In this work,five kinds of crystals were successfully synthesized using the Czochralski method for the first time,namely Dy∶Ca_(3)Li_(0.275)Nb_(1.775)Ga_(2.95)O_(12)(CLNGG),Dy,Tb∶CLNGG,Dy,Eu∶CLNGG,Tb∶CLNGG,and Eu...In this work,five kinds of crystals were successfully synthesized using the Czochralski method for the first time,namely Dy∶Ca_(3)Li_(0.275)Nb_(1.775)Ga_(2.95)O_(12)(CLNGG),Dy,Tb∶CLNGG,Dy,Eu∶CLNGG,Tb∶CLNGG,and Eu∶CLNGG.A detailed investigation of spectral features and energy transfer mechanisms in such crystals was conducted by analyzing their optical absorption spectra,excitation and emission spectra,and fluorescence decay curves at ambient tem-perature.Calculations based on the Judd-Ofelt theory further elucidated these features.The results demonstrate that in the Dy^(3+)system,co-doping with Tb^(3+)and Eu^(3+)ions not only enhances the emission cross-sections in the yellow wavelength re-gion but also improves the fluorescence quantum efficiency.These improvements are particularly beneficial for achieving efficient yellow light output from Dy^(3+).Additionally,the studies confirm the occurrence of reciprocal energy transfer be-tween Dy^(3+)and Tb^(3+)ions in Dy,Tb∶CLNGG crystals,whereas unidirectional energy transfer from Dy^(3+)to Eu^(3+)occurs in Dy,Eu∶CLNGG crystals.Based on the obtained research results,Dy,Tb∶CLNGG and Dy,Eu∶CLNGG crystals could be utilized as compelling and potential laser media for diode-pumped all-solid-state yellow lasers.展开更多
After the hot deformation sample of Ti-10V-2Fe-3Al alloy was treated by solid solution in theα+βtwo-phase region,the coarseβgrains that often appeared in theβsingle phase region were observed in the local region,i...After the hot deformation sample of Ti-10V-2Fe-3Al alloy was treated by solid solution in theα+βtwo-phase region,the coarseβgrains that often appeared in theβsingle phase region were observed in the local region,indicating that the abnormal grain growth occurred in the local microstructural region,and the macrostructure also showed abnormally coarse grains(ACGs).The dynamic recrystallization(DRX)behavior of Ti-10V-2Fe-3Al titanium alloy was systematically investigated through hot compression tests on the Gleeble-3800 system.The DRX model ofβgrains was established,and the quantitative correlation between DRX characteristics and the appearance of ACG was clarified.Based on these results,a numerical simulation platform was developed to realize the visual prediction of ACG distribution.The results show that the increase of deformation temperature and the decrease of strain rate both contribute to a significant increase in the grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains.However,the proper X_(DRX)and smaller d_(DRX))at low deformation temperature and high strain rate make the macro and microstructure show ACGs after solid solution.Interestingly,if the DRX degree is excessive or insufficient,ACGs cannot be produced,indicating that ACGs are solid solution products based on the appropriate DRX degree.According to the flow curves and statistical results of microstructure,the quantitative model of DRX kinetics and DRX grain size model were constructed,and the quantitative criterion model that is related to the formation of ACG with grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains as the key parameters was established,i.e.,d_(DRX)≤2.60µm,72.5%≤X_(DRX)≤87.9%.By integrating the subroutine of coarse grain criterion,the isothermal compression process of cylindrical samples and the actual die forging process of H-shaped parts were simulated by DEFORM-3D software of finite element(FE),respectively,and the visual prediction of the distribution of macroscopic ACGs was realized.There is a good consistency between the tested results and the simulated results,indicating a strong correlation between macroscopic ACGs and microscopic DRX.展开更多
