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Heat and mass transfer in gas-solid packed beds
Get PDFThe present thesis probes the heat and mass transfer phenomena in packed bed of particles. The gap in literature for realistically packed dense particle packings is explored, following which a new methodology to study external heat transfer is presented and evaluated with deep sensitivity analysis. The newly developed method is applied to obtain new closure models for external heat and mass transfer in packed beds of mono-disperse spherical particles and cylindrical particles of different aspect ratios. In addition, the obtained data helps refit the new Ergun constant for pressure drop in these dense packings. A step by step examination for internal mass transfer and reactions depending upon several levels of complexities in literature i.e. different reaction order, multiple reacting species, and gas volume generation/consumption and in practical application of steam methane reforming reveals the need for improvement in industrially viable 1D models. The developed closure models for external heat and mass transfer along with the data from computationally expensive particle-resolved direct numerical simulations (PR-DNS) in dense packings of monodisperse spherical particles with catalytic reactions inside the porous particles are used to verify and improve the internal mass transfer closures for 1D models through multiscale modelling. The enhanced 1D model is then used to simulate an industrial scale packed bed chemical looping reforming (PBCLR) reactor. As an application of the work done in this PhD, an alternative to resolved 3D simulation is also presented in this thesis in form of non-resolved Euler Lagrange 3D simulations. The results obtained are documented and discussed in appropriate chapters of this thesis.RESUMO: A presente tese estuda os fenómenos de transferência de calor e massa em leito fixo de partículas. A lacuna na literatura no que respeita a leitos fixos de partículas é explorada neste trabalho. Deste estudo resultou uma nova estratégia para análise de transferência de calor externa que é descrita e avaliada através uma análise de sensibilidade minuciosa. O método desenvolvido é aplicado no desenvolvivento de novas correlações para transferência de calor externa e transferência de massa em leitos fixos de partículas esféricas mono-dispersas e partículas cilindricas com diferentes proporções. Para além disso, a informação obtida ajuda também a ajustar novas constantes de Ergun para a queda de pressão em leitos densos.
Uma análise detalhada da literatura no que respeita à transferência de massa interna e reacções químicas dependendo de diferentes níveis de complexidade como diferente ordem de reacção, multiplas espécies reaccionais, volume de gás produzido/consumido e considerando a aplicação no processo de “steam methane reforming” revela a necessidade de melhorar os modelos 1D actualmente usuados a nível indústrial. As correlações desenvolvidas para transferência de calor externa e transferência de massa juntamente com a informação obtida de simulações “particle-resolved direct numerical simulations” (PR-DNS) de elevados custos computacionais em leitos densos de particulas esféricas mono-dispersas com reacções químicas dentro de partículas porosas são usadas para verificar e melhorar as correlações de transferência de massa interna em modelos 1D através de uma metodologia de modelação multiescala.
O modelo 1D melhorado é então usado para simular reactores de leito fixo à escala indústrial para o processo de “chemical looping reforming”. O trabalho desenvuelto nesta tese é aplicado em “non-resolved Euler Lagrange 3D simulations” que são uma alternativa às mais complexas “resolved 3D simulations”. Os resultados obtidos são descritos e discutidos nos diferentes capítulos desta tese
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
Study and Implementation of Morphology for Speckle Noise Removal and Edge Detection
No full textM.E. (Electronic Instrumentation and Control)The field of computer vision is concerned with extracting features and information from images in order to make analysis of images easier, so that more and more information can be extracted. The primary goal of this thesis is to remove speckle noise present in images used and then to obtain the useful edges in the output image obtained after noise has been removed. The method use for both noise removal and edge detection is mathematical morphology. On the basis of set theory, mathematical morphology is used for image processing, analyzing and comprehending. It is a powerful tool in the geometric morphological analysis and description. Noise removal is very important preprocessing step. The existence of speckle is unwanted since it disgrace image quality and it affects the tasks of individual interpretation and diagnosis. Eliminating such noise is an important preprocessing step. Nonlinear filtering techniques are becoming increasingly important in image processing applications, and are often better than linear filters at removing noise without distorting image features. One structure for designing nonlinear filters is mathematical morphology. By using combination of mathematical morphological operations like opening and closing help in removing speckle noise very effectively. The next step after noise removal is edge detection. The need of edge detection is to find the discontinuities in depth, discontinuities in surface orientation, changes in material properties and variations in scene illumination. Again mathematical morphological operations are used for edge detection and enhancement of edges that are detected.
For the evaluation of the performance of proposed algorithm parameters like Signal to Noise Ratio (SNR), Root Mean Square Error (RMSE), Correlation of Coefficient (Coc), and Mean Structural Similarity Index Measure (MSSIM). These parameters are used to calculate the image quality of the output image obtained after speckle noise removed by proposed algorithm and help in comparing the results with that of previously used filters for speckle noise. Another parameter named edge preserving index (EPI) is used for measuring the edges preserved and detected by proposed algorithm with that of previously used edge detectors like Sobel, Prewitt and Canny. Based on the values of these parameters the performance of algorithm in terms of speckle noise removal and edge preservation is discussed
Heat and mass transfer in gas-solid packed beds
No full textThe present thesis probes the heat and mass transfer phenomena in packed bed of particles. The gap in literature for realistically packed dense particle packings is explored, following which a new methodology to study external heat transfer is presented and evaluated with deep sensitivity analysis. The newly developed method is applied to obtain new closure models for external heat and mass transfer in packed beds of mono-disperse spherical particles and cylindrical particles of different aspect ratios. In addition, the obtained data helps refit the new Ergun constant for pressure drop in these dense packings. A step by step examination for internal mass transfer and reactions depending upon several levels of complexities in literature i.e. different reaction order, multiple reacting species, and gas volume generation/consumption and in practical application of steam methane reforming reveals the need for improvement in industrially viable 1D models. The developed closure models for external heat and mass transfer along with the data from computationally expensive particle-resolved direct numerical simulations (PR-DNS) in dense packings of monodisperse spherical particles with catalytic reactions inside the porous particles are used to verify and improve the internal mass transfer closures for 1D models through multiscale modelling. The enhanced 1D model is then used to simulate an industrial scale packed bed chemical looping reforming (PBCLR) reactor. As an application of the work done in this PhD, an alternative to resolved 3D simulation is also presented in this thesis in form of non-resolved Euler Lagrange 3D simulations. The results obtained are documented and discussed in appropriate chapters of this thesis
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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