scholarly journals Influence of Meso-Structure Parameters on Wave Propagation in Soil-Rock Mixture

2020 ◽  
Vol 44 (5) ◽  
pp. 365-373
Author(s):  
Fei Zhang ◽  
Kui Wang ◽  
Yaru Dang ◽  
Guoyin Wu
Keyword(s):  
Wave Propagation ◽  
Wave Amplitude ◽  
Engineering Application ◽  
Maximum Amplitude ◽  
Dominant Frequency ◽  
Particle Flow Code ◽  
Structure Parameters ◽  
Feature Size ◽  
Spectral Area ◽  
Off Time

The macro mechanical properties of soil-rock mixture are closely related to the meso-structure features of block stones, namely, content, size, and shape. To promote the engineering application of soil-rock mixture, it is important to explore the meso-structure of the mixture, and evaluate its constitutive properties. The previous studies have shown that the wave propagation in the mixture is highly sensitive to the rock content and compaction. To clarify the meso-structure features of soil-rock mixture, this paper establishes a discrete element model of the mixture based on Particle Flow Code (PFC), investigates the wave propagation features in the model with different meso-structure parameters, and analyzes how the meso-structure parameters affect the wave propagation. The results show that: With the growing rock content, the first wave amplitude increased, while the take-off time shortened; With the growing feature size of block stone, the first wave amplitude gradually decreased, while the take-off time gradually lengthened; The soil-rock mixture containing spherical block stones had the highest first wave amplitude and shortest take-off time, while the mixture containing rectangular block stones had the lowest first wave amplitude and longest take-off time. With the growing rock content, the maximum amplitude, dominant frequency, and spectral area all exhibited an increasing trend; With the growing feature size of block stone, the maximum amplitude, dominant frequency, and spectral area all exhibited a decreasing trend.

Amplitude and frequency characteristics of elastic wave types generated by the underground nuclear detonation, Boxcar

1969 ◽  
Vol 59 (6) ◽  
pp. 2283-2293
Author(s):  
W. W. Hays
Keyword(s):  
Surface Wave ◽  
Elastic Wave ◽  
Wave Amplitude ◽  
Body Wave ◽  
Time Windows ◽  
Maximum Amplitude ◽  
Propagation Distance ◽  
Dominant Frequency ◽  
Frequency Characteristics ◽  
P Wave

abstract Elastic wave types generated by the Boxcar underground nuclear detonation were identified and analyzed to determine their amplitude and frequency characteristics as a function of distance. The amplitude characteristics of the identified wave types were determined to vary with source to recording station distance and frequency. Within each body wave subset, the refracted wave amplitude decays most rapidly and the reflected wave amplitude least rapidly with distance. Fourier amplitude spectra of the P, S, and surface wave time windows exhibit maxima which occur at different spectral frequencies for stations on rock, ranging from a dominant frequency of about 0.8 Hz for the P-wave window to about 0.25 Hz for the surface wave window. The frequency of the maximum amplitude of each of the three wave mode window spectral sets is essentially unaffected by increase in propagation distance over the distance range 22.2-79.1 km.

EEG-correlates of work efficiency level among young persons with stress-induced bruxism

2021 ◽  
pp. 25-29
Author(s):  
A. E. Barulin ◽  
S. V. Klauchek ◽  
A. E. Klauchek
Keyword(s):  
Regression Models ◽  
Alpha Rhythm ◽  
Negative Relationship ◽  
Maximum Amplitude ◽  
Dominant Frequency ◽  
Regression Equations ◽  
Microsoft Excel ◽  
The Subject ◽  
Males And Females ◽  
The Relationship

Purpose of the study. To establish the relationship between neurophysiological status and the level of efficiency in young people with bruxism.Materials and methods. Two groups of 64 and 53 subjects (males and females) aged 20–35 years old with bruxism and non-bruxers were formed according to questionnaire results and physical examination. The level of efficiency was assessed by the results of sensorimotor tracking of a moving object (the ‘Smile’ model). Spectral analysis was performed for evaluation of the baseline electroencephalograms. Microsoft Excel and Statistica 10.0 programs were used for statistical data processing.Results. The level of efficiency was statistically significantly lower in the hardest test of Smile model among the individuals with bruxism (p < 0.05). The bruxers also demonstrated a significantly lower dominant frequency and maximum amplitude of alpha-rhythm (p < 0.05), and significantly higher dominant frequency of beta2 rhythm (p < 0.05). The dominant frequency and the maximum amplitude of the alpha-rhythm are parameters corresponding to significant coefficients of the regression analysis. A negative relationship was found between the degree of error during sensorimotor tracking and the frequency and amplitude of alpha-rhythm.Conclusion. Regression models present the relationship between the level of efficiency and the alpha-rhythm severity. The regression equations make it possible to determine the functional state of the subject using an electroencephalogram.

