IMA Journal of Applied Mathematics Advance Access published online on November 17, 2007
IMA Journal of Applied Mathematics, doi:10.1093/imamat/hxm056
Determination of unknown coefficient in a non-linear elliptic problem related to the elastoplastic torsion of a bar


Department of Mathematics, Kocaeli University, Umuttepe Kampusu, Izmit-Kocaeli 41380, Turkey
Email: ahasanov{at}kou.edu.tr
Corresponding author. Email: aerdem{at}kou.edu.tr
Received on April 24, 2007; Accepted on October 10, 2007
The inverse problem of determining the unknown coefficient of the non-linear differential equation of torsional creep is studied. The unknown coefficient g = g(
2) depends on the gradient
: = |
u| of the solution u(x), x
Rn, of the direct problem. It is proved that this gradient is bounded in C-norm. This permits one to choose the natural class of admissible coefficients for the considered inverse problem. The continuity in the norm of the Sobolev space H1(
) of the solution u(x;g) of the direct problem with respect to the unknown coefficient g = g(
2) is obtained in the following sense: ||u(x;g) – u(x;gm)||1
0 when gm(
)
g(
) point-wise as m
. Based on these results, the existence of a quasi-solution of the inverse problem in the considered class of admissible coefficients is obtained. Numerical examples related to determination of the unknown coefficient are presented.
Keywords: inverse coefficient problem; non-linear elliptic equation; torsional creep; existence of a quasi-solution.