Search for dissertations about: "discrete Fourier transform"

Showing result 1 - 5 of 20 swedish dissertations containing the words discrete Fourier transform.

  1. 1. Optimization of Rotations in FFTs

    Author : Fahad Qureshi; Oscar Gustafsson; Mario Garrido; Jarmo Takala; Linköpings universitet; []
    Keywords : ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Discrete Fourier transform; Fast Fourier transform; twiddle factor multiplication;

    Abstract : The aims of this thesis are to reduce the complexity and increasethe accuracy of rotations carried out inthe fast Fourier transform (FFT) at algorithmic and arithmetic level.In FFT algorithms, rotations appear after every hardware stage, which are alsoreferred to as twiddle factor multiplications. READ MORE

  2. 2. Potential Flow Panel Methods for the Calculation of Free-surface Flows with Lift

    Author : Carl-Erik Janson; Chalmers University of Technology; []
    Keywords : desingularized; shape optimization; Rankine source; waves; OCTOPUS; dipole; MMA; Dawson operator; boundary layer; vortex; Method of Moving Asymptotes; nonlinear; sailing yacht; four point operator; surface piercing wing; Navier-Stokes; numerical method; lift force; raised panel method; discrete Fourier transform; collocation point shift; potential flow; CFD; free surface; induced drag; SHIPFLOW; dispersion; damping; analytical method; hydrofoil;

    Abstract : Two non-linear Rankine-source panel methods are developed and implemented in the same computer code. The first method uses a four-point upwind operator on the free-surface to compute the velocity derivatives and to enforce the radiation condition while the second method uses an analytical expression for the velocity derivatives and a collocation point shift one panel upstream to prevent upstream waves. READ MORE

  3. 3. Arbitrary Waveform Impedance Spectroscopy for Characterization and Diagnostics of High Voltage Insulation

    Author : Björn Sonerud; Chalmers University of Technology; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; insulation testing; aging; monitoring; discrete Fourier transforms; Dielectric measurements; dielectric materials;

    Abstract : In high voltage engineering the dielectric response technique is a widely used tool both for characterization of insulation materials and for diagnostics of components such as transformers and cables. Currently available techniques are not capable of measuring on-line which would be advantageous; when characterizing a material and evaluating the effect of different voltage magnitudes, waveforms and temperatures it is desirable to be able to observe the continuous development of the dielectric properties. READ MORE

  4. 4. Discrete Stochastic Time-Frequency Analysis and Cepstrum Estimation

    Author : Johan Sandberg; Matematisk statistik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; ambiguity domain; time-frequency analysis; time-frequency representations; covariance function; non-stationary random processes; Speaker recognition; MFCC; cepstrum;

    Abstract : The theory of stochastic time-frequency analysis of non-stationary random processes has mostly been developed for processes in continuous time. In practice however, random processes are observed, processed, and interpreted at a finite set of time points. READ MORE

  5. 5. Automating Power Quality Analysis

    Author : Emmanouil Styvaktakis; Chalmers University of Technology; []
    Keywords : pattern classification; expert systems; induction motors; power system transients; voltage dips; power system faults; power quality; Kalman filtering; power system monitoring; transformer saturation; short time Fourier transform;

    Abstract : The increased requirements on supervision, control, and performance in modern power systems make power quality monitoring a common practise for utilities. Large databases are created and automatic processing of the data is required for fast and effective use of the available information. READ MORE