Дисертації з теми "Periodical conditions"
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1
Dean, Camille K. "True Religion: Reflections of British Churches and the New Poor Law in the Periodical Press of 1834." Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc278395/.
Повний текст джерелаАнотація:
This study examined public perception of the social relevance of Christian churches in the year the New Poor Law was passed. The first two chapters presented historiography concerning the Voluntary crisis which threatened the Anglican establishment, and the relationship of Christian churches to the New Poor Law. Chapters 4, 5, and 6 revealed the recurring image of "true" Christianity in its relation to the church crisis and the New Poor Law in the working men's, political, and religious periodical press. The study demonstrated a particular working class interest in Christianity and the effect of evangelicalism on religious renewal and social concerns. Orthodox Christians, embroiled in religious and political controversy, articulated practical concern for the poor less effectively than secularists.
2
Chamaillard, Mathieu. "Effective boundary conditions for thin periodic coatings." Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLY001.
Повний текст джерелаАнотація:
Nous avons traité le cas de l'équation scalaire de Helmholtz. Nous allons tenter de traiter le cas des équations de Maxwell. On s'intéressera aux cas des méta-matériaux. Dans un premier cas la permittivité est négative dans la couche mince et dans le deuxième cas la perméabilité est en (1/delta)^2We have dealt with the case of the scalar Helmholtz equation. We will try to handle the case of Maxwell's equation. We also will focus on the case of meta-materials. In a first case the permittivity is negative in the thin layer and in the second case is the permeability (1/delta) ^ 2
3
Shepherd, Roger. "Coupled non-linear diffusion under periodic boundary conditions." Thesis, University of South Wales, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239985.
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Africa, African People's Democratic Union of Southern. "The Apdusan: African People's Democratic Union of Southern Africa." African People's Democratic Union of Southern Africa, 1999. http://hdl.handle.net/10962/76095.
Повний текст джерелаАнотація:
After many deadlocks, accusations of negotiating in bad faith, marches and lunch-time pickets, more than 600,000 Public Sector Workers went on strike on 24 August 1999. The government then unilaterally implemented a 6.3% increase for public servants against their original demand of 10-15% increase. "The dispute goes back to January 1999, to a workshop dealing with the budgetary process. At this meeting the Department of Finance outlined its Medium-Term Expenditure Framework, for the first time to the public sector workers. In the MTEF the parameters for wage cuts, and 'non-negotiability’ were already set. All unions in the public service bargaining council presented their wage demands - 10% to 15%” [COSATU paper on Public Sector Workers Fight for a Living Wage.] Thereafter COSATU and government officials met over the next few months until May 1999, when a dispute was declared. On the 29th March 1999, COSATU commented ‘To the Unions it is clear, government is not prepared to negotiate - it has already made up its mind’ [COSATU document - Public Sector Workers Fight for a Living Wage] During the period May-June COSATU Unions decided to “throw their weight behind the ANC election campaign.’’[ibid.]. By the August 1999 the unions compromised their demand from 10% to 7.3% increase. Towards the end of August the government unilaterally implemented ei 6.3% increase for public sector workers, and 4% increase for itself. It then went on an ideological media campaign against the workers claiming that the 4% increase for members of parliament is much less than what has been granted to the public sector workers.Vol. 5 no. 3
5
Legan, J. D. "Bacterial competition for methylamine under conditions of periodic nutrient alternation." Thesis, University of Reading, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354086.
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6
Poling, David R. "Airfoil response to periodic disturbances: the unsteady Kutta condition." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/76166.
Повний текст джерелаАнотація:
Unsteady flow fields over a NACA 0012 at an angle of attack are investigated. The first is the classical pitching motion about the airfoil's quarter chord. The second is the flow over a fixed airfoil immersed in the wake of the pitching airfoil. Large reduced frequencies are considered. Measurements were obtained in a water tunnel by Laser-Doppler velocimetry. Ensemble-averaged velocity measurements were obtained in the vicinity of the trailing edges of both the pitching and the fixed airfoils. The flowfields in the wake and at the trailing edges of both airfoils were studied visually. The validity of the quasi-steady and an extension to an unsteady Kutta condition are examined. A new dynamic similarity parameter is proposed. An analytical method based on the dynamics of discrete vortices is employed. Numerical calculations of the flow over the fixed airfoil are compared with experimental results.Ph. D.
7
Anderson, Mark Jule Jr. "Cooperative Behavior in Driven Lattice Systems with Shifted Periodic Boundary Conditions." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30606.
Повний текст джерелаАнотація:
We explore the nature of driven stochastic lattice systems with non-periodic boundary conditions. The systems consist of particle and holes which move by exchanges of nearest neighbor particle-hole pairs. These exchanges are controlled by the energetics associated with an internal Hamiltonian, an external drive and a stochastic coupling to a heat reservoir. The effect of the drive is to bias particle-hole exchanges along the field in such a way that a particle current can be established. Hard-core volume constraints limit the occupation of only one particle (hole) per lattice site. For certain regimes of the overall particle density and temperature, a system displays a homogeneous disordered phase. We investigate cooperative behavior in this phase by using two-point spatial correlation functions and structure factors. By varying the particle density and the temperature, the system orders into a phase separated state, consisting of particle-rich and particle-poor regions. The temperature and density for the co-existence state depend on the boundary conditions. By using Monte Carlo simulations, we establish co-existence curves for systems with shifted periodic boundary conditions.Ph. D.
8
Schwinte, Valentin. "Autour de l'équation du plus bas niveau de Landau." Electronic Thesis or Diss., Université de Lorraine, 2024. http://www.theses.fr/2024LORR0078.
Повний текст джерелаАнотація:
Cette thèse a pour objet l'étude de l'équation du plus bas niveau de Landau, dans plusieurs contextes pertinents en physique et provient des modèles pour les condensats de Bose-Einstein. Nous nous penchons spécifiquement sur trois aspects liés à l'équation. Le premier est l'étude d'une classe de solutions appelées ondes stationnaires, à travers la minimisation d'une fonctionnelle énergie. Nous montrons notamment que la gaussienne est l'unique minimiseur global à symétries près pour un certain paramètre, à l'aide d'algèbre linéaire et bilinéaire. Le deuxième point concerne la conjecture de réseau d'Abrikosov. Nous investiguons l'équation avec ajout de conditions périodiques, et la linéarisons autour des réseaux. Nous aboutirons à la stabilité du réseau hexagonal. Le troisième et dernier aspect porte sur les ondes progressives pour l'équation couplée du plus bas niveau de Landau. Nous classifions de telles solutions ayant un nombre fini de zéros, et en déduisons l'existence de solutions dont les normes de Sobolev croissentThe aim of this thesis is to study the Lowest Landau Level equation, in several contexts relevant to physics and originating from models for Bose-Einstein condensates. In particular, we investigate three aspects of the equation. The first is the study of a class of solutions called stationary waves, through the minimization of an energy functional. In particular, we show that the Gaussian is the only global minimizer up to symmetries for a certain parameter, using linear and bilinear algebra tools. The second point concerns the Abrikosov lattice conjecture. We investigate the equation with the addition of periodic conditions, and linearize it around lattices. This results in the stability of the hexagonal lattice. The third and final aspect concerns progressive waves for the coupled Lowest Landau Level equation. We classify such solutions with a finite number of zeros, and deduce the existence of solutions with growing Sobolev norms
9
Kabadshow, Ivo [Verfasser]. "Periodic Boundary Conditions and the Error-Controlled Fast Multipole Method / Ivo Kabadshow." Wuppertal : Universitätsbibliothek Wuppertal, 2012. http://d-nb.info/1020476176/34.
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10
Sanchez, Juan Eusebio. "Semiconductor device simulation of low-frequency noise under periodic large-signal conditions." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001178.
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Date, James Charles. "Performance prediction of high lift rudders operating under steady and periodic flow conditions." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390722.
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Granat, Robert. "Algorithms and Library Software for Periodic and Parallel Eigenvalue Reordering and Sylvester-Type Matrix Equations with Condition Estimation." Doctoral thesis, Umeå : Department of Computing Science, Umeå Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1415.
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Rattermann, Dale N. "A Fast Poisson Solver with Periodic Boundary Conditions for GPU Clusters in Various Configurations." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397233840.
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14
Rogers, Daniel R. "Design of a Three-Passage Low Reynolds Number Turbine Cascade with Periodic Flow Conditions." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2684.pdf.
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15
Amenoagbadji, Pierre. "Wave propagation in quasi-periodic media." Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAE020.
