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Bulatewicz, Thomas Francis. "Support for model coupling : an interface-based approach /." view abstract or download file of text Connect to the title in UO's Scholars' Bank, 2006. https://scholarsbank.uoregon.edu/dspace/handle/1794/2974.
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Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 191-198). Also available for download via the World Wide Web; free to University of Oregon users.
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Rose, Alexander. "The dynamic coupling interface of G-protein coupled receptors." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17215.
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Um mit ihrer Umgebung zu kommunizieren verfügen lebende Zellen über Rezeptoren, welche die umschließende Membran überbrücken. Die vorherrschende G-Protein-gekoppelte Rezeptoren (GPCR) erhalten Informationen von Außerhalb durch Bindung eines Liganden, wodurch der Rezeptor aktiviert wird. Während der Aktivierung bildet sich innerzellulär ein offener Spalt, in den ein G-Protein (Gαβγ, G) mit seinem C-terminalen Ende koppeln kann. Die Bindung an einen GPCR führt in der Gα-Untereinheit vom Gαβγ zu einen GDP/GTP-Austausch, welcher für die weitere Signalübertragung ins Zellinnere notwendig ist. Die Kopplung von Rezeptor und Gαβγ umfasst eine Reihe von dynamischen strukturellen Änderungen, die Geschwindigkeit und Spezifität der Interaktion regeln. Hier haben wir MD-Simulationen (Molekulardynamik) verwendet, um die molekularen Details der GPCR Gαβγ Kopplung vor und während der GPCR-Gαβγ-Komplexbildung bis hin zum GDP/GTP-Austausch zu untersuchen.To communicate with their environment, living cells feature receptors that provide a bridge across the enclosing membrane. The prevalent G protein-coupled receptors (GPCR) receive outside information through the binding of a ligand, which activates the receptor. During activation, an open intracellular crevice forms, to which a G protein (Gαβγ, G) can couple with its Gα C-terminus. Binding to GPCRs triggers GDP/GTP exchange in the Gα subunit of Gαβγ, necessary for further signal transfer within the cell. The coupling between receptor and Gαβγ involves a series of dynamic structural changes that govern speed and specificity of the interaction. Here we used molecular dynamics (MD) simulations to elucidate molecular details of the GPCR Gαβγ coupling process before and during GPCR Gαβγ complex formation up to the GDP/GTP exchange.
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Teh, Chong-Ann. "Initial studies of structure coupling effects for a trolley/RRDF interface." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FTeh.pdf.
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Mina, Ehab Mouris. "Dehumidification effect by coupling an electroosmotic material with a desiccant interface." online access from Digital Dissertation Consortium, 2004. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?3153384.
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Mindel, Julian Eduardo. "Interface Tracking and Solid-Fluid Coupling Techniques with Coastal Engineering Applications." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4376.
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Multi-material physics arise in an innumerable amount of engineering problems. A broadlyscoped numerical model is developed and described in this thesis to simulate the dynamic interactionof multi-fluid and solid systems. It is particularly aimed at modelling the interactionof two immiscible fluids with solid structures in a coastal engineering context; however it canbe extended to other similar areas of research. The Navier Stokes equations governing thefluids are solved using a combination of finite element (FEM) and control volume finite element(CVFE) discretisations. The sharp interface between the fluids is obtained through thecompressive transport of material properties (e.g. material concentration). This behaviour isachieved through the CVFE method and a conveniently limited flux calculation scheme basedon the Hyper-C method by Leonard (1991). Analytical and validation test cases are provided,consisting of steady and unsteady flows. To further enhance the method, improve accuracy, andexploit Lagrangian benefits, a novel moving mesh method is also introduced and tested. It isessentially an Arbitrary Lagrangian Eulerian method in which the grid velocity is defined bysemi-explicitly solving an iterative functional minimisation problem. A multi-phase approach is used to introduce solid structure modelling. In this approach,solution of the velocity field for the fluid phase is obtained using Model B as explained byGidaspow (1994, page 151). Interaction between the fluid phase and the solids is achievedthrough the means of a source term included in the fluid momentum equations. The interactingforce is calculated through integration of this source term and adding a buoyancy contribution. The resulting force is passed to an external solid-dynamics model such as the Discrete ElementMethod (DEM), or the combined Finite Discrete Element Method (FEMDEM).The versatility and novelty of this combined modelling approach stems from its ability tocapture the fluid interaction with particles of random size and shape. Each of the three maincomponents of this thesis: the advection scheme, the moving mesh method, and the solid interactionare individually validated, and examples of randomly shaped and sized particles areshown. To conclude the work, the methods are combined together in the context of coastal engineeringapplications, where the complex coupled problem of waves impacting on breakwateramour units is chosen to demonstrate the simulation possibilities. The three components developedin this thesis significantly extend the application range of already powerful tools, suchas Fluidity, for fluids-modelling and finite discrete element solids-modelling tools by bringingthem together for the first time.
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Hilty, Floyd W. III. "Raman Spectroscopy View on the Electric-Field-Tuned Molecule-Semiconductor Interface Coupling." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1429109628.
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Tang, Justine Nicole. "Amphibian communication: Coupling of acoustic systems to the medium at the air-water interface." Scholarly Commons, 2016. https://scholarlycommons.pacific.edu/uop_etds/171.
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Sound does not transmit well across the interface of two media. Therefore, most organisms communicate using one medium. Some anurans vocalize at the interface of air and water, though reception of these vocalizations is generally unknown. The túngara frog ( Engystomops pustulosus ) may be the first anuran to have evidence suggesting simultaneous acoustic communication both above and below the air-water interface. This thesis addresses whether the female túngara frog would be receptive to underwater acoustic signals and if males project their advertisement calls at biologically relevant intensities underwater. Females floated and swam with their eardrums and body walls constantly submerged. Using laser Doppler vibrometry, peak vibrations of female eardrums were found to be centered at about 3.5 kHz in air, but dropped to about 1.4 kHz underwater. The peak velocity of the eardrum was about 0.2 mm/s in air and 0.04 mm/s in water when stimulated with tones at 80 dB relative to 20 µPa. Males projected their advertisement calls with a sound pressure level of 121 dB (at 10 cm, re. 20 µPa) in water and 98 dB (at 10 cm, re. 20 µPa) in air. In relation to air, the dominant frequency of the advertisement call (0.8 kHz) was the most intense spectral band underwater whereas the dominant frequency of the chuck (2.5 kHz in air) was less intense. The advertisement signal for the male túngara frog was broadcasted underwater with more energy than in air at its main frequencies. Female eardrums were sensitive to frequencies within the male advertisement call both in air and in water, if the frequencies were transmitted at amplitudes plausible to be encountered in nature. These results strengthen the available evidence of underwater communication, and indicate the presence of auditory specializations in the acoustic communication of this species.
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Munir, Taj [Verfasser], and Gerald [Gutachter] Warnecke. "Analysis of coupling interface problems for bi-domain diffusion equations / Taj Munir ; Gutachter: Gerald Warnecke." Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2020. http://d-nb.info/1223615634/34.
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Krinner, Andreas [Verfasser]. "Multibody systems with lubricated contacts - Cavitation, interface coupling, reduction and quasi-Newton techniques / Andreas Krinner." München : Verlag Dr. Hut, 2018. http://d-nb.info/116276788X/34.
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Molinari, Alan [Verfasser], Horst [Akademischer Betreuer] Hahn, and Ralph [Akademischer Betreuer] Krupke. "Magnetoelectric coupling at the La1-xSrxMnO3/ionic liquid interface / Alan Molinari ; Horst Hahn, Ralph Krupke." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2018. http://d-nb.info/115493215X/34.
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Pérez, Carreras Adrià. "T-H-M coupling with large advection in fractured rock masses using zero-thickness interface elements." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/671102.
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The study of hydro-mechanical (HM) coupled problems in different areas of civil, environmental or petroleum engineering is common in literature, but the effect of a thermal field by means of the heat transport by a fluid through the discontinuities is not considered in the current tools of analysis, in which the effect of the temperature gradient between the fluids flowing through the discontinuities and the in-situ thermal state are not considered.
In geomechanics modeling it is important to distinguish between the hydraulic behavior of the porous medium and that of the discontinuities, together generating a double-permeability system where the discontinuities establish preferential flow paths. Because of high hydraulic velocities in the discontinuities, the advection (transport) may be the dominant heat transfer mode. Thus, the study of THM coupled processes with thermal advection in discontinuities is important in problems with a certain degree of coupling between the mechanical, hydraulic and thermal fields, and in which the hydraulic flow transports heat through the discontinuities.
It is important to establish a numerical model to study the advection phenomena that differentiates the discontinuity network and the porous medium contributions. In this context, this thesis focuses on the study, formulation, numerical implementation and verification of a THM fully-coupled model with large advection, able to reproduce the advective behaviour that occurs in discontinuities, in which heat is transported by the fluid. This numerical approach is carried out using the finite element method (FEM) with zero-thickness interface elements to represent the discontinuities, and assuming saturated conditions and a single incompressible fluid (constant density). It is also assumed that all the non-linear behaviour occurs at the interface elements by means of an elasto-plastic constitutive law based on fracture mechanics.
Additionally, the numerical approach to the thermal advection presents a singularity in comparison with pure diffusive problems. If the fluid velocities are low, the numerical formulation can be made by traditional FEM (Galerkin). However, when the fluid velocities are high and the advection dominates the problem, the standard Galerkin weighting leads to oscillatory results, and the advective term requires a special treatment to stabilize the numerical solution. A review of different methodologies to solve the large advective problem is presented, selecting the Streamline Upwind Petrov-Galerkin method to solve the steady-state. For transient states, this thesis starts with the study of the existing explicit Characteristic Galerkin Method (CGM), which studies the advective phenomena in a Lagrangian manner, following the particle (or heat) with the fluid by setting a moving coordinate system that depends on the fluid velocity and its position in time. Then the implicit CGM is developed, and finally a new variation is proposed adding a parameter alpha that allows determining different temporal derivative positions of the advective volume, leading to the alpha-Implicit CGM, that allows to obtain stable solutions if the Courant condition is fulfilled.
In order to verify the THM model with large advection for continuum medium and zero-thickness interfaces, several simple verification examples are presented. Finally, an application to hydraulic fracture (HF) with a single fracture in 2-D is introduced in order to understand the thermal mechanisms that occur in HF problems and how they affect the mechanical and hydraulic fields. In addition, these results are compared with those obtained using the HM model, where the thermal field is not considered.
