1,720,959 research outputs found
High Energy High Repetition Rate P-P Lasers.
Get PDFA technique for obtaining of the repetitively pulsed operating regime in high-power wide-aperture lasers is proposed and experimentally realized. In this regime, the laser emits a train of pulses with duration of 100–150 ns and a pulse repetition rate of several tens of kilohertz. The main properties of the pulsed regime are theoretically analyzed and the proposed technique is tested in detail employing a test-bench gas-dynamic laser. The results of the test confirmed the conclusions of the theoretical analysis. The possibility of a repetitively pulsed regime in high-power wide-aperture lasers realization without significant reduction in the average output power is experimentally demonstrated
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
High-power optics: lasers and applications
No full textThis book covers the basics, realization and materials for high power laser systems and high power radiation interaction with matter. The physical and technical fundamentals of high intensity laser optics and adaptive optics and the related physical processes in high intensity laser systems are explained. A main question discussed is: What is power optics? In what way is it different from ordinary optics widely used in cameras, motion-picture projectors, i.e., for everyday use? An undesirable consequence of the thermal deformation of optical elements and surfaces was discovered during studies of the interaction with powerful incident laser radiation. The requirements to the fabrication, performance and quality of optical elements employed within systems for most practical applications are also covered. The high-power laser performance is generally governed by the following: (i) the absorption of incident optical radiation (governed primarily by various absorption mechanisms), (ii) followed by a temperature increase and response governed primarily by thermal properties and (iii) the thermo-optical and thermo-mechanical response of distortion, stress, fracture, etc. All this needs to be understood to design efficient, compact, reliable and useful high power systems for many applications under a variety of operating conditions, pulsed, continuous wave and burst mode of varying duty cycles. The book gives an overview of an important spectrum of related topics like laser resonator configurations, intermetallic optical coatings, heat carriers for high power optics, cellular materials, high-repetition-rate lasers and mono-module disk lasers for high power optics
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
HIGH POWER LASERS AND NEW APPLICATIONS
Get PDFThe process of the development of lightning in the thunderstorm clouds is most studied, in this case the lightning can pass to clouds themselves - intra-cloud lightning, and they can strike into the earth - ground-based lightning. For the appearance of lightning it is necessary that in the relatively small, but not less than the certain critical, the volume of cloud was formed the electric field with the tension, sufficient for the beginning of the electrical discharge ~ of 1 MV/m, and in the substantial part of the cloud there would be a field with the average tension, sufficient for maintaining the discharge ~ of 0,1- 0,2 MV/m. Successful developments of high repetition rate P-P powerful lasers technology and technology of “Impulsar” system make it possible to foresee the possibility of well conducting channels realization with the length up to several ten and hundred of kilometers for the purpose of energy transfer for significant distances, creation of new and promising systems for the mastering of outer space power engineering and motivation for significant contribution to be done on that basis to an essential improvements of the global ecology of our planet
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
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