This paper presents a new foundation for positive time{ frequency distributions (TFDs). Based on an integral equation formulation of nonstationary systems, a positive TFD can be constructed from a decomposition of a signal over an orthonormal basis. This basis function de nition of a positive TFD is used to obtain a relationship between the Wigner distribution and the positive TFD. The results ...

‎in this paper‎, ‎a numerical procedure for an inverse problem of‎ ‎simultaneously determining an unknown coefficient in a semilinear ‎parabolic equation subject to the specification of the solution at‎ ‎an internal point along with the usual initial boundary conditions ‎is considered‎. ‎the method consists of expanding the required‎ ‎approximate solution as the elements of the inverse quadrati...