Дисертації з теми "Porte de phase"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Porte de phase.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Porte de phase".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
De, Grandpré Guillaume. "La dynamique locale : une porte d’entrée sur les mécanismes de formation de la phase vitreuse dans des molécules organiques." Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8363.
Анотація:
Les verres moléculaires suscitent depuis quelques années un intérêt croissant. Tapis dans l’ombre des verres polymériques, ils se sont révélés de bien meilleurs matériaux pour des utilisations fort intéressantes en photolithographie et en optoélectronique. Un intérêt particulier pour le laboratoire est qu’un simple changement structural peut amener à des propriétés du verre fort différentes. Les travaux présentés dans ce mémoire ont été motivés par le désir de mieux comprendre cet effet micro ayant un fort impact sur le macro. Pour rendre compte de ces changements, la modélisation moléculaire devient donc un outil de choix.
La raison est que celle-ci a déjà démontré toute sa force dans l’étude des polymères. Les verres moléculaires étant des analogues, et potentiellement des compétiteurs dans certaines situations, il est logique d’appliquer la méthode utilisée pour caractériser les polymères sur les verres moléculaires. La caractérisation étant faite à l’aide de la simulation atomistique, sa sensibilité au détail microscopique la rend toute désignée pour extrapoler les phénomènes microscopiques vers le macro ainsi que leurs effets potentiels sur les propriétés macroscopiques. Il s’agit en fait d’animer les molécules en effectuant une dynamique moléculaire sur le système. En plus de polymères, des verres moléculaires dérivés de la molécule triazine ont déjà été caractérisés par cette méthode. En effet, dans une étude antérieure, l’influence du changement de groupement fonctionnel de la tête sur la température de transition vitreuse et les barrières énergétiques de rotation de ces verres a été investiguée. Les résultats, prometteurs, ont motivé d’étudier ces dérivés de triazines plus en profondeur.
L’étude des effets sur les propriétés macroscopiques dus aux changements structuraux des groupements ancillaires ainsi que des linkers est le but de cette recherche. Il y a deux propriétés macroscopiques ciblées. La température de transition vitreuse, très importante pour les verres puisqu’elle définit leur température d’utilisation et leurs propriétés mécaniques. Puis il y a aussi le Glass Forming Ability (GFA), qui informe sur la propension d’un verre à se cristalliser selon la vitesse de refroidissement. Les verres moléculaires étant plus sensibles à la cristallisation que leurs analogues polymériques, l’étude du GFA est très révélatrice de la viabilité d’un verre moléculaire.
Les verres et leurs propriétés sont caractérisés par le volume libre, les barrières énergétiques de rotation, le déplacement quadratique moyens ainsi que les populations de paires d’angles dièdres. Ceux-ci nécessitent avant tout une préparation. Celle-ci consiste en une montée et descente en température, ce processus est aussi appelé un recuit, suivi d’une compression et dilatation mécaniques. Cette séquence est appliquée 2 fois sur les verres. Au final, ceux-ci atteignent l’équilibre mécanique, la dérivée de l’énergie par rapport à la distance du système de simulation étant égale à 0. Une dernière simulation, permettant d’obtenir des données de coordonnées des molécules, permet au système d’atteindre l’équilibre thermique et chimique. C’est seulement lorsqu’ils atteignent ces trois équilibres que les propriétés macroscopiques des verres peuvent être considérées comme valides.
La série des groupements ancillaires a une relation linéaire entre les températures de transition vitreuse expérimentales et simulées. De plus, elle montre un lien direct entre l’apparition d’un GFA expérimental bas, c’est-à-dire un GFA de 1 qui indique une bonne stabilité du verre en refroidissement, et l’augmentation de l’entropie configurationnelle. Les deux séries de linkers ont aussi une relation linéaire entre leurs températures de transition vitreuse expérimentales et simulées. L’étude de leur GFA montre que les effets du mouvement dans la masse du verre ont aussi une grande importance puisqu’une grande mobilité peut être correlée avec un GFA bas.
2
Ashkarin, Ivan. "Few-body Förster resonances in Rydberg atoms for the implementation of quantum computing." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASP199.
Анотація:
L'application des résonances de Förster à plusieurs corps est étudiée pour réaliser des circuits de portes quantiques multi-qbits. Deux nouveaux types de transitions borroméennes à trois atomes utilisant un atome relais ont été proposées et étudiées numériquement. En particulier, une résonance de Förster à trois atomes non isolée et contrôlée par effet Stark entre des états S et P de niveaux élevés n = 80, 81, 82 avec des atomes de Rb isolés dans des pièges optiques a été modélisée. Une résonance de Förster isolée à trois atomes a également été démontrée pour les états n = 70, 71 des atomes Rb. Les résonances ont été étudiées dans une configuration spatiale fixe, ce qui nous a permis de démontrer l'évolution cohérente de la population et de la phase des états collectifs impliqués. Des schémas de portes de Toffoli à trois qubits ont été développés et modélisés numériquement sur la base des résonances démontrées dans des ensembles à trois atomes. En outre, un schéma généralisé de porte de phase doublement contrôlée CCPHASE a été développé sur la base de la résonance de Förster à trois corps induite par radiofréquence. De plus, un schéma de porte quantique similaire a été proposé sur la base de la résonance de Förster induite par radiofréquence à deux atomes avec un déplacement contrôlé par interaction avec le troisième. Les performances rapides et la grande fidélité des schémas proposés, ainsi que leur robustesse potentielle aux erreurs, nous permettent d'espérer le succès d'une réalisation expérimentale prochainementApplication of few-body Förster resonances for implementation of multiqubit quantum gate circuits has been investigated. New types of three-atom Borromean transitions based on the relay atom have been proposed and numerically studied. In particular, a Stark-controlled non-isolated three-atom Förster resonance between high-lying n = 80, 81, 82 S − P states of Rb atoms isolated in individual optical traps has been modeled. Isolated three-atom Förster resonance has also been demonstrated for n = 70, 71 states of Rb atoms. The resonances were investigated in a fixed spatial configuration, allowing us to demonstrate the coherent population and phase dynamics of the collective states involved. Three-qubit Toffoli gates schemes have been developed and numerically modeled based on the demonstrated resonances. Also, a generalized doubly controlled phase CCPHASE gate scheme has been developed based on the radiofrequency-induced three-body Förster resonance. Additionally, a similar quantum gate scheme has been proposed based on two-atom RF-induced Förster resonance with controlled displacement. The fast performance and high fidelity of the proposed schemes, as well as their potential robustness to errors, allow us to expect a successful experimental implementation in the near future
3
Messager, Valérie. "Nouveaux procédés pour la caractérisation cohérente d'impulsions Femtosecondes et pour la caractérisation des non linéarités du troisième ordre." Limoges, 2002. http://www.theses.fr/2002LIMO0044.
Анотація:
La première partie de ce travail concerne une technique originale de caractérisation complète, en amplitude et en phase, du profil temporel d' impulsions femtosecondes. Cette technique est basée sur l' interférométrie spectrale à décalage. Les modulations spectrales sont isolées par une porte temporelle rapide. Un traitement numérique direct, permet d' accéder à la différence de phase du signal de battements puis de restituer l' amplitude et la phase temporelle de l' impulsion. La seconde partie porte sur une nouvelle technique de caractérisation des non linéarités Kerr d' origine électronique dans divers matériaux. Elle exploite l' évolution de l' intensité et de la largeur spectrale d' excitations femtosecondes, due à l' automodulation de phase dans l' échantillon non linéaire testé, en fonction d' une dispersion variable introduite sur les impulsions d' entrée. Ces deux processus modifient temporellement et spectralement les impulsions. Une analyse numérique permet à partir des données expérimentales traduisant ces modifications, d' extraire la valeur complexe de la non linéarité de l' échantillon testé et le temps de réponse rapide de celle-ciThis first part of this work concerns a new method for characterization in amplitude and phase, of the temporal profile of femtosecondes pulses. This technique is based on shearing interferometry in the spectral domain. Spectral modulations are isolated with a fast time gating. A direct numerical procedure permits to extract the phase difference of the beatings before recovery of the temporal amplitude and phase distributions of the pulse. The second part deals with a new technique for third order nonlinearity measurements. It exploits the changes of femtosecondes excitation, due to self phase modulation in the nonlinear sample under test versus a varying dispersion introduced on the input pulses. These two processes temporally and spectrally modify the pulses. By fitting the experimental data with the curve obtained by numerical simulation of the device we derive the complex value of the non linearity together with its fast time response
4
Suicmez, Vural Sander. "Pore scale simulation of three-phase flow." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441972.
