| 1. |
- Angermann, L., et al.
(författare)
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A nonlinear multiparameter EV problem
- 2018
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Ingår i: Progress In Electromagnetics Research Symposium. - Cham : Springer New York LLC. - 9783319940595 - 9783319940601 ; , s. 55-70
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Konferensbidrag (refereegranskat)abstract
- We investigate a generalization of one-parameter eigenvalue problems arising in the theory of wave propagation in waveguides filled with nonlinear media to more general nonlinear multi-parameter eigenvalue problems for a nonlinear operator. Using an integral equation approach, we derive functional dispersion equations (DEs) whose roots yield the desired eigenvalues. The existence of the roots of DEs is proved and their distribution is described.
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| 2. |
- Samokhin, Alexander, et al.
(författare)
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Stationary iteration methods for solving 3D electromagnetic scattering problems
- 2013
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Ingår i: Applied Mathematics and Computation. - : Elsevier BV. - 0096-3003 .- 1873-5649. ; 222, s. 107-122
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Tidskriftsartikel (refereegranskat)abstract
- Generalized Chebyshev iteration (GCI) applied for solving linear equations with nonselfadjoint operators is considered. Sufficient conditions providing the convergence of iterations imposed on the domain of localization of the spectrum on the complex plane are obtained. A minimax problem for the determination of optimal complex iteration parameters is formulated. An algorithm of finding an optimal iteration parameter in the case of arbitrary location of the operator spectrum on the complex plane is constructed for the generalized simple iteration method. The results are applied to numerical solution of volume singular integral equations (VSIEs) associated with the problems of the mathematical theory of wave diffraction by 3D dielectric bodies. In particular, the domain of the spectrum location is described explicitly for low-frequency scattering problems and in the general case. The obtained results are discussed and recommendations concerning their applications are given. (C) 2013 Elsevier Inc. All rights reserved.
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| 3. |
- Angermann, Lutz, et al.
(författare)
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Eigenmodes of linearised problems of scattering and generation of oscillations on cubically polarisable layers
- 2015
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Ingår i: Inverse Problems and Applications. - Cham : Springer-Verlag New York. - 9783319124988 - 9783319124995 ; , s. 67-80
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Konferensbidrag (refereegranskat)abstract
- In the frequency domain, the resonant properties of nonlinear structures are determined by the proximity of the scattering/generation frequencies of the nonlinear structures to the complex eigenfrequencies of the corresponding homogeneous linear spectral problems with the induced nonlinear permeability of the medium. Here the case of cubically polarisable, canalising, and decanalising layers is considered.
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| 4. |
- Nakonechny, Alexander, et al.
(författare)
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Guaranteed estimation for inverse problems in electromagnetics and acoustics
- 2016
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Ingår i: Proceedings of the 2016 18th International Conference on Electromagnetics in Advanced Applications, ICEAA 2016. ; , s. 374-377
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Konferensbidrag (refereegranskat)abstract
- The analysis is performed and theorems are formulated concerning general form of guaranteed estimates of linear functionals from unknown data of Helmholtz transmission problems arising in electromagnetics and acoustics of inhomogeneous dielectric media.
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| 5. |
- Abgaryan, Garnik V., et al.
(författare)
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TE-Polarized Electromagnetic Wave Diffraction by a Circular Slotted Cylinder
- 2023
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Ingår i: Mathematics. - : MDPI. - 2227-7390. ; 11:9
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Tidskriftsartikel (refereegranskat)abstract
- The problem of diffraction of a TE-polarized electromagnetic wave by a circular slotted cylinder is investigated. The boundary value problem in question for the Helmholtz equation is reduced to an infinite system of linear algebraic equations of the second kind (SLAE-II) using integral summation identities (ISI). A detailed study of the matrix operator of the problem is performed and its Fredholm property in the weighted Hilbert space of infinite sequences is proven. The convergence of the truncation method constructed in the paper for the numerical solution of SLAE-II is justified and the results of computations are presented and discussed, specifically considering the determination of resonance modes.