Повний текст джерелаАнотація:
L'objectif de la thèse est de développer des méthodes numériques originales pour la résolution de l'équation des ondes en régime harmonique dans des milieux quasi-périodiques, dans l'esprit des méthodes développées précédemment pour des milieux périodiques. L'idée est d'utiliser comme dans des travaux d'homogénéisation quasi-périodique le fait que l'étude d'une EDP elliptique avec des coefficients quasi-périodiques se ramène à l'étude d'une EDP elliptiquement dégénérée en dimension supérieure, mais dont les coefficients sont périodiques. Le caractère périodique permet d'utiliser des outils adaptés, mais le caractère non-elliptique rend toutefois l'analyse mathématique et numérique de l'EDP délicate. Une des applications étudiées dans ce manuscrit concerne des problèmes de transmission entre des demi-plans périodiques (typiquement des cristaux photoniques) quand (1) l'interface ne coupe pas les demi-plans périodiques dans une direction de périodicité, ou (2) quand les milieux périodiques n'ont pas des périodes commensurables le long de l'interfaceThe goal of this thesis is to develop efficient numerical methods for the solution of the time-harmonic wave equation in quasiperiodic media, in the spirit of methods previously developed for periodic media. The goal is to use as in quasiperiodic homogenization the idea that an elliptic PDE with quasiperiodic coefficients can be interpreted as the cut of a higher-dimensional PDE which is elliptically degenerate, but with periodic coefficients. The periodicity property allows to use adapted tools, but the non-elliptic aspect makes the mathematical and numerical analysis of the PDE delicate. One application concerns transmission problems between periodic half-spaces (typically photonic crystals) when (1) the interface does not cut the periodic half-spaces in a direction of periodicity, or (2) when the periodic media have noncommensurate periods along the interface
16
Fu, Man. "A Study of Stock Market Fluctuations and their Relations to Business Conditions." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/89.
Повний текст джерелаАнотація:
Most research on stock prices is based on the present value model or the more general consumption-based model. When applied to real economic data, both of them are found unable to account for both the stock price level and its volatility. Three essays here attempt to both build a more realistic model, and to check whether there is still room for bubbles in explaining fluctuations in stock prices. In the second chapter, several innovations are simultaneously incorporated into the traditional present value model in order to produce more accurate model-based fundamental prices. These innovations comprise replacing with broad dividends the more narrow traditional dividends that are more commonly used, a nonlinear artificial neural network (ANN) forecasting procedure for these broad dividends instead of the more common linear forecasting models for narrow traditional dividends, and a stochastic discount rate in place of the constant discount rate. Empirical results show that the model described above predicts fundamental prices better, compared with alternative models using linear forecasting process, narrow dividends, or a constant discount factor. Nonetheless, actual prices are still largely detached from fundamental prices. The bubble-like deviations are found to coincide with business cycles. The third chapter examines possible cointegration of stock prices with fundamentals and non-fundamentals. The output gap is introduced to form the non-fundamental part of stock prices. I use a trivariate Vector Autoregression (TVAR) model and a single equation model to run cointegration tests between these three variables. Neither of the cointegration tests shows strong evidence of explosive behavior in the DJIA and S&P 500 data. Then, I applied a sup augmented Dickey-Fuller test to check for the existence of periodically collapsing bubbles in stock prices. Such bubbles are found in S&P data during the late 1990s. Employing econometric tests from the third chapter, I continue in the fourth chapter to examine whether bubbles exist in stock prices of conventional economic sectors on the New York Stock Exchange. The ‘old economy’ as a whole is not found to have bubbles. But, periodically collapsing bubbles are found in Material and Telecommunication Services sectors, and the Real Estate industry group.
17
Kuczyński, Waldemar. "Investigation into boiling in the refrigerant flow under the conditions of periodically generated disturbance : PhD thesis summary." Rozprawa doktorska, [s.n.], 2009. http://dlibra.tu.koszalin.pl/Content/1197.
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Cai, Yong. "Finite-element time- domain modelling of periodic structures with floquet modal absorbing boundry condition." Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487809.
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Neves, Maxstaley Leninyuri. "A condition-based maintenance policy and input parametersestimation for deteriorating systems under periodic inspection." Universidade Federal de Minas Gerais, 2010. http://hdl.handle.net/1843/BUOS-8C8E4A.
Повний текст джерелаАнотація:
We study the problem of proposing Condition-Based Maintenance policies for machines and equipments. Our approach combines an optimization model and input parameters estimation from empirical data.The system deterioration is described by discrete states ordered from thestate \as good as new" to the state \completely failed". At each periodicinspection, whose outcome might not be accurate, a decision has to be made between continuing to operate the system or stopping and performing its preventive maintenance. This decision-making problem is discussed and we tackle it by using an optimization model based on the Dynamic Programming and Optimal Control theory. We then explore the problem of how to estimate the model input parameters, i.e., how to adequate the model inputs to the empirical data available. The literature has not explored the combination of optimization techniques and model input parameters, through historical data, for problems with imperfectinformation such as the one considered in this work. We develop ourformulation using the Hidden Markov Model theory. We illustrate our framework using empirical data provided by a mining company and the results show the applicability of our models. We conclude by pointing out some possible directions for future research on this field.O foco deste trabalho é a definição de políticas ótimas de manutenção preventiva em função da condição do equipamento. Propomos uma abordagem que combina um modelo de otimização com um modelo de estimação de parâmetros a partir dos dados de campo. A condição do sistema é descrita por estados discretos ordenados do "tão bom quanto novo" até o estado "completamente falhado". A cada inspeção, cujo resultado pode ser impreciso, uma decisão e tomada: continuar a operação ou efetuar a manutenção preventiva. Este problema de tomada de decisão é analisado e propomos um algoritmo de otimização baseado em Programação Dinamica-Estocástica e Controle Ótimo. Em seguida, exploramos o problema de como estimar as entradas do modelo, ou seja, como adequar os parâmetros de entrada em função dos dados disponiveis. Até o momento, a literatura não apresentou uma técnica que lida com otimização e estimação de parâmetros de entrada (usando dados históricos) para problemas com informação imperfeita como o considerado neste trabalho. Desenvolvemos nossa abordagem usando os Modelos Ocultos de Markov. Ilustramos a aplicação dos modelos desenvolvidos com dados de campo fornecidos por uma empresa de mineração. Os resultados mostram a aplicabilidade da nossa abordagem. Concluímos o texto apresentando possíveis direções para pesquisa futura na área.
20
Thai, Ngoc Nguyen [Verfasser], Ingo [Akademischer Betreuer] [Gutachter] Witt, and Wolfram [Gutachter] Bauer. "Radiation conditions for periodic potentials / Nguyen Thai Ngoc ; Gutachter: Ingo Witt, Wolfram Bauer ; Betreuer: Ingo Witt." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1140222910/34.
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21
Hayakawa, Naoki, and Hitoshi Okubo. "Partial discharge characteristics of inverter-fed motor coil samples under ac and surge voltage conditions." IEEE, 2005. http://hdl.handle.net/2237/6764.
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Nestler, Franziska. "An NFFT based approach to the efficient computation of dipole-dipole interactions under different periodic boundary conditions." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-171040.
Повний текст джерелаАнотація:
We present an efficient method to compute the electrostatic fields, torques and forces in dipolar systems, which is based on the fast Fourier transform for nonequispaced data (NFFT). We consider 3d-periodic, 2d-periodic, 1d-periodic as well as 0d-periodic (open) boundary conditions. The method is based on the corresponding Ewald formulas, which immediately lead to an efficient algorithm only in the 3d-periodic case. In the other cases we apply the NFFT based fast summation in order to approximate the contributions of the nonperiodic dimensions in Fourier space. This is done by regularizing or periodizing the involved functions, which depend on the distances of the particles regarding the nonperiodic dimensions. The final algorithm enables a unified treatment of all types of periodic boundary conditions, for which only the precomputation step has to be adjusted.
23
Alzabut, Jehad. "Periodic Solutions And Stability Of Linear Impulsive Delay Differential Equations." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12604901/index.pdf.
