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The stress-velocity relationship of twinning partial dislocations and the phonon-based physical interpretation

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Science China(Physics,Mechanics & Astronomy) 2017年第11期60卷 11-23页

作者： yujie wei ShenYou Peng State Key Laboratory of Nonlinear Mechanics (LNM) Institute of Mechanics Chinese Academy of Sciences School of Engineering Sciences University of Chinese Academy of Sciences

The dependence of dislocation mobility on stress is the fundamental ingredient for the deformation in crystalline materials. Strength and ductility, the two most important properties characterizing mechanical behavior of crystalline metals, are in general governed by dislocation motion. Recording the position of a moving dislocation in a short time window is still challenging, and direct observations which enable us to deduce the speed-stress relationship of dislocations are still missing. Using large-scale molecular dynamics simulations, we obtain the motion of an obstacle-free twinning partial dislocation in face centred cubic crystals with spatial resolution at the angstrom scale and picosecond temporal information. The dislocation exhibits two limiting speeds: the first is subsonic and occurs when the resolved shear stress is on the order of hundreds of megapascal. While the stress is raised to gigapascal level, an abrupt jump of dislocation velocity occurs, from subsonic to supersonic regime. The two speed limits are governed respectively by the local transverse and longitudinal phonons associated with the stressed dislocation, as the two types of phonons facilitate dislocation gliding at different stress levels.

关键词： dislocation mobility transverse and longitudinal phonons subsonic and supersonic velocity stress-velocity relationship molecular dynamics

Research on the mechanics of high speed rails

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Acta Mechanica Sinica 2016年第2期32卷 189-190页

作者： yujie wei LNM Institute of MechanicsChinese Academy of Sciences

In the preceding theme issue on＂Current research progress on mechanics of high speed rails＂（Acta Mechanica Sinica,30：846–909（2014））,we invited several authors in the fiel to present their research on high spee... 详细信息

关键词： durability wheel bearings braking train piezoelectric operational captured Qingdao hasbeen

Resource-saving scheduling scheme for centralized target tracking in multiple radar system under automatic blanket jamming

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Chinese Journal of Aeronautics 2024年第5期37卷 349-362页

作者： Zhengjie LI yujie wei Junwei XIE Haowei ZHANG Yu TIAN Air and Missile Defense College Air Force Engineering UniversityXi’an 710051China Air Force Xi’an Flying College Xi’an 710300China Air and Missile Defense Institute Air Force Research InstituteBeijing 100085China School of Economics and Management Beihang UniversityBeijing 100191China

This paper investigates the problem of Joint Radar Node Selection and Power Allocation(JRNSPA)in the Multiple Radar System(MRS)in the blanket jamming *** radar node independently tracks moving target and subsequently transmits the raw observation data to the fusion center,which formulates a centralized tracking network *** order to establish a practical blanket jamming environment,we suppose that each target carries the self-defense jammer which automatically implements blanket jamming to the radar nodes that exceed the preset interception ***,the Predicted Conditional Cramer-Rao Lower Bound(PC-CRLB)is derived and utilized as the tracking accuracy *** at ensuring both the tracking performance and the Low Probability of Intercept(LPI)performance,the resource-saving scheduling model is formulated to minimize the transmit power consumption while meeting the requirements of tracking ***,the Modified Zoutendijk Method Of Feasible Directions(MZMFD)-based two-stage solution technique is adopted to solve the formulated non-convex optimization *** results show the effectiveness of the proposed JRNSPA scheme.

关键词： Multiple Radar System(MRS) Centralized target tracking Resource scheduling Blanket jamming Low Probability of Intercept(LPI)

Relationship between granitic soil particle-size distribution and shrinkage properties based on multifractal method

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Pedosphere 2020年第6期30卷 853-862页

作者： yujie wei Xinliang WU Jinwen XIA Chongfa CAI Soil and Water Conservation Research Centre College of Resources and EnvironmentHuazhong Agricultural UniversityWuhan 430070China National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and ManagementGuangdong Institute of Eco-environmental Science&TechnologyGuangdong Academy of SciencesGuangzhou 510650China

The mechanical properties of granitic residual soils vary with depth due to changes in soil type and heterogeneity caused by *** purpose of this study was to relate the spatial variation of particle-size distribution(PSD)of granitic soils with soil shrinkage parameters using multifractal *** heterogeneity of PSD and pedogenic processes were depicted in detail by multifractal *** PSD generally increased with the increase of profile depth in accordance with the variation of single fractal dimension(D)ranging from 2.45 to *** shrinkage limit was greatly influenced by the multifractal dimension parameters,including information dimension(D1)and capacity dimension(D0)(Adjusted R2=0.998,P0.97,root sum of squares<0.1),and the water variation corresponding to the maximum change rate of linear extensibility was determined by the silt content(R2=0.81,P<0.01).Overall,the shrinkage of granitic soils was primarily influenced by PSD and soil compactness.