Objective To compare the efficacy of toric implantable collamer lens(Toric-ICL)and femtosecond laser-assisted in situ keratomileusis(FS-LASIK)for myopia correction in patients with moderate to high myopia complicated ...Objective To compare the efficacy of toric implantable collamer lens(Toric-ICL)and femtosecond laser-assisted in situ keratomileusis(FS-LASIK)for myopia correction in patients with moderate to high myopia complicated with astigmatism.Methods We retrospectively collected data from 64 patients(aged 18-42 years)with moderate to high myopia complicated with astigmatism(128 eyes)undergoing either Toric-ICL(28 patients/56 eyes)or FS-LASIK(36 patients/72 eyes)at our department between January,2019 and December,2020.The changes of uncorrected distance visual acuity(UCVA),spherical equivalent(SE),mean astigmatism correction index(CI),corneal endothelial cell density(ECD)and intraocular pressure(IOP)following the procedures were compared between the two groups.Results In FS-LASIK group,all the eyes(72/72)achieved an UCVA≥1.0,similar to the rate in Toric-ICL group(55/56 eyes;P=0.2374).The postoperative SE was also comparable between FS-LASIK and Toric-ICL groups[0.43±0.06 D(range:-1.0 to 1.50 D)vs 0.38±0.05 D(range:-0.75 to 1.00 D);P=0.56].The mean astigmatism CI was significantly higher in FS-LASIK group than in Toric-ICL group(0.8561 vs 0.7176;P<0.0001),and 88.89%of the eyes in FS-LASIK group and 69.64%in Toric-ICL group had postoperative astigmatism≤0.50 D.No significant changes were observed in postoperative corneal ECD in FS-LASIK group,whereas ECD decreased significantly after the procedure in Toric-ICL group(P=0.0057).The patients undergoing Toric-ICL exhibited no significant changes of postoperative IOP,but the patients receiving FS-LASIK had significantly reduced IOP after the procedure(P<0.001).Conclusion Although the patients included in Toric-ICL group had higher myopia and astigmatism,Toric-ICL still showed better predictability and efficacy for astigmatic correction in Toric-ICL group.Toric-ICL is an effective and safe equivalent of FS-LASIK for correcting moderate myopia but can be more advantageous for correcting high myopia with astigmatism.展开更多
The constitutive relationships of Al-Mg-Si alloy deformed at various strain rates,temperatures and strains were studied.The microstructure evolution was quantitatively characterized and analyzed,including recrystalliz...The constitutive relationships of Al-Mg-Si alloy deformed at various strain rates,temperatures and strains were studied.The microstructure evolution was quantitatively characterized and analyzed,including recrystallization fraction,grain sizes,local misorientation,geometrically necessary dislocation and stored strain energy during hot deformation and subsequent heat treatment.The results show that the dislocation density and energy storage are linear with ln Z during hot deformation and subsequent heat treatment,indicating continuous recrystallization occurring in both processes.With higher ln Z,the dislocation density declines more sharply during subsequent heat treatment.When ln Z is less than 28,dislocation density becomes more stable with less reduction during subsequent heat treatment after hot deformation.As these dislocations distribute along low angle grain boundaries,the subgrain has good stability during subsequent heat treatment.The main recrystallization mechanism during hot deformation is continuous dynamic recrystallization,accompanied by geometric dynamic recrystallization at higher ln Z.展开更多
The single crystal of nickel-base super alloy is widely used for making turbine blades.The microstructure of the alloy,especially the deviation of preferred orientation of single crystal,possesses the most important e...The single crystal of nickel-base super alloy is widely used for making turbine blades.The microstructure of the alloy,especially the deviation of preferred orientation of single crystal,possesses the most important effects on the mechanical properties of the blades.In this study,the single crystal ingot and blade of DZ417G alloy are prepared by means of the spiral crystal selector as well as the directional solidification method,and the effect of the parameters(i.e.,the shape of samples,the withdrawal rate)and the structure of the spiral crystal selector on the formation of single crystal and the crystal orientation are investigated.This method can prepare not only the single crystal ingot with simple shape but also the single crystal blades with the complex shape,the simple with rod-shape can form the single crystal easily with a relatively fast withdrawal rate,but the blade with complex shape requires much slower withdrawal rate to form single crystal.The length of the crystal selector almost has no effect on the crystal orientation.However,the angle of selector plays an obvious role on the orientation;the selector with a smaller angle can effectively reduce the deviation of preferred orientation;the appropriate angle of selector to obtain optimal orientation is found to be around30°and the deviation of preferred orientation is about30°for this selector.展开更多
