Abstract: A UHF carrier signal modulated by a video signal, where the frequency and the format of a line synchronization signal are known, is transmitted in a transmission region in a confined medium by a microwave link. In a reception region, two signals are received along two angularly offset privileged axes, each is frequency-demodulated along identical processing channels, the existence in the signal emitted from one of the channels, the "starting channel", of a periodic signal with the line synchronization frequency is checked and this signal is selected if the check proves positive. If the periodic signal disappears, the test is applied to the other channel; if that check is positive, this other channel is selected until this periodic signal disappears. Such a process is especially applicable in tunnels.

Abstract: According to the method fly ash is pre-hydrated using cold water and the mixture is then treated in a receptacle under pressure from superheated or saturated steam at a temperature lying between 130.degree. C. and 250.degree. C. The method is applicable to any substance containing quicklime that is to be slaked.

Abstract: To measure the concentration in a gaseous medium of a known combustible gas a resistive element in the gaseous medium having a catalytic surface or being sensitive to variations in the concentration of the combustible gas in the gaseous medium is electrically heated, the value of a parameter representative of the gas concentration is detected and there is deduced therefrom, using a conversion law obtained previously by calibration, a measurement of said concentration. The element is heated periodically in cycles comprising a heating phase, a second phase in which the intensity I is controlled in such a way as to maintain the resistive element at a set point temperature and the stabilized value of the voltage U at the terminals of the detector is measured, and a third phase in which the heating power is reduced. On average the power of the electric current flowing during the second phase is substantially less than the heating current power.

Abstract: The device has an opening provided through a side wall of the fluidization enclosure and a tube extends outside a enclosure and substantially perpendicular thereto. A duct is connected substantially perpendicularly to the tube and extends downwards. A piston is slidably mounted in sealed manner inside the tube to slide between a first position in which it constitutes a panel closing the opening and a second position in which it at least partially uncovers the opening of the duct into the tube, and control means for controlling displacement of the piston inside the tube.

Abstract: The fluidizing grid of the invention is essentially constituted by pipes (18) forming the diverging walls of the openings (17) through which the fluidizing air is blown. These pipes have a cooling liquid (water) flowing therealong, which water then flows through the heat exchange tubes of the boiler.

Abstract: A direct view remote control method, and a corresponding transmitter and receiver assembly, for rapid and reliable transmission of simultaneous orders to a works machine such as for mines and quarries. Orders from a driver are converted into binary signals; a sequential binary signal is elaborated therefrom so that each sequence comprises synchronization bits with a synchronization binary periodic signal and information bits occupied by a biphased encoded binary signal representative of said binary signals; Amplitude of carrier wave is modulated by said sequential binary signal so as to form a remote control signal to be transmitted; after reception thereof the sequential signal is restored and, through recognition therein of the synchronization signal, converted into appropriate electric signals for the machine.

Abstract: In this combustion process a fluid fuel such as pulverized coal mixed with primary air is injected along an axis and secondary air is injected along a helical path around the axis. Tertiary air is injected around the combustible fluid and the secondary air in substantially the same direction as the combustible fluid, in a substantially circumferentially continuous coaxial ring which is laterally confined downstream of the injection point.

Abstract: Method of controlling the trajectory of a shield-type tunnelling machine equipped with displacement control hydraulic rams (3), characterized in that, these rams being divided into at least three groups of rams (6A, 6B, 6C), the theoretical instantaneous flowrates of fluid to be applied to each of these groups are continuously determined (40) from the curvature characteristics and the overall rate of advance set point trajectory and these groups (7-26-27-28) are supplied with instantaneous flowrates, the values of which correspond to the theoretical values.

Abstract: A substance based on polyurethane from which biodegradable materials can be obtained by rolling comprises, as well as a polyurethane resin serving as its essential constituent, a carbohydrate, at least one second thermoplastic polymer which is miscible in the molten state with the polyurethane resin and/or at least one third biodegradable polymer chosen from among biodegradable aliphatic polyesters, preferably of the same nature as the polyurethane resin used.

Abstract: For transferring signals relative to an electric machine provided with a three-phase power supply cable with three phase conductors, there is applied a signal to be transmitted to a first point in the three-phase cable between anyone of the phase conductors of such cable and both of the other phase conductors taken conjointly, and a reception signal is picked up in another point in said cable between anyone of the phase conductors of such cable and both of the other phase conductors taken conjointly.Preferably, similar capacitors are associated with each of the phase conductors in the cable at each end thereof, a galvanic separation transformer being disposed between such conductors, and the transmitter and the receiver, respectively, and an inductance being disposed between such transformers and conductors.

