Thèses sur le sujet « Median algebra »

Le sujet de cette thèse est les espaces métriques qu'on appelle espaces médians et la direction principale concerne l'étude des actions isométriques sur les espaces médians complète connexe localement compact et de rang fini. On donne d'abord une caractérisation de la compacité local. Puis, on donne une classification dans cette classes les espaces médians qui admettent une action transitive. On montre qu'un tel espace est nécessairement isométrique à mathbb{R}^n munie de la métrique ell^1. Finalement on montre que si le groupe d'isométrie d'un espace médian X vérifie des condition naturelles, alors les orbites de n'importe quelle action isométrique sur X sont discrètes
The subject of this thesis are median spaces and the main direction concerns the study of isometric actions on complete connected locally compact median space of finite rank. We first give a characterization of the local compactness in this context. Then we give a classification theorem in this class for median spaces which admit a transitive action. We show that such median spaces are necessarily isometric to mathbb{R}^n endowed with the ell^1 metric. Finally, we prove that when the isometry group of a median space X verifies certain conditions, then the orbits of any action on X is discrete

This thesis is about an operator algebraic approach towards the derivation of the electrical conductivity in disordered solid states based on the theory of quantum many-particle systems. Such an approach is of interest since it allows for the description of interacting electron gases, which is a feature not present in previous work. In the context of the description of ergodic media, new concepts are introduced, such as covariant states and covariant morphisms. Moreover, the concept of covariant states is combined with the well-known concept of KMS states. In its covariant form, KMS states describe electron gases in ergodic media at thermal equilibrium. Such states are the starting point of the electron gases considered here. An external electric field is applied to the system, influences the electron gas and causes internal electric currents. Thus, the equilibrium position of the system is disturbed, leading to a time evolution of the system, which is described by covariant automorphisms. Summing up, the system is given in a time dependent, covariant state that acts on the algebra of bounded and local operators on the fermionic Fock space defined over some given one-particle Hilbert space. For a discrete model of an extended electron gas in one space dimension with a pair interaction of finite range, explicit constructions of the above states are presented. In addition, for the special case of non-interacting electron gases, the construction of the time dependent covariant state is carried out in arbitrary space dimension. Since measurements in a quantum system are implemented by the action of its state on bounded, local and self-adjoint operators, the concept of a current density operator is introduced. The current density is then defined as the result of the measurement of the current density operator. By an application of Birkhoff’s ergodic theorem, the transformation law of the current density operator together with the covariant transformation law of the state of the electron gas implies the almost sure existence of the spatial mean of the current density. Moreover, the spatial mean current density is almost surely independent of the concrete realisation given. The electric current density describes the linear dependence of the spatial mean current density on the external electric field, for small strengths. Via linear response theory for the noninteracting model of an electron gas, an explicit expression for the current density is derived in terms of a so called Kubo formula. For the derivation the system needs to satisfy a localisation condition, which is specifically designed for non-interacting electron gases. In view of a linear response theory of interacting electron gases, candidates for a generalisation of this localisation criterion that also apply to interacting systems are introduced.

We investigate what the graphics processing units (GPUs) have to offer compared to the central processing units (CPUs) when solving a sparse linear system of equations. This is performed by using a GPU to simulate fluid-flow in a porous medium. Flow-problems are discretized mainly by the mimetic finite element discretization, but also by a two-point flux-approximation (TPFA) method. Both of these discretization schemes are explained in detail. Example-models of flow in porous media are simulated, as well as CO2 -injection into a realistic model of a sub-sea storage-cite. The linear algebra is solved by the conjugate gradient (CG) method without a preconditioner. The computationally most expensive calculation of this algorithm is the matrix-vector product. Several formats for storing sparse matrices are presented and implemented on both a CPU and a GPU. The fastest format on the CPU is different from the format performing best on the GPU. Implementations for the GPU is written for the compute unified driver architecture (CUDA), and C++ is used for the CPU-implementations. The program is created as a plug-in for Matlab and may be used to solve any symmetric positive definite (SPD) linear system. How a GPU differs from a CPU is explained, where focus is put on how a program should be written to fully utilize the potential of a GPU. The optimized implementation on the GPU outperforms the CPU, and offers a substantial improvement compared to Matlab’s conjugate gradient method, when no preconditioner is used.

