1,720,953 research outputs found
Synthesis of Slag-Waste Glass Binary Geopolymer and Its Application as a Sustainable Stabilizing Material
No full textConcrete is the second most consumed material after water. A higher dependency on cement concrete tremendously enhanced the demand and production of Portland cement. Despite its higher demand, the production process of cement has severe environmental issues, including depletion of natural resources, higher energy consumption, and emission of greenhouse gases. Geopolymer is a green binder proposed as an alternative to conventional binders. Any industrial by-product possessing amorphous aluminosilicate components could be used to produce geopolymers through alkali-activation. It has gathered significant attention from researchers due to its better performance and eco-friendly nature. While significant research has been carried out to synthesize geopolymer binders from industrial-based aluminosilicates, recyclable aluminosilicates are also being used as precursors for synthesizing geopolymer binders. Waste glass is one of the recyclable materials with high silica component used for preparing geopolymer binders in combination with alumina-based materials. Hence, in the current study, laboratory investigation was made to synthesize slag-waste glass geopolymer and assess its suitability as a sustainable stabilizer for geotechnical applications. In the first phase of laboratory investigation, the geopolymer binder was synthesized using slag and glass powder (GP) as precursors and sodium hydroxide (NaOH) as an alkali activator. The solubility of silicon, aluminum, and calcium ions from the precursors in the NaOH solution was examined. The fresh and hardened properties of the geopolymer were assessed at different GP contents (0%, 10%, 20%, 30%, and 40%), NaOH concentrations (2 M, 4 M, 6 M, 8 M, and 10 M) and liquid alkali activator-to-solid binder (L/S) ratios (0.25, 0.30, 0.35, 0.40, and 0.45). Mineralogical and microstructural studies were made to substantiate the changes observed in fresh and hardened properties. The effect of synthesis parameters on the compressive strength (CS) was statistically analyzed by developing a statistical model. The CS of slag-GP geopolymer at various temperatures (-15 °C to 90 °C) and curing durations (1 day to 90 days), as well as the effect of initial-temperature curing under sealed and humid conditions, were explored. The strength development in submerged and autoclave curing conditions was also assessed. Further, the durability of geopolymer mortar against high-temperature exposure (HTE) of 200 °C to 1000 °C, wet-dry (W-D) and freeze-thaw (F-T) cycles, water slaking, surface abrasion, alkali-silica reaction (ASR) expansion, and chemical attacks were determined and compared with cement mortar. In the second phase of the investigation, pond ash (PA) was stabilized with slag-GP geopolymer, cement, and lime. The effect of different additive contents (3%, 6%, 9%, 12%, and 15%) on the hydro-mechanical properties of the stabilized PA was assessed. The hydro-mechanical properties include compaction characteristics, unconfined compressive strength (UCS), indirect tensile strength (ITS), California bearing ratio (CBR), hydraulic conductivity, and compressibility index. The durability of the 28-day cured stabilized PA against W-D and F- T cycles, water slaking, water immersion, capillary action, and dispersion was studied. The effect of delayed compaction on the engineering properties of the stabilized PA was also examined. Mineralogical and microstructural analysis were assessed and correlated with strength and durability properties. In addition, leachable concentrations of different metallic ions from stabilized PA were examined. The experimental results indicated that the solubility of the precursors depends on the alkali concentration and reactivity behavior of the precursors. Slag has a higher solubility in NaOH solution compared to GP. The normal consistency of slag-GP geopolymer was increased with an increase in GP content and NaOH concentration. However, the setting period and workability of the geopolymer paste were reduced with increased GP content and NaOH concentration. The final setting period was shortened by 56 min, and the flow diameter was reduced by 26.57% when GP content increased from 0% to 40% at 6 M NaOH concentration. Based on 28-day CS, an optimum NaOH concentration of 8 M and an optimum L/S ratio of 0.35 were observed for slag-based geopolymer. With GP inclusion, the NaOH requirement was reduced by up to 50% due to the availability of alkali cations in GP. At higher GP contents (>20%), the rise of Si/Al, Na/Al, and Si/Ca molar ratios beyond their ideal range causes a decline in the CS of slag-GP geopolymer. However, the resistance to soundness and drying shrinkage improved as GP content increased. The key reaction phases observed in slag-GP geopolymers are sodium alumina silicate hydrate (N-A-S-H), calcium alumina silicate hydrate (C-A-S-H), sodium alumina silicate (N-A-S), and calcium silicate hydrate (C-S-H). A non-linear statistical model developed with GP content, alkali concentration, and L/S ratio as input variables predicts the CS with an R-square of 0.9072. At ambient temperature (30 °C) and prolonged curing (90 days), higher strength was observed at 10% GP content. However, a higher dose of GP is beneficial for specimens cured at elevated temperatures (45 °C to 60 °C). Little improvement in strength with the curing period was noticed for the specimens cured at temperatures below the freezing point of water. Under humid curing, slag-GP geopolymers attained dense microstructure, whereas micro-cracks were observed in the specimens cured under dry environments. Submerged curing in alkali solutions achieved better strength compared to curing in normal and saline water. Autoclave curing showed rapid strength gain due to the advancement in the geopolymer mechanism. Moreover, the proposed analytical models predict the CS well at different GP contents, curing temperatures, and curing durations. The slag-GP binary geopolymer at 10% GP content has better durability against harsh environments, such as HTE, W-T and F-T cycles, water slaking, surface abrasion, and chemical attacks, than slag-based geopolymer and cement. The GP-rich geopolymer (20% to 40% GP) showed better structural integrity after exposure to higher temperatures (> 700 °C) due to the filling of micro-pores with molten glass particles. However, ASR expansion was found to increase marginally with GP contents. In addition, laboratory studies show that the PA can be efficiently stabilized with synthesized slag-GP geopolymer. The PA stabilized with slag-GP geopolymers achieved higher strength properties such as UCS, ITS, and CBR, as well as lower hydraulic conductivity and compressibility index compared to cement and lime-stabilized PA. Further, a denser and more compact microstructure of geopolymer-stabilized specimens achieved excellent durability than cement and lime stabilized specimens. Based on strength and durability properties, it is confirmed that PA stabilized with 6% geopolymer can be effectively used as a cementitious base in flexible pavements as per IRC 37-2018 and cementitious subbase in rigid pavements as per IRC 58-2015. With delayed compaction, the dry density and strength properties were reduced, whereas the hydraulic conductivity and compressibility index increased. At 15% geopolymer content, the compacted dry density was reduced by 11.92%, 18.74%, and 22.62% after 6 h, 24 h, and 72 h delay periods, respectively. Similarly, the UCS was reduced by 18.64%, 54.86%, and 67.35%, respectively. Whereas the hydraulic conductivity and compressibility index values increased by 3.61, 6.59, and 9.61 times, respectively, and by 15.87%, 33.89%, and 55.43%, respectively. The formation and deposition of cementitious products and agglomeration during delay periods lead to poor compaction and deteriorate the mechanical performance. The leachable concentration of iron (Fe), calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), nickel (Ni), and copper (Cu) from the stabilized PA was within the threshold limits of WHO and IS 10500-2012 water quality standards. However, the traces of lead (Pb), mercury (Hg), and arsenic (As) were higher than the permissible limits. The geopolymer-stabilized specimens achieved higher metallic ion encapsulation than cement and lime-stabilized specimens
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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