Orientador: Analice Costacurta Brandi / Banca: Gilcilene Sanchez de Paulo / Banca: Marcio Teixeira Mendonça / Resumo: O presente trabalho investiga a transição laminar-turbulenta devido a ondas de Tollmien-Schlichting para o escoamento de Poiseuille incompressível, bidimensional, de um uido viscoelástico, utilizando a equação constitutiva Giesekus. A Teoria de Estabilidade Linear e a Simulação Numérica Direta são utilizadas para veri car a estabilidade de escoamentos de uidos viscoelásticos a perturbações não estacionárias. Na análise LST a equação de Orr-Sommerfeld é modi cada para um uido viscoelástico e resolvida pelo método da estimativa (Shooting). Enquanto que, na formulação DNS, as equações de Navier-Stokes, juntamente com a equação constitutiva Giesekus, são resolvidas utilizando métodos de diferenças nitas compactas de alta ordem. Com o objetivo de avaliar as curvas neutras de estabilidade e as taxas de ampli cação, diferentes simulações numéricas são realizadas variando-se os parâmetros adimensionais no modelo Giesekus e comparando com o uido Newtoniano. As técnicas LST e DNS mostraram-se ferramentas e cientes na análise espacial da estabilidade de escoamentos viscoelásticos do tipo Giesekus, permitindo uma melhor compreensão da in uência dos parâmetros adimensionais desses escoamentos e contribuindo com resultados originais na veri cação da estabilidade de escoamentos viscoelásticos utilizando o uido Giesekus. / Abstract: The present work investigates the laminar-turbulent transition due to Tollmien-Schlichting waves for the incompressible two-dimensional Poiseuille ow of a viscoelastic uid, using the Giesekus constitutive equation. Linear Stability Theory and Direct Numerical Simulation are used to verify the stability of viscoelastic uid ows to unsteady disturbances. In the LST analysis, the Orr-Sommerfeld equation is modi ed to a viscoelastic uid and solved by Shooting method. Whereas, in the DNS formulation, the Navier-Stokes equations with the Giesekus constitutive equation are solved using high-order compact nite di erence methods. In order to evaluate the neutral stability curves and the ampli- cation rates, di erent numerical simulations are performed by varying the dimensionless parameters in the Giesekus model and their results are compared with the Newtonian uid. The LST and DNS techniques proved to be e cient tools to the spatial stability analysis of viscoelastic uid ows of the Giesekus type, allowing a better comprehension of the dimensionless parameters in uence of those ows, contributing with originals results to veri cation of the viscoelastics uid ows stability using Giesekus uid. / Mestre

Orientador: Cassio Machiaveli Oishi / Banca: Fabrício Simeoni de Sousa / Banca: Messias Meneguette Júnior / Resumo: Neste trabalho é apresentado o estudo de um método numérico para resolver as equações de Navier-Stokes incompressíveis em escoamentos que possuem superfícies livres e mudanças topológicas. As equações governantes são resolvidas por um método de projeção que desacopla as incógnitas velocidade e pressão. A discretização é feita através de aproximações por diferenças finitas aplicadas a uma malha computacional não-uniforme. O método numérico é aplicado para a solução de problemas envolvendo fluidos Newtonianos e não-Newtonianos. Em particular, os efeitos viscoelásticos são descritos pelo modelo Oldroyd-B, utilizando a formulação Cartesiana clássica e uma forma alternativa para a decomposição da parte polimérica do tensor tensão extra. Esta estratégia alternativa de decomposição, conhecida como Formulação Tensão Natural, é muito atual e resultados numéricos são originalmente discutidos neste trabalho. O novo código com malha nãouniforme é testado nos seguintes problemas: escoamento na cavidade (lid-driven cavity), escoamento no cross-slot, e escoamento no canal com contração. A representação da superfície livre é feita através do método Front-Tracking, que descreve a interface de forma explícita através de partículas marcadoras. O algoritmo de mudanças topológicas é baseado em uma técnica que detecta e desfaz embaraçamentos presentes na interface. Este algoritmo é testado em simulações numéricas como: o impacto entre uma gota e uma camada de fluido, o impacto entre gotas e uma pa... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work presents the study of a numerical method for solving the incompressible Navier-Stokes equations for free-surface flows that undergo topological changes. The governing equations are solved through a projection method that decouples the velocity and pressure fields. The discretization is performed via finite differences approximations applied to a non-uniform mesh. The numerical scheme is applied for solving Newtonian and non-Newtonian fluid flows. In particular, the viscoelastic effects are described by the Oldroyd-B model, using the classic Cartesian formulation and also an alternative approach for the decomposition of the polimeric part of the extra stress tensor. This alternative decomposition strategy is known as Natural Stress Formulation, and numerical results are originally discussed in this work. The new code with a non-uniform mesh is tested in the following problems: the lid-driven cavity, the cross-slot problem, and the flow through a channel with contraction. In order to represent the free-surface, a Front-Tracking method that describes the interface explicitly using marker particles is used. The algorithm for topological changes is based in a technique that detects when the interface is tangled and untangles it. This algorithm is tested in numerical simulations such as: the impact between a drop and a layer of fluid, the impact between drops and a solid wall, and the jetting break-up process under the effect of surface tension. / Mestre

