Increase In Vibration Intensity Research Articles

Experimental Investigations on the Response of Bedload Sediment to Vibration

Research results on sediment vibration characteristics are scarce, and knowledge on the effect of the particle size on the sediment vibration response is still limited. In this study, natural pebbles of different heights—A, B and C—were selected (hA < hB < hC). Miniature acceleration sensors were installed inside the pebble. Experimental methods were used to measure the vibration process of pebbles on the rough bed surface and to measure the near-bed velocities simultaneously. The test results show that the sequence of pebble vibration and entrainment is A-C-B as the flow rate increases. The vibration intensity of pebbles A and B tended to increase before approaching the entrainment threshold but weakened when approaching the entrainment threshold; the vibration frequency, on the contrary, first decreased and then increased. The vibration intensity of pebble C decreased first and then increased, and when approaching the entrainment threshold, it rolled directly. The vibration frequency first increased and then decreased, and near the entrainment threshold, there was no vibration. Thus, it was demonstrated that with the increase in pebble height, the average vibration intensity increases, and the average vibration frequency decreases. The results of this research provide a reference for exploring the dynamic mechanism of the bed load in mountain rivers.

Structural, Electronic, and Vibrational Properties of N2O4 under Pressure from First‐Principles Study

This article uses first principles to study a single molecular phase of N2O4. The structural, electronic, and vibrational properties of N2O4 under high pressure are calculated. The a‐axis and c‐axis compressibilities are basically the same. The bandgap of N2O4 decreases as the pressure increases; this is because under the action of pressure, the delocalized electrons in the system increase, so the bandgap decreases. There are two main types of N2O4 vibration: telescopic vibration and bending vibration. Herein, the calculated Raman spectrum and infrared (IR) spectrum are compared with the experimental values, and the agreement is better under normal pressure. With the increase of pressure, both the Raman and IR peaks of N2O4 appear blueshifted. This is because the applied pressure reduces the volume of the unit cell and reduces the distance between atoms, causing the movement between the atoms to intensify, so the vibration intensity increases. At the same time, under the action of pressure, N2O4 increases the IR activity in the high‐frequency region and reduces the IR activity in the low‐frequency region.

Coupled Magnetic-Structural Modeling of Power Transformer for Axial Vibration Analysis Under Short-Circuit Condition

When an external short circuit occurs, the axial electromagnetic force increases dozens of times. Under the effect of the axial short-circuit electromagnetic force, the transformer windings vibrate violently. The spatial distribution of the disks is constantly changing during vibration, which can change the temporal and spatial distributions of the leakage magnetic field and the axial electromagnetic force. This process is called the strong coupling phenomenon of the structural field and the leakage magnetic field. In this article, a strong coupled magnetic-structural model is proposed by using the analysis method. The strong coupling equations, where the independent variables are the axial position of the disks, are obtained. The vibration process with strong coupling phenomenon considered can be obtained. The accuracy of the strong coupling model is verified by the iterative method. By comparing the results calculated by the strong coupling model with those calculated by the weak coupling model, the influence of the strong coupling phenomenon <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</b> the vibration process is obtained. Due to the influence of the strong coupling phenomenon, the winding vibration intensity increases and the maximum displacement of the disks can be doubled, which implied that the strong coupling phenomenon cannot be ignored when investigating the short-circuit strength of power transformers.

Measurement and Analysis of Industrial Forklifts Vibration Levels for Unit Load Testing Purposes

Forklifts are one of the most common types of material handling equipment used in warehouses and distribution centers. Vibration generated by forklifts may have an effect on the performance of unit loads and product damage rates. Historical research projects have focused predominantly on the measurement of vibration for over-the-road transportation. Thus, there is still a lack of understanding of the level of vibration caused by forklifts. The goal of this study was to understand how the vibration that is experienced by unit loads while being transported by forklifts is affected by factors such as speed, road condition, unit load weight, type of forklift, and sensor location. For this study, power spectral density (PSD) measurements were collected using a Lansmont Saver 9X30 data logger. Vibration levels were measured for three different industrial forklifts on two different surface types. The forklifts were driven at two different speeds while carrying two different unit load weights. For all of these conditions, the vibration levels were measured at the forklift carriage, at the back of the fork tine heel, and at the fork tine tips. The results obtained show that the highest vibrational intensity occurred at 3–4 Hz, while the highest overall Grms value observed was 0.145 G2/Hz (between 1–200 Hz). An increase in the forklift speed caused an increase in vibration intensity. In contrast, an increase in the unit load weight carried by the forklift caused a decrease in vibration intensity. Among the three forklifts studied, the gas-powered forklift had the highest vibration intensity, and all forklifts, when driven on asphalt, experienced more vibration.

