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Global Existence and Blow-Up Results for a Classical Semilinear Parabolic Equation

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Chinese Annals of mathematics,Series B 2013年第4期34卷 587-592页

作者： li ma Department of mathematics Henan Normal university

The author studies the boundary value problem of the classical semilinear parabolic equations

关键词： Positive solution Global existence Blow-up Omega limit

Eigenvalue Estimates and L^1 Energy on Closed manifolds

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Acta mathematica Sinica,English Series 2014年第10期30卷 1729-1734页

作者： li ma Department of mathematics He'nan Normal university

In this paper, we study lichnerowicz type estimate for eigenvalues of drifting Laplacian operator and the decay rates of L1 and L2 energy for drifting heat equation on closed Riemannian manifolds with weighted measure.

关键词： Drifting Laplacian lichnerowicz type result eigenvalue estimate monotonicity

Mean-square exponential stability for stochastic time-varying delay systems with markovian jumping parameters:a delay decomposition approach

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Journal of Systems Engineering and Electronics 2011年第5期22卷 816-824页

作者： li ma Feipeng Da Key Laboratory of Measurement and Control for Complex Systems of Engineering Ministry of Education Research Institute of Automation Southeast University Nanjing 210096 E R. China College of Electronic and Information Engineering Jiangsu University Zhenjiang 212013 P. R. China

The mean-square exponential stability problem is investigated for a class of stochastic time-varying delay systems with markovian jumping parameters. By decomposing the delay interval into multiple equidistant subintervals, a new delay-dependent and decay-rate-dependent criterion is presented based on constructing a novel Lyapunov functional and employing stochastic analysis technique. Besides, the decay rate has no conventional constraint and can be selected according to different practical conditions. Finally, two numerical examples are provided to show that the obtained result has less conservatism than some existing ones in the literature.

关键词： stochastic systems time-varying delay markov chain linear matrix inequality (LMI).

On a Class of Generalized Curve Flows for Planar Convex Curves

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Chinese Annals of mathematics,Series B 2021年第3期42卷 367-382页

作者： Huaqiao liU li ma School of mathematics and Statistics Henan UniversityKaifeng 475004HenanChina School of mathematics and Physics University of Science and Technology BeijingBeijing 100083China Department of mathematics Henan Normal universityXinxiang 453007HenanChina

In this paper,the authors consider a class of generalized curve flow for convex curves in the *** show that either the maximal existence time of the flow is finite and the evolving curve collapses to a round point with the enclosed area of the evolving curve tending to zero,i.e.,limt→T A(t)=0,or the maximal time is infinite,that is,the flow is a global *** the case that the maximal existence time of the flow is finite,they also obtain a convergence theorem for rescaled curves at the maximal time.

关键词： Curve flow Convex curve Longtime existence Convergence

Sound Insulation Performance of Pyramidal Truss Core Cylindrical Sandwich Structure

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Acta Mechanica Solida Sinica 2022年第3期35卷 504-517页

作者： Yu-Zhou Wang li ma Center for Composite materials Harbin Institute of TechnologyHarbin 150080China

Recently,cylindrical structures have been exploited in various fields due to their excellent mechanical *** the increase in the application of cylindrical shell structures,researchers are paying more and more attention to its acoustic performance and sound insulation *** inserting the pyramidal truss lattice into the cylindrical shell structure,a cylindrical sandwich structure is obtained and the sound insulation performance of the structure is *** space-harmonic expansion method and the principle of virtual work are employed to establish a theoretical model for the acoustic analysis of cylindrical sandwich *** vibro-acoustic coupling is taken into account by imposing the velocity continuity condition at the fluid-solid *** sound transmission loss(STL)performance of the structure is examined by establishing both theoretical and finite element ***,the influence of various parameters on sound transmission loss is researched and analyzed.

