Том 63, № 5 (2018)

The regularities of transition of phase and group velocities from slow surface waves (whose velocities are below the light speed) to fast surface waves (whose velocities are above the light speed) on the plane boundaries of highly conducting media are investigated when the parameters of media vary. It is shown that the structure of waves does not change qualitatively in the case of this transition: the waves remain to be surface ones in contrast to surface waves of dielectric waveguides. The latter ones are transformed into leaking waves or their structure changes in a more complicated way in the case of such transition. A result relating, in particular, to the Zenneck wave is obtained.

The possible distribution of the field strength of the low-frequency demodulated radiation of the high-power transmitter of the HAARP station (Alaska, USA) over the Earth surface in the Earth–ionosphere waveguide has been numerically simulated. It has been shown that, owing to the extremely weak electromagnetic coupling between the ionosphere and the waveguide in the case of an ionospheric source, the strengths of the electric and magnetic fields of the waveguide waves are relatively low and are at the level of the low-frequency noise even in the immediate vicinity of the center of the distribution. It has been confirmed that, in order to detect such a signal and measure its parameters, it is necessary to use special procedures for processing data from ground-based receivers.

In a two-layer circular screened waveguide with a longitudinally magnetized inner ferrite layer, the presence of different types of complex waves (CWs) both satisfying and not satisfying the energetic orthogonality condition is shown. The CWs are the solutions of a homogeneous boundary value problem, but, in the first case, the waves are energetically independent and, in the second case, they are associated with the source and indirectly coupled through it.

The efficiency of operation of a cylindrical plasma antenna as a function of the degree of longitudinal nonuniformity of the plasma density is examined. The study is based on the method of spectral field expansion into a complete set of functions comprising surface and pseudosurface waves of the plasma column. The system of integrodifferential equations for expansion coefficients determining radiation patterns and the amplitudes of transmitted, reflected, and scattered waves is solved in the case of rapid variation in the plasma density. Dependences of the coefficients of conversion of the surface-wave energy on the plasma-density gradient, the electric length of the section of plasma nonuniformity, and the electric radius of the plasma cylinder are calculated. It is demonstrated by examples that the portion of energy of the surface wave converted into radiation may exceed 50%. It has been found that the radiation patterns are narrow with a single lobe whose maximum is at an angle of several degrees to the direction of propagation of the surface wave. As the plasma-density gradient increases, the lobe width decreases and the lobe itself shifts toward 0°.

The quasi-likelihood, maximum-likelihood, and quasi-optimal algorithms for estimating the instants of appearance and disappearance of an optical pulse with the rectangular intensity profile of an unknown height are synthesized and analyzed. The losses in estimation accuracy due to the a priori unknown intensity of the optical pulse are found.

The growth of single-crystal films of high-temperature superconductors of the NdBa₂Cu₃O_7–x composition with a thickness of 1–1.5 μm on Al₂O₃ + CeO₂ substrates during the laser spraying is investigated. Technological conditions of the epitaxial growth of the films with a temperature of superconducting transition of 95 K and a critical current of more than 10⁶ A/cm² at the temperature of liquid nitrogen are determined. It is shown that the structure of fabricated NdBa₂Cu₃O_7–x films is more perfect and homogeneous than the structure of YBa₂Cu₃O_7–x films widely used in microwave electronics.

TEM measurements are used to experimentally study thermoelastic martensite transformation in Ti₂NiCu tapered plates. The martensite phase is observed at room temperature in the Ti₂NiCu alloy when the plate thickness decreases to, at least, 80 nm, and the austenite phase is observed at smaller thicknesses. It is shown that the temperature of thermoelastic martensite transition in the Ti₂NiCu alloy decreases with a decrease in the thickness of the plate, the transition is blocked at a thickness of less than 20 nm, and a hysteresis dependence is observed. Possible physical and technological reasons for blocking of the martensite phase transition on nanoscale and fundamental limitations on the sizes of micromechanical devices based on the shape-memory Ti₂NiCu alloy are considered.

The algorithm for calculating narrow relativistic electron beams with the straight axis and elliptical cross section in a plane external magnetic field is proposed. The comparison with the case of an axially symmetric magnetic field is made. The solution for the emission in the ρ mode is regularized.

Signal formation in image intensifier with pyroelectric array is considered. Application of panning regime is substantiated, and impossibility of image obturation is shown. A method for processing of thermal image is proposed to eliminate structural noise and allow operation in the absence of shutter. The method is optimized for pyroelectric arrays and practical applications are presented. Development of the method, in particular, with the aid of calibration of the signal of pyroelectric array is considered.