1,720,966 research outputs found
Strong Interference Effects in Surface Brillouin Scattering from a Supported Transparent Film
No full textA measurement of surface Brillouin scattering from a 2250-Å film of silica grown on (001) silicon is presented. The spectrum shows many structures related to Rayleigh, Sezawa, and Lamb waves. We calculate the Brillouin cross section taking the ripple and the elasto-optic coupling mechanisms into account in the two media. Both the mechanisms are found to be important and there is evidence of strong interference effects between the ripple and the elasto-optic contributions to the scattering amplitude
Brillouin Scattering from Surface Phonons in Al-Coated Semiconductors
No full textBrillouin spectra from thermally excited surface acoustic phonons in GaAs and Si surfaces coated with a thin Al film are presented. The measurements show features different from the Al and the semiconductor surfaces. We are able to give a theoretical explanation of the experimental results in terms of the coupling between the normal modes of the film and of the substrate
Brillouin Scattering from Interface Acoustic Phonons
No full textWe present measurements of the Brillouin cross-section for a metallic thin film (aluminium and gold) on a silicon substrate, obtained by using a tandem multipass interferometer. The results for the aluminium coating are explained in terms of scattering from the surface corrugation due to the thermally excited acoustic phonons. In the case of gold we find an appeciable contribution from the elastooptic coupling in the film. In both cases the interface modes are experimentally resolved and theoretically explained
Ripple and Elasto-Optic Coupling in Surface Brillouin Scattering from a Gold Thin Film
No full textThe measured Brillouin spectrum of a thin film of gold deposited on silicon shows surface and interface waves. A calculation of the cross-section gives evidence of a remarkable elastooptic coupling in the film, in addition to the ripple contribution characteristic of scattering from metal surfaces
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
Surface and Interface Acoustic Phonons in Al-Coated Silicon
No full textMeasurements are presented of the Brillouin cross-section for a thin aluminium film on a silicon substrate measured using a tandem multipass interferometer. The measured spectra are compared with the cross-section computed by assuming that the light is inelasically scattered from surface corrugation due to the thermally excited acoustic phonons. By varying the thicness of the aluminium film we observe different spectral features such as the modified Rayleigh mode, the Sezawa modes and tho continuum os states of the sbstrate. The limiting case of a thick coating is also discussed
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
- …
