首页 > 最新文献

European Journal of Applied Mathematics最新文献

英文 中文
A homogenised model for the motion of evaporating fronts in porous media 多孔介质中蒸发锋运动的均匀化模型
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2023-01-23 DOI: 10.1017/s0956792522000419
E. Luckins, C. Breward, I. Griffiths, C. Please
Evaporation within porous media is both a multiscale and interface-driven process, since the phase change at the evaporating interfaces within the pores generates a vapour flow and depends on the transport of vapour through the porous medium. While homogenised models of flow and chemical transport in porous media allow multiscale processes to be modelled efficiently, it is not clear how the multiscale effects impact the interface conditions required for these homogenised models. In this paper, we derive a homogenised model, including effective interface conditions, for the motion of an evaporation front through a porous medium, using a combined homogenisation and boundary layer analysis. This analysis extends previous work for a purely diffusive problem to include both gas flow and the advective–diffusive transport of material. We investigate the effect that different microscale models describing the chemistry of the evaporation have on the homogenised interface conditions. In particular, we identify a new effective parameter, $mathcal{L}$ , the average microscale interface length, which modifies the effective evaporation rate in the homogenised model. Like the effective diffusivity and permeability of a porous medium, $mathcal{L}$ may be found by solving a periodic cell problem on the microscale. We also show that the different microscale models of the interface chemistry result in fundamentally different fine-scale behaviour at, and near, the interface.
多孔介质中的蒸发是一个多尺度和界面驱动的过程,因为孔隙中蒸发界面的相变产生了蒸汽流,并且依赖于蒸汽通过多孔介质的输送。虽然多孔介质中流动和化学输运的均质模型可以有效地模拟多尺度过程,但尚不清楚多尺度效应如何影响这些均质模型所需的界面条件。在本文中,我们推导了一个均匀化模型,包括有效的界面条件,蒸发锋通过多孔介质的运动,使用均匀化和边界层分析相结合。这一分析扩展了以前对纯扩散问题的研究,使之包括气体流动和物质的顺向扩散输运。我们研究了描述蒸发化学过程的不同微尺度模型对均质界面条件的影响。特别地,我们确定了一个新的有效参数$mathcal{L}$,即平均微尺度界面长度,它改变了均匀化模型中的有效蒸发速率。与多孔介质的有效扩散率和渗透率一样,$mathcal{L}$可以通过在微观尺度上求解周期细胞问题来求得。我们还表明,界面化学的不同微尺度模型导致界面上和界面附近的细微尺度行为根本不同。
{"title":"A homogenised model for the motion of evaporating fronts in porous media","authors":"E. Luckins, C. Breward, I. Griffiths, C. Please","doi":"10.1017/s0956792522000419","DOIUrl":"https://doi.org/10.1017/s0956792522000419","url":null,"abstract":"\u0000 Evaporation within porous media is both a multiscale and interface-driven process, since the phase change at the evaporating interfaces within the pores generates a vapour flow and depends on the transport of vapour through the porous medium. While homogenised models of flow and chemical transport in porous media allow multiscale processes to be modelled efficiently, it is not clear how the multiscale effects impact the interface conditions required for these homogenised models. In this paper, we derive a homogenised model, including effective interface conditions, for the motion of an evaporation front through a porous medium, using a combined homogenisation and boundary layer analysis. This analysis extends previous work for a purely diffusive problem to include both gas flow and the advective–diffusive transport of material. We investigate the effect that different microscale models describing the chemistry of the evaporation have on the homogenised interface conditions. In particular, we identify a new effective parameter, \u0000 \u0000 \u0000 \u0000$mathcal{L}$\u0000\u0000 \u0000 , the average microscale interface length, which modifies the effective evaporation rate in the homogenised model. Like the effective diffusivity and permeability of a porous medium, \u0000 \u0000 \u0000 \u0000$mathcal{L}$\u0000\u0000 \u0000 may be found by solving a periodic cell problem on the microscale. We also show that the different microscale models of the interface chemistry result in fundamentally different fine-scale behaviour at, and near, the interface.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47679907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Battleship, tomography and quantum annealing 战舰、层析成像和量子退火
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2023-01-16 DOI: 10.1017/s0956792522000377
W. Casper, Taylor Grimes
The classic game of Battleship involves two players taking turns attempting to guess the positions of a fleet of vertically or horizontally positioned enemy ships hidden on a $10times 10$ grid. One variant of this game, also referred to as Battleship Solitaire, Bimaru or Yubotu, considers the game with the inclusion of X-ray data, represented by knowledge of how many spots are occupied in each row and column in the enemy board. This paper considers the Battleship puzzle problem: the problem of reconstructing an enemy fleet from its X-ray data. We generate non-unique solutions to Battleship puzzles via certain reflection transformations akin to Ryser interchanges. Furthermore, we demonstrate that solutions of Battleship puzzles may be reliably obtained by searching for solutions of the associated classical binary discrete tomography problem which minimise the discrete Laplacian. We reformulate this optimisation problem as a quadratic unconstrained binary optimisation problem and approximate solutions via a simulated annealer, emphasising the future practical applicability of quantum annealers to solving discrete tomography problems with predefined structure.
