Vibrational Excitation Research Articles

Orchestrating Nuclear Dynamics in a Permanganate Doped Crystal with Chirped Pump-Probe Spectroscopy.

Pump-probe spectroscopy is a powerful tool to investigate light-induced dynamical processes in molecules and solids. Targeting vibrational excitations occurring on the time scales of nuclear motions is challenging, as pulse durations shorter than a vibrational period are needed to initiate the dynamics, and complex experimental schemes are required to isolate weak signatures arising from wavepacket motion in different electronic states. Here, we demonstrate how introducing a temporal delay between the spectral components of femtosecond beams, namely a chirp resulting in the increase of their duration, can counterintuitively boost the desired signals by 2 orders of magnitude. Measuring the time-domain vibrational response of permanganate ions embedded in a KClO4 matrix, we identify an intricate dependence of the vibrational response on pulse chirps and probed wavelength that can be exploited to unveil weak signatures of the doping ions─otherwise dominated by the nonresonant matrix─or to obtain vibrational excitations pertaining only to the excited state, suppressing ground-state contributions.

The method for calculating phase angle between exciter force of vibration exciter and roller displacement

Introduction. In the process of soil compaction it is important to have information about the current density of the layer, as it enables to quickly adjust the load on the compacted material. The field methods of compaction quality assessment do not cope with this task, as they make point estimation within the pavement area. Therefore, continuous compaction monitoring systems installed on vibratory road rollers are becoming increasingly common. The systems developed by BOMAG and AMMANN require, among other things, the phase angle between the exciter force and the roller movement to calculate the compaction quality index. The phase angle is determined by the unbalance position sensor, which is very labor-intensive. In addition, continuous compaction monitoring systems include an accelerometer. The purpose of this paper is to develop an indirect method for calculating the phase angle from accelerometer readings.The method of research. In order to achieve the purpose of the work, a roller-soil single-mass model in a typical mode for vibratory rollers (periodic loss of contact) has been studied. As a result of modeling it has been found that the reaction of the compacted material has the main influence on the vertical component of a roller acceleration and practically does not affect the horizontal component. This is confirmed by the experimental data.Results. The phase angle can be determined by mutual correlation of the horizontal and vertical acceleration signals of the roller obtained with the accelerometer.Conclusion. The study proposes a new method of calculating the phase angle between the exciter force and the roller displacement, which eliminates the direct measurement of this angle. The calculation of the angle is based on the readings of a two-axis accelerometer installed on the road roller. The proposed method enables to simplify the system of continuous compaction control and reduce the labor intensity of phase angle measurement.

A Novel Semi-Active Control Approach for Flexible Structures: Vibration Control through Boundary Conditioning Using Magnetorheological Elastomers

This research study explores an alternative method of vibration control of flexible beam type structures via boundary conditioning using magnetorheological elastomer at the support location. The Rayleigh–Ritz method has been used to formulate dynamic equations of motions of the beam with MRE support and to extract its natural frequencies and mode shapes. The MRE-based adaptive continuous beam is then converted into an equivalent single-degree-of-freedom system for the purpose of control implementation, assuming that the system’s response is dominated by its fundamental mode. Two different types of control strategies are formulated including proportional–integral–derivative control and on–off control. The performance of controllers is evaluated for three different loading conditions including shock, harmonic, and random vibration excitations.

Vibrational energy relaxation in shock-heated CO/N2/Ar mixtures.

Experimental and numerical studies were performed on the vibrational energy relaxation in shock-heated CO/N2/Ar mixtures. A laser absorption technique was applied to the time-dependent rovibrational temperature time-history measurements. The vibrational relaxation data of reflected-shock-heated CO were summarized at 1720-3230K. In shock-tube experiments, the rotational temperature of CO quickly reached equilibrium, whereas a relaxation process was found in the time-dependent vibrational temperature. For the mixture with 1.0% CO and 10.0% N2, the vibrational excitation caused a decrease in the macroscopic thermodynamic temperature of the test gas. In the simulations, the state-to-state (StS) approach was employed, where the vibrational energy levels of CO and N2 are treated as pseudo-species. The vibrational state-specific inelastic rate coefficients of N2-Ar collisions were calculated using the mixed quantum-classical method based on a newly developed three-dimensional potential energy surface. The StS predictions agreed well with the measurements, whereas deviations were found between the Schwartz-Slawsky-Herzfeld formula predictions and the measurements. The Millikan-White vibrational relaxation data of the N2-Ar system were found to have the most significant impact on the model predictions via sensitivity analysis. The vibrational relaxation data of the N2-Ar system were then modified according to the experimental data and StS results, providing an indirect way to optimize the vibrational relaxation data of a specific system. Moreover, the vibrational distribution functions of CO and N2 and the effects of the vibration-vibration-translation energy transfer path on the thermal nonequilibrium behaviors were highlighted.

