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Estudio del proceso de pirólisis de polímeros de desecho no clorados para su aplicación en la producción de gas de síntesis a través de la gasificación solar
No full textLos materiales plásticos son un tipo de material de los más versátiles, útiles y esenciales para la vida moderna. Sin embargo, los residuos plásticos generados son una cuestión de preocupación a nivel mundial, debido a su gran producción y consumo, además del hecho de que no existe un método que permita que se degraden fácilmente. Aunque no se conoce con exactitud la cantidad de residuos plásticos presentes en los entornos naturales, existe evidencia que indica que el destino final de los residuos plásticos son los océanos. Una de las principales razones de esta problemática se debe a que los métodos utilizados para su eliminación tienen impactos adversos sobre el ambiente. Existen diferentes vías de valorización de los residuos plásticos, una de esta es mediante el proceso de pirólisis. El proceso de pirólisis es un proceso termoquímico donde se rompen las cadenas poliméricas y se forman componentes de menor complejidad. El objetivo principal de este trabajo fue el estudio de la pirólisis como forma de valorización de los plásticos de desecho, que será un precursor para su futura aplicación en el proceso de gasificación solar para la obtención de productos de alto valor agregado. El uso de plásticos de desecho como materia prima para la producción sustentable de vectores energéticos a través de procesos termoquímicos, puede convertirse en una posible vía para afrontar la problemática que representan los plásticos de un solo uso. Se seleccionaron tres tipos de plástico como materia prima: polipropileno (PP, por sus siglas en inglés), polietileno de baja densidad (LDPE, por sus siglas en inglés) y politereftalato de etileno (PET, por sus siglas en inglés). Para la caracterización de las materias primas seleccionadas se realizaron diferentes análisis experimentales. Primero, se realizó la identificación de los plásticos a través de la técnica de espectroscopía infrarroja por transformada de Fourier (FTIR, por sus siglas en inglés). Los resultados de estos análisis experimentales se compararon con lo reportado en la literatura. Después se realizó el análisis térmico mediante una técnica acoplada de termogravimetría y calorimetría diferencial de barrido (TG - DSC, por sus siglas en inglés). Finalmente, el análisis cualitativo de los productos gaseosos de la degradación térmica de plásticos, se llevó a cabo por medio de un acoplamiento de técnicas de termogravimetría, cromatografía de gases y espectrometría de masas (TG-GC/MS, por sus siglas en inglés). En el análisis termogravimétrico se encontró que la magnitud de los parámetros de temperatura que involucran las reacciones de degradación térmica incrementaron cuando el valor de la tasa de calentamiento también aumentó. De los tres tipos de plástico que fueron estudiados para la identificación de sus productos de pirólisis, los experimentos de la degradación térmica del polipropileno fueron los que presentaron mejores resultados. De los cuatro experimentos realizados para identificación de componentes de los productos de pirólisis del PP, se encontró que el componente 2,4-dimetil-1-hepteno fue el de mayor abundancia en el intervalo de temperaturas donde se presenta la descomposición térmica. Para las cinco tasas de calentamiento evaluadas, el intervalo de temperaturas de la degradación térmica abarcó de 692.55 K como la mínima temperatura de inicio de la degradación hasta 776.3 K como máxima temperatura final de la degradación. El estudio cinético de las reacciones es útil para conocer el comportamiento de la degradación térmica de plásticos. Con datos termogravimétrico se estimaron los principales parámetros cinéticos, como la energía de activación, el factor preexponencial y el modelo de reacción se obtiene mediante diferentes métodos empíricos isoconversionales y de ajuste. Se encontró que los valores de la energía de activación fueron similares para todos los métodos isoconversionales evaluados. Los valores aproximados del valor preexponencial fueron calculados usando los modelos de reacción de los mecanismos de reaccionó más comúnmente utilizados en reacciones de estado sólido. Este trabajo es el preámbulo a la búsqueda de una forma sostenible de valorización de plásticos de desecho más abundantes en México y el planeta. El siguiente paso será la degradación de plásticos de desecho empleando un agente gasificante, esperando obtener moléculas más ligeras que puedan ser de utilidad en otros procesos de producción como materias primas o en vectores energéticos. La termodisociación deberá realizarse empleando una fuente de energía renovable, siendo una buena opción la energía solar concentrada, con la cual es posible obtener elevadas temperaturas.Plastic materials are one of the most versatile, useful and essential materials for the contemporary life. However, plastic waste are a global issue because of their high production and consumption; besides, there is not an easy way to degrade it. It is unknown exactly how much plastic waste are in the natural environment; although, there are evidence that the final destiny of the plastic wastes are the oceans. One of the principal reasons of this issue is because the actual methods of waste disposal have negative environmental impacts. There are different ways for valorization of plastic waste, one of them is through the pyrolysis process. Pyrolysis process is a thermochemical process where the polymeric chain is broken into less complex components. The principal aim of this work was the study of the pyrolysis as a way for valorisation of plastic wastes which will be a precursor for their future application in solar gasification process in order to obtain high value added products. The use of plastics waste as a feedstock for sustainable production of energy vectors through thermochemical processes could be a way to face the big issue related to the single use plastics. It was selected three different plastics as raw material: Polyethylene terephtalate (PET), polypropylene (PP) and low density polyethylene (LDPE). For the characterization of the raw material different experimental analysis were carried out. First, it has been made the identification of the raw material by means of Fourier Transform Infrared Spectroscopy (FTIR).The results of this experimental analysis were compared with the bibliography. Then, a thermal analysis was performed by a coupled technique of Thermogravimetric Analysis with Differential Scanning Calorimetry (TG-DSC). Finally, the qualitative analysis of gaseous products of the thermal degradation of plastics was made by means of a Thermogravimetric Analysis coupled with Gas Chromatography and Mass Spectrometry (TG-GC/MS). In thermogravimetric analysis it was found that the temperature parameters that involve the thermal degradation reactions increased when the heating rate is increased. From the three plastics studied for the identification of their pyrolysis products, the thermal degradation of polypropylene was the one that presented the best results in the four experiments carried out. The 2,4-Dimethyl-1-heptene component was identified in all experiments of PP as the principal and the most abundant component in the temperatures range studied for their thermal decomposition. For the five heating rates evaluated, the range of temperatures for thermal degradation was about from 692.55 K as the lowest value of start of the degradation temperature to 776.3 K as the maximum value of the end of the degradation. The kinetic study is useful to get knowledge about the behaviour of thermal degradation of plastics. With thermogravimetric data was estimated the principal kinetic parameters as activation energy, the preexponential factor and the reaction model was estimated by mean of different empirical isoconversional methods and fitting methods. It was found that the activation energy values were similar for all evaluated isoconversional methods. The aproximated value of the preexponential factor was calculated using reaction models of most common reaction mechanism considered in solid-state reactions. This work is a preliminary research towards to find a sustainable way for plastic waste valorisation in Mexico and the world. The next step will be the thermal degradation of plastic waste employing a gasifying agent, it is expected to obtain as a result of this gasification process less complex molecules that could be used as a raw material or as energy vectors. The thermal dissociation will be making through a renewable energy as the heat source. The solar concentrated energy is a good option because using this kind of energy source it is possible to obtain high temperatures
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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