Calculation of the magnetic field due to a bioelectric current dipole in an ellipsoidInstitute of Mathematics, Czech Academy of Sciences - Tập 53 - Trang 131-142 - 2008
Andrei Irimia
The bioelectric current dipole model is important both theoretically and
computationally in the study of electrical activity in the brain and stomach due
to the resemblance of the shape of these two organs to an ellipsoid. To
calculate the magnetic field B due to a dipole in an ellipsoid, one must
evaluate truncated series expansions involving ellipsoidal harmonics $$
\mathbb{E}_n^m $$ , which are... hiện toàn bộ
Linearized Regression Model with Constraints of Type IIInstitute of Mathematics, Czech Academy of Sciences - - 2003
Lubomír Kubáček
A linearization of the nonlinear regression model causes a bias in estimators of
model parameters. It can be eliminated, e.g., either by a proper choice of the
point where the model is developed into the Taylor series or by quadratic
corrections of linear estimators. The aim of the paper is to obtain formulae for
biases and variances of estimators in linearized models and also for corrected
estima... hiện toàn bộ
Remarks on the a priori bound for the vorticity of the axisymmetric Navier-Stokes equationsInstitute of Mathematics, Czech Academy of Sciences - Tập 67 - Trang 485-507 - 2021
Zujin Zhang, Chenxuan Tong
We study the axisymmetric Navier-Stokes equations. In 2010, Loftus-Zhang used a
refined test function and re-scaling scheme, and showed that $$\left| {{\omega
^r}(x,t)} \right| + \left| {{\omega ^z}(r,t)} \right| \leqslant {C \over
{{r^{10}}}},\,\,\,\,\,0 < r \leqslant {1 \over 2}.$$ By employing the dimension
reduction technique by Lei-Navas-Zhang, and analyzing ωr, ωz and ωθ/r on
different hollo... hiện toàn bộ
A Higher Order Pressure Segregation Scheme for the Time-Dependent Magnetohydrodynamics EquationsInstitute of Mathematics, Czech Academy of Sciences - Tập 64 - Trang 531-556 - 2019
Yun-Bo Yang, Yao-Lin Jiang, Qiong-Xiang Kong
A higher order pressure segregation scheme for the time-dependent incompressible
magnetohydrodynamics (MHD) equations is presented. This scheme allows us to
decouple the MHD system into two sub-problems at each time step. First, a
coupled linear elliptic system is solved for the velocity and the magnetic
field. And then, a Poisson-Neumann problem is treated for the pressure. The
stability is analy... hiện toàn bộ
An adaptive finite element method in reconstruction of coefficients in Maxwell’s equations from limited observationsInstitute of Mathematics, Czech Academy of Sciences - Tập 61 - Trang 253-286 - 2016
Larisa Beilina, Samar Hosseinzadegan
We propose an adaptive finite element method for the solution of a coefficient
inverse problem of simultaneous reconstruction of the dielectric permittivity
and magnetic permeability functions in the Maxwell’s system using limited
boundary observations of the electric field in 3D. We derive a posteriori error
estimates in the Tikhonov functional to be minimized and in the regularized
solution of t... hiện toàn bộ
Convergence of the matrix transformation method for the finite difference approximation of fractional order diffusion problemsInstitute of Mathematics, Czech Academy of Sciences - Tập 62 Số 1 - Trang 15-36 - 2017
Szekeres, Béla J., Izsák, Ferenc
Numerical solution of fractional order diffusion problems with homogeneous
Dirichlet boundary conditions is investigated on a square domain. An appropriate
extension is applied to have a well-posed problem on R2 and the solution on the
square is regarded as a localization. For the numerical approximation a finite
difference method is applied combined with the matrix transformation method.
Here the... hiện toàn bộ
Complete Solution of Tropical Vector Inequalities Using Matrix SparsificationInstitute of Mathematics, Czech Academy of Sciences - Tập 65 Số 6 - Trang 755-775 - 2020
Krivulin, Nikolai
We examine the problem of finding all solutions of two-sided vector inequalities
given in the tropical algebra setting, where the unknown vector multiplied by
known matrices appears on both sides of the inequality. We offer a solution that
uses sparse matrices to simplify the problem and to construct a family of
solution sets, each defined by a sparse matrix obtained from one of the given
matrices... hiện toàn bộ
An accurate active set newton algorithm for large scale bound constrained optimizationInstitute of Mathematics, Czech Academy of Sciences - Tập 56 - Trang 297-314 - 2011
Li Sun, Guoping He, Yongli Wang, Changyin Zhou
A new algorithm for solving large scale bound constrained minimization problems
is proposed. The algorithm is based on an accurate identification technique of
the active set proposed by Facchinei, Fischer and Kanzow in 1998. A further
division of the active set yields the global convergence of the new algorithm.
In particular, the convergence rate is superlinear without requiring the strict
comple... hiện toàn bộ