Dissertations / Theses on the topic 'Dynamical coupling'
To see the other types of publications on this topic, follow the link: Dynamical coupling.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Dynamical coupling.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Hardiman, S. C. "Stratosphere-troposphere dynamical coupling." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603685.
Full textAbstract:
This thesis is concerned with dynamical coupling between the stratosphere and troposphere. The first part of the thesis examines mechanisms whereby dynamical perturbations to the upper stratosphere can lead to a significant response in the lower stratosphere, looking particularly at how this response is determined by the extra-tropical dynamics. A one dimensional model is used to show that the response is much greater when the external parameters are such that the flow has multiple stable states. The same principle is shown to apply to a fully three dimensional flow and does not depend qualitatively on the representation of the troposphere and tropospheric wave forcing. The dependence of the response on the height of the applied dynamical perturbation, the amplitude of planetary wave forcing, and the relaxation to radiative equilibrium temperatures is considered. In the second part of the thesis we consider the interhemispheric differences in the extratropical seasonal cycle and suggest that resonance of topographically forced waves with free travelling planetary waves could be in part responsible for these differences. The seasonal cycle in mass upwelling in the tropical lower stratosphere is also considered. In particular we look at the differences in this upwelling caused by the strength and location of tropospheric wave driving, the thermal relaxation timescale of the atmosphere, baroclinic instability, and the seasonal cycle in the tropospheric radiative equilibrium temperature field. Finally we consider the interannual variability seen in the tropical mass upwelling. We quantify the different parts of this variability – the part that can be considered forced variability and the part that arises due to internal variability. We suggest that the high forced variability seen in the mass upwelling may be due to it being linked, via extratropical wave driving, to sea surface temperatures.
2
Simpson, Isla Ruth. "Solar influence on stratosphere-troposphere dynamical coupling." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504929.
Full text
3
Langen, Franciscus Hendrikus Theodorus de. "The business cycle dynamical coupling and chaotic fluctuations /." Maastricht : Amsterdam : Shaker ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/65930.
Full text
4
Pra, Paolo Dai, Pierre-Yves Louis, and Ida G. Minelli. "Complete monotone coupling for Markov processes." Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2008/1828/.
Full textAbstract:
We formalize and analyze the notions of monotonicity and complete monotonicity for Markov Chains in continuous-time, taking values in a finite partially ordered set. Similarly to what happens in discrete-time, the two notions are not equivalent. However, we show that there are partially ordered sets for which monotonicity and complete monotonicity coincide in continuoustime but not in discrete-time.
5
Murugesan, Manju Shrii. "Delay effects on synchronization in networks of dynamical systems." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2013. http://dx.doi.org/10.18452/16851.
Full textAbstract:
In dieser Dissertation werden wir die Wirkung der Verzögerung Kupplung auf Netzwerke von chaotischen erkunden dynamischer Systeme mit dem Rahmen der Master Stabilität Formalismus. Wir werden untersuchen das Phänomen der Verzögerung-verstärkter und Verzögerungen-induzierte stabile Synchronisation in einer willkürlichen Verzögerung gekoppelt Netzwerk von zeitkontinuierlichen dynamischen Systemen. Wir demonstrieren, dass es immer existieren eine erweiterte Regime des stabilen synchronen Zustand als eine Funktion der Kopplungsstärke geeignete Verbindung Verzögerungen, die nicht ohne Verzögerung in die Kupplung beobachtet werden kann. Wir schlagen eine partielle verzögerung Verbindung als eine Kombination von sowohl den momentanen und der komplett Verzögerung Verbindung mit gewissen Gewichten Bestimmung ihrer Beiträgen. Wir werden zeigen, dass die partielle Verzögerung Verbindung beide Grenzfälle des momentanen und der komplett Verzögerung Kupplung am synchronizabilit von Netzwerken übertrifft. Der Rahmen fuer Master Stabilität Formalismus ist mit einem Netzwerk von intrinsischen Zeitverzögerung Systeme, deren Knoten Dynamik durch Verzögerung Differentialgleichungen beschrieben erweitert, zum ersten Mal in der Literatur und veranschaulicht das allgemeine Verhalten des Master-Stabilisierungsfunktion in Netzwerken skalare Zeit Einschaltverzögerung Systeme auf den Synchronisations-Eigenschaften des Netzes. Außerdem untersuchen wir das Zusammenspiel von Lärm und verzögert in das Phänomen der Lärmverstärkter Phasensynchronisierung in beiden unidirektional und bidirektional gekoppelt zeitverzögerung systeme.In this thesis, we will explore the effect of delay coupling on networks of chaotic dynamical systems using the framework of master stability formalism. We will investigate the phenomenon of delay-enhanced and delay-induced stable synchronization in an arbitrary delay coupled network of time-continuous dynamical systems. We will demonstrate that there always exist an extended regime of stable synchronous state as a function of coupling strength for appropriate coupling delays, which cannot be observed without any delay in the coupling. We will also propose a partial delay coupling as a combination of both the instantaneous and the completely delay coupling with certain weights determining their contributions. We will show that the partial delay coupling outperforms both limiting cases of the instantaneous and the completely delay coupling on the synchronizability of networks. The framework of master stability formalism is extended to a network of intrinsic time-delay systems, whose node dynamics are described by delay differential equations, for the first time in the literature and illustrated the generic behavior of the master stability function in networks of scalar time-delay systems based on the synchronization properties of the network. We also investigate the interplay of noise and delay in the phenomenon of noise-enhanced phase synchronization in both unidirectionally and bidirectionally coupled time-delay systems.
6
Žagar, Nedjeljka. "Dynamical aspects of atmospheric data assimilation in the tropics." Doctoral thesis, Stockholm University, Department of Meteorology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-111.
Full textAbstract:
A faithful depiction of the tropical atmosphere requires three-dimensional sets of observations. Despite the increasing amount of observations presently available, these will hardly ever encompass the entire atmosphere and, in addition, observations have errors. Additional (background) information will always be required to complete the picture. Valuable added information comes from the physical laws governing the flow, usually mediated via a numerical weather prediction (NWP) model. These models are, however, never going to be error-free, why a reliable estimate of their errors poses a real challenge since the whole truth will never be within our grasp.
The present thesis addresses the question of improving the analysis procedures for NWP in the tropics. Improvements are sought by addressing the following issues:
- the efficiency of the internal model adjustment,
- the potential of the reliable background-error information, as compared to observations,
- the impact of a new, space-borne line-of-sight wind measurements, and
- the usefulness of multivariate relationships for data assimilation in the tropics.
Most NWP assimilation schemes are effectively univariate near the equator. In this thesis, a multivariate formulation of the variational data assimilation in the tropics has been developed. The proposed background-error model supports the mass-wind coupling based on convectively-coupled equatorial waves. The resulting assimilation model produces balanced analysis increments and hereby increases the efficiency of all types of observations.
Idealized adjustment and multivariate analysis experiments highlight the importance of direct wind measurements in the tropics. In particular, the presented results confirm the superiority of wind observations compared to mass data, in spite of the exact multivariate relationships available from the background information. The internal model adjustment is also more efficient for wind observations than for mass data.
In accordance with these findings, new satellite wind observations are expected to contribute towards the improvement of NWP and climate modeling in the tropics. Although incomplete, the new wind-field information has the potential to reduce uncertainties in the tropical dynamical fields, if used together with the existing satellite mass-field measurements.
The results obtained by applying the new background-error representation to the tropical short-range forecast errors of a state-of-art NWP model suggest that achieving useful tropical multivariate relationships may be feasible within an operational NWP environment.
7
Harvey, Thomas. "Noise in a dynamical open quantum system : coupling a resonator to an artificial atom." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10829/.
Full textAbstract:
The subject of this thesis is the study of a particular open quantum system consisting of a resonator coupled to a superconducting single electron transistor (SSET). The theoretical model we use is applicable to both mechanical and superconducting stripline resonators leading to a large parameter regime that can be explored. The SSET is tuned to the Josephson quasi-particle resonance, in which the transport occurs via Cooper pairs coherently tunnelling across one junction followed by the incoherent tunnelling of quasi-particles across the other. The SSET can be thought of as an artificial atom since it has a similar energy level structure and transitions to an atom. We investigate to what extent the current and current noise through the SSET can be used to infer the state of the resonator. In order to carry out these investigations we describe the system with a Born-Markov master equation, which we solve numerically. The evolution of the density matrix of the system is described by a Liouvillian superoperator. In order to better understand the results we perform an eigenfunction expansion of the Liouvillian, which is useful in connecting the behaviour of the resonator to the current noise. The mixture of coherent and incoherent processes in the SSET leads to interesting back action effects on the resonator. For weak coupling the SSET acts as an effective thermal bath on the resonator. Depending on the operating point the resonator can be either heated or cooled in comparison to its surroundings. In this regime we can use a set of mean field equations to describe the system and also capture certain aspects of the behaviour with some simple models. For sufficient coupling the SSET can drive the resonator into states of self-sustained oscillations. At the transition between stable and oscillating states of the resonator we also find regions of co-existence between oscillating and fixed point states of the resonator. The current noise provides a way to identify these transitions and the state of the resonator. The system also shows analogies with quantum optical systems such as the micromaser. We calculate the linewidth of the resonator and find deviations from the expected behaviour.