Campus Vibration in Nanwangshan Campus, China University of Geosciences at Wuhan Monitored by Short-Period Seismometers

Continuous seismic observations can record seismic waveforms, and ambient noise, for the purposes of earthquake researches and other applications. Here we deploy three digital seismometers (EPS-2) in and around the Nanwangshan Campus of the China University of Geosciences (Wuhan). This network was running from April 9 to May 9 of 2018. During this period, the seismometers recorded the May 4, 2018 M6.9 Hawaii earthquake. From the recorded waveforms, we could observe clearly the P and S arrivals, and the corresponding particle motions. Analysis of continuous observations of ambient noise shows obvious fluctuation of vibration intensity inside of the campus. The campus is quietest from 0 to 5 am. From 5 am on, the vibration intensity increases, and reaches the peak of entire day at 12 am. The amplitude then decreases to a very low level at 19:30 to 20:00 pm, and reaches another strong noisy time at 21:00 to 21:30 pm. After 21:30 pm, the intensity goes down slowly. We also observed seismic signals that were generated by the interaction of speed-control hump cars and ground. By taking the envelope and smooth operations, we observe different characteristics for different car speeds, which suggests that seismic monitoring approaches can be used for speed measurement of cars. This kind of small seismic network running in a real time fashion, would greatly help understanding of the sources of ambient noise at high frequency bands in interested areas. Analysis of a long-term observed dataset, and real time illustration will help to strengthen campus security and high-precision laboratory deployments, and also contribute to research atmosphere in earthquake science.

Mixing Characteristics of High‐Viscosity Fluids under Forced Vertical Vibration

AbstractThe mixing characteristics of two initially stratified high‐viscosity fluids with a free surface under forced vertical vibration were studied experimentally and numerically. The flow characteristics and dynamics of the free surface and interface between liquids were analyzed and the effects of the vibration parameters on the mixing process were evaluated. The degree of mixing was determined by the frequency and amplitude of vibration. Effective mixing could not be achieved by merely using the deformation of the free surface because of the low fluidity of high‐viscosity fluids. However, an increase in vibration intensity disintegrated the free surface and interface, thereby significantly promoting the mixing of fluids and improving the mixing efficiency.

Analysis of Nonlinear Dynamic Characteristics of a Mechanical-Electromagnetic Vibration System with Rubbing

In this study, a rotor-bearing-runner system (RBRS) considering multiple nonlinear factors is established, and the complex nonlinear dynamic behavior of the coupling system is studied. The effects of excitation current, radial stiffness, and friction coefficient on dynamic characteristics are analyzed by numerical simulation. The research results show that the dynamic properties of the coupling system caused by different nonlinear factors are interactional. With the changes of different parameters, the RBRS presents multiple motion states, including periodic-n, quasi-periodic, and chaotic motion. The increase of the excitation current Ij has a certain inhibitory effect on the response amplitude of the system and makes the motion state of the system more complex, the chaotic motion wider, and the jump discontinuity enhanced. With the increase of radial stiffness kr, the motion complexity of the coupling system increases, the chaotic region increases, the response amplitude increases, and the vibration intensity increases. With the increase of the friction coefficient μ, the chaotic region increases first and decreases, the different motions alternate frequently, and the response amplitude gradually increases. This study can not only help to understand the dynamic characteristics of RBRS, but also help the stable operation of the generator set.

Experimental Research on the Influence of Vibration Intensity on Performance of Cement Stabilized Macadam

In order to study the influence of different vibration intensity on the performance of cement stabilized gravel. Vibration mixing tests of cement stabilized gravel with 5% cement factor were carried out under different vibration intensity, Through the preparation and maintenance of cylindrical specimen and the mid-beam specimen, The unconfined compressive strength test and the drying shrinkage test were carried out, Vibratory mixing can significantly improve the strength of cement stabilized gravel and reduce the level of intensity variation, As the vibration intensity increases, the increase range of specimen strength increases first and then decreases, Considering the mechanical reliability factors, It is reasonable to increase the strength of the material when the vibration intensity is D = 2 ∼ 3. Vibration mixing can improve drying shrinkage property of cement stabilized gravel, the vibration mixing reduces the water loss rate of the specimen at the later stage of shrinkage, with the increase of vibration intensity, the variation of dry shrinkage coefficient becomes smaller during shrink age period, and the coefficient of dry shrinkage decreases with it, Therefore, the greater the vibration intensity, the better drying shrinkage property of cement stabilized gravel. Vibration mixing can improve the mechanical behavior and cracking resistance of cement stabilized gravel simultaneously, it has a wide application prospect.

