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  • 1.
    Monsefi, Farid
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Mathematical Tools Applied in Computational Electromagnetics for a Biomedical Application and Antenna Analysis2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    To ensure a high level of safety and reliability of electronic/electric systems EMC (electromagnetic compatibility) tests together with computational techniques are used. In this thesis, mathematical modeling and computational electromagnetics are applied to mainly two case studies. In the first case study, electromagnetic modeling of electric networks and antenna structures above, and buried in, the ground are studied. The ground has been modelled either as a perfectly conducting or as a dielectric surface.  The second case study is focused on mathematical modeling and algorithms to solve the direct and inverse electromagnetic scattering problem for providing a model-based illustration technique. This electromagnetic scattering formulation is applied to describe a microwave imaging system called Breast Phantom. The final goal is to simulate and detect cancerous tissues in the human female breast by this microwave technique.  

    The common issue in both case studies has been the long computational time required for solving large systems of equations numerically. This problem has been dealt with using approximation methods, numerical analysis, and also parallel processing of numerical data. For the first case study in this thesis, Maxwell’s equations are solved for antenna structures and electronic networks by approximation methods and parallelized algorithms implemented in a LAN (Local Area Network). In addition, PMM (Point-Matching Method) has been used for the cases where the ground is assumed to act like a dielectric surface. For the second case study, FDTD (Finite-Difference Time Domain) method is applied for solving the electromagnetic scattering problem in two dimensions. The parallelized numerical FDTD-algorithm is implemented in both Central Processing Units (CPUs) and Graphics Processing Units (GPUs).

  • 2.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Carlsson, Linus
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Rancic, Milica
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Otterskog, Magnus
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Solution of Two-Dimensional Electromagnetic Scattering Problem by FDTD with Optimal Step Size, Based on a Semi-Norm Analysis2014In: 10TH INTERNATIONAL CONFERENCE ON MATHEMATICAL PROBLEMS IN ENGINEERING, AEROSPACE AND SCIENCES: ICNPAA 2014 Conference date: 15–18 July 2014 Location: Narvik, Norway ISBN: 978-0-7354-1276-7 Editor: Seenith Sivasundaram Volume number: 1637 Published: 10 december 2014 / [ed] Seenith Sivasundaram, American Institute of Physics (AIP), 2014, p. 683-690Conference paper (Refereed)
    Abstract [en]

    To solve the electromagnetic scattering problem in two dimensions, the Finite Difference Time Domain (FDTD)method is used. The order of convergence of the FDTD algorithm, solving the two-dimensional Maxwell’s curl equations,is estimated in two different computer implementations: with and without an obstacle in the numerical domain of the FDTDscheme. This constitutes an electromagnetic scattering problem where a lumped sinusoidal current source, as a source ofelectromagnetic radiation, is included inside the boundary. Confined within the boundary, a specific kind of AbsorbingBoundary Condition (ABC) is chosen and the outside of the boundary is in form of a Perfect Electric Conducting (PEC)surface. Inserted in the computer implementation, a semi-norm has been applied to compare different step sizes in the FDTDscheme. First, the domain of the problem is chosen to be the free-space without any obstacles. In the second part of thecomputer implementations, a PEC surface is included as the obstacle. The numerical instability of the algorithms can berather easily avoided with respect to the Courant stability condition, which is frequently used in applying the general FDTDalgorithm.

  • 3.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Education, Culture and Communication.
    Ekman, Jonas
    Antenna analysis using PEEC and the complex image method2006Conference paper (Other academic)
  • 4.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Elgland, Simon
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Otterskog, Magnus
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rancic, Milica
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Carlsson, Linus
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    GPU Implementation of a Biological Electromagnetic Scattering Problem by FDTD2015In: 16th ASMDA 2015 Conference and Demographics 2015 Proceedings, 2015Conference paper (Refereed)
  • 5.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Jankoski, Radoslav
    Ss. Cyril and Methodius University, FEIT, P.O.Box 574, 1000 Skopje, Macedonia.
    Rancic, Milica
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Evaluating Parameters of Approximate Functions for Representation of Sommerfeld Integrals2015In: ASMDA 2015 Proceedings: 16th Applied Stochastic Models and Data Analysis International ConferenceWith 4th Demographics 2015 Workshop16th Applied Stochastic Models and Data Analysis International ConferenceWith 4th Demographics 2015 Workshop / [ed] Christos H Skiadas, ISAST: International Society for the Advancement of Science and Technology , 2015, p. 711-722Conference paper (Refereed)
    Abstract [en]

    Approximate evaluation of Sommerfeld type integrals has been of great interest for researchers in the field of electromagnetics, in particular in the areas of antenna theory and grounding systems analysis. These integrals arise in the expressions describing the electromagnetic field in the surroundings of such structures when they are located above/inside a semi-conducting media. The fact that these integrals don’t have a closed form solution, enticed researchers to approximately evaluate them either by employing a numerical integration technique, or using some kind of procedure that will approximate them and allow their analytical evaluation.

    A simple procedure for approximate calculation of one type of Sommerfeld integrals occurring in cases of wire conductors buried in semi-conducting ground is proposed. It considers approximation of a part of the integrand using a weighted exponential function with an additional unknown constant complex term. This kind of modification allows the obtained integral to be calculated analytically.