8
Fischer, Christian S. "Non-perturbative propagators, running coupling and dynamical mass generation in ghost-antighost symmetric gauges in QCD." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=967191424.
Full text
9
Eklund, Robert. "Computational Analysis of Carbohydrates : Dynamical Properties and Interactions." Doctoral thesis, Stockholm : Department of Organic Chemistry, Stockholm University, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-538.
Full text
10
Marchenko, Vadim. "On orbital stability of synchronous solutions of some singularly perturbed dynamical systems of relaxation-type oscillators with excitatory coupling /." The Ohio State University, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486398528556623.
Full text
11
Steinbauer, Jakob. "Multi-Orbital Physics in Materials with Strong Electronic Correlations : Hund's Coupling and Inter-Shell Interactions." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX068/document.
Full textAbstract:
Les matériaux corrélés offrent une richesse de nouveaux phénomènes, dont beaucoup ne sont pas encore - ou seulement partiellement - compris. Au centre de cette thèse sont des modèles multi-orbitalaires que j'etudie à travers une palette de méthodes, dont la théorie du champ moyen dynamique. Dans le modèle de Hubbard multi-orbitalaire proche de la transition de Mott, je mets en évidence un régime de mauvais métal induit par le couplage de Hund. Les propriétés de la transition de Mott dans ce système sont analysées. Dans un deuxèime temps, je traite un modèle élargi pour inclure des degrés de liberté des ligands dans les oxydes. Plus spécifiquement, cette thèse étudie les effets des interactions inter-couches entre orbitales corrélés d'un atome de métal de transition et les orbitales p des ligands. Une partie du travail est dédiée au développement de nouvelles méthodes dont une approche de rotateurs esclaves à ce problème. Le dernier chapitre concerne le domaine de la spintronique moléculaire, où j'étudie la physique du "spin-state switching" en fonction de l'hybridation d'un ion de métal de transition avec ses ligands dans les molecules organométalliques du type porphyrine de nickelThe physics of correlated materials offers a wealth of new phenomena, many of which are not yet - or only partially - understood. In this thesis, we focus on multi-orbital models, which we study using various methods, including dynamical mean-field theory. We show that in the multi-orbital Hubbard model close to the Mott transition, Hund's coupling gives rise to a bad metal regime the properties of which we analyze. Furthermore, we consider a more general class of models that include oxygen ligands. More specifically, we study the effect of inter-shell interactions between correlated metal- and ligand p-orbitals. In this context, we develop and test a new slave-rotor approach to treat such interactions in an effective manner. The final chapter constitutes an excursion to the field of molecular spintronics, where we study the physics of the hybridization-induced spin-state switching in organometallic nickel porphyrin molecules
12
Zhou, Bo. "The existence of bistable stationary solutions of random dynamical systems generated by stochastic differential equations and random difference equations." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/14255.
Full textAbstract:
In this thesis, we study the existence of stationary solutions for two cases. One is for random difference equations. For this, we prove the existence and uniqueness of the stationary solutions in a finite-dimensional Euclidean space Rd by applying the coupling method. The other one is for semi linear stochastic evolution equations. For this case, we follows Mohammed, Zhang and Zhao [25]'s work. In an infinite-dimensional Hilbert space H, we release the Lipschitz constant restriction by using Arzela-Ascoli compactness argument. And we also weaken the globally bounded condition for F by applying forward and backward Gronwall inequality and coupling method.
13
Luo, Ye. "Random periodic solutions of stochastic functional differential equations." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16112.
Full textAbstract:
In this thesis, we study the existence of random periodic solutions for both nonlinear dissipative stochastic functional differential equations (SFDEs) and semilinear nondissipative SFDEs in C([-r,0],R^d). Under some sufficient conditions for the existence of global semiflows for SFDEs, by using pullback-convergence technique to SFDE, we obtain a general theorem about the existence of random periodic solutions. By applying coupled forward-backward infinite horizon integral equations method, we perform the argument of the relative compactness of Wiener-Sobolev spaces in C([0,τ],C([-r,0]L²(Ω))) and the generalized Schauder's fixed point theorem to show the existence of random periodic solutions.
14
Lott, Geoffrey Adam 1980. "Probing local conformation and dynamics of molecular complexes using phase-selective fluorescence correlation and coherence spectroscopy." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10914.
Full textAbstract:
xv, 177 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.When two or more fluorescent chromophores are closely spaced in a macromolecular complex, dipolar coupling leads to delocalization of the excited states, forming excitons. The relative transition frequencies and magnitudes are sensitive to conformation, which can then be studied with optical spectroscopy. Non-invasive fluorescence spectroscopy techniques are useful tools for the study of dilute concentrations of such naturally fluorescent or fluorescently labeled biological systems. This dissertation presents two phase-selective fluorescence spectroscopy techniques for the study of dynamical processes in bio-molecular systems across a wide range of timescales. Polarization-modulated Fourier imaging correlation spectroscopy (PM-FICS) is a novel phase-selective fluorescence spectroscopy for simultaneous study of translational and conformational dynamics. We utilize modulated polarization and intensity gratings with phase-sensitive signal collection to monitor the collective fluctuations of an ensemble of fluorescent molecules. The translational and conformational dynamics can be separated and analyzed separately to generate 2D spectral densities and joint probability distributions. We present results of PM-FICS experiments on DsRed, a fluorescent protein complex. Detailed information on thermally driven dipole-coupled optical switching pathways is found, for which we propose a conformation transition mechanism. 2D phase-modulation electronic coherence spectroscopy is a third-order nonlinear spectroscopy that uses collinear pulse geometry and acousto-optic phase modulation to isolate rephasing and nonrephasing contributions to the collected fluorescence signal. We generate 2D spectra, from which we are able to determine relative dipole orientations, and therefore structural conformation, in addition to detailed coupling information. We present results of experiments on magnesium tetraphenylporphyrin dimers in lipid vesicle bilayers. The 2D spectra show clearly resolved diagonal and off-diagonal features, evidence of exciton behavior. The amplitudes of the distinct spectral features change on a femtosecond timescale, revealing information on time-dependent energy transfer dynamics. This dissertation includes co-authored and previously published material.
Committee in charge: Hailin Wang, Chairperson, Physics; Andrew Marcus, Advisor, Chemistry; Stephen Gregory, Member, Physics; Michael Raymer, Member, Physics; Marina Guenza, Outside Member, Chemistry
15
Mancabelli, Tobia [Verfasser], and Achim [Akademischer Betreuer] Hartschuh. "Raman measurements on plasmon-phonon coupled systems : dynamical back-action between a localized plasmon-polariton and phonons in carbon materials and plasmon-phonon coupling in beryllium doped gallium arsenide nanowires / Tobia Mancabelli ; Betreuer: Achim Hartschuh." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1124395725/34.
Full text
16
Smy, Louise Ann. "Atmospheric transport and critical layer mixing in the troposphere and stratosphere." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/2538.
Full textAbstract:
This thesis aims to improve the understanding of transport and critical layer mixing in the troposphere and stratosphere. A dynamical approach is taken based on potential vorticity which has long been recognised as the essential field inducing the flow and thermodynamic structure of the atmosphere. Within the dynamical framework of critical layer mixing of potential vorticity, three main topics are addressed. First, an idealised model of critical layer mixing in the stratospheric surf zone is examined. The effect of the shear across the critical layer on the critical layer evolution itself is investigated. In particular it is found that at small shear barotropic instability occurs and the mixing efficiency of the critical layer increases due to the instability. The effect of finite deformation length is also considered which extends previous work. Secondly, the dynamical coupling between the stratosphere and troposphere is examined by considering the effect of direct perturbations to stratospheric potential vorticity on the evolution of midlatitude baroclinic instability. Both zonally symmetric and asymmetric perturbations to the stratospheric potential vorticity are considered, the former representative of a strong polar vortex, the latter representative of the stratospheric state following a major sudden warming. A comparison of these perturbations gives some insight into the possible influence of pre or post-sudden warming conditions on the tropospheric evolution. Finally, the influence of the stratospheric potential vorticity distribution on lateral mixing and transport into and out of the tropical pipe, the low latitude ascending branch of the Brewer-Dobson circulation, is investigated. The stratospheric potential vorticity distribution in the tropical stratosphere is found to have a clear pattern according to the phase of the quasi-biennial oscillation (QBO). The extent of the QBO influence is quantified, by analysing trajectories of Lagrangian particles using an online trajectory code recently implemented in the Met Office's Unified Model.
17
Weichselbaum, Andreas. "Nanoscale Quantum Dynamics and Electrostatic Coupling." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1091115085.
Full text
18
Müller, Andreas. "Coupling analysis of transient cardiovascular dynamics." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17452.
