The effects of wind-induced inclination on the dynamics of semi-submersible floating wind turbines in the time domain

This study focusses on the coupling effects arising from the changes in the hydrodynamic behaviour of a semi-submersible floating wind turbine when it undergoes large inclinations under wind loading. By means of a range of time-domain simulations, it is shown that both the hull geometric nonlinearity effect and the alteration of viscous hydrodynamic forces can significantly affect the dynamics of a typical floating wind turbine operating in waves at rated conditions. The consequences of said effects for both aligned and misaligned wind and waves are explored. In general terms inclinations are found to increase motions, where the modes that are more affected depend on the relative direction between incident wind and waves. Understanding the sources of aero-hydrodynamic coupling is key to providing sound design and modelling guidelines for the coming generation of floating wind turbines

PLACE DE L'ENTEROSCOPIE PEROPERATOIRE DANS LE DIAGNOSTIC ET LE TRAITEMENT DES HEMORRAGIES DIGESTIVES DE CAUSE INDETERMINEE

PARIS-BIUM (751062103) / SudocCentre Technique Livre Ens. Sup. (774682301) / SudocSudocFranceF

La Loi du 30 juillet 1981 tendant à réprimer certains actes inspirés par le racisme et la xénophobie

Editeur :Schüler HergoldingLieu :Munichinfo:eu-repo/semantics/publishe

Coordinated Learning for Wind Farm Optimization

Optimal efficiency and loads alleviation in a dynamic environment necessitates a wind farm controller that can anticipate and quickly adapt to changing wind and wake conditions. In this work, we explore several strategies for collective learning and optmization, first using a high-level parametric wake model, and then a more complex approach, i.e. Large Eddy Simulation (LES) coupled to a wind turbine model

Colorectal cancer care in elderly patients: Unsolved issues

IF 2.719International audienceColorectal cancers are common in elderly patients. However, cancer screening is poorly used after 75. Elderly patients form a heterogeneous population with specific characteristics. Standards of care cannot therefore be transposed from young to elderly patients. Tumour resection is frequently performed but adjuvant chemotherapy is rarely prescribed as there are no clearly established standards of care. In a metastatic setting, recent phase III studies have demonstrated that doublet front-line chemotherapy provided no survival benefit. Moreover, several studies have established the benefit of bevacizumab in association with chemotherapy. There is a lack of evidence for the efficacy of anti-epidermal growth factor antibodies in elderly patients. Geriatric assessments could help to select the adequate treatment strategy for individual patients. Geriatric oncology is now the challenge we have to face, and more specific trials are needed. (C) 2016 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved

Biomimetic individual pitch control for load alleviation

Individual pitch control has shown great capability of alleviating the oscillating loads experienced by wind turbine blades due to wind shear, atmospheric turbulence, yaw misalignement or wake impingement. This work presents a bio-inspired structure for individual pitch control where neural oscillators produce basic rhythmic patterns of the pitch angles, while a deep neural network modulates them according to the environmental conditions. This mimics, respectively, the central patterns generators present in the spinal chord of animals and their cortex. The mimicry further applies to the neural network as it is trained with reinforcement learning, a method inspired by the trial and error way of animal learning. Large eddy simulations of the reference NREL 5MW wind turbine using this biomimetic controller show that the neural network learns how to reduce fatigue loads by producing smooth pitching commands

Characterisation and Online Update of a Vorticity-Based Wind Skeleton Wake Model

Wind turbine wake physics is by nature unsteady and highly sensitive to the local wind characteristics. While modern Computational Fluid Dynamic methods (eg: Large Eddy Simulation) allow to accurately capture the flow at the wind farm scale, they still come at a prohibitive computational cost preventing their use for online control or Machine Learning schemes. This work pursues the recent efforts undertaken by Marichal et al. (2017) to develop a computationally affordable yet accurate unsteady Wake Model. Marichal et al. (2017) introduced and successfully tested a vorticity-based skeleton Wake Model (WM). This vorticity-based skeleton essentially consists of a regularized Vortex Sheet Tube (VST) in the near wake which then transitions into a Vortex Dipole Line (VDL) in the far wake. The rotor operation itself is modelled using the Blade Element theory. The present study further assesses the performances of the WM: it extends the validation procedure to various wind turbine settings (ie: different Tip Speed Ratios) and inflow conditions. The data recovered from the wake model is compared to that extracted from high fidelity numerical simulations performed on the NREL 5MW wind turbine using an Immersed Lifting Line-enabled Vortex Particle-Mesh (VPM) flow solver. Online model update strategies are then discussed. Indeed, the existing WM still requires the knowledge of the upstream wind conditions in order to provide an accurate downstream wind field estimate. Following Bottasso et al. (2018), an Extended Kalman Filter (EKF) estimating the Rotor-Effective Wind Speed by a Blade-Load- based Estimator is implemented. This EKF allows to estimate the wind profile upstream the wind turbine and eventually to feed it to the vorticity-based skeleton wake model as an input parameter. We finally plan to extend the tools developed to a two-turbines system. The downstream wind profile provided by the Kalman estimator will be compared to that given by the wake model computed by the upstream turbine. Data assimilation techniques will then be used to correct the wake model online

