Loading...

Table of Content

    20 December 2023, Volume 5 Issue 4
    ORIGINAL PAPERS
    L1/LDG Method for the Generalized Time-Fractional Burgers Equation in Two Spatial Dimensions
    Changpin Li, Dongxia Li, Zhen Wang
    2023, 5(4):  1299-1322.  doi:10.1007/s42967-022-00199-w
    Asbtract ( 113 )   PDF  
    References | Related Articles | Metrics
    This paper aims to numerically study the generalized time-fractional Burgers equation in two spatial dimensions using the L1/LDG method. Here the L1 scheme is used to approximate the time-fractional derivative, i.e., Caputo derivative, while the local discontinuous Galerkin (LDG) method is used to discretize the spatial derivative. If the solution has strong temporal regularity, i.e., its second derivative with respect to time being right continuous, then the L1 scheme on uniform meshes (uniform L1 scheme) is utilized. If the solution has weak temporal regularity, i.e., its first and/or second derivatives with respect to time blowing up at the starting time albeit the function itself being right continuous at the beginning time, then the L1 scheme on non-uniform meshes (non-uniform L1 scheme) is applied. Then both uniform L1/LDG and non-uniform L1/LDG schemes are constructed. They are both numerically stable and the L2 optimal error estimate for the velocity is obtained. Numerical examples support the theoretical analysis.
    Four-Order Superconvergent Weak Galerkin Methods for the Biharmonic Equation on Triangular Meshes
    Xiu Ye, Shangyou Zhang
    2023, 5(4):  1323-1338.  doi:10.1007/s42967-022-00201-5
    Asbtract ( 94 )   PDF  
    References | Related Articles | Metrics
    A stabilizer-free weak Galerkin (SFWG) finite element method was introduced and analyzed in Ye and Zhang (SIAM J. Numer. Anal. 58: 2572–2588, 2020) for the biharmonic equation, which has an ultra simple finite element formulation. This work is a continuation of our investigation of the SFWG method for the biharmonic equation. The new SFWG method is highly accurate with a convergence rate of four orders higher than the optimal order of convergence in both the energy norm and the L2 norm on triangular grids. This new method also keeps the formulation that is symmetric, positive definite, and stabilizerfree. Four-order superconvergence error estimates are proved for the corresponding SFWG finite element solutions in a discrete H2 norm. Superconvergence of four orders in the L2 norm is also derived for k ≥ 3, where k is the degree of the approximation polynomial. The postprocessing is proved to lift a Pk SFWG solution to a Pk+4 solution elementwise which converges at the optimal order. Numerical examples are tested to verify the theories.
    TECHNICAL NOTE
    Efficient Sparse-Grid Implementation of a Fifth-Order Multi-resolution WENO Scheme for Hyperbolic Equations
    Ernie Tsybulnik, Xiaozhi Zhu, Yong-Tao Zhang
    2023, 5(4):  1339-1364.  doi:10.1007/s42967-022-00202-4
    Asbtract ( 93 )   PDF  
    References | Related Articles | Metrics
    High-order accurate weighted essentially non-oscillatory (WENO) schemes are a class of broadly applied numerical methods for solving hyperbolic partial differential equations (PDEs). Due to highly nonlinear property of the WENO algorithm, large amount of computational costs are required for solving multidimensional problems. In our previous work (Lu et al. in Pure Appl Math Q 14: 57–86, 2018; Zhu and Zhang in J Sci Comput 87: 44, 2021), sparse-grid techniques were applied to the classical finite difference WENO schemes in solving multidimensional hyperbolic equations, and it was shown that significant CPU times were saved, while both accuracy and stability of the classical WENO schemes were maintained for computations on sparse grids. In this technical note, we apply the approach to recently developed finite difference multi-resolution WENO scheme specifically the fifth-order scheme, which has very interesting properties such as its simplicity in linear weights’ construction over a classical WENO scheme. Numerical experiments on solving high dimensional hyperbolic equations including Vlasov based kinetic problems are performed to demonstrate that the sparse-grid computations achieve large savings of CPU times, and at the same time preserve comparable accuracy and resolution with those on corresponding regular single grids.
