1,721,123 research outputs found
Number decomposition, algebraic equations and number derivatives
No full textThe authors use the point of view of the algebraic equations to study problems associated with number decomposition and number derivative
Relativistic harmonic oscillator, the associated equations of motion, and algebraic integration methods
No full textWe consider the relativistic generalization of the harmonic oscillator problem by addressing different questions regarding its classical aspects. We treat the problem using the formalism of Hamiltonian mechanics. A Lie algebraic technique is used to solve the associated Liouville equations, yielding the phase-space evolution of an ensemble of relativistic particles, subject to a "harmonic" potential. The nonharmonic distortion of the spatial and momentum distributions due to the intrinsic nonlinear nature of the relativistic contributions is discussed. We analyze the relativistic dynamics induced by two types of Hamiltonian, which can be ascribed to those of harmonic oscillator type. Finally, we briefly discuss the quantum aspects of the problem by considering possible strategies for the solution of the associated Salpeter equation. © 2013 American Physical Society
Electron beam transverse longitudinal dynamics for SASE FEL operation
No full textWe present a procedure based on the combined use of analytical and numerical tools, useful for understanding the relative interplay between the various components of a free electron laser (FEL) self-amplified spontaneous emission (SASE) device. We take as reference case the Sorgente Pulsata Auto-amplificata di Radiazione Coerente (SPARC) experiment to analyze how electron beam transverse matching conditions affect the lasing conditions itself and discuss the possibility of implementing new configurations. In particular we show that the procedure can be extended to account for the effect of an on line inserted cavity, with the role of inducing a transverse longitudinal correlation allowing a transfer of the longitudinal and transverse emittance. We discuss the associated benefit on the FEL operation, with particular reference to the nonlinear harmonic generation. The possibility of completing the tool with regards to the beam degradation effects due to CSR is briefly accounted for. © 1965-2012 IEEE
Spectral and intensity diagnostics of the SPARC free-electron-laser
No full textWe describe the instrument that is used for the spectral and intensity diagnostics of the SPARC free-electron-laser facility in Frascati (Italy). The instrument hosts three interchangeable gratings to cover the 50-550 nm spectral region and an EUV-enhanced CCD detector to acquire the spectrum in the single-shot operation with high resolution. The spectral resolution is in the range 2000-10000. The design, characterization and calibration of the instrument are presented and some results obtained at SPARC are discussed
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
- …
