Discrete curvature approximations and segmentation of polyhedral surfaces

The segmentation of digitized data to divide a free form surface into patches is one of the key steps required to perform a reverse engineering process of an object. To this end, discrete curvature approximations are introduced as the basis of a segmentation process that lead to a decomposition of digitized data into areas that will help the construction of parametric surface patches. The approach proposed relies on the use of a polyhedral representation of the object built from the digitized data input. Then, it is shown how noise reduction, edge swapping techniques and adapted remeshing schemes can participate to different preparation phases to provide a geometry that highlights useful characteristics for the segmentation process. The segmentation process is performed with various approximations of discrete curvatures evaluated on the polyhedron produced during the preparation phases. The segmentation process proposed involves two phases: the identification of characteristic polygonal lines and the identification of polyhedral areas useful for a patch construction process. Discrete curvature criteria are adapted to each phase and the concept of invariant evaluation of curvatures is introduced to generate criteria that are constant over equivalent meshes. A description of the segmentation procedure is provided together with examples of results for free form object surfaces

Claude Vivier, Siddhartha, Karlheinz Stockhausen, la nouvelle simplicité et le râga

Siddhartha, pour grand orchestre en huit groupes, est l’une des partitions les plus audacieuses et complexes de Claude Vivier. L’oeuvre d’une trentaine de minutes se déploie à partir d’une mélodie unique qui se transforme continuellement par un processus d’expansion ou de contraction de ses intervalles constituants. L’oeuvre illustre de façon exemplaire l’influence des techniques de composition de Karlheinz Stockhausen sur la pensée de Vivier tout autant que la fascination de ce dernier pour certains procédés caractéristiques des musiques orientales tel le râga indien.Inspirée du célèbre roman de Hermann Hesse, l’oeuvre de Vivier transpose librement dans le domaine du sonore la trame narrative de cette allégorie initiatique au parfum exotique.Siddhartha for large orchestra in eight groups, is one of Claude Vivier’s most audacious and complex scores. This thirty-minute work is elaborated from a single melody which continually transforms through a process of expansion and contraction of its component intervals. This work illustrates in exemplary fashion the influence of the compositional techniques of Karlheinz Stockhausen on the thought of Vivier, as well as his fascination for certain characteristic procedures of Eastern classical music, particularly those of Indian râgas. Inspired by Hermann Hesse’s famous novel, Vivier’s work freely transposes into sound the narrative of this exotic allegory of initiation

Le sort des patients souffrant de troubles mentaux très graves et persistants lorsqu’il n’y a pas d’hôpital psychiatrique : étude de cas

