Abstract: An alloy based on titanium and containing 0.5 to 30% by weight of magnesium, calcium or lithium is produced by vapor quenching to yield a metastable solid solution of solute in titanium. Exemplified alloys containing magnesium have age hardening or solution strengthening characteristics. Vapor quenching enables these alloys to be produced despite the differences in melting temperature between solute and solvent by separate vaporization of each of the species and mixing in the vapor phase. This method provides a route to achieving rapid solidification microstructures unobtainable by other rapid solidification methods. Preferred alloys comprise Ti with 1-15% or 3-7% by weight of magnesium. The alloys may contain other strengthening ingredients currently used in titanium alloys.

Abstract: A high frequency transmitter comprises a large number of narrowband channels spaced over a broad bandwidth transmission. In one arrangement input data to be transmitted is demultiplexed (1101) so that sections of data are transmitted in groups of channels at 50 baud (say), each 50 baud channel produces a number of diversity channels modulated using difference phase shift key (DPSK) (103) and then added (105) for transmission. In the receiver, coherent summation (803) of close-bunched channels can be used and semi-coherent channel addition (805) can be used across the complete bandwidth. The received signal is convened to digital form then processed by an FFT circuit to produce frequency bins corresponding to the transmitted diversity channel frequencies. DPSK demodulation is carried out and running averages are carried out in each channel to determine the proportion of times that the phase difference falls within allowed limits (907).

Abstract: An optical communications system (10) comprises a transmitter (12) and a receiver (14). A source (16) of correlated pairs of photons of conjugate energies provides first and second photon beams (38, 36). The first photon beam (38) passes through a modulated filter (50) to which a communications signal (52) is applied. A variable spectrum beam (54) is produced which is converted to a timing signal (68) of macroscopic optical pulses (66). The second photon beam (36) and timing signal (68) are transmitted to the receiver (14). The received timing signal (84) is converted to a series of electrical timing pulses (90). The received second photon beam (82) passes through an unmodulated filter (94) matched to the modulated filter (50) when the signal (52) is not applied. The unmodulated filter splits the beam (82) into two conjugate spectra photon beams (96, 98) which are then converted to first and second series of electrical pulses (108, 110) respectively.

Abstract: An optical device (10) for use in beamsplitting, recombination and related applications incorporates a rectangular multimode waveguide (20) connecting a first coupling waveguide (18) to two second coupling waveguides (22, 24). The first coupling waveguide (18) operates in its fundamental mode and provides an input which excites a series of symmetric modes of the multimode waveguide (20). Modal dispersion along the multimode waveguide (20) provides for the input excitation (70a) to be transformed into separate output excitations (75a, 75b) cantered on respective second coupling waveguides (22, 24). The radiation intensity distribution (75) goes to zero at multimode waveguide end wall regions (54) between the second coupling waveguides (22, 24). This minimizes reflection and increased beamsplitting efficiency. The device (10) may be operated in reverse as a beam combiner.

Abstract: A system (1) responds to inputs (2) in parallel with a state estimator (4). The controller (6) provides the inputs (2) in response to ordered state inputs (14) and state estimator inputs. An external disturbance vector (f) affects the system (1) so that the observed values of the state variables are not the same as the estimated values. The estimated and measured values are compared (8) to give an error signal (9). The error values are fed to an Ordered State Corrector (11) which computes the error that the order state variable would have in the steady and applies it in the opposite sense to increment the input ordered state (14). If more than one state variable is to be corrected, the correction is applied directly to the control inputs using Multi-State Correction, in which the steady state errors are used to find the control inputs which would cause the errors and then a correction is applied to the control inputs.

Abstract: Ammunition round comprising a forward cartridge 1 including a projectile 6 and a propellant charge 8, a rearward cartridge 2 including a propellant charge 8 and a propellant ignition system 3, 10, 14, and a propellant charge igniter 16 located so as to lie positioned between the first and second propellant charges when the round is loaded, wherein the propellant ignition system includes ignition transfer means 14 for transferring ignition from the rear of the rearward cartridge to the propellant charge igniter and the propellant charge igniter 16 includes ignition propagation means, preferably in the form of igniter cord 26, for spreading ignition laterally to facilitate rapid simultaneous ignition of the two charges.

