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New computation method for average dwell time of general switched systems and positive switched systems

IET CONTROL THEORY AND APPLICATIONS 2018年第16期12卷 2263-2268页

作者： Zhang, Junfeng Li, Miao Zhang, Ridong Hangzhou Dianzi Univ Sch Automat Hangzhou 310018 Zhejiang Peoples R China

Average dwell time (ADT) of switched systems is dependent on two parameters: the decay coefficient of the subsystems and the increase coefficient of the Lyapunov functions of different subsystems, namely,. and mu, respectively. In the literature, the two parameters are prescribed because popular computation techniques cannot deal with bilinear conditions easily. A new method for the computation of ADT is presented in this study, where a suggested optimisation algorithm is proposed to obtain a loose ADT condition. The advantages of the method lie in twofold: (i) the parameters. and mu do not need to be given, and (ii) the presented ADT conditions are tractable to solve. The method is also extended to mode- dependent ADT (MDADT), ADT in asynchronous control, and ADT and MDADT of positive switched systems.

关键词： switching systems (control) Lyapunov methods optimisation computation method average dwell time loose ADT condition general switched systems positive switched systems subsystems decay coefficient Lyapunov functions increase coefficient optimisation algorithm mode-dependent ADT asynchronous control MDADT switching signal

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A Novel computation method for Line-Line Topological Relations Based on Conformal Geometric Algebra 23

A Novel Computation Method for Line-Line Topological Relatio...

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23rd International Conference on Geoinformatics (Geoinformatics)

作者： Jiang, Baode Xie, Zhong Wu, Liang Chen, Zhanlong China Univ Geosci Natl Engn Res Ctr Geog Informat Syst Wuhan Peoples R China China Univ Geosci Fac Informat Engn Wuhan Peoples R China

ISBN: (纸本)9781467376631

Topological relations computation is an important component of spatial analysis and reasoning. In the framework of Euclidean space, topological relations computation is mainly based on computational geometry methods, and it is hard to unify the computation for spatial objects of different dims. But with the birth of conformal geometric algebra (eGA), on one hand, classical geometry can be unified to a simple homogeneous algebraic framework, and with the concise and general algebraic language of eGA for geometric modeling, the classical geometry objects can be simply unified represented by the novel eGA. On the other hand, with the eGA providing fast and robust algebraic processing method for the geometric calculation, it is very easy for classical geometry's computation. This paper aims to provide a novel computation method for line-line topological relations based on eGA. It can be divided into the following two steps. First, using eGA to represent the classical geometry of line. Second, using eGA to calculate line-line topological relations. The computing process shows that the eGA can simplify the computation of line-line topological relations, and the calculation is robust and effective.

关键词： topological relation conformal geometric algebra computation method Geographic Information System (GIS)

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Energy-preserving matrix perturbation theory for coupling dynamic analysis of flexible structures

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COMPUTERS & STRUCTURES 2024年 305卷

作者： Fei, Han Lei, Wu Li, Shiyang Deng, Zichen Fa, Wu Northwestern Polytech Univ Sch Mech Civil Engn & Architecture Xian 710129 Peoples R China Northwestern Polytech Univ Shenzhen Res & Dev Inst Sanhang Sci &Technol Bldg45th Gaoxin South 9th Rd Shenzhen 518063 Peoples R China

Aiming at the reanalysis problem of time-varying eigenvalues of force-shape coupled systems, this paper proposes an energy-preserving matrix perturbation theory (EPMPT) that can maintain the essential physical properties of the system. The classical matrix perturbation method, which employs interpolated shape functions, fails to evaluate and address solution errors promptly during the continuous perturbation process. This limitation has led to the theoretical issue of "eigenvalue drift", a flaw that has persisted in the original method since its introduction 40 years ago. In contrast, the presented method uses the dynamic stiffness method to obtain the system eigenvalues and eigenvectors at one time, and provides a perturbation solution to the time-varying eigenvalue problem. Further combined with the J count test technology in the Wittrick-Williams algorithm, an energy-preserving method that can "self-check and self-correct" the solution was developed. The idea that "continuous perturbation should maintain force-shape dynamic self-consistency in the frequency domain" is proposed, and avoiding the energy dispersion and resulting distortion problems caused by long-term numerical simulation. To illustrate the advantage of the EPMPT, a thermally induced vibration of an aerospace structure including force-shape coupling effect, and the vibration of a flexible space solar power arrays including rigid- flexible coupling effect are investigated. Case studied elucidates that EPMPT possesses the capability to notably enhance the computational efficiency associated with generalized eigenvalue and response reanalysis problems. When juxtaposed against conventional step-by-step integration methods, EPMPT has been found to augment computational efficiency by a margin of at least 70 %, and in some instances, up to 90 %.

