1,720,981 research outputs found
Upgrade and present limitations of solar thermionic-thermoelectric technology up to 1000 K
No full textThe thermal and electrical performance of the innovative solar thermionic-thermoelectric generator (ST2G) has been carefully analyzed by using a high-flux solar simulator. Specific technological solutions have been inte-grated with respect to the first prototype for the operational testing at the moderate temperature range of 700–1000 K. The influence of spacers with different thickness has been studied to quantify the reduction of output current due to space-charge effect, whereas a BaF2-based coating has been deposited on the anode to make its work function (~2.1 eV) approach the cathode one, on which a hydrogen-terminated nitrogen doped nano-diamond film acts as emitter (work function of ~2.0 eV). The engineered ceramic absorber has demon-strated to be a reliable selective solar absorber with a high solar-to-thermal efficiency of 84% for solar con-centration ratio of 200 suns, extrapolated to 83% at 500 suns. As expected, the thermionic energy converter still provides a small converted power. However, the minimum inter-electrode spacing used (50 μm) and the engi-neered anode allow to better figure out the present limitations in the electrical power generation and how to surpass them in the near future
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
Combined electrical resistivity-electron reflectivity measurements for evaluating the homogeneity of hydrogen-terminated diamond surfaces
No full textThe homogeneity of hydrogen termination on single-crystal CVD diamond surfaces exposed to air was studied with a new approach that encloses a combination of sheet resistance measurements, performed using four-point-probe method in Van Der Pauw configuration, and electron reflectivity measurements performed at intermediate kinetic energy to derive surface sensitive information on the chemical terminations (inelastic mean free path <0.8 nm). The coherence between the 2-dimensional spatial distributions of sheet resistance and electron reflectivity maps, as well as their similar dynamic range and consistency with an electron energy loss analysis, demonstrates that the proposed combined approach allows for a reliable and easy evaluation of both the effectiveness and homogeneity of the hydrogen-termination process of a diamond surface
Combined electrical resistivity-electron reflectivity measurements for evaluating the homogeneity of hydrogen-terminated diamond surfaces
No full textThe homogeneity of hydrogen termination on single-crystal CVD diamond surfaces exposed to air was studied with a new approach that encloses a combination of sheet resistance measurements, performed using four-point-probe method in Van Der Pauw configuration, and electron reflectivity measurements performed at intermediate kinetic energy to derive surface sensitive information on the chemical terminations (inelastic mean free path <0.8 nm). The coherence between the 2-dimensional spatial distributions of sheet resistance and electron reflectivity maps, as well as their similar dynamic range and consistency with an electron energy loss analysis, demonstrates that the proposed combined approach allows for a reliable and easy evaluation of both the effectiveness and homogeneity of the hydrogen-termination process of a diamond surface
Reproducibility analysis of diamond pixel detectors for large ionizing radiation fields
No full textThis work reports on reproducibility tests performed on 20 high-quality single-crystal chemical vapour deposition (scCVD) diamond samples. By the analysis of the average mobility-lifetime product of the photogenerated carriers, 12 samples were selected and arranged as pixels in a 2.5 × 2.5 cm2 mosaic detector. Measurements carried out under a large (4 cm diameter) X-ray beam show a very high pixel response uniformity (<1% standard deviation relative to the mean photocurrent value) for a wide range of applied bias voltages (20 ÷ 80 V). Results suggest a very high level of reproducibility, mostly due to the excellent quality of the bulk material, meeting the requirements for monitoring large ionizing radiation fields with no need for individual pixel calibration. Moreover, mobility-lifetime product demonstrated to be the most effective figure of merit for the selection of CVD diamond samples with reproducible detection performance
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
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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