Abstract: A high temperature battery which has a cathode comprising either sulphur or a metal sulphide, an anode comprising either an alkali metal, an alkaline earth metal or an alloy of either and, disposed between them, an electrolyte comprising an alkali metal halide. The materials in the cathode composition are electrochemically in excess to the materials in the anode composition. Potassium chloride, potassium iodide or, preferably, potassium bromide is added to the anode, the cathode and the electrolyte. When potassium bromide is added, ideally, it is added to the electrolyte in excess to the alkali metal halides present in the electrolyte. In one particular example, the cathode comprises iron sulphide, the anode comprises a lithium aluminum alloy, the electrolyte comprises a ternary metal halide and potassium bromide is added to all three. Magnesia can be further added to the anode, cathode and electrode.

Abstract: A rigid thermal sleeve 5 mountable over at least part of a gun barrel 3 in such a way that it is symmetrical about a longitudinal plane A--A to provide a reduced thermal image and radar cross section. The sleeve 5 comprises thermally insulating material 13 between an inner skin 15 and an outer skin 17. The outer skin 17 is arranged to have two mutually convergent planar faces 7,9, each one of which makes up at least 15% of the outer surface of the sleeve 5 and which have a mutual line of convergence extending externally and longitudinally of the sleeve 5.

Abstract: A ferro-electric liquid crystal display is multiplex addressed by strobe waveform applied in sequence to each electrode in one set of electrodes coincidently with data waveforms applied to a second set of electrodes. Liquid crystal material in the display is switched by a d.c. pulse of appropriate polarity, amplitude and time. The strobe waveforms have first and second pulse pairs, each pulse pair comprising two pulses of different amplitude and the same or different sign. The pulse pairs are similar but of opposite sign. Data waveforms are rectangular waveforms of opposite sign. The amplitude and ratio of leading pulse to trailing pulse in each strobe pulse pair are adjusted to obtain the desired switching and contrast. Compensation for temperature changes is arranged by measuring the temperature of the liquid crystal material and using the value obtained to adjust the amplitude value of the leading pulse in each strobe pulse pair.

Abstract: An optical device (10) incorporates a rectangular multimode waveguide (14) with an input aperture (22), and two output optical fibres (26 and 28) with respective input apertures (30 and 32). An input light beam (34) of Gaussian transverse intensity profile is focused to a beam waist (36) at the center of the aperture (22). The beam phase and waist radius w are arranged such that the light beam (34) excites symmetric modes in the waveguide (14). Modal dispersion along the waveguide (14) producestwo electric field intensittlVxima of similar magnitude centered on the fibre input apertures (30 and 32). This provides the beamsplitter function of division of input radiation into two similar intensity outputs. Devices of the invention may be arranged to divide input beams into more than two output beams. The invention may also provide a light beam combiner.

Abstract: Novel polyarylamide derived activated carbon materials are provided by a process comprising the carbonization of polyarylamide fibre at a temperature in excess or 400.degree. C. followed by activation at elevated temperature. The novel materials have the ability to adsorb relatively large quantities or carbon dioxide compared to other activated carbonized polymer materials, Preferably the carbonization and activation steps are carried out by raising the temperature of the materials to between 840.degree. C. and 880.degree. C. in carbonizing/activating atmospheres respectively.

Abstract: In a heavy structure e.g. a bridge which includes an element liable to low frequency vibration during erection, i.e. when the structure is unstable, another element which is an integral structure part after erection is used as the mass of a dynamic absorber for damping this vibration. In the example given, a launch rail (46) for erecting a bridge across a river is cantilevered out over the river, after which a support leg (50) is extended by means of an integral jack to engage the ground and form a stable structure. The support leg includes a lower part (54) which is suspended during erection from the upper part of the leg through a gas spring, with the gas spring and the mass of the lower part together constituting a dynamic absorber for the lauch rail during erection. After erection, structural loads are transmitted directly to the lower leg part via a trunnion.

Abstract: A semiconductor device in the form of a metal insulator field effect transistor (MISFET) (200) is constructed as a heterostructure of narrow bandgap In.sub.1-x Al.sub.x Sb semiconductor materials. The MISFET (200) is formed from four semiconducting layers (112 to 118) arranged in series as follows: a heavily doped p-type first layer (112), a heavily doped relatively wider bandgap p-type second layer (114), a lightly doped p-type third layer (116) and a heavily doped n-type fourth layer (118). A source (202) and a drain (204) are formed in the fourth layer (118) and a gate (116/205) in the third layer. An n.sup.+ p.sup.- junction (124) is formed between the third and fourth layers and a p.sup.+ p.sup.- junction (122) between the second and third layers. The second layer (114) provides a conduction band potential energy barrier to minority carrier (electron) flow to the gate (116/205), and is sufficiently wide to prevent tunnelling of minority carriers therebetween.

