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Cosby, Michael C. "Effects of support grid vane angles on single phase heat transfer within rod bundle subchannels." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202419092/.
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Allgeuer, Philipp [Verfasser]. "Analytic Bipedal Walking with Fused Angles and Corrective Actions in the Tilt Phase Space / Philipp Allgeuer." Bonn : Universitäts- und Landesbibliothek Bonn, 2020. http://d-nb.info/1224966252/34.
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Kombo, Rainah. "Qualitative analysis of flow patterns : two-phase flow condensation at low mass fluxes and different inclination angles." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/61303.
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A great deal of work has been conducted on in-tube condensation in horizontal and vertical smooth tubes. The available literature points to mechanisms governing two-phase condensation heat transfer coefficients and pressure drops, which are directly linked to the local flow pattern for both horizontal and inclined configurations. However, the work has been limited to flow pattern observations, heat transfer, pressure drops and void fractions for both horizontal and inclined tubes at high mass fluxes. No work has been conducted on the analysis of the observed flow patterns and the effect of temperature difference between the average wall temperature and average saturation temperature for different inclination angles at mass fluxes of 100 kg/m2.s and below. The purpose of this study is to carry out a qualitative analysis of flow patterns, and show the effect of temperature difference on the heat transfer coefficient for inclination angles from +90° (upward flow) to -90° (downward flow) at mass fluxes below 100 kg/m2.s. An experimental set-up provided the measurements for the two-phase condensation of R-143a in a smooth tube with an inside diameter of 8.38 mm and a length of 1.5 m. The mass fluxes were 25 kg/m2.s to 100 kg/m2.s, the saturation temperature was 40 °C and the mean qualities were 0.1 to 0.9. A high-speed camera was used to visually analyse and determine the flow patterns for both the inlet and the outlet of the test section. Through the results, eight flow patterns were observed: stratified-wavy, stratified, wavy, wavy-churn, intermittent, churn, annular and wavy-annular. The maximum heat transfer was observed for downward flow between inclination angles of -15° and -30°. The Thome-Hajal flow pattern map correctly predicted horizontal flow patterns, but failed to predict most of the inclined flow patterns. Various flow pattern transitions were identified and proposed for all the investigated inclination angles in this study. Finally, the heat transfer coefficient was found to be dependent on quality, mass flux, temperature difference and inclination angle.Dissertation (MSc)--University of Pretoria, 2016.
Mechanical and Aeronautical Engineering
MSc
Unrestricted
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Saurel, Damien. "Etude de la séparation de phase magnétique dans les manganites à effet CMR par diffusion de neutrons aux petits angles." Phd thesis, Université de Caen, 2005. http://tel.archives-ouvertes.fr/tel-00086550.
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Ce manuscrit présente l?étude par diffusion de neutrons aux petits angles des inhomogénéités magnétiques de l?échelle nanométrique à l?échelle mésoscopique à basse température dans les composés manganites à effet CMR de la série Pr1-xCaxMnO3, x proche de 1/3, et son évolution sous champ magnétique appliqué. Ces systèmes montrent une séparation de phase à grande échelle entre une phase ferromagnétique isolante (FI) et une phase antiferromagnétique isolante (AFI) correspondant à deux phases cristallines distinctes. Ils se transforment en une troisième phase cristalline, ferromagnétique métallique (FM), sous l?effet du champ magnétique. Nous avons tenté de comprendre par quel mécanisme.
Nous avons mis en évidence l?existence d?inhomogénéités magnétiques nanométriques dans chacune des phases FI et AFI. Notre étude sous champ révèle l?apparition d?un fort signal de diffusion dû à une nucléation de clusters de phase FM mésoscopiques (quelques centaines de nanomètres) lors de la transition I-M induite par le champ, faisant ainsi disparaître la diffusion par les objets nanométriques. L?effet CMR n?est donc pas dû à une nucléation à l?échelle nanométrique mais mésoscopique.
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Lopian, Tobias. "Characterization of a metal-extracting water-poor microemulsion." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT206/document.
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Le recyclage des terres rares à partir de déchets électroniques n'a toujours pas trouvé une réalisation industrielle significative. L'une des raisons est le manque de procédures de séparation optimisées en raison de connaissances fondamentales médiocres sur ces systèmes. En raison des similitudes chimiques et physiques de ces métaux, la conception d'une formulation efficace, adaptative et prédictive est toujours hors de portée des possibilités. L'interprétation supramoléculaire de la formation complexe dans la phase organique est de plus en plus importante au cours des dernières années. C'est l'approche la plus prometteuse permettant l'explication de divers phénomènes, tels que la formation de la troisième phase et les signaux forts dans de petites expériences de diffusion et de revenir à des méthodes bien connues de la science des tensioactifs. Notre contribution à une compréhension plus complète dans cette matière est l'analyse du comportement électrodynamique de ces phases et la corrélation de ces résultats avec les résultats des propriétés d'auto-assemblage et du transport de masse dans ces médias. Pour cette étude, nous avons spécifiquement conçu un modèle de référence, en passant un processus d'extraction à ses quatre composants fondamentaux: l'extracteur avant l'extraction (acide Di-(2-éthylhexyl) phosphorique, HDEHP), l'extrait après extraction (son sel de sodium, NaDEHP ), le toluène comme diluant apolaire et de l'eau. Un prisme de phase de Gibbs a été préparé (illustré sur la figure 1), où l'axe z donne le rapport de HDEHP à NaDEHP, ce qui représente le développement d'une extraction. Couvrant le domaine de basse fréquence, la spectroscopie d'impédance a été la méthode de choix afin de déterminer la conductivité dépendant de la fréquence. En utilisant la spectroscopie de relaxation diélectrique, nous révélons des processus dynamiques rapides à haute fréquence. Des mesures combinées SAXS et SANS ont été effectuées pour comparer les tendances électrodynamiques avec les propriétés d'agrégation et les interactions entre groupes. Deux phénomènes ont été identifiés comme responsables du profil de conductivité dans les systèmes micellaires inverse: la formation d'agrégats chargés par la dissimulation et la percolation. Tout au long du système de référence, ces deux processus ont été sondés en fonction de trois variables: la concentration totale d'agent d'extraction, le rapport eau-agent tensioactif et le rapport Na: H. En tant que résultat majeur, l'eau joue un rôle important dans les deux processus. En cas de percolation, les agrégats inverse ne peuvent pas fusionner en l'absence d'eau. Par conséquent, la conductivité électrique est interdite. Dans les systèmes dilués, l'eau facilite le processus de dismutation, entraînant une augmentation de la conductivitéRecycling of rare earths from electronic waste has still not found a significant industrial realization. One reason is the lack of optimized separation procedures due to poor fundamental knowledge on these systems. Due to the chemical and physical similarities of these metals, designing an efficient, adaptive and predictive formulation is still out of scope of possibilities. The supramolecular interpretation of complex-formation in the organic phase has gained an increasing importance in the last years. It is the most promising approach allowing the explanation of diverse phenomena, such as third phase formation and strong signals in small scattering experiments and to revert to methods well known from surfactant science. Our contribution towards a more complete understanding in this matter is the analysis of the electrodynamic behaviour of such phases and the correlation of these findings with the results of self-assembly properties and mass transport in these media.For this study, we specifically designed a reference model, breaking an extraction process down to its four fundamental components: The extractant before extraction (Di-(2-ethylhexyl)phosphoric acid, HDEHP), the extractant after extraction (its sodium salt, NaDEHP), toluene as apolar diluent and water. A Gibbs phase prism has been prepared (illustrated in Figure 1), where the z-axis gives the ratio of HDEHP to NaDEHP, representing the development of an extraction. Covering the low frequency-domain, impedance spectroscopy has been the method of choice in order to determine the frequency-dependent conductivity. Using dielectric relaxation spectroscopy, we reveal fast dynamic processes at high frequencies. Combined SAXS and SANS measurements have been performed to compare the electrodynamic trends with aggregation properties and intercluster interactions.Two phenomena have been identified to be responsible for the conductivity profile in reverse micellar systems: the formation of charged aggregates through dismutation and percolation. Throughout the reference system, these two processes have been probed as function of three variables: total extractant concentration, the water-to-surfactant ratio and the Na:H-ratio. As a major result, water plays a significant role in both processes. In case of percolation, reverse aggregates are not able to merge in the absence of water. Therefore, electrical conductivity is prohibited. In dilute systems, water facilitates the dismutation–process leading to an increase in conductivity
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Impéror-Clerc, Marianne. "Étude de transition de phase vers les phases cubiques des systèmes eau/surfactant." Paris 11, 1992. https://tel.archives-ouvertes.fr/tel-01989797.
