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1
Esposito, Pier Antonio. "Reissner Mixed Variational Theorem for Ritz Sublaminate Generalized Unified Formulation." Thesis, KTH, Lättkonstruktioner, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302787.
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This thesis is about the development of a new numerical method for the analysis of composite shells. The present work is based on Reissner Mixed Variational Theorem (RMVT), the Sublaminate Generalized Unified Formulation (S-GUF), and the Ritz approximation. The present work investigates a more efficient way to compute transverse stresses (sigma_xz, sigma_yz, sigma_zz) based upon RMVT, allowing assigning their order of continuity a priori. This is a great advantage compared to a conventional displacement-based approach. In order to enable computing of both global and local responses (depending on the user’sneeds) the S-GUF framework was adopted. The Generalized Unified Formulation (GUF) enables the implementation of approximations with virtually unlimited algebraic order within a single code, and the order could also vary for different variables. In addition to the GUF, the concept of Sublaminate was utilized, allowing for sub-sectioning of the domain in the thickness direction into sublaminates, and it is then possible to apply different formulations in each of these sub-domains. The curvature of the shells is strictly defined by their radius-to- thickness ratio. The flexibility of S-GUF is helpful in the sense that curvature is only introduced and treated if needed by the particular case at hand. The governing equations obtained applying S-GUF to RMVT were solved in a weak formulation using the Ritz approximation. This choice was made to save computational time, which is one of the main benefits of the presented method. Validation of the code was made by comparing results from the present formulation with solutions available in the literature. Good to excellent agreement was found for several benchmark cases, supporting that the formulation is valid and provides reliable solutions.Finally, numerical and analytical considerations about the developed method were made: its numerical stability, how to tune its parameters, and which models result more correct from an analytical standpoint.Denna avhandling handlar om utvecklingen av en ny numerisk metod för analys av kompositskal.Det aktuella arbetet är baserat på Reissner Mixed Variational Theorem (RMVT), Sublaminate Generalized Unified Formulation (S-GUF) och Ritz-approximationen.Arbetet går ut på att ta fram ett mer effektivt sätt att beräkna spänningar ut ur planet (sigma_xz, sigma_yz, aigma_zz) och utnyttjar RMVT, vilket möjliggör lokal hantering av kontinuitet i varierande ordning, definierad a priori. Detta innebär en stor fördel jämfört med en konventionell förskjutningsbaserad metod. För att möjliggöra beräkning av både global och lokal lösning, beroende påanvändarens behov, antogs S-GUF-ramverket. Den generaliserade enhetliga formuleringen (GUF) gördet möjligt att inom samma formulering implementera approximationer med i princip obegränsad algebraisk ordning, vilka dåocksåkan skilja mellan olika variabler. Förutom GUF används även konceptet Sublaminate som gör det möjligt att dela upp domänen i tjockleksriktningen i underregioner (sublaminate), och det är dåmöjligt att tillämpa olika formuleringar i var och en av dessa subdomäner. Krökningen hos ett skal definiers strikt av förhållandet mellan dess radie och tjocklek. Flexibiliteten hos S-GUF är fördelaktig dåkrökning endast hanteras för de specifika fall där det förekommer. De ekvationer som erhålls genom att applicera S-GUF på RMVT löses påsvag formmed användning av Ritz approximation. Detta val gjordes för att möjliggöra en snabbare beräkningstid, vilket är en av fördelarna med denna metod. Genom att jämföra de resultat med lösningar tillgängliga i litteraturen var det möjligt att validera resultaten och därmed även själva formuleringen. God till utmärkt överensstämmelse påvisades för ett antal olika standardfall vilket styrker att metoden fungerar och attdess lösningar är pålitliga. Slutligen ritades numeriska och analytiska överväganden om metoden här utvecklad, såsom dess numeriska stabilitet, hur man ställer in dess parametrar och vilka modeller somär mer korrekta ur en analytisk synvinkel.
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Le, Roux Christiaan. "Mixed variational problems associated with stationary viscous incompressible free boundary flows." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/15965.
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Bibliography: pages 93-97.A strategy that is often used in the study of capillary free boundary (FB) problems for viscous incompressible flows is the following: (1) Ignore one of the boundary conditions at the FB and prove that for every chosen position of the FB the resultant problem, here called the auxiliary problem (AP), is well posed. (2) Establish regularity results for the solution of the AP. (3) Using (2) and the remaining boundary condition, determine the position of the FB. We study the existence and uniqueness of the weak solution(s) to the AP, i.e., step (1), under minimal regularity constraints on the data and domain. The analysis is carried out for stationary two-dimensional flows, governed by either the Stokes or Navier-Stokes equations, in the context of four standard examples. A Green's formula is derived which allows the AP to be formulated as a mixed variational problem in which the pressure and normal stress appear as Lagrange multipliers. Existence and uniqueness results are obtained by using the Ladyzhenskaya-Babuska-Brezzi theory for mixed problems. By analogy with step (3), the dependence of the normal stress on the position of the FB is investigated.
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Richardson, Kyle Dennis. "Blending and Mixed Variational Principles to Overcome Locking Phenomena in Isogeometric Beams." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6495.
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Two methods for overcoming locking phenomena in isogeometric beams are presented. The first method blends the rotation of a Timoshenko beam with the rotation of a Bernoulli beam to produce realistic displacements in straight beams. The second method uses mixed variational principles, specifically the Hu-Washizu Principle, to produce realistic displacements as well as realistic strains without post-processing.
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Zhang, Fan. "Statistical Methods for Characterizing Genomic Heterogeneity in Mixed Samples." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/419.
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"Recently, sequencing technologies have generated massive and heterogeneous data sets. However, interpretation of these data sets is a major barrier to understand genomic heterogeneity in complex diseases. In this dissertation, we develop a Bayesian statistical method for single nucleotide level analysis and a global optimization method for gene expression level analysis to characterize genomic heterogeneity in mixed samples. The detection of rare single nucleotide variants (SNVs) is important for understanding genetic heterogeneity using next-generation sequencing (NGS) data. Various computational algorithms have been proposed to detect variants at the single nucleotide level in mixed samples. Yet, the noise inherent in the biological processes involved in NGS technology necessitates the development of statistically accurate methods to identify true rare variants. At the single nucleotide level, we propose a Bayesian probabilistic model and a variational expectation maximization (EM) algorithm to estimate non-reference allele frequency (NRAF) and identify SNVs in heterogeneous cell populations. We demonstrate that our variational EM algorithm has comparable sensitivity and specificity compared with a Markov Chain Monte Carlo (MCMC) sampling inference algorithm, and is more computationally efficient on tests of relatively low coverage (27x and 298x) data. Furthermore, we show that our model with a variational EM inference algorithm has higher specificity than many state-of-the-art algorithms. In an analysis of a directed evolution longitudinal yeast data set, we are able to identify a time-series trend in non-reference allele frequency and detect novel variants that have not yet been reported. Our model also detects the emergence of a beneficial variant earlier than was previously shown, and a pair of concomitant variants. Characterization of heterogeneity in gene expression data is a critical challenge for personalized treatment and drug resistance due to intra-tumor heterogeneity. Mixed membership factorization has become popular for analyzing data sets that have within-sample heterogeneity. In recent years, several algorithms have been developed for mixed membership matrix factorization, but they only guarantee estimates from a local optimum. At the gene expression level, we derive a global optimization (GOP) algorithm that provides a guaranteed epsilon-global optimum for a sparse mixed membership matrix factorization problem for molecular subtype classification. We test the algorithm on simulated data and find the algorithm always bounds the global optimum across random initializations and explores multiple modes efficiently. The GOP algorithm is well-suited for parallel computations in the key optimization steps. "
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Vasudevan, S. "Development of new spatially curved non-linear frame finite element using a mixed variational principle and rotations as independent variables." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13069.
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Köhler, Karoline Sophie. "On efficient a posteriori error analysis for variational inequalities." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17635.
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Effiziente und zuverlässige a posteriori Fehlerabschätzungen sind eine Hauptzutat für die effiziente numerische Berechnung von Lösungen zu Variationsungleichungen durch die Finite-Elemente-Methode. Die vorliegende Arbeit untersucht zuverlässige und effiziente Fehlerabschätzungen für beliebige Finite-Elemente-Methoden und drei Variationsungleichungen, nämlich dem Hindernisproblem, dem Signorini Problem und dem Bingham Problem in zwei Raumdimensionen. Die Fehlerabschätzungen hängen vom zum Problem gehörenden Lagrange Multiplikator ab, der eine Verbindung zwischen der Variationsungleichung und dem zugehörigen linearen Problem darstellt. Effizienz und Zuverlässigkeit werden bezüglich eines totalen Fehlers gezeigt. Die Fehleranschätzungen fordern minimale Regularität. Die Approximation der exakten Lösung erfüllt die Dirichlet Randbedingungen und die Approximation des Lagrange Multiplikators ist nicht-positiv im Falle des Hindernis- und Signoriniproblems, und hat Betrag kleiner gleich 1 für das Bingham Problem. Dieses allgemeine Vorgehen ermöglicht das Einbinden nicht-exakter diskreter Lösungen, welche im Kontext dieser Ungleichungen auftreten. Aus dem Blickwinkel der Anwendungen ist Effizienz und Zuverlässigkeit im Bezug auf den Fehler der primalen Variablen in der Energienorm von großem Interesse. Solche Abschätzungen hängen von der Wahl eines effizienten diskreten Lagrange Multiplikators ab. Im Falle des Hindernis- und Signorini Problems werden postive Beispiele für drei Finite-Elemente Methoden, der konformen Courant Methode, der nicht-konformen Crouzeix-Raviart Methode und der gemischten Raviart-Thomas Methode niedrigster Ordnung hergeleitet. Partielle Resultate liegen im Fall des Bingham Problems vor. Numerischer Experimente heben die theoretischen Ergebnisse hervor und zeigen Effizienz und Zuverlässigkeit. Die numerischen Tests legen nahe, dass der aus den Abschätzungen resultierende adaptive Algorithmus mit optimaler Konvergenzrate konvergiert.Efficient and reliable a posteriori error estimates are a key ingredient for the efficient numerical computation of solutions for variational inequalities by the finite element method. This thesis studies such reliable and efficient error estimates for arbitrary finite element methods and three representative variational inequalities, namely the obstacle problem, the Signorini problem, and the Bingham problem in two space dimensions. The error estimates rely on a problem connected Lagrange multiplier, which presents a connection between the variational inequality and the corresponding linear problem. Reliability and efficiency are shown with respect to some total error. Reliability and efficiency are shown under minimal regularity assumptions. The approximation to the exact solution satisfies the Dirichlet boundary conditions, and an approximation of the Lagrange multiplier is non-positive in the case of the obstacle and Signorini problem and has an absolute value smaller than 1 for the Bingham flow problem. These general assumptions allow for reliable and efficient a posteriori error analysis even in the presence of inexact solve, which naturally occurs in the context of variational inequalities. From the point of view of the applications, reliability and efficiency with respect to the error of the primal variable in the energy norm is of great interest. Such estimates depend on the efficient design of a discrete Lagrange multiplier. Affirmative examples of discrete Lagrange multipliers are presented for the obstacle and Signorini problem and three different first-order finite element methods, namely the conforming Courant, the non-conforming Crouzeix-Raviart, and the mixed Raviart-Thomas FEM. Partial results exist for the Bingham flow problem. Numerical experiments highlight the theoretical results, and show efficiency and reliability. The numerical tests suggest that the resulting adaptive algorithms converge with optimal convergence rates.
