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Wyświetlanie 1-15 z 184
Tytuł:
The use of the time reverse acoustics in a shallow sea
Autorzy:
Stromkov, A. A.
Powiązania:
https://bibliotekanauki.pl/articles/331672.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
acoustics
shallow sea
TRM
Opis:
In this report the results of theoretical, numerical and experimental analysis of TRM in a shallow sea are submitted. It is shown that in shallow sea the characteristics of focusing depend first of all on the sizes of the array of imaginary sources which essentially exceeds the sizes of any real array. The method of an experimental research of characteristics of TRM is founded only on the receiving elements and a probe sources is offered. The spatial sizes and the form of focal area of TRM are measuired. It is experimentally confirmed the identity of focal area of TRM with one element and the vertical arrays. The estimation of efficiency of such systems is executed.
Źródło:
Hydroacoustics; 2008, 11; 353-363
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Underwater noise properties in waterway areas of the South Baltic Sea
Autorzy:
Jaśniewicz, D.
Klusek, Z.
Neves, S.
Powiązania:
https://bibliotekanauki.pl/articles/331866.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
shipping noise
shallow sea
Opis:
Results of underwater noise records completed with single and multi-hydrophone systems performed in the shallow water in the close vicinity of shipping lanes to the Gdansk/Gdynia and Świnoujście/Szczecin harbours are presented. Due to the fact that the bottom properties, bathymetry, and temporally varying sea surface alter the original sound spectra and reduce the acoustic energy, the sound transmission losses have been modelled, and an attempt to predict source levels of ships was performed. The KRAKEN sound propagation model illustrates the problems of the recognition of sources noise spectra on the basis of observations in a far zone from the sources. On the basis of the observed noise data, jointly with the AIS system the potential ecological effects of anthropogenic underwater noise on marine organisms are given for the Pomeranian Bight. In the paper, some examples of algorithms of ship noise recognition are given.
Źródło:
Hydroacoustics; 2016, 19; 173-184
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Non-linear water waves - experiments and theory
Autorzy:
Wilde, P.
Sobierajski, E.
Sobczak, Ł.
Powiązania:
https://bibliotekanauki.pl/articles/241057.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
shallow water waves
laboratory experiments
Opis:
The paper concems laboratory experiments on shallow water waves. The waves in our flume were generated as programmed groups, with gentle fading-in and fading-out of amplitudes of the wavemaker's piston's motions. The higher harmonic components have been considered in the motion. Their influence on characteristics of generated waves has also been studied. The measurements were carried out at 6 cross sections along the propagation path; both wave profiles and velocities were recorded. As a description of phenomena, the wave profiles were approximated by harmonic com-ponents according to the Stokes solution. It was noted, that parameters of harmonic components change along the propagation path; there are energy transfers between them. The higher harmonic components are more significant for the description of wave profiles, than for the velocities. The results of the experiments were used in verifications in a research program on the theoretical description and numerical al-gorithm for shallow water waves generated and propagated in a flume.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2001, 48, 2; 107-128
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical investigating the effect of water depth on ship resistance using RANS CFD method
Autorzy:
Hoa, Nguyen Thi Ngoc
Vu, Bich Ngoc
Tran, Ngoc Tu
Chien, Nguyen Manh
Le, Tat Hien
Powiązania:
https://bibliotekanauki.pl/articles/259677.pdf
Data publikacji:
2019
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
ship resistance
shallow water
RANS
Opis:
On inland waterways the ship resistance and propulsive characteristics are strictly related to the depth of the waterway, thus it is important to have an understanding of the influence of water depth on ship hydrodynamic characteristics. Therefore, accurate predictions of hydrodynamic forces in restricted waterways are required and important. The aim of this paper is investigating the capability of the commercial unsteady Reynolds– Averaged Navier–Stokes (RANS) solver to predict the influence of water depth on ship resistance. The volume of fluid method (VOF) is applied to simulate the free surface flow around the ship. The hull resistance in shallow and deep water is compared. The obtained numerical results are validated against related experimental studies available in the literature.
Źródło:
Polish Maritime Research; 2019, 3; 56-64
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Approximate solution to the Boussinesq type equations describing periodic waves
Autorzy:
Szmidt, J. K.
