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Direct observation of Pt nanocrystal coalescence induced by electron-ex.itation-enhanced van der Waals interactions

Nano Research 2014年第3期7卷 308-314页

作者： Ying Jiang Yong Wang Yu Yang Zhang Zhengfei Zhang Wentao Yuan Chenghua Sun x.ao Wei Casey N. Brodsky Chia-Kuang Tsung Jix.e Li x.aofeng Zhang scott x. mao Shengbai Zhang Ze Zhang Center of Electron Microscopy and State Key Laboratory of Silicon Materials Department of Materials Science and Engineering Zhejiang University Hangzhou 310027 China Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy New York 12180 USA Centre for Computational Molecular Science Australian Institute for Bioengineering and Nanotechnology University of Queensland St Lucia QLD 4072 Australia Department of Chemistry Boston College Chestnut Hill MA 02467 USA Hitachi High Technologies America Pleasanton CA 94588 USA Department of Mechanical Engineering and Materials Science University of Pittsburgh Pittsburgh PA 15261 USA

Nanocrystal coalescence has attracted paramount attention in nanostructure fabrication in the past decades. Tremendous endeavor and progress have been made in understanding its mechanisms, benefiting from the development of transmission electron microscopy. However, many mechanisms still remain unclear, especially for nanocrystals that lack a permanent dipole moment standing on a solid substrate. Here, we report an in situ coalescence of Pt nanocrystals on an amorphous carbon substrate induced by electron-ex.itation- enhanced van der Waals interactions studied by transmission electron microscopy and first principles calculations. It is found that the electron-beam-induced ex.itation can significantly enhance the van der Waals interaction between Pt nanocrystals and reduce the binding energy between Pt nanocrystals and the carbon substrate, both of which promote the coalescence. This work ex.ends our understanding of the nanocrystal coalescence observed in a transmission electron microscope and sheds light on a potential pathway toward practical electron- beam-controlled nanofabrication.

关键词： Pt nanocrystals coalescence electron ex.itation van der Waals interactions

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Discrete twinning dynamics and size-dependent dislocation-to twin transition in body-centred cubic tungsten

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Journal of Materials Science & Technology 2022年第11期106卷 33-40页

作者： Jiangwei Wang Anik H.M.Faisal x.yao Li Youran Hong Qi Zhu Hongbin Bei Ze Zhang scott x.mao Christopher R.Weinberger Center of Electron Microscopy and State Key Laboratory of Silicon Materials School of Materials Science and EngineeringZhejiang UniversityHangzhou 310027China Department of Mechanical Engineering Colorado State UniversityCO 80523USA School of Materials Science and Engineering Zhejiang UniversityHangzhou 310027China Department of Mechanical Engineering and Materials Science University of PittsburghPittsburghPA 15261USA Wenzhou Key Laboratory of Novel Optoelectronic and Nano Materials Institute of WenzhouZhejiang UniversityWenzhou 325006China

Body-centred cubic(BCC) metals are known to have unstable intrinsic stacking faults and high resistance to deformation twinning, which can strongly influence their twinning behaviour. Though twinning mechanisms of BCC metals have been investigated for more than 60 years, the atomistic level dynamics of twinning remains under debate, especially regarding its impact on competition between twinning and slip. Here, we investigate the atomistic level dynamics of twinning in BCC tungsten(W) nanowires using in situ nanomechanical testing. Quantitative ex.erimental studies directly visualize that deformation twins in W nanowires have a minimum size of six.layers and grow in increments of approx.mately three-layers at a time, in contrast to the layer-by-layer growth of deformation twins in face-centred cubic metals. These unique twinning dynamics induces a strong competition with ordinary dislocation slip,as ex.ibited by a size-dependent dislocation-to-twin transition in W nanowires, with a transition size of ~40 nm. Our work provides physical insight into the dynamics of twinning at the atomic level, as well as a size-dependent dislocation-twinning competition, which have important implications for the plastic deformation in a broad class of BCC metals and alloys.

