Abstract: A multistage flextensional transducer includes at least one inner elongate driver member within and mechanically coupled to an inner shell that is nested within an outer shell; the inner shell comprising a pair of contact portions abutting the driver member and a pair of transmission portions on opposite sides of the inner shell between the contact portions; the outer shell being arranged so that the transmission portions act as bridging driver members between the said inner and outer shells, flexure of the outer shell being driven, on actuation of the transducer, by movement of the bridging driver members. The transducer may act as a push or pull actuator or sensor, may magnify displacement and may employ smart materials as driver members. Also cylindrical modules containing thin flextensional actuators may provide axial displacement in a downhole environment and may move a device axially along a downhole pipe or close a valve opening or inch along the pipe.

Abstract: A method of performing quantum key distribution across a network. The method involves a first node first agreeing a quantum key with a first intermediate node in the path. Next the intermediate node exchanges a quantum signal with the next node in the path—which is a targeted node. The intermediate node communicates with the first node using the previous established quantum key details of the quantum signal sent or received by the intermediate node. The first node then performs a key agreement step to agree a quantum key directly with the targeted node. Having established a quantum key with the current targeted node the method can be repeated but with the next node in the network path as the targeted node until a destination node is reached. The final quantum key agreed with the destination node can then be used for encrypting communication between those nodes across the network.

Abstract: A measurement device, such as a laser radar, is described that comprises a transmitter portion for transmitting radiation to a remote probe volume, a receiver portion for detecting radiation returned from the remote probe volume and a processor for analysing the detected return radiation. The device is suitable for transmitting and receiving radiation through a window portion having associated window cleaning apparatus (e.g. wiper 62) for cleaning said window portion in response to a cleaning activation signal. The processor is arranged to generate a cleaning activation signal for activating window cleaning apparatus when the properties of said detected return radiation are indicative of a reduction in transmission through at least part of said window portion. In one embodiment, a conically scanned lidar is described that generates a cleaning activation signal when the power of detected return radiation varies as a function of the angle of transmission of radiation from the device.

Abstract: The method involves exchange of a quantum signal between a first quantum node and a second quantum node as is usual in known quantum key distribution (QKD) scheme. The first quantum node communicates details of the quantum signal it sent or received with a first remote node. The first remote node thus has all the information to required to take the place of the first quantum node in the key agreement step with the second quantum node. The first quantum node may be arranged to transmit the quantum signal to the second quantum node, in which ease the invention provides a distributed quantum transmitter with the control logic in the first remote node being distributed remotely from the actual quantum transmitter in the first quantum node. Communications between the first remote node and first quantum node may comprise or be protected by a quantum key derived by conventional QKD.

Abstract: An optical receiver for a quantum key distribution system comprises a plurality of optical components mounted or formed in a substrate and optically coupled by one or more hollow core waveguides formed in the substrate.

Abstract: A method of determining the rate of change of optical thickness of a thin-film during deposition comprising the steps of illuminating the thin-film with electromagnetic radiation having a range of wavelengths, measuring the transmission spectrum of the thin-film at least twice during the deposition process to determine the wavelength ?t or turning points in the transmission spectrum, and using the measurements to determine the rate to change of optical thickness of the thin-film as a function of time. The method further comprises the steps of predicting a time T in the growth process at which the wavelength ?t of the turning point in the transmission spectrum of the thin-film will be substantially equal to the wavelength ?d of the turning point in the transmission spectrum of thin-film at its optical design thickness, and interrupting the growth process such that growth ceases at time T.

Abstract: An iridescent material comprises a diffraction grating incorporating a plurality of sheets (1) of a first substantially transparent material in parallel alignment and spaced away apart by quantities of a second substantially transparent material (2), the second material having a refractive index significantly lower than the refractive index of the first material, the plates being tilted at an angle ? to an axis X and the grating having a period d(X) in the direction of axis X, the angle ? and period d being such that a second diffraction grating is provided along an axis Z, perpendicular to axis X, the second diffraction grating having a period d(Z) and consisting of ten periods or less and whereby, the diffraction conditions of the grating can be simultaneously fulfilled by electromagentic radiation of a range of wavelength thereby causing iridescence.

