1,721,120 research outputs found
Effect of surface passivants on the photoluminescence from Si nanocrystals
No full textRoom-temperature visible photoluminescence (PL) was observed in silicon oxide (SiOx) silicon oxynitride (SiOxNy), and silicon nitride (SiNx) films grown by ion beam sputter deposition. The amounts of oxygen and nitrogen in the films were controlled by using in-situ X-ray photoelectron spectroscopy (XPS). In the SiOx and the SiNx thin films, the PL energies showed blue-shifts due to the quantum-confinement effect with the decreased excess Si and the PL intensities showed maximum values near x = 1.6 and x = 1.1, respectively. We found another large blue-shift of about 0.6 eV in the PL energy between the SiNx and the SiOx films with similar excess Si due to surface passivation of Si nanocrystals. The increase of PL energy from SiOx through SiOx N-y to SiNx can be a direct evidence for a surface passivation effect, which is in agreement with the theoretical prediction. These results indicate that control of the nc-Si size and the surface passivant material are key parameters for enhancing the visible luminescence for a Si-based photonic device
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
PLC-type variable optical attenuator operated at low electrical power
No full textA novel voltage-controlled variable optical attenuator based on a polymeric planar lightwave circuit (PLC) is demonstrated. The fabricated variable attenuator shows 30dB attenuation with only 80mW electrical input power at 1.55 mum. The polarisation dependences at 0 and 10dB attenuations are 0.2 and 1dB, respectively. The rise and fall times are less than 5ms
Thermal expansion of UO2 and simulated DUPIC fuel
No full textThe lattice parameters of simulated DUPIC fuel and UO2 were measured from room temperature to 1273 K using neutron diffraction to investigate the thermal expansion and density variation with temperature. The lattice parameter of simulated DUPIC fuel is lower than that of UO2. and the linear thermal expansion of simulated DUPIC fuel is higher than that of UO2. For the temperature range from 298 to 1273 K, the average linear thermal expansion coefficients for UO2, and simulated DUPIC fuel are 10.471 x 10(-6) and 10.751 x 10(-6) K-1, respectively. (C) 2002 Elsevier Science B,V. All rights reserved
Very low crosstalk 1 x 2 digital optical switch integrated with variable optical attenuators
No full textA novel digital thermo-optic switch based on a polymer waveguide has been demonstrated. The proposed switch consists of a conventional 1x2 digital optical switch and compact variable optical attenuators. with both elements: integrated in series. The switches exhibit very low crosstalk values of -42 and -40d8, and the switching power is similar to 170mW at 1.55 mum
- …
