1,721,182 research outputs found
Single and multiple phase shifts tilted fiber Bragg gratings
Full text linkThe spectral behavior of single and multiple phase shifts tilted fiber Bragg gratings has been experimentally investigated. To this aim, a simple and cost-effective postprocessing technique based on local thermal treatment was used to create arbitrary phase shifts along the tilted grating structure. In particular, UV written tilted fiber Bragg gratings were treated by the electric arc discharge to erase the refractive index modulation in well-defined regions. We demonstrate that these defects give rise to interference pattern for all modes, and thus defect states can be achieved within all the attenuation bands, enabling a simple wavelength independent spectral tailoring of this class of device
A multiplexed FBG based sensor platform for flow and temperature measurements in the Baltic Sea
No full textIn this paper a multiplexed multi-parameter marinized sensory array is described. This was deployed on the continental slope off the Keri Island marine observatory in the Gulf of Finland (Estonia). The sensor array is made up of 4 measurement stations which are connected in series. Across these measurement stations, a total of 16 temperature sensors, 4 attitude sensors (each consisting of 3 individual fiber sensors) and 16 flow sensors were successfully deployed. They were addressed over 1.1 km via 20 single-mode (SMF-28e) optical fibers contained in a single marine compliant ruggedized umbilical. The bio-inspired fiber optic flow sensors are designed to mimic the behavior of the superficial neuromasts naturally found as part of the lateral line sensory organ present in fish. The sensor is composed of optical fibers inscribed with Fiber Bragg Gratings glued together in a polymer matrix which are then encapsulated in a polyurethane shell. The sensors response has been tested in DC flows in a tow tank and have demonstrated the ability of measuring flow speed from 0.05 ms-1 to 2.5 ms-1. The main aim of the deployment was to demonstrate the capabilities of fiber sensor technology for long-term oceanographic applications. The measurement period described lasted over two months and the sensor system performed well in comparison with data was gathered from commercial instrumentation available.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Temperature and RH response of polymer CYTOP FBG treated by gamma radiation
No full textPolymer fiber Bragg grating (FBGs) demonstrate a wider strain range and stronger temperature sensitivity compared to standard silica FBGs. Besides, their advantageous feature is sensitivity to humidity that enables FBG-based relative humidity (RH) sensing. However, practical realization of RH sensors requires temperature cross-sensitivity elimination. A certain optimal fiber pre-strain and gamma irradiation of perfluorinated (CYTOP) FBGs up to certain optimal dose are potential recently proposed solutions for this problem. In this work, we investigate temperature and RH response of FBGs inscribed line-by-line in a few-mode polymer fiber with 20-μm CYTOP core and 250-μm XYLEX overclad. We compare the cases of the pristine FBG sample and the sample received 200 kGy irradiation dose. The 200-kGy dose was previously confirmed to provide temperature sensitivity minimization at 40%RH. Here, we show the close-to-zero temperature sensitivity (≈1pm/℃) for 200-kGy dose at high RH value of 89%. Besides, we briefly analyze the stabilization process of FBGs response to strong and quick RH changes.Fonds De La Recherche Scientifique – FNRS (T.0163.19 "RADPOF"). The research leading to these results has also received funding from the Horizon 2020 programme of the European Union (Marie Skłodowska-Curie Actions - Individual Fellowships) under REA grant agreement No. 844618 (project POSPORI). This work is also funded by the research project INTEGRATED/0918/0031 (LightSense Project) by the Republic of Cyprus through the Research and Innovation Foundation and European Development Fund and the Cyprus University of Technology
Variations on the Author
Full text link“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
Optimization of Cladding Diameter for Refractive Index Sensing in Tilted Fiber Bragg Gratings
Full text linkThis work presents an experimental investigation of the effect of chemical etching on
the refractive index (RI) sensitivity of tilted fiber Bragg gratings (TFBGs). Hydrofluoric acid (HF)
was used stepwise in order to reduce the optical fiber diameter from 125 μm to 13 μm. After each
etching step, TFBGs were calibrated using two ranges of RI solutions: the first one with high RI
variation (from 1.33679 RIU to 1.37078 RIU) and the second with low RI variation (from 1.34722 RIU
to 1.34873 RIU). RI sensitivity was analyzed in terms of wavelength shift and intensity change of
the grating resonances. The highest amplitude sensitivities obtained are 1008 dB/RIU for the high
RI range and 8160 dB/RIU for the low RI range, corresponding to the unetched TFBG. The highest
wavelength sensitivities are 38.8 nm/RIU for a fiber diameter of 100 μm for the high RI range, and
156 nm/RIU for a diameter of 40 μm for the small RI range. In addition, the effect of the etching
process on the spectral intensity of the cladding modes, their wavelength separation and sensor
linearity (R2
) were studied as well. As a result, an optimization of the etching process is provided, so
that the best trade-off between sensitivity, intensity level, and fiber thickness can be obtained
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Concrete curing monitoring using polymer optical fibre Bragg grating sensors
No full textA novel prototype sensing device based on polymer (CYTOP-XYLEX) optical fibre Bragg grating sensors was developed to monitor temperature and relative humidity levels of reinforced concrete from its initial curing phase to a prolonged period. The prototype can be used for concrete quality control offering numerous advantages, such as small size, robustness, high sensitivity, and low-cost continuous in-situ measurements.The research leading to these results has received funding from the Horizon 2020 programme of the European Union (Marie Skłodowska-Curie Actions - Individual Fellowships) under REA grant agreement No. 844618 (project POSPORI). This work is also funded by the research project INTEGRATED/0918/0031 (LightSense Project) by the Republic of Cyprus through the Research and Innovation Foundation and European Development Fund and the Cyprus University of Technology. This paper also reports research developed under financial support provided by "FCT - Fundação para a Ciência e Tecnologia", Portugal, co-funded by the European Social Fund, namely through the post-doc fellowship of José Melo, with reference SFRH/BPD/115352/2016 and by Base Funding - UIDB/04708/2020 and Programmatic Funding - UIDP/04708/2020 of the CONSTRUCT - Instituto de I&D em Estruturas e Construções - funded by national funds through the FCT/MCTES (PIDDAC) relatively to the authors José Melo and Humberto Varum. This work was also supported by FCT/MCTES and FCT/MEC through national funds and when applicable co-funded EU funds under the projects UIDB/50025/2020-UIDP/50025/2020 and grants CEECINST/00026/2018 and 2021.00667.CEECIND
- …
