1,720,977 research outputs found
Improving flood monitoring capabilities using synthetic aperture radar data cubes
Get PDFFlooding poses a significant challenge across much of the world. It ranks as a leading natural disaster in terms of damage and the number of people affected. Effective management of floods requires rapid or Near Real-Time (NRT) mapping, primarily using satellite-based earth observation data. Synthetic Aperture Radar (SAR) data is considered the most suitable for flood mapping operations due to its ability to operate in all weather conditions, both day and night, and its skill at distinguishing between open water and land. The Sentinel-1 SAR system has unrivaled temporal and spatial coverage and thus has been tapped for various flood mapping operations. To better harness the vast Sentinel-1 data holdings, most researchers use data cube solutions. Notable in this regard is the TU Wien flood mapping algorithm. This algorithm is based on Bayes Inference that leverages a Sentinel-1 data cube to define the no-flood probability distribution of pixels via harmonic modeling and flood probability from historical water samples reckoned per incidence angle. It contributes to the Copernicus Emergency Management System's (CEMS) Global Flood Mapping (GFM) ensemble workflow being operated in NRT. While working well in most cases, it has issues such as underestimation in flood transition areas and overestimation in agricultural areas. Further, limitations due to SAR-based flood retrievals necessitate the application of exclusion masks. However, over reliance on exclusion masks also presents an issue. As the TU Wien algorithm's novel Bayesian Inference formulation presents opportunities for improvement, this thesis aims further to improve it in the context of global NRT operations. To do this, we systematically analyzed the algorithm performance and Bayesian Inference components for improvement.First, we compared the performance of change detection algorithms in the northern Philippines as a study area. We tested four well-known change detection algorithms that rely on time-series SAR inputs against reference data from Sentinel Asia and optical imagery. We tested parameterizations such as no-flood estimates or references and threshold determination methods. The TU Wien algorithm was also varied by checking the effect of its low sensitivity masking. Our results suggest that the Bayesian Inference used for the TU Wien algorithm is superior to the other tested algorithms due to its stable performance regardless of parameterization. We then proposed an alternative to non-informative priors using Height Above Nearest Drainage to derive spatially varying priors. The HAND data is used as an input to a two-parameter sigmoid function to generate the priors. We optimized and tested this new formulation of priors on five test events, comparing the HAND-based prior versus the original non-informed priors using CEMS rapid mapping results. Overall, the proposed HAND prior improved the flood mapping results by reducing false negatives, with the added benefit of removing dependence on an external HAND exclusion mask.Further, we explored the use of the exponential filter to estimate a no-flood reference probability and replace the harmonic model. This filter is a promising alternative because it accounts for the most recent backscatter observations, coupled with its recursive formulation, which makes it viable for NRT computation. We compared this filter and its parameterizations for flood mapping performance on four flood events in Europe covered by CEMS rapid activation and three sites in Asia covered by Sentinel Asia flood mapping activations. We then proposed a novel time series assessment of false positive rates to avert the pitfall of overfitting for flooded scenarios.From the time-series assessments, we were able to analyze the causes of overestimation at no-flood scenarios by referencing ERA-5 data. We found that well-known causes of low backscatter, such as frost, dry soil conditions, and lesser-studied agriculture effects, trigger higher FPR at scale. In all cases, the exponential filter showed reduced FP. However, improvement to the exponential filter method is needed as prolonged floods in an area result in poorly estimated no-food references and, thus, poor flood mapping performance. We concluded that the exponential filter is an excellent alternative to the harmonic model.In conclusion, we have established the TU Wien algorithm using the Sentinel-1 data cube as a robust method compared with other change detection algorithms. Further, we have shown improvements in the TU Wien algorithm from incremental changes to its Bayesian Inference framework. These improvements are being (and will be applied) to the TU Wien workflow under the CEMS GFM, thus impacting a true fully automated near-real-time global flood mapping operations
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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