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Energy-decreasing parametric finite element method for geodesic Willmore flow 测地线Willmore流的降能参数有限元法
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-23 DOI: 10.1016/j.cnsns.2026.109783
Cuiling Ma, Xufeng Xiao, Xiaoling Zhang, Xinlong Feng
We propose an energy-decreasing numerical scheme for the geodesic Willmore flow of closed curves on curved surfaces. This geometric flow characterizes the evolution of curves toward the minimization of the geodesic Willmore energy. Our main contributions are the derivation of novel evolution equations governing both the curve parameterization and geodesic curvature, the development of a stable fully discrete approximation combining the linear parametric finite elements in space with the implicit Euler in time, and a rigorous proof of discrete energy decay for the proposed scheme. The method effectively captures curve evolution on implicit surfaces. In addition, we generalize the energy-decreasing framework to the anisotropic geodesic Willmore flow and propose a BDF2 scheme. Through numerical experiments, we demonstrate the convergence and energy-decreasing property of the proposed approach, validating its effectiveness.
我们提出了曲面上闭曲线测地线Willmore流的能量递减数值格式。这种几何流的特征是曲线向测地线威尔莫尔能量最小化的演变。我们的主要贡献是推导了控制曲线参数化和测地线曲率的新型演化方程,开发了一个稳定的全离散近似,将空间中的线性参数有限元与时间中的隐式欧拉结合起来,并严格证明了所提出方案的离散能量衰减。该方法有效地捕捉了隐式曲面上的曲线演化过程。此外,我们将能量递减框架推广到各向异性测地线Willmore流中,并提出了BDF2格式。通过数值实验证明了该方法的收敛性和降能性,验证了该方法的有效性。
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引用次数: 0
A novel deep neural network with the dynamical moving window data for nonlinear system identification 一种新的具有动态移动窗口数据的非线性系统辨识深度神经网络
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109670
Yanjiao Wang, Zhaogui Cai, Muqing Deng
Deep neural networks (DNNs) have the capability to describe complex nonlinear dynamics, which have aroused wide concerns. However, the existing parameter optimization methods in DNNs based on gradient suffer from the limitations of easily falling into local minima and the poor modeling results. To overcome these problems, this paper proposes a mini-batch gradient descent algorithm with dynamical moving window data and constructs a novel deep neural network architecture by using the simpler deep learning network instead of selecting weights through regulation and optimizing its parameters through the dynamical moving window based algorithm. The results of simulation experiments show that the proposed methods have better performance in accuracy and convergence rate compared with the existing methods for identifying nonlinear systems.
深度神经网络(Deep neural network, dnn)具有描述复杂非线性动力学的能力,引起了人们的广泛关注。然而,现有的基于梯度的深度神经网络参数优化方法存在容易陷入局部极小值和建模效果差的局限性。为了克服这些问题,本文提出了一种基于动态移动窗口数据的小批量梯度下降算法,并利用更简单的深度学习网络构建了一种新的深度神经网络架构,而不是通过调节选择权值,并通过基于动态移动窗口的算法优化其参数。仿真实验结果表明,与现有的非线性系统识别方法相比,所提出的方法在精度和收敛速度方面具有更好的性能。
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引用次数: 0
Lazy-learning-based Koopman model predictive control for synchronization of unknown nonlinear systems 基于延迟学习的未知非线性系统同步库普曼模型预测控制
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109746
Xinlong Xu , Xia Huang , Qingyu Shi , Zhen Wang
This paper studies the synchronization problem of a class of unknown nonlinear systems. In response to the challenges in controller design resulting from unknown models, a lazy-learning-based Koopman model predictive control (LL-KMPC) strategy is proposed. The distinctiveness of the proposed control strategy is twofold: (i) exploitation of the global linearization property of the Koopman operator, enabling linear-control methods for synchronization control of unknown nonlinear systems; and (ii) integration of lazy learning (LL), which substantially reduces model mismatch in Koopman-based modeling. Moreover, theoretical results prove that the synchronization error is bounded under the proposed control strategy. Finally, two examples are provided to verify the effectiveness of the proposed control strategy. The experimental results demonstrate that the introduction of the LL technique can effectively improve the modeling performance, and compared to the model-free adaptive control (MFAC) and the model-free adaptive predictive control (MFAPC) approaches, the LL-KMPC strategy exhibits a faster convergence rate and a smaller synchronization error.
