We report the nonlocal imaging of an object by conditional averaging of the random exposure frames of a reference detector,which only sees the freely propagating field from a thermal light source.A bucket detector,syn...We report the nonlocal imaging of an object by conditional averaging of the random exposure frames of a reference detector,which only sees the freely propagating field from a thermal light source.A bucket detector,synchronized with the reference detector,records the intensity fluctuations of an identical beam passing through the object mask.These fluctuations are sorted according to their values relative to the mean,then the reference data in the corresponding time-bins for a given fluctuation range are averaged,to produce either positive or negative images.Since no correlation calculations are involved,this correspondence imaging technique challenges our former interpretations of “ghost” imaging.Compared with conventional correlation imaging or compressed sensing schemes,both the number of exposures and computation time are greatly reduced,while the visibility is much improved.A simple statistical model is presented to explain the phenomenon.展开更多
In this study,microstructure and mechanical behavior of two types of Mg-based bimetal plates with a high formability sleeve were systematically studied,with a great emphasis on the effect of the interface characterist...In this study,microstructure and mechanical behavior of two types of Mg-based bimetal plates with a high formability sleeve were systematically studied,with a great emphasis on the effect of the interface characteristic and the sleeve fraction on the plasticity of composite plates.The rule of mixtures(ROM)for elongation was also addressed.The results show that when there is no or thin diffusion layer with thickness of about 3μm,Mg-based bimetal plates have a good plasticity with elongation of about 19-24%,and the ROM predicted elongations are very close to the experimental ones.In contrast,with a diffusion layer about 95-155μm thick,Mg-based bimetal plates exhibit a poor plasticity with elongation of about 11-17%,and the experimental elongations largely deviate from the ROM predictions.The plasticity of Mg-based bimetal plates increases with increasing sleeve fraction.This study provides new insights on the plastic deformation of Mg-based bimetal composites with a high formability sleeve.展开更多
Spherical micro-Ti particle(TiP)-reinforced AZ91 magnesium alloy composites were fabricated by semi-solid stirring assisted ultrasonic vibration,which were then subjected to hot extrusion.The microstructure results sh...Spherical micro-Ti particle(TiP)-reinforced AZ91 magnesium alloy composites were fabricated by semi-solid stirring assisted ultrasonic vibration,which were then subjected to hot extrusion.The microstructure results showed that the addition of Ti particles refined the grain size and decreased the texture intensity of the as-extruded AZ91 alloy.An Al3Ti phase with a thickness of 100 nm formed at the Ti/Mg interface,which had a non-coherent relationship with the magnesium matrix.The as-extruded 1 vol.%TiP/AZ91 composite exhibited the best comprehensive mechanical properties,with yield strength,ultimate tensile strength,and elongation at break of 366 MPa,456 MPa,and 14.6%,respectively,which were significantly higher than those of the AZ91 alloy.Therefore,the addition of Ti particles can improve the strength and ductility of the AZ91 alloy,demonstrating the value of magnesium matrix composites for commercial applications.展开更多
The corrosion and impact-abrasion-corrosion behaviors of quenching-tempering Fe-Cr martensitic steels for ball mill liner were investigated in the corrosive slurry of a copper mine compared with high manganese steel.I...The corrosion and impact-abrasion-corrosion behaviors of quenching-tempering Fe-Cr martensitic steels for ball mill liner were investigated in the corrosive slurry of a copper mine compared with high manganese steel.It is found that the corrosion resistance and the protectiveness of the passive film of Fe-Cr martensitic steels became worse when the carbon content increased.The quenching-tempering Fe-Cr martensitic steel showed better impact-abrasion-corrosion resistance in the corrosive slurry compared with the high manganese steel,especially the alloy steel with the carbon content of 0.3 wt.%.The synergistic effect between mechanics and corrosion has also been analyzed to further reveal the impact-abrasion-corrosion mechanism of the steels.The damage from pure mechanics accounted for the largest percentage(over 65%)for all steels,demonstrating that mechanical damage played the most important role in the impact-abrasion-corrosion behaviors of the steels.The impact and cracking resistance of the steel should also be paid special attention during the development of new materials for ball mill liner.展开更多
