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Multiple piezoelectric patches shunted with RL-double negative capacitances circuits, which are bonded on the bulkhead, are proposed to control the resonant response of multiple low frequency modes of a moderate thick cabin structure. Dynamic modeling of the electromechanical coupling system of the cabin structure and the piezoelectric shunt circuit is established by employing the three-dimensional finite element. Optimum tuning strategy is based on the trial and error method. It is shown that the proposed approach is effective in enhancing the generalized electromechanical coupling coefficient and controlling the low frequency modes that exhibits coupled deformation of the bulkhead and cabin structure.

Objective Low-frequency vibration accelerates cartilage degeneration in knee osteoarthritis (KOA) rat model. In this article, we investigated whether whole-body vibration (WBV) increases cartilage degeneration by regulating tumor necrosis factor-α (TNF-α) in KOA. Design Proteomics analysis was used to filter candidate protein from synovial fluid (SF) in KOA people after WBV. Enzyme-linked immunosorbent assay (ELISA) was used to estimate changes in TNF-α levels in SF. The C57 mice and TNF-α knock-out mice were sacrificed for the KOA model and WBV intervention. The cartilage was tested by ELISA, histology, terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL), immunohistochemistry, and reverse transcriptase polymerase chain reaction. Luciferase activity test in vitro study was conducted to confirm the relationship between TNF-α and the candidate protein. Results Differentially expressed proteins were enriched in the glycolytic process, glucose catabolic, and regulation of interleukin-8 (IL-8) secretion processes. Phosphoglycerate kinase, triosephosphate isomerase 1, T cell immunoglobulin- and mucin-domain-containing molecules 2, fumarylacetoacetate hydrolase (FAH), and TNF were the hub node. TNF-α expression increased in SF after WBV ( P < 0.05). The cartilage was more degenerated in the TNF-α−/− mice group compared to controls. A significant change was observed in collagen II and FAH ( P < 0.05). TNF-α expression improved in C57 mice ( P < 0.05). Apoptosis of chondrocytes was inhibited in TNF-α−/− mice by the TUNEL test. Luciferase activity significantly increased in TNF-α + FAH-Luc cells ( P < 0.05). Conclusion A novel mechanism underlying WBV-triggered cartilage degeneration was found in KOA that demonstrated the critical regulatory function of TNF-α and FAH during WBV.

Background and Purpose— We aim to determine the potential impact on stroke thrombolysis of drip-and-ship helicopter flights and specifically of their low-frequency vibrations (LFVs). Methods— Mice with a middle cerebral artery autologous thromboembolic occlusion were randomized to receive rtPA (recombinant tissue-type plasminogen activator; or saline) 90 minutes later in 3 different settings: (1) a motion platform simulator that reproduced the LFV signature of the helicopter, (2) a standardized actual helicopter flight, and (3) a ground control. Results— Mice assigned to the LFV simulation while receiving tPA had smaller infarctions (31.6 versus 54.9 mm 3 ; P =0.007) and increased favorable neurological outcomes (86% versus 28%; P =0.0001) when compared with ground controls. Surprisingly, mice receiving tPA in the helicopter did not exhibit smaller infarctions (47.8 versus 54.9 mm 3 ; P =0.58) nor improved neurological outcomes (37% versus 28%; P =0.71). This could be due to a causative effect of the 20- to 30-Hz band, which was inadvertently attenuated during actual flights. Mice using saline showed no differences between the LFV simulator and controls with respect to infarct size (80.9 versus 95.3; P =0.81) or neurological outcomes (25% versus 11%; P =0.24), ruling out an effect of LFV alone. There were no differences in blood-brain barrier permeability between LFV simulator or helicopter, compared with controls (2.45–3.02 versus 4.82 mm 3 ; P =0.14). Conclusions— Vibration in the low-frequency range (0.5–120 Hz) is synergistic with rtPA, significantly improving the effectiveness of thrombolysis without impairing blood-brain barrier permeability. Our findings reveal LFV as a novel, safe, and simple-to-deliver intervention that could improve the outcomes of patients. Visual Overview— An online visual overview is available for this article.

To attenuate the low-frequency vibration transmitted to the driver, a nonlinear seat suspension with high-static-low-dynamic stiffness is designed. First, the force and stiffness characteristics are derived. The nonlinear suspension can achieve the quasi-zero stiffness at the static equilibrium position when the structural parameters are properly designed. Then, a car-seat-human coupled model which consists of a quarter car model, a seat suspension, and a 4 degree-of-freedom human model is established to predict the biodynamic response of the driver. Finally, the isolation performance of the high-static-low-dynamic stiffness seat suspension under two typical road excitations is evaluated separately based on the numerical method. The effects of stiffness ratio, damping ratio, and vehicle speed on the ride comfort are investigated. The results showed that the nonlinear seat suspension outperforms the equivalent linear counterpart and can achieve the best ride comfort when the quasi-zero stiffness condition is satisfied.

