1,721,004 research outputs found
Development, Setup, and Instrumentation of a New High-Performance Test Bench for Diesel Injection Systems: Preliminary Results on Multijet Common-Rail System Dynamics
No full textA General Conservative Homogeneous Two-Phase-Flow Model for Acoustic Cavitation Simulation in High-Pressure Injection Systems
No full textConservative Numerical Model and Analysis of Acoustic Cavitation in High-Pressure Injection Systems
No full textThermal Effect and Cavitation Simulation in High Pressure Injection System Transient Flows
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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
Shock Event Analysis, Characteristics Considerations and Conservativeness Influence in High-pressure Injection System Cavitating Flow Simulations
No full textA comparison between conservative and nonconservative models has been carried out for evaluating the influence of conservativeness on predicting transient flows in presence of cavitation induced discontinuities inside high-pressure injection systems. Even if nonconservative models can assure satisfactory accuracy in the evaluation of the wave propagation phenomena, they introduce fictitious source terms in the discretized equations. Such terms are usually negligible, but can play a significant role when discontinuities in the flow properties occur, producing appreciable errors on the pressure wave speed estimation. An analysis based on fluid characteristics around both the rarefaction and compression wave fronts has been carried out, showing that cavitation desinence is a shock occurrence, leading to a transition from a supersonic to a subsonic flow. For a significant evaluation of conservative and nonconservative model performances a conventional pumpline-nozzle injection system was considered because the pipe flow presented interesting cases of cavitation-induced shocks. The validity of the conservative model is substantiated by the comparison between computed pressure time-histories and experimental results at two pipe locations. The Rankine-Hugoniot jump conditions have been usefully applied to the numerical results obtained by the conservative model in order to calculate the sound speed of the traveling compression waves in the presence of cavitation. A novel algorithm of general application to calculate the shock speed predicted by nonconservative models, which points out the contribution of the internal fictitious fluxes in the wrong estimation of the shock velocity, has been introduced and validated through its application to Burgers' equatio
A comprehensive thermodynamic approach to acoustic cavitation simulation in high-pressure injection systems by a conservative homogeneous barotropic-flow model
No full textA general conservative numerical model for simulation of transmission-line unsteady fluid-dynamics has been developed and applied to high-pressure injection systems. A comprehensive thermodynamic approach for modeling acoustic cavitation, i.e. cavitation induced by wave propagation, was proposed on the basis of a homogeneous barotropic mixture model of a pure liquid in equilibrium with its vapor and a gas, both dissolved and undissolved. For the pure liquid flow simulation outside the cavitation regions, or in the absence of these, temperature variations due to compressibility effects were taken into account, for the first time in injection system simulation, through a thermodynamic state equation which was derived from energy considerations. Nevertheless, in the cavitation regions, an isothermal flow was retained which is consistent with negligible thermal effects due to vaporization because of the tiny amounts of liquid involved. A novel implicit, conservative, one step, symmetrical and trapezoidal scheme of the second-order accuracy was applied to solve the hyperbolic partial differential equations governing the pipe flows. It can also be enhanced at a high-resolution level. The numerical model was applied to wave propagation and cavitation simulation in a high-pressure injection system of the pump-line-nozzle type for light and medium duty vehicles. The system was of relevance to the model assessment because it presented severely cavitating flow conditions. The predicted pressure time histories at two pipe locations and injector needle lift were compared to experimental results, substantiating the validity and robustness of the developed conservative model in simulating cavitation inception and desinence with great degree of accuracy. Cavitation transients and the flow discontinuities induced by them were numerically analyzed and discusse
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