1,721,002 research outputs found
Resistance to breakage and regrowth of agglomerates formed by tannin and Moringa oleifera Lam. addition as an alternative for post-treatment of agricultural effluents co-generated in UASB reactors
No full textNos processos de separação sólido-líquido a existência de aglomerados com determinado tamanho e resistência é um fator crucial, uma vez que esses devem possuir dimensões mínimas para serem facilmente removidos da fase líquida e, também, serem resistentes face ao estresse sofrido durante o transporte através de canais, aberturas e passagens. Igualmente importante é a capacidade dos agregados recrescerem quando eventualmente quebrados, recuperando parcialmente suas características antes de serem removidos do sistema. O presente trabalho investigou a ação dos coagulantes de base natural tanino e moringa na formação, resistência à quebra e recrescimento de aglomerados em efluentes agropecuários mistos da suinocultura e da bovinocultura de leite previamente codigeridos em reatores UASB. Ensaios de bancada foram realizados em um reator estático para simular as etapas de mistura rápida, floculação, quebra e refloculação em condições controladas. Foram investigados cinco diferentes cenários de quebra das partículas, com aplicação de incremento de agitação variando de 80 a 600 rpm. Ensaios sem agente coagulante e com aplicação de cloreto férrico foram realizados como controle, para comparação dos resultados. O monitoramento online do índice de floculação (IF), medida adimensional que indica, indiretamente, o tamanho das partículas existentes no meio, foi realizado ao longo dos ensaios via equipamento de análise de dispersão fotométrica (PDA). Os resultados demonstraram que os coagulantes de base natural contribuíram para a formação de agregados de maior dimensão, quando comparados aos formados nos ensaios-controle. Tanto a adição de Moringa Oleífera Lam (dosagens 0,5 a 40,0 g/L) quanto a de Tanfloc SL® (dosagens 100 a 800 mg/L) geraram aglomerados mais resistentes, com Fator de Resistência superior a 90%. No tocante ao potencial de recrescimento dos aglomerados, os resultados obtidos com o agente químico foram maiores, indicando que os aglomerados formados com cloreto férrico possuem menor tamanho e resistência, mas capacidade de retomada de tamanho quando as condições do meio permitem. Os resultados apontam que existe um ponto ótimo de aplicação dos coagulantes aplicados e, a depender das condições impostas pelo sistema, a utilização da moringa e do tanino no pós-tratamento de reatores UASB é uma alternativa potencialmente viável, com preceitos de economia circular.In the solid-liquid separation processes, the existence of agglomerates with suitable size and resistance is crucial for treatment good performance as flocs must resist stressing during the transport through channels, apertures and orifices. The ability of aggregates regrow when eventually broked is equaly important, recovering partially their characteristics before being removed from the system. The present work investigated the influence of natural coagulants tannin and moringa in formation, resistance and regrowth of agglomerates in animal sewage from swine and dairy cattle husbrandry previously codigested in UASB reactors. Bench tests were conducted in a static reactor to simulate the stages of rapid mixing, flocculation, breakage and refloculation under controlled conditions. Five diferent scenarios of particle´s breaking were investigated, with agitation ranging from 80 to 600 rpm. Trials without coaggulation agent and with application of ferric chloride were performed as control, to compare the results. The online monitoring of Focculation Index (FI), a dimensionless measure that indirectly indicates the size of the particles in the suspension was measured during the tests via photometric dispersion analysis equipment (PDA). The results showed that natural-based coagulants contributed to the formation of larger aggregates, when compared to those formed in the control trials. Both addition of MOL (dosages 0.5 to 40.0 g.L-1) and Tanfloc SL® (dosages 100 to 800 mg.L-1) generated more resistant agglomerates in the applied doses, with an SF greater than 90%. Regarding the potential for regrowth of the agglomerates, the results obtained with the chemical agent were greater, indicating that the agglomerates formed with ferric chloride have less size and resistance, but capacity to recover in size when the conditions of the environment allow. The results indicate that there is an optimum application point for the applied coagulants and, depending on the conditions imposed by the system, the use of moringa and tannin as UASB reactors post treatment is a alternative potentially viable, with precepts of circular econom
