Instantaneous Oscillation Research Articles

Occipital and left temporal instantaneous amplitude and frequency oscillations correlated with access and phenomenal consciousness

Occipital and left temporal instantaneous amplitude and frequency oscillations correlated with access and phenomenal consciousness

A localized pallidal physiomarker in Meige syndrome.

Oscillatory patterns in local field potentials (LFPs) have been recognized as disease-specific physiomarkers, particularly in the context of Parkinson's disease and cervical dystonia. This characteristic oscillatory feature is currently employed in adaptive deep brain stimulation (aDBS). However, for other types of dystonia, especially Meige syndrome, a distinct physiomarker of this nature is yet to be identified. Local field potentials were recorded during microelectrode-guided deep brain stimulation surgery from 28 patients with primary Meige syndrome. Before surgery, the severity of patients' motor syndrome were assessed using the Burke-Fahn-Marsden Dystonia Rating Scale-Motor (BFMDRS-M). An instantaneous oscillation detection method was employed to identify true narrowband oscillations. Subsequently, a linear mixed effects model was utilized to examine the relationship between oscillatory activities (including power amplitude and burst duration) and symptom severity. The focal peaks of "oscillatory activities" detected were predominantly concentrated in the narrow theta band (4-8 Hz), constituting 81.5% of the total detected oscillations in all recording sites near active DBS contacts in the globus pallidus internus (GPi). The linear mixed effects model revealed a positive correlation between the theta burst duration and the severity of preoperative motor impairment, but no correlation with postoperative motor scores. Additionally, there was no significant lateralization effect observed between the left and right GPi. Our findings suggest that the exaggerated narrowband theta activity (mainly the burst duration) in the GPi is predictive of dystonia symptom severity and may be used as a physiomarker for optimized DBS target during surgery and adaptive DBS for the treatment of Meige syndrome.

A Stator Internal Short-Circuit Fault Protection Method for Turbo-Generator Based on Instantaneous Power Oscillation Ratio

For large turbo-generators, the longitudinal differential protection can only reflect the stator internal inter-phase short-circuit fault, and cannot reflect the inter-turn short-circuit fault. The protection methods for inter-turn short-circuit faults have the problem of low sensitivity, such as the longitudinal zero-sequence voltage protection and the negative sequence component-based protection. Therefore, a stator internal short-circuit fault protection method for turbo-generator based on instantaneous power oscillation ratio (IPOR) is proposed in this paper. The instantaneous power variation of the generator before and after the fault is analyzed, and the IPOR is calculated by using the balanced power component and the oscillatory power component. Then, the method to judge whether the generator has an internal short-circuit fault based on the amplitude and phase of IPOR is proposed. The experimental results verify the effectiveness of the proposed protection method, which has a high sensitivity to the inter-turn short-circuit faults with a small turn difference. The protection is stable and does not malfunction during the system oscillation. In addition, the action time of the protection method does not exceed 1.5 power frequency cycles under various working conditions, which can meet the speed requirements of generator protection.

Examination of occurrence probability of vortex-induced vibration of long-span bridge decks by Fokker–Planck–Kolmogorov equation

Vortex-induced vibration (VIV) is a major concern for long-span bridge decks, which may happen especially for closed-box girders under certain environmental wind conditions. Traditionally, sustained VIV is observed as long as the wind speed falls within the lock-in region in wind tunnel tests. However, structural vibration monitoring of long-span bridges has indicated that frequency of VIV events may exhibit a probabilistic pattern. This paper proposes an analytical framework to evaluate the probability of VIV occurrence. First, a nonlinear aeroelastic model with multi-stability limit cycles is used to simulate the bridge deck VIV response within the VIV-triggering wind conditions. The first structural dynamic equilibrium point is usually unstable; the bridge deck instantaneous oscillation amplitude, which is excited by external environmental loads, must exceed this fixed point to trigger the VIV event. The external environmental excitation applied on bridge can be identified from the deck vibration without VIV occurring, then the VIV occurrence probability can be evaluated by Fokker–Planck–Kolmogorov equation. This study utilizes the field measurement data from the Humen Bridge, on which VIV event occurred the first time after 23-year servicing period, because water-filled barriers were placed along the two edges of bridge deck. Afterwards, VIV occurred frequently for over one month. The bridge deck VIV occurrence probability is evaluated by combining environmental wind information, stochastic deck excitation magnitude and a nonlinear aeroelastic VIV model. The results suggest that the proposed methods can approximate the VIV occurrence probability in comparison with empirical estimations using field measurements.

