scholarly journals SYNTHESIS OF THE LOW-FREQUENCY VIBRATION EXCITER

2021 ◽  
Vol 3 ◽  
pp. 66-71
Author(s):  
Dmitry Fedorov ◽  
Andrey Khitrov ◽  
Evgeny Veselkov ◽  
Yuliya Domracheva ◽  
Oksana Kozyreva
Keyword(s):  
Control System ◽  
Low Frequency ◽  
Magnetic Suspension ◽  
National Standard ◽  
Vibration Exciter ◽  
Magnetic Conductor ◽  
Low Frequencies ◽  
Modern Equipment ◽  
Mobile Part ◽  
Low Frequency Vibration

The article is devoted to synthesis of the low-frequency vibration exciter for checking of sensors of acceleration. In many areas of the modern equipment sensors of acceleration working in very low range of frequencies are widely used. For checking and graduation of such sensors the vibration exciter capable to provide rectilinear horizontal harmonic oscillations of the calibrated accelerometer in so low range of frequencies are required. Low frequencies of fluctuations cause the necessity of creation of big amplitudes of movements for ensuring the acceptable values of amplitudes of accelerations. The low-frequency electrodynamic vibration exciter with a magnetic suspension of mobile part which is a component of the National Standard of the vibration movement of the Russian Federation is so far created. However, development of the modern equipment demands expansion of frequency ranges to the area of ultralow frequencies. One of requirements shown to the vibration exciter working in the ultralow range of frequencies is increase in amplitude of horizontal movements of a mobile part as with small amplitudes the speed and acceleration of the harmonious law of the movements proportional according to the frequency of fluctuations and a square of this frequency, will have small amplitude values. One of problems of realization of a control system of the electric drive of the vibration exciter consists in that a mobile part possesses indifferent position of balance. The centre of fluctuations of a mobile part is not defined and can be in any point on magnetic conductor length. That fluctuations had the steady centre in an average point of a magnetic conductor without use of a mechanical spring, the drive is supplied with an additional control system of fluctuations, or a so-called electromagnetic spring.

scholarly journals Specifics of Reduction-Oxidation Processes Exposed to a Low--Frequency Acoustic Field

2020 ◽  
pp. 80-92
Author(s):  
G.N. Fadeev ◽  
V.S. Boldyrev ◽  
N.A. Bogatov ◽  
A.L. Nikolaev
Keyword(s):  
Acoustic Field ◽  
Oxidation Process ◽  
Low Frequency ◽  
Blue Dye ◽  
Active Components ◽  
Low Frequencies ◽  
Oxidation Processes ◽  
Vibration Field ◽  
Low Frequency Vibration ◽  
Qualitative Estimation

The investigation concerned the effects of low-frequency vibrations on a system consisting of two biochemically active components: methylene blue dye and ascorbic acid. Each component can be reversibly oxidized and reduced. This system allows us to trace the effect that a low-frequency vibration field has on the reciprocal reduction-oxidation process and detect specific features of this type of exposure. We discovered that reduction-oxidation processes in such systems do not accelerate but slow down when exposed to low frequencies, unlike those in the previously studied clathrate and chelate structures. We observe an inhibition effect concerning the sonochemical process in a low-frequency acoustic field. We performed a qualitative estimation of the effect.

Harnessing the Quasi-Zero Stiffness From Fluidic Origami for Low Frequency Vibration Isolation

2017 ◽  
Author(s):  
Sahand Sadeghi ◽  
Suyi Li
Keyword(s):  
Vibration Isolation ◽  
Low Frequency ◽  
Harmonic Balance Method ◽  
Design Parameters ◽  
Base Excitation ◽  
Design Guideline ◽  
Low Frequencies ◽  
Cellular Solid ◽  
Low Frequency Vibration ◽  
Internal Volume

This research investigates a quasi-zero stiffness (QZS) property from the pressurized fluidic origami cellular solid, and examines how this QZS property can be harnessed for low-frequency base excitation isolation. The QZS property originates from the nonlinear geometric relations between folding and internal volume change, and it is directly correlated to the design parameters of the constituent Miura-Ori sheets. Two different structures are studied to obtain a design guideline for achieving QZS: one is identical stacked Miura-Ori sheets (ismo) and the other is non-identical stacked Miura-Ori sheets (nismo). Further dynamic analyses based on numerical simulation and harmonic balance method, indicate that the QZS from pressurized fluidic origami can achieve effective base excitation isolation at low frequencies. Results of this study can become the foundation of origami-inspired metamaterials and metastructures with embedded dynamic functionalities.

scholarly journals Hearing in the African lungfish ( Protopterus annectens ): pre-adaptation to pressure hearing in tetrapods?

