1,720,974 research outputs found
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
Spectral and electro-optic characterisation of UV-written waveguides in LiNbO<sub>3</sub>
No full textDomain patterning by strongly absorbed UV light in LiNb0<sub>3</sub> crystals
No full textShort-term exposure of the surface of lithium niobate crystals to focused strongly absorbed UV light leads to persistent inhibition of subsequent ferroelectric domain reversal on the +z face at the irradiated site. The same procedure can be adopted to directly generate domains on the non-polar faces. Investigation of the UV-irradiated tracks by piezoresponse force microscopy reveals the connection between the inhibited domains on the +z face and local lithium depletion, while thermoelectric fields can be invoked to generate the domains on the non-polar faces
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
UV laser-induced poling inhibition produces bulk domains in MgO-doped lithium niobate crystals
No full textLithium niobate (LiNbO3) crystals have been widely used in many nonlinear optical processes such as frequency conversion by quasi-phase matching (QPM). Frequency conversion requires high intensity laser light, which may induce optical damage to the crystal resulting in the distortion of the optical beam. Adequate magnesium oxide (MgO) doping in LiNbO3 can significantly reduced the optical damage [1]. QPM requires periodic domain inversion of the crystal’s spontaneous polarization Ps at submicron-to-few microns periods. A common method used for domain patterning of LiNbO3 is electric field poling (EFP). While this method is an effective way to achieve domain patterning in congruent LiNbO3, it is not always successful when applied to MgO-doped LiNbO3, due to a pronounced sideways domain spreading [2]. In this contribution, we report on the fabrication of bulk domain structures in MgO doped LiNbO3, which are pre-defined by a spatial modulation of the lithium (Li) concentration induced by strongly absorbed UV laser light irradiation
Pyroelectric field assisted ion migration induced by ultraviolet laser irradiation and its impact on ferroelectric domain inversion in lithium niobate crystals
No full textThe impact of UV laser irradiation on the distribution of lithium ions in ferroelectric lithium niobate single crystals has been numerically modelled. Strongly absorbed UV radiation at wavelengths of 244–305nm produces steep temperature gradients which cause lithium ions to migrate and result in a local variation of the lithium concentration. In addition to the diffusion, here the pyroelectric effect is also taken into account which predicts a complex distribution of lithium concentration along the c-axis of the crystal: two separated lithium deficient regions on the surface and in depth. The modelling on the local lithium concentration and the subsequent variation of the coercive field are used to explain experimental results on the domain inversion of such UV treated lithium niobate crystals
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
UV laser assisted domain engineering of lithium niobate
No full textLithium niobate is an important optical ferroelectric crystal which is used widely by the photonics industry mainly due to its electro-optic and non-linear optical properties. High quality crystal wafers are readily available commercially in different stoichiometries and with various dopands as required by the relevant applications
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