Vol 61, No 12 (2019)

We present the results of prediction and extrapolation of the maximum usable frequency (MUF) on the subauroral and midlatitude paths of the Euro-Asian region by adapting the reference ionosphere model IRI-2007 based on the results of the oblique chirp sounding of the ionosphere on the reference and working radio links. It is shown that under conditions of a quiet ionosphere where the adapted ionospheric model is used, the errors of the MUF prediction on the reference path and the error of the MUF extrapolation to the neighboring paths not equipped with diagnostic tools are 2–8%, which is significantly less than the long-term prediction data which amount to 9–20% [1–3].

We propose a new approach to reconstructing complex, spatially distributed systems on the basis of the time series generated by such systems. It allows one to combine two basic steps of such a reconstruction, namely, the choice of a set of phase variables of the system using the observed time series and the development of the evolution operator acting in the chosen phase space with the help of an artificial neural network with special topology. This network, first, maps the initial high-dimensional data onto the lower-dimension space and, second, specifies the evolution operator in this space. The efficiency of this approach is demonstrated by an example of reconstructing the Lorenz system representing a high-dimensional model of atmospheric dynamics.

We have synthesized elliptic bandpass waveguide filters. The resonators of the filter are thin plane-transverse resonant irises with an aperture in the form of a rectangular window with two metal L-shaped ridges. The electrodynamic problem of calculating the complex conductance of the iris is solved. An equivalent circuit of the resonant iris is proposed, and the correspondence of the geometric size of its aperture to the parameters of the circuit is established. The results of synthesis of an elliptic filter for the WR137 rectangular waveguide with a passband of 6.35–6.83 GHz at a level of −3 dB are presented. The longitudinal size of the filter is 34 mm, which ensures the small size of the developed device.

We propose a simple method for estimation of the probabilities of elementary processes of quantum electrodynamics in a strong field. It is shown that quantum-electrodynamic processes run in the quasiclassical or quantum regime depending on the ratio of the characteristic scales of the time of particle acceleration by the field (a quasiclassical effect) and energy absorption by charged particles from the field directly during the process (a purely quantum effect). Using simple kinematic considerations and the uncertainty principle for these regimes, it is possible to reproduce the probabilities of the known processes in a strong field, in particular, spontaneous pair creation, photon emission by an electron, pair photoproduction, and radiation mass correction.