关键词： bulk density fractal dimension multifractal characteristics shrinkage characteristics soil compactness

A multi-scale algorithm for dislocation creep at elevated temperatures

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Theoretical & Applied Mechanics Letters 2021年第1期11卷 42-46页

作者： Lichao Yuan yujie wei State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Future Technology University of Chinese Academy of SciencesBeijing 100049China School of Engineering Sciences University of Chinese Academy of SciencesBeijing 100049China

Dislocation creep at elevated temperatures plays an important role for plastic deformation in crystalline *** using traditional discrete dislocation dynamics(DDD)to capture this process,we often need to update the forces on N dislocations involving~N 2 *** this letter,we introduce a multi-scale algorithm to speed up the calculations by dividing a sample of interest into sub-domain grids:dislocations within a characteristic area interact following the conventional way,but their interaction with dislocations in other grids are simplified by lumping all dislocations in another grid as a super *** a multi-scale algorithm lowers the computational load to~N *** employed this algorithm to model dislocation creep in Al-Mg *** simulation leads to a power-law creep rate in consistent with experimental *** stress exponent of the power-law creep is a resultant of dislocations climb for~5 and viscous dislocations glide for~3.

关键词： Multi-scale algorithm Dislocation glide Dislocation climb High temperature creep Dislocation dynamics

A computational method for the load spectra of large-scale structures with a data-driven learning algorithm

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Science China(Technological Sciences) 2023年第1期66卷 141-154页

作者： CHEN XianJia YUAN Zheng LI Qiang SUN ShouGuang wei yujie The State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBejing 100190China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBejing 100044China School of Enginering Sciences University of Chinese Academy of SciencesBeijing 100049China

For complex engineering systems, such as trains, planes, and offshore oil platforms, load spectra are cornerstone of their safety designs and fault diagnoses. We demonstrate in this study that well-orchestrated machine learning modeling, in combination with limited experimental data, can effectively reproduce the high-fidelity, history-dependent load spectra in critical sites of complex engineering systems, such as high-speed trains. To meet the need for in-service monitoring, we propose a segmentation and randomization strategy for long-duration historical data processing to improve the accuracy of our data-driven model for longterm load-time history prediction. Results showed the existence of an optimal length of subsequence, which is associated with the characteristic dissipation time of the dynamic system. Moreover, the data-driven model exhibits an excellent generalization capability to accurately predict the load spectra for different levels of passenger-dedicated lines. In brief, we pave the way, from data preprocessing, hyperparameter selection, to learning strategy, on how to capture the nonlinear responses of such a dynamic system, which may then provide a unifying framework that could enable the synergy of computation and in-field experiments to save orders of magnitude of expenses for the load spectrum monitoring of complex engineering structures in service and prevent catastrophic fatigue and fracture in those solids.

关键词： load spectrum computational mechanics deep learning data-driven modeling gated recurrent unit neural network

Soil organic carbon stock and fractional distribution across central-south China

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International Soil and Water Conservation Research 2021年第4期9卷 620-630页

作者： Rubing Zeng yujie wei Jianjia Huang Xin Chen Chongfa Cai Key Laboratory of Arable Land Conservation(Middle and Lower Reaches of Yangtze River)of the Ministry of Agriculture College of Resources and EnvironmentHuazhong Agricultural UniversityWuhan430070China

The stock and stability of soil organic carbon(SOC)are critical to soil functions and global carbon cycle,but little quantitative information is available on the precise location and chemical components of SOC for soils across a wide range of climatic ***,a broad range of zonal soils were collected in forest land at topsoil(0-15 cm)and subsoil(15-30 cm)from temperate to tropical climatic gradient in central to south *** stock and stability of SOC were determined in terms of aggregate and humic *** in bulk soils with a less significant geographic variation was comparably higher at Haplic Luvisoils in temperate regions(3637.61 g m^(−2))and Rhodi-Humic Ferrosols in tropical regions(3446.12 g m^(−2))than in the other experimental soils,but a consistent decreasing trend was observed along the soil profiles with the SOC stock was 1.11-1.97 times higher in the topsoil than in the *** addition,insoluble humin residue(HMr)as the dominant components of SOC ranged from 643.95 to 2696.90 g m^(−2) and decreased from temperate to tropical regions,which was consistent with the zonal variation of humic acids(HAs),but contrary to the zonal variation of fulvic acids(FAs)that fluctuated in a range of 39.67-389.55 g m^(−2) across the experimental *** to the results of partial correlation analysis,the variation of FAs stock was significantly attributed to soil pH,bulk density,iron and aluminum oxides,clay,and clay mineral content(|r|>0.61,p<0.05),while these soil physical properties showed a contradictory effects on HAs,iron-linked humin(HMi),clay-combined humin(HMc),and ***,the aggregate-associated carbon stock was mainly stored in macroaggregates(36.34-76.09%)for both SOC and its chemical components,especially in topsoils,and its zonal variation was associated with that of bulk *** general,the redundancy analysis(RDA)revealed that mean annual precipitation(MAP)accounted for 81.8%and 13.8%of the variance in SOC chemical a

