Low-frequency Oscillations Research Articles

Low frequency oscillations reflect neurovascular coupling and disappear after cerebral death

Spectrum power analysis in the low frequency oscillations (LFO) region of functional near infrared spectroscopy (fNIRS) is a promising method to deliver information about brain activation and therefore might be used for prognostication in patients with disorders of consciousness in the neurocritical care unit alongside with established methods. In this study, we measure the cortical hemodynamic response measured by fNIRS in the LFO region following auditory and somatosensory stimulation in healthy subjects. The significant hemodynamic reaction in the contralateral hemisphere correlation with the physiologic electric response suggests neurovascular coupling. In addition, we investigate power spectrum changes in steady state measurements of cerebral death patients and healthy subjects in the LFO region, the frequency of the heartbeat and respiration. The spectral power within the LFO region was lower in the patients with cerebral death compared to the healthy subjects, whereas there were no differences in spectral power for physiological activities such as heartbeat and respiration rate. This finding indicates the cerebral origin of our low frequency measurements. Therefore, LFO measurements are a potential method to detect brain activation in patients with disorders of consciousness and cerebral death. However, further studies in patients are needed to investigate its potential clinical use.

Large-Eddy Simulation of Low-Frequency Flow Oscillations for NACA0012 and Dynarig Sail at Large Attack Angles

Unmanned sailboats, harnessing wind for propulsion, offer great potential for extended marine research due to their virtually unlimited endurance. The sails typically operate at high attack angles, which contrasts with aircraft that maintain small angles to prevent stalling. Despite the reduction in lift during stalling, the resultant increase in drag contributes significantly to the sail’s thrust. However, the sail often experiences vortex shedding due to high attack angles, leading to low-frequency oscillations and erratic navigation. This study employs large-eddy simulations (LESs) on a 3D NACA0012 sail at a Reynolds number of 3.6 × 105, which is validated by experimental data. It observes the lift and drag coefficients across attack angles from 5 to 90 degrees and compares these with a Dynarig sail. The findings reveal that higher attack angles amplify fluctuations in lift and drag coefficients. Vortex shedding, resulting from flow separation, creates pressure changes and oscillations in aerodynamic forces. Fast Fourier transformation (FFT) analysis identifies dominant frequencies between 0.5 and 10 Hz, indicating low-frequency oscillations. The study’s insights into the impact of attack angle and sail type on the oscillation frequency are favorable for the design of unmanned sailboats, aiding in the prediction of wind-induced frequencies and optimal attack angle determination.

Quantitative assessment mechanism of low frequency oscillations in train-network systems

Low frequency oscillations (LFOs) in the electrified train-network system can lead to serious traction blockade accidents. Although impedance models and stability analysis tools have been applied in existing studies to address specific cases, a generalized mechanism to address LFO is still not established so far. This paper proposes a quantitative assessment method to reveal the underlying mechanism of LFOs. Founded on the improved Nyquist criterion, a stability margin indicator is defined to concretely describe system stability, then its corresponding expression is derived by combining the simplified impedance model as the basis for quantitative analysis. To this end, the identified negative resistances in the impedance model are revealed as the root cause of LFOs. Besides, theoretical justification for the impact of parameter tuning on the system stability is provided based on the explicit formula of the stability margin indicator. Finally, the effectiveness and accuracy of the theoretical analysis are verified under simulations and hardware-in-the-loop experimental conditions.

Changes in autonomic regulation in workers under conditions of long-term fluoride intoxication

