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: 1
Citation - Scopus: 1
Airy-Type Relativistic Matter Wave
(Elsevier Gmbh, 2021) Umul, Yusuf Ziya
A new relativistic Airy-type matter wave is introduced as a solution of the kinetic energy based wave equation. The parametric solution of the related differential equation is obtained. The total energy and momentum of the relativistic particle are derived by using a Bohmian type of decomposition of the kinetic energy based equation. The acceleration of the particle is also evaluated. The behavior of the matter wave is investigated numerically.
Citation - WoS: 4
Citation - Scopus: 4
An Analytical Solution for the Plane Wave Diffraction by a Resistive Half-Plane Residing at the Interface of Left and Right Handed Media
(Elsevier Gmbh, 2019) Basdemir, Husnu Deniz
The diffraction of waves by a resistive half-plane lying on the interface of left and right handed media is investigated in this study. Because of the anomalous refraction property of left handed media, shadow boundary shifts toward to the lower surface of the half-plane. In order to obtain the shifted boundary, diffracted waves are divided to subfields. Thus, obtained diffracted waves compensates the deficiency of geometries optics fields at the transition regions. The uniform version of waves is obtained by using the uniform theory of diffraction. The wave behaviors are examined numerically.
Citation - WoS: 1
Citation - Scopus: 1
Application of the Method of Transition Boundary To the Half-Planes With Mixed Boundary Conditions
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
The scattering problems of waves by soft-hard and hard-soft half-planes are investigated by the method of transition boundary. The functional values at the transition boundaries are found to be identical to the ones for the soft and hard half-screens. It is shown that the factorization process should be applied by also taking into account the boundary conditions besides the principle of reciprocity. The exact diffracted field expressions are obtained for both of the half-planes.
Comparison of Diffraction Methods for Lunar Occultations
(Elsevier Gmbh, 2020) Umul, Yusuf Z.
The only analytical method, which is used for the mathematical analysis of lunar occultations, is the Fresnel diffraction. The Fresnel integral is derived from the diffraction integral of Kirchhoff under some approximations. This paper aims to compare this method with the exact solution of Sommerfeld, which is obtained for a perfect electric conductor half-plane. The geometrical optics and diffracted fields are expressed separately. Numerical simulations are given for the comparison of two different total and diffracted waves.
Citation - WoS: 6
Citation - Scopus: 7
Diffraction by a Planar Junction Between Resistive and Perfect Electromagnetic Conductor Half-Screens
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
The interaction of plane electromagnetic waves by a planar junction between resistive and perfect electromagnetic conductor half-planes is investigated. First of all the initial waves for a whole resistive plane is evaluated. Then the scattered geometric optics fields are obtained from the difference of the total geometric optics and initial waves. The diffracted fields are evaluated with the aid of a relation between the scattered geometric optics and diffraction fields at the transition boundaries. It is found that the interaction between the two half-screens occur only for the z-polarized electric fields.
Citation - WoS: 1
Citation - Scopus: 1
Diffraction by an Anomalously Perfect Reflecting Metasurface Half-Plane
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
The scattering process of plane waves by a half-plane, composed of anomalously perfect reflecting surfaces, is investigated. The solution of the problem is obtained in an original way. The boundary condition of the problem is also taken into account in the construction of the edge diffracted field. The limiting case of the problem is the diffraction of waves by a perfect electric conductor half plane. The obtained field expression are analyzed numerically.
Citation - WoS: 2
Citation - Scopus: 3
Diffraction by an Interface Between Perfect Electromagnetic Conductor and Conductive Surfaces
(Elsevier Gmbh, 2021) Umul, Yusuf Ziya
The interaction of electromagnetic plane waves by a planar interface between conductive and perfect electromagnetic conductor half-planes is investigated. The method of transition boundary is used for the solution of the problem. The geometry, under consideration, is divided into two parts by using a relation, obtained for a perfect electromagnetic conductor half-plane. After obtaining the diffracted fields for sub-problems, they are combined into a single field for the coand cross-polarized waves. The behaviors of the total field and its components are analyzed numerically.
Diffraction in Time in the Relativistic Domain
(Elsevier Gmbh, 2021) Umul, Yusuf Ziya
The diffraction of matter waves in time is investigated by using the kinetic energy based relativistic wave equation for the quantum shutter problem. The differential equation is solved with the aid of the Fourier integral transform according to the spatial coordinate. A new Green's function is obtained and a scattering integral is composed for the wave function. The boundary condition of the quantum shutter problem is expressed in the kernel of the integral. Two field components are derived by the asymptotic evaluation of the scattering integral. The behavior of the scattered matter waves is studied in the relativistic and non-relativistic domains numerically.
