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Análise de confiabilidade geotécnica de estruturas de contenção em balanço executadas em areia / Geotechnical reliability analysis of cantilever pile walls in sandFlorêncio, Luiz Augusto da Silva 26 February 2018 (has links)
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Previous issue date: 2018-02-26 / Estruturas geotécnicas estão sujeitas a incertezas decorrentes da variabilidade
natural do solo e do conhecimento limitado dos diversos eventos envolvidos. Nesse
sentido, a avaliação de incertezas em projetos geotécnicos pode ser feita mediante
aplicação da teoria da confiabilidade. Entretanto, apesar da adoção de analises
probabilísticas em normas internacionais e pesquisas científicas, pode-se dizer que,
no Brasil, sua aplicação ainda é escassa, especialmente, em estruturas de
contenção. Desse modo, nesse trabalho apresenta-se um estudo sobre
confiabilidade geotécnica de contenções de estacas em balanço executadas em
areia. Rotinas de cálculo computacional para análise de confiabilidade foram
inicialmente desenvolvidas utilizando-se a linguagem Python. O primeiro grupo de
rotinas foi desenvolvido para Estado Limite Último (ELU) através do método FORM
(First Order Reliability Method) e da simulação de Monte Carlo. O segundo grupo de
rotinas refere-se à análise de confiabilidade para Estado Limite de Serviço (ELS)
mediante simulação de Monte Carlo. Uma contenção com características
tipicamente executadas na cidade de Natal-RN foi analisada utilizando-se as rotinas
desenvolvidas e para a realização de um estudo paramétrico. Para o ELS utilizou-se
ainda o software de elementos finitos Plaxis 2D para obter os deslocamentos
horizontais da contenção. A contenção analisada apresentou alta confiabilidade para
o ELU com probabilidade de falha nula para os dois métodos probabilísticos e alto
índice de confiabilidade tanto para o FORM quanto na simulação de Monte Carlo.
Para o ELS, o aumento dos deslocamentos horizontais máximos permitidos diminuiu
a probabilidade de falha e aumentou o índice de confiabilidade da contenção, em
ambos os casos, com tendência linear. As análises de sensibilidade revelaram que o
ângulo de atrito do solo foi a variável mais influente no ELU e ELS na grande maioria
dos casos. O peso específico seco, por sua vez, teve baixa influência em todas as análises. Os métodos de sensibilidade aplicados juntos com o Plaxis 2D tiveram
resultados satisfatórios para as avaliações da função de estado limite realizadas. Em
relação à análise paramétrica, o superdimensionamento da ficha da contenção
executada diminuiu a influência da variabilidade das propriedades do solo nos
resultados. O efeito da variação das características do solo nos resultados só foi
expressivo adotando-se valores de ficha menores que o executado. Nesse caso,
considerando a profundidade de escavação constante, o aumento da ficha diminuiu
a probabilidade de falha usando os dois métodos probabilísticos e os valores dos
pontos de projeto fornecidos pelo FORM. A distribuição lognormal diminuiu a
probabilidade de falha das análises no ELS. / Geotechnical structures are subject to different uncertainties due to the natural
variability of the soil and because of the limited knowledge of the several related
events. The evaluation of these uncertainties is possible with the application of the
reliability theory. Despite the discussion on this topic presented in international
standards and scientific researches, the application of the probabilistic theory in
Brazil is still unusual, especially for retaining structures. Accordingly, this work
presents a study on geotechnical reliability of cantilever pile walls in sand. First,
computational routines were developed for reliability analysis using the Python
language. The first series of routines was developed to evaluate the reliability for the
Ultimate Limit State (ULS) of the structure using FORM (First Order Reability
Method) and Monte Carlo simulation. The second group of routines was devised to
evaluate the reliability for the Service Limit State (SLS) using Monte Carlo simulation.
A project of a cantilever pile wall embedded in sandy soil, which is typically
constructed in the city of Natal/RN, Brazil, was analyzed using the computational
routines. A parametric study was conducted based on this specific retaining wall.
Particularly for SLS evaluation, the Plaxis 2D finite element software was used to
obtain the horizontal displacement values of the cantilever wall. The retaining
structure presented high reliability for the ULS with insignificant probability of failure
for both probabilistic methods and great reliability index values for the FORM and for
the Monte Carlo simulation. For SLS, the increase in maximum allowed horizontal
displacements decreased the failure probability and increased the pile wall reliability
index, in a linear trend. Sensitivity analysis indicated that the soil friction angle was
the most influential variable in ULS and SLS in most cases. On the other hand, soil
dry unit weight showed a low influence in all analyzed cases. Sensitivity methods coupled with Plaxis 2D exhibited satisfactory results for the implemented evaluations.
Regarding the parametric study, the oversized embedment depth of the structure led
to a reduced influence of soil property variability on reliability analyses. The effect of
soil properties variations on the results was significant only for adopted embedment
depth smaller than that actually executed. For a constant depth of excavation,
increasing embedment depths decreased the failure probability found by the two
probabilistic methods and increased the design points provided by the FORM. The
use of lognormal distribution reduced the failure probability of the SLS analyzes.
