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Unified asymptotic analysis and numerical simulations of singularly perturbed linear differential equations under various nonlocal boundary effects 各种非局部边界效应下奇异扰动线性微分方程的统一渐近分析和数值模拟
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2024-02-01 DOI: 10.4310/cms.2024.v22.n2.a5
Xianjin Chen, Chiun-Chang Lee, Masashi Mizuno
While being concerned with a singularly perturbed linear differential equation subject to integral boundary conditions, the exact solutions, in general, cannot be specified, and the validity of the maximum principle is unassurable. Hence, a problem arises: how to identify the boundary asymptotics more precisely? We develop a rigorous asymptotic method involving recovered boundary data to tackle the problem. A key ingredient of the approach is to transform the “nonlocal” boundary conditions into “local” boundary conditions. Then, we perform an “$varepsilon log varepsilon$-estimate” to obtain the refined boundary asymptotics of its solutions with respect to the singular perturbation parameter $varepsilon$. Furthermore, for the inhomogeneous case, diversified asymptotic behaviors including uniform boundedness and asymptotic blow-up are obtained. Numerical simulations and validations are also presented to further support the corresponding theoretical results.
虽然关注的是受积分边界条件限制的奇异扰动线性微分方程,但一般来说,无法指定精确解,最大原则的有效性也无法保证。因此,问题来了:如何更精确地确定边界渐近线?我们开发了一种涉及恢复边界数据的严格渐近方法来解决这个问题。该方法的一个关键要素是将 "非局部 "边界条件转化为 "局部 "边界条件。然后,我们进行"$varepsilon log varepsilon$-估计",以获得其解相对于奇异扰动参数 $varepsilon$ 的精细边界渐近线。此外,对于非均质情况,还得到了包括均匀有界性和渐近炸裂在内的多样化渐近行为。同时还给出了数值模拟和验证,以进一步支持相应的理论结果。
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引用次数: 0
Lifespan estimates of solutions to the weakly coupled system of semilinear wave equations with space dependent dampings 具有空间相关阻尼的半线性波方程弱耦合系统解的寿命估计
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2024-02-01 DOI: 10.4310/cms.2024.v22.n2.a4
Sen Ming, Han Yang, Xiongmei Fan
$def lv{lvert}defrv{rvert}$ This paper is devoted to investigating the weakly coupled system of semilinear wave equations with space dependent dampings and power nonlinearities ${lv v rv}^p, {lv u rv}^q$, derivative nonlinearities ${lv v_t rv}^p, {lv u_t rv}^q$, mixed nonlinearities ${lv v rv}^q, {lv u_t rv}^p$, combined nonlinearities ${lv v_t rv}^{p_1} + {lv v rv}^{q_1}, {lv u_t rv}^{p_2} + {lv u rv}^{q_2}$, combined and power nonlinearities ${lv v_t rv}^{p_1} + {lv v rv}^{q_1}, {lv u rv}^{q_2}$, combined and derivative nonlinearities ${lv v_t rv}^{p_1} + {lv v rv}^{q_1}, {lv u_t rv}^{p_2}$, respectively. Formation of singularities and lifespan estimates of solutions to the problem in the sub-critical and critical cases are illustrated by making use of test function technique. The main innovation is that upper bound lifespan estimates of solutions are associated with the Strauss exponent and Glassey exponent.
$def lv{lvert}defrv{rvert}$ 本文致力于研究半线性波方程的弱耦合系统,该系统具有空间相关阻尼和功率非线性特性 ${lv v rv}^p、{导数非线性 ${lv v_t rv}^p,{lv u_t rv}^q$,混合非线性 ${lv v rv}^q,{lv u_t rv}^p$,组合非线性 ${lv v_t rv}^{p_1}。+ {lv v rv}^{q_1}, {lv u_t rv}^{p_2}+ {lv u rv}^{q_2}$,组合非线性和功率非线性 ${lv v_t rv}^{p_1}。+ {lv v rv}^{q_1},{lv u rv}^{q_2}$,组合和导数非线性 ${lv v_t rv}^{p_1}。+ {lv v rv}^{q_1},{lv u_t rv}^{p_2}$。利用检验函数技术说明了在次临界和临界情况下问题解的奇点形成和寿命估计。主要创新之处在于解的上限寿命估计值与 Strauss 指数和 Glassey 指数相关联。
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引用次数: 0
Stability and decay rate of viscous contact wave to one-dimensional compressible Navier-Stokes equations 粘性接触波对一维可压缩纳维-斯托克斯方程的稳定性和衰减率
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2024-02-01 DOI: 10.4310/cms.2024.v22.n2.a2
Xinxiang Bian, Lingling Xie
This paper studies the large-time asymptotic stability and optimal time-decay rate of viscous contact wave to one-dimensional compressible Navier–Stokes equations. We prove that one-dimensional compressible Navier–Stokes equations are asymptotically stable for viscous contact wave with arbitrarily large strength, under large initial perturbations. The time optimal decay rate of viscous contact wave is also obtained under the small initial perturbations. In the proof, the Lagrange transform is used to cancel the convection terms, which are difficult to estimate due to the lower spatial derivatives compared with the diffusion terms.
