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Implicit-Explicit Finite Difference Approximations of a Semilinear Heat Equation with Logarithmic Nonlinearity 具有对数非线性的半线性热方程的隐显有限差分逼近
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-31 DOI: 10.1515/cmam-2022-0217
Panagiotis Paraschis, G. E. Zouraris
Abstract We formulate an initial and Dirichlet boundary value problem for a semilinear heat equation with logarithmic nonlinearity over a two-dimensional rectangular domain. We approximate its solution by employing the standard second-order finite difference method for space discretization, and a linearized backward Euler method, or, a linearized BDF2 method for time stepping. For the linearized backward Euler finite difference method, we derive an almost optimal order error estimate in the discrete L t ∞ ⁢ ( L x ∞ ) L^{infty}_{t}(L^{infty}_{x}) -norm without imposing mesh conditions, and for the linearized BDF2 finite difference method, we establish an almost optimal order error estimate in the discrete L t ∞ ⁢ ( H x 1 ) L^{infty}_{t}(H^{1}_{x}) -norm, allowing a mild mesh condition to be satisfied. Finally, we show the efficiency of the numerical methods proposed, by exposing results from numerical experiments. It is the first time in the literature where numerical methods for the approximation of the solution to the heat equation with logarithmic nonlinearity are applied and analysed.
摘要我们在二维矩形域上建立了一个具有对数非线性的双线性热方程的初边值和Dirichlet边值问题。我们通过使用标准的二阶有限差分方法进行空间离散化,并使用线性化的后向Euler方法或线性化的BDF2方法进行时间步进来近似其解。对于线性化后向Euler有限差分法,我们在不施加网格条件的情况下,在离散Lt∞(Lx∞)L^{infty}_{t}^{1}_{x} )-范数,允许满足温和的网格条件。最后,通过数值实验的结果,我们展示了所提出的数值方法的有效性。这是文献中首次应用和分析具有对数非线性的热方程解的近似数值方法。
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引用次数: 0
Recent Advances in Boundary Element Methods 边界元方法的最新进展
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-28 DOI: 10.1515/cmam-2023-0037
U. Langer, O. Steinbach
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引用次数: 0
A Convenient Inclusion of Inhomogeneous Boundary Conditions in Minimal Residual Methods 最小残差法中一种方便的非齐次边界条件包含
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-22 DOI: 10.48550/arXiv.2303.12555
R. Stevenson
Abstract Inhomogeneous essential boundary conditions can be appended to a well-posed PDE to lead to a combined variational formulation. The domain of the corresponding operator is a Sobolev space on the domain Ω on which the PDE is posed, whereas the codomain is a Cartesian product of spaces, among them fractional Sobolev spaces of functions on ∂ Ω partialOmega . In this paper, easily implementable minimal residual discretizations are constructed which yield quasi-optimal approximation from the employed trial space, in which the evaluation of fractional Sobolev norms is fully avoided.
摘要非齐次本质边界条件可以附加到适定偏微分方程,从而得到组合变分公式。相应算子的域是域Ω上的Sobolev空间,PDE是在该域上提出的,而共域是空间的笛卡尔乘积,其中包括函数在¦ΒΩpartialOmega上的分数阶Sobolev空格。在本文中,构造了易于实现的最小残差离散化,该离散化从所使用的试验空间产生准最优逼近,其中完全避免了对分数阶Sobolev范数的评估。
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引用次数: 1
Developments on the Stability of the Non-symmetric Coupling of Finite and Boundary Elements 有限元与边界元非对称耦合稳定性研究进展
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-10 DOI: 10.1515/cmam-2022-0085
M. Ferrari
Abstract We consider the non-symmetric coupling of finite and boundary elements to solve second-order nonlinear partial differential equations defined in unbounded domains. We present a novel condition that ensures that the associated semi-linear form induces a strongly monotone operator, keeping track of the dependence on the linear combination of the interior domain equation with the boundary integral one. We show that an optimal ellipticity condition, relating the nonlinear operator to the contraction constant of the shifted double-layer integral operator, is guaranteed by choosing a particular linear combination. These results generalize those obtained by Of and Steinbach [Is the one-equation coupling of finite and boundary element methods always stable?, ZAMM Z. Angew. Math. Mech. 93 (2013), 6–7, 476–484] and [On the ellipticity of coupled finite element and one-equation boundary element methods for boundary value problems, Numer. Math. 127 (2014), 3, 567–593], and by Steinbach [A note on the stable one-equation coupling of finite and boundary elements, SIAM J. Numer. Anal. 49 (2011), 4, 1521–1531], where the simple sum of the two coupling equations has been considered. Numerical examples confirm the theoretical results on the sharpness of the presented estimates.
