Nonlinear wave processes in media containing cracks partially filled with a viscous liquid

A nonlinear (in the cubic approximation) relaxation equation of state is derived for a rod containing cracks partially filled with an incompressible viscous liquid. The nonlinear effects of the self-action and interaction of low-and high-frequency longitudinal elastic waves propagating in such a rod are studied for the cases of identical and size-varied cracks. Linear and nonlinear acoustic parameters characterizing the self-action and interaction of elastic waves in a cracked rod are determined.     

Wave processes in media with hysteretic nonlinearity: Part 2

Nonlinear processes caused by the propagation of low-frequency and high-frequency acoustic pulses in an unbounded medium and the propagation of continuous waves in a ring resonator are theoretically studied on the basis of two hysteretic equations of state for media with imperfect elasticity. The profiles and parameters of pulses, the resonance curve and the Q factor of the resonator, and the ratio of the nonlinear resonance frequency shift to the nonlinear damping decrement are determined. For nonlinear wave processes in such media, the distinctive features that allow one to choose an appropriate hysteretic equation of state for analytically describing the experimental data are revealed.     

Wave processes in microinhomogeneous elastic media with hysteretic nonlinearity and relaxation

The nonlinear propagation of an initially harmonic acoustic wave in a microinhomogeneous medium containing defects with quadratic hysteretic nonlinearity and relaxation is studied by the perturbation method. The frequency dependences of the effective nonlinearity parameters are determined for the self-action of the quasi-harmonic acoustic wave and the higher harmonic generation processes.     

Self-action of a low-frequency acoustic wave and generation of the second harmonic in dry and water-saturated river sand

The amplitude-phase effects of self-action and generation of the second harmonic are observed for a low-frequency longitudinal acoustic wave propagating in dry and water-saturated (wet) river sand under a static load. On the basis of the measured dependences of the amplitude and phase delay of the fundamental frequency’s carrier wave and its second harmonic’s amplitude on the initial wave’s amplitude, equations of state are proposed for dry and water-saturated sand. The parameters of these equations are determined from the comparison of analytic calculations with experimental data.     

Propagation of weak ultrasonic pulses in an intense low-frequency wave field in a granite resonator

Results of an experimental study of nonlinear attenuation and carrier frequency phase delay of weak ultrasonic pulses under the effect of an intense low-frequency wave in a bar resonator made from Karelian granite are presented. The effects observed in the experiment are analytically described in terms of the phenomenological equation of state containing hysteretic and dissipative nonlinearities. A frequency dependence of nonlinearity is revealed, and the effective values of nonlinear parameters of granite are estimated for the frequency range from 150 kHz to 1 MHz.     

Application of Chemical Kinetics Methods to the Study of Iodonitrotetrazolium Chloride Reduction in the Presence of Bacillus subtilis Cells

It is demonstrated that the reduction of iodonitrotetrazolum chloride in the presence of a Bacillus subtilis suspension in a physiological solution can be described using chemical kinetics equations. The effective kinetic parameters are determined and the role of the diffusion of iodonitrotetrazolium chloride in the process of its reduction involving bacterial cell components is described.

     

Propagation of unipolar strain pulses in media with hysteretic nonlinearity

A theoretical study of the propagation of unipolar strain pulses in a solid medium with an arbitrary power-law hysteretic nonlinearity is carried out. Exact analytical expressions are derived for describing the propagation and evolution of initially sine-shaped and triangular pulses in such media. The solutions found are analyzed both numerically and graphically.     

Self-action of seismic acoustic waves in the moist sandy soil

The effect of phase self-action of the longitudinal seismic acoustic wave observed in moist sandy soil is studied theoretically in framework of the phenomenological equation of state.     

Simulation of the dynamic hystereses in microinhomogeneous media characterized by imperfect elasticity and relaxation

Results of numerical simulations and a comparative graphical analysis are presented for two basic hysteretic models (hysteresis of friction and breakaway hysteresis) of microinhomogeneous media characterized by imperfect elasticity and relaxation under a dynamic deformation.