The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al–Cu alloys was investigated in Al–4.5 Cu–1.5 TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effective...The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al–Cu alloys was investigated in Al–4.5 Cu–1.5 TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effectively, from about 20 h for Al–4.5 Cu alloy decreasing to about 12 h for the Al–4.5 Cu–1.5 TiC. Mechanical property test shows that the age-hardening effect has been improved by the TiC nanoparticles. The increment of yield strength before and after aging is about 84 MPa for Al–4.5 Cu, while, it reaches to about113 MPa for the Al–4.5 Cu–1.5 TiC. After aging heat treatment, precipitates have been observed both in matrix and around TiC nanoparticles. Due to the difference of coefficient of thermal expansion between TiC and Al, high density dislocations in the Al–4.5 Cu–1.5 TiC were generated during water quenching after solution. Dislocations play a role of diffusion path for Cu atoms during aging, which reduces the peak-age time. Alpha-Al lattice distortion resulted from lattice mismatch of TiC/Al interface induces the precipitation of θ' phase around TiC nanoparticles, which increases the number density of θ' and improves the age-hardening effect. This finding is supposed to be also applicable to alloy systems of Al–Cu–Mg,Al–Cu–Mg–Li, Al–Cu–Mg–Ag, etc.展开更多
利用2018年4-9月西北地区共10 189站逐小时降水观测资料及0.25°×0.25°分辨率的欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)预报资料,用V-3θ图及Keras方法,建立了由分类模型和降...利用2018年4-9月西北地区共10 189站逐小时降水观测资料及0.25°×0.25°分辨率的欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)预报资料,用V-3θ图及Keras方法,建立了由分类模型和降水量拟合模型组成的河西走廊降水预报模型,再通过“分类检验损失函数”、“TS检验”和“拟合检验均方根误差”三种方法检验了该降水预报模型的预报效果。结果表明:基于Keras建立的两个神经网络框架,采用“k折交叉”和逻辑回归方法,使模型更加可靠、特征关系更加合理,降低特征量的误差影响;衍生V-3θ图,增加特征值的种类,可缩小河西走廊降水预报模型主观识别偏差,实现了降水垂直结构预报的客观定量化;通过三种方法进行检验,发现该模型总体白天预报结果优于夜间,12—18 h的预报结果与实际值最为符合;利用个例对比发现,该模型可较准确地预报降水过程的发生时间、主要降水时段、降水区域范围及降水中心强度,证实该模型对强降水天气有较强的预报能力。展开更多
基金financially supported by the Key Program of the National Natural Science Foundation of China (No. 51731007)the National Natural Science Foundation of China (No. 51501092)
文摘The influence of in-situ synthesized TiC nanoparticles on age-hardening behavior of Al–Cu alloys was investigated in Al–4.5 Cu–1.5 TiC alloy. It was found that TiC nanoparticles decrease the peak-age time effectively, from about 20 h for Al–4.5 Cu alloy decreasing to about 12 h for the Al–4.5 Cu–1.5 TiC. Mechanical property test shows that the age-hardening effect has been improved by the TiC nanoparticles. The increment of yield strength before and after aging is about 84 MPa for Al–4.5 Cu, while, it reaches to about113 MPa for the Al–4.5 Cu–1.5 TiC. After aging heat treatment, precipitates have been observed both in matrix and around TiC nanoparticles. Due to the difference of coefficient of thermal expansion between TiC and Al, high density dislocations in the Al–4.5 Cu–1.5 TiC were generated during water quenching after solution. Dislocations play a role of diffusion path for Cu atoms during aging, which reduces the peak-age time. Alpha-Al lattice distortion resulted from lattice mismatch of TiC/Al interface induces the precipitation of θ' phase around TiC nanoparticles, which increases the number density of θ' and improves the age-hardening effect. This finding is supposed to be also applicable to alloy systems of Al–Cu–Mg,Al–Cu–Mg–Li, Al–Cu–Mg–Ag, etc.
文摘利用2018年4-9月西北地区共10 189站逐小时降水观测资料及0.25°×0.25°分辨率的欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)预报资料,用V-3θ图及Keras方法,建立了由分类模型和降水量拟合模型组成的河西走廊降水预报模型,再通过“分类检验损失函数”、“TS检验”和“拟合检验均方根误差”三种方法检验了该降水预报模型的预报效果。结果表明:基于Keras建立的两个神经网络框架,采用“k折交叉”和逻辑回归方法,使模型更加可靠、特征关系更加合理,降低特征量的误差影响;衍生V-3θ图,增加特征值的种类,可缩小河西走廊降水预报模型主观识别偏差,实现了降水垂直结构预报的客观定量化;通过三种方法进行检验,发现该模型总体白天预报结果优于夜间,12—18 h的预报结果与实际值最为符合;利用个例对比发现,该模型可较准确地预报降水过程的发生时间、主要降水时段、降水区域范围及降水中心强度,证实该模型对强降水天气有较强的预报能力。
