Permanence of population growth models with impulsive effects

This paper establishes criteria for permanence of populations which undergo impulsive effects at fixed times between intervals of continuous evolution governed by a differential system. It is also shown that suitable impulses may prevent the extinction or unbounded growth of populations whose evolutions are otherwise governed solely by a differential system. Examples are provided to demonstrate the application of the results obtained.     

Essential extensions, excellent extensions and finitely presented dimension

In Section 1 of this paper, we investigate the finitely presented dimension of an essential extension for a module, and obtain results concerning an essential extension of a torsion-free module. We partially answer the question: When is an essential extension of a finitely presented module (an almost finitely presented module) also finitely presented (almost finitely presented)? In Section 2, we study theC-excellent extensions and the finitely presented dimensions. We obtain some results on the homological dimensions of matrix rings and group rings.     

Microscopic derivation of a Markovian Master equation in a deterministic model of chemical reaction

We consider a (deterministic, conservative) one-dimensional system of colored hard points, changing color each time they hit one another with a relative velocity above a threshold. In the limit of rare reactions, theN-particle color distribution follows a Markovian birth-and-death process. Using the reaction rate as an intrinsic time scale, we also obtain the reaction-diffusion equation for a test particle in this hydrodynamic limit. Explicit results are given for a discrete and a Maxwellian velocity distribution.     

Minkowski-Bouligand dimension of solutions of the one-dimensional p-Laplacian

The upper Minkowski-Bouligand dimension of the graph of continuous solutions, denoted by dim_My, is studied for a class of nonlinear one-dimensional p-Laplacian. Some sufficient conditions on the nonlinearities are given such that dim_My takes the prescribed fractional values. Next, a relation between dim_My and the order of growth for singular behaviour of L^p norm of derivatives of solutions is given. Finally, the change and stability of dim_My are considered by means of a double-parametric problem.     

NEW CRITERIA OF EXPONENTIAL STABILITY FOR BAM NEURAL NETWORKS WITH DELAYS

In this Letter,a novel Lyapunov functional is constructed to investigate the exponential stability of the BAM neural networks.New sufficient conditions of the uniqueness and global exponential stability for the equilibrium of BAM neural networks with delays are obtained.The results improve those existing ones.     

绝对稳定性的新频率准则

本文考虑具有多个非线性元素的控制系统的绝对稳定性问题。得出了Ｌｕｒｉｅ型Ｌｙａｐｕｎｏｖ函数存在的充要条件，并由此引导出绝对稳定性的新频率准则，它改进了文献［１］，［２］中的新近结果。     

Technical Stability of Nonstationary Automatic-Control Systems with Variable Structure

Sufficient conditions of technical stability in measure are established for nonstationary automatic-control systems with variable structure and logic control laws dependent on the mismatch error and its derivatives of finite order for all admissible initial perturbations from a predefined measurable set of initial perturbations. The associated systems of differential equations contain time-dependent coefficients. The logic control laws are described by a variable jump control function of the mismatch coordinate and its derivatives of finite order that is no higher than that of the initial system of equations. Using a signal and its derivatives for control increases the quality of discontinuous control. The relationship between the eigenvalues of the quadratic forms of the corresponding Liapunov functions and the criteria of technical stability is revealed. The general results are applied to a variable-structure system of the third order     

Construction of recurrent bivariate fractal interpolation surfaces and computation of their box-counting dimension

Recurrent bivariate fractal interpolation surfaces (RBFISs) generalise the notion of affine fractal interpolation surfaces (FISs) in that the iterated system of transformations used to construct such a surface is non-affine. The resulting limit surface is therefore no longer self-affine nor self-similar. Exact values for the box-counting dimension of the RBFISs are obtained. Finally, a methodology to approximate any natural surface using RBFISs is outlined.     

A noniterative algebraic solution for Riccati equations satisfying two-point boundary-value problems

A noniterative algebraic method is presented for solving differential Riccati equations which satisfy two-point boundary-value problems. This class of numerical problems arises in quadratic optimization problems where the cost functionals are composed of both continuous and discrete state penalties, leading to piecewise periodic feedback gains. The necessary condition defining the solution for the two-point boundary value problem is cast in the form of a discrete-time algebraic Riccati equation, by using a formal representation for the solution of the differential Riccati equation. A numerical example is presented which demonstrates the validity of the approach.The authors would like to thank Dr. Fernando Incertis, IBM Madrid Scientific Center, who reviewed this paper and pointed out that the two-point boundary-value necessary condition could be manipulated into the form of a discrete-time Riccati equation. His novel approach proved to be superior to the authors' previously proposed iterative continuation method.