Effects of the cancellous bone structure in the skull on ultrasonic wave propagation

2020 ◽  
Author(s):  
Itsuki Michimoto ◽  
Keita Yano ◽  
Yasuyo Kobayashi ◽  
Kozue Saito ◽  
Mami Matsukawa
Keyword(s):  
Wave Propagation ◽  
Temporal Bone ◽  
Elderly Women ◽  
Bone Structure ◽  
Cerebral Blood Flow Velocity ◽  
Fdtd Method ◽  
Maximum Amplitude ◽  
Arterial Stenosis ◽  
Skull Bone ◽  
Cancellous Bone Structure

Abstract The Transcranial Doppler method (TCD) enables the measurement of cerebral blood flow velocity and detection of emboli by applying the ultrasound probe to the temporal bone window, orbital, or greater occipital foramen. TCD is widely used for the evaluation of cerebral vasospasm after subarachnoid hemorrhage, early detection of patients with arterial stenosis and the check of brain death. However, measurements often become difficult in elderly women. Among various factors for this problem, we focused on the effect of the skull bone on the ultrasound penetration into the brain. Especially, the effect of the temporal bone structure was investigated. Using a 2D digital bone model, wave propagation through the skull bone was investigated by the Finite-Difference Time-Domain (FDTD) method. We create bone models which have different BV/TV (Bone Volume/Total Volume) in diploe. Around BV/TV about 60% (similar to elderly women), the observed maximum amplitude decrease due to multiple reflection and scattering. The results suggest that effects of osteoposis on the skull make TCD measurement difficult.

scholarly journals Simulation of the effect of stress-induced anisotropy on borehole compressional wave propagation

Geophysics ◽  
2014 ◽  
Vol 79 (4) ◽  
pp. D205-D216 ◽  
Author(s):  
Xinding Fang ◽  
Michael C. Fehler ◽  
Arthur Cheng
Keyword(s):  
Wave Propagation ◽  
Stress Concentration ◽  
Elastic Properties ◽  
Wave Velocity ◽  
Wave Amplitude ◽  
P Wave ◽  
Azimuthal Variation ◽  
P Wave Velocity ◽  
Velocity Region

Formation elastic properties near a borehole may be altered from their original state due to the stress concentration around the borehole. This can lead to an incorrect estimation of formation elastic properties measured from sonic logs. Previous work has focused on estimating the elastic properties of the formation surrounding a borehole under anisotropic stress loading. We studied the effect of borehole stress concentration on sonic logging in a moderately consolidated Berea sandstone using a two-step approach. First, we used an iterative approach, which combines a rock-physics model and a finite-element method, to calculate the stress-dependent elastic properties of the rock around a borehole subjected to an anisotropic stress loading. Second, we used the anisotropic elastic model obtained from the first step and a finite-difference method to simulate the acoustic response of the borehole. Although we neglected the effects of rock failure and stress-induced crack opening, our modeling results provided important insights into the characteristics of borehole P-wave propagation when anisotropic in situ stresses are present. Our simulation results were consistent with the published laboratory measurements, which indicate that azimuthal variation of the P-wave velocity around a borehole subjected to uniaxial loading is not a simple cosine function. However, on field scale, the azimuthal variation in P-wave velocity might not be apparent at conventional logging frequencies. We found that the low-velocity region along the wellbore acts as an acoustic focusing zone that substantially enhances the P-wave amplitude, whereas the high-velocity region caused by the stress concentration near the borehole results in a significantly reduced P-wave amplitude. This results in strong azimuthal variation of P-wave amplitude, which may be used to infer the in situ stress state.

scholarly journals Spin-Wave-Driven Skyrmion Motion in Magnetic Nanostrip

2018 ◽  
Vol 2018 ◽  
pp. 1-5 ◽  
Author(s):  
Guangfu Zhang ◽  
Ye Tian ◽  
Yangbao Deng ◽  
Dongchu Jiang ◽  
Shuguang Deng
Keyword(s):  
Wave Propagation ◽  
Momentum Transfer ◽  
Spin Wave ◽  
Wave Amplitude ◽  
Magnetic Nanostructures ◽  
Ultrafast Laser ◽  
Nanometer Size ◽  
Magnetization State ◽  
Magnetic Skyrmions ◽  
Tremendous Impact

The photon-assisted magnetic recording utilizes the ultrafast laser to excite the spin wave in the magnetic nanostructures and accordingly switch its magnetization state. Here, by means of micromagnetic simulation, the motion of magnetic skyrmions, a topologically protected chiral magnet with few nanometer size, induced by the spin wave is studied. It is found that the magnetic skyrmion can move in the same direction of spin-wave propagation, which is first accelerated and then decelerated exponentially. The magnetic skyrmion motion originated from the robust coupling of the spin waves with the skyrmion, through the SW’s linear momentum transfer torque acting on the skyrmion. Besides amplitude, the reflectivity of the spin wave by skyrmion has tremendous impact on the velocity of skyrmion motion. The skyrmion velocities are mainly determined by the reflectivity, when the spin-wave amplitude is almost identical. Our results give guidance for the design and development of spin-wave control spintronics.