Finally, in order to improve the computational capacities of the FEM code, its parallelization has performed following a subdomain decomposition strategy, leading to a substantial improvement in the speed of the calculations and showing a good degree of scalability.El estudio de problemas hydro-mecánicos (HM) acoplados en diferentes áreas de ingeniería civil, ambiental o del petróleo es común en la literatura, pero los efectos térmicos del fluido transportando calor a través de fracturas o discontinuidades no se considera en las actuales herramientas de análisis, en las cuales el efecto de la diferencia de temperatura entre el fluido inyectado a través de las discontinuidades y la del medio in situ no se tiene en cuenta. No obstante, en algunos problemas geomecánicos los comportamientos mecánico, hidráulico y térmico del medio poroso fracturado pueden aparecer acoplados con fuertes interacciones entre ellos. En modelación geomecánica es importante distinguir el comportamiento hidráulico del medio poroso del de las discontinuidades, ambas generando un sistema de doble permeabilidad en el cual el medio poroso proporciona una pequeña permeabilidad al sistema, mientras que las discontinuidades establecen caminos preferentes y proporcionan gran permeabilidad al mismo. Debido a las elevadas velocidades de fluido que se pueden desarrollar en las discontinuidades, la advección (transporte) puede ser el modo dominante de transferencia de calor. Por ello, el estudio de procesos THM acoplados con advección térmica en discontinuidades es importante en problemas con un cierto grado de acoplamiento entre los campos mecánico, hidráulico y térmico, y en los cuales el flujo hidráulico puede transportar calor a gran velocidad a través de las discontinuidades. Por ello, es importante establecer un modelo numérico para estudiar el fenómeno advectivo que diferencie la contribución de la red de discontinuidades de la del medio continuo poroso. En este contexto, esta tesis está enfocada en el estudio, formulación, implementación numérica y verificación de un modelo THM acoplado monolítico con advección dominante que sea capaz de reproducir el comportamiento advectivo que ocurre en discontinuidades o fracturas, en las cuales el fluido transporta calor. Este estudio se lleva a cabo en el contexto geomecánico de un medio poroso fracturado, empleando el método de los elementos finitos (FEM) con elementos junta de espesor nulo para representar las discontinuidades o fracturas, suponiendo condiciones saturadas, un único fluido incompresible (con densidad constante) y pequeñas deformaciones. También se supone que todo el comportamiento no lineal se desarrolla en las juntas mediante el uso de una ley constitutiva elasto-plástica basada en mecánica de fractura, mientras que el medio continuo poroso se supone de comportamiento poro-elástico. Adicionalmente, la solución numérica del problema térmico advectivo presenta singularidades con respecto a los problemas de difusión pura. Cuando las velocidades del fluido son bajas, la formulación numérica se puede llevar a cabo mediante Elementos Finitos tradicionales (Galerkin). No obstante, cuando las velocidades del fluido son suficientemente elevadas y la advección domina el problema el método estándar de Galerkin conduce a resultados oscilantes, por lo que el término advectivo requiere un tratamiento especial para estabilizar la solución numérica. En este contexto, se presenta una revisión de diferentes metodologías para resolver el problema de advección dominante, seleccionando el método Streamline Upwind Petrov-Galerkin (SUPG) para resolver el problema en régimen permanente, un método bien conocido que conduce a soluciones estables con advección dominante. Para el régimen transitorio esta tesis empieza con el estudio del método de Características Galerkin explícito, un método existente en el que el fenómeno advectivo se estudia de modo Lagrangiano, siguiendo la partícula (o calor) con el movimiento del fluido, y estableciendo para ello un sistema de coordenadas móvil que depende de la velocidad del fluido y de su posición en el tiempo. Seguidamente se desarrolla la forma implícita de este método, y finalmente se propone una nueva variación del método, añadiendo un parámetro 𝛼�𝛼� que permite determinar diferentes posiciones de las derivadas temporales del volumen advectivo, concluyendo en el nuevo 𝛼�𝛼�-Implicit Characteristic Galerkin Method. Con esta nueva metodología se estabiliza el problema de gran advección en régimen transitorio si se cumple la condición de Courant. Con el fin de verificar el modelo THM monolítico acoplado con advección dominante se presentan diversos ejemplos de verificación, tanto para medio continuo poroso como para elementos junta de espesor nulo. Finalmente, se presenta un caso de aplicación a fractura hidráulica (HF), llevando a cabo el análisis numérico de una sola fractura en 2-D con el objetivo de entender los mecanismos térmicos que ocurren en problemas de HF y como éstos afectan sobre los comportamientos mecánico e hidráulico. Además, los resultados de la modelación se comparan con los obtenidos empleando un modelo HM, en el cual no se consideran efectos térmicos. Adicionalmente, con el objetivo de mejorar la eficiencia computacional del código de Elementos Finitos, se ha llevado a cabo la paralelización del mismo mediante una estrategia de partición de subdominios, resultando en una mejora sustancial de la velocidad de los cálculos y mostrando una buena escalabilidad de los mismos.
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Jouan, Alexis. "DC and AC transport in field-effect controlled LaAlO3/SrTiO3 interface." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066073/document.
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Cette thèse est consacrée à l'étude des propriétés de transport statique et dynamique du gaz d'électrons bidimensionnel supraconducteur à l'interface LaAlO3/SrTiO3. Dans un premier temps, nous étudions l'effet du désordre microscopique induit par le dopage en Chrome, sur la supraconductivité et le couplage spin-orbite en fonction de la densité de porteur modulée par effet de champ. Dans une géométrie de grille locale au-dessus du gaz, nous montrons le contrôle électrostatique de la transition supraconducteur-isolant. De même, nous analysons l'ajustement du couplage spin-orbite contrôlé par effet de champ. A l'aide de méthodes de nanofabrication par lithographie électronique, nous démontrons la première réalisation d'un point critique quantique dans LaAlO3/SrTiO3. En changeant le confinement latéral et le niveau de Fermi par effet de champ, nous sommes capables de régler le nombre de canaux conducteurs dans l'état normal et de mesurer la quantification de la conductance. Enfin, nous présentons des mesures radio-fréquence qui donnent accès aux propriétés dynamiques du gaz supraconducteur. L'évolution de la conductivité en fonction de la densité de porteurs et de la température est comparée avec la théorie standard BCS/Mattis-Bardeen d'une part, et avec la théorie BKT d'autre partThis thesis is devoted to the study of static and dynamical transport properties of the superconducting two-dimensional electron gas at the LaAlO3/SrTiO3 interface. Under strong 2D confinement, the degeneracy of the t$_{2g}$ bands of SrTiO$_3$ is lifted at the interface, generating a rich and complex band structure. Starting from a free electron model, we derive numerically a self-consistent calculation of the potential well and the band structure (chapter 1). These simulations highlight the presence of two types of bands d$_{xy}$ and d$_{xz/yz}$ with very different transport properties. We investigate first the effect of microscopic disorder introduced by Cr doping, on superconductivity and spin-orbit coupling over a wide range of back-gate doping (chapter 3). We also describe the first implementation of a field-effect device where the superconductor-insulator transition could be continuously tuned with a top-gate. The presence of a strong spin-orbit coupling that could be controlled with the top-gate voltage is also demonstrated by analyzing the magneto-transport measurements. The gate dependence of the spin-splitting energy, of the order of a few meV, is found to be consistent with Rashba spin-orbit coupling. Going one step further in nanofabrication, we report on the first realization of a quantum point contact in LaAlO$_3$/SrTiO$_3$ using split gates (chapter 6). To go further in the understanding of the LaAlO$_3$/SrTiO$_3$ interface, we present high frequency measurements of the conductivity $\sigma$ (chapter 5). This measurement gives us access to the superfluid stiffness and to the gap energy via the BCS theory. We show that the competition between these two energy scales controls the superconducting Tc in the phase diagram
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Greb, Arthur. "Dynamics of the plasma-surface interface in capacitively coupled radio-frequency oxygen plasmas : coupling numerical simulations with optical diagnostics." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/4980/.
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Plasma processing on industrial scale is becoming increasingly complex, demanding new strategies for process control and monitoring. Of particular interest is the energy transport in the interface region between the non-equilibrium low-pressure plasma and the surface. The individual plasma components have varying properties and exhibit different dynamics, which enable numerous chemical and physical modifications of surfaces simultaneously. Measurements of the in-situ surface condition and important chemically active radical species are extremely challenging. The most promising approach to overcome these challenges to achieve advanced process control is the active coupling of numerical simulations and experiments. In this regard, numerical simulations are a well-established technique to study fundamental plasma parameters and plasma dynamics for a variety of discharge sources. The utilised numerical simulation is an experimentally benchmarked 1D fluid model, with semi-kinetic treatment of electrons and an improved energy dependent ion mobility treatment. This model is applied for a geometrically symmetric and asymmetric capacitively coupled oxygen RF discharge. Within the investigated pressure range of 10 Pa - 100 Pa the simulations predict that changing surface conditions have a significant effect on dynamics of the plasma-surface interface. In particular, the surface loss probability and lifetime of metastable singlet delta oxygen as well as the secondary electron emission coefficient are identified to substantially influence the electronegativity and the plasma sheath dynamics on a nanosecond timescale. Phase resolved optical emission spectroscopy measurements, utilising different surface materials, confirm these predictions by comparing measured and simulated excitation features for three different optical emission lines. Through the synergistic coupling of numerical simulations and experiments, the surface work functions as well as other key surface parameters are assessed. Furthermore, the use of an advanced actinometry technique, demonstrated by coupling simple electron kinetic simulations and optical measurements, enables measurements of the spatial distribution of radical atomic oxygen densities and local electron energies over the total discharge volume.
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Lang, Jens, Gudula Rünger, and Paul Stöcker. "Dynamische Simulationskopplung von Simulink-Modellen durch einen Functional-Mock-up-Interface-Exportfilter." Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-119975.
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Für den Austausch und zur Kopplung von Simulationsmodellen ist die Nutzung herstellerübergreifender Standards wie des Functional Mock-up-Interfaces (FMI) unerlässlich. In diesem Artikel wird eine Methode zum automatisierten Export von Simulationsmodellen aus Simulink in Module nach dem Standard FMI for Co-Simulation vorgestellt. Der automatisierte Export nutzt den Quelltextgenerator von Simulink und passt diesen über Templates für den Target Language Compiler so an, dass der erzeugte Quelltext das Functional Mock-up Interface implementiert. Der Artikel beschreibt die Methode zum Auslesen der Signaldefinitionen inkl. Bezeichner und Typen aus dem Simulink-Modell und die Methode zur Generierung des FMI-Quelltextes.
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Bössinger, Stefan [Verfasser], and Matthias [Akademischer Betreuer] Schneider. "Coupling the thermodynamic state with the dynamics of lipid interface layers - and its possible role for biology / Stefan Bössinger. Betreuer: Matthias Schneider." Augsburg : Universität Augsburg, 2013. http://d-nb.info/1077701756/34.
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Kaiser, Benjamin [Verfasser]. "A generalised interface for multi-level coupling of beam unit cell meso-models to macro finite elements in draping simulation / Benjamin Kaiser." Düren : Shaker, 2020. http://d-nb.info/1220610003/34.
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Ganser, Markus [Verfasser], and M. [Akademischer Betreuer] Kamlah. "On the Electro-Chemo-Mechanical Coupling in Solid State Batteries and its Impact on Morphological Interface Stability / Markus Ganser ; Betreuer: M. Kamlah." Karlsruhe : KIT Scientific Publishing, 2021. http://d-nb.info/1228537348/34.
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Vu, Bich Thi Ngoc. "INTERFACIAL MODIFICATION FOR THE REINFORCEMENT OF SILICONE ELASTOMER COMPOSITES." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin998071429.
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Djati, Nabil. "Study of interface capturing methods for two-phase flows." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI052/document.
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Cette thèse est consacrée au développement et à la comparaison des méthodes de suivi d'interface pour les écoulements diphasiques incompressibles. Elle s'intéresse à la sélection de méthodes robustes de suivi d'interface, puis à leur couplage avec le solveur des équations de Navier-Stokes. La méthode level-set est en premier lieu étudiée, en particulier l'influence du schéma d'advection et de l'étape de réinitialisation sur la qualité des résultats du suivi d'interface. Il a été montré que la méthode de réinitialisation avec contrainte de volume est robuste et précise en combinaison avec des schémas conservatifs WENO d'ordre 5 pour l'advection. Il a été constaté que les erreurs du suivi d'interface augmentent de manière abrupte lorsque la condition CFL est trop petite. Comme remède, la réinitialisation du champ level-set effectuée moins souvent réduit la diffusion numérique et le déplacement non-physique de l'interface. La conservation de la masse n'est pas assurée avec les méthodes level-set. Les méthodes VOF (volume-of-fluid) qui conservent naturellement la masse du fluide de référence sont alors étudiées. Une résolution géométrique avec un schéma consistent et conservatif est alors adoptée, ainsi qu'une autre technique alternative plus aisément extensible en 3D. Il a été trouvé que ces deux dernières méthodes donnent des résultats très proches. La méthode MOF (moment-of-fluid), qui reconstruit l'interface en utilisant le centre de masse du fluide de référence, est plus précise que les méthodes VOF. Différentes méthodes couplées entre level-set et VOF sont alors étudiées, notamment: CLSVOF, MCLS, VOSET et CLSMOF. Il a été observé que la méthode level-set tend à épaissir les filaments minces, tandis que VOF et les méthodes couplées les fragmentent en petites particules. Finalement, on a couplé les méthodes level-set et VOF avec le solveur incompressible des équations de Navier-Stokes. On a comparé différentes manières de prise en compte des conditions de saut à l'interface (lisse et raide). Il a été montré que les méthodes VOF sont plus robustes, et donnent d'excellents résultats pour quasiment toutes les simulations. Deux méthodes level-set donnant de très bons résultats, comparables à ceux de VOF, sont aussi identifiéesThis thesis is devoted to the development and comparison of interface methods for incompressible two-phase flows. It focuses on the selection of robust interface capturing methods, then on the manner of their coupling with the Navier-stokes solver. The level-set method is first investigated, in particular the influence of the advection scheme and the reinitialization step on the accuracy of the interface capturing. It is shown that the volume constraint method for reinitialization is robust and accurate in combination with the conservative fifth-order WENO schemes for the advection. It is found that interface errors increase drastically when the CFL number is very small. As a remedy, reinitializing the level-set field less often reduces the amount of numerical diffusion and non-physical interface displacement. Mass conservation is, however, not guaranteed with the level-set methods. The volume-of-fluid (VOF) method is then investigated, which naturally conserves the mass of the reference fluid. A geometrical consistent and conservative scheme is adopted, then an alternative technique more easily extended to 3D. It is found that both methods give very similar results. The moment-of-fluid (MOF) method, which reconstructs the interface using the reference fluid centroid, is found to be more accurate than the VOF methods. Different coupled level-set and VOF methods are then investigated, namely: CLSVOF, MCLS, VOSET and CLSMOF. It is observed that the level-set method tends to thicken thin filaments, whereas the VOF and coupled methods break up thin structures in small fluid particles. Finally, we coupled the level-set and volume-of-fluid methods with the incompressible Navier-Stokes solver. We compared different manners (sharp and smoothed) of treating the interface jump conditions. It is shown that the VOF methods are more robust, and provide excellent results for almost all the performed simulations. Two level-set methods are also identified that give very good results, comparable to those obtained with the VOF methods
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Rose, Alexander [Verfasser], Klaus-Peter [Akademischer Betreuer] Hofmann, Peter [Akademischer Betreuer] Hildebrand, and Peter [Akademischer Betreuer] Hegemann. "The dynamic coupling interface of G-protein coupled receptors : a molecular dynamics simulations study / Alexander Rose. Gutachter: Klaus-Peter Hofmann ; Peter Hildebrand ; Peter Hegemann." Berlin : Lebenswissenschaftliche Fakultät, 2015. http://d-nb.info/1071885960/34.
