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1
Heidemann, Ralf. "Dynamical phenomena in complex plasmas." Diss., lmu, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-152519.
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Colombini, Giulio. "Synchronisation phenomena in complex neuronal networks." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23904/.
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The phenomenon of neural synchronisation, a simultaneous and repeated firing of clusters of neurons, underlies many physiological functions and pathological manifestations in the brain of humans and animals, ranging from information encoding to epileptic seizures. Neural synchronisation, as a general phenomenon, can be approached theoretically in the framework of Dynamical Systems on Networks. In the present work, we do so by considering complex networks of FitzHugh-Nagumo model neurons. In the first part we consider the most understood models where each neuron treats its presynaptic neurons all on an equal footing, normalising signals with its in-degree. We study the stability of the synchronous state by devising an algorithm that destabilises it by selecting and removing links from the network, so to obtain a bipartite network. The selection is performed using a perturbative expression, which can be regarded as a specialisation of a previously introduced Spectral Centrality measure. The algorithm is tested on Erdős-Renyi, Watts-Strogatz and Barabási-Albert networks, and its behaviour is assessed from a dynamical and from a structural point of view. In the second part we consider the less studied case in which each neuron divides equally its output among the postsynaptic neurons, so to reproduce schematically the situation where a fixed quantity of neurotransmitter is subdivided between several efferent neurons. In this context a self-consistent approach is formulated and its limitations are explored. In order to extend its application to larger networks, a Mean Field Approximation is presented. The predictivity of the Mean Field Approach is then tested on the different random network models, and the results are discussed in terms of the original network properties.
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Grauwin, Sébastian. "Exploring Social Phenomena with Complex Systems Tools." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2011. http://tel.archives-ouvertes.fr/tel-00662484.
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This thesis explores the problems raised by the aggregation of entities into a global, collective level, an old problem encountered in many fields of science. We work on three projects related to the aggregation problem in social systems, using tools derived from statistical physics, and more generally quantitative tools. The first project focus on a paradigmatic model of the emergence of puzzling macroscopic behavior from simple individual rules, Schelling's segregation model. We hence propose an analytical resolution of this model and we studied analytically and via simulations the effect of several forms of cooperation between individual agents on the collective behavior. These questions are tackled in a mutually beneficial way for both economics and physics. The second project is based on the exploration of huge databases on scientific literature. We hence produce several 'science maps' representing the fields of complex systems (its internal structure and coherence being analysed through the references used by ~140000 relevant articles) and the research carried out in a scientific institution such as the ENS de Lyon. Finally, the third project deals with the elaboration of models of social phenomena based on natural sciences tools but sociologically grounded. We hence present the elaboration process of a model built with a team of sociologists. We then propose an opinion model specifically designed to explore a single question: the existence of lasting structure from non lasting entities.
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Chen, Da. "The visual analysis of complex natural phenomena." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760925.
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Optical flow estimation or dense motion estimation for dynamic natural phenomena (water, smoke, fire, etc.) is a significant open problem in Computer Vision. Assumptions such as brightness constancy cannot be relied upon, as natural phenomena scenes contain lots of non- rigid motion, blurred motion, etc. Current approaches tend to be either general, giving poor results, or else be specialised in one phenomenon and therefore fail to generalise well. The literature would benefit from a general solution, and such a solution could be found useful in a diverse set of application areas. In this thesis, we prove that a skeleton based feature can guide the standard optical flow pipeline to obtain state-of-the-art motion results. We also demonstrate that this result can be applied in different applications such as video segmentation, slow motion, etc. First, we describe an approach to estimating dense motion for dynamic phenomena that is simple and can be extended to a wide range of phenomena. The key to our approach is to replace local assumptions such as brightness constancy with the global assumption in which characteristic topographic maps change subtly. This leads to a global sparse motion estimation, which upgrades to dense estimation for final motion results, as suggested in our experiments, are state-of-the-art. We demonstrate the method using lab-based and consumer-level video obtained from our dataset, public dataset and the Internet. Second, the motion result is applied on a slow motion application which contains fewer artefacts than the state-of-the-art commercial software Adobe AfterEffect 2017 CC. Third, we embed the motion result and the skeleton feature in a video segmentation pipeline and outperform the state-of-the-art video segmentation methods including the method which is specially designed for natural phenomena. Fourth, we introduce a dataset containing two types of sequences i.e., sequences based on a 6-sync cameras system and sequences with 88 different kinds of dynamic textures with a single view camera lab set-up. Fifth, since semi-transparent case often happens in natural phenomena, a closed form solution for layer separation is also proposed.
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Fox, Emily Beth. "Bayesian nonparametric learning of complex dynamical phenomena." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55111.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 257-270).
The complexity of many dynamical phenomena precludes the use of linear models for which exact analytic techniques are available. However, inference on standard nonlinear models quickly becomes intractable. In some cases, Markov switching processes, with switches between a set of simpler models, are employed to describe the observed dynamics. Such models typically rely on pre-specifying the number of Markov modes. In this thesis, we instead take a Bayesian nonparametric approach in defining a prior on the model parameters that allows for flexibility in the complexity of the learned model and for development of efficient inference algorithms. We start by considering dynamical phenomena that can be well-modeled as a hidden discrete Markov process, but in which there is uncertainty about the cardinality of the state space. The standard finite state hidden Markov model (HMM) has been widely applied in speech recognition, digital communications, and bioinformatics, amongst other fields. Through the use of the hierarchical Dirichlet process (HDP), one can examine an HMM with an unbounded number of possible states. We revisit this HDPHMM and develop a generalization of the model, the sticky HDP-HMM, that allows more robust learning of smoothly varying state dynamics through a learned bias towards self-transitions. We show that this sticky HDP-HMM not only better segments data according to the underlying state sequence, but also improves the predictive performance of the learned model. Additionally, the sticky HDP-HMM enables learning more complex, multimodal emission distributions.
(cont.) We demonstrate the utility of the sticky HDP-HMM on the NIST speaker diarization database, segmenting audio files into speaker labels while simultaneously identifying the number of speakers present. Although the HDP-HMM and its sticky extension are very flexible time series models, they make a strong Markovian assumption that observations are conditionally independent given the discrete HMM state. This assumption is often insufficient for capturing the temporal dependencies of the observations in real data. To address this issue, we develop extensions of the sticky HDP-HMM for learning two classes of switching dynamical processes: the switching linear dynamical system (SLDS) and the switching vector autoregressive (SVAR) process. These conditionally linear dynamical models can describe a wide range of complex dynamical phenomena from the stochastic volatility of financial time series to the dance of honey bees, two examples we use to show the power and flexibility of our Bayesian nonparametric approach. For all of the presented models, we develop efficient Gibbs sampling algorithms employing a truncated approximation to the HDP that allows incorporation of dynamic programming techniques, greatly improving mixing rates. In many applications, one would like to discover and model dynamical behaviors which are shared among several related time series. By jointly modeling such sequences, we may more robustly estimate representative dynamic models, and also uncover interesting relationships among activities.
(cont.) In the latter part of this thesis, we consider a Bayesian nonparametric approach to this problem by harnessing the beta process to allow each time series to have infinitely many potential behaviors, while encouraging sharing of behaviors amongst the time series. For this model, we develop an efficient and exact Markov chain Monte Carlo (MCMC) inference algorithm. In particular, we exploit the finite dynamical system induced by a fixed set of behaviors to efficiently compute acceptance probabilities, and reversible jump birth and death proposals to explore new behaviors. We present results on unsupervised segmentation of data from the CMU motion capture database.
by Emily B. Fox.
Ph.D.
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Brink, Adam Ray. "Modeling Complex Contact Phenomena with Nonlinear Beamshells." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1429395652.
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Jefferies, Paul. "Emergent phenomena of complex adaptive systems : financial markets." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427625.
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Willshaw, Stephen Kilgour. "On pattern-switching phenomena in complex elastic structures." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/on-patternswitching-phenomena-in-complex-elastic-structures(d013e89e-c413-4612-a1f7-9fc55739cdfb).html.
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We investigate global pattern-switching effects in 2D cellular solids in which the voids are arranged in a square lattice. Uniaxial compression of these structures triggers an elastic instability which brings about a period-doubling transformation of the void shapes at a critical strain. Specifically, a square array of circular voids forms a pattern of mutually orthogonal ellipses and a similar effect is observed for diamond-shaped voids. The onset of instability is governed by the void fraction and size-effects are found for the experimental samples. We establish empirical laws which characterise the stiffness, strength and stability of cellular structures comprising square arrays of circular voids. A comparison of these with predictions from a discrete model implies underestimation of the resistance of the lattice to buckling, although the size effects are replicated. We find similar pattern-switching effects in the cubic lattice, which is a three-dimensional porous cube. The effect of buckling in this system is to produce a 2D pattern in one plane of voids. In two-phase granular crystals, rearrangement of a square lattice of particles results in a new, period-doubled, structural pattern. This switch can occur via an intermediate phase depending on the size ratio of the particles as shown in experiments and numerical simulations.
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Ruiz, Amador Dolly Natalia. "Multilevel aging phenomena analysis in complex ultimate CMOS designs." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENT002/document.
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L'auteur n'a pas fourni de résumé en françaisIntegrated circuits evolution is driven by the trend of increasing operating frequencies and downscaling of the device size, while embedding more and more complex functionalities in a single chip. However, the continuation of the device-scaling race generates a number of technology challenges. For instance, the downscaling of transistor channel lengths induce short-channel effects (drain-induced barrier lowering and punch-through phenomena); high electric field in the devices tend to increase Hot electron effect (or Hot Carrier) and Oxide Dielectric Breakdown; higher temperatures in IC products generates an increase of the Negative Bias Temperature Instability (NBTI) effect on pMOS devices. Today, it is considered that the above reliability mechanisms are ones of the main causes of circuit degradation performance in the field. This dissertation will address the Hot Carrier (HC) and NBTI impacts on CMOS product electrical performances. A CAD bottom-up approach will be proposed and analyzed, based on the Design–in Reliability (DiR) methodology. With this purpose, a detailed analysis of the NBTI and the HC behaviours and their impact at different abstraction level is provided throughout this thesis. First, a physical framework presenting the NBTI and the HC mechanisms is given, focusing on electrical parameters weakening of nMOS and pMOS transistors. Moreover, the main analytical HC and NBTI degradation models are treated in details. In the second part, the delay degradation of digital standard cells due to NBTI, HCI is shown; an in-depth electrical CAD analysis illustrates the combined effects of design parameters and HCI/NBTI on the timing performance of standard cells. Additionally, a gate level approach is developed, in which HC and NBTI mechanisms are individually addressed. The consequences of the degradation at system level are presented in the third part of the thesis. With this objective, data extracted from silicon measures are compared against CAD estimations on two complexes IPs fabricated on STCMOS 45nm technologies. It is expected that the findings of this thesis highly contribute to the understanding of the NBTI and HC reliability wearout mechanisms at the system level.STAR
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Herchig, Ryan Christopher. "Complex Electric-Field Induced Phenomena in Ferroelectric/Antiferroelectric Nanowires." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6710.
