Entrainment Frequency Research Articles

The mechanism of small wear particles entrainment in friction under boundary lubrication

When the lubricating oil flowing between the contact surfaces contains simulated wear particles, it is considered that there is a high possibility for the particles to enter between the contact surfaces if the particles are present on the disk side in a friction test between a fixed ball and a rotating disk. For particles with a diameter of 0.8 μm, it has been previously shown that the entrainment frequency changes with the outside oil film thickness, but the effect of the disk material on the amount of particle deposition and the visualization of particle movement direction due to vortices generated between the contact surfaces had not been performed. In this study, by using SiO2 disks and sapphire disks with different Hamaker constants, the effect on the amount of particle deposition in front of the contact surfaces was experimentally clarified by changing the van der Waals forces acting between the particles and the disks. Additionally, assuming that vortices generated in the oil film between the contact surfaces move the particles to the disk surface side, the flow direction of the lubricating oil was visualized using Navier-Stokes simulation.

Experimental investigation of liquid entrainment in vertical upward annular flow based on fluorescence imaging

The liquid entrainment in annular flow is essential for the prediction of the critical heat flux (CHF), which is one of the important thermal hydraulics parameters in the nuclear boiling water reactor (BWR). However, few investigations have focused on the liquid entrainment in the annular flow inside pipe. In this paper, the liquid entrainment in the vertical upward gas-liquid annular flow was investigated by the Planar Laser-induced Fluorescence. Five types of entrainment have been observed and studied on the basis of the fluorescence imaging and the quantitative measurements. The frequency of occurrence for each entrainment is investigated, and the influencing factors are further discussed. The results show that for entrainment types 2 and 3, the frequency of occurrence decreases with the increasing of wave frequency, while for the entrainment types 4 and 5 that increases as the fluctuation amplitude of the liquid film increases. Finally, the frequency of occurrence for the five types of entrainment is statistically analyzed, and the influences of flow conditions on the fraction distribution of the entrainment are investigated. With the increase of the gas-liquid superficial velocity, the fraction distribution moves to the left and the right respectively. The transformation of fraction distribution corresponds to the variations in the contributions of entrainment types 1–5 to the total entrainment frequency, which could reveal the essence that the gas-liquid superficial velocity affects the size distributions of liquid entrainments. These results can provide a key solution to investigate the characteristics of liquid entrainment and contribute to better understanding of the liquid entrainment in the gas liquid annular flow.

Neural oscillations track natural but not artificial fast speech: Novel insights from speech-brain coupling using MEG

Neural oscillations contribute to speech parsing via cortical tracking of hierarchical linguistic structures, including syllable rate. While the properties of neural entrainment have been largely probed with speech stimuli at either normal or artificially accelerated rates, the important case of natural fast speech has been largely overlooked. Using magnetoencephalography, we found that listening to naturally-produced speech was associated with cortico-acoustic coupling, both at normal (∼6 syllables/s) and fast (∼9 syllables/s) rates, with a corresponding shift in peak entrainment frequency. Interestingly, time-compressed sentences did not yield such coupling, despite being generated at the same rate as the natural fast sentences. Additionally, neural activity in right motor cortex exhibited stronger tuning to natural fast rather than to artificially accelerated speech, and showed evidence for stronger phase-coupling with left temporo-parietal and motor areas. These findings are highly relevant for our understanding of the role played by auditory and motor cortex oscillations in the perception of naturally produced speech.

The Entrainment Frequency of Cardiolocomotor Synchronization in Long-Distance Race Emerges Spontaneously at the Step Frequency.

In forced conditions, where the heart rate and step frequency have been matched, cardiolocomotor synchronization (CLS) has been recognized. However, knowledge about the occurrence of CLS and its triggers in sports gesture in real contexts is little known. To address this gap, the current study tested the hypothesis that CLS in running spontaneous conditions would emerge at entrainment bands of muscle activation frequencies associated with a freely chosen step frequency. Sixteen male long-distance runners undertook treadmill assessments running ten three-minute bouts at different speeds (7, 7.5, 8, 9, 10, 11, 12, 13, 14, and 15 km⋅h–1). Electrocardiography and surface electromyography were recorded simultaneously. The center frequency was the mean of the frequency spectrum obtained by wavelet decomposition, while CLS magnitude was determined by the wavelet coherence coefficient (WCC) between the electrocardiography and center frequency signals. The strength of CLS affected the entrainment frequencies between cardiac and muscle systems, and for WCC values greater than 0.8, the point from which we consider the emerging CLS, the entrainment frequency was between 2.7 and 2.8 Hz. The CLS emerged at faster speeds (13–15 km⋅h–1) most prevalently but did not affect the muscle activation bands. Spontaneous CLS occurred at faster speeds predominantly, and the entrainment frequencies matched the locomotor task, with the entrainment bands of frequencies emerging around the step frequencies (2.7–2.8 Hz). These findings are compatible with the concept that interventions that determine optima conditions of CLS may potentiate the benefits of the cardiac and muscle systems synchronized in distance runners.