The vibration integrated into die-sinking electrical discharge machining is a relatively new solution, so it has been creating the interest of researchers. In this paper, the authors studied the effect of low frequency vibration attached onto workpiece to efficiency of die- sinking electrical discharge machining. Copper electrode and SKD61 die steel were selected to investigate. Material removal rate, tool wear rate and surface roughness were quality indicators investigated in this study. Experimental results showed that the low frequency vibration has a positive effect on the efficiency of die-sinking electrical discharge machining. Comparing to die- sinking electrical discharge machining traditional, when the vibration unit is integrated onto work-piece in die-sinking electrical discharge machining, the largest increase of material removal rate was 34.94 %, the greatest reduction of tool wear rate was 16.0 % and the largest reduction of surface roughness was 26.36 % and profile of machined surface was better.

Colloidal semiconductor nanoplatelets have recently emerged as exciting materials for optoelectronic and biological applications. Their vibrational excitations, or phonon modes, are responsible for...

Structural health monitoring has become increasingly important in the effective evaluation of structural health conditions and the maintenance service of structures. The validity and convenience of obtaining sensor data are critical for data mining, feature extraction, and condition assessment. A fast wireless low-frequency vibration inspection system (FWLVIS) based on wireless sensor networks for offshore platform structural vibration inspection is presented in this paper. The designed system consists of intelligent acquisition equipment and eight wireless nodes with low-frequency acceleration sensors, while the entire system has 64 collection channels. The wireless nodes integrated with a vibration sensing unit, an embedded low-power micro-processing unit, a wireless transceiver unit, and a large-capacity power unit perform functions, which could perform data collection, initial analysis, data storage, and wireless transmission. The intelligent acquisition equipment integrated with a high-performance computation unit, a wireless transceiver unit, a mobile power source, and the embedded data analysis software could completely control the multi-wireless nodes, receive and analyze the data, and implement the parameter identification. Experiments are performed on a single pendulum, and then on an offshore platform model is constructed to verify the FWLVIS. The experimental results show that the system has the following characteristics: fast arrangement, high sampling rate, high resolution, and capacity for low-frequency inspection. Thus, the system has good application prospects and practical value in the field of structural health monitoring and non-destructive inspection.

In this research, we aim to combine origami units with vibration-filtering metastructures. By employing the bistable origami structure as resonant unit cells, we propose metastructures with low-frequency vibration isolation ability. The geometrical nonlinearity of the origami building block is harnessed for the adjustable stiffness of the metastructure’s resonant unit. The quantitative relationship between the overall stiffness and geometric parameter of the origami unit is revealed through the potential energy analysis. Both static and dynamic experiments are conducted on the bistable origami cell and the constructed beam-like metastructure to verify the adjustable stiffness and the tunable vibration isolation zone, respectively. Finally, a two-dimensional (2D) plate-like metastructure is designed and numerically studied for the control of different vibration modes. The proposed origami-based metastructures can be potentially useful in various engineering applications where structures with vibration isolation abilities are appreciated.

Background Transcutaneous vagal nerve stimulation has analgesic potential and might be elicited by abdominally administered low-frequency vibrations. The objective was to study the safety and effect of a combination of music and abdominally administered low-frequency vibrations on pain intensity in elderly patients with chronic musculoskeletal pain. Methods This trial was an international multicenter, randomized controlled pilot study. Patients at age ≥ 65 years with musculoskeletal pain for ≥ 3 months and a daily pain score ≥ 4 out of 10 were recruited at three centers. They were randomized to receive either a combination of music and low-frequency (20–100 Hz) vibrations administered to the abdomen, or a combination with the same music but with higher frequency (200–300 Hz) vibrations administered to the abdomen. Low-frequency vibrations were expected to result in pain reduction measured with a numeric pain rating scale (NRS). Patients in both groups received eight treatments of the music combined with the vibrations in three weeks. Primary outcomes were safety (Serious Adverse Events) and pain intensity measured at baseline, after the last treatment and at six weeks follow-up. Multilevel linear model analyses were performed to study group and time effects. Results A total of 45 patients were analyzed according to intention-to-treat principle. After 344 treatments, 1 Adverse Event was found related to the intervention, while 13 Adverse Events were possibly related. A multilevel linear model showed that the interaction effect of group by time did not predict pain intensity (F[1, 45.93] = 0.002, p = 0.97) when comparing pain intensity at baseline, after the last treatment and at follow-up. Conclusions The combination of music and abdominally administered vibrations was found to be safe and well tolerated by the elderly patients. However, over time, neither the low-frequency treatment group nor the high-frequency treatment group provided clinically meaningful pain relief. There is no evidence that the low-frequency treatment elicited vagal nerve stimulation. Trial registration The trial was prospectively registered in the Netherlands Trial Register (NTR: NL7606) on 21-03-2019.