关键词： Body-centred cubic Deformation twin Twinning dynamics Dislocation-to-twin transition In situ nanomechanical testing

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In situ observation of sublimation-enhanced magnesium ox.dation at elevated temperature

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Nano Research 2016年第9期9卷 2796-2802页

作者： Zijiao Zhang x.aoqian Fu Minmin mao Qian Yu scott x.mao Jix.e Li Ze Zhang Center of Electron Microscopy and State Key Laboratory of Silicon Materials Department of Materials Science & EngineeringZhejiang UniversityHangzhou 310027China Department of Mechanical Engineering & Materials Science University of PittsburghPittsburghPA 15261USA

Ox.dation plays a tremendous role in the long-term performance of metals. As an important lightweight metal for industrial applications, magnesium suffers from its high reactivity with ox.gen and increased evaporation at high temperatures. To understand the ox.dation mechanism of magnesium at elevated temperatures, in situ environmental transmission electron microscopy (E-TEM) was performed on magnesium nanoparticles. At a relatively low temperature, the growth of a MgO lamellae via the outward diffusion of bulk magnesium atoms dominated the ox.dation process. In contrast, a sublimation-enhanced ox.dation via gas phase reaction occurred at 200 °C, leading to the growth of MgO dendrites over the particle that finally leads to the degradation of the magnesium structure. This study provides a direct observation and model of the ox.dation mechanism of a direct gas–gas reaction that improves our understanding of the ox.dation mechanism at elevated temperatures. [Figure not available: see fulltex..] © 2016, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

关键词： ox.dation magnesium sublimation nanoparticle

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In situ atomistic observation of the deformation mechanism of Au nanowires with twin–twin intersection

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Journal of Materials Science & Technology 2020年第18期52卷 118-125页

作者： Shuchun Zhao Qi Zhu x.anghai An Hua Wei Kex.ng Song scott x.mao Jiangwei Wang Center of Electron Microscopy and State Key Laboratory of Silicon Materials School of Materials Science&EngineeringZhejiang UniversityHangzhou 310027China School of Aerospace Mechanical&Mechatronic EngineeringThe University of SydneySydney 2006Australia Center for Hypergravity Ex.erimental and Interdisciplinary Research.Zhejiang University Hangzhou 310027China School of Materials Science&Engineering Henan University of Science and TechnologyLuoyang 471023China Department of Mechanical Engineering and Materials Science University of PittsburghPittsburgh Pennsylvania15261USA

Twin–twin intersections are often observed in face-centered cubic(FCC)metallic nanostructures,which have important contributions to the plastic deformation and strengthening of FCC metals with low stacking fault ***,a deep insight into the underlying mechanism involved in the formation and evolution of twin–twin intersections remains largely lacking,especially in ***,by conducting the in situ straining ex.eriments under high resolution transmission electron microscope(TEM),we directly visualize the dynamic evolution of a twin–twin intersection in Au nanowire at the *** shows that dislocations in the incoming twin can either glide onto or transmit across the barrier twin via dislocation interaction with the twin boundary,resulting in the twin–twin *** twinning and de-twinning of the twin–twin intersection govern the whole deformation of the *** findings reveal the dynamic behaviors of twin–twin intersection under mechanical loading,which benefits further ex.loration of FCC metals and engineering alloys with twin–twin intersection structures.

关键词： In situ TEM Twin-twin intersection Au nanowire Twinning/de-twinning Dislocation-twin interaction

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Environmental landscape determinants of max.mum forest canopy height of boreal forests

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Journal of Plant Ecology 2019年第1期12卷 96-102页

作者： Lingfeng mao Christopher W.Bater John JStadt Barry White Piotr Tompalski Nicholas C.Coops scott E.Nielsen Department of Renewable Resources University of AlbertaEdmontonAlberta T6G 2H1Canada Forest Management Branch Forestry DivisionAlberta Agriculture and ForestryEdmontonAlberta T5K 2M4Canada Department of Forest Resource Management University of British ColumbiaVancouverBritish Columbia V6T 1Z4Canada

