1,720,975 research outputs found
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
Injection System Assessment to Optimize Performance and Emissions of a Non-Road Heavy Duty Diesel Engine: Experiments and CFD Modeling
No full textVariations 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
Gasoline Partially Premixed Combustion: High Efficiency, Low NOx and Low Soot by using an Advanced Combustion Strategy and a Compression Ignition Engine
No full textA light-duty engine Volvo D5 was run with gasoline to demonstrate that
high-octane number fuels, in compression ignition engines, are able to achieve
high effi ciency, low NOx and soot simultaneously. An advanced three stage
injection strategy was developed. A load sweep was performed between 6 and
17 bar IMEP and 2000 rpm. Gross indicated effi ciency stays fairly constant at
47% with very low NOx and soot. In the second section of the paper, diesel was
compared with gasoline, while in the fi nal part the commercial 140°UA nozzle was
compared with the narrower one, 120°, used in the above-mentioned experiments
An Experimental Analysis on Diesel/n-Butanol Blends Operating in Partial Premixed Combustion in a Light Duty Diesel Engine
No full textThis paper reports results of an experimental investigation performed on a commercial diesel engine supplied with fuel blends having low cetane number to attain a simultaneous reduction in NOx and smoke emissions. Blends of 20% and 40% of n-butanol in conventional diesel fuel have been tested, comparing engine performance and emissions to diesel ones. Taking advantage of the fuel blend higher resistance to auto ignition, it was possible to extend the range in which a premixed combustion is achieved. This allowed to match the goal of a significant reduction in emissions without important penalties in fuel consumption.
The experimental activity was carried on a turbocharged, water cooled, 4 cylinder common rail DI diesel engine. The engine equipment included an exhaust gas recirculation system controlled by an external driver, a piezo-quartz pressure transducer to detect the in-cylinder pressure signal and a current probe to acquire the energizing current to the injector. Two operating conditions were tested, [email protected] of BMEP and [email protected] of BMEP. The effect of injection pressure, start of injection and exhaust gas recirculation for these different combustion regimes were explored in order to understand how they affect the combustion process and engine out emissions.
Retarded SOIs joint to reduced O2 concentration at intake allowed to increase the ignition delay providing more time for the air-fuel mixing before auto-ignition. As a result, a partial premixed combustion was achieved for both fuel blends with an improvement in smoke and NOx emissions
Effects of Premixed Low Temperature Combustion of Fuel Blends with high Resistance to Auto-ignition on Performances and Emissions in a High Speed Diesel Engine
No full textThis paper reports results of an experimental investigation to demonstrate the potential to employ blends of fuels having low cetane numbers that can provide high resistance to auto-ignition to reduce simultaneously NOx and smoke. Because of the higher resistance to auto-ignition, blends of diesel and gasoline at different volume fraction may provide more time for the mixture preparation by increasing the ignition delay. The result produces the potential to operate under partially premixed low temperature combustion with lower levels of EGR without excessive penalties on fuel efficiency. In addition to the diesel fuel, the tested blends were mixed by the baseline diesel with 20% and 40% of commercial EURO IV 98 octane gasoline by volume, denoted G20 and G40. The experimental activity has been performed on a turbocharged, water cooled, DI diesel engine, equipped with a common rail injection system. The engine equipment includes an exhaust gas recirculation system controlled by an external driver, a piezo-quartz pressure transducer to detect the in-cylinder pressure signal and a current probe to acquire the energizing current to the injectors. Engine tests have been carried out at the engine speeds of 2500 rpm and a BMEP of 0.8 MPa exploring the effect of the start of injection, exhaust gas recirculation, injection pressure on combustion behavior and engine out emissions. The main results of the investigation have provided to realize a premixed low temperature combustion by the management of EGR rate, injection pressure and the longer ignition delay induced jointly by the higher resistance to auto ignition of fuel blends and their higher volatility. Results of smoke emissions have been cut down to zero for G20 and G40 blends at moderate level of injection pressure and oxygen concentration at the intake
Experimental study on performance and emissions of a high speed diesel engine fuelled with n-butanol diesel blends under premixed low temperature combustion
No full textIn the present paper, results of an experimental investigation carried out in a modern diesel engine running at different operative conditions and fuelled with blends of diesel and n-butanol, are reported. The
exploration strategy was focused on the management of the timing and injection pressure to achieve a condition in which the whole amount of fuel was delivered before ignition. The aim of the paper was to evaluate the potential to employ fuel blends having low cetane number and high resistance to autoignition to reduce engine out emissions of NOx and smoke without significant penalty on engine performance.
Fuel blends were mixed by the baseline diesel (BU00) with 20% and 40% of n-butanol by volume.
The n-butanol was taken by commercial production that is largely produced through petrochemical pathways
although the molecule is substantially unchanged for butanol produced through biological mechanisms.
The experimental activity was performed on a turbocharged, water cooled, DI diesel engine, equipped with a common rail injection system. The engine equipment includes an exhaust gas recirculation system controlled by an external driver, a piezo-quartz pressure transducer to detect the in-cylinder pressure signal and a current probe to acquire the energizing current to the injectors. Engine tests were carried out at 2500 rpm and 0.8 MPa of BMEP exploring the effect of start of injection, O2 concentration at intake
and injection pressure on combustion behavior and engine out emissions. The in-cylinder pressure and rate of heat release were investigated for the neat diesel and the two blends to evaluate engine performance and exhaust emissions both for the conventional diesel and the advanced premixed combustion
processes.
The management of injection pressure, O2 concentration at intake and injection timing allowed to realize a partial premixed combustion by extending the ignition delay, particularly for blends. The main results of the investigation made reach smoke and NOx emissions due to the longer ignition delay and a better mixing control before combustion. The joint effect of higher resistance to auto ignition and higher volatility of n-butanol blends improved emissions compared to the neat diesel fuel with a low penalty on fuel consumption
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
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