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Dixon, Richard Stuart. "Diagnostic studies of symmetric instability." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270255.
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Gomes, Pedro de Carvalho. "Verification of symmetric models using semiautomatic abstractions." Universidade Federal de Minas Gerais, 2010. http://hdl.handle.net/1843/SLSS-86VJCV.
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Model Checking is a powerful method for the formal verification of concurrent systems. It explores automatically the state-space of a model that represents the system to prove its correctness in relation to formal specifications, which are described using some temporal logic. Despite its importance and wide application, Model Checking suffers with the state-space explosion: the number of states of a model is exponential to its size; thus it limits the size of the models that may be verified. Many techniques were proposed to overcome this problem. Among them, the use of abstractions is considered one of the most general and efficient. The adoption of abstractions consists of generating a reduced model from the original model by merging or removing states that are irrelevant to the specification being verified. Another technique is the symmetry reduction. It is based on the observation that several models present some level of symmetry, and states considered equivalent can be grouped. Thus, the state-space to be considered is significantly smaller and the exploration of only one of the states of the same group is sufficient to prove the correctness of some propriety. This work combines both techniques to produce reduced models that can be verified at feasible time. It presents a methodology to generate semiautomatic abstractions, based on the model symmetry. The key idea is that, for the verification of certain proprieties, the removal of symmetric components of a model has a small impact on information loss caused by the abstractions since its symmetric counterpart is still represented. The methodology defines modeling premises to make the abstraction
adoption semiautomatic, i.e., without the need to alter the model description. Moreover, it presents abstraction patterns based on the system symmetry and shows which specifications are consistent with each pattern. The techniques presented in this work are specially useful on the verification of computation systems that present considerable replication of structures. This characteristic can be observed in memories, caches, bus protocols, multi-processes applications
and network protocols. In this work the model of a P2P Live Streaming application was implemented to validate the methodology. At this model each participant receives and forwards data to its partners to reconstruct the original live stream. The fact that all peers are distinct processes that share the same code makes this model highly symmetric and thus a valid example. The reductions obtained by the methodology proved to be very significant. I.e, the calculation of the number of reachable states of the original model, from a total of approximately 273 possible states, has not finished after more than two weeks of intensive computation. In contrast, the same computation for the reduced models finished in less than two minutes in all cases and the maximum number of reachable
states found was approximately 219.A Verificação de Modelos é uma técnica poderosa de verificação automática de sistemas concorrentes. Ela explora automaticamente os estados de um modelo que representa o sistema para provar sua correção com relação a especificações formais, descritas usando alguma lógica temporal. Apesar de sua importância e ampla aplicação, a Verificação de Modelos sofre com o problema da explosão de estados: o número de estados do modelo é exponencial ao seu tamanho; isto limita o tamanho dos modelos possíveis de serem verificados. Diversas técnicas foram propostas para contornar o problema. Dentre elas, o uso de abstrações é considerada uma das mais genéricas e eficientes. A adoção de abstrações consiste em gerar um modelo reduzido a partir do modelo original através da fusão ou remoção de estados que supõe-se irrelevantes com relação à propriedade sendo verificada. Outra técnica é a redução por simetria. Ela baseia-se na observação que diversos sistemas apresentam considerável grau de simetria, e estados considerados equivalentes podem ser agrupados. Assim o espaço dos estados a ser considerado é significantemente menor e a exploração de apenas um dos estados do mesmo grupo é suficiente para provar a correção de alguma propriedade. Este trabalho combina ambas as técnicas para produzir modelos reduzidos, que podem ser verificados em tempo factível. É apresentada uma metodologia para gerar abstrações semiautomáticas, baseada na simetria do modelo. A ideia chave é que, na verificação de certas propriedades, a remoção de componentes simétricos de um modelo tem um impacto pequeno na perda de informação causada pelas abstrações já que a contra-parte simétrica ainda está presente. A metodologia define premissas de modelagem para tornar a adoção das abstrações semiautomática, ou seja, sem a necessidade de alterar a descrição do modelo. Além disso, são apresentados padrões de abstrações baseados na simetria do sistema e mostra-se quais especificações são consistentes com cada padrão. As técnicas apresentadas neste trabalho são especialmente úteis na verificação de sistemas de computação que apresentam uma considerável replicação de estrutura. Tal característica pode ser observada em memórias, caches, protocolos de barramento, programas com vários processos e protocolos de rede. Foi implementado no trabalho o modelo de uma rede P2P Live Streaming para validar a metodologia. Neste modelo cada participante recebe e encaminha dados para seus parceiros para reconstruir o conteúdo ao vivo original. O fato de todos os participantes serem processos distintos que compartilham o mesmo código torna este modelo altamente simétrico e assim um exemplo válido. A redução obtida com a metodologia provou ser bastante significativa. Por exemplo, o cálculo do número de estados alcançáveis do modelo original, de um total de aproximadamente 273 estados possíveis, não terminou após mais de duas semanas de computação intensa. Em contrapartida, a mesma computação para os modelos reduzidos terminou em menos de três minutos em todos os casos e o número máximo encontrado de estados alcançáveis foi de aproximadamente 219.
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Chau, Yu-Xi. "Explosive condensation in symmetric mass transport models." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/77689/.
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Condensation is an emergent phenomenon in complex systems that is observed in both physical and social sciences, from granular polydisperse spheres to macroeconomic studies. The critical behaviour of condensation in such systems is of continual interest in research. In this thesis we study this in the context of interacting particle systems, in particular the recently introduced explosive condensation process. We firstly provide a review of the mathematical foundations of interacting particle systems from the aspects of Markov processes. This includes the formulation of factorised hop rates, stationary product measures, the equivalence of ensembles and how these properties are related to condensation. Subsequently, we give a review of key interacting particle systems of interest, namely the zero-range process, inclusion process and the explosive condensation process. We then introduce two models that have similar stationary weights scaling as the explosive condensation process and include them in our study in the thermodynamic limit. The density and the maximum site occupation are derived under the stationary distribution, and from this we are able to identify the choice of parameters that could lead to a phase transition. Exact results for these models using the generator are di�cult to obtain. For the main results of this study, we therefore analyse the formation of condensate using a heuristic approach. The microscopic interactions leading to the formation of an explosive condensate are structurally studied, and this leads to a comprehensive model with a timescale analysis. The time to condensation is shown to vanish as the thermodynamic limit is reached, depending on the choice of parameter values. Throughout the thesis, theoretical results are supported by Monte Carlo simulation and numerical calculations where appropriate. A modification of the conventional Gillespie algorithm is proposed. The new algorithm improves e�ciencies but is also able to preserve key stochastic properties, and is used throughout the simulation of the main findings.
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Chan, Chou Sin. "Representation of symmetric instability in large scale models." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358408.
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Gagliardini, Lucia. "Chargaff symmetric stochastic processes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8699/.
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Scopo della modellizzazione delle stringhe di DNA è la formulazione di modelli matematici che generano sequenze di basi azotate compatibili con il genoma esistente. In questa tesi si prendono in esame quei modelli matematici che conservano un'importante proprietà, scoperta nel 1952 dal biochimico Erwin Chargaff, chiamata oggi "seconda regola di Chargaff". I modelli matematici che tengono conto delle simmetrie di Chargaff si dividono principalmente in due filoni: uno la ritiene un risultato dell'evoluzione sul genoma, mentre l'altro la ipotizza peculiare di un genoma primitivo e non intaccata dalle modifiche apportate dall'evoluzione. Questa tesi si propone di analizzare un modello del secondo tipo. In particolare ci siamo ispirati al modello definito da da Sobottka e Hart. Dopo un'analisi critica e lo studio del lavoro degli autori, abbiamo esteso il modello ad un più ampio insieme di casi. Abbiamo utilizzato processi stocastici come Bernoulli-scheme e catene di Markov per costruire una possibile generalizzazione della struttura proposta nell'articolo, analizzando le condizioni che implicano la validità della regola di Chargaff. I modelli esaminati sono costituiti da semplici processi stazionari o concatenazioni di processi stazionari. Nel primo capitolo vengono introdotte alcune nozioni di biologia. Nel secondo si fa una descrizione critica e prospettica del modello proposto da Sobottka e Hart, introducendo le definizioni formali per il caso generale presentato nel terzo capitolo, dove si sviluppa l'apparato teorico del modello generale.
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Polak, Malwina Maria, and Marcelina Polak. "Modeling exchange rate using symmetric and asymmetric GARCH models." Thesis, KTH, Matematisk statistik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195824.
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This paper attempts to study GARCH-type models, with emphasis on fitting GARCH models to exchange rate return series. The symmetric GARCH(1,1) model is compared with the asymmetric EGARCH(1,1) model. Both models are analysed with different conditional distributions, namely Normal, Student's t and skew Student's t for the return innovation. Parameter estimation is performed using a maximum-likelihood approximation. The model performance is assessed by looking at the lowest AIC and BIC. Four exchange rate returns are studied using daily data over the period from 2002 to 2015. Moreover, essential ideas of return time series and stylised facts will be analysed. Our results indicate that the asymmetric GARCH model improves generally estimation with fat-tailed densities in the conditional variance. Furthermore, persistence has found to be reduced with the use of heavy-tailed distributions. Asymmetry presence has been detected in the EGARCH model. Besides, we found that "good news" tend to increase volatility in comparison with "bad news".Syftet med uppsatsen är att studera modeller av GARCH-typ, och fokus ligger på att anpassa GARCH-modeller efter växelkurstidsserier. Den symmetriska GARCH(1,1)-modellen jämförs med den asymmetriska EGARCH(1,1)-modellen. Modellerna analyseras för olika fördelningar, såsom normal- och t-fördelning, på avkastningarnas brustermer. För att estimera parametrarna används maximum likelihood-metoden. Modellens prestanda bedöms sedan utifrån AIC- och BIC-kriterierna. Studien är baserad på daglig data från fyra valutapar under perioden 2002 till 2015. Resultaten indikerar att den asymmetriska GARCH-modellen förbättrar estimeringen generellt sett. Genom att använda tjocksvansade fördelningar finner man att persistensen minskar. EGARCH-modellen fångar dessutom upp asymmetrier i avkastningarna, på så sätt att volatiliteten ökar mer vid "goda nyheter" än vid "dåliga nyheter".
