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A Simple Implementation of the Semi-Lagrangian Level-Set Method

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Advances in Applied Mathematics and Mechanics 2017年第1期9卷 104-124页

作者： Weidong Shi jian-jun xu Shi Shu School of Mathematical and Computational Sciences Xiangtan UniversityXiangtanHunan 411105China Chongqing Institute of Green and Intelligent Technology Chinese Academy of SciencesChongqing 400714China

Semi-Lagrangian(S-L)methods have no CFL stability constraint,and are more stable than the Eulerian *** the literature,the S-L method for the levelset re-initialization equation was complicated,which may be *** the re-initialization procedure is auxiliary,we propose to use the first-order S-L scheme coupled with a projection technique to improve the accuracy at the grid points just adjacent to the *** second-order S-L method is used for evolving the level-set convection *** implementation is simple,including on the block-structured adaptive *** efficiency of the S-L method is demonstrated by extensive numerical examples including passive convection of interfaces with corners/kinks/large deformation under given velocity fields,a geometrical flow with topological changes,simulations of bubble/droplet dynamics in incompressible twophase *** terms of accuracy it is comparable to the other existing methods.

关键词： Semi-Lagrangian method level-set method interface motion two-phase flow bubble/droplet dynamics block-structured adaptive mesh

Testing for Changes in the Mean or Variance of Long Memory Processes

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Acta Mathematica Sinica,English Series 2010年第12期26卷 2443-2460页

作者： Yun Xia LI jian jun xu Li Xin ZHANG School of Mathematics and Statistics Zhejiang University of Finance and Economics Hangzhou 310018 P. R. China Department of Mathematics Zhejiang University Hangzhou 310027 P. R. China

In this paper, we study the asymptotic CUSUM tests for detecting changes in the mean or variance of a moving-average process with long memory. When there is no change over [O,T], the asymptotic distribution of the test statistic is derived, which allows us to find asymptotic critical values. When there is a change, the behavior of the test statistic is discussed. Conditions for the consistency of these tests are also discussed. Based on the asymptotic results, simulation studies of testing for changes in the mean show that the CUSUM test proposed performs well.

关键词： Change-point moving-average process long memory invariance principle fractionalBrownian motion

Numerical Study of Surfactant-Laden Drop-Drop Interactions

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Communications in Computational Physics 2011年第7期10卷 453-473页

作者： jian-jun xu Zhilin Li John Lowengrub Hongkai Zhao School of Mathematical and Computational Sciences Xiangtan UniversityXiangtanHunan 411105China Department of Mathematics North Carolina State UniversityRaleighNC27695USA Department of Mathematics University of California IrvineIrvineCA92697USA

In this paper,we numerically investigate the effects of surfactant on dropdrop interactions in a 2D shear flow using a coupled level-set and immersed interface approach proposed in(xu et al.,***.,212(2006),590–616).We find that surfactant plays a critical and nontrivial role in drop-drop *** particular,we find that the minimum distance between the drops is a non-monotone function of the surfactant coverage and Capillary *** non-monotonic behavior,which does not occur for clean drops,is found to be due to the presence of Marangoni forces along the drop *** suggests that there are non-monotonic conditions for coalescence of surfactant-laden drops,as observed in recent experiments of Leal and *** our study is two-dimensional,we believe that drop-drop interactions in three-dimensional flows should be qualitatively similar as the Maragoni forces in the near contact region in 3D should have a similar effect.

关键词： Surfactants drops coalescence surface tension Marangoni effect level-set method immersed interface method Stokes flow

A Coupled Immersed Interface and Level Set Method for Three-Dimensional Interfacial Flows with Insoluble Surfactant

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Communications in Computational Physics 2014年第2期15卷 451-469页

作者： jian-jun xu Yunqing Huang Ming-Chih Lai Zhilin Li School of Mathematical and Computational Sciences Xiangtan UniversityHunan 410005China Department of Applied Mathematics National Chiao Tung UniversityHsinchu 30050Taiwan Department of Mathematics North Carolina State UniversityRaleighNC27695USA .4 Hunan Key Lab for Computation and Simulation in Science and Engineering Hunan 410005China School of Mathematical Sciences Nanjing Normal UniversityNanjingChina.

In this paper,a numerical method is presented for simulating the 3D interfacial flows with insoluble *** numerical scheme consists of a 3D immersed interface method(IIM)for solving Stokes equations with jumps across the interface and a 3D level-set method for solving the surfactant convection-diffusion equation along a moving and deforming *** 3D IIM Poisson solver modifies the one in the literature by assuming that the jump conditions of the solution and the flux are implicitly given at the grid points in a small neighborhood of the *** assumption is convenient in conjunction with the level-set *** allows standard Lagrangian interpolation for quantities at the projection points on the *** interface jump relations are re-derived accordingly.A novel rotational procedure is given to generate smooth local coordinate systems and make effective *** examples demonstrate that the IIM Poisson solver and the Stokes solver achieve second-order accuracy.A 3D drop with insoluble surfactant under shear flow is investigated numerically by studying the influences of different physical parameters on the drop deformation.

关键词： Multigrid method constrained Cauchy-Born elasticity nanoindentation CauchyBorn rule.

