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Wyświetlanie 1-15 z 419
Tytuł:
Pressure field in a plane layer
Autorzy:
Baranowska, A.
Powiązania:
https://bibliotekanauki.pl/articles/331904.pdf
Data publikacji:
2010
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
acoustic waves propagation
acoustic waves
waves generation
Opis:
The paper presents results of analytical and numerical investigations of a plane acoustic waves propagation through a plane layer surrounded by another medium. The waves generation problem is discussed. The mathematical model of the pressure propagation in the layer is proposed. Propagated through the layer changes in pressure, the reflected and transmitted waves were studied. Some results of numerical investigations are presented.
Źródło:
Hydroacoustics; 2010, 13; 9-16
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Generation and propagation of nonlinear waves in a towing tank
Autorzy:
Drzewiecki, Marcin
Sulisz, Wojciech
Powiązania:
https://bibliotekanauki.pl/articles/260177.pdf
Data publikacji:
2019
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
wavemaker
towing tank
nonlinear waves
waves generation
waves propagation
Opis:
The paper presents the results of the research focused on linear and nonlinear wave generation and propagation in a deepwater towing tank equipped with a single flap-type wavemaker of variable draft. The problem of wave generation and propagation has been theoretically formulated and solved by applying an analytical method; linear and nonlinear solutions were obtained. The linear solution has been verified experimentally. The laboratory experiments confirmed that a linear model can be applied to predict the generation and propagation of water waves of low steepness. However, according to the analysis, the discrepancies between wave profiles predicted by applying the linear and nonlinear models rapidly increases with increasing wave steepness. Additionally, the secondary phenomena which occur in the towing tank, including: disintegration of wave profile, wave reflections from the beach and wave damping, were analyzed. Knowledge on the nonlinear processes and phenomena is essential for modeling the environmental conditions during tests carried out to secure the safety of the naval and offshore constructions. The theoretical formulation was derived and the solution was obtained by the Institute of Hydroengineering of the Polish Academy of Sciences IBW PAN while the experimental research was carried out in Ship Hydromechanics Division of the Ship Design and Research Centre CTO S.A.
Źródło:
Polish Maritime Research; 2019, 1; 125-133
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scattering of plane acoustic waves at elastic particles with rough surfaces
Autorzy:
Bjørnø, L.
Powiązania:
https://bibliotekanauki.pl/articles/332313.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
ultrasonic waves
acoustic waves
rough surfaces
Opis:
A comprehensive theoretical and numerical study oj the influence oj surface roughness oj elastic particles in water on the scattering oj ultrasonic waves has been carried out. For near spherical shape oj the particles and with small rms-roughness heights a perturbation method has been developed. In this method the first-order perturbation contribution predicts the contribution to the incoherently scattered acoustic field due to surjace roughness, and the second-order perturbation contribution predicts the change in the coherent field and will satisfy the requirement oj energy conservation. The second-order perturbation contribution is evaluated using the concept ojform function, while the first-order perturbation to the total scattered acoustic field is evaluated using the scattering cross-section. As a junction oj the ka-value and jor different rms-roughness heights a numerical study oj the jorward and backward scattering from rough, elastic particles has been carried out and a substantial roughness influence on the scattered field has been verified. Same experimental resultsfrom measurements oj scattering jrom glass and cast iron spheres have given evidence to the numerical predictions.
Źródło:
Hydroacoustics; 2003, 6; 7-18
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulations of sound wave generation in a random medium
Autorzy:
Murawski, K.
Selwa, M.
Powiązania:
https://bibliotekanauki.pl/articles/1955700.pdf
Data publikacji:
2004
Wydawca:
Politechnika Gdańska
Tematy:
sound waves
random waves
frequency shift
amplitude alteration
Opis:
In turbulent media, both sound wave sources and the speed of sound can be stochastic variables. By means of numerical simulations of one-dimensional Euler equations with random source terms we have studied two cases in a homogeneous stochastic random medium for which the speed of sound and sound sources are: (1) correlated and (2) uncorrelated. The numerical simulations indicate that, if the source and the speed of sound fluctuations are uncorrelated, the acoustic field is incoherent, with a zero expectation value. The mean field is non-zero in the correlated case. The correlated and uncorrelated cases are clearly distinguishable by the mean field, but also - to some extent - in the power spectrum, which displays a modified Lorentzian profile with a shift in frequency.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 1; 109-114
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sound waves in a wave noise
Autorzy:
Murawski, K.
Tarnowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1955702.pdf
Data publikacji:
2004
Wydawca:
Politechnika Gdańska
Tematy:
sound waves
random waves
frequency shift
amplitude alteration
Opis:
We examine by analytical and numerical means sound waves which propagate in a space- and time-dependent random mass density field in the form of dispersionless wave noise of its spectrum E(kappa,omega) ~ E(kappa) delta (omega-crk), where cr is a random speed. Numerical simulations are in agreement with the analytical theory which shows that at cr=omega/k resonance occurs and the cyclic frequency omega tends to infinity. For values of cr which are close to the resonance point, the sound waves are slowed down and attenuated (accelerated and amplified) for cr < omega/k (cr > omega/k).