Introduction. Long-term intake and accumulation of fluoride compounds in the body, in addition to pathological changes in the bronchopulmonary system, bone tissue, liver, leads to changes in the regulatory systems, primarily the autonomic ones, in the conditions of chronic fluoride intoxication. The aim of the study was to assess the nature and severity of the changes in autonomic regulation in workers of the main occupations in aluminum production under exposure to chronic fluoride intoxication. Material and methods. We examined fifty two male workers of aluminum production over the age range from 40 to 56 years; work experience was more than 15 years. Autonomic regulation was assessed using spectral analysis of the heart rate variability, highlighting oscillations in the ranges of very low frequency (0.004–0.08 Hz), low (0.09–0.16 Hz), and high frequencies (0.17–0.5 Hz). Results. Analysis of the heart rate variability made it possible to identify 4 groups of subjects: 16 individuals had a moderate decrease in variability and a predominance of low-frequency oscillations, 12 subjects examined cases had a pronounced decline in variability in all frequency ranges; a decrease in the capabilities of autonomic regulation was manifested during a test with hyperventilation by an increase in very low frequency oscillations frequency indicating the need for activation of suprasegmental autonomic centers. In 24 subjects, the stable predominance of low-frequency oscillations indicates an enhancement in sympathetic influence. In response to the hyperventilation test, most of them (18 subjects were included in the group 3) showed an increase in low and very low frequency oscillations as a sign of a violation of baroreceptor regulation. Limitations. The study was limited by the number of workers with long-term work experience in aluminum production who underwent an in-depth medical examination. Conclusion. Changes in autonomic regulation are observed in the majority of aluminum production workers with long-term work experience, which gives grounds to recommend a study of neurovegetative status using heart rate variability analysis during preventive examinations to identify individuals at high risk of developing comorbid diseases.

Discovery of evolving low-frequency QPOs in hard X-rays (∼100 keV) observed in black hole Swift J1727.8−1613 with AstroSat

ABSTRACT We report the first detection of evolving low-frequency quasi-periodic oscillation (LFQPO) frequencies in hard X-rays upto 100 keV with AstroSat/LAXPC during ‘unusual’ outburst phase of Swift J1727.8−1613 in hard intermediate state (HIMS). The observed LFQPO in 20–100 keV has a centroid $\nu _{_{\rm QPO}}=1.43$ Hz, a coherence factor Q = 7.14 and an amplitude ${\rm rms_{_{\rm QPO}}} = 10.95{{\ \rm per\ cent}}$ with significance σ = 5.46. Type-C QPOs (1.09–2.6 Hz) are found to evolve monotonically during HIMS of the outburst with clear detection in hard X-rays (80−100 keV), where ${\rm rms_{_{\rm QPO}}}$ decreases ($\sim 12\!-\!3{{\ \rm per\ cent}}$) with energy. Further, $\nu _{_{\rm QPO}}$ is seen to correlate (anticorrelate) with low- (high-) energy flux in 2–20 keV (15–50 keV). Wide-band (0.7−40 keV) energy spectrum of NICER/XTI and AstroSat/LAXPC is satisfactorily described by the ‘dominant’ thermal Comptonization contribution (∼88 per cent) in presence of a ‘weak’ signature of disc emissions (kTin ∼ 0.36 keV) indicating the harder spectral distribution. Considering source mass $M_{\rm BH}=10\, \mathrm{M}_\odot$ and distance 1.5 < d (kpc) < 5, the unabsorbed bolometric luminosity is estimated as $\sim 0.03\!-\!0.92{{\ \rm per\ cent}}\, L_{\rm Edd}$. Finally, we discuss the implications of our findings in the context of accretion dynamics around black hole X-ray binaries.

Multi-bounce self-mixing in terahertz metasurface external-cavity lasers

The effects of optical feedback on a terahertz (THz) quantum-cascade metasurface vertical-external-cavity surface-emitting laser (QC-VECSEL) are investigated via self-mixing. A single-mode 2.80 THz QC-VECSEL operating in continuous-wave is subjected to various optical feedback conditions (i.e., feedback strength, round-trip time, and angular misalignment) while variations in its terminal voltage associated with self-mixing are monitored. Due to its large radiating aperture and near-Gaussian beam shape, we find that the QC-VECSEL is strongly susceptible to optical feedback, which is robust against misalignment of external optics. This, in addition to the use of a high-reflectance flat output coupler, results in high feedback levels associated with multiple round-trips within the external cavity-a phenomenon not typically observed for ridge-waveguide QC-lasers. Thus, a new theoretical model is established to describe self-mixing in the QC-VECSEL. The stability of the device under variable optical feedback conditions is also studied. Any mechanical instabilities of the external cavity (such as vibrations of the output coupler), are enhanced due to feedback and result in low-frequency oscillations of the terminal voltage. The work reveals how the self-mixing response differs for the QC-VECSEL architecture, informs other systems in which optical feedback is unavoidable, and paves the way for QC-VECSEL self-mixing applications.

Case Report: Pendular Nystagmus Presenting in Usher Syndrome Type I.

