Oscillation Frequency Research Articles

Parameter constraints on a black hole with Minkowski core through quasiperiodic oscillations

We investigate the geodesic motion of charged particles in the vicinity of regular black holes with a Minkowski core, embedded in a uniform magnetic field, and study the influences of magnetic field and regular black hole parameter on the radial effective potential and angular momentum of the particles’ orbits. We perturb the circular orbit and analyze the characteristic frequencies of the epicyclic oscillations, which are closely related with the quasiperiodic oscillations (QPOs) phenomena of the accretion disc surrounding the black hole. Then using the MCMC simulation, we fit our theoretical results with four observational QPOs events (GRO J1655-40, XTE J1550-564, XTE J1859+226, and GRS 1915+105) and provide constraints on the magnetic field strength B, the characteristic radius r, the mass M, and the regular black hole parameter g. In particular, since the parameter g describes the degree of deviation from the classical Schwarzschild black hole, our studies suggest that, within a certain level of confidence, the black holes in the current model can deviate from the classical singularity structure of Schwarzschild black holes, and exhibit quantum corrections near the core.

Event-triggered synchronisation of unknown heterogeneous coupled harmonic oscillators

This note concentrates on event-triggered synchronisation problem of unknown heterogeneous coupled harmonic oscillators (CHOs). We develop an event-triggered synchronisation algorithm that does not rely on any continuous information transmission among oscillators and global topology information. For this end, we first design an observer to estimate unknown system parameter for each oscillator. Second, each oscillator uses information received from its neighbours to estimate the frequency of leader oscillator and its neighbours' states. Based on estimated frequencies and states, we design an adaptive synchronisation algorithm for CHOs to solve synchronisation problem. We prove that CHOs, under proposed synchronisation algorithm, reach state synchronisation, and there is no Zeno behaviour. In the end, a simulation is presented to check proposed synchronisation algorithm.

Experimental Investigation of the Dynamics of Methane-Oxygen Diffusion Flame Stabilized Over Swirl Coaxial Injector

ABSTRACT The combustion dynamics of methane-oxygen inverse diffusion flames stabilized over a swirl coaxial injector are investigated in detail. Mapping of different regimes of flame dynamics was carried out by classifying the flame into stable flames, oscillating flames, and unstable flames. The dominant frequency of the acoustics associated with different flame characteristics was determined from a free-field microphone measurement of combustion noise, and the respective flame morphology was studied by high-speed imaging of OH* chemiluminescence. Experiments were conducted for different oxidizer jet Reynolds numbers corresponding to each of the three different fuel jet Reynolds numbers. For all three power levels, flame transition from stable to unstable was observed as the oxidizer Reynolds number and equivalence ratio increased from fuel-rich to oxidizer-rich conditions. Strong acoustic-combustion heat release rate coupling was observed in the unstable flames. Modal decomposition techniques were employed to study the spatio-temporal evolution of the flame. The energetic coherent modes corresponding to the frequency of oscillation reveal two different modes of flame oscillation: longitudinal and transverse. All three fuel Reynolds numbers under investigation showed a predominant longitudinal mode of oscillation, while only the highest fuel flow conditions, corresponding to a fuel jet Reynolds number of 765 showed a transverse mode flame oscillation, as the oxidizer Reynolds number increased above 8000.

Age predicts peak gamma frequency and N1 amplitude of visual evoked potential

The current study investigated whether the age of healthy adults could predict the peak gamma frequency and the peak amplitudes of VEP components (N1, P2). 49 healthy participants (aged between 19 and 52 years) underwent EEG recordings during a visual task eliciting clear gamma frequency oscillations and VEP activities. After eliminating noisy and outlier data, data from 41 participants were analysed using simple linear regression. The results indicated that age was a significant predictor of peak gamma frequency and the peak amplitude of VEP-N1 but not the peak amplitude of VEP-P2. Age was negatively associated with peak gamma frequency and the peak amplitude of VEP-N1. These findings support previous research indicating that ageing is associated with decreased cortical inhibition, highlighting the importance of GABA in maintaining cortical E-I balance.