Gamma entrainment frequency affects mood, memory and cognition: an exploratory pilot study

Here we provide evidence with an exploratory pilot study that through the use of a Gamma 40 Hz entrainment frequency, mood, memory and cognition can be improved with respect to a 9-participant cohort. Participants constituted towards three binaural entrainment frequency groups: the 40 Hz, 25 Hz and 100 Hz. Participants attended a total of eight entrainment frequency sessions twice over the duration of a 4-week period. Additionally, participants were assessed based on their cognitive abilities, mood as well as memory, where the cognitive and memory assessments occurred before and after a 5-min binaural beat stimulation. The mood assessment scores were collected from sessions 1, 4 and 8, respectively. With respect to the Gamma 40 Hz entrainment frequency population, we observed a mean improvement in cognitive scores, elevating from 75% average to 85% average upon conclusion of the experimentation at weak statistical significance (alpha = 0.10, p = 0.076). Similarly, memory score improvements at a greater significance (alpha = 0.05, p = 0.0027) were noted, elevating from an average of 87% to 95%. In pertinence to the mood scores, a negative correlation across all populations were noted, inferring an overall increase in mood due to lower scores correlating with elevated mood. Finally, correlation analysis revealed a stronger R^2 value (0.9838) within the 40 Hz group between sessions as well as mood score when compared across the entire frequency group cohort.

Biasing the Perception of Spoken Words with Transcranial Alternating Current Stimulation

Recent neuroimaging evidence suggests that the frequency of entrained oscillations in auditory cortices influences the perceived duration of speech segments, impacting word perception [Kösem, A., Bosker, H. R., Takashima, A., Meyer, A., Jensen, O., & Hagoort, P. Neural entrainment determines the words we hear. Current Biology, 28, 2867-2875, 2018]. We further tested the causal influence of neural entrainment frequency during speech processing, by manipulating entrainment with continuous transcranial alternating current stimulation (tACS) at distinct oscillatory frequencies (3 and 5.5 Hz) above the auditory cortices. Dutch participants listened to speech and were asked to report their percept of a target Dutch word, which contained a vowel with an ambiguous duration. Target words were presented either in isolation (first experiment) or at the end of spoken sentences (second experiment). We predicted that the tACS frequency would influence neural entrainment and therewith how speech is perceptually sampled, leading to a perceptual overestimation or underestimation of the vowel's duration. Whereas results from Experiment 1 did not confirm this prediction, results from Experiment 2 suggested a small effect of tACS frequency on target word perception: Faster tACS leads to more long-vowel word percepts, in line with the previous neuroimaging findings. Importantly, the difference in word perception induced by the different tACS frequencies was significantly larger in Experiment 1 versus Experiment 2, suggesting that the impact of tACS is dependent on the sensory context. tACS may have a stronger effect on spoken word perception when the words are presented in continuous speech as compared to when they are isolated, potentially because prior (stimulus-induced) entrainment of brain oscillations might be a prerequisite for tACS to be effective.

An Experimental Approach to Predict the Behaviour of EHD Contacts under Harmonic Loading

Rolling element bearings, gears and other machine components operate in the lubrication regime known as elastohydrodynamic (EHD), where lubricant film thickness is governed by the hydrodynamic action of the converging surfaces, the elastic deformation of the non-conforming surfaces and the increase of lubricant’s viscosity with pressure. Classic EHD theory indicates that under the assumption of fully flooded conditions in the contact inlet zone the central film thickness increases with the product of entrainment speed and dynamic viscosity and is very little dependent of load variations. EHD lubricating films most often work under transient conditions of load, geometry or speed. These make the behaviour of the lubricant film different from steady-state conditions. Previous studies showed that the squeeze effect generates film perturbations due to entrapment of lubricant inside the contact. This phenomenon becomes significant when both entrainment and squeeze are presented. In practical applications, this type of film perturbation will generate pressure fluctuations, which in turn may influences the fatigue life of the contact. In the present paper the results of a systematic experimental study for predicting the occurrence of film thickness perturbation phenomenon under variable load condition are shown. In the case of a mean load larger than the amplitude of the load variation, it was found that the film perturbation depends of the frequency of the load cycle, the entrainment speed of the lubricant and the overall lubricant film thickness; it also depends of the ratios between the mean load and the amplitude. Film perturbations occur in contacts for which the ratio between half the load cycle period and the average time of transit of the lubricant through the contact in the loading phase of the vibration is less than 2. In the case of mean load smaller than the amplitude, film thickness perturbation has been observed in every single test regardless of entrainment speed, frequency and lubricant viscosity.