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Huo, Shuning. "Bayesian Modeling of Complex High-Dimensional Data." Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/101037.
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With the rapid development of modern high-throughput technologies, scientists can now
collect high-dimensional complex data in different forms, such as medical images, genomics
measurements. However, acquisition of more data does not automatically lead to better
knowledge discovery. One needs efficient and reliable analytical tools to extract useful information
from complex datasets. The main objective of this dissertation is to develop innovative
Bayesian methodologies to enable effective and efficient knowledge discovery from
complex high-dimensional data. It contains two parts—the development of computationally
efficient functional mixed models and the modeling of data heterogeneity via Dirichlet
Diffusion Tree. The first part focuses on tackling the computational bottleneck in Bayesian
functional mixed models. We propose a computational framework called variational functional
mixed model (VFMM). This new method facilitates efficient data compression and
high-performance computing in basis space. We also propose a new multiple testing procedure
in basis space, which can be used to detect significant local regions. The effectiveness
of the proposed model is demonstrated through two datasets, a mass spectrometry dataset
in a cancer study and a neuroimaging dataset in an Alzheimer's disease study. The second
part is about modeling data heterogeneity by using Dirichlet Diffusion Trees. We propose
a Bayesian latent tree model that incorporates covariates of subjects to characterize the
heterogeneity and uncover the latent tree structure underlying data. This innovative model
may reveal the hierarchical evolution process through branch structures and estimate systematic
differences between groups of samples. We demonstrate the effectiveness of the model
through the simulation study and a brain tumor real data.Doctor of Philosophy
With the rapid development of modern high-throughput technologies, scientists can now collect high-dimensional data in different forms, such as engineering signals, medical images, and genomics measurements. However, acquisition of such data does not automatically lead to efficient knowledge discovery. The main objective of this dissertation is to develop novel Bayesian methods to extract useful knowledge from complex high-dimensional data. It has two parts—the development of an ultra-fast functional mixed model and the modeling of data heterogeneity via Dirichlet Diffusion Trees. The first part focuses on developing approximate Bayesian methods in functional mixed models to estimate parameters and detect significant regions. Two datasets demonstrate the effectiveness of proposed method—a mass spectrometry dataset in a cancer study and a neuroimaging dataset in an Alzheimer's disease study. The second part focuses on modeling data heterogeneity via Dirichlet Diffusion Trees. The method helps uncover the underlying hierarchical tree structures and estimate systematic differences between the group of samples. We demonstrate the effectiveness of the method through the brain tumor imaging data.
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Schürg, Marco [Verfasser], Friedrich [Akademischer Betreuer] Gruttmann, Werner [Akademischer Betreuer] Wagner, and Jens [Akademischer Betreuer] Wackerfuß. "Theoretical modeling and parallel programming of a nonlinear composite finite shell element based on a mixed global-local variational principle / Marco Schürg. Betreuer: Friedrich Gruttmann ; Werner Wagner ; Jens Wackerfuß." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2012. http://d-nb.info/1106453999/34.
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Góis, Wesley. "Método dos elementos finitos generalizados em formulação variacional mista." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-14072006-112127/.
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Este trabalho trata da combinação entre a formulação híbrida-mista de tensão (FHMT) (Freitas et al. (1996)), para a elasticidade plana, com o método dos elementos finitos generalizados (MEFG), Duarte et al. (2000). O MEFG se caracteriza como uma forma não-convencional do método dos elementos finitos (MEF) que resulta da incorporação a este de conceitos e técnicas dos métodos sem malha, como o enriquecimento nodal proposto do método das nuvens hp. Como na FHMT são aproximados dois campos no domínio (tensão e deslocamento) e um no contorno (deslocamento), diferentes possibilidades de enriquecimento nodal são exploradas. Para a discretização do modelo híbrido-misto empregam-se elementos finitos quadrilaterais com funções de forma bilineares para o domínio e elementos lineares para o contorno. Essas funções são enriquecidas por funções polinomiais, trigonométricas, polinômios que proporcionam distribuição de tensões auto-equilibradas ou mesmo funções especiais relacionadas às soluções dos problemas de fratura. Uma extensão do teste numérico abordado em Zienkiewicz et al. (1986) é proposta como investigação inicial das condições necessárias para garantia de estabilidade da resposta numérica. O estudo da estabilidade é completado com a análise da condição de Babuka-Brezzi (inf-sup). Esta condição é aplicada nos elementos finitos quadrilaterais híbridos-mistos enriquecidos por meio de um teste numérico, denominado de inf-sup teste, desenvolvido com base no trabalho de Chapelle e Bathe (1993). Exemplos numéricos revelam que a FHMT é uma interessante alternativa para obtenção de boas estimativas para os campos de tensões e deslocamentos, usando-se enriquecimento sobre alguns nós de malhas pouco refinadasThis work presents a combination of hybrid-mixed stress model formulation (HMSMF) (Freitas et al. (1996)), to treat plane elasticity problems, with generalized finite element method (GFEM), (Duarte et al. (2000)). GFEM is characterized as a nonconventional formulation of the finite element method (FEM). GFEM is the result of the incorporation of concepts and techniques from meshless methods. One example of these techniques is the nodal enrichment that was formulated in the hp clouds method. Since two fields in domain (stress and displacement) and one in boundary (displacement) are approximated in the HMSMF, different possibilities of nodal enrichment are tested. For the discretization of the hybrid-mixed model quadrilateral finite elements with bilinear shape functions for the domain and linear elements for the boundary were employed. These functions are enriched with polynomial functions, trigonometric functions, polynomials that generate self-equilibrated stress distribution, or, even special functions connected with solutions of fracture problems. An extension of the numerical test cited in Zienkiewicz et al. (1986) is proposed as initial investigation of necessary conditions to assure the stability of the numerical answer. The stability study is completed with the analysis of the Babuka-Brezzi (inf-sup) condition. This last condition is applied to hybrid-mixed enrichment quadrilaterals finite elements by means of a numerical test, denominated inf-sup test, which was developed based on paper of Chapelle and Bathe (1993). Numerical examples reveal that HMSMF is an interesting alternative to obtain good estimates of the stress and displacement fields, using enrichment over some nodes of poor meshes
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Almeida, Samuel Oliveira de. "Soluções para problemas elípticos envolvendo o expoente crítico de Sobolev." Universidade Federal de Juiz de Fora, 2013. https://repositorio.ufjf.br/jspui/handle/ufjf/1468.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Neste trabalho estudamos a existência de soluções para problemas elípticos envolvendo o expoente crítico de Sobolev. Primeiramente, investigamos a existência de soluções para um problema superlinear do tipo Ambrosetti-Prodi com ressonância em 1, onde 1 é o primeiro autovalor de (−Δ,1 0 (Ω)). Além disso, estudamos resultados de multiplicidade para uma classe de equações elípticas críticas relacionadas com o problema de Brézis-Nirenberg, com condição de contorno de Neumann sobre a bola.
In this work we study the existence of solutions for elliptic problems involving critical Sobolev exponent. Firstly we investigate the existence of solutions for an Ambrosetti-Prodi type superlinear problem with resonance at 1 , where 1 is the first eigenvalue of (−Δ,1 0 (Ω)). Besides, we study multiplicity results for a class of critical elliptic equations related to the Brézis-Nirenberg problem with Neumann boundary condition on a ball.
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Rojas, Gómez Renán Alfredo. "Automatic regularization parameter selection for the total variation mixed noise image restoration framework." Master's thesis, Pontificia Universidad Católica del Perú, 2012. http://tesis.pucp.edu.pe/repositorio/handle/123456789/4461.
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Image restoration consists in recovering a high quality image estimate based only on
observations. This is considered an ill-posed inverse problem, which implies non-unique
unstable solutions. Regularization methods allow the introduction of constraints in such
problems and assure a stable and unique solution. One of these methods is Total Variation,
which has been broadly applied in signal processing tasks such as image denoising, image
deconvolution, and image inpainting for multiple noise scenarios. Total Variation features
a regularization parameter which defines the solution regularization impact, a crucial step
towards its high quality level. Therefore, an optimal selection of the regularization parameter
is required. Furthermore, while the classic Total Variation applies its constraint to the
entire image, there are multiple scenarios in which this approach is not the most adequate.
Defining different regularization levels to different image elements benefits such cases. In
this work, an optimal regularization parameter selection framework for Total Variation image
restoration is proposed. It covers two noise scenarios: Impulse noise and Impulse over
Gaussian Additive noise. A broad study of the state of the art, which covers noise estimation
algorithms, risk estimation methods, and Total Variation numerical solutions, is
included. In order to approach the optimal parameter estimation problem, several adaptations
are proposed in order to create a local-fashioned regularization which requires no
a-priori information about the noise level. Quality and performance results, which include
the work covered in two recently published articles, show the effectivity of the proposed
regularization parameter selection and a great improvement over the global regularization
framework, which attains a high quality reconstruction comparable with the state of the art
algorithms.Tesis
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Rudolf, Robert. "Design methods to mitigate the effects of variation in analogue and mixed-signal circuits." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/374300/.
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The continued scaling of CMOS process features enables ever-faster and denser circuits, which comes at the cost of increased device parameter variation. The performance of analogue and mixed-signal circuits in particular degrades in such a high variation environment, which poses an extraordinary challenge in the design and fabrication of such circuits. This thesis develops a set of tools and methodologies for a post-fabrication calibration system called the Configurable Analogue Transistor (CAT). The principle of the CAT technique is to replace certain transistors in a circuit with calibration devices, which allow adjustment of circuit performance after fabrication to compensate the effects of device parameter variation. Building on initial research on the CAT, this thesis develops a methodology to identify the most suitable calibration devices in their circuit and determine their optimal sizes. Furthermore, the applicability of CAT is extended beyond parameter variation to also include direct compensation of temperature. A complementary technique to post-fabrication calibration is robust design, where a circuit is designed to be inherently robust against variation in device parameters. In this thesis, a novel closed-loop pick-off circuit for force-balanced MEMS accelerometers is presented. It is comparable in performance to other state-of-the-art techniques, but provides vastly improved robustness against parameter variation and a more intuitive design process.