考虑有限元与边界元的非对称耦合,求解无界域上二阶非线性偏微分方程。我们提出了一个新的条件,保证了相关的半线性形式诱导出一个强单调算子,并跟踪了对内域方程与边界积分方程线性组合的依赖。通过选择一个特定的线性组合,证明了非线性算子与位移双层积分算子的收缩常数有关的最优椭圆性条件。这些结果推广了Of和Steinbach[有限元法和边界元法的单方程耦合是否总是稳定的?], zm Z. Angew。数学。[j] .力学93(2013),6-7,476-484].边值问题的耦合有限元和单方程边界元方法的椭圆性,[j] .长春:吉林大学。[j] .数学学报,2014,35(3):567-593],由Steinbach [j] .数值模拟。数学学报,49(2011),4,1521 - 1531],其中考虑了两个耦合方程的简单和。数值算例证实了所提估计的理论结果。
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引用次数: 0
Coupling of Finite and Boundary Elements for Singularly Nonlinear Transmission and Contact Problems 奇异非线性传动与接触问题的有限元与边界元耦合
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-09 DOI: 10.1515/cmam-2022-0120
H. Gimperlein, E. Stephan
Abstract This article discusses the well-posedness and error analysis of the coupling of finite and boundary elements for interface problems in nonlinear elasticity. It concerns 𝑝-Laplacian-type Hencky materials with an unbounded stress-strain relation, as they arise in the modelling of ice sheets, non-Newtonian fluids or porous media. We propose a functional analytic framework for the numerical analysis and obtain a priori and a posteriori error estimates for Galerkin approximations to the resulting boundary/domain variational inequality.
本文讨论了非线性弹性界面问题有限元与边界元耦合的适定性及误差分析。它涉及𝑝-Laplacian-type具有无界应力-应变关系的henky材料,因为它们出现在冰原,非牛顿流体或多孔介质的建模中。我们提出了一个泛函分析框架用于数值分析,并获得了对所得边界/域变分不等式的伽辽金近似的先验和后验误差估计。
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引用次数: 1
CVEM-BEM Coupling for the Simulation of Time-Domain Wave Fields Scattered by Obstacles with Complex Geometries 复杂几何障碍物散射时域波场的cem - bem耦合模拟
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-09 DOI: 10.1515/cmam-2022-0084
L. Desiderio, S. Falletta, M. Ferrari, L. Scuderi
Abstract In this paper, we present a numerical method based on the coupling between a Curved Virtual Element Method (CVEM) and a Boundary Element Method (BEM) for the simulation of wave fields scattered by obstacles immersed in homogeneous infinite media. In particular, we consider the 2D time-domain damped wave equation, endowed with a Dirichlet condition on the boundary (sound-soft scattering). To reduce the infinite domain to a finite computational one, we introduce an artificial boundary on which we impose a Boundary Integral Non-Reflecting Boundary Condition (BI-NRBC). We apply a CVEM combined with the Crank–Nicolson time integrator in the interior domain, and we discretize the BI-NRBC by a convolution quadrature formula in time and a collocation method in space. We present some numerical results to test the performance of the proposed approach and to highlight its effectiveness, especially when obstacles with complex geometries are considered.
