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Research on data assimilation strategy of turbulent separated flow over airfoil

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Applied mathematics and Mechanics(English Edition) 2022年第4期43卷 571-586页

作者： Ying ZHANG Lin DU Weiwei ZHANG Zichen DENG National Key Laboratory of Science and Technology on Aerodynamic Design and Research School of AeronauticsNorthwestern Polytechnical UniversityXi'an 710072China Complex System Dynamics and Control Academic Exchange Center School of Mathematics and StatisticsNorthwestern Polytechnical UniversityXi'an 710119China Rotor Aerodynamics Key Laboratory China Aerodynamics Research and Development CenterMianyang 621000Sichuan ProvinceChina

In order to increase the accuracy of turbulence field reconstruction,this paper combines experimental observation and numerical simulation to develop and establish a data assimilation framework,and apply it to the study of S809 low-speed and high-angle airfoil flow.The method is based on the ensemble transform Kalman filter(ETKF)algorithm,which improves the disturbance strategy of the ensemble members and enhances the richness of the initial members by screening high flow field sensitivity constants,increasing the constant disturbance dimensions and designing a fine disturbance interval.The results show that the pressure distribution on the airfoil surface after assimilation is closer to the experimental value than that of the standard Spalart-Allmaras(S-A)model.The separated vortex estimated by filtering is fuller,and the eddy viscosity field information is more abundant,which is physically consistent with the observation information.Therefore,the data assimilation method based on the improved ensemble strategy can more accurately and effectively describe complex turbulence phenomena.

关键词： turbulence data assimilation ensemble disturbance strategy large angle of attack separation ensemble transform Kalman filter(ETKF)

UNIFORM QUASI-DIFFERENTIABILITY OF SEMIGROUP TO NONLINEAR REACTION-DIFFUSION EQUATIONS WITH SUPERCRITI C AL EXPONENT

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Acta Mathematica Scientia 2017年第2期37卷 301-315页

作者：钟延生孙春友 Department of mathematics Fujian Normal University Fuzhou 350117 China school of mathematics and statistics Lanzhou University Lanzhou 730000 China

A new approach, is established to show that the semigroup {S（t）≥0 generated by a reaction-diffusion equation with supercritical exponent is uniformly quasi-differentiable in L^q（Ω）（2 ≤ q 〈 ∞） with respect to the initial value. As an application, this proves the upper-bound of fractal dimension for its global attractor in the corresponding space.

关键词： Uniform quasi-differentiability semigroup reaction-diffusion equation

Fatigue crack propagation across grain boundary of Al-Cu-Mg bicrystal based on crystal plasticity XFEM and cohesive zone model

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Journal of Materials Science & Technology 2022年第31期126卷 275-287页

作者： Qi Zhao Magd Abdel Wahab Yong Ling Zhiyi Liu school of Materials Science and Engineering Hubei University of Automotive TechnologyShiyan 442002China Faculty of Mechanical-Electrical and Computer Engineering School of Engineering and TechnologyVan Lang UniversityHo Chi Minh CityVietnam Soete Laboratory Faculty of Engineering and ArchitectureGhent UniversityTechnologiepark Zwijnaarde 903B-9052 ZwijnaardeBelgium school of Materials Science and Engineering Central South UniversityChangsha 410083China

In this paper,a methodology integrating crystal plasticity(CP),the eXtended finite element method(XFEM)and the cohesive zone model(CZM)is developed for an Al-Cu-Mg alloy to predict fatigue crack propagation(FCP)across grain boundary(GB)of Al-Cu-Mg alloy during stageІІ.One GB model is incor-porated into FCP constitutive law to describe grain interaction at GB.A bicrystal containing GB is built up to simulate FCP behavior through L participated GBs.Modelling features including GB characteristic,cumulative plastic strain(CPS)distribution and crystal slipping evidence can be identified.The numer-ical results are compared with published experimental data to check the accuracy of model.This work demonstrates that the combination of CP containing GB constitutive laws,XFEM and CZM is a promising methodology in predicting twist angle-controlled crack deflection through GBs.

