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1
Momot, Konstantin I., David G. Regan, and Philip W. Kuchel. "NMR diffusion experiments for complex systems." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196319.
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Momot, Konstantin I., David G. Regan, and Philip W. Kuchel. "NMR diffusion experiments for complex systems." Diffusion fundamentals 2 (2005) 75, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14410.
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Fernandes, Neil Edward Gavalas George R. Gavalas George R. "Diffusion in mesoporous glass : simulations and experiments /." Diss., Pasadena, Calif. : California Institute of Technology, 1997. http://resolver.caltech.edu/CaltechETD:etd-01092008-135803.
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Wohlgemuth, Michael. "Diffusionsexperimente an Nanokapseldispersionen - Diffusion Experiments on Dispersed Nanocapsules." Gerhard-Mercator-Universitaet Duisburg, 2002. http://www.ub.uni-duisburg.de/ETD-db/theses/available/duett-02112002-202840/.
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The central topic if this work was the comparative assessment of two analytical techniques: Pulsed Field Gradient Nuclear Magnetic Resonance (PFG-NMR) Spectroscopy and the Dynamic Nanosizing Microscopy (DNM). They are focused on the same physical parameter: the self diffusion, for determination of diffusion coefficients and particle sizes. With the methods introduced above nanocapsule dispersions are investigated with regard to their use in pharmaceutical applications. In this work especially the long time stability of dispersions, the dynamic of molecules like surfactants, oil and ethanol as well as the molecular exchange between the capsules and the environment were studied.
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Klages, Rainer. "Deterministic chaos and diffusion: from theory to experiments." Diffusion fundamentals 2 (2005) 24, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14354.
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Moroney, Benjamin F., Timothy Stait-Gardner, Gang Zheng, and William S. Price. "Numerical analysis of NMR diffusion experiments in complex systems." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185579.
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Moroney, Benjamin F., Timothy Stait-Gardner, Gang Zheng, and William S. Price. "Numerical analysis of NMR diffusion experiments in complex systems." Diffusion fundamentals 16 (2011) 69, S. 1-3, 2011. https://ul.qucosa.de/id/qucosa%3A13811.
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Fechete, Radu, Daniel Moldovan, Dan Eugen Demco, and Bernhard Blümich. "Laplace inversions applied to multi–component T 2 – T 2 exchange experiments." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192143.
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Two-dimensional (2D) T2-T2 molecular exchange NMR experiments with a period of magnetization storage between the two T2 relaxation encoding periods are presented. The two-dimensional time map was inverted using a fast Laplace algorithm to obtain the
T2–T2 exchange map. T2–MZ(store)–T2 2D 1H NMR spectra recorded at high and low homogeneous magnetic fields of water and oil in sand, air bubbles in water and foams, exchange of liquid / foam and liquid / saturated vapours of chloroform are presented. Uni–
and bi–directional exchange was observed for bubbles in water, superficial liquid shell, and foam.
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Chakraborty, Sumit. "Multicomponent cation diffusion in aluminosilicate garnets: Theory, experiments and applications." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185214.
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Results from experiments in this work have been combined with existing data to yield tracer diffusivities of divalent cations in natural multicomponent garnets at 10-40 kb, 1100 - 1475°C. For the garnet compositions studied in this work, the activation energy for tracer diffusion of Mn < Fe ≃ Mg, while activation volumes increase in the order Mg < Fe < Mn. These data may be used with theoretical models to calculate the full multicomponent diffusion coefficient matrix as a function of pressure, temperature, composition and oxygen fugacity. An analytical model has been developed to describe the relaxation of compositional zoning in metapelitic garnets during metamorphism. It is found that a significant amount of relaxation occurs during heating and the composition at the core of a garnet crystal is disturbed very early in the process. The extent of relaxation depends on a number of factors which include the grain size, the initial shape of the compositional profile, details of the thermal history and the textural mode of occurrence of the garnet. Complications such as oscillations in a compositional profile may be explained by the mathematical form of the equations describing the process. Graphical representation of the results of this model have been provided that allow quick and easy determination of the extent of relaxation or time scale of metamorphic processes. Calculations using the diffusion data indicate that Fe-Mg exchange geothennometry and Sm-Nd geochronology involving garnets may not yield the peak metamorphic conditions for certain geologically realistic situations. Model calculations on natural assemblages suggest that the diffusion data may be used to yield infonnation on metamorphic processes ranging from time scales to crystal growth rates during metamorphism. Veracity of P-T paths calculated from garnet zoning may also be checked using the diffusion data. Illustrative examples of such calculations have been provided.
10
Bosson, Alison. "Experiments with scale-space vision systems." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323309.
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Adem, Ziad, Flavien Guenneau, Marie-Anne Springuel-Huet, and Antoine Gédéon. "Study of the butane diffusion in metal organic framework materials by PFG NMR experiments." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-189409.
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Simon, Jean-Marc, Edith Fardet-Lemaire, Igor Bezverkhyy, Jean-Pierre Bellat, and Florence Baras. "Kinetics of adsorption of linear and branched C6 alkanes onto ZSM-5 zeolite - experiments and molecular simulations." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195653.
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Berner, Tim, and Klaus-Dieter Becker. "Electrical conductivity relaxation experiments on single crystalline cobalt silicate Co 2 SiO 4 by using impedance spectroscopy." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186788.
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Fechete, Radu, Daniel Moldovan, Dan Eugen Demco, and Bernhard Blümich. "Laplace inversions applied to multi–component T 2 – T 2 exchange experiments." Diffusion fundamentals 10 (2009) 14, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14105.
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Two-dimensional (2D) T2-T2 molecular exchange NMR experiments with a period of magnetization storage between the two T2 relaxation encoding periods are presented. The two-dimensional time map was inverted using a fast Laplace algorithm to obtain the
T2–T2 exchange map. T2–MZ(store)–T2 2D 1H NMR spectra recorded at high and low homogeneous magnetic fields of water and oil in sand, air bubbles in water and foams, exchange of liquid / foam and liquid / saturated vapours of chloroform are presented. Uni–
and bi–directional exchange was observed for bubbles in water, superficial liquid shell, and foam.
15
Grinberg, Farida. "Ultraslow molecular dynamics of organized fluids: NMR experiments and Monte-Carlo simulations." Diffusion fundamentals 2 (2005) 119, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14460.
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Hudson, Troy Lee Stevenson David John Aharonson Oded. "Growth, diffusion, and loss of subsurface ice on Mars : experiments and models /." Diss., Pasadena, Calif. : California Institute of Technology, 2008. http://resolver.caltech.edu/CaltechETD:etd-05022008-154254.
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Adem, Ziad, Flavien Guenneau, Marie-Anne Springuel-Huet, and Antoine Gédéon. "Study of the butane diffusion in metal organic framework materials by PFG NMR experiments." Diffusion fundamentals 11 (2009) 18, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A13957.
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Niss, Kristine. "Fast and slow dynamics of glass-forming liquids : what can we learn from high pressure experiments ?" Paris 11, 2007. http://www.theses.fr/2007PA112022.