目的探讨≥45岁中老年人体质量指数(body mass index,BMI)与死亡风险的关系。方法基于中国健康与养老追踪调查(China Health and Retirement Longitudinal Study,CHARLS)数据,对13283名年龄45~100岁的中老年人进行研究,探讨BMI与死亡风...目的探讨≥45岁中老年人体质量指数(body mass index,BMI)与死亡风险的关系。方法基于中国健康与养老追踪调查(China Health and Retirement Longitudinal Study,CHARLS)数据,对13283名年龄45~100岁的中老年人进行研究,探讨BMI与死亡风险之间的关系。根据中国的肥胖标准,用BMI和腰围两项指标来评估肥胖。结果BMI与全因死亡风险大致呈反向J型关系。COX回归结果显示,与体质量正常组相比,偏瘦组死亡风险增大(HR=1.88,95%CI:1.61~2.21,P<0.01);超重组、肥胖组的死亡风险降低(HR=0.76,95%CI:0.66~0.88,P<0.01;HR=0.66,95%CI:0.53~0.82,P<0.01)。腰围与全因死亡风险之间成负相关。结论适当增加体质量,能降低中国中老年人的死亡风险。目前的健康体质量范围可能不适合中国的中老年人,对该群体BMI的解释应与其他共存疾病、功能能力和民族差异相结合。展开更多
The microstructure evolution and properties of medium-carbon cast steel alloyed with different Ni contents after tempering at various temperatures have been investigated.The addition of 0.47-1.59 wt.%Ni content result...The microstructure evolution and properties of medium-carbon cast steel alloyed with different Ni contents after tempering at various temperatures have been investigated.The addition of 0.47-1.59 wt.%Ni content results in the formation of 16%-36% retained austenite(RA).The blocky and irregular-polygonal RA mainly forms along the prior austenite grain boundaries,and the tempering temperature does not affect the RA content.The hardness of medium-carbon cast steel is affected by the precipitation of carbides and the hardness of martensite.Excessive RA content is the main cause of intergranular impact rupture and low impact energy.The long-strip carbides formed after tempering at 320℃ would further reduce the impact energy of medium-carbon cast steel.When tempering at 220 and 380℃,the increase in impact energy is attributed to the formation of rod-like and spherical carbides and the low-carbon martensite.For the medium-carbon cast steel with high impact energy,its impact-abrasive wear resistance is more excellent.Micro-cutting and delamination are the primary wear mechanisms.展开更多
The present study designed two kinds of Fe-18Mn-1.3C-2Cr-(4,11)Al(wt.%)low-density steels.Tensile and impact tests were carried out to evaluate the work hardening and impact toughness properties via aluminum(Al)alloyi...The present study designed two kinds of Fe-18Mn-1.3C-2Cr-(4,11)Al(wt.%)low-density steels.Tensile and impact tests were carried out to evaluate the work hardening and impact toughness properties via aluminum(Al)alloying control.Meanwhile,microstructure evolution and fracture morphology were investigated by X-ray diffraction(XRD),a scanning electron microscope(SEM)equipped with electron backscatter diffraction(EBSD),a transmission electron microscope(TEM),and a stereo-optical microscope(OM).It is found that the Al addition obviously promotes the dislocation planar slipping,resulting in cleavage and brittle impact fracture in 11wt.%Al steel.Besides,the microband-induced plasticity(MBIP)mechanism is found in 4wt.%Al containing steel,introducing considerable work hardening capacity and impact toughness of 156.8±17.4 J.The present study provides a direct illustration of the relationship between work hardening and impact toughness behaviors of these two low-density steels for potential application as impact-resistant components.展开更多
In this study,the deformable titanium(Ti)particles reinforced AZ91 composite was successfully prepared by powder metallurgy and subsequent extrusion.The mechanical properties and microstructural evolution of pure AZ91...In this study,the deformable titanium(Ti)particles reinforced AZ91 composite was successfully prepared by powder metallurgy and subsequent extrusion.The mechanical properties and microstructural evolution of pure AZ91 and 5 Ti/AZ91 composite were studied.The yield strength,ultimate tensile strength,and elongation of 5 Ti/AZ91 composite are measured to be 212 MPa,323 MPa,and 10.1%,respectively.Microstructure analysis revealed that Ti particles are elongated along the extrusion direction,forming a discontinuous strip Ti particles,fine precipitated Mg_(17)Al_(12) phase inhibits dynamic recrystallization(DRX)behavior through Zener pinning effect and hinders the growth of matrix grains,resulting in refiner grains of 5 Ti/AZ91 composite.Heterogeneous deformed Ti particles and magnesium(Mg)matrix to generate additional heterogeneous deformation-induced(HDI)strengthening.Heterogeneous deformation-induced strengthening mainly contributed to the increment of yield strength for 5 Ti/AZ91 composite.展开更多
