When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stra...When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a ＂main key stratum＂, will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway （we can also drill them in the drilling field located high in an air gateway）. Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middie coal group, with a gas drainage radius over 100 m.展开更多
Objective： The aim of this study is to investigate if dual-source computed tomography （DSCT） could guide the percutaneous coronary intervention （PCI） of chronic total occlusion （CTO）. Methods： We enrolled pati...Objective： The aim of this study is to investigate if dual-source computed tomography （DSCT） could guide the percutaneous coronary intervention （PCI） of chronic total occlusion （CTO）. Methods： We enrolled patients who were confirmed to have at least one native coronary artery CTO by DSCT before they underwent selective PCI in the period from December 2007 to October 2008. A CTO was defined as an obstruction of a native coronary artery with no luminal continuity. The CT-guided PCI procedure involved placing CT and fluoroscopic images side-by-side on the screen. DSCT images were analyzed for location, segment, plaque characteristics, calcification, and proximal lumen diameter of the CTO before PCI. The guidewire was advanced and manipulated under CT guidance. The PCI was carried out and the results were compared. Results： Seventy-four CTOs were assessed. PCI was successful in 57 cases of CTOs （77.0%）. According to the results, CTOs were divided into two groups： successfuI-PCI and failed-PCI. All coronary artery paths of CTOs were clearly recognized by DSCT. In the successfuI-PCI group, soft plaques were detected much more often than those in the failed-PCI group, but fibrous and calcified plaques were seen more often in the failed-PCI group. Calcification severity in CTO segments showed a significant difference between the groups （P=0.014）. Calcified plaques were detected in 20 （35.1%） lesions in the successfuI-PCI group. More than 70% of the failures were calcified plaques, of which there were two arc-calcified and one circular-calcified lesions. Occlusions were longer in the failed-PCI group than those in the successfuI-PCI group [（38.8±25.0） vs. （18.0±15.3） mm, respec- tively, P〈0.01]. Fewer guidewires were used in the successfuI-PCI group compared with the failed-PCI group （1.7±1.0 vs. 2.5±0.9, respectively, P〈0.01）. The logistic regression analysis indicated that predictors of recanalization of CTOs included occlusion length （P=-0.0035, risk ratio （RR）=0.93） and calcification severity （P=0.05, RR=0.27）. Multi-linear trends analysis showed that the factors affecting procedural time were CTO location （P=-0.0141） and occlusion length （P=0.0035）. Conclusions： DSCT could delineate the path of CTOs and characterize plaques. The outcomes of PCI were related to thrombolysis in myocardial infarction （TIMI） flow grade, CTO characteristics, severity of calcified plaques and the length of occlusive segments. Occlusion length and calcification severity were independent predictors of CTOs. Occlusion length and CTO segments could also help to estimate the duration of interventional procedures.展开更多
基金Projects 2005CB221503 supported by the National Basic Research Program of China70533050 and 50674089 by the National Natural Science Foundation of China2005BA813B-3-06 by the National Tenth 5-Year Key Scientific and Technological Project
文摘When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a ＂main key stratum＂, will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway （we can also drill them in the drilling field located high in an air gateway）. Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middie coal group, with a gas drainage radius over 100 m.
基金Project (No.2006BAI01A02) supported by the National Science and Technology Pillar Program of the 11th five-year Plan,China
文摘Objective： The aim of this study is to investigate if dual-source computed tomography （DSCT） could guide the percutaneous coronary intervention （PCI） of chronic total occlusion （CTO）. Methods： We enrolled patients who were confirmed to have at least one native coronary artery CTO by DSCT before they underwent selective PCI in the period from December 2007 to October 2008. A CTO was defined as an obstruction of a native coronary artery with no luminal continuity. The CT-guided PCI procedure involved placing CT and fluoroscopic images side-by-side on the screen. DSCT images were analyzed for location, segment, plaque characteristics, calcification, and proximal lumen diameter of the CTO before PCI. The guidewire was advanced and manipulated under CT guidance. The PCI was carried out and the results were compared. Results： Seventy-four CTOs were assessed. PCI was successful in 57 cases of CTOs （77.0%）. According to the results, CTOs were divided into two groups： successfuI-PCI and failed-PCI. All coronary artery paths of CTOs were clearly recognized by DSCT. In the successfuI-PCI group, soft plaques were detected much more often than those in the failed-PCI group, but fibrous and calcified plaques were seen more often in the failed-PCI group. Calcification severity in CTO segments showed a significant difference between the groups （P=0.014）. Calcified plaques were detected in 20 （35.1%） lesions in the successfuI-PCI group. More than 70% of the failures were calcified plaques, of which there were two arc-calcified and one circular-calcified lesions. Occlusions were longer in the failed-PCI group than those in the successfuI-PCI group [（38.8±25.0） vs. （18.0±15.3） mm, respec- tively, P〈0.01]. Fewer guidewires were used in the successfuI-PCI group compared with the failed-PCI group （1.7±1.0 vs. 2.5±0.9, respectively, P〈0.01）. The logistic regression analysis indicated that predictors of recanalization of CTOs included occlusion length （P=-0.0035, risk ratio （RR）=0.93） and calcification severity （P=0.05, RR=0.27）. Multi-linear trends analysis showed that the factors affecting procedural time were CTO location （P=-0.0141） and occlusion length （P=0.0035）. Conclusions： DSCT could delineate the path of CTOs and characterize plaques. The outcomes of PCI were related to thrombolysis in myocardial infarction （TIMI） flow grade, CTO characteristics, severity of calcified plaques and the length of occlusive segments. Occlusion length and calcification severity were independent predictors of CTOs. Occlusion length and CTO segments could also help to estimate the duration of interventional procedures.
