Abstract: A flexible non destructing detonating cord including an inner sheath (2) of 99.5% pure aluminium or silver which is drawn down to an outer diameter of 0.85 mm so as to compress an NHS explosive core (1) to a density of between 1.2 and 1.6 g/cc. The cord also includes an outer sheath (3) of stainless steel which is drawn down to an outer diameter of 2.00 mm into gripping contact with the inner sheath and acts to prevent swelling of the cord when the explosive in the cord is detonated. The invention also provides a method of manufacturing the detonating cord.

Abstract: A ring laser (10) incorporates a laser rod (R) with end faces (R.sub.1, R.sub.2). The first face (R.sub.1) is coated for high reflectivity at the laser wavelength and the second (R.sub.2) for high transmission at this wavelength. The first face (R.sub.1) provides one cavity end mirror, and a concave mirror (M.sub.1) spaced apart from the rod (R) provides the other. A rhombic prism (P) between the rod (R) and mirror (M.sub.1) defines differing (figure of eight) forward and return paths (14 to 17, 18 to 21) for cavity radiation passing from one end mirror (R.sub.1 or M.sub.1) to the other and returning. The prism (P) presents Brewster's angle refracting surfaces. The second rod face (R.sub.2) is tilted to produce an optical path in two planes. A magnetic field (B) along the rod axis (R.sub.a) produces Faraday rotation of polarization. This counteracts rotation arising from non-coplanar optics for one direction of propagation around the laser cavity (10) but not the other.

Abstract: An arrangement to remove drift and wow and flutter in a tape recording comprising recording a control signal tone derived from a reference clock (159) in a dedicated control channel or embedded in a signal channel. The control signal on playback (151) is compared to the reference signal in an up/down counter (172) and the difference is used to correct the speed of the tape drive. The drift corrected control tone signal is connected through a programmable RAM delay (154) and a latch (179) to a D/A converter (156). The delayed analogue control signal and the reference signal are limited then connected to phase comparator counter (158) which is triggered by the leading edge of the reference signal and read by the leading edge of the squared control signal to measure the time delay between them as a number of RAM (154) samples (N) and subsamples (n).

Abstract: Hydroxyterminated prepolymers, used in curing reactions with isocyanates to produce elastomers, are prepared by continuously adding over periods of 12-50 hours an oxetane monomer to a reaction mixture containing a diol initiator and a catalyst capable of catalyzing the cationic quasi-living cationic polymerization of the monomer, the rate of addition to maintain stoichiometric excess over the monomer. Polymerization is terminated by adding brine. Polymers of increased molecular weight and reduced impurity levels result.

Abstract: A patch antenna array having multiple beam-forming capability is formed as a feed network (15) on a lower microstrip substrate with patches (13) overlaying these on an upper substrate. The patch array consists of a number of linear series-connected patch arrays (13a, 13b, 13c) each array being resonant and may have open circuits at each end. A travelling wave arrangement of feed lines (15a, 15b, 15c) is provided and in one embodiment the total number of beams which may be generated is twice the number of feed lines. The invention is useful in small satellite communication earth terminals and is suitable for operation in the region of 10 GHz.

Abstract: An explosive projectile, eg an anti-tank shell, is fitted with a light-sensitive fuze enabling it to be detonated by a laser pulse transmitted at a time after firing the projectile determined by the pre-determined range to the target and the known velocity of the projectile. The fuze is located in the base of the shell (in addition to the usual impact fuze) with the light-signal detector, eg a photo-diode, facing backwards. The detector is connected to the initiator via "fast" electronic circuitry so that the fuze is insensitive to "slow" or "DC" light signals such as the sun, searchlights etc. The laser beam is made slightly divergent to illuminate a suitable target area. The invention allows an anti-tank shell, normally loaded in the tank gun, to be used effectively against "soft" targets (troops, helicopters, etc) for which a direct hit is not necessary. The laser may be part of the gun range-finder system.