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Perovskite ferroelectrics and antiferroelectrics have attracted a lot of attention owing to their potential for device applications including THz sensors, solid state cooling, ultra high density computer memory, and electromechanical actuators to name a few. The discovery of ferroelectricity at the nanoscale provides not only new and exciting possibilities for device miniaturization, but also a way to study the fundamental physics of nanoscale phenomena in these materials. Ferroelectric nanowires show a rich variety of physical characteristics which are advantageous to the design of nanoscale ferroelectric devices such as exotic dipole patterns, a strong dependence of the polarization and phonon frequencies on the electrical and mechanical boundary conditions, as well as a dependence of the transition temperatures on the diameter of the nanowire. Antiferroelectricity also exists at the nanoscale and, due to the proximity in energy of the ferroelectric and antiferroelectric phases, a phase transition from the ferroelectric to the antiferroelectric phase can be facilitated through the application of the appropriate mechanical and electrical boundary conditions. While much progress has been made over the past several decades to understand the nature of ferroelectricity/antiferroelectricity in nanowires, many questions remain unanswered. In particular, little is known about how the truncated dimensions affect the soft mode frequency dynamics or how various electrical and mechanical boundary conditions might change the nature of the phase transitions in these ferroelectric nanowires. Could nanowires offer a distinct advantage for solid state cooling applications? Few studies have been done to elucidate the fundamental physics of antiferroelectric nanowires. How the polarization in ferroelectric nanowires responds to a THz electric field remains relatively underexplored as well. In this work, the aim is to to develop and use computational tools that allow first-principles-based modeling of electric-field-induced phenomena in ferroelectric/antiferroelectric nanowires in order to address the aforementioned questions.
The effective Hamiltonian approach is a well validated model which reliably reproduces many static and dynamic properties of perovskite ferroelectric and antiferroelectrics. We begin by developing an effective Hamiltonian for the prototypical ferroelectric potassium niobate, a lead-free material which undergoes multiple structural phase transitions. Density functional theory calculations within the LDA and GGA are used to determine the effective Hamiltonian parameters for KNbO3 . By simulating an annealing within an NPT ensemble, we find that the KNbO3 parameters found from first principles underestimate the experimental transition temperatures. We apply a universal scaling technique to all of the first-principles derived parameters and are thus able to more accurately reproduce the transition temperatures predicted by experiment as well as a number of other static and dynamic properties of potassium niobate.
Having determined the parameters of the effective Hamiltonian for KNbO3 , we use this as well as previously determined effective Hamiltonian parameters for PbTiO3 and BaTiO3 to study the electrocaloric effect in nanowires made of these materials. We determined that, in general, the electrocaloric effect in ferroelectric nanowires is diminished due to the reduced correlation length resulting from the finite lateral dimensions. However, certain temperature ranges were identified near ambient temperature where the electrocaloric response is enhanced with respect to bulk. The effective Hamiltonian model was also employed to study the response of the spontaneous polarization and temperature to tailored electric fields. We identified a novel means of reversing the polarization in ferroelectric nanowires which could potentially be used in the design of nanoscale THz sensors of ultra high density ferroelectric memory devices.
While the soft mode frequency dynamics of bulk ferroelectrics under various mechanical boundary conditions have been studied extensively, the effects of different mechanical boundary conditions on the soft mode dynamics in ferroelectric nanowires remains relatively under-explored. We conduct a comprehensive study on PbTiO3 nanowires which explores the effects of hydrostatic pressure, applied uniaxial stress, and biaxial strain on the structural properties, transition temperatures, and soft mode dynamics. We found that depending on the particular type of mechanical boundary condition, the nanowire can exhibit either monodomain or polydomain vortex phases, drastically different from what is found for PbTiO3 bulk and originates from the critical role of the depolarizing field. We found a rich variety of dipole patterns, particularly for the polydomain states with the dipoles arranged in single and double polarization vortices depending on the type and strength of the mechanical boundary conditions. The soft mode frequency dynamics are also strongly affected by the mechanical boundary conditions. In particular we find that the frequency of the E mode in the P4mm phase is significantly larger than the A 1 mode which is in contrast with bulk PbTiO3 . This striking finding is attributed to the presence of the depolarizing field along the truncated directions which leads to mode hardening.
In the last chapter, we identify the emergence of a ferroelectric state in antiferroelectric PbZrO3 nanowires and describe possible ways to stabilize the ferroelectric phase. Finally, we explore how our findings could potentially be used to improve existing technologies such as energy storage devices and electromechanical actuators as well as future technologies like solid state cooling devices.
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Mielke, Eric. "Study on the Transport Phenomena in Complex Micro-Reactors." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36040.
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Continuous processing in the pharmaceutical and fine chemical industries, particularly in micro/milli-scale reactors, has been a topic of interest in literature in recent years due to the advantages offered over batch reactions. One such advantage is the enhanced transport properties of operating at smaller scales, although the quantification of the transport phenomena is not straightforward when wall and entrance effects cannot be neglected.
In the first study presented, various micro-mixer geometries and scales were considered to increase the mixing efficiency in liquid-liquid systems of diverse interfacial tensions for fast reactions. The conditions were varied over different flow regimes; including slug flow, parallel flow, and drop flow. A mass-transfer-limited test reaction was used to evaluate the overall volumetric mass transfer coefficients (Korga) as a function of the average rate of energy dissipation (ε) for each mixer design. The onset of drop flow occurred at a lower ε for the LL-Triangle mixer when compared with the Sickle or LL-Rhombus mixers for low interfacial-tension systems (i.e., n-butanol-water). In the drop flow regime for energy dissipation rates of around 20 to 500 W/kg, Korga values ranged from approximatively 0.14 to 0.35 s-1 and 0.004 to 0.015 s-1 for the relatively low and high interfacial-tension (i.e., toluene-water) systems, respectively.
The second investigation explored the heat transfer properties of a FlowPlate® system by Ehrfeld Mikrotechnik BTS. First, in a non-reactive system with rectangular serpentine channels (d_h<1mm, 400
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Turnbull, R. W. "Approximation schemes for statistical mechanics in the complex temperature plane." Thesis, University of Nottingham, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376171.
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Akbar, Muhammad Khalid. "Transport Phenomena in Complex Two and Three-Phase Flow Systems." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4897.
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Two and three-phase flow processes involving gas, liquid and solid, are common in nature and industry, and include some of the most complex and poorly-understood transport problems. In this research hydrodynamics, heat and mass transfer processes in complex two and three-phase flows were investigated. The interfacial surface area concentration in a short vertical column subject to the through flow of fiber-liquid-gas slurry was experimentally measured using the gas absorption technique. The experimental data were statistically analyzed for parametric effects, and were empirically correlated. The absorption of a gaseous species by a slurry droplet with internal circulation and containing reactive micro-particles was simulated, and parametrically studied. The micro-particles were found to enhance the absorption rate. The absorption rate was sensitive to droplet recirculation, and shrinkage of particles with time resulted in declining absorption rates. The transport of soot particles, suspended in laminar hot gas flowing in a tube, was modeled and parametrically studied. Due to coupled thermal radiation and thermophoresis, a radially-nonuniform temperature profile develops, leading to sharp, non-uniform radial soot-concentration profiles. The assumption of monodisperse particles leads to over-prediction of thermophoresis. The transport and removal of particles suspended in bubbles rising in a stagnant liquid pool were modeled based on a Eulerian – Monte Carlo method. The bubble hydrodynamics were treated in Eulerian frame, using the Volume-of-Fluid (VOF) technique, while particle equations of motion were numerically solved in Lagrangian frame. The bubbles undergo shape change, and have complex internal circulation, all of which influence the particle removal. Model predictions were also compared with experimental data. Using a resemblance between two-phase flow in microchannels, and in large channels at microgravity, a simple Weber number-based two-phase flow regime map was developed for microchannels. Based on the available air-water experimental data, a criterion for the prediction of conditions that lead to flow regime transition out of the stratified-wavy flow pattern in horizontal annular channels was proposed. The thermocapillary effects on liquid-vapor interface shape during heterogeneous bubble ebullition in microchannels were analytically studied.
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Heidemann, Ralf [Verfasser], and Gregor [Akademischer Betreuer] Morfill. "Dynamical phenomena in complex plasmas / Ralf Heidemann. Betreuer: Gregor Morfill." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1031380280/34.
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Hou, Xiaofei. "Numerical modeling of complex heat transfer phenomena in cooling applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/309294.
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Multiphase and multicomponent flows are frequently encountered in the cooling applications due to combined heat transfer and phase change phenomena. Two-fluid and homogeneous mixture models are chosen to numerically study these flows in the cooling phenomena. Therefore this work is divided in two main parts. In the first part, a two-fluid model algorithm for free surface flows is presented. The two fluid model is usually used as a tool to simulate dispersed flow. With its extension, it may also be applied to large interface (separated) flow. In the second part, the homogeneous mixture model for the multicomponent flow is employed to solve evaporation problems. Finally the simulation is focused on the mixed transitional or turbulent flow with and without evaporation.
In detail, this thesis consists of six chapters. The first chapter is devoted to an introduction to the two-fluid and homogeneous mixture models employed in the multiphase/multicomponent flow. The multiphase classification is explained and the previous works on the two models are reviewed.