Approximate analytical solutions of nonlinear vibration and bifurcation of dielectric elastomer balloon

Dielectric elastomers (DE), a novel class of actuators, are increasingly employed in fields such as soft robotics and vibration control. Most existing studies investigating the dynamic characteristics of DE structures neglect the viscoelasticity and strain-stiffening effects of materials, with only a few offering approximate analytical solutions. This paper establishes the governing equation for the dynamics of a DE balloon, utilizing the principle of virtual work and considering material viscoelasticity and strain-stiffening effects through linear damping and the Gent hyperelastic model, respectively. The nonlinear governing equations are simplified using the Chebyshev polynomial approximation. The multiple scales method is applied to derive approximate solutions for the structure's free vibration under static voltage excitation and parametrically excited vibration under harmonic voltage excitation. The accuracy of these approximate analytical solutions is validated by comparison with numerical solutions. Additionally, the paper analyzes stability and bifurcation phenomena through time-domain response curves, amplitude-frequency curves, and phase trajectories. Furthermore, the influence of the stretching limit, voltage, and damping on the nonlinear vibration of the balloon structure is studied, providing a valuable theoretical foundation for the future design and utilization of dielectric elastomers.

Octupole vibrational excitations built on shell-model states in Xe, Cs, and Ba isotopes up to mass 142

Octupole vibrational excitations built on shell-model states in Xe, Cs, and Ba isotopes up to mass 142

Experiment on the Excitation of Vapor Behavior and the Vibration by Thermal Flow Under C-Tube Pool Boiling Model

Abstract As an important safety equipment in nuclear system, the passive residual heat removal heat exchanger (PRHR HX) with C-tube is responsible for timely removing heat from the reactor core in accident. A C-tube heating device was setup to investigate the flow characteristics of the in-containment refueling water storage tank (IRWST), which is of the PRHR HX shell-side flow field and the vibration characteristics of the heat exchanger tube. The temperature of the flow field and the acceleration signal of the C-tube were measured. The C-tube frequency in the pool boiling condition is 0–0.660 Hz. There is no resonance with the first natural frequency of 8.98 Hz. The IRWST temperature field can be divided into slow-heating period, fast-heating period, and boiling period. Steam vapor exists in three periods, condensation and collapse of vapor concentrate on horizontal tube. The fast-heating period exists the subcooling degree ΔTsub for the most intense vapor excitation, ΔTsub is in the range of 13–16 °C. In term of thermal flow excitation vibration, the existence of the cross flow with C-plane direction is in the transition period from the slow-heating period to the fast-heating period, which excites the maximum root mean squares (RMS) amplitude 0.039 mm and 0.034 mm at the midpoint of upper horizontal tube and vertical tube. When the fluid enters fast-heating period, the direction of flow changes into the normal C-plane. Normal RMS amplitude reached maximum 0.02 mm at upper 1/4 of the vertical tube in boiling period. The above research provides important data support for the safety and reliability of PRHR HX.

