Vertex-based Compatible Discrete Operator schemes on polyhedral meshes for advection-diffusion equations

International audienceWe devise and analyze vertex-based, Péclet-robust, lowest-order schemes for advection-diffusion equations that support polyhedral meshes. The schemes are formulated using Compatible Discrete Operators (CDO), namely primal and dual discrete differential operators, a discrete contraction operator for advection, and a discrete Hodge operator for diffusion. Moreover, discrete boundary operators are devised to weakly enforce Dirichlet boundary conditions. The analysis sheds new light on the theory of Friedrichs' operators at the purely algebraic level. Moreover, an extension of the stability analysis hinging on inf-sup conditions is presented to incorporate divergence-free velocity fields under some assumptions. Error bounds and convergence rates for smooth solutions are derived, and numerical results are presented on three-dimensional polyhedral meshes

Para-iliac actinomycetoma presenting as sarcoma, a late complication of appendicitis: A case report

AbstractINTRODUCTIONActinomycosis is known to mimic several types of neoplasms, leading to morbid surgical interventions.PRESENTATION OF CASEWe report the particular case of an extensive right para-iliac actinomycetoma presenting as a sarcoma, which to our knowledge has not yet been described in the literature, in a patient with previous ruptured appendicitis. Thanks to the collaborative work between the orthopedic and general surgeons, pathologist and microbiologist, the diagnosis of actinomycosis was made pre-operatively, saving this 15-year-old patient from a tumor resection protocol.DISCUSSIONActinomycetomas have often been reported to present in the same way as several abdominal and gynecological neoplasms, and on rare occasions been described as mimicking other soft-tissue sarcomas, leading to unnecessary morbid tumor resection protocols. The most common cause of abdominal actinomycosis is perforated appendicitis, and may present several years later.CONCLUSIONWhile faced with a soft tissue mass transgressing tissue planes and possibly extending to the region of the right lower quadrant, especially with a history of previous perforated appendicitis, one should consider the possibility of an abscess caused by pathogens of intestinal origin, including the gram positive anaerobe Actinomycosis israelii. Failure to actively search for this pathogen, which is not detectable with routine staining techniques and may take up to 1–2 weeks to isolate, may lead to unnecessary morbid surgical procedures

Learning parameters for the sequence constraint from solutions

This paper studies the problem of learning parameters for global constraints such as Sequence from a small set of positive examples. The proposed technique computes the probability of observing a given constraint in a random solution. This probability is used to select the more likely constraint in a list of candidates. The learning method can be applied to both soft and hard constraint

Conception et évaluation d’ateliers de formation visant à développer un comportement préventif au travail chez les élèves en apprentissage d’un métier

La formation à la prévention offerte dans les programmes de formation professionnelle présente plusieurs lacunes, faisant en sorte que les apprentissages qui y sont faits seraient peu mobilisés à l’entrée sur le marché du travail. Il appert, entre autres, que les ressources pédagogiques utilisées ne cibleraient pas les risques à la santé spécifiques au métier. Concevoir et évaluer des ateliers de formation visant le développement d’un comportement préventif au travail chez les élèves des programmes de secrétariat et de réalisation d’aménagements paysagers. Un processus systématique a été suivi pour concevoir les ateliers de formation. L’évaluation a porté sur trois variables : 1) la perception des apprenants, 2) les apprentissages réalisés et 3) le comportement préventif. Les résultats de cette étude décrivent la démarche de conception des ateliers de formation et suggèrent une amélioration significative sur les trois variables à la suite de la participation des élèves à ces mêmes ateliers. La démarche de conception des ateliers de formation détaillée dans cet article permet la réplication dans d’autres programmes de formation professionnelle. Des bases empiriques sont maintenant connues et peuvent servir de références dans l’élaboration d’études futures.The prevention training offered in vocational programs has several shortcomings, and, as a result, students make little use of it when they enter the labour market. It would appear that the teaching resources employed do not target the specific health risks associated with a given occupation. To design and evaluate workshops aimed at developing preventive behaviour in the workplace among students in secretarial and landscaping programs. A systematic process was followed in the development of the workshops. The evaluation focused on three variables : 1) the satisfaction with the workshops, 2) the apprenticeship, and 3) preventive behaviour. The results of this study describe the process for designing the workshops and suggest a significant improvement in the three variables following the participation of the students in these workshops. The process for designing the workshops described in this article can be replicated in other vocational programs. The empirical bases are now known and can be used as references in the development of future studies.La formación en prevención ofrecida en los programas de capacitación profesional presenta varias lagunas, lo que hace que los aprendizajes que se realizan en estos son poco movilizadores a la entrada en el mercado de trabajo. Parece ser, entre otras cosas, que los recursos educativos utilizados no se enfocan en los riesgos específicos a la profesión. Diseñar y evaluar talleres de capacitación encaminados a desarrollar un comportamiento preventivo en el trabajo en los estudiantes de los programas de secretariado y paisajismo. Se siguió un proceso sistemático para diseñar los talleres de capacitación. La evaluación se centró en tres variables: 1) la percepción de los alumnos, 2) el aprendizaje alcanzado y 3) el comportamiento preventivo. Los resultados de este estudio describen el proceso de diseño de los talleres de capacitación y sugieren una mejora significativa en las tres variables como resultado de la participación de los estudiantes en estos mismos talleres. El proceso de diseño de los talleres de capacitación detallado en este artículo permite la reproducción en otros programas de capacitación profesional. Se conocen ahora las bases empíricas y estas pueden servir como referencias en el desarrollo de estudios futuros