  • 6.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Otterskog, Magnus
    Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Direct and Inverse Computational Methods for Electromagnetic Scattering in Biological Diagnostics2013Report (Other academic)
    Abstract [en]

    Scattering theory has had a major roll in twentieth century mathematical physics. Mathematical modeling and algorithms of direct,- and inverse electromagnetic scattering formulation due to biological tissues are investigated. The algorithms are used for a model based illustration technique within the microwave range. A number of methods is given to solve the inverse electromagnetic scattering problem in which the nonlinear and ill-posed nature of the problem are acknowledged.

  • 7.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Rancic, Milica
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Aleksic, Slavoljub
    University of Nis, Faculty of Electronic Eng., Serbia.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    HF Analysis of Thin Horizontal Central-Fed Conductor above Lossy Homogeneous Soil2014In: IEEE International Symposium on Electromagnetic Compatibility 20 October 2014, 2014, p. 916-921Conference paper (Refereed)
    Abstract [en]

    In this paper, the authors perform HF analysis of a thin horizontal conductor fed in its center, and arbitrarily positioned above lossy homogeneous ground of known electrical parameters. The approach is based on the electric-field integral equation method, and formulation of the Hallén’s integral equation. This equation is then solved for the current using the point-matching method. The Sommerfeld’s integrals that express the influence of the lossy ground, and that appear in these calculations, are solved approximately. Thorough analysis is performed in order to observe the influence of different parameters of the geometry and the ground on current distribution in the specified frequency range. Furthermore, the verification of the method is done by comparison with the exact model based on the full-wave theory.

  • 8.
    Monsefi, Farid
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Rancic, Milica
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Aleksic, Slavoljub
    University of Nis, Faculty of Electronic Eng., Serbia.
    Sommerfeld’s integrals and Hallen’s integral equation in Data Analysis for Horizontal Dipole Antenna above Real Ground2014In: SMTDA 2014 Proceedings / [ed] Christos H. Skiadas, ISAST: International Society for the Advancement of Science and Technology , 2014, p. 507-518Conference paper (Refereed)
    Abstract [en]

    Increase of the radiation power in different frequency bands during the last decades, has called for a study of harmful effects on the living organisms and electronic equipment of the radio frequency energy. An accurate determination of the near field strength, electric as well as magnetic, in the vicinity of higher-power transmitting antennas is necessary for assessing any possible radiation hazard. In that sense, it is of great importance to account for the influence of the finite ground conductivity on the electromagnetic field structure in the surroundings of these emitters. The estimation of this influence has been intensively studied, and a number of approaches has been applied in that sense, ranging from the exact full-wave based ones to different forms of approximate, less time-consuming, ones. Although the approximate methods introduce a certain level of calculation error, their simplicity is of interest in the electomagnetic compatibility (EMC) studies. For that reason, finding an approximate, but satisfyingly accurate method, applicable to wide range of parameters is often a goal of researches done in this field.

    In this paper, the authors perform an analysis of a thin horizontal dipole antenna (HDA) above real ground of known electrical parameters. The approach is based on the electric-field integral equation method, and formulation of the Hallén’s integral equation (HIE). This equation is then solved for the current, which is assumed in a polynomial form, using the point-matching method (PMM). This way obtained system of linear equations involves improper Sommerfeld’s integrals, which express the influence of the real ground and are here solved approximately using simple, so-called OIA and TIA, approximations (one- and two-image approximations). Both types of approximations are in an exponential form, and therefore are similar to those obtained applying the method of images. It should be kept in mind that the goal of this approach is to develop approximations that have a simple form, whose application yields satisfyingly accurate calculations of the Sommerfeld`s type of integrals, and are widely applicable, i.e. their employment is not restricted by the values of electrical parameters of the ground, or the geometry.

    Thorough analysis is performed in order to observe the influence of different parameters of the geometry, and the ground, on current distribution and the input impedance/admittance of the HDA in a wide frequency range. Furthermore, the verification of the method is done by comparison to the exact model based on the full-wave theory, and experimental data. Obtained results indicate a possibility of applying the described methodology to inverse problem involving evaluation of electrical parameters of the ground (or detection of ground type change) based on measured input impedance/admittance of the antenna.

  • 9.
    Peric, Mirjana
    et al.
    University of Nis, Faculty of Electronic Eng., Serbia.
    Ilic, Sasa
    University of Nis, Faculty of Electronic Eng., Serbia.
    Aleksic, Slavoljub
    University of Nis, Faculty of Electronic Eng., Serbia.
    Raicevic, Nebojsa
    University of Nis, Faculty of Electronic Eng., Serbia.
    Monsefi, Farid
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Rancic, Milica
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Analysis of shielded coupled microstrip line with partial dielectric support2014In: 2014 18th International Symposium on Electrical Apparatus and Technologies, SIELA 2014 - Proceedings, IEEE conference proceedings, 2014, p. Article number 6871881-Conference paper (Refereed)
    Abstract [en]

    A shielded coupled microstrip line with partial dielectric support is analysed using the hybrid boundary element method (HBEM) and the finite difference method (FDM). The HBEM is a combination of the equivalent electrodes method (EEM) and the boundary element method (BEM). The microstrip line characteristic parameters: the effective relative permittivity and the characteristic impedance are deter­mined. “Odd” and “even” modes are taken into account. The results are compared with corresponding ones found in the literature.

1 - 9 of 9
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