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Том 62, № 10 (2017)
- Год: 2017
- Статей: 11
- URL: https://journals.rcsi.science/1028-3358/issue/view/12055
Physics
447-449
CsLa(WO4)2, a new SRS-active crystal
Аннотация
The discovery of stimulated Raman scattering (SRS) in a CsLa(WO4)2 crystal and the first results of studying its steady-state χ(3)-nonlinear generation within the visible wavelength range are reported. This result has imparted the status of a multifunctional crystal with laser (with generating Ln3+ ions) and SRS-potential to tetragonal cesium-lanthanum tungstate.
450-453
Analysis of thresholds of optical damage to the potassium and sodium chloride surface by femtosecond laser pulses
Аннотация
Comparative analysis of optical damage thresholds of potassium and sodium chloride surface by pulses with durations of 80 and 40 fs has been carried out. The critical radiation power in a pulse at the optical damage threshold for the ion crystals studied has been determined. An estimate of the optical damage thresholds of the sodium chloride surface by laser pulses with a duration of 20 fs is presented.
454-456
Study of the stability of charged particle dynamics in a Penning–Malmberg–Surko trap with a rotating field
Аннотация
The solutions of equations characterizing the dynamics of charged particles in electromagnetic Penning–Malmberg traps with a rotating transverse electric field are presented and analyzed. The equations of motion are transformed in a way that makes it possible to distinguish between the motions of magnetron and cyclotron particles, reduce the system of equations to a stationary one, and conclude that asymptotically Lyapunov stable solutions of these equations are lacking in a certain parameter interval. This allows one to optimize the confinement of charged particles in such traps.
457-460
Mechanics
Influence of the ambient pressure on thin plate and film bending
Аннотация
The distributed lateral load on a plate located in a gas medium has been determined. The difference in the gas pressures of the plate surfaces results in a pressure drop and a lateral force, which depends on the middle surface curvature. It is shown that both these components of the lateral force must be taken into account in the general case. The influence of the second load component is small at a small ratio of the average pressure to the elastic modulus of the plate material and at a large relative thickness of the plate. At a small relative plate thickness and a large ratio of the average pressure of the medium to the elastic modulus of the plate material, the influence of the second component of the lateral load on the bending becomes significant. Cases of both linear and nonlinear plate bending are considered.
461-464
The optimization method in design problems of spherical layered thermal shells
Аннотация
The inverse problem of designing multilayered spherical shells, intended for thermal cloaking a spherical body or concentrating heat in it, has been analyzed. The stationary heat conduction equation for an anisotropic medium is applied as an original mathematical model. The optimization method is used to reduce this inverse problem to an extreme problem, where the role of controls is played by the thermal conductivities of shell layers. A numerical algorithm for solving the problem is proposed, and the results of computational experiments are discussed.
465-469
Application of the CABARET scheme for calculation of discontinuous solutions of the scalar conservation law with nonconvex flux
Аннотация
The monotonicity of the CABARET scheme approximating the quasi-linear scalar conservation law with nonconvex flux is analyzed. The conditions of monotonicity of this scheme are obtained in the case when the speed of propagation of characteristics of the approximated equation is limited and nonnegative. As an example, the test calculations by the CABARET scheme of discontinuous solutions of the Buckley–Leverett equation are presented.
470-474
Prediction of the effect of plastic-strain stabilization under cyclic deformation based on the structural‒temporal approach
Аннотация
On the basis of modification of the relaxation model of plasticity developed previously for the case of single loading, a new model of cyclic deformation is formulated. It is shown that the introduction of only one constant time parameter dependent on the material structure makes it possible to compose a simple calculation scheme of accumulation of residual strains under multiple cycling of samples.
475-477
Acoustic-wave reflection from a gas−droplet–mixture boundary
Аннотация
The problem on acoustic-wave reflection from the boundary of a gas−droplet mixture is considered. For the interface between the pure gas and the gas−droplet mixture at a wave inclined incidence, a nonmonotonic dependence of the reflectance on the volume content of droplets is established. The values of the critical wave-incidence angle and the volume content of inclusions at which the reflectance vanishes are found and illustrated. The possibility of occurrence of the lowest reflectance in dependence on the frequency of perturbations in a certain interval of the wave-incidence angle related mainly to the difference in the densities of the gas-droplet mixture and the pure gas is shown.
478-481
The capillary instability of the evaporation surface in soil
Аннотация
The stability of the evaporation surface of subsoil waters is investigated in the presence of capillary pressure, when a light liquid (a mixture of air and vapor) is above a heavy liquid (water). It is found that the instability arises in non-wettable and wettable soil with the capillary-pressure gradient.
482-485
Astronomy, Astrophysics, Cosmology
Features in constructing a certificate of strength of extraterrestrial material by the example of the Chelyabinsk meteorite
Аннотация
The mechanical properties of various components of the Chelyabinsk meteorite are studied. A measurement technique allowing one to obtain a strength certificate of the material by a minimum necessary number of samples with allowance for defectiveness is developed. Universal expressions for the chondritic component and impact melting have been obtained. The expressions allow one to make general estimates of the strength boundaries for LL type meteorites.
486-489