Abstract: Optically active naphthalene compounds having the formula: ##STR1## in which X and Y are selected from combinations (a), (b) and (c): (a) X is C.sub.1-10 alkyl or alkoxy and Y is C.sub.4-16 optically active alkyl, (b) X is C.sub.1-10 alkyl or alkoxy and Y is ##STR2## where R.sup.2 is C.sub.4-16 optically active alkyl, (c) X is ##STR3## where R.sup.1 is C.sub.1-10 alkyl or alkoxy and Y is C.sub.4-16 optically active alkyl. Ferroelectric smectic liquid crystal materials being compositions containing these compounds are also described.

Abstract: A laser system includes a first laser (66) and a second laser (68) optically coupled to the first laser (66), characterized in that the first laser (66) is arranged to respond to pumping by producing a first laser output and retaining for a time period a net gain for second laser output radiation, and the second laser (68) is adapted to be pumped by the first laser output and to respond within the time period by producing a second laser output optically coupled to the first laser (66) to effect injection control thereof. The first laser (66) may be an excimer laser and the second laser (68) may be a dye laser. The lasers may be coupled by a common laser mirror (20).

Abstract: A detector system having a channel for comparing the peak amplitude of at least one of two electrical signals, produced at the output of two spaced geophones, against an amplitude threshold, to produce an indication of a moving object when this threshold is exceeded. To reduce the number of false indications, the system includes a parallel channel for measuring the phase difference between the two signals, and a processing circuit responsive to both channels, to ensure that indication is allowed only when the measured phase difference changes sense. The parallel channel includes four flip-flops each to measure the phase difference and the outputs of these flip-flops are added together, to produce a phase dependent signal for controlling the processing circuit. Further discrimination is provided by timing the phase transition, a time gate being used to inhibit indication when the phase transition does not occur within prescribed time limits.

Abstract: The device (10) consists of a bar (12) of high explosive having a planisymmetrical groove (20) along one side lined with a hollow charge liner (28). A pair of backing charges (34, 36) connected by a bridging charge (42) are disposed along the opposite side of the bar. Each backing charge is separated from the bar by a gap (38, 40) which tapers towards the common longitudinal periphery of the bar and charge. The surfaces of the backing charges facing the gaps are lined with liners (46, 48). A linear initiating charge (54) is separated from the bridging charge longitudinally of the device by a gap (61). The facing surface of the charge (54) is lined with a metal strip (58) which, when the charge is detonated, is projected across the gap (61) to initiate the bridging charge linearly. A detonation wave then propagates from the bridging charge down each backing charge towards its peripheral region, projecting the liners (46, 48) across the gaps (38, 40) to initiate the bar.

Abstract: A portable particle analyzer is compact and can determine the size, geometry and number of particles in a sample of fluid. A laser beam (15) intercepts the flow of fluid (17) at the first focal point of a parabolic mirror (11). Light is scattered and collected by radiation collectors (13) and low angle scattered radiation is detected in a second chamber (19) by reflection by an ellipsoid mirror (20) towards a radiation collector (21). Photomultiplier units (23) convert the radiation collected into electrical signals for analysis.

Abstract: A radiation sensor for centimeter, millimeter or sub-millimeter waveband receiption, comprising a metal antenna located close to a supporting dielectric body of intermediate to high dielectric constant value and having a mixer located in between and connected to the limbs of the antenna. The supporting body may itself be of semiconductor material, or if of insulating dielectric material, semiconductor material may be incorporated adjacent the antenna; and the mixer components, diodes, integrated in the semiconductor material. Antennae, as above, may be arranged in close-packed array, and the supporting body configured as, or as part of, a lens.

Abstract: Compounds for use in ferroelectric smectic liquid crystal mixtures of general formula (I), where R.sub.1 is alkyl, Y is COO or OOC, m, n and p are 0 or 1 provided m+n is 2 or less and when Y is OOC, p is 0, X is a mesogenic group, especially 4.sup.1 -alkyl- or alkyl-biphenyl or bicyclohexyl. Methods for preparation of these compounds are given, and ferroelectric smectic liquid crystal mixtures containing them are described.

