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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.


Papers
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Journal ArticleDOI
TL;DR: In this article, the performance of the parallel resonant power converter and the combination series/parallel LCC converter when operated above resonance in a high power factor mode is compared for single phase applications.
Abstract: The performance of the parallel resonant power converter and the combination series/parallel resonant power converter (LCC converter) when operated above resonance in a high power factor mode are determined and compared for single phase applications. When the DC voltage applied to the input of these converters is obtained from a single phase rectifier with a small DC link capacitor, a relatively high power factor inherently results, even with no active control of the input line current. This behavior is due to the pulsating nature of the DC link and the inherent capability of the converters to boost voltage during the valleys of the input AC wave. With no active control of the input line current, the power factor depends on the ratio of operating frequency to tank resonant frequency. With active control of the input line current, near-unity power factor and low-input harmonic currents can be obtained. >

122 citations

Journal ArticleDOI
TL;DR: A good match between analytical predictions and experimental tests validates the proposed current control strategies, including not only the fundamental harmonic of the flux-density distribution but also the higher harmonics that cause high torque oscillations.
Abstract: The performance of a five-phase permanent-magnet (PM) motor is analyzed under postfault conditions. Proper current control strategies are adopted so as to guarantee safe drive operation after any fault occurrence. This paper covers three fault types: the open circuit condition of a single phase, the open circuit condition of two nonadjacent phases, and the open circuit condition of two adjacent phases. Two motors with two different windings (with double and single layers, respectively) are compared under each fault type. This paper aims to highlight the difference in the motor performance of motors adopting these two different windings. A further novelty of this paper is that the proper current control strategies are derived analytically, including not only the fundamental harmonic of the flux-density distribution but also the higher harmonics. It is shown that these harmonics cause high torque oscillations. Owing to this analytical approach, the strategy can be applied to a variety of PM motors. In addition, the postfault current waveforms remain sinusoidal, making the current control easier. For each fault type, the results of both simulations and experimental tests are included. A good match between analytical predictions and experimental tests validates the proposed current control strategies.

122 citations

Journal ArticleDOI
TL;DR: In this paper, a discussion of second harmonic generation with imperfect phase matching in the high conversion limit is presented, where phase modulation of the fundamental pulse, dispersion, central frequency wavevector mismatch, and fundamental depletion are included.
Abstract: -A discussion of second harmonic generation with imperfect phase matching in the high conversion limit is presented. Phase modulation of the fundamental pulse, dispersion, central frequency wavevector mismatch, and fundamental depletion are included. The results show that even small amounts of phase modulation or central frequency wavevector mismatch can limit harmonic generation and must be considered at high conversion efficiency. Both spatial and temporal phase matching parameters are more restrictive at high conversion efficiency because of the narrowing of the central phase matching peak. If the harmonic conversion process is overdriven, severe distortion of the harmonic and transmitted fundamental pulses can result. Cascade harmonic generation of neodymium laser radiation to 266 nm is presented as an example.

122 citations

Journal ArticleDOI
TL;DR: The results of a programme to study the nonlinear propagation in the fields of circular, focused and rectangular transducers are described, and comparisons made with numerical predictions obtained using a finite difference solution to the Khokhlov-Zabolotskaya-Kuznetsov equation are made.

122 citations

Journal ArticleDOI
TL;DR: Multiple frequency fluorescence lifetime imaging microscopy was successfully applied to resolve the fluorescence lifetimes and fluorescence intensity contributions in a rhodamine dye mixture in solution, and green fluorescent protein variants co‐expressed in live cells.
Abstract: The experimental configuration and the computational algorithms for performing multiple frequency fluorescence lifetime imaging microscopy (mfFLIM) are described. The mfFLIM experimental set-up enables the simultaneous homodyne detection of fluorescence emission modulated at a set of harmonic frequencies. This was achieved in practice by using monochromatic laser light as an excitation source modulated at a harmonic set of frequencies. A minimum of four frequencies were obtained by the use of two standing wave acousto-optic modulators placed in series. Homodyne detection at each of these frequencies was performed simultaneously by mixing with matching harmonics present in the gain characteristics of a microchannel plate (MCP) image intensifier. These harmonics arise as a natural consequence of applying a high frequency sinusoidal voltage to the photocathode of the device, which switches the flow of photoelectrons 'on' and 'off' as the sinus voltage swings from negative to positive. By changing the bias of the sinus it was possible to control the duration of the 'on' state of the intensifier relative to its 'off' state, enabling the amplitude of the higher harmonic content in the gain to be controlled. Relative modulation depths of 400% are theoretically possible from this form of square-pulse modulation. A phase-dependent integrated image is formed by the sum of the mixed frequencies on the phosphor of the MCP. Sampling this signal over a full period of the fundamental harmonic enables each harmonic to be resolved, provided that the Nyquist sampling criterion is satisfied for the highest harmonic component in the signal. At each frequency both the phase and modulation parameters can be estimated from a Fourier analysis of the data. These parameters enable the fractional populations and fluorescence lifetimes of individual components of a complex fluorescence decay to be resolved on a pixel-by-pixel basis using a non-linear fit to the dispersion relationships. The fitting algorithms were tested on a simulated data set and were successful in disentangling two populations having 1 ns and 4 ns fluorescence lifetimes. Spatial invariance of the lifetimes was exploited to improve the accuracy significantly. Multiple frequency fluorescence lifetime imaging microscopy was then successfully applied to resolve the fluorescence lifetimes and fluorescence intensity contributions in a rhodamine dye mixture in solution, and green fluorescent protein variants co-expressed in live cells.

122 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,223
20222,724
20211,878
20202,330
20192,612
20182,495