1,720,953 research outputs found
Experimental evaluation of the effect of thermal heat and pressure pre-treatment on primary sludge anaerobic digestion
No full textStudies have proved that anaerobic digesters have been traditionally used for stabilization of sewage sludge before disposal. Methane and carbon dioxide are produced as by products bacterial synthesis of organic material in an oxygen deficient environment (Nopharatana et al., 1998). More recently development of the thermal hydrolysis process pre-treatment of sewage sludge has shown great economic and financial potential in terms of; an increased sludge degradability implying more biogas production, improved digestion rate, stable and highly efficient digester, improved dewaterability of sludge and finally pathogen free cake as a final product which can be used for soil conditioning. The generation of more biogas and class A biosolids would fit into the sustainable developments goals and is in line with the changing paradigms that involve resource recovery from waste. The research questions posed in this investigation is: How does thermal heat and pressure (THP) pre-treatment affect primary sludge input characteristics for anaerobic digestion (AD) process in completely mixed AD systems? The overarching aim of this study is to evaluate the effect of THP, with a reduced temperature and pressure (of 114°C and pressure 1.7 bars) on primary sludge (PS) degradability under Mesophilic (37°C) anaerobic digestion (AD) conditions. The specific objectives are: (i) comparison of selected anaerobic digester performance parameters for pre-treated and untreated primary sludges over the selected varying sludge retention times (SRTs) of 8, 10, 12, 15 and 30 days, (ii) determination of the unbiodegradable particulate fraction (fPS'up) for both the pre-treated and untreated primary sludge and their hydrolysis rates, (iii) complete elemental characterization stoichiometry and weak acid base chemistry for both primary sludges and (iv) graphical comparison of measured data and anaerobic digestion model-predicted results. The effect of thermal heat and pressure (THP) pre-treatment on primary sludge degradability was evaluated. Primary sludge was heated at 114°C at a pressure of 1.7 bars in a pressure cooker (model number 17995) for 1 hour and anaerobically digested. The degradability of the pre-treated primary sludge fed to the digester (Digester 2; D2) was compared to an identical control digester (Digester 1: D1) fed the same sludge without heat pre-treatment. Both digesters were operated for 30, 15, 12, 10 and 8 days SRT. The percentage of Chemical Oxygen Demand (COD) removal for D1 ranged from 17% a to 54%, while that of D2 ranged from 16% to 62% for 8 to 30 day SRT respectively, gas production per liter influent for D1 ranged from 1.94 liter gas/liter influent to 19.08 liter gas/liter influent while that for D2 ranged from 1.81 liter gas/liter influent to 20.01 liter gas/liter influent, methane gas composition for both D1 and D2 remains the same for all the sludge ages varying between 50%-69% for methane and 34% to 45% for carbon dioxide. This signifies stability in both digesters. The effluent volatile fatty acid (VFA) concentration is very low (less than 0.08 g COD/L) in concentration and notably below that measured in the influent for both digesters except for the 15-day SRT D2 which was taken as an outlier. The low effluent VFA concentration signifies stability of both digesters. A Ripley ratio of less than 0.4 in both digesters indicates stable conditions, (Jiang et al. 2012). The effluent H2CO3*Alk., and pH for both digesters D1 and D2 is similar ranging from 1167 to 1990 mg/ L CaCO3 and 1145 to 2016 mg/ L CaCO3 respectively at pH ranging from 6.77 to 7.16 and 6.83 to 7.08 for D1 and D2 respectively. These additional results qualitatively supported that the heat pre-treatment increased the degradability of the primary sludge. To quantify the increase in degradability by heat pre-treatment, the steady state anaerobic digestion (AD) model of Sötemann et al. (2005) was calibrated to the D2 and control D1 results. However, because the values of the measured methane production results were more consistent than the measured effluent COD concentration results, the AD was recast in terms of the methane gas production instead of the effluent COD concentration as the basis for calibration. With statistical curve fitting techniques, the unbiodegradable particulate organic (UPO) fraction of the primary sludge (fPS'up) and saturation (Contois) kinetics specific hydrolysis rate constants were determined for the control D1 AD to be 0.35, KM = 1.595 gCOD/(gCOD.d) and KS = 2.607 gCOD/L. While the KM and KS yield a faster hydrolysis rate than observed by Sötemann et al. (2005), the UPO fraction was closely the same (0.36). For the pre-heated sludge AD D2, the UPO fraction was 0.22 and saturation (Contois) kinetics specific hydrolysis rate constants were KM =1.474 gCOD/ (gCOD.d) and KS = 0.971 gCOD/L. From this it was concluded that the degradability of primary sludge PS was increased in two ways: (1) by converting some (~1/3rd) of the Unbiodegradable Particulate Organics (UPO) to Biodegradable Particulate Organics (BPO) and (2) increased hydrolysis rate of the BPO. The AD model of Sötemann et al. (2005) also comprises a stoichiometric section that is sequential to the part which calculates sludge breakdown (i.e., BPO utilized) via hydrolysis kinetics. This stoichiometric section is used to calculate the changes in H2CO3* Alk., FSA, partial pressure of the biogas and digester pH from the concentration and composition of the BPO utilized. Using this stoichiometric part in reverse, and assuming 100% carbon flux mass balance over the digesters, the composition of the used BPO was determined from the differences in the measured concentrations between influent and effluent. For the control digester D1, the BPO composition was found to be C1H0.647O0.065N0.063 and for D2 with heat pre-treatment it was C1H0.541O0.087N0.067. While these BPO compositions were similar for the D1 and D2 digesters, both are marked different to the BPO compositions previously observed by (Ekama, 2009) e.g. C1.0H2.0O0.571N0.052 by (Sötemann et al., 2005). The different BPO compositions than previously obtained is expected because the composition of the organics depends on the pollutants sources of the wastewater and could vary on a daily basis (Gaszynski, 2021). This research provides evidence that with THP pre-treatment the degradability of primary sludge is improved by increasing both the biodegradable fraction and the hydrolysis rate. However, because this is the first study to provide such evidence, it is recommended the further research be done which should include a method devised for validating the UPO composition (in this case it was set to be the same as observed in literature studies; (Gaszynski, 2021; Ekama et al., 2005). Such a method may involve batch AD of the sludge in question at a long solids retention time (>60d; All organics eventually degrade at very long sludge ages at but sludge ages of above 60d are deemed too high for considered design of AD systems (Sötemann et al., 2005)). Elemental analysis of influent and effluent sludges so that the calculated composition of the BPO is not dependent on the assumed composition of the UPO
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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