1,720,969 research outputs found
Improvement of High Temperature Strength of Al and Co Alloy by L12 Type Coherent Precipitates
No full textThe present work aims at developing a new class of high temperature alloys based on ordered
intermetallic compound that forms coherently with the matrix during solid state transformation.
The chosen intermetallics have L12 ordered structure, which is a derivative of fcc unit cell.
Most popular example of this fcc derivative is Ni3Al that is critical in developing high strength
at high temperatures (~900°C) in commercially successful Ni based superalloys. Similar
ordered structures form either in stable or metastable form can act as a main strengthening
constituent in Al and Co matrices.
For example Al3Sc, Al3Zr, Al3Hf can be dispersed in fcc Al matrix that are stable at
temperatures ~ 400°C due to very low diffusivity of transition metals (Sc, Zr, Hf etc.) in the
matrix. However, due to low solid solubility of these transition metals, the obtained volume
fraction of these precipitates in the matrix is not sufficient to provide adequate room
temperature strength.
In fcc Co matrix, stable Co3Ti phase with L12 ordered structure forms with cuboidal
morphology. However, besides having lower melting point, the precipitates have large misfit
that lowers thermal stability at high temperatures. Recently, addition of Al and W with a proper
ratio in Co is reported to lead the formation of metastable Co3(Al,W) L12 ordered phase in fcc
α-Co matrix. This provides significant strength at high temperatures (~ 900°C). The main
drawback for these alloys is their high densities (9.6 to 10.5 gm.cm-3) due to the requirement of
compulsory addition of W (~ 15 to 25 wt%) for stabilising the ordered phase.
In the present work, these problems are overcome leading to the development of new class of
Al and Co alloys. The thesis is organized in three parts. In the first part, the principles of
strengthening that can be optimized to develop newer high temperature high strength alloys are
reviewed. The ordered L12 structure, which is the mainstay of the current effort of new alloy
development, is elaborated. In the second part we present the results of our effort to the
development a new class of high strength high temperature Al alloys. A new approach has been
adopted to get a microstructure that contains both high temperature stable and room
temperature strengthening precipitates. This has been illustrated by two Al rich compositions,
Al-2Cu-0.1Nb-0.15Zr and Al-2Cu-0.1Hf-0.15Zr (at% unless stated otherwise). Addition of
Nb/Zr or Hf/Zr in Al alloys leads to the formation of high temperature stable L12 ordered
spherical coherent precipitates in the fcc Al matrix. Cu addition gives room temperature
strengthening θ’ and θ” precipitates. The arc melted alloys were chill cast (suction cast) in the
form of 3 mm rods followed by a novel three stage heat treatment process, as shown below.
In the case of Al-2Cu-0.1Nb-0.15Zr alloy, the chill cast structure consists of Cu rich phase at
the boundaries along the α-Al dendrites while Zr and Nb partition inside the α-Al dendrites.
Aging at 400°C leads to an increase in the hardness of the cast alloy due to the precipitation of
coherent L12 ordered Al3(Zr,Nb) spherical precipitates (~5nm) in the α-Al dendrites. Zr
strongly partitions to the L12 ordered precipitate relative to the matrix. Nb exhibits weak
partitioning in the precipitate. Further solutionising was optimized at 535°C for 30 minutes
such that the segregation of Cu in the chill cast samples can be eliminated. The WDS mapping
shows that Cu dissolved uniformly in the α-matrix while the Zr/Nb enriched α-Al dendrites are
still present. The L12 ordered precipitates are mostly found in these Zr/Nb enriched dendrites
formed during solidification. The precipitates sizes are finer (~5 nm) in dendrites and larger in
the interdendritic region. The Nb partitioning increases in the ordered L12 precipitates relative
to the matrix after solutionising. On aging at 190°C, fine θ” precipitates nucleate on prior
Al3(Zr,Nb) precipitates present in α-Al dendrites while the interdendritic regions contain
coarser θ’ nucleated on larger size L12 precipitates. The θ”/θ’ are much finer and higher in
number density for the quaternary alloy compared to binary Al-2Cu alloy subjected to
conventional heat treatment. The quaternary alloy show higher peak hardness of 1500 ± 8 MPa
after 5 hours of aging at 190°C compared to binary Al-2Cu alloy with peak hardness of 1260 ±
11 MPa
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
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
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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