Interference in the data of geochemical hydrocarbon exploration is a large obstacle for anomaly recognition. The multiresolution analysis of wavelet analysis can extract the information at different scales so as to pr...Interference in the data of geochemical hydrocarbon exploration is a large obstacle for anomaly recognition. The multiresolution analysis of wavelet analysis can extract the information at different scales so as to provide a powerful tool for information analysis and processing. Based on the analysis of the geometric nature of hydrocarbon anomalies and background, Mallat wavelet and symmetric border treatment are selected and data pre-processing (logarithm-normalization) is established. This approach provide good results in Shandong and Inner Mongolia, China. It is demonstrated that this approach overcome the disadvantage of backgound variation in the window (interference in window), used in moving average, frame filtering and spatial and scaling modeling methods.展开更多
On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by cor...On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by correlation analysis with a focus on its anomaly before moderate and strong earthquakes. With different spatial scales, temporal scales and time steps, the spatial distribution of earthquakes is converted to a sequence, then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomalies before moderate and strong earthquakes. In the study region center on the epicenter of the 1989 Datong- Yanggao earthquake （Ms5. 9） within a radius of less than 0.8~, with the time length of 3600 days, the longer time length of 3700 days, and the time step of 100 days, the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00, but there were anomalies with values less than 0. 94 in the 2 years before the 1989 Datong-Yanggao earthquake （Ms 5.9）, the 1991 Datong earthquake （ Ms 5.8） and 1999 Hunyuan earthquake （Ms 5. 6 ）, which indicates the spatial distribution of a medium-small earthquake is very different from steady background seismicity. The implication for earthquake prediction from the anomaly of the correlation coefficient is also discussed with the three conclusions： （1） Before moderate and strong earthquakes in Datong and its surrounding areas, the obvious change of spatial distribution patterns of medium-small earthquake can be a kind of seismic precursor of the 2-year time scale for the prediction of an earthquake＇s time. （2） As the study region is restricted within a radius of less than 0. 8~, the result of correlation analysis is also good for the prediction of an earthquake＇s location. （3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.展开更多
The overexploitation of underground water leads to the continuous drawdown of groundwater levels, change of water quality and dry-up in dynamic water level observation wells. Due to land subsidence, the well pipes upl...The overexploitation of underground water leads to the continuous drawdown of groundwater levels, change of water quality and dry-up in dynamic water level observation wells. Due to land subsidence, the well pipes uplift and the observation piping systems are damaged. These environmental geology problems can present serious difficulties for the identification of earthquake anomalies by groundwater level observation. Basied on hydrogeological theories and methods, the paper analyzes the relations of the water balance state of aquifers with stress-strain conditions and the water level regime, and then discusses preliminarily the theory and method for identifying well water level anomalies in a groundwater overdraft area. The result shows that we can accurately judge the nature of the anomaly according to the diffusion character of the drawdown funnel in the well area in combination with the aforementioned theory and method and multi-year variation patterns obtained from existing data. The results of the research are helpful for distinguishing the influence of single centralized water pumping from the long-term overdraft of water on the water level, correctly recognizing water level anomalies in the groundwater overdraft area and increasing the level of earthquake analysis and prediction.展开更多
The Tianwen-1 probe,used in China’s first Mars exploration mission,features multiple flight phases,numerous spatial pointing constraints,and complex working modes.During the braking and capture process,it faces chall...The Tianwen-1 probe,used in China’s first Mars exploration mission,features multiple flight phases,numerous spatial pointing constraints,and complex working modes.During the braking and capture process,it faces challenges such as uplink or downlink command delay,unique capture window,post-control“occultation”,short-time significant change in speed increment,and interference caused by low-frequency and low-damping solid–liquid flexible coupling oscillations.Therefore,high reliability,high autonomy,and high precision are required for the braking and capture process.As the executor of braking and capture control,the GNC(guidance,navigation,and control)subsystem of the orbiter employs an online orbit control strategy reconstruction method based on arc loss compensation to realize high reliability,the main engine anomaly recognition and a seamless switching scheme to realize high autonomy,and the attitude–orbit coupling control algorithm with thrust direction compensation to realize high-precision speed increment control.According to the on-orbit flight validation of the Tianwen-1 probe,the GNC subsystem of the orbiter has completed the braking and capture control task reliably and autonomously with millimeter-per-second-level accuracy,effectively ensuring the successful execution of subsequent landing and patrol tasks.This paper analyzes the online orbit control strategy reconstruction method,anomaly recognition and seamless switching method,and thrust vector control method of the braking and capture process and offers valuable insights for future interplanetary exploration flight control.展开更多
文摘Interference in the data of geochemical hydrocarbon exploration is a large obstacle for anomaly recognition. The multiresolution analysis of wavelet analysis can extract the information at different scales so as to provide a powerful tool for information analysis and processing. Based on the analysis of the geometric nature of hydrocarbon anomalies and background, Mallat wavelet and symmetric border treatment are selected and data pre-processing (logarithm-normalization) is established. This approach provide good results in Shandong and Inner Mongolia, China. It is demonstrated that this approach overcome the disadvantage of backgound variation in the window (interference in window), used in moving average, frame filtering and spatial and scaling modeling methods.
