Technical Physics最新文献

The results of the measurements of spall strength of polycarbonate at a maximum compression stress of 0.6 GPa in the initial temperature range of 20–185°C are presented. It has been found a significant decrease in the spall strength when the polycarbonate reached the glass transition temperature. The strain rates in the plastic compression wave are determined depending on the maximum stress under single and stepwise shock compression. The dependences of the shock wave velocity U_s—mass velocity up in the range of maximum shock compression stresses up to 0.8 GPa at different temperatures are constructed.

This paper presents the results of the sky survey with the TAIGA–HiSCORE installation, an array of 120 wide-angle Cherenkov light detectors spread over an area of 1 km². Data analysis is made for 2 winter seasons (2019–2021) at cosmic ray energies above 200–500 TeV. A modified method of background estimation is tested. Signal significance is estimated using classical Li-Ma method.

The change in the characteristics of a solar battery as a result of a random abrupt change in the properties of individual solar cells, which occurred as a result of a single or systematic impact of adverse factors in near-Earth outer space, is considered. The choice of the calculation scheme for constructing a model of a single solar cell is substantiated. For this situation, analytical mathematical models of typical connections of solar cells have been developed. Using the developed models, the current-voltage and volt-watt characteristics of the solar battery are analyzed in the case of an abrupt decrease in the photocurrent of solar cells with different probabilities. A statistical analysis of the characteristics of damaged solar cells was carried out using simplified logical-analytical models with the introduced circuit loss coefficient. Estimates of the values of the coefficient of circuit losses for typical schemes for connecting solar cells are given.

The activation parameters for various iron structures were calculated by the analytical method based on the paired four-parameter Mie–Lennard-Jones interatomic interaction potential. Within the framework of a single method, all the activation processes parameters were calculated: Gibbs energy, enthalpy, entropy and volume for both the process of electroneutral vacancy formation and for the process of atom self-diffusion. The isobaric temperature dependences of the indicated activation parameters for BCC and FCC iron structures from T = 10 to 1810 K along two isobars: P = 0 and 10 GPa were calculated. It is shown that at the α–γ transition temperature (1184 K), the activation parameters decrease during the isobaric transition from the BCC to the FCC structure. At the γ–δ transition temperature (1667 K), the activation parameters increase during the transition from the FCC to the BCC structure. With increasing pressure, the jumps magnitude for the Gibbs energy and the enthalpy of the activation process increases, and for the entropy and volume of the activation process decreases. It is shown that, at low temperatures, due to quantum regularities, activation parameters strongly depend on temperature, and the entropy of activation processes in this region is negative. In the high temperature region, a good agreement has been obtained with the experimental estimates of activation parameters for different iron structures known from the literature.

CuO nanoparticles obtained in a low-pressure arc discharge plasma followed by annealing in an oxygen atmosphere at 500°C were studied by X-ray diffraction and transmission electron microscopy. The formation of irregularly shaped nanoparticles in the size range of 5–30 nm was found. The Rietveld refinement confirmed the formation of a monoclinic CuO phase with an average crystallite size of ~21 nm. The temperature dependences of the magnetization and permittivity of CuO nanoparticles have been studied. They show antiferromagnetic behavior with a Neel temperature of 230 K and frequency-dependent dispersion behavior in the temperature range of 100–200 K at an external magnetic field induction of 0–1.3 T. The dielectric relaxation mechanism is analyzed and found to follow the Arrhenius behavior. It is shown that hopping conductivity with a variable hop length more accurately describes charge transport in CuO nanoparticles. A magnetodielectric response of about 2.5 was observed at a frequency of 12 kHz at a temperature of 150 K in a magnetic field of 1.3 T.

A series of data on the flux of cosmogenic ¹⁰Be in an ice core recovered from Fuji Dome Station (East Antarctica) covering the period 700–1876 was analyzed. Fourier analysis and wavelet analysis showed the presence of cyclicity in this series with a period of about 36 yr. Since flux of ¹⁰B contains information about variations in cosmic radiation entering the Earth’s atmosphere, mainly associated with changes in solar activity, the identified periodicity may be the result of the corresponding solar cycle. The possible climatic origin of the 36-year variation is also discussed.

The possibility of increasing the static and dynamic strength of the aluminum-magnesium alloy AMg4.5 is shown by using methods of severe plastic deformation, a combination of annealing and additional deformation of ultrafine grained alloy. The strength properties of the material are evaluated using a structural-temporal approach to the analysis of experimental data on the dynamic tension of small samples obtained on split-Hopkinson pressure bar.

The possibility of generating a magnetic field at a large distance (10–15 kpc) from the center of the galaxy has been investigated. The magnetic field can be generated both by the dynamo mechanism, considering nonlinear effects, and by magnetorotational instability. Presumably, the nonlinear effects of the dynamo mechanism play a more significant role at this distance.