We present a time domain approach for the investigation of dispersion mechanisms of a medium in electromagnetic eld problems. Maxwell's equations coupled with a generalized electric polarization model are considered. The polarization is given in terms of a convolution of the electric eld with an impulse response funtion. Existence, uniqueness and continuous dependence of solutions on data are p...

Classical structure of rough set theory was first formulated by Z. Pawlak in [6]. The foundation of its object classification is an equivalence binary relation and equivalence classes. The upper and lower approximation operations are two core notions in rough set theory. They can also be seenas a closure operator and an interior operator of the topology induced by an equivalence relation on a u...