1,721,168 research outputs found
Nonlinear optical components and systems for quantum technologies and communications
No full textThis thesis describes a series of experimental research primarily revolving around the applications of periodically poled lithium niobate (PPLN). Initially, a set of work is described regarding the fabrication and characterisation of PPLN ridge waveguides designed for frequency doubling into the blue/UV range. These waveguides are fabricated via diffusion of zinc into the crystal structure. A precision dicing process creates the sidewall definition for modal confinement and also optical facet preparation. Preliminary results with the most efficient waveguide fabricated produced a maximum conversion efficiency of 6.9%/W in a 14 mm-long device, generating 391 nm light. This was performed with a novel near-IR VECSEL; designed and built as part of a collaboration with the research undertaken in this thesis to investigate new routes for miniaturised UV sources. The development of a non-destructive route to characterise the physical dimensions of a ridge waveguide for nonlinear applications is also presented. This presented methodology uses white light interferometry and standard edge recognition algorithms to determine the waveguide width profile. In combination with numerical propagation constant data for these waveguides, a numerical phasematching spectra can be calculated. A comparison to the experimental phasematching spectra of the second-harmonic generation process enables the discrimination between issues in the fabrication processes. Using bulk PPLN, a final application is presented for communications using mid-IR radiation and all commercial components. This configuration involves the use of differencefrequency generation followed by sum-frequency generation to create the transmitter and receiver systems, respectively. This enables final detection of 809 nm light (firmly within the silicon absorption band). Bit error ratios as low as 10−7 from single-pass nonlinear conversion for both systems without the need for an additional optical amplifier in the receiver. Finally, the propagation of relative intensity noise within the system as the source lasers propagate through a two step nonlinear conversion is presented and discussed within
PhD thesis "Nonlinear optical components and systems "
No full textDataset associated to PhD thesis by Alan C. Gray with complete title "Nonlinear optical components and systems for quantum technologies and communications"</span
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
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