  Inverse problems of electric conductivity are studied that arise in the
design of spherical shielding or cloaking shells and other functional devices
used to control DC electric fields. The shells are considered consisting of a
finite number of layers filled with homogeneous isotropic or anisotropic
medium. The inverse problems under study are reduced to control problems with
the layer electric conductivities taken as controls. A numerical algorithm to
solve these problems is based on particle swarm optimization. Various results
of numerical experiments are discussed. The findings obtained in this study
describe a broad set of specific easy-to-manufacture structures that have the
highest cloaking or shielding performance in the class of layered shells.