L’Estrie est une région du Québec qui n’a jamais eu d’hôpital psychiatrique et s’avère donc un exemple extrême de désinstitutionnalisation. Comment parvient-on à y soigner et à héberger les personnes les plus gravement malades ? Ce système a-t-il des conséquences néfastes ? Les auteurs présentent ici une étude de cas jumelant des données qualitatives et quantitatives pour élucider ces questions. Ils ont repéré 36 patients souffrant de troubles mentaux très graves (prévalence 12,4/100 000). Cette région n’exporte pas ces cas les plus graves et parvient en général à les accueillir dans un réseau de petites et moyennes ressources d’hébergement. Par contre, les auteurs ont pu identifier une certaine dérive vers le réseau carcéral ; les cas à double ou triple diagnostics n’accèdent pas facilement aux soins ; faute d’alternative, les patients à potentiel chronique de violence stagnent parfois à l’hôpital dans des lits de courte durée (prévalence 1,6/100 000). Il semble donc possible d’éliminer le recours à un hôpital psychiatrique pour les patients souffrant de troubles mentaux très graves à condition de prévoir pour eux des milieux de vie très encadrés et de longue durée (besoin : 10-20 places/100 000).The Eastern Townships (Estrie) is an area of Québec which has never had a psychiatric hospital and is thus an extreme example of deinstitutionalization. How can people with the most severe mental illnesses be cared for ? Does this system have harmful consequences ? The authors present a case study with both qualitative and quantitative data to elucidate their questions. They found 36 patients with very severe mental illness (prevalence 12,4/100 000). This region does not send its most severely ill patients outside and generally succeeds in providing them with care and services in a network of small and medium size residential facilities. On the other hand, the authors have also been able to identify a certain drift of patients towards the correctional system ; cases with double or triple diagnosis do not easily have access to care ; through lack of an alternative, patients with potentially chronic violence often are stuck in a hospital in short stay beds (prevalence 1,6/100 000). It thus appears possible to eliminate the use of a psychiatric hospital for patients with very severe mental disorders as long as they are provided with supervised and long term care facilities (need : 10-20 places/100 000).Estrie es una región de Québec que nunca ha tenido hospital psiquiátrico y se reconoce entonces como un ejemplo extremo de desinstitucionalización. ¿Cómo se logra atender y alojar ahí a las personas más gravemente enfermas? ¿Tiene consecuencias nefastas este sistema? Los autores presentan aquí un estudio de caso que reune los datos cualitativos y cuantitativos para elucidar estas cuestiones. Se localizaron 36 pacientes que sufren de trastornos mentales graves (prevalencia 12.4/100,000). Esta región no exporta sus casos más graves y en general logra alojarlos en una red de recursos de alojamiento pequeños y medianos. En cambio, los autores pudieron identificar una cierta desviación hacia la red carcelaria; los casos de diagnóstico doble o triple no tienen fácil acceso a la atención; a falta de alternativas, los pacientes con un potencial crónico de violencia a veces se estancan en el hospital en las camas de corta duración (prevalencia 1.6/100,000). Parece entonces posible eliminar el tener que recurrir a un hospital psiquiátrico para los pacientes que sufren trastornos mentales graves, a condición de que para ellos se prevean medios de vida enmarcados y de larga duración (exigencia: 10-20 lugares/100,000).A Estrie é uma região do Quebec que nunca teve hospital psiquiátrico e revela-se um exemplo extremo de desinstitucionalização. Como conseguir atender e internar as pessoas mais gravemente enfermas? Este sistema tem conseqüências nefastas? Os autores apresentam, aqui, um estudo de caso que associa dados qualitativos e quantitativos para elucidar estas questões. Eles reconheceram 36 pacientes que sofrem de transtornos mentais graves (prevalência 12,4 por 100.000). Esta região não exporta estes casos mais graves e consegue, em geral, acolhê-los em uma rede de pequenos e médios recursos de internação. Entretanto, os autores puderam identificar uma certa deriva em direção à rede carcerária; os casos de duplo ou triplo diagnóstico não têm acesso fácil ao atendimento; sem alternativa, os pacientes com potencial crônico de violência ficam, às vezes, no hospital em leitos de curta duração (prevalência 1,6 por 100.000). Parece, então, que é possível eliminar o recurso a um hospital psiquiátrico para os pacientes que sofrem de transtornos mentais graves, com a condição de prever, para eles, meios de vida muito enquadrados e de longa duração (necessidade: 10-20 lugares por 100.000)

Fault diagnosis based on identified discrete-event models

International audienceFault diagnosis of Discrete-Event Systems consists of detecting and isolating the occurrence of faults within a bounded number of event occurrences. Recently, a new model for discrete-event system identification with the aim of fault detection, called Deterministic Automaton with Outputs and Conditional Transitions (DAOCT), has been proposed in the literature. The model is computed from observed fault-free paths, and represents the fault-free system behavior. In order to obtain compact models, loops are introduced in the model, which implies that sequences that are not observed can be generated leading to an exceeding language. This exceeding language is associated with possible non-detectable faults, and must be reduced in order to use the model for fault detection. After detecting the fault occurrence, its isolation is carried out by analyzing residuals. In this paper, we present a fault diagnosis scheme based on the DAOCT model. We show that the proposed fault diagnosis scheme is more efficient than other approaches proposed in the literature, in the sense that the exceeding language can be drastically reduced, reducing the number of non-detectable fault occurrences, and, in some cases, reducing also the delay for fault diagnosis. A practical example, consisting of a plant simulated by using a 3D simulation software controlled by a Programmable Logic Controller, is used to illustrate the results of the paper