Processing and analysis of friction vibration signal of diamond-like carbon film microtextured dry gas seal rings

PurposeThis paper aims to analyze the characteristics of friction vibration signals and identify the vibration excitation source at the start and stop stage of microtextured end face of dry gas seals.Design/methodology/approachThe friction pair consists of a diamond-like carbon (DLC) film microtextured seal ring and a spiral groove seal ring. Friction vibration signal feature extraction method based on harmonic wavelet packet and spectrum analysis was proposed. Signals were collected using acceleration sensor, acquisition card and LabVIEW software. Vibration acceleration signal was decomposed into 32 frequency bands using MATLAB wavelet packet transformation. The 32nd band coefficient was extracted for reconstruction, time-domain and spectral waveforms were obtained and spectra before/after denoising were compared.FindingsThe end face of the DLC film microtextured seal ring generates a good dynamic pressure effect, and the friction and vibration reduction effects are obvious. The harmonic wavelet packet can decompose the vibration signal conveniently and precisely. In the case of this experiment, the frequency of vibration of the seal ring is 7500 HZ.Originality/valueThe results show that the method is effective for the processing of friction vibration signal and the identification of vibration excitation source. The findings will provide ideas for the frictional vibration signal processing and basis for further research in the field of tribology of dry gas seal ring.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0084/

Effect of Excitation Vibration at Different Frequencies on Pick Cutting

The pick vibration model was established and analyzed, and discussed the influence of vibration at different frequencies on the cutting load. Then a discrete element model of the interface coal seam is established in EDEM to analyze the change of cut load at different vibration frequencies. The conclusion shows that it is more suitable to apply high frequency vibration when the coal seam content is high, and it is more suitable to apply low frequency vibration when the rock layer content is more.

Study of the Myosin Relay Helix Peptide by Molecular Dynamics Simulations, Pump-Probe and 2D Infrared Spectroscopy.

The Davydov model was conjectured to describe how an amide I excitation created during ATP hydrolysis in myosin might be significant in providing energy to drive myosin's chemomechanical cycle. The free energy surfaces of the myosin relay helix peptide dissolved in 2,2,2-trifluoroethanol (TFE), determined by metadynamics simulations, demonstrate local minima differing in free energy by only ~2 kT, corresponding to broken and stabilized hydrogen bonds, respectively. Experimental pump-probe and 2D infrared spectroscopy were performed on the peptide dissolved in TFE. The relative heights of two peaks seen in the pump-probe data and the corresponding relative volumes of diagonal peaks seen in the 2D-IR spectra at time delays between 0.5 ps and 1 ps differ noticeably from what is seen at earlier or later time delays or in the linear spectrum, indicating that a vibrational excitation may influence the conformational state of this helix. Thus, it is possible that the presence of an amide I excitation may be a direct factor in the conformational state taken on by the myosin relay helix following ATP hydrolysis in myosin.

Experimental Research Into Aeroelastic Phenomena in Turbine Rotor Blades Inside ARIAS EU Project

Abstract This paper describes an aeroelastic experimental campaign on a low-pressure turbine-bladed rotor in a rotating wind tunnel that took place as a part of the Advanced Research Into Aeromechanical Solutions (ARIAS) EU project. The campaign can be considered a continuation of the free-flutter test that was performed as part of the FUTURE EU project, where the saturation of asynchronous vibrations due to dry friction was characterized. This new campaign studied new aspects of the physics behind saturated flutter, including the non-linear interaction between synchronous excitation and asynchronous vibration, the effectiveness of different mistuning patterns to suppress flutter, and the viability of under-platform dampers as a technology to control the amplitude of asynchronous vibrations. Furthermore, the campaign explored various operation conditions for the turbine rotor, including near-stall. In general, there was a good agreement between the theoretical predictions regarding all these different aspects of turbine flutter and the test results.

Researching low frequency vibration of automobile-robot

Automobile-robot (self-driving automobile) is being researched and developed vigorously. When the automobile-robot is moving on the road surface, the low frequency vibration excitation not only influences the ride comfort of the automobile-robot but also strongly affects the durability of the vehicle’s structures. To research the automobile-robot’s vibration in the low frequency region, a dynamic model of the vehicle is established to calculate the vibration equations in the time region. Based on the theory of the Laplace transfer function, the automobile-robot’s vibration equations in the time region are transformed and converted to the vibration equations in the frequency region. Then, the effect of the design parameters and operation parameters on the characteristic of the automobile-robot’s acceleration-frequency is simulated and analyzed to evaluate the ride comfort as well as the durability of the automobile-robot’s structures in the frequency region. The research results show that the design parameters of the stiffness, mass, and road wavelength remarkably affect the characteristic of the automobile-robot’s acceleration-frequency. To reduce the resonant amplitude of the acceleration-frequency in the vertical and pitching direction of the automobile-robot, the stiffness parameters of the automobile-robot's and tires should be reduced while the mass of the automobile-robot’s body should be increased. Additionally, the road’s roughness also needs to be decreased or the road’s quality needs to be enhanced to reduce the resonant amplitude of the automobile-robot’s acceleration-frequency.