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Krinner, Andreas [Verfasser], Daniel [Akademischer Betreuer] Rixen, Ron van [Gutachter] Ostayen, and Daniel [Gutachter] Rixen. "Multibody systems with lubricated contacts : Cavitation, interface coupling, reduction and quasi-Newton techniques / Andreas Krinner ; Gutachter: Ron van Ostayen, Daniel Rixen ; Betreuer: Daniel Rixen." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1174633026/34.
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Cordesse, Pierre. "Contribution to the study of combustion instabilities in cryotechnic rocket engines : coupling diffuse interface models with kinetic-based moment methods for primary atomization simulations." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASC016.
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Gardiens de l’espace, les lanceurs de fusée font l’objet d’une amélioration continue et concurrentielle, grâce à des campagnes de tests expérimentaux et numériques. Les simulations prédictives sont devenues indispensables pour accroître notre compréhension de la physique. Ajustables, elles se prêtent parfaitement à la conception et l’optimisation, en particuliers de la chambre de combustion, pour garantir la sureté et maximiser l’efficacité. L’atomisation primaire est l’un des phénomènes déterminants de la combustion du combustible et de l’oxydant, pilotant à la fois la distribution de gouttes et les potentielles instabilités hautes-fréquences en conditions sous-critiques. Elle couvre un large spectre de topologies d’écoulement diphasique, depuis ceux de type phases séparées jusqu’à la phase dispersée, en passant par une région mixte caractérisée par la complexité de la physique à petites échelles et de la topologie de l’écoulement. Les modèles d’ordre réduit constituent de bons candidats pour réaliser des simulations numériques prédictives et relativement peu coûteuses en ressource de calcul sur des configurations industrielles. Cependant, jusqu’à présent ils ne décrivent correctement que la dynamique des grandes échelles et doivent donc être couplés à des modèles de phase dispersée nécessitant un réglage minutieux de paramètres pour prédire la formation du spray. Afin de décrire à la fois les régions mixte et dispersée, l’amélioration de la hiérarchie de modèles d’ordre réduit repose sur quelques principes clefs au cœur de la thèse ci-présente et fournit des problèmes interdisciplinaires faisant appel tant à l’analyse mathématique et la modélisation physique de ces systèmes d’EDP qu’à leur discrétisation numérique et leur implémentation dans des codes de CFD à des fins industriels. Grâce d’une part à l’extension de la théorie des équations de conservation supplémentaires à des systèmes impliquant des termes non-conservatifs et d’autre part à un formalisme de thermodynamique multi-fluide tenant compte des effets non-idéaux, nous proposons de nouvelles pistes pour définir une entropie de mélange strictement convexe et consistante avec le système d’équation et les lois de pression, dans le but de permettre la symmétrisation entropique des modèles diphasiques, de prouver leur hyperbolicité et d’obtenir des termes sources généraux. De plus, en rompant avec la vision géométrique de l’interface, nous proposons une description multi-échelle de l’interface pour décrire un mélange multi-fluide comportant une dynamique interfaciale complexe. Le Principe de Moindre Action a permis de dériver un modèle bifluide à une vitesse couplant grandes et petites échelles de l’écoulement. Nous avons ensuite développé une stratégie de séparation d’opérateurs basée sur la discrétisation par Volumes Finis, et nous avons implémenté le nouveau modèle dans le logiciel industriel multiphysique de CFD, CEDRE, de l’ONERA afin d’évaluer numériquement ce dernier. Enfin, nous avons construit et analysé les fondations d’une hiérarchie de cas tests accessibles à la DNS tout en étant au plus proche de configurations industrielles, dans le but d’évaluer les résultats de simulations du nouveau modèle ou de tout autre modèle à venirGatekeepers to the open space, launchers are subject to intense and competitive enhancements, through experimental and numerical test campaigns. Predictive numerical simulations have become mandatory to increase our understanding of the physics. Adjustable, they provide early-stage optimization processes, in particular of the combustion chamber, to guaranty safety and maximize efficiency. One of the major physical phenomenon involved in the combustion of the fuel and oxidizer is the jet atomization, which pilotes both the droplet distributions and the potential high-frequency instabilities in subcritical conditions. It encompasses a large sprectrum of two-phase flow topologies, from separated phases to disperse phase, with a mixed region where the small scale physics and topology of the flow are very complex. Reduced-order models are good candidates to perform predictive but low CPU demanding simulations on industrial configurations but have only been able so far to capture large scale dynamics and have to be coupled to disperse phase models through adjustable and weakly reliable parameters in order to predict spray formation. Improving the hierarchy of reduced order models in order to better describe both the mixed region and the disperse region requires a series of building blocks at the heart of the present work and give on to complex problems in the mathematical analysis and physical modelling of these systems of PDE as well as their numerical discretization and implementation in CFD codes for industrial uses. Thanks to the extension of the theory on supplementary conservative equations to system of non-conservation laws and the formalism of the multi-fluid thermodynamics accounting for non-ideal effects, we give some new leads to define a strictly convex mixture entropy consistent with the system of equations and the pressure laws, which would allow to recover the entropic symmetrization of two-phase flow models, prove their hyperbolicity and obtain generalized source terms. Furthermore, we have departed from a geometric approach of the interface and proposed a multi-scale rendering of the interface to describe multi-fluid flow with complex interface dynamics. The Stationary Action Principle has returned a single velocity two-phase flow model coupling large and small scales of the flow. We then have developed a splitting strategy based on a Finite Volume discretization and have implemented the new model in the industrial CFD software CEDRE of ONERA to proceed to a numerical verification. Finally, we have constituted and investigated a first building block of a hierarchy of test-cases designed to be amenable to DNS while close enough to industrial configurations in order to assess the simulation results of the new model but also to any up-coming models
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Jacksén, Johan. "Improved techniques for CE-MALDI-MS off-line coupling and MALDI-MS analysis of primarily hydrophobic proteins and peptides." Licentiate thesis, KTH, Chemistry, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4599.
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Due to the hydrophobic nature of integral membrane proteins (IMP) they give rise to several difficulties concerning handling and analysis, which is not the case for the most water soluble proteins. New analysis methods are needed, where the insolubility problems of the hydrophobic proteins due to aggregation and adhesion are tackled. Those problems also affect digestion performance and equipment compatibility for the analysis.
Protocols for analysis and separation specified for IMP are presented in Paper I and III.
The instrumentation used in this work was capillary electrophoresis (CE) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Both instruments are suitable for peptide/proteins analysis.
In Paper I, protocols for a CE separation of bacteriorhodopsin (BR) peptides as model IMP peptides are established. Also, a partially automated manufacturing procedure of a concentration MALDI-target is presented, suitable for fractions from CE. The MS analysis detected 9 out of 10 cyanogen bromide (CNBr) digested BR peptides. A novel technique for the off-line integration of CE to MALDI-MS using a closed-open-closed system is presented in Paper II, where the open part is a microcanal functioning as a MALDI target window. Investigation of the microcanal electro-osmotic flow (EOF) properties and band broadening characteristics was performed. A protein separation was obtained and detected with MALDI-MS analysis in the microcanal. Different protein digestion methods were evaluated using BR in Paper III through MALDI-MS. Several digestion methods as well as MS media were investigated alongside different MALDI matrices. For example, matrices as the hydrophobic 2,6-dihydroxyacetophenone (DHAP) and 2-Hydroxy-3-methoxybenzoic acid (2H3MBA) or 2-Hydroxy-5-methoxybenzoic acid (2H5MBA) mixed with DHB, appeared to be promising matrices for analysis of BR.
Med anledning av integrala membranproteiners (IMP) hydrofoba egenskaper uppstår flera svårigheter vid hantering och analys av IMP, vilket inte är fallet för vattenlösliga proteiner. Nya analysmetoder krävs, som löser löslighetsproblemen för de hydrofoba proteinerna som tex flockning och adsorbtion. Dessa problem påverkar även klyvningsgrad och kompatibilitet med analysutrustningen.
I Artikel I och Artikel III presenteras protokoll för analys och separation specifikt för IMP. Instrumenteringen som har använts i detta arbete är kapillärelektrofores (CE) och matris-assisterad laserdesorptions-joniserings-masspektrometri (MALDI-MS). Båda instrumenten är lämpade för peptid/protein analyser.
I Artikel I, presenteras protokoll för en CE separation av peptider från bacteriorhodopsin (BR), som användes som modellpeptider för IMP. En delvis automatiserat tillverkningsprocedur för en koncentrerande MALDI-platta, som är anpassad för CE fraktionerna beskrivs också. MS-analysen detekterade 9 av 10 BR-peptider från cyanobromid-klyvning (CNBr). En ny teknik för off line-integrering av CE till MALDI-MS genom ett slutet-öppet-slutet system presenteras i Artikel II, där den öppna delen är en mikrokanal som fungerar som detektionsfönster i MALDI. Undersökning av mikrokanalens egenskaper som tex det elektroosmotiska flödet (EOF) och bandbreddningen utvärderades. En proteinseparation genomfördes och detekterades med MALDI–MS i mikrokanalen. Olika proteinklyvningsmetoder för BR undersöktes i Artikel III med MALDI-MS. Flera proteinklyvningsmetoder samt MS-medier utvärderades tillsammans med olika MALDI-matriser. Den hydrofoba matrisen 2,6-dihydroxyacetophenone (DHAP) och 2-Hydroxy-3-methoxybenzoic acid (2H3MBA) eller 2-Hydroxy-5-methoxybenzoic acid (2H5MBA) blandade med DHB, visade sig exempelvis vara lovande matriser för BR-analyser.
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Santos, Judas, and Nidaa Al-Mahdi. "Experimental substructuring of an A600 wind turbine blade : A study of the influence of interface loading." Thesis, Linnéuniversitetet, Institutionen för maskinteknik (MT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-54060.
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Dynamic Substructuring is a powerful tool for simplification of the analysis of complex structures and it has been well established along the years in analytical calculations by means of the Craig-Bampton technique. Recently, a new branch of substructuring, the Experimental Dynamic Substrucuring, appeared as a promising field of research for the engineering community. This area presents several intrinsic difficulties, evincing a need to develop the traditional substructuring methods towards obtaining better results using the experimental approach. In this scenery, the Transmission Simulator technique emerges as an instrument for potential improvement of the achieved results. This work represents a study on the use of the Transmission Simulator technique in the analysis of an Ampair A600 wind turbine blade subjected to loads at the interface to the hub, and it is a part of the benchmarking studies of SEM (Society of Experimental Mechanics). The work consisted of collecting experimental data via vibration tests of a single blade connected to different sizes of transmission simulators. After that, a mathematical representation of the blade was obtained via subtraction of the effect of the transmission simulators via substructuring technique. The computed model was subsequently coupled to a model of the remainder of the wind turbine (the hub plus two blades), and the results were compared to data acquired in tests of the whole assembly. The final findings did not reflect the theory prospects and further investigation is necessary to evaluate the effectiveness of the used methodology.
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Silva, Jonathan Esteban Arroyo. "Acoplamento de interface Iterativo MEF—MEFE para problemas do tipo sólido-fluido no domínio do tempo." Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/6911.