关键词： Grain boundary Twist angle Crystal plasticity Extended finite element method Fatigue crack propagation Cumulative plastic strain

Optimal l~∞ error estimates of finite difference methods for the coupled Gross-Pitaevskii equations in high dimensions

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Science China mathematics 2014年第10期57卷 2189-2214页

作者： WANG TingChun ZHAO XiaoFei school of mathematics and statistics Nanjing University of Information Science and Technology Department of mathematics National University of Singapore

Due to the difficulty in obtaining the a priori estimate,it is very hard to establish the optimal point-wise error bound of a finite difference scheme for solving a nonlinear partial differential equation in high dimensions(2D or 3D).We here propose and analyze finite difference methods for solving the coupled GrossPitaevskii equations in two dimensions,which models the two-component Bose-Einstein condensates with an internal atomic Josephson junction.The methods which we considered include two conservative type schemes and two non-conservative type schemes.Discrete conservation laws and solvability of the schemes are analyzed.For the four proposed finite difference methods,we establish the optimal convergence rates for the error at the order of O(h^2+τ~2)in the l~∞-norm(i.e.,the point-wise error estimates)with the time stepτand the mesh size h.Besides the standard techniques of the energy method,the key techniques in the analysis is to use the cut-off function technique,transformation between the time and space direction and the method of order reduction.All the methods and results here are also valid and can be easily extended to the three-dimensional case.Finally,numerical results are reported to confirm our theoretical error estimates for the numerical methods.

关键词：非线性偏微分方程有限差分方法误差估计解耦合高维爱因斯坦凝聚标准技术有限差分法

MoS_(2)表面镀铜对青铜-石墨-MoS_(2)自润滑摩擦性能的影响

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Journal of central south university 2022年第11期29卷 3608-3619页

作者：王慧灵姜锋童蒙蒙吴明锦蒋靖宇 school of Materials Science and Engineering Central South UniversityChangsha 410083China Light Alloy Research Institute Central South UniversityChangsha 410083China The National Key Laboratory of Science and Technology for National Defence on High-Strength Lightweight Structural Materials Central South UniversityChangsha 410083China

采用粉末冶金法制备了含镀铜MoS_(2)和不镀铜MoS_(2)两种青铜-石墨-MoS_(2)自润滑材料,并在4 N和10 N载荷下分别进行摩擦磨损实验,研究MoS_(2)表面镀铜对材料摩擦性能的影响。研究结果表明,在MoS_(2)表面镀铜可以增强MoS_(2)与基体的结... 详细信息

采用粉末冶金法制备了含镀铜MoS_(2)和不镀铜MoS_(2)两种青铜-石墨-MoS_(2)自润滑材料,并在4 N和10 N载荷下分别进行摩擦磨损实验,研究MoS_(2)表面镀铜对材料摩擦性能的影响。研究结果表明,在MoS_(2)表面镀铜可以增强MoS_(2)与基体的结合性,同时抑制材料中硬质相MoO_(2)的形成。此外,两种材料在摩擦过程中均在表面形成了一层MoS_(2)润滑膜,但是在MoS_(2)表面镀铜后形成的润滑膜更厚,并且具有凹凸不平的形貌,更有利于改善材料的摩擦性能。与常规材料相比,在4 N和10 N载荷下进行滑动摩擦时,镀铜材料的磨损率均降低了一个数量级,摩擦因数也分别降低了22.44%和22.53%,表明在MoS_(2)表面镀铜可以进一步改善青铜-石墨-MoS_(2)自润滑材料的摩擦性能。

关键词：青铜-石墨-MoS2 自润滑材料摩擦磨损磨损机制

Identifying disease modules and components of viral infections based on multi-layer networks

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Science China(Information Sciences) 2016年第7期59卷 15-29页

作者： Yuanyuan LI Xiufen ZOU school of mathematics and statistics Wuhan University Computational Science Hubei Key Laboratory Wuhan University school of Science Wuhan Institute of Technology

With the emergence of multi-dimensional data, we can more comprehensively analyze the pathogenic mechanisms of complex diseases, and thereby improve the diagnosis, treatment and prevention of these diseases.This study presents a novel multi-layer network-based strategy that integrates multi-dimensional data, and identifies disease-related modules and components of viral infections. We first propose a systematic method that constructs a virus-host interaction network with three layers: a viral protein layer, a host protein layer and a host gene layer. This method combines the data of high-throughput gene expression, viral protein interactions,virus-host interactions, protein-protein interactions and transcriptional regulatory relationships. To extract the underlying mechanisms of viral infections from the multi-layer networks, we identify the intra-layer and crosslayer modules, and investigate the conserved modules across multiple datasets. The essential components in the multi-layer networks are detected by singular-value decomposition. The identified conserved modules and essential components are combined into a functional enrichment analysis that reveals their contributions to influenza virus replication. By this analysis, we elucidate the common and specific mechanisms of the replication cycles of two influenza strains. By combining the different layers of information, we can comprehensively understand pathogenic mechanisms of complex diseases.

