WoS İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8653
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Article Citation - WoS: 1Citation - Scopus: 2General Expression of the Diffracted Waves by a Half-Screen With Generalized Impedance Boundary Conditions(Elsevier Gmbh, Urban & Fischer verlag, 2019) Umul, Yusuf ZiyaThe diffraction process of plane waves by a half-screen with generalized impedance boundary conditions is studied. Firstly, the scattered geometrical optics waves are obtained by subtracting the incident field from the total geometrical optics wave. The diffracted field expressions are derived by taking into account the construction of the scattered geometrical optics wave for first, second and third order impedance half-planes. Then the diffracted field expression is generalized for the Nth order half-screen. The uniform representation of the edge diffracted wave is obtained by considering the exact solution of Sommerfeld. The behaviors of the total, total GO and diffracted fields are analyzed numerically.Article Citation - WoS: 1Citation - Scopus: 1Wave Diffraction by a Half-Screen With Nth Order Generalized Sheet Transition Conditions(Elsevier Gmbh, Urban & Fischer verlag, 2019) Umul, Yusuf ZiyaThe scattering of plane waves by a half-plane with Nth order transition conditions is investigated. First of all, the reflection and transmission conditions of the transmissive surface are evaluated by using the generalized sheet transmission boundary conditions. The scattered geometrical optics fields are determined from the total geometrical optics and incident waves. The diffracted field is obtained by using a relation between the scattered geometrical optics and diffracted waves. The behaviors of the total, total geometric optics and diffracted fields are analyzed numerically.Article Citation - WoS: 2Citation - Scopus: 2Scattering of a Bessel Beam by a Resistive Disc(Elsevier Gmbh, Urban & Fischer verlag, 2017) Umul, Yusuf Z.Bessel beam has two important advantages that make it preferable for the illumination process of biological samples in microscopy. These are the properties of non-diffraction and self-healing. In this paper, the interaction of the zeroth order Bessel beam with a resistive disc, which models a cell or tissue, is investigated by using the uniform geometrical theory of diffraction. The geometrical optics and diffracted waves are evaluated. The scattering characteristics of the beam and the property of self-healing are studied numerically for different values of the surface resistivity. (C) 2016 Elsevier GmbH. All rights reserved.Article Wave Diffraction by Material Half-Planes(Elsevier Gmbh, Urban & Fischer verlag, 2017) Umul, Yusuf ZiyaThe diffraction of E-polarized electromagnetic waves by resistive and conductive half planes is studied. The solution of Maliuzhinets for the scattering problem of plane waves from an impedance half-screen is taken into account. The diffracted fields from the resistive and conductive half-planes are obtained by using a relation between the scattered waves from material surfaces. The integrals ofscattering are also constructed in the complex plane. The resultant field expressions are compared with the literature numerically. (C) 2016 Elsevier GmbH. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 5Diffraction of Electromagnetic Waves by a Wedge With Perfectly Absorbing and Impedance Faces(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf ZiyaThe scattering process of electromagnetic waves by a wedge with perfectly absorbing and impedance faces is investigated. The scattered geometric optics waves are obtained for two cases, namely the illumination of single and double faces. The geometric optic field is expressed as a sum of two fields, which represent two wedges with different boundary conditions. The diffracted waves are determined for both of the wedge configurations. The behaviours of the total, total geometric optics and diffracted fields are studied numerically.Article Citation - WoS: 7Citation - Scopus: 8Diffraction of Waves by a Planar Junction Between Perfectly Absorbing and Resistive Sheets(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf ZiyaThe scattering of plane waves by a planar junction between perfectly absorbing and resistive half-planes is studied. The scattered geometrical optics fields are evaluated from the difference of the total geometrical optics and initial fields. The diffracted waves by the junction are obtained with the aid of a relation between the scattered geometrical optics and diffracted fields. The uniform expressions of the diffraction fields are derived by using the uniform theory of diffraction. The behaviors of the total field and its components are analyzed numerically. (C) 2018 Elsevier GmbH. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 2Diffraction by Material Half-Planes for Grazing Incidence(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf ZiyaIt is shown that the actual solutions of the diffraction problem of waves by material half planes do not reduce to the correct diffracted field expressions for grazing incidence. The correct expressions are obtained for the diffracted waves by resistive and conductive half screens. The case for the impedance half-plane directly emerges in terms of the diffracted fields by the previous two semi-screens. The behaviors of the geometric optics and diffraction waves are investigated numerically. (C) 2017 Elsevier GmbH. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Physical Optics Based Simple Expressions for Diffracted Waves by Transmissive Half-Planes(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf ZiyaThe diffracted fields by resistive and conductive half-screens, which transmit a portion of the incident wave and reflect the remaining part, are expressed in terms of simple expressions that are based on the diffraction coefficient of an impedance half-plane. Also alternative representations are derived for the diffracted fields and their effects are studied for different values of surface parameters. The results are examined numerically. (C) 2018 Elsevier GmbH. All rights reserved.Article Citation - WoS: 17Citation - Scopus: 17Integral Theory of Diffraction for Material Junctions(Elsevier Gmbh, Urban & Fischer verlag, 2017) Umul, Yusuf ZiyaA new approach to the scattering problem of waves by junctions is developed with the aid of the modified theory of physical optics (MTPO). The relation between the fundamental MTPO integral and the Fresnel function is given as a theorem with its proof. Then the integrals relation with the geometrical optics (GO) and diffracted waves is put forth with a theorem on the uniform asymptotic evaluation of scattering integrals. A new definition is introduced for the scattering process and it is shown that the solutions of some problems, related with material half-planes and junctions can be obtained easily by only evaluating the GO fields according to the new definition of the scattering phenomenon. The scattered and diffracted fields can be derived directly in terms of the MTPO integrals as a result of the relation between the GO and scattered waves. The resultant diffracted field expressions are investigated numerically. (C) 2016 Elsevier GmbH. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3The Mtpo/Malyughinetz Hybrid Method for the Scattering Analysis of Parabolic Impedance Reflectors(Elsevier Gmbh, Urban & Fischer verlag, 2013) Umul, Yusuf ZiyaThe scattering process of cylindrical waves, radiated by a line source, from a parabolic reflector is investigated with the MTPO/Malyughinetz hybrid method. The geometrical optics and diffracted waves are evaluated asymptotically from the radiation integral. The scattered, diffracted and geometrical optics waves are plotted numerically for different impedance values. (C) 2013 Elsevier GmbH. All rights reserved.