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Il a été montré durant la dernière décennie que la fragilité qui traduit le caractère plus ou moins non-Arrhénien d'un liquide, peut être correlée à de nombreuses propriétés de ce liquide et de son verre. Dans ce travail, des critères de test de ces corrélations utilisant la pression comme nouveau paramètre extérieur ont été mis au point. Ils ont été appliqués à l'étude d'un nouveau jeu de données obtenu pendant ce travail. On a particulièrement étudié la largeur du pic de relaxation alpha par spectroscopie diélectrique, l'intensité relative du pic de bose et le déplacement carré moyen par diffusion de neutron, ainsi que le facteur de non-ergodicité par diffusion inélastique des rayons X. La largeur du pic de relaxation alpha et l'intensité relative du pic du bose ne semblent pas liés à l'effet de la densité sur le temps de relaxation. Pour ces grandeurs, la bonne corélation à considérer serait alors celle avec la fragilité isochore et non la fragilité isobare usuelle. Le déplacement carré moyen est pour sa part, lié aux effets de température et de densité. Par ailleurs, le facteur de non-ergodicité pris à Tg est, lui, correlé à l'effet de la densité sur le ralentissement visqueuxThe degree of departure from Arrhenius temperature dependence of the relaxation time in the viscous liquid, thefragility, has in the course of the last decade been shown to (or suggested to) correlate with a large number of properties in the liquid and the corresponding glass. Here we develop a set of criteria for scrutinizing these types of correlations by introducing pressure as a control variable in addition to temperature. These criteria are used in the analysis of an extensive new set of data. We particularly study the width of the alpha relaxation by dielectric spectroscopy, the relative intensity of the boson peak and the mean square displacement by neutron scattering and the nonergodicity factor by inelastic X-ray scattering. In the study of the width of the alpha relaxation as well as the relative intensity of the boson peak we find that they do not relate to the effect of density on the relaxation time, and that a physically meaningful correlation in these cases should be a correlation to isochoric fragility rather than to the conventional isobaric fragility. The mean square displacement is found to relate to a balanced combination of temperature and density, while we suggest that the nonergodicity factor evaluated at Tg is correlated with the relative effect of density on the viscous slowing down
19
Keil, Frerich J., and Nils E. R. Zimmermann. "Transport barriers as triggered by the idealized microscopic crystal surface and the role of the evaluation protocol of diffusion experiments." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185721.
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Simon, Jean-Marc, Edith Fardet-Lemaire, Igor Bezverkhyy, Jean-Pierre Bellat, and Florence Baras. "Kinetics of adsorption of linear and branched C6 alkanes onto ZSM-5 zeolite - experiments and molecular simulations: Kinetics of adsorption of linear and branched C6 alkanes ontoZSM-5 zeolite - experiments and molecular simulations." Diffusion fundamentals 2 (2005) 37, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14367.
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Berner, Tim, and Klaus-Dieter Becker. "Electrical conductivity relaxation experiments on single crystalline cobalt silicate Co 2 SiO 4 by using impedance spectroscopy." Diffusion fundamentals 12 (2010) 45, 2010. https://ul.qucosa.de/id/qucosa%3A13885.
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Caginalp, Paul Aydin. "Mean square displacements as an alternative to simulating fluorescence correlation spectroscopy experiments." Diss., Online access via UMI:, 2006.
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Keil, Frerich J., and Nils E. R. Zimmermann. "Transport barriers as triggered by the idealized microscopic crystal surface and the role of the evaluation protocol of diffusion experiments." Diffusion fundamentals 16 (2011) 76, S. 1-2, 2011. https://ul.qucosa.de/id/qucosa%3A13819.
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Leroy, Frederic H. R., Hervé Jobic, Bernard Rousseau, and Alain H. Fuchs. "Self-diffusion of n-alkanes in MFI-type zeolites: a molecular dynamics study and a comparison to quasi-elastic neutronscattering experiments." Diffusion fundamentals 3 (2005) 6, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14294.
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Laurin, Mathias. "Diffusion and fluctuations during CO oxidation on Pd supported nanoparticles a combined experiments and simulations study /." [S.l.] : [s.n.], 2005. http://www.diss.fu-berlin.de/2006/13/index.html.
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Harkins, Kevin. "BIOPHYSICAL MECHANISMS OF DIFFUSION WEIGHTED MRI ASSESSED THROUGH COMPUTATIONAL MODELING AND EXPERIMENTS IN BIOREACTOR CELL CULTURES." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195985.
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The apparent diffusion coefficient (ADC) is a quantitative measure of water diffusion in tissue which is sensitive to the microstructural features of brain tissue and can be measured non-invasively with diffusion-weighted MRI (DWMRI). Within minutes after the onset of ischemic stroke, the ADC of water decreases 30-50% within the affected tissue. Although this was initially discovered nearly two decades ago, there is no consensus on the biophysical mechanisms responsible for the drop in ADC after ischemia. This dissertation investigates the biophysical mechanisms which determine the ADC through mathematical models of water diffusion in tissue as well as experiments in hollow fiber bioreactor (HFBR) cell cultures.The mathematical model of water diffusion in tissue predicts that the biophysical mechanisms which affect the ADC are diffusion time dependent. At short diffusion times, the ADC is sensitive to the intrinsic diffusivity of intracellular water, while at long diffusion times, the ADC is sensitive to changes in the intracellular volume fraction. Furthermore, the ADC changes associated with ischemia can be account for completely by a change in the intracellular cell volume fraction when the intracellular T2 is allowed to be lower than the extracellular T2.A unique feature of the HFBR bioreactor cell culture system is that it allows the diffusive properties of intracellular water to be investigated individually. The change after ischemia in the ADC measured from intracellular water (iADC) is dependent upon the diffusion time used to collect iADC measurements. At short diffusion times, the iADC decreases after ischemia, which is likely due to a decrease in the energy dependent movement of water within the cell. At long diffusion times, the iADC increases after ischemia, which is related to cell swelling. The results from the HFBR experiments are consistent with the mathematical model and provide a clear picture of the biophysical mechanisms important to measurements of water diffusion in living and ischemic tissue with DWMRI.
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Juna, Shazia, and Anton Huber. "Translational diffusion coefficients and hydrodynamic radii of normal corn starch in aqueous media from asymmetrical flow field-flow fractionation experiments." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186242.
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Starch is a highly disperse material with broad distributions of molecular sizes and geometries. Its dissolution in aqueous media is difficult to achieve and it tends to form aggregates through both inter- and intra-molecular interactions. Asymmetrical flow field-flow fractionation (AF4) is a suitable technique for the separation of such macromolecular and colloidal systems. A major advantage of AF4 is the direct correlation of translational diffusion coefficients with retention time and experimental parameters. In this article, the hydrodynamic and diffusive mobility of normal corn starch dissolved in 0.035 M KSCN was investigated by systematically varying the cross flow rates (applied forces); the translational diffusion coeffcients for normal corn starch in aqueous medium were found to range between 9.9 x 10-9 cm2/s and ~2.5 x 10-7 cm2/s with varying Fcr rates. Diffusion coefficient ranges shifted to higher diffusion co-efficient values at higher cross flow rates (applied forces). This behaviour, which may be attributed to the increased retention of very large starch molecules/particles at high Fcr rates, is further confirmed by the decrease in apparent molar mass and mass recovery values.
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Chandra, Ashwini. "On the Mechanism of Niobium Electropolishing." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1330544777.
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Saidoun, Mohamed. "Investigations into Asphaltenes Destabilization, Aggregation and Deposition." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3020.
