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1.
本文结合梯度讨论了椭球面上一类最速降线问题 ,应用变分法及 Mathematica软件讨论了椭球面上最短路径问题 ;分析了二者的关系 ,旨在加强应用数学知识的能力 .  相似文献   

2.
对文献[1-3]中的结果:ut= div(|▽u|p-2▽u)在ΩT=Ω×(0,T)上弱解的空间梯度是H?lder连续的做一个补充.在这个注记里,讨论了条件p>max{1,2N/N+2}是怎样由u的性质所决定的.属于LNlocT)空间解的梯度是H?lder连续的条件仅仅是p>1.  相似文献   

3.
一种修正的HS共轭梯度法及全局收敛性   总被引:2,自引:0,他引:2  
<正>1引言考虑无约束极小化问题:(?),(1)其中f(x)连续可微,其梯度函数用g(x)表示.共轭梯度法求解(1)的常用迭代格式为:x_(k+1)=x_k+α_kd_k,(2)(?)(3)其中g_k=▽f(x_k),α_k≥0是由某种线搜索得到的步长因子;d_k为搜索方向,β_k为标量,β_k的不同选择产生了不同的共轭梯度法.著名的β_k公式有:  相似文献   

4.
近期的实验和分子动力学模拟均表明:圆锥面上粘附液滴能自发地定向运动,且自发定向运动的方向与粘附面的亲水、疏水性质无关.针对这一重要现象,拟从曲面微纳米力学几何化的角度,提供一般性的理论解释.借助于粒子对势,研究了孤立粒子与微纳米硬曲面之间的相互作用,分析了粒子/硬曲面相互作用的几何学基础.可以证实:(a)粒子/硬曲面的作用势均具有统一的曲率化形式,均可以统一地表达成曲面平均曲率和Gauss曲率的函数;(b)基于曲率化的作用势,能够实现曲面微纳米力学的几何化;(c)曲率与曲率的内蕴梯度构成卷曲空间上的驱动力;(d)驱动力方向与曲面的亲水、疏水性质无关,解释了自发定向运动实验.  相似文献   

5.
一个改进的记忆梯度法   总被引:1,自引:0,他引:1  
  相似文献   

6.
7.
研究了任意梯度变化的变厚度各向异性转动圆盘的弹性问题.假设圆盘绕刚性轴匀速转动,其材料性能和厚度沿径向任意梯度变化.考虑圆盘在中心转轴处受位移约束,外侧自由,根据各向异性转动圆盘的平衡微分方程,得到关于径向应力的Fredholm积分方程,继而通过对Fredholm积分方程进行数值求解,得到结构的位移场和应力场.对具体梯度变化情况仅需代入相应梯度变化进行求解即可.数值算例部分,通过假设厚度、弹性模量等参数为特殊的幂函数形式,将由Fredholm积分方程求出的数值解与对应的精确解进行对比,以及针对常见的Voigt模型,将由该方法算得的数值解和ANSYS有限元计算结果进行对比,验证了该方法的准确性和精度.其次,针对Voigt模型,重点分析了厚度变化、材料性能梯度参数、各向异性度等对应力场和位移场的影响.提出了针对材料性能和厚度沿径向呈任意梯度变化的圆盘结构弹性分析方法,将为优化功能梯度圆盘的结构和材料参数、有效调整构件应力分布、提高结构安全性,提供强有力的工具;算例分析结果对功能梯度圆盘在复杂条件下的结构安全设计有重要的理论指导意义.  相似文献   

8.
梯度投影法已有许多有效算法,但这些算法还存在三个问题:1)为了保证算法的收敛性,在算法的每一迭代步,需要选取δ-主动约束集,计算量较大.2)在迭代过程中,需要跟踪主动约束集.3)只能处理非线性不等式约束问题.本文讨论非线性等式与不等式约束的优化问题,给出了一个广义梯度投影法,证明了算法的收敛性并且完满地解决了上述三个问题.本文算法结构简单且其处理技巧有普遍意义.  相似文献   

9.
指数型功能梯度材料平面问题热应力通解   总被引:3,自引:2,他引:1  
研究了功能梯度材料平面问题的热应力场,首先引入热弹性位移势函数,得到温度场的应力解;然后引入Airy应力函数,通过求解功能梯度材料平面问题的基本方程,得到不考虑温度时的应力,叠加后得到平面问题的热应力通解.  相似文献   

10.
吴占鹏.秩协方差分析及应用.数理统计与管理,1998,17(3),7~10.在随机区组试验中,区组内往往存在土壤梯度差异,使试验误差增大。为此,本文提出秩协方差分析方法,即把土壤差异εij分解成Δ·xij和δij两个成份,从中剔除土壤梯度差异Δ·xij对试验精度的影响,以提高试验结果的可靠性  相似文献   

11.
In this paper, the problems of exponential convergence and the exponential stability of the periodic solution for a general class of non-autonomous competitive–cooperative neural networks are analyzed via the decomposition approach. The idea is to divide the connection weights into inhibitory or excitatory types and thereby to embed a competitive–cooperative delayed neural network into an augmented cooperative delay system through a symmetric transformation. Some simple necessary and sufficient conditions are derived to ensure the componentwise exponential convergence and the exponential stability of the periodic solution of the considered neural networks. These results generalize and improve the previous works, and they are easy to check and apply in practice.  相似文献   

