1,720,966 research outputs found
Flexible photonics embedded into advanced composites
No full textFlexible and stretchable photonics is a rapidly evolving area, with various materials, design, processing, and device technologies being explored [1] . As with flexible electronics, flexible photonics particularly lends itself to integration upon engineered and natural structures, such as interfacing with the soft, curvilinear, and dynamic surfaces of living organisms. Here we explore a potential new growth opportunity interfacing with engineered structures, namely embedding into advanced composite materials (such as Carbon Fibre Reinforced Polymer and Glass Fibre Reinforced Polymer). The motivation being ultimately new optical functionality and intelligence for engineered structures (e.g. wind turbines, aircraft, civil infrastructure), going beyond what has been developed with embedded optical fibre through realising the full geometric diversity offered by flexible photonics. This work embeds ultra-thin glass [3] , utilising its flexibility in order to be conformal to the shape of composite structures which flex and in parts are non-planar. It is noted that cyclic olefin copolymer planar chips have recently shown feasibility in composite material [2] , whilst these demonstrations use rigid planar optics they do show feasibility for other flexible photonic materials to exploit this application
The effect of temperature on the erosion of polyurethane coatings for wind turbine leading edge protection
No full textWind turbine leading-edge erosion can degrade the aerodynamic properties of blades and reduce their efficiency. Previous theoretical work has suggested that low temperatures might affect the erosion performance of leading-edges and protective leading-edge coatings. Solid particle erosion is caused by dust, sand and hailstones impacting the leading edges. For polymer coatings, temperature is a particular concern; the low temperatures can cause a transition from ductile to brittle failures. Polyurethane (PU) coatings were eroded at two temperatures: ambient (25°C) and cold (-30°C). An adapted solid-air erosion facility was used to accelerate sub-angular sand particles of 96.2 µm mean size to a velocity of 68±8 m/s. Low volumetric sand concentrations of 1.3×10-4 % were studied at two impingement angles of 45 and 90 degrees. The results showed that cold temperatures influenced the erosion rate and erosion mechanism of the coatings, with the erosion rate at the cold temperature increasing significantly. The erosion classification values and the shape of the wear scar suggested plastic erosion behaviour of the PU at cold temperatures, as opposed to the more erosion-resistant elastic behaviour. A temperaturecontrolled nanoindentation study demonstrated that the ratio of hardness to modulus reduced and the plasticity index increased with a reduction in temperature, implying the PU coatings had an increased propensity to plastically deform during cold erosion. This supports the erosion performance seen in experiments; however, the cold erosion surfaces developed more pits than the ambient case. Crosssection analysis of the eroded coatings showed accumulation of damage subsurface with evidence of delamination at the weakest interfaces in the layered coating systems, across all temperatures
Real-time through-thickness and in-plane strain measurement in carbon fibre reinforced polymer composites using planar optical Bragg gratings
No full textA new strain sensor is proposed which can measure both through-thickness and in-plane strains within a laminated fibre-reinforced composite material. The planar sensor uses novel embedded planar optic sensors and is demonstrated on a carbon fibre composite test coupon. The planar optical sensor was fabricated via flame hydrolysis deposition and was physically machined to reduce the substrate thickness to <50µm. Strain components are decoupled through monitoring the transverse electric and transverse magnetic effective refractive indices of two orthogonal planar waveguides. The work investigates if the embedded planar sensors have any mechanical knock down effects on the composite structure and demonstrates their effectiveness at decoupling three orthogonal strain components
Optical switching in glass fibre composite
Full text linkWe demonstrate for the first time the reconfigurability of optical signals within advanced laminated composite. The approach employs an ultra-thin planar optical circuit, embedded within glass fibre reinforced polymer (GFRP) that switches an optical input though Ohmic heating. This advance highlights new opportunities for optical reconfigurability within advanced composites, enabling data transmission redundancy and a consideration of branching optical fibre architectures
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
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