    ORIGINAL PAPERS
    Mathematical Modeling of Biological Fluid Flow Through a Cylindrical Layer with Due Account for Barodiffusion
    N. N. Nazarenko, A. G. Knyazeva
    2023, 5(4):  1365-1384.  doi:10.1007/s42967-022-00203-3
    Asbtract ( 75 )   PDF  
    References | Related Articles | Metrics
    The work proposes a model of biological fluid flow in a steady mode through a cylindrical layer taking into account convection and diffusion. The model considers finite compressibility and concentration expansion connected with both barodiffusion and additional mechanism of pressure change in the pore volume due to the concentration gradient. Thus, the model is entirely coupled. The paper highlights the complexes composed of scales of physical quantities of different natures. The iteration algorithm for the numerical solution of the problem was developed for the coupled problem. The work involves numerical studies of the considered effects on the characteristics of the flow that can be convective or diffusive, depending on the relation between the dimensionless complexes. It is demonstrated that the distribution of velocity and concentration for different cylinder wall thicknesses is different. It is established that the barodiffusion has a considerable impact on the process in the convective mode or in the case of reduced cylinder wall thickness.
    Fourier Continuation Discontinuous Galerkin Methods for Linear Hyperbolic Problems
    Kiera van der Sande, Daniel Appelö, Nathan Albin
    2023, 5(4):  1385-1405.  doi:10.1007/s42967-022-00205-1
    Asbtract ( 95 )   PDF  
    References | Related Articles | Metrics
    Fourier continuation (FC) is an approach used to create periodic extensions of non-periodic functions to obtain highly-accurate Fourier expansions. These methods have been used in partial differential equation (PDE)-solvers and have demonstrated high-order convergence and spectrally accurate dispersion relations in numerical experiments. Discontinuous Galerkin (DG) methods are increasingly used for solving PDEs and, as all Galerkin formulations, come with a strong framework for proving the stability and the convergence. Here we propose the use of FC in forming a new basis for the DG framework.
    A Sparse Kernel Approximate Method for Fractional Boundary Value Problems
    Hongfang Bai, Ieng Tak Leong
    2023, 5(4):  1406-1421.  doi:10.1007/s42967-022-00206-0
    Asbtract ( 107 )   PDF  
    References | Related Articles | Metrics
    In this paper, the weak pre-orthogonal adaptive Fourier decomposition (W-POAFD) method is applied to solve fractional boundary value problems (FBVPs) in the reproducing kernel Hilbert spaces (RKHSs) W04[0, 1] and W1[0, 1]. The process of the W-POAFD is as follows: (i) choose a dictionary and implement the pre-orthogonalization to all the dictionary elements; (ii) select points in [0, 1] by the weak maximal selection principle to determine the corresponding orthonormalized dictionary elements iteratively; (iii) express the analytical solution as a linear combination of these determined dictionary elements. Convergence properties of numerical solutions are also discussed. The numerical experiments are carried out to illustrate the accuracy and efficiency of W-POAFD for solving FBVPs.
    Semi-regularized Hermitian and Skew-Hermitian Splitting Preconditioning for Saddle-Point Linear Systems
    Kang-Ya Lu, Shu-Jiao Li
    2023, 5(4):  1422-1445.  doi:10.1007/s42967-022-00208-y
    Asbtract ( 114 )   PDF  
    References | Related Articles | Metrics
    In this paper, a two-step semi-regularized Hermitian and skew-Hermitian splitting (SHSS) iteration method is constructed by introducing a regularization matrix in the (1,1)-block of the first iteration step, to solve the saddle-point linear system. By carefully selecting two different regularization matrices, two kinds of SHSS preconditioners are proposed to accelerate the convergence rates of the Krylov subspace iteration methods. Theoretical analysis about the eigenvalue distribution demonstrates that the proposed SHSS preconditioners can make the eigenvalues of the corresponding preconditioned matrices be clustered around 1 and uniformly bounded away from 0. The eigenvector distribution and the upper bound on the degree of the minimal polynomial of the SHSS-preconditioned matrices indicate that the SHSS-preconditioned Krylov subspace iterative methods can converge to the true solution within finite steps in exact arithmetic. In addition, the numerical example derived from the optimal control problem shows that the SHSS preconditioners can significantly improve the convergence speeds of the Krylov subspace iteration methods, and their convergence rates are independent of the discrete mesh size.
    Three Kinds of Discrete Formulae for the Caputo Fractional Derivative
    Zhengnan Dong, Enyu Fan, Ao Shen, Yuhao Su
    2023, 5(4):  1446-1468.  doi:10.1007/s42967-022-00211-3
    Asbtract ( 115 )   PDF  
    References | Related Articles | Metrics
    In this paper, three kinds of discrete formulae for the Caputo fractional derivative are studied, including the modified L1 discretisation for α ∈ (0, 1), and L2 discretisation and L2C discretisation for α ∈ (1, 2). The truncation error estimates and the properties of the coefficients of all these discretisations are analysed in more detail. Finally, the theoretical analyses are verified by the numerical examples.
