1,721,165 research outputs found
From 8(m) to 8(mm): wavefront sensing from cosmological to human scales
Full text linkThe largest Field of View Wavefront Sensor ever realized, namely one of the Ground-Layer Wavefront Sensors on-board LINC-NIRVANA, the Fizeau interferometric focal station of the Large Binocular Telescope, has been completed in the Astronomical Observatory of Padova.
This Thesis includes a detailed description of such a sensor, starting from the optical concepts behind it, going through the definition of the alignment procedures ensuring the compliance of each sub-system with its optical tolerances, and concluding with the complete set of results of the system verification as a whole.
At the same time, a similar wavefront sensor, but with a single line of sight, has been realized as a laboratory demonstrator for a system to perform the quality test of artificial Intra-Ocular Lenses (IOL), used in the transplant of human damaged crystalline lens. Such a demonstrator has been designed, procured, aligned and fully characterized, with the goal to retrieve high resolution aberrations of the IOL with a compact, easy to procure and user-friendly system.Questa Tesi descrive il sensore di turbolenza di terra (Ground-layer Wavefront Sensor, GWS) di LINC-NIRVANA, l'interferometro di Fizeau che si sta realizzando fra Italia e Germania al fine di sfruttare appieno le potenzialita' della configurazione interferometrica del Large Binocular Telescope. Il GWS, interamente assemblato ed allineato presso l'Osservatorio Astronomico di Padova, e' il sensore di fronte d'onda con il piu' ampio campo di vista mai realizzato finora (6' di diametro), all'interno del quale possono essere selezionate fino a 12 stelle di guida naturali, ai fini della misura della turbolenza atmosferica di bassa quota.
In questo elaborato e' inclusa una descrizione dettagliata di tale sensore, partendo dai concetti di ottica che ne costituiscono le fondamenta, per passare allo studio delle procedure per l'allineamento dei diversi sottosistemi, che ne assicurano la conformita' alle tolleranze calcolate in fase di disegno ottico, fino a concludere con l'analisi dei risultati ottenuti dalle verifiche effettuate sul sensore.
Contemporaneamente, si e' proceduto alla realizzazione di un secondo sensore di fronte d'onda, basato sul medesimo concetto ottico ma limitato ad un'unica linea di vista. Tale sensore e' il prototipo di un sistema ottico per la misura della qualita' ottica di lenti intraoculari artificiali (Intra-Ocular Lens, IOL) da trapianto, utilizzate per la sostituzione del cristallino umano nelle operazioni chirurgiche per la correzione della cataratta. Tale prototipo e' stato disegnato, realizzato, allineato e completamente caratterizzato, al fine di misurare le aberrazioni introdotte dalle IOL con un sistema che sia il piu' possibile compatto, di semplice utilizzo e prodotto con componenti di facile reperibilita' e limitato costo
PLATO: Telescope Optical Units Design Description - PDR
No full textPLATO (Planetary Transits and Oscillations of stars) is the Cosmic Vision Programme M3 mission selected by the Science Programme Committee (SPC) for launch in 2026. The main goal of the PLATO mission is to detect terrestrial exoplanets in the habitable zone of solar-type stars and to characterise their bulk properties
GMCAO for E-ELT: A feasibility study
Full text linkIn this paper, we discuss the feasibility and the performance assessment of a possible MCAO system for E-ELT, basedon the novel concept of Global MCAO, which takes advantage of a very wide technical FoV to perform adaptive opticscorrection using only natural guide stars, with the aim to increase the sky coverage. The technique envisages thedefinition of Virtual-DMs, as tools for the global reconstruction. This investigation has been carried out during afeasibility study we performed for ESO, in which we combined computations, simulations and literature. The aim of thisanalysis is to identify and review the main parameters and the technical issues, which would act as error sources in a realGMCAO system, evaluating their contribution to the overall performance. The study involves both issues related to thePyramid WFS in general, and to the GMCAO case in particular, including the wavelength and FoV size selection, thenumber of guide stars and reconstructed Virtual-DMs, and actual components parameters
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
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