Elektronik ve Haberleşme Mühendisliği Bölümü Yayın Koleksiyonu
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Article Citation - WoS: 12Citation - Scopus: 17Abstraction-Based Verification of Codiagnosability for Discrete Event Systems(Pergamon-elsevier Science Ltd, 2010) Schmidt, K.In this paper, we investigate the verification of codiagnosability for discrete event systems (DES). That is, it is desired to ascertain if the occurrence of system faults can be detected based on the information of multiple local sites that partially observe the overall DES. As an improvement of existing codiagnosability tests that resort to the original DES with a potentially computationally infeasible state space, we propose a method that employs an abstracted system model on a smaller state space for the codiagnosability verification. Furthermore, we show that this abstraction can be computed without explicitly evaluating the state space of the original model in the practical case where the DES is composed of multiple subsystems. (c) 2010 Elsevier Ltd. All rights reserved.Article Citation - WoS: 2Citation - Scopus: 1Airy-Type Relativistic Matter Wave(Elsevier Gmbh, 2021) Umul, Yusuf ZiyaA 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.Article Citation - WoS: 4Citation - Scopus: 4An 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 DenizThe 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.Article Citation - WoS: 4Citation - Scopus: 5Application of the Complex Point Source Method To the Schrodinger Equation(Elsevier Sci Ltd, 2010) Umul, Yusuf Z.The paraxial wave equation is a reduced form of the Helmholtz equation. Its solutions can be directly obtained from the solutions of the Helmholtz equation by using the method of complex point source. We applied the same logic to quantum mechanics, because the Schrodinger equation is parabolic in nature as the paraxial wave equation. We defined a differential equation, which is analogous to the Helmholtz equation for quantum mechanics and derived the solutions of the Schrodinger equation by taking into account the solutions of this equation with the method of complex point source. The method is applied to the problem of diffraction of matter waves by a shutter. (C) 2010 Elsevier Ltd. All rights reserved.Article Citation - WoS: 1Citation - Scopus: 1Application of the Method of Transition Boundary To the Half-Planes With Mixed Boundary Conditions(Elsevier Gmbh, 2020) Umul, Yusuf ZiyaThe 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.Editorial Citation - WoS: 6Citation - Scopus: 6Applications of Cognitive Radio Networks: Recent Advances and Future Directions(Sage Publications inc, 2016) Pan, Miao; Joshi, Gyanendra Prasad; Gazi, Orhan; He, Jianhua; Coupechoux, Marceau; Kim, Sung W.Article Citation - WoS: 12Citation - Scopus: 12Averaging of Receiver Aperture for Flat-Topped Incidence(Elsevier Sci Ltd, 2013) Kamacioglu, Canan; Baykal, Yahya; Yazgan, ErdemUsing a flat-topped profile for the incident beam, the power scintillation index for weak atmospheric turbulence is formulated and analytically evaluated. Through the use of the aperture averaging factor, the averaging effect of the finite receiver aperture on the intensity fluctuations for a flat-topped incident beam is examined. The influence of the order of flatness on the averaging is investigated. At large propagation lengths, increasing the flatness parameter decreases the power scintillations and it is possible to further reduce the scintillation by increasing the receiver aperture. Increasing the structure constant increases this effect. (C) 2013 Elsevier Ltd. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 8Babinet's Principle in the Fraunhofer Diffraction by a Finite Thin Wire(Elsevier Gmbh, Urban & Fischer verlag, 2011) Umul, Yusuf ZiyaThe 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.Article Citation - WoS: 5Citation - Scopus: 5Boundary Diffraction Wave Theory of Junctions Between Two Surfaces With Different Face Impedances(Elsevier Sci Ltd, 2012) Umul, Yusuf ZiyaThe line integral of the boundary diffraction wave theory is derived for the diffraction process of waves by a junction between two surfaces with different face impedances. The exact solution of Maliuzhinets is used with this aim. The resultant integral is applied to the diffraction of waves by a circular junction between two impedance surfaces. The results are examined numerically. (C) 2011 Elsevier Ltd. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 4Bounds for Generalized Gamma Distributed Fading Channels(Ieee-inst Electrical Electronics Engineers inc, 2011) Gazi, OrhanIn 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.Article Citation - WoS: 11Citation - Scopus: 12Changes of the Centroid Position of Laser Beams Propagating Through an Optical System in Turbulent Atmosphere(Elsevier Sci Ltd, 2013) Ji, Xiaoling; Baykal, Yahya; Jia, XinhongIn this paper, the effects of atmospheric turbulence, initial field amplitude, optical system and thermal blooming on the centroid position of laser beams propagating through the atmosphere are studied in detail. With the average over the ensemble of the turbulent medium, the centroid position is independent of turbulence. However, the centroid position depends on the centroid positions at the source plane and in the far-field, and the elements of ray-transfer-matrix. The physical reason why the centroid position changes on propagation is that the far-field centroid position is not located on the propagation z-axis due to the field phase distortion and the decentred intensity. The centroid position of laser beams with the