1,721,001 research outputs found
Controle ótimo H2 para coluna de flotação.
No full textDevido ao aumento na demanda de recursos naturais não renováveis e a inevitável exaustão das jazidas minerais de alto teor, o desafio de efetuar o beneficiamento de minérios mais complexos, atendendo a especificações cada vez mais rígidas, tem proporcionado um maior destaque ao processo de flotação em coluna no contexto da indústria mineral. Na flotação em coluna, partículas hidrofóbicas, de um fluxo descendente de material alimentado a uma altura de aproximadamente ⅔ da coluna, medidos a partir de sua base, são arrastadas para uma zona de espuma por um fluxo ascendente de bolhas de ar em contracorrente, sendo que as partículas hidrofílicas são levadas para a região de limpeza por um fluxo de água de lavagem. Esta técnica de beneficiamento de minério têm se consolidado por permitir melhorias dos concentrados na aplicação a diferentes tipos de minérios, incluindo os de granulometrias de liberação mais fina, e economia no investimento e manutenção de projeto. Neste trabalho é apresentado um sistema de controle multivariável robusto para o processo de flotação em coluna utilizando um controlador ótimo H2. A utilização desta técnica de controle é bastante pertinente, considerando a sua grande capacidade em manter a estabilidade do processo e rejeitar perturbações. Este sistema de controle no processo de flotação em coluna atua de forma direta sobre as variáveis manipuladas (vazão de água de lavagem, ar e não flotado) de modo a afetar adequadamente as variáveis controladas (nível da camada de espuma, bias e holdup do ar) acompanhando as variações em seus valores de referência e minimizando a interação entre as variáveis, mesmo com a ocorrência de perturbações. É apresentado o desenvolvimento e avaliação do projeto do controlador multivariável H2 para a operação de coluna de flotação visando melhoria no desempenho final do processo. Ferramentas de software são utilizadas para simular diversas condições operacionais sendo que a avaliação da eficiência do controlador proposto é realizada verificando as respostas obtidas das simulações.Due to the increase in demand for non-renewable natural resources and unavoidable depletion of mineral deposits of high-level, the challenge to make the mineral processing more complex, given the increasingly strict specifications, has provided a greater prominence to the column flotation process in the mineral industry. In a column flotation, hydrophobic particles, in a downward flow of material supplied fed to a height of about ⅔ of the column, measured from its bottom, are dragged into a foaming zone on an upward flow of air bubbles in counterflow, and the particles hydrophilic (pulp) are taken to the cleaning zone by a wash water flow. This technique of mineral processing have been consolidated to allow improvements in the concentrates grade in the implementation to different types of minerals, including the liberation of finest grain size, economy in investment and maintenance of projects. This work present a robust multivariable control system for a flotation column process based on a H2 controller. This proposal is quite appropriate, when considering its great capacity to maintain the stability of the process and disturbances rejection of the system. This control system in flotation column process acts directly on the manipulated variables (wash water, air and non-floated fraction flow rates) in order to properly adjust controlled variables (froth layer height, bias and air holdup in the recovery zone), maintaining set-point changes and minimizing the interaction between the variables, even with the occurrence of any perturbations or other disturbances. It is presented the development and evaluation of the design of multivariable H2 controller to column floatation, aiming to improving the performance of the end of the process. Software tools are used to simulate various operating conditions, and the evaluation of the efficiency of the proposed controller is done checking output responses obtained of the simulations
Controle ótimo H2 para coluna de flotação.
No full textDevido ao aumento na demanda de recursos naturais não renováveis e a inevitável exaustão das jazidas minerais de alto teor, o desafio de efetuar o beneficiamento de minérios mais complexos, atendendo a especificações cada vez mais rígidas, tem proporcionado um maior destaque ao processo de flotação em coluna no contexto da indústria mineral. Na flotação em coluna, partículas hidrofóbicas, de um fluxo descendente de material alimentado a uma altura de aproximadamente ⅔ da coluna, medidos a partir de sua base, são arrastadas para uma zona de espuma por um fluxo ascendente de bolhas de ar em contracorrente, sendo que as partículas hidrofílicas são levadas para a região de limpeza por um fluxo de água de lavagem. Esta técnica de beneficiamento de minério têm se consolidado por permitir melhorias dos concentrados na aplicação a diferentes tipos de minérios, incluindo os de granulometrias de liberação mais fina, e economia no investimento e manutenção de projeto. Neste trabalho é apresentado um sistema de controle multivariável robusto para o processo de flotação em coluna utilizando um controlador ótimo H2. A utilização desta técnica de controle é bastante pertinente, considerando a sua grande capacidade em manter a estabilidade do processo e rejeitar perturbações. Este sistema de controle no processo de flotação em coluna atua de forma direta sobre as variáveis manipuladas (vazão de água de lavagem, ar e não flotado) de modo a afetar adequadamente as variáveis controladas (nível da camada de espuma, bias e holdup do ar) acompanhando as variações em seus valores de referência e minimizando a interação entre as variáveis, mesmo com a ocorrência de perturbações. É apresentado o desenvolvimento e avaliação do projeto do controlador multivariável H2 para a operação de coluna de flotação visando melhoria no desempenho final do processo. Ferramentas de software são utilizadas para simular diversas condições operacionais sendo que a avaliação da eficiência do controlador proposto é realizada verificando as respostas obtidas das simulações.Due to the increase in demand for non-renewable natural resources and unavoidable depletion of mineral deposits of high-level, the challenge to make the mineral processing more complex, given the increasingly strict specifications, has provided a greater prominence to the column flotation process in the mineral industry. In a column flotation, hydrophobic particles, in a downward flow of material supplied fed to a height of about ⅔ of the column, measured from its bottom, are dragged into a foaming zone on an upward flow of air bubbles in counterflow, and the particles hydrophilic (pulp) are taken to the cleaning zone by a wash water flow. This technique of mineral processing have been consolidated to allow improvements in the concentrates grade in the implementation to different types of minerals, including the liberation of finest grain size, economy in investment and maintenance of projects. This work present a robust multivariable control system for a flotation column process based on a H2 controller. This proposal is quite appropriate, when considering its great capacity to maintain the stability of the process and disturbances rejection of the system. This control system in flotation column process acts directly on the manipulated variables (wash water, air and non-floated fraction flow rates) in order to properly adjust controlled variables (froth layer height, bias and air holdup in the recovery zone), maintaining set-point changes and minimizing the interaction between the variables, even with the occurrence of any perturbations or other disturbances. It is presented the development and evaluation of the design of multivariable H2 controller to column floatation, aiming to improving the performance of the end of the process. Software tools are used to simulate various operating conditions, and the evaluation of the efficiency of the proposed controller is done checking output responses obtained of the simulations
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
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