1,720,960 research outputs found
Influence of laser powder bed fusion process parameters on the properties of CuZn42 components: case study of the laser surface energy density
No full textAlthough additive manufacturing (AM) technologies have been rarely used to produce lead-containing brass, the same AM technologies have never been adopted to produce lead-free brass parts based on the CuZn42 alloy. This study aims to fill the gap, demonstrating the feasibility of lead-free brass alloys by laser powder bed fusion (LPBF) technology and investigating structural and mechanical properties of the produced specimens, focusing attention on the role of surface energy density on material properties. Starting from a raw powder of CuZn42 alloy containing alpha, beta and gamma brass phases, fully dense samples with high hardness values were obtained by LPBF. The structural and mechanical properties of the samples were investigated by scanning electron microscopy (SEM), energy-dispersive microanalysis (EDS), X-ray diffraction (XRD) and density and hardness measurements. Results showed that density, hardness and the relative amount of the brass phases depend on the surface energy density (SED) E-s. The investigated range of SED allowed defining the process window ranging from 2 J/mm(2) to 10 J/mm(2), within which fully dense samples can be obtained. A linear dependence of hardness on density was also found, suggesting that deformation mechanisms are mainly due to the presence of residual pores and internal cavities rather than to microstructural features, such as the relative amount of brass phases and crystallographic defects. All results obtained in this work demonstrated, for the first time, that LPBF is suitable to produce components based on the CuZn42 alloy, and that structural and mechanical properties of the produced parts can be properly designed by controlling SED
Biocompatibility of Ti-48Al-2Cr-2Nb produced by electron beam powder bed fusion (EB-PBF)
No full textTi-48Al-2Cr-2Nb is a well-known material for fabricating bulky parts using the electron beam powder bed fusion process. This work investigates the biocompatibility of this material as an alternative to the most common titanium alloys, which contain toxic elements such as Vanadium. The viability and proliferation of NIH-3T3 fibroblasts on Ti-48Al-2Cr-2Nb scaffolds are investigated. The in vitro viability tests are performed after incubation for 1, 4 and 7 days
Biomechanical performances of PCL/HA micro- and macro-porous lattice scaffolds fabricated via laser powder bed fusion for bone tissue engineering
No full textThe present experimental study aims to extend know-how on resorbable polycaprolactone/hydroxyapatite (PCL/HA, 70/30 wt%) scaffolds, produced by Laser Powder Bed Fusion (LPBF) technology, to geometrically complex lattice structures and micro porous struts. Using optimized LPBF printing parameters, micro- and macro-porous scaffolds for bone tissue regeneration were produced by regularly repeating in space Diamond (DO) and Rhombic Dodecahedron (RD) elementary unit cells. After production, scaffolds were submitted to structural, mechanical, and biological characterization. The interaction of scaffolds with human Mesenchymal Stem Cells (hMSCs) allowed studying the degradative processes of the PCL matrix. Biomechanical performances and biodegradation of scaffolds were compared to literature results and bone tissue data. Mechanical compression test, biological viability up to 4 days of incubation and degradation rate evidenced strong dependence of scaffold behavior on unit cell geometry as well as on global geometrical features
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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