PubMed İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/8650
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Browsing PubMed İndeksli Yayınlar Koleksiyonu by Author "42699"
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Article Diffraction by a black half plane: Modified theory of physical optics approach(Optical Soc Amer, 2005) Umul, YZ; Umul, Yusuf Ziya; 42699The scattered fields from a black half plane which absorbs all the incoming electromagnetic energy are evaluated by defining a new modified theory of physical optics surface current. This current eliminates the reflected fields, coming from the first stationary point of the reflection integral and only creates a reflected diffracted field. The incident scattered fields are found from the same integral, written for the perfectly conducting half plane. The scattered fields are evaluated by using the stationary phase method and edge point technique. The evaluated fields are plotted numerically. (c) 2005 Optical Society of America.Article Diffraction of evanescent plane waves by a resistive half-plane(Optical Soc Amer, 2007) Umul, Yusuf Z.; Umul, Yusuf Ziya; 42699Diffraction of evanescent plane waves by a resistive half-plane is examined. The scattering integrals are constructed with the modified theory of physical optics. These integrals are evaluated uniformly by using an unusual method. The scattered fields of evanescent waves are obtained by giving the angle of incidence a complex value. The diffracted waves are plotted numerically for different parameters of the incident field. (c) 2007 Optical Society of America.Article Diffraction of homogeneous and inhomogeneous plane waves by a planar junction between perfectly conducting and impedance half-planes(Optical Soc Amer, 2007) Umul, Yusuf Z.; Umul, Yusuf Ziya; 42699The problem of diffraction of homogeneous and inhomogeneous plane waves at the discontinuity formed by perfectly conducting and impedance half-planes is examined by the method of modified theory of physical optics (MTPO). The MTPO integral of the reflected scattered waves by the perfectly conducting half-plane is reconstructed in order to include the effect of the diffracted wave coming from the edge of the impedance halfplane. The integrals are evaluated by a uniform asymptotic method. The results are plotted numerically and compared with the literature. (C) 2007 Optical Society of AmericaArticle Diffraction of plane electromagnetic waves by a resistive half-screen for skew incidence(Optical Soc Amer, 2020) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699The scattering process of electromagnetic plane waves by a resistive half-screen is investigated for oblique incidence. First of all, it is shown that the existing solution in the literature is not correct, because the problem was solved by considering the normal components of the electromagnetic field, in terms of which the boundary conditions cannot be expressed. Instead of these, the components of the electric field, which is parallel to the edge discontinuity, are taken into account. The diffracted fields are obtained with the aid of the method of transition boundary. The uniform field expressions are obtained by using the Fresnel function. The behaviors of the total field and its subcomponents are analyzed numerically. (C) 2019 Optical Society of AmericaArticle Edge-dislocation waves in the diffraction process by an impedance half-plane(Optical Soc Amer, 2007) Umul, Yusuf Z.; Umul, Yusuf Ziya; 42699Edge-dislocation waves, created in the diffraction of plane waves by an impedance half-plane, are examined by the method of modified theory of physical optics. The integrals, obtained by a related technique, are decomposed according to their boundaries and evaluated by using uniform asymptotic methods. The results are plotted and are investigated numerically. (c) 2007 Optical Society of AmericaArticle Equivalent functions for the Fresnel integral(Optical Soc Amer, 2005) Umul, YZ; Umul, Yusuf Ziya; 42699Fresnel integral is modeled with three equivalent functions. The first function is derived by considering the sum of the first term of the Fresnel integral's asymptotic expansion {(F) over cap (x)} and an exponential function which approaches to infinity at the zero of the Fresnel function's argument and has the properties of a unit step function. The second one is the sum of a unit step function and the transition function defined for the simplified uniform theory of diffraction. The third function considers directly eliminating the infinity coming from (F) over cap (x). The amplitude and the phase of Fresnel integral and its equivalent functions are compared numerically. The result is applied to the modified theory of physical optics solution of the diffraction of edge waves from a half plane problem. (c) 2005 Optical Society of America.Article Modified theory of physical optics(Optica Publishing Group, 2004) Umul, YZ; Umul, Yusuf Ziya; 42699A new procedure for calculating the scattered fields from a perfectly conducting body is introduced. The method is defined by considering three assumptions. The reflection angle is taken as a function of integral variables, a