Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu

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

Browse

Now showing 1 - 20 of 57

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.
Citation - Scopus: 1
Relativistic Wave Equation for a Quantum Particle With Potential Energy
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
A new relativistic wave equation is derived for a quantum particle which moves in a potential. The relativistic equation of energy is reconsidered with the potential energy term. The energy-momentum relation is obtained for this case. The related differential equation is derived by taking into account a wave function in terms of a plane wave. It is shown that the new equation directly reduces to the Schrodinger equation of a particle, moving in a potential in the non-relativistic limit. The wave equation is applied to the interaction of wave function with a potential barrier.
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.
Modified Theory of Physical Optics Approach To Impedance Surfaces for Skew Incidence
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
A three dimensional modified theory of physical optics integral is constructed for the impedance surfaces, illuminated by a plane wave for skew incidence. The scalar fields are taken into account. The kernel of the physical optics integral is evaluated by using a relation with the geometric optics waves and stationary phase evaluation of the integral. The obtained surface integral is applied to the diffraction problem of waves by an impedance half-plane. The scattered fields are investigated numerically.
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.
The Standing Matter Waves and Bohm's Quantum Potential
(Elsevier Gmbh, 2021) Umul, Yusuf Ziya
The standing wave type wave functions are investigated in terms of Bohm's decomposition of the Schro spacing diaeresis dinger equation. It is shown that the quantum potential, obtained for the standing matter waves, is always different from zero. However, it is also put forth that the wave function do not satisfy the Bohm's equations except one case, which is defined in the Cartesian coordinates. The Airy type matter wave is also analyzed in terms of the Bohmian approach.
Citation - WoS: 3
Citation - Scopus: 5
Modified Theory of Physical Optics and the Correction Terms of the Physical Theory of Diffraction
(Elsevier Gmbh, 2018) Umul, Yusuf Ziya
The methods of physical optics and physical theory of diffraction are reviewed for electromagnetic waves. The Fermat principle and its' modified version are investigated and the necessity of the introduction of a variable unit vector is put forth. The scattering integrals of modified theory of physical optics are reviewed in this context. Recent comments on the modified theory of physical optics are discussed and refuted clearly. A proof is given on the nature of the physical theory of diffraction's correction terms. The proof is visualized with some numerical simulations.
Citation - WoS: 1
Citation - Scopus: 2
The Surface Wave Phenomenon on an Impedance Half-Plane
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
The excitation of surface waves on an impedance half-plane is investigated by considering the complex integral of scattering. The poles of the split function are examined with respect to some criteria, obtained from an inhomogeneous plane wave. It is shown that two poles of the complex integral lead to null fields. The surface wave expressions were derived according to the remaining two poles. The diffraction of the surface waves at the edge discontinuity of the half-plane is studied by using the theory, developed for grazing incidence. The uniform representation of the diffracted field is performed according to the uniform theory for evanescent waves. The behaviors of the obtained field expressions were examined numerically.
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.
A New Approach To the Dirac Equation
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
Dirac equation is based on a novel method that expresses the roots of a square-root operation in terms of matrices. Instead of this technique we propose an alternative approach. The square-root expression is represented as a hypotenuse and it is written in terms of a trigonometric summation of the remaining two edges of a right-angle triangle. Both of the positive and negative energy terms are taken into account and a new matrix equation is obtained. The plane wave solutions of the new differential equation are studied.
Wave Diffraction by an Impedance Wedge
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
A new diffraction field expression is proposed for a wedge with different face impedances. The modified theory of physical optics based diffraction coefficient is taken into account. The reflection coefficients are expressed in terms of the split functions that occur in the double integral solution of the resistive half-plane problem. The effects of wedge's each faces are represented separately. The uniform field expression is obtained and compared with the literature for a right-angled impedance wedge numerically.
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: 4
Citation - Scopus: 5
Surface Wave Contribution in Physical Optics Type Scattering Integrals
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
The contribution of the poles in a real valued physical optics integral is investigated. First of all, a complex integral of scattered waves is taken into account. The edge diffracted and surface wave components are evaluated by the methods of saddle point and Cauchy integral theorem. The physical optics integral is constructed with the aid of the asymptotic expressions of the edge diffraction field. A second PO integral is obtained for the surface waves. The theory is applied to an impedance half-plane.
Citation - WoS: 2
Citation - Scopus: 2
Scattering of Electromagnetic Waves by a Perfectly Conducting Half-Screen at the Interface of Two Different Media: E-Polarization
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
The interaction of electromagnetic waves with a perfectly conducting half-screen, which is residing between two media with different electromagnetic properties, is investigated for electric polarization. The diffracted fields, in two regions, are determined by using a relation between diffraction and scattered geometric optics waves. Additional terms are included in the diffracted waves in order to satisfy the boundary conditions in the interface. The behavior of the total field and its components are analyzed numerically.
Citation - WoS: 12
Citation - Scopus: 13
Three Dimensional Modified Theory of Physical Optics
(Elsevier Gmbh, 2016) Umul, Yusuf Ziya
The three dimensional version of the modified theory of physical optics is introduced with the aid of a Green's function that satisfies the Helmholtz equation in local spherical coordinates. The algorithm which leads to the construction of the scattering integral is given. The method is applied to the three dimensional diffraction problem of plane waves by a perfectly conducting half-plane. The comparison of the resulting field expressions with the literature shows that the modified theory of physical optics leads to the exact solution. (C) 2015 Elsevier GmbH. All rights reserved.
Citation - WoS: 1
Citation - Scopus: 1
Kinetic Energy Based Relativistic First Order Wave Equations
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
A relativistic wave equation is derived for spin-1/2 particles. The energy relation is taken into account with respect to the kinetic energy term. Two first order differential equations are obtained from the kinetic energy based relativistic equations. The spin information is integrated to the new equations in two alternative forms.
Citation - WoS: 14
Citation - Scopus: 15
Scattering of Electromagnetic Waves by a Perfect Electromagnetic Conductor Half-Screen
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya
The diffraction of plane electromagnetic waves by a perfect electromagnetic conductor half screen is investigated. The total geometrical optics fields are obtained by using the boundary conditions of a perfect electromagnetic conductor surface. A general relation is defined for the scattered fields in terms of waves by soft and hard surfaces. The total scattered field is derived by using this relation. Some numerical simulations are also given.
Citation - WoS: 2
Citation - Scopus: 8
Scattering of Electromagnetic Waves by an Impedance Sheet Junction in Anisotropic Plasma
(Elsevier Gmbh, 2020) Umul, Yusuf Ziya
The diffraction of electromagnetic plane waves by the edge discontinuity of an impedance sheet junction, which is located in an anisotropic plasma, is investigated. The problem is solved by the integral theory of diffraction. The scattering integral is obtained from the scattered geometric optics wave. The diffracted fields are derived by the edge point evaluation of the scattering integral. The evaluated field expressions are analyzed numerically.
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
Wedge Diffraction Model in Gravitational Lensing by Cosmic Strings
(Elsevier Gmbh, 2018) Umul, Yusuf Ziya
A cosmic string forms a conical topology, which enables a diffraction phenomenon by a wedge with an inner angle, equals to the double of the deficit angle. A wedge, on the edge of which the string is located, is defined in the flat space-time. The radiated wave from a star is represented by two plane waves, propagating on the two surfaces of the wedge for grazing incidence. The uniform expressions of the diffracted waves are obtained and investigated numerically. (C) 2017 Elsevier GmbH. All rights reserved.

Browse

Browsing Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu by Publisher "Elsevier Gmbh"