1,721,046 research outputs found
Pulsed laser deposition of thin film magneto-optic materials and lasing waveguides
No full textThe aim of this thesis was to study and improve the properties of optical materials deposited by the film growth technique called Pulsed Laser Deposition (PLD), a relatively fast, inexpensive and versatile deposition method using a laser to ablate a target and transfer material on top of a substrate. The materials of interest were titanium-doped sapphire (Ti:sapphire or Ti:Al2O3) for fabrication of compact, low-loss, high-efficiency and high-power waveguide lasers, which could be also operated in ultra-fast highrepetition-rate pulsed mode, and magneto-optic garnets, e.g. yttrium iron garnet (YIG, Y3Fe5O12), for fabrication of low-loss magneto-optic and microwave devices with high performance.Deposition conditions were optimised for Ti:sapphire and YIG film growth and a multilaser multi-target PLD system (multi-PLD) was used to tune the composition of YIG film by co-ablation of two different targets (e.g. YIG and Y2O3 or Fe2O3 or Bi2O3 or CeO2). Ti:sapphire waveguides were fabricated and their optical performances (e.g. transmission losses and lasing characteristics) measured. A study of the effect of compositional variation on structural, optical and magnetic properties of magneto optic garnet films was carried out and it demonstrated the feasibility of the multi-PLD approach, which was shown to be capable to grow complex crystalline oxide materials, such as YIG and yttrium ferrite (YFeO3), from ablation of their precursor targets (Y2O3 or Fe2O3) with different ablation rates and deposition of material on different substrates and, in particular, yttrium aluminium garnet (YAG or Y3Al5O12) and sapphire (Al2O3). Some YIG films were also used to demonstrate Laser-Induced Forward Transfer (LIFT) of crystalline materials and the applicability of PLD-grown YIG films in novel meta-material microwave devices
ARCHITETTURA SISTEMICA. MATERIALI ED ELEMENTI COSTRUTTIVI (III EDIZIONE AGGIORNATA E CON ILLUSTRAZIONI A COLORI)
Full text linkQuesta terza edizione di Architettura Sistemica, rispetto alla seconda del 2010 che introduceva illustrazioni a colore, poggia ancora sulla struttura del testo elaborato nella prima edizione e sulla stessa veste grafica. Ma abbiamo constatato che talune questioni, anche se di uso limitato, erano state tra- lasciate e che, al contrario, altri concetti ed espressioni della cultura tecnologica in questi ultimi anni hanno assunto un’in- discussa rilevanza.
Pertanto l’edizione attuale si propone di integrare e ag- giornare il testo con tre questioni particolari. La prima si riferisce ai materiali di nuova generazione, riferibili alle nanoscienze e alle nanotecnologie, che stanno provocando un salto innovativo nel campo dei materiali, utilizzati in molti settori manifatturieri, e dei servizi; in particolare sono specificati i significati dei termini e sono descritti i diversi processi per la produzione dei materiali nanostrut- turati, le proprietà e i tipi che li caratterizzano, le applica- zioni nei diversi settori e, infine, i prodotti nanostrutturati che sono impiegati in architettura
Nanotechnology for Conservation: The Case of Archaeological Sites
No full textL'articolo espone le principali problematiche conservative dei siti archeologici e analizza la possibilità di applicazione dei nuovi nanomateriali, derivanti dalle nanotecnologie come soluzioni innovative per affrontare problematiche irrisolte con i prodotti tradizionali.The article presents the main conservation problems of archaeological sites and analyzes the possibility of new nanomaterials application, deriving from nanotechnologies as innovative solutions to address unresolved problems with traditional products
STUDIO MINERALOGICO-PETROGRAFICO E PROBLEMI CONSERVATIVI
No full textIl capitolo illustra le risultanze dello studio delle problematiche conservative e della caratterizzazione mineralogico petrografica dei materiali lapidei del teatro ellenistico di Morgantina (Enna). Tale attività è stata finalizzata alla definizione dell'intervento conservativo del teatro.The chapter illustrates the results of the study of conservation issues and petrographic mineralogical characterization of the stone materials of the Hellenistic theater of Morgantina (Enna). This activity was aimed at defining the conservative intervention of the theatre
Low-loss Ti:sapphire waveguides fabricated by pulsed laser deposition
No full textWe report the fabrication and characterisation of Ti:sapphire films epitaxially grown on c-cut sapphire substrates by pulsed laser deposition (PLD). Deposition conditions have been studied extensively and optimised in order to produce high-performance optical waveguides. In particular we have studied the effects of different values of oxygen pressure, background gases and substrate temperature on the resultant surface roughness, composition, crystallinity, fluorescence and waveguide losses. For instance we found that Ti:sapphire films deposited in Ar feature higher fluorescence than those grown in O2 and N2 (see Figure 1) under the same deposition conditions: laser fluence F ~ 3.3 J/cm2, laser repetition rate f = 20 Hz, substrate temperature T ~ 1050°C, gas pressure P ~ 2.10-3 mbar, target-substrate distance d = 4 cm
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
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