Hz Vibration Research Articles

Analysis of shaking-induced cherry fruit motion and damage

High percentage of shaking-induced fruit damage is the major obstacle for mechanical harvesting of fresh-market sweet cherry. This study focused on the evaluation of the effect of vibration frequency on fruit motion, detaching time and damage during mechanical cherry harvesting with a shaker. A high-speed camera was used to capture the fruit trajectory on eighteen limbs excited at the frequencies of 10, 14 and 18 Hz. Fruit detaching time and number of fruit-to-fruit and fruit-to-limb impact were extracted from the high speed videos for determining the factors affecting fruit removal and damage. Results showed that the majority of the four identified motion patterns were tilting and beam-column motion, accounting for more than 70% of all patterns. Fruit detaching time was significantly affected by vibration frequency with fast detaching at high frequencies. Vibration frequency affected the overall fruit damage percentage substantially, with the lowest damage percentage of 47.1% in 14 Hz, which might be caused by high percentage of beam-column motion during vibration at the frequency. Meanwhile, 18 Hz vibration resulted in a higher percentage (35%) of unmarketable fruits than that of 10 Hz and 14 Hz. On average, a fruit experienced 3.8 impacts against limbs and other fruit at 18 Hz excitation, substantially lower than that of 11.8 impacts at 14 Hz or 11.7 impacts at 10 Hz excitation. Overall, the results indicate that shorter duration of high-level mechanical impacts could induce higher fruit damage.

Low-frequency, low-magnitude vibrations (LFLM) enhances chondrogenic differentiation potential of human adipose derived mesenchymal stromal stem cells (hASCs).

The aim of this study was to evaluate if low-frequency, low-magnitude vibrations (LFLM) could enhance chondrogenic differentiation potential of human adipose derived mesenchymal stem cells (hASCs) with simultaneous inhibition of their adipogenic properties for biomedical purposes. We developed a prototype device that induces low-magnitude (0.3 g) low-frequency vibrations with the following frequencies: 25, 35 and 45 Hz. Afterwards, we used human adipose derived mesenchymal stem cell (hASCS), to investigate their cellular response to the mechanical signals. We have also evaluated hASCs morphological and proliferative activity changes in response to each frequency. Induction of chondrogenesis in hASCs, under the influence of a 35 Hz signal leads to most effective and stable cartilaginous tissue formation through highest secretion of Bone Morphogenetic Protein 2 (BMP-2), and Collagen type II, with low concentration of Collagen type I. These results correlated well with appropriate gene expression level. Simultaneously, we observed significant up-regulation of α3, α4, β1 and β3 integrins in chondroblast progenitor cells treated with 35 Hz vibrations, as well as Sox-9. Interestingly, we noticed that application of 35 Hz frequencies significantly inhibited adipogenesis of hASCs. The obtained results suggest that application of LFLM vibrations together with stem cell therapy might be a promising tool in cartilage regeneration.

Hybrid distributed acoustic and temperature sensor using a commercial off-the-shelf DFB laser and direct detection.

We demonstrate a hybrid distributed acoustic and temperature sensor (DATS) using a commercial off-the-shelf (COTS) distributed feedback (DFB) laser, a single-mode optical fiber, and a common receiver block. We show that the spectral and frequency noise characteristics of the laser, combined with a suitable modulation scheme, ensure the inter-pulse incoherence and intra-pulse coherence conditions required for exploiting the fast denoising benefits of cyclic Simplex pulse coding in the hybrid measurement. The proposed technique enables simultaneous, distributed measurement of vibrations and temperature, with key industrial applications in structural health monitoring and industrial process control systems. The sensor is able to clearly identify a 500 Hz vibration at 5 km distance along a standard single-mode fiber and simultaneously measure the temperature profile along the same fiber with a temperature resolution of less than 0.5°C with 5 m spatial resolution.

In vivo, high-frequency three-dimensional cardiac MR elastography: Feasibility in normal volunteers.