5
Piri, Mohammad. "Pore scale modelling of three-phase flow." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407699.
6
Al-Gharbi, Mohammed Saif Hilal. "Dynamic pore-scale modelling of two-phase flow." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409745.
7
Topomondzo, Joseph Désiré. "Etude des effets de biréfringence induite dans les amplificateurs optiques à semi-conducteurs : applications dans les systèmes de communications optiques." Phd thesis, Télécom ParisTech, 2004. http://pastel.archives-ouvertes.fr/pastel-00001104.
Анотація:
Dans le cadre des futurs réseaux de télécommunication optiques, les phénomènes non-linéaires dans les amplificateurs optiques à semi-conducteurs (AOS) telles que la modulation croisée de polarisation (XPolM) et la modulation de phase croisée sont exploités pour réaliser des fonctions de traitement tout-optique nouvelles. Ces fonctions sont dédiées au routage, à la commutation de paquets et la reconnaissance des en-têtes dans les réseaux de transmission optiques. L'objectif de ce travail était double: d'une part la compréhension de la biréfringence induite dans l'AOS et en particulier le phénomène de couplage dans la XPolM grâce à une approche expérimentale, et d'autre part la mise en œuvre de cet effet pour réaliser des portes logiques tout-optiques. Un modèle théorique bidimensionnel de l'AOS est présenté. Il prend en compte les composantes TE et TM de l'onde optique, les gains optiques, les phases TE et TM et le couplage d'énergie entre les deux modes propres de l'AOS. Un banc de mesure en espace libre de type pompe et sonde a été soigneusement mis en place afin de contrôler finement les états de polarisation des signaux optiques et d'extraire des paramètres de la modulation croisée de polarisation dans la bande utile [1550-1565] nm. L'impact de la puissance de pompe et de sa polarisation sur la modification des axes propres de l'AOS est mis en évidence. Une étude expérimentale et théorique est proposée afin d'étudier l'impact de la dépendance en polarisation du gain de l'AOS sur l'efficacité de la XPolM. Cette étude est basée sur la théorie des modes couplés et les paramètres de Stokes déterminés expérimentalement. Une validation du modèle est proposée. La XPolM est exploitée pour réaliser des fonctions optiques telles que des portes logiques tout-optiques (AND, NOR, NOTXOR) à 2.5 Gbit/s au format NRZ en utilisant un unique AOS. L'efficacité de ces fonctions est estimée en mesurant le taux d'extinction. La biréfringence induite est également exploitée pour réaliser un commutateur et une porte logique tout-optique à 10 Gbit/s.
8
Al, Nahari Alhashmi Zaki Mahmoud Sharif. "Modelling single-phase fluid-fluid reactive transport at the pore-scale." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/41967.
Анотація:
Reactive transport is an important field of study in the earth sciences. It captures both natural phenomena, and industrial and environmental applications, including transport of pollutants in the subsurface, nuclear waste storage, and carbon storage. The aim of this thesis is to provide a better understanding of coupled physico-chemical processes governing these phenomena as well as to be used as tools for better understanding these environmental applications. We introduce from first principles a novel pore-scale modelling approach capable of simulating single-phase fluid-fluid reactive transport directly on voxels of 3D images of porous media constructed from X-ray tomography. We use a streamline-based particle tracking method for simulating flow and transport, while for reaction to occur, both reactants must be within a diffusive distance. We assign a probability of reaction, as a function of the reaction rate constant and the diffusion length. The model for reaction is validated against analytical solutions in a free fluid as well as against experimental data on reactive transport in porous media. It takes into account the degree of incomplete mixing present at the sub-pore level. We demonstrate the nature of dynamic changes in the reaction rate, which is related to the degree of pore-scale mixing. Our model does not use any calibrating parameters to fit empirical data unlike other models published in the literature. The model is then extended to investigate the impact of pore structure heterogeneity, transport, and reaction conditions on the overall reaction rate in porous media by studying different classes of porous media. The overall reaction rate varies significantly according to the degree of heterogeneity and transport conditions. It is found that the rate of reaction is a subtle combination of the amount of mixing and spreading that cannot be predicted from the dispersion coefficient alone. At low Péclet number, the effective reaction rate is principally controlled by the amount of mixing due to diffusion. On the other hand, at high Péclet number the reaction rate is controlled by a combination of pore-scale mixing due to spreading and the degree of heterogeneity of the pore structure.
9
Sisavath, Sourith. "Fundamental pore-scale modelling of single-phase flow through sedimentary rocks." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394470.
10
Correia, Márcia Sofia Barbosa. "Internship report in clinical studies coordination at IPO-Porto." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/12949.
Анотація:
Mestrado em Biomedicina FarmacêuticaThis report describes my activities as study coordinator (SC) intern, at the “Unidade de Investigação Clínica” (UIC) in the Oncology Portuguese Institute of Porto (IPOP). This training occurred during the second year of the Pharmaceutical Biomedicine Master at the University of Aveiro. My internship took place between 21st January, 2013 and 4th October, 2013 with the main objective to gain experience and expertise in oncology coordinating clinical trials. I present the state-of-the-art of clinical research with emphasis on current situation in Portugal as well as in oncology. At the beginning of internship I performed generic training in Good Clinical Practices (GCP) and Electronic Data Capture systems and familiarised myself with terminology and classification/assessment systems regarding the oncology area to support the clinical trial coordination activities in the context of the oncology protocols. In UIC, I participated in 6 phase II and 25 phase III clinical trials of 9 clinics of pathology: Urology, Gynaecology, Digestive, Lung, Soft Tissue and Skin, Head and Neck, Onco-Haematology, Breast and Paediatry. Within of these clinics, I intensively participated and acquired more autonomy in clinical trials of the Digestive pathology. The Onco-Haematology clinic includes the more complex procedures of the clinical trials protocols. As SC, I could intensively participate in the conduction clinical trial activities, namely: Randomisation Period, including Screening and Randomisation of patients, Clinic Visits and Monitoring Visits. The experience gained during my curricular internship was very enriching and enabled me to acquire professional and interpersonal skills and competences and to face unexpected situations, developing strategies to deal with them. Additionally, it was possible to consolidate and apply the theoretical knowledge acquired during Master Course in Pharmaceutical Medicine at different stages of clinical trials coordination. In conclusion, during my curricular internship, I gathered the competences, motivation and experience to pursue a career in clinical research, particularly, as SC.
Este relatório descreve as actividades como coordenadora de estudos estagiária, na Unidade de Investigação Clínica (UIC) do Instituto Português de Oncologia do Porto (IPOP). Este estágio foi parte integrante das actividades curriculares do segundo ano do Mestrado em Biomedicina Farmacêutica da Universidade de Aveiro. O estágio decorreu entre 21 de Janeiro de 2013 e 4 de Outubro de 2013, com o principal objectivo em adquirir experiência e especialização na coordenação de ensaios clínicos em oncologia. No documento é apresentado o estado de arte de arte da investigação clínica com ênfase na actual situação em Portugal bem como em oncologia. Na fase inicial do estágio realizei treino genérico em Boas Práticas Clínicas e sistemas de Captura de Dados Electrónicos e familiarizei-me com terminologia e sistemas classificação/avaliação próprios da área de oncologia para suportar as actividades de coordenação de ensaios clínicos no contexto dos protocolos de oncologia. Na UIC, participei em vários estudos de fase II e III de 9 clínicas de patologia: Urologia, Ginecologia, Digestivos, Pulmão, Pele e Tecidos Moles, Cabeça e Pescoço, Onco-Hematologia, Mama e Pediatria. Dentro destas clínicas, participei intensivamente e adquiri mais autonomia nos ensaios clínicos da patologia de Digestivos. A clínica de Onco-Hematologia, agrega os protocolos de ensaios clínicos com procedimentos mais complexos. Como coordenadora de ensaios clínicos pude participar intensivamente nas actividades de condução de um ensaio clínico, nomeadamente: Período de Randomização incluindo Rastreio e Randomização de doentes, Visitas Clínicas e Visitas de Monitorização. A experiência adquirida ao longo do estágio curricular foi muito enriquecedora e permitiu-me adquirir capacidades e competências profissionais e interpessoais e aprender a enfrentar situações inesperadas, desenvolvendo estratégias para lidar com as mesmas. Para além disso possibilitou-me a consolidar e aplicar os conhecimentos teóricos adquiridos no Curso de Mestrado nas diferentes fases de coordenação dos estudos. Em conclusão, ao longo do estágio adquiri competências, motivação e experiência para enveredar por uma carreira na área de investigação clínica, especialmente como Coordenadora de Ensaios Clínicos.