Full textAbstract:
Die Untersuchung kausaler Zusammenhänge in komplexen dynamischen Systemen spielt in der Wissenschaft eine immer wichtigere Rolle. Ziel dieses aktuellen, interdisziplinären Forschungsbereiches ist ein grundlegendes, tiefes Verständnis der vorherrschenden Prozesse und deren Wechselwirkungen in solchen Systemen. Die Untersuchung von Zeitreihen mithilfe moderner Kopplungsanalysemethoden liefert dabei Möglichkeiten zur Modellierung der betreffenden Systeme und somit bessere Vorhersagemethoden und fortgeschrittene Interpretationsmöglichkeiten der Ergebnisse. In der vorliegenden Arbeit werden zunächst einige existierende Kopplungsmaße mit ihren jeweiligen Anwendungsgebieten vorgestellt. Eine Gemeinsamkeit dieser Maße liegt in der Voraussetzung stationärer Zeitreihen, um die Anwendbarkeit zu gewährleisten. Daher wird im Verlauf der Dissertation eine Möglichkeit zur Erweiterung solcher Maße vorgestellt, die eine Kopplungsanalyse mit einer sehr hohen Zeitauflösung und somit auch die Untersuchung nichtstationärer, transienter Ereignisse ermöglicht. Die Erweiterung basiert auf der Verwendung von Ensembles von Messreihen und der Schätzung der jeweiligen Maße über das Ensemble anstatt über die Zeit. Dies ermöglicht eine Zeitauflösung bei der Analyse in der Größenordnung der Abtastrate des ursprünglichen Signals, die nur von der Art der verwendeten Kopplungsmaße abhängt. Der Ensemble-Ansatz wird auf verschiedene Kopplungsmaße angewandt. Zunächst werden die Methoden ausführlich an verschiedenen theoretischen Modellen und unter verschiedenen Bedingungen getestet. Anschließend erfolgt eine zeitaufgelöste Kopplungsanalyse kardiovaskulärer Zeitreihen, die während transienter Ereignisse aufgenommen wurden. Die Ergebnisse dieser Analyse bestätigen zum einen aktuelle Studienresultate, liefern aber auch neue Erkenntnisse, die es in Zukunft ermöglichen können, Modelle des Herz-Kreislauf-Systems zu erweitern und zu verbessern.The analysis of causal relationships in complex dynamic systems plays a more and more important role in various scientific fields. The aim of this current, interdisciplinary field of research is a fundamental, deep understanding of predominant processes and their interactions in such systems. The study of time series using modern coupling analysis tools allows the modelling of the respective systems and thus better prediction methods and advanced interpretation possibilities for the results. In this work, initially some existing coupling measures and their fields of application are introduced. One trait these measures have in common is the requirement of stationary time series to ensure their applicability. Therefore, in the course of this thesis a possibility to extend these measures is presented, which allows a coupling analysis with a high temporal resolution and thus also the analysis of transient, nonstationary events. The extension is based on the use of ensembles of time series and the calculation of the respective measures across these ensembles instead of across time. This allows for a temporal resolution of the same order of magnitude as the sampling rate in the original signal. The resolution only depends on the kind of coupling analysis method employed. The ensemble extension is applied to different coupling measures. To begin with, the regarded tools are tested on various theoretical models and under different conditions. This is followed by a coupling analysis of cardiovascular time series recorded during transient events. The results on the one hand confirm topical study outcomes and on the other hand deliver new insights, which will allow to extend and improve cardiovascular system models in the future.
19
Wu, Yue. "Pathwise anticipating random periodic solutions of SDEs and SPDEs with linear multiplicative noise." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/15991.
Full textAbstract:
In this thesis, we study the existence of pathwise random periodic solutions to both the semilinear stochastic differential equations with linear multiplicative noise and the semilinear stochastic partial differential equations with linear multiplicative noise in a Hilbert space. We identify them as the solutions of coupled forward-backward infinite horizon stochastic integral equations in general cases, and then perform the argument of the relative compactness of Wiener-Sobolev spaces in C([0, T],L2Ω,Rd)) or C([0, T],L2(Ω x O)) and Schauder's fixed point theorem to show the existence of a solution of the coupled stochastic forward-backward infinite horizon integral equations.
20
Gou, Jia. "Oscillatory dynamics for PDE models coupling bulk diffusion and dynamically active compartments : theory, numerics and applications." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57603.
Full textAbstract:
We formulate and investigate a relatively new modeling paradigm by which spatially segregated dynamically active units communicate with each other through a signaling molecule that diffuses in the bulk medium between active units. The modeling studies start with a simplified setting in a one-dimensional space, where two dynamically active compartments are located at boundaries of the domain and coupled through the feedback term to the local dynamics together with flux boundary conditions at the two ends. For the symmetric steady state solution, in-phase and anti-phase synchronizations are found and Hopf bifurcation boundaries are studied using a winding number approach as well as parameter continuation methods of bifurcation theory in the case of linear coupling. Numerical studies show the existence of double Hopf points in the parameter space where center manifold and normal form theory are used to reduce the dynamics into a system of amplitude equations, which predicts the configurations of the Hopf bifurcation and stability of the two modes near the double Hopf point. The system with a periodic chain of cells is studied using Floquet theory. For the case of a single active membrane bound component, rigorous spectral results for the onset of oscillatory dynamics are obtained and in the finite domain case, a weakly nonlinear theory is developed to predict the local branching behavior near the Hopf bifurcation point. A previously developed model by Gomez et al.\cite{Gomez-Marin2007} is analyzed in detail, where the phase diagrams and the Hopf frequencies at onset are provided analytically with slow-fast type of local kinetics. A coupled cell-bulk system, with small signaling compartments, is also studied in the case of a two-dimensional bounded domain using the method of asymptotic expansions. In the very large diffusion limit we reduce the PDE cell-bulk system to a finite dimensional dynamical system, which is studied both analytically and numerically. When the diffusion rate is not very large, we show the effect of spatial distribution of cells and find the dependence of the quorum sensing threshold on influx rate.Science, Faculty of
Mathematics, Department of
Graduate
21
Jedynak, Maciej. "Coupling and stochasticity in mesoscopic brain dynamics." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/404102.
Full textAbstract:
The brain is known to operate under the constant influence of noise arising from a variety of sources. It also organises its activity into rhythms spanning multiple frequency bands. These rhythms originate from neuronal oscillations which can be detected via measurements such as electroen-cephalography (EEG) and functional magnetic resonance (fMRI). Experimental evidence suggests that interactions between rhythms from distinct frequency bands play a key role in brain processing, but the dynamical mechanisms underlying this cross-frequency interactions are still under investigation. Some rhythms are pathological and harmful to brain function. Such is the case of epileptiform rhythms characterising epileptic seizures.
Much has been learnt about the dynamics of the brain from computational modelling. Particularly relevant is mesoscopic scale modelling, which is concerned with spatial scales exceeding those of individual neurons and corresponding to processes and structures underlying the generation of signals registered in the EEG and fMRI recordings. Such modelling usually involves assumptions regarding the characteristics of the background noise, which represents afferents from remote, non-modelled brain areas. To this end, Gaussian white noise, characterised by a flat power spectrum, is often used. In contrast, macroscopic fluctuations in the brain typically follow a `1/f b ¿ spectrum, which is a characteristic feature of temporally correlated, coloured noise. In Chapters 3-5 of this Thesis we address by means of a stochastically driven mesoscopic neuronal model, the three following questions. First, in Chapter 3 we ask about the significance of deviations from the assumption of white noise in the context of brain dynamics, and in particular we study the role that temporally correlated noise plays in eliciting aberrant rhythms in the model of an epileptic brain. We find that the generation of epileptiform dynamics in the model depends non-monotonically on the noise correlation time. We show that this is due to the maximisation of the spectral content of epileptogenic rhythms in the noise. These rhythms fall into frequency bands that indeed were experimentally shown to increase in power prior to epileptic seizures. We explain these effects in terms of the interplay between specific driving frequencies and bifurcation structure of the model.
Second, in Chapter 4 we show how coupling between cortical modules leads to complex activity patterns and to the emergence of a phenomenon that we term collective excitability. Temporal patterns generated by this model bear resemblance to clinically observed characteristics of epileptic seizures. In that chapter we also introduce a fast method of tracking a loss of stability caused by excessive inter-modular coupling in a neuronal network. Third, in Chapter 5 we focus on cross-frequency interactions occurring in a network of cortical modules, in the presence of coloured noise. We suggest a mechanism that underlies the increase of power in a fast rhythm due to driving with a slow rhythm, and we find the noise parameters that best recapitulate experimental power spectra. Finally, in Chapter 6, we examine models of haemodynamic and metabolic brain processes, we test them on experimental data, and we consider the consequences of coupling them with mesoscopic neuronal models.