关键词： Cylindrical sandwich structure Pyramidal truss core Sound transmission loss(STL) Vibro-acoustic coupling

Injectivity radius bound of Ricci flow with positive Ricci curvature and applications

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Frontiers of mathematics in China 2013年第5期8卷 1129-1137页

作者： li ma Anqiang ZHU Zhongyuan Institute of mathematics and Department of mathematics Henan Normal University Xinxiang 453007 China Department of mathematics Wuhan University Wuhan 430072 China

We study the injectivity radius bound for 3-d Ricci flow with bounded curvature. As applications, we show the long time existence of the Ricci flow with positive Ricci curvature and with curvature decay condition at i... 详细信息

关键词： Injectivity radius bound Ricci flow positive Ricci curvature global solution

Distributed Reduced-order Optimal Fusion Kalman Filters for Stochastic Singular Systems

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自动化学报 2006年第2期32卷 286-290页

作者： SUN Shu-li ma Jing Department of Automation Heilongjiang University Harbin 150080

Based on the optimal fusion algorithm weighted by matrices in the linear minimum variance (LMV) sense, a distributed full-order optimal fusion Kalman filter (DFFKF) is given for discrete-time stochastic singular systems with multiple sensors, which involves the inverse of a high-dimension matrix to compute matrix weights. To reduce the computational burden, a distributed reduced-order fusion Kalman filter (DRFKF) is presented, which involves in parallel the inverses of two relatively low-dimension matrices to compute matrix weights. A simulation example shows the effectiveness.

关键词：多传感器信息融合 Kalman滤波随机奇异系统

Multi-sensor control for precise assembly of optical components

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Chinese Journal of Aeronautics 2014年第3期27卷 613-621页

作者： ma li Rong Weibin Sun lining School of Mechatronic Engineering and Automation Shanghai University State Key Laboratory of Robotics and System Harbin Institute of Technology

In order to perform an optical assembly accurately, a multi-sensor control strategy is developed which includes an attitude measurement system, a vision system, a loss measurement system and a force sensor. A 3-DOF attitude measuring method using linear variable differential transformers （LVDT） is designed to adjust the relation of position and attitude between the spher- ical mirror and the resonator. A micro vision feedback system is set up to extract the light beam and the diaphragm, which can achieve the coarse positioning of the spherical mirror in the optical assembly process. A rapid self-correlation method is presented to analyze the spectrum signal for the fine positioning. In order to prevent the damage of the optical components and realize sealing of the resonator, a hybrid force-position control is constructed to control the contact force of the optical components. The experimental results show that the proposed multi-sensor control strategy succeeds in accomplishing the precise assembly of the optical components, which consists of parallel adjustment, macro coarse adjustment, macro approach, micro fine adjustment, micro approach and optical contact. Therefore, the results validate the multi-sensor control strategy.

关键词： Assembly Attitude measurement Force control Multi-sensor Vision

Study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam

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Science China(Technological Sciences) 2018年第9期61卷 1404-1416页

作者： YAO MingHui ma li ZHANG Wei Beijing Key Laboratory of Nonlinear Vibrations and Strength of Mechanical Structures College of Mechanical EngineeringBeijing University of Technology

In this paper, a simplified model of the bistable piezoelectric cantilever beam with magnets is established, and the potential energy of the bistable system is analyzed. We have proposed the bistable L-shaped beam structure, which has the same geometry dimensions of the bistable straight beam in the first time. The comparative study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam plays an important role in exploring excellent piezoelectric *** experiment structure includes the base layer and the piezoelectric layer. The harmonic excitation is given to the *** analysis results show that the potential energy function of the system has two obvious steady potential wells. In addition, the depth of the upper potential well is different from that of the lower potential well when the gravity potential energy is considered. Experimental results demonstrate that the power generation for the straight beam is better than that of the horizontally placed L-shaped beam when the excitation amplitude is 450 m V. There is the existence that the energy harvesting capacity of the bistable L-shaped beam is better than that of the bistable straight beam when the excitation amplitude is 400 m ***, the power generation of the bistable L-shaped beam with the upper potential well is obviously better than that of the bistable L-shaped beam with the lower potential well. In addition, comparing with the straight beam, the dynamic response of the bistable L-shaped beam is more complex when the external excitation frequency is changed. It is also observed that the distance between the magnets has the obvious influence on the dynamic response of the bistable system. It is very effective to select the appropriate distance between the magnets to improve the power generation of the bistable energy harvester under the fixed excitation conditions.

关键词： bistable straight beam bistable L-shaped beam power generation dynamic response