Closed-loop amplitude modulation control of reacting premixed turbulent jet

AIAA Journal ◽  
1991 ◽  
Vol 29 (12) ◽  
pp. 2155-2162 ◽  
Author(s):  
E. Gutmark ◽  
T. P. Parr ◽  
D. M. Hanson-Parr ◽  
K. C. Schadow
Keyword(s):  
Amplitude Modulation ◽  
Closed Loop ◽  
Turbulent Jet ◽  
Loop Amplitude ◽  
Modulation Control

Multiple-S-Shaped Critical Manifold and Jump Phenomena in Low Frequency Forced Vibration with Amplitude Modulation

2019 ◽  
Vol 29 (05) ◽  
pp. 1930012 ◽  
Author(s):  
Yue Yu ◽  
Qianqian Wang ◽  
Qinsheng Bi ◽  
C. W. Lim
Keyword(s):  
Amplitude Modulation ◽  
Large Amplitude ◽  
Low Frequency ◽  
Slow Variable ◽  
Critical Manifold ◽  
Singular Orbit ◽  
Modulation Control ◽  
Cycle Oscillation ◽  
Tuning Frequency ◽  
Complex Mechanical Systems

Motivated by the forced harmonic vibration of complex mechanical systems, we analyze the dynamics involving different waves in a double-well potential oscillator coupling amplitude modulation control of low frequency. The combination of amplitude modulation factor significantly enriches the dynamical behaviors on the formation of multiple-S-shaped manifold and multiple jumping phenomena that alternate between epochs of slow and fast motion. We can conduct bifurcation analysis to identify two harmonic vibrations. One is that the singular orbit makes multiple jumps to a fast trajectory segment from one attracting equilibrium to another as the expression of slow variable by using the DeMoivre formula. With the increase of tuning frequency, the system exhibits relaxation-type oscillations whose small amplitude oscillations are produced by nonlinear local cycles together with a distinct large amplitude cycle oscillation accounting for the Melnikov threshold values. The tuning frequency may not only affect the asymptotic expressions for the solution curves near fold singularities but also allow for the large amplitude orbit vibrations near fold-cycle singularities. Numerical analysis for computing critical manifolds and their intersections is used to detect the dynamical features in this paper.

scholarly journals Transient amplitude modulation of alpha-band oscillations by short-time intermittent closed-loop tACS

2020 ◽  
Author(s):  
G. Zarubin ◽  
C. Gundlach ◽  
V. Nikulin ◽  
A. Villringer ◽  
M. Bogdan
Keyword(s):  
Individual Differences ◽  
Visual System ◽  
Amplitude Modulation ◽  
Closed Loop ◽  
Alternating Current ◽  
Stimulation Protocol ◽  
Spatial Filters ◽  
Alpha Oscillations ◽  
Transcranial Alternating Current Stimulation ◽  
Short Time

AbstractNon-invasive brain stimulation techniques such as transcranial alternating current stimulation (tACS) have recently become extensively utilized due to their potential to modulate ongoing neuronal oscillatory activity and consequently to induce cortical plasticity relevant for various cognitive functions. However, the neurophysiological basis for stimulation effects as well as their inter-individual differences are not yet understood. In the present study we used a closed-loop EEG transcranial alternating current stimulation protocol (EEG-tACS) to examine the modulation of alpha oscillations generated in occipito-parietal areas. In particular, we investigated the effects of a repeated short-time intermittent stimulation protocol (1 s in every trial) applied over the visual cortex (Cz and Oz) and adjusted according to the phase and frequency of visual alpha oscillations on the amplitude of these oscillations. Based on previous findings, we expected higher increases in alpha amplitudes for tACS applied in-phase with ongoing oscillations as compared to an application in anti-phase and this modulation to be present in low-alpha amplitude states of the visual system (eyes opened) but not high (eyes closed).Contrary to our expectations, we found a transient suppression of alpha power in inter-individually derived spatially specific parieto-occipital components obtained via the estimation of spatial filters by using the common spatial patterns approach. The amplitude modulation was independent of the phase relationship between tACS signal and alpha oscillations, and the state of the visual system manipulated via closed- and open-eye conditions. It was also absent in conventionally analyzed single-channel and multi-channel data from an average parieto-occipital region.The fact that the tACS modulation of oscillations was phase-independent suggests that mechanisms driving the effects of tACS may not be explained by entrainment alone, but rather require neuroplastic changes or transient disruption of neural oscillations. Our study also supports the notion that the response to tACS is subject specific, where the modulatory effects are shaped by the interplay between the stimulation and different alpha generators. This favors stimulation protocols as well as analysis regimes exploiting inter-individual differences, such as spatial filters to reveal otherwise hidden stimulation effects and, thereby, comprehensively induce and study the effects and underlying mechanisms of tACS.

Amplitude modulation control of escape from a potential well

2014 ◽  
Vol 378 (16-17) ◽  
pp. 1104-1112 ◽  
Author(s):  
R. Chacón ◽  
A. Martínez García-Hoz ◽  
J.J. Miralles ◽  
P.J. Martínez
Keyword(s):  
Amplitude Modulation ◽  
Potential Well ◽  
Modulation Control

Closed-Loop Vectoring Control of a Turbulent Jet Using Periodic Excitation

2003 ◽  
Vol 19 (4) ◽  
pp. 646-654 ◽  
Author(s):  
D. Rapoport ◽  
I. Fono ◽  
K. Cohen ◽  
A. Seifert
Keyword(s):  
Closed Loop ◽  
Turbulent Jet ◽  
Periodic Excitation

Tuning of PI/PID Controllers Based on Specification on Maximum Closed-Loop Amplitude Ratio.

1999 ◽  
Vol 32 (6) ◽  
pp. 783-788 ◽  
Author(s):  
Cheng-Liang Chen ◽  
Hsiao-Ping Huang ◽  
Chung-Tyan Hsieh
Keyword(s):  
Closed Loop ◽  
Amplitude Ratio ◽  
Pid Controllers ◽  
Loop Amplitude
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