Taken together, our results show the combined influence of noise and coupling in computational models of neuronal activity. Moreover, they demonstrate the relevance of dynamical properties of neuronal systems to specific physiological phenomena, in particular related to cross-frequency interactions and epilepsy. Insights from this Thesis could in the future empower studies of epilepsy as a dynamic disease, and could contribute to the development of treatment methods applicable to drug-resistant epileptic patients.El cervell opera sota la influència de sorolls amb diversos orígens. També organitza la seva activitat en una sèrie de ritmes que s'expandeixen en diverses bandes de freqüència. Aquests ritmes tenen el seu origen en les osci∙lacions neuronals i poden detectar-se via mesures com les electroencefalogràfiques (EEG) o la ressonància magnètica funcional (fMRI). Les evidències experimentals suggereixen que les interaccions entre ritmes operant en bandes de freqüència diferents juguen un paper central en el processat cerebral però els mecanismes dinàmics subjacents a les interaccions inter-freqüència encara estan investigant-se. Alguns ritmes són patològics i fan malbé el funcionament cerebral. És el cas dels ritmes epileptiformes que caracteritzen les convulsions epilèptiques. Fent servir el modelatge computacional s'ha après molt sobre la dinàmica del cervell. Especialment rellevant és el modelatge a l’escala mesoscòpica, que té a veure amb les escales espacials superiors a les de les neurones individuals i que correspon als processos que generen EEG i fMRI. Tal modelatge, en general, implica supòsits relatius a les característiques del soroll de fons que representa zones remotes del cervell no modelades. Amb aquesta finalitat s'utilitza sovint el soroll blanc gaussià, que es caracteritza per un espectre de potència pla. Les fluctuacions macroscòpiques en el cervell, però, normalment segueixen un espectre '1/fb', que és un tret característic de les correlacions temporals i el soroll de color. Als Capítols 3-5 d'aquesta tesi abordem mitjançant un model neuronal mesoscòpic forçat estocàsticament, les tres preguntes següents. En primer lloc, en el Capítol 3 ens preguntem sobre la importància de les desviacions de l'assumpció de soroll blanc en el context de la dinàmica del cervell i, en particular, estudiem el paper que juga el soroll amb correlació temporal en l'obtenció de ritmes aberrants d'un cervell epilèptic. Trobem que la generació de les dinàmiques epileptiformes depèn de forma monòtona del temps de correlació del soroll. Aquests ritmes es divideixen en bandes de freqüència que, segons, s'ha mostrat experimentalment, augmenten la seva potència espectral abans de les crisis epilèptiques. Expliquem aquests efectes en termes de la interacció entre les freqüències específiques del forçament i l'estructura de bifurcació del model. En segon lloc, en el Capítol 4 es mostra com l'acoblament entre mòduls corticals condueix a patrons d'activitat complexes i a l'aparició d'un fenomen que anomenem excitabilitat col∙lectiva. Els patrons temporals generats per aquest model s'assemblen a les observacions clíniques de les convulsions epilèptiques. En aquest capítol també introduïm un mètode d'anàlisi de la pèrdua d'estabilitat causada per l'acoblament inter-modular excessiu en les xarxes neuronals. En tercer lloc, en el Capítol 5 ens centrem en les interaccions inter-freqüència que es produeixen en una xarxa de mòduls corticals en presència de soroll de color. Suggerim un mecanisme subjacent a l'augment de la potència spectral de ritmes ràpids a causa del forçament amb un ritme lent, i veiem quins paràmetres del soroll descriuen millor els espectres de potència experimental. Finalment, en el Capítol 6, estudiem models dels processos hemodinàmics i metabòlics del cervell, els comparem amb dades experimentals i considerem les conseqüències del seu acoblament amb models neuronals mesoscopics. En conjunt, els nostres resultats mostren la influència combinada del soroll i l'acoblament en models computacionals de l'activitat neuronal. D'altra banda, també demostren la importància de les propietats dinàmiques dels sistemes neuronals en fenòmens fisiològics específics com les interaccions inter-frequència i l'epilèpsia. Els resultats d'aquesta Tesi contribueixen a potenciar l’estudi de l'epilèpsia com una malaltia dinàmica, i el desenvolupament de mètodes de tractament aplicables a pacients epilèptics resistents als fàrmacs.
22
Ponzoni, Luca. "Knowledge-based identification of functional domains in proteins." Doctoral thesis, SISSA, 2016. http://hdl.handle.net/20.500.11767/4920.
Full textAbstract:
The characterization of proteins and enzymes is traditionally organised according to the sequence-structure-function paradigm.
The investigation of the inter-relationships between these three properties has motivated the development of several experimental and computational techniques, that have made available an unprecedented amount of sequence and structural data. The interest in developing comparative methods for rationalizing such copious information has, of course, grown in parallel.
Regarding the structure-function relationship, for instance, the availability of experimentally resolved protein structures and of computer simulations have improved our understanding of the role of proteins' internal dynamics in assisting their functional rearrangements and activity.
Several approaches are currently available for elucidating and comparing proteins' internal dynamics. These can capture the relevant collective degrees of freedom that recapitulate the main conformational changes. These collective coordinates have the potential to unveil remote evolutionary relationships between proteins, that are otherwise not easily accessible from purely sequence- or structure-based investigations.
Starting from this premise, in the first chapter of this thesis I will present a novel and general computational method that can detect large-scale dynamical correlations in proteins by comparing different representative conformers. This is accomplished by applying dimensionality-reduction techniques to inter-amino acid distance fluctuation matrices. As a result, an optimal quasi-rigid domain decomposition of the protein or macromolecular assembly of interest is identified, and this facilitates the functionally-oriented interpretation of their internal dynamics.
Building on this approach, in the second chapter I will discuss its systematic application to a class of membrane proteins of paramount biochemical interest, namely the class A G protein-coupled receptors. The comparative analysis of their internal dynamics, as encoded by the quasi-rigid domains, allowed us to identify recurrent patterns in the large-scale dynamics of these receptors. This, in turn, allowed us to single out a number of key functional sites. These were, for the most part, previously known -- a fact that at the same time validates the method, and gives confidence for the viability of the other, novel sites.
Finally, for the last part of the thesis, I focussed on the sequence-structure relationship. In particular, I considered the problem of inferring structural properties of proteins from the analysis of large multiple sequence alignments of homologous sequences. For this purpose, I recasted the strategies developed for the dynamical features extraction in order to identify compact groups of coevolving residues, based only on the knowledge of amino acid variability in aligned primary sequences.
Throughout the thesis, many methodological techniques have been taken into considerations,
mainly based on concepts from graph theory and statistical data analysis (clustering). All these topics are explained in the methodological sections of each chapter.
23
Pais, Artur Luna. "Dynamic coupling of multiple structures through soil." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/34305.
Full text
24
Moreira, Evaldinólia Gilbertoni. "Dynamic coupling of multiscale land change models." Instituto Nacional de Pesquisas Espaciais, 2009. http://urlib.net/sid.inpe.br/mtc-m18@80/2008/11.10.16.23.
Full textAbstract:
Mudanças terrestres são resultados de uma complexa rede de interações entre fatores humanos e biofísicos, que atuam em diferentes escalas temporais e espaciais. Entender estes processos de mudanças terrestres de escalas locais a globais e seus impactos no sistema acoplado homem-natureza é um enorme desafio científico. Modelos em uma única escala podem não ser capazes capturar tais interações e processos de mudança. Esta tese apresenta uma metodologia para a construção de modelos de mudanças terrestre multiescala e multilocalidade, incluindo interações top-down e bottom-up. Numa primeira etapa, conceituamos dois tipos de relações espaciais entre objetos geográficos em diferentes escalas. Relações hierárquicas são propostas para tratar das interações entre objetos espacialmente aninhados, e relações de "ação à distância" são propostas para tratar de interações entre redes e objetos espaciais. Então, numa segunda etapa, apresentamos uma proposta de organização modular do software dos modelos. Consideramos neste trabalho o caso onde modelos para cada escala são independentemente construídos, possivelmente com abordagens distintas, e então dinamicamente acoplados. Conceitos de acopladores de modelos são introduzidos para definir o fluxo de informação bidirecional entre escalas. Estes conceitos foram implementado no ambiente de modelagem TerraME. Como prova de conceito, apresentamos um exemplo com duas escalas hierárquicas para Amazônia Brasileira. A conclusão deste trabalho aponta que a combinação de relações espaciais hierárquicas com relações baseadas em redes provê um arcabouço conceitual abrangente para lidar com interações top-down e bottom-up em modelos multiescala de mudanças terrestres. A organização modular e o conceito de acopladores propostos são bastante genéricos para serem usados com outros tipos de aplicação, e com isso contribuir para criação de modelos ambientais integrados, considerando escalas locais a globais.Land changes are the result of a complex web of interactions between human and biophysical factors, which act over a wide range of temporal and spatial scales. Understanding processes of change from local to global scale and their impacts on the coupled human-environmental system is a main scientific challenge. No single model or scale can fully capture such interactions and processes of land change. This thesis presents a methodology for building multiscale, multi-locality land change models that include top-down and bottom-up relations. At first, we conceptualize two types of spatial relations among geographic objects at different scales. To handle the interaction of nested spatial objects at different scales, we propose hierarchical relations. To handle the interaction between networks and spatial objects, we propose action-at-a-distance relations. Then in a second step, we propose a modular software organization to build multiscale land change models. We consider the case when single-scale models, using different modeling approaches, are independently built and then dynamically coupled. We introduce the concepts of Model Couplers to define the bi-directional flow of information between the scales. We implement these concepts using the TerraME modeling environment. As a proof of concept, we present a hierarchical two-scale example for the Brazilian Amazon. The conclusion of this work points out that combining hierarchical and network-based spatial relations provides a comprehensive conceptual framework to include top-down and bottom-up interactions and feedbacks in multi-scale land-change models. The modular software organization and concept of Model Couplers are general enough to be used for other types of applications, and to contribute to the creation of Integrated Environmental Models from local to global scales.
