Abstract: A method of making semiconductor quantum wires, and a light emitting device employing such wires, employs a semiconductor wafer as starting material. The wafer is weakly doped p type with a shallow heavily doped p layer therein for current flow uniformity purposes. The wafer is anodized in 20% aqueous hydrofluoric acid to produce a layer 5 microns thick with 70% porosity and good crystallinity. The layer is subsequently etched in concentrated hydrofluoric acid, which provides a slow etch rate. The etch increases porosity to a level in the region of 80% or above. At such a level, pores overlap and isolated quantum wires are expected to form with diameters less than or equal to 3 nm. When excited, the etched layer exhibits photoluminescence emission at photon energies well above the silicon bandgap (1.1 eV) and extending into the red region (1.6-2.0 eV) of the visible spectrum.

Abstract: A calibration system includes an air system having a blower unit (10), a flow meter (16) and means (15) for controlling an airflow through a mixing manifold (17) to which a metered amount of a test gas can be added from either a mass flow controller (19) or a syringe drive unit (21).

Abstract: An aircraft flight instrument display panel (10) has a combined speed and heading indicator in the form of a central square (11) surrounded by a scaled matrix (12). Displacement of an aircraft (100), in which the display is installed, from a desired speed and heading being indicated by displacement of an aircraft symbol (14) in the y and x directions from the central square. The aircraft (100) has an attitude sensor system (102) and the flight instrument display (108) has a flight instrument control system (104), the attitude sensor system and the flight instrument control system having an interconnection (106) with control laws such that, when the aircraft (100) is displaced from its desired speed and heading, pilot adjustment of pitch and roll, respectively, in a manner tending to return the aircraft (100) to the desired speed and heading, causes the aircraft symbol (14) to move towards the central symmetrical square (11).

Abstract: Multiplex addressed ferroelectric liquid crystal devices containing liquid crystal mixtures composed of components A, B and C. Component A consists of one or more optically active compounds capable of imparting a spontaneous polarization to the material. Component B is a compound or compounds of the formula: ##STR1## where R.sub.1 and R.sub.2 independently represent straight or branched chain C.sub.3 -C.sub.12 alkyl or alkoxy groups, a, b and c are independently 0, 1 or 2 and the total of a+b+c is not greater than 4. Component C is selected from a range of liquid crystal components.

Abstract: A novel LCP material based on fumarate and maleate di-esters is disclosed having general formula (I); R.sub.1 and R.sub.2 may may not be the same but have general structure (II); (a)=(b), (c), (d); p=2 to 14; q=0 or 1; r=1 or 2; s=1 or 2; X.dbd.O, CO.sub.2, O.sub.2 C, CH.sub.2 ; Y.dbd.C.sub.2 H.sub.4, O, CO.sub.2, O.sub.2 C; Z.dbd.CN, halogen, R, CO.sub.2 R, OR, O.sub.2 CR, wherein R=chiral or achiral.

Abstract: An ear defender having one or more microphones (1) for detecting the sound level in the proximity of the wearer's ear, one or more speakers (4) for generating a noise reduction signal within the earshell, and a digital feedback controller (W) for generating a feedback signal derived from the output of the microphones and for applying said feedback signal to the speaker inputs, and estimation means (F') for providing an estimation of the earshell transfer function and subtracting from the input to the feedback controller a signal representing the estimated electroacoustic transfer function of the system. The operation of the digital feedback controller may be controllable by the output of a computational circuit (C) operable on the difference between the microphone output and the feedback controller input modified by a model (F") of the electroacoustic transfer function.

Abstract: Liquid crystal compounds having the formula (I) ##STR1## in which A.sub.1 is alkyl, alkoxy or alkenyl; X.sub.1, X.sub.2, X.sub.3 and X.sub.4 are independently halogens, m, n, p and q are independently 0, 1, 2, 3 or 4 such that m+n+p+q.noteq.0; Y is O or COO; and A.sub.2 is an end group of the formula (II), ##STR2## where Z is halogen, CH.sub.3, CN, CF.sub.3 or, CHF.sub.2 ; R is a linear or branched alkyl group or H; and R.sub.1 is a linear or branched alkyl group or H.

Abstract: A broadband electrical signal spectrum analyser comprises a spatial light modulator such as a Bragg cell located within at least one resonant cavity and illuminated by a polychromatic source of light. The signal to be analysed is connected to the Bragg cell. The tuned cavity is arranged to lase the diffracted light to thereby enhance the signal before detection. In one arrangement the cavity is formed by opposed mirrors set at the Bragg angle and one of the mirrors is oscillated through a range of frequencies required by the broadband application. In a second arrangement a plurality of narrow band channels is formed by a fibre optic array. The fibres are arranged such that first ends of the fibres form a linear input array and the second ends form a linear output array. Light at the Bragg angle passes into an appropriate one or more of the output array fibres, passes around the looped fibres to the input array where the light (zero order) is transmitted through the Bragg cell and then back to the fibre loop.

