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Wozniak, Trevor Mathew. "Four Fluctuations for Chamber Ensemble or Chamber Orchestra." Kent State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=kent1291050505.
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Barthélemy, Jean. "Four essays on macroeconomic fluctuations : trends, cycles and regime switching in rationalexpectations models." Paris, EHESS, 2011. http://www.theses.fr/2011EHES0016.
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Cette thèse se divise en deux grandes parties. La première partie est consacrée à la décomposition cycle-tendance des fluctuations macroéconomiques. Cette partie contient deux essais. Le premier estime un modèle DSGE en économie fermée, le second en économie ouverte. Les deux intègrent des chocs persistants afin de reproduire les fluctuations de long terme. La deuxième partie contient également deux essais et traite des changements de régime. Le premier essai explore la possibilité d'une réaction non-linéaire de la BCE à la croissance de la monnaie dans un modèle DSGE; tandis que le second étend les méthodes à perturbations afin de résoudre les modèles à anticipations rationnelles et changements de régime dépendant de l'état de l'économieThis dissertation is divided into two parts. The first part examines the decomposition of macroeconomic fluctuations into trends and cycles. This part consists of two essays that estimate DSGE models in presence of permanent shocks, in closed and in open economy respectively. The second part deals with regime switching and consists of two essays as well. The first of these two essays assesses the existence of a non-linear reaction from the ECB to money growth in an estimated DSGE model whereas the second extends the perturbation approach to solve Rational Expectations models with state-dependent regime switching
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Embrey, Christopher. "Controlling local quantum fluctuations of light using four-wave mixing in an atomic vapour." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6440/.
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The spatial character of the noise on a light field affects its usefulness for imaging. Multi-spatial-mode (MSM) squeezed light has noise below the quantum noise limit in multiple spatial modes, and can be used for super resolution imaging. The generation of such light has long been an experimental goal within the field of quantum optics. This work introduces the theory behind the generation of squeezed light, and its measurement using a homodyne detector. A four-wave mixing process in a rubidium 85 vapour is used to experimentally generate squeezed light. The properties of this squeezed light are investigated, through the use of homodyne detection with a bichromatic LO. This thesis further investigates how the squeezed quadrature changes from amplitude to phase over a range of 40 MHz. The MSM nature of a squeezed light field is directly investigated. The field is shown to contain at least 75 squeezed spatial modes in the frequency domain, each squeezed at a level of up to -2.5 dB. This thesis develops techniques to measure the spatial character of noise on a light field in the time domain. These are promising techniques for the analysis of the MSM nature of a squeezed light in the time domain.
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Callahan, B. J. "Modelling and evaluation of two-stroke and four-stroke engines with in-cycle speed fluctuations." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411036.
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Pedurand, Richard. "Instrumentation for Thermal Noise Spectroscopy." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1356.
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La résolution des interféromètres gravitationnels est limitée par le mouvement Brownien - ou bruit thermique - de leurs miroirs dans la partie centrale de leur bande de détection, entre 10Hz et 1kHz. La répartition en fréquence de ce bruit thermique est dictée par les mécanismes de dissipation d'énergie mécanique à l'origine de cette vibration aléatoire, en accord avec le théorème fluctuation-dissipation. Cette dissipation provient principalement des revêtements optiques déposés sur les miroirs pour leur donner leur réflectivité. Dans le but de réduire le bruit thermique, une nouvelle génération de détecteurs d'ondes gravitationnelles employant des miroirs refroidis à température cryogénique a été proposée. Le développement de nouveaux matériaux optiques en couche mince à faible dissipation mécanique, opérant à la fois à température ambiante et température cryogénique, demande donc de nouveaux outils expérimentaux. L'objet principal de cette thèse est la construction d'un nouvel instrument, le CryoQPDI, qui consiste en l'association d'un interféromètre haute résolution et d'un cryostat basé sur un refroidisseur pulse tube. Il est capable de mesurer directement le mouvement Brownien d'un microlevier entre 300 K et 7 K. En combinant des mesures effectuées sur un microlevier avant et après le dépôt d'une couche mince, il est possible de caractériser la dissipation mécanique interne de cette couche mince. Cet instrument participera ainsi à l'optimisation des revêtements optiques des futurs interféromètres gravitationnels, dans le but de minimiser les nuisances dues au bruit thermiqueThe resolution limit of gravitational wave interferometers is set by their mirrors' Brownian motion – or thermal noise - in the central part of their detection band, from 10Hz to 1kHz. This thermal noise frequency distribution is given by the mechanical energy dissipation mechanisms it originates from, in agreement with the fluctuation-dissipation theorem. This dissipation mainly derives from the optical coatings deposited on the mirrors to give them their reflectivity. To reduce this thermal noise, a new generation of gravitational wave detectors employing mirrors cooled to cryogenic temperature has been suggested. The development of new optical thin-film materials with low mechanical dissipation, operating at both room and cryogenic temperatures, therefore requires new experimental tools. The main object of this thesis is the construction of a new instrument, the CryoQPDI, which is an association between a high-resolution interferometer and a cryostat based on a pulse tube cooler. It can directly measure the Brownian motion of a microcantilever between 300 K and 7 K. By combining measurements made on a microcantilever before and after the deposition of a thin film, it is possible to characterize the internal mechanical dissipation of this thin film. This instrument will eventually contribute to the optimisation of optical coatings of future gravitational wave detectors, aiming at minimizing the limitations due to thermal noise
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ROSA, VICTOR JORGE LIMA GALVAO. "STOCHASTIC HARMONIC MODEL FOR PRICE FLUCTUATIONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32379@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Consideramos o oscilador harmônico com amortecimento aleatório em presença de ruído externo. Os ruídos, representando perturbações externas e internas, são modelados pelo processo de Ornstein-Uhlenbeck ou ruído branco e pelo processo dicotômico ou ruído branco, respectivamente. Usando técnicas de sistemas dinâmicos, analisamos o valor médio e a dispersão da posição e da velocidade do oscilador harmônico estocástico, apresentando resultados analíticos e numéricos. Em particular, obtemos expressões para a expansão de baixa-ordem em relação ao tempo de correlação da perturbação interna, no caso da atuação do ruído dicotômico. Finalmente, usando o modelo de oscilador harmônico com amortecimento aleatório como referência, investigamos a série intradiária de preços do mercado brasileiro.