Повний текст джерелаАнотація:
In this thesis, we investigate impulsive differential systems with delays of the form
And more generally of the form
The dissertation consists of five chapters. The first chapter serves as introduction, contains preliminary considerations and assertions that will be encountered in the sequel. In chapter 2, we construct the adjoint systems and obtain the variation of parameters formulas of the solutions in terms of fundamental matrices. The asymptotic behavior of solutions of systems satisfying the Perron condition is investigated in chapter 3. In chapter4, we give a result that characterizes the behavior of solutions in the case there is a bounded solution. Moreover, a necessary and sufficient condition for the existence of periodic solutions is obtained. In the last chapter, a series of consequences on the existence of periodic solutions of functionally equivlent impulsive systems with delays is established.
24
Höhn, Tomáš. "Modelování kmitočtově selektivních povrchů v programu COMSOL Multiphysics." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217463.
Повний текст джерелаАнотація:
Metoda konečných prvků implementovaná v programu COMSOL Multiphysics je využívána k analýze tzv. free-standing kmitočtově selektivních povrchů ve 3D. Tyto modely jsou následně doplněny o periodické okrajové podmínky. Dále jsou free-standing povrchy doplněny o vrstvy dielektrika a je zkoumán jejich vliv na modul činitele odrazu. V analytické části jsou vyhodnoceny vlivy počtu elementů diskretizační mřížky na přesnost výsledku a délku výpočtů. Výsledky jsou srovnávány vzhledem k výsledkům uvedeným v literatuře [5]. V závěrečné části práce je vysvětlen postup při generování m-file pro obdélníkový element a použití globálního optimalizačního algoritmu PSO, který automaticky upravuje rozměry vodivého motivu tak, aby bylo dosaženo průběhu modulu činitele odrazu podle požadovaného průběhu.
25
Ward, Thomas Boulton. "Topological entropy and periodic points for Zd actions on compact abelian groups with the Descending Chain Condition." Thesis, University of Warwick, 1989. http://wrap.warwick.ac.uk/73322/.
Повний текст джерелаАнотація:
This thesis deals with the ergodic theory of actions of Zd on compact abelian groups satisfying a regularity condition: the descending chain condition. Using results of Klaus Schmidt, Bruce Kitchens and Doug Lind, we show that the descending chain condition guarantees that the global topological entropy of such an action coincides with the growth rate of periodic points whenever this exists (§II.3). This links the global entropy to the dynamics of such systems and allows the global entropy to be computed for some important examples (§II4). The algebraic entropy of a Zd action on a discrete abelian group is defined. Following Justin Peters, we show that this entropy coincides with the topological entropy of the adjoint action on the compact dual group (§III.1). Two possible zeta functions for actions are introduced, and their poles are found for expansive systems with the descending chain condition (§IV.2). We comparethese functions with the one-dimensional case of a single automorphism, where the least real pole of the zeta function lies at exp(-entropy). We relate an instance of convergence at a pole with the Mahler measure of a polynomial described as a limit of one dimensional Mahler measures (§IV.3). Appendix A is a paper written with Doug Lind in which the basic onedimensional entropy formula (Yuzvinskii's formula) is computed using adelic methods. Appendix B reproduces for the sake of completeness the higher-dimensional entropy formula due to Doug Lind and Klaus Schmidt. Appendix C contains some examples of calculations of numbers of periodic points for simple higher-dimensional systems.
26
Jia, H.-X., G. Xi, L. Müller, R. Mailach, and K. Vogeler. "Effect of clocking on unsteady rotor blade loading in a low-speed axial compressor at design and off-design operating conditions." Sage, 2008. https://publish.fid-move.qucosa.de/id/qucosa%3A38439.
Повний текст джерелаАнотація:
This paper presents the results of stator clocking investigations at a design point and an operating point near the stability limit in a low-speed research compressor (LSRC). The unsteady flow field of the LSRC at several clocking configurations was investigated using a three-dimensional unsteady, viscous solver. The unsteady pressure on the rotor blades at midspan (MS) was measured using time-resolving piezoresistive miniature pressure transducers. The effect of clocking on the unsteady pressure fluctuation at MS on the rotor blades is discussed for different operating points. Based on the unsteady profile pressures, the blade pressure forces were calculated. The peak-to-peak amplitudes of the unsteady blade pressure forces are presented and analysed for different clocking positions at both the design point and the operating point near the stability limit of the compressor.
27
Zhang, Peng. "Systèmes elliptiques issus de la modélisation des supraconducteurs." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1115/document.
Повний текст джерелаАнотація:
Ce travail porte sur des équations aux dérivées partielles issues de la physique mathématique, plus particulièrement sur celles régissant la supraconductivité. Ainsi, la majorité du travail concerne le modèle de Ginzburg-Landau, qui est un modèle macroscopique de supraconducteurs de type-II. Ce travail est divisé en deux parties principales: La première partie se focalise sur l'analyse des vortex du modèle de Ginzburg-Landau en deux dimensions pour les supraconducteurs de type-II, modèle conduisant à une estimation de la variation du nombre de vortex et à l'optimalité du réseau d'Abrikosov parmi les réseaux de Bravais. Nous avons également étudié certains modèles de stuctures des matériaux comme ceux de Lennard-Jones et de Thomas-Fermi. La seconde partie est consacrée à la fonctionnelle de Ginzburg-Landau en dimension $n$. Deux résultats principaux sont obtenus. L'un porte sur l'énergie renormalisée pour les minimiseurs de la fonctionnelle de Ginzburg-Landau. L'autre concerne les limites des solutions de l'équation de Ginzburg-Landau. Ces deux résultats sont fortement reliés aux applications $n$-harmoniquesOur work focus on the elliptic partial differential Equations arising from the mathematical physics, especially from the superconductivity. Therefore most of our work is on the Ginzburg-Landau model, which is a macroscopic model for the type-II superconductors. The work is divided into two big parts : this first part is on the vortices analysis of the Ginzburg-Landau model of Type-II superconductors in 2 dimensions, including the variations of the number of vortices and optimality of Abrikosov lattices among Bravais Lattices. We also have done some work related to the material structure, for example, the Lennard-Jones model and the Thomas-Fermi model. This second part is on the Ginzburg-Landau functional in $n$-dimensional case. Two main results are contained in this part: One is on the renormalized energy for minimizer of $n$-dimensional Ginzburg-Landau functional; The other one is on the limits of solutions to Ginzburg-Landau equations in $n$ dimension. Both of these two results are closely related to the p-harmonic maps
28
Asselle, Luca [Verfasser], Alberto [Akademischer Betreuer] Abbondandolo, and Gerhard [Akademischer Betreuer] Knieper. "On the existence of orbits satisfying periodic or conormal boundary conditions for Euler-Lagrange flows / Luca Asselle. Gutachter: Alberto Abbondandolo ; Gerhard Knieper." Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1089007183/34.
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Garrione, Maurizio. "Existence and multiplicity of solutions to boundary value problems associated with nonlinear first order planar systems." Doctoral thesis, SISSA, 2012. http://hdl.handle.net/20.500.11767/4930.
Повний текст джерелаАнотація:
The monograph is devoted to the study of nonlinear first order systems in the plane where the principal term is the gradient of a positive and positively 2-homogeneous Hamiltonian (or the convex combination of two of such gradients). After some preliminaries about positively 2-homogeneous autonomous systems, some results of existence and multiplicity of T-periodic solutions are presented in case of bounded or sublinear nonlinear perturbations. Our attention is mainly focused on the occurrence of resonance phenomena, and the corresponding results rely essentially on conditions of Landesman-Lazer or Ahmad-Lazer-Paul type. The techniques used are predominantly topological, exploiting the theory of coincidence degree and the use of the Poincaré-Birkhoff fixed point theorem. At the end, other boundary conditions, including the Sturm-Liouville ones, are taken into account, giving the corresponding existence and multiplicity results in a nonresonant situation via the shooting method and topological arguments.
30
Chew, Wendy Poh Yoke. "Consuming femininity : nation-state, gender and Singaporean Chinese women." University of Western Australia. School of Humanities, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0135.
Повний текст джерелаАнотація:
My research seeks to understand ways in which English-educated Chinese women in cosmopolitan Singapore bolstered their identity while living under the influences of Confucian values, patriarchal nation-building and racial concerns. My thesis examines women who have themselves been lost in translation when they were co-opted into the creation of a viable state after 1965. Often women are treated as adjuncts in the patriarchal state, particularly since issues of gender are not treated with the equality they deserve in the neo-Confucian discourse. This thesis takes an unconventional approach to how women have been viewed by utilizing primary sources including Her World and Female magazines from the 1960s and 1990s, and subsequent material from the blogosphere. I analyze images of women in these magazines to gain an understanding of how notions of gender and communitarianism/race intersect. By looking at government-sponsored advertising, my work also investigates the kind of messages the state was sending out to these women readers. My examination of government-sponsored advertisements, in tandem with the existing mainstream consumer advertising directed at women provides therefore a unique historical perspective in understanding the kinds of pressures Singaporean women have faced. Blogging itself is used as a counterpoint to show how new spaces have opened up for those who have felt constricted in certain ways by the authorities, women included. It would be fair to say that women?s magazines and blogging have served as ways for women to bolster their self worth, despite the counter-argument that some highly idealized and unhealthy images of women are purveyed. The main target group of glossy women?s magazines is English-educated women readers who are, by virtue of the Singapore?s demographics, mostly Chinese.
