1,720,982 research outputs found
Il sensore di fronte d'onda Ingot dedicato a sorgenti estese astronomiche
No full textL'ottica Adattiva ha l'obiettivo di migliorare le prestazioni di un sistema ottico quale un telescopio, cercando di raggiungere, almeno in principio, il limite di diffrazione dello strumento. Questo risultato viene si ottiene misurando le aberrazioni che un fronte d'onda che proviene da un oggetto astronomico subisce quando attraversa gli strati turbolenti dell'atmosfera. Un sistema di ottica adattiva per funzionare ha bisogno di un oggetto di riferimento in cielo, da utilizzare per acquisire quali siano le condizioni turbolente in atmosfera, e compensando poi con una correzione complementare al fronde d'onda aberrato tramite uno specchio deformabile. In un sistema di Ottica Adattiva classico, la stella guida deve trovare all'interno di un certo angolo solido, noto come "Angolo Isoplanatico", insieme all'oggetto scientifico che si vuole osservare. Questa richiesta, come e' facile immaginare limita notevolmente la porzione di cielo che si possa osservare. Per ovviare a questo inconveniente e' possibile usare come riferimento in cielo, quelle che sono te come Stelle Guida Laser (LGS). Questo strumento, rende possibile attraverso un lanciatore laser di riprodurre in cielo, all'interno dell'angolo isoplanatico una stella di riferimento. Sfortunatamente gli LGS, non riescono a riprodurre le medesime caratteristiche di una stella naturale. Gli LGS non sono approssimabili ad un oggetto puntiforme, quale una stella naturale, ma sono anzi estesi in uno spazio tridimensionale. I classici sensori di fronte d'onda, quale ad esempio lo Shack-Hartmann possono avere delle difficolta' a sensare un oggetto esteso, perdendo quindi informazioni preziose per la ricostruzione. In questo contesto nasce l'idea di un nuovo sensore di fronte d'onda di piano di pupilla, che chiamiamo INGOT, e che almeno in prima approssimazione e' in grado di usare tutta la geometria della LGS senza perdite di segnale e informazioni. In questo lavoro, riportiamo una descrizione completa del sensore di fronte d'onda INGOT, che e' stato progettato tenendo in riferimento le caratteristiche dello ELT. Abbiamo sviluppato il disegno ottico del sensore, in due varianti, e testato l'INGOT presso un banco ottico gia' esistente in grado di riprodurro in sistema di ottica adattiva quasi reale, ed in aggiunta progettato un banco di prova presso l'Osservatorio Astronomico dove poter testare in autonomia le prestazioni di questo nuovo sensore di fronte d'onda.Adaptive Optics aims to improve the performance of an optical system such as a telescope, providing at least in principle diffraction-limited imaging. This result is obtained, measuring the wavefront aberration imposed by the earth atmosphere using of suitably bright reference star and compensating for these aberrations through a deformable mirror. In a classical adaptive optic, such reference must be located close to the scientific target, within the so-called Isoplanatic Angle. This requirement reduces dramatically the fraction of the sky that can be efficiently corrected with this technique. A possible solution to this problem is to create an artificial reference in the sky, the so-called Sodium Laser Guide Star (LGS). Unlikely, The Sodium LGS is not a point-like source in the sky, as is valid for the natural guide stars, but more an elongated object in a 3D volume, when launched from the side of a large (or extremely large) telescope. The Sodium LGS nature gave birth to the idea of a new pupil plane wavefront sensor that can be deployed in a similar 3D manner, that can cope with the natural elongation of the LGS. This new device is called Ingot Wavefront Sensor.
In this work, we propose a full description of the Ingot Wavefront Sensor, which has been designed taking into account the characteristics of the European-Extremely Large Telescope (ELT). We performed the optical design, and, both simulations and laboratory tests to investigate which are the performances of the Ingot Wavefront Sensor
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
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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