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An inverse problem of Bilayer textile thickness determination in dynamic heat and moisture transfer

APPLICABLE ANALYSIS 2014年第3期93卷 445-465页

作者： Xu, Dinghua Wen, Lei Xu, Boxi Zhejiang Sci Tech Univ Dept Math Zhejiang 310018 Peoples R China Fudan Univ Coll Math Sci Shanghai 200433 Peoples R China

An inverse problem of bilayer textile thickness determination in dynamic heat and moisture transfer is presented satisfying the heat-moisture comfort level of human body. Heat and mass transfer law in bilayer textiles is displayed by proving the existence and uniqueness of solution to the coupled partial differential equations with initial-boundary value conditions. The finite difference method is employed to derive the numerical solution to partial differential equations. The regularized solution of the inverse problem is reformulated into solving function minimum problem through the Tikhonov regularization method. The golden section method is applied to solve the direct search problem and achieve the optimal solution to the inverse problem. numerical algorithm and its numerical results provide theoretical explanation for textile materials research and development.

关键词： inverse problems of thickness determination numerical algorithm well-posedness partial differential equations of parabolic type bilayer textile materials regularized solution

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Faster and more accurate computation of the field of values boundary for n by n matrices

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LINEAR & MULTILINEAR ALGEBRA 2014年第5期62卷 554-567页

作者： Uhlig, Frank Auburn Univ Dept Math & Stat Auburn AL 36849 USA

We revisit an earlier idea of Marcus and Pesce from 1987 for generating fields of values of by matrices via 2 by 2 matrix compressions and their easily constructed elliptical field of values. This approach is used to reduce the cost of finding the FOV boundary curve of a matrix and makes it more accurate at the same time. The new algorithm succeeds by using fewer eigenanalyses and constructing 2 by 2 matrix compression ellipses of for approximating instead of only eigenanalyses. An application to verify a counterexample to the Zemanek Conjecture for companion matrices of monic polynomials and their normalized derivatives in and , respectively, in dimension 4 is given.

关键词： MATLAB code numerical algorithm matrix compression numerical range matrix pencil extreme eigenvalues field of values ellipse

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Efficient simulation of the Schrodinger equation with a piecewise constant positive potential

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MATHEMATICS AND COMPUTERS IN SIMULATION 2019年 166卷 315-323页

作者： Yang, Xuxin Rasila, Antti Sottinen, Tommi Hunan First Normal Univ Dept Math Changsha 410205 Hunan Peoples R China Guangdong Technion Israel Inst Technol Coll Sci 241 Daxue Rd Shantou 515063 Guangdong Peoples R China Univ Vaasa Sch Technol & Innovat POB 700 FIN-65101 Vaasa Finland

We introduce a new method for the Monte Carlo simulation of a weak solution of the Schrodinger-type equation where the potential is piecewise constant and positive. The method, called the killing walk-on-spheres algorithm, combines the classical walk-on-spheres algorithm with killing that can be determined by using panharmonic measures. This paper continues our earlier work in which simulation of the solutions of the Yukawa and the Helmholtz partial differential equations were developed. (C) 2019 International Association for Mathematics and Computers in Simulation (IMACS). Published by Elsevier B.V. All rights reserved.

关键词： Brownian motion Killing walk-on-spheres Harmonic measure numerical algorithm Yukawa equation Schrodinger equation

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The finite element method for computing the stationary distribution of an SRBM in a hypercube with applications to finite buffer queueing networks

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QUEUEING SYSTEMS 2002年第1期42卷 33-62页

作者： Shen, XY Chen, H Dai, JG Dai, WY Univ British Columbia Fac Commerce & Business Adm Vancouver BC Canada Georgia Inst Technol Sch Ind & Syst Engn Atlanta GA 30332 USA Georgia Inst Technol Sch Math Atlanta GA 30332 USA Nanjing Univ Dept Math Nanjing 210008 Peoples R China

This paper proposes an algorithm, referred to as BNAfm (Brownian network analyzer with finite element method), for computing the stationary distribution of a semimartingale reflecting Brownian motion (SRBM) in a hypercube. The SRBM serves as an approximate model of queueing networks with finite buffers. Our BNAfm algorithm is based on the finite element method and an extension of a generic algorithm developed by Dai and Harrison [14]. It uses piecewise polynomials to form an approximate subspace of an infinite-dimensional functional space. The BNAfm algorithm is shown to produce good estimates for stationary probabilities, in addition to stationary moments. This is in contrast to the BNAsm algorithm (Brownian network analyzer with spectral method) of Dai and Harrison [14], which uses global polynomials to form the approximate subspace and which sometimes fails to produce meaningful estimates of these stationary probabilities. Extensive computational experiences from our implementation are reported, which may be useful for future numerical research on SRBMs. A three-station tandem network with finite buffers is presented to illustrate the effectiveness of the Brownian approximation model and our BNAfm algorithm.