31
Kambisseri, Roby Neelu. "Wireless communication using metasurfaces for condition monitoring in motor." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-246051.
Повний текст джерелаАнотація:
Wireless sensors are used widely for condition monitoring in electric machines. The metal enclosure of an electric motor restricts the signal from sensors to radiate outside. The signal from the metal cavity needs to be guided to the only opening in the enclosure, through a narrow gap between the stator and the rotating rotor. Gap waveguide technology is proposed as a solution by texturing the stator surface with electromagnetic band gap (EBG) structures. Arrays of periodic holey structures are used to realize the metasurface waveguide. Two Bravais lattice structures – square and hexagonal, are explored for guiding waves along a desired path in a parallel plate waveguide. Simulations are carried out to study the influence of various dimensions of the unit cells. A waveguide with hexagonal hole-type unitcell is designed and manufactured for experimental verification. The possibility of extending the same technology to cylindrical surface is confirmed by simulations.Trådlösa sensorer används allmänt för tillståndsövervakning i elektriska maskiner. Metallhöljet hos en elektrisk motor begränsar signalen från sensorerna från att stråla utåt. Signalen från metallhåligheten behöver styras till den enda öppningen i höljet, genom ett smalt mellanrum mellan statorn och den roterande rotorn. Gap-vågledarteknik föreslås som en lösning genom att strukturera statorytan med elektromagnetiska bandgap-strukturer (EBG). Arrayer av periodiskt håliga strukturer används för att realisera metayt-vågledare. Två Bravais gitterkonstruktioner –kvadratiska och sexkantiga, undersöks för styrning av vågor längs en önskad väg i en parallellplattvågledare. Simuleringar utförs för att studera påverkan av olika dimensioner hos enhetscellerna. En vågledare med hexagonal håltypsenhetscell är konstruerad och tillverkad för experimentell verifiering. Möjligheten att utvidga samma teknik till cylindrisk yta bekräftas genom simuleringar.
32
Nandamuri, Sasank Sai. "A Multiscale Computational Study of the Mechanical Properties of the Human Stratum Corneum." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1458300092.
Повний текст джерела
33
Ozturk, Burak. "Combined effects of Reynolds number, turbulence intensity and periodic unsteady wake flow conditions on boundary layer development and heat transfer of a low pressure turbine blade." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1150.
Повний текст джерела
34
Riihimäki, Eva-Stina. "A Theoretical Investigation of the Octapeptide Region in the Human Prion Protein." Doctoral thesis, KTH, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4423.
Повний текст джерелаАнотація:
Den kopparbindande egenskapen hos prionproteiner är sannolikt kopplad till proteinets funtion. Det mänskliga prionproteinet innehåller ett kopparbindande oktapeptidområde, där PHGGGWGQ-sekvensen upprepas fyra gånger i följd. Syftet med detta arbete är att undersöka strukturen och dynamiken i oktapeptidområdet genom att använda teoretiska metoder. Med kvantkemisk strukturoptimering genomfördes en detaljerad jämförelse av växelverkan mellan flera katjoner och det kopparbindande området. Enligt dessa beräkningar är rodium(III) en möjlig ersättare för koppar(II) i NMR-specktroskopiska koordinationsstudier. Alternativa solvatiseringsmodeller i molekyldynamiksimuleringar har också jämförts. Periodiska randvillkor är mest lämpade för användning i de system som undersöks i detta arbete. Molekyldynamiksimuleringar användes för att jämföra oktapeptidområdets struktur och dynamik med och utan kopparjoner. Växelverkan mellan aminosyrornas ringar påverkar starkt strukturen i detta område i frånvaro av kopparjoner. Fyra olika icke-bindande och bindande modeller har studerats, vilka skiljer i sin beskrivning av växelverkan mellan koppar och proteinet. Teoretiska EXAFS spektra beräknades från dem simulerade strukturerna. Spektra som genererats för den bindande modellen är nästan identiska med experimentiella resultat, vilket stöder användandet av den bindande modellen. Detta arbete visar att kopparjoner interagerar med histidin imidazolringens Nδ, deprotonerade amidkväven hos de därpå följande glycinerna samt karbonylsyret hos den andra glycinen. Simuleringarna kunde visa att kopparjonen inte stabilt binder några axiella vattenmolekyler i lösning, till skillnad från en kristallstruktur av koordinationsstrukturen. Indolringen hos tryptofan interagerar direkt med kopparjonen genom stabiliserande katjon-π växelverkan utan direkt medverkan av någon vattenmolekyl. Växelverkan mellan indolringen och kopparjonen var väldefinierad och observerades kunna ske på båda sidor av koordinationsplanet. Molekyldynamiksimuleringarna med kopparjoner och oktapeptidområdet visade hur närvaron av kopparjoner ledde till ett mer strukturerat oktapeptidområde.The copper-binding ability of the prion protein is thought to be closely related to its function. The human prion protein contains a copper-binding octapeptide region, where the octapeptide PHGGGWGQ is repeated four times consecutively. This work focuses on investigation of the structure and the dynamics of the octapeptide region by means of theoretical methods. Quantum chemical structural optimization allowed a detailed comparison of the interaction of several cations at the copper coordination site. These calculations identified rhodium(III) as a potent substitute for copper(II) that could be used to study the coordination site with NMR-spectroscopic methods. Solvation models that could be used in molecular dynamics simulations as an alternative to periodic boundary conditions were evaluated. Periodic boundary conditions are the best method for modeling the aqueous bulk in the kind of systems that are studied in this work. Molecular dynamics simulations were used to compare the behavior of the octapeptide region in the absence and presence of copper ions. Interaction between nonpolar rings strongly influences the structure of the region in the absence of copper ions. Four different non-bonded and bonded models for describing the interaction between copper and the protein were evaluated. Theoretical EXAFS spectra were calculated from the simulated structures. The results obtained for the bonded model are nearly identical with experimental data, which validates the use of the bonded model. This work thus shows strong evidence for copper(II) ions interacting with the octapeptide region through the histidine imidazole Nδ, the deprotonated nitrogen atoms of the following two glycine residues and the carbonyl oxygen atom of the second glycine residue. Notably, the simulations show that the axial sites of the copper ion do not stably coordinate water molecules in solution, as opposed to the crystal structure reported for the coordination site. Instead, the tryptophan indole ring interacted directly with the copper ion through stabilizing cation-π interaction without water mediation. The interaction of the indole ring with the copper ion was well-defined and was observed to occur on both sides of the coordination plane. The investigations of the interaction between copper ions and the octapeptide region with molecular dynamics simulations show how the presence of copper ions results in a more structured octapeptide region.
QC 20100816
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Nespoulet, Hugo. "Oxygénation en conditions hypoxiques : rôle de la chémosensibilité sur la tolérance à l'altitude, plasticité et amélioration par pression positive expiratoire." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENS041/document.
