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International audience; Floating Offshore Wind Turbines (FOWT's) are subjected to different types of dynamic loads such as environmental loads (wave and wind), aero-structure interaction loads and mechanical loads (inertial and controller effects). These loads induce vibrations in the WT mast that are transmitted in the floating foundation and mooring lines, increasing the overall ultimate loads and fatigue cycling. In this paper the potentiality of a passive nonlinear mechanical system for the reduction of WT mast vibrations is studied. This kind of absorber called Nonlinear Energy Sink (NES) is based on the energy pumping phenomenon. The feasibility and efficiency of the absorber is first demonstrated by means of a simplified full-scale numerical model composed of two degrees of freedom, one for the WT mast (first bending mode) and one for NES. Then, an equivalent reduced scale model is considered and analyzed by numerical simulations and experiments. The study is concluded with the sizing of an optimized absorber for the full-scale system. Some sensitivity analyses considering variations of the mast structural characteristics (stiffness and structural damping) are performed to investigate the NES efficiency limits, confirming the performances of the NES: reduction of vibratory level around 8-10 dB over a large range of functioning loads.

Reliability assessment has always been a major concern in the design of computing systems. The results of the assessment highlight and guide enhancements which trigger redesign cycles; thus early and accurate reliability assessment is of profound importance. For the purposes of early reliability analysis, abstract models of the design (which are available in early design stages) are typically used. These models, however, may not be completely accurate compared to the actual final design. Existing literature has not quantified this inaccuracy, through a comparison between Register-Transfer-Level (RTL) and microarchitecture-level reliability assessment on the same commercial microprocessor design. In this paper, we perform reliability assessment using statistical fault-injection on the RTL and Microarchitectural models of the same commercial ARM Cortex-A9 processor. The assessment was performed using the same benchmark workloads and equivalent configurations of the hardware structures. The results show that, compared to RTL model, the almost 200x faster microarchitectural model reports an average difference of 0.7 percentile units (10%) on the vulnerability estimation of register file and 3 percentile units (20%) on the vulnerability estimation of L1 data cache.

Advanced multifunctional computing systems realized in forthcoming technologies hold the promise of a significant increase of the computational capability that will offer end-users ever improving services and functionalities (e.g., next generation mobile devices, cloud services, etc.). However, the same path that is leading technologies toward these remarkable achievements is also making electronic devices increasingly unreliable, posing a threat to our society that is depending on the ICT in every aspect of human activities. Reliability of electronic systems is therefore a key challenge for the whole ICT technology and must be guaranteed without penalizing or slowing down the characteristics of the final products. CLERECO EU FP7 (GA No. 611404) research project addresses early accurate reliability evaluation and efficient exploitation of reliability at different design phases, since these aspects are two of the most important and challenging tasks toward this goal.

International audience; In this talk, it is presented the main facts about targeted energy transfer in Acoustics.

National audience; Dans le cadre du projet ANR « ADYNO », le laboratoire vise à développer des absorbeurs non-linéaires acoustiques en basses fréquences fonctionnant sur le principe du pompage énergétique. Il s'agit de contrôler le champ acoustique en réalisant un transfert irréversible de l'énergie du milieu acoustique (système linéaire) vers un dispositif à raideur non linéaire : l'absorbeur. Aujourd'hui, le pompage énergétique en acoustique est bien maitrisé avec des absorbeurs utilisant d'une membrane visco-élastique fine et très faiblement pré-tendue [1]. Dans cette étude, nous cherchons à utiliser directement un haut-parleur (HP) comme absorbeur non-linéaire. Deux solutions peuvent être envisagées pour « construire » la non-linéarité : modifier la suspension du HP pour le rendre non-linéaire, ou utiliser le HP au-delà de son régime de fonctionnement normal (linéaire). La technologie « haut-parleur » ouvre de nouvelles voies comme la possibilité de contrôler en temps réel la dissipation introduite par l'absorbeur et/ou de récupérer de l'énergie transférée au HP. Enfin, notons que l'étude numérique a été grandement facilitée par le fait que le comportement dynamique d'un HP reste, à basse fréquence, proche de celui d'un oscillateur à 1 degré de liberté. Des essais expérimentaux de type quasi-statiques et dynamiques réalisés sur des haut-parleurs avec et sans modifications ont permis de maitriser les modifications à apporter au HP et de développer un modèle simplifié à un degré de liberté capable de reproduire son comportement élastique non-linéaire et dissipatif. Des simulations numériques ont permis de valider la technologie HP dans le cas de réponse libre et forcée. De plus les avantages liés à la possibilité de contrôler la dissipation ont été mis en évidence. Un montage expérimental a été dimensionné sur la base de ces simulations, il est actuellement en phase de réalisation. [1] R. Bellet, B. Cochelin, P. Herzog, P.-O. Mattei, Experimental study of energy pumping in acoustics, Proceedings of IDETC/CIE 2007 - ASME 2007, Las Vegas, Nevada, USA.

Aim of the present report is the analysis of the data related to the full scale trials in rough sea on Bettica ship.