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 composite material comprises magnetic particles dispersed in electrically insulating material. The magnetic particles have an aspect ratio greater than 1 (preferably greater than 10) and a concentration sufficiently high to produce negative permeability. The magnetic particles may be magnetic flakes of reduced carbonyl iron of average diameter 50 ?m, average thickness 1 ?m and aspect ratio 50, the magnetic flakes being at least 25% by volume of the composite material. The magnetic flakes may be aligned to produce enhanced permeability. The electrically insulating material may be paraffin wax, particulate PTFE, or another polymer. To control permittivity, the composite material may include an electrically conducting component such as graphite or conductive coatings upon the magnetic flakes.

Abstract: The invention relates to methods and apparatus for Quantum key distribution. Such methods including authenticating a first node in a communications network with a remote node in the communications network. The authentication may include connecting an authentication device to the first node, agreeing a quantum key between the first node and the remote node based on a quantum signal transmitted or received by the first node and performing an authentication step between the authentication device and the remote node on an encrypted channel. Authentication between the authentication device and remote node may be taken as authentication of the first node.

Abstract: Optical sensors comprising a fluidic channel through which fluid carrying magnetised beads may be passed, an optical source for illuminating fluid as is passes through the channel, a sensor for detecting fluorescence emitted by the beads when illuminated by the optical source, and magnet means arranged to temporarily capture and retain the magnetic beads at an assay point in the fluidic channel illuminated by the optical source and monitored by the sensor. Methods and further apparatus relating to the same.

Abstract: A method for modelling integrity of a filtered global navigation satellite system, by calculating component navigation system error distributions for a set of fault conditions and a fault free condition, and determining overall navigation error distribution by forming a mixture distribution from these component navigation system error distributions. The mixture distribution may be determined by weighted summation of navigation system error (NSE) distributions with weightings determined according to prior probabilities for the fault conditions. Once the overall NSE mixture distribution is determined in this way, it can be used to derive one or more statistical quantities relevant to the integrity of the navigation system such as the probability of exceeding given alert limits in a desired coordinate geometry.

Abstract: A gear reduction mechanism, particularly for use in an offset final drive unit for vehicular applications, has an input gear meshing directly with the output gear and two additional gear trains between the input and output gears. Three separate load paths therefore exist for the transmission of torque from the input gear to the output gear which means that the face widths of all the gears can be substantially reduced in comparison with a conventional single-mesh arrangement and the overall mechanism can therefore be of reduced width.

Abstract: The invention provides rupturing devices for mitigating the explosive reaction of a casing (121), hollow tubular body or container, particularly a munition, when it is subject to an external thermal hazard threat. The devices are based on the use of shape memory alloys. The device comprises an element of shape memory alloy (123) which is joined together by a connector (122) to form an annulus, which may be located on an exterior surface of a munitions casing (121) or launch such that upon heating through its transition temperature range will cause the annulus to contract radially inwardly, thereby rupturing the munition (121), allowing any build up of pressure to be released quickly. Advantageously, the connector (122) is. reversible such that the device will be capable of being retro-fitted or removed during normal servicing of the munition (121).

Abstract: An electro-optic waveguide polarization modulator (20) comprising a waveguide core (4) having first and second faces defining a waveguide core plane, a plurality of primary electrodes (22, 24) arranged at a first side of the waveguide core plane and out of said plane, and at least one secondary electrode (26) arranged at a second side of the waveguide core plane and out of said plane, wherein the electrodes (22, 24, 26) are adapted in use to provide an electric field having field components (13, 15) in two substantially perpendicular directions within the waveguide core (4) so as modulate the refractive index thereof such that electromagnetic radiation propagating through the core (4) is converted from a first polarization state to a second polarization state.

Abstract: A sensor system includes a sensor and processing means adapted to process the signals from the sensor, and to provide a distance measurement or estimate from the sensor to a metallic object of interest, such as a turbine blade. The sensor, typically an eddy current sensor, provides a signal to which the processing means fits a curve, and parameters including pulse width and height are taken from the fitted curve and used in calculating the distance measurement or estimate. Look-up tables may be used to produce the measurement or estimate. Average values of the parameters may calculated to reduce random noise effects and may be subsequently used to produce correction factors to correct instantaneous measurements.

