In this paper, a wave propagation model is developed to investigate the wave propagation in fluid-filled steel pipe. Based on the Kennard shell equations the investigation is achieved under the conditions of coupling between the shell elastic acoustic field and the interior fluid acoustic field. Tests are conducted on fluid-filled pipeline blockage detection. An active acoustic source is used t...

The Wigner distribution (WD) is perhaps the most prominent quadratic time–frequency signal representation. In this paper, which has mainly tutorial character but also contains some new results, we describe extensions of the WD concept to multidimensional vector signals, nonstationary random processes, linear time-varying systems (deterministic and random), linear signal spaces, and frames. We d...