To see the other types of publications on this topic, follow the link: Contacted phases.
Dissertations / Theses on the topic 'Contacted phases'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Contacted phases.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Никольский, Валерий Евгеньевич. "Синергетические реакционно-массообменные процессы в газожидкостных аппаратах и топливных агрегатах химической технологии." Thesis, Украинский государственный химико-технологический университет, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24524.
Full textAbstract:
Диссертация на соискание ученой степени доктора технических наук по специальности 05.17.08 – процессы и оборудование химической технологии. – Национальный технический университет "Харьковский политехнический институт" Министерства образования и науки Украины, Харьков, 2016 г.
Диссертационная работа посвящена решению актуальной инжиниринговой научно-технической проблемы: разработать современные энергоэффективные экологически чистые технологии, средства генерирования и потребления тепловой энергии с применением систем рекуперации теплоты на основе синергетического единства аппаратурно-технологического оформления процессов и системного подхода. В работе разработаны научно-методологические основы и практические способы повышения эффективности использования топлива в газожидкостных аппаратах и топливных агрегатах химической технологии за счет интенсификации тепловых процессов в их рабочем пространстве. С позиции совершенствования топливо– и материалосберегающих техники и технологий созданы новые конструкции газожидкостных аппаратов и топливных агрегатов. На их основе синтезированы экологически чистые энергоэффективные технологические системы (ЭТС), приемлемые для химической технологии и других сфер промышленности, коммунального, сельского хозяйства, отвечающие современным энергетическим и экологическим требованиям. Систематизированы методы интенсификации гетерогенных процессов в теплотехнологических аппаратах; предложены новые перспективные РТ и АК методы интенсификации и обоснована целесообразность их практического использования при синтезе новых ЭТС на базе синергетически совмещенных реакционно-разделительных процессов (обеспечение неоднофазности, наложение электрических и магнитных полей на контактирующие фазы, оптимизация параметров пульсаций в гетерогенных системах, одно- и многотипное комбинирование теплогенерирующих аппаратов, обеспечение многократных входных и концевых эффектов, соударения, закручивания, взаимной эжекции контактирующих фаз и их осциллирования, циклический подвод энергии). Разработанные и приведенные в диссертации аппараты, технологические процессы и оборудование широко внедрены на предприятиях Минхимпрома, Минметаллургии, Минавтопрома, Минкоммунхоза Украины и стран СНГ.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
2
Нікольський, Валерій Євгенович. "Синергетичні реакційно-масообмінні процеси в газорідинних апаратах і паливних агрегатах хімічної технології." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24517.
Full textAbstract:
Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.17.08 – процеси та обладнання хімічної технології. – Національний технічний університет "Харківський політехнічний інститут" Міністерства освіти і науки України, Харків, 2016 р.
Дисертаційна робота присвячена вирішенню актуальної інжинірингової науково-технічної проблеми: розробити сучасні енергоефективні екологічно чисті технології, засоби генерування та споживання теплової енергії із застосуванням систем рекуперації теплоти на основі синергетичної єдності апаратурно-технологічного оформлення процесів і системного підходу. У роботі розроблено науково-методологічні основи та практичні способи підвищення ефективності використання палива в газорідинних апаратах і паливних агрегатах хімічної технології за рахунок інтенсифікації теплових процесів в їх робочому просторі. З позиції вдосконалення паливо- і матеріалозберігаючих техніки і технологій створено нові конструкції газорідинних апаратів і паливних агрегатів. На їх основі синтезовано екологічно чисті енергоефективні технологічні системи (ЕТС), прийнятні для хімічної технології та інших сфер промисловості, комунального, сільського господарства, які відповідають сучасним енергетичним та екологічним вимогам. Розроблено високоефективну контактно-модульну систему (КМС), обладнану апаратами зануреного горіння (АЗГ) з багатократною інверсією і модуляцією коливань контактуючих фаз для потреб теплопостачання промислових будівель і споруд, житлових і сільськогосподарських комплексів, яка виключає використання котельних і бойлерних установок з утилізацією теплоти продуктів згоряння, тепловою потужністю 200, 400, 600, 1000, 2000 кВт і вище залежно від потреби в генерованій теплоті. Витрати на обігрівання будівель і споруд при використанні пристрою знижуються в 2,5-2,8 рази в порівнянні з традиційними способами обігрівання. КМС пройшла державні тепло-екологічні випробування, які підтвердили її високу енергоефективність, екологічність, надійність в роботі. Отримано технічні умови на серійне її виготовлення і експлуатацію в різних галузях народного господарства. Розроблені і наведені в дисертації апарати, технологічні процеси і устаткування широко впроваджені на підприємствах Мінхімпрому, Мінметалургіі, Мінавтопрому, Мінкомунгоспу України та країн СНД.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
3
Herbaut, Rémy. "Dynamique des liquides sur substrat froid, avec solidification." Thesis, Sorbonne Paris Cité, 2019. http://www.theses.fr/2019USPCC006.
Full textAbstract:
Nous étudions l’étalement de liquides sur une surface froide, avec solidification. L’application visée est le secteur aéronautique qui est confronté à des problèmes de givrage lorsque l’avion est au sol. Le dégivrage s’effectue actuellement par un jet d’éthylène glycol, qui contribue à un surcoût pour les compagnies et une pollution non négligeable. Nos objectifs portent tout d’abord sur des questions fondamentales d’étalement d’une goutte sur un substrat à une température inférieure à la température de solidification. Sur une surface donnée, est-on capable de prédire si la goutte se solidifie ou s’étale dès son impact ? Quelles sont les formes prises par celle-ci, avant, pendant et après la solidification? Quel est le mécanisme de solidification et son influence sur la dynamique d’étalement ? Quel sont les paramètres qui contrôlent la dynamique des processus mis en jeu ? Plusieurs dispositifs et modélisations seront mis en œuvre en vue d’apporter des éléments de réponses à ces questions. Nos objectifs portent aussi sur des stratégies en vue d’éviter la congélation des gouttes et leur permettre de glisser avant leur congélation. La mise en oscillation d’une goutte ou le greffage de polymère en vue modifier l’état de surface seront également envisagés. Cette thèse tente d’apporter quelques éléments de compréhension nouveaux en se concentrant sur deux types d’écoulements très différent. Premièrement, l’avancée d’une ligne de contact en présence de solidification. Deuxièmement, la croissance d’une goutte solide sous alimentation continue en liquideWe study the liquids spreading on cold substrate, with solidification. The intended application is the aeronautical sector, which faces icing problems when the aircraft is on the ground. The deicing is currently carried out by an ethylene glycol jet, which contributes to an additional cost for the companies and a significant pollution. Our objectives focus on fundamental issues of spreading a drop on a substrate at a temperature below the solidification temperature. On a given surface, is it possible to predict whether the drop solidifies or spreads as soon as it is impacted ? What are the forms taken by it, before, during and after solidification? What is the solidification mechanism and its influence on the spreading dynamics? What are the parameters that control the dynamics of the processes involved ? Several devices and models will be implemented to provide some answers to these questions. Our goals also include strategies to avoid freezing drops and allowing them to slide before freezing. Oscillation of a droplet or grafting of polymer to modify the surface condition will also be considered. This thesis attempts to bring some new elements of understanding by focusing on two very different types of flows. First, the advance of a line of contact in the presence of solidification. Second, the growth of a solid drop under continuous liquid feed
4
Députier, Stéphanie. "Metallurgie des contacts metal-semiconducteur iii-v : DIAGRAMME DE PHASES ET INTERDIFFUSION EN PHASE SOLIDE DANS LES SYSTEMES Ni/A1AS ET Er/GaAs." Rennes 1, 1992. http://www.theses.fr/1992REN10039.
Full textAbstract:
Dans la technologie des semiconducteurs (sc) iii-v, la fabrication reproductible de contacts metal/sc fiables et de bonne qualite reste un probleme imparfaitement resolu. En principe, un tel contact peut etre obtenu par interdiffusion en phase solide d'une couche mince de metal avec le sc. Mais, contrairement au silicium, la presence d'un semiconducteur compose introduit la possibilite de formation de phases ternaires. Aussi, la necessite absolue de la determination experimentale du diagramme ternaire m-iii-v pour comprendre et interpreter les sequences de formation des phases obtenues par interdiffusions en couches minces a-t-elle ete clairement mise en evidence. Les diagrammes ternaires ni-al-as et er-ga-as ont ete determines a 800c et caracterises par diffraction x, microscopie electronique a balayage et microsonde de castaing. Seul le diagramme ni-al-as montre l'existence de phases ternaires originales derivees de la structure-type nias. Les interdiffusions en phase solide entre un film metallique (ni,er) et le substrat (alas, gaas), apres traitements thermiques entre 200 et 800c ont ete caracterisees par diverses techniques complementaires d'analyse (diffraction x, rbs, met, mesure de resistivite). Lors de ces deux etudes, le metal depose sur le sc ne conduit pas a la formation de composes ternaires stables et epitaxies, mais a des melanges de binaires et ternaires fortement textures. Les binaires epitaxies nial et eras apparaissent comme des candidats potentiels pour la formation de contacts stables m/sc iii-v. Pour la realisation d'heterostructures sc/m/sc, les arseniures de terres rares presentent toutefois des avantages non negligeables sur les composes metaux de transition-elements iii
5
Martin, Sylvain. "Contribution à la modélisation du frittage en phase solide." Thesis, Compiègne, 2014. http://www.theses.fr/2014COMP2144/document.