11
Cardoso, Ana Veronica Santos. "Pandemic Influenza A (H1N1)v in the North of Portugal - Epidemiology, Clinical Presentation and Prognosis during Containmente Phase." Master's thesis, Faculdade de Medicina da Universidade do Porto, 2009. http://hdl.handle.net/10216/50163.
12
Cardoso, Ana Veronica Santos. "Pandemic Influenza A (H1N1)v in the North of Portugal - Epidemiology, Clinical Presentation and Prognosis during Containmente Phase." Dissertação, Faculdade de Medicina da Universidade do Porto, 2009. http://hdl.handle.net/10216/50163.
13
Ernst, Vincent Y. "Caractérisation de deux-ports bruyants par la méthode de variation de phase/fréquence." Doctoral thesis, Universite Libre de Bruxelles, 1993. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212776.
14
Fang, Wei. "Model-based retrieval of phase-related quantities for two-port microwave devices." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/26900.
Анотація:
In this thesis a new method is proposed for the retrieval of phase-related quantities from magnitude-only measurements on two-port microwave systems. The method is applicable when a microwave system is manufactured in relatively large quantities. A reduced-order model is developed using the prototype of such a system. Such a reduced-order model will include a number of quantities or "coefficients" (other than frequency) whose value is determined using a full vector data set on the prototype. Establishing the form required for the reduce-order model acts as the additional constraints that are needed to provide a unique relationship between the transfer function magnitude and its phase. When later production models are tested using magnitude-only measurements, optimization is used (with the above-mentioned "coefficients" as the optimization variables, for which only small adjustments are needed from one device to another) to match the measured and modeled magnitude responses. The retrieved "coefficients" are then used to predict the phase response using the model. The use of the model-based retrieval technique is demonstrated through its application to three different types of device.
15
Davis, R. G. "Two-port millimetre wave oscillators and their stabilisation with phase-locked loops." Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383542.
16
Matharoo, Rishi. "1/f Additive Phase Noise Analysis for One-Port Injection Locked Oscillators." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1430772754.
17
Hippauf, Felix. "Tailoring Pore Size and Polarity for Liquid Phase Adsorption by Porous Carbons." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-223482.
Анотація:
Adsorption is a versatile purification technique to selectively separate different peptide fractions from a mixture using mild operation conditions. Porous carbons are ideally suited to separate ACE-inhibiting dipeptides by combining tailored size exclusion and polarity selectivity. The desired peptide fraction is mostly hydrophobic and very small and should adsorb inside hydrophobic micropores.
The second topic of this thesis is linked to energy storage. The lithium-sulfur battery is a promising alternative to common lithium-ion batteries with theoretical capacities of up to 1672 mAh g−1 sulfur. The second aim of this thesis is to conduct an in-depth investigation of polysulfides interacting with selected carbon materials in a simplified battery electrolyte environment. The focus of this study is laid on the impact of surface polarity and pore size distribution of the carbon to develop a quantitative correlation between polysulfide retention and porosity metrics.
Both, the enrichment of ACE-inhibitors and the retention of polysulfides rely on liquid phase adsorption in porous materials, linking the above mentioned topics. This thesis not only aims to develop an enrichment process or to find a superior battery cathode but also strives to explore structure-property relationships that are universally valid. Understanding the complex interplay of pore size and polarity leading to selective interactions between pore wall and the adsorbed species is given a high priority.
18
Dearie, Helen Sara. "Capillary electrochromatography on conventional and wide pore stationary phases." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248374.
19
Sibold, Jeremias. "Phase separation of biomimetic membranes:." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://hdl.handle.net/21.11130/00-1735-0000-0005-12CA-3.
20
Irizarry, Julia Tonge. "Modeling the effects of three-dimensional pore geometry on gas hydrate phase stability." Thesis, University of Oregon, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1596317.
Анотація:
Porous media affect hydrate stability by forcing hydrate-liquid interfaces to form high curvature geometries and by forcing the molecules of the hydrate, liquid, and sedimentary particles that compose the medium to interact where they are in close proximity. To evaluate these effects we first create synthetic spherical packings to approximate pore space geometry. We use the synthetic pore space to calculate the perturbation to the chemical potential caused by the geometrical constraints. Our model predictions agree with published data for ice-water and water-vapor systems. When particles are well-approximated as spheres, our model fits the data with R-squared values that range between about 80% to over 99%. However, our model needs to be improved for porous media that contain a significant fraction of non-equant particles such as clay. Lastly, we demonstrate how our model can be used in predictions for the evolution of hydrate saturation.
This thesis includes unpublished co-authored material.
21
Rabbani, Harris. "Pore-scale investigation of wettability effects on two-phase flow in porous media." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/porescale-investigation-of-wettability-effects-on-twophase-flow-in-porous-media(4da35c39-fc12-4d2c-8645-53bb617696aa).html.
Анотація:
Physics of immiscible two-phase flow in porous media is relevant for various industrial and environmental applications. Wettability defined as the relative affinity of fluids with the solid surface has a significant impact on the dynamics of immiscible displacement. Although wettability effects on the macroscopic fluid flow behaviour are well known, there is a lack of pore-scale understanding. Considering the crucial role of wettability in a diverse range of applications; this research aims to provide a pore-scale picture of interface configuration induced by variations in the wetting characteristics of porous media. Besides, this study also relates the pore-scale interfacial phenomena with the macroscopic response of fluids. High-resolution direct numerical simulations (DNS) at multiscale (single capillary and a highly heterogeneous porous media) were performed using computational fluid dynamics (CFD) approach in which the Navier-Stokes equation coupled with the volume of fluid method is solved to represent immiscible displacement. Numerical results demonstrate that at pore scale as the wettability of porous media changes from strong to intermediate wet the effects of pore geometry (that includes corner angle and orientation angle) on the interfacial dynamics also enhances. This was demonstrated by the non-monotonic behaviour of entry capillary pressure at the junction of pore, curvature reversal in the converging-diverging capillary and the co-existence of concave and convex interfaces in heterogeneous porous media with uniform contact angle distribution. In addition to simulations, theoretical argument is also presented that rationalize the underlying physics of complex, yet intriguing interfacial phenomena shown by DNS. Overall this research extends the fundamental understanding of multiphase flow in porous media and paves the way for future studies on porous media.
22
Irizarry, Julia. "Modeling the Effects of Three-Dimensional Pore Geometry on Gas Hydrate Phase Stability." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19304.
Анотація:
Porous media affect hydrate stability by forcing hydrate-liquid interfaces to form high curvature geometries and by forcing the molecules of the hydrate, liquid, and sedimentary particles that compose the medium to interact where they are in close proximity. To evaluate these effects we first create synthetic spherical packings to approximate pore space geometry. We use the synthetic pore space to calculate the perturbation to the chemical potential caused by the geometrical constraints. Our model predictions agree with published data for ice-water and water-vapor systems. When particles are well-approximated as spheres, our model fits the data with R-squared values that range between about 80% to over 99%. However, our model needs to be improved for porous media that contain a significant fraction of non-equant particles such as clay. Lastly, we demonstrate how our model can be used in predictions for the evolution of hydrate saturation.
This thesis includes unpublished co-authored material.
23
Erzeybek, Selin. "Pore Network Modeling Of Fissured And Vuggy Carbonates." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609626/index.pdf.
Анотація:
Carbonate rocks contain most of the world&rsquos proven hydrocarbon reserves. It is essential to predict flow properties and understand flow mechanisms in carbonates for estimating hydrocarbon recovery accurately. Pore network modeling is an effective tool in determination of flow properties and investigation of flow mechanisms. Topologically equivalent pore network models yield accurate results for flow properties. Due to their simple pore structure, sandstones are generally considered in pore scale studies and studies involving carbonates are limited. In this study, in order to understand flow mechanisms and wettability effects in heterogeneous carbonate rocks, a novel pore network model was developed for simulating two-phase flow. The constructed model was composed of matrix, fissure and vug sub domains and the sequence of fluid displacements was simulated typical by primary drainage followed by water flooding. Main mechanisms of imbibition, snap-off, piston like advance and pore body filling, were also considered. All the physically possible fluid configurations in the pores, vugs and fissures for all wettability types were examined. For configurations with a fluid layer sandwiched between other phases, the range of capillary pressures for the existence of such a layer was also evaluated. Then, results of the proposed model were compared with data available in literature. Finally, effects of wettability and pore structure on flow properties were examined by assigning different wettability conditions and porosity features. It was concluded that the proposed pore network model successfully represented two phase flow in fissured and vuggy carbonate rocks.
