Abstract: A method for early detection of the vortex ring state in a helicopter includes steps of establishing flight control signals for flight control with regard to the vertical movement axis of the helicopter, detecting resultant movements in the vertical movement axis of the helicopter, and detecting an impending vortex ring state of the helicopter in accordance with a correlation between the flight control signals and the vertical movements in the vertical movement axis.

Abstract: The present disclosure relates to a vibrating element which is planar parallelly to an electrical crystallographic axis of a piezoelectric material such as quartz. The element comprises a beam holding electrodes, a stationary portion rigidly connected to one end of the beam, and a solid portion rigidly connected to the other end of the beam. The structure with facets from the chemical machining of the element has an axis of symmetry parallel to the electrical axis, and the solid portion has a center of gravity on the axis of symmetry. The useful vibration modes of the vibrating element, according to which the solid portion is reciprocatingly rotated about the axis of symmetry and reciprocatingly moved parallel to the plane of the element, are uncoupled. The measurement of an angular speed by a rate gyroscope including said vibrating elements is more precise.

Abstract: Method, apparatus, and system for preparing a cellular material based on hollow metal beads. According to the description, at least one bead chain in which said hollow metal beads are linked to one another in pairs by means of an articulation is used as elementary structure constituting the cellular material.

Abstract: The present disclosure relates to a method for monitoring targets on a runway, wherein emitting modules and receiving modules are alternately distributed along each one of longitudinal sides of the runway. Orthogonal signals are emitted in a narrowband by the emitting modules and coherently received in a coherent manner by the receiving modules. An object is detected on the runway on the basis of a distribution of the modules into meshes each including three pairs of neighbouring emitting modules and receiving modules and on the basis of a radio location of the object through triangulation and interferometry in at least one mesh. The modules are also used for analyzing a target moving on the runway, and for monitoring the trajectographies of an air target in the surroundings of the runway.

Abstract: A monolithic miniature accelerometer machined in a plate of material, comprising a fixed part, two first mobile mass parts referred to as inertial masses, two hinge blades each having one end fastened to one of the two mobile mass parts, and two resonators each having one end fastened to one of the two mobile mass parts, a third mobile mass part fastened to the other end of each of the two resonators and of each of the two hinge blades, and a flexible stem situated between the first two mobile mass parts and connecting the third mobile mass part to the fixed part.

Abstract: The invention relates to conjugated compounds of general formula (I) ##STR1## wherein X.sub.1 and X.sub.2 are, independently of one another, electron-withdrawing or electron-donating systems, and to a process for the preparation of these compounds.The invention also relates to any material which includes the compounds of general formula I and to the use of said compounds or of any material which includes them in electronic, optoelectronic, nonlinear optical and electrooptical devices.

Abstract: A thermal barrier coating for a superalloy part used, in particular, in turbomachines comprises a ceramic coating and a sub-layer interposed between the superalloy substrate and the ceramic coating, the sub-layer being composed of a nickel and/or cobalt aluminide containing at least one platinum-like metal and at least one metal for promoting the formation of a layer of oxide constituted by the alpha-allotropic variety of alumina.

Abstract: A monocrystalline superalloy with a nickel based matrix and particularly intended for the manufacture of turbine blades, has the following composition, by weight: Al=5.4% to 6.2%; Co=4% to 7%; Cr=6% to 9%; Mo=0% to 2.5%; Ta=5.5% to 8%; Ti=O% to 1%; W=7% to 9%; and Ni=balance to 100%.The invention also provides a method of improving the alloy's resistance to creep, in which the Ni.sub.3 Al type .gamma.' phase is put completely into solution at a first temperature, and then the .gamma.' phase is precipitated into the .gamma. solid solution at a temperature greater than 1000.degree. C. This treatment considerably increases the alloy's resistance to creep over a wide range of temperatures.

Abstract: A system for transmitting optical information uses several transmitters and receivers connected by optical fibers. The transmitters and receivers are arranged in individual networks in each of which all the optical fibers leaving the transmitters are coupled to one another and all the optical fibers arriving at the receivers are coupled to one another. In addition, all the optical fibers leaving the transmitters in each individual network are interconnected to the corresponding optical fibers, i.e., those leaving the transmitters, in all the other networks.

Abstract: An iodine chemical laser is disclosed comprising: a laser cavity; a combustion chamber; a first injector injecting into said combustion chamber an iodine compound as a fuel; a first supply means for supplying the fuel to said first injector; a second injector for injecting F.sub.2 and NF.sub.3 into said combustion chamber; a second supply means for supplying said F.sub.2 and NF.sub.3 to said second injector; combustion initiating means for initiating combustion of the mixture fuel-combustion supporter in said combustion chamber; a supersonic nozzle for extracting products resulting from said combustion fuel-combustion supporter and supplying them into said laser cavity; supply means for supplying singlet oxygen into said laser cavity at the same time as said combustion resulting products; said fuel being in excess with respect to stoichiometric proportions corresponding to said combustion, richness .phi. of said iodine compound fuel with respect to said stoichiometric proportions being 0.5<.phi.<2.

Abstract: Apparatus for processing digitized images, the apparatus being of the type comprising a matrix memory (104) of pixels (106) organized as N lines (108) by P columns (110), together with processing means (130) for determining which pixels (106) are in the excited state by reading the memory (104). The processing means (130) operate by determining and storing the address of an excited pixel (106) that occupies an extreme position in a line or a column position, by switching said pixel (106) to a non-excited state, and by reiterating these operations until none of the pixels (106) is excited.

