A Review of the Properties of Nb3Sn and Their Variation with A15 Composition, Morphology and Strain State

This article gives an overview of the available literature on simplified, well defined (quasi-)homogeneous laboratory samples. After more than 50 years of research on superconductivity in Nb3Sn, a significant amount of results are available, but these are scattered over a multitude of publications. Two reviews exist on the basic properties of A15 materials in general, but no specific review for Nb3Sn is available. This article is intended to provide such an overview. It starts with a basic description of the Niobium-Tin intermetallic. After this it maps the influence of Sn content on the the electron-phonon interaction strength and on the field-temperature phase boundary. The literature on the influence of Cu, Ti and Ta additions will then be briefly summarized. This is followed by a review on the effects of grain size and strain. The article is concluded with a summary of the main results.Comment: Invited Topical Review for Superconductor, Science and Technology. Provisionally scheduled for July 200

On the bubble shape in a magnetically compensated gravity environment

International audienceWe investigate the shape of bubbles in liquid oxygen under magnetic levitation conditions: a magnetic field is applied that polarizes bulk oxygen, and its spatial variation induces a body force opposed to its weight. In these conditions, bubbles appear to have a smooth ellipsoidal shape, which may be prolate (elongated in the vertical direction), oblate (elongated in the horizontal plane) or perfectly spherical. The dependence of the elongation ratio η on the volume and levitation position is explored. It is found that the bubble shape is prescribed by the minimization of the sum of surface tension, demagnetization and magnetic–gravitational potential energies

Tarification par des jeux Coopératifs avec Demandes Élastiques

We propose here a pricing Model which is an extension of the Cooperative Game concept and which includes a notion of Elastic Demand. We present some existence results as well as some algorithms. We conclude by discussing this model in the context of some Production and Transportation problems

Perfect magnetic compensation of gravity along a vertical axis

International audienceMagnetic compensation of gravity allows for ground-based experiments to be carried out under weightless conditions at reasonable cost and without the time limitation of systems such as zero-g airplanes or drop towers. Most of the time classical superconducting solenoids are operated to perform such experiments, which lead to a poor quality of the gravity compensation due to the non-ideal shape of the current and field distribution. In order to improve the quality of simulated microgravity, scientists need to build novel ground-based systems fully dedicated to magnetic levitation. The magnetic design of these levitation apparatuses would be based on theoretical studies of magnetic forces and associated field distributions. The work presented in this paper demonstrates the possibility of producing a magnetic force on paramagnetic and diamagnetic materials that is constant, thus providing a uniform gravity compensation, along a segment in a 3D geometry. These results come from both the decomposition in spherical harmonics of the magnetic field and specific conditions applied on the magnetic force. The magnetic field configuration leads to conical-shape isohomogeneity of the resulting acceleration. As an additional remark to previous works, the impossibility to get a magnetic force varying as 1/r(2) is briefly described

Programme linéaire pour la gestion synchronisée de la production et de la consommation d'hydrogène

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