Slow Vibration Research Articles

Archery-inspired catapult mechanism with controllable energy release for efficient ultralow-frequency energy harvesting

Ultralow-frequency (< 5 Hz) vibration energy is abundant in the environment, but its efficient utilization is still highly difficult due to the frequency-mismatch problem encountered by the vibratory energy harvesters and the slow rotation of rotary energy harvesters (REHs). To solve this issue, we developed herein a high-performance REH (named AI-REH) based on the archery-inspired catapult mechanism, which breaks through the limitation of the slow vibration source to the REH rotation speed through an innovative magnetic coupling strategy between the vibration source and the AI-REH. By employing an accumulator spring as the energy reservoir, the AI-REH also realizes the accumulation and controllable release of ultralow-frequency vibration energy via the interaction between the magnetic coupling and the elastic force. High-speed kinetic energy can thus be acquired for efficiently powering the rotor, contributing to significantly accelerated rotor speeds and enhanced electric outputs. Compared with the traditional counterpart, the AI-REH achieves 3.6-fold increase in rotor speed, 3.5-fold increase in output voltage and 3.0-fold increase in output power under an ultralow-frequency vibration of 4 Hz. A power backpack was also constructed and tested, which demonstrates the superior capability of the AI-REH in harnessing real ultralow-frequency amplitude-varying vibration energy. The AI-REH proposed in this study provides a new pathway for efficiently exploiting environmental ultralow-frequency vibration energy toward self-sufficient systems with various purposes.

Slow vibration via acoustoelastic coupling: Quasi-bound states in the continuum

Elastic bound states in the continuum (BICs) have recently garnered significant attention due to their remarkably high Q-factor, leading to the decoupling of the confined mode from spectrally coexisting radiational channels. In this presentation, we introduce a novel state capable of generating a slow vibration phenomenon, exhibiting multiphysics analogous to the concept of slow light observed in electromagnetically induced transparency (EIT). This state arises from the interaction of acoustoelastic coupling within a composite structure, featuring two acoustic cavities enclosed in an elastic bar. The proposed design facilitates quasi-BICs with exceptional spatial efficiency localized within a specific area, enabling tuning of the Purcell factor by approximately six orders of magnitude. The findings of such quasi-BICs may expand the BIC family and opens new avenues for applications in diverse fields, including lasing, sensing, screening, and energy storage platforms, where ultrahigh-Q-factor modes coexist with radiative channels.

Preliminary Analysis of Ionospheric Anomalies before Strong Earthquakes in and around Mainland China

The aims of the present study were to use Langmuir Probe payload electron density data and Plasma Analyzer Package payload O+ density data from the Zhangheng-1 electromagnetic satellite to statistically analyze anomalies in electron and oxygen ion densities before strong earthquakes (Ms ≥ 6.0) in western China and its neighboring areas. The goal was to investigate the physical mechanisms underlying electron and oxygen ion generation by evaluating the correlations between such anomalies and the seismic activity before the 6.4-magnitude earthquake in Yangbi, Yunnan, China, on 21 May 2021. Nine (75%) of the twelve earthquakes that occurred during the study period and were not affected by magnetic storms were preceded by anomalous electron or oxygen ion densities of 1.1–4.5 × 1010/m3 and 2.8–6.0 × 1010/m3, respectively. The anomalies were generally observed within the two weeks preceding the earthquakes and were associated with most strike-slip and thrust earthquakes, which were mainly located on the southeastern and northwestern edges of the Tibetan Plateau—but not normal fault earthquakes. The anomalies were likely the result of acoustic-gravity waves generated by slow vibrations of the Earth’s surface reaching the ionosphere, where they cause oscillations in ionospheric electron and ion densities. In addition, the association between ionospheric anomalies and strong earthquakes was confirmed by the observation of other atmospheric anomalies before the Yangbi earthquake.

저전력 가변 이득 증폭기 설계

This paper presents a low-power variable gain amplifier (VGA) for the automotive radar. The proposed VGA comprises a gain control stage and an amplifier stage with active inductors. The gain control stage on the circuit is designed to be adjustable in 5 steps from 0 dB to 20 dB. The chip area can be reduced using an active inductor. This circuit also has a lower power dissipation, which reduces slow vibrations. The VGA is fabricated by TSMC 0.13 μm CMOS process. In comparison to conventional research results, the proposed VGA showed a lower power consumption of 17.88 mW, a low noise figure of less than 3.424 dB, and a relatively low active area of 0.034 mm².

