Absence Of Vibration Research Articles

A broadband vibrational energy harvester

We propose a design for an energy harvester which has the potential to harvest vibrational energy over a broad range of ambient frequencies. The device uses two flexible ceramic piezoelectric elements arranged in a buckled configuration in the absence of vibrations. Experimental data show that this design allows enhanced harvesting of energy relative to a comparable cantilever design, both for periodic and stochastic vibrations. Moreover, the data suggest that this harvester has its peak energy generation when it responds with chaotic vibrations.

Influence of Sound Vibration on Diamond-Like Carbon Deposition Rate

This work examines how vapor-deposited coating of DLC (partially diamond) on stainless steel 304 substrate is affected by the sound vibration. For this, a specially designed chemical vapor deposition (thermal CVD and hot filament) apparatus having facility of generating sound vibration at different frequency is fabricated. A coating of DLC (partially diamond) has been deposited on the substrate, and the characterization of the coating has been done by SEM, EDX, and XRD. The coating of carbon is identified by EDX, and the allotropic forms of graphite and diamond peaks of carbon are found by XRD analysis. By SEM analysis, it is found that the microstructures of deposited coatings are more compact and smoother under vibration than those in absence of vibration. The experiments were conducted under different ranges of vibration including sonic and ultrasonic range. Studies have shown that the growth rate of deposited coating on a unit area is higher under vibration than that in absence of vibration. It is found that deposition rate varies with the distance between substrate and activation heater and frequency of vibration. The deposition rate does not vary significantly with the change of frequency in the sonic range. The amount of deposition under ultrasonic vibration increases significantly with the frequency of vibration upto 5-6 mm distance between substrate and activation heater. Within this distance, the difference of deposition rate under vibration and without vibration conditions increases almost linearly with the increase of frequency of vibration. Beyond this distance, the effect of frequency on deposition rate becomes almost constant. In addition, the higher the distance, the less is the effectiveness of frequency of vibration on the deposition rate in that range. The deposition rate increases due to the extra vibration of sound added to the system which may enhance the activation energy by increasing its kinetic energy. The experimental results are compared with those available in the literature, and physical explanations are provided.

Effect of vibration on solid-to-liquid transition in small granular systems under shear

The effect of vibration on the solid-to-liquid-like transition of a dense granular assembly under planar shear is studied numerically using soft particle molecular dynamics simulations in two dimensions. We focus on small systems in a thin planar Couette cell, examining the bistable region while increasing shear, with varying amounts of vertical vibration, and determine statistics of the shear required for fluidization. In the absence of vibration, the threshold value of the shear stress depends on the preparation of the system and has a broad distribution. However, adding periodic vibration both lowers the mean fluidization threshold value of the shear stress and decreased its variability. A previous study performed similar simulations using random noise; the results from these two studies exhibit excellent agreement with proper normalization over appropriate ranges of parameters.

Field emission of electrons from a single carbon fiber with a nanostructured emitting surface

The field emission of electrons from a single fine carbon fiber with a nanostructured emitting surface is studied experimentally. It is found that the fiber can serve as an effective field emitter of electrons at voltages of ∼102–103 under the conditions of technical vacuum and the emission current density may reach ∼102 A/cm2. At a certain threshold voltage, the fiber starts executing flexural mechanical vibrations. The onset of mechanical vibrations is accompanied by a change in the field emission conditions. Namely, in the absence of vibrations, the mode of steady current extraction is observed. When mechanical vibrations set in, the field emission switches to the mode of current periodic oscillations with a constant component.

Jamming, Yielding, and Rheology of Weakly Vibrated Granular Media

We establish that the rheological curve of dry granular media is nonmonotonic, both in the presence and absence of external mechanical agitations. In the presence of weak vibrations, the nonmonotonic flow curves govern a hysteretic transition between slow but steady and fast, inertial flows. In the absence of vibrations, the nonmonotonic flow curve governs the yielding behavior of granular media. Finally, we show that nonmonotonic flow curves can be seen in at least two different flow geometries and for several granular materials.

