Truncation error estimation in the Discontinuous Galerkin Spectral Element Method

En esta tesis, el método de estimación de error de truncación conocido como restimation ha sido extendido de esquemas de bajo orden a esquemas de alto orden. La mayoría de los trabajos en la bibliografía utilizan soluciones convergidas en mallas de distinto refinamiento para realizar la estimación. En este trabajo se utiliza una solución en una única malla con distintos órdenes polinómicos. Además, no se requiere que esta solución esté completamente convergida, resultando en el método conocido como quasi-a priori T-estimation. La aproximación quasi-a priori estima el error mientras el residuo del método iterativo no es despreciable. En este trabajo se demuestra que algunas de las hipótesis fundamentales sobre el comportamiento del error, establecidas para métodos de bajo orden, dejan de ser válidas en esquemas de alto orden, haciendo necesaria una revisión completa del comportamiento del error antes de redefinir el algoritmo. Para facilitar esta tarea, en una primera etapa se considera el método conocido como Chebyshev Collocation, limitando la aplicación a geometrías simples. La extensión al método Discontinuouos Galerkin Spectral Element Method presenta dificultades adicionales para la definición precisa y la estimación del error, debidos a la formulación débil, la discretización multidominio y la formulación discontinua. En primer lugar, el análisis se enfoca en leyes de conservación escalares para examinar la precisión de la estimación del error de truncación. Después, la validez del análisis se demuestra para las ecuaciones incompresibles y compresibles de Euler y Navier Stokes. El método de aproximación quasi-a priori r-estimation permite desacoplar las contribuciones superficiales y volumétricas del error de truncación, proveyendo información sobre la anisotropía de las soluciones así como su ratio de convergencia con el orden polinómico. Se demuestra que esta aproximación quasi-a priori produce estimaciones del error de truncación con precisión espectral. ABSTRACT In this thesis, the τ-estimation method to estimate the truncation error is extended from low order to spectral methods. While most works in the literature rely on fully time-converged solutions on grids with different spacing to perform the estimation, only one grid with different polynomial orders is used in this work. Furthermore, a non timeconverged solution is used resulting in the quasi-a priori τ-estimation method. The quasi-a priori approach estimates the error when the residual of the time-iterative method is not negligible. It is shown in this work that some of the fundamental assumptions about error tendency, well established for low order methods, are no longer valid in high order schemes, making necessary a complete revision of the error behavior before redefining the algorithm. To facilitate this task, the Chebyshev Collocation Method is considered as a first step, limiting their application to simple geometries. The extension to the Discontinuous Galerkin Spectral Element Method introduces additional features to the accurate definition and estimation of the error due to the weak formulation, multidomain discretization and the discontinuous formulation. First, the analysis focuses on scalar conservation laws to examine the accuracy of the estimation of the truncation error. Then, the validity of the analysis is shown for the incompressible and compressible Euler and Navier Stokes equations. The developed quasi-a priori τ-estimation method permits one to decouple the interfacial and the interior contributions of the truncation error in the Discontinuous Galerkin Spectral Element Method, and provides information about the anisotropy of the solution, as well as its rate of convergence in polynomial order. It is demonstrated here that this quasi-a priori approach yields a spectrally accurate estimate of the truncation error.

Da tradução ou não de pronomes e partículas pronominais do Italiano ao Português: algumas escolhas feitas por dois tradutores

