Timofey Krit

Lomonosov Moscow State University | MSU · Faculty of Physics

Measurements of the nonlinear parameter of a gel-like medium were carried out in an acoustical resonator fixed without slipping between two solid-state boundaries. A sample of thickness L is fixed on an oscillating plate (x = 0). The other plate of finite mass on the free surface of the sample (x = L) moves together with this surface. By changing t...

An algorithm has been developed for measuring the shear modulus in an anisotropic media – along and across the organic or artificial fibers that cause the anisotropy. The algorithm is based on the well-known and widely used method for generating shear waves in homogeneous isotropic media. Shear modulus depending on the static load applied to the st...

No PDF available ABSTRACT Shear modulus in the biceps of volunteers was measured with standard ultrasound equipment, the at loads from 0 to 50 N. The measurements were carried out by shear wave elastography in the clinic according to the medical protocol. The volunteer held a sport weight of known mass to load the bicep. Shear wave was excited in t...

We applied a commercial ultrasonic clinical diagnostic system for studies of human biceps. The investigated area was visualized in B-mode at a frequency of 8 MHz. We selected 1 cm and 2.5 cm depths for shear wave excitation. On these depths, the focused ultrasonic wave caused the acoustical radiation force. Due to nonlinear mechanism of excitation,...

The features of the propagation of undamped thermal (temperature) waves in air are investigated. The presence of these waves is a consequence of solution of the heat equation taking into account the relaxation of local thermal perturbation. It is shown that such waves can exist only in media with a finite (nonzero) time of local thermal relaxation,...

The common algorithm of shear waves excitation for diagnostical ultrasonic devices was modified for measurements in muscles. We measured the speed of shear waves, excited by a focused ultrasound at a frequency of 5 MHz in the muscles of the volunteers. Siemens Acuson S2000 was used for in vivo measurements. The suggested algorithm was tested on the...

The problems of the existence, generation, propagation and registration of long-distant undamped thermal waves formed in pulse radiative processes have been theoretically analyzed and confirmed experimentally. These waves may be used for the analysis of short-time processes of interaction of particles or electromagnetic fields with different target...

The authors study reduction of longitudinal ultrasonic oscillations in sodium chlorate crystals within the temperature range of 78 - 525 K and relative amplitudes of oscillatory deformation of 10⁻⁷ - 10⁻⁵ according to the method of compound piezoelectric vibrator at the frequencies of ≈ 10 ⁵ Hz.

Standing shear waves in a resonator in the form of layer of gel-like medium placed between two rigid plates are studied. The bottom plate is fixed to the vibrator and oscillates in the horizontal direction with a preset amplitude. Two rubber threads attached to the upper plate can displace the plate by a specified value in the horizontal direction....

We studied standing shear waves in anisotropic resonator represented by a rectangular parallelepiped (layer) fixed without slipping between two wooden plates of finite mass. The viscoelastic layer with edges of 70 mm × 40 mm × 15 mm was made of a rubber-like polymer plastisol with rubber bands inside. The bands were placed vertical between the top...

The authors study reduction of longitudinal ultrasonic oscillations (internal friction Q-1 and logarithmic decrement δ) in NaClO3 crystals within the temperature range of 78 - 525 K and relative amplitudes of oscillatory deformation of 10-7 - 10-5 according to the method of compound piezoelectric vibrator at the frequencies of ≈ 105 Hz. Q-1 maximum...

We studied shear waves of finite amplitude in a resonator in the form of a rectangular parallelepiped made of viscoelastic material with gas-filled through cavities on the side surface. The cavities are parallel to the parallelepiped bases and perpendicular to the oscillations direction. The centers of the cavities are displaced to one of the bases...

It has been found that of P-type defects to total defect formation is larger in GaAs samples irradiated with high-energy (65 MeV) protons or fast neutrons. The E4 and E5 defects are annealed out after heat treatment of such samples at a temperature near 200°C; as a result, the shape and intensity of the U band change somewhat.

The given article considers acoustic analogues of elasticity theory ratios determining Poisson’s ratios of Sm1-xYxS alloy by their elastic parameters. The article discusses behavior of sound velocities, elastic moduli, Poisson’s ratios, Grüneisen parameter and brittleness-plasticity criterion ratios depending on the concentration of alloy component...

Static shear deformations of a plane-parallel layers of several viscoelastic media created simultaneously with the uniaxial compression are considered. Each layer is fixed between two rigid plates. Displacement of one plate relative to the other resulted in shear strain of the layer. This strain could reach 0.6 of the layer thickness. At such strai...

Static shear deformations of a plane-parallel layer of rubber-like material created simultaneously with the uniaxial compression are considered. The layer is fixed between the rigid plates. Displacement of one plate relative to the other resulted in shear strain of the layer. This strain could reach 0.6 of the layer thickness. At such strain, effec...

We study finite-amplitude shear waves in one-dimensional resonator represented by a layer of rubber-like medium with inhomogeneities in the form of through holes made on the side face. The holes are parallel to the bases and perpendicular to the direction of vibrations. Two different configurations of the resonator: with holes at the bottom and at...

Shear waves with finite amplitude in a one-dimensional resonator in the form of a layer of a rubber-like medium with a rigid plate of finite mass at the upper surface of the layer are investigated. The lower boundary of the layer oscillates according to a harmonic law with a preset acceleration. The equation of motion for particles in a resonator i...

A modification of the finite-element method is proposed for calculating shear standing waves in a resonator filled with an incompressible elastic medium with allowance for the finite dimensions of the resonator and inhomogeneities of the shear modulus. Resonance curves are calculated for resonators with inhomogeneities in the form of cavities and e...

Standing shear waves arising in layered media the shear modulus of which varies in a stepwise manner at the plain boundaries between the layers are considered. A general solution is obtained for the shear wave amplitudes in a resonator with an N-layer structure the lower boundary of which performs harmonic vibrations while a finite-mass plate is at...

Standing shear waves in a plane-parallel rubberlike layer fixed without slippage between two rigid plates with finite masses are investigated. The lower plate, which underlies the layer, oscillates in the direction parallel to its surface under an external harmonic force, whereas the upper plate freely overlies the layer. It is shown both theoretic...