文摘In this work,five kinds of crystals were successfully synthesized using the Czochralski method for the first time,namely Dy∶Ca_(3)Li_(0.275)Nb_(1.775)Ga_(2.95)O_(12)(CLNGG),Dy,Tb∶CLNGG,Dy,Eu∶CLNGG,Tb∶CLNGG,and Eu∶CLNGG.A detailed investigation of spectral features and energy transfer mechanisms in such crystals was conducted by analyzing their optical absorption spectra,excitation and emission spectra,and fluorescence decay curves at ambient tem-perature.Calculations based on the Judd-Ofelt theory further elucidated these features.The results demonstrate that in the Dy^(3+)system,co-doping with Tb^(3+)and Eu^(3+)ions not only enhances the emission cross-sections in the yellow wavelength re-gion but also improves the fluorescence quantum efficiency.These improvements are particularly beneficial for achieving efficient yellow light output from Dy^(3+).Additionally,the studies confirm the occurrence of reciprocal energy transfer be-tween Dy^(3+)and Tb^(3+)ions in Dy,Tb∶CLNGG crystals,whereas unidirectional energy transfer from Dy^(3+)to Eu^(3+)occurs in Dy,Eu∶CLNGG crystals.Based on the obtained research results,Dy,Tb∶CLNGG and Dy,Eu∶CLNGG crystals could be utilized as compelling and potential laser media for diode-pumped all-solid-state yellow lasers.
基金Projects(52275388,52075474)supported by the National Natural Science Foundation of ChinaProject(236Z1008G)supported by the Special Project of Hebei Provincial Central Government Guiding Local Science and Technology Development,China+1 种基金Project(E2022203206)supported by the Natural Science Foundation of Hebei Province,ChinaProject(241080457A)supported by the Shijiazhuang's University-Industry-Academia Cooperation Project in Hebei Province-Major Science and Technology Special Project,China。
文摘After the hot deformation sample of Ti-10V-2Fe-3Al alloy was treated by solid solution in theα+βtwo-phase region,the coarseβgrains that often appeared in theβsingle phase region were observed in the local region,indicating that the abnormal grain growth occurred in the local microstructural region,and the macrostructure also showed abnormally coarse grains(ACGs).The dynamic recrystallization(DRX)behavior of Ti-10V-2Fe-3Al titanium alloy was systematically investigated through hot compression tests on the Gleeble-3800 system.The DRX model ofβgrains was established,and the quantitative correlation between DRX characteristics and the appearance of ACG was clarified.Based on these results,a numerical simulation platform was developed to realize the visual prediction of ACG distribution.The results show that the increase of deformation temperature and the decrease of strain rate both contribute to a significant increase in the grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains.However,the proper X_(DRX)and smaller d_(DRX))at low deformation temperature and high strain rate make the macro and microstructure show ACGs after solid solution.Interestingly,if the DRX degree is excessive or insufficient,ACGs cannot be produced,indicating that ACGs are solid solution products based on the appropriate DRX degree.According to the flow curves and statistical results of microstructure,the quantitative model of DRX kinetics and DRX grain size model were constructed,and the quantitative criterion model that is related to the formation of ACG with grain size(d_(DRX)))and volume fraction(X_(DRX))of DRXed grains as the key parameters was established,i.e.,d_(DRX)≤2.60µm,72.5%≤X_(DRX)≤87.9%.By integrating the subroutine of coarse grain criterion,the isothermal compression process of cylindrical samples and the actual die forging process of H-shaped parts were simulated by DEFORM-3D software of finite element(FE),respectively,and the visual prediction of the distribution of macroscopic ACGs was realized.There is a good consistency between the tested results and the simulated results,indicating a strong correlation between macroscopic ACGs and microscopic DRX.
