Elektronik ve Haberleşme Mühendisliği Bölümü

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Citation - WoS: 0
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A new approach to the Dirac equation
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
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.
Citation - WoS: 0
Citation - Scopus: 0
A new series solution associated with the quantum harmonic oscillator
(Elsevier Gmbh, 2021) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
In the non-relativistic case, the problem of quantum harmonic oscillator is solved by the aid of the Schro spacing diaeresis dinger equation. An additional term of potential energy that is related with the square of the spatial coordinate is also included in the equation. A second order linear differential equation is obtained in the stationary state. The direct solution gives the wave function in terms of the parabolic cylinder functions. This solution leads to the Hermite polynomials when the quantization of energy is considered. However, the derived expression of the wave function does not yield the correct functions for the limiting case, in which the potential energy is zero. We put forth an alternative solution for the second order linear differential equation. First of all, a new series expression is suggested as an ansatz for the power series solution of differential equations. The coefficients of the series are obtained in terms of recurrence relations. Some computational simulations are given.
Citation - WoS: 0
Citation - Scopus: 0
A relativistic electron interacting with electromagnetic waves
(Elsevier Gmbh, 2021) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
A relativistic electron, in an electromagnetic wave is studied. The relativistic energy-momentum relation is taken into consideration for the derivation of a wave equation for spin-1/2 particle. The electromagnetic wave is represented by the electric scalar and magnetic vector potentials. Thus the spin information of the electron is integrated into the relativistic differential equation. A relativistic quantum wave equation is derived by using the derivatives with respect to time and spatial coordinates with respect to the kinetic energy and momentum of the electron. It is shown that the obtained relativistic equation directly reduces to the Pauli equation in the non-relativistic limit.
Citation - WoS: 1
Citation - Scopus: 1
A survey of the new proposal about the photon momentum
(Elsevier Gmbh, 2017) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
Bahadoran et al. [1] proposed that the new approach to photon momentum, introduced by Umul [2], was not correct, because they obtained a negative energy expression for the absorbed photon. In this comment, we show that this proposal is wrong, since the related authors made a mistake in their derivations. (C) 2017 Elsevier GmbH. All rights reserved.
Citation - WoS: 3
Citation - Scopus: 3
A survey on Klein paradox
(Elsevier Gmbh, 2019) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The solution of the relativistic tunneling problem with the aid of the Klein-Gordon and kinetic energy based wave equations are reviewed. The behaviors of the transmitted and reflected wave functions by the potential barrier are studied for different values of the barrier's energy. The reason of the Klein's paradox is put forth in terms of the structures of the wave equations.
Citation - WoS: 1
Citation - Scopus: 0
A uniform function for the diffraction of spherical waves
(Elsevier Gmbh, Urban & Fischer verlag, 2017) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
A function which occurs in the scattering problem of the spherical waves by a perfectly conducting half-plane is introduced for constructing the transition functions of the uniform theory of diffraction and uniform asymptotic theory of diffraction. The important properties of the function, related with the geometrical optics and diffracted field components, are derived mathematically. A uniform asymptotic theory of wedge diffraction is introduced based on the new function. The resultant field expressions-are investigated numerically. (C) 2016 Elsevier GmbH. All rights reserved.
