农业自然灾害可接受风险水平的确定是实现农业灾害风险管理和区域农业可持续发展的有效途径。基于2010—2020年中国农业和农业自然灾害(包括干旱、洪涝、地质灾害、台风、风雹、低温冷冻和雪灾等)损失数据(不含港澳台地区数据),分析农...农业自然灾害可接受风险水平的确定是实现农业灾害风险管理和区域农业可持续发展的有效途径。基于2010—2020年中国农业和农业自然灾害(包括干旱、洪涝、地质灾害、台风、风雹、低温冷冻和雪灾等)损失数据(不含港澳台地区数据),分析农业自然灾害的时空分布特征,并在最低合理可行原则(As Low As Reasonably Practicable,即ALARP原则)下,应用F-N曲线法,构建不同风险厌恶程度的全国及其7大地理分区的农业自然灾害可接受风险曲线。结果表明:(1)2010—2020年中国农作物受灾率总体呈下降趋势,农作物成灾率为先波动上升至2015年达最高值后又波动下降,农作物绝收率总体呈上升趋势;华北和西北地区是我国农作物年均受灾率和成灾率最大的地区,而华南地区是农作物年均成灾率和绝收率最小的地区;(2)风险厌恶程度分别为1、1.5和2时,农业自然灾害致1万hm^(2)农作物年绝收的累计频率分别不超过0.12、0.07和0.02为可接受风险,超过0.50、0.15和0.07为不可接受风险。不区分风险厌恶程度,农业自然灾害导致农作物年绝收面积超过300万hm2,其年绝收的累计频率为任意值均是不可接受的。同理,7大地理分区的农业自然灾害可接受风险水平也被依次确定。该研究结果可为中国农业自然灾害风险管理提供决策建议。展开更多
Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability...Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.展开更多
The half-metallic Heusler alloy CO_(2)FeSi is an ideal material in spintronic devices due to its higher spin polarization,higher Curie temperature and lower damping parameters.In this work,the dynamic magnetism of CO_...The half-metallic Heusler alloy CO_(2)FeSi is an ideal material in spintronic devices due to its higher spin polarization,higher Curie temperature and lower damping parameters.In this work,the dynamic magnetism of CO_(2)FeSi is modulated by electric field and it is demonstrated that the charge-spin conversion efficiencyξis continuous and controllable by the electric field.We further find an extremely highξin ferromagnetic/ferroelectric(FM/FE)heterostructures,which could be ascribed to interfacial effect in FM/FE interface.Moreover,we investigate that the charge-spin conversion efficiency varies with the electric field in a butterfly-like behavior,which accords with the S–E curve of Pb(Mg_(1/3)Nb_(2/3))O_3-Pb_(0.7)Ti_(0.3)O_(3)(PMN-PT)and could be attributed to strain effect.The modulation of charge-spin conversion efficiency in FM/FE heterostructures via electric field presents a profound potential for next-generation spintronic devices and applications of current-induced magnetization switching.展开更多
合理的地震灾害经济可接受风险水平可以有效管理防灾减灾的投入。基于1991~2020年中国内地地区地震灾害经济损失数据,利用F-D曲线法(Frequency-Damage curve),建立不同震级(M S<5.0、M S 5.0~5.9、M S 6.0~6.9和M S≥7.0)和不同灾情...合理的地震灾害经济可接受风险水平可以有效管理防灾减灾的投入。基于1991~2020年中国内地地区地震灾害经济损失数据,利用F-D曲线法(Frequency-Damage curve),建立不同震级(M S<5.0、M S 5.0~5.9、M S 6.0~6.9和M S≥7.0)和不同灾情等级(微灾、小灾、中灾、大灾和巨灾)的地震灾害经济可接受风险曲线,并以此为标准讨论30年间由地震产生直接经济损失事件的可接受风险等级。研究结果表明:中国内地地区地震灾害造成0.020亿元直接经济损失的灾损率不超过1.29×10-2/a为可接受经济风险,直接经济损失超过14.763亿元其灾损率为任意值均是不可接受经济风险。由此判断,30年间有18.07%的地震灾害属于不可接受经济风险事件。同理,不同震级和不同灾情等级地震灾害的可接受经济风险水平也被确定,并得到M S<5.0、M S 5.0~5.9、M S 6.0~6.9和M S≥7.0地震灾害分别有23.91%、27.45%、34.78%和30.77%的事件属于不可接受经济风险,微灾、小灾、中灾、大灾和巨灾地震分别有56.00%、48.62%、41.73%、40.00%和44.44%的事件属于不可接受经济风险。该研究结果可以为我国地震灾害经济风险的防范提供相关的理论和实践支撑。展开更多
Split Hopkinson pressure bar(SHPB)was utilized to explore the effects of loading strain rate on the dynamic compressing strength of the titanium alloy lattice material.Results reveal that the yield strength of alloy l...Split Hopkinson pressure bar(SHPB)was utilized to explore the effects of loading strain rate on the dynamic compressing strength of the titanium alloy lattice material.Results reveal that the yield strength of alloy lattice material reaches 342 MPa initially and then drops to 200 MPa before it rebounds to 252 MPa while the loading strain rate correspondingly increases from the static value 1401/s to 2084/s.Numerical simulations were then carried out to explore the possible reason underlying.Results show that the lattice structure changed the stress distribution and caused significate stress concentration at finite strain with high strain rate.It is believed that the strain rate strengthening effect and layer-wise failure mode are the main reasons of the above mechanical properties change.展开更多
文摘农业自然灾害可接受风险水平的确定是实现农业灾害风险管理和区域农业可持续发展的有效途径。基于2010—2020年中国农业和农业自然灾害(包括干旱、洪涝、地质灾害、台风、风雹、低温冷冻和雪灾等)损失数据(不含港澳台地区数据),分析农业自然灾害的时空分布特征,并在最低合理可行原则(As Low As Reasonably Practicable,即ALARP原则)下,应用F-N曲线法,构建不同风险厌恶程度的全国及其7大地理分区的农业自然灾害可接受风险曲线。结果表明:(1)2010—2020年中国农作物受灾率总体呈下降趋势,农作物成灾率为先波动上升至2015年达最高值后又波动下降,农作物绝收率总体呈上升趋势;华北和西北地区是我国农作物年均受灾率和成灾率最大的地区,而华南地区是农作物年均成灾率和绝收率最小的地区;(2)风险厌恶程度分别为1、1.5和2时,农业自然灾害致1万hm^(2)农作物年绝收的累计频率分别不超过0.12、0.07和0.02为可接受风险,超过0.50、0.15和0.07为不可接受风险。不区分风险厌恶程度,农业自然灾害导致农作物年绝收面积超过300万hm2,其年绝收的累计频率为任意值均是不可接受的。同理,7大地理分区的农业自然灾害可接受风险水平也被依次确定。该研究结果可为中国农业自然灾害风险管理提供决策建议。
