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Article
Publication date: 1 September 2005

Bernd Flemisch, Barbara Wohlmuth, Francesca Rapetti and Yvon Maday

We present a method for the simulation of the dynamical behavior of a coupled magneto‐mechanical system given in terms of a conductor moving through an electromagnetic field.

257

Abstract

Purpose

We present a method for the simulation of the dynamical behavior of a coupled magneto‐mechanical system given in terms of a conductor moving through an electromagnetic field.

Design/methodology/approach

For the magnetic part, we consider a model based on an electric vector and a magnetic scalar potential, whereas the mechanical part is modelled by the equation of a rigid body motion. A weak coupling is employed: at each time step the resulting forces are calculated yielding the new displacement of the conductor.

Findings

Numerical results are given for the simulation of an electromagnetic brake with axisymmetric geometry. They indicate that the proposed method is especially well suited for eddy current problems involving moving conductors.

Research limitations/implications

Further research should be undertaken toward the application of the proposed method to real 3D problems.

Originality/value

The spatial discretization of the problem relies on the use of two independent triangulations to approximate the two involved potentials. Whereas the scalar magnetic potential is discretized by means of nodal H1‐conforming finite elements on a grid covering the global computational domain, the vector electric potential is approximated by Hcurl‐conforming edge elements on another grid only covering the conductor. The coupling between the two grids is accomplished via the mortar finite element method. At each time step, only the coupling matrix has to be reassembled, all other involved matrices remain the same. Moreover, no remeshing is necessary when the conductor changes its position. The paper should be valuable for any researcher interested in the numerical simulation of eddy current problems.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 April 1991

K. Horio and H. Yanai

I‐V characteristics of GaAs n‐i‐n structures are calculated by considering impact ionization of carriers. Impact ionization at reverse‐biased n‐i junction becomes a cause of steep…

38

Abstract

I‐V characteristics of GaAs n‐i‐n structures are calculated by considering impact ionization of carriers. Impact ionization at reverse‐biased n‐i junction becomes a cause of steep current rise when an acceptor density in the i‐layer is high. It is shown that an optimum acceptor density exists to keep a good isolation. Photoconduction transients of GaAs n‐i‐n structures are also simulated, and are shown to be strongly affected by existence of n‐i junctions.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 10 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 April 1986

Michal Polácek

In the course of development of human communities towards industrially advanced societies of today, there have been changes not only in economic conditions in the majority of…

280

Abstract

In the course of development of human communities towards industrially advanced societies of today, there have been changes not only in economic conditions in the majority of fields of human activity but also in the ways of providing for food, which went hand in hand with changes in living conditions. Large‐scale industrial production has brought about major changes in the way of life of the population. The development of industrial agglomerations results in a growing number of city dwellers, most of whom have no chance of producing foodstuffs of their own in kind. The distance between residential and industrial areas has been growing, the number of employed women has risen considerably. These are but a few factors affecting the way of boarding, particularly in households.

Details

The Tourist Review, vol. 41 no. 4
Type: Research Article
ISSN: 0251-3102

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Article
Publication date: 23 January 2025

Weiqiang Tang, Chengbin Wang, Liuwei Shan and Haiyan Gao

This paper aims to solve the uncertainty problem of hypersonic vehicle tracking control; an adaptive terminal sliding mode control (TSMC) method based on extended state observer…

14

Abstract

Purpose

This paper aims to solve the uncertainty problem of hypersonic vehicle tracking control; an adaptive terminal sliding mode control (TSMC) method based on extended state observer (ESO) is proposed. The combination of adaptive techniques, TSMC and ESO offers an effective approach for managing uncertain systems.

Design/methodology/approach

The dynamic model of a hypersonic vehicle is transformed into two control-oriented subsystems. The control system design incorporates an adaptive technique, an ESO and a TSMC. The ESO estimates the primary uncertainties, while the adaptive technique determines the upper limit of secondary uncertainties. These estimates are used for the design of the TSMC law. In addition, the filter is used to generate the reference trajectory to improve the dynamic performance of the system. The stability of the closed-loop system is proved by the Lyapunov stability theory.

