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Article
Publication date: 1 January 1994

Andrzej Krawczyk

In 1993 the 200th anniversary of George Green, a great physicist and mathematician's, birth was celebrated. His contribution to world's science is beyond the question…

Abstract

In 1993 the 200th anniversary of George Green, a great physicist and mathematician's, birth was celebrated. His contribution to world's science is beyond the question. This can best be seen in the frequency of mentioning his name and quoting his works in other physicists' and mathematicians' works. Some of historians of science and researchers are deeply convinced that George Green together with Maxwell originated modern electromagnetism. George Green is also famous for his inventions as far as light, stress and accoustic theories are concerned but electromagnetism ows him most of all. Indeed, none of those who have ever dealt with mathematical electromagnetism will question George Green's part and position. In nearly each paper referring to it, Green's function or Green's identities are the terms that are mentioned or quoted. Without these notions contemporary numerical techniques such as finite element method (first Green's identity) or boundary element method (second Green's identity) or integral methods (Green's function) are hard to imagine.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 13 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 August 1998

J.K. Sykulski, A. Krawczyk and S. Wiak

The paper presents a historical review, the state of the art and recent advances in the field of computational electromagnetics at leading universities and research…

Abstract

The paper presents a historical review, the state of the art and recent advances in the field of computational electromagnetics at leading universities and research institutes in Poland. Contributions made by Polish scientists to the development of fundamental electromagnetism, as well as to computational methods, are emphasized, and some conclusions are drawn regarding expected future developments.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 17 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 7 September 2012

Arkadiusz Miaskowski, Andrzej Krawczyk and Yoshiyuki Ishihara

The purpose of this paper is to use numerical methods and modelling to estimate the effect of a passive, metallic (conducting) implant on eddy currents distribution in a

Abstract

Purpose

The purpose of this paper is to use numerical methods and modelling to estimate the effect of a passive, metallic (conducting) implant on eddy currents distribution in a human knee model. There exists a concern among wearers of such implants that they alter electromagnetic field (eddy currents) significantly and there is a need for standardization of that problem.

Design/methodology/approach

The numerical model of a human knee has been built on the base of Visual Human Project and electromagnetic field calculations were carried out using Meep FDTD engine. In total, two scenarios have been considered: the knee model with and without a metallic implant. The knee implant model has been prepared as the knee model with overestimated electrical parameters of bone tissues by titanium metal. Alternating eddy current distribution has then been evaluated for both models using FDTD low frequency algorithm.

Findings

The highest values of eddy currents occurred on the interface between skin and muscle tissues when the model without an implant is considered. However, when the bone tissues have been replaced with titanium metal, the highest values have occurred in the implant (about 100 times higher than the previous one). This means that an implant can be heated by external electromagnetic fields and that the location of the highest values of eddy currents can be shifted to the proximity of the implant. Moreover, one should realize that in this model the implant is like a knee bone with all anatomical details. It has emerged from this that the implant's shape and size are essential when evaluating its effect on eddy currents distribution.

Practical implications

The interaction of electromagnetic field with implants should be generally further investigated, at least for the presumable worst cases. Such investigation has already been done by some researches but they have been devoted to radio frequencies. The authors believe that the presented research will be helpful in the standardization process, when talking about low frequency electromagnetic field.

Originality/value

The presented methodology can be used in the development of computer aid diagnosis systems. Overestimation of electrical parameters of some parts of the model allows us to predict the distribution of electromagnetic field in the model under investigation very quickly. The results presented in the paper can be used during the standardization process.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 13 July 2010

Arkadiusz Miaskowski, Andrzej Krawczyk and Yoshiyuki Ishihara

The paper aims to clarify the method/methodology of establishing a computer model of the electromagnetic therapy connected with some knee joint problems. Two cases are…

Abstract

Purpose

The paper aims to clarify the method/methodology of establishing a computer model of the electromagnetic therapy connected with some knee joint problems. Two cases are considered: the arthritis of the knee and the fracture of bone. In both cases the analysis of eddy current distribution in the knee is made. It gives results which can be helpful in the planning of treatment. The paper presents the exemplary results of eddy current distribution inside a bone. A short discussion on the safety aspect of magnetotherapy has been carried out.

