The perfect single crystal has ultra-high strength but is often accompanied by catastrophic failures after yielding.This study reveals that nano-lamellar TiAl single crystals alleviate the catastrophic failure due to ...The perfect single crystal has ultra-high strength but is often accompanied by catastrophic failures after yielding.This study reveals that nano-lamellar TiAl single crystals alleviate the catastrophic failure due to a post-yielding dislocation retraction through atomistic simulations and theoretical analyses.This dislocation retraction leads to a retained post-yielding strength of1.03 to 2.33 GPa(about 50%of the yielding strength).It is shown that this dislocation retraction is caused by local stress relaxation and interface-mediated image force.The local stress relaxation is due to successive dislocation nucleation in different slip systems,and the interface-mediated image force is caused by the heterogeneous interface.Based on dislocation theory,this study demonstrates that the size effect also plays a vital role in dislocation retraction.Theoretical modeling shows that the dislocation retraction occurs when the lamellar thickness is less than approximately 12 nm.Additionally,the post-yielding dislocation retraction is more pronounced at higher temperatures,making it more effective in alleviating catastrophic failures.These findings demonstrate a viable option for avoiding catastrophic failure of single crystals through nanoscale-lamellar design.展开更多
Alice Walker is a famous African-American female author whose short story“Everyday Use”takes the conflict between a mother and her two daughters over the final ownership of“a quilt”as the main line and creates thr...Alice Walker is a famous African-American female author whose short story“Everyday Use”takes the conflict between a mother and her two daughters over the final ownership of“a quilt”as the main line and creates three black women characters with bright personality.This paper will focus on the living conditions and spiritual world of black women,and reflects the anxiety of black women on ethnic cultural heritage within the white world and reveals the suppression of the strong culture to the weak culture,and the self-preservation of the weak culture from the perspective of post-colonialism.展开更多
On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the r...On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the relaxation process and its temporal-spatial characteristics are determined by the viscoelastic model.In this paper,we assume that the mantle media are types of common linear rheological models,i.e.,the Burgers body,the standard linear solid,and the Maxell body,and we calculate the dislocation Love number and Green function for a spherically symmetric,non-rotating,viscoelastic,and isotropic(SNRVEI)Earth model.The characteristics of the post-seismic relaxation deformations corresponding to the different models are compared.Our results show that for a short time period,the Burgers body and standard linear solid are similar;while for the long time period,the Burgers body and Maxwell body are similar.This suggests that the observations of post-seismic deformation on the surface have a great potential for the inversion of underground viscoelastic structures.However,the potential of using surface displacement to distinguish different rheological models is limited when the observation period is not long enough.展开更多
The co seismic and post seismic deformation velocities of M s 8.1 Kunlunshan earthquake on Nov. 14, 2001 were calculated from the results of 1991-2001 GPS data and 4 repeated GPS surveys after the event. The result in...The co seismic and post seismic deformation velocities of M s 8.1 Kunlunshan earthquake on Nov. 14, 2001 were calculated from the results of 1991-2001 GPS data and 4 repeated GPS surveys after the event. The result indicates the maximum co seismic and post seismic changes are 1.9 m and 0.08 m respectively. On the basis of the result of post seismic velocity, we used an elastic dislocation model to inverse the crustal deformation characteristics of eastern Kunlun active fault. The result shows that the domain motion of eastern Kunlun fault is left lateral and strike slip. The trend of eastward motion for the southern block of Kunlun fault implies redistribution and reaccumulation of energy after the earthquake. It is possible that the seismicity will migrate to eastern region in the future according to the trend that strong earthquakes along Kunlun fault extended from west to east during the last several decades.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2019YFA0705400)the National Natural Science Foundation of China(Grant No.51535005)+2 种基金the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(Grant No.MCMS-I-0419K01)the Fundamental Research Funds for the Central Universities(Grant Nos.NJ2020003,and NZ2020001)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘The perfect single crystal has ultra-high strength but is often accompanied by catastrophic failures after yielding.This study reveals that nano-lamellar TiAl single crystals alleviate the catastrophic failure due to a post-yielding dislocation retraction through atomistic simulations and theoretical analyses.This dislocation retraction leads to a retained post-yielding strength of1.03 to 2.33 GPa(about 50%of the yielding strength).It is shown that this dislocation retraction is caused by local stress relaxation and interface-mediated image force.The local stress relaxation is due to successive dislocation nucleation in different slip systems,and the interface-mediated image force is caused by the heterogeneous interface.Based on dislocation theory,this study demonstrates that the size effect also plays a vital role in dislocation retraction.Theoretical modeling shows that the dislocation retraction occurs when the lamellar thickness is less than approximately 12 nm.Additionally,the post-yielding dislocation retraction is more pronounced at higher temperatures,making it more effective in alleviating catastrophic failures.These findings demonstrate a viable option for avoiding catastrophic failure of single crystals through nanoscale-lamellar design.
文摘Alice Walker is a famous African-American female author whose short story“Everyday Use”takes the conflict between a mother and her two daughters over the final ownership of“a quilt”as the main line and creates three black women characters with bright personality.This paper will focus on the living conditions and spiritual world of black women,and reflects the anxiety of black women on ethnic cultural heritage within the white world and reveals the suppression of the strong culture to the weak culture,and the self-preservation of the weak culture from the perspective of post-colonialism.
基金the National Natural Science Foundation of China(Nos.41774088,41974093,41331066,and 41474059)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(No.QYZDY-SSW-SYS003)+1 种基金the China Postdoctoral Science Foundation(2020M680649)the Special Research Assistant Program of the Chinese Academy of Sciences.
文摘On a long time(>1 a)scale,the viscoelastic properties of mantle media significantly affect post-seismic deformation.The stress field disturbance in viscoelastic medium caused by fault slip gradually relax,and the relaxation process and its temporal-spatial characteristics are determined by the viscoelastic model.In this paper,we assume that the mantle media are types of common linear rheological models,i.e.,the Burgers body,the standard linear solid,and the Maxell body,and we calculate the dislocation Love number and Green function for a spherically symmetric,non-rotating,viscoelastic,and isotropic(SNRVEI)Earth model.The characteristics of the post-seismic relaxation deformations corresponding to the different models are compared.Our results show that for a short time period,the Burgers body and standard linear solid are similar;while for the long time period,the Burgers body and Maxwell body are similar.This suggests that the observations of post-seismic deformation on the surface have a great potential for the inversion of underground viscoelastic structures.However,the potential of using surface displacement to distinguish different rheological models is limited when the observation period is not long enough.
文摘The co seismic and post seismic deformation velocities of M s 8.1 Kunlunshan earthquake on Nov. 14, 2001 were calculated from the results of 1991-2001 GPS data and 4 repeated GPS surveys after the event. The result indicates the maximum co seismic and post seismic changes are 1.9 m and 0.08 m respectively. On the basis of the result of post seismic velocity, we used an elastic dislocation model to inverse the crustal deformation characteristics of eastern Kunlun active fault. The result shows that the domain motion of eastern Kunlun fault is left lateral and strike slip. The trend of eastward motion for the southern block of Kunlun fault implies redistribution and reaccumulation of energy after the earthquake. It is possible that the seismicity will migrate to eastern region in the future according to the trend that strong earthquakes along Kunlun fault extended from west to east during the last several decades.