We describe a 42-year-old patient with reported "shaking" vision referred due to concerns of possible vestibular system dysfunction. The patient has known history of Usher syndrome type I, bilateral cochlear implants, and severe vision impairment. This case describes an unusual nystagmus previously only reported in individuals with central demyelinating disorders, significant light deprivation, or in congenital / early-onset visual pathway impairment. Case study. Retrospective chart review of vestibular function. Vestibular function was likely absent in this case. There was no evidence of vestibular (jerk) nystagmus for sinusoidal harmonic acceleration stimuli or repeatable responses for cervical vestibular evoked myogenic potentials. Significant pendular low amplitude high frequency oscillations of approximately 6 Hz were present for horizontal and vertical tracings throughout testing. Nystagmus may not always be associated with vestibular system impairment. In this case, the patient's reported "shaking" vision was attributed to pendular low amplitude high frequency nystagmus and hypothesized to relate to long-standing significant vision impairment. This presentation is unusual in adults and has historically been associated with individuals with significant central pathology or in those with long duration light deprivation.

Coordination of PSS and Multiple FACTS-POD to Improve Stability and Operation Economy of Wind-thermal-bundled Power System

Aims and Background: Focusing on the low-frequency oscillation and system power loss problem in wind-thermal-bundled (WTB) transmission systems and the interaction problem due to different controllers, this study aimed to improve the low-frequency oscillation characteristics of WTB transmission system while ensuring the economy of operation and suppressing the adverse interaction between controllers. Methods: For this purpose, a coordination and optimization strategy for a power system stabilizer (PSS), static synchronous series compensator with additional power oscillation damping controller (SSSC-POD), and static synchronous compensator with additional power oscillation damping controller (STATCOM-POD) is proposed based on multi-objective salp swarm algorithm (MSSA). The controller regulation characteristics are taken into account in the coordination method. Results: Several designed scenarios, including changing the transmission power of the tie line and increasing wind power output, are considered in the IEEE 4-machine 2-area to test the proposed method. The power flow analysis, characteristic root analysis, and time-domain simulation are used to analyze the simulation results. Conclusion: Simulation results demonstrate that the proposed approach can effectively suppress the low-frequency oscillation of the WTB system while reducing its net loss. The application in engineering issues for MSSA is supplemented.

Damping Characteristics Improvement of Wind-PV Hybrid System by Coordinated Optimization of SVC-POD Controller Parameters

Background: With the increasing penetration of new energy resources such as wind farms and photovoltaic power plants, there is concern about the stability of power systems. Methods: Aiming at the low-frequency oscillation issue of the wind-PV hybrid system, a coordinated optimal design strategy based on Static Var Compensator (SVC) and Power Oscillation Damping (POD) control is proposed. Modal analysis is used to locate the controller, then the Whale Optimization Algorithm (WOA) is introduced to optimize the SVC-POD controller parameters. To solve the wind-PV hybrid energy system's low frequency oscillation issues, the damping ratio and angular velocity of the generator rotor are considered in the objective function. Results: Taking IEEE four-machine two-area system as an example, several working conditions are designed, including changing the power of the contact line. The eigenvalue analysis and simulation findings verify that the suggested proposed method can successfully raise the damping ratio of the system, keep the generator speed stable, and restrain the occurrence of low-frequency oscillation. Conclusion: Simulation results demonstrate that this method efficiently suppresses the lowfrequency oscillation and increases the robustness of the system.

Grid control strategy of wind turbines based on LADRC voltage control

Traditional grid-controlled wind turbines are required to rely on AC power grid operation, but when the power grid fluctuates, it will cause a series of oscillation instability problems in wind turbines, such as low-frequency oscillation, subsynchronous oscillation, etc. The safe and stable operation of the crisis power grid needs to be ensured. In this study, the virtual synchronous machine is supposed to be adopted as the main control strategy for grid-type control, transforming the traditional system into a more robust and reliable one. Additionally, a converter model of the grid-type control network is set up. By implementing grid-type control, voltage support and frequency support can be offered without relying solely on AC power grid operation. This approach effectively addresses issues caused by preventive such as reliance on wind turbines. The stability of the networked control system is dependent on maintaining stable system power. When there are fluctuations in system power, it impacts the stability of the networked control system. To mitigate these effects and enhance overall stability, this paper proposes using linear active disturbance rejection control (LADRC) based voltage and grid controls to suppress voltage fluctuations through linear active disturbance rejection techniques. The overall system performance is demonstrated through simulations conducted using Matlab/Simulink platform.

