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A Three-Dimensional Model of Skeletal Muscle Tissues 骨骼肌组织的三维模型
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-05-07 DOI: 10.1137/22m1506985
Javier A. Almonacid, Sebastián A. Domínguez-Rivera, Ryan N. Konno, Nilima Nigam, Stephanie A. Ross, Cassidy Tam, James M. Wakeling
SIAM Journal on Applied Mathematics, Ahead of Print.
Abstract. Skeletal muscles are living tissues that can undergo large deformations in short periods of time and that can be activated to produce force. In this paper we use the principles of continuum mechanics to propose a dynamic, fully nonlinear, and three-dimensional model to describe the deformation of these tissues. We model muscles as a fiber-reinforced composite and transversely isotropic material. We introduce a flexible computational framework to approximate the deformations of skeletal muscle to provide new insights into the underlying mechanics of these tissues. The model parameters and mechanical properties are obtained through experimental data and can be specified locally. A semi-implicit in-time, conforming, finite element in space scheme is used to approximate the solutions to the governing nonlinear dynamic model. We provide a series of numerical experiments demonstrating the application of this framework to relevant problems in biomechanics and also discuss questions around model validation.
SIAM 应用数学期刊》,提前印刷。 摘要骨骼肌是一种活的组织,可在短时间内发生巨大变形,并可被激活以产生力。在本文中,我们利用连续介质力学原理提出了一种动态、完全非线性的三维模型来描述这些组织的变形。我们将肌肉建模为纤维增强复合材料和横向各向同性材料。我们引入了一个灵活的计算框架来逼近骨骼肌的变形,从而为这些组织的基本力学提供新的见解。模型参数和力学性能是通过实验数据获得的,并可在本地指定。采用半隐式时间、符合、空间有限元方案来近似求解非线性动态模型。我们提供了一系列数值实验,展示了这一框架在生物力学相关问题中的应用,并讨论了围绕模型验证的问题。
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引用次数: 0
Analysis and Simulation of a Nonlocal Gray–Scott Model 非局部格雷-斯科特模型的分析与模拟
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-05-06 DOI: 10.1137/22m1542441
Loic Cappanera, Gabriela Jaramillo, Cory Ward
SIAM Journal on Applied Mathematics, Volume 84, Issue 3, Page 856-889, June 2024.
Abstract. The Gray–Scott model is a set of reaction-diffusion equations that describes chemical systems far from equilibrium. Interest in this model stems from its ability to generate spatio-temporal structures, including pulses, spots, stripes, and self-replicating patterns. We consider an extension of this model in which the spread of the different chemicals is assumed to be nonlocal and can thus be represented by an integral operator. In particular, we focus on the case of strictly positive, symmetric, [math] convolution kernels that have a finite second moment. Modeling the equations on a finite interval, we prove the existence of small-time weak solutions in the case of nonlocal Dirichlet and Neumann boundary constraints. We then use this result to develop a finite element numerical scheme that helps us explore the effects of nonlocal diffusion on the formation of pulse solutions.
SIAM 应用数学杂志》第 84 卷第 3 期第 856-889 页,2024 年 6 月。摘要格雷-斯科特模型是一组描述远离平衡的化学系统的反应-扩散方程。人们之所以对该模型感兴趣,是因为它能够产生时空结构,包括脉冲、斑点、条纹和自我复制模式。我们考虑对这一模型进行扩展,假定不同化学物质的扩散是非局部的,因此可以用积分算子来表示。我们尤其关注具有有限第二矩的严格正对称[数学]卷积核的情况。将方程建模在有限区间上,我们证明了在非局部 Dirichlet 和 Neumann 边界约束的情况下,小时间弱解的存在性。然后,我们利用这一结果开发了一种有限元数值方案,帮助我们探索非局部扩散对脉冲解形成的影响。
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引用次数: 0
Phase Transition in a Periodic Tubular Structure 周期管状结构中的相变
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-05-06 DOI: 10.1137/23m157274x
Alexander V. Kiselev, Kirill Ryadovkin
SIAM Journal on Applied Mathematics, Volume 84, Issue 3, Page 890-914, June 2024.
Abstract. We consider an [math]-periodic ([math]) tubular structure, modeled as a magnetic Laplacian on a metric graph, which is periodic along a single axis. We show that the corresponding Hamiltonian admits norm-resolvent convergence to an ODE on [math] which is fourth order at a discrete set of values of the magnetic potential (critical points) and second order generically. In a vicinity of critical points we establish a mixed-order asymptotics. The rate of convergence is also estimated. This represents a physically viable model of a phase transition as the strength of the (constant) magnetic field increases.