关键词： computation method Energy-preserving method Dynamic stiffness method Thermal induced vibration Time-varying system

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Motor Magnetic Field Analysis Using the Alpha Finite Element method (αFEM)

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INTERNATIONAL JOURNAL OF computationAL methodS 2025年

作者： Peng, M. D. Zhang, G. Y. He, Z. C. Huang, Y. Y. Gao, H. Hunan Univ State Key Lab Adv Design & Mfg Technol Vehicle Changsha Peoples R China Tech Ctr SAIC GM Wuling Automobile Co Ltd Shanghai Peoples R China Liuzhou Wuling New Energy Vehicle Co Ltd Liuzhou Guangxi Peoples R China

This paper delves into the application of the alpha finite element method (alpha FEM) in the simulation of electromagnetic fields within electric machines, with a particular focus on permanent magnet synchronous motors. Electromagnetic simulation analysis based on the finite element method (FEM) has become a critical tool for the design and optimization of electric machines. Traditional FEM, which employ linear triangular elements, often encounter challenges regarding computational accuracy and efficiency in complex electromagnetic scenarios. alpha FEM, a variant within the smooth finite element method (S-FEM) family, enhances the capabilities of conventional FEM by scaling physical coordinates or strain gradients in the Jacobian matrix with an adjustable factor "alpha." This modification yields more precise numerical solutions, rendering alpha FEM particularly effective in dynamic problems such as vibration, acoustics, and plate analysis. Widely acknowledged for its stability and convergence properties, alpha FEM is utilized in this study to analyze computational performance in simulating the electromagnetic fields of motor. Numerical examples presented confirm that alpha FEM achieves higher computational accuracy with the same mesh model compared to conventional FEM.

关键词： computation method alpha finite element method (alpha FEM) permanent magnet synchronous motor electromagnetic field

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Theoretical analysis of structural stability and allied properties of new brittle perovskites: RbTaO3 and RbNbO3

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INDIAN JOURNAL OF PHYSICS 2023年第7期97卷 2061-2076页

作者： Sarwan, M. Singh, S. Govt Coll Harrai Dept Phys Chhindwara 480224 MP India Barkatullah Univ Bhopal Dept Phys Bhopal 462026 MP India

The structural, electronic, elastic and thermodynamic properties of cubic Rb-based perovskite materials RbTaO3 and RbNbO3 have been explored. All these properties are studied by means of the FP-LAPW method employed in density functional theory. To predict the structural stability, we have employed GGA schemes and concluded that both materials are more stable with the least energy. The ground-state properties like lattice parameter, unit cell volume, bulk modulus and pressure derivative of bulk modulus are computed, and it is verified that our GGA lattice parameters are well-matched with available experimental lattice parameters. Band structures of both materials predict the indirect bandgap of 2.19 and 1.6 eV for RbTaO3 and RbNbO3 respectively, promoting their semiconductor nature. The band gap calculations under different pressures manifest a surge in band gaps with pressure. The bonding nature is also estimated by the density of states and charge density plots. Charge density plots confirm the ionic as well as covalent bonding amid Rb-O and Ta/Nb-O atoms. The high-pressure behaviour of elastic properties is also investigated by analysing various elastic parameters. The large hardness and stiffness of these materials, at high pressure, are also observed which make them modest materials for the fabrication of hard devices/instruments. The Pugh ratio, Poisson's ratio and Cauchy relation approve the brittle behaviour of both compounds. The anisotropic nature of these materials has been observed at zero pressure and at high pressure as well. The detailed analysis of diverse thermodynamic quantities has also been conducted under high pressure and temperature. All these investigated properties are reported for the first time for RbTaO3, and very few data are available for RbNbO3 that are in fair compromise with present results.

关键词： Semiconductor computation method Electronic properties Thermodynamic properties Perovskite materials

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Calibration method for an extended depth-of-field microscopic structured light system

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OPTICS EXPRESS 2022年第1期30卷 166-178页

作者： Chen, Liming Hu, Xiaowei Zhang, Song Purdue Univ Sch Mech Engn W Lafayette IN 47907 USA Tsinghua Univ Dept Elect Engn Beijing 100084 Peoples R China

This paper presents a calibration method for a microscopic structured light system with an extended depth of field (DOF). We first employed the focal sweep technique to achieve large enough depth measurement range, and then developed a computational framework to alleviate the impact of phase errors caused by the standard off-the-shelf calibration target (black circles with a white background). Specifically, we developed a polynomial interpolation algorithm to correct phase errors near the black circles to obtain more accurate phase maps for projector feature points determination. Experimental results indicate that the proposed method can achieve a measurement accuracy of approximately 1.0 mu m for a measurement volume of approximately 2,500 mu m (W) x 2,000 mu m (H) x 500 mu m (D). (c) 2021 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

关键词： computation method Extended depth of field Structured light Systems design Three dimensional measurement Wavefront encoding

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Quantitative evaluation of the severity of wrinkles in carbon fiber composites

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MECHANICS OF ADVANCED MATERIALS AND STRUCTURES 2022年第26期29卷 5596-5607页

作者： Shen, Chuanchuan Ma, Li Wen, Ange Guo, Jing Xu, Ping Zheng, Jinyang Zhejiang Univ Inst Proc Equipment Hangzhou 310027 Peoples R China Zhejiang Univ Technol Inst Appl Mech Hangzhou 310014 Peoples R China Zhejiang Univ Inst Appl Mech Hangzhou Peoples R China

A new method combining three-dimensional digital image correlation (3D-DIC) with a novel numerical framework was proposed to evaluate the severity of wrinkles in composite laminates. In this numerical framework, the micromechanics model of wrinkles based on a two-step homogenization technique was embedded in three-dimensional finite element method (FEM). The influence of waviness ratio (the ratio of wrinkle amplitude to wavelength) and stacking sequence on mechanical behaviors of wrinkled laminates under axial tension load was studied. Numerical results showed that the out-of-plane displacement in the vicinity of wrinkle zones obviously increases by 10%-20%. The simulation was then verified by experimental observations.

