Abstract: A liquid crystal display apparatus using a ferroelectric liquid crystal with negative dielectric anisotropy in which a blanking pulse having a width that is at least twice of a selecting period and a polarity opposite to a strobe pulse to be applied to a scanning electrode in the selecting period is applied to the scanning electrode before the selecting period during one frame period. Another liquid crystal display apparatus using a ferroelectric liquid crystal with negative dielectric anisotropy in which a strobe pulse is applied to a scanning electrode in a trailing part of the selecting period and a predetermined period that follows the selecting period. A blanking pulse of opposite polarity to the strobe pulse is applied to the scanning electrode before the selecting period in one frame period. A non-selecting period which is at least three times longer than the selecting period is provided between the blanking pulse and the selecting period.

Abstract: A method of tracking a system (1) having sensors (3) (e.g. gas turbine engines) by providing a computer model (4) which, from changes in sensor readings, can track (follow) changes in performance parameters of the system. These may be e.g. efficiencies of various of components such as compressors and turbines. In the common embodiment, the method used (Singular Value Decomposition) is a way of computing the most likely solution when there are more performance parameters than the number of sensors used and thus a degree of redundancy. The method allows system diagnosis and most importantly a tracked model allows the selection of a tailored control regime (9) which results in optimum efficiency for the individual system (engine).

Abstract: A compound of formula I ##STR1## wherein n=3-30; X and Y are independently chosen from C.sub.1-6 alkyl, phenyl or formula II:(CH.sub.2).sub.p O--M IIwherein p=1-20 and M is a group of formula III: ##STR2## wherein a, b and g are independently chosen from 0 and 1; G is selected from CO.sub.2, OCO and is a single bond when g=0; j=0-4; F indicates that one or more of the phenyl rings may be laterally fluorinated; Z is chosen from R, OR, CO.sub.2 R, OCOR or CN wherein R is selected from chiral C.sub.4-20 branched chain alkyl, provided that at least one of X and Y is selected from formula II and that the positions of X and Y relative to each other provide stereo-isomers.

Abstract: A circuit module for a phased array radar (10) incorporates radar frequency (RF) mixers (54a, 54b) connected to an RF splitter/combiner (52) and to in-phase and quadrature RF reference signals. The RF mixers (54a, 54b) are also connected to intermediate frequency (IF) processing circuitry (60 to 68) providing for phase control of RF signals and IF reference signals. In transmission mode, the RF mixer (54a, 54b) receive phase-controlled, digitally synthesised IF signals from clock-activated generators (68a, 68b). Their outputs are combined at the RF splitter/combiner (52) to provide single sideband upconversion of the phase-controlled IF signals. In reception mode, the RF splitter/combiner (52) and the RF mixers (54a, 54b) act as an image rejection mixer circuit in which the phase-controlled IF signals are local oscillator signals.

Abstract: A ferroelectric liquid crystal display comprises a matrix of pixels addressable by first and second sets of electrode tracks crossing one another at the locations of the pixels. The pixels ale addressed by applying data pulses to the first set of electrode tracks and strobe pulses to the second set of electrode tracks to switch certain pixels selected by the data pulses from a first state to a second state under the effect of the voltage difference between the data pulses and the strobe pulses, and blanking pulses are applied to the second set of electrode tracks to set the pixels to the first state in advance of the application of subsequent strobe pulses to switch selected pixels from the first state to the second state.

Abstract: A material of general formula I: ##STR1## where E=0 indicates a non-cyclic system, and E=1 indicates a cyclic system;G is R.sub.3 SiR.sub.1 R.sub.2 (O).sub.kR.sub.1, R.sub.2, R.sub.3 are independently selected from C.sub.1-16 alkyl which may be partly or fully halogenated, H and formula IA: ##STR2## wherein Y is a propylene group which may be partially halogenated with fluorine or chlorine and Y.sub.1 is independently selected from COO, OCO, O, S, CHOH, CHF, CO or CH.sub.2 ;Q and Q.sub.1 are independently selected from (CH.sub.2).sub.n wherein one or more non-adjacent methylenes may be replaced by O andn=0-20;Z and Z.sub.1 are independently selected from O, S, single covalent bond, COO or OCO; ##STR3## represents a mesogenic group and is given by the general structure II ##STR4## A, B, D are selected from the following rings: ##STR5## the above rings may be substituted with one or more of the following substituents in at least one of the available substitution positions: F, Cl, Br, CH.sub.