本文提出了一种基于曲面虚元法(CVEM)和边界元法(BEM)耦合的模拟均匀无限介质中障碍物散射波场的数值方法。特别地,我们考虑了边界上具有Dirichlet条件(声-软散射)的二维时域阻尼波动方程。为了将无限域简化为有限计算域,我们引入了一个人工边界,并在其上施加了边界积分非反射边界条件(BI-NRBC)。在内域采用CVEM与Crank-Nicolson时间积分器相结合的方法,在时间上采用卷积求积公式,在空间上采用配点法对BI-NRBC进行离散。我们给出了一些数值结果来测试所提出的方法的性能并突出其有效性,特别是在考虑具有复杂几何形状的障碍物时。
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引用次数: 3
Force Computation for Dielectrics Using Shape Calculus 用形状微积分计算电介质的力
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-08 DOI: 10.1515/cmam-2022-0112
P. Panchal, N. Ren, R. Hiptmair
Abstract We are concerned with the numerical computation of electrostatic forces/torques in only piece-wise homogeneous materials using the boundary element method (BEM). Conventional force formulas based on the Maxwell stress tensor yield functionals that fail to be continuous on natural trace spaces. Thus their use in conjunction with BEM incurs slow convergence and low accuracy. We employ the remedy discovered in [P. Panchal and R. Hiptmair, Electrostatic force computation with boundary element methods, SMAI J. Comput. Math. 8 (2022), 49–74]. Motivated by the virtual work principle which is interpreted using techniques of shape calculus, and using the adjoint method from shape optimization, we derive stable interface-based force functionals suitable for use with BEM. This is done in the framework of single-trace direct boundary integral equations for second-order transmission problems. Numerical tests confirm the fast asymptotic convergence and superior accuracy of the new formulas for the computation of total forces and torques.
摘要我们关注的是使用边界元方法(BEM)仅在逐片均匀材料中静电力/转矩的数值计算。基于麦克斯韦应力张量的常规力公式产生了在自然迹空间上不连续的泛函。因此,它们与边界元法结合使用会导致收敛缓慢和精度低。我们采用了[P.Panchal和R.Hiptair,边界元法的静电力计算,SMAI J.Comput.Math.8(2022),49-74]中发现的补救措施。受使用形状演算技术解释的虚功原理的启发,并使用形状优化的伴随方法,我们导出了适用于边界元法的基于稳定界面的力泛函。这是在二阶传输问题的单迹直接边界积分方程的框架下完成的。数值试验证实了计算总力和总力矩的新公式的快速渐近收敛性和优越的精度。
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引用次数: 1
On Split Monotone Variational Inclusion Problem with Multiple Output Sets with Fixed Point Constraints 带不动点约束的多输出集的分裂单调变分包含问题
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-03-01 DOI: 10.1515/cmam-2022-0199
V. A. Uzor, T. O. Alakoya, O. Mewomo
Abstract In this paper, we introduce and study the concept of split monotone variational inclusion problem with multiple output sets (SMVIPMOS). We propose a new iterative scheme, which employs the viscosity approximation technique for approximating the solution of the SMVIPMOS with fixed point constraints of a nonexpansive mapping in real Hilbert spaces. The proposed method utilises the inertial technique for accelerating the speed of convergence and a self-adaptive step size so that its implementation does not require prior knowledge of the operator norm. Under mild conditions, we obtain a strong convergence result for the proposed algorithm and obtain a consequent result, which complements several existing results in the literature. Moreover, we apply our result to study the notions of split variational inequality problem with multiple output sets with fixed point constraints and split convex minimisation problem with multiple output sets with fixed point constraints in Hilbert spaces. Finally, we present some numerical experiments to demonstrate the implementability of our proposed method.