An Online Newton's Method for Time-varying Linear Equality Constraints

We consider online optimization problems with time-varying linear equality constraints. In this framework, an agent makes sequential decisions using only prior information. At every round, the agent suffers an environment-determined loss and must satisfy time-varying constraints. Both the loss functions and the constraints can be chosen adversarially. We propose the Online Projected Equality-constrained Newton Method (OPEN-M) to tackle this family of problems. We obtain sublinear dynamic regret and constraint violation bounds for OPEN-M under mild conditions. Namely, smoothness of the loss function and boundedness of the inverse Hessian at the optimum are required, but not convexity. Finally, we show OPEN-M outperforms state-of-the-art online constrained optimization algorithms in a numerical network flow application.Comment: Version takes into account reviewer comments. The contributions have been clarified. The assumptions regarding the variation of optima have been clarified. The figures have more explicit labeling of the axes. Several small typos were addressed including problems with parentheses and unnecessary line

Modularity for Large Virtual Reality Applications

International audienceThis paper focuses on the design of high performance VR applications. These applications usually involve various I/O devices and complex simulations. A parallel architecture or grid infrastructure is required to provide the necessary I/O and processing capabilities. Developing such applications faces several difficulties, two important ones being software engineering and performance issues. We argue that application modularity is a key concept to help the developer handle the complexity of these applications. We discuss how various approaches borrowed from other existing works can be combined to significantly improve the modularity of VR applications. This led to the development of the FlowVR middleware that associates a data-flow model with a hierarchical component model. Different case studies are presented to discuss the benefits of the approach proposed

Évaluation des habiletés de vie autonome chez les personnes psychotiques

Ce texte détaille les caractéristiques métrologiques de l'Échelle des habiletés de Vie Autonome (EHVA) mesurant les habiletés requises chez des personnes psychotiques, pour fonctionner de façon autonome au sein de la communauté. Ce questionnaire, qui comprend 65 items répartis en dix échelles d'habiletés, a été administré à 276 personnes psychotiques. Les résultats indiquent que, dans l'ensemble, la fidélité de cet instrument est bonne, mesurée par l'accord interjuges et les coefficients alpha. Trois des 10 échelles, soit les échelles Déplacement, Recherche d'emploi et Maintien de l'emploi, n'ont pu être conservées dans la version finale. Les quatre aspects de la validité examinés dans cette étude se révèlent très satisfaisants; il s'agit du degré de convergence entre l'évaluation faite par les participants eux-mêmes et par un membre du personnel soignant, des analyses discriminantes, des corrélations convergentes-divergentes avec d'autres instruments de mesure du fonctionnement psychosocial et de l'analyse factorielle exploratoire. Après ces analyses, la version finale de l'EHVA comprend 48 items répartis sous sept échelles. La discussion fait ressortir les qualités psychométriques d'un tel instrument en langue française et suggère des pistes de recherche pour poursuivre le développement de l'EHVA.This article studies in detail the metrological characteristics of the "Autonomous Life Skills Test" ("Echelle des Habiletés de Vie Autonome" or "EHVA") which measures the skills required of psychotic patients to function on their own in the community. The questionnaire, distributed to 276 psychotic patients, made use of 10 parameters of skills broken down into 65 items. Results show that, overall, this instrument is quite reliable, as measured by the inter-rater reliability and alpha coefficients. Three of the ten parameters, namely Mobility, Employment Search and Employment Holding, were not retained in the final version. The four validity aspects were found to be very satisfactory, namely the degree of convergence between the participant's self-evaluation and the evaluation provided by healthcare personnel, (discriminating analysis), convergent-divergent correlations with other instruments measuring psychosocial functioning and the exploratory factorial analysis. Following these analysis, the final version of the "EHVA" includes 48 items covering seven parameters. A discussion of results underscores the psychometric qualities of such a French-language instrument and suggests avenues to pursue the development of the "EHVA"

