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Size distribution of inclusions in 12%Cr stainless steel with a wide range of solidification cooling rates

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International Journal of Minerals,Metallurgy and Materials 2015年第11期22卷 1157-1162页

作者： Han-song Yu jian-guo Li School of Materials Science and Engineering Shanghai Jiao Tong University

The effect of solidification cooling rate on the size and distribution of inclusions in 12%Cr stainless steel was investigated. A wide range of solidification cooling rates（from 0.05 to 106 K·s^-1） was achieved using various solidification processes, including conventional casting, laser remelting, and melt spinning. The size and distribution of inclusions in the steel were observed and statistically collected. For comparison, mathematical models were used to calculate the sizes of inclusions at different solidification cooling rates. Both the statistical size determined from observations and that predicted from calculations tended to decrease with increasing cooling rate; however, the experimental and calculated results did not agree well with each other at excessively high or low cooling rate. The reasons for this discrepancy were theoretically analyzed. For the size distribution of inclusions, the effect of cooling rate on the number densities of large-sized（〉 2 μm） inclusions and small-sized（≤ 2 μm） inclusions were distinct. The number density of inclusions larger than 1 μm was not affected when the cooing rate was less than or equal to 6 K·s^-1 because inclusion precipitation was suppressed by the increased cooling rate.

关键词： solidification cooling rate inclusions size distribution number density stainless steels

A generalized L_2-discrepancy for cubature and uncertainty quantification of nonlinear structures

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Science China(Technological Sciences) 2016年第6期59卷 941-952页

作者： CHEN jian Bing song Peng Yan State Key Laboratory of Disaster Reduction in Civil Engineering & School of Civil Engineering Tongji University College of Civil Engineering and Architecture Hebei University

The numerical method for multi-dimensional integrals is of great importance, particularly in the uncertainty quantification of engineering structures. The key is to generate representative points as few as possible but of acceptable accuracy. A generalized L2（GL2）-discrepancy is studied by taking unequal weights for the point set. The extended Koksma-Hlawka inequality is discussed. Thereby, a worst-case error estimate is provided by such defined GL2-discrepancy, whose dosed-form expression is available. The characteristic values of GL2-discrepancy are investigated. An optimal strategy for the selection of the representative point sets with a prescribed cardinal number is proposed by minimizing the GL2-discrepancy. The three typical examples of the multi-dimensional integrals are investigated. The stochastic dynamic response analysis of a nonlinear structure is then studied by incorporating the proposed method into the probability density evolution method. It is shown that the proposed method is advantageous in achieving tradeoffs between the efficiency and accuracy of the exemplified problems. Problems to be further studied are discussed.

关键词： Koksma-Hlawka inequality cubature L2-discrepancy nonlinear structure stochastic dynamics

A Review on Cable-driven Parallel Robots

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Chinese Journal of Mechanical Engineering 2018年第4期31卷 37-47页

作者： Sen Qian Bin zi Wei-Wei Shang Qing-song Xu School of Mechanical Engineering Hefei University of Technology Department of Automation University of Science and Technology of China Department of Electromechanical Engineering Faculty of Science and TechnologyUniversity of Macao

Cable-driven parallel robots(CDPRs) are categorized as a type of parallel manipulators. In CDPRs, flexible cables are used to take the place of rigid links. The particular property of cables provides CDPRs several advantages, including larger workspaces, higher payload-to-weight ratio and lower manufacturing costs rather than rigid-link robots. In this paper, the history of the development of CDPRs is introduced and several successful latest application cases of CDPRs are presented. The theory development of CDPRs is introduced focusing on design, performance analysis and control theory. Research on CDPRs gains wide attention and is highly motivated by the modern engineering demand for large load capacity and workspace. A number of exciting advances in CDPRs are summarized in this paper since it is proposed in the 1980 s, which points to a fruitful future both in theory and application. In order to meet the increasing requirements of robot in different areas, future steps foresee more in-depth research and extension applications of CDPRs including intelligent control, composite materials, integrated and reconfigurable design.

