The onset of bioconvection in a suspension of negatively geotactic microorganisms with high-frequency vertical vibration

2005 ◽  
Vol 32 (9) ◽  
pp. 1119-1127 ◽  
Author(s):  
A.V. Kuznetsov
Keyword(s):  
High Frequency ◽  
Vertical Vibration

In Situ Measurement of Ground Vibration Induced by Inter-City Express Train

2012 ◽  
Vol 204-208 ◽  
pp. 502-507 ◽  
Author(s):  
Quan Min Liu ◽  
Xun Zhang ◽  
Zhi Jun Zhang ◽  
Xiao Zhen Li
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Ground Vibration ◽  
Vertical Vibration ◽  
Test Results ◽  
Low Frequency Vibration ◽  
Express Train ◽  
Environmental Vibration ◽  
Logarithmic Relationship

On the basis of the measured ground borne vibration of some inter-city express railway viaduct, test results analysis shows that: the test environmental vibration is under the limit set by standard of environmental vibration in urban area; whether transverse or vertical vibration, a rapid attenuation of the peak acceleration with the distance to the up-track center is observed, however the vibration at 7.5m appears to be amplified; the ground vibration with the distance conforms to a logarithmic relationship; the horizontal ground vibration at 7.5m caused by the elevated rail transit is larger 3.6cm/s2 than the vertical vibration; low-frequency vibration transfers farther than high frequency vibration; the eccentric effect of two-track viaduct is obvious.

scholarly journals Temperature development of cardboard in contact with high-frequency vibrating metal surfaces

BioResources ◽  
2019 ◽  
Vol 14 (2) ◽  
pp. 3975-3990
Author(s):  
Albrecht Löwe ◽  
Marek Hauptmann ◽  
André Hofmann ◽  
Jens-Peter Majschak
Keyword(s):  
Temperature Gradient ◽  
Moisture Content ◽  
Contact Pressure ◽  
High Frequency ◽  
Initial Temperature ◽  
Vertical Vibration ◽  
Maximum Temperature ◽  
Material Surface ◽  
Internal Dissipation ◽  
Temperature Development

The heating of cardboard was studied when it is in contact with ultrasonic sonotrodes, whose vibrations were orientated parallel and perpendicular to the material surface. The parameters that were varied included the contact pressure on the sonotrode, vibration amplitude, and moisture content of the material. It was shown that there was a major decrease in the contact pressure shortly after the beginning of the experiment when the gap between the sonotrode and anvil was kept constant and thus a decrease in the temperature gradient of the material occurred. With parallel vibration, the material heated up from the sonotrode side, whereas heating started from the center of the material in the case of vertical vibration. This suggested that in cases of vertical vibration, heat is mostly generated by internal dissipation, and in cases of parallel vibration, heat is generated by friction losses on the surface. Furthermore, the results revealed the influence of the parameters on the initial temperature gradient, the maximum temperature, and the moisture content of the material.

scholarly journals Vertical Track Irregularity Influence on the Wheel High-Frequency Vibration in Wheel-Rail System

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Yang Lei ◽  
Xinyu Tian ◽  
Falin Qi ◽  
Dongsheng Chen ◽  
Tian Tian
Keyword(s):  
High Frequency ◽  
Natural Frequencies ◽  
Vertical Vibration ◽  
Vibration Measurement ◽  
Central Difference ◽  
Nonlinear Simulation ◽  
Contact Parameter ◽  
High Frequency Vibration ◽  
Rail System ◽  
Track Irregularity

A three-dimensional deformable finite element model of wheel-rail system is established. The vertical vibration natural frequencies are calculated by modal analysis. The improved central difference method by ABAQUS explicit nonlinear dynamics module is chosen to calculate the vertical vibration of wheel axle. Through the vibration measurement experiment ofLMAwheel by China Academy of Railway Sciences, the contact parameter is optimized and the model is modified. According to the nonlinear simulation results, the important influence of vertical track irregularity on the wheel set high-frequency vibration is discovered. The advantage frequencies through spectrum are close to the vertical vibration natural frequencies of seventh, eighth, ninth, and tenth mode. When the velocity is 350 km/h, system’s nonlinear dynamic characteristic is higher than the results at 200 km/h. The critical wavelength of vertical track irregularity on the wheel vertical vibration is about 0.8 m. In addition, a particular attention should be paid to one situation that the main dominant frequency amplitude is more than 50% of the acceleration amplitude even if the peak acceleration is low.