The second chapter is mainly focused on the application of the Fractional step method algorithm in the two-fluid model. In addition, the Conservative Level Set method(interface sharpening) is applied to overcome the weakness of the two-fluid model (numerical diffusion of the interface), which is often encountered in the simulations using this model. With the proposed algorithm, the two-fluid model suitable for the dispersed flow is extended to the separated flow.
The homogeneous mixture model is introduced in the third chapter. As an application of this model, different evaporation cases have been tested. A hydrodynamically fully developed laminar flow in a horizontal duct is firstly studied. It is used to verify the model in a laminar flow considering constant physical properties. Water falling films are often applied to enhance the heat transfer. Therefore the second case analyzes the natural convection in a cavity with liquid film (assuming variable physical properties), and validates the falling film model. Finally, a third case is focused
on mixed convective flow interacting with a water falling liquid film. The effects of heat flux on the evaporation rate and the flow structure are investigated employing numerical experiments.
In the fourth chapter, the laminarization phenomena of turbulent forced flow in a vertical pipe with constant heat flux is studied. These studies validate the prediction ability of large eddy simulation in this complex situation. Afterwards additional cases in a long vertical pipe (100 times diameters) are conducted and the results are compared with the existing experimental data. Throughout the whole pipe, the flow state follows a complicated process, which includes turbulent-laminar and laminar-turbulent transitions. This problem is of great significance in industrial applications for it may result in the enhancement or impairment of heat transfer.
Based on the previous verification of the model in turbulent and transitional flow, the simulation of the cooling in a uniformly heated vertical tube is conducted in the fifth chapter with an ascending flow of air and a falling film. This case also involves the transitional complex flow and boundary conditions of falling film with simultaneous heat/mass transfer. The variable factors affecting the evaporation and thermal efficiency have been analyzed.
In Appendix C, as an application in engineering of the work developed within the thesis, a series of flows in a complex geometry of a refrigerator chamber without or with fins are simulated to obtain their effects on the flow distribution and mixing feature.
In the last chapter, the main conclusions are summarized and the future works are listed.Debido a la transferencia de calor y de cambio de fase, fenomenología multifase y multicomponente se encuentra en las aplicaciones de refrigeración. Dependiendo de la estructura de interfaz multifase pueden clasificarse como flujo separado (flujo estratificado), de transición o mezclado flujo y flujo disperso. Dependiendo de los diferentes estados de flujo de dos fases, se deben aplicar diferentes modelos. La presente tesis se centra principalmente en flujo separado. Modelos de mezcla homogénea de dos fluidos se emplean para simular fenómenos de enfriamiento en multifase. Este trabajo se divide en dos partes principales. En la primera parte, un algoritmo de modelo de dos fluidos de la superficie libre se presenta. El modelo de dos fluidos se utiliza generalmente como una herramienta para simular flujo disperso. En la segunda parte, el modelo de mezcla homogénea para flujo multicomponente se emplea para resolver el problemas de evaporación. Finalmente se simulan flujos turbulentos con influencia de la fuerza de flotabilidad. El objetivo a largo plazo es acoplar los dos modelos, que podrían resolver todos los regímenes de flujo y tendrian aplicación en problemas industriales. La presente tesis se compone de seis capítulos. El primer capítulo está dedicado a una introducción a los modelos de mezcla homogénea de dos fluidos empleados en el flujo multifásico / multicomponente. La clasificación de múltiples fases se explica y se revisa la bibliografia existente. El segundo capítulo se centra principalmente en la aplicación del Fractional Step Method en bifasico. Con el algoritmo propuesto, el modelo de dos fluidos adecuado para el flujo disperso se extiende al flujo separado. El modelo para mezcla homogénea se introduce en el tercer capítulo con las mismas ecuaciones de masa, cantidad de movimiento, energía y concentración. Se aplica en casos de evaporación y condensación. El flujo laminar completamente desarrollado en un conducto horizontal se estudia en primer lugar considerando propiedades físicas constantes para verificar el modelo en un flujo laminar. La simulacion de convección natural en una cavidad con propiedades físicas variables y película de líquido se realiza numéricamente para validar el modelo de película descendente. Finalmente, el flujo de convección mixta se investiga en un film descendente. Los efectos de los diferentes parámetros en la evaporación y el flujo son investigados mediante experimentos numéricos. En el cuarto capítulo, la laminarización de flujo turbulento forzado en un tubo vertical con flujo de calor constante se estudia para validar la capacidad de predicción de los modelos LES en el flujo de convección mixta de transición turbulenta-laminar con fuerte fuerza de flotación. Se llevan a cabo estudios numericos y los resultados se comparan con los datos experimentales existentes. A lo largo de toda el conducto, el estado de flujo sigue un proceso complicado, que incluye turbulencia.
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Wagner, Carsten. "Transport phenomena in complex turbulent flows : numerical and experimental methods." kostenfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:30077.
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Lym, Youngbin. "Three essays on unveiling complex urban phenomena: toward improved understanding." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595283291505878.
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Raeisi, Dehkordi Amir Hooshang. "Investigation of flow boiling phenomena in small-scale complex geometries." Thesis, Heriot-Watt University, 2012. http://hdl.handle.net/10399/2531.
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This study concerns measurement and prediction of single-phase and flow boiling heat transfer coefficients and pressure drops in mini multi-channel geometries with and without interconnecting passages, including plate channel; parallel channel; in-line pin-fin and in-line off-set pin-fin surfaces. Experiments were performed with refrigerant R113 and deionised water at atmospheric pressure. Single-phase and flow boiling heat transfer coefficients and pressure drops were obtained over a range of effective heat fluxes and mass fluxes. For the plate and parallel channel surfaces, the results obtained have been compared with several published macro- and micro-channels correlations. For the in-line and in-line off-set pin fin surfaces, as the geometries have some similarities with tube bundles, the results obtained have been predicted using the standard correlations for tube bundles. The results also have been compared with several existing correlations developed based on macro-scale tube bundles and micro-pin-fin surfaces data. The saturated flow boiling heat transfer coefficients for the parallel channel and pin-fin surfaces were similar to within the experimental uncertainty, and considerably higher than the plate channel values, all dependent on heat flux and reasonably independent of mass flux and vapour mass fraction. This indicated that the dominant heat-transfer mechanism in the saturated boiling flow regime was nucleate boiling for all surfaces. The parallel channel, in-line and off-set pin-fin surfaces improved heat transfer by increasing the surface area and the heat transfer coefficient in comparison with the plate channel surface. The two-phase pressure drops in the parallel channel and pin-fin surfaces were considerably larger than that for the plate channel surface. Thus, the reduction in wall temperature is achieved by a significant pressure drop penalty. For the pin-fin surfaces, at low vapour qualities the heat transfer coefficients were in reasonable agreement with the conventional scale tube bundles correlations however as the vapour quality increases, the correlations were not able to predict the heat transfer coefficient as unlike the conventionally-sized tube bundles, the convective enhancement does not happen in the mini-pin-fin surfaces tested. The nucleate pool boiling correlation of Cooper (1984) provided a good agreement with the data for all surfaces tests with R113 and deionised water. The measured two-phase pressure drops for both pin-fin surfaces tests with R113 and deionised water were in a good agreement with the predicted values obtained from standard correlations for tube bundles, indicating pressure drop methods maybe transferable.
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Heidemann, Ralf Verfasser], and G. E. [Akademischer Betreuer] [Morfill. "Dynamical phenomena in complex plasmas / Ralf Heidemann. Betreuer: Gregor Morfill." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-152519.
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Hartley, Adrian. "The complex strategy : epistemology at the edge of chaos." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341008.
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Block, Michael. "Analysis and control of complex growth phenomena in physics and biology." [S.l.] : [s.n.], 2007. http://opus.kobv.de/tuberlin/volltexte/2007/1542.
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Lenoci, Leonardo. "Computer simulations of self-assembly, and critical phenomena in complex fluids." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/12404.
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The self-assembly of model peptides has been studied using Brownian dynamics (BD) computer simulations. In particular, a bead-spring coarse-grained model (a model in which a set of molecules is represented by a single bead and the bonding interactions by simple spring forces) has been designed to mimic small proteins called ‘silaffins’ observed to favour the formation of amorphous silica nanospheres in vitro and involved in the biomineralisation of certain diatoms cell walls. The coarse-grained model used in the simulations keeps the primary characteristics of the silaffins, these being a 15 amino acid hydrophilic backbone and two modified lysine residues near the ends of the backbone each carrying a hydrophobic polyamine chain. In the simulations, the model peptides self-assemble to form micelles, networks of strands, or discontinuous structures depending on the peptide concentration and the system temperature. The simulation results show that over a broad range of peptide volume fractions (0.05-25%) the characteristic structural lengthscales fall in the range 12-45 nm. This suggests that the self-assembled structures observed may act as either nucleation points or scaffolds for the deposition of 10-100 nm silica-peptide composite building blocks from which diatom skeletons and synthetic nanospheres are made. A systematic coarse-grained computer-simulation study of the role of putrescine homologues H2N-(CN2)n-NH2 on silica morphogenesis is presented. Brownian dynamics simulations of model putrescine are performed highlighting the importance of aggregation on the degree of silica deposition. The results suggest that over a broad range of solute concentration (15-50 mM) the characteristic lengthscales of the observed self-assembled structures correlate with structural properties of the silicas observed in vitro.
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Crippa, Simone. "Accurate physical and numerical modeling of complex vortex phenomena over delta wings." Licentiate thesis, Stockholm : School of engineering sciences, Royal Institute of Technology, 2006. http://www.diva-portal.org/kth/theses/abstract.xsql?dbid=4164.
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Gopalkrishnan, Prasad. "INTER-PARTICLE LIQUID BRIDGES: A BUILDING BLOCK TO MODEL COMPLEX MIXING PHENOMENA." online version, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1085169849.
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Hoppe, Konrad. "Complex networks with node intrinsic fitness : on structural properties and contagious phenomena." Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10345.
