Harmonic

About: Harmonic is a research topic. Over the lifetime, 44833 publications have been published within this topic receiving 495922 citations. The topic is also known as: overtone & partial.

A novel control method for forced commutated cycloconverters using instantaneous values of input line-to-line voltages

Abstract: The authors present a novel control method for forced commutated cycloconverters (PWM cycloconverters). Using this control method the sinusoidal input and output current waveforms and the unity input displacement factor can be obtained. Moreover, the compensation of the asymmetrical and/or harmonic contaminated input source voltages is easily realized. This control method allows the input displacement factor not to be controllable, but to be fixed at approximately unity. Since a unity input displacement factor is desirable for motordrive use for the PWM cycloconverters, this constraint is not a new obstacle. Feasibility of the proposed control method is verified by simulations and experiments. >

Pseudorandom signals to estimate apparent transfer and coherence functions of nonlinear systems: applications to respiratory mechanics

Abstract: For pseudorandom (PRN) input stimuli, general expressions are derived for the apparent transfer (Z) and coherence ( gamma /sup 2/) functions of nonlinear systems that can be represented by a Volterra series. To avoid the problems that are shown here to be associated with harmonic distortions and to minimize the influence of crosstalk, a family of pseudorandom signals which are especially suited for the estimation of Z and gamma /sup 2/ in mechanical measurement of physiological systems at low frequencies is proposed. The components in the signals cannot be reproduced as linear combinations of two or more frequency components of the input. In a second-order system, this completely eliminates the bias, while in higher order but not strongly nonlinear systems, the interactions among the components are reduced to such a level that the response can be considered as if it were measured with independent sine waves of an equivalent amplitude. It is also shown that the values of gamma /sup 2/ are not appropriate for assessing linearity of the system. The theory is supported by simulation results and experimental examples. >

Frequency analysis of the peripheral pulse wave detected in the finger with a photoplethysmograph

Abstract: A photoelectric plethysmograph that performs a frequency analysis of the peripheral volume pulse wave using a portable computer is described. It was used to determine how the pulse shape varied with age using 54 subjects in three age groups: 10-29, 30-59, and 60-89 years. The youngest group had a larger power in the second harmonic (normalized to the fundamental), with p >

A comparison of spectral magnitude and phase-locking value analyses of the frequency-following response to complex tones

Abstract: Two experiments, both presenting diotic, harmonic tone complexes (100 Hz fundamental), were conducted to explore the envelope-related component of the frequency-following response (FFRENV), a measure of synchronous, subcortical neural activity evoked by a periodic acoustic input. Experiment 1 directly compared two common analysis methods, computing the magnitude spectrum and the phase-locking value (PLV). Bootstrapping identified which FFRENV frequency components were statistically above the noise floor for each metric and quantified the statistical power of the approaches. Across listeners and conditions, the two methods produced highly correlated results. However, PLV analysis required fewer processing stages to produce readily interpretable results. Moreover, at the fundamental frequency of the input, PLVs were farther above the metric's noise floor than spectral magnitudes. Having established the advantages of PLV analysis, the efficacy of the approach was further demonstrated by investigating how different acoustic frequencies contribute to FFRENV, analyzing responses to complex tones composed of different acoustic harmonics of 100 Hz (Experiment 2). Results show that the FFRENV response is dominated by peripheral auditory channels responding to unresolved harmonics, although low-frequency channels driven by resolved harmonics also contribute. These results demonstrate the utility of the PLV for quantifying the strength of FFRENV across conditions.

Gap resonance and higher harmonics driven by focused transient wave groups

Abstract: The first- and higher-harmonic components of the resonant fluid response in the gap between two identical fixed rectangular boxes are experimentally investigated in a wave basin. Gap response is excited by transient wave groups (being based on scaled versions of the autocorrelation function of sea state spectra, representing NewWaves, the average shape of large waves in a sea state). Several different wave groups with different maximum surface elevations, spectral peak frequencies and bandwidths are used, while the bilge shape of the boxes and approach angle of the waves are also varied. Unlike a simple regular wave, it is complicated to separate the harmonic components for a transient wave group due to non-linear wave-wave and wave-structure interactions. A four-phase combination methodology is used to separate the first four harmonic components, and this also allows higher-harmonic components to be isolated with simple digital frequency filtering. Harmonic components up to 14th order in the incident wave amplitude have been extracted. It is shown that for an incident group with appropriate frequency content, the linear gap response may be substantially smaller than the second-harmonic component, which is strongly driven via quadratic coupling of the linear terms from the incident wave and occurs in the gap resonant modes. Double frequency excitation may have important practical implications for offshore operations. Fourth and zeroth (long wave) harmonics in the gap are further driven via quadratic coupling of the second-harmonic itself. Linear damping coefficients for the first few modes of the gap resonant response are derived from measured time series using a numerical fit and shown to be higher than those from linear diffraction calculations.