1,720,954 research outputs found
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
Laser a Cascata Quantica in quasicristalli fotonici bidimensionali
No full textDurante l’ultimo decennio è stata svolta un’intensa attività di ricerca volta a generare sorgenti luminose in grado di emettere radiazione nella regione dello spettro elettromagnetico compresa tra i 30µm e i 1000µm di lunghezza d’onda (regione THz). A causa della bassa energia del fotone (1–40meV) l’implementazione di sorgenti laser a semiconduttore operanti all’interno della regione del THz risulta particolarmente complicata. Progressi ragguardevoli sono stati ottenuti a seguito della realizzazione di sorgenti laser a cascata quantica (QCL) operanti nella regione del THz. I livelli energetici degli stati che sostengono l’emissione di radiazione luminosa all’interno di un QCL sono sostanzialmente indipendenti dal band-gap elettronico dei materiali semiconduttori utilizzati, ma sono determinati dallo spessore degli strati che compongono l’eterostruttura. Questa particolare progettazione permette di ingegnerizzare opportunamente le transizioni intersottobanda, consentendo ai QCL di coprire l’intera regione dello spettro elettromagnetico dal medio al lontano infrarosso (dai 3µm ai 300µm di lunghezza d’onda). Nei QCL operanti nella regione del THz (QCL THz), la guida d’onda per la radiazione elettromagnetica è realizzata (nella maggior parte dei casi) inserendo la eterostruttura tra uno strato metallico (nella parte superiore) ed uno strato inferiore ad alto drogaggio (guide d’onda SISP, Semi Insulating Surface Plasmon) oppure tra due strati metallici (guide d’onda MM, Metal Metal). Il fascio della radiazione uscente risulta avere tipicamente una elevata divergenza ottica, a causa delle strutture geometriche stesse trapezoidali dei dispositivi. Per ovviare a questo problema sono stati sviluppati laser QCL con emissione superficiale, in cui un pattern opportuno di scatteratori è inciso sullo strato di metallizzazione superiore del dispositivo. In particolare, un pattern periodico di scatteratori agisce per la radiazione elettromagnetica all’interno della eterostruttura come un cristallo fotonico (PC). Il campo elettrico all’interno di un QCL risulta essere orientato nella direzione di crescita degli strati: questo rende complicata la progettazione di un QCL THz con emissione superficiale. In generale infatti, nei QCL THz la radiazione estratta non risulta ben collimata e con intensità uniforme, aspetto rilevante per diversi tipi di applicazioni tecnologiche. Inoltre, per motivi di simmetria, il modo della radiazione elettromagnetica su cui il laser opera, presenta una bassa efficienza radiativa.
Il presente lavoro di tesi verte sullo studio teorico e sulla realizzazione sperimentale di dispositivi QCL con emissione superficiale basati su quasicristalli fotonici (PQC); lo studio teorico effettuato su questo tipo di strutture ha evidenziato l’esistenza di un modo “quasi-stazionario”, con un buon fattore di qualità ed un un profilo di emissione uniforme e contenuto all’interno di un cono con apertura di circa 5 gradi. I PQC a differenza dei PC, non godono di alcuna simmetria traslazionale, ma sono caratterizzati comunque dall’essere strutture ordinate. Il PQC usato in questo lavoro è stato realizzato a partire da una tessellatura di Penrose tipo P2, sostituendo ai vertici dei triangoli di Robinson, degli scatteratori circolari di raggio opportuno. A causa dell’assenza di simmetria traslazionale si sono effettuati i calcoli su una struttura limitata e bidimensionale utilizzando il Metodo dell’Indice di rifrazione Efficace (EIM), con un solutore numerico FD-FEM (Metodo agli Elementi Finiti nel Dominio della Frequenza). Le stime numeriche ottenute implementando i metodi citati su dispositivi THz QCL operanti a 3THz hanno evidenziato la possibilità di ingegnerizzare strutture QCL quasiperiodiche in cui l’emissione di radiazione avviene in maniera uniforme e ben collimata.
I primi test di fabbricazione e caratterizzazione di dispositivi QCL THz con struttura aperiodica di tipo Penrose style hanno esibito un regime di trasporto quantistico adeguato alle strutture attive di riferimento, potenziale per lo studio delle proprietà ottiche dei suddetti emettitori
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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