1,721,036 research outputs found
Laser dissimilar weldability of cast and rolled CoCrFeMnNi high-entropy alloys for cryogenic applications
No full textThis study investigates the effects of welding velocity on weldability of dissimilar cast/rolled high-entropy alloys and the applicability of cryogenic temperatures. Cast HEA side of dissimilar weld metal (WM) indicates a larger dendrite packet and dendrite arm spacing (DAS) than rolled WM. Size difference is associated with epitaxial growth from each base metal (BM). As the welding velocity increases (6-10 m min(-1)), shrinkage voids and DASs decreases. Dissimilar welds show tensile properties comparable to cast BM, where there are tensile fractures of dissimilar welds. Cryogenic properties of dissimilar welds are superior to those of room-temperature welds, because deformation twins and dislocation densities are significantly formed at 77 K. Therefore, dissimilar welds can be applied to the production of cryogenic products.11Nsciescopu
Effect of Fabrication Process Parameters on Microstructure Evolution and Spectral Characteristics of Silicon Carbide Quantum Dots
No full text11scopu
Weldability of cast CoCrFeMnNi high-entropy alloys using various filler metals for cryogenic applications
No full textThis study investigates the effect of stainless steel (STS) 308 L and high-entropy alloy (HEA) filler metals on gas tungsten arc (GTA) welding. The weldability of the cast CoCrFeMnNi HEAs was determined based on the microstructural and mechanical properties of the welds. The cast HEA exhibited larger dendrite packets than the weld metals (WMs). The hardness in the WM was superior compared with that in the base metal (BM). The WM using STS 308 L exhibited a fully face-centred cubic (FCC) structure with no indication of 8-ferrite and lower hardness than that using HEA filler. The GTA welds using both fillers showed tensile properties comparable to the cast BM at 298 K, and the tensile fracture of the transverse welds occurred near the cast BM. The cryogenic tensile properties in the GTA welds were superior compared with the room-temperature property due to the significant formation of deformation twins and high dislocation density at 77 K. This was probably due to the decrease in the stacking fault energy at the cryogenic temperature compared with that at the room temperature. Therefore, it is possible to apply commercial STS 308 L filler metal for the CoCrFeMnNi HEA in cryogenic applications. (C) 2019 Elsevier B.V. All rights reserved.11Nsciescopu
Superior-tensile property of CoCrFeMnNi alloys achieved using friction-stir welding for cryogenic applications
No full textThe friction-stir weld (FSW) was investigated based on the relationship between microstructural and mechanical properties at room and cryogenic temperatures for rolled and cast Co0.2Cr0.2Fe0.2Mn0.2Ni0.2 high entropy alloys (HEAs). The rolled and cast HEA welds exhibited good weldability without welding defects. The grain size (GS) of the stir zone (SZ) for rolled and cast HEAs was smaller than that of the base metal (BM). The W, Cr, and C particles caused by the wear of the WC-Co tool formed fine M23C6 carbides, due to the heat generated during the FSW, and accelerated the recrystallization via the particle stimulated nucleation (PSN) effect. Therefore, the area with M23C6 carbide exhibited a finer grain size compared with the area without M23C6 carbide. The rolled HEA was fractured in the SZ owing to the thinning phenomenon, and the cast HEA was fractured in the BM owing to the GS of the SZ, which was much finer than the GS of the BM. However, both HEA welds had larger room temperature strength than BM, and the cryogenic strength was also improved owing to the primary twin, secondary twin, and tangled dislocation. The PSN effect due to the carbides contributed to the increase in strength. Therefore, the FSW of the rolled and cast HEAs produced in this study is suitable for cryogenic applications.11Nsciescopu
Effect of post weld heat treatment on weldability of high entropy alloy welds
No full textThe effect of post weld heat treatment (PWHT) temperature on laser beam welds in high-entropy alloys (HEAs) using a cold-rolled cantor system (CoCrFeMnNi) was investigated. Laser welding of low heat input was applied to reduce thermal distortion. The cold-rolled HEA welds indicated larger grain size and inferior tensile/hardness properties as compared to the base metal (BM). By applying PWHT, the welds showed superior hardness to the BM with no variation in the face-centred cubic phase and a decrease in the size and fraction of CrMn oxide inclusions. As the PWHT temperature increased (800-1000 degrees C), the variation in the grain size decreased between the weld metal and heat-affected zone, thus resulting in approximately the same tensile strength and elongation of the transverse welds as compared to the BM.11Nsciescopu
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
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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