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Huamán, René Negrón. "On integrable deformations of semi-symmetric space sigma-models." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-06112018-011344/.
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In this thesis we review some aspects of Yang-Baxter deformations of semi-symmetric space sigma models. We start by giving a short review of the sigma model description of superstrings and then we offer a self contained introduction to the Yang-Baxter deformation technique. We then show how to obtain an integrable deformation of the hybrid sigma model. Also, we show that the gravity dual of beta-deformed ABJM theory can be obtained as a Yang-Baxter deformation. This is done by selecting a convenient combination of Cartan generators in order to construct an Abelian r-matrix satisfying the classical Yang-Baxter equation.Nesta tese revisamos alguns aspectos das deformações de Yang-Baxter de modelos sigma em espaços semi-simétricos. Damos uma breve revisão do modelo sigma de supercordas e, em seguida, oferecemos uma introdução ao método de deformação de Yang-Baxter. Em seguida, mostramos como obter uma deformação integrável do modelo sigma híbrido. Além disso, mostramos que o dual gravitacional da teoria ABJM beta-deformada pode ser obtida como uma deformação de Yang-Baxter. Isso é feito selecionando-se uma combinação conveniente de geradores de Cartan para construir uma matriz r Abeliana satisfazendo a equação clássica de Yang-Baxter.
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Vasconcelos, Julio Cezar Souza. "Modelo linear parcial generalizado simétrico." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/11/11134/tde-26072017-105153/.
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Neste trabalho foi proposto o modelo linear parcial generalizado simétrico, com base nos modelos lineares parciais generalizados e nos modelos lineares simétricos, em que a variável resposta segue uma distribuição que pertence à família de distribuições simétricas, considerando um preditor linear que possui uma parte paramétrica e uma não paramétrica. Algumas distribuições que pertencem a essa classe são as distribuições: Normal, t-Student, Exponencial potência, Slash e Hiperbólica, dentre outras. Uma breve revisão dos conceitos utilizados ao longo do trabalho foram apresentados, a saber: análise residual, influência local, parâmetro de suavização, spline, spline cúbico, spline cúbico natural e algoritmo backfitting, dentre outros. Além disso, é apresentada uma breve teoria dos modelos GAMLSS (modelos aditivos generalizados para posição, escala e forma). Os modelos foram ajustados utilizando o pacote gamlss disponível no software livre R. A seleção de modelos foi baseada no critério de Akaike (AIC). Finalmente, uma aplicação é apresentada com base em um conjunto de dados reais da área financeira do Chile.In this work we propose the symmetric generalized partial linear model, based on the generalized partial linear models and symmetric linear models, that is, the response variable follows a distribution that belongs to the symmetric distribution family, considering a linear predictor that has a parametric and a non-parametric component. Some distributions that belong to this class are distributions: Normal, t-Student, Power Exponential, Slash and Hyperbolic among others. A brief review of the concepts used throughout the work was presented, namely: residual analysis, local influence, smoothing parameter, spline, cubic spline, natural cubic spline and backfitting algorithm, among others. In addition, a brief theory of GAMLSS models is presented (generalized additive models for position, scale and shape). The models were adjusted using the package gamlss available in the free R software. The model selection was based on the Akaike criterion (AIC). Finally, an application is presented based on a set of real data from Chile\'s financial area.
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Sarisaman, Mustafa. "Target Space Pseudoduality in Supersymmetric Sigma Models on Symmetric Spaces." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/357.
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We discuss the target space pseudoduality in supersymmetric sigma models on symmetric spaces. We first consider the case where sigma models based on real compact connected Lie groups of the same dimensionality and give examples using three dimensional models on target spaces. We show explicit construction of nonlocal conserved currents on the pseudodual manifold. We then switch the Lie group valued pseudoduality equations to Lie algebra valued ones, which leads to an infinite number of pseudoduality equations. We obtain an infinite number of conserved currents on the tangent bundle of the pseudodual manifold. Since pseudoduality imposes the condition that sigma models pseudodual to each other are based on symmetric spaces with opposite curvatures (i.e. dual symmetric spaces), we investigate pseudoduality transformation on the symmetric space sigma models in the third chapter. We see that there can be mixing of decomposed spaces with each other, which leads to mixings of the following expressions. We obtain the pseudodual conserved currents which are viewed as the orthonormal frame on the pullback bundle of the tangent space of G tilde which is the Lie group on which the pseudodual model based. Hence we obtain the mixing forms of curvature relations and one loop renormalization group beta function by means of these currents. In chapter four, we generalize the classical construction of pseudoduality transformation to supersymmetric case. We perform this both by component expansion method on manifold M and by orthonormal coframe method on manifold SO(M). The component method produces the result that pseudoduality tranformation is not invertible at all points and occurs from all points on one manifold to only one point where riemann normal coordinates valid on the second manifold. Torsion of the sigma model on M must vanish while it is nonvanishing on M tilde, and curvatures of the manifolds must be constant and the same because of anticommuting grassmann numbers. We obtain the similar results with the classical case in orthonormal coframe method. In case of super WZW sigma models pseudoduality equations result in three different pseudoduality conditions; flat space, chiral and antichiral pseudoduality. Finally we study the pseudoduality tansformations on symmetric spaces using two different methods again. These two methods yield similar results to the classical cases with the exception that commuting bracket relations in classical case turns out to be anticommuting ones because of the appearance of grassmann numbers. It is understood that constraint relations in case of non-mixing pseudoduality are the remnants of mixing pseudoduality. Once mixing terms are included in the pseudoduality the constraint relations disappear.
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Dang, Hoang-Vu. "Symmetric sets and graph models of set and multiset theories." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608930.
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Ventura, Marcelo dos Santos. "Monte Carlo simulation studies in log-symmetric regressions." Universidade Federal de Goiás, 2018. http://repositorio.bc.ufg.br/tede/handle/tede/8278.
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Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG
This work deals with two Monte Carlo simulation studies in log-symmetric regression models, which are particularly useful for the cases when the response variable is continuous, strictly positive and asymmetric, with the possibility of the existence of atypical observations. In log- symmetric regression models, the distribution of the random errors multiplicative belongs to the log-symmetric class, which encompasses log-normal, log- Student-t, log-power- exponential, log-slash, log-hyperbolic distributions, among others. The first simulation study has as objective to examine the performance for the maximum-likelihood estimators of the model parameters, where various scenarios are considered. The objective of the second simulation study is to investigate the accuracy of popular information criteria as AIC, BIC, HQIC and their respective corrected versions. As illustration, a movie data set obtained and assembled for this dissertation is analyzed to compare log-symmetric models with the normal linear model and to obtain the best model by using the mentioned information criteria.
Este trabalho aborda dois estudos de simulação de Monte Carlo em modelos de regressão log- simétricos, os quais são particularmente úteis para os casos em que a variável resposta é contínua, estritamente positiva e assimétrica, com possibilidade da existência de observações atípicas. Nos modelos de regressão log-simétricos, a distribuição dos erros aleatórios multiplicativos pertence à classe log-simétrica, a qual engloba as distribuições log-normal, log-Student- t, log-exponencial- potência, log-slash, log-hyperbólica, entre outras. O primeiro estudo de simulação tem como objetivo examinar o desempenho dos estimadores de máxima verossimilhança desses modelos, onde vários cenários são considerados. No segundo estudo de simulação o objetivo é investigar a eficácia critérios de informação populares como AIC, BIC, HQIC e suas respectivas versões corrigidas. Como ilustração, um conjunto de dados de filmes obtido e montado para essa dissertação é analisado para comparar os modelos de regressão log-simétricos com o modelo linear normal e para obter o melhor modelo utilizando os critérios de informação mencionados.
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Taylor, Tara D. "Spatially self-similar spherically symmetric cosmological models with two scalar fields." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ57263.pdf.
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Dewald, Lee Samuel, and Peter A. W. Lewis. "Times series models with a specified symmetric non-normal marginal distribution." Thesis, Monterey, California. Naval Postgraduate School, 1985. http://hdl.handle.net/10945/21585.
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Zheng, Xinyu. "Moist zonally-symmetric models and their applications to West African monsoons." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/44484.
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Usta, Ebru. "Application of a symmetric total variation diminishing scheme to aerodynamics of rotors." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/13018.
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Wills, Andrew Johan. "Abacus-Tournament Models of Hall-Littlewood Polynomials." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/64427.
