Behaviour of hardening and serration yield of a Fe-Ni-Cr alloy under isothermal cycling （ISC） and out-phase TMF was studied on the basis of varied hysteresis loops. Cycling hardening and serrated yielding for ISC de...Behaviour of hardening and serration yield of a Fe-Ni-Cr alloy under isothermal cycling （ISC） and out-phase TMF was studied on the basis of varied hysteresis loops. Cycling hardening and serrated yielding for ISC depend on the temperature and the total strain range, stronger hardening with serrated yielding at higher strain range under ISC at 600 ℃, but no hardening and serrated yielding occurred under ISC at 800 ℃. Stronger hardening with stress serration occurred at the thermal path going to the lowest temperature, no stress serration occurred at the highest temperature under the out-phase. The hardening also depends on the total strain range, higher total strain range with lower cycling temperature resulted in a stronger hardening and remarkable serration yielding behavior. Weaker hardening without serrated yielding occurred at near 800℃ may due to an obvious cycling stress drop under out-phase TMF. Change in the shape of the hysteresis loops also expresses the degree of the damage of the tested alloy under out-phase and ISC.展开更多
The influences of out-phase electromagnetic field on the as-cast structure of horizontal direct chill casting aluminum alloy ingot were experimental by and numerical by studied. The results of numerical analysis show ...The influences of out-phase electromagnetic field on the as-cast structure of horizontal direct chill casting aluminum alloy ingot were experimental by and numerical by studied. The results of numerical analysis show that the interaction of the out-phase electromagnetic field and the melt can generate an electromagnetically induced forced flow in the melt, which, in turn, changes flow pattern and temperature field in the mold. The as-cast structure of the ingot can be greatly improved by the changes of flow pattern and temperature field. The results of experimental analysis show that with application of out-phase electromagnetic field, temperature distribution in the melt is more uniform, grain morphology changes from columnar grains to equiaxed grains and grain size decreases.展开更多
目的探讨氢质子磁共振波谱(1H-MRS)和双回波正反相位(in-phase and out-phase)MRI成像技术在骨髓脂肪沉积中的价值,并比较两种方法一致性。方法前瞻性选择经我院双能X线骨密度测量仪(DXA)确诊的38例骨质疏松者及30例骨量正常者分别行MR...目的探讨氢质子磁共振波谱(1H-MRS)和双回波正反相位(in-phase and out-phase)MRI成像技术在骨髓脂肪沉积中的价值,并比较两种方法一致性。方法前瞻性选择经我院双能X线骨密度测量仪(DXA)确诊的38例骨质疏松者及30例骨量正常者分别行MRI常规检查、1H-MRS及双回波正反相位成像,并收集资料,分别测量L2椎体的反相位和正相位信号比值(SIR)、水脂比(LRW)和脂肪分数(FF)。采用t检验比较两组的SIR、LRW及FF差异;采用ROC曲线分析SIR值、LRW及FF对骨质疏松诊断效能,并初步确定骨质疏松各指标诊断阈值;Kolmogorov-Snimov法进行正态性检验,资料符合正态分布,选择pearson相关分析分别检验SIR与LRW和FF的相关性。结果得到横轴位和矢状位各68幅MRI腰椎正反相位图,得到68幅单体素MRS波谱图,骨质疏松组SIR值、LWR及FF分别为0.498±0.160、3.677±3.093、0.732±0.176,骨量正常组SIR值、LWR及FF分别为0.350±0.971、2.094±1.892、0.573±0.211,两组间SIR、LWR FF差异均有统计学意义(t值分别为6.404、2.035、2.738,P值均<0.05);正反相位所测SIR区分骨质疏松的ROC曲线下面积为0.784,SIR阈值为0.3850,灵敏度78.9%,特异度为66.7%。MRS中LWR、FF区分骨质疏松的ROC曲线下面积分别为0.706、0.740,阈值分别为2.063、0.674,灵敏度分别为75.0%,79.2%,特异度分别为71.4%、72.4%。Pearson相关分析SIR与LRW和FF的r值和P值,结果P值均<0.05。结论1H-MRS和正反相位MRI两种方法均能提供腰椎骨髓脂肪沉积定量信息,可以无创、快速协助诊断骨质疏松,二者指标间有相关性。展开更多
