This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360...This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360MPa to∼258MPa as the ram speed increases from 0.4mm/s to 2.4 mm/s,and the elongation increases from∼3.9%to∼12.2%.The microstructure changes from bimodal grain feature to the complete dynamical recrystallization(DRX)with increase of the extrusion speed.The ultrafine DRXed grains in size of∼0.85μm,the numerous nano-Mg_(2)Ca particles dispersing along the grain boundaries and interiors,as well as the high density of residual dislocations,should account for the high strength.It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys.展开更多
Functional materials with high viscosity and solid materials have received more and more attentions in flexible pressure sensors,which are inadequate in the most used molding method.Herein,laser direct writing(LDW)met...Functional materials with high viscosity and solid materials have received more and more attentions in flexible pressure sensors,which are inadequate in the most used molding method.Herein,laser direct writing(LDW)method is proposed to fabricate flexible piezoresistive sensors with microstructures on PDMS/MWCNTs composites with an 8%MWCNTs mass fraction.By controlling laser energy,microstructures with different geometries can be obtained,which significantly impacts the performances of the sensors.Subsequently,curved microcones with excellent performance are fabricated under parameters of f=40 kHz and v=150 mm·s^(-1).The sensor exhibits continuous multi-linear sensitivity,ultrahigh original sensitivity of 21.80%kPa^(-1),wide detection range of over 20 kPa,response/recovery time of~100 ms and good cycle stability for more than 1000 times.Besides,obvious resistance variation can be observed when tiny pressure(a peanut of 30 Pa)is applied.Finally,the flexible piezoresistive sensor can be applied for LED brightness controlling,pulse detection and voice recognition.展开更多
Based on paper of "Theoretical derivation of risk-ratios for assessing wind damage in coastal forest",wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investig...Based on paper of "Theoretical derivation of risk-ratios for assessing wind damage in coastal forest",wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investigated for four successive growing seasons.Besides wind damage,the wind profiles outside and inside the coastal forest stand and the distributions of optical stratification porosity (OSP) were also observed.Based on these data,risk-ratios of wind damage for both individual trees and stands were estimated according to the methods developed in "Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest".The results showed that risk-ratios of wind damage,which were calculated from the meen height and diameter only and from the combination of wind and stand sructure profiles,accurately predicted wind damage in the plantation.Relationships between different thinning ratios and incidence of wind damage showed that stand stability decreased soon after the thinning.This was due to the immediate effects of thinning on increasing the canopy roughness and wind load,and on decreasing the sheltering effects from surrounding trees.However,thinning strategies could improve the stability by long-term effects on growthand development of trees against extreme wind.Only canopy damage was recorded during the experimental period,no stem damage was found,even though the maximum 10-min wind speed outside the coastal forest attained 30.2m s^-1.The results obtained in this study indicate that thinning is the most effective silvicultural strategy available for managing coastal forest despite the increased probability of wind damage soon after thinning.展开更多
目的分析安徽省蚌埠市2021-2022年新报告HIV感染者基因亚型、治疗前耐药特征和HIV分子传播网络情况,为当地制定干预措施提供依据。方法收集蚌埠市2021-2022年新报告HIV感染者样本90份,扩增pol基因并测序,借助Blast HIV sequence databas...目的分析安徽省蚌埠市2021-2022年新报告HIV感染者基因亚型、治疗前耐药特征和HIV分子传播网络情况,为当地制定干预措施提供依据。方法收集蚌埠市2021-2022年新报告HIV感染者样本90份,扩增pol基因并测序,借助Blast HIV sequence database对每条序列进行同源性分析,采用MEGA 7.0构建NJ系统进化树判定所有HIV感染者基因亚型。将所得序列上传至美国斯坦福大学HIV耐药数据库,分析基因型耐药情况。利用Cytoscape实现传播网络的可视化,分析新报告HIV感染者耐药传播特点和网络关联情况。结果蚌埠市85例新报告HIV感染者基因亚型主要为CRF01_AE(58.82%)和CRF07_BC(23.53%),耐药率为10.59%(9/85),主要为非核苷类药物耐药(5/85,5.88%)。在0.5%基因距离阈值下的分子传播网络中,CRF01_AE入网率为44%,存在1个较大的耐药传播簇,耐药位点为L33F;CRF07_BC入网率为10%。分子传播网络中的HIV感染者主要为五河县50岁及以上男性,文化程度较低。结论蚌埠市新报告HIV感染者耐药率较高,形成了耐药传播簇,传播风险较高,应采取有效措施进行干预,减少HIV的传播。展开更多
