arXiv subjects

Masaru Ikehata

Publications and source records attributed to Masaru Ikehata.

58 records · Page 4Linked to original sources

arXiv2007

A remark on the enclosure method for a body with an unknown homogeneous background conductivity

Previous applications of the enclosure method with a finite set of observation data to a mathematical model of electrical impedance tomography are based on the assumption that the conductivity of the background body is homogeneous and known. This paper considers the case when the conductivity is homogeneous and unknown. It is shown that, in two dimensions if the domain occupied by the background body is enclosed by an ellipse, then it is still possible to extract some information about the location of unknown cavities or inclusions embedded in the body without knowing the background conductivity provided the Fourier series expansion of the voltage on the boundary does not contain high frequency parts (band limited) and satisfies a non vanishing condition of a quantity involving the Fourier coefficients.

math.AP↗

arXiv2006

Travel Time and Heat Equation. One space dimensional case II

Three inverse boundary value problems for the heat equations in one space dimension are considered. Those three problems are: extracting an unknown interface in a heat conductive material, an unknown boundary in a layered material or a material with a smooth heat conductivity by employing a single set of the temperature and heat flux on a known boundary as the observation data. Some extraction formulae of those discontinuities which suggest a relationship between the travel time of a {\it virtual} signal and the observation data are given by applying the enclosure method to the problems.

math.AP↗

arXiv2006

Two sides of probe method and obstacle with impedance boundary condition

An inverse boundary value problem for the Helmholtz equation in a bounded domain is considered. The problem is to extract information about an unknown obstacle embedded in the domain with unknown impedance boundary condition (the Robin condition) from the associated Dirichlet-to-Neumann map. The main result is a characterization of the unknown obstacle via the sequences that are constructed by the Dirichlet-to-Neumann map, under smallness conditions on the wave number and the upper bound of the impedance. Moreover two alternative simple proofs of a previous result of Cheng-Liu-Nakamura which are based on only some energy estimates, an analysis of the blowup of the energy of so-called reflected solutions and an application of the enclosure method to the problem are also given.

math.AP↗

arXiv2006

An inverse source problem for the heat equation and the enclosure method

An inverse source problem for the heat equation is considered. Extraction formulae for information about the time and location when and where the unknown source of the equation firstly appeared are given from a single lateral boundary measurement. New roles of the plane progressive wave solutions or their complex versions for the backward heat equation are given.

math.AP↗