1,721,629 research outputs found
Analytically Solvable Model for Polarons Trapping Kinetics in Iron-Doped Lithium Niobate Crystal
No full textThe problem of the kinetic description of a light-induced, small-electron polaron population decay in a lithium niobate crystal (LiNbO3, LN) doped with Fe is considered on the basis of the Marcus-Holstein hopping model for polaron migration and trapping. Starting from the possible reaction channels involving the different polaron species in LN (free polarons, bound polarons and Fe traps), we compose closed kinetic equations for the concentration of reactants and pair distribution functions describing the dynamics of correlations arising during reactions. Analytical solutions are then obtained for the rate constants of a multistage reaction controlled by polaron mobility, for the trapping kinetics of polarons and their lifetimes. The temperature and composition dependences of the observed quantities are analyzed. Finally, our results were used to fit experimental decay kinetics and lifetimes obtained by time-resolved Light Induced Transient Absorption spectroscopy determining poorly known parameters such as the polaron diffusion coefficient and the characteristic lengths of Marcus-Holstein hopping probabilities
Knowledge discovery mediante SAS Enterprise Miner nelle telefonate registrate da un Call Center
No full textProteste, richieste e proposte. Creazione di un sistema di ascolto dei clienti di APS-Ambiente mediante analisi delle telefonate
No full textNella nota si introduce e si applica una metodologia per l’analisi di informazioni registrate “in chiaro” dal Call Center di un’azienda che eroga servizi al pubblico. L’applicazione riguarda le registrazioni “in chiaro” delle telefonate inerenti al servizio di mobilità urbana erogato nel 2002 dall’APS – Azienda Padova Servizi, già municipalizzata del Comune di Padova. Le telefonate sono esaminate nel loro contenuto, “svelandone il significato” (knowledge discovery), con l’obiettivo sia di attivare un servizio di risposta automatica al reclamo, o alla richiesta di servizio segnalata, sia di trarne indicazioni di tipo statistico per rappresentare la qualità del servizio. Per trasformare i testi delle telefonate in conoscenza trattabile con il metodo statistico si utilizza il package SAS Enterprise Miner e poi si effettuano vari altri passaggi per la ricostruzione efficiente del loro significat
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
Polaron trapping and migration in iron-doped lithium niobate
Full text linkPhotoinduced charge transport in lithium niobate for standard illumination, composition and temperature conditions occurs by means of small polaron hopping either on regular or defective lattice sites. Starting from Marcus-Holstein’s theory for polaron hopping frequency we draw a quantitative picture illustrating two underlying microscopic mechanisms besides experimental observations, namely direct trapping and migration-accelerated polaron trapping transport. Our observations will be referred to the typical outcomes of transient light induced absorption measurements, where the kinetics of a polaron population generated by a laser pulse then decaying towards deep trap sites is measured. Our results help to rationalize the observations beyond simple phenomenological models and may serve as a guide to design the material according to the desired specifications
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
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