Quadratic Spline Collocation (QSC) methods of optimal order of convergence have been recently developed for the solution of elliptic Partial Differential Equations (PDEs). In this paper, linear solvers based on Fast Fourier Transforms (FFT) are developed for the solution of the QSC equations. The complexity of the FFT solvers is O(N2 logN), where N is the gridsize in one dimension. These direct...

OBJECTIVE Heart rate variability (HRV) analysis, which is an important tool for activity assessment of the cardiac autonomic nervous system, very often includes the estimation of power spectra for series of interbeat intervals (IBI). Ectopic beats and artifacts have a destructive effect on the standard methods (Fourier transform, FFT) for frequency analysis. This study investigates an alternati...

BACKGROUND Computer analysis of the sleep electroencephalogram (EEG) waveforms is widely employed, but there have been no systematic studies of its reliability. METHODS The most commonly used computer methods are power spectral analysis with the fast-Fourier transform (FFT) and period amplitude analysis (PAA) with zero cross or zero first derivative half-wave measurement. We applied all three...

Improved selection of patients with suspected sustained ventricular tachycardia (VT) for programmed ventricular stimulation is needed. To determine if frequency analysis detects patients in whom sustained VT might be induced, we first obtained fast-Fourier transforms (FFT) of signal-averaged electrocardiograms (ECGs) from 20 patients with spontaneous sustained VT (group 1) and compared them wit...

BACKGROUND During coronary artery bypass grafting (CABG), the ratio of powers of the fundamental frequency and its first harmonic (F0/H1) in fast Fourier transformation (FFT) analysis of the graft's flow waves has been used in the field of evaluation of the patency in anastomosis. But there is no report about using the FFT method to evaluate the magnitude of competitive flow. This study is aimi...

Wave generation methodology has been developed and validated by simulating wave in CFD. In this analysis, Flap type wave maker has been modeled numerically with wave basin to generate waves for marine experimental analysis. Irregular waves are arrived from the wave spectrum, and this wave has been simulated in CFD. Generated irregular wave has been compared with an analytical wave. Simulated wa...

Beamforming methods using antenna arrays have been used to suppress co-channel interferences in OFDM systems. These methods are grouped into two general classes of pre-FFT and post-FFT schemes. Post-FFT schemes normally exhibit better performance than their pre-FFT counterparts. However, in pilot-assisted OFDM systems the performance of post-FFT schemes drastically degrades due to subcarrier cl...