Findings

A robust control system for hypersonic vehicles is developed with guaranteed stability and strong adaptability to various uncertainties such as parameter variations, external disturbances and actuator faults. Furthermore, the proposed system demonstrates enhanced dynamic performance compared to observer-based sliding mode control. Specifically, for the velocity and altitude tracking control, the settling time of the proposed sliding mode control is approximately 100 s and 70 s shorter than that of the observer-based sliding mode control, respectively.

Originality/value

Different from the single equivalent treatment, various uncertainties here are classified and treated with different strategies, which improves the disturbance rejection ability of the control system. This ability is of great significance for enhancing the autonomy, adaptability and reliability of hypersonic vehicles in extreme environments.

Details

Aircraft Engineering and Aerospace Technology, vol. 97 no. 2
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 23 August 2024

Wenling Wang and Caiqin Song

The paper aims to study the constraint solutions of the periodic coupled operator matrix equations by the biconjugate residual algorithm. The new algorithm can solve a lot of…

28

Abstract

Purpose

The paper aims to study the constraint solutions of the periodic coupled operator matrix equations by the biconjugate residual algorithm. The new algorithm can solve a lot of constraint solutions including Hamiltonian solutions and symmetric solutions, as special cases. At the end of this paper, the new algorithm is applied to the pole assignment problem.

Design/methodology/approach

When the studied periodic coupled operator matrix equations are consistent, it is proved that constraint solutions can converge to exact solutions. It is demonstrated that the solutions of the equations can be obtained by the new algorithm with any arbitrary initial matrices without rounding error in a finite number of iterative steps. In addition, the least norm-constrained solutions can also be calculated by selecting any initial matrices when the equations of the periodic coupled operator matrix are inconsistent.

Findings

Numerical examples show that compared with some existing algorithms, the proposed method has higher convergence efficiency because less data are used in each iteration and the data is sufficient to complete an update. It not only has the best convergence accuracy but also requires the least running time for iteration, which greatly saves memory space.

Originality/value

Compared with previous algorithms, the main feature of this algorithm is that it can synthesize these equations together to get a coupled operator matrix equation. Although the equation of this paper contains multiple submatrix equations, the algorithm in this paper only needs to use the information of one submatrix equation in the equation of this paper in each iteration so that different constraint solutions of different (coupled) matrix equations can be studied for this class of equations. However, previous articles need to iterate on a specific constraint solution of a matrix equation separately.

Details

Engineering Computations, vol. 41 no. 7
Type: Research Article
ISSN: 0264-4401

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Book part
Publication date: 30 December 2013

Guido Erreygers and Roselinde Kessels

In this chapter we explore different ways to obtain decompositions of rank-dependent indices of socioeconomic inequality of health, such as the Concentration Index. Our focus is…

Abstract

In this chapter we explore different ways to obtain decompositions of rank-dependent indices of socioeconomic inequality of health, such as the Concentration Index. Our focus is on the regression-based type of decomposition. Depending on whether the regression explains the health variable, or the socioeconomic variable, or both, a different decomposition formula is generated. We illustrate the differences using data from the Ethiopia 2011 Demographic and Health Survey (DHS).

Details

Health and Inequality
Type: Book
ISBN: 978-1-78190-553-1

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Book part
Publication date: 21 November 2014

Jiti Gao and Maxwell King

This paper considers a class of parametric models with nonparametric autoregressive errors. A new test is established and studied to deal with the parametric specification of the…

Abstract

This paper considers a class of parametric models with nonparametric autoregressive errors. A new test is established and studied to deal with the parametric specification of the nonparametric autoregressive errors with either stationarity or nonstationarity. Such a test procedure can initially avoid misspecification through the need to parametrically specify the form of the errors. In other words, we estimate the form of the errors and test for stationarity or nonstationarity simultaneously. We establish asymptotic distributions of the proposed test. Both the setting and the results differ from earlier work on testing for unit roots in parametric time series regression. We provide both simulated and real-data examples to show that the proposed nonparametric unit root test works in practice.