Orientador: Geraldo Francisco Donegá Zafalon / Banca: Carlos Roberto Valêncio / Banca: Wladimir Seixas / Resumo: Um quadrotor é um veículo aéreo não-tripulado (VANT). Diversos estudos sobre o controle de seu voo foram conduzidos nos últimos anos. As técnicas de domínio da dinâmica de voos são assuntos interessantes em diversas áreas em que podem ser aplicadas e a maioria das pesquisas é realizada em ambiente interno com a presença de sensores. A aplicação em ambiente externo ainda é pouco estudada devido à falta de autocontrole de voo do próprio quadrotor. Nesse cenário, foi encontrada a motivação para a confecção da proposta apresentada no trabalho, cujo principal objetivo é aplicar o método da decomposição de Adomian e analisar as soluções com outros métodos aplicados, por meio de simulações computacionais, para se ter uma solução que pode ser implementada no autocontrole de voo. Nas simulações realizadas, obtêm-se os resultados bons e significativos em relação às velocidades angulares, cuja eficiência é melhor do que outros métodos comparados. Portanto, a utilização do método da decomposição de Adomian nas equações da dinâmica de voos apresenta um bom desempenho / Abstract: The quadrotor is an unmanned aerial vehicle (UAV). Several studies on the control of its flight have been conducted in recent years. The domain techniques of dynamic flights are interesting subjects in the various areas where they can be applied and most research is carried out in the indoor environment with the presence of sensors. The outdoor applications are still little studied due to lack of self-control quadrotor own flight. In this scenario, the motivation to develop this work was found, whose aim is to apply the Adomian decomposition method and analyze the solutions with other methods applied through computer simulations to have a solution that can be deployed in flight self. In the simulations, we obtain the good and significant results in relation to the angular velocity, whose efficiency is better than other methods compared. Therefore, the use of the Adomian decomposition method in equations of dynamic flight has a good performance / Mestre

