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物理信息神经网络的一种自适应配置点算法
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作者 张凌海 周彬 +1 位作者 罗毅 冯俊 《力学学报》 EI CAS CSCD 北大核心 2024年第10期3069-3083,共15页
物理信息神经网络(PINN)能够将方程模型融入到损失最小化训练中,能同时学习输入数据分布和物理规律,大多数PINN是通过均匀采样配置点来覆盖整个求解区域,且各个配置点间都同等发挥作用,其配置点策略简便易行,但也使得PINN增加了部分不... 物理信息神经网络(PINN)能够将方程模型融入到损失最小化训练中,能同时学习输入数据分布和物理规律,大多数PINN是通过均匀采样配置点来覆盖整个求解区域,且各个配置点间都同等发挥作用,其配置点策略简便易行,但也使得PINN增加了部分不必要的配置点,且对部分复杂规律的学习能力不足.文章提出一种配置点自适应设置策略,以提高PINN学习能力和学习效率.首先通过损失函数残差及梯度联合分布确定配置点选择概率,同时在迭代一定次数后进行重采样,避免过早陷入局部最优,这样可以使一部分配置点分布在损失较高或变化较明显处,从而改善配置点的分布情况,达到以较少的配置点也能准确反映方程模型的效果,提升学习效率;其次引入配置点的变权重设定,使每个配置点对方程残差的影响有所侧重,在网络迭代训练中自动提高损失值较高部分配置点的权重,从而使PINN更专注于损失较大的部分,即复杂规律的学习.最后通过Burgers方程、Schrodinger方程、Helmholtz方程和Navier-Stokes方程4种典型算例与传统PINN及其各种改进方法进行比较实验.数值结果表明,该算法可以在较少的配置点数量和迭代次数设定下,有效提升求解精度和计算效率. 展开更多
关键词 物理信息神经网络 梯度分布 自适应权重 配置点分布 方程残差
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Standing Wave Solutions in Nonhomogeneous Delayed Synaptically Coupled Neuronal Networks
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作者 zhang linghai STONER Melissa Anne 《Journal of Partial Differential Equations》 2012年第4期295-329,共35页
The authors establish the existence and stability of standing wave solutions of a nonlinear singularly perturbed system of integral differential equations and a non- linear scalar integral differential equation. It wi... The authors establish the existence and stability of standing wave solutions of a nonlinear singularly perturbed system of integral differential equations and a non- linear scalar integral differential equation. It will be shown that there exist six standing wave solutions ((u(x,t),w(x,t)) = (U(x),W(x)) to the nonlinear singularly perturbed system of integral differential equations. Similarly, there exist six standing wave so- lutions u(x,t) = U(x) to the nonlinear scalar integral differential equation. The main idea to establish the stability is to construct Evans functions corresponding to several associated eigenvalue problems. 展开更多
关键词 Nonhomogeneous synaptically coupled neuronal networks standing wave solu-tions EXISTENCE STABILITY eigenvalue problems Evans functions.
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UNIFORM STABILITY AND ASYMPTOTIC BEHAVIOR OF SOLUTIONS OF 2-DIMENSIONAL MAGNETOHYDRODYNAMICS EQUATIONS
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作者 zhang linghai 《Chinese Annals of Mathematics,Series B》 SCIE CSCD 1998年第1期35-58,共24页
This paper is concerned with uniform stability and asymptotic behavior for solutions of 2-dimensional Magnetohydrodynamics equations. The author establishes the corresponding temporal decay estimates when the initial ... This paper is concerned with uniform stability and asymptotic behavior for solutions of 2-dimensional Magnetohydrodynamics equations. The author establishes the corresponding temporal decay estimates when the initial data is in the following Sobolev spaces H 2, L 1∩H 2 with ∫(u 0, A 0)dx≠0, or L 1∩H 2 with ∫(u 0, A 0)dx=0, respectively. Most of the decay rates in these estimates are optimal. Moreover, the author proves various uniform stability results, like sup t>0 ‖(w, E, r)(t))‖ YC‖(w 0, E 0)‖ X, where X and Y are Sobolev spaces. It should be pointed out that the decay estimates of the solutions for the case (u 0, A 0)∈L 1∩H 2 follow from the uniform stability estimates. The author utilizes the Fourier splitting method invented by Professor Schonbek and the new elaborate global energy estimates. 展开更多
关键词 Uniform stability Asymptotic behavior Magnetohydrodynamics equations Fourier transform Energy estimates
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