1,720,956 research outputs found
Tribology and wettability of nano-machined silicon rough surfaces
No full text1 – Introduction
The more and more pressing demand for eliminating liquid lubricants in mechanical devices, due to their environmental costs, represents an important challenge for the tribological community. Low-friction coatings, like layered materials (graphite, Mo2S), soft metals (Ag, Au), non-layered metal oxides (MoO3, V2O5), can substitute liquid lubricants, but presently they are characterized by poor mechanical properties. On the other hand, hard ceramic coatings, like CrN, TiN, TiCN, TiAlN, have been studied for the last three decades for their high hardness, chemical inertness, high oxidation resistance and low wear rate.
The aim of our study is to couple the properties of hard ceramics with those of soft metals low friction coatings. The nanostructuring of CrN-Ag ternary coating represents an appealing solution.
2 – Main Body of Text
We studied the tribo-mechanical properties of CrN-Ag ternary coatings, where Ag clusters are dispersed in a CrN thick film. Some preliminary tests were also performed on a similar system, composed by Ag/CrN multilayers. CrN-Ag composite coatings were deposited on Si(100) and on a steel (20MnCr5) using PVD Magnetron Sputtering in a mixed N2+Ar atmosphere (P=5mtorr), with temperature ranging from RT to 500°. Structure, composition and morphology of both systems were characterized by Auger Electron Spectroscopy, X-rays diffraction and cross sectional analysis (depth-profiling AES, FIB cross section). The co-deposition of CrN and Ag in N2 atmosphere leads to the formation of a composite nanostructured coating, where Ag clusters behave as solid lubricant in the hard CrN bulk.
Tribo-mechanical properties were measured with a ball-on-disc tribometer and a Berckovich nanoindenter.
3 – Conclusion
By tuning the preparation conditions we were able to control the size, the distribution and the self organization of Ag nanoclusters in the CrN matrix, thus controlling frictional behavior
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
Ag Surface Diffusion and Out-of-Bulk Segregation in CrN-Ag Nano-Composite Coatings
No full textCrN-Ag nanocomposite coatings are deposited on Si(100) wafers and 20MnCr5 steel disks in amixed Ar+N2 atmosphere by reactive magnetron sputtering. Structure, composition and morphologywere investigated by Scanning Electron Microscopy (SEM), Auger Electron Spectroscopy (AES),X-ray Photoemission Spectroscopy (XPS), X-ray Diffraction (XRD) and Focused Ion Beam (FIB)cross sectional analysis. The as deposited film matrix is mainly composed by CrN phase (78%), buta relevant part (28%) is composed by Cr2N. Ag agglomerates in the CrN matrix forming elongatedgrains 200–400 nm wide and 50–100 nm high, which extends on the top of CrN columns. At thesurface Ag aggregates into two different structures: large tetrahedral crystalline clusters, with typicaldimension ranging from 200 to 500 nm, and smaller Ag nanoparticles with diameter of 15–25 nm.The annealing in N2 atmosphere up to 500 C does not affect size and distribution of the Aggrains in the sub-surface region, while it induces a size increase of the bigger Ag clusters onthe surface, mainly related to Ag surface diffusion and clusters coalescence. Annealing at highertemperature leads to an evident Ag out-of-bulk segregation, generating Ag depleted voids in thenear-surface region, and further increasing of the Ag clusters size at the surface. Tribological testson as deposited CrN-Ag film reveal a coefficient of friction against a steel ball reduced with respectto CrN film, probably related to the presence of Ag which acts as solid lubricant, but the coatingis removed after a very short sliding distance. The poor mechanical properties of the realized Agbasedcoatings are confirmed by lower hardness and Young modulus values with respect to pureCrN
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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