Abstract: A low density superalloy having good resistance to oxidation has the following composition by weight:Co: 5.0 to 6.0%W: 4.8 to 5.2%Cr: 7.8 to 8.3%Al: 5.8 to 6.1%Ta: 3.3 to 3.7%Mo: 2.1 to 2.4%Ti: 1.8 to 2.2%B: .ltoreq.10 ppmZr: .ltoreq.50 ppmNi: balance to 100%.

Abstract: The occurrence and frequency of a periodic component embedded in a composite waveform including noise is detected by real time calculating the autocorrelation function of the waveform and deducing the frequency of the periodic component from the value of the autocorrelation function coefficients. An analog-to-digital converter periodically transforms the waveform into samples having q bits. The samples are delayed by a predetermined time interval .DELTA.t and multiples thereof, to derive 2n delayed samples, x.sub.i, x.sub.i-1 . . . x.sub.i-2n. The delayed samples are multipled to derive 2n products, such that the first n products are represented by x.sub.1 .multidot.x.sub.i-k and the second n products are represented by x.sub.1-n .multidot.x.sub.i-(n+k), where k is selectively 1 . . . n. Difference between the first and second products are obtained as (P.sub.1 -P.sub.n+1) . . . (P.sub.n-1 -P.sub.2n), where P.sub.1 =x.sub.i .multidot.x.sub.i-1, P.sub.n-1 =x.sub.i .multidot.x.sub.i-n, P.sub.+1 =x.sub.i-n .

Abstract: A low density superalloy having good resistance to oxidation has the following composition by weight:______________________________________ Co: 5.0 to 6.0% W: 4.8 to 5.2% Cr: 7.8 to 8.3% Al: 5.8 to 6.1% Ta: 3.3 to 3.7% Mo: 2.1 to 2.4% Ti: 1.8 to 2.2% B: .ltoreq.10 ppm Zr: .ltoreq.50 ppm Ni: balance to 100%.

Abstract: A propeller nozzle, particularly for a missile, comprises a revolution pipe having a forward convergent portion, a minimum section, and a rearward divergent portion with a large outlet throat section. The invention is designed to minimize lateral forces in the nozzle due to a separation of gaseous fluid exhausting from the propeller, during the start of the propeller pressure increase. For this purpose, the pipe comprises means disposed in the vicinity of a section internal to the divergent portion and substantially downstream from the minimum section for making a gaseous fluid separation stable, symmetrical and coaxial to the nozzle. These means can include a groove and/or a projection, preferably destroyable through mechanical erosion and/or melting under the effects of the gaseous fluid.

Abstract: The mean line (F) of each blade (1) is formed by a flat continuous curve contained in a plane OZ-OY.sub.o forming with the plane of rotation of the propeller an angle .phi..sub.o between 35.degree. and 55.degree. and preferably between 40.degree. and 50.degree., said curve having a first part of negative Y.sub.o and positive Z coordinates, and a second part of positive Y.sub.o and positive Z coordinates, the coordinate point Y.sub.o =0 being situated between the values of Z included between 0.75 and 0.85 R (R designating the radius of the propeller), the tangent to this curve has its end corresponding to the end of the blade forming with the axis Oz an angle between 30.degree. and 50.degree. and preferably between 35.degree. and 45.degree..

Abstract: The invention provides improvements to aerial propellers, particularly for aircraft propulsive units, wherein the cowling of the propeller is defined by a meridian line having: at its origin (B) a maximum curvature greater than 15; then a curvature decreasing rapidly from the maximum value to a value of 7; then a curvature decreasing linearly from the value 7 to a value of 0; than a curvature decreasing more slowly from the value 0 to a minimum value between -3 and -5; then a curvature increasing rapidly from the minimum value to a value of 0.

Abstract: The electron gun comprises an ionization chamber, adjacent to a high voltage chamber. In the wall common the both chambers provision is made for an extraction grid. On the opposite side, the ionization chamber comprises an outlet window for the electrons similar in shape to the extraction grid, and accompanied by a fine metallic foil. The high voltage chamber comprises a cathode brought to a high negative voltage. By giving the two grids the shape of similar parallel strips, a masking effect and a focusing effect are obtained at one and the same time which allows the efficiency of the electron gun to be increased.

Abstract: The invention relates to improvements to air propellers in so far as the profile of their blades is concerned. The law of evolution of the curvatures of the extrados 2 is the following: the curvature, maximum at the leading edge A, increases first of all rapidly to reach a value of about 4 at the point B at about 4% of the length of the chord, and then decreases regularly to reach a substantially zero value at the trailing edge F. The law of evolution of the curvatures of intrados 3 is the following: the curvature, maximum at the leading edge A, decreases first of all rapidly to reach a value of about 8 at a point D at about 3.5% of the length of the chord, then decreases less rapidly to reach a zero value at a point E situated between 10% and 60% of the length of the chord, decreases further to a slightly negative value and then remains practically constant as far as the trailing edge F.

Abstract: The invention provides a string resonator vibrating under flexion whose oscillation is maintained by piezoelectric, electrostatic or magnetic exitation means.Decoupling is obtained by inertia masses which oscillate in the vibration plane of the string, between the string and fixing supports, with a movement of rotation about an axis orthogonal to the vibration plane of the string and at the level of flexible elements. The resonator is easy to manufacture, inexpensive and hase a good coefficient of quality. It may be used for force, pressure sensors or gyroscopes.