基金grant from Institute of Crustal Dynamics, China Earthquake Administration (No. ZDJ2011 - 01) and (No. ZDJ2010 - 26)
文摘On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by correlation analysis with a focus on its anomaly before moderate and strong earthquakes. With different spatial scales, temporal scales and time steps, the spatial distribution of earthquakes is converted to a sequence, then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomalies before moderate and strong earthquakes. In the study region center on the epicenter of the 1989 Datong- Yanggao earthquake （Ms5. 9） within a radius of less than 0.8~, with the time length of 3600 days, the longer time length of 3700 days, and the time step of 100 days, the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00, but there were anomalies with values less than 0. 94 in the 2 years before the 1989 Datong-Yanggao earthquake （Ms 5.9）, the 1991 Datong earthquake （ Ms 5.8） and 1999 Hunyuan earthquake （Ms 5. 6 ）, which indicates the spatial distribution of a medium-small earthquake is very different from steady background seismicity. The implication for earthquake prediction from the anomaly of the correlation coefficient is also discussed with the three conclusions： （1） Before moderate and strong earthquakes in Datong and its surrounding areas, the obvious change of spatial distribution patterns of medium-small earthquake can be a kind of seismic precursor of the 2-year time scale for the prediction of an earthquake＇s time. （2） As the study region is restricted within a radius of less than 0. 8~, the result of correlation analysis is also good for the prediction of an earthquake＇s location. （3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.
基金The research was funded by the National Science and Technology Support Programof China under Grant No2006BAC01B0203
文摘The overexploitation of underground water leads to the continuous drawdown of groundwater levels, change of water quality and dry-up in dynamic water level observation wells. Due to land subsidence, the well pipes uplift and the observation piping systems are damaged. These environmental geology problems can present serious difficulties for the identification of earthquake anomalies by groundwater level observation. Basied on hydrogeological theories and methods, the paper analyzes the relations of the water balance state of aquifers with stress-strain conditions and the water level regime, and then discusses preliminarily the theory and method for identifying well water level anomalies in a groundwater overdraft area. The result shows that we can accurately judge the nature of the anomaly according to the diffusion character of the drawdown funnel in the well area in combination with the aforementioned theory and method and multi-year variation patterns obtained from existing data. The results of the research are helpful for distinguishing the influence of single centralized water pumping from the long-term overdraft of water on the water level, correctly recognizing water level anomalies in the groundwater overdraft area and increasing the level of earthquake analysis and prediction.
基金supported by the National Natural Science Foundation of China(Grant No.11672126).
文摘The Tianwen-1 probe,used in China’s first Mars exploration mission,features multiple flight phases,numerous spatial pointing constraints,and complex working modes.During the braking and capture process,it faces challenges such as uplink or downlink command delay,unique capture window,post-control“occultation”,short-time significant change in speed increment,and interference caused by low-frequency and low-damping solid–liquid flexible coupling oscillations.Therefore,high reliability,high autonomy,and high precision are required for the braking and capture process.As the executor of braking and capture control,the GNC(guidance,navigation,and control)subsystem of the orbiter employs an online orbit control strategy reconstruction method based on arc loss compensation to realize high reliability,the main engine anomaly recognition and a seamless switching scheme to realize high autonomy,and the attitude–orbit coupling control algorithm with thrust direction compensation to realize high-precision speed increment control.According to the on-orbit flight validation of the Tianwen-1 probe,the GNC subsystem of the orbiter has completed the braking and capture control task reliably and autonomously with millimeter-per-second-level accuracy,effectively ensuring the successful execution of subsequent landing and patrol tasks.This paper analyzes the online orbit control strategy reconstruction method,anomaly recognition and seamless switching method,and thrust vector control method of the braking and capture process and offers valuable insights for future interplanetary exploration flight control.