Este estudo é movido pela curiosidade quanto a como se resolvem, nas traduções do italiano para o português, questões de colocação pronominal. Encontramos, normal e frequentemente, na língua italiana, principalmente na língua falada, pronomes cujos equivalentes em português existem em gramáticas normativas da língua portuguesa, mas que, na prática, não são utilizados pelos falantes e escritores brasileiros. Encontramos, também, na língua italiana, um significativo número de verbos pronominais (como esserci, volerci, averne etc.) e um considerável número de verbos pronominais múltiplos (como andarsene, farcela, fregarsene etc.) que, juntamente com esses pronomes, constituem, para os professores brasileiros de italiano língua estrangeira (LE), elementos difíceis de trabalhar na sala de aula. Além disso, tais elementos também podem dificultar o trabalho dos tradutores, que devem fazer determinadas escolhas ao traduzi-los para o português. Como são traduzidos os pronomes combinados do italiano nas versões brasileiras? Será que os portugueses, que possuem, por exemplo, tais pronomes utilizam-nos em todos os casos em que os encontramos nos textos de partida? E as partículas pronominais são simplesmente eliminadas no texto de chegada ou são substituídas? Tais aspectos, se observados e organizados, podem levar a uma melhor compreensão das duas línguas em contato e dar subsídios a estudantes, professores e tradutores. Pensando nessa dificuldade, esta pesquisa buscou e listou alguns autores e obras disponíveis para consulta e analisou um corpus com cento e sessenta e três ocorrências de pronomes no italiano, mais sete acréscimos de pronomes no português brasileiro (PB) e/ou português europeu (PE), partindo do romance Uno, nessuno e centomila de Luigi Pirandello e suas respectivas traduções em PB e PE. Nosso objetivo consiste em encontrar respostas úteis à diminuição do estranhamento, por parte de um italiano, que escuta, de um brasileiro, frases sem pronomes (ainda que o italiano as entenda) e/ou a sensação de inadequação e, até mesmo, de desconforto, por parte de um brasileiro, ao produzir frases com todos os pronomes. No corpus analisado, temos uma amostra das escolhas e respectivas traduções propostas pelos tradutores para casos de pronomes reflexivos, de pronomes pessoais do caso reto, de pronomes pessoais do caso oblíquo, de pronomes combinados e de partículas pronominais ne, ci e vi, com manutenções, omissões, trocas por outros pronomes (possessivos, retos, oblíquos, demonstrativos) e, até mesmo, uma espécie de compensação numérica com a inclusão de palavra inexistente no texto de partida.

Logic-Based Outer Approximation for the Design of Discrete-Continuous Dynamic Systems with Implicit Discontinuities

We address the optimization of discrete-continuous dynamic optimization problems using a disjunctive multistage modeling framework, with implicit discontinuities, which increases the problem complexity since the number of continuous phases and discrete events is not known a-priori. After setting a fixed alternative sequence of modes, we convert the infinite-dimensional continuous mixed-logic dynamic (MLDO) problem into a finite dimensional discretized GDP problem by orthogonal collocation on finite elements. We use the Logic-based Outer Approximation algorithm to fully exploit the structure of the GDP representation of the problem. This modelling framework is illustrated with an optimization problem with implicit discontinuities (diver problem).

Amélioration a posteriori de la traduction automatique par métaheuristique

La traduction automatique statistique est un domaine très en demande et où les machines sont encore loin de produire des résultats de qualité humaine. La principale méthode utilisée est une traduction linéaire segment par segment d'une phrase, ce qui empêche de changer des parties de la phrase déjà traduites. La recherche pour ce mémoire se base sur l'approche utilisée dans Langlais, Patry et Gotti 2007, qui tente de corriger une traduction complétée en modifiant des segments suivant une fonction à optimiser. Dans un premier temps, l'exploration de nouveaux traits comme un modèle de langue inverse et un modèle de collocation amène une nouvelle dimension à la fonction à optimiser. Dans un second temps, l'utilisation de différentes métaheuristiques, comme les algorithmes gloutons et gloutons randomisés permet l'exploration plus en profondeur de l'espace de recherche et permet une plus grande amélioration de la fonction objectif.

Amélioration a posteriori de la traduction automatique par métaheuristique

La traduction automatique statistique est un domaine très en demande et où les machines sont encore loin de produire des résultats de qualité humaine. La principale méthode utilisée est une traduction linéaire segment par segment d'une phrase, ce qui empêche de changer des parties de la phrase déjà traduites. La recherche pour ce mémoire se base sur l'approche utilisée dans Langlais, Patry et Gotti 2007, qui tente de corriger une traduction complétée en modifiant des segments suivant une fonction à optimiser. Dans un premier temps, l'exploration de nouveaux traits comme un modèle de langue inverse et un modèle de collocation amène une nouvelle dimension à la fonction à optimiser. Dans un second temps, l'utilisation de différentes métaheuristiques, comme les algorithmes gloutons et gloutons randomisés permet l'exploration plus en profondeur de l'espace de recherche et permet une plus grande amélioration de la fonction objectif.

