Том 60, № 9 (2018)

We realize the possibilities for positioning of ionospheric irregularities and the Earth’s surface roughness with the chirp-signal ionosonde–radio direction finder used as an over-the-horizon HF radar of bistatic configuration on the Cyprus — Rostov-on-Don and Australia — Rostov-on-Don paths. It is established that the small-amplitude diffuse signals coming from azimuths of 310^°–50^° on the Cyprus — Rostov-on-Don path in the evening and at night at frequencies above the maximum observable frequency (MOF) of the forward signal are due to backscattering by small-scale irregularities of the mid-latitude ionospheric F Layer. It is shown that the backward obliquesounding signals recorded on the Cyprus — Rostov-on-Don path are caused by the sideband scattering of radio waves from the Caucasus mountain ranges, the Iranian highlands, and the Balkan mountains. It is found that the anomalous signals observed on the Alice Springs (Australia) — Rostov-on-Don path, which come from azimuths of 10^°–25^° with delays by 10–16 ms exceeding the delay of the forward signal are due to scattering of radio waves by the high-latitude ionospheric F-layer irregularities localized in the evening sector of the auroral oval at latitudes of 70^°–80^° N.

We calculate the shapes, dimensions, density distributions, and orientations of dipoles in clouds consisting of millions of the dipoles, which are formed during fractions of a second when such clouds are injected into air at a high speed, using the three-dimensional nonstationary formulation and applying the Monte Carlo method and aerodynamics equations for the motion of electric dipoles. The values of the optical density, radiation intensity, and backscattering cross sections of such clouds are calculated for different directions and polarizations of the incident and detected scattered resonance and nonresonance radiation. Great influence of small distortions in the rectilinear form of the dipoles is demonstrated. It is shown that a great part of the dipoles of metallized fiberglass does not take part in the scattering due to shielding, which reduces the backscattering cross sections by many times.

We develop the methods of electromagnetic computer near-field microwave tomography of distributed subsurface inhomogeneities of complex dielectric permittivity and of holography (shape retrieval) of internally homogeneous subsurface objects. The methods are based on the solution of the near-field inverse scattering problem from measurements of the resonance-parameter variations of microwave probes above the medium surface. The capabilities of the proposed diagnostic technique are demonstrated in the numerical simulation for sensors with a cylindrical capacitor as a probe element, the edge capacitance of which is sensitive to subsurface inhomogeneities.

We consider a network of Kuramoto phase oscillators with randomly blinking couplings. Applicability of the averaging method for small switching intervals is rigorously substantiated. Using this method, we analytically estimate the threshold coupling force for synchronizing the ensemble oscillators. The threshold synchronization is studied as a function of the switching interval for various network sizes. The effect of preserving synchronization for a significant increase in the switching interval is found, which is the key feature of the system since a slight increase in this interval usually leads to the synchronization failure. The intermittent-synchronization possibility for small network sizes and large switching intervals is shown. An increase in the network size is shown to result in a stability increase due to the decreasing probability of appearance of uncoupled configurations. The regions corresponding to the global synchronization of oscillators are singled out in the system-parameter space.