Full textAbstract:
Cette thèse traite de la modélisation du frittage à l’échelle du Volume Élémentaire Représentatif de la pastille de matériau. L’objectif est de développer des outils numériquesde compréhension des phénomènes physiques mis en jeu lors du frittage. Le domaine d’application ciblé est la fabrication du combustible nucléaire. Une approche multi-Échelle a été mise en oeuvre. Dans un premier temps une modélisation à l’échelle d’un empilement, basée sur la méthode des Éléments Discrets, a été adoptée. Différentes études utilisant cette approche ont été proposées dans la littérature ces dernières années. Tous ces travaux utilisent une méthode discrète explicite. Si certains résultats ont pu être validés expérimentalement,une des limites vient de l’utilisation des méthodes explicites dontle pas de temps critique est très petit. Afin d’augmenter le pas de temps, la masse des particules y est augmentée artificiellement de plusieurs ordres de grandeur. Or,il a été démontré que cette pratique conduit, dans certains cas, à une diminution du réarrangement des particules au sein de l’empilement. Dans cette thèse, une méthode Éléments Discrets implicite appelée Dynamique des Contacts a été adaptée au frittage. Elle permet l’utilisation d’un pas de temps très supérieur à celui des méthodes discrètes explicites et ne nécessite pas d’augmenter artificiellement la massedes particules. La comparaison entre la Dynamique des Contacts et la Méthode des Éléments Discrets explicite montre que notre approche conduit à une représentation plus fidèle du réarrangement. Une validation expérimentale par Microtomographie X ainsi qu’une étude paramétrique sur le frittage des poudres bidispersés sont également présentées pour montrer les possibilités de l’approche discrète appliquée au frittage.La seconde partie est consacrée à une modélisation à l’échelle de deux particules parla méthode des Éléments Finis. Ce modèle repose sur une approche mécanique et vise à représenter de façon plus précise le comportement de deux particules en contact. Les diffusions au joint de grains, en surface et en volume peuvent être représentées. Pour le moment, seules les diffusions en surface et au joint de grains ont été étudiées. Si certaines optimisations restent nécessaires pour que le code soit fonctionnel, plusieurs aspects apparaissent déjà déterminants, comme la courbure de la surface à proximité du joint de grains. A l’avenir, le modèle Dynamique des Contacts du frittage pourra être complété etamélioré grâce aux éléments apportés par le modèle mécanique à l’échelle du grainThis thesis deals with the simulation of the sintering of nuclear fuel on a pellet scale. The goal is to develop numerical tools which can contribute to a better understandingof the physical phenomena involved in the sintering process. Hence, a multi scale approach is proposed. First of all, a Discrete Element model is introduced. It aims at modeling the motion of particles on a Representative Elementary Volume scale using an original Discrete Element Method. The latter is a Non Smooth Method called Contact Dynamics. Recently, there have been numerous papers about the simulation of sintering using Discrete Element Method. As far as we know, all these papers use smooth methods. Different studies show that the results match well experimental data. However, some limits come from the fact that smooth methods use an explicit scheme which needsvery small time steps. In order to obtain an acceptable time step, the mass of particles have to be dramatically increased. The Non Smooth Contact Dynamics uses an implicit scheme, thus time steps can be much larger without scaling up the mass of particles. The comparison between smooth and non smooth approaches shows thatour method leads to a more realistic representation of rearrangement. An experimental validation using synchrotron X-Ray microtomography is then presented, followedby a parametric study on the sintering of bimodal powders that aims at showing the capacity of this model.The second part presents a mechanical model on the sub-Granular scale, using a Finite Element method. This targets a better understanding of the behavior of twograins in contact. The model is currently being developped but the first results already show that some parameters like the shape of the surface of the neck are very sensitive.In the future, the Non smooth Contact Dynamics model of sintering may be improvedusing the results obtained by the sub-Granular scale mechanical model
6
Wales, Michael Dean. "Membrane contact reactors for three-phase catalytic reactions." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20589.
Full textAbstract:
Doctor of PhilosophyChemical Engineering
Mary E. Rezac
Membrane contact reactors (MCRs) have been evaluated for the selective hydro-treating of model reactions; the partial hydrogenation of soybean oil (PHSO), and the conversion of lactic acid into commodity chemicals. Membranes were rendered catalytically active by depositing metal catalyst onto the polymer "skin" of an asymmetric membrane. Hydrogen was supplied to the support side of the membrane and permeated from the support side to the skin side, where it adsorbed directly onto the metal surface. Liquid reactant was circulated over the membrane, allowing the liquid to come into direct contact with the metal coated surface of the membrane, where the reaction occurred. Our membrane contact reactor approach replaces traditional three-phase batch slurry reactors. These traditional reactors possess inherent mass transfer limitations due to low hydrogen solubility in liquid and slow diffusion to the catalyst surface. This causes hydrogen starvation at the catalyst surface, resulting in undesirable side reactions and/or extreme operating pressures of 100 atmospheres or more. By using membrane reactors, we were able to rapidly supply hydrogen to the catalyst surface. When the PHSO is performed in a traditional slurry reactor, the aforementioned hydrogen starvation leads to a high amounts of trans-fats. Using a MCR, we were able to reduce trans-fats by over 50% for equal levels of hydrogenation. It was further demonstrated that an increase in temperature had minimal effects on trans-fat formation, while significantly increasing hydrogenation rates; allowing the system to capture higher reaction rates without adversely affecting product quality. Additionally, high temperatures favors the hydrogenation of polyenes over monoenes, leading to low amounts of saturated fats. MCRs were shown to operator at high temperatures and: (1) capture high reaction rates, (2) minimize saturated fats, and (3) minimize trans-fats. We also demonstrated lactic acid conversion into commodity chemicals using MCRs. Our results show that all MCR experiments had faster reaction rate than all of our controls, indicating that MCRs have high levels of hydrogen coverage at the catalyst. It was also demonstrated that changing reaction conditions (pressure and temperature) changed the product selectivities; giving the potential for MCRs to manipulate product selectivity.
7
Zhao, Lei. "Dynamics and Statics of Three-Phase Contact Line." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/102649.
Full textAbstract:
Wetting, which addresses either spontaneous or forced spreading of liquids on a solid surface, is a ubiquitous phenomenon in nature and can be observed by us on a daily basis, e.g., rain drops falling on a windshield and lubricants protecting our corneas. The study of wetting phenomena can be traced back to the observation of water rising in a capillary tube by Hauksbee in 1706 and still remains as a hot topic, since it lays the foundation for a wide spectrum of applications, such as fluid mechanics, surface chemistry, micro/nanofluidic devices, and phase change heat transfer enhancement. Generally, wetting is governed by the dynamic and static behaviors of the three-phase contact line. Therefore, a deep insight into the dynamics and statics of three-phase contact line at nanoscale is necessary for the technological advancement in nanotechnology and nanoscience. This dissertation aims to understand the dynamic wetting under a molecular kinetic framework and resolve the reconfiguration of liquid molecules at the molecular region of contact line.
Water spreading on polytetrafluoroethylene surfaces is selected as a classical example to study the dynamic behaviors of three-phase contact line. To accommodate the moving contact line paradox, the excess free energy is considered to be dissipated in the form of molecular dissipation. As-formed contact line friction/dissipation coefficient is calculated for water interacting with PTFE surfaces with varying structures and is found to be on the same order of magnitude with dynamic viscosity. From an ab initio perspective, contact line friction is decomposed into contributions from solid-liquid retarding and viscous damping. A mathematical model is established to generalize the overall friction between a droplet and a solid surface, which is able to clarify the static-to-kinetic transition of solid-liquid friction without introducing contact angle hysteresis. Moreover, drag reduction on lotus-leaf-like surface is accounted for as well. For the first time, the concept of contact line friction is used in the rational design of a superhydrophobic condenser surface for continuous dropwise condensation.
We focus on the transport and reconfiguration of liquid molecules confined by a solid wall to shed light on the morphology of the molecular region of a three-phase contact line. A governing equation, which originates from the free energy analysis of a nonuniform monocomponent system, is derived to describe the patterned oscillations of liquid density. By comparing to the Reynolds transport theorem, we find that the oscillatory profiles of interfacial liquids are indeed governed in a combined manner by self-diffusion, surface-induced convection and shifted glass transition. Particularly for interfacial water, the solid confining effects give rise to a bifurcating configuration of hydrogen bonds. Such unique configuration consists of repetitive layer-by-layer water sheets with intra-layer hydrogen bonds and inter-layer defects. Molecular dynamics simulations on the interfacial configuration of water on solid surfaces reveal a quadratic dependence of adhesion on solid-liquid affinity, which bridges the gap between macroscopic interfacial properties and microscopic parameters.Doctor of Philosophy
8
Burke, Dave. "The mechanics of the contact phase in trampolining." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/16744.
Full textAbstract:
During the takeoff for a trampoline skill the trampolinist should produce sufficient vertical velocity and angular momentum to permit the required skill to be completed in the aerial phase without excessive horizontal travel. The aim of this study was to investigate the optimum technique to produce forward somersault rotation. A seven-segment, subject-specific torque-driven computer simulation model of the takeoff in trampolining was developed in conjunction with a model of the reaction forces exerted on the trampolinist by the trampoline suspension system. The ankle, knee, hip, and shoulder joints were torque-driven, with the metatarsal-phalangeal and elbow joints angle-driven. Kinematic data of trampolining performances were obtained using a Vicon motion capture system. Segmental inertia parameters were calculated from anthropometric measurements. Viscoelastic parameters governing the trampoline were determined by matching an angle-driven model to the performance data. The torque-driven model was matched to the performance data by scaling joint torque parameters from the literature, and varying the activation parameters of the torque generators using a simulated annealing algorithm technique. The torque-driven model with the scaled isometric strength was evaluated by matching the performance data. The evaluation produced close agreement between the simulations and the performance, with an average difference of 4.4% across three forward rotating skills. The model was considered able to accurately represent the motion of a trampolinist in contact with a trampoline and was subsequently used to investigate optimal performance. Optimisations for maximum jump height for different somersaulting skills and maximum rotation potential produced increases in jump height of up to 14% and increases of rotation potential up to 15%. The optimised technique for rotation potential showed greater shoulder flexion during the recoil of the trampoline and for jump height showed greater plantar flexion and later and quicker knee extension before takeoff. Future applications of the model can include investigations into the sensitivity of the model to changes in initial conditions, and activation, strength, and trampoline parameters.
9
Thiele, Roman. "Modeling of Direct Contact Condensation With OpenFOAM." Thesis, KTH, Reaktorteknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-49825.
Full textAbstract:
Within the course of the master thesis project, two thermal phase change models for direct contact conden-sation were developed with different modeling approaches, namely interfacial heat transfer and combustionanalysis approach.After understanding the OpenFOAM framework for two phase flow solvers with phase change capabilities,a new solver, including the two developed models for phase change, was implemented under the name ofinterPhaseChangeCondenseTempFoam and analyzed in a series of 18 tests in order to determine the physicalbehavior and robustness of the developed models. The solvers use a volume-of-fluid (VOF) approach withmixed fluid properties.It has been shown that the approach with inter-facial heat transfer shows physical behavior, a strong timestep robustness and good grid convergence properties. The solver can be used as a basis for more advancedsolvers within the phase change class.