Design/methodology/approach

In order to calculate the eddy current distribution in human knee joint the low frequency finite‐difference time‐domain algorithm has been applied. The numerical model of the leg was based on US Air Force Research Laboratory data and the electrical properties of tissues were modeled using 4‐Cole‐Cole approximation with parameters taken from Gabriels.

Findings

The paper presents the general methodology which can be used in magnetotherapy to estimate a magnetic flux density of stimulators and value of current density inside the knee joint. Both factors mentioned above can be helpful in therapeutical processes, i.e. in magnetoteraphy.

Research limitations/implications

The eddy current distribution is limited to the presented model and it is obvious it can be different for another one as it is shown in the paper but it is also shown that the biggest value of eddy current density is just in the vicinity of the joint, so it can help in a therapeutical process.

Practical implications

The methodology of estimating the values of current density and magnetic flux density can be used by physiologists and doctors to determine the value of current density which gives therapeutical effect.

Originality/value

The efficient application of low frequency finite‐difference time‐domain algorithm to the electromagnetic therapy connected with some knee joint problems has been shown and the general methodology has been conducted.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 July 2006

R. Kubacki, J. Sobiech, J. Kieliszek and A. Krawczyk

The assessing of the specific absorption rate (SAR) of living organisms or phantoms is difficult to realize and this paper seeks to do this. SAR much more precisely…

Abstract

Purpose

The assessing of the specific absorption rate (SAR) of living organisms or phantoms is difficult to realize and this paper seeks to do this. SAR much more precisely describes the energy absorbed by biological objects than values of electric field strength (E [V/m]) or power density (S [W/m2]) measured at the point of exposition. However, for living objects the assessing of SAR is not an easy task by measuring methods or even in calculation evaluations. Numerical techniques, especially the finite‐difference time‐domain method (FDTD), offer different possibilities of calculations. The important problem with FDTD method introduced to lossy objects with complex shapes is that this method is not verified with the measuring data.

Design/methodology/approach

In this work the results of calculations and measuring data of ellipsoidal phantoms filled with specimen of electrical parameters like muscle tissue are presented. The calculations of SAR have been realized for two cases, e.g. for plane wave incident and for waveguide condition. Measurements for verifying the obtained data were done by waveguide method. The comparison of numerical (the package CONCERTO (Vector Fields Ltd)) and measurement methods were done at frequencies 900 and 1,800 MHz.

Findings

Calculations of SAR of lossy objects by FDTD method have been confirmed by measurements and analytical method of calculations. This documents that the package CONCERTO (Vector Fields Ltd) (Concerto User Guide) can be used for such calculations.

Originality/value

This paper presents the results of calculations of SAR of ellipsoidal phantoms filled with specimens of electrical parameters of equivalent muscle tissue.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 25 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 6 July 2012

Arkadiusz Miaskowski, Bartosz Sawicki and Andrzej Krawczyk

The purpose of this paper is to present the basic ideas of magnetic nanoparticles' usage in the breast cancer treatment, which is called magnetic fluid hyperthermia. The…

Abstract

Purpose

The purpose of this paper is to present the basic ideas of magnetic nanoparticles' usage in the breast cancer treatment, which is called magnetic fluid hyperthermia. The proposed approach offers a relatively simple methodology of energy deposition, allowing an adequate temperature control at the target tissue, in this case a cancerous one. By means of a numerical method the authors aim to investigate two heating effects caused by varying magnetic fields, i.e. to compare the power density heating effects of eddy currents and magnetic nanoparticles.

Design/methodology/approach

In order to numerically investigate the combination of the overheating effect of magnetic nanoparticles and eddy currents, the Finite Element Method solver based on FEniCS project has been prepared. To include the magnetic fluid in the model it has been assumed that power losses in the magnetic nanoparticles are completely converted into heat, according to experimentally developed formula. That formula can be interpreted as the hysteresis losses with regard to the volume of magnetic fluid. Finally, the total power density has been calculated as the product of the sum of power density from eddy currents and hysteresis losses. That methodology has been applied to calculate the effectiveness of magnetic fluid hyperthermia with regard to the female breast phantom.