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Complex networks is a vibrant research field and has received much attention over the last decade. Central to this area is the question of how networks around us are constructed. The essential notion of network research is that these systems are assembled in a decentralised way, thus no central agent is planning the network beforehand. Despite this lack of central coordination, many networks present intriguing universalities, such as broad degree distributions, in the form of power-laws. The subject of study in this thesis is a class of networks that are constructed by a node intrinsic variable, called fitness. The way these networks grow could be called a rich-get-richer mechanism. The fitter a node is, the more likely it is to acquire new connections inside the network. Several aspects that are directly connected to these networks are explored in this thesis. In the first part, the properties of growing networks that are driven by fitness are investigated and it is shown that the introduction of growth leads to a topological structure that is different from its static counterpart. In the subsequent chapter, percolation on fitness driven networks is studied. The results give insights into possible mechanisms that can stabilise systems. Furthermore, the theory can be used to identify vulnerable structures around us. In the following chapter, the world trade network is discussed. This numerical investigation highlights possible improvements to the methodology to make statistical analysis more robust. That chapter is followed by an analysis of time-varying networks. Time-varying networks represent an interesting construct that allows a formulation of stochastic processes on the same time-scale as the evolution of the network itself. This possibility is highly relevant to the investigation of epidemics, for instance. In the last chapter, a study of a system of clusters and their self-organised formation is presented.
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Gómez, Cerdà Vicenç. "Algorithms and complex phenomena in networks: Neural ensembles, statistical, interference and online communities." Doctoral thesis, Universitat Pompeu Fabra, 2008. http://hdl.handle.net/10803/7548.
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Aquesta tesi tracta d'algoritmes i fenòmens complexos en xarxes.En la primera part s'estudia un model de neurones estocàstiques inter-comunicades mitjançant potencials d'acció. Proposem una tècnica de modelització a escala mesoscòpica i estudiem una transició de fase en un acoblament crític entre les neurones. Derivem una regla de plasticitat sinàptica local que fa que la xarxa s'auto-organitzi en el punt crític.
Seguidament tractem el problema d'inferència aproximada en xarxes probabilístiques mitjançant un algorisme que corregeix la solució obtinguda via belief propagation en grafs cíclics basada en una expansió en sèries. Afegint termes de correcció que corresponen a cicles generals en la xarxa, s'obté el resultat exacte. Introduïm i analitzem numèricament una manera de truncar aquesta sèrie.
Finalment analizem la interacció social en una comunitat d'Internet caracteritzant l'estructura de la xarxa d'usuaris, els fluxes de discussió en forma de comentaris i els patrons de temps de reacció davant una nova notícia.
This thesis is about algorithms and complex phenomena in networks.
In the first part we study a network model of stochastic spiking neurons. We propose a modelling technique based on a mesoscopic description level and show the presence of a phase transition around a critical coupling strength. We derive a local plasticity which drives the network towards the critical point.
We then deal with approximate inference in probabilistic networks. We develop an algorithm which corrects the belief propagation solution for loopy graphs based on a loop series expansion. By adding correction terms, one for each "generalized loop" in the network, the exact result is recovered. We introduce and analyze numerically a particular way of truncating the series.
Finally, we analyze the social interaction of an Internet community by characterizing the structure of the network of users, their discussion threads and the temporal patterns of reaction times to a new post.
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Paunovski, Ognen. "Exploring emergent phenomena : towards analysis and synthesis of emergent formations in complex systems." Thesis, University of Sheffield, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.632818.
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Wan, Muhammad Wan Mujtahiddin. "FEM assisted analyze of the spring-back phenomena for steel sheet with complex microstructure." Master's thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-38165.
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Mamalis, Dimitrios. "Phase change and complex phenomena in drops and bubbles of pure and binary fluids." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25477.
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Evaporation, wetting and multiphase flows of drops and bubbles are everyday life phenomena with potential impact in many industrial, biological, medical or engineering applications. The understanding and controlling of the physical and chemical mechanisms governing these phenomena have become of paramount importance. This thesis encompasses three topics: evaporation of sessile droplets of polymer solutions, the role of thermocapillarity on self-rewetting fluid dynamics and migration of bubbles in liquid flows. Firstly, the evaporative behaviour of sessile droplets of aqueous polymer solutions and the effect of different molecular weights on the drying process has been studied. Drop shape analysis allowed monitoring the evolution of all stages during drying and indicating the transitions between stages. The mechanisms taking place during the crucial stages of pinning and depinning were illustrated, revealing the effects of adhesion and contact line friction forces on the final morphology of the dried polymeric deposits. Additionally, the effect of varying substrates from hydrophilic to hydrophobic was examined demonstrating the importance of interfacial interaction phenomena. The initial spreading dynamics of binary alcohol mixtures (and pure liquids) deposited on different substrates in partially wetting situations, under non-isothermal conditions was systematically investigated. Moreover, the temporal and spatial thermal dynamics within pure droplets and alcohol mixtures using IR thermography revealed the existence of characteristic thermal patterns due to thermal and/or solutal instabilities. The contribution of the Marangoni effect as an important heat transport mechanism within the evaporating droplets was investigated. The motion of buoyancy-driven bubbles in a vertical microchannel and the significant role of thermocapillarity was reported in this series of experiments. The behaviour of the bubbles in self-rewetting fluid flows departed considerably from that of pure liquids flows. Furthermore, heat transfer coefficient calculations in the single and two phase flows demonstrated that the presence of Marangoni (surface tension) stresses resulted in the enhancement of the heat transfer distribution in the self-rewetting fluid flows compared with the pure ones.
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Liu, Weigang. "A General Study of the Complex Ginzburg-Landau Equation." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/90886.
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In this dissertation, I study a nonlinear partial differential equation, the complex Ginzburg-Landau (CGL) equation. I first employed the perturbative field-theoretic renormalization group method to investigate the critical dynamics near the continuous non-equilibrium transition limit in this equation with additive noise. Due to the fact that time translation invariance is broken following a critical quench from a random initial configuration, an independent ``initial-slip'' exponent emerges to describe the crossover temporal window between microscopic time scales and the asymptotic long-time regime. My analytic work shows that to first order in a dimensional expansion with respect to the upper critical dimension, the extracted initial-slip exponent in the complex Ginzburg-Landau equation is identical to that of the equilibrium model A. Subsequently, I studied transient behavior in the CGL through numerical calculations. I developed my own code to numerically solve this partial differential equation on a two-dimensional square lattice with periodic boundary conditions, subject to random initial configurations. Aging phenomena are demonstrated in systems with either focusing and defocusing spiral waves, and the related aging exponents, as well as the auto-correlation exponents, are numerically determined. I also investigated nucleation processes when the system is transiting from a turbulent state to the ``frozen'' state. An extracted finite dimensionless barrier in the deep-quenched case and the exponentially decaying distribution of the nucleation times in the near-transition limit are both suggestive that the dynamical transition observed here is discontinuous. This research is supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award DE-FG02-SC0002308Doctor of Philosophy
The complex Ginzburg-Landau equation is one of the most studied nonlinear partial differential equation in the physics community. I study this equation using both analytical and numerical methods. First, I employed the field theory approach to extract the critical initial-slip exponent, which emerges due to the breaking of time translation symmetry and describes the intermediate temporal window between microscopic time scales and the asymptotic long-time regime. I also numerically solved this equation on a two-dimensional square lattice. I studied the scaling behavior in non-equilibrium relaxation processes in situations where defects are interactive but not subject to strong fluctuations. I observed nucleation processes when the system under goes a transition from a strongly fluctuating disordered state to the relatively stable “frozen” state where its dynamics cease. I extracted a finite dimensionless barrier for systems that are quenched deep into the frozen state regime. An exponentially decaying long tail in the nucleation time distribution is found, which suggests a discontinuous transition. This research is supported by the U. S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award DE-FG02-SC0002308.
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Atmakidis, Theodoros [Verfasser]. "Investigation of transport phenomena in systems with complex geometry using computational fluid dynamics / Theodoros Atmakidis." München : Verlag Dr. Hut, 2016. http://d-nb.info/1111160414/34.
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Chen, S. "An experimental investigation of drop impact phenomena with complex fluids on heated and soft surfaces." Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3011893/.
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The present thesis is the result of a four year experimental research, which aims at studying the impact of non-Newtonian droplets (i.e., droplets of complex fluids such as polymer solutions) on heated surfaces (i.e., surfaces with a temperature above the Leidenfrost point) and soft surfaces (i.e., surfaces that undergo temporary or permanent deformations upon drop impact) through high-speed imaging. In the first year we focused on the Leidenfrost drop impact of different model fluids with matching flow curves. We demonstrate that the total kinetic energy carried by low-viscosity Newtonian drops during retraction is partly transformed into rotational kinetic energy rather than dissipated (published on Physical Review E, 2016). In the second year we extended the Leidenfrost drop impact experiment to viscoplastic fluids. The results show that the main contribution to drop rebound is due to surface forces rather than the elasticity of vapour cushion (published on Soft Matter, 2016). A systematic investigation on the impact of viscoplastic drops onto viscoplastic substrates was carried out in the third year. It is shown that the yield stress magnitude of drop/substrate strongly affects the final shape of the impacting drop (published on Soft Matter, 2017). The fourth year was devoted to the drop impact on spherical elastic surfaces. The dynamic contact angle measured using a novel digital image processing scheme is found to be significantly affected by the impact parameters and a quantitative estimation of the deformation energy is proposed (published on Physics of Fluids, 2017).
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Miguel, Baños Narcís. "Transport phenomena and anomalous diffusion in conservative systems of low dimension." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400611.
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Apart from this introductory chapter, the contents of the thesis is splitted among four more chapters. Chapters 2, 3 and 4 deal with the planar case, while chapter 5 deals with the 3D volume preserving case. More specifically,
- In Chap. 2 we start by considering conservative quadratic Hénon maps (both orientation preserving and orientation reversing cases). First, we study the main features of the domain of stability of these two maps, mainly from the point of view of the area that they occupy, and how it does evolve as parameters change. To be as exhaustive as possible, we review the theory that allows to explain what one can observe in the phase space of these maps. We finish the chapter by considering the Chirikov standard map (1.13) in the 2-torus T2 for large values of the parameter, k ≥ 1. The most prominent sources of regular area in this setting are accelerator modes that appear periodically in k, and scaled somehow. We give numerical evidence of such a scaling, and guided by the experimental evidence, we derive limit representations for the dynamics in some compact set containing these islands, which turn out to be conjugated to the orientation preserving quadratic Hénon map or conjugated to the square of the orientation reversing quadratic Hénon map. Some of these islands are the accelerator modes we checked that appeared in Sect. 1.3. This motivates the following chapter.
