一类带概率互补约束的随机优化问题的最优性条件

主要讨论了一类带概率互补约束的随机优化问题的最优性条件.首先利用一类非线性互补(NCP)函数将概率互补约束转化成为一个通常的概率约束.然后,利用概率约束的相关理论结果,将其等价地转化成一个带不等式约束的优化问题.最后给出了这类问题的弱驻点和最优解的最优性条件.     

Existence of a solution for a Signorini contact problem for Maxwell-Norton materials

The aim of this article is to study the quasistatic evolutionof a Maxwell–Norton three-dimensional viscoelastic solidwith contact constraints. After introducing the appropiate functionalframework, we will discretize the problem in time using an implicitscheme whose resultant variational inequality is well posed.By using monotonicity arguments together with compensated compactnesstechniques, we will prove that the corresponding discrete solutionconverges to a solution of the continuous problem.     

On a problem with a shift and with the Frankl condition on a segment of the degeneration line for a class of equations of mixed type

We consider the Frankl-Nakhushev problem. By using the maximum principle, we prove the uniqueness of the solution of the problem in the class of Hölder functions, and by using the method of integral equations, in particular, the recently developed method of Wiener-Hopf equations, we prove its existence.     

Nonlocal problem for an equation of mixed type in a domain whose elliptic part is a half-strip

For the Gellerstedt equation, we study a problem with shift in a domain whose elliptic part is an infinite half-strip. By using generalized fractional differentiation operators, we specify a linear combination that relates the value of the solution on characteristics of the equation with the value of the solution and its derivative on the parabolic degeneration line. We prove the unique solvability of this problem.     

离散共振问题的非平凡解

研究了一类二阶非线性差分方程两点边值问题非平凡解的存在性.假设该问题在无穷远点及零点处均是共振的,利用变分方法,同时考虑正、负能量泛函的临界点,在一定的假设条件下,通过临界群的计算,证明了该问题至少存在一个非平凡解.     

Optimal control for a population dynamics with age-dependent and diffusion in a periodic environment

Here we consider the optimal harvesting problem for a periodic age-dependent population dynamics with diffusion. Namely, we investigate the model with periodic vital rates and a periodic forcing term that sustains oscillations. By using Mazur’s theorem, we demonstrate existence of solutions of the optimal control problem and by the conception of normal cone, we also obtain the first order necessary conditions of optimality for the problem. Our results extend some known criteria.     

The existence of solutions for a second-order discrete Neumann problem with a p-Laplacian

In this paper, we investigate the solutions of second-order discrete Neumann boundary value problem with a p-Laplacian. By using critical point theory the existence results are obtained.     

Cauchy problem for a second-order ordinary differential equation with a continual derivative

For a second order linear ordinary differential equation with a continual derivative, we construct a fundamental solution. By using the fundamental solution, we find the solution of the Cauchy problem for the considered equation.     

Two solutions for a discrete problem with a p-Laplacian

In this paper, we investigate the existence of two solutions for second-order discrete Sturm-Liouville boundary value problem with a p-Laplacian. By using critical point theory, the existence of at least two solutions is obtained.     

Mixed problem for a system of fractional partial differential equations

We study a mixed boundary value problem in the general setting for a system of Riemann–Liouville fractional partial differential equations with constant matrix coefficients. By using a system of Volterra integral equations of the second kind, we reduce the problem to a special case for which the solution was earlier constructed in terms of the Green matrix. Existence and uniqueness theorems are proved for the problem in question.     

An approach for solving of a moving boundary problem

In this paper we shall study moving boundary problems, and we introduce an approach for solving a wide range of them by using calculus of variations and optimization. First, we transform the problem equivalently into an optimal control problem by defining an objective function and artificial control functions. By using measure theory, the new problem is modified into one consisting of the minimization of a linear functional over a set of Radon measures; then we obtain an optimal measure which is then approximated by a finite combination of atomic measures and the problem converted to an infinite-dimensional linear programming. We approximate the infinite linear programming to a finite-dimensional linear programming. Then by using the solution of the latter problem we obtain an approximate solution for moving boundary function on specific time. Furthermore, we show the path of moving boundary from initial state to final state.     

