Browsing by Subject "Extrapolation"

Now showing 1 - 6 of 6

Open Access
Coupled deconvolution for frequency extrapolation of electromagnetic solutions with matrix pencil method
(IEEE, 2005) Gürel, Levent; Yıldırım, Ferhat
Matrix pencil method (MPM) has been widely used to estimate the parameters of complex-exponential based models. An important application is the extrapolation of the frequency-domain solutions of electromagnetic problems. In this paper, we present a mathematical tool, namely, coupled deconvolution, which improves the performance of the MPM-based extrapolation of electromagnetic solutions.
Open Access
Coupled matrix pencil method for frequency extrapolation of electromagnetic solutions
(IEEE, 2005) Yıldırım, Ferhat; Gürel, Levent
Matrix pencil method (MPM) is used to extrapolate the available electromagnetic solutions in frequency domain to estimate the high-frequency solutions. A new approach, namely, coupled MPM, is introduced to obtain the electromagnetic solutions at intermediate frequencies using the available low-frequency and high-frequency data.
Open Access
Energy and mass of 3D and 2D polarons in the overall range of the electron-phonon coupling strength
(Institute of Physics Publishing Ltd., 1994) Ercelebi, A.; Senger, R. T.
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 canonical transformation of the strong coupling ansatz and consists of a variationally determined perturbative extension serving for the theory to interpolate in the overall range of the coupling constant. Specializing our considerations to the bulk and strict two-dimensional polaron models we see that the theory yields significantly improved energy upper bounds in the strong coupling regime and, moreover, extrapolates itself successfully towards the well-established weak coupling limits for all polaron quantities of general interest.
Open Access
Evaluating predictive performance of judgemental extrapolations from simulated currency series
(Elsevier, 1999) Pollock, A. C.; Macaulay, A.; Önkal-Atay, D.; Wilkie-Thomson, M. E.
Judgemental forecasting of exchange rates is critical for financial decision-making. Detailed investigations of the potential effects of time-series characteristics on judgemental currency forecasts demand the use of simulated series where the form of the signal and probability distribution of noise are known. The accuracy measures Mean Absolute Error (MAE) and Mean Squared Error (MSE) are frequently applied quantities in assessing judgemental predictive performance on actual exchange rate data. This paper illustrates that, in applying these measures to simulated series with Normally distributed noise, it may be desirable to use their expected values after standardising the noise variance. A method of calculating the expected values for the MAE and MSE is set out, and an application to financial experts' judgemental currency forecasts is presented.
Open Access
Extrapolation with the matrix pencil method to combine low-frequency and high-frequency electromagnetic scattering results
(2005) Yıldırım, Ahmet Ferhat
Accurate frequency domain solutions of electromagnetic scattering problems are known to require high computing resources as the solution frequency increases. On the other hand, high-frequency techniques provide us solutions with limited accuracy in the relatively high-frequency regions. In this thesis we aimed to fill the intermediate gap by using extrapolation techniques. Matrix pencil method (MPM) is presented to find the parameters of the model in our model-based extrapolation approach. In order to fully incorporate the two separate available data sources, i.e., accurate low-frequency solvers and asymptotic high-frequency solvers, we proposed two methods of coupling, namely coupled MPM and coupled deconvolution MPM. Results of proposed extrapolation methods are tested both on analytically generated backscattering solution of conducting sphere and numerical solutions of various three dimensional bodies.
Open Access
Resolution enhancement of low resolution wavefields with POCS algorithm
(The Institution of Engineering and Technology, 2003) Çetin, A. Enis; Özaktaş, H.; Özaktaş, Haldun M.
The problem of enhancing the resolution of wavefield or beam profile measurements obtained using low resolution sensors is addressed by solving the problem of interpolating signals from partial fractional Fourier transform information in several domains. The iterative interpolation algorithm employed is based on the method of projections onto convex sets (POCS).