Abstract: ABA triblock polymers, the A block being rigid having a transition away from its rigid phase above 70.degree. C., the B block being wholly or partly ion-coordinating, elastomeric or amorphous, the B/A block length ratio being greater than 1. When the B block is complexed with an ionic salt these polymers act as polymeric electrolytes which may be used in cells etc. Preferred polymers are those where HC.dbd.CH sites in the polybutadiene segment of a polystyrene-polybutadiene-polystyrene polymer are replaced by --CH.sub.2 CH--X--(CH.sub.2 CH.sub.2 O).sub.m --R, where X is link, R is alkyl. A preferred salt is LiCF.sub.3 SO.sub.3.

Abstract: An avalanche photodiode quenching circuit (20) incorporates an avalanche photodiode (APD) (22) and a first comparator (C1) responsive to reduction in APD voltage. The comparator (C1) is arranged to activate an APD quench circuit (38) in response to APD avalanche initiation. The circuit (20) also includes a second comparator (C2) arranged to reset the first comparator input (N2) in response to a further reduction in APD voltage caused by initiation of quenching. The second comparator (C2) is also connected to a monostable circuit (48) arranged to latch the first comparator output response to resetting. The monostable circuit (48) maintains the first comparator output level constant until the APD (22) has recharged.

Abstract: The invention provides an electronic tilt measuring system for measuring the relative tilts of various platforms such as weapons on a ship. The basic system comprises an inclinometer (1) at each platform, a central control and display unit (2) and a computer (4). The output signals from the inclinometers (1) are passed to the central unit (2) and averaged over a synchronized time period to give an average inclination measurement with respect to the gravity vector over the measurement period. The data is then passed to the computer (4) where it is analysed. The computer (4) is programmed to calculate measured tilts and relative tilts and to produce graphical representations of the data.

Abstract: A gas turbine engine combustor, eg of annular combustor configuration, has air inlets, typically in the dilution zone, which incorporate vortex generators operative to trip the inlet jet flow causing stabilizing vortex flow at the lateral edges of the jet. The vortex generators can comprise an inwardly directed abrupt change of section between forward and rearward parts of the air inlets. The rearward section of the air inlets can have a configuration operative to reinforce the jet stabilizing effect of the vortex flow. The combustor exhibits improved uniformity of jet and crossflow mixing.

Abstract: A color display formed of information of one color on a different color background is projected onto a screen. Light from the bulb is passed serially through a neutral polarizer, a smectic liquid crystal cell, and a further polarizer. The cell comprises a smectic liquid crystal material incorporating an amount of a cholesteric material and a dye contained between two cell walls carrying electrodes and surface treated to give a molecular twist and alignment to the liquid crystal material. Information is written into the cell by scanning the laser beam over the cell, causing localized heating, in combination with or without an applied electric field to form selected areas with a twisted structure on a background of homeotropic structure, or vice versa. Thus plane polarized light is passed through the cell with its plane selectively rotated or non rotated. This provides a two color display of information of one color on a background of the other color.

Abstract: Heat treatable titanium alloys of the Ti.sub.3 Al type comprise 20 to 23 Al - 9 to 15 Nb-0.5 to 1.0 Si balance essentially T; (at %). These alloys exhibit a good balance of properties at room temperature and at high temperature (600.degree. C. plus) especially when solution treated in the .beta. field and artifically aged. Zr, V and Mo can be included in the alloys.

Abstract: A contactless heating apparatus for thin filaments comprises means to linearly support a length of filament (10), an induction coil (11) provided adjacent to the filament with its axis substantially parallel to the length of filament, a source (15) of alternating current in the frequency range from HF to UHF connected to the coil, and a conducting rod (16) connected to one of the end turns of the indication coil (11) and disposed substantially parallel to the length of filament (20); the arrangement being such that heating of the filament occurs adjacent to the conducting rod. The filament (20) is run through a vertical cylindrical chamber (21) in which a reducing atmosphere is maintained. The coil (11) is non-uniform in diameter, the diameter being larger at the end (14) to which the rod (16) is attached and the end (12) of the coil opposite to that to which the rod is attached is earthed (13).