本文研究了粘性接触波对一维可压缩纳维-斯托克斯方程的大时间渐近稳定性和最佳时间衰减率。我们证明,在大的初始扰动下,一维可压缩 Navier-Stokes 方程对于任意大强度的粘性接触波是渐近稳定的。在小的初始扰动下,还得到了粘性接触波的时间最优衰减率。在证明过程中,使用了拉格朗日变换来消除对流项,与扩散项相比,对流项的空间导数较低,难以估计。
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引用次数: 0
Global existence of perturbed Navier–Stokes system around Landau solutions with slowly decaying oscillation 具有缓慢衰减振荡的朗道解周围扰动纳维-斯托克斯系统的全局存在性
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2024-02-01 DOI: 10.4310/cms.2024.v22.n2.a10
Jiayan Wu, Cuili Zhai, Jingjing Zhang, Ting Zhang
In this paper, we consider the perturbed Navier–Stokes system around the Landau solutions. Using the energy method and the continuation method, we show the global existence of the $L^2$ local energy solution for the perturbed Navier–Stokes system with the oscillation decay initial data $v_0 in E^2_{sigma} + L^3_{operatorname{uloc}} ,$.
本文考虑了围绕朗道解的扰动纳维-斯托克斯系统。利用能量法和延续法,我们证明了具有振荡衰减初始数据 $v_0 in E^2_{sigma} + L^3_{operatorname{uloc}} 的扰动纳维-斯托克斯系统的 $L^2$ 局域能量解的全局存在性。,$.
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引用次数: 0
A stochastic Galerkin method for the direct and inverse random source problems of the Helmholtz equation 亥姆霍兹方程直接和反向随机源问题的随机伽勒金方法
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2024-02-01 DOI: 10.4310/cms.2024.v22.n2.a11
Ning Guan, Dingyu Chen, Peijun Li, Xinghui Zhong
This paper investigates a novel approach for solving both the direct and inverse random source problems of the one-dimensional Helmholtz equation with additive white noise, based on the generalized polynomial chaos (gPC) approximation. The direct problem is to determine the wave field that is emitted from a random source, while the inverse problem is to use the boundary measurements of the wave field at various frequencies to reconstruct the mean and variance of the source. The stochastic Helmholtz equation is reformulated in such a way that the random source is represented by a collection of mutually independent random variables. The stochastic Galerkin method is employed to transform the model equation into a two-point boundary value problem for the gPC expansion coefficients. The explicit connection between the sine or cosine transform of the mean and variance of the random source and the analytical solutions for the gPC coefficients is established. The advantage of these analytical solutions is that the gPC coefficients are zero for basis polynomials of degree higher than one, which implies that the total number of the gPC basis functions increases proportionally to the dimension, and indicates that the stochastic Galerkin method has the potential to be used in practical applications involving random variables of higher dimensions. By taking the inverse sine or cosine transform of the data, the inverse problem can be solved, and the statistical information of the random source such as the mean and variance can be obtained straightforwardly as the gPC basis functions are orthogonal. Numerical experiments are conducted to demonstrate the efficiency of the proposed method.