Повний текст джерелаАнотація:
A l'éveil comme au cours du sommeil, en plaine comme en haute altitude, le maintien d'une oxygénation artérielle stable et élevée est un marqueur essentiel d'une bonne réponse physiologique de l'organisme. L'intolérance à l'altitude regroupe des pathologies graves voire fatales dont le développement est en lien direct avec le taux d'oxygénation artériel des sujets. D'autre part, en plaine, la prévalence élevée du syndrome d'apnées obstructives du sommeil (SAOS) incite les chercheurs au développement de modèles d'études spécifiques, permettant d'investiguer les conséquences du principal stimulus du SAOS : l'hypoxie intermittente. La chémosensibilité pourrait avoir un impact important dans ces deux pathologies, ayant pour rôle le maintien des gaz du sang à des valeurs normales, en adaptant la ventilation aux conditions externes ou internes à l'organisme.Les objectifs de ce travail étaient de comprendre l'impact de la chémosensibilité (avec d'autres mécanismes décrits dans la littérature) sur l'oxygénation et la tolérance à l'altitude, d'étudier les effets de la résistance expiratoire sur l'amélioration de l'oxygénation, ainsi que les conséquences de l'hypoxie intermittente chronique sur la plasticité du chémoréflexe.Il en ressort que la chémosensibilité périphérique à l'hypoxie a un impact majeur sur le développement de l'intolérance à l'altitude. Cela semble en outre être un facteur prédictif de la survenue de ces pathologies. En hypoxie, une amélioration efficace de l'oxygénation a été obtenue par l'utilisation d'une résistance expiratoire calibrée à 10 cm H2O permettant l'amélioration de la diffusion alvéolo-capillaire. L'exposition à l'hypoxie intermittente chronique nocturne a provoqué une fragmentation du sommeil ainsi qu'une intensification de la chémosensibilité à l'hypoxie et à l'hypercapnie.Ainsi, une altération de la réponse des corps carotidiens à l'hypoxémie participerait au développement du mal aigu des montagnes et de ses complications, tout en facilitant sa prédiction avant ascension. L'utilisation d'une résistance expiratoire pourrait permettre de combler la désaturation exagérée retrouvée chez les sujets sensibles à l'altitude lors d'un séjour en haute montagne. Il apparaît également que la chémosensiblité périphérique et centrale (CO2 et O2) fasse preuve d'une plasticité importante en réponse à l'hypoxie intermittente nocturne chez des sujets sainsAt awakening and during sleep, at sea level or in high altitude, maintaining a high level in arterial blood oxygenation is a marker for an adaptated physiological response external and internal factors.High altitude illness encompasses pathologies, that sometimes could be fatal, and which seems to be correlated with the level of arterial oxygenation in hypoxia.Secondly, at sea level and in general population, the high prevalence of obstructive sleep apnea syndrome (OSAS) encourage scientists to develop new models for studying consequences of the main OSAS' stimulus: intermittent hypoxia.Chemosensitivity could play an important role in those two different diseases, with regulation of blood gases and homeostasis by controlling ventilation.Our objectives was to investigate (1) impact of chemosensitivity on blood oxygenation and tolerance to high altitude, comparatively to other physiological factors commonly involved, (2) effects of using positive expiratory pressure in order to improve oxygenation in hypoxia, and (3) consequences of chronic exposure to nocturnal intermittent hypoxia on chemoreflexe plasticity.We found that peripheral chemoresponse to hypoxia play a crucial role in high altitude illness development. Moreover, this variable seems to be a predictive factor for those diseases. In hypoxic conditions, using a positive expiratory pressure (10 cmH2O) lead to a significant improve in arterial oxygenation, by increasing pulmonary diffusion. Finally, nocturnal intermittent hypoxia induced significant sleep disturbances and major changes in chemoresponse to hypoxia and hypercapnia
36
Raimbault, Nathaniel. "Gauge-invariant magnetic properties from the current." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30179/document.
Повний текст джерелаАнотація:
De nombreux phénomènes physiques ne peuvent être compris qu'en s'intéressant à la structure électronique. Cette dernière peut être interprétée en termes de propriétés électromagnétiques, chacune de ces propriétés révélant diverses informations sur le système étudié. Il est donc important d'avoir des outils efficaces afin de calculer de telles propriétés. C'est dans ce contexte que cette thèse a été écrite, notre principal objectif ayant été de développer une méthode générale donnant accès à une vaste gamme de propriétés électromagnétiques. Dans la première partie de cette thèse, nous décrivons le socle théorique au sein duquel nous travaillons, en particulier la théorie de la fonctionnelle de la densité de courant dépendante du temps (TDCDFT), qui est une approche qui permet de décrire la réponse du système à un champ magnétique. La seconde partie est consacrée à la méthode que nous avons mise au point pour calculer diverses propriétés magnétiques en préservant l'invariance de jauge. Nous démontrons en particulier qu'en utilisant une simple règle de somme, il est possible de placer les courants diamagnétique et paramagnétique sur un pied d'égalité, évitant par là même les écueils habituels intrinsèques au calcul de propriétés magnétiques, comme la dépendance en l'origine de la jauge du vecteur potentiel. Nous illustrons notre méthode en l'appliquant notamment au calcul de la magnétisabilité et du dichroïsme circulaire, qui est une propriété possédant d'importantes applications pratiques, notamment en biologie. Dans la dernière partie, plus exploratoire, nous tentons d'étendre notre formalisme aux systèmes périodiques. Nous y discutons plusieurs stratégies afin de calculer l'aimantation dans des systèmes décrits par des conditions aux limites périodiquesVarious phenomena of matter can only be understood by probing its electronic structure. The latter can be interpreted in terms of electromagnetic properties, each property revealing a different piece of information. Having a reliable method to calculate such properties is thus of great importance. This thesis is to be regarded in this context. Our main goal was to develop a general method that gives access to a wide variety of electromagnetic properties. In the first part of this thesis, we describe the theoretical background with which we work, and in particular time-dependent current-density-functional theory (TDCDFT), which is a density-functional approach that can describe the response due to a magnetic field. The second part is dedicated to the method we developed in order to calculate various magnetic properties in a gauge-invariant manner. In particular, we show that by using a simple sum rule, we can put the diamagnetic and paramagnetic currents on equal footing. We thus avoid the usual problems that arise when calculating magnetic properties, such as the dependence on the gauge origin of the vector potential. We illustrate our method by applying it to the calculation of magnetizabilities and circular dichroism, which has important applications, notably in biology. In the last part, which is more explorative, we aim at extending our formalism to periodic systems. We discuss several strategies to calculate magnetization in systems described with periodic boundary conditions
37
Jangara, Juliana. "“Beautiful powerful you” : an analysis of the subject positions offered to women readers of Destiny magazine." Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1013395.
Повний текст джерелаАнотація:
Women's magazines are popular cultural forms which offer readers representations intended to advise women on how to work towards and achieve idealised femininities. They perform such a function within the wider socio-historical context of gender relations. In a country such as South Africa, where patriarchal gender relations have historically been structured to favour men over women and masculinity over femininity, the representation of femininity in contemporary women's magazines may serve to reinforce or challenge these existent unequal gender relations. Informed by a feminist poststructuralist understanding of the gendered positioning of subjects through discourse, this study is a textual analysis that investigates the subject positions or possible identities offered to readers of Destiny, a South African business and lifestyle women's magazine. Black women, who make up the majority of Destiny's readership, have historically been excluded from the formal economy. In light of such a background, Destiny offers black women readers, through its representations of well-known business women, possible identities to take up within the white male dominated field of business practice. The magazine also offers 'lifestyle content', which suggests to readers possible ways of being in other areas of social life. Through a method of critical discourse analysis, this study critically analyses the subject positions offered to readers of Destiny, in order to determine to what extent the magazine's representations of business women endorse or confront unequal gender relations. The findings of this study are that Destiny offers women complex subject positions which simultaneously challenge and reassert patriarchy. While offering readers positions from which to challenge race based gender discrimination – a legacy of the apartheid past – the texts analysed tend to neglect non-racially motivated gender prejudice. It is concluded that although not comprehensively challenging unequal gender relations, the magazine whittles away some tenets of patriarchy.
38
See, Chan H. "Computation of electromagnetic fields in assemblages of biological cells using a modified finite difference time domain scheme. Computational electromagnetic methods using quasi-static approximate version of FDTD, modified Berenger absorbing boundary and Floquet periodic boundary conditions to investigate the phenomena in the interaction between EM fields and biological systems." Thesis, University of Bradford, 2007. http://hdl.handle.net/10454/4762.
