The effects of strain rate on microstructure and formability of AZ31B magnesium alloy sheets were investigated through uniaxial tensile tests and hemispherical punch tests with strain rates of 10^-4, 10^-3, 10^-2, 10^...The effects of strain rate on microstructure and formability of AZ31B magnesium alloy sheets were investigated through uniaxial tensile tests and hemispherical punch tests with strain rates of 10^-4, 10^-3, 10^-2, 10^-1 s^-1 at 200℃. The results show that the volume fraction of dynamic recrystallization grains increases and the original grains are gradually replaced by recrystallization grains with the strain rate decreasing. A larger elongation and a smaller r-value are obtained at a lower strain rate, moreover the erichsen values become larger with the strain rate reducing, so the formability improves. This problem arises in part from the enhanced softening and the coordination of recrystallization grains during deformation.展开更多
Artificial photosynthesis is a new approach to generate sustainable energy. In order to constrain reaction solution in a solid state structure and increase the reaction efficiency in artificial photosynthesis reaction...Artificial photosynthesis is a new approach to generate sustainable energy. In order to constrain reaction solution in a solid state structure and increase the reaction efficiency in artificial photosynthesis reactions, we presented two methods to fabricate the chitosan scaffold with interconnected micro channels as construction structure of a novel artificial photosynthesis device. We built 3D chitosan structure with a home-made heterogeneous 3D rapid prototyping machine, and we used lyophilization method to generate the micron-scale pores inside the chitosan scaffold. Chitosan in acetic acid could achieve different viscosities. We found a proper chitosan recipe to construct 3D scaffold by our own rapid prototyping machine. Optional support material sodium bicarbonate was used in printing 3D scaffold for holding the printed structures, and the results images indicate that this method can make the scaffold stronger and more stable.展开更多
Objective：Free-hand pedicle screw placement has a high incidence of pedicle perforation which can be reduced with fluoroscopy,navigation or an alternative rapid prototyping drill guide template.In our study the error...Objective：Free-hand pedicle screw placement has a high incidence of pedicle perforation which can be reduced with fluoroscopy,navigation or an alternative rapid prototyping drill guide template.In our study the error rate of multi-level templates for pedicle screw placement in lumbar and sacral regions was evaluated.Methods：A case series study was performed on 11 patients.Seventy-two screws were implanted using multilevel drill guide templates manufactured with selective laser sintering.According to the optimal screw direction preoperatively defined,an analysis of screw misplacement was performed.Displacement,deviation and screw length difference were measured.The learning curve was also estimated.Results：Twelve screws （17％） were placed more than 3.125 mm out of its optimal position in the centre of pedicle.The tip of the 16 screws （22％） was misplaced more than 6.25 mm out of the predicted optimal position.According to our predefined goal,19 screws （26％） were implanted inaccurately.In 10 cases the screw length was selected incorrectly：1 （1％） screw was too long and 9 （13％） were too short.No clinical signs of neurovascular lesion were observed.Learning curve was insignificantly noticeable （P=0.129）.Conclusion：In our study,the procedure of manufacturing and applying multi-level drill guide templates has a 26％ chance of screw misplacement.However,that rate does not coincide with pedicle perforation incidence and neurovascular injury.These facts along with a comparison to compatible studies make it possible to summarize that multi-level templates are satisfactorily accurate and allow precise screw placement with a clinically irrelevant mistake factor.Therefore templates could potentially represent a useful tool for routine pedicle screw placement.展开更多
基金Project(CSTC2010AA4035) supported by Scientific and Technological Project of Chongqing Science and Technology Commission, ChinaProject(CDJZR11130008) supported by the Fundamental Research Funds for the Central Universities,ChinaProject (2008DFR50040) supported by the Ministry of Science and Technology of China
文摘The effects of strain rate on microstructure and formability of AZ31B magnesium alloy sheets were investigated through uniaxial tensile tests and hemispherical punch tests with strain rates of 10^-4, 10^-3, 10^-2, 10^-1 s^-1 at 200℃. The results show that the volume fraction of dynamic recrystallization grains increases and the original grains are gradually replaced by recrystallization grains with the strain rate decreasing. A larger elongation and a smaller r-value are obtained at a lower strain rate, moreover the erichsen values become larger with the strain rate reducing, so the formability improves. This problem arises in part from the enhanced softening and the coordination of recrystallization grains during deformation.
文摘Artificial photosynthesis is a new approach to generate sustainable energy. In order to constrain reaction solution in a solid state structure and increase the reaction efficiency in artificial photosynthesis reactions, we presented two methods to fabricate the chitosan scaffold with interconnected micro channels as construction structure of a novel artificial photosynthesis device. We built 3D chitosan structure with a home-made heterogeneous 3D rapid prototyping machine, and we used lyophilization method to generate the micron-scale pores inside the chitosan scaffold. Chitosan in acetic acid could achieve different viscosities. We found a proper chitosan recipe to construct 3D scaffold by our own rapid prototyping machine. Optional support material sodium bicarbonate was used in printing 3D scaffold for holding the printed structures, and the results images indicate that this method can make the scaffold stronger and more stable.
文摘Objective：Free-hand pedicle screw placement has a high incidence of pedicle perforation which can be reduced with fluoroscopy,navigation or an alternative rapid prototyping drill guide template.In our study the error rate of multi-level templates for pedicle screw placement in lumbar and sacral regions was evaluated.Methods：A case series study was performed on 11 patients.Seventy-two screws were implanted using multilevel drill guide templates manufactured with selective laser sintering.According to the optimal screw direction preoperatively defined,an analysis of screw misplacement was performed.Displacement,deviation and screw length difference were measured.The learning curve was also estimated.Results：Twelve screws （17％） were placed more than 3.125 mm out of its optimal position in the centre of pedicle.The tip of the 16 screws （22％） was misplaced more than 6.25 mm out of the predicted optimal position.According to our predefined goal,19 screws （26％） were implanted inaccurately.In 10 cases the screw length was selected incorrectly：1 （1％） screw was too long and 9 （13％） were too short.No clinical signs of neurovascular lesion were observed.Learning curve was insignificantly noticeable （P=0.129）.Conclusion：In our study,the procedure of manufacturing and applying multi-level drill guide templates has a 26％ chance of screw misplacement.However,that rate does not coincide with pedicle perforation incidence and neurovascular injury.These facts along with a comparison to compatible studies make it possible to summarize that multi-level templates are satisfactorily accurate and allow precise screw placement with a clinically irrelevant mistake factor.Therefore templates could potentially represent a useful tool for routine pedicle screw placement.
