1,720,953 research outputs found
Design and fabrication of integrated optical couplers for information processing applications
No full textEn este trabajo se estudian acopladores ópticos integrados de Nitruro de Silicio (S i3N4) sobre dióxido de Silicio (S iO2) y en un sustrato de Silicio (S i) que pueden ser utilizados como divisores de potencia y separadores o mezcladores de frecuencia. Se desarrollan módulos de diseño utilizando herramientas de cómputo basadas en diferencias finitas y con estos, se estudia el efecto de las dimensiones geométricas de las guías, la longitud de onda y el contraste dieléctrico en los diseños de los acopladores. Los resultados de estos estudios muestran que son necesarias dimensiones submicrométricas de las guías de onda y la separación entre las guías, para que los acopladores puedan ser empleados en aplicaciones de fotónica integrada. Con ayuda de los módulos de diseño, se definen condiciones geométricas para las cuales las guías de onda son monomodales, bimodales y multimodales. Además, se estudian las pérdidas de potencia por propagación debidas a la curvatura de los brazos del acoplador y al acoplamiento entre modos espaciales y de polarización. De este estudio, se demuestra que se pueden escoger radios de curvatura de los brazos, para los cuales, se garantice que el modo de interés llegue a la parte central del acoplador y al mismo tiempo se generen bajas pérdidas de potencia. Adicionalmente, se diseñan dos divisores de potencia 50 : 50 para una longitud de onda de 0.826 µm y un separador (mezclador) de frecuencias para las longitudes de onda 0.826 µm y 1.550 µm y se demuestra su funcionamiento propagando luz por los acopladores con ayuda de paqueterías de Lumerical. En cuanto a la parte experimental, se desarrolla una metodología que permite fabricar estructuras de guías de onda con dimensiones submicrométricas en el Laboratorio Nacional de Nanofabricación (LaNNaFab) del Centro de Nanociencias y Nanofabricación (CNyN) que pertenece a la Universidad Nacional Autónoma de México (UNAM). Por último, se fabrican acopladores ópticos integrados en fotoresina y se caracteriza su morfología con microscopía óptica y microscopía de fuerza atómica (AFM por sus siglas en inglés). Esta caracterización muestra, que los acopladores fabricados, tienen dimensiones submicrométricas.In this work, we study integrated optical couplers of Silicon Nitride (S i3N4) on silicon dioxide (S iO2) and on a Silicon substrate (S i) that can be used as power splitters and frequency demultiplexor o multiplexor. Design modules are developed using finite difference-based computational tools and with these, the effect of guide geometrical dimensions, wavelength, and dielectric contrast on the coupler designs are studied. The results of these studies show that submicrometer dimensions of the waveguides and the spacing between the waveguides are necessary for couplers to be used in integrated photonics applications. With the help of the design modules, geometrical conditions are defined for which the waveguides are single-mode, bimode, and multimode. In addition, propagation power losses due to the curvature of the coupler arms and the coupling between spatial and polarization modes are studied. From this study, it is shown that it is possible to choose arm curvature radii that guarantee that the mode of interest reaches the central part of the coupler and at the same time generates low power losses. Additionally, two 50 : 50 power splitters are designed at a 0.826 µm wavelength and a frequency demultiplexor (multiplexor) for 0.826 µm and 1.555 µm wavelengths and their operation is demonstrated by propagating light through the couplers with the help of Lumerical packages. As for the experimental part, a methodology is developed to fabricate waveguide structures with submicrometer dimensions in the Laboratorio Nacional de Nanofabricación (LaNNaFab) of the Centro de Nanociencias y Nanofabricación (CNyN) that belongs to the Universidad Nacional Autónoma de México (UNAM). Finally, photoresistintegrated optical couplers are fabricated and their morphology is characterized by optical microscopy and Atomic Force Microscopy (AFM). This characterization shows that the fabricated couplers have submicrometer dimensions
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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