Effect Of Phase Synchronization Research Articles

Tailoring transcranial alternating current stimulation based on endogenous event-related P3 to modulate premature responses: a feasibility study.

Transcranial alternating current stimulation (tACS) is a brain stimulation method for modulating ongoing endogenous oscillatory activity at specified frequency during sensory and cognitive processes. Given the overlap between event-related potentials (ERPs) and event-related oscillations (EROs), ERPs can be studied as putative biomarkers of the effects of tACS in the brain during cognitive/sensory task performance. This preliminary study aimed to test the feasibility of individually tailored tACS based on individual P3 (latency and frequency) elicited during a cued premature response task. Thus, tACS frequency was individually tailored to match target-P3 ERO for each participant. Likewise, the target onset in the task was adjusted to match the tACS phase and target-P3 latency. Twelve healthy volunteers underwent tACS in two separate sessions while performing a premature response task. Target-P3 latency and ERO were calculated in a baseline block during the first session to allow a posterior synchronization between the tACS and the endogenous oscillatory activity. The cue and target-P3 amplitudes, delta/theta ERO, and power spectral density (PSD) were evaluated pre and post-tACS blocks. Target-P3 amplitude significantly increased after activetACS, when compared to sham. Evoked-delta during cue-P3 was decreased after tACS. No effects were found for delta ERO during target-P3 nor for the PSD and behavioral outcomes. The present findings highlight the possible effect of phase synchronization between individualized tACS parameters and endogenous oscillatory activity, which may result in an enhancement of the underlying process (i.e., an increase of target-P3). However, an unsuccessful synchronization between tACS and EEG activity might also result in a decrease in the evoked-delta activity during cue-P3. Further studies are needed to optimize the parameters of endogenous activity and tACS synchronization. The implications of the current results for future studies, including clinical studies, are further discussed since transcranial alternating current stimulation can be individually tailored based on endogenous event-related P3 to modulate responses.

Experimental study on noise reduction of multi-rotor by phase synchronization

Phase synchronization implies that the rotors are synchronized to the same rotation speed and different phases to minimize rotor noise in specific directions. In this study, the influence of phase synchronization on noise directivity and the reducing effect of a multi-rotor were studied experimentally. Based on the multi-rotor noise test platform built in the anechoic chamber, to study the noise control effect of phase synchronization, tests were performed on a small-scale dual-rotor and quadrotor. The influence of phase synchronization on the noise directivity and frequency characteristics was analyzed. Furthermore, the effectiveness of the proposed method was verified using noise-reduction experiments for the target points and regions. The experimental results revealed that: (1) phase synchronization is more advantageous for co-rotating rotors than counter-rotating rotors. Phase synchronization reduces the noise level in all azimuths for the co-rotating rotors, and only a few directions for the counter-rotating rotors. (2) Phase synchronization effectively reduces the sound pressure level in the low-frequency band and multiple harmonic frequencies for a single observation point, especially at the blade-passing frequency. (3) The regional noise is reduced by 1–5 dB and 1–11 dB for the counter-rotating and co-rotating dual-rotor, respectively. Therefore, the experiments show that phase synchronization has a significant advantage in noise control for multi-rotor aircraft.

Emulation of Astrocyte Induced Neural Phase Synchrony in Spin-Orbit Torque Oscillator Neurons.

Astrocytes play a central role in inducing concerted phase synchronized neural-wave patterns inside the brain. In this article, we demonstrate that injected radio-frequency signal in underlying heavy metal layer of spin-orbit torque oscillator neurons mimic the neuron phase synchronization effect realized by glial cells. Potential application of such phase coupling effects is illustrated in the context of a temporal “binding problem.” We also present the design of a coupled neuron-synapse-astrocyte network enabled by compact neuromimetic devices by combining the concepts of local spike-timing dependent plasticity and astrocyte induced neural phase synchrony.