new unit vector, dividing the angle between incident and reflected rays into two equal parts is evaluated and the perfectly conducting (PEC) surface is considered with the aperture part, together. This integral is named as Modified Theory of Physical Optics (MTPO) integral. The method is applied to the reflection and edge diffraction from a perfectly conducting half plane problem. The reflected, reflected diffracted, incident and incident diffracted fields are evaluated by stationary phase method and edge point technique, asymptotically. MTPO integral is compared with the exact solution and PO integral for the problem of scattering from a perfectly conducting half plane, numerically. It is observed that MTPO integral gives the total field that agrees with the exact solution and the result is more reliable than that of classical PO integral. (C) 2004 Optical Society of America.Article Modified theory of physical optics approach to wedge diffraction problems(Optica Publishing Group, 2005) Umul, YZ; Umul, Yusuf Ziya; 42699The problem of diffraction from a perfectly conducting wedge is examined with the modified theory of physical optics (MTPO). The exact wedge diffraction coefficient is compared with the asymptotic edge waves of MTPO integral and related surface currents are evaluated. The scattered electric fields are expressed by using these current components. The total, incident and reflected diffracted fields are compared with the exact series solution of the wedge problem, numerically. (C) 2005 Optical Society of America.Article Modified theory of the physical-optics approach to the impedance wedge problem(Optical Soc Amer, 2006) Umul, YZ; Umul, Yusuf Ziya; 42699The problem of a wedge with equal face impedances is examined with a modified theory of physical optics. The surface integral is constructed by use of the impedance boundary condition. The aperture equivalent current is estimated from the behavior of the reflected diffracted field. The integrals obtained are evaluated asymptotically and compared with the exact solution numerically. (c) 2006 Optical Society of America.Article Physical optics theory for the diffraction of waves by impedance surfaces(Optical Soc Amer, 2011) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699The solution of the scattering problem of waves by a half-screen with equal face impedances, which was introduced by Malyughinetz, is transformed into a physical optics integral by using the inverse edge point method. The obtained integral is applied to the diffraction problem of plane waves by an impedance truncated circular cylinder and the scattered waves are derived asymptotically. The results are examined numerically. (C) 2011 Optical Society of AmericaArticle Physical optics-based diffraction coefficient for a wedge with different face impedances(Optical Soc Amer, 2018) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699A new diffraction field expression is introduced with the aid of the modified theory of physical optics for a wedge with different face impedances. First, the scattered geometrical optics fields are determined when both faces of the wedge are illuminated by the incident wave. The geometrical optics waves are then expressed in terms of the sum of two different fields that occur for different impedance wedges. The diffracted fields are determined for the two cases separately, and the total diffracted field is obtained as a sum of these waves. Lastly, the uniform field expressions are obtained, and the resultant fields are numerically compared with the solution of Maliuzhinets. (C) 2018 Optical Society of AmericaArticle Scattering of a Gaussian beam by an impedance half-plane(Optical Soc Amer, 2007) Umul, Yusuf Z.; Umul, Yusuf Ziya; 42699The diffraction of a Gaussian beam by an impedance half-plane is studied through the method of the modified theory of physical optics. An electric line source, which is defined in the complex space, is used to represent the Gaussian beam. The uniform evaluation of the diffraction integral is performed and the scattering patterns of the field are investigated for various numerical parameters of the incident wave. (c) 2007 Optical Society of America.Article Scattering of inhomogeneous plane waves by a resistive half-screen(Optical Soc Amer, 2013) Umul, Yusuf Ziya; Umul, Yusuf Ziya; 42699The scattering process of inhomogeneous plane waves by a resistive half-plane is investigated by using the exact diffracted field expressions. The uniform field representations are obtained with the aid of the uniform theory, put forward by Umul. The geometrical optics and diffracted and scattered fields are examined numerically. (C) 2013 Optical Society of AmericaArticle Simplified uniform theory of diffraction(Optica Publishing Group, 2005) Umul, YZ; Umul, Yusuf Ziya; 42699Simple exponential functions that approach zero for reflection and shadow boundaries are considered to cancel the infinite values of diffraction coefficients at these regions. This method is applied to a wedge diffraction coefficient, and the resultant uniform coefficient is compared with the exact diffracted fields numerically. (c) 2005 Optical Society of America.
