1,721,107 research outputs found
A scalable fire danger index based on sentinel imagery
Full text linkThe incidence of wildfires and megafires and their disastrous consequences is increasing all over the planet. According to the latest European Forest Fire Information System annual fire report, in 2021 alone wildfires burned a surface area more than twice the size of Luxembourg, including more than a thousand square kilometres of Natura 2000 protected areas. In addition, 2022 has registered the highest number of wildfires since 2006, and will also be recorded as one of the driest years on record. Assuming that the most efficient and cost-effective way limit the damage caused by wildfires consists in their prevention, building tools to allow the decision makers to allocate resources using state of the art technology and fresh data is of the utmost importance. To this end, the combined usage of data from weather and satellite platforms capable to provide data on a regional or national scale and at a high temporal frequency provides the optimal solution for assessing and monitoring the state of the vegetation. However, users of fire danger product users often complain about the resolution of the provided products. While moderate- or coarse-resolution products may be adequate to cover the regional or national scale, high-resolution products are required to properly describe the fire danger in relatively small-sized areas of high interest in fire danger modelling, such as wildland-urban interfaces, national parks or protected areas. Using a different fire danger product based on the spatial scale of the target may be impractical and increase the workload and training requirements for the personnel. For this reason, we propose a scalable fire danger index based on Sentinel imagery that is able to cover different spatial scales by exploiting the surface reflectances provided by different Sentinel products (i.e. Sentinel-2 and Sentinel-3).
This novel index, named Daily Fire Danger Index, exploits both weather and satellite data to estimate all the main variables of fire danger, such as the amount of dead fuel, moisture of the dead and live fuels, wind speed, evapotranspiration etc, and is calibrated using the historical records of wildfire occurrence in the target region. In particular, the live fuel moisture content is estimated using a state of the art procedure based on the inversion of radiative transfer models of the PROSAIL family. The index was tested in Sardinia, a region well-known for its proneness to wildfires and which is also regularly affected by megafires, and the performance comparison with the Canadian Fire Weather Index shows very significant improvements on the capability to discriminate fire danger even at a moderate resolution. Finally, the 2021 Planargia-Montiferru megafire was selected as a case study to showcase the added value of the high-resolution version of the index
A comparison of three basic conjugate direction methods
No full textIn this paper three basic conjugate direction methods for solving non-symmetric linear systems are described and compared. All three have entirely different basic structures and, consequently, completely different characteristics. The motivation for this work is the comparative assessment of the methods in order to decide which of the three is the most suitable for further development. ©1996 by John Wiley & Sons, Ltd
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
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
Stima della della produzione dei pascoli alpini con tecniche modellistiche e di remote sensing
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