Rescaling method for blow-up solutions of nonlinear wave equations

We develop a hybrid scheme based on a finite difference scheme and a rescaling technique to approximate the solution of nonlinear wave equation. In order to numerically reproduce the blow-up phenomena, we propose a rule of scaling transformation, which is a variant of what was successfully used in the case of nonlinear parabolic equations. A careful study of the convergence of the proposed scheme is carried out and several numerical examples are performed in illustration.Comment: 20 pages, 5 figures, 2 table

Fault diagnosis and fault-tolerant control design for neutral time delay system

This paper presents a new approach of fault-tolerant control (FTC) for the transmission line as a neutral variable time-delay system. The main goal of this work guarantees faulty neutral variable time delay system stabilization using the state feedback control design based on Lyapunov function and the Linear Matrix Inequality resolution. The use of the FTC method is to achieve actuator and sensor fault compensation. This method is based on two steps. The first one is the synthesis of a nominal control, which remains to maintain the closed-loop system stability. The second step is based on adding a new control law to the nominal one to compensate the fault effect on system behaviour and maintain the desired performance in the closed loop system. Then, a conception of an adaptive observer is used to detect and estimate the fault. Finally, the developed approach is applied for the transmission line. The given results are presented to prove the effectiveness of this approach

Étude et résolution de la rupture sismique par une méthode volumes finis dans un milieu bidimensionnel hétérogène

Dans ce travail, on présente une nouvelle méthode basée sur une formulation volumes finis pour la simulation d'une faille préexistante. Dans un premier temps, la représentation de la source par un ensemble d'éléments permet la validation de la méthode par comparaison aux résultats obtenus par une méthode de type différences finies. On s'intéresse ensuite à la représentation de la faille par un ensemble de segments et non plus d'éléments. Une étude d'énergie s'avère alors nécessaire afin d'assurer la stabilité du schéma et la précision des solutions. La validations des résultats se fait en comparant les solutions obtenues par l'approche par segments à celle par éléments

A genome-wide comparison between selected and unselected Valle del Belice sheep reveals differences in population structure and footprints of recent selection

About three decades of breeding and selection in the Valle del Belìce sheep are expected to have left several genomic footprints related to milk production traits. In this study, we have assembled a dataset with 451 individuals of the Valle del Belìce sheep breed: 184 animals that underwent directional selection for milk production and 267 unselected animals, genotyped for 40,660 single-nucleotide polymorphisms (SNPs). Three different statistical approaches, both within (iHS and ROH) and between (Rsb) groups, were used to identify genomic regions potentially under selection. Population structure analyses separated all individuals according to their belonging to the two groups. A total of four genomic regions on two chromosomes were jointly identified by at least two statistical approaches. Several candidate genes for milk production were identified, corroborating the polygenic nature of this trait and which may provide clues to potential new selection targets. We also found candidate genes for growth and reproductive traits. Overall, the identified genes may explain the effect of selection to improve the performances related to milk production traits in the breed. Further studies using high-density array data, would be particularly relevant to refine and validate these results

Automatic Registration of Terrestrial Laser Scanning Point Clouds using Panoramic Reflectance Images

This paper presents a new approach to the automatic registration of terrestrial laser scanning (TLS) point clouds using panoramic reflectance images. The approach follows a two-step procedure that includes both pair-wise registration and global registration. The pair-wise registration consists of image matching (pixel-to-pixel correspondence) and point cloud registration (point-to-point correspondence), as the correspondence between the image and the point cloud (pixel-to-point) is inherent to the reflectance images. False correspondences are removed by a geometric invariance check. The pixel-to-point correspondence and the computation of the rigid transformation parameters (RTPs) are integrated into an iterative process that allows for the pair-wise registration to be optimised. The global registration of all point clouds is obtained by a bundle adjustment using a circular self-closure constraint. Our approach is tested with both indoor and outdoor scenes acquired by a FARO LS 880 laser scanner with an angular resolution of 0.036° and 0.045°, respectively. The results show that the pair-wise and global registration accuracies are of millimetre and centimetre orders, respectively, and that the process is fully automatic and converges quickly

Etude et simulation numérique de la rupture dynamique des séismes par des méthodes d'éléments finis discontinus

Début de rédaction : Décembre 2006Fin de rédaction : Octobre 2007This work is devoted to the study and the numerical simulation of 2D and 3D dynamic crack rupture by a discontinuous Galerkin finite element method. The initial partial differential equations are transformed in order to get a symmetric pseudo-conservative form, for which we design a discontinuous Galerkin formulation with centered numerical fluxes and explicit leap-frog time scheme. Throughout the study of a discrete energy, we specify in a weak sense the boundary conditions on the fault surface for the shear rupture mode. We demonstrate that this energy is conserved when no traction is applied on the fault. We investigate various complex test-cases and we compare our solutions with those obtained by other methods. The fine agreement with other results validates our approach and illustrates the good behavior of the method we propose.Ce travail est dédié à l´étude et la simulation numérique de la rupture dynamique des séismes en deux et trois dimensions d´espace par une méthode d´éléments finis discontinus. Après avoir transformé le système de l´élastodynamique en un système hyperbolique symétrique du premier ordre, nous proposons un schéma numérique basé sur des flux centrés et un schéma explicite en temps de type saute-mouton. A travers l´étude d´une énergie discrète du système, nous spécifions les conditions aux limites sur la faille afin de prendre en compte de manière faible la rupture en mode cisaillant que nous traitons. Nous montrons, qu´en l´absence de tractions tangentielles sur la faille, cette énergie est parfaitement conservée. Nous illustrons la capacité de notre méthode à travers divers cas tests sur des configurations complexes grâce à une implémentation parallèle

Fast Global Registration of 3D Sampled Surfaces Using a Multi-Z-Buffer Technique

We present a new method for the global registration of several overlapping 3D surfaces sampled on an object. The method is based on the ICP algorithm and on a segmentation of the sampled points in an optimized set of z-buffers. This multi-z-buffer technique provides a 3D space partitioning which greatly accelerates the search of the nearest neighbours in the establishment of the point-to-point correspondence between overlapping surfaces. Then a randomized iterative registration is processed on the surface set. We have tested an implementation of this technique on real sampled surfaces. It appears to be rapid, accurate and robust, especially in the case of highly curved objects. 1. Introduction A single scan of a complex 3D object is in general not sufficient to fully describe its surface because of the presence of occluded parts. Additional scans from different view points are thus required to recover the occluded parts and improve the surface description. To reach these different vie..