    Standard Dual Quaternion Optimization and Its Applications in Hand-Eye Calibration and SLAM
    Liqun Qi
    2023, 5(4):  1469-1483.  doi:10.1007/s42967-022-00213-1
    Asbtract ( 80 )   PDF  
    References | Related Articles | Metrics
    Several common dual quaternion functions, such as the power function, the magnitude function, the 2-norm function, and the kth largest eigenvalue of a dual quaternion Hermitian matrix, are standard dual quaternion functions, i.e., the standard parts of their function values depend upon only the standard parts of their dual quaternion variables. Furthermore, the sum, product, minimum, maximum, and composite functions of two standard dual functions, the logarithm and the exponential of standard unit dual quaternion functions, are still standard dual quaternion functions. On the other hand, the dual quaternion optimization problem, where objective and constraint function values are dual numbers but variables are dual quaternions, naturally arises from applications. We show that to solve an equality constrained dual quaternion optimization (EQDQO) problem, we only need to solve two quaternion optimization problems. If the involved dual quaternion functions are all standard, the optimization problem is called a standard dual quaternion optimization problem, and some better results hold. Then, we show that the dual quaternion optimization problems arising from the hand-eye calibration problem and the simultaneous localization and mapping (SLAM) problem are equality constrained standard dual quaternion optimization problems.
    Norms of Dual Complex Vectors and Dual Complex Matrices
    Xin-He Miao, Zheng-Hai Huang
    2023, 5(4):  1484-1508.  doi:10.1007/s42967-022-00215-z
    Asbtract ( 81 )   PDF  
    References | Related Articles | Metrics
    In this paper, we investigate some properties of dual complex numbers, dual complex vectors, and dual complex matrices. First, based on the magnitude of the dual complex number, we study the Young inequality, the Hölder inequality, and the Minkowski inequality in the setting of dual complex numbers. Second, we define the p-norm of a dual complex vector, which is a nonnegative dual number, and show some related properties. Third, we study the properties of eigenvalues of unitary matrices and unitary triangulation of arbitrary dual complex matrices. In particular, we introduce the operator norm of dual complex matrices induced by the p-norm of dual complex vectors, and give expressions of three important operator norms of dual complex matrices.
    Separable Symmetric Tensors and Separable Anti-symmetric Tensors
    Changqing Xu, Kaijie Xu
    2023, 5(4):  1509-1523.  doi:10.1007/s42967-022-00217-x
    Asbtract ( 85 )   PDF  
    References | Related Articles | Metrics
    In this paper, we first initialize the S-product of tensors to unify the outer product, contractive product, and the inner product of tensors. Then, we introduce the separable symmetry tensors and separable anti-symmetry tensors, which are defined, respectively, as the sum and the algebraic sum of rank-one tensors generated by the tensor product of some vectors. We offer a class of tensors to achieve the upper bound for rank(A) ≤ 6 for all tensors of size 3×3×3. We also show that each 3×3×3 anti-symmetric tensor is separable.
    Inequalities for Sums and Products of Complex Zeros of Solutions to ODE with Polynomial Right Parts
    Michael Gil'
    2023, 5(4):  1524-1533.  doi:10.1007/s42967-022-00219-9
    Asbtract ( 90 )   PDF  
    References | Related Articles | Metrics
    The paper is devoted to non-homogeneous second-order differential equations with polynomial right parts and polynomial coefficients. We derive estimates for the partial sums and products of the zeros of solutions to the considered equations. These estimates give us bounds for the function counting the zeros of solutions and information about the zero-free domains.
