Changes In Amplitude Of Oscillations Research Articles

Study on energy conversion efficiency of wave generation in shake plate mode

In recent years, increasing attention has been paid to factors affecting the efficiency of converting wave energy from kinetic energy using shake plates. This research was based on the volume of fluid method to evaluate the energy conversion efficiency of waves generated in the shake plate mode. The effects of different shake plate parameters and water depths on the kinetic energy conversion efficiency were studied, and the results agreed well with experimental data. Results indicated that the angular velocity of the shake plate had the highest influence on kinetic energy conversion efficiency. In the range of ωx to 1.8ωx, the maximum kinetic energy conversion efficiency was 52.1 %. The influence of the oscillation amplitude of the shake plate on the kinetic energy conversion rate was relatively low. As a result, the kinetic energy conversion efficiency remained at approximately 18.10 % even with changes in oscillation amplitude. The kinetic energy conversion efficiency of the shake plate increased with an increase in water depth, with maximum increase 87.39 % seen between 0.15 and 0.2 m. Our research is expected to serve as a reference for the implementation of efficient wave energy generation systems worldwide.

Research on the effects of coal dust parameters on the venting characteristics of gas/dust two-phase explosions

Based on the correlation analysis of venting flame propagation and pressure rise both sides of vessel, the dynamics venting characteristics of gas/dust explosions and influence of dust parameters were studied. Venting parameter appeared a variation process of firstly rising and then reducing with increasing coal dust concentration (q). As q=300 g/m3, venting parameters were the greatest. But it was gradually increased as dust diameter reduced. Venting flame could be affected by dust parameters. As the flame extinguished, an evident oscillation phenomenon emerged and its oscillation amplitude change was similar to venting parameter. A secondary venting flame appeared after extinguishing and got more dramatically with increasing dust diameter. Besides, the pressure at the venting port exhibited an obvious negative value and its appearance moment was corresponding to flame oscillation. And the temperature contour showed the same morphology as flame image. Temperature distribution was related to explosion intensity and affected by dust parameters.

Intermittent properties of the quasi-periodic oscillations of MAXI J1820+070 revealed by Insight-HXMT

We investigate the dynamical properties of low-frequency quasi-periodic oscillations (QPOs) observed from the black hole X-ray binary MAXI J1820+070 during the early part of its 2018 outburst, when the system was in a bright hard state. To do this, we used a series of observations from the Hard X-ray Modulation Telescope Insight-HXMT and applied a wavelet decomposition (weighted wavelet Z-transforms) to the X-ray light curve. We find that the QPO phenomenon is intermittent within each individual observation, with some subintervals in which the oscillation is strongly detected (high root-mean-square amplitude) and others in which it is weak or absent. The average lifetime of individual QPO segments is about 5 oscillation cycles, with a 3σ tail of up to about 20 cycles. There is no substantial difference between the energy spectra during intervals with strong and weak or absent QPOs. Alternatively, we suggest that the changes in oscillation amplitude can be caused by changes in the jet speed. We discuss a possible reason for the intermittent QPO strength within the precessing-jet model previously proposed for MAXI J1820+070: we suggest that the changes in oscillation amplitude are caused by changes in the jet speed. We argue that a misaligned precessing-jet scenario is also consistent with other recent observational findings that suggest that the oscillation of the Compton reflection component is in phase with the QPOs.

Analysis and Implementation of Harmonic Injection Locking in Cross-Coupled Oscillators Exploiting Inter-Harmonic Translations

This paper proposes a new approach to above- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{max}$ </tex-math></inline-formula> power detection, using harmonic injection locking of a cross-coupled oscillator and the resulting change in oscillation amplitude. The paper starts with the development of a theoretical framework for this receiver. Two previous methodologies are combined: analyzing an injection-locked oscillator as an active device in a positive feedback loop with a frequency selective network; and the more recently proposed way of modeling non-linearities by using inter-harmonic translation coefficients. Using this framework, a compact equation for the expected voltage response of the receiver is derived. Finally, the design of a receiver consisting of a 200 GHz cross-coupled oscillator with a 600 GHz folded dipole antenna as its tank inductor is discussed. A Noise Equivalent Power (NEP) of 2.3 pW/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sqrt {\text {Hz}}$ </tex-math></inline-formula> is achieved with the proposed receiver.