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Neste trabalho será proposto um método de acoplamento iterativo de interface com um esquema de subcycling no tempo eficiente e preciso. Este será aplicado a pro-blemas do tipo sólido-fluido discretizados, respectivamente, pelos métodos dos elementos finitos clássico (MEF) e espectral (MEFE). Adicionalmente, será proposta uma melhoria no esquema de subcycling, de modo que para convergir não sejam necessários métodos de relaxação. Aplicando o MEFE em subdomínios com geometrias pouco distorcidas, pode-se usufruir da alta precisão numérica com baixo custo de armazenamento oferecidos pelo método ao mesmo tempo em que é possível aplicar o MEF aos subdomínios com geometrias complexas, acrescentando versatilidade ao método. Diferentes exemplos nu-méricos são apresentados e analisados para demonstrar a precisão e a potencialidade das formulações numéricas propostas.
In this work, an iterative interface coupling method with an efficient and precise time subcycling scheme is proposed. It is applied to solid-fluid type problems discretized respectively by classical finite element method (FEM) and spectral finite element method (SFEM), additionally, an improvement in the subcycling scheme is proposed so as not to require relaxation methods to converge. Applying the SFEM in subdomains with low distorted geometries one can take advantage of the high numerical precision with low cost of storage offered by the method, while it is possible to apply the FEM in subdomains with complex geometries, adding versatility to the method. Many numerical examples are presented and analyzed here to show the accuracy and potentiality of the proposed numerical formulations.
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Robineau, Mathieu. "Risques de corrosion associés à une interface hétérogène acier-matériau de remplissage-argilites : couplages galvaniques, cinétique et évolution dans le temps." Thesis, La Rochelle, 2018. http://www.theses.fr/2018LAROS020/document.
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La présente étude porte sur les problématiques d’entreposage de colis de déchets nucléaires. En France, via le projet Cigéo, il est envisagé d’entreposer les déchets radioactifs de moyenne et haute activité à vie longue à 500 mètres de profondeur dans un conteneur en acier API 5L X65 (chemisage) déposé dans des galeries creusées au sein d’une formation argileuse (argilites). Une température maximum de 90°C est attendue à la surface de l’acier en raison de l’intense radioactivité. Finalement, un coulis cimentaire (matériau de remplissage) sera injecté entre le chemisage et les argilites. La synthèse de couches de produits de corrosion susceptibles d’être rencontrées à la surface de l’acier dans les conditions de stockage a constitué le premier objectif de ce travail. Les conditions pour l’obtention de sidérite (FeCO3), de mackinawite (FeS) et de magnétite (Fe3O4) ont été déterminées. Par la suite, des essais de couplage impliquant deux électrodes recouvertes de produits différents ont été réalisés dans le but de simuler le comportement d’une surface d’acier recouverte d’une couche hétérogène de produits de corrosion. Il est apparu que l’acier recouvert d’une couche de mackinawite se comportait dans chaque cas comme une cathode. Ce phénomène est associé au caractère plutôt protecteur de la couche de mackinawite. Parallèlement, les essais de formation de la mackinawite par polarisation anodique ont montré que la formation d’une couche de produits de corrosion composée de magnétite/mackinawite était associée à un phénomène de corrosion localisée. Le comportement de l’acier au contact du matériau de remplissage envisagé pour combler l’espace entre le chemisage et les argilites a ensuite été étudié. Ce deuxième volet de l’étude a montré que la couche de produits de corrosion se formant à la surface de l’acier était principalement composée de magnétite, associée à des sulfures de fer tels que la mackinawite. L’hétérogénéité du matériau de remplissage, la présence de sulfures en son sein et la présence d’oxygène dissous dans les solutions de test sont les principales causes de l’apparition d’un phénomène de corrosion localisée. Ce résultat traduit également le caractère imparfaitement protecteur des couches d’oxyde se formant sur l’acier au contact du matériau cimentaire. Enfin, la dernière partie de ce travail de recherche a porté sur l’étude d’éventuels effets galvaniques entre une zone recouverte d’argilites et une zone recouverte de matériau de remplissage impliquant la présence de magnétite et de mackinawite et pouvant faire office de cathode. De tels effets n’ont pas été mis en évidence, ce qui est attribué à l’absence d’un véritable état passif de l’acier en contact avec le matériau cimentaireThe present study relates to the problem of long-term disposal of nuclear waste. In France, with the Cigéo project, it is envisaged to store high and intermediate level long lived radioactive waste at a depth of 500m inside a carbon steel (API 5L X65) casing in a deep geological disposal, drilled in a very stiff clay formation. A maximum temperature of 90°C is expected at the carbon steel surface, because of the intense radioactivity. Finally, a specific cement grout will be injected between the carbon steel casing and the argilites. The synthesis of corrosion product layers likely to form on the steel surface was the first objective of this work. The different parameters to obtain siderite (FeCO3), mackinawite (FeS) and magnetite (Fe3O4) have been determined. Subsequently, coupling tests were carried out with two steel electrodes covered with different corrosion products in order to simulate the behaviour of a steel surface covered with a heterogeneous corrosion product layer. It appeared that the steel electrode covered with mackinawite was in each case the cathode. This phenomenon is associated with the somewhat protective properties of the mackinawite layer. Besides, anodic polarization experiments conducted to prepare mackinawite layers showed that the formation of a corrosion product layer composed of magnetite/mackinawite was associated with localized corrosion. The behaviour of carbon steel in contact with cement grout envisaged to fill the gap between casing and argillites was studied next. This second part of the study showed that the corrosion product layer forming on the steel surface was mainly composed of magnetite, associated with iron sulphides such as mackinawite. Heterogeneity of the cement grout, presence of sulphide within it, and presence of dissolved oxygen in the test solutions are the main causes of the appearance of localized corrosion processes. This result also shows that the oxide layers forming on the steel surface in the specific cement grout only provides an imperfect protection. Finally, the last part of this research work focused on the study of possible galvanic effects between a zone covered with argilites, and a zone covered with cement grout implying the presence of magnetite and mackinawite and thus able to act as cathode. Such effects could not be evidenced which is attributed to the absence of a real passive state of the steel in contact with the cement grout
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Bonnet, Guillaume. "Seamount subduction in the Zagros Suture Zone : structural and petrologic characterization and implications for seismogenesis." Electronic Thesis or Diss., Sorbonne université, 2018. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2018SORUS526.pdf.
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Les monts sous-marins subductés jouent un rôle majeur dans le comportement mécanique et sismogénique des zones de subduction: sont-ils des barrières à la propagation des séismes ou bien des aspérités permettant leur nucléation ? Les rares exemples naturels arrachés de la plaque plongeante le long de l'interface de subduction et préservés de la subduction représentent donc des témoins précieux des processus profonds. Cette thèse de doctorat reporte l'existence d'un mont sous-marin dans la zone de suture du Zagros (l'unité de Siah Kuh). Cette unité de 20x12 km de large et d'un minimum de 1.5 km de hauteur est composée de basaltes en coussins couverts de calcaire récifal et s'est formée au sein d'un arc volcanique au Crétacé supérieur. La présence de minéraux de HP-BT dans l'ensemble de la structure et dans des zones de déformation compressive localisée montrent qu'elle a été subductée jusqu' à environ 30 km. La déformation synchrone de la subduction, liée à l'écaillage interne du mont sous-marin, est assistée par des décollements enracinés dans la serpentinite ou dans des sédiments, ce qui limite possiblement l'essentiel de l'activité sismique, étant donné qu'une unique pseudotachylite a été observée, témoignant d'un séisme de magnitude Mw2-3.Nous discutons des processus océaniques de déstabilisation de pente et de subsidence, et des processus de subduction comme le couplage mécanique, les surpressions de fluide et/ou tectoniques ainsi que la nature des fluides de subduction. Nous finissons en proposant un modèles d'évolution de cette unité en relation avec les autres unités océaniques héritées de la NéotethysEamounts are for the most part subducted with the downgoing oceanic plate. They are expected to critically impact the mechanical and seismogenic behavior of subduction zones, but their exact role is strongly debated (i.e. as to whether they represent barriers to propagation or asperities promoting nucleation). Rare natural examples of metamorphosed seamounts, that got sliced off the slab along the plate interface are therefore precious witnesses to document processes operating at depth.This PhD thesis reports the existence of a former seamount in the Zagros suture zone (the Siah Kuh unit).This 20x12 kilometer-large, minimum 1.5 km-high unit composed of pillow basalts capped by reef limestone was formed in an arc environment during the Late Cretaceous.HP-LT minerals (lawsonite, aragonite veins, blue amphibole) found across the whole structure, particularly in zones of localized compressive deformation, indicate that this seamount was shallowly subducted at 30 km. Syn-subduction deformation is assisted by dŽcollement rooting in serpentinite and/or oceanic sediments and is related to the internal slicing of the seamount. The presence of soft layers may prevent most of the seismic activity, since only one pseudotachylite, recording a Mw2-3 earthquake has been found. The Siah Kuh unit is also a perfect target to investigate oceanic processes such as slope destabilization and subsidence, and subduction processes such as mechanical coupling, fluid/tectonic overpressure and the nature of subduction fluids. We finally build a model for the tectonic evolution of the Siah Kuh unit and its relationship with other ophiolites
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Baber, Katherina [Verfasser], and Rainer [Akademischer Betreuer] Helmig. "Coupling free flow and flow in porous media in biological and technical applications : from a simple to a complex interface description / Katherina Baber. Betreuer: Rainer Helmig." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2015. http://d-nb.info/1065670397/34.
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Ye, Fan. "Surface plasmon polaritons along metal surfaces with novel structures." Thesis, Boston College, 2014. http://hdl.handle.net/2345/bc-ir:103747.
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Thesis advisor: Michael J. NaughtonSurface plasmon polaritons (SPPs) are hybridized quasiparticles of photons and electron density waves. They are confined to propagate along metal-dielectric interfaces, and decay exponentially along the direction perpendicular to the interfaces. In the past two decades, SPPs have drawn intensive attention and undergone rapid development due to their potential for application in a vast range of fields, including but not limited to subwavelength imaging, biochemical/biomedical sensing, enhanced light trapping for solar cells, and plasmonic logic gates. These applications utilize the following intrinsic properties of SPPs: (1) the wavelength of SPPs is shorter (and can be much shorter) than that of free photons with the same frequency; (2) the local electric field intensity associated with SPPs can be orders of magnitude larger than that of free photons; and (3) SPPs are bound to metal surfaces, and are thus easily modulated by the geometry of those surfaces. Here, we present studies on SPPs along metal surfaces with novel structures, including the following: (1) SPP standing waves formed along circular metal surfaces that lead to a "plasmonic halo" effect; (2) directional reflectionless conversion between free photons and SPPs in asymmetric metal-insulator-metal arrays; and (3) broadband absorbance enhancement of embedded metallic nanopatterns in a photovoltaic absorber layer. These works may prove useful for new schemes for SPP generation, plasmon-photon modulation, ultrasensitive dielectric/bio sensing, and high efficiency thin film solar cells
Thesis (PhD) — Boston College, 2014
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
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Baudey-Laubier, Louis-Henri. "Modélisation et simulation numérique des transferts de masse et de chaleur induits par évaporation." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1086/document.
