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Evolution of microstructure and texture in copper during repetitive extrusion-upsetting and subsequent annealing

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Journal of Materials Science & Technology 2017年第7期33卷 690-697页

作者： Q.Chen D.Y.Shu J.Lin Y.wu X.S.Xia S.H.Huang z.D.zhao O.V.Mishin G.L.wu State Key Laboratory of Mechanical Transmission Chongqing University Chongqing 400044 China

The evolution of the microstructure and texture in copper has been studied during repetitive extrusionupsetting（REU） to a total von Mises strain of 4.7 and during subsequent annealing at different temperatures. It is found that the texture is significantly altered by each deformation pass. A duplex 001 ＋ 111 fiber texture with an increased 111 component is observed after each extrusion pass,whereas the 110 fiber component dominates the texture after each upsetting pass. During REU, the microstructure is refined by deformation-induced boundaries. The average cell size after a total strain of 4.7 is measured to be ~0.3 μm. This refined microstructure is unstable at room temperature as is evident from the presence of a small number of recrystallized grains in the deformed matrix. Pronounced recrystallization took place during annealing at 200？C for 1 h with recrystallized grains developing predominantly in high misorientation regions. At 350？C the microstructure is fully recrystallized with an average grain size of only 2.3 μm and a very weak crystallographic texture. This REU-processed and subsequently annealed material is considered to be potentially suitable for using as a material for sputtering targets.

关键词： Severe plastic deformation Repetitive extrusion-upsetting Copper Deformation microstructure Texture Annealing

Rice Interploidy Crosses Disrupt Epigenetic Regulation, Gene Expression, and Seed Development

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Molecular Plant 2018年第2期11卷 300-314页

作者： Limei wang Jingya Yuan Yujie Ma wu Jiao wenxue Ye Dong-Lei Yang Chuandeng Yi z. Jeffrey Chen State Key Laboratory of Crop Genetics and Germplasm Enhancement Nanjing Agricultural University 1 Weigang Road Nanjing 210095 China Department of Molecular Biosciences Institute for Cellular and Molecular Biology Center for Computational Biology and Bioinformatics The University of Texasat Austin Austin TX 78712 USA Jiangsu Key Laboratory of Crop Genetics and Physiology Yangzhou University Yangzhou 225009 China

Seed development in angiosperms requires a 2：1 maternal-to-paternal genome ratio （2m：lp） in the endo- sperm. when the ratio is disrupted, the seed development is impaired. Rice interploidy crosses result in endosperm failures, but the underlying molecular mechanisms remain unclear. Here, we report that the defective endosperm in rice interploidy crosses was associated with nonadditive expression of small RNAs and protein-coding genes. Interestingly, 24-nt small interfering RNAs were enriched in the 5＇ and 3＇ flanking sequences of nonadditively expressed genes in the interploidy crosses and were negatively associated with the expression of imprinted genes. Furthermore, some PRC2 family genes and DNA methylaUon-related genes including OsMETlb and OsCMT3a were upregulated in the 2x4 cross （polli- nating a diploid ＂mother＂ with a tetraploid ＂father＂） but repressed in the reciprocal cross. These different epigenetic effects could lead to precocious or delayed cellularization during endosperm development. Notably, many endosperm-preferred genes, including starch metabolic and storage protein genes during grain filling, were found to be associated with DNA methylation or H3K27me3, which are repressed in both 2×4 and 4 ×2 crosses. wuSCHEL homeobox2 （wOX2）-Iike （wOX2L）, an endosperm-preferred gene, was expressed specifically in the rice endosperm, in contrast to wOX2 expression in the Arabidopsis embryo. Disruption of wOX2L in transgenic rice by CRISPR/Cas9-mediated gene editing blocked starch and protein accumulation, resulting in seed abortion. In addition to gene repression, disrupting epigenetic process in the interploidy crosses also induced expression of stress-responsive genes. Thus, maintaining the 2m：lp genome ratio in the endosperm is essential for normal grain development in rice and other cereal crops.