- Chap. 3 is devoted to study the role of these islands of stability that ’jump’ when the standard map is considered in the cylinder. The stability domain of these islands is determined and studied independently from the standard map Mk in Chap. 2, and is recovered in some regions in the phase space of Mk under suitable scalings. We focus in two main observables: the squared mean displacement of the action under iteration of Mk and the trapping time statistics. We study them both in an adequate range of the parameters, where we can see the effect of considering more and more iterations and the fact that we change parameters and the size of the gaps of a Cantorus change. We provide evidence of the fact that the trapping time statistics behave as the superposition of the effect of two distinctive phenomena: the one of the stickiness, detected as power-law statistics, and the one of the outermost Cantorus, detected as bumps. These bumps change their position in the time axis accordingly to the change of the size of the largest gap in the Cantorus.
First, assuming that the stickiness effect gives rise to power law statistics with a certain value of the exponent, and under some other mild conditions (that also are suggested by the simulations), we are able to give a lower bound on the growth of the mean squared displacement of the actions. This is the way these two phenomena are related to each other in this context.
Then, the fact that we can identify the source of the bumps as being due to the effect of the outermost Cantorus, motivates the topic of the next chapter: studying this effect by its own in a proper context.
- In Chap. 4 we return to the Chirikov standard map, but for values of the parameter close to the destruction of the last RIC, that is, for value of the parameter close but larger than k(G) and approaching it from above. In this setting, we study escape rates across this Cantorus, and we deal with this problem from two different points of view.
First, as k decreases to k(G). In this setting, it is known that the mean escape ratio
across the Cantorus, that we will denote as hNki, behaves essentially as (k−kG)−B,B ≈ 3. The Greene-MacKay renormalisation theory, and the interpretation of DeltaW as an area justify that, in fact, hNki (k − kG)B should eventually be periodic in a suitable logarithmic scale, as k → kG. In this chapter we give the first evidence of the shape of this periodic behaviour, and perform a numerical study of a region surrounding the Cantorus that allows to give a first (partial) explanation of it.
Second, we consider a problem related to the previous topic but for each fixed value of k: the probability that an orbit crosses the Cantorus in a prescribed time. We explain how to compute these statistics, and we show that in logarithmic scale in the number of iterates, as k → kG, they seem to behave the same way, but shifted in this log-scale in time.
- Finally, Chap. 5 is devoted to study the stickiness problem in the 3D volume preserving setting. To do so, a map inspired in the Standard map is constructed following the scheme in Sect. 1.3. This map depends on various parameters, one of them, say ε, being a distance-to-integrable one. The map is considered in such a way that:
1. Invariant tori subsist until moderate values of ε, and
2. At integer values of the parameter the origin becomes an accelerator mode, and that exactly at integer values it undergoes a Hopf-Saddle-Node bifurcation, giving rise to a stability bubble.
The normal form of the unfolding of this bifurcation justifies that, in fact, there are just two relevant parameters (since it is a co-dimension 2 bifurcation). An analysis inspired in that of Chap. 3 is performed by fixing one of them. Also in this case one can observe a power law decay of the trapping time statistics, but with slightly different values of the exponent in different ranges of the number of iterates. Preliminary results of more massive simulations seem to indicate that the effect decreases as the number of iterates increases.
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Flanagan, Joan Frances. "The Yeast SWI/SNF Complex Structure and Function: A Dissertation." eScholarship@UMMS, 2001. https://escholarship.umassmed.edu/gsbs_diss/187.
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DNA is packaged within the cells' nucleus as a highly compact chromatin structure ranging between 100-400 nm fibers. The organization and alteration of this structure is mandatory in order to arbitrate DNA-mediated processes of the cell, including transcription, DNA replication, recombination and repair. Many different kinds of enzymes modify chromatin components and, in turn, regulate the accessibility of DNA. These multi-subunited enzymes have emerged as key regulators for several processes of the cell. Central to understanding how DNA-mediated processes are regulated is to comprehend the consequences of these modifications of chromatin, which lead to altered states of either activation or inactivation.
One class of factors known to modify chromatin structure is the ATP-dependent chromatin remodeling enzymes. This class of enzymes encompasses evolutionarily conserved multi-subunited enzymes, which appear to function by using the energy of ATP hydrolysis to disrupt histone-DNA interactions. The prototype of ATP-dependent chromatin remodelers is the Saccharomyces cerevisiae SWI/SNF complex. The yeast SWI/SNF complex is required for the full functioning of several transcriptional activators and for the expression of a subset of yeast genes, a notable number being inducible and mitotic genes. The purified complex is comprised of the following eleven different polypeptides: Swi2p/Snf2p, Swi1p, Swi3p, Snf5p, Snf6p, Swp73p, Arp7p, Arp9p, Swp82p, Swp29p and Snf11 p. It has been established that a core of homologous subunits (Swi2p, Swi3p, Swp73p, Snf5p and the Arp proteins) is conserved among the SWI/SNF-related complexes from several organisms (yRSC, hSWI/SNF, hRSC, DrosophilaBrahma). However, the functional contribution of these polypeptides in the complexes for altering chromatin structure is largely unknown. In this study, biochemistry is used to examine the structure of the complex and function of individual subunits of the yeast SWI/SNF complex to understand better how these proteins are acting in concert to remodel chromatin. In addition, we examine a role for SWI/SNF complex in the process of DNA replication.
The relative stoichiometry of the SWI/SNF complex subunits was determined by in vitrobiochemical studies. Co-immunoprecipitation has demonstrated that there is only one copy of Swi2p/Snf2p per complex. Subsequent radioactive labeling of the purified complex revealed that the complex contains one copy of each subunit per complex with the exception of Swi3p and Snf5p, which are present in two copies per complex.
The subunit organization of SWI/SNF complex has been more clearly defined by determining direct subunit-subunit interactions in the complex. The Swi3p component has previously been shown to be critical for complex function in vivo and essential for the integrity of the complex in vitro, and this study demonstrates that Swi3p serves as a scaffolding protein that nucleates SWI/SNF complex assembly. In vitrobinding studies with Swi3p have revealed that Swi3p displays self-association, as well as direct interactions with the Swi2p, Snf5p, Swp73p, Swi1p and Snf6p members of the complex.
The direct interactions of the yeast SWI/SNF subunits with transcriptional activators, thought to be important for yeast SWI/SNF targeting, were examined. In vitrobinding assays demonstrate that individual SWI/SNF subunits, Snf5p, Snf6p and Swi1p, and sub-complexes Swi2p/Swi3p and Swp73p/Swi3p can directly interact with specific domains of transcriptional activators of either the Swi5p zinc-finger DBD or VP16 acidic activation domain. This work begins to characterize the functional contribution of individual subunits, and cooperative sub-complexes that are critical for the SWI/SNF complex functional activities.
The yeast SWI/SNF complex was investigated for the ability to playa role in DNA replication. Interestingly, plasmid stability assays reveal that minichromosomes that contain DNA replication origin ARS121 is weakened when the SWIISNF complex is non-functional. ARS121's SWI/SNF dependency is overcome by the over-expression of DNA replication regulatory protein, Cdc6p. Thus, this suggests SWI/SNF may either indirectly effect DNA replication by effecting the expression of Cdc6p, or has a redundant function with Cdc6p. In addition, several crippled derivatives of ARS1 acquire SWI/SNF dependence, and it is found that the SWI/SNF complex requires a transcriptional activation domain to enhance ARS1 function. These results reinforce the view that SWI/SNF play a role in two chromatin-mediated processes', transcription and DNA replication.
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Makongo, Mangan Julien Pierre Amelie. "A Case Study of Complex Metallic Alloy Phases: Structure and Disorder Phenomena of Mg-Pd Compounds." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1235570638125-80764.
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The phase diagram of the Mg-Pd system was redetermined in the range from 50 at. % Mg to 100 at. % Mg. It contains several intermediate phases with some of them being complex metallic alloy phases (CMAs), i.e., characterized by (i) giant unit cells with more than hundred atoms, (ii) inherent disorder, (iii) the presence of a cluster substructure. Phase fields and heterogeneous equilibria of the intermediate phases β- Mg6Pd, γ-Mg57Pd13, δ-Mg56.4Pd13.6, ε-Mg306Pd77, ζ-Mg64Pd17, η-Mg3Pd, θ-Mg5Pd2, ι- Mg2Pd and κ-MgPd were determined. The first five phases are CMAs with Mackay clusters as fundamental structural units. The crystal structure of the most magnesium-rich compound β-Mg6Pd was redetermined. It was found to be more complicated than previously thought due to correlated disorder of only two atom sites in the cubic unit cell. The γ-, ε- and ζ-phases form in a small window of temperature (50 oC) and composition (3 at. %) close to 80 at. % Mg. A new structure type was assigned to Mg3Pd (Cu3P, P63cm). The single phase field of the θ-phase is caused by constitutional vacancies. The new ι-phase crystallizes with NiTi2 structure-typeDas Phasendiagramm des Systems Mg–Pd wurde im Bereich von 50 bis 100 At.-% Mg neu bestimmt. In diesem Phasendiagramm finden sich mehrere intermediäre Phasen, darunter auch komplexe intermetallische Verbindungen (engl.: complex intermetallic alloys, CMAs). CMAs sind charakterisiert durch (i) große Elementarzellen mit mehr als einhundert Atomen, (ii) intrinsischer Fehlordnung und (iii) dem Vorhandensein einer Cluster- Substruktur. Die Phasenfelder und heterogenen Gleichgewichte der intermediären Phasen β-Mg6Pd, γ- Mg57Pd13, δ-Mg56.4Pd13.6, ε-Mg306Pd77, ζ-Mg64Pd17, η-Mg3Pd, θ-Mg5Pd2, ι-Mg2Pd und κ- MgPd wurden bestimmt. Die ersten fünf der eben genannten Phasen sind CMAs mit Mackay Clustern als fundamentales strukturelles Einheit. Alle übrigen Phasen besitzen einen einfacheren kristallografischen Aufbau. Die Kristallstruktur der Mg-reichsten Verbindung β-Mg6Pd wurde neu bestimmt und ist weitaus sich als komplizierter als bisher angenommen. Die Ausdehnung des Einphasenfeldes von β-Mg6Pd lässt sich jedoch sehr einfach mit korrelierter Fehlordnung von lediglich zwei Atomen in der kubischen Elementarzelle verstehen. Die γ-, ε-, und ζ-Phasen bilden sich in einem schmalen Temperatur- (50 °C) und Zusammensetzungsbereich (3 at. %) nahe 80 at. % Mg. Der Verbindung Mg3Pd (Cu3P, P63cm) wurde ein neuer Strukturtyp zugewiesen. Die Ausdehnung des Einphasenfeldes der θ-Phase lässt sich mit dem Einbau konstitutioneller Leerstellen erklären. Die neue ι-Phase kristallisiert im NiTi2 Strukturtyp
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Makongo, Mangan Julien Pierre Amelie. "A Case Study of Complex Metallic Alloy Phases: Structure and Disorder Phenomena of Mg-Pd Compounds." Doctoral thesis, Technische Universität Dresden, 2008. https://tud.qucosa.de/id/qucosa%3A23850.