文摘Objective To compare the efficacy of toric implantable collamer lens(Toric-ICL)and femtosecond laser-assisted in situ keratomileusis(FS-LASIK)for myopia correction in patients with moderate to high myopia complicated with astigmatism.Methods We retrospectively collected data from 64 patients(aged 18-42 years)with moderate to high myopia complicated with astigmatism(128 eyes)undergoing either Toric-ICL(28 patients/56 eyes)or FS-LASIK(36 patients/72 eyes)at our department between January,2019 and December,2020.The changes of uncorrected distance visual acuity(UCVA),spherical equivalent(SE),mean astigmatism correction index(CI),corneal endothelial cell density(ECD)and intraocular pressure(IOP)following the procedures were compared between the two groups.Results In FS-LASIK group,all the eyes(72/72)achieved an UCVA≥1.0,similar to the rate in Toric-ICL group(55/56 eyes;P=0.2374).The postoperative SE was also comparable between FS-LASIK and Toric-ICL groups[0.43±0.06 D(range:-1.0 to 1.50 D)vs 0.38±0.05 D(range:-0.75 to 1.00 D);P=0.56].The mean astigmatism CI was significantly higher in FS-LASIK group than in Toric-ICL group(0.8561 vs 0.7176;P<0.0001),and 88.89%of the eyes in FS-LASIK group and 69.64%in Toric-ICL group had postoperative astigmatism≤0.50 D.No significant changes were observed in postoperative corneal ECD in FS-LASIK group,whereas ECD decreased significantly after the procedure in Toric-ICL group(P=0.0057).The patients undergoing Toric-ICL exhibited no significant changes of postoperative IOP,but the patients receiving FS-LASIK had significantly reduced IOP after the procedure(P<0.001).Conclusion Although the patients included in Toric-ICL group had higher myopia and astigmatism,Toric-ICL still showed better predictability and efficacy for astigmatic correction in Toric-ICL group.Toric-ICL is an effective and safe equivalent of FS-LASIK for correcting moderate myopia but can be more advantageous for correcting high myopia with astigmatism.
基金Project(2016YFB0300901)supported by the National Key R&D Program of ChinaProject(TC190H3ZV/2)supported by the National Building Project of Application Demonstration Platform on New Materials Products,ChinaProject(15308469779)supported by Key Laboratory of National Science and Technology for Equipment Pre-research,China。
文摘The constitutive relationships of Al-Mg-Si alloy deformed at various strain rates,temperatures and strains were studied.The microstructure evolution was quantitatively characterized and analyzed,including recrystallization fraction,grain sizes,local misorientation,geometrically necessary dislocation and stored strain energy during hot deformation and subsequent heat treatment.The results show that the dislocation density and energy storage are linear with ln Z during hot deformation and subsequent heat treatment,indicating continuous recrystallization occurring in both processes.With higher ln Z,the dislocation density declines more sharply during subsequent heat treatment.When ln Z is less than 28,dislocation density becomes more stable with less reduction during subsequent heat treatment after hot deformation.As these dislocations distribute along low angle grain boundaries,the subgrain has good stability during subsequent heat treatment.The main recrystallization mechanism during hot deformation is continuous dynamic recrystallization,accompanied by geometric dynamic recrystallization at higher ln Z.
基金Project(51074105)supported by the National Natural Science Foundation of ChinaProjects(08DZ1130100,10520706400)supported by the Science and Technology Commission of Shanghai Municipality,ChinaProject(2007CB613606)supported by the National Basic Research Program of China
文摘The single crystal of nickel-base super alloy is widely used for making turbine blades.The microstructure of the alloy,especially the deviation of preferred orientation of single crystal,possesses the most important effects on the mechanical properties of the blades.In this study,the single crystal ingot and blade of DZ417G alloy are prepared by means of the spiral crystal selector as well as the directional solidification method,and the effect of the parameters(i.e.,the shape of samples,the withdrawal rate)and the structure of the spiral crystal selector on the formation of single crystal and the crystal orientation are investigated.This method can prepare not only the single crystal ingot with simple shape but also the single crystal blades with the complex shape,the simple with rod-shape can form the single crystal easily with a relatively fast withdrawal rate,but the blade with complex shape requires much slower withdrawal rate to form single crystal.The length of the crystal selector almost has no effect on the crystal orientation.However,the angle of selector plays an obvious role on the orientation;the selector with a smaller angle can effectively reduce the deviation of preferred orientation;the appropriate angle of selector to obtain optimal orientation is found to be around30°and the deviation of preferred orientation is about30°for this selector.
