1,721,059 research outputs found
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
Synthesis and characterization of new luminescent materials containing various substituted 8-quinolinolate
No full textNovel thermally stable aluminium and zinc complexes, Al(Clq)(3), Al(Brq)(3), Zn(Clq)(2), Zn(Brq)(2) and Zn(MeClq)(2) (Clq = 5,7-dichloro-8-quinolinolate, Brq = 5,7-dibromo-8-quinolinolate, MeClq = 5,7-dichloro-2-methyl-8-quinolinolate) were synthesized and characterized. The organic electroluminescent (EL) device ITO/TPD/emitting material/LiF/Al (ITO = indium-tin oxide, TPD = N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine) was employed to investigate their EL properties. In case of Al(Clq)(3), the EL device exhibits yellow light with maximum luminance of 375 cd/m(2) at 8V.MIC , Bk21 Project and KOSE
Luminescent spectral changes in polymer light-emitting diodes after heat treatments
No full textLuminescent spectra of polymer light-emitting diodes (LEDs) would depend upon the heat treatment condition and procedure greatly. We have tried thermal annealing at the temperature above T-g of poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV), before and after Al deposition respectively, in ITO/MEH-PPV/Al structure. The pre-deposition annealing makes the PL and EL spectrum red-shifted and more broadened. After annealing, the optical hand-gap of MEH-PPV thin film decreases by about 0.1 eV relative to that of the dilute solution. The annealing also makes an excimer emission dominant in PL and EL spectra. In contrast, after post-deposition annealing, the EL spectrum was blue-shifted and narrowed. In addition, the excimer emission is withdrawn remarkably after the port-annealing
Effect of ion concentration in the ionomers used as an electron injecting layer in polymer light-emitting diodes
No full textThe polymer light-emitting diodes (LEDs) were fabricated using poly[2-methoxy-5-(2'-(ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) as an emissive material and sodium sulfonated polystyrene (SSPS) ionomer with various ionic mole percents as an electron injecting material. The optimum ion concentration of SSPS was found at 6.7 mol% in the ITO/MEH-PPV/ionomer/Al structure. The quantum efficiency of the device is greatly enhanced near the critical ion concentration (CIC) of the ionomers, which is depending upon by the number of charge carriers and their mobility. The increase of charge carriers in the region below the CIC of ionomers enhances the quantum efficiency of the device by introducing more electrons. On the contrary, in the region above the CIC, the quantum efficiency is reduced by the restricted mobility of the ions due to the cluster formation. (C) 2000 Elsevier Science S.A. All rights reserved
Surface morphology study of corona-poled thin films derived from sol-gel processed organic-inorganic hybrid materials for photonics applications
No full textDye-doped and a dye-attached sol-gel films using the chromophore (E)-N-butyl-(4-{2-[4-bis(2-hydroxyethyl)amino]phenyl}ethenyl)pyridinium tetraphenylborate (BPTP) and N,N-bis(2-hydroxyethyl)amino-N'-methylstibazoliumtoluene-p-sulfonate (BAST) were fabricated by sol-gel processing. Surface morphology of the films was studied using an atomic force microscope. In the dye-doped film, many surface defects were observed. The morphology of the surface defects varied as a function of chromophore concentration. The shapes of the defects became more complicated as the chromophore concentration increased. On the other hand, no evidence of such defects was present in the dye-attached sim and the quality of the film was high. Also for the dye-attached film, the surface was optically hat and smooth, and the surface roughness was measured to be less than 4 nm. It was found that corona poling processes also affected the quality of the dye-attached film significantly. Corona poling with a needle electrode resulted in many irregular shaped defects in the film. However, poling with a tungsten wire stabilized the corona discharge and thus prevented the formation of defects, which led to films of excellent quality. The electro-optic coefficient, r(33), of the BPTP dye-attached film was measured to be 5.0 pm V-1 and this value was maintained even after 54 days at room temperature
Improved quantum efficiency by overneutralization of ionomers used in polymer light-emitting diodes
No full textPolymer light-emitting diodes are fabricated using poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) as an emissive material, and sodium sulfonated polystyrene (SSPS) ionomers with several different neutralization levels as an electron injecting and hole blocking layer. The SSPS with higher neutralization level makes the EL device more efficient. The highest efficiency was found at 200% overneutralization of the ionomer. The main reason fur this is that the overneutralization in the ionomer helps to form a more favorable morphology to block holes better by Lightening the cluster
Improvement of EL efficiency in polymer light-emitting diodes by heat treatments
No full textEfficiency of polymer light-emitting diodes (LEDs) would depend upon the heat treatment condition and procedure greatly. We have tried thermal annealing at the temperature above T-g of the emissive polymer, poly[2-methoxy-5-(2'-ethly-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV), before and after Al deposition, respectively, in ITO/MEH-PPV/A1 structure. The anomalous semiconducting behavior of an unannealed device has been screened out by appropriate heat treatments. It is remarkable that the annealing treatment after Al deposition makes the EL efficiency enhanced by two orders and reduces the operating voltage about 40%. The high temperature annealing after Al deposition enhances the interface adhesion between the emissive polymer and the Al cathode, and might form an interfacial polymer layer with wide band gap, which seems to play a critical role to improve the efficiency of EL devices. (C) 2001 Elsevier Science B.V. All rights reserved
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
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