Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/260

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Citation - WoS: 6
Citation - Scopus: 8
Babinet's Principle in the Fraunhofer Diffraction by a Finite Thin Wire
(Elsevier Gmbh, Urban & Fischer verlag, 2011) Umul, Yusuf Ziya
The scattered waves by a thin finite wire are evaluated by using the Rayleigh-Sommerfeld integral in the Fraunhofer approximation. The scattered fields by the complementary thin wire are also obtained with the aid of the Babinet's principle. The scattering integrals are evaluated directly. It is shown that Babinet's principle holds excellently for this problem. The scattered fields are examined numerically. (C) 2010 Elsevier GmbH. All rights reserved.
Comment on "a Survey of the New Proposal About the Photon Momentum" (Vol 148, Pg 342, 2017)
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Z.
Citation - WoS: 8
Citation - Scopus: 8
Cylindrical-Sinc Beam
(Elsevier Gmbh, Urban & Fischer verlag, 2014) Bayraktar, Mert; Basdemir, H. Deniz
Propagation of diffracted beams in free space has already been identified. One possible solution is derived from the Helmholtz wave equation and this solution is named as cylindrical-sinc beam. Therefore, cylindrical-sinc beam is a new beam type which can be obtained from Helmholtz equation. Diffraction properties of this new beam type were observed from an opaque aperture screen. Additionally, geometrical theory of diffraction is used to determine numerical values of diffracted fields. This new beam type which does not exist in the literature was observed by using these methods passing through an opaque aperture. The obtained expression was analyzed numerically. Simulation results of the beam depending on the length of aperture and distance to the observation point were added. (C) 2014 Elsevier GmbH. All rights reserved.
Citation - WoS: 2
Citation - Scopus: 2
Diffraction by Material Half-Planes for Grazing Incidence
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Ziya
It 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.
Citation - WoS: 5
Citation - Scopus: 5
Diffraction of Electromagnetic Waves by a Wedge With Perfectly Absorbing and Impedance Faces
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Ziya
The 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.
Citation - Scopus: 1
Diffraction of Waves by a Conductive Half-Plane
(Elsevier Gmbh, Urban & Fischer verlag, 2017) Umul, Yusuf Ziya
The scattering process of plane waves by a conductive half-plane is investigated. The scattered geometrical optics waves are obtained by subtracting the incident field from the total geometrical optics waves. The physical optics integral is constructed from the scattered geometrical optics fields. The diffracted waves are evaluated by the application of the edge point method to the physical optics integral. A correction field is added to the diffracted waves in order to satisfy the conductive boundary conditions on the surfaces of the half plane. The uniform diffracted fields are evaluated and the resultant scattered waves are compared with the literature numerically. (C) 2016 Elsevier GmbH. All rights reserved.
Citation - WoS: 7
Citation - Scopus: 8
Diffraction of Waves by a Planar Junction Between Perfectly Absorbing and Resistive Sheets
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Ziya
The 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.
Citation - WoS: 6
Citation - Scopus: 6
Directive Line Source Scattering by a Half-Plane Between Two Isorefractive Media
(Elsevier Gmbh, Urban & Fischer verlag, 2017) Basdemir, Husnu Deniz
A perfectly conducting half-plane which is lying at the interface between two isorefractive media is investigated for a directive line source illumination. For this purpose, a directive line source is defined by passing a plane-wave from an aperture. Also, more suitable function than the Fresnel function is defined for cylindrical sources. The scattered field and its subfields are obtained by a new method. Consequently, all the mentioned fields are analyzed numerically. (C) 2016 Elsevier GmbH. All rights reserved.
Emission of Matter Waves by Photons
(Elsevier Gmbh, Urban & Fischer verlag, 2012) Umul, Yusuf Ziya
A new hypothesis, based on the dualistic nature of matter and light, is proposed. The frequency shift of a photon creates an electron. The phenomenon is investigated according to the conservation laws of energy and momentum. The concept of particle velocity and wavelength of a photon, based on a relation between the energy and momentum conservation laws, is also introduced. The proposal is also supported by some experiments on matter-antimatter creation by the collision of photons. (C) 2011 Elsevier GmbH. All rights reserved.