SIAM 应用数学杂志》第 84 卷第 3 期第 890-914 页,2024 年 6 月。 摘要。我们考虑了一个[math]-周期([math])管状结构,它被建模为一个度量图上的磁拉普拉奇,它沿单轴是周期性的。我们证明,相应的哈密顿方程可以收敛到[math]上的一个 ODE 的规范残差,在磁势的一组离散值(临界点)上是四阶的,而在一般情况下是二阶的。在临界点附近,我们建立了混合阶渐近线。我们还估算了收敛速率。这代表了一个随着(恒定)磁场强度增加而发生相变的物理可行模型。
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引用次数: 0
Early-Warning Inverse Source Problem for the Elasto-Gravitational Equations 弹性引力方程的预警反源问题
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-05-03 DOI: 10.1137/23m1564651
L. Baldassari, M. V. de Hoop, E. Francini, S. Vessella
SIAM Journal on Applied Mathematics, Volume 84, Issue 3, Page 831-855, June 2024.
Abstract. Through coupled physics, we study an early-warning inverse source problem for the constant-coefficient elasto-gravitational equations. It consists of a mixed hyperbolic-elliptic system of partial differential equations describing elastic wave displacement and gravity perturbations produced by a source in a homogeneous bounded medium. Within the Cowling approximation, we prove uniqueness and Lipschitz stability for the inverse problem of recovering the moment tensor and the location of the source from early-time measurements of the changes of the gravitational field. The setup studied in this paper is motivated by gravity-based earthquake early warning systems, which are gaining much attention recently.
SIAM 应用数学杂志》第 84 卷第 3 期第 831-855 页,2024 年 6 月。 摘要。通过耦合物理,我们研究了恒系数弹性重力方程的预警反源问题。它由双曲-椭圆混合偏微分方程系统组成,描述了同质有界介质中的源产生的弹性波位移和重力扰动。在考林近似中,我们证明了从引力场变化的早期时间测量中恢复力矩张量和声源位置的逆问题的唯一性和 Lipschitz 稳定性。本文所研究的设置是基于重力的地震预警系统所激发的,该系统近来备受关注。
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引用次数: 0
On Long Waves and Solitons in Particle Lattices with Forces of Infinite Range 论具有无限范围力的粒子晶格中的长波和孤子
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-05-03 DOI: 10.1137/23m1607209
Benjamin Ingimarson, Robert L. Pego
SIAM Journal on Applied Mathematics, Volume 84, Issue 3, Page 808-830, June 2024.
Abstract. We study waves on infinite one-dimensional lattices of particles that each interact with all others through power-law forces [math]. The inverse-cube case corresponds to Calogero–Moser systems which are well known to be completely integrable for any finite number of particles. The formal long-wave limit for unidirectional waves in these lattices is the Korteweg–de Vries equation if [math], but with [math] it is a nonlocal dispersive PDE that reduces to the Benjamin–Ono equation for [math]. For the infinite Calogero–Moser lattice, we find explicit formulas that describe solitary and periodic traveling waves.
SIAM 应用数学杂志》第 84 卷第 3 期第 808-830 页,2024 年 6 月。 摘要。我们研究由粒子组成的无限一维晶格上的波,每个粒子都通过幂律力与其他粒子相互作用[数学]。反立方情况对应于 Calogero-Moser 系统,众所周知,该系统对于任何有限数量的粒子都是完全可积分的。这些晶格中单向波的形式长波极限是[math]的 Korteweg-de Vries 方程,但在[math]的情况下,它是一个非局部色散 PDE,可以简化为[math]的 Benjamin-Ono 方程。对于无限卡洛吉罗-莫泽晶格,我们找到了描述孤行波和周期行波的明确公式。
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引用次数: 0
Stoichiometry-Dependent Fear Effect in a Food Chain Model 食物链模型中依赖化学计量的恐惧效应
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-05-02 DOI: 10.1137/23m1581613
Tianxu Wang, Hao Wang
SIAM Journal on Applied Mathematics, Volume 84, Issue 3, Page 783-807, June 2024.
Abstract. Evidence shows that resource quality can determine the costs and benefits of the fear effect on consumer dynamics. However, mechanistic modeling and analysis are lacking. This paper formulates a tritrophic level food chain model that integrates both stoichiometric food quality and fear effect. We establish the well-posedness of the model and examine the existence and stability of equilibria. Through extensive numerical simulations, we validate our findings and visually explore the interactive effects of fear and food quality. Our results reveal that the fear effect from predators stabilizes the system. Furthermore, we demonstrate that the fear effect amplifies the influence of food quality on consumers. When food quality is favorable, the fear effect enhances consumer production efficiency, whereas, in the case of poor food quality, the fear effect exacerbates the decline in production efficiency caused by low-nutrient food.
