Modélisation de résultats d'inspection en présence de champs stochastiques de dégradation

Les inspections de structures existantes par des techniques de contrôles non-destructifs (CND) ne fournissent pas un résultat exact et il est courant de modéliser leur fiabilité en terme de probabilité de détection (PoD), probabilité de fausse alarme (PFA) et courbes de performance (ROC). Ces probabilités sont déterminées soit à partir de campagnes d'intercalibration soit par modélisation des densités de probabilité du bruit et du signal. Dans ce dernier cas, lorsque le bruit et le signal dépendent de la localisation sur la structure, les PoD et PFA sont des fonctions de l'espace. Cet article présente comment définir ces grandeurs lorsque le dommage et la procédure de détection sont des champs stochastiques

Efeito do pré-condicionamento ácido nas forças de adesão em esmalte in vitro de dois sistemas adesivos: universal vs. self-etch

Tese de Mestrado, Medicina Dentária, Universidade de Lisboa, Faculdade de Medicina Dentária, 2014Objectives: The purpose of this study was to evaluate the effect of pre-etching on in vitro enamel bond strength of two adhesive systems: one universal adhesive and one two-step self-etch. Methods: In this study were used 8 caries-free human molars. The specimens were partially split in two halves and were assigned to two groups (n=8). On the enamel surfaces were applied two different adhesive systems: Scotchbond Universal (3M ESPE Seefeld, Germany) following manufacturer's instructions as a total-etch; Clearfil SE Bond (Kuraray, Okayama, Japan) applied as a total-etch. Build-ups were constructed with ENAMEL plus HRi (Micerium S.p.A. Avegno (GE) Italy) and cured in three increments of 2mm each. Specimens were kept in 37ºC destilated water for 24 hours and then sectioned with a slow-speed Diamond saw under water in X and Y directions to obtain bonded beams that were tested to failure in tension at a crosshead speed of 1 mm/minute. Statistical analyses were computed using T-student. The failures interfaces were observed under an optical microscope and registered. Results: There were not statistically significant differences among the two groups. Conclusions: A new universal adhesive system has similar bond strength than a two-step self-etch adhesive when pre-etching is performed.Objetivos: O presente trabalho tem como objetivo avaliar o efeito do pré-condicionamento ácido nas forças de adesão em esmalte in vitro de dois sistemas adesivos: um adesivo universal e um self-etch de dois passos. Materiais e Métodos: Neste estudo utilizaram-se 8 dentes molares humanos livres de cárie. Foram realizados cortes de maneira a hemissecionar as coroas dos dentes mesiodistalmente e estas foram aleatoriamente divididas em 2 grupos (n=8). Às superfícies em esmalte foram aplicados 2 sistemas adesivos distintos: Scotchbond Universal (3M ESPE Seefeld, Germany) segundo instruções do fabricante pela técnica total-etch; Clearfil SE Bond (Kuraray, Okayama, Japan) pela ténica total-etch, tendo sido restauradas com o compósito ENAMEL plus HRi (Micerium S.p.A. Avegno (GE) Italy) fotopolimerizados em três incrementos, cada um com 2mm. Os espécimenes foram armazenados em água destilada a 37ºC durante 24h e depois seccionados em palitos de aproximadamente 1mm2 com um disco de diamante sob refrigeração com água, nas direções X e Y de maneira a obter palitos. Todas as amostras foram testadas até à fratura em testes de microtração, a uma velocidade de 1mm/minuto. A análise estatística foi feita utilizando o T-student. As fraturas foram observadas num estereomicroscópio e registadas. Resultados: Os dois grupos estudados não apresentam diferenças estatisticamente significativas (p<0,05). Conclusão: Um adesivo universal parece proporcionar forças de adesão em esmalte similares a adesivos self-etch de dois passos quando efectuado pré-condicionamento ácido

Méthode X-SFEM pour le calcul de structure à géométrie aléatoire : application au calcul d'un joint de soudure

In structural analysis, stochastic finite element methods offer a robust tool to deal with randomness on material properties or loadings. Unfortunately, there is still no available efficient strategy to deal with uncertainties on the geometry. Here, we bring an answer to this problem by proposing a new method based on an extension to the stochastic framework of the eXtended Finite Element Method (X-FEM). This method lies on the use of the level set technique for the implicit description of the random geometry and the use of Galerkin approximation at deterministic and stochastic levels. Here, this method is applied to the analysis of a random welded joint

