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Elliptical fibre dielectric waveguides: a transverse transmission line analysis

IET OPTOELECTRONICS 2020年第1期14卷 1-9页

作者： Boucouvalas, Anthony C. Papageorgiou, Christos Georgantzos, Euripides Univ Peloponnese Dept Informat & Telecommun Arcadia 22100 Greece Natl Tech Univ Athens Dept Elect Engn Iroon Politech 9 Athens 16121 Greece

The authors present a new method for determining the optical properties of arbitrary refractive index elliptical core fibres. The method applies the elliptic cylindrical coordinate system to Maxwell's equations and appropriately, using Fourier Transforms, operated on an elliptical core optical fibre waveguide, derives a flexible algorithm, which can be used to determine the optical properties of elliptical fibre waveguides. By dividing the fibre into a series of uniform consecutive thin dielectric layers transversely across the elliptical cross section with suitable transforming functions representing voltage and current themselves based on the electromagnetic field components, leads to transverse transmission line equations. The resonance frequencies of the cascaded matrices determine the mode propagation constants. The analysis leads to a numerical algorithm for calculating the exact modes of propagation constants. The method is analytically exact and computationally accurate, leading to algorithmic implementation, without making use of Mathieu functions which are solutions for step index waveguide. The advantage of this work is also the fact that it can be applied to arbitrary refractive index profiles. They present results of modal $\bar b - V$b over bar -V diagrams for various fibre ellipticities and also apply this method to determine the birefringence of graded index profile fibres and mode cut-off frequencies.

关键词： Maxwell equations electromagnetic fields optical fibres gradient index optics dielectric waveguides birefringence refractive index uniform consecutive thin dielectric layers elliptical cross section suitable transforming functions transmission line equations mode propagation constants numerical algorithm algorithmic implementation step index waveguide arbitrary refractive index profiles fibre ellipticities graded index profile fibres elliptical fibre dielectric waveguides transverse transmission line analysis optical properties arbitrary refractive index elliptical core fibres elliptic cylindrical coordinate system Maxwell's equations Fourier Transforms elliptical core optical fibre waveguide flexible algorithm elliptical fibre waveguides

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A 3D non-orthogonal plastic damage model for concrete

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COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2020年第0期360卷 112716-000页

作者： Zhou, Xin Lu, Dechun Du, Xiuli Wang, Guosheng Meng, Fanping Beijing Univ Technol Minist Educ Key Lab Urban Secur & Disaster Engn Beijing 100124 Peoples R China

A plastic damage model with the non-orthogonal flow rule is developed, which is consisted of the damage part driven by plastic strain and the plastic part based on effective stress. In the damage characterization, the degeneration law of elastic stiffness is described by the damage variable in the form of exponential function. In the plastic characterization, the evolution for plastic strain increment (PSI) is characterized from the magnitude and direction perspective. The direction of PSI is obtained directly by the fractional gradient of yield surface and the need for the construction of plastic potential function is bypassed. The magnitude of PSI is calculated based on the effective hardening function and the yield function, where the effective hardening function corresponding to the undamaged material is derived by both the normal hardening/softening function corresponding to the damaged material and the damage variable. The Next Increment Corrects Error (NICE) algorithm integrating the computational accuracy and efficiency is used for the numerical implementation of model. The ability of model to capture the complex mechanical behavior of concrete is assessed by the monotonous and cyclic test data from the literature. (C) 2019 Elsevier B.V. All rights reserved.

