1,720,956 research outputs found
Automated moving mesh techniques and re-meshing strategies in CFD applications using morphing and rigid motions
Full text linkReport on activity presented to RAS.The presence of moving meshes when motions of fluids and solids are being simulated requires a good control of the topological deformations that can take place both into the surface mesh and into the volume cells. The work done in getting the control of the mesh morphing techniques in CFD applications of fluid-structure interactions and rigid bodies motions is here presented. The effects of imposed rigid body motions on a fluid mesh surrounding or surrounded by a solid body are analysed. Surface boundary mesh extraction and CAD geometry updating strategies for the preservation of a good quality mesh during the calculation are investigated and developed. Java programming is employed in order to automate the process of re-meshing to avoid degeneration
Sugli spazi omogenei di dimensione tre SO(2) - isotropi
No full textIn this thesis we studied some problems from the theory of the submanifolds
of the three-dimensional Riemannian manifolds. Our intention is to evaluate
which properties of the submanifolds depend by the dimension of the group
of isometries. We considered a two-parameter family of three-dimensional
Riemannian manifolds (M, ds2
ℓ,m), endowed with the Cartan - Vranceanu
metrics. These metrics can be found in the classification of 3-dimensional
homogeneous metrics given by L. Bianchi. Their geometric interest lies in
the following fact: the family of metrics includes all 3-dimensional homogeneous
metrics whose group of isometries has dimension 4 or 6, except for
those of constant negative sectional curvature. The group of isometries of
these spaces has a subgroup isomorphic to the group SO(2), so there exist
surfaces of revolution around z-axis. We explicitly obtained the Lie algebra
of the Killing vector fields and thus the group of isometries for the C-V
metrics. We determined the equations of the geodesics using the Killing
vector fields and obtain explicitly the equation of the surface which con-
tains the geodesics. After having determined the totally geodesics surfaces
isometrically immersed in the C-V spaces, we studied the totally umbili-
cal submanifolds of these spaces, proving that the only totally umbilical
submanifolds are totally geodesic. We found the geodesics for the SO(2)-
invariant surfaces of the Cartan-Vranceanu spaces, deduced the conditions
that meridians and parallels must satisfy in order to be geodesics and show
the analogies with the euclidian case
Re-meshing strategies in CFD simulations of moving meshes
Full text linkMisc - august 2012.The presence of moving meshes when motions of fluids and solids are being simulated requires a good control of the cells topological deformations. The work done in getting the control of the mesh morphing techniques in Computational Fluid Dynamics (CFD) applications of fluid-structure interactions and rigid bodies motions is here presented. The effects of imposed rigid body motions on a fluid mesh surrounding a solid body are analysed and strategies for maintaining a reasonable quality mesh during its deformation are investigated and developed. Java programming is employed in order to automate the process of re-meshing when the mesh deformation is dangerously close to the degeneration
Automated moving mesh techniques in CFD. Application to fluid-structure interactions and rigid motions problems
Full text linkCollana seminari interni 2012, Number 20120411.In the Computational Fluid Dynamics (CFD) simulation codes, the physical domain is divided into a finite number of small control volumes, corresponding to the cells of a computational grid, where discrete versions of the integral form of the continuum transport equations are applied. For the simulation of the moving meshes (fluids or solids), we employ specific morphing techniques combined with rigid motions. Since morphing strategies can easily lead to poor quality cells, it becomes important to keep under control the topological deformations that can take place both into the surface mesh and into the volume cells, by means of specific mesh quality metrics and re-meshing procedures. The work done in getting the control of the morphing/re-meshing techniques in order to use them in applications that principally treat with fluid-structure interactions and rigid bodies motions is here presented. In such applications, when local deformations of surfaces occur, bad topological effects like warped, twisted or self-intersected faces can easily lead to the appearance of negative volume cells, determining the simulation to stop running. We give a demonstration of how various morphing techniques have been applied to simulations that especially treat with structural and moving parts, in particular, in cases where the deformations arise from considerations related to solid displacements and stresses (pipe's walls vibrations) or to rigid body motions (translations). Surface boundary mesh extraction and CAD geometry updating strategies to avoid mesh degeneration are investigated and developed. Java programming is employed for the automation of the re-meshing procedures
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
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