Doubly Fed Induction Machine-Based DC Voltage Generator with Reduced Oscillations of Torque and Output Voltage

The doubly fed induction machine (DFIM)-based DC voltage generator is equipped with a stator-connected diode rectifier. The six-pulse diode rectifier as a nonlinear circuit introduces harmonics in the stator and rotor current and distorts the machine stator voltage, as well as the stator flux. This causes electromagnetic torque oscillations and instantaneous power components oscillations. The torque oscillations adversely impact the mechanical parts of the drive-train and oscillations of the p component of instantaneous power influence DC-bus voltage oscillations. The oscillations can be somewhat cancelled by control methods. However, cancellation of electromagnetic torque is not strictly coupled with cancellation of oscillations of the p component of instantaneous power. The paper presents an analysis of influence of the control methods aimed at a reduction of torque oscillations on the output voltage oscillations level in the stand-alone DFIM-based DC voltage generator. Field-oriented control FOC with current controllers and space vector modulation-based direct torque control DTC-SVM with flux module regulation have been compared with control in which electromagnetic torque is one of the commanded variables, whereas the second variable is the dot product of stator flux and rotor current space vectors. The contributions of this paper are the introduction of a new variable in the second control path in the DTC-SVM method instead of flux vector length and the proof that it can reduce torque and DC-bus voltage oscillations in the DFIG-DC system. Additionally, this paper reveals that for proper stator-to-rotor-turns ratio of a doubly fed machine necessary for reduction of the rotor converter power, lower DC-bus voltage can be obtained than is required for full realization rotor side voltage requested by rotor current controllers. This is the reason why, regardless of the control method, torque oscillations cannot be always fully cancelled, and a comparative study of the methods at these conditions has been conducted in simulation and in laboratory tests.

Coherent Many-Body Oscillations Induced by a Superposition of Broken Symmetry States in the Wake of a Quantum Phase Transition.

It is now widely accepted that quenches through the critical region of quantum phase transitions result in post-transition states populated with topological defects-analogs of the classical topological defects. However, consequences of the very nonclassical fact that the state after a quench is a superposition of distinct, broken-symmetry vacua with different numbers and locations of defects have remained largely unexplored. We identify coherent quantum oscillations induced by such superpositions in observables complementary to the one involved in symmetry breaking. These oscillations satisfy Kibble-Zurek dynamical scaling laws with the quench rate, with an instantaneous oscillation frequency set primarily by the gap of the system. In addition to the obvious fundamental significance of a superposition of different broken symmetry states, quantum coherent oscillations can be used to verify unitarity and test for imperfections of the experimental implementations of quantum simulators.

CFD simulation of instantaneous shape oscillation with rising velocity fluctuation for single bubble rising in water

Bubble instantaneous hydrodynamics including bubble trajectory, bubble shape and rising velocity is investigated for a single bubble rising in quiescent water. To analyze unregular shape oscillation, a new criterion, namely bubble deformation factor is calculated by three-dimensional normalized bubble interfacial area. Regarding long-term bubble hydrodynamics, a moving reference frame is applied. The relationship between bubble shape and rising velocity is discussed, and the impact of surface tension on bubble hydrodynamics is illustrated. The accuracy of simulation results is validated based on the experimental data, while the feasibility of the present method is verified by comparing it to the theoretical correlation. The results show that the introduction of bubble deformation factor standing for shape oscillation is feasible and bubble shape oscillation is sensitive to bubble motion pattern. In the presence of straight trajectory, the local minima of bubble deformation factor are associated with the local rising velocity maxima and vice versa. In terms of zigzag or helical trajectory, the velocity-shape dependence is under the influence of bubble horizontal motion. As for the damped shape oscillation, the oscillation dynamics of bubble deformation factor and rising velocity are highly sensitive to the variation in Eötvös number. In the quasi-stable stage, the increasing Eötvös number leads to a slight increase in terminal bubble deformation factor and a significant decrease in terminal velocity.

