PubMed İndeksli Yayınlar Koleksiyonu
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Browsing PubMed İndeksli Yayınlar Koleksiyonu by Institution Author "Umul, Yusuf Z."
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Article Citation - WoS: 22Citation - Scopus: 23Alternative Interpretation of the Edge-Diffraction Phenomenon(Optical Soc Amer, 2008) Umul, Yusuf Z.An alternative interpretation of the phenomenon of edge diffraction is proposed according to a new separation of the Fresnel function. The subfields are investigated in the problem of diffraction of a plane wave by a perfectly conducting half-plane, and the results are compared numerically with other interpretations. (c) 2008 Optical Society of America.Article Citation - WoS: 7Citation - Scopus: 8Apertured Paraxial Bessel Beams(Optical Soc Amer, 2010) Umul, Yusuf Z.The paraxial Bessel beam is obtained by applying an approximation in the wavenumbers. The scattering of the beams by a circular aperture in an absorbing screen is investigated. The scattered fields are expressed in terms of the Fresnel integrals by evaluating the Kirchhoff diffraction integral in the paraxial approximation. The results are examined numerically. (C) 2010 Optical Society of AmericaArticle Citation - WoS: 34Citation - Scopus: 37Diffraction of Evanescent Plane Waves by a Resistive Half-Plane(Optical Soc Amer, 2007) Umul, Yusuf Z.Diffraction 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 Citation - WoS: 8Citation - Scopus: 8Diffraction of Homogeneous and Inhomogeneous Plane Waves by a Planar Junction Between Perfectly Conducting and Impedance Half-Planes(Optical Soc Amer, 2007) Umul, Yusuf Z.The 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 Citation - WoS: 23Citation - Scopus: 24Edge-Dislocation Waves in the Diffraction Process by an Impedance Half-Plane(Optical Soc Amer, 2007) Umul, Yusuf Z.Edge-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 Citation - WoS: 11Citation - Scopus: 11Effect of the Shadow Geometry in Wedge Diffraction(Optica Publishing Group, 2009) Umul, Yusuf Z.The surface integrals of the modified theory of physical optics are divided into two parts for diffraction by a wedge. Each integral represents the incident or reflected field scattered by one of the faces of the wedge. The results are investigated numerically and compared with the uniform theory of diffraction. (C) 2009 Optical Society of AmericaArticle Citation - WoS: 15Citation - Scopus: 15Effect of the Shadow Geometry on Diffraction(Optical Soc Amer, 2008) Umul, Yusuf Z.The effect of the scatterer surface on the shadow region is examined by using the surface integrals of the modified theory of physical optics. It is shown that the shadow geometry has a considerable effect on the structure of the edge diffracted waves. The diffracted fields for the illuminated and shadowed surface of a half-plane are evaluated in terms of Fresnel integrals and plotted numerically. (C) 2008 Optical Society of AmericaArticle Citation - WoS: 4Citation - Scopus: 4Fictitious Diffracted Waves in the Diffraction Theory of Kirchhoff(Optical Soc Amer, 2010) Umul, Yusuf Z.The diffraction theory of Kirchhoff is applied to the semi-infinite aperture of a black half-screen. The derivative of the spherical Green's function is taken into account without any approximation. The uniformly evaluated scattering integral is compared with the physical optics solution. It is shown that the non-omitted term causes the existence of fictitious diffracted waves. (C) 2009 Optical Society of AmericaArticle Citation - WoS: 25Citation - Scopus: 6Improved Equivalent Source Theory(Optical Soc Amer, 2009) Umul, Yusuf Z.The equivalent source theorem, which is an important technique in the study of radiation and scattering by apertures, is improved by using the two axioms of the modified theory of physical optics. The method is applied to the problem of radiation of electromagnetic waves by a parallel plate waveguide. The results are investigated numerically. (C) 2009 Optical Society of AmericaArticle Citation - WoS: 16Citation - Scopus: 15Integral Representation of the Edge Diffracted Waves Along the Ray Path of the Transition Region(Optical Soc Amer, 2008) Umul, Yusuf