Noninvasive stiffness imaging techniques (elastography) can image myocardial tissue biomechanics in vivo. For cardiac MR elastography (MRE) techniques, the optimal vibration frequency for in vivo experiments is unknown. Furthermore, the accuracy of cardiac MRE has never been evaluated in a geometrically accurate phantom. Therefore, the purpose of this study was to determine the necessary driving frequency to obtain accurate three-dimensional (3D) cardiac MRE stiffness estimates in a geometrically accurate diastolic cardiac phantom and to determine the optimal vibration frequency that can be introduced in healthy volunteers. The 3D cardiac MRE was performed on eight healthy volunteers using 80 Hz, 100 Hz, 140 Hz, 180 Hz, and 220 Hz vibration frequencies. These frequencies were tested in a geometrically accurate diastolic heart phantom and compared with dynamic mechanical analysis (DMA). The 3D Cardiac MRE was shown to be feasible in volunteers at frequencies as high as 180 Hz. MRE and DMA agreed within 5% at frequencies greater than 180 Hz in the cardiac phantom. However, octahedral shear strain signal to noise ratios and myocardial coverage was shown to be highest at a frequency of 140 Hz across all subjects. This study motivates future evaluation of high-frequency 3D MRE in patient populations. Magn Reson Med 77:351-360, 2017. © 2016 Wiley Periodicals, Inc.

A multiphysics model of the Pacinian corpuscle.

The Pacinian corpuscle (PC) is a dermal mechanoreceptor that responds to high-frequency (20-1000 Hz) vibrations. The PC's structure allows transmission of vibrations through its layers (lamellae) to the centrally-located nerve fiber (neurite). This work combines mechanical models of the PC with an electrochemical model of peripheral nerves to simulate the tactile response of the entire system. A three-stage model of response to a vibratory input was developed, consisting of (1) outer core mechanics, (2) inner core mechanics, and (3) neurite electrochemistry. The model correctly predicts the band-pass nature of the PC's frequency response, showing that the PC structure can amplify oscillatory strains within its target frequency band. Specifically, strain induced by a vibratory stimulus is amplified by a factor of 8-12 from the PC surface to the neurite. Our results also support the hypothesis that PC rapid adaptation is affected by the lamellar structures without requiring neuronal adaptivity. Simulated different-sized PCs showed a shift in frequency response, suggesting that clusters of different-sized PCs could enable more nuanced tactile encoding than uniform clusters. By modeling the PC's mechano-to-neural transduction, we can begin to characterize the mechanosensation of other receptors to understand how multiple receptors interact to create our sensation of touch.

TO A QUESTION OF FEASIBILITY OF APPLICATION OF 100 HZ VIBRATION IN TREATMENT AND REHABILITATION OF THE PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY DISEASE

The aim of this research is study of feasibility of application of instrumental 100 Hz vibration of the thorax for rehabilitation of COPD patients. Materials and methods . This aim is achieved by clinical observation of 43 COPD patients of 1st and 2nd severity, 77.4 % from which were patients with low risk of exacerbations. Research has been carried out during the stable period of disease. The following parameters have been analyzed: dynamics of the clinical state, spirometry data, clinical - biochemical indicators of blood reflecting presence of the inflammatory process activity, a number of indicators of immune system. Two groups of patients, which were equivalent in an initial state on age, disease severity, expressiveness of functional violations, have been isolated. The 1st group contained 20 persons was the main one. It received 100 Hz vibration impact on the thorax on the background of exercises with physical therapy and inhalations of physiological solution. The 2nd group contained 23 persons obtained in addition sea-buckthorn paste. Results. It has been revealed that the course of 100 Hz vibration impact on the thorax is accompanied, mainly, with positive subjective dynamics in the form of decrease of frequency and expressiveness of complaints. At that it has been noted improvement of bronchial passability due to improved drainage of bronchial tubes, but only at the patients with initial violations of ventilation. Only additional reception of sea-buckthorn paste on the background of vibrotherapy contributes to decrease of subclinical inflammation activity and strengthening of immunological protection. Essential positive results of treatment have been reached only for a half of the surveyed patients that allows to speak about non-expediency or low expediency of use of 100 Hz vibration for CODT patients even 1st and 2nd severity in the stable period of course of the disease.

