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Hardening effects of sheared precipitates on {1121} twinning in magnesium alloys

Journal of Magnesium and Alloys 2023年第2期11卷 580-591页

作者： Jing Tang Wentao Jiang Qingyuan Wang Xiaobao Tian dean Wei Haidong Fan Department of Mechanics Sichuan UniversityChengdu 610065China School of Mechanics and Engineering Southwest Jiaotong UniversityChengdu 610031China

The interactions between a plate-like precipitate and two twin boundaries(TBs)({1012},{1121}) in magnesium alloys are studied using molecular dynamics(MD) simulations. The precipitate is not sheared by {1012} TB, but sheared by {1121} TB. Shearing on the(110) plane is the predominant deformation mode in the sheared precipitate. Then, the blocking effects of precipitates with different sizes are studied for {1121} twinning. All the precipitates show a blocking effect on {1121} twinning although they are sheared, while the blocking effects of precipitates with different sizes are different. The blocking effect increases significantly with the increasing precipitate length(in-plane size along TB) and thickness, whereas changes weakly as the precipitate width changes. Based on the revealed interaction mechanisms, a critical twin shear is calculated theoretically by the Eshelby solutions to determine which TB is able to shear the precipitate. In addition, an analytical hardening model of sheared precipitates is proposed by analyzing the force equilibrium during TB-precipitate interactions. This model indicates that the blocking effect depends solely on the area fraction of the precipitate cross-section, and shows good agreement with the current MD simulations. Finally, the blocking effects of plate-like precipitates on the {1012} twinning(non-sheared precipitate), {1121} twinning(sheared precipitate) and basal dislocations(non-sheared precipitate) are compared together. Results show that the blocking effect on {1121} twinning is stronger than that on {1012} twinning, while the effect on basal dislocations is weakest. The precipitate-TB interaction mechanisms and precipitation hardening models revealed in this work are of great significance for improving the mechanical property of magnesium alloys by designing microstructure.

关键词： Magnesium alloys Precipitate-twin boundary interactions Sheared precipitate Precipitation hardening model Molecular dynamics simulations

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Effect of Laminar Cooling on Phase Transformation Evolution in Hot Rolling Process

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Journal of Iron and Steel Research International 2010年第10期17卷 28-32,44页

作者： NING Lin-xin YANG Dai-jun J Lin T A dean Shougang Technology Institute Shougang Group Beijing 100041 China Department of Mechanical and Manufacturing Engineering University of Birmingham Birmingham B15 2TT UK

The effect of temperature variation owing to the cooling pattern （CP） on the microstructural evolution was investigated by establishing a thermomechanical coupled FE （finite element） model. A set of constitutive equations of phase transformation was implanted into the commercial FE solver MARC through the user defined subroutine CR- PLAW, and the temperature field was calculated by another user defined subroutine FILM. The results show that the final mierostructure is completely bainite phase for CP one, 98% of bainite phase and 2% of ferrite phase for CP two, and 55% of bainite phase, 35% of pearlite phase and 10% of ferrite phase for CP three.

关键词： hot rolling laminar cooling system cooling pattern thermomechanical modelling microstructural evolution constitutive equation phase transformation

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自动巡航草方格固沙机结构设计分析及试验

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农机化研究 2024年第4期46卷 92-98页

作者：王红军廖滔张嘉谋林子钧尤德安彭志锋华南农业大学工程学院广州510642 华南农业大学电子工程学院(人工智能学院) 广州510642

针对荒漠化治理对草方格固沙机的需求,提出了一种集底盘、开沟机构、草箱机构、插草机构、覆压沙机构、播种及洒水机构、升降机构与一体的多功能草方格固沙机。分析了“T+一”式草方格种植模式的优势,提出了自动巡航草方格固沙机整体结... 详细信息

