具有时滞的一般型脉冲神经网络的指数稳定性

讨论具有时滞的一般性脉冲神经网络的稳定性.在不假定激励函数有界或可导的前提下,利用非光滑分析和Lyapunov泛函,得到了这类神经网络系统平衡点的存在唯一性和全局指数稳定性判别准则.作为特例,得到了Hopfield神经网络,时滞细胞神经网络,双向联想记忆神经网络的平衡点的存在唯一性和全局指数稳定性判定定理.     

含脉冲的Hopfield神经网络的全局指数稳定性

研究了一类含脉冲的Hopfield神经网络的全局指数稳定性.利用同胚映射理论、Lyapunov函数思想和不等式技巧,给出了平衡点的存在唯一性和全局指数稳定性的新的判别准则.     

一类变时滞Cohen-Grossberg神经网络的全局指数稳定性

研究了一类具变时滞的C ohen-Grossberg神经网络的全局指数稳定性.利用同胚映射理论、Lya-punov函数思想和不等式技巧,给出了平衡点存在唯一性和全局指数稳定性的新的判别准则.     

带有比例时滞的复值神经网络全局指数稳定性

研究了带有比例时滞的复值神经网络全局指数稳定性问题.借助向量Lyapunov函数思想和同胚映射原理,并使用M-矩阵理论和不等式技巧,建立了网络平衡点存在性、唯一性和全局指数稳定性的判定条件.     

具有扩散影响的Hopfield型神经网络的全局渐近稳定性

对具有扩散影响的Hopfield型神经网络平衡点的存在唯一性和全局渐近稳定性进行了研究.在激活函数单调非减、可微且关联矩阵和Liapunov对角稳定矩阵有关时,利用拓扑度理论得到了系统平衡点存在的充分条件.通过构造适当的平均Liapunov函数,分析了系统平衡点的全局渐近稳定性.所得结论表明系统的平衡点(如果存在)是全局渐近稳定的而且也蕴含着系统的平衡点的唯一性.     

Ivlev型捕食系统的全局动力学分析

研究捕食者与食饵均具有线性密度制约的Ivlev型捕食动力系统.应用常微分方程定性方法,得到了正平衡点的全局稳定性和非小振幅极限环的存在唯一性的充分条件.特别地,在一定条件下,证明了极限环的存在唯一性与正平衡点的局部不稳定性是等价的,正平衡点的局部稳定性隐含它的全局稳定性,因此,系统的全局动力学性质完全由正平衡点的局部性质所决定.     

具有时滞的细胞神经网络的全局指数稳定性

利用Liapunov函数方法,结合积分不等式技巧,分析了时滞细胞神经网络的平衡点存在的唯一性和全局指数稳定性,保证时滞细胞神经网络全局指数稳定的一个新的充分判据被得到.所得判据比已有文献具有更少的限制,为实际应用提供了方便.     

时滞切换神经网络系统的鲁棒指数稳定性

研究了具有时间滞后切换不确定细胞神经网络(UCNNs)系统的指数稳定性.利用同胚映射和M矩阵理论,得到UCNNs系统平衡点存在性,唯一性和指数稳定性的充分条件;利用平均驻留时间方法,研究了时滞切换UCNNs系统限制切换下的鲁棒指数稳定性,并得到确保系统全局指数稳定的充分条件.     

带有时滞的Clifford值神经网络的全局指数稳定性

研究了带有离散时滞和分布时滞的Clifford值递归神经网络的全局指数稳定性问题.首先运用M矩阵的性质和不等式技巧证明了Clifford值递归神经网络平衡点的存在性和唯一性;然后通过数学分析方法,得到了Clifford值递归神经网络全局指数稳定的判定条件;最后数值仿真例子验证了获得结果的有效性.     