Slow monomer vibrations in formic acid dimer: Stepping up the ladder with FTIR and Raman jet spectroscopy.

In an effort to extend the cold gas phase spectroscopic database of the cyclic formic acid dimer (FAD), we present and analyze the jet-cooled vibrational infrared and Raman spectrum of (HCOOH)2 in the monomer fingerprintregion between 600 and 1500 cm-1. The present study bridges the gap between the intermolecular dimerization-induced and the carbonyl stretching fundamentals that have already been reexamined using jet-cooled or high-resolution spectroscopy. This completes the characterization of the jet-cooled vibrational (HCOOH)2 spectrum below the complex OH (CH) stretching fundamentals, and we report resonance-induced FAD combination/overtone transitions that will serve as a valuable reference for a theoretical modeling of its vibrational dynamics. As a by-product, several new formic acid trimer fundamentals are identified in the jet spectra and assigned with the help of second-order vibrational perturbation theory (VPT2). The polar formic acid dimer still eludes detection in a supersonic jet, but we are able to estimate an experimental upper-bound of the polar dimer-to-trimer-to-cyclic dimer intensity ratio to about 1:10:100 under typical expansion conditions. Using VPT2 with resonance treatment (VPT2+K), we reinvestigate the notorious ν22 resonance triad. Generally, we find that VPT2, which is, of course, inadequate for modeling the resonance-rich OH stretching spectrum of FAD, is performing very satisfactorily in predicting fundamental and two-quantum state term values for the slower modes below 1500 cm-1. As these modes are the building blocks for the ultrafast energy dissipation in the OH stretching region, the present work opens the door for its quantitative understanding.

Bio-inspired soft bistable actuator with dual actuations

Soft bending actuators, as one of the most important components of soft robotics, have attracted significantly increasing attention due to their robustness, compliance, inherent safety, and ease of manufacture. However, the key disadvantages can be the low output force, slow response speed, large deformation and vibration, which can potentially be addressed by introducing a bistable mechanism enabled by a prestressed steel shell. This work proposes a novel soft actuator with bistable property, which can maintain the predefined initial state and enhance bending motion at the corresponding stable state. A novel dual-actuation mechanism, which utilises pneumatic pressure for closing and tendon-driven for opening process, is proposed for autonomous transition between both states, and for a fast response. Mathematical model is proposed and compared with the experimental result for triggering pressure, which serves as a threshold to activate the transition of the stable state. Experimental results also indicate that closing and opening speeds are enhanced by 9.82% and more than ten times, respectively, as compared with the existing pneumatic bistable reinforced actuator design. Mathematical and experimental results suggest that a programmable bending angle at the second stable state can also be achieved by adjusting the preset tendon extension. The tendon arrangement also acts as a passive damping mechanism to reduce the oscillation while closing. The damping ratio is increased by more than four times, indicating that the oscillation decay is significantly accelerated for quick stabilization. Finally, a three-finger soft gripper is developed based on the proposed actuator design, which demonstrates promising performance in grasping objects with various shapes and sizes. The experimental results also show that the proposed bistable gripper can grasp the object with a weight up to 2067 g, which is more than 17 times heavier than that of three actuators.

A New Method to Verify the Measurement Speed and Accuracy of Frequency Modulated Interferometers

The measurement speed and measurement accuracy of a displacement measuring interferometer are key parameters. To verify these parameters, a fast and high-accuracy motion is required. However, the displacement induced by a mechanical actuator generates disadvantageous features, such as slow motion, hysteresis, distortion, and vibration. This paper proposes a new method for a nonmechanical high-speed motion using an electro-optic modulator (EOM). The method is based on the principle that all displacement measuring interferometers measure the phase change to calculate the displacement. This means that the EOM can be used to accurately generate phase change rather than a mechanical actuator. The proposed method is then validated by placing the EOM into an arm of a frequency modulation interferometer. By using two lock-in amplifiers, the phase change in an EOM and, hence, the corresponding virtual displacement could be measured by the interferometer. The measurement showed that the system could achieve a displacement at 20 kHz, a speed of 6.08 mm/s, and a displacement noise level &lt; 100 pm//√Hz above 2 kHz. The proposed virtual displacement can be applied to determine both the measurement speed and accuracy of displacement measuring interferometers, such as homodyne interferometers, heterodyne interferometers, and frequency modulated interferometers.

