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Smoothing Technique (smoothing + technique)

Distribution by Scientific Domains

Engineering	85%

Selected Abstracts

Local volume-conserving free surface smoothing

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2007
F. S. Sousa
Abstract Removing high-frequency undulations in surfaces is a problem that appears in different fields, such as computer graphics and computational fluid mechanics. This problem is typically handled by surface smoothing techniques, such as Laplacian filters, that eliminate high-frequency undulations but degrade the volume encompassed by the surface. The need for conserving volume (or mass) rules out the use of such techniques in several application, as for example incompressible flows. In this work we present a smoothing technique that suppresses undulations while conserving local volumes, ensuring that the global mass is conserved. The effectiveness of the proposed technique is illustrated in synthetic datasets as well as in free surface flows simulation. Comparisons between our smoothing approach and the well-known Laplacian filter are also presented. Copyright © 2006 John Wiley & Sons, Ltd. [source]

A novel singular node-based smoothed finite element method (NS-FEM) for upper bound solutions of fracture problems

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2010
G. R. Liu
Abstract It is well known that the lower bound to exact solutions in linear fracture problems can be easily obtained by the displacement compatible finite element method (FEM) together with the singular crack tip elements. It is, however, much more difficult to obtain the upper bound solutions for these problems. This paper aims to formulate a novel singular node-based smoothed finite element method (NS-FEM) to obtain the upper bound solutions for fracture problems. In the present singular NS-FEM, the calculation of the system stiffness matrix is performed using the strain smoothing technique over the smoothing domains (SDs) associated with nodes, which leads to the line integrations using only the shape function values along the boundaries of the SDs. A five-node singular crack tip element is used within the framework of NS-FEM to construct singular shape functions via direct point interpolation with proper order of fractional basis. The mix-mode stress intensity factors are evaluated using the domain forms of the interaction integrals. The upper bound solutions of the present singular NS-FEM are demonstrated via benchmark examples for a wide range of material combinations and boundary conditions. Copyright © 2010 John Wiley & Sons, Ltd. [source]

A G space theory and a weakened weak (W2) form for a unified formulation of compatible and incompatible methods: Part I theory

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 9 2010
G. R. Liu
Abstract This paper introduces a G space theory and a weakened weak form (W2) using the generalized gradient smoothing technique for a unified formulation of a wide class of compatible and incompatible methods. The W2 formulation works for both finite element method settings and mesh-free settings, and W2 models can have special properties including softened behavior, upper bounds and ultra accuracy. Part I of this paper focuses on the theory and fundamentals for W2 formulations. A normed G space is first defined to include both continuous and discontinuous functions allowing the use of much more types of methods/techniques to create shape functions for numerical models. Important properties and a set of useful inequalities for G spaces are then proven in the theory and analyzed in detail. These properties ensure that a numerical method developed based on the W2 formulation will be spatially stable and convergent to the exact solutions, as long as the physical problem is well posed. The theory is applicable to any problems to which the standard weak formulation is applicable, and can offer numerical solutions with special properties including ,close-to-exact' stiffness, upper bounds and ultra accuracy. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Simultaneous untangling and smoothing of moving grids

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2008
Ezequiel J. López
Abstract In this work, a technique for simultaneous untangling and smoothing of meshes is presented. It is based on an extension of an earlier mesh smoothing strategy developed to solve the computational mesh dynamics stage in fluid,structure interaction problems. In moving grid problems, mesh untangling is necessary when element inversion happens as a result of a moving domain boundary. The smoothing strategy, formerly published by the authors, is defined in terms of the minimization of a functional associated with the mesh distortion by using a geometric indicator of the element quality. This functional becomes discontinuous when an element has null volume, making it impossible to obtain a valid mesh from an invalid one. To circumvent this drawback, the functional proposed is transformed in order to guarantee its continuity for the whole space of nodal coordinates, thus achieving the untangling technique. This regularization depends on one parameter, making the recovery of the original functional possible as this parameter tends to 0. This feature is very important: consequently, it is necessary to regularize the functional in order to make the mesh valid; then, it is advisable to use the original functional to make the smoothing optimal. Finally, the simultaneous untangling and smoothing technique is applied to several test cases, including 2D and 3D meshes with simplicial elements. As an additional example, the application of this technique to a mesh generation case is presented. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Remeshing for metal forming simulations,Part I: Two-dimensional quadrilateral remeshing

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2002
Dae-Young Kwak
Abstract In this paper, a general framework of practical two-dimensional quadrilateral remeshing, which includes the determination of remeshing time, automatic quadrilateral mesh generation, and data transfer process, will be formulated. In particular, the current work contains new algorithms of mesh density specification according to the distribution of effective strain-rate gradients, mesh density smoothing by fast Fourier transform (FFT) and low-pass filtering techniques, coarsening it by node placement scheme, and a modified Laplacian mesh smoothing technique. The efficiency of the developed remeshing scheme was tested through three practical two-dimensional metal forming simulations. The results clearly indicate that the algorithms proposed in this study make it possible to simulate two-dimensional metal forming problems efficiently and automatically. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Performance analysis of velocity,pressure smoothing for direction-of-arrival estimation of coherent signals

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2010
Yougen Xu
Abstract In this paper, we consider the problem of direction-of-arrival (DOA) estimation of coherent signals by using a number of identically oriented acoustic vector-sensors, wherein source decorrelation can be achieved by velocity,pressure smoothing. We examine the effect of velocity,pressure smoothing on the performance of MUSIC-type methods in terms of the overall root mean-square errors (RMSE) of DOA estimates. The closed-form expression for the overall RMSE is derived and analyzed. We also compare velocity,pressure smoothing with the conventional spatial smoothing technique. Simulation results are given to confirm the analyses. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Generalized likelihood ratio tests for the structure of semiparametric additive models

THE CANADIAN JOURNAL OF STATISTICS, Issue 3 2007
Jiancheng Jiang
Abstract Semiparametric additive models (SAMs) are very useful in multivariate nonparametric regression. In this paper, the authors study nonparametric testing problems for the nonparametric components of SAMs. Using the backfitting algorithm and the local polynomial smoothing technique, they extend to SAMs the generalized likelihood ratio tests of Fan &Jiang (2005). The authors show that the proposed tests possess the Wilks-type property and that they can detect alternatives nearing the null hypothesis with a rate arbitrarily close to root- n while error distributions are unspecified. They report simulations which demonstrate the Wilks phenomenon and the powers of their tests. They illustrate the performance of their approach by simulation and using the Boston housing data set. Étude de tests du rapport des vraisemblances généralisés permettant d'éprouver la structure des modèles additifs semiparamétriques Les modèles additifs semiparamétriques (MAS) sont très utiles en régression multivariée non paramétrique. Dans cet article, les auteurs s'intéressent à la façon de tester non paramétriquement les composantes non paramétriques des MAS. En se servant de l'algorithme de backfitting et de la technique de lissage par polyn,mes locaux, ils adaptent aux MAS les tests du rapport des vraisemblances généralisés de Fan &Jiang (2005). Ils montrent que les tests possèdent une propriété de type Wilks et qu'ils peuvent détecter des contre-hypothèses s'approchant de l'hypothèse nulle à un taux arbitrairement proche de radical n, peu importe la loi des erreurs. Ils font état de simulations illustrant le phénomène de Wilks et la puissance de leurs tests. Ils évaluent la performance de leur approche à l'aide de simulations et d'un jeu de données sur la valeur des propriétés à Boston. [source]