针对荒漠化治理对草方格固沙机的需求,提出了一种集底盘、开沟机构、草箱机构、插草机构、覆压沙机构、播种及洒水机构、升降机构与一体的多功能草方格固沙机。分析了“T+一”式草方格种植模式的优势,提出了自动巡航草方格固沙机整体结构方案,并对开沟机构、草箱机构、插草机构、覆压沙机构、播种及洒水机构、升降机构等关键组件的功能和结构进行了详细分析。应用三维建模软件建立虚拟机构模型,对推草和插草机构进行了运动仿真分析,并对整机进行了作业性能试验。结果表明:各机构构件间无干涉,构件运动仿真轨迹符合功能要求,杆件尺寸参数设计合理,机器作业效率高,可有效保证草方格铺设的准确性和有效性,满足机械化固沙的要求,具有良好的通用性和适应性。

关键词：沙漠治理草方格固沙机防风固沙自动巡航

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基于GNSS+IMU的草方格固沙机自动巡航控制系统

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农机化研究 2024年第5期46卷 37-44页

作者：林子钧尤德安廖滔张嘉谋彭志锋王红军华南农业大学电子工程学院(人工智能学院) 广州510642 华南农业大学工程学院广州510642

为了实现草方格固沙机的智能化工作,提出了一种基于GNSS+IMU的草方格固沙机自动巡航控制系统。系统以STM32F407VGT6作为主控芯片,将GNSS(全球导航卫星系统)和IMU(惯性测量单元)的位置、速度和航向角数据通过卡尔曼滤波算法融合,得到最... 详细信息

为了实现草方格固沙机的智能化工作,提出了一种基于GNSS+IMU的草方格固沙机自动巡航控制系统。系统以STM32F407VGT6作为主控芯片,将GNSS(全球导航卫星系统)和IMU(惯性测量单元)的位置、速度和航向角数据通过卡尔曼滤波算法融合,得到最优估计数据;然后,将最优估计数据输入增量式PID算法,以实现草方格固沙机在预定义区域内稳定的导航工作。同时,设计了Android APP终端,实现了用户终端对草方格固沙机的智能监控。研究结果表明:系统导航工作直线航向角偏差RMS不超过0.45,最大偏差不超过1.5°,满足草方格固沙机自动巡航工作的基本需求,体现了草方格固沙机在智能化定位导航方面的可行性与稳定性,可为草方格固沙机实现荒漠化治理提供依据。

关键词：草方格固沙机 GNSS IMU 卡尔曼滤波 PID 自动巡航

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Denitrification from nitrogen-fixing biologically crusted soils in a cool desert environment,southeast Utah,USA

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Ecological Processes 2013年第1期2卷 156-164页

作者： Nichole N Barger Sarah C Castle Gavin N dean Department of Ecology and Evolutionary Biology University of ColoradoCampus Box 334BoulderCO 80309-0334USA Department of Ecosystem and Conservation Sciences College of Forestry and ConservationUniversity of MontanaMissoulaMT59812USA.

Introduction:Nitrogen fixation by microorganisms within biological soil crust(“biocrust”)communities provides an important pathway for N inputs in cool desert environments where soil nutrients are low and symbiotic N-fixing plants may be *** of N fixation in biocrusts often greatly exceed that of N accretion rates leading to uncertainty regarding N loss ***:In this study we examined nitrogen fixation and denitrification rates in biocrust communities that differed in N fixation potential(low N fixation=light cyanobacterial biocrust,high N fixation=dark cyanolichen crust)at four temperature levels(10,20,30,40°C)and four simulated rainfall levels(0.05,0.2,0.6,1 cm rain events)under controlled laboratory ***:Acetylene reduction rates(AR,an index of N fixation activity)were over six-fold higher in dark crusts relative to light *** biocrusts also exhibited eight-fold higher denitrification *** was no consistent effect of temperature on denitrification rates,but there was an interactive effect of water addition and crust *** light crusts,denitrification rates increased with increasing water addition,whereas the highest denitrification rates in dark crusts were observed at the lowest level of water ***:These results suggest that there are no clear and consistent environmental controls on short-term denitrification rates in these biologically crusted *** together,estimates of denitrification from light and dark biocrusts constituted 3 and 4%of N fixation rates,respectively suggesting that losses as denitrification are not significant relative to N inputs via *** estimate is based on a previously published conversion ratio of ethylene produced to N fixed that is low(0.295),resulting in high estimates of N *** future N fixation studies in biologically crusted soils show that these ratios are closer to the theoretical 3:1 ratio,denitrification may constitute a more significant