2010 ◽  
Vol 7 (1) ◽  
pp. 139-141 ◽  
Author(s):  
Jakob Christensen-Dalsgaard ◽  
Christian Brandt ◽  
Maria Wilson ◽  
Magnus Wahlberg ◽  
Peter T. Madsen
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
West African ◽  
Low Frequencies ◽  
Frequency Responses ◽  
Protopterus Annectens ◽  
Vibration Detection ◽  
Low Frequency Vibration ◽  
African Lungfish ◽  
Early Tetrapods

Lungfishes are the closest living relatives of the tetrapods, and the ear of recent lungfishes resembles the tetrapod ear more than the ear of ray-finned fishes and is therefore of interest for understanding the evolution of hearing in the early tetrapods. The water-to-land transition resulted in major changes in the tetrapod ear associated with the detection of air-borne sound pressure, as evidenced by the late and independent origins of tympanic ears in all of the major tetrapod groups. To investigate lungfish pressure and vibration detection, we measured the sensitivity and frequency responses of five West African lungfish ( Protopterus annectens ) using brainstem potentials evoked by calibrated sound and vibration stimuli in air and water. We find that the lungfish ear has good low-frequency vibration sensitivity, like recent amphibians, but poor sensitivity to air-borne sound. The skull shows measurable vibrations above 100 Hz when stimulated by air-borne sound, but the ear is apparently insensitive at these frequencies, suggesting that the lungfish ear is neither adapted nor pre-adapted for aerial hearing. Thus, if the lungfish ear is a model of the ear of early tetrapods, their auditory sensitivity was limited to very low frequencies on land, mostly mediated by substrate-borne vibrations.

scholarly journals Reduction of gravity effect on the results of low-frequency accelerometer calibration

ACTA IMEKO ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 365
Author(s):  
G. P. Ripper ◽  
C. D. Ferreira ◽  
R. S. Dias ◽  
G. B. Micheli
Keyword(s):  
Approximation Method ◽  
Low Frequency ◽  
Systematic Errors ◽  
Experimental Results ◽  
Vibration Exciter ◽  
Air Bearing ◽  
Gravity Effect ◽  
Calibration System ◽  
Low Frequencies ◽  
Bearing Vibration

This paper describes a study on the possible sources of systematic errors during the calibration of accelerometers at low-frequencies. This study was carried out on a primary calibration system that uses an air-bearing vibration exciter APS Dynamics 129 and applying the sine-approximation method. Tests performed and actions taken to reduce the effect on experimental results are presented.

Impacts of Insulation and Joiner Treatments on Low Frequency Vibration in Marine Structures with Finite Element Applications

2014 ◽  
Author(s):  
Eric A. Favini ◽  
Jesse H. Spence
Keyword(s):  
Finite Element ◽  
Low Frequency ◽  
Accurate Method ◽  
Substantial Effect ◽  
Vibration Response ◽  
Finite Element Models ◽  
Marine Structures ◽  
Low Frequencies ◽  
Acoustical Properties ◽  
Low Frequency Vibration

Marine insulation and joiner facing out fittings are known to affect the acoustical properties of the surface they cover. Measured results provided in this paper show that these treatments can also have a substantial effect on the vibration response of ship structures at low frequencies (below 100 Hz). The accuracy of finite element models of marine vibration response to machinery and propeller sources can be improved by accounting for these effects. Two objectives are discussed in this paper: 1) quantifying the effect of various insulation and joiner treatments on the vibration response of a typical ship bulkhead based on measured data and 2) developing an efficient and accurate method to integrate these effects into finite element models for the prediction of vibrations on ships and marine structures.

scholarly journals Rectangular Closed Double Magnetic Circuit Offering Ultra-Long Stroke for Ultra-Low-Frequency Vibration Exciter

2020 ◽  
Vol 10 (17) ◽  
pp. 6118
Author(s):  
Junning Cui ◽  
Wei Li ◽  
Xingyuan Bian ◽  
Zhangqiang He ◽  
Limin Zou
Keyword(s):  
High Performance ◽  
Magnetic Circuit ◽  
Harmonic Distortion ◽  
Low Frequency ◽  
Fem Analysis ◽  
Magnetic Flux Density ◽  
Vibration Exciter ◽  
Low Frequency Vibration ◽  
Lumped Parameter ◽  
Long Stroke

High-performance magnetic circuit offering uniform magnetic flux density (MFD) along ultra-long stroke is the key to develop a vibration exciter for ultra-low-frequency (ULF) vibration calibration. In this paper, a rectangular closed double magnetic circuit (RCDMC) offering ultra-long stroke up to 1.2 m is modeled and optimized. In order to overcome the modeling difficulty arising from the long stroke, a high-accuracy theoretical model is established taking advantage of the structural symmetry of the RCDMC through lumped parameter magnetic equivalent circuit method. Matrix equations are derived based on Kirchhoff’s law and solved by iteration calculation to deal with the strong nonlinear characteristics of the yoke material. The deviations between the model and finite element method (FEM) analysis results are less than 1% for non-saturated yokes and ~10% for saturated yokes. Theoretically, an MFD up to 122 mT and an acceleration waveform harmonic distortion (AWHD) as low as 0.45% are achieved through model-based optimization. Experiments are carried out using an RCDMC prototype assembled in a horizontal vibration exciter. The experimental results show that an MFD of 102 mT and an AWHD of 0.27% along 1.2 m stroke are achieved, making the proposed RCDMC a solution for ULF vibration exciter.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

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