Dissertationen zum Thema „Interface phenomenon“
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1
Ramos, Roberto Luiz da Cunha Barroso. „Aeroservoelastic analysis of the blade-sailing phenomenon in the helicopter-ship dynamic interface“. Instituto Tecnológico de Aeronáutica, 2007. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=368.
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This thesis proposes a Rotary-Wing Aeroservoelasticity approach to the modeling, analysis and control of the blade-sailing phenomenon in the helicopter-ship dynamic interface (DI), based on the identification, response evaluation and control of flow and ship motion induced loads, during the engagement/disengagement flight regimes, in order to establish some principles for the design and safe operation of shipboard rotorcraft systems. The nonlinear aeroelastic analysis revealed that the nonlinearity due to large flapping deflections and to the centrifugal forces is not relevant for normal operating conditions, whereas the nonlinear effects due to the flapping stops in articulated rotors influence significantly the blade-sailing vibrations. These nonlinear effects related to the stops can be tackled with approximate stiffness functions. The nonlinear analysis confirmed that hingeless rotor blade-sailing vibrations are lower than that of the articulated rotor, however, the differences are small for rotors with similar structural/geometric characteristics. The blade-sailing phenomenon in the DI and the flapping response during engagement/disengagement shipboard operations can be analyzed trough an oscillator system with nonlinear stiffness related to the droop and flap stops and time-varying coefficients related to the undisturbed flow velocity and to the parameters of the proposed active proportional-derivative individual blade control (PD-IBC). The aeroelastic analysis also showed that blade sailing is a cooperative phenomenon. Though the mean flow vertical velocity gradient across the rotor be the single most important factor, the combination of horizontal wind velocities, fluctuating flow vertical velocities, gravity and ship motion effects may give rise to excessive flapping vibrations. The proposed active proportional-derivative state feedback individual blade control (PD-IBC) can obtain blade-sailing flapping vibration reduction of 30% for shipboard articulated rotors at moderate wind-over-deck (WOD) conditions/advance ratios, without monitoring the DI environment, and a reduction greater than 40% if combined with shipboard rotor plant modifications, involving an increase of the blade flapwise stiffness and an aerodynamic design of the ship flight deck, considering the current blade pitch input limits of the actuators. Therefore, the implementation of active feedback aeroelastic control methods may be one of the most important measures for blade-sailing mitigation in the DI.
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Bunting, I. „An ethnographic study of the development interface : knowledge, power, culture and the phenomenon of the development community“. Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636175.
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This study is an analytical description of the process of Development Intervention. It is facilitated by way of a historiography of intervention in Tanzania, an analysis of development discourse and an ethnography of the development interface, i.e. "the space of contact" between that set of institutional relationships, programmes, mechanisms, methods and ideology that constitute the development apparatus. It is an ethnography of the interface between development assistance agencies, local bureaucracies, and indigenous communities. I have structured the work in three parts. (1) An ethnographic survey and analysis of the development assistance community. I have recorded the experiences and responses from persons from persons engaged in the development interface. It is informed by observations of behaviour within the development interface. This I have done by improvising with a concept of "An Observing Participant". (2) The second part explores the theoretical aspects of development intervention and the nature of cross-cultural encounter it generates. The social construction of meaning in development discourses and the power-knowledge nexus is central to my analysis of the socio-cultural, psychological implications of development intervention in Africa. (3) The third part of the study is reflexive whereby I look at the Socio-economic and cultural heritage of interpretative social science in the context of imperialism and locating myself as an observing participant in the development drama. I provide insights into the power relations and cultural manifestations of development programmes on indigenous institutional capacity and reformation in the dominated but resisting communities of Africa. It highlights and describes processes in which ideas, technologies and institutions are engaged, the ideology infusing these engagements and the effects of this on cultural change together with the individuals and different cultural groups engaged and affected.
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Seth, Umesh Kumar. „Message Passing Interface parallelization of a multi-block structured numerical solver. Application to the numerical simulation of various typical Electro-Hydro-Dynamic flows“. Thesis, Poitiers, 2019. http://www.theses.fr/2019POIT2264/document.
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Plusieurs types d’applications industrielles complexes, relèvent du domaine multidisciplinaire de l’Electro-Hydro-Dynamique (EHD) où les interactions entre des particules chargées et des particules neutres sont étudiées dans le contexte couplé de la dynamique des fluides et de l’électrostatique. Dans cette thèse, nous avons étudié par voie de simulation numérique certains phénomènes Electro-Hydro-Dynamiques comme l’injection unipolaire, le phénomène de conduction dans les liquides peu conducteurs et le contrôle d’écoulement avec des actionneurs plasma à barrières diélectriques (DBD). La résolution de tels systèmes physiques complexes exige des ressources de calculs importantes ainsi que des solveurs CFD parallèles dans la mesure où ces modèles EHD sont mathématiquement raides et très consommateurs en temps de calculs en raison des gammes d’échelles de temps et d’espace impliquées. Cette thèse vise à accroitre les capacités de simulations numériques du groupe Electro-Fluido-Dynamique de l’Institut Pprime en développant un solveur parallèle haute performance basé sur des modèles EHD avancés. Dans une première partie de cette thèse, la parallélisation de notre solveur EHD a été réalisée avec des protocoles MPI avancés comme la topologie Cartésienne et les Inter-communicateurs. En particulier, une stratégie spécifique a été conçue pour prendre en compte la caractéristique multi-blocs structurés du code. La nouvelle version parallèle du code a été entièrement validée au travers de plusieurs benchmarks. Les tests de scalabilité menés sur notre cluster de 1200 cœurs ont montré d’excellentes performances. La deuxième partie de cette thèse est consacrée à la simulation numérique de plusieurs écoulements EHD typiques. Nous nous sommes intéressés entre autres à l’électroconvection induite par l'injection unipolaire entre deux électrodes plates parallèles, à l’étude des panaches électroconvectifs dans une configuration d'électrodes lame-plan, au mécanisme de conduction basé sur la dissociation de molécules neutres d'un liquide faiblement conducteur. Certains de ces nouveaux résultats ont été validés avec des simulations numériques entreprises avec le code commercial Comsol. Enfin, le contrôle d’écoulements grâce à un actionneur DBD a été simulé à l’aide du modèle Suzen-Huang dans diverses configurations. Les effets de l’épaisseur du diélectrique, de l’espacement inter-électrodes, de la fréquence de la tension appliquée et sa forme d’onde, sur la vitesse maximale du vent ionique induit ainsi que sur la force électrique moyenne ont été étudiésSeveral intricately coupled applications of modern industries fall under the multi-disciplinary domain of Electrohydrodynamics (EHD), where the interactions among charged and neutral particles are studied in context of both fluid dynamics and electrostatics together. The charge particles in fluids are generated with various physical mechanisms, and they move under the influence of external electric field and the fluid velocity. Generally, with sufficient electric force magnitudes, momentum transfer occurs from the charged species to the neutral particles also. This coupled system is solved with the Maxwell equations, charge transport equations and Navier-Stokes equations simulated sequentially in a common time loop. The charge transport is solved considering convection, diffusion, source terms and other relevant mechanisms for species. Then, the bulk fluid motion is simulated considering the induced electric force as a source term in the Navier-Stokes equations, thus, coupling the electrostatic system with the fluid. In this thesis, we numerically investigated some EHD phenomena like unipolar injection, conduction phenomenon in weakly conducting liquids and flow control with dielectric barrier discharge (DBD) plasma actuators.Solving such complex physical systems numerically requires high-end computing resources and parallel CFD solvers, as these large EHD models are mathematically stiff and highly time consuming due to the range of time and length scales involved. This thesis contributes towards advancing the capability of numerical simulations carried out within the EFD group at Institut Pprime by developing a high performance parallel solver with advanced EHD models. Being the most popular and specific technology, developed for the distributed memory platforms, Message Passing Interface (MPI) was used to parallelize our multi-block structured EHD solver. In the first part the parallelization of our numerical EHD solver with advanced MPI protocols such as Cartesian topology and Inter-Communicators is undertaken. In particular a specific strategy has been designed and detailed to account for the multi-block structured grids feature of the code. The parallel code has been fully validated through several benchmarks, and scalability tests carried out on up to 1200 cores on our local cluster showed excellent parallel speed-ups with our approach. A trustworthy database containing all these validation tests carried out on multiple cores is provided to assist in future developments. The second part of this thesis deals with the numerical simulations of several typical EHD flows. We have examined three-dimensional electroconvection induced by unipolar injection between two planar-parallel electrodes. Unsteady hexagonal cells were observed in our study. 3D flow phenomenon with electro-convective plumes was also studied in the blade-plane electrode configuration considering both autonomous and non-autonomous injection laws. Conduction mechanism based on the dissociation of neutral molecules of a weakly conductive liquid has been successfully simulated. Our results have been validated with some numerical computations undertaken with the commercial code Comsol. Physical implications of Robin boundary condition and Onsager effect on the charge species were highlighted in electro-conduction in a rectangular channel. Finally, flow control using Dielectric Barrier Discharge plasma actuator has been simulated using the Suzen-Huang model. Impacts of dielectric thickness, gap between the electrodes, frequency and waveform of applied voltage etc. were investigated in terms of their effect on the induced maximum ionic wind velocity and average body force. Flow control simulations with backward facing step showed that a laminar flow separation could be drastically controlled by placing the actuator at the tip of the step with both electrodes perpendicular to each other
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Li, Hao. „Approche multi-échelle pour les écoulements polyphasiques en présence de phénomènes interfaciaux“. Electronic Thesis or Diss., Université de Lorraine, 2024. http://www.theses.fr/2024LORR0081.