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Les phases cubiques des systèmes binaires eau/surfactant sont un cas d'organisation liquide-cristalline de la matière très surprenant. Leur structure allie, a un ordre local liquide, une périodicité tridimensionnelle à l'échelle mésoscopique, qui en fait de véritables cristaux de films fluides. Elle se caractérise également par une topologie bicontinue tout à fait remarquable. Partant de l'observation de la croissance en épitaxie d'une phase cubique (de groupe d'espace Ia3d, le plus fréquent) à partir des mésophases lamellaire et hexagonale, nous nous sommes attaches à décrire comment, d'un point de vue purement structural, il est possible de déduire la structure cubique de celles, plus simples, de ces autres mésophases. Tout d'abord, la croissance en épitaxie de la phase cubique a été observée en diffusion des rayons X sur des échantillons monocristallins, ainsi qu'au microscope polarisant. Des désordres caractéristiques de chacune des mésophases, liés à leur nature liquide cristalline, ont également été mis en évidence grâce aux clichés de diffraction X et analyses. Nous avons ensuite utilisé des modèles géométriques récents, pour poser le problème du passage d'une phase à l'autre en termes purement topologiques de transformations de surfaces. Des intermédiaires possibles pour les deux transitions ont été conçus : les surfaces tours pour la transition hexagonale/cubique et les tunnels entre plans pour la transition lamellaire/cubique, expliquant notamment l'apparition de la topologie bicontinue de la phase cubique.
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Fay, Hélène. "Films Lubrifiants Supramoléculaires Organisés : de la Microstructure aux Propriétés Tribologiques." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00715178.
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Les lubrifiants à base aqueuse sont très largement utilisés dans les procédés de mise en forme des métaux comme le tréfilage, car ils combinent d'excellentes capacités calorifiques à de bonnes propriétés tribologiques. L'objectif de ces travaux est d'établir le lien entre l'organisation des molécules en solution dans le lubrifiant et son pouvoir lubrifiant. La démarche expérimentale consiste à déterminer les propriétés structurales et tribologiques d'un système modèle aqueux, composé d'acides gras et d'éthylène diamine, principaux ingrédients des lubrifiants. Le diagramme de phases du système modèle est établi en s'appuyant sur des techniques de microscopie optique de polarisation, diffusion des rayons X aux petits angles (DXPA) et cryofracture. Pour un rapport molaire entre la diamine et les acides gras supérieur à 1, une succession de phases lamellaire, hexagonale et micellaires, biréfringente sous écoulement et isotrope, est observée avec la dilution. Une attention particulière est accordée à la phase lamellaire qui présente des défauts à l'approche de la transition vers la phase hexagonale. Les analyses réalisées en DXPA, cryofracture et Résonance Magnétique Nucléaire relient leur existence à une modulation de l'épaisseur de la bicouche et une augmentation de la courbure liées au couplage entre les acides gras et les contre-ions amines. Les propriétés lubrifiantes de l'ensemble de ces phases sont également comparées à l'aide d'un tribomètre qui réalise un contact entre un disque et une bille sous une cinématique de contact contrôlée, en régime de lubrification élastohydrodynamique. En plus des mesures de frottement, l'observation simultanée du contact permet de suivre la formation du film lubrifiant entre les surfaces et son évolution. L'influence de l'organisation supramoléculaire du lubrifiant sur son comportement est mise en évidence : les échantillons présentant une organisation lamellaire fournissent les meilleurs résultats en termes de réduction du frottement. L'organisation en bicouches de la phase lamellaire au sein du contact et ses propriétés piézovisqueuses peuvent expliquer sa portance accrue et sa prédisposition naturelle à la réduction du frottement.
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Héraut-Chéliout, Fawzia. "Rôle des trois chefs du triceps sural et du peroneus longus sur les angles tibio-calcanéen et de voûte plantaire externe pendant la phase d'appui de la marche humaine." Paris 11, 1987. http://www.theses.fr/1987PA112425.
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Kurtisovski, Erol. "Relation structure-propriétés dans les bicouches gonflées de phases lamellaires." Paris 6, 2007. http://www.theses.fr/2007PA066229.
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Les bicouches de tensioactifs sont des modèles de membranes cellulaires. La constante de rigidité détermine la forme de l'assemblage des membranes ou des processus comme la fusion de membranes, l'adhérence de protéine. . . Nous avons étudié l'évolution de la constante de rigidité d'une bicouche de tensioactifs non ioniques (CiEj) en phase lamellaire en fonction de ses paramètres structuraux. Dans une approche expérimentale, nous avons montré que diminue avec l'aire ou la longueur de la tête polaire, et qu'elle augmente avec la longueur de chaîne aliphatique à aire par molécule de tensioactif constante. Nos travaux ont mis en évidence le couplage des monocouches en phase ternaire CiEj- eau-dodécane et le rôle déterminant de la conformation des CiEj sur . L'ajout de glycérol augmente . Nous proposons deux processus pour l'expliquer. Dans une approche de dynamique moléculaire, nous avons paramétré les molécules CiEj dans le champ de force GROMOS G53A6 et avons simulé des bicouches de 900 tensioactifs dans l'eau sur plus de 50 ns. La constante de rigidité et les paramètres structuraux sont reproduits avec un bon ordre de grandeur. Les simulations avec glycérol appuient les deux processus que nous avons proposés.
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Héraut-Chéliout, Fawzia. "Rôle des 3 chefs du triceps sural et du Peroneus longus sur les angles tibio-calcanéen et de voûte plantaire externe pendant la phase d'appui de la marche humaine." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376058928.
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Chirat, Mathieu. "Synthèse de nouveaux tensioactifs macromoléculaires complexants et étude de leurs interactions avec le cobalt pour le développement d’un procédé de décontamination des textiles en milieu CO2 dense." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2012. http://www.theses.fr/2012ENCM0018/document.
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Cette étude porte sur la décontamination de matrices textiles en milieu CO2 dense (CO2 liquide ou CO2 supercritique). Elle s'inscrit dans le cadre de la décontamination des textiles utilisés dans l'industrie nucléaire. Le CO2 dense est proposé comme alternative au milieu aqueux utilisé dans le procédé actuel et qui génère une importante quantité d'effluents aqueux contaminés nécessitant un post-traitement. Le contaminant étudié est le cobalt qui peut se présenter sous forme ionique ou particulaire. L'extraction du cobalt en milieu CO2 dense est assurée par un additif : un tensioactif macromoléculaire CO2-phile/CO2-phobe complexant. Plusieurs familles d'additifs ont été synthétisées par polymérisation radicalaire contrôlée : des copolymères à gradient comportant des motifs CO2-philes, siliciés ou fluorés, et des motifs CO2-phobes complexants de types acétoacétoxys, diéthylphosphonates ou acides phosphoniques. Le comportement de ces copolymères dans le CO2 dense a été évalué grâce à la détermination des diagrammes de phases copolymère-CO2 (par la mesure du point de trouble) et grâce à l'étude de leur autoorganisation dans le CO2 dense (par diffusion de neutrons aux petits angles). Les copolymères fluorés se sont avérés être les plus avantageux en termes de solubilité. Néanmoins, les copolymères siliciés présentent une solubilité compatible avec le procédé et ils constituent donc une alternative intéressante pour éviter la présence de fluor gênant pour le conditionnement des déchets nucléaires. L'étude de la complexation du cobalt par les copolymères (par spectrométrie UV-visible et par torche à plasma couplée à un spectromètre d'émission atomique) a permis d'établir des relations entre le type de motif complexant et l'affinité avec le cobalt. La solubilité dans le CO2 dense de ces complexes copolymères-cobalt est comparable à celle des copolymères seuls. De plus, l'étude de l'auto-organisation en milieu CO2 dense a révélé un faible taux d'agrégation des complexes copolymères-cobalt. Enfin, les copolymères synthétisés ont été mis en oeuvre dans les procédés de décontamination particulaire et ionique. Dans le cas du procédé de décontamination ionique, l'emploi du copolymère à gradient poly(acrylate de 1,1,2,2-tétrahydroperfluorodécyle-co-diacide vinylbenzylphosphonique) a permis d'atteindre environ 70% de décontamination grâce à la formation d'une microémulsion d'eau dans le CO2 dense. L'efficacité du procédé dedécontamination a été portée à 97% grâce à l'emploi de pyridine comme tiers additifThis study is about textile decontamination in dense CO2 (liquid CO2 or supercritical CO2). The study is carried out in the framework of decontamination of textile used in the nuclear industry. The dense CO2 offers an alternative to aqueous medium used in the current process which generates a huge quantity of contaminated aqueous effluent requiring a post-treatment. Cobalt is the targeted contamination and can be found as ionic species or particles. The cobalt extraction in dense CO2 is achieved with an additive : a complexing CO2-philic/CO2-phobic macromolecular surfactant. Several types of additives were synthesized by controlled free radical polymerization : gradient copolymers made with CO2-philic groups (silicone-based or fluorinated moieties) and CO2-phobic complexing groups (acetoacetoxy, diethylphosphonate or phosphonic acid moieties). The copolymer behavior in dense CO2 was determined by phase diagram measurements (cloud point method) and their self-assembly in dense CO2 was investigated by small angle neutron scattering. The fluorinated copolymers were found advantageous in terms of solubility. Nevertheless, the silicone-based copolymers showed solubilities which are compatible with the process, therefore they are a good alternative to avoid fluorinated compounds which are unwanted in the conditioning of nuclear wastes. The study of cobalt complexation by the copolymers (UV-vis spectroscopy and inductively coupled plasma-mass spectroscopy) established relations between the type of complexing group and the affinity with the cobalt. The solubility of copolymer-cobalt complexes in dense CO2 is similar to those of copolymers. Moreover, the self-assembly study of the complex revealed a low aggregation. Finally, the synthesized copolymers were used in particle or ionic decontamination processes. In the case of ionic decontamination process, a rate of 70% of decontamination was reached with the use of gradient copolymer poly(1,1,2,2-tetrahydroperfluorodecyle acrylate-covinylbenzylphosphonic diacid) which allowed the formation of water-in-CO2 microemulsion. The efficiency of the decontamination process was even improved up to 97% with the addition of pyridine in the process
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Millot, Coraline. "Multi-scale characterization of deformation mechanisms of bulk polyamide 6 under tensile stretching below and above the glass transition." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0028/document.