关键词： Brownian approximation heavy traffic semimartingale reflecting Brownian motion stationary distribution performance analysis queueing networks finite buffer finite element method BNAfm BNAsm basic adjoint relationship numerical algorithm

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Online modeling of environmental constraint region for complex-shaped parts assembly

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ASSEMBLY AUTOMATION 2022年第6期42卷 881-890页

作者： Gan, Shuai Liu, Yang Chen, Ziyu Univ Sci & Technol Beijing Sch Mech Engn Beijing Peoples R China Chinese Acad Sci Inst Automat Beijing Peoples R China

PurposeThe paper aims to propose a method to build environmental constraint region online in complex-shaped peg-in-hole assembly tasks. Design/methodology/approachCompared with conventional way which using computer-aided design (CAD) models of assembly parts to construct the environmental constraint region offline, the paper provides an online approach that consists of three aspects: modeling assembly parts through visual recognition, decomposing complex shapes into multiple primitive convex shapes and a numerical algorithm to simulate the peg-in-hole insertion contact. Besides, a contrast experiment is performed to validate the feasibility and effectiveness of the method. FindingsThe experiment result indicates that online construction takes less time than the offline way under the same task conditions. Furthermore, due to the CAD models of the parts are not required to be known, the method proposed in the paper has a broader application in most assembly scenarios. Originality/valueWith the improvement of customization and complexity of manufactured parts, the assembly of complex-shaped parts has drawn greater attention of many researchers. The assembly methods based on attractive region in environment (ARIE) have shown great performance to achieve high-precision manipulation with low-precision systems. The construction of environmental constraint region serves as an essential part of ARIE-based theory, directly affect the formulation and application of assembly strategies.

关键词： numerical algorithm Environmental constraint region Online modeling Configuration decomposition

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Two-dimensional shifted Legendre polynomials operational matrix method for solving the two-dimensional integral equations of fractional order

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APPLIED MATHEMATICS AND COMPUTATION 2018年 322卷 40-54页

作者： Hesameddini, Esmail Shahbazi, Mehdi Shiraz Univ Technol Dept Math Sci POB 71555-313 Shiraz Iran

This work approximates the unknown functions based on the two-dimensional shifted Legendre polynomials operational matrix method (2D-SLPOM) for the numerical solution of two-dimensional fractional integral equations. The present method reduces these equations to a system of algebraic equations and then this system will be solved numerically by Newton's method. Moreover, an estimation of the error bound for this algorithm will be shown by preparing some theorems. Some examples are presented to demonstrate the validity and applicability of the proposed method with respect to the two-dimensional block pulse functions method (2D-BPFs) and two-dimensional Bernstein polynomials operational matrix method (2D-BPOM). (C) 2017 Elsevier Inc. All rights reserved.

关键词： Two-dimensional shifted Legendre polynomials Two-dimensional fractional integral equations Error estimate numerical algorithm

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Shape optimization of concrete free-form shells considering material damage

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ENGINEERING OPTIMIZATION 2022年第12期54卷 1981-1998页

作者： San, Bingbing Feng, Dongming Qiu, Ye Hohai Univ Coll Civil & Transportat Engn Nanjing Peoples R China Southeast Univ Key Lab Concrete & Prestressed Concrete Struct Nanjing Peoples R China

Shape optimization is a pervasive tool for designing concrete free-form shells. However, the existing shape optimization approaches for free-form shells usually assume the material is purely elastic without considering material damage, which may produce undesired results in real-world structural applications, especially in the case of concrete structures. In this article, a framework is presented for performing the shape optimization of concrete free-form shells while considering concrete damage. In the proposed optimization algorithm, the Mazars model is coupled with finite element analysis for modelling structural responses subjected to material damage. Through a series of numerical examples, the proposed algorithm is validated and the effects of material damage on optimal results are investigated. It is demonstrated that the consideration of material damage leads to a more robust design, which highlights the importance of accounting for the material damage during the shape optimization process of concrete free-form shells.

