A simple modified analytic EAM model for bcc Fe and fcc Al was used to calculate the lattice constant and elastic constants of B2 FeAl and DO3 Fe3Al alloys. The formation energies of ...A simple modified analytic EAM model for bcc Fe and fcc Al was used to calculate the lattice constant and elastic constants of B2 FeAl and DO3 Fe3Al alloys. The formation energies of vacancy and antisite were also calculated. The present calculations are in agreement with the experimental data and the theoretical results obtained by other authors.展开更多
世界时与协调世界时差值(difference between universal time and coordinated universal time,UT1-UTC)是地球定向参数(Earth orientation parameters,EOP)的重要组成部分,其高精度和快速预测对全球卫星导航系统气象学、人造卫星精密...世界时与协调世界时差值(difference between universal time and coordinated universal time,UT1-UTC)是地球定向参数(Earth orientation parameters,EOP)的重要组成部分,其高精度和快速预测对全球卫星导航系统气象学、人造卫星精密轨道确定等实时应用领域至关重要。传统UT1-UTC预报方法在中长期预测中精度衰减明显,难以满足北斗导航系统及战争环境的精确制导等高精度需求。提出了一种融合地球流体有效角动量(effective angular momentum,EAM)信息的轴向分量χ_(3)数据与EOP14 C04序列的卷积长短期记忆神经网络(convolutional long short-term memory,ConvLSTM)模型预报UT1-UTC的新方法。实测数据分析结果发现,EAM轴向分量χ^(3)和经跳秒与潮汐改正后的UT1-UTC数据具有强相关性,其振幅和相位具有一致的频谱特性,说明EAM轴向分量χ^(3)是UT1-UTC的主要激发源。与参与第二届EOP预报比赛的各家精度进行对比,在90~360 d的中长期预报跨度中,ConvLSTM模型预报精度最优,改善幅度为30.27%~92.44%。对比公报A,时间跨度为60 d、180 d和360 d的中长期预报精度分别提升41.46%、70.07%和59.43%,证实了ConvLSTM能够显著改善UT1-UTC的中长期预报精度。展开更多
Persistent slip band （PSB） is an important and typical microstructure generated during fatigue crack initiation. Intensive work has been done to investigate the mechanisms of the formation of persistent slip bands s...Persistent slip band （PSB） is an important and typical microstructure generated during fatigue crack initiation. Intensive work has been done to investigate the mechanisms of the formation of persistent slip bands since the 1950s when Wadsworth[1] observed the fatigue fracture in copper. Simulations have indicated that PSBs formation during fatigue crack initiation is related to the dislocation driving force and interaction. In this paper, a molecular dynamics （MD） simulation associated with embedded atom model （EAM） is applied to the PSBs formation in nickel-base superalloys with different microstructure and temperature under tensile- tensile loadings. Five MD models with different microstructure （pure 5/ phase and γ/γ＇ phase）, grain orientation （[1 0 0][0 1 0][0 0 1] and [1 1 1][1 0 1][1 2 1]） and simulation temperature （300 K, 600 K, 900 K） were built up in these simulations. Our results indicated that within the γ phase by massive dislocations, pile-up and propagation which can penetrate the grain. Also, it is found that the temperature will affect the material fatigue performance and blur PSBs appearance. The simulation results are in strong agreement with published experimental test result. This simulation is based on the work[2]. The highlights of the article include： 1） investigation of the PSB formation via molecular dynamics simulation with three different parameters, 2） conduct of a new deformation and velocity combination controlled simulation for the PSB formation, 3） high-performance computing of PSB formation, and 4） systematic analysis of the PSB formation at the atomic scale in which the dislocation plays a critical role.展开更多
文摘A simple modified analytic EAM model for bcc Fe and fcc Al was used to calculate the lattice constant and elastic constants of B2 FeAl and DO3 Fe3Al alloys. The formation energies of vacancy and antisite were also calculated. The present calculations are in agreement with the experimental data and the theoretical results obtained by other authors.
文摘世界时与协调世界时差值(difference between universal time and coordinated universal time,UT1-UTC)是地球定向参数(Earth orientation parameters,EOP)的重要组成部分,其高精度和快速预测对全球卫星导航系统气象学、人造卫星精密轨道确定等实时应用领域至关重要。传统UT1-UTC预报方法在中长期预测中精度衰减明显,难以满足北斗导航系统及战争环境的精确制导等高精度需求。提出了一种融合地球流体有效角动量(effective angular momentum,EAM)信息的轴向分量χ_(3)数据与EOP14 C04序列的卷积长短期记忆神经网络(convolutional long short-term memory,ConvLSTM)模型预报UT1-UTC的新方法。实测数据分析结果发现,EAM轴向分量χ^(3)和经跳秒与潮汐改正后的UT1-UTC数据具有强相关性,其振幅和相位具有一致的频谱特性,说明EAM轴向分量χ^(3)是UT1-UTC的主要激发源。与参与第二届EOP预报比赛的各家精度进行对比,在90~360 d的中长期预报跨度中,ConvLSTM模型预报精度最优,改善幅度为30.27%~92.44%。对比公报A,时间跨度为60 d、180 d和360 d的中长期预报精度分别提升41.46%、70.07%和59.43%,证实了ConvLSTM能够显著改善UT1-UTC的中长期预报精度。
基金supported by School of Engineering and Built Environment,Glasgow Caledonian University,National Natural Science Foundation of China(Nos.51405044,51105061 and 11472075)the EPSRC funded ARCHIE-WESt high-performance computer(www.archie-west.ac.uk)(No.EP/K000586/1)
文摘Persistent slip band （PSB） is an important and typical microstructure generated during fatigue crack initiation. Intensive work has been done to investigate the mechanisms of the formation of persistent slip bands since the 1950s when Wadsworth[1] observed the fatigue fracture in copper. Simulations have indicated that PSBs formation during fatigue crack initiation is related to the dislocation driving force and interaction. In this paper, a molecular dynamics （MD） simulation associated with embedded atom model （EAM） is applied to the PSBs formation in nickel-base superalloys with different microstructure and temperature under tensile- tensile loadings. Five MD models with different microstructure （pure 5/ phase and γ/γ＇ phase）, grain orientation （[1 0 0][0 1 0][0 0 1] and [1 1 1][1 0 1][1 2 1]） and simulation temperature （300 K, 600 K, 900 K） were built up in these simulations. Our results indicated that within the γ phase by massive dislocations, pile-up and propagation which can penetrate the grain. Also, it is found that the temperature will affect the material fatigue performance and blur PSBs appearance. The simulation results are in strong agreement with published experimental test result. This simulation is based on the work[2]. The highlights of the article include： 1） investigation of the PSB formation via molecular dynamics simulation with three different parameters, 2） conduct of a new deformation and velocity combination controlled simulation for the PSB formation, 3） high-performance computing of PSB formation, and 4） systematic analysis of the PSB formation at the atomic scale in which the dislocation plays a critical role.