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Notre étude a porté sur la compréhension microscopique des mécanismes de déformation du polyamide 6 (PA6) à l’état massif. Par des traitements thermiques appropriés, on a obtenu un jeu d’échantillons présentant des microstructures semi-cristallines variées, avec différentes formes cristallographiques (allotropes : α, γ ou β), différents taux de cristallinité (de 24 à 35%), différentes périodes de l’empilement des lamelles cristallines (de 7 à 12nm), ceci pour deux masses moléculaires différentes. Les propriétés mécaniques en traction ont été caractérisées au-dessus et au-dessous de la transition vitreuse de la phase amorphe (Tg). Les différents matériaux présentent des différences notables de comportements. Le taux de cristallinité semble être le facteur prédominant au-dessus de Tg, mais d’autres facteurs sont à prendre en compte en dessous de Tg, comme la forme cristalline et la morphologie lamellaire (épaisseur et facteur de forme). Grâce à un dispositif expérimental fabriqué sur mesure, des essais de traction ont été suivis par diffusion des rayons X aux petits (SAXS) et grands angles (WAXS) sur la ligne D2AM, ESRF, pour caractériser les déformations à l’échelle des empilements lamellaires et à l’échelle de la maille cristalline. Dans les échantillons présentant principalement de la phase cristalline β, les lamelles tendent à s’orienter perpendiculairement à la direction de traction (TD). Ce mécanisme d’orientation local (que nous appelons « modèle de réseau de chaînes ») est induit par la transmission des contraintes par les chaînes amorphes reliant les lamelles cristallines adjacentes. L’allongement local est plus faible que l’allongement macroscopique dans les lamelles perpendiculaire à TD, ce qui implique que les lamelles inclinées doivent être cisaillées. De plus, la phase β se transforme en phase α aux fortes extensions. Dans les échantillons présentant principalement de la phase α (la plus rigide), au-dessus de Tg, dans le régime élastique, les chaînes tendent d’abord à s’orienter perpendiculairement à TD, ce qui implique que les lamelles s’orientent parallèlement à TD (« modèle de lamelles rigides »). Ensuite, dans le régime plastique, une majeure partie des lamelles se réoriente perpendiculairement à TD, comme dans le « modèle de réseau de chaînes », tandis qu’une fraction mineure reste orientée parallèlement à TD. Une morphologie fibrillaire fortement orientée est finalement obtenue pour tous les échantillons quelle que soit la températureMechanical properties of bulk polyamide 6 (PA6) have been studied in relation to microscopic deformation mechanisms. By applying various thermal treatments, sets of samples with different semi-crystalline microstructures, namely various crystalline allotropic forms (denoted α, γ and β) and different values of the crystallinity index (from 24 to 35%) and of the long period of the lamellar stacks (from 7 to 12 nm), have been obtained, for two different molecular masses. Mechanical properties have been measured in the linear (viscoelastic) and nonlinear (plastic) regimes below and above the glass transition of the amorphous phase (Tg). Differences of behavior have been observed depending on the microstructure. While the crystallinity index seems to be the predominant factor affecting the mechanical behavior above Tg, other structural parameters such as the crystalline form and the lamellar morphology (thickness and aspect ratio) have to be taken into account below Tg. Deformations at the scales of lamellar stacks and of the crystalline unit cell have been characterized by small and wide angle X-ray scattering (SAXS and WAXS) performed in-situ during tensile tests. In samples with predominantly β phase, lamellae tend to orient perpendicular to the tensile direction (TD). This orientation mechanism (which we denote as ‘Chain Network model’) is driven by the amorphous chains which transmit the stress between adjacent lamellae. The tensile strain in lamellar stacks perpendicular to TD is lower than the macroscopic tensile strain, which must be compensated by increased shear in inclined stacks. Also, at high extension ratios, the β phase transforms into α phase. In samples with predominantly α phase and above Tg, morphology changes are more complex. In a first step, chains orient perpendicular to TD, which implies that lamellar planes tend to orient parallel to TD, possibly due to their high aspect ratio (denoted as ‘Rigid Lamella’ model). In a second step, beyond the yield, a major fraction of crystallites then reorients normal to TD, i.e. chains themselves become parallel to TD, while a minor fraction remains oriented along TD. A highly oriented fibrillar morphology is ultimately obtained in all cases
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Zhang, Li. "The study of phase separation in the miscibility gap and ion specific effects on the aggregation of soft matter system." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS106/document.
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Le procédé de séparation de phase est importante car elle détermine la structure des matériaux finaux. Il existe de nombreux systèmes qui ont plus d'une phase tels que des mousses et des gels. Les mousses sont des dispersions aqueuses de bulles de gaz dans une phase aqueuse et gels apparaissent lorsque certains microscopique unité de base commence à se rassembler formant un grand réseau solide qui enjambe l'espace macroscopique. Ils ont de nombreuses applications dans l'industrie et la vie quotidienne. Dans cette thèse, tout d'abord, je me concentre sur l'étude de différents types de séparation de phase. Deuxièmement, je étudié les effets spécifiques d'ions sur l'agrégation des particules colloïdales et tensioactif, le but est de faire des mousses stables. Dans la lacune de miscibilité il existe deux types de séparation de phase: la croissance nucléation et la décomposition spinodale, ils ont différents mécanismes et de la cinétique de croissance. Par conséquent, mon premier projet est d'étudier le processus d'évolution d'eux et de leurs effets sur la structure finale du matériau. Les gels peuvent être préparés par l'ajout de sel à la dispersion de particules colloïdales, ils ont un grand nombre d'applications telles que dans les aliments et la science des matériaux. Dans cette thèse, nous utilisons différents types de sels de comparer les propriétés de gel à partir de deux aspects macroscopiques et microscopiques. Obtenir des mousses stables est significatif dans la vue de leur beaucoup d'applications, mais les moyens de les faire sont pour la plupart compliqué. Dans cette thèse, nous pouvons obtenir des mousses stables par l'intermédiaire de deux façons. On est tout simplement en ajoutant des sels de solutions de tensioactifs, à travers lequel nous pouvons faire la mousse ultra-stable. Une autre façon est d'utiliser la phase de gel, nous avons étudié en tant que phase continue dans les mousses à arrêter le vieillissement de la moussePhase separation process is important as it determines the structure of the final materials. There are many systems that have more than one phase such as foams and gels. Aqueous foams are dispersions of gas bubbles in a water phase and gels appear when some basic microscopic unit starts to aggregate forming a large solid network that spans macroscopic space. They have many applications in industry and daily life. In the present thesis, firstly, I focus on studying different types of phase separation. Secondly, I studied the ion specific effects on the aggregation of colloidal particles and surfactant, the purpose is to make stable foams. In the miscibility gap there are two types of phase separation: Nucleation growth and spinodal decomposition, they have different growth mechanisms and kinetics. Therefore, my first p project is to investigate the evolution process of them and their effects to the final structure of material. Gels can be made by adding salt to the dispersion of colloidal particles, they have a large number of applications such as in food and material science. In this dissertation, we use different types of salts to compare gel properties from both macroscopic and microscopic aspects. Obtaining stable foams is significant in the view of their plenty of applications, but the ways to make them are mostly complicated. In this thesis, we can obtain stable foams via two ways. One is simply by adding salts to surfactant solutions, through which we can make ultrastable foam. Another way is using the gel phase we have studied as the continuous phase in foams to arrest the foam aging
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Gallois, Charlotte. "Etude des propriétés physico-chimiques de suspensions de boehmite. Application aux supports catalytiques." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066553/document.