Mechanisms for transient localization in a diatomic nonlinear chain

We investigate transient nonlinear localization, namely the self-excitation of energy bursts in an atomic lattice at finite temperature. As a basic model we consider the diatomic Lennard-Jones chain. Numerical simulations suggest that the effect originates from two different mechanisms. One is the thermal excitation of genuine discrete breathers with frequency in the phonon gap. The second is an effect of nonlinear coupling of fast, lighter particles with slow vibrations of the heavier ones. The quadratic term of the force generate an effective potential that can lead to transient grow of local energy on time scales the can be relatively long for small mass ratios. This heuristics is supported by a multiple-scale approximation based on the natural time-scale separation. For illustration, we consider a simplified single-particle model that allows for some insight of the localization dynamics.

Steady state evoked potential (SSEP) responses in the primary and secondary somatosensory cortices of anesthetized cats: Nonlinearity characterized by harmonic and intermodulation frequencies

When presented with an oscillatory sensory input at a particular frequency, F [Hz], neural systems respond with the corresponding frequency, f [Hz], and its multiples. When the input includes two frequencies (F1 and F2) and they are nonlinearly integrated in the system, responses at intermodulation frequencies (i.e., n1*f1+n2*f2 [Hz], where n1 and n2 are non-zero integers) emerge. Utilizing these properties, the steady state evoked potential (SSEP) paradigm allows us to characterize linear and nonlinear neural computation performed in cortical neurocircuitry. Here, we analyzed the steady state evoked local field potentials (LFPs) recorded from the primary (S1) and secondary (S2) somatosensory cortex of anesthetized cats (maintained with alfaxalone) while we presented slow (F1 = 23Hz) and fast (F2 = 200Hz) somatosensory vibration to the contralateral paw pads and digits. Over 9 experimental sessions, we recorded LFPs from N = 1620 and N = 1008 bipolar-referenced sites in S1 and S2 using electrode arrays. Power spectral analyses revealed strong responses at 1) the fundamental (f1, f2), 2) its harmonic, 3) the intermodulation frequencies, and 4) broadband frequencies (50-150Hz). To compare the computational architecture in S1 and S2, we employed simple computational modeling. Our modeling results necessitate nonlinear computation to explain SSEP in S2 more than S1. Combined with our current analysis of LFPs, our paradigm offers a rare opportunity to constrain the computational architecture of hierarchical organization of S1 and S2 and to reveal how a large-scale SSEP can emerge from local neural population activities.

Single beam low frequency 2D Raman spectroscopy.

Low frequency Raman spectroscopy resolves the slow vibrations resulting from collective motions of molecular structures. This frequency region is extremely challenging to access via other multidimensional methods such as 2D-IR. In this paper, we describe a new scheme which measures 2D Raman spectra in the low frequency regime. We separate the pulse into a spectrally shaped pump and a transform-limited probe, which can be distinguished by their polarization states. Low frequency 2D Raman spectra in liquid tetrabromoethane are presented, revealing coupling dynamics at frequencies as low as 115 cm-1. The experimental results are supported by numerical simulations which replicate the key features of the measurement. This method opens the door for the deeper exploration of vibrational energy surfaces in complex molecular structures.

Sustained Self-Starting Orbital Motion of a Glass-Fiber “Nanoengine” Driven by Photophoretic Forces

Controllable optically driven rotation of microscopic objects is desirable in many applications, but is difficult to achieve. Here we report a sustained self-starting orbital motion of a clamped elongated nanostructure, a glass-fiber nanospike, when a CW laser beam is focused axially onto its tip. Analysis shows that photophoretic antitrapping forces, acting on the nanospike with a delayed response, introduce optomechanical gain into the mechanical motion, overcoming the intrinsic mechanical dissipation and resulting in growth from noise of oscillations at the resonant frequency of the nanospike. These photophoretic forces further enable phase-locking of the orthogonal fast and slow vibrations of the nanospike (induced by slight mechanical anisotropy), giving rise to a self-sustained orbital motion. The locked phase of orbital motion can be changed by tuning the gas pressure and adjusting the geometrical asymmetry of the system. This light-driven nanoengine opens up a new degree of freedom for controlling the rotational motion of elongated nano-objects.