关键词： Cable-driven parallel robots Design and modelling Control and planning Performance and optimization

Fatigue life prediction model of 2.5D woven composites at various temperatures

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Chinese Journal of Aeronautics 2018年第2期31卷 310-329页

作者： jian song Weidong WEN Haitao CUI College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics Department of Mechanical and Biomedical Engineering City University of Hong Kong

As one of the new structural layout in the family of woven composites, 2.5D Woven Composites（2.5D-WC） have recently attracted an increasing interest owing to its excellent properties, i.e. high specific strength and fatigue resistance, in the aerospace and automobile industry. Indepth understanding of the fatigue behavior of this material at un-ambient temperatures is critical for the engineering applications, especially in aero-engine field. Here, fatigue behavior of 2.5D-WC at different temperatures was numerically investigated based on the unit cell approach. Firstly, the unit cell model of 2.5D-WC was established using ANSYS software. Subsequently, the temperature-dependent fatigue life prediction model was built up. Finally, the fatigue lives alongside the damage evolution processes of 2.5D-WC at ambient temperature（20 ℃） and unambient temperature（180 ℃） were analyzed. The results show that numerical results are in good agreement with the relevant experimental results at 20 and 180 ℃. Fatigue behavior of 2.5D-WC is also sensitive to temperature, which is partially attributed to the mechanical properties of resin and the change of inclination angle of warp yarns. We hope that the proposed fatigue life prediction model and the findings could further promote the engineering application of 2.5D-WC, especially in aero-engine field.

关键词： ANSYS Fatigue behavior Fatigue life prediction model Temperature 2.5D woven composites

Wake flow and vortex structures behind emergent vegetation patches elongated in the longitudinal direction

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Journal of Hydrodynamics 2021年第6期33卷 1148-1161页

作者： zi-jian Yu Yu-qi Shan Chao Liu Xing-nian Liu State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and HydropowerSichuan UniversityChengdu 610065China Department of Civil and Environmental Engineering University of AlbertaEdmontonCanada Institute for Disaster Management and Reconstruction Sichuan UniversityChengdu 610065China

In natural rivers,patches of vegetation generally expand over their steady wake region in the streamwise direction,forming elongated patches with length(L)greater than their width(b).This paper studies how the wake flows and the vortices develop as the emergent patches expand their length in the streamwise *** patches are modeled with the same width but different lengths in laboratory *** the patches,the steady wake region(L_(w))is not related to the width-related flow blockage(C_(d)ab),where C_(d) is the drag coefficient,a is the vegetation ***,L_(w) is related to the length-related flow blockage(C_(d)aL).On this basis,a model is proposed for predicting L_(w),which is in good agreement with the *** a patch becomes denser and/or longer(as C_(d)aL increases),the steady wake region becomes shorter(L_(w) decreases),and vortices are observed closer to the patch trailing edge,producing a turbulence of a greater magnitude beyond L_(w).When the flow blockage increases to the limit(C_(d)aL>8),the Karman vortices are observed directly behind the porous *** results can be used to explain the longitudinal elongation of the vegetation patches in the field.

关键词： Velocity profiles turbulent kinetic energy wakes vortex streets vegetation patch

An elasto-visco-plastic constitutive model of polypropylene incorporating craze damage behavior and its validation

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Journal of Central South University 2017年第6期24卷 1263-1268页

作者： GUI Zhong-xiang HU Xiao WANG zi-jian The 38th Research Institute of China Electronics Technology Group Corporation Hefei 230088China State Key Laboratory of Materials Processing and Die&Mould Technology Huazhong University of Science and TechnologyWuhan 430074China

An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding and stress-whitening phenomena. In addition, the developed constitutive model was implemented into finite element codes in Abaqus to simulate the tensile deformation. The standard uniaxial tensile tests were carried out. The stress-strain curves from the uniaxial tensile tests show that the stress keeps decreasing after yielding and the yield stress rises with the increasing of the strain rate. It is worth noting that the craze damage is more visible with higher strain rate. The stress-whitening can be seen clearly around the fracture. The uniaxial tensile tests using specially designed specimen with circular holes weakening were performed for the validation of the developed model. The simulation results of the tensile deformation of the hole-weakened specimen suggest that the stress-whitening could be attributed to the equivalent visco-plastic strain. By comparing between the simulation analysis and the experimental results, the proposed model can describe the stress whitening phenomenon with good accuracy.

