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Transition from source-to stress-controlled plasticity in nanotwinned materials below a softening temperature

npj Computational Materials 2019年第1期5卷 1105-1111页

作者： Seyedeh Mohadeseh Taheri Mousavi Haofei Zhou guijin zou Huajian Gao School of Engineering Brown UniversityProvidenceRI 02912USA Department of Materials Science and Engineering Massachusetts Institute of Technology77 Massachusetts AvenueCambridgeMA 02139USA

Nanotwinned materials have been widely studied as a promising class of nanostructured materials that exhibit an exceptional combination of high strength,good ductility,large fracture toughness,remarkable fatigue resistance,and creep ***,an apparent controversy has emerged with respect to how the strength of nanotwinned materials varies as the twin thickness is *** a transition from hardening to softening was observed in nanotwinned Cu when the twin thickness is reduced below a critical value,continuous hardening was reported in nanotwinned ceramics and nanotwinned ***,by conducting atomistic simulations and developing a theoretical modeling of nanotwinned Pd and Cu systems,we discovered that there exists a softening temperature,below which the material hardens continuously as the twin thickness is reduced(as in nanotwinned ceramics and diamond),while above which the strength first increases and then decreases,exhibiting a maximum strength and a hardening to softening transition at a critical twin thickness(as in nanotwinned Cu).This important phenomenon has been attributed to a transition from source-to stress-controlled plasticity below the softening temperature,and suggests that different hardening behaviors may exist even in the same nanotwinned material depending on the temperature and that at a given temperature,different materials could exhibit different hardening behaviors depending on their softening temperature.

关键词： softening stress creep

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Synthesis of Block Copolymers of 2-Ethylhexyl Methacrylate, n-Hexyl Methacrylate and Methyl Methacrylate via Anionic Polymerization at Ambient Temperature

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Chinese Journal of Chemistry 2018年第10期36卷 934-938页

作者： guijin zou Anna Zheng Dafu wei Zheng Li Ling Su Tongyuan Zhang Xiang Xu Yong Guan School of Materials Science and Engineering Key Laboratory for Ultrafine Materials of Ministry of Education East China University of Science andTechnology Shanghai 200237 China

It still remains a concern to break through the bottlenecks of anionic polymerization of polar monomers, such as side reactions, low conver- sion and low temperature （-78 ℃）. In this work, potassium tert-butoxide （t-BuOK） was chosen to initiate the anionic polymerization of 2-ethylhexyl methacrylate （EHMA） in tetrahydrofuran. The conversions were above 99% at 0 or 30 ℃, and above 95% at 60 ℃ without side reaction inhibitors. The high conversions implied t-BuOK could suppress the side reactions. A series of block copolymers of EHMA, n-hexyl methacrylate （HMA） and methyl methacrylate （MMA） were further synthesized at 0 ℃, and the conversions were all above 99%. The GPC and IH NMR results confirmed the successful synthesis of the block copolymers. The molecular size of monomer and the state of t-BuOK （free ion pairs or aggregates） remarkably affected the polymerization rates and the molecular structures of the products. The DMA results indicated that the glass transition temperatures of PEHMA or PHMA block and PMMA block were 20 ℃ and 60 ℃, respectively, which deviated from -2 ℃ and 105 ℃ of homopolymer, respectively, due to the partial com- patibility of the blocks. This work explored a route of the anionic polymerization of polar monomers at room temperature.

关键词： anionic polymerization methacrylate polar monomer potassium tert-butoxide

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基于命名数据网络的区块链信息传输机制

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通信学报 2018年第1期39卷 24-33页

作者：刘江霍如李诚成邹贵今黄韬刘韵洁北京邮电大学网络与交换技术国家重点实验室北京100876 北京工业大学北京未来网络科技高精尖创新中心北京100124

近年来关于区块链的研究得到极大关注,然而基于TCP/IP的通信对这种大量数据内容广播模式的支撑并不充分。基于命名数据网络,设计全新的支持区块链推送服务的节点模型和特殊的读写表过程,提出完善的信息传输机制,通过请求聚合和数据缓存... 详细信息

近年来关于区块链的研究得到极大关注,然而基于TCP/IP的通信对这种大量数据内容广播模式的支撑并不充分。基于命名数据网络,设计全新的支持区块链推送服务的节点模型和特殊的读写表过程,提出完善的信息传输机制,通过请求聚合和数据缓存减少网内冗余流量并加速通信传输。同时给出基于本架构的虚拟货币应用实例,并通过仿真验证本方案性能的优势,进一步展望未来相关的研究方向。

关键词：命名数据网络区块链信息推送内容广播反向读写表项

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Publisher Correction:Transition from source-to stresscontrolled plasticity in nanotwinned materials below a softening temperature

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npj Computational Materials 2019年第1期5卷 1047-1047页

The original version of this Article was incorrectly labelled as a‘Review Article’.This has now been corrected to‘Article’in both the HTML and PDF versions.

关键词： HTML Publisher Transition

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