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An Interpolation Method for Karhunen-Loève Expansion of Random Field Discretization

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Computer Modeling in Engineering & Sciences 2024年第1期138卷 245-272页

作者： zi han Zhentian Huang Department of Engineering Mechanics Hohai UniversityNanjing211100China College of Civil and Transportation Engineering Shenzhen UniversityGuangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and UtilizationInstitute of Deep Earth Sciences and Green EnergyShenzhenChina

In the context of global mean square error concerning the number of random variables in the representation,the Karhunen–Loève(KL)expansion is the optimal series expansion method for random field *** computational efficiency and accuracy of the KL expansion are contingent upon the accurate resolution of the Fredholm integral eigenvalue problem(IEVP).The paper proposes an interpolation method based on different interpolation basis functions such as moving least squares(MLS),least squares(LS),and finite element method(FEM)to solve the *** with the Galerkin method based on finite element or Legendre polynomials,the main advantage of the interpolation method is that,in the calculation of eigenvalues and eigenfunctions in one-dimensional random fields,the integral matrix containing covariance function only requires a single integral,which is less than a two-folded integral by the Galerkin *** effectiveness and computational efficiency of the proposed interpolation method are verified through various one-dimensional ***,based on theKL expansion and polynomial chaos expansion,the stochastic analysis of two-dimensional regular and irregular domains is conducted,and the basis function of the extended finite element method(XFEM)is introduced as the interpolation basis function in two-dimensional irregular domains to solve the IEVP.

关键词： Random field discretization KL expansion IEVP MLS FEM stochastic analysis

Minimum safe thickness of rock plug in karst tunnel according to upper bound theorem

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Journal of Central South University 2016年第9期23卷 2346-2353页

作者： YANG zi-han ZhanG Jia-hua School of Civil Engineering Central South University Changsha 410075 China

High pressure and water-bearing caverns ahead of a karst tunnel face tend to cause geological disasters, such as water and mud bursts. So, the determination of safe thickness of the reserved rock plug is a key technical problem to be solved for karst tunnel construction. Based on the Hoek-Brown nonlinear failure criterion, the minimum safe thickness of rock plug was investigated in the light of the limit analysis theory. On the basis of the proposed failure mode, the expression of the minimum thickness for rock plug was obtained by means of upper bound theorem in combination with variational principle. The calculation results show the influence of each parameter on safe thickness and reveal the damage range of rock plug. The proposed method is verified by comparing the results with those of the drain cavern of Maluqing Tunnel. The research shows that with the increase of compressive strength and tensile strength as well as constant A of Hoek-Brown criterion, the safe thickness decreases, whereas with the increase of cavern pressure, tunnel diameter, and constant B from Hoek-Brown criterion, the safe thickness increases. Besides, the tensile strength, or constants A and B affect the shear failure angle of rock plug structure, but other parameters do not. In conclusion, the proposed method can predict the minimum safe thickness of rock plug, and is useful for water burst study and prevention measures of tunnels constructed in high-risk karst regions.

关键词： karst tunnels rock plug minimum safe thickness upper limit theorem failure mode

Cross-talk between hepatic stellate cells and T lymphocytes in liver fibrosis

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Hepatobiliary & Pancreatic Diseases International 2021年第3期20卷 207-214页

作者： Hao Li Peng Ding bo Peng Ying-zi Ming Research Center of Chinese Health Ministry on Transplantation Medicine Engineering and Technology the Third Xiangya Hospital of Central South UniversityChangsha 410003China

Background: Fibrosis results from inflammation and healing following injury. The imbalance between extracellular matrix(ECM) secretion and degradation leads to the ECM accumulation and liver fibrosis. This process is regulated by immune cells. T lymphocytes, including alpha beta( αβ) T cells, which have adaptive immune functions, and gamma delta( γδ) T cells, which have innate immune functions, are considered regulators of liver fibrosis. This review aimed to present the current understanding of the cross-talk between T lymphocytes and hepatic stellate cells(HSCs), which are the key cells in liver fibrosis. Data sources: The keywords "liver fibrosis", "immune", and "T cells" were used to retrieve articles published in Pub Med database before January 31, 2020. Results: The ratio of CD8 +(suppressor) T cells to CD4+(helper) T cells is significantly higher in the liver than in the peripheral blood. T cells secrete a series of cytokines and chemokines to regulate the inflammation in the liver and the activation of HSCs to influence the course of liver fibrosis. In addition, HSCs also regulate the differentiation and proliferation of T cells. Conclusions: The cross-talk between T cells and HSCs regulates liver fibrosis progression. The elucidation of this communication process will help us to understand the pathological process of liver fibrosis.