Full textAbstract:
The phase diagram of the Mg-Pd system was redetermined in the range from 50 at. % Mg to 100 at. % Mg. It contains several intermediate phases with some of them being complex metallic alloy phases (CMAs), i.e., characterized by (i) giant unit cells with more than hundred atoms, (ii) inherent disorder, (iii) the presence of a cluster substructure. Phase fields and heterogeneous equilibria of the intermediate phases β- Mg6Pd, γ-Mg57Pd13, δ-Mg56.4Pd13.6, ε-Mg306Pd77, ζ-Mg64Pd17, η-Mg3Pd, θ-Mg5Pd2, ι- Mg2Pd and κ-MgPd were determined. The first five phases are CMAs with Mackay clusters as fundamental structural units. The crystal structure of the most magnesium-rich compound β-Mg6Pd was redetermined. It was found to be more complicated than previously thought due to correlated disorder of only two atom sites in the cubic unit cell. The γ-, ε- and ζ-phases form in a small window of temperature (50 oC) and composition (3 at. %) close to 80 at. % Mg. A new structure type was assigned to Mg3Pd (Cu3P, P63cm). The single phase field of the θ-phase is caused by constitutional vacancies. The new ι-phase crystallizes with NiTi2 structure-type.Das Phasendiagramm des Systems Mg–Pd wurde im Bereich von 50 bis 100 At.-% Mg neu bestimmt. In diesem Phasendiagramm finden sich mehrere intermediäre Phasen, darunter auch komplexe intermetallische Verbindungen (engl.: complex intermetallic alloys, CMAs). CMAs sind charakterisiert durch (i) große Elementarzellen mit mehr als einhundert Atomen, (ii) intrinsischer Fehlordnung und (iii) dem Vorhandensein einer Cluster- Substruktur. Die Phasenfelder und heterogenen Gleichgewichte der intermediären Phasen β-Mg6Pd, γ- Mg57Pd13, δ-Mg56.4Pd13.6, ε-Mg306Pd77, ζ-Mg64Pd17, η-Mg3Pd, θ-Mg5Pd2, ι-Mg2Pd und κ- MgPd wurden bestimmt. Die ersten fünf der eben genannten Phasen sind CMAs mit Mackay Clustern als fundamentales strukturelles Einheit. Alle übrigen Phasen besitzen einen einfacheren kristallografischen Aufbau. Die Kristallstruktur der Mg-reichsten Verbindung β-Mg6Pd wurde neu bestimmt und ist weitaus sich als komplizierter als bisher angenommen. Die Ausdehnung des Einphasenfeldes von β-Mg6Pd lässt sich jedoch sehr einfach mit korrelierter Fehlordnung von lediglich zwei Atomen in der kubischen Elementarzelle verstehen. Die γ-, ε-, und ζ-Phasen bilden sich in einem schmalen Temperatur- (50 °C) und Zusammensetzungsbereich (3 at. %) nahe 80 at. % Mg. Der Verbindung Mg3Pd (Cu3P, P63cm) wurde ein neuer Strukturtyp zugewiesen. Die Ausdehnung des Einphasenfeldes der θ-Phase lässt sich mit dem Einbau konstitutioneller Leerstellen erklären. Die neue ι-Phase kristallisiert im NiTi2 Strukturtyp.
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Dupuis, Romain. "Surrogate models coupled with machine learning to approximate complex physical phenomena involving aerodynamic and aerothermal simulations." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0017/document.
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Les simulations numériques représentent un élément central du processus de conception d’un avion complétant les tests physiques et essais en vol. Elles peuvent notamment bénéficier de méthodes innovantes, telle que l’intelligence artificielle qui se diffuse largement dans l’aviation. Simuler une mission de vol complète pour plusieurs disciplines pose d’importants problèmes à cause des coûts de calcul et des conditions d’opérations changeantes. De plus, des phénomènes complexes peuvent se produire. Par exemple, des chocs peuvent apparaître sur l’aile pour l’aérodynamique alors que le mélange entre les écoulements du moteur et de l’air extérieur impacte fortement l’aérothermie autour de la nacelle et du mât. Des modèles de substitution peuvent être utilisés pour remplacer les simulations haute-fidélité par des approximations mathématiques afin de réduire le coût de calcul et de fournir une méthode construite autour des données de simulations. Deux développements sont proposés dans cette thèse : des modèles de substitution utilisant l’apprentissage automatique pour approximer des calculs aérodynamiques et l’intégration de modèles de substitution classiques dans un processus aérothermique industriel. La première approche sépare les solutions en sous-ensembles selon leurs formes grâce à de l’apprentissage automatique. En outre, une méthode de reéchantillonnage complète la base d’entrainement en ajoutant de l’information dans des sous-ensembles spécifiques. Le deuxième développement se concentre sur le dimensionnement du mât moteur en remplaçant les simulations aérothermiques par des modèles de substitution. Ces deux développements sont appliqués sur des configurations avions afin de combler l’écart entre méthode académique et industrielle. On peut noter que des améliorations significatives en termes de coût et de précision ont été atteintesNumerical simulations provide a key element in aircraft design process, complementing physical tests and flight tests. They could take advantage of innovative methods, such as artificial intelligence technologies spreading in aviation. Simulating the full flight mission for various disciplines pose important problems due to significant computational cost coupled to varying operating conditions. Moreover, complex physical phenomena can occur. For instance, the aerodynamic field on the wing takes different shapes and can encounter shocks, while aerothermal simulations around nacelle and pylon are sensitive to the interaction between engine flows and external flows. Surrogate models can be used to substitute expensive high-fidelitysimulations by mathematical and statistical approximations in order to reduce overall computation cost and to provide a data-driven approach. In this thesis, we propose two developments: (i) machine learning-based surrogate models capable of approximating aerodynamic experiments and (ii) integrating more classical surrogate models into industrial aerothermal process. The first approach mitigates aerodynamic issues by separating solutions with very different shapes into several subsets using machine learning algorithms. Moreover, a resampling technique takes advantage of the subdomain decomposition by adding extra information in relevant regions. The second development focuses on pylon sizing by building surrogate models substitutingaerothermal simulations. The two approaches are applied to aircraft configurations in order to bridge the gap between academic methods and real-world applications. Significant improvements are highlighted in terms of accuracy and cost gains
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Ramaciotti, Morales Pedro. "Theoretical and numerical aspects of wave propagation phenomena in complex domains and applications to remote sensing." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX063/document.