关键词： elasto-visco-plastic constitutive model craze yielding stress-whitening finite element implementation

Time trends and gender disparities of Chinese cataract burden and their predictions

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International Journal of Ophthalmology(English edition) 2023年第9期16卷 1527-1534页

作者： Tian-Hong Wu Bo jiang Wei-Ming Liu jian-Qing Li zi-Yue song Pei-Rong Lu Department of Ophthalmology the First Affiliated Hospital of Soochow UniversitySuzhou 215006Jiangsu ProvinceChina

AIM:To evaluate the trends and changes in the number and rates of disability-adjusted life years(DALYs)and prevalence of cataract in China between 1990 and 2019,and to predict the trends of cataract burden from 2020 to ***:The Global Burden of Diseases(GBD)database was employed to collect the data on DALYs and the prevalence of cataract in China,which was distinguished by age and sex during the past three decades from 1990 to 2019,and then changes in the number and rates of cataract from 2020 to 2030 were *** data were analyzed by the R program(version 4.2.2)and GraphPad Prism 9.0 statistics ***:The number of DALYs of cataract increased from 449322.84 in 1990 to 1087987.61 in 2019,number of cataract cases increased from 5607600.94 in 1990 to 18142568.96 in *** age-standardized DALY rates(ASDR)generally increased slightly[estimated annual percentage change(EAPC=0.1;95%CI:-0.24 to 0.45)],age-standardized prevalence rates(ASPR)also increased(EAPC=0.88;95%CI:0.6 to 1.15).Cataract burden increased with age and female *** the causes of cataract,air pollution was the most important,followed by smoking,high fasting plasma glucose,and high body mass index(BMI).The burden of cataract is predicted to grow persistently from 2020 to 2030,the number of DALYs and prevalence for cataract will rise to 2336431 and 43698620 respectively by 2030,the ASDR is predicted to be 85/100000 and ASPR will be 1586/100000 in 2030,females will still be at greater risk of suffering from cataract than ***:The burden of cataract in China kept rising from 1990 to *** age and female gender are risk factors for *** pollution,smoking,high fasting plasma glucose,and high BMI are associated with *** burden of cataract in China will gradually increase from 2020 to 2030,the elderly women in particular need *** results may be of help for providing reference strategies to reduce cataract burden in the near future

关键词： cataract disease burden tendency prediction

PT Symmetry Induced Rings of Lasing Threshold Modes Embedded with Discrete Bound States in the Continuum

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Chinese Physics Letters 2021年第8期38卷 50-56页

作者： Qianju song Shiwei Dai Dezhuan Han Z.Q.Zhang C.T.Chan jian zi College of Physics Chongqing UniversityChongqing 401331China Department of Physics Hong Kong University of Science and TechnologyClear Water BayHong KongChina Department of Physics Key Laboratory of Micro-and Nano-Photonic Structures(MOE)and State Key Laboratory of Surface PhysicsFudan UniversityShanghai 200433China

It is well known that spatial symmetry in a photonic crystal(PhC)slab is capable of creating bound states in the continuum(BICs),which can be characterized by topological charges of polarization ***,we show that when a PT-symmetric perturbation is introduced into the PhC slab,a new type of BICs(pt-BICs)will arise from each ordinary BIC together with the creation of rings of lasing threshold modes with pt-BICs embedded in these *** from ordinary BICs,the Q-factor divergence rate of a pt-BIC is reduced and anisotropic in momentum ***,pt-BICs can even appear at off-high symmetry lines of the Brillouin *** pt-BICs also carry topological charges and can be created or annihilated with the total charge conserved.A unified picture on pt-BICs and the associated lasing threshold modes is given based on the temporal coupled mode *** findings reveal the new physics arising from the interplay between PT symmetry and BIC in PhC slabs.

关键词： polarization symmetry lasing

A Novel Genetic Algorithm Preventing Premature Convergence by Chaos Operator

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Journal of Central South University 2000年第2期12卷 100-103页

作者： LIU Juan CAI zi-xing LIU jian-qin College of Information Science and Engineering Central South University of TechnologyChangsha 410083China

An improved genetic algorithm (GA) is proposed based on the analysis of population diversity within the framework of Markov chain. The chaos operator to combat premature convergence concerning two goals of maintaining diversity in the population and sustaining the convergence capacity of the GA is introduced. In the CHaos Genetic Algorithm (CHGA), the population is recycled dynamically whereas the most highly fit chromosome is intact so as to restore diversity and reserve the best schemata which may belong to the optimal solution. The characters of chaos as well as advanced operators and parameter settings can improve both exploration and exploitation capacities of the algorithm. The results of multimodal function optimization show that CHGA performs simple genetic algorithms and effectively alleviates the problem of premature convergence.

关键词： chaos genetic algorithm premature convergence population diversity