1,720,981 research outputs found
SciExpeM - 10.5281/zenodo.8283321
No full textIssayev, Gani; Giri, Binod Raj, 0000-0001-9812-4455; Elbaz, Ayman M.; Shrestha, Krishna Prasad, 0000-0001-5672-7354; Mauss, Fabian, 0000-0002-6305-8213; Roberts, William L.; Farooq, Aamir - Renewable Energy, 2022, (181), 1353-137
SciExpeM - 10.5281/zenodo.8326025
No full textIssayev, Gani; Giri, Binod Raj, 0000-0001-9812-4455; Elbaz, Ayman M.; Shrestha, Krishna Prasad, 0000-0001-5672-7354; Mauss, Fabian, 0000-0002-6305-8213; Roberts, William L.; Farooq, Aamir - Renewable Energy, 2022, (181), 1353-137
Autoignition and reactivity studies of renewable fuels and their blends with conventional fuels
No full textPopulation growth and increasing standards of living have resulted in a rapid demand for energy. Our primary energy production is still dominated by fossil fuels. This extensive usage of fossil fuels has led to global warming, environmental pollution, as well as the depletion of hydrocarbon resources. The prevailing difficult situation offers not only a challenge but also an opportunity to search for alternatives to fossil fuels. Hence, there is an urgent need to explore environmentally friendly and cost-effective renewable energy sources. Oxygenates (alcohols, ethers) and ammonia are among the potential renewable alternative fuels of the future.
This thesis investigates the combustion characteristics of promising alternative fuels and their blends using a combination of experimental and modelling methodologies. The studied fuels include ethanol, diethyl ether, dimethyl ether, dimethoxy methane, γ-valerolactone, cyclopentanone, and ammonia. For the results presented in this thesis, the studies may be classified into three main categories:
1. Ignition delay time measurements of ethanol and its blends by using a rapid compression machine and a shock tube. The blends studied include binary mixtures of ethanol/diethyl ether and ternary mixtures of ethanol/diethyl ether/ethyl levulinate. A chemical kinetic model has been constructed and validated over a wide range of experimental conditions. The results showed that a high-reactivity fuel, diethyl ether, may be blended with a low-reactivity fuel, ethanol, in varying concentrations to achieve the desired combustion characteristics. A ternary blend of ethanol/diethyl ether/ethyl levulinate may be formulated from a single production stream, and this blend is shown to behave similarly to a conventional gasoline.
2. Ignition delay time and flame speed measurements of ammonia blended with combustion promoters by utilizing a rapid compression machine and a constant volume spherical reactor. The extremely low reactivity of ammonia makes it unsuitable for direct use in many combustion systems. One of the potential strategies to utilize ammonia is to blend it with a combustion promoter. In this work, dimethyl ether, diethyl ether, and dimethoxy methane are explored as potential promoters of ammonia combustion. Chemical kinetic models were developed and validated in the high temperature regime by using flame speed data and in the low-to-intermediate temperature regime by using ignition delay time data. The results showed that even a small addition (~ 5 – 10%) of combustion promoters can significantly alter ammonia combustion, and diethyl ether was found to have the highest propensity to enhance ammonia ignition and flame propagation. Blends of combustion promoters with ammonia can thus be utilized in modern downsized turbo-charged engines.
3. Octane boosting and emissions minimization effects of next generation oxygenated biofuels. These studies were carried out using a cooperative fuel research engine operating in a homogenous charge compression ignition (HCCI) mode. The oxygenated fuels considered here include γ-valerolactone and cyclopentanone. The results showed that γ-valerolactone and cyclopentanone can be effective additives for octane boosting and emission reduction of conventional fuels.
Overall, the results and outcomes of this thesis will be highly useful in choosing and optimizing alternative fuels for future transportation systems
Measurements of OH* and NH* profiles in hydrogen-ammonia-air counterflow diffusion flames
No full text
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
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