Powiązania:
https://bibliotekanauki.pl/articles/240984.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
Boussinesq type equations
shallow water
Opis:
The paper concerns the non-linear problem of description of shallow-water waves of finite amplitude. The description is based on the conservation-law formulation, which seems to be particularly convenient in constructing an approximate solution of the problem considered. The analysis is confined to the one-dimensional case of waves propagating in water of constant depth. In the model considered, vertical acceleration of the fluid is taken into account, and thus, the fundamental equations of the problem are similar to those given by Boussinesq (Abbott 1979). The equations differ from those frequently used in shallow-water hydrodynamics which are based on the assumption of hydrostatic pressure. An approximate solution of the problem is constructed by means of a perturbation scheme with the third order expansion of the equations with respect to a small parameter. It is demonstrated that the solution procedure may be successfully applied only within a certain range of the two ratios defining wave height to water depth and the depth to wave length, respectively.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2003, 50, 3; 269-285
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tracking of the broadband source of the underwater noise in the very shallow water conditions
Autorzy:
Grelowska, G.
Kozaczka, E.
Powiązania:
https://bibliotekanauki.pl/articles/331537.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
broadband signals
shallow water
sound propagation
Opis:
The paper contains the results, both theoretical and experimental, connected with the tracking of the underwater noise source as small ships, pontoon, diver and so on. The problem of security in the shallow water area is the challenge for underwater acousticians. In this paper there is taken into account the detection of the sources that move on the surface of the sea or underwater in shallow and very shallow water. The main goal deals with characterization of the sound propagation at the shallow water channel. The next problem is formulation of the sound propagation inside of this acoustic duct including normal mode creations and dispersion of the acoustic energy. When we take into account the small ships noise the two main sources are analyzed. The first one is the vibration energy produced by the mechanisms located inside of the ship hull. The acoustical energy is transformed through structural elements of the hull to surrounding water. This energy propagates as broadband underwater noise. The next source is the ship propeller. The sources of the underwater noise give the some deposit to the total acoustical energy that means the ambient noise. The problem that should be solved is to discover these acoustical disturbances along with their classification, identification and tracking.
Źródło:
Hydroacoustics; 2015, 18; 77-86
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental studies of low-frequency acoustic fields in a shallow sea
Autorzy:
Luchinin, A. G.
Powiązania:
https://bibliotekanauki.pl/articles/332794.pdf
Data publikacji:
2009
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
experimental studies
acoustic fields
shallow sea
Opis:
The results of the studies of excitation and propagation of low-frequency acoustic fields in a shallow sea, which have been carried out at the IAP RAS for several years, are discussed. A novel equipment complex designed specially for these experiments and intended for the selective excitation and reception of waveguide modes is described. Examples of measurements of various characteristics of low-order mode acoustic signals are given, which demonstrate high efficiency of the applied equipment and measurement technique.
Źródło:
Hydroacoustics; 2009, 12; 117-126
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Metodika ocenki dvizenia sudov na melkovodnyh ucastkah
Techniques for the assessment of ships in shallow areas
Autorzy:
Arefyev, I.
Powiązania:
https://bibliotekanauki.pl/articles/359847.pdf
Data publikacji:
2012
Wydawca:
Akademia Morska w Szczecinie. Wydawnictwo AMSz
Tematy:
transport
shallow water
ship
environment
evaluation
Opis:
A method for assessing the impact of low water in the fairway on the movement of ships in the rivers and canals is shown in the work. The growth speed of the ship breaks down the river (channel), the territory of the area. It is important that when the motion is regular. This paper is an analysis of this problem.
Źródło:
Zeszyty Naukowe Akademii Morskiej w Szczecinie; 2012, 31 (103); 19-23
1733-8670
2392-0378
Pojawia się w:
Zeszyty Naukowe Akademii Morskiej w Szczecinie
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A method of hybrid MT for related languages
Autorzy:
Homola, P.
Kubon, V.
Powiązania:
https://bibliotekanauki.pl/articles/969803.pdf
Data publikacji:
2010
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
machine translation
related languages
shallow methods
Opis:
The paper introduces a hybrid approach to a very specific field in machine translation - the translation of closely related languages. It mentions previous experiments performed for closely related Scandinavian, Slavic, Turkic and Romanic languages and describes a novel method, a combination of a simple shallow parser of the source language (Czech) combined with a stochastic ranker of (parts of) sentences in the target language (Slovak, Russian, Slovenian). The ranker exploits a simple stochastic model of the target language and its main task is to choose the best translation among those provided by the system. The last section of the paper presents results indicating better translation quality compared to the existing MT system for Czech and Slovak and compares them with the results obtained by the translation from Czech to Russian using the same system.
