Abstract: In a nonlinear optical medium such as the gallium arsenide, two collinear incident monochromatic waves are injected to generate a monochromatic wave. The medium induces between the three waves a propagation phase-shift that has a value ? if the three waves travel a coherence length in the medium and that is compensated at the value 0 modulo 2? each time that the three waves have travelled a periodic distance in the medium. In order to significantly increase the conversion efficiency, the periodic distance between two successive bounces of total internal reflection of the waves in zig-zag is strictly less than the coherence length. The high conversion efficiency on a very short material length leads to product high-power coherent optical sources particularly with wavelengths of approximately 10 ?m.

Abstract: The oscillator comprises two resonant cavities in which a non-linear crystal (3) is situated. The incident pumping radiation Rpe follows an emitting path across the crystal, the generated signal and complementary radiation carry out numerous emitted and return paths in the cavities, hence across the crystal and are thus converted into an inverse pumping radiation on the return paths thereof. According to the invention, a device (4) is incorporated in the oscillator for reflection of a fraction of the pumping radiation equivalent to the inverse pumping radiation in the absence of the device.

Abstract: The invention aims to integrate a two-wave stationary interferometer on a photodetector during fabrication in order to constitute a miniature stationary Fourier transform spectrometer. The interferometer essentially comprises a plate having a first plane face coinciding with an image plane on semiconductor photosensitive elements and a second face that is not parallel to the first face. The second face reflects a wave that has a phase difference relative to the incident wave interfering with it that is a function of the local thickness of the plate.

Abstract: The invention provides alloys or superalloys based on nickel essentially comprising the following elements in the amounts indicated as percentages by weight: Cr: 11.5% to 13.5%; Co: 11.5% to 16.0%; Mo: 3.4% to 5.0%; W: 3.0% to 5.0%; Al: 2.2% to 3.2%; Ti: 3.5% to 5.0%; Nb: 0.5% to 2.0%; Hf: 0.25% to 0.35%; Zr: 0 to 0.07%; C: 0.015% to 0.030%; B: 0.01% to 0.02%; and Ni: complement to 100%. The alloy is for use in the production of turbine or compressor disks for turbo-machines, using powder metallurgy techniques.

Abstract: The present invention relates to a sandwich-structure flat active actuator that is symmetrical relative to the mid-plane comprising at least one piezoelectric flat layer having an active direction superpose and fixedly attached to at least one passive flat layer of fabric with rigid warp and weft oriented in two directions forming a mesh; the two directions of each layer of fabric are the same. The active direction of each piezoelectric layer is oriented along one and the same diagonal of the mesh of the layers of fabric. The invention is also aimed at a device consisting of two actuators mounted head-to-tail. The invention applies to the active torsion of structures such as, for example, a helicopter blade.

Abstract: A sensor comprises two identical vibrating members operating with a common working frequency and joined to each other by a mechanical decoupling device. The device comprises a frame and two connecting bridges each supporting one member. The frame comprises a succession of mass portions and thinned portions so that the frequency of one mode of structural resonance of the frame is substantially equal to the common working frequency, and each connecting bridge is disposed in a node of vibration of the frame at the common working frequency. Thus, the vibrations of the two vibrating members are decoupled from each other.

Abstract: In a nonlinear optical medium such as the gallium arsenide, two collinear incident monochromatic waves are injected to generate a monochromatic wave. The medium induces between the three waves a propagation phase-shift that has a value ? if the three waves travel a coherence length in the medium and that is compensated at the value 0 modulo 2? each time that the three waves have travelled a periodic distance in the medium. In order to significantly increase the conversion efficiency, the periodic distance between two successive bounces of total internal reflection of the waves in zig-zag is strictly less than the coherence length. The high conversion efficiency on a very short material length leads to product high-power coherent optical sources particularly with wavelengths of approximately 10 ?m.

Abstract: The invention concerns a passive radar receiver with an array of antennas for a OFDM received signal comprising frames of symbols each emitted on coded orthogonal carriers. After formatting received signals into digital symbols, dummy signals from dummy OFDM emitters at different distances from and in different directions relative to the receiver are generated and added to the signals picked up by the antennas. The modified received signals are filtered by means of inverse covariance matrices in order to eliminate at least unwanted zero Doppler effect signals and to provide an isotropic reception diagram without blind sector of direct path being generated and by detecting mobile targets along the direct path.

Abstract: The invention concerns an installation with piezoelectric element for transmitting or receiving ultrasonic waves in a structure, the electrodes (8) of said element (7) being connected, as the case may be, to a powering circuit producing energizing electric signals designed to enable it to transmit ultrasonic signals in said structure (6), or to a circuit receiving electric signals transmitted by said element under an energizing ultrasound received by it from said structure, said piezoelectric element (7) being integrated in the structure. The powering or receiving circuits of said piezoelectric elements (7) consist each of a magnetic induction loop (9) likewise comprised in the structure (6) and capable of receiving from an external circuit (10, 11) or respectively transmitting thereto, electromagnetic signals.