    High-Order Method with Moving Frames to Compute the Covariant Derivatives of Vectors on General 2D Curved Surfaces
    Sehun Chun
    2023, 5(4):  1534-1563.  doi:10.1007/s42967-022-00225-x
    Asbtract ( 97 )   PDF  
    References | Related Articles | Metrics
    The covariant derivative is a generalization of differentiating vectors. The Euclidean derivative is a special case of the covariant derivative in Euclidean space. The covariant derivative gathers broad attention, particularly when computing vector derivatives on curved surfaces and volumes in various applications. Covariant derivatives have been computed using the metric tensor from the analytically known curved axes. However, deriving the global axis for the domain has been mathematically and computationally challenging for an arbitrary two-dimensional (2D) surface. Consequently, computing the covariant derivative has been difficult or even impossible. A novel high-order numerical scheme is proposed for computing the covariant derivative on any 2D curved surface. A set of orthonormal vectors, known as moving frames, expand vectors to compute accurately covariant derivatives on 2D curved surfaces. The proposed scheme does not require the construction of curved axes for the metric tensor or the Christoffel symbols. The connectivity given by the Christoffel symbols is equivalently provided by the attitude matrix of orthonormal moving frames. Consequently, the proposed scheme can be extended to the general 2D curved surface. As an application, the Helmholtz-Hodge decomposition is considered for a realistic atrium and a bunny.
    An Efficient Randomized Fixed-Precision Algorithm for Tensor Singular Value Decomposition
    Salman Ahmadi-Asl
    2023, 5(4):  1564-1583.  doi:10.1007/s42967-022-00218-w
    Asbtract ( 95 )   PDF  
    References | Related Articles | Metrics
    The existing randomized algorithms need an initial estimation of the tubal rank to compute a tensor singular value decomposition. This paper proposes a new randomized fixed-precision algorithm which for a given third-order tensor and a prescribed approximation error bound, it automatically finds the tubal rank and corresponding low tubal rank approximation. The algorithm is based on the random projection technique and equipped with the power iteration method for achieving better accuracy. We conduct simulations on synthetic and real-world datasets to show the efficiency and performance of the proposed algorithm.
    Existence of Two Limit Cycles in Zeeman’s Class 30 for 3D Lotka-Volterra Competitive System
    Yaoqi Li
    2023, 5(4):  1584-1590.  doi:10.1007/s42967-022-00220-2
    Asbtract ( 87 )   PDF  
    References | Related Articles | Metrics
    Gyllenberg and Yan (Discrete Contin Dyn Syst Ser B 11(2): 347–352, 2009) presented a system in Zeeman’s class 30 of 3-dimensional Lotka-Volterra (3D LV) competitive systems to admit at least two limit cycles, one of which is generated by the Hopf bifurcation and the other is obtained by the Poincaré-Bendixson theorem. Yu et al. (J Math Anal Appl 436: 521–555, 2016, Sect. 3.4) recalculated the first Liapunov coefficient of Gyllenberg and Yan’s system to be positive, rather than negative as in Gyllenberg and Yan (2009), and pointed out that the Poincaré-Bendixson theorem is not applicable for that system. Jiang et al. (J Differ Equ 284: 183–218, 2021, p. 213) proposed an open question: “whether Zeeman’s class 30 can be rigorously proved to admit at least two limit cycles by the Hopf theorem and the Poincaré-Bendixson theorem?” This paper provides four systems in Zeeman’s class 30 to admit at least two limit cycles by the Hopf theorem and the Poincaré-Bendixson theorem and gives an answer to the above question.
    Efficient Finite Difference/Spectral Method for the Time Fractional Ito Equation Using Fast Fourier Transform Technic
    Dakang Cen, Zhibo Wang, Seakweng Vong
    2023, 5(4):  1591-1600.  doi:10.1007/s42967-022-00223-z
    Asbtract ( 80 )   PDF  
    References | Related Articles | Metrics
    A finite difference/spectral scheme is proposed for the time fractional Ito equation. The mass conservation and stability of the numerical solution are deduced by the energy method in the L2 norm form. To reduce the computation costs, the fast Fourier transform technic is applied to a pair of equivalent coupled differential equations. The effectiveness of the proposed algorithm is verified by the first numerical example. The mass conservation property and stability statement are confirmed by two other numerical examples.
    Two-Parameter Block Triangular Splitting Preconditioner for Block Two-by-Two Linear Systems
    Bo Wu, Xingbao Gao
    2023, 5(4):  1601-1615.  doi:10.1007/s42967-022-00222-0
    Asbtract ( 80 )   PDF  
    References | Related Articles | Metrics
    This paper proposes a two-parameter block triangular splitting (TPTS) preconditioner for the general block two-by-two linear systems. The eigenvalues of the corresponding preconditioned matrix are proved to cluster around 0 or 1 under mild conditions. The limited numerical results show that the TPTS preconditioner is more efficient than the classic block-diagonal and block-triangular preconditioners when applied to the flexible generalized minimal residual (FGMRES) method.
