Based on the Morlet complex wavelet transformation,the authors put forward a kind of new method for distinguishing periods of seismic activity and quietude and a new physical thought on the time-dependent wavelet accu...Based on the Morlet complex wavelet transformation,the authors put forward a kind of new method for distinguishing periods of seismic activity and quietude and a new physical thought on the time-dependent wavelet accumulation energy spectrum with periods, the time-frequency distribution of wavelet vibration period spectrum and period-specific wavelet vibration spectrum. By applying the above methods to a time series which is composed of earthquake accumulation energy per year for the world, the Chinese continent and North China, respectively, we obtained some new information about the rhythm of shallow earthquake activity. Considering the historic earthquakes and the rhythm characteristics of current strong earthquake activity, the earthquake tendency in the next years is discussed.展开更多
Some problems encountered in applying Smith's technique to predict the PIO tendency for non-linear pilot-vehicle loop, are thoroughly analyzed. Subsequently, modified PIO predictable criteria are developed, in add...Some problems encountered in applying Smith's technique to predict the PIO tendency for non-linear pilot-vehicle loop, are thoroughly analyzed. Subsequently, modified PIO predictable criteria are developed, in addition, to make also a certain improvement on Smith's PIO definition and PIO types. These modified criteria are applied to predict PIO tendency of various different configurations on the variable stability aircraft NT-33 in case of supposed non-linearity, and predicted results are compared with the flight tests and analytical results in the case of linear hypothesis given in Ref. (4)展开更多
文摘Based on the Morlet complex wavelet transformation,the authors put forward a kind of new method for distinguishing periods of seismic activity and quietude and a new physical thought on the time-dependent wavelet accumulation energy spectrum with periods, the time-frequency distribution of wavelet vibration period spectrum and period-specific wavelet vibration spectrum. By applying the above methods to a time series which is composed of earthquake accumulation energy per year for the world, the Chinese continent and North China, respectively, we obtained some new information about the rhythm of shallow earthquake activity. Considering the historic earthquakes and the rhythm characteristics of current strong earthquake activity, the earthquake tendency in the next years is discussed.
文摘Some problems encountered in applying Smith's technique to predict the PIO tendency for non-linear pilot-vehicle loop, are thoroughly analyzed. Subsequently, modified PIO predictable criteria are developed, in addition, to make also a certain improvement on Smith's PIO definition and PIO types. These modified criteria are applied to predict PIO tendency of various different configurations on the variable stability aircraft NT-33 in case of supposed non-linearity, and predicted results are compared with the flight tests and analytical results in the case of linear hypothesis given in Ref. (4)