Study of floc strength and reflocculation aiming drink water treatment using image analysis and light scattering techniques
No full textEsta dissertação teve como objetivos a investigação da resistência e do recrescimento de flocos, produzidos durante a floculação de água destinada ao abastecimento, e foi dividida em duas etapas. Em primeiro lugar a resistência de agregados à quebra induzida por distúrbio hidrodinâmico foi investigada por meio de três técnicas macroscópicas de medição, a saber: fator de resistência (FR), a tensão local (σ) e o coeficiente de resistência do floco (γ). Num segundo momento a capacidade de recuperação do tamanho dos agregados foi investigada. O diâmetro estável (d) e o parâmetro característico da função de distribuição de tamanho de agregados (β) foram utilizados para analisar o processo refloculação após a quebra induzida dos agregados. Para obtenção das variáveis de interesse, foi utilizado método não intrusivo de análise de imagem e equipamento baseado em dispersão de luz. As águas de estudo foram preparadas em laboratório a partir de solução de ácido húmico (água tipo 1) e suspensão de caulinita (tipo 2), e coaguladas por dosagem de sal de alumínio em região do mecanismo de varredura. A floculação ocorreu em gradientes de velocidade médios (G) entre 20 e 120 s-1, e a ruptura ocorreu sob condições controladas com Gquebra de 800 s-1 por 10 segundos. Após a ruptura, a condição inicial foi reestabelecida para análise da recuperação de tamanho do agregado. Os resultados mostraram, para as duas água de estudo, uma tendência crescente para FR em resposta ao aumento de G. A mesma tendência foi observada para γ o que pode indicar que condições elevadas de agitação produzem flocos mais resistentes. Os resultados da análise da refloculação apontaram que o agregado não recupera totalmente seu tamanho, tanto para os flocos de Al-ácido húmico como para os de Al-caulinita. Para água tipo 1, o diâmetro estável dos agregados diminuiu de 332 μm antes da quebra, para 157 μm após a recuperação, e de 233 para 132 μm na água tipo 2, utilizando G de 20 s-1. O parâmetro β que exprime a distribuição de tamanho dos agregados, também apontou para uma diminuição geral do tamanho dos agregados, de forma que após a quebra a distribuição foi deslocada para as faixas de classificação de menor tamanho.This dissertation has aimed to investigate the strength and re-growth during the flocculation of drinking water, and was divided into two steps. The first one was investigate the rupture of floc caused by shear induced forces through three macroscopic techniques, namely: strength factor (FR), the average strength per unit area at the plane of rupture (σ) and the floc strength coefficient (γ). The second one was investigate the re-growth ability of flocs. The stable diameter (d) and the characteristic parameter of the aggregate size distribution function (β) were used to analyze the re-growth process after the induced breakage of the aggregates. The method was based on a non-intrusive image analysis monitoring technique and a light scattering equipment. The study waters were prepared in laboratory from humic acid solution (water type 1) and kaolinite suspension (type 2) and coagulated by dosing aluminum salt in the region of the “sweep flocculation” mechanism. The flocculation occurred for average velocity gradients (G) from 20 to 120 s-1 and the breakage occurred under controlled conditions for Gquebra of 800 s-1 for 10 seconds. After breakage, the initial condition was re-established for aggregate size recovery analysis. For the two study waters the results showed an increasing trend for FR in response to the increase of G. The same trend was observed for γ which may indicate that high agitation conditions produce more resistant flocs. The reflocculation analysis results showed that the aggregate did not fully recover its size, both for the aliquots of Al-humic acid and those of Al-kaolinite. The stable diameter of the aggregates for water type 1 decreased from 332 μm before breakage, to 157 μm after recovery, and from 233 to 132 μm in water type 2, using G of 20 s-1. The parameter β expressing the aggregate size distribution also pointed to a general decrease in aggregate size, so that after the breakage the distribution was shifted to the smaller size ranges.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)33004056089P
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
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