Advances in distributed parameter approach to the dynamics and control of activated sludge processes for wastewater treatment

This paper presents a review of modelling and control of biological nutrient removal (BNR)-activated sludge processes for wastewater treatment using distributed parameter models described by partial differential equations (PDE). Numerical methods for solution to the BNR-activated sludge process dynamics are reviewed and these include method of lines, global orthogonal collocation and orthogonal collocation on finite elements. Fundamental techniques and conceptual advances of the distributed parameter approach to the dynamics and control of activated sludge processes are briefly described. A critical analysis on the advantages of the distributed parameter approach over the conventional modelling strategy in this paper shows that the activated sludge process is more adequately described by the former and the method is recommended for application to the wastewater industry (c) 2006 Elsevier Ltd. All rights reserved.

On functionally-fitted Runge-Kutta methods

Functionally-fitted methods are generalizations of collocation techniques to integrate an equation exactly if its solution is a linear combination of a chosen set of basis functions. When these basis functions are chosen as the power functions, we recover classical algebraic collocation methods. This paper shows that functionally-fitted methods can be derived with less restrictive conditions than previously stated in the literature, and that other related results can be derived in a much more elegant way. The novelty in our approach is to fully retain the collocation framework without reverting back into derivations based on cumbersome Taylor series expansions.

Analysis of trigonometric implicit Runge-Kutta methods

Using generalized collocation techniques based on fitting functions that are trigonometric (rather than algebraic as in classical integrators), we develop a new class of multistage, one-step, variable stepsize, and variable coefficients implicit Runge-Kutta methods to solve oscillatory ODE problems. The coefficients of the methods are functions of the frequency and the stepsize. We refer to this class as trigonometric implicit Runge-Kutta (TIRK) methods. They integrate an equation exactly if its solution is a trigonometric polynomial with a known frequency. We characterize the order and A-stability of the methods and establish results similar to that of classical algebraic collocation RK methods. (c) 2006 Elsevier B.V. All rights reserved.

An action research study with low proficiency learners in Japan to promote the learning of vocabulary through collocations.

This action research (AR) study explores an alternative approach to vocabulary instruction for low-proficiency university students: a change from targeting individual words from the general service list (West, 1953) to targeting frequent verb + noun collocations. A review of the literature indicated a focus on collocations instead of individual words could potentially address the students’ productive challenges with targeted vocabulary. Over the course of four reflective cycles, this thesis addresses three main aspects of collocation instruction. First, it examines if the students believe studying collocations is more useful than studying individual lexical items. Second, the thesis investigates whether a focus on collocations will lead to improvements in spoken fluency. This is tested through a comparison of a pre-intervention spoken assessment task with the findings from the same task completed 15 weeks later, after the intervention. Third, the thesis explores different procedures for the instructing of collocations under the classroom constraints of a university teaching context. In the first of the four reflective cycles, data is collected which indicates that the students believe a focus on collocations is superior to only teaching individual lexical items, that in the students’ opinion their productive abilities with the targeted structures has improved, and that delexicalized verb collocations are problematic for low-proficiency students. Reflective cycle two produces evidence indicating that productive tasks are superior to receptive tasks for fluency development. In reflective cycle three, productively challenging classroom tasks are investigated further and the findings indicate that tasks with higher productive demands result in greater improvements in spoken fluency. The fourth reflective cycle uses a different type of collocation list: frequent adjective + noun collocations. Despite this change, the findings remain consistent in that certain types of collocations are problematic for low-proficiency language learners and that the evidence shows productive tasks are necessary to improve the students’ spoken ability.

Collocations

J R Firth first gave prominence to collacation in linguistic theory. Halliday, Sinclair, Stubbs, and Hoey have all extended Firth's ideas. Palmer and Hornby recognized the pedagogical value of collocation, and incorporated it into their early EFL dictionaries. More recent EFL dictionaries, based on large, computerized language corpora, have used complex software and statistical measures to gain further insights into the way that collocational patterns are woven into language, and the results are visible in the dictionary entries of later editions. This has fed back into language pedagogy, and is also influencing translation and computational research. © 2006 Elsevier Ltd. All rights reserved.

