Temat: surface impedance - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Surface Impedance Boundary Conditions applied to solving nonlinear electrodynamic systems
Autorzy:: Pawłowski, S.
Plewako, J.
Tematy:: nonlinear electrodynamics
Surface Impedance Boundary Conditions
harmonic fields
quasi-stationary fields
skin effect; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/141489.pdf Link otwiera się w nowym oknie
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.
Dostawca treści:: Biblioteka Nauki

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Tytuł:: Propagation in dielectric rectangular waveguides
Autorzy:: Yeap, K. H.
Teh, K. H.
Yeong, K. C.
Lai, K. C.
Loh, M. C.
Tematy:: dielectric rectangular waveguide
transverse wave numbers
attenuation coefficient
surface impedance
propagation constant
fundamental mode; Pokaż więcej
Wydawca:: Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Powiązania:: https://bibliotekanauki.pl/articles/173566.pdf Link otwiera się w nowym oknie
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.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Analysis of sound absorption performance of acoustic absorbers made of fibrous materials
Autorzy:: Meissner, Mirosław
Zieliński, Tomasz G.
Tematy:: sound absorption
multi-layer absorber
surface impedance
fibrous materials
air gap
chłonność akustyczna
wielowarstwowy pochłaniacz dźwięku
materiały włókniste
szczelina powietrzna; Pokaż więcej
Wydawca:: Politechnika Poznańska. Instytut Mechaniki Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/2202433.pdf Link otwiera się w nowym oknie
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.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

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.
Tematy:: ultrasonic methods
speed of sound
acoustic impedance
surface tension
thermal conductivity
physicochemical properties; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/176703.pdf Link otwiera się w nowym oknie
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 Z_a, 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.
Dostawca treści:: Biblioteka Nauki

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