IMA Journal of Applied Mathematics最新文献_第9页

Radiation of sound waves from a coaxial duct with perforated screen 带穿孔屏的同轴管道的声波辐射

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-06-01 DOI: 10.1093/imamat/hxab016

Burhan Tiryakioglu;Ayse Tiryakioglu

引用次数: 1

The factorization method for the scattering by a mixed inhomogeneous medium 混合非均匀介质散射的分解方法

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-06-01 DOI: 10.1093/imamat/hxab017

Jianli Xiang;Guozheng Yan

引用次数: 0

Optimizing the spring constants of forced, damped and circular spring-mass systems—characterization of the discrete and periodic bi-Laplacian operator 优化强制，阻尼和圆形弹簧-质量系统的弹簧常数-离散和周期双拉普拉斯算子的表征

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-06-01 DOI: 10.1093/imamat/hxab021

L L A de Oliveira;M V Travaglia

{"title":"Optimizing the spring constants of forced, damped and circular spring-mass systems—characterization of the discrete and periodic bi-Laplacian operator","authors":"L L A de Oliveira;M V Travaglia","doi":"10.1093/imamat/hxab021","DOIUrl":"10.1093/imamat/hxab021","url":null,"abstract":"We optimize the spring constants \u0000<tex>$k^{i,j}$</tex>\u0000 (stiffness) of circular spring-mass systems with nearest-neighbour (NN) and next-nearest-neighbour (NNN) springs only. In this optimization problem, such systems are also subjected to damping and periodic external forces. The function to be minimized is the average ratio of the square norm of the on-site internal forces (response) to the square norm of the external on-site forces (input). Under the average of this response/input ratio is meant the average over time and over all configurations of external forces. As main result, it is established that the optimum stiffness matrix converges to the discrete and periodic bi-Laplacian operator as the size \u0000<tex>$n$</tex>\u0000 of the system increases. Such a result is obtained under the following assumptions: (a) the system has the natural mode shape (eigenvector) of alternating \u0000<tex>$1$</tex>\u0000s and \u0000<tex>$-1$</tex>\u0000s; and (b) the (external) forcing frequency is at least \u0000<tex>$1.095$</tex>\u0000 times higher than the highest natural frequency. It is remarkable that this optimum stiffness matrix exhibits negative stiffness for the springs linking NNN point masses. More specifically, as \u0000<tex>$n$</tex>\u0000 increases, \u0000<tex>$0> k^{i,i+2} , , = , , - tfrac{1}{4} , k^{i,i+1}$</tex>\u0000 is the relation between the optimum NNN spring constant and the optimum NN spring constant. Such systems illustrate that the introduction of negative stiffness springs in some specific positions does in fact reduce the average response/input ratio. Numerical tables illustrating the main result are given.","PeriodicalId":56297,"journal":{"name":"IMA Journal of Applied Mathematics","volume":"86 1","pages":"785-807"},"PeriodicalIF":1.2,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45366354","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

Critical domain sizes of a discrete-map hybrid and reaction-diffusion model on hostile exterior domains 敌对外部域上离散映射混合反应扩散模型的临界域尺寸

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-06-01 DOI: 10.1093/imamat/hxab019

Mostafa Fazly

引用次数: 0

On a subdiffusive tumour growth model with fractional time derivative 一个具有分数时间导数的次扩散肿瘤生长模型

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-06-01 DOI: 10.1093/imamat/hxab009

Marvin Fritz;Christina Kuttler;Mabel L Rajendran;Barbara Wohlmuth;Laura Scarabosio

引用次数: 15

The maximum likelihood ensemble filter for computational flame and fluid dynamics 计算火焰与流体动力学的最大似然集合滤波器

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-06-01 DOI: 10.1093/imamat/hxab010

