1,721,542 research outputs found
Ring fiber with flat-top profile for extremely large mode area single mode operation
No full textWe propose novel optical fiber for extremely large mode area with flat-top output beam. Numerical simulations show a record effective-area larger than 11,000µm2 from just a 58µm diameter core with flat-top output in rod-type configuration
Trench-assisted large mode area fiber for high power fiber lasers
No full textHigh power fiber lasers have tremendously contributed to mankind for high power fiber laser applications. Now fiber lasers are being as seen as the potential candidates for next-generation particle accelerators, nuclear transmutation, nuclear waste treatment, astrophysics, and other industrial applications. Unfortunately, non-linear effects are detrimental to the power scaling and pose severe challenges for further power scaling. One route to increase output power level is to increase the effective area of the fundamental mode. However, increasing the core diameter to increase the effective area of the fundamental mode leads to propagation of several modes and deteriorates the output beam quality. Hence, a trade-off exists between large effective area and beam quality for power scaling. Several large mode area fiber designs have been proposed to achieve effective single-mode operation by offering suppression to the higher order modes. However, these fiber designs are difficult to fabricate and suffers from several other problems. We have proposed a novel all-solid "trench assisted" fiber designs, which are easy to fabricate and offer significant enhancement to mode area scaling capability. Fiber having core diameter as large as 90µm has been experimentally demonstrated to guide single mode operation. We believe that these designs offer potential to address the challenges being faced by high power fiber lasers
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
Trench fiber for high power fiber lasers
No full textFiber lasers offer several advantages such as low cost, all-fiberized device, compact device size, and diffraction-limited beam quality over other lasers thanks to their outstanding features. However, fiber lasers are unable to keep these advantages with increasing power level due to non-linear and bend-induced detrimental effects. Novel fiber designs are required to address these challenges. I have been studying all-solid trench fibers, which are all-solid and cylindrical symmetrical fiber and offers good suppression of the higher order modes, making them ideal for mass-scale production for high power fiber lasers. Comparative analysis of trench fibers with other competitive fibers shows better performance for fiber laser applications. In this talk, I will review progress towards trench fibers
Next generation optical fiber designs for power scaling
No full textFiber lasers offer advantages over other lasers thanks to their outstanding features. However, fiber lasers still are unable to fulfil the demand of wide range of application. Fiber lasers are better than other lasers but not best. There are few challenges such as non-linear effects, bend-induced detrimental effects, modal-instability, and increasing cost which do not let fiber lasers to be best. Novel fiber designs are required to fill the gap between better and best
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