Modelling of IPFC with multifunctional VSC for low-frequency oscillations damping and system stability improvement

The unified power flow controller (UPFC) approach maximizes active power transfer with the least amount of losses by independently controlling both reactive and active power flow. This makes it possible to use individual transmission lines more effectively. The interline power flow controller (IPFC) utilizes the concept of UPFC for economic operation and control, management of multiline transmission systems. In its most basic form, the IPFC consists of many DC to AC converters such as voltage source inverters (VSCs), each of which performs the same purpose as the UPFC: providing series compensation for every line in multiline transmission system. A novel idea for the efficient power flow control management and compensation in multiline transmission system is the IPFC. This research proposed a backup controller for an effective modelling of IPFC in order to reduce low-frequency oscillations using four different damping controller options. The choice of an efficient damping control signal is discussed in this work in order to create a durable IPFC damping controller that can withstand changes in system loads and power supply problems. Using the proposed control approach, it is feasible to acquire both oscillation damping and independent interline power flow regulation. The results obtained in this research was improved the dynamic stability of the system using VSC based IPFC and proposed control strategy.

Coordination of Controllers to Development of Wide-Area Control System for Damping Low-Frequency Oscillations Incorporating Large Renewable and Communication Delay

The modern power systems incorporate high penetration of renewable is a large, composite, interconnected network with dynamic behavior. The small disturbances occurring in the system may induce low-frequency oscillations (LFOs) in the system. If the (LFOs) are not suppressed within a stipulated time, it may cause system islanding or even blackouts. Hence, it is essential to investigate the behavior of the system under various levels of disturbances and control action must be taken to damp these oscillations. The established approach to damping the LFOs is by installing power system stabilizers (PSS). PSS uses the local signals from generators to control the oscillations. The dominant source of inter-area oscillations in power systems is due to overloaded weak interconnected lines, converter-interfaced generation, and the action of the high gain exciter present in the system. Consequently, wide area control is needed to control the inter-area oscillations existent in the system. This paper developed a coordinated design of conventional PSS, static compensator, renewable converters, and wide area controller for damping the local and inter-area oscillations in renewable incorporated power systems. The performance of the developed controller is evaluated through the time domain analysis and eigenvalue analysis. A comparison of the introduced controller has been done with other standard conventional methods. The choice of input signals for the wide area controller from the wide-area measurement system is done based on the controllability index. Additionally, the location of the controller must be identified to dampen the inter-area oscillations in the system. In this paper, the controllability index is calculated to find out the highly affected wide area signals for considering it as the feedback signal to a developed controller. The location of the controller is recognized by computing the participation factor. The developed controller has experimented on renewable incorporated large study power systems when time delay and noise are present in wide area signals.

Development of a Benchmark for Thermal Striping in Gas-Cooled Fast Reactors

This paper presents the development of a benchmark for predicting thermal striping through simulation. This work utilized large eddy simulation and will be used to benchmark future models. The testing domain was created using both the STRUCT and the Reynolds-averaged Navier-Stokes turbulence models and is based on an earlier design of the General Atomics Fast Modular Reactor upper plenum. The plenum features two adjacent, identical hexagonal bundles each with a center-placed axial rod drive, with a hot left coolant stream and a cold right coolant stream. The simulation solves the nondimensional Navier-Stokes equations, with temperature accounted as a passive scalar. First- and second-order flow statistics were obtained after 600 convective time units of averaging. The first-order statistics reveal that the hot jet is damped by a recirculatory flow from the near wall. At the same location, the second-order statistics show strong oscillations both in velocity and temperature. The power spectral density was utilized to determine that a low-frequency oscillation occurs here that is within the range of interest for thermal striping. Furthermore, proper orthogonal decomposition was used to identify coherent structures that confirm the oscillatory behavior, indicative of thermal striping. Overall, this benchmark can aid in the development of future models for predicting thermal striping in nuclear reactors, potentially leading to improved reactor safety and performance.

Perceptual Expectations Are Reflected by Early Alpha Power Reduction.

