Abstract: An acoustic transducer is arranged as a ladder having uprights and rungs consisting of contact pads and interdigital fingers respectively. The transducer has inter-rung spaces 17 occupied by arrays of reflector strips. Each reflector strip is offset by .lambda./8 from a respective position distant 1/2n.lambda. from a transducer finger center, .lambda. being the transducer finger center and n as integer. The .lambda./8 offset reflector strips provide constructive interference between transducer output waves travelling in one direction and destructive interference in the opposite direction. This provides a transducer with undirectional properties which can be manufactured in one metal deposition process. Unwanted reflections at fingers may be reduced by additional blooming reflector banks or by repositioning reflector strips to provide both unidirectional and blooming properties.

Abstract: A six-port reflectometer has first and second directional couplers, a first waveguide and a third directional coupler providing a series connection from a source to a test device. The first coupler is connected to two detectors. The second coupler is connected to a third detector and to a fourth waveguide having two ports connected via a waveguide and a further port connected to an absorber. The third coupler is connected to a detector and a reflector. The second waveguide and the reflector receive radiation coupled by the second and third couplers respectively. The third and fourth couplers provide equivalent transmission paths. Equal path lengths are traversed by signals leaving the second coupler and returning to it from the reflector and the fourth coupler respectively. With broad-band couplers and waveguides, this arrangement gives broad-band performance.

Abstract: A particulate coding material, e.g. for identifying the origin of a product by introducing it at source without its presence being readily apparent, comprises particles formed as thin transverse sections of an assembly of elongated elements, e.g. of plastic or natural fibres, of different colors and/or compositions forming a transversely united structure, e.g. having their longitudinal surfaces in adherent contact or contained in a matrix. The assembly can be produced by combining pre-existing filaments, e.g. by twisting, or by extrusion through a die, and may be drawn-down to a desired size (e.g. 10-150 .mu.m across) before sectioning. The resulting plurality of distinguishable areas in each particle (and, if desired, their relative locations) provide a coding facility. Larger flat bodies similarly formed, and the unsectioned elongated assemblies, also have identifying uses.

Abstract: The invention provides a digital data processor which has been systemetized down to bit level. The processor includes a regular array of identical processing cells which perform a logic operation on incoming bits. The cells repeatedly perform a cell operation under the control of clocks which govern the inputting to and outputting from the cell of data bits. Each bit takes part in a maximum of one cell operation in one repetition of the clock having the highest repetition frequency. Processing cell arrays for dealing with larger numbers may be readily built up from smaller arrays used for smaller numbers. Having obtained a fully working design for one type of processing cell, the full array consisting of a plurality of cells is proven.

Abstract: Aluminum alloys having compositions within the ranges (in Wt %) 0.2 to 3 lithium -0 to 4 magnesium -0.4 to 5 zinc -0 to 2 copper -0 to 0.2 zirconium -0 to 0.5 manganese -0 to 0.5 nickel -0 to 0.4 chromium-balance aluminum. The alloys are precipitation hardenable and exhibit a range of properties, according to heat treatment, which made them suitable for engineering applications where light weight and high strength are necessary.

Abstract: Apparatus and method for providing access to the underside of a bridge deck. A tower is supported vertically beside a bridge deck by means of a launch frame mounted on a stabilized support pillar; the tower in turn supporting a platform horizontally beneath the bridge-deck by means of a centilever frame. The apparatus is made quickly deployable by providing that the tower is engageable with the launch frame so as to allow it to be launched over the parapet of the bridge-deck while being supported in a substantially horizontal position with the platform supported substantially vertically to the tower, and to be rotatable into a substantially vertical portion adjacent the bridge deck to bring the platform into position underneath the bridge-deck. Access is gained to the underside of the bridge deck by climbing down the tower and onto and along the platform.

Abstract: The invention provides a ventilated immersion suit for aircrew and includes a waterproof overall (1), an air vent (8) in the upper region of the overall, a shut-off valve (19) for closing the air vent, and means (16) responsive to hydrostatic pressured in a tube 5 which is generated by immersion in water so as to operate the shut-off valve and thereby close the air vent.

Abstract: A heterocyclically substituted ethane having a formula:R.sub.1 --Cy--CH.sub.2.CH.sub.2 --A--R.sub.2 Formula IwhereinA represents a heterocyclic ring selected from a trans 2,5 disubstituted 1,3 dioxan ring and a 2,5 disubstituted 1,3-pyrimidine ring;R.sub.1 represents an alkyl group having from 1 to 15 carbon atoms and R.sub.2 represents a group selected from hydrogen, alkyl having from 1 to 15 carbon atoms and alkoxy having from 1 to 15 carbon atoms provided that where A is a trans 2,5 disubstituted 1,3 dioxan ring R.sub.2 is alkyl; andCy represents a trans-1,4 disubstituted cyclohexane ring.

Abstract: A novel liquid crystal compound has a formula: ##STR1## where: ##STR2## is a trans-2,5-disubstituted-1,3-dioxan ring or a 2,5-disubstituted-1,3-pyrimidine ring ##STR3## is a 1,4-disubstituted benzene ring optionally containing one or more F, Cl or CH.sub.3 groups as lateral substituents; R.sub.1 is an alkyl group; andX is a terminal group selected from H, CN, Cl, F and R.sub.2 where R.sub.2 is selected from alkyl R.sub.3, alkoxy OR.sub.3, alkylcarbonyloxy OCOR.sub.3 and alkoxycarbonyloxy OCOOR.sub.3.