Mg−9Al−1Zn(AZ91)magnesium matrix composites reinforced by Ti−6Al−4V(TC4)particles were successfully prepared via powder metallurgical method.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)show...Mg−9Al−1Zn(AZ91)magnesium matrix composites reinforced by Ti−6Al−4V(TC4)particles were successfully prepared via powder metallurgical method.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)showed a mountain-like tendency with the increase of the TC4 content.The mechanical properties of AZ91 magnesium matrix composites reached the optimal point with TC4 content of 10 wt.%,realizing YS,UTS,and EL of 335 MPa,370 MPa,and 6.4%,respectively.The improvement of mechanical properties can be attributed to the effective load transfer from the magnesium matrix to the TC4 particles,dislocations associated with the difference in the coefficient of thermal expansion,good interfacial bonding between the Mg matrix and TC4 particles,and grain refinement strengthening.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 60978002the National Basic Research Program of China under Grant Nos 2010CB922904 and 2007CB814800the National High Technology R&D Program of China under Grant No 2011AA120102。
文摘We report the nonlocal imaging of an object by conditional averaging of the random exposure frames of a reference detector,which only sees the freely propagating field from a thermal light source.A bucket detector,synchronized with the reference detector,records the intensity fluctuations of an identical beam passing through the object mask.These fluctuations are sorted according to their values relative to the mean,then the reference data in the corresponding time-bins for a given fluctuation range are averaged,to produce either positive or negative images.Since no correlation calculations are involved,this correspondence imaging technique challenges our former interpretations of “ghost” imaging.Compared with conventional correlation imaging or compressed sensing schemes,both the number of exposures and computation time are greatly reduced,while the visibility is much improved.A simple statistical model is presented to explain the phenomenon.
基金supported by the National Key Research and Development Program of China (No.2022YFB3708400)the Guangdong Major Project of Basic and Applied Basic Research (No.2020B0301030006)+3 种基金the Guangdong Academy of Science Fund (No.2020GDASYL-20200101001,2021GDASYL-20210102002,2021GDASYL-20210103103)the National Natural Science Foundation of China (Nos.51905111 and 12002092)the Youth Talent Support Programme of Guangdong Provincial Association for Science and Technology (No.SKXRC202301)the Natural Science Foundation of Guangdong Province (Nos.2021A1515011730 and 2019A1515012096).
文摘In this study,microstructure and mechanical behavior of two types of Mg-based bimetal plates with a high formability sleeve were systematically studied,with a great emphasis on the effect of the interface characteristic and the sleeve fraction on the plasticity of composite plates.The rule of mixtures(ROM)for elongation was also addressed.The results show that when there is no or thin diffusion layer with thickness of about 3μm,Mg-based bimetal plates have a good plasticity with elongation of about 19-24%,and the ROM predicted elongations are very close to the experimental ones.In contrast,with a diffusion layer about 95-155μm thick,Mg-based bimetal plates exhibit a poor plasticity with elongation of about 11-17%,and the experimental elongations largely deviate from the ROM predictions.The plasticity of Mg-based bimetal plates increases with increasing sleeve fraction.This study provides new insights on the plastic deformation of Mg-based bimetal composites with a high formability sleeve.
基金supported by the National Natural Science Foundation,China (No.52074131)the National Key R&D Project,China (No.2022YFC3900500)+2 种基金the International Technology Cooperation Program of Guangdong Academy of Sciences,China (No.2020GDASYL-20200504001)the Open Competition to Select the Best Candidate of Shangrao,China (No.2021A005)the BL13HB beamline of Shanghai Synchrotron Radiation Facility (SSRF)for providing synchrotron radiation beamtime (Nos.2020-SSRF-PT-011937,2021-SSRF-PT-017645).