Caputo分数阶时滞细胞神经网络的稳定性分析

研究了一类Caputo分数阶时滞细胞神经网络模型的稳定性.通过利用分数阶微积分中的常数变分法,得到了Caputo分数阶时滞细胞神经网络解的差分形式,推导出模型的有界解和平衡点的存在性与唯一性,最后证明了神经网络的全局指数稳定性.     

横观各向同性多孔超弹性矩形板的单向拉伸

利用横观各向同性超弹性材料的广义neo-Hookean应变能函数研究了含有多个微孔的超弹性矩形板在单向拉伸作用下的有限变形和受力分析．给出了含有某种对称性分布的多个微孔的矩形板的变形模式，通过求解该变形模式满足的微分方程，将它用两个参数表示出来．可应用最小势能原理导出变分近似解，从而得到矩形板的变形和应力分布的解析解．分析了板中微孔的增长及微孔边缘应力的分布情况，讨论了板的各向异性程度及微孔的大小和孔间距离的影响，得刭了单个、三个及五个微孔板中微孔的增长变形和孔边应力分布的一些基本规律规律，并进行了相互比较．     

Interpolation by neural network operators activated by ramp functions

In this paper, a family of interpolation neural network operators are introduced. Here, ramp functions as well as sigmoidal functions generated by central B-splines are considered as activation functions. The interpolation properties of these operators are proved, together with a uniform approximation theorem with order, for continuous functions defined on bounded intervals. The relations with the theory of neural networks and with the theory of the generalized sampling operators are discussed.     

On second-order periodic elliptic operators in divergence form

We consider second-order, strongly elliptic, operators with complex coefficients in divergence form on . We assume that the coefficients are all periodic with a common period. If the coefficients are continuous we derive Gaussian bounds, with the correct small and large time asymptotic behaviour, on the heat kernel and all its H?lder derivatives. Moreover, we show that the first-order Riesz transforms are bounded on the -spaces with . Secondly if the coefficients are H?lder continuous we prove that the first-order derivatives of the kernel satisfy good Gaussian bounds. Then we establish that the second-order derivatives exist and satisfy good bounds if, and only if, the coefficients are divergence-free or if, and only if, the second-order Riesz transforms are bounded. Finally if the third-order derivatives exist with good bounds then the coefficients must be constant. Received in final form: 28 February 2000 / Published online: 17 May 2001     

Response of multiwall carbon nanotubes to impact loading

Dynamic behaviors of multiwall carbon nanotubes (MWCNTs) with finite length are investigated using an analytical method. Multiple elastic shells and linearized model of van der Waals forces are used for development a comprehensive continuum dynamic model of MWCNTs. By applying Laplace transform, analytical solution for thin and thick MWCNTs under dynamic loading are obtained. Dynamic responses of 3-, 9-, and 11-layer MWCNTs under external pressure shock are examined and accuracy of results are verified by comparison the results with those obtained by numerical methods. Both displacement and stress analysis are performed for layers of MWCNTs and frequencies of oscillations are obtained. Also, effects of axial wave created by external pressure shock are studied in MWCNTs with two-dimensional analyses. Dynamic responses of MWCNTs with initial axial displacement are also proposed and the propagation of the axial wave through the length of tubes is illustrated. Furthermore, wave propagation velocity is found by analysis of time history diagram.     

一个新锥模型信赖域算法

1引言本文考虑的无约束最优化问题为(?)f(x),(1.1)其中f(x)为连续可微函数.解此问题的很多算法一般都采用二次函数模型去逼近f(x) ([10],[15]).对于一些非二次性态强、曲率变化剧烈的函数,用二次函数模型去逼近可能效果不好,因此Davidon于1980年首次提出了解无约束优化问题的锥模型方法.锥模型是二次模型的推广,比二次函数具有更多的自由度,因此期望能够更充分地逼近原函数.对于一些在极小点附近很不对称,或曲率变化剧烈的函数,或在某个区域内变化大的函数,全部或部分用锥模型去逼近的效果可能好于用二次模型去逼近.     