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The influence of working memory on the quality of linguistic predictions during speech understanding in adverse listening conditions : Comparing cortical responses using MEGAllander, Karin January 2022 (has links)
Speech understanding is a fundamental human ability that enable flexible communication among individuals. Understanding natural speech in normal conditions is a fast and automatic process. It is facilitated through integration between prior knowledge about a speech signal and multimodal speech inputs. In situations where listening conditions are adverse, for example due to hearing impairment or environmental noise, speech understanding is challenged and reliance on prior knowledge increases. Prior knowledge about phonology and semantics are involved in predictive mechanisms that generates more successful speech understanding. Working memory processing seems to be involved in influencing the quality of such predictions. To evaluate the role of working memory in the quality of linguistic predictions, a cortical comparison using MEG was used. MEG data from a previous experiment, where participants performed an auditory sentence completion task with background noise was analyzed. Results from statistical analysis, time-domain analysis and time frequency analysis suggests that differences in working memory processing does not influence the quality of linguistic predictions. Further research is required to assess what factors are involved in the quality of linguistic predictions which could lead to unsuccessful speech understanding, in order to improve communication in everyday situations.
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Sartre, critique des poètes / Sartre, The critic of poetsSalem, Bilel 07 November 2014 (has links)
Ma thèse traite d’un aspect de la critique sartrienne : la critique poétique. Elle se présente sous forme de triptyque. En effet, chaque partie traite de la figure d’un poète. Dans les deux premières parties de ma thèse, j’aborde deux poètes du XIXème siècle : Baudelaire et Mallarmé. Les deux livres qui m’ont servi de support pour étudier cette critique poétique sont le Baudelaire de Sartre et Mallarmé, La lucidité et sa face d’ombre. Ces deux essais ont radicalement bouleversé la manière avec laquelle on appréhendait jusqu’à là la figure de ces deux poètes. Si le XIXème siècle en a fait des monstres sacrés qui ont apporté la nouveauté dans le genre poétique, Sartre quant à lui, sape certaines idées reçues. Baudelaire est le premier à qui il s’attaque en dénonçant son désengagement. Il critique son dandysme outrancier qui en a fait selon lui un poète stérile. Cet essai est aussi l’occasion pour Sartre d’exposer sa théorie de l’existentialisme et de montrer que l’Engagement et la Littérature vont de pair et illustrent la liberté de l’Homme. Dans la seconde partie qui traite de Mallarmé, la lucidité et sa face d’ombre, la critique poétique se mêle à la critique historique. Sartre commence par brosser un tableau de la société du XIXème siècle en mettant l’accent sur le désœuvrement de ce siècle. Mallarmé semble comme Baudelaire illustrer une certaine forme de désengagement. Pourtant Sartre semble omettre un élément essentiel, c’est que ces poètes de la deuxième moitié du XIXème siècle font partie de ce que l’on appelle « Les Héritiers de l’athéisme ». Mallarmé dévoile l’absence d’un Dieu en caressant l’idée du suicide. Celui-ci apparaît dans ses poèmes puisque le poète expérimente sa propre mort comme pour réaffirmer l’absence de Dieu. En conséquence, il existe une liberté inhérente à ces deux poètes que sont Baudelaire et Mallarmé, mais cette liberté est bien différente de la liberté sartrienne qui se conçoit comme un absolu. Enfin dans la troisième partie de la thèse, c’est Genet qui est à l’honneur. Sartre manifeste là toute son admiration pour ce génie créateur qui a su assumer pleinement ses choix et qui n’a cessé de revendiquer la singularité de son être. La conception que se fait Genet de l’existence se situe aux antipodes de l’attitude baudelairienne. Chez Genet, la poésie s’est imposée comme un acte libérateur. Sartre n’hésite pas à comparer parfois indirectement les poètes. En effet, à ses yeux Baudelaire ne s’est aucunement illustré dans le mal. Genet, lui, par contre a fait de ce mal une véritable splendeur. Il l’a célébré et a fini par l’incarner. En abordant la destinée singulière de trois poètes, Sartre illustre en même temps sa propre philosophie existentielle. Il démontre l’absence d’un Inconscient qui expliquerait toutes nos actions et réaffirme la liberté absolue de l’Homme. / My thesis deals with one aspect of Sartre's critic: the poetic criticism. It has three major parts. The first and the second parts of my thesis discuss two poets of the nineteenth century: Baudelaire and Mallarmé.Baudelaire and Mallarmé, La lucidité et sa face d’ombre represent two principals books which have been support my study. Both essays play a great role to change the way in which we thought about them before Sartre’s studies.The nineteenth century has made Baudelaire and Mallarmé as two most important poets, however Sartre brought innovation and tried to broke our popular belief. In the first part, Sartre has been denouncing Baudelaire’s disengagement.In the second part which deals with Mallarmé, la lucidité et sa face d’ombre,, Sartre describe the poets of second half of the nineteenth century as “The heirs of Atheism” . As a result, Sartre creates a new notion of freedom which is totally different from those of Mallarmé and Baudelaire. Finally, in the third part Sartre chose to express his admiration for Genet because he assumed his responsibility for his choice of being. Genet’s conception of existence is contradicted with that of Baudelaire.To crown it all, Sartre show his existential philosophy throughout these three poets of XIX and XX centuries. In relation to Sartre there is no Unconscious that would explain our actions. Consequently, he confirms the absolute freedom of Man.
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