Alpha-band sensory entrainment alters the duration of temporal windows in visual perception

The phase and frequency of neural oscillations in the alpha band (8–12 Hz) have been recently proposed as key parameters for the temporal resolution of visual perception. Here, we tested the possible causal links between these oscillatory features and temporal integration/segregation. The individual alpha frequency (IAF) peak as obtained from resting-state electroencephalography was used to set the frequency of sensory (audio-visual) entrainment for the lower (IAF − 2 Hz) and upper (IAF + 2 Hz) alpha. Entrainment at IAF ± 2 Hz was administered in the prestimulus interval to align oscillations to a faster or slower rhythm. We densely sampled in time the accuracy for integration/segregation by using identical stimuli with different instructions. The spectral peaks of performance fluctuations over time were found in the upper or lower alpha band for the IAF + 2 and IAF − 2 Hz entrainment, respectively, implying that faster entrainment resulted in faster behavioral fluctuations. Moreover, the entrainment frequency had opposite effects on temporal resolution: faster entrainment improved segregation while slower entrainment improved integration. Performance fluctuations were almost in anti-phase between the two tasks, such that highest integration performance coincided with lowest segregation performance. These findings provide evidence for a direct link between changes in the alpha band and the temporal resolution of perception.

The Role of Oscillatory Phase in Determining the Temporal Organization of Perception: Evidence from Sensory Entrainment.

Recent behavioral, neuroimaging, and neurophysiological studies have renewed the idea that the information processing within different temporal windows is linked to the phase and/or frequency of the ongoing oscillations, predominantly in the theta/alpha band (∼4–7 and 8–12 Hz, respectively). However, being correlational in nature, this evidence might reflect a nonfunctional byproduct rather than having a causal role. A more direct link can be shown with methods that manipulate oscillatory activity. Here, we used audiovisual entrainment at different frequencies in the prestimulus period of a temporal integration/segregation task. We hypothesized that entrainment would align ongoing oscillations and drive them toward the stimulation frequency. To reveal behavioral oscillations in temporal perception after the entrainment, we sampled the segregation/integration performance densely in time. In Experiment 1, two groups of human participants (both males and females) received stimulation either at the lower or the upper boundary of the alpha band (∼8.5 vs 11.5 Hz). For both entrainment frequencies, we found a phase alignment of the perceptual oscillation across subjects, but with two different power spectra that peaked near the entrainment frequency. These results were confirmed when perceptual oscillations were characterized in the time domain with sinusoidal fittings. In Experiment 2, we replicated the findings in a within-subject design, extending the results for frequencies in the theta (∼6.5 Hz), but not in the beta (∼15 Hz), range. Overall, these findings show that temporal segregation can be modified by sensory entrainment, providing evidence for a critical role of ongoing oscillations in the temporal organization of perception.SIGNIFICANCE STATEMENT The continuous flow of sensory input is not processed in an analog fashion, but rather is grouped by the perceptual system over time. Recent studies pinpointed the phase and/or frequency of the neural oscillations in the theta/alpha band (∼4–12 Hz) as possible mechanisms underlying temporal windows in perception. Here, we combined two innovative methodologies to provide more direct support for this evidence. We used sensory entrainment to align neural oscillations to different frequencies and then characterized the resultant perceptual oscillation with a temporal dense sampling of the integration/segregation performance. Our results provide the first evidence that the frequency of temporal segregation can be modified by sensory entrainment, supporting a critical role of ongoing oscillations in the integration/segregation of information over time.