Nonstatistical Unimolecular Decay of the CH2OO Criegee Intermediate in the Tunneling Regime.

Unimolecular decay of the formaldehyde oxide (CH2OO) Criegee intermediate proceeds via a 1,3 ring-closure pathway to dioxirane and subsequent rearrangement and/or dissociation to many products including hydroxyl (OH) radicals that are detected. Vibrational activation of jet-cooled CH2OO with two quanta of CH stretch (17-18 kcal mol-1) leads to unimolecular decay at an energy significantly below the transition state barrier of 19.46 ± 0.25 kcal mol-1, refined utilizing a high-level electronic structure method HEAT-345(Q)Λ. The observed unimolecular decay rate of 1.6 ± 0.4 × 106 s-1 is 2 orders of magnitude slower than that predicted by statistical unimolecular reaction theory using several different models for quantum mechanical tunneling. The nonstatistical behavior originates from excitation of a CH stretch vibration that is orthogonal to the heavy atom motions along the reaction coordinate and slow intramolecular vibrational energy redistribution due to the sparse density of states.

Tailoring Vibrational Excitation Pathways for High-Yield Oxidation of Methane to Methanol

Tailoring Vibrational Excitation Pathways for High-Yield Oxidation of Methane to Methanol

Current-induced local heating and extractable work in nonthermal vibrational excitation

Current-induced local heating and extractable work in nonthermal vibrational excitation

Influence of trailing edge radius of intake struts on excitation force and vibration of rotor blades

Adjusting the trailing edge radius of the intake struts may be advantageous in suppressing the vibration of compressor rotor blades. To explore the impact of the intake struts trailing edge radius on the excitation force and vibration, this study focuses on a compressor with intake struts, and fluid and vibration calculations were conducted. The study revealed that decreasing the trailing edge radius led to a reduction in separation near the strut’s trailing edge, resulting in a narrower wake and weakened mixing near the trailing edge. This caused the total pressure loss region induced by the wake to become more elongated in the low-frequency component, leading to a nonlinear decrease in total pressure amplitude with the reduction of the trailing edge radius. As the trailing edge radius decreased, the excitation force and vibration amplitude of the first-stage compressor rotor blades decreased, while the excitation force distribution showed little variation. The research findings provide insights for the design of intake struts.

Ударное возбуждение магнитоупругой системы периодической последовательностью сверхкоротких импульсов поля

The nonlinear magnetization precession in normal magnetized ferrite film which has magnetic, elastic and magnetoelastic properties is investigated. The excitation field is presented as a vibration on resonance frequency which is modulated by short pulses which frequency is more lower than resonance frequency. It is proposed the formation procedure of periodic succession of ultra-short pulses by the involution to even degree of modulation signal sine. It is found two different cases of excitation: first when modulate pulse duration is larger than initial signal period and second when modulate pulse duration is smaller than initial signal period. In the first case the modulated signal has the form of main frequency vibrations tandem and in the second case the modulated signal has the form of unit sign-variation pulse. It is investigated the time development of magnetic and elastic vibrations whish are firmed by excitation field. It is shown that in the first case the magnetization vibrations at first hat sharp jump to upward and after this decreases by exponent. In this case the elastic vibrations after the same jump at first increases and then decreases by exponent. The elastic vibrations behaviour is interpret as energy pump from magnetic system to elastic system. In the second case the initial jump both vibrations is absent. It is investigated the degree modulation index influence to excited vibrations. It is shown that by increasing of this index the amplitude of magnetic and elastic vibrations decreases. It is investigated the magnetization excited vibrations character by different degree of magnetoelastic connection. It is introduced the coefficient multiple of magnetoelastic constant which is equal to ratio of considered constant to value of magnetoelastic constant of yttrium iron garnet. It is shown that by increasing of multiple coefficient the magnetization vibrations period is increased. It is found the sharp increasing the period by determined value of multiple coefficient which has a threshold character. It is investigated the excitation of magnetization in large time interval when the multiple coefficient is above the threshold value. It is found the principle difference between two cases when pulse duration is large or smaller as alternating field period. It is shown that in the first case the magnetization vibrations has the character of equilibrium position precession in conditions of orientational transition. In the second case the magnetization vibrations has the form of periodic re-orientational jumps from one equilibrium position to another. It is mentioned some properties of observed phenomena and proposed some recommendations for further investigations.

