非线性期望和非线性估价的次可加性

证明了在适当的条件下F-期望的次可加性蕴涵条件F-期望的次可加性,F-估价的次可加性蕴涵Ft-相容非线性估价的次可加性.     

带非线性边界条件的非线性抛物型方程组

本文讨论带非线性边界条件的抛物型方程组ｕｔ＝Δｕｍ，ｖｔ＝Δｖｍ，ｘ∈Ω，ｔ＞０，ｕｎ＝ｖｐ，ｖｎ＝ｕｑ，ｘ∈Ω，ｔ＞０，ｕ（ｘ，０）＝ｕ０（ｘ）δ＞０，ｖ（ｘ，０）＝ｖ０（ｘ）δ＞０，ｘ∈Ω（Ｉ）解的整体存在性和在有限时刻爆破问题．其中ｍ，ｐ，ｑ＞０，ΩＩＲＮ是有界光滑区域，δ＞０可以充分小．     

Nonlinear Feedback Shift Registers via Nonlinear Evolution

Methods for the forward and exact inverse computation of digital data are developed using reversible fully discrete nonlinear evolution equations. Some elementary examples are presented. A special case of the evolution equation presented here reduces to well‐known linear feedback shift registers (LFSRs). LFSRs and various nonlinear versions (NLFSRs) have been studied and used in a variety of applications.     

Nonlinear Wave Interactions in Nonlinear Nonintegrable Systems

The main goal of this article is to understand the qualitative appearances of regular arrays of pulses that come up in nonintegrable systems in a variety of contexts, particularly in fluid dynamics. It is shown that even nonintegrable systems have a kind of particle dynamics made up of solitary waves. But the interaction of these solitary waves is not absolutely “clean” as in the case of the KdV and other integrable equations.     

Nonlinear Degenerate Parabolic Equation with Nonlinear Boundary Condition

In this paper, we obtain the necessary and sufficient conditions on the global existence of all positive （weak） solutions to a nonlinear degenerate parabolic equation with nonlinear boundary condition.     

Nonlinear viscoelasticity

The equations of state of a nonlinear viscoelastic medium are investigated in the form of functionals in time.Mekhanika Polimerov, Vol. 1, No. 6, pp. 30–39, 1965     

Nonlinear Programming

Journal of the Operational Research Society -     

一类具有两个非线性项的四阶非线性系统的稳定性

利用"类比法"构造了一类四阶非线性系统的Lyapunov函数,给出了该系统零解稳定性的充分条件.     

求解非线性不适定问题的隐式迭代法

将处理线性不适定算子方程的隐式迭代法推广到非线性不适定问题,证明了迭代解误差序列的单调性,并进一步利用迭代误差的单调性得出求解非线性不适定问题隐式迭代法对精确方程和扰动方程的收敛性.     

A Nonlinear Diffusion System with Coupled Nonlinear Boundary Flux

This paper studies a nonlinear diffusion system with coupled nonlinear boundary flux and two kinds of inner sources （positive for the first and negative for the second）, where the four nonlinear mechanisms are described by eight nonlinear parameters. The critical exponent of the system is determined by a complete classification of the eight nonlinear parameters, which is represented via the characteristic algebraic system introduced to the problem.     

带有非线性阻尼项的二阶非线性差分方程的振动性

本文给出了二阶非线性阻尼差分方程△2xn pnφ(xn,△xn) qnf(xn 1)g(△xn)=0,n∈Z 一切解均为振动的若干新的充分条件.     

Nonlinear mechanics of polymers

The most general of all possible nonlinear viscoelastic theories is presented. Various partial and, at the same time, fairly broad cases of nonlinear creep and relaxation theories are described, and their physical interpretation is given. Effective methods are proposed for the solution of nonlinear boundary problems, and the regions of existence and uniqueness are elucidated.M. V. Lomonosov State University, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 12–23, January–February, 1972.     

Observability of Nonlinear Systems

We consider the observability of systems of the form = Ax +Nx, y = Fx, where A is a linear operator and N and F are nonlinear.We show that if the system is linearized about an equilibriumpoint x_e and the linearized system is continuously initiallyobservable, then the nonlinear system is continuously initiallyobservable in some neighbourhood of x_e. We then look at conditionsunder which solutions of the nonlinear system can be extendedfor all time and consider the problem of stabilizing the systemby feedback controls such that the solutions are eventuallyin the observability neighbourhood of x_e. Finally, we applythese ideas to two systems: a wave equation and a diffusionequation with nonlinear perturbations and nonlinear observations.     

Nonlinear Waves of Vorticity

This is a review of solutions of the vorticity equation for two-dimensional flow of an inviscid incompressible fluid that represent nonlinear waves. Geophysical applications are emphasized. Some of the solutions are valid in the beta-plane of Rossby. Some are related to weakly nonlinear perturbations of basic parallel flows and axisymmetric flows, to initial-value problems of hydrodynamic instability and to variational principles of minimal enstrophy or maximal entropy. Some have been found by exploiting well-known ideas of the theory of solitons. In addition to listing known solutions and presenting a synthesis of their relationship to other fluid dynamic results, we report a few new ideas and new solutions for strongly nonlinear waves.     

Nonlinear mechanics of accretion

We formulate a geometric nonlinear theory of the mechanics of accretion. In this theory, the material manifold of an accreting body is represented by a time-dependent Riemannian manifold with a time-independent metric that at each point depends on the state of deformation at that point at its time of attachment to the body, and on the way the new material is added to the body. We study the incompatibilities induced by accretion through the analysis of the material metric and its curvature in relation to the foliated structure of the accreted body. Balance laws are discussed and the initial boundary value problem of accretion is formulated. The particular cases where the growth surface is either fixed or traction-free are studied and some analytical results are provided. We numerically solve several accretion problems and calculate the residual stresses in nonlinear elastic bodies induced from accretion.

     

Nonlinear Methods of Approximation

Abstract. Our main interest in this paper is nonlinear approximation. The basic idea behind nonlinear approximation is that the elements used in the approximation do not come from a fixed linear space but are allowed to depend on the function being approximated. While the scope of this paper is mostly theoretical, we should note that this form of approximation appears in many numerical applications such as adaptive PDE solvers, compression of images and signals, statistical classification, and so on. The standard problem in this regard is the problem of m -term approximation where one fixes a basis and looks to approximate a target function by a linear combination of m terms of the basis. When the basis is a wavelet basis or a basis of other waveforms, then this type of approximation is the starting point for compression algorithms. We are interested in the quantitative aspects of this type of approximation. Namely, we want to understand the properties (usually smoothness) of the function which govern its rate of approximation in some given norm (or metric). We are also interested in stable algorithms for finding good or near best approximations using m terms. Some of our earlier work has introduced and analyzed such algorithms. More recently, there has emerged another more complicated form of nonlinear approximation which we call highly nonlinear approximation. It takes many forms but has the basic ingredient that a basis is replaced by a larger system of functions that is usually redundant. Some types of approximation that fall into this general category are mathematical frames, adaptive pursuit (or greedy algorithms), and adaptive basis selection. Redundancy on the one hand offers much promise for greater efficiency in terms of approximation rate, but on the other hand gives rise to highly nontrivial theoretical and practical problems. With this motivation, our recent work and the current activity focuses on nonlinear approximation both in the classical form of m -term approximation (where several important problems remain unsolved) and in the form of highly nonlinear approximation where a theory is only now emerging.