1,721,029 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
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
The influence of ZnNb 2O 6 on the microwave dielectric properties of ZrTi 2O 6 ceramics
No full textCeramics in the system (1-x)ZrTi 2O 6-xZnNb 2O 6 (for 0.1≤x≤0.85) have been prepared by the mixed oxide route; specimens fired in oxygen at 1260°-1300°C achieved 97% theoretical density for most compositions. X-ray diffraction analysis confirmed the co-existence of a disordered α-PbO 2-type structured phase and a rutile-structured second phase for 0.1≤x≤0.25, a single phase having a disordered α-PbO 2-type structure for 0.3≤x≤0.7, and a columbite-type structured phase for x≥0.85. Wavelength dispersive spectroscopy (WDS) revealed that the TiO 2-rich second phase contained significant amounts of ZrO 2, Nb 2O 5, and ZnO. In the two-phase region relative permittivities (ε r) are predominantly in the range 39-47 (with a peak at x=0.24), quality factor (Q×f) values peak at 34 000 GHz, and temperature coefficient of resonant frequency (τ f) decreases with increase in ZnNb 2O 6 content and tune through zero at x=0.24. In the single-phase α-PbO 2 region ε r decreases, Q×f increases to 49 000 GHz and τ f decreases to -58 ppm/°C with increasing ZnNb 2O 6. In the ordered columbite structure region (x≥0.85) the ε r falls to 28, Q×f increases to 59 000 GHz and τ f is more positive (-20 ppm/°C). Ceramics with x=0.24 exhibited an excellent combination of properties: ε r=47, Q×f=34 000 GHz, and τ f∼0 ppm/°C. © 2005 The American Ceramic Society
Thermoelectric Oxides
No full textThermoelectric oxides are of increasing interest as they are produced from relatively abundant, low cost and low toxicity materials. The production of the precursors and the ceramic fabrication methods are discussed with reference to the effect on final properties. The different oxide systems that are in common use are then described. Finally some of the future challenges for wide scale commercialization of these materials are outlined
Enhancing the Thermoelectric Properties of Sr1−xPr2x/3x/3TiO3±δ through Control of Crystal Structure and Microstructure
No full textA-site deficient perovskites are among the most important n-type thermoelectric oxides. Ceramics of Sr1−xPr2x/3x/3TiO3 (x = 0.1 to 1.0) were prepared by solid state reaction at 1700-1723 K using highly reducing atmospheres. Samples with the highest Sr content had a cubic crystal structure (Pm3 ̅m); incorporating Pr with A-site vacancies, led to a reduction in symmetry to tetragonal (I4/mcm) and then orthorhombic (Cmmm) crystal structures. HRTEM showed Pr2/3TiO3 had a layered structure with alternating fully and partially occupied A-sites and a short-range order along (100) direction. Electrical conductivity was highest in samples of high symmetry (x ≤ 0.40), where the microstructures featured core-shell and domain structures. This enabled a very high power factor of ~1.75×10−3 W m−1 K−2 at 425 K. In contrast, at high Pr content, structural distortion led to reduced electron transport; enhanced phonon scattering (from mass contrast, local strain and cation-vacancy ordering) led to reduced, glass-like, thermal conductivity. Carbon burial sintering increased the oxygen deficiency leading to increased carrier concentration, a maximum power factor of ~1.80×10−3 W m−1 K−2 at 350 K and thermoelectric figure of merit of 0.26 at 865 K. The paper demonstrates the importance of controlling both crystal structure and microstructure to enhance thermoelectric performance
Thermoelectric Oxides
No full textThermoelectric oxides are of increasing interest as they are produced from relatively abundant, low cost and low toxicity materials. The production of the precursors and the ceramic fabrication methods are discussed with reference to the effect on final properties. The different oxide systems that are in common use are then described. Finally some of the future challenges for wide scale commercialization of these materials are outlined
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