1,720,957 research outputs found
A simplified Mean Value Model of the combustion process for the simulation of Energetic Systems.
No full textCurrent environmental issues require continuous improvements of the performance of energetic systems, which are mainly based on combustion processes. In order to find solutions for maximizing the energy output while minimizing the fuel consumption and pollutants emissions, the optimization of the combustion processes within the plants plays a fundamental role. The purpose of this work was the creation of a flexible code for the fast simulation of combustion processes calculating the chemical equilibrium composition and adiabatic flame temperature of the mixture of products from the combustion of a generic CnHmOr fuel. Seven dissociation reactions have been taken into consideration, yielding eleven products species: CO2, CO, H2O, H2, O2, N2, OH, NO, O, N, H. The non-linear system of equations describing the equilibrium conditions has been numerically solved via the non- linear optimization tools of the Matlab® environment, using the Gauss-Newton and Levenberg-Marquardt algorithms. The adiabatic flame temperature and chemical composition of combustion products can be evaluated for both constant-volume and constant- pressure systems. A 0-D Simulink® model of the compression and expansion strokes of an Internal Combustion Engine (ICE) was then developed, using the described calculation code. The combustion process has been modeled as a sequence of instantaneous constant-volume reactions which involve a fraction of the total amount of fuel. At each simulation step the model evaluates temperature, pressure, volume and chemical composition at the equilibrium conditions through the well-known conservation equations. The fraction of burned fuel at each simulation time step is determined by a fuel burning rate (FBR) curve, which can be used to describe different combustion processes. The Matlab® calculation code has been validated by comparison with results obtained from the open literature, and proved to be accurate and robust. The Simulink® model demonstrates the potential applications of the developed program in the simulation of combustion-based energy systems, allowing the evaluation of changes in the thermodynamic state variables and equilibrium composition of the system
Un modello semplificato ai valori medi del processo di combustione per la simulazione dei Sistemi Energetici.
No full textMean Value Modeling of intake and exhaust systems of automotive engines: models identification and related errors
No full textControl and management issues are playing an important role in automotive applications to improve engine and powertrain performance and to lower specific fuel consumption and pollutant emissions. Mean Value Engine Models (MVEM) based on “grey-box” or faster “black-box” algorithms are usually adopted for control applications since they allow for real-time simulation of actual automotive engines. However, “grey“ or “black-box” models usually requires a significant amount of data (usually
from experimental investigations) for the identification of sub-models of each component: these data are often not available with the same degree of accuracy and, moreover, are usually gathered in operating conditions that are far from real on-engine
conditions.
In the paper a brief description of the identification procedures for MVMs of intake and exhaust systems developed by the authors is given. Uncertainties and shifts that affect results given by MVMs is analysed with reference to the accuracy of the identification procedure. To this extent a MVM of an actual turbocharged engine was used to analyse the effects on calculated outputs of defined shifts introduced in the identification parameters of intake/exhaust systems sub-models (with particular reference to
sub-models of compressor, turbine and EGR valves). Obtained results are reported in the paper to point out what sub-models have major effects on MVMs outputs and to study the degree of accuracy needed for their identification
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
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
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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