10
Walker, Claudio. "Numerical Methods for Two-Phase Flow with Contact Lines." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-17462.
Full textAbstract:
This thesis focuses on numerical methods for two-phase ows, and especially ows with a moving contact line. Moving contact lines occur where the interface between two uids is in contact with a solid wall. At the location where both uids and the wall meet, the common continuum descriptions for uids are not longer valid, since the dynamics around such a contact line are governed by interactions at the molecular level. Therefore the standart numerical continuum models have to be adjusted to handle moving contact lines. In the main part of the thesis a method to manipulate the position and the velocity of a contact line in a two-phase solver, is described. The Navier-Stokes equations are discretised using an explicit nite di erence method on a staggered grid. The position of the interface is tracked with the level set method and the discontinuities at the interface are treated in a sharp manner with the ghost uid method. The contact line is tracked explicitly and its dynamics can be described by an arbitrary function. The key part of the procedure is to enforce a coupling between the contact line and the Navier-Stokes equations as well as the level set method. Results for di erent contact line models are presented and it is demonstrated that they are in agreement with analytical solutions or results reported in the literature. The presented Navier-Stokes solver is applied as a part in a multiscale method to simulate capillary driven ows. A relation between the contact angle and the contact line velocity is computed by a phase eld model resolving the micro scale dynamics in the region around the contact line. The relation of the microscale model is then used to prescribe the dynamics of the contact line in the macro scale solver. This approach allows to exploit the scale separation between the contact line dynamics and the bulk ow. Therefore coarser meshes can be applied for the macro scale ow solver compared to global phase eld simulations, reducing the overall computational coasts. One of the major drawbacks of the level set method is that it does not conserve the mass of the uids. The application of the conservative level set method (CLSM) o ers a solution to this problem. Three of the attached articles address details concerning the implementation of the CLSM using a nite di erence method. A nite di erence discretisation of the CLSM based on stencils used in the Navier-Stokes solver is described and tested. Various methods to compute the curvature in the CLSM are assessed for the use in the ghost uid method. It is shown that the reinitialisation of the CLSM can lead to spurious deformations of the interface, a stabilised constrained reinitialisation is developed in an attempt to prevent the interface from deforming
11
Daivasagaya, Daisy. "CMOS contact and phase imaging of biochemical sensor microarray." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117067.
Full textAbstract:
In this Thesis, we present two systems for gaseous oxygen (O2) sensing. First, we describe a compact luminescent sensor microsystem that is based on the direct integration of sensor elements with a polymeric optical filter and placed on a low power Complementary Metal-Oxide Semiconductor (CMOS) imager Integrated Circuit (IC). The second system is a hand-held scale phase fluorometric system. This system is based on a new single-chip integrated circuit that can perform the activities of sinusoidal signal generation using Direct Digital Synthesis and phase angle extraction of the detection luminescence signal from the sensor films using Discrete Fourier Transform. For O2 sensing, the sensors operate on the measurement of excited-state emission intensity of O2-sensitive luminophores tris(4,7-diphenyl-1,10- phenanthroline) ruthenium(II) ([Ru(dpp)3]2+) encapsulated in sol-gel derived xerogel thin-films. For the compact luminescent sensor microsystem, we incorporate a polymeric optical filter that is made with polydimethylsiloxane (PDMS) that is mixed with color die Sudan-II. The surface of the PDMS filter is molded to incorporate arrays of pyramidal microstructures that serve to focus the optical sensor signals on to the photodetectors. The xerogel sensor arrays are contact printed on top of the PDMS pyramidal lens-like microstructures. The CMOS imager uses a 32x32 (1024 elements) array of active pixel sensors and each pixel includes a high-gain phototransistor to convert the detected optical signals into electrical currents. Correlated double sampling circuit, pixel address, digital control and signal integration circuits are also implemented on-chip. The CMOS imager data is read out as a serial coded signal. The developed CMOS sensor microsystems provide a useful platform for the development of miniaturized, analytically reliable, and accurate optical chemical gaseous and aqueous sensors.Dans cette thèse, nous présentons deux systèmes pour détecter l'oxygène gazeux (O2). Tout d'abord, nous décrivons un microsystème compact à senseur luminescent qui est basée sur l'intégration directe d'éléments de senseur avec un filtre optique polymère qui est placé sur un imageur circuits intégrés (CI) à faible énergie de type Complementary metal oxide semi-conductor (CMOS). Le second système est un système portatif qui permet de détecter la différence de phase fluorométrique. Ce système est basé sur un circuit intégré à puce unique qui permet de générer des signaux sinusoïdal en utilisant la synthèse directe de signaux digitaux et l'extraction de l'angle de phase du signal luminescent, provenant des films du senseur, en utilisant des transformées de Fourier discrète sur ce signal. Pour la détection du dioxygène, les senseurs mesure l'intensité d'émission des luminophores tris (4,7-diphényl-1, 10 - phénanthroline) ruthénium (II) ([Ru(dpp)3]2+) à l'état excité encapsulés dans des sol-gel provenant de micro film xérogel. Le microsystème compact à senseur luminescent comprend un filtre optique polymère à base de polydiméthylsiloxane (PDMS), qui est mélangée avec le colorant Soudan-II. La surface du filtre PDMS est moulée pour ainsi incorporer les réseaux de microstructures pyramidales qui servent à concentrer les signaux des senseurs optiques sur les photodétecteurs. Les réseaux de senseur à base de xérogel sont imprimés par contact sur le dessus des microstructures PDMS pyramidales qui agissant comme des lentilles. L'imageur CMOS utilise une matrice de 32x32 (1024 éléments) servant de pixels actifs et chaque un de ces pixels comporte un phototransistor à gain élevé pour convertir les signaux détectés optiques en courants électriques. La corrélation de circuit d'échantillonnage double, l'adresse de pixel, et les circuits de commande numérique d'intégration de signaux sont également résolue par la puce. Les données sont lues par l'imageur en tant que signaux codé en série. Les capteurs CMOS fournissent une plateforme utile pour le développement des systèmes miniaturisés pour l'analyse fiable et précis des composantes chimiques gazeuse et aqueuse par des moyens optiques.
12
Camenzind, Kathy(Katherine A. ). "Non-contact voltage monitoring of three-phase power cables." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127909.
Full textAbstract:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 117-119).
Non-contact voltage monitoring involves continuously measuring conductor voltages without contacting the conductors. This thesis explores several methods of using parasitic capacitive coupling to monitor AC voltages in three-phase power cables. Using an existing sensor architecture, three-phase line voltages are accurately reconstructed through intrusive calibration techniques. Experimental results are presented for measuring 60 Hz line voltages using high-frequency calibration. This thesis also describes a new method of voltage monitoring, presenting a new circuit designed to monitor line-line voltages without requiring intrusive control of or injection onto the line voltages during calibration. Analysis and simulation of this system is shown, demonstrating accurate reconstruction for reasonably balanced line-line voltages.
by Kathy Camenzind.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
13
Holmgren, Hanna. "Modelling of Moving Contact Lines in Two-Phase Flows." Doctoral thesis, Uppsala universitet, Avdelningen för beräkningsvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329059.
Full textAbstract:
Moving contact line problems appear in many natural and industrial processes. A contact line is formed where the interface between two immiscible fluids meets a solid wall. Examples from everyday life include raindrops falling on a window and water bugs resting on water surfaces. In many cases the dynamics of the contact line affects the overall behavior of the system. Industrial applications where the contact line behavior is important include gas and oil recovery in porous media, lubrication, inkjet printing and microfluidics. Computer simulations are fundamental tools to understand and predict the behavior. In this thesis we look at numerical simulations of dynamic contact line problems. Despite their importance, the physics of moving contact lines is poorly understood. The standard Navier-Stokes equations together with the conventional no-slip boundary condition predicts a singularity in the shear stresses at the contact line. Atomistic processes at the contact line come into play, and it is necessary to include these processes in the model to resolve the singularity. In the case of capillary driven flows for example, it has been observed that the microscopic contact line dynamics has a large impact on the overall macroscopic flow. In Paper I we present a new multiscale model for numerical simulation of flow of two immiscible and incompressible fluids in the presence of moving contact points (i.e. two-dimensional problems). The paper presents a new boundary methodology based on combining a relation between the apparent contact angle and the contact point velocity, and a similarity solution for Stokes flow at a planar interface (the analytic Huh and Scriven velocity). The relation between the angle and the velocity is determined by performing separate microscopic simulations. The classical Huh and Scriven solution is only valid for flow over flat walls. In Paper II we use perturbation analysis to extend the solution to flow over curved walls. Paper III presents the parallel finite element solver that is used to perform the numerical experiments presented in this thesis. Finally, the new multiscale model (presented in Paper I) is applied to a relevant microfluidic research problem in Paper IV. For this problem it is very important to have a model that accurately takes the atomistic effects at contact lines into account.
14
Rhodes, Nicholas Peter. "Platelet interactions and contact phase activation on polymeric catheters." Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317216.
Full textAbstract:
There are many conflicting views about the blood-response to polymeric materials. In order to be satisfied that a material performs appropriately when used as a device in contact with blood it must be evaluated under relevant conditions. Central venous catheters suffer from problems related to thrombosis and embolism since they are implanted for very long periods of time within the vascular system. The aim of this study was to evaluate the most appropriate method for assessing catheter thrombogenicity, establish data for a number of relevant parameters and correlate these findings with various physico-chemica1 characteristics of the materials. Accordingly, a dynamic model was developed which allowed the assessment of platelet adhesion by measurement of "Cr-labelled platelets and platelet a-granule and lysosomal secretion by flow cytometry, after labelling with anti- GMPl40 and anti-GPS3 antibodies, in whole blood after the perfusion of the blood along the tubing at physiologically relevant shear rates (up to 1000 s") at 37OC. In addition, contact phase activation was assessed by measuring the time taken for an aliquot of plateletfree plasma to clot after contact with catheter material (partial thromboplastin time or P'IT) and the ability of the materials to cause factor XII activation by measuring the quantity of FXIIa-Cl-Inh complexes formed by enzyme-linked immunosorbent assay after the contact of platelet-free plasma with catheter tubing. An attempt was made at finding the identity of the proteins adsorbed onto silicone using a number of electrophoretic techniques. The ability of the materials to cause haemolysis and the cytotoxicity of an extract derived from the materials after SO days incubation in PBS including the identification of these potential leachables by supercritical fluid extraction was also investigated. In addition, these data were discussed in relation to parameters of surface roughness, as viewed by SEM and the ratio of hard and soft segments appearing at the material surface by XPS. It was found that significant differences could be detected in (i) platelet adhesion, where Pellethane was shown to have poor performance; (ii) a-granule release, where all the polyurethanes displayed better performance than any of the other materials and (iii) lysosomal granule release where most materials fared similarly, except for glass which was much worse. Silicone was shown to be best in the PIT assay, Pellethane worst. Surprisingly, no correlation was found with these results and those from FXIIa assay, where Desmopan and Davathane were highly active. New and important data on the initial activation kinetics and the ability of materials to activate factor XII are shown. Silicone produced the greatest haemolysis, PVC the greatest extract toxicity. No correlation was found between the physico-cbemical data and any of the biocompatibility data.