关键词： Carbon stock Humic substance Soil aggregation

Chalcogen-dependent catalytic properties of RuX2 (X = S/Se/Te) nanoparticles decorated carbon nanofibers for hydrogen evolution in acidic and alkaline media

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Nano Research 2024年第4期17卷 2528-2537页

作者： Chengkai He Yue wei Jia Xu yujie wei Tao Wang Rongfei Liu Lvlv Ji Zhun Liu Sheng Wang School of Materials Science and Engineering Zhejiang Sci-Tech UniversityHangzhou 310018China Department of Physics Shaoxing UniversityShaoxing 312000China Zhejiang Kangjiesi New Material Technology Co. LTDZhuji 311800China

Transition metal dichalcogenides(TMDs),with the general formula MX_(2)(M=Mo/W/Fe/Co/Ni,etc.;X=S/Se/Te),have attracted extensive research interests for hydrogen evolution reaction(HER).Compared with numerous studies on noble-metal-free TMDs,the chalcogen-dependent HER catalytic properties of noble-metal-based TMDs are lack of sufficient research ***,a facile electrospinning-assisted synthetic strategy is proposed to synthesize ruthenium dichalcogenides(RuX_(2),X=S/Se/Te)nanoparticles decorated carbon nanofibers(CNFs).Benefiting from the identical nanofibrous morphology and exposed crystal planes of RuX_(2)(111),the catalytic activities of RuX_(2)@CNFs samples were investigated and compared in a fair and direct *** electrochemical measurements coupled with density functional theory calculations were carried out to probe their intrinsic HER catalytic activities,resulting in the catalytic activity order of RuS_(2)@CNFs>RuSe_(2)@CNFs>RuTe_(2)@CNFs in acidic media and that of RuS_(2)@CNFs>RuTe_(2)@CNFs>RuSe_(2)@CNFs in alkaline *** superior catalytic performance of RuS_(2)@CNFs mainly stems from the relative lower HER energy barriers and thereby the higher intrinsic catalytic activity of RuS_(2)(111),leading to ultralow overpotentials of 44 and 9 mV at 10 mA·cm^(-2) in acidic and alkaline media,***_(2)(111)is endowed with the more optimized Gibbs free energy of hydrogen adsorption(ΔGH*)than RuTe_(2)(111),but RuTe_(2)(111)shows enhanced catalytic property for H_(2)O dissociation and OH-desorption than RuSe_(2)(111),therefore,resulting in the altered catalytic activity sequences for RuSe_(2) and RuTe_(2) in acidic and alkaline media.

关键词： hydrogen evolution reaction transition metal dichalcogenides carbon nanofibers electrocatalysis catalytic activity

Contents of soil organic carbon and nitrogen in water-stable aggregates in abandoned agricultural lands in an arid ecosystem of Northwest China

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Journal of Arid Land 2016年第3期8卷 350-363页

作者： WANG Junqiang LIU Lichao QIU Xiaoqing wei yujie LI Yanrong SHI Zhiguo Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Gansu Academy of Agricultural Engineering and Technology Wuwei 733006 China Gansu Polytechnic College of Animal Husbandry & Engineering Wuwei 733006 China

Soil organic matter content in water-stable aggregates（WSA） in the arid ecosystems（abandoned agricultural lands especially） of China is poorly understood. In this study, we examined the WSA sizes and stability, and soil organic carbon（OC） and nitrogen（N） contents in agricultural lands with abandonment ages of 0, 3, 12, 20, 30 and 40 years, respectively, in the Minqin Oasis of Northwest China. The total soil OC and N contents at depths of 0–20, 20–40 and 40–60 cm in abandoned agricultural lands were compared to those in cultivated land（the control）. Agricultural land abandonment significantly（P0.25 mm） as the age of agricultural land abandonment increased. The effect of abandonment ages of agricultural lands on MWD was determined by the changes of OC and N accumulation in WSA sizes ＆gt;2 mm. The total OC and N contents presented a stratification phenomenon across soil depths in this arid ecosystem. That is, both of them decreased significantly at depths of 0–20 and 40–60 cm while increased at the depth of 20–40 cm. The WSA sizes ＆lt;0.053 mm had the highest soil OC and N contents（accounting for 51.41%–55.59% and 42.61%–48.94% of their total, respectively）. Soil OC and N contents in microaggregates（sizes 0.053–0.25 mm） were the dominant factors that influenced the variations of total OC and N contents in abandoned agricultural lands. The results of this study suggested that agricultural land abandonment may result in the recovery of WSA stability and the shifting of soil organic matter from the silt＋clay（＆lt;0.053 mm） and microaggregate fractions to the macroaggregate fractions. However, agricultural land abandonment did not increase total soil OC and N contents in the short-term.

关键词： aggregate stability water-stable aggregates agricultural abandonment soil organic carbon total nitrogen northwestern China