Technical Physics最新文献

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.

The paper proposes a method for detecting small oscillations in the length of interference fiber-optic sensors, which makes it possible to compensate for the problem of slow drift of the working point with a remote sensor. The result is achieved by combining homodyne demodulation methods with a tandem low-coherence interferometer. Theoretically and experimentally, the possibility of detecting acoustic effects in the operating frequency band of 4 kHz with a sensitivity of up to 0.3 nm has been shown.

This study assesses promising field electron sources based on silicon carbide monolithic field emission array (FEA). FEA is fabricated on single-crystal wafers of silicon carbide (0001C) 6H-SiC of n-type conductivity using the technology of two-stage reactive ion etching in SF₆/O₂/Ar atmosphere. To implement conditions close to breakdown, an experimental setup based on high-voltage narrow pulses generating device GKVI-300 was used. A series of nanosecond voltage pulses with amplitudes from 120 to 250 kV was generated. To study the characteristics of the FEA in the pre-breakdown state, the beam of field emitted electrons was separated from the ion torch or cathode plasma, formed in the following breakdown phases, by placing a 50-μm-thick titanium foil under zero potential into the interelectrode gap. Current-voltage characteristics of peak-currents vs. peak-voltages passing through the foil are close to rectilinear in the Fowler–Nordheim coordinates. The current-voltage characteristics plotted for each of the pulses along increasing and decreasing branches show a discrepancy (hysteresis). After the experiments, the silicon carbide cathode FEA was studied in a scanning electron microscope.

The remote sensing data of Phobos are analyzed based on the data from “MarsExpress” and “Viking Orbiter” space missions. Based on this study, a structural model of Phobos was constructed. According to the results obtained, we conclude that the relief of Phobos is very ambiguous. Its entire surface is covered with many traces of meteorite impacts—craters. The parameters for a series of impact craters were obtained and their multi-factor analysis was performed.

Novel method of nonlinear interchannel distortions generation in coherent multichannel fiber-optic transmission was proposed. Series of experiments was made to measure nonlinear interference noise in links with distributed amplification by co-propagating Raman pump. Based on the measurement results, a correction term to known GN-model formulas for calculating the power of nonlinear interference noise was proposed. Proposed formula demonstrate acceptable accuracy.

Main emission characteristics of thermal field and cold field electron cathodes were calculated. Emitters surface forms are approximated by second-order surfaces and anodes are approximated by equipotential surfaces. Systems, consisting of 18 first order ordinary differential equations, are solved using the numerical Runge–Kutta method. As a result, trajectories of the “boundary” electrons were obtained, which determine beam shapes and sizes and density distributions charges and electric field strengths. Analysis of beam parameters let to determine special properties of scanning electron microscopes with thermal field electron cathodes and with cold field electron cathodes for studying biological samples.

In the Markov relaxation and locally quasi-equilibrium distribution approximation, analogues of Onzager’s relations for the response functions of the spin current in the nonlinear by intense mechanical and thermodynamic effects regime were obtained by the Kubo method.