15
Hall, David Wesley. "Benzyl alcohol oxidation in a phase-transfer catalytic microporous contactor reactor." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251004.
Full text
16
Belchev, Borislav Stefanov, and University of Lethbridge Faculty of Arts and Science. "Deformation quantization for contact interactions and dissipation." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, c2010, 2010. http://hdl.handle.net/10133/2490.
Full textAbstract:
This thesis studies deformation quantization and its application to contact interactions
and systems with dissipation. We consider the subtleties related to quantization
when contact interactions and boundaries are present. We exploit the idea that discontinuous
potentials are idealizations that should be realized as limits of smooth
potentials. The Wigner functions are found for the Morse potential and in the proper
limit they reduce to the Wigner functions for the infinite wall, for the most general
(Robin) boundary conditions. This is possible for a very limited subset of the
values of the parameters -- so-called fine tuning is necessary. It explains why Dirichlet
boundary conditions are used predominantly. Secondly, we consider deformation
quantization in relation to dissipative phenomena. For the damped harmonic oscillator
we study a method using a modified noncommutative star product. Within this
framework we resolve the non-reality problem with the Wigner function and correct
the classical limit.iii, 188 leaves ; 29 cm
17
Chauvin, Martin. "Effet Josephson dans les contacts atomiques / The Josephson Effect in Atomic Contacts." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00107465.
Full textAbstract:
L'effet Josephson apparaît lorsqu'une structure de couplage faible établit une cohérence de phase entre deux supraconducteurs. Une théorie unificatrice de cet effet est apparue dans les années 90 dans le cadre de la physique mésoscopique. Basée sur deux concepts fondamentaux, celui de canaux de conduction et celui de réflexion d'Andreev, elle prédit la relation courant-phase pour la structure de couplage de base : un canal unique de transmission arbitraire.Cette thèse illustre ce point de vue mésoscopique par des expériences sur des contacts atomiques supraconducteurs. En particulier, nous avons étudié le pic de supercourant près de la tension nulle, avons mis en évidence les courants Josephson alternatifs dans un contact polarisé par une tension constante (résonances de Shapiro et réflexions multiples d'Andreev assistées par des photons) et avons mesuré directement la relation courant-phase.
18
Jackson, Monique I. "The mechanics of the table contact phase of gymnastics vaulting." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6330.
Full textAbstract:
A computer simulation model of the table contact phase of gymnastics vaulting was developed to gain an understanding of the mechanics of this phase of the vault. The model incorporated a gymnast and a vaulting table, and used a novel two-state contact phase representation to simulate the interaction between these two bodies during the table contact phase. The gymnast was modelled in planar form using seven segments, with torque generators acting at the wrist, shoulder, hip and knee joints. The model also allowed for shoulder retraction and protraction, displacement of the glenohumeral joint centre and flexion/extension of the fingers. The table was modelled as a single rigid body that could rotate. The model was personalised to an elite gymnast so that simulation outputs could be compared with the gymnast's performance. Kinematic data of vaulting performances were obtained using a optoelectronic motion capture system. Maximal voluntary joint torques were also measured using an isovelocity dynamometer, and a torque - angle - angular velocity relationship was used to relate joint torques to joint angles and angular velocities. A set of model system parameters was determined using a gymnast-specific angle-driven model by matching four simulations to their respective performances concurrently. The resulting parameters were evaluated using two independent trials, and found to be applicable to handspring entry vaults. The torque-driven model was successfully evaluated, and shown to produce realistic movements, with mean overall differences between simulations and recorded performances of 2.5% and 8.6% for two different handspring entry vaults. The model was applied to further understanding of the mechanics of the table contact phase of gymnastics vaulting. Optimisation showed that there was limited potential (1.3%) for the gymnast to improve performance through technique changes during the table contact phase. However, with additional changes in configuration at table contact post-flight rotation could be increased by 9.8% and post-flight height could be increased by 0.14m. Angular momentum was found to always decrease during the table contact phase of the vault, although the reductions were less when maximising post-flight rotation.
19
Ge, Daibin Gogotsi Yury. "TEM investigation of contact loading induced phase transformation in silicon /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/280.
Full text
20
Maroo, Shalabh Chandra. "Nano-scale transport mechanisms associated with three-phase contact lines." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0041071.
Full text
21
Thierry-Jebali, Nicolas. "Caractérisations et modélisations physiques de contacts entre phases métalliques et Nitrure de Gallium semi-conducteur." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00744661.
Full textAbstract:
Les composés III-N, et le Nitrure de Gallium (GaN) en particulier, sont devenus des matériaux semi conducteurs importants pour l'ensemble de l'humanité. Depuis la fin des années 1990, ils ont permis le développement de composants électroluminescents fiables, diodes LED et diodes laser, qui constituent une solution de remplacement à rendement énergétique amélioré par rapport aux composants à incandescence. Il est possible qu'ils jouent aussi un rôle dans les nouvelles générations de composants pour l'électronique de puissance. Lors du développement des composants, des recherches expérimentales permettent de trouver assez rapidement des solutions pour réaliser les briques technologiques indispensables, mais le temps manque pour comprendre les mécanismes physiques mis en jeu. Nos travaux ont eu pour objectif d'approfondir la compréhension de l'influence de la structure physico-chimique sur les propriétés électriques des contacts ohmiques et Schottky sur GaN de type N.
22
Al-Muhammedawi, Hameed B. Mahood. "Experimental and theoretical investigation of a three-phase direct contact condenser." Thesis, University of Surrey, 2016. http://epubs.surrey.ac.uk/809827/.
Full textAbstract:
In the present work, for the first time, an experimental and theoretical study of the heat transfer characteristics of a bubble type three-phase direct contact condenser has been carried out. The experiments were conducted using a Perspex column of 70 cm in total height and 4 cm inner diameter, as a direct contact condenser. The active column height throughout the experiments was 48 cm. Pentane vapour at three different initial temperatures (40℃, 43.5℃ and 47.5℃), was used as the dispersed phase while tap water at a constant temperature (19℃) was used as the continuous phase. Seven different dispersed phase mass flow rates and five different continuous phase mass flow rates were tested. The experiments considered the transient temperature distribution along the direct contact condenser, the steady-state temperature distribution, the volumetric heat transfer coefficient, the heat transfer rate per unit volume and the holdup ratio. Also, the efficiency and capital cost of the direct contact condenser were estimated, and the heat transfer of the three-phase direct contact condenser during flooding was studied. Theoretical models describing the direct contact condenser were developed. These models included the transient temperature distribution, the steady-state temperature distribution and the volumetric heat transfer coefficient. These models implicitly involved new derivations for the surface heat transfer coefficient, the two-phase bubble size, the relative velocity of two-phase bubbles, the drag coefficient and the added mass of the two-phase bubble. All expressions were derived analytically except for the transient temperature distribution along the condenser which was found numerically, using MATLAB. The results showed that the mass flow rate ratio has a significant effect on the heat transfer characteristics of the condenser, while the initial temperature of the dispersed phase has only a slight effect. The models developed were fitted the experimental data well.
23
Pauly, Fabian. "Phase-coherent electron transport through metallic atomic-sized contacts and organic molecules." [S.l. : s.n.], 2007. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000007521.
Full text
24
Radulescu, Fabian. "Pd-Ge ohmic contact on to GaAs formed by the solid phase epitaxy of Ge : a microstructure study /." Full text open access at:, 2000. http://content.ohsu.edu/u?/etd,226.
Full text
25
Hili, Joslyn. "Film forming and friction properties of single phase and two phase lubricants in high-speed rolling/sliding contact." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7133.
Full textAbstract:
Single-phase (neat oil) and two-phase (oil-in-water emulsions) lubricants are widely used in metal forming processes, where speeds as high as 20 m s-1 are reached. Most of the previous work done on both neat oil and on oil-in-water emulsions has focused on low speed behaviour (below 5 m s-1) and, as a result, the low speed behaviour of oil-in-water emulsions is well understood. Under these conditions, the lubricating oil film is composed predominantly of oil and the thickness of the film is similar to that for neat oil. However, the behaviour at high speed is entirely different. No experimental film thickness and friction results at speeds above 5 m s-1 are available for neat oil and only one study (Zhu et al., 1994) has reported the film thickness behaviour of oil-in- water emulsions above this speed whereas no friction measurements at speeds above 3.5 m s-1 have been carried out using oil-in-water emulsions. Consequently, to date, the behaviour of neat oil and the relation of emulsion composition to film forming ability at high rolling speeds could not be described. This project is aimed at investigating the mechanism of film formation and the film forming and friction properties of single-phase and two-phase lubricants in high speed rolling/sliding contacts. An EHD test rig was modified to measure film thickness and friction of oil-inwater emulsions in very high speed, rolling/sliding conditions (up to a mean rolling speed of 20 m s-1). Ultrathin film interferometry was used to investigate film thickness while infrared temperature mapping of the contact was used to obtain maps showing the rate of heat input into the surface, from which shear stresses and friction could be calculated. Light induced fluorescence was also employed using a water-soluble and an oil-soluble dye to allow visualization of the contact (at low speeds) and help in investigating the composition of the entrained lubricant at these high speeds. Results showed that, for neat oils, the major factor affecting the film formed at high speed is shear heating. For dilute emulsions at the highest speeds, the film thickness and friction are close to those obtained with pure water. More concentrated emulsions give slightly higher film thicknesses. A comparison of the results with earlier theoretical predictions was carried out. Together with the fluorescence results, this suggested that high speed leads to the entrainment of a micro-emulsion.
26
Seviour, Robert Francis. "Quasiclassical studies of phase-coherent transport in superconducting nanostructures." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310577.