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Du fait des problèmes industriels reliés aux asphaltènes lors de l’extraction, du traitement et du transport des hydrocarbures, les champs pétrolifères sont développés de manière conservatrice avec des moyens de prévention de dépôts surdimensionnés. Les répercussions économiques sur les architectures et les opérations se quantifient en centaines de millions de dollars par an autour du globe terrestre.De nombreuses études menées sur les asphaltènes dans des solvants dispersants, tels que les solvants aromatiques, ont permis une description extensive des propriétés et structures moléculaires des asphaltènes durant les 20 dernières années. Malgré la connaissance accrue sur les dispersions d’asphaltènes en solution colloïdales, leur incompatibilité avec certains composés plus légers, tels que les alcanes, demeure mal comprise. En effet, la présence d’alcanes ou d’autres constituants légers comme le dioxyde de carbone induit une déstabilisation des asphaltènes. Sous ces conditions de mélanges, ceux-ci tendent à s’agréger et/ou à s’accumuler sur les parois des installations. De nombreuses études montrent que les théories de transfert de masse peuvent expliquer ces phénomènes dans des solution de pétrole + alcanes liquides préparées en laboratoire. Plus la concentration volumique de mauvais solvants est grande dans la solution, plus la quantité d’asphaltènes instables et leur vitesse d’agrégation sont grandes. En réalité, la décroissance de la pression dans les conduites, pendant l’écoulement du fluide, induit une augmentation significative du volume des composés hydrocarbures légers ou du CO2. Ainsi, avec l’allègement du solvant liquide certaines fractions d’asphaltènes peuvent être déstabilisées et causer des problèmes. Des expériences de solutions liquides à pression atmosphérique ont précédemment été conçues pour ajuster des paramètres théoriques nécessaires aux modélisations, tels que la constante d’agrégation des asphaltènes instables, leur nombre ou leur diffusivité. En revanche, ces coefficients sont inconnus dans les conditions de déstabilisation industrielles en raison de la difficulté à les déterminer expérimentalement. En pratique, ceci limite la prédiction des risques de dépôts d’asphaltènes dans des cas industriels. La volonté de cette thèse est d’améliorer la prédiction du comportement des asphaltènes dans les conditions d’opérations de l’industrie pétrolière. Son objectif est d’abord de développer la compréhension des systèmes liquides aux conditions atmosphériques afin d’en extraire les mécanismes dominants et limitants. Dans un premier temps, les observations expérimentales sont donc menées sur des mélanges de pétrole et d’heptane. Une fois les mécanismes bien compris, un parallèle est réalisé avec d’autres alcanes, dont le methane.La première partie de cette dissertation est une investigation des deux phénomènes qui ont lieu simultanément dans la phase liquide pendant l’ajout ininterrompu d’heptane : la déstabilisation et l’agrégation des asphaltènes en suspension.Dans une seconde partie, l’utilisation d’un résonateur en cristal de quartz, immergé dans le fluide d’étude, permet pour la première fois de mesurer la quantité de dépôt d’asphaltènes pendant le changement continu du solvant. Le modèle de diffusion proposé pour expliquer le transfert de masse des asphaltènes dans le fluide vers la surface solide est en accord avec de précédentes recherches. Les particules primaires d’asphaltènes instables sont identifiées comme contributrices principales du processus de déposition et le taux de changement de composition volumique de la solution liquide est un facteur dominant de leur génération.En dernière partie, les concepts ci-dessus sont vérifiés pour des systèmes à gaz dissouts avec un appareil analogue à capteurs immergés sous pression. Pour la première fois, le taux de déposition et la concentration en asphaltènes instables peuvent être quantifiées, en laboratoire, au cours d’une dépressurisation d’un pétroleAsphaltenes have been known, since decades, to occasionally cause severe industrial problems during crude oil extraction and during its transport. Petroleum fields are apprehensively developed with oversized and costly prevention approaches due to the limited understanding on asphaltenes deposition in conditions of oil production.Previous fundamental researches provided extensive descriptions of asphaltenes properties in good solvents, such as aromatic solvents. The incompatibility of asphaltenes with alkanes induces their destabilization, their aggregation and their deposition. The aggregation and the mass transfer behavior of asphaltenes have been explained by theoretical concepts for oil + liquid alkane systems. The amount of destabilized asphaltenes and their aggregation rate both increase as the volume fraction of the anti-solvent increases. Quantitative laboratory measurements have been accordingly developed for liquid systems at atmospheric pressure. However, risks related to the instability of asphaltenes are only qualitatively understood during the primary production of crude oils. In the oil fields, the pressure decrease of the oil causes the light constituents, such as methane or carbon dioxide, to increase their volume fraction in the liquid phase. Experimental determination of theoretical parameters related to asphaltene deposition under pressure is therefore a key.The first part of this dissertation addresses the understanding of bulk behavior (destabilization and aggregation) related to asphaltenes in oil-heptane systems. Analytical equations are proposed to distinctly model both phenomena. Numerical results obtained by combining both equations provide excellent agreements with experimental measurements. The study reconciles the continuum consideration of asphaltene molecules in crude oils with the notion of flocculation "onset" by distinguishing the destabilization and the aggregation kinetics. A reasonable match is found between the transition of the theoretical and the adjusted colloidal stability ratio, indicating that underlying physics are captured by considering simultaneous destabilization and aggregation kinetics.A fully immersed quartz crystal resonator is used to record the mass of deposit on solid surfaces in contact with varying liquid solutions. The deposition rate of asphaltenes is studied during continuous addition of heptane. A diffusion-limited model, designed for studied geometry, can explain experimental results and agrees with previous research on different apparatus. The mass transfer relationship reveals that primary unstable aggregates of asphaltenes mainly contribute to the deposition process and have an average hydrodynamic radius of 7 nanometers (± 50%). A linear relationship is found between the generation rate and the deposition rate of unstable asphaltenes in the investigated conditions. However, the initial presence of large suspending unstable aggregates slows down the asphaltenes deposition process.In the last phase of this work, the validity of defined concepts for the destabilization, the aggregation and the deposition induced by heptane additions is verified for oil-methane systems. The rate of change of solution properties is found to be the predominant variable affecting the deposition of asphaltenes. The effect of methane is significantly more pronounced than liquid alkanes on the asphaltene deposition.For the first time, the bulk concentration of unstable asphaltenes and their deposition rate can be quantitatively measured during the depressurization of live oils (light constituent dissolved). Although first tendencies are de-rived from this work, the effect of the anti-solvent nature still needs further research with the identified variables in order to fully elucidate the thermodynamic driving quantity which controls the amount of destabilized asphaltenes
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Karnik, Umesh. "Experiments on the structure of turbulence and the diffusion of heat from a line source in uniformly sheared flows." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5118.
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Han, Tao. "Ultrasound and insertion force effects on microneedles based drug delivery : experiments and numerical simulation." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19591.
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Transdermal drug delivery (TDD) is limited by high resistance of the outer layer of the skin, namely stratum corneum which blocks any molecule that is larger than 500 Da. Research on TDD has become very active in recent years and various technologies have been developed to overcome the resistance of the stratum corneum. In particular, researchers have started to consider the possibility of combining the TDD technologies in order to achieve further increment for drug permeability. Microneedles (MNs) and sonophoresis are both promising technologies that can perform notable enhancement in drug permeation via different mechanisms and therefore give a good potential for combining with each other. We discuss the possible ways to achieve this combination as well as how this combination would increase the permeability. Some of the undeveloped (weaker) research areas of MNs and sonophoresis are also discussed in order to understand the true potential of combining the two technologies when they are developed further in the future. We propose several hypothetical combinations based on the possible mechanisms of MNs and sonophoresis.
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Juna, Shazia, and Anton Huber. "Translational diffusion coefficients and hydrodynamic radii of normal corn starch in aqueous media from asymmetrical flow field-flow fractionation experiments." Diffusion fundamentals 15 (2011) 7, S. 1-8, 2011. https://ul.qucosa.de/id/qucosa%3A13843.