Orientador: Marcelo Messias / Banca: Luis Fernando de Osório Mello / Banca: Vanessa Avansini Botta Pirani / Resumo: Nesta dissertação fazemos um estudo de modelos biológicos do tipo Lotka-Volterra, utilizando como ferramenta principal a teoria qualitativa das equações diferenciais ordinárias. Abordamos, no plano e no espaço, alguns modelos do tipo predador-presa. Analisamos os comportamentos das soluções sob a variação dos parâmetros e tratamos com detalhes a bifurcação de Hopf, que dá origem a uma órbita periódica isolada (ciclo limite). Estudamos também um teorema devido a Li e Muldowney [16] sobre a estabilidade global de um ponto de equilíbrio para um sistema x˙ = f(x), x ∈ Rn. Aplicamos este resultado no estudo de um modelo de HIV tridimensional, provando a estabilidade global de um ponto de equilíbrio, para certos valores dos parâmetros. Para o mesmo modelo, verificamos a ocorrência de uma dupla bifurcação de Hopf, que leva ao surgimento e posterior desaparecimento de um ciclo limite, ao variarmos um dos parâmetros envolvidos no sistema. As bifurcações de Hopf ocorrem simultaneamente à perda de estabilidade global do ponto de equilíbrio / Abstract: In this work we present a study of biological models of Lotka-Volterra type, using as main tool the qualitative theory of ordinary differential equations. We analyze some two and three dimensional predator-prey models. The behavior of the solutions are studied under the variation of parameters and it is shown that a Hopf bifurcation occurs, leading to the creation of an isolated periodic orbit (limit cycle). We also study a theorem due to Li and Muldowney [16] about the global stability of an equilibrium point of a system x˙ = f(x), x ∈ Rn. We apply this result in the analysis of a three dimensional model of HIV with treatment, showing the global stability of an equilibrium point, for certain parameter values. For the same model, we prove the occurrence of two Hopf bifurcations, leading to the birth and subsequent death of a limit cycle, when we vary one of the parameters of the model. The Hopf bifurcations occurs simultaneously to the lack of global stability of the equilibrium point / Mestre

Orientador: Cássio Machiaveli Oishi / Banca: Messias Meneguette Júnior / Banca: Fabrício Simeoni de Souza / Resumo: Neste trabalho, analisamos métodos de diferenças finitas para solução numérica da equação de Poisson em domínios irregulares com condições do tipo Dirichlet, fazendo um estudo detalhado de cada um desses métodos numéricos. Em particular, analisamos o Método das Interfaces Imersas (MII), Métodos Clássicos usando interpolações linear (MCL) e quadrática (MCQ) e um Método do tipo Fronteiras Imersas modificado (MFIM). Inicialmente, comparamos os resultados obtidos por esses métodos na solução numérica de uma equação elíptica unidimensional, envolvendo uma interface localizada em um ponto que não coincide com a malha. No caso unidimensional provamos que o MCL e o MFIM são equivalentes. Posteriormente, analisamos os resultados obtidos por esses métodos na solução numérica de problemas elípticos bidimensionais, com condições de contorno definida sobre geometrias irregulares. Em geral, os métodos foram consistentes com a solução exata. No caso unidimensional o MII e o MCQ apresentaram resultados semelhantes, com ordem de precisão quadrática, enquanto que o MCL e o MFIM são menos precisos para esses testes. Após isso, realizamos testes preliminares envolvendo geometrias bidimensionais irregulares. Os resultados apontam que o MFIM e o MII são mais acurados e possuem ordem de convergência quadrática / Abstract: In this work, we study finite difference methods for the numerical solution of PoissonŠs equation on irregular domains with Dirichlet-type boundary conditions, performing a detailed study of these schemes. In particular, we analyze the Immersed Interfaces method (IIM), the classical method with linear (CML) and quadratic (CMQ) interpolation and the modified immersed boundary method (MIBM). Firstly, we compare the results obtained from these methods for solving a one-dimensional elliptic equation. In this equation, an interface is located at an irregular grid point. In general, all methods have been found consistent to the exact solution. In the one-dimensional case, IIM and CMQ have showed similar results, with second-order accuracy while MBIM and CML have presented less accurate results. Finally, we conduct preliminary results for two-dimensional irregular geometries. The results show that IIM and MIBM are more accurate than the classical method with linear interpolation / Mestre

Graph Isomorphism is one of the very few classical problems in NP of unsettled complexity status. The families of highly regular structures, for example Steiner 2-designs, strongly regular graphs and primitive coherent configurations, have been perceived as difficult cases for graph isomorphism. These highly regular structures arise naturally as obstacles for both the classical group theory and combinatorial approaches for the graph isomorphism problem. In this thesis we investigate the isomorphism problem of highly regular structures. We present new results to understand the combinatorial structure of highly regular structures, and propose some new algorithms to compute the canonical forms (and thus isomorphism testing) of highly regular structures based on the structural theorems. We also give an algorithm solving the isomorphism problem of two unknown graphs in the property testing setting. Our new algorithm has sample complexity matching the information theoretical lower bound up to some multiplicative subpolynomial factor.