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La poudre de boehmite, précurseur de l’alumine utilisée pour la production de supports catalytiques variés, est produite suite à une étape de séchage par atomisation. Cet oxyhydroxyde d’aluminium est composé de particules anisotropes chargées. Ces dernières années, il a été ont montré que les propriétés physico-chimiques des suspensions avaient une influence sur les caractéristiques des poudres. La morphologie des grains (sphère creuse, tore…) ainsi que les propriétés des poudres (dispersibilité, résistance mécanique…) peuvent être modifiées en jouant sur les caractéristiques des suspensions.Ce travail de thèse porte sur la compréhension des liens entre les propriétés physico-chimiques et rhéologiques de suspensions de deux boehmites industrielles et les propriétés des grains obtenus après séchage. Dans une première partie, nous avons caractérisé les particules en suspension de ces deux boehmites grâce à une approche multi-technique (SAXS, DLS, MET). Une étude rhéologique des suspensions obtenues par stress osmotique a ensuite permis de construire précisément le diagramme de phase de ces deux boehmites dans le plan force ionique – fraction volumique. La diffusion des rayons X aux petits angles et la diffusion dynamique de la lumière ont été utilisées pour déterminer l’organisation structurale des suspensions. Enfin, des expériences de séchage suivies optiquement et par micro-tomographie X ont été réalisées sur des suspensions de boehmite afin d’étudier l’impact de la concentration et de la force ionique sur l’évolution de la goutte au cours du séchageIn the catalyst supports industry, one important step of alumina powder production is the spray-drying of boehmite suspensions. This aluminium oxyhydroxyde is often used as precursor for various types of alumina catalyst supports. Boehmite is composed of anisotropic particles bearing an electric charge. In the past decade, it has been shown that the properties of the dry powder depend not only on the drying conditions but on physico-chemical properties of the sprayed suspensions. For instance, different grains morphologies (doughnut-shaped grains, hollow spheres,…) as well as various dry grains properties (textural properties, mechanical resistance,…) may be obtained by tuning the physico-chemical properties of the suspension.This study focus on the understanding of the links between the physico-chemical properties of suspensions of two industrial boehmites and the characteristics of the final dry grain. Since these two boehmites were not well-known, the first step of the study was to characterize boehmite particles present in suspension thanks to a multi-technical approach. A rheological study was performed on boehmite suspensions obtained thanks to osmotic stress to build precisely the phase diagrams of the both boehmites according to the system of ionic strength vs. volume fraction. Small angle X ray scattering and dynamic light scattering were used to investigate the existence of an orientational order of boehmite particles in suspension. Finally, drying experiments of boehmite suspensions were conducted on an optical set-up and on fast micro-tomography X, to examine the impact of both concentration and ionic strength on the evolution of the droplet during drying
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Magozore, Caxton. "DSP phase angle controlled three phase to single phase uninterruptible power supply." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/5177.
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Maamache, Mustapha. "Phase de berry, angle de annay et etats coherents action angle." Nice, 1993. http://www.theses.fr/1993NICE4625.
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Ce travail de physique theorique porte sur les relations entre la phase de berry et l'angle de hannay qui sont deux notions geometriques decrivant des transports naturels en physique respectivement quantique et classique. Le but principal de ce travail a ete d'elaborer un nouveau formalisme, celui des etats quantiques action angle (generalisation des etats coherents de l'oscillateur harmonique), dans lequel le transport classique apparait comme un cas particulier du transport quantique. Cela a permis non seulement d'etablir plusieurs derivations quantiques inedites de l'angle de hannay, mais aussi d'apporter des eclairages originaux sur la relation entre la phase de berry et l'angle de hannay a travers l'introduction des notions de principe variationnel moyenne ou de minimisation de metriques sur les etats quantiques ou les trajectoires classiques. Le rapport entre la phase de berry et l'angle de hannay a egalement ete examine dans le cas des systemes grassmaniens
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Alps, Mike. "The phase transformation friction angle of sand." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442864.
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Leibly, Frank J. (Frank Joseph). "Measurement and digitization of phase angle modulated sensor data." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37753.
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Eaton, Elizabeth Jane. "Paradoxical breathing and arousal from sleep." Thesis, Manchester Metropolitan University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320131.
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Morris, Darryl William Seymour. "Low angle protein phasing." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341631.
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Ellgardt, Anders. "Wide-angle scanning wide-band phased array antennas." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10225.
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This thesis considers problems related to the design and the analysis of wide-angle scanning phased arrays. The goals of the thesis are the design and analysis of antenna elements suitable for wide-angle scanning array antennas, and the study of scan blindness effects and edge effects for this type of antennas. Wide-angle scanning arrays are useful in radar applications, and the designs considered in the thesis are intended for an airborne radar antenna.After a study of the wide-angle scanning limits of three candidate elements, the tapered-slot was chosen for the proposed application.A tapered-slot antenna element was designed by using the infinitive array approach and the resulting element is capable of scanning out to 60° from broadside in all scan planes for a bandwidth of 2.5:1 and an active reflection coefficient less than -10 dB. This design was implemented on an experimental antenna consisting of 256 elements.The predicted performance of the antenna was then verified by measuring the coupling coefficients and the embedded element patterns, and the measurements agreed well with the numerical predictions.Since the radar antenna is intended for applications where stealth is important, an absorbing layer is positioned on top of the ground plane to reduce the radar cross section for the antenna's cross-polarization.This absorbing layer attenuates guided waves that otherwise lead to scan blindness, but does not adversely affect the antenna performance for the desired scan directions and frequencies.The highest frequency limit of the tapered-slot element is set by scan blindnesses. One of these scan blindnesses is found to be unique to tapered-slot elements positioned in triangular grids. This scan blindness is studied in detail and a scan blindness condition is presented and evaluated.The evaluation of the experimental antenna shows that edge effects reduce the H-plane performance of the central elements.These edge effects are further studied and characterized, by comparing the scattering parameters for finite-by-infinite arrays and infinite arrays.In this way it is possible to divide the edge effects into two categories: those caused by finite excitation, and those caused by perturbed currents due to the geometry of the edge. A finite difference time domain code with time shift boundaries is used to compute the active reflection coefficients needed to compute the scattering parameters, but this code cannot directly compute the active reflection coefficient for all the required phase shifts.Hence, an additional method is presented that makes it possible to compute arbitrary phase shifts between the elements using any numerical code with limited scan directions.QC 20100712
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Sadler, Peter Andrew. "Harmonic elimination and voltage control in three phase AC power converters." Thesis, Manchester Metropolitan University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285285.
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Byrd, Mark Steven. "Representations of SU(3) and geometric phases for three-state systems /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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Allison, Steven David. "The effects of interblade phase angle on pitch oscillating, transonic, cascade flows." Thesis, University of Salford, 2011. http://usir.salford.ac.uk/26530/.
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A series of compressor blades, aligned as a cascade, situated in a transonic flow has been studied using a two-dimensional Computational Fluid Dynamics (CFD) technique. An objective of the research was to discover, using a CFD code, how the total aerodynamic stability of a compressor cascade was affected by blade pitching oscillations, vibrating at certain interblade phase angles and oscillation frequencies. The analysis focused on the way in which the interblade phase angle, a, is likely to affect the stability of the cascade over a range of oscillation frequencies between 200Hz and 1 OOOHz, for a series of interblade phase angles between 0° and 180°. Two turbulence models were assessed to determine the sensitivity of turbulence coding, namely the Baldwin-Lomax and Johnson-King models. A validation of the CFD code against published data from the NASA Lewis Research Centre was carried out. The interaction of the passage shock, formed between the blades, and on the positive pressure surface of the blade was shown to have the greatest influence on the aerodynamic stability of the cascade; the shocks formed on the suction side had a somewhat smaller effect. Any flow separation, on either the suction or pressure surfaces, was also shown to decrease cascade stability.
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Cocquerelle, Jean-Louis. "Étude des associations en triphasé : gradateur en angle de phase - transformateur - résistances." Lille 1, 1985. http://www.theses.fr/1985LIL10107.
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Pour régler de façon continue le débit du réseau de distribution dans un récepteur triphasé résistif, à l'aide d'un dispositif présentant de très faibles pertes, il est usuel de disposer un gradateur fonctionnant en "angle de phase" entre la source et la charge. Il est presque toujours nécessaire, dans les équipements de forte puissance, d'ajouter un transformateur. L'analyse du fonctionnement de l'ensemble transformateur - gradateur - charge est très complexe, pour plusieurs raisons :- D'abord, ces dispositifs fonctionnent en commutation libre, c'est à dire que l'on ne peut commander que la mise en conduction des thyristors. - Ensuite, la présence du transformateur modifie totalement, par le couplage magnétique qu'il introduit entre les phases, le comportement du gradateur. En effet, les instants d'extinction des thyristors ne sont pas uniquement dépendant des tensions d'alimentation, mais à la fois du couplage des enroulements, de l'emplacement des composants, du niveau de la charge, ainsi que de l'état magnétique du transformateur. La première partie du mémoire est consacrée à l'étude analytique du fonctionnement en régime permanent. La deuxième partie concerne la comparaison des divers montages, en régime permanent, mais également face à un défaut comme la rupture d'une résistance de charge. Une méthode par simulation est alors introduite, elle permet d'élaborer la meilleure "loi de commande" du gradateur disposé dans une structure donnée.
