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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1071

Continuous Permeability Measurement During Unidirectional Vacuum Infusion Processing

Hoagland, David Wayne 01 July 2017 (has links)
Composite materials have traditionally been used in high-end aerospace parts and low-end consumer parts. The reason for this separation in markets is the wide gap in technology between pre-preg materials processed in an autoclave and chop strand fiberglass blown into an open mold. Liquid composite molding has emerged as a bridge between inexpensive tooling and large, technical parts. Processes such as vacuum infusion have made it possible to utilize complex layups of reinforcement materials in an open mold style set-up, creating optimal conditions for composites to penetrate many new markets with rapid innovation. Flow simulation for liquid composite molding is often performed to assist in process optimization, and requires the permeability of the reinforcement to be characterized. For infusion under a flexible membrane, such as vacuum infusion, or for simulation of a part with non-uniform thickness, one must test the permeability at various levels of compaction. This process is time consuming and often relies on interpolation or extrapolation around a few experimental permeability measurements. To accelerate the process of permeability characterization, a small number of methodologies have been previously presented in the literature, in which the permeability may be tested at multiple fiber volume contents in a single test. Some of the methods even measure the permeability over a continuous range of thicknesses, thus requiring no later interpolation of permeability values. A novel method is presented here for the rapid measurement of permeability over a continuous range of fiber volume content, in a single unidirectional vacuum infusion flow experiment. The thickness gradient across the vacuum bag, as well as the fluid pressure at several locations in the mold, were concurrently measured to calculate the fabric compressibility. An analytical flow model, which accounts for the compressibility, is then used by iterating the fitting constant in a permeability model until the predicted flow front progression matches empirical measurement. The method is demonstrated here for two reinforcement materials: 1) a fiberglass unbalanced weave and 2) a carbon bi-ax non-crimped fabric. The standard deviation of calculated permeabilities across the multiple infusion experiments for each material and flow orientation ranged from 12.8% to 29.7%. Validation of these results was performed by comparing the resulting permeability with multiple non-continuous permeability measurement methods.
1072

Contribution au développement d’une pince universelle pour la manipulation des matériaux souples / Contribution of the development of a universal gripper for handling flexible materials