文摘Behaviour of hardening and serration yield of a Fe-Ni-Cr alloy under isothermal cycling （ISC） and out-phase TMF was studied on the basis of varied hysteresis loops. Cycling hardening and serrated yielding for ISC depend on the temperature and the total strain range, stronger hardening with serrated yielding at higher strain range under ISC at 600 ℃, but no hardening and serrated yielding occurred under ISC at 800 ℃. Stronger hardening with stress serration occurred at the thermal path going to the lowest temperature, no stress serration occurred at the highest temperature under the out-phase. The hardening also depends on the total strain range, higher total strain range with lower cycling temperature resulted in a stronger hardening and remarkable serration yielding behavior. Weaker hardening without serrated yielding occurred at near 800℃ may due to an obvious cycling stress drop under out-phase TMF. Change in the shape of the hysteresis loops also expresses the degree of the damage of the tested alloy under out-phase and ISC.
基金Supported by Postdoctor Fund of Northeastern University
文摘The influences of out-phase electromagnetic field on the as-cast structure of horizontal direct chill casting aluminum alloy ingot were experimental by and numerical by studied. The results of numerical analysis show that the interaction of the out-phase electromagnetic field and the melt can generate an electromagnetically induced forced flow in the melt, which, in turn, changes flow pattern and temperature field in the mold. The as-cast structure of the ingot can be greatly improved by the changes of flow pattern and temperature field. The results of experimental analysis show that with application of out-phase electromagnetic field, temperature distribution in the melt is more uniform, grain morphology changes from columnar grains to equiaxed grains and grain size decreases.
文摘目的探讨氢质子磁共振波谱(1H-MRS)和双回波正反相位(in-phase and out-phase)MRI成像技术在骨髓脂肪沉积中的价值,并比较两种方法一致性。方法前瞻性选择经我院双能X线骨密度测量仪(DXA)确诊的38例骨质疏松者及30例骨量正常者分别行MRI常规检查、1H-MRS及双回波正反相位成像,并收集资料,分别测量L2椎体的反相位和正相位信号比值(SIR)、水脂比(LRW)和脂肪分数(FF)。采用t检验比较两组的SIR、LRW及FF差异;采用ROC曲线分析SIR值、LRW及FF对骨质疏松诊断效能,并初步确定骨质疏松各指标诊断阈值;Kolmogorov-Snimov法进行正态性检验,资料符合正态分布,选择pearson相关分析分别检验SIR与LRW和FF的相关性。结果得到横轴位和矢状位各68幅MRI腰椎正反相位图,得到68幅单体素MRS波谱图,骨质疏松组SIR值、LWR及FF分别为0.498±0.160、3.677±3.093、0.732±0.176,骨量正常组SIR值、LWR及FF分别为0.350±0.971、2.094±1.892、0.573±0.211,两组间SIR、LWR FF差异均有统计学意义(t值分别为6.404、2.035、2.738,P值均<0.05);正反相位所测SIR区分骨质疏松的ROC曲线下面积为0.784,SIR阈值为0.3850,灵敏度78.9%,特异度为66.7%。MRS中LWR、FF区分骨质疏松的ROC曲线下面积分别为0.706、0.740,阈值分别为2.063、0.674,灵敏度分别为75.0%,79.2%,特异度分别为71.4%、72.4%。Pearson相关分析SIR与LRW和FF的r值和P值,结果P值均<0.05。结论1H-MRS和正反相位MRI两种方法均能提供腰椎骨髓脂肪沉积定量信息,可以无创、快速协助诊断骨质疏松,二者指标间有相关性。