Study on Pressure Fluctuation and Fluctuation Reduction of a Micro Vortex Pump

2014 ◽  
Author(s):  
Feixi Zhang ◽  
Peng Wu ◽  
Dazhuan Wu
Keyword(s):  
Pressure Fluctuation ◽  
Vortex Motion ◽  
Maximum Amplitude ◽  
Dominant Frequency ◽  
Distribution Method ◽  
Noise And Vibration ◽  
Flow Noise ◽  
Static Pressure Distribution ◽  
Vortex Pump ◽  
Increasing Demand

With the increasing demand of small-flow and high-head pumps, vortex pump, which can be used in industry, agriculture, medical and aerospace etc., has become more and more popular as low specific pump. However, the pressure fluctuation of fluid in the vortex pump would cause flow noise and vibration which may result in damage to the equipment. Clearly, it is important to reduce the fluctuation causing by fluid flow as much as possible. This study examined and discussed the law of pressure fluctuation in a micro vortex pump by the method of numerical simulation. In addition, a random distribution method was applied to design two new impellers with different blade spacing. Moreover, the influence on pressure fluctuation of different blade positions was predicted by theoretical analysis and CFD analysis. The results show that the blade passing frequency is dominative in the pressure fluctuation. Although the average static pressure distribution on the circumference of the micro vortex pump increased gradually along inlet to outlet, the pressure pulse amplitudes were fluctuant and the maximum amplitude area was close to the stripper. Affected by the vortex motion in the pump, there were clutters in the spectrum from inlet to outlet even for the vortex pump with uniform circumferential blade spacing. The study also indicated that uneven circumferential spacing would yield additional frequency in the spectrum compared with even one and reduce the magnitude of the dominant frequency without decreasing the performance of the pump sharply. Based on the consequence, this paper proves the feasibility of applying uneven blade spacing to reduce pressure fluctuation in a vortex pump. And it could be meaningful for the noise and vibration reduction as well as development of vortex pumps.

The role of the tymbal in cicada sound production

1995 ◽  
Vol 198 (4) ◽  
pp. 1001-1020 ◽  
Author(s):  
D Young ◽  
H Bennet-Clark
Keyword(s):  
Sound Production ◽  
Muscle Power ◽  
Maximum Amplitude ◽  
Dominant Frequency ◽  
Acoustic Properties ◽  
Muscle Shortening ◽  
Frequency Changes ◽  
Work Supports ◽  
Peak Value

1. The tymbal of Cyclochila australasiae consists of a biconvex membrane bearing alternating long and short ribs anteriorly and an irregularly shaped tymbal plate posteriorly. These sclerotised regions are coupled together by the surrounding highly flexible cuticle, which contains resilin. Dorsally, there is a thick pad of resilin, which functions as a spring, returning the tymbal to the out position and maintaining the stress on the long ribs. 2. Contraction of the tymbal muscle causes the tymbal plate to swing inwards, acting as a lever so that the surface of the tymbal moves through more than twice the distance of muscle shortening. This produces an inward movement and twisting of the dorsal ends of the long ribs, which then buckle in sequence, with each rib undergoing a sudden deformation from a convex to a V-shaped profile. Buckling takes place at the rib's weakest point, which is the narrow, highly sclerotised mid-region. 3. Inward buckling of the tymbal generates a loud click with a dominant frequency around 4 kHz. Resonances close to 4 kHz can be demonstrated in a buckled-in tymbal when driven by internal sound or by vibration at the tymbal plate. These resonances occur in sealed cicadas and those in which the abdominal air sac has been opened at both its anterior and posterior ends, which shows that the resonances are not due to the air sac; the tymbal itself is a resonant system. The maximum amplitude of tymbal vibration occurs at the V-shaped dimples in the centre of the long ribs. 4. When the tymbal plus abdominal air sac system is driven by vibration at the tymbal plate, the Q3dB of the sound radiated through the tympana is about 12.5, which is approximately the sum of those of the tymbal (Q=9.3) and of the air sac (Q=3.4) resonators. When the tymbal is not loaded by the air sac, i.e. in the sealed cicada and open cicada preparations, the Q3dB of its resonance is higher, between 13 and 20. 5. The click produced as the tymbal pops out is over 20 dB quieter than the in-click and has a dominant frequency around 6 kHz. When driven in the resting position, resonances are found close to 6 kHz but there is only a weak general vibration of the ribs and tymbal plate. When the tymbal is pushed in gradually, the resonant frequency changes from about 5.5 kHz to about 4.3 kHz as the tymbal buckles inwards. The left and right tymbals of the same insect may differ slightly in their acoustic properties. 6. As the tymbal buckles inwards, it displaces a volume of approximately 6 &micro;l into the abdominal air sac volume of about 2 ml. The resulting sound pressure inside the air sac attains peak values of 155&shy;159 dB SPL; the root mean square values are 141&shy;144 dB SPL. The mean peak value just outside the tympana is 148.5 dB SPL. 7. Overall, the present work supports and extends our earlier model of cicada sound production: the tymbal click provides a coherent resonant source that drives the abdominal resonator, from which sound is radiated via the tympana. At the same time, the system provides the pressure transformation between muscle power and sound power that is desirable for efficient sound radiation.

