scholarly journals Choice of the regularization parameter for the Cauchy problem for the Laplace equation

2020 ◽  
Vol 30 (10) ◽  
pp. 4475-4492
Author(s):  
Magda Joachimiak
Keyword(s):  
Cauchy Problem ◽  
Laplace Equation ◽  
Chebyshev Polynomials ◽  
Regularization Parameter ◽  
Rectangular Domain ◽  
Heated Wall ◽  
Cauchy Type ◽  
Type Problem ◽  
Content Type ◽  
Cauchy Type Problem

Purpose In this paper, the Cauchy-type problem for the Laplace equation was solved in the rectangular domain with the use of the Chebyshev polynomials. The purpose of this paper is to present an optimal choice of the regularization parameter for the inverse problem, which allows determining the stable distribution of temperature on one of the boundaries of the rectangle domain with the required accuracy. Design/methodology/approach The Cauchy-type problem is ill-posed numerically, therefore, it has been regularized with the use of the modified Tikhonov and Tikhonov–Philips regularization. The influence of the regularization parameter choice on the solution was investigated. To choose the regularization parameter, the Morozov principle, the minimum of energy integral criterion and the L-curve method were applied. Findings Numerical examples for the function with singularities outside the domain were solved in this paper. The values of results change significantly within the calculation domain. Next, results of the sought temperature distributions, obtained with the use of different methods of choosing the regularization parameter, were compared. Methods of choosing the regularization parameter were evaluated by the norm Nmax. Practical implications Calculation model described in this paper can be applied to determine temperature distribution on the boundary of the heated wall of, for instance, a boiler or a body of the turbine, that is, everywhere the temperature measurement is impossible to be performed on a part of the boundary. Originality/value The paper presents a new method for solving the inverse Cauchy problem with the use of the Chebyshev polynomials. The choice of the regularization parameter was analyzed to obtain a solution with the lowest possible sensitivity to input data disturbances.

Stable method for solving the Cauchy problem with the use of Chebyshev polynomials

2019 ◽  
Vol 30 (3) ◽  
pp. 1441-1456 ◽  
Author(s):  
Magda Joachimiak ◽  
Michał Ciałkowski ◽  
Andrzej Frąckowiak
Keyword(s):  
Heat Flux ◽  
Cauchy Problem ◽  
Chebyshev Polynomials ◽  
Heat Flux Density ◽  
Rectangular Domain ◽  
Cauchy Type ◽  
Laplace’S Equation ◽  
Content Type ◽  
Laplace's Equation ◽  
The Cauchy Problem

Purpose The purpose of this paper is to present the method for solving the inverse Cauchy-type problem for the Laplace’s equation. Calculations were made for the rectangular domain with the target temperature on three boundaries and, additionally, on one of the boundaries, the heat flux distribution was selected. The purpose of consideration was to determine the distribution of temperature on a section of the boundary of the investigated domain (boundary Γ1) and find proper method for the problem regularization. Design/methodology/approach The solution of the direct and the inverse (Cauchy-type) problems for the Laplace’s equation is presented in the paper. The form of the solution is noted as the linear combination of the Chebyshev polynomials. The collocation method in which collocation points had been determined based on the Chebyshev nodes was applied. To solve the Cauchy problem, the minimum of functional describing differences between the target and the calculated values of temperature and the heat flux on a section of the domain’s boundary was sought. Various types of the inverse problem regularization, based on Tikhonov and Tikhonov–Philips regularizations, were analysed. Regularization parameter α was chosen with the use of the Morozov discrepancy principle. Findings Calculations were performed for random disturbances to the heat flux density of up to 0.01, 0.02 and 0.05 of the target value. The quality of obtained results was next estimated by means of the norm. Effect of the disturbance to the heat flux density and the type of regularization on the sought temperature distribution on the boundary Γ1 was investigated. Presented methods of regularization are considerably less sensitive to disturbances to measurement data than to Tikhonov regularization. Practical implications Discussed in this paper is an example of solution of the Cauchy problem for the Laplace’s equation in the rectangular domain that can be applied for determination of the temperature distribution on the boundary of the heated element where it is impossible to measure temperature or the measurement is subject to a great error, for instance on the inner wall of the boiler. Authors investigated numerical examples for functions with singularities outside the domain, for which values of gradients change significantly within the calculation domain what corresponds to significant changes in temperature on the wall of the boiler during the fuel combustion. Originality/value In this paper, a new method for solving the Cauchy problem for the Laplace’s equation is described. To solve this problem, the Chebyshev polynomials and nodes were used. Various types of regularization of this problem were considered.