Diffraction of Cylindrical Waves by an Impedance Half-Plane
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
The reflection coefficient of an impedance half-screen, illuminated by a line source field, is not the same with the one of a half-screen for plane wave incidence. This process also affects the structure of the diffraction coefficient. A new diffracted field should be obtained for the illumination of cylindrical waves. This paper introduces a new diffraction coefficient for the impedance half-plane, fed by cylindrical waves. The total and total geometric optics waves are also derived. The variation of the fields is studied numerically.
Citation - WoS: 4
Citation - Scopus: 5
Diffraction of Electromagnetic Waves by a Planar Interface Between Perfectly Absorbing and Anomalously Transmitting Metasurface Half-Planes
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
The interaction process of electromagnetic waves by a planar interface between perfectly absorbing and anomalously refracting metasurface half-planes is investigated. First of all, the scattered geometric optics field is obtained from the difference of the total geometric optics and initial waves. The diffracted fields are determined by using a relation between the scattered geometric optics and diffraction waves at the transition boundaries. It consists of the diffraction fields of perfectly absorbing and anomalously refracting metasurface half-screens. The behaviors of the total, total geometric optics and diffracted waves are studied numerically.
Citation - WoS: 3
Citation - Scopus: 3
Diffraction of Electromagnetic Waves by an Anomalously Transmitting Metasurface Half-Plane in Anisotropic Plasma
(Elsevier Gmbh, 2020) Umul, Yusuf Z.
The paper deals with the scattering of magnetic polarized electromagnetic plane waves by a anomalously transmitting metasurface half-plane, located in anisotropic plasma. Such a medium occurs for cold magnetized plasma, in which a static magnetic field exists. In this case the permittivity of the medium is expressed as a tensor, the elements of which are functions of the magnetostatic field, electron's mass and charge and angular frequency of the plasma. The metasurface half-plane transmits part of the incoming electromagnetic wave with a different angle from the angle of incidence, absorbing the remaining part. First of all, we will obtain the scattered geometric optics wave by subtracting the incident field from the total geometric optics wave. Then the kernel of a physical optics type scattering integral will be constructed with the aid of the integral theory of diffraction. The uniform diffracted magnetic field will be obtained from the physical optics integral. The total magnetic field will be evaluated as a sum of the total geometric optics and diffracted waves. The behaviours of the derived fields will be analyzed numerically.
Citation - WoS: 2
Citation - Scopus: 2
Diffraction of Plane Waves by the Interface Between Black and Soft/Hard Semi-Planes
(Elsevier Gmbh, 2012) Umul, Yusuf Z.
A theory of scattering, based on the non-perturbation of the incident field, is developed for the black bodies. The method is applied to the diffraction problem of plane waves by an interface between the black and soft/hard half-planes. The solutions are obtained in terms of infinite series and then transformed into Fresnel integrals. The scattered fields are investigated numerically. (C) 2011 Elsevier GmbH. All rights reserved.
Diffraction of Waves by a Discontinuous Edge Contour
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
An edge contour which is discontinuous is taken into account. The geometric optics and edge diffracted waves are obtained for the oblique incidence of a plane wave. The discontinuity in the geometry is expressed in terms of a unit step function. By using a property of the Fresnel function, the corner diffracted field is expressed.
Citation - WoS: 12
Citation - Scopus: 13
Diffraction of Waves by a Wedge Residing Between Two Different Media
(Elsevier Gmbh, 2018) Umul, Yusuf Ziya
The scattering problem of plane waves by a perfectly electric conducting wedge, residing at the planar interface of two media with different electromagnetic properties, is investigated. The structure of the scattered geometrical optics waves is used in order to determine the diffracted waves, which are expressed in terms of a split function that arises in the solution of the diffraction problem by a resistive half-plane. The uniform diffraction fields are obtained with the aid of uniform theory of diffraction. The behavior of the total, total geometrical optics and diffracted waves are studied numerically. (C) 2018 Elsevier GmbH. All rights reserved.