关键词： Hepatic stellate cells T lymphocytes Inflammatory cytokines Fibrosis

Mobile-robotic machining for large complex components:A review study

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Science China(Technological Sciences) 2019年第8期62卷 1388-1400页

作者： TAO bo ZHAO XingWei DING han State Key Laboratory of Digital Manufacturing Equipment and Technology School of Mechanical Science and EngineeringHuazhong University of Science and Technology

Even though the robotic machining has achieved great success in machining of small components, it lacks the competence to machine large complex components, such as wind turbine blade, train carriage, and aircraft wing. In order to cope with this issue,the mobile machining robot system, which consists of a robot arm integrated with a mobile platform, is proposed to achieve the large workspace and high dexterity, and thus has the potential to machine the large complex components. However, due to the limitation of motion accuracy and structural stiffness, the current mobile-robots are hard to satisfy the high precision requirement of machining tasks. In this paper, some historical mobile-robotic machining systems are reviewed firstly, followed by some key techniques related to structure optimization, dynamics of the machining process, localization, and control techniques, which are fundamental for the structural stiffness and motion accuracy of mobile-robots. Finally, the prospect of mobile-robotic machining and the open questions are addressed.

关键词： robotic machining industrial robot mobile-robot accuracy stiffness

Backstepping Based Global Exponential Stabilization of a Tracked Mobile Robot with Slipping Perturbation

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Journal of Bionic Engineering 2011年第1期8卷 69-76页

作者： bo Zhou Jianda han Xianzhong Dai Key Laboratory of Measurement and Control of CSE (School of Automation Southeast University) Ministry of Education Nanjing 210096 P. R. China Shenyang Institute of Automation CAS Shenyang 110016 P. R. China

While the nonholonomic robots with no-slipping constraints are studied extensively nowadays, the slipping effect is inevitable in many practical applications and should be considered necessarily to achieve autonomous navigation and control purposes especially in outdoor environments. In this paper the robust point stabilization problem of a tracked mobile robot is discussed in the presence of track slipping, which can be treated as model perturbation that violates the pure nonholonomic constraints. The kinematic model of the tracked vehicle is created, in which the slipping is assumed to be a time-varying pa- rameter under certain assumptions of track-soil interaction. By transforming the original system to the special chained form of nonholonomic system, the integrator backstepping procedure with a state-scaling technique is used to construct the controller to stabilize the system at the kinematic level. The global exponential stability of the final system can be guaranteed by Lyapunov theory. Simulation results with different initial states and slipping parameters demonstrate the fast convergence, robustness and insensitivity to the initial state of the proposed method.

关键词： tracked mobile robot nonholonomic system stabilization backstepping Lyapunov function

Annealing Effect on Wear Resistance of Nanostructured 316L Stainless Steel Subjected to Dynamic Plastic Deformation

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Journal of Materials Science & Technology 2012年第10期28卷 871-877页

作者： bo Wang Bin Yao Zhong han Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang110016China

Bulk nanostructured 316L austenitic stainless steel （SS） samples with nano-scale twin bundles embedded in nano-sized grains were synthesized by using dynamic plastic deformation （DPD）. Subsequent thermal an-nealing of the as-DPD sample leads to a single austenitic structure with static recrystallized （SRX） grains in nanostructured matrix. Oil-lubricated sliding tests of ball-on-disc type were carried out for the as-DPD and the as-annealed DPD steel samples in comparison with coarse grained （CG） steel samples. Experimental results show that the as-DPD 316L steel exhibits a little enhanced wear resistance under a load of 10 N, and nearly identical wear resistance under a load of 30 N relative to that of the CG sample. After annealing, the wear resistance roughly follows the Archard equation under a load of 10 N. However, the wear resistance increases with increasing hardness, and decreases with a further increase in hardness under a load of 30 N. The highest wear resistance can be found in the DPD sample annealed at 750 ℃ for about 20 min, which is more than 46% higher than that of the CG steel sample. This phenomenon is originated from the microstructure with an optimized combination of strength and ductility as a result of moderate plastic deformation in SRX grained regions.