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Starch is a highly disperse material with broad distributions of molecular sizes and geometries. Its dissolution in aqueous media is difficult to achieve and it tends to form aggregates through both inter- and intra-molecular interactions. Asymmetrical flow field-flow fractionation (AF4) is a suitable technique for the separation of such macromolecular and colloidal systems. A major advantage of AF4 is the direct correlation of translational diffusion coefficients with retention time and experimental parameters. In this article, the hydrodynamic and diffusive mobility of normal corn starch dissolved in 0.035 M KSCN was investigated by systematically varying the cross flow rates (applied forces); the translational diffusion coeffcients for normal corn starch in aqueous medium were found to range between 9.9 x 10-9 cm2/s and ~2.5 x 10-7 cm2/s with varying Fcr rates. Diffusion coefficient ranges shifted to higher diffusion co-efficient values at higher cross flow rates (applied forces). This behaviour, which may be attributed to the increased retention of very large starch molecules/particles at high Fcr rates, is further confirmed by the decrease in apparent molar mass and mass recovery values.
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Ludwig, Lars. "Analytical investigations and numerical experiments for singularly perturbed convection-diffusion problems with layers and singularities using a newly developed FE-software." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-137301.
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In the field of singularly perturbed reaction- or convection-diffusion boundary value problems the research area of a priori error analysis for the finite element method, has already been thoroughly investigated. In particular, for mesh adapted methods and/or various stabilization techniques, works have been done that prove optimal rates of convergence or supercloseness uniformly in the perturbation parameter epsilon.
Commonly, however, it is assumed that the exact solution behaves nicely in that it obeys certain regularity assumptions although in general, e.g. due to corner singularities, these regularity requirements are not satisfied. So far, insufficient regularity has been met by assuming compatibility conditions on the data.
The present thesis originated from the question: What can be shown if these rather unrealistic additional assumptions are dropped? We are interested in epsilon-uniform a priori estimates for convergence and superconvergence that include some regularity parameter that is adjustable to the smoothness of the exact solution.
A major difficulty that occurs when seeking the numerical error decay is that the exact solution is not known. Since we strive for reliable rates of convergence we want to avoid the standard approach of the "double-mesh principle". Our choice is to use reference solutions as a substitute for the exact solution.
Numerical experiments are intended to confirm the theoretical results and to bring further insights into the interplay between layers and singularities. To computationally realize the thereby arising demanding practical aspects of the finite element method, a new software is developed that turns out to be particularly suited for the needs of the numerical analyst. Its design, features and implementation is described in detail in the second part of the thesis.
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Parditka, Bence. "Investigation of diffusion and solid state reactions on the nanoscale in silicon based systems of high industrial potential : experiments and simulations." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4348/document.
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La première partie de mes résultats concerne les phénomènes de diffusion induits par des effets de contrainte. Nous avons étudié ces effets d’un point de vu théorique, afin de comprendre le rôle de la contrainte dans la diffusion. Les résultats montrent que l’effet de contrainte ne semble pas induire d’effet mesurable sur le coefficient cinétique à l’interface, cependant le taux de mélange semble diminuer. La seconde partie concerne des mesures expérimentales, par EXAFS et GIXRF utilisées sur des empilements Ta/a-Si/Ni/a-Si/Ta/substrat permettant de suivre la formation des phases ainsi que la croissance, à une température donnée, et ce jusqu’à la formation de la phase Ni2Si et au delà. La troisième partie concerne le système Cu-Si. Nous avons suivi les premiers stades de la formation de la phase Cu3Si, en utilisant les techniques XRD, APT, SNMS, ainsi qu’un profilomètre et une mesure de résistance quatre points sur différents échantillons réalisés par pulvérisation. Dans le cas de l’empilement Cu/a-Si/substrat, la formation de phases a suivi une cinétique linéaire. Nous avons notamment mis en évidence la formation très rapide d’une phase qui apparait directement après le premier recuit très court, démontrant ainsi le rôle déterminant de la préparation des échantillons dans l’étude des processus de formation de phases. La quatrième partie s’intéresse au silicène : cette structure bidimensionnelle de silicium dite en « nid d’abeilles », réalisée sur un substrat d’argent et qui présente de grandes similitudes avec le graphène. En utilisant de façon complémentaire les techniques AES-LEED-STM, nous avons déterminé la limite de solubilité du silicium dans l’argentDiffusion and related solid state reaction phenomena have been studied in four different material couples. The first section of the results concerned the diffusion related stress effects. We analyzed the question theoretically, for planar model geometry, to find the role of stress in diffusion. We obtained that stress effects do not have any measurable effects on the kinetic coefficient of the interface shift. However, the intermixing rate decreases. The second section we performed EXAFS and GIXRF experiments on sandwich structured Ta/a- Si/Ni/a-Si/Ta/substrate samples and followed the phase formation and growth at a given temperature at which the Ni2Si phase has formed and continued to grow. The third section we obtained in the Cu-Si system. We followed the early stages of phase formation of the Cu3Si phase under different circumstances. We performed XRD, APT, SNMS, profilometer and 4 wire resistance measurements on sputtering deposited samples. We found that in case of the Cu/a-Si/substrate samples the phase formation was followed by a linear kinetics. Secondly, prior to the linear phase growth, we observed an extremely fast phase formation that appeared immediately after the very first and shortest annealing, which showed that the preparation sequence of the sample is a crucial point in phase formation processes. The fourth section deals with the silicene. It is the honeycomb structured formation of Si atoms with properties similar to graphene. We investigated the dissolution of Si into Ag. We performed a combination of AES, LEED, STM measurements. We determined the dissolution limit of Si in Ag from data obtained from the AES measurements
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Deshpande, Rutooj D. "UNDERSTANDING AND IMPROVING LITHIUM ION BATTERIES THROUGH MATHEMATICAL MODELING AND EXPERIMENTS." UKnowledge, 2011. http://uknowledge.uky.edu/cme_etds/4.
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There is an intense, worldwide effort to develop durable lithium ion batteries with high energy and power densities for a wide range of applications, including electric and hybrid electric vehicles. For improvement of battery technology understanding the capacity fading mechanism in batteries is of utmost importance. Novel electrode material and improved electrode designs are needed for high energy- high power batteries with less capacity fading. Furthermore, for applications such as automotive applications, precise cycle-life prediction of batteries is necessary.
One of the critical challenges in advancing lithium ion battery technologies is fracture and decrepitation of the electrodes as a result of lithium diffusion during charging and discharging operations. When lithium is inserted in either the positive or negative electrode, there is a volume change associated with insertion or de-insertion. Diffusion-induced stresses (DISs) can therefore cause the nucleation and growth of cracks, leading to mechanical degradation of the batteries. With different mathematical models we studied the behavior of diffusion induces stresses and effects of electrode shape, size, concentration dependent material properties, pre-existing cracks, phase transformations, operating conditions etc. on the diffusion induced stresses. Thus we develop tools to guide the design of the electrode material with better mechanical stability for durable batteries.
Along with mechanical degradation, chemical degradation of batteries also plays an important role in deciding battery cycle life. The instability of commonly employed electrolytes results in solid electrolyte interphase (SEI) formation. Although SEI formation contributes to irreversible capacity loss, the SEI layer is necessary, as it passivates the electrode-electrolyte interface from further solvent decomposition. SEI layer and diffusion induced stresses are inter-dependent and affect each-other. We study coupled chemical-mechanical degradation of electrode materials to understand the capacity fading of the battery with cycling. With the understanding of chemical and mechanical degradation, we develop a simple phenomenological model to predict battery life.
On the experimental part we come up with a novel concept of using liquid metal alloy as a self-healing battery electrode. We develop a method to prepare thin film liquid gallium electrode on a conductive substrate. This enabled us to perform a series of electrochemical and characterization experiments which certify that liquid electrode undergo liquid-solid-liquid transition and thus self-heals the cracks formed during de-insertion. Thus the mechanical degradation can be avoided. We also perform ab-initio calculations to understand the equilibrium potential of various lithium-gallium phases.
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Liu, Xing. "R & D of a High-Aaverage-Power Fabry-Pérot resonator for Thomson scattering experiments." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS532/document.
