3,140 research outputs found
Novel optical fibre distributed temperature sensor based on the Landau-Placzek ratio
No full textWe report our latest results on a compact, diode pumped optical fibre distributed temperature sensor based on Brillouin scattering. A high power, short pulse Q-switched Erbium/Ytterbium fibre laser and a double pass in-fibre Mach-Zehnder interferometer make this Brillouin distributed temperature sensor an attractive commercial device. A spatial and temperature resolution of 10 metres and + or - 1.7°C has been demonstrated
The application of Brillouin scattering to distributed fibre optic sensing
No full textThis thesis reports on an investigation into the application of Brillouin scattering for the purpose of distributed fibre optic sensing. The main focus of the work has been centred on a Brillouin optical time domain reflectometer (BOTDR) system.The behaviour of short (3m), medium (60m) and long (6km) erbium doped fibre amplifiers using narrow bandwidth pulsed signals has been investigated and the most suitable configuration for the source requirement of the BOTDR identified.The operation of a (BOTDR) system has been demonstrated at the low loss window of 1.5µm wavelength.Multiple Stokes orders of stimulated Brillouin scattering in a medium length erbium doped fibre amplifier using pulsed excitation are reported. The observed stimulated Brillouin threshold power is significantly reduced as a result of optical gain. The points of origin within the fibre of the generated Stokes pulses are located using space-time diagrams and are observed to depend on the Brillouin and Erbium pump powers. This has therefore been identified as a possible mechanism for sensing applications utilizing the novel technique of varying the pump powers to spatially interrogate the fibre.Measurements of the Brillouin scattering coherence length in silica fibre using a fibre Mach Zehnder interferometer are presented. As the Brillouin pump power is increased from below to above stimulated threshold, the line shape narrows and changes from that of a Lorentzian to a Gaussian. It is also shown that the Brillouin bandwidth approaches a limiting value.It is shown experimentally that the ratio of the intensities of Rayleigh and Brillouin backscattered light (Landau Placzek ratio) in an optical fibre has a temperature dependence which may be used for the basis of a distributed temperature sensor. This result, combined with the known frequency dependence of the Brillouin backscattering on temperature and strain, indicates spontaneous Brillouin backscatter may be used for the unique determination of either temperature or strain in a distributed fibre optic sensing system.Because of the coherent nature of Rayleigh scattering, use of the same narrow bandwidth source as required for the Brillouin signal in the Landau Placzek ratio method, results in significant coherent noise in the Rayleigh signal. A novel technique is demonstrated whereby the amplified spontaneous emission noise and amplifying properties of an erbium doped fibre amplifier may be exploited to reduce the coherent noise on the Rayleigh backscatter signal. This results in a significant improvement in both temperature and spatial resolution
Good Things Come to Those Who Wait…
No full textThornton (2017), writing on the website Leading in Context, explains that the well-known quote used as the title of this blog may be attributed to British author Violet Fane (Mary M. Singleton) in 1892. As she contends, good things may indeed come to those who wait, “but only after certain important conditions have been met”
Good Things Come to Those Who Wait…
No full textThornton (2017), writing on the website Leading in Context, explains that the well-known quote used as the title of this blog may be attributed to British author Violet Fane (Mary M. Singleton) in 1892. As she contends, good things may indeed come to those who wait, “but only after certain important conditions have been met”
Waiting... with Rachel and Peter: Podcast funded by Arts Council England/Wellcome Trust
No full textFuel, Roundhouse and King’s Cultural Institute present
Waiting… with Rachel and Peter
By Stefan Kaegi in collaboration with Anna Jordanous and Niki Neecke. Voices by Acapela Group.
Waiting… with Rachel and Peter is the fourth in our new series of podcasts called While You Wait, each of which is a different meditation on the idea of waiting and created by artists in collaboration with academics from King's College London.
Waiting… with Rachel and Peter has been made by Berlin based artist Stefan Kaegi in collaboration with Anna Jordanous, Research Associate, Centre for e-Research and sound designer Niki Neecke.
While You Wait is funded by Arts Council England and a Wellcome Trust Arts Award.
An accompanying video interview featuring Stefan Kaegi and Anna Jordanous is available at https://www.youtube.com/watch?v=GcG43H_jMN
Wait
No full textThe article discusses the digital artwork "Wait" by Julie Andreyev and Simon Overstall. "Wait" features an interactive video installation on human and canine communication methods. It is part of the series "Animal Lover" which addresses human-companion interaction and interspecies collaboration. Also presented is information about the artists' careers.Peer reviewedarticlePublishe
Feeling Numbers: KP Brehmer and the Supermarket
No full textA publication that documents the presentation of To refuse/To wait/To sleep and M&A beginning on January 12, 2017, and continuing until complete. Jamie Hilder contributes an essay about KP Brehmer.final article publishe
Evolution of a curriculum for junior doctor general practice placements in South Australia
No full textBrenton Wait, Peter Donohoe, Alison Marrinan and Helen Mullne
Wait-times Benchmarks for risk-based prioritization in Transcatheter Aortic Valve Implantation: a simulation study.
No full textDemand for transcatheter aortic valve implantation (TAVI) has increased in the last decade, resulting in prolonged wait-times and undesirable health outcomes in many health systems. Risk-based prioritization and wait-times benchmarks can improve equitable access to patients. We used simulation models to follow-up a synthetic population of 50,000 individuals from referral to completion of TAVI. Based on their risk of adverse events, patients could be classified as "low-", "medium-" and "high-risk", and shorter wait-times were assigned for the higher risk groups. We assessed the impacts of the size and wait-times for each risk group on waitlist mortality, hospitalization and urgent TAVIs. All scenarios had the same resource constraints, allowing us to explore the trade-offs between faster access for prioritized patients and deferred access for non-prioritized groups. Increasing the proportion of patients categorized as high-risk, and providing more rapid access to the higher-risk groups achieved the greatest reductions in mortality, hospitalizations and urgent TAVIs (relative reductions of up to 29%, 23% and 38%, respectively). However, this occurs at the expense of excessive wait-times in the non-prioritized low-risk group (up to 25 weeks). We propose wait-times of up to 3 weeks for high-risk patients and 7 weeks for medium-risk patients. Prioritizing higher-risk patients with faster access leads to better health outcomes, however this also results in unacceptably long wait-times for the non-prioritized groups in settings with limited capacity. Decision-makers must be aware of these implications when developing and implementing waitlist prioritization strategies. [Abstract copyright: © The Author(s) 2024. Published by Oxford University Press on behalf of the European Society of Cardiology.
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