A compact and highly sensitive interferometric vibration sensor fabricated with two segments of asymmetric multicore fiber rotated 180º with respect to each other is presented. The sensor performs well for frequencies below 1 Hz.

Low frequency vibration monitoring has significant implications on environmental safety and engineering practices. Vibration expressed by visual information should contain sufficient spatial information. RGB-D camera could record diverse spatial information of vibration in frame images. Deep learning can adaptively transform frame images into deep abstract features through nonlinear mapping, which is an effective method to improve the intelligence of vibration monitoring. In this paper, a multi-modal low frequency visual vibration monitoring system based on Kinect v2 and 3DCNN-ConvLSTM is proposed. Microsoft Kinect v2 collects RGB and depth video information of vibrating objects in unstable ambient light. The 3DCNN-ConvLSTM architecture can effectively learn the spatial-temporal characteristics of muti-frequency vibration. The short-term spatiotemporal feature of the collected vibration information is learned through 3D convolution networks and the long-term spatiotemporal feature is learned through convolutional LSTM. Multi-modal fusion of RGB and depth mode is used to further improve the monitoring accuracy to 93% in the low frequency vibration range of 0–10 Hz. The results show that the system can monitor low frequency vibration and meet the basic measurement requirements.

Introduction: The aim of this dissertation is an evaluation of the effect of low frequency vibration on serum lipid profiling women. Materials and Methods: A group of females aged 28-64 years old were assessed twice, before and after 19 days of exposure to low frequency vibration. The parameters of the vibration used (frequency and amplitude) and the short exposition time were selected in order to comply with standards established to safeguard human health; mechanical stimulus safe for human health according to the Polish Standard PN EN ISO 2631-1:1997. The parameters used were as follows: frequency 3.5Hz, amplitude 4 mm and duration time 20 min. The main exclusion criteria for this study were: neoplasm, history of myocardial infarction, history of stroke, history of bone fracture within the two years prior to the study. To assess the effect of low frequency vibration with the parameters as specified above the following physiological and biochemical variables were used: total cholesterol serum level, high density lipoprotein (HDL) cholesterol serum level, low density lipoprotein (LDL) cholesterol serum level, triglycerides (TGD) serum level. Biochemical blood parameters were assessed before and after the trial. Friedawald’s formula was used for the assessment of LDL cholesterol serum level. Upon completion of the study and the subsequent analysis of the results obtained the following conclusions were formulated. Results: A statistically significant lowering of total serum cholesterol and LDL serum cholesterol was observed. Conclusions: The use of the vibration platform with the operational parameters specified had a beneficial effect on the variables measured.

Increasing demands call for the burr-free workpiece in precision manufacturing. Low-frequency vibration-assisted drilling (LFVAD) has been applied to improve the fabrication process. Prediction and minimization of burr size are one of the major research topics in precision machining. In this paper, an LFVAD parameters optimization model was proposed including harmony search (HS) algorithm and a modified LFVAD burr height analytical model. The burr height model of LFVAD was developed using existing analytical burr height model for conventional drilling (CD) and vibration-assisted drilling (VAD). The developed burr height models were then employed with HS algorithm, which is a new meta-heuristic optimization method based on the imitation of music improvisation process, to determine the optimal machining parameters for a given twist drill that results in minimum exit burr height. Experimental results show that the burr height of the optimized LFVAD decreased by 52.75% compared with the CD, and decreased by 17.59% compared with the un-optimized LFVAD. The simulation and experimental results demonstrate that under suitable LFVAD parameters, the burr height could be reduced.

In order to control the low frequency vibration of railway vehicles, a vertical two degrees of freedom (2DOF) low frequency dynamic vibration absorber (DVA) based on acceleration is proposed. Parameters of the dynamic vibration absorber are put forth to control the low frequency vibration of car body bouncing and pitching. Next, the acceleration power spectrum density (PSD) and ride quality of the car body are calculated based on the pseudo excitation method (PEM) and covariance algorithm, respectively. According to the requirement of 2DOF low frequency DVA, the isolators with high static low dynamic stiffness (HSLDS) are designed. A high-speed train dynamic model containing HSLDS isolators is established to validate the effects on the car body vibration. The results reveal that the 2D low frequency DVA can significantly reduce the vibration of the car body bouncing and pitching. Thus, the ride quality of the vehicle is increased, and passenger comfort is improved.