Abstract: A two-stage method of producing N.sub.2 O.sub.5 in nitric acid from N.sub.2 O.sub.4 in nitric acid consists of a first production stage in which the anodic oxidation of N.sub.2 O.sub.4 in nitric acid and cathodic reduction of nitric acid are separated by a non-ionic or anionic ion exchange membrane, and a second production phase in which the product of the first stage anodic reaction is subjected to further anodic oxidation, the anodic and cathodic reactions being separated by a cationic ion exchange membrane. The use of a cationic membrane in the second stage promotes, through leakage of N.sub.2 O.sub.4 to the catholyte, an increase in N.sub.2 O.sub.5 concentration and decrease in N.sub.2 O.sub.4 concentration within the anolyte acid while avoiding a significant loss of current efficiency. The two stages may be connected in series and operated continuously to produce a nitric acid solution containing typically 32 wt. % N.sub.2 O.sub.5 and less than 2 wt. % N.sub.2 O.sub.4.

Abstract: A linkage for rotatably joining two members of a structure together including a rod member (1); a sleeve (8) slideable over a bifurcated, cylindrical end portion of the rod member; a link member (3) pivoted within the ends of the said end portion and having two parallel sides profiled to provide a sliding fit within the sleeve, an angled side portion (16) against which the end of the sleeve is urged when the linkage is in a partly open position and a rounded, profiled end portion to provide clearance of the sleeve when the linkage is opening; pin and guide elements (12,14) for limiting the sliding movement of the sleeve on the end portion; and a coil spring (10) located around the end portion and between one end of the sleeve and a step on the rod member to provide a torque for opening the linkage when released from the closed position.

Abstract: A lightweight radar reflector comprising two converging lenses (21 and 22) with a reflecting surface (26) applied to the outer convex surface of one of the lenses. The lenses are preferably meniscus lenses provided with peripheral mating flanges (24 and 25) for assembly. In one form the lenses are moulded from a mixture of silica powder and polyester resin to give a dielectric constant of 3.414 for each lens. In one arrangement there may be provided means to allow the lenses to be set to a predetermined separation so that the radar reflectance of the combination can be adjusted. In a further form the lenses may comprise thin shells of polycarbonate filled with silica powder to produce the desired dielectric constant.

Abstract: Methods for the preparation of a tellurium or selenium compound of formula Ra M Rb wherein M is tellurium or selenium and Ra and Rb are different C.sub.1-20 alkyl, alkenyl or aryl groups are provided in which a compound of formula (Ra).sub.2 M.sub.2 is reacted with a compound of formula (Rb).sub.2 M in each compound M being the same. Compounds of formula RaMMRb may also be isolated as an intermediate. Ra M Rb compounds are useful as precursors for metal organic vapor phase epitaxy processes.

Abstract: An object deployment unit for use under various sea states which allows deployment of objects (1) in any required sequence the deployment unit comprising a flexible tube shaped elongate body, means (2) to releasably attach objects to the body, one or more ballast members (3a, b), one or more buoyancy members (4) and a means for automatic buoyancy control. Preferably the deployment unit also includes a remotely actuated release mechanism for the release of objects. The automatic buoyancy control means ensures maintenance of depth. Typical usage is the deployment of mines.

Abstract: Laterally fluorinated 4-cyanophenyl and 4'-cyanobiphenyl benzoates are diosed of general formula I: ##STR1## in which R is R.sup.1 or R.sup.1 O, wherein R.sup.1 is C.sub.1 -C.sub.12 alkyl, m and n are 0 or 1 provided that (n+m) is 0 or 1, each of a, b, c and d are independently 0 or 1, provided (a+b+c+d) is not zero, but excluding the case where a and b are 0 and one of c and d is 0, being useful constituents of nematic liquid crystal materials.

Abstract: A read-out circuit for a photodetector incorporates a photodiode detector (1) connected via a preamplifier (2) to a storage capacitor (C.sub.5). The capacitor (C.sub.5) is also connected to a constant current circuit (C.sub.c, T.sub.3 to T.sub.7) providing a correction current controlled by a voltage on a reference capacitor (C.sub.c). The reference capacitor (C.sub.c) is charged by the amplified photodiode output current during a calibration phase. During a measurement phase, the storage capacitor (C.sub.5) integrates the difference between the amplified photodiode output current and the correction current. This provides pedestal signal substraction at the signal integration point. An array of photodetectors may be provided with a corresponding array of read-out circuits integrated in a single semiconductor substrate.