Effects of whole-body vibration and resistance training on knee extensors muscular performance

Whole-body vibration (WBV) is being promoted as an efficient complement to resistance training. The aim of this study was to investigate the effects of an 8-week program of WBV in combination with resistance training on knee extensors muscular performance. A group of 29 young adults (25 men, 4 women; age 21.8±1.5) performed a WBV plus resistance training program (WBV+RES) or an identical exercise program in absence of vibration (placebo plus resistance training, PL+RES). Participants were evaluated for anthropometry, muscle strength (half-squat three repetition maximum, 3RM), knee extensors isokinetic dynamometry (180° and 60°s(-1)) and counter-movement jump (CMJ). After the intervention, percent body fat significantly decreased 2.1% only in WBV+RES (P<0.001), while muscle mass significantly increased in both groups (P<0.01): 2.2 and 2.8kg in PL+RES and WBV+RES, respectively. No significant differences were observed in isokinetic strength or CMJ, and 3RM significantly increased in both groups (P<0.001): 64.2kg (52% of baseline) in PL+RES, and 46.9kg (43%) in WBV+RES. The addition of WBV to resistance training during 8weeks, in recreationally active young adults, did not result in a larger muscular performance improvement compared to an identical exercise program in absence of vibration. Muscle mass also seemed to be equally affected with or without vibration, yet body fat could be exclusively decreased by WBV. Further research is required to clarify whether WBV, as a complement to resistance training, produces additional specific benefits.

Evidence for involvement of TRPA1 in the detection of vibrations by hair bundle mechanoreceptors in sea anemones

A homolog of TRPA1 was identified in the genome of the anemone, Nematostella vectensis (nv-TRPA1a), and predicted to possess six ankyrin repeat domains at the N-terminus and an ion channel domain near the C-terminus. Transmembrane segments of the ion channel domain are well conserved among several known TRPA1 polypeptides. Inhibitors of TRPA1 including ruthenium red decrease vibration-dependent discharge of nematocysts in N. vectensis and Haliplanella luciae. Activators of TRPA1 including URB-597 and polygodial increase nematocyst discharge in the absence of vibrations. Co-immunoprecipitation yields a band on SDS-PAGE gels at the predicted mass of the nv-TRPA1a polypeptide among other bands. Co-immunoprecipitation performed in the presence of antigenic peptide decreases the yield of this and several other polypeptides. In untreated controls, anti-nv-TRPA1a primarily labels the base of the hair bundle with some labeling also distributed along the length of stereocilia. Tissue immunolabeled in the presence of the antigenic peptide exhibits reduced labeling. Activating chemoreceptors for N-acetylated sugars induce immunolabel to distribute distally in stereocilia. In anemones, activating chemoreceptors for N-acetylated sugars induce hair bundles to elongate among several other structural and functional changes. Taken together, these results are consistent with the possibility that nv-TRPA1a participates in signal transduction of anemone hair bundles.

Quantized attractors in wave models of torsion vibrations of deep-hole drill strings

We pose the problem of self-excitation of elastic wave torsional vibrations of a rotating drill string, which arise as a result of frictional interaction of the drill bit with the rock at the bottom of the deep hole. We use d’Alembert’s solution of the wave equation to construct a mathematical model of the wave torsion pendulum in the form of a nonlinear ordinary differential equation with retarded argument. We show that there exists a range of variation in the angular velocity of the drill string rotation, where, along with the unstable stationary solution characterized by the absence of vibrations, there are oscillatory solutions in the form of a stable limit cycle (attractor). The self-excitation of these vibrations is soft, and the self-oscillations themselves belong to the class of relaxation vibrations, because their period can be divided into several separated intervals corresponding to slow and fast variations in the state of the system. The velocities of the drill bit elastic motions on each of these time intervals remain constant, and the durations of all of them are the same and equal to the time interval (quantum) of the twist mode propagation from the drill bit to the drill string top and conversely.

Journey of an intruder through the fluidization and jamming transitions of a dense granular media

We study experimentally the motion of an intruder dragged into an amorphous monolayer of horizontally vibrated grains at high packing fractions. This motion exhibits two transitions. The first transition separates a continuous motion regime at comparatively low packing fractions and large dragging force from an intermittent motion one at high packing fraction and low dragging force. Associated to these different motions, we observe a transition from a linear rheology to a stiffer response. We thereby call "fluidization" this first transition. A second transition is observed within the intermittent regime when the intruder's motion is made of intermittent bursts separated by long waiting times. We observe a peak in the relative fluctuations of the intruder's displacements and a critical scaling of the burst amplitudes' distributions. This transition occurs at the jamming point phi(J) defined as the point where the static pressure (i.e., the pressure measured in the absence of vibration) vanishes. Investigating the motion of the surrounding grains, we show that below the fluidization transition, there is a permanent wake of free volume behind the intruder. This transition is marked by the evolution of the reorganization patterns around the intruder, which evolve from compact aggregates in the flowing regime to long-range branched shapes in the intermittent regime, suggesting an increasing role of the stress fluctuations. Remarkably, the distributions of the kinetic energy of these reorganization patterns also exhibit a critical scaling at the jamming transition.