Calculating the fragmentation process in quadrupole ion traps

The present theoretical study calculates the consequences of an ion dissociating in a quadrupole field, describing both 3D and linear ion traps. The dissociation induces a change in q-stability parameter, resulting in fragment ions abruptly changing their trajectories. This includes a change in oscillation amplitude and mean-square velocity, i.e., effective collisional temperature. While the first one can lead to ions being lost to the electrodes, the latter one can be used to determine how likely fragment ions are to be further excited. During the collisional focusing process, ions can endure internal heating, just like during the injection process. The difference here is that fragment ions start this process with already elevated internal energies. The process is calculated by making use of the well-known phase-space ellipses. It is shown that fragment ions of lower m/z in average decrease their oscillation amplitude and are thus better trapped. Only very light ions close to the LMCO have a high chance of being lost. However, lighter fragment ions in average start with higher mean-square velocities than the precursor was assumed to need to have to induce dissociation, suggesting further collisional heating. Despite the harsh collisional environment m/z ratios close to the LMCO in average have to endure, a small percentage of these ions drastically decrease their oscillation amplitude, not requiring any collisional focusing. Fragment ions of higher m/z in average increase their oscillation amplitudes, however, their low velocities make further internal heating unlikely. The used calculations have been uploaded to Github: https://github.com/NeugebauerT/ion-trap.

Power spectrum slope confounds estimation of instantaneous oscillatory frequency

Oscillatory neural dynamics are highly non-stationary and require methods capable of quantifying time-resolved changes in oscillatory activity in order to understand neural function. Recently, a method termed ‘frequency sliding’ was introduced to estimate the instantaneous frequency of oscillatory activity, providing a means of tracking temporal changes in the dominant frequency within a sub-band of field potential recordings. Here, the ability of frequency sliding to recover ground-truth oscillatory frequency in simulated data is tested while the exponent (slope) of the 1/fx component of the signal power spectrum is systematically varied, mimicking real electrophysiological data. The results show that 1) in the presence of 1/f activity, frequency sliding systematically underestimates the true frequency of the signal, 2) the magnitude of underestimation is correlated with the steepness of the slope, suggesting that, if unaccounted for, slope changes could be misinterpreted as frequency changes, 3) the impact of slope on frequency estimates interacts with oscillation amplitude, indicating that changes in oscillation amplitude alone may also influence instantaneous frequency estimates in the presence of strong 1/f activity; and 4) analysis parameters such as filter bandwidth and location also mediate the influence of slope on estimated frequency, indicating that these settings should be considered when interpreting estimates obtained via frequency sliding. The origin of these biases resides in the output of the filtering step of frequency sliding, whose energy is biased towards lower frequencies precisely because of the 1/f structure of the data. We discuss several strategies to mitigate these biases and provide a proof-of-principle for a 1/f normalization strategy.

The broadband seismic equipment application in problems of roadbed railway smart monitoring

We present our experience of broadband seismic equipment application to detect changes of roadbed railway state in operation.&#x0D; Aim: to obtain experimental validation to expand the scientific basis of geophysical surveys in roadbed railway state monitoring and identifying hazardous processes at an early stage.&#x0D; Methods: seismic records were obtained by the authors on the Northern railway section. Seismic data were processed using a low-frequency filter of 0.5 Hz and analysis of points movement trajectories of the roadbed railway, we performed numerical modelling of the stress-strain state of the soil when specifying various physical parameters, the results were compared with the experiment.&#x0D; Results: We have shown experimentally and by numerical simulation that by conducting near the railway track vibrations registration formed by passing trains and analyzing the amplitudes change of these vibrations in the low-frequency band (periods of about 100 seconds), it is possible to identify potentially dangerous phenomena in the roadbed. Field observations showed changes in amplitude of oscillations during seasonal flooding; the results are consistent with modeling. The possibility of identifying the stages of freezing-thawing of the soil and associated negative processes is considered. By discussing the parameters of modern seismic equipment, the possibilities and applicability of different types of seismic sensors for roadbed railway monitoring as well as the organization of a smart monitoring system are shown.&#x0D; Conclusion: The possibility of using passing trains vibrations to detect changes of the roadbed railway state by analyzing the amplitudes of these vibrations is proved. Recommendations for seismic sensors choice and organization of smart roadbed state monitoring system are presented.

A novel phase-shift-based amplitude detector for a high-speed atomic force microscope.

