1,720,953 research outputs found
Design and fabrication of diffractive elements for the generation of structured light beams
No full textEn este trabajo de tesis se presenta un estudio de haces estructurados estos, en general, son básicamente un tren de ondas electromagnéticas que se propagan con propiedades topológicas y dinámicas peculiares. En particular, los haces adifraccionales son aquellos que poseen una estructura tal que mantiene su perfil de intensidad transversal invariante al propagarse. Los haces estructurados poseen propiedades únicas tales como la transferencia de momento angular orbital que pueden ser empleados en diversas aplicaciones como la manipulación de micropartículas y óptica no lineal. Una familia de haces adifraccionales son los Bessel; éstos haces tienen la propiedad de mantener invariante su perfil transversal de intensidad al propagarse lo que es importante en diversas áreas de investigación como la microscopía de hoja de luz, en la cual es necesario un haz adifraccional que ilumine una muestra. Se presenta un estudio numérico y experimental de las tres formas principales de generación de haces Bessel: anillo en propagación libre, anillo en plano focal anterior de una lente y usando un axicón. Se analiza la estructura de estos y se muestran las diferencias de sus perfiles de intensidad lateral y axial. También se empleó un modulador espacial de luz (SLM, por sus siglas en inglés) para generar la fase que un axicón introduce cuando un haz se propaga a través de éste. Debido a las condiciones inherentes a los métodos experimentales, estos haces presentan variaciones de intensidad axial y para algunas aplicaciones, como el caso de la microscopía, es necesario un perfil de intensidad axial constante. Por lo anterior, se muestra analítica y numéricamente una técnica de modulación axial de haces Bessel. Esta técnica de modulación permite generar perfiles de intensidad diversos siguiendo funciones constantes, crecientes o decrecientes en el eje del haz. Así mismo, este trabajo propone un método para generar elementos ópticos difrangentes (DOE por sus siglas en inglés) de fase con películas fotográficas, esto se realiza mediante un proceso de revelado y blanqueado para generar haces estructurados de manera sencilla y de bajo costo, los cuales pueden sustituir la función de un SLM en aquellos experimentos que requieren uno o varios sistemas de modulación estática.In this thesis work, a study of structured beams is presented these, in general, are basically a train of electromagnetic waves that propagate with peculiar topological and dynamic properties. In particular, non-diffractive beams are those that have a structure that preserve its invariant transverse intensity profile when propagating. Structured beams have unique properties such as orbital angular momentum transfer that can be used in various applications such as microparticle manipulation and nonlinear optics. A family of non-diffractive beams are the Bessel; these beams have the property of keeping their transverse intensity profile invariant as they propagate, which is important in various research areas such as light sheet microscopy, in which a non-diffractional beam is necessary to illuminate a sample. A numerical and experimental study of the three main way of generating Bessel beams is presented: ring in free propagation, ring at the back focal plane of a lens and using an axicon. The structure of these beams is analyzed and the differences in their lateral and axial intensity profiles are shown. A spatial light modulator (SLM) was also used to generate the phase that an axicon introduces when a beam propagates through it. Due to the inherent conditions to the experimental methods, these beams present variations in axial intensity and for some applications, such as the case of microscopy, a constant axial intensity profile is necessary. Therefore, analytically and numerically, a technique for Bessel beam axial modulation is shown. This modulation technique makes it possible to generate different intensity profiles following constant, increasing or decreasing functions at the beam axis. Likewise, this work proposes a method to generate phase diffractive optical elements (DOE) with the use of photographic films, this is done by a developing and bleaching process to generate structured beams in a simple and low-cost way, which can replace the function of an SLM in those experiments that require one or more static modulation systems
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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