Determination of parameters of mechanical pulse action on the weld pool for the metal structuring in automatic arc deposition welding

The strength and other operational characteristics of the metal during arc deposition welding processes are determined by the presence of columnar crystals, the growth of which occurs as a result of metal overheating in the molten bath. To control the columnar crystals growth, a variety of methods are used, including pulse impacts on the weld pool or creating mechanical vibrations of the part during deposition welding. In the latter case, the periodic removal of the heat source from the point of the weld pool overheating prevents the growth of columnar crystallites and thus improves the weld metal structure. The developed engineering method for calculating the effective parameters of the mechanical vibrations of the weld pool during automatic deposition welding of cylindrical parts in CO2 is based on the theory of heat transfer at welding. It is shown that deposit welding on the mild steel St.3 with the Sv08G2C wire of the 1.2 mm diameter should be carried out with the 1...12 Hz vibration frequency at the amplitude equal to 1/2 of the deposition welding step. Experimental verification of various mode parameters showed that, compared to the welding performed without vibration of the weld pool, the weld bead width is increased by 16...23% in the deposited layer, there are no cracks, and its durability improved by 1.3...1.7 times. The improvement of mechanical properties of the deposited layer is due to grinding of metal grains exposed to the controlled vibrations of the part. At that, there are hardly any weld metal columnar structures, which are observed at conventional deposition welding.

Effect of Tendon Vibration on Hemiparetic Arm Stability in Unstable Workspaces.

Sensory stimulation of wrist musculature can enhance stability in the proximal arm and may be a useful therapy aimed at improving arm control post-stroke. Specifically, our prior research indicates tendon vibration can enhance stability during point-to-point arm movements and in tracking tasks. The goal of the present study was to investigate the influence of forearm tendon vibration on endpoint stability, measured at the hand, immediately following forward arm movements in an unstable environment. Both proximal and distal workspaces were tested. Ten hemiparetic stroke subjects and 5 healthy controls made forward arm movements while grasping the handle of a two-joint robotic arm. At the end of each movement, the robot applied destabilizing forces. During some trials, 70 Hz vibration was applied to the forearm flexor muscle tendons. 70 Hz was used as the stimulus frequency as it lies within the range of optimal frequencies that activate the muscle spindles at the highest response rate. Endpoint position, velocity, muscle activity and grip force data were compared before, during and after vibration. Stability at the endpoint was quantified as the magnitude of oscillation about the target position, calculated from the power of the tangential velocity data. Prior to vibration, subjects produced unstable, oscillating hand movements about the target location due to the applied force field. Stability increased during vibration, as evidenced by decreased oscillation in hand tangential velocity.

The role of vibration in tactile speed perception.

The relative motion between the surface of an object and our fingers produces patterns of skin deformation such as stretch, indentation, and vibrations. In this study, we hypothesized that motion-induced vibrations are combined with other tactile cues for the discrimination of tactile speed. Specifically, we hypothesized that vibrations provide a critical cue to tactile speed on surfaces lacking individually detectable features like dots or ridges. Thus masking vibrations unrelated to slip motion should impair the discriminability of tactile speed, and the effect should be surface-dependent. To test this hypothesis, we measured the precision of participants in discriminating the speed of moving surfaces having either a fine or a ridged texture, while adding masking vibratory noise in the working range of the fast-adapting mechanoreceptive afferents. Vibratory noise significantly reduced the precision of speed discrimination, and the effect was much stronger on the fine-textured than on the ridged surface. On both surfaces, masking vibrations at intermediate frequencies of 64 Hz (65-μm peak-to-peak amplitude) and 128 Hz (10 μm) had the strongest effect, followed by high-frequency vibrations of 256 Hz (1 μm) and low-frequency vibrations of 32 Hz (50 and 25 μm). These results are consistent with our hypothesis that slip-induced vibrations concur to the discrimination of tactile speed.

