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Tytuł:
Nonlinear Excitation of the Non-Wave Perturbations by the Magnetoacoustic Waves in the Non-Isentropic Plasma
Autorzy:
Perelomova, A.
Powiązania:
https://bibliotekanauki.pl/articles/177449.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
magnetoacoustic waves
dynamics of plasma
nonlinear acoustics
Opis:
Nonlinear excitation of slow modes by the planar magnetosonic perturbations in a plasma is discussed. Plasma is an open system due to radiation and external heating. This may stipulate enhancement of wave perturbations and hence the acoustical activity of plasma. Plasma is assumed to be a homogeneous ideal gas with infinite electrical conductivity. The straight magnetic field is orthogonal to the velocity of fluid’s elements. Nonlinear excitation of the non-wave modes (that is, the Alfvén and the entropy modes) by periodic and aperiodic planar magnetoacoustic perturbations, is discussed. The sawtooth wave and the small-magnitude harmonic wave are considered as examples of periodic in time perturbations. The conclusions concern acoustically active and thermally unstable flows as well.
Źródło:
Archives of Acoustics; 2018, 43, 1; 21-29
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical analysis of the onset of condensation in the IMP PAN nozzle for cases without the appearance of shock waves in the steam flow
Autorzy:
Kornet, S.
Banaszkiewicz, M.
Badur, J.
Powiązania:
https://bibliotekanauki.pl/articles/175439.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
spinodal
binodal
spontaneous condensation
SCWS model
IMP PAN nozzle
wilson line
Opis:
The present paper focuses on the prediction of the spontaneous condensation phenomena in the wet steam flow depending on the inlet temperature. The basic tests including comparison with experimental data have been performed using the planar symmetrical nozzle with the de Laval geometry (IMP PAN nozzle). It was assumed in calculations that steam is pure and does not contain heterogeneous sources of condensation. Numerical analysis was performed for boundary conditions which correspond to the flow regime without the shock wave. The present work includes simulations results of the onset of condensation and shows whether initiation of phase transition is located in the region between a spinodal and a binodal. Numerical results along the nozzle axis are presented on thermodynamic diagrams for all considered flow conditions.
Źródło:
Transactions of the Institute of Fluid-Flow Machinery; 2017, 138; 107-123
0079-3205
Pojawia się w:
Transactions of the Institute of Fluid-Flow Machinery
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulations of acoustic waves with the graphic acceleration GAMER code
Autorzy:
Murawski, K.
Schive, H.
Powiązania:
https://bibliotekanauki.pl/articles/201677.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
numerical simulation
acoustic waves
graphic acceleration GAMER code
Opis:
We present results of numerical simulations of acoustic waves with the use of the Graphics Processing Unit (GPU) acceleration GAMER code which implements a second-order Godunov-type numerical scheme and adaptive mesh refinement (AMR). The AMR implementation is based on constructing a hierarchy of grid patches with an octree data structure. In this code a hybrid model is adopted, in which the time-consuming solvers are dealt with GPUs and the complex AMR data structure is manipulated by Central Processing Units (CPUs). The code is highly parallelized with the Hilbert space-filling curve method. These implementations allow us to resolve well desperate spatial scales that are associated with acoustic waves. We show that a localized velocity (gas pressure) pulse that is initially launched within a uniform and still medium triggers acoustic waves simultaneously with a vortex (an entropy mode). In a flowing medium, acoustic waves experience amplitude growth or decay, a scenario which depends on a location of the flow and relative direction of wave propagation. The amplitude growth results from instabilities which are associated with negative energy waves.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2012, 60, 4; 787-792
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metallization of ceramic materials based on the kinetic energy of detonation waves
Autorzy:
Chmielewski, T.
Golański, D.
Włosiński, W.