25
Smith, Edward. "On the coupling of molecular dynamics to continuum computational fluid dynamics." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/15610.
Full textAbstract:
Molecular dynamics (MD) is a discrete modelling technique that is used to capture the nanoscale motion of molecules. MD can be used to accurately simulate a range of physical problems where the continuum assumption breaks down. Examples include surface interaction, complex molecules, local phase changes, shock waves or the contact line between fluids. However, beyond very small systems and timescales (μm and msec), MD is prohibitively expensive. Continuum computational fluid dynamics (CFD), on the other hand, is easily capable of simulating scales of engineering interest, (m and s). However, CFD is unable to capture micro-scale effects vital for many modern engineering fields, such as nanofluidics, tribology, nano-electronics and integrated circuit development. This work details the development of a set of techniques that combine the advantages of both continuum and molecular modelling methodologies, allowing the study of cases beyond the range of either technique alone. The present work is split into both computational and theoretical developments. The computational aspect involves the development of a new high-performance MD code, as well as a coupler (CPL) library to link it to a continuum solver. The MD code is fully verified, has similar performance to existing MD software and allows simulation of a wide range of cases. The CPL library is a robust, flexible and language independent API and the source code has been made freely available under the GNU GPL v3 license. Both MD and CPL codes are developed to allow very large scale simulation on high performance computing (HPC) facilities. The theoretical aspect includes the development of a rigorous mathematical framework and its application to develop novel coupling methodologies. The mathematical framework allows a discrete molecular system to be expressed in terms of the control volume (CV) formulation from continuum fluid dynamics. A discrete form of Reynolds’ transport theorem, is thus obtained, allowing both molecular and continuum systems to be expressed in a consistent manner. This results in a number of important insights into the molecular definition of stress. This CV framework allows mathematical operations to be localised to a control volume in space. It is ideally suited to apply coupling constraints to a region in space. To link the CFD and MD solvers in a rigorous and physically consistent manner, the CV framework is combined with the variational principles of classical mechanics. The result is a unification of a number of existing forms used in the coupling literature and a rigorous derivation of a new and more general coupling scheme.
26
Ziogas, Vaios. "Transport at strong coupling and black hole dynamics." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12683/.
Full textAbstract:
In this thesis we study aspects of transport in strongly coupled quantum systems with broken translational symmetry. Using holographic duality, we also examine the associated dynamical problem in asymptotically Anti-de Sitter, spatially modulated black holes. More precisely, in chapter 2 we consider the transport of conserved charges in spatially inhomogeneous quantum systems with a discrete lattice symmetry. When the DC conductivities are finite, we derive a set of generalised Einstein relations, relating the diffusion constants of the conserved charges to the DC conductivities and static susceptibilities. We also develop a long-wavelength expansion in order to explicitly construct the heat and charge diffusive modes within hydrodynamics on curved manifolds. In chapter 3 we used analogous techniques to construct the thermoelectric diffusive quasinormal modes in a large class of black hole spacetimes that are holographically dual to strongly coupled field theories in which spatial translations are broken explicitly. These modes satisfy a set of constraints on the black hole horizon, from which we find that their dispersion relations are given by the generalised Einstein relations. In chapter 4 we define a boost incoherent current in spontaneously modulated phases, and we show that in holographic theories, its DC conductivity can be obtained from solving a system of horizon Stokes equations.
27
Robertson, Christopher. "Vibronic coupling, symmetry and dynamics in unsaturated hydrocarbons." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6283/.
Full textAbstract:
This theoretical work looks at excited state photochemistry - the study of the molecular processes triggered by the absorption/e mission of light to/from electronically excited states. The approach taken here is that of using approximate vibronic coupling models, as well as extending the methods and algorithms to construct them. These are then used in quantum dynamic calculations to obtain time-dependent properties, compute spectra and calculate dissociation cross-sections. A genetic algorithm which aids to the fitting of diabatic model parameters is described in detail and tested in two systems. The neutral and cationic surfaces of cyclo-butadiene is one of the systems for which this fitting algorithm was used and the photo-electron spectrum was then calculated to compare with the experimental one. We show how one can generate polynomial functions which are invariant with respect to the non-Abelian point groups. These invariant polynomials are then used for the construction of an acetylene model, where photo-dissociation cross sections are calculated for all possible angles. A bigger system Tolan, the monomial of a family of a photo-active dendritic antenna, was modelled. Comparison between the experimental and calculated absorption spectra validates the model and is subsequently used to model the first few picoseconds of population transfer.
28
Bright, Vivien Bianca. "Street canyon atmospheric composition : coupling dynamics and chemistry." Thesis, University of Birmingham, 2013. http://etheses.bham.ac.uk//id/eprint/4414/.
Full textAbstract:
A new model for the simulation of street canyon atmospheric chemical processing has been developed, by integrating an existing Large-Eddy Simulation (LES) dynamical model of canyon atmospheric motion with a detailed chemical reaction mechanism, the Reduced Chemical Scheme (RCS), comprising 51 chemical species and 136 reactions, based upon a subset of the Master Chemical Mechanism (MCM). The combined LES-RCS model is used to investigate both the effects of mixing and chemical processing upon air quality within an idealised street canyon. The effect of the combination of dynamical (segregation) and chemical effects is determined by comparing the outputs of the full LES-RCS canyon model with those obtained when representing the canyon as a zero-dimensional box model (i.e. assuming mixing is complete and instantaneous). The LES-RCS approach predicts lower (canyon-averaged) levels of NOX, OH and HO2, but higher levels of O3, compared with the box model run under identical chemical and emission conditions. Chemical processing of emissions within the canyon leads to a significant increase in the Ox flux from the canyon into the overlying boundary layer, relative to primary emissions, for the idealised case and a number of pollution scenarios considered. These results demonstrate that within-canyon atmospheric chemical processing can substantially alter the concentrations of pollutants injected into the urban canopy layer, compared with the raw emission rates within the street canyon and that such variations have a considerable effect on average within canyon concentrations and the flux of pollutants out of the canyon into the urban background environment.
29
McGlashan, Laurence Robert. "Coupling population balances to computational fluid dynamics solvers." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607919.
Full text
30
Forbes, David C. "Coupling road vehicle aerodynamics and dynamics in simulation." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25565.
Full textAbstract:
A fully coupled system in which a vehicle s aerodynamic and handling responses can be simulated has been designed and evaluated using a severe crosswind test. Simulations of this type provide vehicle manufacturers with a useful alternative to on road tests, which are usually performed at a late stage in the development process with a proto- type vehicle. The proposed simulations could be performed much earlier and help to identify and resolve any aerodynamic sensitivities and safety concerns before significant resources are place in the design. It was shown that for the simulation of an artificial, on-track crosswind event, the use of the fully coupled system was unnecessary. A simplified, one-way coupled system, in which there is no feedback from the vehicle s dynamics to the aerodynamic simulation was sufficient in order to capture the vehicle s path deviation. The realistic properties of the vehicle and accurately calibrated driver model prevented any large attitude changes whilst immersed in the gust, from which variations to the aerodynamics could arise. It was suggested that this system may be more suited to other vehicle geometries more sensitive to yaw motions or applications where a high positional accuracy of the vehicle is required.
31
Rong, Guoxin. "Probing cell membrane dynamics using plasmon coupling microscopy." Thesis, Boston University, 2013. https://hdl.handle.net/2144/12840.
Full textAbstract:
Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.The plasma membrane of mammalian cells is depicted as a two-dimensional hybrid material which is compartmentalized into submicron-sized domains. These membrane domains play a pivotal role in cellular signaling processes due to selective recruitment of specific cell surface receptors. The structural dynamics of the membrane domains and their exact biological functions are, however, still unclear, partially due to the wave nature of light, which limits the optical resolution in the visible light to approximately 400 nm in conventional optical microscopy. Here, we provide a non-fluorescence based approach for monitoring distance changes on subdiffraction limit length scales in a conventional far-field optical microscope. This approach, which is referred to as plasmon coupling microscopy (PCM), utilizes the distance dependent near-field coupling between noble metal nanoparticle (NP) labels to resolve close contacts on the length scale of approximately one NP diameter. We firstly utilize this PCM strategy to resolve interparticle separations during individual encounters of gold NP labeled fibronectin-integrin complexes in living Hela cells. We then further refine this ratiometric detection methodology by augmenting it with a polarization-sensitive detection, which enables simultaneous monitoring of the distance and conformation changes in NP dimers and clusters. We apply this polarization resolved PCM approach to characterize the structural lateral heterogeneity of cell membranes on submicron length scales. Finally, we demonstrate that PCM can provide quantitative information about the structural dynamics of individual epidermal growth factor receptor (ErbB1)-enriched membrane domains in living cells.
32
Yamaguchi, T., T. Matsuoka, and S. Koda. "Mode-coupling study on the dynamics of hydrophobic hydration." American Institute of Physics, 2004. http://hdl.handle.net/2237/7065.
Full text
33
Louis, Pierre-Yves. "Coupling, space and time Mixing for parallel stochastic dynamics." Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2011/5156/.