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Article
Publication date: 13 September 2017

Marsha B. Keune, Timothy M. Keune and Linda A. Quick

Voluntary changes in accounting principle represent explicit and fundamental decisions by managers to exercise accounting discretion. This paper develops an organizing framework…

192

Abstract

Voluntary changes in accounting principle represent explicit and fundamental decisions by managers to exercise accounting discretion. This paper develops an organizing framework to review prior literature on voluntary changes, provides descriptive insights on contemporary changes, and identifies opportunities for future research on voluntary changes. The voluntary change literature is robust and has examined many questions using data prior to the Sarbanes-Oxley Act of 2002 (SOX). We find that contemporary voluntary changes often vary across the pre-SOX, post-SOX, and post-SFAS No. 154 periods by the materiality of their income effect, issue type, and justifications provided by managers, suggesting that manager use of voluntary changes has evolved over time. Our future research opportunities consider potential determinants of voluntary changes including strategic incentives, environmental conditions, and manager characteristics, as well as the potential direct or moderating role of corporate governance and auditors on manager use of voluntary changes. They also consider user reactions to voluntary changes. By providing insight into both extant voluntary change research and the contemporary use of voluntary changes, our study informs standards setters who grant managers the ability to exercise this form of accounting discretion, as well as researchers who plan to study accounting choice through voluntary changes.

Details

Journal of Accounting Literature, vol. 39 no. 1
Type: Research Article
ISSN: 0737-4607

Keywords

Available. Open Access. Open Access
Article
Publication date: 21 March 2023

Abdelmoumene Djabi

The paper presents a mathematical problem involving quasistatic contact between a thermo-electro-viscoelastic body and a lubricated foundation, where the contact is described…

617

Abstract

Purpose

The paper presents a mathematical problem involving quasistatic contact between a thermo-electro-viscoelastic body and a lubricated foundation, where the contact is described using a version of Coulomb’s law of friction that includes normal damped response conditions and heat exchange with a conductive foundation. The constitutive law for the material is thermo-electro-viscoelastic. The problem is formulated as a system that includes a parabolic equation of the first kind for the temperature, an evolutionary elliptic quasivariational inequality for the displacement and a variational elliptic equality for the electric stress. The author establishes the existence of a unique weak solution to the problem by utilizing classical results for evolutionary quasivariational elliptic inequalities, parabolic differential equations and fixed point arguments.

Design/methodology/approach

The author establishes a variational formulation for the model and proves the existence of a unique weak solution to the problem using classical results for evolutionary quasivariational elliptic inequalities, parabolic difierential equations and fixed point arguments.

Findings

The author proves the existence of a unique weak solution to the problem using classical results for evolutionary quasivariational elliptic inequalities, parabolic difierential equations and fixed point arguments.

Originality/value

The author studies a mathematical problem between a thermo-electro-viscoelastic body and a lubricated foundation using a version of Coulomb’s law of friction including the normal damped response conditions and the heat exchange with a conductive foundation, which is original and requires a good understanding of modeling and mathematical tools.

Details

Arab Journal of Mathematical Sciences, vol. 31 no. 1
Type: Research Article
ISSN: 1319-5166

Keywords

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Article
Publication date: 7 November 2016

Juan Wen, Yinnian He and Xin Zhao

The purpose of this paper is to propose a new stabilized finite volume element method for the Navier-Stokes problem.

93

Abstract

Purpose

The purpose of this paper is to propose a new stabilized finite volume element method for the Navier-Stokes problem.

Design/methodology/approach

This new method is based on the multiscale enrichment and uses the lowest equal order finite element pairs P1/P1.

Findings

The stability and convergence of the optimal order in H1-norm for velocity and L2-norm for pressure are obtained.

Originality/value

Using a dual problem for the Navier-Stokes problem, the convergence of the optimal order in L2-norm for the velocity is obtained. Finally, numerical example confirms the theory analysis and validates the effectiveness of this new method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 8
Type: Research Article
ISSN: 0961-5539

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