Time Frequency Analysis of Blasting Vibration Superposing Signal under Different Millisecond Intervals

2012 ◽  
Vol 170-173 ◽  
pp. 3097-3101
Author(s):  
Wei Zhang ◽  
Shi Hai Chen
Keyword(s):  
Vibration Reduction ◽  
Maximum Amplitude ◽  
Vibration Signal ◽  
Dominant Frequency ◽  
Single Stage ◽  
Blasting Vibration ◽  
Reduction Theory ◽  
Time Frequency ◽  
Vibration Effect ◽  
Signal Time

Based on the measured single-stage blasting vibration signal, time-frequency characteristics of two single-stage superposing signals were analyzed under the condition of different millisecond intervals ranging from 1ms to 350ms, also, variation laws of dominant frequency, amplitude and energy of the blasting vibration superposing signal with the delay time and the determination method of rational millisecond interval of similar engineering were put forward. Then, changing laws of the millisecond interval with the interference effect was obtained. It is found that, millisecond delay blasting does not follow the disturbance vibration reduction theory strictly that the vibration effect is weakened when interval is (2n-1)T/2 and strengthened when interval is nT, and the more similar the vibration characteristics of single-stage signals are, the larger the maximum amplitude declining rate of the obtained superposing signal is.

Research on Dynamic Characteristic of Marine Shafting-Oil Film-Stern Structure System

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Liang-Xiong Dong ◽  
Shao-Hua Wang
Keyword(s):  
Engineering Application ◽  
Maximum Amplitude ◽  
Coupled System ◽  
Propulsion System ◽  
Lubricating Oil ◽  
Wave Loads ◽  
Structure System ◽  
Oil Film ◽  
Motion Characteristics ◽  
Wave Induced

The working conditions of the propulsion system of ships are affected by many factors and partially by hull deformations and lubricating oil film. In order to solve the problem of engineering application of reliability assessment and control of ship propulsion system on heavy sea, a mechanical model of ship shafting-oil film-stern structure coupled system is established. The hull and shafting are studied as a whole, and a test rig with the wave loads system is assembled. By carrying out the integrative analysis and physical experiment, the motion characteristics of the system are analyzed. According to the various types of wave loads which ship faces on ocean, the influence of the stern structure on the vibration characteristics of the shafting is obtained. It is concluded that the coupling degree of shafting and stern structure is correlated with the natural frequency of the coupled system, and the wave-induced loads response is correlated with wave encountering frequency. The characteristics of the shafting-oil film-stern structure system, such as the maximum amplitude of tail shaft and the minimum oil film thickness of bearing, are significantly modified under the influence of stern structure.

Simulation of Effect of Structural Parameters on the Ejector

2014 ◽  
Vol 960-961 ◽  
pp. 539-542
Author(s):  
Bin Li ◽  
Hai Xia Li
Keyword(s):  
Flow Field ◽  
Nozzle Exit ◽  
Structural Parameters ◽  
Engineering Application ◽  
Structure Parameters ◽  
Entrainment Coefficient ◽  
Nozzle Position ◽  
Simulation Results ◽  
Effect Of Structure

The effect of structure size on the flow field in the ejector was investigated by simulating structural parameters of ejector. Simulation results show that the shock occurred in the flow field of the ejector. The entrainment coefficient shows different trends as different structure parameters change. The effects of nozzle position, inlet diameter and nozzle exit ratio were studied respectively. The simulation result revealed that the structural parameters impact the performance of the gas ejector, having certain engineering application value.

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