Discrete element calculations of the top-coal drawing process for diferent gangue-coal density ratios were conducted to investigate the efect of the gangue-coal density ratio on the drawing mechanism in longwall top-c...Discrete element calculations of the top-coal drawing process for diferent gangue-coal density ratios were conducted to investigate the efect of the gangue-coal density ratio on the drawing mechanism in longwall top-coal caving.The efects were analyzed for the drawing body,the top-coal boundary,and the recovery of top coal.The results show that for increasing density ratio,the initial drawing body on the goaf side is farther away from the drawing support and its width and volume gradually increase.The upper part of the sickle-shaped drawing body extends near the initial drawing body with increasing density ratio in the normal cycling stage,and the distance from the drawing body to the initial drawing body is its maximum width.The larger the density ratio,the smaller the height of the top coal above the goaf at the end of the initial drawing process.The height of the top-coal boundary decreases with increasing density ratio,until it reaches a limit.In a normal cycle,due to hysteretic development,the top-coal boundary moves toward the goaf until the density ratio is approximately 2.0,which is consistent with the physical experiment results.Finally,increasing the advance length of the working face is benefcial for increasing the overall recovery of top coal.展开更多
The field test of high concentration polymer flooding has the characteristics of high cost, long cycle and irreversibility of the reservoir development process. In order to ensure the best development effect of the de...The field test of high concentration polymer flooding has the characteristics of high cost, long cycle and irreversibility of the reservoir development process. In order to ensure the best development effect of the development block, this paper simulated and calculated the high concentration polymer flooding development case of the polymer flooding pilot test area through numerical simulation research, and selected the best case through the comparison of various development indicators. The simulation results showed that the larger the polymer dosage and the higher the concentration, the better the oil displacement effect. The best injection method in the construction process was the overall injection of high concentration polymer. The test area should implement high concentration polymer oil displacement as soon as possible. The research results provided theoretical guidance for the future development and management of the pilot area.展开更多
目的分析突发性聋(突聋)患者的内耳三维真实重建反转恢复(three dimensional real inversion recovery,3D Real IR)成像表现,探讨内耳不同信号强度与突聋预后的关系。方法选取2022年9月25日—2023年4月10日郑州大学第五附属医院耳鼻咽...目的分析突发性聋(突聋)患者的内耳三维真实重建反转恢复(three dimensional real inversion recovery,3D Real IR)成像表现,探讨内耳不同信号强度与突聋预后的关系。方法选取2022年9月25日—2023年4月10日郑州大学第五附属医院耳鼻咽喉科住院治疗及门诊治疗的单侧突聋患者60例,按照听力曲线将患者分为低频下降型4例、高频下降型1例、平坦下降型34例和全聋型21例。由于平坦下降型和全聋型治疗方法一致,将平坦下降型和全聋型的55例患者按治疗有效与否分为无效组25例和有效组30例;按治疗前听力分级,分为轻度听力损失组11例、中度听力损失组7例、重度听力损失组16例和极重度听力损失组21例;根据听力下降与否分为患耳组55耳和健耳组55耳。比较患耳和健耳的耳蜗信号强度,并测量延髓信号强度,分别计算耳蜗/延髓(cochlea/medulla ratio,CM)比值,分析耳蜗信号强度与治疗结果之间关系。结果无效组CM比值明显高于治疗有效组,差异有统计学意义(P<0.001);患耳组与健耳组CM比值比较,差异有统计学意义(P<0.05)。轻度、中度、重度和极重度听力损失组患耳CM比值比较(2.57±3.02 vs 1.77±0.87 vs 2.04±1.98 vs 2.51±2.33),差异无统计学意义(F=0.304,P=0.823)。结论内耳3D Real IR可显示突聋患者血-迷路屏障通透性的改变,CM比值可以更精确了解突聋患者内耳受损的程度,CM比值大小与听力损失程度并不一致,可以单独作为一种判断突聋预后的因素。突聋患者CM比值高于1.58提示可能预后不良。展开更多
目的分析突聋患者的内耳钆造影MRI三维真实重建反转恢复(three dimensional real inversion recovery,3D real IR)成像上的表现,探讨血-迷路屏障的通透性与突聋发病机制及其预后的关系。方法对41例单侧突聋患者行内耳钆造影MRI,测量患...目的分析突聋患者的内耳钆造影MRI三维真实重建反转恢复(three dimensional real inversion recovery,3D real IR)成像上的表现,探讨血-迷路屏障的通透性与突聋发病机制及其预后的关系。方法对41例单侧突聋患者行内耳钆造影MRI,测量患耳和健耳的耳蜗信号强度,并测量延髓信号强度,分别计算出耳蜗/延髓比值(cochlear/medulla ratio,CM ratio),以CM比值作为血-迷路屏障通透性的标志物,分析突聋患者患耳、健耳CM比值的不对称程度与疗效之间的关系。结果41例患者中,33例(80.48%)患耳的CM比值高于健耳,差异有统计学意义(P<0.05);患耳CM比值为健耳的1.5倍以下者18例,治疗有效率为77.78%(14/18);患侧CM比值不高于健侧者8例,治疗有效率为100%;达到健耳的1.5倍至1.75倍之间者7例,治疗有效率为100%(7/7);达到健耳的1.75倍至2.0倍之间者2例,治疗有效率为50%(1/2);达到健耳的2.0倍以上者14例,治疗有效率为14.28%(12/14);差异有统计学意义(P<0.05)。结论内耳3D Real IR可显示突聋患者血-迷路屏障通透性的改变,80.48%的突聋患者患侧耳蜗出现高信号,患耳CM比值达健耳的1.75倍以上者多数预后不良。展开更多
