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Now showing items 1 - 16 of 3048

  • DEVICE FOR PROTECTING FROM LIGHTNING

    Device for protecting from lightning (30), said device being intended to form at least a portion of an external surface of a structure to be protected and comprising a ground plane (32), a dielectric substrate (34) arranged on the ground plane, and an array of first metal elements (36) arranged on the dielectric substrate (34) and extending substantially parallel to the ground plane (32) in such a way that any pair of consecutive elements from said first metal elements (36) is separated by a distance comprised between 0.01 millimetres and 10 millimetres, said first metal elements being distributed in juxtaposed similar patterns, each of said patterns including first metal elements of different dimensions corresponding respectively to different electromagnetic resonant frequencies the juxtaposition of which defines an electromagnetic absorption band of the pattern.
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  • ANTENNA WITH RESONANT CAVITY

    The invention relates to an antenna (1) comprising: • a resonant cavity (2) delimited by: - a partially reflecting surface (4) comprising an array of resonant cells, each resonant cell forming a micro-antenna, - a totally reflecting surface (5) facing said partially reflecting surface, • a radiating source (3) disposed in said resonant cavity and configured so as to radiate a wave between the partially reflecting surface and the totally reflecting surface, said wave illuminating resonant cells of the partially reflecting surface, the partially reflecting surface being curved and resonant cells being individually configured to introduce upon the passage of the incident wave radiated by the source a phase shift dependent on the curvature of the partially reflecting surface at the level of the corresponding resonant cell.
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  • ELECTROMAGNETIC ABSORBER

    The invention relates to an electromagnetic absorber (1) comprising: a metal ground plane (2); an insulating dielectric substrate (3) arranged on said metal ground plane; and an array of resonating metal elements (4) arranged on said insulating dielectric substrate, the electromagnetic resonant frequency of a resonant element being adjusted by adapting the dimensions of the resonant element, the array of resonant elements comprising resonant elements of various sizes in order to allow, via juxtaposition of different electromagnetic resonant frequencies, a preset electromagnetic absorption band to be produced. An elementary pattern formed by a plurality of metal resonant elements may be repeated periodically.
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  • COATING FOR THE CONCEALMENT OF OBJECTS FROM THE ELECTROMAGNETIC RADIATION OF ANTENNAS

    The invention relates to an assembly comprising a device (20) and an obstacle (10) subjected to an incident electromagnetic wave of wavelength λ. The obstacle (10) is formed from an electrically conductive material and has a substantially cylindrical shape of transverse dimensions r with respect to a longitudinal axis (O; ez), said longitudinal axis is substantially perpendicular to a propagation direction of the incident electromagnetic wave. The obstacle (10) further has a maximum transverse dimension d such that the ratio d/λ is less than 1. The device (20) is placed on all or part of a surface of the obstacle (10) and comprises a sleeve with a dielectric coating (21) of equivalent relative dielectric permittivity εreq, of height hp along a longitudinal axis of said sleeve, substantially equal to formula (A), and a sleeve with an electrically conductive coating (22) placed on the periphery of the dielectric coating (21).
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  • DEVICE FOR DECOUPLING ANTENNAS, IN PARTICULAR PATCH ANTENNAS MOUNTED ON AN AIRCRAFT

    The invention relates to a high-impedance passive surface (11) making it possible to carry out the radio decoupling of two antennas (17, 18) which operate at least partially within a common frequency band and which are arranged on the surface (19) of a supporting structure. Said device is characterized in that it comprises a substrate (15) consisting of a layer of a flexible dielectric material having a given thickness e, at the surface of which patches (13) of conductive material, having a given shape and arrangement, are arranged, as well as a means (16) for ensuring the attachment thereof onto a floorplan at the surface (19) of the structure such that the layer consisting of the patches (13) is separated from the surface (19) of the structure by the body of the substrate. The substrate thickness e is determined on the basis of the size, number, and arrangement of the patches (13), as well as on the basis of the aerodynamic constraints imposed on the device, the latter having an impedance causing the desired decoupling in the frequency band in question.
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  • STEERABLE MICROWAVE ANTENNA

    A steerable microwave antenna includes a resonant cavity (1) comprising a partially reflecting surface (PRS) formed of an array of transmitting-receiving cells (CF2) each of which is adapted for control in transmissivity and directivity and a totally reflecting surface (TRS). A radiating element (RE) laid within the resonant cavity is provided in the vicinity of the totally reflecting surface (TRS) so as to generate microwaves. A circuit (Bx, By) for controlling transmissivity and directivity of each transmitting-receiving cell (CF2) and of the partially reflecting surface (PRS) is further provided. Such an antenna can be implemented as an antenna for Wifi connections and cellular telephone handset.
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  • ANTENNA

    The invention relates to an antenna (10) comprising: - a resonant cavity (12) bounded by: - a partially reflective surface (16) comprising an array of resonant cells, each resonant cell forming one micro-antenna, - and a completely reflective surface (18) facing said partially reflective surface; - and a radiating source (14) placed in said resonant cavity and configured to radiate a wave between the partially reflective surface and the completely reflective surface, said wave illuminating the resonant cells of the partially reflective surface, wherein the partially reflective surface (16) comprises a dielectric substrate having a dielectric-permittivity gradient.
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  • CONFIGURABLE AND ORIENTABLE ANTENNA AND CORRESPONDING BASE STATION

    The invention relates to an antenna, permitting the configuration of at least one radioelectric wave beam (4, 5, 61, 62, 91, 92) of at least one fixed wavelength, of the type comprising at least one transmitting element (2), preferably of the passive type, arranged in a set of essentially parallel, wave-reflecting wires or bars (1), made from a photonic band gap (BIP) material and forming a given structure. Said given structure comprises faults for shaping said at least one beam in a direction as a function of the position and/or the configuration of said faults. According to the invention, said wires or bars and the faults are arranged on a set of N curves which are closed and concentric on a plane, N being greater than or equal to 1 and the transmitting element is arranged within the innermost curve. The curves are preferably circular and the wires/bars can be controlled to pass from a wave-conducting/reflecting state to a transparent state.
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  • O MARXISMO DE ANDRé GORZ

    L?wy Michael  

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  • NOTA SOBRE O CONCEITO DE “REFORMAS REVOLUCIONÁRIAS” DE ANDRÉ GORZ

    Silva, Josué Pereira da  

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  • Lettre de J.-Alexandre Thérien à André Bachand

    Thérien   J.-Alexandre  

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  • André Gide, Un album de famille

    Laberge   Yves  

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  • La vie après le suicide de Joanne André

    Parat, Hélène  

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  • André Orléan: L’Empire de la valeur. Refonder l’économie

    Potthast   J?rg  

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  • Tempo de trabalho e imaterialidade na teoria social de André Gorz

    Silva, Josué Pereira da  

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  • Journées André Collet de la Chiralité (JACC 2012)

    Crassous, Jeanne   Amabilino, David   Berova, Nina  

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