Search results

1 – 10 of 11
Per page
102050
Citations:
Loading...
Access Restricted. View access options
Article
Publication date: 6 March 2009

G. Of, M. Kaltenbacher and O. Steinbach

A wide range of micro‐electro‐mechanical‐systems are based on the electrostatic principle, and for their design the computation of the electric capacities is of great importance…

395

Abstract

Purpose

A wide range of micro‐electro‐mechanical‐systems are based on the electrostatic principle, and for their design the computation of the electric capacities is of great importance. The purpose of this paper is to efficiently compute the capacities as a function of all possible positions of the two electrode structures within the transducer by an enhanced boundary element method (BEM).

Design/methodology/approach

A Galerkin BEM is developed and the arising algebraic system of equations is efficiently solved by a CG‐method with a multilevel preconditioner and an appropriate fast multipole algorithm for the matrix‐vector operations within the CG‐iterations.

Findings

It can be demonstrated that the piecewise linear and discontinuous trial functions give an approximation, which is almost as good as the one of the piecewise constant trial functions on the refined mesh, at lower computational costs and at about the same memory requirements.

Originality/value

The paper can proof mathematically and demonstrate in practice, that a higher order of convergence is achieved by using piecewise linear, globally discontinuous basis functions instead of piecewise constant basis functions. In addition, an appropriate preconditioner (artificial multilevel boundary element preconditioner, which is based on the Bramble Pasciak Xu like preconditioner) has been developed for the fast iterative solution of the algebraic system of equations.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 28 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Access Restricted. View access options
Article
Publication date: 1 January 1991

P. LEE, J.E. PASCIAK and S. PISSANETZKY

In this paper, a parallel preconditioning technique based on the additive variant of overlapping domain decomposition is described and implemented to solve magnetostatic field…

29

Abstract

In this paper, a parallel preconditioning technique based on the additive variant of overlapping domain decomposition is described and implemented to solve magnetostatic field problems. This technique involves covering the domain with a number of overlapping subdomains. The pre‐conditioner results from adding together approximate inversions on the subdomains, Theoretical estimates for the rate of convergence for the resulting algorithm are available and are based on the properties of underlying differential equations. Numerical experiments are given to demonstrate the effectiveness of this algorithm.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 10 no. 1
Type: Research Article
ISSN: 0332-1649

Access Restricted. View access options
Article
Publication date: 1 August 1999

Gh. Juncu

The paper analyses the preconditioning of non‐linear nonsymmetric equations with approximations of the discrete Laplace operator. The test problems are non‐linear 2‐D elliptic…

167

Abstract

The paper analyses the preconditioning of non‐linear nonsymmetric equations with approximations of the discrete Laplace operator. The test problems are non‐linear 2‐D elliptic equations that describe natural convection, Darcy flow, in a porous medium. The standard second order accurate finite difference scheme is used to discretize the models’ equations. The discrete approximations are solved with a double iterative process using the Newton method as outer iteration and the preconditioned generalised conjugate gradient (PGCG) methods as inner iteration. Three PGCG algorithms, CGN, CGS and GMRES, are tested. The preconditioning with discrete Laplace operator approximations consists of replacing the solving of the equation with the preconditioner by a few iterations of an appropriate iterative scheme. Two iterative algorithms are tested: incomplete Cholesky (IC) and multigrid (MG). The numerical results show that MG preconditioning leads to mesh independence. CGS is the most robust algorithm but its efficiency is lower than that of GMRES.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 9 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Access Restricted. View access options
Article
Publication date: 11 February 2021

Vahid Lotfi and Ali Lotfi

Subsequently, the response of idealized Morrow Point arch dam is studied due to stream, vertical and cross-stream ground motions for reservoir bottom/sidewalls conditions of both…

126

Abstract

Purpose

Subsequently, the response of idealized Morrow Point arch dam is studied due to stream, vertical and cross-stream ground motions for reservoir bottom/sidewalls conditions of both fully reflective and absorptive. For each combination, different orders of Hagstrom–Warburton (HW) condition are evaluated from accuracy point of view by comparing them against exact solutions. It should be emphasized that normalized length of reservoir near-field region is taken as a very low value of L/H = 0.2 during this process which makes it a very challenging test for any kind of truncation boundary condition.

Design/methodology/approach

In present study, dynamic analysis of concrete arch dam-reservoir systems is formulated by FE-(FE-TE) approach [i.e. finite element-(finite element-truncation element)]. In this technique, dam and reservoir are discretized by solid and fluid finite elements. Moreover, the HW high-order condition imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model. The formulation is initially explained in details.

Findings

The trend in gaining accuracy with increase in order of HW condition were basically the same for all three types of excitations under both full reflective and absorptive reservoir bottom/sidewalls conditions. The only exception was for cross-stream excitation response which was showing less accurate results near the first major peak for moderate orders of HW (e.g. O3-2) in comparison to what was observed for responses due to symmetric excitations (stream and vertical). This is mainly attributed to the selection of evanescent-type parameters of HW condition which is based on the first symmetric mode of reservoir. However, it is noted that error diminishes even for cross-stream excitation as order increases. High orders of HW condition, such as O5-5 considered herein, generate highly accurate responses for all three possible excitations under both types of full reflective and absorptive reservoir bottom/sidewalls conditions. It is such that responses are hardly distinguishable from corresponding exact responses. This reveals that proposed FE-(FE-TE) analysis technique based on HW condition is quite successful, and one may fully rely on that for accurate and efficient analysis of concrete arch dam-reservoir systems.

