1,720,958 research outputs found
Mechanical and wear properties of Si3N4 reinforced titanium composites
No full textIn the present study, Si3N4 reinforced titanium composites have been produced by the powder metallurgy method. The effect of various percentages of Si3N4 (0-9 wt. %) on the microstructure, density, hardness and compressive strength of titanium (It) composites have been investigated. After sintering at 1100 degrees C for 120 min., the mechanical properties have been significantly developed up to 3 wt. % Si3N4. The highest hardness and the greatest compressive strength have been obtained for 3 wt. % Si3N4 reinforced composite (698.5 HV and 1093 MPa) when compared to pure titanium (414.2 HV and 826 MPa). Si3N4 addition improved the wear properties of composites when compared to pure titanium. The lowest wear rate (1.36 x 10(-5), 2.75 x 10(-5) and 5.15 x 10(-5) mm(3) / Nm for 10 N, 20 N and 30 N, respectively) have been obtained for 3 wt. % Si3N4 reinforced titanium composite. Above this ratio, the properties of composites have deteriorated due to agglomeration tendency of Si3N4 powder. The scanning electron image, elemental mapping and line analyses confirm the uniform distribution of Si3N4 powder in Ti matrix. There has been no in-situ formed second phase of composite structure from the X-ray diffraction analyses
Mechanical and wear properties of Si3N4 reinforced titanium composites
Get PDF1027-1036In the present study, Si3N4 reinforced titanium composites have been produced by the powder metallurgy method. The effect of various percentages of Si3N4 (0-9 wt. %) on the microstructure, density, hardness and compressive strength of titanium (It) composites have been investigated. After sintering at 1100 oC for 120 min., the mechanical properties have been significantly developed up to 3 wt. % Si3N4. The highest hardness and the greatest compressive strength have been obtained for 3 wt. % Si3N4 reinforced composite (698.5 HV and 1093 MPa) when compared to pure titanium (414.2 HV and 826 MPa). Si3N4 addition improved the wear properties of composites when compared to pure titanium. The lowest wear rate (1.36 x 10-5, 2.75 x 10-5 and 5.15 x 10-5 mm3 / Nm for 10 N, 20 N and 30 N, respectively) have been obtained for 3 wt. % Si3N4 reinforced titanium composite. Above this ratio, the properties of composites have deteriorated due to agglomeration tendency of Si3N4 powder. The scanning electron image, elemental mapping and line analyses confirm the uniform distribution of Si3N4 powder in Ti matrix. There has been no in-situ formed second phase of composite structure from the X-ray diffraction analyses
Effect of pure titanium particle size on density, hardness, wear resistance and microstructure properties
No full textIn this study, pure titanium particle samples with different particle sizes were produced by powder metallurgy method. In the sample production, pure titanium particles having a different particle size of <= 30 mu m, <= 43 mu m, <= 150 mu m were used. Titanium (Ti) samples were sintered at 1100 degrees C for 120 min. Density, hardness, wear resistance and microstructure analyzes were performed on the Titanium samples. According to the results, the best mechanical properties values were obtained with <= 30 mu m particle size of Titanium. The best density and hardness results are 4.28 g.cm(-3) and 419.8 HV, respectively. The results of the wear rate were found under 30 N load of 8.21 x 10(-5) mm(-3).Nm. Mass loss results were measured as 5.2 mg (under load of 30 N). SEM analyses showed that a good bonding and strong neck formation between the particles were observed for particle size of <= 30 mu m
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
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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