We consider the random damping harmonic oscillator in presence of external noise. The noises, representing external and internal perturbations, are modeled as an Ornstein-Uhlenbeck process or a white noise and as a dichotomous process or a white noise, respectively. Using dynamical systems tools, we analyze the expected value as well as the dispersion of the stochastic harmonic oscillator s position and velocity, presenting analytical and numerical results. In particular, we also provide expressions for the low-order expansion in the correlation time of the internal perturbation, in the case the dichotomous noise is at play. Using random damped harmonic oscillator model as a reference, we conclude by investigating the intra-day Brazilian stock price series.
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Speranza, Antony John. "Stochastic congruence equations for spacetime fluctuations." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78491.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 45-46).
This work considers some implications of viewing gravity as an emergent force. In such a viewpoint, general relativity arises as the thermodynamic limit of some microscopic theory. As such, one would expect the macroscopic variables such as the curvature tensors to fluctuate about their mean. This thesis presents a method for analyzing the effects of curvature fluctuations on spacetime thermodynamics. This is done by examining the evolution equations for time-like and null congruences, and recasting them as stochastic differential equations. The purpose of viewing the congruence evolution equations as stochastic is in the spirit of nonequilibrium thermodynamics, and may lead to an application of the fluctuation-dissipation theorem to spacetime. It is expected that this reformulation of the congruence equations will lead to further insights on the effects of fluctuations in general relativity.
by Antony John Speranza.
S.B.
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Gundermann, Julia. "The Crooks Fluctuation Theorem Derived for Two-Dimensional Fluid Flow and its Potential to Improve Predictions." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-156748.
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The weather dynamics are significantly determined by the motion of the atmosphere and the ocean. This motion is often turbulent, characterized by fluctuations of the flow velocity over wide spatial and temporal scales. This fact, besides limited observability and inaccurate models, impedes the predictability of quantities such as the velocity of winds, which are relevant for the everyday life. One is always interested in improving such predictions - by employing better models or obtaining more information about the system.
The Crooks fluctuation theorem is a relation from nonequilibrium thermodynamics, which has its typical applications in nanoscale systems. It quantifies the distribution of imposed work in a process, where the system is pushed out of thermal equilibrium. This distribution is broadened due to the fluctuations of the microscopic degrees of freedom in the system.
The fluctuations of the velocity field in turbulent flow suggest the derivation of an analogy of Crooks' theorem for this macroscopic system. The knowledge about the validity of such a relation is additional information, which one in reverse could use to improve predictions about the system. In this thesis both issues are addressed: the derivation of the theorem, and the improvement of predictions.
We illustrate the application of Crooks' theorem to hydrodynamic flow within a model of a two-dimensional inviscid and incompressible fluid field, when pushed out of dynamical equilibrium. The flow on a rectangular domain is approximated by the two-dimensional vorticity equation with spectral truncation. In this setting, the equilibrium statistics of the flow can be described through a canonical ensemble with two conserved quantities, kinetic energy and enstrophy. To perturb the system out of equilibrium, we change the shape of the domain according to a protocol, which changes the kinetic energy but leaves the enstrophy constant. This is interpreted as doing work to the system. Evolving along a forward and its corresponding backward process, we find that the distributions of the work performed in these processes satisfy the Crooks relation with parameters derived from the canonical ensembles.
We address the issue of prediction in this thesis in a concrete setting: There are examples where the distributions of a variable in the forward and the backward process collapse into one, hence Crooks' theorem relates the distribution of one variable with itself. For a finite data set drawn from such a distribution, we are interested in an estimate of this variable to exceed a certain threshold. We demonstrate that, using the knowledge about Crooks' relation, forecast schemes can be proposed which improve compared to a pure frequency estimate on the data set. The findings are illustrated in three examples, studies of parameters such as exceedance threshold and data set size are presented.
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Etminan, S. "Simulation of high-speed static reactive compensation for suppression of power system disturbances." Thesis, University of Sunderland, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253748.
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Gundermann, Julia. "The Crooks Fluctuation Theorem Derived for Two-Dimensional Fluid Flow and its Potential to Improve Predictions." Doctoral thesis, Technische Universität Dresden, 2014. https://tud.qucosa.de/id/qucosa%3A28433.
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The weather dynamics are significantly determined by the motion of the atmosphere and the ocean. This motion is often turbulent, characterized by fluctuations of the flow velocity over wide spatial and temporal scales. This fact, besides limited observability and inaccurate models, impedes the predictability of quantities such as the velocity of winds, which are relevant for the everyday life. One is always interested in improving such predictions - by employing better models or obtaining more information about the system.
The Crooks fluctuation theorem is a relation from nonequilibrium thermodynamics, which has its typical applications in nanoscale systems. It quantifies the distribution of imposed work in a process, where the system is pushed out of thermal equilibrium. This distribution is broadened due to the fluctuations of the microscopic degrees of freedom in the system.
The fluctuations of the velocity field in turbulent flow suggest the derivation of an analogy of Crooks' theorem for this macroscopic system. The knowledge about the validity of such a relation is additional information, which one in reverse could use to improve predictions about the system. In this thesis both issues are addressed: the derivation of the theorem, and the improvement of predictions.
We illustrate the application of Crooks' theorem to hydrodynamic flow within a model of a two-dimensional inviscid and incompressible fluid field, when pushed out of dynamical equilibrium. The flow on a rectangular domain is approximated by the two-dimensional vorticity equation with spectral truncation. In this setting, the equilibrium statistics of the flow can be described through a canonical ensemble with two conserved quantities, kinetic energy and enstrophy. To perturb the system out of equilibrium, we change the shape of the domain according to a protocol, which changes the kinetic energy but leaves the enstrophy constant. This is interpreted as doing work to the system. Evolving along a forward and its corresponding backward process, we find that the distributions of the work performed in these processes satisfy the Crooks relation with parameters derived from the canonical ensembles.
We address the issue of prediction in this thesis in a concrete setting: There are examples where the distributions of a variable in the forward and the backward process collapse into one, hence Crooks' theorem relates the distribution of one variable with itself. For a finite data set drawn from such a distribution, we are interested in an estimate of this variable to exceed a certain threshold. We demonstrate that, using the knowledge about Crooks' relation, forecast schemes can be proposed which improve compared to a pure frequency estimate on the data set. The findings are illustrated in three examples, studies of parameters such as exceedance threshold and data set size are presented.
