We present the superconducting(SC) property and high-robustness of structural stability of kagome CsV_3Sb_5 under in situ high pressures.For the initial SC-I phase,its T_c is quickly enhanced from 3.5 K to 7.6 K and t...We present the superconducting(SC) property and high-robustness of structural stability of kagome CsV_3Sb_5 under in situ high pressures.For the initial SC-I phase,its T_c is quickly enhanced from 3.5 K to 7.6 K and then totally suppressed at P-10 GPa.With further increasing pressure,an SC-Ⅱ phase emerges at P-15 GPa and persists up to 100 GPa.The T_c rapidly increases to the maximal value of 5.2 K at P=53.6 GPa and slowly decreases to 4.7 K at P=100 GPa.A two-dome-like variation of T_c in CsV_3Sb_5 is concluded here.The Raman measurements demonstrate that weakening of E_(2g) mode and strengthening of E_(1g) mode occur without phase transition in the SC-II phase,which is supported by the results of phonon spectra calculations.Electronic structure calculations reveal that exertion of pressure may bridge the gap of topological surface nontrivial states near E_F,i.e.,disappearance of Z2 invariant.Meanwhile,the Fermi surface enlarges significantly,consistent with the increased carrier density.The findings here suggest that the change of electronic structure and strengthened electron-phonon coupling should be responsible for the pressure-induced reentrant SC.展开更多
over the past few months have shocked the public.Most of the deceased were confumed to have been suffering from depression and in many cases were senior editors.
The wear-resistant tin bronze （Cu-10Sn-4Ni-3Pb） with tin content above 8 wt.% prepared by traditional melting and casting process usually defects such as low density, poor properties and segregations. The crystalliz...The wear-resistant tin bronze （Cu-10Sn-4Ni-3Pb） with tin content above 8 wt.% prepared by traditional melting and casting process usually defects such as low density, poor properties and segregations. The crystallization under pressure processing of Cu-10Sn-4Ni-3Pb alloy was investigated. The microstructures were observed and analyzed and compared with that by traditional melting and casting process. The results show that the dendrite has obviously disappeared and the dendritic segregation alleviated by using the crystallization under 680 MPa pressure process, in comparison with the remarkably dendrite microstructure and severe as-cast defects of alloy prepared by traditional melting and casting technology. Based on the experimental study, the properties and microstructures of Cu-10Sn-4Ni-3Pb tin bronze prepared by crystallization under pressure have been improved significantly.展开更多
China’s annual university entrance exam is a time of tension,tears and celebration for both students and their parents At 5 p.m. on June 8, a crowd of adults waited quietly and eagerly at the gate of No. 2 Middle Sch...China’s annual university entrance exam is a time of tension,tears and celebration for both students and their parents At 5 p.m. on June 8, a crowd of adults waited quietly and eagerly at the gate of No. 2 Middle School in Fuzhou City, capital of Fujian Province展开更多
As the yuan appreciates against the dollar, Ba Shusong, Deputy Director of the Financial Research Institute under the Development Research Center of the State Council, a government think tank, casts some light on the ...As the yuan appreciates against the dollar, Ba Shusong, Deputy Director of the Financial Research Institute under the Development Research Center of the State Council, a government think tank, casts some light on the underlying reason for the trend-there simply are too many greenbacks. The following is an excerpt of his article titled "The Dollar Is Like a 'Spoiled Child,'" originally published in the People's Daily Overseas Edition.展开更多
As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult...As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult to evaluate the ram BOP shear force,leading to frequent shear failure accidents in oilfields.Aiming at the above problems,this paper takes the double-V ram BOP as the research object,and integrates the methods of theoretical analysis,simulation modeling,and test verification to analyze the shear force in the pipe shear process under both static and moving conditions.A ram BOP shear force evaluation method is proposed based on equivalent stress.Finally,by comparing with calculation data and experimental data,the error between them is less than 5%,demonstrating the applicability and effectiveness of the proposed method.The research results can provide a theoretical basis for oilfield operations of ram BOPs.展开更多