Ebraheem, Yousef 15 September 2014 (has links)
Le travail présenté dans ce mémoire concerne le développement d’un système universel de manipulation de matériaux textiles souples. Il s’agit d’une pince de manipulation universelle qui se compose de trois techniques de manipulation, technique de vide, technique d’intrusion, technique de pincement. Cette pince universelle a été développée pour manipuler une surface textile de 100 x 100 mm². Les buts de cette pince sont les suivants: Acquérir une seule couche à partir d'un empilement de tissus.Tenir une seule couche, la transférer et la manipuler jusqu’au poste suivant.La technique de vide est la première technique développée dans notre recherche, elle se compose des organes de préhension qui sont « trois ventouses pneumatiques » dont les matériaux varient en fonction des matériaux textiles à manipuler, trois compensateurs de hauteur pour fixer les ventouses pneumatique et d'un générateur de vide pour créer le vide nécessaire grâce à un régulateur de pression. Les trois ventouses pneumatiques sont placées précisément sur les têtes d’un triangle équilatéral, au-dessus de la pièce textile. La technique d’intrusion est la deuxième technique développée dans notre recherche, cette technique est constituée de deux parties principales: Une partie qui donne le mouvement et l'actionnement des organes de préhension.Une partie de préhension qui contient des éléments de préhension qui sont des aiguilles.L’ensemble est commandé, au travers de vérins, par de l’air comprimée. La technique de pincement est la troisième technique développée dans notre recherche, elle comprend des organes de serrage opposés qui sont à mis en mouvement de façon alternative par deux vérins pneumatiques Deux types de validation des éléments constituant de la pince de préhension développée ont été réalisés avec succès, une validation statique en utilisant un support de fixation, une validation dynamique en utilisant un bras de robot. Pendant la validation statique, nous avons trouvé que la technique de vide fonctionnait très bien avec les matériaux imperméables à l’air et avec des matériaux ayant une porosité inférieure à 80% et/ou une perméabilité inférieure à 1500 L/m²/s sous 200 Pa.Pour les matériaux textiles ayant une porosité supérieure à 80% et/ou d’une perméabilité supérieure à 1500 L/m²/s sous 200 Pa, la consommation importante d’air comprimé interdit l’utilisation de cette technique et la force réelle d’attraction dépendant des propriétés du matériau manipulé suivant :La porosité, La perméabilité à l’air, La masse surfacique de matériau. Concernant la technique d’intrusion, nous trouvé que cette technique permet une manipulation efficace des matériaux textiles qui sont difficiles à manipuler par la technique de vide. Elle fonctionne très bien pour des matériaux perméables à l’air (tissus d’armure toile, tricots) alors qu’elle endommage les matériaux imperméables. Les risques liés à cette technique est le prélèvement de plusieurs couches à la fois si la profondeur de perçages des aiguilles n’est pas contrôlé précisément. Pendant la validation statique de la technique de pincement, nous avons trouvé que cette technique ne fonctionne pas bien seule.Pour résoudre ce problème, nous avons utilisé, la combinaison de deux technologies La technique d’intrusion technique La technique de pincement Et La technique de vide. La technique de pincement Les résultats trouvés pendant la validation de cette technique sont les suivants : la technologie de vide associée à la technique de serrage est la combinaison la plus efficace et la plus fiable, par contre un des inconvénients de cette technique est le contrôle de la force de serrage afin d’éviter l’endommagement de la surface de matériau manipulé. [...] / The work presented in this thesis concerns the development of a universal system for handling flexible textile materials. This is a universal gripper for manipulation, which consists of three technologies of manipulations, vacuum technology, intrusion technology, pinch technology. This new universal system was developed to handle a pieces of cut fabrics a square shape which had the dimensions of 100 mm×100 mm. The aims of this gripper are: Acquiring a single ply from a stack of woven fabrics Acquiring a single ply, handling and transfer it to the next station.The vacuum technology is the first technique developed in our research, it consists of a grippers which are « three pneumatic flat suction pads with stops » whose materials vary according to the manipulate textile materials, three level compensators for fixing the penumatic flat suction pads and a pneumatic vacuum generator to create the necessary vacuum thanks to a pressure regulator. The three pneumatic flat suction pads are precisely placed on the heads of an equilateral triangle, above the textile piece.The intrusion technology is the second technique developed in our research; this technique consists of two main parts: A party that gives movement and actuation of the gripper A party for gripping witch include the gripping elements that are needles The both parties are controlled, through a penumatic cylinder, by compressed air.The pinch technology is the third technique developed in our research; it comprises clamping grippers which are placed oppositely to moving alternately by two pneumatic cylinders.Two types of validation of the elements constituting of the gripper developed are performed, static validation by using a bracket, dynamic validation by using the robot arm.During the validation static, we found that the vacuum technology performs well for non-permeable materials and with the materials whose their porosity less of the 80 % and their air permeability less than 1500 L/m²/s under 200 pa.For the materials textiles whose their porosity more than 80 % and their permeability more than 1500 L/m²/s under 200 pa, the high consumption of compressed air prohibits the use of this technique, and the real force of attraction dependent on the following material manipulated properties: • Porosity of the material• Air permeability• Weight of the material.Concerning the intrusion technique, we found that this technique allows realizing an effective handling of textile materials which are difficult to handle by the vacuum technique. It performs very well for air permeable materials (plain weave fabrics, knitted fabrics), while damaging waterproof materials. The risk associated with this technique is the manipulation multiplies of the layers at a time if the depth of the piercing of the needles is not precisely controlled.During the static validation of the pinch technique, we found that this technique does not function well alone. To solve this problem, we used, the combination of two technologies: Intrusion technology Pinch technology and Vacuum technology Pinch technologyThe results found during the validation of this technique are: the vacuum technology associated with the pinch technology is the most effective combination and more reliable, by against one disadvantage of this technique is the control of the clamping forces to prevent the damage of the material surface manipulated.For the dynamic validation of the gripper developed, we used the robot manipulation STÄUBLI. We fixed the gripper on the end of the arm of robot and after setting it, we varied the speed of manipulation to determine the limits of the manipulation by each technology.These validation procedures have in evidence the limits of our new gripper in terms of capacity of the gripping, consumption of the compressed air, characteristics and limitations of the flexible materials handled. [...]
1073