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Newey, Scott. "Population fluctuations in mountain hares : a role for parasites? /." Umeå : Swedish University of Agricultural Sciences, 2005. http://diss-epsilon.slu.se/archive/00000808/.
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Thesis (doctoral)--Swedish University of Agricultural Sciences, 2005.Appendix includes reproductions of six papers and manuscripts co-authored with others. Includes bibliographical references. Also issued electronically via World Wide Web in PDF format; online version lacks appendix of papers.
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Newey, Scott-John. "Population fluctuations in mountain hares : a role for parasites? /." Umeå : Dept. of Animal Ecology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200526.pdf.
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Nguyen, Jennifer Kim Thu. "Rapid nutrient fluctuations and their implications for bacterial growth." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129902.
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Thesis: Ph. D. to the Microbiology Graduate Program, Massachusetts Institute of Technology, Department of Biology, February, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references.
Bacteria, like all lifeforms, rely on resource acquisition for growth, and the tight coupling between bacterial growth physiology and nutrient availability has long been observed. When nutrient environments shift on timescales of hours, days or seasons, bacteria adapt to a physiological steady state characteristic of the new environment. However, the microscopic heterogeneity inherent of bacterial habitats implies that nutrient concentrations often fluctuate on timescales of seconds or minutes, timescales too rapid for bacteria to reach the steady state corresponding to the instantaneous environment. Despite this, steady-state growth is expansively used as a model to understand bacterial physiology, even in dynamic environments. In this Thesis, I experimentally demonstrate that bacterial growth in rapidly fluctuating environments cannot be predicted from steady-state growth models. Using a custom microfluidic device coupled with single-cell microscopy and image analysis, I quantified the growth physiology of thousands of individual E. coli cells experiencing either (1) periodic nutrient fluctuations on timescales ranging from 30 seconds to 60 minutes or (2) steady environments of equal average nutrient concentration. Growth rate in fluctuating environments was 16-50% smaller than in comparable steady environments, corresponding to a 10²- to 10⁸-fold loss in daily biomass production. However, cells grown in fluctuating environments had a growth advantage in the minutes after a nutrient shift over cells grown in steady environments. Cell size also displayed deviations from steady-state trends, with a particular fluctuating timescale producing cell sizes 54% larger than expected. These significant deviations from steady-state predictions highlight the importance of nutrient timescale and challenges our classical understanding of bacterial growth.
by Jennifer Kim Thu Nguyen.
Ph. D. to the Microbiology Graduate Program
Ph.D.totheMicrobiologyGraduateProgram Massachusetts Institute of Technology, Department of Biology
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Windridge, David. "A fluctuation analysis for optical cluster galaxies." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302173.
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Zeileis, Achim, and Kurt Hornik. "Generalized M-Fluctuation Tests for Parameter Instability." SFB Adaptive Information Systems and Modelling in Economics and Management Science, WU Vienna University of Economics and Business, 2003. http://epub.wu.ac.at/716/1/document.pdf.
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A general class of fluctuation tests for parameter instability in an M-estimation framework is suggested. The tests are based on partial sum processes of M-estimation scores for which functional central limit theorems are derived under the null hypothesis of parameter stability and local alternatives. Special emphasis is given to parameter instability in (generalized) linear regression models and it is shown that the introduced M-fluctuation tests contain a large number of parameter instability or structural change tests known from the statistics and econometrics literature. The usefulness of the procedures is illustrated using artificial data and data for the German M1 money demand, historical demographic time series from Großarl, Austria, and youth homicides in Boston.Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"
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Valdez-Balderas, Daniel. "Models for inhomogeneities and thermal fluctuations in two-dimensional superconductors." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180117179.
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Kaiser, Marcus. "Variational structures for dynamical fluctuations, in and out of equilibrium." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.767566.
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In this thesis, we investigate variational structures for fluctuations in Markov processes, with a particular focus on interacting particle systems (such as the simple exclusion process and the zero-range process). A great part of this thesis is devoted to time-reversal symmetry. We discuss the acceleration of convergence to the steady state for dissipative systems, where we revisit the fact that 'breaking detailed balance' accelerates the convergence to equilibrium and extend known results to the case of interacting particle systems and their hydrodynamic scaling limits. The theoretical findings are supported by simulations of independent particles and the zero-range process in one and two space dimensions. We further investigate a general Ψ-Ψ? structure for the Onsager-Machlup functional Φ, which can be used to represent several large-deviation rate functions for particle diffusions, Markov chains and Macroscopic Fluctuation Theory. We discuss a splitting of the thermodynamic force acting on the system in time-reversal symmetric and antisymmetric parts, for which we prove a 'generalised Hamilton-Jacobi orthogonality'. Finally, we apply this structure to a special class of interacting particle systems (which includes the simple-exclusion process and a large class of zero-range processes) and show how the individual terms of the Ψ-Ψ? structure converge to their hydrodynamic counterparts (as known from Macroscopic Fluctuation Theory).
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Romano, Pablo. "Markov Models for the Conformational Kinetics in DNA Breathing Fluctuations." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23126.
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As the genetic content is internally located within DNA duplexed form, it has long been hypothesized that DNA undergoes a series of thermally induced conformational changes that assist in protein recognition events. The biological mechanisms for protein-DNA interactions have long been sought after, as little is still known mechanistically about how these complexes form. To study the local contributions to these breathing modes several atomistic simulations of DNA oligonucleotides were generated and analyzed by statistical models to predict metastable conformational states, the system timescales, and the kinetic pathways between states.
In order to sample time-series DNA constructs, microsecond molecular dynamics (MD) simulation were performed. MD simulations provide atomstic resolution of macromolecules in explicit solvent and with modern computational workflows can extend well into microsecond timescales. While MD is a powerful tool, it creates a tremendous amount of time-dependent data. In recent years, Markov State Models (MSM), which project the dynamics of MD simulations onto discrete coordinates that follow a Markov chain, have become an invaluable tool to model and describe the kinetics of these large datasets. These models can be coarse-grained for chemical insight, however there does not yet exist a method which consistently and ``crisply'' describe the metastable barriers.
