Abstract: The present invention relates to a system and method for processing imagery, such as may be derived from a coherent imaging system e.g. a synthetic aperture radar (SAR). The system processes sequences of SAR images of a region taken in at least two different passes and generates Coherent Change Detection (CCD) base images from corresponding images of each pass. A reference image is formed from one or more of the CCD base images images, and an incoherent change detection image formed by comparison between a given CCD base image and the reference image. The technique is able to detect targets from tracks left in soft ground, or from shadow areas caused by vehicles, and so does not rely on a reflection directly from the target itself. The technique may be implemented on data recorded in real time, or may be done in post-processing on a suitable computer system.

Abstract: A multi-functional, laminated composite comprises a plurality of cloth layers (3) penetrated by an infused matrix, wherein at least one cell (1) for energy storage is supported by and integrally built up from at least one of the cloth layers (3), the cell (1) being embedded in the matrix. The cell may comprise first and second electrodes (6,7) separated by a porous, separator layer (2) that has a liquid electrolyte-permeable, matrix-free intra-electrode region to which the electrolyte (2?) may be added before or after resin infusion to activate the cell. The structural composite may have integrated energy storage comprising a lithium-ion rechargeable cell, optionally of printed construction.

Abstract: The present invention relates to an improved quantum signal transmitter, which has a plurality of quantum output channels having at least one optical source and at least one optical splitter acting on the output of said at least one source. Such a transmitter can easily be used with existing passive optical network (PON) systems and can be a compact piece of equipment.

Abstract: Random number generation apparatus (2) is described that comprises a threshold detector (4) and an electrical noise generator (6). The electrical noise generator (6) has at least two channels (8a-8d) and each channel is arranged to generate an electrical noise signal. The threshold detector (4), which may comprise a digital input-output (DIO) card, is arranged to periodically compare this electrical noise signal with a threshold and to provide a binary data output that indicates whether the threshold has been exceeded. Each channel of the electrical noise generator comprises at least two amplifiers (10a-10c) electrically connected in series that preferably provide a gain of 50,000 or more. Use of the random number generation apparatus (2) for quantum cryptography applications is also described.

Abstract: A method of authentication between first (QNodeX) and second (QNodeY) network nodes within a network suitable for implementing quantum cryptography comprises steps in which the first and second nodes each generate a cryptographic hash ([MXY]AI, [MYX]AJ) of a message ([MXY], [MYX]) using respective authentication keys (AI, AJ) shared with a third network node (QNodeW). The messages may be those exchanged between the first and second nodes during agreement of a quantum key to be used between the nodes. An authentication key to be shared by the first and second nodes may be established using the quantum key. The invention therefore allows an authentication key to be established and shared between the first and second network nodes without direct physical intervention. Networks having large numbers of network nodes may be re-keyed following replacement or maintenance of a network node much more quickly and easily than is the case where re-keying is achieved by physically supplying shared authentication keys.

Abstract: A method of key distribution from a first entity to a second entity including the first entity communicating with a moveable key device so as to share a secret data with said moveable key device, relocating said moveable key device to a location having a quantum link with said second entity, transmitting a quantum signal from said moveable key device to said second entity on said quantum link, the quantum signal being based on said secret data; and said first entity and said second entity undertaking key agreement based on the quantum signal received by the second entity. Such a method allows the principles of quantum key distribution to be applied even in the absence of a suitable quantum communications link between the first and second entities.

Abstract: A non-linear optical device includes a frequency-conversion waveguide and first and second input waveguides. The longitudinal axes of the input waveguides are inclined to that of the frequency-conversion waveguide such a first transverse mode is excited in the latter at the input frequency in operation of the device. The frequency-conversion waveguide supports a second transverse mode at an output frequency of the device, such that the phase velocity of the second transverse mode at the output frequency is substantially equal to that of the first transverse mode at the input frequency, thus providing phase-matching by balancing the effects of chromatic and modal dispersion.

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.

Abstract: Casings and housings for use in high speed airflow (for example for mounting on a high speed vehicle) are described. In one embodiment, a housing for imaging equipment is described. The housing has a tapering form with symmetrical angular truncations such that it tapers in the form of a wedge with two substantially planar regions. At least one substantially planar region includes an aperture formed of optically transparent material.