SIAM 应用数学杂志》第 84 卷第 3 期第 783-807 页,2024 年 6 月。摘要有证据表明,资源质量可以决定消费者动态恐惧效应的成本和收益。然而,目前还缺乏机理模型和分析。本文建立了一个三营养级食物链模型,该模型综合了食物质量和恐惧效应。我们建立了该模型的良好假设性,并检验了平衡的存在性和稳定性。通过大量的数值模拟,我们验证了我们的发现,并直观地探讨了恐惧和食物质量的交互效应。我们的结果表明,捕食者的恐惧效应使系统趋于稳定。此外,我们还证明了恐惧效应会放大食物质量对消费者的影响。当食物质量较好时,恐惧效应会提高消费者的生产效率,而当食物质量较差时,恐惧效应会加剧低营养食物导致的生产效率下降。
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引用次数: 0
Multistability for Nematic Liquid Crystals in Cuboids with Degenerate Planar Boundary Conditions 具有退化平面边界条件的立方体中向列液晶的多稳定性
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-04-26 DOI: 10.1137/23m1604606
Baoming Shi, Yucen Han, Apala Majumdar, Lei Zhang
SIAM Journal on Applied Mathematics, Volume 84, Issue 2, Page 756-781, April 2024.
Abstract. We study nematic configurations within three-dimensional (3D) cuboids, with planar degenerate boundary conditions on the cuboid faces, in the Landau–de Gennes framework. There are two geometry-dependent variables: the edge length of the square cross-section, [math], and the parameter [math], which is a measure of the cuboid height. Theoretically, we prove the existence and uniqueness of the global minimizer with a small enough cuboid size. We develop a new numerical scheme for the high-index saddle dynamics to deal with the surface energies. We report on a plethora of (meta)stable states, and their dependence on [math] and [math], and in particular how the 3D states are connected with their two-dimensional counterparts on squares and rectangles. Notably, we find families of almost uniaxial stable states constructed from the topological classification of tangent unit-vector fields and study transition pathways between them. We also provide a phase diagram of competing (meta)stable states as a function of [math] and [math].
SIAM 应用数学杂志》第 84 卷第 2 期第 756-781 页,2024 年 4 月。 摘要。我们在 Landau-de Gennes 框架内研究了三维(3D)立方体内的向列构型,立方体面上有平面退化边界条件。有两个与几何相关的变量:正方形横截面的边长 [math] 和参数 [math],后者是长方体高度的度量。从理论上讲,我们证明了在足够小的长方体尺寸下全局最小化的存在性和唯一性。我们为高指数鞍动力学开发了一种新的数值方案来处理表面能。我们报告了大量(元)稳定态,以及它们与[math]和[math]的关系,特别是三维态与正方形和长方形上的二维对应态之间的联系。值得注意的是,我们从切线单位矢量场的拓扑分类中发现了几乎单轴的稳定态族,并研究了它们之间的过渡路径。我们还提供了竞争(元)稳定态的相图,它是 [math] 和 [math] 的函数。
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引用次数: 0
Multiplicity of Endemic Equilibria for a Diffusive SIS Epidemic Model with Mass-Action 具有大规模行动的扩散性 SIS 流行病模型的地方性均衡的多重性
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-04-16 DOI: 10.1137/23m1613888
Keoni Castellano, Rachidi B. Salako
SIAM Journal on Applied Mathematics, Volume 84, Issue 2, Page 732-755, April 2024.
Abstract. We study a diffusive Susceptible-Infected-Susceptible (SIS) epidemic model with the mass-action transmission mechanism and show, under appropriate assumptions on the parameters, the existence of multiple endemic equilibria (EE). Our results answer some open questions on previous studies related to disease extinction or persistence when [math] and the multiplicity of EE solutions when [math]. Interestingly, even with such a simple nonlinearity induced by the mass-action, we show that the diffusive epidemic model may have an S-shaped or backward bifurcation curve of EE solutions. This strongly highlights the impacts of environmental heterogeneity on the spread of infectious diseases as the basic reproduction number alone is insufficient as a threshold quantity to predict its extinction. Our results also shed some light on the significance of disease transmission mechanisms.
