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1
Coiculescu, Ion. "Dynamics, Thermodynamic formalism and Perturbations of Transcendental Entire Functions of Finite Singular Type." Thesis, University of North Texas, 2005. https://digital.library.unt.edu/ark:/67531/metadc4783/.
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In this dissertation, we study the dynamics, fractal geometry and the topology of the Julia set of functions in the family H which is a set in the class S, the Speiser class of entire transcendental functions which have only finitely many singular values. One can think of a function from H as a generalized expanding function from the cosh family. We shall build a version of thermodynamic formalism for functions in H and we shall show among others, the existence and uniqueness of a conformal measure. Then we prove a Bowen's type formula, i.e. we show that the Hausdorff dimension of the set of returning points, is the unique zero of the pressure function. We shall also study conjugacies in the family H, perturbation of functions in the family and related dynamical properties. We define Perron-Frobenius operators for some functions naturally associated with functions in the family H and then, using fundamental properties of these operators, we shall prove the important result that the Hausdorff dimension of the subset of returning points depends analytically on the parameter taken from a small open subset of the n-dimensional parameter space.
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Gatse, Franchel. "Spectre ordonné et branches analytiques d'une surface qui dégénère sur un graphe." Electronic Thesis or Diss., Orléans, 2020. http://www.theses.fr/2020ORLE3205.
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Dans ce travail, nous donnons un cadre général de surfaces riemanniennes qui dégénèrent sur des graphes métriques que nous appelons surfaces décomposables en cylindres et en jonctions. Les surfaces décomposables en cylindres et en jonctions dépendent d’un paramètre t qui traduit le mécanisme d’écrasement sur le graphe. Quand le paramètre t tend vers 0, les circonférences des cylindres tendent vers 0 et leurs longueurs restent fixes. On obtient ainsi les arêtes du graphe limite. Les jonctions, elles, sont écrasées dans toutes les directions et donc dégénèrent sur les sommets du graphe limite. Nous étudions alors le comportement asymptotique du spectre de ces variétés lors de cette déformation. Nous adoptons les points de vue de la convergence des valeurs propres ordonnées et de celle des branches analytiques. Ces deux approches sont fondamentalement différentes. Le cas des valeurs propres ordonnées est assez classique et nous retrouvons la convergence vers le spectre du graphe limite. L’étude des branches analytiques est plus original. Nous montrons la convergence et donnons une caractérisation des limites possibles. Ces résultats s’appliquent dans le cas des surfaces de translations qui possèdent une direction complètement périodiqueIn this work, we give a general framework of Riemannian surfaces that can degenerate on metric graphs and that we call surfaces made from cylinders and connecting pieces. The latter depend on a parameter t that describes the degeneration. When t goes to 0, the waists of the cylinders go to 0 but their lengths stay fixed. We thus obtain the edges of the limiting graph. The connecting pieces are squeezed in all directions and degenerate on the vertices of the limiting graph. We then study the asymptotic behaviour of the spectrum of these surfaces when t varies from two different points of view, considering the spectrum either as a sequence of ordered eigenvalues or as a collection of analytic eigenbranches. In the case of ordered eigenvalues, we recover a rather classical statement, and prove that the spectrum converges to the spectrum of the limiting object. The study of the analytic eigenbranches is more original. We prove that any such eigenbranch converges and we give a characterisation of the possible limits. These results apply to translation surfaces on which there is a completely periodic direction
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Neuner, Christoph. "On Supersingular Perturbations." Doctoral thesis, Stockholms universitet, Matematiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-147396.
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This thesis consists of four papers and deals with supersingular rank one perturbations of self-adjoint operators and their models in Hilbert or Pontryagin spaces. Here, the term supersingular describes perturbation elements that are outside the underlying space but still obey a certain regularity conditions. The first two papers study certain Sturm-Liouville differential expressions that can be realised as Schrödinger operators. In Paper I we show that for the potential consisting of the inverse square plus a comparatively well-behaved term we can employ an existing model due to Kurasov to describe these operators in a Hilbert space. In particular, this approach is in good agreement with ODE techniques. In Paper II we study the inverse fourth power potential.While it is known that the ODE techniques still work, we show that the above model fails and thus that there are limits to the above operator theoretic approach. In Paper III we concentrate on generalising Kurasov's model. The original formulation assumes that the self-adjoint operator is semi-bounded, whereas we drop this requirement. We give two models with a Hilbert and Pontryagin space structure, respectively, and study the connections between the resulting constructions. Finally, in Paper IV, we consider the concrete case of the operator of multiplication by the independent variable, a self-adjoint operator whose spectrum covers the real line, and study its perturbations. This illustrates some of the formalism that was developed in the previous paper, and a number of more explicit results are obtained, especially regarding the spectra of the appearing perturbed operators.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
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Pond, Jarrad W. T. "Perturbation analysis of fluctuations in the universe on large scales, including decaying solutions and rotational velocities." Honors in the Major Thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1309.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.Bachelors
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Physics
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Hiller, Steven Mark. "Automatic acoustic analysis of waveform perturbations." Thesis, University of Edinburgh, 1985. http://hdl.handle.net/1842/18962.
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ROCCHI, Marta. "Ecosystem response to perturbations: insight from qualitative analysis." Doctoral thesis, Università degli studi di Ferrara, 2017. http://hdl.handle.net/11392/2488077.
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Present changing environment calls for improvements of our knowledge of natural systems structure and function through a holistic view. Such a whole system perspective might help to better understand responses of ecosystems to perturbations. Models of ecological networks have proven to be very useful tools for understanding structure, and dynamics of ecosystems. I am presenting two modelling techniques to deal with the whole system approach: topological food web analysis (chapter 2) and loop analysis (chapter 3 and 4). Both these studies privilege the qualitative analysis over the quantitative one, to overcome the lack of data.
In chapter 2 the topology of the food web is considered to study the functioning of the Baja California Sur ecosystem. I identified through centrality indices key node species and analyzed system resilience to the removal of the most vulnerable fish species based on a previous classification of high, medium and low risk species. Effects are evaluated by using global indices. Results highlight the structural resilience of the web to removals, but also that removals of highly vulnerable species result in significant changes in system attributes compared to random removal.
In chapter 3 the evolution of the Black Sea ecosystem during the period 1960-1990 is evaluated through qualitative models (i.e. loop analysis). These models reconstruct the linkage structure of the whole community. I validated the outcomes of loop analysis with statistical investigation of biomass time series. This helped to understand how the structure of the interactions can explain variations in the biomass level of the variables and what hypotheses about drivers and mechanisms responsible for the changes could be shaped accordingly.
In chapter 4 a database of real and random food webs was taken into account. I studied these food webs through loop analysis to unveil how positive input on basal and top species affects top and basal species, respectively. The aim was to identify possible differences in the propagation of indirect impacts in response to positive perturbations that occur at the extreme of the food webs (i.e. either targeting basal or top species). I compared real systems (i.e. marine, terrestrial and freshwater food webs) with random networks. I found an overrepresentation of positive predictions (i.e. the species are predicted to increase their abundance) and an underrepresentation of negative predictions for the top species when basal species are perturbed. This occurs in both real and random systems. Considering the latter the same trend (i.e. overrepresentation of positives signs and underrepresentation of negative ones) was found when predicting the responses of basal species following perturbations on top species. I showed that these findings are due to the topological structure of the food webs (e.g. number and length of trophic paths) rather than depending on the patterning of interactions strengths. Thus, the responses of top species following perturbations on basal species are predictable, while the same trend does not hold when studying the responses of basal species after perturbations targeted on top species. These results are particularly relevant and interesting considering the importance of basal and top species as target for many anthropogenic impacts.
This thesis contributes to unfold a path toward: 1) the understanding of the effect of disturbance on ecological communities and ecosystems; 2) an improved comprehension of the interplay between top-down and bottom-up control; 3) the capability to deal with uncertainty in assessing the response of communities and ecosystems in the face of disturbance. I used relatively simple methodologies that focus on the qualitative arrangement of trophic interactions. This may seem a limitation. However, I show there are cases for which even the study of qualitative data can be of crucial importance in terms of management (i.e. ecosystem-based management).I cambiamenti ambientali in atto richiedono un miglioramento delle conoscenze su struttura e funzionamento dei sistemi naturali attraverso un approccio olistico. Una visione d’insieme potrebbe aiutare a comprendere meglio la risposta degli ecosistemi alle perturbazioni. E’ stato provato che lo studio dei network ecologici è utile per comprendere la struttura e le dinamiche degli ecosistemi. In questa tesi presento due tecniche modellistiche: l’analisi topologica di food web (capitolo 2) e la loop analysis (capitolo 3 e 4). Entrambi gli studi privilegiano l’analisi qualitativa a quella quantitativa per superare la mancanza di dati. Nel capitolo 2 ho considerato alcune caratteristiche topologiche per lo studio del funzionamento dell’ecosistema di Baja California Sur. Ho identificato, attraverso gli indici di centralità, le specie chiave e analizzato la resilienza del sistema alla rimozione delle specie definite più vulnerabili (es. precedente classificazione di alto, medio e basso rischio). Gli effetti sono stati valutati attraverso indici globali. I risultati evidenziano la resilienza strutturale della food web alle rimozioni, ma anche che la rimozione delle specie più vulnerabili cambia significatamente alcuni attributi del sistema rispetto alle rimozioni random. Nel capitolo 3 ho valutato l’evoluzione dell’ecosistema del Mar Nero nel periodo 1960-1990 attraverso la loop analysis. I modelli qualitativi indagati ricostruiscono la struttura dei legami dell’intera comunità. Ho validato i risultati emersi con indagini statistiche sulle serie temporali di biomasse per capire come la struttura delle interazioni può spiegare le variazioni nei livelli di biomassa delle variabili e quali ipotesi possono essere fatte sui drivers e i meccanismi responsabili dei cambiamenti. Nel capitolo 4 ho costruito un database di food web reali e random, che ho studiato attraverso la loop analysis, per capire come un input positivo sulle specie basali e apicali si ripercuote rispettivamente sulle specie apicali e basali. Lo scopo era quello di identificare possibili differenze nella propagazione degli effetti indiretti in risposta a input positivi che si verificano agli estremi delle food web. Ho confrontato sistemi reali (marini, terrestri e di acqua dolce) con networks random. Ho trovato una sovrarappresentazione di predizioni positive (aumento dell’abbondanza delle specie) e una sottorappresentazione di predizione negative per le specie apicali a seguito di un input positivo sulle specie basali, sia nei sistemi reali che in quelli random. Considerando questi ultimi lo stesso trend (sovrarappresentazione di segni positivi e sottorappresentazione di segni negativi) è stato trovato nelle predizioni riguardanti la risposta delle specie basali a seguito di un input sulle specie apicali. Ho mostrato che questi risultati sono dovuti alla struttura topologica delle food web (es. il numero e la lunghezza dei percorsi trofici) piuttosto che alla forza delle interazioni. Sembra che le risposte delle specie apicali a seguito di perturbazioni delle specie basali siano prevedibili, al contrario delle risposte delle specie basali a seguito di un input sulle apicali. Questi risultati sono particolarmente rilevanti e interessanti considerando l’importanza delle specie basali e apicali come target degli impatti antropici. Questa tesi contribuisce allo sviluppo di un percorso verso: 1)la comprensione degli effetti di disturbo sulle comunità ecologiche e sugli ecosistemi; 2)una migliore comprensione delle interazioni di controllo top-down e bottom-up; 3)la capacità di affrontare l'incertezza per valutare la risposta delle comunità e degli ecosistemi di fronte al disturbo. Nonostante l’uso di metodologie relativamente semplici che si concentrano sulla disposizione qualitativa delle interazioni trofiche, ho dimostrato che vi sono casi in cui anche lo studio di dati qualitativi può essere di cruciale importanza in termini di gestione.
