1,720,956 research outputs found
Fluid Jet Polishing
No full textThe goal of this thesis research was to investigate the possibilities and limitations of the Fluid Jet Polishing (FJP) technique. FJP is a new optical fabrication technique that is capable of making shape corrections and reducing the surface roughness of glass and other materials. The principle of operation is that a mixture of water and abrasives (the slurry) is sprayed on the surface at a low pressure. The experimental setup has been described in detail in this thesis. The advantage of FJP over existing techniques is the fact that it can both grind and polish and that areas can be reached that are not accessible with existing techniques. Measuring techniques are important in order to judge the effect of a shaping or polishing technique. Therefore, special attention has been given to in-process measurement techniques. One of the described techniques is iTIRM (intensity-detecting Total Internal Reflection Microscopy). iTIRM can be used for in-process monitoring of the total surface quality, which includes the surface roughness, sub-surface damage, and scratches in the surface. The iTIRM technique can measure the surface quality of both very rough and very smooth surfaces (total range from some m to 0.8 nm). Surface roughness improvements of 0.1 nm rms can be detected with this technique. The surface shape can also be measured in-process. A measurement technique is shown that is based on the interference of an object and a reference beam that both reflect from the inside of the surface to be measured at the total internal reflection condition. The information on the surface shape is obtained from the reflected beams via a temporal phase unwrapping method. Unwrapping problems are avoided by comparing successive images instead of comparing any image to the first image. In order to gain a better understanding of the FJP technique several models have been described. Some have been found in literature, others have been developed especially for FJP. The formation of cracks has been described with Lawn's model [law75]. The theoretical pressure distribution in the slurry has been described by the numerical calculation developed by Rehbinder [reh76] and Leach and Walker [lea66]. Based on the pressure distribution as developed by Rehbinder, a prediction of the stationary footprint that occurs in the case of a cylindrical nozzle has been computed for the FJP case. Based on a general description of flows by Milne-Thomson [mil77] the velocity of the flow in the case of FJP has been computed, the trajectory of the particles in the flow has been derived, and the position and velocity at the moment of impact with the surface has been determined. The interaction between the abrasive particle and the surface of impact has been considered at the microscopic level by a description of three different analysis: first of all, the finite element approach as developed by Woytowitz and co-workers [woy99], secondly, a very simple estimation derived in this thesis, based on the material removal as observed with a SEM, and finally, Finnie's estimation [fin58] which describes the material removal of a single impacting particle in air as a function of the angle of impact. Since the material removal should be known over an area larger than the footprint of the nozzle an analysis has been described that explains the material removal in the case of scanning or rotation of the work piece with respect to the nozzle. The shape inaccuracies that can occur in the center of a work piece have been described as well. In order to get a better understanding of the resulting surface roughness a model has been developed that predicts the roughness as a function of the initial surface and some process parameters. This model is based on the random impacts of particles on a surface. The effect of various process parameters on the material removal and the surface roughness has been investigated experimentally as well. These parameters include the slurry parameters such as the number of particles, the type and size of the particles, the particle velocity, and several process parameters such as the processing time, the processed material, the impact angle and the nozzle type. We also report on some relevant experiments that we carried out with the FJP setup, like the reproducibility of the process, the homogeneity of a translating spot, the degradation of the slurry over time, the formation and removal of mid-spatial frequencies, and the detection whether the FJP process is ductile or brittle. The shaping capabilities have been shown, by prescribing a surface and attempting to produce this surface shape. Some roughness experiments have been described, showing a.o. the roughness as a function of time, the effect of the initial roughness on the final roughness, the roughness as a function of the pressure, and the lowest roughness that could be obtained. Conclusions are drawn and two alternative setups are suggested. The conclusions concerning the shaping accuracy and the roughness reduction are that shape corrections are limited to an accuracy of 4% in depth in the setup that is used at this moment. The material removal is accurate to 1% when the effects of the pressure fluctuation and of the abrasive particle diameter average out by processing the surface several times. A roughness reduction on BK7 can be obtained in a one-step process (one slurry, one fixed pressure during the entire process) from a fine-ground surface (average roughness R a = 300 nm) to R a = 3.6 nm. The first suggestion for comparable techniques that has been described is chemically assisted FJP, the second alternative is a close contact version of FJP. Some initial experiments that have been conducted with this second alternative have been described as well. Fluid Jet Polishing is a new technique that is well suited for making shape alterations to glass surfaces, and for reducing the surface roughness of glasses to a few nanometers. Especially harder to reach areas can ideally be treated with FJP.Applied Science
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
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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