Abstract: A method of monitoring electrical activity non-invasively (such as uterine activity) which includes applying a localized group of electrodes to a patient's skin and monitoring signals thereon. The electrodes are localized sufficiently such that their muscular signal contributions simulate a single source despite source non-stationarity. The signals are amplified, filtered and digitized. They are then digitally filtered and processed by independent component analysis (ICA) to separate a muscular activity source from other sources. The method may be used to monitor maternal uterine activity, fetal activity and maternal and fetal cardiac activity simultaneously with the aid of additional electrodes and associated circuitry.

Abstract: A mooring failure detector, for attachment to a mooring chain or wire rope, includes a power source, which is activated by the rupture of a rupture element, caused by a change in depth and hence pressure of the device. Activation of the power QC source provides power to a transmitter to signal the failure, either by acoustic or radio frequency means. The device can operate on an inclined mooring such that failure above or below the point of attachment results in a failure signal being transmitted.

Abstract: This invention relates to electronic circuit packages designed to hold high frequency circuits operating particularly, but not exclusively, in the microwave, millimeter wave, and sub-millimeter wave bands. The invention provides a package incorporating a cavity in a material for containment of the circuits, wherein the package further incorporates at least one conductive surface mounted on an inner surface extending into the cavity, the conductivity thereof being adapted to be at least partially absorbent to electromagnetic radiation. The conductive surface according to the present invention will tend to attenuate electromagnetic radiation present within the cavity, and so help to prevent undesired coupling from one point to another within the cavity. The conductivity of the conductive material is preferably arranged to match the impedance of the radiation mode estimated or computed to be present within the cavity.

Abstract: The present invention relates to an imaging system which employs the same principles as coded aperture imaging. High angular resolution coded aperture imagers require a small aperture size and relatively large spacing between the coded aperture array and the detector. At such high resolutions diffraction effects can start to dominate and can degrade image quality. The present invention provides a detector array which receives radiation from a scene via a coded diffractive mask. The coded diffractive mask is designed such that its diffraction pattern at the waveband of interest is a well conditioned coded intensity pattern having a strong autocorrelation function with low sidelobes. Thus radiation reaching the detector array is diffracted by the diffractive mask but in a defined way and it is the diffraction pattern of the mask which provides the coding.

Abstract: Range-finding apparatus comprises a source of pulsed radiation of variable repetition rate and a beam-splitter for dividing the pulsed radiation into two portions which are directed respectively to a local retro-reflector and to a retro-reflector co-located with a remote target the range of which is to be determined. The source, beam-splitter and retro-reflectors are arranged in the form of Michelson interferometer together with a detector. The repetition rate of the source is tuned to frequencies f such that round-trip distance to the remote target is mc/f where m is an integer, this condition being detected by observing a heterodyne signal at the detector. Two such frequencies enable range to be determined. The precision with which range is determined may be increased by carrying out interferometry using the two portions. The accuracy of the method does not depend on absolute range (as with triangulation) and is not limited by the speed of timing electronics, as is the case for time-of-flight techniques.

Abstract: Testing of a safety valve is described in relation to a valve stem biased relative to a valve body, and comprising a rotor mounted helically on said valve stem, and a driver adapted to rotate the rotor. Rotation of the rotor causes an axial force between the valve stem and the rotor and allows the rotor to be moved into and out of engagement. When engaged the rotor can apply a pre-load to the stem, and may provide sufficient force to achieve valve lift. Alternatively a two stage actuator system may be employed, the second stage providing lift after application of the pre-load.