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Chang, Xiao-Wen. "Perturbation analysis of some matrix factorizations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0023/NQ29906.pdf.
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Dendievel, Sarah. "Skip-free markov processes: analysis of regular perturbations." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209050.
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A Markov process is defined by its transition matrix. A skip-free Markov process is a stochastic system defined by a level that can only change by one unit either upwards or downwards. A regular perturbation is defined as a modification of one or more parameters that is small enough not to change qualitatively the model.This thesis focuses on a category of methods, called matrix analytic methods, that has gained much interest because of good computational properties for the analysis of a large family of stochastic processes. Those methods are used in this work in order i) to analyze the effect of regular perturbations of the transition matrix on the stationary distribution of skip-free Markov processes; ii) to determine transient distributions of skip-free Markov processes by performing regular perturbations.
In the class of skip-free Markov processes, we focus in particular on quasi-birth-and-death (QBD) processes and Markov modulated fluid models.
We first determine the first order derivative of the stationary distribution - a key vector in Markov models - of a QBD for which we slightly perturb the transition matrix. This leads us to the study of Poisson equations that we analyze for finite and infinite QBDs. The infinite case has to be treated with more caution therefore, we first analyze it using probabilistic arguments based on a decomposition through first passage times to lower levels. Then, we use general algebraic arguments and use the repetitive block structure of the transition matrix to obtain all the solutions of the equation. The solutions of the Poisson equation need a generalized inverse called the deviation matrix. We develop a recursive formula for the computation of this matrix for the finite case and we derive an explicit expression for the elements of this matrix for the infinite case.
Then, we analyze the first order derivative of the stationary distribution of a Markov modulated fluid model. This leads to the analysis of the matrix of first return times to the initial level, a charactersitic matrix of Markov modulated fluid models.
Finally, we study the cumulative distribution function of the level in finite time and joint distribution functions (such as the level at a given finite time and the maximum level reached over a finite time interval). We show that our technique gives good approximations and allow to compute efficiently those distribution functions.
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Un processus markovien est défini par sa matrice de transition. Un processus markovien sans sauts est un processus stochastique de Markov défini par un niveau qui ne peut changer que d'une unité à la fois, soit vers le haut, soit vers le bas. Une perturbation régulière est une modification suffisamment petite d'un ou plusieurs paramètres qui ne modifie pas qualitativement le modèle.
Dans ce travail, nous utilisons des méthodes matricielles pour i) analyser l'effet de perturbations régulières de la matrice de transition sur le processus markoviens sans sauts; ii) déterminer des lois de probabilités en temps fini de processus markoviens sans sauts en réalisant des perturbations régulières.
Dans la famille des processus markoviens sans sauts, nous nous concentrons en particulier sur les processus quasi-birth-and-death (QBD) et sur les files fluides markoviennes.
Nous nous intéressons d'abord à la dérivée de premier ordre de la distribution stationnaire – vecteur clé des modèles markoviens – d'un QBD dont on modifie légèrement la matrice de transition. Celle-ci nous amène à devoir résoudre les équations de Poisson, que nous étudions pour les processus QBD finis et infinis. Le cas infini étant plus délicat, nous l'analysons en premier lieu par des arguments probabilistes en nous basant sur une décomposition par des temps de premier passage. En second lieu, nous faisons appel à un théorème général d'algèbre linéaire et utilisons la structure répétitive de la matrice de transition pour obtenir toutes les solutions à l’équation. Les solutions de l'équation de Poisson font appel à un inverse généralisé, appelé la matrice de déviation. Nous développons ensuite une formule récursive pour le calcul de cette matrice dans le cas fini et nous dérivons une expression explicite des éléments de cette dernière dans le cas infini.
Ensuite, nous analysons la dérivée de premier ordre de la distribution stationnaire d'une file fluide markovienne perturbée. Celle-ci nous amène à développer l'analyse de la matrice des temps de premier retour au niveau initial – matrice caractéristique des files fluides markoviennes.
Enfin, dans les files fluides markoviennes, nous étudions la fonction de répartition en temps fini du niveau et des fonctions de répartitions jointes (telles que le niveau à un instant donné et le niveau maximum atteint pendant un intervalle de temps donné). Nous montrerons que cette technique permet de trouver des bonnes approximations et de calculer efficacement ces fonctions de répartitions.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Preciso, Luca. "Perturbation Analysis of the Conformal Sewing Problem and Related Problems." Doctoral thesis, Università degli studi di Padova, 1998. http://hdl.handle.net/11577/3425905.
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In this dissertation, we develop two related problems in the nonlinear functional analysis. The first is the analyticity of the Cauchy singular integral in Schauder spaces which is motivated by the second problem, namely the perturbation analysis of the conformal sewing problem in Schauder and Roumieu spaces. In Chapter II, we consider the Cauchy singular integral
f (t)φ0 (t) f ◦ φ(−1) (ξ)
1 1
C[φ, f ]( · ) ≡ p. v. dt = p. v. dξ
2πi ∂D φ(t) − φ(·) 2πi φ ξ − φ(·)
where the oriented simple closed curve φ and the density function f are both defined on the counterclockwise oriented boundary ∂D of the plane unit disk D. Although the linear operator C[φ, ·], for a fixed φ, and the numerical computation of C[φ, f ] have been extensively studied for the last century, in view to several applications to integral equations and boundary value problems (cf. e.g. Muskhelishvili (1953) and Gakhov (1966)), the analysis of the nonlinear functional dependence of C[φ, f ] upon both its arguments seems to be a subject analyzed only more recently (see Introduction Ch. II). This new subject of research finds application in the nonlinear problems of perturbation nature which involve the Cauchy singular integral. In Chapter II we extend the analyticity result for the operator C[·, ·] of Coifman & Meyer (1983b) to a Schauder spaces setting. We assume that both φ and f belong to a Schauder space, say C∗m,α (∂D, C), of complex-valued function of class C m,α on ∂D, with m a positive natural number and α ∈ ]0, 1[. As it is well-known, under such conditions on φ and f , the function C[φ, f ](·) is also of class C m,α . By proving the unique solvability of a boundary value problem of elliptic nature in D and by applying Implicit Function Theorem to a suitable functional equation, we show the real analyticity of C[·, ·]. Then we show the complex analyticity of C[·, ·] and we compute all its differentials. This result of Lanza & Preciso (1998) will be applied in the second part of this dissertation and in another perturbation problem associated to a nonlinear integral equation (cf. Lanza & Rogosin (1997)). In Chapter III, we introduce the conformal sewing problem associated to a shift φ of ∂D, i.e. a homeomorphism of ∂D to itself. It consists in finding a pair of conformal functions (F, G) defined in D and C \ cl D, respectively, such that their continuous extensions to cl D e C \ D, Fe and G e respectively, satisfy Fe(φ(t)) = G(t) for all t ∈ ∂D. A simple normalization condition and well-known results ensure that the sewing problem associated to φ has a unique solution (F, G) and we denote by (F [·], G[·]) the pair of operators which maps φ to the trace on ∂D of such solution. The regularity properties of the operators F [φ] and G[φ] in spaces of regular functions can be used in the study of Teichmüller spaces, which constitute an important subject in geometric function theory (see Nag (1996)). Our aim is to find natural Banach spaces of regular functions where to obtain the analyticity of F [·] and G[·]. First we study the regularity of such operators in Schauder spaces C∗m,α (∂D, C), with m ≥ 1, α ∈ ]0, 1[. By using the classical integral equation approach to the sewing problem, we show that G[φ] and F [φ] = G[φ] ◦ φ(−1) belong to C∗m,α (∂D, C) when φ belongs to C∗m,α (∂D, C). In this setting, by using the analyticity of the Cauchy singular integral (cf. Ch. II) and by applying Implicit Function Theorem to a suitable integral equation, we show that G[·] extends to a complex analytic operator. Then we prove that this Schauder spaces setting is not sufficient in order to obtain an analytic extension of the operator F [·]. Indeed a natural assumption in order to have F [·] analytic, is that φ belongs to a space of real analytic functions of ∂D to C. In Chapter IV we introduce Banach spaces of real analytic functions, namely the Roumieu spaces associated to the differentiation operator. In this setting we show that G[·] and F [·] can be extended to complex analytic operators by employing the regularity results on the composition and on the inversion operator of Lanza (1994 and 1996b).
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Onen, Onursal. "Analytical Modeling, Perturbation Analysis and Experimental Characterization of Guided Surface Acoustic Wave Sensors." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4555.