Full textAbstract:
We first introduce some coupling of a finite number of Probabilistic Cellular
Automata dynamics (PCA), preserving the stochastic ordering. Using this tool, for a general attractive probabilistic cellular automata on SZd, where S is finite, we prove that a condition (A) is equivalent to the (time-) convergence towards equilibrium of this Markovian parallel dynamics, in the uniform norm, exponentially fast. This condition (A) means the exponential decay of the influence from the boundary for the invariant measures of the system restricted to finite ‘box’-volume. For a class of reversible PCA dynamics on {−1, +1}Zdwith a naturally associated Gibbsian potential ϕ, we prove that a Weak Mixing condition for ϕ implies the validity of the assumption (A); thus the ‘exponential ergodicity’ of the dynamics towards the unique Gibbs measure associated to ϕ holds. On some particular examples of this PCA class, we verify that our assumption (A) is weaker than the Dobrushin-Vasershtein ergodicity condition. For some special PCA, the ‘exponential ergodicity’ holds as soon as there is no phase transition.
34
Yamamoto, Miharu. "Coupling of Arterial Wall Cell Dynamics and Blood Flow." Thesis, University of Canterbury. Centre for Bioengineering, 2011. http://hdl.handle.net/10092/6288.
Full textAbstract:
The objective of this research is to investigate both mathematically and numerically the effects of vascular geometry upon the cellular dynamics in the endothelium and its consequence in the localisation of atherosclerosis. It is widely accepted that the formation of atherosclerotic plaques preferentially occurs at specific locations in the vasculature, such as arterial branches and bends. It has also been observed that, at the sites of plaque formation, the physiological functions of the vascular endothelium are impaired due to a defect in the production mechanisms of or diminished activities of endothelial nitric oxide (NO). From these observations, a correlation between the vascular geometry, which is effected via local haemodynamic forces, and local bioavailability of endothelial NO has been postulated. The research areas that have been involved in the investigation of atherosclerosis's localisation in the past, haemodynamics, medicine, calcium dynamics, NO kinetics and endothelial cell biology, have been studied individually, and there appears to be no integrated model to date that allows investigation of coupled haemodynamic and cellular mechanism applied in physiologically realistic model geometries. An integrated numerical model that includes these mechanisms will be developed in this research, which will lead to a further, more comprehensive understanding of the pathogenesis of atherosclerosis.
35
Scarlett, Liam. "Nuclear Dynamics in the Molecular Convergent Close-Coupling Method." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/87913.
Full textAbstract:
Theoretical and computational modelling of collisions between electrons and the hydrogen molecule (H2) as well as its five isotopologues has been conducted. The technique applied is the molecular convergent close-coupling (MCCC) method, with a particular focus on the treatment of nuclear dynamics in the MCCC calculations. Cross sections for over 60,000 vibrationally-resolved transitions have been calculated within the adiabatic-nuclei approximation, and a new vibrational-electronic close-coupling method has been developed to study resonant electron-molecule collisions.
36
Rose, Alexander. "The dynamic coupling interface of G-protein coupled receptors." Doctoral thesis, Humboldt-Universität zu Berlin, Lebenswissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17215.
Full textAbstract:
Um mit ihrer Umgebung zu kommunizieren verfügen lebende Zellen über Rezeptoren, welche die umschließende Membran überbrücken. Die vorherrschende G-Protein-gekoppelte Rezeptoren (GPCR) erhalten Informationen von Außerhalb durch Bindung eines Liganden, wodurch der Rezeptor aktiviert wird. Während der Aktivierung bildet sich innerzellulär ein offener Spalt, in den ein G-Protein (Gαβγ, G) mit seinem C-terminalen Ende koppeln kann. Die Bindung an einen GPCR führt in der Gα-Untereinheit vom Gαβγ zu einen GDP/GTP-Austausch, welcher für die weitere Signalübertragung ins Zellinnere notwendig ist. Die Kopplung von Rezeptor und Gαβγ umfasst eine Reihe von dynamischen strukturellen Änderungen, die Geschwindigkeit und Spezifität der Interaktion regeln. Hier haben wir MD-Simulationen (Molekulardynamik) verwendet, um die molekularen Details der GPCR Gαβγ Kopplung vor und während der GPCR-Gαβγ-Komplexbildung bis hin zum GDP/GTP-Austausch zu untersuchen.To communicate with their environment, living cells feature receptors that provide a bridge across the enclosing membrane. The prevalent G protein-coupled receptors (GPCR) receive outside information through the binding of a ligand, which activates the receptor. During activation, an open intracellular crevice forms, to which a G protein (Gαβγ, G) can couple with its Gα C-terminus. Binding to GPCRs triggers GDP/GTP exchange in the Gα subunit of Gαβγ, necessary for further signal transfer within the cell. The coupling between receptor and Gαβγ involves a series of dynamic structural changes that govern speed and specificity of the interaction. Here we used molecular dynamics (MD) simulations to elucidate molecular details of the GPCR Gαβγ coupling process before and during GPCR Gαβγ complex formation up to the GDP/GTP exchange.
37
Huck, Petra Ellen. "The Coupling of Dynamics and Chemistry in the Antarctic Stratosphere." Thesis, University of Canterbury. Physics and Astronomy, 2007. http://hdl.handle.net/10092/1410.
Full textAbstract:
This thesis addresses the parameterisation of chemical and dynamical processes in the Antarctic stratosphere. Statistical models for the inter- and intra-annual variability in Antarctic stratospheric ozone depletion were developed based on theory and an understanding of the coupling of dynamics and chemistry in the atmosphere. It was confirmed that the primary driver of the long-term trend in the severity of the Antarctic ozone hole is halogen loading in the stratosphere. The year-to-year variability in ozone mass deficit, a measure of the severity of Antarctic ozone depletion, could be described by a linear combination of South Pole temperatures and midlatitude wave activity. A time lag of two weeks between wave activity effects and ozone depletion indicates the predictive capability of meteorological parameters for seasonal projections of the severity of the Antarctic ozone hole. The statistical model describing the inter-annual variability in ozone mass deficit was regressed against observations from 1979 to 2004. The resulting regression coefficients were applied to South Pole temperature and wave activity fields from 28 chemistry-climate models. This analysis indicates a slight increase in the year-to-year variability in the severity of Antarctic ozone depletion. As a prelude to analysing the seasonal evolution of Antarctic ozone depletion, an improved ozone mass deficit measure was derived by replacing the constant 220 DU threshold with a seasonal varying pre-ozone hole background which leads to better capturing the true extent of the depleted ozone. Furthermore, it was shown that the new measure represents the chemical ozone loss within the Antarctic vortex provided that no mixing occurs through the vortex boundary. This new measure has many advantages over previous stratospheric ozone depletion indices. The conventional ozone mass deficit omits large amounts of depleted mass of ozone, and the onset of ozone depletion does not coincide with the timing of when sunlight first reaches areas of polar stratospheric clouds as expected from theory. Chemical ozone loss derived with a tracer-tracer correlation technique depends on ozone and passive tracer profile measurements which are not as readily available as the total column ozone fields required for the new ozone mass deficit presented in this thesis. As such, the new ozone depletion measure combines the simplicity of the old ozone mass deficit index with higher accuracy of the actual amount of chemically depleted stratospheric ozone. Furthermore, when applying the new definition of ozone mass deficit to chemistry-climate model outputs, model intercomparisons should become easier to interpret because biases in the models can be avoided. Based on theory and understanding of the coupling of chemistry and dynamics in the Antarctic stratosphere, two semi-empirical models were developed to describe the intra-seasonal evolution of chlorine activation and ozone depletion. Regression of the models against chlorine monoxide and ozone mass deficit from observations results in coefficients that capture key sensitivities in the real atmosphere. The seasonal evolution of ozone mass deficit can be described with these coefficients and readily available meteorological fields (temperature and wind fields). The predictive capability of these models was demonstrated for 2005 and 2006. Given temperature and wind fields, which for example can be obtained from general circulation models, these models can predict the size and depth of the Antarctic ozone hole. Important applications of the semi-empirical models could be chemistry-climate model validation by comparing the sensitivities from observations and models which may provide new insights into potential sources of differences in chemistry-climate model projections of Antarctic ozone depletion. Furthermore, projection of the inter-annual and intra-seasonal evolution of the Antarctic ozone hole into the future can help to assess the potential recovery of the Antarctic ozone hole.
38
Koroleva, Van Do Mai. "Control of spin dynamics for applications in Nuclear Magnetic Resonance." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11137.
Full textAbstract:
Sophisticated electromagnetic pulse sequences that control spin dynamics have been developed in Nuclear Magnetic Resonance (NMR) over the last few decades. However, due to more and more demanding criteria, such as unknown parameters, larger bandwidths, higher signal to noise ratio (SNR), less power consumption, etc., new pulse sequences are constantly needed. This thesis presents new pulse sequences for several important applications of NMR.Engineering and Applied Sciences
39
Cai, Mingchao. "Modeling and numerical simulation for the coupling of surface flow with subsurface flow /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MATH%202008%20CAI.
Full text
40
Liu, Xiao. "Optical Characterization of Dynamic Exchange Coupling Interaction in Ferromagnetic Heterostructures." W&M ScholarWorks, 2019. https://scholarworks.wm.edu/etd/1582642582.
