Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 2006

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: monochromatic waves

Sortuj według:

Ogranicz wyniki do:

Laboratoryjne wytwarzanie fali spolaryzowanej częściowo

Czyż Z., Rodziejczak W.

Prace Przemysłowego Instytutu Telekomunikacji

2006

Vol. 56, z. 138

1-16

Zaproponowano metodę wytwarzania dowolnego 4-wektora fali spolaryzowanej częściowo polegającą na złożeniu dwu częściowo koherentnych fal o różnych polaryzacjach całkowitych i fazach. Opis metody poprzedzono analizą składania fal traktowanych jako ergodyczne procesy stacjonarne. Propozycję metody poprzedzono polaryzacyjną analizą składania fal, uproszczoną w sposób istotny przez ograniczenie przypadkowości procesów do różnicy faz. Dzięki temu, przez zastąpienie fal quasi-monochromatycznych równoważnymi polarymetrycznie falami monochromatycznymi, możliwe było zaniechanie uwzględnienia w rozważaniach widm częstotliwości.

A method has been proposed how any desired 4-vector of a partially polarized wave can be formed by composition of two completely but differently polarized waves treated as ergodic stationary processes, mutually partially coherent, with a given effective phase difference. An essential simplification of the method has been obtained when limiting randomness of processes to the phase difference only. That permitted to resign of frequency spectra considerations by just substitution of two usually observed quasi-monochromatic waves with polarimetrically equivalent monochromatic ones.

Influence of coupling through porosity changes on the propagation of acoustic waves in linear poroelastic materials

Albers B., Wilmanski K.

Archives of Mechanics

2006

Vol. 58, nr 4-5

313-325

In earlier works it has been shown that linearization of thermodynamical models of poroelastic materials yields a contribution to stresses in the form ......., where ... is the current porosity, ... denotes its value in the thermodynamical equilibrium and ... is a material parameter. It has been also claimed on the basis of rough estimates that this parameter gives only negligible contributions to the properties of acoustic waves. The purpose of this work is twofold. We investigate the influence of ß on the propagation of acoustic waves in more details. We use the full linear model of saturated poroelastic materials in which an additional coupling to porosity changes appears. This results from the presence of a term with the porosity gradient in the momentum sources. Such a model becomes identical with Biot's model without any added mass contribution in the limit if infinite relaxation time of porosity ... and for the parameters ß=0, and N=0, where the latter is describing the above mentioned influence of porosity gradient on the momentum sources. The analysis of influence of the parameter N, i.e. the influence of the porosity gradient on properties of acoustic waves, is the second purpose of this work. We also indicate a correction of the permeability contribution to the momentum source. The permeability coefficient ... is assumed in Biot's model to be dependent on the frequency. This is inconsistent with other temporal contributions to field equations. In order to obtain such a dependence in the Fourier space, one has to assume a viscous effect to enter the momentum source and we do so in the general equations. However, we do not use this general relation in the analysis of monochromatic waves.