Originality/value

Dynamic analysis of concrete arch dam-reservoir system is formulated by new method. HW high-order condition is applied for a very low and challenging reservoir length. Different orders are evaluated against exact solution with excellent agreement. Generalized matrices of truncation element are derived for FEM programmers. The method is discussed for all types of excitation and reservoir base conditions.

Details

Engineering Computations, vol. 38 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Access Restricted. View access options
Article
Publication date: 3 October 2016

Seyed Iman Zare Estakhraji and Vahid Lotfi

Recently, the original Wavenumber approach was introduced for dynamic analysis of dam-reservoir systems in frequency domain in the context of pure finite element programming. But…

160

Abstract

Purpose

Recently, the original Wavenumber approach was introduced for dynamic analysis of dam-reservoir systems in frequency domain in the context of pure finite element programming. But its main disadvantages are that it cannot be implemented in time domain. The purpose of this paper is to propose an approximation to the original approach which enables one to carry out this effective method in time domain as well as in frequency domain. Based on the present investigation, it is proven that the Approximate Wavenumber approach has inherent characteristics, which allows it to be envisaged as an effective technique for calculating the response of concrete gravity dam-reservoir systems in time domain.

Design/methodology/approach

The method is described initially. Subsequently, the response of an idealized triangular dam-reservoir system is obtained by the proposed approach as well as by applying two other well-known absorbing conditions which are widely utilized in practice. The results are also controlled against the corresponding exact responses. It should be emphasized that all results presented herein are obtained by the FE-FE method under different absorbing conditions applied on the truncation boundary. These include two well-known absorbing conditions referred to as Sommerfeld and Sharan as well as the proposed approach of the present study (i.e. Approximate Wavenumber condition).

Findings

It is concluded that the maximum error for the Approximate Wavenumber approach is in the range of 10 percent at the major peaks of the response. This occurs mainly for the very low reservoir lengths under full reflective reservoir base condition and vertical excitation. This is a remarkable result for any kind of robust truncation boundary simulation that one may expect. The fundamental frequency of the system is captured correctly for the Approximate Wavenumber approach, even in cases of low reservoir length.

Originality/value

Based on this investigation, it is proven that the Approximate Wavenumber approach has inherent characteristics, which allows it to be envisaged as an effective technique for calculating the response of concrete gravity dam-reservoir systems in time domain. It is concluded that the maximum error for the Approximate Wavenumber approach is in the range of 10 percent at the major peaks of the response. This occurs mainly for the very low reservoir lengths under full reflective reservoir base condition and vertical excitation. This is a remarkable result for any kind of robust truncation boundary simulation that one may expect.

Details

Engineering Computations, vol. 33 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

Access Restricted. View access options
Article
Publication date: 11 January 2024

Vahid Lotfi and Hesamedin Abdorazaghi

The response of the Pine Flat dam–water–foundation rock system is studied by a new described approach (i.e. FE-(FE-TE)-FE). The initial part of study is focused on the time…

41

Abstract

Purpose

The response of the Pine Flat dam–water–foundation rock system is studied by a new described approach (i.e. FE-(FE-TE)-FE). The initial part of study is focused on the time harmonic analysis. In this part, it is possible to compare the transfer functions against corresponding responses obtained by the FE-(FE-HE)-FE approach (referred to as exact method which employs a rigorous fluid hyper-element). Subsequently, the transient analysis is carried out. In that part, it is only possible to compare the results for low and high normalized reservoir length cases. Therefore, the sensitivity of results is controlled due to normalized reservoir length values.

Design/methodology/approach

In the present study, dynamic analysis of a typical concrete gravity dam–water–foundation rock system is formulated by the FE-(FE-TE)-FE approach. In this technique, dam and foundation rock are discretized by plane solid finite elements while, water domain near-field region is discretized by plane fluid finite elements. Moreover, the H-W (i.e. Hagstrom–Warburton) high-order condition is imposed at the reservoir truncation boundary. This task is formulated by employing a truncation element at that boundary. It is emphasized that reservoir far-field is excluded from the discretized model.

Findings

High orders of H-W condition, such as O5-5 considered herein, generate highly accurate responses for both possible excitations under both types of full reflective and absorptive reservoir bottom conditions. It is such that transfer functions are hardly distinguishable from corresponding exact responses obtained through the FE-(FE-HE)-FE approach in time harmonic analyses. This is controlled for both low and high normalized reservoir length cases (L/H = 1 and 3). Moreover, it can be claimed that transient analysis leads practically to exact results (in numerical sense) when one is employing high order H-W truncation element. In other words, the results are not sensitive to reservoir normalized length under these circumstances.