Radial forging(RF)is an economical manufacturing forging process,in which four dies arranged radially around the workpiece simultaneously act on the workpiece with high-frequency radial movement.In this study,a ZK60 m...Radial forging(RF)is an economical manufacturing forging process,in which four dies arranged radially around the workpiece simultaneously act on the workpiece with high-frequency radial movement.In this study,a ZK60 magnesium alloy step-shaft bar was processed under different accumulated strains by RF at350℃.The deformation behavior,microstructure evolution,and mechanical responses of this bar were systematically investigated via numerical simulations and experiments.At the early deformation stage of forging,the material undergoes pronounced grain refinement but an inhomogeneous grain structure is formed due to the strain gradient along the radial direction.The grains in different radial parts were gradually refined by increasing the RF pass,resulting in a bimodal grained structure comprising coarse(~14.1μm)and fine(~2.3μm)grains.With the RF pass increased,the initial micro-sizeβ-phases were gradually crushed and dissolved into the matrix mostly,eventually evolving to form a higher area fraction of nano-sized Zn2 Zr spheroidal particles uniformly distributed through the grain interior.The texture changed as the RF strain increased,with the c-axes of most of the deformed grains rotating in the RD.Additionally,excellent mechanical properties including higher values of tensile strengths and ductility were attained after the three RFed passes,compared to the as-received sample.展开更多
基金This work is supported by National Natural Science Foundation of China(Nos.51525101,U1610253,51701211,and 51971053)funded by the Project of Promoting Talents in Liaoning province(No.XLYC1808038)+2 种基金H.C.Pan acknowledges the financial assistance from the State Key Laboratory of Solidification Processing in NPU(No.SKLSP201920)the Fundamental Research Funds for the Central Universities(No.N2002011)joint R&D fund of Liaoning-Shenyang National Research Center for Materials Science(No.2019JH3/30100040).
文摘This work reported the effect of extrusion speeds on the microstructures and mechanical properties of Mg-Ca binary alloy.The results showed that yield strength of the as-extruded Mg-1.2wt.%Ca alloys decrease from∼360MPa to∼258MPa as the ram speed increases from 0.4mm/s to 2.4 mm/s,and the elongation increases from∼3.9%to∼12.2%.The microstructure changes from bimodal grain feature to the complete dynamical recrystallization(DRX)with increase of the extrusion speed.The ultrafine DRXed grains in size of∼0.85μm,the numerous nano-Mg_(2)Ca particles dispersing along the grain boundaries and interiors,as well as the high density of residual dislocations,should account for the high strength.It is believed that the high degree of dynamic recrystallization and the resulting texture randomization play the critical roles in the ductility enhancement of the high-speed extruded Mg alloys.
基金supported by the National Natural Science Foundation of China(No.51922092,No.51705439)Domain Foundation of Equipment Advance Research of 13th Five-year Plan(JZX7Y20190243000801)+1 种基金the Natural Science Foundation of Fujian Province of China(No.2017J06015)Science and Technology Plan Project of Xiamen City(No.3502Z20173024).
文摘Functional materials with high viscosity and solid materials have received more and more attentions in flexible pressure sensors,which are inadequate in the most used molding method.Herein,laser direct writing(LDW)method is proposed to fabricate flexible piezoresistive sensors with microstructures on PDMS/MWCNTs composites with an 8%MWCNTs mass fraction.By controlling laser energy,microstructures with different geometries can be obtained,which significantly impacts the performances of the sensors.Subsequently,curved microcones with excellent performance are fabricated under parameters of f=40 kHz and v=150 mm·s^(-1).The sensor exhibits continuous multi-linear sensitivity,ultrahigh original sensitivity of 21.80%kPa^(-1),wide detection range of over 20 kPa,response/recovery time of~100 ms and good cycle stability for more than 1000 times.Besides,obvious resistance variation can be observed when tiny pressure(a peanut of 30 Pa)is applied.Finally,the flexible piezoresistive sensor can be applied for LED brightness controlling,pulse detection and voice recognition.