A Numerical and Analytical Study of Phase Synchronization in Coupled SC-CNN Based Non-Identical Chaotic Systems

This paper seeks to address the phase synchronization phenomenon using the drive-response concept, in our proposed model, State Controlled Cellular Neural Network (SC-CNN) based on variant of MuraliLakshmanan-Chua (MLCV) circuit. Using this unidirectionally coupled chaotic non autonomous circuits, we described the transition of unsynchronous to synchronous state, by numerical simulation method as well as the results are confirmed by solving explicit analytical solution. In this aspect, the system undergoes the new effect of phase synchronization (PS) phenomenon have been observed before complete synchronization (CS) state. To characterize these phenomena by the phase portraits and the time series plots. Also particularly characterize for PS by the method of partial Poincare section map using phase difference versus time, numerically and analytically. The study of dynamics involved in SC-CNN circuit systems, mainly applicable in the field of neurosciences and in telecommunication fields.

Electron spin noise under the conditions of nuclei-induced frequency focusing

We study theoretically the electron spin noise in quantum dots under non-equilibrium conditions caused by the pumping by a train of circularly polarized optical pulses. In such a situation, the nuclear spins are known to adjust in such a way, that the electron spin precession frequencies become multiples of the pump pulse repetition frequency. This so called phase synchronization effect was uncovered in [Science {\bf 317}, 1896 (2007)] and termed nuclei-induced frequency focusing of electron spin coherence. Using the classical approach to the central spin model we evaluate the nuclear spin distribution function and the electron spin noise spectrum. We show that the electron spin noise spectrum consists of sharp peaks corresponding to the phase synchronization conditions and directly reveal the distribution of the nuclear spins. We discuss the effects of nuclear spin relaxation after the pumping is over and analyze the corresponding evolution of nuclear spin distributions and electron spin noise spectra.

Automated impact device with non-synchronous impacts: a practical solution for modal testing during operation

Previous study has shown that synchronization of phases between impacts and the cyclic load component should be avoided to improve the effectiveness of operational modal testing, i.e. impact-synchronous modal analysis in obtaining a cleaner frequency response function (FRF) estimation with fewer number of averages. However, avoiding the phase synchronization effect is rarely achievable with the current manual impact hammer because of the lack of control of the impact timing. We investigate how to improve FRF estimation in the presence of harmonic disturbances, such as those present in operating rotating machines. An auto impact device is therefore introduced to replace the manual impact hammer. This device ensures that impact intervals can be applied at non-synchronous instances with respect to the harmonic disturbance. We demonstrate that this new device is a viable option for operational modal testing. It allows significant improvement in FRF estimation and shows good correlation of modal extraction data with benchmark experimental modal analysis results.

Assessment of the phase synchronization effect in modal testing during operation

The impact-synchronous modal analysis (ISMA), which uses impact-synchronous time averaging (ISTA), allows modal testing to be performed during operation. ISTA is effective in filtering out the non-synchronous cyclic load component, its harmonics, and noises. However, it was found that at operating speeds that coincide with the natural modes, ISMA would require a high number of impacts to determine the dynamic characteristics of the system. This finding has subsequently reduced the effectiveness and practicality of ISMA. Preservation of signatures during ISTA depends on the consistency of their phase angles on every time block but not necessarily on their frequencies. Thus, the effect of phase angles with respect to impact is seen to be a very important parameter when performing ISMA on structures with dominant periodic responses due to cyclic load and ambient excitation. The responses from unaccounted forces that contain even the same frequency as that contained in the response due to impact are diminished with the least number of impacts when the phase of the periodic responses is not consistent with the impact signature for every impact applied. The assessment showed that a small number of averages are sufficient to eliminate the non-synchronous components with 98.48% improvement on simulation and 95.22% improvement on experimental modal testing when the phase angles with respect to impact are not consistent for every impact applied.