Full textAbstract:
This thesis presents the optical characterization of interfacial exchange coupling interaction in ferromagnetic bilayer heterostructures. Both static and dynamic magnetic response are investigated in the exchange-coupled Co2FeAl/(Ga,Mn)As bilayer system using static magneto-optical Kerr effect (MOKE) and time-resolved magneto optical Kerr effect (TRMOKE) techniques. The goal of this thesis is to understand the underlying physics of the interfacial exchange coupling effect on the ultrafast spin dynamics in a ferromagnetic metal/ferromagnetic semiconductor bilayer heterostructure. Our finding provides a viable pathway for designing advanced semiconductor spintronic devices for ultrafast low-power spin manipulation. First, a significant enhancement of the excitation efficiency of coherent magnetization precession is observed in the ferromagnetically exchangecoupled Co2FeAl/(Ga,Mn)As bilayer heterostructures at temperatures below the Curie temperature of (Ga,Mn)As, TC = 50 K, under photoexcitation of lowfluence, near-infrared pump pulses. The coherent magnetization precession persists to room temperature, indicating that proximity-induced ferromagnetism plays an important role in the optical excitation mechanism. A subsequent simulation of the temperature-dependent precession amplitude and frequency behavior is performed based on the Landau-Lifshitz-Gilbert (LLG) equation, suggesting that the high-efficiency excitation mechanism can be attributed to the modulation of the exchange coupling field at the interfacial area, which is induced by the emergence of the dynamic exchange coupling effect between the precessing magnetizations in the two ferromagnets. Second, the Gilbert damping property of the magnetization precession in the Co2FeAl/(Ga,Mn)As bilayer system is studied. At temperatures below the Curie temperature of (Ga,Mn)As, TC = 50 K, ultrafast pump excitation creates a counter-precessing, exchange-coupled mode in the ferromagnetic bilayer. The precessing magnetization in the Co2FeAl layer transfers a pure spin current directly into the (Ga,Mn)As layer at a certain intensity of external magnetic field where the Fe(Co) spins and the Mn spins precess at the same frequency. A photo-induced enhancement of the Gilbert damping constant α is observed, indicating that spin-angular momentum is transferred at the resonance magnetic fields. This can be attributed to the effect of the interfacial dynamic exchange coupling interaction between the precessing magnetizations in two ferromagnetic layers. A corresponding phase shift of the magnetization precession is also observed at the resonance field where the Gilbert damping peak appears.
41
Toner, David Lawrence Kinnersley. "Concentration oscillations in single cells : the roles of intracellular noise and intercellular coupling." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8902.
Full textAbstract:
Concentration oscillations are a ubiquitous characteristic of intracellular dynamics. The period of these oscillations can vary from few seconds to many hours, well known examples being calcium oscillations (seconds to minutes), glycolytic oscillations (minutes) and circadian rhythms (1 day). Considerable advances into understanding the mechanisms and functionality of concentration oscillations have been made since glycolytic oscillations were observed in the late 1950s, and mathematical methods have been an essential part of this process. With increasing ability to experimentally measure oscillations in single cells as well as in cell ensembles, the gold standard of modelling is to provide tools that can elucidate how the system-wide dynamics in complex organisms emerge from a system of single cells. Both abstract and detailed mechanistic models are complementary in the insight they can bring, and for networks of coupled cells considerations such as intrinsic intracellular noise, cellular heterogeneity and coupling strength are all expected to play a part. Here, we investigate separately the potential roles played by intrinsic noise arising from finite numbers of interacting molecules and by coupling among cellular oscillators. Regarding the former, it is well known that internal or molecular noise induces concentration oscillations in chemical systems whose deterministic models exhibit damped oscillations. We show, using the linear-noise approximation of the chemical master equation, that noise can also induce oscillations in biochemical systems whose deterministic descriptions admit no damped oscillations, i.e., systems with a stable node. This non-intuitive phenomenon is remarkable since, unlike noise-induced oscillations in systems with damped deterministic oscillations, it cannot be explained by noise excitation of the deterministic resonant frequency of the system. We here prove the following general properties of stable-node noise-induced oscillations for systems with two species: (i) the upper bound of their frequency is given by the geometric mean of the real eigenvalues of the Jacobian of the system, (ii) the upper bound of the Q-factor of the oscillations is inversely proportional to the distance between the real eigenvalues of the Jacobian, and (iii) these oscillations are not necessarily exhibited by all interacting chemical species in the system. The existence and properties of stable-node oscillations are verified by stochastic simulations of the Brusselator, a cascade Brusselator reaction system, and two other simple chemical systems involving autocatalysis and trimerization. We also show that external noise induces stable node oscillations with different properties than those stimulated by internal noise. Having demonstrated and explored this non-intuitive effect of noise, we extend the work to investigate the phenomenon of noise induced oscillations in cellular reaction systems characterised by the ‘bursty’ production of one or more species. Experiments have shown that proteins are typically translated in sharp bursts and similar bursty phenomena have been observed for protein import into subcellular compartments. We investigate the effect of such burstiness on the stochastic properties of downstream pathways by considering two identical systems with equal mean input rates, except in one system molecules (e.g., proteins) are input one at a time and in the other molecules are input in bursts according to some probability distribution. We find that the stochastic behaviour falls in three categories: (i) both systems display or do not display noise-induced oscillations; (ii) the non-bursty input system displays noiseinduced oscillations whereas the bursty input system does not; (iii) the reverse of (ii). We derive necessary conditions for these three cases to classify pathways involving autocatalysis, trimerization and genetic feedback loops. Our results suggest that single cell rhythms can be controlled by regulation of burstiness in protein production. We go on to investigate roles played by intercellular coupling in whole organ-level oscillations with an experimental analysis of circadian rhythms in Arabidopsis thaliana †. Circadian clocks in animals are known to be tightly coupled among the cells of some tissues, and this coupling profoundly affects cellular rhythmicity. However, research on the clock in plant cells has largely ignored intercellular coupling. Our research group used luciferase reporter gene imaging to monitor circadian rhythms in leaves of Arabidopsis thaliana plants, with both a lower resolution, high throughput method and a high-resolution (cellular level), lower throughput method. Leaves were grown and imaged in a variety of light conditions to test the relative importance of intercellular coupling and cellular coupling to the environmental signal. We analysed the high throughput data and described the circadian phase by the timing of peak expression. Leaves grown for three weeks without entrainment reproducibly showed spatio-temporal waves of gene expression, consistent with intercellular coupling. A range of patterns was observed among the leaves, rather than a unique spatio-temporal pattern, although some patterns were more often observed. All of the measured leaves exposed to lightdark entrainment cycles had fully synchronised rhythms, which could desynchronise rather quickly when placed in a non-entraining environment (i.e., constant light conditions). After four days in constant light some of these leaves were as desynchronised as leaves grown without any rhythmic input, as described by the phase coherence across the leaf. The same fast transition was observed in the reverse experimental scenario, i.e., applying light-dark cycles to leaves grown in constant light resulted in full synchronisation within two to four days. From these results we conclude that single-cell circadian oscillators were coupled far more strongly to external light-dark cycles than to the other cellular oscillators. Leaves did not spontaneously completely desynchronise, which is consistent with a presence of intercellular coupling among heterogeneous clocks. We also developed a methodology, based on the notion of two functional spatial scales of expression across the leaf, to analyse the high-resolution microscope data and determine whether there is a difference in the phase of circadian expression between vein cells and mesophyll cells in the leaf. The result from a single leaf suggests that the global phase wave dominates the phase behaviour but that there are small delays in the veins compared to their nearby mesophyll cells. This result can be validated by applying the methodology developed here to new microscope leaf data which is currently being collected in the research group. † This work was performed as a collaboration between David Toner (DT) and Benedicte Wenden (BW). BW designed and carried out the experiments, DT performed the data analysis and led on data visualisation.
42
Geier, Kevin Thomas. "Probing Dynamics and Correlations in Cold-Atom Quantum Simulators." Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/351120.
