Le recours aux logiciels de simulation basés sur la méthode des éléments finis devenant de plus en plus systématique dans les différents secteurs de l'industrie, l'efficacité et la précision de ces derniers deviennent des propriétés déterminantes. Dans les situations les plus courantes, les structures minces nécessitent une analyse précise et efficace, rendue possible par les éléments coques. En présence de structures dans lesquelles coexistent des parties minces et des zones plus épaisses, l'utilisation de ces éléments est encore plus cruciale. Ce travail est une contribution au développement et à la validation d'éléments finis solide-coques. Les déplacements nodaux sont les seuls degrés de liberté et ils sont munis d'un ensemble de points d'intégration distribués le long d'une direction préférentielle, désignée comme “l'épaisseur”. Une intégration réduite dans le plan moyen est utilisée. La loi élastique 3D est modifiée pour s'approcher de la situation coque et atténuer les verrouillages. Grâce à ses formulations particulières, ces éléments solide-coques se connectent naturellement aux éléments 3D et présentent une bonne performance dans des applications de structures minces et pour des problèmes dominés par la flexion. Il s'agit des trois nouveaux éléments isoparamétriques SHB6, SHB15, et SHB20. L'analyse détaillée d'une potentielle déficience du rang de la matrice de raideur a révélé que ces derniers ne possèdent pas de modes à énergie nulle et qu'aucune stabilisation n'est donc nécessaire. Néanmoins, nous proposons des modifications basées sur la méthode bien connue “Assumed Strain”, pour l'opérateur gradient discrétisé de l'élément SHB6, dans le but d'améliorer sa vitesse de convergence. Pour illustrer les capacités de ces éléments, ses performances sont évaluées sur un ensemble de cas tests en configurations linéaire ou non-linéaire, communément utilisés dans la littérature pour tester les éléments finis de type coques. En particulier, il est montré que le nouvel élément SHB6 joue un rôle très utile en tant que complément à l'élément hexaèdre SHB8PS, ce qui nous permet ainsi de mailler des géométries arbitraires.

The summer after Amanda S. Frasier left K-12 teaching to return to high education, she received an email stating that her students’ end-of-year assessments were in. When she looked at the scores, she was pleased to see they had done so well, even though she questions the value of standardized accountability measures and didn’t learn anything new from the results. Frasier discusses why these scores are not helpful and advocates more meaningful measures.

So far the optimization of integration processes between heterogeneous data sources is still an open challenge. A first step towards sufficient techniques was the specification of a universal benchmark for integration systems. This DIPBench allows to compare solutions under controlled conditions and would help generate interest in this research area. However, we see the requirement for providing a sophisticated toolsuite in order to minimize the effort for benchmark execution. This demo illustrates the use of the DIPBench toolsuite. We show the macro-architecture as well as the micro-architecture of each tool. Furthermore, we also present the first reference benchmark implementation using a federated DBMS. Thereby, we discuss the impact of the defined benchmark scale factors. Finally, we want to give guidance on how to benchmark other integration systems and how to extend the toolsuite with new distribution functions or other functionalities.

The ever increasing demand for Internet traffic, storage and processing requires an ever increasing amount of hardware resources. In addition to this, infrastructure providers over-provision system architectures to serve users at peak times without performance delays. Over-provisioning leads to underutilization and thus to unnecessary power consumption. Therefore, there is a need for workload management strategies to map and schedule different services simultaneously in an energy-efficient manner without compromising performance, specially for heterogeneous micro-server architectures. This requires statistical models of how services interfere with each other, thereby affecting both performance and energy consumption. Indeed, the performance-energy behavior when mixing workloads is not well understood. This paper presents an interference analysis for heterogeneous workloads (i.e., CPU- and memory-intensive) on a big.LITTLE MPSoC architecture. We employ state-of-the-art tools to generate multiple single-application mappings and characterize the interference among two different services. We observed a performance degradation factor between 1.1 and 2.5. For some configurations, executing on different clusters resulted in reduced energy consumption with no performance penalty. This kind of detailed analysis give us first insights towards more general models for future workload management systems.

Data centres and similar server clusters consume a large amount of energy. However, not all consumed energy produces useful work. Servers consume a disproportional amount of energy when they are idle, underutilised, or overloaded. The effect of these conditions can be minimised by attempting to balance the demand for and the supply of resources through a careful prediction of future workloads and their efficient consolidation. In this paper we extend the cutting stock problem for consolidating workloads having stochastic characteristics. Hence, we employ the aggregate probability density function of co-located and simultaneously executing services to establish valid patterns. A valid pattern is one yielding an overall resource utilisation below a set threshold. We tested the scope and usefulness of our approach on a 16-core server with 29 different benchmarks. The workloads of these benchmarks have been generated based on the CPU utilisation traces of 100 real-world virtual machines which we obtained from a Google data centre hosting more than 32000 virtual machines. Altogether, we considered 600 different consolidation scenarios during our experiment. We compared the performance of our approach-system overload probability, job completion time, and energy consumption-with four existing/proposed scheduling strategies. In each category, our approach incurred a modest penalty with respect to the best performing approach in that category, but overall resulted in a remarkable performance clearly demonstrating its capacity to achieve the best trade-off between resource consumption and performance.