Flow topology of a container train wagon subjected to varying local loading configurations

How the positioning and length of a container placed on an arbitrary train wagon in an otherwise fully loaded train affects the local aerodynamics, and consequently the contribution to drag, is examined here. Results from scale-model wind-tunnel tests undertaken at a Reynolds number of 0.3 × 106 for a combination of 49 upstream and downstream gap spacings (Gf,Gr) are presented. Surface flow topology, pressure profiles and planar velocity fields are measured. Gf dominated the drag variations, with Gr only causing a secondary effect. The greatest drag reduction potential is found between gaps size of 1.77W and 3.23W, where W represents the wagon width. Over the range of Gf and Gr investigated, a number of distinct physical mechanisms were observed. These affect the separation size and the nature of boundary layer enveloping the wagon, which have a direct impact on the entrainment and shedding frequency of the wake.

A theoretical analysis of anatomical and functional intestinal slow wave re-entry

Intestinal bioelectrical slow waves are a key regulator of intestinal motility. Peripheral pacemakers, ectopic initiations and sustained periods of re-entrant activities have all been experimentally observed to be important factors in setting the frequency of intestinal slow waves, but the tissue-level mechanisms underpinning these activities are unclear. This theoretical analysis aimed to define the initiation, maintenance, and termination criteria of two classes of intestinal re-entrant activities: anatomical re-entry and functional re-entry. Anatomical re-entry was modeled in a three-dimensional (3D) cylindrical model, and functional rotor was modeled in a 2D rectangle model. A single-pulse stimulus was used to invoke an anatomical re-entry and a prolonged refractory block was used to invoke the rotor. In both cases, the simulated re-entrant activities operated at frequencies above the baseline entrainment frequency. The anatomical re-entry simulation results demonstrated that a temporary functional refractory block would be required to initiate the re-entrant activity in a single direction around the cylindrical model. The rotor could be terminated by a single-pulse stimulus delivered around the core of the rotor. In conclusion, the simulation results provide the following new insights into the mechanisms of intestinal re-entry: (i) anatomical re-entry is only maintained within a specific range of velocities, outside of which the re-entrant activities become either an ectopic activity or simultaneous activations of the intestinal wall; (ii) a maintained rotor entrained slow waves faster in the antegrade direction than in the retrograde direction. Simulations are shown to be a valuable tool for achieving novel insights into the mechanisms of intestinal slow wave dysrhythmia.

Addressing the urban stream disturbance regime

AbstractThresholds for particle entrainment and natural disturbance frequency vary across hydrogeomorphic settings, but urbanization increases the rate and extent of channel erosion and sediment transport in alluvial channels. The urban disturbance regime is a change in the frequency, magnitude, and duration of hydrologically induced disturbance on the stream channel and ecosystem that can lead to geomorphic and ecological degradation. To preserve stream stability and ecological function, stormwater management systems should be optimized to maintain the natural disturbance regime of streambed material within the context of societal and environmental goals. Our proposed framework, based on data from 195 sites across 2 continents, shows that the tools of river mechanics can be used to develop relatively simple, regionally appropriate, streambed-specific guidance for stormwater designers, so that engineers can calibrate stormwater facilities that address the urban stream disturbance regime. In the absence of...

Phase-locking index and power of 40-Hz auditory steady-state response are not related to major personality trait dimensions.

Although a number of studies have demonstrated state-related dependence of auditory steady-state responses (ASSRs), the investigations assessing trait-related ASSR changes are limited. Five consistently identified major trait dimensions, also referred to as "big five" (Neuroticism, Extraversion, Openness, Agreeableness and Conscientiousness), are considered to account for virtually all personality variances in both healthy people and those with psychiatric disorders. The purpose of the present study was, for the first time, to establish the link between 40-Hz ASSR and "big five" major personality trait dimensions in young healthy adults. Ninety-four young healthy volunteers participated (38 males and 56 females; mean age±SD 22.180±2.75). The 40-Hz click trains were presented for each subject 30 times with an inter-train interval of 1-1.5s. The EEG responses were recorded from F3, Fz, F4, C3, Cz, C4, P3, Pz and P4 locations according to 10/20 electrode placement system. Phase-locking index (PLI) and event-related power perturbation (ERSP) were calculated, each providing the following characteristics: peak time, entrainment frequency, peak value and mean value. For assessing "big five" personality traits, NEO Personality Inventory Revised (NEO-PI-R) was used. No significant correlation between 40-Hz ASSR PLI or ERSP and "big five" personality traits was observed. Our results indicate that there is no dependence between 40-Hz ASSR entrainment and personality traits, demonstrating low individual 40-Hz variability in this domain. Our results support further development of 40-Hz ASSR as a neurophysiological marker allowing distinguishing between healthy population and patients with psychiatric disorders.

