The Experts below are selected from a list of 20022 Experts worldwide ranked by ideXlab platform
Karl E. Lonngren - One of the best experts on this subject based on the ideXlab platform.
-
Rarefactive ion acoustic soliton excitation using a modulated high-frequency sinusoidal wave in a negative ion plasma
Physics of Plasmas, 1997Co-Authors: Seungjun Yi, Karl E. LonngrenAbstract:Experiments on the excitation of rarefactive ion acoustic solitons using a Fine Mesh grid in a negative ion plasma are described. The excitation is novel in that a modulated high-frequency sinusoidal wave voltage signal is applied to the grid. An interpretation of the velocity modulation and bunching of free-streaming ions that pass through the grid to which the signal is applied is given.
-
Ion acoustic soliton excitation using a modulated high-frequency sinusoidal wave
Physics of Plasmas, 1997Co-Authors: Seungjun Yi, Karl E. LonngrenAbstract:Experiments on the excitation of ion acoustic solitons using a Fine Mesh grid in a normal two component plasma are described. The excitation is novel in that a modulated high-frequency sinusoidal wave voltage signal is applied to the grid. The carrier frequency of the high-frequency sinusoidal wave is above the ion plasma frequency. An interpretation of the velocity modulation and bunching of free streaming ions that pass through the grid to which the signal is applied is given.
Seungjun Yi - One of the best experts on this subject based on the ideXlab platform.
-
Rarefactive ion acoustic soliton excitation using a modulated high-frequency sinusoidal wave in a negative ion plasma
Physics of Plasmas, 1997Co-Authors: Seungjun Yi, Karl E. LonngrenAbstract:Experiments on the excitation of rarefactive ion acoustic solitons using a Fine Mesh grid in a negative ion plasma are described. The excitation is novel in that a modulated high-frequency sinusoidal wave voltage signal is applied to the grid. An interpretation of the velocity modulation and bunching of free-streaming ions that pass through the grid to which the signal is applied is given.
-
Ion acoustic soliton excitation using a modulated high-frequency sinusoidal wave
Physics of Plasmas, 1997Co-Authors: Seungjun Yi, Karl E. LonngrenAbstract:Experiments on the excitation of ion acoustic solitons using a Fine Mesh grid in a normal two component plasma are described. The excitation is novel in that a modulated high-frequency sinusoidal wave voltage signal is applied to the grid. The carrier frequency of the high-frequency sinusoidal wave is above the ion plasma frequency. An interpretation of the velocity modulation and bunching of free streaming ions that pass through the grid to which the signal is applied is given.
M A Crisfield - One of the best experts on this subject based on the ideXlab platform.
-
instabilities induced by coarse Meshes for a nonlinear shell problem
Engineering Computations, 1996Co-Authors: M A Crisfield, X PengAbstract:Presents a range of numerical results obtained from the geometrically nonlinear analysis of a cantilevered cylindrical shell. Shows that, while the Fine‐Mesh solution involves no limit points, as the Mesh is coarsened, an increasing series of “false limit points” is encountered.
-
coarse Fine Mesh preconditioners for the iterative solution of finite element problems
International Journal for Numerical Methods in Engineering, 1995Co-Authors: M C Dracopoulos, M A CrisfieldAbstract:A class of preconditioners built around a coarse/Fine Mesh framework is presented. The proposed method involves the reconstruction of the stiffness equations using a coarse/Fine Mesh idealization with relative degrees-of-freedom derived from the element shape functions. This approach leads naturally to effective preconditioners for iterative solvers which only require a factorization involving coarse Mesh variables. A further extension is the application of the proposed method to super-elements in conjunction with substructuring (domain decomposition) techniques. The derivation of the coarse/Fine Mesh discretization via the use of transformation matrices, allows a straightforward implementation of the proposed techniques (as well as multigrid type procedures) within an existing finite element system.
M C Dracopoulos - One of the best experts on this subject based on the ideXlab platform.
-
coarse Fine Mesh preconditioners for the iterative solution of finite element problems
International Journal for Numerical Methods in Engineering, 1995Co-Authors: M C Dracopoulos, M A CrisfieldAbstract:A class of preconditioners built around a coarse/Fine Mesh framework is presented. The proposed method involves the reconstruction of the stiffness equations using a coarse/Fine Mesh idealization with relative degrees-of-freedom derived from the element shape functions. This approach leads naturally to effective preconditioners for iterative solvers which only require a factorization involving coarse Mesh variables. A further extension is the application of the proposed method to super-elements in conjunction with substructuring (domain decomposition) techniques. The derivation of the coarse/Fine Mesh discretization via the use of transformation matrices, allows a straightforward implementation of the proposed techniques (as well as multigrid type procedures) within an existing finite element system.
Owe Axelsson - One of the best experts on this subject based on the ideXlab platform.
-
extensions of a coarse Fine Mesh stabilized schwarz alternating iteration domain decomposition method
Journal of Computational and Applied Mathematics, 2020Co-Authors: Owe AxelssonAbstract:Abstract For the numerical solution of a domain decomposed discretized elliptic operator (PDE) problem a particular kind of Schwarz alternating iteration method is used, based on maximal overlap between neighboring domains. It is stabilized not by the more traditional coarse Mesh method but by a combined coarse–Fine Mesh method. As has been demonstrated earlier for 2D problems this method can converge very rapidly and is not sensitive to how accurate the arising subdomain systems and the coarse–Fine Mesh system are solved. A short presentation of the method is given followed by extensions of the method to 3D problems and to porous media problems.
-
a coarse Fine Mesh stabilization for an alternating schwarz domain decomposition method
Numerical Linear Algebra With Applications, 2019Co-Authors: Owe Axelsson, Ivar GustafssonAbstract:Domain decomposition methods can be solved in various ways. In this paper, domain decomposition in strips is used. It is demonstrated that a special version of the Schwarz alternating iteration method coupled with coarse-Fine-Mesh stabilization leads to a very efficient solver, which is easy to implement and has a behavior nearly independent of Mesh and problem parameters. The novelty of the method is the use of alternating iterations between odd- and even-numbered subdomains and the replacement of the commonly used coarse-Mesh stabilization method with coarse-Fine-Mesh stabilization.
-
a two level method for the discretization of nonlinear boundary value problems
SIAM Journal on Numerical Analysis, 1996Co-Authors: Owe Axelsson, William LaytonAbstract:We consider a two-level method for the discretization and solution of nonlinear boundary value problems. The method basically involves (i) solving the nonlinear problem on a {\it very} coarse Mesh, (ii) linearizing about the coarse Mesh solution, and solving the linearized problem on the Fine Mesh, one time! We analyze the accuracy of this procedure for strongly monotone nonlinear operators (\S2) and general semilinear elliptic boundary value problems (without monotonicity assumptions). In particular, the scaling between the Fine and coarse Mesh widths required to ensure optimal accuracy of the Fine Mesh solution is derived as a byproduct of the error estimates herein.