SIAM 应用数学杂志》第 84 卷第 2 期第 732-755 页,2024 年 4 月。 摘要。我们研究了一个具有大规模作用传播机制的扩散性易感-感染-易感(SIS)流行病模型,并证明在适当的参数假设下,存在多个流行病均衡(EE)。我们的结果回答了以往研究中的一些公开问题,这些问题涉及当[math]时疾病的灭绝或持续以及当[math]时 EE 解的多重性。有趣的是,即使由质量作用引起的非线性如此简单,我们仍然发现扩散流行病模型的 EE 解可能呈 S 形或向后分叉曲线。这有力地凸显了环境异质性对传染病传播的影响,因为仅凭基本繁殖数量不足以作为预测其灭绝的临界量。我们的研究结果还揭示了疾病传播机制的重要性。
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引用次数: 0
Moving Singularities of the Forced Fisher–KPP Equation: An Asymptotic Approach 强迫费希尔-KPP方程的移动奇点:渐近方法
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-04-15 DOI: 10.1137/23m1552905
Markus Kaczvinszki, Stefan Braun
SIAM Journal on Applied Mathematics, Volume 84, Issue 2, Page 710-731, April 2024.
Abstract. The creation of hairpin or lambda vortices, typical for the early stages of the laminar-turbulent transition process in various boundary layer flows, in some sense may be associated with blow-up solutions of the Fisher–Kolmogorov–Petrovsky–Piskunov equation. In contrast to the usual applications of this nonlinear evolution equation of the reaction-diffusion type, the solution quantity in the present context needs to stay neither bounded nor positive. We focus on the solution behavior beyond a finite-time point blow-up event, which consists of two moving singularities (representing the cores of the vortex legs) propagating in opposite directions, and their initial motion is determined with the method of matched asymptotic expansions. After resolving subtleties concerning the transition between logarithmic and algebraic expansion terms regarding asymptotic layers, we find that the internal singularity structure resembles a combination of second- and first-order poles in the form of a singular traveling wave with a time-dependent speed imprinted through the characteristics of the preceding blow-up event.
SIAM 应用数学杂志》第 84 卷第 2 期第 710-731 页,2024 年 4 月。 摘要发夹涡或λ涡的产生是各种边界层流动中层流-湍流过渡过程早期阶段的典型现象,在某种意义上可能与 Fisher-Kolmogorov-Petrovsky-Piskunov 方程的炸裂解有关。与这种反应扩散型非线性演化方程的通常应用不同,本课题中的解量既不需要保持有界,也不需要保持正值。我们的重点是有限时间点炸裂事件之后的解行为,它由两个向相反方向传播的移动奇点(代表涡旋腿的核心)组成,它们的初始运动通过匹配渐近展开法确定。在解决了有关渐近层的对数和代数展开项之间过渡的微妙问题后,我们发现内部奇点结构类似于二阶极点和一阶极点的组合,其形式为奇点行波,其速度随时间变化,并通过前一个炸毁事件的特征留下了印记。
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引用次数: 0
Stability for Inverse Source Problems of the Stochastic Helmholtz Equation with a White Noise 带有白噪声的随机亥姆霍兹方程反源问题的稳定性
IF 1.9 4区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2024-04-11 DOI: 10.1137/23m1586331
Peijun Li, Ying Liang
SIAM Journal on Applied Mathematics, Volume 84, Issue 2, Page 687-709, April 2024.
Abstract. This paper is concerned with the stability estimates for inverse source problems of the stochastic Helmholtz equation driven by white noise. The well-posedness is established for the direct source problems, which ensures the existence and uniqueness of solutions. The stability estimates are deduced for the inverse source problems, which aim to determine the strength of the random source. To enhance the stability of the inverse source problems, we incorporate a priori information regarding the regularity and support of the strength. In the case of homogeneous media, a Hölder stability estimate is established, providing a quantitative measure of the stability for reconstructing the source strength. For the more challenging scenario of inhomogeneous media, a logarithmic stability estimate is presented, capturing the intricate interactions between the source and the varying medium properties.
SIAM 应用数学杂志》第 84 卷第 2 期第 687-709 页,2024 年 4 月。 摘要本文主要研究白噪声驱动的随机亥姆霍兹方程反源问题的稳定性估计。针对直接源问题建立了良好拟合,从而确保了解的存在性和唯一性。推导出了逆源问题的稳定性估计,其目的是确定随机源的强度。为了增强反源问题的稳定性,我们纳入了有关强度的规则性和支持性的先验信息。在均质介质的情况下,我们建立了霍尔德稳定性估计,为重建源强度提供了稳定性的量化指标。对于非均质介质这种更具挑战性的情况,则提出了对数稳定性估计,以捕捉源和不同介质特性之间错综复杂的相互作用。
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引用次数: 0
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SIAM Journal on Applied Mathematics
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