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Les phénomènes interfaciaux suscitent un intérêt croissant dans divers domaines industriels et fondamentaux tels que les industries pétrolière, alimentaire, cosmétique ou l'imprimerie, etc. Cette thèse se concentre particulièrement sur les phénomènes impliquant des gouttes et des bulles, notamment leur coalescence, étalement, drainage et éclatement dans des fluides non newtoniens. Plusieurs méthodes expérimentales ont été utilisées, incluant un système d'acquisition électrique DC ultra-rapide, une caméra rapide et un micro-PIV à grande vitesse. La première partie de l'étude explore le contact initial et l'étalement (coalescence) d'une goutte non newtonienne sur une surface solide ou liquide. L'évolution de la conductance électrique, en corrélation avec la largeur d'étalement de la goutte, a été détectée dans les premières microsecondes. L'étalement d'une dispersion opaque de nanoparticules a été entrepris, révélant les mécanismes sous-jacents et les régimes par une loi d’échelle sans dimension. La quantification des champs de vitesse à l'intérieur de la goutte a également été réalisée. La deuxième partie compare la durée de vie et l'éclatement d'une bulle unique à différentes surfaces liquides, y compris celles chargées de particules superhydrophobes. L'épaisseur de la calotte de la bulle a été mesurée grâce à l'imagerie à grande vitesse. Les champs de vitesse autour de la cavité de bulle ont été mesurés, montrant le rôle de la couche de particules et la viscoélasticité des fluides dans la transition d'une rupture rapide à une disparition lente de la bulle. Enfin, la troisième partie examine la coalescence d'une goutte non newtonienne avec une phase liquide de la même nature à travers des interfaces air-liquide chargées de particules. Les champs de vitesse au sein de la goutte et dans le liquide ont été évalués, et une analyse du signal électrique a mis en évidence la différence avec la coalescence à des surfaces sans particules. Le rôle complexe de la couche de particules comme barrière et pont a été dévoilé, ainsi que sa relation avec la viscoélasticité du fluideInterfacial phenomena as a research domain have attracted focus and resources from areas of industrial and fundamental interests: cosmetics, printing, food industries, and glass productions, etc. What charms the defender most is the phenomena with drops and bubbles - their processes of coalescing, spreading, draining, and bursting - involving non-Newtonian fluids. Multiple experimental methods such as ultra-high-speed DC electrical acquisition system, high-speed camera and high-speed micro-PIV were jointly adopted for the investigation. The first part focused on experimental research on initial contact and spreading (coalescing) of a non-Newtonian drop on a solid (liquid) planar surface. The evolution of the electrical conductance in close relation with the drop spreading (coalescing) width was detected at first microseconds. Spreading (coalescing) behaviors of an opaque dispersion of nanoparticles was examined. Regimes and mechanism behind were revealed via dimensionless scaling. The quantification of flow fields inside a spreading (coalescing) drop was performed. The second part comparatively investigated the lifetime and bursting behavior of a single bubble at different liquid surfaces and through particle-laden liquid surfaces. Bubble cap thickness was quantitatively compared based on the high-speed imaging results. Velocity fields and profiles around bubble cavity were drafted and analyzed. The role of particle layer, together with fluids’ viscoelasticity, was confirmed in the shift for a bubble from a quick rupture death to a slow shrinking disappearance. The last part studied the coalescence of a non-Newtonian drop with its bulk phase through particle-laden air-liquid surfaces. A characteristic evaluation of speed fields within the drop and the bulk was conducted. An electrical signal analysis was carried out to highlight the difference with the coalescence of a drop with particle-free surfaces. The complicate role of particle layer as a barrier and bridge at the same time was confirmed and its relationship with fluid’s viscoelasticity was demonstrated
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Bao, Qinye. „Interface Phenomena in Organic Electronics“. Doctoral thesis, Linköpings universitet, Ytors Fysik och Kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-118922.
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Organic electronics based on organic semiconductors offer tremendous advantages compared to traditional inorganic counterparts such as low temperature processing, light weight, low manufacturing cost, high throughput and mechanical flexibility. Many key electronic processes in organic electronic devices, e.g. charge injection/extraction, charge recombination and exciton dissociation, occur at interfaces, significantly controlling performance and function. Understanding/modeling the interface energetics at organic-electrode/organic-organic heterojunctions is one of the crucial issues for organic electronic technologies to provide a route for improving device efficiency, which is the aim of the research presented in this thesis. Integer charge transfer (ICT) states pre-existed in the dark and created as a consequence of Fermi level equilibrium at donor-acceptor interface have a profound effect on open circuit voltage in organic bulk heterojunction photovoltaics. ICT state formation causes vacuum level misalignment that yields a roughly constant effective donor ionization potential to acceptor electron affinity energy difference at the donor-acceptor interface, even though there is a large variation in electron affinity for the fullerene series. The large variation in open circuit voltage for the corresponding device series instead is found to be a consequence of trap-assisted recombination via integer charge transfer states. Based on the results, novel design rules for optimizing open circuit voltage and performance of organic bulk heterojunction solar cells are proposed. Doping and insertion of interlayer are two established methods for enhancing charge injection/extraction properties at organic-electrode interface. By studying the energy level alignment behavior at low to intermediate doping levels for molecule-doped conjugated polymer/electrode interfaces, we deduce that two combined processes govern the interface energetics: (i) equilibration of the Fermi level due to oxidation (or reduction) of polymer sites at the interface as per the ICT model and (ii) a double dipole step induced by image charge from the dopant-polymer charge transfer complex that causes a shift of the work function. Such behavior is expected to hold in general for low to intermediate level doped organic semiconductor systems. The unified model is further extended to be suitable for conjugated electrolyte/electrode interfaces, revealing the design rules for achieving the smallest charge injection/extraction barrier for both thin tunneling and thick charge transporting conjugated electrolyte interlayers. To probe into the energy level spatial extension at interfaces, we employ the original approach of building and characterizing multilayers composed of a well-defined number of polymer monolayers with the Langmuir-Shäfer method to control polymer film uniformity and thicknesses, avoiding the problems associated with spin-coating ultrathin films. The disordered/amorphous films feature smaller, and in fact negligible, energy level bending compared to the more well-ordered films, in contradiction with existing models. It is found that that energy level bending depends on the ICT state distribution rather than the density of states of the neutral polymer chains in relation to the Fermi energy, thus taking into account the Coulomb energy associated with charging the polymer chain and transferring a charge across the interface. Based on this work, a general model for energy level bending in absence of significant doping of conjugated polymer films is proposed. Organic semiconductors are sensitive to ambient atmosphere that can influence the energetics. The degradation effects of common PCBM film induced by oxygen and water are found to be completely different. Upon exposure to oxygen, the work function is down-shifted by ~ 0.15 eV compared to the ICT curve of the pristine PCBM film, originating from the weak interaction between the fullerene part of PCBM and oxygen, and this can be reversed by thermal treatment in vacuum. The down-shift in energetics will cause a loss in open circuit voltage at electrode interface, but aids free charge generation at donor-acceptor interface. Upon exposure to water, there is irreversible extensive broadening and bleaching of the valence electronic structure features as well as a substantial decrease of work function and ionization potential, severely degrading the transport properties. Overall, the research results in this thesis thus give a deeper understanding of interface phenomena in organic electronics, especially regard to organic solar cells, aimed to further improve the device operation efficiency and lifetime.
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Villanueva, Walter. „Diffuse-Interface Simulations of Capillary Phenomena“. Doctoral thesis, Stockholm : Kungl. tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4402.
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Zahedi, Sara. „Numerical Modeling of Fluid Interface Phenomena“. Licentiate thesis, Stockholm : Skolan för datavetenskap och kommunikation, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10507.
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Wheale, Samantha Hilary. „Physicochemical phenomena at the plasma-polymer interface“. Thesis, Durham University, 1997. http://etheses.dur.ac.uk/4977/.
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Non-isothennal plasma modification of polymer surfaces is of scientific and technological interest, since it can be used to improve wettability, adliesion, etc. This thesis covers three main areas, firstly a study of the processes occuixing at the plasma - polymer interface using a newly developed technique, secondly the fluorination of polymer surfaces using a novel transportable reagent and lastly the oxidation of rubber substrates. The interaction of N(_2), O(_2), air and H(_2) glow discharges with polyethylene surfaces has been studied using a newly developed mass spectrometric technique. The species permeating through to the reverse side of the polymer substrate can be detected and characterised. Compared to previously reported approaches, this method is capable of sampling reaction products within closer proximity to the plasma - polymer interface, thereby circumventing the complication of primary product species undergoing secondary processes within the bulk of the electrical discharge prior to detection. The nature of the feed gas is found to strongly influence the chemical reaction pathways occurring at the plasma - polymer interface. Xenon difluoride (XeF(_2)) plasma treatment of a series of polymers containing different repeat units gives rise to surface fluorination. A comparison with CF(_4) plasma modification shows that XeF(_2) electrical discharges are more effective at fluorinating polymers. The extent of fluorine incorporation can be accounted for in terms of a structure-behaviour relationship derived from extended Huckel molecular orbital calculations. Exposure of polyethylene and polystyrene to xenon difluoride (XeF(_2)) in the presence of vacuum ultraviolet (VUV) irradiation also causes surface fluorination. The extent of reaction is found to depend upon the VUV absorption characteristics of the XeF(_2) feed gas as well as those of the polymer substrate. Low pressure glow discharge, dielectric barrier discharge and ozone treatments all oxidise additive-free rubber substrates. The oxidation susceptibility of the rubber substrates differed during all three treatments, and was found to be dependent upon the concentration of unsaturated carbons, saturated carbons and phenyl rings. The additives placed ill rubbers to improve properties such as tear resistance influence their degree of oxidation.
