Bulletin of the Russian Academy of Sciences: Physics最新文献

The use of pulsed acoustic microscopy (50–200 MHz) makes it possible to analyze the three-dimensional microstructure and uniformity of the elastic properties of hydrated composite biomaterials. This paper proposes a method for local assessment of acoustic properties in spongy polymer samples, based on visualizing the microstructure, measuring attenuation, and sound velocity. This approach is relevant to the study of biopolymer composite materials and their structures, as it allows for in situ observation of structural degradation under external influences, as well as investigation of the evolution of native tissue replacement, if necessary.

A kinetic theory was constructed for the radioelectric effect in a superlattice based on a 3D Dirac crystal in a constant electric field. It was shown that, when the Bloch frequency is a multiple of the frequency of the electromagnetic wave, there is a resonance in current density, which can lead to a change in the direction of the current density. The amplitude dependence of the radioelectric current density was studied.

A three-dimensional surface-wave tomography scheme of inhomogeneities of the shear-wave velocities has been proposed, which does not require the reconstruction of the dispersion dependences of surface waves in a studied region. The results of the numerical modeling implemented for the conditions of the Hawaiian Archipelago have been presented, which indicate the operability of the proposed approach.

A fully quantum approach is used to study the mutual influence of simultaneously occurring processes of second harmonic generation and parametric down conversion. The effect of quantum pump depletion is revealed. A balance is found between the considered processes and obtaining the equilibrium number of photons in field modes. The generation of a highly entangled two-mode field is demonstrated.

The Rayleigh wave meta-Rayleigh scattering on a three-dimensional deterministic roughness of an isotropic solid is obtained. It violates and expands the fundamental conception of the Rayleigh law of scattering and is described by the new topological laws in the Rayleigh limit, obtained in the present work. It gives the new principal physical results, enabling the construction of arbitrary arbitrary frequency and angular spectrum of scattering through its meta-Rayleigh modulation by a roughness structure in two independent space dimensions in the Rayleigh limit.

An expression was obtained from which one can determine the law of plasma waves ω(k) in a two-dimensional semiconductor superlattice under the influence of a nonlinear electromagnetic wave. In the extreme case of weak nonlinearity, an analytical expression for ω(k) is found. The possibility of controlling the frequency of the plasma wave by varying the parameters of a nonlinear wave was established.

An analytical model was developed for optical radiation diffraction on chirped multilayer inhomogeneous diffraction structures formed by the holographic method in photopolymerizing composites with nematic liquid crystals having smooth optical heterogeneity in layer thickness. Numerical calculation showed that the chirping method can multiply broaden the angular and spectral characteristics of multilayer inhomogeneous holographic diffraction structures formed in photopolymerizing composites with nematic liquid crystals.

A problem of nonstationary diffraction of a monopolar TM-polarized electromagnetic pulse with a flat front on a thin slit in a perfectly conducting screen has been considered. The computational experiment techniques have been used to show that if the slit width is much smaller than the spatial length of a pulse, then a field is formed behind the screen in the form of a cylindrical monopolar pulse, i.e., there is a transformation of the shape of the incident field front without changing its pattern (monopolarity).

A scheme for implementing a microwave photonics device for receiving microwave signals for the formation and registration of radio holograms was proposed. The operation of such a receiving device was studied numerically and experimentally. A data processing method was proposed to reduce the error in determining the angle of arrival of a signal in the case of sphericity of the reflected wave at an insufficient distance of the receiver from the object.

The authors propose an improved numerical execution of the two-dimensional functional-analytical algorithm for reconstructing spatial distributions of the speed of sound and coefficient of absorption in a region of tomography. The high accuracy of the obtained tomograms even at large wave sizes and a complicated internal structure of the given object is demonstrated.