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In this dissertation, we introduce combinatorial interpretations for three types of HallLittlewood polynomials (denoted Rλ, Pλ, and Qλ) by using weighted combinatorial objects called abacus-tournaments. We then apply these models to give combinatorial proofs of properties of Hall-Littlewood polynomials. For example, we show why various specializations of Hall-Littlewood polynomials produce the Schur symmetric polynomials, the elementary symmetric polynomials, or the t-analogue of factorials. With the abacus-tournament model, we give a bijective proof of a Pieri rule for Hall-Littlewood polynomials that gives the Pλ-expansion of the product of a Hall-Littlewood polynomial Pµ with an elementary symmetric polynomial ek. We also give a bijective proof of certain cases of a second Pieri rule that gives the Pλ-expansion of the product of a Hall-Littlewood polynomial Pµ with another Hall-Littlewood polynomial Q(r) . In general, proofs using abacus-tournaments focus on canceling abacus-tournaments and then finding weight-preserving bijections between the sets of uncanceled abacus-tournaments.Ph. D.
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Dimitriou, Ioanna Matilde [Verfasser]. "Symmetric Models, Singular Cardinal Patterns, and Indiscernibles / Ioanna Matilde Dimitriou. Mathematisch-Naturwissenschaftliche Fakultät." Bonn : Universitäts- und Landesbibliothek Bonn, 2012. http://d-nb.info/1020630655/34.
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Lowe, Brian D. "Modelling the additivity of perceived exertion in symmetric, mid-sagittal lifting." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06112009-063305/.
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Atmander, Elias. "FEDERAL FUNDS RATE ON BITCOIN VOLATILITY : Using the symmetric GARCH and asymmetric EGARCH models." Thesis, Umeå universitet, Nationalekonomi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-184979.
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This thesis examines the volatility of Bitcoin during four years from 2014-04-01 until 2020-04-01. The main objective of the thesis was to answer the research question: “Is the return volatility of Bitcoin affected by interest rate change announcements by the FOMC?” and given Bitcoin’s decentralized characteristics, the hypothesis to this was that Bitcoin should not be affected by such changes. The GARCH (1,1) and EGARCH (1,1) models were used to analyze the transformed logarithmic returns of Bitcoin. The number of observations sum to 1462 observations (days). Additionally, 13 observations of change announcements in the federal funds rate were used with a dummy variable approach to analyze for effects on Bitcoin volatility. The main findings of this thesis indicate that Bitcoin is not affected by announcements of a change in the federal funds rate, and thus, the hypothesis that Bitcoin is immune to changes in the federal funds rate is supported.
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Reyes, Juan Daniel Bojowald Martin. "Spherically symmetric loop quantum gravity connections to two-dimensional models and applications to gravitational collapse /." [University Park, Pa.] : Pennsylvania State University, 2009. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-4758/index.html.
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Gong, Xue. "Dynamical Systems in Cell Division Cycle, Winnerless Competition Models, and Tensor Approximations." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1458303716.
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LIMA, FILHO Luiz Medeiros de Araújo. "Modelos simétricos não lineares de produção e crescimento em volume de clones de Eucalyptus spp." Universidade Federal Rural de Pernambuco, 2012. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5176.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Knowledge of growth and production present and future of trees in forest stands is a key element in sustainable forest management. It is intended in this thesis to estimate the frequency distribution by diameter class, estimate and compare volumetric equations via symmetric nonlinear models as well, propose to compare models and adjust volume growth via symmetrical nonlinear models in Eucalyptus spp. clones in the region of the Araripe - PE. The experiment was conducted at the Experimental Station of the Agricultural Research Company of Pernambuco (IPA), located in the municipality of Araripina - PE. This experiment consists of 15 clones of Eucalyptus spp., species and hybrids resulting from natural crossing and controlled pollination. The database is composed of all the survival trees of the experiment, corresponding to 1189 trees, divided into three groups. To estimate the diameter distributions were adopted probability distributions Normal, with three parameters Weibull, Log-normal and Gamma. The next step was to fit of the model of Schumacher and Hall and Spurr model associated the following symmetric distributions: Normal, Student t, Exponential Power and Logistics II. The volume growth models in this thesis were adjusted with symmetric distributions associated with them. In the estimation of the diameter distributions, the results were similar in the three groups, with emphasis on the Log-normal distribution. This distribution was the most appropriate for most of the period. Analyzing the volumetric equations, it was found that the model was Schumacher and Hall the most suitable, when associated with the Student t distribution with three degrees .of freedom and Exponential Power (t = 0,8) respectively to groups I and II. In group III, the model Spurr associated with Exponential Power (t = 0,8) distribution had the best performance. Comparing the volume growth models, it was observed that the proposed models best fits obtained in this thesis, when the distributions associated with the Student t with three degrees of freedom and Exponential Power (t = 0,8), respectively, in groups I and III. In group II, the Chapman-Richards model associated with Student t distribution with three degrees of freedom had the best performance.
O conhecimento do crescimento e da produção presente e futura de árvores em povoamentos florestais é elemento fundamental no manejo florestal sustentável. Desta forma, pretende-se nesta tese estimar a distribuição de frequência por classe diamétrica, estimar e comparar equações volumétricas via modelos simétricos não lineares, bem como, propor, ajustar e comparar modelos de crescimento em volume via modelos simétricos não lineares em clones de Eucalyptus spp. na região da Chapada do Araripe - PE. O experimento foi desenvolvido na Estação Experimental da Empresa Pernambucana de Pesquisa Agropecuária (IPA), localizada no município de Araripina - PE. Esse experimento é composto por 15 clones de Eucalyptus spp., resultantes de espécies e híbridos de cruzamento natural e polinização controlada. A base de dados foi composta por todas as árvores sobreviventes do experimento, que corresponde a 1189 árvores, dividida em três grupos. Para estimar as distribuições diamétricas foram adotadas as distribuições de probabilidade Normal, Weibull com três parâmetros, Log-normal e Gama. Em seguida, procedeu-se com os ajustes dos modelos volumétricos de Schumacher e Hall e de Spurr associados as seguintes distribuições simétricos: Normal, t de Student, Exponencial Potência e Logística II. Posteriormente, os modelos de crescimento em volume propostos nesta tese foram ajustados associados às mesmas distribuições simétricas. Na estimativa das distribuições diamétricas, os resultados foram similares nos três grupos, com destaque para a distribuição Log-normal. Essa distribuição foi a mais significativa na maior parte do período avaliado. Analisando as equações volumétricas, observou-se que o modelo de Schumacher e Hall obteve o melhor desempenho, quando associado as distribuições t de Student com três graus de liberdade e Exponencial Potência (t = 0,8), respectivamente, para os grupos I e II. No grupo III, o modelo de Spurr associado a distribuição Exponencial Potência (t = 0,8) obteve o melhor desempenho. Comparando os modelos de crescimento em volume, observou-se que os modelos propostos nesta tese obtiveram melhores ajustes, quando associados as distribuições t de Student com três graus de liberdade e Exponencial Potência (t = 0,8), respectivamente, nos grupos I e III. No grupo II, o modelo de Chapman-Richards associado a distribuição t de Student com três graus de liberdade obteve o melhor desempenho.
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Medeiros, Marcio Jose de. "Métodos de diagnóstico em modelos autoregressivos simétricos." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-04092007-220727/.
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Os modelos autoregressivos simétricos são modelos de regressão em que os erros são correlacionados -- AR(1) -- e pertencem à classe de distribuições simétricas. O objetivo deste trabalho é discutir métodos de diagnóstico de influência para esses modelos. Para ilustrar a metodologia, são apresentados exemplos do modelo de precificação de ativos (CAPM).The symmetric autoregressive models are regression models in which the errors are correlated and belong to the class of symmetrical distributions. The aim of this work is to discuss influence diagnostic methods for those models. To illustrate the methodology, examples of Capital Asset Pricing Models (CAPM) are presented.
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Macêra, Márcia Aparecida Centanin. "Uso dos métodos clássico e bayesiano para os modelos não-lineares heterocedásticos simétricos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-14092011-164458/.
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Os modelos normais de regressão têm sido utilizados durante muitos anos para a análise de dados. Mesmo nos casos em que a normalidade não podia ser suposta, tentava-se algum tipo de transformação com o intuito de alcançar a normalidade procurada. No entanto, na prática, essas suposições sobre normalidade e linearidade nem sempre são satisfeitas. Como alternativas à técnica clássica, foram desenvolvidas novas classes de modelos de regressão. Nesse contexto, focamos a classe de modelos em que a distribuição assumida para a variável resposta pertence à classe de distribuições simétricas. O objetivo geral desse trabalho é a modelagem desta classe no contexto bayesiano, em particular a modelagem da classe de modelos não-lineares heterocedásticos simétricos. Vale ressaltar que esse trabalho tem ligação com duas linhas de pesquisa, a saber: a inferência estatística abordando aspectos da teoria assintótica e a inferência bayesiana considerando aspectos de modelagem e critérios de seleção de modelos baseados em métodos de simulação de Monte Carlo em Cadeia de Markov (MCMC). Uma primeira etapa consiste em apresentar a classe dos modelos não-lineares heterocedásticos simétricos bem como a inferência clássica dos parâmetros desses modelos. Posteriormente, propomos uma abordagem bayesiana para esses modelos, cujo objetivo é mostrar sua viabilidade e comparar a inferência bayesiana dos parâmetros estimados via métodos MCMC com a inferência clássica das estimativas obtidas por meio da ferramenta GAMLSS. Além disso, utilizamos o método bayesiano de análise de influência caso a caso baseado na divergência de Kullback-Leibler para detectar observações influentes nos dados. A implementação computacional foi desenvolvida no software R e para detalhes dos programas pode ser consultado aos autores do trabalhoThe normal regression models have been used for many years for data analysis. Even in cases where normality could not be assumed, was trying to be some kind of transformation in order to achieve the normality sought. However, in practice, these assumptions about normality and linearity are not always satisfied. As alternatives to classical technique new classes of regression models were developed. In this context, we focus on the class of models in which the distribution assumed for the response variable belongs to the symmetric distributions class. The aim of this work is the modeling of this class in the bayesian context, in particular the modeling of the nonlinear models heteroscedastic symmetric class. Note that this work is connected with two research lines, the statistical inference addressing aspects of asymptotic theory and the bayesian inference considering aspects of modeling and criteria for models selection based on simulation methods Monte Carlo Markov Chain (MCMC). A first step is to present the nonlinear models heteroscedastic symmetric class as well as the classic inference of parameters of these models. Subsequently, we propose a bayesian approach to these models, whose objective is to show their feasibility and compare the estimated parameters bayesian inference by MCMC methods with the classical inference of the estimates obtained by GAMLSS tool. In addition, we use the bayesian method of influence analysis on a case based on the Kullback-Leibler divergence for detecting influential observations in the data. The computational implementation was developed in the software R and programs details can be found at the studys authors
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Wang, Xing. "Inferences about Parameters of Trivariate Normal Distribution with Missing Data." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/933.