In-Datacenter Performance Analysis of a Tensor Processing Unit

Many architects believe that major improvements in cost-energy-performance must now come from domain-specific hardware. This paper evaluates a custom ASIC---called a Tensor Processing Unit (TPU)---deployed in datacenters since 2015 that accelerates the inference phase of neural networks (NN). The heart of the TPU is a 65,536 8-bit MAC matrix multiply unit that offers a peak throughput of 92 TeraOps/second (TOPS) and a large (28 MiB) software-managed on-chip memory. The TPU's deterministic execution model is a better match to the 99th-percentile response-time requirement of our NN applications than are the time-varying optimizations of CPUs and GPUs (caches, out-of-order execution, multithreading, multiprocessing, prefetching, ...) that help average throughput more than guaranteed latency. The lack of such features helps explain why, despite having myriad MACs and a big memory, the TPU is relatively small and low power. We compare the TPU to a server-class Intel Haswell CPU and an Nvidia K80 GPU, which are contemporaries deployed in the same datacenters. Our workload, written in the high-level TensorFlow framework, uses production NN applications (MLPs, CNNs, and LSTMs) that represent 95% of our datacenters' NN inference demand. Despite low utilization for some applications, the TPU is on average about 15X - 30X faster than its contemporary GPU or CPU, with TOPS/Watt about 30X - 80X higher. Moreover, using the GPU's GDDR5 memory in the TPU would triple achieved TOPS and raise TOPS/Watt to nearly 70X the GPU and 200X the CPU.Comment: 17 pages, 11 figures, 8 tables. To appear at the 44th International Symposium on Computer Architecture (ISCA), Toronto, Canada, June 24-28, 201

Well-posedness of the scalar and the vector advection-reaction problems in Banach graph spaces

An extension of the well-posedness analysis of the scalar and the vector advection-reaction problem in Banach graph spaces of power p ∈ (1, ∞) is proposed. This analysis is based on the sign of the associated Friedrichs tensor, taking positive, null or reasonably negative values

Approximation des problèmes de transport scalaire et vectoriel sur maillages polyédriques

This thesis analyzes, at the continuous and at the discrete level on polyhedral meshes, the scalar and the vector transport problems in three-dimensional domains. These problems are composed of a diffusive term, an advective term, and a reactive term. In the context of Friedrichs systems, the continuous problems are analyzed in Lebesgue graph spaces. The classical positivity assumption on the Friedrichs tensor is generalized so as to consider the case of practical interest where this tensor takes null or slightly negative values. A new scheme converging at the order 3/2 is devised for the scalar advection-reaction problem using scalar degrees of freedom attached to mesh vertices. Two new schemes considering as well scalar degrees of freedom attached to mesh vertices are devised for the scalar transport problem and are robust with respect to the dominant regime. The first scheme converges at the order 1/2 when advection effects are dominant and at the order 1 when diffusion effects are dominant. The second scheme improves the accuracy by converging at the order 3/2 when advection effects are dominant. Finally, a new scheme converging at the order 1/2 is devised for the vector advection-reaction problem considering only one scalar degree of freedom per mesh edge. The accuracy and the efficiency of all these schemes are assessed on various test cases using three-dimensional polyhedral meshesCette thèse étudie, au niveau continu et au niveau discret sur des maillages polyédriques, les équations de transport tridimensionnelles scalaire et vectorielle. Ces équations sont constituées d'un terme diffusif, d'un terme advectif et d'un terme réactif. Dans le cadre des systèmes de Friedrichs, l'analyse mathématique est effectuée dans les espaces du graphe associés aux espaces de Lebesgue. Les conditions de positivité usuelles sur le tenseur de Friedrichs sont étendues au niveau continu et au niveau discret afin de prendre en compte les cas d'intérêt pratique où ce tenseur prend des valeurs nulles ou raisonnablement négatives. Un nouveau schéma convergeant à l'ordre 3/2 est proposé pour le problème d'advection-réaction scalaire en considérant des degrés de liberté scalaires associés aux sommets du maillage. Deux nouveaux schémas considérant également des degrés de libertés aux sommets sont proposés pour le problème de transport scalaire en traitant de manière robuste les différents régimes dominants. Le premier schéma converge à l'ordre 1/2 si les effets advectifs sont dominants et à l'ordre 1 si les effets diffusifs sont dominants. Le second schéma améliore la précision de ce schéma en convergeant à l'ordre 3/2 lorsque les effets advectifs sont dominants. Enfin, un nouveau schéma convergeant à l'ordre 1/2 est obtenu pour le problème d'advection-réaction vectoriel en considérant un seul et unique degré de liberté scalaire sur chaque arête du maillage. La précision et les performances de tous ces schémas sont examinées sur plusieurs cas tests utilisant des maillages polyédriques tridimensionnel