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        1 2 3 4 5 6 7 8 | Last

Journal Cover   Applied Numerical Mathematics
  [SJR: 1.163]   [H-I: 49]   [7 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0168-9274 - ISSN (Online) 0168-9274
   Published by Elsevier Homepage  [2800 journals]
  • Relative perturbation theory for definite matrix pairs and hyperbolic
           eigenvalue problem
    • Abstract: Publication date: Available online 24 August 2015
      Source:Applied Numerical Mathematics
      Author(s): Ninoslav Truhar, Suzana Miodragović
      In this paper, new relative perturbation bounds for the eigenvalues as well as for the eigensubspaces are developed for definite Hermitian matrix pairs and the quadratic hyperbolic eigenvalue problem. First, we derive relative perturbation bounds for the eigenvalues and the sin ⁡ Θ type theorems for the eigensubspaces of the definite matrix pairs ( A , B ) , where both A , B ∈ C m × m are Hermitian nonsingular matrices with particular emphasis, where B is a diagonal of ±1. Further, we consider the following quadratic hyperbolic eigenvalue problem ( μ 2 M + μ C + K ) x = 0 , where M , C , K ∈ C n × n are given Hermitian matrices. Using proper linearization and new relative perturbation bounds for definite matrix pairs ( A , B ) , we develop corresponding relative perturbation bounds for the eigenvalues and the sin ⁡ Θ type theorems for the eigensubspaces for the considered quadratic hyperbolic eigenvalue problem. The new bounds are uniform and depend only on matrices M, C, K, perturbations δM, δC and δK and standard relative gaps. The quality of new bounds is illustrated through numerical examples.


      PubDate: 2015-08-26T10:39:53Z
       
  • On the stability of approximations for the Stokes problem using different
           finite element spaces for each component of the velocity
    • Abstract: Publication date: Available online 20 August 2015
      Source:Applied Numerical Mathematics
      Author(s): F. Guillén-González, J.R. Rodríguez Galván
      The stability of velocity and pressure mixed approximations of the Stokes problem is studied, when different finite element (FE) spaces for each component of the velocity field are considered. Using the macro-element technique of Stenberg, analytical results are obtained for some new combinations of FE with globally continuous and piecewise linear pressure. These new combinations are introduced with the idea of reducing the number of degrees of freedom in some of the velocity components. Although the resulting FE are not stable in general, we show their stability in a wide family of meshes (uniformly unstructured meshes). Moreover, this method can be extended to any mesh family whenever a post-processing be performed in order to convert it in an unstructured mesh. Some 2D and 3D numerical simulations are provided agree with the previous analysis.


      PubDate: 2015-08-22T09:56:36Z
       
  • A linearised singularly perturbed convection–diffusion problem with
           an interior layer
    • Abstract: Publication date: Available online 14 August 2015
      Source:Applied Numerical Mathematics
      Author(s): E. O'Riordan, J. Quinn
      A linear time dependent singularly perturbed convection-diffusion problem is examined. The convective coefficient contains an interior layer (with a hyperbolic tangent profile), which in turn induces an interior layer in the solution. A numerical method consisting of a monotone finite difference operator and a piecewise-uniform Shishkin mesh is constructed and analysed. Neglecting logarithmic factors, first order parameter uniform convergence is established.


      PubDate: 2015-08-14T07:52:23Z
       
  • An improved superconvergence error estimate for the LDG method
    • Abstract: Publication date: Available online 14 August 2015
      Source:Applied Numerical Mathematics
      Author(s): Slimane Adjerid, Nabil Chaabane
      In this manuscript we present an error analysis for the local discontinuous Galerkin method for a model elliptic problem on Cartesian meshes when polynomials of degree at most k and an appropriate approximation of the boundary condition are used. This special approximation allows us to achieve k + 1 order of convergence for both the potential and its gradient in the L 2 norm. Here we improve on existing estimates for the solution gradient by a factor h .


      PubDate: 2015-08-14T07:52:23Z
       
  • θ-Maruyama methods for nonlinear stochastic differential delay
           equations
    • Abstract: Publication date: Available online 12 August 2015
      Source:Applied Numerical Mathematics
      Author(s): Xiaojie Wang, Siqing Gan, Desheng Wang
      In this paper, mean-square convergence and mean-square stability of θ-Maruyama methods are studied for nonlinear stochastic differential delay equations (SDDEs) with variable lag. Under global Lipschitz conditions, the methods are proved to be mean-square convergent with order 1 2 , and exponential mean-square stability of SDDEs implies that of the methods for sufficiently small step size h > 0 . Further, the exponential mean-square stability properties of SDDEs and those of numerical methods are investigated under some non-global Lipschitz conditions on the drift term. It is shown in this setting that the θ-Maruyama method with θ = 1 can preserve the exponential mean-square stability for any step size. Additionally, the θ-Maruyama method with 1 2 ≤ θ ≤ 1 is asymptotically mean-square stable for any step size, provided that the underlying system with constant lag is exponentially mean-square stable. Applications of this work to some special problem classes show that the results are deeper or sharper than those in the literature. Finally, numerical experiments are included to demonstrate the obtained theoretical results.


      PubDate: 2015-08-14T07:52:23Z
       
  • Numerical simulations for the stabilization and estimation problem of a
           semilinear partial differential equation
    • Abstract: Publication date: Available online 13 August 2015
      Source:Applied Numerical Mathematics
      Author(s): Jorge Tiago
      We deal with the numerical approximation of the problem of local stabilization of Burgers equation. We consider the case when only partial boundary measurements are available. An estimator is coupled with a feedback law in order to stabilize the discretized system. Two different feedback laws are compared. Their performance is analyzed in different domains related to idealized cardiovascular geometries, with increasing complexity.