本文研究了一种基于广义多项式混沌(gPC)近似的新方法,用于解决带有加性白噪声的一维亥姆霍兹方程的直接和逆随机源问题。直接问题是确定随机源发出的波场,而逆问题则是利用不同频率波场的边界测量值来重建源的均值和方差。随机亥姆霍兹方程的重新表述方式是用一组相互独立的随机变量来表示随机源。采用随机伽勒金方法将模型方程转化为 gPC 扩展系数的两点边界值问题。随机源的均值和方差的正弦或余弦变换与 gPC 系数的解析解之间建立了明确的联系。这些解析解的优势在于,对于阶数大于 1 的基多项式,gPC 系数为零,这意味着 gPC 基函数的总数与维数成正比增加,表明随机伽勒金方法有可能用于涉及更高维度随机变量的实际应用。通过对数据进行正弦或余弦逆变换,可以求解逆问题,由于 gPC 基函数是正交的,因此可以直接获得随机源的统计信息,如均值和方差。通过数值实验证明了所提方法的高效性。
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引用次数: 0
Description of random level sets by polynomial chaos expansions 用多项式混沌展开描述随机水平集
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2023-12-07 DOI: 10.4310/cms.2024.v22.n1.a4
Markus Bambach, Stephan Gerster, Michael Herty, Aleksey Sikstel
We present a novel approach to determine the evolution of level sets under uncertainties in their velocity fields. This leads to a stochastic description of level sets. To compute the quantiles of random level sets, we use the stochastic Galerkin method for a hyperbolic reformulation of the equations for the propagation of level sets. A novel intrusive Galerkin formulation is presented and proven to be hyperbolic. It induces a corresponding finite-volume scheme that is specifically tailored to uncertain velocities.
我们提出了一种新方法来确定水平集在其速度场不确定的情况下的演变。这导致了对水平集的随机描述。为了计算随机水平集的量值,我们使用随机伽勒金方法对水平集传播方程进行双曲重述。我们提出了一种新颖的侵入式 Galerkin 公式,并证明它是双曲的。该方法可产生专门针对不确定速度的相应有限体积方案。
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引用次数: 1
A new priori error estimation of nonconforming element for two-dimensional linearly elastic shallow shell equations 二维线性弹性浅壳方程中不符元素的新先验误差估计
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2023-12-07 DOI: 10.4310/cms.2024.v22.n1.a7
Rongfang Wu, Xiaoqin Shen, Qian Yang, Shengfeng Zhu
In this paper, we mainly propose a new priori error estimation for the two-dimensional linearly elastic shallow shell equations, which rely on a family of Kirchhoff–Love theories. As the displacement components of the points on the middle surface have different regularities, the nonconforming element for the discretization shallow shell equations is analysed. Then, relying on the enriching operator, a new error estimate of energy norm is given under the regularity assumption $vec{zeta}_H times zeta_3 in (H^{1+m} (omega))^2 times H^{2+m} (omega)$ with any $m gt 0$. Compared with the classic error analysis in other shell literature, convergence order of numerical solution can be controlled by its corresponding approximation error with an arbitrarily high order term, which fills the gap in the computational shell theory. Finally, numerical results for the saddle shell and cylindrical shell confirm the theoretical prediction.
本文主要针对二维线性弹性浅壳方程提出了一种新的先验误差估计方法,该方法依赖于基尔霍夫-洛夫理论族。由于中面上各点的位移分量具有不同的规律性,因此分析了离散化浅壳方程的非符合元素。然后,依靠富集算子,在任意 $m gt 0$ 的正则假设 $vec{zeta}_H times zeta_3 in (H^{1+m} (omega))^2 times H^{2+m} (omega)$ 下给出了能量规范的新误差估计。与其他壳文献中的经典误差分析相比,数值解的收敛阶数可以由其对应的近似误差以任意高阶项来控制,这填补了计算壳理论的空白。最后,鞍形壳和圆柱形壳的数值结果证实了理论预测。
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引用次数: 0
Unipolar Euler–Poisson equations with time-dependent damping: blow-up and global existence 具有随时间变化的阻尼的单极欧拉-泊松方程:爆炸和全局存在性
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2023-12-07 DOI: 10.4310/cms.2024.v22.n1.a8
Jianing Xu, Shaohua Chen, Ming Mei, Yuming Qin
This paper is concerned with the Cauchy problem for one-dimensional unipolar Euler–Poisson equations with time-dependent damping, where the time-asymptotically degenerate damping in the form of $-dfrac{mu}{(1+t)^lambda} rho mu$ for $lambda gt 0$ with $mu gt 0$ plays a crucial role for the structure of solutions. The main issue of the paper is to investigate the critical case with $lambda=1$. We first prove that, for all cases with $lambda gt 0$ and $mu gt 0$ (including the critical case of $lambda=1$), once the initial data is steep at a point, then the solutions are locally bounded but their derivatives will blow up in finite time, by means of the method of Riemann invariants and the technical convex analysis. Secondly, for the critical case of $lambda=1$ with $mu gt 7/3$, we prove that there exists a unique global solution, once the initial perturbation around the constant steady-state is sufficiently small. In particular, we derive the algebraic convergence rates of the solution to the constant steady-state, which are piecewise, related to the parameter $mu$ for $7/3 lt mu leq 3$, $3 lt mu leq 4$ and $mu gt 4$. The adopted method of proof in this critical case is the technical time-weighted energy method and the time-weight depends on the parameter $mu$. Finally, we carry out some numerical simulations in two cases for blow-up and global existence, respectively, which numerically confirm our theoretical results.
