1,720,974 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
New correction approaches for mitigating ionospheric higher order effects in GNSS applications
No full textBy combining two or more signals of Global Navigation Satellite Systems (GNSS) more than 99% of the ionospheric propagation delay can be corrected in real time precise positioning. However, higher order propagation effects such as ray path bending errors remain uncorrected in dual- or triple-frequency ionosphere-free combination. The range computation between a satellite and a ground receiver is affected up to several centimeters due to higher order ionospheric terms. Therefore, they cannot be neglected in precise point positioning applications, especially during times of high total electron content (TEC). Neglecting the ray path bending by assuming a straight Line of Sight (LOS) propagation introduces mainly two errors in the range computation. Firstly, the TEC along a curved path is slightly larger than that along the straight LOS. This causes differential TEC between two GNSS signal paths which results in uncorrected ray path bending error in the first-order ionosphere-free combination in addition to the higher order terms of the refractive index. Secondly, the total length of a curved path is slightly longer than the LOS one. Since, the ionosphere is dispersive in nature; the path length will not be the same for two GNSS signals. This indicates that the dual-frequency range equation must have additional terms for correcting differential bending. It has been found that in the range equation the excess TEC and excess path terms practically compensate each other. In other words, if we consider one term ignoring the other term would degrade the accuracy of the range computation. To mitigate the LOS propagation assumption error, i.e., the ray path bending error, we have derived different correction formulas based on simulation studies. Our study shows that in average about 60-70% and above 80% of the excess path and excess TEC errors can be corrected by different correction approaches during high and low solar activity conditions, respectively
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
Mitigation of Ionospheric Mapping Function Error
No full textIonospheric delay is currently considered as a major error source for satellite based navigation systems. The operational standards set by the International Civil Aviation Organization (ICAO) for Wide Area Differential GPS (WADGPS) ensure Space Based Augmentation System (SBAS) users an ionospheric delay correction in addition to satellite clock and orbit corrections. In the current standard, the SBAS broadcasts vertical ionospheric delays in meters at the ionospheric grid points (IGP) located at every five degrees of latitude and longitude. The SBAS user receivers convert them to the slant delay using the so called obliquity factor derived under the assumption of a thin-shell ionosphere fixed at 350 km height. Although the ionospheric correction is available for all broadcast IGPs, the user does bilinear interpolation between IGPs those surround the ionospheric piercing point (IPP) at the thin-shell height. In this paper we present a new mapping function approach for vertical to slant delay conversion. Considering broadcast delays not only at a single IPP rather at different geographic locations along the ray path projected on the thin-shell at 350 km height, our algorithm incorporates the horizontal gradients in the slant delay computation. Instead of collapsing the vertical structure of the ionosphere into a thin-shell we consider the Chapman layer assumption for describing the vertical electron density distribution of the ionosphere. Our investigation shows that using the proposed algorithm instead of the thin-shell algorithm we can reduce the mapping function error by about 50% under high as well as low solar activity conditions
Harnessing LEO and CubeSat constellations for ionospheric irregularity detection
No full textLow-earth orbiting (LEO) satellite missions are frequently using the Global Navigation Satellite System (GNSS) Radio Occultation (RO) technique for atmospheric and ionospheric remote sensing. The application of GNSS RO technique has increased manifolds with the advent of CubeSat technology. In this study, we investigated the simultaneous occurrence of local nighttime F-layer ionospheric irregularities and amplitude scintillations in low-latitude equatorial regions using 1 Hz COSMIC-2 electron density profiles (ionPrfs) and high rate 50 Hz ionospheric profiles (conPhs) from Spire’s CubeSat constellation, respectively. Both datasets are accessed from the University Corporation for Atmospheric Research (UCAR) repository.
An ionospheric irregularity detection algorithm is developed using a digital non-recursive finite impulse response (FIR) high-pass filter and applied on both the electron density (Ne) and total electron content (TEC) profiles from COSMIC-2 mission. The filter operates in the s domain, where s is defined as the distance between the highest and lowest tangent point heights. If the fluctuations in Ne and TEC exceed a set threshold, the corresponding COSMIC-2 profile is identified as having irregularities. In case of Spire GNSS-RO profiles, scintillation events are identified when the amplitude scintillation index (S4) at GPS L1 frequency exceeds the set threshold. COSMIC-2 and Spire datasets from September 2021 until May 2023 (20 months) are used in this long-term comparative study.
We observe a good agreement in the statistics of number of Spire and COSMIC-2 profiles detecting (showing possible signature of) scintillations/ ionospheric irregularities. Both Spire and COSMIC-2 data show that the scintillation occurrence rate is much higher during the equinoxes (spring and autumn seasons) agreeing well with existing scintillation literature. From the COSMIC-2 data alone, we also notice a direct relation with the solar activity, i.e., the number of irregularity events slowly increases as we approach the solar maximum. This study indicates the capability of LEO satellites and CubeSat missions, especially in GNSS-RO configuration, for providing an important contribution to scintillation monitoring
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