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Cette thèse s'inscrit dans le sujet des opérateurs intégraux de frontière définis sur le disque unitaire en trois dimensions, leurs relations avec les problèmes externes de Laplace et Helmholtz, et leurs applications au préconditionnement des systèmes linéaires obtenus en utilisant la méthode des éléments finis de frontière.On décrit d'abord les méthodes intégrales pour résoudre les problèmes de Laplace et de Helmholtz en dehors des objets à frontière régulière lipschitzienne, et en dehors des surfaces bidimensionnelles ouvertes dans un espace tridimensionnel. La formulation intégrale des problèmes de Laplace et de Helmholtz pour ces cas est décrite formellement. La mise en oeuvre d'une méthode numérique utilisant la méthode des éléments finis de frontière est également décrite. Les avantages et les défis inhérents à la méthode sont abordés : la complexité du calcul numérique (de mémoire et algorithmique) et le mal conditionnement inhérentes à des systèmes linéaires associés.Dans une deuxième partie on expose une technique optimale de préconditionnement (indépendante de la discrétisation) sur la base des opérateurs intégraux de frontière. On montre comment cette technique est facilement réalisable dans le cas de problèmes définis en dehors d'un objet régulier à frontière lipschitzienne, mais qu'elle pose des problèmes quand ils sont définis en dehors d'une surface ouverte dans un espace tridimensionnel. On montre que les opérateurs intégraux de frontière associés à la résolution des problèmes de Dirichlet et Neumann définis en dehors des surfaces ont des inverses bien définis. On montre également que ceux-ci pourraient conduire à des techniques de préconditionnement optimales, mais que ses formes explicites ne sont pas faciles à obtenir. Ensuite, on montre une méthode pour obtenir de tels opérateurs inverses de façon explicite lorsque la surface sur laquelle ils sont définis est un disque unitaire dans un espace tridimensionnel. Ces opérateurs inverses explicites seront, cependant, en forme des séries, et n'auront pas une adaptation immédiate pour leur utilisation dans des méthodes des éléments finis de frontière.Dans une troisième partie on montre comment certaines modifications aux opérateurs inverses mentionnés permettent d'obtenir des expressions variationnelles explicites et fermées, non plus sous la forme des séries, en conservant certaines caractéristiques importantes pour l'effet de préconditionnement cherché. Ces formes explicites sont en effet applicables aux méthodes des éléments finis frontière. On obtient des expressions variationnelles précises et on propose des calculs numériques pour leur utilisation avec des éléments finis frontière. Ces méthodes numériques sont testées en utilisant différentes identités obtenues dans la théorie développée, et sont ensuite utilisées pour produire des matrices préconditionnantes. Leur performance en tant que préconditionneurs de systèmes linéaires associés à des problèmes de Laplace et Helmholtz à l'extérieur du disque est testée. Enfin, on propose extension de cette méthode pour couvrir les cas de surfaces diverses. Ceci est illustré et étudié dans les cas précis des problèmes extérieurs à des surfaces en forme de carré et en forme de L dans un espace tridimensionnelThis thesis is about some boundary integral operators defined on the unit disk in a three-dimensional spaces, their relation with the exterior Laplace and Helmholtz problems, and their application to the preconditioning of the systems arising when solving these problems using the boundary element method.We begin by describing the so-called integral method for the solution of the exterior Laplace and Helmholtz problems defined on the exterior of objects with Lipschitz-regular boundaries, or on the exterior of open two-dimensional surfaces in a three-dimensional space. We describe the integral formulation for the Laplace and Helmholtz problem in these cases, their numerical implementation using the boundary element method, and we discuss its advantages and challenges: its computational complexity (both algorithmic and memory complexity) and the inherent ill-conditioning of the associated linear systems.In the second part we show an optimal preconditioning technique (independent of the chosen discretization) based on operator preconditioning. We show that this technique is easily applicable in the case of problems defined on the exterior of objects with Lipschitz-regular boundary surfaces, but that its application fails for problems defined on the exterior of open surfaces in three-dimensional spaces. We show that the boundary integral operators associated with the resolution of the Dirichlet and Neumann problems defined on the exterior of open surfaces have inverse operators, and that these operators would provide optimal preconditioners, but that they are not easily obtainable. Then we show a technique to explicitly obtain such inverse operators for the particular case when the open surface is the unit disk in a three-dimensional space. Their explicit inverse operators will be given, however, in the form of series, and will not be immediately applicable in the use of boundary element methods.In the third part we show how some modifications to these inverse operators allow us to obtain variational explicit and closed form expressions, no longer expressed as series, but also conserve nonetheless some characteristics that are relevant for their preconditioning effect. These explicit and closed forms expressions are applicable in boundary element methods. We obtain precise variational expressions for them and propose numerical schemes to compute the integrals needed for their use with boundary elements. The proposed numerical methods are tested using identities available within the developed theory and then used to build preconditioning matrices. Their performance as preconditioners for linear systems is tested for the case of the Laplace and Helmholtz problems for the unit disk. Finally, we propose an extension of this method that allows for the treatment of cases of open surfaces other that the disk. We exemplify and study this extension in its use on a square-shaped and an L-shaped surface screen in a three-dimensional space
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Schulz, Sebastian [Verfasser]. "Flow and heat transfer phenomena in a complex impingement system for integrally cooled turbine blades / Sebastian Schulz." München : Verlag Dr. Hut, 2018. http://d-nb.info/1155056094/34.
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Shin, Yun Kyung. "The water-amorphous silica interface: electrokinetic phenomena in a complex geometry, and treatment of interactions with biomolecules." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1299587783.
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Berthaud, Elena. "Acquisition des phénomènes linguistiques complexes en roumain langue maternelle (enfants de 6 à 10 ans)." Thesis, Paris 5, 2012. http://www.theses.fr/2012PA05H030.
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Ce travail de recherche a pour objectif d’expliquer comment des enfants d’âges différents acquièrent des phénomènes linguistiques supposés complexes en roumain langue maternelle. Dans cette recherche nous avons retenu les phénomènes complexes suivants :- les verbes complexes ;- les relatives explicatives et déterminatives ;- les prédications complexes à deux compléments locatifs et deux temporels ;- les prédications complexes par réduction de deux prédications simples et- les prédications à trois verbes opérateurs.Pour décrire le parcours acquisitionnel des enfants, nous avons décrit les procédures de reformulation que des enfants de 6, 8, et 10 ans mettent en place lorsqu’ils restituent une histoire venant de leur être lue. Après l’analyse des procédures de reformulation pour chaque tranche d’âge nous sommes arrivées aux conclusions suivantes :A 6 ans :- les enfants ont tendance à effacer ou à simplifier les verbes complexes. Ces verbes complexes sont remplacés par des verbes lexicalement plus simples et plus fréquents.- les enfants restituent souvent les énoncés sources par des reformulations partielles et lacunaires.- ils ont tendance à reformuler la suite principale-relative en ne gardant que la principale. A cet âge les enfants utilisent un lexique simple, plus courant ou moins contraint.A 8 ans :- les enfants diversifient de plus en plus leurs procédures de reformulation : répétition, paraphrase sémantique, fonctionnelle et restructuration. Toutefois, la procédure de reformulation majoritaire est la paraphrase définitoire analytique lacunaire ce qui confirme le fait que les verbes complexes constituent un phénomène linguistique complexe.- les enfants reformulent les relatives explicatives en un nombre nettement supérieur par rapport aux enfants de 6 ans. Ils diversifient beaucoup plus les procédures de reformulation paraphrastique. Certaines reformulations maintiennent le degré de complexité de l’énoncé source (synthétisation de deux informations en un mot). Toutefois, les enfants à cet âge ont encore des difficultés à reformuler une relative déterminative contenant une métaphore ou à reformuler une prédication complexe composée de deux prédications élémentaires.A 10 ans :- les enfants reformulent sans difficulté les énoncés qui contiennent des relatives explicatives. Ils produisent un nombre supérieur de reformulations par paraphrase sémantique par rapport aux plus jeunes. C’est à cet âge également qu’ils complexifient de plus en plus les énoncés sources, cas de reformulation définitoire analytique complète et restructurations des deux prédications en sont un exemple.A cet âge, les enfants n’ont pas encore acquis les énoncés qui ont un haut degré de complexité syntaxique et sémantique comme la relative déterminative avec une métaphore, ce qui confirme l’hypothèse de la complexité de ce phénomèneThe aim of this research is to explain how children of different ages acquire linguistic phenomena which are supposed to be complex in Romanian as a mother-tongue language. In this research, we selected the following complex phenomena:- Complex verbs;- Non-restrictive and restrictive relative clauses;- Complex predication with two locative and two temporal complements.- Complex predication by reduction of two simple predications and- Predication with three operator verbsTo describe the learning path of children, we described the reformulation procedures that children aged 6, 8 and 10 follow when they reproduce a story that has just been read to them. After analyzing the reformulation procedures for each age group, we came to the following conclusions:At 6 years:- children tend to erase or simplify complex verbs. These complex verbs are replaced by lexically simpler and more frequent verbs.- they often reproduce source phrases by partial and incomplete reformulations.- they tend to reformulate relative clauses by simple phrases with a single predicate or erase information of complex phrases (non-restrictive and restrictive relatives). At this age, children use simple, more frequent or less restrained vocabulary.At 8 years:- children increasingly diversify their reformulation procedures: repetition, semantic and functional paraphrasing and restructuring. However, the reformulation procedure which is widely used is the incomplete analytical definitional paraphrase which confirms the fact that complex verbs constitute a complex phenomenon.- At this age, the number of reformulated non-restrictive clauses is significantly high as compared to that of children at the age of 6 year. They diversify much more paraphrastic reformulation procedures. Some reformulations maintain the same degree of complexity as the source phrases (synthesizing information). However, children at this age still have difficulties reformulating restrictive relative clauses that contains a metaphor or reformulating a complex predication composed of two elementary predications.At 10 years:- children reformulate non-restrictive phrases without any difficulties. They produce a high number of reformulations by semantic paraphrasing as compared to younger children. It is also at this age that they increasingly complexify the source phrase (the case of complete analytical definitional reformulation and restructuring of the two predications are good examples).- At this age, children have not yet acquired phrases with high degree of syntactic and semantic complexity such as the restrictive relative clauses with a metaphor, which confirms the hypothesis that this phenomenon is complex
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Boutkhamouine, Brahim. "Stochastic modelling of flood phenomena based on the combination of mechanist and systemic approaches." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0142/document.