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Quinn, Amy May. „The study of contact phenomena using ultrasound“. Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271847.
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Chiu, Patrick Y. „Computational modeling of atomistic phenomena at the interface“. [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024892.
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Legrand, Frédéric. „Glissement aux parois des polymères fondus enchevêtrés“. Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10288.
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On etudie tout d'abord le glissement sur une surface metallique usinee, qui adsorbe fortement le polymere. Pour atteindre les forts taux de deformation necessaires, une filiere d'extrusion bidimentionnelle a ete construite. Les mesures de vitesses dans l'ecoulement sont faites en suivant le mouvement de particules solides. Des mesures de birefringence de contrainte sont faites soit globalement par la methode des franges, soit localement au moyen d'un appareil a modulateur photo-elastique. Trois polymeres sont etudies : un polydimethylsiloxane, un polybutadiene et un styrene-butadiene statistique. Les mesures apportent une comprehension du lien entre le glissement et l'instabilite elastique qui se declenche en amont de la filiere. Une experience complementaire utilisant des marqueurs fluorescents permet de mesurer le champ de vitesse a une distance de la paroi de l'ordre du micrometre. Elle montre que le glissement se fait sur un plan localise dans le volume du polymere, juste au dessus des rugosites de la surface. Le mecanisme du glissement est donc un desenchevetrement de la couche piegee par les rugosites par rapport au polymere en ecoulement. Dans un deuxieme temps, le glissement d'un polydimethylsiloxane est obtenu sur des surfaces qui adsorbent faiblement le polymere, au moyen d'une methode de rheometrie cone-plan capable d'operer a faible taux de cisaillement. Le glissement obtenu sur la silice propre et sur la silice recouverte d'une monocouche organique montre l'influence du taux d'adsorption des chaines sur le seuil de glissement. Apres avoir etabli un modele qui calcule la contrainte necessaire a la desorption des chaines, nous en concluons que le glissement se fait ici aussi par desenchevetrement des chaines adsorbees par rapport au fondu en ecoulement. Enfin, un glissement a l'interface entre un polydimethylsiloxane et un polybutadiene est etudie et interprete la encore en terme de desenchevetrement dans la couche d'interpenetration.
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Hernandez, Medina Santiago. „Turbulent interface phenomena in a temporally developing boundary layer“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14721/.
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The purpose of the current study was to examine the characteristics and behavior of the turbulent/non-turbulent interface on a temporally developing boundary layer.
Flow topology, turbulent statistics, enstrophy budgets and spectral statistics were computed with the purpose of acquiring meaningful results.
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Herescu, Alexandru. „Two-Phase Flow In Microchannels| Morphology And Interface Phenomena“. Thesis, Michigan Technological University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3565323.
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The existence and morphology, as well as the dynamics of micro-scale gas-liquid interfaces is investigated numerically and experimentally. These studies can be used to assess liquid management issues in microsystems such as PEMFC gas flow channels, and are meant to open new research perspectives in two-phase flow, particularly in film deposition on non-wetting surfaces. For example the critical plug volume data can be used to deliver desired length plugs, or to determine the plug formation frequency. The dynamics of gas-liquid interfaces, of interest for applications involving small passages (e.g. heat exchangers, phase separators and filtration systems), was investigated using high-speed microscopy - a method that also proved useful for the study of film deposition processes.
The existence limit for a liquid plug forming in a mixed wetting channel is determined by numerical simulations using Surface Evolver. The plug model simulate actual conditions in the gas flow channels of PEM fuel cells, the wetting of the gas diffusion layer (GDL) side of the channel being different from the wetting of the bipolar plate walls. The minimum plug volume, denoted as critical volume is computed for a series of GDL and bipolar plate wetting properties. Critical volume data is meant to assist in the water management of PEMFC, when corroborated with experimental data. The effect of cross section geometry is assessed by computing the critical volume in square and trapezoidal channels. Droplet simulations show that water can be passively removed from the GDL surface towards the bipolar plate if we take advantage on differing wetting properties between the two surfaces, to possibly avoid the gas transport blockage through the GDL.
High speed microscopy was employed in two-phase and film deposition experiments with water in round and square capillary tubes. Periodic interface destabilization was observed and the existence of compression waves in the gas phase is discussed by taking into consideration a naturally occurring convergent-divergent nozzle formed by the flowing liquid phase. The effect of channel geometry and wetting properties was investigated through two-phase water-air flow in square and round microchannels, having three static contact angles of 20, 80 and 105 degrees. Four different flow regimes are observed for a fixed flow rate, this being thought to be caused by the wetting behavior of liquid flowing in the corners as well as the liquid film stability. Film deposition experiments in wetting and non-wetting round microchannels show that a thicker film is deposited for wetting conditions departing from the ideal 0 degrees contact angle. A film thickness dependence with the contact angle theta as well as the Capillary number, in the form hR ≈ Ca(2/3 )/cos(&thetas;) is inferred from scaling arguments, for contact angles smaller than 36 degrees. Non-wetting film deposition experiments reveal that a film significantly thicker than the wetting Bretherton film is deposited. A hydraulic jump occurs if critical conditions are met, as given by a proposed nondimensional parameter similar to the Froude number. Film thickness correlations are also found by matching the measured and the proposed velocity derived in the shock theory. The surface wetting as well as the presence of the shock cause morphological changes in the Taylor bubble flow.
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Haidou, Konstantina. „The syntax-pragmatics interface of focus phenomena in Greek“. Thesis, SOAS, University of London, 2012. http://eprints.soas.ac.uk/13635/.
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Taleb, Mandana. „PHENOMENES AUX INTERFACES DES ISOLANTS : MESURE ET SIMULATION“. Phd thesis, Université Paul Sabatier - Toulouse III, 2011. http://tel.archives-ouvertes.fr/tel-00670594.
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Les matériaux polymères sont largement utilisés en tant qu'isolants dans les domaines du génie électrique, de l'électronique de puissance et de la microélectronique. Ces diélectriques sont principalement en contact avec d'autres composants: avec des semi-conducteurs et des métaux dans les câbles haute tension, avec des substrats et d'autres diélectriques dans les systèmes multicouches. Ces interfaces sont omniprésentes, et contribuent à l'injection et l'accumulation de charges d'espace dans les diélectriques solides. D'autre part, au cours de leur vie, ils sont soumis à de nombreuses contraintes, de température, de champ... Ces contraintes peuvent conduire à la dégradation prématurée et à la rupture diélectrique du matériau par une distorsion du champ électrique, et conduire au dysfonctionnement du système. Des études antérieures, expérimentales et de simulations, ont montré l'importance des interfaces sur la génération de charges à l'intérieur du diélectrique, mais les approches théoriques comme la loi d'injection Schottky ne fournissent pas une description adéquate pour des courants expérimentaux. Cependant les recherches récentes montrent que les états de surface qui se forment à l'interface métal/isolant jouent un rôle important sur le comportement des diélectriques. L'injection de charges est principalement affectée par la nature du contact et des états de surface. L'enjeu de ce travail est de comprendre les phénomènes en jeu à une interface métal/isolant, afin de les modéliser correctement. Ce travail est basé sur une approche duale modélisation et expérience. L'isolant retenu est ici est le polyéthylène basse densité (LDPE). Dans un premier temps, nous avons caractérisé expérimentalement des interfaces métal/isolant. Dans un seconde temps, nous avons développé un modèle numérique capable de prendre en compte les états de surface. L'approche est originale, puisque l'étude porte sur l'injection et le transport de charges en tenant compte d'une distribution exponentielle des états d'énergie à l'interface.
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Sirisathitkul, C. „Studies of transport phenomena at ferromagnet/semiconductor interfaces“. Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325445.
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Vlachos, Georgios. „Adhesion and dewetting phenomena of surfaces and interfaces“. Thesis, University of Sheffield, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414622.
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Graham, John Samuel. „Electrical phenomena at interfaces in liquid phase reprographics“. Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261192.
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Hens, Philip [Verfasser]. „Interface-Phenomena in 3C-SiC Heteroepitaxy on Silicon / Philip Hens“. Aachen : Shaker, 2011. http://d-nb.info/1071529080/34.
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Wormald, Mark R. „An investigation of some interface phenomena using nuclear magnetic resonance“. Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237990.
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Jamie, Elizabeth A. G. „Colloidal interfaces in confinement“. Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:26b47a79-7198-4983-9109-174ac2d3e01d.
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A fluid-fluid demixing colloid-polymer system provides us with an opportunity to study interfacial phenomena that cannot be observed in molecular systems due to unfavourable length and timescales. We develop such a system compatible with cells of varying dimensions, allowing us to investigate confined interfacial behaviour in real space using Confocal Scanning Laser Microscopy. The degree to which a system is affected by the sedimentation-diffusion gradient is dependent on the ratio of the suspension height to the gravitational length of the colloids. We illustrate that we may control the distance of our interface to the critical point by altering the suspension height, determining the importance of the gravitational field. Furthermore, the timescale on which the sedimentation- diffusion gradient is established is considerably longer than that of initial fluid-fluid demixing. We show that after the formation of the macroscopic interface, the system passes through a series of local mechanical equilibria on the way to achieving full equilibrium. Should the system be of sufficient height, it will pass through the gas-liquid critical point opening up new ways to study critical phenomena. The time and length scales of the fluid-fluid demixing of our system may be manipulated by altering the density and viscosity of our solvent. We exploit a slowed phase separation process to study the interplay between demixing and wetting phenomena of systems in the vicinity of a single wetting surface, and confined between two parallel plates. We demonstrate that the presence of a surface strongly affects the morphology of phase separation. The growth of the wetting layer is determined by the demixing regime of the system, and may be accelerated by hydrodynamics. The additional restriction by a second surface limits the lengthscale of coarsening domains and may further alter the mechanism of wetting layer growth.
