1,720,972 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
Ground based measurements of aerosol properties using Microtops instruments
No full textAtmospheric aerosols originate from a wide variety of sources in both the marine and the continental environments. Aerosol properties vary significantly in space and time depending upon whether the air mass is anthropogenic or natural, marine or continental, rural or urban.
Aerosol particles influence the radiation field of the earth. Variations of aerosol properties in time and space are the dominating source of the variability of remote sensing signals in the optical spectral range. Consequently, the contribution of aerosols to the signals at top of the atmosphere must be accounted for remote sensing of the ocean and land surface, which is known as atmospheric correction. Validation of atmospheric correction procedures require ground based measurements of aerosol properties. Ground based measurements of aerosol properties give also a basis for validation of the aerosol models used by atmospheric correction algorithms. More, measurements of aerosol properties are useful for climate studies because aerosol particles have an impact on the radiation balance of the earth due to its influence on the radiation field.
Ground based measurements of aerosol properties have been performed in the coastal area of the southern Baltic Sea and near Berlin with a Microtops II Sunphotometer and a Microtops II ozone monitor. The data set at the Baltic Sea includes 7 observation periods at 4 different locations. The present paper reports some experience how to perform and analyze measurements with the Microtops instruments. Some advice is provided both for measurements at the land surface and onboard ships. Finally some results are presented.
Sunphotometer measurements over several years require a large effort to maintain accurate radiometric calibration of the instruments. Sensor calibration was found to be very stable. Sensor degradation per year is less than 0.1% with exception of the 1020 nm channel, where it is about 1% per year.
The dataset includes very clear and very turbid conditions. Situations with dominating large aerosol particles have been observed as well as situations with dominating small aerosol particles. Aerosol optical thickness at 550 nm varies from 0.04 to 0.7 and the Angstrœm exponent ranges from 0.25 to 1.8. Variations of the observed optical aerosol parameters in the coastal area show no clear relation to the related wind and humidity conditions, because the dataset is still too small for this kind of analysis.
Validation of atmospheric correction algorithms is demonstrated with a comparison of column aerosol optical thickness resulting from satellite data with aerosol optical thickness from ground based measurements at time of satellite overpass. The agreement is better than ±0.03 at 750 nm. Another example uses the aerosol properties found from ground based measurements as input to radiative transfer modeling of the signals received at satellite. The agreement between modeled and measured signals is fine within the expectable uncertainty
Estimation of optical thickness of volcanic ash clouds using satellite data
No full textRadiance measurements within the O2A-absorption band contain information about height distribution of scattering particles. This is widely used for estimation of cloud-top height from satellite data. Within cloud free scenes over the ocean, there is still enough information contained for separation of aerosol loading within the maritime boundary layer and enhanced aerosol loading in the upper troposphere or stratosphere. If stratospheric aerosol content is low, then thin cirrus clouds can be observed. Alternatively, a volcanic ash cloud within the stratosphere or upper troposphere can be investigated after volcanic eruptions. This is demonstrated within this paper by one application exampl
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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