Correlation of angiotensin converting enzyme gene polymorphism with perioperative myocardial protection under extracorporeal circulation

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Asian Pacific Journal of Tropical Medicine 2012年第12期5卷 995-999页

作者： Wei Yang Xiao Dong Bin Li Xiao-Qiang Zhang Yuan Zeng Yi-Ping Wei jian-Liang Zhou Yan-Hua Tang jian-jun xu Department of Cardiothoracic Surgery Second Affiliated Hospital to Nanchang University

Objective:To observe the expression of angiotensin converting enzyme(ACE),angiotensinⅡ(AngⅡ),cardiac troponin 详细信息

Objective:To observe the expression of angiotensin converting enzyme(ACE),angiotensinⅡ(AngⅡ),cardiac troponin

关键词： Angiotensin converting enzyme ACE gene polymorphism Cardiopulmonary bypass perioperative Myocardial injury Myocardial markers

Interactive Effects of Lead and Bensulfuron-Methyl on Decomposition of ^(14)C-Glucose in Paddy Soils

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Pedosphere 2009年第5期19卷 577-587页

作者： HOU Xian-Wen WU jian-jun xu jian-Ming TANG Cai-Xian Institute of Soil and Water Resources and Environmental Science Zhejiang Provincial Key Laboratory of SubtropicalSoil and Plant Nutrition Zhejiang University Hangzhou 310029 （China） Institute of Environmental and Plant Protection Chinese Academy of Tropical Agricultural Sciences Danzhou 571737（China） Department of Agricultural Sciences La Trobe University Victoria 3086 （Australia）

Little information is available on the interactive effects of inorganic and organic pollutants on carbon utilization by soil *** study examined the effects of two common soil pollutants,lead(Pb) and bensulfuron-methyl herbicide(BSM),on decomposition of an adscititious carbon source(14C-glucose).Two contrasting paddy soils,a silty clay soil and a clay loam soil,were incubated with different concentrations and combinations of pollutants for 60 *** rotatable central composite design was adopted to design the combinations of the pollutant concentrations so that rate response curves could be *** decomposition of 14C-glucose occurred in the first three days for both soils where no Pb or BSM was added(control).Overall,63%-64% of the added 14C-glucose was decomposed in the control over the 60-day *** addition of Pb or BSM significantly decreased the decomposition of 14C-glucose during the first week but increased the decomposition thereafter;as a result,the percentages of 14C-glucose decomposed(57%-77%) over the 60-day period were similar to or higher than those of the *** of the pollutants in combination did not further inhibit decomposition compared with the ***,decomposition rates were lower in the silty clay soil than in the clay loam soil,which was related to the soil texture,cation exchange capacity,and *** relationship between the decomposition rates and the pollutants could be well characterized by the quadratic regression orthogonal rotation *** initial antagonistic effects of the pollutants followed by the synergistic effects on microbial activity might result from changes of the concentrations of the pollutants.

关键词： carbon source compound pollution herbicide microbial activity

Observation of topological charge transformations in acoustic vortex using passive periodic systems

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Science China(Physics,Mechanics & Astronomy) 2025年第1期Mechanics & Astronomy) .卷 140-147页

作者： Di-Chao Chen Xie Liu Changqing xu Da-jian Wu Ying Cheng Xiao-jun Liu School of Physics and Technology Nanjing Normal University Key Laboratory of Modern Acoustics School of Physics Nanjing University

Vortex transmutation utilizes a periodic system, which not only enables the alteration of the topological charge(TC) of unstable input vortices but also facilitates their transformation into stable structures. This approach is crucial for investigating the characteristics of vortices in various wave systems. Here, we achieve acoustic vortex TC transmutation by employing a welldesigned dual-structured plate external system(DPES). The interactions between the acoustic vortex and the finite-order discrete rotational symmetry lead to the transformation of its topological charge when complete rotational symmetry is broken to Nthorder discrete symmetry. Our results experimentally demonstrate the acoustic vortex TC transmutation based on passive artificial structures, enabling numerous applications in particle manipulation and information multiplexing as well as advancing our understanding and control over free-space acoustic vortices.

关键词： acoustic vortex topological charge transformation artificial structure

Approach from the laboratory to the field: New strategies in the control of mosquito-borne infectious diseases

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Science China Life Sciences 2025年第1期68卷 303-305页

作者： Ziqian xu Lianpan Dai jun Liu National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Diseases (NITFID) National Institute for Viral Disease Control and PreventionChinese Center for Disease Control and Prevention CAS Key Laboratory of Pathogen Microbiology and Immunology Institute of MicrobiologyChinese Academy of Sciences

Vector-borne viruses, transmitted among humans and animal hosts through bites of vectors such as mosquitoes and ticks,pose a great and ongoing threat to public health and biosafety(Yang et al., 2022).Among them, dengue virus-induced epidemics, have dramatically increased worldwide in recent decades. The report released by the World Health Organization(WHO) at the end of 2023 showed that dengue epidemic globally surged in2023, with the number of reported cases nearing a historical peak.

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Seismic stability safety evaluation of gravity dam with shear strength reduction method

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Water Science and Engineering 2009年第2期2卷 52-60页

作者： Da-sheng WANG Liao-jun ZHANG jian-jun xu Ming-jie HE Wei-di ZHANG East China Investigation ＆ Design Institute Hangzhou 310014 P. R. China College of Water Conservancy and Hydropower Engineering Hohai University Nanjing 210098 P. R. China

A new method of numerical seismic stability safety evaluation for a rock slope is proposed based on the analysis of a gravity dam foundation subjected to earthquake loading. The shear strengths of the weak discontinuities are divided by different shear strength reduction ratios （K） and numerical seismic analysis is carried out after the static analysis is completed. With different K values, the curves of the permanent horizontal displacement of key points of the dam foundation （K-displacement curves） are studied. According to the curve change, the distribution of plastic zones in the foundation, and the slow convergence of the finite element method （FEM）, the seismic stability safety factor is defined as Kwhen the gravity dam is in the limit equilibrium state subjected to earthquake loading. These concepts were applied to the evaluation of seismic stability safety of a gravity dam for a hydropower project. The analysis of the example shows that the proposed method is feasible and is an effective method of seismic stability safety evaluation.

关键词： dynamic stability shear strength reduction ratio, gravity dam permanent horizontaldisplacement ADINA system