Afin de répondre aux besoins de l'industrie pétrolière d'une description plus fine de la géométrie et des propriétés pétrophysiques des bassins et des réservoirs, la simulation numérique des écoulements en milieux poreux doit évoluer vers des algorithmes plus performants et plus robustes vis à vis de la taille des simulations, de la complexité des maillages et des hétérogénéités du milieu poreux. Les méthodes de décomposition de domaine constituent une alternative aux méthodes multigrilles et pourraient permettre de lever les difficultés précédentes en terme de robustesse et d'efficacité sur architectures parallèles. Elles sont par nature plus adaptées au calcul parallèle et sont plus robustes en particulier lorsque les sous domaines sont résolus par des méthodes directes. Elles permettent aussi de traiter dans un cadre unique les couplages de modèles comme les puits ou les failles conductrices et s'étendent au cas des systèmes couplés. Le travail de thèse traite plus particulièrement de méthodes définies au niveau algébrique. On ne suppose pas avoir une connaissance préalable du problème continu dont la matrice provient. On n'a pas non plus accés aux matrices avant assemblage. Ce manque d'informations a priori rend plus difficile la construction de méthodes efficaces. On propose deux nouvelles méthodes de construction de méthodes de décomposition de domaine au niveau algébrique: la construction de conditions d'interface optimisées et d'une grille grossière. Ce dernier point est particulièrement important pour avoir des méthodes robustes vis à vis du nombre des sous-domaines. Les méthodes sont adaptatives et basées sur l'analyse de l'espace de Krylov généré durant les premières itérations de la méthode de Schwarz classique. A partir des vecteurs de Ritz correspondant aux plus basses valeurs propres, on construit des conditions d'interface et des grilles grossières qui annihilent l'erreur sur ces composantes. Les méthodes ont été testées sur des calculateurs parallèles pour des matrices issues de la simulation de milieux poreux.

The thesis presents a research that focuses on how children's learning processes occur when algebra is introduced as a language-in-use. The research incorporates graphic calculators as a means for providing children with a computing environment where communication is held by using a symbolic language similar in syntax and notation to the algebraic code. The use of calculators is shaped by a set of tasks specifically designed for this study. The tasks are arranged in order to simulate the social processes through which children learn the mother tongue. The design of the learning environment is based on Bruner's research on children's language acquisition. According to this, the major aim of the study is to investigate the ways in which the calculator's symbolic code shapes children's expressions of general relationships, and more specifically the kinds of notions and strategies that children develop through using calculator language. The study seeks for an explanatory framework that might provide a better understanding of the potential of technological resources in the teaching of algebra. The study drew promising results that provide evidence for an alternative approach to teaching algebra. The thesis offers a discussion of the theoretical background and its relationship with the teachina method. It also provides an analysis of children's achievements and difficulties.