基金supported by the National Natural Science Foundation of China(No.52071035)Guangdong Major Project of Basic and Applied Basic Research,China(No.2020B0301030006)。
基金supported by the Guangdong Major Project of Basic and Applied Basic Research (2020B0301030006)the Guangdong Academy of Sciences'Project of Science and Technology Development (2020GDASYL-20200101001).
文摘Spherical micro-Ti particle(TiP)-reinforced AZ91 magnesium alloy composites were fabricated by semi-solid stirring assisted ultrasonic vibration,which were then subjected to hot extrusion.The microstructure results showed that the addition of Ti particles refined the grain size and decreased the texture intensity of the as-extruded AZ91 alloy.An Al3Ti phase with a thickness of 100 nm formed at the Ti/Mg interface,which had a non-coherent relationship with the magnesium matrix.The as-extruded 1 vol.%TiP/AZ91 composite exhibited the best comprehensive mechanical properties,with yield strength,ultimate tensile strength,and elongation at break of 366 MPa,456 MPa,and 14.6%,respectively,which were significantly higher than those of the AZ91 alloy.Therefore,the addition of Ti particles can improve the strength and ductility of the AZ91 alloy,demonstrating the value of magnesium matrix composites for commercial applications.
基金financially supported by National Natural Science Foundation of China(No.51905110)Guangdong Province Key Area R&D Program(No.2020B0101340004)+2 种基金Guangdong Academy of Science(No.2021GDASYL-20210102002)International Science and Technology Cooperation Project of Guangdong Province(No.2021A0505030051)Natural Science Foundation of Guangdong Province(No.2021A1515010620).
文摘The corrosion and impact-abrasion-corrosion behaviors of quenching-tempering Fe-Cr martensitic steels for ball mill liner were investigated in the corrosive slurry of a copper mine compared with high manganese steel.It is found that the corrosion resistance and the protectiveness of the passive film of Fe-Cr martensitic steels became worse when the carbon content increased.The quenching-tempering Fe-Cr martensitic steel showed better impact-abrasion-corrosion resistance in the corrosive slurry compared with the high manganese steel,especially the alloy steel with the carbon content of 0.3 wt.%.The synergistic effect between mechanics and corrosion has also been analyzed to further reveal the impact-abrasion-corrosion mechanism of the steels.The damage from pure mechanics accounted for the largest percentage(over 65%)for all steels,demonstrating that mechanical damage played the most important role in the impact-abrasion-corrosion behaviors of the steels.The impact and cracking resistance of the steel should also be paid special attention during the development of new materials for ball mill liner.
文摘目的探讨≥45岁中老年人体质量指数(body mass index,BMI)与死亡风险的关系。方法基于中国健康与养老追踪调查(China Health and Retirement Longitudinal Study,CHARLS)数据,对13283名年龄45~100岁的中老年人进行研究,探讨BMI与死亡风险之间的关系。根据中国的肥胖标准,用BMI和腰围两项指标来评估肥胖。结果BMI与全因死亡风险大致呈反向J型关系。COX回归结果显示,与体质量正常组相比,偏瘦组死亡风险增大(HR=1.88,95%CI:1.61~2.21,P<0.01);超重组、肥胖组的死亡风险降低(HR=0.76,95%CI:0.66~0.88,P<0.01;HR=0.66,95%CI:0.53~0.82,P<0.01)。腰围与全因死亡风险之间成负相关。结论适当增加体质量,能降低中国中老年人的死亡风险。目前的健康体质量范围可能不适合中国的中老年人,对该群体BMI的解释应与其他共存疾病、功能能力和民族差异相结合。
基金supported by the National Key Research and Development Program of China(2021YFB3701204)National Natural Science Foundation of China(52001072)+3 种基金National High-End Foreign Expert Project(G2022030064L)Guangdong Province Key Area R&D Program(2020B0101340004)GDAS'Project of Science and Technology Development(2022GDASZH-2022010103)Double Thousand Plan of Jiangxi Province(S2020CXTD0356)。
文摘The microstructure evolution and properties of medium-carbon cast steel alloyed with different Ni contents after tempering at various temperatures have been investigated.The addition of 0.47-1.59 wt.%Ni content results in the formation of 16%-36% retained austenite(RA).The blocky and irregular-polygonal RA mainly forms along the prior austenite grain boundaries,and the tempering temperature does not affect the RA content.The hardness of medium-carbon cast steel is affected by the precipitation of carbides and the hardness of martensite.Excessive RA content is the main cause of intergranular impact rupture and low impact energy.The long-strip carbides formed after tempering at 320℃ would further reduce the impact energy of medium-carbon cast steel.When tempering at 220 and 380℃,the increase in impact energy is attributed to the formation of rod-like and spherical carbides and the low-carbon martensite.For the medium-carbon cast steel with high impact energy,its impact-abrasive wear resistance is more excellent.Micro-cutting and delamination are the primary wear mechanisms.