Sparse measurements challenge fault location in distribution networks.This paper proposes a method for asymmetric ground fault location in distribution networks with limited measurements.A virtual injected current vec...Sparse measurements challenge fault location in distribution networks.This paper proposes a method for asymmetric ground fault location in distribution networks with limited measurements.A virtual injected current vector is formulated to estimate the fault line,which can be reconstructed from voltage sags measured at a few buses using compressive sensing(CS).The relationship between the virtual injected current ratio(VICR)and fault position is deduced from circuit analysis to pinpoint the fault.Furthermore,a two-stage recovery strategy is proposed for improving reconstruction accuracy of the current vector,where two different sensing matrixes are utilized to improve the incoherence.The proposed method is validated in IEEE 34 node test feeder.Simulation results show asymmetric ground fault type,resistance,fault position and access of distributed generators(DGs)do not significantly influence performance of our method.In addition,it works effectively under various scenarios of noisy measurement and line parameter error.Validations on 134 node test feeders prove the proposed method is also suitable for systems with more complex structure.展开更多
基金supported by the Natural Science Foundation of China,China(Grant No.51904305)the Research Fund of the State Key Laboratory of Coal Resources and Safe Mining,China University of Mining and Technology(Grant No.SKLCRSM19KF023)+2 种基金the Fundamental Research Funds for the Central Universities(Grant No.2022YQNY03)the Research Fund of Key Laboratory of Safety and High-efficiency Coal Mining,Ministry of Education(Grant No.JYBSYS2021204)the Open Fund of State Key Laboratory of Coal Resources and Safe Mining(Grant No.SKLCRSM21KFA09).
文摘Discrete element calculations of the top-coal drawing process for diferent gangue-coal density ratios were conducted to investigate the efect of the gangue-coal density ratio on the drawing mechanism in longwall top-coal caving.The efects were analyzed for the drawing body,the top-coal boundary,and the recovery of top coal.The results show that for increasing density ratio,the initial drawing body on the goaf side is farther away from the drawing support and its width and volume gradually increase.The upper part of the sickle-shaped drawing body extends near the initial drawing body with increasing density ratio in the normal cycling stage,and the distance from the drawing body to the initial drawing body is its maximum width.The larger the density ratio,the smaller the height of the top coal above the goaf at the end of the initial drawing process.The height of the top-coal boundary decreases with increasing density ratio,until it reaches a limit.In a normal cycle,due to hysteretic development,the top-coal boundary moves toward the goaf until the density ratio is approximately 2.0,which is consistent with the physical experiment results.Finally,increasing the advance length of the working face is benefcial for increasing the overall recovery of top coal.
文摘The field test of high concentration polymer flooding has the characteristics of high cost, long cycle and irreversibility of the reservoir development process. In order to ensure the best development effect of the development block, this paper simulated and calculated the high concentration polymer flooding development case of the polymer flooding pilot test area through numerical simulation research, and selected the best case through the comparison of various development indicators. The simulation results showed that the larger the polymer dosage and the higher the concentration, the better the oil displacement effect. The best injection method in the construction process was the overall injection of high concentration polymer. The test area should implement high concentration polymer oil displacement as soon as possible. The research results provided theoretical guidance for the future development and management of the pilot area.
