The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
P.m. Johansen - One of the best experts on this subject based on the ideXlab platform.
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Time-domain version of the Physical Theory of diffraction
IEEE Transactions on Antennas and Propagation, 1999Co-Authors: P.m. JohansenAbstract:A time-domain version of the equivalent edge current (EEC) formulation of the Physical Theory of diffraction is derived. The time-domain EECs (TD-EECs) apply to the far-field analysis of diffraction by edges of perfectly conducting three dimensional (3-D) structures with planar faces illuminated by a time-domain plane wave. By adding the field predicted by the TD-EECs to the time-domain Physical optics (TD-PO) field, a significant improvement is obtained compared to what can be achieved by using TD-PO alone. The TD-EECs are expressed as the integral of the time-domain fringe wave current (the exact current minus the TD-PO current) on the canonical wedge along truncated incremental strips. Closed-form expressions for the TD-EECs are obtained in the half-plane case by analytically carrying out the integration along the truncated incremental strip directly in the time domain. In the general wedge case, closed-form expressions for the TD-EECs are obtained by transforming the corresponding frequency-domain EECs to the time-domain. The TD-EECs are tested numerically on the triangular cylinder and the results are compared with those obtained using the method of moments in combination with the inverse fast Fourier transform.
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Uniform Physical Theory of diffraction equivalent edge currents for implementation in general computer codes
IEEE Antennas and Propagation Society International Symposium. 1996 Digest, 1996Co-Authors: P.m. JohansenAbstract:New uniform closed-form expressions for Physical Theory of diffraction equivalent edge currents are derived for truncated incremental wedge strips. In contrast to previously reported expressions, the new expressions are well-behaved for all directions of incidence and observation and take a finite value for zero strip length. Consequently, the new equivalent edge currents are, to the knowledge of the author, the first that are well-suited for implementation in general computer codes.
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Uniform Physical Theory of diffraction equivalent edge currents for truncated wedge strips
IEEE Transactions on Antennas and Propagation, 1996Co-Authors: P.m. JohansenAbstract:New uniform closed-form expressions for Physical Theory of diffraction equivalent edge currents are derived for truncated incremental wedge strips. In contrast to previously reported expressions, the new expressions are well behaved for all directions of incidence and observation and take a finite value for zero strip length. This means that the expressions are well suited for implementation in general computer codes. The new expressions are expressed as the difference between two terms. The first term is obtained by integrating the exact fringe wave current on a wedge along an untruncated incremental strip extending from the leading edge of the structure under consideration. The second term is calculated from an integration of the asymptotic fringe wave (FW) current along another untruncated incremental strip extending from the trailing edge of the structure. The new expressions are tested numerically on a triangular cylinder and the results are compared with those obtained using the method of moments and the previously reported expressions.
Pyotr Ya. Ufimtsev - One of the best experts on this subject based on the ideXlab platform.
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Diffraction at a Rectangular Plate: First-Order PTD Approximation
IEEE Transactions on Antennas and Propagation, 2016Co-Authors: Gokhan Apaydin, Feray Hacivelioglu, Levent Sevgi, William B. Gordon, Pyotr Ya. UfimtsevAbstract:Physical Theory of diffraction (PTD) is developed for the field scattered at a perfectly conducting rectangular plate. Grazing incidence and grazing scattering are analyzed. High-frequency asymptotic estimations are derived. Bistatic and monostatic scenarios are considered. Comparison is presented with known experimental and numeric results obtained by the method of moments (MoM).
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Wedge Diffracted Waves Excited by a Line Source: Method of Moments (MoM) Modeling of Fringe Waves
IEEE Transactions on Antennas and Propagation, 2014Co-Authors: Gokhan Apaydin, Feray Hacivelioglu, Levent Sevgi, Pyotr Ya. UfimtsevAbstract:Method of moments (MoM) simulation of fringe waves generated by a line source that excites a perfectly reflecting wedge is introduced and compared with the exact Physical Theory of diffraction (PTD) fringe waves.
Ahmed A. Kishk - One of the best experts on this subject based on the ideXlab platform.
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Physical Theory for Particle Swarm Optimization
Progress in Electromagnetics Research-pier, 2020Co-Authors: Said M. Mikki, Ahmed A. KishkAbstract:We propose an inter-disciplinary approach to particle swarm optimization (PSO) by establishing a molecular dynamics (MD) formulation of the algorithm, leading to a Physical Theory for the swarm environment. The Physical Theory provides new insights on the operational mechanism of the PSO method. In particular, a thermodynamic analysis, which is based on the MD formulation, is introduced to provide deeper understanding of the convergence behavior of the basic classical PSO algorithm. The thermodynamic Theory is used to propose a new acceleration technique for the PSO. This technique is applied to the problem of synthesis of linear array antennas and very good improvement in the convergence performance is observed. A macroscopic study of the PSO is conducted by formulating a diffusion model for the swarm environment. The Einstein’s diffusion equation is solved for the corresponding probability density function (pdf) of the particles trajectory. The diffusion model for the classical PSO is used, in conjunction with Schrodinger’s equation for the quantum PSO, to propose a generalized version of the PSO algorithm based on the Theory of Markov chains. This unifies the two versions of the PSO, classical and quantum, by eliminating the velocity and introducing position-only update equations based on the probability law of the method.
