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Article
Publication date: 1 January 1993

J. SIKORA, W. KWIATKOWSKI and H. KRAUS

A new method of designing electromagnetic devices especially high‐voltage ones, is presented. As a result of applying a sequential quadratic programing algorithm and a very…

44

Abstract

A new method of designing electromagnetic devices especially high‐voltage ones, is presented. As a result of applying a sequential quadratic programing algorithm and a very effective algorithm for non‐linear minimax optimization, a flexible method for computer aided design of high‐voltage and semiconductor devices has been obtained. The minimax algorithm is based on a successive linear approximation of the functions defining the problem. In each iteration step these functions are computed with the aid of the finite element method. The resulting linear subproblems are solved in the minimax sense subject to the linear equality and inequality constraints. Applications of these two methods for the designing some parts of the high‐voltage devices are presented.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 12 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 March 1988

Jan SIKORA

In this paper, Sensitivity Method (SM) was used to the identification of boundary conditions. Particular attention in this paper was paid to the Levenberg‐Marquardt (L‐M…

57

Abstract

In this paper, Sensitivity Method (SM) was used to the identification of boundary conditions. Particular attention in this paper was paid to the Levenberg‐Marquardt (L‐M) regularization method, because the inverse problems of the electromagnetic field are not well conditioned in typical cases. It was proved that using some information about the expected solution, the L‐M regularization method gives satisfactory results even in such cases where the singular value analysis (SVA) fails. The identified boundary conditions were compared with the results obtained by using the direct least squares (LS) method.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 7 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 January 1985

JAN SIKORA, JERZY SKOCZYLAS, JAN SROKA and STANISLAW WINCENCIAK

This paper discusses an electrostatic, homogeneous field in a uniform two‐dimensional domain with Neumann's boundary conditions. The boundary conditions are known only at some…

45

Abstract

This paper discusses an electrostatic, homogeneous field in a uniform two‐dimensional domain with Neumann's boundary conditions. The boundary conditions are known only at some segments of the boundary. The synthesis is understood as the computation of the remaining boundary conditions which would ensure the required potential distribution in some subdomains within the boundary. The introduction of a single‐layer potential leads to Fredholm's equation of the second order. Stepwise approximation of the source distribution along the boundary rearranges Fredholm's equation and the requirements concerning the single layer potential distribution. It leads to a matrix equation with a rectangular coefficient matrix. In order to solve approximately this equation, in the sense of the least squares minimization, the singular value decomposition (SVD) method is used. The choice of subdomains with determined potential distribution influences significantly the conditioning of the equation. Easy selection of an acceptable solution among all possible solutions proves the suitability of the SVD method in the above problem. The numerical experiments reported in the paper are a good illustration of this.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 4 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 June 2000

A. Savini

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community…

1157

Abstract

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 4 April 2019

John J. Sikora Jr., Stephen P. Wink, Douglas K. Yatter and Naim Culhaci

To analyze the settled order of the US Securities and Exchange Commission (SEC) against TokenLot LLC (TokenLot), which was the SEC’s first action charging a seller of digital…

68

Abstract

Purpose

To analyze the settled order of the US Securities and Exchange Commission (SEC) against TokenLot LLC (TokenLot), which was the SEC’s first action charging a seller of digital tokens as an unregistered broker-dealer.

Design/methodology/approach

Analyzes the SEC’s order within the context of other recent actions by the SEC on cryptocurrencies and digital tokens and discusses future implications of the order in this area.

Findings

The SEC’s order against TokenLot as an unregistered broker-dealer was a logical next step in its enforcement activity in the cryptocurrency and digital token space.The order demonstrates that the SEC expects firms in the cryptocurrency space to use the well-established constructs of federal securities laws to evaluate their business activities to ensure those activities are legally compliant.

Originality/value

Practical guidance from experienced securities and financial services lawyers analyzing recent developments in a nascent area of SEC enforcement.

Details

Journal of Investment Compliance, vol. 20 no. 1
Type: Research Article
ISSN: 1528-5812

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Article
Publication date: 1 January 1993

S.‐Y. HAHN, I.‐H. PARK, H.‐K. JUNG and J. SIKORA

In the shadow of X‐ray tomography and nuclear magnetic resonance tomography a new tomographic technique based on low‐frequency electric currents has been successfully developed in…

102

Abstract

In the shadow of X‐ray tomography and nuclear magnetic resonance tomography a new tomographic technique based on low‐frequency electric currents has been successfully developed in the past decade. Impedance computed tomography (ICT), although it gives poor spatial resolution images, is unmatched in certain cases. Two different approaches to the sensitivity analysis are presented in this paper. The direct differentiation method has been applied, but the adjoint variable method has not been used in ICT reconstruction algorithms until now. Some problems associated with the adjoint variable method of sensitivity analysis are discussed. The new algorithm is compared with the direct differentiation approach.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 12 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 9 November 2012

J. Hoła, Z. Matkowski, K. Schabowicz, J. Sikora, K. Nita and S. Wójtowicz

This paper aims to present a new non‐destructive method of brick wall dampness testing in real building structures. The electrical impedance tomography (EIT) method makes it…

432

Abstract

Purpose

This paper aims to present a new non‐destructive method of brick wall dampness testing in real building structures. The electrical impedance tomography (EIT) method makes it possible to obtain a distribution of wall dampness. The paper aims to give basic information about the measuring system, including prototype equipment. The setup was used to determine the dampness of test brick walls on a specially built laboratory test rig. The paper seeks to compare test results obtained by the non‐destructive impedance tomography method with the results obtained by the conventional destructive dry‐weight method.

