Génie électrique
MULTIPHASE LEVEL SETS MODEL APPLIED TO WELD RADIOGRAPHIC IMAGES SEGMENTATION.
This paper is devoted to a crucial task in image analysis which is segmentation. Our aim is to give the structural form of industrial radiographic images. In this purpose, we have used an implicit region oriented deformable model. In this context the criteria to stop the curves’ evolution is the statistical information of the image grey level, this gives many advantages compared to those that used the gradient.The functional is minimized via a piecewise constant approximation and Multiphase level set. In this situation we need n level set function to represent up to 2n segments or regions. The model avoids automatically the problems of vacuum and overlap. The numerical results for synthetic and weld radiographic images are satisfactory. Voir les détails
Mots clés : Weld Radiographic image, image segmentation, Level Set Methods, Chan-Vese Model, Multiphase segmentation
Restauration d’images bruitées par les équations aux dérivées partielles (EDP)
La restauration d’images bruitées a fait l’objet de nombreuses recherches en traitement d’images. La difficulté principale vient du fait que les contours des objets et les discontinuités de l’image doivent être préservés. Les méthodes basées sur les équations aux dérivées partielles et les techniques de filtrage anisotropes répondent à ces exigences. Dans cet article nous proposons deux nouvelles variantes sous la forme d’un double schéma itératif non linéaire de Perona-Malik, qui peut enlever le bruit, préserver les bords et garder leur localisation exacte. Les tests effectués sur des images bruitées ont démontré que nos variantes atteignent des performances appréciables. Voir les détails
Mots clés : filtrage isotrope, filtrage anisotrope, Equation de Perona-Malik, Restauration des images.
Image Segmentation by the Level Set Methods Using Third Order WENO
All level set based image segmentation methods are based on an assumption that the level set function is or close to a signed distance function (SDF). Small time step and costly re-initialization procedure must be applied to guarantee this assumption, and in order to calculate the gradient, simple numerical schemes, based on finite differences, are applied.In this paper, in order to achieve higher order accuracy in the temporal discretization, we have used Total Variation Diminishing (TVD) Runge Kutta (RK) methods. The spatial derivatives are determined by using the Weighted Essentially Non-Oscillatory methods (WENO-3) that accurately capture the formation of sharp gradients in the moving fronts. Experiments results show that we have obtained good results both on synthetic and real images. Voir les détails
Mots clés : Active contour, ENO and WENO schemes, Level set, PDE
Detection of Weld Defects in Radiographic Image by the Level Set Methods.
All level set based image segmentation methods are based on an assumption that the level set function is or close to a signed distance function (SDF). Small time step and costly reinitialization procedure must be applied to guarantee this assumption, and in order to calculate the gradient, simple numerical schemes, based on finite differences, are applied. In this paper, in order to achieve higher order accuracy in the temporal discretization, we have used Total Variation Diminishing (TVD) Runge Kutta (RK) methods. The spatial derivatives are determined by using the Essentially Non- Oscillatory methods (ENO) that accurately capture the formation of sharp gradients in the moving fronts. Experiments results show that we have obtained good results both on synthetic and real images. Voir les détails
Mots clés : ENO and WENO schemes, Edge detection, Image processing, image segmentation
COMPARAISON ENTRE LE SNAKE GVF ET LE MODELE DU BALLON POUR LA SEGMENTATION DES IMAGES RADIOGRAPHIQUES DE SOUDURE
Les contours actifs (ou snakes) introduits par Kass et al à la fin des années 80, font l’objet de nombreux travaux récents dans la littérature et sont utilisés aujourd’hui sous des formes plus évoluées. Ce sont des courbes définies paramétriquement qui peuvent se déformer progressivement de manière itérative afin de minimiser une fonctionnelle d’énergie. L’évolution de la courbe est sujette à de fortes contraintes et les difficultés reposent tant sur l’initialisation que sur le choix de l’énergie à minimiser. Des modifications ont été introduites par la suite dans le modèle de contour actif pour résoudre certains des problèmes rencontrés avec la méthode originale des « snakes ». Dans cet article, nous présentons une comparaison entre deux méthodes de segmentation par contour actif pour notre application : le modèle du ballon et le snake GVF. Après une brève présentation du modèle "snake" classique, nous détaillerons les deux méthodes et nous donnerons les résultats obtenus sur des images tests synthétiques ainsi que sur des images radiographiques de soudure Voir les détails
Mots clés : segmentation d’images, contours actifs, snake GVF, modèle de ballon
Segmentation of Radiographic Images of Weld Applying Traditional and GVF Snakes.