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Black, M. J. „Electrical phenomena observed at Nb-Si superconductor-semiconductor interfaces“. Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596675.
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A range of tunnelling phenomena were observed in clean Nb-Si interfaces. In the most non-transmissive Nb-Si interfaces, the Schottky barrier acted as an insulating tunnel barrier. Thus, electrical characteristics similar to those obtained from normal-insulator-superconductor junctions were observed with a conductance dip about the Nb superconducting energy gap. As the transmission through the interface was increased, analysis of differential resistance bias dependence measurements indicated that only a small percentage of the contact contributed to conduction. This was attributed to the formation of a highly non-uniform Schottky barrier when the depletion width is comparable with the inter-dopant spacing. Evidence of constructive quantum interference between electrons and Andreev reflected holes was observed and its insensitivity to an applied magnetic indicated that it was caused by the presence of a disordered elastic scattering region adjacent to the Nb-Si interface. Subsequent enhancement in the transmissivity of the junctions indicated that Andreev reflection induced weak localization was occurring as predicted by theory. The fundamental limit in Nb-Si barrier transmissivity was found to be caused by the Fermi velocity mismatch between the Nb and the Si. When Nb3Si particles were present at the Nb-Si interface, a dramatic enhancement in conductance was observed when the temperature was lowered past the Nb3Si superconducting critical temperature. The presence of Nb3Si particles reduced the tunnelling path length through the Schottky barrier and opened new conduction channels. As the temperature was lowered further, the normal coherence length exceeded the Nb-Nb3Si separation distance so that interfacial Josephson junctions were formed. The critical current of these Josephson junctions could be measured directly by applying a large d.c. voltage bias across the interface. The critical current of the Josephson junctions was quantized as a function of temperature because the junction cross-sectional area increased with decreasing temperature. This phenomenon was successfully modelled by assuming that superconductivity was suppressed at the edge of a Nb3Si particle over a temperature dependent coherence length and that the Josephson junction cross-sectional width is equivalent to the width of the Nb3Si particle. This provides a temperature dependent expression for the number of one-dimensional quantized modes passing through the Josephson junction which is in good agreement with the experimentally observed critical current dependence.
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FábIán, Balázs. „Molecular Modeling of Interfacial Phenomena“. Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD041.
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Les outils de simulation numérique permettent désormais l'analyse des interfaces à l'échelle moléculaire, tant du point de vue de leur structure que de leur comportement dynamique. Ainsi, dans mon travail de thèse, j'ai développé le logiciel PYTIM qui comprend les procédures les plus populaires d’analyse inter faciale à l'échelle moléculaire, fournissant une base solide pour les travaux de recherche sur les surfaces et interfaces.En utilisant ces méthodes, j’ai étudié le comportement dynamique des molécules situées aux interfaces de différents systèmes d'intérêt biologiques et atmosphériques. Ce faisant, j’ai étudié la corrélation entre la dynamique des molécules à la surface et les interactions intermoléculaires correspondantes.De plus, j’ai travaillé sur le calcul des profils de pression dans les systèmes simulés. Dans ce cas, définir localement une quantité macroscopique, la pression, à l’échelle microscopique représente un obstacle considérable. Nous avons cependant montré que les profils de pression peuvent être calculés dans des systèmes comprenant des charges ponctuelles via le contour de Harasima avec la méthode de sommation d’Ewald (PME). Par ailleurs, j'ai montré comment les contraintes rigides souvent utilisées dans les simulations introduisent un couplage entre les degrés de liberté translationnels (positions) et les degrés de liberté de rotation. La conséquence de ce couplage est que le tenseur d’énergie cinétique n'est plus constant même dans des systèmes en équilibre, ce qui peut introduire une différence significative dans le calcul de la tension de surface.Les méthodes développées au cours de mon travail de thèse ont permis de calculer, pour différents systèmes, la distribution de la tension superficielle près de l’interface, la relation entre la pression spinodale et le minimum du profil de pression latérale. Elles ont également permis de mieux comprendre les liens entre pression et mécanisme d’action des molécules anesthésiques,fournissant ainsi des bases moléculaires à l'hypothèse de Cantor.Enfin, j’ai étudié également l'équilibre gaz/solide en caractérisant, à l’aide de simulation de Monte Carlo dans l'ensemble grand canonique, le piégeage de molécules d'ammoniac dans un clathrate, sous conditions de pression et de température caractéristiques d'environnements extraterrestresThe tools of numerical simulation enable the analysis of interfaces at themolecular scale, both in terms of their structure and their dynamic behavior.Thus, in my thesis work, I developed the PYTIM software that includes the mostpopular procedures for interfacial analysis at the molecular level, providing asolid foundation for research work on surfaces and interfaces.Using these methods, I investigated the dynamic behavior of molecules at theinterfaces of different biological and atmospheric systems of interest. Indoing so, I studied the correlation between the dynamics of molecules on thesurface and the corresponding intermolecular interactions. In addition, Iworked on the calculation of pressure profiles in simulated systems. Inparticular, the localization of an inherently non-local quantity, the pressure,represents a considerable technical difficulty. I have shown that the pressureprofiles can be calculated in systems containing point charges via the Harasimacontour with mesh Ewald methods (PME). Moreover, I showed how the rigidconstraints often used in simulations introduce a coupling between thetranslational degrees of freedom and the rotational degrees of freedom. Theconsequence of this coupling is that the kinetic energy tensor is no longerconstant, even in equilibrium systems, which -- if neglected -- can introducesignificant errors in the calculation of the surface tension.The methods developed during my thesis work provided means to study variousproblems, such as the distribution of the surface tension near the interface,the relation between the spinodal pressure and the minimum of the lateralpressure profile. They also enabled the investigation of the possible linksbetween the lateral pressure profiles and the mechanism of action of anestheticmolecules, thus providing a molecular basis for the hypothesis ofCantor.Finally, I also studied gas/solid equilibrium characterizing, by Monte Carlosimulation in the grand canonical ensemble, the trapping of ammonia moleculesin a clathrate under conditions of pressure and temperature representative ofextraterrestrial environments
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Dedinaite, Andra. „Surface force studies of association phenomena at solid-liquid interfaces“. Doctoral thesis, KTH, Chemistry, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2849.
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The main topics of this thesis, association phenomena inbulk and at solid-liquid interfaces in polar and non-polarmedia, were studied by a range of methods. Direct forcemeasurements employing the interferometric surface forceapparatus (SFA) was the chief technique. In addition, atomicforce microscopy (AFM), X-ray photoelectron spectroscopy (XPS),small angle neutron scattering (SANS), dynamic light scattering(DLS), turbidimetric and electrophoretic mobility measurementswere also applied. These techniques give complementaryinformation, and together they can provide a rather detailedpicture of the fairly complex systems studied.
The first system studied was designed to explore particleinteractions in non-polar media. It consisted of polar or,alternatively, non-polar surfaces immersed in a non-polarmedium, triolein, in some cases containing additives such asphospholipids, polyglycerol polyricinoleate (PGPR), and traceamounts of water. It was investigated how triolein mediates thesurface interactions and how these interactions are affected bythe presence of additives. Triolein adsorbs onto mica surfacesthus producing a barrier against flocculation of the particles.The additives mentioned interact with the surfaces and witheach other, thus altering the surface interactions. Water, forinstance, being strongly polar, preferentially adsorbs ontomica and disturbs the triolein ordering at the mica surfacescausing the barrier against flocculation to vanish. Owing tocapillary condensation of water, a strong adhesion between thesurfaces is instead developed. On the other hand, it could beshown that in the presence of phospholipids, the effect ofwater was opposite: long-range repulsive forces develop due toweakly adsorbed reversed phospholipid aggregates.
The second type of system studied contained cationicpolyelectrolytes and oppositely charged surfactants. Suchsystems occur in numerous technological processes: wastewatertreatment and ore recovery as well as laundry and body care.Polyelectrolytes and surfactants associate in bulk solution,and they also adsorb on surfaces. Thus, the relation betweenthe bulk properties of polyelectrolyte-surfactant mixtures andtheir properties at the solid-liquid interface is of greatscientific and industrial interest. The bulk properties ofpolyelectrolyte-surfactant aggregates were characterised byDLS, SANS, turbidimetry and electrophoretic mobilitymeasurements. It was concluded that to a certain extent theinterfacial properties of polyelectrolyte-surfactant aggregatescan be rationalised by considering their bulk properties.However, it was also shown that the presence of a surfaceaffects the association between polyelectrolytes andsurfactants. The chemical composition of adsorbed aggregates isdifferent from that of aggregates in solution, and, moreover,the structure of surface-bound polyelectrolyte-surfactantaggregates changes slowly with time.
Keywords:Triolein, phosphatidiylethanolamine,phospholipid, lecithin, capillary condensation, polyglycerolpolyricinoleate, aggregation, adsorption, surface forces,structural forces, mica, polar surface, non-polar surface,polyelectrolyte, surfactant, sodium dodecyl sulphate,polyelectrolyte-surfactant association, turbidity,electrophoretic mobility, AFM, SANS, DLS, SFA.
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Zhang, Zhiming. „Modélisation mécanique des interfaces multi-contacts dans une pile à combustible“. Thesis, Evry-Val d'Essonne, 2010. http://www.theses.fr/2010EVRY0035/document.
