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单晶锗纳米尺度分层多次切削的分子动力学模拟 被引量:3
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作者 杨晓京 余证 +1 位作者 刘宁 赵垒 《材料科学与工程学报》 CAS CSCD 北大核心 2021年第3期437-444,451,共9页
运用分子动力学方法研究了单晶锗材料在多次切削过程中晶体结构的演化和相变。比较了在相同的总加工深度下采用两次不同预设切削深度加工单晶锗后表面/亚表面损伤程度、温度和应力的变化。研究结果表明:切削过程中切削区原子发生高压相... 运用分子动力学方法研究了单晶锗材料在多次切削过程中晶体结构的演化和相变。比较了在相同的总加工深度下采用两次不同预设切削深度加工单晶锗后表面/亚表面损伤程度、温度和应力的变化。研究结果表明:切削过程中切削区原子发生高压相变,原子结构从Ge-Ⅰ结构转变为无定形结构,使工件发生塑性变形,切屑以塑性方式去除;切削结束后由于压力和温度释放,少量无定形结构原子重新转变为Ge-Ⅰ结构或六方金刚石结构,而无定形结构主要是β-tin结构和非晶体结构;预设切削深度增加,材料的去除量和亚表面损伤深度增加,其损伤深度不受前一次切削深度影响,仅与最终预设切削深度相关,并且在同样条件下,多次切削比单次切削更有利于降低亚表面损伤深度和提升加工效率。此外,原子相变与σ_(xx)和σH_(yd)相关,亚表面损伤深度与σ_(yy)相关,两次预设切削深度接近或相等时,工件内部应力均衡有利于形成较好的加工表面。 展开更多
关键词 单晶锗 晶体结构演化 分子动力学 亚表层质量
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Comparison of the Evolvement Structure of Chenopodium album L.under the Stress of Different Saline Environments
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作者 魏健 盖玉红 +2 位作者 蔡立格 陆静梅 王光野 《Agricultural Science & Technology》 CAS 2011年第7期1055-1058,共4页
[Objective] The aim of this study was to reveal the evolvement structures,especially the crystal characteristics of Chenopodium album L.under saline stress,so as to providing the first-hand data for utilizing biologic... [Objective] The aim of this study was to reveal the evolvement structures,especially the crystal characteristics of Chenopodium album L.under saline stress,so as to providing the first-hand data for utilizing biological techniques to control saline environment.[Method] Employing high definition display method of plant crystal structure and paraffin-section method,we performed a comparative study on the evolvement structures of C.album growing in high salinity areas in the coast of Egyptian Red Sea and common salinity areas in the grasslands in Changling County of Jilin Province.[Result] The regionally distributed crystal and the developed assimilating tissue of C.album are the key structural characteristics to antagonize the saline stress during the evolving process.Stem cortex of C.album growing in both the high salinity areas in coast of Egyptian Red Sea and common salinity areas in the grasslands in Changling County of Jilin Province has similar discontinuous crystal rings.Assimilating tissue in C.album growing in high salinity areas is highly developed than that in common salinity environment.Comparative analysis indicates that the developed stratum corneum and marrow is also the key structural characteristics to antagonize the saline stress.[Conclusion] Our results provide a valuable approach to study the salt-tolerance mechanism of plant using structural botanical techniques,i.e.,crystal may become the identification characteristics of salt tolerant plant. 展开更多
关键词 Chenopodium album L. CRYSTAL Antagonism to the saline stress Evolvement structure
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