Abstract: The radio station comprises a receiver antenna system responsive to direct transmissions from each of the other radio stations in the system with two remote transmitters operated alternately, i.e. one can be moved while the other is transmitting. The antennae system provides input signals to a receiver bank, each receiver being responsive to the current transmission frequency of a respective one of the other radio stations in the system. The received signals, comprising packets of data addressed to a particular station, are processed in decrypt section and switch section, then the data packets are either passed to a database, one of the workstations or rejected, depending on the addressee of each packet. Data from the database or any of the workstations for transmission to specified addresses are processed and stored in the switch section ready to be transmitted from one of the two remote transmitters during one or more subsequent transmission periods.

Abstract: An electromagnetic radiation sensor for use at microwave frequencies compes a sheet substrate bearing an array of dipolar antennas. The antennas have respective mixer diodes connected between adjacent dipole limbs, and the antenna array is located in the focal plane of a dielectric lens. Individual antenna center positions correspond to different beam directions for radiation incident on the lens, and the antenna center positions are in accordance with the Rayleigh resolved spot criterion. The dimensions, dielectric properties and relative positioning of the lens and substrate are such as to provide for the antennas to couple predominantly to radiation passing through the lens. The substrate thickness may lie between the lens and antenna array, or alternatively the array may lie between the substrtate and lens. In the latter case, the lens is of higher dielectric constant material than the substrate, at least in the lens region adjacent the array.

Abstract: A rectifier circuit comprises two Zener diodes (3,4) having substantially the same characteristic Zener voltage which are connected to receive a sinusoidal input signal via a low impedance buffer (8). A half-wave rectified signal appearing on line (17) has a DC bias equal to the Zener voltage which is removed by the operational amplifier (15). A low pass filter (20) provides a smoothed DC voltage output on line (21). The circuit may be used as an AC to DC converter or for the detection of signals ranging from several volts down to a few millivolts. Its linear response over a wide dynamic range and at small signal levels is an advantage over conventional silicon diode rectifier circuits which suffer distortion at low signal levels.

Abstract: A high power, low frequency flextensional transducer for underwater use comprises a number of spaced piezo-electric element stacks between opposed inserts. The stacks are placed on the plane through the major axis of an elliptical flexural shell and the inserts are shaped to conform with the elliptical shape. The stacks are assembled with first tapered supports and complementary tapered slides are wedged between the shell inserts and the tapered supports until a required pre-stress is exerted by the shell on the piezo-electric stacks. End-plates are attached to the elliptical shell to complete the transducer; the shell having a compression bonded layer of neoprene applied, including a peripheral serrated lip seal to seal against the end-plate while permitting flexing of the shell. A means to provide wide band-width performance is also disclosed. To extend the range of operational depths the cavity within the transducer is filled with a gas whose vapor pressure can be temperature-controlled.

Abstract: The invention relates to charge balancing of cells of rechargeable batteries. The battery comprises means to balance the distribution of hydrogen between all of the cells and means to remove the hydrogen from the cells. The battery further includes means to monitor the charge of each cell to detect if the charge of a cell becomes out of balance with the other cells. Hydrogen is added to the cells when the charges are out of balance to obtain self-discharge.

Abstract: An automatic data plotting apparatus consists of three main parts: a processor; a serial and parallel interface; and a plotter. The plotter is a flat-bed X-Y plotter. The data processor is programmed to handle one or more data inputs and instruct the plotter to record information relating to the data inputs on a plot. The processor translates the incoming data into times, bearings, tracks and any other characteristics. A pause facility is provided to suspend plotting, the incoming data being stored in a data store while the pause facility is in operation and being recorded on the plot when the pause is discontinued. An automatic data plotting apparatus provides a focal point at which incoming information can be co-ordinated and displayed. The displayed information can then be evaluated and/or stored for later analysis.

Abstract: A very short range missile launcher comprises a magazine (10) rotatable about a vertical axis and carrying a number of missiles (11, 35) vertically. An electronically steerable radar is mounted above the magazine. On perceiving a threat a wall member (12) hinged along its lower edge (13) and carrying a number of missiles loaded from the magazine is opened by an elevation control (18). An electro-optic tracker (17) is mounted on the hinged wall member for launch determination. Deflector plates (21) are mounted on the hinged wall to deflect the missile exhaust. In a further arrangement opposed end wall members (33, 34) carrying missiles are rotated by an elevation control (36, 37). Missiles are supported in the magazine between upper and lower conveyors (41, 42) operated by an indexing control (58, 59, 68) for loading missiles for launch.

