Browsing by Author "Umul, Yusuf Ziya"

Now showing 1 - 20 of 112

Citation - WoS: 3
Citation - Scopus: 3
A hybrid Maliuzhinets/PO method for diffraction problems by impedance wedges
(Elsevier Science Bv, 2011) Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The solution of Maliuzhinets of the diffraction problem of waves by an impedance wedge is transformed into a physical optics integral. The resultant expression is suitable for the investigation of various diffraction problems having impedance wedges. The method is applied to the scattering of waves by an impedance spherical reflector with wedge structure at its discontinuity. The results are examined numerically. (C) 2011 Elsevier B.V. All rights reserved.
A new approach to the Dirac equation
(Elsevier Gmbh, 2019) 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: 6
Citation - Scopus: 5
A new representation of the Kirchhoffs diffraction integral
(Elsevier Science Bv, 2013) Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The diffraction integral of Kirchhoff is rearranged according to its integral boundaries. The new approach is based on the theory of the edge dislocation waves and provides a more correct field representation for the semi-infinite and infinite integrals in the direct numerical computation. The integral is studied on the diffraction problem of plane waves by a perfectly conducting half-plane. The correctness of the scattering diagrams is compared with the classical approach and the Fresnel integral representation of the scattered waves numerically. (c) 2012 Elsevier B.V. All rights reserved.
A new series solution associated with the quantum harmonic oscillator
(Elsevier Gmbh, 2021) 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.
A relativistic electron interacting with electromagnetic waves
(Elsevier Gmbh, 2021) 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; 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; 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
A uniform function for the diffraction of spherical waves
(Elsevier Gmbh, Urban & Fischer verlag, 2017) 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: 1
Citation - Scopus: 1
Airy-type relativistic matter wave
(Elsevier Gmbh, 2021) 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: 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; 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: 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; 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.
Babinet's principle in the Fraunhofer diffraction by a finite thin wire
(Elsevier GMBH, 2011) 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
Citation - WoS: 4
Citation - Scopus: 4
Beam diffraction by a resistive half-plane
(Optical Soc Amer, 2015) Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The scattering of a Gaussian beam by a resistive half-screen is investigated. Far-field approximation is used in evaluation of geometrical optics and diffracted waves. The uniform expression of the diffracted waves by the resistive half-plane, which was found with the Sommerfeld-Maliuzhinets method, is obtained. The scattered fields for the case of the beam incidence are evaluated with the technique of a complex point source. The resultant wave expressions are examined numerically. (C) 2015 Optical Society of America
Citation - WoS: 4
Citation - Scopus: 4
Boundary diffraction wave theory approach to corner diffraction
(Springer, 2019) 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: 5
Citation - Scopus: 5
Boundary diffraction wave theory of junctions between two surfaces with different face impedances
(Elsevier Sci Ltd, 2012) Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The 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.
Citation - WoS: 1
Citation - Scopus: 1
Boundary diffraction wave theory of resistive surfaces with edge discontinuities
(Elsevier, 2011) Umul, Yusuf Ziya; 42699; Elektronik ve Haberleşme Mühendisliği
The line integral of the boundary diffraction wave theory is derived by considering the exact diffracted fields of a resistive half-plane. The line integral is generalized for arbitrary resistive surface with edge discontinuity. The method is applied to the diffraction problem of waves by a convex resistive spherical reflector and the resultant field expressions are investigated numerically. (C) 2011 Elsevier B.V. All rights reserved.
Comparison of physical optics integral and exact solutions for cylinder problem
(2003) Umul, Yusuf Ziya; Yengel, Emre; Aydın, Ayhan; Elektronik ve Haberleşme Mühendisliği; Elektrik-Elektronik Mühendisliği; Bilgisayar Mühendisliği
The sound source composition of the urban sound environment varies depending on the geography and socio-cultural context. Current sound taxonomies in the literature categorize urban sound sources by their source types (e.g., human-made, natural, electromechanical) and respective semantic attributes. This study aims to add another taxonomical layer to the existing urban sound source categorization methods. The additional layer is a recently proposed sound source classification framework (CLIC). The CLIC framework identifies sound sources based on their Diegesis and Intention parametric attributes. The former parametric attribute, diegesis, was derived from film sound design. The geographical and socio-cultural context of the built environment can be considered as its narrative; hence, every event that happens within the functional context can be called diegetic, while the events that do not belong to that specific place can be called nondiegetic. The latter parametric attribute, intention, was derived from product design. One of the prominent sound source categorization methods in product sound design is to group the product emitted sounds as consequential and intentional. Combining these two parametric attributes with the existing taxonomies, the CLIC framework outputs a place-specific design guideline, clearly dictating the actions a sound designer should take. The two parametric attributes group the sound sources under four distinct areas, which dictates the degree of influence of designers on the specific sound source. The four zones are defined as the creation zone, limitation zone, isolation zone, and control zone. Each zone dictates step-by-step sound design instructions for the sound designer. This study consists of two main phases: field recordings and web-based listening tests. The sound sources present in the urban sound environment were identified in the field recordings phase. Later, in the web-based listening tests phase, the identified sound sources were evaluated based on the CLIC framework, and hence, their respective zones on the model were identified. The outcomes of the study propose clear step-by-step design guidelines and present action suggestions for environmental sound designers.
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; 42699; Elektronik ve Haberleşme Mühendisliği
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; 42699; Elektronik ve Haberleşme Mühendisliği
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; 42699; Elektronik ve Haberleşme Mühendisliği
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.