Es ist eine weit verbreitete Wahrnehmung, dass der Übergang zwischen der Mathematik der gymnasialen Oberstufe und der Mathematik an der Universität für Studierende problematisch sein kann. Besondere Verständnisschwierigkeiten in Bereich der lineare Algebra (lA) bereiten den Studierenden die verschiedenen Herangehensweisen auf diesen beiden Ebenen. Dies lässt sich auf die strukturell-axiomatischer Herangehensweisen an die lA an der Universität, im Gegensatz zu ihrer arithmetisch-geometrischen Darstellung in der Schule, zurückführen. Dies bedingt ebenfalls Unterschiede im prozeduralen und konzeptuellen Verständnis. Ziel dieser Arbeit ist es, zu untersuchen, wie Schüler konzeptuelles Verständnis, Bezug nehmend auf die Theorien von concept definition/image in Verbindung mit multiplen Modi der Beschreibung und des Denkens von Konzepten wie Bilinearität z.B. Skalarprodukt und Multilinearität z.B. Determinanten gewinnen können. Um dies zu erreichen wurde eine substanzielle Lehr-Lernumgebung unter Verwendung einer dynamischen Geometriesoftware (DGS) entwickelt. Die Lerneinheit wurde an einem Berliner Gymnasium eingesetzt und dabei ein vollständiger design-based research Zyklus durchlaufen und eine multiple-level Datenanalyse durchgeführt. Die Ergebnisse der Untersuchung zeigen nicht nur, dass eine Erweiterung der Vorstellungen der Schüler, eine Entwicklung multipler Denkmodi und ein Gewinn tieferen konzeptuellen Verständnisses in der lA erfolgreich vermittelt werden können, sondern geben auch Einblicke in ein mögliches theoretisches Modell, mit dessen Hilfe sich diese Prozesse weiter untersuchen lassen. Weiterhin werden die interaktiven Lehr-Lernmaterialien für die weitere Verwendung im Rahmen von Lehre und Forschung zur Verfügung gestellt. Es öffnen sich neue Forschungsfragen hinsichtlich lokalen Axiomatisierens in der lA der gymnasialen Oberstufe, welches auf einer Integration geometrischer, algebraischer und axiomatischer Denkmodi, unterstützt durch DGS, basieren könnte.
A common perception among researchers in mathematics education is that the transition between secondary- and tertiary level of mathematics may be problematic for the students. In particular, the exact and abstract nature of the theory of Linear algebra versus its arithmetic-geometric presentation in school appears to be difficult for the novice students. The application of properties for defining concepts at university in contrast to their usage for describing concepts in school points out a possible occurrence of obstacles for learning and discrepancies in procedural and conceptual understanding. The aim of this study is to examine how could upper-high school students develop a conceptual understanding based on concept definition and concept image in connection to multiple modes of description and thinking about concepts such as bi-linearity exemplified by the dot product of vectors and multi-linearity exemplified by determinants. In order to achieve this, I have created a specific teaching/ learning sequence in a dynamic geometry environment (DGE), then implemented it and evaluated it in a high school in Berlin, following a complete cycle of design-based research and conducting a multiple-level data analysis. The findings of the study show not only that widening students' concept images, developing multiple modes of thinking and gaining deeper conceptual understanding can successfully be mediated by dynamic geometries, but also give insights into an eventual theoretical model of how can they be further examined. Moreover, the study promotes authorized open-source interactive teaching/ learning materials for further sustainable practice and research. It opens new research questions about revisiting axiomatic approaches on local levels in upper high-school Linear algebra which may base on the integration of all three modes of description and thinking geometric, algebraic and abstract possibly facilitated by DGE.
Честа перцепција кај многумина истражувачи во областа на математичкото образование е дека транзицијата помеѓу средното и високото образование по математика може да биде проблематична за студентите. Егзакноста и апстрактноста на теоријата по Линеарна алгебра наспроти нејзината аритметичко-геометриска презентација во средното гимназиско образование се покажува како особено тешка за студентите. Примена на својствата на математичките поими за нивно дефинирање на универзитетско ниво наспроти нивното употреба за опишување на претходно дефинирани поими на училишно ниво, укажува на можна појава на тешкотии при нивното изучување и несовпаѓање на процедуралното и концептуалното разбирање на истите. Целта на оваа студија е да истражи како средношколците би можеле да развијат концептуално разбирање на поимите врз основа на концепт дефиниција и концепт слика во врска со мулти-моди на мислење, конкретно за поими како билинеарност, пр. скаларен производ на вектори, и мултилинеарност, пр. детерминанти. За да ја постигнам оваа цел, креирав наставна содржина поддржана од еден динамичен геометриски систем (ДГС) и следејќи целосен циклус на т.н. design-based research и спрoведувајќи мулти-анализа на податоци, истата ја имплементирав и евалуирав во едно средно училиште во Берлин. Резултатите од студијата укажуваат не само на фактот дека проширувањето на концепт сликите на учениците, развојот на мулти-моди на мислење и стекнувањето на длабоко концептуално разбирање на поимите можат да бидат успешно посредувани од ДГС туку овозможија и увид во еден теоретски модел за тоа коко тие можат понатаму да се истражуваат. Уште повеќе, студијата промовира авторизирани open-source интерактивни материјали за предавање и учење на содржините кои може да служат за понатамошни одржливи истражувања и развој. Студијата отвора нови истражувачки прашања за средношколската Линеарна алгебра која може да се базира на интеграција на сите три моди на мислење, геометриски, алгебарски и апстрактен, поддржан од ДГС.