To address this, I developed a new method, called Gradient Adaptive Decomposition (GRAD), which optimizes the macrostate model by refining borders with respect to the gradient along the free energy surface. The proposed method requires only a small number of initial microstates because it corrects for errors produced by limited number of seeds. Whereas many methods rely on fuzzy, or overlapping, partitions for proper statstical analysis of timescales, GRAD retains accuracy and crisp decomposition.
I present a workflow of GRAD refined MSM to analyze the long timescale MD simulations of DNA oligonucleotides to assess the stacking conformational dynamics of DNA. Evaluating the complex network of transitions accessible found evidence suggesting that chiral directed mechanisms are critical in how DNA bases unstack. I explore how these local effects may be significant to long timescale dynamics and the biological impact in relation to breathing fluctuations.
This dissertation includes unpublished co-authored material.
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Hulton, Sarah. "Renormalization of wave function fluctuations for a generalized Harper equation." Thesis, University of Stirling, 2006. http://hdl.handle.net/1893/208.
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A renormalization analysis is presented for a generalized Harper equation (1 + α cos(2π(ω(i + 1/2) + φ)))ψi+1 + (1 + α cos(2π(ω(i − 1/2) + φ)))ψi−1 +2λ cos(2π(iω + φ))ψi = Eψi. (0.1) For values of the parameter ω having periodic continued-fraction expansion, we construct the periodic orbits of the renormalization strange sets in function space that govern the wave function fluctuations of the solutions of the generalized Harper equation in the strong-coupling limit λ→∞. For values of ω with non-periodic continued fraction expansions, we make some conjectures based on work of Mestel and Osbaldestin on the likely structure of the renormalization strange set.
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Dorosz, Sven. "Fluctuation Relations for Stochastic Systems far from Equilibrium." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/26687.
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Fluctuations are of great importance in systems of small length and energy scales. Measuring the pulling of single molecules or the stationary fiow of mesospheres dragged through a viscous media enables the direct analysis of work and entropy distributions. These probability distributions are the result of a large number of repetitions of the same experiment. Due to the small scale of these experiments, the outcome can vary significantly from one realization to the next. Strong theoretical predictions exist, collectively called Fluctuation Theorems, that restrict the shape of these distributions due to an underlying time reversal symmetry of the microscopic dynamics. Fluctuation Theorems are the strongest existing statements on the entropy production of systems that are out of equilibrium.
Being the most important ingredient for the Fluctuation Theorems, the probability distribution of the entropy change is itself of great interest. Using numerically exact methods we characterize entropy distributions for various stochastic reaction-diffusion systems that present different properties in their underlying dynamics. We investigate these systems in their steady states and in cases where time dependent forces act on them. This study allows us to clarify the connection between the microscopic rules and the resulting entropy production. The present work also adds to the discussion of the steady state properties of stationary probabilities and discusses a non-equilibrium current amplitude that allows us to quantify the distance from equilibrium. The presented results are part of a greater endeavor to find common rules that will eventually lead to a general understanding of non-equilibrium systems.Ph. D.
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Leary, Stephen J. "Least-Squares methods with adjustable nodes for steady hyperbolic PDEs." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312565.
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Li, Wei. "An embedded energy storage system for attenuation of wind power fluctuations." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94995.
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Wind power has its unique characteristics other than conventional generators. As wind installations have been increasing rapidly over the world, uncontrollable wind power fluctuations are a major challenge for power systems to accommodate wind power. Embedding an energy storage system in a wind energy system can smooth the output of a wind turbine generator. This thesis proposes an embedded energy storage solution, addressing technology, topology, size, and control schemes to mitigate the adverse impacts of wind power fluctuations on power systems. A flow-battery supercapacitor hybrid storage system, which takes advantage of the two complementary technologies to provide both high energy and power capacities, is proposed for the wind applications. Cooperation of the two storage technologies also provides the system with other advantages, including fast response, high efficiency, and longer life-span. A novel control and energy management scheme, which aims to attenuate wind power fluctuations in a particular frequency range to improve the performance to size ratio, is applied to the hybrid system. Topology, configuration, and size are investigated through a benchmark system demonstrating feasibility. The operation under various situations show that the embedded storage solution can effectively attenuate the wind power fluctuations in the targeted frequency region, in terms of the fluctuation harmonic content, an index of fluctuation intensity of wind powers. The power quality, i.e., wind-induced local voltage variations and system frequency deviations, is improved. The simulation results are cross-validated using two different types of software and the prototype storage controller is verified through real time hardware-in-the-loop tests.Les caratéristiques de l'énergie éolienne sont uniques par rapport aux autres formes de génération conventionnelles. Avec la rapide augmentation des installations éoliennes au niveau mondial, les fluctuations incontrôlables d'énergie éolienne posent un problème majeur aux réseaux électriques qui veulent les intégrer. L'intégration d'un système de stockage d'énergie dans un parc éolien peut réduire les fluctuations de l'énergie produite. Cette thèse propose une solution pour atténuer ces fluctuations en utilisant un système de stockage d'énergie intégrée. Elle définit les technologies, topologies, dimensions et systèmes de commande. Un système hybride consistant en une batterie et un condensateur de grande capacité est proposé. Ces deux technologies complémentaires peuvent fournir à la fois de grandes quantités d'énergie et de puissance. Il en résulte un système qui offre au niveau du réseau électrique dautres avantages telles qu'une réponse rapide, un rendement élevé et une longue durée de vie. La nouvelle méthode de stockage d'énergie, qui vise à atténuer les fluctuations de puissance éolienne dans une gamme particulière de fréquence est réalisée. La topologie, la configuration, et le dimensionnement sont étudiés dans un réseau type. Les performances du stockage hybride sous diverses conditions d'opération montrent que la solution de stockage intégré peut efficacement atténuer les fluctuations de puissance éolienne dans la région de fréquence ciblée. Les variations locales de tension et les écarts de fréquence du système qui résultent des variations de la puissance éolienne sont atténuées. Les résultats de simulation sont validés en utilisant deux logiciels différents, et la commande du système de stockage est vérifiée sur un simulateur en temps réel. fr
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Hilderman, Trevor Lloyd. "Stochastic simulation of concentration fluctuations for an effective toxic load model." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq22604.pdf.