Study on Properties of Filling Systems in Plastic Axial Vibration Injection Processing

Adding the axial oscillation into the polymer plastic processing is the dynamic processing of polymer. There are two sections, the axial shearing section and the axial extrusion section, in the effect of vibration on the melting. The experiments show that the composites in the axial shearing section have a smaller mean particle diameter and a narrower particle size distribution, compared to those in the absence of vibration. So the vibration on melting ameliorates the filled properties of polymer composite. The experiments of the High-density polyethylene and Calcium carbonate (HDPE/CaCO3) filling system prove that the analyses are right.

Final report of RILEM TC 205-DSC: durability of self-compacting concrete

Because of the different mix design in comparison with traditional concrete and the absence of vibration, different durability characteristics might be expected for self-compacting concrete. The state- of-the-art report, prepared by RILEM Technical Committee TC 205-DSC focuses on the Durability of SCC, by first gathering the available information concerning pore structure, air-void system and trans- port mechanisms. The available durability results are studied and summarised keeping in mind the funda- mental mechanisms and driving forces. All relevant durability issues are considered, like carbonation, chloride penetration, frost resistance, ASR, sulphate attack, thaumasite formation, fire resistance, etc... It is not the intention to give a review on these durability aspects for concrete in general. The aim however is to point at the specifics related to the use of SCC, e.g. due to the addition of a large amount of limestone filler, etc... This paper summarizes the main conclusions of the State-of-the-Art Report.

Mass transfer in shallow aerated vibrated powder beds

Mass transfer rates are reported for granular beds (depths = 24 and 1 mm) aerated by upward flow of nitrogen both in absence of vibration and also subjected to vibration at intensities affording maximum accelerations = two and four times gravity. Nitrogen flows were both below and above minimum gas-fluidizing velocities in absence of vibration. At both 24- and 1-mm bed depths, vibration at intensity four times gravity can enhance mass transfer by a factor between about 1.4 and 2. For mass transfer, bed depth is an important variable, with or without vibration. Without vibration, mass transfer at 1-mm depth can be ∼ 10 to 15 times greater than transfer in a 24-mm bed. A correlation is available that deals successfully with influence of bed depth in our data, both with and without vibration. Data reported herein at 1-mm depth bear upon performance of a chemical microreactor with cross-flow of gaseous reactants through particles in the coherent-expanded (CE) vibrated-bed state. The data suggest that a mass-transfer limitation need not ordinarily be taken into account in analysis of microreactor kinetic data for a chemical reaction for which a fluid bed reactor is an appropriate commercial choice.

傾斜磁場変動による振動が拡散強調画像に与える影響について

Diffusion-weighted images (DWIs) with high b-factor in the body are often used to detect and diagnose cancer at MRI. The echo planar imaging (EPI) sequence and high motion probing gradient pulse are used at diffusion weighted imaging, causing high table vibration. The purpose of this study was to assess whether the diffusion signal and apparent diffusion coefficient (ADC) values are influenced by this vibration because of time-varying magnetic fields. Two DWIs were compared. In one, phantoms were fixed on the MRI unit's table transmitting the vibration. In the other, phantoms were supported in air, in the absence of vibration. The phantoms called "solution phantoms" were made from agarose of a particular density. The phantoms called "jelly phantoms" were made from agarose that was heated. The diffusion signal and ADC value of each image were compared. The results showed that the signal of DWI units using the solution phantom was not affected by vibration. However, the signal of DWI and ADC were increased in the low-density jelly phantom as a result of vibration, causing the jelly phantom to vibrate. The DWIs of vibrating regions such as the breast maybe be subject to error. A countermeasure seems to be to support the region adequately.