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Marais, Sarel Jacobus. "The quadrifilar helix antenna and its application to wide angle phase-steered arrays." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/21675.
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Thesis (MScIng)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: The quadrifilar helix antenna has frequently been employed to provide the wide angle, circularly polarized radiation pattern which is preferable for mobile satellite communications. A detailed study of this antenna and its varieties is presented. When used as an element in wide angle scanning arrays for aeronautical satellite tracking applications, the additional requirement of a low profile with light weight applies. This further complicates the realization of good circular polarization close to the horizon. A top disk is incorporated into various antenna structures in an effort to improve the radiation performance when used within a closely spaced array while reducing the height of the radiating element. The array performance of these elements are investigated which hints at a supported traveling mode aiding the ability to accomplish the wide angle beam steering. Subsequent study of leakywave antennas initiated the study and implementation of leaky-wave structures in phased arrays of quadrifilar helix elements.
AFRIKAANSE OPSOMMING: Die vierledige heliksantenna word dikwels gebruik vir toepassings wat ’n wye, sirkulêr gepolariseerde stralingspatroon benodig. ’n Verskeidenheid van hierdie antennas is noukeurig bestudeer en hul toepaslikheid vir mobiele sattelietkommunikasie ondersoek. Wanneer hierdie antennas in fase gestuurde skikkings gebruik word, word dit ook vereis dat die eenhede liggewig is met ’n lae profiel. Dit bemoeilik die verkryging van goeie sirkulêre polarisasie naby die horison aansienlik. In ’n poging om die wyehoek straling met kort antennas te verbeter, is ’n oorhoofse skyf tot verskillende heliksstrukture toegevoeg. In nou gespasieerde skikkings maak hierdie skywe ’n positiewe bydrae to wyehoekstralingeienskappe. Die invloed van lekmodusse wat binne die struktuur voortplant is ondersoek en gebruik in skikkings waarvan die bundel naby aan die horison gestuur word.
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Swann, Joshua Michael George. "Characterising pH response in phase separated hydrogels using small angle X-ray scattering." Thesis, University of Sheffield, 2010. http://etheses.whiterose.ac.uk/14968/.
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A range of (methyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate)block- poly(methyl methacrylate) [PMMA-block-PDEA-block-PMMA] and poly(methyl methacrylate )-block-poly(methacrylic acid)-block-poly(methyl methacrylate) [PMMA-blockPMAA- block-PMMA] triblock copolymers have been prepared via group transfer and anionic polymerisation respectively. These hydrophilic-hydrophobic block copolymers were characterized with respect to their chemical composition and molecular weights by 1 H and by gel permeation chromatography respectively. Morphological development in solvent cast films were followed using SAXS by monitoring changes in the structure peak. [PM MA-block-PMAA-block-PM MA] triblocks were found to be mechanically weak and therefore not suitable as chemical actuators. Using SAXS the "static" equilibrium molecular response of phase separated films of [PMMA-block-PDEA-block-PMMA] triblock copolymers to changes in pH, ionic strength and salt identity was evaluated. Changes in pH were effected using a controlled set of buffers, namely citric acid, sodium phosphate and ethanol amine. The ionic strength of the buffers was fixed using a series of salts from the Hofmeister series, namely NaAce, NaCl, NaBr, Nal, NaN03 and NaSCN. At a fixed pH and ionic strength the equilibrium expansion ratio of the polymer was found to be highly dependent on the identity of the salt. The extent of swelling was correlated with the surface charge density of the anionic component of the salt. Hydrogels swollen in solution containing more polar anions were found to have a larger expansion ratio. This was explained in terms of the water perturbing effect of the ion. The swelling of the polymer was also monitored as a function of pH. A drastic collapse of the polymer was observed at a specific pH corresponding to the apparent pKa of the PDEA block. The apparent pKa of [PMMA-block-PDEA-block-PMMA] copolymers was found to be dependent on the overall molecular weight, where higher molecular weight material had a lower apparent pKa. Below the apparent pKa the extent of swelling in solutions prepared at 0.1 M ionic strength was found to be dependent on the pH. This has been attributed to the . complex interplay of citrate species in the buffer. The effect of ionic strength on the "swelling was also investigated at fixed pH and salt identity using buffer and simple mineral acid. A modified Donnan theory has been used to interpret the results. SAXS was found to be a highly sensitive technique for measuring the "static response" of the hydrogels. The use of SAXS was also investigated as a technique for measuring the swelling "kinetics" of [PMMA-block-PDEA-block-PMMA] hydrogels. Thin annealed films of hydrogel were swollen in a range of control buffered solutions. The in-situ nature of the technique afforded high resolution data. The kinetics of swelling was monitored by following the change in the structure peak position and its half height peak width, which gave the expansion ratio and diffusive behavior respectively. Swelling stresses induced in the samples made measuring the kinetics problematic and this limited the technique. Finally, to avoid the expense and limited availability of SAXS beam lines a new technique was used to monitor the response of the hydrogels. A diffraction grating was imprinted onto the surface of the hydrogel, and "static" and "kinetic" response was measured by monitoring the change in the diffraction pattern. This technique was found to offer similar accuracy as SAXS, at a Significantly reduced cost.
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Schmidt, Nico [Verfasser]. "Phase transformation behaviour of polylactide probed by small angle light scattering / Nico Schmidt." Paderborn : Universitätsbibliothek, 2020. http://d-nb.info/1209601370/34.
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Collins, Edward Randolph Jr. "Torque and speed control of single-phase induction motors using an adjustable amplitude and phase angle auxiliary winding power supply." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/15472.
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Al-Tameemi, Wameedh Turki Mohammad. "Two-phase flow in straight pipes and across 90 degrees sharp-angled mitre elbows." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/20832/.
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Pressure drop of single-phase flow across 90 ◦ sharp-angled mitre elbows connecting straight circular pipes is studied in a bespoke experimental facility by using water and air as working fluids flowing in the range of bulk Reynolds number 500 < Re < 60000. To the best of our knowledge, the dependence on the Reynolds number of the pressure drop across the mitre elbow scaled by the dynamic pressure, i.e. the pressure-loss coefficient K, is reported herein for the first time. The coefficient is shown to decrease sharply with the Reynolds number up to about Re=20000 and, at higher Reynolds numbers, to approach mildly a constant K=0.9, which is about 20% lower than the currently reported value in the literature. We quantify this relation and the dependence between K and the straight-pipe friction factor at the same Reynolds number through two new empirical correlations, which will be useful for the design of piping systems fitted with these sharp elbows. The pressure drop is also expressed in terms of the scaled equivalent length, i.e. the length of a straight pipe that would produce the same pressure drop as the elbow at the same Reynolds number. Air-water flow in horizontal and vertical straight pipes and through 90 ◦ sharp-angled mitre elbows, is investigated visually by using high-speed high-resolution camera. The flow is studied in pipes with three diameters for about 600 conditions of air-water flows, characterized by superficial velocities in the ranges of jL =0.297-1.015 m/s for water and jG =0.149-33.99 m/s for air. The portion of the pipe upstream of the elbow is always positioned horizontally, while the portion of the pipe downstream of the elbow is oriented horizontally or vertically with the flow moving upward. Plug, slug, slug-annular and annular flows are observed in horizontal straight pipes, while slug, churn and annular regimes are recorded in vertical straight pipes. These flow patterns are well predicted by the Mandhaneet al. [1] map for horizontally oriented straight pipes and by the Hewitt and Roberts [2] map for vertically oriented straight pipes. The prediction of the flow patterns along the straight portions of the pipe improves by expressing the maps in non-dimensional form. The changes of the flow patterns as the fluids pass through the mitre elbows are thoroughly discussed. A multiple membrane flow structure is observed in the vertical upward flow at much higher Reynolds numbers, based on the water superficial velocity, than in the vertical downward case previously reported in the literature. The flow patterns through the elbows are expressed for the first time in terms of rescaled Mandhane et al. [1] maps, which simultaneously represent the flow patterns both upstream and downstream of the elbows. The dimensional analysis proves that a rigorous way to present the flow regimes of an incompressible isothermal air-water flow for a given geometry is a map in the space of the Reynolds numbers based on the superficial velocities of air and water for fixed Froude number. The pressure drop generated by air-water flows was measured in horizontal and vertical straight pipes and across 90◦ sharp-angled mitre elbows for the same flow conditions of visual investigations. Two new pattern-based values of the Lockhart-Martinelli parameter C are found for the pressure drop in horizontal pipes with the presence of mitre elbows. A dimensional analysis is employed to scale the pressure drop data for straight pipes and across the elbows. New pattern-based empirical correlations are proposed to fit the scaled frictional pressure drops for the flows through the straight portions of the pipe and across the elbows. The flow perturbation length upstream of the elbow is located at less than 32.5D for single-phase and two-phase flows, while the flow recovery length downstream of the lbow was less than 32.5D ∗ and 60D ∗ for single-phase and two-phase flows, respectively. The peripheral pressure upstream and downstream of the elbow is found to be axially symmetric farther than 7D upstream and downstream of the elbow for horizontal orientation in single-phase and two-phase flows.