Structure and Efficiency in Bacterial Photosynthetic Light Harvesting.

Photosynthetic organisms use networks of chromophores to absorb and deliver solar energy to reaction centers. We present a detailed model of the light-harvesting complexes in purple bacteria, including explicit interaction with sunlight, radiative and nonradiative energy loss, and dephasing and thermalizing effects of coupling to a vibrational bath. We capture the effect of slow vibrations by introducing time-dependent disorder. Our model describes the experimentally observed high efficiency of light harvesting, despite the absence of long-range quantum coherence. The one-exciton part of the quantum state fluctuates continuously but remains highly mixed at all times. These results suggest a relatively minor role for structure in determining efficiency. We build hypothetical models with randomly arranged chromophores but still observe high efficiency when nearest-neighbor distances are comparable to those in nature. This helps explain the high transport efficiency in organisms with widely differing antenna structures and suggests new design criteria for artificial light-harvesting devices.

Acceptability testing and development of a novel wood lathe balanced rest

Abstract The utility model discussed in this study discloses a wood lathe balancing rest that is advantageous in terms of design, ergonomics, and functions. The study aimed to fabricate a safety device for the wood lathe machine to prevent kickback and slow down vibration from the workpiece attached to the lathe machine to avoid the vibration of the workpiece and to avoid an accident to the operator and to avoid damage of the materials. The utility model is planned not exclusively to spare time yet also for the wellbeing of the laborers amid activity. It is designed to hold the workpiece when turning and control the vibration, it can be mounted on the bed of the lathe near the center of the turning planetary.

Multiphoton ionization dissociation dynamics of iodoethane studied with velocity map imaging technique

Halogenated alkanes destroy the ozone layer, and iodoethane is one of the important representative halogenated alkanes. Time-of-flight mass spectrometry and velocity map imaging technique are used for investigating the photoionization dissociation dynamics of iodoethane, induced by 800 nm femtosecond laser. The dissociation mechanisms of iodoethane are obtained and discussed by analyzing the velocity distributions and angular distributions of the fragment ions generated in the dissociation. The measurements by time-of-flight mass spectrometry show that iodoethane cations generates C2H5+, I+, CH2I+, C2H2+, C2H3+ and C2H4+. The fragments related to CI bond fragmentation are C2H5+ ions and I+ ions, and the dissociation mechanisms are C2H5I+ C2H5++I and C2H5I+ C2H5+I+ respectively. Comparison between the configurations before and after ionization shows that the CI bond length is 0.2220 nm before ionization and turns longer and becomes 0.2329 nm after ionization. This indicates that the CI bond becomes more unstable after ionization and is more prone to dissociation. Moreover, the velocity map images of C2H5+ and I+ ions are acquired, from which the speed and angular distribution of C2H5+ and I+ are obtained. The analysis of speed distribution of the fragment ions shows that there are two channels, i.e. high energy channel and low energy channel in the dissociation process for producing C2H5+ and I+ ion. The difference between the ratios of the high energy channel and the low energy channel is small, indicating that the high energy channel and the low energy channel of the two dissociation processes are similar. According to the further analysis of the angular distribution of the fragment ions, it is found that the anisotropy parameter of C2H5+ is close to 0 (isotropic), the production channel of which may correspond to the slow vibration predissociation process. The anisotropy parameters of I+ ions are higher, which may be due to the rapid dissociation process on the repulsive potential energy surface. In addition, the density functional theory is used to calculate the configuration change of the iodoethane molecule before and after ionization, the energy level and oscillator strength for the ionic state in order to obtain more insights into the photodissociation dynamics.

Vibrational resonance in an inhomogeneous medium with periodic dissipation.

