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1

Experimental study on the effects of vibrational frequency on the permeability of gas-containing coal rocks

Bairu Zhu, Yang Song, Beining Wu, Yongqi Li

Archives of Mining Sciences

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2021

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Vol. 66, no. 2

265--278

EN

Low-frequency mechanical vibrations can trigger disasters such as coal-gas outbursts. An in-house “vibration-triaxial stress-seepage” experimental apparatus was used to measure the gas flow rate of rock specimens with varying vibrational frequency, gas pressure, and confining pressure. The results of these tests were then used to derive expressions that describe how the permeability of gas-containing coal rocks is related to these aforementioned factors. In addition, sensitivity coefficients were defined to characterise the magnitude of the permeability response to each permeability-affecting factor (i.e., vibrational frequency and gas pressure). The following insights were gained, regarding the effects of vibrational frequency on the permeability of gas-containing coal rocks: (1) If gas pressure and confining pressure are fixed, the permeability of gas-containing coal rocks rapidly increases, before gradually decreasing, with increasing vibrational frequency. Thus, the permeability of the gas-containing coal rock is always larger with vibrations than without. (2) If vibrational pressure and confining pressure are fixed, the relationship between the permeability of gas-containing coal rocks and gas pressure is consistent with the “Klinkenberg effect,” i.e., the permeability initially decreases, and then increases, with increasing gas pressure. (3) The change in permeability induced by each unit change in gas pressure is proportional to the gas pressure sensitivity coefficient. (4) The change in permeability induced by each unit change in vibrational frequency is proportional to the vibrational frequency sensitivity coefficient.

2

Vibration of a composite elastic beam on an inhomogeneous elastic foundation

Sahin Onur

Journal of Applied Mathematics and Computational Mechanics

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2020

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Vol. 19, nr 2

107--119

EN

The lowest vibration modes of a composite beam resting on an inhomogeneous elastic foundation in the case of a clamped-free boundary condition are investigated. It is observed that the relation between the frequency and foundation constant has an effect on the valid solution of the problem. An asymptotic procedure is employed to derive the eigenfrequencies as well as the eigenforms revealing that only under certain conditions on the ratios of material parameters. Numerical illustrations are presented to confirm that the obtained asymptotic frequencies agree well with the exact frequencies in the lowest frequency range. Comparisons of asymptotic and exact displacements are also presented and a remarkable agreement is observed for high-contrast beam components.

3

Modern Methods of Irrigation Water Purification by a Mesh-Filter Using Influence of Low Frequency Vibration

Bilokon S., Turbal Y., Kunanets N., Pasichnyk V.

ECONTECHMOD : An International Quarterly Journal on Economics of Technology and Modelling Processes

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2019

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Vol. 8, No 2

21--26

EN

The article is devoted to the analysis of different methods of irrigation water purification from suspended particles. There have been considered the problems of irrigation water purification by using the low-frequency vibration technology and the effects arising from the influence of vibration on the water with different floating impurities. Vibration parameters that allow obtaining the effect of standing wave was substantiated. Also in the article have been disclosed the influence of low-frequency vibration on the quality of water purification depending on the types of pollution and their granulometric composition. Obtained the hydraulic characteristics of the mesh such as the effect of vibration on the pressure loss.

4

Test do diagnozowania dokładności pracy operatora maszyny roboczej

Romańska-Zapała A.

Diagnostyka

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2007

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nr 3(43)

115-118

PL

W artykule podano podstawowe informacje na temat dokładności sterowania ręcznego. Przedstawiono krótki opis badań eksperymentalnych, mających na celu poprawę jakości sterowania ręcznego operatorów maszyn roboczych. Omówiono strukturę oraz możliwości diagnostyczne testu komputerowego, stworzonego do celów monitorowania dokładności pracy operatorów maszyn roboczych poddanych m.in. oddziaływaniu drgań niskich częstotliwości w warunkach laboratoryjnych.

EN

The paper provides the basic information about the precision of manual control. Experimental tests are described that are used to improve the quality of manual control among machine operators. The main focus is on the structure and diagnostic potentials of a computer test, developed to monitor the working precision of machine operators exposed to low-frequency vibrations in laboratory conditions.

5

The Effects of Low-Frequency Vibrations on Osteal Profile of Blood

Damijan Z.

Molecular and Quantum Acoustics

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2006

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Vol. 27

71-79

EN

Vibrating platforms are widely employed in sport facilities and fitness clubs to help people develop muscles and improve their physical condition, in rare cases they are also used to support therapy (e.g Military Sanatorium in Busko), apparently because of high costs. The applied vibration frequencies range from 30 to 60 Hz, vibration amplitudes are regarded as "considerable". Few reports in literature explore the potential applications of low-frequency vibrations in therapy. Therefore a research program was undertaken at the AGH University of Science and Technology to investigate the effects of low-frequency vibration on selected parameters of osseous profile of human blood. Cyclic fluctuations of bone loading were induced by the applied harmonic vibration 3.5 Hz and amplitude 4 mm. Research data show that low-frequency vibrations can be treated as isometric physical training and might be well applied to support the therapy of numerous civilisation-related diseases, such as: overweight, hypertension, osteoporosis and anaemia. This paper is the continuation of the study covering the effects of low-fre-quency vibrations on selected physiological parameters of the human body. The experiments were conducted to find the answer to the question if vibration exposure (total duration of training sessions 6 hours 20 min) should produce any changes in osseous profile of blood. The experiments utilising two vibrating platforms were performed in the Laboratory of Structural Acoustics and Biomedical engineering AGH-UST. The applied vibrations were harmless and not annoying, in accordance with the standard PN-EN ISO 130901-1, 1998. 23 women volunteers had 19 sessions on subsequent working days, at the same time of day. During the tests the participants remained in the standing position, passive. Research data reveal a statistically significant decrease of phosphorus and calcium levels in blood serum.

6

Changes of selected biochemical parameters of blood, densytometric and strength bones of rats under low frequency vibration

Damijan Z.

Archives of Acoustics

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2005

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Vol. 30, No. 4

495-505

EN

The aim of the research is to analyze the changes of selected biochemical blood, densitometric parameters and bone strength of rats under exposure to low-frequency vibrations. Experiments were run on 30 Wistar rats randomly divided into three groups: the first group was first exposed to vibrations when rats were 20 days old: _20 - before puberty, the second group was subjected to vibrations from the 70-th day on: _70 - after reaching puberty, the third is the control group: _K. On the 145-th day the rats' _20 and _70 bones were subjected to biochemical examination, followed by densitometric and bone strength tests.