      PubDate: 2015-08-14T07:52:23Z
       
  • A volume integral equation method for periodic scattering problems for
           anisotropic Maxwell's equations
    • Abstract: Publication date: Available online 14 August 2015
      Source:Applied Numerical Mathematics
      Author(s): Dinh-Liem Nguyen
      This paper presents a volume integral equation method for an electromagnetic scattering problem for three-dimensional Maxwell's equations in the presence of a biperiodic, anisotropic, and possibly discontinuous dielectric scatterer. Such scattering problem can be reformulated as a strongly singular volume integral equation (i.e., integral operators that fail to be weakly singular). In this paper, we firstly prove that the strongly singular volume integral equation satisfies a Gårding-type estimate in standard Sobolev spaces. Secondly, we rigorously analyze a spectral Galerkin method for solving the scattering problem. This method relies on the periodization technique of Gennadi Vainikko that allows us to efficiently evaluate the periodized integral operators on trigonometric polynomials using the fast Fourier transform (FFT). The main advantage of the method is its simple implementation that avoids for instance the need to compute quasiperiodic Green's functions. We prove that the numerical solution of the spectral Galerkin method applied to the periodized integral equation converges quasioptimally to the solution of the scattering problem. Some numerical examples are provided for examining the performance of the method.


      PubDate: 2015-08-14T07:52:23Z
       
  • Error estimates for the interpolating moving least-squares method in
           n-dimensional space
    • Abstract: Publication date: Available online 8 August 2015
      Source:Applied Numerical Mathematics
      Author(s): J.F. Wang, F.X. Sun, Y.M. Cheng, A.X. Huang
      In this paper, the interpolating moving least-squares (IMLS) method is discussed in details. A simpler expression of the approximation function of the IMLS method is obtained. Compared with the moving least-squares (MLS) approximation, the shape function of the IMLS method satisfies the property of Kronecker δ function. Then the meshless method based on the IMLS method can overcome the difficulties of applying the essential boundary conditions. The error estimates of the approximation function and its first and second order derivatives of the IMLS method are presented in n-dimensional space. The theoretical results show that if the weight function is sufficiently smooth and the order of the polynomial basis functions is big enough, the approximation function and its partial derivatives are convergent to the exact values in terms of the maximum radius of the domains of influence of nodes. Then the interpolating element-free Galerkin (IEFG) method based on the IMLS method is presented for potential problems. The advantage of the IEFG method is that the essential boundary conditions can be applied directly and easily. For the purpose of demonstration, some selected numerical examples are given to prove the theories in this paper.


      PubDate: 2015-08-09T06:46:01Z
       
  • Well-balanced central finite volume methods for the Ripa system
    • Abstract: Publication date: November 2015
      Source:Applied Numerical Mathematics, Volume 97
      Author(s): R. Touma, C. Klingenberg
      We propose a new well-balanced central finite volume scheme for the Ripa system both in one and two space dimensions. The Ripa system is a nonhomogeneous hyperbolic system with a non-zero source term that is obtained from the shallow water equations system by incorporating horizontal temperature gradients. The proposed numerical scheme is a second-order accurate finite volume method that evolves a non-oscillatory numerical solution on a single grid, avoids the process of solving Riemann problems arising at the cell interfaces, and follows a well-balanced discretization that ensures the steady state requirement by discretizing the geometrical source term according to the discretization of the flux terms. Furthermore the proposed scheme mimics the surface gradient method and discretizes the water height according to the discretization of the water level. The proposed scheme is then applied and classical one and two-dimensional Ripa problems with flat or variable bottom topographies are successfully solved. The obtained numerical results are in good agreement with corresponding ones appearing in the recent literature, thus confirming the potential and efficiency of the proposed method.


      PubDate: 2015-08-09T06:46:01Z
       
  • Existence and uniqueness of optimal solutions for multirate partial
           differential algebraic equations
    • Abstract: Publication date: Available online 5 August 2015
      Source:Applied Numerical Mathematics
      Author(s): Bernd Kugelmann, Roland Pulch
      The numerical simulation of electric circuits including multirate signals can be done by a model based on partial differential algebraic equations. In the case of frequency modulated signals, a local frequency function appears as a degree of freedom in the model. Thus the determination of a solution with a minimum amount of variation is feasible, which allows for resolving on relatively coarse grids. We prove the existence and uniqueness of the optimal solutions in the case of initial-boundary value problems as well as biperiodic boundary value problems. The minimisation problems are also investigated and interpreted in the context of optimal control. Furthermore, we construct a method of characteristics for the computation of optimal solutions in biperiodic problems. Numerical simulations of test examples are presented.


      PubDate: 2015-08-09T06:46:01Z
       
  • Reconstructions that combine interpolation with least squares fitting
    • Abstract: Publication date: November 2015
      Source:Applied Numerical Mathematics, Volume 97
      Author(s): Francesc Aràndiga, José Jaime Noguera
      We develop a reconstruction that combines interpolation and least squares fitting for point values in the context of multiresolution a la Harten. We study the smoothness properties of the reconstruction as well as its approximation order. We analyze how different adaptive techniques (ENO, SR and WENO) can be used within this reconstruction. We present some numerical examples where we compare the results obtained with the classical interpolation and the interpolation combined with least-squares approximation.