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Ewall-Wice, Aaron. "Chasing ancient demons : tools for measuring 21 cm fluctuations before reionization." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/115013.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 379-428).
In this thesis, we take the first steps towards measuring the fluctuations in HI emission before reionization which carry information on the first X-ray emitting compact objects and hot interstellar gas heated by the deaths of the first stars (ancient demons). First, we show that existing and planned interferometers are sensitive enough to place interesting constraints on the astrophysics of X-ray heating. Second, we obtain first upper limits on the pre-reionization fluctuations with the Murchison Widefield Array. We also use these measurements to explore the impact of low-frequency systematics, such as increased foreground brightness and the ionosphere. We discover that contamination by fine-scale frequency structure introduced by the instrument is the leading obstacle to measuring the 21 cm power spectrum before reionization. This motivates the design of a next-generation experiment, HERA, with acceptable levels of intrinsic spectral structure. We also perform a careful examination of whether traditional calibration strategies are sufficient to suppress instrumental spectral structure. We find that while existing calibration techniques have critical flaws, there exist promising strategies to overcome these deficiencies which we are now pursuing.
by Aaron Ewall-Wice.
Ph. D.
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Povoledo, Laura. "Dynamic stochastic general equilibrium models for the study of economic fluctuations." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1445796/.
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The thesis applies a variety of DSGE models to a set of problems whose common link is the analysis of economic fluctuations. The DSGE methodology is applied first to the analysis of economic fluctuations in Italy. After documenting' the crucial features of economic fluctuations in Italy (high volatility of hours worked and low volatility of employment), the thesis explains why the standard RBC model cannot reproduce them. Therefore, a modified RBC model with labour adjustment costs and an underground sector is introduced, and its performance analysed. Then, the thesis utilizes DSGE theory to study how fluctuations are transmitted within and between countries. Using a two-country general equilibrium model with monopolistic competition and sticky prices, it examines first the relative effects of a wide range (money, supply and demand) of shocks, and then the aggregate effects separately. The relative effects are the consequences of shocks for the relative price and quantities of domestic tradeables versus nontradeables. The main finding is that not only sector- specific shocks affect these relative prices and allocations, but also aggregate monetary shocks, thus contributing to explain why money has sectoral effects, as in the empirical literature. The aggregate effects are the consequences of shocks for the main macroeconomic variables. The analysis of the aggregate effects differs from the most recent literature because: 1) the role of critical parameters in the transmission is analysed simultaneously 2) the analysis is not confined to monetary shocks 3) supply and demand shocks are disaggregated by sector 4) the assumptions that the marginal productivity of labour may be decreasing, and that individuals cannot work in both sectors, are introduced. The aggregate effects of the shocks depend on the choice of parameters. The assump tion that individuals cannot work in both sectors leads to a lower elasticity of marginal costs with respect to output.
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Williams, Paul. "An investigation of neural networks for fault identification in the electricity supply industry." Thesis, Bangor University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261950.
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Mebrate, Netsanet Zerihun. "High order fluctuation splitting schemes for hyperbolic conservation laws." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/1346/.
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This thesis presents the construction, the analysis and the verification of a new form of higher than second order fluctuation splitting discretisation for the solution of steady conservation laws on unstructured meshes. This is an alternative approach to the two existing higher than second order fluctuation splitting schemes, which use submesh reconstruction (developed by Abgrall and Roe) and gradient recovery (developed by Caraemi) to obtain the loacl higher degree polynomials used to evaluate the fluctuation. The new higher than second order approach constructs the polynomial interpolant of the values of the dependent variables at an appropriate number of carefully chosen mesh nodes. As they stand, none of the higher than second order methods can guarantee the absence of spurious oscillations from the flow without the application of an additional smoothing stage. The implementation of a technique that removes unphysical oscillations (devised by Hubbard) as part of a new higher than second order approach will be outlined. The design steps and theoretical bases are discussed in depth. The new higher than second order approach is examined and analysed through application to a series of linear and nonlinear scalar problems, using a pseudo-time-stepping technique to reach steady state solution on two-dimensional structured and unstructured meshes. The results demonstrate its effectiveness in approximating the linear and nolinear scalar problems. This thesis also addresses the development and examination of a multistage high order (in space and time) fluctuation splitting scheme for two-dimensional unsteady scalar advection on triangular unstructured meshes. the method is similar in philosophy to that of multistep high order (in space and time) fluctuation splitting scheme for the approximation of time-dependent hyperbolic conservation laws. The construction and implementation of the high order multistage time-dependent method are discussed in detail and its performance is illustrated using several standard test problems. The multistage high order time-dependent method is evaluated in the context of existing fluctuation splitting approaches to modelling time-dependent problems and some suggestions for their future development are made. Results presented indicate that the multistage high orer method can produce a slightly more accurate solution than the multistep high order method.
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Bulnes, Cuetara Gregory. "Fluctuation theorem for quantum electron transport in mesoscopic circuits." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209435.
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Dans cette thèse nous étudions les propriétés statistique des courants dans des systèmes à l'échelle mésoscopique. Nous utilisons le formalisme de la statistique de comptage afin de caractériser les fluctuations de courant importantes à cette échelle. Celle-ci est obtenue en partant du Hamiltonien microscopique décrivant la dynamique des électrons sur le circuit considéré dans le régime quantique.Nous considérons deux modèles particuliers de circuits à deux canaux, chacun comportant deux électrodes. Le premier modèle étudié est constitué de deux plots quantiques en couplage capacitif, et chacun échangeant des électrons avec deux électrodes. Le deuxième modèle est quant à lui constitué d'un double plot quantique connecté à deux électrodes et modulant le courant dans un point quantique formé lui-même par la jonction de deux électrodes. Pour ces deux modèles, chaque canal est soumis à une différence de potentiel, ou force thermodynamique, générant des courants stationnaires fluctuants.
La statistique des courants pour ces deux modèles est obtenue en utilisant une équation maîtresse pour les probabilités d'occupation dans les plots quantiques et le nombre d'électrons transférés entre ceux-ci et les électrodes. Nous vérifions que la distribution de probabilité jointes des courants dans chaque canal ainsi obtenue vérifie un théorème de fluctuation dans la limite des temps long faisant intervenir les forces thermodynamique des deux canaux.