Źródło:
Control and Cybernetics; 2010, 39, 2; 421-438
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
White noise excited vibrations of viscoelastic shallow shells
Autorzy:
Nizioł, J.
Kozień, M. S.
Powiązania:
https://bibliotekanauki.pl/articles/279764.pdf
Data publikacji:
2000
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
shallow shells
vibrations
viscoelasticity
white noise
Opis:
The paper presents the results of the analysis of randomly excited vibrations of viscoelestic shallow shells. The parameter of interest is the dispersion of velocity normal to the element surface. The choice of parameter is motivated by estimation of the noise generated by a vibrating panel.
Drgania lepkosprężystych powłok małowyniosłych poddanych wymuszeniu losowemu typu białego szumu W artykule omówiono rezultaty analiz drgań powłok małowyniosłych wykonanych z materiału lepkosprężystego i poddanych wymuszeniu losowemu typu białego szumu. Jako parametr opisujący drgania przyjęto dyspersję składowej prędkości normalnej do powierzchni środkowej powłoki. Wybór tego parametru jest uzasadniony faktem, iż jego wartość może być miarą wartości mocy akustycznej promieniowanej przez drgający element.
Źródło:
Journal of Theoretical and Applied Mechanics; 2000, 38, 2; 351-366
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the vertical distribution of the sound speed of the Gulf of Gdansk in the years 2000-2010
Autorzy:
Grelowska, G.
Witos, D.
Powiązania:
https://bibliotekanauki.pl/articles/332481.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Akustyczne
Tematy:
shallow water acoustics
underwater acoustic climate
Opis:
The conditions of the acoustic wave propagation in the southern Baltic are much more complex than in other shallow waters. In the typical shallow water, seasonal changes in acoustical conditions in the upper layer, of the depth of about 60-70 m, are observed. They are caused by variation of the annual meteorological conditions. Most often, in the deep water layer, acoustical conditions are stable throughout the year. However, in the Southern Baltic they change during the year also in the deep water layer. They depend on the inflows of highly saline water from the Northern Sea through the Danish Straits, which evoke a dense bottom current increasing the salinity at the bottom. The vertical sound speed distribution in the Southern Baltic is strongly dependent on the hydrological conditions. In the paper the characteristic elements of acoustic climate of the Southern Baltic will be considered, based on data concerning the Gulf of Gdansk. Averaged characteristics of temperature, salinity and sound speed for the years 2000-2010, as well as anomalies, have been determined.
Źródło:
Hydroacoustics; 2016, 19; 129-137
1642-1817
Pojawia się w:
Hydroacoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Two-dimensional shallow water model for rapidly and gradually varied flow
Autorzy:
Szydłowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/241012.pdf
Data publikacji:
2001
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
Two-dimensional shallow water model
rapidly varied flow
gradually varied flow
shallow water equations
eddy viscosity terms
Opis:
The numerical solution of full shallow water equation (SWE) including the eddy viscosity terms is presented. In the first part of the paper the solution of the homogeneous part of SWE for discontinuous, rapidly varied flow is reported. The method presented here is based on Roe idea of numerical fluxes of mass and momentum. The numerical solution of SWE on unstructured, triangular mesh is reported and the influence of geometry approximation is examined. The imposing of the boundary condition on a triangular numerical mesh is described in detail. The consistent with finite volume method (FVM) approximation of the viscous part of SWE is presented. The procedure similar to the finite element method (FEM) is used to calculate the function derivatives inside the finite volumes. The specific difficulties of source terms numerical integration are studied and some methods to avoid these problems are presented. To integrate the bottom friction term the splitting technique is implemented. The computed results are compared to analytical solution of Saint-Venant equations, experimental data and results available in the literature. Good agreement between these results is observed.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2001, 48, 1; 35-61
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of Groundwater Vulnerability Using the DRASTIC Method in Ouargla Shallow Aquifer (Algerian Sahara)
Autorzy:
Satouh, Adel
Boualem, Bouselsal
Chellat, Smaine
Benaabidate, Lahcen
Powiązania:
https://bibliotekanauki.pl/articles/1838286.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
Ouargla
shallow aquifer
vulnerability
DRASTIC
land-use
Opis:
Groundwater is the main source for many uses around the city of Ouargla. In this study, the DRASTIC method was used to assess the vulnerability of the groundwater aquifer. Seven hydrogeological parameters of the model (D water depth, R efficient charging, A aquifer type, S soil type, T topography, I unsaturated zone and C hydraulic conductivity) were measured and mapped. The intrinsic vulnerability map of the shallow aquifer, using the DRASTIC method, shows a high to very high vulnerability to pollution; 91.6% of the study area has high vulnerability, 8.4% of it has very high vulnerability. The comparison of the DRASTIC maps with the land use map illustrates that the agglomerations and irrigated areas are the most vulnerable areas to pollution, due to the low depth of the aquifer and the infiltration of significant domestic and irrigation wastewater. The results show that the relationship coefficient between the DRASTIC index and nitrate concentration is R = 0.73. This indicates that the groundwater vulnerability mapping by using the DRASTIC method can be applied for sensible groundwater resources management and land-use planning in the study area.
