X-ray in-line phase contrast imaging enables weakly to absorb specimens to be imaged successfully with high resolution and definition. In this paper we use computer simulation method to analyze how each parameter infl...X-ray in-line phase contrast imaging enables weakly to absorb specimens to be imaged successfully with high resolution and definition. In this paper we use computer simulation method to analyze how each parameter influences the quality of the image. It can avoid wasting unnecessary time and materials in the course of experiment to get ideal images.展开更多
聚焦离子束(focused Ion beam,FIB)作为一种用于金刚石微铣刀的特种加工方式,其引发的损伤程度直接关联到刀具的加工性能和寿命。课题组采用LAMMPS软件进行分子动力学(Molecular Dynamics,MD)模拟,结合SRIM软件的分析结果,探究单晶金刚...聚焦离子束(focused Ion beam,FIB)作为一种用于金刚石微铣刀的特种加工方式,其引发的损伤程度直接关联到刀具的加工性能和寿命。课题组采用LAMMPS软件进行分子动力学(Molecular Dynamics,MD)模拟,结合SRIM软件的分析结果,探究单晶金刚石亚表层损伤的形成机理和入射离子能量对损伤深度和范围的影响。模拟结果表明:随着入射离子能量的提升,离子束在材料内的渗透深度及引起的非晶层和点缺陷损伤均有所增加;进一步的研究发现损伤形成过程中材料局部温度的上升可能诱发自退火现象,且与离子入射能量成正比,该现象对于理解聚焦离子束加工引起的损伤有着至关重要的意义;而势能的变化与损伤形成之间的显著对应关系揭示了第一邻近原子的势能明显高于第二邻近原子,进而高于Other类型原子,这一发现有助于深入理解损伤形成的微观过程。因此,精确控制入射能量是实现金刚石材料高精度聚焦离子束加工的关键,且对自退火效应和势能变化的研究对损伤监控与控制同样重要。展开更多
In order to investigate the effects of two mineral admixtures （i. e., fly ash and ground slag）on initial defects existing in concrete microstructures, a high-resolution X-ray micro-CT（ micro-focus computer tomogra...In order to investigate the effects of two mineral admixtures （i. e., fly ash and ground slag）on initial defects existing in concrete microstructures, a high-resolution X-ray micro-CT（ micro-focus computer tomography）is employed to quantitatively analyze the initial defects in four series of highperformance concrete （HPC）specimens with additions of different mineral admixtures. The nigh-resolution 3D images of microstructures and filtered defects are reconstructed by micro- CT software. The size distribution and volume fractions of initial defects are analyzed based on 3D and 2D micro-CT images. The analysis results are verified by experimental results of watersuction tests. The results show that the additions of mineral admixtures in concrete as cementitious materials greatly change the geometrical properties of the microstructures and the spatial features of defects by physical-chemistry actions of these mineral admixtures. This is the major cause of the differences between the mechanical behaviors of HPC with and without mineral admixtures when the water-to-binder ratio and the size distribution of aggregates are constant.展开更多
文摘X-ray in-line phase contrast imaging enables weakly to absorb specimens to be imaged successfully with high resolution and definition. In this paper we use computer simulation method to analyze how each parameter influences the quality of the image. It can avoid wasting unnecessary time and materials in the course of experiment to get ideal images.
文摘聚焦离子束(focused Ion beam,FIB)作为一种用于金刚石微铣刀的特种加工方式,其引发的损伤程度直接关联到刀具的加工性能和寿命。课题组采用LAMMPS软件进行分子动力学(Molecular Dynamics,MD)模拟,结合SRIM软件的分析结果,探究单晶金刚石亚表层损伤的形成机理和入射离子能量对损伤深度和范围的影响。模拟结果表明:随着入射离子能量的提升,离子束在材料内的渗透深度及引起的非晶层和点缺陷损伤均有所增加;进一步的研究发现损伤形成过程中材料局部温度的上升可能诱发自退火现象,且与离子入射能量成正比,该现象对于理解聚焦离子束加工引起的损伤有着至关重要的意义;而势能的变化与损伤形成之间的显著对应关系揭示了第一邻近原子的势能明显高于第二邻近原子,进而高于Other类型原子,这一发现有助于深入理解损伤形成的微观过程。因此,精确控制入射能量是实现金刚石材料高精度聚焦离子束加工的关键,且对自退火效应和势能变化的研究对损伤监控与控制同样重要。
基金The Scholarship Supported by Ministry of Education of China for Research Abroad(No.3037[2006])the Excellent Doctoral Dissertation Foundation of Southeast University (No.YBTJ-0512)the National Basic Research Program of China(973Program)(No.2009CB623203)
文摘In order to investigate the effects of two mineral admixtures （i. e., fly ash and ground slag）on initial defects existing in concrete microstructures, a high-resolution X-ray micro-CT（ micro-focus computer tomography）is employed to quantitatively analyze the initial defects in four series of highperformance concrete （HPC）specimens with additions of different mineral admixtures. The nigh-resolution 3D images of microstructures and filtered defects are reconstructed by micro- CT software. The size distribution and volume fractions of initial defects are analyzed based on 3D and 2D micro-CT images. The analysis results are verified by experimental results of watersuction tests. The results show that the additions of mineral admixtures in concrete as cementitious materials greatly change the geometrical properties of the microstructures and the spatial features of defects by physical-chemistry actions of these mineral admixtures. This is the major cause of the differences between the mechanical behaviors of HPC with and without mineral admixtures when the water-to-binder ratio and the size distribution of aggregates are constant.