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L’évaporation d’une solution solvant/soluté est un processus transitoire qui prend fin lorsque le solvant a totalement disparu. Le refroidissement créé par le changement de phase provoque des gradients à la fois thermiques et de concentration en solvant. Ces homogénéités diffusent ensuite dans l’épaisseur de la solution et sont susceptibles d’engendrer un écoulement fluide. L’origine de cette convection peut être liée à des variations de tension de surface ou de densité. Des travaux expérimentaux ont montré que l’épaisseur des dépôts issus de séchages de solutions solvant/soluté semblait pouvoir être corrélée avec les cellules de convection de la zone fluide. Une compréhension approfondie des phénomènes à l’origine de la convection devrait donc participer à un meilleur contrôle de la qualité des dépôts.Sur la base de travaux numériques et expérimentaux publiés, nous avons étudié l’apparition de la convection pour trois types de modèles représentant le processus d’évaporation d’une solution de Polyisobutylène-Toluène : un modèle purement thermique qui s’applique pour les temps courts, un modèle solutal qui est valable sur les temps longs et enfin un modèle couplé thermique/solutal qui représente les transferts sur l’ensemble de la gamme des temps étudiés. Le caractère transitoire de l’évaporation induit une difficulté pour caractériser la naissance de la convection à partir d’un régime de conduction. En effet, cette convection apparaît à partir d’un germe qui est une petite perturbation de la solution diffusive. Si l’amplitude de cette perturbation est trop faible, son amplification à des intensités suffisantes ne pourra pas avoir lieu avant la fin du régime transitoire et l’écoulement ne deviendra donc jamais convectif. Le rôle de la perturbation est donc primordial. Dans des travaux numériques antérieurs, cette perturbation a été imposée à l’état initial, généralement avec une distribution aléatoire du champ thermique ou de vitesse. Lors de cette thèse, nous avons opté pour un modèle plus physique, basé sur l’introduction d’un transfert thermique sur les parois latérales qui joue le rôle de perturbateur de l’écoulement diffusif transitoire.Dans cette thèse, nous avons établi par voie numérique les seuils de transition entre une solution diffusive et un écoulement convectif pour les modèles thermique, solutal et couplé, dans le cas d’une approximation bidimensionnelle du film liquide et des simulations pleinement tridimensionnelles. Des diagrammes spatio-temporels et l’étude des cellules à la surface libre par des reconstructions de Voronoï nous ont permis de mieux comprendre la naissance et la propagation des instabilités dans la solution fluideThe evaporation of a solvent/solute solution is a transient phenomenon which ends when the whole solvent has disappeared. Phase change generates a cooling of the liquid-gas interface, and consequently, it creates thermal and solutal gradients. These homogeneities spread in the core solution and produce, eventually, a fluid flow. This convection can be due to the surface tension and/or buoyancy variations. Experimental works have shown that some coating thicknesses stemming from drying processes are correlated to the size of the convection cells in the fluid region. A thorough understanding of the physical phenomena responsible to fluid convection should contribute to improve the control of deposit quality.Based on numerical and experimental works, we have studied the onset of convection for three kinds of models for the drying process of a Polyisobutylene-Toluène solution: A pure thermal model which is valid for short times, a solutal model devoted to the simulation of long times, only, and a thermal/solutal coupled model which takes into account the heat and mass transfer over a long time period of the evaporation process. The transient nature of the evaporation problem raises the issue of how to define the onset of the convective flow from a diffusive solution. Indeed, this flow motion occurs from a seed which is a small perturbation of the transient diffusive solution. If the perturbation is too weak, the necessary time interval for a significant growing of its magnitude will be greater than the time scale of the transient regime: thus the solution will never be considered as convective. Consequently, the influence of the perturbation is fundamental. In previous numerical works, this perturbation was imposed at the initial state, often through a random spatial distribution applied to the velocity or temperature field. In the present contribution, we have adopted a physical model where the adiabatic lateral walls have been replaced by diathermal walls: The local thermal inhomogeneities create a very weak flow acting as a small disturbance for the transient diffusive solution.In this thesis, we have developed a numerical model to evaluate the thresholds between the diffusive solutions and the convective flows, for the thermal, solutal and thermal/solutal coupled models, for two- and three-dimensional approximations of the Polyisobutylene-Toluène liquid film. Space-time diagrams and convective cell reconstructions at the liquid-gas interface by a Voronoï algorithm allowed us to get a better understanding of the way the disturbances propagate from the lateral walls for finally giving rise to a convective flow in the core fluid
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Limaiem, Sarra. "Étude et développement d’une interface fibre-matrice spécifique dans les composites à matrice thermoplastique renforcés en fibres de verre continues." Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH8553.
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Au cours de cette étude, il a été question de développer une méthodologie d’élaboration et d’évaluation de la qualité de l’interface fibre-matrice au sein d’un composite à matrice polyamide 12 renforcé par du verre. Un modèle macroscopique a été élaboré dans un premier temps sous forme d’un assemblage lame de verre/film polyamide 12, et plusieurs promoteurs d’adhésion, principalement des organosilanes, de fonctionnalités différentes et compatibles avec la matrice polyamide ont été testés. La qualité du greffage a pu être caractérisée grâce à des techniques d’analyses physico-chimiques adaptées (AFM, PM-IRRAS, mouillabilité,…), et la performance adhésive des assemblages a pu être évaluée par des tests mécaniques spécifiques (pelage, clivage). Dans une seconde étape, le protocole de dépôt décrit à l’échelle macroscopique a été adapté à l’échelle des fibres de verre, plus particulièrement à l’échelle mésoscopique des fibres optiques. Des essais mécaniques spécifiques à l’échelle microscopique (fragmentation) ont été réalisés afin d’évaluer la performance adhésive de l’interface dans les assemblages concernés. Une étude focalisée sur la compréhension des mécanismes interfaciaux a également été réalisée afin de clarifier la nature des interactions établies à l’interface fibre-matrice. Grâce aux différentes techniques de caractérisation physico-chimiques il a été possible de mettre en évidence l’influence de différents paramètres expérimentaux, tels que la durée du greffage, la densité de greffage et la chimie des surfaces traitées, sur la cristallisation de la matrice à l’interface. La dernière partie de ce travail de thèse concerne le passage à l’échelle du semi-produit sous forme de rubans. Des analyses des propriétés de l’interface ainsi que des caractéristiques mécaniques ont été réaliséesDuring this study, the aim was to develop a methodology to elaborate and evaluate the quality of the fiber-matrix interface in a glass fiber reinforced polyamide 12 composite.At first, a macroscopic model was developed using a glass slide/polyamide 12 film assembly. Several organosilane adhesion promoters with different features and compatible with the polyamide matrix were tested. The grafting quality was characterized through appropriate physico-chemical analytical techniques (AFM, PM-IRRAS, Wetting…), and the adhesive performance of the assemblies was evaluated by specific mechanical tests (Peel test, Wedge test). In a second step, the deposition procedure described in macroscopic scale has been adapted to the glass fibers’ scale, more particularly to optical fibers. Specific mechanical tests were performed (fragmentation test) to assess the adhesive performance at the interface of the concerned assemblies.A study focused on the understanding of the interfacial mechanisms was also conducted to clarify the nature of the interactions established at the fiber-matrix interface. Thanks to the different physico-chemical characterization techniques, it has been possible to demonstrate the influence of various experimental parameters such as the surface treatment time, the grafting density and the chemistry on the treated surfaces on the crystallization of the matrix at the interface. The last part of this work concerns the transition to the semi-scale form of ribbons. The analysis of the interface’s properties and the mechanical characteristics has been investigated
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Nilsing, Mattias. "Computational Investigation of Dye-Sensitized Solar Cells." Doctoral thesis, Uppsala universitet, Avdelningen för kvantkemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7673.
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Interfaces between semiconductors and adsorbed molecules form a central area of research in surface science, occurring in many different contexts. One such application is the so-called Dye-Sensitized Solar Cell (DSSC) where the nanostructured dye-semiconductor interface is of special interest, as this is where the most important ultrafast electron transfer process takes place. In this thesis, structural and electronic aspects of these interfaces have been studied theoretically using quantum chemical computations applied to realistic dye-semiconductor systems. Periodic boundary conditions and large cluster models have been employed together with hybrid HF-DFT functionals in the modeling of nanostructured titanium dioxide. A study of the adsorption of a pyridine molecule via phosphonic and carboxylic acid anchor groups to an anatase (101) surface showed that the choice of anchor group affects the strength of the bindings as well as the electronic interaction at the dye-TiO2 interface. The calculated interfacial electronic coupling was found to be stronger for carboxylic acid than for phosphonic acid, while phosphonic acid binds significantly stronger than carboxylic acid to the TiO2 surface. Atomistic and electronic structure of realistic dye-semiconductor interfaces were reported for RuII-bis-terpyridine dyes on a large anatase TiO2 cluster and perylene dyes on a periodic rutile (110) TiO2 surface. The results show strong influence of anchor and inserted spacer groups on adsorption and electronic properties. Also in these cases, the phosphonic acid anchor group was found to bind the dyes significantly stronger to the surface than the carboxylic acid anchor, while the interfacial electronic coupling was stronger for the carboxylic anchor. The estimated electron injection times were twice as fast for the carboxylic anchor compared to the phosphonic anchor. Moreover, the electronic coupling was affected by the choice of spacer group, where unsaturated spacer groups were found to mediate electron transfer more efficiently than saturated ones.
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Lindberg, Eskil. "A Vibro-Acoustic Study of Vehicle Suspension Systems : Experimental and Mathematical Component Approaches." Doctoral thesis, KTH, MWL Strukturakustik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121575.
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The objective of the present work is to study the vehicle suspension as a vibro-acoustic system of high complexity, consisting of many sub-systems with fundamentally different acoustical properties. In a parallel numerical and experimental modelling effort, important contributions to the understanding of its behaviour have been achieved. These findings are based on a balance between component investigations and global modelling of the complete system; they have been formulated for the transmission of both tyre-road excitation and friction-induced vibrations in the brake system. Initially an experimental study was conducted on a full vehicle test rig studying the broadband interior brake noise problem of, here named, roughness noise. The purpose of the study was twofold: first, to determine if the transmission from the source to the interior of the vehicle was structure-borne; second, to study the complexity of the suspension as a vibro-acoustic system. Parameters a_ecting the vibro-acoustic source were varied to gain understanding of the source mechanisms. This experimental study laid the foundation of the first part of this thesis (paper A) and provided the directions for the second part, the development of a mathematical modelling approach (paper B and C). In these two papers, methods for analysing the complex vibro-acoustic transfer of structure-borne sound in a vehicle suspension system were developed. The last part was then focussed on the wheel rim influence on the vibro-acoustic behaviour (paper D) of the suspension system. As a whole, the work clearly demonstrates that it is possible to conduct component studies of subsystems in the vehicle suspension system; and from these component studies it is possible draw conclusions that very well may avoid severe degradations in the interior noise of future vehicle generations.QC 20130503
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Subhedar, Amol [Verfasser], Fathollah [Gutachter] Varnik, and Ingo [Gutachter] Steinbach. "Phase-field modelling of solidification in the presence of melt flow : a Galilean invariant coupling scheme in the thin interface limit / Amol Subhedar ; Gutachter: Fathollah Varnik, Ingo Steinbach ; Fakultät für Maschinenbau." Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1167505395/34.
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Lundqvist, Maria J. "Quantum Chemical Modeling of Dye-Sensitized Titanium Dioxide : Ruthenium Polypyridyl and Perylene Dyes, TiO2 Nanoparticles, and Their Interfaces." Doctoral thesis, Uppsala universitet, Kvantkemi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7141.
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Quantum chemical calculations have been used to model dye-sensitized nanostructured titanium dioxide systems that can be used in solar cells for solar energy to electricity conversion. Structural, electronic and spectral properties of isolated dyes and both bare and dye-sensitized TiO2 have been calculated with density functional theory, providing detailed information about both the separate parts and the dye-TiO2 interface. The connection between the geometry, the ligand field splitting and the lifetime of the triplet metal-to-ligand charge transfer (MLCT) excited state has been explored for a series of ruthenium polypyridyl dyes. Moreover, the relative energetics of MLCT and metal centered triplet excited states have been studied for a number of such systems. It was found that small alterations of the polypyridyl ligands can result in significant changes in ligand field splitting and in the energetics of the triplet states. Attachment of the dyes to the TiO2 surface is achieved via anchor and spacer groups. The influence of such groups on various properties of the dye and their ability to act as mediators of photo-induced surface electron transfer has been studied. Delocalization of the lowest unoccupied dye orbital onto the spacer and/or anchor group indicates that certain unsaturated groups can mediate electron transfer. With a combination of methods that enables efficient computations and a scheme for construction of metal oxide clusters, chemical models for bare TiO2 nanocrystals in the 1-2 nm size range have been developed. The electronic structures show well-developed band structures with essentially no electronic band gap defect states. Atomistic models of the interface between TiO2 nanocrystals and Ru(II)-bis-terpyridine dyes, the so-called N3 dye as well as perylene dyes are reported. Electronic coupling strengths, which provide estimates for the electron injection times, are extracted from the interfacial electronic structure and the lowest electronic excitations are calculated.
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Zhang, Rongwei. "Novel conductive adhesives for electronic packaging applications: a way towards economical, highly conductive, low temperature and flexible interconnects." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39548.
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Isotropically conductive adhesives (ICAs) are promising as a lead-free interconnect material; However, ICAs have a higher resistivity compared to tin/lead solder. The higher resistivity of ICAs results from the large contact resistance between conductive fillers. Several novel approaches to engineer the interface between electrically conductive fillers were studied to develop highly conductive ICAs. Shown in this dissertation are three methodologies to reduce contact resistance: low temperature sintering, fast sintering and in-situ reduction. Furthermore, two approaches, surface modification and in-situ protection, were developed to prevent oxidation and corrosion of silver-coated copper flakes to produce low cost ICAs. The findings and insights in this dissertation significantly contribute to (1) understanding of filler-filler, filler-polymer and structure-property relationships of ICAs; (2) the structural design and formulation of high performance ICAs; and (3) the wider use of ICAs in emerging applications such as printed electronics and solar cells.
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Torres, Olivier. "Représentation des flux turbulents à l’interface air-mer et impact sur les transports de chaleur et d’eau dans un modèle de climat." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV002/document.