Abstract: A liquid crystal array device comprises a liquid crystal material contained between two substrates, a first and a second plurality of electrodes defining a plurality of pixels and driving circuitry for applying a first signal (Strobe Voltage) in succession to the first plurality of electrodes and for applying a plurality of second signals (Data Voltage) to each of the second plurality of electrodes. Each second signal comprises one of at least a first waveform and a second waveform and the first waveform and the second waveform each comprise first and second signal levels. The first waveform and the second waveform further comprise at least one portion at a third signal level different from the first and second signal levels. This provides a limited difference in heating effect upon the array between a signal comprising a plurality of first waveforms and an alternating succession of first and second waveforms.

Abstract: Apparatus which allows selection and generation of a variety of hologrammatic optical wavefronts. A device, which comprises a substrate layer of varying thickness and an electro optic layer, with a voltage dependent refractive index mismatch between the two, is used to modulate transmitted light, thus generating a hologrammatic wavefront. Said modulation can be changed by variation of an applied voltage and this changes the wavefront which is generated. The range of wavefronts which can be generated is defined by the distribution of substrate layer thicknesses across the device.

Abstract: A means and method of controlling the muzzle velocity of a gun launched projectile to ensure that the muzzle velocities of several rounds of the same type tend towards the same value or that of an individual round approaches some nominal value. A sensor means measures a parameter related to the muzzle velocity of a projectile and a control means instructs an electrothermal energy unit to discharge a fixed amount of energy into the gun barrel after a certain time delay, the time delay being derived from the measured parameter and being such to ensure that discharge causes the projectile to achieve a controlled muzzle velocity.

Abstract: Compounds of formula ##STR1## are provided which may be used in a variety of devices including liquid crystal devices, piezoelectric devices, pyroelectric devices and in optical recording media, where m=at least 5; and R.sub.x, R.sub.y and R.sub.z are independently from formula (IA), ##STR2## where Y is selected from COO, OCO, O, S, CHOH, CHF, CH.sub.2 ; Q=(CH.sub.2).sub.n wherein one or more non-adjacent methylenes may be replaced by O and n=1-20; Z is selected from O, S, a single covalent bond, COO, a OCO; when Y is CH.sub.2 then n may also be 0; formula (IB) is ##STR3## and represents any mesogenic group; and R.sub.x, R.sub.y and R.sub.z are also independently selected from H, OH, OCOR.sup.1, COOH, CO.sub.2 R.sup.1 (CH.sub.2).sub.p OH, (CH.sub.2).sub.p CO.sub.2 H, --(CH.sub.2).sub.p OR.sup.1 or --(CH.sub.2).sub.p CO.sub.2 R.sup.1 and p=1-20, R.sup.1 =H or C.sub.1-16 alkyl, when R.sup.1 =C.sub.2-16 alkyl the terminal CH.sub.3 group may be replaced by Br or Cl; provided that at least one of and R.sub.x, R.

Abstract: A cryptographic receiver (10) includes photon detectors (52, 54, 56, 58) arranged to detect photons arriving from filters (22) and (24). A fiber coupler (14) randomly distributes each received photon (16) from an optical fiber toone of two photon channels (18, 20). The filters (22, 24) are each unbalanced Mach-Zehner interferometers with a phase modulator (34, 44) in one arm (28, 38). The filters (22, 24) impose non-orthogonal measurement bases on photons within the respective channels (18, 20). A signal processor (60) derives a cryptographic key-code by analysis of signals received from the photon detectors (52, 54, 46, 58).