CEE, Etats-Unis, Japon : une comparaison de leurs commerces extérieurs

[fre] Les trois principaux pôles du commerce mondial sont la Communauté économique européenne considérée comme une entité (c'est-à-dire abstraction faite des échanges entre ses douze membres), les Etats-Unis et le Japon. La CEE demeure le premier exportateur malgré la percée du Japon. Elle n'est désormais que le second importateur, les Etats-Unis l'ayant dépassée depuis 1984. La CEE est relativement moins tournée vers les pays industrialisés que ne le sont les deux autres pôles. Elle est plus insérée dans son environnement géo-économique, c'est-à-dire le reste du continent européen, l'Afrique et le Moyen-Orient. C'est avec cette zone d'influence qu'elle réalise la majeure partie de ses échanges, et c'est grâce à elle qu'elle a réalisé en 1986 un excédent unique au cours des vingt années considérées. C'est sur elle qu'elle est parvenue à préserver sa part de marché, tandis que les Etats-Unis réussissaient à ne pas en perdre sur leur propre zone d'influence. Des « chasses gardées » subsistent clairement face à la poussée ancienne du Japon et plus récente des NPI asiatiques qui réalisent leur percée de deux autres manières : d'une part sur la zone d'influence de la CEE au détriment des Etats-Unis et sur celle des Etats-Unis au détrirrrent de la CEE ; d'autre part directement sur les marchés intérieurs de ces deux pôles. L'amélioration récente du solde commercial de la CEE est due à la fois aux produits énergétiques (à l'importation et à l'exportation), aux matières premières et produits alimentaires (au détriment des Etats-Unis) et aux produits manufacturés. Pour ces derniers la CEE apparaît moins spécialisée que les Etats- Unis et le Japon dans les hautes technologies et ses résultats sont meilleurs à l'importation qu'à l'exportation. Elle parvient à contenir ses importations, mais non à accroître fortement ses exportations. Son excédent apparaît donc fragile dans une période où les Etats-Unis disposent à nouveau d'un taux de change bas et considèrent, comme d'ailleurs les pays asiatiques, que la CEE constitue le débouché extérieur le plus prometteur pour les prochaines années. [eng] The External Trade of the EEC, Japan and the United States : A Comparison Division de l'environnement international du département des diagnostics de l'OFCE The three main poles of world trade are the European Economic Community regarded here as a whole (i.e. after excluding the internal trade between its twelve members), the United States and Japan. The EEC remains the first exporter in spite of the Japanese breakthrough. As far as imports are concerned the United States overtook the Community in 1984 which from then has been in the second position. The EEC directs much less its trade towards the industrialized countries than the other two do. The Community is indeed much more linked to its geographical and economic environment, which can be defined as the remainder of the European continent plus Africa and the Middle East. This area of influence enabled the EEC to record in 1986 (and for the first time in twenty years) an overall trade surplus. The EEC has succeeded in maintaining its market shares on its priviledged zone while the US have managed to avoid any reduction in theirs on their own area of influence. Therefore the buoyancy of Japan and the NIC's have not yet been able to evict the EEC and the US from their respective traditional outlets. However Japan and the NIC's broke through in other ways. They successfully competed with the US on the European area of influence and with the EEC on the United States'. Besides they increased their market shares both in Europe and in the United States. So far the Community has achieved relatively better results in controlling the import growth than it has in promoting exports. Therefore the European external surplus appears frail especially at a time when the dollar exchange rate is low and when the European market is more and more regarded by the US and the Asian countries as the most attractive outlet for the years to come.