Abstract: An aircraft-launched pyrotechnic decoy flare for luring an incoming missile away from the aircraft's exhaust which comprises a compactly clustered substantially void free array of discrete pieces of a gassy high intensity infra-red emitting pyrotechnic composition contained in a rupturable air-tight container. On ignition of the flare, combustion spreads rapidly along the interfaces between the discrete pieces to produce gaseous combustion products. When the pressure within the air-tight container reaches a predetermined level the container ruptures and the discrete pieces burst apart. The plurality of pieces have a large combined surface area over which combustion occurs and so produce a high intensity emission of infra-red radiation. In a preferred embodiment the discrete pieces comprise a mixtured fibrous activated carbon cloth impregnated with a metallic salt and coated with a mixture of an oxidizing halogenated polymer, an oxidizable metallic material and an organic binder. FIG. 1.

Abstract: Liquid crystal compounds of the formula:R.sup.1 --Z.sup.1).sub.m --(Z.sup.2)--X--(Z.sup.3)--(Z.sup.4).sub.n --R.sup.2These compounds may be mixed with other liquid crystal compounds to give liquid crystal mixtures which may then be used in liquid crystal devices. In the formula X is COS, CSS and CSO; each of Z.sup.1, Z.sup.2, Z.sup.3, and Z.sup.4 are independently phenyl, substituted phenyl, where substitution is lateral substitution selected from F, Cl, Br, NO.sub.2, CN, NCS; naphthalene, substituted naphthalene, where substitution is lateral substitution selected from F, Cl, Br, NO.sub.2, CN, NCS, CH.sub.3 ; thiophene, pyridine and pyrimidine; each of A.sup.1 and A.sup.2 is independently selected from single bond, C.tbd.C, CH.dbd.CH; A.sup.3 is selected from C.tbd.C and single bond; each of R.sup.1 and R.sup.2 are independently selected from CN, NCS, CH.dbd.C(CN).sub.2, C.tbd.C--CN, C.tbd.C--CF.sub.

Abstract: A novel LCP material based on di-esters of itaconic acid is disclosed having general formula (I), where R.sub.1 and R.sub.2 may or may not be the same and have general structure (II); (a)=(b), (c), (d); p=2 to 14; q=0 or 1; r=1 or 2; s=1 or 2; X =O, CO.sub.2, O.sub.2 C, CH.sub.2 ; Y=C.sub.2 H.sub.4, O, CO.sub.2, O.sub.2 C; Z=CN, halogen, R, CO.sub.2 R, OR, O.sub.2 CR; wherein R=chiral or achiral; excluding X=O and X=CH.sub.2 when A=phenyl, r=s=1, Y=CO.sub.2, O.sub.2 C, q=1 and Z=CN, R, CO.sub.2 R, OR.

Abstract: An improved ionizable gas or vapor detector device and method are provided which are capable in preferred forms of sampling 4.times.10.sup.-3 cubic meters or more of air sec.sup.-1 and are responsive to ionizable gas fluctuations at a rate of up to 100Hz. Use of the device of the present invention has proved to provide sensitivity to UV ionizable gas or vapor of over 500 times that of prior devices, giving detection of propylene tracer gas at concentrations of 2 parts per 1,000,000,000 and thus increasing the range from the gas source at which the device may be reliably used. Use for detection of leaks of volatile UV ionizable compounds and for monitoring processes where vapors are emitted is also provided.

Abstract: A ceramic filament comprising a tungsten core and an outer layer of silicon carbide, the tungsten core and the outer layer being separated by an intermediate layer of titanium carbide. Also claimed is a process for the deposition of a titanium carbide coating on a tungsten filament which comprises heating the filament and passing the heated filament through a deposition chamber containing gases which on contact with the hot filament deposit the coating, the gases comprising a hydrocarbon and a titanium halogenated compound, said titanium halogenated compound contacting the tungsten filament before the hydrocarbon.

Abstract: A freezing bag (10) for the storage of blood cells is formed from two sheets (11) of material joined together with welds (15, 18) defining a containment zone (19). A pocket (20) leads from the containment area (19) and in the weld (18) defining this pocket is an access port (17). An access tube (23) is secured to the port (17) and normally lies within the bounds of a pouch (21) formed by extensions of the sheets (11) beyond the containment zone (19).