Long-term evolution of decayless kink oscillations of solar coronal loops

ABSTRACT Long-term evolution of instantaneous parameters of decayless kink oscillations of six solar coronal loops observed for longer than 2 h each is studied. The oscillations are analysed by processing sequences of 171 Å images obtained with the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) in the time interval from 2020 December till 2021 June, with the motion magnification technique. It is established that decayless kink oscillations could exist for more than 30 or 40 oscillation cycles. Neither the loop brightness nor instantaneous parameters of the oscillations show a monotonic increase or decrease during the oscillation. The observed instantaneous oscillation periods and amplitudes are found to vary randomly in time, with distributions around the mean values that resemble Gaussian profiles. Mean values of the oscillation periods and amplitudes are consistent with previous observations of this phenomenon. A power-law dependence of the oscillation period on the displacement amplitude is found, with the power-law index of 0.41 and with the 95 per cent confidence interval of [0.39, 0.71]. In general, we established the lack of correlation between instantaneous oscillation parameters and loop brightness. One exception is an event with relatively strong anticorrelation of the amplitude and the loop’s brightness, with the cross-correlation coefficient of about −0.81, but this effect requires a further study. Fourier power spectra of the envelopes of the time-evolving instantaneous amplitudes and periods are white noise, indicating that consecutive values of the instantaneous parameters are independent of each other. The results obtained provide an empirical ground for validating and comparing existing and future theoretical models of decayless kink oscillations of coronal loops.

Oscillation frequency measurement of gaseous diffusion flames using electrostatic sensing techniques

The oscillation frequency of a burner flame is closely related to the combustion conditions and flame stability. Oscillation frequency measurement is essential for optimized operation of the combustion process. In this paper, the novel use of electrostatic sensors in conjunction with power spectral analysis is presented for the oscillation frequency measurement of a gaseous laminar diffusion flame. Experimental tests carried out on a combustion rig demonstrate that the developed system realises oscillation frequency measurement with a relative deviation from the reference value from an imaging system within ± 6% over a constant fuel flow rate from 0.60 L/min to 0.80 L/min. The oscillation frequency increases with the fuel flow rate and the oscillation frequencies in different regions of the diffusion flame are similar for each fuel flow rate. Under varying fuel flow rate conditions, the system can measure the instantaneous oscillation frequency with a relative deviation from the reference value from an imaging system mostly between −10% and 0%.

DC‐link low‐frequency current and voltage ripple analysis in multiphase voltage source inverters with unbalanced load

Inverter's performance and operating mode may be negatively affected by inverter input (dc-link) current and voltage ripple. It is a common experience that even theoretically balanced loads with perfectly balanced supply voltages, such as multiphase ac motors supplied by pulse-width modulation (PWM) inverters, in practice show a certain degree of current unbalance, in the range of a few percent, which introduces a low-frequency instantaneous power oscillation. This reflects in current and voltage low-frequency ripple on the dc-link inverter side (i.e. at the double-fundamental frequency). A possible method to analyse this matter is through the symmetric sequence components. In particular, based on the first negative current sequence component and by considering the equivalent dc-link impedance calculated at the dominant double-fundamental frequency, the amplitude of the corresponding dc-link voltage ripple component is calculated in this work for a general multiphase load. Finally, the design of the dc-link capacitor in multiphase inverters is proposed considering requirements referred to the double-fundamental dc voltage ripple. The feasibility of the proposed developments has been verified for three-, five- and seven-phase inverters by both numerical simulations and comprehensive experimental tests, always showing a good matching.

