1,720,982 research outputs found
Numerical study of hetero-adsorption and diffusion on (100) and (110) surfaces of Cu, Ag and Au
No full textQuenched molecular dynamics simulations and density-functional theory (DFT) calculations are used to study the adatom hetero-diffusion on the (100) and (110) surfaces of four systems: Au/Ag, Ag/Au, Au/Cu, Cu/Au. Atomic interactions are described by embedded-atom method potentials, that are validated by a comparison with DFT results on diffusion barriers. The local relaxation of surface atoms around the adatom is analyzed, together with adsorption energies and hopping diffusion barriers. We find that atomic relaxation is qualitatively different between (100) and (110) surfaces, with the exception of the Au/Cu case. Hopping diffusion barriers are larger on the (100) than on the (110) surface. Many-body and relaxation effects cause significant differences between Ag/Au and Au/Ag barriers, and between Cu/Au and Au/Cu barriers
Adsorption and diffusion of Pt, Cu, Ag and Au on missing row reconstructed Pt(110) surfaces: An ab initio investigation
No full textWe present density functional theory (DFT) calculations for the heterodiffusion and adsorption for Ag, Au and Cu adatoms on the Pt(110)(1 × 1) (1 × 2) and (1 × 3) surfaces. The adsorption energy shows an important variation as function of the reconstruction order for Pt/Pt and Au/Pt systems, while the adsorption energy varies slightly for Cu/Pt and Ag/Pt. Likewise, the activation energy is examined for different systems and geometries and the highest barrier was found for Pt adatom diffusion. In addition, the estimated diffusion barriers are found to be influenced by reconstruction order for all systems under consideration but with different magnitudes of variation as function of reconstruction order for each system. Indeed, we found that the activation energy varies as function of the reconstruction order but the magnitude of variation is important for Pt/Pt and Cu/Pt systems, whereas the diffusion barrier for Ag/Pt and Au/Pt systems has a slight dependence on the reconstruction order. The analysis of the adatom relaxation with its neighbor atoms as well as the variation of the bond length was provided to more deeply explain the observed trends for each system. The general trend of activation energies for these systems is consistent with available experimental and theoretical data
Heterodiffusion of Ag adatoms on imperfect Au(1 1 0) surfaces
No full textThe hetero-diffusion of Ag adatoms on imperfect Au(1Â 1Â 0) surfaces is studied using Molecular Dynamics (MD) simulations. The atomic interactions are described by an Embedded Atom Method (EAM) potential. Static activation energies governing various diffusion processes (jumps and exchanges) are calculated by quenched MD, finding that activation energies for interlayer mobility at straight step edges are somewhat larger than those on the flat surface in the cross-channel [1Â 0Â 0]-direction, while interlayer barriers at kinks are considerably lower. Dynamic activation energies are calculated at high temperature from the Arrhenius plots of different diffusion mechanisms and compared to static barriers
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
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