This study proposes an active-controlled hydraulic low-frequency vibration isolator. The vibration isolator can achieve large equivalent mass and quasi-zero dynamic stiffness by combining the fluid inerter with the hydraulic active compensation. Thus, good vibration isolation performance at ultra-low frequency can be realised. The model for the dynamics of the device is set up. The principle of low-frequency vibration isolation is explicated. The natural frequency and its influencing factors are analysed. Finally, preliminary experimental research works are carried out. The results indicate that low-frequency vibration can be effectively isolated by the device proposed in this study.

It is necessary to increase the damping of a machine support structure (support damping) to reduce the residual vibrations caused by rocking vibration. The stiffness of the machine support system (support stiffness) is also an important parameter that needs to be considered while designing machine tools, to avoid low frequency vibrations. However, conventional passive damper supports decrease the support stiffness while increasing the damping. In our previous study, a passive viscoelastic non-linear damper system for shear vibrations, where the vertical preload determines its damping coefficient, was developed to increase the support damping without decreasing the stiffness by focusing on the horizontal component of rocking vibration. The magnitude dependency of the damping capacity has been modeled. However, this damper system has a tradeoff relationship between natural frequency and damping capacity caused by changes in the preload distribution. Thus, adjustment of the vertical preload applied on the damper is essential for the model-based installation of this damper system. So far, no method has been proposed considering this issue. The vertical preload has been adjusted by trial and error methods. This study proposes a method to determine the damper preload conditions systematically by considering the tradeoff relationship between natural frequency and damping capacity caused by changes in the preload distribution. This method is described based on the case study of a machining center. First, the relationship between preload distribution and support stiffness is investigated using the support stiffness model. Then, the relationship between damping capacity and vertical preloads on the damper is investigated based on material test results. Based on these investigations, the tradeoff relationships are simulated on a machining center by utilizing the damper model. The simulation results are verified with the experimental results. The results show that the proposed method can estimate the tradeoff relationship between natural frequency and damping capacity caused by the changes in the preload distribution. By utilizing this estimated relationship, the preferred preload condition can be decided depending upon the user’s demand.

The main challenge in predicting structure-borne sound in wood buildings is to accurately model the vibration transmission between the source and the receiving room. Large variations in model parameters make it difficult to predict absolute vibration levels and to make conclusions regarding the relative effects of different designs. A step towards establishing reliable models is to investigate the possibilities and limitations of using deterministic methods, which requires correlations between simulations and measurements. In this paper, we present a multi-level model correlation approach for low-frequency vibration transmission in wood buildings. We apply the proposed approach to a scaled-size experimental structure representing a part of a two-storey wood building, and we evaluate the results for frequencies up to 100 Hz. We perform correlations between simulations and measurements four different levels: structural components (viz. beams and boards), planar structures (viz. floor, ceiling and walls), room structures and the complete structure. The results indicate that the dynamic behaviour of the experimental structure was to a great extent captured by the developed model. Based on the observations made in the multi-level correlations, we discuss important model parameters and propose modelling guidelines. We conclude that it is possible to employ deterministic methods in order to simulate the low-frequency vibration transmission in wood buildings provided that measurement data for calibration purposes are available. The developed numerical model can be used as a reference model for investigations on the effects of variations and uncertainties in the modelling.

The objective of this article was to conduct a systematic review of the literature to contrast the existing evidence on the effect of mechanical vibrations, either high or low frequency, as an alternative to accelerate orthodontic tooth movement in humans. A literature search from 2010 to June 2021 was conducted in the electronic databases: PubMed, NCBI, Google Scholar, EBSCO, Cochrane, and Ovid, using the eligibility criteria to identify the studies. Only randomized clinical trials (RCT) were included. The certainty of the evidence was assessed using the GRADE tool and the risk of bias (RoB) in individual studies was evaluated according to the Cochrane bias risk tool. Fifteen RTCs were included for final review. Overall, the RoB was classified as low (3), moderate (5), and high (7). Three articles with low RoB, four with moderate RoB, and four with high RoB found no significant effect in the use of vibrations on orthodontic movement. Only four articles, three of them with high RoB and one with moderate RoB, found that mechanical vibrations are effective at accelerating orthodontic tooth movement. The results seemed to indicate that there is no evidence that vibratory stimuli can increase the rate of dental movement or reduce neither the time of dental alignment nor canine retraction during orthodontic treatment. It is important to note that a greater number of high-quality randomized controlled trials are urgently needed.