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L’imagerie effectuée avec des rayons X est largement utilisée de nos jours dans de nombreuses disciplines telles que la physique du solide, les sciences du vivant et la médecine. Les sources de rayons X basées sur la diffusion Thomson d’un faisceau laser par des paquets d’électrons permettent d’obtenir des faisceaux de bonnes qualités pour un faible coût et un faible encombrement. Plusieurs instituts de recherche académiques se sont récemment lancés dans la construction de telles sources qui sont constituées d’un anneau des stockage d’électrons et d’un résonateur optique. Le résonateur optique permet de stocker des impulsions laser focalisées au point d’interaction laser-électron à des fréquences de plusieurs dizaines de méga Hertz. Des flux de rayons X dépassants 10^{11} ph/s peuvent ainsi être obtenus. Dans ce travail de thèse un modèle de stockage d’impulsion a été développé. Ce modèle prend en compte les effets de la phase CEP (carrier-envelope phase) et des décalages temporels permettant d’obtenir des résonances secondaires. Ces résonances sont observées couramment et nous avons pu calculer les gains et finesses équivalentes. Nous avons aussi calculé les corrections non-paraxiales des modes propres d’une cavité non-planaires. Nous avons résolu les équations perturbatives de Lax pour des faisceaux gaussiens elliptiques généralisés. Nous avons pu ainsi décrire qualitativement des résultats expérimentaux obtenus avec une cavité non-planaire constituée de quatre miroirs. Nous avons aussi modélisé l’effet des déformations thermoélastiques des miroirs de cavité en utilisant le modèle simplifié de Winkler. Sur le plan expérimental, nous avons effectué des études sur le résonateur optique prototype du projet EQUIPEX THOMX. Nous avons tout d’abord proposé une nouvelle méthode d’asservissement laser-cavité basée sur l’utilisation d’une possible différence de phase induite par la réflexion des ondes s et p. Comparée à la méthode de Pound-Drever-Hall, notre méthode ne nécessite pas de modulation et démodulation de fréquence. Nous avons effectué les calculs de modélisation ainsi qu’une démonstration expérimentale. En parallèle, nous avons effectué des expériences de stockage de puissance dans la cavité prototype de finesse 26000 et nous avons obtenu une puissance moyenne de 383 kW correspondant à un gain de 10000. Nous avons atteint un niveau de puissance pour laquelle des instabilités modales induites par les déformations thermoélastiques des miroirs de notre cavité deviennent dominantes et perturbent l’asservissement laser-cavité. Une machine à rayon X Thomson, TTX, existe aussi à l’université de Tsinghua. Celle-ci est basée sur un accélérateur linéaire et une source laser femtoseconde terawatt. Un nouveau projet basé sur un anneau de stockage compact d’électrons, TTX2, voit actuellement le jour à l’université de Tsinghua. Nous présentons le design du système optique de ce futur projetAt present, X-rays imaging is widely applied in solid-state physics, in the life sciences, in medical applications and in other disciplines. An X-ray source based on laser-electron interaction, that is, a Thomson scattering X-ray source, can be used to produce high-quality X-rays at a low cost and small footprint. The construction of compact laser electron sources, consisting of an electron storage ring and an optical enhancement cavity, has recently attracted the interest of many institutions. The optical enhancement cavity is mainly used to amplify the injected power, circulate the pulses at a high repetition frequency (tens of megahertz) and produce a beam with a small waist at the interaction point. When introduced into the electron storage ring, the laser pulses produced in the high-average-power cavity scatter off high-energy electrons at a high repetition frequency. Thus, a high X-ray flux of more than 10^{11} ph/s can be obtained.In order to study the physical process inside a high-power resonator a model has been developed. As a first step, we establish a precise transient model of the laser pulse stacking technique considering the CEP (carrier-envelope phase) effect and time detuning leading to secondary resonances. The results of this model in the time and frequency domains match very well. A cavity with a given finesse and no detuning has a narrower linewidth than a detuned cavity with a higher finesse if both cavities have the same gain; consequently, it is easier to lock a laser to the latter cavity. Next, for the first time, we derived the non-paraxial corrections for general astigmatic beams so as to explain the S-shaped cavity mode observed in a non-planar four-mirror cavity. We solved Lax perturbation series of the wave equation for general elliptic Gaussian beams and S-shaped beam modes appear as the beam propagates away from the cavity symmetry point. This feature agrees qualitatively with observations made on a highly divergent non-planar four-mirror cavity. In addition, we study the thermal effect by using Winkler’s deformation model. The cavity gain is very sensitive to the mirror deformation in open loop. A strong feedback and ultra-low expansion mirrors are indispensable to reach a high power stored in the cavity.Several significant experiments were performed on a prototype cavity of the EQUIPEX project THOMX. Firstly, we proposed a new frequency stabilization method based on the polarization of a folded cavity and tuning of the cavity mirror reflectivity. Sufficient s- and p-wave phase detuning can be obtained by special design of the cavity mirrors’ coatings, which gives rise to an error signal that can be used for locking. Compared to the traditional Pound-Drever-Hall method, this technique is simpler without need for frequency modulation and demodulation. Theoretical calculations and experimental results demonstrate the feasibility of the proposed method. Meanwhile, high-power experiments on the prototype cavity for ThomX were demonstrated. A cavity finesse of approximately 26,000 is measured using four different methods, and the deposition of dust on the cavity mirrors is found to have an enormous effect on the finesse. We achieved a stable average power as high as 383 kW with a cavity gain of 10,000. In addition, modal instabilities which limit this power were observed. We believe that this effect originates from cavity modal frequency degeneracy induced by thermal effect.Tsinghua University hosts a compact, low-repetition-frequency X-ray source knownas TTX, which is based on a linac system and a terawatt femtosecond laser system. The next step is to upgrade TTX to a high-repetition-frequency X-ray machine called TTX2, consisting of an optical cavity and an electron storage ring. We present the complete design of a prototype optical cavity for TTX2
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Klímová, Eliška. "Mechanické a transportní vlastnosti hybridních hydrogelových systémů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2021. http://www.nusl.cz/ntk/nusl-444534.
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This master´s thesis deals with the study on mechanical and transport properties of hybrid hydrogel systems. Considering applications of hydrogels, especially in chemical industry, pharmacy, or eventually medical applications, for the study gellan and alginate-based hydrogels were selected. In order to compare individual characteristics physical and hybrid hydrogels were prepared. Gellan hydrogels were prepared in deionization aqua solution, calcium chloride dihydrate and tween 80 solution. Alginate hydrogels were prepared in calcium chloride dihydrate solution as well, and polyacrylamide with N,N´–methylenbisacrylamide. For the study of mechanical properties moisture analyser and rheology measurements were selected. Transport properties were studied using the diffusion experiments combined with UV-VIS spectroscopic detection. Concluding of this thesis is summarization of measured values, which provides comprehensive review of the problematics. It was discovered that the conveniently selected concentrations of structural components of hydrogel matrix and the additives can influence both the mechanical as well as the transport properties of studied hydrogels.
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Ngono, Mebenga Frédéric. "Investigations from experiments and simulations of amorphous forms of lactulose obtained by different routes." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10213.