研究了一类未知非线性系统的同步问题。针对未知模型给控制器设计带来的挑战,提出了一种基于惰性学习的Koopman模型预测控制(LL-KMPC)策略。该控制策略的独特之处在于:(i)利用Koopman算子的全局线性化特性,使线性控制方法能够用于未知非线性系统的同步控制;(ii)懒学习(LL)的集成,这大大减少了基于koopman的建模中的模型不匹配。此外,理论结果证明了在该控制策略下,同步误差是有界的。最后,通过两个算例验证了所提控制策略的有效性。实验结果表明,引入LL- kmpc技术可以有效地提高建模性能,与无模型自适应控制(MFAC)和无模型自适应预测控制(MFAPC)方法相比,LL- kmpc策略具有更快的收敛速度和更小的同步误差。
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引用次数: 0
Novel subgradient extragradient methods for equilibrium problems in Hilbert spaces 希尔伯特空间平衡问题的新次梯度外聚方法
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109777
Pham Ky Anh , Ngo Thi Thuong , Nguyen The Vinh
In this paper, by combining the inertial technique and subgradient extragradient method with a new strategy of stepsize selection, we propose a novel extragradient-type method to solve pseudomonotone equilibrium problems in real Hilbert spaces. Our method is designed such that the stepsize sequence is increasing after a finite number of iterations. This distinguishes our method from most other extragradient-type methods for equilibrium problems. The weak and strong convergence of new algorithms under standard assumptions are established. We examine the performance of our methods on the Nash-Cournot oligopolistic equilibrium models of electricity markets. The reported numerical results demonstrate the efficiency of the proposed method.
本文将惯性技术和亚梯度法结合起来,采用一种新的步长选择策略,提出了一种新的求解实数Hilbert空间中伪单调平衡问题的梯度法。我们的方法被设计成步长序列在有限次迭代后增加。这使我们的方法区别于大多数其他用于平衡问题的外梯度型方法。建立了新算法在标准假设下的弱收敛性和强收敛性。我们检验了我们的方法在电力市场的纳什-古诺寡头垄断均衡模型上的性能。数值结果表明了该方法的有效性。
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引用次数: 0
Credit risk for large portfolios of green and brown loans: Extending the ASRF model 大型绿色和棕色贷款组合的信用风险:扩展ASRF模型
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109750
Alessandro Ramponi, Sergio Scarlatti
Inspired by the classical Vasicek approach to credit risk, we propose an extended model for portfolios composed of green and brown loans, widening the Asymptotic Single Risk Factor framework via a two-factor copula structure. Systematic risk is modeled using potentially skewed distributions, allowing for asymmetric creditworthiness effects, while idiosyncratic risk remains Gaussian. Under a non-uniform exposure setting, we establish convergence in quadratic mean of the portfolio loss to a limit reflecting the distinct characteristics of the two loan segments. Numerical results confirm the theoretical findings and illustrate how value-at-risk is affected by portfolio granularity, default probabilities, factor loadings, and skewness. Our model accommodates differential sensitivity to systematic shocks and offers a tractable basis for further developments in credit risk modeling, including granularity adjustments, collateralized default obligations pricing, and empirical analysis of green loan portfolios.
受经典的Vasicek信贷风险分析方法的启发,我们提出了一个由绿色贷款和棕色贷款组成的投资组合的扩展模型,通过一个双因素关联结构扩大了渐近单风险因素框架。系统风险使用可能偏斜的分布建模,允许不对称的信誉效应,而特殊风险仍然是高斯的。在非均匀风险敞口设置下,我们建立了投资组合损失的二次均值收敛到反映两个贷款部分不同特征的极限。数值结果证实了理论发现,并说明了风险价值如何受到投资组合粒度、违约概率、因素负荷和偏度的影响。我们的模型适应了对系统性冲击的不同敏感性,并为信用风险建模的进一步发展提供了可处理的基础,包括粒度调整、抵押违约债券定价和绿色贷款组合的实证分析。
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引用次数: 0
Lyapunov methods for dissipative Caputo fractional differential equations with two indices 双指标耗散卡普托分数阶微分方程的Lyapunov方法
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109737
Peter E. Kloeden , Doan Thai Son , Hoang The Tuan
The asymptotic behaviour of a class of dissipative Caputo fractional differential equations with two indices is investigated. Using Lyapunov methods and a comparison principle, results on ultimate boundedness and Mittag-Leffler stability are obtained for these systems. Two examples illustrate these results.
