1,720,958 research outputs found
Discrete Boltzmann Numerical Simulation of Simplified Urban Flooding Configurations Caused by Dam Break
No full textThe Discrete Boltzmann Equation (DBE) is a versatile simulation method, consisting of linear advection equations, which can be applied to the Shallow Water Equations (SWE). The aim of this study is to assess the accuracy of the DBE to simulate dam-break of shallow water flows in presence of obstacles. Dam-break flows in the presence of obstacles can be regarded as simplified models for floods in urban areas. In this study, three cases of dam-break flows in the presence of obstacles are considered: two with an isolated obstacle and the third in presence of an idealized city. A comparison between DBE and benchmark results shows a fair agreement, confirming the validity of the DBE as simulation method for the SWE
Dam-Break Modeling: LBM as the Way towards Fully 3D, Large-Scale Applications
No full textFree-surface flows play an important role in many environmental hydraulic problems. Owing to their characteristic large spatial and temporal scales, reduced complexity models, such as depth-integrated shallow water (DI-SW) models, have so far been largely preferred to three-dimensional (3D) approaches. Even if they can reproduce water levels satisfactorily, DI-SW models do not natively provide flow velocity at the bed, which is pivotal for estimating scour effects induced by impulsive flows, such as those resulting from dam breaks. However, resort to fully 3D modeling is often impractical due to the high computational demand required; nonetheless, recent works have shown impressive performance of the lattice Boltzmann method (LBM) compared to classical numerical methods while proving to be as accurate in many fields, suggesting LBM makes such computations affordable on desktop computers. So far, a comprehensive assessment of a LBM-based, fully 3D, free-surface model is still lacking. In this work, a LBM model is compared to data from a large series of dam-break-flow experiments, in terms of water levels and, where available, flow velocities. Comparisons with available DI-SW models are also carried out. Results show that the LBM model can correctly simulate both water levels and velocity distributions, the latter often being inaccurately reproduced by DI-SW models. To provide guidelines for the correct modeling of such flows, considerations are also given to opportunities to use either no-slip or free-slip boundary conditions, the latter being preferable if underresolved boundary layers are present
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
Assessing the Mobilization of Trapped Mass of Emulsions Flowing in an Idealized Pore Using the Lattice Boltzmann Method
No full textIn this work, a Lattice Boltzmann model for multi-component fluids augmented with repulsive near-contact interactions is employed to simulate the dynamics of flowing emulsions within idealized pores. The model is firstly tested on experimental data of droplets' self-assembly in diverging-converging micro-channels from literature and then used to investigate the trapping/mobilization of the dispersed phase of an emulsion in an idealized series of pores, as influenced by both the Capillary number and the solid walls wettability. Both parameters may vary as the result of an injection of surfactants, a procedure commonly adopted in soil remediation and Enhanced Oil Recovery applications. The analysis shows that the proposed model is able to reproduce correctly the experimental data and gives interesting insights on the trapping/mobilization phenomenon resulting from a modification of the flow conditions caused by the injection of surfactants
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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