关键词： Concrete Constitutive model Non-orthogonal flow rule Dilatancy Damage numerical algorithm

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Competition in defensive and offensive advertising strategies in a segmented market

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EUROPEAN JOURNAL OF CONTROL 2020年 53卷 98-108页

作者： Machowska, Dominika Nowakowski, Andrzej Univ Lodz Fac Econ & Sociol Dept Econometr Rewolucji 1905 R 41 PL-90214 Lodz Poland Univ Lodz Fac Math & Comp Sci S Banacha 22 PL-90238 Lodz Poland

We propose the new goodwill model ala Nerlove-Arrow defined on a competitive segmented market. Based on the dual dynamic approach, we give the sufficient condition under which the open-loop equilibrium exists for the new game. We also introduce e-open-loop equilibrium as a basis for the numerical algorithm using a construction of the optimal solution in the finite steps. The numerical algorithm enables an analysis of how the level of the homogeneity of given competitive products and customer recommendations modify optimal goodwill and the total profit of each player. (C) 2019 European Control Association. Published by Elsevier Ltd. All rights reserved.

关键词： Open-loop Nash equilibrium Goodwill Market segmentation Dual dynamic approach numerical algorithm

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Optimized sparse fractional Fourier transform: Principle and performance analysis

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SIGNAL PROCESSING 2020年 174卷 107646-107646页

作者： Zhang, Hongchi Shan, Tao Liu, Shengheng Tao, Ran Beijing Inst Technol Sch Informat & Elect Beijing 100081 Peoples R China Southeast Univ Sch Informat Sci & Engn Nanjing 210096 Peoples R China

For the input signals that can be sparsely represented in the fractional Fourier domain, sparse discrete fractional Fourier transform (SDFrFT) has been proposed to accelerate the numerical computation of discrete fractional Fourier transform. While significantly alleviating the computational load, SDFrFT has narrow applicability since it is more suitable for large-scale input signals. In this regard, the objective of this work is to overcome the limitation and further optimize the numerical computation of SDFrFT by exploiting the underlying phase information. We first employ Neyman-Pearson approach to achieve a noise-robust detection. Then, we derive the probability distribution function of the phase error in the location stage and, accordingly, design a location error correction algorithm. The proposed algorithm, termed optimized sparse fractional Fourier transform (OSFrFT), can reduce the computational complexity while guarantee sufficient robustness and estimation accuracy. Simulation results are provided to validate the effectiveness of the proposed algorithm. A successful application of OSFrFT to continuous wave radar signal processing is also presented. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Fractional Fourier transform Time-frequency analysis Computational complexity Sparse representation numerical algorithm

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A NOVEL METHOD FOR NONLINEAR IMPULSIVE DIFFERENTIAL EQUATIONS IN BROKEN REPRODUCING KERNEL SPACE

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Acta Mathematica Scientia 2020年第3期40卷 723-733页

作者： Liangcai MEI Zhuhai Campus Beijing Institute of TechnologyZhuhai 519088China

In this article,a new algorithm is presented to solve the nonlinear impulsive differential *** the first time,this article combines the reproducing kernel method with the least squares method to solve the second-order nonlinear impulsive differential ***,the uniform convergence of the numerical solution is proved,and the time consuming Schmidt orthogonalization process is *** algorithm is employed successfully on some numerical examples.

关键词： Nonlinear impulsive differential equations Broken reproducing kernel space numerical algorithm

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On algorithmic Coxeter spectral analysis of positive posets

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APPLIED MATHEMATICS AND COMPUTATION 2020年 386卷 125507-125507页

作者： Gasiorek, Marcin Nicolaus Copernicus Univ Fac Math & Comp Sci Ul Chopina 12-18 PL-87100 Torun Poland

