Oscillation of second-order elliptic equations with damping terms

Some oscillation criteria are given for the second-order elliptic differential equation with damping terms

     

Some elliptic problems with singular natural growth lower order terms

In this paper we deal with a nonlinear elliptic problem, whose model is

     

On some elliptic optimal control problems with state constraints

In this paper optimality conditions will be derived for elliptic optimal control problems with a restriction on the state or on the gradient of the state. Essential tools are the method of transposition and generalized trace theorems and green's formulas from the theory of elliptic differential equations.     

Cubic analogues of the Jacobian theta functions and the Jacobian elliptic functions

In this paper, the Jacobian theta functions, the Jacobian elliptic functions, and their cubic analogues are introduced. Then, the properties satisfied the cubic analogues are discussed.     

First-order partial differential equations with large high-frequency terms

Systems of first-order semilinear partial differential equations with terms that oscillate at a frequency ω ? 1 in a single variable and are proportional to \(\sqrt \omega \) are considered. The Krylov-Bogolyubov-Mitropol’skii averaging method is substantiated for such equations. Based on the two-scale expansion method, an algorithm for constructing complete asymptotics of solutions is proposed and justified.     

On the comparison principle for unbounded solutions of elliptic equations with first order terms

We prove a comparison principle for unbounded weak sub/super solutions of the equation

$\lambda u?\text{div}(A(x)Du)=H(x,Du)\text{ in }\mathrm{\Omega }$

where $A(x)$ is a bounded coercive matrix with measurable ingredients, $\lambda \ge 0$ and $\xi ?H(x,\xi )$ has a super linear growth and is convex at infinity. We improve earlier results where the convexity of $H(x,?)$ was required to hold globally.     

Some reformulated properties of Jacobian elliptic functions

Various properties of Jacobian elliptic functions can be put in a form that remains valid under permutation of the first three of the letters c, d, n, and s that are used in pairs to name the functions. In most cases 12 formulas are thereby replaced by three: one for the three names that end in s, one for the three that begin with s, and one for the six that do not involve s. The properties thus unified in the present paper are linear relations between squared functions (16 relations being replaced by five), differential equations, and indefinite integrals of odd powers of a single function. In the last case the unification entails the elementary function RC(x,y)=RF(x,y,y), where RF(x,y,z) is the symmetric elliptic integral of the first kind. Explicit expressions in terms of RC are given for integrals of first and third powers, and alternative expressions are given with RC replaced by inverse circular, inverse hyperbolic, or logarithmic functions. Three recurrence relations for integrals of odd powers hold also for integrals of even powers.     

Systems of reaction–convection–diffusion equations invariant under Galilean algebras

Systems, which are invariant under Galilean algebras (with and without mass operator), and their main extensions by operators of scale and projective transformations are selected from a class of systems of reaction–convection–diffusion equations for two-dimensional vector field with one space variable.     

Stability of discontinuous differential equations with finite number of retarded terms by lyapunov functions

We consider here a class of second-order discontinuous differential equations with a finite number of nterms with retarded arguments; using lyapunov-type functions we prove, under suitable conditions, that the zero solutions of these Equations are globally uniformly asympototically stable.     

Branches of positive and free boundary solutions for some singular quasilinear elliptic problems

We study the existence and multiplicity of solutions, strictly positive or nonnegative having a free boundary (the boundary of the set where the solution vanishes) of some one-dimensional quasilinear problems of eigenvalue type with possibly singular nonlinear terms.     

On elliptic solutions of nonlinear ordinary differential equations

The problem of constructing and classifying exact elliptic solutions of autonomous nonlinear ordinary differential equations is studied. An algorithm for finding elliptic solutions in explicit form is presented.     

A Fully Nonlinear Boundary value Problem for the Laplace Equation in Dimension Two

We study the regularity up to the boundary of solutions to the boundary value problem:[math001] in D, ∣?u∣= g on &;pardD, where D is the unit disc. This problem finds its application in the study of geophysical and geomagnetic surveys. If g?C^,[math001](D) and is strictly positive, we prove that uis in the Holder class C1,α(D). An example shows that this is no longer true if g has some zeroes on ?D. In this case u isproved to be of class C¹(D)     

On the zeros of polynomials of Jacobian elliptic functions

An estimate of the number of zeros of the function F(r)=P(r, sn r), where P(X, Y) C[X,Y], and sn z is the Jacobian elliptic function, is obtained.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 44, No. 11, p. 1624, November, 1992.     

An iterative method for the solution of some semilinear elliptic systems with discontinuities

We present a general iterative method which can be used, in particular, to find solutions of a kind of semilinear elliptic system with discontinuities. The algorithm is obtained by adapting some ideas which have been previously introduced by C. Moreno and the second author in the framework of a single equation. More precisely, it relies on fixed-point reformulation and exact regularization. A convergence result is proven under quite general assumptions.     

非线性脉冲时滞抛物型偏微分方程的强迫振动性

考虑一类具强迫项的非线性脉冲时滞抛物型偏微分方程，利用脉冲时滞微分不等式，获得了该类方程的解强迫振动的若干充分判据。     

含分布滞量的非线性双曲偏微分方程组解的振动性

研究了一类具有连续分布时滞变量的非线性双曲型偏微分方程组解的振动性.获得了该方程组在Robin边值条件和Dircichlet边值条件下解振动的充分条件.