The purpose of this quasi-experimental study was to investigate the effect of using Twitter by high school mathematics students learning linear equations in Algebra 1. This quasi-experimental study used ninth grade Algebra 1 classes that were learning linear equations for 18 school days. First, the nonequivalent control group design, a pretest-posttest quasi-experimental design, was used in this quasi-experimental study. The research hypotheses were tested using a factorial analysis of covariance (ANCOVA) with the pretest on linear equations score as the covariate. The control group had three classes (n = 73) and the experimental group had three classes (n = 78). The experimental group received tweets on a daily basis as students learned linear equations. The tweets contained mathematical content, classroom logistics, or both. Lastly, the control group received the same information in class. The quantitative findings of this quasi-experimental study show that overall Twitter, content tweets, logistics tweets, and tweets containing both (content and logistics) did not have a statistically significant effect on the mean linear equations posttest score. Second, this quasi-experimental study looked at students’ performance on various subtopics throughout the unit. The ANCOVA showed that there were no statistically significant differences between the control group and the experimental groups in most of the quizzes. However, statistically significant differences were found in Quiz #2 and Quiz #4 among the logistics groups. Third, the experimental group took a 10-item survey. The purpose of survey was to understand the students’ opinion of using Twitter as they learned course content in Algebra 1. It can be concluded from the results of that survey that students had, for the most part, a positive attitude towards using Twitter as part of learning mathematics in high school. In conclusion, the use of Twitter is not likely to show an increase in students’ mean posttest linear equations score. However, the findings of the survey conducted after the study did show that the use of Twitter might be able to increase student motivation. The results of this quasi-experimental study made major contributions to the literature by investigating the effects of using Twitter in high school Algebra 1.

Zugl.: Kassel, Universiẗat, Diss., 1997 u.d.T.: Scheuermann, Hellmut: Entwicklung von anwendungsbezogenen Aufgaben für den computerunterstützten Analysisunterricht in der Fachoberschule und Erfahrungen beim unterrichtlichen Einsatz unter Verwendung des Computer-Algebra-Systems DERIVE.