Abstract: A filament winding machine suitable for winding a hollow closed fibre-reinforced body such as a radome comprises a rotateable former 1, an annular spider 3 supporting a plurality of asymmetrically spaced filament guides 19 movable so as to be able to traverse the length of the former to a position beyond the closed end thereof, and an array of circumferentially spaced spigots 26 at or near the closed end of the body to retain laid fibres such that there is no slippage of fibres as they are laid over the closed end of the body.

Abstract: An optically immersed infra-red detector assembly comprises a planar sapphire substrate bearing a detector with radially disposed lens contact pads. The detector and contact pads are produced by etching a single portion of cadmium mercury telluride and have mutually coplanar surfaces. A hemispherical silicon optical immersion lens is bonded to the pads by applying dilute adhesive to lens-pad interfaces. Capillary attraction draws the adhesive between the lens and the pads to form very thin layers of adhesive after solvent evaporation. The adhesive layers ensure that an air gap is produced between the lens and detector, the gap being much smaller than the infra-red wavelength of interest as required to ensure optical immersion of the detector by the lens.

Abstract: A polar coordinate display of full 360.degree. arc comprises an electrically responsive medium between two electrode bearing substrates. One set of electrodes is configured as a number of concentric spirals, allowing connection at the display periphery. The other set of electrodes may be radial or counter spiral. The display may be addressed using a set of isogonal signals--for example psuedo-random binary sequence coded signals.

Abstract: A process for the manufacture of 2,2', 4,4', 6,6-hexanitrostilbene (HNS) from dipicrylethane (DPE) or trinitrotoluene (TNT) which consists of oxidizing DPE or TNE substrate in the presence of an aprotic solvent and a basic salt of a carboxylic acid. The acid preferably consists of an ammonium or an alkali metal salt of a monocarboxylic or a dicarboxylic acid. The reaction step consists of heating the substrate and salt dissolved in the solvent to between 15.degree. and 50.degree. C., and contacting the reaction mixture with dry air or oxygen for up to 2 hours. The HNS product is precipitated out by quenching the reaction mixture in acidified water, and is optionally purified by washing first in methanol and then in acetone.

Abstract: New bicyclohexyls of the formula IR.sup.1 --Cy--Cy--R.sup.2wherein R.sup.1 and R.sup.2 are each alkyl which has 1-10 C atoms and in which one or two CH.sub.2 group(s) can be replaced by O atoms, and Cy is 1,4-cyclohexylene,are suitable for use as the components of liquid-crystal dielectrics.

Abstract: A device for degrading and pumping anti-misting kerosene has a centrifugal pump leading to a mill including interfitting cylinders with opposing coaxially aligned grooves.

Abstract: A transmission system which provides a tracked vehicle with a maximum rate of turn that decreases as higher forward gear-ratios are selected and, consequently, high low-speed manoeuvrability combined with relatively low, and therefore safe, maximum rates of turn at high vehicle speeds. This is achieved by means of a modifying differential arranged to rotate a steering input member of a steering differential at a rate equal to a multiple of the rotational speed of a power input member less a multiple of the rotational speed of the output member of a gear unit.

Abstract: A quick release fastener (QRF) for a restraint harness the fastener having a base plate with a lug retainer boss projecting therefrom, a cover plate hinged to the base plate and recessed to receive the free end of the boss, and a lock for locking the cover plate to the base. The lock requires two directionally different operations to open same and may incorporate an intermediate closure device for holding the fastener in a lug-loading configuration.

Abstract: A gas turbine combustion including a combustion wall having a plurality of generally cylindrical passages therein which extend around and are generally parallel to, the chamber axis, each of said passages having a series of air inlets disposed along the passage and tangentially directed thereinto, generally towards the center of the chamber, and means for directing cooling air into the series of air inlets in each passage to set up a forced vortex therein. The series of air inlets may be arranged to set up forced vortices of opposite rotation in adjacent passage. A means for directing cooling air into the tube inlets may comprise an annular shroud which extends around the air inlets and directs airflow into the air inlets.

Abstract: A cathode ray tube (1) having a body (3) of glass material and a faceplate (5) of solid phosphor material. The body (3) and faceplate (5) are sealed together by a sealant (15) of malleable halide material--for example silver chloride, or lead-silver chloride eutectic. Sealing is effected by inserting a ring (15) of sealant material between abutting surfaces of the body (3) and the faceplate (5), heating in vacuum to above the melting point of the sealant, and cooling to allow the sealant to solidify. The faceplate (5) may be of single crystal material--e.g. zinc tungstate or calcium borate, or may be of hot pressed solid material--e.g. zinc yttrium silicate.

Abstract: A method of producing a trialkyl gallium compound (R.sub.A).sub.3 Ga, where R.sub.A is selected from methyl and ethyl, includes the step of reacting a gallium trihalide with a Grignard reagent of formula R.sub.A Mg Q, where Q is a halogen, the reaction being carried out in the presence of an ether of the formula R.sub.1 R.sub.2 O having a boiling point at least 50 Celsius degrees above that of the trialkyl gallium compound (R.sub.A).sub.3 Ga, wherein R.sub.1 and R.sub.2 are organic radicals at least one of which has at least 5 carbon atoms.The organic radicals R.sub.1 and R.sub.2 may be aromatic and/or aliphatic radicals. They are preferably alkyl or phenyl radicals. Preferably R.sub.1 R.sub.2 O is an ether having a boiling point more than 100.degree. C. above that of the trialkyl gallium compound. The radicals R.sub.1 and R.sub.2 may each independently have from 1 to 14 carbon atoms but preferably together R.sub.1 and R.sub.2 have between seven and twelve carbon atoms inclusive.Desirably, R.sub.1 R.sub.