Findings

The paper presents the methodology which can be used in magnetic fluid hyperthermia therapy planning and Computer Aid Diagnosis (CAD). Furthermore, it is shown how to overcome one of the most serious engineering challenges connected with hyperthermia, i.e. achieving adequate temperature in deep tumors without overheating the body surface.

Practical implications

The obtained results connected with the assessment of eddy currents effect suggest that during hyperthermia treatment the configuration which consists of an exciting coil and human body, plays a curial role. Moreover, the authors believe that these results will help to predict the skin surface overheating that accompanies deep heating. The presented methodology can be used by engineers in the development of Computer Aid Diagnosis systems.

Originality/value

In a given patient's situation a number of choices must be made to determine the parameters of the hyperthermia treatment. These include the need of multiple‐point temperature measurements for accurate and thorough monitoring. Treatment planning will require accurate characterization of the applicator deposition pattern and the tissue parameters, as well as the numerical techniques to predict the resultant heating pattern. The presented paper shows how to overcome these problems from the numerical point of view at least.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 May 2020

Jorge Furtado Falorca and João Carlos Gonçalves Lanzinha

This paper presents a reflection on the effectiveness of using drones in the technical inspection of building facades, as a practical alternative to more expensive and…

Abstract

Purpose

This paper presents a reflection on the effectiveness of using drones in the technical inspection of building facades, as a practical alternative to more expensive and heavier conventional means. In order to verify this assumption qualitatively, a number of field tests are presented and discussed.

Design/methodology/approach

The first stage consisted of a literature review. The analysis initially investigated drone technology. Then, an insight into some general applications in Civil Engineering was compiled, focusing in particular on the Construction Industry (CI), as well as the scope of building envelope inspections. In the second stage, field tests with drones were performed and the resulting data was appraised in order to get facade pathologies diagnosis as accurate as possible.

Findings

Through this study, the adaptability and versatility of using drones were checked. Thus, it has been confirmed that drone technology is an effective and promising alternative methodology to support technical inspection and diagnosis of building envelope pathologies. In fact, drones seem to be a worthwhile tool for supporting certain Civil Engineering activities–particularly when displaying a multirotor configuration, loading high-definition (HD) cameras, for both stills photography and video.

Research limitations/implications

As the main goal of this approach was simply a qualitative assessment of evidence on the advantages of using drones compared with conventional means, other kinds of comparative analysis were not discussed in depth. However, this and other potential restrictive issues may represent an opportunity to push more developments. A deeper knowledge of data handling and clear procedures for the use of drones could be very valuable for the CI and for building envelope inspections.

Practical implications

In investigating this subject, this research can offer valuable input to enable a greater awareness of the use of drones in the technical inspection of buildings, particularly in hard-to-reach locations, to the detriment of conventional means. In these circumstances, this methodology can bring great benefits, particularly from an environmental impact point of view, since the resources used are much lower. In addition, a very reliable diagnosis can be achieved more quickly, and at a much lower cost.

Originality/value

The introduction of a standard for drone inspection practice is still at an early stage, with initial steps being taken in an apparently well-focused effort to achieve consolidation. Research studies of this kind may have an important role to play in drawing the stakeholders' attention to the benefits of using this technique, particularly for those working in the building usage phase.

Details

International Journal of Building Pathology and Adaptation, vol. 39 no. 2
Type: Research Article
ISSN: 2398-4708

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Article
Publication date: 31 December 2020

Tomasz Rymarczyk, Konrad Kania, Michał Gołąbek, Jan Sikora, Michał Maj and Przemysław Adamkiewicz

The purpose of this study is to develop a reconstruction and measurement system for data analysis using ultrasonic transmission tomography. The problem of reconstruction…

Abstract

Purpose

The purpose of this study is to develop a reconstruction and measurement system for data analysis using ultrasonic transmission tomography. The problem of reconstruction from the projection is encountered in practical implementation, which consists in reconstructing an image that is an estimation of an unknown object from a finite set of projection data. Reconstructive algorithms used in transmission tomography are based on linear mathematical models, which makes it necessary to process non-linear data into estimates for a finite number of projections. The application of transformation methods requires building a mathematical model in which the projection data forming the known and unknown quantities are functions with arguments from a continuous set of real numbers, determining the function describing the unknown quantities sought in the form of inverse relation and adapting it to operate on discrete and noisy data. This was done by designing a tomographic device and proprietary algorithms capable of reconstructing two-dimensional images regardless of the size, shape, location or number of inclusions hidden in the examined object.