Application of measure of noncompactness to a Cauchy problem for fractional differential equations in Banach spaces

2013 ◽  
Vol 16 (4) ◽  
Author(s):  
Asadollah Aghajani ◽  
Ehsan Pourhadi ◽  
Juan Trujillo
Keyword(s):  
Differential Equation ◽  
Cauchy Problem ◽  
Fixed Point ◽  
Measure Of Noncompactness ◽  
Existence Of Solutions ◽  
Cauchy Type ◽  
Type Problem ◽  
Nonlinear Fractional Differential Equation ◽  
Cauchy Type Problem ◽  
Fractional Differential

AbstractThis paper is devoted to study the existence of solutions of a Cauchy type problem for a nonlinear fractional differential equation, via the techniques of measure of noncompactness. The investigation is based on a new fixed point result which is a generalization of the well known Darbo’s fixed point theorem. The main result is less restrictive than those given in the literature. Some illustrative examples are given.

scholarly journals A modified Tikhonov regularization method based on Hermite expansion for solving the Cauchy problem of the Laplace equation

2020 ◽  
Vol 18 (1) ◽  
pp. 1685-1697
Author(s):  
Zhenyu Zhao ◽  
Lei You ◽  
Zehong Meng
Keyword(s):  
Cauchy Problem ◽  
Laplace Equation ◽  
Tikhonov Regularization ◽  
Regularization Method ◽  
Regularization Parameter ◽  
Solution Process ◽  
Tikhonov Regularization Method ◽  
Hermite Expansion ◽  
The Cauchy Problem ◽  
Ill Posed

Abstract In this paper, a Cauchy problem for the Laplace equation is considered. We develop a modified Tikhonov regularization method based on Hermite expansion to deal with the ill posed-ness of the problem. The regularization parameter is determined by a discrepancy principle. For various smoothness conditions, the solution process of the method is uniform and the convergence rate can be obtained self-adaptively. Numerical tests are also carried out to verify the effectiveness of the method.

Expansions with Poisson kernels and related topics

2010 ◽  
Vol 53 (1) ◽  
pp. 153-173 ◽  
Author(s):  
Cristina Giannotti ◽  
Paolo Manselli
Keyword(s):  
Unit Disc ◽  
Poisson Kernel ◽  
Cauchy Type ◽  
Two Dimensional ◽  
Type Problem ◽  
Special Sequence ◽  
Poisson Kernels ◽  
Cauchy Type Problem ◽  
In Series

AbstractLet P(r, θ) be the two-dimensional Poisson kernel in the unit disc D. It is proved that there exists a special sequence {ak} of points of D which is non-tangentially dense for ∂D and such that any function on ∂D can be expanded in series of P(|ak|, (·)–arg ak) with coefficients depending continuously on f in various classes of functions. The result is used to solve a Cauchy-type problem for Δu = μ, where μ is a measure supported on {ak}.

scholarly journals Solution of Volterra-type integro-differential equations with a generalized Lauricella confluent hypergeometric function in the kernels

2005 ◽  
Vol 2005 (8) ◽  
pp. 1155-1170 ◽  
Author(s):  
R. K. Saxena ◽  
S. L. Kalla
Keyword(s):  
Hypergeometric Function ◽  
Fractional Derivatives ◽  
Confluent Hypergeometric Function ◽  
Several Complex Variables ◽  
Cauchy Type ◽  
Type Problem ◽  
Volterra Type ◽  
Caputo Fractional Derivatives ◽  
Cauchy Type Problem ◽  
Special Cases

The object of this paper is to solve a fractional integro-differential equation involving a generalized Lauricella confluent hypergeometric function in several complex variables and the free term contains a continuous functionf(τ). The method is based on certain properties of fractional calculus and the classical Laplace transform. A Cauchy-type problem involving the Caputo fractional derivatives and a generalized Volterra integral equation are also considered. Several special cases are mentioned. A number of results given recently by various authors follow as particular cases of formulas established here.

scholarly journals Fractional Cauchy Problem with Caputo Nabla Derivative on Time Scales

2015 ◽  
Vol 2015 ◽  
pp. 1-23 ◽  
Author(s):  
Jiang Zhu ◽  
Ling Wu
Keyword(s):  
Explicit Solutions ◽  
Cauchy Type ◽  
Type Problem ◽  
Initial Value ◽  
Laplace Transform Method ◽  
Transform Method ◽  
Cauchy Type Problem ◽  
Definition Of ◽  
Nabla Derivative ◽  
Fractional Cauchy Problem

The definition of Caputo fractional derivative is given and some of its properties are discussed in detail. After then, the existence of the solution and the dependency of the solution upon the initial value for Cauchy type problem with fractional Caputo nabla derivative are studied. Also the explicit solutions to homogeneous equations and nonhomogeneous equations are derived by using Laplace transform method.

scholarly journals Coupled system of a fractional order differential equations with weighted initial conditions

2019 ◽  
Vol 17 (1) ◽  
pp. 1737-1749
Author(s):  
Ahmed M. A. El-Sayed ◽  
Sheren A. Abd El-Salam
Keyword(s):  
Fractional Order ◽  
Continuous Dependence ◽  
Initial Conditions ◽  
Coupled System ◽  
Cauchy Type ◽  
Type Problem ◽  
Integrable Solution ◽  
Fractional Order Differential Equations ◽  
Cauchy Type Problem ◽  
Uniqueness Of The Solution

Abstract Here, a coupled system of nonlinear weighted Cauchy-type problem of a diffre-integral equations of fractional order will be considered. We study the existence of at least one integrable solution of this system by using Schauder fixed point Theorem. The continuous dependence of the uniqueness of the solution is proved.

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