1,721,043 research outputs found
Prediction Capabilities of a One-dimensional Wall-flow Particulate Filter Model
Full text linkThis work is focused on the formulation of a numerical model for prediction of flow field inside a particulate filter. More specifically, a one-dimensional mathematical model of the gas flow in a particulate trap-cell is deduced and solved numerically. The results are given in terms of velocity, pressure, and filtration velocity. In addition, the dependence of the pressure drop on the main governing parameters has been investigated. More specifically, the permeability of the porous medium and the hydraulic diameter play a fundamental role in the pressure dro
Influence of Nanoparticles and Magnetic Field on the Laminar Forced Convection in a Duct Containing an Elastic Fin
Full text linkIn the present paper, an investigation of the effect of a magnetic field and nanoparticles suspended in pure water on the forced flow in a duct containing an elastic rectangular fin is performed. The nanofluid, i.e., CuO nanoparticles suspended in water, flow in the duct with an inlet fully developed velocity profile and a cold temperature. The lower boundary of the duct is kept at a hot temperature, while the upper boundary is adiabatic. According to the ALE formulation, numerical simulations of the laminar flow are carried out, by employing the software package Comsol Multiphysics, to solve the governing equation system: mass, momentum, energy, and deformation. The behavior of the Nusselt number, of the temperature and velocity fields as well as of the stress profiles are presented and interpreted. As a result, the addition of CuO nanoparticles to pure water improves the local and global heat transfer rate by up to 21.33% compared to pure water. On the other hand, it causes an additional deformation of the elastic fin as well as the increase of the stress due to the presence of the nanoparticles, leading to an increase of its maximum displacement of 34.58% compared to the case of pure water flow. Moreover, the enhancement of the flexibility of the fin (and thus its deformation) leads to a relative reduction in terms of convective heat transfer rate, especially downstream of the fin
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
Pulsatile flow through an idealized arterial bypass graft: an application of the constructal design method
No full textBypass grafts promote blood flow impaired by a partial obstruction (stenosis) of arteries by fat accumulation. This type of
system’s computational modeling is used to understand the flow characteristics and look for reasons and solutions for postoperative
failures. The present work deals with the effects of changes in geometry in the performance of a system consisting
of an idealized partially obstructed artery and a bypass graft. The constructal design method has been employed in previous
works in the analysis of such system assuming steady-state flow. In the present work, blood flow is modeled as transient
and pulsatile. The constructal design method is used to determine the performance indicator (dimensionless pressure drop),
constraints (system volume and stenosis degrees–50% and 75%) and degrees of freedom: junction angle (30o ≤ α ≤ 70o) and
diameter ratio (0.5 ≤ D1/
D ≤ 1). The response surface methodology was used to evaluate the conditions of minimum pressure
drop in transient conditions. As the junction angle decreased to 30o, and the diameter ratio increased to 1, the pressure drop
decreased, and there was a considerable dependence of pressure drop on the stenosis degree. The effects of the diameter
ratio were more pronounced than those of the junction angle. A resistance model based on an analogy with an electronic
circuit was introduced, resulting in a correlation for the pressure drop due to the bypass. This correlation confirmed that the
point (, D1∕D) = (30◦, 1) is a point of minimization of flow resistance. The application of the constructal design method
in hemodynamics might be an excellent alternative to configuring enhanced performance and providing valuable results to
the understanding of biological flows
Constructal design of passive micromixers with multiple obstacles via computational fluid dynamics
Full text linkPassive micromixers have applications mainly in the chemical, pharmaceutical, and materials industries. Two or more fluids mix while flowing through microchannels in these devices. Due to the small dimensions and low flow rates, the flow is essentially laminar, and mixing takes place mainly by mass diffusion. One way to increase the mixing rate in micromixers is the addition of obstacles that increase the advective effects. This work aimed to introduce high-performance designs of passive micromixers with multiple obstacles. These designs were obtained by combining the Constructal Design method with the Response Surface Optimization method and Computational Fluid Dynamics (CFD). The micromixers were Y-shaped tubes with grooves and circular obstacles in cells that repeated along the device. From the first design inspired by a high-performance design from the literature, the evolutionary design of the system was achieved by increasing the number of obstacles and finding the best configuration for each evolution level (number of obstacles per cell, from three to seven). The effects on mixing percentage, pressure difference, and mixing energy cost (MEC) of obstacles’ vertical and horizontal distances were investigated with CFD simulations. Increasing the number of obstacles made it possible to increase the mixture percentage of the micromixer. At the same time, the total pressure drop rises faster than the mixing percentage. However, analyzing the pressure locally, it was shown that the lower the number of obstacles, the greater the local pressure drop, which could cause flow obstructions. The vertical distance of the obstacles had a more significant impact on the mixing than their horizontal distance. Both vertical and horizontal distances had a substantial effect on the pressure drop. As the number of obstacles increased, the effect of the horizontal distance became weaker as its variation was limited. The three-obstacles design presented a MEC equal to 2.47 and a mixing percentage equal to 67.12% mixing index. The latest design evolution (i.e., seven obstacles) achieved the best mixing percentage, 70.30%, with MEC equal to 2.97. By modifying the degrees of freedom, it was possible to understand and propose a path to the evolutionary design of the system to increase its performance while still using simple designs
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
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