Повний текст джерелаАнотація:
yesThere is an increasing need for accurate models describing the electrical behaviour of individual biological cells exposed to electromagnetic fields. In this area of solving linear problem, the most frequently used technique for computing the EM field is the Finite-Difference Time-Domain (FDTD) method. When modelling objects that are small compared with the wavelength, for example biological cells at radio frequencies, the standard Finite-Difference Time-Domain (FDTD) method requires extremely small time-step sizes, which may lead to excessive computation times. The problem can be overcome by implementing a quasi-static approximate version of FDTD, based on transferring the working frequency to a higher frequency and scaling back to the frequency of interest after the field has been computed. An approach to modeling and analysis of biological cells, incorporating the Hodgkin and Huxley membrane model, is presented here. Since the external medium of the biological cell is lossy material, a modified Berenger absorbing boundary condition is used to truncate the computation grid. Linear assemblages of cells are investigated and then Floquet periodic boundary conditions are imposed to imitate the effect of periodic replication of the assemblages. Thus, the analysis of a large structure of cells is made more computationally efficient than the modeling of the entire structure. The total fields of the simulated structures are shown to give reasonable and stable results at 900MHz, 1800MHz and 2450MHz. This method will facilitate deeper investigation of the phenomena in the interaction between EM fields and biological systems. Moreover, the nonlinear response of biological cell exposed to a 0.9GHz signal was discussed on observing the second harmonic at 1.8GHz. In this, an electrical circuit model has been proposed to calibrate the performance of nonlinear RF energy conversion inside a high quality factor resonant cavity with known nonlinear device. Meanwhile, the first and second harmonic responses of the cavity due to the loading of the cavity with the lossy material will also be demonstrated. The results from proposed mathematical model, give good indication of the input power required to detect the weakly effects of the second harmonic signal prior to perform the measurement. Hence, this proposed mathematical model will assist to determine how sensitivity of the second harmonic signal can be detected by placing the required specific input power.
39
Maati, Amel. "Mise en œuvre de formalismes pour la modélisation de grands réseaux périodiques d'antennes." Thesis, Limoges, 2018. http://www.theses.fr/2018LIMO0009/document.
Повний текст джерелаАнотація:
Cette thèse se place dans le contexte général de la modélisation de réseaux d’antennes de grande taille, avec pour objectif d’atteindre un niveau de précision suffisamment élevé pour permettre une optimisation complète des performances et en particulier une amélioration de l’efficacité énergétique. Partant du constat que l’optimisation électromagnétique de grands réseaux représente un verrou si les couplages doivent être modélisés efficacement, cette thèse propose la mise en œuvre d’une méthode permettant la modélisation fine de grands réseaux d'antennes tout en réduisant les temps de calcul et en conservant un haut degré de précision. L'objectif est de montrer qu'une approche dérivée des formalismes périodiques infinis connus de la littérature permet d'obtenir une matrice [S] complète d'un réseau depuis l'étude d'une cellule unitaire. Après avoir présenté un état de l'art sur les réseaux d'antennes et leurs méthodes d'analyse, l'approche de modélisation proposée est détaillée. Des véhicules de test numériques et expérimentaux, permettant de valider cette méthode de modélisation, sont ensuite réalisés. L'approche est enfin utilisée avec succès pour deux types d'applicationThis thesis is organized in the general context of modeling a large antenna arrays with the aim of achieving a high level of precision. This modeling allows a complete optimization of the performances and an enhancement of the energy efficiency. Given that the electromagnetic optimization of large arrays still represents a challenge if the mutual coupling is not efficiently modeled. This work offers the implementation of a method allowing the precise modeling of large antenna arrays while reducing the computation time and maintaining a high degree of precision. The aim is to demonstrate that the derived approach from the infinite periodic formalisms makes it possible to obtain a full [S] matrix of an array based on the study of a unit cell. After presenting a state of the art of antenna arrays and their methods of analysis, the proposed modeling approach is explained. Numerical and Experimental demonstrators are then made for the validation. Finally, this method is successfully used for two types of applications
40
Lee, Richard Todd. "A novel method for incorporating periodic boundaries into the FDTD method and the application to the study of structural color of insects." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29772.
Повний текст джерелаАнотація:
Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Smith, Glenn; Committee Member: Buck, John; Committee Member: Goldsztein, Guillermo; Committee Member: Peterson, Andrew; Committee Member: Scott, Waymond. Part of the SMARTech Electronic Thesis and Dissertation Collection.
41
See, Chan Hwang. "Computation of electromagnetic fields in assemblages of biological cells using a modified finite difference time domain scheme : computational electromagnetic methods using quasi-static approximate version of FDTD, modified Berenger absorbing boundary and Floquet periodic boundary conditions to investigate the phenomena in the interaction between EM fields and biological systems." Thesis, University of Bradford, 2007. http://hdl.handle.net/10454/4762.
Повний текст джерелаАнотація:
There is an increasing need for accurate models describing the electrical behaviour of individual biological cells exposed to electromagnetic fields. In this area of solving linear problem, the most frequently used technique for computing the EM field is the Finite-Difference Time-Domain (FDTD) method. When modelling objects that are small compared with the wavelength, for example biological cells at radio frequencies, the standard Finite-Difference Time-Domain (FDTD) method requires extremely small time-step sizes, which may lead to excessive computation times. The problem can be overcome by implementing a quasi-static approximate version of FDTD, based on transferring the working frequency to a higher frequency and scaling back to the frequency of interest after the field has been computed. An approach to modeling and analysis of biological cells, incorporating the Hodgkin and Huxley membrane model, is presented here. Since the external medium of the biological cell is lossy material, a modified Berenger absorbing boundary condition is used to truncate the computation grid. Linear assemblages of cells are investigated and then Floquet periodic boundary conditions are imposed to imitate the effect of periodic replication of the assemblages. Thus, the analysis of a large structure of cells is made more computationally efficient than the modeling of the entire structure. The total fields of the simulated structures are shown to give reasonable and stable results at 900MHz, 1800MHz and 2450MHz. This method will facilitate deeper investigation of the phenomena in the interaction between EM fields and biological systems. Moreover, the nonlinear response of biological cell exposed to a 0.9GHz signal was discussed on observing the second harmonic at 1.8GHz. In this, an electrical circuit model has been proposed to calibrate the performance of nonlinear RF energy conversion inside a high quality factor resonant cavity with known nonlinear device. Meanwhile, the first and second harmonic responses of the cavity due to the loading of the cavity with the lossy material will also be demonstrated. The results from proposed mathematical model, give good indication of the input power required to detect the weakly effects of the second harmonic signal prior to perform the measurement. Hence, this proposed mathematical model will assist to determine how sensitivity of the second harmonic signal can be detected by placing the required specific input power.
42
Musgrave, Jeffrey. "Integrodifference Equations in Patchy Landscapes." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/26129.
Повний текст джерелаАнотація:
In this dissertation, we study integrodifference equations in patchy landscapes. Specifically, we provide a framework for linking individual dispersal behavior with population-level dynamics in patchy landscapes by integrating recent advances in modeling dispersal into an integrodifference equation.
First, we formulate a random-walk model in a patchy landscape with patch-dependent diffusion, settling, and mortality rates. We incorporate mechanisms for individual behavior at an interface which, in general, results in the probability-density function of the random walker being discontinuous at an interface. We show that the dispersal kernel can be characterized as the Green's function of a second-order differential operator and illustrate the kind of (discontinuous) dispersal kernels that arise from our approach. We examine the dependence of obtained kernels on model parameters.
Secondly, we analyze integrodifference equations in patchy landscapes equipped with discontinuous kernels. We obtain explicit formulae for the critical-domain-size problem, as well as, explicit formulae for the analogous critical size of good patches on an infinite, periodic, patchy landscape. We examine the dependence of obtained formulae on individual behavior at an interface. Through numerical simulations, we observe that, if the population can persist on an infinite, periodic, patchy landscape, its spatial profile can evolve into a discontinuous traveling periodic wave. We derive a dispersion relation for the speed of the wave and illustrate how interface behavior affects invasion speeds.
Lastly, we develop a strategic model for the spread of the emerald ash borer and its interaction with host trees. A thorough literature search provides point estimates and interval ranges for model parameters. Numerical simulations show that the spatial profile of an emerald ash borer invasion evolves into a pulse-like solution that moves with constant speed. We employ Latin hypercube sampling to obtain a plausible collection of parameter values and use a sensitivity analysis technique, partial rank correlation coefficients, to identify model parameters that have the greatest influence on obtained speeds. We illustrate the applicability of our framework by exploring the effectiveness of barrier zones on slowing the spread of the emerald ash borer invasion.
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Alqawasmeh, Yousef. "Models for Persistence and Spread of Structured Populations in Patchy Landscapes." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36845.
Повний текст джерелаАнотація:
In this dissertation, we are interested in the dynamics of spatially distributed populations. In particular, we focus on persistence conditions and minimal traveling
periodic wave speeds for stage-structured populations in heterogeneous landscapes.