基金Project supported by the National Natural Science Foundation of China(Grant Nos.62205231 and 22002102)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX223271)Jiangsu Key Laboratory for Environment Functional Materials。
文摘Multilevel phase-change memory is an attractive technology to increase storage capacity and density owing to its high-speed,scalable and non-volatile characteristics.However,the contradiction between thermal stability and operation speed is one of key factors to restrain the development of phase-change memory.Here,N-doped Ge_(2)Sb_(2)Te_(5)-based optoelectronic hybrid memory is proposed to simultaneously implement high thermal stability and ultrafast operation speed.The picosecond laser is adopted to write/erase information based on reversible phase transition characteristics whereas the resistance is detected to perform information readout.Results show that when N content is 27.4 at.%,N-doped Ge_(2)Sb_(2)Te_(5)film possesses high ten-year data retention temperature of 175℃and low resistance drift coefficient of 0.00024 at 85℃,0.00170 at 120℃,and 0.00249 at 150℃,respectively,owing to the formation of Ge–N,Sb–N,and Te–N bonds.The SET/RESET operation speeds of the film reach 520 ps/13 ps.In parallel,the reversible switching cycle of the corresponding device is realized with the resistance ratio of three orders of magnitude.Four-level reversible resistance states induced by various crystallization degrees are also obtained together with low resistance drift coefficients.Therefore,the N-doped Ge_(2)Sb_(2)Te_(5)thin film is a promising phase-change material for ultrafast multilevel optoelectronic hybrid storage.
基金the National Natural Science Foundation of China(Grant No.11974149)the Natural Science Foundation of Gansu Province(Grant No.21JR7RA472)。
文摘The half-metallic Heusler alloy CO_(2)FeSi is an ideal material in spintronic devices due to its higher spin polarization,higher Curie temperature and lower damping parameters.In this work,the dynamic magnetism of CO_(2)FeSi is modulated by electric field and it is demonstrated that the charge-spin conversion efficiencyξis continuous and controllable by the electric field.We further find an extremely highξin ferromagnetic/ferroelectric(FM/FE)heterostructures,which could be ascribed to interfacial effect in FM/FE interface.Moreover,we investigate that the charge-spin conversion efficiency varies with the electric field in a butterfly-like behavior,which accords with the S–E curve of Pb(Mg_(1/3)Nb_(2/3))O_3-Pb_(0.7)Ti_(0.3)O_(3)(PMN-PT)and could be attributed to strain effect.The modulation of charge-spin conversion efficiency in FM/FE heterostructures via electric field presents a profound potential for next-generation spintronic devices and applications of current-induced magnetization switching.
文摘合理的地震灾害经济可接受风险水平可以有效管理防灾减灾的投入。基于1991~2020年中国内地地区地震灾害经济损失数据,利用F-D曲线法(Frequency-Damage curve),建立不同震级(M S<5.0、M S 5.0~5.9、M S 6.0~6.9和M S≥7.0)和不同灾情等级(微灾、小灾、中灾、大灾和巨灾)的地震灾害经济可接受风险曲线,并以此为标准讨论30年间由地震产生直接经济损失事件的可接受风险等级。研究结果表明:中国内地地区地震灾害造成0.020亿元直接经济损失的灾损率不超过1.29×10-2/a为可接受经济风险,直接经济损失超过14.763亿元其灾损率为任意值均是不可接受经济风险。由此判断,30年间有18.07%的地震灾害属于不可接受经济风险事件。同理,不同震级和不同灾情等级地震灾害的可接受经济风险水平也被确定,并得到M S<5.0、M S 5.0~5.9、M S 6.0~6.9和M S≥7.0地震灾害分别有23.91%、27.45%、34.78%和30.77%的事件属于不可接受经济风险,微灾、小灾、中灾、大灾和巨灾地震分别有56.00%、48.62%、41.73%、40.00%和44.44%的事件属于不可接受经济风险。该研究结果可以为我国地震灾害经济风险的防范提供相关的理论和实践支撑。
文摘Split Hopkinson pressure bar(SHPB)was utilized to explore the effects of loading strain rate on the dynamic compressing strength of the titanium alloy lattice material.Results reveal that the yield strength of alloy lattice material reaches 342 MPa initially and then drops to 200 MPa before it rebounds to 252 MPa while the loading strain rate correspondingly increases from the static value 1401/s to 2084/s.Numerical simulations were then carried out to explore the possible reason underlying.Results show that the lattice structure changed the stress distribution and caused significate stress concentration at finite strain with high strain rate.It is believed that the strain rate strengthening effect and layer-wise failure mode are the main reasons of the above mechanical properties change.
