The collision frequencies of electron-neutral-particle in weakly ionized complex plasmas with the non-Maxwellian velocity distributions are studied. The average collision frequencies of electron-neutral-particle in plasmas are accurately derived. We find that these collision frequencies are significantly dependent on the power-law spectral indices of non-Maxwellian distribution functions and so they are generally different from the collision frequencies in plasmas with a Maxwellian velocity distribution, which will affect the transport properties of the charged particles in plasmas. Numerically analyses are made to show the roles of the spectral indices in the average collision frequencies respectively.

Abstract. Detection of sonar platform excitations has been a formidable obstacle towards the estimation and evaluation of mechanical self-noise in the sonar cavity. In view of the complexity of transmission of excitations from mechanical vibration equipments to sonar platform, an inversion technique, i.e., indirectly estimating the outside excitations by means of measurement of vibratory responses, would be the most applicable and feasible. An equivalent excitation method is proposed in this paper, by the hypothesis that responses resulted from equivalent excitations would be equal to that from actual excitations, to deal with the excitation inverse problem in situations where there is no knowing about the location and distribution of dynamic excitation forces acting on structures. Influential factors in estimation of equivalent excitations, including determination of master modals, number and arrangement of observation points and equivalent excitation points, are well reasoned based on modal theory of panel structures, with analytical analysis method. And it could be concluded that the equivalent excitation inversion would be a practical method for evaluation of environmental excitations.