1,721,004 research outputs found
CFD analysis of a realistic reduced-scale modeling equipped with axial jet fan
No full textTypically, in the experimental scale road tunnel model, the air flow induced by ventilation system is provided by an external fan. In this paper, the authors have numerically simulated full and reduced-scale tunnel in order to evaluate the possibility to realize a reduced scale of a road tunnel model with a realistic ventilation system consisting of impulsive jet fans. In particular, two different types of longitudinal ventilation systems were considered, traditional and alternative. The last one was equipped with jet fans that have the inlet/outlet sections inclined at a fixed pitch angle (α=6°) toward the tunnel floor. The jet fan was simulated as a simple momentum source that provides a pressure rise (pressure drop) across them as a function of the outflow air velocity. The analyzed tunnel consists in a 800 m one directional bore with circular cross section 5.05 m radius; the jet fans were installed at 5.67 m from the floor. Furthermore a burning Heavy Good Vehicle (HGV), placed at 450 m far away the tunnel entrance, was considered. To simulate numerically the burning vehicle, the species transport equation combustion model with Eddy-Dissipation-Concept (EDC) model was adopted. In order to create a reduced-scale model from a full scale, Froude method was applied to preserve geometrical, kinematical and dynamical similitude. Temperature and axial velocity profiles, in different tunnel sections for both considered models (full and scaled) and ventilation systems, were provided. The numerical results showed a good agreement for the both ventilation system
Evaluating hourly charging profiles for different electric vehicles and charging strategies
No full textThis study evaluates the potential increase in hourly electricity demand from the electrification of road transport in an Alpine region considering different charging strategies within a multi-node framework. The python-based emobpy tool generates hourly charging profiles for passenger cars, buses, light commercial vehicles and heavy trucks considering a tailored charging infrastructure for each vehicle type. Oemof framework, a linear programming model, is then used to analyse the regional energy system with a multi-node representation integrating smart charging and vehicle-to-grid options with a multi-node representation at the regional scale. Baseline results without demand management indicate peak load increases of 12–59 % by 2030–2050. Implementing smart charging for passenger cars in the high electrification 2050 scenario reduces this peak by 34 % by aligning loads to renewable generation surplus periods. Enabling vehicle-to-grid technology yields an additional 60 % reduction in imports from surrounding regions by utilizing electric vehicles as distributed energy resources. The study provides insights into fleet transitions and the role of flexible demand-side options in renewable power system integration, with a high level of detail in the modelling process
Saccardo nozzle ventilation system: cfd analysis to upgrade the performance of the ventilation system
No full textThis paper presents the results of a 3D numerical investigation carried out on a Saccardo ventilation system operating in road tunnel, with the aim to improve the Performance of the Ventilation System, Pvs. 1D mathematical model, here presented, has highlighted that the pitch angle and length of inflow opening are the main parameters that influence the Pvs. The results have shown that the pitch angle of the Saccardo nozzle, influences moderately the Pvs, instead the opening inflow lengths influence considerably the transferring of the momentum, increasing the mass flow rate. Pvs trend vs opening inflow length shows an improvement up to 47% with respect to the reference opening inflow length
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
The Influence of the Filling Percentage Traffic on Required Ventilation Thrust in Road Tunnel
No full textFor an accurate and reliable prediction of the thrust value of a ventilation system for a highway road tunnel, it is necessary to evaluate the losses due to the presence of vehicles. Typically the vehicles losses were evaluated by semi empirical formula based on additively principle, i.e. the traffic jam losses are equal to the sum of each vehicle losses corrected by means empirical coefficient. The aim of this paper is compare results carried out by the 3-D CFD model, with those obtained by the semi-empirical correlation, provided in literature. Several traffic jam conditions for a fixed tunnel geometry and average air velocity have to be considered in order to evaluate the influence of the Filling Percentage Traffic (FPT) of the tunnel on required ventilation thrust from point of view of energy saving
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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