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In this dissertation, guided surface acoustic wave sensors were investigated theoretically and experimentally in detail for immunosensing applications. Shear horizontal polarized guided surface acoustic wave propagation for mass loading sensing applications was modeled using analytical modeling and characterized by perturbation analysis. The model verification was performed experimentally and a surface acoustic wave immunosensor case study was presented. The results of the immunosensing were also investigated using the perturbation analysis.
Guided surface acoustic wave propagation problem was investigated in detail for gravimetric (or mass loading) guided wave sensors, more specifically for immunosensors. The analytical model was developed for multilayer systems taking viscoelasticity into account. The closed form algebraic solutions were obtained by applying appropriate boundary conditions. A numerical approach was used to solve dispersion equation. Detailed parametric investigation of dispersion curves was conducted using typical substrate materials and guiding layers. Substrate types of ST-cut quartz, 41° YX lithium Niobate and 36° YX lithium tantalate with guiding layers of silicon dioxide, metals (chromium and gold), and polymers (Parylene-C and SU-8) were investigated. The effects of frequency and degree of viscoelasticity were also studied. The results showed that frequency only has effect on thickness with same shaped dispersion curves. Dispersion curves were found to be unaffected by the degree of viscoelasticity. It was also observed that when there was a large shear velocity difference between substrate and guiding layer, a transition region with a gradual decrease in phase velocity was obtained. However, when shear velocities were close, a smooth transition was observed. Furthermore, it was observed that, large density differences between substrate and guiding layer resulted in sharp and with nearly constant slope transition. Smooth transition was observed for the cases of minimal density differences. Experimental verification of the model was done using multi-layer photoresists. It was shown that with modifications, the model was able to represent the cases studied.
Perturbation equations were developed with first order approximations by relating the slope of the dispersion curves with sensitivity. The equations were used to investigate the sensitivity for material selection (substrate, guiding layer, and mass perturbing layer) and degree of viscoelasticity. The investigations showed that the sensitivity was increased by using guiding layers with lower shear velocities and densities. Among the guiding layers investigated, Parylene C showed the highest sensitivity followed by gold and chrome. The perturbation investigations were also extended to viscoelasticity and to protein layers for immunosensing applications. It was observed that, viscous behavior resulted in slightly higher sensitivity; and sensitivity to protein layers was very close to sensitivity for polymers. The optimum case is found to be ST-cut quartz with Parylene-C guiding layer for protein layer sensing.
Finally, an immunosensing case study was presented for selective capture of protein B-cell lymphoma 2 (Bcl-2), which is elevated in many cancer types including ovarian cancer. The immunosensor was designed, fabricated, and experimentally characterized. An application-specific surface functionalization scheme with monoclonal antibodies, ODMS, Protein A/G and Pluronic F127 was developed and applied. Characterization was done using the oscillation frequency shift of with sensor used as the feedback element of an oscillator circuit. Detection of Bcl-2 with target sensitivity of 0.5 ng/ml from buffer solutions was presented. A linear relation between frequency shift and Bcl-2 concentration was observed. The selectivity was shown with experiments by introducing another protein, in addition to Bcl-2, to the buffer. It was seen that similar detection performance of Bcl-2 was obtained even with presence of control protein in very high concentrations. The results were also analyzed with perturbation equations.
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Knudson, Wade E. "Orbital perturbation analysis of earth-crossing asteroids." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306616.
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Thesis (Degree of Aeronautical and Astronautical Engineer) Naval Postgraduate School, December 1995.Thesis advisor(s): I.M. Ross. "December 1995." Includes bibliographical references. Also available online.
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Adams, Richelle Vive-Anne. "Infinitesimal Perturbation Analysis for Active Queue Management." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19844.
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Active queue management (AQM) techniques for congestion control in Internet Protocol (IP) networks have been designed using both heuristic and analytical methods. But so far, there has been found no AQM scheme designed in the realm of stochastic optimization. Of the many options available in this arena, the gradient-based stochastic approximation method using Infintesimal Perturbation Analysis (IPA) gradient estimators within the Stochastic Fluid Model (SFM) framework is very promising. The research outlined in this thesis provides the theoretical basis and foundational layer for the development of IPA-based AQM schemes. Algorithms for computing the IPA gradient estimators for loss volume and queue workload were derived for the following cases: a single-stage queue with instantaneous, additive loss-feedback, a single-stage queue with instantaneous, additive loss-feedback and an unresponsive competing flow, a single-stage queue with delayed, additive loss-feedback, and a multi-stage tandem network of $m$ queues with instantaneous, additive loss-feedback. For all cases, the IPA gradient estimators were derived with the control parameter, $ heta$, being the buffer-limits of the queue(s). For the single-stage case and the multi-stage case with instantaneous, additive loss-feedback, the IPA gradient estimators for when the control parameter, $ heta$, is the loss-feedback constant, were also derived. Sensitivity analyses and optimizations were performed with control parameter, $ heta$, being the buffer-limits of the queue(s), as well as the loss-feedback constant.
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Wong, Chin Pin. "Kato's Perturbation Theorem and honesty theory." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:c72c308b-d96d-4e31-a854-f2a10e99eeb6.
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We study an additive perturbation theorem for substochastic semigroups which is known as Kato's Theorem. There are two previously-known generalisations of Kato's Theorem, namely for abstract state spaces and for KB-spaces. We prove a version of Kato's Theorem for a class of spaces which encompasses both, namely ordered Banach spaces with generating cone and monotone norm. We also study a property of the perturbed semigroup in Kato's Theorem known as honesty of the semigroup. We add a few results to the fairly extensive existing theory of honesty for Kato's Theorem for abstract state spaces. In light of our new generalisation of Kato's Theorem to ordered Banach spaces with monotone norm, we investigate generalising the theory of honesty to these spaces as well. The results for the general case are less complete as many of the results for the case of abstract state spaces depend on the additive norm structure of the space. We also consider some new applications of honesty theory in abstract state spaces. We begin by applying honesty theory to the study of the heat equation on graphs. We prove that honesty of the heat semigroup coincides with a concept known as stochastic completeness of the graph which has been studied independently of honesty. We then look at the application of honesty theory to quantum dynamical semigroups. We show that honesty is the natural generalisation of the concept of conservativity of quantum dynamical semigroups. Conservative quantum dynamical semigroups are known to have certain "nice" properties. We show that similar properties hold for honest semigroups using honesty theory results. Finally, we consider a form of boundary perturbations in the context of transport semigroups. There exists an analogous theory of honesty for this set-up. We formulate a general result from which honesty results of both Kato's Theorem and transport semigroups can be derived.
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Michalski, Milosz R. "Perturbation theory for the topological pressure in analytic dynamical systems." Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39745.
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We develop a systematic approach to the problem of finding the perturbative
expansion for the topological pressure for an analytic expanding
dynamics (/, M) on a Riemannian manifold M. The method is based on
the spectral analysis of the transfer operator C. We show that in typical
cases, when / depends real-analytically on a set of perturbing parameters
,", the related operators C~ form an analytic family. This gives rise to the
rigorous construction of the power series expansion for the pressure via the
analytic perturbation theory for eigenvalues, [Kato]. Consequently, the pressure
and related dynamical indices, such as dimension spectra, Lyapunov exponents, escape rates and Renyi entropies inherit the real-analyticity in ~
from (I,M).Ph. D.
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Kawelke, Jens. "Perturbation and error analysis considerations in robust control." Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30177.
Full textAbstract:
This thesis deals with perturbation and error analysis in robust control, mainly H control, but the H2 norm is also considered. Perturbation analysis investigates the sensitivity of a solution or structure to perturbations or uncertainties in the input data. Error analysis is used to make statements about the numerical stability of an algorithm and uses results from perturbation analysis. Although perturbation and error analysis is a well-developed field in linear algebra, very little work has been done to introduce these concepts into the field of control. This thesis attempts to improve this situation. The main emphasis of the thesis is on H norm computations. Nonlinear and linear perturbation bounds are derived for the H norm. A rigorous error analysis is presented for two methods of computing the H norm: the Hamiltonian method and the SVD method. Numerical instability of the Hamiltonian method is shown with several examples. The SVD method, which is shown to be numerically stable, is updated with new upper and lower bounds for the frequency response between two given frequency points. Then using an upper frequency bound, a new algorithm is presented. This new algorithm can be implemented in a parallel process and has a similar performance to the Hamiltonian method in terms of computing time. In addition, nonlinear and linear perturbation bounds are derived for the H2 norm, and for the solutions of Lyapunov equations. Finally the H control problem is considered and perturbation bounds for the corresponding parameterized Riccati equations are derived. This leads to an estimation of the norm of the perturbation in the H controller.
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DuTôt, Meghan. "Comparing cell polarization models using local perturbation analysis." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46357.
Full textAbstract:
Patterns are ubiquitous in nature, but the underlying mechanisms giving rise to them are not always understood. One such pattern is the inhomogeneous domain of a cell that is established during polarization. Cell polarization is a way in which cells respond to and interact with their environment. For example, white blood cells locate and destroy bacteria, and yeast cells create buds for reproduction. Signalling proteins such as GTPases are redistributed throughout the cell and, through downstream effects, rearrangement of the actin cytoskeleton follows. This redistribution can occur in response to a stimulus, such a chemoattractant, or it may be spontaneous. Because many biological details are unknown, mathematical models are developed to recreate features of cell polarization and determine the minimal modules or characteristics for these features. Polarization models are often simple, conceptual reaction-diffusion equations for one or more signalling molecules. But comparing these models is often difficult, and there are many models in the literature for different cell types or behaviour.
A new method of nonlinear stability analysis, called local perturbation analysis (LPA), was developed by Stan Maree, and later Bill Holmes, to take advantage of models with substantial diffusion disparities. This method recapitulates the dynamics of a pulse applied to a reaction-diffusion system using a system of ordinary differential equations. Bifurcation analysis of these equations is relatively easy, and LPA detects pattern formation through threshold and Turing dynamics and provides bifurcation maps of these regimes for any parameter. LPA is well-suited to cell polarization models, because the signalling proteins we model often have both fast-diffusing inactive and slow-diffusing active forms. In this thesis, I introduce LPA and its use through a wave pinning model and its extension, a model for actin waves. I then review and analyze five additional cell polarization models using combinations of LPA, simulations, and Turing analysis. In many cases, I discovered new dynamics of the models. LPA helps us to map patterning regimes and their robustness to changes in parameters, and provides a new avenue for us to compare many current models for cell polarization.