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Ghai, Dhruva V. "Variability-aware low-power techniques for nanoscale mixed-signal circuits." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc9850/.
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New circuit design techniques that accommodate lower supply voltages necessary for portable systems need to be integrated into the semiconductor intellectual property (IP) core. Systems that once worked at 3.3 V or 2.5 V now need to work at 1.8 V or lower, without causing any performance degradation. Also, the fluctuation of device characteristics caused by process variation in nanometer technologies is seen as design yield loss. The numerous parasitic effects induced by layouts, especially for high-performance and high-speed circuits, pose a problem for IC design. Lack of exact layout information during circuit sizing leads to long design iterations involving time-consuming runs of complex tools. There is a strong need for low-power, high-performance, parasitic-aware and process-variation-tolerant circuit design. This dissertation proposes methodologies and techniques to achieve variability, power, performance, and parasitic-aware circuit designs. Three approaches are proposed: the single iteration automatic approach, the hybrid Monte Carlo and design of experiments (DOE) approach, and the corner-based approach. Widely used mixed-signal circuits such as analog-to-digital converter (ADC), voltage controlled oscillator (VCO), voltage level converter and active pixel sensor (APS) have been designed at nanoscale complementary metal oxide semiconductor (CMOS) and subjected to the proposed methodologies. The effectiveness of the proposed methodologies has been demonstrated through exhaustive simulations. Apart from these methodologies, the application of dual-oxide and dual-threshold techniques at circuit level in order to minimize power and leakage is also explored.
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Guo, Yu-yau. "Behavioral modeling and simulaitons [sic] of mixed-signal integrated circuits with process variations and physical defects /." View online ; access limited to URI, 2003. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3115630.
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Carlson, Peter John, and University of Lethbridge Faculty of Arts and Science. "Seasonal and inter-annual variation in carbon dioxide exchange and carbon balance in a mixed grassland." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2000, 2000. http://hdl.handle.net/10133/115.
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Seasonal and inter-annual variation in carbon dioxide exchange and carbon balance in a mixed grassland by Peter Carlson Chairperson of the Supervisory Committee: Professor Lawrence Flanagan Department of Biological Science Eddy covariance measurements were carried out to document the seasonal and inter-annual variation in CO2 flux in a mixed prairie grassland. There was very different net ecosystem carbon exchange between the two years of study. In 1998 the maximum net ecosystem carbon exchange was 4.95 g C m-2d-1, compared to 2.50 g C m-2d-1 in 1999. The most important environment control on CO2 uptake was volumetric soil moisture content through its affect on leaf area index. There was evidence of stomatal limitation of CO2 uptake, during periods of atmospheric drought. The total seasonal net ecosystem carbon gain for 1998 was 190.0 g C m-2, compared with 46.8 g C m-2 in 1999. This grassland is a large carbon sink in a growing season of above normal precipitation. In a year of normal summer precipitation, this grassland is a small carbon sink, replacing slightly more carbon than is lost through winter respiration.xi, 99 leaves : ill. ; 28 cm.
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Wever, Linda A., and University of Lethbridge Faculty of Arts and Science. "Seasonal and interannual variation in water vapor fluxes and energy balance in a moist mixed grassland." Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, 2001, 2001. http://hdl.handle.net/10133/124.
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Fluxes of sensible and latent heat were measured over a grassland during 1998 and 1999 using the eddy covariance technique. The study objectives were to document seasonal and interannual variation evapotranspiration. Bowen ratios were lower in 1998 (0.5-3.0) than in 1999 (2.5-8.5) due to lower evapotranspiration rates (E). Maximum E also occurred later in 1998 than in 1999; Day 188 (10.4 mmol m-2s-1) versus Day 152 (5.6 mmol m-2s-1). Daily evapotranspiration rates were positively correlated with net radiation, canopy conductance, plant nitrogen content, leaf area index and soil moisture. Based on calculations of the decoupling coefficient (O). evapotranspiration was more constrained by canopy conductance in 1999 (O<0.2) than in 1998 (O>0.3). Evapotranspiration and energy partitioning in this grassland were sensitive to seasonal changes in soil moisture and interannaual variation in spring precipitation. Annual evapotranspiration was 300 mm.x, 70 leaves : ill. ; 28 cm.
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Wever, Linda A. "Seasonal and interannual variation in water vapor fluxes and energy balance in a moist mixed grassland." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ61047.pdf.
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Carlson, Peter John. "Seasonal and inter-annual variation in carbon dioxide exchange and carbon balance in a mixed grassland." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0029/MQ61038.pdf.
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Zemmel, Nicola Elise. "Intermarriage, variations on a theme : examining the reality of mixed and conversionary marriage in contemporary Anglo-Jewry." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343505.
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Knopp, Jasmin. "Individual differences in response to brief psychological interventions : using a mixed methods design to identify the role of user characteristics in the treatment of Obsessive-Compulsive Disorder (OCD)." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/individual-differences-in-response-to-brief-psychological-interventions-using-a-mixed-methods-design-to-identify-the-role-of-user-characteristics-in-the-treatment-of-obsessivecompulsive-disorder-ocd(8e5409f1-0c2f-434e-9ba6-a0c402afbc7d).html.
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Background: OCD is a debilitating mental health condition. Poor access to evidence-based psychological treatment has motivated the implementation of low intensity interventions in UK mental health services for OCD. Around one half of those accessing care remain clinically unwell. Service users, providers, and treatment decision-makers could benefit from understanding users' views of low intensity interventions and knowing which users are more likely to benefit from diverse low intensity approaches in order to match individuals with treatments of known efficacy. Aim and objectives: The primary aim of this research was to determine user characteristics associated with engagement and outcome in low intensity interventions for OCD. The objectives of the study were: 1) to review the published literature on predictors of psychological therapy outcome in OCD, 2) to explore individual variation in intervention acceptability, uptake, and engagement, and 3) to identify user characteristics, which moderate intervention engagement and outcome. Methods: This mixed methods thesis was conducted in three parts. Firstly, a systematic review of published trial data was conducted to identify predictors of therapy outcome. Secondly, primary data were collected as part of a large effectiveness trial: 1) qualitative interviews with 36 trial participants, randomised to one of two low intensity interventions (guided self-help; cCBT); and 2) quantitative trial assessments conducted at baseline and at 3-months follow-up. Data from the systematic review and the qualitative study were used to identify possible moderators of outcome. Confirmatory analyses were then conducted on these variables, using data from the quantitative assessments. Results: Objective 1: The systematic review identified 43 studies, examining predictors of outcome. Robust effects were rare and the applied utility of these findings is limited by methodological weaknesses. Objective 2: Six themes were identified from the qualitative study, three relate to the general acceptability of low intensity interventions: 1) Predisposing concepts of high quality psychological therapies, 2) Engaging with low intensity interventions, and 3) The perceived value of therapist support. Three are specific to individuals with OCD: 4) Positive aspects of OCD, 5) Recognition and accommodation of OCD users' needs, and 6) OCD disclosure. Objective 3: User attachment style, expressed emotion, OCD symptom subtype, and prior help seeking for OCD were examined in confirmatory interaction tests. Symmetry/order/exactness symptoms were associated with a greater likelihood of engagement in guided self-help than cCBT. Contamination/washing symptoms were associated with improved outcome in guided self-help over cCBT. Conclusions: This study has made an original contribution through using a mixed methods design to identify individual differences in response to low intensity interventions in OCD. There is significant individual variation in the acceptability of, and engagement with, low-intensity interventions for OCD, linked to the mode and intensity of therapist support preferable to the individual user. However, few moderators could be identified. Future research should focus on maximising the reliability of stratified medicine research to allow related findings to inform clinical decision-making.
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O'Shannessy, Carmel Therese. "Language contact and children's bilingual acquisition: learning a mixed language and Warlpiri in northern Australia." University of Sydney, 2006. http://hdl.handle.net/2123/1303.
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Doctor of Philosophy (PhD)This dissertation documents the emergence of a new language, Light Warlpiri, in the multilingual community of Lajamanu in northern Australia. It then examines the acquisition of Light Warlpiri language, and of the heritage language, Lajamanu Warlpiri, by children. Light Warlpiri has arisen from contact between Lajamanu Warlpiri (a Pama-Nyungan language), Kriol (an English-based creole), and varieties of English. It is a Mixed Language, meaning that none of its source languages can be considered to be the sole parent language. Most verbs and the verbal morphology are from Aboriginal English or Kriol, while most nouns and the nominal morphology are from Warlpiri. The language input to children is complex. Adults older than about thirty speak Lajamanu Warlpiri and code-switch into Aboriginal English or Kriol. Younger adults, the parents of the current cohort of children, speak Light Warlpiri and code-switch into Lajamanu Warlpiri and into Aboriginal English or Kriol. Lajamanu Warlpiri and Light Warlpiri, the two main input languages to children, both indicate A arguments with ergative case-marking (and they share one allomorph of the marker), but Lajamanu Warlpiri includes the marker much more consistently than Light Warlpiri. Word order is variable in both languages. Children learn both languages from birth, but they target Light Warlpiri as the language of their everyday interactions, and they speak it almost exclusively until four to six years of age. Adults and children show similar patterns of ergative marking and word order in Light Warlpiri. But differences between age groups are found in ergative marking in Lajamanu Warlpiri - for the oldest group of adults, ergative marking is obligatory, but for younger adults and children, it is not. Determining when children differentiate between two input languages has been a major goal in the study of bilingual acquisition. The two languages in this study share lexical and grammatical properties, making distinctions between them quite subtle. Both adults and children distribute ergative marking differently in the two languages, but show similar word order patterns in both. However the children show a stronger correlation between ergative marking and word order patterns than do the adults, suggesting that they are spearheading processes of language change. In their comprehension of sentences in both Lajamanu Warlpiri and Light Warlpiri, adults use a case-marking strategy to identify the A argument (i.e. N+erg = A argument, N-erg = O argument). The children are not adult-like in using this strategy at age 5, when they also used a word order strategy, but they gradually move towards being adult-like with increased age.
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Nicolopoulos-Salle, Anouk. "Formulations variationnelles d'équations de Maxwell résonantes et problèmes aux coins en propagation d'ondes." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS276.