Shape preserving polynomial curves

We introduce particular systems of functions and study the properties of the associated Bézier-type curve for families of data points in the real affine space. The systems of functions are defined with the help of some linear and positive operators, which have specific properties: total positivity, nullity diminishing property and which are similar to the Bernstein polynomial operator. When the operators are polynomial, the curves are polynomial and their degrees are independent of the number of data points. Examples built with classical polynomial operators give algebraic curves written with the Jacobi polynomials, and trigonometric curves if the first and the last data points are identical.     

Pulse and constant control schemes for epidemic models with seasonality

Control schemes for infectious disease models with time-varying contact rate are analyzed. First, time-constant control schemes are introduced and studied. Specifically, a constant treatment scheme for the infected is applied to a SIR model with time-varying contact rate, which is modelled by a switching parameter. Two variations of this model are considered: one with waning immunity and one with progressive immunity. Easily verifiable conditions on the basic reproduction number of the infectious disease are established which ensure disease eradication under these constant control strategies. Pulse control schemes for epidemic models with time-varying contact rates are also studied in detail. Both pulse vaccination and pulse treatment models are applied to a SIR model with time-varying contact rate. Further, a vaccine failure model as well as a model with a reduced infective class are considered with pulse control schemes. Again, easily verifiable conditions on the basic reproduction number are developed which guarantee disease eradication. Some simulations are given to illustrate the threshold theorems developed.     

Comparative study of cable parallel manipulators with and without hybrid-driven planar five-bar mechanism

Cable parallel manipulators (CPMs) relay on cables instead of rigid links to support and manipulate the end-effector. The CPMs are required not only for operations with lower inertia and high payload, but also for output with greater flexibility. The paper is devoted to present and analyze a cable parallel manipulator with and without hybrid-driven planar five-bar mechanism (HDPM). The cable parallel manipulator with the HDPM combines positive features of both the cable parallel manipulator and the HDPM. Comparative study of kinematics and dynamics of the CPMs with and without HDPM are studied. Drive torques and drive powers are given to compare the load carrying capacity of the two manipulators, and workspace, stiffness performance, singularity analysis are also carried out. Simulation examples are presented to demonstrate the CPMs with and without HDPM and their mechanics performance.     

The systems approach and fuzzy set theory bridging the gap between mathematical and language-oriented economists

Ideas are presented to show how fuzzy mathematics can be applied in macro-economics in combination with the systems approach in order to bridge the gap between mathematical and language-oriented economists.Two reasons are given.From a mathematical point of view, fuzzy sets, fuzzy relations and fuzzy logic are not fuzzy at all. They are all well defined, but tend to be more complicated than traditional, mathematical concepts used in economics.From a language-oriented economist's point of view, fuzzy sets, etc. are used to express mathematically the type of concepts which are typical in language and most valuable in dealing with complex systems like an economy.The paper deals with economics in general terms, but examples are provided to illustrate the ideas.     

Permutation Tests for Multivariate Location Problems

The paper presents some permutation test procedures for multivariate location. The tests are based on projected univariate versions of multivariate data. For one-sample cases, the tests are affine invariant and strictly distribution-free for the symmetric null distribution with elliptical direction and their permutation counterparts are conditionally distribution-free when the underlying null distribution of the sample is angularly symmetric. For multi-sample cases, the tests are also affine invariant and permutation counterparts of the tests are conditionally distribution-free for any null distribution with certain continuity. Hence all of the tests in this paper are exactly valid. Furthermore, the equivalence, in the large sample sense, between the tests and their permutation counterparts are established. The power behavior of the tests and of their permutation counterparts under local alternative are investigated. A simulation study shows the tests to perform well compared with some existing tests in the literature, particularly when the underlying null distribution is symmetric whether light-tailed or heavy-tailed. For revealing the influence of data sparseness on the effect of the test, some simulations with different dimensions are also performed.