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HIGH TEMPERATURE PROPERTIES OF ULTRA-HIGH TEMPERATURE CERAMICS (MB2, M = Ti, Zr, Nb, Hf, Ta)
No full textThe primary aim of this dissertation is to develop and validate an environmental conical nozzle levitator (E-CNL) system for high temperature standard thermal analysis and to use levitation techniques to determine the melting temperature and thermal expansion of ultra-high temperature ceramics. Specifically, this work focuses on four key objectives: (i) to validate the capabilities of the E-CNL and quantify the error associated with temperature measurements; (ii) to develop a technique for synthesizing dense, pure, highly spherical ceramic samples for use in aerodynamic levitation; (iii) to use the E-CNL to determine the melting temperature of transition metal diborides (TiB2, ZrB2, HfB2, and TaB2); and (iv) to use aerodynamic levitation with in-situ x-ray diffraction to determine the lattice thermal expansion of transition metal diborides (TiB2, ZrB2, NbB2, HfB2, and TaB2) and other materials and examine the thermostructural trends.Ultimately, this work aims to advance the understanding of ultra-high temperature ceramics by accurately characterizing their melting temperatures and thermal expansion behaviors at temperatures reaching up to ~4000 K
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
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Characterization of Octapole Lamp Furnace for in situ High Temperature Ceramic Characterization Techniques
Get PDFCharacterization of materials utilizing in situ experimentation techniques is critical for understanding the nature of materials in those conditions. The processing of polymer derived ceramics from pyrolyzing polymer precursors is especially important for understanding the change in their microstructure and material properties as they pyrolyze and form a ceramic material. In this thesis, an octapole lamp furnace (OLF) is characterized for the heat treatment of samples in an open and inert-gas environment. The heat is generated by tungsten-filament halogen lamps that are focused into the center of the furnace. This furnace was constructed to be coupled with X-ray characterization techniques, particularly micro-computed tomography, for in situ high temperature characterization. Investigating the capabilities of the OLF culminated in determining the temperatures the furnace reach up to maximum operating power as well as the temperature gradients occurring inside of the furnace. A preceramic polymer, polycarbosilane SMP-10, was pyrolyzed in the furnace to assess its capabilities for pyrolysis experiments. Temperature measurements were made using thermocouples, and ceramic samples were prepared and melted in the furnace for further assessing the OLF capabilities. The thermocouple-determined maximum temperature of the furnace was 1504±23 °C, and highest melting point sample melted in the furnace was BaTiO3 (MP: 1625 °C). The temperature gradient results determined that the hottest spot in the furnace is ~3 mm in each Cartesian x-y-z direction with respect to the geometric center of the OLF. Pyrolysis experiments determined that the OLF is capable of pyrolyzing SMP-10 with a sufficient ramp rate that does not induce thermal shock of the samples. These results demonstrate the OLFs heating capabilities as well as its feasibility for pyrolyzing materials such that it is capable for use in in situ high temperature characterization in air and in inert environments
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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