Abstract: In this combustion process a fluid fuel such as pulverized coal mixed with primary air is injected along an axis and secondary air is injected along a helical path around the axis. Tertiary air is injected around the combustible fluid and the secondary air in substantially the same direction as the combustible fluid, in a substantial circumferentially continuous coaxial ring which is laterally confined downstream of the injection point.

Abstract: A heat exchanger comprises two fluidization chambers separately supplied with fluidization gas. A heat transfer medium in the form of particulate material is supplied to the first chamber which is in communication with the second chamber. The second chamber has an outlet for discharging the heat transfer medium and contains a plurality of heat exchange tubes immersed in the fluidized bed therein. The particles of the heat transfer medium have average dimensions between 50 and 3,000 micrometers, and the maximum speed of the fluidizing gas in the second chamber is between 1.5 times and 10 times the minimum speed of fluidization of the particles of the heat transfer medium. Adjacent heat exchange tubes are arranged to be spaced by a horizontal distance which is between 1.4 times and 2.1 times the external diameter of these tubes. Additionally, the tubes have a vertical spacing between 1.4 and 2.1 times the external diameter of these tubes.

Abstract: In a fluidized bed there is immersed an internal heat-exchanger connected to a heat-transfer fluid discharge line which feeds an external heat-exchanger fitted in a fluidizing gas delivery line with a by-pass line connected to a flow-control valve so that the heat withdrawn from the fluidized bed and not used is reintroduced therein by means of the fluidizing gas.

Abstract: A portable individular dust collector has a cover which surrounds a rotatable cup. A hood is supported on the cover and houses a prefiltration unit carrying an auxiliary cup containing a filtering foam. The prefiltration unit and said hood define an external peripheral space which is in communication with an annular volume provided beneath said prefiltration unit around a central air inlet in the direction of the rotatable cup to retain the coarser particles of dust.

Abstract: A fluidized bed heat generator with improved collector for ash removal and heat recovery comprises a central hearth having a fluidization grid at its lower end. The side wall of the hearth is enclosed by a hollow peripheral enclosure to define an intermediate volume therebetween which is connected both to the upper part of the hearth and to fume tubes. These fume tubes extend through the peripheral enclosure and open into a fume exit conduit such that fumes and entrained ash from the hearth can be directed via the intermediate volume and the fume tubes to the fume exit conduit. Water is arranged to circulate within the peripheral enclosure around the hearth and fume tubes.

Abstract: A power circuit comprises a current amplifier circuit connected between a minimum potential line and a maximum potential line. It further comprises, connected between these lines together with the aforementioned main circuit, a protection circuit which has a control input. A trigger and distributor circuit is connected in parallel with these circuits and is adapted to neutralize the protection circuit, via its control input, when the voltage across the main circuit is below a threshold value. Is it also adapted to activate the protection circuit when the voltage across the main circuit reaches this threshold value, while maintaining the voltage across the main circuit at an approximately constant ratio to the voltage between the two potential lines. The circuit is applicable in particular to controling failsafe alarm circuits, by means of logic signals, for example.

Abstract: A system for transferring bulk explosive materials comprises at least one bulk explosive material storage tank and a transfer hose connected to this tank. The hose is used to fill a receptacle, typically a borehole in a mine, with explosive material, at least in part. A detonation arrestor device comprises a central channel in the hose adapted to have the explosive materials pass along its outside and fumes to pass along its inside in the event of an unintentional explosion.

Abstract: A centrifugal drier drum for wet granular material has a peripheral drying wall arranged for rotation about its axis and an entry part for receiving the material to be dried and directing this material to within the drum. The entry part is fixed to the wall of the drum by a number of supports. Material fed to the drum impacts the entry part at an impact zone, and is received within the drum at a projection zone. An annular retaining space for retaining the material to be dried is formed at both the impact zone and the projection zone such that the circulating material strikes the surfaces of material retained in these retaining spaces.

Abstract: Fluidizing apparatus comprises a grid defining cavities and main fluidizing gas blower channels connected to these cavities. Complementary channels pass through openings in swellings at the intersections of the cavities. Their upper ends are above the level of the grid. They are adapted to blow a complementary gas into an active area disposed above each swelling. A heat exchanger is adapted to exchange heat with the fluidized bed. It comprises at least one tube shaped so as to extend over the grid and through a plurality of these active areas. The rate of heat exchange may be modified by altering the complementary gas flowrate, without modifying the fluidization velocity.

Abstract: A gravimetric metering apparatus with a constant throughput is enclosed inside a sealed chamber and connected through the wall of the chamber, by a first pipe, to a pneumatic conveyor line operating under a pressure of n bars and, by a second pipe, to an intermittentently operated external loading hopper. The chamber is filled with gas under a pressure of n bars which is equal to that inside the pneumatic conveyor line.