1,720,963 research outputs found
Tribological analysis of thin films by pin-on-disc: evaluation of friction and wear measurement uncertainty
No full textPin-on-disc is widely used to evaluate tribological properties of thin films. However, the results are often present without standard uncertainties; moreover, in many cases the standard uncertainty is replaced by standard deviation, which is a strong underestimation of real uncertainty. In this study we have followed ISO and NIST guidelines to investigate the possible sources of uncertainties related to friction and wear rate measurement and to apply them on two selected coating systems – TiN and DLC. We show that influence of operator is a significant contribution to the uncertainty of the wear rate, particularly in the case of very low wear of DLC coatings. We discuss why variance should be used instead statistic deviation and suggest a method to calculate uncertainties in case of small number of measurements. The paper could be used as a guide to evaluate friction and wear data of thin films and coatings using the pin-on-disc technique
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
Tribological behaviour of nanostructured Ti-C:H coatings for biomedical applications
No full textThe development of a mechanically stable, functionally graded Ti-doped a-C:H interface layer in combination with a functional a-C:H coating requires a reduction of the brittle phases which induce generally problems in the transitions from Ti to TiC/a-C:H. The core objective of this study was to develop an optimum interlayer between the substrate and the functional top layer for biomedical applications, namely for tooth implants. Since the interlayer may be exposed to the sliding process, in the case of local failure of the top layer it has to fulfil the same criteria: biocompatibility, high wear resistance and low friction.The functional Ti-C:H layers with thickness in the range 2.5–3.5 ?m were deposited by a magnetron sputtering/PECVD hybrid process by sputtering a Ti-target in a C2H2 + Ar atmosphere in dc discharge regime. The sets of coating samples were prepared by varying the C and H concentrations controlled by the C2H2 flow during the deposition process. The tribological properties were evaluated on a pin-on-disc tribometer at room temperature (RT) and at 100 °C using 440C balls with a diameter of 6 mm. The tests at 100 °C were performed to investigate the effect of the sterilization temperature on the tribological properties and the coating lifetime as well. The tribological performance was examined with respect to the friction coefficient, the wear rates of the coating and the counter-parts and the analysis of the wear debris. The Ti/C ratio decreased almost linearly from 4.5 to 0.1 with increasing C2H2 flow; the hydrogen content showed a minimum of 5 at.% at C2H2 flow of 30 sccm, while for lower flows it was about 10 at.%. The coatings could be divided into three groups based on the C2H2 flow: (i) 10–15 sccm, exhibiting severe abrasive damage during the sliding tests, (ii) 20–45 sccm, showing the highest hardness and friction values, and (iii) 52–60 sccm, with moderate hardness and minimal values of the friction coefficient and the wear rate
Structure and tribology of biocompatible Ti–C:H coatings
No full textTi–C:H coatings with different carbon content for biomedical applications were deposited by PECVD. Ti was varied by magnetron sputtering a Ti-target with different power in a dc discharge regime having Ar in the atmosphere. Ti–C:H coating was tribologically tested reflecting its expected use as an interlayer for improving the adhesion of functional a-C:H coatings. The tribological properties were studied using a pin-on-disc CSM Tribometer in order to ensure stable tribological properties of the whole Ti–C:H/DLC system for any case of top layer failure. The sliding tests were carried out at room temperature in room environment with relative air humidity 40 ± 5%, in 0.9% NaCl water solution (physiological solution, PS) and in 10% fetal bovine serum (FBS) dissolved in Ringer's saline solution using 440C steel balls with a diameter of 8 mm. The variation of the C2H2 flow led to carbon contents in the range [18–91 at.%]. The Ti-rich coatings exhibited poor wear resistance, while the best tribological properties were achieved for TiC/a-C:H coatings deposited with the highest C2H2 flows. When tested in biological solutions, the friction and wear resistance were analyzed with respect to their corrosion propertie
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
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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