1,720,953 research outputs found
Growth and properties of single transition metal nitride-carbide superlattices
No full textAugust 2024School of EngineeringTransition metal nitrides (TMNs) and carbides (TMCs) are desirable materials for applications such as hard coatings, diffusion barriers, and optical coatings due to their high intrinsic mechanical strength, hardness, and thermal and chemical stability. Superlattices, nanoscale laminate composites consisting of alternating layers of two materials, allow for mechanical property enhancements through local strain variations and shear modulus mismatch which result in interfacial dislocation pinning at specific bilayer periods. Nanoscale engineering of TMNs and TMCs into superlattices increases the appeal within the application of hard, wear resistant coatings without significant alterations to existing fabrication techniques. I have studied three sets of single transition metal nitride/carbide superlattices, including TiN/TiC, MoN/MoC, and VN/VC, in order to investigate their hardness and elastic modulus as a function of bilayer period and the effect of material selection on the mechanical properties of superlattices. Further investigations develop a fundamental understanding of the effects of lattice constant and shear modulus mismatch on the potential enhancements of superlattice mechanical properties beyond intrinsic material values. Additionally, I have studied three sets of TiN/TiC superlattice series grown with different crystalline quality and growth orientations to better understand the effect that these properties have on superlattice hardening.Rocksalt structured TiN(001)/TiC0.5(001) superlattices with bilayer periods from 1.5 to 30 nm are grown on MgO(001) substrates via DC reactive magnetron sputtering in alternating Ar/N2 and Ar/CH4 gas mixtures at 1100 C. Microstructural characterization confirm epitaxial TiN(001) and TiC0.5x(001) demonstrating cube-on-cube epitaxy with the MgO(001) substrate, such that TiN/TiC[100] || MgO[100]. Measured XRD data shows an average superlattice relaxed lattice constant ao = 4.25 Å. The TiN(001)/TiC0.5(001) superlattices demonstrate superlattice enhancement at = 6 nm of H = 34 GPa, 1.4 the hardness of pure TiN and 1.1 that of pure TiC. Elastic modulus also has an enhancement at the same bilayer period with E = 750 GPa increasing 1.7 above that of pure TiN and TiC. The enhancements are attributed to shear modulus mismatch and lattice constant mismatch of 1.3 % forming coherency strains, both of which inhibit dislocation motion at superlattice interfaces and improve the mechanical properties. Additional rocksalt structured TiN/TiC superlattice series are grown on MgO(001) and Al2O3(0001) with increased carbon content. Microstructural characterization of TiN/TiC on MgO(001) confirms the presence of both (001) and (111) orientations, with a preferred (001) orientation. Hardness initially increases with bilayer period, reaching a maximum at = 7.5 nm of H = 17.9 GPa before decreasing with further increasing bilayer period. TiN/TiC on Al2O3(0001) demonstrates strong (111) growth and exhibits no increase in hardness above the intrinsic values of the separate materials. Overall, polycrystalline TiN/TiC superlattices have a reduced hardness and modulus relative to epitaxial samples, and the (001) orientations have increased mechanical properties compared to (111) orientations.
1.2 m thick molybdenum nitride/carbide superlattices with bilayer period = 1.5 to 30 nm are grown on MgO(001) substrates by DC reactive magnetron sputtering at 800 ℃. XRD confirms rock-salt structured MoN/MoC on MgO(001) with approximately random grain orientations. Mechanical property measurements yield a maximum of H = 12 GPa and E = 255 GPa at = 15 nm. The measured superlattice hardness is 471% and 50% larger than that of measured pure MoN and MoC, respectively. The superlattice hardening is the result of an 85 GPa shear modulus mismatch between MoN and MoC, as well as a 3.2 % lattice mismatch which generates stress fields and prevents dislocation motion.
Vanadium nitride/carbide superlattices 1.5 m thick are also grown on MgO(001) substrates with bilayer period = 1.9 to 30 nm at Ts = 1000 ℃. XRD measurements confirm that the VN/VC films exhibit an epitaxial rock-salt structured matrix, with cube-on-cube epitaxy with the MgO(001) substrate, such that VN/VC[100] || MgO[100]. Results of XRD on VN/VC superlattices show a measured relaxed lattice constant ao = 4.158 Å. Additionally, XRD,RSM, and SEM indicate that the samples are predominantly epitaxial with misoriented grains present. Reciprocal space mapping indicates increasing in-plane compressive strain as a function of increasing bilayer period. XPS and EDS measurements confirm stoichiometric VC but reduced nitrogen content. The VN/VC superlattice films indicate a decreased hardness with increasing bilayer period, from H = 16.4 to 11.1 GPa, and elastic modulus E = 260 GPa that is constant as a function of bilayer period. Although the material system does have a shear modulus mismatch of 67 GPA, the superlattice hardness values do not exceed those of pure VN or VC likely due to a low lattice mismatch (1.0 %) which suppresses the typical mechanical property enhancement exhibited by superlattices.Ph
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
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
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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