24
Atig, Dyhia. "Propriétés physiques et mécaniques de l’hydrate de méthane à l’échelle du pore." Thesis, Pau, 2019. http://www.theses.fr/2019PAUU3021.
Анотація:
Les hydrates de gaz sont des composés cristallins stables à haute pression et à basse température, très répandus sur terre, notamment dans les fonds marins au niveau des marges continentales, où ils contribuent à la stabilité des sédiments par leur cohésion et leur adhésion aux surfaces minérales. Cependant, le comportement mécanique des hydrates en soi a été peu ou pas étudié à l’échelle du pore. L’objectif de cette thèse est d’étudier les conditions de stabilité et les propriétés mécaniques en traction de l’hydrate de méthane à l’échelle du pore, dans une configuration comparable à celle qu’on peut trouver dans les milieux poreux sédimentaires.Ici, nous étudions d’abord par microscopie optique les conditions de formation, de croissance et de dissociation de l’hydrate de méthane à l’interface eau/CH4 dans un micro-capillaire en verre utilisé à la fois comme un pore modèle et comme une cellule optique résistante à haute pression et à basse température. Ensuite, en développant une méthode originale in situ et sans contact : "dépression thermo-induite" on détermine les propriétés mécaniques en traction d’une coquille polycristalline d’hydrate de méthane. L’hydrate est nucléé à basse température sur l’interface eau/CH4, qui est rapidement recouverte d’une "croûte" polycristalline d’hydrate. À partir de cette croûte, l’hydrate pousse de part et d’autre de l’interface : dans l’eau sous forme "d’aiguilles" cristallines, dans le gaz, sous forme de "filaments" cristallins, et enfin entre le substrat et le gaz sous forme d’un "halo". Le halo qui est un film polycristallin avançant sur le substrat, en chevauchant un film d’eau, ralentit et finit par s’immobiliser et s’accrocher au substrat. À partir de ce moment, "la coquille" polycristalline, constituée de la croûte et du halo, forme une barrière entre l’eau et le gaz. Les tests de traction sont effectués par génération d’une dépression dans le compartiment eau en augmentant la température à pression de méthane constante.Les propriétés élastiques en traction de la coquille (module élastique et contrainte de rupture) sont déterminées en fonction de la taille des grains, contrôlée ici par les deux paramètres : le sous-refroidissement par rapport à la température d’équilibre, et le temps de mûrissement. On trouve un comportement élastoplastique à caractères ductile et fragile mélangés. Nos données de contrainte de rupture s’insèrent dans un écart de cinq ordres de grandeurs de taille de grain, et de trois ordres de grandeurs de la contrainte de rupture (entre des données de simulation à l’échelle nanomètrique et des données expérimentales à l’échelle millimétrique). L’effet de taille de grain sur la contrainte de rupture de l’hydrate de méthane peut être un facteur contribuant à la déstabilisation des pentes continentalesGas hydrates are ice-like crystals stable at high pressure and low temperature. They are ubiquitous on earth, notably at the edges of continental shelves, where they contribute to the mechanical stability of marine sediments, by hydrate cohesion and hydrate adhesion to mineral particles. However, the mechanical behavior of gas hydrates at pore scale has been hardly or not at all studied. The purpose of this thesis is to study the stability conditions and the tensile mechanical properties of methane hydrate at pore scale in a representative pore habit of gas hydrate in a sedimentary medium.Here, using optical microscopy, first the formation, growth and dissociation conditions of methane hydrate are investigated across a water/CH4 interface in glass micro-capillaries used both as a pore model and as an optical cell resisting high pressure and low temperature. Then by developing a contactless and an in situ method, "thermally induced depressing", tensile mechanical properties of polycrystalline methane hydrate shell are determined. At low enough temperature, the hydrate nucleates as a polycrystalline "crust" over the water/CH4 interface. From this crust, the hydrate continues growing on both sides of the interface: in the water as "needle like crystals", in the gas as "hair like crystals", and finally between the gas and the substrate as a polycrystalline film, the "halo". The halo advances slowly on the substrate, riding over a water film, and comes to rest and adheres to the substrate. From then on, the "shell" (crust and halo) isolates the water from the gas. Tensile tests are carried out by generating a depression in the water compartment by increasing temperature at constant methane pressure.Tensile elastic properties of the shell (elastic modulus and the tensile strength) are determined as a function of the grain size, controlled here by two parameters, supercooling compared to the equilibrium temperature and the annealing time. We find elastoplastic behavior, with mixed ductile and brittle characteristics. Our data on tensile strength contribute to fit the gap of five orders of magnitude of grain size, and three orders of magnitude of tensile strength (between molecular simulations at nanometre scale and current experiment at millimetre to centimetre scale). The effect of grain size on the tensile strength of methane hydrate could be a factor contributing to the destabilization of continental slopes
25
REYNAL, SYLVAIN. "Transitions de phase dans les systèmes de spins régis par des interactions à longue portée." Phd thesis, Université de Cergy Pontoise, 2005. http://tel.archives-ouvertes.fr/tel-00010256.
Анотація:
Dans cette thèse, nous explorons le comportement critiques de chaînes de spins gouvernées par des interactions à décroissance algébrique. Dans une première partie, nous étudions le diagramme de phase d'une chaîne de Potts en utilisant un algorithme multicanonique. Nous proposons une nouvelle méthode de détection de l'ordre des transitions de phase exploitant les points spinodaux. A l'aide de cette méthode, nous localisons la ligne séparant les transitions du premier et du second ordre avec une précision sans précédent, et mettons en évidence un effet de taille finie inhabituel. Dans une deuxième partie, nous introduisons une nouvelle méthode multicanonique intégrant un algorithme de mise-à-jour collective des spins. Cette méthode, extrêmement souple, étend considérablement l'intervalle de tailles simulables, et s'avère bien plus précise que les méthodes multicanoniques usuelles. Nous appliquons cette méthode à l'étude d'effets de taille finie dans le cadre de transitions du premier ordre : les résultats suggèrent fortement que les configurations correspondant à des phases en coexistence sont caractérisées par une dimension fractale dépendent du taux de décroissance de l'interaction. Dans un dernier chapitre, nous étudions une chaîne d'Ising régie par des interactions à longue portée en présence de champs aléatoires à distribution bimodale, et prouvons l'existence d'un point tricritique pour des interactions à décroissance lente.
26
Kayser, Avril Freda Francina. "The lived experiences of intermediate phase teachers of curriculum renewal processes from 1998 to 2012 in Port Elizabeth." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1020063.
Анотація:
This research study has emerged as a result of my concern regarding many of my colleagues’ apparent low morale in the teaching profession. Since the new dispensation in 1994 the South African education system has undergone numerous and intensive curriculum changes as varying policies aimed at transforming education in South Africa have been implemented (Asmal, 2009). I, therefore, decided to investigate the lived experiences of Intermediate Phase teachers regarding curriculum renewal processes in South Africa over a fifteen year period from 1998 to 2012. This period encompasses the four curriculum renewal processes which have been implemented since 1994. The research undertaken was an empirical study and qualitative methods were used for data gathering purposes. Data collection tools included unstructured, individual, in-depth interviews and reflective journal entries. The qualitative data generated suggest that many teachers in the Port Elizabeth Metropole appear to be demotivated by the uncertainty around curriculum renewal and the impact this has on curriculum implementation in their respective classrooms. According to Ornstein and Hunkins (2004), the implementation process of a new curriculum requires extensive actions by the designers and implementers of the new programme and Smith (2008) asserts that managing change in education, and improvement in classroom instruction, are very complex tasks which teachers and learners face worldwide. The study revealed that the main obstacles to successful curriculum change initiatives are insufficient training of teachers, lack of support for teachers and time constraints under which teachers work. An investigation into the lived experiences of teachers regarding the post- apartheid curriculum renewal processes should make a valuable contribution to the debate in terms of providing insights for curriculum implementers of possible alternative curriculum implementation strategies for more effective curriculum renewal processes in the future.
27
Fédou, Roland. "Modélisation de l'infiltration chimique en phase vapeur, CVI isotherme et isobare : étude de l'infiltration d'un pore rectiligne par diverses céramiques." Bordeaux 1, 1992. http://www.theses.fr/1992BOR10512.