Design/methodology/approach

The paper adopts a tomography approach to control humidity inside of the brick walls. In case of brick walls other nondestructive methods fields, for example, the ultrasonic tomography is useless. On the other hand the most popular dry‐weight method is strictly forbidden for historical buildings. As a forward solver, functionally graded material boundary element method was used.

Findings

The paper proves that diffuse tomography could provide reliable results with respect of humidity content inside the brick walls. This method could provide 3D humidity distribution inside of the brick walls.

Research limitations/implications

It is expected that the technique's impact will be limited to site inspection of building following floods or to evaluate older damp buildings.

Practical implications

The presented technique can eventually lead to much simpler, cheaper and more efficient evaluation of the moisture content in walls. This can revolutionize some procedures in civil engineering.

Social implications

The application has commercial potential and could result in more cost‐effective repair of old buildings, which has an economic impact on society.

Originality/value

The authors propose application of the diffuse tomography for nondestructive investigation of brick walls. According to the authors' best knowledge this is a novel approach.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 8 October 2018

Tomasz Rymarczyk, Jan Sikora and Paweł Tchórzewski

The paper aims to present an innovative solution for evaluation study of the dampness level of walls and historical buildings.

165

Abstract

Purpose

The paper aims to present an innovative solution for evaluation study of the dampness level of walls and historical buildings.

Design/methodology/approach

Electrical tomography enables one to obtain a distribution pattern of wall dampness. The application of modern tomographic techniques in conjunction with topological algorithms will allow one to perform very accurate spatial assessment of the dampness levels of buildings. The proposed application uses the total variation, Gauss–Newton and level set method to solve the inverse problem in electrical tomography.

Findings

Research shows that electrical tomography can provide effective results in damp buildings. This method can provide 2D/3D moisture distribution pattern.

Research limitations/implications

The impact of this technique will be limited to inspection of the facility after floods or assessment of historical buildings.

Practical implications

The presented method could eventually lead to a much more effective evaluation of moisture in the walls.

Social implications

The solution has commercial potential and could result in more cost-effective monitoring of historical buildings, which have an economic impact on society.

Originality/value

The authors propose a system for imaging spatial moistness of walls and historic buildings based on electrical tomography and consisting of a measuring device, sensors and image reconstruction algorithms.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

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Book part
Publication date: 31 December 2010

Joanna Sikora and Lawrence J. Saha

Our first goal is to discuss new information for national policymaking which may arise from the analyses of international achievement study data. The second is to illustrate this…

Abstract

Our first goal is to discuss new information for national policymaking which may arise from the analyses of international achievement study data. The second is to illustrate this potential by exploring determinants of students' career plans in a cross-national perspective. Using neo-institutionalism as our theoretical framework, we propose that the influence of a global educational ideology encourages high levels of occupational ambitions among students. This is particularly the case in countries where the transfer of this ideology is supported by the reception of aid for education, where economic prosperity is at modest levels but the service sector employment is expanding. To explore this proposition, we analyze students' occupational expectations using the 2006 PISA surveys from 49 countries. We account for a broad range of possible determinants by estimating three-level hierarchical models in which students are clustered in schools and schools within countries. We find that at individual and school levels, ambition is positively correlated with economic and noneconomic resources. In contrast, students in poorer countries, where secondary education is not yet universally accessible, tend to be more ambitious. The global educational ideology, indicated by the reception of education-related aid, is associated with student career optimism, while students in affluent nations with less economic inequality have modest occupational plans. In addition, the rate of service sector expansion is positively related to high levels of ambition. These patterns hold even after we control for cross-national variation in the extent to which PISA respondents represent populations of 15-year-olds in their countries.

Details

The Impact of International Achievement Studies on National Education Policymaking
Type: Book
ISBN: 978-0-85724-449-9

Available. Open Access. Open Access
Article
Publication date: 4 January 2021

Radosław Wajman

Crystallization is the process widely used for components separation and solids purification. The systems for crystallization process evaluation applied so far, involve numerous…

2716

Abstract

Purpose

Crystallization is the process widely used for components separation and solids purification. The systems for crystallization process evaluation applied so far, involve numerous non-invasive tomographic measurement techniques which suffers from some reported problems. The purpose of this paper is to show the abilities of three-dimensional Electrical Capacitance Tomography (3D ECT) in the context of non-invasive and non-intrusive visualization of crystallization processes. Multiple aspects and problems of ECT imaging, as well as the computer model design to work with the high relative permittivity liquids, have been pointed out.

Design/methodology/approach

To design the most efficient (from a mechanical and electrical point of view) 3D ECT sensor structure, the high-precise impedance meter was applied. The three types of sensor were designed, built, and tested. To meet the new concept requirements, the dedicated ECT device has been constructed.

Findings

It has been shown that the ECT technique can be applied to the diagnosis of crystallization. The crystals distribution can be identified using this technique. The achieved measurement resolution allows detecting the localization of crystals. The usage of stabilized electrodes improves the sensitivity of the sensor and provides the images better suitable for further analysis.

Originality/value

The dedicated 3D ECT sensor construction has been proposed to increase its sensitivity in the border area, where the crystals grow. Regarding this feature, some new algorithms for the potential field distribution and the sensitivity matrix calculation have been developed. The adaptation of the iterative 3D image reconstruction process has also been described.

Details

Sensor Review, vol. 41 no. 1
Type: Research Article
ISSN: 0260-2288

Keywords

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