Compression Deformation Mechanisms at the Nanoscale in Magnesium Single Crystal

The dominant deformation mode at low temperatures for magnesium and its alloys is generally regarded to be twinning because of the hcp crystal structure. More recently, the phenomenon of a ＂loss＂ of the twins has been reported in microcompression experiments of the magnesium single crystals. Molecular dynamics simulation of compression deformation shows that the pyramidal 〈α ＋ c〉 slip dominates compression behavior at the nanoscale. No compression twins are observed at different temperatures at different loadings and boundary conditions. This is explained by the analyses, that is, the {10^_12} and {10^11} twins can be activated under c-axis tension, while compression twins will not occur when the c/α ratio of the hcp metal is below √3. Our theoretical and simulation results are consistent with recent microcompression experiments of the magnesium （0001） single crystals.

核辐射的交互作用

本书作者是麻省理工学院核科学与工程系的教授。本书是作者为第一年研究生课程所著，书中讲述了核科学和工程的基础知识。与传统的核工程和核物理基础课程不同，本书的重点是让作为未来的核工程师的学生们了解核辐射以及核辐射与环境物质的相互作用。此外，为了能够有效使用核辐射，我们必须理解其属性，从而能够开发出新的、更安全的、有效的、耐用而经济的新型装置。