Effects of vibration force field on structure and properties of HDPE/CaCO 3 nanocomposites

HDPE/CaCO 3 nanocomposites were prepared using an electromagnetic dynamic extruder, which introduces a vibration force field into the whole extrusion process. Effects of vibration force field on the morphology, the crystallization behavior and mechanical properties of HDPE/CaCO 3 nanocomposites were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and mechanical testing. SEM examinations show that the nanocomposites extruded in the presence of a vibration force field have a smaller average particle diameter and a narrower particle size distribution, compared with those in the absence of vibration. Correspondingly, they exhibit a higher melting temperature and a smaller average crystal size, which was determined by DSC and WAXD, respectively. Both the tensile and impact strengths of HDPE/CaCO 3 nanocomposites increase and then decrease with vibration intensity, reaching a maximum when the vibration amplitude is 80 μm and the frequency is 10 Hz.

Vibrational thermocapillary instabilities

We study vibrational instabilities of the thermocapillary return flow driven by a constant temperature gradient along the free surface of an infinite layer that vibrates in its normal direction with acceleration of amplitude $g_1 $ and frequency $\omega _1 $ . The layer is unstable to hydrothermal waves in the absence of vibrations beyond a critical Marangoni number $M$ . Modulated gravitational instabilities with $M\,{=}\,0$ are also possible beyond a critical Rayleigh number $R$ based on $g_1 $ . We employ two-time-scale high-frequency asymptotics to derive the equations governing the mean field. The influence of vibrations on the hydrothermal waves is found to be characterized by a dimensionless parameter $G$ that is proportional to $R^2.$ The return flow at $G\,{=}\,0$ is also a mean field basic flow and we study its linear instability at different Prandtl numbers $P$ . The hydrothermal waves are stabilized with increasing $G$ and reverse their direction of propagation at particular values of $G$ that decrease with increasing $P$ . At finite frequencies, a time-periodic base state exists and we study its linear instability by calculating the Floquet exponents. The stability boundaries in the $(R,M)$ -plane are found to be composed of two intersecting branches emanating from the points of pure thermocapillary or buoyant instabilities. Three-dimensional modes are always preferred and the region of stability, while anchored at the point of hydrothermal waves corresponding to $R\,{=}\,0$ , is found to grow without bound along the $R$ -axis with increasing frequencies. Results from the two approaches are shown to be in asymptotic agreement at large frequencies.

Effect of slow, small movement on the vibration-evoked kinesthetic illusion

The study reported in this paper investigated how vibration-evoked illusions of joint rotation are influenced by slow (0.3 degrees /s), small (2-4 degrees ) passive rotation of the joint. Normal human adults (n=15) matched the perceived position of the left ("reference") arm with the right ("matching") arm while vibration (50 pps, 0.5 mm) was applied for 30 s to the relaxed triceps brachii of the reference arm. Both arms were constrained to rotate horizontally at the elbow. Three experimental conditions were investigated: (1) vibration of the stationary reference arm, (2) slow, small passive extension or flexion of the reference arm during vibration, and (3) slow, small passive extension or flexion of the reference arm without vibration. Triceps brachii vibration at 50 pps induced an illusion of elbow flexion. The movement illusion began after several seconds, relatively fast to begin with and gradually slowing down to a stop. On average, triceps vibration produced illusory motion at an average latency of 6.3 s, amplitude of 9.7 degrees , velocity of 0.6 degrees /s, and duration of 16.4 s. During vibration, slow, small ( approximately 0.3 degrees /s, 1.3 degrees ) passive rotations of the joint dramatically enhanced, stopped, or reversed the direction of illusory movement, depending on the direction of the passive joint rotation. However, the subjects' perceptions of these passive elbow rotations were exaggerated: 2-3 times the size of the actual movement. In the absence of vibration, the subjects accurately reproduced these passive joint rotations. We discuss whether the exaggerated perception of slow, small movement during vibration is better explained by contributions of non muscle spindle Ia afferents or by changes in the mechanical transmission of vibration to the receptor.

Vibratory antinociception: effects of vibration amplitude and frequency

The ability of cutaneous vibration to compromise detection of a nociceptive stimulus was examined in 2 sets of psychophysical experiments. The noxious stimulus was a 10-millisecond burst of radiant heat from a CO 2 laser; at the near-threshold levels used it generally yielded a mild pricking sensation. In both experiments, the detectability (d e′) of the laser was measured in the presence of different vibratory stimuli and in the absence of vibration. Periods of vibration lasted 10 seconds, bracketing the time of occurrence of the laser. Vibratory and laser stimuli were presented 2.3 cm apart on the dorsal surface of the forearm. Confidence rating procedures yielded receiver operating characteristic curves from which detectability of the laser was calculated. In an amplitude study, vibrations ranging from 10 to 45 dB above threshold were used; results indicated that nociceptive sensitivity gradually declined as vibration amplitude increased. In a frequency study, vibrations ranging from 20 to 230 Hz were used; all interfered with nociception. Combining the results of the 2 studies permitted the conclusion that signals in multiple vibrotactile channels are able to modulate nociception. No one mechanoreceptive channel appears to have a privileged role.