On the F word:a corpus-based analysis of the media representation of feminism in British and German press discourse, 1990-2009

Research in social psychology has shown that public attitudes towards feminism are mostly based on stereotypical views linking feminism with leftist politics and lesbian orientation. It is claimed that such attitudes are due to the negative and sexualised media construction of feminism. Studies concerned with the media representation of feminism seem to confirm this tendency. While most of this research provides significant insights into the representation of feminism, the findings are often based on a small sample of texts. Also, most of the research was conducted in an Anglo-American setting. This study attempts to address some of the shortcomings of previous work by examining the discourse of feminism in a large corpus of German and British newspaper data. It does so by employing the tools of Corpus Linguistics. By investigating the collocation profiles of the search term feminism, we provide evidence of salient discourse patterns surrounding feminism in two different cultural contexts. © The Author(s) 2012.

A colocação de pronomes clíticos em sentenças infinitivas preposicionadas na escrita brasileira dos séculos XIX e XX

In this work we present the description and analysis of the clitics collocation patterns in prepositional infinitive sentences within the Brazilian writing in the centuries XIX and XX. The corpus in analysis is comprised of letters of newspaper readers and newspaper writers, as well as of advertisements (ads) taken from Brazilian newspapers from different regions / states – Rio de Janeiro, Bahia, Ceará and Pernambuco – and written in the Centuries XIX and XX. They belong to the common minimum corpus of the project named Projeto para a História do Português Brasileiro (PHPB or Project to the History of the Brazilian Portuguese, in English). Its analysis is based on theoreticalmethodological postulates of the Theory of Variation and Change (WEINREICH; LABOV; HERZOG, 1968[2006]; LABOV, 1972[2008]); on the Theory of Principles and Parameters (CHOMSKY, 1981, 1986) and on the model of Grammar Competition (KROCH, 1989; 2001). By trying to articulate those presuppositions from both the theories we present a proposition of theoretical interface between the Variation Theory and the Grammar one. Concerning the empirical results achieved by means of this research, we could figure that, in the context in which there were prepositional infinitive sentences, the most significant independent variable to the occurrence of the proclisis is the type of preposition that comes before the verb in the infinitive. Before that, we found out that there are prepositions which strongly direct the proclisis, as it is the case of the prepositions in Portuguese sem, por, de and para, with all of them presenting Relative Weights over 0,52. Another important result is the one attested in the data referring the state of Rio de Janeiro (RJ). This state is the only one of the sample which is located in the Southeastern region and also presents itself as the main proclisis conditioner amongst the localities pertaining to the sample. In order to explain those results, we raised the hypothesis that the proclisis implementation may be more advanced in the Southeastern than in the Northeastern Brazil, however that hypothesis must be confirmed or refuted in future works. We also present, in this work, a theoretical explanation about the clitics colocation in prepositional infinitive sentences within the Brazilian writing in the XIX and XX centuries. The theoretical explanation we found to interpret the achieved results associates Magro’s proposition (2005), regarding the existence of prepositions occupying the nucleus PP and the existence of prepositions which can play the role of a completer and occupy the nucleus CP, according to Galves (2000; 2001), regarding the existent relation between the clitic colocation and the association of traits-phi to the functional categories COMP, Tense and Person. Our proposition is that the occurrence of prepositions which occupy the nucleus CP causes changes in the values attributed to the traits-phi and to the strong Vtraits in the functional categories COMP, Tense and Person. Thus, we defend that proclisis in Brazilian Portuguese (BP) is derived from the movement of the verb to the functional category tense in which there is the association of traits +V and traits +AGR, what legitimates the proclisis according to Galves´s proposition (2000; 2001).

Paraphrasage des liens de fonctions lexicales

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Paraphrasage des liens de fonctions lexicales

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

La fijación léxica en el "Corpus diacrónico del español del Reino de Granada (CORDEREGRA)"

El estudio de las combinaciones léxicas según su grado de fijación y su distinción en combinaciones libres, colocaciones y locuciones ha sido realizado desde la perspectiva sincrónica. Planteamos la posibilidad de aplicar las pautas para distinguir estos tipos de estructuras en materiales de tipo diacrónico. Concretamente, nos basamos en los documentos que componen el Corpus del Español del Reino de Granada (CORDEREGRA) para valorar los materiales de este corpus histórico-lingüístico y comprobar si los criterios sincrónicos se pueden aplicar al estudio de documentos de otros siglos.