L’imagerie polarimétrique de Mueller est une technique optique émergente pour la diagnostique non invasive des tissus. Cette technique optique explore la très haute sensibilité de la lumière polarisée sur la microstructure d’un échantillon et fournit des informations les plus complètes sur les propriétés polarimétriques de cet échantillon.Premièrement, le potentiel du microscope Mueller à transmission fonctionnant dans la gamme du spectre visible pour l’analyse histologique automatisé a été étudié sur des coupes non colorées d’équivalents de peaux humaines. La décomposition logarithmique des matrices de Mueller expérimentales a été combinée à l’algorithme statistique du clustering basé sur la densité des points dans l’espace paramétrique pour les applications avec bruit (DBSCAN) pour la segmentation diagnostique des images microscopiques des modèles de peau humaine. La validité du formalisme de Mueller différentiel pour les milieux dépolarisants homogènes fluctuants a été confirmée expérimentalement pour les tissus biologiques. Une nouvelle méthode est suggérée pour modérer l’impact de la variation d’épaisseur qui pourrait affecter la précision des diagnostique polarimétrique des coupes histoligiques. Une nouvelle version de l’algorithme DBSCAN a été développée pour réduire les temps de calculs et ainsi permettre d’analyserles ensembles de données de grande taille. Dans ces ensembles de données, les valeurs aberrantes (ou bruit) ont été filtrées efficacement, le contraste entre les zones dermiques et épidermiques de peau humaine a été considérablement augmenté. En utilisant la méthode Monte Carlo polarisée pour modéliser les matrices de Mueller expérimentales pour les coupes minces de modèles de peaux humaine, nous avons confirmé que le dichroïsme linéaire et l'anisotropie de la dépolarisation détectés dans la zone dermique sont dus à la présence de fibres de collagène bien alignées.Les études ex-vivo de la preuve de principe de la sensibilité de la lumière polarisée rétrodiffusée à une structure hautement ordonnée de substance blanche cérébrale saine sont présentées dans la deuxième partie. Des coupes épaisses de cerveau humain fixées au formol, et de la cervelle de veau fraiche ont été imagées en mode réflexion avec un polarimètre de Mueller à grand champ, opérant dans la gamme de longueurs d’onde visibles.Il est connu que les tumeurs cérébrales rompent la structure hautement ordonnée de la substance blanche du cerveau, car les cellules tumorales se développent de manière chaotique. Cependant, cette différence de complexité structurelle est difficilement détectable, même avec un microscope opératoire, pendant la neurochirurgie en raison du faible contraste visuel entre la tumeur et le tissu cérébral sain. Nous avons étudié la capacité de l’imagerie polarimétrique de Mueller à grand champ à visualiser les faisceaux de fibres de la substance blanche cérébrale saine en détectant l'anisotropie de son indice de réfraction (c'est-à-dire la biréfringence de la substance blanche du cerveau qui sera effacée par la tumeur). Les matrices de Mueller expérimentales d’échantillons de cerveau ont été traitées à l’aide de l’algorithme de décomposition Lu-Chipman. Les cartes des azimuts de l’axe optique du milieu biréfringent uniaxial corrèlent incontestablement avec les images microscopiques des coupes histologiques des tissus cérébraux colorées à l’argent, qu’est la technique de référence pour la visualisation ex-vivo des faisceaux de fibres de substance blanche du cerveau.Ces résultats montrent le potentiel de l’imagerie polarimétrique de Mueller à grand champ pour fournir des informations sur l'orientation spatiale relative des faisceaux de fibres cérébrales, ce qui aiderait à détecter la frontière exacte entre la tumeur et le tissu cérébral saine, et guiderait le neurochirurgien lors de la résection de la tumeur et améliorerait les résultats pour des patients
Imaging Mueller polarimetry represents an emerging optical technique for a non-invasive diagnostics of tissue. This optical modality explores the extreme sensitivity of polarized light to the microstructure of a sample under study and provides the most complete information on sample polarimetric properties.First, the potential of the transmission Mueller microscope operating in the visible wavelength range for digital histology analysis was studied on the unstained histological sections of human skin equivalents. Logarithmic decomposition of the experimental Mueller matrices was combined with the statistical density-based clustering algorithm for the applications with noise (DBSCAN) for diagnostic segmentation of the microscope images of human skin models. The validity of the differential Mueller matrix formalism for fluctuating homogenous depolarizing media was confirmed experimentally for biological tissue. An original method was suggested to mitigate the impact of thickness variation that could affect the accuracy of polarimetric diagnostics of thin tissue sections. A new version of the DBSCAN algorithm was developed to reduce the calculation time and, thus, to allow clustering of large size datasets. When dataset outliers (noise) were effectively filtered out, the contrast between the dermal and epidermal zones of human skin equivalents was significantly increased. Polarized Monte Carlo modeling of the experimental Mueller matrices of thin sections of human skin equivalents confirmed that both linear dichroism and anisotropy of depolarization detected within the dermal zone are due to the presence of well-aligned collagen fibers.The ex-vivo proof-of-principle studies of the sensitivity of backscattered polarized light to the highly ordered structure of healthy brain white matter are presented in the second part. The thick sections of the formalin-fixed human brain and fresh calf brain were imaged in reflection configuration using wide-field imaging Mueller polarimeter operating in the visible wavelength range. It is known that brain tumors break the highly ordered structure of brain white matter because tumor cells grow in a chaotic way. However, this difference in structural complexity is hardly detectable with a state-of-the-art operative microscope during neurosurgery because of low visual contrast between tumor and healthy brain tissue. We studied the capability of the wide-field imaging Mueller polarimetry to visualize the fiber tracts of healthy brain white matter by detecting the anisotropy of its refractive index (i.e. birefringence of brain white matter that will be erased by tumor). The experimental Mueller matrices of brain specimens were processed using the algorithm of Lu-Chipman polar decomposition. The maps of the azimuth of the optical axis of uniaxial linear birefringent medium demonstrated the compelling correlation with the microscopy images of silver-stained histological sections of brain tissue that is a gold standard technique for the visualization of brain white matter fiber tracts ex-vivo. These results show the potential of wide-field imaging Mueller polarimetry to provide information on the relative spatial orientation of brain fiber tracts, which can help to detect the exact border between the tumor and surrounding brain tissue, guide neurosurgeon during tumor resection and improve patient outcomes