Abstract: A method of determining the location of an unknown source (10) transmitting an unknown signal to satellite relays (14 and 16) comprises receiving the signal from the relays at respective receivers (18). The receivers (18) receive reference signals via respective relays from a common source (22). The unknown signal and reference signal received by each receiver (18) are processed coherently to preserve their timing and phase information relative to one another independently of signals received elsewhere. The signals are frequency downconverted and digitised, and transferred to a common processing computer (150). The computer (150) performs cross ambiguity function processing of the reference signals to determine their relative Differential Time Offset (DTO) and Differential Frequency Offset (DFO).

Abstract: A liquid crystal device is provided with a pair of substrates (12, 16) containing a liquid crystal material (22). A wall structure comprising, for example, a plurality of walls (14) is provided between the two substrates. The wall structure provides mechanical strength to the device and resistance to flow of liquid crystal material which can cause deterioration in the device performance. The walls may extend in two mutually different directions (FIG. 8, 40) to provide mechanical strength and resistance to flow in two directions while the device can still be readily filled. The device is particularly applicable to a ferroelectric liquid crystal device.

Abstract: An electronic circuit for Euclidean distance determination includes two floating gate transistors (M1, M2) connected in parallel. Voltages representing a reference point and its complement are applied to input lines (22, 24) and corresponding charges become stored on the transistors' floating gates (F1, F2). Voltages representing a data point and its complement are input to control gates (G1, G2). The transistors (M1, M2) produce a combined output current which is a quadratic or exponential function of the distance between the data and reference points according to whether the transistors are above or below threshold. The circuit (10 ) includes a diode-connected load device (M3) for deriving the square root of the output current, which is proportional to Euclidean distance when the transistors are operated above threshold. Refresh means (M44, M45) may be provided for resetting reference points. An array of circuits of the invention is employed for determination of distances between vector quantities.

Abstract: Methods for loading and alignment of liquid crystal polymers in electro-optic and electro-active devices comprise in-situ polymerisation between substrates of monomer material in the presence of a cationic initiator. This allows for the synthesis of liquid crystal polymers containing polyether backbones.

Abstract: An acoustic generating system is described incorporating a bubble generator (1) for forming pressurised gas bubbles and directing the bubbles in a plume from an outlet (7), and a low frequency sound source (2) to apply a varying pressure to the base of the plume of bubbles to modulate (8) the plume of bubbles, whereby a source of low frequency sound waves is produced. A method for generating and transmitting a low frequency acoustic wave using is also described.

Abstract: An addressable matrix display comprises an addressable matrix of pixels, a first set of electrode tracks on one side of the matrix and a second set of electrode tracks on the other side of the matrix. The sets of electrode tracks cross one another at the locations of the pixels, and the pixels are switchable by the application of respective switching waveforms to the electrode tracks. Furthermore at least one of the electrode tracks has a resistance which varies along the length of the electrode track in order to provide increased temperature uniformity over the display due to power dissipation during switching by the switching waveforms applied to the electrode tracks. More particularly the resistance in an intermediate section of the electrode track is greater than the resistance in two end sections of the electrode track.

Abstract: In a ferroelectric liquid crystal element, in order to excite a reverse electric field within the element in response to a waveform of a non-rewriting voltage, properties of the ferroelectric liquid crystal material, an element structure, driving waveforms, or other factors are adjusted so that molecules of the ferroelectric liquid crystal are allowed to switch between bistable states in response to a waveform of a rewriting voltage, while the ferroelectric liquid crystal exerts an anti-memory phenomenon in response to a waveform of a non-rewriting voltage.

Abstract: Semiconductor devices are prepared by growth of epitaxial layers on a substrate from metalorganic compounds of the formula MR.sub.3, R being an alkyl group, or its amine adduct. The metalorganic compound was prepared by reacting a Grignard reagent with a metal halide in an amine solvent.

Abstract: Liquid crystal polymer materials used in liquid crystal devices, piezoelectric devices, pyroelectric devices and recording media are described.