关键词： Biological soil crust Colorado Plateau Cool desert Denitrification Nitrogen fixation Soil nitrogen cycling

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Contributions of biofilm and suspended sludge to nitrogen transformation and nitrous oxide emission in hybrid sequencing batch system

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Journal of Environmental Sciences 2010年第7期22卷 953-960页

作者： Ingwei Wayne Lo Kwang Victor Lo Don S Mavinic dean Shiskowski William Ramey Department of Civil Engineering University of British Columbia Associated Engineering Ltd. Department of Microbiology & Immunology University of British Columbia

Hybrid system combines the nature of suspended growth and attached growth has been widely applied to wastewater treatment. In this research, the contributions to N transformation and N2O emission by biofilm and suspended sludge in the hybrid sequencing- batch reactor for a simultaneous nitrification, denitrification and phosphorus removal process were investigated. For the hybrid system, nitrification occurred mostly in the suspended sludge, while the biofilm played the major role in denitrification. The interaction of the biofilm and the suspended sludge in the same reactor resulted in a better overall nitrogen removal performance with simultaneous nitrification and denitrification. However, N2O emission was the main end product of nitrogen removal for the hybrid system; while it was N2 for the biofilm. The relative low N2O emissions from the pure biofilm and the pure suspended sludge corresponded to the relatively high nitrate at the end of the aeration period compared with the hybrid system.

关键词： N2O emission biofilm suspended sludge hybrid system

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Orthogonal quantification of soluble inducible T-cell costimulator(ICOS)in healthy and diseased human serum

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Journal of Pharmaceutical Analysis 2022年第2期12卷 317-323页

作者： Kevin McKinski dean McNulty Francesca Zappacosta Mary Birchler Matt Szapacs Christopher Evans Bioanalysis Immunogenicity&BiomarkersGlaxoSmithKlineCollegevillePA19426USA

Inducible T-cell costimulator(ICOS),a homodimeric protein expressed on the surface of activated T-cells,is being investigated as a potential therapeutic target to treat various *** studies have reported aberrant increases in the soluble form of ICOS(sICOS)in human serum in disease-state patients,primarily using commercial ELISA ***,results from our in-house immunoassay did not show these aberrant increases,leading us to speculate that commercial sICOS ELISAs may be prone to *** directly tested that hypothesis and found that one widely used commercial kit yields falsepositives and is prone to human anti-mouse antibody *** then analyzed a panel of healthy,cancer,chronic hepatitis C virus,systemic lupus erythematosus,and diffuse cutaneous systemic sclerosis human serum using our in-house immunoassay and reported the measured sICOS concentrations in these *** even well characterized immunoassay methods are prone to non-specific interference,we also developed a novel sICOS LC-MS/MS method to confirm the *** these orthogonal approaches,we show that sICOS is a low abundance soluble protein that cannot be measured above approximately 20 pg/mL in human serum.