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Multivariate normal distribution is commonly encountered in any field, a frequent issue is the missing values in practice. The purpose of this research was to estimate the parameters in three-dimensional covariance permutation-symmetric normal distribution with complete data and all possible patterns of incomplete data. In this study, MLE with missing data were derived, and the properties of the MLE as well as the sampling distributions were obtained. A Monte Carlo simulation study was used to evaluate the performance of the considered estimators for both cases when ρ was known and unknown. All results indicated that, compared to estimators in the case of omitting observations with missing data, the estimators derived in this article led to better performance. Furthermore, when ρ was unknown, using the estimate of ρ would lead to the same conclusion.
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Nguyen, Viet anh. "Contributions to tensor models, Hurwitz numbers and Macdonald-Koornwinder polynomials." Thesis, Angers, 2017. http://www.theses.fr/2017ANGE0052/document.
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Dans cette thèse, j’étudie trois sujets reliés : les modèles de tenseurs, les nombres de Hurwitz et les polynômes de Macdonald-Koornwinder. Les modèles de tenseurs généralisent les modèles de matrices en tant qu’une approche à la gravité quantique en dimension arbitraire (les modèles de matrices donnent une version bidimensionnelle). J’étudie un modèle particulier qui s’appelle le modèle quartique mélonique. Sa spécialité est qu’il s’écrit en termes d’un modèle de matrices qui est lui-même aussi intéressant. En utilisant les outils bien établis, je calcule les deux premiers ordres de leur 1=N expansion. Parmi plusieurs interprétations, les nombres de Hurwitz comptent le nombre de revêtements ramifiés de surfaces de Riemann. Ils sont connectés avec de nombreux sujets en mathématiques contemporaines telles que les modèles de matrices, les équations intégrables et les espaces de modules. Ma contribution principale est une formule explicite pour les nombres doubles avec 3-cycles complétées d’une part. Cette formule me permet de prouver plusieurs propriétés intéressantes de ces nombres. Le dernier sujet de mon étude est les polynôme de Macdonald et Koornwinder, plus précisément les identités de Littlewood. Ces polynômes forment les bases importantes de l’algèbre des polynômes symétriques. Un des problèmes intrinsèques dans la théorie des fonctions symétriques est la décomposition d’un polynôme symétrique dans la base de Macdonald. La décomposition obtenue (notamment si les coefficients sont raisonnablement explicites et compacts) est nommée une identité de Littlewood. Dans cette thèse, j’étudie les identités démontrées récemment par Rains et Warnaar. Mes contributions incluent une preuve d’une extension d’une telle identité et quelques progrès partiels vers la généralisation d’une autreIn this thesis, I study three related subjects: tensor models, Hurwitz numbers and Macdonald-Koornwinder polynomials. Tensor models are generalizations of matrix models as an approach to quantum gravity in arbitrary dimensions (matrix models give a 2D version). I study a specific model called the quartic melonic tensor model. Its specialty is that it can be transformed into a multi-matrix model which is very interesting by itself. With the help of well-established tools, I am able to compute the first two leading orders of their 1=N expansion. Among many interpretations, Hurwitz numbers count the number of weighted ramified coverings of Riemann surfaces. They are connected to many subjects of contemporary mathematics such as matrix models, integrable equations and moduli spaces of complex curves. My main contribution is an explicit formula for one-part double Hurwitz numbers with completed 3-cycles. This explicit formula also allows me to prove many interesting properties of these numbers. The final subject of my study is Macdonald-Koornwinder polynomials, in particular their Littlewood identities. These polynomials form important bases of the algebra of symmetric polynomials. One of the most important problems in symmetric function theory is to decompose a symmetric polynomial into the Macdonald basis. The obtained decomposition (in particular, if the coefficients are explicit and reasonably compact) is called a Littlewood identity. In this thesis, I study many recent Littlewood identities of Rains and Warnaar. My own contributions include a proof of an extension of one of their identities and partial progress towards generalization of one another
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Relvas, Carlos Eduardo Martins. "Modelos parcialmente lineares com erros simétricos autoregressivos de primeira ordem." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-28052013-182956/.
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Neste trabalho, apresentamos os modelos simétricos parcialmente lineares AR(1), que generalizam os modelos parcialmente lineares para a presença de erros autocorrelacionados seguindo uma estrutura de autocorrelação AR(1) e erros seguindo uma distribuição simétrica ao invés da distribuição normal. Dentre as distribuições simétricas, podemos considerar distribuições com caudas mais pesadas do que a normal, controlando a curtose e ponderando as observações aberrantes no processo de estimação. A estimação dos parâmetros do modelo é realizada por meio do critério de verossimilhança penalizada, que utiliza as funções escore e a matriz de informação de Fisher, sendo todas essas quantidades derivadas neste trabalho. O número efetivo de graus de liberdade e resultados assintóticos também são apresentados, assim como procedimentos de diagnóstico, destacando-se a obtenção da curvatura normal de influência local sob diferentes esquemas de perturbação e análise de resíduos. Uma aplicação com dados reais é apresentada como ilustração.In this master dissertation, we present the symmetric partially linear models with AR(1) errors that generalize the normal partially linear models to contain autocorrelated errors AR(1) following a symmetric distribution instead of the normal distribution. Among the symmetric distributions, we can consider heavier tails than the normal ones, controlling the kurtosis and down-weighting outlying observations in the estimation process. The parameter estimation is made through the penalized likelihood by using score functions and the expected Fisher information. We derive these functions in this work. The effective degrees of freedom and asymptotic results are also presented as well as the residual analysis, highlighting the normal curvature of local influence under different perturbation schemes. An application with real data is given for illustration.
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Kapetanopoulos, Tobias [Verfasser], Amin [Akademischer Betreuer] Coja-Oghlan, Amin [Gutachter] Coja-Oghlan, and Nicola [Gutachter] Kistler. "The replica symmetric phase in diluted mean-field models and the sharp threshold for jigsaw percolation in random graphs / Tobias Kapetanopoulos ; Gutachter: Amin Coja-Oghlan, Nicola Kistler ; Betreuer: Amin Coja-Oghlan." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2019. http://d-nb.info/119312607X/34.
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Vertongen, Gilles. "The fall and rise of antimatter: probing leptogenesis and dark matter models." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210200.
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Big Bang Nucleosynthesis (BBN), together with the analyses of the Cosmic Microwave Background (CMB) anisotropies, confirm what our day to day experience of life attests :antimatter is far less present than matter in the Universe. In addition, these observables also permit to evaluate that there exists about one proton for every 10^{10} photons present in the Universe. This is in contradiction with expectations coming from the standard hot big bang, where no distinction between matter and antimatter is made, and where subsequent annihilations would lead to equal matter and antimatter contents, at a level 10^{−10} smaller than the observed one. The Standard Model of fundamental interactions fails to explain this result, leading us to search for ‘Beyond the Standard Model’ physics.Among the possible mechanism which could be responsible for the creation of such a matter asymmetry, leptogenesis is particularly attractive because it only relies on the same ingredients previously introduced to generate neutrino masses. Unfortunatelly, this elegant proposal suffers from a major difficulty :it resists to any tentative of being probed by our low energy observables. In this thesis, we tackle the problem the other way around and propose a way to falsify this mechanism. Considering the type-I leptogenesis mechanism, i.e. a mechanism based on the asymmetric decay of right-handed neutrinos, in a left-right symmetric framework, we show that the observation of a right-handed gauge boson W_R at future colliders would rule out any possibility for such mechanism to be responsible of the matter asymmetry present in our Universe.
Another intriguing question that analyses of the anisotropies of the CMB confirmed is the presence of a non-baryonic component of matter in our Universe, i.e. the dark matter. As hinted by observations of galactic rotation curves, it should copiously be present in our galactic halo, but is notoriously difficult to detect directly. We can take advantage on the fact that antimatter almost disappeared from our surroundings to detect the contamination of cosmic rays from standard sources the annihilation products of dark matter would produce.
The second subject tackled in this work is the study of the imprints the Inert Doublet Modem (IDM) could leave in (charged) cosmic rays, namely positrons, antprotons and antideuterons. This model, first proposed to allow the Bout-Englert-Higgs particle to evade the Electroweak Precision Test (EWPT) measurements, introduces an additional scalar doublet which is inert in the sense that it does not couple directly to fermions. This latter property brings an additional virtue to this additional doublet :since it interacts weakly with particles, it can play the role of dark matter. This study will be done in the light of the data recently released by the PAMELA, ATIC and Fermi-GLAST collaborations, which reported e^± excesses in two different energy ranges.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Darbari, Ashish. "Symmetry reduction for STE model checking using structured models." Thesis, University of Oxford, 2006. https://eprints.soton.ac.uk/266029/.
