1,720,959 research outputs found
Identification of lightning strike damage using Pulse Thermography through integration of thermal data
Full text linkPulse Thermography (PT) is based on the use of infrared imaging systems to detect thermal decay from a pulsed energy source as it passes through a component or sample. Carbon Fiber Reinforced Polymer (CFRP) composite materials damaged by simulated lightning strike are inspected using PT. A new damage detection approach is proposed which exploits the integral of the difference in temperature data over time between each pixel and a reference non-damaged pixel. The resulting integration provides a value for the thermal decay pixel-by-pixel relative to a non-damaged region, which provides a quantitative damage severity parameter. The proposed data processing method is evaluated using calibrated plate sample made from Glass Fiber Reinforced Polymer (GFRP) composite with known defects, and also to investigate CFRP samples damaged by lightning strikes. The calibrated GFRP plates are 4-ply stitched bi-axial E-glass fibers with a total laminate thickness of 2.4 mm. The known defects are 20 mm square PTFE inserts placed between plies to simulate a delamination. The resulting colormap correctly identifies the known defects and displays constant severity over the PTFE insert region. The same method is applied to the lightning damaged CFRP sample made of 5-ply stitched dry fabric. The resulting integration reveals the full extent of the damage, which cannot be identified by visual inspection
Damage in CFRP composites subjected to simulated lighting strike
No full textCarbon fibre composite materials are increasingly being used in the wind turbine, aerospace, and automotive industries to reduce the structural weight of components due to their high strength to weight and stiffness to weight ratios. However, the anisotropic material properties of Carbon Fibre Reinforced Polymers (CFRP), specifically their electrical and thermal conductivities, create challenges when protecting structures from lightning strike. Moreover, the exposure of CFRP structures/components to electric currents from lightning discharges can cause significant damage. This work investigates the damage inflicted and residual mechanical properties of a CFRP composite material that has been exposed to simulated lightning strike. Seven different CFRP laminate specimens were struck with simulated lightning strike using three different waveforms: the so-called 10/350 μs waveform, which simulates the first return stroke during a direct strike according to IEC 61400-24 Ed1.0, the second was a unipolar long stroke component, and the third was a combination of the first return stroke and the long stroke. Test specimens were prepared from CFRP panels that were damaged due to the lightning strike. The test specimens were subsequently subjected to compression and shear loading to determine the post-strike mechanical properties. The compression tests were conducted using uniaxial coupons and loaded in accordance with ASTM standard D6641. The shear tests were conducted using V-notch specimens utilizing an Iosipescu test rig in accordance with ASTM standard D5379. Digital Image Correlation was used to capture the strain fields on the specimens. The test results were compared against data obtained for pristine CFRP coupon samples that were not exposed to electrical current. The shear and compression strengths, compressive and shear stress-strain curves, compressive and shear moduli, and the maximum temperature captured in the specimens during the tests are presented and discussed. Key results include that the largest reduction of strength occurred in the specimens that were subjected to the largest current and specific energy, and further that damaged specimens respond with a higher degree of nonlinear behaviour than the pristine specimens
Delamination prediction on CFRP materials subjected to a lightning strike
Full text linkThis paper presents a coupled thermal-electric-mechanical model to predict the delamination damage of a Carbon Fiber Reinforced Polymer (CFRP) material when subjected to a lightning strike. A Finite Element Model (FEM) is used to predict the heat response of the CFRP material by solving the Joule heating governing equations. The results of the heat response are coupled with thermal stresses to predicte interlaminar stresses. A bilinear traction law is used to predict the delamination of the laminate. Solutions to the model are developed using a time dependent simulation with the 10/350µs standard waveform to mimic a typical lightning strike on a wind turbine blade in accordance to IEC61400 section 24 Ed 1.0. The time dependent model implements damage criteria and is able to identify damaged elements. The COMSOL software engine was used to derive the results from the thermal-electrical-mechanical model. The final result is a delamination map of the CFRP panel subjected to a lightning discharge
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
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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