1,720,955 research outputs found
Fabrication and characterisation of short fibre reinforced elastomer composites for bending and twisting magnetic actuation
Full text linkPolydimethylsiloxane (PDMS) films reinforced with short Nickel-coated Carbon Fibres (NiCF) were suc-cessfully fabricated, with the fibres aligned along different directions using an external magnetic field.The fibres were dispersed in the host matrix using sonication and mechanical mixing before being curedfor 48 h in the magnetic field; thanks to the nickel functionalisation, the fibre orientation was achieved bya low intensity field (<0.2 T) which required an inexpensive experimental set-up. The main focus of thisstudy was looking at the actuation potential of this magnetic composite material; successful actuationwas achieved, showing its large displacement capability. The results confirm the presence of an instabilitycontrolled by the magnetic torque, as predicted by the introduced model. The composite films undergo atransition from a bending-only deformed configuration for the 0°fibre specimen, to a twisting-only con-figuration, achieved for fibres at 90°, whereas all the intermediate angles show both bending and twisting.This behaviour mirrors that which is used to propel a selection of marine mammal
Orientation effects in short fibre-reinforced elastomers
No full textThe large strain behaviour of a short fibre-reinforced composite is studied through numerical simulations. The reinforcing fibres yield the macroscopic response transversely isotropic which is indeed the case of many reinforcements currently used in composites: short carbon fibres, cellulose whiskers, carbon nanotubes. As a result of the analysis, it is shown that the reorientation of the fibres that takes place at large strain has a significant effect on the overall material response by changing the axis of isotropy. This behaviour can be adequately described by using a transversely isotropic model whose strain energy function depends on three invariants: two isotropic and one representing the stretch along the direction of the fibres. To assess its capabilities, the model is compared to the results of experiments carried out by the authors on nickel-coated chopped carbon fibres in a vulcanised natural rubber matrix for which the fibre orientation is achieved by controlling an external magnetic field prior to curing. Possible applications include micro-sized propulsion devices and actuators. Copyright © 2014 by ASME
Magnetic alignment of short carbon fibres in curing composites
Full text linkAlignment of magnetic particles into a viscous fluid by a homogeneous magnetic field has been studied both experimentally and theoretically, but very few studies have investigated the effects of viscosity changes on the capability of achieving complex fibre assemblies in composite materials. In this paper, we study the alignment of short carbon fibres into a viscous matrix whose viscosity is made dependent on the time, in order to simulate the curing process of the composite. A simple model is derived which gives the evolution of fibre position and orientation in terms of the external field and shows good agreement with the experimental evidence on nickel coated carbon fibres embedded in PDMS. The model is used to predict the fibre distribution at curing and hence could be a useful tool to predict the mechanical, electrical and magnetic properties of the composite. A closed form expression of the minimum magnetic field intensity necessary to achieve the desired orientation is derived in terms of the magnetic and geometric properties of the fibres. This equation can be used to guide experiments, and offers a way to discriminate which matrix/fibre configuration can be most proficiently used to have a highly ordered composite
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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