The functional role of oscillatory dynamics in neocortical circuits: A computational perspective

The dynamics of neuronal systems are characterized by hallmark features such as oscillations and synchrony. However, it has remained unclear whether these characteristics are epiphenomena or are exploited for computation. Due to the challenge of selectively interfering with oscillatory network dynamics in neuronal systems, we simulated recurrent networks of damped harmonic oscillators in which oscillatory activity is enforced in each node, a choice well supported by experimental findings. When trained on standard pattern recognition tasks, these harmonic oscillator recurrent networks (HORNs) outperformed nonoscillatory architectures with respect to learning speed, noise tolerance, and parameter efficiency. HORNs also reproduced a many characteristic features of neuronal systems, such as the cerebral cortex and the hippocampus. In trained HORNs, stimulus-induced interference patterns holistically represent the result of comparing sensory evidence with priors stored in recurrent connection weights, and learning-induced weight changes are compatible with Hebbian principles. Implementing additional features characteristic of natural networks, such as heterogeneous oscillation frequencies, inhomogeneous conduction delays, and network modularity, further enhanced HORN performance without requiring additional parameters. Taken together, our model allows us to give plausible a posteriori explanations for features of natural networks whose computational role has remained elusive. We conclude that neuronal systems are likely to exploit the unique dynamics of recurrent oscillator networks whose computational superiority critically depends on the oscillatory patterning of their nodal dynamics. Implementing the proposed computational principles in analog hardware is expected to enable the design of highly energy-efficient and self-adapting devices that could ideally complement existing digital technologies.

A New Method to Enhance the Light–Matter Interaction by Controlling the Resonance of Electrons

The manipulation of surface plasmon polaritons (SPPs) plays an essential role in plasmonic science and technology. However, the modulation efficiency and size of the device in the traditional method suffer from weak light–matter interaction. Herein, we propose a new method to enhance the light–matter interaction by controlling the resonance of electrons in a sandwich structure which is composed of an interdigital electrode, dielectric, and doped semiconductor. The numerical results show that the resonance of electrons occurs when their vibrational frequency under electrostatic field matches well with the oscillation frequency of the propagating SPPs. The intensity of the electric field is enhanced about 8%, which can be utilized to improve the modulation efficiency and minimize the footprint of device to a great extent. These findings pave a new way towards higher precision sensor and more compact modulator.

Exploring Ion Dynamics in Laser‐Produced Plasmas

ABSTRACTCharged particle dynamics during transient plasma expansion have traditionally been studied within a consistent framework, supporting the advancement of applications like thin film deposition through pulsed laser ablation. However, reported plasma parameters often show inconsistencies, particularly in the relationship between ion mass and oscillation frequencies. Recent insights into charge current temporal traces have highlighted challenges in interpreting modulated probe currents. In this study, we present data on laser‐produced plasma (LPP) from Co targets and explore additional phenomena that more accurately describe the behavior of highly energetic, rapidly diffusing LPP.

Investigation of InAlGaN/GaN HEMT Device with SiC Substrate and Cap Layer in Self Heating Resistance for Microwave Applications

The electrical and radio frequency (RF) characteristics of InAlGaN/GaN high electron mobility transistors (HEMTs) device with cap layer are presented in this work. In this work, Silicon carbide was used as a substrate for its excellent thermal conductivity. Here, the thermal model was used to investigate the simulation of temperature distribution at 300k. Moreover, the DC and AC performance characteristics of the device were investigated using Silvaco Atlas Technology Computer Aided Design TCAD simulator. The results showed that, the maximum obtained drain current that was 1.35 A. In addition to, the RF parameters were extracted. The cut-off frequency ft is (73 GHz), the maximum oscillation frequency fmax is (353 GHz), maximum stable gain (Gms) and maximum available gain (Gma) with a value of about (116 dB). The obtained results showed that the InAlGaN/GaN HEMT device based on SiC performance is suitable for microwave applications.

Oscillation rheometry of curing process of epoxy binders modified with polyetherimide

Objectives. The aim of this study is to ascertain the influence of polyetherimide on the curing process of epoxy binders.Methods. The storage modulus and loss modulus of epoxyamine systems were measured as a function of curing time on the Anton Paar MCR 302 rheometer. The experiments were carried out at an oscillation frequency of 1 Hz, with an amplitude aligned with the linear viscoelasticity region, and across a range of temperatures (160, 170, and 180°C). The crossover point was determined when the components of the complex modulus of elasticity are equal according to the obtained dependencies.Results. The influence of polyetherimide on the curing process of epoxyamine binders was investigated at a thermoplastic content of 5 to 20 pts. wt at three temperatures. In a system modified with 20 pts. wt of polyetherimide, phase separation was observed during the curing process. In systems modified with 10 and 20 pts. wt of polyetherimide, the limiting value of the modulus of elasticity was observed to be higher at 170°C than at 180°C.Conclusions. The modification of epoxyamine binders with thermoplastic in an amount of 5–20 pts. wt has been observed to extend the time required to reach the crossover point. Furthermore, the curing process markedly slows down in the system comprising 10 pts. wt of thermoplastic content, in which it takes the longest time to reach the crossover point at all three experimental temperatures.

