1,720,970 research outputs found
Stable two-mode operation of a unidirectional ring laser via controlled spatial hole-burning
No full textUnidirectional ring lasers are commonly used to eliminate spatial hole-burning in the gain medium and hence allow single-axialmode operation of the laser. A number of applications require two (or more) laser outputs, each of which comprises a single frequency, i.e., not accompanied by adjacent modes, and which are stable in frequency and amplitude. Here we report a technique for achieving this, either cw or Q-switched, in a unidirectional ring laser. The technique is based on the presence of a small degree of beam overlap in the gain region of the laser
Laser irradiation of microspheres and shard-like chalcogenide glass particles on a silica surface
No full textThe effect of micro-particle shape on the laser-irradiation-field forward transmitted in a particle-on-a-surface system, and the resulting differences in processing, are reported
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
Ultrafast laser cleaning of museum artifacts
No full textA new method oflaser ablation, having high pulse-rate of the order of MHz, with short ps and sub-ps pulses, has been recently developed at the ANU. As a preliminary test for the short-pulse ablation applied to art conservation for selective removal of unwanted surface layers, we used the ps laser to clean brass samples coated with contaminant layers such as rust, paint and wax. We demonstrated the laser cleaning system with 2nd (λ2=532nm) and 4th (λ4=266nm) harmonics of a Nd: YVO4 ultra-fast laser, combined with a constantvelocity scanning system. Great flexibility in cleaning the surfaces selectively was demonstrated by removal of the wax coating from the black-painted surface without altering the black paint surface sub-structure. Major conservation and restoration challenges were considered where ultrafast laser cleaning might playa vital role.</p
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