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Ergodic degrees for continuous-time Markov chains

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Science China Mathematics 2004年第2期47卷 161-174页

作者： mao Yonghua Department of Mathematics Beijing Normal University Beijing 100875China

This paper studies the existence of the higher orders deviation matrices for continuous time Markov chains by the moments for the hitting times. An estimate of the polynomial convergence rates for the transition matri... 详细信息

关键词： Markov chain, ergodic degree, hitting time, convergence to stationary.

Secreted miR-34a in astrocytic shedding vesicles enhanced the vulnerability of dopaminergic neurons to neurotoxins by targeting Bcl-2

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Protein & Cell 2015年第7期6卷 529-540页

作者： Susu mao State Key Laboratory of Pharmaceutical Biotechnology Nanjing Advanced Institute for Life Sciences (NAILS) Nanjing University School of Life Sciences Nanjing 210093 China Jiangsu Engineering Research Center for microRNA Biology and Biotechnology Nanjing 210093 China Center of Kidney Disease 2nd Affiliated Hospital Nanjing Medical University Nanjing 210003 China

MicroRNAs （miRNAs） are a class of noncoding RNAs that regulates target gene expression at posttranscrip- tional level, leading to further biological functions. We have demonstrated that microvesicles （MVs） can deliver miRNAs into target cells as a novel way of intercellular communication. It is reported that in central nervous system, glial cells release MVs, which modulate neu-ronal function in normal condition. To elucidate the potential role of glial MVs in disease, we evaluated the effects of secreted astrocytic MVs on stress condition. Our results demonstrated that after Lipopolysaccharide （LPS） stimulation, astrocytes released shedding vesi- cles （SVs） that enhanced vulnerability of dopaminergic neurons to neurotoxin. Further investigation showed that increased astrocytic miR-34a in SVs was involved in this progress via targeting anti-apoptotic protein Bcl-2 in dopaminergic neurons. We also found that inhibition of astrocytic miR-34a after LPS stimulation can postpone dopaminergic neuron loss under neurotoxin stress. These data revealed a novel mechanism underlying astrocyte-neuron interaction in disease.

关键词： astrocyte shedding vesicles miR-34a,dopaminergic neurons Bcl-2

Astrophysical applications of gravitational microlensing

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Research in Astronomy and Astrophysics 2012年第8期12卷 947-972页

作者： Shude mao National Astronomical Observatories Beijing 100012 China

Since the first discovery of microlensing events nearly two decades ago, gravitational microlensing has accumulated tens of TBytes of data and developed into a powerful astrophysical technique with diverse applications. The review starts with a theoretical overview of the field and then proceeds to discuss the scientific highlights. （1） Microlensing observations toward the Magellanic Clouds rule out the Milky Way halo being dominated by MAssive Compact Halo Objects （MAChos）. This confirms most dark matter is non-baryonic, consistent with other observations. （2） Microlensing has discovered about 20 extrasolar planets （16 published）, including the first two Jupiter-Saturn like systems and the only five ＂cold Neptunes＂ yet de- tected. They probe a different part of the parameter space and will likely provide the most stringent test of core accretion theory of planet formation. （3） Microlensing pro- vides a unique way to measure the mass of isolated stars, including brown dwarfs and normal stars. Half a dozen or so stellar mass black hole candidates have also been pro- posed. （4） High-resolution, target-of-opportunity spectra of highly-magnified dwarf stars provide intriguing ＂age＂ determinations which may either hint at enhanced he- lium enrichment or unusual bulge formation theories. （5） Microlensing also measured limb-darkening profiles for close to ten giant stars, which challenges stellar atmo- sphere models. （6） Data from surveys also provide strong constraints on the geometry and kinematics of the Milky Way bar （through proper motions）; the latter indicates predictions from current models appear to be too anisotropic compared with observa- tions. The future of microlensing is bright given the new capabilities of current surveys and forthcoming new telescope networks from the ground and from space. Some open issues in the field are identified and briefly discussed.

关键词： Galaxy: structure -- formation -- bulge -- gravitational lensing --planetary systems: formation

Nonlinear perturbation developments in flow around a vibrating cylinder

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Journal of Hydrodynamics 2021年第6期33卷 1129-1138页

作者： Jian Deng Xuerui mao State Key Laboratory of Fluid Power and Mechatronic Systems Department of MechanicsZhejiang UniversityHangzhou 310027China Faculty of Engineering University of NottinghamNottinghamUK

We investigate the flow around a circular cylinder vibrating with a prescribed magnitude and frequency at Reynolds number *** Navier-stokes equations and the adjoint equations are solved to search for the 3-D nonlinear optimal initial perturbation,which is amplified by the attached shear via the Orr mechanism and then activates wake *** energy growth and the spanwise distributions of the nonlinear optimal perturbation vary significantly with the initial phase to introduce the *** the initial perturbation energy increases,linear amplification,nonlinear saturation and nonlinear growth are sequently *** last one is owing to the generation of a spanwise homogeneous mode,which modifies the pressure distributions on the cylinder surface and induces an extra lift ***,at all the initial phases,this force is opposite to the acceleration of the cylinder,illustrating the potential to reduce the magnitude of vibration.