关键词： seed polyploidy small RNA gene expression endosperm epigenetics

EFFECT OF STRUCTURAL PARAMETERS ON THE THERMAL STRESS OF A NiFe_(2)O_(4)-BASED CERMET INERT ANODE IN ALUMINUM ELECTROLYSIS

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Acta Metallurgica Sinica(English Letters) 2007年第2期20卷 139-147页

作者： J. Li z.G. wang Y.Q. Lai Y.Y. wu S.L. Ye School of Metallurgy Science and Engineering Central South University Changsha 410083 China

Inert anode has been a hot issue in the aluminum industry for many decades. with the help of FEA （finite element analysis） software ANSYS, a model was developed to simulate the thermal stress distribution working condition of an inert anode. To reduce its thermal stress, the effect of some parameters on the thermal stress distribution was investigated, including the anode height, the anode radius, the hole depth, the hole radius, and the radius of inner chamfer and outer chamfer. The results showed that in the actual working condition of an inert anode, there existed a large axial tensile stress near the tangent interface between the anode and bath, which was the major cause of anode breaking. Increasing the anode height and reducing the hole depth properly seemed to be beneficial for the stress distribution. with the increase of anode radius, the stress distribution became better first and then deteriorated, the reasonable value was between 0.045 to 0.06m. The hole radius had a significant effect on the stress and a smaller radius would reduce the thermal stress. The effect of the radius of the inner chamfer and the outer chamfer was less than other parameters.

关键词： inert anode thermal stress structural parameter aluminum electrolysis

The Effect of Leader Positive Affectivity on Team Member Turnover Intention and Team Organizational Citizenship Behavior

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Frontiers of Business Research in China 2013年第3期7卷 311-332页

作者： Lynda Jiwen Song Kelly z. Peng Chi-Sum wong weiku wu School of Business Renmin University of China Beijing 100872 China Department of Business Administration Enterprise & Social Development Research CentreHong Kong Shue Yan University Hong Kong China Department of Management The Chinese University of Hong Kong Hong Kong China Department of Leadership and Organization Management Tsinghua University Beijing100084 China

This paper develops two models to investigate the effect of team leader positive affectivity （PA） on team member turnover intention and team organizational citizenship behavior （OCB）, at the individual and team levels, respectively. A two-wave longitudinal study was conducted involving a survey of 58 team leaders and 174 team members in a large Chinese telecom company across a three-month period. we found that team members＇ organization-based self-esteem （OBSE） at Time 1 mediates the relationship between team leader PA at Time 1 and team member turnover intention at Time 2, whereas team aggregated OBSE at Time 1 mediates the relationship between leader PA at Time1 and team OCB at Time 2.

关键词： positive affectivity organization-based self-esteem (OBSE) teamorganizational citizenship behavior (OCB)

Effect of static annealing on superplastic behavior of a friction stir welded Ti-6Al-4V alloy joint and microstructural evolution during deformation

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Journal of Materials Science & Technology 2022年第35期130卷 112-123页

作者： C.L.Jia L.H.wu P.Xue D.R.Ni B.L.Xiao z.Y.Ma Shi-Changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China

Structural integration is one of the most critical developing directions in the modern aerospace field,in which large-scale complex components of Ti alloys are proposed to be fabricated via the method of welding + superplastic ***,the undesired strain localization appeared during superplastic deformation of the entire joint has largely hindered the development of this *** our study,a combination process of friction stir welding(FSw) + static annealing+ superplastic deformation was first time proposed to eliminate severe local *** achieve this result,a fully fine lamellar structure was obtained in the nugget zone(Nz) via FSw,which was totally different from the mill-annealed structure in the base material(BM).After annealing at 900℃ for 180 min,the BM and Nz then exhibited the similar elongation of> 500% and similar flow stress at 900 ℃,3 × 10^(-3)s^(-1),which was the precondition for achieving uniform superplastic deformation in the entire ***,the different microstructures in the BM and Nz tended to become the similar equiaxed structure after deformation,which was the result of different microstructural evolution mechanisms in the Nz and *** the Nz,there was a static and dynamic spheroidization of the fully lamellar structure during the process,which could largely reduce the flow softening of the fully lamellar *** the BM,a new view of "Langdon-CRSS theory"(CRSS,critical resolved shear stress) was proposed to describe the fragmentation of the coarse equiaxed structure,which established the relationship between grain boundary sliding and intragranular deformation during deformation.

