Signals reflected from a randomly layered medium are nonstationary stochastic processes that can have very complicated structure. In [l, 21 we considered pulse reflection from a randomly layered half space when the pulse width is large compared to the size of the layers but small compared to the large-scale variations of the layering. Then the reflected signals have a particular structure: they...

The statistical properties of acoustic signals re ected by a randomly layered medium are analyzed when a pulsed spherical wave issuing from a point source is incident upon it. The asymptotic analysis of stochastic equations and geometrical acoustics is used to arrive at a set of transport equations that characterize multiply scattered signals observed at the surface of the layered medium. The r...

Dynamic Ratcheting (DR) is a nonlinear dynamic phenomenon occurring in hysteretic damping systems. It means the structural plastic deformation increases asymmetrically in successive cycles under an earthquake excitation. Although it is generally recognized that DR is closely related to the frequency contents of an earthquake excitation applied to thestructure, no targeted analysis has bee...

the educational system is one of the important trends in every society in order to develop and promote individuals’ entrepreneurial skills. the purpose of this study is the contents of vocational training textbooks of middle school program based on the entrepreneurial components. the method of this study is descriptive with the content analysis type. the population includes the contents of thre...

In this study, the characteristics of the total electron content (TEC) fluctuations and their regional differences over China were analyzed by utilizing the rate of the TEC index (ROTI) based on GPS data from 21 reference stations across China during a solar cycle. The results show that there were significant regional differences at different latitudes. Strong ionospheric TEC fluctuations were ...