On a class of inverse optimal control problems

Four distinct, though closely related, inverse optimal control problems are considered. Given a closed, convex setU in a real Hilbert spaceX and an elementu ₀ inU, it is desired to find all functionals of the form (u,Ru) such that (i)R is a self-adjoint positive operator and (u,Ru) is minimized over the setU at the pointu ₀, (ii)R is self-adjoint, positive definite and (u,Ru) is minimized overU atu ₀, (iv)R is self-adjoint, positive definite and (u,Ru) is uniquely minimized overU atu ₀. The interrelationships among the sets of solutions of these problems are pointed out. Necessary and sufficient conditions which explicitly characterize the solutions to each of these problems are derived. The question of existence of a solution (namely, Given a particular setU and a particular elementu ₀, under what conditions does there exist an operatorR having certain required properties?) is discussed. The results derived are illustrated by an example.     

Two inverse problems of finding a coefficient in a parabolic equation

For a parabolic equation, we consider inverse problems of reconstructing a coefficient that depends on the space variables alone. The first problem is to find a lower-order coefficient c(x) multiplying u(x, t), and the second problem is to find the coefficient a(x) multiplying Δu. As additional information, the integral of the solution with respect to time with some weight function is given. The coefficients of the equation depend both on time and on the space variables. We obtain sufficient conditions for the existence of generalized solutions of our problems; moreover, for the first problem, we also prove uniqueness and construct an iterative sequence that converges to the desired coefficient almost everywhere in the domain. We present examples of input data of these problems for which the assumptions of our theorems are necessarily true.     

On stability of solutions of the coefficient inverse extremal problems for the stationary convection-diffusion equation

The coefficient inverse extremal problems are studied for the stationary convectiondiffusion equation in a bounded domain under mixed boundary conditions on the boundary of the domain. The role of control is played by the velocity vector of a medium and the functions that are involved in the boundary conditions for temperature. The solvability of the extremal problems is proven both for an arbitrary weakly lower semicontinuous quality functional and for the particular quality functionals. On the basis of analysis of the optimality system some sufficient conditions are established on the initial data providing the uniqueness and stability of optimal solutions under sufficiently small perturbations of both the quality functional and one of the functions involved in the original boundary value problem.     

Analytical solutions of a class of optimum orbit modifications

This paper presents the complete analytical solution of several fundamental problems in orbital correction. The initial orbit is represented by a given point in the phase space, while the final orbit is constrained to stay in a given curve which can be bounded, unbounded, or composed of a finite number of segments of different curves. The inclusion of atmospheric maneuver as part of the optimum process is discussed; its analytical treatment can be carried out by modifying the final state to include the set of orbits having their perigee at the boundary of the atmosphere.The selection of the apogee and perigee distances as state variables gives a symmetric form to the problem and results in a linear differential equation of the first order for the ratio of the adjoint variables. The introduction of a curve of comparison, called the separatrix, facilitates the discussion of the existence of a corner on an optimal trajectory.This work was supported by NASA Contract No. NASr 54(06).     

Slowly oscillating solutions of parabolic inverse problems

We first extend slowly oscillating functions to a more general setting and investigate their properties. Then we show the existence and uniqueness of slowly oscillating solutions of parabolic equations and parabolic inverse problems.     

Numerical solutions of some parabolic inverse problems

In this article we transform a large class of parabolic inverse problems into a nonclassical parabolic equation whose coefficients consist of trace type functionals of the solution and its derivatives subject to some initial and boundary conditions. For this nonclassical problem, we introduce a variational form by defining a new function. Both continuous and discrete Galerkin procedures are illustrated in this paper. The error estimates are also derived.     

The factorization method for a class of inverse elliptic problems

In this paper the factorization method from inverse scattering theory and impedance tomography is extended to a class of general elliptic differential equations in divergence form. The inverse problem is to determine the interface ?Ω of an interior change of the material parameters from the Neumann‐Dirichlet map. Since absorption is allowed a suitable combination of the real and imaginary part of the Neumann‐Dirichlet map is needed to explicitely characterize Ω by the data. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A uniqueness result for a general class of inverse problems

In this paper, we prove that a bounded, compactly supported potential q can be uniquely determined by its scattering amplitude at a fixed non-L ² eigen value for a general class of differential operators.     

Source and coefficient inverse problems for an elliptic equation in a rectangle

The inverse problems of determining the source and coefficient of an elliptic equation in a rectangle are studied. Additional information on the solution to the direct problem (overdetermination) is the trace of its solution on an interval inside the rectangle. Sufficient existence and uniqueness conditions (global) are derived for the inverse problems. The study is performed in the class of continuously differentiable functions whose derivatives satisfy a Hölder condition.     

Nonsimilarity solutions of a class of free convection problems

The nonsimilarity solutions of laminar boundary layer free convection flows along a rotating isothermal plate under nonuniform gravity and along a non isothermal vertical plate have been obtained. The governing nonlinear partial differential equations are reduced to a set of ordinary differential equations and then solved numerically using the method of ‘shooting’ with least square convergence criterion. The results for large values of axial distance are found to be more accurate than those obtained by series and integral methods, but for small values of axial distance they are in good agreement.     

一类Riemann-Hilbert边值逆问题

给出解析函数的一类R iem ann-H ilbert边值逆问题的数学提法,依据解析函数R iem ann-H ilbert边值问题的经典理论,讨论了此边值问题的可解性,给出了该边值问题的可解条件和解的表示式.     

Multibump solutions for a class of nonlinear elliptic problems

The paper is concerned with a class of semilinear elliptic Dirichlet problems approximating degenerate equations. By using variational methods, it is proved that, if the degeneration set consists of connected components, then there exist at least multibump positive solutions. Received March 25, 1996 / Accepted May 26, 1997     

Discontinuous solutions of a class of quasiregular variational problems

We establish the existence of discontinuous solutions for a positive definite, seminormal, quasiregular variational problem when the order of growth of the integrand of the functional is degenerate on lines parallel to the Oy axis.     

Explicit solutions to a class of nonlinear filtering problems

In this paper we obtain the solution of a class of nonlinear filtering problems in the form of a series expansion in terms of multiple Wiener integrals. The solution is explicit in the sense that the kernels of the integrals in the expansion are explicitly determine.     

Analytical solutions for a class of nonlinear differential equations using altran

What follows is a discussion on the application of a digital computer to solve analytically a class of nonlinear ordinary differential equations. The asymptotic method of Krylov, Bogoliubov and Mitropolsky is employed to obtain analytical solutions. In addition, a procedure has been developed through which the initial amplitude and phase can be expressed as functions of initial displacement and velocity without the need of integration. Since the algorithms are analytical in nature, the truncated power series capability of the symbolic algebraic system ALTRAN has been used to generate analytical solutions automatically.     

Analytical solutions to two matrix Riemann-Hilbert problems

Two matrix Riemann-Hilbert problems derived from boundary-value problems in the kinetic theory of gases are solved analytically.

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Riassunto Vengono risolti analiticamente due problemi relativi alla matrice di Riemann-Hilbert, che si incontrano in problemi con condizioni al contorno nella teoria cinetica dei gas.