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Les flux turbulents à l’interface air-mer représentent le lien entre l’océan et l’atmosphère et jouent donc un rôle majeur dans le système climatique. Dans les modèles de climat, les processus turbulents sont des processus sous-maille, non résolus explicitement, et doivent donc être paramétrés. Ils sont estimés à partir des variables d’états atmosphériques et océaniques au moyen de modèles mathématiques qu’on nomme « paramétrisations bulk ». Ce travail de thèse a pour objectif de caractériser et comprendre les liens entre la représentation des flux turbulents à l’interface air-mer et le fonctionnement d’un modèle de climat à différentes échelles de temps dans les régions tropicales. Pour étudier ces liens, j’ai développé une stratégie de modélisation utilisant un modèle 1D atmosphérique (SCM), un modèle de circulation générale océanique (OGCM) où atmosphérique (AGCM) et un modèle couplé (GCM). L’analyse des simulations SCM permet d’étudier la réponse directe d’un modèle à la modification de la paramétrisation des flux turbulents. On montre que cette dernière régule la quantité d’eau, d’énergie et de quantité de mouvement disponible pour le système et donc son fonctionnement. Elle représente plus de 60% des différences de flux de chaleur latente simulées entre deux modèles de climat dans les périodes convectives. L’impact spatial de la paramétrisation des flux turbulents est étudié au travers des simulations AGCM. Elles mettent en évidence le lien entre la paramétrisation, son effet sur les gradients d’humidité et de température à grande échelle, et donc son influence sur la circulation atmosphérique. L’étude des simulations OGCM souligne quant à elle le rôle principal du vent pour le fonctionnement des océans tropicaux. Si le vent pilote les variations de SST dues à son impact sur la dynamique océanique et principalement sur le sous-courant équatorial, l’humidité, la température et les flux radiatifs n’influencent quant à eux que la surface océanique et sont donc d’une moindre importance. Enfin, l’analyse des simulations GCM met en évidence les rétroactions et l’ajustement engendrés par la modification des flux turbulents. Lors du couplage des deux composantes l’océan agi comme un tampon et absorbe la modification des flux turbulents ce qui entraine une modification de la SST. L’ajustement qui se produit entraine une modification des variables atmosphériques qui amène à un nouvel état d’équilibre du système. La paramétrisation des flux turbulents de surface agit au premier ordre sur l'équilibre énergétique d'un modèle couplé et peut donc amener à des climats simulés différents. Cette étude étant centrée sur les tropiques, une perspective intéressante serait d’étendre l’étude de la représentation des flux turbulents à d’autres échelles spatio-temporelles (i.e. zones extratropicales/fréquence journalière). Cela permettrait de valider le fonctionnement systématique des paramétrisations définies dans cette thèse à l’échelle globaleThe turbulent fluxes at the air-sea interface represent the link between the ocean and the atmosphere and therefore play a major role in the climate system. In climate models, turbulent processes are subgrid scale processes, not explicitly resolved, and must therefore be parameterized. They are estimated from atmospheric and oceanic state variables using mathematical models called “bulk parameterizations”. This thesis aims to characterize and understand the links between the representation of turbulent fluxes at the air-sea interface and the behavior of a climate model at different time scales in tropical regions. To study these links, I developed a modeling strategy using an atmospheric 1D model (SCM), an oceanic (OGCM) or atmospheric (AGCM) general circulation model and a coupled model (GCM). The analysis of SCM simulations allows us to study the direct response of a model to modifications of the turbulent fluxes parameterization. It is shown that it regulates the amount of water, energy and momentum available to the system and therefore its behavior. It can thus represent more than 60% of simulated latent heat flux differences between two climate models in convective periods. The spatial impact of the parameterization of turbulent fluxes is studied through AGCM simulations. They highlight the link between parameterization, its effect on large-scale moisture and temperature gradients, and thus its influence on atmospheric circulation. The study of OGCM simulations underlines the main role of the wind for the behavior of the tropical oceans. If the wind drives changes in SST due to its impact on ocean dynamics and mainly on the equatorial undercurrent, humidity, temperature and radiative flux only influence the ocean surface and are therefore of lesser importance. Finally, the analysis of GCM simulations highlights the feedbacks and the adjustment generated by the modification of turbulent fluxes. When coupling the two components, the ocean acts as a buffer and absorbs the modification of the turbulent fluxes, which leads to a modification of the SST. The adjustment that occurs causes a modification of the atmospheric variables which leads to a new state of equilibrium of the system. The parameterization of surface turbulent fluxes acts at first order on the energy equilibrium of a coupled model and can therefore lead to different simulated climate state. Since this study is focused on the tropics, an interesting perspective would be to extend the study of the turbulent fluxes representation to other spatio-temporal scales (i.e. extra-tropical areas / daily frequency). This would make it possible to validate the systematic behavior of the parameterizations defined in this thesis on a global scale
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Fabbri, Heber Agnelo Antonel. "Modeling the effects of natural fractures on the permeability of reservoir rocks /." Bauru, 2019. http://hdl.handle.net/11449/190698.
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Orientador: Osvaldo Luís ManzoliAbstract: This work presents a numerical method based on Discrete Fracture Model (DFM) and the Finite Element Method (FEM), where the fractures are approximated by a reduced model. The flow along and across the fracture is described by a simplified set of equations considering both conductive fractures and barriers. The coupled hydromechanical model is composed of a linear poroelastic Biot medium and a nonlinear model based on damage mechanics for the fractures, which captures the nonlinear normal deformation and shear dilation according to the Barton-Bandis model. Both flow and geomechanical models are approximated using the finite element model. Fractures are explicitly represented by three-node standard finite elements with high aspect ratio (i.e. ratio between the largest and the smallest element dimensions) and appropriate constitutive laws. These interface high aspect ratio elements represent a regularization method which continuously approximate the discontinuous pressure and displacement fields on a narrow material band around the fracture. The complete mathematical formulation is presented together with the algorithm suggested for its numerical implementation. The efficiency of the proposed method is demonstrated through numerical examples, as well as the effects of fractures in the hydraulic properties of porous rocks and its dependency of the stress state.
Resumo: Este trabalho apresenta um método numérico baseado no Modelo de Fratura Discreta (MFD) e no Método dos Elementos Finitos (MEF), onde as fraturas são aproximadas por um modelo reduzido. O fluxo ao longo e através da fratura é descrito por um conjunto simplificado de equações, considerando tanto fraturas condutoras quanto barreiras. O modelo hidromecânico acoplado é composto por um meio poroelástico linear e um modelo não linear para fraturas, baseado na mecânica do dano e que captura a deformação normal não linear e a dilatância ao cisalhamento de acordo com o modelo de Barton-Bandis. Os modelos de fluxo e geomecânico são aproximados usando o método dos elementos finitos. As fraturas são explicitamente representadas por elementos finitos triangulares de três nós com elevada razão de aspecto (isto é, a razão entre a maior e a menor dimensão do elemento) e leis constitutivas apropriadas. Esses elementos de elevada razão de aspecto representam um método de regularização que aproxima de forma contínua os campos de pressão e deslocamento descontínuos em uma estreita faixa material ao redor da fratura. A formulação matemática completa é apresentada juntamente com o algoritmo sugerido para sua implementação numérica. A eficiência do método proposto é demonstrada através de exemplos numéricos, bem como os efeitos de fraturas nas propriedades hidráulicas de rochas porosas e sua dependência do estado de tensão.
Mestre
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Sitte, Astrid [Verfasser], Kai [Akademischer Betreuer] Tittmann, and Ulf [Akademischer Betreuer] Diederichsen. "Catalysis at the Interface- Elucidation of the Activation Process and Coupling of Catalysis and Compartmentalization of the Peripheral Membrane Protein Pyruvate Oxidase from Escherichia coli / Astrid Sitte. Gutachter: Kai Tittmann ; Ulf Diederichsen. Betreuer: Kai Tittmann." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://d-nb.info/1047237008/34.
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O'Reilly, Ossian. "Coupled High-Order Finite Difference and Unstructured Finite Volume Methods for Earthquake Rupture Dynamics in Complex Geometries." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-155471.
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The linear elastodynamic two-dimensional anti-plane stress problem, where deformations occur in only one direction is considered for one sided non-planar faults. Fault dynamics are modeled using purely velocity dependent friction laws, and applied on boundaries with complex geometry. Summation-by-parts operators and energy estimates are used to couple a high-order finite difference method with an unstructured finite volume method. The unstructured finite volume method is used near the fault and the high-order finite difference method further away from the fault where no complex geometry is present. Boundary conditions are imposed weakly on characteristic form using the simultaneous approximation term technique, allowing explicit time integration to be used. Numerical computations are performed to verify the accuracy and time stability, of the method.
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Rodrigues, Eduardo Alexandre. "Um modelo multiescala concorrente para representar o processo de fissuração do concreto." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/3/3144/tde-10052016-113532/.
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Este trabalho propõe uma técnica de modelagem multiescala concorrente do concreto considerando duas escalas distintas: a mesoescala, onde o concreto é modelado como um material heterogêneo, e a macroescala, na qual o concreto é tratado como um material homogêneo. A heterogeneidade da estrutura mesoscópica do concreto é idealizada considerando três fases distintas, compostas pelos agregados graúdos e argamassa (matriz), estes considerados materiais homogêneos, e zona de transição interfacial (ZTI), tratada como a parte mais fraca entre as três fases. O agregado graúdo é gerado a partir de uma curva granulométrica e posicionado na matriz de forma aleatória. Seu comportamento mecânico é descrito por um modelo constitutivo elástico-linear, devido a sua maior resistência quando comparado com as outras duas fases do concreto. Elementos finitos contínuos com alta relação de aspecto em conjunto com um modelo constitutivo de dano são usados para representar o comportamento não linear do concreto, decorrente da iniciação de fissuras na ZTI e posterior propagação para a matriz, dando lugar à formação de macrofissuras. Os elementos finitos de interface com alta relação de aspecto são inseridos entre todos os elementos regulares da matriz e entre os da matriz e agregados, representando a ZTI, tornando-se potenciais caminhos de propagação de fissuras. No estado limite, quando a espessura do elemento de interface tende a zero (h ?0) e, consequentemente, a relação de aspecto tende a infinito, estes elementos apresentam a mesma cinemática da aproximação contínua de descontinuidades fortes (ACDF), sendo apropriados para representar a formação de descontinuidades associados a fissuras, similar aos modelos coesivos. Um modelo de dano à tração é proposto para representar o comportamento mecânico não linear das interfaces, associado à formação de fissuras, ou até mesmo ao eventual fechamento destas. A fim de contornar os problemas causados pela malha de elementos finitos de transição entre as malhas da macro e da mesoescala, que, em geral, apresentam diferenças expressivas 5 de refinamento, utiliza-se uma técnica recente de acoplamento de malhas não conformes. Esta técnica é baseada na definição de elementos finitos de acoplamento (EFAs), os quais são capazes de estabelecer a continuidade de deslocamento entre malhas geradas de forma completamente independentes, sem aumentar a quantidade total de graus de liberdade do problema, podendo ser utilizados tanto para acoplar malhas não sobrepostas quanto sobrepostas. Para tornar possível a análise em multiescala em casos nos quais a região de localização de deformações não pode ser definida a priori, propõe-se uma técnica multiescala adaptativa. Nesta abordagem, usa-se a distribuição de tensões da escala macroscópica como um indicador para alterar a modelagem das regiões críticas, substituindo-se a macroescala pela mesoescala durante a análise. Consequentemente, a malha macroscópica é automaticamente substituída por uma malha mesoscópica, onde o comportamento não linear está na iminência de ocorrer. Testes numéricos são desenvolvidos para mostrar a capacidade do modelo proposto de representar o processo de iniciação e propagação de fissuras na região tracionada do concreto. Os resultados numéricos são comparados com os resultados experimentais ou com aqueles obtidos através da simulação direta em mesoescala (SDM).A concurrent multiscale analysis of concrete is presented, in which two distinct scales are considered: the mesoscale, where the concrete is modeled as a heterogeneous material and the macroscale that treats the concrete as a homogeneous material. The mesostructure heterogeneities are idealized as three phase materials composed of the coarse aggregates, mortar matrix and the interfacial transition zone (ITZ). The coarse aggregates are generated from a grading curve and placed into the mortar matrix randomly. Their behavior is described using an elastic-linear constitutive model due to their significant higher strength when compared with the other two phases of the concrete. Special continuum finite elements with a high aspect ratio and a damage constitutive model are used to describe the nonlinear behavior associated to the propagation of cracks, which initiates in the ITZ and then propagates to the mortar matrix given place to a macro-crack formation. These interface elements with a high aspect ratio are inserted in between all regular finite elements of the mortar matrix and in between the mortar matrix and aggregate elements, representing the ITZ. In the limit case, when the thickness of interface elements tends to zero (h ?0) and consequently the aspect ratio tends to infinite, these elements present the same kinematics as the continuous strong discontinuity approach (CSDA), so that they are suitable to represent the formation of discontinuities associated to cracks, similar to cohesive models. A tensile damage model is proposed to model the nonlinear mechanical behavior of the interfaces, associated to the crack formation and also to the possible crack closure. To avoid transition meshes between the macro and the mesoscale meshes, a new technique for coupling non-matching meshes is used. This technique is based on the definition of coupling finite elements (CFEs), which can ensure the continuity of displacement between independent meshes, without increasing the total number of degrees of freedom of the problem. This technique can be used to couple non-overlapping and overlapping meshes.To make possible the concurrent multiscale analysis, where the strain localization region cannot be defined a priori, an adaptive multiscale model is proposed. In this approach the macroscale stress distribution is used as an indicator to properly change from the macroscale to the mesoscale modeling in the critical regions during the analysis. Consequently, the macroscopic mesh is automatically replaced by a mesoscopic mesh where the nonlinear behavior is imminent. A variety of tests are performed to show the ability of the proposed methodology in predicting the behavior of initiation and propagation of cracks in the tensile region of the concrete. The numerical results are compared with the experimental ones or with those obtained by the direct simulation in mesoscale (DSM).