Źródło:
Journal of Ecological Engineering; 2021, 22, 6; 12-19
2299-8993
Pojawia się w:
Journal of Ecological Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of Groundwater Vulnerability Using the DRASTIC Method in Ouargla Shallow Aquifer (Algerian Sahara)
Autorzy:
Satouh, Adel
Boualem, Bouselsal
Chellat, Smaine
Benaabidate, Lahcen
Powiązania:
https://bibliotekanauki.pl/articles/1838393.pdf
Data publikacji:
2021
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
Ouargla
shallow aquifer
vulnerability
DRASTIC
land-use
Opis:
Groundwater is the main source for many uses around the city of Ouargla. In this study, the DRASTIC method was used to assess the vulnerability of the groundwater aquifer. Seven hydrogeological parameters of the model (D water depth, R efficient charging, A aquifer type, S soil type, T topography, I unsaturated zone and C hydraulic conductivity) were measured and mapped. The intrinsic vulnerability map of the shallow aquifer, using the DRASTIC method, shows a high to very high vulnerability to pollution; 91.6% of the study area has high vulnerability, 8.4% of it has very high vulnerability. The comparison of the DRASTIC maps with the land use map illustrates that the agglomerations and irrigated areas are the most vulnerable areas to pollution, due to the low depth of the aquifer and the infiltration of significant domestic and irrigation wastewater. The results show that the relationship coefficient between the DRASTIC index and nitrate concentration is R = 0.73. This indicates that the groundwater vulnerability mapping by using the DRASTIC method can be applied for sensible groundwater resources management and land-use planning in the study area.
Źródło:
Journal of Ecological Engineering; 2021, 22, 6; 12-19
2299-8993
Pojawia się w:
Journal of Ecological Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The extent of the unconfined aquifer based on the Dempster-Shafer theory on the example of postglacial sandur area
Autorzy:
Kachnic, M.
Powiązania:
https://bibliotekanauki.pl/articles/2063008.pdf
Data publikacji:
2010
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
unconfined aquifer
shallow aquifer
Dempster-Shafer theory
probabilistic
Opis:
The research aimed to present an application of the technique based on the Dempster-Shafer theory for the determination of the shallow unconfined aquifer extent in a nonparametric (probabilistic) scale. The geology of research area is predominantly composed of the Pleistocene postglacial sediments. Only unconfined aquifers were taken into account in the study described in these paper. The resulting image showed a map of the aquifers’ extents in a probabilistic scale i.e. in a range between 0 (the lack of the aquifer, which is confirmed by research) and 1 (confirms the occurrence of the aquifer proved by research). Data analyses were carried out in the Geographic Information System. All the data were imported to the IDRISI. The Dempster-Shafer probability theory supported by the module BELIEF of IDRISI software was applied to the algebra of pixel maps.
Źródło:
Biuletyn Państwowego Instytutu Geologicznego; 2010, 441 Hydrogeologia z. 10; 55--61
0867-6143
Pojawia się w:
Biuletyn Państwowego Instytutu Geologicznego
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 184

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