Réfrigération magnétique Etat de l'art et développements récents

La réfrigération magnétique, basée sur l'effetmagnétocalorique, est une thématique relativement récente etprometteuse devant permettre de réaliser des systèmes moinsénergivores que la technologie conventionnelle et sans impact surl'environnement. Pluridisciplinaire, elle implique de maîtrisertoute une filière, du matériau à l'application et de lever desverrous scientifiques et technologiques. L'article fait un état del'art, discute des derniers travaux réalisés, et illustre lesproblèmes soulevés en particulier dans le domaine thermique ens'appuyant sur l'expérience acquise au G2Elab.</p

Additional value of three-dimensional echocardiography in patients with cardiac resynchronization therapy

SummaryBackgroundThere is no gold standard technique for quantification of ventricular dyssynchrony.AimTo investigate whether additional real-time three-dimensional morphologic assessment of ventricular dyssynchrony affects response after biventricular pacing.MethodsForty-one patients with severe heart failure were implanted with a biventricular pacing device and underwent two-dimensional (time dispersion of 12 left ventricular electromechanical delays) and three-dimensional echocardiographic assessment of ventricular dyssynchrony (dispersion of time to minimum regional volume for 16 left ventricular segments), before implantation, 2 days postimplantation with optimization of the pacing interventricular delay and 6 months postimplantation.ResultsIndividual optimization of sequential biventricular pacing based on three-dimensional ventricular dyssynchrony provided more improvement (p<0.05) in left ventricular ejection fraction and cardiac output than simultaneous biventricular pacing. During the different configurations of sequential biventricular pacing, the changes in three-dimensional ventricular dyssynchrony were highly correlated with those of cardiac output (r=−0.67, p<0.001) and ejection fraction (r=−0.68, p<0.001). The correlations between two-dimensional ventricular dyssynchrony and cardiac output or ejection fraction were significant but less (r=−0.60, p<0.01 and r=−0.56, p<0.05, respectively). After 6 months, 76% of patients were considered responders (10% decrease in end-systolic volume). Before implantation, we observed a significant difference between responders and non-responders in terms of three-dimensional (p<0.05) – but not two-dimensional – ventricular dyssynchrony.ConclusionThis prospective study demonstrated the additional value of three-dimensional assessment of ventricular dyssynchrony in predicting response after biventricular pacing and optimizing the pacing configuration

MgB2-Based MVDC Superconducting Power Cable in Liquid Hydrogen for Hybrid Energy Distribution

The combination of liquid hydrogen and superconducting cables presents a unique opportunity to distribute both hydrogen and bulk electricity in the same infrastructure. In particular, liquid hydrogen around 20 K is ideally suited for cooling the MgB 2 superconductor, resulting in a compact power cable that also leaves sufficient place for the hydrogen flow. Such a hybrid system operating in the MVDC range at 25 kV and 20 kA constitutes one of the main goals of the European project SCARLET. After a description of the rationale and benefits of the electricity – hydrogen system, various possible applications and a first distribution system are presented. Furthermore, the different cable components already designed are discussed along with the research challenges and general strategy for the development.MgB2-Based MVDC Superconducting Power Cable in Liquid Hydrogen for Hybrid Energy DistributionacceptedVersio

Estimating Capital Value and Depreciation of Fishing Fleets: Application to French Fisheries

While the need to solve problems of overcapitalization and excess investment in fisheries is now broadly admitted, very little information exists on the level of capitalization and the structure of capital invested in the fishing sector. This paper presents the first results of a research program aiming at assessing the value of capital, investments and depreciation in fisheries. Results presented are derived from a field survey operated by Ifremer and record transaction on the fishing vessel second hand market. Statistical analysis is carried out according to a set of fishing components, such as vessel hull, engine, electronics and storage equipment. Firstly, hedonic price functions are estimated for the vessel and its main components. Secondly, a depreciation function of vessels according to their age and fleet is proposed. Finally, indicators of gross value of capital, net physical value as well as market value are estimated for different significant groups of fishing units belonging to the NSCA less than 24 m. fleet

Magnetic refrigeration around room temperature

La réfrigération magnétique est une technologie de rupture pour produire du froid qui n’utilise pas de gaz à effet de serre et est plus efficace que la réfrigération à compression de gaz. Elle est basée sur l’effet magnétocalorique, une propriété de certains matériaux à changer de température lorsqu’ils sont soumis à une variation de champ magnétique. Ces travaux de thèse ont porté sur l’étude des systèmes de réfrigération magnétique. Nous avons effectué une analyse critique des prototypes existants et proposé de nouveaux critères de performances pour les comparer de manière effective. Nous avons développé un modèle numérique des transferts thermiques au sein des réfrigérateurs magnétiques, pour étudier leur comportement en régime transitoire et permanent. Une analyse fine de la source de champ et de son interaction avec le matériau a permis de proposer des règles de conception et de dimensionnement d’un système performant.Magnetic refrigeration is a good alternative to gas compression refrigeration systems because it does not involve the use of greenhouse gases and it is more efficient. This technology is based on the magnetocaloric effect, which manifests itself as a temperature change of a magnetocaloric material upon changing the magnetic field. This thesis is dedicated to the study of magnetic refrigerators. We reviewed the former prototypes and defined a set of performance criteria to make an accurate comparison. A numerical model of heat transfer in magnetic refrigerators was developed, and the transient and steady state response were studied. A thorough analysis of magnetic field sources was performed and we proposed guidelines to design a new magnetic refrigerator

