1,720,966 research outputs found
La tutela della libertà religiosa nel sistema internazionale di salvaguardia dei diritti fondamentali dell'uomo
No full textDegenerate tetrahedra removal
No full textStandard 3D mesh generation algorithms may produce a low quality tetrahedral mesh, i.e., a mesh where the tetrahedra have very small dihedral angles. In this paper, we propose a series of operations to recover these badly-shaped tetrahedra.
In particular, we will focus on the shape of these undesired mesh elements by proposing a novel method to distinguish and classify them. For each of these configurations, we apply a suitable sequence of operations to get a higher mesh quality. Finally, we employ a random algorithm to avoid locks and loops in the procedure.
The reliability of the proposed mesh optimization algorithm is numerically proved with several examples
Advances in computation of local problems for a flow-based upscaling in fractured reservoirs
Get PDFIn this article we present some numerical techniques to increase efficiency and applicability of a flow-based upscaling procedure used to solve single and multi-phase flows in naturally fractured reservoirs. These geological formations may be characterized by hundreds up to hundreds of thousands of fractures, ranging from small to medium scales, spreading all over the reservoir. In these scenarios numerical simulations using an explicit discretization of all fractures become rapidly unfeasible.
The problem may be overcome by upscaling procedures. In this work we assume that the flow in the reservoir is simulated by using a corner-point grid completely unrelated to the fracture network. The presence of the latter is accounted for by a numerical upscaled procedure that employs an embedded discrete fracture model (EDFM).
To characterize the scaled up problem, we consider a flow-based upscaling procedure where multiple sub-regions are used to derive transmissibilities, mean depths and pore volumes related to the degrees of freedom associated with fractures and rock matrix. An important aspect of the work with respect to others presented in the literature is the enhancement of the upscaling process by splitting the degrees of freedom associated with unconnected portions of the rock matrix. Numerical examples confirm the effectiveness of the proposed approach. We also compare two ways of setting up the boundary conditions of the local problems, that is a well known open issue, used to compute the upscaled transmissibility between cells. Though the experiments lead to a similar result, at the best of our knowledge, it is the first time that such a comparison is made for fractured reservoir
An XFEM/DG approach for fluid-structure interaction problems with contact
Get PDFsummary:In this work, we address the problem of fluid-structure interaction (FSI) with moving structures that may come into contact. We propose a penalization contact algorithm implemented in an unfitted numerical framework designed to treat large displacements. In the proposed method, the fluid mesh is fixed and the structure meshes are superimposed to it without any constraint on the conformity. Thanks to the Extended Finite Element Method (XFEM), we can treat discontinuities of the fluid solution on the mesh elements intersecting the structure. The coupling conditions at the fluid-structure interface are enforced via a discontinuous Galerkin mortaring technique, which is a penalization method that ensures the consistency of the scheme with the underlining problem. Concerning the contact problem, we consider a frictionless contact model in a master/slave approach. By considering the coupled FSI-contact problem, we perform some numerical tests to assess the sensitivity of the proposed method with respect to the discretization and contact parameters and we show some examples in the case of contact between a flexible body and a rigid wall and between two deformable structures
Reconstruction of 3D scattered data via radial basis functions by efficient and robust techniques
No full textWe propose new algorithms to overcome two of the most constraining limitations of surface reconstruction methods in use. In particular, we focus on the large amount of data characterizing standard acquisitions by scanner and the noise intrinsically introduced by measurements. The first algorithm represents an adaptive multi-level interpolating approach, based on an implicit surface representation via radial basis functions. The second algorithm is based on a least-squares approximation to filter noisy data. The third approach combines the two algorithms to merge the correspondent improvements. An extensive numerical validation is performed to check the performances of the proposed techniques
An upscaling procedure for fractured reservoirs with embedded grids
Get PDFUpscaling of geological models for reservoir simulation is an active and important area of research. In particular, we are interested in reservoirs where the rock matrix exhibits an intricate network of fractures, which usually acts as a preferential path to the flow. Accounting for fractures' contribution in the simulation of a reservoir is of paramount importance. Here we have focused on obtaining effective parameters (e.g., transmissibility) on a 3-D computational grid on the reservoir scale, which account for the presence, at a finer spatial scale, of fractures and a network of fractures. We have essentially followed the idea illustrated in Karimi-Fard et al. (2006), yet this work has some notable aspects of innovation in the way the procedure has been implemented, and in its capability to consider rather general corner-point grids, like the ones normally used in reservoir simulations in the industry, and complex and realistic fracture networks, possibly not fully connected inside the coarse cells. In particular, novel contribution is the employment of an Embedded Discrete Fracture Model (EDFM) for computing fracture-fracture and matrix-fracture transmissibilities, with a remarkable gain in speedup. The output is in the form of transmissibility that, although obtained by considering single-phase flow, can be used for coarse-scale multiphase reservoir simulations, also via industrial software, such as Eclipse, Intersect, or GPRS. The results demonstrate the effectiveness and computational efficiency of the numerical procedure which is now ready for further testing and industrialization
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
- …
