1,720,974 research outputs found
Thermal stability of ultrafine-grained pure titanium processed by high-pressure torsion
No full textHigh-pressure torsion (HPT) was conducted under 6.0 GPa on commercial purity titanium up to 10 turns. An ultrafine-grained (UFG) pure Ti with an average grain size of ~96 nm was obtained. The thermal properties of these samples were studied by using differential scanning calorimeter (DSC) which allowed the quantitative determination of the evolution of stored energy, the recrystallization temperatures, the activation energy involved in the recrystallization of the material and the evolution of the recrystallized fraction with temperature. The results show that the stored energy increases, beyond which the stored energy seems to level off to a saturated value with increase of HPT up to 5 turns. An average activation energy of about 101 kJ/mol for the recrystallization of 5 turns samples was determined. Also, the thermal stability of the grains of the 5 turns samples with subsequent heat treatments were investigated by microstructural analysis and Vickers microhardness measurements. It is shown that the average grain size remains below 246 nm when the annealing temperature is below 500 ̊C, and the size of the grains increases significantly for samples at the annealing temperature of 600 ̊C
In situ TEM observations of thickness effect on grain growth in pure titanium thin films
No full textUltrafine-grained materials have a strong tendency to transform into coarse-grained materials due to the high density of grain boundaries at elevated temperature. In this study, pure titanium was processed by high-pressure torsion for 10 turns to give an ultrafine-grained (UFG) structure with an average grain size of ~96 nm. The recrystallization behavior of the UFG Ti was investigated by in-situ transmission electron microscopy (TEM). It is found that the gradient microstructures with average grain size ranging from ~129 nm to ~655 nm are formed under in-situ TEM heating up to 800 °C for 30 min. The Kossel-Möllenstedt (K-M) fringes in a convergent-beam electron diffraction (CBED) pattern were used to provide an accurate measure of the sample thicknesses. The results demonstrate that grain growth is significantly suppressed in the UFG pure Ti thin film compared to bulk material. Mechanism analysis shows the combined effects of driving force and drag force on grain boundary migration is the primary cause of the grain growth inhibition in the UFG pure Ti thin film.</p
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
Fracture mechanism of electrically-assisted micro-tension in nanostructured titanium using synchrotron radiation X-ray tomography
No full textA coarse-grained (CG) Ti with an average grain size of ~50 μm was processed by high-pressure torsion (HPT) under a pressure of 6.0 GPa through 10 turns at room temperature (RT) to produce nanostructured titanium (Nano-Ti) with an average grain size of ~95 nm. Electrically-assisted (EA) micro-tensions of CG-Ti and Nano-Ti were performed using pulsed unidirectional current with a current density of 750A/mm2, pulse width of 10-4 s. The stress drop is higher for Nano-Ti compared with CG-Ti. The results of fractograph observations show many cleavage steps in Nano-Ti while the CG-Ti is dominated by dimples. The spatial distribution of voids in tensile specimens was revealed after testing using synchrotron radiation X-ray tomography. The results demonstrate that applying a pulse current can effectively reduce the number and volume of voids before fracture. A model is presented describing the fracture mechanism of CG-Ti and Nano-Ti during EA micro-tension
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
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