The model includes structured populations of two age groups, juveniles and adults,
in patchy landscapes. First, we present a stage-structured population model, where we divide the population into pre-reproductive and reproductive stages. We assume that all parameters of the two age groups are piecewise constant functions in space. We derive explicit formulas for population persistence in a single-patch landscape and in heterogeneous habitats. We find the critical size of a single patch surrounded by a non-lethal matrix habitat. We derive the dispersion relation for the juveniles-adults model in homogeneous and heterogeneous landscapes. We illustrate our results by comparing the structured population model with an appropriately scaled unstructured model. We find that a long pre-reproductive state typically increases habitat requirements for persistence and decreases spatial spread rates, but we also identify scenarios in which a population with intermediate maturation rate spreads fastest. We apply sensitivity and elasticity formulas to the critical size of a single-patch landscape and to the minimal traveling wave speed in a homogeneous landscape.
Secondly, we use asymptotic techniques to find an explicit formula for the traveling
periodic wave speed and to calculate the spread rates for structured populations in
heterogeneous landscapes. We illustrate the power of the homogenization method by comparing the dispersion relation and the resulting minimal wave speeds for the
approximation and the exact expression. We find an excellent agreement between
the fully heterogeneous speed and the homogenized speed, even though the landscape period is on the same order as the diffusion coefficients and not as small as the formal derivation requires. We also generalize this work to the case of structured populations of n age groups.
Lastly, we use a finite difference method to explore the numerical solutions for the
juveniles-adults model. We compare numerical solutions to analytic solutions and
explore population dynamics in non-linear models, where the numerical solution for
the time-dependent problem converges to a steady state. We apply our theory to
study various aspects of marine protected areas (MPAs). We develop a model of
two age groups, juveniles and adults, in which only adults can be harvested and
only outside MPAs, and recruitment is density dependent and local inside MPAs and
fishing grounds. We include diffusion coefficients in density matching conditions at
interfaces between MPAs and fishing grounds, and examine the effect of fish mobility
and bias movement on yield and fish abundance. We find that when the bias towards
MPAs is strong or the difference in diffusion coefficients is large enough, the relative
density of adults inside versus outside MPAs increases with adult mobility. This
observation agrees with findings from empirical studies.
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Råsmark, Per Johan. "On the Structure and Dynamics of Polyelectrolyte Gel Systems and Gel-surfactant Complexes." Doctoral thesis, Uppsala universitet, Fysikalisk-kemiska institutionen, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4652.
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This thesis describes the results of experimental work on polyelectrolyte gels and their interaction with oppositely charged surfactants, and presents two new algorithms applicable to the simulation of colloid and polymer systems. The model systems investigated were crosslinked poly(acrylate) (PA) and poly(styrene sulphonate) (PSS), and the surfactant was dodecyl trimethylammonium bromide (DoTAB). Pure gel materials were studied using dynamic light scattering. It was shown that the diffusion coefficient (D) increases with increasing degree of swelling and the concentration dependence is larger than predicted by scaling arguments. For gels at swelling equilibrium D increases with increasing degree of crosslinking. In subsequent studies on gel particles in DoTAB solution, Raman spectra were recorded at different positions in the gel. For both types of gels two distinct regions could be observed. For PA the surfactant is localised in the outer phase without any surfactant in the core, while for PSS the surfactant was distributed such that it had the same concentration relative to the polymer throughout the gel. In a second experiment, the kinetics for the deswelling of microscopic PSS particles in DoTAB solution was studied. It was found that the final volume varied linearly with the DoTAB concentration, and the rate of volume decrease could be fitted to a single exponential indicating stagnant layer diffusion to be the rate limiting process for the deswelling of the PSS particles. In the second part, I first describe an algorithm showing an efficient way to detect percolation in simulations, with periodic boundary conditions, using recursion. Spherical boundary conditions is an alternative to periodic boundary conditions for systems with long-range interactions. In the last part, the possibility to use the surface of a hypersphere in four dimensions for simulations of polymer systems is investigated, and algorithms for Monte Carlo and Brownian dynamics simulations are described.
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Laino, Teodoro. "Multigrid QM/MM approaches in ab initio molecular dynamics." Doctoral thesis, Scuola Normale Superiore, 2006. http://hdl.handle.net/11384/85799.
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Navarrete, Manuel Alejandro Gonzalez. "Modelo de Ising ferromagnético com campo externo periódico." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-28082015-000711/.
Повний текст джерелаАнотація:
Estudamos o diagrama de fases para uma classe de modelos de Ising ferromagnéticos em $ \\mathbb^2 $, com campo magnético externo periódico. O campo externo assume dois valores: $ h $ e $ -h $, onde $ h> 0 $. Os sítios associados a valores positivos e negativos do campo externo, formam uma configuração em forma de tabuleiro de xadrez (nós chamamos de {\\it cell-board configuration}), com células retangulares de tamanho $ L_1 \\times L_2 $ sítios, de tal forma que o valor total do campo externo é zero. Como principal resultado, mostramos a presença de uma transição de fase de primeira ordem. A transição de fase existe para $ h <\\frac + \\frac $, onde $ J $ é uma constante de interação. A prova é construida usando o método de {\\it reflection positivity (RP)}. Aplicamos uma desigualdade que é normalmente referida como a estimativa de {\\it chessboard}. Além disso, incluímos uma região de unicidade da medida de Gibbs em $h>4J$, isto usando um critério baseado nas ideias de percolação em desacordo.We study the low-temperature phase diagram for a ferromagnetic Ising model on $\\mathbb^2$, with a periodical external magnetic field. The external field takes two values: $h$ and $-h$, where $h>0$. The sites associated with positive and negative values of external field form a cell-board configuration with rectangular cells of sides $L_1\\times L_2$ sites, such that the total value of the external field is zero. As a main result, we show the presence of a first-order phase transition. The phase transition holds if $h<\\frac+ \\frac$, where $J$ is an interaction constant. We use the reflection positivity (RP) method. We apply a key inequality which is usually referred to as the chessboard estimate. Furthermore, we prove uniqueness for Gibbs measure in $h>4J$, using a uniqueness condition obtained in terms of disagreement percolation.
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Rouot, Jérémy. "Méthodes géométriques et numériques en contrôle optimal et applications au transfert orbital à poussée faible et à la nage à faible nombre de Reynolds." Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4103/document.
Повний текст джерелаАнотація:
Dans la première partie, on propose une étude sur le problème de nage à faible nombre de Reynolds à partir d'unnageur modélisant la nage des copépodes et du nageur historique de Purcell.En minimisant l’énergie dissipée par les forces de trainée sur le fluide, laquelle est reliée au concept d’efficacitéd’une nage, on utilise les outils géométriques et numériques du contrôle optimal. Le principe du maximum estutilisé pour calculer les contrôles optimaux périodiques satisfaisant une condition de transversalité fine reliée à laminimisation de l’énergie mécanique pour un déplacement fixé où à la maximisation de l’efficacité. Ce sont desproblèmes sous-Riemanniens ce qui permet d’utiliser des techniques efficaces telles que l’approximation nilpotentepour calculer des nages de faible amplitude et qui est utilisée pour calculer des nages sur le vrai système parcontinuation. Les conditions nécessaires et suffisantes du second ordre sont calculées pour sélectionner desminimiseurs faible dans le cas d’une famille de nages périodiques.Dans la seconde partie, on s‘intéresse à la trajectoire d’un engin spatial contrôlé sous l’action d’un champ à forcecentral et où l’on considère les perturbations conservatives dues à l’effet lunaire et à l’aplatissement de la Terre àses pôles. Notre approche est basée sur des techniques moyennisation appliquées sur le système issu du principedu maximum. Nous donnons des résultats de convergence entre le système moyenné et le système non moyenné.Enfin, nous simulons les trajectoires du système non moyennée en utilisant les solutions du système moyennépour initialiser des méthodes numériques indirectesThe first part of this work is devoted to the study of the swimming at low Reynolds number where we consider a2-link swimmer to model the motion of a Copepod and the seminal model of the Purcell Three-link swimmer. Wepropose a geometric and numerical approach using optimal control theory assuming that the motion occursminimizing the energy dissipated by the drag fluid forces related with a concept of efficiency of a stroke. TheMaximum Principle is used to compute periodic controls considered as minimizing control using propertransversality conditions, in relation with periodicity, minimizing the energy dissipated for a fixed displacement ormaximizing the efficiency of a stroke. These problems fall into the framework of sub-Riemannian geometry whichprovides efficient techniques to tackle these problems : the nilpotent approximation is used to compute strokeswith small amplitudes which are continued numerically for the true system. Second order optimality, necessary orsufficient, are presented to select weak minimizers in the framework of periodic optimal controls.In the second part, we study the motion of a controlled spacecraft in a central field taking into account thegravitational interaction of the Moon and the oblateness of the Earth. Our purpose is to study the time minimalorbital transfer problem with low thrust. Due to the small control amplitude, our approach is to define anaveraged system from the Maximum Principle and study the related approximations to the non averaged system.We provide proofs of convergence and give numerical results where we use the averaged system to solve the nonaveraged system using indirect method
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Nascimento, Moisés Aparecido do. "Hipoelipticidade global de campos vetoriais no toro TN." Universidade Federal de São Carlos, 2010. https://repositorio.ufscar.br/handle/ufscar/5869.