Анотація:
La technique d'infiltration chimique en phase vapeur (cvi) est utilisee pour densifier des preformes poreuses constituees de fibres ceramiques en vue de preparer des composites thermostructuraux a matrice ceramique. Une modelisation numerique du procede cvi est proposee, qui prend en compte les couplages entre transferts de masse (par diffusion de fick et de knudsen) et processus chimiques heterogenes se produisant a l'interieur d'un pore rectiligne. Ce modele, qui peut integrer une loi cinetique quelconque representant la reaction de depot, est applique a divers systemes chimiques conduisant a l'infiltration de diverses ceramiques: sic, zro#2, y#2o#3, pyrocarbone. L'influence des parametres experimentaux (temperature, pression totale, composition de la phase gazeuse) et de la geometrie du pore sur la qualite de l'infiltration, est mise en evidence et confrontee a des profils experimentaux
28
Puig, Montellà Eduard. "Modeling capillarity and two-phase flow in granular media : from pore-scale to network scale." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI046/document.
Анотація:
Les simulations numériques à l'échelle du pore sont fréquemment utilisées pour étudier le comportement des écoulements multiphasiques largement rencontrées dans phénomènes naturels et applications industrielles. Dans ce travail, la morphologie de structures liquides et l'action capillaire sont examinées à l'échelle des pores par la méthode de Boltzmann sur réseau (LBM) à plusieurs composants selon le modèle de Shan-Chen. Les résultats numériques obtenus sont en bon accord avec les solutions théoriques. Les simulations numériques sont étendues à microstructures complexes au-delà du régime pendulaire.La LBM a été utilisée pour modéliser l'écoulement multiphasique à travers un milieu poreux idéalisé dans des conditions de drainage primaire quasi-statique. Les simulations LBM ont fourni une excellente description du déplacement de l'interface fluide-fluide à travers les grains. Pendant le drainage, les simulations LBM sont capables de reproduire la déconnexion d'une phase dans le milieu granulaire sous la forme de ponts pendulaires ou structures liquides complexes. Malheureusement, le temps de calcul nécessaire pour ce type de simulations est assez élevé. Afin d’optimiser les ressources de calcul, nous présentons un modèle 2D (modèle Throat-Network) basé sur des solutions analytiques pour décrire l'écoulement biphasique à travers un ensemble de disques dans un temps de calcul très réduit, donc le modèle 2D est susceptible de remplacer les simulations LBM lorsque les ressources de calcul sont limitées. L'approche souligne l'importance de simuler le problème a l'échelle de la gorge du pore pour obtenir les relations volume - pression capillaire locales. Le modèle Throat-Network est un point de départ pour le modèle hybride proposé pour résoudre les problèmes en 3D. Le modèle hybride combine l’efficacité de l’approche réseau de pores et la précision du LBM à l’échelle des pores. Le modèle hybride est basé sur la décomposition de l’échantillon en petits sous-domaines, dans lesquels des simulations LBM sont effectuées pour déterminer les propriétés hydrostatiques principales (pression capillaire d'entrée, courbe de drainage primaire et morphologie du liquide pour chaque gorge du pore). Malgré la réduction significative des temps de calcul obtenus avec le modèle hybride, le temps n’est pas négligeable et les modélisations numériques d'échantillons de grandes tailles ne sont pas réalistes. Les approximations données par les méthodes Incircle et MS-P, qui prédisent les propriétés hydrostatiques, sont comparées à celles de LBM et du modèle hybrideNumerical simulations at the pore scale are a way to study the behavior of multiphase flows encountered in many natural processes and industrial applications. In this work, liquid morphology and capillary action are examined at the pore-scale by means of the multicomponent Shan-Chen lattice Boltzmann method (LBM). The accuracy of the numerical model is first contrasted with theoretical solutions. The numerical results are extended to complex microstructures beyond the pendular regime.The LBM has been employed to simulate multiphase flow through idealized granular porous media under quasi-static primary drainage conditions. LBM simulations provide an excellent description of the fluid-fluid interface displacement through the grains. Additionally, the receding phase trapped in the granular media in form of pendular bridges or liquid clusters is well captured. Unfortunately, such simulations require a significant computation time. A 2D model (Throat-Network model) based on analytical solutions is proposed to mimic the multiphase flow with very reduced computation cost, therefore, suitable to replace LBM simulations when the computation resources are limited. The approach emphasizes the importance of simulating at the throat scale rather than the pore body scale in order to obtain the local capillary pressure - liquid content relationships. The Throat-Network model is a starting point for the a hybrid model proposed to solve 3D problems. The hybrid model combines the efficiency of the pore-network approach and the accuracy of the LBM at the pore scale to optimize the computational resources. The hybrid model is based on the decomposition of the granular assembly into small subsets, in which LBM simulations are performed to determine the main hydrostatic properties (entry capillary pressure, capillary pressure - liquid content relationship and liquid morphology for each pore throat). Despite the reduction of computation time, it is still not negligible and not affordable for large granular packings. Approximations by the Incircle and the MS-P method, which predict hydrostatic properties, are contrasted with the results provided by LBM and the hybrid model. Relatively accurate predictions are given by the approximations
29
Mirabelli, Thomas G. "The effect of gravity on the evolution of pore and grain structure during liquid-phase sintering." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20021.
30
Scott, Brian Lee. "Fabrication and Characterization of a Porous Clad Optical Fiber Gas Sensor." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/30906.
Анотація:
An optical fiber has been developed that can be used as a chemical gas sensor. Fabrication of the optical fiber produces a fiber that has a solid core with a porous cladding. The porous cladding region is made from a spinodally phase separable glass where the secondary phase is removed through dilute acid leaching. A non-phase separable glass composition is used for the core region. The properties of the phase separable glass are dependent on the processing conditions and the thermal history of the glass after the porosity has been achieved. Investigation of how processing conditions affected the pore structure was conducted to determine what pore characteristics are achievable for the glass composition used. Phase separation temperature, removal of silica gel deposited in the pores, and the post fabrication heat treating were used as experimental processing conditions. A maximum useable average pore size of approximately 29 nm was achieved. Maximum pore volume in the experimental groups was 0.4399 cc/g. Most heat treatments of the porous glass caused consolidation of the pore structure, with some conditions producing pore coarsening.Master of Science
31
Soll, Wendy Eileen. "Development of a pore-scale model for simulating two and three phase capillary pressure-saturation relationships." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13899.
32
Al-Dhahli, Adnan. "Pore- to field-scale modelling of three-phase flow processes in heterogeneous reservoirs with arbitrary wettability." Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2646.
Анотація:
Most reservoirs, such as carbonate reservoirs not only have structural heterogeneities (e.g. complexly shaped geobodies or fractures). But they also have distributed wettabilities and are mixed- to oil-wet. The interplay of structural and wettability heterogeneities impacts sweep efficiency and oil recovery. Choosing the appropriate Improved Oil Recovery (IOR) or Enhanced Oil Recovery (EOR) technique based on adequate predictions of oil recovery requires a sound understanding of the fundamental controls on fluid flow in mixed- to oil-wet andstructurally complex rocks. The underlying multiphase flow processes are modelled with physically robust flow functions, i.e. relative permeability and capillary pressure functions. Obtaining these flow functions is a challenging task, especially when three fluid phases coexist, such as during Water-Alternating-Gas (WAG) injection. In this work we use pore-network modelling, a reliable and physically based simulation tool, to predict three-phase flow functions. We have developed a new three-phase flow pore-network model for rocks with arbitrary wettability, which allows us to analyse the fundamental multi-phase displacement processes. Unlike other models, our model combines three main features: (I) A novel thermodynamic criterion for formation and collapse of oil layers that strongly depends on the fluid spreading behaviour and the rock wettability. The model hence captures film/layer flow of oil accurately, which impacts, in particular, the oil relative permeability at low oil saturation and hence the accurate prediction of residual oil. (II) Multiple displacement chains, where injection of one phase at the inlet triggers a chain of interface displacements throughout the network. This allows accurate modelling of the mobilization of disconnected phase clusters that arise during higher order (WAG) floods. (III) The model takes as input realistic 3D pore-networks extracted from pore-space reconstruction methods and Computed Tomography (CT) images, preserving both topology and pore shape of the rock. The model comprises a constrained set of parameters that can be tuned to mimic the wetting state of a given reservoir. We have validated our model against available experimental data for a range of wettabilities. We demonstrate the importance of film and layer flow for the continuity of the various phases during subsequent WAG cycles and for the residual oil saturations. A sensitivity analysis has been carried out with the full 3D model to predict three-phase relative permeabilities and residual oil saturations for WAG cycles under various wetting conditions with different flood end-points and for different rock types. This revealed a wide range of three-phase relative permeabilities and residual saturations. The pore-scale generated three-phase flow functions have then been used in a heterogeneous reservoir model. Here we demonstrate their impact on the sweep efficiency after gas injection and WAG for a range of realistic wettability scenarios. We show that the uncertainty in flow functions can be as big as the geological uncertainty in a reservoir model that was history matched for an extended waterflood.