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La pile à combustible transforme l'énergie chimique en énergie électrique grâce à un empilement de différentes structures lamellaires. Des phénomènes mécaniques présents aux interfaces agissent de manière plus ou moins directe sur les performances et la durée de vie de la pile. Nous avons montré que la précompression par boulons tirants pendant l'assemblage, la déformation de la couche de diffusion gazeuse (GDL), le contact et la configuration de la plaque bipolaire (BPP) avaient des influences importantes sur la résistance de contact, la porosité et la perméabilité de la pile. La résistance de contact est déterminée par la zone de contact et la pression de contact. La porosité et la perméabilité sont liées à la déformation aux interfaces. Le contact entre les différentes structures a un rôle majeur dans le fonctionnement de la pile. Ce problème a été modélisé par la méthode des éléments finis. Différents paramètres de la pile comme la précompression, la structure géométrique des dents de la plaque BPP ou encore la porosité de la GDL ont été étudiés et ont permis de connaître l'état de contact ainsi que les déformations dans les structures. L'influence de certains paramètres sur les résultats mécaniques de la pile a ensuite été abordée. L'objectif de cette étude est de fournir des valeurs optimales de ces paramètres pour obtenir la meilleure performance possible de la pileThe fuel cell transforms chemical energy to electrical power sources through a stack of different planar structures. Mechanical phenomena presented on the multi-contact interface acts more or less the fuel cell's performance and lifetime. We have shown that the pre-load by stacking bolts, the deformation of the gas diffusion layer (GDL), the contact and the configuration of the bipolar plate (BPP) had influences on the contact resistance, the porosity and the permeability of the fuel cell. The contact resistance is determined by the contact area and contact pressure. The porosity and permeability are related to the interfacial deformation. The contact between the different structures has a major role in the fuel cell operation. This problem is solved by the finite element method. Various parameters of the fuel cell as the pre-load, the geometric structure of teeth of BPP as well as the porosity of the GDL were studied and allowed to know the contact behavior and the deformation. The influence of some parameters on the mechanical results of fuel cell stack was then tackled. The purpose of this study is to provide optimum values of these parameters to obtain the best performance of fuel cells
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Pongsaksawad, Wanida. „Numerical modeling of interface dynamics and transport phenomena in transport-limited electrolysis processes“. Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36209.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 111-117).
Electrochemical reactions in materials and processes induce morphological instability on the cathode, which can lead to porous deposits or system failure. The growth of the protrusion is a complex phenomenon which involves chemical, electrical, and momentum driving forces in the system. Thus, it is important to understand the effect of electrochemistry in phase boundary evolution in order to optimize the performance of such processes. This thesis contributes to predicting and controlling such interface instability phenomena by developing a computational model that captures them. Successful application of the model to emerging metal extraction processes demonstrates its usefulness. A phase field model of electrochemical interface is developed for transport-limited electrolysis with rapid charge redistribution. This new Cahn-Hillard phase field formulation includes a model electrostatic free energy term, which captures the behavior of the diffuse interface under the applied electric field, in addition to transport by free energy gradient and convection. The model agrees with published stability criterion for a solid cathode. When the electrodes and electrolyte are low-viscosity fluids, flow stabilizes the interface.
(cont.) A new stability criterion for metal reduction in a liquid-liquid system is derived and agrees well with the model results. Next, the phase field model is extended for a ternary system to model titanium reduction in a supported electrolyte system. The model can simulate phase boundaries migration depending on the composition of the electrolyte and also electronically mediated reactions. Finally, Solid Oxide Membrane Electrolytic Smelting with Rotating Cathode (SOMERC), an emerging technology to electrolytically reduce titanium oxide from molten salt, is investigated. In the SOMERC process, rotational flow is introduced to create shear force that is expected to stabilize the interface. Computational fluid dynamics models of rotational flow are carried out to estimate the relationship between cathode rotational speed, shear strain rate, and boundary layer thicknesses. The phase field model presented in this thesis can be applied to any electrochemical reduction processes that are in the mass-transport controlled regime. Stability criteria and detailed morphology in two and three dimensions can be explored.
by Wanida Pongsaksawad.
Ph.D.
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Dhopatkar, Nishad. „UNDERSTANDING THE ADSORPTION AT SOLID-LIQUID INTERFACE AND ITS CONSEQUENCES ON INTERFACIAL PHENOMENA“. University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron149944490923674.
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Mathew, Anoop. „Study of interfacial phenomena in thin films using photoelectron spectroscopy“. Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 2.05 Mb., 74 p, 2006. http://wwwlib.umi.com/dissertations/fullcit/1435840.
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CLOITRE, MICHEL. „Phenomenes d'agregation de particules sur une interface, induits par interaction capillaire, a deux dimensions“. Paris 6, 1989. http://www.theses.fr/1989PA066108.
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Etude du mecanisme de croissance et des proprietes geometriques d'amas qui se forment sous l'action de forces d'interaction d'origine capillaire. Etude analytique de l'interaction capillaire entre deux particules de formes quelconques et entre deux agregats. Caracterisation des agregats autosimilaires dans l'espace direct et dans l'espace reciproque. Determination de la lacunarite des amas. Enfin, etude numerique et experimentale des phenomenes de croissance dans les configurations particules-amas et amas-amas
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Rhamdhani, Muhammad Akbar Brooks Geoffrey. „Reaction kinetics and dynamic interfacial phenomena in liquid metal-slag systems“. *McMaster only, 2005.
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Costa, Marcelo Henrique de Araújo Santos. „Fenômenos de Transporte em Meios Porosos e Interfaces Fractais“. reponame:Repositório Institucional da UFC, 2006. http://www.repositorio.ufc.br/handle/riufc/12377.
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COSTA, Marcelo Henrique de Araújo Santos. Fenômenos de Transporte em Meios Porosos e Interfaces Fractais. 2006. 103 f. Tese (Doutorado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2006.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-05-22T18:08:10Z No. of bitstreams: 1 2006_tese_mhascosta.pdf: 4361476 bytes, checksum: d1ad57b4bdfc1adb7ee1dc8cafc3333d (MD5)
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In this work, we investigate different transport phenomena through irregular media by means of numerical simulations. Initially, we study the effect of the critical percolation disorder on pore networks under diffusion-reaction conditions. Our results indicate the existence of three distinct regimes of reactivity, determined by the dimensionless parameter E=D/(Kl^2), where D is the molecular diffusivity of the reagent, K is its chemical reaction coefficient, and l is the length scale of the pore. At low values of E, the flux of the reacting species penetrating the network follows the classical scaling behavior, namely F~LE^(1/2). At intermediate values of E, the influence of the fractal morphology of the percolating cluster results in an anomalous behavior, F~L^(A/2)E^B, with an exponent B=0.34. At high values of E, the flux of the reagent reaches a saturation limit, F_SAT, that scales with the system size as F_SAT=L^A, with an exponent A=1.89, corresponding to the fractal dimension of the sample-spanning cluster. In the second part of this work, we study how the irregularity of the geometry influences the sequential deactivation of an interface accessed by diffusion. By using the notion of active zone, we propose a conjecture which constitutes an extension of Makarov theorem. In the third part, we investigate the steady-state heat transport in a fluid flowing through a two-dimensional channel whose walls are irregular interfaces. Once more, we apply the notion of active zone to investigate the effect of the interface geometry on the heat exchange efficiency of the system for different conductive-convective conditions. Compared with the behavior of a channel with smooth interfaces and under conditions in which the mechanism of heat conduction dominates, the results indicate that the effect of roughness is almost negligible on the efficiency of the heat transport system. On the other hand, when the convection becomes dominant, the role of the interface roughness is to generally increase both the heat flux across the wall as well as the active length of heat exchange, when compared with the smooth channel. Finally, we show that this last behavior is closely related with the presence of recirculation zones in the reentrant regions of the fractal geometry.
Neste trabalho investigamos diversos fenômenos de transporte tendo lugar através de meios irregulares por meio de simulação computacional. Inicialmente, tratamos do efeito da desordem crítica em redes percolantes de poros sujeitas à difusão e reação química. Verificamos a existência de três regimes distintos, determinados pelo parâmetro adimensional E=D/(Kl^2), onde D é a difusão molecular, K o coeficiente de reação química e l um comprimento característico. Para valores baixos de E, o fluxo de reagente que penetra a rede obedece à relação de escala clássica, F~LE^(1/2). Para valores intermediários de E, a influência da morfologia fractal do agregado de percolação resulta em um regime anômalo, F~L^(A/2)E^B, com um expoente B=0.34. Para valores altos de E, o fluxo de reagente atinge um limite de saturação, F_SAT, e escala com o tamanho do sistema na forma F_SAT=L^A, onde A=1.89 corresponde à dimensão fractal do agregado incipiente de percolação. Em uma segunda etapa do trabalho, analisamos o efeito da geometria irregular na desativação seqüencial de uma interface acessada por difusão. Aplicando o conceito de zona ativa, propomos uma conjectura que se constitui numa extensão do teorema de Makarov. Na terceira parte deste trabalho, investigamos o transporte estacionário de calor no escoamento de um fluido através de um tubo bidimensional, cujas paredes são interfaces irregulares. Mais uma vez, utilizando o conceito de zona ativa, investigamos o efeito da geometria da interface na eficiência de troca térmica do sistema em diferentes condições difusivo-convectivas. Em condições nas quais o mecanismo de transporte dominante é a condução, a comparação entre os resultados dos tubos liso e rugosos indica que o efeito da rugosidade é quase desprezível sobre a eficiência de dispositivos de transporte de calor. Por outro lado, quando a convecção torna-se dominante, a rugosidade passa a ter um papel importante e, em geral, o fluxo de calor e o comprimento da zona ativa aumentam com a rugosidade da interface de troca. Finalmente, mostramos que esse último comportamento está relacionado com as zonas de recirculação, presentes nas reentrâncias da geometria fractal.
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Ledyastuti, Mia. „First Principles and Classical Molecular Dynamics of Oil-Quartz Interfacial Phenomena in Nanogeoscience“. 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157547.