摘要本文引入并研究了具有多输出集的分裂单调变分包含问题(SMVIPMOS)的概念。我们提出了一种新的迭代方案,该方案采用粘性近似技术来近似实Hilbert空间中非扩张映射的不动点约束SMVIPMOS的解。所提出的方法利用惯性技术来加速收敛速度和自适应步长,使得其实现不需要算子范数的先验知识。在温和的条件下,我们获得了所提出算法的强收敛性结果,并获得了相应的结果,这补充了文献中的几个现有结果。此外,我们将我们的结果应用于Hilbert空间中具有不动点约束的多输出集的分裂变分不等式问题和具有不动点限制的多输出集中的分裂凸最小化问题的概念。最后,我们给出了一些数值实验来证明我们提出的方法的可实现性。
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引用次数: 10
The Tracking of Derivative Discontinuities for Delay Fractional Equations Based on Fitted L1 Method 基于拟合L1方法的延迟分数阶方程导数不连续跟踪
IF 1.3 4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-02-28 DOI: 10.1515/cmam-2022-0231
Dakang Cen, Seakweng Vong
Abstract In this paper, the analytic solution of the delay fractional model is derived by the method of steps. The theoretical result implies that the regularity of the solution at s + {s^{+}} is better than that at 0 + {0^{+}} , where s is a constant time delay. The behavior of derivative discontinuity is also discussed. Then, improved regularity solution is obtained by the decomposition technique and a fitted L ⁢ 1 {L1} numerical scheme is designed for it. For the case of initial singularity, the optimal convergence order is reached on uniform meshes when α ∈ [ 2 3 , 1 ) {alphain[frac{2}{3},1)} , α is the order of fractional derivative. Furthermore, an improved fitted L ⁢ 1 {L1} method is proposed and the region of optimal convergence order is larger. For the case t > s {t>s} , stability and min ⁡ { 2 ⁢ α , 1 } {min{2alpha,1}} order convergence of the fitted L ⁢ 1 {L1} scheme are deduced. At last, the numerical tests are carried out and confirm the theoretical result.
摘要本文采用分步法导出了时滞分数模型的解析解。理论结果表明,在s+{s^{+}}处解的正则性优于在0+{0^{+}处的正则性,其中s是恒定的时间延迟。还讨论了导数不连续性的行为。然后,利用分解技术得到了改进的正则性解,并设计了拟合的L1{L1}数值格式,当α∈[23,1){alphain[frac{2}{3},1)},α是分数阶导数时,在均匀网格上达到了最优收敛阶。此外,提出了一种改进的拟合L1{L1}方法,并且最优收敛阶的区域更大。对于t>s{t>s}的情况,稳定性和min⁡ 推导了拟合L1{L1}格式的{2α,1}阶收敛性。最后进行了数值试验,验证了理论结果。
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引用次数: 1
Robust Finite Element Discretization and Solvers for Distributed Elliptic Optimal Control Problems 分布椭圆型最优控制问题的鲁棒有限元离散化及求解方法
4区 数学 Q3 MATHEMATICS, APPLIED Pub Date : 2023-02-18 DOI: 10.1515/cmam-2022-0138
Ulrich Langer, Richard Löscher, Olaf Steinbach, Huidong Yang
Abstract We consider standard tracking-type, distributed elliptic optimal control problems with L 2 L^{2} regularization, and their finite element discretization. We are investigating the L 2 L^{2} error between the finite element approximation u ϱ h u_{varrho h} of the state u ϱ u_{varrho} and the desired state (target) u ¯ overline{u} in terms of the regularization parameter 𝜚 and the mesh size ℎ that leads to the optimal choice ϱ = h 4 varrho=h^{4} . It turns out that, for this choice of the regularization parameter, we can devise simple Jacobi-like preconditioned MINRES or Bramble–Pasciak CG methods that allow us to solve the reduced discrete optimality system in asymptotically optimal complexity with respect to the arithmetical operations and memory demand. The theoretical results are confirmed by several benchmark problems with targets of various regularities including discontinuous targets.
摘要考虑具有l2 L^{2}正则化的标准跟踪型分布椭圆型最优控制问题及其有限元离散化问题。我们正在研究状态u ϱ u_{varrho}与期望状态(目标)u¯overline{u}在正则化参数𝜚和网格尺寸方面的有限元近似u ϱ¹h u_{varrho h}之间的l2 L^{2}误差,从而得出最优选择ϱ =h 4 varrho=h^{4}。事实证明,对于正则化参数的选择,我们可以设计简单的类雅可比预条件MINRES或Bramble-Pasciak CG方法,这些方法允许我们在算术操作和内存需求方面以渐进最优的复杂度解决减少的离散最优性系统。通过几个具有不同规律目标(包括不连续目标)的基准问题验证了理论结果。
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引用次数: 1
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Computational Methods in Applied Mathematics
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