      PubDate: 2015-07-31T15:52:16Z
       
  • A predictor–corrector approach for pricing American options under
           the finite moment log-stable model
    • Abstract: Publication date: November 2015
      Source:Applied Numerical Mathematics, Volume 97
      Author(s): Wenting Chen, Xiang Xu, Song-Ping Zhu
      This paper investigates the pricing of American options under the finite moment log-stable (FMLS) model. Under the FMLS model, the price of American-style options is governed by a highly nonlinear fractional partial differential equation (FPDE) system, which is much more complicated to solve than the corresponding Black–Scholes (B–S) system, with difficulties arising from the semi-globalness of the fractional operator, in conjunction with the nonlinearity associated with the early exercise nature of American-style options. Albeit difficult, in this paper, we propose a new predictor–corrector scheme based on the spectral-collocation method to solve for the prices of American options under the FMLS model. In the current approach, the nonlinearity of the pricing system is successfully dealt with using the predictor–corrector framework, whereas the non-localness of the fractional operator is elegantly handled. We have also provided an elegant error analysis for the current approach. Various numerical experiments suggest that the current method is fast and efficient, and can be easily extended to price American-style options under other fractional diffusion models. Based on the numerical results, we have also examined quantitatively the influence of the tail index on American put options.


      PubDate: 2015-07-28T09:04:27Z
       
  • Fourier collocation algorithm for identifying the spacewise-dependent
           source in the advection–diffusion equation from boundary data
           measurements
    • Abstract: Publication date: November 2015
      Source:Applied Numerical Mathematics, Volume 97
      Author(s): Alemdar Hasanov, Balgaisha Mukanova
      In this study, we investigate the inverse problem of identifying an unknown spacewise-dependent source F ( x ) in the one-dimensional advection–diffusion equation u t = Du xx − vu x + F ( x ) H ( t ) , ( x , t ) ∈ ( 0 , 1 ) × ( 0 , T ] , based on boundary concentration measurements g ( t ) : = u ( ℓ , t ) . Most studies have attempted to reconstruct an unknown spacewise-dependent source F ( x ) from the final observation u T ( x ) : = u ( x , T ) , but from an engineering viewpoint, the above boundary data measurements are feasible. Thus, we propose a new algorithm for reconstructing the spacewise-dependent source F ( x ) . This algorithm is based on Fourier expansion of the direct problem solution followed by minimization of the cost functional by taking a partial K-sum of the Fourier expansion. Tikhonov regularization is then applied to the ill-posed problem that is obtained. The proposed approach also allows us to estimate the degree of ill-posedness for the inverse problem considered in this study. We then establish the relationship between the noise level γ > 0 , the parameter of regularization α > 0 , and the truncation (or cut-off) parameter K. A new numerical filtering algorithm is proposed for smoothing the noisy output data. Our numerical results demonstrated that the results obtained for random noisy data up to noise levels of 7% had sufficiently high accuracy for all reconstructions.


      PubDate: 2015-07-28T09:04:27Z
       
  • Editorial Board
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96




      PubDate: 2015-07-28T09:04:27Z
       
  • On a fictitious domain method with distributed Lagrange multiplier for
           interface problems
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Ferdinando Auricchio , Daniele Boffi , Lucia Gastaldi , Adrien Lefieux , Alessandro Reali
      In this paper we propose a new variational formulation for an elliptic interface problem and discuss its finite element approximation. Our formulation fits within the framework of fictitious domain methods with distributed Lagrange multipliers. For the underlying mixed scheme we prove stability and convergence. Some preliminary numerical tests confirm the theoretical investigations.


      PubDate: 2015-07-06T14:29:41Z
       
  • Efficient and accurate implementation of hp-BEM for the Laplace operator
           in 2D
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Markus Bantle , Stefan Funken
      We discuss the accurate and efficient implementation of hp-BEM for the Laplace operator in two dimensions. Using Legendre polynomials and their antiderivatives as local bases for the discrete ansatz spaces, we are able to reduce both the evaluation of potentials and the computation of Galerkin entries to the evaluation of basic integrals. For the computation of these integrals we derive recurrence relations and discuss their accurate evaluation. Our implementation of p- and hp-BEM produces accurate results even for large polynomial degrees ( p > 1000 ) while still being efficient. While this work only treats Symm's integral equation for the Laplace operator in 2D, our approach can be used to solve Symm's, hypersingular and mixed integral equations for Laplace, Lamé and Stokes problems in two dimensions.


      PubDate: 2015-07-06T14:29:41Z
       
  • Finite element potentials
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Ana Alonso Rodríguez , Alberto Valli
      We present an explicit and efficient way for constructing finite elements with assigned gradient, or curl, or divergence. Some simple notions of homology theory and graph theory applied to the finite element mesh are basic tools for devising the solution algorithms.


      PubDate: 2015-07-06T14:29:41Z
       
  • Energy norm based error estimators for adaptive BEM for hypersingular
           integral equations
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Markus Aurada , Michael Feischl , Thomas Führer , Michael Karkulik , Dirk Praetorius
      For hypersingular integral equations in 2D and 3D, we analyze easy-to-implement error estimators like ( h − h / 2 ) -based estimators, two-level estimators, and averaging on large patches and prove their equivalence. Moreover, we introduce some ZZ-type error estimators. All of these a posteriori error estimators are analyzed within the framework of localization techniques for the energy norm.


