Fabry-Pérot (FP) sensors have been used to produce in-vivo photoacoustic images of exquisite quality. However, for simplicity of construction FP sensors are produced in a planar form. Planar sensors suffer from a limited detection aperture, due to their planarity. We present a novel sensor geometry that allowed a greater field of view by placing a second sensor orthogonal to the first. This captured data from the deeper lying regions of interest and mitigated the limited view.
The application of distributed acoustic sensing (DAS) for shallow marine seismic investigations is assessed, in particular with respect to the collection of seismic surface wave data in an intertidal setting. Appropriate selection and directional sensitivity of fiber-optic cables is considered and the measured data is validated with respect to conventional seismic data acquisition approaches, using geophones and hydrophones, along with independent borehole and seismic cone penetration test (SCPT) data. In terms of cable selection, a reduction in amplitude and frequency response of an armored cable is observed, when compared with an unarmored cable. For seismic surface wave surveys in an offshore environment where the cable would need to withstand significant stresses, the use of the armored variant with limited loss in frequency response may be acceptable from a practical perspective. The DAS approach also has indicated good consistency with conventional means of surface wave data acquisition, and the inverted [Formula: see text] also is very consistent with downhole SCPT data. Observed differences in phase velocity between high tide (Scholte wave propagation) and low tide (Rayleigh wave propagation) are not thought to be related to the particular type of interface wave due to shallow water depth. These differences are more likely to be related to the development of capillary forces in the partially saturated granular medium at low tide. Overall, this study demonstrates that our novel approach of DAS using seabed fiber-optic cables in the intertidal environment is capable of rapidly providing near-surface S-wave velocity data across considerable spatial scales (multikilometer) at high resolution, which is beneficial for the design of subsea cables routes and landfall locations. The associated reduction in deployment and survey duration, when compared with conventional approaches, is particularly important when working in the marine environment due to potentially short weather windows and expensive downtime.
The light activated position sensing array will bring great independence to many persons with disabilities. Enabling those that have limited to no use of their limbs, this product will allow its user to perform many day to day activities that may have not otherwise been possible without outside assistance. The system is a hands-free electric wheelchair control that will also function as a powerful environmental control tool. Guided by a light emitter worn on the user's head, it will replace orally activated (sip and puff) switches, as well as any other switches that may be mounted on or near the user's head.
Fabry–Pérot sensors have been used to produce in-vivo photoacoustic images of exquisite quality. However, for ease of construction and interrogation, they are produced in a planar form. Planar arrays suffer from a limited detection aperture, which leads to artifacts in the reconstruction of the initial pressure distribution. Here, an L-shaped detection geometry is described that allows a greater field of view by placing a second planar array orthogonal to the first. This captures data from the deeper lying regions of interest and mitigates the limited view, thus reducing artifacts in the reconstructed initial pressure distribution.
The application of the light-guided environmental control device will greatly increase the quality of life of certain persons with disabilities. This hands-free mechanism will allow the user to perform many daily tasks without the need of an aid. It is an environmental control and a wheelchair control that is driven by a light emitting head switch. One of the main foci of the project is to remove many of the cumbersome control switches being implemented today, and replacing them with one compact model. This product is to perform all operations currently performed by head arrays and switches, as well as standard joysticks. It is being designed to be used primarily by those people without the use of their limbs, especially those looking to gain a great deal of independence.
Planar sensor arrays have advantages when used for photoacoustic imaging: they do not require the imaging target to be enclosed, and they are easier to manufacture than curved arrays. However, planar arrays have a limited view of the acoustic field due to their finite size; therefore, not all of the acoustic waves emitted from a photoacoustic source can be recorded. This loss of data results in artifacts in the reconstructed photoacoustic image. A detection array configuration which combines a planar Fabry–Pérot sensor with perpendicular acoustic reflectors is described and experimentally implemented. This retains the detection advantages of the planar sensor while increasing the effective detection aperture in order to improve the reconstructed photoacoustic image.
Planar Fabry-Pérot (FP) ultrasound sensor arrays have been used to produce in-vivo photoacoustic images of high quality due to their broad detection bandwidth, small element size, and dense spatial sampling. However like all planar arrays, FP sensors suffer from the limited view problem. Here, a multi-angle FP sensor system is described that mitigates the partial view effects of a planar FP sensor while retaining its detection advantages. The possibility of improving data acquisition speed through the use of sub-sampling techniques is also explored. The capabilities of the system are demonstrated with 3D images of pre-clinical targets
Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation S. D. Sharples, T. Stratoudaki, R. J. Ellwood, I. J. Collison, M. Clark, M. G. Somekh; LASER ULTRASONICS FOR DETECTION OF ELASTIC NONLINEARITY USING COLLINEAR MIXING OF SURFACE ACOUSTIC WAVES. AIP Conference Proceedings 22 February 2010; 1211 (1): 287–294. https://doi.org/10.1063/1.3362406 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search
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