The relationship between dynamic strain aging and serrated flow behaviour in magnesium alloy

The relationship between dynamic strain ageing (DSA) and serrated flow has been investigated via alternately switching strain rates at various temperatures in a Mg–3Nd–1Zn alloy. The results reveal that serrated flow is enhanced with decreasing strain rate and increasing temperature and tends to vanish, while the DSA continually intensifies as revealed by a higher flow stress even after the serration flow disappears. A mechanism is proposed, which could explain some abnormal deformation behaviour, such as a negative strain rate sensitivity and thermal hardening.     

Closing the Vocabulary Gap?: A Review of Research on Early Childhood Vocabulary Practices

Our qualitative literature review of 31 published studies found that (a) three major approaches are used in early childhood classrooms to support children's vocabulary learning—exposing children to advanced words, providing direct word-meaning instruction, and employing mixed-method interventions; (b) these practices support children's learning of targeted vocabulary words and/or general vocabulary knowledge gains, but various methods have differential impacts on children's depth of word knowledge; and (c) theme-based multimethod interventions are the most likely approach to close the gap. Based on these findings, we suggest future research directions and discuss implications for classroom practice.     

试论历史档案资源的空间分布特点及其成因

本文从空间分布的整体状况、空间分布的国内格局、空间分布的载体特征和类型特点四个方面对我国历史档案资源的空间分布特征进行了系统地探讨,并在此基础上揭示了这些特征形成的复杂的历史文化原因.