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| 6. |
- Derevyanchuk, E. D., et al.
(författare)
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Reconstruction of Electromagnetic Parameters of a Thin Anisotropic Dielectric Slab
- 2018
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Ingår i: 2018 Progress in Electromagnetics Research Symposium (PIERS-Toyama). - 9784885523151 ; , s. 1968-1972
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Konferensbidrag (refereegranskat)abstract
- Reconstruction of electromagnetic parameters of artificial materials is an urgent problem [1], [2]. In practice, as a rule, these parameters cannot be directly measured. Therefore, methods of mathematical modeling must be applied. Conventional waveguide measurement equipment employs network analyzers and dielectric samples having the simplest shape of a parallelepiped adjusted to the walls of a standard rectangular waveguide. Such setups open the way to use well-developed analytical-numerical techniques [3], [4] of determining permittivity and other parameters of the inclusion using accurate closed-form solutions and asymptotic approximations. This work is a continuation of the series of papers [3], [4] devoted to the analysis of inverse problems of finding permittivity and permeability of layered materials. We apply a specially developed mathematical and numerical technique that combines analytical and numerical approaches providing the results with guaranteed accuracy. Particularly, we develop the methods [3] of determining permittivity and permeability tensors of anisotropic materials in a rectangular waveguide.
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| 7. |
- Ivanchenko, I., et al.
(författare)
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Reconstructing complex permittivity of local inhomogeneities in a radio-transparent dielectric matrix located in a waveguide
- 2016
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Ingår i: 2016 22nd International Conference on Applied Electromagnetics and Communications (ICECOM). - 9789536037711 - 9781509049998
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Konferensbidrag (refereegranskat)abstract
- The results are presented of the numerical solution to the forward problem of the electromagnetic wave scattering by inhomogeneous dielectric bodies in a waveguide and inverse problem of determining parameters of dielectric inclusions from the values of the transmission coefficient of the scattered electromagnetic wave. A comparison with the results of mesurements and analysis of the achieved threshold computational accuracy levels enable one to estimate and validate the simulation results and formulate the ways of improving the model and codes.
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| 8. |
- Kuzmina, E. A., et al.
(författare)
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Complex waves in a dielectric rod and Goubau line
- 2017
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Ingår i: 2017 International Conference on Electromagnetics in Advanced Applications (ICEAA). - : Institute of Electrical and Electronics Engineers Inc.. - 9781509044528 - 9781509044511 - 9781509044504 ; , s. 963-966
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Konferensbidrag (refereegranskat)abstract
- Existence of complex TM and TE waves in a dielectric waveguide of circular cross section and a Goubau line is proved by analyzing functional properties of the dispersion equations (DEs) using the theory of functions of several complex variables and validating the existence of complex roots of DE. The method proceeds from the analysis of general setting involving hybrid nonsymmetric azimuthally dependent real and complex waves.
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| 9. |
- Lagovsky, B. A., et al.
(författare)
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Pulse characteristics of antenna array radiating UWB signals
- 2016
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Ingår i: 2016 10th European Conference on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 9788890701863
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Konferensbidrag (refereegranskat)abstract
- Dispersion properties of the mutual impedance of emitters significantly alter the shape and spectrum of ultra-wideband (UWB) signals which must be taken into account when forming the signal. In order to take into consideration mutual coupling of elements we propose to use pulse characteristics in the antenna performance analysis and calculations. This approach allows us to simplify calculations of UWB antenna systems and improve their accuracy.
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| 10. |
- Lagovsky, B. A., et al.
(författare)
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Regression Methods of Obtaining Angular Superresolution
- 2019
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Ingår i: 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC). - New Dehli : IEEE. - 9789082598759 - 9789082598742 - 9781538685518
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Konferensbidrag (refereegranskat)abstract
- New methods of signal processing based on nonlinear regression methods are presented. They allow us to restore images of individual objects of group targets with superresolution at signal-to-noise ratios that are significantly lower than those provided by the known methods.
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