Vibration Performance in Frequency Domain of CRTS I Double-Block Ballastless Track

2017 ◽  
Author(s):  
Feng Dai ◽  
Ying Zhu ◽  
Xueyi Liu
Keyword(s):  
Decay Rate ◽  
Frequency Domain ◽  
High Frequency ◽  
Structural Characteristics ◽  
Superposition Principle ◽  
Vertical Vibration ◽  
High Frequency Range ◽  
Frequency Range ◽  
Ballastless Track ◽  
Vibration Performance

According to the structural characteristics of the double-block track, using the Green’s function and superposition principle, the analytical model of the vertical vibration of the double-block track in frequency domain was established to analyze the responses of the double-block track in frequency domain and the influences of fastener stiffness, bedplate thickness and subgrade supporting stiffness on it. The results show that there are three obvious peaks for the rail mobility which are caused by bedplate resonance (35 Hz), rail resonance (200 Hz) and pinned-pinned resonance (1 kHz). Within the frequency range of less than 35 Hz, the bedplate mobility is determined by the bedplate supporting stiffness. Also the bedplate vibration decay rate increases with the increasing frequency. The bedplate resonance and wheel-rail coupling resonance have the most significant effect on the bedplate displacement. The frequency range where the rail high vibration decay rate lies gets wider with the larger fastener stiffness. Increasing the bedplate mass cannot attenuate its vibration in the mid-high frequency range.

Investigation of Stability of a Suspension of Motile Microorganisms Subjected to a High-Frequency Vibration

2005 ◽  
Author(s):  
A. V. Kuznetsov
Keyword(s):  
High Frequency ◽  
Fluid Layer ◽  
Finite Depth ◽  
Vertical Vibration ◽  
Mean Flow ◽  
High Frequency Vibration ◽  
Averaged Equations ◽  
Dilute Suspension ◽  
The Mean ◽  
The Stability

This paper investigates the effect of vertical vibration on the stability of a dilute suspension of negatively geotactic microorganisms in a fluid layer of finite depth. The case of high-frequency vibration is considered. Solutions of governing equations are decomposed into two components: one which varies slowly with time and a second which varies rapidly with time. An averaging method is utilized to derive the equations describing the mean flow. Linear stability analysis is used to investigate stability of the obtained averaged equations.

Contact and creep characteristics of wheel–rail system under harmonic corrugation excitation

2020 ◽  
pp. 107754632095335
Author(s):  
Zhenyu Lei ◽  
Zhiqiang Wang
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
Low Frequency ◽  
Vertical Vibration ◽  
Vibration Acceleration ◽  
Characteristic Frequencies ◽  
Rail Corrugation ◽  
Average Value ◽  
Creep Characteristics ◽  
Creep Force

To study the wheel–rail contact and creep characteristics and the evolution law of corrugation with different wavelengths, the wave-like wear is idealized as continuous harmonic excitations consisting of three wavelengths and wave depths, and the vehicle–track space coupled dynamic model is established for specific analysis. The results show that when the wavelength is fixed and the wave depth increases, the average values of rail/wheel vertical vibration acceleration and wheel–rail longitudinal creepage/creep force increase and the average value of transverse creepage/creep force decreases. But, when the wave depth is fixed and the wavelength increases, the average values of rail/wheel vertical vibration acceleration and longitudinal creepage/creep force decrease and the average value of transverse creepage/creep force increases. Both longitudinal and transverse creepages/creep forces contain the characteristic frequency consistent with the passing frequency of initial irregularity. The characteristic frequencies of longitudinal creepages/creep forces tend to develop in the high-frequency band with the increase of wave depth, whereas the characteristic frequencies of transverse creepages/creep forces concentrate in the low-frequency band and decrease with the increase of wave depth. Under the condition of the same wavelength, with the increase of operation times, the wear amount increases slightly in the low-frequency band but greatly in the middle- and high-frequency bands, which shows that rail corrugation will gradually develop toward short wavelength corrugation at the constant velocity. When rail corrugation is formed, its development speed will gradually slow down with the increase of vehicle running times, and the development speed of short wavelength corrugation is faster than that of long wavelength corrugation.

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