Finite element numerical analysis of structural vibration of a certain pump station

Abstract In the process of pump station operation, the vibration of factory structure caused by hydraulic or mechanical factors will seriously threaten the ordinary operation of pump station; reduce the efficiency of units; shorten the service lifespan of equipment, and even lead to failure of units. In this paper, ANSYS software and modal analysis method are applied to simulate the vibration effect on pump station under natural vibration, unit vibration excitation and hydraulic excitation. The intrinsic vibration features of pump station structure under diverse boundary conditions, different working conditions and distinct external excitation sources are studied. According to the results of modal and harmonic response analysis, it can be concluded that: 1. A cross relationship has been found existing between pump station structure and unit excitation of speed frequency. 2. In addition to the upper part of the pump station fragile structure, the vibration of the pier is more noteworthy. 3. The vibration amplitude of the whole pump station along vertical direction is larger than that in other directions while the deformation following the unit axis and flow direction presents a strong tendency. 4. In general, the influence of hydraulic load on the structural force of pump station is relatively small.

Threshing cylinder unbalance detection using a signal extraction method based on parameter-adaptive variational mode decomposition

The threshing cylinder will wear and deform during the threshing process, causing dynamic balance problems. The combine harvester has multiple vibration excitation sources and a complex vibration environment, making it challenging to extract weak unbalanced signals from strong background noise. A novel three-step filtering framework is proposed in this paper. A zero phase filter was used as the pre-processing layer to filter out the high frequency components in the original signal and reduce the number of parameter-adaptive variational mode decompositions (PAVMD) needed. The PAVMD was used to decompose the non-stationary vibration signal before Adaptive Neuron Linear (Adaline) function was used to fit sinusoidal signal parameters. A measurement index, termed the correlation amplitude (CA) index, is constructed. The parameterisation of PAVMD was guided by the CA index, and the modal component of the unbalanced fault features were located. The simulation and real cylinder signals proved that the proposed method could effectively extract unbalanced signals under noise interference, and the unbalance was identified accurately by the influence coefficient method. Experiments on a threshing cylinder showed that the amplitude identification error was <24 g in single-sided unbalance identification, and the amplitude identification error was <27 g in double-sided unbalance identification. The proposed method had high robustness and small identification error, especially under short-time working conditions, compared with other similar approaches.

Exploring the Use of Cold Atmospheric Plasma for Sound and Vibration Generation.

In this study, we investigate the potential of cold atmospheric plasma (CAP) as a non-contact excitation device, comparing its performance with an ultrasound transmitter. Utilizing a scanning Laser Doppler Vibrometer (LDV), we visualize the acoustic wavefront generated by a CAP probe and an ultrasound sensor within a designated 50 mm × 50 mm area in front of each probe. Our focus lies in assessing the applicability of a CAP probe for exciting a small polymethyl methacrylate (PMMA) sample. By adjusting the dimensions of the sample to resonate at the excitation frequency of the probe, we can achieve high vibrational velocities, enabling further mechanical analysis. In contrast with traditional vibration excitation techniques such as electrodynamical shakers and hammer impact excitation, a plasma probe can offer distinct advantages without altering the structure's dynamics since it is contactless. Furthermore, in comparison with laser excitation, plasma excitation provides a higher power level. Additionally, while pressurized air systems are applicable for limited low frequencies, plasma probes can perform at higher frequencies. Our findings in this study suggest that CAP is comparable with acoustic excitation, indicating its potential as an effective mechanical excitation method.