      PubDate: 2015-07-06T14:29:41Z
       
  • Parallel multilevel solvers for the cardiac electro-mechanical coupling
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): P. Colli Franzone , L.F. Pavarino , S. Scacchi
      We develop a parallel solver for the cardiac electro-mechanical coupling. The electric model consists of two non-linear parabolic partial differential equations (PDEs), the so-called Bidomain model, which describes the spread of the electric impulse in the heart muscle. The two PDEs are coupled with a non-linear elastic model, where the myocardium is considered as a nearly-incompressible transversely isotropic hyperelastic material. The discretization of the whole electro-mechanical model is performed by Q1 finite elements in space and a semi-implicit finite difference scheme in time. This approximation strategy yields at each time step the solution of a large scale ill-conditioned linear system deriving from the discretization of the Bidomain model and a non-linear system deriving from the discretization of the finite elasticity model. The parallel solver developed consists of solving the linear system with the Conjugate Gradient method, preconditioned by a Multilevel Schwarz preconditioner, and the non-linear system with a Newton–Krylov-Algebraic Multigrid solver. Three-dimensional parallel numerical tests on a Linux cluster show that the parallel solver proposed is scalable and robust with respect to the domain deformations induced by the cardiac contraction.


      PubDate: 2015-07-06T14:29:41Z
       
  • Editorial Board
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95




      PubDate: 2015-07-06T14:29:41Z
       
  • Special Issue: Fourth Chilean Workshop on Numerical Analysis of Partial
           Differential Equations (WONAPDE 2013), Universidad de Concepción,
           Chile
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Raimund Bürger , Gabriel N. Gatica , Norbert Heuer , Rodolfo Rodríguez , Mauricio Sepúlveda



      PubDate: 2015-07-06T14:29:41Z
       
  • Application of optimal control to the cardiac defibrillation problem using
           a physiological model of cellular dynamics
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Nagaiah Chamakuri , Karl Kunisch , Gernot Plank
      Optimal control techniques are investigated with the goal of terminating reentry waves in cardiac tissue models. In this computational study the Luo–Rudy phase-I ventricular action potential model is adopted which accounts for more biophysical details of cellular dynamics as compared to previously used phenomenological models. The parabolic and ordinary differential equations are solved as a coupled system and an AMG preconditioner is used to solve the discretized elliptic equation. The numerical results demonstrate that defibrillation is possible by delivering a single strong shock. The optimal control approach also leads to successful defibrillation and demands less total current. The present study motivates us to further investigate optimal control techniques on realistic geometries by incorporating the structural heterogeneity in the cardiac tissue.


      PubDate: 2015-07-06T14:29:41Z
       
  • Modified fully discretized projection method for the incompressible
           Navier–Stokes equations
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Daniel X. Guo
      The stability and convergence of a second-order fully discretized projection method for the incompressible Navier–Stokes equations is studied. In order to update the pressure field faster, modified fully discretized projection methods are proposed. It results in a nearly second-order method. This method sacrifices a little of accuracy, but it requires much less computations at each time step. It is very appropriate for actual computations. The comparison with other methods for the driven-cavity problem is presented.


      PubDate: 2015-07-06T14:29:41Z
       
  • A note on the stability of cut cells and cell merging
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Marsha Berger
      Embedded boundary meshes may have cut cells of arbitrarily small volume which can lead to stability problems in finite volume computations with explicit time stepping. We show that time step constraints are not as strict as often believed. We prove this in one dimension for linear advection and the first order upwind scheme. Numerical examples in two dimensions demonstrate that this carries over to more complicated situations. This analysis sheds light on the choice of time step when using cell merging to stabilize the arbitrarily small cells that arise in embedded boundary schemes.


      PubDate: 2015-07-06T14:29:41Z
       
  • Mechanical quadrature methods and their extrapolations for solving the
           first kind boundary integral equations of Stokes equation
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Chong Chen , Xiaoming He , Jin Huang
      In this article the mechanical quadrature methods (MQMs) and their extrapolations are proposed and analyzed for solving the first kind boundary integral equations of Stokes equation with closed smooth boundary or closed piecewise curved boundary. It is straightforward and cost efficient to obtain the entries in the linear system arising from the MQMs. The condition numbers of the discrete matrices are of only O ( h − 1 ) and the MQMs achieve higher accuracy than the collocation and Galerkin methods. The analysis of MQMs is more challenging than that of the collocation and Galerkin methods since its theory is no longer within the framework of the projection theory. In this article the convergence of the MQM solutions and the asymptotic expansions of the MQM solution errors are proved for both of the two types of boundary. In order to further improve the accuracy, a Richardson extrapolation is constructed for the mechanical quadrature solution on the smooth boundary and a splitting extrapolation is constructed for the mechanical quadrature solution on the piecewise curved boundary based on the asymptotic expansions of the errors. Numerical examples are provided to illustrate the features of the proposed numerical methods.


      PubDate: 2015-07-06T14:29:41Z
       
  • Timestepping schemes for the 3d Navier–Stokes equations
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Youngjoon Hong , Djoko Wirosoetisno
      It is well known that the (exact) solutions of the 3d Navier–Stokes equations remain bounded for all time if the initial data and the forcing are sufficiently small relative to the viscosity. They also remain bounded for a finite time for arbitrary initial data in L 2 . In this article, we consider two temporal discretisations (semi-implicit and fully implicit) of the 3d Navier–Stokes equations in a periodic domain and prove that their solutions remain uniformly bounded in H 1 subject to essentially the same respective smallness conditions as the continuous system (on initial data and forcing or on the time of existence) provided the time step is small.