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 1; 103-108
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Interaction of internal and surface waves in a two-layer fluid with free surface
Autorzy:
Naradovy, V.
Powiązania:
https://bibliotekanauki.pl/articles/115568.pdf
Data publikacji:
2013
Wydawca:
Fundacja na Rzecz Młodych Naukowców
Tematy:
internal waves
surface waves
fluid layer
multiple scales
stability
Opis:
The interaction of internal and surface waves in a two-layer fluid with free surface has been considered. The stability of wave packets propagation on the contact surface and free surface of hydrodynamic system „layer with rigid bottom - layer with free surface” was investigated. The amplitudes of the second harmonics of the elevations of the contact surface and the free surface are investigated.
Źródło:
Challenges of Modern Technology; 2013, 4, 3; 3-9
2082-2863
2353-4419
Pojawia się w:
Challenges of Modern Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An application of critically refracted longitudinal ultrasonic subsurface waves (LCR) to industrial nondestructive testing of thin walled pipe shaped elements of shock absorbers, axle shafts and transmission shafts
Autorzy:
Bicz, A.
Bicz, W.
Korzeniowski, M.
Ambroziak, A.
Powiązania:
https://bibliotekanauki.pl/articles/114523.pdf
Data publikacji:
2016
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
ultrasonic waves
subsurface waves
head waves
LCR
creeping waves
flaw detection in friction butt welds
MIAB welding
ultrasonic testing of thin walled pipes
Opis:
The paper describes the application of critically refracted longitudinal ultrasonic subsurface waves (LCR, known also as lateral, creeping or head waves) to nondestructive flaw detection in friction welding or MAIB welded thin walled pipe shaped parts. The theory, a practical laboratory and industrial applications are presented.
Źródło:
Measurement Automation Monitoring; 2016, 62, 7; 227-233
2450-2855
Pojawia się w:
Measurement Automation Monitoring
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The interaction between local factors and the Convectively Coupled Equatorial Waves over Indonesia during the Western North Pacific and Australian monsoon phase
Autorzy:
Pramuwardani, Ida
Sunarto, Hartono
Sopaheluwakan, Ardhasena
Powiązania:
https://bibliotekanauki.pl/articles/108463.pdf
Data publikacji:
2020
Wydawca:
Instytut Meteorologii i Gospodarki Wodnej - Państwowy Instytut Badawczy
Tematy:
Convectively Coupled Equatorial Waves
Kelvin waves
local factor
monsoon
Indonesia
Opis:
A large scale perturbation by the Convectively Coupled Equatorial Waves (CCEW) is often observed in the tropics as a precursor to influence weather condition, for example over the Indonesian archipelago (Maritime Continent (MC)). This study examines the interaction between local factors and CCEW with regard to convection and vertical interferences on a local scale over Indonesia during extreme Western North Pacific (WNP) and Australian (AU) monsoon phases. Through space-time spectra analysis of a 15 year (2001-2015) Tropical Rainfall Measuring Mission (TRMM) 3B42 dataset, the propagation of CCEW, i.e. Kelvin, Equatorial Rossby (ER) and Mixing Rossby-Gravity (MRG) waves was assessed. An Empirical Orthogonal Function (EOF) 1 and 2 for each wave evolution across the region of Indonesia, was then compared with daily precipitation anomalies and multilevel wind observations from seven locations in Indonesia to assess the interaction between local factors and CCEW. Results suggest there is evidence of local convection associated with Kelvin waves in the afternoon through to the evening in Tangerang, Surabaya and Makassar during WNP monsoon phases. Local convection associated with MRG waves only occurred in Makassar at the last evolution day during the same period, while there is no clear evidence for an interaction between local factors for ER waves. Low-level westerly winds appear to be significantly coupled with convection from Kelvin waves in Tangerang, Surabaya, and Makassar during the WNP monsoon phase, while the interaction is less significant for MRG-coupled convections (except in Makassar during the same monsoon phase) and absent for ER waves. This study suggests that the global scale phenomena of the Kelvin wave is associated with local scale factors in controlling convection, particularly during an extreme WNP phase in Indonesia.
Źródło:
Meteorology Hydrology and Water Management. Research and Operational Applications; 2020, 8, 1; 84-89
2299-3835
2353-5652
Pojawia się w:
Meteorology Hydrology and Water Management. Research and Operational Applications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effects of liquid loadings on lamb waves in context of size dependent couple stress theory
Autorzy:
Sharma, V.
Kumar, S.