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Dans une 1ere partie, on construit des formulations variationnelles associées aux équations de Maxwell résonantes. Les équations dégénèrent dans le domaine, entraînant la non-unicité et la singularité des solutions. L’ajout de viscosité permet de les désingulariser, et par un procédé d’absorption limite, lorsque ce paramètre de viscosité tend vers zéro, on identifie la solution physique. Mais la dégénérescence sépare le problème à la limite en deux équations sur des domaines différents couplées par leur interface, le long de laquelle les solutions explosent. Ce travail caractérise la solution limite de manière explicite comme solution d’une formulation bien posée, ce qui permet d’approcher numériquement la solution physique des équations de Maxwell résonantes. L’étude est motivée par la modélisation de résonances hybrides dans un plasma de fusion. Une 2nde partie concerne les méthodes numériques de décomposition de domaine (DDM). En présence de coins et de points de croisement, lorsqu’on utilise un mailleur automatique par exemple, il est nécessaire de traiter ces points pour obtenir des conditions d’absorption (ABC) ou de transmission (TC) d’ordre supérieur à 1. Nous définissons des ABC d’ordre 2 pour l’équation de Helmholtz sur un domaine à coins, avec en vue des TC traitant les points de croisement. Chaque algorithme présenté est lié à une énergie décroissante et convergeIn 1st part, variational formulations associated with resonant Maxwell equations are constructed. The equations degenerate in the domain, leading to the non-unicity and singularity of the solutions. Adding viscosity desingularizes the equations, and a limiting absorption process, when this viscosity parameter goes to zero, allows to identify the physical solution. The degeneracy separates the problem at the limit into two equations on different domains coupled by their interface, along which the solutions blow up. This work explicitly characterizes the limit solution as a solution of a well-posed formulation, which allows the numerical approximation of the physical solution to the resonant Maxwell equations. The study is motivated by the modeling of hybrid resonances in fusion plasma. A 2nd part concerns numerical domain decomposition methods (DDM). In the presence of corners and cross points, when using an automatic mesher for example, it is necessary to treat these points to obtain absorption (ABC) or transmission (TC) conditions of order higher than 1. We define ABCs of order 2 for the Helmholtz equation on a polygonal domain, with the further intention of deriving TCs treating cross points. Each algorithm presented is endowed with a decreasing energy and is convergent
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Roy, Joseph. "The Perfect Approach to Adverbs: Applying Variation Theory to Competing Models." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30341.
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The question of adverbs and the meaning of the present perfect across varieties of English is central to sociolinguistic variationist methodologies that have approached the study of the present perfect (Winford, 1993; Tagliamonte, 1997; van Herk, 2008, 2010; Davydova, 2010; Tagliamonte, 2013). This dissertation attempts to disentangle the effect of adverbial support from the three canonical readings of the present perfect (Resultative, Experiential and Continuative). Canadian English, an understudied variety of English, is used to situate the results seen in the Early Modern English data. Early Modern English reflects the time period in which English has acquired the full modern use of the present perfect with the three readings.
In order to address both these questions and current controversies over statistical models in sociolinguistics, different statistical models are used: both the traditional Goldvarb X (Sankoff, Tagliamonte and Smith, 2005) and the newer mixed-effects logistic regression (Johnson, 2009). What is missing from the previous literature in sociolinguistics that advocates logistic mixed-effects models, and provided in this dissertation, is a clear statement of where they are inappropriate to use and their limitations.
The rate of adverbial marking of the present perfect in Canadian English falls between rates reported for US and British English in previous studies. The data show in both time periods that while adverbs are highly favored in continuative contexts, they are strongly disfavored in experiential and resultative contexts. In Early Modern English, adverbial support functions statistically differently for resultatives and experientials, but that difference collapses in the Canadian English sample. Both this and the other linguistic contexts support a different analysis for each set of data with respect to adverbial independence from the meaning of the present perfect form. Finally, when the focus of the analysis is on linguistic rather than social factors, both the traditional and newer models provide similar results. Where there are differences, however, these can be accounted for by the number of tokens and different estimation techniques for each model.
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House, Amanda N. "Racial/Ethnic Variation in Parenting Styles: The Experience of Multiracial Adolescents." Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1320162825.
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Satchwell, Alexander. "Ethnic variation in access to treatment for First-Episode Psychosis in the East Midlands : a mixed methods study." Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/29256.
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Literature Review: Purpose: To determine differences in Duration of Untreated Psychosis (DUP) and Pathways to Care (PtC) between ethnic groups for service users with first-episode psychosis. Method: Literature searches were conducted using the online databases PsychInfo, Medline, Science Direct, Web of Science, Scopus and ASSIA. Keywords selected for searches included the terms Duration of Untreated Psychosis, Pathways to Care and Ethnic* or Cultur* or Diversity. Results: Ten relevant articles were identified. Five were cohort studies and five were cross-sectional studies. Conclusions: Mixed evidence was found regarding the influence of ethnicity on DUP. Findings on PtC were clearer, with minority ethnic groups often reported as more likely to access care via negative pathways, such as criminal justice agencies. Research Report: Objectives: 1) To explore the effects of ethnicity and other variables on DUP and PtC in an EIP service in Leicestershire and Rutland. 2) To develop an understanding of the barriers GPs experience when presented with a service user with first-episode psychosis. Method: A mixed methods design was adopted. Firstly, a naturalistic cohort study involving 426 individuals from an EIP service was analysed. Semi-structured interviews were also conducted with six GPs and one focus group. Interview data was analysed using Thematic Analysis. Results: No associations were found between ethnicity and any DUP variables. Ethnic differences were reported for three PtC: Criminal Justice Agencies; Accident and Emergency services; and Inpatient services. Thematic Analysis of GP interviews indicated three key themes. These were ‘a grey area’, ‘dilemmas’, and ‘more in depth mental health training’. Conclusions: Ethnic differences were only observed with specific PtC, which supported evidence by Ghali et al. (2012). GP and public education programmes were perceived as necessary in reducing delay, and minimising the impact stigma and shame have on service users’ and families’ help-seeking behaviour. Critical Appraisal: A reflective account of the research process and learning outcomes are described and discussed.
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Lindberg, Aron. "The Origin, Evolution, and Variation of Routine Structures in Open Source Software Development: Three Mixed Computational-Qualitative Studies." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1436527665.
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Yelamarthi, Kumar. "Process Variation-Aware Timing Optimization with Load Balance of Multiple Paths in Dynamic and Mixed-Static-Dynamic CMOS Logic." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1213880942.
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Sotoudehnia, Fariba. "A spatial and social analysis of green space access : a mixed-methods approach for analysing variations in access perceptions." Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/28625.
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Much research has considered facility access in terms of geographic location (physical distance) and how access varies for different groups. Perceptions of facilities are known to affect access behaviours but little research has considered how access perceptions interact with access behaviours and location. This PhD thesis addresses this gap and combined qualitative and quantitative analyses in a mixed-methods approach that included GIS-based network analyses, capturing access perceptions through questionnaires, and access behaviours through participatory mapping and in-depth interviews, in relation to green spaces in Leicester, UK. In this process, a large integrated dataset was generated combing questionnaire responses (n=452), access routes captured via participatory mapping (n=245) and in-depth interviews about access perceptions (n=14). The outcomes and methods of this research augment standard distance-based on measures of access by combining these with analyses of green space access perceptions and behaviours: a multi-dimensional approach. Adopting a mixed-methods approach supported a multi-dimensional concept and analysis of accessibility. The questionnaire data highlighted the variations between different social groups, access perceptions and behaviours. Analysis of GIS-based network analysis together with the results of the participatory mappings showed that 31% of the participants travel to green spaces rather than using their local facilities and that the route respondents took to their preferred green space were not the shortest path as determined by a GIS-based network analysis. The in-depth interviews, capturing respondent perceptions of access, highlighted the importance of other access-related factors that influenced their perceptions of access and access behaviours. The key message of arising from this research is that measuring accessibility using only spatial analysis provides a narrow definition of access in terms of distance/travel time. Rather, access should be considered as a broad and multi-dimensional concept that requires holistic investigation within which perceptions of access and access behaviours are also included.
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Ezhilan, Madhumitha. "Commissioning a Commercial Laser Induced Fluorescence System for Characterization of Static Mixer Performance." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1499793560290147.
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Masconi, Katya. "The occurance of genetic variations in the MYH9 gene and their association with CKD in a mixed South African population." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71697.
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Thesis (MScMedSc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The purpose of this study was to investigate the association of the selected MYH9 single nucleotide polymorphisms (SNPs) with chronic kidney disease (CKD) and its related co-morbidities in the South African mixed ancestry population residing in Bellville South, Cape Town. In 2008, two landmark studies identified SNPs in the MYH9 gene which explained most of the increased risk for non-diabetic CKD in African Americans. These polymorphisms were later found to be weakly associated with diabetic nephropathy. Three SNPs that exhibited independent evidence for association with CKD were selected (rs5756152, rs4821480 and rs12107). These were genotyped using a Taqman genotyping assay on a BioRad MiniOpticon and confirmed by sequencing in 724 subjects from Bellville South, Cape Town, South Africa. Prevalent CKD was defined based on the estimated glomerular filtration rate calculated using the modification of diet in renal disease (MDRD) formula. Chronic kidney disease was present in 214 subjects (29.6%), 96.3% were stage 3 and only 8 subjects were stage 4. In additive allelic models, adjusted for age and gender, rs5756152 demonstrated an association with kidney function whereby each G allele of rs5756152 increased eGFR by 3.67 ml/min/1.73, reduced serum creatinine by 4.5% and increased fasting plasma glucose by 0.51 mmol/L. When an interaction model was used, the effect of rs5756152 on serum creatinine, eGFR and blood glucose levels was retained, and enhanced, but only in diabetic subjects. In addition, rs4821480 T allele increased eGFR while rs12107 A allele decreased glucose levels in diabetic subjects. In contrast to reports that MYH9 SNPs are strongly associated with non-diabetic end stage renal disease, our study demonstrated that rs5756152 and rs4821480 are associated with early kidney function derangements in type 2 diabetes whilst rs12107 is associated with glucose metabolism. Our findings, along with previous reports, suggest that the MYH9 gene may have a broader genetic risk effect on different types of kidney diseases than previously thought.