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Molecular dynamics formulation of the particle swarm optimization method
2007 IEEE Antennas and Propagation Society International Symposium, 2007Co-Authors: Said M. Mikki, Ahmed A. KishkAbstract:We propose an inter-disciplinary approach to particle swarm optimization (PSO) by establishing a molecular dynamics (MD) formulation of the algorithm, leading to a Physical Theory for the swarm environment. The Physical Theory provides new insights on the operational mechanism of the PSO method. In particular, a thermodynamic analysis, which is based on the MD formulation, is introduced to provide deeper understanding of the convergence behavior of the basic classical PSO algorithm. The thermodynamic Theory is used to propose a new acceleration technique for the PSO. This technique is applied to the problem of synthesis of linear array antennas and very good improvement in the convergence performance is observed.
Gokhan Apaydin - One of the best experts on this subject based on the ideXlab platform.
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Bistatic scattering at soft–hard strips and plates: method of moments (MoM), Theory of edge diffraction (TED), and Physical Theory of diffraction (PTD) analysis
IET Microwaves Antennas & Propagation, 2020Co-Authors: Pyotr. Ya. Ufimtsev, Gokhan ApaydinAbstract:Diffraction at a strip with one face soft (electric) and the other hard (magnetic) is studied. New results obtained by the method of moments (MoM) are compared with the asymptotic Theory of edge diffraction (TED) for the totally soft and hard strips. Attention is given to diffraction of oblique incident waves including the grazing diffraction. Novel analytic estimations for the forward and backward grazing scattering are established via the advanced Physical Theory of diffraction (PTD) free of grazing singularities. These estimations are demonstrated for the infinitely long strips and finite size rectangular plates.
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Diffraction at Rounded Edges
2019 Fifth International Electromagnetic Compatibility Conference (EMC Turkiye), 2019Co-Authors: Gokhan Apaydin, Levent SevgiAbstract:This study aims to visualize the diffraction effects of objects with rounded edges using method of moments (MoM). The comparison of scattering effects of wedges and trilateral cylinders are shown with and without rounded edges using fringe integral equations with Physical Theory of diffraction (PTD).
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Diffraction at a Rectangular Plate: First-Order PTD Approximation
IEEE Transactions on Antennas and Propagation, 2016Co-Authors: Gokhan Apaydin, Feray Hacivelioglu, Levent Sevgi, William B. Gordon, Pyotr Ya. UfimtsevAbstract:Physical Theory of diffraction (PTD) is developed for the field scattered at a perfectly conducting rectangular plate. Grazing incidence and grazing scattering are analyzed. High-frequency asymptotic estimations are derived. Bistatic and monostatic scenarios are considered. Comparison is presented with known experimental and numeric results obtained by the method of moments (MoM).
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Wedge Diffracted Waves Excited by a Line Source: Method of Moments (MoM) Modeling of Fringe Waves
IEEE Transactions on Antennas and Propagation, 2014Co-Authors: Gokhan Apaydin, Feray Hacivelioglu, Levent Sevgi, Pyotr Ya. UfimtsevAbstract:Method of moments (MoM) simulation of fringe waves generated by a line source that excites a perfectly reflecting wedge is introduced and compared with the exact Physical Theory of diffraction (PTD) fringe waves.
Levent Sevgi - One of the best experts on this subject based on the ideXlab platform.
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Diffraction at Rounded Edges
2019 Fifth International Electromagnetic Compatibility Conference (EMC Turkiye), 2019Co-Authors: Gokhan Apaydin, Levent SevgiAbstract:This study aims to visualize the diffraction effects of objects with rounded edges using method of moments (MoM). The comparison of scattering effects of wedges and trilateral cylinders are shown with and without rounded edges using fringe integral equations with Physical Theory of diffraction (PTD).
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Diffraction at a Rectangular Plate: First-Order PTD Approximation
IEEE Transactions on Antennas and Propagation, 2016Co-Authors: Gokhan Apaydin, Feray Hacivelioglu, Levent Sevgi, William B. Gordon, Pyotr Ya. UfimtsevAbstract:Physical Theory of diffraction (PTD) is developed for the field scattered at a perfectly conducting rectangular plate. Grazing incidence and grazing scattering are analyzed. High-frequency asymptotic estimations are derived. Bistatic and monostatic scenarios are considered. Comparison is presented with known experimental and numeric results obtained by the method of moments (MoM).
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Wedge Diffracted Waves Excited by a Line Source: Method of Moments (MoM) Modeling of Fringe Waves
IEEE Transactions on Antennas and Propagation, 2014Co-Authors: Gokhan Apaydin, Feray Hacivelioglu, Levent Sevgi, Pyotr Ya. UfimtsevAbstract:Method of moments (MoM) simulation of fringe waves generated by a line source that excites a perfectly reflecting wedge is introduced and compared with the exact Physical Theory of diffraction (PTD) fringe waves.
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electromagnetic wave scattering from a wedge with perfectly reflecting boundaries analysis of asymptotic techniques
IEEE Antennas and Propagation Magazine, 2011Co-Authors: F Hacivelioglu, Levent Sevgi, P Y UiimtsevAbstract:High-frequency asymptotic (HFA) techniques are reviewed through a classical, canonical problem: electromagnetic wave scattering from a wedge-shaped object with perfectly electrically conducting (PEC) boundaries. The Physical Optics (PO) and Physical Theory of Diffraction (PTD) approaches are compared against the exact solution through many scenarios and illustrations.