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Sutherland, Andrew Mackinnon. "Automatic speaker verification based on waveform perturbation analysis." Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/13041.
Full textAbstract:
This thesis describes the research carried out to assess the applicability of speech waveform perturbation analysis to the problem of automatic speaker verification. It also describes the development of the technique into an operational system. The techniques of waveform perturbation analysis have been studied in the past with a view to their use as potential indicators of vocal fold dysfunction. In essence, they quantify the natural cycle-to-cycle fluctuations of vocal fold vibrations, also known as pitch periods, and are thus related to the perceived hoarseness and roughness of the voice. A major aim of this thesis is to determine if such features offer a viable dimension in speaker space along which discrimination can take place. The field of speaker verification is reviewed, and a number of previously exploited techniques are described. The likely mechanism for the production of speech waveform perturbation, separated into 'jitter' of period durations and 'shimmer' of peak amplitude values, are examined, and the existing techniques of quantification reviewed. In order to ensure accurate cycle-to-cycle measurement of period durations in real time, a new pitch determination algorithm, based on multi-feature investigation of the waveform peaks, has been developed. Its accuracy was assessed using both previously used pitch determination algorithms, and a laryngograph device. It was found to offer high accuracy pitch synchronous period estimates. The quantification of perturbation was carried out using the technique of median smoothing. This technique approximates removal of the more gradual changes in pitch period due to intonation. Measures of residual irregularity are then combined with additional long term intonational measures, to form a 10-dimensional profile of the speaker. Using an all male population of 72 speakers, a verification accuracy of 87% was achieved. The system was trained on approximately 60 seconds of continuous speech (from each speaker), and tested on 10 second utterances. A number of approaches to allow accurate classifiction of talkers are discussed, and their relative merits investigated experimentally. The effects of time spacing the training and testing data are studied. Also, the effectiveness of extending the speaker profile to include long term, spectrum combinations of features. The techniques of feature selection, used to limit the effects of finite training data, are also explored and extended. Results are presented for a study which employed professionally trained mimics in order to assess the effectiveness of the system under the most stringent conditions. The distribution of error rates within a population (i.e. the existence of particularly inconsistent speakers, or 'goats') is also studied, with a view to minimising their detrimental effects on system efficacy. Finally, this thesis describes the translation of the above system into an operational near real-time system, employing a digital signal processing microprocessor device.
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Shankar, Uday J. "Singular-perturbation analysis of climb-cruise-dash optimization." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45736.
Full textAbstract:
The method of singular-perturbation analysis is applied to the determination of range-fuel-time optimal aircraft trajectories.
The problem is shown to break down into three sub-problems which are studied separately. In particular, the inner layer containing the altitude path-angle dynamics is analyzed in detail. The outer solutions are discussed in an earlier work.
As a step forward in solving the ensuing nonlinear two-point boundary-value problem, linearization of the equations is suggested. Conditions for the stability of the linearized boundary-layer equations are discussed. Also, the question of parameter selection to fit the solution to the split boundary conditions is resolved. Generation of feedback laws for the angle-of-attack from the linear analysis is discussed.
Finally, the techniques discussed are applied to a numerical example of a missile. The linearized feedback solution is compared to the exact solution obtained using a multiple shooting method.Master of Science
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PIETROBON, DAVIDE. "Making the best of cosmological perturbations: theory and data analysis." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1197.
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Grazie a esperimenti estremamente raffinati, la cosmologia moderna si trova oggi in quella che puo' essere defi nita l' epoca della precisione. I
cosmologi dispongono di una grande quatita' di strumenti per testare il cosiddetto modello cosmologico di concordanza e vincolarne i principali parametri. In particolare, la radiazione cosmica di fondo (CMB) ha svolto, e svolge
tutt'oggi, un ruolo chiave in questo ambito. Numerose domande rimangono
tuttavia ancora in attesa di una risposta, in particolare quelle che riguardano la fisica dell'inflazione, che ha governato l'Universo nelle prime fasi di
evoluzione, e la natura dell' accelerazione dell' espansione dell'Universo, che e' stata osservata negli ultimi anni.
La mia attivita' di ricerca ha contribuito ad approfondire lo studio e la conoscenza su entrambe le tematiche, che sono state accomunate dallo sviluppo
e dall'utilizzo delle needlets - una nuova "frame" sulla sfera - per analizzare
la CMB. Con questo strumento, abbiamo misurato l'effetto Sachs-Wolfe integrato, correlando i dati di WMAP e NVSS, e caratterizzato le proprieta'
della dark energy, seguendo un approccio fenomenologico che si basa sull'approssimazione
di fl uido perfetto. Stimolati dai risultati ottenuti, abbiamo studiato in dettaglio un modello unifi cato per le componenti di dark energy e dark matter,
che fa uso di un'equazione di stato affi ne, e investigato i vincoli sui parametri
di questo modello provenienti da WMAP e SDSS.
Abbiamo quindi applicato le needlets ai dati di WMAP 5-anni allo scopo
di studiare la gaussianita' della distribuzione delle perturbazioni della CMB.
Ci siamo dapprima concentrati sulle mappe, rilevando la presenza di regioni anomale, localizzate nell' emisfero meridionale, e studiando l'effetto che
queste regioni hanno sullo spettro di potenza angolare. Successivamente, abbiamo misurato la funzione di correlazione a tre punti (bispettro) delle needlets caratterizzandola in termini della sua ampiezza complessiva, descritta dal parametro fNL, e secondo la geometria delle configurazioni triangolari che contribuiscono al segnale totale. Abbiamo misurato una significativa anomalia nelle confi gurazioni isosceli, nuovamente presente nell'emisfero
meridionale.
Infine, ci siamo concentrati sulla costruzione di un estimatore per il bispettro delle needlets, includendo l'effetto spurio che puo' essere introdotto
dalla presenza di eventuale segnale residuo, proveniente da sorgenti di natura prevalentemente Galattica.Cosmology has entered the precision epoch thanks to several very accurate experiments. Cosmologists now have access to an array of tools to test the cosmological concordance model and constrain its parameters; the Cosmic Microwave Background radiation (CMB), in particular, has been playing a crucial role in this ambition. Many questions remain nonetheless unanswered, especially concerning the physics of the early Universe, the infl ationary mechanism which set the initial conditions for the Universe expansion, and the nature of the late time acceleration of the Universe expansion. My research contributes to both of these sub jects, the common ground being the development of a statistical tool - needlets, a new "frame" on the sphere - to analyse the CMB. By means of needlets, we measure the Integrated Sachs Wolfe effect by cross-correlating WMAP and NVSS datasets and characterise dark energy properties using a phenomenological fluid model. Motivated by our findings, we study in detail a parameterisation of the dark components, dark matter and dark energy, which makes use of an affine equation of state, constraining the parameters of the model by combining WMAP and SDSS datasets. We apply needlets to the WMAP 5-year data release testing the Gaussianity of the CMB perturbations. Our approach is twofold: we first focus on the maps, detecting anomalous spots located in the southern hemisphere and check their effect on the angular power spectrum. We next measure the needlet three-point correlation function (bispectrum) and characterise it in terms of its overall amplitude, constraining the primordial fNL parameter, and considering its properties according to the geometry of the triangle configurations which contribute to the total power. We find a significant anomaly in the isosceles confi gurations, again in the southern hemisphere. Finally we focus on the construction of an optimal estimator for the (needlets) bispectrum, taking into account foreground residuals due mainly to Galactic emission.
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Lemaitre, Paul. "Analyse de sensibilité en fiabilité des structures." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0061/document.
Full textAbstract:
Cette thèse porte sur l'analyse de sensibilité dans le contexte des études de fiabilité des structures. On considère un modèle numérique déterministe permettant de représenter des phénomènes physiques complexes.L'étude de fiabilité a pour objectif d'estimer la probabilité de défaillance du matériel à partir du modèle numérique et des incertitudes inhérentes aux variables d'entrée de ce modèle. Dans ce type d'étude, il est intéressant de hiérarchiser l'influence des variables d'entrée et de déterminer celles qui influencent le plus la sortie, ce qu'on appelle l'analyse de sensibilité. Ce sujet fait l'objet de nombreux travaux scientifiques mais dans des domaines d'application différents de celui de la fiabilité. Ce travail de thèse a pour but de tester la pertinence des méthodes existantes d'analyse de sensibilité et, le cas échéant, de proposer des solutions originales plus performantes. Plus précisément, une étape bibliographique sur l'analyse de sensibilité puis sur l'estimation de faibles probabilités de défaillance est proposée. Cette étape soulève le besoin de développer des techniques adaptées. Deux méthodes de hiérarchisation de sources d'incertitudes sont explorées. La première est basée sur la construction de modèle de type classifieurs binaires (forêts aléatoires). La seconde est basée sur la distance, à chaque étape d'une méthode de type subset, entre les fonctions de répartition originelle et modifiée. Une méthodologie originale plus globale, basée sur la quantification de l'impact de perturbations des lois d'entrée sur la probabilité de défaillance est ensuite explorée. Les méthodes proposées sont ensuite appliquées sur le cas industriel CWNR, qui motive cette thèseThis thesis' subject is sensitivity analysis in a structural reliability context. The general framework is the study of a deterministic numerical model that allows to reproduce a complex physical phenomenon. The aim of a reliability study is to estimate the failure probability of the system from the numerical model and the uncertainties of the inputs. In this context, the quantification of the impact of the uncertainty of each input parameter on the output might be of interest. This step is called sensitivity analysis. Many scientific works deal with this topic but not in the reliability scope. This thesis' aim is to test existing sensitivity analysis methods, and to propose more efficient original methods. A bibliographical step on sensitivity analysis on one hand and on the estimation of small failure probabilities on the other hand is first proposed. This step raises the need to develop appropriate techniques. Two variables ranking methods are then explored. The first one proposes to make use of binary classifiers (random forests). The second one measures the departure, at each step of a subset method, between each input original density and the density given the subset reached. A more general and original methodology reflecting the impact of the input density modification on the failure probability is then explored.The proposed methods are then applied on the CWNR case, which motivates this thesis
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Kyriakopoulos, Nikos. "Flocking in active matter systems : structure and response to perturbations." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231666.