基金This work was financially supported by the Guangdong Province Key Area R&D Program(Grant No.2020B0101340004)the International Science and Technology Cooperation Project of Guangdong Province(Grant No.2021A0505030051)+2 种基金the Innovation and Technology Fund(ITF)(Grant No.ITP/020/21AP)the Young Talent Support Project of Guangzhou Association for Science and Technology(Grant No.QT20220101075)the GDAS'Project of Science and Technology Development(Grant No.2022GDASZH-2022010103).
文摘The present study designed two kinds of Fe-18Mn-1.3C-2Cr-(4,11)Al(wt.%)low-density steels.Tensile and impact tests were carried out to evaluate the work hardening and impact toughness properties via aluminum(Al)alloying control.Meanwhile,microstructure evolution and fracture morphology were investigated by X-ray diffraction(XRD),a scanning electron microscope(SEM)equipped with electron backscatter diffraction(EBSD),a transmission electron microscope(TEM),and a stereo-optical microscope(OM).It is found that the Al addition obviously promotes the dislocation planar slipping,resulting in cleavage and brittle impact fracture in 11wt.%Al steel.Besides,the microband-induced plasticity(MBIP)mechanism is found in 4wt.%Al containing steel,introducing considerable work hardening capacity and impact toughness of 156.8±17.4 J.The present study provides a direct illustration of the relationship between work hardening and impact toughness behaviors of these two low-density steels for potential application as impact-resistant components.
基金financially supported by the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030006)the National Natural Science Foundation of China(Nos.52171133 and 52171103)the“111 Project”(B16007)by the Ministry of Education and Fundamental Research Fund of Central Universities in China(No.2018CDJDCL0019)。
文摘In this study,the deformable titanium(Ti)particles reinforced AZ91 composite was successfully prepared by powder metallurgy and subsequent extrusion.The mechanical properties and microstructural evolution of pure AZ91 and 5 Ti/AZ91 composite were studied.The yield strength,ultimate tensile strength,and elongation of 5 Ti/AZ91 composite are measured to be 212 MPa,323 MPa,and 10.1%,respectively.Microstructure analysis revealed that Ti particles are elongated along the extrusion direction,forming a discontinuous strip Ti particles,fine precipitated Mg_(17)Al_(12) phase inhibits dynamic recrystallization(DRX)behavior through Zener pinning effect and hinders the growth of matrix grains,resulting in refiner grains of 5 Ti/AZ91 composite.Heterogeneous deformed Ti particles and magnesium(Mg)matrix to generate additional heterogeneous deformation-induced(HDI)strengthening.Heterogeneous deformation-induced strengthening mainly contributed to the increment of yield strength for 5 Ti/AZ91 composite.
基金Acknowledgments The authors acknowledge the financial support from the Guangdong Major Project of Basic and Applied Basic Research,China(No.2020B0301030006)the National Natural Science Foundation of China(Nos.52171133,52171103)+1 种基金the“111 Project”by the Ministry of Education of China(No.B16007)Fundamental Research Fund of Central Universities in China(No.2018CDJDCL0019)。
文摘Mg−9Al−1Zn(AZ91)magnesium matrix composites reinforced by Ti−6Al−4V(TC4)particles were successfully prepared via powder metallurgical method.The yield strength(YS),ultimate tensile strength(UTS),and elongation(EL)showed a mountain-like tendency with the increase of the TC4 content.The mechanical properties of AZ91 magnesium matrix composites reached the optimal point with TC4 content of 10 wt.%,realizing YS,UTS,and EL of 335 MPa,370 MPa,and 6.4%,respectively.The improvement of mechanical properties can be attributed to the effective load transfer from the magnesium matrix to the TC4 particles,dislocations associated with the difference in the coefficient of thermal expansion,good interfacial bonding between the Mg matrix and TC4 particles,and grain refinement strengthening.
