A new Edge Detector Based on Parametric Surface Model: Regression Surface Descriptor

In this paper we present a new methodology for edge detection in digital images. The first originality of the proposed method is to consider image content as a parametric surface. Then, an original parametric local model of this surface representing image content is proposed. The few parameters involved in the proposed model are shown to be very sensitive to discontinuities in surface which correspond to edges in image content. This naturally leads to the design of an efficient edge detector. Moreover, a thorough analysis of the proposed model also allows us to explain how these parameters can be used to obtain edge descriptors such as orientations and curvatures. In practice, the proposed methodology offers two main advantages. First, it has high customization possibilities in order to be adjusted to a wide range of different problems, from coarse to fine scale edge detection. Second, it is very robust to blurring process and additive noise. Numerical results are presented to emphasis these properties and to confirm efficiency of the proposed method through a comparative study with other edge detectors.Comment: 21 pages, 13 figures and 2 table

Geometrical Draping of Nonwoven Fabrics

This paper presents an optimization-based kinematic method for simulation of forming processes of nonwoven-fabric-reinforced composites using geometrical approach. The geometrical approach allows the defining of the 3D ply shapes, 2D flat pattern, and fiber distortions. Some numerical simulations of draping are proposed and compared with the experimental results

Triangulation sous contraintes en dimension quelconque

Résumé disponible dans le fichier PD

Modeling and Optimization of Materials and Structures

Preface : The current economic and ecological context requires different industries towards the optimization of structures. One of the most striking examples is the soaring price of oil, which launched the major aircraft manufacturers Airbus and Boeing in a race to relief structures, to reduce their consumption. Therefore, the need of competitive products, both in terms of reliability, performance or operating cost, is pervasive and growing, aviation and elsewhere. Thus, work on the material parts by offering innovative solutions to reduce their weight and improve their performance (new materials, new processes, etc.) is essential and becomes more than ever a major industrial challenge. One way of increasing the selected aircraft is use of composite materials. Indeed, their high ratio mechanical / density properties and excellent resistance to environmental significantly improve the structural performance of the aircraft while generating a significant weight gain (20 to 30% weight of a structure). They were originally implemented in the design of secondary structures of aircraft, but improving their manufacturing processes and a better understanding of their mechanical properties and their degradation mechanisms are they now used for the manufacture of primary structures, such as the fuselage or the central box of an aircraft wing. If applications were rather the military origin, composites now particularly interested in civil aviation, the constraints are much stricter certification, which requires predictability of behavior and life of structures much finer Thus, at present, they account for over 50% of the mass of newer aircraft such as the Airbus A350, the Airbus A380 or the Boeing 787. The potential of composite materials is important, but will speak only on one condition: work not only on the basic constituents of the material (fibers, resin, ...) on the injection preparation conditions (methods, thermal cycle, shaped in the mold, ...) but also and above all on the function of the material in the structure. Indeed, the aterial is a component of a more complex system, consisting of parts, assemblies, subassemblies and the structure itself. This vision system involves understanding the material as parameters, not data, an overall optimization of the structure. This link between material and structure is evident for composites where fiber orientation, or reinforcements in a more general way, in the direction of efforts can greatly increase the performance / weight ratio. We understand that optimizing the structure requires, among other things, a design material to locally respond to the "just need" structural. The main objectives of this special issue (consisting mainly of a selection of papers presented at 5th International Symposium on AirCraft MAterials ACMA 2014) are, by means of modeling strategies and simulation out with conventional strategies, pushing the current limits in modeling and computation in response industrial and societal challenges. It is also to control the calculations and models in a framework that takes into account the major sources of uncertainty to optimize materials and structures. Particular attention is made to the modeling and validation of composite materials and structures

Adaptive Triangular-Quadrilateral Mesh Generation

In this paper, we begin by recalling an adaptive mesh generation method governed by isotropic and anisotropic discrete metric maps, by means of the generation of a unit mesh with respect to a riemannian structure. We propose then an automatic triangular to quadrilateral mesh conversion scheme, which generalizes the standard case to the anisotropic context. In addition, we introduce an optimal vertex smoothing procedure. Application test examples, in particular a CFD test, are given to demonstrate the efficiency of the proposed method

Maillage géométrique de surfaces. Partie II : appauvrissement

Ce rapport présente la seconde partie d'une étude relative au maillage géométrique de surfaces. Dans la première partie, on a proposé une méthode pour enrichir une triangulation arbitraire d'une surface vis-à-vis de sa géométrie et de la qualité en forme de ses éléments. Cette partie concerne une application particulière, la simplification géométrique de maillages. L'objectif est de réduire le nombre d'éléments d'un maillage donné en préservant l'approximation géométrique et en controlant la qualité du maillage résultant. Quelques exemples de maillages surfaciques destinés à des applications différentes viennent illustrer l'efficacité de la méthode de simplification

BLSURF - Mesh Generator for Composite Parametric Surfaces - User's Manual

This technical report describes BLSURF, an automatic surface mesh generator. This software creates the mesh of a composite parametric surface while conforming to a prescribed size map. To this end, analytical functions defining the surface, as well as their first and possibly second derivatives, must be externally provided (for instance by a CAD system). Also, each patch must be described by giving its 2D parametric domain. The method used is based on an incremental Delaunay approach adapted to a Riemannian metric

Maillage géométrique de surfaces. Partie I : enrichissement

Ce rapport présente une méthode pour obtenir un maillage géométrique enrichi de type élément fini à partir d'une triangulation initiale arbitraire d'une surface. Pour ce faire, on construit, en premier lieu, un support géométrique de continuité d'ordre $G^1$ associé à la triangulation initiale de la surface, représentant ainsi une approximation adéquate de la géométrie de la surface sous-jacente. Puis on optimise la triangulation initiale au regard de cette géométrie et de la qualité en forme des éléments. Quelques exemples de maillages surfaciques destinés à des applications différentes viennent illustrer l'efficacité de la méthode proposée

Qualité des maillages de surfaces. Partie I : spécifications isotropes

Ce rapport est consacré à l'étude de la qualité en taille et la qualité en forme des maillages de surfaces gouvernés, la contrainte étant relative soit à une métrique quelconque donnée, soit à une métrique géométrique associée à la géométrie. Les requis en forme sont ceux des méthodes d'éléments finis. Les mesures proposées permettent de valider les maillages de surfaces dans un schéma général d'adaptation de maillages, tel que ceux rencontrés dans les simulations numériques par des méthodes d'éléments finis pour lesquels la carte de métrique est fournie par un estimateur d'erreur a posteriori. Dans cette première partie de l'étude sur la qualité des maillages de surfaces, nous traitons le cas des métriques isotropes, les métriques anisotropes faisant l'objet d'une seconde partie. Différents exemples sont présentés pour illustrer la pertinence des critères proposés

The BL2D Mesh Generator: Beginner's Guide, User's and Programmer's Manual

The BL2D software package is a bidimensional, adaptive and anisotropic mesh generator. Its architecture is very modular. This report is made up of three main parts: a beginner's guide (for users who are new to BL2D), a user's manual (for more experienced users) and a programmer's manual (for developers wishing to add new functionalities)