Based on the elastic-plastic large deformation finite element formulation as well as the shell element combined discrete Kirchhoff theoretical plate element (DKT) with membrane square element, deep-drawing bending spr...Based on the elastic-plastic large deformation finite element formulation as well as the shell element combined discrete Kirchhoff theoretical plate element (DKT) with membrane square element, deep-drawing bending springback of typical U-pattern is studied. At the same time the springback values of the drawing of patterns' unloading and trimming about the satellite aerial reflecting surface are predicted and also compared with those of the practical punch. Above two springbacks all obtain satisfactory results, which provide a kind of effective quantitative pre-prediction of springback for the practical engineers.展开更多
The sorption of Eu species onto nano-size silica-water interfaces was investigated using fluorescence spectroscopy for pH ranges of 1-8.5 and an initial Eu concentration (C Eu) of 2×10 -4 M. The sorption rate...The sorption of Eu species onto nano-size silica-water interfaces was investigated using fluorescence spectroscopy for pH ranges of 1-8.5 and an initial Eu concentration (C Eu) of 2×10 -4 M. The sorption rate of Eu was initially low, but significantly increased at pH>4. The sorption density of Eu species on a silica surface was ～1.58×10 -7 mol/m2 when the dissolved Eu species were completely sorbed onto silica-water interfaces at pH=～5.8. The sorbed Eu species at pH<6 is aquo Eu 3+, which is sorbed onto silica-water interfaces as an outer-sphere complex at pH<5, but may be sorbed as an inner-sphere bidentate complex at 5<pH<6, due to the decrease of N H 2O to ～6 at pH=6. At pH=6-8.5, Eu(OH)+ 2, Eu(CO 3)+ and Eu(CO 3)- 2 formed in the solutions, and Eu(CO 3)+ is dominant at pH=～7.5. These ions may be sorbed onto silica-water interfaces as inner-sphere bidentate complexes.展开更多
We relocated 2098 earthquakes that occurred in Beijing area between 1980 and 2000 using a double-dif- ference (DD) earthquake location algorithm, and obtained the high-precision relative locations of 1825 events. b va...We relocated 2098 earthquakes that occurred in Beijing area between 1980 and 2000 using a double-dif- ference (DD) earthquake location algorithm, and obtained the high-precision relative locations of 1825 events. b values versus depth were investigated with the relocated hypocen- ters. The results show that the b values decrease with the increasing hypocentral depth systematically. A dramatic variation in b is observed around the depth of 8 km. It indi- cates that there are more smaller earthquakes at shallow depth (0―8 km), while more larger earthquakes at greater depth (8―25 km). The physical mechanism behind this phe- nomenon can be explained by the variations in material het- erogeneity and lithostatic stress condition. Large earth- quakes are more likely to nucleate at greater depth with more homogenous material and higher lithostatic stress. On the basis of the results, we suggest that future strong earth- quakes in Beijing area tend to occur below the depth of 8 km.展开更多
基金This project is supported by National Natural Science Foundation of China (No.19832020)Provincial Natural Science Foundation of Jilin (No.20000519)
文摘Based on the elastic-plastic large deformation finite element formulation as well as the shell element combined discrete Kirchhoff theoretical plate element (DKT) with membrane square element, deep-drawing bending springback of typical U-pattern is studied. At the same time the springback values of the drawing of patterns' unloading and trimming about the satellite aerial reflecting surface are predicted and also compared with those of the practical punch. Above two springbacks all obtain satisfactory results, which provide a kind of effective quantitative pre-prediction of springback for the practical engineers.
文摘The sorption of Eu species onto nano-size silica-water interfaces was investigated using fluorescence spectroscopy for pH ranges of 1-8.5 and an initial Eu concentration (C Eu) of 2×10 -4 M. The sorption rate of Eu was initially low, but significantly increased at pH>4. The sorption density of Eu species on a silica surface was ～1.58×10 -7 mol/m2 when the dissolved Eu species were completely sorbed onto silica-water interfaces at pH=～5.8. The sorbed Eu species at pH<6 is aquo Eu 3+, which is sorbed onto silica-water interfaces as an outer-sphere complex at pH<5, but may be sorbed as an inner-sphere bidentate complex at 5<pH<6, due to the decrease of N H 2O to ～6 at pH=6. At pH=6-8.5, Eu(OH)+ 2, Eu(CO 3)+ and Eu(CO 3)- 2 formed in the solutions, and Eu(CO 3)+ is dominant at pH=～7.5. These ions may be sorbed onto silica-water interfaces as inner-sphere bidentate complexes.
基金supported by the Nationa1 Development and Reform Commission Program(Grant No.2004-1138)the National Key Project of Basic Condition Platform(Grant No.2003DIA6N005)+1 种基金the Preliminary Special Project for Key Basic Research of Ministry of Science and Technology of China(Grant No.2003CCB00600)the National Natural Science Foundation of China(Grant No.40474067).
文摘We relocated 2098 earthquakes that occurred in Beijing area between 1980 and 2000 using a double-dif- ference (DD) earthquake location algorithm, and obtained the high-precision relative locations of 1825 events. b values versus depth were investigated with the relocated hypocen- ters. The results show that the b values decrease with the increasing hypocentral depth systematically. A dramatic variation in b is observed around the depth of 8 km. It indi- cates that there are more smaller earthquakes at shallow depth (0―8 km), while more larger earthquakes at greater depth (8―25 km). The physical mechanism behind this phe- nomenon can be explained by the variations in material het- erogeneity and lithostatic stress condition. Large earth- quakes are more likely to nucleate at greater depth with more homogenous material and higher lithostatic stress. On the basis of the results, we suggest that future strong earth- quakes in Beijing area tend to occur below the depth of 8 km.