Low rank approximation of multidimensional data

In the last decades, numerical simulation has experienced tremendous improvements driven by massive growth of computing power. Exascale computing has been achieved this year and will allow solving ever more complex problems. But such large systems produce colossal amounts of data which leads to its own difficulties. Moreover, many engineering problems such as multiphysics or optimisation and control, require far more power that any computer architecture could achieve within the current scientific computing paradigm. In this chapter, we propose to shift the paradigm in order to break the curse of dimensionality by introducing decomposition to reduced data. We present an extended review of data reduction techniques and intends to bridge between applied mathematics community and the computational mechanics one. The chapter is organized into two parts. In the first one bivariate separation is studied, including discussions on the equivalence of proper orthogonal decomposition (POD, continuous framework) and singular value decomposition (SVD, discrete matrices). Then, in the second part, a wide review of tensor formats and their approximation is proposed. Such work has already been provided in the literature but either on separate papers or into a pure applied mathematics framework. Here, we offer to the data enthusiast scientist a description of Canonical, Tucker, Hierarchical and Tensor train formats including their approximation algorithms. When it is possible, a careful analysis of the link between continuous and discrete methods will be performed.IV Research and Transfer Plan of the University of SevillaInstitut CarnotJunta de AndalucíaIDEX program of the University of Bordeau

QTL detection by multi-parent linkage mapping in oil palm (Elaeis guineensis Jacq.)

A quantitative trait locus (QTL) analysis designed for a multi-parent population was carried out and tested in oil palm (Elaeis guineensis Jacq.), which is a diploid cross-fertilising perennial species. A new extension of the MCQTL package was especially designed for crosses between heterozygous parents. The algorithm, which is now available for any allogamous species, was used to perform and compare two types of QTL search for small size families, within-family analysis and across-family analysis, using data from a 2 × 2 complete factorial mating experiment involving four parents from three selected gene pools. A consensus genetic map of the factorial design was produced using 251 microsatellite loci, the locus of the Sh major gene controlling fruit shell presence, and an AFLP marker of that gene. A set of 76 QTLs involved in 24 quantitative phenotypic traits was identified. A comparison of the QTL detection results showed that the across-family analysis proved to be efficient due to the interconnected families, but the family size issue is just partially solved. The identification of QTL markers for small progeny numbers and for marker-assisted selection strategies is discussed

Biotecnología y selección de la palma de aceite: la Palma Dorada del futuro

Los marcadores de ADN, la secuenciación con sistemas NGS, la manipulación genética y las tecnologías de cultivo in vitro, combinadas con la caracterización fenotípica de alta tecnología, ponen al alcance de los cultivadores las variedades que desearían cultivar sin que hubieran podido imaginar siquiera que fuese posible sembrarlas. Se espera que las variedades de palma de aceite sufran muchos cambios desde el día de hoy hasta el año 2050, por medio de una selección biotecnológica de las especies E. guineensis y E. oleifera. La productividad de la palma de aceite está ligada estrechamente a su potencial fisiológico. El determinismo genético completamente dilucidado de la morfología de la fertilidad del fruto permite que existan nuevas variedades que solo contengan pulpa, tales como las pisifera fértiles y tenera partenocárpicos. El bajo crecimiento del tallo y la voluminosidad reducida logran que las palmas se cultiven en menos hectáreas de tierra, lo cual genera una cosecha menos costosa. La reducción de la frecuencia de cosecha (tan baja como una vez al mes) será posible gracias al no desprendimiento de frutos. La baja actividad de lipasa en la pulpa de los frutos maduros garantizará la producción de un aceite de palma sin ácidos libres significativos en los racimos entregados a las plantas extractoras, lo cual asegurará la producción en campo sin incurrir en pérdidas económicas. Las variedades con hasta 90 % de ácido oleico entrarán al mercado y este novedoso aceite de palma “aceitunado” se venderá a precios marcadamente más competitivos para la mesa de la mayoría de las personas del mundo, destronando así al mercado privilegiado del aceite de oliva mediterráneo, de mayor costo. El imperio del cultivo de palma de aceite ha expandido sus territorios a lo largo de América del Sur gracias a las variedades interespecíficas resistentes a la enfermedad de la Pudrición del cogollo, a la vez que se preservan considerablemente la mayoría de los bosques naturales al convertir los grandes pastizales en palmares

eXtended Stochastic Finite Element Method for the numerical simulation of heterogenous materials with random material interfaces

International audienceAn eXtended Stochastic Finite Element Method has been recently proposed for the numerical solution of partial differential equations defined on random domains. This method is based on a mariage between the eXtended Finite Element Method and spectral stochastic methods. In this paper, we propose an extension of this method for the numerical simulation of random multi-phased materials. The random geometry of material interfaces is described implicitly by using random level-set functions. A fixed deterministic finite element mesh, which is not conforming the random interfaces, is then introduced in order to approximate the geometry and the solution. Classical spectral stochastic finite element approximation spaces are not able to capture the irregularities of the solution field with respect to spatial and stochastic variables, which leads to a deterioration of the accuracy and convergence properties of the approximate solution. In order to recover optimal convergence properties of the approximation, we propose an extension of the partition of unity method to the spectral stochastic framework. This technique allows the enrichment of approximation spaces with suitable functions based on an a priori knowledge of the irregularities in the solution. Numerical examples illustrate the efficiency of the proposed method and demonstrate the relevance of the enrichment procedure