关键词： multi-dimensional data multi-layer network complex disease virus infection disease modules

废旧锂电池回收过程中氟的迁移及其原位掺杂再生制备LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)正极材料

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Science China Materials 2023年第9期66卷 3433-3444页

作者：王天宇易晨星葛鹏王丽孙伟吴美容张驰杨越 school of Minerals Processing and Bioengineering Central South UniversityChangsha 410083China school of Chemical Engineering Zhengzhou UniversityZhengzhou 450001China

氟是废旧锂电池回收难以回避的典型杂质元素,其迁移转化行为复杂,制约了高品质正极材料的可控再生制备.本研究通过揭示废旧锂电池在热解、浸出及高镍LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)材料再生过程中氟的迁移转化规律,为氟的定向调控... 详细信息

氟是废旧锂电池回收难以回避的典型杂质元素,其迁移转化行为复杂,制约了高品质正极材料的可控再生制备.本研究通过揭示废旧锂电池在热解、浸出及高镍LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)材料再生过程中氟的迁移转化规律,为氟的定向调控及材料的可控再生制备奠定理论基础实验结果表明:热解过程中部分氟(45.71%)以气态热解产物的形式释放到大气中,而另一部分氟(52.34%)则向废三元材料的晶格内发生迁移,并随着湿法浸出溶解到镍钴锰的浸出液中.浸出液中少量的氟会在共沉淀制备前驱体过程中迁移到Ni_(0.9)Co_(0.05)Mn_(0.05)(OH)2前驱体材料,并随着配锂烧结掺杂到再生LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)材料表面.进一步通过调控氟含量发现,当浸出液中氟浓度控制在0.30 g L^(-1)时,引入到再生LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)材料中的氟不仅不会引起不利相变,而且能够稳定材料结构,从而有效提升再生高镍材料的循环稳定性(1 C电流密度下循环100圈的容量保持率高达95.7%).因此,本研究不仅揭示了废旧锂电池回收过程中氟的迁移转化行为,而且可控再生制备了高性能氟掺杂高镍LiNi_(0.9)Co_(0.05)Mn_(0.05)O_(2)正极材料,为废旧锂离子电池回收过程中氟的调控提供了理论依据.

关键词：正极材料三元材料废旧锂离子电池高镍回收过程废旧锂电池循环稳定性氟掺杂

Existence,Uniqueness and Asymptotic Behavior for the Vlasov–Poisson System with Radiation Damping

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Acta Mathematica Sinica,English Series 2017年第5期33卷 635-656页

作者： Jing CHEN Xian Wen ZHANG Ran GAO College of Science Zhongyuan University of Technology school of mathematics and statistics Huazhong University of Science and Technology

We investigate the Cauchy problem for the Vlasov–Poisson system with radiation damping.By virtue of energy estimate and a refined velocity average lemma, we establish the global existence of nonnegative weak solution and asymptotic behavior under the condition that initial data have finite mass and energy. Furthermore, by building a Gronwall inequality about the distance between the Lagrangian flows associated to the weak solutions, we can prove the uniqueness of weak solution when the initial data have a higher order velocity moment.

关键词： Vlasov–Poisson system radiation damping velocity averages weak solution uniqueness

Tensor product weight modules of Schrodinger-Virasoro algebras

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Frontiers of mathematics in China 2019年第2期14卷 381-393页

作者： Dong LIU Xiufu ZHANG Department of mathematics Huzhou UniversityHuzhou 313000China school of mathematics and statistics Jiangsu Normal UniversityXuzhou 221116China

It is known that the Schrddinger-Virasoro algebras, including the original Schrddinger-Virasoro algebra and the twisted Schr?dinger-Virasoro algebra, are playing important roles in mathematics and statistical physics. In this paper, we study the tensor products of weight modules over the Schr?dinger- Virasoro algebras. The irreducibility criterion for the tensor products of highest weight modules with intermediate series modules over the Schr?dinger-Virasoro algebra is obtained.

关键词： Harish-Chandra module tensor product highest weight module intermediate series module Schrodinger-Virasoro algebra