Coupled Thermal-Hydrological-Mechanical-Chemical Processes In Geothermal And Shale Energy Developments

Kamali-Asl, Arash 01 January 2019 (has links)
Coupled Thermal-Hydrological-Mechanical-Chemical (THMC) processes that exist in the development of different geo-resources (e.g. deep geothermal and shale gas) affect the fracture response (i.e. aperture and permeability), which in turn influences the reservoir production. The main goal of this study was to experimentally evaluate the impact of THMC processes on the response of rock specimens relevant for deep geothermal and shale gas formations. The effects of THMC processes were investigated on: (i) success of the hydraulic fracturing/hydro-shearing mechanism during stimulation stage, and (ii) closure of the created network of fractures during production stage. The elastic, cyclic, creep, and failure characteristics of different intact reservoir rocks in both short- and long-term were investigated to evaluate their response in stimulation stage. In addition, a series of flow tests on fractured reservoir cores were conducted to evaluate how THMC processes affect fracture response subjected to different stress levels, temperatures, composition of injected fluid, and injection rate. Moreover, the sensitivity of ultrasonic signatures (i.e. velocity, amplitude, attenuation, and time-frequency content) to (i) microstructural changes in the intact rocks, and (ii) flow-induced alterations of aperture/permeability in the fractured rocks were investigated. Analysis of hydraulic data, chemical composition of the effluent, ultrasonic signatures, and X-Ray micro-CT and SEM images, provided invaluable information that facilitated interpretation of the effects of coupled THMC processes on fracture response.
1074

Fault Seal Analysis for CO2 Storage: Fault Zone Architecture, Fault Permeability, and Fluid Migration Pathways in Exposed Analogs in Southeastern Utah

Richey, David J. 01 May 2013 (has links)
Geologic storage of anthropogenic carbon dioxide (CO2) by injection into underground porous sandstone reservoirs has been proposed as a method for the reduction of anthropogenic greenhouse gas emissions. Upwards migration and leakage of injected fluids along natural fault and fracture networks is a key risk factor for potential injection locations. We examine exposed natural analogs to evaluate the impacts of faulting and fracturing on reservoir and top-seal pairs and to evaluate evidence for paleomigration of fluids along the fault zone. We examine the Iron Wash fault, a 25-km long normal fault which cuts Jurassic sedimentary rocks and has throws that range from 20-120 m, to examine how a fault may affect seal integrity. Field mapping, kinematic analysis, petrographic analysis, characterization of the fault zone facies and fault architecture, analysis of altered and mineralized rocks in and around the fault zone, and modeling of fault seal capacity was conducted to provide an understanding of the Iron Wash fault zone. Field data and observations were combined with well log and borehole data to produce three types of models for the Iron Wash fault: 1) geometric model of the fault in the subsurface, 2) predictive models of fault zone behavior and fault seal analysis, and 3) predictive geomechanical models of the response of the fault zone to an imposed stress field and increasing the effective stress on the fault. We conclude that the Iron Wash fault zone has low sealing capacity and will likely not behave as a seal for fluids against the fault zone due primarily to modest throw on the fault and high frequency of fractures associated with the fault zone. Analysis of fluid alteration and mineralization around the fault zone indicates that the fault zone was conduit for paleo-fluids. We conclude that the fault is not likely to develop a sealing membrane and therefore will most likely fail as a seal to fluids moving through the reservoirs modeled here. Modeling results indicate that a reduction in the effective normal stress on fault surfaces may induce failure of faults resulting in earthquakes or increased hydraulic conductivity of fractures.
1075