Powiązania:
https://bibliotekanauki.pl/articles/949331.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
couple stress
characteristic length
Lamb waves
elastic waves
liquid loadings
Opis:
For understanding the effects of an internal microstructure, generalised microcontinuum theories with additional microstructural parameters are developed. One such a parameter, called the characteristic length of the material comparable with the internal cell size of the material is involved in the couple stress theory. The problem of propagation of Lamb waves in a plate with an internal microstructure and loaded with an inviscid liquid on both sides is studied using the couple stress theory. The dispersion equation of Lamb waves with the liquid loadings is derived. The impact of the liquid loadings is studied on the propagation of Lamb waves. The effect of the characteristic length is also studied on the phase velocity of Lamb waves in the plate for various modes in the presence of liquid loadings.
Źródło:
Journal of Theoretical and Applied Mechanics; 2015, 53, 4; 925-934
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The dependency between annual air temperature and solar activity. A case study of Warsaw in 1951-2010.
Autorzy:
Boryczka, Jerzy
Stopa-Boryczka, Maria
Kossowska-Cezak, Urszula
Wawer, Jolanta
Powiązania:
https://bibliotekanauki.pl/articles/2108255.pdf
Data publikacji:
2017-10-04
Wydawca:
Uniwersytet Warszawski. Wydział Geografii i Studiów Regionalnych
Tematy:
Cold waves
heat waves
solar activity
regression sinusoid
period
interference
Opis:
The paper demonstrates a dependency between the annual average daily air temperature course (cycle) in Warsaw and the profile of annual solar activity linked to rotation (with a period of 25-31 days). Waves of cold (ΔT <0) or heat (ΔT≥ 0) were defined as ΔT deviations of daily average temperature (T) using a regression sinusoid f (t) with a period of 365 days. Cold waves were found to generally occur at times of low daily average solar activity (relative to 60-year average), while hot waves tended to coincide with high Wolf numbers. The cycles of the variables were derived using the sinusoid regression method (Boryczka 1998). The maximum sinusoid regression of the annual air-temperature cycle T is delayed by nearly one month vis-à-vis the maximum declination of the Sun. The maximum of the regression sinusoid of daily average Wolf numbers (W) was delayed from the maximum declination by more than two months.
Źródło:
Miscellanea Geographica. Regional Studies on Development; 2017, 21, 3; 132-138
0867-6046
2084-6118
Pojawia się w:
Miscellanea Geographica. Regional Studies on Development
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of signals of the range 10-3 - 10-4 Hz registered by water-tube tiltmeters in the underground geodynamic laboratory in Książ (SW Poland)
Autorzy:
Kaczorowski, Marek
Kasza, Damian
Zdunek, Ryszard
Wronowski, Roman
Powiązania:
https://bibliotekanauki.pl/articles/2174941.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Centrum Badań Kosmicznych PAN
Tematy:
interferometry
time series analysis
tides
planetary waves
acoustic gravity waves
surface waves
free oscillations
ionosphere interactions
atmosphere interactions
Opis:
The Geodynamic Laboratory in Książ includes investigations of various kinds of geodynamic signals. Among others, we registered harmonic signals of the range 10-3 - 10-4 Hz. These signals had been found in the measurement series of the long water-tube (WT) tiltmeters. The discovered signals consist of two classes of harmonics associated with various kinds of phenomena. The first class of these signals belongs to viscoelastic vibrations of the Earth’s solid body, while the second class is produced possibly by the extremely long atmospheric infrasound waves. The signals of the vibrations of the Earth had been well recognized by the characteristic frequencies of the Earth’s free vibrations’ resonance, which occur mainly after strong earthquakes. The atmospheric pressure microvibrations affected the water level in the hydrodynamic systems of the WTs as a result of an inverse barometric effect. We observed that signals from both classes blend in the harmonics of similar frequencies and jointly affect the hydrodynamic systems of the WTs. We found that the amplitude of the secondclass signals strongly depends on the location of water-tube gauges inside the underground, while the amplitudes of the first-class signals are similar for all the gauges. These observations clearly indicate the atmospheric origin of the second class of registered signals.
Źródło:
Artificial Satellites. Journal of Planetary Geodesy; 2022, 57, 4; 210--236
2083-6104
Pojawia się w:
Artificial Satellites. Journal of Planetary Geodesy
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exact Cnoidal Solutions of the Extended KdV Equation
Autorzy:
Infeld, E.
Karczewska, A.
Rowlands, G.
Rozmej, P.
