卷 62, 编号 6 (2017)

The solution of a boundary electromagnetic problem with impedance boundary conditions is considered using the method based on the invariance of the Maxwell equations to the Lorentz transformations. The results of solution of problems about the wave propagation in a circular waveguide with imperfectly conducting bounding surfaces are compared.

Two approaches to the phase-only synthesis of nulls in radiation patterns (RPs) of the phased array antenna (PAA) of a coordinate meter are considered. The approaches use the specificity of the structure of the sheet of the measuring PAA. Such a PAA forms the sum RP and two difference RPs, which ensure measuring of the angular coordinates of an object. The problem of the phase-only synthesis of pattern nulls in prescribed directions in one or several PAA RPs with the angular orientation of the nulls of difference RPs kept in the RP scanning direction is solved. Design relationships are derived and a RP synthesis method, which is based on iterative univariate minimization of a nonlinear functional and includes analytic determination of the minimum of this functional at each iteration, is described. Examples of the array pattern synthesis are presented. The effect the phasing increment on the depth of formed nulls is analyzed and the dependence of the value of the PAA RP in the scanning direction on the position of the formed null is investigated. The effect of synthesized nulls on the shape of the PAA direction-finding characteristic is analyzed.

The results of experimental investigations and calculations of the energy characteristics of four-element arrays of combined antennas excited by a single generator of bipolar voltage pulses with a duration of 1 ns through a power divider are presented. Based on the proposed criteria, the optimum structure of arrays is determined.

Effect of signal decorrelation in channels of phased antenna arrays (PAAs) on the efficiency of spatial filtering is analyzed with allowance for the relationship of parameters that characterize the decorrelation and correspond to the correlation coefficients of signals in the PAA channels. The decorrelation is classified as regular and quasi-random. Each factor that causes decorrelation provides an additional eigenvalue of the correlation matrix of input signals for each basic signal eigenvalue. High-order eigenvalues emerge in more complicated systems with several signal sources and several sources of decorrelation. Decorrelation characteristics (number of decorrelation sources and mean correlation coefficients) and the needed number of the degrees of freedom in the system with adaptive spatial filtering can experimentally be estimated. The results of analytical calculation and numerical simulation are in good agreement with the experimental results.

A specific analog device (spin echo processor) is proposed for processing of pulsed data in functional electronic devices under certain conditions. It is shown that a disadvantage of such devices related to generation of multiple noise signals upon processing of multipulse trains can be eliminated with the aid of magnetically ordered working substance using an additional channel that forms magnetic field in the working substance.

A procedure for analysis, calculation, and optimization of the parameters of electric system for power supply of inductive discharge is developed. The conditions for the maximum efficiency of the power supply systems in high-frequency ion engines are analyzed. An equivalent circuit of the inductive discharge with capacitive coupling is proposed using the analysis of schemes of different high-frequency ion engines and transformed into a complex equivalent impedance connected in the inductor circuit to calculate matching reactive elements. Equivalent parameters of the plasma of inductive discharge are estimated using the wave model. Calculated and experimental results are used to formulate the main requirements on the laboratory models of the high-frequency oscillators and matching units of the radio-frequency ion engines.

Equations of the multifrequency nonlinear theory of the traveling wave tube are derived using the fundamental frequency method. Basic results of the numerical calculation of the output parameters of a traveling wave tube operating in the multifrequency mode are presented. The level of sideband components in traveling wave tubes with uniform and nonuniform slow-wave structures and the way of suppression of sideband components are investigated.

The issues of shaping a ribbon beam with elliptical and rounded-rectangular cross sections in an external magnetic field directed at an angle to the cathode are discussed based on the classical paraxial theory.

The effect of implantation of Ba⁺ and Nb⁺ ions on the composition and emission properties of Мо (111) single crystals is investigated. It is shown that implantation of Ba⁺ ions leads to the complete purification of the Мо surface from С and О atoms, rapid decrease in the work function, and intensification of the secondary and photoelectron emission coefficients, while implantation of Nb⁺ ions leads to rapid (up to 30 at %) growth of the surface concentration of С. It is established that, after heating at Т = 1400 K, the surface is completely purified from carbon and Nb + Мо nanocrystalline phases are formed.