在经典的《战舰》游戏中,两名玩家轮流猜测隐藏在10美元× 10美元格子中的敌方舰队的垂直或水平位置。这款游戏的一个变体,也被称为《Battleship Solitaire》、《Bimaru》或《Yubotu》,将游戏与x射线数据结合在一起,即通过了解敌人棋盘上每一行和每一列中占据了多少个位置来表示。本文研究了战列舰难题:利用x射线数据重建敌方舰队的问题。我们通过类似于Ryser交换的反射转换来生成《战舰》谜题的非唯一解决方案。此外,我们证明了通过寻找使离散拉普拉斯最小的相关经典二进制离散层析问题的解,可以可靠地获得战舰谜题的解。我们将此优化问题重新表述为二次无约束二进制优化问题,并通过模拟退火器近似解决,强调量子退火器在解决具有预定义结构的离散层析问题方面的未来实际适用性。
{"title":"Battleship, tomography and quantum annealing","authors":"W. Casper, Taylor Grimes","doi":"10.1017/s0956792522000377","DOIUrl":"https://doi.org/10.1017/s0956792522000377","url":null,"abstract":"\u0000 The classic game of Battleship involves two players taking turns attempting to guess the positions of a fleet of vertically or horizontally positioned enemy ships hidden on a \u0000 \u0000 \u0000 \u0000$10times 10$\u0000\u0000 \u0000 grid. One variant of this game, also referred to as Battleship Solitaire, Bimaru or Yubotu, considers the game with the inclusion of X-ray data, represented by knowledge of how many spots are occupied in each row and column in the enemy board. This paper considers the Battleship puzzle problem: the problem of reconstructing an enemy fleet from its X-ray data. We generate non-unique solutions to Battleship puzzles via certain reflection transformations akin to Ryser interchanges. Furthermore, we demonstrate that solutions of Battleship puzzles may be reliably obtained by searching for solutions of the associated classical binary discrete tomography problem which minimise the discrete Laplacian. We reformulate this optimisation problem as a quadratic unconstrained binary optimisation problem and approximate solutions via a simulated annealer, emphasising the future practical applicability of quantum annealers to solving discrete tomography problems with predefined structure.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2023-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43618966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Partial Euler operators and the efficient inversion of Div 偏欧拉算子及Div的有效反演
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-12-16 DOI: 10.1017/S0956792523000037
P. Hydon
Abstract The problem of inverting the total divergence operator is central to finding components of a given conservation law. This might not be taxing for a low-order conservation law of a scalar partial differential equation, but integrable systems have conservation laws of arbitrarily high order that must be found with the aid of computer algebra. Even low-order conservation laws of complex systems can be hard to find and invert. This paper describes a new, efficient approach to the inversion problem. Two main tools are developed: partial Euler operators and partial scalings. These lead to a line integral formula for the inversion of a total derivative and a procedure for inverting a given total divergence concisely.