This thesis is an examination of the printed media in France (1955-1963), as represented by two mainstream newspapers: Le Monde (left-centrist) and Le Figaro (right-centrist). Using these newspapers, as well as Gallup polls recorded at the time, this study explores correlations of what was reported in newspapers and how French public opinion evolved during the course of the war. These two major sources of information are shown to have given contradictory information, thus accounting for some of the paradoxes found in public opinion polls. Specifically, the paradoxes analyzed in the study concern the Front de Libération Nationale (FLN) and the Pieds-Noirs (the European population of North Africa).

The ongoing European Refugee Crisis has been one of the most popular trending topics on Twitter for the past 8 months. This paper applies topic modeling on bulks of tweets to discover the hidden patterns within these social media discussions. In particular, we perform topic analysis through solving Non-negative Matrix Factorization (NMF) as an Inexact Alternating Least Squares problem. We accelerate the computation using techniques including tweet sampling and augmented NMF, compare NMF results with different ranks and visualize the outputs through topic representation and frequency plots. We observe that supportive sentiments maintained a strong presence while negative sentiments such as safety concerns have emerged over time.

O presente trabalho visa entender como o rádio se distingue dos demais sons do mundo. A hipótese aqui formulada é a de que o rádio, em sua definição, é uma linguagem, e não um aparelho. Dessa maneira, há a busca por uma caracterização da linguagem radiofônica seguindo as ideias implicadas em uma Estética da Linguagem (Derrida e antiessencialistas como Ziff, Weitz e Kennick). Com isso, há um estudo detalhado do rádio em seu jogo de linguagem (Wittgenstein) e em seus diferendos (Lyotard), considerados aqui enquanto parergon e ergon, ou seja, enquanto recorte e modelo operacional da linguagem em sua intersecção com o mundo. Para a investigação do jogo de linguagem, foram utilizados conteúdos relacionados à Filosofia Analítica, à Lógica Algébrica e à Teoria dos Jogos para desenvolver um método analítico denonimado Jogo Lógico, voltado para o estudo de jogos de linguagem comunicacionais. Já para a investigação dos diferendos, foram utilizadas as ideias pragmáticas acerca da performatividade e da lógica ilocucionária (Austin e Searle) para analisar os gêneros radiofônicos (a saber: musical, radiojornalismo, esportivo, variedades [talk radio], humorístico, ficção e publicidade). Essas duas investigações formam aquilo que é chamado aqui de Gramática do Rádio - considerando o conceito wittgensteiniano de gramática -, o ponto nodal que nos permite caracterizar o rádio enquanto linguagem.
The present work aims to understand how the radio distinguishes itself from other sounds of the world. The hypothesis formulated here is that the radio, in its definition, is a language, not a machine. Thus, there is the search for a characterization of radio\'s language following the ideas involved in an Aesthetics of Language (Derrida and anti-essentialists like Ziff, Weitz and Kennick). Here, there is a detailed study of the radio in its language-game (Wittgenstein) and their differends (Lyotard), considered in this work as parergon and ergon, i.e. as the cut and the operational model of language in its intersection with the world. For the investigation of the language-game, we used content related to Analytic Philosophy, to Algebraic Logic, and to Game Theory to develop an analytical method called Logic Game, dedicated to the communicative language-games\' study. As for the investigation of differends, we used the pragmatic concepts about the performative and illocutionary logic (Searle and Austin) to analyze the radio genres (ie: music, radio journalism, sports, talk radio, humor, fiction and advertising). These two studies form what is called here the Radio Grammar - considering the Wittgensteinian concept of grammar - the key point that allows us to characterize the radio as a language.

