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Problem of disturbance identification by measurement in the vicinity of a point

100%

Leble S. , Vereshchagina I.

tom Vol. 20, No 2

131--141

A problem of wave identification is formulated. We propose a diagnostic analysis of medium disturbances based on distinguishing of components of a wave vector that is specific for each kind of the wave mode. Mathematically it is realized by projection operator technique. An example is considered in conditions of a one-dimensional Cauchy problem for a conventional wave equation in the matrix form and its version with weakly x-dependent coefficients as a demonstration of the method application for the simplest adiabatic theory of one-dimensional acoustics. The case of acoustics in a gas with a dissipation account is also discussed from the point of view of the wave and entropy mode diagnostics.

Virial coefficients from cubic KZK

100%

Leble S. , Vereshchagina I.

tom Vol. 2

251--256

We start from the cubic KZK equation for ultrasonics beam that accounts first, second and third powers of density in pressure Taylor series expansion. In a condition of moderate amplitude and nearfield one can use approximate solutions provided by perturbation method including terms resonant to the multiple frequencies on a transducer. We consider three resonant harmonics within Rayleigh distance range. The second and third harmonics averaged over the beam cross-section are expressed in terms of some standard integrals and nonlinear constants. Fourier transforms of a signal on a receiver are equalized to the results of the evaluation that give equations for the non-linear constants determination. This in tum allows to compute constants B/A and C/A of the equation of state (virial expansion).