关键词： ICOS Immunoassay LC-MS/MS Biomarker HAMA

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Effect of Dislocation Mechanism on Elastoplastic Behavior of Crystals with Heterogeneous Dislocation Distribution

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Acta Mechanica Solida Sinica 2020年第4期33卷 487-495页

作者： Songjiang Lu Jian Xiong dean Wei Yifan Ding Bo Zhang Ronghai Wu Xu Zhang Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu 610031China School of Mechanics Civil Engineering and ArchitectureNorthwestern Poly technical UniversityX i’an 710129China

Gradient structures have excellent mechanical properties,such as synergetic strength and *** is desirable to reveal the connection between the gradient structure and mechanical ***,few studies have been conducted for materials with heterogeneous dislocation *** the present study,we use the discrete dislocation dynamics(DDD)method to investigate the effect of dislocation density gradient on the elastoplastic behavior of single crystals controlled by source *** contrast to the intuitive expectation that gradient structure affects the mechanical properties,the DDD simulations show that the elastic moduli and yield stresses of three gradient samples(i.e.,no gradient,low gradient,and high gradient)are almost *** from the progressive elastic-plastic transition in the samples controlled by Taylor hardening(i.e.,the mutual interaction of dislocation segments),the flow stresses of source activation ones enter into a stage of nearly ideal plasticity(serrated flow)immediately after *** microstructure evolution demonstrates that the mean dislocation spacing is relatively ***,there are only a few or even one dislocation source activated during the plastic *** intermittent operation of sources leads to intensive fluctuation of stress and dislocation density,as well as a stair-like evolution of plastic *** present work reveals that the effect of dislocation density gradient on the mechanical response of crystals depends on the underlying dislocation mechanisms controlling the plastic deformation of materials.

关键词： Dislocation dynamics Microplasticity Dislocation mechanism Dislocation density gradient

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School of Physics,Southeast University

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Frontiers of physics 2021年第4期16卷 F0003-F0003,I0003页

作者： Zhenhua Ni dean School of Physics Telephone

Overview Originated from the"Gezhi"department of Sanjiang Normal School established in 1904,the physics discipline of Southeast University(SEU)has evolved for more than one *** the past century,numerous distinguished scholars have either studied or worked in our school of physics and its predecessors,including ***-Shiung Wu,***-Hsun Wu,***-Yao Chao,and *** ***,the School of Physics in SEU is focusing on cutting edge scientific researches and first-class education.

关键词： Southeast School discipline

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Three-dimensional ultrasound subwavelength arbitrary focusing with broadband sparse metalens

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Science China(Physics,Mechanics & Astronomy) 2022年第2期65卷 50-56页

作者： Xue Jiang JiaJie He ChuanXin Zhang HuaLiang Zhao WeiQi Wang dean Ta Cheng-Wei Qiu Center for Biomedical Engineering School of Information Science and TechnologyFudan UniversityShanghai 200433China Department of Electrical and Computer Engineering National University of SingaporeSingapore 117583Singapore

Ultrasound focusing in three-dimensional(3 D)space is of crucial and enduring significance in a variety of biomedical and industrial *** ultrasound focusing based on active phase array or passive geometry of bulky size is unable to realize the 3 D arbitrary focusing with subwavelength *** metamaterial of complex deep-subwavelength microstructure has facilitated the advanced airborne-sound-focusing but is inevitably not applicable for underwater ultrasound,restricted by the law between the multi-modes coupling/thermal viscosity and the feature size of the ***,we aim to circumvent the restriction by increasing the feature size of the metamaterial while keeping the compact overall geometry,and realize the robust subwavelength ultrasound focusing with the sparse metalens of the wavelength-scale *** theoretically propose and demonstrate numerically and experimentally the broadband arbitrary ultrasound focusing in 3 D *** axial and off-axis ultrasound focusing with the subwavelength resolution(FWHM<0.58λ)are achieved by the spatially sparse and compact metalens within one-octave *** advantages of 3 D freewheeling focusing,subwavelength resolution,spatial sparsity,geometric simplicity,and broadband,the sparse metalens would offer more initiatives to advanced researches in ultrasound focusing and empower applications such as precise biomedical imaging and therapy,nondestructive evaluation,integrated and multiplexed ultrasound devices.

关键词： broadband ultrasound focusing sparse metalens subwavelength resolution three-dimensional focusing

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