1,721,001 research outputs found
SIMPLE METAL-SURFACES AND IMAGE POTENTIAL STATES
No full textThe surfaces of Al and Na are simple systems, but they show several important features like surface states and image resonances. Using the weighted density approximation within the density functional theory we are able to account self-consistently for image effects in the description of their electronic properties
CHEMICAL ORDER IN AMORPHOUS COVALENT ALLOYS - A THEORETICAL-STUDY OF A-SiC
No full textThe microscopic structure and electronic properties of amorphous silicon carbide at stoichiometric composition have been investigated with ab-initio molecular dynamics simulations. Our results show that a-SiC can be classified neither as chemically ordered nor as completely random and has a structure much more complex than commonly believed. Our data also indicate that a detailed analysis of each atomic species is crucial to the understanding of the material properties
STRUCTURAL-PROPERTIES OF AMORPHOUS SiC VIA AB-INITIO MOLECULAR-DYNAMICS
No full textWe have investigated a-SiC at stoichiometric composition at room temperature using a first principles molecular dynamics technique. This method has proven to be very successful in predicting a variety of properties of disordered systems, amongst them a-C and a-Si. From our results, we analyzed the short range order of the system, in particular whether it is chemically ordered or has a random distribution of Si-C bonds and the different kind of bonding configurations attained by the two species
STRUCTURAL AND DYNAMIC PROPERTIES OF SURFACES FROM AB-INITIO MOLECULAR-DYNAMICS
No full textThe recent application to the semiconductor surfaces of the powerful ab-initio molecular dynamics (Car-Parrinello) method [R. Car,M. Parrinello,Phys. Rev. Lett. 55,2471 (1985)] will be reviewed. The essential features of the method will be addressed first,then we will review a number of recent sudies on the properties of the clean and adsorbate covered surfaces of Si,Ge and GaAs,obtained through Car-Parrinello simulations. Finally an original application of the ab-initio molecular dynamics for the clean and hydrogenated GaAs(110) surfaces is presented
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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