Topology-based Physical Simulation

International audienceThis paper presents a framework to design mechanical models relying on a topological basis. Whereas naive topological models such as adjacency graphs provide low topological control, the use of efficient topological models such as generalized maps guarantees the quasi-manifold property of the manipulated object: Topological inquiries or changes can be handled robustly and allow the model designer to focus on mechanical aspects. Even if the topology structure is more detailed and consumes more memory, we show that an efficient implementation does not impact computation time and still enables real-time simulation and interaction. We analyze how a simple mass/spring model can be embedded within this framework

Antibioprophylaxie en chirurgie vétérinaire : bilan sur des données actuelles

L’infection est un risque permanent inhérent à l’acte chirurgical. La plaie opératoire offre un milieu favorable aux micro-organismes bactériens, que les défenses naturelles locales amoindries ne sont plus capables de combattre totalement. Le rôle de l’antibioprophylaxie est de s’opposer à la prolifération bactérienne et de diminuer ainsi la survenue de complications post-opératoires telles que les infections. L’émergence de bactéries multi-résistantes et leur fréquence, ont conduit à reconsidérer l’usage des antibiotiques chez l’homme et l’animal. Même si l’antibiothérapie est la première remise en cause, la prophylaxie doit aussi être raisonnée. Ce travail est un recueil bibliographique des données existantes et actualisées sur l’antibioprophylaxie chez le chien et le chat. Il fournit également des éléments de comparaison avec la pratique en médecine humaine. Les principes de l’antibioprophylaxie sont présentés dans la première partie. La seconde partie fait état d’un panel de protocoles utilisés par des vétérinaires praticiens. La troisième partie répertorie des recommandations par type d’intervention à partir de données vétérinaires éclairées par des recommandations disponibles chez l’homme

Adaptive Resolution for Topology Modifications in Physically-based Animation

This paper shows the interest of basing a mechanical mesh upon an efficient topological model in order to give any simulation the ability to refine this mesh locally and apply topological modifications such as cutting, tear and matter destruction.Refinement and modifications can indeed be combined in order to get a more precise result.The powerful combinatorial map model provides the mathematical background which ensures that the quasi-manifold property is guaranteed for the mesh after any topological modification.The obtained results offer the versatility and time efficiency that are expected in applications such as surgical simulation

Efficient Simulation of Fluids

Fluid simulation is based on Navier-Stokes equations. Efficient simulation codes may rely on the smooth particle hydrodynamic toolbox (SPH), a method that uses kernel density estimation. Many variants of SPH have been proposed to optimize the simulation, like implicit incompressible SPH (IISPH) or predictive-corrective incompressible SPH (PC-ISPH). This chapter recalls the formulation of SPH and focuses on its effective parallel implementation using the Nvidia common unified device architecture (CUDA), while message passing interface (MPI) is another option. The key to effective implementation is a dedicated accelerating structure, and therefore some well-chosen parallel design patterns are detailed. Using a rough model of the ocean, this type of simulation can be used directly to simulate a tsunami resulting from an underwater earthquake

Association Mouvement/Géométrie pour représentations volumiques

Session: AnimationNational audienceLes modèles particulaires permettent de produire des animations riches et variées. Ils sont particulièrement adaptés à certains effets d'animation. Mais intrinsèquement, ils ne sont pas basés sur des représentations surfaciques ou volumiques d'objets. Ainsi, visualiser le mouvement qu'ils décrivent peut poser problème car ils ne contiennent souvent pas assez d'information pour reconstruire la moindre topologie spatiale sous-jacente. Plus précisément, un mouvement produit par de tels modèles peut être rendu via différentes formes géométriques et mener à autant d'interprétations visuelles, sans contrôle de l'utilisateur. À notre connaissance, il n'existe pas de méthode générique associant des mouvements basés points, comme ceux produits par un modèle particulaire, ou n'importe quel ensemble de points en mouvement, à une structure topologique. Dans cet article, nous proposons un "framework" permettant d'associer, selon les souhaits de l'utilisateur, n'importe quelle forme volumique à n'importe quel mouvement basé points, et de contrôler les changements topologiques. Il est ainsi possible de créer différents résultats visuels avec une unique description de mouvement. Ce "framework" est séparé en trois processus distincts : l'association entre particules et sommets, la définition de l'application du mouvement aux sommets du maillage, et les modifications topologiques et les événements qui les déclenchent. Nous montrons comment la manipulation de ces paramètres permet d'expérimenter différentes associations sur un même mouvement

Adolescents’ Developing Sensitivity to Orthographic and Semantic Cues During Visual Search for Words