AFRIKAANSE OPSOMMING: Hierdie studie het ondersoek ingestel na die verband tussen drie gekose MYH9-enkelnukleotied-polimorfismes (SNP’s) en chroniese niersiekte (hierna ‘niersiekte’), wat verwante ko-morbiditeite insluit, onder ’n Suid-Afrikaanse populasie van gemengde afkoms in Bellville-Suid, Kaapstad. Twee rigpuntstudies het in 2008 op SNP’s in die MYH9-geen afgekom wat verklaar het waarom Afro-Amerikaners ’n hoër risiko vir niediabetiese niersiekte toon. Later is bevind dat hierdie polimorfismes ook ’n swak verband met diabetiese nefropatie het. Drie SNP’s wat elk onafhanklik bewys gelewer het van ’n verband met niersiekte is vervolgens gekies (rs5756152, rs4821480 en rs12107). Die SNP’s is daarná met behulp van die Taqman-toets op ’n BioRad MiniOpticon aan genotipering onderwerp, en is toe deur middel van reeksbepaling by 724 proefpersone van Bellville-Suid, Kaapstad, Suid-Afrika, bevestig. Die voorkoms van niersiekte is bepaal op grond van die geraamde glomerulêre filtrasietempo (eGFR), wat aan die hand van die ‘niersiekte-dieetveranderings’- (MDRD-)formule bereken is. Daar is bevind dat 214 proefpersone (29,6%) aan chroniese niersiekte ly – 96,3% was in fase 3 en slegs agt proefpersone in fase 4. In toegevoegde alleliese modelle wat vir ouderdom en geslag aangepas is, het rs5756152 ’n verband met nierfunksie getoon: Elke G-allel van rs5756152 het eGFR met 3,67 ml/min/1,73 verhoog, serumkreatinien met 4,5% verlaag en vastende plasmaglukose met 0,51 mmol/L verhoog. Toe ’n interaksiemodel gebruik is, is die effek van rs5756152 op serumkreatinien, eGFR en bloedglukosevlakke behou en versterk, hoewel slegs by diabetiese proefpersone. Daarbenewens het die T-allel van rs4821480 eGFR verhoog, terwyl die A-allel van rs12107 ook glukosevlakke by diabetiese proefpersone verlaag het. In teenstelling met bewerings dat MYH9-SNP’s ’n sterk verband met niediabetiese eindstadiumniersiekte toon, het hierdie studie bewys dat rs5756152 en rs4821480 met vroeë nierfunksieversteurings by tipe 2-diabetes verband hou, terwyl rs12107 weer met glukosemetabolisme verbind word. Tesame met vorige studies, doen hierdie navorsingsbevindinge dus aan die hand dat die MYH9-geen dalk ’n groter genetiese risiko-effek op verskillende tipes niersiekte het as wat voorheen vermoed is.
Cape Peninsula University of Technology Research Fund
University of Stellenbosch Merit Bursary
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Osman, Abdimajid. "Studies on warfarin treatment with emphasis on inter-individual variations and drug monitoring." Doctoral thesis, Linköping : Linköping University, 2007. http://www.bibl.liu.se/liupubl/disp/disp2007/med1000s.pdf.
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White, Stephen John. "The evolutionary genetics of behavioural variation : multivariate perspectives on personality in the Trinidadian guppy." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/30848.
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Animal personality is found in a wide range of taxa, yet our knowledge of what maintains consistent among-individual variation in behaviour is still incomplete. Many personality traits are associated with fitness, leading to the expectation that, under selection, genetic (and among-individual) variation will be eroded over time. Several adaptive models have been developed in order to explain this maintenance of variation. These include state-dependence, state-behaviour feedback loops, life-history and behavioural coadaptation and the Pace of Life syndrome. These models represent good starting points for thinking about what drives and maintains among-individual variation in behaviour, and while empirical support for these models is mixed, one thing they do have in common is the assumption of a significant genetic basis underpinning personality traits. Significant heritability is required for an evolutionary response to selection and for among-individual variation to be adaptive. The univariate estimates of heritability for personality traits that are growing in the literature, while useful, are likely insufficient to predict how personality traits will respond to selection. This thesis uses the Trinidadian guppy, Poecilia reticulata, and other species to explore patterns of among-individual and genetic variation in personality traits, advocating the benefits of using multivariate perspectives throughout. Firstly, the among-individual covariance structure between measures of boldness, growth and metabolic rate are estimated in a test of the Pace of Life syndrome. Secondly, an appraisal of the relative strength of maternal and genetic effects on offspring personality and how it changes over ontogeny. Next, a comprehensive treatment of sexual dimorphism in behaviour and size followed by analysis of genotype-by-sex interactions using both univariate and multivariate methods. Finally, a comparative analysis of personality in 7 species of small fish, identifying the main axis of among-individual variation from a single assay in each and quantifying the phylogenetic signal.
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Ji, Xiang. "The association of variations in hip and pelvic geometry with pregnancy-related sacroiliac joint pain based on a longitudinal analysis." Kyoto University, 2019. http://hdl.handle.net/2433/242658.
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Janzén, David. "Standard two-stage and Nonlinear mixed effect modelling for determination of cell-to-cell variation of transport parameters in Saccharomyces cerevisiae." Thesis, Linköpings universitet, Reglerteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78486.
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The interest for cell-to-cell variation has in recent years increased in a steady pace. Several studies have shown that a large portion of the observed variation in the nature originates from the fact that all biochemical reactions are in some respect stochastic. Interestingly, nature has evolved highly advanced frameworks specialized in dealing with stochasticity in order to still be able to produce the delicate signalling pathways that are present in even very simple single-cell organisms. Such a simple organism is Saccharomyces cerevisiae, which is the organism that has been studied in this thesis. More particulary, the distribution of the transport rate in S. cerevisiae has been studied by a mathematical modelling approach. It is shown that a two-compartment model can adequately describe the flow of a yellow fluorescent protein (YFP) between the cytosol and the nucleus. A profile likelihood (PLH) analysis shows that the parameters in the two-compartment model are identifiable and well-defined under the experimental data of YFP. Furthermore, the result from this model shows that the distribution of the transport rates in the 80 studied cells is lognormal. Also, in contradiction to prior beliefs, no significant difference between recently divided mother and daughter cells in terms of transport rates of YFP is to be seen. The modelling is performed by using both standard two-stage(STS) and nonlinear mixed effect model (NONMEM). A methodological comparison between the two very different mathematical STS and NONMEM is also presented. STS is today the conventional approach in studies of cell-to-cell variation. However, in this thesis it is shown that NONMEM, which has originally been developed for population pharmacokinetic/ pharmacodynamic (PK/PD) studies, is at least as good, or in some cases even a better approach than STS in studies of cell-to-cell variation. Finally, a new approach in studies of cell-to-cell variation is suggested that involves a combination of STS, NONMEM and PLH. In particular, it is shown that this combination of different methods would be especially useful if the data is sparse. By applying this combination of methods, the uncertainty in the estimation of the variability could be greatly reduced.
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Rodrigues, Diego Samuel. "Tratamento numérico da mecânica de interfaces lipídicas: modelagem e simulação." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-04042016-114915/.
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A mecânica celular jaz nas propriedades materiais da membrana plasmática, fundamentalmente uma bicamada fosfolipídica com espessura de dimensões moleculares. Além de forças elásticas, tal material bidimensional também experimenta tensões viscosas devido ao seu comportamento fluido (presumivelmente newtoniano) na direção tangencial. A despeito da notável concordância entre teoria e experimentos biofísicos sobre a geometria de membranas celulares, ainda não se faz presente um método computacional para simulação de sua (real) dinâmica viscosa governada pela lei de Boussinesq-Scriven. Assim sendo, introduzimos uma formulação variacional mista de três campos para escoamentos viscosos de superfícies fechadas curvas. Nela, o fluido circundante é levado em conta considerando-se uma restrição de volume interior, ao passo que uma restrição de área corresponde à inextensibilidade. As incógnitas são a velocidade, o vetor curvatura e a pressão superficial, todas estas interpoladas com elementos finitos lineares contínuos via estabilização baseada na projeção do gradiente de pressão. O método é semi-implícito e requer a solução de apenas um único sistema linear por passo de tempo. Outro ingrediente numérico proposto é uma força que mimetiza a ação de uma pinça óptica, permitindo interação virtual com a membrana, onde a qualidade e o refinamento de malha são mantidos por remalhagem adaptativa automática. Extensivos experimentos numéricos de dinâmica de relaxação são apresentados e comparados com soluções quasi-analíticas. É observada estabilidade temporal condicional com uma restrição de passo de tempo que escala como o quadrado do tamanho de malha. Reportamos a convergência e os limites de estabilidade de nosso método e sua habilidade em predizer corretamente o equilíbrio dinâmico de compridas e finas elongações cilíndricas (tethers) que surgem a partir de pinçamentos membranais. A dependência de forma membranal com respeito a uma velocidade imposta de pinçamento também é discutida, sendo que há um valor limiar de velocidade abaixo do qual um tether não se forma de início. Testes adicionais ilustram a robustez do método e a relevância dos efeitos viscosos membranais quando sob a ação de forças externas. Sem dúvida, ainda há um longo caminho a ser trilhado para o entendimento completo da mecânica celular (há de serem consideradas outras estruturas tais como citoesqueleto, canais iônicos, proteínas transmembranares, etc). O primeiro passo, porém, foi dado: a construção de um esquema numérico variacional capaz de simular a intrigante dinâmica das membranas celulares.Cell mechanics lies on the material properties of the plasmatic membrane, fundamentally a two-molecule-thick phospholipid bilayer. Other than bending elastic forces, such a two-dimensional interfacial material also experiences viscous stresses due to its (presumably Newtonian) surface fluid tangential behaviour. Despite the remarkable agreement on membrane shapes between theory and biophysical experiments, there is no computational method for simulating its (actual) viscous dynamics governed by the Boussinesq- Scriven law. Accordingly, we introduce a mixed three-field variational formulation for viscous flows of closed curved surfaces. In it, the bulk fluid is taken into account by means of an enclosed-volume constraint, whereas an area constraint stands for the membranes inextensible character. The unknowns are the velocity, vector curvature and surface pressure fields, all of which are interpolated with linear continuous finite elements by means of a pressure-gradient-projection scheme. The method is semi-implicit and it requires the solution of a single linear system per time step. Another proposed ingredient is a numerical force that emulates the action of an optical tweezer, allowing for virtual interaction with the membrane, where mesh quality and refinement are maintained by adaptively remeshing. Extensive relaxation experiments are reported and compared with quasi-analytical solutions. Conditional time stability is observed, with a time step restriction that scales as the square of the mesh size. We discuss both convergence and the stability limits of our method, its ability to correctly predict the dynamical equilibrium of the tether due to tweezing. The dependence of the membrane shape on imposed tweezing velocities is also addressed. Basically, there is a threshold velocity value below which the tethers shape does not arise at first. Further tests illustrate the robustness of the method and show the significance of viscous effects on membranes deformation under external forces. Undoubtedly, there is still a long way to track toward the understanding of celullar mechanics (one still has to account other structures such as cytoskeleton, ion channels, transmembrane proteins, etc). The first step has given, though: the design of a numerically robust variational scheme capable of simulating the engrossing dynamics of fluid cell membranes.
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Souza, Daniel Câmara de. "Eletrodinâmica variacional e o problema eletromagnético de dois corpos." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26012015-213657/.
