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Modified micro-mechanics based multiscale model for progressive failure prediction of 2D twill woven composites

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Chinese Journal of Aeronautics 2020年第7期33卷 2070-2087页

作者： Meng WANG Peiwei ZHANG Qingguo fei fei guo Institute of Aerospace Machinery and Dynamics Southeast UniversityNanjing 211189China Department of Engineering Mechanics Southeast UniversityNanjing 211189China

To consider fiber random distribution at the microscale for the multiscale model based on the micro-mechanics failure(MMF)theory,clustering method is used for the extraction of amplification *** the clustering method is a kind of unsupervised machine learning method,the elements with similar mechanical behavior under external loading can be included in a cluster automatically at the *** this modification,the fiber random distribution model can be used for multiscale damage analysis in the framework of MMF *** validate the modified multiscale analysis method,progressive damage analysis of a kind of 2D twill woven composites is conducted based on different microscale *** stress values for microscale models with fiber hexagonal and random distribution patterns are compared *** higher stress concentration is generated in the fiber random distribution model due to the smaller inter-fiber distance especially under longitudinal shear *** obtained cluster distribution results exhibit the characters of the stress distribution in the two microscale ***,tensile and compressive responses of the 2D twill woven composite are predicted with the modified multiscale analysis method and accuracy of the method is verified through comparison with published experimental *** the simulation results,it can be found that the matrix damage initiation from the model based on the fiber random distribution model is premature compared with that from the model based on the fiber hexagonal distribution ***,under tensile loading,the damage all initiates from the fill tows and propagates to the wrap ***,under compressive loading,the matrix damage initiates from the wrap tows in the model based on the fiber random distribution model.

关键词： 2D twill woven composites Clustering analysis Fiber distribution patterns Micro-mechanics failure theory Multiscale damage model

Strain-Rate-Dependent In-Plane Compressive Properties of 3D Fine Weave Pierced C/C Composite:Failure Mechanism and Constitutive Model

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Acta Mechanica Solida Sinica 2022年第1期35卷 63-78页

作者： fei guo Qingguo fei Yanbin LiL Nikhil Gupta Jiangsu Engineering Research Center of Aerospace Machinery Southeast UniversityNanjing 211189China Department of Engineering Mechanics Southeast UniversityNanjing 211189China School of Mechanical Engineering Southeast UniversityNanjing 211189China Composite Materials and Mechanics Laboratory Department of Mechanical and Aerospace EngineeringTandon School of EngineeringNew York UniversityBrooklynNY 11201USA

In-plane compression experiments are performed on 3D fine weave pierced C/C composite at a wide strain rate range of 0.0001/s-1000/*** in-plane compressive failure mechanism of the composite at quasi-static and high strain rates is analyzed by a scanning electron *** results show that the in-plane compressive modulus,maximum stress and the corresponding strain increase with increasing strain *** quasi-static in-plane compressive failure mode of the 3D fine weave pierced C/C composite is characterized by the shear failure at the angle of 45°and the local buckling of the^direction fiber *** comparison,the high strain rate in-plane compression failure mode of the composite is characterized by the compressive fracture of the interlaminar matrix and the progressive compression failure of the a>direction fiber bundles.A strain-rate-dependent in-plane compressive constitutive model is proposed to predict the dynamic in-plane compressive response of the *** proposed constitutive model is verified by experimental data.

关键词： C/C composite Compression Failure mechanism Constitutive model

Multiplicity of Periodic Solutions for Second Order Hamiltonian Systems with Asymptotically Quadratic Conditions

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Acta Mathematica Sinica,English Series 2020年第1期36卷 55-65页

作者： Peng LIU fei guo School of Mathematics Tianjin University

A class of second order non-autonomous Hamiltonian systems with asymptotically quadratic conditions is considered in this *** Fountain Theorem,one multiplicity result of periodic solutions is obtained,which improves s... 详细信息

关键词： Second order Hamiltonian systems asymptotically quadratic conditions Fountain Theorem periodic solution multiplicity

