目的 探讨基于机器学习的自动阿尔伯塔卒中项目早期计算机断层扫描评分(Alberta Stroke Program Early CT Score,ASPECTS)对不同部位的急性脑梗死(acute cerebral infarction,ACI)患者重组组织型纤溶酶原激活剂(rt-PA)静脉溶栓治疗预后...目的 探讨基于机器学习的自动阿尔伯塔卒中项目早期计算机断层扫描评分(Alberta Stroke Program Early CT Score,ASPECTS)对不同部位的急性脑梗死(acute cerebral infarction,ACI)患者重组组织型纤溶酶原激活剂(rt-PA)静脉溶栓治疗预后的评估价值。方法 回顾性连续收集2021年1月-2023年2月在南昌大学第二附属医院接受静脉溶栓治疗的急性缺血性卒中患者,以DWI序列高信号作为梗死标准,由人工智能软件基于CT的自动ASPECTS评分,收集患者的一般临床资料、自动ASPECTS评分及溶栓3个月后mRS评分。结果 共纳入急性脑梗死患者135例,分为预后良好组(78例)与预后不良组(57例)。预后不良组豆状核、尾状核、岛叶及M1256区的发生率高于预后良好组(P<0.05)。预后不良组的入院NHISS评分、自动ASPECTS评分与预后良好组比较,差异有统计学意义(P<0.05);二元Logistic回归显示基于梗死位置中的豆状核(0R=0.249,95%CI:0.065~0.956,P=0.043)、尾状核(OR=6.036,95%CI:2.119~17.190,P=0.001)、岛叶(OR=0.280,95%CI:0.096~0.812,P=0.019)及M1区(OR=0.289,95%CI:0.704~6.038,P=0.032)是脑梗死预后不良的独立危险因素。NHISS评分(OR=1.072,95%CI:1.004~1.144,P=0.038),ASPECTS评分(OR=0.520,95%CI:0.387~0.699,P<0.001)。结论 梗死位置可以作为急性脑梗死患者溶栓预后评估的重要预测指标,不同区域的自动ASPECTS评分对预后的预估存在差异,豆状核区、尾状核区、岛叶区或M1区梗死的预后较差,我们的发现对于识别溶栓治疗后有预后不良风险的患者具有价值。展开更多
Laser-welded Ti-6Al-4 V is prone to severe residual stresses,microstructural variation,and structural de-fects which are known detrimental to the mechanical properties of weld joints.Residual stress removal is typical...Laser-welded Ti-6Al-4 V is prone to severe residual stresses,microstructural variation,and structural de-fects which are known detrimental to the mechanical properties of weld joints.Residual stress removal is typically applied to weld joints for engineering purposes via heat treatment,in order to avoid prema-ture failure and performance degradation.In the present work,we found that proper welding residual stresses in laser-welded Ti-6Al-4 V sheets can maintain better ductility during uniaxial tension,as op-posed to the stress-relieved counterparts.A detailed experimental investigation has been performed on the deformation behaviours of Ti-6Al-4 V butt welds,including residual stress distribution characteriza-tions by focused ion beam ring-coring coupled with digital image correlation(FIB-DIC),X-ray comput-erized tomography(CT)for internal voids,and in-situ DIC analysis of the subregional strain evolutions.It was found that the pores preferentially distributed near the fusion zone(FZ)boundary,where the compressive residual stress was up to-330 MPa.The removal of residual stress resulted in a changed failure initiation site from the base material to the FZ boundary,the former with ductile and the latter with brittle fracture characteristics under tensile deformation.The combined effects of residual stresses,microstructures,and internal pores on the mechanical responses are discussed in detail.This work high-lights the importance of inevitable residual stress and pores in laser weld pieces,leading to key insights for post-welding treatment and service performance evaluations.展开更多
In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical...In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.展开更多
基金supported by the National Key Re-search&Development Plan of China(No.2020YFA0405900)the Major Research Plan of the National Natural Science Foundation of China(No.92263201)Y.P.Xia would like to thank the support by the Jiangsu Funding Program for Excellent Postdoctoral Talent.All authors thank the Advanced Material Research Institute of Jiangsu Industrial Technology Research Institute(JITRI,Suzhou,China)for the experimental support.
文摘Laser-welded Ti-6Al-4 V is prone to severe residual stresses,microstructural variation,and structural de-fects which are known detrimental to the mechanical properties of weld joints.Residual stress removal is typically applied to weld joints for engineering purposes via heat treatment,in order to avoid prema-ture failure and performance degradation.In the present work,we found that proper welding residual stresses in laser-welded Ti-6Al-4 V sheets can maintain better ductility during uniaxial tension,as op-posed to the stress-relieved counterparts.A detailed experimental investigation has been performed on the deformation behaviours of Ti-6Al-4 V butt welds,including residual stress distribution characteriza-tions by focused ion beam ring-coring coupled with digital image correlation(FIB-DIC),X-ray comput-erized tomography(CT)for internal voids,and in-situ DIC analysis of the subregional strain evolutions.It was found that the pores preferentially distributed near the fusion zone(FZ)boundary,where the compressive residual stress was up to-330 MPa.The removal of residual stress resulted in a changed failure initiation site from the base material to the FZ boundary,the former with ductile and the latter with brittle fracture characteristics under tensile deformation.The combined effects of residual stresses,microstructures,and internal pores on the mechanical responses are discussed in detail.This work high-lights the importance of inevitable residual stress and pores in laser weld pieces,leading to key insights for post-welding treatment and service performance evaluations.
基金funding support from the National Natural Science Foundation of China(Grant No.12172019).
文摘In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.