Klein–Gordon oscillators in traversable wormhole rainbow gravity spacetime: Conditional exact solvability via a throat radius and oscillator frequency correlation

In this study, we discuss an analytical solution for a set of the Klein–Gordon (KG) oscillators’ energies through a correlation between the frequency of the KG-oscillators and the traversable wormhole (TWH) throat radius. Under such restricted parametric correlation (hence the notion of conditionally exact solvability is unavoidable in the process), we report the effects of throat radius, rainbow parameter, disclination parameter and oscillator frequency on the spectroscopic structure of a vast number of [Formula: see text]-states (the radial and magnetic quantum numbers, respectively). In the process, we only use two loop quantum gravity motivated rainbow functions pairs. Only rainbow functions clearly and reliably fully adhere to the rainbow gravity model and secure Planck energy [Formula: see text] as the maximum possible energy for particles and anti-particles alike. Near the asymptotically flat upper and lower universes connected by the TWH, i.e. for the throat radius [Formula: see text], the energies tend to cluster around the rest mass energies, i.e. [Formula: see text]. Whereas, for [Formula: see text], the energies tend to approach [Formula: see text].

Multimode dynamics of a monolithically integrated, tunable, bidirectional, gain switched optical comb source.

A three-sectioned, bidirectionally coupled, tunable, optical comb source is presented. The photonic integrated circuit (PIC) consists of a gain section, a slotted mirror section and a Fabry-Perot (FP) section. Optical frequency combs (OFCs) are produced by gain switching the FP section via a high power radio frequency (RF) signal. An investigation into the effect of the RF frequency on the quality of the OFC is performed. Multimode behavior is observed with OFCs produced in multiple modes as well as the overall degradation in the quality of the combs in each mode. A minimal extension multimode rate equation model is presented that reproduces the experimental results extremely well using experimentally determined values for numerical parameters. The appearance of multimode behavior is interpreted as relating to the modified relaxation oscillation frequency of the bidirectionally coupled system.

Optimizing fuzzy power system stabilizers for microgrid frequency stability using improved water cycle algorithm

Abstract This research assignment has incorporated electric vehicles and robust Fuzzy Power System Stabilizer (Fuzzy-PSS) controller for improving stability behavior of an AC microgrid. Load dynamics, wind fluctuation , variations in solar intensity, etc, have a major impact on the performance of an islanded AC microgrid. The anticipated Fuzzy-PSS controller acts as the secondary load frequency control loop of the microgrid and mitigates the frequency oscillation problems in the microgrid. The suggested Fuzzy Power System stabilizer (Fuzzy-PSS) technique is the best bet for addressing system frequency stability in different disturbances. Under various circumstances, the Improved Water Cycle Algorithm (I-WCA) is recommended for tuning the controller gains through a suitable objective function. Regarding microgrid’s frequency regulation, the effectiveness of the ideal Fuzzy PSS controller is contrasted with that of the conventional fuzzy controller and PID controller. The suggested Fuzzy-PSS approach strongly outperforms the standard Fuzzy PID controller in regard to stability improvement of the EV injected AC microgrid. The suggested Fuzzy-PSS technique has the ability to settle ∆F 2 (area 2 microgrid frequency) by 150.56% and 216.72%, respectively, as compared to the standard Fuzzy PID and PID approaches. To demonstrate the superiority of the suggested I-WCA over standard PSO approach, its dynamic performance is examined from an optimization point of view.