Dynamics of electrochemical oscillators with electrode size disparity: asymmetrical coupling and anomalous phase synchronization

Experiments are carried out in dual electrode oscillatory Ni electrodissolution in which the two electrodes have different surface areas. The transition to phase synchronization is analyzed as asymmetrical coupling strength, induced by placing a cross resistance between the electrodes, is varied. It is shown that because of nonisochronicity (phase shear, i.e., strong dependence of period on amplitude) of the oscillators, anomalous phase synchronization effects can be observed: advanced/delayed synchronization and, to a lesser extent, frequency difference enhancement. The type of synchronization is strongly affected by the underlying heterogeneities of the oscillators; in the experiments with a slow driver (large surface area) electrode the synchronization is advanced, with a fast driver electrode the synchronization is delayed with respect to symmetrical coupling. The findings thus reveal that the interplay of asymmetrical coupling with the types of inherent heterogeneities plays an important role for the interpretation of size effects in the dynamical behavior of a nonlinear chemical reaction.

PHASE SYNCHRONIZATION OF LINEARLY AND NONLINEARLY COUPLED OSCILLATORS WITH INTERNAL RESONANCE

Phase synchronization between linearly and nonlinearly coupled systems with internal resonance is investigated in this paper. By introducing the conception of phase for a chaotic motion, it demonstrates that the detuning parameter σ between the two natural frequencies ω1and ω2affects phase dynamics, and with the increase in the linear coupling strength, the effect of phase synchronization between two sub-systems was enhanced, while increased firstly, and then decayed as nonlinear coupling strength increases. Further investigation reveals that the transition of phase states between the two oscillators are related to the critical changes of the Lyapunov exponents, which can also be explained by the diffuse clouds.

TRACKING PHASE SYNCHRONIZATION OF TWO COUPLED RÖSSLER OSCILLATORS WITH INTERNAL RESONANCE

Phase synchronization between linearly and nonlinearly coupled systems with internal resonance is investigated in this paper. By introducing the conception of phase for a chaotic motion, we tune the linear coupling parameter to obtain the two Rössler oscillators in a synchronized regime and analyze the effect of a nonlinear coupling on the phase synchronized state. It demonstrates that the detuning parameter σ between the two natural frequencies ω1and ω2affects phase dynamics, and with the increase of the nonlinear coupling strength, for the primary resonance, the effect of phase synchronization between two sub-systems was decayed, while increasing with frequency ratio 1:2. Further investigation reveals that the transition of phase states between the two oscillators are related to the critical changes of the nonlinear coupling strength.

Influence of periodic variations in water level on regional seismic activity around a large reservoir: Field data and laboratory model

The reservoir-induced changes of the regional seismic activity around the Enguri high dam reservoir in western Georgia are found to be influenced by the water level of the reservoir. The water level variations of the Enguri high dam reservoir and the seismic data sets recorded by the local network have been analyzed by means of statistical, linear, nonlinear and phase synchronization analysis methods. It is shown that seismic activity increases during the flooding period, according to the well-known concepts of reservoir-induced seismicity (RIS). As a new result we see that the released energy value essentially decreases when the variation of the water level in the reservoir becomes periodic. Furthermore acoustic emission data obtained during laboratory stick–slip experiments with superimposed weak periodic perturbations have been investigated as a model of natural seismicity. We conclude that the decrease in seismic activity around Enguri high dam is induced by periodic changes of water level in the reservoir. Based on the field and laboratory data analysis we have generalised our conclusion and suppose that probability of decrease of strong earthquakes’ occurrence around large reservoirs may be explained by the phase synchronization effect between the complex seismic process and small periodic influences related to changes in water level.

Synchronized chaotic intermittent and spiking behavior in coupled map chains

We study phase synchronization effects in a chain of nonidentical chaotic oscillators with a type-I intermittent behavior. Two types of parameter distribution, linear and random, are considered. The typical phenomena are the onset and existence of global (all-to-all) and cluster (partial) synchronization with increase of coupling. Increase of coupling strength can also lead to desynchronization phenomena, i.e., global or cluster synchronization is changed into a regime where synchronization is intermittent with incoherent states. Then a regime of a fully incoherent nonsynchronous state (spatiotemporal intermittency) appears. Synchronization-desynchronization transitions with increase of coupling are also demonstrated for a system resembling an intermittent one: a chain of coupled maps replicating the spiking behavior of neurobiological networks.