求总散度算子的逆问题是求给定守恒律分量的核心问题。对于标量偏微分方程的低阶守恒定律来说,这可能并不费力,但可积系统具有任意高阶的守恒定律,必须借助计算机代数才能找到。即使是复杂系统的低阶守恒定律也很难找到和反转。本文描述了一种新的、有效的反演方法。开发了两个主要工具:偏欧拉算子和偏标度。这些推导出了求总导数逆的线积分公式和求给定总散度逆的过程。
{"title":"Partial Euler operators and the efficient inversion of Div","authors":"P. Hydon","doi":"10.1017/S0956792523000037","DOIUrl":"https://doi.org/10.1017/S0956792523000037","url":null,"abstract":"Abstract The problem of inverting the total divergence operator is central to finding components of a given conservation law. This might not be taxing for a low-order conservation law of a scalar partial differential equation, but integrable systems have conservation laws of arbitrarily high order that must be found with the aid of computer algebra. Even low-order conservation laws of complex systems can be hard to find and invert. This paper describes a new, efficient approach to the inversion problem. Two main tools are developed: partial Euler operators and partial scalings. These lead to a line integral formula for the inversion of a total derivative and a procedure for inverting a given total divergence concisely.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48745043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Two approximate symmetry frameworks for nonlinear partial differential equations with a small parameter: Comparisons, relations, approximate solutions 小参数非线性偏微分方程的两个近似对称框架:比较,关系,近似解
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-12-16 DOI: 10.1017/S0956792522000407
Mahmood R. Tarayrah, Brian Pitzel, A. Cheviakov
Abstract The frameworks of Baikov–Gazizov–Ibragimov (BGI) and Fushchich–Shtelen (FS) approximate symmetries are used to study symmetry properties of partial differential equations with a small parameter. In general, it is shown that unlike the case of ordinary differential equations (ODEs), unstable BGI point symmetries of unperturbed partial differential equations (PDEs) do not necessarily yield local approximate symmetries for the perturbed model. While some relations between the BGI and FS approaches can be established, the two methods yield different approximate symmetry classifications. Detailed classifications are presented for two nonlinear PDE families. The second family includes a one-dimensional wave equation describing the wave motion in a hyperelastic material with a single family of fibers. For this model, approximate symmetries can be used to compute approximate closed-form solutions. Wave breaking times are found numerically and using the approximate solutions, which yield comparable results.
摘要利用Baikov-Gazizov-Ibragimov (BGI)和Fushchich-Shtelen (FS)近似对称框架研究了小参数偏微分方程的对称性。一般来说,与常微分方程(ode)的情况不同,非摄动偏微分方程(PDEs)的不稳定BGI点对称性不一定产生摄动模型的局部近似对称性。虽然BGI和FS方法之间可以建立一些联系,但这两种方法产生了不同的近似对称分类。给出了两个非线性偏微分方程族的详细分类。第二类包括一维波动方程,描述具有单一纤维族的超弹性材料中的波动运动。对于该模型,近似对称性可以用来计算近似闭型解。波浪破碎时间是用数值方法和近似解求得的,得到了可比较的结果。
{"title":"Two approximate symmetry frameworks for nonlinear partial differential equations with a small parameter: Comparisons, relations, approximate solutions","authors":"Mahmood R. Tarayrah, Brian Pitzel, A. Cheviakov","doi":"10.1017/S0956792522000407","DOIUrl":"https://doi.org/10.1017/S0956792522000407","url":null,"abstract":"Abstract The frameworks of Baikov–Gazizov–Ibragimov (BGI) and Fushchich–Shtelen (FS) approximate symmetries are used to study symmetry properties of partial differential equations with a small parameter. In general, it is shown that unlike the case of ordinary differential equations (ODEs), unstable BGI point symmetries of unperturbed partial differential equations (PDEs) do not necessarily yield local approximate symmetries for the perturbed model. While some relations between the BGI and FS approaches can be established, the two methods yield different approximate symmetry classifications. Detailed classifications are presented for two nonlinear PDE families. The second family includes a one-dimensional wave equation describing the wave motion in a hyperelastic material with a single family of fibers. For this model, approximate symmetries can be used to compute approximate closed-form solutions. Wave breaking times are found numerically and using the approximate solutions, which yield comparable results.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42174109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Constant rank factorisations of smooth maps, with applications to sonar 光滑地图的常秩因子分解及其在声纳中的应用
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-12-01 DOI: 10.1017/s0956792522000365
Michael Robinson
Sonar systems are frequently used to classify objects at a distance by using the structure of the echoes of acoustic waves as a proxy for the object’s shape and composition. Traditional synthetic aperture processing is highly effective in solving classification problems when the conditions are favourable but relies on accurate knowledge of the sensor’s trajectory relative to the object being measured. This article provides several new theoretical tools that decouple object classification performance from trajectory estimation in synthetic aperture sonar processing. The key insight is that decoupling the trajectory from classification-relevant information involves factoring a function into the composition of two functions. The article presents several new general topological invariants for smooth functions based on their factorisations over function composition. These invariants specialise to the case when a sonar platform trajectory is deformed by a non-small perturbation. The mathematical results exhibited in this article apply well beyond sonar classification problems. This article is written in a way that supports full mathematical generality.