33
Shi, Zhang. "Pore-scale modelling of two phase flow in porous media with dynamic wettability and topological disorder." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23525.
Анотація:
Multiphase flow into a porous medium is widely encountered in many fields, e.g., oil recovery, carbon geosequestration and soil science. In this dissertation, focuses are placed on investigating the microscopic dynamic wettability using liquid bridges with a varying contact line geometry, and the topological disorder effects in two-phase flow at the mesoscale level. Both the capillary tube and liquid bridge are modelled via using the lattice Boltzmann method (LBM), to compare dynamic contact angles in a liquid bridge with these in a capillary tube, which finds that the dynamic contact angle behaves differently in the liquid bridge case. To validate the difference, a liquid bridge experiment is then set up. These results elucidate that the sensitivity of dynamic contact angles on the capillary number is strongly correlated to variation of the contact line length. Regarding the disorder effect, the objectives are divided into (a) demonstrating the topological disorder effect on unsaturated porous media via using the Shan-Chen LBM and (b) quantifying the disorder impact on the fluid-fluid displacement pattern in the dynamic drainage using the pore network model (PNM). It is found that the disorder can enhance the liquid cluster connectivity and make the wet granular system enter the funicular stage early at an increasing saturation. A proposed capillary index incorporating both the disorder and wettability is successfully quantitatively correlated with the shape of liquid retention and relative permeability curves. In addition, this work provides a first pore-to-pore validation of the PNM. Using the verified PNM, the fluid displacement patterns including viscous fingering, capillary fingering and stable displacement are observed in varied disordered media at a varying capillary number Ca and mobility ratio M, which ends up with full Ca-M phase diagrams. The fundamental findings in this work warrant an improved modelling approach for the complicated behaviour in multiphase flow, i.e., fluid displacement and the water retention-related phenomena (e.g., slope instability).
34
Mancois, Vincent. "Non-equilibrium long-range phase transition in cold atoms : theory and experiment." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS427.
Анотація:
Nous avons étudié les effets de la force longue portée résultante de l’absorption de faisceaux lasers dans un nuage d’atomes froids à deux dimensions. La force créée est attractive et reproduit la gravité Newtonienne le long du faisceau. Le nuage d’atomes, composé de strontium 88 (bosons), est refroidi et piégé sur la transition d’intercombinaison. En transférant les atomes dans un piège dipolaire à deux dimensions à la longueur d’onde magique, une transition de phase hors d’équilibre se produit dans l’ensemble canonique. En dessous d’une température critique, un système de particules autogravitantes peut collapser, phénomène rappelant le processus de formation des étoiles. Nous avons observé expérimentalement, des régimes de compressions transitoires, un résultat en partie satisfaisant qui pourrait être amélioré avec l’utilisation de pièges dipolaires plus puissants. La seconde partie de la thèse se penche sur la réalisation théorique d’un moteur Brownien à partir d’un système de particules piégées à deux dimensions, une situation similaire à notre expérience de collapse à deux dimensions. L’obtention d’un moteur Brownien est caractérisée par l’apparition d’un courant macroscopique de particules. Nous avons montré que ce transport est indépendant des détails du piège et dépend seulement d’une double brisure de symétrie : Résultant de la présence de deux bains thermiques suivant deux axes orthogonaux et d’un piège anisotrope désaligné des axes thermiquesWe study the long-range force arising from the absorption of non-saturating laser beams in a two-dimensional cloud of cold atoms. The force created by the lasers is at- tractive and similar to the usual Newtonian gravity along the beam. The cloud is composed of bosonic strontium 88 cooled and trapped on the intercombination line. Transferring the atoms in a two-dimensional optical dipole trap in a magical wavelength configuration, a canonical non-equilibrium phase transition is expected. Below a critical temperature, self- gravitating particles in two dimensions can collapse, nearly by the same mechanism stars are forming. We observed experimentally transient compressions, a halfway satisfactory result originating from the power limitation of our dipole trap. The second part of the thesis focuses on the theoretical realization a minimal Brownian motor within a system of trapped particles in 2D, similarly to our experimental situation. The phenomenon char- acterizing the Brownian motor is the appearance of a macroscopic current of particles. We have shown that this direct transport of particles is independent of the details of the trapping potential and obtained if and only if two symmetries are jointly broken: By the presence of two heat baths along orthogonal directions together and an anisotropic trap misaligned from the temperature axes
35
Sousa, Fernando Rangel de. "Application du corrélateur " Five-Port " aux PLLs, à la récupération de porteuse et à un MODEM de télécommunications dans la bande 1,8 - 5,5 Ghz." Paris, ENST, 2004. https://pastel.archives-ouvertes.fr/pastel-00000987.
Анотація:
Le corrélateur "Five-Port" est un dispositif qui calcule précisément le rapport complexe entre deux signaux hyperfréquences à partir de la mesure des valeurs de puissance aux sorties d'un circuit interférométrique à cinq accès. Son application est connue dans les systèmes radars, les systèmes de détermination de la direction d'arrivée de signaux RF, les démodulateurs homodynes et, comme nous proposons dans ce travail, dans les boucles à verrouillage de phase et de récupération de porteuse. Tandis que les corrélateurs cartésiens classiques projettent le vecteur représentant le signal à démoduler sur une base composée de deux vecteurs orthogonaux, le corrélateur "Five-Port" effectue cette projection sur une "base" à trois vecteurs décalés en phase idéalement de 120°. Grâce à la redondance introduite par le troisième vecteur, le corrélateur "Five-Port" se présente moins sensible aux désappariements de phase et d'amplitude, fournit une variable permettant d'estimer les produits inter-modulation d'ordre pair et peut fonctionner dans une bande de fréquences large. Cette thèse apporte quelques contributions au domaine de la radiocommunication mobile, notamment aux émetteurs-récepteurs multi-bande et multi-mode. Le premier apport original est l'application de la technique "Five-Port" aux boucles à verrouillage de phase reconfigurables. Cette application est exploitée par la suite dans une boucle de récupération de porteuse multi-mode. Ensuite nous proposons une méthode de caractérisation originale mise en place pour calibrer les corrélateurs \FiveP. Finalement nous proposons et évaluons une nouvelle architecture d'émetteur-récepteur fondée sur une base à trois vecteursThe five-port correlator accurately computes the complex ratio between two radiofrequency signals from the power values measured at the output of a five-port interferometer circuit. Its application has been reported in radars, DOA systems, direct conversion receivers and, as we propose in this work, in PLLs and carrier recovery loops. Whereas classic cartesian correlators project a vector representing a modulated signal over an orthogonal basis, the five-port correlator performs this projection over a \textsl{basis} composed of three vectors ideally phase-shifted of 120°. Thanks to the redundancy added by the third vector, the five-port correlator is less sensible to phase and amplitude imbalances, allows for the estimation of the IM2 products and operates in a wider frequency band. This PhD research contributes to the mobile radiocommunication area, in particular to the multi-mode and multi-band transceivers. The first contribution is the application of the five-port technique to reconfigurable phase-locked loops. Secondly, these reconfigurable loops are exploited in a multi-mode carrier recovery loop. Then, we present an original five-port characterization method. Finally, we propose and evaluate a novel transceiver architecture based on a three-vector basis
36
Urata, Yumi. "Effect of thermal pressurization with dilatancy and phase transitions of pore water on spontaneous dynamic rupture propagation." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157783.
37
Jonsson, Alexander. "Investigation of pore size effects at separation of oligonucleotides using Ion-pair RP HPLC : Examining of how the particle pore size of the stationary phase affects separations of oligonucleotides in therapeutic range." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-73367.