The removal of unwanted gas bubbles is an important operation in many processes. In this paper, the mechanism of the degassing of highly viscous fluids by low-frequency vibration is studied numerically using the computational fluid dynamics (CFD). The effects of vibration frequency and amplitude on the degassing rate are investigated. The results show that the superimposed mechanical vibration largely affects the degassing rate of shear-thinning fluids but exerts no effect on that of Newtonian fluids. The de-gassing rate of shear-thinning fluids depends on the vibration frequency and amplitude. What’s more, low-frequency and small-amplitude vibration is particularly useful in re-moving gas bubbles from viscous shear-thinning fluids, however, high-frequency or large-amplitude vibration may intensify air entrapment and brings new gas bubbles into fluids.

Advanced research equipment like the SOLARIS synchrotron requires specific working conditions. One of the major disturbances are vibrations of the synchrotron foundation plate, derived from internal equipment and external sources. The purpose of the present research was to identify the dominant sources and to analyze the wave propagation path. In basic research, a set of circulating pumps for cooling liquid was selected and under controlled conditions measurements were made. As a result of the analysis of the data obtained, was revealed an inability to which could affect the work of the synchrotron. The paper presents partial results and conclusions from the research conducted.

This paper presents an advanced method of selecting the number of poles slots so as to reduce the vibration of a traction motor for a gearless elevator system. The vibration source, i.e., the radial electromagnetic force, of the prototype was examined through its analytical derivation. The expression indicated the vibration orders and frequencies of the radial electromagnetic force that was caused by the interactions within or between armature reaction and permanent magnet fields including the stator slotting effect. More specifically, the prototype with 14 poles and 18 slots displayed a problem in terms of the vibration at the two times line frequency; this was due to the lowest vibration order 2. The vibration at two times line frequency was decreased by approximately 77.27% through a selection of 24 poles and 54 slots with a lowest vibration order of 6. A tower test was then conducted in order to validate the proposed method. Finally, an experiment on models having other rated load and pole-slot combinations was also carried out to improve the overall reliability.

The hoop truss structure with extended arm has large diameter and great flexibility. These two characteristics cause low frequency and affect the technical requirements of modern satellite system. This article investigates the active vibration control of the hoop truss structure with extended arm. At first, proportional plus derivative algorithm and least mean square adaptive filtering algorithm are applied to derive the vibration control equation. Then, based on the first two modes calculated by finite elements method, the positions of the actuators are optimized. Finally, the excitation simulation and the closed-loop control simulation for suppressing the low frequency vibration are established. The simulation result illustrates that the amplitudes of the responses are decreased significantly under the steady state excitation after adopting the intelligent control algorithm.

The use of energy harvesting technologies for supplying power generating energy to wireless devices and sensors, particularly in scenarios where it is difficult to exchange or recharge batteries, has recently attracted considerable research attention. In this context, we report the design of a piezoelectric energy harvesting system that can be used to harvest energy from the ocean. The harvester is composed of a piezoelectric cantilever structure and a magnet as the tip-mass of the piezoelectric module, atop which a rail (tube) with a metal ball is positioned. The system is tested with a setup that simulates ocean waves. Our findings indicate that our approach can be utilized in the design of multipurpose piezoelectric energy harvesting systems for low frequency vibration and in “sea-based” applications involving buoys and boats.

Objective: This study examined the effects of low-frequency vibration on physiological recovery from exhaustive exercise. Methods: Twelve college males were recruited in this randomized crossover-designed study, and were asked to perform one of three treatments following a graded cycling exercise test: nonvibration (0 Hz, 0 mm, CON), high-amplitude vibration (8 Hz, 8 mm, HVT), or low-amplitude vibration (8 Hz, 2 mm, LVT). After the 10-min treatment, participants were asked to rest in a supine position for a 1-h recovery. The oxygen uptake, heart rate (HR), and blood lactate concentration (La) were measured during the trials. Results: The oxygen uptake during HVT were significantly higher than those in the CON and LVT (p < 0.05, effect size = 1.52−1.63). The La immediately following HVT was significantly lower than that following CON (HVT vs. CON = 11.52 ± 1.85 vs. 12.95 ± 1.78 mmol•L-1, p < 0.05, effect size = 1.94). Additionally, the Las following HVT and LVT at the post 30-min were significantly lower than that following the CON (HVT vs. LVT vs. CON = 4.72 ± 0.97 vs. 4.58 ± 1.06 vs. 5.98 ± 1.49 mmol•L-1, p < 0.05). No significant differences were found on the HRs, or on the time and frequency domain indices of HR variability among treatments during the recovery period. Conclusion: These results indicated that vibration with low frequency (8 Hz) can facilitate the removal of metabolic by-products after exhaustive exercise, but it has little effect on the autonomic nervous modulation of HR recovery.