      PubDate: 2015-07-06T14:29:41Z
       
  • The study of a fourth-order multistep ADI method applied to nonlinear
           delay reaction–diffusion equations
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Dingwen Deng
      In this paper, a high-order compact alternating direction implicit (HOC ADI) method, which combines fourth-order compact difference approximation to spatial derivatives and second order backward differentiation formula (BDF2) for temporal integration, is derived for nonlinear delay reaction–diffusion equations. By the discrete energy method, its optimal error estimates in L 2 - and H 1 -norms are constructively obtained. Then, a class of Richardson extrapolation algorithms (REAs) are established to improve computational efficiency. Besides, a modified HOC ADI solver is devised to reduce time cost as delay is very small. Numerical results confirm the theoretical results and performance of our algorithms.


      PubDate: 2015-07-06T14:29:41Z
       
  • Penalization of Robin boundary conditions
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Bouchra Bensiali , Guillaume Chiavassa , Jacques Liandrat
      This paper is devoted to the mathematical analysis of a method based on fictitious domain approach. Boundary conditions of Robin type (also known as Fourier boundary conditions) are enforced using a penalization method. A complete description of the method and a full analysis are provided for univariate elliptic and parabolic problems using finite difference approximation. Numerical evidence of the predicted estimations is provided as well as numerical results for a nonlinear problem and a first extension of the method in the bivariate situation is proposed.


      PubDate: 2015-07-06T14:29:41Z
       
  • Uniformly convergent difference schemes for a singularly perturbed third
           order boundary value problem
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Hans-Goerg Roos , Ljiljana Teofanov , Zorica Uzelac
      In this paper we consider a numerical approximation of a third order singularly perturbed boundary value problem by an upwind finite difference scheme on a Shishkin mesh. The behavior of the solution, and the stability of the continuous problem are discussed. The proof of the uniform convergence of the proposed numerical method is based on the strongly uniform stability and a weak consistency property of the discrete problem. Numerical experiments verify our theoretical results.


      PubDate: 2015-07-06T14:29:41Z
       
  • Comparison results for the Stokes equations
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): C. Carstensen , K. Köhler , D. Peterseim , M. Schedensack
      This paper enfolds a medius analysis for the Stokes equations and compares different finite element methods (FEMs). A first result is a best approximation result for a P 1 non-conforming FEM. The main comparison result is that the error of the P 2 P 0 -FEM is a lower bound to the error of the Bernardi–Raugel (or reduced P 2 P 0 ) FEM, which is a lower bound to the error of the P 1 non-conforming FEM, and this is a lower bound to the error of the MINI-FEM. The paper discusses the converse direction, as well as other methods such as the discontinuous Galerkin and pseudostress FEMs. Furthermore this paper provides counterexamples for equivalent convergence when different pressure approximations are considered. The mathematical arguments are various conforming companions as well as the discrete inf-sup condition.


      PubDate: 2015-07-06T14:29:41Z
       
  • Post-processing procedures for an elliptic distributed optimal control
           problem with pointwise state constraints
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Susanne C. Brenner , Li-Yeng Sung , Yi Zhang
      We consider an elliptic distributed optimal control problem with state constraints and compare three post-processing procedures that compute approximations of the optimal control from the approximation of the optimal state obtained by a quadratic C 0 interior penalty method.


      PubDate: 2015-07-06T14:29:41Z
       
  • Integral equations requiring small numbers of Krylov-subspace iterations
           for two-dimensional smooth penetrable scattering problems
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Yassine Boubendir , Oscar Bruno , David Levadoux , Catalin Turc
      This paper presents a class of boundary integral equations for the solution of problems of electromagnetic and acoustic scattering by two-dimensional homogeneous penetrable scatterers with smooth boundaries. The new integral equations, which, as is established in this paper, are uniquely solvable Fredholm equations of the second kind, result from representations of fields as combinations of single and double layer potentials acting on appropriately chosen regularizing operators. As demonstrated in this text by means of a variety of numerical examples (that resulted from a high-order Nyström computational implementation of the new equations), these “regularized combined equations” can give rise to important reductions in computational costs, for a given accuracy, over those resulting from previous iterative boundary integral equation solvers for transmission problems.


      PubDate: 2015-07-06T14:29:41Z
       
  • A numerical study of divergence-free kernel approximations
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Arthur A. Mitrano , Rodrigo B. Platte
      Approximation properties of divergence-free vector fields by global and local solenoidal bases are studied. A comparison between interpolants generated with radial kernels and multivariate polynomials is presented. Numerical results show higher rates of convergence for derivatives of the vector field being approximated in directions enforced by the divergence operator when a rectangular grid is used. We also compute the growth of Lebesgue constants for uniform and clustered nodes and study the flat limit of divergence-free interpolants based on radial kernels. Numerical results are presented for two- and three-dimensional vector fields.


      PubDate: 2015-07-06T14:29:41Z
       
  • Pure Lagrangian and semi-Lagrangian finite element methods for the
           numerical solution of Navier–Stokes equations
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): M. Benítez , A. Bermúdez
      In this paper we propose a unified formulation to introduce Lagrangian and semi-Lagrangian velocity and displacement methods for solving the Navier–Stokes equations. This formulation allows us to state classical and new numerical methods. Several examples are given. We combine them with finite element methods for spatial discretization. In particular, we propose two new second-order characteristics methods in terms of the displacement, one semi-Lagrangian and the other one pure Lagrangian. The pure Lagrangian displacement methods are useful for solving free surface problems and fluid-structure interaction problems because the computational domain is independent of the time and fluid–solid coupling at the interphase is straightforward. However, for moderate to high-Reynolds number flows, they can lead to high distortion in the mesh elements. When this happens it is necessary to remesh and reinitialize the transformation to the identity. In order to assess the performance of the obtained numerical methods, we solve different problems in two space dimensions. In particular, numerical results for a sloshing problem in a rectangular tank and the flow in a driven cavity are presented.