Following a general framework of Coxeter spectral analysis of signed graphs Delta and finite posets I introduced by Simson (SIAM J. Discrete Math. 27:827-854, 2013) we present efficient numerical algorithms for the Coxeter spectral study of finite posets I = ({1,..., n}, <= I) that are positive in the sense that the symmetric Gram matrix G(I) := 1/2 (C-I + C-I(tr)) is an element of M-n (Q) is positive definite, where C-I is an element of M-n(Z) is the incidence matrix of I encoding the relation <= I. In the framework of scientific computing we present a complete Coxeter spectral classification of finite positive posets I of size n = vertical bar I vertical bar < 20. It extends one of the main results obtained in Gasiorek et al. (Eur. J. Comb. 48:127-142, 2015) for posets of size n <= 10. We also show that the connectivity of such posets I is determined by the complex Coxeter spectrum specc I subset of C;equivalently, by the Coxeter polynomial cox(I) (t) is an element of Z[t] od I. One of the main results of the paper is a new technique to compute in a polynomial time a Z-invertible matrix B-I is an element of M-n (Z) such that B-I(tr) center dot C-I center dot B-I = G(DI), where. G(D) is an element of M-n (Z) is a nonsymmetric Gram matrix of a simply-laced Dynkin diagram D-I is an element of {A(n), D-n, E-6, E-7, E-8} associated with a finite positive poset I. (c) 2020 Elsevier Inc. All rights reserved.

关键词： positive poset edge-bipartite graph spectral graph theory Dynkin type Coxeter spectrum numerical algorithm

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The validation of a semi-recursive vehicle dynamics model for a real-time simulation

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MECHANISM AND MACHINE THEORY 2020年 151卷 103907-103907页

作者： Pan, Yongjun Xiang, Saidi He, Yansong Zhao, Jian Mikkola, Aki Chongqing Univ Sch Automot Engn State Key Lab Mech Transmiss Chongqing 400044 Peoples R China Dalian Univ Technol Sch Automot Engn State Key Lab Struct Anal Ind Equipment Dalian 116024 Peoples R China Lappeenranta Univ Technol Dept Mech Engn Lappeenranta 53850 Finland

Semi-recursive formulations and their various versions have made it possible to describe complex nonlinear systems such as vehicles precisely while still solving the relevant equations of motion in real time. An optimal combination of an efficient multibody formulation and a fast numerical time integration scheme are needed to accurately simulate complex systems in real time. This paper introduces a double-step semi-recursive multibody formulation and analyzes its performance with high-order numerical time-integration algorithms for real-time simulation. The Runge-Kutta, Gill, Runge-Kutta-Fehlberg, Adams-Bashforth-Moulton, and adaptive time step Runge-Kutta numerical methods are explained and compared. Results are verified against a commercial multibody software solution. A 15-degree-of-freedom sedan vehicle model serves as a benchmark to verify the theoretical results. The results highlight the differences between the numerical algorithms and suggest appropriate approaches for a nonlinear vehicle dynamics model, particularly for cases where simulation times are long. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Real-time simulation Semi-recursive formulation numerical algorithm Vehicle dynamics Benchmark problem

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Stochastic subspace identification based data-driven approach for monitoring electromechanical dynamics from phasor measurement units

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IET GENERATION TRANSMISSION & DISTRIBUTION 2020年第19期14卷 3983-3991页

作者： Jiang, Tao Yuan, Haoyu Zhao, Junbo Wu, Tianying Li, Fangxing Jia, Hongjie Northeast Elect Power Univ Dept Elect Engn Jilin 132012 JL Peoples R China Univ Tennessee Dept Elect Engn & Comp Sci Knoxville TN 37996 USA Mississippi State Univ Dept Elect & Comp Engn Starkville MS 39762 USA Washington State Univ Sch Elect Engn & Comp Sci Pullman WA 99163 USA Tianjin Univ Minist Educ Key Lab Smart Grid Tianjin 300072 Peoples R China

This study proposes to extend the numerical algorithm for subspace state space system identification (N4SID) for power grid electromechanical dynamics monitoring using the multi-channel noisy synchrophasor measurements. The oscillation modes, mode shapes, participation factors and coherent groups are estimated in a comprehensive manner. It consists of five key steps: (i) estimation of power system state subspace model via N4SID;(ii) electromechanical modes discrimination from the trivial modes by developing the generalised inverse and mode assurance criterion;(iii) calculations of the mode shapes using the estimated states and output subspace matrices;(iv) estimation of participation factors estimated by the calculated mode shapes and (v) the generator coherency identification by developing the direction cosine denoted coherency inductor. Test results on the IEEE 16-machine 68-bus test system and the practical China Southern power Grid using field synchrophasor measurements are performed. Comparison results with other existing methods show that the proposed method achieves better accuracy and efficiency for power system electromechanical dynamics monitoring in the presence of measurement noise.

