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    Wyświetlanie 1-4 z 4
    Tytuł:
    Surface Impedance Boundary Conditions applied to solving nonlinear electrodynamic systems
    Autorzy:
    Pawłowski, S.
    Plewako, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/141489.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    nonlinear electrodynamics
    Surface Impedance Boundary Conditions
    harmonic fields
    quasi-stationary fields
    skin effect
    Opis:
    The paper presents a method for solving electromagnetic field problems by applying impedance boundary conditions for systems including conducting bodies of nonlinear magnetic properties in an excited harmonic field. Three types of impedance boundary conditions were derived. A procedure for computing surface impedance based on the transfer matrix is proposed. This procedure has been tested by comparing computational results to calculations where time function distortions were considered, and to the experimental data.
    Źródło:
    Archives of Electrical Engineering; 2017, 66, 2; 433-446
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Propagation in dielectric rectangular waveguides
    Autorzy:
    Yeap, K. H.
    Teh, K. H.
    Yeong, K. C.
    Lai, K. C.
    Loh, M. C.
    Powiązania:
    https://bibliotekanauki.pl/articles/173566.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dielectric rectangular waveguide
    transverse wave numbers
    attenuation coefficient
    surface impedance
    propagation constant
    fundamental mode
    Opis:
    We present a fundamental and accurate approach to compute the attenuation of electromagnetic waves propagating in dielectric rectangular waveguides. The transverse wave numbers are first obtained as roots of a set of transcendental equations developed by matching the fields with the surface impedance of the wall. The propagation constant is found by substituting the values of transverse wave numbers into the dispersion relation. We have examined the validity of our model by comparing the computed results with those obtained from Marcatili’s equations and the finite element method. In our results, it is shown that the fundamental mode is identical with that found in a perfectly conducting waveguide. Our analysis also shows that a hollow waveguide is found to have much lower attenuation than its dielectric counterparts. Since the cutoff frequency is usually affected by the constitutive properties of the dielectric medium, for a waveguide designed for wave with the same cutoff frequency, hollow waveguides turn out to be relatively larger in size.
    Źródło:
    Optica Applicata; 2016, 46, 2; 317-330
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of sound absorption performance of acoustic absorbers made of fibrous materials
    Autorzy:
    Meissner, Mirosław
    Zieliński, Tomasz G.
    Powiązania:
    https://bibliotekanauki.pl/articles/2202433.pdf
    Data publikacji:
    2022
    Wydawca:
    Politechnika Poznańska. Instytut Mechaniki Stosowanej
    Tematy:
    sound absorption
    multi-layer absorber
    surface impedance
    fibrous materials
    air gap
    chłonność akustyczna
    wielowarstwowy pochłaniacz dźwięku
    materiały włókniste
    szczelina powietrzna
    Opis:
    Absorbing properties of multi-layer acoustic absorbers were modeled using the impedance translation theorem and the Garai and Pompoli empirical model, which enables a determination of the characteristic impedance and propagation constant of fibrous sound-absorbing materials. The theoretical model was applied to the computational study of performance of single-layer acoustic absorber backed by a hard wall and the absorber consisting of one layer of absorbing material and an air gap between the rear of the material and a hard back wall. Simulation results have shown that a high thickness of absorbing material may cause wavy changes in the frequency relationship of the normal and random incidence absorption coefficients. It was also found that this effect is particularly noticeable for acoustic absorbers with a large thickness of air gap between the absorbing material and a hard back wall.
    Źródło:
    Vibrations in Physical Systems; 2022, 33, 2; art. no. 2022205
    0860-6897
    Pojawia się w:
    Vibrations in Physical Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of Ultrasonic Methods for Evaluation of High-Pressure Physicochemical Parameters of Liquids
    Autorzy:
    Kiełczyński, Piotr
    Ptasznik, Stanisław
    Szalewski, Marek
    Balcerzak, Andrzej
    Wieja, Krzysztof
    Rostocki, Aleksander J.
    Powiązania:
    https://bibliotekanauki.pl/articles/176703.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    ultrasonic methods
    speed of sound
    acoustic impedance
    surface tension
    thermal conductivity
    physicochemical properties
    Opis:
    An emerging ultrasonic technology aims to control high-pressure industrial processes that use liquids at pressures up to 800 MPa. To control these processes it is necessary to know precisely physicochemical properties of the processed liquid (e.g., Camelina sativa oil) in the high-pressure range. In recent years, Camelina sativa oil gained a significant interest in food and biofuel industries. Unfortunately, only a very few data characterizing the high-pressure behavior of Camelina sativa oil is available. The aim of this paper is to investigate high pressure physicochemical properties of liquids on the example of Camelina sativa oil, using efficient ultrasonic techniques, i.e., speed of sound measurements supported by paralel measurements of density. It is worth noting that conventional low-pressure methods of measuring physicochemical properties of liquids fail at high pressures. The time of flight (TOF) between the two selected ultrasonic impulses was evaluated with a cross-correlation method. TOF measurements enabled for determination of the speed of sound with very high precision (of the order of picoseconds). Ultrasonic velocity and density measurements were performed for pressures 0.1-660 MPa, and temperatures 3-30°C. Isotherms of acoustic impedance Za, surface tension σ and thermal conductivity k were subsequently evaluated. These physicochemical parameters of Camelina sativa oil are mainly influenced by changes in the pressure p, i.e., they increase about two times when the pressure increases from atmospheric pressure (0.1 MPa) to 660 MPa at 30°C. The results obtained in this study are novel and can be applied in food, and chemical industries.
    Źródło:
    Archives of Acoustics; 2019, 44, 2; 329-337
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-4 z 4

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