文摘目的分析突发性聋(突聋)患者的内耳三维真实重建反转恢复(three dimensional real inversion recovery,3D Real IR)成像表现,探讨内耳不同信号强度与突聋预后的关系。方法选取2022年9月25日—2023年4月10日郑州大学第五附属医院耳鼻咽喉科住院治疗及门诊治疗的单侧突聋患者60例,按照听力曲线将患者分为低频下降型4例、高频下降型1例、平坦下降型34例和全聋型21例。由于平坦下降型和全聋型治疗方法一致,将平坦下降型和全聋型的55例患者按治疗有效与否分为无效组25例和有效组30例;按治疗前听力分级,分为轻度听力损失组11例、中度听力损失组7例、重度听力损失组16例和极重度听力损失组21例;根据听力下降与否分为患耳组55耳和健耳组55耳。比较患耳和健耳的耳蜗信号强度,并测量延髓信号强度,分别计算耳蜗/延髓(cochlea/medulla ratio,CM)比值,分析耳蜗信号强度与治疗结果之间关系。结果无效组CM比值明显高于治疗有效组,差异有统计学意义(P<0.001);患耳组与健耳组CM比值比较,差异有统计学意义(P<0.05)。轻度、中度、重度和极重度听力损失组患耳CM比值比较(2.57±3.02 vs 1.77±0.87 vs 2.04±1.98 vs 2.51±2.33),差异无统计学意义(F=0.304,P=0.823)。结论内耳3D Real IR可显示突聋患者血-迷路屏障通透性的改变,CM比值可以更精确了解突聋患者内耳受损的程度,CM比值大小与听力损失程度并不一致,可以单独作为一种判断突聋预后的因素。突聋患者CM比值高于1.58提示可能预后不良。
文摘目的分析突聋患者的内耳钆造影MRI三维真实重建反转恢复(three dimensional real inversion recovery,3D real IR)成像上的表现,探讨血-迷路屏障的通透性与突聋发病机制及其预后的关系。方法对41例单侧突聋患者行内耳钆造影MRI,测量患耳和健耳的耳蜗信号强度,并测量延髓信号强度,分别计算出耳蜗/延髓比值(cochlear/medulla ratio,CM ratio),以CM比值作为血-迷路屏障通透性的标志物,分析突聋患者患耳、健耳CM比值的不对称程度与疗效之间的关系。结果41例患者中,33例(80.48%)患耳的CM比值高于健耳,差异有统计学意义(P<0.05);患耳CM比值为健耳的1.5倍以下者18例,治疗有效率为77.78%(14/18);患侧CM比值不高于健侧者8例,治疗有效率为100%;达到健耳的1.5倍至1.75倍之间者7例,治疗有效率为100%(7/7);达到健耳的1.75倍至2.0倍之间者2例,治疗有效率为50%(1/2);达到健耳的2.0倍以上者14例,治疗有效率为14.28%(12/14);差异有统计学意义(P<0.05)。结论内耳3D Real IR可显示突聋患者血-迷路屏障通透性的改变,80.48%的突聋患者患侧耳蜗出现高信号,患耳CM比值达健耳的1.75倍以上者多数预后不良。
基金supported in part by Key-Area Research and Development Program of Guangdong Province(No.2020B010166004)State Key Program of National Natural Science Foundation of China under Grant(No.U1866210)Natural Science Foundation of Guangdong Province(No.2022A1515011587).
文摘Sparse measurements challenge fault location in distribution networks.This paper proposes a method for asymmetric ground fault location in distribution networks with limited measurements.A virtual injected current vector is formulated to estimate the fault line,which can be reconstructed from voltage sags measured at a few buses using compressive sensing(CS).The relationship between the virtual injected current ratio(VICR)and fault position is deduced from circuit analysis to pinpoint the fault.Furthermore,a two-stage recovery strategy is proposed for improving reconstruction accuracy of the current vector,where two different sensing matrixes are utilized to improve the incoherence.The proposed method is validated in IEEE 34 node test feeder.Simulation results show asymmetric ground fault type,resistance,fault position and access of distributed generators(DGs)do not significantly influence performance of our method.In addition,it works effectively under various scenarios of noisy measurement and line parameter error.Validations on 134 node test feeders prove the proposed method is also suitable for systems with more complex structure.