In this paper, we employ the active contour models (Snakes) for edge detection and segmentation of welds radiographic defects. These models are widely used in many applications, including edge, shape modeling, segmentation, and motion tracking. The first model defined and implemented is the classical snake formulated by Kass & al. Snake is a method of deformation a closed contour to the boundary of an object in an image. The snake model is a controlled continuity closed contour that deforms under the influence of internal forces, image forces and external constraint forces. The snake model algorithms suffer from the inability to converge a contour to severe object concavities. Another problem is the generation of false contours due to the creation of unwanted contour loops. In order to remedy to these drawbacks, we apply a the method, called Gradient Vector Flow (GVF). This method proposes gradient vector flow as the external force. GVF snake gives good results on radiographic images of weld. Voir les détails
Mots clés : Active contour models, Edge detection, gradient vector flow, weld radiographic defects
Detection of defects in weld radiograph imagesby using the Gradient Vector Flow active contour
In this paper we use the active contour gradient vector flow models for edge detection and segmentation of weld radiographic defects. These models are widely used in many applications, including edge, shape modeling, segmentation and motion tracking. Active contour is a method which deforms a closed contour to the boundary of an object in an image. This deformation is made under the influence of internal forces, image forces and external constraint forces. Gradient Vector Flow (GVF) is an external force for active contour model which replaces the image force.We have chosen this model among many other models of active contours because this one gives a best convergence to concave boundaries compared with the traditional snake. Voir les détails
Mots clés : Active contour models, Edge detection, gradient vector flow, weld radiographic defects
Modeling and Optimal Sizing of a Wind Energy System for the Electrification of an Algerian Territory.
Wind energy is a renewable energy promoting diversification energy independence of our country. So, wind power is probably the most promising sustainable energy resource. This paper makes easy the task of the assessment models of the power systems for a multitude of applications through a mathematical formulation which gives the stages of wind energy conversion system. Many decisions about the configuration of the system should be made, parameters optimized and losses due to wake effect reduced, a task that Homer takes in hand. It simulates the operation of a system by making energy balance calculations for each of the 8,760 hours a year. Voir les détails
Mots clés : Homer, mathematical formulation, wind turbine output power
Impacts of Inductive and Conductive Interference due to High Voltage Power Lines on Metallic Pipelines
The electromagnetic interference caused by power transmission lines to oil and gas buried pipelines is under investigation for many years. Especially during fault conditions, large currents and voltages are induced. Even under normal operating conditions, voltages and currents are induced on the pipeline that may pose danger to working personnel or may accelerate the corrosion of the pipeline’s metal. In this research, the induced voltage in the oil buried pipelines due to the magnetic fields produced by nearby 400kV transmission lines have been computed on normal and fault conditions Voir les détails
Mots clés : AC interference, Induced Voltages, Electric Power Transmission Lines, pipeline, AC Corrosion
INFLUENCES DUES AUX LIGNES AERIENNES DE TRANSPORTD'ENERGIE SUR LES PIPELINES ENTERRESPROBLÈMES ET SOLUTIONS
L'interférence électromagnétique causée par des lignes de transport d'énergie électrique haute tension aux canalisations enterrées de pétrole et de gaz est à l'étude pendant beaucoup d’années. Particulièrement pendant les conditions de panne, et même en fonctionnement normal, des courants et des tensions sont induits sur les canalisations qui peuvent accélérer la corrosion du métal de la canalisation. Les résultats présentés dans ce document illustrent bien la tension induite due au champ magnétique sur les pipelines produits par les lignes électriques de haute tension en fonctionnement normal. Cet effet résulte un processus de corrosion auxquels nous avons proposé certaines solutions. Voir les détails
Mots clés : Ligne électrique HT, champ magnétique, pipelines, tension induite, corrosion, Protection cathodique