研究了一类双指标耗散Caputo分数阶微分方程的渐近性质。利用Lyapunov方法和比较原理,得到了这些系统的极限有界性和Mittag-Leffler稳定性。两个例子说明了这些结果。
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引用次数: 0
Backward problem in a coupled time-fractional reaction diffusion system by optimization method 用最优化方法求解耦合时间-分数反应扩散系统的逆向问题
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109778
Liangliang Sun, Zhaoqi Zhang
In this paper, we study a backward problem in a system controlled by two coupled time-fractional diffusion equations from the final measurement data. Firstly, we prove the well-posedness of the state problem by introducing the Riemann-Liouville weak formulation, and give some regularity results of the solution to the state problem by employing the properties of the Mittag-Leffler function. In order to solve this inverse problem, we then transform it into a least square optimization problem. Subsequently, we establish the existence of the minimizer and also prove its uniqueness and a stability estimates with respect to the input data. Finally, we provide some numerical results for the optimal control problem using the Landweber iterative method.
本文从最终测量数据出发,研究了由两个耦合时间分数扩散方程控制的系统的后向问题。首先,通过引入Riemann-Liouville弱公式证明了状态问题的适定性,并利用Mittag-Leffler函数的性质给出了状态问题解的一些正则性结果。为了解决这个反问题,我们将其转化为最小二乘优化问题。随后,我们建立了最小器的存在性,并证明了它的唯一性和一个关于输入数据的稳定性估计。最后,用Landweber迭代法给出了最优控制问题的一些数值结果。
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引用次数: 0
Viscoelastic surfactant flowback model with rod-like micelle leading to differential variational-hemivariational inequality 具有棒状胶束的粘弹性表面活性剂反排模型导致微分变分-半变分不等式
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109767
Yaojia Zhang , Tao Chen , Stanislaw Migórski
This paper investigates a system of two nonlinear elliptic equations coupled with a variational-hemivariational inequality (VHVI) under constraints. The system provides a critical mathematical model for the flowback problem of viscoelastic surfactant fluids in shale gas extraction. The model features strong couplings among the chloride ion concentration, rod-like micelle density, and flowback velocity, governed by nonsmooth multivalued frictional boundary laws and nonlinear diffusion mechanisms. Under minimal regularity assumptions on the data, we prove the existence of at least one weak solution to the system. The proof combines techniques from nonsmooth analysis, the theory of pseudomonotone operators, elliptic hemivariational inequalities, monotonicity and compactness methods, and exploits the Kakutani–Ky Fan fixed point theorem for set-valued maps.
研究了在约束条件下两个非线性椭圆方程与一个变分-半变分不等式耦合的方程组。该系统为页岩气开采中粘弹性表面活性剂返排问题提供了一个重要的数学模型。该模型具有氯离子浓度、棒状胶束密度和返排速度之间的强耦合,受非光滑多值摩擦边界律和非线性扩散机制控制。在数据的最小正则性假设下,我们证明了该系统存在至少一个弱解。该证明结合了非光滑分析、伪单调算子理论、椭圆半变不等式、单调性和紧性方法等技术,并利用集值映射的Kakutani-Ky Fan不动点定理。
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引用次数: 0
Extreme learning machines with decaying penalties for nonlinear partial differential equations 非线性偏微分方程的具有衰减惩罚的极限学习机
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109775
Yudong Zhou, Qinghui Zhang
Deep neural network (DNN) methods generally achieve about 1E-4 accuracy (for L2 relative errors) when solving partial differential equations (PDEs). Extreme learning machines (ELMs), a sort of shallow neural networks, can realize spectral accuracy for certain PDEs. Studies on ELM are mostly focused on the linear PDEs, where training process can be equivalent to linear least square problems and Pseudo inverse operations. The training of ELM with Gauss-Newton method for the nonlinear PDEs poses big challenges, including sensitivity to initial guess, a great number of iterations, and robustness. These issues are largely caused by ill-posed nature of the problem in a sense that the condition number of discrete matrix is extremely large. We propose a novel Gauss-Newton method of ELM for the nonlinear PDEs, which is composed of three major strategies. (a) The conventional loss function based on ELM is penalized to establish a penalized nonlinear least square problem (PNLS). (b) The PNLS problem is approximated using a first-order Taylor expansion of the residual vector to avoid the explicit Hessian calculation, as executed in the conventional Gauss-Newton method. (c) Most importantly, the penalty decays to zero as the iteration progresses. The new method is referred to as DPELM (the ELM with decaying penalties). The motivation of DPELM is both to improve the conditioning of the discrete matrix by adding the penalty and to avoid the loss of accuracy (caused by the penalty) by making the penalty decay to zero. The effectiveness of the proposed method is validated by numerous numerical experiments of the nonlinear PDEs, including minimal surface equations, Navier-Stokes equations, nonlinear reaction-diffusion equations, etc. The comparisons with the existing neural network methods, the DNN and conventional ELM, are also made.
