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Article
Publication date: 21 May 2021

Zhi Gong and Shiyou Yang

The purpose of this work is to develop a computational paradigm for performance analysis of low-frequency electromagnetic devices containing both magnetic metamaterials…

Abstract

Purpose

The purpose of this work is to develop a computational paradigm for performance analysis of low-frequency electromagnetic devices containing both magnetic metamaterials (MTMs) and natural media.

Design/methodology/approach

A time domain finite element method (TDFEM) is proposed. The electromagnetic properties of the MTMs are modeled by a nonstandard Lorentz model. The time domain governing equation is derived by converting the one from the frequency domain into the time domain based on the Laplace transform and convolution. The backward difference is used for the temporal discretization. An auxiliary variable is introduced to derive the recursive formula.

Findings

The numerical results show good agreements between the time domain solutions and the frequency domain solutions. The error convergence trajectory of the proposed TDFEM conforms to the first-order accuracy.

Originality/value

To the best knowledge of the authors, the presented work is the first one focusing on TDFEMs for low-frequency near fields computations of MTMs. Consequently, the proposed TDFEM greatly benefits the future explorations and performance evaluations of MTM-based near field devices and systems in low-frequency electrical and electronic engineering.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 December 1997

D.J. Wilcox and M. Condon

The paper presents a new method of solving the Telegraphers’ equations, resulting in a transmission‐line model based on natural modes of oscillation. By means of…

Abstract

The paper presents a new method of solving the Telegraphers’ equations, resulting in a transmission‐line model based on natural modes of oscillation. By means of eigenvalue analysis, it is shown how each natural mode can be accessed individually using a linear transformation. Initially, the model is formed in the frequency domain so as to take account of frequency‐dependent parameters and losses, notably arising from skin‐effect in the conducting paths. It is then shown how the frequency‐domain prototype can be transferred into the time domain using third‐order z‐transform approximations of the exact frequency domain representation. An illustrative case confirms that it is possible to effect the transition from the frequency domain to the time domain with minimal loss of accuracy.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 16 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 September 2002

M. Condon

The paper presents a new technique for the transient analysis and simulation of lossy coupled interconnects. The approach is based on identifying natural modes of…

Abstract

The paper presents a new technique for the transient analysis and simulation of lossy coupled interconnects. The approach is based on identifying natural modes of oscillation unlike many other transmission‐line models which are based on travelling waves. The approach follows directly from that previously presented by the author (Wilcox and Condon 1997) for the simulation of a single‐phase coaxial power cable. The technique is readily applicable to modelling coupled interconnects and avoids the time‐consuming convolution of many existing transmission‐line modelling approaches.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 21 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 July 2021

Shuzhen Zhu, Xiaofei Wu, Zhen He and Yining He

The purpose of this paper is to construct a frequency-domain framework to study the asymmetric spillover effects of international economic policy uncertainty on China’s…

Abstract

Purpose

The purpose of this paper is to construct a frequency-domain framework to study the asymmetric spillover effects of international economic policy uncertainty on China’s stock market industry indexes.

Design/methodology/approach

This paper follows the time domain spillover model, asymmetric spillover model and frequency domain spillover model, which not only studies the degree of spillover in time domain but also studies the persistence of spillover effect in frequency domain.

Findings

It is found that China’s economic policy uncertainty plays a dominant role in the spillover effect on the stock market, while the global and US economic policy uncertainty is relatively weak. By decomposing realized volatility into quantified asymmetric risks of “good” volatility and “bad” volatility, it is concluded that economic policy uncertainty has a greater impact on stock downside risk than upside risk. For different time periods, the sensitivity of long-term and short-term spillover economic policy impact is different. Among them, asymmetric high-frequency spillover in the stock market is more easily observed, which provides certain reference significance for the stability of the financial market.

Originality/value

The originality aims at extending the traditional research paradigm of “time domain” to the research perspective of “frequency domain.” This study uses the more advanced models to analyze various factors from the static and dynamic levels, with a view to obtain reliable and robust research conclusions.