Full text
27
Irvine, Linda. "Blood - biomaterial interactions : investigations into granulocyte elastase release and contact phase activation." Thesis, University of Strathclyde, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332481.
Full text
28
Kuoch, Kevin. "Processus de contact avec ralentissements aléatoires : transition de phase et limites hydrodynamiques." Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05S020/document.
Full textAbstract:
Dans cette thèse, on étudie un système de particules en interaction qui généralise un processus de contact, évoluant en environnement aléatoire. Le processus de contact peut être interprété comme un modèle de propagation d'une population ou d'une infection. La motivation de ce modèle provient de la biologie évolutive et de l'écologie comportementale via la technique du mâle stérile, il s'agit de contrôler une population d'insectes en y introduisant des individus stérilisés de la même espèce: la progéniture d'une femelle et d'un individu stérile n'atteignant pas de maturité sexuelle, la population se voit réduite jusqu'à potentiellement s'éteindre. Pour comprendre ce phénomène, on construit un modèle stochastique spatial sur un réseau dans lequel la population suit un processus de contact dont le taux de croissance est ralenti en présence d'individus stériles, qui forment un environnement aléatoire dynamique. Une première partie de ce document explore la construction et les propriétés du processus sur le réseau Z^d. On obtient des conditions de monotonie afin d'étudier la survie ou la mort du processus. On exhibe l'existence et l'unicité d'une transition de phase en fonction du taux d'introduction des individus stériles. D'autre part, lorsque d=1 et cette fois en fixant l'environnement aléatoire initialement, on exhibe de nouvelles conditions de survie et de mort du processus qui permettent d'expliciter des bornes numériques pour la transition de phase. Une seconde partie concerne le comportement macroscopique du processus en étudiant sa limite hydrodynamique lorsque l'évolution microscopique est plus complexe. On ajoute aux naissances et aux morts des déplacements de particules. Dans un premier temps sur le tore de dimension d, on obtient à la limite un système d'équations de réaction-diffusion. Dans un second temps, on étudie le système en volume infini sur Z^d, et en volume fini, dans un cylindre dont le bord est en contact avec des réservoirs stochastiques de densités différentes. Ceci modélise des phénomènes migratoires avec l'extérieur du domaine que l'on superpose à l'évolution. À la limite on obtient un système d'équations de réaction-diffusion, auquel s'ajoutent des conditions de Dirichlet aux bords en présence de réservoirsIn this thesis, we study an interacting particle system that generalizes a contact process, evolving in a random environment. The contact process can be interpreted as a spread of a population or an infection. The motivation of this model arises from behavioural ecology and evolutionary biology via the sterile insect technique ; its aim is to control a population by releasing sterile individuals of the same species: the progeny of a female and a sterile male does not reach sexual maturity, so that the population is reduced or potentially dies out. To understand this phenomenon, we construct a stochastic spatial model on a lattice in which the evolution of the population is governed by a contact process whose growth rate is slowed down in presence of sterile individuals, shaping a dynamic random environment. A first part of this document investigates the construction and the properties of the process on the lattice Z^d. One obtains monotonicity conditions in order to study the survival or the extinction of the process. We exhibit the existence and uniqueness of a phase transition with respect to the release rate. On the other hand, when d=1 and now fixing initially the random environment, we get further survival and extinction conditions which yield explicit numerical bounds on the phase transition. A second part concerns the macroscopic behaviour of the process by studying its hydrodynamic limit when the microscopic evolution is more intricate. We add movements of particles to births and deaths. First on the d-dimensional torus, we derive a system of reaction-diffusion equations as a limit. Then, we study the system in infinite volume in Z^d, and in a bounded cylinder whose boundaries are in contact with stochastic reservoirs at different densities. As a limit, we obtain a non-linear system, with additionally Dirichlet boundary conditions in bounded domain
29
Alkazaz, Malaz. "Synthèse de films minces de phases MAX par recuit thermique - Application à la formation de contacts ohmiques sur SiC." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2328/document.
Full textAbstract:
Les phases MAX sont des carbures ou nitrures ternaires dont les propriétés sont généralement décrites comme la combinaison exceptionnelle des meilleures propriétés des métaux et des céramiques. Sous forme de couches minces, ces matériaux sont prometteurs en tant que contact ohmique sur des substrats de SiC pour la microélectronique de puissance. Des approches originales dédiées à l'obtention de films minces épitaxiés des phases MAX Ti2AlN, Ti3SiC2 et Ti3(Si,Ge)C2 sont développées dans ce travail. Des recuits à 750°C de systèmes multicouches (Ti+Al)/AlN permettent ainsi de former des couches de Ti2AlN fortement texturées sur des substrats de SiC ou Al2O3. La seconde approche consiste à recuire à 1000°C des couches de TixAly ou TixGey, déposés sur 4H-SiC, pour obtenir des films minces épitaxiés de Ti3SiC2 et Ti3(Si,Ge)C2. Ces derniers présentent les caractéristiques d'un contact ohmique sur SiCMAX phases are a family of ternary carbides or nitrides which properties are generally described as an exceptional combination of the best properties of metals and ceramics. Thin films of MAX phases being considered as good candidates for ohmic contacts on SiC substrates for power microelectronics devices, thin films of Ti2AlN and Ti3(Si,Ge)C2 were synthesized by using original approaches. Highly textured Ti2AlN thin films were so obtained by thermal annealing at 750°C of (Ti+Al)/AlN multilayers whereas epitaxial thin films of Ti3SiC2 on 4H-SiC were achieved after an annealing at 1000°C of TixAly or TixGey layers. Good ohmic contact behaviors of Ti3SiC2 layers were confirmed in this work whereas Ti2AlN thin films behave as Schottky barriers
30
Can, Van Hao. "Processus de contact sur des graphes aléatoires." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4709/document.
Full textAbstract:
Le processus de contact est l'un des systèmes de particules en interaction les plus étudiés. Il peut s'interpréter comme un modèlepour la propagation d'un virus dans une population ou sur un réseau. L'objectif de cette thèse est d'étudier la relation entre la structure locale du réseau et le comportement global du processus sur le réseau tout entier.Le cadre typique dans lequel on se place est celui d’une suite de graphes aléatoires $(G_n)$ convergeant localement vers un graphe limite $G$.On étudie alors le comportement asymptotique du temps d’extinction $tau_n$ du processussur $G_n$; lorsqu’initialement tous les individus sont infectés. Nous montrons sur plusieurs exemples qu’il existe unetransition de phase lorsque $lambda$ - le taux d'infection du processus - traverse une valeur critique $ lambda_c (G)$, qui ne dépend que de $G$.Plus précisément, pour certains modèles de graphes aléatoires comme le modèle de configuration, le graphe d'attachement préférentiel, le graphe géométrique aléatoire, le graphe inhomogène, nous montrons que $ tau_n $ est d'ordre soit logarithmique soit exponentiel; selon que $ lambda$ est soit inférieur ou supérieur à $lambda_c (G) $.De plus, dans certains cas, nous montrons des résultats de métastablité: en régime sur-critique, $ tau_n $ divisé par son espérance converge en loi vers une variable aléatoire exponentielle de moyenne $1$, et la densité des sites infectés reste stable (et non nulle) sur une période de temps d’ordre typiquement $tau_n$The contact process is one of the most studied interacting particle systems and is also often interpreted as a model for the spread of a virus in a population or a network. The aim of this thesis is to study the relationship of the local structure of the network and the global behavior of the contact process (the virus) on the whole network. Let $(G_n)$ be a sequence of random graphs converging weakly to a graph $G$. Then we study $tau_n$, the extinction time of the contact process on $G_n$ starting from full occupancy. We prove in some examples that there is a phase transition of $tau_n$ when $lambda$ - the infection rate of the contact process crosses a critical value $lambda_c(G)$ depending only on $G$. More precisely, for some models of random graphs, such as the configuration model, preferential attachment graph, random geometric graph, inhomogeneous graph, we show that $tau_n$ is of logarithmic (resp. exponential) order when $lambda < lambda_c(G)$ (resp. $lambda < lambda_c(G)$). Moreover, in some cases we also prove metastable results: in the super-critical regime, $tau_n$ divided by its expectation converges in law to an exponential random variable with mean $1$, and the density of the infected sites is stable for a long time
31
Abou, Hamad Valdemar. "Elaboration et caractérisation de contacts électriques à base de phases MAX sur SiC pour l'électronique haute température." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI079.
Full textAbstract:
Les applications de puissance dans lesquelles la température ambiante est élevée, provoquent l’augmentation de la température dans les dispositifs électroniques. De ce fait, il est important de développer les dispositifs électroniques pour pouvoir supporter des densités de courant et de puissance plus élevées. Dans cette thèse, nous avons pour objectif de jeter les bases d’une technologie en totale rupture avec celles existantes pour la fabrication d’une nouvelle génération de contacts électriques à base de Ti3SiC2, stables, fiables et reproductibles sur le Carbure de Silicium pour les applications à très hautes températures (300 – 600ºC). Deux méthodes d’élaborations seront étudiées, dans cette thèse, pour synthétiser le Ti3SiC2. La première est par voie réactionnelle, et la deuxième approche consistera à utiliser la technique Pulsed Laser Deposition (PLD), en utilisant une cible de Ti3SiC2. Le but est de développer des contacts ohmiques de bonne qualité. Des caractérisations physico-chimiques, électriques (TLM) et mécaniques (W-H et RSM) ont été effectuées sur les contacts de Ti3SiC2. Ces échantillons ont subi un vieillissement, à 600ºc pendant 1500h sous Argon, dans le but d’étudier la stabilité et la fiabilité des contacts électriques aux hautes températures. Les résultats des caractérisations ont montré que la fiabilité et la stabilité chimique entre Ti3SiC2 et SiC ont permis aux contacts de garder le comportement ohmique avec une faible résistivité électrique et un bon comportement mécanique, même après 1500h de vieillissement. De plus, les simulations réalisées ont servi à déterminer l’effet des ITR sur la dissipation de la chaleur et sur les contraintes mécaniques exercées sur une diode PN haute puissance. Dans cette thèse, nous avons montré qu’un contact ohmique, à base de Ti3SiC2, peut rester stable et fiable sur un substrat 4H-SiC, dans des températures allant jusqu’à 600ºCPower applications in which the ambient temperature is high, cause the increase of temperature in electronic components. Therefore, it is important to develop electronic devices that are able to withstand high current and high-power densities. In this thesis, our objective is to lay the foundations of a new technology for the manufacture of a new generation of Ti3SiC2 MAX phase-based electrical contacts, stable, reliable and reproducible on Silicon Carbide for very high temperature applications (300 - 600ºC). To synthesize Ti3SiC2 on SiC, two elaboration methods were studied in this thesis. The first approach is a reaction method, and the second approach consists on using a Ti3SiC2 target via the Pulsed Laser Deposition (PLD) technique. Our goal is to develop a good quality ohmic contacts. Physico-chemical, electrical (TLM) and mechanical (W-H and RSM) characterizations were performed on the Ti3SiC2 contacts. These samples underwent a thermal aging test at 600°C for 1500 hours under Argon, in order to study the stability and reliability of the electrical contacts at high temperatures. The obtained results showed that the reliability and the chemical stability between Ti3SiC2 and SiC allowed the contacts to keep an ohmic behavior with low electrical resistivity, in addition to a good mechanical behavior, even after 1500 hours of aging at 600ºC. Furthermore, the thermomechanical simulations performed were used to determine the effects of Interfacial Thermal Resistances on the heat dissipation and the mechanical stresses exerted on a high power PN diode. In this thesis, we have shown that an ohmic contact, based on Ti3SiC2, can remain stable and reliable on a 4H-SiC substrate, in temperatures up to 600ºC
32
Lapkin, Alexei A. "Porous membrane phase contactor for gas-liquid homogeneous catalytic reactions : direct hydration of propene." Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760743.