Multiplicity of Homoclinic Solutions for Second Order Hamiltonian Systems with Local Conditions at the Origin

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Acta Mathematica Sinica,English Series 2022年第4期38卷 735-744页

作者： Peng LIU fei guo School of Mathematics Tianjin UniversityTianjin 300354P.R.China Tianjin Key Laboratory of Brain-Inspired Intelligence Technology Tianjin 300354P.R.China

In this paper,the multiplicity of homoclinic solutions for second order non-autonomous Hamiltonian systemsü(t)-L(t)u(t)+▽uW(t,u(t))=0 is obtained via a new Symmetric Mountain Pass Lemma established by Kajikiya,where L∈C(R,RN×N)is symmetric but non-periodic,W∈C1(R×RN,R)is locally even in u and only satisfies some growth conditions near u=0,which improves some previous results.

关键词： Second order non-autonomous Hamiltonian systems Homoclinic solutions multiplicity new symmetric mountain pass lemma

String kernels construction and fusion:a survey with bioinformatics application

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Frontiers of Computer Science 2022年第6期16卷 145-158页

作者： Ren QI fei guo Quan ZOU College of Intelligence and Computing Tianjin UniversityTianjin300350China Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengdu610056China Hainan Key Laboratory for Computational Science and Application Hainan Normal UniversityHaikou571158China

The kernel method,especially the kernel-fusion method,is widely used in social networks,computer vision,bioinformatics,and other *** deals effectively with nonlinear classification problems,which can map linearly inseparable biological sequence data from low to high-dimensional space for more accurate differentiation,enabling the use of kernel methods to predict the structure and function of ***,the kernel method is significant in the solution of bioinformatics *** kernels applied in bioinformatics are explained clearly,which can help readers to select proper kernels to distinguish *** biological sequence data occur in practical *** of the use of machine learning methods to obtain knowledge,and how to explore the structure and function of biological methods for theoretical prediction,have always been emphasized in *** kernel method has gradually become an important learning algorithm that is widely used in gene expression and biological sequence *** review focuses on the requirements of classification tasks of biological sequence *** studies kernel methods and optimization algorithms,including methods of constructing kernel matrices based on the characteristics of biological sequences and kernel fusion methods existing in a multiple kernel learning framework.

关键词： multiple kernel learning kernel fusion methods support vector machines biological sequences analysis

Multiplicity of Periodic Bouncing Solutions for Sublinear Damped Variation Systems via Nonsmooth Variational Methods

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Acta Mathematica Sinica,English Series 2023年第7期39卷 1332-1350页

作者： Si Qi WANG fei guo School of Mathematics Tianjin UniversityTianjin 300354China Tianjin Key Laboratory of Brain-Inspired Intelligence Technology Tianjin 300354China

Two results about the multiplicity of nontrivial periodic bouncing solutions for sublinear damped vibration systems-x=g(t)x+f(t,x) are obtained via the Generalized Nonsmooth Saddle Point Theorem and a technique established by Wu Xian and Wang *** of them imply the condition "f≥0" required in some previous papers can be weakened,furthermore,one of them also implies the condition about ■F(t,x)/■t required in some previous papers,such as "|■F(t,x)/■t|=σ_(0)F(t,x)" and "|■F(t,x)/■t|≤C(1+F(t,x))", is unnecessary,where F(t,x):=∫_(0)~xf(t,x)ds,and σ_(0),C are positive constants.

关键词： Damped vibration systems generalized Nonsmooth Saddle Point Theorem sublinear conditions periodic bouncing solutions multiplicity

Homoclinic Solutions for a Class of Perturbed Fractional Hamiltonian Systems with Subquadratic Conditions

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Acta Mathematica Sinica,English Series 2024年第5期40卷 1177-1196页

作者： Ying LUO fei guo Yan LIU School of Mathematics Tianjin UniversityTianjin 300354P.R.China Tianjin Key Laboratory of Brain-Inspired Intelligence Technology Tianjin300354P.R.China