Motion of a Thin Oblique Layer of a Pseudoplastic Fluid

Motion of a thin layer of the Williamson fluid over an inclined solid surface in the gravitational field is considered. Expressions are obtained for the stationary motion of the film in the gravitation field. The influence of the latter and tangential vibrations of the solid surface on the flow in the layer is analyzed. It is shown that the vibrations generate a pronounced averaged fluid flow even in the weak gravitational field in which the film is at rest in the absence of vibrations. The effect of the nonmonotonic dependence of the mean flow velocity of the film on the vibration frequency of the surface is found.

Improved oil recovery by application of vibro-energy to waterflooded sandstones

The final oil recovery of reservoirs after waterflooding usually does not exceed 50%. Therefore, the problem of additional oil production in water-flooded oilfields, or after depletion, is of major importance. A method of enhanced oil recovery based on the use of powerful surface-based vibro-seismic sources is discussed here, and results of laboratory tests and their application at several oilfields in Russia and in other states formed from the former USSR are presented. In laboratory experiments, natural core samples and synthetic sandpacks were used. The rate of displacement of oil by water in the presence of applied vibro-energy was studied and compared to the displacement rate in the absence of vibrations. Dependence of relative permeability to oil and to water on application of vibro-energy was analyzed. Effect of vibro-energy on residual oil saturation in the porous medium was also studied. It was shown that the rate of oil displacement increases and the percentage of residual oil decreases if vibro-energy is applied to the porous medium containing oil. Another important phenomenon studied in the synthetic porous models is the increase in the rate of degassing due to applied vibration energy. Results of both laboratory and pilot-field testing of the proposed enhanced oil recovery method showed an increase in both oil recovery and the producing oil/water ratio. This proposed vibro-seismic methodology will serve as an additional tool for increasing oil recovery, possibly in conjunction with application of direct electric current, chemical floods, and other processes.

Regulation of muscle stiffness during periodic length changes in the isolated abdomen of the hermit crab.

Reflex activation of the ventral superficial muscles (VSM) in the abdomen of the hermit crab, Pagurus pollicarus, was studied using sinusoidal and stochastic longitudinal vibration of the muscle while recording the length and force of the muscle and the spike times of three exciter motoneurons. In the absence of vibration, the interspike interval histograms of the two larger motoneurons were bimodal; cutting sensory nerves containing most of the mechanoreceptor input removed the short interval peak in the histogram, indicating that the receptors are important in maintaining tonic firing. Vibration of the muscle evoked a reflex increase in motoneuron frequency that habituated after an initial peak but remained above control levels for the duration of stimulation. Motoneuron frequency increased with root mean square (rms) stimulus amplitude. Average stiffness during stimulation was about two times the stiffness of passive muscle. The reflex did not alter muscle dynamics. Estimated transfer functions were calculated from the fast Fourier transform of length and force signals. Coherence was >0.9 for the frequency range of 3-35 Hz. Stiffness magnitude gradually increased over this range in both reflex activated and passive muscle; phase was between 10 and 20 degrees. Reflex stiffness decreased with increasing stimulus amplitudes, but at larger amplitudes, this decrease was much less pronounced; in this range stiffness was regulated by the reflex. The sinusoidal frequency at which reflex bursts were elicited was approximately 6 Hz, consistent with previous measurements using ramp stretch. During reflex excitation, there was an increase in amplitude of the short interval peak in the interspike interval histogram; this was reduced when the majority of afferent pathways was removed. A phase histogram of motoneuron firing during sinusoidal vibration had a peak at approximately 110 ms, also suggesting that an important component of the reflex is via direct projections from the mechanoreceptors. These results are consistent with the hypothesis that a robust feedforward regulation of abdominal stiffness during continuous disturbances is achieved by mechanoreceptors signalling the absolute value of changing forces; habituation of the reflex, its high-threshold for low frequency disturbances and the activation kinetics of the muscle further modify reflex dynamics.