Background: Understanding the potential effects on stroke outcome of the unique physical factors present in a helicopter ambulance flight is critical in the era of thrombectomy. However, this factor in patient care has not been adequately investigated. Methods: This was a prospective randomized blinded end-point animal study. A murine model of middle cerebral artery autologous thromboembolic occlusion (eMCAO) with rtPA reperfusion was exposed to three different settings: 1) a standardized actual helicopter flight, 2) a motion platform simulator that delivered the exact LFV signature of the helicopter, and 3) a ground control. Outcome measures included infarct size and BBB permeability on MRI, and neurological scores. Results: A total of 106 mice were analyzed. Within the rtPA group, LFV simulator mice displayed lower infarction volumes on MRI (31.6 vs. 54.9 mm 3 , p=0.007) and improved neurological scores (87 vs. 28%, p=0.0001) compared to ground control mice. By contrast, mice receiving saline did not show change in either infarction volume (80.9 vs. 95.3, p=0.8) or neurological scores (37 vs. 28%, p=0.7). No differences were seen in the actual helicopter flight group as compared with ground control. No treatment group showed any difference in permeability of the blood brain barrier, assessed by MRI. Conclusion: We found a synergistic beneficial effect of combining helicopter-like LFV and rtPA, which could provide a novel, safe, and potentially more efficacious intervention for patients with stroke. These results also suggest that non-LFV helicopter physical factors, such, as hypobaric environment, accelerations and noise, may have a negating effect on the otherwise positive effect of helicopter vibration on stroke outcomes. If so, strategies to minimize these negating factors might be expected to improve patient outcome.

In order to realize a small-sized energy harvester with high output, this study prototypes a small motor-driven gyroscopic power generator. Supplying energy to sensors and devices is the biggest problem for Internet of Things (IoT) systems. One solution is gyroscopic power generators, which are a type of vibrational generator that amplify the inertia force of weights by rotating them at high speed, and in doing so can obtain greater output than conventional generators that use simple vibration for the same mass weight. This paper reports on a motor-driven type gyroscopic generator in which the flywheel is spun with an embedded motor, and which is superior in applicability to random vibration generators. The generators of this type that have been studied thus far are very large and have been primarily used for wave power generation in the ocean. However, when the shape of this gyroscopic power generator type is miniaturized proportionally, the output per volume decreases in proportion to the fifth power of the dimension. This makes it difficult to maintain the power output while miniaturizing the generator size. In this research, the structure of the gyroscopic power generator is thoroughly refined and miniaturization is realized by making full use of the available space. By using a motor with high design freedom, the spindle motor and flywheel are unified. From this accomplishment, not only is the required space reduced, the number of mechanical parts and the friction loss are decreased as well. The prototype generator has a size of about 150 mm on its long side. When a swinging vibration of 50 degrees in amplitude and 2 Hz in frequency is applied, a net output of 0.104 W is obtained. This output power is sufficient to drive sensors and low power wide area (LPWA) radio circuits.

Low-frequency vibration has been troublesome for a mechanical system. Despite the measurement difficulties, low-frequency vibration also creates several environmental effects such as high noise level that is harmful to the human body. One of the methods to reduce vibration is tuning the vibration isolation i.e. spring and damping coefficient. However, the latter method is found to be effective only for the mid-high frequency range. Therefore, this paper proposes an optimization of the spring a.k.a. stiffness coefficient in order to reduce the low-frequency vibration. The Taguchi method is used as an optimization tool since it offers simplicity yet powerful for any field of application, particularly in engineering. Two significant parameters in the spring geometry were selected as the optimization variable in the Taguchi method and evaluated using vibration transmissibility concept. The result shows that the Taguchi method has been successfully obtained the optimum value for the spring geometry purposely to reduce the vibration transmissibility.

This paper introduces the circulation modes of table grapes, analyzes the damage of table grapes in the circulation process, and points out that the vibration effect of transport process is an important reason for the threshing of table grapes. In this study, a vibration monitoring system was designed and applied in the study of table grapes damage to explore the relationship between vibration and threshing of table grape under stable vibration conditions, providing experimental ideas and providing the relationship between threshing and damage energy according to Palmgren-Miner theory. Under the low frequency vibration, the lower the vibration frequency, the easier the table grape threshing.