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Dans cette thèse, nous avons étudié l'influence de la voie d'amorphisation sur les propriétés physiques et chimiques du lactulose. Ce sucre présente la caractéristique de pouvoir exister sous plusieurs formes tautomériques différentes. Quatre voies d'amorphisation très différentes dans leur principe ont été étudiées: la trempe du liquide, la lyophilisation, l'atomisation et le broyage mécanique. Les résultats indiquent que la voie d'amorphisation utilisée a une répercussion directe sur la composition tautomérique du matériau. L'influence de cette composition sur la transition vitreuse du matériau amorphe a été étudiée en détail. De plus les différences structurales potentielles engendrés par les différentes voies d'amorphisation ont été étudiées à la fois par diffusion neutronique et par simulation (dynamique moléculaire). Les résultats indiquent l'existence d'une structure locale ordonnée particulière dans l’amorphe obtenu par atomisation qui semble pouvoir expliquer le degré de stabilité plus élevé de l'amorphe obtenu par cette voie. Par ailleurs, la cinétique d'amorphisation induite directement à l'état solide par d'un broyage mécanique à haute énergie a pu être caractérisée en détail. Cela a nécessité l'utilisation d'une méthode originale de calorimétrie de dissolution isothermeIn this thesis, we have investigated the influence of the amorphisation route on the physical and chemical properties of lactulose. This sugar has the characteristic of being able to exist in several different tautomeric forms. Four amorphisation routes very different in their principle have been studied: quenching from the melt, freeze-drying, spray-drying and mechanical milling. The results indicate that the amorphisation route used has a direct effect on the tautomeric composition of the material. The influence of this composition on the glass transition of the amorphous material has been studied in detail. Moreover, the eventual structural differences generated by the various amorphisation routes have been studied both by neutron scattering and by simulation (molecular dynamics). The results indicate the existence of a particular locally ordered structure in the amorphous material obtained by spray-drying which seems to be able to explain the higher degree of stability of the amorphous material obtained by this route. Furthermore, the amorphisation kinetic induced directly in the solid state by a high energy mechanical milling has been characterised in detail. This has required the use of an original method of isothermal calorimetry of dissolution
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Lin, Heng. "CROSSOVER FROM UNENTANGLED TO ENTANGLED DYNAMICS: MONTE CARLO SIMULATION OF POLYETHYLENE, SUPPORTED BY NMR EXPERIMENTS." Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1142028839.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2006."May, 2006." Title from electronic dissertation title page (viewed 10/11/2006) Advisor, Wayne L. Mattice; Committee members, Ernst D. von Meerwall, Ali Dhinojwala, Gustavo A. Carri, Richard J. Elliott; Department Chair, Mark D. Foster; Dean of the College, Frank N. Kelley; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Ånäs, Kristoffer. "The Significance of Giant Flank Collapses on Magma Ascent in the NE Rift Zone of Tenerife, Canary Islands: A Structural Modelling and Diffusion Approach." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-438578.
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On the volcanic ocean island Tenerife in the Canary archipelago, several giant flank collapses haveoccurred over the last one million years. The link between the lateral collapses and the resultingvolcanism in the rift zones is not fully understood and was investigated within the framework of thisproject. A field survey along the north eastern rift zone on Tenerife was performed, where dyke intrusionstructural data was collected to analyse the exact distribution of dykes in the area. To determine themagma ascent rate, diffusion analysis of major elements in olivine crystals was conducted incollaboration with ETH Zürich. Additionally, analogue gelatine model experiments were performed toimprove the understanding of the processes that reconfigure linear rift zones to triaxial or multiaxial riftzones. Injections of fluid into the gelatine ridges produced fractures which mainly were linear andfollowed the along strike direction. Position A’ in the centre of the unstable section, produced the mostdiverse injection patterns and had a roughly 30 % higher acceleration compared to position A, positionedat the border of the unstable section. From the results of the diffusion modelling of Mg in olivinephenocrysts an ascent rate of the magma was calculated to an average ascent velocity of 10.4–14.0 km/h.This is extremely fast and suggests that the Orotava collapse is strongly connected to the formation ofankaramite dykes in the area as a result of sudden decrease in the lithostatic pressure.På vulkanön Teneriffa i den kanariska övärlden har flera jättelika skred skett. Kopplingen mellan dessaskred och vulkanismen i sprickzonerna på ön har undersökts inom ramen för detta arbete. Enfältundersökning genomfördes längs den nordöstra sprickzonen på Teneriffa, där data ommagmagångarnas orientering och läge insamlades. För att bestämma hur snabbt magman steg till ytan,genomfördes diffusionsanalys av Mg i olivinkristaller från ankaramitgångar i samarbete med ETH iZürich. Utöver det utfördes även experiment med analoga gelatinmodeller för att förbättra förståelsenför de processer som förändrar linjära riftzoner till treaxliga eller fleraxliga riftzoner. Injiceringen avvätskan i gelatinmodellerna producerade sprickor som i huvudsak var linjära och följde strykriktningenpå riftzonen. Position A’, i mitten av den instabila sektorn i modellen gav högst variation avinjiceringarna och hade omkring 30 % högre acceleration jämfört med position A placerad i kanten avden instabila sektorn. Baserat på resultatet av diffusionsmodelleringen kunde en uppstigningshastighetför magman beräknas till en medelhastighet på 10,4–14,0 km/h. Detta är extremt snabbt och visar attkollapsen av Orotava är starkt kopplad till bildningen av ankaramitgångar i området som ett resultat aven plötslig minskning av det litostatiska trycket.
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Hurtig, Tomas. "Plasma cloud penetration across magnetic boundaries." Doctoral thesis, KTH, Alfvén Laboratory, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3804.
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Hsu, Sheng-Yen. "Flame Spread and Extinction Over Solids in Buoyant and Forced Concurrent Flows: Model Computations and Comparison with Experiments." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1238144733.
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Thesis (Ph.D.)--Case Western Reserve University, 2009Abstract Department of Mechanical and Aerospace Engineering Title from PDF (viewed on 14 April 2009) Available online via the OhioLINK ETD Center
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Sheng-Yen, Hsu. "Flame Spread and Extinction Over Solids in Buoyant and Forced Concurrent Flows: Model Computations and Comparison with Experiments." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1238144733.
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Jesko, Karol. "Studying divertor relevant plasmas in linear devices : experiments and transport code modelling." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0010.
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Les prédictions concernant le fonctionnement des divertors de tokamak reposent généralement sur des codes de transport de bord, consistant en un code de plasma fluide associé à un code de Monte Carlo pour les espèces neutres. Les machines linéaires Magnum-PSI et Pilot-PSI chez DIFFER, produisant des plasmas comparables à ceux d'ITER ($T_e \sim 1$ eV, $n_e\sim10^{20}$ m$^{- 3}$). Dans cette thèse, les décharges de plasma ont été étudiées expérimentalement et par modélisation utilisant le code Soledge2D-Eirene afin de: a) rechercher quels phénomènes doivent être inclus dans la modélisation pour reproduire les tendances expérimentales et b) pour mieux interpréter les expériences . Expérimentalement, l’effet de la pression neutre $P_n$ a été étudié par diffusion Thomson, par une sonde de Langmuir, par spectroscopie visible et par calorimétrie. Nous avons montré qu'un faisceau de plasma peut être efficacement terminé par une couche de gaz neutre. Ensuite, à partir de comparaisons d’expériences et de simulations, nous avons montré qu’il était essentiel d’inclure les collisions élastiques entre le plasma et les molécules pour pouvoir reproduire les expériences. De plus, la $T_e$ proche de la cible est systématiquement surestimé, ce qui sous-estime le taux de recombinaison. Enfin, nous avons montré expérimentalement l’importance de l’inclusion de la recombinaison de surface dans le flux d’énergie de surface dans les plasmas à basse température. Les travaux présentés dans cette thèse contribuent à la compréhension des interactions plasma-neutre, en particulier dans les concepts de divertors plus fermés de nouvelle génération (MAST-upgrade, DIII-D)Predictions for the operation of tokamak divertors typically rely on edge transport codes, consisting of a fluid plasma code in combination with a Monte Carlo code for neutral species. The linear devices Magnum-PSI and Pilot-PSI at DIFFER, operating with a cascaded arc plasma source that produces plasmas comparable to those expected in the ITER divertor ($T_e \sim 1 $ eV, $n_e \sim 10^{20}$m$^{-3}$). In this thesis, plasma discharges have been studied both experimentally and by modelling using the Soledge2D-Eirene code in order to a) investigate which phenomena need to be included in the modeling to reproduce experimental trends and b) provide new insights to the interpretation of experiments. Experimentally, the effect of neutral pressure $P_n$ was investigated using Thomson scattering, a Langmuir probe, visible spectroscopy and calorimetry. We have shown that a plasma beam can be effectively terminated by a blanket of neutral gas. Next, from comparisons of experiments and simulations, we have found that it is critical to include elastic collisions between the plasma and molecules if experiments are to be reproduced. Furthermore, the near-target $T_e$ is systematically overestimated by the code, underestimating the recombination rate thereby. Lastly, we have experimentally shown the importance of the inclusion of surface recombination to the surface energy flux in low temperature plasmas, an effect that is generally known but difficult to measure in fusion devices. The work presented in this thesis contributes to the understanding of plasma-neutral interactions especially in new generation, closed divertor concepts (i.e. MAST-upgrade, DIII-D)
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Peretzki, Patrick [Verfasser], Michael [Akademischer Betreuer] Seibt, Michael [Gutachter] Seibt, and Christian [Gutachter] Jooß. "Implementation and quantification of scanning transmission EBIC experiments for measuring nanometer diffusion lengths in manganite-titanite p-n heterojunctions / Patrick Peretzki ; Gutachter: Michael Seibt, Christian Jooß ; Betreuer: Michael Seibt." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1175204919/34.