关键词： Friction stir welding Titanium alloys Superplasticity Static annealing Microstructure

Effects of friction stir processing and nano-hydroxyapatite on the microstructure,hardness,degradation rate and in-vitro bioactivity of wE43 alloy for biomedical applications

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Journal of Magnesium and Alloys 2024年第1期12卷 209-224页

作者： Bo wu Farazila Yusof Fuguo Li Huan Miao A.R.Bushroa Mohd Ridha Bin Muhamad Irfan Anjum Badruddin Mahmoud z.Ibrahim Department of Mechanical Engineering Faculty of EngineeringUniversiti MalayaKuala Lumpur 50603Malaysia Centre of Advanced Manufacturing and Material Processing(AMMP Centre) Universiti MalayaKuala Lumpur 50603Malaysia Center of Foundation studies in Science Universiti MalayaKuala Lumpur 50603Malaysia State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Mechanical Engineering Department College of EngineeringKing Khalid UniversityAbha 61421Saudi Arabia Design and Production Engineering Faculty of EngineeringAin Shams UniversityCairo 11517Egypt

Nowadays,magnesium alloys are emerging in biomedical implants for their similar properties to natural ***,the rapid degradation of magnesium alloys in biological media hinders successful *** of microstructure,as well as reinforcement particles can significantly improve the degradation *** this work,multi-pass friction stir processing(FSP)was proposed to synthesize wE43/nano-hydroxyapatite(n HA)surface composite,the microstructure,reinforced particle distribution,micro-hardness,corrosion behavior and in-vitro bioactivity were *** subsequent FSP passes of wE43 alloy and wE43/n HA composite refined the grain size which was reduced by 94.29%and 95.92%(2.63 and 1.88μm,respectively)compared to base metal after three *** resulted in increasing the microhardness by 120%(90.86 HV0.1)and 135%(105.59 HV0.1)for the wE43 and wE43-n HA,*** is found that increasing FSP passes improved the uniform distribution of n HA particles within the composite matrix which led to improved corrosion resistance and less degradation *** corrosion rate of the FSPed wE43/n HA composite after three passes was reduced by 38.2%(4.13 mm/year)and the degradation rate was reduced by 69.7%(2.87 mm/y).This is attributed to secondary phase(Mg24Y5and Mg41Nd5)particle fragmentation and redistribution,as well as a homogeneous distribution of n ***,the growing Ca-P and Mg(OH)2layer formed on the surface represented a protective layer that reduced the degradation *** wettability test revealed a relatively hydrophilic surface with water contact angle of 49.1±2.2°compared to 71.2±2.1°for base ***,biomineralization test showed that apatite layer grew after immersion 7d in simulated body fluid with atomic ratio of Ca/P 1.60 approaching the stoichiometric ratio(1.67)indicating superior bioactivity of FSPed wE43/n HA composite after three *** results raise that the grain refinement by FSP and introduction of n HA partic

关键词： Friction stir processing Magnesium-based composite Nano-hydroxyapatite Corrosion behavior In-vitro bioactivity

Upper-Ocean Lateral Heat Transports in the Nino3.4 Region and Their Connection with ENSO

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Journal of Meteorological Research 2022年第2期36卷 360-373页

作者： He zHAO Tongwen wu Laurent zXLI Fanghua wu weihua JIE Xiangwen LIU Ronghua zHANG Chengjun XIE Chinese Academy of Meteorological Sciences China Meteorological AdministrationBeijing 100081China College of Earth and Planetary Sciences University of Chinese Academy of SciencesBeijing 100049China Beijing Climate Center China Meteorological AdministrationBeijing 100081China Laboratoire de Météorologie Dynamique Centre National de la Recherche ScientifiqueSorbonne UniversitéEcole Normale SupérieureEcole PolytechniqueParis 75252France Key Laboratory of Ocean Circulation and waves Institute of Oceanologyand Center for Ocean Mega-ScienceChinese Academy of SciencesQingdao 266071China Center for Excellence in Quaternary Science and Global Change Chinese Academy of SciencesXi’an 710061China