The Lift Enhancement Effect of a New Fluidic Oscillator on High-Lift Wings

Fluidic oscillators have emerged as a prominent topic of research in the field of flow control, owing to their broad sweep range and enhanced control efficiency. However, the underlying mechanisms governing the operation of fluidic oscillators remain poorly understood, and the effect of oscillation frequency on flow control performance has yet to be conclusively determined. In this study, a novel fluidic oscillator is proposed that achieves frequency decoupling by replacing the conventional feedback channel with synthetic jets, thereby enabling modulation of oscillation frequency at a constant momentum coefficient. When applied to a high-lift airfoil, results show that at a momentum coefficient of 14.1%, the lift coefficient increase achieved under F+ = 1 control outperforms that under F+ = 10 by more than 0.3. This finding suggests the presence of an optimal frequency for fluidic oscillators, which maximizes their flow control effectiveness. Notably, this optimal frequency is unaffected by variations in the momentum coefficient. A deeper analysis of the fluidic oscillator’s working principle reveals that periodic oscillations dominate the turbulent kinetic energy and Reynolds shear stress, driving enhanced chordwise momentum exchange. This increased energy transfer strengthens the boundary layer’s resistance to separation, effectively mitigating flow detachment and improving lift enhancement. Finally, the periodic flow field on the surface of the high-lift airfoil under fluidic oscillator control was examined. It was observed that, at low frequencies, the fluidic oscillator effectively controls the shedding of separation vortices, ensuring that the frequency of vortex shedding aligns with the oscillation frequency of the fluidic oscillator. This alignment likely contributes to the superior lift enhancement observed under low-frequency conditions.

Modified Klein–Gordon oscillator in Ellis-Bronnikov-type wormhole spacetime with cosmic string and global monopole

Abstract In this paper, we investigate the modified relativistic oscillator with the Cornell potential via the quadri-potential given by X μ = (0, mωr + A/r, 0, 0) in the Ellis-Bronnikov-type wormhole spacetime with a global monopole and a cosmic string. We obtain the angular and radial wave functions exactly, as well as the eigenenergies. The radial wave function is expressed in terms of Heun polynomials, involving the quantum number n and the eigenenergies. By setting the value of n incrementally, the oscillation frequency ω is quantized with respect to l and m. Finally, as an example, we analyze the ground state and graphically investigate the influence of the global monopole, cosmic string, and A on the oscillator frequency, eigenenergies, and radial probability density, as well as the effect of the wormhole curvature on the radial probability density.

All-Optical Generation and Detection of Coherent Acoustic Vibrations in Single Gallium Phosphide Nanoantennas Probed near the Anapole Excitation.

Nanostructured high-index dielectrics have shown great promise as low-loss photonic platforms for wavefront control and enhancing optical nonlinearities. However, their potential as optomechanical resonators has remained unexplored. In this work, we investigate the generation and detection of coherent acoustic phonons in individual crystalline gallium phosphide nanodisks on silica in a pump-probe configuration. By pumping the dielectric above its bandgap energy and probing over its transparent region, we observe the radial breathing mode of the disk with an oscillation frequency around 10 GHz. We find that the detection efficiency peaks near the fundamental anapole state, matching numerical simulations. By comparing to reference gold plasmonic resonators, the dielectric nanoantennas display a modulation amplitude up to ∼5 times larger. We further demonstrate the launching of acoustic waves through the underlaying substrate and the mechanical coupling between two nanostructures placed 3 μm apart, laying the basis for photonic-phononic signal processing using dielectric nanoantennas.

Major individual and regional variations in unit entrainment by oscillations of different frequencies

In vitro studies have shown that a neuron’s electroresponsive properties can predispose it to oscillate at specific frequencies. In contrast, network activity in vivo can entrain neurons to rhythms that their biophysical properties do not predispose them to favor. However, there is limited information on the comparative frequency profile of unit entrainment across brain regions. Therefore, this study aimed to characterize the frequency profile of unit entrainment in cortex, thalamus, striatum, and basolateral amygdala (BLA) in rats of either sex. Neurons recorded simultaneously in a given brain region and behavioral state generally had very similar frequency profiles of unit entrainment. While cortical, striatal, and thalamic neurons were more strongly entrained by low than high local field potential (LFP) frequencies, increases in the power of these oscillations were linked to decreased firing rates for low frequencies versus increased firing rates for high frequencies. Deviating from this general trend, BLA neurons were more strongly entrained by high gamma than all other frequency bands in all subjects and states. By contrast, neurons in other regions displayed marked inter-individual variability. That is, although neurons in some regions had exceptionally high entrainment values in particular frequency bands, these were not observed consistently across rats. Based on these findings, some might infer that oscillations play a minor role or that different oscillatory patterns can support the same functions. Alternatively, the oscillations critical to brain function could be those not investigated here, namely those arising transiently in response to specific task variables or contexts. Perhaps those are less susceptible to genetic variations. While our findings do not allow us to determine which explanation is correct, they do highlight the perils of averaging.