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Estudamos a Eletrodinâmica de Wheeler-Feynman usando um princípio variacional para um funcional de ação finito acoplado a um problema de valor na fronteira. Para trajetórias C2 por trechos, a condição de ponto crítico desse funcional fornece as equações de movimento de Wheeler-Feynman mais uma condição de continuidade dos momentos parciais e energias parciais, conhecida como condição de quina de Weierstrass-Erdmann. Estudamos em detalhe um sub-caso mais simples, onde os dados de fronteira têm um comprimento mínimo. Nesse caso, mostramos que a condição de extremo se reduz a um problema de valor na chegada para uma equação diferencial com retardo misto dependente do estado e do tipo neutro. Resolvemos numericamente esse problema usando um método de shooting e um método de Runge-Kutta de quarta ordem. Para os casos em que as fronteiras mínimas têm velocidades descontínuas, elaboramos uma técnica para resolver as condições de quina de Weierstrass-Erdmann junto com o problema de valor na chegada. As trajetórias com velocidades descontínuas previstas pelo método variacional foram verificadas por experimentos numéricos. Em um segundo desenvolvimento, para o caso mais difícil de fronteiras de comprimento arbitrário, implementamos um método de minimização com gradiente fraco para o princípio variacional e problema de fronteira acima citado. Elaboramos dois métodos numéricos, ambos implementados em MATLAB, para encontrar soluções do problema eletromagnético de dois corpos. O primeiro combina o método de elementos finitos com o método de Newton para encontrar as soluções que anulam o gradiente fraco do funcional para fronteiras genéricas. O segundo usa o método do declive máximo para encontrar as soluções que minimizam a ação. Nesses dois métodos as trajetórias são aproximadas dentro de um espaço de dimensão finita gerado por uma Galerkiana que suporta velocidades descontínuas. Foram realizados diversos testes e experimentos numéricos para verificar a convergência das trajetórias calculada numericamente; também comparamos os valores do funcional calculados numericamente com alguns resultados analíticos sobre órbitas circulares.We study the Wheeler-Feynman electrodynamics using a variational principle for an action functional coupled to a finite boundary value problem. For piecewise C2 trajectories, the critical point condition for this functional gives the Wheeler-Feynman equations of motion in addition to a continuity condition of partial moments and partial energies, known as the Weierstrass-Erdmann corner conditions. In the simplest case, for the boundary value problem of shortest length, we show that the critical point condition reduces to a two-point boundary value problem for a state-dependent mixed-type neutral differential-delay equation. We solve this special problem numerically using a shooting method and a fourth order Runge-Kutta. For the cases where the boundary segment has discontinuous velocities we developed a technique to solve the Weierstrass-Erdmann corner conditions and the two-point boundary value problem together. The trajectories with discontinuous velocities presupposed by the variational method were verified by numerical experiments. In a second development, for the harder case with boundaries of arbitrary length, we implemented a method of minimization with weak gradient for the variational principle quoted above. Two numerical methods were implemented in MATLAB to find solutions of the two-body electromagnetic problem. The first combines the finite element method with Newtons method to find the solutions that vanish the weak gradient. The second uses the method of steepest descent to find the solutions that minimize the action. In both methods the trajectories are approximated within a finite-dimensional space generated by a Galerkian that supports discontinuous velocities. Many tests and numerical experiments were performed to verify the convergence of the numerically calculated trajectories; also were compared the values of the functional computed numerically with some known analytical results on circular orbits.
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Mint, brahim Maimouna. "Méthodes d'éléments finis pour le problème de changement de phase en milieux composites." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0157/document.
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Dans ces travaux de thèse on s’intéresse au développement d’un outil numérique pour résoudre le problème de conduction instationnaire avec changement de phase dans un milieu composite constitué d’une mousse de graphite infiltrée par un matériau à changement de phase tel que le sel, dans le contexte du stockage de l’énergie thermique solaire.Au chapitre 1, on commence par présenter le modèle sur lequel on va travailler. Il estséparé en trois sous-parties : un problème de conduction de chaleur dans la mousse, un problème de changement de phase dans les pores remplis de sel et une condition de résistance thermique de contact entre les deux matériaux qui est traduite par une discontinuité du champ de température.Au chapitre 2, on étudie le problème stationnaire de conduction thermique dans un milieu composite avec résistance de contact. Ceci permet de se focaliser sur la plus grande difficulté présente dans le problème qui est le traitement de la condition de saut à l’interface.Deux méthodes d’éléments finis sont proposées pour résoudre ce problème : une méthode basée sur les éléments finis Lagrange P1 et une méthode hybride-duale utilisant les éléments finis Raviart-Thomas d’ordre 0 et P0. L’analyse numérique des deux méthodes est effectuée et les résultats de tests numériques attestent des efficacités des deux méthodes [10]. Les matériaux à changement de phase qu’on étudie dans le cadre de cette thèse sont des matériaux pures, par conséquent le changement de phase s’effectue en une valeur de température fixe qui est la température de fusion. Ceci est modélisé par un saut dans la fonction fraction liquide et par conséquent dans la fonction enthalpie du matériau. Cette discontinuité représente une difficulté numérique supplémentaire qu’on propose de surmonter en introduisant un intervalle de régularisation autour de la température de fusion.Cette procédure est présentée dans le chapitre 3 où une étude analytique et numérique montre que l’erreur sur la température se comporte comme " en dehors de la zone de mélange, où " est la largeur de l’intervalle de régularisation. Cependant, à l’intérieur l’erreur se comporte comme p " et on montre que cette estimation est optimale. Cette diminution de vitesse de convergence est due à l’énergie qui reste bloquée dans la zone de mélange [58].Dans le chapitre 4 on présente quatre des schémas les plus utilisés pour le traitement de la non-linearité due au changement de phase: mise à jour du terme source, linéarisation de l’enthalpie, la capacité thermique apparente et le schéma de Chernoff. Différents tests numériques sont réalisés afin de tester et comparer ces quatre méthodes pour différents types de problèmes. Les résultats montrent que le schéma de linéarisation de l’enthalpie est le plus précis à chaque pas de temps tans dis que le schéma de la capacité thermique apparente donne de meilleurs résultats au bout d’un certain temps de calcul. Cela indique que si l’on s’intéresse aux états transitoires du matériaux le premier schéma est lemeilleur choix. Cependant, si l’on s’intéresse au comportement thermique asymptotique du matériau le second schéma est plus adapté. Les résultats montrent également que le schéma de Chernoff est le plus rapide parmi les quatre schémas en terme de temps de calcul et donne des résultats comparables à ceux des deux plus précis.Enfin, dans le chapitre 5 on utilise le schéma de Chernoff avec la méthode d’éléments finis hybride-duale Raviart-Thomas d’ordre 0 et P0 pour résoudre le problème non-linéaire de conduction thermique dans un milieu composite réel avec matériau à changement de phase. Le but étant de déterminer si un matériau composite avec une distribution uniforme de pores est assimilable à un matériau à changement de phase homogènes avec des propriétés thermo-physiques équivalentes. Pour toutes les expériences numériques exposées dans ce manuscrit on a utilisé le logiciel libre d’éléments finis FreeFem++ [41]In this thesis we aim to develop a numerical tool that allow to solve the unsteady heatconduction problem in a composite media with a graphite foam matrix infiltrated witha phase change material such as salt, in the framework of latent heat thermal energystorage.In chapter 1, we start by explaining the model that we are studying which is separated in three sub-parts : a heat conduction problem in the foam, a phase change problem in the pores of the foam which are filled with salt and a contact resistance condition at the interface between both materials which results in a jump in the temperature field.In chapter 2, we study the steady heat conduction problem in a composite media withcontact resistance. This allow to focus on the main difficulty here which is the treatment of the thermal contact resistance at the interface between the carbon foam and the salt. Two Finite element methods are proposed in order to solve this problem : a finite element method based on Lagrange P1 and a hybrid dual finite element method using the lowest order Raviart-Thomas elements for the heat flux and P0 for the temperature. The numerical analysis of both methods is conducted and numerical examples are given to assert the analytic results. The work presented in this chapter has been published in the Journal of Scientific Computing [10].The phase change materials that we study here are mainly pure materials and as a consequence the change in phase occurs at a single point, the melting temperature. This introduces a jump in the liquid fraction and consequently in the enthalpy. This discontinuity represents an additional numerical difficulty that we propose to overcome by introducing a smoothing interval around the melting temperature. This is explained in chapter 3 where an analytical and numerical study shows that the error on the temperature behaves like " outside of the mushy zone, where _ is the width of the smoothing interval. However, inside the error behaves like p " and we prove that this estimation is optimal due to the energy trapped in the mushy zone. This chapter has been published in Communications in Mathematical Sciences [58].The next step is to determine a suitable time discretization scheme that allow to handle the non-linearity introduced by the phase change. For this purpose we present in chapter 4 four of the most used numerical schemes to solve the non-linear phase change problem : the update source method, the enthalpy linearization method, the apparent heat capacity method and the Chernoff method. Various numerical tests are conducted in order to test and compare these methods for various types of problems. Results show that the enthalpy linearization is the most accurate at each time step while the apparent heat capacity gives better results after a given time. This indicates that if we are interestedin the transitory states the first scheme is the best choice. However, if we are interested in the asymptotic thermal behavior of the material the second scheme is better. Results also show that the Chernoff scheme is the fastest in term of calculation time and gives comparable results to the one given by the first two methods.Finally, in chapter 5 we use the Chernoff method combined with the hybrid-dual finiteelement method with P0 and the lowest order Raviart-Thomas elements to solve thenon-linear heat conduction problem in a realistic composite media with a phase change material. Numerical simulations are realised using 2D-cuts of X-ray images of two real graphite matrix foams infiltrated with a salt. The aim of these simulations is to determine if the studied composite materials could be assimilated to an equivalent homogeneous phase change material with equivalent thermo-physical properties. For all simulationsconducted in this work we used the free finite element software FreeFem++ [41]
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Griffith, Kereen. "Effects of Vegetation Structure and Canopy Exposure on Small-scale Variation in Atmospheric Deposition Inputs to a Mixed Conifer Forest in California." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500055/.
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Data on rates of atmospheric deposition is limited in many montane ecosystems, where high spatial variability in meteorological, topographic, and vegetation factors contributes to elevated atmospheric inputs and to the creation of deposition hotspots. Addressing the ecological consequences of increasing deposition in these areas will require a better understanding of surface controls influencing atmospheric deposition rates at both large and small-scales. The overarching objective of this thesis research was to understand the influence of vegetation structure and canopy exposure on small-scale patterns of atmospheric sulfate, nitrate, and chloride deposition inputs to a conifer forest in the Santa Cruz Mountains, California. Throughfall ion fluxes (i.e., ions delivered in water that pass from the forest canopy to the forest floor), bulk deposition (i.e., primarily wet deposition), and rainfall data were collected during the rainy period from October 2012 to May 2013. Throughfall SO42-, Cl-, and NO3- fluxes were measured beneath eight clusters of Douglas fir (Pseudotsuga menziesii) trees (three trees per cluster) differing in tree size (i.e., diameter at breast height; DBH) and canopy exposure. In each cluster, a throughfall collector was placed 1-meter from the bole of an individual tree, for a total of 24 individual collectors. The position of each throughfall collector was recorded with a Trimble® GPS. In addition, tree height, tree diameter, and leaf area index, were measured for all trees. LiDAR data were obtained from GeoEarthScope’s Northern California Airborne LiDAR project and used to model the elevation (DEM), canopy surface height (DSM), tree height (CHM), slope, and curvature of the canopy surface across the entire study area. Over the rainy season, total throughfall flux of SO42--S, a conservative tracer of total deposition (wet + dry + fog), to Douglas fir clusters ranged from 1.44 - 3.84 kg S ha-1 wet season-1, while dry and fog deposition ranged from 0.13 -2.37 kg S ha-1 wet season-1. Total deposition to exposed mature tree clusters was 1.7-2.7 times higher than other clusters. Patterns of total Cl- fluxes (17.10 – 54.14 kg Cl- ha-1 wet season-1) resembled patterns of total SO42--S inputs. Overall, net throughfall fluxes (throughfall – bulk deposition) to Douglas fir trees clusters were more variable than total throughfall fluxes. Net SO42--S and Cl- fluxes to individual collectors increased with tree DBH and the convexity of the canopy surface. Compared to SO42--S and Cl- in throughfall, total NO3--N fluxes (0.17 - 4.03 kg N ha-1 wet season-1) were low and appeared to vary with small-scale changes in elevation. Geospatial technologies and remote sensing tools, such as LiDAR, are promising in the study of relationships between atmospheric deposition and topography (including vegetation), and in scaling-up estimates of atmospheric deposition to larger spatial scales. Understanding small-scale surface controls on atmospheric deposition has implications for different areas of research within geography, including modeling the spread of emerging infectious disease and assessing the effects of nitrogen cycling on native and invasive plant species composition.