Enhanced Bandwidth Nonlinear Resonance Electromagnetic Human Motion Energy Harvester Using Magnetic Springs and Ferrofluid

An enhanced bandwidth nonlinear resonant electromagnetic energy harvester has been designed to harness low frequency energy from basic human motions. The inertial mass of the proposed harvester is formed by four stacked ring permanent magnets (PMs), which is suspended axially by two magnetic springs and circumferentially by ferrofluid within a carbon fiber tube. The magnetic springs are made up of two button PMs adhered, respectively, to the end cap at each end of the carbon fiber tube to provide varying repulsive forces to the PM stack, resulting in enhanced resonance frequency band and higher efficiency in energy harvesting. The ferrofluid that self-assembles around the edges of the PM stack acts as its bearing system to minimize frictional losses during its movement. Copper wire is wrapped outside the tube to form the armature winding. The stiffness characteristic of the magnetic springs and the optimum equilibrium position and number of windings have been determined by finite element method analysis. As a proof of concept, a portable prototype of the proposed energy harvester that weighs 110 g and with a volume of only 37.7 cm $^3$ is fabricated. A series of experiments is carried out and the results show that the frequency band of the harvester becomes wider as the external vibration intensity increases. In addition, the effectiveness of ferrofluid in reducing friction is demonstrated under walking and running conditions. Without ferrofluid, the maximum average outputs are 10.15 and 32.53 mW, respectively, for walking and running. With ferrofluid, the maximum outputs are 17.72 and 54.61 mW, representing an increase of $74.58\%$ and $67.88\%$ , respectively. Furthermore, the prototype exhibits an average power density of 1.45 mW/cm $^3$ during running motions, which compares favorably with existing harvesters used in low power wearable devices.

Dynamic friction in sheared fault gouge: Implications of acoustic vibration on triggering and slow slip

AbstractFriction and deformation in granular fault gouge are among various dynamic interactions associated with seismic phenomena that have important implications for slip mechanisms on earthquake faults. To this end, we propose a mechanistic model of granular fault gouge subject to acoustic vibrations and shear deformation. The grain‐scale dynamics is described by the Shear‐Transformation‐Zone theory of granular flow, which accounts for irreversible plastic deformation in terms of flow defects whose density is governed by an effective temperature. Our model accounts for stick‐slip instabilities observed at seismic slip rates. In addition, as the vibration intensity increases, we observe an increase in the temporal advancement of large slip events, followed by a plateau and gradual decrease. Furthermore, slip becomes progressively slower upon increasing the vibration intensity. The results shed important light on the physical mechanisms of earthquake triggering and slow slip and provide essential elements for the multiscale modeling of earthquake ruptures. In particular, the results suggest that slow slip may be triggered by tremors.

An Intensified Vibratory Milling Process for Enhancing the Breakage Kinetics during the Preparation of Drug Nanosuspensions.

As a drug-sparing approach in early development, vibratory milling has been used for the preparation of nanosuspensions of poorly water-soluble drugs. The aim of this study was to intensify this process through a systematic increase in vibration intensity and bead loading with the optimal bead size for faster production. Griseofulvin, a poorly water-soluble drug, was wet-milled using yttrium-stabilized zirconia beads with sizes ranging from 50 to 1500 μm at low power density (0.87 W/g). Then, this process was intensified with the optimal bead size by sequentially increasing vibration intensity and bead loading. Additional experiments with several bead sizes were performed at high power density (16 W/g), and the results were compared to those from wet stirred media milling. Laser diffraction, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and dissolution tests were used for characterization. Results for the low power density indicated 800 μm as the optimal bead size which led to a median size of 545 nm with more than 10% of the drug particles greater than 1.8 μm albeit the fastest breakage. An increase in either vibration intensity or bead loading resulted in faster breakage. The most intensified process led to 90% of the particles being smaller than 300 nm. At the high power intensity, 400 μm beads were optimal, which enhanced griseofulvin dissolution significantly and signified the importance of bead size in view of the power density. Only the optimally intensified vibratory milling led to a comparable nanosuspension to that prepared by the stirred media milling.

The influence of air on period doubling motion in vertically vibrated grains beds

We investigated the effects of interstitial air on the impact bifurcations of period doubling motion in vertically vibrated grains beds. The impact of grains on the container bottom undergoes a series of subharmonic bifurcations as the vibration intensity increases. With the presence of air, the vibration acceleration of the bifurcation points caused by the air drag on grains increases as the size of grains decreases. Especially, for grains with sufficiently small diameters, higher-order bifurcations become unobservable. We also found that with the decrease of the grains size, the dependence of the bifurcation points on the size of grains and vibrating frequency becomes more obvious due to the air drag, and such a dependence disappears when a vacuumed or porous-bottomed container is used.