La question de l'émergence d'un théorème de fluctuation effectif pour la distribution de probabilité marginale du courant dans un des deux canaux est également investiguée. Nous montrons que dans la limite ou le rapport des courants est grande, un tel théorème de fluctuation effectif est satisfait individuellement pour le canal de plus faible courant comme observé expérimentalement. Ce théorème fait intervenir une affinité effective dépendante des forces thermodynamiques des deux canaux et des spécificités du modèle considéré. Son étude détaillée est faite pour les deux modèles mentionnés.
Par ailleurs, nous posons également la question de l'existence d'un théorème de fluctuation pour des temps de mesure finis. Nous montrons qu'en présence d'un théorème de fluctuation dans la limite de temps longs, un critère peut être énoncé sur la condition initiale des plots quantiques menant à un théorème de fluctuations à temps fini. Ce critère est également étendu au cas des théorèmes de fluctuations effectifs.
Finalement, nous faisons une étude thermodynamique du modèle composé d'un double plot quantique en présence de différences de potentiel électrique et de température entre les électrodes du circuit.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Pandey, Anamika [Verfasser]. "Meshfree Method for Fluctuating Hydrodynamics / Anamika Pandey." München : Verlag Dr. Hut, 2013. http://d-nb.info/1043892540/34.
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Kar, K. C. "Three-thermocouple technique for fluctuating temperature measurement." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403757.
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Knorr, Paul Octavius. "The case for high-order, pleistocene sea-level fluctuations in Southwest Florida." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001791.
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Fabiani, Silvia. "Technological change and output fluctuations : an empirical analysis for the G7 countries." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313897.
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Coad, D. Stephen. "Outcome-dependent randomisation schemes for clinical trials with fluctuations in patient characteristics." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:970a8103-24fc-496e-82c0-0645f2b4e9c4.
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A clinical trial is considered in which two treatments are to be compared. Treatment allocation schemes are usually designed to assign approximately equal numbers of patients to each treatment. The purpose of this thesis is to investigate the efficiency of estimation and the effect of instability in the response variable for allocation schemes which are aimed at reducing the number of patients who receive the inferior treatment. The general background to outcome-dependent allocation schemes is described in Chapter 1. A discussion of ethical and practical problems associated with these methods is presented together with brief details of actual trials conducted. In Chapter 2, the response to treatment is Bernoulli and the trial size is fixed. A simple method for estimating the treatment difference is proposed. Simulation results for a selection of allocation schemes indicate that the effect of instability upon the performance of the schemes can sometimes be substantial. A decision-theory approach is taken in Chapter 3. The trial is conducted in a number of stages and the interests of both the patients in the trial and those who will be treated after the end of the trial are taken into account. Using results for conditional normal distributions, analytical results are derived for estimation of the treatment difference for both a stable and an unstable normal response variable for three allocation schemes. Some results for estimation are also given for other responses. The problem of sequential testing is addressed in Chapter 4. With instability in the response variable, it is shown that the error probabilities for the test for a stable response variable can be approximately preserved by using a modified test statistic with appropriately-widened stopping boundaries. In addition, some recent results for estimation following sequential tests are outlined. Finally, the main conclusions of the thesis are highlighted in Chapter 5.
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Van, Zyl Verena Helen. "Searching for histogram patterns due to macroscopic fluctuations in financial time series." Thesis, Stellenbosch : University of Stellenbosch, 2007. http://hdl.handle.net/10019.1/3078.
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Thesis (MComm (Business Management))--University of Stellenbosch, 2007.ENGLISH ABSTRACT: his study aims to investigate whether the phenomena found by Shnoll et al. when applying histogram pattern analysis techniques to stochastic processes from chemistry and physics are also present in financial time series, particularly exchange rate and index data. The phenomena are related to fine structure of non-smoothed frequency distributions drawn from statistically insufficient samples of changes and their patterns in time. Shnoll et al. use the notion of macroscopic fluctuations to explain the behaviour of sequences of histograms. Histogram patterns in time adhere to several laws that could not be detected when using time series analysis methods. In this study general approaches are reviewed that may be used to model financial markets and the volatility of price processes in particular. Special emphasis is placed on the modelling of highfrequency data sets and exchange rate data. Following previous studies of the Shnoll phenomena from other fields, different steps of the histogram sequence analysis are carried out to determine whether the findings of Shnoll et al. could also be applied to financial market data. The findings of this thesis widen the understanding of time varying volatility and can aid in financial risk measurement and management. Outcomes of the study include an investigation of time series characteristics in terms of the formation of discrete states, the detection of the near zone effect as proclaimed by Shnoll et al., the periodic recurrence of histogram shapes as well as the synchronous variation in data sets measured in the same time intervals.
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ONO, YUICHIRO, SHIN'YA YAMADA, MASASHI FURUTA, HISATAKA SAKAKIBARA, TAKA'AKI KONDO, HIROKAZU IGUCHI, HIROSHI KUNO, et al. "The Scale Method as a Spectral Analysis for Accommodative Fluctuation." Nagoya University School of Medicine, 1987. http://hdl.handle.net/2237/17496.
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Kanazawa, Kiyoshi. "Statistical mechanics for athermal fluctuation: Non-Gaussian noise in physics." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199084.
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Wood, William Alfred. "Multi-dimensional Upwind Fluctuation Splitting Scheme with Mesh Adaption for Hypersonic Viscous Flow." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29772.
