THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between c...THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between crystallographic orientation,grain boundary(GB)proximity,and pore characteristics(size/location).This study compares single-crystal nickel models along[100],[110],and[111]orientations with equiaxed polycrystalline models containing 0,1,and 2.5 nm pores in surface and subsurface configurations.Our results reveal that crystallographic anisotropy manifests as a 24.4%higher elastic modulus and 22.2%greater hardness in[111]-oriented single crystals compared to[100].Pore-GB synergistic effects are found to dominate the deformation behavior:2.5 nm subsurface pores reduce hardness by 25.2%through stress concentration and dislocation annihilation at GBs,whereas surface pores enable mechanical recovery via accelerated dislocation generation post-collapse.Additionally,size-dependent deformation regimes were identified,with 1 nm pores inducing negligible perturbation due to rapid atomic rearrangement,in contrast with persistent softening in 2.5 nm pores.These findings establish atomic-scale design principles for defect engineering in nickel-based aerospace components,demonstrating how crystallographic orientation,pore configuration,and GB interactions collectively govern nanoindentation behavior.展开更多
E-Learning自诞生以来,受到商业组织和学术机构的广泛关注。利用共词分析、聚类分析、社会网络分析、网络社区分析等方法对Web of Science数据库收录的E-Learning研究文献进行的深度剖析发现:国际E-Learning研究发展大体可以分为三个阶...E-Learning自诞生以来,受到商业组织和学术机构的广泛关注。利用共词分析、聚类分析、社会网络分析、网络社区分析等方法对Web of Science数据库收录的E-Learning研究文献进行的深度剖析发现:国际E-Learning研究发展大体可以分为三个阶段:1968-1993年,E-Learning相关研究开始出现,但研究文献较少,以案例研究等定性研究方法为主,处于以概念探讨为主的初级研究阶段;1994-2003年,研究文献增多,研究方法逐渐偏向于定量研究,开始形成较为稳定的研究主题领域,并逐渐出现主题分化和主题融合;2004-2013年,研究主题不断细化,研究深度进一步增强。总体来看,国际E-Learning研究经历从"技术导向"到"行为导向"再到"行为和技术导向"相融合、从单一强调"学习者"或"教学者"的自我导向学习研究到同时强调"教学者"和"学习者"的互动协作学习研究等主题演化特征,跨文化、跨学科研究成为全球化背景下国际E-Learning研究方向,研究模型设计越来越注重中介变量和调节变量的作用。混合式网络学习环境研究、强调个性化和智能化的E-Learning系统研究、基于认知心理的学习效能研究可能成为未来E-Learning研究的潜在热点领域。展开更多
基金The National Natural Science Foundation of China(Grant No.12462006)Beijing Institute of Structure and Environment Engineering Joint Innovation Fund(No.BQJJ202414).
文摘THE mechanical response and deformation mechanisms of pure nickel under nanoindentation were systematically investigated using molecular dynamics(MD)simulations,with a particular focus on the novel interplay between crystallographic orientation,grain boundary(GB)proximity,and pore characteristics(size/location).This study compares single-crystal nickel models along[100],[110],and[111]orientations with equiaxed polycrystalline models containing 0,1,and 2.5 nm pores in surface and subsurface configurations.Our results reveal that crystallographic anisotropy manifests as a 24.4%higher elastic modulus and 22.2%greater hardness in[111]-oriented single crystals compared to[100].Pore-GB synergistic effects are found to dominate the deformation behavior:2.5 nm subsurface pores reduce hardness by 25.2%through stress concentration and dislocation annihilation at GBs,whereas surface pores enable mechanical recovery via accelerated dislocation generation post-collapse.Additionally,size-dependent deformation regimes were identified,with 1 nm pores inducing negligible perturbation due to rapid atomic rearrangement,in contrast with persistent softening in 2.5 nm pores.These findings establish atomic-scale design principles for defect engineering in nickel-based aerospace components,demonstrating how crystallographic orientation,pore configuration,and GB interactions collectively govern nanoindentation behavior.
文摘E-Learning自诞生以来,受到商业组织和学术机构的广泛关注。利用共词分析、聚类分析、社会网络分析、网络社区分析等方法对Web of Science数据库收录的E-Learning研究文献进行的深度剖析发现:国际E-Learning研究发展大体可以分为三个阶段:1968-1993年,E-Learning相关研究开始出现,但研究文献较少,以案例研究等定性研究方法为主,处于以概念探讨为主的初级研究阶段;1994-2003年,研究文献增多,研究方法逐渐偏向于定量研究,开始形成较为稳定的研究主题领域,并逐渐出现主题分化和主题融合;2004-2013年,研究主题不断细化,研究深度进一步增强。总体来看,国际E-Learning研究经历从"技术导向"到"行为导向"再到"行为和技术导向"相融合、从单一强调"学习者"或"教学者"的自我导向学习研究到同时强调"教学者"和"学习者"的互动协作学习研究等主题演化特征,跨文化、跨学科研究成为全球化背景下国际E-Learning研究方向,研究模型设计越来越注重中介变量和调节变量的作用。混合式网络学习环境研究、强调个性化和智能化的E-Learning系统研究、基于认知心理的学习效能研究可能成为未来E-Learning研究的潜在热点领域。
