The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan statio...The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan station,Beijing where there are two different gravimeters( namely,L&R-804 and PET-031). Based on the original raw tidal records of two gravimeters from 2008 to 2011,we first remove various interference from raw data by the standard procedure software-Tsoft; then we model the solid earth tides, ocean tidal loading and pole tide through related parameters; after that we adopt a new segmented polynomial fitting method based on Tsoft to fit the complex drift of spring gravimeter; and finally we calculate the atmospheric loading effects by a linear regression model. After a series of processing we gain the non-tidal variation of the two gravimeters at Baijiatuan site,Beijing. Furthermore,to analyze the non-tidal variation preliminarily,we study the main component of related tidal data by power spectral density. Comparing the non-tidal variation of two different gravimeters,we find seasonal fluctuations in non-tidal results, which are in accordance with the water storage change. Therefore,we take into account the relevance of gravity changes and water storage based on the gravity data of GRACE and water data of the CMAP model from 2003 to 2011 at different sites in the Chinese mainland( Beijing, Chengdu, Shenyang and Shiquanhe), and make a preliminary analysis on the relationship between gravity changes and water storage.展开更多
Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of lo...Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of local damage to roof structures, par- ticularly at the edges and comers of long-span roofs. Thus, comparative errors would occur if a Gaussian model is used to de- scribe a non-Gaussian wind load, and structural security would not be guaranteed. This paper presents a simplified method based on the inverse fast Fourier transform （IFFT）, in which the amplitude spectrum is established via a target power spectrum. Also, the phase spectrum is constructed by introducing the exponential peak generation （EPG） model. Finally, a random pro- cess can be generated via IFFT that meets the specified power spectral density （PSD）, skewness and kurtosis. In contrast to a wind tunnel experiment, this method can avoid the coupled relation between the non-Gaussian and the power spectrum char- acteristics, and lead to the desired computational efficiency. Its fitting accuracy is not affected by phase spectrum. Moreover, the fitting precision of the kurtosis and PSD parameters can be guaranteed. In a few cases, the fitting precision of the skewness parameter is fairly poor, but kurtosis is more important than skewness in the description of the non-Gaussian characteristics. Above all, this algorithm is simple and stable and would be an effective method to simulate a non-Gaussian signal.展开更多
基金sponsored by the Basic Scientific Research of Institute of Geophysics,CEA(DQJB12B20,DQJB12C03,DQJB12B14)
文摘The non-tidal variation gained from continuous gravity observations in stations usually reflects the regional continuous gravity changes. In this paper we focus on studying the non-tidal variation of Baijiatuan station,Beijing where there are two different gravimeters( namely,L&R-804 and PET-031). Based on the original raw tidal records of two gravimeters from 2008 to 2011,we first remove various interference from raw data by the standard procedure software-Tsoft; then we model the solid earth tides, ocean tidal loading and pole tide through related parameters; after that we adopt a new segmented polynomial fitting method based on Tsoft to fit the complex drift of spring gravimeter; and finally we calculate the atmospheric loading effects by a linear regression model. After a series of processing we gain the non-tidal variation of the two gravimeters at Baijiatuan site,Beijing. Furthermore,to analyze the non-tidal variation preliminarily,we study the main component of related tidal data by power spectral density. Comparing the non-tidal variation of two different gravimeters,we find seasonal fluctuations in non-tidal results, which are in accordance with the water storage change. Therefore,we take into account the relevance of gravity changes and water storage based on the gravity data of GRACE and water data of the CMAP model from 2003 to 2011 at different sites in the Chinese mainland( Beijing, Chengdu, Shenyang and Shiquanhe), and make a preliminary analysis on the relationship between gravity changes and water storage.
基金supported by the National Natural Science Fund for Distinguished Young Scholars (Grant No. 51125031)
文摘Compared with Gaussian wind loads, there is a higher probability of strong suction fluctuations occurrence for non-Gaussian wind pressures. These instantaneous and intermittent fluctuations are the initial cause of local damage to roof structures, par- ticularly at the edges and comers of long-span roofs. Thus, comparative errors would occur if a Gaussian model is used to de- scribe a non-Gaussian wind load, and structural security would not be guaranteed. This paper presents a simplified method based on the inverse fast Fourier transform （IFFT）, in which the amplitude spectrum is established via a target power spectrum. Also, the phase spectrum is constructed by introducing the exponential peak generation （EPG） model. Finally, a random pro- cess can be generated via IFFT that meets the specified power spectral density （PSD）, skewness and kurtosis. In contrast to a wind tunnel experiment, this method can avoid the coupled relation between the non-Gaussian and the power spectrum char- acteristics, and lead to the desired computational efficiency. Its fitting accuracy is not affected by phase spectrum. Moreover, the fitting precision of the kurtosis and PSD parameters can be guaranteed. In a few cases, the fitting precision of the skewness parameter is fairly poor, but kurtosis is more important than skewness in the description of the non-Gaussian characteristics. Above all, this algorithm is simple and stable and would be an effective method to simulate a non-Gaussian signal.
