pectral subtraction is a method for restoration of the power spectrum or the magnitude spectrum of a signal observed in additive noise, through subtraction of an estimate of the average noise spectrum from the noisy signal spectrum. The noise spectrum is usually estimated, and updated, from the periods when the signal is absent and only the noise is present. The assumption is that the noise is ...

nowadays with increasing use of numerous nonlinear loads, voltage and current harmonics in power systems are one of the most important problems power engineers encounter. many of these nonlinear loads, because of their dynamic natures, inject time-varying harmonics into power system. common techniques applied for harmonics measurement and assessment such as fft have significant errors in presen...

We discuss the probability distributions of Fourier modes of cosmological density fields using the central limit theorem as it applies to weighted integrals of random fields. It is shown that if the cosmological principle holds in a certain sense, i.e., the universe approaches homogeneity and isotropy sufficiently rapidly on very large scales, the one-point distribution of each Fourier mode of ...

This paper presents a new method of detecting Analog to Digital Converter harmonic distortion. The new method is based on Wavelet multi-resolution process to identify instantaneous harmonic components. In classical testing, Fourier transform algorithm was long adopted to estimate Total Harmonic Distortion by obtaining signal power spectrum. While the conventional method of Fourier transform ten...

Coded ultrafast optical pulses can be treated as onedimensional (1-D) images in the time domain. We have converted space-domain images into time-domain images using diffraction from dynamic holograms inside a Fourier pulse shaper, with photorefractive quantum wells (QW’s) used as the dynamic holographic medium. We present several examples, in which amplitude or phase modulation of the hologram ...

Visual and auditory analysis of respiratory sound signals promises improved detection of certain types of lung diseases. LabVIEW software was used to design a system that monitors the respiratory activity of the patient. The program developed calculates the respiratory rate, displays the time expanded waveform of the lung sound, and computes the fast Fourier transform and short-time Fourier tra...

The paper presents a review of optical cryptography techniques using joint transform correlation (JTC) algorithm. The given input image contains confidential information, such as personal identification, photo, which is then encrypted using an encryption key. Optical JTC technique is employed to perform the encryption and decryption processes using optical lenses and other equipments. The input...

This paper describes a new kind of power spectrum which, when properly employed, can provide hitherto unseen accuracy in probing the resonance spectrum of the vocal tract. By drawing on new signal processing techniques developed by Nelson and his collaborators [2, 3], a method for computing a power spectrum has been implemented in Matlab, and applied to the problem of the accurate measurement o...

Isotropic Gaussian random fields on the sphere are characterized by Karhunen–Loève expansions with respect to the spherical harmonic functions and the angular power spectrum. The smoothness of the covariance is connected to the decay of the angular power spectrum and the relation to sample Hölder continuity and sample differentiability of the random fields is discussed. Rates of convergence of ...

Based on log-polar mapping and phase correlation, this paper presents a novel digital image watermarking scheme that is invariant to rotation, scaling, and translation (RST). We embed watermark in the log-polar mappings of Fourier magnitude spectrum of original image, and use the phase correlation between the LPM of the original image and the LPM of the watermarked image to calculate the displa...