      PubDate: 2015-07-06T14:29:41Z
       
  • A priori hp-estimates for discontinuous Galerkin approximations to linear
           hyperbolic integro-differential equations
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Samir Karaa , Amiya K. Pani , Sangita Yadav
      An hp-discontinuous Galerkin (DG) method is applied to a class of second order linear hyperbolic integro-differential equations. Based on the analysis of an expanded mixed type Ritz–Volterra projection, a priori hp-error estimates in L ∞ ( L 2 ) -norm of the velocity as well as of the displacement, which are optimal in the discretizing parameter h and suboptimal in the degree of polynomial p are derived. For optimal estimates of the displacement in L ∞ ( L 2 ) -norm with reduced regularity on the exact solution, a variant of Baker's nonstandard energy formulation is developed and analyzed. Results on order of convergence which are similar in spirit to linear elliptic and parabolic problems are established for the semidiscrete case after suitably modifying the numerical fluxes. For the completely discrete scheme, an implicit-in-time procedure is formulated, stability results are derived and a priori error estimates are discussed. Finally, numerical experiments on two dimensional domains are conducted which confirm the theoretical results.


      PubDate: 2015-07-06T14:29:41Z
       
  • Two essential properties of (q,h)-Bernstein–Bézier curves
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Ron Goldman , Plamen Simeonov
      The ( q , h ) -Bernstein–Bézier curves are generalizations of both the h-Bernstein–Bézier curves and the q-Bernstein–Bézier curves. We investigate two essential features of ( q , h ) -Bernstein bases and ( q , h ) -Bézier curves: the variation diminishing property and the degree elevation algorithm. We show that the ( q , h ) -Bernstein bases for a non-empty interval [ a , b ] satisfy Descartes' law of signs on [ a , b ] when q > − 1 , q ≠ 0 , and h ≤ min ⁡ { ( 1 − q ) a , ( 1 − q ) b } . We conclude that the corresponding ( q , h ) -Bézier curves are variation diminishing. We also derive a degree elevation formula for ( q , h ) -Bernstein bases and ( q , h ) -Bézier curves over arbitrary intervals [ a , b ] . We show that these degree elevation formulas depend only on the parameter q and are independent of both the parameter h and the interval [ a , b ] . We investigate the convergence of the control polygons generated by repeated degree elevation. We show that unlike classical Bézier curves, the control polygons generated by repeated degree elevation for ( q , h ) -Bézier curves with 0 < q < 1 do not converge to the original ( q , h ) -Bézier curve, but rather to a piecewise linear curve with vertices that depend only on q and the monomial coefficients of the q-Bézier curve having the same control points as the original ( q , h ) -Bézier curve. A similar result holds when q > 1 . Here the control polygons generated by repeated degree elevation converge to a piecewise linear curve that depends only on q and the monomial coefficients of the 1 / q -Bézier curve with the control points of the original ( q , h ) -Bézier curve in reverse order.


      PubDate: 2015-07-06T14:29:41Z
       
  • Editorial Board
    • Abstract: Publication date: August 2015
      Source:Applied Numerical Mathematics, Volume 94




      PubDate: 2015-07-06T14:29:41Z
       
  • A hybrid discontinuous Galerkin method for
           advection–diffusion–reaction problems
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Dong-wook Shin , Youngmok Jeon , Eun-Jae Park
      A hybrid discontinuous Galerkin (HDG) method for the Poisson problem introduced by Jeon and Park can be viewed as a hybridizable discontinuous Galerkin method using a Baumann–Oden type local solver. In this work, an upwind HDG method with super-penalty is proposed to solve advection–diffusion–reaction problems. A super-penalty formulation facilitates an optimal order convergence in the L 2 norm as well as the energy norm. Several numerical examples are presented to show the performance of the method.


      PubDate: 2015-07-06T14:29:41Z
       
  • Numerical solution of a multidimensional sedimentation problem using
           finite volume-element methods
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Ricardo Ruiz-Baier , Héctor Torres
      We are interested in the reliable simulation of the sedimentation of monodisperse suspensions under the influence of body forces. At the macroscopic level, the complex interaction between the immiscible fluid and the sedimentation of a compressible phase may be governed by the Navier–Stokes equations coupled to a nonlinear advection–diffusion–reaction equation for the local solids concentration. A versatile and effective finite volume element (FVE) scheme is proposed, whose formulation relies on a stabilized finite element (FE) method with continuous piecewise linear approximation for velocity, pressure and concentration. Some numerical simulations in two and three spatial dimensions illustrate the features of the present FVE method, suggesting their applicability in a wide range of problems.


      PubDate: 2015-07-06T14:29:41Z
       
  • A relaxation Riemann solver for compressible two-phase flow with phase
           transition and surface tension
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Christian Rohde , Christoph Zeiler
      The dynamics of two-phase flows depend crucially on interfacial effects like surface tension and phase transition. A numerical method for compressible inviscid flows is proposed that accounts in particular for these two effects. The approach relies on the solution of Riemann-like problems across the interface that separates the liquid and the vapour phase. Since the analytical solutions of the Riemann problems are only known in particular cases an approximative Riemann solver for arbitrary settings is constructed. The approximative solutions rely on the relaxation technique. The local well-posedness of the approximative solver is proven. Finally we present numerical experiments for radially symmetric configurations that underline the reliability and efficiency of the numerical scheme.


