1,720,973 research outputs found
Detección automática de meteoros en redes de cámaras comerciales de seguridad
Get PDFThe recovery of meteorites is one of the most valuable resources to provide clues to
understand the origin, formation and composition of our Solar System. Thousands
of them hit the Earth’s atmosphere every day, but the vast majority disintegrate fastly during their path and do not reach the ground. In contact with the air
molecules and due to their high kinetic energies, they leave luminous trails in the
sky, called meteors, from which it is possible to calculate their trajectory, both
before entering, in their orbit, and later, when they impact. Having appropriate
instruments to detect them at its entry and being able to analyze all the data
obtained with them is necessary so, in case of impact, we can know the location
and origin of the meteorite. In this work, the architecture of the Fireball Alert
and Exploration Terrestial Observation Network (FAETON) meteor network has
been implemented, which uses commercial video surveillance cameras for detecting bright meteors. In addition, a software for processing the image sequences,
analyzing them and confirming the presence of meteors has been developed. Furthermore, different techniques currently used in Computer Vision have been introduced, with the intention of enlarging the state-of-the-art in the tracing and
characterization of its trajectory in images with geometric distortion. A total of
2824 possible detections have been analyzed using Neural Networks, reaching a
precision of 88.0 % in correctly classified meteors and a 4.6 % of false positives
Natural Night Sky Brightness during solar minimum
No full textDesde el comienzo de los tiempos, la observaci´on del cielo estrellado ha sido una de las actividades predilectas en el desarrollo cultural y cient´ıfico del ser humano y uno de los pocos placeres
comunes a todas las poblaciones que han habitado nuestro planeta. Una parte importante de las
primeras teor´ıas cient´ıficas y filos´oficas surgieron de la contemplaci´on y admiraci´on de los cielos
y la gran mayor´ıa de las labores humanas estaban regidas por el movimiento de los astros. La
situaci´on a d´ıa de hoy es muy diferente. El 80% de la poblaci´on mundial vive en lugares donde
existe contaminaci´on lum´ınica artificial y aproximadamente un tercio de ella no pueden ver la
V´ıa L´actea. Quedan ya muy pocos lugares en el planeta donde se pueda apreciar, observar y
medir la oscuridad natural. En este trabajo se han utilizado datos de 44 de estos lugares, cuyos
cielos est´an poco o muy poco contaminados, para realizar el primer estudio sistem´atico de la
oscuridad natural y su variabilidad. Para ello, se han utilizado fot´ometros de bajo coste, desarrollados por el proyecto europeo STARS4ALL y calibrados en el Laboratorio de Instrumentaci´on
Cient´ıfica Avanzada de la Universidad Complutense de Madrid. Estos dispositivos tienen un
sensor TSL237 al igual que el ampliamente utilizado SQM, pero cubren un rango espectral ligeramente mayor, entre 400-750 nm. En total se han utilizado 18 millones de datos, recogidos en
estos 44 lugares desde el a˜no 2018 y de acceso p´ublico a toda la comunidad. En la primera parte
de este trabajo se han comprobado los errores instrumentales y de calibraci´on que presentan,
0.002 y 0.044 mag/arcsec2
respectivamente, mostrando su consistencia con los publicados en la
literatura. Adem´as, se ha realizado un desarrollo te´orico sencillo para demostrar las ventajas
de la fotometr´ıa diferencial en la reducci´on de la incertidumbre a la hora de comparar datos de
distintos fot´ometro
Grandes espectáculos celestes
Get PDFLos mayores espectáculos que pueden observarse en los cielos de nuestro planeta son los eclipses totales de Sol y de Luna, las Auroras Polares y las Tormentas de Estrellas. Estos espectáculos celestes son el objetivo principal de las expediciones científicas que organiza la asociación Shelios, nacida a mediados de 1998, y que desde su creación ha organizado diversas expediciones a los lugares más remotos de la Tierra, como por ejemplo Turquía, Groenlandia, Teide, Zimbabwe, desierto de Australia, Sudáfrica, Antártida, desierto de Líbia o China.The greatest shows that can be seen in the skies of our planet are a total eclipse of the sun and moon, Polar Aurora and Stara storms. These celestial events are the main target of the scientific expeditions organized Shelios association, born in 1998, and since its creation has organized several expeditions to the remotest parts of Earth, such as Turkey, Greenland, Teide, Zimbabwe, desert of Australia, South Africa, Antarctic, desert of Libya or China
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
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