Design/methodology/approach

The application consists of a device and measuring sensors, as well as proprietary algorithms for image reconstruction. Ultrasonic transmission tomography makes it possible to analyse processes occurring in an object without interfering with the examined object. The proposed solution uses algorithms based on ray integration, the Fermat principle and deterministic methods. Two applications were developed, one based on C and implemented on the embedded device, while the other application was made in Matlab.

Findings

Research shows that ultrasonic transmission tomography provides an effective analysis of tested objects in closed tanks.

Research limitations/implications

In the presented technique, the use of ultrasonic absorption wave has been limited. Nevertheless, the effectiveness of such a solution has been confirmed.

Practical implications

The presented solution can be used for research and monitoring of technological processes.

Originality/value

Author’s tomographic system consisting of a measuring system and image reconstruction algorithms.

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: 29 February 2008

Jacek B. Krawczyk

The aim of this paper is to propose and analyse policies capable of generating left‐skewed pension distributions. Such policies can deliver large pension values with high…

Abstract

Purpose

The aim of this paper is to propose and analyse policies capable of generating left‐skewed pension distributions. Such policies can deliver large pension values with high probability and hence are of interest to practical fund managers.

Design/methodology/approach

The paper uses a computational method capable of solving stochastic optimal control problems. The optimal strategies obtained through the method are used to simulate dynamic portfolio management.

Findings

The paper finds that optimisation of locally non‐concave performance measures has produced left‐skewed payoff distributions of small VaR and CVaR. The distributions remain left‐skewed for relatively large values of the diffusion parameter.

Practical implications

On the basis of the findings, it would seem beneficial for real‐world fund managers to implement this kind of optimising “cautious‐relaxed” policy.

Originality/value

A novel non‐concave performance measure has been proposed in the paper to describe a portfolio manager's aim. The computed “cautious‐relaxed” policies have been shown to realise this aim.

Details

The Journal of Risk Finance, vol. 9 no. 2
Type: Research Article
ISSN: 1526-5943

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Article
Publication date: 11 October 2018

Mariusz Krawczyk, Cezary Jerzy Szczepanski and Albert Zajdel

This paper aims to present a concept of an automatic directional control system of remotely piloted aerial system (RPAS) during the taxiing phase. In particular, it shows…

Abstract

Purpose

This paper aims to present a concept of an automatic directional control system of remotely piloted aerial system (RPAS) during the taxiing phase. In particular, it shows the initial stages of the control laws synthesis – mathematical model and simulation of taxiing aircraft. Several reasons have emerged in recent years that make the automation of taxiing an important design challenge including decreased safety, performance and pilot workload.

Design/methodology/approach

The adapted methodology follows the model-based design approach in which the control system and the aircraft are mathematically modelled to allow control laws synthesis. The computer simulations are carried out to analyse the model behaviour.

Findings

Chosen methodology and modelling technique, especially tire-ground contact model, resulted in a taxing aircraft model that can be used for directional control law synthesis. Aerodynamic forces and moments were identified in the wind tunnel tests for the full range of the slip angle. Simulations allowed to compute the critical speeds for different taxiway conditions in a 90° turn.

Practical implications

The results can be used for the taxi directional control law synthesis and simulation of the control system. The computed critical speeds can be treated as safety limits.

Originality/value

The taxi directional control system has not been introduced to the RPAS yet. Therefore, the model of taxiing aircraft including aerodynamic characteristics for the full range of the slip angle has a big value in the process of design and implementation of the future auto taxi systems. Moreover, computed speed safety limits can be used by designers and standard creators.

Details

Aircraft Engineering and Aerospace Technology, vol. 91 no. 3
Type: Research Article
ISSN: 1748-8842

Keywords

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