A theoretical study of the initiation, maintenance and termination of gastric slow wave re-entry.

Gastric slow wave dysrhythmias are associated with motility disorders. Periods of tachygastria associated with slow wave re-entry were recently recognized as one important dysrhythmia mechanism, but factors promoting and sustaining gastric re-entry are currently unknown. This study reports two experimental forms of gastric re-entry and presents a series of multi-scale models that define criteria for slow wave re-entry initiation, maintenance and termination. High-resolution electrical mapping was conducted in porcine and canine models and two spatiotemporal patterns of re-entrant activities were captured: single-loop rotor and double-loop figure-of-eight. Two separate multi-scale mathematical models were developed to reproduce the velocity and entrainment frequency of these experimental recordings. A single-pulse stimulus was used to invoke a rotor re-entry in the porcine model and a figure-of-eight re-entry in the canine model. In both cases, the simulated re-entrant activities were found to be perpetuated by tachygastria that was accompanied by a reduction in the propagation velocity in the re-entrant pathways. The simulated re-entrant activities were terminated by a single-pulse stimulus targeted at the tip of re-entrant wave, after which normal antegrade propagation was restored by the underlying intrinsic frequency gradient. (i) the stability of re-entry is regulated by stimulus timing, intrinsic frequency gradient and conductivity; (ii) tachygastria due to re-entry increases the frequency gradient while showing decreased propagation velocity; (iii) re-entry may be effectively terminated by a targeted stimulus at the core, allowing the intrinsic slow wave conduction system to re-establish itself.

Experimental investigation of liquid entrainment in vertical up tee branch with double-end gas inlets

Tee branches are widely used in nuclear power plants for varying purposes. The tee branch is adopted by the fourth stage Automatic Depressurization System (ADS-4) in Westinghouse AP600/AP1000 to depressurize the primary loop during the small break loss of coolant accident (SBLOCA). However, large amount of coolant will be entrained simultaneously through the ADS-4 branch which poses the threat of core uncovering and melting. Visualization experiments with double-end gas inlets were conducted to investigate the ADS-4 tee branch entrainment phenomena in AP1000. Entrainment process were recorded by high speed camera and analyzed in detail. The onset of liquid entrainment and entrainment rate data were obtained and compared with existing data and correlations, and discrepancies were found in the comparison due to the difference of test section geometric configuration. The gas flow rate has little effect on the branch quality at the same dimensionless gas chamber height in entrainment rate tests. The entrainment frequency was also studied. The test data reveal that the entrainment period decreases rapidly with the increase of entrainment rate in low range of the entrainment rate, and gradually stabilizes in high range of the entrainment rate.

Functional correlates of exaggerated oscillatory activity in basal ganglia output in hemiparkinsonian rats

Exaggerated beta range (13–30Hz) synchronized activity is observed in the basal ganglia of Parkinson's disease (PD) patients during implantation of deep brain stimulation electrodes and is thought to contribute to the motor symptoms of this disorder. To explore the translational potential of similar activity observed in a rat model of PD, local field potentials (LFPs) and spiking activity in basal ganglia output were characterized in rats with unilateral dopamine cell lesion during a range of behaviors. A circular treadmill was used to assess activity during walking; hemiparkinsonian rats could maintain a steady gait when oriented ipsiversive to the lesioned hemisphere, but were less effective at walking when oriented contraversive to lesion. Dramatic increases in substantia nigra pars reticulata (SNpr) LFP oscillatory activity and spike-LFP synchronization were observed within the beta/low gamma range (12–40Hz) in the lesioned hemisphere, relative to the non-lesioned hemisphere, with the dominant frequency of spike-LFP entrainment and LFP power varying with behavioral state. At 3weeks postlesion, the mean dominant entrainment frequency during ipsiversive treadmill walking and grooming was 34Hz. Other behaviors were associated with lower mean entrainment frequencies: 27–28Hz during alert non-walking and REM, 17Hz during rest and 21Hz during urethane anesthesia with sensory stimulation. SNpr spike-LFP entrainment frequency was stable during individual treadmill walking epochs, but increased gradually over weeks postlesion. In contrast, SNpr LFP power in the 25–40Hz range was greatest at the initiation of each walking epoch, and decreased during walking to stabilize by 6min at 49% of initial values. Power was further modulated in conjunction with the 1.5s stepping rhythm. Administration of l-dopa improved contraversive treadmill walking in correlation with a reduction in SNpr 25–40Hz LFP power and spike synchronization in the dopamine cell lesioned hemisphere. These effects were reversed by the serotonergic 1A agonist, 8-OH-DPAT. While the prominent spike-LFP phase locking observed during ongoing motor activity in the hemiparkinsonian rats occurs at frequencies intriguingly higher than in PD patients, the synchronized activity in the SNpr of this animal model has much in common with oscillatory activity recorded from the basal ganglia of the PD patients. Results support the potential of this model for providing insight into relationships between synchronization of basal ganglia output induced by loss of dopamine and motor symptoms in PD.