Full textAbstract:
Flocking, the collective motion of systems consisting of many agents, is a ubiquitous phenomenon in nature, observed both in biological and artificial systems. The understanding of such systems is important from both a theoretical point of view, as it extends the field of statistical physics to non-equilibrium systems, and from a practical point of view, due to the emergence of applications that are based on the modelling. In the present thesis I numerically investigated several aspects of flocking dynamics, simulating systems consisting of up to millions of particles. One first problem I worked on regarded the flocks response to external perturbations, something that had received little attention so far. The result was a scaling relation, connecting the asymptotic response of a flock to the strength of the external fleld affecting it. Additionally, my preliminary results point towards a generalised fluctuation-dissipation relation for the short-time response, with two different effective temperatures depending on the direction at which the perturbing field is applied. Another aspect I studied was the stability and dynamical properties of non-confined active systems (finite flocks in open space). The results showed that these flocks are stable only when an attracting 'social force' keeps the agents from drifting away from each other. The velocity fluctuations correlations were found to be different than the asymptotic limit predictions of hydrodynamic theories for infinite flocks. Finally, I studied the clustering dynamics of flocking systems. The conclusion was that the non-equilibrium clustering in the ordered phase is regulated by an anisotropic percolation transition, while it does not drive the order-disorder transition, contrary to earlier conjectures. I believe the results of this work answer some important questions in the field of ordered active matter, while at the same time opening new and intriguing ones, that will hopefully be tackled in the near future.
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Li, Yuemeng. "Spectral Analysis of Directed Graphs using Matrix Perturbation Theory." Thesis, The University of North Carolina at Charlotte, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10618933.
Full textAbstract:
The spectral space of the adjacency matrix contains important structural information of a given network (graph), where such information can be leveraged in developing a variety of algorithms in applications such as graph partition, structural hierarchy discovery, and anomaly detection. Although many prominent works have laid the foundation for studying the graph spectra, it is still challenging to analyze the spectral space properties for directed graphs due to possible complex valued decompositions. Matrix factorization techniques such as Laplacian and normalized Laplacian have been widely adopted to study the associated spectral spaces, but network structural properties may not be well preserved in those spectral spaces due to transformations.
In this dissertation work, we explore the adjacency eigenspace of directed graphs using matrix perturbation theory and examine the relationships between graph structures and the spectral projection patterns. We study how to detect dominant structures such as clusters or anomalous nodes by establishing a connection between the connectivity of nodes and the geometric relationships in the adjacency eigenspace. We leverage selected key results from perturbation theory, linear algebra and graph theory as our tools to derive theoretical results that help to elaborate observed graph spectral projection patterns. In order to validate our theoretical results, novel algorithms including spectral clustering for both signed and unsigned networks, asymmetry analysis for network dominance, and anomaly analysis for streaming network data are developed and tested on both synthetic and real datasets. The empirical evaluation results suggest that our algorithms performs better when compared with existing state-of-the-art methods.
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Luo, Min. "Perturbation analysis and optimization of fork-join queueing networks." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/14901.
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Ahmad, M. Masood. "Sensitivity estimates via perturbation analysis in power system simulations." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15408.
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Ivandich, Steven A. "Performance analysis of adaptive arrays with projected perturbation sequences." Thesis, Curtin University, 1999. http://hdl.handle.net/20.500.11937/94.
Full textAbstract:
Perturbation techniques are useful in the design of low complexity adaptive antenna arrays for estimating the gradient required in stochastic descent algorithms. Implementing projected perturbation sequences in an adaptive array allows the simultaneous reception of signals and the adaptation of the array weights while preserving the constraints imposed on the array weights.This thesis quantifies the performance of narrowband adaptive array processors that employ projected perturbation techniques. For different perturbation receiver structures the performance is determined under idealised conditions and importantly also when practical implementation issues are taken into account.The arrays performance is characterised by analysing the transient performance of the weight covariance matrix and by determining the misadjustment. By drawing similarities between two established analysis techniques a new misadjustment analysis technique is introduced.Practical implementation can impact on the arrays performance such that the benefit of the projected perturbation approach is lost. By characterising the array's sensitivity to perturbation noise additional projections which counteract some implementation effects are identified. The level of loss of performance due to weight quantisation and the limited dynamic range of the array weights is determined.
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Ivandich, Steven A. "Performance analysis of adaptive arrays with projected perturbation sequences." Curtin University of Technology, Australian Telecommunications Research Institute, 1999. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10431.
Full textAbstract:
Perturbation techniques are useful in the design of low complexity adaptive antenna arrays for estimating the gradient required in stochastic descent algorithms. Implementing projected perturbation sequences in an adaptive array allows the simultaneous reception of signals and the adaptation of the array weights while preserving the constraints imposed on the array weights.This thesis quantifies the performance of narrowband adaptive array processors that employ projected perturbation techniques. For different perturbation receiver structures the performance is determined under idealised conditions and importantly also when practical implementation issues are taken into account.The arrays performance is characterised by analysing the transient performance of the weight covariance matrix and by determining the misadjustment. By drawing similarities between two established analysis techniques a new misadjustment analysis technique is introduced.Practical implementation can impact on the arrays performance such that the benefit of the projected perturbation approach is lost. By characterising the array's sensitivity to perturbation noise additional projections which counteract some implementation effects are identified. The level of loss of performance due to weight quantisation and the limited dynamic range of the array weights is determined.
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Bennett, James Cameron, and james bennett@student rmit edu au. "Mathematical Analysis of Film Blowing." RMIT University. Mathematical and Geospatial Sciences, 2008. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20081128.115021.
Full textAbstract:
Film blowing is a highly complex industrial process used to manufacture thin plastic films for uses in a wide range of applications; for example, plastic bags. The mathematical modelling of this process involves the analysis of highly nonlinear differential equations describing the complex phenomena arising in the film blowing process, and requires a sophisticated mathematical approach. This dissertation applies an innovative combination of tools, namely analytic, numerical and heuristic mathematical techniques to the analysis of the film blowing process. The research undertaken examines, in particular, a two-point boundary value problem arising from the modelling of the radial profile of the polymer film. For even the simplest modelling of this process, namely the isothermal Newtonian model, the resulting differential equation is a highly nonlinear, second order one, with an extra degree of difficulty due to the presence of a small parameter multiplying the highest derivative. Thus, the problem falls into the category of a nonlinear singular perturbation problem. Analytic techniques are applied to the isothermal Newtonian blown film model to obtain a closed form explicit approximation to the film bubble radius. This is then used as a base approximation for an iterative numerical scheme to obtain an improved numerical solution of the problem. The process is extended to include temperature variations, varying viscosity (Power law model) and viscoelastic effects (Maxwell model). As before, closed form approximations are constructed for these models which are used to launch numerical schemes, whose solutions display good accuracy. The results compare well with results obtained by purely numerical solutions in the literature.
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Farina, Sofia. "A physical interpretation of network laplacian: role of perturbations and masses." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16345/.
Full textAbstract:
Il presente elaborato si propone di studiare il laplaciano associato ad un network, oggetto di interesse sia perchè dalla sua analisi spettrale è possibile ricavare delle tecniche di ricostruzione e rappresentazione della rete efficienti e al contempo semplici da implementare, ma anche per la sua possibile intepretazione fisica.
Il lavoro si struttura in due sezioni: la prima, riguardante l'analisi numerica dello spettro del laplaciano di un network con particolari proprietà di simmetria e regolarità anche in seguito alla sua perturbazione in termini di rimozone casuale di nodi e di link; la seconda incentrata su un suo modello intepretativo in chiave fisica che ci permette di ragionare sul reticolo immaginandolo come una serie di masse collegate tra loro da molle, dotate di una lunghezza caratteristica e di una costante elastica, e di vedere la sua rappresentazione come la visualizzazione dello stato di equilibrio raggiunto da questo sistema.
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Metelkina, Asya. "Perturbations à oscillations lentes de l'opérateur de Schrödinger périodique." Phd thesis, Université Paris-Nord - Paris XIII, 2011. http://tel.archives-ouvertes.fr/tel-00714033.
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On étudie l'opérateur de Schrödinger Ha + V(x) + W(x dans L où V est un potentiel périodique générique. On suppose que w est périodique et a (O, 1) de sorte que la perturbation W(x soit à oscillations asymptotiquement lentes. On étudie l'asymptotique des solutions de l'équation propre associée par deux approches différentes. La première approche, qui est basée sur une méthode de Sirnon---Zhu, utilise des approximations périodiques. On obtient une formule explicite pour la densité d'états intégrée pour Ha. Puis, on prouve l'existence et on donne une formule pour l'exposant de Lyapounov pour presque toutes les énergies. Nous décrivons aussi l'ensemble exceptionnel des énergies, qui contient le spectre singulier continu de Ha.La seconde méthode est nouvelle : elle utilise des approximations quasi- périodiques plutôt que périodiques. On approxime la résolvante de Ha par les résolvantes des opérateurs quasi-périodiques Hz,e + V(x) + W(Ex + z) pour des paramètres z et E bien choisis. Afin de pou- voir appliquer la méthode de la résolvante approchée à Ha, on étudie des solutions de l'équation propre pour à l'aide de la méthode BKW complexe de Fedotov--Klopp. On obtient les asymptotiques des solutions et des matrices de monodroimie quand tend vers zéro. Sous la condition c > , on construit des solutions de l'équation propre pour Ha ayant une asymptotique simple en x sur de grands intervalles. Puis, par l'étude des matrices de transfert associées, on obtient une nouvelle description, plus précise que la précédente, de l'ensemble exceptionnel des énergies.
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Ettenhuber, Christian. "Computational approaches for metabolic flux analysis in 13C perturbation experiments." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=974209961.
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Pang, Wyming Lee. "Quantitative analysis of genetic expression responses to dynamic microenvironmental perturbation." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3245319.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed March 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 320-337).