Full textAbstract:
Cold-atom quantum simulators offer unique possibilities to prepare, manipulate, and probe quantum many-body systems. However, despite the high level of control in modern experiments, not all observables of interest are easily accessible. This thesis aims at establishing protocols to measure currently elusive static and dynamic properties of quantum systems. The experimental feasibility of these schemes is illustrated by means of numerical simulations for relevant applications in many-body physics and quantum simulation. In particular, we introduce a general method for measuring dynamical correlations based on non-Hermitian linear response. This enables unbiased tests of the famous fluctuation-dissipation relation as a probe of thermalization in isolated quantum systems. Furthermore, we develop ancilla-based techniques for the measurement of currents and current correlations, permitting the characterization of strongly correlated quantum matter. Another application is geared towards revealing signatures of supersolidity in spin-orbit-coupled Bose gases by exciting the relevant Goldstone modes. Finally, we explore a scenario for quantum-simulating post-inflationary reheating dynamics by parametrically driving a Bose gas into the regime of universal far-from-equilibrium dynamics. The presented protocols also apply to other analog quantum simulation platforms and thus open up promising applications in the field of quantum science and technology.I simulatori quantistici ad atomi freddi offrono possibilità uniche per preparare, manipolare e sondare sistemi quantistici a molti corpi. Tuttavia, nonostante l'alto livello di controllo raggiunto negli esperimenti moderni, non tutte le osservabili di interesse sono facilmente accessibili. Lo scopo di questa tesi è quello di stabilire protocolli per misurare delle proprietà statiche e dinamiche dei sistemi quantistici attualmente inaccessibili. La fattibilità sperimentale di questi schemi è illustrata mediante simulazioni numeriche per applicazioni rilevanti nella fisica a molti corpi e nella simulazione quantistica. In particolare, introduciamo un metodo generale per misurare le correlazioni dinamiche basato su una risposta lineare non hermitiana. Ciò consente test imparziali della famosa relazione fluttuazione-dissipazione come sonda di termalizzazione in sistemi quantistici isolati. Inoltre, sviluppiamo tecniche basate su ancilla per la misura di correnti e correlazioni di corrente, consentendo la caratterizzazione della materia quantistica fortemente correlata. Un'altra applicazione è orientata a rivelare l'impronta della supersolidità nei gas Bose con accoppiamento spin-orbita eccitando il corrispondente modo di Goldstone. Infine, esploriamo uno scenario per la simulazione quantistica della dinamica di riscaldamento post-inflazione modulando parametricamente un gas Bose e portandolo nel regime della dinamica universale lontana dall'equilibrio. I protocolli presentati si applicano anche ad altre piattaforme di simulazione quantistica analogica e aprono quindi applicazioni promettenti nel campo della scienza e della tecnologia quantistica.
Quantensimulatoren auf Basis ultrakalter Atome eröffnen einzigartige Möglichkeiten zur Präparation, Manipulation und Untersuchung von Quanten-Vielteilchen-Systemen. Trotz des hohen Maßes an Kontrolle in modernen Experimenten sind jedoch nicht alle interessanten Observablen auf einfache Weise zugänglich. Ziel dieser Arbeit ist es, Protokolle zur Messung aktuell nur schwer erfassbarer statischer und dynamischer Eigenschaften von Quantensystemen zu etablieren. Die experimentelle Realisierbarkeit dieser Verfahren wird durch numerische Simulationen anhand relevanter Anwendungen in der Vielteilchenphysik und Quantensimulation veranschaulicht. Insbesondere wird eine allgemeine Methode zur Messung dynamischer Korrelationen basierend auf der linearen Antwort auf nicht-hermitesche Störungen vorgestellt. Diese ermöglicht unabhängige Tests des berühmten Fluktuations-Dissipations-Theorems als Indikator der Thermalisierung isolierter Quantensysteme. Darüber hinaus werden Verfahren zur Messung von Strömen und Strom-Korrelationen mittels Kopplung an einen Hilfszustand entwickelt, welche die Charakterisierung stark korrelierter Quantenmaterie erlauben. Eine weitere Anwendung zielt auf die Enthüllung spezifischer Merkmale von Supersolidität in Spin-Bahn-gekoppelten Bose-Einstein-Kondensaten ab, indem die relevanten Goldstone-Moden angeregt werden. Schließlich wird ein Szenario zur Quantensimulation post-inflationärer Thermalisierungsdynamik durch die parametrische Anregung eines Bose-Gases in das Regime universeller Dynamik fern des Gleichgewichts erschlossen. Die dargestellten Protokolle lassen sich auch auf andere Plattformen für analoge Quantensimulation übertragen und eröffnen damit vielversprechende Anwendungen auf dem Gebiet der Quantentechnologie.
43
Ickes, Jacob. "Improved Helicopter Rotor Performance Prediction through Loose and Tight CFD/CSD Coupling." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1408476196.
Full text
44
Duncan, Gregory S. "Milling dynamics prediction and uncertainty analysis using receptance coupling substructure analysis." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015544.
Full text
45
Ghoneim, Ayman Ahmed Sabry Abdel Rahman Information Technology & Electrical Engineering Australian Defence Force Academy UNSW. "Local-global coupling in strategy games: extracting signatures and unfolding dynamics." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Information Technology and Electrical Engineering, 2008. http://handle.unsw.edu.au/1959.4/38723.
Full textAbstract:
Complexity underlying life is largely governed by the dynamics of interaction within and between living and nonliving entities. Evolutionary strategy games are extensively used in modelling and understanding complex behaviors in a wide range of fields including theoretical biology, social interactions, economics, politics, defense and security. Strategy games are said to distill the key elements of interactions be- tween real-world entities and organizations - one of the challenges lies in determining the mapping of complex real life situation dynamics to that of a certain game. That leads us to the two major research questions outlined below. In this thesis, we are taking evolutionary games a step further to investigate the interplay between local and global dynamics, where local dynamics are repre- sented by locally pairwise interactions among the population's players governed by the Iterated Prisoner's Dilemma game. To represent the global dynamics, two main modelling ideas are proposed, in the first model; a mixed evolutionary game is in- troduced where players are competing globally on the population level in a minority game. The interplay between local and global dynamics in this model represents the interplay between different scopes of competition between the same players. Sec- ondly, we introduce a model for studying the effect of sharing global information concerning a population of players, shedding light on how global information can alter the emerging dynamics of local interactions. Furthermore, the thesis addresses the question of whether games - with different dynamics - have unique signatures (footprints) that can be used in recognizing and differentiating among them, and whether these footprints are consistent along the evolutionary path of these games. We show here that by building winning networks between players, and determining network motifs of these winning networks, we can obtain motifs' counts signals that are sufficient to categorize and recognize the game's utility matrix used by the players. We also demonstrate that these footprints - motifs' counts - are consistent along the evolutionary path of the games, due to a hyper-cyclic behavior that exists between strategies. Finally, we show that this approach is capable of identifying whether a certain population is driven by local dynamics or both local and global dynamics using the proposed mixed game.
46
Sandmann, Constantin Marius [Verfasser]. "Dynamics models and coupling in medical 4D imaging / Constantin Marius Sandmann." Lübeck : Zentrale Hochschulbibliothek Lübeck, 2017. http://d-nb.info/1142037606/34.
Full text
47
Schmid, Bernhard [Verfasser]. "Mode-coupling theory: generalizations, high dimensions and microscopic dynamics / Bernhard Schmid." Mainz : Universitätsbibliothek Mainz, 2011. http://d-nb.info/1026802563/34.
Full text
48
Emery, Michael Aaron. "The effects of torsional-lateral coupling on the dynamics of a gear coupled rotor." Texas A&M University, 2005. http://hdl.handle.net/1969.1/4727.
Full textAbstract:
This thesis focuses on the torsional-lateral interactions seen in gear coupled rotors. Of
particular interest are cases where the torsional stiffness parameters affect the lateral
critical speeds and where lateral stiffness and damping parameters affect torsional
critical speeds and amplitudes. A common procedure for critical speed calculations has
been to solve lateral and torsional systems separately. This procedure is tested through
an eigenvalue analysis. It is shown in this thesis, however, that torsional-lateral
interactions play major roles in each other's critical speeds. Some research has
seemingly uncoupled two lateral degrees of freedom from the gear system by choosing
bearing forces and a coordinate system pointing along the line of action and normal to
the line of action. This simplification method has been tested for cases when the lateral
bearing stiffness becomes asymmetric. The force generated by a rotating imbalance also
creates a variable moment arm as the center of mass rotates about the geometric center
of the gear. This variable moment arm is commonly neglected, but is included in the last
case study and its effects are displayed in the results section of this thesis.
49
Shim, Sangyun. "Coupled dynamic analysis of floating offshore wind farms." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2564.
Full text
50
Ruscher, Céline. "The Voronoi liquid : a new model to probe the glass transition." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE027/document.
Full textAbstract:
Comprendre l’origine microscopique du ralentissement de la dynamique au voisinage de la transition vitreuse reste l’un des problèmes fondamentaux de la physique de la matière condensée. Au cours de ce travail, nous introduisons un nouveau modèle de liquide, appelé liquide de Voronoï, et dont les interactions sont directement reliées aux propriétés géométriques des tessellations de Voronoï. Pour cette classe de liquides, les interactions sont à plusieurs corps et agissent de telle sorte que le système est toujours sous tension tout en restant stable. Le but de ce travail est d’étudier un mélange binaire du liquide de Voronoï et de voir de quelles façons ces interactions exotiques affectent le scénario habituel de la transition vitreuse. Tout au long de ce travail, nous caractérisons le liquide de Voronoï bidisperse théoriquement et par le biais des simulations numériques. Nous proposons également des comparaisons avec des liquides de Lennard-Jones surfondus bien décrit dans la littératureUnderstanding the origin of the important slowing down of the dynamics near glass transition is still one of the remaining fundamental problems of condensed matter physics. During this work we introduced a brand-new model of liquids named Voronoi liquid, whose interactions are directly related to the geometrical properties of Voronoi tessellations. For these class of liquids interactions are intrinsically manybody and act in such a way that the liquid is always under tension but remains stable. The aim of this work is to use a binary mixture of the Voronoi liquid to see to what extend these exotic interactions may affect the classical scenario of glass transition. Throughout this work we characterize theoretically and by mean of numerical simulation the bidisperse Voronoi liquid. Comparisons with well-known Lennard-Jones glass formers are systematically performed