# American Institute of Mathematical Sciences

doi: 10.3934/eect.2020008

## Regularized solution for a biharmonic equation with discrete data

 1 Applied Analysis Research Group, Faculty of Mathematics and Statistics, Ton Duc Thang University, Ho Chi Minh City, Vietnam 2 Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam 3 School of Mathematics, Statistics and Applied Mathematics, National University of Ireland, Galway, Ireland

Corresponding author: thnguyen2683@gmail.com(Nguyen Huy Tuan)

Received  January 2019 Revised  April 2019 Published  August 2019

In this work, we focus on the Cauchy problem for the biharmonic equation associated with random data. In general, the problem is severely ill-posed in the sense of Hadamard, i.e, the solution does not depend continuously on the data. To regularize the instable solution of the problem, we apply a nonparametric regression associated with the Fourier truncation method. Also we will present a convergence result.

Citation: Tran Ngoc Thach, Nguyen Huy Tuan, Donal O'Regan. Regularized solution for a biharmonic equation with discrete data. Evolution Equations & Control Theory, doi: 10.3934/eect.2020008
##### References:
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##### References:
 [1] D. Adams, $L^p$ potential theory techniques and nonlinear PDE. Potential theory, Potential Theory (Nagoya, 1990), Berlin: de Gruyter, (1992), 1–15.  Google Scholar [2] A. Benrabah and N. Bousetila, Modified nonlocal boundary value problem method for an ill-posed problem for the biharmonic equation, Inverse Problem in Science and Engnineering, 27 (2019), 340–368, https://doi.org/10.1080/17415977.2018.1461859. doi: 10.1080/17415977.2018.1461859.  Google Scholar [3] R. L. Eubank, Nonparametric Regression and Spline Smoothing, CRC Press, 1999.   Google Scholar [4] D. Lesnic and A. Zeb, The method of fundamental solutions for an inverse internal boundary value problem for the biharmonic equation, Int. J. Comput. Methods, 6 (2009), 557-567.  doi: 10.1142/S0219876209001991.  Google Scholar [5] J. C. Li, Application of radial basis meshless methods to direct and inverse biharmonic boundary value problems, Commun. Numer. Methods Eng., 21 (2005), 169-182.  doi: 10.1002/cnm.736.  Google Scholar [6] T. N. Luan, T. T. Khieu and T. Q. Khanh, Regularized solution of the cauchy problem for the biharmonic equation, Bulletin of the Malaysian Mathematical Sciences Society, to appear, (2018), 1–26. doi: 10.1007/s40840-018-00711-7.  Google Scholar [7] L. Marin and D. Lesnic, The method of fundamental solutions for inverse boundary value problems associated with the two-dimensional biharmonic equation, Math. Comput. Modelling, 42 (2005), 261-278.  doi: 10.1016/j.mcm.2005.04.004.  Google Scholar [8] V. V. Meleshko, Selected topics in the history of the two-dimensional biharmonic problem, Appl. Mech. Rev., 56 (2003), 33-85.  doi: 10.1115/1.1521166.  Google Scholar [9] S. G. Mikhlin, Integral Equations and Their Applications to Certain Problems in Mechanics, Mathematical Physics and Technology, ed. 2, The Macmillan Co., New York, 1964.  Google Scholar [10] P. W. Schaefer, On existence in the Cauchy problem for the biharmonic equation, Compositio Math., 28 (1974), 203-207.   Google Scholar [11] A. B. Tsybakov, Introduction to Nonparametric Estimation, Springer, New York, 2009. doi: 10.1007/b13794.  Google Scholar [12] A. Zeb, L. Elliott, D. B. Ingham and D. Lesnic, Cauchy problem for the biharmonic equation solved using the regularization method, Boundary Element Research in Europe (Southampton, 1998), Comput. Mech., Southampton, (1998), 285–294.  Google Scholar
The exact and regularized solutions at $y = 0$ (a) and its errors (b)
The exact and regularized solutions at $y = 0.1$ (a) and its errors (b)
The exact and regularized solutions at $y = 0.2$ (a) and its errors (b)
The exact and regularized solutions at $y = 0.3$ (a) and its errors (b)
The exact solution $u$ (a) and the regularized solution $\widehat v$ (b)
The errors between the exact solution and the regularized solution at $y \in \{0.1, \, 0.2, \, 0.3\}$
 Errors $n = 20$ $n=50$ $n=100$ $\mathrm{Err}(0.1)$ 0.016631443540398 0.017785494891671 0.016885191385811 $\mathrm{Err}(0.2)$ 0.018572286169882 0.016934217726270 0.017559567667446 $\mathrm{Err}(0.3)$ 0.012505879576731 0.012581413283707 0.015940532272324
 Errors $n = 20$ $n=50$ $n=100$ $\mathrm{Err}(0.1)$ 0.016631443540398 0.017785494891671 0.016885191385811 $\mathrm{Err}(0.2)$ 0.018572286169882 0.016934217726270 0.017559567667446 $\mathrm{Err}(0.3)$ 0.012505879576731 0.012581413283707 0.015940532272324
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