The enclosure method for inverse obstacle scattering problems with dynamical data over a finite time interval: II. Obstacles with a dissipative boundary or finite refractive index and back-scattering data

In this paper, a wave is generated by the initial data whose support is localized at the outside of unknown obstacles and observed in a limited time on a known closed surface or the same position as the support of the initial data. The observed data in the latter process are nothing but the back-scattering data. Two types of obstacles are considered. One type is of obstacles with a dissipative boundary condition, which is a generalization of the sound-hard obstacles; another type is of obstacles with a finite refractive index, the so-called transparent obstacles. For each type of obstacle, two formulas that yield explicitly the distance from the support of the initial data to unknown obstacles are given. (paper)