Details

Kybernetes, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0368-492X

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Article
Publication date: 3 January 2017

Zhiyong Zeng, Xiaoliang Jin and Rongxiang Zhao

The model for digitally controlled three-phase pulse width modulation (PWM) boost rectifiers is a sampled data model, which is different from the continuous time domain

Abstract

Purpose

The model for digitally controlled three-phase pulse width modulation (PWM) boost rectifiers is a sampled data model, which is different from the continuous time domain models presented in previous studies. The controller, which is tuned according to the model in continuous time domain and discretized by approximation methods, may exhibit some unpredictable performances and even result in unstable systems under some extreme situations. Consequently, a small-signal discrete-time model of digitally controlled three-phase PWM boost rectifier is required. The purpose of this paper is to provide a simple but accurate small-signal discrete-time model of digital controlled three-phase PWM boost rectifier, which explains the effect of the sampling period, modulator and time delays on system dynamic and improves the control performance.

Design/methodology/approach

Based on the Laplace domain analysis and the waveforms of up-down-count modulator, the small signal model of digital pulse width modulation (DPWM) in the Laplace domain is presented. With a combination of state-space average and a discrete-time modeling technique, a simplified large signal discrete time model is developed. With rotation transformation and feed-forward decoupling, the large-signal model is decoupled into a single input single output system with rotation transformation. Then, an integrated small signal model in the Laplace domain is constructed that included the time delay and modulation effect. Implementing the modified z-transform, a small-signal discrete-time model is derived from the integrated small signal model.

Findings

In a digital control system, besides the circuit parameters, the location of pole of open-loop transfer function is also related to system sampling time, affecting the system stability, and the time delay determines the location of the zero of open-loop transfer function, affecting the system dynamic. In addition to the circuit parameters discussed in previous literature, the right half plane (RHP) zero is also determined by the sampling period and the time delay. Furthermore, the corner frequency of the RHP zero is mainly determined by the sampling period.

Originality/value

The model developed in this paper, accounting for the effect of the sampling period, modulator and time delays on the system dynamic, give a sufficient insight into the behavior of the digitally controlled three-phase PWM rectifier. It can also explain the effect of sampling period and control delay time on system dynamic, accurately predict the system stability boundary and determine the oscillation frequency of the current loop in critical stable. The experimental results verify that the model is a simple and accurate control-oriented small-signal discrete-time model for the digitally controlled three-phase PWM boost rectifier.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 3 July 2017

Omar Ramadan

The purpose of this paper is to derive a unified formulation for incorporating different dispersive models into the explicit and implicit finite difference time domain

Abstract

Purpose

The purpose of this paper is to derive a unified formulation for incorporating different dispersive models into the explicit and implicit finite difference time domain (FDTD) simulations.

Design/methodology/approach

In this paper, dispersive integro-differential equation (IDE) FDTD formulation is presented. The resultant IDE is written in the discrete time domain by applying the trapezoidal recursive convolution and central finite differences schemes. In addition, unconditionally stable implicit split-step (SS) FDTD implementation is also discussed.

Findings

It is found that the time step stability limit of the explicit IDE-FDTD formulation maintains the conventional Courant–Friedrichs–Lewy (CFL) constraint but with additional stability limits related to the dispersive model parameters. In addition, the CFL stability limit can be removed by incorporating the implicit SS scheme into the IDE-FDTD formulation, but this is traded for degradation in the accuracy of the formulation.

Research limitations/implications

The stability of the explicit FDTD scheme is bounded not only by the CFL limit but also by additional condition related to the dispersive material parameters. In addition, it is observed that implicit JE-IDE FDTD implementation decreases as the time step exceeds the CFL limit.

Practical implications

Based on the presented formulation, a single dispersive FDTD code can be written for implementing different dispersive models such as Debye, Drude, Lorentz, critical point and the quadratic complex rational function.

Originality/value

The proposed formulation not only unifies the FDTD implementation of the frequently used dispersive models with the minimal storage requirements but also can be incorporated with the implicit SS scheme to remove the CFL time step stability constraint.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 3 May 2013

Przemyslaw Lopato, Tomasz Chady, Ryszard Sikora, Stanislaw Gratkowski and Marcin Ziolkowski

The purpose of this paper is to describe the full‐wave modelling of pulsed terahertz systems utilized in non‐destructive testing.

Abstract

Purpose

The purpose of this paper is to describe the full‐wave modelling of pulsed terahertz systems utilized in non‐destructive testing.