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Fatourechi, Mehrdad. „Design of a self-paced brain computer interface system using features extracted from three neurological phenomena“. Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/302.
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Self-paced Brain computer interface (SBCI) systems allow individuals with motor disabilities to use their brain signals to control devices, whenever they wish. These systems are required to identify the user’s “intentional control (IC)” commands and they must remain inactive during all periods in which users do not intend control (called “no control (NC)” periods).
This dissertation addresses three issues related to the design of SBCI systems: 1) their presently high false positive (FP) rates, 2) the presence of artifacts and 3) the identification of a suitable evaluation metric.
To improve the performance of SBCI systems, the following are proposed: 1) a method for the automatic user-customization of a 2-state SBCI system, 2) a two-stage feature reduction method for selecting wavelet coefficients extracted from movement-related potentials (MRP), 3) an SBCI system that classifies features extracted from three neurological phenomena: MRPs, changes in the power of the Mu and Beta rhythms; 4) a novel method that effectively combines methods developed in 2) and 3 ) and 5) generalizing the system developed in 3) for detecting a right index finger flexion to detecting the right hand extension. Results of these studies using actual movements show an average true positive (TP) rate of 56.2% at the FP rate of 0.14% for the finger flexion study and an average TP rate of 33.4% at the FP rate of 0.12% for the hand extension study. These FP results are significantly lower than those achieved in other SBCI systems, where FP rates vary between 1-10%.
We also conduct a comprehensive survey of the BCI literature. We demonstrate that many BCI papers do not properly deal with artifacts. We show that the proposed BCI achieves a good performance of TP=51.8% and FP=0.4% in the presence of eye movement artifacts. Further tests of the performance of the proposed system in a pseudo-online environment, shows an average TP rate =48.8% at the FP rate of 0.8%.
Finally, we propose a framework for choosing a suitable evaluation metric for SBCI systems. This framework shows that Kappa coefficient is more suitable than other metrics in evaluating the performance during the model selection procedure.
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Shih, Grace Hwei-Pyng. „Nanostructure and Optoelectronic Phenomena in Germanium-Transparent Conductive Oxide (Ge:TCO) Composites“. Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228175.
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Nanostructured composites are attracting intense interest for electronic and optoelectronic device applications, specifically as active elements in thin film photovoltaic (PV) device architectures. These systems implement fundamentally different concepts of enhancing energy conversion efficiencies compared to those seen in current commercial devices. This is possible through considerable flexibility in the manipulation of device-relevant properties through control of the interplay between the nanostructure and the optoelectronic response. In the present work, inorganic nanocomposites of semiconductor Ge embedded in transparent conductive indium tin oxide (ITO) as well as Ge in zinc oxide (ZnO) were produced by a single step RF-magnetron sputter deposition process.It is shown that, by controlling the design of the nanocomposites as well as heat treatment conditions, decreases in the physical dimensions of Ge nanophase size provided an effective tuning of the optical absorption and charge transport properties. This effect of changes in the optical properties of nanophase semiconductors with respect to size is known as the quantum confinement effect. Variation in the embedding matrix material between ITO and ZnO with corresponding characterization of optoelectronic properties exhibit notable differences in the presence and evolution of an interfacial oxide within these composites. Further studies of interfacial structures were performed using depth-profiling XPS and Raman spectroscopy, while study of the corresponding electronic effects were performed using room temperature and temperature-dependent Hall Effect. Optical absorption was noted to shift to higher onset energies upon heat treatment with a decrease in the observed Ge domain size, indicating quantum confinement effects within these systems. This contrasts to previous investigations that have involved the introduction of nanoscale Ge into insulating, amorphous oxides. Comparison of these different matrix chemistries highlights the overarching role of interfacial structures on quantum-size characteristics. The opportunity to tune the spectral response of these PV materials, via control of semiconductor phase assembly in the nanocomposite, directly impacts the potential for the use of these materials as sensitizing elements for enhanced solar cell conversion efficiency.
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Schumacher, Daniel [Verfasser]. „Interplay between magnetic and dielectric phenomena at tranistion metal oxide interfaces / Daniel Schumacher“. Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1036292681/34.
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Noever, Simon J. [Verfasser], und Bert [Akademischer Betreuer] Nickel. „Surface and interface phenomena in organic thin film transistors / Simon J. Noever ; Betreuer: Bert Nickel“. München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1135136203/34.
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Stadig, Degerman Mari, Caroline Larsson und Jan Anward. „When metaphors come to life : at the interface of external representations, molecular processes and student learning“. Linköpings universitet, Institutionen för teknik och naturvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-76140.
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When studying the molecular aspect of the life sciences, learners must be introduced to somewhat inaccessible phenomena that occur at the sub-micro scale. Despite the difficulties, students need to be familiar with and understand the highly dynamic nature of molecular processes. Thus, external representations1 (ERs) can be considered unavoidable and essential tools for student learning. Besides meeting the challenge of interpreting external representations, learners also encounter a large array of abstract concepts2, which are challenging to understand (Orgill & Bodner, 2004). Both teachers and learners use metaphorical language as a way to relate these abstract phenomena to more familiar ones from everyday life. Scientific papers, as well as textbooks and popular science articles, are packed with metaphors, analogies and intentional expressions. Like ERs, the use of metaphors and analogies is inevitable and necessary when communicating knowledge concerning molecular phenomena. Therefore, a large body of published research related to metaphors concerns science teachers’ and textbook writers’ interpretation and use of metaphors (Harrison & Treagust, 2006). In this paper we present a theoretical framework for examining metaphorical language use in relation to abstract phenomena and external representations. The framework was verified by using it to analyse students’ meaning-making in relation to an animation representing the sub-microscopic and abstract process of ATP-synthesis in Oxidative Phosphorylation. We seek to discover the animator’s intentions while designing the animation and to identify the metaphors that students use while interacting with the animation. Two of these metaphors serve as examples of a metaphor analysis, in which the characteristics of metaphors are outlined. To our knowledge, no strategies to identify and understand the characteristics, benefits, and potential pitfalls of particular metaphors have, to date, been presented in science education research. Our aspiration is to contribute valuable insights into metaphorical language use at the interface between external representations, molecular processes, and student learning.
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Costa, Marcelo Henrique de AraÃjo Santos. „FenÃmenos de Transporte em Meios Porosos e Interfaces Fractais“. Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=155.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoNeste trabalho investigamos diversos fenÃmenos de transporte tendo lugar atravÃs de meios irregulares por meio de simulaÃÃo computacional. Inicialmente, tratamos do efeito da desordem crÃtica em redes percolantes de poros sujeitas à difusÃo e reaÃÃo quÃmica. Verificamos a existÃncia de trÃs regimes distintos, determinados pelo parÃmetro adimensional E=D/(Kl^2), onde D à a difusÃo molecular, K o coeficiente de reaÃÃo quÃmica e l um comprimento caracterÃstico. Para valores baixos de E, o fluxo de reagente que penetra a rede obedece à relaÃÃo de escala clÃssica, F~LE^(1/2). Para valores intermediÃrios de E, a influÃncia da morfologia fractal do agregado de percolaÃÃo resulta em um regime anÃmalo, F~L^(A/2)E^B, com um expoente B=0.34. Para valores altos de E, o fluxo de reagente atinge um limite de saturaÃÃo, F_SAT, e escala com o tamanho do sistema na forma F_SAT=L^A, onde A=1.89 corresponde à dimensÃo fractal do agregado incipiente de percolaÃÃo. Em uma segunda etapa do trabalho, analisamos o efeito da geometria irregular na desativaÃÃo seqÃencial de uma interface acessada por difusÃo. Aplicando o conceito de zona ativa, propomos uma conjectura que se constitui numa extensÃo do teorema de Makarov. Na terceira parte deste trabalho, investigamos o transporte estacionÃrio de calor no escoamento de um fluido atravÃs de um tubo bidimensional, cujas paredes sÃo interfaces irregulares. Mais uma vez, utilizando o conceito de zona ativa, investigamos o efeito da geometria da interface na eficiÃncia de troca tÃrmica do sistema em diferentes condiÃÃes difusivo-convectivas. Em condiÃÃes nas quais o mecanismo de transporte dominante à a conduÃÃo, a comparaÃÃo entre os resultados dos tubos liso e rugosos indica que o efeito da rugosidade à quase desprezÃvel sobre a eficiÃncia de dispositivos de transporte de calor. Por outro lado, quando a convecÃÃo torna-se dominante, a rugosidade passa a ter um papel importante e, em geral, o fluxo de calor e o comprimento da zona ativa aumentam com a rugosidade da interface de troca. Finalmente, mostramos que esse Ãltimo comportamento està relacionado com as zonas de recirculaÃÃo, presentes nas reentrÃncias da geometria fractal.
In this work, we investigate different transport phenomena through irregular media by means of numerical simulations. Initially, we study the effect of the critical percolation disorder on pore networks under diffusion-reaction conditions. Our results indicate the existence of three distinct regimes of reactivity, determined by the dimensionless parameter E=D/(Kl^2), where D is the molecular diffusivity of the reagent, K is its chemical reaction coefficient, and l is the length scale of the pore. At low values of E, the flux of the reacting species penetrating the network follows the classical scaling behavior, namely F~LE^(1/2). At intermediate values of E, the influence of the fractal morphology of the percolating cluster results in an anomalous behavior, F~L^(A/2)E^B, with an exponent B=0.34. At high values of E, the flux of the reagent reaches a saturation limit, F_SAT, that scales with the system size as F_SAT=L^A, with an exponent A=1.89, corresponding to the fractal dimension of the sample-spanning cluster. In the second part of this work, we study how the irregularity of the geometry influences the sequential deactivation of an interface accessed by diffusion. By using the notion of active zone, we propose a conjecture which constitutes an extension of Makarov theorem. In the third part, we investigate the steady-state heat transport in a fluid flowing through a two-dimensional channel whose walls are irregular interfaces. Once more, we apply the notion of active zone to investigate the effect of the interface geometry on the heat exchange efficiency of the system for different conductive-convective conditions. Compared with the behavior of a channel with smooth interfaces and under conditions in which the mechanism of heat conduction dominates, the results indicate that the effect of roughness is almost negligible on the efficiency of the heat transport system. On the other hand, when the convection becomes dominant, the role of the interface roughness is to generally increase both the heat flux across the wall as well as the active length of heat exchange, when compared with the smooth channel. Finally, we show that this last behavior is closely related with the presence of recirculation zones in the reentrant regions of the fractal geometry.