Aims Canopy height is a key driver of forest biodiversity and carbon *** estimates of canopy height are needed for assess-ing mechanisms relating to ecological patterns and processes of tree height *** global scales forest canopy height patterns are largely controlled by climate,while local variation at fine scales is due to differences in disturbance history and local patterns in envir-onmental *** relative effect of local environmental driv-ers on canopy height is poorly understood partly due to gaps in data on canopy height and methods for ex.mining limiting ***,we used airborne laser scanning(ALS)data on vegetation structure of boreal forests to ex.mine the effects of environmental factors on potential max.mum forest canopy *** Relationships between max.mum canopy height from ALS meas-ures and environmental variables were ex.mined to assess factors limiting tree ***,we used quantile regression at the 0.90 quantile to relate max.mum canopy height with environmental characteristics of climate(*** annual temperature[MAT]and mean annual precipitation),terrain(***)and depth-to-water(DTW)across a 33000 km2 multiple use boreal forest landscape in northeast Alberta,*** Findings Max.mum canopy height was positively associated with MAT,ter-rain slope and terrain-derived DTW,collectively ex.laining 33.2%of the variation in *** strongest ex.lanatory variable was DTW ex.laining 26%of canopy height variation with peatland forests having naturally shorter max.mum canopy heights,but also more sites currently at their max.mum potential *** con-trast,the most productive forests(*** to x.ric upland forests)had the fewest sites at their potential max.mum height,illustrating the effects of long-term forest management,wildfires and general anthropogenic footprints on reducing the ex.ent and abundance of older,taller forest habitat in Alberta’s boreal forest.

关键词： forest succession vegetation structure quantile regression remote sensing airborne laser scanning(ALS)

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Epidemiology, causes, clinical manifestation and diagnosis, prevention and control of coronavirus disease (COVID-19) during the early outbreak period: a scoping review

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Infectious Diseases of Poverty 2020年第2期9卷 90-91页

作者： Sasmita Poudel Adhikari Sha Meng Yu-Ju Wu Yu-Ping mao Rui-x.e Ye Qing-Zhi Wang Chang Sun Sean Sylvia scott Rozelle Hein Raat Huan Zhou West China School of Public Health and West China Fourth Hospital Sichuan UniversityChengduChina 不详

Background:The coronavirus disease(COVID-19)has been identified as the cause of an outbreak of respiratory illness in Wuhan,Hubei Province,China beginning in December *** of 31 January 2020,this epidemic had spread to 19 countries with 11791 confirmed cases,including 213 *** World Health Organization has declared it a Public Health Emergency of International ***:A scoping review was conducted following the methodological framework suggested by Arksey and O'*** this scoping review,65 research articles published before 31 January 2020 were analyzed and discussed to better understand the epidemiology,causes,clinical diagnosis,prevention and control of this *** research domains,dates of publication,journal language,authors'affiliations,and methodological characteristics were included in the *** the findings and statements in this review regarding the outbreak are based on published information as listed in the ***:Most of the publications were written using the English language(89.2%).The largest proportion of published articles were related to causes(38.5%)and a majority(67.7%)were published by Chinese *** articles initially focused on causes,but over time there was an increase of the articles related to prevention and *** thus far have shown that the virus7 origination is in connection to a seafood market in Wuhan,but specific animal associations have not been *** symptoms include fever,cough,fatigue,pneumonia,headache,diarrhea,hemoptysis,and *** measures such as masks,hand hygiene practices,avoidance of public contact,case detection,contact tracing,and quarantines have been discussed as ways to reduce *** date,no specific antiviral treatment has proven effective;hence,infected people primarily rely on symptomatic treatment and supportive ***:There has been a rapid surge in research in response to the outbreak of *** t

关键词： COVID-19 Epidemiology Causes Prevention and control Review

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Meet Uniform Continuous Posets

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Journal of Mathematical Research with Applications 2019年第5期39卷 459-468页

作者： x.x.n mao Luoshan x. College of Science Nanjing University of Aeronautics and Astronautics Department of Mathematics Yangzhou University

In this paper, as a generalization of uniform continuous posets, the concept of meet uniform continuous posets via uniform scott sets is introduced. Properties and characterizations of meet uniform continuous posets are presented. The main results are:(1) A uniform complete poset L is meet uniform continuous iff ↑(U ∩↓ x. is a uniform scott set for each x.∈ L and each uniform scott set U;(2) A uniform complete poset L is meet uniform continuous iff for each∨∨x. L and each uniform subset S, one has x.∧S ={x.∧ s | s ∈ S}. In particular, a complete lattice L is meet uniform continuous iff L is a complete Heyting algebra;(3) A uniform complete poset is meet uniform continuous iff every principal ideal is meet uniform continuous iff all closed intervals are meet uniform continuous iff all principal filters are meet uniform continuous;(4) A uniform complete poset L is meet uniform continuous if L1 obtained by adjoining a top element1 to L is a complete Heyting algebra;(5) Finite products and images of uniform continuous projections of meet uniform continuous posets are still meet uniform continuous.