Full text
33
Seger, Johan. "Interaction of Ni with SiGe for electrical contacts in CMOS technology." Doctoral thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-111.
Full text
34
Lino, Ulysses de Ribeiro Augusto. "Compositional and phase behaviour of gas condensate multiple-contact processes with different injectants." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286459.
Full text
35
Chung, Lip Yong. "Biochemical responses of the skin in the pre-immunologic phase of contact allergy." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314737.
Full text
36
Budnitzki, Michael. "Constitutive modeling and experimental investigations of phase transitions in silicon under contact loading." TU Bergakademie Freiberg, 2014. https://tubaf.qucosa.de/id/qucosa%3A70886.
Full textAbstract:
Modeling the interaction of a silicon (Si) surface with a pointed asperity is a crucial step towards the understanding of several phenomena related to machining of this important semiconductor.
If subjected to pressure or contact loading, Si undergoes a series of stress-driven phase transitions accompanied by large volume changes.
We developed a finite deformation constitutive model that captures the semiconductor-to-metal (cd-Si ➙ β-Si) and metal-to-amorphous (β-Si ➙ a-Si) transitions within the framework of thermodynamics with internal variables.
The model was implemented as a user material subroutine for the finite element code Abaqus/Std. in analogy to pressure sensitive, rate independent, non-associated, non-smooth multisurface plasticity. Material parameters were identified from indentation load-displacement curves in (111)-Si using a Berkovich indenter tip.
The constitutive model was verified by successfully predicting the load-displacement curves for different indenters, the residual surface profile, as well as the size and shape of the transformation zone under the indenter tip as compared to TEM results.
37
Bond, Nicole. "Inorganic Phase Characterization, Corrosion Modelling and Refractory Selection for Direct Contact Steam Generation." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41951.
Full textAbstract:
Technological advances are required to reduce the environmental impact of the Canadian oil sands. Oxy-direct contact steam generation (DCSG) is one such way to move toward this goal, by producing steam for oil sands operations with a higher efficiency, lower fresh water consumption, and lower CO₂ emissions than traditional once-through steam generators. For DCSG, untreated process water, which may contain a variety of inorganics, is injected directly into the combustor to produce steam. The inorganic material that may deposit in the combustor as a result of that process water was studied for two applications of DCSG in the Canadian oil sands: (1) steam assisted gravity drainage (SAGD), and (2) mining, in order to inform refractory material selection for the combustor.
For SAGD, free water knockout tank discharge was used as the process water and resulting deposits in the combustor were predicted to be high in silica and sodium oxide, and enriched with sodium sulfate as the potential operating temperature of the combustor was lowered. At the lowest combustor temperature studied (1075 °C), a low viscosity molten salt phase rich in sodium sulfate was also expected to form. It is recommended that the operating temperature of the combustor be as low as possible while still remaining above the formation temperature of this potentially corrosive salt phase, thus in the range of 1200-1250 °C in the regions of the wall where solids are expected to impact it. A number of candidate refractory materials were assessed through corrosion models and corrosion tests. Aluminosilicate based refractory materials should be avoided due to their potential reaction with the sodium oxide in the slag. This can result in formation of low density solid phases such as nepheline, which can damage the refractory material through volume expansion. Of the three refractories tested, mullite zirconia yielded the worst corrosion resistance, with dissolution of the binder phase and full penetration by sodium oxide. Chromia corundum yielded the greatest resistance to penetration of the materials tested, though some dissolution of the chromia in the slag was still evident. Further investigation into high chrome refractory materials is recommended for this application.
For mining applications, mature fine tailings water (MFT) combined with an oil sands processing water (OPW) was used as the process water for injection. Due to the high liquidus of the resulting inorganic deposits, co-injection of a fluxant is recommended to reduce the liquidus and viscosity of the resulting slag solution, thereby maximizing the combustor efficiency by reducing the required operating temperature. Dolomite was identified as the optimal fluxant, at a concentration of 20 wt % CaMgO₂ in the fluxed slag. This mixture was found to have a viscosity of just under 25 Pa·s at 1300 °C, making this a good operating point for the DCSG combustor, as the slag should flow freely and not cause plugging. The corrosion resistance of several candidate refractory materials was assessed through modelling and laboratory scale testing for both the fluxed and non-fluxed slag. Similar to the results for SAGD, of the refractories tested, chromia corundum offered the greatest resistance to penetration, while mullite zirconia was most deeply penetrated by sodium oxide. Again, a chromia-containing refractory is recommended for further investigation for use in the DCSG combustor. Other candidate refractories investigated in the models that warrant testing are chromia spinel and magnesium aluminate spinel. For future work, further corrosion tests at multiple durations are recommended, as well as characterization of refractory samples from CanmetENERGY’s DCSG pilot plant and quantification of the effects of slag exposure on the mechanical strength of the refractory materials.
38
Soulé, Paul. "Étude des Bords des Phases de l’Effet Hall Quantique Fractionnaire dans la Géométrie d’un Contact Ponctuel Quantique." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112215/document.
Full textAbstract:
Dans cette thèse, je présente une étude que j'ai réalisée à l'université Paris-sud sous la direction de Thierry Jolicœur sur les phases des Hall Quantiques Fractionnaire (HQF) dans la géométrie du cylindre.Après une rapide introduction dans le premier chapitre, je présente dans le second quelques concepts de base de l'effet HQF et j'introduit certains aspects de la géométrie cylindrique.Le chapitre 3 est consacré à l'étude de la limite du cylindre fin, c'est à dire lorsque la circonférence du cylindre est de l'ordre de quelques longueurs magnétiques. Dans cette limite, on sait que la fonction d'onde de Laughlin au remplissage 1/q se réduit à un cristal unidimensionnel, où une orbitale sur q est occupée. Dans le but d'étudier un limite intermédiaire, nous conservons les quatre premiers termes du développement de l’Hamiltonien lorsque la circonférence est petite devant la longueur magnétique. On trouve alors une expression exacte de l'état fondamental au moyen d'opérateurs de "squeezing" ou de produits de matrices. Nous trouvons également une écriture similaire pour les quasi- trous, les quasi-électron et la branche magnétoroton.Dans les chapitres 4 et 5, je me concentre sur l'étude des excitations de bord chirales des phases de HQF. Je présente une étude microscopique de ces états de bord dans la géométrie du cylindre, lorsque les quasi-particules peuvent passer d'un bord à l'autre par effet tunnel. J'étudie d'abord dans le chapitre 4 la phase de HQF principale dont l'état fondamental est bien décrit par la fonction d'onde de Laughlin. Pour un échelle d'énergie plus faible que le gap du volume, le théorie effective est donnée par un fluide d'électrons unidimensionnel bien particulier : un liquide de Luttinger chiral. À l'aide de diagonalisations numériques exactes, nous étudions le spectre des états de bord formé de le combinaison des deux bord contre-propageant sur chacun des cotés du cylindre. Nous montrons que les deux bords se combinent pour former un liquide de Luttinger non-chiral, où le terme de courant reflète le transfert de quasi-particules entre les bords. Cela nous permet d'estimer numériquement les paramètre de Luttinger pour un faible nombre de particules, et nous trouvons une valeur cohérente avec la théorie de X. G. Wen.J'analyse ensuite dans le chapitre 5 les modes de bord des phases de HQF au remplissage 5/2. À partir une construction basée sur la Théorie des Champs Conformes (TCC), Moore et Read (Nucl. Phys. B, 1991) ont proposé que la physique essentielle de cette phase soit décrite par un état apparié de fermion composites. Une propriété importante de cet état est que ses excitations émergentes permutent sous une statistique non-abéliène. Lorsqu'elles sont localisées sur les bords, ces excitations sont décrites par un boson chiral et un fermion de Majorana. Dans la géométrie du cylindre, nous montrons que le spectre des excitations de bord est fomé des tours conformes du modèle IsingxU(1). De plus, par une méthode Monte-Carlo, nous estimons les différentes dimensions d'échelle sur des grands systèmes (environ 50 électrons), et nous trouvons des valeurs en accord avec les prédictions de la TCC.Dans le dernier chapitre de ce manuscrit, je présente un travail que j'ai réalisé à UBC (Vancouver) en collaboration avec Marcel Franz sur les phase de Hall quantiques de spin induites dans le graphène par des adatomes. Dans ce système, les adatomes induisent un couplage spin-orbite sur les électrons des la feuille de graphène et introduisent du désordre qui est susceptible de détruire le gap spectral. Nous montrons dans ce chapitre que le gap spectral est préservé lorsque des valeurs réalistes de paramètres sont usités. De plus, au moyen de calculs analytiques à base énergie et de diagonalisations numériques exactes, nous identifions un signal caractéristique dans la densité d'états locale mettant en évidence la présence d'un gap topologique. Ce signal pourrait être observé au moyen d'un microscope à effet tunnelI present in this thesis a study that I did in the university Paris-sud under the supervision of Thierry Jolicœur onto Fractional Quantum Hall (FQH) phases in the cylinder geometry. After a short introduction in the first chapter, I present some basic concept relative to the FQH effect in the second one and introduce some essential features relative to the cylinder geometry, useful for the chapters 3, 4, and 5. The chapter 3 is dedicated to the study of the thin cylinder limit, i.e. when the circumference of the cylinder is of the order of a few magnetic length. In this limit, it is known that