Z.The expression of the edge diffracted fields, in terms of the Fresnel integral, is transformed into a path integral. The obtained integral considers the integration of the incident field along the ray path of the transition region. The similarities of the path integral with Kirchhoff's theory of diffraction and the modified theory of physical optics are examined. (C) 2008 Optical Society of America.Article Citation - WoS: 39Citation - Scopus: 43Modified Diffraction Theory of Kirchhoff(Optical Soc Amer, 2008) Umul, Yusuf Z.The diffraction theory of Kirchhoff is reinterpreted and a new form of a surface diffraction integral is developed by using the axioms of the modified theory of physical optics, which leads to the exact scattered fields by conducting bodies. The new integral is arranged according to the interpretation of Young, and the diffracted waves are expressed in terms of a line integral. The method is applied to the diffraction problem by a semi-infinite edge contour. (c) 2008 Optical Society of America.Article Citation - WoS: 19Citation - Scopus: 19Scattering of a Gaussian Beam by an Impedance Half-Plane(Optical Soc Amer, 2007) Umul, Yusuf Z.The 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 Citation - WoS: 21Citation - Scopus: 21Scattering of a Line Source by a Cylindrical Parabolic Impedance Surface(Optical Soc Amer, 2008) Umul, Yusuf Z.The scattering of the radiated fields of a line source by a cylindrical parabolic reflector, which has impedance boundary conditions on its surface, is obtained by using the surface integrals of the modified theory of physical optics. The reflected geometrical optics and edge diffracted fields are evaluated by using the asymptotic methods. The scattered fields are plotted numerically for various parameters such as surface impedance and angles of the edges. (c) 2008 Optical Society of AmericaArticle Citation - WoS: 11Citation - Scopus: 11Uniform Boundary Diffraction Wave Theory of Rubinowicz(Optical Soc Amer, 2010) Umul, Yusuf Z.Rubinowicz introduced a uniform asymptotic evaluation of the boundary diffraction wave at the transition region [Ann. Phys. (Leipzig) 378, 339 (1924)]. The uniform theory of Rubinowicz is generalized for the improved integrals of the boundary diffraction wave. The technique is applied to the scattering problem of plane waves by an impedance half-plane, and the diffracted waves are examined numerically. (C) 2010 Optical Society of AmericaArticle Citation - WoS: 14Citation - Scopus: 15Uniform Line Integral Representation of Edge-Diffracted Fields(Optical Soc Amer, 2008) Umul, Yusuf Z.A uniform line integral representation is derived for edge-diffracted fields by using the modified theory of physical optics and uniform asymptotic evaluation methods. The method is applied to the problem of diffraction of plane waves by a semi-infinite edge, which creates tip-diffracted fields with edge-diffracted waves. The uniform diffracted fields are plotted and examined numerically. (c) 2007 Optical Society of America.Article Citation - WoS: 28Citation - Scopus: 29Uniform Theory for the Diffraction of Evanescent Plane Waves(Optical Soc Amer, 2007) Umul, Yusuf Z.A uniform diffracted field is obtained in terms of Fresnel functions with complex argument by subtracting the unit step function from the Fresnel integral. The method is applied to the problem of diffraction of inhomogeneous plane waves by a perfectly conducting half-plane and wedge. The results are plotted numerically and compared with results reported in the literature. (c) 2007 Optical Society of America.Article Citation - WoS: 15Citation - Scopus: 15Young-Kirchhoff Theory of Diffraction in the Light of Sommerfeld's Solution(Optical Soc Amer, 2008) Umul, Yusuf Z.Kirchhoff's theory of diffraction is derived by transforming the exact solution of Sommerfeld into surface integrals for the half-plane problem. It is shown that the exact solution directly yields the integral theorem of Kirchhoff in the context of the modified diffraction theory of Kirchhoff. The line integrals of Young-Rubinowicz are also derived by considering the rigorous solution of the reflected scattered fields for grazing incidence. (C) 2008 Optical Society of America