Анотація:
Oligonucleotides may become a new class of therapies with the potential of curing many today untreatable diseases. Oligonucleotides becomes increasingly more difficult to separate with an increase in length since the relative difference in retention of these very similar compounds becomes increasingly smaller. Therefore, coelution of impurities formed during synthesis may result in insufficient purity, which is necessary for therapeutic treatments. Oligonucleotides are also relatively large biomolecules, possibly consisting of hundreds of nucleotides. As a result, oligonucleotides may have limited diffusion through the stationary phase pores which affects separation performance. Surprisingly few studies have be published in this research area and a wider knowledge in how this affects separation is needed. In this master thesis, separation of deoxythymidine oligonucleotides with 5-30 mers in length were separated with 60, 100, 200 and 300 Å pore size reversed phase C4 columns. It was concluded that pore size resulted in more restricted diffusion if insufficient pore size was used. Poor peak performance was also observed with too large pore sizes which lead to less efficient separations.
38
Williams, Andrew Robert. "Cracking Potential and Temperature Sensitivity of Metakaolin Concrete." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6603.
Анотація:
Metakaolin is a pozzolanic material with the potential to reduce permeability and chloride ingress; however, quantification of the effects of metakaolin use on the cracking sensitivity of concrete mixtures is needed to ensure that these improvements in performance are not compromised. This study was conducted to investigate the early age cracking potential due to restraint stresses from incorporating metakaolin in concrete. Calorimetry testing showed that metakaolin was more sensitive to temperature than mixtures with only Portland cement. Results showed more shrinkage, less stress relaxation, and higher restraint stress from the inclusion of metakaolin, potentially increasing cracking sensitivity of mixtures.
1 This section was published in Construction and Building Materials[57]. Permission is included in Appendix A
39
Xu, Zhi Guo. "An investigation of two-phase flow of organic working fluids in the inlet port of a Lysholm screw expander." Thesis, City University London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294052.
40
Reynolds, Catriona Anne. "Two-phase flow behaviour and relative permeability between CO2 and brine in sandstones at the pore and core scales." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44499.
Анотація:
In this thesis we have performed an experimental investigation into steady-state two-phase flow behaviour at the core and pore scales and visualised the fluid distributions using medical and fast synchrotron X-ray computed tomography. We performed an experimental study of steady-state, drainage relative permeability curves with CO2-brine and N2-deionised water, on a single Bentheimer sandstone core with a simple two-layer heterogeneity over reservoir conditions of 10.3-20.7 MPa, 38-91°C and 0-5 mol kg-1 NaCl brine. We demonstrate that, if measured in the viscous limit, relative permeability is invariant with changing reservoir conditions, and is consistent with the continuum-scale multiphase flow theory for water wet systems. Furthermore, we show that under capillary limited conditions, the CO2-brine system is very sensitive to heterogeneity in capillary pressure, and by performing core-floods under capillary limited conditions, we produce effective relative permeability curves that are flow rate and fluid parameter dependent. We show that the appropriate conditions for measuring intrinsic or effective relative permeability curves can be selected simply by scaling the driving force for flow by a quantification of capillary heterogeneity and use this methodology to make measurements of CO2-brine relative permeability for target CO2 storage reservoirs in the UK. A new type of pore-scale flow behaviour was identified, that we term dynamic connectivity, using fast synchrotron X-ray computed tomography to image the capillary dominated steady-state flow of N2 and 1.5 mol kg-1 KI brine at 50°C and 10 MPa. Non-wetting phase flow occurred via a stable connected pathway at low capillary numbers and through a series of transient connections between a network of static ganglia with a dynamic connectivity at increasing capillary numbers. We speculate that changes observed in the strength and character of hysteresis between drainage and imbibition during capillary and viscous dominated core-scale experiments is a consequence of this pore-scale flow mechanism.
41
Kaufmann, Josef. "Experimental identification of damage mechanisms in cementitious porous materials on phase transition of pore solution under frost deicing salt attack /." Lausanne, 2000. http://library.epfl.ch/theses/?nr=2037.
42
Hippauf, Felix Verfasser], Stefan [Akademischer Betreuer] [Kaskel, and Thomas [Gutachter] Henle. "Tailoring Pore Size and Polarity for Liquid Phase Adsorption by Porous Carbons / Felix Hippauf ; Gutachter: Thomas Henle ; Betreuer: Stefan Kaskel." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1133110630/34.
43
Hippauf, Felix [Verfasser], Stefan [Akademischer Betreuer] Kaskel, and Thomas [Gutachter] Henle. "Tailoring Pore Size and Polarity for Liquid Phase Adsorption by Porous Carbons / Felix Hippauf ; Gutachter: Thomas Henle ; Betreuer: Stefan Kaskel." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1133110630/34.
44
Weishaupt, Kilian [Verfasser], and Rainer [Akademischer Betreuer] Helmig. "Model concepts for coupling free flow with porous medium flow at the pore-network scale : from single-phase flow to compositional non-isothermal two-phase flow / Kilian Weishaupt ; Betreuer: Rainer Helmig." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1215101848/34.
45
Duhem, François. "Diagramme de phase du réseau Kondo : aspects statiques et dynamiques." Université Joseph Fourier (Grenoble), 1999. http://www.theses.fr/1999GRE10121.
Анотація:
Nous avons fait une etude theorique de certaines proprietes du reseau kondo dans sa phase paramagnetique, utilisant un modele incorporant des correlations antiferromagnetiques a courte portee. Nous nous sommes limites au cas de la bande de conduction a moitie pleine et avons utilise une methode de champ moyen. Les resultats obtenus sont les suivants : _ on montre qu'il est possible d'obtenir des solutions metalliques pour une bande de conduction a moitie pleine en modifiant la structure de bande, ceci nous amene a definir une temperature de transition isolant-metal qui est comparee aux temperatures kondo et de coherence. _ nous recherchons ensuite des phases magnetiquement ordonnees par deux methodes : introduction d'un moment magnetique sur chaque site comme parametre de champ moyen et etude de la susceptibilite statique en rpa. Nous obtenons ainsi des phases purement kondo ou purement magnetiques, mais nous n'avons pas trouve de phase mixte kondo-magnetique. _ les fluctuations des parametres kondo et magnetique sont ensuite traitees dans le cadre de l'approximation rpa. Ceci permet de calculer leur contribution a la chaleur specifique. Un comportement de fermion lourd est mis en evidence pour certaines valeurs des constantes de couplage. Au voisinage de la transition isolant-metal, un comportement de non liquide de fermi est obtenu.
46
Uzun, Ilkay. "Use Of Pore Scale Simulators To Understand The Effects Of Wettability On Miscible Carbon Dioxide Flooding And Injectivity." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606876/index.pdf.
Анотація:
This study concentrates on the modelling of three phase flow and miscible CO2 flooding in pore networks that captures the natural porous medium of a reservoir. That is to say, the network, that is a Matlab code, consists of different sided triangles which are located randomly through the grids. The throats that connect the pores are also created by the model. Hence, the lengths and the radii of the throats are varying. The network used in this research is assumed to be representative of mixed-wet carbonates in 2-D. Mixed wettability arises in real porous media when oil renders surfaces it comes into prolonged contact with oil-wet while water-filled nooks and crannies remain water-wet. The model developed is quasi-static approach to simulate two phase and three phase flows. By this, capillary pressures, relative permeabilities, saturations, flow paths are determined for primary drainage, secondary imbibition, and CO2 injection cases. To calculate the relative permeability, capillary entry pressures are first determined. Then, hydraulic conductances and flow rates of the network for each grid are obtained. Phase areas and saturations are also determined. It is accepted that the displacement mechanism in drainage and CO2 injection is piston-like whereas in imbibition it is either piston-like or snap-off.
The results of the model are compared with the experimental data from the literature. Although, the pore size distribution and the contact angle of the model are inconsistent with the experimental data, the agreement of the relative permeabilities is promising.
The effect of contact angle in the same network for three phase flow where immiscible CO2 is injected as a third phase at supercritical temperature (32 °C) is investigated. And it is found that, the increase in the intrinsic angles causes decrease in relative permeability values. As another scenario, two phase model is developed in which miscible CO2 &
#8211
water is flooded after the primary drainage of the same 2-D network at supercritical temperature (32 °
C). This case is compared with the previous case and the effects of miscibility are investigated such that it causes the relative permeability values to increase. Adsorption is another concern of which its effects are analyzed in a single pore model. The model is compared with the reported experimental data at high temperature and pressures. A reasonable fit is obtained.
47
Dulina, I. O., T. F. Lobunets, L. O. Klochkov, and A. V. Ragulya. "Synthesis of Ni/NiO Nanosize Powders with Different Phase Ratio by Thermal Decomposition of Nickel Acetate Amines." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35125.