基金Supported by the National Key Research and Development Program of China (Grant Nos.2017YFA0304700,2018YFE0202601,and2016YFA0300600)the National Natural Science Foundation of China (Grant Nos.51922105,11804184,11974208,and 51772322)+2 种基金the Chinese Academy of Sciences (Grant No.QYZDJ-SSW-SLH013)the Beijing Natural Science Foundation (Grant No.Z200005)the Shandong Provincial Natural Science Foundation (Grant Nos.ZR2020YQ05,ZR2019MA054,and 2019KJJ020)。
文摘We present the superconducting(SC) property and high-robustness of structural stability of kagome CsV_3Sb_5 under in situ high pressures.For the initial SC-I phase,its T_c is quickly enhanced from 3.5 K to 7.6 K and then totally suppressed at P-10 GPa.With further increasing pressure,an SC-Ⅱ phase emerges at P-15 GPa and persists up to 100 GPa.The T_c rapidly increases to the maximal value of 5.2 K at P=53.6 GPa and slowly decreases to 4.7 K at P=100 GPa.A two-dome-like variation of T_c in CsV_3Sb_5 is concluded here.The Raman measurements demonstrate that weakening of E_(2g) mode and strengthening of E_(1g) mode occur without phase transition in the SC-II phase,which is supported by the results of phonon spectra calculations.Electronic structure calculations reveal that exertion of pressure may bridge the gap of topological surface nontrivial states near E_F,i.e.,disappearance of Z2 invariant.Meanwhile,the Fermi surface enlarges significantly,consistent with the increased carrier density.The findings here suggest that the change of electronic structure and strengthened electron-phonon coupling should be responsible for the pressure-induced reentrant SC.
文摘over the past few months have shocked the public.Most of the deceased were confumed to have been suffering from depression and in many cases were senior editors.
基金supported by the National Natural Science Foundation of China(Nos.51075122 and U1034002)
文摘The wear-resistant tin bronze （Cu-10Sn-4Ni-3Pb） with tin content above 8 wt.% prepared by traditional melting and casting process usually defects such as low density, poor properties and segregations. The crystallization under pressure processing of Cu-10Sn-4Ni-3Pb alloy was investigated. The microstructures were observed and analyzed and compared with that by traditional melting and casting process. The results show that the dendrite has obviously disappeared and the dendritic segregation alleviated by using the crystallization under 680 MPa pressure process, in comparison with the remarkably dendrite microstructure and severe as-cast defects of alloy prepared by traditional melting and casting technology. Based on the experimental study, the properties and microstructures of Cu-10Sn-4Ni-3Pb tin bronze prepared by crystallization under pressure have been improved significantly.
文摘China’s annual university entrance exam is a time of tension,tears and celebration for both students and their parents At 5 p.m. on June 8, a crowd of adults waited quietly and eagerly at the gate of No. 2 Middle School in Fuzhou City, capital of Fujian Province
文摘As the yuan appreciates against the dollar, Ba Shusong, Deputy Director of the Financial Research Institute under the Development Research Center of the State Council, a government think tank, casts some light on the underlying reason for the trend-there simply are too many greenbacks. The following is an excerpt of his article titled "The Dollar Is Like a 'Spoiled Child,'" originally published in the People's Daily Overseas Edition.
基金This research acknowledges the financial support provided by the Key Program of National Natural Science Foundation of China(52234007).
文摘As the“throat”of the drilling well control system,ram blowout preventers(BOPs)can effectively prevent blowout accidents.However,the ram shear mechanism under complex working conditions is unclear,and it is difficult to evaluate the ram BOP shear force,leading to frequent shear failure accidents in oilfields.Aiming at the above problems,this paper takes the double-V ram BOP as the research object,and integrates the methods of theoretical analysis,simulation modeling,and test verification to analyze the shear force in the pipe shear process under both static and moving conditions.A ram BOP shear force evaluation method is proposed based on equivalent stress.Finally,by comparing with calculation data and experimental data,the error between them is less than 5%,demonstrating the applicability and effectiveness of the proposed method.The research results can provide a theoretical basis for oilfield operations of ram BOPs.
