Along with the economic development,large tunnels need to be constructed in many high mountains or complex structure regions,and the design and construction of detailed tunnel exploration become particularly important...Along with the economic development,large tunnels need to be constructed in many high mountains or complex structure regions,and the design and construction of detailed tunnel exploration become particularly important.Transient electromagnetic method( TEM) uses a non-grounded loop or an electrode to send a primary electromagnetic pulse into the ground,and observes spatial and temporal distribution of secondary electromagnetic field,which is widely applied in mineral resource exploration,engineering geology,etc.The application of TEM in the tunnel construction of Kaiyuan Temple is researched in this study.The smoke loop inversion is adopted for inverting the transient electromagnetic data.The drilling data and high density resistivity method data are combined for comparison.The obtained inversion result greatly coincides with the actual conditions.Therefore,the geophysical prospecting basis can be provided for the division of stratum,delineation of geological structure,and design and construction of tunnel pavement.By virtue of TEM,drilling data and high density resistivity method,the tunnel construction of Kaiyuan Temple has obtained satisfactory results.展开更多
Based on the magnetic field and plasma data obtained by GEOTAIL in 1992-1995 and WIND in1994-2009, the magnetic field and plasma properties in the magnetotail near lunar orbit were studied statistically using the supe...Based on the magnetic field and plasma data obtained by GEOTAIL in 1992-1995 and WIND in1994-2009, the magnetic field and plasma properties in the magnetotail near lunar orbit were studied statistically using the superposed epoch analysis. The results showed that near the 0° sector the plasma density was negatively correlated with Dst index while the temperature was positively correlated with Dst index. The plasma velocity and magnetic field strength had little correlation with Dst index. Around the current sheet near the lunar orbit, the Bx varied between -15-15 nT, the plasma density was less than 0.4 cm^-3, the median of plasma density for all events was less than 0.1 cm^-3, the temperature varied from 0.016 to 8.98 keV, the median of the plasma temperature for all the events was -3 keV, the median of speed was about 200 km/s and the maximum speed was up to 1500 km/s. The tailward and earthward flows could be observed accompanied with the current sheet. For the current sheet cases with tailward flow, the Bx varied from -15 to 15 nT, the upper quartile of plasma velocity was more than 400 krn/s, the maximum speed was up to 1500 km/s. For the current sheet cases with tailward flow, the Bx varied from -10 to 10 nT, the upper quartile of plasma velocity was less than 400 km/s, the maximum speed was up to 1200 km/s. The median of plasma density, temperature and velocity were similar for the two categories. This paper discussed the relationship between above results and magnetic reconnection at magnetic tail, compared the above results with the observation in the far magnetotail. We fitted the statistical results according to the Harris current sheet model, and the observation was consistent with Harris current sheet model. The above results can provide useful information for the design and protection of lunar-orbiting spacecraft and can be used as the background magnetic field and plasma parameters in the numerical simulation of mid-magnetotail reconnection.展开更多
文摘Along with the economic development,large tunnels need to be constructed in many high mountains or complex structure regions,and the design and construction of detailed tunnel exploration become particularly important.Transient electromagnetic method( TEM) uses a non-grounded loop or an electrode to send a primary electromagnetic pulse into the ground,and observes spatial and temporal distribution of secondary electromagnetic field,which is widely applied in mineral resource exploration,engineering geology,etc.The application of TEM in the tunnel construction of Kaiyuan Temple is researched in this study.The smoke loop inversion is adopted for inverting the transient electromagnetic data.The drilling data and high density resistivity method data are combined for comparison.The obtained inversion result greatly coincides with the actual conditions.Therefore,the geophysical prospecting basis can be provided for the division of stratum,delineation of geological structure,and design and construction of tunnel pavement.By virtue of TEM,drilling data and high density resistivity method,the tunnel construction of Kaiyuan Temple has obtained satisfactory results.
基金supported by the National Natural Science Foundation ofChina (Grant No. 40831061)the National Key Laboratory Special Fund and the Open Research Foundation of Science and Technology on Aerospace Flight Dynamics Laboratory (Grant No. 2012afd1034)
文摘Based on the magnetic field and plasma data obtained by GEOTAIL in 1992-1995 and WIND in1994-2009, the magnetic field and plasma properties in the magnetotail near lunar orbit were studied statistically using the superposed epoch analysis. The results showed that near the 0° sector the plasma density was negatively correlated with Dst index while the temperature was positively correlated with Dst index. The plasma velocity and magnetic field strength had little correlation with Dst index. Around the current sheet near the lunar orbit, the Bx varied between -15-15 nT, the plasma density was less than 0.4 cm^-3, the median of plasma density for all events was less than 0.1 cm^-3, the temperature varied from 0.016 to 8.98 keV, the median of the plasma temperature for all the events was -3 keV, the median of speed was about 200 km/s and the maximum speed was up to 1500 km/s. The tailward and earthward flows could be observed accompanied with the current sheet. For the current sheet cases with tailward flow, the Bx varied from -15 to 15 nT, the upper quartile of plasma velocity was more than 400 krn/s, the maximum speed was up to 1500 km/s. For the current sheet cases with tailward flow, the Bx varied from -10 to 10 nT, the upper quartile of plasma velocity was less than 400 km/s, the maximum speed was up to 1200 km/s. The median of plasma density, temperature and velocity were similar for the two categories. This paper discussed the relationship between above results and magnetic reconnection at magnetic tail, compared the above results with the observation in the far magnetotail. We fitted the statistical results according to the Harris current sheet model, and the observation was consistent with Harris current sheet model. The above results can provide useful information for the design and protection of lunar-orbiting spacecraft and can be used as the background magnetic field and plasma parameters in the numerical simulation of mid-magnetotail reconnection.