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Chu, Yeou-Li. „Investigation of the interface phenomena and its effect on erosion and corrosion in aluminum die casting /“. The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487944660930011.
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Silvestri, Lorenzo. „Numerical study of wind-wave interfacial phenomena“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14643/.
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A DNS simulation has been performed in order to study the wind-wave interaction, especially focusing the attention on the interfacial phenomena. The numerical model is founded to reproduce gravity waves generation under the action of a turbulent wind. The VOF (volume of fraction) method is used in order to capture and model the free surface, while the wind is generated by imposing an external pressure gradient. This last choice, in contrast with the usual ways of simulating wind by a moving wall, turned out to be very effective from both the computational and the physical point of view.
The simulation can be described by two fundamental parameters: the friction Reynolds number is about 330 and the wave age is 35. The wave age has been calculated by a spectral analysis of the free surface: through this analysis the wavelength of the main ripple is found to be about 5 cm, while its phase speed results to be 0.7 m/s. This wavelength and phase speed seems reasonable by comparing it with experiments and observations.
The turbulent boundary layer is significantly modified by waves in a way that resembles rough turbulence. The spatially and time averaged mean velocity profile is affected by the roughness of waves as much as the fluctuating field. In this study a sea surface roughness of 0.017 is founded by observing the behaviour of the wind close to the free surface. This similarity between a rough wall and waves, can be relevant for modelling flows over wavy walls or predicting wind and wave currents, especially in the Geophysical fluid dynamic field.
Finally, the Phillips mechanism (turbulent pressure fluctuations along the free surface) and the sheltering mechanism (positive and negative pressure fluctuations respectively in front and on the leeside of the wave due to the boundary layer separation) have been clearly observed.
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Coronado, Hernández Óscar Enrique. „Transient phenomena during the emptying process of water in pressurized pipelines“. Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/120024.
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[ES] El análisis de los fenómenos transitorios durante las operaciones de llenado en conducciones de agua ha sido estudiado de manera detallada comparado con las maniobras de vaciado. En este último se encontró que no existen modelos matemáticos capaces de predecir el fenómeno. Esta investigación inicia estudiando el fenómeno transitorio generado durante el vaciado en una tubería simple, como paso previo para entender el comportamiento de las variables hidráulicas y termodinámicas durante el vaciado de agua en conducciones presurizadas de perfil irregular. Los análisis son realizados considerando dos situaciones: (i) la situación No. 1 corresponde al caso donde no hay válvulas de aire instaladas o cuando éstas han fallado por problemas operacionales o de mantenimiento, que representa la condición más desfavorable con respecto a la depresión máxima alcanzada; y (ii) la situación No. 2 corresponde al caso en donde se han instalado válvulas de aire en los puntos más elevados de la conducción para dar fiabilidad mediante el aire introducido al sistema previniendo de esta manera la depresión máxima.
En esta tesis doctoral se ha desarrollado un modelo matemático para predecir el comportamiento de las operaciones de vaciado. El modelo matemático es propuesto para las dos situaciones mencionadas anteriormente. La fase líquida (agua) es simulada con un modelo de columna rígida, en el cual se desprecia la elasticidad del agua y de la tubería debido a que la elasticidad del aire es mucho mayor que estas; y la interfaz aire-agua es modelada con un modelo de flujo pistón, el cual asume que la columna de agua es perpendicular a la dirección principal del flujo. La fase de aire es modelada usando tres ecuaciones: (a) un modelo politrópico basado en el comportamiento energético, que considera la expansión de las bolsas de aire; (b) la formulación de las válvulas de aire para cuantificar la magnitud del caudal de aire admitido; y (c) la ecuación de continuidad de la bolsa de aire. Un sistema ordinario de ecuaciones diferenciales es solucionado utilizando la herramienta de Simulink de Matlab.
El modelo matemático es validado empleando bancos experimentales localizados en los laboratorios de hidráulica de la Universitat Politècnica de València (Valencia, España) y en el Instituto Superior Técnico de la Universidad de Lisboa (Lisboa, Portugal). Los resultados muestran que el modelo matemático predice adecuadamente los datos experimentales de las presiones de las bolsas de aire, las velocidades del agua y las longitudes de las columnas de agua.
Finalmente, el modelo matemático es aplicado a un caso de estudio para mostrar su aplicabilidad a situaciones prácticas, con el fin de poder ser empleado por ingenieros para estudiar el fenómeno en conducciones reales y así tomar decisiones acerca de la planificación de esta operación.[CAT] L'anàlisi dels fenòmens transitoris durant les operacions d'ompliment en conduccions d'aigua ha sigut estudiat de manera detallada comparat amb les maniobres de buidatge. En este últim es va trobar que no hi ha models matemàtics capaços de predir el fenomen. Esta investigació inicia estudiant el fenomen transitori generat durant el buidatge en una canonada simple, com a pas previ per a entendre el comportament de les variables hidràuliques i termodinàmiques durant el buidatge d'aigua en conduccions pressuritzades de perfil irregular. Les anàlisis són realitzats considerant dos situacions: (i) la situació No. 1 correspon al cas on no hi ha vàlvules d'aire instal·lades o quan estes han fallat per problemes operacionals o de manteniment, que representa la condició més desfavorable respecte a la depressió màxima aconseguida; i (ii) la situació No. 2 correspon al cas on s'han instal·lat vàlvules d'aire en els punts més elevats de la conducció per a donar fiabilitat per mitjà de l'aire introduït al sistema prevenint d'esta manera la depressió màxima. En esta tesi doctoral s'ha desenrotllat un model matemàtic per a predir el comportament de les operacions de buidatge. El model matemàtic és proposat per a les dos situacions mencionades anteriorment. La fase líquida (aigua) és simulada amb un model de columna rígida, en el qual es desprecia l'elasticitat de l'aigua i de la canonada pel fet que l'elasticitat de l'aire és molt major que estes; i la interfície aire-aigua és modelada amb un model de flux pistó, el qual assumix que la columna d'aigua és perpendicular a la direcció principal del flux. La fase d'aire és modelada usant tres equacions: (a) un model politròpic basat en el comportament energètic, que considera l'expansió de les bosses d'aire; (b) la formulació de les vàlvules d'aire per a quantificar la magnitud del cabal d'aire admés; i (c) l'equació de continuïtat de la bossa d'aire. Un sistema ordinari d'equacions diferencials és solucionat utilitzant la ferramenta de Simulink de Matlab. El model matemàtic és validat emprant bancs experimentals localitzats en els laboratoris d'hidràulica de la Universitat Politècnica de València (València, Espanya) i en l'Institut Superior Tècnic de la Universitat de Lisboa (Lisboa, Portugal). Els resultats mostren que el model matemàtic prediu adequadament les dades experimentals de les pressions de les bosses d'aire, les velocitats de l'aigua i les longituds de les columnes d'aigua. Finalment, el model matemàtic és aplicat a un cas d'estudi per a mostrar la seua aplicabilitat a situacions pràctiques, a fi de poder ser empleat per enginyers per a estudiar el fenomen en conduccions reals i així prendre decisions sobre la planificació d'esta operació.
[EN] The analysis of transient phenomena during water filling operations in pipelines of irregular profiles has been studied much more compared to emptying maneuvers. In the literature, there is a lack of knowledge about mathematical models of emptying operations. This research starts with the analysis of a transient phenomenon during emptying maneuvers in single pipelines, which is a previous stage to understand the emptying operation in pipelines of irregular profiles. Analysis are conducted under two typical situations: (i) one corresponding to either the situation where there are no air valves installed or when they have failed due to operational and maintenance problems which represents the worse condition due to causing the lowest troughs of subatmospheric pressure, and (ii) the other one corresponding to the situation where air valves have been installed at the highest point of hydraulic installations to give reliability by admitting air into the pipelines for preventing troughs of subatmospheric pressure. Particularly, this research developed a mathematical model to predict the behavior of the emptying operations. The mathematical model is proposed for the two aforementioned situations. The liquid phase (water) is simulated using a rigid water column model (RWCM), which neglects the pipe and water elasticity given that the elasticity of the entrapped air pockets is much higher than the one from the pipe and the water. The air-water interface is simulated with a piston flow model assuming that the water column is perpendicular with the main direction of the flow. Gas phase is modeled using three formulations: (a) a polytropic model based on its energetic behavior, which considers an expansion of air pockets; (b) an air valve characterization to quantify the magnitude of admitted air flow; and (c) a continuity equation of the air. An ordinary differential equations system is solved using the Simulink tool of Matlab. The proposed model has been validated using experimental facilities at the hydraulic laboratories of the Universitat Politècnica de València, Valencia, Spain, and the Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal. The results show how the mathematical model adequately predicts the experimental data, including the pressure oscillation patterns, the water velocities, and the lengths of the water columns. Finally, the mathematical model is applied to a case study to show a practical application, which can be used for engineers to study the phenomenon in real pipelines to make decisions about performing of the emptying operation.
