1,720,955 research outputs found
Novel olive stone biochar particle network for piezoresistive strain sensing in natural fiber‐reinforced composites
Full text linkNatural fiber‐reinforced composites (NFRCs) suffer from water absorption and low temperature stability, resulting in fiber degradation and subsequent material failure. Built‐in piezoresistive sensors are investigated to monitor the deformation/strain of the component. As a low‐cost material from renewable resources biochar particles derived from olive stones were applied on flax plies and yarn bundles that served as model systems. Carbon black samples as petrochemical variants were used as a reference material. Biochar and carbon black‐covered fiber systems were laminated in epoxy resin followed by tensile tests. The electrical resistance was recorded simultaneously during testing. Biochar with a broad size distribution from nano to high micrometer range (D < 200 μm) was superior in sensor performance compared to carbon black and biochar with a smaller particle size range D < 20 μm. Gauge factors (GF) of NFRC samples with integrated biochar particles reached 30–80 while carbon black could not exceed a GF of 8. To obtain maximum GFs, yarn count of flax yarn/ply substrate should be as thin as possible, but still enable percolation of the adhering particle network. Comparatively large particle size was identified as a contributing factor enabling the high GF for coarse biochar compared to carbon black.
Highlights
- A nonfossil biochar built‐in piezoresistive sensor in natural fiber‐reinforced composites was fabricated
- Deposing biochar directly on flax fibers facilitates processing
- The biochar piezoresistive sensor exhibits superior sensitivity compared to carbon blac
Environmentally Resistant Flax Fiber-Reinforced Composites for Aircraft Applications: Aviation Stress Tests with Optical and Mechanical Analyses
Full text linkFlax fiber-reinforced composites (FFRCs) must be resistant to environmental conditions to use them for external components in aviation. It was investigated how contact with typical aviation liquids, i.e. water, jet fuel and hydraulic oil, affects the optical and mechanical properties of twill fabric epoxy resin-based FFRCs. These influences were compared to the effect of UV weathering. Samples were exposed to these conditions for up to 28 days at RT. Uncoated samples with different fiber contents served as references and were compared with coated samples. A polyurethane/epoxy-based aircraft coating system and a partially biobased automotive interior coating as a more sustainable alternative were examined. The main damage for the uncoated samples was caused by UV weathering and water. UV light leads to photo-oxidation, causing material erosion. Water is absorbed by the hydrophilic flax fibers. Subsequent swelling leads to deformation and delamination. Thus, the damage was more severe for a higher fiber content. No effect could be demonstrated by immersion in jet fuel and hydraulic oil, as they are hardly absorbed by the fibers. Both coatings showed good protection against UV weathering and delayed water absorption. Nevertheless, mechanical damage was found for the FFRC covered with the fossil coating after 28 days of immersion in water. FFRC with an appropriate coating could therefore be suitable for use in aviation, but prolonged contact with water should be avoided. Protective measures should focus on preventing water uptake and UV irradiation, as these cause significantly more damage than jet fuel and hydraulic oil
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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