Citation - WoS: 110
Citation - Scopus: 112
Active laser radar systems with stochastic electromagnetic beams in turbulent atmosphere
(Optica Publishing Group, 2008) Cai, Yangjian; Korotkova, Olga; Eyyuboglu, Halil T.; Baykal, Yahya; 7688; 7812
Propagation of stochastic electromagnetic beams through paraxial ABCD optical systems operating through turbulent atmosphere is investigated with the help of the ABCD matrices and the generalized Huygens-Fresnel integral. In particular, the analytic formula is derived for the cross-spectral density matrix of an electromagnetic Gaussian Schell-model (EGSM) beam. We applied our analysis for the ABCD system with a single lens located on the propagation path, representing, in a particular case, the unfolded double-pass propagation scenario of active laser radar. Through a number of numerical examples we investigated the effect of local turbulence strength and lens' parameters on spectral, coherence and polarization properties of the EGSM beam. (C) 2008 Optical Society of America
Citation - WoS: 1
Citation - Scopus: 1
Airy-type relativistic matter wave
(Elsevier Gmbh, 2021) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 4269; Elektronik ve Haberleşme Mühendisliği
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; Başdemir, Hüsnü Deniz; 20399; Elektronik ve Haberleşme Mühendisliği
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: 183
Citation - Scopus: 193
Analysis of reciprocity of cos-Gaussian and cosh-Gaussian laser beams in a turbulent atmosphere
(Optical Soc Amer, 2004) Eyyuboglu, HT; Baykal, Y; 7688; 7812
In a turbulent atmosphere, starting with a cos-Gaussian excitation at the source plane, the average intensity profile at the receiver plane is formulated. This average intensity profile is evaluated against the variations of link lengths, turbulence levels, two frequently used free-space optics wavelengths, and beam displacement parameters. We show that a cos-Gaussian beam, following a natural diffraction, is eventually transformed into a cosh-Gaussian beam. Combining our earlier results with the current findings, we conclude that cos-Gaussian and cosh-Gaussian beams act in a reciprocal manner after propagation in turbulence. The rates (paces) of conversion in the two directions are not the same. Although the conversion of cos-Gaussian beams to cosh-Gaussian beams can happen over a wide range of turbulence levels (low to moderate to high), the conversion of cosh-Gaussian beams to cos-Gaussian beams is pronounced under relatively stronger turbulence conditions. Source and propagation parameters that affect this reciprocity have been analyzed. (C) 2004 Optical Society of America.
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; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
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 - WoS: 53
Citation - Scopus: 58
Average intensity and spreading of an elegant Hermite-Gaussian beam in turbulent atmosphere
(Optical Soc Amer, 2009) Yuan, Yangsheng; Cai, Yangjian; Qu, Jun; Eyyuboglu, Halil T.; Baykal, Yahya; 7688; 7812
The propagation of an elegant Hermite-Gaussian beam (EHGB) in turbulent atmosphere is investigated. Analytical propagation formulae for the average intensity and effective beam size of an EHGB in turbulent atmosphere are derived based on the extended Huygens-Fresnel integral. The corresponding results of a standard Hermite-Gaussian beam (SHGB) in turbulent atmosphere are also derived for the convenience of comparison. The intensity and spreading properties of EHGBs and SHGBs in turbulent atmosphere are studied numerically and comparatively. It is found that the propagation properties of EHGBs and SHGBs are much different from their properties in free space, and the EHGB and SHGB with higher orders are less affected by the turbulence. What's more, the SHGB spreads more rapidly than the EHGB in turbulent atmosphere under the same conditions. Our results will be useful in long-distance free-space optical communications. (C) 2009 Optical Society of America
Citation - WoS: 112
Citation - Scopus: 115
Average irradiance and polarization properties of a radially or azimuthally polarized beam in a turbulent atmosphere
(Optical Soc Amer, 2008) Cai, Yangjian; Lin, Qiang; Eyyuboglu, Halil T.; Baykal, Yahya; 7688; 7812
Analytical formulas are derived for the average irradiance and the degree of polarization of a radially or azimuthally polarized doughnut beam (PDB) propagating in a turbulent atmosphere by adopting a beam coherence-polarization matrix. It is found that the radial or azimuthal polarization structure of a radially or azimuthally PDB will be destroyed (i.e., a radially or azimuthally PDB is depolarized and becomes a partially polarized beam) and the doughnut beam spot becomes a circularly Gaussian beam spot during propagation in a turbulent atmosphere. The propagation properties are closely related to the parameters of the beam and the structure constant of the atmospheric turbulence. (C) 2008 Optical Society of America.