Phase synchronization of chaotic intermittent oscillations.

We study phase synchronization effects of chaotic oscillators with a type-I intermittency behavior. The external and mutual locking of the average length of the laminar stage for coupled discrete and continuous in time systems is shown and the mechanism of this synchronization is explained. We demonstrate that this phenomenon can be described by using results of the parametric resonance theory and that this correspondence enables one to predict and derive all zones of synchronization.

Stochastic resonance: Noise-enhanced phase coherence

We study stochastic resonance in periodically driven stochastic bistable systems in terms of phase synchronization. By introduction of an instantaneous phase for the output we show explicitly the effect of phase locking between the input and output. The stochastic dynamics of the phase difference between input and output appears to be similar to that of synchronized classical self-sustained oscillators. The degree of phase coherence is estimated by employing the effective diffusion constant for the phase difference. This coherence becomes maximal for optimal noise intensities. However, phase synchronization effects can only be observed for sufficiently large magnitude of the periodic inputting signal.

Phase synchronization effects in a lattice of nonidentical Rössler oscillators

We study phase synchronization in a chain of weakly coupled chaotic oscillators. In the synchronous state, the phases of oscillators are locked, while the amplitudes remain chaotic. We demonstrate that the coexistence of several clusters of mutually synchronized elements and global synchronization of all oscillators is possible. Two mechanisms of the transition to global synchronization are shown. The dynamics of spatiotemporal defects is discussed for the cases of phase-coherent and funnel R\ossler oscillators.

Phase synchronization in driven and coupled chaotic oscillators

We describe the effect of phase synchronization of chaotic oscillators. It is shown that phase can be defined for continuous time dynamical oscillators with chaotic dynamics, and effects of phase and frequency locking can be observed, We introduce several tools which characterize this weak synchronization and demonstrate phase and frequency locking by external periodic force, as well as due to weak interaction of nonidentical chaotic oscillators. In the synchronous state the phases of two systems are locked, while the amplitudes remain chaotic and noncorrelated. The intermittency phenomenon at the synchronization transition is considered. The application to the analysis of bivariate experimental data is discussed.

Phase synchronization of chaotic oscillators.

We present the new effect of phase synchronization of weakly coupled self-sustained chaotic oscillators. To characterize this phenomenon, we use the analytic signal approach based on the Hilbert transform and partial Poincar\'e maps. For coupled R\ossler attractors, in the synchronous regime the phases are locked, while the amplitudes vary chaotically and are practically uncorrelated. Coupling a chaotic oscillator with a hyperchaotic one, we observe another new type of synchronization, where the frequencies are entrained, while the phase difference is unbounded. A relation between the phase synchronization and the properties of the Lyapunov spectrum is studied.

Perpendicular Magnetic Recording Performance with Ring-Type Heads for Electroless-Plated CoNiReP/NiFeP Double-Layered Media

The perpendicular magnetic recording performance of electroless CoNiReP/NiFeP double-layered media using ring-type heads was investigated, focusing upon the recording processes and the effect of underlayer coercivity (Hc(u)=5∼160 Oe). For the recording on medium whose Hc(u) value is higher than several tens of Oe, the underlayer is also magnetized by a head field, and the phase of such a longitudinal magnetization of the underlayer is shifted in proportion to the change of magneto-motive force (MMF). In the low MMF region, the phases of perpendicular transition and longitudinal transition are synchronized, forming the horseshoe mode through the perpendicular layer and the underlayer. Consequently, the output voltage, by maintaining single-peak shaped signals, drastically increased by the so-designated “phase synchronization” effect. Greater improvement of reproduced voltage by such a phase synchronization effect was obtained for the higher Hc(u) medium.