The effect of hydrogen-related shallow thermal donors and acceptor-like defects arising under proton irradiation of silicon on the breakdown voltage of a high-voltage p–n junction is considered. The relations making it possible to compute the breakdown voltage of the irradiated p–n junction taking into account the increase in critical field intensity during the ingress of hydrogen-related shallow thermal donors into the region of collisional ionization of the p–n junction are obtained. A technique for determination of the layer position and the minimum dose of hydrogen-related shallow thermal donors making it possible to decrease the breakdown voltage by a specified amount is proposed.

Problems arising during the design of stripline combline filters, which until quite recently were considered as all-stop microwave structures, are considered. It has been shown that the electromagnetic coupling coefficient of quarter-wave stripline resonators increases with the value of material permittivity ε_r, the operating frequency, and the thickness of the filter resonators. For ε_r = 92 and a thickness of stripline resonators of 4 mm, it exceeds 12% at frequencies higher than 2.2 GHz. Two alternative versions of combline filters have been designed: a filter with a coupling strip and a filter without a coupling strip. Experimental data for a nine-resonator combline filter with a thickness of 4 mm, ε_r = 9.7, and the center frequency f₀ = 2.4 GHz are presented. A method for increasing the selectivity of combline filters with the same number of resonators is proposed. It has been found that amplitude–frequency responses of stripline combline filters are near-symmetric, unlike the responses of microstrip combline filters.

The appearance of inexpensive high-quality video cameras and depth cameras resulted in the development of a large number of object-tracking algorithms. In this paper, a new descriptor-based algorithm for real-time object tracking using the information from a Microsoft Kinect depth camera is proposed. As a descriptor for the object tracked, histograms of oriented gradients calculated from the circular sliding regions of the scene image are used. The information on the depth of the scene is used when the image of the object of interest is partially occluded by other objects in the scene. To speed up the tracking process, a model for predicting the object motion is used. To ensure real-time tracking with the proposed algorithm, a multicore graphics processor is used.

A novel time- and memory-efficient algorithm for solving the problem of finding the most economical (i.e., having the lowest overall cost) transformation of an arbitrary oriented graph representing a disjoint union of chains and cycles into another graph of the same type is proposed. The correctness of this algorithm (i.e., the fact that it always yields the minimum of the overall cost functional) and the linearity of the estimated memory and time of its operation are demonstrated.

The conditional probability (fraction) of the successful decoding of erasure patterns of high (greater than the code distance) weights is investigated for linear codes with the partially known or unknown weight spectra of code words. The estimated conditional probabilities and the methods used to calculate them refer to arbitrary binary linear codes and binary Hamming, Panchenko, and Bose–Chaudhuri–Hocquenghem (BCH) codes, including their extended and shortened forms. Error detection probabilities are estimated under erasure-correction conditions. The product-code decoding algorithms involving the correction of high weight erasures by means of component Hamming, Panchenko, and BCH codes are proposed, and the upper estimate of decoding failure probability is presented.

We describe a new class of positive linear discrete-time switching systems for which the problems of stability or stabilizability can be resolved constructively. The systems constituting this class can be treated as a natural generalization of systems with the so-called independently switching state vector components. Distinctive feature of such systems is that their components can be arbitrarily “re-connected” in parallel or in series without loss of the “constructive resolvability” property for the problems of stability or stabilizability of a system. It is shown also that, for such systems, the individual positive trajectories with the greatest or the lowest rate of convergence to the zero can be built constructively.

In this paper, we study a class of algorithms for decentralized dynamic resource reservation in Wi-Fi networks in which each station chooses and reserves time intervals for future transmission. To avoid interference, information on reserved time intervals is regularly sent to neighboring stations. To minimize the amount of transmitted control information, the reserved intervals are strictly periodic and have the same duration. We have developed two algorithms for decentralized resource reservation and have proven by mathematical modeling that these algorithms require smaller channel resource for streaming variable bitrate flows with given quality of service requirements than the existing algorithm. The developed algorithms can be used to allocate resource among base stations in dense infrastructure networks and among mesh-stations in selforganizing Wi-Fi networks.

Some problems arising when the search for publications in Scopus is performed with the “Affiliation search” and “Document search” options are considered. Examples showing possible ways to correct the institution profile are presented.

The paper addresses dynamic combinatorial clustering. First, a systematic literature survey on dynamic/online clustering is presented (problems, methods, applications). Second, restructuring approach to clustering is described (one-stage clustering, multi-stage clustering, sorting). Third, two network application examples of dynamic/multistage clustering are examined: (a) multi-stage connection of users to access points, (b) partition coloring problem in optical networks (wavelength routing and assignment).