Abstract: An electroluminescent silicon device (10) includes a silicon structure (12) which comprises a bulk silicon layer (14) and a porous silicon layer (16). The porous layer (16) has merged pores (20) which define silicon quantum wires (18). The quantum wires (18) have a surface passivation layer (22). The porous layer (16) exhibits photoluminescence under ultra-violet irradiation. The porous layer (16) is pervaded by a conductive material such as an electrolyte (24) or a metal (48). The conductive material (24) ensures that an electrically continuous current path extends through the porous layer (16); it does not degrade the quantum wire surface passivation (22) sufficiently to render the quantum wires (18) non-luminescent, and it injects minority carriers into the quantum wires. An electrode (26) contacts the conductive material (24) and the bulk silicon layer has an Ohmic contact (28). When biased the electrode (26) is the anode and the silicon structure (12) is the cathode.

Abstract: An aircraft launched pyrotechnic decoy flare (1) which comprises a pellet (2) configured with a cavity (4) which extends along a fore-and-aft axis (8) of the pellet (2) and is vented at its rearward end (12). Part of the external surface of the pellet (2) is covered with a casing (16) to prevent combustion of said part of the surface. The pellet (2) is made of a gassy pyrotechnic composition including an organic binder, and an oxidizing halogenated polymer and an oxidizable metallic material which react with each other on ignition and emit infrared radiation. When the flare (1) is ignited the surface of the cavity (4) combusts and produces hot gaseous products which escape from the cavity (4) through the vent (22) thus propelling the flare (1) in a forwards direction. In this way the flare (1) can be propelled in the same direction as the aircraft to reduce the rate at which the flare (1) separates from the aircraft exhaust.

Abstract: A circuit and method for compressing or generating a pulse, particularly a chirp pulse, which uses infinite impulse response filtering (3.2). The infinite impulse response filters (3.9, 3.10, 3.11, 3.12) simulate the responses of finite impulse response filters. This is achieved by pre-processing the signal by passing it through a pre-processing filter (3.3) which has zero response at the resonant frequencies of the infinite impulse response filters (3.9, 3.10, 3.11, 3.12). The pre-processing and infinite impulse response filtering may be incorporated into a matched filter for detection of a chirp waveform input signal. This can be implemented in the time domain or the frequency domain. The matched filter also can incorporate beating to the base band techniques. The matched filter can also act as a generator by applying a pulse to the input which has the unit impulse function causing a chirp signal, equivalent to the transfer function of the filter, to be produced as the output.

Abstract: Differential amplifier (10) incorporates five metal oxide field effect transistors (MOSFETs) (M1 to M5). The transistors (M1 to M5) are a source-coupled pair of input transistors (M1, M2) with sources connected to a current control transistor (M5) and having respective drain load transistors (M3, M4). The transistors (M1 to M5) have floating gates (F1 to F5) and input gates (G1 to G5). The amplifier (10) is adjusted to counteract differing input transistor threshold voltage by charging one of the input transistor floating gates (G1 , G2) to reduce amplifier offset voltage extrapolated to zero input transistor drain current. It is then adjusted to reduce discrepancies between actual and design values of input transistor drain voltage by charging one or both of the drain load transistor floating gates (F3, F4). The amplifier may be arranged as an operational amplifier (20) with a second state (16) connected to an input transistor drain.

Abstract: A device and a process for enabling an incident wide bandwidth (greater than about 1 GHz) short duration (less than about 10 microseconds) individual pulse of electromagnetic radiation to be digitally sampled at a sampling rate that is achievable by available digital sampling circuits. The incident pulse is modulated onto an optical signal to form a modulated optical signal and the whole, or successive or randomly selected parts, of the modulated optical signal are replicated using optical time delay means. The resulting plurality of modulated optical signal representations of the whole or parts of the incident pulse can then be digitally sampled at a sampling rate which is reduced in proportion to the number of replications to obtain a complete digital representation of the incident pulse.

Abstract: HF aerials for ship-shore communications consist of spaced dipole arrays. By appropriate adaptive phasing very high gain HF aerials are formed. On transmission a feedback signal is required from the receiver, otherwise similar algorithms are used to control the beamforming. A random phase algorithm has been devised for the phases applied to the array aerials, operating in four tranches of 100 iteration steps with progressively reduced maximum phase variation. The initial step has a phase variation in the range .+-.180.degree.. The algorithm has the advantage that there is a high probability that a relatively high gain beam will be immediately formed in the required direction and thus the system can quickly settle towards a direction where the signal is weak. When in the transmit mode the receiver returns a signal to the transmitter giving the step number of the random phases which gives the maximum received signal.