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Les systèmes de prévision des crues décrivent les transformations pluie-débit en se basant sur des représentations simplifiées. Ces représentations modélisent les processus physiques impliqués avec des descriptions empiriques, ou basées sur des équations de la mécanique classique. Les performances des modèles actuels de prévision des crues sont affectées par différentes incertitudes liées aux approximations et aux paramètres du modèle, aux données d’entrée et aux conditions initiales du bassin versant. La connaissance de ces incertitudes permet aux décideurs de mieux interpréter les prévisions et constitue une aide à la décision lors de la gestion de crue. L’analyse d’incertitudes dans les modèles hydrologiques existants repose le plus souvent sur des simulations de Monte-Carlo (MC). La mise en œuvre de ce type de techniques requiert un grand nombre de simulations et donc un temps de calcul potentiellement important. L'estimation des incertitudes liées à la modélisation hydrologique en temps réel reste donc une gageure. Dans ce projet de thèse, nous développons une méthodologie de prévision des crues basée sur les réseaux Bayésiens (RB). Les RBs sont des graphes acycliques dans lesquels les nœuds correspondent aux variables caractéristiques du système modélisé et les arcs représentent les dépendances probabilistes entre ces variables. La méthodologie présentée propose de construire les RBs à partir des principaux facteurs hydrologiques contrôlant la génération des crues, en utilisant à la fois les observations disponibles de la réponse du système et les équations déterministes décrivant les processus concernés. Elle est conçue pour prendre en compte la variabilité temporelle des différentes variables impliquées. Les dépendances probabilistes entre les variables (paramètres) peuvent être spécifiées en utilisant des données observées, des modèles déterministes existants ou des avis d’experts. Grâce à leurs algorithmes d’inférence, les RBs sont capables de propager rapidement, à travers le graphe, différentes sources d'incertitudes pour estimer leurs effets sur la sortie du modèle (ex. débit d'une rivière). Plusieurs cas d’études sont testés. Le premier cas d’étude concerne le bassin versant du Salat au sud-ouest de la France : un RB est utilisé pour simuler le débit de la rivière à une station donnée à partir des observations de 3 stations hydrométriques localisées en amont. Le modèle présente de bonnes performances pour l'estimation du débit à l’exutoire. Utilisé comme méthode inverse, le modèle affiche également de bons résultats quant à la caractérisation de débits d’une station en amont par propagation d’observations de débit sur des stations en aval. Le deuxième cas d’étude concerne le bassin versant de la Sagelva situé en Norvège, pour lequel un RB est utilisé afin de modéliser l'évolution du contenu en eau de la neige en fonction des données météorologiques disponibles. Les performances du modèle sont conditionnées par les données d’apprentissage utilisées pour spécifier les paramètres du modèle. En l'absence de données d'observation pertinentes pour l’apprentissage, une méthodologie est proposée et testée pour estimer les paramètres du RB à partir d’un modèle déterministe. Le RB résultant peut être utilisé pour effectuer des analyses d’incertitudes sans recours aux simulations de Monte-Carlo. Au regard des résultats enregistrés sur les différents cas d’études, les RBs se révèlent utiles et performants pour une utilisation en support d’un processus d'aide à la décision dans le cadre de la gestion du risque de crueFlood forecasting describes the rainfall-runoff transformation using simplified representations. These representations are based on either empirical descriptions, or on equations of classical mechanics of the involved physical processes. The performances of the existing flood predictions are affected by several sources of uncertainties coming not only from the approximations involved but also from imperfect knowledge of input data, initial conditions of the river basin, and model parameters. Quantifying these uncertainties enables the decision maker to better interpret the predictions and constitute a valuable decision-making tool for flood risk management. Uncertainty analysis on existing rainfall-runoff models are often performed using Monte Carlo (MC)- simulations. The implementation of this type of techniques requires a large number of simulations and consequently a potentially important calculation time. Therefore, quantifying uncertainties of real-time hydrological models is challenging. In this project, we develop a methodology for flood prediction based on Bayesian networks (BNs). BNs are directed acyclic graphs where the nodes correspond to the variables characterizing the modelled system and the arcs represent the probabilistic dependencies between these variables. The presented methodology suggests to build the RBs from the main hydrological factors controlling the flood generation, using both the available observations of the system response and the deterministic equations describing the processes involved. It is, thus, designed to take into account the time variability of different involved variables. The conditional probability tables (parameters), can be specified using observed data, existing hydrological models or expert opinion. Thanks to their inference algorithms, BN are able to rapidly propagate, through the graph, different sources of uncertainty in order to estimate their effect on the model output (e.g. riverflow). Several case studies are tested. The first case study is the Salat river basin, located in the south-west of France, where a BN is used to simulate the discharge at a given station from the streamflow observations at 3 hydrometric stations located upstream. The model showed good performances estimating the discharge at the outlet. Used in a reverse way, the model showed also satisfactory results when characterising the discharges at an upstream station by propagating back discharge observations of some downstream stations. The second case study is the Sagelva basin, located in Norway, where a BN is used to simulate the accumulation of snow water equivalent (SWE) given available weather data observations. The performances of the model are affected by the learning dataset used to train the BN parameters. In the absence of relevant observation data for learning, a methodology for learning the BN-parameters from deterministic models is proposed and tested. The resulted BN can be used to perform uncertainty analysis without any MC-simulations to be performed in real-time. From these case studies, it appears that BNs are a relevant decisionsupport tool for flood risk management
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Uechi, Risa. "Modeling of Biological and Economical Phenomena Based on Analysis of Nonlinear Competitive Systems." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199432.
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Rothkegel, Alexander [Verfasser]. "Synchronization phenomena in complex networks of pulse-coupled oscillators: self-generated changes between randomness and order / Alexander Rothkegel." Bonn : Universitäts- und Landesbibliothek Bonn, 2014. http://d-nb.info/1049984765/34.
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Salman, Mario Munir [Verfasser], Katharina [Akademischer Betreuer] Krischer, Michael [Gutachter] Eikerling, and Katharina [Gutachter] Krischer. "Modeling Complex Phenomena in Open Electrochemical Systems / Mario Munir Salman ; Gutachter: Michael Eikerling, Katharina Krischer ; Betreuer: Katharina Krischer." München : Universitätsbibliothek der TU München, 2020. http://d-nb.info/122628759X/34.
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Modi, Bhavi P. "GENETIC AND EPIGENETIC MECHANISMS OF COMPLEX REPRODUCTIVE DISORDERS." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4574.
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Common, complex disorders are polygenic and multifactorial traits representing interactions between environmental, genetic and epigenetic risk factors. More often than not, contributions of these risk factors have been studied individually and this is especially true for complex reproductive traits where application of genomic technologies has been challenging and slow to progress. This thesis explores the potential of genetic and epigenetic components contributing to a better understanding of the biological pathways underlying disease risk in two specific female complex reproductive traits - polycystic ovary syndrome (PCOS) and preterm premature rupture of membranes (PPROM). The PCOS projects focus on characterization of a gene, DENND1A, whose association to PCOS has been established by Genome Wide Association Studies (GWAS) and is known to contribute to PCOS steroidogenic phenotype. In addition, differential microRNAs expression contributing to DENND1A expression regulation in PCOS theca cells was identified. The studies on PPROM utilize a Whole Exome Sequencing approach to identify rare variants in fetal genes contributing to extracellular matrix composition and synthesis contributing to PPROM risk. The results suggest that fetal contribution to PPROM is polygenic and is driven by a significant genetic burden of potentially damaging rare variants in genes contributing to fetal membrane strength and integrity. Tissue and location specific expression patterns of the Chromosome 21 miRNA cluster (miR-99a, miR-125b, let-7c) in fetal membranes from term pregnancies with spontaneous rupture were investigated. The results suggest that these miRNAs play potential roles in fetal membrane rupture and fetal membrane defects associated with T21.
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Kransdorf, Evan Paul. "Purification and Characterization of a Methyl-DNA Binding Protein Complex from Primary Erythroid Cells." VCU Scholars Compass, 2004. http://hdl.handle.net/10156/1685.
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Yang, Byong-Seon. "Morphosyntactic phenomena of Korean in role and reference grammar : psych-verb constructions, inflectional verb morphemes, complex sentences, and relative clauses /." Seoul : Hankuk publ. = Han kuk mun hoa sa, 1994. http://catalogue.bnf.fr/ark:/12148/cb37527015b.
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Batista, João Luiz Bunoro. "Dinâmica de opinião de Krause-Hegselmann em redes complexas." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-18032013-163714/.
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Fenômenos coletivos em redes sociais como a formação de linguagem ou cultura, crenças, emergência de consenso em relação a algum assunto, aquisição de conhecimento e aprendizagem, dentre outros, tem conduzido a um grande interesse no estudo de comportamentos cooperativos e fenômenos sociais, resultando numa grande variedade de dinâmicas de opinião. Nestes modelos, uma população de agentes interagentes carrega uma variável (ou um conjunto delas) numérica cujo valor representa uma opinião sobre um tópico, com interpretações distintas em cada contexto. Inspirados em conceitos de mecânica estatística e mecanismos sociais, estes estados evoluem governados por regras matemáticas que controlam a dinâmica de interação entre os agentes e a influência de fatores externos. Outro ingrediente importante na modelagem de sistemas reais é que a representação das interações entre agentes difere bastante de reticulados ou misturas homogêneas, sendo mais bem descritas por redes complexas. Neste trabalho, estudamos a dinâmica de opinião de Krause e Hegselmann. Neste modelo, agentes possuem opiniões que assumem valores contínuos e são atualizados de acordo com a vizinhança compatível, definida pelo princípio da confiança limitada. Após apresentar uma revisão da literatura, estudamos a dinâmica de opinião no contexto de Redes Complexas, seguido de modificações do modelo que consideram a ação de ruído e campo externo (propaganda). Finalmente, propomos um modelo de consenso cuja interpretação está inserida no contexto de aquisição de conhecimento por agentes interagentes que realizam observações sujeitas a erros. Os resultados mostram como os diferentes tipos de topologia influenciam no comportamento das dinâmicas.Collective phenomena in social networks such as formation of language or culture, beliefs, emergence of consensus on any subject, knowledge acquisition and learning, among others, has led to an increasing interest in the study of cooperative behavior and social phenomena, resulting in great variety of opinion dynamics. In these models, a population of interacting agents holds a variable (or a set of them) whose numerical value is an opinion on a topic, with different interpretations in each context. Inspired by concepts from statistical mechanics and social mechanisms, these states evolve governed by mathematical rules that control the dynamics of interaction between agents and the influence of external factors. Another important ingredient in the modeling of real systems is the representation of the interactions between agents, which strongly differs from lattices or fully mixed states, being better described by complex networks. In the present work, we study the opinion dynamics of Krause and Hegselmann. In this model, agents hold opinions that assume continuous values and are updated according to their compatible neighborhood, defined by the bounded confidence principle. After presenting a literature review, we studied the opinion dynamics in the context of complex networks, followed by modifications of the model considering the effect of noise and external field (advertising). Finally, we propose a consensus model interpreted as a process of knowledge acquisition by interacting agents that make observations subject to errors. The results show how the topology influences the dynamic behavior.
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Smith, Corey Lewis. "Functional and Structural Analysis of the Yeast SWI/SNF Complex: a Dissertation." eScholarship@UMMS, 2004. https://escholarship.umassmed.edu/gsbs_diss/13.
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Modulating chromatin structure is an important step in maintaining control over the eukaryotic genome. SWI/SNF, one of the complexes belonging to the growing family of ATP-dependent chromatin remodeling enzymes, is involved in controlling the expression of a number of inducible genes whose proper regulation is vital for metabolism and progression through mitosis. The mechanism by which SWI/SNF modulates chromatin structure at the nucleosome level is an important aspect of this regulation. The work in this dissertation focuses on how the Saccharomyces cerevisiae SWI/SNF complex uses the energy of ATP-hydrolysis to alter DNA-histone contacts in nucleosomes. This has been approached in a two part fashion. First, the three-dimensional structure and subunit composition of SWI/SNF complex has been determined. From this study we have identified a potential region of the SWI/SNF complex that might [be] a site for nucleosomal interaction. Second, functional analysis of the ATPase domain of Swi2p, the catalytic subunit of SWI/SNF, has revealed that a specific conserved motif is involved in coupling ATP hydrolysis to the mechanism of chromatin remodeling. These results provide a potential model for the function of the SWI/SNF chromatin remodeling complex at the nucleosome level.