声纳系统经常用于通过使用声波回波的结构作为物体形状和成分的代理来对远处的物体进行分类。当条件有利时,传统的合成孔径处理在解决分类问题方面非常有效,但它依赖于传感器相对于被测量对象的轨迹的准确知识。本文提供了几种新的理论工具,将合成孔径声纳处理中的目标分类性能与轨迹估计解耦。关键的见解是,将轨迹与分类相关信息脱钩涉及将一个函数分解为两个函数的组合。基于光滑函数在函数组合上的因子分解,给出了几种新的光滑函数的一般拓扑不变量。这些不变量专门用于声纳平台轨迹因非小扰动而变形的情况。本文所展示的数学结果远远超出了声纳分类问题的应用范围。这篇文章的写作方式支持数学的全面通用性。
{"title":"Constant rank factorisations of smooth maps, with applications to sonar","authors":"Michael Robinson","doi":"10.1017/s0956792522000365","DOIUrl":"https://doi.org/10.1017/s0956792522000365","url":null,"abstract":"\u0000 Sonar systems are frequently used to classify objects at a distance by using the structure of the echoes of acoustic waves as a proxy for the object’s shape and composition. Traditional synthetic aperture processing is highly effective in solving classification problems when the conditions are favourable but relies on accurate knowledge of the sensor’s trajectory relative to the object being measured. This article provides several new theoretical tools that decouple object classification performance from trajectory estimation in synthetic aperture sonar processing. The key insight is that decoupling the trajectory from classification-relevant information involves factoring a function into the composition of two functions. The article presents several new general topological invariants for smooth functions based on their factorisations over function composition. These invariants specialise to the case when a sonar platform trajectory is deformed by a non-small perturbation. The mathematical results exhibited in this article apply well beyond sonar classification problems. This article is written in a way that supports full mathematical generality.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43371338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A modelling framework for efficient reduced order simulations of parametrised lithium-ion battery cells 参数化锂离子电池单元高效降阶模拟的建模框架
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-11-29 DOI: 10.1017/S0956792522000353
M. Landstorfer, Mario Ohlberger, S. Rave, M. Tacke
Abstract In this contribution, we present a modelling and simulation framework for parametrised lithium-ion battery cells. We first derive a continuum model for a rather general intercalation battery cell on the basis of non-equilibrium thermodynamics. In order to efficiently evaluate the resulting parameterised non-linear system of partial differential equations, the reduced basis method is employed. The reduced basis method is a model order reduction technique on the basis of an incremental hierarchical approximate proper orthogonal decomposition approach and empirical operator interpolation. The modelling framework is particularly well suited to investigate and quantify degradation effects of battery cells. Several numerical experiments are given to demonstrate the scope and efficiency of the modelling framework.