The predictability of a stimulus can be characterized by its transitional probability. Perceptual expectations derived from the transitional probability of the stimulus were found to modulate the early alpha oscillations in the sensory regions of the brain when neural responses to expected versus unexpected stimuli were compared. The objective of our study was to find out the extent to which this low-frequency oscillation reflects stimulus predictability. We aimed to detect the alpha-power difference with smaller differences in transitional probabilities by comparing expected stimuli with neutral ones. We studied the effect of expectation on perception by applying an unsupervised visual statistical learning paradigm with expected and neutral stimuli embedded in an image sequence while recording EEG. Time-frequency analysis showed that expected stimuli elicit lower alpha power in the window of 8-12 Hz and 0-400 msec after stimulus presentation, appearing in the centroparietal region. Comparing previous findings of expectancy-based alpha-band modulation with our results suggests that early alpha oscillation shows an inverse relationship with stimulus predictability. Although current data are insufficient to determine the origin of the alpha power reduction, this could be a potential sign of expectation suppression in cortical oscillatory activity.

Identification of power grids low-frequency oscillations through a combined MEEMD-Prony method

Currently, the primary focus of power systems is to enhance precision and resilience against interference in identifying low-frequency oscillation modes. This research proposes a new method combined with ensemble empirical mode decomposition (MEEMD) to improve the sensitivity of traditional Prony to noise in parameter analysis of low-frequency oscillation signals. The method decomposes the measurement signal into intrinsic mode functions (IMF) using MEEMD, introduces permutation entropy to detect randomness, and reconstructs the remaining IMF components. The reconstructed signal was analyzed using the Prony method to extract the characteristic parameters associated with the low-frequency oscillation frequency. Simulations using numerical signals and the EPRI-36 node system confirm the method effectively suppresses modal mixing, mitigates noise interference, and accurately identifies low-frequency oscillation parameters. This approach offers advantages over traditional methods, including enhanced resistance to noise and increased accuracy.

Evolutionary origin of alpha rhythms in vertebrates.

The purpose of this review extends beyond the traditional triune brain model, aiming to elucidate the evolutionary aspects of alpha rhythms in vertebrates. The forebrain, comprising the telencephalon (pallium) and diencephalon (thalamus, hypothalamus), is a common feature in the brains of all vertebrates. In mammals, evolution has prioritized the development of the forebrain, especially the neocortex, over the midbrain (mesencephalon) optic tectum, which serves as the prototype for the visual brain. This evolution enables mammals to process visual information in the retina-thalamus (lateral geniculate nucleus)-occipital cortex pathway. The origin of posterior-dominant alpha rhythms observed in mammals in quiet and dark environments is not solely attributed to cholinergic pontine nuclei cells functioning as a 10 Hz pacemaker in the brainstem. It also involves the ability of the neocortex's cortical layers to generate traveling waves of alpha rhythms with waxing and waning characteristics. The utilization of alpha rhythms might have facilitated the shift of attention from external visual inputs to internal cognitive processes as an adaptation to thrive in dark environments. The evolution of alpha rhythms might trace back to the dinosaur era, suggesting that enhanced cortical connectivity linked to alpha bands could have facilitated the development of nocturnal awakening in the ancestors of mammals. In fishes, reptiles, and birds, the pallium lacks a cortical layer. However, there is a lack of research clearly observing dominant alpha rhythms in the pallium or organized nuclear structures in fishes, reptiles, or birds. Through convergent evolution, the pallium of birds, which exhibits cortex-like fiber architecture, has not only acquired advanced cognitive and motor abilities but also the capability to generate low-frequency oscillations (4-25 Hz) resembling alpha rhythms. This suggests that the origins of alpha rhythms might lie in the pallium of a common ancestor of birds and mammals.

A method to assess linear self-predictability of physiologic processes in the frequency domain: application to beat-to-beat variability of arterial compliance.

The concept of self-predictability plays a key role for the analysis of the self-driven dynamics of physiological processes displaying richness of oscillatory rhythms. While time domain measures of self-predictability, as well as time-varying and local extensions, have already been proposed and largely applied in different contexts, they still lack a clear spectral description, which would be significantly useful for the interpretation of the frequency-specific content of the investigated processes. Herein, we propose a novel approach to characterize the linear self-predictability (LSP) of Gaussian processes in the frequency domain. The LSP spectral functions are related to the peaks of the power spectral density (PSD) of the investigated process, which is represented as the sum of different oscillatory components with specific frequency through the method of spectral decomposition. Remarkably, each of the LSP profiles is linked to a specific oscillation of the process, and it returns frequency-specific measures when integrated along spectral bands of physiological interest, as well as a time domain self-predictability measure with a clear meaning in the field of information theory, corresponding to the well-known information storage, when integrated along the whole frequency axis. The proposed measure is first illustrated in a theoretical simulation, showing that it clearly reflects the degree and frequency-specific location of predictability patterns of the analyzed process in both time and frequency domains. Then, it is applied to beat-to-beat time series of arterial compliance obtained in young healthy subjects. The results evidence that the spectral decomposition strategy applied to both the PSD and the spectral LSP of compliance identifies physiological responses to postural stress of low and high frequency oscillations of the process which cannot be traced in the time domain only, highlighting the importance of computing frequency-specific measures of self-predictability in any oscillatory physiologic process.