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Howell, William Casey. "Simulation optimization of traffic light signal timings via perturbation analysis." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3779.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Applied Mathematics and Scientific Computation Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Koreshi, Zafar-Ullah. "Monte Carlo perturbation applications for nuclear fusion reactor blanket analysis." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386090.
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Hoffmann, Peter, and Christoph Jacobi. "Analysis of planetary waves seen in ionospheric total electron content (TEC) perturbations." Universität Leipzig, 2006. https://ul.qucosa.de/id/qucosa%3A15490.
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Am DLR Neustrelitz wird kontinuierlich die totale Ionosation der Atmosphäre bestimmt und globale Karten der vertikal integrierten Elektronendichte erstellt. Es werden dazu die Signale der Navigationssatelliten-Systeme GPS und GLONASS verwendet. In dieser
Arbeit wird die Verteilung des totalen Elektronengehalt (TEC) oberhalb der mittleren Breiten während der Übergangssaison September bis November 2004 auf langperiodische Variationen im Bereich von mehreren Tagen sowie zonalen Wellenzahlen bis zu 5 untersucht. Die Ergebnisse werden mit einer Analyse von planetaren Wellen aus assimilierten Stratosphärendaten, Radardaten für Temperatur vom Collm Observatorium (51.3◦N, 13.0◦O) und Beobachtungen der kritischen Plasmafrequenz der F2-Schicht (f0F2) mit der Ionosonde in Juliusruh (54.6◦N, 13.4◦O) verglichen, um den meteorologischen Einfluss auf die Variation der Ionosphäre zu studieren.The DLR Neustrelitz regularly produces maps of the total total electron content (TEC) on a global scale using the navigation satellite systems GPS and GLONASS to forecast space weather. In this study we turn our attention to the higher middle latitudes TEC variations during September to November 2004 in a long-period range of several days with a zonal wavenumber up to 5. The results are compared with a planetary wave analysis using assimilated stratospheric data, mesosphere/lower thermosphere radar temperature data at Collm observatory (51.3◦N, 13.0◦E) and the ionosonde observed critical plasma frequency of the F2-layer (f0F2) at Juliusruh (54.6◦N, 13.4◦E) to investigate the meteorological influences on ionospheric variability.
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Nardone, Marco. "Analysis of Voice Perturbations Using an Asymmetric Model of the Vocal Folds." Bowling Green State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1183755009.
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Hoffmann, Peter, and Christoph Jacobi. "Analysis of planetary waves seen in ionospheric total electron content (TEC) perturbations." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-221930.
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Am DLR Neustrelitz wird kontinuierlich die totale Ionosation der Atmosphäre bestimmt und globale Karten der vertikal integrierten Elektronendichte erstellt. Es werden dazu die Signale der Navigationssatelliten-Systeme GPS und GLONASS verwendet. In dieser Arbeit wird die Verteilung des totalen Elektronengehalt (TEC) oberhalb der mittleren Breiten während der Übergangssaison September bis November 2004 auf langperiodische Variationen im Bereich von mehreren Tagen sowie zonalen Wellenzahlen bis zu 5 untersucht. Die Ergebnisse werden mit einer Analyse von planetaren Wellen aus assimilierten Stratosphärendaten, Radardaten für Temperatur vom Collm Observatorium (51.3◦N, 13.0◦O) und Beobachtungen der kritischen Plasmafrequenz der F2-Schicht (f0F2) mit der Ionosonde in Juliusruh (54.6◦N, 13.4◦O) verglichen, um den meteorologischen Einfluss auf die Variation der Ionosphäre zu studierenThe DLR Neustrelitz regularly produces maps of the total total electron content (TEC) on a global scale using the navigation satellite systems GPS and GLONASS to forecast space weather. In this study we turn our attention to the higher middle latitudes TEC variations during September to November 2004 in a long-period range of several days with a zonal wavenumber up to 5. The results are compared with a planetary wave analysis using assimilated stratospheric data, mesosphere/lower thermosphere radar temperature data at Collm observatory (51.3◦N, 13.0◦E) and the ionosonde observed critical plasma frequency of the F2-layer (f0F2) at Juliusruh (54.6◦N, 13.4◦E) to investigate the meteorological influences on ionospheric variability
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Anselmi, Stefano. "Semi-analytical approaches to cosmological perturbations in the mildly non-linear regime." Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3421616.
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One of the most interesting challenges of present cosmology concerns the understanding of structure formation and evolution. This physical process encodes fundamental information about the nature of our Universe. The analysis of the growth of density and velocity perturbations gives us an excellent opportunity to address basic questions such as the amount of dark matter or the reason for the present accelerated expansion of the Universe (known as the Dark Energy problem).
On large scales the growth of perturbations can be described by linear perturbation theory. The results on these scales have been largely confirmed by numerical simulations and employed in real data analysis.
Future galaxy surveys will be able to give constraints on the perturbations growth with unprecedent precision. Moreover relevant physical information is encoded in scales smaller than O(100 Mpc), where where the structures are more clustered and linear perturbation theory breaks down. Higher orders in the perturbative expansion are not manifestly suppressed by a small expansion parameter, so that their use depends on the scale, redshift, and on features of initial conditions such as the shape of the primordial power spectrum and of the other statistical correlators (bispectrum, trispectrum, etc.).
The main implemented tools to face the problem of nonlinear structure formation are the N-body simulations, even though they show inconveniences. Indeed, simulations give less physical insight with respect to analytical or semi-analytical approach. Furthermore simulations are limited by the long computational time involved.
Given the motivations above, different semi-analytical approaches to the problem have appeared in the last years. These are based on the possibility of recasting the cosmological perturbation series in an appropriate way. Most of these new theories reorganize the series expansion by redefining the building blocks of the perturbative expansion. In particular the nonlinear propagator gains a fundamental role and it has been analytically computed by means of different approximations. It represents the cross-correlation between the final density, or velocity, perturbations and the initial ones.
The main purpose of this thesis is to go beyond the known nonlinear propagator approximations leveraging on the exact evolution equations for the propagator which we derive. We analytically develop a well motivated approximation scheme by including a larger class of perturbative corrections which are neglected in other analytic re-summations. More specifically, this method allows us to take into account also the corrections given by a generic non linear matter power spectrum. Furthermore we compute the non linear propagator considering two different approximations for the full nonlinear power spectra. This problem has been addressed both with analytic and numerical techniques. As a general result we find that the precedent approaches lead to a wrong prediction on the sign of the propagator corrections. This clarifies a controversial problem and points out that further comparisons with N-body simulations are necessary. We find that the new corrections are significant at the relevant scales and therefore cannot be neglected in a re-summation scheme aiming at an accuracy compatible with future generation galaxy surveys. Furthermore we propose a method to implement the power spectrum computation taking into account this results.Una delle sfide più importanti della cosmologia riguarda la comprensione della formazione e dell'evoluzione delle strutture. Questi processi fisici ci forniscono informazioni fondamentali sulla natura del nostro Universo. L'analisi della crescita delle perturbazioni di densita' e di velocita' ci offre un'importante opportunita' per quantificare con piu' accuratezza la percentuale di materia oscura o comprendere le cause che guidano l'espansione accelerata dell'Universo (il cosiddetto problema dell'Energia Oscura). A grandi scale la crescita delle fluttuazioni puo' essere descritta con la teoria delle perturbazioni lineari. I risultati a queste scale sono stati largamente confermati dalla simulazioni numeriche e utilizzati nell'analisi dei dati reali. Le future osservazioni di galassie ci permetteranno di porre dei vincoli sulla crescita delle perturbazioni con una precisione mai raggiunta prima. Inoltre, informazioni fisiche rilevanti sono presenti a scale piu' piccole di O(100 Mpc), dove le strutture sono molto piu' raggruppate e la teoria delle perturbazioni lineare non e' piu' valida. Le tecniche piu' utilizzate per affrontare il problema della formazione delle strutture sono le simulazioni ad N-corpi, anche se mostrano alcuni inconvenienti. Infatti, le simulazioni rendono piu' difficile la comprensione della fisica rispetto all'approccio analitico e semi-analitico. Inoltre le simulazioni sono limitate dal lungo tempo di calcolo che caratterizza questi studi. Date le precedenti motivazioni, differenti approcci semi-analitici al problema sono apparsi negli ultimi anni. Essi sono basati sulla possibilita' di riformulare la serie di perturbazioni cosmologiche in maniera appropriata. La maggior parte di queste nuove teorie riorganizza l'espansione in serie ridefinendo le grandezze fondamentali dello sviluppo perturbativo. In particolare il propagatore non lineare assume un ruolo fondamentale ed e' stato calcolato analiticamente con approcci differenti. Esso rappresenta il cross-correlatore tra le perturbazioni finali e iniziali di densita', o di velocita'. L'obiettivo principale di questa tesi e' quello di andare oltre le approssimazioni note relative al calcolo del propagatore non lineare facendo uso delle equazioni esatte di evoluzione per il propagatore. Abbiamo sviluppato e motivato un metodo di approssimazione analitico che ci ha permesso di includere una piu' ampia classe di correzioni perturbative che sono state trascurate in altre risommazioni analitiche. In particolare, questo metodo ci permette di considerare le correzioni date da un generico spettro di potenza non lineare. Inoltre abbiamo calcolato il propagatore non lineare considerando due differenti approssimazioni per lo spettro di potenza esatto. Questo problema e' stato trattato sia con tecniche analitiche che numeriche. Come risultato generale, abbiamo trovato che gli approcci predenti portano ad un risultato errato per quanto riguarda il segno delle correzioni del propagatore. Questo chiarisce un problema controverso e suggerisce che sono necessari ulteriori confronti con le simulazioni a N-corpi. Abbiamo trovato che le nuove correzioni sono significative alle scale rilevanti e quindi non possono essere trascurate in uno schema di risommazione che mira a raggiungere un'accuratezza compatibile con le future osservazioni astrofisiche. Inoltre proponiamo un metodo per calcolare lo spettro di potenza tenendo conto di questi risultati.
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Blenkinsop, Glen M. "Postural control : learning to balance and responses to mechanical and sensory perturbations." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/17109.