Abstract: An unmanned aerial vehicle (UAV) in the form of a “tail sitter” flying wing adapted for vertical take off and landing and transitions between flight as a helicopter and wing-borne flight. The vehicle is electrically powered from onboard batteries and equipped with rotors on miniature helicopter rotor heads at the tips of the wing for both lift, during take off and landing, and forward thrust. In planform the wing comprises, to each side of its longitudinal axis, an inner section with swept back leading and trailing edges, and an outer section with a leading edge more perpendicular to the longitudinal axis, being only mildly swept back or substantially unswept, and a swept forward trailing edge.

Abstract: Optical apparatus for simultaneously focussing first and second coaxially spaced object planes in respective separate first and second areas of a common image plane 13 (such as the sensor of a CCD camera) comprises non-diffractive beamsplitter means for receiving light from said object planes along a common path 2 for transmission to said first and second image areas along respective first and second optical paths 3, 4, and reflective or transmissive focussing means 8 arranged to bring said first and second object planes into focus in said first and second areas. The object planes may be differentiated by having different length paths 3,4 (different physical lengths and/or using a differential optical delay), and/or by having different focussing powers in the two paths. In an add-on for a camera, differently curved mirrors of long focal length modify the main camera lens. Polarising optics may be used to separate the two images. The apparatus may be used for 3-D imaging or wavefront analysis.

Abstract: A method and system for detecting gravitational anomalies comprises measuring surface structures, measuring gravitational field characteristics, and estimating the effect of the surface structures on the gravitational measurements. The estimations are then used to derive a representation of nearby non visible features such as changes in rock density, voids, or oil and gas deposits. The surface structures may be measured by a video camera, with the video sequence being processed to estimate 3D positions of structures relative to the measurement point. Other methods may be used, such as lidar or acoustic techniques as appropriate. The method may be applied above ground and also has efficacy in borehole and sewer surveying applications.

Abstract: A pyrolytic hydrogen generator comprising a pressure vessel containing a plurality of cardboard receptacles for the thermally decomposable hydrogen generating material and an associated ignition system. Also, a modular pellet tray assembly for use in the generator comprises a plurality of trays having pellet holders and associated igniters and held in a stack by support rods that also provide electrical connectivity to the trays. Also, a pellet tray assembly comprises a plurality of pellet holders, wherein some of more outwardly disposed pellet holders contain only outwardly facing vents and are fired first. Also, the generator has an array of hydrogen generating elements arranged side by side and separated from one another into cells by partitioning provided with directional venting that only permits laterally exiting gases to vent outwardly. Alternatively, the elements can be separated into cells by a baffle system comprising gas confining and gas venting elements, which may be heat conductive.

Abstract: This invention relates to a novel insensitive munition comprising one warhead and also munitions comprising one or more warheads. In particular, the invention lies in the field of insensitive munition warheads. There are further provided methods of preparing the warheads of the invention, methods of controllably detonating the warheads and a kit suitable for preparing such a warhead. The warhead comprises at least two portions of high explosive separated by a non-detonative material, wherein each portion has a cross section below its critical detonation cross section, and wherein the at least two portions are arranged such that the total cross section of the at least two portions exceeds the critical detonation cross section of said high explosive, such that in use only simultaneous detonation of the at least two high explosives causes detonation to occur.

Abstract: Apparatus for testing a safety valve by applying a force to the valve stem and detecting the resultant motion of the valve. The actuator used is generally a hollow cylinder of piezoelectric material or other solid state actuator, which is adapted to locate concentrically about the valve stem. The concentric placement and lack of moving parts creates reliability and even force distribution while maintaining a small overall size.

Abstract: A composite material having a plasma frequency comprising a random mixture of conductive and non-conductive particles. A material having smaller conductive than non-conductive particles and a concentration of conductive particles approximately at, close to or above the percolation threshold for mixtures of the conducting and non-conducting particles may show a plasma frequency well below plasma frequencies for conventional bulk materials.