摘要在这篇文章中,我们提出了一个参数化锂离子电池的建模和仿真框架。我们首先在非平衡热力学的基础上推导了一个相当普遍的插层电池的连续体模型。为了有效地评估由此产生的参数化非线性偏微分方程组,采用了降基方法。降阶基法是一种基于增量层次近似自正交分解方法和经验算子插值的模型降阶技术。该建模框架特别适合于研究和量化电池单元的退化影响。给出了几个数值实验来证明建模框架的范围和效率。
{"title":"A modelling framework for efficient reduced order simulations of parametrised lithium-ion battery cells","authors":"M. Landstorfer, Mario Ohlberger, S. Rave, M. Tacke","doi":"10.1017/S0956792522000353","DOIUrl":"https://doi.org/10.1017/S0956792522000353","url":null,"abstract":"Abstract In this contribution, we present a modelling and simulation framework for parametrised lithium-ion battery cells. We first derive a continuum model for a rather general intercalation battery cell on the basis of non-equilibrium thermodynamics. In order to efficiently evaluate the resulting parameterised non-linear system of partial differential equations, the reduced basis method is employed. The reduced basis method is a model order reduction technique on the basis of an incremental hierarchical approximate proper orthogonal decomposition approach and empirical operator interpolation. The modelling framework is particularly well suited to investigate and quantify degradation effects of battery cells. Several numerical experiments are given to demonstrate the scope and efficiency of the modelling framework.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49274262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Exact nonclassical symmetry solutions of Lotka–Volterra-type population systems lotka - volterra型种群系统的精确非经典对称解
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-11-25 DOI: 10.1017/S095679252200033X
P. Broadbridge, R. Cherniha, J. Goard
Abstract New classes of conditionally integrable systems of nonlinear reaction–diffusion equations are introduced. They are obtained by extending a well-known nonclassical symmetry of a scalar partial differential equation to a vector equation. New exact solutions of nonlinear predator–prey systems with cross-diffusion are constructed. Infinite dimensional classes of exact solutions are made available for such nonlinear systems. Some of these solutions decay towards extinction and some oscillate or spiral around an interior fixed point. It is shown that the conditionally integrable systems are closely related to the standard diffusive Lotka–Volterra system, but they have additional features.
摘要介绍了一类新的非线性反应-扩散方程的条件可积系统。它们是通过将标量偏微分方程的一个众所周知的非经典对称性扩展到向量方程而获得的。构造了具有交叉扩散的非线性捕食者-被捕食系统的新的精确解。对于这样的非线性系统,可以得到无限维类的精确解。这些解中的一些朝着消光衰减,一些围绕内部不动点振荡或螺旋。结果表明,条件可积系统与标准扩散Lotka-Volterra系统密切相关,但它们具有额外的特征。
{"title":"Exact nonclassical symmetry solutions of Lotka–Volterra-type population systems","authors":"P. Broadbridge, R. Cherniha, J. Goard","doi":"10.1017/S095679252200033X","DOIUrl":"https://doi.org/10.1017/S095679252200033X","url":null,"abstract":"Abstract New classes of conditionally integrable systems of nonlinear reaction–diffusion equations are introduced. They are obtained by extending a well-known nonclassical symmetry of a scalar partial differential equation to a vector equation. New exact solutions of nonlinear predator–prey systems with cross-diffusion are constructed. Infinite dimensional classes of exact solutions are made available for such nonlinear systems. Some of these solutions decay towards extinction and some oscillate or spiral around an interior fixed point. It is shown that the conditionally integrable systems are closely related to the standard diffusive Lotka–Volterra system, but they have additional features.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42441098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Existence and stability of singular patterns in a fractional Ginzburg–Landau equation with a mean field 具有平均场的分数阶Ginzburg-Landau方程奇异模式的存在性和稳定性
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-11-11 DOI: 10.1017/s0956792522000286
Mingchen Gao, M. Winter, Wen Yang
In this paper, we consider the existence and stability of singular patterns in a fractional Ginzburg–Landau equation with a mean field. We prove the existence of three types of singular steady-state patterns (double fronts, single spikes, and double spikes) by solving their respective consistency conditions. In the case of single spikes, we prove the stability of single small spike solution for sufficiently large spatial period by studying an explicit non-local eigenvalue problem which is equivalent to the original eigenvalue problem. For the other solutions, we prove the instability by using the variational characterisation of eigenvalues. Finally, we present the results of some numerical computations of spike solutions based on the finite difference methods of Crank–Nicolson and Adams–Bashforth.