Powiązania:
https://bibliotekanauki.pl/articles/201124.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
metallization of ceramics
detonation spraying
coatings
metalizacja ceramiki
powłoki
wybuch rozpylający
Opis:
The paper presents an innovatory low-energy detonation-spraying method suitable for the metallization of ceramic materials, in which the energy necessary for joining the metallic coating with the ceramic is delivered in a mechanical way. In the proposed method, the metallic particles, shot from the spraying gun, impinge onto the ceramic substrate with a high velocity, and their kinetic energy is transformed into heat delivered in a specified portion directly to the region of the metal/ceramic joint being formed. The stress distribution and the temperature field at the coating/substrate interface were analyzed also numerically with the aim to optimize the metallization process parameters so as to stimulate the formation of the coating/ceramic joint and, at the same time, to control the region of heat dissipation, the temperature, and the stress state induced in the joint.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2015, 63, 2; 449-456
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Identification of structural defects of metal composite castings with the use of elastic waves
Identyfikacja defektów struktury metalowych odlewów kompozytowych za pomocą fal sprężystych
Autorzy:
Bejger, A.
Gawdzińska, K.
Powiązania:
https://bibliotekanauki.pl/articles/354088.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
emisja akustyczna
transformacja falkowa
jakość odlewów kompozytowych
acoustic emission
wavelet transform
quality of composite castings
Opis:
The method of elastic wave propagation was applied to detect defects in composite castings (ingots). If a defect occurs, which is detected by the radiography, elastic wave propagation changes locally, i.e. causes disturbance of elastic wave propagation. Methods of signal analysis based on wavelet decomposition were used. Calculations related with wavelet analysis were made in the MATLAB environment using standard Wavelet Toolbox functions.
Wykorzystano metodę badań bazującą na propagacji fal sprężystych do wykrywania wad odlewów kompozytowych. Poddano obserwacji lokalne zmiany propagacji fali sprężystej podczas analizowania defektów, których występowanie potwierdzono za pomocą defektoskopii radiologicznej. Zastosowano metody analizy sygnałów oparte na dekompozycji falkowej. Obliczenie transformat falkowych wykonano w środowisku MATLAB z wykorzystaniem standardowych funkcji Wavelet Toolbox.
Źródło:
Archives of Metallurgy and Materials; 2011, 56, 1; 129-133
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photoacoustic transformation at oppositely directed interaction electromagnetic waves in the magnetoactive two-layer medium
Transformacja fotoakustyczna przy oddziaływaniu przeciwbieżnych wiązek elektromagnetycznych w magnetoaktywnych ośrodkach dwuwarstwowych
Autorzy:
Mityurich, G. S.
Aleksiejuk, M.
Sviridova, V. V.
Serdyukov, A. N.
Powiązania:
https://bibliotekanauki.pl/articles/351166.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
photoacoustic signal gas-microphone method
thermooptical sound generation
magnetic circular dichroism
tunnel interference of electromagnetic waves
metoda foto-akustyczna generacji dźwięku
magnetoaktywne układy dwuwarstwowe
termooptyczna genaracja dźwięku
tunelowa interferencja fal elektromagnetycznych
Opis:
The paper treats the thermooptical sound generation in the magnetoactive two-layered medium on the condition of tunnel interference of electromagnetic waves. It were studied the conditions of complete suppression of the photoacoustic signal amplitude in response to the polarization type of oppositely interacting waves, the difference in their initial phases as well as the intensities of one of the oppositely interacted beams. The given paper provides an effective method of managing the thermooptical sound generation in the magnetoactive structural element during the tunnel electromagnetic interference of electromagnetic waves.
Celem pracy są badania nad foto-akustyczną generacją dźwięku w magnetoaktywnych układach dwuwarstwowych, w warunkach interferencji tunelowej fal elektromagnetycznych. Badano warunki całkowitego wytłumienia amplitudy sygnału fotoakustycznego w funkcji polaryzacji przeciwbieżnych, oddziałujących wzajemnie fal, ich faz początkowych oraz intensywności jednej z przeciwbieżnych wiązek. Praca przedstawia efektywną metodę sterowania termooptyczną generacją dźwięku w strukturach magnetoaktywnych, podczas tunelowej interferencji fal elektromagnetycznych.
Źródło:
Archives of Metallurgy and Materials; 2013, 58, 4; 1419-1423
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Numerical Study of The Heat Transfer Intensification Using High Amplitude Acoustic Waves
Autorzy:
Rulik, S.
Wróblewski, W.
Powiązania:
https://bibliotekanauki.pl/articles/177492.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
cavity noise
sound wave cooling
flow over a cavity
transient cooling
blade cooling intensification
Opis:
The current practice in the efforts aiming to improve cooling conditions is to place emphasis on the application of non-stationary flow effects, such as the unsteady jet heat transfer or the heat transfer intensification by means of a high-amplitude oscillatory motion. The research presented in this paper follows this direction. A new concept is put forward to intensify the heat transfer in the cooling channels with the use of an acoustic wave generator. The acoustic wave is generated by a properly shaped fixed cavity or group of cavities. The sound generated by the cavity is a phenomenon analysed in various publications focused on the methods of its reduction. The phenomenon is related to the feedback mechanism between the vortices flowing from the leading edge and the acoustic waves generated within the cavity. The acoustic waves are generated by the interaction between the vortices and the cavity walls. Strong instabilities can be observed within a certain range of the free flow velocities. The investigations presented in this paper are oriented towards the use of the phenomenon for the purposes of the heat transfer process intensification. The first part of the work presents the numerical model used in the analysis, as well as its validation and comparison with empirical relations. The numerical model is constructed using the commercial CFD Ansys CFX-16.0 commercial program. The next part includes determining of the relationship between the amplitude of the acoustic oscillations and the cooling conditions within the cavity. The calculations are performed for various flow conditions.
Źródło:
Archives of Acoustics; 2018, 43, 1; 31-47
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Noise Analysis of Differential Multiport Networks : the Wave Approach
Autorzy:
Dobrowolski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/226027.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
differential networks
noise analysis
noise waves
noise correlation matrix
differential noise figure
Opis:
In this paper there is presented and discussed a general analysis method for noise characterization of noisy multiport differential networks. It is based on mixed mode, differential and common mode, noise waves representation of noise, generalized mixed-mode scattering parameters and generalized mixed-mode noise wave correlation parameters for the network. There are derived analytical relation between the noise figure for a given output port and the noise matrix and the scattering parameters of the network, as well as the correlations between the input port noise waves. The signal to noise ratio degradation factor is derived and discussed, too. Presented results can be implemented directly in a CAD software noise analysis of differential microwave multiport networks with differential as well as with conventional single ended ports.
Źródło:
International Journal of Electronics and Telecommunications; 2014, 60, 4; 281-286
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Noise Characterization of Differential Multi-Element Multiport Networks : the Wave Approach
Autorzy:
Dobrowolski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/226146.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
differential networks
differential noise figure
noise waves
noise correlation matrix
Opis:
In this paper there is presented and discussed a general analysis method for noise characterization of noisy multi-element multiport differential networks. It is based on mixed mode, differential and common mode, noise waves representation of noise, generalized mixed-mode scattering parameters and generalized mixed-mode noise wave correlation parameters for the network. There are derived analytical relation between the noise figure for a given output port and the noise matrix and the scattering parameters of the network, as well as the correlations between the input port noise waves. The signal to noise ratio degradation factor is derived and discussed, too. Presented results can be implemented directly in a CAD software for noise analysis of differential microwave multi-element multiport networks with differential as well as with conventional single ended ports.
Źródło:
International Journal of Electronics and Telecommunications; 2015, 61, 4; 395-401
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Technique for Measuring Spatial Distribution of the Surface Acoustic Wave Velocity in Metals
Autorzy:
Mokryy, O.
Tsyrulnyk, O.
Powiązania:
https://bibliotekanauki.pl/articles/177231.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
ultrasound
surface acoustic waves
acoustic wave velocity
spatial resolution
Opis:
In this paper a possibility of determining a local velocity of the surface acoustic Rayleigh waves using a transducer, with the rigidly connected emitting and receiving parts, is considered. A problem on spatial resolution of such a transducer for investigation of inhomogeneous specimens is also examined. A high spatial resolution can be obtained due to the transducer displacement by a value less than the distance between the emitting and receiving parts. It is shown that in this case it is not necessary to measure the transducer displacement with a high accuracy for precise determination of the velocity. Such an effect is obtained through measuring the velocity of surface waves in one local region of the specimen with respect to the other. The criterion for optimal spatial resolution selection during spatially inhomogeneous specimens study is also proposed. The proposed criterion use is illustrated on the example of the determination of spatial distribution of the surface acoustic velocity in a steel specimen subjected to inhomogeneous plastic deformation.
Źródło:
Archives of Acoustics; 2016, 41, 4; 741-746
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Numerical Study of the Relation Between the Acoustic Generator Geometry and the Heat Transfer Conditions
Autorzy:
Rulik, S.
Wróblewski, W.
Rusin, K.
Powiązania:
https://bibliotekanauki.pl/articles/140076.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
cavity noise
cavity cooling
new cooling techniques
acoustic cooling
acoustic waves
heat transfer in cavities
thermoacoustics
szum aerodynamiczny
chłodzenie zewnętrzne
nowe techniki chłodzenia
chłodzenie akustyczne
fale akustyczne
przepływ ciepła
termoakustyka
Opis:
Modern gas turbine systems operate in temperatures ranging from 1200°C to even 1500°C, which creates bigger problems related to the blade material thermal strength. In order to ensure appropriate protection of the turbine blades, a sophisticated cooling system is used. Current emphasis is placed on the application of non-stationary flow effects to improve cooling conditions, e.g., the unsteady-jet heat transfer or the heat transfer enhancement using high-amplitude oscillatory motion. The presented research follows a similar direction. A new concept is proposed of intensification of the heat transfer in the cooling channels with the use of an acoustic wave generator. The acoustic wave is generated by an appropriately shaped fixed cavity or group of cavities. The phenomenon is related to the coupling mechanism between the vortex shedding generated at the leading edge and the acoustic waves generated within the cavity area. Strong instabilities can be observed within a certain range of the free flow velocities. The presented study includes determination of the relationship between the amplitude of acoustic oscillations and the cooling conditions within the cavity. Different geometries of the acoustic generator are investigated. Calculations are also performed for variable flow conditions. The research presented in this paper is based on a numerical model prepared using the Ansys CFX-17.0 commercial CFD code.
Źródło:
Archive of Mechanical Engineering; 2018, LXV, 1; 5-26
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Noise Control Transmission Methods of the Combustion Engine by Means of Reduction of the Vibration
Autorzy:
Žiaran, S.
Chlebo, O.
Powiązania:
https://bibliotekanauki.pl/articles/176754.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
combustion engine
low frequency waves
transmission
health
measures
silnik spalinowy
fale niskiej częstotliwości
skrzynia biegów
zdrowie
środki
Opis:
Transmission of vibroacoustic energy from an internal combustion engine (ICE) to its surroundings largely depends on how it is mounted, on available transmission paths and on the construction of the vehicle body and/or its surrounding structures. This is especially true in low speed engines in enclosed areas which generate perceptually weak noise, but strong low-frequency waves which energy has a negative impact on human health, comfort and driving safety especially in prolonged exposure to the source. The primary aim of the article was to analyse components of the ICE unit which had a determining impact on the reduction of low-frequency waves. Thus, the structurally transmitted noise from the ICE to its surrounding structure (body of the passenger vehicle) was analysed. The results of the vibroacoustic measurements were compared to modal analysis in order to determine possible resonance sources in the vehicle body and/or for assessing the influence of the vehicles safety gear on the generated vibroacoustic energy transfer into the cabin area of the passenger vehicle. Measurements were made for a passenger vehicle at rest and operating in its most common operational speed as well as for the stationary ICE of a cogenerate unit (CGU). Measurements and FFT analysis were used for the detection of the vibroacoustic energy sound pressure level (noise) and mechanical vibration. Firstly, the low-frequency noise sources were determined and their direct effects on the human body were investigated. Finally, this paper suggests some measures which may contribute to the reduction of undesirable vibroacoustic energy in enclosed areas.
Źródło:
Archives of Acoustics; 2016, 41, 2; 277-284
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the influence of the complex structure of clay hollow bricks on the values of electric field intensity by using the FDTD method
Autorzy:
Choroszucho, A.
Powiązania:
https://bibliotekanauki.pl/articles/140952.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
building materials
electromagnetic waves propagation
finite-difference time-domain method (FDTD)
wireless communication systems
Opis:
The study presents the analysis of the effects occurring at the propagation of electromagnetic waves within an area containing non-ideal, non-homogenous and absorbing dielectric. The analysed models are connected with housing constructions and include single and double-layered walls made of clay hollow bricks. The influence of the size of holes, the contained clay mass percentage and conductivity of brick on the distribution of electric field is presented. Double-layered wall causes more heterogeneity in distribution of electric field and numerous maxima and minima to compare with singlelayered construction. The presented results refer to the electromagnetic field generated by a wireless communication system (Wi-Fi), operating within the standard frequencies (2.4 GHz and 5 GHz). A FDTD method was used to the analysis of electric field distribution. Also in this paper all formulations of difference method (FDTD) is presented. The possibilities of modifying the described method are indicated too. The obtained values of electric field intensity allow to determining the attenuation coefficient for different variants of the walls. Detailed analysis of influence of different types of building construction will make it possible to better understand the wave phenomena and counteract local fading at planning of wireless networks systems.
Źródło:
Archives of Electrical Engineering; 2016, 65, 4; 745-759
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Minimizing the number of layers of the quasi one-dimensional phononic structures
Autorzy:
Garus, Sebastian
Sochacki, Wojciech
Kubanek, Mariusz
Nabiałek, Marcin
Powiązania:
https://bibliotekanauki.pl/articles/2173523.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
mechanical waves
phononic
transfer matrix
band gap
genetic algorithm
fale mechaniczne
fononiczny
macierz przejścia
pasmo wzbronione
algorytm genetyczny
Opis:
In the work, multi-criteria optimization of phononic structures was performed to minimize the transmission in the frequency range of acoustic waves, eliminate high transmission peaks with a small half-width inside of the band gap, and what was the most important part of the work – to minimize the number of layers in the structure. Two types of the genetic algorithm were compared in the study. The first one was characterized by a constant number of layers (GACL) of the phononic structure of each individual in each population. Then, the algorithm was run for a different number of layers, as a result of which the structures with the best value of the objective function were determined. In the second version of the algorithm, individuals in populations had a variable number of layers (GAVL) which required a different type of target function and crossover procedure. The transmission for quasi-one-dimensional phononic structures was determined with the use of the transfer matrix method algorithm. Based on the research, it can be concluded that the developed GAVL algorithm with an appropriately selected objective function achieved optimal solutions in a much smaller number of iterations than the GACL algorithm, and the value of the k parameter below 1 leads to faster achievement of the optimal structure.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2022, 70, 1; e139394, 1--8
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Standing Waves in One-Dimensional Resonator Containing an Ideal Isothermal Gas Affected by the Constant Mass Force
Autorzy:
Perelomova, A.
Powiązania:
https://bibliotekanauki.pl/articles/177416.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
acoustic resonator
non-uniform media
standing waves
Opis:
The study is devoted to standing acoustic waves in one-dimensional planar resonator which containing an ideal gas. A gas is affected by the constant mass force. Two types of physically justified boundary conditions are considered: zero velocity or zero excess pressure at both boundaries. The variety of nodal and antinodal points is determined. The conclusion is that the nodes of pressure and antinodes of velocity do not longer coincide, as well as antinodes of pressure and nodes of velocity. The entropy mode may contribute to the total field in a resonator. It is no longer isobaric, in contrast to the case when the external force is absent. Examples of perturbations inherent to the entropy mode in the volume of a resonator are discussed.
Źródło:
Archives of Acoustics; 2017, 42, 2; 263-271
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł

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