Proprioceptive Interaction between the Two Arms in a Single-Arm Pointing Task.

Proprioceptive signals coming from both arms are used to determine the perceived position of one arm in a two-arm matching task. Here, we examined whether the perceived position of one arm is affected by proprioceptive signals from the other arm in a one-arm pointing task in which participants specified the perceived position of an unseen reference arm with an indicator paddle. Both arms were hidden from the participant’s view throughout the study. In Experiment 1, with both arms placed in front of the body, the participants received 70–80 Hz vibration to the elbow flexors of the reference arm (= right arm) to induce the illusion of elbow extension. This extension illusion was compared with that when the left arm elbow flexors were vibrated or not. The degree of the vibration-induced extension illusion of the right arm was reduced in the presence of left arm vibration. In Experiment 2, we found that this kinesthetic interaction between the two arms did not occur when the left arm was vibrated in an abducted position. In Experiment 3, the vibration-induced extension illusion of one arm was fully developed when this arm was placed at an abducted position, indicating that the brain receives increased proprioceptive input from a vibrated arm even if the arm was abducted. Our results suggest that proprioceptive interaction between the two arms occurs in a one-arm pointing task when the two arms are aligned with one another. The position sense of one arm measured using a pointer appears to include the influences of incoming information from the other arm when both arms were placed in front of the body and parallel to one another.

Effects of Short-Period Whole-Body Vibration of 20 Hz on Selected Blood Biomarkers in Wistar Rats.

There is a growing interest in the use of vibration generated by oscillating/vibratory platforms - also known as whole-body vibration (WBV) - for achieving therapeutic, preventative and/or physical performance goals. This study investigated the effects of vibration generated by an oscillating platform on the concentration of blood biomarkers in rats. Wistar rats (n = 8) were divided in 2 groups, sedated and individually positioned on an oscillating platform. The experimental group (EG) was subjected to vibrations of 20 Hz for one min per day for one week while the control group (CG) experienced no vibration. Samples of heparinized whole blood were drawn by cardiac puncture for biochemical analysis. Concentrations of total cholesterol, triglycerides, HDL, LDL, VLDL, glucose, CK, albumin, alkaline phosphates, TGP, TGO, γGT, lipase, amylase, urea and creatinine were determined. White blood cell count and a platelet hemogram were also performed. Following seven sessions of exposure to the vibration, a significant (P < 0.05) reduction in γGT, VLDL and leukocytes was found. A weekly 1-min/day exposure of 20 Hz vibration can was shown to alter the concentrations of selected blood biomarkers in rats. The action mechanism associated with these effects seems highly complex, but the findings might contribute to the understanding of these mechanisms related to the exposure to 20 Hz vibration.

Effect of higher frequency components and duration of vibration on bone tissue alterations in the rat-tail model

To formulate more accurate guidelines for musculoskeletal disorders (MSD) linked to Hand-Arm Vibration Syndrome (HAVS), delineation of the response of bone tissue under different frequencies and duration of vibration needs elucidation. Rat-tails were vibrated at 125 Hz (9 rats) and 250 Hz (9 rats), at 49 m/s2, for 1D (6 rats), 5D (6 rats) and 20D (6 rats); D=days (4 h/d). Rats in the control group (6 rats for the vibration groups; 2 each for 1D, 5D, and 20D) were left in their cages, without being subjected to any vibration. Structural and biochemical damages were quantified using empty lacunae count and nitrotyrosine signal-intensity, respectively. One-way repeated-measure mixed-model ANOVA at p<0.05 level of significance was used for analysis. In the cortical bone, structural damage quantified through empty lacunae count was significant (p<0.05) at 250 Hz (10.82 ± 0.66) in comparison to the control group (7.41 ± 0.76). The biochemical damage was significant (p<0.05) at both the 125 Hz and 250 Hz vibration frequencies. The structural damage was significant (p<0.05) at 5D for cortical bone while the trabecular bone showed significant (p<0.05) damage at 20D time point. Further, the biochemical damage increased with increase in the duration of vibration with a significant (p<0.05) damage observed at 20D time point and a near significant change (p=0.08) observed at 5D time point. Structural and biochemical changes in bone tissue are dependent upon higher vibration frequencies of 125 Hz, 250 Hz and the duration of vibration (5D, 20D).

