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Manikas A.,Imperial College London | Kamil Y.I.,Silixa Ltd. | Willerton M.,Imperial College London
IEEE Transactions on Signal Processing | Year: 2012

In this paper, a novel source/target localization approach is proposed using a number of sensors (surrounding or not surrounding one or more sources) to form a sparse large aperture array of known geometry. Under a large array aperture, the array response (manifold vector) obeys a spherical wave rather than a plane wave propagation model. By rotating the array reference point to be at each of the array sensors, a number of covariance matrices are constructed. It is shown that the eigenvalues of these covariance matrices are related to the source location with respect to the array reference point. The proposed approach is robust to channel fading and considers both wideband and narrowband assumptions. The performance of the proposed approach is evaluated via simulations as a function of array geometry, number of snapshots (L) and signal to noise ratio (SNR) and is shown to exceed existing techniques. © 1991-2012 IEEE. Source


Patent
Chevron and Silixa Ltd. | Date: 2013-07-17

A method and apparatus for monitoring a structure using an optical fiber based distributed acoustic sensor (DAS) extending along the length of the structure. The DAS is able to resolve a separate acoustic signal with a spatial resolution of 1 m along the length of the fibre, and hence is able to operate with an acoustic positioning system to determine the position of the riser with the same spatial resolution. In addition, the fiber can at the same time also detect much lower frequency mechanical vibrations in the riser, for example such as resonant mode vibrations induced by movement in the surrounding medium. By using vibration detection in combination with acoustic positioning then overall structure shape monitoring can be undertaken, which is useful for vortex induced vibration (VIV) visualisation, fatigue analysis, and a variety of other advanced purposes. The structure may be a sub-sea riser.


Patent
Chevron and Silixa Ltd. | Date: 2013-07-17

A method and apparatus for monitoring a structure using an optical fiber based distributed acoustic sensor (DAS) extending along the length of the structure. The DAS is able to resolve a separate acoustic signal with a spatial resolution of 1 m along the length of the fibre, and hence is able to operate with an acoustic positioning system to determine the position of the riser with the same spatial resolution. In addition, the fiber can at the same time also detect much lower frequency mechanical vibrations in the riser, for example such as resonant mode vibrations induced by movement in the surrounding medium. By using vibration detection in combination with acoustic positioning then overall structure shape monitoring can be undertaken, which is useful for vortex induced vibration (VIV) visualisation, fatigue analysis, and a variety of other advanced purposes. The structure may be a sub-sea riser.


Patent
SILIXA Ltd and Chevron | Date: 2015-04-30

Exemplary embodiments include an apparatus for imaging a volume of material contained inside a vessel. The apparatus includes a plurality of synchronized acoustic sensors positioned at a periphery of an inner volume of the vessel. A processor combines the outputs of the acoustic sensors to identify at least one ambient noise source of the industrial process generating a noise field that illuminates an internal volume of the vessel and to provide an image of the material by temporal and spatial coherent processing of the transmission and reflection of the noise field generated by the noise source.


Patent
Silixa Ltd. | Date: 2011-11-08

The invention relates to installations for fibre optic monitoring of articles, and apparatus and methods for forming such installations, including a modular system and components for forming a fibre optic monitoring installation. Applications of the invention include the monitoring of vessels, chambers, and fluid conduits in industrial processing plants, and the invention has particular application to monitoring large vessels, for example temperature monitoring of vessels used in catalytic reforming processes. Convenient installation on or removal from the article being monitored is achieved by providing a support structure for the fibre optic length, which presents the fibre optic length in a preconfigured orientation suitable for monitoring the article. In a particular embodiment of the invention, the fibre optic length is disposed on a panel in a plurality of dense spiral patterns.

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