1,720,959 research outputs found
Experimental crushing analysis of thermoplastic and hybrid composites
Get PDFIn this work the mechanical properties of composites specimens made of thermosetting and thermoplastic
materials are compared. The behaviour of a traditional carbon/epoxy laminate is compared with those of a fully
polypropylene composite and of a hybrid composite. The hybrid composite is made by stacking different layers
of thermoplastic and thermosetting material. The influence of different production processes, for the hybrid
composite, are also investigated. The capability of energy absorption are investigated studying the crushing
behaviour of impact attenuators. The impact attenuators made of carbon fibre reinforced plastic exhibit the
highest load capability with the highest energy absorption. However, the failure mode is brittle with debris
formation. Conversely, a failure mode of plastic crushing is observed in the structures made of fully polypropylene.
The experimental tests on the specimen made of hybrid laminates proved a strong influence of the
production process of the components on the mechanical properties. In the hybrid laminates, the different
chemical properties of the base materials lead to a pre-existing delamination state in the final. The results
highlight that curing the thermoplastic material before the compaction with the thermosetting laminates is the
best solution to guarantee the highest impact resistance
Experimental Characterization and Finite Element Modelling of a thermoplastic composite lamina subjected to large shear deformation
Get PDFIn this work, the behaviour of a woven lamina for thermoplastic composite material is experimentally and numerically investigated. A thermoplastic composite made of hot-pressed polypropylene (PP) woven laminas is the object of the study. The laminas are composed by tapes which are made up of co-extruded core and skins. Experimental tests were carried out to determine the properties of the lamina. The experimental data are used to develop numerical models for the simulation of the experimental test. Three modelling techniques are proposed: the first one implements a macro-mechanical material model, the second one uses a meso-mechanical approach, and the third one discretizes the geometry at the yarn level. The global response of the meso-mechanical material model showed the best agreement with the experimental test, even if it does not represent the optimal solution from the computational-cost point of view
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
Methodology for parameter identification on a thermoplastic composite crash absorber by the Sequential Response Surface Method and Efficient Global Optimization
Get PDFNumerical simulations for crashworthiness require the definition of material properties that are not always predictable with standard experimental tests. This paper deals with the numerical optimization of a thermoplastic composite material model. The component is a vehicle impact attenuator made of an innovative All-PP (PolyPropylene) composite material. The peculiar failure mechanism of this material makes the numerical simulation of the collapse a difficult challenge to achieve with a trial-and-error calibration of the material card. Therefore, an optimization procedure is proposed to determine the material parameters. The optimization is implemented in LS-OPT, where the mean square error between the experimental and numerical load-displacement curves is the objective function to be minimized. Two test cases are considered: (1) optimization of the material card based on the full load-displacement curve from the experimental tests and (2) optimization of relevant parameters of a numerical trigger added to control initial contact instabilities between the impacting rigid wall and the component in the numerical simulations. The optimization strategies Sequential Response Surface Method (SRSM) and Efficient Global Optimization (EGO) are used. The results show that the presented methodology allows characterizing the studied composite material and thus obtaining a more efficient numerical model
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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