The role of nonlinear dissipation in vibrational resonance (VR) is investigated in an inhomogeneous system characterized by a symmetric and spatially periodic potential and subjected to nonuniform state-dependent damping and a biharmonic driving force. The contributions of the parameters of the high-frequency signal to the system's effective dissipation are examined theoretically in comparison to linearly damped systems, for which the parameter of interest is the effective stiffness in the equation of slow vibration. We show that the VR effect can be enhanced by varying the nonlinear dissipation parameters and that it can be induced by a parameter that is shared by the damping inhomogeneity and the system potential. Furthermore, we have apparently identified the origin of the nonlinear-dissipation-enhanced response: We provide evidence of its connection to a Hopf bifurcation, accompanied by monotonic attractor enlargement in the VR regime.

Self-excited multi-scale skin vibrations probed by optical tracking micro-motions of tracers on arms

The self-excited multi-scale mechanical vibrations, their sources and their mutual coupling of different regions on the forearms of supine subjects, are experimentally investigated, using a simple noncontact method, optical video microscopy, which provides 1 μm and 25 ms spatiotemporal resolutions. It is found that, in proximal regions far from the radial artery, the vibrations are the global vibrations of the entire forearm excited by remote sources, propagating through the trunk and the limb. The spectrum is mainly composed of peaks of very low frequency motion (down to 0.05 Hz), low frequency respiration modes, and heartbeat induced modes (about 1 Hz and its harmonics), standing out of the spectrum floor exhibiting power law decay. The nonlinear mode-mode coupling leads to the cascaded modulations of higher frequency modes by lower frequency modes. The nearly identical waveforms without detectable phase delays for a pair of signals along or transverse to the meridian of regions far away from the artery rule out the detectable contribution from the propagation of Qi, some kind of collective excitation which more efficiently propagates along meridians, according to the Chinese medicine theory. Around the radial artery, in addition to the global vibration, the local vibration spectrum shows very slow breathing type vibration around 0.05 Hz, and the artery pulsation induced fundamental and higher harmonics with descending intensities up to the fifth harmonics, standing out of a flat spectrum floor. All the artery pulsation modes are also modulated by respiration and the very slow vibration.

Experimental research of rectilinear translational vibrations of a screen box excited by a ball balancer

The vibrations of the screen box excited by the ball balancer are experimentally investigated. The stand of the screen and two-frequency vibration exciter in the form of the ball balancer has been created for this purpose. The elastic supports of the box allow it to perform three principal vibrational motions corresponding to three resonant speeds of the shaft rotation: vertical rectilinear, angular oscillatory around one of two transverse central axes of the box. During the adjustment of the stand, it has been defined that the ball balancer excites almost ideal two-frequency vibrations of the screen box. The slow frequency corresponds to the rotational speed of the balls centers around the longitudinal axle of the shaft, and the fast one corresponds to the rotational speed of the shaft with the unbalanced mass attached to it. The two-frequency mode arises in a broad range of parameters and its general characteristics can be changed by changing: the mass of the balls and unbalanced mass; angular velocity of the shaft rotation. It is experimentally defined that the balls get stuck at the lowest resonance frequency, thus exciting the first form of the box vibrations. As a result, the box makes almost pure translational rectilinear vibrations and there are no angular components. In this regard, there is no need to impose additional kinematic constraints on the box motions. On the assumption that the box makes two-frequency vibrations, in the software package for statistical analysis Statistica, the coefficients in the relevant law have been picked up. At the same time, it has been defined that: – the process of determination of the coefficients values is stable (robust), the coefficients practically do not vary with the time interval of measurement of the law of the box motion; – the amplitude of the slow vibrations is directly proportional to the total mass of the balls; – the amplitude of the fast vibrations is directly proportional to the unbalanced mass. The discrepancy between the laws of motion obtained experimentally and with the statistical analysis methods is less than 1 %.