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Yilmaz, Nejat Tevfik. "Dualisation Of Supergravity Theories." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604804/index.pdf.
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By using the Kaluza-Klein reduction, the derivation of the maximal supergravities from the D=11 supergravity theory, as well as the Abelian Yang-Mills supergravities from the D=10 type I supergravity theory are discussed. After a thorough review of the symmetric spaces the symmetric space sigma model is studied in detail. The first-order formulation of both the pure and the matter coupled symmetric space sigma model is presented in a general formalism. The dualisation of the non-gravitational Bosonic sectors of the D=11, IIB and the maximal supergravities are also reviewed in a concise but a self-contained formulation. As an example of the dualisation of the matter coupled supergravities, the doubled formalism is constructed for the D=8 Salam-Sezgin supergravity.
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LIMA, FILHO Luiz Medeiros de Araújo. "Modelos simétricos transformados não-lineares com diferentes distribuições dos erros: aplicações em ciências florestais." Universidade Federal Rural de Pernambuco, 2009. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5175.
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Historically, the wood of the eucalyptus is used for the most varied applications, such as; firewood, charcoal, cellulose, railway sleepers, posts for electrification, bark to tan leather, essential oils, civil construction, etc. The Gypsum Pole of Araripe in Pernambuco is a great firewood consumer for the gypsum production. Due to great need to find economical and environmental alternatives for the area, the sustainable production of eucalyptus that is a fast growth tree with great versatility has an important role. In the planning of the sustainable forest management there is a variable of extreme importance: the growth. To model the growth is fundamental in the prognosis of the productivity, site quality and dynamics of populations. Usually, the growth curves are fitted through nonlinear models developed empirically to relate, for instance, height and age. The Chapman-Richards model is a nonlinear model frequently used to model forest growth. In studies of this type, in general, it is assumed that the errors follow approximately the normal distribution. However, to model the growth assuming that the errors have a normal distribution is quite sensitive to atypical values that can happen, and generate bad estimates of the parameters. To correct that problem a new class of transformed symmetrical models was developed considering for the errors symmetrical continuous distributions with heavier tails than the normal distribution and allowing a possible nonlinear structure for the mean. With the expectation of obtaining better estimates of eucalyptus growth, it was applied to the Chapman-Richards model the following distributions of the errors: normal, t of Student, Cauchy, exponential potency, logistics I and logistics II. The t distribution of Student with 2 degrees of freedom was the most efficient to estimate height and circumference growth of eucalyptus in the Gypsum Pole of Pernambuco.
Historicamente, a madeira do Eucalyptus é usada para os mais variados fins, tais como; lenha, carvão vegetal, celulose, dormentes ferroviários, postes para eletrificação, casca para curtir couro, óleos essenciais, construção civil, etc. O Pólo Gesseiro do Araripe em Pernambuco é um grande consumidor de madeira para produção de gesso. Devido à grande necessidade de se buscar uma alternativa econômica e ambiental para a região é de interesse obter uma produção sustentável para o Eucalyptus, uma vez que esta é uma árvore de rápido crescimento e grande versatilidade. No planejamento do manejo florestal sustentado uma variável é de extrema importância: o crescimento. Sua modelagem é fundamental na prognose da produtividade, qualidade do local e dinâmica de populações. Geralmente, as curvas de crescimento são estudadas por meio de modelos não-lineares desenvolvidos empiricamente para relacionar, por exemplo, altura e idade. Um modelo não-linear bastante utilizado na prática para modelar curvas de crescimento é o modelo de Chapman-Richards. Em estudos deste tipo, em geral, assume-se que os erros seguem distribuição normal. Contudo, a modelagem sob a suposição de erros com distribuição normal é bastante sensível a valores atípicos que por ventura possam ocorrer, podendo distorcer as estimativas dos parâmetros. Para corrigir esse problema Cordeiro et al. (2009) desenvolveram uma nova classe de modelos simétricos transformados considerando para os erros distribuições contínuas simétricas com caudas mais pesadas do que a distribuição normal e permitindo uma possível estrutura não-linear para a média. Dessa forma, com a expectativa de obter melhores estimativas de crescimento de Eucalyptus, aplicaram-se ao modelo de Chapman-Richards as seguintes distribuições dos erros: normal, t de Student, Cauchy, exponencial potência, logística I e logística II que apresentou a distribuição t de Student com 2 graus de liberdade com melhores estimativas de crescimento em altura e circunferência de Eucalyptus no Pólo Gesseiro de Pernambuco.
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Cuadros, Torres David Edgardo, and Vargas Gef Sinder Jiménez. "Estimación de la zona crítica de diseño en naves industriales con diferentes alturas libres que soporten puentes grúas de diferentes capacidades de carga." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2021. http://hdl.handle.net/10757/656641.
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El presente estudio tiene como finalidad encontrar la zona crítica de diseño en naves industriales que combinen la premisa de diferentes alturas libres con la ubicación de distintas capacidades de carga de un puente grúa.
Se propuso un total de nueve modelos simétricos en planta con una disposición de pórticos a dos aguas. El sistema estructural contempla pórticos a momento y pórticos arriostrados. El recorrido del puente grúa de manera longitudinal y transversal determinó entre 10 a 90 ubicaciones donde la carga del puente grúa está concentrada para el análisis. Las cargas contempladas para el análisis y diseño fueron las producidas por carga muerta, carga viva, viento y sismo.
Para el diseño de los elementos de las naves industriales se ha considerado la Norma E.090 del Reglamento Nacional de Edificaciones y como complemento se ha utilizado las normas: ASCE y AISC. El diseño de los elementos estructurales se basó en el método LRFD.
El resultado de la investigación encontró una zona crítica de diseño en los márgenes izquierdo y derecho de cada modelo. Los valores de ambos márgenes correspondientes a la capacidad de carga del puente grúa son iguales en cada una de sus posiciones simétricas. Se comprobó que en la zona crítica existe una única ubicación que genera los máximos desempeños en los elementos de las naves industriales. Se determinó los ratios de costo de los perfiles de las naves industriales; los cuales, varían entre 51 y 190 dólares por metro cuadrado.The purpose of this study is to find the critical design area in industrial buildings that combine the premise of different free heights with the location of different load capacities of an overhead crane. A total of nine symmetrical models were proposed in plan with a gabled portico arrangement. The structural system includes frames at the moment and braced frames. The span of the overhead crane longitudinally and transversely determined between 10 to 90 locations where the overhead crane load is concentrated for the analysis. The loads considered for the analysis and design were those produced by dead load, live load, wind and earthquake. For the design of the elements of the industrial buildings, Standard E.090 of the National Building Regulations has been considered and as a complement the following standards have been used: ASCE and AISC. The design of the structural elements was based on the LRFD method. The result of the investigation found a critical design zone on the left and right margins of each model. The values of both margins corresponding to the load capacity of the overhead crane are equal in each of their symmetrical positions. It was found that in the critical zone there is a single location that generates the maximum performances in the elements of the industrial buildings. The cost ratios of the profiles of the industrial buildings were determined; which, vary between 51 and 190 dollars per square meter.
Tesis
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Durgin, Natalie. "Abelian Sandpile Model on Symmetric Graphs." Scholarship @ Claremont, 2009. https://scholarship.claremont.edu/hmc_theses/217.
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The abelian sandpile model, or chip firing game, is a cellular automaton on finite directed graphs often used to describe the phenomenon of self organized criticality. Here we present a thorough introduction to the theory of sandpiles. Additionally, we define a symmetric sandpile configuration, and show that such configurations form a subgroup of the sandpile group. Given a graph, we explore the existence of a quotient graph whose sandpile group is isomorphic to the symmetric subgroup of the original graph. These explorations are motivated by possible applications to counting the domino tilings of a 2n × 2n grid.
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Latulipe, Celine. "A Symmetric Interaction Model for Bimanual Input." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/2915.
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People use both their hands together cooperatively in many everyday activities. The modern computer interface fails to take advantage of this basic human ability, with the exception of the keyboard. However, the keyboard is limited in that it does not afford continuous spatial input. The computer mouse is perfectly suited for the point and click tasks that are the major method of manipulation within graphical user interfaces, but standard computers have a single mouse. A single mouse does not afford spatial coordination between the two hands within the graphical user interface. Although the advent of the Universal Serial Bus has made it possible to easily plug in many peripheral devices, including a second mouse, modern operating systems work on the assumption of a single spatial input stream. Thus, if a second mouse is plugged into a Macintosh computer, a Windows computer or a UNIX computer, the two mice control the same cursor. Previous work in two-handed or bimanual interaction techniques has often followed the asymmetric interaction guidelines set out by Yves Guiard's Kinematic Chain Model. In asymmetric interaction, the hands are assigned different tasks, based on hand dominance. I show that there is an interesting class of desktop user interface tasks which can be classified as symmetric. A symmetric task is one in which the two hands contribute equally to the completion of a unified task. I show that dual-mouse symmetric interaction techniques outperform traditional single-mouse techniques as well as dual-mouse asymmetric techniques for these symmetric tasks. I also show that users prefer the symmetric interaction techniques for these naturally symmetric tasks.
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Gehrmann, Helene. "Graphical Gaussian models with symmetries." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:5f69e996-3f8e-4bfa-891f-0e1ec8d0f9fb.