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A multi-dimensional upwind fluctuation splitting scheme is developed and implemented for two-dimensional and axisymmetric formulations of the Navier-Stokes equations on unstructured meshes. Key features of the scheme are the compact stencil, full upwinding, and non-linear discretization which allow for second-order accuracy with enforced positivity. Throughout, the fluctuation splitting scheme is compared to a current state-of-the-art finite volume approach, a second-order, dual mesh upwind flux difference splitting scheme (DMFDSFV), and is shown to produce more accurate results using fewer computer resources for a wide range of test cases. The scalar test cases include advected shear, circular advection, non-linear advection with coalescing shock and expansion fans, and advection-diffusion. For all scalar cases the fluctuation splitting scheme is more accurate, and the primary mechanism for the improved fluctuation splitting performance is shown to be the reduced production of artificial dissipation relative to DMFDSFV. The most significant scalar result is for combined advection-diffusion, where the present fluctuation splitting scheme is able to resolve the physical dissipation from the artificial dissipation on a much coarser mesh than DMFDSFV is able to, allowing order-of-magnitude reductions in solution time. Among the inviscid test cases the converging supersonic streams problem is notable in that the fluctuation splitting scheme exhibits superconvergent third-order spatial accuracy. For the inviscid cases of a supersonic diamond airfoil, supersonic slender cone, and incompressible circular bump the fluctuation splitting drag coefficient errors are typically half the DMFDSFV drag errors. However, for the incompressible inviscid sphere the fluctuation splitting drag error is larger than for DMFDSFV. A Blasius flat plate viscous validation case reveals a more accurate vertical-velocity profile for fluctuation splitting, and the reduced artificial dissipation production is shown relative to DMFDSFV. Remarkably the fluctuation splitting scheme shows grid converged skin friction coefficients with only five points in the boundary layer for this case. A viscous Mach 17.6 (perfect gas) cylinder case demonstrates solution monotonicity and heat transfer capability with the fluctuation splitting scheme. While fluctuation splitting is recommended over DMFDSFV, the difference in performance between the schemes is not so great as to obsolete DMFDSFV. The second half of the dissertation develops a local, compact, anisotropic unstructured mesh adaption scheme in conjunction with the multi-dimensional upwind solver, exhibiting a characteristic alignment behavior for scalar problems. This alignment behavior stands in contrast to the curvature clustering nature of the local, anisotropic unstructured adaption strategy based upon a posteriori error estimation that is used for comparison. The characteristic alignment is most pronounced for linear advection, with reduced improvement seen for the more complex non-linear advection and advection-diffusion cases. The adaption strategy is extended to the two-dimensional and axisymmetric Navier-Stokes equations of motion through the concept of fluctuation minimization. The system test case for the adaption strategy is a sting mounted capsule at Mach-10 wind tunnel conditions, considered in both two-dimensional and axisymmetric configurations. For this complex flowfield the adaption results are disappointing since feature alignment does not emerge from the local operations. Aggressive adaption is shown to result in a loss of robustness for the solver, particularly in the bow shock/stagnation point interaction region. Reducing the adaption strength maintains solution robustness but fails to produce significant improvement in the surface heat transfer predictions.Ph. D.
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Ahmed, Syed Naeem. "Quantum fluctuations in a segmented ionization chamber for beam monitoring of synchrotron radiation." [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=957510330.
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Mobley, John Thomas Jr. "An exploration of models for estimating evapotranspiration from stream fluctuations in riparian corridors." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1442921.
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Seshadri, Srivathsan. "Dynamically adjusting the number of kanbans for demand fluctuations and stochastic process times." Diss., Online access via UMI:, 2007.
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Camba-Mendez, Gonzalo. "Can real equilibrium models account for the fluctuations of the UK business cycle." Thesis, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363403.
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Dinsenmeyer, Alice. "Probabilistic approach for the separation of the acoustic and aerodynamic wall pressure fluctuations." Thesis, Lyon, 2020. http://theses.insa-lyon.fr/publication/2020LYSEI087/these.pdf.
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Avec l'apparition des MEMS et la diminution globale du coût des capteurs, les acquisitions multivoies se généralisent, notamment dans le domaine de l'identification de sources acoustiques. La qualité de la localisation et de la quantification des sources peut être dégradée par la présence de bruit de mesure ambiant ou induit par le système d'acquisition. En particulier, dans le cas de mesures en présence d'un écoulement, la couche limite turbulente qui se développe sur le système de mesure peut induire des fluctuations de pression de niveau bien supérieur à celles des sources acoustiques. Il devient alors nécessaire de traiter les acquisitions pour extraire chaque composante du champ mesuré. Pour cela, on propose de décomposer la matrice spectrale mesurée en la somme d'une matrice associée à la contribution acoustique et d'une matrice pour le bruit aérodynamique. Cette décomposition exploite les propriétés statistiques de chaque champ de pression. En supposant que la contribution acoustique est fortement corrélée sur les capteurs, le rang de la matrice interspectrale associée se limite au nombre de sources décorrélées équivalentes. Concernant la matrice du bruit aérodynamique, deux modèles statistiques sont proposés. Un premier modèle fait l'hypothèse d'un champ totalement décorrélé sur les capteurs, et un second repose sur un modèle physique préexistant. Ce problème de séparation est résolu par une approche d'optimisation bayésienne, qui permet de prendre en compte les incertitudes sur chaque composante du modèle.Les performances de cette méthode sont d'abord évaluées sur des mesures en soufflerie puis sur des données industrielles particulièrement bruitées, provenant de mesures microphoniques effectuées sur le fuselage d'un avion de ligne en volWith the emergence of MEMS and the overall decrease in the cost of sensors, the acquisitions multichannel are becoming more widespread, particularly in the field of acoustic source identification. The quality of source localization and quantification can be degraded by the presence of ambient or electronic noise. In particular, in the case of in flow measurements, the turbulent boundary layer that develops over the measuring system can induce pressure fluctuations that are much greater than those of acoustic sources. It then becomes necessary to process the acquisitions to extract each component of the measured field. For this purpose, it is proposed in this thesis to decompose the measured spectral matrix into the sum of a matrix associated with the acoustic contribution and a matrix for aerodynamic noise. This decomposition exploits the statistical properties of each pressure field. Assuming that the acoustic contribution is highly correlated on the sensors, the rank of the corresponding cross-spectral matrix is limited to the number of equivalent uncorrelated sources. Concerning the aerodynamic noise matrix, two statistical models are proposed. A first model assumes a totally uncorrelated field on the sensors, and a second is based on a pre-existing physical model. This separation problem is solved by a Bayesian optimization approach, which takes into account the uncertainties on each component of the model. The performance of this method is first evaluated on wind tunnel measurements and then on particularly noisy industrial measurement, coming from microphones flushmounted on the fuselage of an inflight large aircraft
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Goodman, Steven Blake. "Correlations Between Near Wake Velocity Fluctuations and Aerodynamic Efficiency for the SD7003 Airfoil." University of Dayton / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1524137507116155.
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Lepird, Hannah Hataipan. "Spectroscopic Analysis of Electric Field Fluctuations and Cofactor Dynamics: Insights for Enzyme Design." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2855.