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Spiess, Rachel. "La phrase clivée en it- en anglais contemporain." Aix-Marseille 1, 2002. http://www.theses.fr/2002AIX10094.
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La phrase clivée est généralement considérée comme un procédé de mise en relief servant à établir un contraste avec ce qui précède. Pourtant, elle n'est pas contrastive en elle-même et on peut se demander ce que "mise en relief" signifie. Cette thèse a pour but de décrire les différents emplois de la phrase clivée et accessoirement de remettre en question les nombreuses idées reçues qui circulent sur le sujet en évitant les termes qui prêtent à confusion (comme celui de focus) et en définissant clairement les concepts utilisés. La phrase clivée sera vue comme un focalisateur syntaxique. La focalisation définie au niveau sémantico-pragmatique étant la notion centrale de cette étude. Après un inventaire plus riche que ne le prétendent les grammaires, des constituants qui peuvent être clivés, des propositions subordonnées qui peuvent accompagner ce constituant et des temps auxquels peuvent se mettre les deux verbes de la phrase clivée et après un examen rapide des principales descriptions théoriques qui ont été proposées sur la phrase clivée, on s'intéresse à la portée de deux sortes d'unités porteuses de champ : la négation et les adverbes. La négation qui, contrairement à l'appréciation générale, ne porte pas uniquement sur le constituant clivé mais rend généralement toute la proposition négative. Et l'adverbe dont la phrase clivée permet de déterminer le degré d'intégration. Après cela, il n'y a plus qu'à identifier les différents emplois (et les effets de sens correspondants) de la phrase clivée. Ce travail s'appuie sur un corpus personnel de 800 exemples composé d'extraits de tous types d'écrits ainsi que sur un très grand nombre d'exemples sur des sites Internet.
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Chavan, Harshad S. "Investigation of ß-phase poly (vinylidene fluoride) films using small-angle x-ray scattering." Cincinnati, Ohio : University of Cincinnati, 2006. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1145990710.
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Polavieja, Gonzalo Garcia de. "Geometric phase and angle for noncyclic adiabatic change, revivals and measures of quantal instability." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325986.
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CHAVAN, HARSHAD S. "INVESTIGATION OF β-PHASE POLY (VINYLIDENE FLUORIDE) FILMS USING SMALL- ANGLE X-RAY SCATTERING." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1145990710.
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Harada, Tamotsu. "Ultra-Small-Angle Scattering Study of Formation Mechanism and Phase Transition of Colloidal Crystals." Kyoto University, 2001. http://hdl.handle.net/2433/150664.
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McCann, John Forrest. "On the design of large bandwidth arrays of slot elements with wide scan angle capabilities." Connect to resource, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1209590321.
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Xia, Tao. "Frequency Monitoring Network (FNET) Algorithm Improvements and Application Development." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/77296.
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The Internet Based real-time GPS synchronized wide-area Frequency Monitoring Network (FNET) is an extremely low cost and quickly deployable wide-area frequency measurement system with high dynamic accuracy which consists of Frequency Disturbance Recorder (FDR) distributed to more than 100 places around North America and an Information Management System situated at Virginia Tech. Since its first FDR deployment in 2003, the FNET system has been proved to be able to reliably receive phasor data accurately measured at and instantaneously sent via the Internet from different locations of interest, and efficiently run the analyzing program to detect and record significant system disturbances and subsequently estimate the location of disturbance center, namely the event location, in the electric grid based on the information gathered. The excellent performance of the FNET system so far has made power grid situation awareness and monitoring based on distribution level frequency measurements a reality, and thus advances our understanding of power system dynamics to a higher level and in a broader dimensionality.
Chapter 1 and Chapter 2 of this dissertation briefly introduce the genesis and the architecture of the FNET system, followed by a summary of its concrete implementations. Chapter 3 and Chapter 4 outline FNET frequency estimation algorithm and phase angle estimation algorithm, including their attributes and the new methodologies to enhance them. In Chapter 5, the report discusses the algorithms developed at FNET to detect the frequency disturbance and estimate the disturbance location by the triangulation procedure using real-time frequency data and geographic topology of the FNET units in the power grid where the disturbance occurs. Then, the dissertation proceeds to introduce the FNET angle-based power system oscillation detection and present some research about Matrix Pencil Modal Analysis of FNET phase angle oscillation data in the following two chapters. Lastly, the content of this report is summarized and the future work envisioned in Chapter 8.Ph. D.
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Sédiri, Ammar. "Temps, aspect-phase et modalisation en anglais et en arabe : analyse contrastive métaopérationnelle." Paris 3, 1994. http://www.theses.fr/1994PA030117.
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Notre recherche porte sur les questions du temps, de l'aspect et de la modalisation dans une perspective contrastive (l'arabe et l'anglais notamment) et metaoperationnelle (l'analyse en termes de phases). Le premier chapitre introduit a la fois les langues concernees et le modele d'analyse. Le seuxieme soumet le systeme verbal de l'arabe a une analyse en termes de phases. La confrontation avec des donnees de la langue anglaise fait l'objet d'un troisieme chapitre. Le quatrieme chapitre a pour objet la comparaison des enonces arabes et anglais a structure complexe. Enfin, le dernier chapitre propose une analyse contrastive de quelques metaoperateurs anglais et arabes en rapport avec la modalisation. L'objectif de la these est de jeter une lumiere nouvelle sur ces categories dans leur fonctionnement systematique au sein des langues concernees et definir la part de l'universel qui, au-dela des systemes particuliers, se rapporte au langage en generalThis thesis is a metaoperational approach to tense, aspect and modality in arabic and english through an application of the theory of phases to english and arabic verbal systems concerning these issues. The first chapter introduces both the language and the model of analysis of the arabic verbal system. Then a comparison with english is conducted in the third chapter. The fourth chapter deals with english and arabic utterances with an auxiliary component. The final chapter concerns modalization : a contrastive analysis of some english and arabic modal operators. The aim of the metaoperational grammar is to bring to light the systematic workinf og particular tonguesand the universals of human language
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Thakkar, Kairavee K. "A Geometric Analysis of Time Varying Electroencephalogram Vectors." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613745734396658.
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Uriarte, Fabian. "Modeling, Detection, and Localization of High-Impedance Faults In Low-Voltage Distribution Feeders." Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/30810.
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High-impedance faults (HIFs) on distribution feeders are abnormal electrical conditions that cannot be detected by conventional protection schemes. These faults pose a threat on human lives when neighboring objects become in contact with the lineâ s bare and energized conductors. An accurate electrical model for a HIF is implemented to investigate typical patterns in the lineâ s current that allow for the detection of these faults. The occurrence of HIFs is detected with harmonic-current phase analysis and localized with recloser-sectionalizer technology as presented in this work. A sectionalizer algorithm is then presented showing the decision criteria for HIF declaration and shown to discriminate against nominal behavior in distribution feeders of similar harmonic content. Finally, it is shown that the algorithm will not produce a misreading when a current transformer enters saturation.Master of Science
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Dowsett, Amy. "The improvement of vehicle noise variability through the understanding of phase angle and NVH analysis methods." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/35880.