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This thesis is concerned with graphical Gaussian models with equality constraints on the concentration or partial correlation matrix introduced by Højsgaard and Lauritzen (2008) as RCON and RCOR models. The models can be represented by vertex and edge coloured graphs G = (V,ε), where parameters associated with equally coloured vertices or edges are restricted to being identical. In the first part of this thesis we study the problem of estimability of a non-zero model mean μ if the covariance structure Σ is restricted to satisfy the constraints of an RCON or RCOR model but is otherwise unknown. Exploiting results in Kruskal (1968), we obtain a characterisation of suitable linear spaces Ω such that if Σ is restricted as above, the maximum likelihood estimator μ(with circumflex) and the least squares estimator μ* of μ coincide for μ ∈ Ω, thus allowing μ and Σ to be estimated independently. For the special case of Ω being specified by equality relations among the entries of μ according to a partition M of the model variables V, our characterisation translates into a necessary and sufficient regularity condition on M and (V,ε). In the second part we address model selection of RCON and RCOR models. Due to the large number of models, we study the structure of four model classes lying strictly within the sets of RCON and RCOR models, each of which is defined by desirable statistical properties corresponding to colouring regularity conditions. Two of these appear in Højsgaard and Lauritzen (2008), while the other two arise from the regularity condition ensuring equality of estimators μ(with circumflex) = μ* we find in the first part. We show each of the colouring classes to form complete lattices, which qualifies the corresponding model spaces for an Edwards-Havránek model selection procedure (Edwards and Havránek, 1987). We develop a coresponding algorithm for one of the model classes and give an algorithm for a systematic search in accordance with the Edwards-Havránek principles for a second class. Both are applied to data sets previously analysed in the literature, with very encouraging performances.
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Baines, Clare Elizabeth. "Topics in functions with symmetry." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343778.
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Bigun, Josef. "Circular Symmetry Models in Image Processing." Licentiate thesis, Linköpings universitet, Bildbehandling, 1986. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-53397.
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New methods for feature extraction based on the spectral properties of local neighbourhoods is presented. The spectral behaviour of the neighbourhoods is investigated in the spatial domain using the Parseval relation applied to partial derivative pictures. Two types of such properties are considered for circular symmetric and linear symmetric neighbourhoods. These two properties are the existence of point concentration and line concentration in the spectra. For the circular symmetry investigation a new basis function set is introduced. To obtain a spectrum in the terms of these basis function sets, a scalar product is introduced for circular neighbourhoods. The same is carried out for linear symmetry spectra using the well-known basis set and the scalar product consisting of cosines and 𝓛2(Ω) scalar product. Confidence parameters are introduced to measure the significance of the extracted features. These are basically different types of variance measures and they are shown to be specific for the desired information: The existence of point concentration or line concentration in the spectra of the local neighbourhoods.
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Privé, Nikki C. 1977. "Zonally symmetric monsoon dynamics in a general circulation model." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/59100.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002.Includes bibliographical references (p. 97-98).
The MIT general circulation model is used with simplified setup to study steady zonally averaged monsoon circulations. Two dimensional model runs are made with a zonally symmetric continent north of 15N and a slab ocean of uniform sea surface temperature to study the applicability of axisymmetric theory. Forcing to drive the monsoon is applied by heating the subtropical land surface. The dynamical constraints of axisymmetry prevent low-level cross-equatorial flow and inhibit the northward transport of moisture onto the continent when there is no temperature gradient across the equator. The ocean cannot supply adequate moisture to feed the monsoon, and the ground hydrology strictly controls the behavior of the monsoon. A second set of two dimensional runs with similar continent, but with an SST gradient across the equator, result in a viable steady monsoon with low-level cross-equatorial flow providing moisture to the monsoon. The surface forcing required to induce a monsoon is reasonable given the constraints of the axisymmetric model setup. A series of three dimensional model runs with a zonally symmetric continent are made to study the role of zonally asymmetric flow on the zonal mean monsoon. It is found that greater land surface forcing is required to induce a zonally averaged monsoon circulation in the three dimensional runs than in similar axisymmetric runs. The behavior of the monsoon disturbances in the three dimensional runs is similar to the observed Asian monsoon in that there is low-level cross-equatorial flow which is southwesterly along the coastline, and in that a large-scale angular momentum conserving meridional circulation develops with ascent over the continent and subsidence in the opposite hemisphere. Moisture transport is found to play a very strong role in the monsoon dynamics in all of the model runs.
by Nikki C. Privé.
S.M.
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Bennett, Philip Desmond. "Spherically symmetric model atmospheres for late-type giant stars." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30908.
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The ATHENA computer code has been developed to model the extended atmospheres of late-type giant and supergiant stars. The atmospheres are assumed to be static, spherically
symmetric and in radiative and hydrostatic equilibrium. Molecular line blanketing (for now) is handled using the simplifying assumption of mean opacities. The complete linearization method of Auer and Mihalas [7], adapted to spherical geometry, is used to solve the model system. The radiative transfer is solved by using variable Eddington factors to close the system of moment transfer equations, and the entire system of transfer
equations plus constraints is solved efficiently by arrangement into the Rybicki [83] block matrix form. The variable Eddington factors are calculated from the full angle-dependent formal solution of the radiative transfer problem using the impact parameter method of Hummer, Kunasz and Kunasz [47]. We were guided by the work of Mihalas and Hummer [72] in their development of extended models of O stars, but our method differs in the choice of the independent variable. The radius depth scale used by Mihalas and Hummer was found to fail because of the strongly temperature-dependent opacities of late-type atmospheres. Instead, we were able to achieve an exact linearization of the radius. This permitted the use of the numerically well-behaved column mass or optical
depth scales. The resulting formulation is analogous to the plane-parallel complete linearization method and reduces to this method in the compact atmosphere limit.
Models of M giants were calculated for T[formula omitted] = 3000K and 3500K with opacities of the CN, TiO and H₂0 molecules included, and the results were in general agreement with other published spherical models. These models were calculated assuming radiative equilibrium. The importance of convective energy transport was estimated by calculating the convective flux that would result from the temperature structure of the models. The
standard local mixing length theory was used for this purpose. Convection was found to be important only at depths with Ƭ[formula omitted] > 15 for the low gravity models with log g = 0, but significant out to Ƭ[formula omitted] ~ 1 at the most transparent frequencies for the higher gravity models with log g = 2. Thus, the temperature structure of the surface layers and the emergent flux for the log g = 0 models should be accurately modelled but the emergent flux for the log g = 2 models may be in error by up to 5% at the most transparent frequencies.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Acion, Cristina Laura. "Criteria for generalized linear model selection based on Kullback's symmetric divergence." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2665.
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Model selection criteria frequently arise from constructing estimators of discrepancy measures used to assess the disparity between the data generating model and a fitted approximating model. The widely known Akaike information criterion (AIC) results from utilizing Kullback's directed divergence (KDD) as the targeted discrepancy. Under appropriate conditions, AIC serves as an asymptotically unbiased estimator of KDD. The directed divergence is an asymmetric measure of separation between two statistical models, meaning that an alternate directed divergence may be obtained by reversing the roles of the two models in the definition of the measure. The sum of the two directed divergences is Kullback's symmetric divergence (KSD).
A comparison of the two directed divergences indicates an important distinction between the measures. When used to evaluate fitted approximating models that are improperly specified, the directed divergence which serves as the basis for AIC is more sensitive towards detecting overfitted models, whereas its counterpart is more sensitive towards detecting underfitted models. Since KSD combines the information in both measures, it functions as a gauge of model disparity which is arguably more balanced than either of its individual components. With this motivation, we propose three estimators of KSD for use as model selection criteria in the setting of generalized linear models: KICo, KICu, and QKIC. These statistics function as asymptotically unbiased estimators of KSD under different assumptions and frameworks.
As with AIC, KICo and KICu are both justified for large-sample maximum likelihood settings; however, asymptotic unbiasedness holds under more general assumptions for KICo and KICu than for AIC. KICo serves as an asymptotically unbiased estimator of KSD in settings where the distribution of the response is misspecified. The asymptotic unbiasedness of KICu holds when the candidate model set includes underfitted models. QKIC is a modification of KICo. In the development of QKIC, the likelihood is replaced by the quasi-likelihood. QKIC can be used as a model selection tool when generalized estimating equations, a quasi-likelihood-based method, are used for parameter estimation. We examine the performance of KICo, KICu, and QKIC relative to other relevant criteria in simulation experiments. We also apply QKIC in a model selection problem for a randomized clinical trial investigating the effect of antidepressants on the temporal course of disability after stroke.
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Arizou, Ramin. "Distortional Lateral Torsional Buckling of Doubly Symmetric Wide Flange Beams." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41574.
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Distortional lateral-torsional buckling theories assume that the flanges remain undistorted, while the web is free to distort as a thin plate. Most theories adopt a cubic polynomial distribution along the web height to relate the lateral displacement of the web to the displacements and angles of twist both flanges. The present study develops a family of finite element solutions for the distortional buckling of wide flange beams in which the flanges are assumed to remain undistorted. In contrast to past theories, the lateral displacement distribution along the web height is characterized by superposing (a) two linear modes intended to capture the classical non-distortional lateral-torsional behavior and (b) any number of user-specified Fourier terms intended to capture additional web distortion. In the longitudinal direction, all displacement fields characterizing the lateral displacements are taken to follow a cubic distribution.
The first contribution of the thesis develops a finite element formulation that is able to replicate the classical non-distortional lateral torsional buckling solutions when the distortional modes are suppressed while enabling more accurate predictions for distortional lateral torsional buckling compared to those solutions based on the conventional cubic interpolation of the lateral displacement. The formulation is used to conduct an extensive parametric study to quantify the reduction in critical moments due to web distortion relative to the classical non-distortional predictions in the case of simply-supported beams, cantilevers, and beams with an overhang. The solution is then used to generate interaction curves for beams with an overhang subjected to various proportions of uniformly distributed and point loads.
