Reactive control of wave energy devices – the modelling paradox

The implementation of energy maximising control systems (EMCSs) in wave energy converter (WEC) devices is an important step towards commercially viable operation of WECs. During the design stage of such EMCSs, linear hydrodynamic models are commonly used and are, in fact, the most viable option due to the real–time computational requirements of optimisation routines associated with energy-maximising optimal control techniques. However, the objective function of EMCSs, i.e. maximising the generated power by exaggerating WEC motion, inherently violates the underlying assumption of the linear hydrodynamic control design models, i.e. small amplitude device motion (compared to the device dimensions). Consequently, the linear models, used as a basis for EMCSs, in fact conspire to violate the very assumption upon which they were built - hence leading to a modelling paradox. It is important to evaluate WEC controllers in realistic physical or numerical environments, to gain knowledge of the disparity between the performance prediction from the EMCS design and performance evaluation models. This paper presents a comprehensive assessment of the performance prediction by a linear and non–linear hydrodynamic model of three different EMCSs, implemented in two different WEC structures, in an attempt to quantify the severity of this modelling disparity, or paradox

Blood biomarker changes following therapeutic hypothermia in ischemic stroke

Biomarkers; Hypothermia; IschemiaBiomarcadores; Hipotermia; IsquemiaBiomarcadors; Hipotèrmia; IsquèmiaIntroduction Therapeutic hypothermia is a promising candidate for stroke treatment although its efficacy has not yet been demonstrated in patients. Changes in blood molecules could act as surrogate markers to evaluate the efficacy and safety of therapeutic cooling. Methods Blood samples from 54 patients included in the EuroHYP-1 study (27 treated with hypothermia, and 27 controls) were obtained at baseline, 24 ± 2 h, and 72 ± 4 h. The levels of a panel of 27 biomarkers, including matrix metalloproteinases and cardiac and inflammatory markers, were measured. Results Metalloproteinase-3 (MMP-3), fatty-acid-binding protein (FABP), and interleukin-8 (IL-8) increased over time in relation to the hypothermia treatment. Statistically significant correlations between the minimum temperature achieved by each patient in the hypothermia group and the MMP-3 level measured at 72 h, FABP level measured at 24 h, and IL-8 levels measured at 24 and 72 h were found. No differential biomarker levels were observed in patients with poor or favorable outcomes according to modified Rankin Scale scores. Conclusion Although the exact roles of MMP3, FABP, and IL-8 in hypothermia-treated stroke patients are not known, further exploration is needed to confirm their roles in brain ischemia

Finite-order hydrodynamic approximation by moment-matching (FOAMM) toolbox for wave energy applications

—Cummins’ equation is commonly used to describe the motion of Wave Energy Converters (WECs), where the radiation force is characterised by a convolution operation. The computational effort associated with the solution of the convolution term, often represents a drawback for e.g. optimisation or exhaustive-search studies. To overcome this disadvantage, and given that the convolution operator intrinsically defines a dynamical system, the convolution term is commonly approximated using suitable finite-order parametric models. To this end, the Centre for Ocean Energy Research has recently presented a moment-matching based identification method for the radiation force subsystem and the complete force-to-motion WEC dynamics (i.e. wave excitation force to device velocity). Motivated by the theory and the obtained results, already reported by the authors, the FOAMM MATLAB application has been developed, which systematically implements the moment-matching based identification strategy from raw frequency-domain data, provided by hydrodynamic solvers, in a user-friendly fashion. The aim of this paper is to describe the theoretical background behind the identification strategy, and the structure, organisation and characteristics of the developed application. Additionally, the relevant modes of operation, along with the different options of the toolbox are explained, and, at the end, a step-by-step example of how to use the FOAMM application is provided, along with recommendations from the author

Blood biomarker changes following therapeutic hypothermia in ischemic stroke

Therapeutic hypothermia is a promising candidate for stroke treatment although its efficacy has not yet been demonstrated in patients. Changes in blood molecules could act as surrogate markers to evaluate the efficacy and safety of therapeutic cooling.Instituto de Salud Carlos III, Grant/Award Number: PI18/00804; European Commission; The European Union’s Seventh Framework Programme, Grant/Award Numbers: FP7/2007-2013, 278709; The Spanish Neurovascular Disease Research Network, Grant/Award Numbers: RICORS-ICTUS, RD21/0006/0007Peer reviewe

Prise en charge de l hépatite C : étude rétrospective dans le service de médecine interne du centre hospitalier de Charleville-Mézières entre 2005 et 2013.