In the Nino3.4 region(tropical Pacific,5°S-5°N,170°-120°w),sea surface temperature(SST)changes are highly correlated with temperature variations in the upper 40-m *** study explores the upper-ocean heat budget in the Nino3.4 region using Ocean Reanalysis System 5(ORAS5)monthly data from 1979 to 2018,with a focus on ocean heat transports at lateral boundaries in the top 40-m layer and their correlation with temperature *** the region,there is a well-defined structure of opposite meridional circulation in the upper and lower parts of the thermocline,characterized by divergence in the upper layer above 40 m and convergence in the lower *** change of mean temperature in the upper layer is determined by the sum of zonal,meridional,and vertical heat transports,which,however,tend to largely compensate for each *** general,part of the surface heat flux from the atmosphere to the ocean and the heat transport from the subsurface ocean are transported out of the domain by meridional and zonal currents,leaving only a tiny part to warm or cool the upper *** amplitude of the net surface heat flux effective for the entire 40-m layer of the ocean is weaker than the lateral heat *** an interannual timescale,variations of heat transports in both zonal and meridional are positively correlated with temperature anomalies,while the vertical heat transport from the subsurface ocean is negatively *** analyses for five El Nino events and five La Nina events also revealed that there is a positive contribution of horizontal transport convergence to temperature anomalies during the evolution of El Nino(warming)and La Nina(cooling),while vertical transport acts against temperature variations.

关键词： heat budget lateral heat transport surface heat flux Ni?o3.4 region El Nino–Southern Oscillation(ENSO)

HIGH STRAIN RATE SUPERPLASTICITY IN A SiC_w/2024Al COMPOSITE MADE BY SQUEEzE CASTING

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Acta Metallurgica Sinica(English Letters) 1998年第4期11卷 275-280页

作者： X.J.Xu D. zhang z.L. Shi C.z.zhao and R.J. wu (State Key Laboratory of Metal Matrir Composites, Shanghai Jiaotong University, Shanghai 200030, China) Shanghai Jiaotong Univ Shanghai China

In this paper,the superplastic characteristics of the beta-SiC whisker reinforced 2024aluminum composite, fabricated by squeeze casting and hot-rolling after extrusion were investigated. The compsite had a fine grain size of about 2μm, and exhibited a strain rate sensitivity of about 0.35 and a maximum elongation of 350% at an initial strain rate of 1.1×10-1s-1 at 803K. In addition, the superplastic deformation mechanisme of the composite were also examined.

关键词： high strain rate superplasticity aluminum matrix composite squeeze casting

This research was supported by ***6 Integrated Project“Molecular Imaging”LSHG-CT-2003-503259 and ***7 Collaborative Project“FMT-XCT”.*** support from the Marie Curie Program EST-MolecImag Early Stage Training MEST-CT-2004-007643.

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Journal of Innovative Optical Health Sciences 2009年第4期2卷 365-374页

作者： MAHSA RANJI SHOKO NIOKA HE N.XU BAOHUA wu LIN z.LI DwIGHT L.JAGGARD BRITTON CHANCE Biophotonics Laboratory Department of Electrical Engineering and Computer Science University of wisconsin-Milwaukee MilwaukeeWI 53211USA Department of Electrical and Systems Engineering University of Pennsylvania PhiladelphiaPA 19104USA Department of Biochemistry and Biophysics University of Pennsylvania PhiladelphiaPA 19104USA Department of Radiology University of Pennsylvania PhiladelphiaPA 19104USA

we have imaged mitochondrial oxidation-reduction states by taking a ratio of mitochondrial fluorophores:NADH(reduced nicotinamide adenine dinucleotide)to Fp(oxidized flavoprotein).Although NADH has been investigated for tissue metabolic state in cancer and in oxygen deprived tissues,it alone is not an adequate measure of mitochondrial metabolic state since the NADH signal is altered by dependence on the number of mitochondria and by blood *** redox ratio,NADH/(Fp+NADH),gives a more accurate measure of steady-state tissue metabolism since it is less dependent on mitochondrial number and it compensates effectively for hemodynamic *** ratio provides important diagnostic information in living *** this study,the emitted fluorescence of mouse colon in situ is passed through an emission filter wheel and imaged on a CCD *** ratio images of the healthy and hypoxic mouse intestines clearly showed significant ***,the corrected redox ratio indicated an increase from an average value of 0.51±0.10 in the healthy state to 0.92±0.03 in dead tissue due to severe ischemia(N=5).we show that the CCD imaging system is capable of displaying the metabolic differences in normal and ischemic tissues as well as quantifying the redox ratio in vivo as a marker of these changes.

关键词： Optical diagnosis NADH flavoprotein in vivo ischemia fluorescence.