Abstract: Methods and apparatus for ensuring the computer security of users of a computer system are described. A user is allocated a security grading relating to how secure their computer system (2) is, for instance in terms of anti-virus software, firewalls and up-to-date security patches. Methods and apparatus (10, 12) for providing a security grading of a user's computer system are also disclosed. Users without a security grading or with low level security grading may then be accorded only basic access to the data or functionality of another computer system (8), for instance such as on-line banking services or the like. This ensures therefore that those users that take responsibility for their own security are allowed full access without undue security protocols whereas users without proper security do not have so much access.

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: A timing and synchronization apparatus and method for a quantum cryptography system is disclosed. A gating pulse is generated by a clock and synchronized to the receipt of transmitted photons at the detector. The apparatus is arranged to only accept photon detection events occurring during the gating period.

Abstract: A DDS based system, such as a radar, includes means for generating a plurality of transmission signals using a DDS, and means for integrating signals derived therefrom, such as received signals. The system further includes means for varying the relative starting phase of the plurality of transmission signals, or adjusting the DDS input clock while maintaining similar primary output frequency characteristics of the transmission signals. The approach has the effect of changing the location of unwanted frequency spurs in each of the transmission signals, and hence the effects of these are decreased in the integration process. An improvement in the sensitivity of the system results. Although primarily suited to radar applications the invention may find utility in other systems such as sonar or lidar systems.

Abstract: A method of establishing a quantum key for use between a first network node (QNode1) and a second network node (QNode3) in a network for carrying out quantum cryptography includes a key agreement step carried out by a third node (QNode2) and the second node (QNode3) and a subsequent authentication step carried out by the first and second nodes directly. As the key agreement step does not involve QNode1, another key agreement step may be simultaneously performed by another pair of network nodes QNode4, QNode5 to agree a quantum key for use by network nodes QNode1 and QNode5. The invention allows respective quantum keys to be established between a network node and each of a set of other nodes more rapidly than is the case if each quantum key is established serially by key agreement and authentication steps.

Abstract: A gun-fired projectile or ballistic missile (1) is equipped with a pair of canards (3) and an array of tail fins (2). Selected tail fins can be retracted or jettisoned following the ballistic phase to vary the geometry of the array from a rotationally symmetrical configuration to an asymmetric configuration for the glide phase, which together with the canards tends to stabilize the projectile in roll. The canards (3) can be independently extended and retracted with respect to the body of the projectile to generate differential lift for banking the projectile to turn. The canards (3) also preferably have a positive dihedral angle with respect to the intended gliding attitude. In an alternative embodiment the canards are replaced by functionally equivalent thrusters.

Abstract: A method of evaluating a composite structure in which a portion of the structure is imaged and subsequently transformed to provide a 2D output of the angular distribution of features, eg a 2D FFT. A weighting function is applied to the output to compensate for variation in the angular density of pixel population. The weighted output is then used to provide an angular distribution of feature intensity. The structure can be imaged in two or more intersecting planes to allow a 3D determination of feature direction to be obtained.

Abstract: A visual aid for the pilot of an aircraft approaching to land on an aircraft carrier comprises a series of lights (9) embedded along the landing deck and controlled in response to pitch and heave of the vessel so that the light(s) illuminated at any time indicate a visual aim point which is stabilised with respect to a specified glideslope (5) onto the vessel irrespective of such vertical excursions of the vessel. It is used in conjunction with a marker on a head up display or helmet mounted display for example so that registry of the marker with the illuminated light at any time indicates that the aircraft is on the correct glideslope.

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: The present invention relates to an improved quantum key device for use in quantum key distribution, which device comprises a quantum detector unit for detecting a quantum signal and a plurality of logic units operably connected to the quantum detector unit wherein each logic unit is arranged to derive a separate quantum key from the quantum signal detected. In this way, a single quantum key distribution (QKD) receiver can generate separate quantum keys for separate users.

Abstract: The invention relates to a method of fabricating a semiconductor device, the method including: providing a stacked semiconductor structure having a substrate, a buffer layer and one or more device layers; depositing a layer of AlSb on one or more regions of the upper surface of the stacked structure; and oxidising the AlSb layer in the presence of water to form a layer of aluminium oxide on the one or more regions of the upper surface. The semiconductor device is preferably a field effect transistor, and the method preferably includes the additional step of depositing source, drain and/or gate electrodes. In preferred embodiments, the method is controlled so as to avoid exposing the intermediate AlSb structure to the atmosphere and/or the oxidation step is conducted at a temperature between 100° and 300° C.