1,720,989 research outputs found
Thermodynamics of CVD Synthesis of Multiwalled Carbon Nanotubes: A Case Study
No full textGalvanic cells with CaF2 single crystal as electrolyte were utilized to determine the thermodynamic quantities of the solid-state process: delta NdNi5 (mu m) + MWCNT = {MWCNT-[NdNi5(nm)](delta)} where multiwalled carbon nanotubes (MWCNT) react with NdNi5 which is the catalyst of the chemical vapor deposition (CVD) synthesis of MWCNTs through the decomposition of a light hydrocarbon. It was shown elsewhere that the nucleation and growth of a MWCNT occurs by the nanodusting of the micrometer size powder of the unsupported catalyst. The composite {MWCNT-[NdNi5(nm)](delta)} is a nanoparticle of catalyst bonded to one of the ends of the MWCNT. The thermodynamic quantities of this process combined with those available for graphite to MWCNTs transformation and for decomposition of a light hydrocarbon, CH4, for instance, provide to obtain a complete picture of the thermodynamics of the CVD synthesis: CH4(g)+delta NdNi5(mu m) = {MWCNT-[NdNi5(nm)](delta)} + 2H(2)(g). At the standard state, the synthesis becomes feasible at T> 800 K. Between 300 and 1300 K, Delta H-r(T)theta and Delta S-r(T)theta are both positive, changing from 81 to 20 kJ mol(-1) and from 87 to 58 J K-1 mol(-1), respectively. To derive the thermodynamic quantities of formation of {MWCNT-[NdNi5(nm)](delta)}, the formation of NdNi5 was also studied by making use of a suitable CaF2 electrolyte cell. Between 600 and 1000 K, the formation of {MWCNT-[NdNi5(nm)](delta)} is always favored while Delta H-f(T)theta and Delta S-f(T)theta are positive but scarcely dependent on T (Delta H-f(T)theta approximate to 7 kJ mol(-1) Delta S-f(T)theta approximate to 12 J K-1 mol(-1)). A microscopic modeling of the process leading to the formation of {MWCNT-[NdNi5(nm)](delta) also been presented and discussed
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
High temperature determination of surface free energy of Copper nanoparticles”
No full textThe experimental study of the thermodynamic properties of nanoparticles at high temperatures is still a challenge. In this work we report the experimental determination of the surface free energy, gamma, of copper nanoparticles in the temperature range from 750 to 950 K. The solid electrolyte galvanic cell technique makes it possible to study the system under strict equilibrium conditions. The experiment was designed to avoid nanoparticle coalescence, which is one of most severe obstacles to the attainment of reliable results. The surface free energy (in J m(-2)) of 20 nm Cu nanoparticles changes with temperature according to the equation gamma = 60.97 - 0.234T + 3.09 x 10(-4) T-2 - 1.37 x 10(-7) T-3. At the lowest explored temperature, i.e., 750 K, a surface free energy of 1.70 +/- 0.03 J m(-2) was found. This value is in good agreement with numerical simulation data for copper nanoparticles previously reported in literature. A theoretical model is also proposed that accounts for the behavior of the surface energy on temperature
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