This paper deals with loosening performance of bolts of transmission towers under low frequency vibration. To evaluate the loosening performance, 30 transverse tests for bolted joint are issued, whose frequency ranges from 1 Hz to 3Hz. The results show that double-nut bolts feature better loosening performance than single-nut bolts, and the loosening performance decreases along with the incensement of vibration frequency.

This paper mainly introduces the research progress of MEMS electromagnetic vibration energy harvester, hoping to provide valuable guidance and reference for researchers in related fields. In this paper, recent studies are divided into three groups according to their objectives and approaches: reducing the resonant frequency of the harvester to collect low frequency vibration energy from the environment; broadening the bandwidth of the harvester to increase the utilization of the random vibration energy; and developing new process compatible with MEMS for mass production. Besides, maintaining valuable output performances, such as power and power density, is also an important concern in these studies. Limited to the current technology, it is impossible to make a perfect harvester with low resonant frequency, wide frequency band, good compatibility with MEMS, and good output performances at the same time. However, we can focus on one or two characteristics according to the application, to which this paper provides valuable reference. More works on simulation, new process, and detailed design of the components are required in MEMS electromagnetic vibration energy harvesters.

Power plant of shunting locomotive is a powerful source of infrasound. If the level of infrasound is more than 100 dB, the time of operator work should be limited. The paper presents a simultaneous measurement of infrasound and low-frequency vibration at various modes and loads. The levels of infrasound and low-frequency vibration were measured inside the cabin and near the shunting locomotive. It was detected that infrasound depends on low-frequency vibration. There was a relationship between the level of infrasound and the opened window inside the cabin. Some recommendations to reduce the infrasound level were developed. The results indicate, overall, that the level of infrasound exceeds the standard values. The implementation of developed recommendation could reduce the level of infrasound.

We present a piezoelectric energy harvester with stopper-engaged dynamic magnifier which is capable of significantly increasing the operating bandwidth and the energy (power) harvested from a broad range of low frequency vibrations (

In this paper, an experimental investigation on the influence of glue on the low frequency vibroacoustic performance (up to 200 Hz) of wooden T-junctions is presented along with a discussion of modelling issues related to the junctions. The mock-ups studied represent cut-outs of full size timber floor assemblies typically used in Sweden. Their dynamic performance was first studied experimentally by means of modal analysis. Moreover, finite element (FE) simulations of the T-junctions were carried out to establish reliable prediction tools, using the measurement data as calibration input. Modelling issues were addressed to investigate the influence of different features that must be taken into account when simulating the connections as part of larger structures. Guidelines for modelling these type of connections, when developing low frequency FE predictive tools, are presented here.

Objective To explore ocular vestibular evoked myogenic potentials (oVEMP) to low-frequency vertex vibration (125 Hz) as a diagnostic test for superior canal dehiscence (SCD) syndrome. Methods The oVEMP using 125 Hz single cycle bone-conducted vertex vibration were tested in 15 patients with unilateral superior canal dehiscence (SCD) syndrome, 15 healthy controls and in 20 patients with unilateral vestibular loss due to vestibular neuritis. Amplitude, amplitude asymmetry ratio, latency and interaural latency difference were parameters of interest. Results The oVEMP amplitude was significantly larger in SCD patients when affected sides (53 μVolts) were compared to non-affected (17.2 μVolts) or compared to healthy controls (13.6 μVolts). Amplitude larger than 33.8 μVolts separates effectively the SCD ears from the healthy ones with sensitivity of 87% and specificity of 93%. The other three parameters showed an overlap between affected SCD ears and non-affected as well as between SCD ears and those in the two control groups. Conclusions oVEMP amplitude distinguishes SCD ears from healthy ones using low-frequency vibration stimuli at vertex. Significance Amplitude analysis of oVEMP evoked by low-frequency vertex bone vibration stimulation is an additional indicator of SCD syndrome and might serve for diagnosing SCD patients with coexistent conductive middle ear problems.

The effect of using a novel additional anti-vibration sleeper track (AAST) to reduce low-frequency vibrations (40–80 Hz) is investigated via numerical and field tests. A computational model is used to investigate the effects of sleeper spacing and track support stiffness. To verify the performance of the AAST, a field test was performed. The results confirmed that sleeper spacing and track support stiffness could be adjusted to control the vibration of subgrade in the targeted low-frequency range. The numerical and field test results demonstrated that the AAST can effectively reduce the low-frequency vibrations by reducing vibration transmission to the subgrade.