本文研究了一类具有平均域的分数阶Ginzburg-Landau方程奇异模式的存在性和稳定性。通过求解其一致性条件,证明了三种奇异稳态模式(双锋、单尖峰和双尖峰)的存在性。在单尖峰情况下,通过研究一个等价于原特征值问题的显式非局部特征值问题,证明了单小尖峰解在足够大的空间周期内的稳定性。对于其他解,我们利用特征值的变分刻画证明了其不稳定性。最后,我们给出了基于Crank-Nicolson和Adams-Bashforth有限差分方法的一些脉冲解的数值计算结果。
{"title":"Existence and stability of singular patterns in a fractional Ginzburg–Landau equation with a mean field","authors":"Mingchen Gao, M. Winter, Wen Yang","doi":"10.1017/s0956792522000286","DOIUrl":"https://doi.org/10.1017/s0956792522000286","url":null,"abstract":"\u0000 In this paper, we consider the existence and stability of singular patterns in a fractional Ginzburg–Landau equation with a mean field. We prove the existence of three types of singular steady-state patterns (double fronts, single spikes, and double spikes) by solving their respective consistency conditions. In the case of single spikes, we prove the stability of single small spike solution for sufficiently large spatial period by studying an explicit non-local eigenvalue problem which is equivalent to the original eigenvalue problem. For the other solutions, we prove the instability by using the variational characterisation of eigenvalues. Finally, we present the results of some numerical computations of spike solutions based on the finite difference methods of Crank–Nicolson and Adams–Bashforth.","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45218613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A deterministic gradient-based approach to avoid saddle points 基于确定性梯度的避鞍点方法
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-11-09 DOI: 10.1017/s0956792522000316
L. M. Kreusser, S. J. Osher, B. Wang

Loss functions with a large number of saddle points are one of the major obstacles for training modern machine learning (ML) models efficiently. First-order methods such as gradient descent (GD) are usually the methods of choice for training ML models. However, these methods converge to saddle points for certain choices of initial guesses. In this paper, we propose a modification of the recently proposed Laplacian smoothing gradient descent (LSGD) [Osher et al., arXiv:1806.06317], called modified LSGD (mLSGD), and demonstrate its potential to avoid saddle points without sacrificing the convergence rate. Our analysis is based on the attraction region, formed by all starting points for which the considered numerical scheme converges to a saddle point. We investigate the attraction region’s dimension both analytically and numerically. For a canonical class of quadratic functions, we show that the dimension of the attraction region for mLSGD is $lfloor (n-1)/2rfloor$, and hence it is significantly smaller than that of GD whose dimension is $n-1$.

具有大量鞍点的损失函数是有效训练现代机器学习(ML)模型的主要障碍之一。梯度下降(GD)等一阶方法通常是训练ML模型的首选方法。然而,对于初始猜测的某些选择,这些方法收敛到鞍点。在本文中,我们对最近提出的拉普拉斯平滑梯度下降(LSGD) [Osher et al., arXiv:1806.06317]提出了一种修正,称为修正LSGD (mLSGD),并证明了其在不牺牲收敛速度的情况下避免鞍点的潜力。我们的分析是基于引力区域的,引力区域由所考虑的数值方案收敛于鞍点的所有起点组成。我们用解析法和数值法研究了引力区域的维数。对于一类典型的二次函数,我们证明了mLSGD的吸引域的维数为$lfloor (n-1)/2rfloor$,因此它明显小于维数为$n-1$的GD的吸引域。
{"title":"A deterministic gradient-based approach to avoid saddle points","authors":"L. M. Kreusser, S. J. Osher, B. Wang","doi":"10.1017/s0956792522000316","DOIUrl":"https://doi.org/10.1017/s0956792522000316","url":null,"abstract":"<p>Loss functions with a large number of saddle points are one of the major obstacles for training modern machine learning (ML) models efficiently. First-order methods such as gradient descent (GD) are usually the methods of choice for training ML models. However, these methods converge to saddle points for