文摘Based on paper of "Theoretical derivation of risk-ratios for assessing wind damage in coastal forest",wind damage in the pine coasteal forest,which was thinned at four levels in December of 1997,was investigated for four successive growing seasons.Besides wind damage,the wind profiles outside and inside the coastal forest stand and the distributions of optical stratification porosity (OSP) were also observed.Based on these data,risk-ratios of wind damage for both individual trees and stands were estimated according to the methods developed in "Theoretical derivation of risk-ratios for assessing wind damage in a coastal forest".The results showed that risk-ratios of wind damage,which were calculated from the meen height and diameter only and from the combination of wind and stand sructure profiles,accurately predicted wind damage in the plantation.Relationships between different thinning ratios and incidence of wind damage showed that stand stability decreased soon after the thinning.This was due to the immediate effects of thinning on increasing the canopy roughness and wind load,and on decreasing the sheltering effects from surrounding trees.However,thinning strategies could improve the stability by long-term effects on growthand development of trees against extreme wind.Only canopy damage was recorded during the experimental period,no stem damage was found,even though the maximum 10-min wind speed outside the coastal forest attained 30.2m s^-1.The results obtained in this study indicate that thinning is the most effective silvicultural strategy available for managing coastal forest despite the increased probability of wind damage soon after thinning.
文摘目的分析安徽省蚌埠市2021-2022年新报告HIV感染者基因亚型、治疗前耐药特征和HIV分子传播网络情况,为当地制定干预措施提供依据。方法收集蚌埠市2021-2022年新报告HIV感染者样本90份,扩增pol基因并测序,借助Blast HIV sequence database对每条序列进行同源性分析,采用MEGA 7.0构建NJ系统进化树判定所有HIV感染者基因亚型。将所得序列上传至美国斯坦福大学HIV耐药数据库,分析基因型耐药情况。利用Cytoscape实现传播网络的可视化,分析新报告HIV感染者耐药传播特点和网络关联情况。结果蚌埠市85例新报告HIV感染者基因亚型主要为CRF01_AE(58.82%)和CRF07_BC(23.53%),耐药率为10.59%(9/85),主要为非核苷类药物耐药(5/85,5.88%)。在0.5%基因距离阈值下的分子传播网络中,CRF01_AE入网率为44%,存在1个较大的耐药传播簇,耐药位点为L33F;CRF07_BC入网率为10%。分子传播网络中的HIV感染者主要为五河县50岁及以上男性,文化程度较低。结论蚌埠市新报告HIV感染者耐药率较高,形成了耐药传播簇,传播风险较高,应采取有效措施进行干预,减少HIV的传播。
基金the financial support of the National Natural Science Foundation of China(Nos.U1910213 and U1610253)the Key Research and Development Program of Shanxi Province(Nos.201603D111004,201803D121026 and 201903D121088)+1 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(No.2019L0614)the Taiyuan University of Science and Technology Scientific Research Initial Funding(TYUST SRIF)(No.20192002)。
文摘Radial forging(RF)is an economical manufacturing forging process,in which four dies arranged radially around the workpiece simultaneously act on the workpiece with high-frequency radial movement.In this study,a ZK60 magnesium alloy step-shaft bar was processed under different accumulated strains by RF at350℃.The deformation behavior,microstructure evolution,and mechanical responses of this bar were systematically investigated via numerical simulations and experiments.At the early deformation stage of forging,the material undergoes pronounced grain refinement but an inhomogeneous grain structure is formed due to the strain gradient along the radial direction.The grains in different radial parts were gradually refined by increasing the RF pass,resulting in a bimodal grained structure comprising coarse(~14.1μm)and fine(~2.3μm)grains.With the RF pass increased,the initial micro-sizeβ-phases were gradually crushed and dissolved into the matrix mostly,eventually evolving to form a higher area fraction of nano-sized Zn2 Zr spheroidal particles uniformly distributed through the grain interior.The texture changed as the RF strain increased,with the c-axes of most of the deformed grains rotating in the RD.Additionally,excellent mechanical properties including higher values of tensile strengths and ductility were attained after the three RFed passes,compared to the as-received sample.