Effects of Aspirin and its Derivatives in Combination with Electroporation for Drug Delivery in Cultured Cells

Langham, Jennifer 01 July 2004 (has links)
The purpose of this research was to investigate the effects that aspirin (ASA) and its metabolites, salicylic acid (SA) and acetic acid (AA), have on the delivery of drugs across biological barriers when used in conjunction with electroporation. Electroporation is a technique used to enhance drug delivery across bio-membranes in which a transmembrane potential is induced into cellular membranes, resulting in the creation of aqueous pores that allow molecules to pass through the otherwise impermeable barrier. Aspirin is a widely used drug that has been used for over a century and has been proven relatively safe at normal doses as indicated by the low number of reports of poisoning cases it has been involved in. Components of aspirin are known to soften the cellular membranes by solubilizing the cell's surface proteins. B16F10 murine melanoma cancer cells were used in this investigation and treated with a 120µM buffered solution of calcein, a fluorescent indicator, in which the amount of delivered tracer molecules was measured using fluorescence. Identical concentrations of ASA and SA were investigated (1mM, 5mM, and 10mM) separately, focusing the effects concentration has electroporation delivery. Diluted acetic acid was also investigated at pH values of 6.42, 5.36, and 4.40. The concentration of acetic acid that had the lowest pH and ASA with the highest concentration had the greatest impacts on the augmentation of calcein delivery. Therefore, this demonstrates that aspirin and acetic acid have the potential to improve targeted molecular delivery in combination with electroporation.
1076

Hydraulic, Diffusion, and Retention Characteristics of Inorganic Chemicals in Bentonite

Muhammad, Naim 18 June 2004 (has links)
Inorganic contaminants, while transported through the bentonite layer, are chemically adsorbed onto the particle surfaces and exhibit a delay in solute breakthrough in hydraulic barriers. Transport of inorganic leachate contaminants through bentonite occurs by advection, diffusion or a combination of these two mechanisms. During the process of chemical solute transport through low permeability bentonite, the amount of cation exchange on the clay particle surface is directly related to the cation exchange capacity (CEC) of montmorillonite and other mineral constituents. The process of diffusion and advection of various inorganic leachate contaminants through bentonite is thoroughly investigated in this study. Diffusion characteristics are of specific interest as they have a prominent effect on the long term properties of bentonite compared to advection. This is mostly true if the hydraulic conductivity of the material is less than 10-8 cm/s and if the thickness of the barrier is small. Chemical reactions in the form of cationic exchange on the clay particle surfaces has been incorporated in the analysis of the diffusion process. Adsorption-desorption (sorption) reactions of chemical compounds that influence the concentrations of inorganic leachates during transport in bentonite clay have been modeled using the Fick's fundamental diffusion theory. Partition coefficients of the solutes in pore space, which affect the retardation factor of various individual ions of chemical solutions, have been investigated during transient diffusion and advection processes. Several objectives have been accomplished during this research study. An evaluation has been carried out of the hydraulic conductivity of bentonite with respect to single species salts and various combinations of electrolyte solutions. Diffusion properties of inorganic leachates through bentonite have been characterized in terms of apparent and effective diffusion coefficients. Time-dependent behavior of the diffusive ions has been analyzed in order to determine the total retention capacity of bentonite before electrical conductivity breakthrough and steady-state chemical stability are reached. An analytical solution of the attenuation of various inorganic ions concentrations through bentonite has been developed. Finally, recommendations were made for landfill liners exposed to highly concentrated inorganic leachates.
1077