关键词： Free-form shells shape optimization concrete damage numerical algorithm

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Analysis on radiation of antenna mounted on perfectly conducting convex surfaces by using NURBS-UTD method

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IET MICROWAVES ANTENNAS & PROPAGATION 2017年第6期11卷 935-941页

作者： Wang, Nan Dang, Xiaojie Yuan, Haobo Liang, Changhong Xidian Univ Sch Elect Engn Xian 710071 Shaanxi Peoples R China

This paper studies the use of NURBS-UTD method in analyzing radiation of antenna set on perfectly conducting convex surfaces. The electromagnetic ray path is traced by numerical algorithm built from parametric domain in order to take advantage of the mapping definition for parametric surfaces. The presented algorithm can be applied to arbitrary shaped surfaces and provide accurate and stable geometrical parameters to calculation of electromagnetic fields afterwards. The algorithm is verified by cylinder on which analytical solution of ray path is available and good agreement is achieved by comparison. Radiation patterns of antennas mounted on arbitrary shaped surfaces are calculated and compared to commercial software to testify the accuracy and ability of the presented method. Evaluated by RMS error, the deviation between the presented method and commercial software is about 1dB.

关键词： splines (mathematics) antenna radiation patterns geometry monopole antennas nonuniform rational b-spline uniform geometrical theory of diffraction method NURBS-UTD method perfectly conducting convex surfaces electromagnetic ray path EM ray path numerical algorithm arbitrary-shaped surfaces geometrical parameters EM fields antenna radiation patterns commercial software root mean square error ray-tracing algorithm monopole antenna

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Real-Time Torque Control of IPMSM Under Flux Variations

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IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS 2022年第3期10卷 3345-3356页

作者： Kim, Hyeon-Sik Sul, Seung-Ki Gachon Univ Dept Elect Engn Seongnam 13120 South Korea Seoul Natl Univ Dept Elect & Comp Engn Seoul 08826 South Korea

For interior permanent magnet synchronous motor (IPMSM) drives, accurate torque control and loss-minimizing operation are essential issues to keep up the excellent features of IPMSM. However, flux linkage variations owing to various operating conditions make it challenging to maintain their efficiency at the highest level during overall operating conditions. In this article, a real-time torque control is proposed to satisfy both torque control accuracy and high-efficiency operation in consideration of flux linkage variations. First, torque control under the minimum copper loss is modeled as a constrained optimization problem to satisfy both torque reference tracking and loss-minimizing operation in both maximum torque per ampere (MTPA) and flux-weakening regions. Current references are calculated through robust numerical and region identification algorithms in a command optimizer. Moreover, both stator flux linkages and dynamic inductances are estimated to reflect the flux variations in real time, which are the parts of a parameter estimator. The proposed estimators are designed to extract the fundamental flux linkages and their variations while maintaining high dynamic performance. The performance of the proposed methods is verified by the simulation and experimental results where premade lookup tables are not utilized at all.

关键词： Couplings Torque control Torque Mathematical model Real-time systems Heuristic algorithms Vehicle dynamics Command optimizer dynamic inductance estimator flux linkage variations flux observer interior permanent magnet synchronous motor (IPMSM) minimum copper-loss operation numerical algorithm torque control

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Incremental transmission loss allocation under pool dispatch

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IEEE TRANSACTIONS ON POWER SYSTEMS 2002年第1期17卷 26-33页

作者： Galiana, FD Conejo, AJ Kockar, I McGill Univ Dept Elect & Comp Engn Montreal PQ Canada Univ Castilla La Mancha Dept Elect Engn La Mancha Spain McGill Univ Dept Elect & Comp Engn Montreal PQ Canada

Incremental transmission loss analysis has been used for decades, but recent interest in its application to loss allocation calls for new in-depth results. This paper demonstrates that, for incremental methods to be applied correctly in loss allocation, it is first necessary to specify the load distribution and loss supply strategies. Incremental loss allocation among bus power injections is shown to be arbitrary and, therefore, open to challenge as discriminatory. Loss allocation is possible among incremental loads and/or generators, but the proportion of the total losses assigned to either one is arbitrary. Unique, nonarbitrary incremental loss allocations are however possible among the "equivalent" incremental bilateral exchanges between generators and loads. From these basic components it is possible then to calculate the allocation among generators or loads in any specified proportion. The main results, although developed initially for small increments, are extended to large variations. Finally, a general incremental loss allocation algorithm is developed and tested.

关键词： equivalent bilateral contracts incremental transmission loss analysis loss allocation loss supply numerical algorithm pool dispatch

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