In any atomic force microscope operated in amplitude modulation mode, aka "tapping mode" or "oscillating mode," the most crucial operation is the detection of the cantilever oscillation amplitude. Indeed, it is the change in the cantilever oscillation amplitude that drives the feedback loop, and thus, the accuracy and speed of amplitude detection are of utmost importance for improved atomic force microscopy operation. This becomes even more crucial for the operation of a high-speed atomic force microscope (HS-AFM), where feedback operation on a single or a low number of cantilever oscillation cycles between 500 kHz and 1000 kHz oscillation frequency is desired. So far, the amplitude detection was performed by Fourier analysis of each oscillation, resulting in a single output amplitude value at the end of each oscillation cycle, i.e., 360° phase delay. Here, we present a novel analog amplitude detection circuit with theoretic continuous amplitude detection at 90° phase delay. In factual operation, when exposed to an abrupt amplitude change, our novel amplitude detector circuit reacted with a phase delay of ∼138° compared with the phase delay of ∼682° achieved by the Fourier analysis method. Integrated to a HS-AFM, the novel amplitude detector should allow faster image acquisition with lower invasiveness due to the faster and more accurate detection of cantilever oscillation amplitude change.

Modeling the interaction of microbubbles: Effects of proximity, confinement, and excitation amplitude

The interaction of closely spaced microbubbles (MBs) exposed to a transient external pressure field is relevant for a variety of industrial and medical applications. We present a computational framework employing an interface tracking approach to model the transient dynamics of multiple, interacting, insonated MBs in arbitrary settings. In particular, this technique allows studying the effects of mutual proximity, confinement, and variations in excitation amplitude on the translatory motion of pairs of differently sized MBs. Domains of mutual repulsion or attraction are observed for closely spaced MBs in the investigated range of excitation frequencies. The repulsion domain widens and shifts to lower frequencies with increasing excitation pressure amplitude. When the MBs are confined in rigid tubes of decreasing diameters, we observe a shift of the translatory patterns towards lower frequencies, accompanied by a change in relative strength of the two translation modes. This effect is correlated to a decrease of the resonance frequency due to confinement which causes changes in oscillation amplitude and phase shift between the bubble vibrations. Coupling to the viscous host liquid gives rise to phenomena such as collective MB drift, non-symmetric attraction or repulsion, and reversal of translation direction. A system comprising six MBs inside a narrow tube highlights the potential of the computational framework to treat complex setups with multiple bubbles.

Vibration Characteristic Similarity Appraisal of Conticaster Vibration Table

Measured vibration displacement data of conticaster vibration table at different casting speeds, use of "correlation" theory to evaluate the measured data. Get similarity change curve and oscillation amplitude change curve of the four measured points at different casting speeds. The results reflect the crystallizer’s real situation during exercise. Provide a reliable basis for field equipment maintenance and control.

Effect of oscillation amplitude on velocity distributions in an oscillatory baffled column (OBC)

This paper presents a numerical study of the effect of oscillation amplitude in oscillatory baffled column (OBC) using computational fluid dynamics. The numerical work was carried out for single phase liquid flow for an unsteady 3-D model using commercial software, Fluent (2006). This work was concentrated on the effect of oscillation amplitude. Three amplitudes of 5, 10 and 15mm with constant frequency of 1Hz are applied. Vortex and cycle average velocities at different points are analyzed. The studies show the maximum velocity for 5mm, 10mm and 15mm in an OBC are 0.11m/s, 0.25m/s and 0.40m/s respectively in the first cycle of oscillation. At a constant frequency, greater oscillation amplitude displaces the liquid to a further distance and builds a larger vortex. Vortex length was 1.5 times bigger when oscillation amplitude changes from 5mm to 10mm and 2 times when the amplitude is triple from 5mm. The detailed validation is presented somewhere else; this research is focused on the effect of oscillation.