Yijun Wang;Stephen Guzik;Milija Zupanski;Xinfeng Gao

{"title":"The maximum likelihood ensemble filter for computational flame and fluid dynamics","authors":"Yijun Wang;Stephen Guzik;Milija Zupanski;Xinfeng Gao","doi":"10.1093/imamat/hxab010","DOIUrl":"10.1093/imamat/hxab010","url":null,"abstract":"The numerical solution of partial differential equations that govern fluid dynamics with turbulence and combustion is challenging due to the multiscale nature of the dynamical system and the need to resolve small-scale physical features. In addition, the uncertainties in the dynamical system, including those in the physical models and parameters, initial and boundary conditions and numerical methods, impact the computational fluid dynamics (CFD) prediction of turbulence and chemical reactions. To improve the CFD prediction, this study focuses on the development and application of a maximum likelihood ensemble filter (MLEF), an ensemble-based data assimilation (DA), for flows featuring combustion and/or turbulence. MLEF finds the optimal analysis and its uncertainty by maximizing the posterior probability density function. The novelty of the study lies in the combination of advanced DA and CFD methods for a new comprehensive application to predict engineering fluid dynamics. The study combines important aspects, including an ensemble-based DA with analysis and uncertainty estimation, an augmented control vector that simultaneously adjusts initial conditions and model empirical parameters and an application of DA to CFD modeling of combustion and flows with complex geometry. The DA performance is validated by a turbulent Couette flow. The new CFD–DA system is then applied to solve the time-evolving shear-layer mixing with methane-air combustion and the turbulent flow over a bluff-body geometry. Results demonstrate the improvement of estimates of model parameters and the uncertainty reduction in initial conditions (ICs) for CFD modeling of flames and flows by the MLEF method.","PeriodicalId":56297,"journal":{"name":"IMA Journal of Applied Mathematics","volume":"86 1","pages":"631-661"},"PeriodicalIF":1.2,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/imamat/hxab010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44645899","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

Stability of Fixed Points in an Approximate Solution of the Spring-mass Running Model 弹簧质量运行模型近似解中不动点的稳定性

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-05-15 DOI: 10.21203/RS.3.RS-563354/V1

Zofia Wr'oblewska, P. Kowalczyk, Lukasz Plociniczak

引用次数: 0

On the instability, nonexistence and spatial behaviour of the one-dimensional response of a new class of elastic bodies 一类新弹性体一维响应的不稳定性、不存在性和空间行为

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-04-01 DOI: 10.1093/imamat/hxab014

R Quintanilla;K R Rajagopal

引用次数: 0

An initial-boundary value problem for the general three-component nonlinear Schrödinger equations on a finite interval 有限区间上一般三分量非线性Schrödinger方程的初边值问题

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-04-01 DOI: 10.1093/imamat/hxab007

Zhenya Yan

{"title":"An initial-boundary value problem for the general three-component nonlinear Schrödinger equations on a finite interval","authors":"Zhenya Yan","doi":"10.1093/imamat/hxab007","DOIUrl":"10.1093/imamat/hxab007","url":null,"abstract":"The general three-component nonlinear Schrödinger (gtc-NLS) equations are completely integrable and contain the self-focusing, defocusing and mixed cases, which are applied in many physical fields. In this paper, we would like to use the Fokas method to explore the initial-boundary value (IBV) problem for the gtc-NLS equations with a \u0000<tex>$4times 4$</tex>\u0000 matrix Lax pair on a finite interval based on the inverse scattering transform. The solutions of the gtc-NLS equations can be expressed using the solution of a \u0000<tex>$4times 4$</tex>\u0000 matrix Riemann–Hilbert (RH) problem constructed in the complex \u0000<tex>$k$</tex>\u0000-plane. The jump matrices of the RH problem can be explicitly found in terms of three spectral functions related to the initial data, and the Dirichlet–Neumann boundary data, respectively. The global relation between the distinct spectral functions is also proposed to derive two distinct but equivalent types of representations of the Dirichlet–Neumann boundary value problems. Particularly, the relevant formulae for the boundary value problems on the finite interval can generate ones on the half-line as the length of the interval closes to infinity. Finally, we also analyse the linearizable boundary conditions for the Gel'fand–Levitan–Marchenko representation. These results will be useful to further study the solution properties of the IBV problem of the gtc-NLS system by using the Deift–Zhou's nonlinear steepest descent method and some numerical methods.","PeriodicalId":56297,"journal":{"name":"IMA Journal of Applied Mathematics","volume":"86 1","pages":"427-489"},"PeriodicalIF":1.2,"publicationDate":"2021-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1093/imamat/hxab007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45172944","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: 11

Steady slip flow of Newtonian fluids through tangential polygonal microchannels 牛顿流体通过切向多边形微通道的稳态滑移流

IF 1.2 4区数学

IMA Journal of Applied Mathematics Pub Date : 2021-04-01 DOI: 10.1093/imamat/hxab008

Grant Keady

引用次数: 5