certain choices of initial guesses. In this paper, we propose a modification of the recently proposed Laplacian smoothing gradient descent (LSGD) [Osher et al., arXiv:1806.06317], called modified LSGD (mLSGD), and demonstrate its potential to avoid saddle points without sacrificing the convergence rate. Our analysis is based on the attraction region, formed by all starting points for which the considered numerical scheme converges to a saddle point. We investigate the attraction region’s dimension both analytically and numerically. For a canonical class of quadratic functions, we show that the dimension of the attraction region for mLSGD is <span>\u0000<span>\u0000<img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20230705121909977-0335:S0956792522000316:S0956792522000316_inline1.png\"/>\u0000<span data-mathjax-type=\"texmath\"><span>\u0000$lfloor (n-1)/2rfloor$\u0000</span></span>\u0000</span>\u0000</span>, and hence it is significantly smaller than that of GD whose dimension is <span>\u0000<span>\u0000<img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20230705121909977-0335:S0956792522000316:S0956792522000316_inline2.png\"/>\u0000<span data-mathjax-type=\"texmath\"><span>\u0000$n-1$\u0000</span></span>\u0000</span>\u0000</span>.</p>","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138539587","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A deterministic gradient-based approach to avoid saddle points 基于确定性梯度的避鞍点方法
IF 1.9 4区 数学 Q1 Mathematics Pub Date : 2022-11-09 DOI: 10.1017/s0956792522000316
L. M. Kreusser, S. J. Osher, B. Wang

Loss functions with a large number of saddle points are one of the major obstacles for training modern machine learning (ML) models efficiently. First-order methods such as gradient descent (GD) are usually the methods of choice for training ML models. However, these methods converge to saddle points for certain choices of initial guesses. In this paper, we propose a modification of the recently proposed Laplacian smoothing gradient descent (LSGD) [Osher et al., arXiv:1806.06317], called modified LSGD (mLSGD), and demonstrate its potential to avoid saddle points without sacrificing the convergence rate. Our analysis is based on the attraction region, formed by all starting points for which the considered numerical scheme converges to a saddle point. We investigate the attraction region’s dimension both analytically and numerically. For a canonical class of quadratic functions, we show that the dimension of the attraction region for mLSGD is $lfloor (n-1)/2rfloor$, and hence it is significantly smaller than that of GD whose dimension is $n-1$.

具有大量鞍点的损失函数是有效训练现代机器学习(ML)模型的主要障碍之一。梯度下降(GD)等一阶方法通常是训练ML模型的首选方法。然而,对于初始猜测的某些选择,这些方法收敛到鞍点。在本文中,我们对最近提出的拉普拉斯平滑梯度下降(LSGD) [Osher et al., arXiv:1806.06317]提出了一种修正,称为修正LSGD (mLSGD),并证明了其在不牺牲收敛速度的情况下避免鞍点的潜力。我们的分析是基于引力区域的,引力区域由所考虑的数值方案收敛于鞍点的所有起点组成。我们用解析法和数值法研究了引力区域的维数。对于一类典型的二次函数,我们证明了mLSGD的吸引域的维数为$lfloor (n-1)/2rfloor$,因此它明显小于维数为$n-1$的GD的吸引域。
{"title":"A deterministic gradient-based approach to avoid saddle points","authors":"L. M. Kreusser, S. J. Osher, B. Wang","doi":"10.1017/s0956792522000316","DOIUrl":"https://doi.org/10.1017/s0956792522000316","url":null,"abstract":"<p>Loss functions with a large number of saddle points are one of the major obstacles for training modern machine learning (ML) models efficiently. First-order methods such as gradient descent (GD) are usually the methods of choice for training ML models. However, these methods converge to saddle points for certain choices of initial guesses. In this paper, we