Amplitude and frequency of human gait synchronization with a machine oscillator system

Humans sometimes synchronize their steps to mechanical oscillations in the environment (e.g., when walking on a swaying bridge or with a wearable robot). Previous studies have discovered discrete frequencies and/or amplitudes where individuals spontaneously synchronize to external oscillations, but these parameters are often chosen arbitrarily or for convenience of a successful experiment and are sparsely sampled due to time constraints on subject availability. As a result, the parameter space under which human gait synchronization occurs is still relatively underexplored. Here we systematically measure synchronization over a broad range of parameters in machine oscillations, applied vertically near the body center of mass during walking. Two complementary experiments were utilized to characterize the amplitudes and frequencies where subjects’ gait matched the oscillation frequency within ± 0.02 Hz for at least 80% of 20 consecutive steps (i.e., synchronization). Individuals were found to synchronize at lower amplitudes and in less time when the oscillation frequency was nearer their baseline step frequency, as well as over a broader range of frequencies during larger oscillation amplitudes. Subjects also had a greater tendency to synchronize with oscillation frequencies below (rather than above) their baseline step frequencies. The results of this study provide a comprehensive mapping of parameters where synchronization occurs and could inform the design of exoskeletons, rehabilitation devices and other gait-assistive technologies.

On the Frequency of Internal Gravity Waves in the Atmosphere: Comparing Theory with Observations

This paper is devoted to the dynamics of the propagation of non-planetary scale internal gravity waves (IGWs) in the stratified atmosphere. We consider the system of equations describing internal gravity waves in three approximations: (1) the incompressible fluid approximation, (2) the anelastic gas (compressible fluid) approximation, and (3) a new approximation called the non-Boussinesq gas approximation. For each approximation, a different dispersion relation is given, from which it follows that the oscillation frequency of internal gravity waves depends on the direction of propagation, the horizontal and vertical components of the wave vector, the vertical gradient of the background temperature, and the background wind shear. In each of the three cases, the maximum frequency of internal gravity waves is different. Moreover, in the anelastic gas approximation, the maximum frequency is equal to the Brunt–Väisälä buoyancy frequency, and in the incompressible fluid approximation, it is larger than the Brunt–Väisälä frequency by a factor of 7≅2.6. In the model proposed in this paper, the value of the maximum frequency of internal gravity waves occupies an intermediate position between the above limits. The question arises: which of the above fluid representations adequately describe the dynamics of internal gravity waves? This paper compares the above theories with observational data and experiments.

The spinal premotor network driving scratching flexor and extensor alternation.

Rhythmic motor behaviors are generated by neural networks termed central pattern generators (CPGs). Although locomotor CPGs have been extensively characterized, it remains unknown how the neuronal populations composing them interact to generate adaptive rhythms. We explored the non-linear cooperation dynamics among the three main populations of ipsilaterally projecting spinal CPG neurons - V1, V2a, V2b neurons - in scratch reflex rhythmogenesis. Ablation of all three neuronal subtypes reduced the oscillation frequency. Activation of excitatory V2a neurons enhanced the oscillation frequency, while activating inhibitory V1 neurons caused atonia. These findings required the development of a novel neuromechanical model that consists of flexor and extensor modules coupled via inhibition, in which rhythm in each module is generated by self-bursting excitatory populations and accelerated by intra-module inhibition. Inter-module inhibition coordinates the phases of flexor and extensor activity and slows the oscillations, while facilitation mechanisms in excitatory neurons explain the V2a activation-driven increase in frequency.

Hydrogen and Pionic Atoms Under the Effects of Oscillations in the Global Monopole Spacetime

In this analysis, we investigate hydrogen and pionic atoms subjected to Dirac and Klein-Gordon oscillators, respectively, in the global monopole spacetime. Through a purely analytical analysis, we determine solutions of bound state, in which we define the allowed energy values for the lowest energy state of both proposed systems. In addition to the influence of the topological defect on the results obtained, we note another quantum effect: the oscillation frequencies of both systems depend on the system quantum numbers, that is, the angular frequencies are quantized.