Escoamentos multifásicos em meios porosos são modelados por um sistema de equações diferenciais parciais e o estudo da aproximação das soluções dessas equações desempenha papel crucial na simulação e previsão de problemas de grande interesse prático e impacto econômico e social, tais como a recuperação secundária de petróleo, o armazenamento geológico de CO2 e o transporte de poluentes em aquíferos. O presente trabalho tem como objetivo o desenvolvimento de um simulador numérico tridimensional para avaliar com precisão o transporte de dois fluidos imiscíveis em um meio poroso heterogêneo e que utiliza computação paralela multithread para computadores multiprocessados de memória compartilhada. O sistema de equações diferenciais parciais é decomposto em um subsistema elíptico para a determinação do campo de velocidades dos fluidos e uma equação hiperbólica não-linear para o transporte das fases fluidas. Para esta última, foi utilizado um método numérico de volumes finitos, não-oscilatório de alta ordem baseado em esquemas centrais e que admite uma formulação semi-discreta com coeficientes variáveis no espaço. Experimentos numéricos em modelos tridimensionais foram realizados considerando problemas de escoamentos lineares e não lineares postos em configurações típicas de simulação de reservatórios de petróleo. Os resultados mostraram-se satisfatórios por apresentarem conservação da massa, boa captura das ondas de choque e pequena difusão numérica, independente do passo de tempo.
Multiphase flows in porous media are modeled by a system of partial differential equations and the study of the numerical approximation to the solutions of these plays a crucial role in the simulation and prediction of problems that are of great practical interest and of economic and social impact, such as secondary oil recovery, geological storage of CO2 and transport of pollutants in aquifers. The goal of this work is the development of a three-dimensional numerical simulator that precisely evaluates the transport of two immiscible fluids in a heterogeneous porous media using multithread parallel programming to shared memory multiprocessors computers. The system of partial differential equations is decomposed into a elliptic subsystem used to determine the velocity field and into a hyperbolic equation (nonlinear) to determine the transport of the fluid phases. The approximation to the solution of the latter one is calculated using a high order non-oscillatory finite-differences numerical method based on central schemes that allows a semi-discrete formulation which an extension that enables to work with variable space coefficients. Numerical experiments on three-dimensional models were performed considering linear and nonlinear flow problems in typical settings of oil reservoirs simulations. The results were satisfactory since they presented mass conservation, precise capture of shock waves and small numeric diffusion, regardless of the time step.

acase@tulane.edu
This essay seeks a more robust understanding of the ways in which domestic Islamic radicalization is presented and discussed in the French public sphere. It illuminates the ways in which the print media across the political spectrum has taken a historical amnesic approach to representing the causes and origins of domestic radicalization, neglecting to convey the significant postcolonial and neocolonial dimensions, and instead employing a selective and misrepresentative discourse that over-simplifies the crucial dynamics of the issue. In doing so, it not only explores the communicative frameworks of a phenomenon that in recent years has come to the forefront of national security issues, but also comments on the larger socio-political trends that have led to such a unified approach to emerge across the political spectrum of France’s otherwise pluralistic press landscape. Analyzing the period between 1995 and the present day, this essay draws from the archives of three major newspapers in France (Le Monde, Le Figaro, and Libération) and focuses on three major incidents of domestic Islamic radicalization to examine the methods by and reasons why newspapers across the political spectrum represent the dynamics and causes of domestic Islamic radicalization in such a formulaic and repetitive nature.
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Charles Tarpey