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Previous issue date: 2010-06-21In this work, we will see that if the transpose operator of a smooth real vector field L defined on the N-dimensional torus, regarded as a linear differential operator with coefficients in C1(TN), is globally hypoelliptic, then there exists a vector field with constant coefficients L0 such that L and L0 are C1-conjugated, with such constants satisfying a condition called Diofantina (*). We will also show the converse of this fact, that is, if there is a coordinate system such that in this new system L has constant coefficients with such constant satisfying the Diophantine condition (*) then its transpose L* is globally hypoelliptic. We will see that the Diophantine condition implies that the flow generated by the field, regarded as a Dynamical system is minimal.
Neste trabalho, veremos que se o operador transposto de um campo vetorial real suave L definido no toro N-dimensional, visto como um operador diferencial linear com coeficientes em C1(TN), for globalmente hipoelíptico, então existe um campo vetorial com coeficientes constantes L0 tal que L e L0 são C1- conjugados, com tais constantes satisfazendo uma condição chamada de Diofantina (*). Mostraremos também a recíproca deste fato, isto é, se existir um sistema de coordenadas tal que, neste novo sitema L possui coeficientes constantes com tais constantes satisfazendo a condição Diofantina (*) então, seu transposto L* é globalmente hipoelíptico. Veremos que a condição Diofantina implica que, os fluxos gerados pelo campo, vistos como um sistema dinânico, são minimais.
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Boulmé, Audren. "Conception et caractérisation de sondes cMUT large bande pour l'imagerie conventionnelle et l'évaluation du tissu osseux." Thesis, Tours, 2013. http://www.theses.fr/2013TOUR3319/document.
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Les transducteurs ultrasonores capacitifs micro-usinés (cMUT : capacitive Micromachined Ultrasound Transducers) apparaissent, au vu de leur maturité croissante, comme une alternative de plus en plus viable à la technologie piézoélectrique. Caractérisés par une large bande passante et une large directivité, ces transducteurs sont des solutions intéressantes pour le développement de sondes ultrasonores « exotiques » dont les spécifications sont difficilement atteignables en technologie piézoélectrique. C'est dans ce contexte et fort de l'expérience acquise par notre laboratoire sur cette technologie pendant plus d'une dizaine d'années, que s'est inscrit ce travail de thèse. L'originalité du travail rapporté ici est d'aller de l'analyse du comportement général des barrettes cMUT jusqu'à un exemple précis de conception de sonde cMUT pour l'évaluation du tissu osseux. Des outils de modélisation précis et rapides, basés sur l'introduction de conditions de périodicité, ont été développés. Plusieurs modèles ont ainsi été mis en place afin d'adapter la stratégie de modélisation à la topologie du dispositif cMUT à modéliser : cellule isolée, colonne de cellules, matrice de cellules et élément de barrette. Ces modèles ont permis d'étudier le comportement des éléments de barrette cMUT et d'améliorer notre connaissance sur les mécanismes physiques mis en jeu. De cette façon, l'origine des effets de baffle, problème récurrent du comportement des barrettes cMUT, a clairement été interprété par l'intermédiaire d'une analyse modale. Des solutions ont ainsi été identifiées et proposées afin d'optimiser le comportement des barrettes cMUT, de façon à réduire la présence des effets de baffle et à augmenter leur bande passante. Le développement d'une barrette cMUT dédiée à l'évaluation du tissu osseux est présenté dans sa totalité, afin d'illustrer les différents aspects liés à la conception d'une sonde de cette technologie. Un travail original de caractérisation a été réalisé sur cette barrette, afin d'estimer l'homogénéité inter-cellules à l'échelle de l'élément et l'homogénéité inter-éléments à l'échelle de la barrette. Enfin, une confrontation a été réalisée avec une sonde PZT de même topologie sur plusieurs fantômes osseux. Il a ainsi été démontré que la sonde cMUT permettait la détection d'un plus grand nombre de modes guidés, et par conséquent, une meilleure évaluation du tissu osseuxFollowing recent advances, the capacitive Micromachined Ultrasound Transducers (cMUT) technology seems to be a good alternative to the piezoelectric technology. For specific applications, the requirements and specifications of the probe are sometimes difficult to obtain with the traditional PZT technology. The cMUT technology, with both large bandwidth and angular directivity, can be an interesting way to overcome these limitations. This PhD has been carried out in this context, in a laboratory which has nearly 10 years of experience in the field of cMUT technology. The originality of the work sustained in this PhD is that it covers the cMUT technology, from general aspects dealing of modeling and characterization up to a complete example of cMUT-based probe applied to the assessment of cortical bone. Fast and accurate modeling tools, based on periodicity conditions, have been developed. Several models have been proposed to match the modeling strategy to the topology of the cMUT array : isolated cell, columns of cells, 2-D matrix of cells and array element. These models have been used to analyze the cMUT array behavior and to understand how mutual couplings between cMUTs impact the response of one element. Origins of the baffle effect, well-known as a recurrent problem in cMUT probe, have been explained using an original method based on the normal mode decomposition of the radiated pressure field. Thus, solutions have been identified and tested to optimize the cMUT frequency response, i.e. to increase the bandwidth, and to suppress parasitic disturbances linked to baffle effect in the electroacoustic response. The development of a dedicated cMUT array for the assessment of bone tissue is accurately detailed in the manuscript, including description of the design rules, fabrication steps and packaging procedure. An original characterization work has been carried out in order to check the device homogeneity, first from cell to cell and then from element to element. Finally, a comparison with a PZT probe with the same topology has been performed on bone mimicking phantom. Nice results has been obtained, showing that cMUT probe allows detecting higher number of guided modes in the cortical shell, and consequently, improving the cortical bone assessment
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Oliveira, Gustavo Charles Peixoto de. "Jato transversal de gotas: simulações por ALE/FEM e efeitos interfaciais." Universidade do Estado do Rio de Janeiro, 2015. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=8094.
Повний текст джерелаАнотація:
Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorUm código computacional para escoamentos bifásicos incorporando metodologia híbrida entre oMétodo dos Elementos Finitos e a descrição Lagrangeana-Euleriana Arbitrária do movimento é usado para simular a dinâmica de um jato transversal de gotas na zona primária de quebra. Os corpos dispersos são descritos por meio de um método do tipo front-tracking que produz interfaces de espessura zero através de malhas formadas pela união de elementos adjacentes em ambas as fases e de técnicas de refinamento adaptativo. Condições de contorno periódicas são implementadas de modo variacionalmente consistente para todos os campos envolvidos nas simulações apresentadas e uma versão modificada do campo de pressão é adicionada à formulação do tipo um-fluido usada na equação da quantidade de movimento linear. Simulações numéricas diretas em três dimensões são executadas para diferentes configurações de líquidos imiscí veis compatíveis com resultados experimentais encontrados na literatura. Análises da hidrodinâmica do jato transversal de gotas nessas configurações considerando trajetórias, variação de formato de gota, espectro de pequenas perturbações, além de aspectos complementares relativos à qualidade de malha são apresentados e discutidos.
A two-phase flow computational code taking a hybrid Arbitrary Lagrangian-Eulerian desciption of movement along with the Finite Element Method is used to simulate the dynamics of an incompressible drop jet in crossflow in the primary breakup zone. Dispersed entities are described by means of a front-tracking method which produces zero-thickness interfaces through contiguous element meshing and adaptive refinement techniques. Periodic boundary conditions are implemented in a variationally consistent way for all the scalar fields involved in the presented simulations and amodified version of the pressure field is added to the one-fluid formulation employed in the momentum equation. Three-dimensional direct numerical simulations for different flow configurations of immiscible liquids pertinent to experimental results found in literature. Analyses of the hydrodynamics of the drop jet in crossflow in these configurations considering trajectories, drop shape variations, spectrum of small disturbances, besides additional aspects relating to mesh quality are presented and discussed.