the Laughlin wave function at the filling factor 1/q is reduced to a one dimensional crystal in the lowest Landau level orbitals where one every q orbitals is occupied. We Taylor expand the Hamiltonian when the circumference is small compare to the magnetic length in order to study an intermediate limit. When only the first four terms of the development are kept, it is possible to find exact representations of the ground state with "squeezing" operators or matrix products. We also find similar representations for quasiholes, quasielectrons and the magnetorton branch. These results have been published in the article Phys. Rev. B 85, 155116 (2012). In the chapter 4 and 5 I focus onto the gapless chiral edge excitations of FQH phases. I present a microscopic study of those edges states in the cylindrical geometry where quasiparticles are able to tunnel between edges. I first study the principal FQH phase at the filling fraction 1/3 whose ground state is well described by the Laughlin wave function in the chapter 4. For an energy scale lower than the bulk gap, the effective theory is given by a very peculiar one dimensional electron fluid localized at the edge: a chiral Luttinger liquid. Using numerical exact diagonalizations, we study the spectrum of edge modes formed by the two counter-propagating edges on each side of the cylinder. We show that the two edges combine to form a non-chiral Luttinger liquid, where the current term reflects the transfer of quasiparticles between edges. This allows us to estimate numerically the Luttinger parameter for a small number of particles and find it coherent with the one predicted by X. G. Wen theory. We published this work in Phys. Rev. B 86, 115214 (2012). I then analyze edge modes of the FQH phase at filling fraction 5/2 in the chapter 5. From a Conformal Field Theory (CFT) based construction, Moore and Read (Nucl. Phys. B, 1991) proposed that the essential physics of this phase is described by a paired state of composite fermions. A striking property of this state is that emergent excitations braid with non-Abelian statistics. When localized along the edge, those excitations are described through a chiral boson and a Majorana fermion. In the cylinder geometry, we show that the spectrum of edge excitations is composed of all conformal towers of the IsingxU(1) model. In addition, with a Monte Carlo method, we estimate the various scaling dimensions for large systems (about 50 electrons), and find them consistent with the CFT predictions.In the last chapter of my manuscript, I present a work that I did in UBC (Vancouver) in collaboration with Marcel Franz onto quantum spin Hall phases in graphene induced by adatoms. In this system, adatoms induce a spin orbit coupling for electrons in the graphene sheet and create some disorder which might be responsible for destruction the spectral gap. We show in this chapter and in the article [Phys. Rev. B 89, 201410(R) (2014)] that the spectral gap remains open for a realistic range of parameters. In addition, with analytical computations in the low energy approximation and numerical exact diagonalizations, we find characteristic signal in the local density of states highlighting the presence of topological gap. This signal might be observed in scanning tunneling spectroscopy experiments
39
Tang-Mu, Wei. "Oxydation photocatalytique d'hydrocarbures cycliques en phase liquide à température ambiante au contact de TiO2." Lyon 1, 1992. http://www.theses.fr/1992LYO10137.
Full textAbstract:
L'oxydation menagee d'hydrocarbures cycliques, satures ou non, a ete realisee a temperature ambiante et en phase liquide par photocatalyse heterogene au contact de tio#2 en utilisant l'oxygene de l'air. Contrairement a certaines methodes d'oxydation ce procede evite la formation de rejets polluants. Les influences de divers parametres sur le regime photocatalytique ont ete determines dans le cas du cyclohexane. La proportionnalite entre l'activite et la masse en dessous d'un seuil correspondant a la saturation d'absorption des photons montre qu'il s'agit d'un phenomene catalytique. L'absence d'influence de la temperature prouve que la reaction n'est pas activee et qu'elle est donc de nature photocatalytique. Les variations de la vitesse avec la concentration initiale de cyclohexane dans l'acetonitrile correspondent a une loi du type langmuir-hinshelwood avec reaction en phase adsorbee entre l'hydrocarbure non dissocie et une espece oxygene activee qui d'apres des etudes anterieures du laboratoire serait monoatomique. La proportionnalite entre la vitesse de reaction et le flux energetique pour les faibles valeurs de ce dernier montre que la reaction est proportionnelle a la concentration en trous positifs formes. Pour les flux plus importants, la variation de la vitesse avec la racine carree de montre que la recombinaison electron-trou peut devenir preponderante. Le produit principal d'oxydation menagee du cyclohexane est la cyclohexanone (selectivite de 85%). Il se forme 3% de cyclohexanol et 12% de co#2. L'isomere le plus abondamment forme a partir du methylcyclohexane est la methyl-3 cyclohexanone (selectivite de 53%). La decaline fournit principalement la decalone-2 (selectivite de 86%). Ces selectivites pourraient s'expliquer par les modes d'adsorption de ces hydrocarbures a la surface de tio#2. Le cyclohexene reagit principalement en position allylique avec formation de 56% de cyclohexanone et 27% de cyclohexenol; il se forme egalement 9% d'epoxyde. La tetraline (tetrahydronaphtalene) s'oxyde en position 1 en formant la tetralone-1 (76%) et le tetralol-1 (23%); la formation de seulement 0,8% co#2 illustre la stabilite introduite par le noyau aromatique. Le dopage cationique substitutionnel de tio#2 et le depot de platine a la surface de ce semiconducteur favorisent les recombinaisons electron-trou et donc inhibent la reaction. En conclusion, ces resultats montrent que la photocatalyse heterogene peut etre une methode interessante pour oxyder selectivement en certaines cetones des hydrocarbures cycliques, satures ou non, en phase liquide
40
Enquebecq, Richard. "Influence des sollicitations de fretting sur le comportement en bruit de phase de contacts HF." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC005.
Full textAbstract:
Suivant les applications, les composants électroniques passifs dont les connecteurs hyperfréquences évoluent dans des environnements vibratoires importants. Les sollicitations vibratoires induisent des micro déplacements qui se traduisent par l’apparition d’un fretting usure sur les contacts. Ces dégradations modifient les propriétés électriques et HF des connecteurs. Dans cette étude doctorale nous nous intéressons en particulier à l’influence du fretting usure sur le bruit de phase. Pour comprendre l’ensemble des mécanismes mis en jeu, une stratégie multi échelle basée sur le développement de 3 bancs d’essais V1, V2, V3 a été mise en place. Il est donc possible d’étudier les phénomènes macro et micro qui se produisent au sein d’un connecteur HF et d’un système composé de plusieurs connecteurs. Plusieurs phénomènes ont été mis en évidence, notamment la relation entre la résistance électrique de contact et le bruit de phase. En effet, l’expertise des contacts usés révèlent l’apparition d’oxydes au moment de l’augmentation du bruit de phase. Des lois comportementales permettant de prédire la durée de vie en bruit de phase d’un contact HF ont été établies en fonction de l’épaisseur de dépôt appliquée ou de l’amplitude de débattement imposé. De nouveaux axes de recherches ont été définis pour déterminer la durée de vie du contact en fonction de nouveaux paramètres comme la force normaleIn many applications passive electronic components such as microwave connectors operate in severe vibratory environments. Vibratory stresses induce micro displacements which result in surface damage by fretting-wear. Ultimately, this type of damage leads to a change in electric and HF properties of the concerned components. In this doctoral thesis the influence of fretting-wear on phase noise was studied. In order to identify all mechanisms involved in this type of damage, a multi-scale strategy based on the development of three test benches V1, V2 and V3 was established. As a result of this study it is possible to study the macro and micro phenomena that occur within RF connectors and in systems composed of multiple connectors. Several phenomena have been identified, in particular the relation between electrical contact resistance and phase noise. As a matter of fact, the analysis of worn contacts revealed that the presence of oxides coincides with an increase of phase noise. We established a description for the evolution of phase noise in an RF contact as a function of the applied coating thickness and the imposed sliding amplitude. Future areas of research have been proposed in order to determine in how far the lifetime of contacts is influenced by other key parameters such as normal force
41
Mickel, Walter. "Geometry controlled phase behavior in nanowetting and jamming." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00868861.
Full textAbstract:
This thesis is devoted to several aspects of geometry and morphology in wetting problems and hard sphere packings. First, we propose a new method to simulate wetting and slip on nanostructured substrates: a phase field model associated with a dynamical density theory approach. We showed omniphobicity, meaning repellency, no matter the chemical properties of the liquid on monovalued surfaces, i.e. surfaces without overhangs, which is in contradiction with the macroscopic Cassie-Baxter-Wenzel theory, can produce so-called We checked systematically the impact of the surface parameters on omniphobic repellency, and we show that the key ingredient are line tensions, which emerge from needle shaped surface structures. Geometrical effects have also an important influence on glassy or jammed systems, for example amorphous hard sphere systems in infinite pressure limit. Such hard sphere packings got stuck in a so-called jammed phase, and we shall demonstrate that the local structure in such systems is universal, i.e. independent of the protocol of the generation. For this, robust order parameters - so-called Minkowski tensors - are developed, which overcome robustness deficiencies of widely used order parameters. This leads to a unifying picture of local order parameters, based on geometrical principles. Furthermore, we find with the Minkowski tensor analysis crystallization in jammed sphere packs at the random closed packing point
42
Merlin, Kevin. "Caractérisation thermique d'un matériau à changement de phase dans une structure conductrice." Thesis, Nantes, 2016. http://www.theses.fr/2016NANT4004/document.
