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    Wyświetlanie 1-7 z 7
    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:
    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:
    Differential and Common Mode Noise Waves and Correlation Matrices
    Autorzy:
    Dobrowolski, J. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/226394.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    differential and common mode noise waves
    mixed-mode noise wave correlation matrices
    generalized multiport mixed-mode noise wave correlation matrice
    Opis:
    This paper presents an innovative extention of the noise wave definition to mixed mode, differential – and common-mode noise waves which can be used for noise analysis of differential microwave networks. Mixed mode noise waves are used next to define generalized mixed mode noise wave correlation matrices of microwave multiport networks. Presented approach may be used for noise analysis of microwave differential networks with differential ports as well as with conventional single ended ports.
    Źródło:
    International Journal of Electronics and Telecommunications; 2014, 60, 2; 133-141
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The influence of wave-noise on wave speeds and amplitudes of surface-gravity waves
    Autorzy:
    Murawski, K.
    Zawada, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/1954094.pdf
    Data publikacji:
    2004
    Wydawca:
    Politechnika Gdańska
    Tematy:
    random waves
    dispersion relation
    wave-noise
    Opis:
    We have analytically examined surface-gravity waves which propagate in space- and time-dependent random velocity fields. Using a perturbative method, we have derived a dispersion relation which is solved for the case of wave-noise whose spectrum E(k,omega) ~ E(k)delta(omega-crk), where delta is Dirac's delta-function and cr is the random phase speed. We have found that for a dispersionless noise resonance occurs when cr is equal to the group velocity cg of the surface-gravity wave. In this resonance the real part of the wave frequency is finite, but its imaginary part exhibits the characteristic 1/x singularity. The wave-noise interacts with a packet of the surface-gravity waves in such a way that the waves are attenuated for cr < cg and are amplified for cr > cg. As the real part is positive for high values of k, the surface-gravity waves are accelerated by the wave-noise.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 3; 321-326
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Propagation of ship-generated noise in shallow sea
    Autorzy:
    Kozaczka, E.
    Grelowska, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/259166.pdf
    Data publikacji:
    2018
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    shallow water acoustics
    propagation of acoustic waves in water layer
    wave modes in shallow sea
    underwater noise produced by ship
    Opis:
    Contamination of sea environment by noise and any energy radiated to water constitutes today a problem to which more and more attention is paid, in view, a.o., of consequences of an impact of these factors onto marine fauna. European Union has introduced a directive by which EU countries are made responsible to undertake efforts aimed at reaching a good envirenmental status of European seas by 2020. A main source of underwater noise is sea transport of any kind. Propagation of underwater acoustic disturbances in the Baltic Sea highly differs from the course of the phenomenon in a deep sea. Model of spherical propagation cannot be applied to this case in view of water environment limitation by seabed and free water surface, i.e. a reduction of the problem to wave propagation in a water layer of the depth comparable with acoustic wave length. This paper is aimed at demonstration of possible assessment of range of acoustic disturbances generated by a ship sailing in shallow sea, by using a method described in the work [13]. The research was made on the basis of results of own measurements of underwater noise produced by ships in the Gdansk Bay area. An important factor which decIdes on a range of underwater disturbances is a kind of seabed sediments. In this paper there are presented results of numerical investigations based on real data dealing with noise produced by a selected floating unit (ship) for selected characteristic spectral components. The simulations were conducted for the shallow sea model of definite physical parameters such as acoustic wave propagation velocity, geometrical dimensions (water depth) and seabed acoustic parameters as well.
    Źródło:
    Polish Maritime Research; 2018, 2; 37-46
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    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:
    Application of passive seismic to shallow geological structures in urban areas
    Autorzy:
    Mendecki, Maciej Jan
    Glazer, Michał
    Mycka, Mateusz
    Powiązania:
    https://bibliotekanauki.pl/articles/2027258.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    pas sive seis mic
    Re frac tion Microtremor (ReMi)
    seis mic noise
    Mul ti chan nel Anal y sis of Sur face Waves
    (MASW)
    Re sis tiv ity Im ag ing (RI)
    ur ban area
    Opis:
    To study the shal low geo log i cal struc ture the Re frac tion Microtremor (ReMi) method was ap plied. This tech nique uses seis mic noise anal y sis where a source of this small vi bra tions is the hu man ac tiv ity e.g.: traf fic, pro duc tion, fac tories. The sur veys were car ried out in se lected ur ban ar eas in the re gion of the Up per Silesian In dus trial Dis trict: Sosnowiec–Pogoñ , Chorzów–Chorzów Stary and Bytom–Karb. Each area is char ac ter ized by the pres ence of nearby roads with a very high traf fic. The re sults of pas sive seis mic (ReMi) were con fronted with data ob tained us ing Mul ti - chan nel Anal y sis of Sur face Waves (MASW) and re sis tiv ity im ag ing (RI). Seis mic sur veys were per formed by ap pa - ra tus PASI with 24 chan nels us ing geo phones of 4.5Hz. The re sults showed that pas sive seis mic can be sat is fac to rily used in such ur ban con di tions. The shal low geo log i cal struc ture in ter preted by seis mic meth ods have been well-cor re - lated with re sis tiv ity stud ies.
    Źródło:
    Studia Quaternaria; 2014, 31; 115-122
    1641-5558
    2300-0384
    Pojawia się w:
    Studia Quaternaria
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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