Heterodyne interferometry for the detection of elastic waves: a tutorial and open-hardware project

Non-contacting acoustic and ultrasonic measurements are of interest in applications ranging from nondestructive evaluation to rock physics and medical imaging. The fundamental workings of the detector—the interferometer—are easily explained in undergraduate physics courses, but practical implementations are dominated by specialized, and commercial, devices. We present a robust and relatively inexpensive detector, which consists of a heterodyne interferometer and phase locked loop frequency demodulator, as an open-source alternative. We illustrate the broadband capabilities with the detection of ultrasonic waves in a mudstone sample, and low-frequency (100 Hz) vibrations of a piston.

Effect of vibration during GTAW welding on microstructure and mechanical properties of Ti6Al4V

Grain growth in Ti6Al4V alloy during fusion welding decreases yield stress and tensile strength. This study examined the effect of mechanical vibration of the work piece during GTAW welding on the mechanical and metallurgical properties of Ti6Al4V. The structures of all welded specimens at different levels of vibration was examined and it was found that, during 330 Hz vibration, grain size in the welded metal zone decreased significantly over that of pieces welded without vibration. GTAW at 330 Hz significantly increased the mechanical properties and produced the highest yield strength, tensile strength and percentage of elongation. The highest level of hardness in the welded metal zone was achieved under this condition.

Thermal and Element Analyses for Supercritical RP-3 Surface Coke Deposition under Stable and Vibration Conditions

A surface coke deposition mechanism on the supercritical aviation kerosene RP-3 was studied under stable and vibration conditions. The flowing RP-3 kerosene is pressurized to 5 MPa and heated from 400 to 723 K in a stainless tube (inner diameter, 1.8 mm; outer diameter, 2.2 mm; and length, 1800 mm) with a constant heat flux. The experimental mass flow rate is fixed at 3 g/s (1180 kg m–2 s–1), and the working fuel flows downward through the test tube. The 1 h stable, 1 h with 600 Hz vibration, and long duration with 566 Hz vibration tube jam experiments were performed. The two vibration frequencies are close to the main frequencies of the combustion chamber vibration when it works. Flow resistance, heat-transfer characteristics, coking amount, and component analysis were compared between stable and vibration conditions. The results indicate that vibration can affect the coking distribution much more uniformly and extend the tube working time. Also, vibration inhibits the exponential growth of flow resistan...

Effects of Hand Vibration on Motor Output in Chronic Hemiparesis

Background.Muscle vibration has been shown to increase the corticospinal excitability assessed by transcranial magnetic stimulation (TMS) and to change voluntary force production in healthy subjects.Objectives.To evaluate the effect of vibration on corticospinal excitability using TMS and on maximal motor output using maximal voluntary contraction (MVC) in individuals with chronic hemiparesis.Methodology.Nineteen hemiparetic and 17 healthy control subjects participated in this study. Motor evoked potentials (MEPs) and MVC during lateral pinch grip were recorded at first dorsal interosseous muscle in a single session before, during, and after one-minute trials of 80 Hz vibration of the thenar eminence.Results.In hemiparetic subjects, vibration increased MEP amplitudes to a level comparable to that of control subjects and triggered a MEP response in 4 of 7 patients who did not have a MEP at rest. Also, vibration increased the maximal rate of force production (dF/dtmax⁡) in both control and hemiparetic subjects but it did not increase MVC.Conclusion.Motor response generated with a descending cortical drive in chronic hemiparetic subjects can be increased during vibration. Vibration could be used when additional input is needed to reveal motor responses and to increase rate of force generation.

