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Numerical modelling and analysis of combustion in DI and PFI CNG engines - A study under different EGR dilution and Hydrogen doping conditions.
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
CFD modelling of natural gas combustion in IC engines under different EGR dilution and H2-doping conditions
Full text linkThe present paper provides a contribution to the CFD modelling of reacting flows in IC engines fueled with natural gas. Despite the fact that natural gas has been widely investigated into in the last decades, the literature still lacks reliable models and correlations to be exploited so as to efficiently support the design of internal combustion engines. The paper deals with the development of an accurate CFD model, capable of capturing the effects of the engine working conditions and mixture compositions on the combustion process. The CFD model is based on the Extended Coherent Flame Model combustion model coupled to a laminar flame speed one through a user subroutine, which replaces the commonly adopted empirical correlations. The flame speed values have been derived from the application of a reaction mechanism for natural gas-air-residual gases mixtures.
In the second part of the paper, the model is validated and applied to the investigation of the dependence of the combustion quality on the fuel doping with hydrogen as well as on the mixture dilution with EGR. As a matter of fact, the attractiveness of the mixture dilution with EGR relies on the potential in containing engine-out NOx emissions as well as in reducing the pumping losses, thus further abating fuel consumption at part loads. Finally, the effects of fuel blending with H2 on the EGR tolerance is discussed in the paper
Paper-based miniaturized device for detection of beta- lactam antibiotics in milk
No full textThis paper showcases a paper-based pillar array device for detection of beta-lactam group of antbiotics in milk which works on the induction principal. Presence of beta-lactam antibiotics in milk poses a risk for human health including allergy, carcinogenicity and microbial drug resistance. Simple to operate and inexpensive devices are required for detection of antibiotics in milk especially in remote areas where medical facilities are limited. Here we illustrate the design, fabrication and working principle of the device along with detection of beta-lactam group of antibiotics in milk samples. Ultimately, the device will be used for antimicrobial resistance testing in Dairy settings
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
Variations 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
Experimental and Numerical Analysis of Diluted Combustion in a Direct Injection CNG Engine Featuring Post- Euro-VI Fuel Consumption Targets
Full text linkThe present paper is concerned with part of the work performed by Renault, IFPEN and Politecnico di Torino within a research project founded by the European Commission. The project has been focused on the development of a dedicated CNG engine featuring a 25% decrease in fuel consumption with respect to an equivalent Diesel engine with the same performance targets. To that end, different technologies were implemented and optimized in the engine, namely, direct injection, variable valve timing, LP EGR with advanced turbocharging, and diluted combustion. With specific reference to diluted combustion, it is rather well established for gasoline engines whereas it still poses several critical issues for CNG ones, mainly due to the lower exhaust temperatures. Moreover, dilution is accompanied by a decrease in the laminar burning speed of the unburned mixture and this generally leads to a detriment in combustion efficiency and stability. The optimization of in-cylinder turbulence plays a fundamental role in compensating this trend.
The present paper is specifically focused on the characterization of the diluted combustion in the direct injection engine. The results of an experimental activity have been presented, aimed at characterizing the in-cylinder combustion process and the exhaust temperatures at 2000 rpm and variable load, both without dilution and with 20% of external EGR. At the same time, a 3-D numerical model for the in-cylinder turbulence and combustion simulation has been developed in Converge. The model embeds a user-specified laminar-flame speed submodel, which was derived from a 1-D combustion simulation model with detailed chemistry. The model has been calibrated against experimental data and then used to characterize the heat release dependence on the dilution. The experimental activity has evidenced the potential of EGR to increase the engine efficiency, by allowing to increase the boost level at full load and by reducing pumping losses at partial load. As far as the maximum allowed EGR rate is concerned, the CFD activity showed that the limit can be detected on the basis of a threshold value of the MFB0-50 interval. At 2000 rpm and medium load the maximum EGR rate ranged around 35% and showed an increasing trend versus load. It also demonstrated a decreasing trend against the engine speed
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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