关键词： oscillations phasor measurement eigenvalues and eigenfunctions state-space methods stochastic processes power system transient stability matrix algebra power system stability power system control power system measurement power grids power system electromechanical dynamics measurement noise stochastic subspace identification data-driven approach monitoring electromechanical dynamics phasor measurement units numerical algorithm subspace state space system identification N4SID power grid electromechanical dynamics multichannel noisy synchrophasor measurements oscillation modes participation factors coherent groups comprehensive manner power system state subspace model electromechanical modes discrimination trivial modes generalised inverse mode assurance criterion output subspace matrices calculated mode shapes generator coherency identification direction cosine denoted coherency inductor IEEE 16-machine 68-bus test system practical China Southern power Grid using field synchrophasor measurements

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Research on eddy current losses algorithm in solid rotor of high speed squirrel cage induction motor

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IET ELECTRIC POWER APPLICATIONS 2020年第6期14卷 1023-1029页

作者： Chou, Weixiang Liang, Yanping Gao, Lianlian Wang, Dongmei Harbin Univ Sci & Technol Coll Elect & Elect Engn Harbin Peoples R China

Aiming at the shortcomings of the analytical algorithm and numerical algorithm for calculating the eddy current losses in the solid rotor of high speed squirrel cage induction motor, this study proposes a semi-analytical algorithm. Based on the magnetic field of the rotor surface and Maxwell's equations, the analytical formula of this algorithm is derived. According to the law of energy conservation, the losses in rotor and rotor bars are calculated, respectively, so that the eddy current losses in the solid rotor are calculated indirectly. Taking a high speed squirrel cage induction motor as an example, the eddy current losses in the solid rotor are calculated by the semi-analytical method. The calculation result is verified by the two-dimensional transient finite-element method, and the calculation result meets the basic requirements of engineering practice.

关键词： rotors squirrel cage motors finite element analysis eddy current losses energy conservation magnetic fields Maxwell equations eddy current losses algorithm solid rotor analytical algorithm numerical algorithm semianalytical algorithm rotor surface rotor bars semianalytical method high speed squirrel cage induction motor magnetic field Maxwell equations energy conservation two-dimensional transient finite-element method

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Longitudinal maneuvering motions of the supercavitating vehicle

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EUROPEAN JOURNAL OF MECHANICS B-FLUIDS 2020年 81卷 105-113页

作者： Zou, Wang Wang, Benlong Shanghai Jiao Tong Univ Sch Naval Architecture Ocean & Civil Engn Key Lab Hydrodynam Minist Educ Shanghai 200240 Peoples R China

As the supercavitating flows theory and technology developing, to develop a supercavitating vehicle with maneuverability is a significant trend. In order to achieve this goal, it is prerequisite to establish a dynamics model, reflecting the supercavitating flows' unsteady characteristics and the supercavitating vehicle's dynamics characteristics as much as possible, and an effective control method. The maneuvering supercavity model proposed in our previous work, where the gravity effect model is further improved here, is applied to the vehicle dynamics modeling in the longitudinal motions. Based on the dynamics model, a numerical method that integrates the fourth order Runge-Kutta algorithm with the cavitation number correction algorithm, the exactly feedback linearizing control and the linear quadratic regulator methods is proposed to simulate the level flight, climbing and diving of the vehicle. numerical results confirm that the developed dynamics model and numerical method are effective for the vehicle's maneuvering motions and that the method with control laws is robust to velocity perturbation and trajectory mutation. (C) 2019 Elsevier Masson SAS. All rights reserved.

关键词： Supercavitating vehicle Dynamics model numerical algorithm Maneuvering motion

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