1,720,999 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
Laboratory Characterisation of a Commercial RGB CMOS Camera for Measuring Night Sky Brightness
Full text linkThe use of RGB cameras in photometric applications has grown over the last few decades in many fields such as industrial applications, light engineering and the analysis of the quality of the night sky. In this last field, they are often used in conjunction with a Sky Quality Meter (SQM), an instrument used for the measurement of night sky brightness (NSB), mainly when there is a significant amount of artificial light at night (ALAN). The performances of these two instruments are compared here. A simple source composed of nine narrowband LEDs in an integrating sphere was used to excite the two instruments and therefore measure the spectral responsivity of the SQM and of the three channels of the camera. The estimated uncertainties regarding spectral responsivity were less than 10%. A synthetic instrument approximating the SQM's responsivity can be created using a combination of the R, G and B channels. The outputs of the two instruments were compared by measuring the spectral radiance of the night sky. An evaluation of the spectral mismatch between the two instruments completed the analysis of their spectral sensitivity. Finally, the measurements of real SQMs in four sites experiencing different levels of light pollution were compared with the values obtained by processing the recorded RGB images. Overall, the analysis shows that the two instruments have significantly different levels of spectral responsivity, and the alignment of their outputs requires the use of a correction which depends on the spectral distribution of the light coming from the sky. A synthetic SQM will always underestimate real SQM measures; an average correction factor was evaluated considering nine sky spectra under low and medium levels of light pollution; this was determined to be 1.11 and, on average, compensated for the gap. A linear correction was also supposed based on the correlation between the NSB levels measured by the two instruments; the mean squared error after the correction was 0.03 mag arcsec-2
Instrument assessment and atmospheric phenomena in relation to the night sky brightness time series
No full textSeveral networks of Sky Quality Meters show long-term trends in measuring the night sky brightness. Causes of this variation could be ageing of the instruments and variations of the sky emission. The data from Ekar Observatory (Italy) are here considered. No significant ageing effect was detected on 9-year-old housing windows. A 9-year-old IR blocking filter shows a variation of its spectral transmittance up to 80%. No trend on the SQM output was found due to only the variation of the spectral distribution of the night sky emission. Together with ageing of the IR blocking filter, it causes a reduction of the SQM output of about 0.01 magSQM arcsec-2 per year. Slow trend of the aerosol optical depth suggests the air near the considered site is changing towards less polluted conditions. It reduces scattering of the artificial light and consequently sky glow in the light polluted considered site
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
Évaluation de la stabilité de la couleur des œnocyanines
No full textProbably the oldest natural food colorant was «enocyanin». It is produced from grape skins as a by-product of the wine industry in a number of countries, particularly Italy. The recovery of pigments from grape by-products has received considerable attention. Since wine grape skins are waste disposal problem, obviously the source material is available at very low cost. The pigments in the Vitis vinifera group are 3-monoglucosides of cyanidin, peonidin, malvidin, petunidin, plus the same compounds acylated with acetic, coumaric or caffeic acid. The hybrids may also contain the 3-5-diglucosides of the same aglycones and acylated compounds. Colorants from grapes may be expected to contain a number of other flavonoids, tannin, organic acids, etc. The anthocyanins show greatest stability under acidic conditions, but are generally unstable and degrade easily according to various reaction mechanisms. The degradation is influenced by oxygen, ascorbic acid, light, pH and temperature. Processing conditions used for the extraction and purification of pigments from wine grape skins can influence color stability. The present work was undertaken to study how pH (pH 2,3,4,5), time (15 days, 30 days, 60 days, 90 days) and temperature (4°C, 24°C, 36°C) influence the color stability of enocyanins concentrated by ultrafiltration, inverse osmosis and under vacuum. The color of the different samples has been measured both by spectrophotometry and by Hunter L*, a*, b* values. The spectrophotometric (A420 ; A520 ; T ; I) and colorimetric (L*, a*, b*) data resulted correlated significantly. Therefore colorimetric parameters which can be obtained by using a simple, rapid and easy method were used in order to study the color changes of the different enocyanins in the storage conditions. The obtained results have shown that the concentration techniques by ultrafiltration and inverse osmosis produced enocyanins characterized by a distinct red color, which was intense, but unstable in relation to pH variation. On the contrary, the enocyanins concentrated under vacuum resulted characterized by a poor red color, which was stable in relation to pH changes. In our experimental conditions, the results obtained showed that the degradation of the red color, in relation to time and temperature, proved to be independent of the concentration technique used. A ready visualization of the chromatic evolution of the different enocyanins, with reference to the stability parameters studied, was obtained using the color diagram
Calibration of digital compact cameras for sky quality measures
No full textThis work presents the possibility of using the extremely popular compact digital cameras of smartphones or action cameras to perform sky photometry. The newest generation of these devices allows to save raw images. They are not as good as digital single-lens reflex camera, in particular in terms of sensitivity, noise and pixel depth (10 bit versus 12 bit or more), but they have the advantage of being extremely widespread on the population and relatively cheap. These economical digital compact cameras work with an electronic shutter, it overcomes the consumption of mechanics and allows to gather images for long time. The work uses a simple calibration method to transfer raw data from the proprietary RGB color space to the standard CIE 1931 color space. It allows the measurement of sky luminance in cd m−2 with an expected uncertainty of about 20%. Furthermore, the colorimetric calibration allows to know the correlated color temperature of a portion of the sky, it can help the identification of the kind of polluting sources. Aiming at better clarifying the performances of calibrated digital compact cameras, a comparison with a calibrated DSLR camera is presented in outdoor situations showing a good agreement both for luminance and color temperature measurements
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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