Abstract: The optical device for detecting in situ traces of gaseous hydrogen in an environment at cryogenic temperature, using a sensor having a fine film of palladium whose optical properties vary as a function of the concentration of hydrogen in contact with the film comprises, a palladium micromirror deposited in the form of a film at a first end of a first optical fiber, a first light source emitting a light signal at a predetermined wavelength into a second end of the first optical fiber, and means for detecting the light signal as modified after passing in contact with the palladium micromirror disposed in the environment at cryogenic temperature, processor circuits for responding to variation in the intensity of the light signal contacting the palladium micromirror to determine hydrogen concentration, and means for localized heating of the palladium micromirror, by light radiation so as to keep the palladium of the micromirror in its &agr; phase.

Abstract: An optical-fiber polarimetric sensor for measuring the displacement of an object relative to a frame, the sensor comprising a measurement optical fiber secured, over a fraction of its length, both to a central point of the object and to first and second fixed points of the frame, means disposed at one end of the measurement fiber and serving to emit a light beam of determined polarization into said measurement fiber, means for exerting twist on the measurement fiber so as to modify the polarization of the light beam, and means disposed at another end of the measurement fiber and serving firstly to detect the resulting light beam and secondly to determine the displacement of the object by analyzing the polarization modified in this way, wherein said measurement fiber is stripped, over said fraction of its length, of the covering that imparts mechanical strength thereto, and it is slid into a deformable guide sheath fixed both to the rotary object and also to the frame.

Abstract: A device and method for protecting a site against lightning strikes. The device detects the approach of a lightning discharge towards the site. In response, the device forms an ionized channel in the vicinity of the site to direct the electrical lightning discharge towards a lightning conductor.

Abstract: The present invention relates to a fast bichromatic pyrometer for measuring the temperature T of a gas or of a moving surface, the pyrometer comprising: a measurement probe placed facing the surface or immersed in the gas and picking up thermal radiation that is characteristic of the temperature of said surface or of said gas; a single optical fiber connected to the measurement probe and transmitting said radiation; an optical block connected to the optical fiber and receiving said radiation, the optical block including inlet collimation means for transmitting all of said radiation, separation means formed by a dichroic slide for separating the transmitted radiation into two distinct spectral bands, and outlet focusing means for concentrating the two separated bands of radiation; a quantum detection circuit receiving said separated bands of radiation and converting them into two color voltages Vr, Vb; and a treatment circuit receiving the voltage signals and including analog-to-digital conversion means, a dig

Abstract: A fastening system for laths made of wood or similar material, serving to form a floor. The system makes it possible to fasten the laths so that they are juxtaposed without damaging them by using tongues in which bearings, provided with teeth, have been stamped. These tongues are placed on the subfloor and are either fastened directly, or secured in place by gravity using flexible rubber supports and alignment laths securing them at an equal distance from one another, thereby not damaging the subflooring. This fastening system makes it possible to easily install and remove laths and is very well adapted for its use with prevarnished wooden laths.

Abstract: A process and a device for the optical measurement of vibrations of rotating turbine blades moving with a specified speed of rotation. In one embodiment, the process comprises the steps of generating three reference signals in response to the detection, by an optical detector, of the passing of a marking made on the hub of a turbine wheel; detecting measurement signals, by another optical detector, in response to the passing of another marking made on at least one of the parts of a turbine blade, the blade undergoing oscillation; determining the time offsets existing between each of the reference signals and each of the measurement signals, these offsets being, in the absence of oscillations of the blade, zero or equal to specified constant values; and calculating the amplitude, frequency and phase components of blade vibration from the various offsets recorded.

Abstract: This invention relates to a spinning installation for making fiber spun yarns, the yarns comprising a central core of discontinuous fibers covered with an external sheath also of discontinuous fibers. The fibers forming the core and the sheath come from a common drawing system at the outlet of which they are projected onto two condenser elements. The assembly is subjected to the action of a false twist spindle. The condenser element on which the fibers forming the core are projected comprises a rotary guide associated with a mobile roller which blocks the extension of twist communicated by the false twist spindle.

Abstract: Reconstruction of two-dimensional distribution of attenuation coefficients or sound velocities in a cross-sectional plane of an object is achieved by carrying out a plurality of measurements of absorption or of flight time with ultrasound bursts directed by elementary transmitting probes along several different incidences in the sectional plane. Switching between successive measurements is carried out by electronic scanning, without movement of the individual probes. Focusing of the burst energy transmitted by a group of probes is achieved by applying a same electrical signal to the probes with appropriate delays. The secured signals are stored and, after completion of the scanning, they are combined for computation of the distribution.