      PubDate: 2015-07-06T14:29:41Z
       
  • Nonlinear PDE based numerical methods for cell tracking in zebrafish
           embryogenesis
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Karol Mikula , Róbert Špir , Michal Smíšek , Emmanuel Faure , Nadine Peyriéras
      The paper presents numerical algorithms leading to an automated cell tracking and reconstruction of the cell lineage tree during the first hours of animal embryogenesis. We present results obtained for large-scale 3D+time two-photon laser scanning microscopy images of early stages of zebrafish (Danio rerio) embryo development. Our approach consists of three basic steps – the image filtering, the cell centers detection and the cell trajectories extraction yielding the lineage tree reconstruction. In all three steps we use nonlinear partial differential equations. For the filtering the geodesic mean curvature flow in level set formulation is used, for the cell center detection the motion of level sets by a constant speed regularized by mean curvature flow is used and the solution of the eikonal equation is essential for the cell trajectories extraction. The core of our new tracking method is an original approach to cell trajectories extraction based on finding a continuous centered paths inside the spatio-temporal tree structures representing cell movement and divisions. Such paths are found by using a suitably designed distance function from cell centers detected in all time steps of the 3D+time image sequence and by a backtracking in the steepest descent direction of a potential field based on this distance function. We also present efficient and naturally parallelizable discretizations of the aforementioned nonlinear PDEs and discuss properties and results of our new tracking method on artificial and real 4D data.


      PubDate: 2015-07-06T14:29:41Z
       
  • Analysis and discretization of the volume penalized Laplace operator with
           Neumann boundary conditions
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Dmitry Kolomenskiy , Romain Nguyen van yen , Kai Schneider
      We study the properties of an approximation of the Laplace operator with Neumann boundary conditions using volume penalization. For the one-dimensional Poisson equation we compute explicitly the exact solution of the penalized equation and quantify the penalization error. Numerical simulations using finite differences allow then to assess the discretization and penalization errors. The eigenvalue problem of the penalized Laplace operator with Neumann boundary conditions is also studied. As examples in two space dimensions, we consider a Poisson equation with Neumann boundary conditions in rectangular and circular domains.


      PubDate: 2015-07-06T14:29:41Z
       
  • Deterministic particle method approximation of a contact inhibition
           cross-diffusion problem
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Gonzalo Galiano , Virginia Selgas
      We use a deterministic particle method to produce numerical approximations to the solutions of an evolution cross-diffusion problem for two populations. According to the values of the diffusion parameters related to the intra- and inter-population repulsion intensities, the system may be classified in terms of an associated matrix. When the matrix is definite positive, the problem is well posed and the finite element approximation produces convergent approximations to the exact solution. A particularly important case arises when the matrix is only positive semi-definite and the initial data are segregated: the contact inhibition problem. In this case, the solutions may be discontinuous and hence the (conforming) finite element approximation may exhibit instabilities in the neighborhood of the discontinuity. In this article we deduce the particle method approximation to the general cross-diffusion problem and apply it to the contact inhibition problem. We then provide some numerical experiments comparing the results produced by the finite element and the particle method discretizations.


      PubDate: 2015-07-06T14:29:41Z
       
  • Semi-implicit finite volume level set method for advective motion of
           interfaces in normal direction
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Peter Frolkovič , Karol Mikula , Jozef Urbán
      In this paper a semi-implicit finite volume method is proposed to solve the applications with moving interfaces using the approach of level set methods. The level set advection equation with a given speed in normal direction is solved by this method. Moreover, the scheme is used for the numerical solution of eikonal equation to compute the signed distance function and for the linear advection equation to compute the so-called extension speed [1]. In both equations an extrapolation near the interface is used in our method to treat Dirichlet boundary conditions on implicitly given interfaces. No restrictive CFL stability condition is required by the semi-implicit method that is very convenient especially when using the extrapolation approach. In summary, we can apply the method for the numerical solution of level set advection equation with the initial condition given by the signed distance function and with the advection velocity in normal direction given by the extension speed. Several advantages of the proposed approach can be shown for chosen examples and application. The advected numerical level set function approximates well the property of remaining the signed distance function during whole simulation time. Sufficiently accurate numerical results can be obtained even with the time steps violating the CFL stability condition.


      PubDate: 2015-07-06T14:29:41Z
       
  • An adaptive multiresolution method for ideal magnetohydrodynamics using
           divergence cleaning with parabolic–hyperbolic correction
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Anna Karina Fontes Gomes , Margarete Oliveira Domingues , Kai Schneider , Odim Mendes , Ralf Deiterding
      We present an adaptive multiresolution method for the numerical simulation of ideal magnetohydrodynamics in two space dimensions. The discretization uses a finite volume scheme based on a Cartesian mesh and an explicit compact Runge–Kutta scheme for time integration. Harten's cell average multiresolution allows to introduce a locally refined spatial mesh while controlling the error. The incompressibility of the magnetic field is controlled by using a Generalized Lagrangian Multiplier (GLM) approach with a mixed hyperbolic–parabolic correction. Different applications to two-dimensional problems illustrate the properties of the method. For each application CPU time and memory savings are reported and numerical aspects of the method are discussed. The accuracy of the adaptive computations is assessed by comparison with reference solutions computed on a regular fine mesh.