    On High-Resolution Entropy-Consistent Flux with Slope Limiter for Hyperbolic Conservation Laws
    Xuan Ren, Jianhu Feng, Supei Zheng, Xiaohan Cheng, Yang Li
    2023, 5(4):  1616-1643.  doi:10.1007/s42967-022-00232-y
    Asbtract ( 84 )   PDF  
    References | Related Articles | Metrics
    This paper proposes a new version of the high-resolution entropy-consistent (EC-Limited) flux for hyperbolic conservation laws based on a new minmod-type slope limiter. Firstly, we identify the numerical entropy production, a third-order differential term deduced from the previous work of Ismail and Roe [11]. The corresponding dissipation term is added to the original Roe flux to achieve entropy consistency. The new, resultant entropy-consistent (EC) flux has a general and explicit analytical form without any corrective factor, making it easy to compute and a less-expensive method. The inequality constraints are imposed on the standard piece-wise quadratic reconstruction to enforce the pointwise values of bounded-type numerical solutions. We design the new minmod slope limiter as combining two separate limiters for left and right states. We propose the EC-Limited flux by adding this reconstruction data method to the primitive variables rather than to the conservative variables of the EC flux to preserve the equilibrium of the primitive variables. These resulting fluxes are easily applied to general hyperbolic conservation laws while having attractive features: entropy-stable, robust, and non-oscillatory. To illustrate the potential of these proposed fluxes, we show the applications to the Burgers equation and the Euler equations.
    On Fixed-Parameter Solvability of the Minimax Path Location Problem
    Hao Lin, Cheng He
    2023, 5(4):  1644-1654.  doi:10.1007/s42967-022-00238-6
    Asbtract ( 89 )   PDF  
    References | Related Articles | Metrics
    The minimax path location problem is to find a path P in a graph G such that the maximum distance dG(v, P) from every vertex vV(G) to the path P is minimized. It is a well-known NP-hard problem in network optimization. This paper studies the fixed-parameter solvability, that is, for a given graph G and an integer k, to decide whether there exists a path P in G such that $\mathop {\max }\limits_{v \in V(G)} {d_G}(v,P) \le k$. If the answer is affirmative, then graph G is called k-patheccentric. We show that this decision problem is NP-complete even for k = 1. On the other hand, we characterize the family of 1-path-eccentric graphs, including the traceable, interval, split, permutation graphs and others. Furthermore, some polynomially solvable special graphs are discussed.
    On the Fractional Derivatives with an Exponential Kernel
    Enyu Fan, Jingshu Wu, Shaoying Zeng
    2023, 5(4):  1655-1673.  doi:10.1007/s42967-022-00233-x
    Asbtract ( 102 )   PDF  
    References | Related Articles | Metrics
    The present article mainly focuses on the fractional derivatives with an exponential kernel (“exponential fractional derivatives” for brevity). First, several extended integral transforms of the exponential fractional derivatives are proposed, including the Fourier transform and the Laplace transform. Then, the L2 discretisation for the exponential Caputo derivative with α ∈ (1, 2) is established. The estimation of the truncation error and the properties of the coefficients are discussed. In addition, a numerical example is given to verify the correctness of the derived L2 discrete formula.
    Finite Difference Schemes for Time-Space Fractional Diffusion Equations in One- and Two-Dimensions
    Yu Wang, Min Cai
    2023, 5(4):  1674-1696.  doi:10.1007/s42967-022-00244-8
    Asbtract ( 99 )   PDF  
    References | Related Articles | Metrics
    In this paper, finite difference schemes for solving time-space fractional diffusion equations in one dimension and two dimensions are proposed. The temporal derivative is in the Caputo-Hadamard sense for both cases. The spatial derivative for the one-dimensional equation is of Riesz definition and the two-dimensional spatial derivative is given by the fractional Laplacian. The schemes are proved to be unconditionally stable and convergent. The numerical results are in line with the theoretical analysis.
    Robust Falk-Neilan Finite Elements for the Reissner-Mindlin Plate
    Shangyou Zhang
    2023, 5(4):  1697-1712.  doi:10.1007/s42967-023-00266-w
    Asbtract ( 104 )   PDF  
    References | Related Articles | Metrics
    The family of Falk-Neilan Pk finite elements, combined with the Argyris Pk+1 finite elements, solves the Reissner-Mindlin plate equation quasi-optimally and locking-free, on triangular meshes. The method is truly conforming or consistent in the sense that no projection/reduction is introduced. Theoretical proof and numerical confirmation are presented.