Tunable MEMS piezoelectric energy harvesting device

This work is focused on low frequency (<300 Hz) vibrations due to the fact that many industrial and commercial devices operate at those frequencies. The aim of the present work is to model by numerical simulation a Si cantilever beam with an AlN piezoelectric layer concept that tunes its resonant frequency post-processing, while reducing the separation of the first two modes of resonance in order to broaden its quality factor and, therefore, to harvest more environmental energy. This paper investigates by numerical simulation the influence of perforating sections of the Si beam has on the resonant frequencies of the cantilever. The authors have found that the distance between these modes is decreased by 30 % when 0.002 mm3 is extracted in a specific location of the initial structure. This difference between modes can be reduced above 80 % if a volume of 0.004 mm3 in a specific part of the initial design is subtracted. In these conditions, the first mode is decreased about 20 % the initial value and the second mode about 60 %.

Effect of higher frequency components and duration of vibration on bone tissue alterations in the rat-tail model.

To formulate more accurate guidelines for musculoskeletal disorders (MSD) linked to Hand-Arm Vibration Syndrome (HAVS), delineation of the response of bone tissue under different frequencies and duration of vibration needs elucidation. Rat-tails were vibrated at 125 Hz (9 rats) and 250 Hz (9 rats), at 49 m/s(2), for 1D (6 rats), 5D (6 rats) and 20D (6 rats); D=days (4 h/d). Rats in the control group (6 rats for the vibration groups; 2 each for 1D, 5D, and 20D) were left in their cages, without being subjected to any vibration. Structural and biochemical damages were quantified using empty lacunae count and nitrotyrosine signal-intensity, respectively. One-way repeated-measure mixed-model ANOVA at p<0.05 level of significance was used for analysis. In the cortical bone, structural damage quantified through empty lacunae count was significant (p<0.05) at 250 Hz (10.82 ± 0.66) in comparison to the control group (7.41 ± 0.76). The biochemical damage was significant (p<0.05) at both the 125 Hz and 250 Hz vibration frequencies. The structural damage was significant (p<0.05) at 5D for cortical bone while the trabecular bone showed significant (p<0.05) damage at 20D time point. Further, the biochemical damage increased with increase in the duration of vibration with a significant (p<0.05) damage observed at 20D time point and a near significant change (p=0.08) observed at 5D time point. Structural and biochemical changes in bone tissue are dependent upon higher vibration frequencies of 125 Hz, 250 Hz and the duration of vibration (5D, 20D).

Study on the Characteristics of Low-Frequency Vibration of the Core of Single Phase Transformer Set Caused by GIC

The study on characteristics of transformer vibration caused by GIC is the foundation of studies on transformer noise caused by GIC, location selection of monitoring vibration and noise. In this study, the characteristics of low-frequency vibration of the core of single phase transformer sets caused by GIC have been analyzed through building mathematical models and experimental analysis. The results show that when DC bias occurs the vibration signals contain 50 Hz and 150 Hz vibration. With the degree of DC bias the 50 Hz vibration grows by linear increase and 150 Hz vibration grows by square increase. Affected by GIC, the 50 Hz and 150 Hz vibration waveform’s phase changes with alternate 0 andπ. The characteristics of 50 Hz and 150 Hz vibration discriminate between core vibration caused by GIC and HVDC grounding currents. This study has significance for vibration monitoring of transformer faults, and can assist in determining the level of GIC.

Mechanical Amplifier for Translational Kinetic Energy Harvesters

This paper reports the design, optimization, and test results of a mechanical amplifier coupled to an electromagnetic energy harvester to generate power from low- amplitude (±1 mm) and low-frequency (<5 Hz) vibrations in the presence of large static displacements. When coupled to a translational kinetic energy harvester, the amplifier boosts small vibration amplitudes by as much as 4x while accommodating translational displacements of more than 10x of vibration amplitudes. A complete electromagnetic energy harvester using this mechanical amplifier produces 16x improvement in output power (30 mW vs 1.9 mW without amplifier at 5 Hz), and a high power density of 170 μW/cm3.