Vol 61, No 11 (2016)

Within the framework of the Willis−Harrison model, the effect of taking into account d−d-electron couplings nondiagonal in the magnetic quantum number between the neighboring atoms in a transition metal on the partial pair potentials and the free energy of mixing of an Fe–Co liquid alloy near the melting temperature is investigated. It is found that an increase in the fraction of nondiagonal couplings results in a decrease in the depth of the first minimum of the partial pair potentials and in the displacement of its position towards larger r. It is shown that taking this factor into account considerably improves the agreement with experimental data of the concentration dependence of the free energy of mixing of the system under consideration.

A spatially distributed system with the 1/_f spectrum of fluctuation power is modeled by two nonlinear stochastic equations. The numerical methods show the formation of 1/_f and 1/_k spectra of extreme fluctuations against the background of the formation and motion of waves under the effect of white noise. The distribution of extreme fluctuations corresponds to the maximum of entropy, which testifies to their stability. Under an external periodic perturbation in the system, it is possible to observe space−time stochastic resonance.

Spectral and amplitude–time characteristics of PMMA radiation under the impact of runaway electrons with subnanosecond duration are studied. The PMMA radiation spectra for a subnanosecond electron beam pulse duration are determined for the first time. The studies show that radiation of the band with a maximum at about 490 nm the intensity of which decreases toward the short-wave spectral region is recorded in the glow spectra. The glow intensity of this band varies proportionally to the number of electrons in the beam, which allows the possibility of using this radiation for determination of the number of high energy electrons in electron beams.

Inverse heat-transfer problems related to constructing special thermal devices such as cloaking shells, thermal-illusion or thermal-camouflage devices, and heat-flux concentrators are studied. The heatdiffusion equation with a variable heat-conductivity coefficient is used as the initial heat-transfer model. An optimization method is used to reduce the above inverse problems to the respective control problem. The solvability of the above control problem is proved, an optimality system that describes necessary extremum conditions is derived, and a numerical algorithm for solving the control problem is proposed.

A new model describing the vibration caused by the interaction between the moving ice cover and a structure attached to the bottom is proposed. The equations obtained estimate the forces affecting the structure under its interaction with ice. The influence of the velocity of ice movement on different vibration conditions is analyzed.

Branching of equilibria of a system of three parallel conducting nano/microlayers, which is used to detect changes in the external and internal mechanical and electric characteristics (for example, conductivity, tension force, and gap between layers), has been investigated. A change in the physical parameters may cause asymmetric bending of the outer layers and deformation of the formerly neutral middle layer. By changing the current in one of the outer layers slowly, their initial symmetry (neutrality of the inner layer) can be restored and the change that occurred in the parameters can be determined.

The results of long-term studies of cosmogenic radionuclide production rates along the orbits of 39 chondrites that fell to the Earth between 1959 and 2013 are presented. They constitute a long series of homogeneous data, a statistical smoothing of which demonstrate some general patterns of the distribution and variations of Galactic cosmic rays (GCRs) with energy >100 MeV in the inner (<5 AU) heliosphere. A correlation analysis of the production rates of radionuclides with different half-lives suggests that the solar GCR modulation mechanism is constant over at least ~1 million years. The role of stochastic factors in the polarity reversal of the general solar magnetic field for the phases of maximum solar activity has been revealed. The subtle sensitivity of the ⁵⁴Mn production rate in the Chelyabinsk chondrite to the short-term closure of the heliosphere for positively charged particles over 14 months between June 2012 and July 2013 is used as an example to show the high resolution of the method of using cosmogenic radionuclides in meteorites as natural GCR detectors.