Modélisation et conception de systèmes de réfrigération magnétique autour de la température ambiante

Magnetic refrigeration is a good alternative to gas compression refrigeration systems because it does not involve the use of greenhouse gases and it is more efficient. This technology is based on the magnetocaloric effect, which manifests itself as a temperature change of a magnetocaloric material upon changing the magnetic field. This thesis is dedicated to the study of magnetic refrigerators. We reviewed the former prototypes and defined a set of performance criteria to make an accurate comparison. A numerical model of heat transfer in magnetic refrigerators was developed, and the transient and steady state response were studied. A thorough analysis of magnetic field sources was performed and we proposed guidelines to design a new magnetic refrigerator.La réfrigération magnétique est une technologie de rupture pour produire du froid qui n’utilise pas de gaz à effet de serre et est plus efficace que la réfrigération à compression de gaz. Elle est basée sur l’effet magnétocalorique, une propriété de certains matériaux à changer de température lorsqu’ils sont soumis à une variation de champ magnétique. Ces travaux de thèse ont porté sur l’étude des systèmes de réfrigération magnétique. Nous avons effectué une analyse critique des prototypes existants et proposé de nouveaux critères de performances pour les comparer de manière effective. Nous avons développé un modèle numérique des transferts thermiques au sein des réfrigérateurs magnétiques, pour étudier leur comportement en régime transitoire et permanent. Une analyse fine de la source de champ et de son interaction avec le matériau a permis de proposer des règles de conception et de dimensionnement d’un système performant

8th International Symposium on Reproductive Physiology of Fish ; June 3-8, 2007 - Saint-Malo (France). Abstract Book

International audienc

Light acclimation and photosynthetic response of beech (Fagus sylvatica L.) saplings under artificial shading or natural mediterranean conditions

Acclimation of beech (Fagus sylvatica L.) to different light conditions was studied in natural regeneration below black pine canopies (Pinus nigra ssp. nigricans) in Mont-Ventoux (Vaucluse, France) and with potted saplings - from the same origin - under shaded tunnels in southern France (Avignon, Vaucluse), and north-eastern France (Nancy, Meurthe-et-Moselle). Leaf mass to area ratio and leaf carbon content per unit mass increased, while leaf nitrogen content per unit mass (Nm) remained constant, with increasing relative irradiance (RI). Maximum carboxylation rate (Vcmax) and maximum electron transport flux (Jmax) increased with RI and were higher in the natural regeneration than in the potted saplings. These two parameters were higher for the potted saplings in north-eastern France than for those in southern France. Leaf nitrogen allocation to carboxylation (Pr) or bioenergetics (Pb) did not vary with RI. Pr and Pb were higher in the natural regeneration than in the potted saplings, whereas Nm was lower in the natural regeneration than in the fertilised potted saplings. Seasonal time course of these parameters in the natural regeneration in Mont-Ventoux, from bud burst to the beginning of summer drought, showed that after the leaf expansion period, leaf composition and photosynthetic parameters remain globally constant

Modélisation et conception de systèmes de réfrigération magnétique autour de la température ambiante

La réfrigération magnétique est une technologie de rupture pour produire du froid qui n utilise pas de gaz à effet de serre et est plus efficace que la réfrigération à compression de gaz. Elle est basée sur l effet magnétocalorique, une propriété de certains matériaux à changer de température lorsqu ils sont soumis à une variation de champ magnétique. Ces travaux de thèse ont porté sur l étude des systèmes de réfrigération magnétique. Nous avons effectué une analyse critique des prototypes existants et proposé de nouveaux critères de performances pour les comparer de manière effective. Nous avons développé un modèle numérique des transferts thermiques au sein des réfrigérateurs magnétiques, pour étudier leur comportement en régime transitoire et permanent. Une analyse fine de la source de champ et de son interaction avec le matériau a permis de proposer des règles de conception et de dimensionnement d un système performant.Magnetic refrigeration is a good alternative to gas compression refrigeration systems because it does not involve the use of greenhouse gases and it is more efficient. This technology is based on the magnetocaloric effect, which manifests itself as a temperature change of a magnetocaloric material upon changing the magnetic field. This thesis is dedicated to the study of magnetic refrigerators. We reviewed the former prototypes and defined a set of performance criteria to make an accurate comparison. A numerical model of heat transfer in magnetic refrigerators was developed, and the transient and steady state response were studied. A thorough analysis of magnetic field sources was performed and we proposed guidelines to design a new magnetic refrigerator.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF