Abstract: Apparatus for admixing dispersion inhibitive polymer into liquid hydrocarbon fuel and comprising a polymer supply hopper mounted on a fuel feed tube and a rotary mill having a cutting edge for cutting swarf from the polymer and a duct for conveying the swarf to the interior of the tube.

Abstract: A bridge pier is constructed from a number of serially gradated cribs nestable one within the other for transportation and manually mountable one upon the other in order of decreasing size on arrival at a site by the use of rotatable davits attachable to each upper-most crib in turn. When used for dry gap bridging the cribs are assembled upon a pair of adjustable length telescopic legs each pivotally connected to a load-spreading grillage and adjustable for use on slopes of up to 1 in 20. Both initial levelling and subsequent adjustment for ground settlement can be achieved by adjustment of the telescopic legs. When required for use in deep water bridging the cribs may be mounted directly upon a pontoon.

Abstract: Novel liquid crystal compounds exhibiting a low dielectric anisotropy have a structural formula: ##STR1## where R.sub.1 is an alkyl group, R.sub.2 is a group containing an alkyl group R and is either an alkyl group R, an alkoxy group OR, an alkylcarbonyloxy group OCOR or an alkoxycarbonyloxy group OCOOR, R.sub.1 and R containing up to 18 carbon atoms, ##STR2## is a trans-1,4-disubstituted cyclohexane ring ##STR3## or a 1,4-disubstituted bicyclo(2,2,2)octane ring ##STR4## and Ar is a 1,4 disubstituted benzene ring ##STR5## a 3-fluoro-1,4 disubstituted benzene ring ##STR6## or a 2,6 disubstituted naphthalene ring ##STR7## These compounds may be used in liquid crystal mixture compositions for use in a number of known electro-optic effects.The compounds may be prepared by routes in which the individual steps involved are known.

Abstract: A thermoplastic polymeric material comprises a copolymer which is a poly(bisphenol A tere- and/or isophthalate) copolycarbonate having a molar ratio of phthalate to carbonate units in the inclusive range from 2 to 10, preferably 3 to 8. The material, which may be prepared by techniques which are known, may be used in applications for high temperature transparent thermoplastics, eg transparencies for the aerospace industry.

Abstract: A two track surface acoustic wave device is provided with a phase plate interposed between input and output transducers on one of the two tracks. An electrical coupler is connected across the output transducers to produce a sum signal at at least one of its outputs corresponding to surface waves making a single transit of each track. The coupler combines other signals having a different phase relationship--eg those corresponding to a triple transit of each track to give a null at one of these outputs. The coupler is connected into matched output loads to provide mutual isolation at its inputs. Tracks of different length may be used instead of the phase plate. Instead of electrical coupling, acoustic coupling may be provided between the two tracks to produce a similar result.

Abstract: A respirator comprising a hood and visor adapted to protect a wearer against an undesirable substance and so closely to fit and envelop the wearer's head as to be susceptible of being worn underneath a helmet, the visor being formed to accommodate an oronasal mask and the respirator having purge gas supply means for maintaining a positive pressure within the respirator and for washing over the visor in visual regions thereof as well as breathing gas supply means.

Abstract: A gas gun has a charge chamber, an inlet valve to admit a charge of compressed gas to the charge chamber and either a plane or rifled barrel which communicates at its breech end with the charge chamber via a rotary outlet valve. Preferably the inlet valve is linked to the outlet valve so that closing of the inlet valve immediately precedes the opening of the outlet valve. The outlet rotary valve includes a frestoconical valve member which rotates within a complementary seat and has a radial bore which can connect two or more ports in the wall of the seat and is strongly biassed to the open position. The inlet and outlet valves may be combined in a three-way valve. In use a projectile is placed at the breech end of the barrel and the inlet valve is opened and the outlet valve closed. After compressed gas, preferably helium, has been introduced to the charge chamber to the desired pressure, the gun is fired by closing the inlet valve and immediately thereafter opening the outlet valve.

Abstract: In a radiation detector including a substrate of photoconductive material having input and output contacts, the photocarrier flow-path between the two contacts includes regions of conductive material. These regions may be formed as strips overlying the substrate, or may be formed in grooves in the substrate. Alternatively, the substrate may comprise a number of separate regions of photoconductive material interconnected by regions of conductive material. The substrate is preferably of cadmium mercury telluride photoconductive material and the conductive regions of gold. Chromium may be used to provide a bond between the gold and cadmium mercury telluride. The substrate may be slotted to increase flow-path length between the two contacts.

Abstract: A thrust unit for a space vehicle has a container in which an electrolyte is electrolyzed to produce combustible gases (for example, water producing hydrogen and oxygen). At a predetermined pressure the gases are ignited and combustion products are exhausted from the container through a thrust nozzle. The pulsed nature of the thrust unit operation, and the duration of each pulse, are such that overheating of the unit is avoided.

Abstract: A process for preparing a surface for adhesive bonding to a second surface having the steps of abrasion cleaning the surface and then applying an adhesive thereon, wherein the improvement over prior art processes comprises the displacement of atmospheric gases from the surface by means of a dry inert gas. The abrasion cleaning is preferably achieved by bombarding the surface with particulate matter and removing the particulate matter before application of adhesive to the surface. The process is suitable for preparing metal surfaces for metal to metal bonds.

Abstract: A hydraulic servo valve suitable for controlling flow of a pressurized fluid in dirty and explosive environments, comprises a control valve actuated by a contamination-free sealed pilot circuit of electroviscous fluid commanded by electroviscous valves requiring minimal electrical power. Fluid is circulated in the pilot circuit by pressure pulses derived from the pressurized fluid by means of a fluidic oscillator and transmitted to the pilot circuit via flexible diaphragms.

Abstract: A reflector antenna comprising a reflector system, and a feed system, for instance a log-periodic feed system, the phase center of which moves with frequency, for illuminating the reflector system to produce a substantially focussed antenna beam. To compensate for frequency variations in the position of the phase-center of the feed system, the reflector system includes a frequency dependent reflector the effective surface of reflection of which varies with frequency to cause the focus of the reflector system to move with the phase-center of the feed system. A number of different forms of suitable frequency dependent reflectors are described, employing composite arrangements frequency selective mesh or grid reflector elements, or arrays of reflecting horns or wedges.

Abstract: A method of fabricating a series-connected combination of two-terminal semiconductor devices on a common substrate comprising: forming a layer of high quality semiconductor material, 4, on the surface of a temporary substrate, 2 and 3, to provide active areas for the devices, forming first contact pattern conductors, 6, 9, 10, on the free surface of the high quality semiconductor layer to provide a separate first contact to this layer for each of the devices, bonding an insulating support substrate, 12, to the first contact pattern, removing the temporary substrate, forming second contact pattern conductors, 17, 18, 19, on the other surface of the high quality layer to provide a separate second contact to this layer for each of the devices, removing regions, 8, of the high quality layer separating the conductors of a pattern at any stage after beginning formation of the first contact pattern in order to define the device active areas so that parts of the first contact pattern are exposed when both the tempora

Abstract: A length of microstrip line turns through successive right-angle corners to form a rectangular pattern comprising successive quartets of such corners. Each right-angle corner radiates with a polarization which is predominantly diagonal, and the strip lengths between the corners of each quartet are made such, in relation to the operating wavelength in the strip, that the radiation from each quartet sums to produce a desired polarization direction, e.g. vertical, horizontal, or circular of either hand. Some forms of the invention can be used in a resonant as well as a travelling-wave mode, the latter giving a main lobe whose direction sweeps with frequency.

Abstract: An ultrasonic flaw detection system automatically measures attenuation of an input signal from a receiver transducer that provides a reference level. Successive amplifier stages having stepped gains provide graduated output levels that are detected and stored by individual peak readers. Sampled output levels are compared in comparators and with a reference voltage generated by a digital-to-analog converter to produce a binary output corresponding to each signal as a first coarse attenuation level. Logic control and timing circuitry selects the output level corresponding to one of the signals having a peak voltage in a predetermined range. A logarithmic converter and comparator provide a fine attenuation reading which is summed with the coarse reading in digital form. This is decoded and displayed as a total attenuation readout.

Abstract: A method of fabricating a field effect transistor comprising the steps of forming an active layer of semiconductor material (GaAs) over a surface of a first substrate of semiconductor material (GaAs), applying a second substrate of insulating material, e.g. glass, over the surface of the active layer, removing the first substrate so that the active layer is now supported on the insulating second substrate, and forming source, drain and gate electrodes over the free surface of the active layer. To facilitate removal of the GaAs first substrate by selective etching, a buffer layer of GaAlAs resistant to the GaAs etchant, may be formed between the active layer and the first substrate, which buffer layer is removed, following removal of first substrate, using a selective etchant to which the GaAs active layer is resistant. The technique is particularly applicable to high frequency FETs requiring a very thin active channel region interfaced to a substrate having good insulating properties.

Abstract: A method of fabricating a field effect transistor comprising the steps of forming an active layer of semiconductor material, e.g. GaAs over the surface of a first substrate of semiconductor material, e.g., also GaAs, forming source, drain and gate electrodes over the surface of the active layer, applying a second substrate of insulating material to the surface of this structure, and removing the first substrate. To facilitate the removal of the GaAs first substrate by selective etching, a buffer layer of GaAlAs resistant to the GaAs etchant may be formed between the first substrate and active layer, which buffer layer is removed, following removal of the first substrate, using a selective etchant to which the GaAs active layer is resistant. A second gate electrode may be formed on the active layer following removal of the first substrate. The technique is particularly applicable to high frequency FET devices.

Abstract: Scanning radiation source detecting apparatus, comprising means for deriving a general response signal in response to radiation from any part of a field of view, and a central response signal in response to radiation from a central part of the field of view, with means for producing audio signals of a frequency dependent on the magnitude of the central response signal. The apparatus may produce a constant frequency signal in response to the general response signal, and the central response signal may be derived from the general response by a gate circuit controlled by a scanning mirror mechanism. The gate circuit may be connected to a voltage controlled oscillator by a sample-and-hold circuit or, by an integrating circuit. Alternatively the apparatus may comprise a light emitting diode energized by a radiation detector, an optical system arranged to form an image of the diode and two separate detectors placed in the optical system to form the general response and central response signals.

Abstract: A method of fabricating a field effect transistor comprising the steps of forming an active layer of semiconductor material, e.g., GaAs, over a surface of a first substrate of semiconductor material, e.g., also GaAs, forming a gate electrode on the surface of the active layer, applying a second substrate of insulating material to the surface of this structure, removing the first substrate, and forming source and drain electrodes on the opposite surface of the active layer to the gate electrode. To facilitate removal of the GaAs first substrate by selective etching, a buffer layer of GaAlAs resistant to the GaAs etchant, may be formed between the active layer and the first substrate, which buffer layer is removed, following removal of the first substrate, using a selective etchant to which the GaAs active layer is resistant. A second gate electrode may be formed on the opposite surface of the active layer to that on which the first gate electrode is formed.

Abstract: An accelerometer includes a thermocouple circuit which comprises a movable member and a second member which abuts the movable member, wherein the abutting parts of the members include a cutting portion and wherein said parts are composed of dissimilar metals, for example steel and tungsten carbide, and recording means connected to the members for recording a thermoelectric signal generated when the cutting portion cuts the abutting part of the other member during acceleration.