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Enzyme design is a steadily growing field of computational chemistry, but its successes are limited by the current available knowledge and application of enzyme conformational dynamics. In this work a series of FTIR and 2D IR spectroscopic methods, for observing the conformational dynamics of an enzymatic active site and its surrounding residues, are characterized. The enzyme model system for these studies is the promiscuous ene-reductase from Pyrococcus horikoshii (PhENR) which is capable of binding substrates in multiple orientations. In one method, the spectral lineshape of an aryl-nitrile substrate-analog vibrational label is analyzed using a frequency fluctuation correlation function (FFCF) and compared to the lineshape of a corresponding aryl-azide label. This analysis revealed dynamic and electrostatic active site anisotropy which may influence substrate catalysis. The second method utilizes the intramolecular vibrations of the enzymatic cofactor, flavin mononucleotide (FMN), which is shown to be sensitive to electric field changes associated with substrate binding. The final method places a site-specific nonnatural amino acid containing an azide probe within the enzyme’s hydrophobic core. Additionally, a double-mutant cycle was identified via a common design program, the Rosetta Modeling Suite, and used to analyze the effects of mutation on enzyme dynamics. Altogether, these methods demonstrate the ability of 2D IR spectroscopy to observe enzyme conformational dynamics. Application of these methods to various other enzyme model systems should provide valuable insight for the improvement of future dynamic enzyme design protocols.
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Vidmar, Matija. "Markov chain approximations to, and some fluctuation results for, Lévy processes." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/65625/.
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We introduce, and analyze in terms of convergence rates of transition kernels, a continuous-time Markov chain approximation to Lévy processes. A full fluctuation theory for what are right-continuous random walks embedded into continuous-time as compound Poisson processes, is provided. These results are applied to obtaining a general algorithm for the calculation of the scale functions of a spectrally negative Lévy process. In a related result, the class of Lévy processes having non-random overshoots is precisely characterized.
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Xillo, Olivier III. "A Sampling Probe for Fluctuating Concentration Measurements in Supersonic Flow." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36670.
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The study of mixing processes in supersonic flow has a great
interest for a number of applications including scramjet
developments. However, the usual tools employed are very
limited. Sampling probes generally have a poor frequency
response, and that makes measurements of fluctuating
concentration problematic. The goal of this study is to
design, build and test a probe capable of measuring
concentration fluctuations of at least 1 kHz. This study
shows the design of such a probe and how a high frequency
response was achieved. A prototype was built and tested.
The tests consist of a calibration phase and experiments
inside a hypersonic wind tunnel. These last tests served
two purposes. The first one was to verify that the
measurements made with the probe gave the correct value of
the concentration. The second purpose was to assess the
frequency response of the probe by putting it through a
concentration step change. Tests were conducted with
various known mixtures of Helium and air from 0% to 100%
flowing at Mach 2.0 with Tt=300 degree K and Pt=4.4 atm.
The probe proved capable of measuring concentration
fluctuations up to approximately 2.5 kHz while also giving
the adequate accuracy for values of mean concentration.Master of Science
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Mechraoui, Ahmed. "A relaying scheme for the protection of major transmission lines during fast power swings." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319924.
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Asta, Adelchi Jacques. "Listening to the electrical noise for nanofluidic sensing." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS444.
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Le passage de la microfluidique, qui est aujourd'hui un domaine bien établi, à la nanofluidique nécessite le développement de techniques numériques. En utilisant la méthode de Lattice Boltzmann sur réseau électrocinétique (LBE), nous pouvons coupler l'équation de Navier-Stokes avec la théorie de Poisson-Nernst Planck et ainsi étudier les fluides confinés et chargés à l'échelle nanométrique. Les électrochimistes ont commencé à utiliser les fluctuations électriques qui en découlent pour extraire des informations sur les phénomènes interfaciaux et donc sur les processus microscopiques sous-jacents (par exemple: la détection de molécules uniques ou l’adsorption/désorption). Ceci nécessite de pouvoir modéliser des nanocondensateurs avec une différence de potentiel constante entre les deux électrodes, ce qui est la principale nouveauté ajoutée à l'algorithme LBE. Enfin, en couplant cette méthode à la méthode de propagation des moments, nous avons été en mesure de fournir un outil de calcul efficace, capable d'analyser les effets hydrodynamiques, électrocinétiques, d'adsorption/désorption et de taille finie dans des fluides confinés à l'échelle nanométrique, pour des géométries arbitraires, en régime linéaire et non linéaire, ainsi que dans les régimes transitoires et stationnaires. Dans le contexte du bruit électrique, la réponse temporelle de la charge à une perturbation de tension peut être liée à l'impédance et donc aux fluctuations électriques. A l'avenir, nous pourrons également étudier la réponse électrocinétique liée à la réponse de corrélation croisée entre la masse et les courants électriquesMoving from microfluidics, which is now a well-established field, to nanofluidics requires the development of computational tools. Using the Lattice Boltzmann Electrokinetics (LBE) method, we can couple the Navier-Stokes equation with the Poisson-Nernst Planck theory and thus study charged confined fluids at the nanoscale. Electrochemists have begun to use the electrical fluctuations arising from them to extract information on the interfacial phenomena and thus the underlying microscopic processes (e.g. single molecule detection, adsorption/desorption). This requires to be able to model nanocapacitors with a constant potential difference between the two electrodes, which was the main novelty added to the LBE algorithm. Finally by coupling this method with the moment propagation method, we have been able to provide an efficient computational tool capable to analyse, hydrodynamic, electrokinetic, adsorption/desorption and finite size effects in fluids confined at the nanoscale, for arbitrary geometries, in both linear and non-linear regimes, as well as in the transient and steady state regimes. Within the context of electrical noise, the temporal charge response to a voltage perturbation can be linked to the impedance and thus to the electrical fluctuations. In the future we will also be able to study the electrokinetic response related to the cross correlation response between mass and electric currents
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Thomas, Scott Walter Hartfield Roy J. "Methods for optimization of a launch vehicle for pressure fluctuation levels and axial force." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SUMMER/Aerospace_Engineering/Thesis/Thomas_Scott_37.pdf.
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Chen, Aaron. "Imprinted Magnetic Traps for Study on Particle Fluctuation, Ordering and Microfluidic Applications." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364490203.
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