Water Movement in Unsaturated Concrete: Theory, Experiments, Models

Leech, Craig Anthony Unknown Date (has links)
Prediction of contaminant transport in concrete subjected to short cyclical wetting and drying processes is integrally bound to prediction of the moisture flux. The concrete is unsaturated and the non-linear contaminant and moisture fluxes are not described by simple constant diffusion methods. This thesis presents, and partially justifies, a thermodynamic model for prediction of moisture movement in concrete, at all moisture contents commonly encountered. The wetting process is examined with Nuclear Magnetic Resonance (NMR) images during a simple absorption (sorptivity) experiment. Diffusivity functions are derived via a novel analytical approach and a universal diffusivity is suggested. Water sorption and desorption isotherms are measured on large concrete samples. van Genuchten’s retention function is successfully used to model the results. The unrelia-bility of the water sorption method at high moisture contents is illustrated by comparison with Mercury Intrusion Porosimetry (MIP). The BJH method is exploited to provide a methodology for estimating the water sorption isotherm from MIP. Mualem’s conductivity model is assessed with the water retention and NMR results. This thorough validation of the model yields a tortuosity parameter that is different to that commonly assumed. An analytical relationship between the sorptivity and the saturated permeability suggests the experimental the long-term unsaturated permeability overesti-mates the unsaturated conductivity function, and as such should be used judiciously when predicting unsaturated flow processes. Mualem’s conductivity model is further exploited to provide unsaturated air and vapour functions that are experimentally justified. The thermodynamic description of water movement and the hydraulic functions that are developed in the thesis are incorporated into T r inCet , a transient heat and mass trans-fer model based on the Finite Element Method (FEM). The complex coupled behaviour of air, liquid, vapour and temperature are well handled under a variety of common cyclical boundary conditions. The thesis presents all necessary experimental results required for validation of a com-plex, but easily described, model for moisture movement. It covers disparate ground to provide a powerful numerical model of unsaturated moisture movement in concrete under short-term cyclical processes.
1078

Water Movement in Unsaturated Concrete: Theory, Experiments, Models

Leech, Craig Anthony Unknown Date (has links)
Prediction of contaminant transport in concrete subjected to short cyclical wetting and drying processes is integrally bound to prediction of the moisture flux. The concrete is unsaturated and the non-linear contaminant and moisture fluxes are not described by simple constant diffusion methods. This thesis presents, and partially justifies, a thermodynamic model for prediction of moisture movement in concrete, at all moisture contents commonly encountered. The wetting process is examined with Nuclear Magnetic Resonance (NMR) images during a simple absorption (sorptivity) experiment. Diffusivity functions are derived via a novel analytical approach and a universal diffusivity is suggested. Water sorption and desorption isotherms are measured on large concrete samples. van Genuchten’s retention function is successfully used to model the results. The unrelia-bility of the water sorption method at high moisture contents is illustrated by comparison with Mercury Intrusion Porosimetry (MIP). The BJH method is exploited to provide a methodology for estimating the water sorption isotherm from MIP. Mualem’s conductivity model is assessed with the water retention and NMR results. This thorough validation of the model yields a tortuosity parameter that is different to that commonly assumed. An analytical relationship between the sorptivity and the saturated permeability suggests the experimental the long-term unsaturated permeability overesti-mates the unsaturated conductivity function, and as such should be used judiciously when predicting unsaturated flow processes. Mualem’s conductivity model is further exploited to provide unsaturated air and vapour functions that are experimentally justified. The thermodynamic description of water movement and the hydraulic functions that are developed in the thesis are incorporated into T r inCet , a transient heat and mass trans-fer model based on the Finite Element Method (FEM). The complex coupled behaviour of air, liquid, vapour and temperature are well handled under a variety of common cyclical boundary conditions. The thesis presents all necessary experimental results required for validation of a com-plex, but easily described, model for moisture movement. It covers disparate ground to provide a powerful numerical model of unsaturated moisture movement in concrete under short-term cyclical processes.
1079