In today’s technology driven society, software is becoming increasingly important in more areas of our lives. The domain of software extends beyond the obvious domain of computers, tablets, and mobile phones. Smart devices and the internet-of-things have inspired the integra- tion of digital and computational technology into objects that some of us would never have guessed could be possible or even necessary. Fridges and freezers connected to social media sites, a toaster activated with a mobile phone, physical buttons for shopping, and verbally asking smart speakers to order a meal to be delivered. This is the world we live in and it is an exciting time for software engineers and computer scientists. The sheer volume of code that is currently in use has long since outgrown beyond the point of any hope for proper manual maintenance. The rate of which mobile application stores such as Google’s and Apple’s have expanded is astounding. The research presented here aims to shed a light on an emerging field of research, called Genetic Improvement ( GI ) of software. It is a methodology to change program code to improve existing software. This thesis details a framework for GI that is then applied to explore fitness landscape of bug fixing Python software, reduce execution time in a C ++ program, and integrated into a live system. We show that software is generally not fragile and although fitness landscapes for GI are flat they are not impossible to search in. This conclusion applies equally to bug fixing in small programs as well as execution time improvements. The framework’s application is shown to be transportable between programming languages with minimal effort. Additionally, it can be easily integrated into a system that runs a live web service.

Orientador: Fernando Antônio Moala / Banca: Sergio Minouru Oikawa / Banca: Carlos Aparecido dos Santos / Resumo: Devido aos inúmeros campos para aplicações na Análise de Sobrevivência, diferentes funções de risco são necessárias para modelar os mais diversos casos em estudo. Portanto, ao criar novas distribuições pode-se obter diferentes funções de risco com suas diferentes curvas, que podem ser utilizadas para diversos tipos de dados. Serão apresentadas três novas distribuições de probabilidade, criadas a partir de três diferentes métodos, sendo a Gama Exponenciada Estendida de Marshall Olkin, Gama Exponenciada Poisson Truncada no Zero e também a Gama Exponenciada Bivariada. Para as distribuições de probabilidade univariadas foram obtidos resultados probabilísticos, tais como o n-ésimo momento; r-ésimo momento de vida média residual; r-ésimo momento de vida média residual invertido; ordenação estocástica; entropias; desvios médios; curvas de Bonferroni e de Lorenz; assimetria, curtose e seus gráficos; estatísticas de ordem e parâmetro stress − strength. Em relação a distribuição Gama Exponenciada Bivariada foi encontrada sua função acumulada; função densidade; função marginal; função condicional e seu n-ésimo momento. Para as novas distribuições univariadas encontradas, também foram feitas simulações para diferentes valores de parâmetros com o intuito de verificar qual o melhor método de estimação, para cada parâmetro de cada distribuição. Os métodos utilizados foram: estimador de máxima verossimilhança, Mínimos Quadrados, Mínimos Quadrados Ponderados, Cramér-von-Mises, Anderson Darli... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Due to the many fields for applications in Survival Analysis, different hazard functions are needed to modelling the various case studies. Therefore, creating new distributions can obtains different hazard functions with different graphics, which can be used for various types of data. There will be presented three new probability distributions, created from three different methods, the Marshall Olkin Extendet Exponentiated Gamma, Poisson Zero Truncated Exponentiated Gamma and the Bivariate Exponentiated Gamma. For such univariate probability distributions it will be obtained some probabilistics results, like n-th time, rth moment of residual life, r-th moment of residual life inverted, stochastic ordering, entropies, mean deviation, Bonferroni and Lorenz curve, skewness, kurtosis, order statistics and stress-strength parameter. Regarding the Bivariate Gamma Exponentiated was found your acumulated and density function; marginal function; conditional function and it's n-th moment. For the new univariate distributions found, were also made simulations for different parameter values in order to find the best estimation method for each parameter. The methods used were: maximum likelihood, ordinary least-squares, weighted least-squares, Cramér-von-Mises, Anderson Darling, Anderson Darling - RT (right-tail), Anderson Darling - LT (left-tail), Anderson Darling - 2LT (left-tail second order), Kolmogorov and bayesian estimator with the prior Gamma... (Complete abstract click electronic access below) / Mestre

