The gestation and occurrence of strong earthquakes are closely related to fault activity, which is not only revealed by abundant experimentation and seismism but also proved by modern seismology. On the Chinese mainla...The gestation and occurrence of strong earthquakes are closely related to fault activity, which is not only revealed by abundant experimentation and seismism but also proved by modern seismology. On the Chinese mainland, the relation between earthquake activity and active faults is one of the bases for partitioning potential seismic sources, analyzing the seismotectoulcs and estimating location of strong earthquakes.Due to the nonuniformity of earth media, instability of observation systems and disturbance of the environment, etc, the variety of observational data is complicated, that is, there is no absolutely ＂normal＂ or ＂abnormal＂, and seismic anomalies can be divided into many mutually exdusive＂ abnormal states＂. In different conditions of combined time-spacestrength, determining seismic anomalies by different monomial forecast methods and its efficiency could be different due to the uncertainty of a precursor itself or complexity of the relationship between a precursor and earthquake gestation. It is very difficult to discover and dispose of this difference in actual application in a ＂two-state＂ model. But in a ＂multi-state＂ model, the difference can be easily reflected and the optimal combination of forecasting parameters for a forecast method can also be determined easily. Based on the ＂multi-state＂ precursory model and the optimization method for parameters of earthquake forecast model under the condition of optimal forecast efficiency, the relationship of the spatial location of earthquake with M ≥ 6.0 and active faults in three seismic belts are analyzed. The results demonstrate that in the Hetao Seismic Belt, seismicity is mostly concentrated in the range of 20 km along the fault, the optimization model can forecast the location of potential earthquakes of M ≥ 6.0 near the faults with a relatively high accuracy and the reliability is 0.5 ; while in the Qilian Mt. Seismic Belt, the reliability only reaches 0.14 when we use the model to estimate earthquakes within 30 km range along the faults. The ＂multi-state＂ precursory model, the efficiency-evaluating model and the parameter selection of individual earthquake forecast model based on optimal efficiency are of certain revelatory and practicable meanings for developing knowledge about precursors, investigating the laws of earthquake preparation and searching for optimal forecasting methods.展开更多
The complex structure at trailing edge reduces the manufacturing precision, which results in an error in the size of the trailing edge structure. In this study, the performance of a stage high-pressure turbine(HP turb...The complex structure at trailing edge reduces the manufacturing precision, which results in an error in the size of the trailing edge structure. In this study, the performance of a stage high-pressure turbine(HP turbine) is calculated out in three dimensions. In the HP turbine guide vane, the trailing edge cutback configuration is adopted. Through three-dimensional simulation, the complex flow around the trailing edge with cutback cooling configuration is presented in this study, and the manufacturing precision reduction due to the complex structure at trailing edge is considered. Furthermore, the effect of trailing edge lip thickness and deflection of the stator on the turbine performance is discussed. Overall, as the press-side lip thickness increasing, the turbine efficiency and turbine inlet flow are reduced. However, the changes in the turbine work output are relatively complex. On the other hand, as the spacing between suction-side lip and press-side lip increases, turbine performance becomes worse. Both of the turbine efficiency and the turbine work output become smaller, while the turbine inlet flow becomes bigger. The effect of the spacing between suction-side lip and press-side lip is obviously greater than that of the press-side lip thickness. The change of the press-side lip thickness has little effect on the relation between the turbine performance and the spacing between suction-side lip and press-side lip. However, when the spacing between suction-side lip and press-side lip deviates from the baseline value, the effect law of the press-side lip thickness on the turbine performance will be affected. As the press-side lip thickness increases, it leads to an increase in the low-velocity zone at both of the pressure-side and suction-side trailing edge. And more main stream is affected or mixed into the wake flow. When the spacing between suction-side lip and press-side lip becomes smaller, the low-velocity zone at the trailing edge is smaller, and the change of vortex with the press-side lip thickness is affected. With a bigger spacing between suction-side lip and press-side lip, the variation is contrary.展开更多