      PubDate: 2015-07-06T14:29:41Z
       
  • A simple weighted essentially non-oscillatory limiter for the correction
           procedure via reconstruction (CPR) framework
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): Jie Du , Chi-Wang Shu , Mengping Zhang
      In this paper, we adapt a simple weighted essentially non-oscillatory (WENO) limiter, originally designed for discontinuous Galerkin (DG) schemes [45], to the correction procedure via reconstruction (CPR) framework for solving conservation laws. The objective of this simple WENO limiter is to simultaneously maintain uniform high order accuracy of the CPR framework in smooth regions and control spurious numerical oscillations near discontinuities. The WENO limiter we adopt in this paper is particularly simple to implement and will not harm the conservativeness of the CPR framework. Also, it uses information only from the target cell and its immediate neighbors, and thus can maintain the compactness of the CPR framework. Since the CPR framework with the WENO limiter does not in general preserve positivity of the solution, we also extend the positivity-preserving limiters in [43,44,42] to the CPR framework. Numerical results in one and two dimensions are provided to illustrate the good behavior of this procedure.


      PubDate: 2015-07-06T14:29:41Z
       
  • Numerical identification of constitutive functions in scalar nonlinear
           convection–diffusion equations with application to batch
           sedimentation
    • Abstract: Publication date: September 2015
      Source:Applied Numerical Mathematics, Volume 95
      Author(s): S. Diehl
      A fast and simple method for the identification of nonlinear constitutive functions in scalar convection–diffusion equations is presented. No a priori information is needed on the form of the constitutive functions, which are obtained as continuous piecewise affine functions. Accurate and frequent measurements in space and time are required. Synthetic data of batch sedimentation of particles in a liquid and traffic flow are chosen as examples where a convective flux function and a function modelling compression are identified. Real data should first undergo a denoising procedure, which is also presented. It consists of a sequence of convex optimization problems, whose constraints originate from fundamental physical properties. The methodology is applied on data from a batch sedimentation experiment of activated sludge in wastewater treatment.


      PubDate: 2015-07-06T14:29:41Z
       
  • Stability analysis and classification of Runge–Kutta methods for
           index 1 stochastic differential-algebraic equations with scalar noise
    • Abstract: Publication date: October 2015
      Source:Applied Numerical Mathematics, Volume 96
      Author(s): Dominique Küpper , Anne Kværnø , Andreas Rößler
      The problem of solving stochastic differential-algebraic equations (SDAEs) of index 1 with a scalar driving Wiener process is considered. Recently, the authors have proposed a class of stiffly accurate stochastic Runge–Kutta (SRK) methods that do not involve any pseudo-inverses or projectors for the numerical solution of the problem. Based on this class of approximation methods, classifications for the coefficients of stiffly accurate SRK methods attaining strong order 0.5 as well as strong order 1.0 are calculated. Further, the mean-square stability of the considered class of SRK methods is analyzed. As the main result, families of A-stable efficient order 0.5 and 1.0 stiffly accurate SRK methods with a minimal number of stages for SDEs as well as for SDAEs are presented.


      PubDate: 2015-07-06T14:29:41Z
       
  • Simultaneous optical flow and source estimation: space-time discretization
           and preconditioning
    • Abstract: Publication date: Available online 14 May 2015
      Source:Applied Numerical Mathematics
      Author(s): R. Andreev , O. Scherzer , W. Zulehner
      We consider the simultaneous estimation of an optical flow field and an illumination source term in a movie sequence. The particular optical flow equation is obtained by assuming that the image intensity is a conserved quantity up to possible sources and sinks which represent varying illumination. We formulate this problem as an energy minimization problem and propose a space-time simultaneous discretization for the optimality system in saddle-point form. We investigate a preconditioning strategy that renders the discrete system well-conditioned uniformly in the discretization resolution. Numerical experiments complement the theory.


      PubDate: 2015-05-20T13:22:30Z
       
  • Projected finite elements for reaction-diffusion systems on stationary
           closed surfaces
    • Abstract: Publication date: Available online 29 April 2015
      Source:Applied Numerical Mathematics
      Author(s): N. Tuncer , A. Madzvamuse , A.J. Meir
      In this paper we present a robust, efficient and accurate finite element method for solving reaction-diffusion systems on stationary spheroidal surfaces (these are surfaces which are deformations of the sphere such as ellipsoids, dumbbells, and heart-shaped surfaces) with potential applications in the areas of developmental biology, cancer research, wound healing, tissue regeneration, and cell motility among many others where such models are routinely used. Our method is inspired by the radially projected finite element method introduced in [39]. (Hence the name “projected” finite element method). The advantages of the projected finite element method are that it is easy to implement and that it provides a conforming finite element discretization which is “logically” rectangular. To demonstrate the robustness, applicability and generality of this numerical method, we present solutions of reaction-diffusion systems on various spheroidal surfaces. We show that the method presented in this paper preserves positivity of the solutions of reaction-diffusion equations which is not generally true for Galerkin type methods. We conclude that surface geometry plays a pivotal role in pattern formation. For a fixed set of model parameter values, different surfaces give rise to different pattern generation sequences of either spots or stripes or a combination (observed as circular spot-stripe patterns). These results clearly demonstrate the need for detailed theoretical analytical studies to elucidate how surface geometry and curvature influence pattern formation on complex surfaces.


      PubDate: 2015-05-13T12:42:30Z
       
 
 
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