Rock bursts are serious natural disasters encountered worldwide in coal mining and rock engineering.In order to forecast rock bursts more effectively,a new rock burst forecasting index E,consisting of intensity and th...Rock bursts are serious natural disasters encountered worldwide in coal mining and rock engineering.In order to forecast rock bursts more effectively,a new rock burst forecasting index E,consisting of intensity and the number of pulses,is proposed,on the basis of abnormal characteristic symptoms of electromagnetic radiation(EMR) generated before rock bursts,combined with statistical theory.The index is distributed as a χ2 distribution with 2 degrees of freedom,i.e.,E～χ 2(2).Via this index,a quantitative comprehensive forecasting criterion of EMR was initially established.E values were calculated when the occurrence probability of the occurrence of a rock burst was 50%,70% and 90%.Appropriate measures should be taken when using these values on the scene.Using EMR data collected in the Nanshan Mine of the Hegang mining area,we verified that the analytical result were consistent with actual situations.This index is of theoretical importance and as a reference for forecasting rock bursts in coal mines.展开更多
We propose a novel method that combines gray system theory and robust M-estimation method to suppress the interference in controlled-source electromagnetic data. We estimate the standard deviation of the data using a ...We propose a novel method that combines gray system theory and robust M-estimation method to suppress the interference in controlled-source electromagnetic data. We estimate the standard deviation of the data using a gray model because of the weak dependence of the gray system on data distribution and size. We combine the proposed and threshold method to identify and eliminate outliers. Robust M-estimation is applied to suppress the effect of the outliers and improve the accuracy. We treat the M-estimators of the preserved data as the true data. We use our method to reject the outliers in simulated signals containing noise to verify the feasibility of our proposed method. The processed values are observed to be approximate to the expected values with high accuracy. The maximum relative error is 3.6676%, whereas the minimum is 0.0251%. In processing field data, we observe that the proposed method eliminates outliers, minimizes the root-mean-square error, and improves the reliability of controlled-source electromagnetic data in follow-up processing and interpretation.展开更多
Security monitoring system of coal mines is indispensable to ensure the safe and efficient production of colliery. Due to the special and narrow underground field of the coal mine, the electromagnetic interference can...Security monitoring system of coal mines is indispensable to ensure the safe and efficient production of colliery. Due to the special and narrow underground field of the coal mine, the electromagnetic interference can cause a series of misstatements and false positives on the monitoring system, which will severely hamper the safe production of coal industry. In this paper, first, the frequency characteristics of the interference source on the power line are extracted when equipment runs normally. Then the finite difference time domain method is introduced to analyze the effects of the electromagnetic interference parameters on the security monitoring signal line. And the interference voltage of the two terminal sides on the single line is taken as evaluating indexes. Finally, the electromagnetic interference parameters are optimized by orthogonal experimental design based on the MATLAB simulation on the normal operation of equipment.展开更多
In order to investigate the suprathermal electron flux(>30 ke V) around dipolarization fronts(DFs), we statistically studied the suprathermal electron flux variations and pitch angle distributions of hundreds of ea...In order to investigate the suprathermal electron flux(>30 ke V) around dipolarization fronts(DFs), we statistically studied the suprathermal electron flux variations and pitch angle distributions of hundreds of earthward propagating DFs observed by THEMIS spacecraft during its tail seasons in years 2008–2009. We focused on the electron flux variations across DFs and electron anisotropies behind DFs. We divided DF into three sectors in the equatorial plane: Dusk, central and dawn sectors. The sectors are defined according to the DF normals with respect to DF's meridian in the equatorial plane(the symmetric line of DF). We found that events with electron flux increases and decreases behind the fronts had no particular dependence on the observation locations. In addition, there was no obvious dependence of electron anisotropy behind DF on the different sectors of DF.展开更多
基金supported by the National High Technology Research and Development Program of China (No.2006AA06Z119)the Ministry of Education Support Program for New Century Excellent Talent (No.NCET-06-0477)
文摘Rock bursts are serious natural disasters encountered worldwide in coal mining and rock engineering.In order to forecast rock bursts more effectively,a new rock burst forecasting index E,consisting of intensity and the number of pulses,is proposed,on the basis of abnormal characteristic symptoms of electromagnetic radiation(EMR) generated before rock bursts,combined with statistical theory.The index is distributed as a χ2 distribution with 2 degrees of freedom,i.e.,E～χ 2(2).Via this index,a quantitative comprehensive forecasting criterion of EMR was initially established.E values were calculated when the occurrence probability of the occurrence of a rock burst was 50%,70% and 90%.Appropriate measures should be taken when using these values on the scene.Using EMR data collected in the Nanshan Mine of the Hegang mining area,we verified that the analytical result were consistent with actual situations.This index is of theoretical importance and as a reference for forecasting rock bursts in coal mines.
基金supported by the National Natural Science Foundation of China(No.41227803)the State High-Tech Development Plan of China(No.2014AA06A602)the Fundamental Research Funds for the Central Universities of Central South University(No.2017557)
文摘We propose a novel method that combines gray system theory and robust M-estimation method to suppress the interference in controlled-source electromagnetic data. We estimate the standard deviation of the data using a gray model because of the weak dependence of the gray system on data distribution and size. We combine the proposed and threshold method to identify and eliminate outliers. Robust M-estimation is applied to suppress the effect of the outliers and improve the accuracy. We treat the M-estimators of the preserved data as the true data. We use our method to reject the outliers in simulated signals containing noise to verify the feasibility of our proposed method. The processed values are observed to be approximate to the expected values with high accuracy. The maximum relative error is 3.6676%, whereas the minimum is 0.0251%. In processing field data, we observe that the proposed method eliminates outliers, minimizes the root-mean-square error, and improves the reliability of controlled-source electromagnetic data in follow-up processing and interpretation.
文摘Security monitoring system of coal mines is indispensable to ensure the safe and efficient production of colliery. Due to the special and narrow underground field of the coal mine, the electromagnetic interference can cause a series of misstatements and false positives on the monitoring system, which will severely hamper the safe production of coal industry. In this paper, first, the frequency characteristics of the interference source on the power line are extracted when equipment runs normally. Then the finite difference time domain method is introduced to analyze the effects of the electromagnetic interference parameters on the security monitoring signal line. And the interference voltage of the two terminal sides on the single line is taken as evaluating indexes. Finally, the electromagnetic interference parameters are optimized by orthogonal experimental design based on the MATLAB simulation on the normal operation of equipment.
基金supported by the National Natural Science Foundation of China(NSFC)(Grant Nos.41174147,41274170 and 41331070)Natural Science Foundation of Jiangxi Province(Grant No.20142BCB23006)
文摘In order to investigate the suprathermal electron flux(>30 ke V) around dipolarization fronts(DFs), we statistically studied the suprathermal electron flux variations and pitch angle distributions of hundreds of earthward propagating DFs observed by THEMIS spacecraft during its tail seasons in years 2008–2009. We focused on the electron flux variations across DFs and electron anisotropies behind DFs. We divided DF into three sectors in the equatorial plane: Dusk, central and dawn sectors. The sectors are defined according to the DF normals with respect to DF's meridian in the equatorial plane(the symmetric line of DF). We found that events with electron flux increases and decreases behind the fronts had no particular dependence on the observation locations. In addition, there was no obvious dependence of electron anisotropy behind DF on the different sectors of DF.
