonante entre a radiação eletromagnética incidente e a oscilação coletiva de elétrons livres na superfície metálica. É evidenciado que a partir de um projeto adequado da camada de ouro, as perdas efetivas podem ser reduzidas e uma dispersão cromática zero pode ser alcançada como resultado do acoplamento entre os modos da fibra e os plasmons de superfície.
The guidance of THz waves has been found of great importance to improve the performance of spectroscopy, imaging and sensing setups. One of the major challenges in designing such structures is the mitigation of the high losses presented by dielectric media in the THz spectral range (0.1 up to 10 THz). This work performs an analytical and numerical modeling of porous fibers with gold inclusions for THz guidance. The design of these metal-dieletric interface is capable to confine THz waves in the air region of the porous fiber, through the excitation of surface plasmons, modes that result from the resonant interaction between the incident electromagnetic radiation and the collective oscillation of free electrons on the metal surface. It is shown that from a suitable design of the gold layer, the effective losses can be reduced and a zero chromatic dispersion can be achieved as result of the coupling between the fiber modes and the surfasse plasmons.
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46

Costa, Ana Sara Silva Rodrigues da. "Suportes porosos com topografia de fibras alinhadas para a regeneração neuronal." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/8484.

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47

Queiroz, Alex Sander Barros. "Estudo do desempenho de componentes baseados em fibras ópticas especiais: fibras de cristal fotônico e de metamateriais e suas aplicações em comunicações." reponame:Repositório Institucional da UFC, 2015. http://www.repositorio.ufc.br/handle/riufc/14728.

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QUEIROZ, A. S. B. Estudo do desempenho de componentes baseados em fibras ópticas especiais: fibras de cristal fotônico e de metamateriais e suas aplicações em comunicações. 177 f. 2015. Tese (Doutorado em Engenharia de Teleinformática) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2015.
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In this paper we present a numerical study of the Sagnac interferometer based on photonic crystals and optical coupler metamaterial. In the simulation of the interferometer effects of light propagation were analyzed, considering the dispersion of the group velocity (GVD) and third order (TOD), intrapulse Raman scattering, self-slope (self-steepening) and self-modulation phase in the generalized non-linear Schrödinger equation. The first time the study was conducted for four power division ratio of factors incident in one of the device ports and three dimensions for the device ring length. To characterize the system performance, were analyzed the transmission curves, extinction ratio, crosstalk and compression factor of the transmitted pulse. In the second moment, the performance of the non-linear switching was observed for obtaining gate under Pulse Amplitude Modulation (PAM). Exciting the two device input ports with logical levels "0" and "1", observing their behavior in one of the device outputs. Initially, the modulation is varied adjustment parameter (| ε |), obtaining only the logical OR gate. And in a second application, the fixed modulation parameter remained and was varied the phase of the input ports 0 to 2π rad, lying type logic gate OR, AND and XOR. The characteristics of a metamaterial guide that has the real part of electrical permittivity and magnetic permeability negatives were also studied. This metamaterial guide is coupled to a conventional guide, observing the transmission characteristics and critical power of this type of coupler and compared with a conventional coupler. For this analysis we used a decreasing automodulation profile linearly with five minimum, observing a hysteresis behavior.
Neste trabalho foi realizado um estudo numérico do interferômetro de Sagnac baseado em cristais fotônicos e de acoplador óptico de metamaterial. Na simulação do interferômetro foram analisados os efeitos da propagação da luz, considerando-se a dispersão de velocidade de grupo (GVD) e de terceira ordem (TOD), espalhamento Raman intrapulso, auto-inclinação (Self-steepening) e auto-modulação de fase na equação não linear de Schrödinger generalizada. No primeiro momento foi realizado o estudo para quatro fatores de razão de divisão da potência incidente em uma das portas do dispositivo e três dimensões para o comprimento do anel do dispositivo. Para caracterizar o desempenho do sistema, foram analisadas as curvas de transmissão, taxa de extinção, crosstalk e fator de compressão do pulso transmitido. No segundo momento, foi verificada a performance do chaveamento não-linear para obtenção de porta lógica sob Modulação por Amplitude de Pulsos (PAM). Excitando-se as duas portas de entrada do dispositivo com níveis lógicos "0" e "1", observando o seu comportamento em uma das saídas do dispositivo. Inicialmente, variou-se o parâmetro de ajuste da modulação (|ε|), obtendo-se apenas a porta lógica OR. E, em uma segunda aplicação, manteve-se o parâmetro da modulação fixa e variou-se a fase de uma das portas de entrada, de 0 a 2π rad, encontrando-se portas lógicas do tipo OR, AND e XOR. Também foram estudadas as características de um guia metamaterial que possui a parte real da permissividade elétrica e da permeabilidade magnética negativas. Esse guia metamaterial é acoplado com um guia convencional, observando-se as características de transmissão e potência crítica desse tipo de acoplador e, comparando-se com um acoplador convencional. Para essa análise foi utilizado um perfil de automodulação decrescente linearmente com cinco valores mínimo, observando-se um comportamento de histerese.
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48

Cid, Jacques. "Influence des caractéristiques structurales sur le transfert de l'humidité en milieux poreux fibreux sous contraintes mécaniques." Toulouse, INPT, 1990. http://www.theses.fr/1990INPT090H.

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En plus de leurs applications classiques comme isolants thermiques, la laine de verre et la laine de roche peuvent servir de substrat pour la culture hors-sol. Le but de ce travail est d'etudier le transfert de l'humidite en phase liquide dans un milieu poreux fibreux a haute porosite, anisotrope et susceptible de se deformer, lorsque sa masse volumique apparente est faible. Dans un premier temps, pour determiner l'influence des parametres constitutifs du milieu, les lois de variation des coefficients de conductivite hydraulique et de diffusion sont mesurees dans des echantillons rendus rigides. Ensuite, la loi de variation de la masse volumique apparente du milieu, en fonction de la contrainte effective qui est exercee, est etablie. Le systeme de mesure est base sur l'attenuation de deux rayons gamma. Finalement, ces resultats sont appliques, a partir d'une simulation numerique, pour l'etude de l'arrosage par goutteurs, dans des milieux susceptibles, ou non, de se deformer
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49

Doutres, Olivier Dauchez Nicolas Genevaux Jean-Michel. "Caractérisation mécanique de matériaux fibreux en vibro-acoustique." [S.l.] : [s.n.], 2007. http://cyberdoc.univ-lemans.fr/theses/2007/2007LEMA1015.pdf.

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50

Peng, Ling [Verfasser], and Seema [Akademischer Betreuer] Agarwal. "Bicomponent Porous Fibrous Membranes with Special Fiber Morphologies and Properties / Ling Peng ; Betreuer: Seema Agarwal." Bayreuth : Universität Bayreuth, 2018. http://d-nb.info/1159632944/34.

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