Liu, Jia. / "August 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (p. 69-72). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Related Work --- p.3 / Chapter 3 --- Privacy Preserving Network Publication against Structural Attacks --- p.5 / Chapter 3.1 --- Background and Motivation --- p.5 / Chapter 3.1.1 --- Adversary knowledge --- p.6 / Chapter 3.1.2 --- Targets of Protection --- p.7 / Chapter 3.1.3 --- Challenges and Contributions --- p.10 / Chapter 3.2 --- Preliminaries and Problem Definition --- p.11 / Chapter 3.3 --- Solution:K-Isomorphism --- p.15 / Chapter 3.4 --- Algorithm --- p.18 / Chapter 3.4.1 --- Refined Algorithm --- p.21 / Chapter 3.4.2 --- Locating Vertex Disjoint Embeddings --- p.30 / Chapter 3.4.3 --- Dynamic Releases --- p.32 / Chapter 3.5 --- Experimental Evaluation --- p.34 / Chapter 3.5.1 --- Datasets --- p.34 / Chapter 3.5.2 --- Data Structure of K-Isomorphism --- p.37 / Chapter 3.5.3 --- Data Utilities and Runtime --- p.42 / Chapter 3.5.4 --- Dynamic Releases --- p.47 / Chapter 3.6 --- Conclusions --- p.47 / Chapter 4 --- Global Privacy Guarantee in Serial Data Publishing --- p.49 / Chapter 4.1 --- Background and Motivation --- p.49 / Chapter 4.2 --- Problem Definition --- p.54 / Chapter 4.3 --- Breach Probability Analysis --- p.57 / Chapter 4.4 --- Anonymization --- p.58 / Chapter 4.4.1 --- AG size Ratio --- p.58 / Chapter 4.4.2 --- Constant-Ratio Strategy --- p.59 / Chapter 4.4.3 --- Geometric Strategy --- p.61 / Chapter 4.5 --- Experiment --- p.62 / Chapter 4.5.1 --- Dataset --- p.62 / Chapter 4.5.2 --- Anonymization --- p.63 / Chapter 4.5.3 --- Evaluation --- p.64 / Chapter 4.6 --- Conclusion --- p.68 / Bibliography --- p.69

A survey of algorithms for free unification is given, followed by an overview of the computability and complexity of unification problems. Second-order unification is known to be undecidable, and a proof is given that the first-order problem is also undecidable under an arbitrary set of axioms. A new systolic algorithm is introduced for term minimisation or term compaction. This is a general-purpose tool for systems using structure sharing. Apart from time and space savings, its use allows subterms to be tested for equality in constant time. The use of compact terms greatly simplifies free term matching and gives rise to a linear-time algorithm with lower processing overheads than the Paterson-Wegman unification algorithm. A sublinear-time solution to the same problem is also given, assuming preloaded data. No existing algorithm for free unification has a sublinear-time implementation and this is related to the notion of a sparse P-complete problem. The complexity of restricted associative-commutative term matching is analysed. Contrary to an earlier conjecture the problem is NP-complete if variables occur at most twice but their number is unrestricted. Parallel methods are suggested as efficient solutions for the | tractable | linear and 1-variable versions of the problem. Results presented here should be useful in the implementation of fast symbolic ma- nipulation systems.