Citation - WoS: 19
Citation - Scopus: 17
Effects of Liver Tissue Turbulence on Propagation of Annular Beam
(Elsevier Gmbh, 2018) Baykal, Yahya; Gokce, Muhsin Caner
Effects of tissue turbulence on the propagation properties of an annular laser beam is examined. In this respect, the average intensity profile and the beam spread at the observation plane are formulated and evaluated after the annular laser beam propagates through the turbulent liver tissue. In our formulation, the extended Huygens-Fresnel method is utilized with the involvement of the turbulence power spectrum of the liver tissue. Results obtained from the performed simulations include the variations of the received average intensity and the effective beam size of the annular beam against the changes in the liver tissue turbulence and the laser beam parameters, i.e., against the laser wavelength, tissue length, primary and secondary source sizes of the annular laser beam. Our work in this paper will prove to be helpful in obtaining clues to diagnose abnormalities such as cancer and tumor in a liver tissue.
Citation - WoS: 12
Citation - Scopus: 12
Estimation of Scintillation and Bit Error Rate Performance of Sine Hollow Beam Via Random Phase Screen
(Elsevier Gmbh, 2019) Bayraktar, Mert
We study scintillation and bit error rate performance of sine hollow beam in turbulent atmosphere. Since source field expression involves higher order term, we model atmosphere utilizing random phase screen. We show that normal sine hollow beam (a = b) having higher order has the least scintillation index considering point like scintillation. This brings us bit error rate(BER) of this type of beam in turbulent atmosphere is less comparing with Gauss beam when we use point like receiver. BER of anomalous beam (a not equal b) having less scintillation index is lower than Gauss beam in strong turbulence region. In terms of aperture averaged scintillation, first order normal sine hollow beam and anomalous beams have less scintillation than Gauss beam.
Citation - Scopus: 1
The Factorization Process in the Modified Theory of Physical Optics
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
The factorization process is integrated to the procedure of the modified theory of physical optics. The scattering integral for the diffraction problem of waves by a soft half-plane is taken into account. The values of the kernel is obtained for two special values of the scattering angle beta. By considering the behavior of the integrand at these special values, a technique for the factorization process is determined. The new approach is applied to the problems of hard, impedance and conductive half-screens.
Citation - WoS: 7
Citation - Scopus: 8
Hermite Hyperbolic/Sinusoidal Gaussian Beams in Abcd Systems
(Elsevier Gmbh, 2007) Eyyuboglu, Halil Tanyer
For a Hermite hyperbolic/sinusoidal Gaussian beam with focusing properties, passing through an arbitrarily shaped rectangular aperture on the source plane and an on-axis x-y asymmetric ABCD system, the receiver plane expression is derived using the Collins integral. The specific example of a single thin lens placed on the propagation path is examined at selected source, propagation and optical element parameters. Viewing the progress of the beam in propagation, we find that subjecting the source beam to an aperture will give rise to excessive spreading during propagation. The lens setup will act to concentrate the energy of the beam around its focal point as expected, while in some circumstances it will also execute beam profile changes. By adjusting the aperture opening in the shape of a narrow slit, the beam will become aligned in the opposite direction after propagating after having traveled sufficiently. The results are presented as intensity graphs in the form of contour plots and 3D illustrations. (c) 2006 Elsevier GmbH. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 4
Impedance Surface Diffraction Analysis for a Strip With the Boundary Diffraction Wave Theory
(Elsevier Gmbh, 2013) Basdemir, H. Deniz
The content of the present paper is mainly about the application of the boundary diffraction wave theory to an impedance strip. This method reduces the diffraction surface integrals to line integrals. Hence, line integral directly gives the diffraction integral. Evaluation of diffraction integral gives only the diffracted fields. The vector potential which is used for the construction of the line integral is reduced to the modified theory of physical optics (MTPO) integral. With the assistance of this method diffracted fields are directly obtained and investigated numerically. (c) 2012 Elsevier GmbH. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Interaction of Electromagnetic Waves by a Cylindrical Parabolic Mesh Reflector
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
A cylindrical parabolic reflector, composed of mesh grid, is modeled by a resistive surface. The analysis of the scattered waves is performed by the physical optics integral, which was developed for resistive surfaces. The integral is evaluated asymptotically for large values of the wave-number in high-frequencies. The geometrical optics and diffracted fields are obtained by the methods of stationary phase and edge point respectively. The uniform forms of the diffracted waves are derived. The total wave and its components are investigated numerically for different values of surface resistivity.

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