REIMS-BU Santé (514542104) / SudocSudocFranceF

LA MALADIE DE LYME ET SES ATTEINTES NEUROLOGIQUES (A PROPOS DE 42 CAS)

REIMS-BU Santé (514542104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

ATTEINTE MEDULLAIRE INFECTIEUSE D'EVOLUTION DRAMATIQUE A STREPTOCOCCUS ANGINOSUS, A STREPTOCOCCUS CONSTELLATUS ET A PREVOTELLA BUCCAE (A PROPOS D'UN CAS)

REIMS-BU Santé (514542104) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Assessment of the Evaluation Framework for Energy Maximising Control Systems for the Wavestar Wave Energy Converter

During the design process and evaluation of energy maximising control systems (EMCSs) for wave energy converters (WECs), control techniques rely heavily on numerical modelling. For fast computation, these numerical models are mostly based on low-fidelity boundary element method (BEM) codes and linear hydrodynamic models. However, to ensure optimal performance in a physical environment, more realistic, high-fidelity numerical frameworks, such as Computational Fluid Dynamics (CFD) based numerical wave tanks (CNWTs), should be considered during the evaluation of EMCSs. This paper investigates the influence of different numerical evaluation frameworks on the performance evaluation of EMCSs. The Wavestar WEC, subject to three different EMCSs with varying aggressiveness, i.e. resistive, reactive and moment-based control, is chosen as the case study. Results show that more aggressive EMCSs require high-fidelity numerical modelling to correctly evaluate their performance

A high-fidelity wave-to-wire simulation platform for wave energy converters: Coupled numerical wave tank and power take-off models

Performing rigorous technical and commercial assessment of wave energy converters (WECs) numerically, before engaging in expensive wave tank and open ocean tests, is vital for the economically successful development of prototypes. To that end, this paper presents a high-fidelity wave-to-wire simulation platform (the HiFiWEC), where a Computational Fluid Dynamics (CFD)-based numerical wave tank is coupled to a high-fidelity power take-off (PTO) model, which enables assessment of WEC performance with greater accuracy than with previous wave-to-wire approaches. A test case, simulating the performance of a heaving point absorber type WEC in realistic conditions, is presented and compared against traditional lower fidelity modelling methods. The WEC response is evaluated with a number of different approaches, including different techniques to model hydrodynamic wave-structure interactions and the power take-off system, and the benefits of the HiFiWEC are highlighted. The results highlight that excessive simplifications in the modelling of the PTO system can lead to significant overestimation in generated energy output, with relative deviations (∊) of up to 150% compared to the HiFiWEC. In addition, uncertainty in viscous drag parameters added to hydrodynamic models based on boundary element method solvers, reinforce the necessity of CFD-based models for applications where high-fidelity is essential. Finally, it is demonstrated that minor/insignificant inaccuracies in the hydrodynamic model (∊) can result in significant differences in the estimation of the final energy generation (∊), highlighting the need for a coupled high-fidelity platform

Threshold level approach for streamflow drought analysis in the Central Andes of Argentina: a climatological assessment

A streamflow drought climatology was developed over the Central Andes of Argentina, a semi-arid region highly vulnerable to climatic variations, based on the analysis of daily historical streamflow records. A threshold level approach was applied on a daily basis for three different severity levels in order to depict the main characteristics of droughts–number of drought events, mean duration and mean severity–over the period 1957–2014. Based on three annual indices that summarize the frequency of drought events, their duration and severity, we identified the main regional dry periods and the main modes of variability through an empirical decomposition. These modes are linked to La Niña conditions on inter-annual time scales and the Pacific Decadal Oscillation for the decadal variations, showing the influence of the tropical Pacific Ocean in the development of streamflow drought conditions and its relevance for potential predictability of hydroclimatic variations over the region.Fil: Rivera, Juan Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentina. Universidad "Juan Agustín Maza"; ArgentinaFil: Araneo, Diego Christian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Penalba, Olga Clorinda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentin