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1
Content available remote

Application of the Golden Numerical Rings for Configure Acoustic Systems of Fine Resolution

100%
Riznyk W.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6A
1046-1049
EN
The paper presents a new mathematical principle for improving the quality indices of acoustic systems with non-uniform structure (e.g. overlapping masks utilizing the entire ultra-acoustic aperture) with respect to the wavelength scale, where each pair of holes serves as an interferometer selecting the signal component at a spatial frequency, using novel design based on the combinatorial sequencing theory, namely the concept of golden numerical rings. The concept can be used for finding optimal placement of structural elements in spatially distributed systems, for example, positioning of holes elements in sonar antenna array. Golden numerical rings are cyclic sequences of positive integers which form perfect partitions of a finite interval [1, S] of integers. The sums of connected sub-sequences of a GRB enumerate the set of integer [1, S] exactly R-times. These design techniques make it possible to configure non-redundant masks in order to avoid interference of signal components of the same spatial frequency because phases of the components are unknown.
2
Content available remote

Analysis of Acoustic Wave Propagation in a Power Transformer Model

63%
Wotzka D., Boczar T., Zmarzły D.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
428-431
EN
Analyses of acoustic wave propagation in a model power transformer are presented in the paper. The acoustic wave is induced by partial discharges that are simulated at predefined coordinates in the core and winding. Propagation of the numerical calculated acoustic wave is analyzed within the transient state. Achieved results indicate that the space and time distributions of the acoustic pressure depend on the induction position. Furthermore, a greater pressure gradient is observed in domains with higher speed of sound while the largest amplitude occurs at the vicinity of the induction position.
3
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Characteristic of Acoustic Signals Generated by Operation of On Load Tap Changers

63%
Cichon A., Fracz P., Zmarzly D.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
585-588
EN
Possibilities of application of the acoustic method for the on load tab changers diagnosis has been presented in the paper. The analysis of measurement results gathered during research works performed under laboratory conditions has been presented in detail. The registered acoustic signals have been analyzed in time and time-frequency domains. The time domain analysis has been performed by presentation of time runs and their envelopes determined by use of the Hilbert transform. Evaluation of the time-frequency components has been performed by use of the short-time Fourier transform, the discrete and the continuous wavelet transforms.
4
Content available remote

The Application of the Selected Time-Frequency Descriptors Detection of the Acoustic Emission Signals Generated by Multisource Partial Discharges

63%
Cichon A.
Acta Physica Polonica A
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2009
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vol. 116
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issue 3
290-293
EN
The paper presents the comparative analysis results of the acoustic emission signals generated by various forms of partial discharges occurring in multisource systems. Modern methods of the signal digital processing: a short-time Fourier transform and continuous and discrete wavelet transforms were applied for the assessment of the results in the time-frequency domain. The acoustic emission signals generated by partial discharges were registered with a WD AH17 contact transducer by the Physical Acoustics Corporation placed on the external part of the tub.
5
Content available remote

Characteristics of Acoustic Emission Signals Generated by the Contacts of the Selector

63%
Cichoń A., Borucki S., Wotzka D., Szmajda M.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
804-807
EN
An important part of electric power transformer is the on load tap changer which enables for voltage regulation in the network. Due to high level of failure frequency of these devices it is necessary to look for new diagnostic methods which enable for theirs technical state estimation under transformer normal operating condition. Presently at the Electric Power Institute at Opole University of Technology there are works in progress aspiring to determine the application possibility of the acoustic emission method for on load tap changer diagnosis. Results of scientifically-research works aiming to characterize the acoustic emission signals generated by a separated selector are presented in the paper. Measurements have been performed in a setup with a model of on load tap changer type VEL-110-27 from ELIN. Acoustic emission signals generated by the selector have been analyzed in detail. Analysis of the time-frequency components of signals generated by on load tap changer has been carried out with the short time Fourier transform and continuous wavelet transform. Based on the comparison outcome of acoustic emission signals generated by the power changer and by the selector two measuring paths endowed with wide band contact transducers have been proposed for the practical application.
6
Content available remote

Reduction of Vibration of Fluid Loaded Plate with Piezoelectric Elements - a Comparison of Analytical, FEM Harmonic Analysis, and Real Results

51%
Iwański D., Wiciak J.
Acta Physica Polonica A
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2013
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vol. 123
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issue 6
1040-1043
EN
In the present paper, a comparison of analytical calculations, FEM harmonic analysis, and real data from laboratory stand of fluid-loaded structure were taken under consideration. Resonant frequencies of the investigated structure were measured using swept sine technique on laboratory stand. Analytical calculations of the first twelve modes were made and the numerical model was build using the finite element method. Results from real data, analytical calculations, and numerical calculations are comparable.
7
Content available remote

Phase-Locked Particle Image Velocimetry Visualization of the Sound Field at the Outlet of a Circular Tube

51%
Weyna S., Mickiewicz W.
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vol. 125
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issue 4A
A-108-A-112
EN
The shedding process and acoustic flow formation in the region of outlet of a cylinder duct has been investigated by means of the particle image velocimetry (PIV) technique. The research work on the behavior of the sound field at outlets of waveguides addresses issues of importance to industrial applications. The obtained results can be used in a number of industrial applications involving pipes, ducts and tubing. In our investigation the acoustics flow fields are measured with a phase-locked PIV system with high sampling rate and large internal memory block using DAVIS v. 8.11 software. A cross-correlation method, in conjunction with the FFT analysis, is used as a vector processing algorithm. A series of PIV vector maps was used to evaluate the acoustic velocity field at the open end of circular tube throughout the acoustic cycle for frequencies of 700 Hz and 1400 Hz. Six phase steps were assumed for one frequency cycle and the characteristic signal was extracted from the velocity data step and shown graphically.
8
Content available remote

Comparison of Efficiency of Different Shapes of Homogeneous and Two-Part Piezo Elements on Vibration Reduction

51%
Trojanowski R., Wiciak J.
Acta Physica Polonica A
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2012
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vol. 122
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issue 5
905-907
EN
The subject of this work is a numerical analysis of efficiency of different piezo element shapes and types used for vibration (and later structural sound) reduction. The shapes of both types of piezo elements used are as follows: square, right-angled triangle, and parallelogram. There are 2 types of piezo elements used in this study: homogeneous elements and elements consisting of 2 parts (inner and outer) of different composition. These are attached to steel plate clamped on all sides. For every simulation 5 elements are used as actuators, with 1 as disturbance source, and other 4 as active dampers. On the other side of a plate 4 elements are placed acting as vibration sensors. The actuator used as a disturbance source as well as sensors are always in the shape of a square. 4 modes were taken into account (analyzed each one singular and all together). Analyses were made with the use of ANSYS software.
9
Content available remote

The Effect of Material Composition of Piezoelectric Elements with Chosen Shapes on Plate Vibration Reduction

51%
Wiciak J., Trojanowski R.
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vol. 125
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issue 4A
A-179-A-182
EN
This paper presents numerical analysis of efficiency of different shapes and material composition of piezoelectric actuators used for vibration reduction. Four numerical models representing a plate clamped on all sides with two attached piezoelectric elements were created. For each model, one element had the same shape and composition and was used for plate excitation, and the other one, used for vibration reduction, had different shape and possibly material composition and could be of square or circular shape with either homogeneous or two-part material composition. Two modes were taken into account: the first mode and the fifth mode. Analysis of results was performed with ANSYS software.
10
Content available remote

Comparison of Vibration and Acoustic Pressure Reduction Using Different Types of Piezo actuators

51%
Wiciak J., Trojanowski R.
Acta Physica Polonica A
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2015
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vol. 128
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issue 1A
A-62-A-66
EN
This paper presents results of numerical simulations on reduction of sound pressure radiated from a square plate using different types of piezo actuators. For this purpose a FEM model was developed using ANSYS software with said steel plate with a hemisphere of air on one side of the plate. There are two criteria by which the reduction is measured: minimising vibrations of plate area and minimising sound pressure on a half sphere surrounding the plate. Changes in the results for both the radiated sound pressure and plate vibration are discussed.
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