关键词： uniform set uniform scott set complete Heyting algebra meet uniform continuous poset principal ideal uniform continuous projection

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GATSBY-A MODERN AMERICAN DON QUIx.TE

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西南大学学报(社会科学版) 1986年第S1期 93-98页

作者： mao Ruix.an

Francis scott Fitzgerald (1896—1940) won his international fame with hisThe Great Gatsby,which was published in 1925 but has always been somethingnew and ex.iting to literary critics and readers of many *** successfulportrayal of Jay Gatsby has made the fictional character a household name,alegendary figure,a symbol,and a modern American Don *** story takes place in the early 20’*** was then booming in thereestablished international order after World War I,yet it could hardly afford to

关键词： GATSBY-A MODERN AMERICAN DON QUIx.TE World DON

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寒带森林中最大冠层高度与群落系统发育结构相关

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植物生态学报(英文版) 2023年第4期16卷 64-77页

作者： Ling-Feng mao Yu-Ran Dong Bing-Bing x.ng You-Hua Chen Jacqueline Dennett Christopher Bater John J.Stadt scott ENielsen Co-Innovation Center for Sustainable Forestry in Southern China College of Biology and the EnvironmentNanjing Forestry UniversityNanjing 210037China Department of Renewable Resources University of AlbertaEdmontonAB T6G 2H1Canada Chengdu Institute of Biology Chinese Academy of SciencesChengdu 610041China Forest Management Branch Forestry DivisionAlberta Agriculture and ForestryEdmontonAB T5K 2M4Canada

了解最大冠层高度和森林群落构建的关系至关重要,但相关研究较少。最大冠层高度受到不同生态过程(如生态位分化和环境过滤),以及历史和随机因素的影响。然而,对影响冠层最大高度的生态过程的实证研究仍较少。本研究旨在揭示最大冠层高... 详细信息

了解最大冠层高度和森林群落构建的关系至关重要,但相关研究较少。最大冠层高度受到不同生态过程(如生态位分化和环境过滤),以及历史和随机因素的影响。然而,对影响冠层最大高度的生态过程的实证研究仍较少。本研究旨在揭示最大冠层高度与群落系统发育结构之间的关系。首先,我们从一项加拿大阿尔伯塔省东北部北方森林样方调查数据集(466个50 m×50 m的采样点)中调查了最大树冠高度。在此基础上,以净谱系亲缘关系指数(NRI)和净最近种间亲缘关系指数(NTI)表征样方中种子植物的系统发育结构,探讨了机载激光雷达测量的最大冠层高度与群落系统发育结构的关系。研究结果表明,最大冠层高度越高,主要进化分枝间的系统发育越聚集,这说明北方森林中存在非生物因子驱动的环境过滤。然而我们也发现,在每个主要演化分支内部,最大冠层高度更高的群落中系统发育结构更发散,这意味着其生态位分化更强烈。总之,最大冠层高度越高的群落可能经历了更强烈的历史非生物环境过滤和近期的生态位分化。这些发现将有助于森林生物多样性的监测和管理。

关键词：森林群落系统发育结构生态位分化竞争层次结构环境过滤随机过程群落构建

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锂离子电池电极材料力学问题研究

锂离子电池电极材料力学问题研究

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中国力学大会——2013

作者： He Yu Wang Yanhong Zheng Jieyun Zheng Hao Luo Fei Fan Feifei Zhu Ting Wang Jiangwei mao scott x. Aifantis K.E. Li Hong Chen Liquan Huang x.ejie 中国科学院物理研究所

将基于在高容量硅负极方面的与力学行为有关的几个研究,包括:(1)致密硅薄膜的裂纹演化;(2)无定形Ti-Si复合膜的裂纹演化;(3)微柱与微孔膜的裂纹演化;(4)硅微柱体积变化的有限元模拟;(5)采用扫描探针显微技术中力曲线模式实现Si表面固体...

将基于在高容量硅负极方面的与力学行为有关的几个研究,包括:(1)致密硅薄膜的裂纹演化;(2)无定形Ti-Si复合膜的裂纹演化;(3)微柱与微孔膜的裂纹演化;(4)硅微柱体积变化的有限元模拟;(5)采用扫描探针显微技术中力曲线模式实现Si表面固体电解质膜杨氏模量三维分布的测量等,结合文献工作,分析锂离子电池中的力学问题。

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