1,720,988 research outputs found
ZrB 2-SiC/Ti6Al4V joints: Wettability studies using Ag- and Cu-based braze alloys
No full textIn this paper, a study is presented on the wettability of ZrB 2 ceramics (pure ZrB 2 and ZrB 2-SiC composite) and of the Ti6Al4V alloy by pure Cu and Ag and their alloys with Ti to be used in subsequent brazing processes. Wettability tests aimed at elucidating the interfacial interactions and the role of active metal additions (i.e. Ti) in the brazing procedure, performed in a temperature range between 950 and 1150 °C, showed that Cu wets pure ZrB 2 quite well (contact angle θ = 70°), while Ag does not. The composite was wetted in a similar way by Cu, while for Ag a θ = 97° was found. The addition of Ti improved the wetting (θ between ̃0° and 20°) and segregation at the metal- ceramic interface occurred. As expected, both Cu(Ti) and Ag(Ti) wetted the Ti6Al4V alloy very well. In particular, it was shown that Cu can already produce a liquid phase at 950 °C with partial dissolution of the solid phase. These results are discussed in terms of interfacial reactions and taking into account the sintering aids used for the ceramic body. This study is aimed at defining a brazing process that leads to reliable metal-ceramic joints as a result of chemical interactions of the liquid phase with and diffusion into the adjoining solids. Exploratory joining tests were performed that showed, by means of shear tests coupled with microstructural and microchemical description of the interfaces, the possibility to design sound ZrB 2-SiC/Ti6Al4V joints. © Springer Science+Business Media, LLC 2012
Diamond–metal interfaces in cutting tools: a review
No full textThis paper reviews studies undertaken on diamond cutting tools, with particular regard to the characteristics and performance of diamond/metal interfaces. The affinity of carbon to metals, as well as the wettability of diamond by molten metals and the advantage of using coated diamonds under certain cutting conditions, are described. The choice of the appropriate metallic matrix in the field of both impregnated and brazed diamond tools, is discussed in terms of the diamond/alloy interface, mechanical properties of the segment, diamond wear speed and desired cutting performance. The effect of several principal elements and elements added in minor amounts to the metallic matrix is critically evaluated. Relevant open questions, related to the optimization of cutting tools performance, are outlined, with special attention directed towards the need for advanced fundamental studies on the functional link between Work of Adhesion and Work of Fracture
Wettability of transparent YAG (Y<inf>3</inf>Al<inf>5</inf>O<inf>12</inf>) by molten Ag-Cu-Ti alloys
No full text
Joining of ZrB2 ceramics to Ti6Al4V by Ni-based interlayers
No full textPure ZrB2 and ZrB2-SiC composites were joined to Ti6Al4V at 1100°C using
B-Ni50 (at.%) as a filler alloy. The brazing medium and the processing
parameters were chosen on the basis of specific wetting tests which showed
the good adhesion properties of the B-Ni alloy with both the ceramic and the
Ti alloy; interfacial reactions were foreseen and interpreted by phase diagram
analysis.A multilayer metal-ceramic interfacial structure was observed in the joints and
a key role was played by Ti coming from Ti6Al4V: it worked as the active
element enhancing the adhesion of the liquid on to the ceramic and
segregated at the interface forming TiB. A satisfactory mechanical
performance was obtained for ZrB2-SiC/Ti6Al4V joints, which exhibited a
room temperature shear strength of 74 MPa
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
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