Abstract: This invention provides a ferromagnetic material Fe.sub.60 M.sub.x N.sub.y where M is at least one element selected from Al, Ga, In and Tl, N is at least one element selected from P, As, Sb and Bi, x has a range of 1.ltoreq..times..ltoreq.39 and x+y=40 and excluding Fe.sub.60 Ga.sub.X AS.sub.y. A preferred ferromagnetic material is Fe.sub.60 Ga.sub.x As.sub.y , preferably when x has a range of 3.ltoreq..times..ltoreq.37, more preferably when x has a range of 20.ltoreq..times..ltoreq.37, and even more preferably when x has a range of 30.ltoreq..times..ltoreq.37. Typically, ferromagnetic materials of this type can be homogenised by annealing or melt spinning. Melt spun Fe.sub.60 Ga.sub.x As.sub.y can show Curie Temperatures (T.sub.c) of about 470.degree. C. and saturation magnestions of about 89 emu/g. Typically a ferromagentic material of the Fe.sub.60 M.sub.x N.sub.y has a B8.sub.2 type structure.

Abstract: Apparatus for producing refractory material filaments comprises an enclosure (11), means for heating the constituents of the refractory material, non-contacting means to support a drop (17) of molten material such as silicon, being one of the constituents of the refractory material within the enclosure and means to transport a filament (10) such as carbon, being a second constituent of the refractory material, through the drop of molten material in use. A levitation coil and/or an inert gas jet is used to support the drop of molten material and a silica glass or other refractory tube (13) is used to direct the gas jet. The enclosure has opposed side arms (15, 16) respectively for entry and exit of the filament (10) or the filament may be passed vertically through the molten silicon drop. An inclined side tube may be provided through which grains of silicon may be introduced into the enclosure for addition to the molten drop.

Abstract: Precursors for metal matrix composites are produced by coating a long fibre ceramic reinforcement with alternating layers of dissimilar species of matrix materials to an aggregate thickness sufficient to yield the intended matrix volume fraction in a consolidated product without additional material. This duplex coating of fibres is performed by vapor phase deposition comprising vapor condensation, sputtering or chemical vapor reaction. The precursor includes an aggregate coating of at least 5% of fibre diameter, preferably at least 20%. Various duplex systems are disclosed, each having one component significantly more frangible than the other to render damage tolerant properties to the resultant metal composite.Product materials are produced from the duplex matrix coated fibres by consolidation of an assembly of coated fibres under conditions of elevated temperature and pressure to cause inter-fibre matrix flow and bonding of matrix materials.

Abstract: A method of testing oil for unstable reactive compounds include reacting unstable compound from an oil sample with an acid catalyst to form a reaction product, the color of which is then related to the presence and/or amount of reactive compound in the oil. Kits combining the necessary materials and reagents for performing the test method are also provided.

Abstract: A dye laser amplifier is formed by a stimulated brillouin scattering (SBS) dye cell which receives both dye laser light to be amplified and a pump beam along a common optical path. Phase conjugation and amplification of received energy are reflected from the SBS cell. The cell comprises an SBS medium that is a solvent for the laser dye used. Typical SBS mediums are methanol, acetone, isopropyl alcohol, etc. Typical dyes are Rhodamine 6G, Rhodamine B, Rhodamine 560, Rhodamine 575, Sulphorhodamine B, Kiton Red, DCM, Courrarun 523, etc. A plurality of amplifiers may be connected in series to provide increased amplification. The action of the phase conjugation corrects optical distorsions, thereby preserving beam quality and bandwidth even after multiple amplifications. A typical dye laser beam of 590 nm wavelength, about 1 .mu.J may be amplified to about 120 mJ, with a 17 nsec pulse width, and <500 MHz bandwidth.

Abstract: An intensity dividing device (10) incorporates a rectangular multimode waveguide (20) connected to an input waveguide (18) and a set of four output waveguides (22). The input waveguide (18) provides a fundamental mode input excitation of CO.sub.2 laser radiation to the multimode waveguide (20). The input waveguide (18) is offset from the multimode waveguide longitudinal axis (24). Consequently, both symmetric and antisymmetric modes of the multimode waveguide (20) are excited. Modal dispersion along the multimode waveguide produces electric field intensity maxima of differing magnitude centred on respective output waveguides (22). This provides division of the input radiation into a range of differing intensity outputs.