Full textAbstract:
La récupération de chaleur fatale est un véritable challenge pour l’amélioration de l’efficacité énergétique. Le stockage par chaleur latente est une solution qui répond à cet enjeu. Nous nous intéressons aux procédés industriels avec un rapport puissance sur énergie élevé. L’un des procédés identifiés est la stérilisation de produits agroalimentaires. Cependant, les matériaux à changement de phase, peu conducteurs, ne permettent pas d’obtenir des puissances thermiques suffisantes pour ces applications. L’amélioration de la surface d’échange ou l’augmentation de la conductivité thermique du matériau sont alors nécessaires. Un premier dispositif expérimental de stockage thermique comparant différentes techniques d’intensification des transferts a été réalisé. Le concept à base de paraffine et de Graphite Naturel Expansé (GNE) s’est montré le plus performant par rapport à des solutions de type ailettes ou poudre de graphite. La caractérisation thermique du matériau composite GNE/paraffine sélectionné a été réalisée par plusieurs méthodes. Des valeurs de conductivité thermique effective de l’ordre 20 W.m-1.K-1 ont été obtenues. Dans un second temps, un démonstrateur de 100kW/6kW.h est dimensionné et réalisé. Ce dispositif testé sur un procédé de stérilisation existant permet une économie d’énergie de 15%, conforme aux prévisions. L’identification de la conductivité thermique plane du matériau et l’influence de la résistance thermique de contact sont réalisées à l’aide d’un dispositif expérimental, couplé à un modèle numérique. Enfin, le développement d’un dispositif de vieillissement permet l’étude de la stabilité thermique de ce matériauWaste heat recovery is a challenge for the improvement of energy efficiency. Latent heat storage is a solution that addresses this issue. We focus on industrial processes with high energy on power ratios. One of the identified processes is the sterilization of food products. However, phase change materials, which have low thermal conductivities, do not provide sufficient thermal powers for these applications. The improvement of the heat exchange surface or the increase in thermal conductivity of the material are then necessary. A first experimental thermal storage comparing various heat transfer intensification techniques was achieved. The concept based on paraffin and Expanded Natural Graphite (ENG) has proven to be the most efficient compared to solutions using fins or graphite powder. The thermal characterization of the selected composite material ENG/paraffin was performed by several methods. Effective thermal conductivities values of about 20 W.m-1.K-1 were obtained. In a second step, a 100kW/6kW.h demonstrator is designed and realized. This device tested on an existing sterilization process provides an energy saving of 15%, as expected. The identification of the planar thermal conductivity of the composite material and the influence of the thermal contact resistance are carried out using an experimental device, coupled to a numerical model. Finally, an aging device is used to study the thermal stability of this material
43
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.
Full textAbstract:
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.
44
Tachon, Loïc. "Développement d'outils numériques et expérimentaux dédiés à l'étude de l'évaporation en présence de ligne triple." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10027/document.
Full textAbstract:
Les travaux réalisés au cours de cette thèse visent à apporter une aide à la compréhension des mécanismes régissant l'évaporation des films liquides. La physique des problèmes à changement de phase avec ligne de contact est gouvernée par des mécanismes agissant au niveau de ces dernières ainsi qu'au niveau des interfaces gaz-liquide. La description géométrique des interfaces est donc un point clef dans cette étude tant d'un point de vue numérique qu'expérimental. Un outil numérique tridimensionnel de suivi d'interface infiniment fine a été créé afin d'anticiper la simulation numérique de ces problèmes. Cet algorithme repose sur une description quadratique de l'interface qui est une surface du maillage. L’ordre de convergence de cette méthode relatif à différentes caractéristiques (courbure, normale, position) de l'interface ainsi que sa qualité conservative ont été étudiés.Parallèlement à cette approche numérique, une technique expérimentale d'inversion optique a été développée. Celle-ci permet la mesure dynamique du profil d'une interface au voisinage de la ligne de contact dans le cadre de fluide très mouillant. Cette méthode, appliquée dans le cadre d'un problème de film en évaporation quasi axisymétrique a permis, dans le cadre d'une expérience simple, une première quantification des flux de chaleur et de masse échangés au niveau de la ligne de contactThe tasks fulfilled during this study aim at providing tools for understanding the mechanisms of liquid film evaporation. Evaporation in the presence of a triple lines is ruled by physical mechanisms acting on these singularities as well as on the gas liquid interfaces. Thus, the interface description, under it numerical as experimental aspects, is a key point of this study. A numerical tridimentionnal sharp interface tracking tool has been developed to be used in further numerical simulation of the evaporation problem. In this algorithm, the interface is described as a quadratic grid surface. Its convergence orders relatively to geometrical parameters of the interface (curvature, normal, position) has been studied.In the mean time, an experimental optical inversion technique has been developed and validated. It allows a dynamic measurement of the interface shape in the vicinity of the triple line of highly wetting fluid. This method has been applied to the case of a quasi axisymetric evaporating film and provides a first quantification of the heat and mass transfers generated by the triple line region
45
Abi, Tannous Tony. "Croissance de la phase MAX sur SiC contact ohmique stable et fiable à haute température." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0141.
Full textAbstract:
Nous avons pour objectif de jeter les bases d’une technologie en totale rupture avec celles existantes pour la fabrication d’une nouvelle génération de composants électroniques à base du Carbure de Silicium pour les applications à très hautes températures (jusqu’à 600°C). Cette nouvelle technologie est basée sur l'emploi d'une nouvelle génération de matériaux pour les contacts ohmiques haute température. Nous avons ciblé la phase Ti3SiC2, qui est une phase céramique/métallique, pour former un bon contact ohmique stable et fiable à haute et très haute température. A savoir que l’aspect céramique est nécessaire pour assurer une bonne stabilité thermique à haute température, et l’aspect métallique est nécessaire pour obtenir des bonnes propriétés électriques (bonne conductivité électrique, faible résistance électrique…). Dans le but d’élaborer le Ti3SiC2 sur SiC, un film mince de 200 nm d’un alliage TixAl1-x a été déposé sur SiC-4H suivit d’un recuit sous Ar. Dans cette étude, on a fait varier la concentration du Ti et d’Al dans le dépôt métallique (Ti20Al80, Ti30Al70, Ti50Al50 et Ti), et on a aussi varié la température de recuit de 900°C à 1200°C. Des analyses structurales comme le DRX, MET, MEB et XPS ont été effectuées après recuit. Pour caractériser électriquement la couche Ti3SiC2 synthétisée sur SiC, des motifs TLM ont été réalisés. Des caractérisations électriques à température ambiante et à très haute température (jusqu’à 600°C) ont été mis en œuvre pour chaque type de dépôt et par conséquence la hauteur de barrière de potentielle a été également déterminée. Enfin, pour étudier la stabilité thermique du Ti3SiC2 sur SiC, des tests de vieillissement ont été réalisé à 600°C sous ArThe growth of Ti3SiC2thin films was studied onto 4H-SiC (0 0 0 1) 8◦and 4◦-off substrates by thermalannealing of TixAl1−x(0.5 ≤ x ≤ 1) layers. The annealing time was fixed at 10 min under Argon atmosphere.The synthesis conditions were also investigated according to the annealing temperature (900–1200◦C)after deposition. X-Ray Diffraction (XRD) and Transmission Electron Microscope (TEM) show that thelayer of Ti3SiC2is epitaxially grown on the 4H-SiC substrate. In addition the interface looks sharp andsmooth with evidence of interfacial ordering. Moreover, during the annealing procedure, the formationof unwanted aluminum oxide was detected by using X-Ray Photoelectron Spectroscopy (XPS); this layercan be removed by using a specific annealing procedure. Using TLM structures, the Specific Contact Resistance (SCR) at room temperature of all contacts was measured. The temperature dependence up to 600°C of the SCR of the best contacts was studied to understand the current mechanisms at the Ti3SiC2/SiC interface. Experimental results are in agreement with the thermionic field emission (TFE) theory. With this model, the barrier height of the contact varies between 0.71 to 0.85 eV
46
Tulsky, Emma Teresa Teeter. "The Effects of Contact Metamorphism by Diabase Intrusion on the Carbon and Sulfur Bearing Phases in the Siltstones of the Culpeper Basin." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/77926.
Full textAbstract:
Many of the large igneous provinces during the Phanerozoic have been temporally linked to mass extinction events. The intrusion of magma into country rock has been hypothesized to facilitate the release of carbon and sulfur bearing volatiles and has been proposed as one of mechanisms that drove these mass extinctions. In this study I examine a dike of the Central Atlantic Magmatic Province and its interaction with adjacent sedimentary rocks in the Culpeper Basin of Virginia. Sampling was done at the 0.5 m scale along transects of sedimentary lithologies perpendicular to the ~170 m wide diabase intrusion. The observed mineralogical and geochemical changes in sedimentary rocks occur in a much narrower zone from the intrusion than predicted by the applied thermal model. Carbon isotopes of organic matter within the sedimentary rocks are enriched in 13C toward the intrusion indicating the generation of thermogenic methane within the first meter from the intrusion. Additionally, geochemical and petrologic textures suggest both the addition of magmatic sulfur into the country rock, shown through the isotopic signatures of sulfide minerals with mantle compositions. The possible thermal break down of sedimentary pyrite is evidenced by highly negative isotopic composition of sulfide minerals and general lack of pyrite. I suggest that sedimentary pyrite initially reacted to pyrrhotite, which was then converted to chalcopyrite through reactions with copper in fluids derived from the magma. These reactions also allowed for the formation of magnetite, which is elevated near the dike-sedimentary contact and at the end of the transect. A simple illustrative model of a hypothesis of fluid flow along the bed is used to explain the observed isotopic signatures and mineralogical changes along the transect. This study highlights how models for volatile generation through magma-country rock interaction may have overestimated the volatile fluxes from these environments and the roles that heterogeneity of sedimentary rocks and kinetic factors may have in the variance in these fluxes.Master of Science
47
Miftah, el kheir Laila. "Smart devices for biomedical applications." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD054.
Full textAbstract:
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
48
Guido, Christopher James. "Improvements to Whole Lens Reconstruction for Saline Submerged Soft Contact Lenses." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/612612.
Full textAbstract:
A method for measuring the thickness and surface profiles of soft contact lenses while submerged in a saline solution has been implemented utilizing a low coherence Twyman-Green Interferometer. Although the original measurements demonstrated that features on the contact lens surfaces could be accurately determined, it was believed that the layout of the system also induced surface profile distortions. A new opto-mechanical layout has been implemented which eliminates many of these low frequency distortions. Improvements to the original phase unwrapping algorithms have also been developed to overcome the low visibility output inherent to the measurement allowing for a more complete analysis of the two surfaces of a contact lens.
49
Li, Biao. "Hydrophobic-Hydrophilic Separation Process for the Recovery of Ultrafine Particles." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/103278.
Full textAbstract:
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.
50
Matata, Bashir Mnene. "Blood response to biomaterials : in vitro and clinical investigation of the contact phase of blood coagulation." Thesis, University of Strathclyde, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297340.
Full text