Entrainment of Brain Oscillations by Transcranial Alternating Current Stimulation

Novel methods for neuronal entrainment [1-4] provide the unique opportunity to modulate perceptually relevant brain oscillations [5, 6] in a frequency-specific manner and to study their functional impact on distinct cognitive functions. Recently, evidence has emerged that tACS (transcranial alternating current stimulation) can modulate cortical oscillations [7-9]. However, the study of electrophysiological effects has been hampered so far by the absence of concurrent electroencephalogram (EEG) recordings. Here, we applied 10Hz tACS to the parieto-occipital cortex and utilized simultaneous EEG recordings to study neuronal entrainment during stimulation. We pioneer a novel approach for simultaneous tACS-EEG recordings and successfully separate stimulation artifacts from ongoing and event-related cortical activity. Our results reveal that 10Hz tACS increases parieto-occipital alpha activity and synchronizes cortical oscillators with similar intrinsic frequencies to the entrainment frequency. Additionally, we demonstrate that tACS modulates target detection performance in a phase-dependent fashion highlighting the causal role of alpha oscillations for visual perception.

Mean-field and mean-ensemble frequencies of a system of coupled oscillators

We investigate interacting phase oscillators whose mean field is at a different frequency from the mean or mode of their natural frequencies. The associated asymmetries lead to a macroscopic travelling wave. We show that the mean ensemble frequency of such systems differs from their entrainment frequency. In some scenarios these frequencies take values that, counter-intuitively, lie beyond the limits of the natural frequencies. The results indicate that a clear distinction should be drawn between the two variables describing the macroscopic dynamics of cooperative systems. This has important implications for real systems where a non-trivial distribution of parameters is common.

Oscillatory Sensory Selection Mechanisms during Intersensory Attention to Rhythmic Auditory and Visual Inputs: A Human Electrocorticographic Investigation

Oscillatory entrainment mechanisms are invoked during attentional processing of rhythmically occurring stimuli, whereby their phase alignment regulates the excitability state of neurons coding for anticipated inputs. These mechanisms have been examined in the delta band (1-3 Hz), where entrainment frequency matches the stimulation rate. Here, we investigated entrainment for subdelta rhythmic stimulation, recording from intracranial electrodes over human auditory cortex during an intersensory audiovisual task. Audiovisual stimuli were presented at 0.67 Hz while participants detected targets within one sensory stream and ignored the other. It was found that entrainment operated at twice the stimulation rate (1.33 Hz), and this was reflected by higher amplitude values in the FFT spectrum, cyclic modulation of alpha-amplitude, and phase-amplitude coupling between delta phase and alpha power. In addition, we found that alpha-amplitude was relatively increased in auditory cortex coincident with to-be-ignored auditory stimuli during attention to vision. Thus, the data suggest that entrainment mechanisms operate within a delimited passband such that for subdelta task rhythms, oscillatory harmonics are invoked. The phase of these delta-entrained oscillations modulates alpha-band power. This may in turn increase or decrease responsiveness to relevant and irrelevant stimuli, respectively.

DYNAMIC MODELING OF ROTOR SHAFT WITH INTERNAL DAMPING DRIVEN THROUGH A DISSIPATIVE COUPLING

The paper presents the dynamic behavior of a hollow rotor shaft with internal damping driven by a dissipative coupling. The coupling in the system is absolutely flexible in transverse and bending; however, it is assumed to be torsionally rigid. Bond graph is adopted for modeling as it facilitates the system modeling from the physical paradigm itself, and the model can be easily extended to incorporate modifications. Simulation results show interesting phenomenon of limiting behavior of rotor shaft with internal damping beyond the threshold speed of instability. It is further shown that the shaft entrainment frequency of the rotor shaft primarily depends on the ratio of external and internal damping.