Outils de base pour l'extraction de caractéristiques de surfaces numérisées

La construction d'une surface paramétrique à partir de données issues de la numérisation d'un objet réel est une étape longue et fastidieuse pour l'utilisateur. La difficulté principale de ce processus réside dans la décomposition de la surface de l'objet en carreaux comportant, de préférence, quatre côtés. La segmentation la plus naturelle pour l'utilisateur est une décomposition supportée par des lignes caractéristiques de la surface (arêtes vives, lignes de changement de courbure,...). En effet, l'utilisation de ces propriétés permet d'obtenir une décomposition représentative des caractéristiques géométriques de la surface. Les algorithmes développés utilisent un modèle polyédrique. La technique proposée repose sur des approximations de courbures faites sur les entités (sommets et arêtes) du polyèdre pour extraire, dans un premier temps, les "arêtes vives" et, par la suite, une première segmentation de la surface. Les "arêtes vives" sont identifiées par un algorithme basé sur des critères appelés invariants de courbures discrètes. Ces critères sont calculés pour chaque sommet et arête du polyèdre. Ils sont à rapprocher des approximations de courbures discrètes classiques, mais ils définissent la "forme" d'une surface au voisinage d'un sommet ou d'une arête. Le principe d'extraction consiste alors à sélectionner un ensemble ordonné d'arêtes vérifiant certaines propriétés géométriques. Chaque partition (ensemble connecté de faces) est une zone de la surface ayant une courbure locale plus ou moins constante. Les partitions sont identifiées grâce à une technique de propagation de fronts. Les faces adjacentes au front sont insérées dans celui-ci si les approximations de courbures calculées sur leurs sommets vérifient les critères de l'algorithme. Les "arêtes vives" préalablement extraites permettent de prendre en compte des discontinuités de courbures qui constituent des contraintes complémentaires pour la propagation de chaque front.In many areas of industry, it is desirable to create geometric models of existing objects for which no such model is available. Starting from a polyhedral representation on the digitized points measured on the object, this approach proposes a first phase of a segmentation process from a polyhedral surface prior to the generation of a NURBS model. Its main idea is to find a curve network, which divides the surfaces by means of a series of "feature polygonal lines". The advantage of this approach is that the patch structure will reflect the user's concept of the structure of the surface. Noise reduction and smoothing processes take place before the segmentation process to produce adequate input data for it. The approach is based on different approximations of curvature measurements of the surface to extract, at first, the sharp edges and secondly areas forming a first segmentation of the surface. This approach is interactive and allows the user to adapt threshold values to the various areas of the object. The sharp edges are found by an algorithm, which uses criteria based on discrete curvature invariant. These criteria are based on the approximation of curvatures (mean, gaussian, absolute), which strictly describe the local form of the surface around an edge or a vertex. According to a user threshold, the result of this algorithm is a set of list of edges. Each partition of the segmentation is an area of the surface with an almost constant curvature. Each of them is found with a frontal method. A front is initiated from a face, which satisfies a discrete curvature criterion. Faces adjacent to this front are admitted in it if the value of a curvature approximation for each of their vertices verifies the same discrete curvature criterion. Sharp edges defined beforehand express curvature or tangency discontinuities, which form complementary constraints for the front propagation algorithm

Immunoregulatory CD4-CD8- T cells as a potential therapeutic tool for transplantation, autoimmunity, and cancer

A central objective in organ transplantation and the treatment or prevention of autoimmune disease is the achievement of antigen-specific immune tolerance. An additional challenge in bone marrow transplantation for the treatment of hematological malignancies is the prevention of graft-vs-host disease (GVHD) while maintaining graft-vs-tumor activity. Interestingly, CD4-CD8- (double negative, DN) T cells, which exhibit a unique antigen-specific immunoregulatory potential, appear to exhibit all of the properties to respond to these challenges. Herein, we review the therapeutic potential of immunoregulatory DN T cells in various immunopathological settings, including graft tolerance, GVHD, cancer, and autoimmunity