The calming effect of a new wearable device during the anticipation of public speech

We assessed the calming effect of doppel, a wearable device that delivers heartbeat-like tactile stimulation on the wrist. We tested whether the use of doppel would have a calming effect on physiological arousal and subjective reports of state anxiety during the anticipation of public speech, a validated experimental task that is known to induce anxiety. Two groups of participants were tested in a single-blind design. Both groups wore the device on their wrist during the anticipation of public speech, and were given the cover story that the device was measuring blood pressure. For only one group, the device was turned on and delivered a slow heartbeat-like vibration. Participants in the doppel active condition displayed lower increases in skin conductance responses relative to baseline and reported lower anxiety levels compared to the control group. Therefore, the presence, as opposed to its absence, of a slow rhythm, which in the present study was instantiated as an auxiliary slow heartbeat delivered through doppel, had a significant calming effect on physiological arousal and subjective experience during a socially stressful situation. This finding is discussed in relation to past research on responses and entrainment to rhythms, and their effects on arousal and mood.

Slow brushing reduces heat pain in humans.

C-tactile (CT) afferents are unmyelinated low-threshold mechanoreceptors optimized for signalling affective, gentle touch. In three separate psychophysical experiments, we examined the contribution of CT afferents to pain modulation. In total, 44 healthy volunteers experienced heat pain and CT optimal (slow brushing) and CT sub-optimal (fast brushing or vibration) stimuli. Three different experimental paradigms were used: Concurrent application of heat pain and tactile (slow brushing or vibration) stimulation; Slow brushing, applied for variable duration and intervals, preceding heat pain; Slow versus fast brushing preceding heat pain. Slow brushing was effective in reducing pain, whereas fast brushing or vibration was not. The reduction in pain was significant not only when the CT optimal touch was applied simultaneously with the painful stimulus but also when the two stimuli were separated in time. For subsequent stimulation, the pain reduction was more pronounced for a shorter time interval between brushing and pain. Likewise, the effect was more robust when pain was preceded by a longer duration of brush stimulation. Strong CT-related pain reduction was associated with low anxiety and high calmness scores obtained by a state anxiety questionnaire. Slow brushing - optimal for CT activation - is effective in reducing pain from cutaneous heating. The precise mechanisms for the pain relief are as yet unknown but possible mechanisms include inhibition of nociceptive projection neurons at the level of the dorsal horn as well as analgesia through cortical mechanisms. Slow brushing stimuli - optimal for activation of C-tactile fibres - can reduce pain from cutaneous heating. No such effect was seen with fast brushing or vibration. These observations indicate the role of C-tactile fibres in pain modulation.

Research by a 3D modelling of the screen box flat translatory vibrations excited by a ball auto-balancer

The study investigates vibrations of a screen box with its flat translational motion being excited by a ball auto-balancer. The CAD system Solidworks is used to develop a 3D model of a vibration machine and a dual-frequency vibroexciter in the form of a ball auto-balancer. The 3D modeling has helped establish the law of motion of the center of mass of the box. The trajectory of its motion is studied, and the tests have shown that the motion is the sum of two circular motions: – a slow circular motion at an angular velocity of the balls’ rotation; – a fast circular motion at an angular velocity of the rotor rotation. The motion trajectory of the center of mass of the box is an epitrochoid. The projections of the center of mass of the box onto the coordinate axes in the motion plane allegedly change under the law of dual-frequency vibrations. Under the assumption that the projections of the center of mass of the box produce dual-frequency vibrations, the software package Statistica for statistical analysis was used to choose the coefficients under a relevant law. Eventually, it has been established that: – the process of determining the values of the coefficients is steady (robust), and the coefficients practically do not change with changes in the time interval; – the amplitude of slow vibrations is directly proportional to the total mass of the balls; – the amplitude of fast vibrations is directly proportional to the unbalance on the auto-balancer body. For both short and long intervals of time (during several slow vibrations of the box), the discrepancy between the law of vibrations of the center of mass of the box that was found through the 3D modeling and the law of dual-frequency of vibrations found by the method of statistical analysis does not exceed 1 %. The results of the study show that the auto-balancer works as two independent inertial vibroexciters. The first vibroexciter is formed by the balls that are closely pressed to each other. They rotate around the longitudinal axis of the shaft at the frequency of the box’s own vibrations. It generates its slow resonant circular vibrations. The second vibroexciter is formed by the unbalanced mass on the auto-balancer body. It excites a fast circular motion of the box at the speed of the shaft rotation.