12.
This paper studies approximation capability to L2(Rd) functions of incremental constructive feedforward neural networks(FNN) with random hidden units.Two kinds of therelayered feedforward neural networks are considered:radial basis function(RBF) neural networks and translation and dilation invariant(TDI) neural networks.In comparison with conventional methods that existence approach is mainly used in approximation theories for neural networks,we follow a constructive approach to prove that one may simply randomly choose parameters of hidden units and then adjust the weights between the hidden units and the output unit to make the neural network approximate any function in L2(Rd) to any accuracy.Our result shows given any non-zero activation function g :R+→R and g(x Rd) ∈ L2(Rd) for RBF hidden units,or any non-zero activation function g(x) ∈ L2(Rd) for TDI hidden units,the incremental network function fn with randomly generated hidden units converges to any target function in L2(Rd) with probability one as the number of hidden units n→∞,if one only properly adjusts the weights between the hidden units and output unit.  相似文献   

13.
In this paper, exponential synchronization for hybrid multi-weighted complex networks is studied via aperiodically intermittent control. Different from previous work, both Markov jump and reaction-diffusion effects are simultaneously considered into multi-weighted complex networks. By employing network split technique, graph theory, and Lyapunov method, several synchronization criteria are derived. These criteria show the effects of multiple weights, Markov jump, and reaction-diffusion on exponential synchronization. Furthermore, an application to Cohen–Grossberg neural networks is conducted, and the corresponding synchronization criterion is given. Finally, some numerical simulations are presented to show the effectiveness of the obtained theoretical results.  相似文献   

14.
本文研究了CohenGrossberg神经网络模型的指数稳定性.为避免构造Lyapunov函数的困难,我们采用广义相对Dalquist数方法来分析神经网络的稳定性.借助这一方法,我们不但得到了CohenGrossberg神经网络模型平衡解的存在性、唯一性和全局指数稳定性的新的充分条件,而且给出了神经网络的指数衰减估计.所获结论改进了已有文献的相关结果.  相似文献   

15.
连续型BAM神经网络的指数稳定性   总被引:1,自引:0,他引:1  
首先将连续型双向联想记忆神经网络转化成一个特殊的Hopfield网络模型.在此基础上,对连续BAM神经网络的指数稳定性进行了新的分析,证明了神经网络连接权矩阵在给定的约束条件下有唯一平衡点.所做的分析可以用于设计全局指数稳定的神经网络.  相似文献   

16.
This note examines issues concerning global exponential convergence of neural networks with unbounded distributed delays. Sufficient conditions are derived by exploiting exponentially fading memory property of delay kernel functions. The method is based on comparison principle of delay differential equations and does not need the construction of any Lyapunov functionals. It is simple yet effective in deriving less conservative exponential convergence conditions and more detailed componentwise decay estimates. The results of this note and [Chu T. An exponential convergence estimate for analog neural networks with delay. Phys Lett A 2001;283:113–8] suggest a class of neural networks whose globally exponentially convergent dynamics is completely insensitive to a wide range of time delays from arbitrary bounded discrete type to certain unbounded distributed type. This is of practical interest in designing fast and reliable neural circuits. Finally, an open question is raised on the nature of delay kernels for attaining exponential convergence in an unbounded distributed delayed neural network.  相似文献   

17.
We propose two new approaches to the construction of artificial neural networks: a Fourier neural network and a binary neural network. A distinctive feature of the approaches proposed is the availability of simple, linear, single-step learning algorithms, which enables one to apply them to the construction of networks with a fairly large number of neurons and weights.  相似文献   

18.
When modeling neural networks in a real world, not only diffusion effect and fuzziness cannot be avoided, but also self-inhibitions, interconnection weights, and inputs should vary as time varies. In this paper, we discuss the dynamical behaviors of delayed reaction–diffusion fuzzy cellular neural networks with varying periodic self-inhibitions, interconnection weights as well as inputs. By using Halanay’s delay differential inequality, MM-matrix theory and analytic methods, some new sufficient conditions are obtained to ensure the existence, uniqueness, and global exponential stability of the periodic solution, and the exponentially convergent rate index is also estimated. In particular, the traditional assumption on the differentiability of the time-varying delays is no longer needed. The methodology developed in this paper is shown to be simple and effective for the exponential periodicity and stability analysis of neural networks with time-varying delays. Two examples are given to show the usefulness of the obtained results that are less restrictive than recently known criteria.  相似文献   

19.
The purpose of this paper is to investigate the robust exponential stability of discrete‐time uncertain impulsive neural networks with time‐varying delay. By using Lyapunov functions together with Razumikhin technique, some new robust exponential stability criteria are presented. The obtained results show that the robust stability can be retained under certain impulsive perturbations for the neural network, which has the robust stability property. The obtained results also show that impulses can robustly stabilize the neural network, which does not have the robust stability property. Some examples, together with their simulations, are also given to show the effectiveness and the advantage of the presented results. It should be noted that the impulsive robust exponential stabilization result for discrete‐time neural network with time‐varying delay is given for the first time. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

20.
In this paper, we study the global exponential stability of fuzzy cellular neural networks with delays and reaction–diffusion terms. By constructing a suitable Lyapunov functional and utilizing some inequality techniques, we obtain a sufficient condition for the uniqueness and global exponential stability of the equilibrium solution for a class of fuzzy cellular neural networks with delays and reaction–diffusion terms. The result imposes constraint conditions on the network parameters independently of the delay parameter. The result is also easy to check and plays an important role in the design and application of globally exponentially stable fuzzy neural circuits.  相似文献   

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