The Distribution of Polar Ejection Forces Determines the Amplitude of Chromosome Directional Instability

Polar ejection forces have often been hypothesized to guide directional instability of mitotic chromosomes, but a direct link has never been established. This has led, in part, to the resurgence of alternative theories. By taking advantage of extremely precise femtosecond pulsed laser microsurgery, we abruptly alter the magnitude of polar ejection forces by severing vertebrate chromosome arms. Reduction of polar ejection forces increases the amplitude of directional instability without altering other characteristics, thus establishing a direct link between polar ejection forces and the direction of chromosome movements. We find that polar ejection forces limit the range of chromosome oscillations by increasing the probability that motors at a leading kinetochore abruptly disengage or turn off, leading to a direction reversal. From the relation between the change in oscillation amplitude and the amount a chromosome arm is shortened, we are able to map the distribution of polar ejection forces across the spindle, which is surprisingly different from previously assumed distributions. These results allow us to differentiate between the mechanisms proposed to underlie the directional instability of chromosomes.

Development of AC microelectrophoresis for rapid protein affinity evaluation

We have developed a new method for evaluating the affinity interactions between two different proteins by applying an alternating current (AC) voltage to a micro-flow channel. An AC voltage was applied to the protein-modified microspheres in the micro-flow channel, which resulted in the oscillation of the microspheres owing to their surface charges. The oscillation amplitude showed a linear relationship with the charge density of the microspheres. As an example for protein affinity measurement, the amplitude changes of a profilin-modified microsphere were measured by the addition of actin. In the same electrical condition, the oscillation amplitude of the profilin-modified microsphere increased by ≈175% by binding with actin. Similar results in the principle were obtained for the affinity interaction between biotin and streptavidin. The results showed that the higher the charge density of the microspheres induced by binding with different proteins, the higher the oscillation amplitude of the microspheres, thus, suggesting a possible application of the micro-flow channel and AC voltage on the protein property study, as well as on the biosensor application using the oscillation amplitude changes.

On the time resolution of event-related desynchronization: a simulation study

Objectives: To investigate the time resolution of different methods for the computation of event-related desynchronization/synchronization (ERD/ERS), including one based on Hilbert transform.Methods: In order to better understand the time resolution of ERD/ERS, which is a function of factors such as the exact computation method, the frequency under study, the number of trials, and the sampling frequency, we simulated sudden changes in oscillation amplitude as well as very short and closely spaced events.Results: Hilbert-based ERD yields very similar results to ERD integrated over predefined time intervals (block ERD), if the block length is half the period length of the studied frequency. ERD predicts the onset of a change in oscillation amplitude with an error margin of only 10–30ms. On the other hand, the time the ERD response needs to climb to its full height after a sudden change in oscillation amplitude is quite long, i.e. between 200 and 500ms. With respect to sensitivity to short oscillatory events, the ratio between sampling frequency and electroencephalographic frequency band plays a major role.Conclusions: (1) The optimal time interval for the computation of block ERD is half a period of the frequency under investigation. (2) Due to the slow impulse response, amplitude effects in the ERD may in reality be caused by duration differences. (3) Although ERD based on the Hilbert transform does not yield any significant advantages over classical ERD in terms of time resolution, it has some important practical advantages.

Quartz tuning fork biosensor

The use of quartz tuning forks for biosensor applications is investigated. The basis of the sensor is to coat the tuning fork surfaces with specific biomolecules and measure subsequent mass loading from the selective binding of complementary analytes. Two experimental setups are evaluated, direct mechanical excitation and self-excitation. Mechanical excitation is achieved by mounting the fork on a piezoelectric plate and it is found that the change in oscillation amplitude on adsorption can be monitored to give the change in mass. However, a major drawback is that the sensitivity is determined by the Q-factor, which varies significantly between different sensors and different experimental arrangements. In self-excitation mode, tuning fork motion is activated and detected by placing the fork within a tuned circuit. Using self-excitation mode, anti-human IgG modified tuning forks can sense the binding of human IgG in the range of 5–100 μg ml −1. The significance of this study is that quartz tuning forks are routinely made using standard microfabrication process, thus suggesting the possibility of facile microfabrication of arrays of quartz sensors.

Further studies of the effect of magnetic fields on the oscillating peroxidase–oxidase reaction

We have performed an experimental study of the effect of DC magnetic fields on the oscillating peroxidase–oxidase reaction to obtain additional information about the mechanism of the action of the magnetic field. The changes in oscillation amplitude and frequency were measured at low (5.1) and high (6.3) pH, respectively. Furthermore, the effect of a magnetic field with a field strength of 1000 G on the oscillation amplitude was measured at different concentrations of enzyme and the modifiers methylene blue and 4-hydroxybenzoic acid. Changes in pH and the concentration of methylene blue seemed to have little or no effect on the reaction's magnetosensitivity. However, increases in the enzyme concentration or the concentration of 4-hydroxybenzoic acid were accompanied by increases in magnetosensitivity. These results lend support to a previously proposed mechanism in which the magnetosensitive steps involve the transfer of electrons to two enzyme intermediates, compounds I and II.