Mélanine produite par oxydation de la dopamine : films minces et interactions avec des multicouches de polyélectrolytes

Bernsmann, Falk 12 July 2010 (has links) (PDF)
L'oxydation spontanée de la dopamine en solution légèrement basique a été étudiée sur la base de la publication de Lee [Science, 318:426-430, 2007], et le produit de la réaction a été identifié comme de la mélanine. La capacité de la mélanine de lier des groupements amines de façon covalente a été confirmée par la quantification des sites de liaison correspondants. En outre il est possible de rédisperser des agrégats de mélanine dans des solutions fortement basiques. Les grains de mélanine ainsi obtenus ont été utilisés pour construire des films multicouches avec le poly(diallyldimethyl ammonium) (PDADMA). Différentes méthodes d'oxydation de la dopamine pour former des films de mélanine à l'interface solide-liquide ont été développées. Toutes les méthodes mènent à la formation de films continus de mélanine ayant des morphologies de surface similaires. Elles deviennent imperméables à des sondes électrochimiques à partir d'une épaisseur de l'ordre de 10 nm. Une plus grande perméabilité à des sondes chargées positivement ou neutres qu'à des sondes négatives a été confirmée. L'adsorption de protéines à des revêtements de mélanine a été expliquée par une combinaison d'interactions électrostatiques et covalentes. Pour arriver à cette explication le potentiel zêta de dépôts de mélanine a été mesuré en fonction du pH. La formation de la mélanine dans des films multicouches de poly(L-lysine) (PLL) et de hyaluronate (HA) a été étudiée: la mélanine est capable de remplir des films (PLL-HA)n de manière homogène, et les composés ainsi obtenus peuvent être détachés de leurs substrats comme membranes autosupportées préparées par une méthode biomimétique sous conditions douces.
1080

Intestinal Permeability and Presystemic Extraction of Fexofenadine and R/S-verapamil

Tannergren, Christer January 2004 (has links)
<p>The main objective of this thesis was to investigate the in vivo relevance of membrane transporters and cytochrome P450 (CYP) 3A4-mediated metabolism in the intestine and liver for the bioavailability of drugs in humans after oral administration.</p><p>In the first part of the thesis, the main transport mechanisms involved in the intestinal absorption and bioavailability were investigated for fexofenadine, a minimally metabolized drug, which is a substrate for P-glycoprotein (P-gp) and members of organic anion transporting polypeptide (OATP) family. Jejunal perfusion studies revealed that co-perfusion with verapamil increased the bioavailability of fexofenadine by decreasing the first-pass liver extraction as the low intestinal permeability was unchanged by the transport inhibitors studied. The mechanism behind the interaction probably involves inhibition of OATP-mediated sinusoidal uptake and/or P-gp-mediated canalicular secretion of fexofenadine. Results from the Caco-2 model supported that the intestinal absorption of fexofenadine is mainly determined by the low passive permeability of the drug, even though fexofenadine clearly is a P-gp substrate. </p><p>In the second part of the thesis, the effect of repeated oral administration of the P-gp and CYP3A4 inducer St. John’s wort on the in vivo intestinal permeability and presystemic metabolism of the dual P-gp and CYP3A4 substrate verapamil was investigated in a jejunal perfusion study. St. John’s wort decreased the bioavailability of the enantiomers of verapamil by inducing the CYP3A4-mediated presystemic metabolism, probably mainly in the gut. It was also concluded that induction of efflux transporters, such as P-gp, does not affect the intestinal transport or the gut wall extraction of high permeability substrates like verapamil. Data from Caco-2 cells with induced CYP3A4-activity supported these findings. The plasma levels of the enantiomers of norverapamil also decreased despite an increased formation, which was attributed to induction of CYP3A4 and/or other metabolic routes. </p>

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