Citation - WoS: 5
Citation - Scopus: 8
Babinet's principle in the Fraunhofer diffraction by a finite thin wire
(Elsevier Gmbh, Urban & Fischer verlag, 2011) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
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.
Citation - WoS: 4
Citation - Scopus: 4
Boundary diffraction wave theory approach to corner diffraction
(Springer, 2019) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The scattering process of plane waves by a discontinuous edge contour is studied with the three dimensional boundary diffraction wave theory. The edge and corner diffracted fields are obtained from the stationary phase and edge point evaluations of the line integral. A new corner diffraction coefficient is derived. The behaviors of the uniform edge and corner diffracted waves are investigated numerically.
Citation - WoS: 4
Citation - Scopus: 4
Bounds for generalized gamma distributed fading channels
(Ieee-inst Electrical Electronics Engineers inc, 2011) Gazi, Orhan; Gazi, Orhan; 102896; Elektronik ve Haberleşme Mühendisliği
In this article, upper bounds for the outage probability and moment generating functions of the fading channels with alpha - mu distribution are derived. The proposed upper bound for the moment generating function is used in the performance evaluation of M - PSK communication systems. The derived expressions are simple to use and do not require complex software tools to evaluate. We verified the proposed expressions via numerical computations.
Citation - WoS: 7
Citation - Scopus: 8
Collision free row column s-random interleaver
(Ieee-inst Electrical Electronics Engineers inc, 2009) Gazi, Orhan; Gazi, Orhan; Yilmaz, A. Oezguer; 102896; Elektronik ve Haberleşme Mühendisliği
Parallel decodable turbo codes (PDTCs) are suitable for concurrent decoding and hence have low latency. Memory collision issue is an important problem met during parallel processing. In this article, we propose a collision free interleaver for parallel processing operations. The performance of PDTCs is analyzed with the proposed random interleaver preventing the memory collision problem. Distance spectra of PDTCs with the proposed interleaves are computed and compared to those with S-random interleaver.
Citation - WoS: 0
Citation - Scopus: 0
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.; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
Citation - WoS: 8
Citation - Scopus: 8
Comparative analysis on wavelet-based detection of finite duration low-amplitude signals related to ventricular late potentials
(Iop Publishing Ltd, 2004) Mousa, A; Yilmaz, A
Ventricular late potentials (VLPs) are considered as a noninvasive marker of patients with myocardial infarction, who are prone to the development of ventricular tachycardia. This paper investigates the effects of variations in physical properties of myocardial infarcts in terms of their effects on the parametric variations in VLP analysis. A sufficiently large set of signals underlining the behavior of physical parameters was employed to represent the effect of physical size, position, orientation and type of infarct. The approximated signals are variations from real electrocardiography signals by adding potentials representing late potentials based on duration, frequency, amplitude and position. The aim is not to exactly model VLP but rather to generate an approximate set of signals to examine the performance of the standard methods for different possibilities in infarct dynamics. We investigate some of the detection approaches together with their related assumptions, and try to pinpoint the drawbacks and inaccuracies of these methods and also their assumptions. The three widely accepted criteria-QRS duration, root-mean-square and duration of the signal at the end of QRS for VLP detection-were used in the investigation. Results from the application of these parameters to the set of signals are presented. In addition we investigate the physical nature of an infarct and list a number of possible reasons that might be the cause of a low success rate for the detection of additive potentials. To improve the performance of the common methods, two more wavelet transform parameters are added to those of the standard methods. The method derived from this analysis is presented as an alternative means for the detection of late signals named as delayed potentials, a more general class that includes VLP as a subset.
Citation - WoS: 0
Citation - Scopus: 0
Comparison of Diffraction Methods for Lunar Occultations
(Elsevier Gmbh, 2020) Umul, Yusuf Z.; Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
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.

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