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GEORGE-JEHOULET, ISABELLE. "Etude physico-chimique et mecanique des systemes multicouches silicium/polyimide/silicium. Application a la realisation de micro-capteurs." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10259.
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Dans le cadre de l'optimisation d'une technique d'assemblage silicium/polymere/silicium dans le domaine des micro-capteurs, ce travail porte sur l'etude de l'adhesion des polyimides sur des substrats de silicium a l'aide d'un agent d'adherence organosilane. La demarche experimentale s'appuie sur des approches physico-chimique et mecanique et met en jeu differentes techniques, complementaires dans les enseignements et les echelles d'observation. Des mecanismes acido-basiques responsables de la formation initiale des liaisons interfaciales entre le silicium, l'agent d'adherence et l'acide polyamique ont ete observes par analyse xps. Une etude infrarouge en reflexion totale attenuee a, de plus, mis en evidence qu'au cours du recuit, un phenomene d'interdiffusion entre les couches organiques renforcait l'adhesion purement chimique. L'adherence des systemes multicouches silicium/polyimide/silicium est etudiee par divers tests mecaniques. Des tests de traction et de cisaillement ont permis de determiner les contraintes de rupture des assemblages sous certaines conditions de chargement et de traitement thermique. L'investigation des modes de rupture a conduit a un critere de rupture privilegie de type decohesion interfaciale. Une relation entre l'epaisseur de la couche adherente et le taux de restitution critique des systemes assembles a ete etablis, puis validee par une analyse globale de la rupture des systemes a l'aide d'un test de clivage (mode i, deformation plane). La faisabilite de la technique d'assemblage ainsi caracterisee et optimisee a ete demontree par la realisation d'un micro-capteur a mesure capacitive. D'un point de vue technologique, le materiau polymere offre la possibilite de sceller des substrats de silicium a basse temperature, de planariser des surfaces et de repondre ainsi a certaines exigences en terme de performance et de cout de production
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Dias, Otávio Augusto Titton [UNESP]. "Desenvolvimento de compósitos de engenharia baseados em polipropileno reforçado com lignina." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/148754.
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As preocupações ambientais e o esgotamento dos combustíveis fósseis resultaram em um interesse crescente em materiais ambientalmente amigáveis, à base de polímeros naturais. Esforços estão sendo feitos para introduzir a lignina em compostos plásticos, tais como polipropileno, com o objetivo de produzir materiais com boas características mecânicas e, ao mesmo tempo, ambientalmente amigáveis. A lignina é uma matéria-prima amplamente disponível na natureza, que contém alta densidade de compostos aromáticos, os quais são atualmente, em sua maioria, derivados do petróleo. No entanto, grande parte da lignina é utilizada para geração de energia e pode ser um potencial agente poluidor se não destinada de forma adequada. Desse modo, é importante encontrar uma maneira econômica de converter esse polímero natural em materiais de alto valor agregado, como compósitos com alto desempenho mecânico e térmico. Neste estudo, compósitos de polipropileno e de lignina kraft de pinus (LKI) e de bagaço de cana (LBC) foram submetidos à extrusão, e os corpos de prova foram produzidos pelo processo de injeção. Os materiais produzidos foram analisados quanto às propriedades mecânicas, térmicas (TGA, DSC, HDT), química (FTIR), reológica (índice de fluidez) e morfológica (MEV). Os objetivos desta pesquisa foram desenvolver novos compósitos de polipropileno contendo lignina e proporcionar propriedades mecânicas comparáveis aos polipropilenos comerciais, além de obter compósito com alto grau de afinidade entre a lignina e o polipropileno. Os resultados mostraram que a incorporação de lignina na matriz de polipropileno originou, de maneira geral, compósitos com propriedades adequadas para vários segmentos industriais, especialmente aqueles em que características mecânicas e térmicas são cruciais, tais como a substituição de plásticos de engenharia e polipropileno com cargas minerais.
Environmental concerns and the depletion of fossil fuels resulted in a growing interest in environmentally friendly materials based on natural polymers. Efforts are being made to introduce the lignin in plastic composites such as polypropylene, in order to produce materials with good mechanical characteristics and at the same time environmentally friendly. Lignin is a biopolymer widely available which contains high density of aromatic compounds. Nowadays, the aromatic compounds are almost exclusively derived from petroleum. However, the lignin is used mainly to generate energy and can be a pollution potential if not properly treated. Lignin, however, can improve the performance of composites. Moreover, it is important to find an economical way to convert lignin into high value-added materials. In this study, blends of polypropylene, pine kraft lignin (LKI) and sugar cane bagasse lignin (LBC) were subjected to extrusion and the specimens were produced by injection process. The materials produced were analyzed for their mechanical, thermal (TGA, DSC, HDT), chemical (FTIR), rheological (melt flow index) and morphological (SEM) properties. The objective of this research was to develop new lignin-based polypropylene composite with mechanical properties comparable to commercial polypropylene. The results showed that the incorporation of lignin in polypropylene matrix resulted in composites, in general, with properties suitable for various industrial segments, especially those in which mechanical and thermal properties are crucial, such as the replacement of engineering plastics and polypropylene mineral filled.
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Folkuenig, Engelbert de Souza. "Investigação teórica da quimisssorção do ânion metanossulfonato em eletrodos de platina (111) e (100) via método semi-empírico." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2010. http://tede2.uepg.br/jspui/handle/prefix/2085.
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Previous issue date: 2010-05-10Several electrochemical processes, such as electrocatalysis of organic substrates, make use of mediators. One of the mediators is the most commonly used anion methanesulfonate, CH3SO3, which has several advantages for such use, and chemical stability considered one of them. However, experimental studies indicate the possibility of this compound suffer the adsorption and decomposition on platinum electrodes. To get an understanding at the molecular level these processes, computer simulations were performed with the aid of the semi-empirical PM6. The cluster approach was used in the modeling of platinum surfaces with crystallographic orientations (111) and (100). The symmetries of most stable adsorption calculated for the anion in these areas correspond to the experimental data: C3V symmetry in (111) surface and C1 in (100) surface. To simulate the potential applied to the electrode, external electric fields with a positive sign and perpendicular to the surface of the clusters were applied. Changes in the lengths and angles of bonds adsorbed anion, as well as its values of dipole moment were observed. The infrared spectra of the systems anion-clusters were calculated and the values for the Stark tunning rate (Δstark) of mode δs CH3 were compared with the experimental value. Both for the free anion and for systems where the anion is adsorbed, it was found that the values of Δstark assumed negative values (indicating that the frequency of the vibrational mode δs CH3 diminished with increasing external eletric field), opposite to the experimental positive value (frequency mode δs CH3 increases with the increase in potential). Only with the addition of water molecules in the systems studied, in order to simulate the aqueous solvent is that the values of Δstark started to assume a positive value. The comparison showed the importance of the presence of water molecules in the simulation of an electrochemical system and prompted a detailed analysis of the frontier orbitals involved in this process. It was found that the dipole-dipole coupling between water molecules and the adsorbed anion is responsible for the Stark effect, while the electrostatic interactions between various molecules adsorbed anion affect the intensity of the absorption band mode δs CH3 in the spectra calculated. In (100) surfaces, the joint action of external field and water molecules, lead the anion molecule to adopt the adsorption geometries more inclined to systems without water molecules, indicating that this may be an important factor in explaining the greater reactivity of the anion on the surface.
Vários processos eletroquímicos, como por exemplo a eletrocatálise de substratos orgânicos, fazem uso de mediadores. Um dos mediadores mais utilizados é o ânion metanossulfonato, CH3SO3¯, que apresenta várias vantagens para tal uso, sendo a estabilidade química considerada uma delas. No entanto, estudos experimentais apontam para a possibilidade desse ânion sofrer processos de adsorção e decomposição em eletrodos de platina. Para se obter uma compreensão em nível molecular desses processos, simulações computacionais foram efetuadas com auxílio do método semi-empírico PM6. A aproximação de cluster foi utilizada na modelagem de superfícies de platina com orientações cristalográficas (111) e (100). As simetrias de adsorção mais estáveis calculadas para o ânion nessas superfícies correspondem aos dados experimentais: simetria C3v em superfície (111) e C1 em superfície (100). Para simular o potencial aplicado ao eletrodo, campos elétricos externos de sinal positivo e perpendiculares à superfície dos clusters foram aplicados. Alterações nos comprimentos e ângulos de ligações do ânion adsorvido, bem como em seus valores de momento dipolar foram observados. Os espectros de infravermelho dos sistemas ânion-clusters foram calculados e os valores para a taxa de variação Stark (Δstark) do modo δs CH3 foram comparados com o valor experimental. Tanto para o ânion livre quanto para os sistemas onde o ânion se encontra adsorvido, verificou-se que os valores de Δstark assumiam valores negativos (indicando que a frequência vibracional do modo δs CH3 diminuía com o aumento da intensidade do campo externo), ao contrário do valor experimental, positivo (frequência do modo δs CH3 aumenta com o aumento do potencial). Apenas com a adição de moléculas de água aos sistemas estudados, de modo a simular o solvente aquoso, é que os valores de Δstark passaram a assumir um valor positivo. Essa comparação revelou a importância da presença de moléculas de água na simulação de um sistema eletroquímico e motivou uma análise pormenorizada dos orbitais de fronteira envolvidos nesse processo. Verificou-se que a interação dipolo-dipolo entre as moléculas de água e o ânion adsorvido é o responsável pelo efeito Stark, enquanto as interações eletrostáticas entre várias moléculas do ânion adsorvidas afetam a intensidade da banda de absorção do modo δs CH3 nos espectros calculados. Nas superfícies (100), a ação conjunta do campo externo e das moléculas de água, levam a molécula do ânion a adotar geometrias de adsorção mais inclinadas em relação aos sistemas sem as moléculas de água, indicando que este pode ser um fator importante para explicar a maior reatividade do ânion sobre esse tipo de superfície.
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Huang, Xingrong. "Optimization of dynamic behavior of assembled structures based on generalized modal synthesis." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC038/document.