The development and use of a practical method for producing antioxidants (less energy-consuming and more economically viable) is relevant and contributes to the expansion of the market of “functional” products and the receipt of new dietary supplements. An experimental model of a laboratory low-frequency vibration extractor was developed to intensify the technological process of extraction from plant material containing ALS. Some technological parameters of the anthocyanins extraction process have been determined: raw material / extractant ratio, % extractant concentration, as well as some design parameters of a pilot plant (vibration extractor). The possibility of obtaining anthocyanins from the waste of the fruit and berry industry with a high percentage yield of biologically active substances has been experimentally shown.

Paper and paper products banknotes play an important role in daily life. Two terahertz (THz) time-domain spectrometers (TDS) with combined spectral coverage from 0.5 to 10 THz were used to characterize the optical properties of several types of paper and banknotes. We found that the paper and banknotes show remarkable fingerprints in the terahertz regime, which are highly related to the vibrational modes of the main component of paper and banknotes — cellulose. Meanwhile, THz transmission imaging measurements had been performed and shown the capability of imaging the key anti-counterfeit labels of banknotes such as watermarks, security threads and optically variable inks. The presented study here indicates that the THz spectroscopy together with the imaging method could provide a visible, contactless and nondestructive alternative to delineating paper and paper product banknotes.

Swimming pools need some sort of alarm system to indicate if someone or an article have dropped into the water. This article conveys the methods and practices used in the detection and analysis of low frequency vibrations in water for this purpose. Logged data are used to develop a digital signal processing system that is able to distinguish between different vibration signatures to determine the source of the vibration. Conclusions are drawn from the results and the viability of the technology is evaluated.

An articulated railway vehicle (ARV) experienced an abnormal vibration on car body which deteriorates its riding comfort significantly. On-track experiments were conducted considering the wheel-rail interaction, the vibration transmission of primary and secondary suspensions, to locate the vibration sources and find a solution. Compared to the existing dynamics tests performed on a railway vehicle, the modes of car body motions were further recorded as well as its structural modes when the vehicle was operated on track. Furtherly, the lateral motion of the wheelset and car body were recorded by a video surveillance on-board to check the modes of motion of the vehicle system for the first time. The tests performed in this work extends the field measurement techniques and can be used on track for the railway vehicle dynamics analysis. It is shown that measured wheel profiles have a small radius difference which lead to a low equivalent conicity of wheelset, which in turn introduces a low-frequency hunting motion of wheelset in case of a soft steering. The yaw motion of the car body was excited by the wheelset hunting and then the coupled vibration between the wheelset and car body deteriorates the ride comforts of ARV. A solution of this low frequency vibration on vehicle system is to increase the wheelset conicity and has been verified on-track. Additionally, reduce the stiffness of the anti-yaw damper can improve the ride comfort in case of a low conicity.

Several mechanisms of wear can occur in rolling element bearings (REBs). As the wear evolves, the vibration level will increase with the growth of internal clearance of bearings due to the variation of contact force and dynamic excitation. Therefore, for accurate fault severity diagnosis, internal clearance increase caused by inevitable wear has to be taken into account. In this paper, clearance variation caused by the wear of tapered rolling bearings (TRBs) is investigated experimentally and clearance estimation is carried out based on analysis of low frequency vibrations and the deviation of the fault features. An experimental study is ingeniously designed to simulate the wear evolutions and evaluate their influence on well-accepted envelope signatures according to vibrations measured from TRBs. The defective bearings were diagnosed in two aspects: the magnitude variation of vibrations in the low frequency band and the peak frequency deviation. The experimental results give out a signature shift with regard to the wear evolution, also vibration magnitude of the low frequency band grew remarkably. Therefore, unavoidable wear can be estimated and consequently the fault severity diagnosis improved.

The rotation of flat parts relative to the center of mass in vibration is analytically described. It is demonstrated that specific relative orientations of complex two-dimensional parts may be ensured in automatic assembly.

In order to set integrated procedures involving geotechnical and structural aspects finalized to buildings diagnostics, uncertainty aspects are discussed concerning three-axis accelerometers and inclinometers for a distributed sensor network. This network allows to operate in a selective manner, preferring the most critical situations. To this aim, the main aspects affecting the measurement uncertainty of sensors to be used for building diagnostic should be known. As the firstly step of the uncertainty evaluation procedure, we focused on the calibration of sensors used for the task. The requirement of low cost and complexity of sensors and test benches was considered. Experimental results show that satisfactory calibration accuracy could be achieved, also for the low frequency range, 0–10 Hz. Systematic errors are minimized and main parameters affecting uncertainty are identified, such as: the motion positioning of the accelerometer with respect to the vertical axis, the imposed motion law, the parameter used as the reference and, finally, the real radial positioning of the sensor. Requirements to be satisfied by the sensor are also analysed.