关键词： Nanostructrued metals Stainless steel Wear resistance Annealing Subsurfacemicrostructure

Embedding ensemble tracking in a stochastic framework for robust object tracking

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第10期10卷 1476-1482页

作者： Yu GU Ping LI bo han Institute of Industrial Process Control Zhejiang University Hangzhou 310027 China

We propose an algorithm of embedding ensemble tracking in a stochastic framework to achieve robust tracking performance under partial occlusion,illumination changes,and abrupt *** operates on likelihood images generated by the ensemble method,and combines mean shift and particle filtering in a principled way,where a better proposal distribution is de-signed by first propagating particles via a motion model,and then running mean shift to move towards their local peaks in the likelihood *** observation model in the particle filter incorporates global and local information within a region,and an adaptive motion model is adopted to depict the evolution of the object *** algorithm needs fewer particles to manage the tracking task compared with the general particle filter,and recaptures the object quickly after occlusion *** on two image sequences demonstrate the effectiveness and robustness of the proposed algorithm.

关键词： Ensemble tracking Particle filter Mean shift Likelihood mean

Microstructure evolution of an ultra-high strength metal alloy with tempering temperature

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Rare Metals 2012年第5期31卷 442-445页

作者： WU Sujun HU Bin han bo School of Materials Science and Engineering Beijing University of Aeronautcs and Astronautics Beijing 100191 China

Optical microscopy (OM) and transmission electron microscopy (TEM) were used to investigate the effect of tempering temperature on the experimental extra-high carbon steels. It is found that tempering reaction can reduce austenite content and influence the stability of the austenite. As-normalized microstructure is a mixture of twinned martensite and retained austenite. Tempered at 250 °C for 2 h, lath martensite can occasionally be found nearby the diffusionally decomposed austenite area. It also is found that tempering at 650 °C for 2 h, nanoparticles of carbides precipitate in the martensite and decomposed austenite. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

关键词： Austenite Carbides Carbon steel High strength alloys Martensite Microstructure Optical microscopy Transmission electron microscopy

Strain rate analyses during elliptical vibration cutting of Inconel 718 using finite element analysis,Taguchi method,and ANOVA

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Advances in Manufacturing 2020年第3期8卷 316-330页

作者： Hai-bo Xie zi-Qing Yang Na Qin Zhan-Jiang Wang Tribology Research Institute Department of Mechanical EngineeringSouthwest Jiaotong UniversityChengdu610031People’s Republic of China

The high strain rate in metal cutting significantly affects the mechanical properties of the work piece by altering its *** study outlines the material strain rates during elliptical vibration *** finite element analysis,Taguchi method,and analysis of variance(ANOVA)were employed to analyze the effects and contributions of cutting and vibration process parameters(feed rate,rake angle,tangential amplitude,and frequency of vibration)on the variation of strain rates during machining of Inconel *** signal-to-noise analysis on an L18(2^1×3^3)orthogonal array was used to determine the optimum parametric combination for the maximum strain rate,and ANOVA was applied to evaluate the significance of control parameter factors on the strain *** results of the finite element analysis under different conditions illustrated that the feed rate and rake angle were negatively related to the strain rate,whereas the tangential amplitude and frequency had a positive ***,ANOVA results indicated that the effect of the feed rate,tool rake angle,vibration frequency,and tangential amplitude on the strain rate were all statistically significant,with a reliability level of 95%.Of these,the dominant parameter affecting the strain rate was the feed rate,with a percentage contribution of 40.36%.The estimation of the optimum strain rate and confirmation tests proved that the Taguchi method could successfully optimize the working conditions to obtain the desired maximum strain rate.

关键词： Elliptical vibration cutting Strain rate Finite element(FE) Taguchi method Analysis of variance(ANOVA)