Abstract: A digital cross and auto correlator or structurator receives a stream of pulses of varying time separation forming an input signal. A plurality of channels each receives this input signal which is sampled to provide a series of digital numbers in successive sample time intervals. Each channel has a delay for delaying an input signal to a delay value to provide a delayed signal, and an arithmetic section for receiving at one input a non-delayed input signal and at another input the delayed signal. An accumulator receives the output of the arithmetic section. The collective output of the channels provides the required auto or cross correlation function. The correlator has means in each channel for providing a sample time interval and a delay value that are independent of one another and of other channels. The sample time and delay value are set by the frequency of and phase difference respectively between clock pulses.

Abstract: A processor is provided which is suitable for constrained least squares computations. It incorporates a systolic array of boundary, internal, constraint and multiplier cells arranged as triangular and rectangular sub-arrays. The triangular sub-array contains boundary cells along its major diagonal and connected via delays, together with above-diagonal internal cells. It computes and updates a QR decomposition of a data matrix X incorporating successive data vectors having individual signals as elements. The rectangular sub-array incorporates constraint cell columns each implementing a respective constraint vector and terminating at a respective multiplier cell. The constraint cells store respective conjugate constraint factors obtained by constraint vector transformation in the triangular sub-array. Rotation parameters produced by QR decomposition in the triangular sub-array are employed by the rectangular sub-array to rotate a zero input and update stored constraint factors.

Abstract: A high power, low frequency flextensional transducer for underwater use comprises a number of spaced piezo-electric element stacks between opposed inserts. The stacks are placed on the plane through the major axis of an elliptical flexural shell and the inserts are shaped to conform with the elliptical shape. The stacks are assembled with first tapered supports and complementary tapered slides are wedged between the shell inserts and the tapered supports until a required pre-stress is exerted by the shell on the piezo-electrical stacks. End-plates are attached to the elliptical shell to complete the transducer; the shell having a compression bonded layer of neoprene applied, including a peripheral serrated lip seal to seal against the end-plate while permitting flexing of the shell. A means to provide wide band-width performance is also disclosed. To extend the range of operational depths the cavity within the transducer is filled with a gas whose vapour pressure can be temperature-controlled.

Abstract: A method and apparatus of deriving a directional polar diagram from the signals R received by a synthetic-aperture aerial (in direction-finding applications), or P from such an aerial (in radio-beacon applications), these signals including a carrier of frequency .omega. which is phase-modulated at the scanning frequency .omega..sub.m of the individual aerials. The method comprises generating an "estimated" signal (26) of frequency .omega. phase-modulated at frequency .omega..sub.m, and multiplying (25) the generated signal by the received signal to derive an output which includes a selectable Bessel Function (J.sub.O) representing the directional polar diagram. The phase (with circular aerial arrays) (27) or amplitude (with linear aerial arrays) of .omega..sub.m as applied to phase-modulate the generated signal is controlled to maximize or minimize, as appropriate, the selected Bessel Function and thereby control the bearing direction of the polar diagram. The zero-order Function J.sub.

Abstract: A photodetector of semiconductor material includes a photosensitive region adjacent to a minority carrier extraction region arranged when biased to depress the photosensitive region minority carrier concentraction, and means for inhibiting injection of minority carriers to the photosensitive region. Depression of the minority carrier concentration produces low noise and high responsivity properties as obtained by cooling, but without the need for cooling equipment. The minority carrier extraction region may be a pn homo- or heterojunction. Minority carrier injection may be inhibited by a homo- or hetero-structure excluding contact to the photosensitive region, or alternatively by providing the photosensitive region with at least one subsidiary pn junction biasable to inhibit minority carrier flow. The photosensitive region may have an array of extraction regions spaed by less than a minority carrier diffusion length. The extraction regions may have separate outputs to provide respective pixels in a display.

Abstract: Infrared transmitting optical components having a wide variety of substrates (e.g. ZnS, ZnSe, Ge, Si, SiO.sub.2) are disclosed all with an optical coating of boron phosphide (BP). The boron phosphide may be a single layer coating or one layer of a multilayer coating in which case it is preferably the penultimate layer. Coated components are provided which are very low in absorption, which are operable at high temperatures with minimal transmission loss, and which are transmitting in two IR wavebands. The boron phosphide layer is deposited by plasma-assisted chemical vapor deposition at a temperature in the range 300.degree.-500.degree. C. preferably using feedstock gases which are hydrogen-fee. Boron phosphide coatings of up to 40 .mu.m in thickness have been achieved.