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Shen, Huanhuan. "Interferometric out-of-focus imaging and digital holography for the characterization of droplets or bubbles : theory, optical design, characterization of a flow, synchronized experiments." Rouen, 2014. http://www.theses.fr/2014ROUES015.
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Un simulateur original d'imagerie interférométrique en défaut de mise au point (ILIDS), permettant de modéliser n'importe quel système optique, est développé. Le formalisme de ce simulateur repose sur l'intégrale de Huygens-Fresnel généralisée. Le champ initial diffusé par des gouttes est simplifié par deux glare points. Un système original d'ILIDS, utilisant une configuration cylindrique, est conçu grâce au simulateur. Cette nouvelle configuration permet d'obtenir simultanément la position en trois dimensions et la taille des gouttelettes ou des bulles. Elle comprend une lentille cylindrique supplémentaire ayant un angle de rotation approprié autour de l'axe optique. Cette configuration anamorphique permet de lier l'orientation des franges d'interférence d'une part, et la forme de l'image en défaut de mise au point d'autre part, à la position axiale de la particule. Trois expériences sont réalisées successivement : l'observation de gouttes d'eau dans l'air, de bulles dans l'eau au sein d'un aquarium cubique et de bulles dans la glycérine située dans un canal cylindrique. Les comparaisons entre simulations et expériences montrent des résultats cohérents. Les précisions des positions axiales et des talles obtenus par la configuration cylindrique d'ILILDS sont évaluées expérimentalement. Les positions axiales sont validées par une comparaison avec leurs valeurs calibrées, tandis que les diamètres sont vérifiés grâce à une configuration couplée deux techniques: holographie numérique sur l'axe et configuration cylindrique d'ILIDSAn original simulator of Interferometric Laser Imaging for Droplet Sizing (ILIDS), allowing predicting the image patterns obtained by any imaging system, is developed. The formalism of the simulator relies on the generalized Huygens-Fresnel integral. The initial field scattered by the droplet is simplified by two glare points. An original ILIDS system is designed due to the simulator. The advantage of this configuration is that the three dimensional locations and sizes of droplets can be obtained simultaneously. The cylindrical ILIDS configuration includes a supplemental cylindrical lens rotated in a proper angle with respect to the axis of imaging system. The anamorphic configuration allows to change the orientation of the fringes and the form of the out-of-focus image with respect to the axial location of the particle. Three experiments are successively conducted: water droplets in air, bubbles in water at cubic aquarium and bubbles in glycerin at cylindrical channel. The comparisons of the simulations and experiments show good consistence. The precisions of the axial location and diameter obtained by cylindrical ILIDS technique are evaluated experimentally. The axial locations obtained by cylindrical ILIDS configuration are validated by comparing them with calibrated values, while the diameters are validated due a synchronized experiment coupling Digital In-Line Holography technique and cylindrical ILIDS technique
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Berhane, Tedros Mesfin. "KINETIC AND EQUILIBRIUM SORPTION EXPERIMENTS INVESTIGATING PALYGORSKITE-MONTMORILLONITE AS A POTENTIAL FILTER MEDIUM FOR REMOVAL OF PHARMACEUTICALS AND ENDOCRINE-DISRUPTING COMPOUNDS." Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1429882830.
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Minissale, Marco. "Physique et Chimie sur la surface de la poussière interstellaire : effet de la diffusion des atomes d’oxygène et de la désorption chimique sur le réseau chimique H-C-N-O." Thesis, Cergy-Pontoise, 2014. http://www.theses.fr/2014CERG0721/document.
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Le milieu interstellaire (MIS) est la matière presente dans l'espace au sein des galaxies.Cette matière est composée de gaz et de grains de poussière. Jusqu'à présent, les radioastronomes principalement ont identifié plus de 170 molécules différentes dans le MIS.La présence de la plupart de ces molécules est expliquée à travers des réactions dans la phase gazeuse, mais la synthèse de beaucoup de ces molécules (comme H2, H2O, CO2) nécessite l'intervention d'uncatalyseur, donc des réactions dans la phase solide, sur la surface des grains de poussière. Les objectifs de cette thèse sont de comprendre quels sont les processus physico-chimiques qui ont lieu (par exemple, la diffusion et désorption) sur la surface des grains de poussière interstellaire et comment ils conduisent à la synthèse de molécules de plus en plus complexes.En particulier, l'objet de ma thèse est d'étudier:- le rôle de la diffusion des atomes d'oxygène (noté « O ») et les processus d'oxydation dans la formation des glaces interstellaires;- le couplage thermique et non thermique entre la phase gaz et la phase solide.L'astrochimie ne tendait à considérer que la diffusion des atomes d'hydrogène et les réactions d'hydrogénation, ignorant souvent le rôle de l'oxygénation ainsi que l'importance des processus d'adsorption et de désorption, d'où mes recherches approfondies sur ces thématiques.Évidemment, une meilleure connaissance de ces processus physico-chimiques et des réactions de surface aiderait les astronomes à comprendre la formation des glaces interstellaires, l'augmentation de la complexité moléculaire, et l'équilibre entre le gaz et la phase solide.Pour répondre à ces questions, de nombreuses expériences ont été réalisées avec le dispositif FORMOLISM, situé à l'Université de Cergy-Pontoise dans le cadre du LERMA (Observatoire de Paris). Via deux jets de particules avec un pompage différentiel, les atomes et les molécules sont déposés sur un échantillon froid (> 6,5 K) dans une chambre ultravide. Les produits des réactions sont ensuite sondés en utilisant la spectroscopie de masse et la spectroscopie infrarouge.Pour simuler différents environnements astrophysiques, la physique-chimie de l'état solide a été étudiée dans différentes conditions expérimentales:- La morphologie de substrat (glace d'eau amorphe soit poreuse, soit compacte, glace d'eau cristalline, silicate amorphe ou graphite)- Les espèces déposées et leur rapport relatif- La couverture des espèces déposées, de 0,1 à 2 monocouches- La température du substrat, de 6,5 à 60 K.En ce qui concerne les processus d'oxydation, les résultats montrent que l'O est très réactif avec de nombreuses espèces ; la diffusion des atomes d'O semble être beaucoup plus rapide que prévu et peut se produire par effet tunnel à des températures aussi basses que 6,5 K. Nous avons comparé les valeurs expérimentales des coefficients de diffusion et constaté que les taux de diffusion sur chaque surface, basés sur les résultats de la modélisation, étaient considérablement plus élevés que ceux prévus pour les atomes lourds tels que l'O. Nos résultats montrent que les atomes O peuvent rencontrer tous les partenaires disponibles de réaction à un taux plus rapide que le taux d'accrétion. En particulier, dans les nuages interstellaires très denses, le rapport O/H est tel que O devient l'un des partenaires réactifs dominants avec H. Ceci a un impact sur la formation de certaines espèces et sur l'abondance relative des produits formés.En ce qui concerne les processus de couplage solide-gaz (c'est à dire, l'adsorption, désorption thermique, désorption chimique), les résultats montrent que chaque processus est influencé d'une manière différente par le substrat (glace d'eau, de silicate ou graphite). Enfin, nous fournissons une liste utile des énergies de liaison de plusieurs espèces et de l'efficacité de désorption chimique des différentes réactions sur ces substratsThe interstellar medium is