The second contribution of the thesis adds two additional features to the formulation (a) to capture the destabilizing effect due to the load height relative to the shear center and (b) a module that incorporates any number of user-defined multi-point kinematic constraints. The additional features are employed to investigate the effect of load height, bracing height, and combined effects thereof in practical design problems. A distortional indicator is then introduced to characterize the distribution of web distortion along the beam span as the beam undergoes distortional lateral buckling. A systematic design optimization technique is then devised to identify the location(s) along the span at which the addition of transverse stiffeners would maximize the critical moment capacity.
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Tabatabaey, S. M. Mehdi (Seyed Mohammad Mehdi) Carleton University Dissertation Mathematics and Statistics. "Preliminary test approach estimation: regression model with spherically symmetric errors." Ottawa, 1995.
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Dießner, Philip. "Phenomenological Study of the Minimal R-Symmetric Supersymmetric Standard Model." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-212431.
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The Standard Model (SM) of particle physics gives a comprehensive description of numerous phenomena concerning the fundamental components of nature. Still, open questions and a clouded understanding of the underlying structure remain. Supersymmetry is a well motivated extension that may account for the observed density of dark matter in the universe and solve the hierarchy problem of the SM. The minimal supersymmetric extension of the SM (MSSM) provides solutions to these challenges. Furthermore, it predicts new particles in reach of current experiments. However, the model has its own theoretical challenges and is under fire from measurements provided by the Large Hadron Collider (LHC). Nevertheless, the concept of supersymmetry has an elegance which not only shines in the MSSM. Hence, it is also of interest to examine non-minimal supersymmetric models. They have benefits similar to the MSSM and may solve its shortcomings. R-symmetry is the only global symmetry allowed that does not commutate with supersymmetry and Lorentz symmetry. Thus, extending a supersymmetric model with R-symmetry is a theoretically well motivated endeavor to achieve the complete symmetry content of a field theory. Such a model provides a natural explanation for non-discovery in the early runs of the LHC and leads to further predictions distinct from those of the MSSM. The work described in this thesis contributes to the effort by studying the minimal R-symmetric supersymmetric extension of the SM (MRSSM). Important aspects of its physics and the dependence of observables on the parameter space of the MRSSM are investigated. The discovery of a scalar particle compatible with the Higgs boson of the SM at the LHC was announced in 2012. It is the first and crucial task of this thesis to understand the underlying mechanisms leading to the correct Higgs boson mass prediction in the MRSSM. Then, the relevant regions of parameter space are investigated and it is shown that they are also in agreement with other Higgs observables. Another observable that is measured with great accuracy and especially sensitive to corrections from additional supersymmetric states is the mass of the W boson. Contributing effects within the MRSSM are identified and their dependency on the model parameters is studied. The presence of a stable supersymmetric particle as candidate for dark matter is a prediction of the MRSSM. The interplay of the relevant processes generating the correct abundance of dark matter in the universe and explaining the non-discovery by direct searches is investigated. Moreover, results of Run 1 of the LHC are used to study the electroweak MRSSM sector. This leads to a classification of viable regions of parameter space consistent with dark matter and LHC constraints. In the last part of this thesis the different observables are analyzed in coherence. This allows to identify valid regions of parameter space and highlights promising predictions of the MRSSM for the coming runs of the LHC and other experimentsDas Standardmodell (SM) der Elementarteilchenphysik liefert eine prägnante Beschreibung der Phänomene, welche die grundlegenden Bestandteile der Natur betreffen. Es verbleiben aber weiterhin offene Fragen und eine fehlende Einsicht in die zugrunde liegenden Strukturen. Supersymmetrie ist eine wohl begründete Erweiterung, welche es ermöglicht die beobachtete dunkle Materiedichte im Universum zu erklären und das Hierarchieproblem des SM zu lösen. Die minimale supersymmetrische Erweiterung des SM (MSSM) besitzt diese Eigenschaften. Darüber hinaus sagt es neue Teilchen in Reichweite aktueller Experimente vorher. Die eigenen theoretischen Herausforderungen des Modells und Einschränkungen durch Messungen am Large Hadron Collider (LHC) schränken es jedoch stark ein. Dennoch birgt das Konzept der Supersymmetrie eine Eleganz, die eine ansprechende Grundlage für weitere Modelle bietet. Daher ist es auch von Interesse, nicht-minimale supersymmetrische Modelle zu untersuchen. Diese bieten mit dem MSSM vergleichbare Vorteile und können dessen Diskrepanzen auflösen. R-Symmetrie ist die einzig mögliche globale Symmetrie, die nicht mit Super- und Lorentzsymmetrie kommutieren. Ein auf diese Weise konstruiertes Modell enthält somit alle grundlegenden Symmetrien einer Feldtheorie. Durch die Inklusion von R-Symmetrie können die bisherige Nichtentdeckung am LHC erklärt und vom MSSM unterscheidbare Vorhersagen gemacht werden. In dieser Arbeit wird die Untersuchung des minimale R-symmetrische supersymmetrische Erweiterung des SM (MRSSM). Wichtige Aspekte der Phänomenologie und die Abhängigkeit der Observablen von den Parametern des MRSSM werden untersucht. Die Entdeckung eines skalaren Teilchens kompatibel mit dem Higgs-Boson des SM am LHC wurde im Jahre 2012 bekannt gegeben. Die Untersuchung der zugrunde liegenden Mechanismen, welche die Masse des Higgs Bosons im MRSSM korrekt verwirklichen, ist Hauptbestandteil des erste Teils dieser Arbeit. Dabei wird der Parameterraum des Modells untersucht und gezeigt, dass auch Übereinstimmung mit weiteren Observablen der Higgsphysik möglich ist. Ein weitere wichtige Messgröße, welche mit hoher Genauigkeit bestimmt und empfindlich auf Beiträge supersymmetrischer Teilchen ist, ist die Masse des W Bosons. Beiträge innerhalb des MRSSM werden identifiziert und ihre Abhängigkeit von Modellparametern untersucht. Die Existenz eines stabilen supersymmetrischen Teilchens als Kandidat für dunkle Materie ist eine Vorhersage des MRSSM. Es wird untersucht, wie die relevanten Prozesse zusammenspielen, um die korrekte Dichte an dunkler Materie im Universum zu erzeugen und die Nichtentdeckung bei direkte Suche zu erklären. Des weiteren werden die ersten Ergebnisse des LHC verwendet, um den elektroschwachen Sektor des MRSSM zu untersuchen. Im letzten Teil dieser Arbeit wird das Zusammenspiel verschiedener Observablen analysiert. Auf diese Weise können erlaubte Parameterregionen festgestellt und Vorhersagen für zukünftige Experimente gemacht werden
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Abdelhady, A. M. H. H. "Scattering in soliton models and crossing symmetry." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71664.
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Thesis (MSc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Crossing symmetry relates scattering and annihilation processes to each other. Its derivation is straightforward in perturbative approaches to quantum field theory: it merely reflects the exchange of in- and outgoing states in Feynman diagram computations. In soliton models, the situation is much more complicated because the scattering and the annihilation processes concern distinct topological sectors that are not related by any continuous transformation. In this thesis a simple soliton model will be employed to address this problem numerically. First, in the unit topological sector we extract asymptotically the phase shift of the scattering process of a wave packet off the kink-solution. To this end we solve the time-dependent equation of motion of the non-integrable '4 field model in (1+1) spacetime dimensions for two distinct initial conditions: the wave packet in a trivial vacuum background and in the background of the kink-solution. Second, in the topologically trivial sector we present numerical solutions of the kink– antikink interaction in the same model. We find that the final state of this interaction varies dramatically with the impact velocity. As result, we analyze our numerical solutions for the kink–antikink collisions system in two regimes. For the initial velocity of the system less than some critical velocity, vc 0:26, the kink and the antikink either annihilate or inelastically scatter. On the other hand, the kink and the antikink always inelastically scatter when the initial velocity of the system is higher than this critical velocity. However, the scattering processes of the kink–antikink with initial velocity below and above the critical velocity are different. Below the critical velocity the kink and the antikink collide and always undergo n-bounces (n 2) before they depart to infinity. When the initial velocity of the system is higher than vc, the kink and the antikink depart to infinity after only one bounce. We present a qualitative description for these bounce effects between the kink and the antikink motivated by earlier studies as well as our numerical simulations. We utilize collective coordinates to study the dynamics of the kink–antikink system in two degrees of freedom. In this regime, we modify the ansätze of the kink–antikink system from earlier studies to account for relativistic effects. We perform a comparison between this approximation and the full system. We end our discussion of this sector by discussing the scattering data for the inelastic scattering and the annihilation processes of the kink–antikink. Third, we compare the extracted scattering data for the scattering process of a wave packet off the kink-solution and the annihilation process of the kink–antikink to each other. Finally, these studies of different sectors allow us to make a conjecture about the validity of crossing symmetry within the non-integrable '4 field model.