Design/methodology/approach

At the outset, some basic information on the terahertz NDT are outlined and then, general remarks on its numerical modelling are presented. Frequency domain FEM and time domain FDTD analysis is carried out. Finally comparison of computed and measured signals is shown in order to prove numerical analysis correctness.

Findings

It is possible to model in a relatively simple way a terahertz system for nondestructive evaluation of dielectric materials. In contrast to other published work, the entire measuring setup is modelled, including photoconductive antenna with hemispherical lens, focusing lens and evaluated material with exemplary defect.

Originality/value

This paper gives a description of the terahertz non‐destructive testing system with comparison of simulated and measured results.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 32 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 10 July 2021

Tadeusz Sobczyk, Michał Radzik and Jarosław Tulicki

This paper aims to omit the difficulties of directly finding the periodic steady-state solutions for electromagnetic devices described by circuit models.

Abstract

Purpose

This paper aims to omit the difficulties of directly finding the periodic steady-state solutions for electromagnetic devices described by circuit models.

Design/methodology/approach

Determine the discrete integral operator of periodic functions and develop an iterative algorithm determining steady-state solutions by a multiplication of matrices only.

Findings

An alternative method to creating finite-difference relations directly determining steady-state solutions in the time domain.

Research limitations/implications

Reduction of software and hardware requirements for determining steady-states of electromagnetic.

Practical implications

A unified approach for directly finding steady-state solutions for ordinary nonlinear differential equations presented in the normal form.

Originality/value

Eliminate the necessity of solving high-order finite-difference equations for steady-state analysis of electromagnetic devices described by circuit models.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 5 September 2016

Lorenzo Travaglini, Sergio Ricci and Giampiero Bindolino

The purpose of this paper is to describe the development of an integrated framework suitable for preliminary airframe design, called PyPAD (Python module for Preliminary…

Abstract

Purpose

The purpose of this paper is to describe the development of an integrated framework suitable for preliminary airframe design, called PyPAD (Python module for Preliminary Aircraft Design), providing the capability to define models to compute loads and to perform the structural sizing.

Design/methodology/approach

The modules developed until now allow for the definition of multi-fidelity aero-structural models starting from a Common Parametric Aircraft Configuration Schema (CPACS) input file and to compute static loads (trim) and flutter margin with minimum user effort. PyPAD take advantages of Abaqus-CAE, and the main functions are developed in Python, to take advantages of the simplicity in terms of software development and maintenance, but the core routines are developed in Fortran, taking advantages of parallel programming to get the best performances.

Findings

A complete test case, starting from the CPACS input and ending with the definition of structural, aerodynamic and aero-elastic models, with the computation of different design loads, is reported. An example will show that the framework developed is able to handle different problematics of the preliminary projects using quite complex global models.

Practical implications

All the tools developed in the framework, and the ones currently under development, could be a valid help during the preliminary design of a new aircraft, speeding up the iterative process and improving the design solution.

Originality/value

PyPAD is the first framework developed around Abaqus-CAE for the preliminary aircraft design and is one of the few tools looking at the different problematics involved in a preliminary airframe design: design, loads and aero-elasticity, sizing and multi-disciplinary optimization.

Details

Aircraft Engineering and Aerospace Technology, vol. 88 no. 5
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 25 July 2019

Fotios Kasolis and Markus Clemens

This paper aims to develop an automated domain decomposition strategy that is based on the presence of nonlinear field grading material, in the context of model order…

Abstract

Purpose

This paper aims to develop an automated domain decomposition strategy that is based on the presence of nonlinear field grading material, in the context of model order reduction for transient strongly nonlinear electro-quasistatic (EQS) field problems.

Design/methodology/approach

The paper provides convincing empirical insights to support the proposed domain decomposition algorithm, a numerical investigation of the performance of the algorithm for different snapshots and model order reduction experiments.

Findings

The proposed method successfully decomposes the computational domain, while the resulting reduced models are highly accurate. Further, the algorithm is computationally efficient and robust, while it can be embedded in black-box model reduction implementations.

Originality/value

This paper fulfills the demand to effectively perform model order reduction for transient strongly nonlinear EQS field problems.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 38 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

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