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Dans le processus de conception des véhicules, la vibration et le bruit sont des sujets d’étude très importants. En effet, les vibrations sont susceptibles d’affecter le comportement dynamique des structures et le bruit dégrade le confort acoustique des passagers. L’objectif principal de la thèse est de proposer un ensemble de méthodes pour l’optimisation du comportement dynamique des systèmes complexes afin de réduire les vibrations des structures et le bruit dans l’habitacle. À cet effet, on s’intéresse à des stratégies de contrôle des interfaces, comme le collage de couches viscoélastiques sur les zones les plus déformées, ou l’introduction de dispositifs frottants calibrés pour ajouter de l’amortissement à certaines fréquences de résonance. Les structures assemblées résultantes sont étudiées numériquement par une méthode de synthèse modale généralisée. La méthode de synthèse modale proposée contient plusieurs niveaux de condensation. Le premier concerne les degrés de libertés (DDL) internes de chaque sous-structure. La deuxième condensation s’effectue sur les modes de branches, de sorte à réduire le nombre de DDL aux interfaces entre les sous-structures. Pour les systèmes couplés fluide/structure, une troisième condensation portant sur les DDL du fluide est proposée. Suite à ces condensations, la dimension du système est fortement réduite. Cette méthode permet alors d’obtenir aussi bien la réponse forcée de la structure que les fluctuations du champ de pression dans le fluide. Les chemins de transmission acoustiques et vibratoires peuvent également être déduits des contributions modales intermédiaires. On montre que ces paramètres modaux peuvent être utilisés comme fonctions objectif pour une démarche d’optimisation des interfaces. Le front de Pareto des conceptions optimales est obtenu avec un algorithme génétique multi-objectif élitiste, appliqué à une approximation par krigeage de la fonction objectif. Cette approche modale est étendue à l’étude de systèmes non-linéaires. L’hypothèse fondamentale est que les modes non-linéaires sont faiblement couplés. Les paramètres modaux non-linéaires (fréquences propres, amortissements...), dépendent des amplitudes modales. L’idée est alors de calculer des modes normaux non-linéaires en fonction de leur amplitude et de superposer leurs réponses pour obtenir celle de la structure. La méthode est appliquée à des systèmes incorporant des non-linéarités de type Duffing et de frottement sec. Le cas particulier du frottement sec est considéré à travers un modèle de Masing généralisé. Deux approches modales sont développées : l’une basée sur les modes complexes, et l’autre basée sur les modes réels. L’utilisation de modes complexes ou réels dans la synthèse modale conduit à des termes d’amortissement par frottement différents. On montre que la synthèse modale non-linéaire combinée au modèle de Masing généralisé aboutit à une méthode numérique simple, rapide et efficace pour décrire le comportement non-linéaire de structures soumise à du frottement secNoise and vibration are important topics in the automotive industry for several reasons, including passenger comfort and structural integrity. The main objective of this thesis is to propose a series of appropriate methods to optimize structural system characteristics, so that the vibration and noise can be reduced. To achieve this goal, interface control strategies are employed, including bonding viscoelastic layers onto the most heavily deformed zones and introducing frictional damping devices calibrated on certain resonance frequencies. Such built-up structural systems are numerically investigated via a generalized modal synthesis approach that incorporates several groups of modes. The employed modal synthesis approach consists of several levels of condensation. The first one is on the internal degrees of freedoms (DOFs) of each substructure, and the second condensation is on the branch modes so as to reduce the boundary DOFs among substructures. For coupled fluid-structural systems, a third condensation on the fluid DOFs is suggested. With these condensation techniques, the system dimension can be significantly reduced. The method allows us to obtain the forced response of the structures as well as the pressure variation of the fluids. Additionally, modal parameters characterizing vibration and noise transmission paths can be deduced as mid-stage results. We show that these modal parameters can be used as optimization objective during the interface configuration design. The Pareto front of the optimal design is achieved by employing Kriging approximations followed with an elitist multi-objective genetic algorithm. Another advantage of the modal approach is that a modal overview on the system characteristics is provided by analyzing the natural frequencies, modal damping ratios and the aforementioned modal parameters. The modal synthesis approach is further extended to study nonlinear systems. The basic assumption is that the nonlinear modes are weakly coupled. Nonlinear modal parameters, such as modal frequency and modal damping ratio, contain the essential nonlinear information and depend on modal amplitude. The main idea is to compute nonlinear normal modes according to their modal amplitude and superimpose the response of several nonlinear modes to obtain the overall forced response. The method is applied to systems involving Duffing and dry friction nonlinearities. In the case of dry friction, a generalized Masing model is considered to capture the dry friction nature. Both complex modes and real modes are used in the modal synthesis, leading to different frictional damping terms. We show that the nonlinear modal synthesis combined with the generalized Masing model yields a simple, fast and efficient numerical method to describe nonlinear performance of structures with dry friction
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Nicola, Ernesto Miguel. "Interfaces between Competing Patterns in Reaction-diffusion Systems with Nonlocal Coupling." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2002. http://nbn-resolving.de/urn:nbn:de:swb:14-1036499969687-26395.
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In this thesis we investigate the formation of patterns in a simple activator-inhibitor model supplemented with an inhibitory nonlocal coupling term. This model exhibits a wave instability for slow inhibitor diffusion, while, for fast inhibitor diffusion, a Turing instability is found. For moderate values of the inhibitor diffusion these two instabilities occur simultaneously at a codimension-2 wave-Turing instability. We perform a weakly nonlinear analysis of the model in the neighbourhood of this codimension-2 instability. The resulting amplitude equations consist in a set of coupled Ginzburg-Landau equations. These equations predict that the model exhibits bistability between travelling waves and Turing patterns. We present a study of interfaces separating wave and Turing patterns arising from the codimension-2 instability. We study theoretically and numerically the dynamics of such interfaces in the framework of the amplitude equations and compare these results with numerical simulations of the model near and far away from the codimension-2 instability. Near the instability, the dynamics of interfaces separating small amplitude Turing patterns and travelling waves is well described by the amplitude equations, while, far from the codimension-2 instability, we observe a locking of the interface velocities. This locking mechanism is imposed by the absence of defects near the interfaces and is responsible for the formation of drifting pattern domains, i.e. moving localised patches of travelling waves embedded in a Turing pattern background and vice versa.
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Nicola, Ernesto M. "Interfaces between competing patterns in reaction diffusion systems with nonlocal coupling." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10236292.
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Nicola, Ernesto Miguel. "Interfaces between Competing Patterns in Reaction-diffusion Systems with Nonlocal Coupling." Doctoral thesis, Technische Universität Dresden, 2001. https://tud.qucosa.de/id/qucosa%3A24181.
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In this thesis we investigate the formation of patterns in a simple activator-inhibitor model supplemented with an inhibitory nonlocal coupling term. This model exhibits a wave instability for slow inhibitor diffusion, while, for fast inhibitor diffusion, a Turing instability is found. For moderate values of the inhibitor diffusion these two instabilities occur simultaneously at a codimension-2 wave-Turing instability. We perform a weakly nonlinear analysis of the model in the neighbourhood of this codimension-2 instability. The resulting amplitude equations consist in a set of coupled Ginzburg-Landau equations. These equations predict that the model exhibits bistability between travelling waves and Turing patterns. We present a study of interfaces separating wave and Turing patterns arising from the codimension-2 instability. We study theoretically and numerically the dynamics of such interfaces in the framework of the amplitude equations and compare these results with numerical simulations of the model near and far away from the codimension-2 instability. Near the instability, the dynamics of interfaces separating small amplitude Turing patterns and travelling waves is well described by the amplitude equations, while, far from the codimension-2 instability, we observe a locking of the interface velocities. This locking mechanism is imposed by the absence of defects near the interfaces and is responsible for the formation of drifting pattern domains, i.e. moving localised patches of travelling waves embedded in a Turing pattern background and vice versa.
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Widarda, Dina Rubiana. "Longitudinal forces in continuously welded rails due to nonlinear track-bridge interaction for loading sequences." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1238081328011-05497.
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The use of continuously welded rails (CWR) governs the longitudinal stress caused by seasonal temperature changes, bending of supporting structure and braking/accelerating due to passing trains. Those three loads have been regulated in Eurocode1 and accomplished by the national codes like DIN Fb-101 in Germany. An additional loading case identified and treated in this thesis is the load due to a change of the coupling stiffness in longitudinal direction between the track and bridge. This additional load occurs as a consequence of the employment of a nonlinear stiffness law which increases the restoring force by a factor of 3 when the situation of the track changes from ‘unloaded’ to ‘loaded’ due to a passing train. This particular phenomenon has not been mentioned in the codes so far though it is a natural consequence of fundamental conditions in those codes. For CWR the longitudinal coupling between the rail and bridge plays an important role. This coupling interface is created either by a ballast, for a ballasted track, or by a fastening system in the case of slab track. The deformation state of the coupling interface characterizes the behaviour of the system, whether elastic or plastic. Therefore, the nonlinear behaviour is valid for the system. To accommodate the nonlinear nature, a sequential loading analysis is used, taking into account the loading history. As the change situation due to a passing train happens in a short time, the influence of the mass acceleration should be taken into account in the system’s equilibrium. This aspect is investigated by treating the dynamic load as an impulse-like load. However, a realistic load needs some time to affect the whole bridge, thus the continuous change of stiffness is used to simulate the dynamic analysis. There is a lack of information on determining the value of coupling stiffness in longitudinal direction caused by a passing train. Therefore, it is important to evaluate the coupling stiffness from field measurements in order to find reliable values. The implementation of the load onto several typical bridges shows that the change of the coupling stiffness increases the stresses and it should not be neglected. The evaluation of the load due to a change of the coupling stiffness accompanied by bending of the supporting structure gives satisfactory results by using the static analysis only. Thus, a dynamic analysis can be avoided. Multiple cycles of passing trains occurring after seasonal temperature change indicate a significant increase of elastic parts along the track-bridge coupling interface and a decrease in stresses in the rails. Thus the danger of deterioration is reduced significantlyDie Verwendung von durchgehend geschweißten Schienen auf Brücken führt zu zusätzlichen Längsspannungen infolge der Lastfälle jahreszeitliche Temperaturänderung, Brückendurchbiegung und Bremsen/Anfahren. Diese drei Lasten sind durch den Eurocode 1 vorgegeben und in die nationale deutsche Norm DIN Fb-101 integriert. In dieser Arbeit wird erstmals ein weiterer Lastfall identifiziert und behandelt, der durch den Wechsel der Koppelsteifigkeit in Längsrichtung zwischen Gleis und Tragwerk bei der Zugüberfahrt begründet wird. Dieser Lastfall wird hier mit „Ruck“ bezeichnet und ist eine zwangsläufige Konsequenz des nichtlinearen Längsverschiebewiderstandes, wie er im EC 1 und im DIN Fb-101 vorgegeben ist. Dennoch wurden die Auswirkungen auf das Systemverhalten bisher nicht untersucht. Bei einem Wechsel vom unbelasteten Gleis zum belasteten Gleis während einer Zugüberfahrt erhöht sich zum Beispiel der Längsverschiebewiderstand für ein Schottergleis um den Faktor 3! Die dadurch bedingte Veränderung des Zusammenwirkens zwischen Gleis und Tragwerk führt zu einer Veränderung des Systemzustandes und damit zu veränderten Schienenspannungen. Für durchgehend geschweißte Schienen spielt die Längskopplung zwischen Schiene und Brücke eine wesentliche Rolle. Beim Schottergleis wird sie dargestellt durch die Einbettung des Gleisrostes im Schotterbett im Zusammenwirken mit der Schienenbefestigung. Bei der festen Fahrbahn durch das Befestigungssystem. Für kleine Deformationen ist die Koppelsteifigkeit proportional zur Relativverschiebung zwischen Gleis und Brücke. Darüberhinaus geht das linear elastische Verhalten in ein quasi plastisches Verhalten mit konstanter Koppelkraft über. Folgerichtig ist die Behandlung einer Lastenfolge nur in inkrementeller Weise unter Einbeziehung der Verformungsgeschichte mechanisch korrekt. Die Lastfälle Bremsen/Anfahren, Brückendurchbiegung und Ruck ereignen sich nur während der Zugüberfahrt; also in relativ kurzer Zeit, dann allerdings mit einem erheblichen Lastgradienten. Somit stellt sich die Frage nach dem Einfluss der Massenbeschleunigungen, die in dieser Arbeit geklärt wird. Die im Fachbericht genanntenWerte für den Längsverschiebewiderstand des belasteten Gleises basieren auf einer relativ geringen Datenmenge. Aus diesem Grund werden die Messdaten einer umfangreichen Feldmessung mit Zugüberfahrten zu Aussagen über den Längsverschiebewiederstand herangezogen und die Problematik derartiger Messungen beleuchtet. Die unterschiedlichen Modellierungen des Lastfalls „Ruck“, einmal rein statisch und zum anderen dynamisch, ergeben übereinstimmende Schienenlängsspannungen für die statische und die kontinuierliche dynamische Variante. Somit kann auf die aufwändige dynamische Analyse verzichtet werden. Mehrere Zyklen von Zugüberfahrten im Anschluss an eine jahreszeitliche Temperaturänderung bewirken einen signifikanten Abbau der Durchrutschbereiche, also eine Erhöhung der elastischen Abschnitte in der Koppelfuge zwischen Bauwerk und Gleis verbunden mit einer Abnahme der Schienendruckspannungen. Somit hilft dieser Effekt dem System, der jahreszeitlichen Temperaturänderung zu widerstehen
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Tymichova, Michaela. "Relation between toughness and molecular coupling at cross-linked polymer/solid interfaces." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060712.125012/index.html.
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