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Barrios, rodriguez Alexander José. "Influence des variations des facteurs environnementaux sur la croissance de poissons de l’atlantique." Thesis, Rennes, Agrocampus Ouest, 2017. http://www.theses.fr/2017NSARH100/document.
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Les paramètres de croissance de poissons pélagiques et démersaux ont été étudiés durant la période de 1990 à 2015 dans le but d’examiner l’impact de facteurs biotiques comme la densité-dépendance, le recrutement, la mortalité totale et de facteurs abiotiques tels que l’intensité d’upwelling, la température et la concentration en chlorophylle a. Les paramètres d’histoire de vie des espèces peuvent varier selon les espèces, d’une région à l’autre, et dans le temps au sein d’une même région en raison de leur plasticité et de la pression de la pêche. Une comparaison inter-espèces et inter-régions a été réalisée. Le modèle non linéaire à effets mixtes a été utilisé pour différentes populations de l’Océan Atlantique afin d’établir les paramètres de croissance aux niveaux individuel et de la population. Les variations des paramètres de croissance d’une sélection d’espèces ont été mises en corrélation avec des facteurs biotiques et abiotiquesLes espèces (Sardinella aurita, sardinelle ronde, Atherinella brasiliensis, tinicalo, Merlangius merlangus, merlan, Melanogrammus aeglefinus, églefin et Solea solea, sole) montrent des réponses différentes aux facteurs biotiques et abiotiques. Au niveau spatial pour le merlan et l’églefin, la croissance est affectée par la latitude et la température, tandis qu’au niveau temporel la croissance du merlan est affectée par la température et la densité. Il y avait un intérêt pour savoir si les variables morphométriques et le diamètre de l’otolithe de tinicalo étaient de bons indicateurs de la croissance : c’est la longueur standard qui a présentéThe impact of biotic factors such as density-dependent processes, recruitment, total mortality, and abiotic factors such as upwelling intensity, temperature and chlorophyll a concentration on the variation of growth parameters of pelagic and demersal fish were studied during the periods 1990 - 2008 (pelagic) and 1971 - 2015 (demersal). Life history parameters vary according to the species and from one region to another and over time within a given area because of their plasticity and the high fishing pressure. Interspecies and inter-regional comparison were carried out. Non-linear mixed effects models were used on different fish species of the Atlantic Ocean in order to estimate the growth parameters at the individual and population levels. Variations in growth parameters of selected species were correlated with biotic and abiotic factors.Selected species (Sardinella aurita, round sardinella, Xenomelaniris brasiliensis, tinicalo, Merlangus merlangus, whiting, Melanogrammus aeglefinus, haddock and Solea solea, sole) showed different responses to biotic and abiotic factors. Regardind the spatial component for whiting and haddock, the variation of growth parameters was affected by latitude and temperature. Concerning the temporal component, whiting was affected by temperature and density-dependent processes. There was also an interest to know if the morphometric variables and the diameter of the otolith of Atherinella brasilensis were good growth indicators. Among the morphometric parameters examined, the standard length-Age relationship showed the best fit (r2 = 0.90), foll
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Rangel, Murueta Jhonnatan. "Variations linguistiques et langue en danger. Le cas du numte ʔoote ou zoque ayapaneco dans l’Etat de Tabasco, Mexique." Thesis, Paris, INALCO, 2019. http://www.theses.fr/2019INAL0001.
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L’ayapaneco, zoque ayapaneco ou numte ʔoote (ethnonyme) est une langue en danger appartenant à la famille mixe-zoque et parlée exclusivement dans l’état de Tabasco, au Mexique, par environ 11 personnes âgées entre 69 et 95 ans. L’ayapaneco est l’une des langues de cette famille la moins étudiée et la moins documentée. Depuis les années 1950, elle ne se transmet plus aux nouvelles générations et son utilisation est actuellement très limitée dans le quotidien des locuteurs. Cette thèse documente, décrit et analyse tant la situation sociolinguistique de l’ayapaneco que sa réalité linguistique, en particulier l’existence de variations linguistiques. Bien que la variation soit un phénomène inhérent à toutes les langues du monde, les langues en danger présentent des défis théoriques et méthodologiques pour l’analyse des variations. Après avoir expliqué les variations linguistiques et les mécanismes qui les caractérisent en ayapaneco, cette thèse propose d’apporter des éléments nouveaux qui n’étaient pas pris en considération auparavant pour l’étude de la variation linguistique d’une langue vivant une situation de danger critique comme l’ayapaneco. Ceci contribue à questionner les analyses traditionnelles et à impulser, à partir d’une analyse multifactorielle, des explications originales pour faire avancer nos connaissances sur la nature des variations et du changement linguistique dans les langues en dangerAyapaneco, Zoque Ayapaneco or numte ʔoote (ethnonyme) is a critically endangered language spoken by approximately 11 people between the ages of 69- and 95-years-old in the state of Tabasco, Mexico. Ayapaneco is the least studied and least documented language in the Mixe-Zoque family. The intergenerational transmission of the language was interrupted in the 1950s. Today, it has a very limited role in the daily language practices of its remaining speakers.This thesis documents, describes and analyzes the sociolinguistic situation of Ayapaneco as well as its linguistic characteristics, focusing on language variation. Although variation is a phenomenon inherent to all world languages, studying variation within the context of critically endangered languages presents specific theoretical and methodological challenges.After presenting the characteristics of language variation in Ayapaneco, this thesis offers new perspectives on the study of these variations in critically endangered languages. A multifactorial analysis is used to question traditional approaches and propose new insights, contributing to the fields of language variation and language change in the context of critically endangered languages
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Stötzner, Ailyn. "Optimal Control of Thermoviscoplasticity." Universitätsverlag der Technischen Universität Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A31887.
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This thesis is devoted to the study of optimal control problems governed by a quasistatic, thermoviscoplastic model at small strains with linear kinematic hardening, von Mises yield condition and mixed boundary conditions. Mathematically, the thermoviscoplastic equations are given by nonlinear partial differential equations and a variational inequality of second kind in order to represent the elastic, plastic and thermal effects.
Taking into account thermal effects we have to handle numerous mathematical challenges during the analysis of the thermoviscoplastic model, mainly due to the low integrability of the nonlinear terms on the right-hand side of the heat equation. One of our main results is the existence of a unique weak solution, which is proved by means of a fixed-point argument and by employing maximal parabolic regularity theory. Furthermore, we define the related control-to-state mapping and investigate properties of this mapping such as boundedness, weak continuity and local Lipschitz continuity. Another major result is the finding that the mapping is Hadamard differentiable; a main ingredient is the reformulation of the variational inequality, the so called viscoplastic flow rule, as a Banach space-valued ordinary differential equation with non-differentiable right-hand side. Subsequently, we consider an optimal control problem governed by thermoviscoplasticity and show the existence of a minimizer. Finally, close this thesis with numerical examples.Diese Arbeit ist der Untersuchung von Optimalsteuerproblemen gewidmet, denen ein quasistatisches, thermoviskoplastisches Model mit kleinen Deformationen, mit linearem kinematischen Hardening, von Mises Fließbedingung und gemischten Randbedingungen zu Grunde liegt. Mathematisch werden thermoviskoplastische Systeme durch nichtlineare partielle Differentialgleichungen und eine variationelle Ungleichung der zweiten Art beschrieben, um die elastischen, plastischen und thermischen Effekte abzubilden. Durch die Miteinbeziehung thermischer Effekte, treten verschiedene mathematische Schwierigkeiten während der Analysis des thermoviskoplastischen Systems auf, die ihren Ursprung hauptsächlich in der schlechten Regularität der nichtlinearen Terme auf der rechten Seite der Wärmeleitungsgleichung haben. Eines unserer Hauptresultate ist die Existenz einer eindeutigen schwachen Lösung, welches wir mit Hilfe von einem Fixpunktargument und unter Anwendung von maximaler parabolischer Regularitätstheorie beweisen. Zudem definieren wir die entsprechende Steuerungs-Zustands-Abbildung und untersuchen Eigenschaften dieser Abbildung wie die Beschränktheit, schwache Stetigkeit und lokale Lipschitz Stetigkeit. Ein weiteres wichtiges Resultat ist, dass die Abbildung Hadamard differenzierbar ist; Hauptbestandteil des Beweises ist die Umformulierung der variationellen Ungleichung, der sogenannten viskoplastischen Fließregel, als eine Banachraum-wertige gewöhnliche Differentialgleichung mit nichtdifferenzierbarer rechter Seite. Schließlich runden wir diese Arbeit mit numerischen Beispielen ab.
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Henzelmann, Martin. "Hentschel, Gerd (Hrsg.), Variation und Stabilität in Kontaktvarietäten. Beobachtungen zu gemischten Formen der Rede in Weißrussland, der Ukraine und Schlesien: Buchbesprechung." De Gruyter, 2014. https://tud.qucosa.de/id/qucosa%3A71372.
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Der von Gerd Hentschel herausgegebene Band umreißt allgemeine und grundsätzliche Problemfelder sprachlicher Formen, deren wesentliches Merkmal die Mischung unterschiedlicher Codes ist. Drei Autoren stellen jeweils ein Beispiel in polnischer, ukrainischer und deutscher Sprache vor, an dem sie veranschaulichen, dass bestimmte Forschungsansätze hinsichtlich der gemischten Rede im Kontext der Slavia ausbaufähig sind. Erkennbare Stabilisierungstendenzen spielen für sie eine entscheidende Rolle im Hinblick auf neue theoretische Ansätze.