Compensation of Oscillating Instantaneous Power in Modern Microgrids Based on the Conservative Power Theory


 Considering the application of multi-functional grid-tied inverters in modern microgrids, this paper proposes a novel control strategy derived from the Conservative Power Theory (CPT), which makes possible the compensation of instantaneous power oscillations. Such approach is based on the instantaneous power and instantaneous reactive energy terms defined by the CPT, allowing the extraction of oscillating power components directly in the abc frame. Simulation results are presented to demonstrate the applicability of the control strategy considering the scenario of a weak microgrid with linear, non-linear, and unbalanced loads, as well as comprising a three-phase multi-functional grid-tied inverter with LCL filter. The results show that active power dispatchability can be offered by the inverter, while concomitantly supporting the microgrid to operate at constant instantaneous power. Experimental results comprising a 3.6 kVA inverter prototype also validate the proposed decomposition of oscillating power terms, showing that they can be satisfactorily employed on compensation purposes.
 

Artefacts of finite span in vortex-induced vibration simulations

The effects of finite-span computational domain with periodic boundaries for vortex-induced vibration simulations are investigated. Coupled fluid-solid dynamics of an elastically-mounted rigid circular cylinder are performed using detached eddy simulations with four computational domains of different span lengths. Simulations with span less than five-cylinder diameters give erroneous results including, under/overprediction of displacement amplitude, premature lock-in, etc. Spectra of transverse loading and displacement, instantaneous oscillation frequency, and phase lag between transverse force and displacement are analyzed. High spanwise coherence is found to be the primary cause of the artefacts observed in small-span simulations.

A 0.045- to 2.5-GHz Frequency Synthesizer With TDC-Based AFC and Phase Switching Multi-Modulus Divider

A 0.045- to 2.5- GHz wideband frequency synthesizer (FS) employing time-to-digital converter (TDC) based automatic frequency calibration (AFC) method and phase switching (PS) multi-modulus divider (MMD) is presented in this paper. The traditional counter-based AFC method takes several reference cycles to calculate the instantaneous voltage-controlled oscillator (VCO) frequency, while the proposed TDC-based technique consumes only 2 cycles. In order to suppress the quantization noise caused by the sigma-delta modulator (SDM) in the MMD, the loop division step is reduced from 2 to 0.5 by adopting the PS technique. The FS is designed and implemented using TSMC 180nm RF CMOS process and provides the phase noise performance of −99.5 / −123.5 dBc/Hz at 10kHz/1MHz offsets under 2.4 GHz carrier frequency. The AFC time measurement results for a 6-bit cap-array are 1.25-, 2.5- and 5- $\mathrm {\mu s}$ when employing 48-, 24- and 12-MHz reference frequencies respectively. The chip area including pads and I/Os is 2.31 mm $^{\mathbf {2}}$ and the total power consumption is 108 mW.

A new insight on a mechanism of airborne and underwater sound of a drop impacting a liquid surface

We report on an experimental study of the impact of a water drop on a liquid surface in the regime of the so-called irregular entrainment. The hydrodynamics of the phenomenon has been correlated finely to the features of the acoustic signal, both underwater and in the air, thanks to the synchronization of images and sounds in a home-made setup. If the origin of the acoustic signal is known to be caused by the capture of a bubble during the hydrodynamic flow following the impact, for the first time, a new mechanism responsible for the formation of the air bubble is highlighted. The latter is caused by the closing, like a liquid zipper, of the cavity induced by the retraction of the Rayleigh jet, by a secondary droplet detached from this jet. The comparison of the experimental data with the Minnaert model and plane wave theories reveals: (i) the time-dependence of the instantaneous oscillation frequency, (ii) a dominant frequency about 30% higher than the Minnaert prediction, (iii) a higher damping characteristic time, and (iv) a two orders of magnitude higher water–air transmission coefficient. All these results can be explained by the proximity of the bubble to the air–water interface, and by the too small dimensions of the tank to avoid underwater echoes in the measured underwater signal.

Modified Instantaneous Power Control With Phase Compensation and Current-Limited Function Under Unbalanced Grid Faults

In distributed generation systems, power quality is one of the main concerns during short-term unbalanced grid voltage faults. However, for the most common three-phase three-wire grid-connected inverter-based power systems, there may be a tradeoff between power oscillations and current harmonics during the unbalanced grid fault ride-through control, which has a crucial impact on the installed inverters for different applications. In this article, a modified instantaneous power control-based voltage phase compensation control strategy is proposed to enhance the inverter current quality, while, at the same time, mitigating the active/reactive instantaneous power oscillations. Moreover, a simplified peak current-limited control strategy is developed to improve the reliability of the grid-connected system, and it does not need the extraction of the grid voltage and/or current fundamental positive/negative sequence components, which significantly reduce the computation burden. Finally, the experimental tests based on dSPACE-DS1007 and MATLAB/Simulink are carried out to verify the effectiveness of the proposed strategy.