AFRIKAANSE OPSOMMING: Kruising-simmetrie beskryf ’n verband tussen verstrooiings- en vernietigingsprosesse. Die afleiding daarvan binne die raamwerk van steuringsteorie is eenvoudig: dit behels bloot die omruil van ingaande en uitgaande toestande in die Feynman-diagram. In soliton-modelle is die situasie egter meer ingewikkeld aangesien die verstrooiings- en vernietigingsprosesse in verskillende topologiese sektore plaasvind wat nie deur kontinue transformasies aan mekaar gekoppel is nie. In hierdie tesis word daar van ’n eenvoudige soliton-model gebruik gemaak om hierdie probleem numeries te ondersoek. Eerstens word die faseverskuiwing van die verstrooiingsproses van ’n golfpakkie vanaf ’n kinkoplossing asimptoties in die topologiese eenheidssektor bepaal. Vir hierdie doel word die tydafhanklike bewegingsvergelykings van die klassieke, nie-integreerbare 4-veldeteorie in (1+1) dimensionele ruimte-tyd opgelos. Twee beginkondisies word ondersoek: ’n golfpakkie in die triviale vakuum agtergrond asook in die kinkoplossing agtergrond. Tweedens ondersoek ons ook numeriese oplossings vir die kink-antikink wisselwerking binne die triviale topologiese sektor van dieselfde model. Hier vind ons dat die finale toestand van hierdie wisselwerkingsproses op ’n uiters sensitiewe wyse van die impaksnelheid afhang. Ons ondersoek gevolglik die numeriese oplossings vir die kink-antikink botsings in twee gebiede. Vir beginsnelhede onder die kritieke snelheid vc 0:26 sal die kink en antikink mekaar óf vernietig óf nie-elasties verstrooi. In teenstelling hiermee sal die kink-antikink altyd nie-elastiese verstrooiing ondergaan as die beginsnelheid die kritieke snelheid oorskry. Die aard van die verstrooiingsprosesse vir beginsnelhede bo en onder die kritieke snelheid is egter verskillend. Onder die kritieke snelheid sal die kink en antikink ’n n-bots proses (n 2) ondergaan voor hulle finaal van mekaar weg beweeg. Bo die kritieke snelheid sal die kink-antikink egter net ’n enkele botsing ondergaan en dan uitmekaar beweeg. Ons lewer ’n kwalitatiewe beskrywing vir die bons-effek tussen die kink en antikink wat deur vorige studies asook ons numeriese resultate gemotiveer word. Ons maak gebruik van ’n kollektiewe koördinaatstelsel om die dinamika van die kink-antikink in terme van twee vryheidsgrade te bestudeer. In hierdie gebied pas ons ook die ansatz vir die kink-antikink stelsel aan om relatiwistiese effekte in ag te neem. Ons vergelyk dan hierdie benadering met die oplossing van die volle sisteem. Die bespreking van hierdie sektor word afgesluit met ’n analise van die verstrooiingsdata vir die verstrooiing- en vernietingsprosesse van die kink-antikink. Derdens vergelyk ons die verstrooiingsdata vir die verstrooiing van ’n golfpakkie vanaf ’n kinkoplossing met die van die vernietigingsproses van die kink-antikink. Ons studie van die verskillende sektore laat ons dan toe om ’n vermoede te formuleer oor die geldigheid van kruissing-simmetrie binne die nie-integreerbare 4-model.
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Marshall, Gardner Rush. "Supersymmetric Leptophilic Models of Electroweak Symmetry Breaking." W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539623607.
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Over the years, the Standard Model has proved itself to be an extremely durable theory. In spite of its success, very few empirical clues have emerged about the nature of the electroweak symmetry breaking that lies at its heart. With results from the LHC around the corner, this will hopefully change soon. In this dissertation we examine several possibilities for electroweak symmetry breaking and discuss various extensions to the Standard Model to resolve known problems. We begin by providing a brief overview of electroweak symmetry breaking, two Higgs doublet models, and supersymmetry. We then present a supersymmetric model that allows for small, Dirac neutrino masses. We find that it yields dramatic multi-lepton signatures, which have extremely small backgrounds. Next we discuss the leptophilic two Higgs doublet model and construct its supersymmetric analogue. Bounds on this model as well as its phenomenology are presented. We then show that an extension of this model includes a dark matter candidate that is capable of explaining a possibly observed excess of gamma-rays coming from the Galactic Center.
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Ryssens, Wouter. "Symmetry breaking in nuclear mean-field models." Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/235692.
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Dans les années 1970, Vautherin et Brink ont effectué les premiers calculs auto-consistents du problème à N-corps nucléaire en utilisant une interaction de Skyrme. Aujourd’hui la méthode de la fonctionnelle de densité (EDF) ou la méthode champ-moyen est toujours utilisée à grande échelle pour étudier la structure nucléaire. Le premier point fort de cette méthode est sa simplicité computationnelle qui permet de l'appliquer dans l'entièreté de la charte nucléaire, des noyaux les plus légers aux éléments super lourds à plus que 250 nucléons. Depuis le début des années 1980, les initiales `BFH', représentant Paul Bonche, Hubert Flocard et Paul-Henri Heenen, ont signé un grand nombre des papiers depuis 1984. Ces trois scientifiques sont les auteurs de trois codes numériques iconiques EV8, CR8 et EV4. Des versions évoluées de ces codes sont toujours utilisées fréquemment aujourd’hui par des nombreux chercheurs. Au fil des années, deux désavantages de ces trois codes sont apparus. Le premier désavantage est lié à la physique: bien que EV8, EV4 et CR8 offrent à l'utilisateur accès à une variété de combinaisons de symétries conservées et brisées, un grand nombre n'est pas accessible. De plus en plus souvent, les applications traitant des noyaux exotiques demandent des calculs champ-moyen qui sont moins limités par les symétries imposées. Le deuxième désavantage est d'une nature plus pratique: le maintien au même niveau d'une combinaison de trois codes qui ont des buts comparables est difficile. Le projet de mon doctorat était de construire un code qui unifie et généralise les fonctionnalités de EV8, CR8 et EV4. Aujourd'hui MOCCa, un acronyme de MOdular Cranking Code, est capable de reproduire toutes les fonctionnalités des codes BFH. De plus, il est maintenant possible d'effectuer des calculs champ-moyen pour un nombre des combinaisons de symétries conservées et brisées, offrant un domaine d'applications énorme. Quatre symétries ont été toujours imposées dans les codes BFH, et sont maintenant toutes soumises au choix de l'utilisateur, qui peut les conserver où les briser indépendamment. Ceci résulte en 16 modes d'opération différents du code, dont tous ont des intérêts physiques pour décrire des phénomènes nucléaires. La déformation octupolaire du 224Ra et les bandes chirales du 138Nd sont des exemples récents d'intérêt expérimental, dont la description théorique est maintenant abordable avec un seul outil. Cet outil fait preuve d'une grande complexité: sur le plan physique, des méthodes ont été développées pour résoudre les équations du champ-moyen en l'absence des symétries facilitant le problème, tandis que sur le plan pratique, le traitement d'un nombre de degrés de liberté non-physiques a eté amelioré. La dernière partie de la thèse, la plus importante probablement du point de vue des futurs collaborateurs, est pour cette raison constituée d'un manuel d'utilisateur. Deux applications de la méthode sont ainsi présentées: la description des transitions de forme dans les isotopes de Radium et une étude de l'évolution des rayons de charge dans la chaîne isotopique du mercure démontrent la viabilité de la méthode.Option Physique du Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Bücheler, Steffen. "Semiklassische Quantisierung chaotischer Billardsysteme mit C 4v -Symmetrie." [S.l. : s.n.], 2001. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10447211.
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Wilson, Iain. "Are international exchange and mobility programmes effective tools of symmetric public diplomacy?" Thesis, Aberystwyth University, 2010. http://hdl.handle.net/2160/f0bee0ac-09cf-46fb-ba79-f5ad2d9e17cc.
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Governments often fund foreign nationals to live, work and study in their countries, creating specialist programmes tasked with promoting international mobility. In this thesis I establish that much of this funding is intended to serve a public diplomacy agenda, improving international relations to the benefit of the sponsor. Expectations about how offering funding to foreigners affects international relations have come to centre on what I label the ‘symmetric public diplomacy model’, which suggests that governments intend to influence other countries’ behaviour by influencing their citizens. I tested this model using a combination of panel surveys and interviews with students who took part in these programmes. Although mobility programmes do bring many educational and personal benefits to participants, my results do not support the expectation that they endow most visiting foreigners with more helpful attitudes than they would have developed had they not taken part in the programmes. While other studies have come to different conclusions on this issue, the research design employed in this thesis is better-suited to the task than most others. Mobility programmes may bring diplomatic benefits by other means. One possibility is that the act of creating, for example, scholarships for foreign nationals sends signals to foreign governments. The histories of major British scholarship programmes suggest that they were originally created to signal goodwill or distract attention from potentially-embarrassing policies. Despite this, administrators now present these programmes as tools of public diplomacy. The symmetric public diplomacy model has been applied to these programmes long after they were initially created, and I suggest that the model may have been adopted because it is useful for attracting funding to continue and expand mobility programmes.
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Mustapha, Nazeem. "Aspects of a spherically symmetric model of the post-decoupling universe." Master's thesis, University of Cape Town, 1997. http://hdl.handle.net/11427/17524.
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Bibliography: pages 84-88.The central aim of this thesis is to consider aspects of the spherically symmetric Lemaitre-Tolman-Bondi (LTB) solution as a model of the post-decoupling universe. To do this comprehensively is a massive task and is not our aim here. Indeed, far from it, we will concentrate on select instances of this programme and attempt in some places to indicate possibilities for further study. There are many solutions of the EFE which satisfy what we consider to be 'reasonable criteria' for a cosmology and others that do not. The LTB solution may be accepted as a reasonable cosmological model because ■ It allows non-empty solutions. ■ It allows expanding solutions. ■ It has a homogeneous and isotropic limit. ■ It allows for inhomogeneity.