1,720,952 research outputs found
Development of a hybrid ion exchange-catalyst system to denitrify ion exchange waste brine
Get PDFNitrate is the most common groundwater contaminant in the United States and is regulated in drinking water by the EPA due to its harmful health impacts. Ion exchange (IX) is frequently used to treat nitrate and is very effective, but suffers from inefficiencies associated with the regeneration process. When the IX resin is saturated, it requires regeneration, which is accomplished through back-washing with a high-salt brine, which treatment plants use only one time prior to disposal. The cost of salt to make fresh brine and disposal requirements of waste brine are expensive processes for the water treatment plant. Additionally, this process merely transfers the nitrate to another phase (from resin to brine) rather than destroying it, leading to significant environmental impacts of the brine disposal process. Recently, a hybrid system that incorporates catalytic denitrification of IX waste brine has been shown to be technically feasible. Using a bimetallic palladium-indium on activated carbon catalyst, nitrate in waste brine can be selectively reduced to inert dinitrogen gas. This technology has the potential to significantly reduce the cost and environmental burden of the convention IX process for nitrate treatment.
In order to improve the hybrid-IX system, the following research objectives were pursued: (1) Using an experimental and modeling approach, determine whether the accumulation of bicarbonate and sulfate in reused waste brine will negatively impact the hybrid system performance and model key IX system variables using a case-study approach, (2) Evaluate reactor performance in continuously stirred and fixed bed reactors; and optimize a fixed bed reactor to reduce hydrogen mass transfer limitations to the catalyst surface, and (3) Evaluate selectivity of Pd-In/AC catalyst using different reactor types and matrix conditions.
A model of the IX-catalyst system was developed, calibrated and validated using experimental data. Results from modeling simulations show that concentrations of non-target ions like sulfate and bicarbonate will buildup in waste brines over repeated cycles of reuse, but this buildup will not negatively impact IX performance or lead to permanent deactivation of the Pd metal catalyst. IX columns were tested experimentally to verify the modeling results. The key IX variables evaluated using the model and case study approach based on data from Chino, CA were resin regeneration length, treatment time, and addition of make-up salt. Overall, salt costs and waste brine volumes can be decreased by up to 80% with the hybrid system. A fixed-bed catalytic reactor was used to evaluate a real brine from Chino, CA and demonstrated consistent reduction, however the overall activity was very low due to hydrogen mass transfer limitations. This led to prohibitively high predicted catalyst costs for a commercial-scale hybrid system, leading to a focus on reactor design in an attempt to reduce mass transfer limitations.
Based on its significant use in industrial catalytic applications and the known ability to facilitate high mass transfer rates, a trickle bed reactor (TBR) was chosen as the new reactor design for use in the hybrid IX-catalyst system. The 2” ID TBR with two 10” beds of catalyst and recycling flow was designed in accordance with reactor design guidelines and evaluated across a range of liquid and gas superficial velocities. Synthetic waste brines were treated with two Pd-In/AC catalysts that had different support sizes. In comparison to a previously tested up-flow fixed-bed reactor, the same catalyst in the TBR demonstrated c. 300% higher activity. While the results showed a major step forward in reactor performance, the TBR activity was only 8.3% of the activity found in batch, indicating significant mass transfer limitations remained.
The impact of catalyst dilution was evaluated in the TBR and had been previously shown to improve reactor performance. The catalyst was diluted at a ratio of 1 part catalyst : 2 parts inert support. Continuous flow experiments using the diluted TBR did not demonstrate better performance and, to the contrary, showed a significant decrease in selectivity of catalyst. The TBR with non-diluted catalyst resulted in c. 50% selectivity towards N2, which is the desired end product due to its inert nature. The TBR with 1:2 diluted catalyst resulted in selectivity of nearly 100% towards NH4+. To better understand reduction mechanisms and selectivity, a series of experiments were performed and it was found the support had no direct role in selectivity. Rather, the change in selectivity was due to high hydrogen concentrations on the catalyst surface. In the diluted catalyst bed, reactive metal surfaces were geographically dispersed, allowing more time for hydrogen mass transfer from the gas to liquid phase. This led to higher hydrogen concentrations on the catalyst surface, which altered the N:H ratio and shifted selectivity towards NH4+. In contrast, in the non-diluted catalyst bed, reactive metal surfaces are found throughout the reactor, leaving less time for hydrogen mass transfer and resulting in a lower concentration of hydrogen on each metal surface.
Overall, this thesis advanced the state of the art for a hybrid IX-catalyst system and brought the system closer to economic feasibility. The modeling and experimental approaches served to more thoroughly evaluate the system and provide focus on the remaining barriers to increased improvement. This thesis also highlighted the critical role hydrogen mass transfer played as a barrier to a significant step forward in technology development. Reactor design contributed to improvements in the catalytic system, but were unable to completely overcome mass transfer limitations thus far. The findings from this thesis supported additional research directions regarding hydrogen delivery, reactor design and techno-economic analysis.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-12-01The student, Allison Bergquist, accepted the attached license on 2016-11-21 at 09:50.The student, Allison Bergquist, submitted this Dissertation for approval on 2016-11-21 at 10:02.This Dissertation was approved for publication on 2016-11-21 at 15:55.DSpace SAF Submission Ingestion Package generated from Vireo submission #10281 on 2017-02-28 at 14:36:35Made available in DSpace on 2017-03-01T16:36:53Z (GMT). No. of bitstreams: 3
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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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