Wideband 67−116 GHz receiver development for ALMA Band 2

Context. The Atacama Large Millimeter/submillimeter Array (ALMA) has been in operation since 2011, but it has not yet been populated with the full suite of its planned frequency bands. In particular, ALMA Band 2 (67−90 GHz) is the final band in the original ALMA band definition to be approved for production. Aims. We aim to produce a wideband, tuneable, sideband-separating receiver with 28 GHz of instantaneous bandwidth per polarisation operating in the sky frequency range of 67−116 GHz. Our design anticipates new ALMA requirements following the recommendations of the 2030 ALMA Development Roadmap. Methods. The cryogenic cartridge is designed to be compatible with the ALMA Band 2 cartridge slot, where the coldest components – the feedhorns, orthomode transducers, and cryogenic low noise amplifiers – operate at a temperature of 15 K. We use multiple simulation methods and tools to optimise our designs for both the passive optics and the active components. The cryogenic cartridge is interfaced with a room-temperature (warm) cartridge hosting the local oscillator and the downconverter module. This warm cartridge is largely based on GaAs semiconductor technology and is optimised to match the cryogenic receiver bandwidth with the required instantaneous local oscillator frequency tuning range. Results. Our collaboration has resulted in the design, fabrication, and testing of multiple technical solutions for each of the receiver components, producing a state-of-the-art receiver covering the full ALMA Band 2 and 3 atmospheric window. The receiver is suitable for deployment on ALMA in the coming years and it is capable of dual-polarisation, sideband-separating observations in intermediate frequency bands spanning 4−18 GHz for a total of 28 GHz on-sky bandwidth per polarisation channel. Conclusions. We conclude that the 67−116 GHz wideband implementation for ALMA Band 2 is now feasible and that this receiver provides a compelling instrumental upgrade for ALMA that will enhance observational capabilities and scientific reach.

Modelling and Control of Photovoltaic System using the incremental conductance method for maximum power point tracking

This paper presents the modeling and simulation of the electrical operation of a photovoltaic (PV) system. A DC-DC boost converter was chosen for the regulation of the output voltage at the peak power point while also providing a constant voltage. Maximum Power Point Tracker (MPPT) control that allows extraction of maximum available power from the photovoltaic (PV) panel has been included. The maximum efficiency is achieved when PV works at its maximum power point which depends on insolation and temperature. Since the insolation and temperature always change with time, a PV system which able to track the maximum power point needs to be developed to produce more energy. This research was aimed to explore the performance of a maximum power point tracking system which implements Incremental Conductance (IC) method. The IC algorithm was designed to control the duty cycle of Boost converter and to ensure the MPPT control work at its maximum efficiency. The simulation results obtained with Matlab / Simulink show the instantaneous oscillation of the operating point of the photovoltaic module around the MPP independently to weather changes, the proper functioning of the converter which provides a voltage at its output greater than that supplied by the PV generator, (a yield of the order of 90%) and the low power losses supplied by this module (less than 10%) allowed to conclude that the PV system simulated during this work was working properly and was satisfactory

Multiscale Analysis of the Instantaneous Eccentricity Oscillations of the Planets of the Solar System from 13 000 BC to 17 000 AD