Анотація:
Ni/NiO nanopowders with different phase ratio have been prepared using thermal decomposition of nickel acetate ammine complexes containing various ammonia content in air at the temperature range 300 – 500 °C. Obtained powders have been characterized by IR-spectroscopy, XRD and TG, DTA, DTG, TEM, laser granulometry and adsorption-structural method. Thermal decomposition of nickel ammine complexes occurred with forming nickel hydroxide, carbonate and hydroxocarbonate ammines precursors. Composition of the precursors depended on temperature and ammonia content in initial complex. Mean crystallite size of nickel depended on temperature only. In the temperature range from 350 to 500 °C the crystallite size of nickel has grown from 50 to 55 nm. Mean crystallite size of nickel oxide depended on temperature and ammonia content. In the temperature range from 350 to 500 °C the crystallite size of NiO has grown from 5 to 25 nm. Increasing ammonia content from 3.6 to 14.4 mol/mol Ni led to decreasing NiO crystallite size from 8 – 10 to 5 nm.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35125
48
Soulaine, Cyprien. "Modélisation des écoulements dans les garnissages structurés : de l'échelle du pore à l'échelle de la colonne." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0089/document.
Анотація:
Une colonne de séparation d'air réalise un écoulement liquide-gaz à contre courant dans une structure complexe, le garnissage. Au sein de ce garnissage, l'écoulement du liquide est du type film drainé par gravité, alors que l'écoulement du gaz est turbulent. La fonction de ces contacteurs est de développer une surface d'échange interfaciale aussi grande que possible pour favoriser le transfert d'un composé chimique de la phase liquide vers la phase vapeur (et inversement) tout en offrant des pertes de charge raisonnables. Ces dispositifs sont constitués par l'assemblage de plaques métalliques ondulées, avec ou sans perforations, où deux plaques adjacentes sont respectivement inclinées d'un angle et son opposé par rapport à l'axe de la colonne. Ce type de contacteur peut être considéré comme un milieu poreux bi-structuré avec un taux de porosité élevé. Les écoulements peuvent être décrits à deux échelles : une échelle du pore et une échelle macroscopique. A cause de cette double structuration, la modélisation macroscopique des écoulements dans ce type de structure reste un problème difficile. En particulier, les mécanismes macroscopiques qui entraînent l'étalement d'un jet dans les garnissages sont incompris. Par ailleurs, une difficulté de modélisation supplémentaire est due aux effets liés à la turbulence. Au cours de cette thèse, nous avons développé, à partir d'une méthode de changement d'échelle, un modèle complet pour simuler les écoulements et le transfert de matière dans les colonnes équipées de garnissages structurés. Notre étude se focalise sur les trois points suivants. Premièrement, nous avons obtenu, à l'aide d'une prise de moyenne volumique, une loi de Darcy-Forchheimer qui inclue les effets de la turbulence. Ensuite, pour modéliser la dispersion radiale du liquide dans la colonne, nous avons trouvé pratique de séparer la phase liquide en deux films distincts, qui s'écoulent sur chaque plaque ondulée selon des directions préférentielles différentes. Ces phases fictives ne sont pas indépendantes puisque de la matière peut passer de l'une à l'autre au niveau des points de contact entre les feuilles ondulées. Finalement, nous avons proposé un modèle macroscopique pour simuler le transport d'espèces chimiques dans un système diphasique, multiconstituants. Tous les paramètres effectifs qui apparaissent dans ce modèle sont évalués à partir de solutions analytiques ou numériques de l'écoulement à la petite échelle. Les résultats de simulation ont été comparés avec succès à des mesures expérimentales obtenues en laboratoire ou sur pilote industrielStructured packings play a large role in chemical engineering processes involving gasliquid separation such as air distillation unit or CO2 absorption columns. Such structures maximize the exchange surface between gas and liquid while pressure drops remain low enough. Generally, the columns are operated in the counter-current flow mode : a liquid gravity film is sheared by the turbulent flow of a gas phase. The packings are made of an assembly of corrugated sheets where two adjacent sheets are respectively inclined by an angle and the opposite of this angle from the vertical axis. We can apprehend such a device as a bi-structured porous medium with high porosity defining two scales of description : a pore-scale and a macro-scale assimilated to the packing scale. Due to this peculiar structured geometry, the flow modeling from a macroscopic point of view, remains a challenging problem that has to be overcome to design enhanced devices. In particular, the macroscopic phenomena that leads to the spreading of a liquid point source at the top of a packing are still unknown, and the classical two-phase flow models in porous media failed to properly catch the liquid distribution within the column. Moreover, turbulence effects lead to additional difficulties. We developed a comprehensive mathematical model based on a multi-scale analysis to simulate gas-liquid flow through the distillation columns. We investigate three main points. First, we derived a Darcy-Forchheimer law that includes turbulence effects using the method of volume averaging. Then, to model the liquid spreading, we found convenient to split the liquid phase into two fictitious phases flowing along each sheet with a preferential direction. Moreover, these phases are not (except perhaps at very low saturation) completely independent since adjacent sheets are in contact and the liquid can flow from one sheet to the other. Finally, we proposed a macro-scale dispersion model to simulate two-phase, multicomponent transport in structured packing. All the effective properties that appear in this model are evaluated from either simulations or analytical solutions of the flow at the pore-scale. Simulation results have been successfully compared to laboratory-scale experiments and industrial-scale measurements
49
Singh, Kamaljit Engineering & Information Technology Australian Defence Force Academy UNSW. "Dynamics of residual non-aqueous phase liquids in porous media subject to freeze-thaw." Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/44875.
Анотація:
This project concerns the effect of freeze-thaw cycles on the pore-scale structure of nonaqueous phase liquid (NAPL) contaminants in water-saturated porous media. This problem is of critical importance to the entrapment of such contaminants in cold temperate, polar and high altitude regions, and has not been examined in the literature to date. This research work is conducted in three stages: (i) two-dimensional nondestructive visualisation of residual light non-aqueous phase liquid (LNAPL), and dense non-aqueous phase liquid (DNAPL), in porous media subject to successive freeze-thaw cycles; (ii) three-dimensional experiments on LNAPL in porous media subject to freeze-thaw, with quantification of phase volumes by X-ray micro-computed tomography (micro-CT); and (iii) the explanation of results by several pore scale mathematical and conceptual models. The two-dimensional cell experiments (using a monolayer of 0.5 mm diameter glass beads held between two glass sheets), and three-dimensional X-ray micro-CT experiments reveal a substantial mobilisation and rupture of ganglia during successive freeze-thaw cycles; this includes the detachment of smaller ganglia from larger ganglia and the mobilisation of NAPL in the direction of freezing front. The experiments also reveal significant shedding of numerous single/sub-singlet ganglia along narrow pore corridors, their entrapment in growing polycrystalline ice, and the coalescence of such small ganglia during thawing to form larger singlets. These changes were more predominant where the freezing commenced. The results of the experimental studies were interpreted by developing several mathematical and conceptual models, including freezing-induced pressure model, Darcy's law model, multipore ganglia model (rupture coefficient) and ice-snap off model.
50
Oliveira, Roberto Teodoro Gurgel de. "Modelo de ashkin-teller de tr?s cores na rede ponte de wheatstone." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/16560.
Анотація:
Made available in DSpace on 2014-12-17T15:14:51Z (GMT). No. of bitstreams: 1
RobertoTGO_DISSERT.pdf: 394069 bytes, checksum: fbb8faf7e24cc92335302e442b92ec43 (MD5)
Previous issue date: 2010-02-22Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
In this work we study the phase transitions of the ferromagnetic three-color Ashkin-Teller Model in the hierarquical lattice generated by the Wheatstone bridge using real space renormalization group approach. With such technique we obtain the phase diagram and its critical points with respective critical exponents v. This model presents four phases: ferromagnetic, paramagnetic and two intermediates. Nine critical points were found, three of which are of Ising model type, three are of four states Potts model type, one is of eight states Potts model type and the last two which do not correspond to any Potts model with integer number of states. iv
Neste trabalho estudamos as transi??es de fase do modelo de Ashkin-Teller de tr?s cores ferromagn?tico na rede hier?rquica ponte de Wheatstone utilizando o m?todo de grupo de renormaliza??o no espa?o real. Com a utiliza??o desta t?cnica obtemos o diagrama de fases e seus pontos cr?ıticos com respectivos expoentes cr?ticos v. O modelo apresenta quatro fases: ferromagn?tica, paramagn?tica e duas intermedi?rias. Nove pontos cr?ıticos foram encontrados, sendo tr?s de classe de universalidade Ising, tr?s Potts de quatro estados, um Potts de oito estados e dois com classe de universalidade n?o correspondente a nenhum Potts com n?mero inteiro de estados