It’s dissertated the relationship of the drive precision of large telescope, optical quality of the telescope and Seeing of atmosphere in the observatory in the article. And it gives the evaluation for drive precisio...It’s dissertated the relationship of the drive precision of large telescope, optical quality of the telescope and Seeing of atmosphere in the observatory in the article. And it gives the evaluation for drive precision of large telescope from mathematics matrix. If the value of evaluation for drive precision is high, it shows that the practical error of drive is small. Or it shows the practical error of drive is large. Based on 2 16 meter telescope, the right ascension drive gear system, optical system and Seeing in Xinglong observatory, a value of evaluation of this drive system in the current condition is calculated. Three other values of evaluation are calculated for supposed conditions. From that we can infer the basic and super standard limits of evaluation for drive precision of the drive precision error which is required when building large telescope.展开更多
Coal seams in Tashan Mine of Datong Coal Group in China average 15 m thick and have been mined by the top coal caving longwall mining method of large mining height. Mining height was 3.8 m and the top coal caving heig...Coal seams in Tashan Mine of Datong Coal Group in China average 15 m thick and have been mined by the top coal caving longwall mining method of large mining height. Mining height was 3.8 m and the top coal caving height was 11.2 m. The gateroad pillar between panels was 38 m. During retreat mining,serious bumps occurred in the gateroads on both sides of the pillar affecting safety production. Therefore,pillarless mining was experimented. Using numerical modeling and comparative study of cases of similar mining condition,it was decided to employ a 6 m wide pillar,rather than the previous 38 m wide pillar.Support system for the gateroads was designed and implemented. During gateroad development,pillar failure conditions and entry deformation were monitored. Hydraulic fracturing method was employed to cut off the K3 sandstone along the entry rib so as to reduce the abutment pressure induced during retreat mining. Support reinforcement method combining grouting and advanced reinforcement methods was proposed to insure stable gateroad ahead of mining. Methane drainage and nitrogen injection were implemented to eliminate hazards associated with mine fire and spontaneous combustion. Since the development of gateroad has just completed,and retreat mining has not begun,the effectiveness of the proposed methods is unknown at this point. However,monitoring will continue until after mining.The results will be published in a separate paper.展开更多
From a nonlinear quasi-geostrophic barotropic vorticity equation including frictional dissipation, thermal driving and large topography used by Charney in investigation of the multiple flow equilibria and blocking, us...From a nonlinear quasi-geostrophic barotropic vorticity equation including frictional dissipation, thermal driving and large topography used by Charney in investigation of the multiple flow equilibria and blocking, using the Serrin-Joseph energy method and the variational principle, we found the nonlinear barotropic stability criteria of the zonal basic flow with the total energy, total enstrophy and their linear combination respectively, and compared the criteria with Charney's results.展开更多
文摘It’s dissertated the relationship of the drive precision of large telescope, optical quality of the telescope and Seeing of atmosphere in the observatory in the article. And it gives the evaluation for drive precision of large telescope from mathematics matrix. If the value of evaluation for drive precision is high, it shows that the practical error of drive is small. Or it shows the practical error of drive is large. Based on 2 16 meter telescope, the right ascension drive gear system, optical system and Seeing in Xinglong observatory, a value of evaluation of this drive system in the current condition is calculated. Three other values of evaluation are calculated for supposed conditions. From that we can infer the basic and super standard limits of evaluation for drive precision of the drive precision error which is required when building large telescope.
基金funded by the United Foundation key project fund,Chinese Natural Science Committee (No.U1261207)Datong Coal Group,Tashan Coal Mine,and supported by the Natural Science Foundation of Ningbo of China (No.U1261207)
文摘Coal seams in Tashan Mine of Datong Coal Group in China average 15 m thick and have been mined by the top coal caving longwall mining method of large mining height. Mining height was 3.8 m and the top coal caving height was 11.2 m. The gateroad pillar between panels was 38 m. During retreat mining,serious bumps occurred in the gateroads on both sides of the pillar affecting safety production. Therefore,pillarless mining was experimented. Using numerical modeling and comparative study of cases of similar mining condition,it was decided to employ a 6 m wide pillar,rather than the previous 38 m wide pillar.Support system for the gateroads was designed and implemented. During gateroad development,pillar failure conditions and entry deformation were monitored. Hydraulic fracturing method was employed to cut off the K3 sandstone along the entry rib so as to reduce the abutment pressure induced during retreat mining. Support reinforcement method combining grouting and advanced reinforcement methods was proposed to insure stable gateroad ahead of mining. Methane drainage and nitrogen injection were implemented to eliminate hazards associated with mine fire and spontaneous combustion. Since the development of gateroad has just completed,and retreat mining has not begun,the effectiveness of the proposed methods is unknown at this point. However,monitoring will continue until after mining.The results will be published in a separate paper.
文摘From a nonlinear quasi-geostrophic barotropic vorticity equation including frictional dissipation, thermal driving and large topography used by Charney in investigation of the multiple flow equilibria and blocking, using the Serrin-Joseph energy method and the variational principle, we found the nonlinear barotropic stability criteria of the zonal basic flow with the total energy, total enstrophy and their linear combination respectively, and compared the criteria with Charney's results.