Powiązania:
https://bibliotekanauki.pl/articles/1030809.pdf
Data publikacji:
2018-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
shallow water waves
extended KdV equation
analytic solutions
inverted cnoidal waves
Opis:
The KdV equation can be derived within the shallow water limit of the Euler equations. Over the last few decades, this equation has been extended to include both higher order effects (KdV2) and an uneven river bottom. Although this equation is not integrable and has only one conservation law, exact periodic and solitonic solutions exist for the even bottom case. The method used to find them assumes the same functional forms as for KdV solutions. The KdV2 equation imposes more constraints on the parameters of solutions. Quite unexpectedly, we found two regions in m parameter space for periodic solutions. For the range of m close to one the cnoidal waves are upright as expected, but are inverted in the m region close to zero which is a completely new feature. The properties of exact solutions for KdV and KdV2 are compared. Numerical evolution of all the discussed exact solutions to KdV2 is stable and confirms the properties of the analytic solutions.
Źródło:
Acta Physica Polonica A; 2018, 133, 5; 1191-1199
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
General dynamic projecting of Maxwell equations
Autorzy:
Wojda, P.
Leble, S.
Powiązania:
https://bibliotekanauki.pl/articles/1940709.pdf
Data publikacji:
2017
Wydawca:
Politechnika Gdańska
Tematy:
general electrodynamics
electromagnetic waves
dynamic projecting operators
hybrid waves
parabolic equation
Opis:
A complete – system of Maxwell equations is splitting into independent subsystems by means of a special dynamic projecting technique. The technique relies upon a direct link between field components that determine correspondent subspaces. The explicit form of links and corresponding subspace evolution equations are obtained in conditions of certain symmetry, it is illustrated by examples of spherical and quasi-one-dimensional waves.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2017, 21, 2; 85-96
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical simulations of Alfv´en waves in the solar atmosphere with the PLUTO code
Autorzy:
Wołoszkiewicz, P.
Murawski, K.
Musielak, Z. E.
Mignone, A.
Powiązania:
https://bibliotekanauki.pl/articles/205850.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
MHD
Alfv´en waves
Opis:
With an adaptation of the PLUTO code, we present a 2.5-dimensional Cartesian magnetohydrodynamic model with the invariant (∂/∂z = 0) coordinate z of propagating magnetohydrodynamic- gravity waves in the solar atmosphere, permeated by curved magnetic field and constant gravity field g = −gˆy. This code implements second-order accurate Godunov-type numerical scheme and MPI for high level of parallelization. We show that the inhomogeneous grid, originally built in the code, resolves well the system dynamics, resulting from the localized pulse initially launched in the transverse component of velocity Vz. We consider two cases for background magnetic field Be = [Bex,Bey,Bez] with its transverse component: (a) Bez = 0 and (b) Bez 6= 0. In case (a), the initial pulse triggers only Alfv´en waves, described solely by Vz. These waves drive by ponderomotive forces the magnetoacoustic waves, associated with perturbations in Vx and Vy. As a result of Bez 6= 0, in the (b) case, Alfv´en waves are coupled to their magnetoacoustic counterparts and all three velocity components are perturbed. We show that in this case the PLUTO code is accurate, its order being 1.97 and the numerically induced flow is of magnitude ≈ 0.1 km s−1, i.e. by a factor of at least ≈ 103 lower than the characteristic (Alfv´en) speed of the system. The errors, associated with the selenoidal condition, are low with the max |∇ ・ B| ≈ 1.3 ・ 10−10 Tesla km−1. We conclude that the PLUTO code copes well with resolving all spatial and temporal scales that appear in this numerically challenging system.
Źródło:
Control and Cybernetics; 2014, 43, 2; 321-335
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On elastodynamics of biperiodic composite media
O elastodynamice dwuperiodycznych kompozytów
Autorzy:
Woźniak, M.
Woźniak, C.
Powiązania:
https://bibliotekanauki.pl/articles/280122.pdf
Data publikacji:
2003
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
modelling
composites
waves
dispersion
Opis:
The aim of this paper is twofold. First, we formulate a mathematical model for the analysis of waves propagating in a linear-elastic composite, which in every plane normal to a certain straight line has an identical periodic structure. Secong, we apply the derived model equations to the investigations of waves propagating across a laminated medium with periodically folded laminae. Lower and higher propagation speeds for the longtudinal and transversal waves are calculated and for the long waves represented in the form of simple asymptotic formulas.
W artykule przedstawiono dwa problemy. Po pierwsze, sformułowano matematyczny model umożliwiający badanie propagacji fal w liniowo-sprężystych kompozytach, dla których każda płaszczyzna prostopadła do pewnej prostej ma taką samą dwuwymiarową strukturę periodyczną. Po drugie, otrzymany model zastosowano do analizy propagacji fal w laminacie o periodycznie pofałdowanych warstwach. Dla przypadku tego wyznaczono niższą i wyższą prędkość fazową propagacji, które w przypadku fal długich dają się wyrazić za pomocą prostych formuł asymptotycznych.
Źródło:
Journal of Theoretical and Applied Mechanics; 2003, 41, 2; 289-304
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 419

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