Originality/value

Dynamic analysis of concrete gravity dam–water–foundation rock systems is formulated by a new method. The salient aspect of the technique is that it utilizes H-W high-order condition at the truncation boundary. The method is discussed for all types of excitation and reservoir bottom conditions.

Access Restricted. View access options
Article
Publication date: 1 March 1985

Mark J. FRIEDMAN

A new finite element‐boundary integral procedure for the solution of the magnetostatic field problem has been introduced previously by the author and J.S. Colonias. The approach…

42

Abstract

A new finite element‐boundary integral procedure for the solution of the magnetostatic field problem has been introduced previously by the author and J.S. Colonias. The approach there involved a reformulation of an integral equation in the iron domain as a weak formulation combining a differential operator in the iron domain and an integral operator on the iron boundary. The reformulated problem is discretized by finite element techniques in solenoidal piecewise polynomial subspaces. In this paper we modify the above formulation to obtain one with a differential operator inside a sphere containing the iron domain and an integral operator on the boundary of the sphere. We then consider a numerical realization of our method in the two dimensional case. This new formulation considerably simplifies the computation of the discrete operator on the boundary.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 4 no. 3
Type: Research Article
ISSN: 0332-1649

Access Restricted. View access options
Article
Publication date: 1 March 1997

A. Boersma and P. Wriggers

Presents an implementation of the algebraic multigrid method. It can work in two ways: as pure multigrid method and as a pre‐conditioner for the conjugate gradient method. Shows…

507

Abstract

Presents an implementation of the algebraic multigrid method. It can work in two ways: as pure multigrid method and as a pre‐conditioner for the conjugate gradient method. Shows applications of the iterative solvers for problems in linear and non‐linear elasticity. Shows the range of possible applications with different examples with regular and non‐regular meshes and three‐dimensional problems.

Details

Engineering Computations, vol. 14 no. 2
Type: Research Article
ISSN: 0264-4401

Keywords

Access Restricted. View access options
Article
Publication date: 21 February 2019

Elizabeth Velazquez and Maria Hernandez

The purpose of this paper is to review current research on police officer mental health and to explore the reasons why police officers do not seek mental health treatment.

10409

Abstract

Purpose

The purpose of this paper is to review current research on police officer mental health and to explore the reasons why police officers do not seek mental health treatment.

Design/methodology/approach

A comprehensive, systematic search of multiple academic databases (e.g. EBSCO Host) were used to identify studies conducted within the USA, identified definitions of first responders, identified the type of duty-related trauma expected by police officers, how influential stigma is amongst the police culture and what current intervention strategies are employed to assist police officer mental health wellness.

Findings

This research was conducted to identify police officer trauma-related mental health and the stigma behind seeking treatment. The research highlights job-related trauma and stress leads to the development of post-traumatic stress disorder, depression, substance use disorder and suicide or suicide ideation. The stigma behind seeking mental health treatment is associated with law enforcement organizations and environmental factors. Organizational factors include occupational stress characteristics such as day-to-day of the job and environmental factors such as abiding by social and law enforcement culture ideologies. Further research should be conducted to understand why law enforcing agencies and personnel are unknowingly promoting stigmas.

Originality/value

This is the most current meta-review of research examining the severity of mental health in police officers, the stigma behind acquiring treatment and innovative treatment approaches in police officer mental health. This study will provide a useful resource for those researchers interested in continuing to examine the different aspects of police officer mental health and how to potently approach innovative interventions to help law enforcement personals mental wellness thrive in a field where trauma is experienced daily.

Details

Policing: An International Journal, vol. 42 no. 4
Type: Research Article
ISSN: 1363-951X

Keywords

Access Restricted. View access options
Article
Publication date: 16 November 2015

Angela Workman-Stark

The purpose of this paper is to examine the cultural aspect of policing, particularly as it relates to the role of gender, and proposes an alternative approach to addressing the…

2833

Abstract

Purpose

The purpose of this paper is to examine the cultural aspect of policing, particularly as it relates to the role of gender, and proposes an alternative approach to addressing the culture of masculinity within policing.

Design/methodology/approach

First, the author provides a brief overview of the nature of policing. This is followed by a review of the relevant literature on policing and gender and the implications for men, women, and police organizations of adhering to a militarized or hegemonic form of masculinity. Finally, the author discusses Ely and Myerson’s proposed theory for “undoing gender” and its relevance for policing.

Findings

The findings of this paper suggest that the police culture continues to reinforce the masculine image of policing, thereby representing a significant barrier to the advancement of women. The findings also suggest that this barrier may be overcome through shared goals that advance collective well-being, definitions of competence linked to task requirements, and a learning orientation toward work.

Originality/value

This paper makes an important contribution to the existing literature on gender and policing, as it specifically focusses on the cultural influences of masculinity and considers the structural, behavioral, and cultural changes required to create margins of safety for police officers to experiment with new behaviors.

Details

Equality, Diversity and Inclusion: An International Journal, vol. 34 no. 8
Type: Research Article
ISSN: 2040-7149

Keywords

1 – 10 of 11
Per page
102050