1,720,970 research outputs found
Pyrolysis Chemical Kinetics of Polyoxymethylene Dimethyl Ethers of Various Chain Lengths
Get PDFMedium- and heavy-duty trucks powered primarily by diesel engines create ~26% of the transportation-related US greenhouse gas emissions. These types of engines, which are not likely to be eliminated in the near future due to their ubiquitous use, also produce soot and NOx emissions which are detrimental to health and the environment. Polyoxymethylene dimethyl ethers (PODEs) are a family of oxygenated hydrocarbon fuel additives that have shown promise for their soot emissions reduction properties. However, their uncertain chemistry must be better understood before PODEs may be used as a drop in diesel additive. The pyrolysis of PODEs of various chain lengths was explored in this work using reaction rate theory and pyrolysis chemical kinetic sub-mechanisms were developed for PODE combustion modeling. These models were validated against experimental data and they clarified the role of carbenes and other radicals products in PODE thermal decomposition. The results from this work provide useful insights into structural effects on oxymethylene ether decomposition chemistry.</p
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
Pyrolysis Chemical Kinetics of Polyoxymethylene Dimethyl Ethers of Various Chain Lengths
Get PDFMedium- and heavy-duty trucks powered primarily by diesel engines create ~26% of the transportation-related US greenhouse gas emissions. These types of engines, which are not likely to be eliminated in the near future due to their ubiquitous use, also produce soot and NOx emissions which are detrimental to health and the environment. Polyoxymethylene dimethyl ethers (PODEs) are a family of oxygenated hydrocarbon fuel additives that have shown promise for their soot emissions reduction properties. However, their uncertain chemistry must be better understood before PODEs may be used as a drop in diesel additive. The pyrolysis of PODEs of various chain lengths was explored in this work using reaction rate theory and pyrolysis chemical kinetic sub-mechanisms were developed for PODE combustion modeling. These models were validated against experimental data and they clarified the role of carbenes and other radicals products in PODE thermal decomposition. The results from this work provide useful insights into structural effects on oxymethylene ether decomposition chemistry.</p
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
Design of a Novel Microreactor to Study Short Residence Time Combustion
Get PDFMicroreactors are useful tools for understanding the short residence time reactions of biomass polymers and fuel molecules. When coupled with sensitive detection methods, microreactors have the ability to detect all molecules produced in the reactor, including stable, meta-stable, and radical species, making microreactors one of the few experiments where nearly all chemical species may be detected. At the University of Colorado Boulder, our microreactor studies have involved very small (~1 mm internal diameter, ~28 mm long) silicon carbide (SiC) tubes to study short residence time pyrolysis reactions in conjunction with photoionization mass spectrometry (PIMS) and Fourier transform infrared spectroscopy (FTIR). While much has been learned from this configuration, qualitative analysis is hampered by the fact that the pressure and velocity vary greatly within the reactor. To improve the performance of the Boulder microreactor system, this work explores modifying the reactor geometry to achieve better control over the thermofluid properties. Computational fluid dynamics (CFD) simulations were employed to explore how thermofluid properties within the reactor change as a function of reactor geometry, and a converging-nozzle structure was found to be the ideal geometry to control the internal thermodynamic conditions. New reactor prototypes were fabricated based on the simulation results. To verify the results of the CFD simulations for the new reactor geometry, a series of experiments are proposed to compare the performance of the original Boulder reactors with the new prototype reactors. These experiments will be conducted with the reactors installed in the PIMS configuration. Finally, a survey of potential alternative micro-reactor materials was conducted for future microreactor development. Currently, the SiC microreactor is limited to thermal decomposition experiments due to SiC reactivity with oxygen. To move towards oxidation experiments, a new material for the microreactor must be identified. Thermal conductivity, structural stability, and non-reactivity were all considered in the survey. The new microreactor designed in this thesis will assist scholars to carry out fundamental kinetic measurements of short residence time oxidation reactions of fuels in the future, which will lead a deeper understanding of fuel properties and promote the development of new fuel efficient, less-polluting engine technology
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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