关键词： Composite laminate computation method wrinkle defects digital image correlation quantitative evaluation

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Numerical and Experimental Investigation of Bearing Capacity for Compressed Stiffened Composite Panel with Different Stringer Section Geometries

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APPLIED COMPOSITE MATERIALS 2022年第4期29卷 1507-1535页

作者： Zhang, Xiulu Dai, Weibing Cai, Bing Li, Changyou Huang, Wenchao Fang, Caiwen Northeastern Univ Sch Mech Engn & Automat Shenyang Peoples R China Shenyang City Univ Sch Intelligent Syst Engn Shenyang Peoples R China AVIC SAC Commercial Aircraft Co Ltd Shenyang Peoples R China

In this paper, the bearing capacity of the compressed stiffened composite panel with I and T stringer section is detailly-investigated. The finite element simulation is employed to simulate an instability path of the structures with different factors for a series of 54 models. Moreover, the accuracy of the simulation model is verified by the strain assurance criterion (SAC). An engineering approach is proposed to establish constitutive equations and predict the buckling load. The values calculated by analytical solution and finite element simulation are compared with the experimental ones. The results confirm the accuracy of analytical methods. Furthermore, the effect of various cross-section geometries of stringers on the bearing capacity of the composite stiffened panel is investigated. A reasonable distance between stringers is six times the effective skin width. The recommended area ratio delta between the stringer and skin is recommended 3.5:6.5 or 5:5. This study presents a method for designing an optimal stringer and promotes the composite stiffened panel structure's application in civil aviation aircraft.

关键词： Composite material computation method Stiffened panel Different cross-section geometries Experimental validation

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A structural stiffness matrix-based computational mechanics method of epithelial monolayers

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2022年 169卷

作者： Yin, Xu Wang, Bi-Cong Liu, Lei Zhang, Li-Yuan Xu, Guang-Kui Xi An Jiao Tong Univ Sch Aerosp Engn Dept Engn Mech Lab Multiscale Mech & Med SciSVL Xian 710049 Peoples R China China Aerodynam Res & Dev Ctr State Key Lab Aerodynam Mianyang 621000 Sichuan Peoples R China Univ Sci & Technol Beijing Sch Mech Engn Beijing 100083 Peoples R China

Epithelial monolayers are the simplest tissues in multicellular organisms, yet they play a vital role in many physiological processes, including development, growth, and wound healing. During these processes, the epithelia are usually subjected to mechanical cues, and involve multiple scales acting at molecular, cellular, and tissue levels. computational techniques provide a useful and convenient means to investigate biological and mechanical behaviors of cell monolayers. Here, we propose a structural stiffness matrix-based computational method that can accurately and rapidly evaluate the mechanical properties of cell monolayers. By harmoniously calculating spatial movements of cellular positions and changes in cellular shapes over time, the present method holds higher computational efficiency than orthodox vertex model, especially the time ratio of these two methods exceeds an order of magnitude for large-scale cell monolayers. Furthermore, the structural features of cells, neglected in other methods, can be naturally inte-grated in the present approach. Then, this method is employed to examine the effects of cell division direction and molecular and cellular level changes on mechanical behaviors of cell monolayers. Our predictions are in good agreement with a broad range of experiments. The proposed method with high accuracy and efficacy holds great promise for application in simu-lating large-scale biological tissues.

关键词： Epithelial monolayer Vertex model computation method Mechanical behavior Cell division

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Advanced computation methods for soil-structure interaction analysis of structures resting on soft soils

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INTERNATIONAL JOURNAL OF GEOTECHNICAL ENGINEERING 2019年第4期13卷 352-359页

作者： Far, Harry UTS Sch Civil & Environm Engn Ctr Built Infrastruct Ultimo Australia

Adopting the most accurate and realistic modelling technique and computation method for treatment of dynamic soil-structure interaction (SSI) effects in seismic analysis and design of structures resting on soft soil deposits is one of the most discussed and challenging issues in the field of seismic design and requalification of different structures. In this study, a comprehensive critical review has been carried out on available and well-known modelling techniques and computation methods for dynamic SSI analysis. Discussing and comparing the advantages and disadvantages of employing each method, in this study, the most precise and reliable modelling technique as well as computation method have been identified and proposed to be employed in studying dynamic SSI analysis of structures resting on soft soil deposits.

关键词： Dynamic soil-structure interaction seismic analysis and design soft soil deposits modelling technique computation method

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