1,720,969 research outputs found
Red-emitting LiLa(2)O(2)BO(3): Sm(3+),Eu(3+) phosphor for near-ultraviolet light-emitting diodes-based solid-state lighting
No full textA red-emitting LiLa(2)O(2)BO(3):Sm(3+),Eu(3+) phosphor has been synthesized and characterized optically for white light-emitting diodes (LEDs). Because the oxyborate group (O(2)BO(3)(-7)) can contain high Eu(3+) concentration without concentration quenching, LiLa(2)O(2)BO(3) is a suitable host material for red-emitting phosphor for near-ultraviolet (n-UV) LEDs. When LiLa(2)O(2)BO(3):Eu(3+) was co-doped with Sm(3+), emission intensity of Eu(3+) was enhanced by similar to 30% than that of the sample without Sm(3+) owing to the energy transfer from Sm(3+) to Eu(3+). This energy transfer was confirmed by faster decay times of Sm(3+) as energy donors. LiLa(2)O(2)BO(3):Sm(3+),Eu(3+) showed a relative brightness of 334.7% of that of Y(2)O(2)S:Eu(3+), commercial red-emitting phosphor for n-UV LEDs. (C) 2008 The Electrochemical Society
Origin of the discrepancy between photoluminescence brightness of TAG:Ce and electroluminescence brightness of TAG:Ce-based white LED expected from phosphor brightness
No full textA yellow-emitting Tb3Al5O12: Ce3+ (TAG:Ce) phosphor was coated on blue light-emitting diodes (LEDs) to obtain white LEDs (WLEDs). Since TAG:Ce showed 90% of the brightness of Y3Al50O12: Ce3+ (YAG:Ce), it was expected that TAG:Ce-based WLEDs showed 90% of brightness of YAG:Ce-based ones. However, the TAG:Ce-based WLED showed 74% of the brightness of YAG:Ce-based one. Considering the density and size of the phosphors, the higher density and larger size of TAG:Ce induced a great deal of sedimentation of TAG:Ce particles in an epoxy resin. It is believed that this is one of main reasons for the reduced optical power of the TAG:Ce-based WLED compared to that of the WLED expected from the brightness of TAG:Ce. (c) 2008 Optical Society of Americ
Mechanism for strong yellow emission of Y3Al5O12:Ce3+ phosphor under electron irradiation for the application to field emission backlight units
No full textThis letter reports a strong yellow emission of Y3Al5O12:Ce3+ (YAG:Ce) mixed with ZnS:Ag, Cl under electron excitation. The penetration depths of electron of 1 keV and photon of 2.7 eV in YAG: Ce were estimated to be approximately 1450 angstrom and 4.65 mm, respectively. Deeper penetration of blue light from ZnS: Ag, Cl helps to excite a larger number of Ce3+ in a mixture (ZnS:Ag, Cl + YAG:Ce), and YAG:Ce showed strong yellow emission via both cathodoluminescence and photoluminescence. The mixture showed the brightness of 120.5% compared to R, G, B phosphor mixture. This mixture of two phosphors was applied to a carbon nanotube field emission backlight unit. (c) 2007 American Institute of Physics
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
Tunable full-color-emitting La0.827Al11.9O19.09:Eu2+,Mn2+ phosphor for application to warm white-light-emitting diodes
No full textLa0.827Al11.9O19.09:Eu2+,Mn2+ showed three emission bands when excited by ultraviolet light. A blue emission originates from Eu2+, whereas both green and red emissions originate from Mn2+. The luminescent mechanism is explained invoking the energy transfer of Eu2+-> Mn2+ and Mn2+(tetrahedral site)-> Mn2+(octahedral site). This energy transfer was confirmed by faster decay times of the blue and green emissions as energy donors. The emitted color of La0.827Al11.9O19.09:Eu2+,Mn2+ can be easily tailored from blue to red through variations of the Mn2+ content. The white-light-emitting diode fabricated via a combination of an ultraviolet light-emitting diode (lambda(peak)=385 nm) with La0.827Al11.9O19.09:Eu2+,Mn2+ showed a warm white light (T-c=3559 K). (c) 2006 American Institute of Physics
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
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