Full textAbstract:
The purpose of the current research was to examine how a novel balance task is learnt by individuals with a mature neurological system, and to investigate the responses of experienced hand balancers to mechanical and sensory perturbations. Balance in each posture was assessed by various techniques, including: traditional measures of centre of pressure, nonlinear time series analysis of centre of pressure, estimates of feedback time delay from cross correlations and delayed regression models, and calculation of small, medium, and large movement corrections. Data from this study suggests that the best balance metric for distinguishing between each of the balance conditions was the traditional balance measure of sway velocity. However, sway velocity cannot provide any further information on the underlying process of balance. Nonlinear measures of balance offer insight into the underlying deterministic processes that control balance, offering measures of system determinism, complexity, and predictability. Assessments of feedback time delay and movement corrections provide both an insight into the control of posture and help distinguish one condition from another. Both feedback time delay and movement corrections and magnitudes may be used simultaneously to delve further into the control of posture. Delayed regression models seem to be an appropriate and useful tool for estimating feedback time delays during balance. Findings support the use of the third term in the adapted regression model as a means of estimating the effect of passive stiffness on feedback time delay. Generally, with increased duration in handstand subjects displayed reduced sway as measured by traditional measures of balance. A more marked change in nonlinear measures of balance can be seen, with quicker reductions in variance for some nonlinear measures of balance than in the traditional measures. It may be that more pronounced changes in nonlinear measures represent changes in the subjects underlying process of postural control, whereas less pronounced changes in traditional measures relate more to their general ability or performance in the balance task.
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Dalla, Riva Matteo. "Potential theoretic methods for the analysis of singularly perturbed problems in linearized elasticity." Doctoral thesis, Università degli studi di Padova, 2008. http://hdl.handle.net/11577/3426270.
Full textAbstract:
The dissertation is made of two chapters. The first chapter is dedicated to the investigation of some properties of the layer potentials of a constant coefficient elliptic partial differential operator. In the second chapter, we focus our attention to the Lamè equations, which are related to the physic of an isotropic homogeneous elastic body.
In particular, in the first chapter, we investigate the dependence of the single layer potential upon perturbation of the density, the support and the coefficients of the corresponding operator. Under some more restrictive assumptions on the operator, we prove a real analyticity theorem for the single layer potential and its derivatives.
As a first step, we introduce a particular fundamental solution of a given constant coefficient partial differential operator. For this purpose, we exploite the construction of a fundamental solution given by John (1955). We have verified that, if the coefficients of the operator are constrained to a bounded set, then there exist a particular fundamental solution which is a sum of functions which depend real analytically on the coefficients of the operator. Such a result resembles the results of Mantlik (1991, 1992) (see also Tréves (1962)), where more general assumptions on the operator are considered. We observe that it is not a corollary. Indeed, we need a suitably detailed expression for the fundamental solution, which cannot be deduced by Mantlik's results.
The next step is to introduce the support of our single layer potentials. It will be a compact sub-manifold of the the n-dimensional euclidean space parametrized by a suitable diffeomorphism defined on the boundary of a fixed domain.
Then, we will be ready to state in Theorem 1.7 the main result of this chapter, which is a real analyticity result in the frame of Shauder spaces. The main idea of the proof stems from the papers of Lanza de Cristoforis & Preciso (1999) and by Lanza de Cristoforis & Rossi (2004, 2005) and exploits the Implicit Mapping Theorem for real analytic functions. Indeed, our main Theorem 1.7 is in some sense a natural extension of theorems obtained by Lanza de Cristoforis & Preciso (1999) and by Lanza de Cristoforis & Rossi (2004, 2005), for the Cauchy integral and for the Laplace and Helmholtz operators, respectively. Here we confine our attention to elliptic operators which can be factorized with operators of order 2.
In the last section of the first chapter, we consider some applications of Theorem 1.7. In particular, we deduce a real analyticity theorem for the single and double layer potential which arise in the analysis of the boundary value problems for the Lamè equations and for the Stokes system.
In the second chapter, we focus our attention to the Lamè equations. We consider some boundary value problems defined in a domain with a small hole. For each of them, we investigate the behavior of the solution and of the corresponding energy integral as the hole shrinks to a point.
This kind of problem is not new at all and has been long investigated by the techniques of asymptotic analysis. It is perhaps difficult to give a complete list of contributions. Here we mention the work of Keller, Kozlov, Movchan, Maz'ya, Nazarov, Plamenewskii, Ozawa and Ward. The results that we present are in accordance with the behavior one would expect by looking at the above mentioned literature, but we adopt a different approach proposed by Lanza de Cristoforis (2001, 2002, 2005, 2007.) To do so, we exploit the real analyticity results for the elastic layer potentials obtained in the first chapter.
We now briefly outline the main difference between our approach and the one of asymptotic analysis. Let d>0 be a parameter which is proportional to the diameter of the hole, so that the singularity of the domain appears when d=0. By the approach of the asymptotic analysis, we can expect to obtain results which are expressed by means of known functions of d plus an unknown term which is smaller than a positive power of d. Whereas, our results are expressed by means of real analytic functions of d defined in a whole open neighborhood of d=0 and by, possibly singular, but completely known functions of d, such as d^(2-n) or log d.
Moreover, not only we can consider the dependence upon d, we can also investigate the dependence of the solution and the corresponding energy integral upon perturbations of the coefficients of the operator, and of the point where the hole is situated, and of the shape of the hole, and of the shape of the outer domain, and of the boundary data on the boundary of the hole, and of the boundary data on the boundary of the outer domain, and of the interior data. Also in this case we obtain results expressed by means of real analytic functions and completely known functions such as d^(2-n) and log d.
The first boundary value problem we have studied is a Dirichlet boundary value problem with homogeneous data in the interior. Then, we turned to investigate a Robin boundary value problem with homogeneous data in the interior. In this case we have also described the behavior of the solution and the corresponding energy integral when both the domain and the boundary data display a singularity for d=0. Finally, we have studied a Dirichlet boundary value problem with non-homogeneous data in the interior.
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Birman, Michael, Tatyana Suslina, and tanya@petrov stoic spb su. "Threshold Effects near the Lower Edge of the Spectrum for Periodic." ESI preprints, 2001. ftp://ftp.esi.ac.at/pub/Preprints/esi992.ps.
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Civin, Damon. "Stability of charged rotating black holes for linear scalar perturbations." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/247397.
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In this thesis, the stability of the family of subextremal Kerr-Newman space- times is studied in the case of linear scalar perturbations. That is, nondegenerate energy bounds (NEB) and integrated local energy decay (ILED) results are proved for solutions of the wave equation on the domain of outer communications. The main obstacles to the proof of these results are superradiance, trapping and their interaction. These difficulties are surmounted by localising solutions of the wave equation in phase space and applying the vector field method. Miraculously, as in the Kerr case, superradiance and trapping occur in disjoint regions of phase space and can be dealt with individually. Trapping is a high frequency obstruction to the proof whereas superradiance occurs at both high and low frequencies. The construction of energy currents for superradiant frequencies gives rise to an unfavourable boundary term. In the high frequency regime, this boundary term is controlled by exploiting the presence of a large parameter. For low superradiant frequencies, no such parameter is available. This difficulty is overcome by proving quantitative versions of mode stability type results. The mode stability result on the real axis is then applied to prove integrated local energy decay for solutions of the wave equation restricted to a bounded frequency regime. The (ILED) statement is necessarily degenerate due to the trapping effect. This implies that a nondegenerate (ILED) statement must lose differentiability. If one uses an (ILED) result that loses differentiability to prove (NEB), this loss is passed onto the (NEB) statement as well. Here, the geometry of the subextremal Kerr-Newman background is exploited to obtain the (NEB) statement directly from the degenerate (ILED) with no loss of differentiability.
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Hamouda, Makram. "Perturbations singulières pour des EDP linéaires et non linéaires en presence de discontinuités." Phd thesis, Université Paris Sud - Paris XI, 2001. http://tel.archives-ouvertes.fr/tel-00001931.
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Ma thèse porte sur l'étude des couches limites et de perturbations singulières (\textit{i.e.} des problèmes caractérisés par la présence d'un petit paramètre qui tend vers zéro) dans des conditions plus délicates que d'habitude, à savoir lorsque la solution limite n'est pas régulière. Je considère ainsi deux classes de problèmes réguliers associes à un laplacien et à un bilaplacien, et un problème non linéaire dérivé du problème de Plateau (surfaces minimas), pour lequels la fonction limite possède une singularité (discontinuité simple pour les premiers problèmes, dérivée normale infinie sur certaines parties de la frontière pour le second).\\ La première partie de cette thèse est consacrée à l'étude de deux modèles linéaires singuliers associés à des perturbations singulières pour des EDPs ayant une fonction source singulière. Ce type d'équations fait l'objet de plusieurs applications, par exemple les problèmes de flambement en élasticité, les tourbillons singuliers en mécanique des fluides, le problème de la charge critique pour une poutre ou une plaque élastoplastique, le problème du contrôle automatique de la trajectoire d'un mobile et le problème du bord arrière pour l'écoulement autour d'une aile. De manière classique, la présence d'un petit paramètre dans des équations aux dérivées partielles entraîne, dans certains cas, l'apparition d'une couche limite classique près du bord du domaine pour la solution dite régularisée. Cependant, si on considère en plus une fonction source discontinue (voire une distribution), on constate que de nouvelles couches limites apparaissent à l'intérieur du domaine; l'étude de celles-ci constitue le principal but de cette première partie. Dans la deuxième partie, on s'intéresse à l'étude du problème des surfaces minimales sur une couronne. Pour certaines classes de données au bord, ce problème n'admet pas de solution et sa solution faible dite ``généralisée'' admet une dérivée infinie. On introduit alors une méthode de régularisation elliptique qui entraîne une couche limite près du bord. Le résultat fondamental de cette partie consiste à donner explicitement une approximation pour cette solution régularisée.
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Wiklund, Susanne. "Spectroscopic data and multivariate analysis : tools to study genetic perturbations in poplar trees." Doctoral thesis, Umeå : Department of Chemistry, Umeå Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1396.
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Cox, Neil Bernard. "Assessment of vocal pathology through computerized analysis of perturbation in vowels." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29081.