Two eye-tracking experiments were conducted to assess the influence of words either looking like the target word (orthographic distractors) or semantically related to the target word (semantic distractors) on visual search for words within lists by adolescents of 11, 13, and 15 years of age. In Experiment 1 (literal search task), participants saw the target word before the search (e.g., “raven”), whereas in Experiment 2 (categorical task) the target word was only defined by its semantic category (e.g., “bird”). In both experiments, participants’ search times decreased from fifth to ninth grade, both because older adolescents gazed less often at non-target words during the search and because they could reject non-target words more quickly once they were fixated. Progress in visual search efficiency was associated with a large increase in word identification skills, which were a strong determinant of average gaze durations and search times for the categorical task, but much less for the literal task. In the literal task, the presence of orthographic or semantic distractors in the list increased search times for all age groups. In the categorical task, the impact of semantic distractor words was stronger than in the literal task because participants needed to gaze at the semantic distractors longer than at the other words before rejecting them. Altogether, the data support the assumption that the progressive automation of word decoding up until the age of 12 and the better quality of older adolescents’ lexical representations facilitate a flexible use of both the perceptual and semantic features of words for top-down guidance within the displays. In particular, older adolescents were better prepared to aim at or reject words without gazing at them directly. Finally, the overall similar progression of the maturation of single word visual search processes and that of more real-life information search within complex verbal documents suggests that the young adolescents’ difficulties in searching the Web effectively could be due to their insufficiently developed lexical representations and word decoding abilities

A Survey of Ocean Simulation and Rendering Techniques in Computer Graphics

This paper presents a survey of ocean simulation and rendering methods in computer graphics. To model and animate the ocean's surface, these methods mainly rely on two main approaches: on the one hand, those which approximate ocean dynamics with parametric, spectral or hybrid models and use empirical laws from oceanographic research. We will see that this type of methods essentially allows the simulation of ocean scenes in the deep water domain, without breaking waves. On the other hand, physically-based methods use Navier-Stokes Equations (NSE) to represent breaking waves and more generally ocean surface near the shore. We also describe ocean rendering methods in computer graphics, with a special interest in the simulation of phenomena such as foam and spray, and light's interaction with the ocean surface

CONSTRUÇÃO E EFICIÊNCIA DE UM FOTORREATOR DE RADIAÇÃO ULTRAVIOLETA DE BAIXO CUSTO PARA DESINFECÇÃO DE ÁGUA

A água é um bem imprescindível para sobrevivência e desenvolvimento dos seres vivos, e sua qualidade pode ser diretamente relacionada à saúde daqueles que a consomem ou utilizam. Nesse sentido, para minimizar os riscos de agentes biológicos presentes nas águas, a radiação ultravioleta (UV-C, 254 nm) é uma importante alternativa de desinfecção, pois inativa o material genético dos microrganismos sem o uso de oxidantes químicos. Portanto, no presente estudo objetivou-se a construção de um fotorreator UV de baixo custo e a análise de sua eficiência na desinfecção de água. Inicialmente, foram pesquisados sistemas comerciais que empregam a radiação UV para finalidade proposta. Em seguida procedeu-se a construção do fotorreator com materiais alternativos e a análise da sua eficiência na desinfecção de três amostras de efluente sanitário tratado, provenientes da região metropolitana de Porto Alegre - RS. A eficiência de desinfecção foi avaliada por meio da comparação da contagem de microrganismos crescidos em placas de Petri contendo ágar MacConkey, durante 48 h a 36 ºC, após operação do fotorreator em batelada, em diferentes tempos: 0, 3, 6, 9, 12, 15, 18 e 21 minutos, além de um controle com a água da companhia de abastecimento. Os resultados foram avaliados por ANOVA, seguido de teste Tukey ao nível de 5% de probabilidade.  Como resultados, tem-se a montagem do fotorreator de 15 W em PVC, de 1,6 L, ao custo total de R$ 137,88, ou seja, equivalente a 53,05% do custo de outro fotorreator disponível via e-commerce, de dimensões inferiores. As análises das amostras do efluente, nos tempos de detenção descritos, indicaram que não houve diferença estatística entre as UFC mL-1 da água fornecida pela companhia de abastecimento e o efluente após desinfecção por 9 minutos no fotorreator. Também se verificou redução significativa no número de colônias nos 3 primeiros minutos de operação do reator. Contudo, pode-se inferir que o melhor tempo de detenção hidráulica foi de 15 minutos, tendo em vista a maior redução da concentração de UFC mL-1 que foi de 99,25% em relação ao efluente estudado. Portanto, conclui-se que o sistema pode ser empregado na desinfecção de águas residuárias ou como solução para regiões onde não há tratamento adequado

La disgrâce de l'échelon communal et des CCAS s'accentue au profit du jacobinisme départemental

International audienceCommentaire de la loi du 29 juillet 199