Coronado Hernández, ÓE. (2019). Transient phenomena during the emptying process of water in pressurized pipelines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/120024
TESIS
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Shin, Yun Kyung. „The water-amorphous silica interface: electrokinetic phenomena in a complex geometry, and treatment of interactions with biomolecules“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299587783.
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Phimphivong, Samrane. „Applications of Total Internal Reflection Fluorescence Microscopy for Studies of Chemical Phenomena at the Substrate-Liquid Interface“. Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194335.
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Applications of TIRFM for quantitative measurements of cells are limited due to high background fluorescence which can result in a low S/N ratio and therefore contribute to inaccuracy of measurements. Time-resolved total internal reflection fluorescence microscopy (TR-TIRFM) was developed by temporally gating a CCD camera using a liquid crystal shutter to optically filtering the short-live fluorescence and recording only the long-live emission. This technique was then applied to examine the extent of cell-substrate contacts. Tb+3 chelates such as DTPA-PhenylAS-Tb+3 was synthesized and applied as a membrane staining agent but was observed to internalized into the cell nucleus. A modified chelate molecule was therefore synthesized using DOPE as a carrier molecule. DOPE-DTPA-pAS-Tb+3 has a similar emission lifetime (1.5 msec) and appeared to stain only the cell membrane. TR-TIRF was applied to examine adherent cells on polystyrene-coated substrate. TR-TIRF images showed cellular autofluorescence and polystyrene emissions were optically filtered out, while the long-lived emission intensity of Tb+3 chelate was recorded. These results conclude that TR-TIRFM, with the use of long-live emission label (Tb+3 and Eu+3 chelates), is suitable as an analytical tool for probing a large number of cellular and molecular events occurring in the cell membrane and on the cell surface where background fluorescence would usually be problematic. Detection of K+ transported across a cell membrane is a prerequisite in the development of devices for screening drugs targeting K+ ion channels. K+ sensing film was fabricated by encapsulating a squaraine dye (aza-crown-SQR) in a sol-gel matrix for detection of K+. Sol-gel films were prepared by the hydrolysis and condensation reactions of TEOS or TMOS, APTS and GOPS mixtures. Formation of a DPhPC bilayer on sol-gel films was achieved by the vesicle fusion method and had diffusion coefficients of 2.3 and 2.1x10-8 cm2s-1 as measured by FRAP on TEOS-APTS-GOPS and TMOS-APTS-GOPS film, respectively. The time-based fluorescence intensity data from the H+ blocking experiments showed the sol-gel-supported DPhPC bilayers are impermeable to H+, and the K+ blocking experiments showed K+ was passively transported across a DPhPC bilayer by valinomycin.
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Schönhals, Alexander [Verfasser], Rainer [Akademischer Betreuer] Waser und Tobias G. [Akademischer Betreuer] Noll. „Non-standard switching phenomena and interface effects in resistive switching devices / Alexander Schönhals ; Rainer Waser, Tobias G. Noll“. Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1211345912/34.
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Schönhals, Alexander Verfasser], Rainer [Akademischer Betreuer] [Waser und Tobias G. [Akademischer Betreuer] Noll. „Non-standard switching phenomena and interface effects in resistive switching devices / Alexander Schönhals ; Rainer Waser, Tobias G. Noll“. Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1211345912/34.
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Charlier, Quentin. „Adhesion phenomena in thermoplastic composites based on acrylic matrices obtained by free radical polymerization“. Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI140.
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Ce mémoire de thèse s’intéresse aux phénomènes d’adhésion dans des composites à matrice thermoplastique obtenus par polymérisation radicalaire de mélanges réactifs. Après une courte introduction bibliographique sur les thématiques d’adhésion et d’adhérence, les propriétés générales des principaux éléments constitutifs des assemblages finaux sont étudiées séparément pour discuter de leur pertinence en vue d’une application composite. Une attention particulière est portée sur les systèmes réactifs acryliques à l’état liquide. L’étude se concentre ensuite sur les mécanismes réactionnels et l’évolution des propriétés des systèmes réactifs lors de la polymérisation. Ces problématiques sont de première importance pour anticiper les mécanismes gouvernant l’adhésion dans les composites obtenus mais aussi pour appréhender les potentielles problématiques à venir lors des étapes de mise en forme. Enfin, une étude est spécifiquement dédiée au cas de l’adhésion entre matrice acrylique et fibres de verre dans des composites à fibres de renfort continues. Les propriétés à l’interface verre/acrylique ont été évaluées à l’échelle microscopique dans des systèmes modèles et à l’échelle macroscopique dans des composites unidirectionnels, c'est à dire pouvant les défauts d’adhésion générés lors de la mise en forme. L’ensemble de ces résultats permet de se positionner quant à l’utilisation de solutions acryliques thermoplastiques pour des applications composites structurauxThese PhD research works focus on adhesion phenomena involved in thermoplastic composites based on acrylic matrices obtained by free radical polymerization. After a short bibliographic section introducing some basics on adhesion phenomena and practical adhesion measurements, properties of elementary constituents are assessed to discuss their relevancy for composite applications. Special attention is paid to acrylic reactive systems and properties of acrylic resins at liquid state. Then, the reaction mechanisms involved in free radical polymerization are detailed. The changes in acrylic system properties during polymerization are investigated to anticipate further processing-related issues. At last, a study is dedicated to the assessment of interfacial adhesion between glass fiber and acrylic matrices in fiber reinforced composites. Interfacial properties are characterized at microscale in model systems and at macroscale in real-sized composites, i.e. integrating process-induced defects. From overall results, the relevancy of acrylic thermoplastic solutions for structural composite applications is discussed
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明, 北山, und Akira Kitayama. „Molecular aspect of interfacial phenomena affecting particle characteristics of drug substances“. Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13155961/?lang=0, 2020. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13155961/?lang=0.
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実験・理論・数値シミュレーションに加え，データ科学（統計解析）も含めたアプローチを活用し、低分子医薬品の原薬粒子形態に影響を与える界面現象に対してメカニズムを検討した。具体的には液－液相互拡散を伴う系での相互拡散現象、結晶核生成機構について分子動力学シミュレーション、また粉砕工程での共粉砕物間の固－固界面でのアモルファス化について離散要素法シミュレーションと統計的手法の組合せによる解析を行った。The mechanisms of interfacial phenomena affecting the particle morphology of small-molecule drugs were investigated using experimental, theoretical and numerical simulations as well as data science (statistical analysis). The mechanisms of mutual diffusion and crystal nucleation in systems with liquid-liquid interface were studied by molecular dynamics simulations, and amorphization at the solid-solid interface between co-milled materials during milling process was simulated by a combination of discrete element method and statistical methods.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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Li, Linjun. „Systems Driven out of Equilibrium with Energy Input at Interfaces or Boundaries“. Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77884.
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We study the non-equilibrium behavior of systems that are driven out of equilibrium from the interface. In the first part of this thesis, we study a model of a two-dimensional lattice gas that is in contact with two heat baths that are at different temperatures. Performing Monte Carlo simulations, we find that there are three possible types of non-equilibrium steady states, depending on the values of certain system parameters. They include a disordered phase, a fully phase separated state, and an interesting state with striped patterns in the half of the lattice where the temperature is lower. The last one is a novel non-equilibrium steady state that we study systematically by varying the system parameters. To obtain the non-equilibrium finite-size phase diagram, we perform a spectrum analysis to classify not only the three major states, but also the sub-states of the striped phase. In the second part of the thesis, we study magnetic friction that results when two Potts systems move with respect to each other. In this research, we first study a model that consists of two interacting Potts blocks, where one block moves on top of the other. As a result, the system is driven out of equilibrium constantly. In our research we find for weak interfacial couplings that the contacting surfaces behave rather similar to a free surface. If the interfacial coupling is strong, however, anisotropic spin patterns appear on the contacting surfaces. This study is extended to a three-dimensional Potts wedge with a tip sliding along the surface of a Potts block. It is found that the shape of the Potts lattice influences the surface behavior of the system.Ph. D.
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TAOUD, SOULMA. „Role du soufre sur la stabilite des interfaces argent-nickel en relation avec les phenomenes de segregation“. Nantes, 1989. http://www.theses.fr/1989NANT2038.
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L'etude de la segregation du soufre aux interfaces ag/ni nous a conduit a utiliser des resultats de segregation et de cosegregation superficielles dans les alliages binaires et les alliages ternaires ag(ni), ni(ag) et ni(ag,s). L'etude par xps de la segregation superficielle du nickel dans ag(ni) a mis en evidence des deplacements importants de l'energie des electrons des niveaux du cur du nickel. Ceci nous a conduit a l'hypothese d'un renforcement de la liaison ag(ni) au voisinage de la surface, etant donne que le nickel segrege en sandwich. A partir de la valeur du deplacement chimique, nous avons evalue l'energie de segregation du nickel sur les alliages ag(ni). L'etude par aes de la segregation superficielle de l'argent sur les alliages ni(ag) montre une forte tendance de l'argent a segreger en surface; en presence du soufre il y a cosegregation ag-s avec competition de sites et c'est l'isotherme du soufre qui pilote celle de l'argent. L'etude des interfaces ag/ni montre que celles-ci sont de faibles energie; ceci s'explique bien avec l'hypothese d'un renforcement de la liaison ag-ni comme en surface. En presence du soufre, l'interface est detruite. Ce resultat a ete interprete dans le cadre des phenomenes de cosegregation superficielle. Des resultats comparables ont ete observes dans le cas de cu/fe
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Nigam, Poonam. „Interaction of water-soluble surfactants with self-assembled lipid monolayers at the vapor-liquid interface equilibrium and dynamic phenomena /“. Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1157987838.
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