Abstract: The invention concerns a passive radar receiver for a received orthogonal frequency division multiplex-type signal consisting of symbol frames each emitted on coded orthogonal carriers. After formatting the received signals into digital symbols (S1 S1), a filtering circuit (2) eliminates by subtraction or using a covariance matrix, in the symbol signal at least unwanted signals with null Doppler effect so as to apply a filtered signal (X?) including essentially signals backscattered by mobile targets to a Doppler-distance correlator (4).

Abstract: The invention aims to integrate a two-wave stationary interferometer on a photodetector during fabrication in order to constitute a miniature stationary Fourier transform spectrometer. The interferometer essentially comprises a plate having a first plane face coinciding with an image plane on semiconductor photosensitive elements and a second face that is not parallel to the first face. The second face reflects a wave that has a phase difference relative to the incident wave interfering with it that is a function of the local thickness of the plate.

Abstract: The invention concerns a transducer constituting the sensitive member of a sensor whose frequency varies as a function of the intensity of force applied to it. The force transducer comprises a beam having length and rectangular cross-section with thickness and width and flexionally vibrating. The beam has a thickness reduced over a central portion of its length, its width remaining constant.

Abstract: An emitter for emitting electromagnetic pulses includes a generator for generating an electromagnetic pulse, an optical fiber that transmits the eletromagnetic pulse, and an optical cavity. The optical cavity is placed in the path of the incident electromagnetic pulse transmitted by the optical fiber and has an input provided with a first partially reflecting mirror and an output provided with a second partially reflecting mirror. The first partially reflecting mirror is placed between first and second fiber lengths of the optical fiber and the second partially reflecting mirror is placed between the second and a third fiber length of the optical fiber. The length of the second fiber and a transmission/reflection ratio of the first and second mirrors are adjusted such that a train of electromagnetic pulses, having variable geometry characteristics, is emitted.

Abstract: A radial turbine with a novel inlet and a outlet is combined with a centrifugal compressor, also having novel inlet and outlet, so as to obtain a turbocompressor unit wherein the respective inlets and/or exhausts of which are improved. The combination of above improves the overall efficiency of the turbocompressor unit. In addition, the combination limits the axial bulk of such a unit at the cost of a limited increase both in the cross section and the weight and structural complexity of the turbocompressor unit. Such a turbomachine: a radial turbine with an optional centrifugal compressor can be produced using two-microelectronic dimensional machining techniques of the microelectronic type.

Abstract: The invention concerns a method comprising a step which consists in producing, on a precursor alloy powder containing at least the elements Cr, Al and Y, using a chemical or electrolytic deposition bath, a deposition containing at least a modifying element such as platinum, palladium, ruthenium or rhenium. The modifying element enhances the capacity of the coating to form from phase &bgr;, by exposure to oxygen at high temperature, an adhesive alumina surface barrier. The invention is useful for protecting against corrosion and oxidation at high temperatures aviation turbine blades.

Abstract: A process for forming metal components of controlled porosity by welding, in which a predetermined amount of metal elements (50) of oblong shape is introduced into a mold (10) in which it is distributed isotropically. The metal elements are then subjected to increasing pressure (P) until the component has its final shape. The walls of the mold are then held in position and an electric current (I) flows through the metal elements and welds them together by local melting at the points of contact due to the Joule effect.

Abstract: In a process for analyzing the wavefront of a light beam, a diffraction grating with rectangular meshing is placed in a plane perpendicular to the light beam to be analyzed and optically conjugate with the analysis plane. Different emergent beams from the grating interfere to form an image whose deformations are related to the slopes of the wavefront analyzed. The grating multiplies an intensity function, implemented by a two-dimensional intensity grating, which defines a rectangular meshing of sub-pupils transmitting the light from the beam to be analyzed into a plurality of emergent beams disposed in accordance with a rectangular meshing, with a phase function implemented by a two-dimension phase grating which introduces a phase shift between two adjacent emergent beams such that the two emergent beams are in phase opposition.

Abstract: An aerodynamic surface, such as a wing, empennage, angle of drift, nacelle pylon and the like for an aircraft includes at least one lightening hole pertaining to the trailing edge of the underwing, at least one hinged baffle that can be mounted in the lightening hole of the underwing, whereby the chord thereof is equal to a several hundredths of the chord of the aerodynamic surfacer and an actuator for the moveable baffle so that it can rotate around the hinge line.

Abstract: A method and device for measuring the speed of at least one object by Doppler effect, whereby the light diffused by an object illuminated by a laser sheet is transmitted to a CCD video camera by spectral filtering means which are substantially tuned to the laser illumination frequency, means being provided to generate reference monochromatic luminous fluxes having frequencies which are different from the laser illumination frequency by fixed known amounts, and the reference luminous fluxes being transmitted to the CCD video camera.

Abstract: The invention concerns a transducer constituting the sensitive member of a sensor whose frequency varies as a function of the intensity of force applied to it. The force transducer comprises a beam having length and rectangular cross-section with thickness and width and flexionally vibrating. The beam has a thickness reduced over a central portion of its length, its width remaining constant.