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Noise, vibration and harshness (NVH)levels in the luxury automotive industry are used by customers as a subjective method of determining the vehicle quality. This can be achieved by adjusting the vehicle design, where simulations are used to predict the NVH behaviour. Changes can be expensive and time consuming when made after the design stage has been completed, so it is important to produce accurate simulations of the product. Variability exists to some extent in all products, even those just off the production line, however, if a high level of variability exists then only a small portion of products will meet the predicted behaviour. The aim of the project is to provide information that may lead to the reduction of variability in an automotive vehicle. This is achieved by quantifying the statistical spread of FRFs (frequency response function) in a set of nominally identical vehicles. Once overall levels have been calculated, the location of the most variable sources can be identified. Project also seeks to develop new methods of analysis for the system phase response to determine whether further information may be extracted compared to the magnitude response. There are three main themes that run throughout this thesis, with the first being the quantification of variability due to the measurement taking process which is covered in chapter 3. A novel application of a method to separate the measurement variability from the overall system uncertainty was achieved as well as the quantification of the vehicle to- vehicle variability. The second theme that runs through the study concerns the identification of variability sources. This is realised in chapter 4 and chapter 6 as a set of structural and acoustic tests on a luxury sedan door. The trim was found to be held to the door panel by a series of 11 polymer clips and 4 metal screws. The variability of small changes to a significant boundary condition at the door trim was quantified, showing that the removal of rigid clips had a more significant effect on the overall variability that if a loose clip has been removed. It was also found that clips at the corners were the most sensitive to change. The final theme outlines and tests new analysis methods on the phase and compares the statistical spread of the phase with the equivalent spread of the magnitude. Data taken from the same tests was used and for most of the cases the two results were found to be approximately the same.
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Bucher, Thomas M. Jr. "CAPILLARITY AND TWO-PHASE FLUID TRANSPORT IN MEDIA WITH FIBERS OF DISSIMILAR PROPERTIES." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3653.
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Capillarity is a physical phenomenon that acts as a driving force in the displacement of one fluid by another within a porous medium. This mechanism operates on the micro and nanoscale, and is responsible for countless observable events. This can include applications such as absorption in various hygiene products, self-cleaning surfaces such as water beading up and rolling off a specially-coated windshield, anti-icing, and water management in fuel cells, among many others.
The most significant research into capillarity has occurred within the last century or so. Traditional formulations for fluid absorption include the Lucas–Washburn model for porous media, which is a 1-D model that reduces a porous medium to a series of capillary tubes of some educated equivalent radius. The Richards equation allows for modeling fluid saturation as a function of time and space, but requires additional information on capillary pressure as a function of saturation (pc(S)) in order to solve for absorption. In both approaches, the surface can only possess one fluid affinity. This thesis focuses on developing capillary models necessary for predicting fluid absorption and repulsion in fibrous media. Some of the work entails utilizing approximations based on pore space available to the fluid, which allows for capillary pressure simulation in media with arbitrary fiber orientation. This thesis also presents models for tracking the fluid interface in fibrous media and coatings with simpler geometries such as horizontally and vertically aligned fibers and orthogonal fiber layers. This method hinges on solving for the true fluid interface shape between the fibers based on the balance of forces across it, ensuring the accurate location and total content of fluid in the medium, and therefore accurate pc(S). Using this approach also allows, for the first time, fibers of different fluid affinities to exist in the same structure, to examine their combined influence on fluid behavior. The models in this thesis focus mainly on absorbent fabrics and superhydrophobic coatings, but can be easily expanded for use in other applications such as water filtration from fuel, fluid transport and storage in microchannels, polymer impregnation in fiber-reinforced composite materials, among countless others.
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Pontoni, Diego. "Small-angle X-ray scattering studies of phase transitions and growth processes on colloidal dispersions." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271227.
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Chedin, Georges. "Comparaison des syntagmes verbaux habituels et des locutions verbales en anglais américain avec l'usage en anglais britannique." Paris 4, 1988. http://www.theses.fr/1988PA040055.
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J'ai d'abord constitué un corpus d'environ 600 syntagmes verbaux à partir du dictionnaire Webster's new world dictionary, de 1970 où Mathews a marqué les américanismes d'un astérisque. J'ai mis au point un questionnaire, et une méthode d'enquête. Je partis enquêter aux Etats-Unis en 1974, 1978, 1983, et en Grande-Bretagne en 1977, 1979, 1982, auprès d'informants sélectionnés selon certaines variables sociolinguistiques. Mon corpus passait de 600 à 900 entrées entre 1974 et 1983. L'enquête aux Etats-Unis avait pour but de déterminer la fréquence, le niveau et le contexte d'usage des syntagmes verbaux et locutions verbales, auprès d'informants représentatifs, c'est-à-dire sélectionnés selon des variables socio-linguistiques (zone dialectale, âge, sexe, profession, milieu socio-culturel etc. ) L'enquête en Grande-Bretagne, auprès d'informants britanniques, représentatifs, sélectionnés selon les mêmes variables, socio-linguistiques, avait pour but de mesurer le degré de pénétration des américanismes en anglais britannique, et de faire ressortir les différences d'usage, ou de faire surgir des équivalents britanniques. J'ai pu constater une forte pénétration des américanismes en anglais britannique et aussi une résistance à l'usage de certains syntagmes verbaux. Pour les Etats-Unis j'ai pu établir des rapports entre l'usage de tel syntagme verbal et telle variable socio-linguistique. Pour terminer j'ai comparé mon travail à celui des lexicologuesI first put together a corpus of about 600 phrasal and prepositional verbs, using Webster's new world dictionary, 1970, in which Mathews had marked americanisms with an asterix. I then devised a questionnaire and a method of investigation. In 1974, 1978, 1983 i went to the states, and in 1977, 79, 82, i went to Britain, to carry out a field survey on informants selected according to several socio-linguistic variables. Between 1974 and 1983 my corpus increased from 600 to 900 lexical items. The purpose of my field survey in the US was to assess the frequency, level, and usage in which the phrasal and prepositional verbs were used by informants, selected as representative of different categories (dialectal zone, age, sex, occupation, socio-economic and educational background). The field survey carried out in Britain with representative informants, selected according to the same socio-linguistic variables, was designed to evaluate the degree to which americanisms had entered into British speech and to underline differences in usage, and to elicit British equivalents. The results of this study show a high degree of assimilation with respect to certain americanisms as well as a reluctance on the part of British informants to use certain verbal idioms. As for the us, i was able to establish a correlation between the usage of a given verb and a given socio-linguistic variable. Finally, i compared my work with that of the lexicologists
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Chakraborty, Saonti. "SHORT - RANGE ORDER IN THE NEMATIC PHASE OF REDUCED SYMMETRYTHERMOTROPIC MESOGENS." Kent State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=kent1385158954.
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Miftah, el kheir Laila. "Smart devices for biomedical applications." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD054.
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Dans cette thèse, nous nous sommes intéressés aux systèmes intelligents pour des applicationsmédicales et cosmétiques. Ainsi, nous avons conçu et réalisé trois instruments. Le premier estdédié à la mesure de la mouillabilité de la peau. L’originalité de ce dispositif réside en sa capacité àdonner une image 3D de la goûte de la surface de la peau explorée et de donner le comportementdynamique de la goûte. Cette stratégie nous donnera la possibilité de créer de nouvelles basesde données relatives à la mouillabilité de tout le corps humain. En effet, nous disposons que desdonnées sur la mouillabilité de l’avant-bras. Le deuxième instrument intelligent concerne la mesurede la réflectance d’une surface. Ce dispositif assure une mesure de très haute résolution angulairede la BRDF et une très bonne répétabilité de la mesure. Il a été validé sur la peau pour la mesurede l’ éclat. Et enfin le troisième instrument, basé sur une méthode originale de mesure de vibrationà l’aide d’un système de stéréo-vision associée à un motif périodique. Il a été appliqué pour lamesure du mouvement thoracique et abdominal lors de la respiration. Notre principale motivationpour développer ce système fut la réduction des artefacts, dus aux mouvements d’un patient lorsd’un examen radiologiqueSmart Devices have been widely used by health care and cosmetics professionals. Indeed, they helpin many aspects of clinical practice by providing an efficient way for medical diagnosis, supportingbetter clinical decision-making and improving patient outcomes. In this thesis, we have beeninterested in three applications. The first one is related to the wettability measurement, especially forthe human skin. So we propose, a held-hand device that is based on the contact angle measurementto determine skin wettability. Besides, the device allows the visualization of the liquid dropletspreading in both dynamic and static modes. Moreover, it can measure the top and the left views ofthe droplet and provides the 3D droplet and the skin explored area profiles. The second applicationpermits the skin radiance measurement. For this purpose, we propose a miniaturized device havingan original method for the BRDF measurement associated with 3D profile measurement of the areastudied. As regards the third application, it is a non-invasive method for breath measurement that usesa stereovision system and a pseudo-periodic pattern. This system allows a high-resolution threedimensionaldisplacement measurement for the recording of the thoracoabdominal wall respiratorymovement. The devices developed during this research gives us a high accuracy, a good resolutionand repeatability of measurements
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Boulonnais, Dominique. "Elements pour une definition de la notion de phrase, avec application a l'anglais." Paris 3, 1989. http://www.theses.fr/1989PA030116.