The high-resolution Jet Propulsion Laboratory DE431 and DE432 planetary ephemeris are used to evaluate the instantaneous eccentricity functions of the orbits of the planets of the solar system from 13 000 BC to 17 000 AD at different time scales. Spectral analyses are performed to determine the frequencies and the amplitudes of the detected perturbations from 0.1-year to 10 000-year periods. Taken as contiguous pairs (Mercury-Venus, Earth-Mars, Jupiter-Saturn, and Uranus-Neptune), we found anti-phase patterns between contiguous planets at specific time scales (30 000 years): namely, the eccentricity of one planet increases while the other decreases. Venus and Earth instead appear in phase. However, on shorter time scales the phase coupling becomes more complex and irregular. Yet, Jupiter and Saturn present a π/2 phase coupling at the 1000-year scale. Periodogram analysis of the planetary eccentricity functions shows several fast fluctuations whose magnitudes indicate the strength of their mutual interactions where the Jovian planets significantly perturb the orbits of the inner planets. Besides, the wavelet power spectrum and wavelet squared coherence spectrum analyses are adopted to examine the relationships in time-frequency space between the eccentricity functions of each couple of terrestrial and Jovian planets. The analysis reveals the complexity and the evolution of the gravitational couplings perturbing each other planetary orbits. In some cases and for specific frequencies, this analysis technique also led to the discovery that the coherence phase can rotate clockwise or anticlockwise. The eccentricity function of the orbit of Jupiter presents large oscillations with periods of about 60 and 900- 960 years, mostly due to the interaction with Saturn. These oscillations also correspond to oscillations found in several geophysical records. The eccentricity functions of Uranus and Neptune are characterized by a large 4300-year oscillation. The eccentricity function of Pluto is characterized by a large nearly 20 000-year modulation.

Brain oscillation-synchronized stimulation of the left dorsolateral prefrontal cortex in depression using real-time EEG-triggered TMS

BackgroundRepetitive transcranial magnetic stimulation (rTMS) of the left dorsolateral prefrontal cortex (DLPFC) is an effective treatment for major depressive disorder (MDD), but response rates are low and effect sizes small. Synchronizing TMS pulses with instantaneous brain oscillations can reduce variability and increase efficacy of TMS-induced plasticity. ObjectiveTo study whether brain oscillation-synchronized rTMS is feasible, safe and has neuromodulatory effects when targeting the DLPFC of patients with MDD. MethodsUsing real-time EEG-triggered TMS we conducted a pseudo-randomized controlled single-session crossover trial of brain oscillation-synchronized rTMS of left DLPFC in 17 adult patients with antidepressant-resistant MDD. Stimulation conditions in separate sessions were: (1) rTMS triggered at the negative EEG peak of instantaneous alpha oscillations (alpha-synchronized rTMS), (2) a variation of intermittent theta-burst stimulation (modified iTBS), and (3) a random alpha phase control condition. ResultsTriggering TMS at the negative peak of instantaneous alpha oscillations by real-time analysis of the electrode F5 EEG signal was successful in 15 subjects. Two subjects reported mild transient discomfort at the site of stimulation during stimulation; no serious adverse events were reported. Alpha-synchronized rTMS, but not modified iTBS or the random alpha phase control condition, reduced resting-state alpha activity in left DLPFC and increased TMS-induced beta oscillations over frontocentral channels. ConclusionsAlpha-synchronized rTMS of left DLPFC is feasible, safe and has specific single-session neuromodulatory effects in patients with antidepressant-resistant MDD. Future studies need to further elucidate the mechanisms, optimize the parameters and investigate the therapeutic potential and efficacy of brain oscillation-synchronized rTMS in MDD.

Control of Three-Phase Solid-State Transformer With Phase-Separated Configuration for Minimized Energy Storage Capacitors

This paper presents the control structure of a solid-state transformer for three-phase ac/ac, to reduce the required size of capacitors. The structure consists of an ac/dc converter based on cascaded H-bridge converters, isolated dc/dc converters, and a dc/ac inverter. The phase separated configuration requires a high capacitance for the smoothing capacitors owing to the instantaneous power oscillation at the double-line frequency. This paper reviews control methods of the dc/dc converter to achieve synchronous instantaneous power with the ac/dc converter, and thereby cancel the double-line frequency component applied to the capacitors between the ac/dc and dc/dc converters. This study also proposes incorporating a control method to cancel the oscillating instantaneous power caused by unbalanced load current. The overall control was demonstrated using a 6-kVA laboratory prototype. The required minimum capacitance, which is decided by the switching frequency, is discussed, and the demonstration of a design case study on a 300-kVA system is described. The likely increase in loss in the isolated dc/dc converter owing to the power oscillation controls was evaluated with a 10-kW loss evaluation-model of a dc/dc converter.