1,721,247 research outputs found
Locations and thickness of sediment-laden basal ice zones at Jutulstraumen Glacier onset (East Antarctica)
No full textUnderstanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice-sheet dynamics. Yet, direct data are sparse and difficult to acquire, necessitating geophysical data for analysis. Here, we employed high-resolution ultra-wideband radar to map high-backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. Our results revealed that the basal ice in an area of ~ 10,000 square kilometers is composed of along-flow oriented sediment-laden basal ice units connected to the basal substrate, extending up to several hundred meters of thickness. Three-dimensional thermomechanical modeling suggests these units formed via basal freeze-on of subglacial water originating further upstream. Our findings suggest that basal freeze-on, and the entrainment and transport of subglacial material play a significant role for an accurate representation of material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice-sheet modeling.
Here, we publish locations and thickness of high-backscatter zones at the onset of the Jutulstraumen glacier in East Antarctica
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
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
Modeled freeze-on rates at Jutulstraumen Glacier onset (East Antarctica)
No full textUnderstanding the material properties and physical conditions of basal ice is crucial for a comprehensive understanding of Antarctic ice-sheet dynamics. Yet, direct data are sparse and difficult to acquire, necessitating geophysical data for analysis. Here, we employed high-resolution ultra-wideband radar to map high-backscatter zones near the glacier bed within East Antarctica's Jutulstraumen drainage basin. Our results revealed that the basal ice in an area of ~ 10,000 square kilometers is composed of along-flow oriented sediment-laden basal ice units connected to the basal substrate, extending up to several hundred meters of thickness. Three-dimensional thermomechanical modeling suggests these units formed via basal freeze-on of subglacial water originating further upstream. Our findings suggest that basal freeze-on, and the entrainment and transport of subglacial material play a significant role for an accurate representation of material, physical, and rheological properties of the Antarctic ice sheet's basal ice, ultimately enhancing the accuracy and reliability of ice-sheet modeling.
Here, we publish the outputs of our three-dimensional thermomechanical modeling
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
High-frequency electromagnetic wave scattering from rough surfaces
No full text"A new technique in solving the rough surface scattering problem is presented. The method employed, entitled the ""shooting and bouncing rays"" (SBR) method, is based on a combination of the geometric optics (GO) theory and the physical optics (PO) theory. The SBR method improves on the Kirchhoff approximation by considering the mutual interactions between the irregularities of the surface (i.e., shadowing and multiple scattering are accounted for). In addition, the SBR technique is more efficient than the Method of Moments (MoM) solution, because it does not involve matrix equations, which makes solving the full three-dimensional problem possible. The numerical results, obtained by implementing the SBR technique in solving the scattering problem by one-dimensional random rough surfaces, are compared to the Kirchhoff approximation solutions and the method of moments solutions. The agreement between the SBR technique results and the MoM solution results proves the feasibility and the accuracy of this new approach. Furthermore, the SBR technique is proven to produce more accurate results than the Kirchhoff approximation when shadowing and multiple scattering effects are important. Finally, the SBR technique is implemented in solving the scattering problem by two-dimensional periodic rough surfaces. The results obtained prove the capability of the SBR method in handling the full three-dimensional problem."Made available in DSpace on 2011-05-07T14:07:15Z (GMT). No. of bitstreams: 2
license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5)
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Development and applications of ionospheric tomography
No full textRecently, several tomographic techniques for ionospheric electron density imaging have been proposed. These techniques reconstruct a vertical slice image of electron density using total electron content data. The data are measured between a low orbit beacon satellite and fixed receivers located along the projected orbital path of the satellite. By using such tomographic techniques, it may be possible to inexpensively (relative to incoherent scatter techniques) image the ionospheric electron density in a vertical plane several times per day. The satellite and receiver geometry used to measure the total electron content data causes the data to be incomplete; that is, the measured data do not contain enough information to completely specify the ionospheric electron density distribution in the region between the satellite and the receivers. A new algorithm is proposed which allows the incorporation of other complementary measurements, such as those from ionosondes, and also includes ways to include a priori information about the unknown electron density distribution in the reconstruction process. The algorithm makes use of two-dimensional basis functions. Illustrative application of this algorithm is made to simulated cases with good results. The technique is also applied to real total electron content (TEC) records collected in Scandinavia in conjunction with the EISCAT incoherent scatter radar. The tomographic reconstructions are compared with the incoherent scatter electron density images of the same region of the ionosphere.Made available in DSpace on 2011-05-07T13:22:04Z (GMT). No. of bitstreams: 2
license.txt: 4922 bytes, checksum: 910b249b4beec47e7ab768910c8f966f (MD5)
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