一类二阶非线性微分方程多点共振边值问题的可解性

讨论了一类二阶非线性微分方程多点共振边值问题,通过运用Mawhin连续定理,我们在一个较简单的条件下得到了问题的解的存在性结果.     

On a weighted boundary-value problem in an infinite half-strip for a biaxisymmetric Helmholtz equation

We study a boundary-value problem for a generalized biaxisymmetric Helmholtz equation. Boundary conditions in this problem depend on equation parameters. By the method of separation of variables, using the Fourier-Bessel series expansion and the Hankel transform, we prove the unique solvability of the problem and establish explicit formulas for its solution.     

一类带p-Laplacian的Sturm-Liouville型四点边值问题多个正解的存在性

研究了一类带p-Laplacian的四点边值问题.通过运用锥上的不动点定理,我们得到了该类Sturm-Liouville型边值问题三个正解的存在性.     

Global Stability for the Cauchy Problem of a Class of Reaction-diffusion Systems

By using invariant region argument together with Liapunov function technique for ODE, we give under certain circumstances a global stability analysis of the solutions for Cauchy problem of reaction-diffusion systems.     

Flow regulation for water quality restoration in a river section: Modeling and control

This work is devoted to the numerical resolution of an optimal control problem that arises in the management of a reservoir for the remediation of a polluted river section. By using mathematical modeling and optimal control techniques we set the mathematical formulation of the problem (as a hyperbolic optimal control problem with control constraints), and obtain a fully discretized problem. Finally, we propose a gradient-free method to solve it, and present realistic numerical results.     

Periodic solutions to a class of biological diffusion models with hysteresis effect

This paper is concerned with a class of biological models which consists of a nonlinear diffusion equation and a hysteresis operator describing the relationship between some variables of the equations. By the viscosity approach, we show the existence of periodic solutions of the problem under consideration. More precisely, with the help of the subdifferential operator theory and Leray–Schauder theorem, we show the existence of periodic solutions to the approximation problem and then obtain the solution of the original problem by using a passage-to-limit procedure.     

Numerical Computation of Optimal Feed Rates for a Fed-Batch Fermentation Model

In this paper, we consider a model for a fed-batch fermentation process which describes the biosynthesis of penicillin. First, we solve the problem numerically by using a direct shooting method. By discretization of the control variable, we transform the basic optimal control problem to a finite-dimensional nonlinear programming problem, which is solved numerically by a standard SQP method. Contrary to earlier investigations (Luus, 1993), we consider the problem as a free final time problem, thus obtaining an improved value of the penicillin output. The results indicate that the assumption of a continuous control which underlies the discretization scheme seems not to be valid. In a second step, we apply classical optimal control theory to the fed-batch fermentation problem. We derive a boundary-value problem (BVP) with switching conditions, which can be solved numerically by multiple shooting techniques. It turns out that this BVP is sensitive, which is due to the rigid behavior of the specific growth rate functions. By relaxation of the characteristic parameters, we obtain a simpler BVP, which can be solved by using the predicted control structure (Lim et al., 1986). Now, by path continuation methods, the parameters are changed up to the original values. Thus, we obtain a solution which satisfies all first-order and second-order necessary conditions of optimal control theory. The solution is similar to the one obtained by direct methods, but in addition it contains certain very small bang-bang subarcs of the control. Earlier results on the maximal output of penicillin are improved.     

一类奇性边值问题的正解

本文运用锥上的不动点理论和渐近逼近方法,讨论了一类与一阶导函数有关 的二阶奇性泛函边值问题的正解存在性．     

一类具有P-Laplacian算子的非线性分数阶微分方程解的存在性研究

通过构造Green函数的性质,利用Banach不动点定理,研究了一类带有P-Lapalcian算子Caputo型非线性分数阶微分方程的正解问题;并通过构造第二变元的Lipschitz条件,在P-Lapalcian算子参数取不同值的范围下,分别证明了边值问题正解的存在性与唯一性.