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La these presentee examine la pertinence de la notion de phrase en linguistique. A partir d'une etude de la portee des subordonnees adverbiales, on construit une representation semantique hierarchisee du produit langagier. La phrase est definie comme la combinaison d'un tropique, ou signe de mode, et d'un phrastique, ou contenu prepositionnel, dans une version revisee du travail de hare (1970). Le tropique a pour equivalent syntaxique minimal le temps, defini de maniere a inclure toutes les formes verbales, finies et non finies, en un systeme symetrique. La notion de temps est egalement etendue aux small clauses. On examine ensuite les structures predicatives non phrastiques, comme les complements des verbes de perception et les differentes formes d'attributs, de maniere a les distinguer des formes phrastiques avec ou sans verbe. La derniere partie est consacree a une breve description de la structure et de la distribution des phrases enchassees de l'anglais. On conclut enfin en montrant la specificite de la phrase dans la theorie x-barreThe present dissertation examines the legitimacy of the concept of sentence and its role in linguistic theory. A semantic definition is first constructed, based on a study of the scope of adverbial clauses, which points to the existence of different levels of organization in linguistic expressions. Sentences are described as the combination of a tropic, or sign of mood, and a phrastic, or propositional content, in a revised version of hare's 1970 work. Tense, defined so as to include all verbal forms, finite and non finite, in a symmetrical system, is given as the minimal syntactic equivalent of the tropic, and thus as the constitutive element of sentences. The notion of tense is also extended to small clauses. Non-sentential predicative structures, such as perception verb and suject or object complements, are examined in an attempt to distinguish them from verbal and non-verbal sentential forms. The structure and distribution of embedded sentences, divided into two groups of primary and derived forms, are then given a brief description. In conclusion, the specificity of sentences is demonstrated within the framework of x-bar theory
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Oliveira, Pablo Gustavo de. "Ângulo de fase como indicador de desfechos negativos em pacientes cirúrgicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/61738.
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Introdução: A Bioimpedância Elétrica (BIA) é um método fácil de usar, rápido, barato, não invasivo e de fácil reprodutibilidade utilizado para verificar as mudanças na composição corporal. O Ângulo de Fase (AF), obtido através da BIA, reflete a relativa contribuição dos fluidos e membranas para o corpo humano, sendo associado como um marcador prognóstico em diversas situações clínicas. Objetivos: Avaliar o AF como indicador de desfechos negativos em pacientes cirúrgicos (ocorrência de infecção e/ou morte e tempo de permanência hospitalar). Metodologia: Foram avaliados pacientes com idade de 18 a 80 anos internados no Hospital de Clínicas de Porto Alegre com indicação de cirurgia eletiva. As avaliações foram realizadas no momento da internação, 48 e 72 horas após a cirurgia. Foram avaliados peso, altura e Índice de Massa Corporal (IMC), estado nutricional através da Avaliação Nutricional Subjetiva Global (ANSG) e Ângulo de Fase através da BIA. Resultados: Foram avaliados 142 pacientes, segundo o IMC, 59,2% dos pacientes foram classificados como eutróficos, 3,5% moderadamente desnutridos e 37,3% apresentaram algum grau obesidade. A avaliação por ANSG verificou que 76,1% dos pacientes estavam eutróficos, 23,2% moderadamente desnutridos e 0,7% desnutridos graves. Os baixos valores para o AF obtidos nas 3 avaliações não se apresentaram como indicadores de desfechos negativos em pacientes cirúrgicos. Conclusões: O AF não se demonstrou um indicador para desfechos negativos em pacientes cirúrgicos.Introduction: Electrical Bioimpedance (BIA) is an easy to use, fast, inexpensive, noninvasive and highly reproducible used to verify the changes in body composition. The Phase Angle (PA), obtained by BIA reflects the relative contribution of fluid and membranes for the human body, being associated as a prognostic marker in various clinical situations. Objectives: To evaluate the AF as an indicator of negative outcomes in surgical patients. Methodology: We studied patients aged 18 to 80 years at the Hospital de Clínicas de Porto Alegre with indication of elective surgery. Evaluations were performed at admission, 48 and 72 hours after surgery. Body weight, height and Body Mass Index (BMI), nutritional status by Subjective Global Assessment (SGA) and Phase Angle through the BIA. Results: According to BMI, 59.2% of patients were classified as eutrophic, 3.5% moderately malnourished and 37.3% had some degree obesity. The assessment by SGA found that 76.1% of patients were eutrophic, 23.2% moderately malnourished and 0.7% severely malnourished. The low values obtained for the AF in three evaluations were not presented as indicators of negative outcomes in surgical patients. Conclusions: AF is not an indicator to show negative outcomes in surgical patients.
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Li, Biao. "Hydrophobic-Hydrophilic Separation Process for the Recovery of Ultrafine Particles." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/103278.
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The demands for copper and rare earth elements (REEs) in the U.S. will keep rising due to their applications in green energy technologies. Meanwhile, copper production in the U.S. has been declining over the past five years due to the depletion of high-grade ore deposits. The situation for REEs is worse; there is no domestic supply chain of REEs in the U.S. since the demise of Molycorp, Inc. in 2016. Studies have shown that the rejected materials from copper and coal processing plants contain significant amounts of valuable metals. As such, this rejected material can be considered as potential secondary sources for extracting copper and REEs, which may help combat future supply risks for the supply of copper and REEs in the U.S. However, the valuable mineral particles in these resources are ultrafine in size, which poses considerable challenges to the most widely used fine particle beneficiation technique, i.e., froth flotation. A novel technology called the Hydrophobic-Hydrophilic Separation (HHS) process, developed at Virginia Tech, has been successfully applied to recover fine coal in previous research. The results of research into the HHS process showed that the process has no lower particle size limit, similar to solvent extraction. Therefore, the primary objective of this research is to explore the feasibility of using the new process to recover ultrafine particles of coal, copper minerals, and rare earth minerals (REMs) associated with coal byproducts.
In the present work, a series of laboratory-scale oil agglomeration and HHS tests have been carried out on coal with the objectives of assisting the HHS tests in pilot-scale, and the scale-up of the process. The knowledge gained from this study was successfully applied to solving the problems encountered in the pilot-scale tests. Additionally, a new and more efficient equipment known as the Morganizer has been designed and constructed to break up the agglomerates in oil phase as a means to remove entrained gangue minerals and water. The effectiveness of the new Morganizers has been demonstrated in laboratory-scale HHS tests, which may potentially result in the reduction of capital costs in commercializing the HHS process. Furthermore, the prospect of using the HHS process for processing high-sulfur coals has been explored. The results of this study showed that the HHS process can be used to increase the production of cleaner coal from waste streams.
Application of the HHS process was further extended to recover the micron-sized REMs from a thickener underflow sample from the LW coal preparation plant, Kentucky. The results showed that the HHS process was far superior to the forced-air flotation process. In one test conducted during the earlier stages of the present study, a concentrate assaying 17,590 ppm total REEs was obtained from a 300 ppm feed. In this test, the Morganizer was not used to upgrade the rougher concentrate due to the lack of proper understanding of the fundamental mechanisms involved in converting oil-in-water (o/w) Pickering emulsions to water-in-oil (w/o) Pickering emulsions. Many of the studies has, therefore, been focused on the studies of phase inversion mechanisms. The results showed that phase inversion requires that i) the oil contact angles (θo) of the particles be increased above 90o, ii) the phase volume of oil (ϕo) be increased, and iii) the o/w emulsion be subjected to a high-shear agitation. It has been found that the first criterion can be readily met by using a hydrophobicity-enhancing agent. These findings were applied to produce high-grade REM concentrates from an artificial mixture of micron-sized monazite and silica.
Based on the improved understanding of phase inversion, a modified HHS process has been developed to recover ultrafine particles of copper minerals. After successfully demonstrating the efficacy and effectiveness of this process on a series of artificial copper ore samples, the modified HHS process was used to produce high-grade copper concentrates from a series of cleaner scavenger tails obtained from operating plants.Doctor of Philosophy
Recovery and dewatering of ultrafine particles have been the major challenges in the minerals and coal industries. Based on the thermodynamic advantage that oil droplets form contact angles about twice as large as those obtainable with air bubbles, a novel separation technology called the hydrophobic-hydrophilic separation (HHS) process was developed at Virginia Tech to address this issues. The research into the HHS process previously was only conducted on the recovery of ultrafine coal particles; also, the fundamental aspects of the HHS process were not fully understood, particularly the mechanisms of phase inversion of oil-in-water emulsions to water-in-oil emulsions. As a follow-up to the previous studies, emulsification tests have been conducted using ultrafine silica and chalcopyrite particles as emulsifiers, and the results showed that phase inversion requires high contact angles, high phase volumes, and high-shear agitation. These findings were applied to improve the HHS process for the recovery of ultrafine particles of coal, copper minerals, and rare earth minerals (REMs). The results obtained in the present work show that the HHS process can be used to efficiently recover and dewater fine particles without no lower particle size limits.
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Clark, Matthew A. "The Harmonic Distortion Reduction of Phase-Angle Fired SCRs Feeding a Resistive Load using Fuzzy Logic." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1271111941.
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