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Brillouin Optical Time Domain Analysis Sensor for Active Vibration Control of a Cantilever Beam
Get PDFBrillouin Optical Time Domain Analysis in silica fibers at 850 nm wavelength
No full textBrillouin scattering properties of silica fibers at 850 nm wavelength were experimentally investigated using a Brillouin optical time-domain analysis (BOTDA) scheme. In the single-mode 780-HP fiber, the Brillouin frequency shift (BFS) and FHWM of the Brillouin Gain Spectrum were found to be ∼ 19795 MHz and 90 MHz, respectively. The estimated peak Brillouin gain is 0.32(mW)-1. The temperature and strain dependences of BFS were determined as well. Distributed sensing capability was demonstrated at a minimum spatial resolution of 1.5 m and a fiber length of 100 m. As a proof-of-principle, the temperature and strain dependencies of the BFS in SFM-28 fiber have been determined at 850 nm and 1550 nm wavelengths, suggesting its possible use for temperature/strain discrimination
Heterodyne slope-assisted Brillouin optical time-domain analysis for dynamic strain measurements
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Wind Turbine Blade Monitoring with Brillouin-Based Fiber-Optic Sensors
Get PDFWind turbine (WT) blade is one of the most important components in WTs, as it is the key component for receiving wind energy and has direct influence on WT operation stability. As the size of modern turbine blade increases, condition monitoring and maintenance of blades become more important. Strain detection is one of the most effective methods to monitor blade conditions. In this paper, a distributed fiber-optic strain sensor is used for blade monitoring. Preliminary experimental tests have been carried out over a 14 m long WT composite blade, demonstrating the possibility of performing distributed strain and vibration measurements.</jats:p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
NSTH New Smart distributed optical fiber Transducers made of Hybrid composite material for civil and enviromental monitoring
No full textIl trasduttore è stato sviluppato con sensore in fibra ottica distribuito in tecnologia ibrida vetro-carbonio e resina poliestere.
Il sistema di monitoraggio con trasduttori in fibra ottica distribuita con tecnologia ibrida vetro-carbonio, offre enormi vantaggi se associato a sistemi convenzionali di monitoraggio. Tali vantaggi sono connessi alla possibilità di riconoscere in tempi compatibili con la definizione di un sistema Early Warning, lo sviluppo di fenomeni deformativi.
Le limitazioni delle tradizionali tecniche di monitoraggio possono essere superate grazie all’uso di sensori in fibra ottica distribuiti incorporati all’interno del nuovo trasduttore ibrido vetro-carbonio basati sul fenomeno fisico dello “scattering di Brillouin” laddove una singola fibra ottica consente di ricostruire, con elevata risoluzione spaziale, il profilo termico e/o deformativo per tutto il tratto strumentato, sino a lunghezze di centinaia di metri.
Il trasduttore realizzato è caratterizzato da uno spessore “s” di 5 cm e può assumere una lunghezza che può raggiungere centinaia di metri con un interasse “i” per connessioni di 50 cm.
È possibile realizzare tre prototipi di trasduttore che presentano tre diverse configurazioni.
Il primo prototipo presenta la seguente configurazione di base, caratterizzata da fibre di vetro e fibre di carbonio con una grammatura di 200 gr/mq:
Il secondo prototipo presenta una configurazione di elevata flessibilità caratterizzata da fibre di vetro disposte sia superiormente che inferiormente con una grammatura di 200 gr/mq:
Il terzo prototipo presenta una configurazione di elevata rigidezza e resistenza meccanica, caratterizzata da fibre di carbonio disposte sia superiormente che inferiormente con grammatura di 200 gr/mq
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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