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Trampus, Franc Igor. "The effects of work force variation and conspecific preference in single and mixed-species colonies of Leptothorax longispinosus (Roger) and Leptothorax ambiguus (Emery) (Hymenoptera: Formicidae: Leptothoracini)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0026/MQ51601.pdf.
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Ko, James Yue-on. "Consistency and variation in classroom practice : a mixed-method investigation based on case studies of four EFL teachers of a disadvantaged secondary school in Hong Kong." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11363/.
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This mixed methods study was based on teacher case studies examining classroom practices of four EFL teachers of the same department of an underperforming secondary school in a socially-disadvantaged area in Hong Kong. Beside two international classroom observation instruments used for the quantitative classroom observations, extensive qualitative field notes were collected concurrently. Confirmatory factor analyses using the lesson as the unit of analysis generated a six-factor and a three-factor of model teaching behaviours respectively. For both instruments, results showed strong validity and reliability for strongly correlated underlying dimensions of teaching practices. Considerable differential teaching effectiveness in terms of inconsistency in observed teaching behaviours of the four teachers was noted across the various dimensions and across contexts. The qualitative field notes provided evidence that increased understanding of the variation in observed practice. Two teachers showed teaching behaviours more inconsistent across dimensions and lessons, though their effectiveness in certain dimensions in some lessons was found. Their fluctuating teaching effectiveness seemed to be under the influences of student year groups, class composition, subject content, school policy on learning, rather than class size. Themes emerged from the interviews with these teachers, the department head and the school principal suggested that cultural and school contexts might result in inconsistent teaching behaviours and revealed challenges and contradictions at individual, department, school, and system levels. This study was significant in demonstrating that both the generic and differentiated theories of teacher effectiveness may be required to account for the full spectrum of observed teaching behaviours. It also contributed to testing validity and reliability of two classroom observation instruments as it indicated that the high-inference instrument used by the inspectors might be slightly better in predicting overall judgment of lesson quality, while the lower inference instrument developed by the academics tended to generate underlying dimensions that were more distinguishable.
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Stöber, Jakob [Verfasser], Claudia [Akademischer Betreuer] Czado, Roger M. [Akademischer Betreuer] Cooke, and Andrew J. [Akademischer Betreuer] Patton. "Regular Vine Copulas with the simplifying assumption, time-variation, and mixed discrete and continuous margins / Jakob Stöber. Gutachter: Roger M. Cooke ; Andrew J. Patton ; Claudia Czado. Betreuer: Claudia Czado." München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1037198476/34.
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Greenwood, Sarah. "Investigating the response of subtropical forests to environmental variation through the study of the Abies kawakamii treelines in Taiwan." Thesis, University of Stirling, 2014. http://hdl.handle.net/1893/21561.
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Altitudinal treeline advance represents a sensitive and well-studied example of species response to climate warming. Although a great deal of work has been conducted globally, few studies have considered subtropical alpine treelines and little is known about their structure and function. This research aims to investigate the response of high altitude forests in Taiwan to climate variation by characterising treeline advance in the area, exploring the mechanisms driving the advance, and considering the consequences of advance for the wider community. The thesis consists of a general introduction to the topic followed by a series of papers, exploring: (1) Possible consequences of treeline shifts for biodiversity and ecosystem function. (2) The advance of the Abies kawakamii treeline through aerial photograph analysis. (3) The changes in growth rate of Abies kawakamii at treeline and the influence of altitude and temperature on growth. (4) Regeneration patterns at treeline and the importance of microclimate and topographic sheltering. (5) Consequences of the range shift for the wider forest community. The work is then concluded with a general discussion and synthesis. The main aims of this work are therefore to characterise and understand the pattern and pace of treeline advance and forest structural change throughout the Central Mountain Range of Taiwan. Treeline advance is characterised through the study of repeat aerial photographs and the mechanisms behind the observed shift are explored through the study of two key responses associated with forest advance: tree growth at treeline and seedling establishment beyond treeline. The consequences of treeline advance for the wider subalpine community are investigated through the study of epiphytic lichen communities at treeline sites. This investigation of an understudied region will allow for improved understanding of treeline response at a global scale.
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Legner, Nicole [Verfasser], Christoph [Akademischer Betreuer] Leuschner, and Frank [Akademischer Betreuer] Thomas. "Spatial variation of photosynthetic capacity of early-, mid-, or late-successional broad-leaved tree species in a temperate mixed forest / Nicole Legner. Gutachter: Christoph Leuschner ; Frank Thomas. Betreuer: Christoph Leuschner." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044249838/34.
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Fleurette-Delobbe, Valérie. "Variations du type structural reo::(3) dans des fluorures et oxyfluorures de niobium iv : etude des interactions magnetiques." Paris 6, 1987. http://www.theses.fr/1987PA066373.
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Determination de la structure cristalline de nbf::(4) par diffraction de rayons x et de neutrons: structure bidimensionnelle a octaedres nbf::(6) etires; mise en evidence d'interactions antiferromagnetiques d'apres la variation thermique de la susceptibilite magnetique. Nbof::(2) possede le type structural reo::(3); absence de l'antiferromagnetisme attendu. Etude des proprietes magnetiques de tif::(3) et tinbof::(5): existence de couplages antiferromagnetiques avec des temperatures de neel de 48 et 54k respectivement. Determination des structures nucleaire et magnetique de fenbf::(6) qui est antiferromagnetique avec une composante ferromagnetique tres faible; etude par effet moessbauer: il y aurait une inversion cationique partielle et on determine les temperatures de mise en ordre pour les sites correspondants
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Amand, Maelle. "A sociophonetic analysis of Tyneside English in the DECTE corpus : the case of FACE, GOAT, PRICE and MOUTH." Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7040.
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Cette thèse propose une analyse sociophonétique synchronique et diachronique de l’anglais de Tyneside à partir de deux sous-corpus du Corpus Diachronique de l’Anglais de Tyneside (DECTE) datant des années 1970 et de 1990 (Corrigan, Buchstaller, Mearns, & Moisl, 2012). Elle comporte deux grands volets : (1) une analyse de la variation inter et intra-locuteurs par le biais de transcriptions phonétiques des variantes linguistiques de FACE, GOAT, PRICE et MOUTH (Wells 1982) à l’aide d’une analyse factorielle multiple (AFM, Escofier 2008, Husson et al. 2011) (2) une étude acoustique des trajectoires formantiques de ces quatre ensembles lexicaux à l’aide de modèles mixtes additifs généralisés afin de vérifier la pertinence du codage (GAMMs, Wood 2015). Pour ce premier volet, nous proposons un profilage sociolinguistique de 44 locuteurs de Gateshead et de Newcastle, à partir de données phonétiques transcrites dans les années 1970 lors de l’Enquête Linguistique de Tyneside (TLS, Strang 1968). Bien que notre analyse porte sur la totalité des transcriptions du système phonétique des locuteurs, l’accent est davantage porté sur FACE, GOAT, PRICE and MOUTH. Selon l’AFM suivi d’une classification, FACE est l’ensemble lexical le plus déterminant dans la catégorisation sociolinguistique des locuteurs. La symétrie entre FACE et GOAT (Watt 1999), PRICE et MOUTH est plus nette chez les femmes : celles de la classe moyenne privilégient une diphtongue fermantes dans entre FACE et GOAT et une attaque de diphthongue ouverte pour PRICE et MOUTH, tandis que les femmes issues de classes plus populaires optent pour la monophtongue pan-régionale pour FACE et GOAT, avec une attaque davantage fermée et antérieure chez PRICE et MOUTH. La monophtongue centrale de GOAT la variante privilégiée par des hommes à l’accent local moins marqué, ce qui entre en cohérence avec les résultats de Watt (1998) dans le sous-corpus des années 1990 du DECTE.Le second volet analyse les trajectoires formantiques de FACE, GOAT et PRICE. Le but premier de cette analyse est de vérifier la correspondance des transcriptions avec le contour formantique. Les résultats confirment la pertinence du codage au niveau des liste de mots (TLS & PVC). Les différences entre les deux variantes principales de PRICE ([aɪ] vs. [eɪ]) se révèlent être foncièrement différentes tant sur le plan de l’attaque, de la trajectoire et de la cibleThe present thesis offers both apparent-time and real-time analyses of two sub-corpora of the Diachronic Electronic Corpus of Tyneside English (DECTE) : one from the 1970s and another one compiled in the 1990s (Corrigan et al., 2012). It comprises two main parts: (1) an analysis of inter and intra-speaker variation in the lexical sets FACE, GOAT, PRICE and MOUTH (Wells 1982) based on a multiple factor analysis (MFA, Escofier 2008, Husson et al. 2011) (2) a dynamic acoustic analysis of formant trajectories of these vowels using Generalised additive mixed models (GAMMs, Wood 2015) followed by a static analysis of onsets in PRICE. The first part establishes the sociolinguistic profiles of 44 speakers from Gateshead and Newcastle based on the original phonetic transcriptions of the Tyneside Linguistic Survey (TLS, Strang 1968). Although the profiling analysis are based on the entire phonetic system transcribed by the original TLS team, the main focus is on FACE, GOAT, PRICE and MOUTH only. Results indicate that FACE the main determinant of TE speech. The symmetry between FACE et GOAT as found by Watt 1999, was also observed in PRICE et MOUTH among women. While middle-class women clearly favour a closing diphthong in FACE et GOAT and have a low onset in PRICE and MOUTH, working-class women tend to have higher frequency scores of pan-northern monophthongs in the first pair of lexical sets. They also exhibit more frequent raised onsets in in PRICE and MOUTH. In addition, the central monophthong GOAT is more often used by men with a less traditional accent in the 1970s corpus, which is in line with Watt’s findings for the 1990s corpus (Watt 1998).The second part analyses formant trajectories in FACE, GOAT and PRICE. The main aim was to compare the original phonetic transcriptions with the corresponding formant trajectories. Results confirm the pertinence of the transcriptions in the wordlist section of the corpora (TLS & PVC). Differences between the two main variants of PRICE ([aɪ] vs. [eɪ]) appeared to be strikingly different be in terms of both onsets / offset heights and trajectory shape
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Banerjee, Debashis. "Intelligent real-time environment and process adaptive radio frequency front-ends for ultra low power applications." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53882.
Full textAbstract:
In the thesis the design of process tolerant, use-aware radio-frequency front-ends were explored. First, the design of fuzzy logic and equation based controllers, which can adapt to multi-dimensional channel conditions, are proposed. Secondly, the thesis proves that adaptive systems can have multiple modes of operation depending upon the throughput requirements of the system. Two such modes were demonstrated: one optimizing the energy-per-bit (energy priority mode) and another achieving the lowest power consumption at the highest throughput (data priority mode). Finally, to achieve process tolerant channel adaptive operation a self-learning methodology is proposed which learns the optimal re-configuration setting for the system on-the-fly. Implications of the research are discussed and future avenues of further research are proposed.