1,720,978 research outputs found
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
NO2 sensitivity of WO3 thin film obtained by high vacuum thermal evaporation
No full textThe gas sensitivity, selectivity and stability properties of WO3 thin films for the detection of NO2 gas in the concentration range 0.2-5 ppm, have been evaluated and discussed in the light of the preparation conditions and working temperature. Thin films were obtained by evaporating high purity WO3 powder by an electrically heated crucible at about 5 x 10(-4) Pa on sapphire substrates provided with Pt interdigital type sputtered electrodes and annealed for 1 h at 400, 500 and 600 degrees C. The film morphology, crystalline phase and chemical composition were characterised through AFM, low angle XRD and XPS. The electrical response was measured by means of DC current mode. The annealed films showed crystallographic orientation belonging to the triclinic structure of WO3, while the as deposited films were found to be amorphous. The binding energies of O 1s and W 4f confirmed the existence of the WO3 phase, with a stoichiometric ratio close to the theoretical one. All the films showed the highest sensitivity to NO2 at a working temperature of 200 degrees C. The 500 degrees C annealed film was found to be the most sensitive to NO2 gas, compared to those annealed at 400 and 600 degrees C, No cross sensitivity effects were found by exposing the sensors to CO, CH4. WO3 films showed strong sensitivity to C2H5OH and H2O, Long term stability test at a working temperature of 350 degrees C, performed by cycling the films in dry air and 5 ppm NO2 revealed no substantial change in the electrical properties in terms of drift and sensitivity
Microstructural effect on NO2 sensitivity of WO3 thin film gas sensors .1. Thin film devices, sensors and actuators
No full textMicrostructures of thermally evaporated WO3 thin films on sapphire substrates are investigated by wide-angle X-ray diffraction, atomic force microscope and X-ray photoelectron spectrum. The as-deposited film is amorphous and crack-free with WO3 stoichiometry on the surface. After annealing at above 400 degrees C, the film is crystallized. Compared to the monoclinic phase of the starting WO3 powder, fewer peaks are evident at room temperature for the annealed film, This highlights that the film grown on the sapphire has a preferential orientation of WO3 (200), probably because of the atomic arrangement similar to the sapphire. The crystallite sizes are estimated from the major peak to be 17.5-23.9 nm according to the Scherrer equation. The increasing of annealing temperature exhibits positive effects on the surface roughness or fractal dimension, surface area and grain size of the film. However, abnormal increments in the topographical parameters occur in case of annealing at 600 degrees C. The binding energy of the annealed film is close to that of WO3, and a small downshift of 0.1 eV reflects the formation of oxygen vacancies on the surface. The heterogeneity parameter of the film is introduced into the Schottky barrier equation. The highest sensitivity of the 500 degrees C-annealed sensor is explained in terms of the annealing temperature effect on the geometrical and chemical heterogeneities
Investigation on the cross sensitivity of NO2 sensors based on In2O3 thin films prepared by sol-gel and vacuum thermal evaporation
No full textIn2O3 thin films have been prepared from commercially available pure In2O3 powders by high vacuum thermal evaporation (HVTE) and from indium iso-propoxide solutions by sol-gel techniques (SG). The films have been deposited on sapphire substrates provided with platinum interdigital sputtered electrodes. The as-deposited HVTE and SG films have been annealed at 500 degrees C for 24 and I h, respectively. The film morphology, crystalline phase and chemical composition have been characterised by SEM, glancing angle XRD and XPS techniques. After annealing at 500 degrees C the films' microstructure turns from amorphous to crystalline with the development of highly crystalline cubic In2O3-x (JCPDS card 6-0416). XPS characterisation has revealed the formation of stoichiometric In2O3 (HVTE) and nearly stoichiometric In2O3-x (SG) after annealing. SEM characterisation has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO2 gas (0.7-7 ppm concentration range), at 250 degrees C working temperature. At this temperature and 0.7 ppm NO2 the calculated sensitivities (S = R-g/R-a) yield S = 10 and S = 7 for SG and HVTE, respectively. No cross sensitivity have been found by exposing the In2O3 films to CO and CH4. Negligible H2O cross has resulted in the 40-80% relative humidity range, as well as to I ppm Cl-2 and 10 ppm NO. Only 1000 ppm C2H5OH has resulted to have a significant cross to the NO2 response. (C) 1999 Published by Elsevier Science Ltd. All rights reserved
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
Cross-Sensitivity and stability of NO2 Sensors from WO3 Thin Film
No full textThe H2O, C2H5OH, CO, CH4, NO and SO2 cross sensitivity to NO2 gas, as well as the long term stability of the electrical response of WO3 thin films have been evaluated and discussed in the light of different preparation conditions and working temperatures. Thin films have been obtained by evaporating high purity WO3 powder at 5 x 10(-4) Pa on sapphire substrates provided with Pt interdigital sputtered electrodes and annealed at 500 degrees C for 6, 12 and 24 h. The film morphology, crystalline phase and chemical composition have been characterised through AFM, glancing angle XRD and XPS. The as-deposited film is amorphous with WO3 stoichiometry on the surface, after annealing at 500 degrees C the films are well crystallised but with preferential orientation of WO3 along the (200) plane, The increasing of the annealing time shows a positive effect on the crystallite and grain size of the film, while the mean roughness and surface area difference slightly decrease. The binding energies of the annealed films are close to that of WO3 and small downshifts from the characteristic binding energy of W 4f(7/2) reflects the formation of oxygen vacancies on the longer time annealed films. All the films show the highest sensitivity to NO2 gas (0.7-5 ppm concentration range), at 250 degrees C working temperature. At this temperature and 1.7 ppm NO2 the calculated sensitivities yield S = 12, S = 43 and S = 45 for 6, 12 and 24 h annealed films, respectively. No cross sensitivity has been found by exposing the WO3 films to CO and CH4. Negligible H2O cross to NO2 has resulted for the 24 h annealed film in the 40-80% relative humidity range, as well as to 300 ppm SO2 and 10 ppm NO. Only 1000 ppm C2H5OH has resulted in a significant cross to the NO2 measure. The increase in the annealing time had positive effects on the sensitivity, cross sensitivity and long term stability properties. The 45-fold increase in the resistance of the 24 h annealed on exposure to 1.7 ppm of NO2, as well as the good long term stability properties of its electrical response, suggest the possibility of utilising the sensor for air-quality monitoring
NO2 response of In2O3 thin film gas sensors prepared by sol-gel and vacuum thermal evaporation techniques
No full textIn2O3 thin films have been prepared by high vacuum thermal evaporation (HVTE) and by sol-gel (SG) techniques. The deposited HVTE and SG films have been annealed at 500 degrees C for 24 and 1 h, respectively. After annealing at 500 degrees C, the films are highly crystalline cubic In2O3. XPS characterization has revealed the formation of stoichiometric In2O3 (HVTE) and nearly stoichiometric In2O3-x (SG). SEM characterization has highlighted substantial morphological differences between the SG (highly porous microstructure) and HVTE (denser) films. All the films show the highest sensitivity to NO2 gas (0.7-7 ppm concentration range), at 250 degrees C working temperature. Negligible H2O cross has resulted in the 40-80% relative humidity range. Only 1000 ppm C2H5OH has resulted in a significant cross to the NO2 response. (C) 2000 Elsevier Science S.A. All rights reserved
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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