The phase vocoder[1] has long been a well established tool in pitch shifting technology. It analyzes and synthesizes audio signal via short-time Fourier Transform. Unfortunately, Fourier Transform leads to the inevitable inherent frequency leakage which decreases the accuracy of the pitch shifting effect [2]. In order to restrain this side effect, window functions are used to intercept audio. H...

Ultrasound imaging is one of the important noninvasive technique that using in medical diagnosis. Unfortunately the far field beam pattern in ultrasound is a sinc function which has a better main-lobe (the resolution of ultrasound imaging) and high side-lobe about 13dB down from the maximum on axis value (the contrast of ultrasound imaging).The result for that is one of a famous artifact in med...

BACKGROUND High-frequency (e.g., gamma 30 to 50 Hz) coherent neural activity has been postulated to underlie binding of independent neural assemblies and thus integrate processing across distributed neuronal networks to achieve a unified conscious experience. Prior studies suggest that gamma activity may play a role in perceptual mechanisms, but design limitations raise concerns. Thus, controve...

Initial experience is reported with the Scanditronix PC 2048-15B, a 15-slice positron emission tomography (PET) system using multicrystal/multiphoto-multiplier modules to obtain high spatial resolution. Random and scattered events are reduced using an orbiting (68)Ge rod source for transmission scans by only accepting coincidence lines which intersect the instantaneous position of the source. S...

A novel feature set for low-dimensional signal representation, designed for classification or clustering of non-stationary signals with complex variation in time and frequency, is presented. The feature representation of a signal is given by the first left and right singular vectors of its ambiguity spectrum matrix. If the ambiguity matrix is of low rank, most signal information in time directi...

Fluctuations in the solar wind characteristics such as speed, temperature, magnetic strength and density are associated with pulsations in the magnetosphere. Coherent magnetohydrodynamic waves in the solar wind may sometimes be a direct source of periodic pulsations in the frequency interval 1 to 7 mHz in the magnetosphere. In studies of the solar wind and the way its variation affects the magn...

Studies on Performance of Pulse Shaped OFDM Signal Written by Administrator Wednesday, 16 March 2011 08:55 Last Updated Monday, 21 March 2011 07:29 The Orthogonal Frequency Division Multiplexing (OFDM) transmission system is one of the optimum versions of the multi-carrier transmission scheme. The OFDM is referred in the literature as Multi-carrier, Multi-tone and Fourier Transform based modula...

Nuclear cardiac imaging is a noninvasive, sensitive method providing information on cardiac structure and physiology. Single photon emission tomography (SPECT) evaluates myocardial perfusion, viability, and function and is widely used in clinical routine. The quality of the tomographic image is a key for accurate diagnosis. Image filtering, a mathematical processing, compensates for loss of det...

--Projection data acquired for image reconstruction of low-dose computed tomography (CT) are degraded by many factors. These factors complicate noise analysis on the projection data and render a very challenging task for noise reduction. In this study, we first investigate the noise property of the projection data by analyzing a repeatedly acquired experimental phantom data set, in which the ph...

This note outlines the techniques routinely used in sonar systems to implement time domain and frequency domain beamforming systems. It takes a very simplistic approach to the problem and should not be considered as definitive in any sense. Consider an array of hydrophones receiving signals from an acoustic source in the far-field (Figure 1a). If the outputs from the 'phones are simply added to...