基金This project was sponsored by the Joint Earthquake Science Foundation of CEA(Grant No.103075 and No.104016)
文摘The gestation and occurrence of strong earthquakes are closely related to fault activity, which is not only revealed by abundant experimentation and seismism but also proved by modern seismology. On the Chinese mainland, the relation between earthquake activity and active faults is one of the bases for partitioning potential seismic sources, analyzing the seismotectoulcs and estimating location of strong earthquakes.Due to the nonuniformity of earth media, instability of observation systems and disturbance of the environment, etc, the variety of observational data is complicated, that is, there is no absolutely ＂normal＂ or ＂abnormal＂, and seismic anomalies can be divided into many mutually exdusive＂ abnormal states＂. In different conditions of combined time-spacestrength, determining seismic anomalies by different monomial forecast methods and its efficiency could be different due to the uncertainty of a precursor itself or complexity of the relationship between a precursor and earthquake gestation. It is very difficult to discover and dispose of this difference in actual application in a ＂two-state＂ model. But in a ＂multi-state＂ model, the difference can be easily reflected and the optimal combination of forecasting parameters for a forecast method can also be determined easily. Based on the ＂multi-state＂ precursory model and the optimization method for parameters of earthquake forecast model under the condition of optimal forecast efficiency, the relationship of the spatial location of earthquake with M ≥ 6.0 and active faults in three seismic belts are analyzed. The results demonstrate that in the Hetao Seismic Belt, seismicity is mostly concentrated in the range of 20 km along the fault, the optimization model can forecast the location of potential earthquakes of M ≥ 6.0 near the faults with a relatively high accuracy and the reliability is 0.5 ; while in the Qilian Mt. Seismic Belt, the reliability only reaches 0.14 when we use the model to estimate earthquakes within 30 km range along the faults. The ＂multi-state＂ precursory model, the efficiency-evaluating model and the parameter selection of individual earthquake forecast model based on optimal efficiency are of certain revelatory and practicable meanings for developing knowledge about precursors, investigating the laws of earthquake preparation and searching for optimal forecasting methods.
基金The National Natural Science Foundation of China (Grant No. 51575444)Aviation Power Foundation of China (Grant No. 6141B090319)the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2018JM5173) supported this work
文摘The complex structure at trailing edge reduces the manufacturing precision, which results in an error in the size of the trailing edge structure. In this study, the performance of a stage high-pressure turbine(HP turbine) is calculated out in three dimensions. In the HP turbine guide vane, the trailing edge cutback configuration is adopted. Through three-dimensional simulation, the complex flow around the trailing edge with cutback cooling configuration is presented in this study, and the manufacturing precision reduction due to the complex structure at trailing edge is considered. Furthermore, the effect of trailing edge lip thickness and deflection of the stator on the turbine performance is discussed. Overall, as the press-side lip thickness increasing, the turbine efficiency and turbine inlet flow are reduced. However, the changes in the turbine work output are relatively complex. On the other hand, as the spacing between suction-side lip and press-side lip increases, turbine performance becomes worse. Both of the turbine efficiency and the turbine work output become smaller, while the turbine inlet flow becomes bigger. The effect of the spacing between suction-side lip and press-side lip is obviously greater than that of the press-side lip thickness. The change of the press-side lip thickness has little effect on the relation between the turbine performance and the spacing between suction-side lip and press-side lip. However, when the spacing between suction-side lip and press-side lip deviates from the baseline value, the effect law of the press-side lip thickness on the turbine performance will be affected. As the press-side lip thickness increases, it leads to an increase in the low-velocity zone at both of the pressure-side and suction-side trailing edge. And more main stream is affected or mixed into the wake flow. When the spacing between suction-side lip and press-side lip becomes smaller, the low-velocity zone at the trailing edge is smaller, and the change of vortex with the press-side lip thickness is affected. With a bigger spacing between suction-side lip and press-side lip, the variation is contrary.