Effect of normal vibrations of a flat horizontal heater on the second boiling crisis

The effect of normal vibrations of a flat horizontal heater on the second boiling crisis is considered within the framework of the hydrodynamic theory of boiling crises. The critical heat flux is estimated by characteristics of growth of the most dangerous disturbances destroying the liquid-vapor interface. As the vibration intensity increases, the interface can be destroyed either owing to the Rayleigh-Taylor instability or by virtue of parametrically excited disturbances with wavelengths corresponding to resonance zones. In the domain of parameters where the parametric instability in the first resonance zone is the most dangerous factor, it is possible to significantly reduce the critical heat flux, as compared with the value corresponding to the case with no vibrations. With a further increase in vibration intensity, the critical heat flux increases as a whole. The nonmonotonic character of the critical heat flux as a function of vibration intensity allows an effective control of the critical heat flux whose value can be made higher or lower than the value in the case without vibrations.

Study of the Technological Parameters of Ultrasonic Nebulization

The principle of an ultrasonic nebulizer is based on the vibrations of a piezoelectric crystal driven by an alternating electrical field. These periodic vibrations are characterized by their frequency, their amplitude, and their intensity, which corresponds to the energy transmitted per surface unit. When the vibration intensity is sufficient, cavitation occurs, and droplets are generated. Ventilation enables airflow to cross the nebulizer and to expel the aerosol droplets. For a given nebulizer, the vibration frequency of the piezoelectric crystal is fixed, often in the range 1–2.5 MHz. In most cases, an adjustment in vibration intensity is possible by modifying vibration amplitude. The ventilation level is adjustable. The vibrations may be transmitted through a coupling liquid—commonly water—to a nebulizer cup containing the solution to be aerosolized. In this work, we studied the influence of the technological parameters of ultrasonic nebulization on nebulization quality. Our study was carried out with a 9% sodium chloride solution and a 2% protein solution (α1 protease inhibitor). Three different ultrasonic nebulizers were used. An increase in vibration frequency decreased the size of droplets emitted. The coupling liquid absorbed the energy produced by the ultrasonic vibrations and canceled out any heating of the solution, which is particularly interesting for thermosensitive drugs. An increase in vibration intensity did not modify the size of droplets emitted, but decreased nebulization time and raised the quantity of protein nebulized, thus improving performance. On the other hand, an increase in ventilation increased the size of emitted droplets and decreased nebulization time and the quantity of protein nebulized because more drug was lost on the walls of the nebulizer. High intensity associated with low ventilation favors drug delivery deep into the lungs.

Influence of the technological parameters of ultrasonic nebulisation on the nebulisation quality of α1 protease inhibitor (α1PI)

The principle of an ultrasonic nebuliser is based on the vibrations of a piezo-electric crystal driven by an alternating electrical field. These periodical vibrations are characterised by their frequency, their amplitude and their intensity which corresponds to the energy transmitted per surface unit. When the vibration intensity is sufficient, cavitation appears and generates droplets. Ventilation enables an airflow to cross the nebuliser and to expulse the aerosol droplets. For a given nebuliser, the vibration frequency of the piezo-electric crystal is fixed and is often in the range of 1–2.5 MHz. In most cases, an adjustment in vibration intensity is possible by modifying vibration amplitude. The ventilation level is adjustable. The influence of these two parameters on the efficiency of ultrasonic nebulisation is studied. The study was carried out with a protein solution that had to be administered into the lungs. The solution used presented a viscosity of 1.25 mPa and a surface tension of 53 mN/m. The integrity of the protein was checked which was submitted to different vibration conditions. Nebulisation efficiency was evaluated by determining droplet size, the percentage of drug nebulised and nebulisation time. An increase in vibration intensity does not modify the size of droplets emitted, but decreases nebulisation time and raises the quantity of protein nebulised, thus improving performance. On the other hand, an increase in ventilation increases the size of droplets emitted, decreases nebulisation time and the quantity of protein nebulised because more drug is lost on the walls of the nebuliser. High intensity associated with low ventilation favours drug delivery deep into the lungs.

Radiation postpolymerization in devitrifying matrices: Different polymerization activity of acrylic and methacrylic monomers

Investigation of the effect of the α-CH 3-group on low-temperature postpolymerization in devitrifying matrices leads to the following conclusions. 1. The low-temperature postpolymerization in supercooled alcohol solutions ( T g ∼ 102 K) is quite efficient with acrylic monomers. Inactivity of their methacrylic analogues under these conditions is attributed to steric screening of the unpaired electron in the growing radicals. 2. As the temperature is raised and the CH 3-group vibration intensity increases, the screening effect fades. Thus in devitrifying water-alcohol solutions of NaAA and NaMAA, at higher temperatures the postpolymerization is efficient in both cases. Data on copolymerization of NaAA and NaMAA indicate that at ∼ 170 K the steric limitations due to the CH 3-group are eliminated. 3. In a glycerine matrix ( T g ⋍ 195 K ), all the acrylic and methacrylic monomers studied show efficient polymerization over virtually the same temperature range. It is concluded that the a-CH 3-group in methacrylic monomers appreciably affects their polymerization activity only at low temperatures, where steric screening of the growing polymer radical becomes important.