1,720,969 research outputs found
Implacement and fluctuations of the Antarctic Ice Sheet across the Eocene-Oligocene transition
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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
MAJIS instrument characterization
No full textThe JUICE (JUpiter ICy moons Explorer) mission by ESA aims to explore the emergence of habitable worlds around gas giants and the Jupiter system as an archetype for gas giants. MAJIS (Moons and Jupiter Imaging Spectrometer) is the visible to near-infrared imaging spectrometer onboard JUICE which will characterize the surfaces and exospheres of the icy moons and perform monitoring of the Jupiter atmosphere. The launch is scheduled for June 2022 with the first MAJIS observations inside the Jovian system occurring more than 7.5 years later. MAJIS will use two Teledyne H1RG detectors for both spectrometer channels (VIS-NIR and IR). For this mission, they will be operated in a non-standard way. The detectors will allow near/full-frame retrieval over short integration times (<< 1 sec) while maintaining good noise performance. This is due to the relatively high levels of irradiance of the targets compared to the detector well depths, and to mitigate the high rate of radiation spikes from the Jovian environment. Additionally, the detectors will operate at higher temperatures than previous space missions due to stringent resources constraints, impacting the dark current levels. We will present the characterization strategy suitable for evaluating the performances of the VIS-NIR and MW-IR channel according to the MAJIS operational specifications. This methodology was tested during two characterization campaigns using two MAJIS Engineering Grade detectors. The first campaign was performed at the Institut d'Astrophysique Spatiale for the MW-IR detector. The second campaign was performed at the Institut royal d'Aeronomie Spatiale de Belgique for the VIS-NIR detector. This MSc thesis will describe the analyses and results of both campaigns. Based on these results, the capacity of MAJIS to reach its scientific objectives will be discussed.JUICEMAJISAerospace Engineerin
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
On the effect of laser altimeter crossover observables on orbit determination with the JUICE mission as case study
Full text linkThis thesis' work aims to evaluate the potential added benefit to spacecraft orbit determination procedures upon using non-conventional measurements for orbit reconstruction. As a spacecraft orbits a celestial body, its ground tracks will naturally cross previous ground tracks at many points. These locations, known as crossover points, yield valuable information about the orbited body and the spacecraft trajectory using the spacecraft altitude measured during both passages at each crossover location. To evaluate the impact of altimetry crossover measurements on orbit determination, the mission scenario of the planetary mission Jupiter Icy moons Explorer (JUICE) by the European Space Agency (ESA) is used as case study. As the mission's measurements will only be available several years from now, the resulting analysis is done with synthetic measurements obtained through numerical simulations. Herein, the necessary mathematical expressions for the inclusion of crossover measurements into orbit determination algorithms are presented, verified and evaluated. In doing so, it is shown that a first-order approximation of these expressions, as used in previous efforts, is insufficient and a more detailed expression is developed. Furthermore, the used crossover determination algorithm is presented in detail as well as the crossover selection filters in accordance to mission requirements. Finally, the sensitivities and intricacies of crossover measurements are discussed and their added value to orbit determination schemes is shown.Aerospace Engineerin
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