Now showing items 1-20 of 40

    • Accurate plane-wave excitation in the FDTD method 

      Gürel, L.; Oğuz, U.; Arikan, O. (IEEE, Piscataway, NJ, United States, 1997)
      Different techniques are developed to implement plane-wave excitation on the finite-difference time-domain (FDTD) method, such as the initial-condition, the hard-source, and the connecting-condition techniques, for the ...
    • Adaptive correction and look-up table based interpolation of quadrature encoder signals 

      Ulu, E.; Ulu, N.G.; Cakmakci, M. (2012)
      This paper presents a new method to increase the available measurement resolution of quadrature encoder signals. The proposed method features an adaptive signal correction phase and an interpolation phase. Typical imperfections ...
    • Computation of holographic patterns between tilted planes 

      Esmer, G. B.; Onural, L. (S P I E - International Society for Optical Engineering, 2006)
      Computation of the diffraction pattern that gives the desired reconstruction of an object upon proper illumination is an important process in computer generated holography. A fast computational method, based on the plane ...
    • DCT coding of nonrectangularly sampled images 

      Gündüzhan, E.; Çetin, A. E.; Tekalp, A. M. (IEEE, 1994)
      Discrete cosine transform (DCT) coding is widely used for compression of rectangularly sampled images. In this letter, we address efficient DCT coding of nonrectangularly sampled images. To this effect, we discuss an ...
    • The effect of distribution of information on recovery of propagating signals 

      Karabulut, Özgecan (Bilkent University, 2015-09)
      Interpolation is one of the fundamental concepts in signal processing. The analysis of the di fficulty of interpolation of propagating waves is the subject of this thesis. It is known that the information contained in a ...
    • An efficient and accurate technique for the incident-wave excitations in the FDTD method 

      Oğuz, U.; Gürel, L.; Arıkan, O. (Institute of Electrical and Electronics Engineers, 1998-06)
      An efficient technique to improve the accuracy of the finite-difference time-domain (FDTD) solutions employing incident-wave excitations is developed. In the separate-field formulation of the FDTD method, any incident wave ...
    • Energy and mass of 3D and 2D polarons in the overall range of the electron-phonon coupling strength 

      Ercelebi, A.; Senger, R. T. (Institute of Physics Publishing Ltd., 1994)
      The ground-state characterization of the polaron problem is retrieved within the framework of a variational scheme proposed previously by Devreese et al for the bound polaron. The formulation is based on the standard ...
    • Fractional free space, fractional lenses, and fractional imaging systems 

      Sümbül, U.; Ozaktas, H. M. (OSA - The Optical Society, 2003)
      Continuum extensions of common dual pairs of operators are presented and consolidated, based on the fractional Fourier transform. In particular, the fractional chirp multiplication, fractional chirp convolution, and ...
    • Harmonic Besov spaces on the ball 

      Gergün, S.; Kaptanoğlu, H. T.; Üreyen, A. E. (World Scientific Publishing, 2016)
      We initiate a detailed study of two-parameter Besov spaces on the unit ball of ℝn consisting of harmonic functions whose sufficiently high-order radial derivatives lie in harmonic Bergman spaces. We compute the reproducing ...
    • Input sequence estimation and blind channel identification in HF communication 

      Khames, M.; Miled, B. H.; Arikan, O. (IEEE, Piscataway, NJ, United States, 2000)
      A new algorithm is proposed for reliable communication over HF tropospheric links in the presence of rapid channel variations. In the proposed approach, using fractionally space channel outputs, sequential estimation of ...
    • Interpolating between periodicity and discreteness through the fractional Fourier transform 

      Özaktaş, H. M.; Sümbül, U. (IEEE, 2006)
      Periodicity and discreteness are Fourier duals in the same sense as operators such as coordinate multiplication and differentiation, and translation and phase shift. The fractional Fourier transform allows interpolation ...
    • Interpolation for completely positive maps: Numerical solutions 

      Ambrozie, C.; Gheondea, A. (Societatea de Stiinte Matematice din Romania, 2018)
      We present a few techniques to find completely positive maps between full matrix algebras taking prescribed values on given data, based on semidefinite programming, convex minimization supported by a numerical example, as ...
    • An interpolation problem for completely positive maps on matrix algebras: solvability and parametrization 

      Ambrozie, C. G.; Gheondea, A. (Taylor & Francis, 2015)
      We present certain existence criteria and parameterizations for an interpolation problem for completely positive maps that take given matrices from a finite set into prescribed matrices. Our approach uses density matrices ...
    • Interpolation techniques to improve the accuracy of the plane wave excitations in the finite difference time domain method 

      Oğuz, U.; Gürel, L. (Wiley-Blackwell Publishing, Inc., 1997-11)
      The importance of matching the phase velocity of the incident plane wave to the numerical phase velocity imposed by the numerical dispersion of the three-dimensional (3-D) finite difference time domain (FDTD) grid is ...
    • Linear algebraic analysis of fractional fourier domain interpolation 

      Öktem, F. S.; Özaktaş, H. M. (IEEE, 2009)
      In this work, we present a novel linear algebraic approach to certain signal interpolation problems involving the fractional Fourier transform. These problems arise in wave propagation, but the proposed approach to these ...
    • Linear algebraic theory of partial coherence: discrete fields and measures of partial coherence 

      Ozaktas, H. M.; Yuksel, S.; Kutay, M. A. (OSA Publishing, 2002)
      A linear algebraic theory of partial coherence is presented that allows precise mathematical definitions of concepts such as coherence and incoherence. This not only provides new perspectives and insights but also allows ...
    • LQ optimal design at finitely many frequencies 

      Köroğlu, H.; Morgül, Ö. (Institute of Electrical and Electronics Engineers, 1998)
      The notion of Linear Quadratic (LQ) optimality at a single frequency is developed in single-input single-output (SISO) linear time-invariant (LTI) system/quasi-stationary signal framework and the optimality condition is ...
    • Multilevel PO algorithm for nonuniform triangulations 

      Manyas, A.; Gürel, L. (2006)
      Fast physical optics (FPO) algorithm provides a speedup for computing the physical optics (PO) integral over complex bodies for a range of aspect angles and frequencies. In this paper, this algorithm is further developed ...
    • Nonseperable two-dimensional fractional Fourier transform 

      Sahin, A.; Kutay, M. A.; Ozaktas, H. M. (Optical Society of America, 1998)
      Previous generalizations of the fractional Fourier transform to two dimensions assumed separable kernels. We present a nonseparable definition for the two-dimensional fractional Fourier transform that includes the separable ...
    • On the mixed sensitivity minimization for systems with infinitely many unstable modes 

      Gümüşsoy, S.; Özbay, H. (Elsevier, 2004)
      In this note we consider a class of linear time invariant systems with infinitely many unstable modes. By using the parameterization of all stabilizing controllers and a data transformation, we show that ℋ ∞ controllers ...