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Global navigation satellite system reflectometry(GNSS-R)has shown great potential in surface and marine environment parameters monitoring, with the advantages of extensive data sources, low cost, high spatial and temporal resolution, and has become an important approach for sea surface height(SSH)inversion. The existing research mainly focuses on the short-term GPS sea surface inversion within 3-6 months, which is difficult to reflect the seasonal variation and interannual characteristics of SSH. Meanwhile, only the influence of vertical velocity is considered in the dynamic sea surface correction, and the vertical acceleration of sea surface fluctuation is ignored, resulting in the poor estimation accuracy of low and high tide levels. For the above issues, a shore-based tracking station BRST in France was taken as an example, and the reflected signals of 3 consecutive years from BDS/GPS/GLONASS/Galileo system were used to estimate SSH. Based on Lomb-Scargle spectrum analysis and second-order dynamic tide level correction model, a robust regression strategy was adopted. The estimation results were compared with tide gauge records to analyze the trend of sea level change. The results show that the inversion results of GNSS-R technology are in good agreement with tide gauge records, and the inversion accuracy has a tendency to improve year by year, with a root mean square error(RMSE)of 7.57 cm and a correlation coefficient of 0.935 for the three-year daily average; the seasonal variation of SSH is obvious, the average SSH is high in autumn and winter, and low in summer, and the seasonal variation of SSH is opposite to that of temperature; the differences of amplitude for nine tidal constituents including M2, S2, K1, O1, N2, K2, P1, Q1 and M4, range from 0.06 cm to 6.76 cm with the mean absolute error(MAE)of 1.60 cm, and the differences of phase range from 0.03° to 6.96° with the MAE of 2.45°. It is further verified that the reliability of GNSS-R technology in monitoring SSH change in the frequency domain. [ABSTRACT FROM AUTHOR]

The Jianzha Basin is located in the northeastern margin of Tibetan Plateau, and contains a thick sequence of Cenozoic sediments, which is composed of the sequence of eolian red clay with a bit part fluviolacustrine deposits. The Jiarang section in Jianzha Basin is an ideal section for cyclostratigraphy, because of its high resolution on magnetostratigraphy and environmental magnetism. Based on the systematic cyclostratigraphy of 3 - 361 m sedimentary strata of Late Miocene in Jiarang section, the absolute astronomical time scale of Jiarang section was established, and the dominant period of earth orbital parameters affecting the paleoclimate evolution in Jianzha Basin was extracted, in order to provide basic data for the further comparison between land and sea, and the paleoclimatic and environmental evolution. The result of spectrum analyses of frequency-dependent magnetic susceptibility (Xfd) in depth domain shows that there is a stable 26 m sedimentary cycle representing long eccentricity period in the 3 - 361 m interval, and the sedimentary cycles representing other astronomical orbital periods are also present, but not stable. Based on the identified sedimentary cycles, the long eccentricity period was used to tune frequency-dependent magnetic susceptibility data series in depth domain of 3 - 361 m. Combined with the magnetostratigraphic chronological framework of Jiarang section, the absolute astronomical time scale of 11. 758 - 5. 890 Ma was established. The astronomical tuning for frequency-dependent magnetic susceptibility data series in time domain is consistent with the paleomagnetic age, which indicates that the astronomical time scale is reliable. The spectrum analyses for frequency-dependent magnetic susceptibility and marine oxygen isotope records show that there are obvious periodic shifts in about 7. 2 Ma. This record reveals that the East Asian summer monsoon (EASM) is dominated by 41 ka obliquity period before 7. 2 Ma, and controlled by 100 ka short eccentricity period after 7. 2 Ma. [ABSTRACT FROM AUTHOR]

In order to study the effect of carbon dioxide phase change cracking process on the structure, the response spectrum analysis was carried out on the data obtained from field tests. First of all, the velocity signal is subjected to fast Fourier transform to analyze its spectral characteristics; then, the velocity signal is directly differentiated, the low-pass denoising is performed by using ensemble empirical mode decomposition(EEMD), and the reconstructed signal of the main characteristic frequency band is extracted to obtain a clear acceleration-time history curve; the acceleration curve after the denoising is used as the input signal to study the response spectrum of the carbon dioxide phase change cracking signal with different damping ratios. The results show that the frequency of carbon dioxide phase change cracking signal is concentrated in low frequency, the peak velocity and the main frequency are within the safe allowable range, and it is suitable for vibration sensitive environment; EEMD can effectively inhibit the high frequency oscillation caused by direct differentiation of the velocity signal, and the signal to noise ratio can reach up to 25 dB; the carbon dioxide phase change cracking response spectrum is simple, and the peak corresponding period is small, which is conducive to structural safety; the peak values of the relative displacement and the relative velocity response spectrums decrease with the increase of damping ratio, but the peak corresponding cycle is constant; the peak values of the absolute acceleration and the standard acceleration response spectrums are equal at non-zero damping ratio, which is not affected by damping ratio; attention is paid to the period in the response spectrum that has a large influence on the structure, and the stability of the structure can be guaranteed to some extent. [ABSTRACT FROM AUTHOR]