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This thesis involved the development, validation and "calibration" of computerized methodologies for analysis of short-time perturbations in vowels, including mathematical analyses of the effect of measurement errors, verification using synthesized data, and evaluation using real data. Such methodologies have been proposed for improved diagnosis and management of laryngeal pathology.
Significant effects were observed in mathematical analyses of quantization and pitch-period demarcation for three popular algorithms; the harmonics-to-noise ratio (HNR), the relative average perturbation (RAP) and the directional perturbation quotient (DPQ). A severe underestimation of the HNR caused by such errors was demonstrated. The effect was shown to depend on high frequency components of the vowel. Errors affecting the use of the RAP in measurement of jitter and shimmer were quantified, and methods of compensation were proposed. The DPQ demonstrated a dependence on perturbation magnitude. Such errors influence the interpretation and comparison of results.
A number of new measures were developed. The RAP and the DPQ were generalized for variation of the number and spacing of points. The HNR was modified to account for a data offset and for reduction of the influence of jitter and shimmer. A new measure of time domain noise called the correlation factor (CF) was introduced, along with new measures of cyclic perturbation. Issues in Fourier spectrum analysis that affect measures of spectral noise were discussed. Methods for taking advantage of fast Fourier transforms and window tapering were described, along with methods for reducing dependence on formant structure.
A new method for "optimizing" pitch-period demarcation markers was shown to be effective at reducing errors for all but the most severely perturbed waveforms. Cross-correlation was combined with parabolic interpolation to obtain high resolution pitch-period demarcation at moderate sampling frequencies.
An analysis of synthetic vowels was used to comparatively evaluate the influences of fundamental frequency, vowel type, perturbation type, perturbation level, pitch-period demarcation and quantization. Some findings were:
1) Interpolation is recommended for most measures when the
sampling frequency is 20 kHz or less.
2) Optimization of pitch-period markers significantly
improved the analyses.
3) Both the offset and the accuracy of pitch-period
demarcation can significantly affect measures of time domain noise.
4) Measures of shimmer and noise were affected by fundamental
frequency and vowel type.
5) Jitter affected measures of other characteristics.
6) Window tapering reduced the sensitivity of measures of
spectral noise to pitch-period demarcation errors.
7) Measures of spectral noise were far more sensitive to
jitter than measures of time domain noise. Prolongations of /a/ from 206 male subjects and 194 female subjects were analyzed. The computed measures were correlated with subjective judgements of hoarseness, and used to discriminate among pathologies. Some findings were:
1) Logarithmic transformation was recommended for measures of
jitter and shimmer.
2) Measures of time domain noise were generally superior to
measures of jitter, shimmer or spectral noise.
3) The best single measure was the correlation factor (CF).
4) The correlation with hoarseness was improved through
linear combination of the CF with a measure of jitter, leading to r≈.84 for males and r≈.80 for females.
5) Segregation of sexes was recommended.
6) Improved classification for males was obtained through
separation into four diagnostic classes.
7) Improved classification for both males and females was
obtained through inclusion of measures of perturbation patterns.
8) In an open test, the best classifiers had an average
recognition rate of approximately 74% for distinguishing normal speakers, and 71% for detecting cancer subjects.
9) Computer classification matched or exceeded the ability of
trained listeners.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Abedi, Vida. "System-identification of gene regulatory networks by systematic gene perturbation analysis." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28254.
Full textAbstract:
Systems biology is an interdisciplinary field that combines engineering and molecular biology to better understand the 'design principles' of biological systems. One of the main goals in systems biology is to understand and map complex biological networks. In order to achieve this goal, tools able to process the non-linearity and high dimensionality of biological systems are urgently needed. To develop, test and benchmark tools for investigation of biological processes, it is important to utilize a model system that is able to provide a glimpse of complexity found in higher organisms, and be simple enough such that detailed studies can be performed rapidly, accurately, and reproducibly. Here, we have developed a system-identification framework for the extraction of quantitative and mechanistic information about causal relationship among genes using the canonical galactose utilization pathway in Saccharomyces cerevisiae. This framework, referred to as s&barbelow;ystematic g&barbelow;ene p&barbelow;erturbation a&barbelow;nalysis (SGPA), is based on the effects of systematic pair-wise gene deletions. In essence, the method establishes dynamical models of the regulatory network from single-cell measurements of steady-state input-output relationships, in systematically perturbed networks. SGPA framework is successful in identifying the network structure for the GAL system. This strategy leads the way to a better application of available resources and provides a scalable framework for system-identification and reverse-engineering of biological networks based on in vivo systematic data generation.
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Kebarighotbi, Ali. "Perturbation analysis in fluid scheduling and optimization of stochastic hybrid systems." Thesis, Boston University, 2012. https://hdl.handle.net/2144/31576.
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Thesis (Ph.D.)--Boston UniversityPLEASE 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.
This dissertation is dedicated to optimization of Stochastic Hybrid Systems (SHS). The concentration is on both online optimization of these systems and extending the known optimal policies in Discrete-Event Systems (DES) to a broader context of SHS. A SHS involves both continuous and discrete dynamics and is suitable for modeling almost any physical system of interest. The first part of this dissertation focuses on applications of SHS and, particularly, a subclass known as Stochastic Flow Models (SFM) used in fluid scheduling. To this end, a classic problem for optimally allocating a resource to multiple competing user queues is considered in the DES context and placed in the framework of SFMs. Infinitesimal Perturbation Analysis (IPA) is used to calculate the gradient estimates for the average holding cost of this system with respect to resource allocation parameters. The monotonicity property of these estimates allows us to prove the optimality of a well-known rule called the "c - mu-rule" under non-idling policies. Furthermore, nonlinear cost functions are considered, yielding simple distribution-free cost sensitivity estimates. Next, we take the first step in using IPA for optimally calculating timeout thresholds in SHS. A Transmission Control Protocol (TCP) communication link is used to examine the effectiveness of SHS and IPA in calculating derivative estimates of a goodput objective with respect to a timeout parameter. The analysis is also extended to the case of multinode communications. Our results reveal a great potential in using IPA to control delay thresholds and motivate more investigations in future. Finally, we propose a general framework for analysis and on-line optimization of SHS which facilitates the use of IPA. In doing so, we modify the previous structure of a Stochastic Hybrid Automaton (SHA) and show that every transition is associated with an explicit event which is defined through a "guard function." This enables us to uniformly treat all events observed on the sample path of the SHS. As a result, a unifying matrix notation for IPA equations is developed which eliminates the need for the case-by-case analysis of event classes as usually done in prior works involving IPA for SHS.
2031-01-01
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Neugebauer, Christoph Johannes. "Perturbation theory analysis of non-equilibrium lattice models with spatial heterogeneity." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611122.
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Ashokkumar, C. R. "Eigenvalue/eigenvector perturbation for time response analysis of linear uncertain systems /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487858417983696.
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DE, SANTI FRANCESCA. "Perturbation dynamics in laminar and turbulent flows. Initial value problem analysis." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2613156.
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Stability and turbulence are often studied as separate branches of fluid dynamics, but they are actually the two faces of the same coin: the existence of equilibrium, laminar in one case and steady in the mean in the other. The link between these two faces is transition. Initial value problems are considered to analyse the dynamics of disturbances in the three phases.
In the context of stability, linearised equations of motion can be used. Although this is a substantial simplification, the results that are obtained with this
analysis are far from being trivial. The transition to turbulence through the dynamics of disturbances is discussed in the context of the zig-zag instability: a particular kind of instability that occurs in geophysical flows. Eventually, the perturbations dynamics in turbulent flows is used to analyse the mixing process between water-vapour in clouds and clear air in the surroundings, in the presence of a meteorological inversion.
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Davoren, Elmarie. "A metabolomics study of selected perturbations of normal human metabolism / Elmarie Davoren." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4219.
Full textAbstract:
Metabolism is an integrated network of biochemical pathways involving a series of enzymecatalysed
anabolic or catabolic reactions in cells. Metabolites are chemical compounds that are
involved in or are products of metabolic pathways, and the metabolome is defined as the total
complement of all the low molecular weight metabolites present in a cell at any given time.
Metabolomics is a relatively new research technology utilised for the global investigation,
identification and quantification of the metabolome. Three aims were defined for the
metabolomics study presented here:
• The use of metabolomics technology to generate new biological information;
• Application of the metabolomics technology to gain information on the three natural
perturbations, namely the menstrual cycle, pregnancy and aging; and
• Reflection on metabolomic studies as a hypothesis-generating approach.
I obtained three sets of urine samples from women during their menstrual cycle, samples from
sixteen pregnant and eleven non-pregnant women for the second natural perturbation, and data
sets from previous investigations on infant and child groups, as well as thirty-two urine samples
from adults for the study of the metabolomic profiles due to age. These urine samples were
analysed to determine the organic acid metabolite profiles. The metabolites were identified by
means of AMDIS and were manually quantified. Data matrixes were compiled, which underwent
certain data reduction steps, prior to statistical analysis. Different statistical approaches were
used to generate information on these three natural perturbations due to the clear differences
between the three experimental groups used. The investigation of the menstrual cycle did not
show a distinct difference between the three phases involved in the cycle, whereas the
pregnancy perturbation showed a difference between pregnant groups and non-pregnant
groups. The most pronounced difference in metabolite profiles were found when the different
age groups were compared to one another. Finally a hypothesis on the effect of age on
metabolism was defined and an experimental approach was proposed to evaluate this
hypothesis.
In conclusion three proposals were formulated from this investigation:
1. If it appears that an insufficient number of participants can be generated for a
metabolomics study, such a study should be discarded in the interest of a more feasible
investigation.
2. It is advisable that a number of appropriate analytical validation parameters should be
incorporated in the early stages of a metabolomics study, specifically linked to the
context of the perturbation chosen for the investigation. 3. The control and experimental groups should be homogenous that is to say as
comparable as possible with regard to age, ethnicity, diet, and gender, lifestyle habits
and other possible confounding influences, except for the specific perturbation being
studied. In a perfect world this would be possible, specifically when hypothesis
formulation, testing and finally the expansion of scientific knowledge is a desired
outcome of the investigation.Thesis (M.Sc. (Biochemistry))--North-West University, Potchefstroom Campus, 2010.