本文关注的是具有时间相关阻尼的一维单极欧拉-泊松方程的考奇问题,其中对于$lambda gt 0$的$mu gt 0$,以$-drac{mu}{(1+t)^lambda}rhomu$形式存在的时间渐近退化阻尼对解的结构起着至关重要的作用。本文的主要问题是研究 $lambda=1$ 的临界情况。我们首先通过黎曼不变式和技术凸分析的方法证明,对于$lambda gt 0$和$mu gt 0$的所有情况(包括$lambda=1$的临界情况),一旦初始数据在某一点陡峭,那么解是局部有界的,但是它们的导数会在有限时间内爆炸。其次,对于$mu gt 7/3$的$lambda=1$临界情况,我们证明一旦恒定稳态周围的初始扰动足够小,就存在唯一的全局解。特别是,我们推导出了在 $7/3 lt mu leq 3$、$3 lt mu leq 4$和 $mu gt 4$条件下,解向恒定稳态的代数收敛率,这些收敛率与参数 $mu$ 是片断相关的。在这种临界情况下采用的证明方法是技术时间加权能量法,时间加权取决于参数 $mu$。最后,我们分别对爆炸和全局存在两种情况进行了数值模拟,从数值上证实了我们的理论结果。
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引用次数: 0
A general framework for nonlocal Neumann problems 非局部 Neumann 问题的一般框架
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2023-12-07 DOI: 10.4310/cms.2024.v22.n1.a2
Guy Foghem, Moritz Kassmann
Within the framework of Hilbert spaces, we solve nonlocal problems in bounded domains with prescribed conditions on the complement of the domain. Our main focus is on the inhomogeneous Neumann problem in a rather general setting. We also study the transition from exterior value problems to local boundary value problems. Several results are new even for the fractional Laplace operator. The setting also covers relevant models in the framework of peridynamics.
在希尔伯特空间的框架内,我们解决了有界域中的非局部问题,并对域的补集规定了条件。我们的主要重点是在一个相当普遍的环境中解决非均质 Neumann 问题。我们还研究了从外部值问题到局部边界值问题的过渡。即使对于分数拉普拉斯算子,也有若干新结果。这一设置还涵盖了周动力学框架中的相关模型。
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引用次数: 20
Energy method for the Boltzmann equation of monatomic gaseous mixtures 单原子气体混合物波尔兹曼方程的能量法
IF 1 4区 数学 Q2 MATHEMATICS, APPLIED Pub Date : 2023-12-07 DOI: 10.4310/cms.2024.v22.n1.a6
Laurent Boudin, Bérénice Grec, Milana Pavić-Čolić, Srboljub Simić
In this paper, we present an energy method for the system of Boltzmann equations in the multicomponent mixture case, based on a micro-macro decomposition. More precisely, the perturbation of a solution to the Boltzmann equation around a global equilibrium is decomposed into the sum of a macroscopic and a microscopic part, for which we obtain a priori estimates at both lower and higher orders. These estimates are obtained under a suitable smallness assumption. The assumption can be justified a posteriori in the higher-order case, leading to the closure of the corresponding estimate.
在本文中,我们提出了一种基于微观-宏观分解的多组分混合物情况下波尔兹曼方程系统的能量方法。更确切地说,玻尔兹曼方程解在全局平衡点附近的扰动被分解为宏观部分和微观部分之和,对此我们获得了低阶和高阶的先验估计值。这些估计值是在一个合适的微小性假设下获得的。在高阶情况下,该假设可以后验,从而得到相应的闭合估计值。
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引用次数: 3
期刊
Communications in Mathematical Sciences
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