Abstract: A process and apparatus are provided for producing hydrogen from a hydrocarbon fuel by combining the fuel with a gas comprising both oxygen and steam, and passing the resulting mixture through a plasma generated by a microwave plasma generator between opposed electrodes. At least one of the electrodes defines a duct for outflow of gaseous material from the vicinity of the plasma, and the gas mixture emerging from the outflow duct contains hydrogen. The fuel undergoes partial oxidation and steam reforming, the reactions being initiated by the plasma rather than by a catalyst.

Abstract: A semiconductor device comprises an active layer above a first confinement layer. The active layer comprises a layer of ?-Sn less than 20 nm thick. The first confinement layer is formed of material with a wider band gap than ?-Sn, wherein the band gap offset between ?-Sn and this material allows confinement of charge carriers in the active layer so that the active layer acts as a quantum well. A similar second confinement layer may be formed over the active layer. This semiconductor device may be a p-FET. A method of fabricating such a semiconductor device is described.

Abstract: An eye tracking apparatus for monitoring the movement of a user's eye, the apparatus including: a display for displaying an image; an eye imaging sensor for monitoring the user's eye and for providing an output indicative of the user's point of regard in the user's field of vision; an optical combiner arranged, in use, in optical communication with the display, the eye imaging sensor and the user's eye; said optical combiner arranged to receive the displayed image from the display, to project said image into the user's field of vision, to receive electromagnetic radiation reflected from the user's eye and to pass said reflected radiation to the eye imaging sensor; wherein the optical combiner is adapted to substantially correct for aberrations in the reflected radiation introduced therein by the optical combiner.

Abstract: An oil and gas well shaped charge perforator capable of providing an exothermic reaction after detonation is provided, having a housing, a high explosive, and a reactive liner where the high explosive is positioned between the reactive liner and the housing. The reactive liner is produced from a composition which is capable of sustaining an exothermic reaction during the formation of the cutting jet.

Abstract: Methods and apparatus for quantum key distribution are described, in particular including methods and networks 300 arranged to improve and/or ensure the security of data transmitted thereby by (i) ensuring a certain level of loss within at least part of the network, (ii) placing a penultimate and an endpoint nodes in situated in a secure second enclave, (iii) analysing a transmitted bit stream to ensure that it does not provide an unacceptable amount of information about the key that may be generated therefrom, and/or (iv) varying the order in which bits are used to generate a key.

Abstract: The clearance between a stationary object (such as a gas turbine engine casing) and one or more moving objects (such as the blades of a rotating turbine) is measured using a pair of electrical proximity sensors mounted on the stationary object with their sensitive fields directed towards the path of the moving object(s) and at angle to each other. The clearance is calculated by deriving a time interval between interceptions of the respective moving object with the sensitive fields of the two sensors and from the geometry of the set up.

Abstract: This invention relates to a security label for the detection of counterfeiting and tampering. The invention comprises a combination of an iridescent laminated or multilayered material with a lenticular layer. The iridescent layer exhibits an angular dependence in its coloration in reflection and/or transmission and the lenticular layer acts as a filter to light of a given angle of incidence.

Abstract: The sensor module carries one or more sensor element, such as microphones or imaging devices, for detecting events in use. The sensor module has a locator for determining its location and preferably an orientation sensor for determining it location and a transceiver for communicating with other modules in the network or with a base station. The module also has a processor which is adapted such that, in use, the module communicates with other sensor modules and determines whether to operate in a sensing mode to detect events or a controlling mode. In this way a self organizing adaptive network is provided.

Abstract: A Communications system for communicating over low bandwidth or high latency links incorporates a router MR7 configured to route a message to any like-configured router MR8, MR9 linked to it. Communications are implemented at network layer with UDP IP message packets. There are no hello messages. The message format 20 includes routing information but not designated and backup routers, which avoids loss of service from designated router changes and reduces bandwidth requirements. Configured routers MR7 to MR9 have different message formats 20, 40 for communicating with configured routers MR7 to MR9 and with unconfigured routers R1 to R6 respectively, and can link different protocols. A configured router MR7 deletes routes to like-configured routers MR8, MR9 with route metrics not superior to other routes with like destination. It also deletes routes with inferior metrics to related routes in an incoming message, and retains received route information regarding a new route or a route with superior metric.

Abstract: A variable optical attenuator device is described that comprises a first optical input, a first optical output, a first optical path between the first optical input and the first optical output, and means for moving a shutter across said first optical path. A hollow core waveguide is provided to substantially guide light along the first optical path of the device. The device may also be used to provide an analogue beam splitting or switch function in telecommunication systems and the like.