spherical aberration and the decentred intensity is examined analytically. When laser beams with the decentred intensity propagate through the atmosphere, the effect of thermal blooming on the centroid position is investigated by using the four-dimensional (4D) computer code of the time-dependent propagation of high power laser beams through the atmosphere. (C) 2013 Elsevier Ltd. All rights reserved.Article Citation - WoS: 7Citation - Scopus: 8Collision Free Row Column S-Random Interleaver(Ieee-inst Electrical Electronics Engineers inc, 2009) Yilmaz, A. Oezguer; Gazi, OrhanParallel 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.Correction 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.Editorial Citation - WoS: 5Citation - Scopus: 5Comments on "on the Modified Theory of Physical Optics(Ieee-inst Electrical Electronics Engineers inc, 2014) Umul, Yusuf Z.Article 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.Article Citation - WoS: 8Citation - Scopus: 8Cylindrical-Sinc Beam(Elsevier Gmbh, Urban & Fischer verlag, 2014) Bayraktar, Mert; Basdemir, H. DenizPropagation 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.Article Citation - WoS: 45Citation - Scopus: 47Density Functional Study of Albn Clusters for N=1-14(Elsevier Science Sa, 2011) Boyukata, Mustafa; Guvenc, Ziya B.Density functional theory (DFT) B3LYP at 6-311++G(d,p) level is employed to optimize the structures of AlBn (n = 1-14) microclusters. Analysis of the energetic and structural stability of these clusters and their various isomers are presented. Total and binding energies of the clusters have been calculated. Their harmonic frequencies, point symmetries, and the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps have been determined. Results are evaluated by comparing to the previous similar works. (C) 2011 Elsevier B.V. All rights reserved.Article Citation - WoS: 15Citation - Scopus: 15A Density Functional Study of Small Li-B and Li-B Clusters(Pergamon-elsevier Science Ltd, 2009) Yildirim, E. K.; Guvenc, Z. B.In this work we present the results of a detailed theoretical research for the small LinBm clusters and their hydrogen storage properties by means of density functional theory. All calculations were performed by using Gaussian03 program. For the optimization of the clusters 6-311++G(d,p) basis set was employed. We have chosen global minimum of B-6 cluster as the starting point and replaced the boron atoms one at a time, in a stepwise manner, with Li atoms. For these new structures we have searched for the stable configurations, and calculated their energies, HOMO-LUMO energy gaps, Raman and infrared data, average boron, and lithium charge distribution, and vibrational frequencies. Our results show that as the number of Li atoms increases, stability of the clusters decreases and they become more reactive. In addition to that, there are significant charge transfers from boron atoms to lithium atoms on average. The hydrogen storage capabilities of the most stable isomers of LinBm and B-6 clusters have also been investigated by the same methods, and the results are compared. The Li3B3 has the highest hydrogen storage capacity among the clusters investigated in this study. Furthermore, formation of hydrogen molecules is observed in the vicinity of the clusters, some of which are attached to the Li atoms. In addition, as the number of hydrogen atoms increases, the boron atoms are separated from the other boron atoms, and they form satellite BHx (x = 3,4) clusters around the center. These are attached to the system by a bridging bond of a hydrogen or a Li atom. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.Article Citation - WoS: 4Citation - Scopus: 3Developing Interaction Potential for H (2h) → Cu(111) Interaction System: a Numerical Study(Elsevier Science Bv, 2010) Vurdu, Can D.; Guevenc, Ziya B.In this study, we have used London-Eyring-Polanyi-Sato (LEPS) functional form as an interaction potential energy function to simulate H (2H) -> Cu(1 1 1) interaction system The parameters of the LEPS function are determined in order to analyze reaction dynamics via molecular dynamics computer simulations of the Cu(1 1 1) surface and H/(2H) system. Nonlinear least-squares method is used to find the LEPS parameters. For this purpose, we use the energy points which were calculated by a density-functional theory method with the generalized gradient approximation including exchange-correlation energy for various configurations of one and two hydrogen atoms on the Cu(1 1 1) surface. After the fitting procedures, two different parameters sets are obtained that the calculated root-mean-square values are close to each other. Using these sets, contour plots of the potential energy surfaces are analyzed for H -> Cu(1 1 1) and 2H -> Cu(1 1 1) interactions systems. In addition. sticking, penetration, and scattering sites on the surface are analyzed by using these sets. (C) 2009 Elsevier B.V. All rights reserved.Article Citation - WoS: 13Dft Study of Al Doped Cage B12hn Clusters(Pergamon-elsevier Science Ltd, 2011) Boyukata, Mustafa; Guvenc, Ziya B.Density Functional Theory (DFT) with B3LYP/6-311++g** level has been performed to investigate the electronic structures of cage B12Hn for up to n <= 12 and AlB12Hn for up to n <= 13. Moreover, the computations has been extended to the charged clusters of [B12H12](q), [AlB12H12](q) and [AlB12H13](q) where (q = +/- 1 and +/- 2). Their energetics are calculated and structural analysis have been carried out. Cage form of the B-12 remains stable against to hydrogen adsorptions. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