propose a modification of the recently proposed Laplacian smoothing gradient descent (LSGD) [Osher et al., arXiv:1806.06317], called modified LSGD (mLSGD), and demonstrate its potential to avoid saddle points without sacrificing the convergence rate. Our analysis is based on the attraction region, formed by all starting points for which the considered numerical scheme converges to a saddle point. We investigate the attraction region’s dimension both analytically and numerically. For a canonical class of quadratic functions, we show that the dimension of the attraction region for mLSGD is <span>\u0000<span>\u0000<img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20230705121909977-0335:S0956792522000316:S0956792522000316_inline1.png\"/>\u0000<span data-mathjax-type=\"texmath\"><span>\u0000$lfloor (n-1)/2rfloor$\u0000</span></span>\u0000</span>\u0000</span>, and hence it is significantly smaller than that of GD whose dimension is <span>\u0000<span>\u0000<img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20230705121909977-0335:S0956792522000316:S0956792522000316_inline2.png\"/>\u0000<span data-mathjax-type=\"texmath\"><span>\u0000$n-1$\u0000</span></span>\u0000</span>\u0000</span>.</p>","PeriodicalId":51046,"journal":{"name":"European Journal of Applied Mathematics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138539663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
期刊
European Journal of Applied Mathematics
全部 Acc. Chem. Res. ACS Applied Bio Materials ACS Appl. Electron. Mater. ACS Appl. Energy Mater. ACS Appl. Mater. Interfaces ACS Appl. Nano Mater. ACS Appl. Polym. Mater. ACS BIOMATER-SCI ENG ACS Catal. ACS Cent. Sci. ACS Chem. Biol. ACS Chemical Health & Safety ACS Chem. Neurosci. ACS Comb. Sci. ACS Earth Space Chem. ACS Energy Lett. ACS Infect. Dis. ACS Macro Lett. ACS Mater. Lett. ACS Med. Chem. Lett. ACS Nano ACS Omega ACS Photonics ACS Sens. ACS Sustainable Chem. Eng. ACS Synth. Biol. Anal. Chem. BIOCHEMISTRY-US Bioconjugate Chem. BIOMACROMOLECULES Chem. Res. Toxicol. Chem. Rev. Chem. Mater. CRYST GROWTH DES ENERG FUEL Environ. Sci. Technol. Environ. Sci. Technol. Lett. Eur. J. Inorg. Chem. IND ENG CHEM RES Inorg. Chem. J. Agric. Food. Chem. J. Chem. Eng. Data J. Chem. Educ. J. Chem. Inf. Model. J. Chem. Theory Comput. J. Med. Chem. J. Nat. Prod. J PROTEOME RES J. Am. Chem. Soc. LANGMUIR MACROMOLECULES Mol. Pharmaceutics Nano Lett. Org. Lett. ORG PROCESS RES DEV ORGANOMETALLICS J. Org. Chem. J. Phys. Chem. J. Phys. Chem. A J. Phys. Chem. B J. Phys. Chem. C J. Phys. Chem. Lett. Analyst Anal. Methods Biomater. Sci. Catal. Sci. Technol. Chem. Commun. Chem. Soc. Rev. CHEM EDUC RES PRACT CRYSTENGCOMM Dalton Trans. Energy Environ. Sci. ENVIRON SCI-NANO ENVIRON SCI-PROC IMP ENVIRON SCI-WAT RES Faraday Discuss. Food Funct. Green Chem. Inorg. Chem. Front. Integr. Biol. J. Anal. At. Spectrom. J. Mater. Chem. A J. Mater. Chem. B J. Mater. Chem. C Lab Chip Mater. Chem. Front. Mater. Horiz. MEDCHEMCOMM Metallomics Mol. Biosyst. Mol. Syst. Des. Eng. Nanoscale Nanoscale Horiz. Nat. Prod. Rep. New J. Chem. Org. Biomol. Chem. Org. Chem. Front. PHOTOCH PHOTOBIO SCI PCCP Polym. Chem.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
0
微信
客服QQ
Book学术公众号 扫码关注我们
反馈
×
意见反馈
请填写您的意见或建议
请填写您的手机或邮箱
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
现在去查看 取消
×
提示
确定
Book学术官方微信
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术
文献互助 智能选刊 最新文献 互助须知 联系我们:info@booksci.cn
Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。
Copyright © 2023 Book学术 All rights reserved.
ghs 京公网安备 11010802042870号 京ICP备2023020795号-1