1,721,040 research outputs found
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
In situ diagnosis of chemical species for the growth of carbon nanotubes in microwave plasma-enhanced chemical vapor deposition
No full textA synthesis of multi-wall carbon nanotubes (MWNTs) by microwave plasma-enhanced chemical vapor deposition using CH4/H-2/NH3 gases on Ni/Cr-coated glass at low temperature, was investigated by optical emission spectroscopy (OES) and quadrupole mass spectroscopy (MS). It was observed that the MWNTs were gown within a very restrictive range of the gas compositions. Optical emission lines were observed primarily from atomic hydrogen H-alpha, molecular hydrogen, and CN radicals. The quadrupole mass spectrum also showed the formation of C2H2 and HCN. An addition of a small amount of NH3 resulted in a decrease of C2H2, which could be used to estimate amounts of carbon sources present in the plasma for the growth of MWNTs, and increases of CN and H-alpha radicals acting as etching species of amorphous carbon. These results show that the etching species of amorphous carbon as well as the growth species are necessary and the ratio between two species have to be in appropriate condition for the synthesis of carbon nanotubes at low temperature. The optimum C2H2/H-alpha ratio in the gas mixture for the growth of MWNTs at low temperature was found to be 1:5 in this study. (C) 2002 Elsevier Science B.V. All rights reserved
Field emission characteristics of multiwalled carbon nanotubes grown at low temperatures using electron cyclotron resonance chemical vapor deposition
No full textVertically aligned multiwalled carbon nanotubes were synthesized by electron cyclotron resonance chemical vapor deposition on Ni-coated glass substrates at temperatures as low as 400 degreesC. Negative self-biases were induced to the substrates by radio frequency plasma to give ion bombardment to the growing surface. An increase of self-bias voltages from -50 to -200 V resulted in an evolution of the microstructures from amorphous carbon to nanorods, subsequently to nanotubes. Nanotubes grown above - 150 V were more straight in morphology and better in crystallinity than nanorods grown at - 100 V. In the field emission (FE) measurements, the electric fields to obtain 1 muA/cm(2) were 4.6 and 11.1 V/mum for the nanorods and nanotubes grown at - 100 and - 200 V, respectively. The emission areas, calculated from the Fowler-Nordheim plots, were much larger in the nanorods than the nanotubes. It is considered that a larger amount of crystalline defects in nanorods plays a major role in improving their FE characteristics. (C) 2003 American Vacuum Society.This work was supported by the Center for Electronic Packaging Materials of the Korea Science and Engineering Foundation
Structural characteristics of carbon nanorods and nanotubes grown using electron cyclotron resonance chemical vapor deposition
No full textDifferent types of carbonaceous materials were synthesized by electron cyclotron resonance chemical vapor deposition on Ni-coated glass substrates with radio-frequency (rf) self-biasing using a gas mixture of CH4 and Ar. Vertically aligned carbon nanorods and multiwalled carbon nanotubes (MWNTs) were obtained at the rf bias voltages of -100 and -200 V, respectively. High-resolution transmission electron microscopy indicated that the distance between two graphene layers of carbon nanorods is much larger than that of well-graphitized MWNTs having a typical value of graphite. Structural characteristics of carbon nanorods and well-graphitized MWNTs were investigated by electron-energy-loss spectra, in which the energy of pi+sigma plasmon peak obtained from carbon nanorods shifts to a lower value of 23.8 eV, compared to 25.5 eV from well-graphitized MWNT. Low-energy loss plasmon due to pi electrons at 6 eV was not observed in carbon nanorods, but clearly defined for well-graphitized MWNTs. In addition, x-ray photoelectron spectroscopy showed that the delocalization of pi electrons becomes more pronounced as the structure of carbonaceous films evolves into more crystalline phase from carbon nanowalls to well-graphitized MWNTs with increasing rf bias voltages. These results can suggest that ionic bombardment energy at high rf bias voltages provides sufficient internal energy for dehydrogenation from hydrocarbon molecules, and thus well-graphitized MWNTs can be synthesized even at low temperatures. (C) 2003 American Institute of Physics
Effect of ion bombardment on microstructures of carbon nanotubes grown by electron cyclotron resonance chemical vapor deposition at low temperatures
No full textVertically aligned multi walled carbon nanotubes (MWNTs) were synthesized by electron cyclotron resonance chemical vapor deposition on Ni-coated glass substrates at temperatures as low as 400degreesC. Negative self-biases were applied to the substrates by radio-frequency (RF) plasma for ion bombardment of the growing surface. It was observed that ion bombardment by RF biasing to the substrates had a great effect upon the growth of carbon nanotubes and their morphologies. High-resolution transmission electron microscopy revealed that the degree of ordering of graphene layers in the synthesized nanotubes increased with RF bias. Raman spectroscopic analyses indicated that the shortening of C-C bonds within the graphene layers of the MWNTs occurred at larger negative biases, which seemed to result from removal of bonded hydrogen from the MWNTs by ion bombardment
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