深度神经网络(Deep neural network, DNN)方法在求解偏微分方程(PDEs)时,一般能达到约1E-4的精度(L2相对误差)。极限学习机(elm)是一种浅层神经网络,可以实现某些偏微分方程的谱精度。ELM的研究主要集中在线性偏微分方程上,其训练过程可以等效为线性最小二乘问题和伪逆操作。用高斯-牛顿方法训练非线性偏微分方程的ELM具有初始猜测灵敏度高、迭代次数多、鲁棒性差等特点。这些问题很大程度上是由于问题的病态性,即离散矩阵的条件数非常大。针对非线性偏微分方程提出了一种新的高斯-牛顿ELM方法,该方法由三种主要策略组成。(a)对基于ELM的传统损失函数进行惩罚,建立惩罚非线性最小二乘问题(PNLS)。(b) PNLS问题近似使用残差向量的一阶泰勒展开式,以避免在传统的高斯-牛顿方法中执行的显式Hessian计算。(c)最重要的是,随着迭代的进行,惩罚逐渐衰减为零。这种新方法被称为DPELM(带有衰减惩罚的ELM)。DPELM的动机是通过增加惩罚来改善离散矩阵的条件,并通过使惩罚衰减到零来避免精度损失(由惩罚引起的)。通过对极小曲面方程、Navier-Stokes方程、非线性反应-扩散方程等非线性偏微分方程的数值实验,验证了该方法的有效性。并与现有的神经网络方法DNN和传统ELM进行了比较。
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引用次数: 0
A reaction-diffusion-taxis model for toxicant-predator-prey interaction dynamics 毒物-捕食者-猎物相互作用动力学的反应-扩散-趋向性模型
IF 3.8 2区 数学 Q1 MATHEMATICS, APPLIED Pub Date : 2026-01-22 DOI: 10.1016/j.cnsns.2026.109760
Xiumei Deng , Qihua Huang , Hai-Yang Jin
We develop a reaction-diffusion-taxis model to investigate the dynamic interactions between a toxicant and a predator-prey system within a contaminated aquatic ecosystem. The model includes taxis terms induced by the toxicant to capture the evasive movement of individuals as they seek to avoid exposure to the toxicant. We establish the global well-posedness of solutions for the reaction-diffusion-taxis system. We prove the global asymptotic stability of spatially uniform steady states. Through linear stability analysis, we derive sufficient conditions for the destabilization of these uniform steady states. Numerically, we explore the influence of key toxicant-related parameters—such as toxicant input rate, toxicant-taxis intensity, and species susceptibility to toxicants—on the persistence and spatial distribution of prey and predator populations. Our results demonstrate that: (i) High-intensity toxicant-taxis can induce spatial segregation and aggregation patterns between the toxicant and populations; (ii) when predators are more susceptible to toxicants than their prey, a moderate increase in toxicant concentration may, counterintuitively, enhance prey persistence; and (iii) spatially heterogeneous toxicant inputs can promote species persistence, thereby supporting ecosystem biodiversity.
我们开发了一个反应-扩散-趋向性模型来研究被污染的水生生态系统中有毒物质和捕食者-猎物系统之间的动态相互作用。该模型包括由有毒物质诱导的出租车术语,以捕捉个体在寻求避免暴露于有毒物质时的逃避运动。我们建立了反应-扩散-趋向性系统解的全局适定性。证明了空间一致稳态的全局渐近稳定性。通过线性稳定性分析,我们得到了这些均匀稳态失稳的充分条件。在数值上,我们探讨了与毒物相关的关键参数——如毒物输入率、毒物趋向性强度和物种对毒物的易感性——对猎物和捕食者种群的持久性和空间分布的影响。研究结果表明:(1)高强度毒物趋向性可导致毒物与种群之间的空间分离和聚集模式;(ii)当捕食者比猎物更容易受到有毒物质的影响时,与直觉相反,有毒物质浓度的适度增加可能会增强猎物的持久性;(3)空间异质性毒物输入可以促进物种持久性,从而支持生态系统的生物多样性。
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引用次数: 0
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Communications in Nonlinear Science and Numerical Simulation
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