关键词： Vortex induced vibration nonlinear optimal perturbation Orr mechanism

On the Taylor principles for plastic deformation of polycrystalline metals

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Frontiers of Materials Science 2016年第4期10卷 335-345页

作者： Weimin mao School of Materials and Metallurgy Inner Mongolia University of Science and Technology Arding Street 7 Baotou 014010 China Department of Materials University of Science and Technology Beijing Xue-Yuan Road 30 Beijing 100083 China

Grain orientation evolutions and texture formation based on the Taylor principles offer important references to reveal crystallographic mechanisms of deforma- tion behaviors. Strain equilibrium between grains is achieved in Taylor theory, however, stress equilibrium has not yet been reached perfectly even in many modifications of the theory though the textures predicted become very close to those of experimental observations. A reaction stress model is proposed, in which mechanical interactions between grains are considered in details and grain deformation is conducted by penetrating and non-penetrating slips. The new model offers both of the stress and strain equilibria and predicts the same textures indicated by Taylor theory. The rolling texture simulated comes very close to the experimental observations if the relaxation effect of the non-penetrating slips on the up-limits of reaction stresses is included. The reaction stress principles open theoretically a new field of vision to consider deformation behaviors of poiycrystaliine materials, whereas the Taylor principles become unnecessary both theoretically and practically. Detailed engineering conditions have to be included in simulations if the deformation textures of industrial products should be predicted.

关键词： Taylor principles micormechanical equilibrium plastic deformation dislocation slip texture simulation

Physics-informed neural networks with residual/gradient-based adaptive sampling methods for solving partial differential equations with sharp solutions

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Applied Mathematics and Mechanics(English Edition) 2023年第7期44卷 1069-1084页

作者： Zhiping mao Xuhui MENG School of Mathematical Sciences Fujian Provincial Key Laboratory of Mathematical Modeling and High-Performance Scientific ComputingXiamen UniversityXiamen 361005Fujian ProvinceChina Institute of Interdisciplinary Research for Mathematics and Applied Science School of Mathematics and StatisticsHuazhong University of Science and TechnologyWuhan 430074China

We consider solving the forward and inverse partial differential equations(PDEs)which have sharp solutions with physics-informed neural networks(PINNs)in this *** particular,to better capture the sharpness of the solution,we propose the adaptive sampling methods(ASMs)based on the residual and the gradient of the *** first present a residual only-based ASM denoted by ASMⅠ.In this approach,we first train the neural network using a small number of residual points and divide the computational domain into a certain number of sub-domains,then we add new residual points in the sub-domain which has the largest mean absolute value of the residual,and those points which have the largest absolute values of the residual in this sub-domain as new residual *** further develop a second type of ASM(denoted by ASMⅡ)based on both the residual and the gradient of the solution due to the fact that only the residual may not be able to efficiently capture the sharpness of the *** procedure of ASMⅡis almost the same as that of ASMⅠ,and we add new residual points which have not only large residuals but also large *** demonstrate the effectiveness of the present methods,we use both ASMⅠand ASMⅡto solve a number of PDEs,including the Burger equation,the compressible Euler equation,the Poisson equation over an Lshape domain as well as the high-dimensional Poisson *** has been shown from the numerical results that the sharp solutions can be well approximated by using either ASMⅠor ASMⅡ,and both methods deliver much more accurate solutions than the original PINNs with the same number of residual ***,the ASMⅡalgorithm has better performance in terms of accuracy,efficiency,and stability compared with the ASMⅠ*** means that the gradient of the solution improves the stability and efficiency of the adaptive sampling procedure as well as the accuracy of the ***,we also employ the similar adaptive sampling technique fo

关键词： physics-informed neural network(PINN) adaptive sampling high-dimension L-shape Poisson equation accuracy

Strongly Gorenstein graded modules

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Frontiers of Mathematics in China 2017年第1期12卷 157-176页

作者： Lixin mao Department of Mathematics and Physics Nanjing Institute of Technology Nanjing 211167China

Let R be a graded ring. We define and study strongly Gorenstein gr-projective, gr-injective, and gr-flat modules. Some connections among these modules are discussed. We also explore the relations between the graded an... 详细信息

关键词： Strongly Gorenstein gr-projective module strongly Gorenstein gr-injective module strongly Gorenstein gr-flat module

COMPREHENSIVE STUDY OF COMBINING FLOW CONDITIONS AT PIPE JUNCTIONS

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Journal of Hydrodynamics 1996年第1期8卷 76-84页

作者： mao, Zeyu Tsinghau Univ Beijing China

Theoretical and experimental investigation for the behavior of pipe junction, either 45 or 90 degree, has been performed. The junction was formed by the meeting of three equal diameter pipe, which all had equal invert levels. The characteristics of each type of junctions were discussed. These equations were then incorporated into computer program and the numerical solution of St. Venant equations were obtained by using characteristic-difference method. The presented equations may also be used to determine the limiting capacity of a junction, if surcharge of the system was to be avoided. Excellent agreement was found to exist between the observed unsteady flow conditions at junction and those predicted using the derives relationships.

关键词： Channel flow Computer simulation Finite element method Flow interactions Fluid structure interaction Numerical analysis Unsteady flow

Towards Connecting Discrete Mathematics and Software Engineering

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Tsinghua Science and Technology 2020年第3期25卷 325-335页

作者： Tun Li Wanwei Liu Juan Chen Xiaoguang mao Xinjun mao the School of Computer National University of Defense Technology and are also with Laboratory of Software Engineering for Complex Systems

To enhance training in software development,we argue that students of software engineering should be exposed to software development activities early in the *** entails meeting the challenge of engaging students in software development before they take the software engineering *** this paper,we propose a method to connect courses in the software engineering curriculum by setting comprehensive development projects to students in prerequisite courses for software *** the Discrete Mathematics(DM)course as an example,we describe the implementation of the proposed method and teaching practices using several practical and comprehensive projects derived from topics in discrete *** descriptions of the sample projects,their application,and training results are *** and lessons learned from applying these practices show that it is a promising way to connect courses in the software engineering curriculum.

关键词： Discrete Mathematics(DM) software engineering proof checker database management system symbolic execution engine