Citation - WoS: 5
Citation - Scopus: 5
Exact Form of the Physical Optics Integral
(Elsevier Gmbh, Urban & Fischer verlag, 2017) Umul, Yusuf Ziya
The exact structure of the physical optics integral is obtained. With this aim, the rigorous solution of the diffraction problem of waves by a perfectly conducting half-plane is considered. The Fresnel integrals of the incident and reflected scattered fields are transformed into the physical optics integrals by defining a suitable variable transform. The relation of the obtained integral with the modified theory of physical optics is discussed. (C) 2016 Elsevier GmbH. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Excitation of Electromagnetic Waves by a Discontinuous Electric Line Source
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Ziya
The radiation process of electromagnetic waves is investigated when a discontinuity on an electric line source is created. Three cases are taken into account. In the first case, an abrupt discontinuity is formed on the antenna geometry. The edge discontinuity of the line source is excluded from space as the second case. The third situation considers the isolation of the continuous part of the antenna. The excitation of current and charge densities are studied for the two situations. The magnetic vector and electric scalar potentials are evaluated from the sources and the electric and magnetic fields are obtained. Computational MATLAB simulations are given for the behaviors of the radiated electromagnetic waves in free space.
Citation - WoS: 5
Citation - Scopus: 5
Fringe Waves in Wedge Diffraction
(Elsevier Gmbh, Urban & Fischer verlag, 2012) Umul, Yusuf Z.
Explicit expressions for the non-uniform currents of the physical theory of diffraction are derived in terms of Fresnel functions for wedge diffraction by taking into account the surface integrals of the modified theory of physical optics. The obtained fringe waves are compared numerically by the asymptotic representations, found in the literature. (C) 2011 Elsevier GmbH. All rights reserved.
Citation - Scopus: 1
Fringe Waves on an Impedance Cylinder
(Elsevier Gmbh, Urban & Fischer verlag, 2013) Basdemir, H. Deniz
Surface diffraction of the plane waves from an impedance cylinder was investigated by the method of physical theory of diffraction (PTD). Physical optics (PO) method was used to gain the uniform scattered fields which are produced by the induced surface currents. Nonuniform currents and scattered fields were obtained by the method of PTD with the assistance of the exact solutions. (C) 2013 Elsevier GmbH. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 2
General Expression of the Diffracted Waves by a Half-Screen With Generalized Impedance Boundary Conditions
(Elsevier Gmbh, Urban & Fischer verlag, 2019) Umul, Yusuf Ziya
The 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.
Citation - WoS: 17
Citation - Scopus: 17
Integral Theory of Diffraction for Material Junctions
(Elsevier Gmbh, Urban & Fischer verlag, 2017) Umul, Yusuf Ziya
A 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.
Citation - WoS: 8
Citation - Scopus: 8
Kinetic Energy Based Relativistic Wave Equation
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Ziya
The Schrodinger equation is based on a Hamiltonian, which is the sum of kinetic and potential energies. The energy term, in the relativistic energy-momentum relation, is divided into its kinetic and rest energy components according to the Hamiltonian of the Schrodinger equation. The differential equation is obtained by using the plane wave representation. It is found that the derived form of the Klein-Gordon equation is more similar to the Schrodinger equation than the classical one. Non-relativistic limit is also studied.
Citation - WoS: 3
Citation - Scopus: 3
The Mtpo/Malyughinetz Hybrid Method for the Scattering Analysis of Parabolic Impedance Reflectors
(Elsevier Gmbh, Urban & Fischer verlag, 2013) Umul, Yusuf Ziya
The 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.
Citation - WoS: 7
Citation - Scopus: 6
The Photon Momentum
(Elsevier Gmbh, Urban & Fischer verlag, 2013) Umul, Yusuf Ziya
The momentum expression of a photon is derived by taking into account the absorption process by an electron. The defect of the actual momentum representation is shown by using the equations of energy and momentum conservation. The phase and group velocities of the photon that represents the particle aspect of light are also obtained with the aid of the new formulation. (C) 2013 Elsevier GmbH. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Physical Optics Based Simple Expressions for Diffracted Waves by Transmissive Half-Planes
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Ziya
The 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.
Radiation of Electromagnetic Waves by a Time-Harmonic Surface Charge Density
(Elsevier Gmbh, Urban & Fischer verlag, 2018) Umul, Yusuf Ziya
The radiation process of waves by a time harmonic electric charge density, located on the surface of a conducting sphere, is investigated. The current density is evaluated using the continuity equation. The scalar and vector potential are obtained by using the integral solution of the inhomogeneous Helmholtz equation. The radiated electric and magnetic fields are derived. The effect of the ground is put forth. The behaviors of the waves are studied numerically. (C) 2018 Elsevier GmbH. All rights reserved.

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