In this paper,we consider the following perturbed fractional Hamiltonian systems{tD_(∞)^(α)(_(-∞)D_(t)^(α)u(t))+L(t)u(t)=■_(u)W(t,u(t))+■(u)G(t,u(t)),t∈R,u∈H^(α)(R,R^(N)),whereα∈(1/2,1],L∈C(R,R^(N×N))is symmetric and not necessarily required to be positive definite,W∈C1(R×R^(N,R))is locally subquadratic and locally even near the origin,and perturbed term G∈C1(R×R^(N,R))maybe has no parity in *** the perturbed method improved by the authors,a sequence of nontrivial homo clinic solutions is obtained,which generalizes previous results.

关键词： Perturbed fractional Hamiltonian systems subquadratic condition perturbed method homoclinic solutions multiplicity

Secure Power and Subcarrier Auction in Uplink FullDuplex Cellular Networks

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China Communications 2015年第S1期12卷 157-165页

作者： LI Mingliang guo Yunfei HUANG Kaizhi guo fei National Digital Switching System Engineering & Technological R&D Center

We consider a cellular network with a full-duplex base station, multiple uplink users and an eavesdropper. The full-duplex base station transmits jamming signals to degrade the eavesdropper channel when receiving secure multi-user signals. To maximize the secrecy rate of uplink communications, we propose a distributed ascending-clock auction(ACA) algorithm to allocate subcarriers and jamming power. Specifically, the impact of the self-interference of the full-duplex base station on the secrecy rate is considered. The proposed algorithm consists of two parts. Firstly, subcarriers and the jamming power are respectively priced by the base station. Secondly, users select the subcarrier and the jamming power based on the price. Moreover, the convergence of the proposed auction algorithm is mathematically proved. Simulation results show that the proposed auction algorithm is more beneficial to improve the uplink secrecy performance compared to traditional auction algorithms.

关键词： uplink auction physical layer security full-duplex self-interference

A Closed-Loop Dynamic Controller for Active Vibration Isolation Working on A Parallel Wheel-Legged Robot

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Chinese Journal of Mechanical Engineering 2023年第3期36卷 147-160页

作者： fei guo Shoukun Wang Daohe Liu Junzheng Wang School of Automation Beijing Institute of TechnologyBeijing 100081China National Key Laboratory of Human Factors Engineering China Astronaut Research and Training CenterBeijing 100094China China State Shipbuilding Corporation Systems Engineering Research Institute Beijing 100048China

Serving the Stewart mechanism as a wheel-legged structure,the most outstanding superiority of the proposed wheel-legged hybrid robot(WLHR)is the active vibration isolation function during rolling on rugged ***,it is difficult to obtain its precise dynamic model,because of the nonlinearity and uncertainty of the heavy *** paper presents a dynamic control framework with a decentralized structure for single wheel-leg,position tracking based on model predictive control(MPC)and adaptive impedance module from inside to *** the Newton-Euler dynamic model of the Stewart mechanism,the controller first creates a predictive model by combining Newton-Raphson iteration of forward kinematic and inverse kinematic calculation of *** actuating force naturally enables each strut to stretch and retract,thereby realizing six degrees-of-freedom(6-DOFs)position-tracking for Stewart *** adaptive impedance control in the outermost loop adjusts environmental impedance parameters by current position and force feedback of wheel-leg along *** adjustment allows the robot to adequately control the desired support force tracking,isolating the robot body from vibration that is generated from unknown *** availability of the proposed control methodology on a physical prototype is demonstrated by tracking a Bezier curve and active vibration isolation while the robot is rolling on decelerate *** comparing the proportional and integral(PI)and constant impedance controllers,better performance of the proposed algorithm was operated and evaluated through displacement and force sensors internally-installed in each cylinder,as well as an inertial measurement unit(IMU)mounted on the robot *** proposed algorithm structure significantly enhances the control accuracy and vibration isolation capacity of parallel wheel-legged robot.

关键词： Wheel-legged hybrid robot Adaptive impedance control Model predictive control Stewart mechanism Vibration isolation Parallel robot