Extrasynaptic GABAA receptors in central medial thalamus mediate anesthesia in rats

Neuronal depression in the thalamus underlies anesthetic-induced loss of consciousness, while the precise sub-thalamus nuclei and molecular targets involved remain to be elucidated. The present study investigated the role of extrasynaptic GABAA receptors in the central medial thalamic nucleus (CM) in anesthesia induced by gaboxadol (THIP) and diazepam (DZP) in rats. Local lesion of the CM led to a decrease in the duration of loss of righting reflex induced by THIP and DZP. CM microinjection of THIP but not DZP induced anesthesia. The absence of righting reflex in THIP-treated rats was consistent with the increase of low frequency oscillations in the delta band in the medial prefrontal cortex. CM microinjection of GABAA receptor antagonist SR95531 significantly attenuated the anesthesia induced by systemically-administered THIP, but not DZP. Moreover, the rats with declined expression of GABAA receptor δ-subunit in the CM were less responsive to THIP or DZP. These findings explained a novel mechanism of THIP-induced loss of consciousness and highlighted the role of CM extrasynaptic GABAA receptors in mediating anesthesia.

Research on additional damping control strategy of flexible distribution transformer

Disturbances to the power system may lead to relative swing between synchronous generator rotors, causing low-frequency oscillation problems in the absence of damping. In this article, based on the single-machine infinity system containing flexible distribution transformer and synchronous generator, the linearized state equations of the system is deduced by the small-signal modeling. The mechanism of flexible distribution transformer on the rotor speed of synchronous generator is analyzed. The influence factors of flexible distribution transformer on the rotor speed of synchronous generator are analyzed. The equation of the additional damping provided by the flexible distribution transformer to this system is constructed. It was concluded that by controlling the output voltage of the regulating converter in the flexible distribution transformer, the rotor speed of the synchronous generator can be varied to increase the system damping. An additional damping control strategy for flexible distribution transformer is proposed. The simulation verifies that the proposed control strategy can effectively suppress the oscillation amplitude of each electrical quantity and shorten the oscillation duration when the system is subjected to large and small perturbations. The proposed additional damping control strategy of flexible distribution transformer can effectively improve the damping of the system and alleviate the problem of low frequency oscillation.

Recovery of High-energy Low-frequency Quasiperiodic Oscillations from Black Hole X-Ray Binary MAXI J1535–571 with a Hilbert–Huang Transform Method

We propose a method based on the Hilbert–Huang transform (HHT) to recover the high-energy waveform of low-frequency quasiperiodic oscillations (QPOs). Based on the method, we successfully obtain the modulation of the phase-folded light curve above 170 keV using the QPO phase reconstructed at lower energies in MAXI J1535–571 with Insight-HXMT observations. A comprehensive simulation study is conducted to demonstrate that such modulation indeed originates from the QPO. Thus, the highest energies turn out to significantly exceed the upper limit of ∼100 keV for QPOs reported previously using the Fourier method, marking the first opportunity to study QPO properties above 100 keV in this source. Detailed analyses of these high-energy QPO profiles reveal different QPO properties between the 30–100 and 100–200 keV energy ranges: the phase lag remains relatively stable, and the amplitude slightly increases below ∼100 keV, whereas above this threshold, soft phase lags and a decrease in amplitude are observed. Given the reports of a hard-tail detection in broad spectroscopy, we propose that the newly discovered QPO properties above 100 keV are dominated by the hard-tail component, possibly stemming from a relativistic jet. Our findings also indicate a strong correlation between the QPOs originating from the jet and corona, supporting the scenario of jet–corona coupling precession. We emphasize that our proposed HHT-based method can serve as an efficient manner in expanding the high-energy band for studying QPOs, thereby enhancing our understanding of their origin.