the matter that exists in the space between the star systems in a galaxy. It is composed of gas and elongated tiny dust grains. To date, plenty of molecules (> 170) are known to exist in the interstellar medium. The presence of most of them can be understood in terms of gas phase reactions but the synthesis of some key species (H2, H2O, CO2) need the intervention of solid-state reactions on dust grains surface. The aims of this thesis are to understand what are the relevant physical-chemical processes (i.e., diffusion and desorption) occurring on the surface of interstellar dust grains and how these processes influence synthesis of more and more complex molecules. In particular, the focus of my thesis is the investigation of:1) the role of O-atom diffusion and the oxidation processes in the formation of interstellar ices;2) the thermal and non-thermal processes coupling gas and solid phase.The reasons of these investigations lie on the realization that, up to now, only hydrogen diffusion and hydrogenation reactions are commonly considered in solid astrochemistry and the role of oxygenation as well as the importance of adsorption and desorption processes are often disregarded.Evidently, a better knowledge of such physical-chemical processes and, in general, of the solid state physical-chemistry could help astronomers to understand the formation of interstellar ices, the increase on molecular complexity, and the equilibrium between gas and solid phase.To answer these questions, many experiments have been performed with the FORMOLISM set-up, i.e., FORmation of MOLecules in the ISM, located in the Universitè de Cergy Pontoise, Observatoire de Paris. Via two triply differentially pumped beams, atoms and molecules were aimed at a cold (>6.5 K) sample held in a Ultra high vacuum chamber. The products were probed using Mass spectroscopy and Reflexion Absorption Infrared Spectroscopy.To simulate different astrophysical environments, the solid state physical-chemistry has been studied in different experimental conditions:-The substrate morphology (Amorphous water ice, porous (p) and compact (np), crystalline (c) ice, amorphous silicate, and graphite)-The species deposited and their relative ratio-The coverage of deposited species, from 0.1 to 2 ML-The substrate temperature, from 6.5 to 60 KConcerning oxidation processes and O-atom reactivity, the results show that oxygen is very reactive with many species (i.e., H, CO, NO, H2CO, HCOOH); O diffusion appears to be much faster than previously expected and can occur via quantum mechanical tunnelling at temperatures as low as 6.5 K. We compared the experimental values of the diffusion coefficients and found that the rates of diffusion on each surface, based on modelling results, were considerably higher than those expected for heavy atoms such as oxygen. Our findings show that O atoms can scan any available reaction partners (e.g., either another H atom, if available, or a surface radical like O, OH, CO) at a faster rate than that of accretion. In particular, in very dense interstellar clouds, the O/H ratio is such that O becomes one of the dominant reactive partners together with H. This has an impact on the chemistry occurring at the surface of dust grains as either the formation of some species may be enhanced, or at least the relative abundances of the final products will be affected. An important example of how O-atom mobility can modulate the abundances of key species of ices in the ISM is the case of the H2O/CO2 ratio via the CO+O and H2CO+O pathways.Concerning gas-solid coupling processes (i.e., adsorption, sticking, thermal desorption, chemical desorption), the results show that each processes is influenced in a different way by the substrate (i.e., water ice, silicate or graphite). Moreover, we provide a useful list of binding energies of several species and chemical desorption efficiency for different reactions on different subst
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Ludwig, Lars [Verfasser], Hans-Görg [Akademischer Betreuer] Roos, and Gunar [Akademischer Betreuer] Matthies. "Analytical investigations and numerical experiments for singularly perturbed convection-diffusion problems with layers and singularities using a newly developed FE-software / Lars Ludwig. Gutachter: Hans-Görg Roos ; Gunar Matthies. Betreuer: Hans-Görg Roos." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://d-nb.info/1068445858/34.
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Hashim, Leïla. "Unraveling the grain size evolution in the Earth’s upper mantle : experimental observations and theoretical modeling." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2025/document.
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La taille de grains dans le manteau terrestre a des implications cruciales sur les processus à grande échelle, telles que la propagation des ondes sismiques, la perméabilité et la rhéologie des roches. Cependant, la taille de grains évolue constamment avec le temps, car la croissance de grains statique induit une augmentation de la taille moyenne tandis que la recristallisation dynamique contribue à sa décroissance. La croissance d’olivine au sein d’agrégats mantelliques dans un milieu inter-granulaire sec, en présence de liquide magmatique ou dans des conditions sursaturées en eau a été modélisée dans le cadre de cette thèse. En s’appuyant sur la théorie de croissance cristalline ainsi que sur des expériences à 1-atmosphère et hautes températures précédemment publiées, la loi de croissance d’olivine sèche a été déterminée. Le facteur limitant est, dans ce cas, la diffusion du silicium aux joints de grains à travers une épaisseur effective de 30 nm. La croissance d’agrégats en présence de liquide magmatique et fluide aqueux a été contrainte par de nouvelles expériences haute pression/haute température. Ces données indiquent que les taux de croissance sont significativement plus importants que dans des conditions sèches et sont limités par des réactions aux interfaces cristal/liquide. Nous proposons une loi de croissance générale régulée par une combinaison de joints de grains secs et mouillés, grâce aux paramètres de contiguité et de mouillabilité. Cette loi de croissance unifiée est fondamentale pour extrapoler les tailles de grains expérimentales à des échelles de temps, des profondeurs et des quantités de liquides relatives au manteau supérieurGrain size in the Earth’s mantle is a fundamental parameter that has crucial implications on large-scale processes, such as seismic wave propagation, the permeability and the rheology of rocks. However, grain size is constantly evolving with time, where static grain growth implies an increase of the average grain size whereas dynamic recrystallization contributes to its decrease. Static grain growth of olivine-rich mantle aggregates in an intergranular medium being dry, melt-bearing and water-oversaturated has been here modeled. By using the appropriate theoretical background, the dry olivine grain growth law has been established from previously published experimental grain growth data at 1-atmosphere and high-temperature conditions. Grain growth rates for these samples are limited by silicon diffusion at grain boundaries through an effective width of 30 nm. Grain growth for melt- and water-bearing aggregates was, however, constrained by new high-pressure and high-temperature experiments. This data indicates that grain growth rates for liquid-bearing samples are significantly faster than for dry samples and are limited by precipitation reactions at the crystal/liquid interface rather by diffusion through the liquid phase. We propose a general grain growth law, which takes into account dry grain boundaries as well as wetted grain-grain interfaces, through the contiguity and wetness parameters. This unified law is fundamental to extrapolate experimental grain sizes to time scales, depths and liquid contents that are relevant of the upper mantle