Perturbations of Simple Oscillations and Complex Dynamics in the Peroxidase−Oxidase Reaction Using Magnetic Fields

The effect of dc magnetic fields of the order of 0−4000 G on the oscillating peroxidase−oxidase (PO) reaction was studied. Specifically the effects of magnetic fields on the amplitude of simple periodic oscillations and on complex dynamic states were investigated. Magnetic fields induce a biphasic change in oscillation amplitude: At field strengths up to 1500 G, the amplitude decreases gradually by 11%. At higher field strengths the decrease in amplitude is less, and it vanishes at field strengths of 4000 G and higher. The effect of magnetic fields on complex dynamics is generally to shift the dynamics from one state to a neighboring state. Numerical simulations of a detailed model of the PO reaction support the hypothesis that the magnetosensitive step is the reduction of compound II to ferric peroxidase or the reduction of compound I to compound II or both.

A Functional Analysis of Human Mirror Movements

In this report, an experimental method for investigating the effect of variations in force, amplitude, and frequency of oscillations of the isometric pincer grasp on mirror movements (MM) is described. Normal adults (N = 24) were used as experimental subjects. The magnitude of MM was greater at relatively high static force levels maintained by the passive hand (26% of maximum volitional force or MVF) than at low force levels (4% MVF) in the passive hand. By contrast, the magnitude of MM was smaller at relatively large (20.5% MVF) than at small (9.5% MVF) mean force levels of the active hand when the static force in the passive hand as well as the amplitude and range of oscillation frequencies of the active hand were held constant. The magnitude of MM relative to active hand oscillation was smaller when the active hand oscillated around a relatively large amplitude (22% of MVF) than when it did so around a small amplitude (8% of MVF) at constant mean force levels and oscillation frequencies. The absolute magnitude of MM was not affected by this change in oscillation amplitude. In all experiments, the magnitude of MM was consistently less at relatively high than at low frequencies of oscillation in the active hand. Intrinsic variables of motor control have a major effect on the inducation and modulation of MM, and their contribution may be as great as that of subject variables. The present results differed substantially from those of others who have used similar experimental paradigms. The major difference was the direction of change in power transfer from the active to the passive hand with changes of force in the active hand. Possible reasons for these differences are discussed.

Arsenic reflection from GaAs and AlGaAs surfaces during molecular-beam epitaxy

An ion gauge with a direct line-of-sight view of the substrate can be used to monitor the reflected pressure of the group V species at all stages in the molecular-beam epitaxial growth sequence. During growth of GaAs on rotating substrates, periodic oscillations in the pressure signal are observed when As2 is used for surface stabilization, but not with As4. These oscillations can be correlated to arrival of reflected As2 from the reconstructed surface of GaAs. Changes in oscillation amplitude as the substrate temperature is varied, or the arsenic flux is changed, are found to correspond with the onset of different surface reconstructions. Additionally, abrupt changes in the pressure and reflection mass spectrometry signals, which occur on initiating epitaxial deposition, are quantifiably proportional to relative growth rates. Thus, following an appropriate calibration, such measurements can be used for both growth rate and alloy composition estimation during normal epitaxial deposition sequences.

Stable vortex structures: A flat plate model of dragonfly hovering

To understand the unsteady separated flow mechanisms associated with the hovering flight of certain insects, flat plates of varying thicknesses were sinusoidally driven back and forth using a broad range of motion amplitude and rate conditions in the absence of a mean flow. Flow visualization and hotwire anemometry techniques were used to characterize the resulting vortical structures and velocity profiles. The initiation, development, and perseverance of vortical structures were quantitatively and qualitatively assessed. Only a narrow range of oscillation parameters elicited the cohesive types of flow structures that appear to be utilized by dragonflies. These structures were selectively sensitive to variations in specific parameters. For thin plates, vortical structures were influenced most by changes in oscillation amplitude, not oscillation frequency. The reverse was observed for thick plates. Vorticity accumulation, and the initiation, development and shedding of vortex structures from an oscillating flat plate are accounted for using a simplified physical model.