On the possibility of determining internal wave characteristics from the ray arrival time distribution in an underwater sound channel under conditions of Ray Chaos

We describe the simplest mechanism of cluster structure formation in the timefront of an acoustic signal propagating in a submerged channel under ray chaos conditions. It is shown that this cluster structure is related to the phase space structure. This relation allows, in principle, the characteristics of an inhomogeneous medium to be determined from the timefront shape parameters. As an example, the period of inhomogeneity is calculated for a periodic perturbation in the sound velocity caused by an internal wave propagation.     

Fuel‐Consumption‐Minimum‐Based Selection of the Regime of Heating of a Metal by the Main Optimization Method

Consideration is given to the solution of the problem of minimization of fuel consumption in heating a rectangular prism in a continuous furnace.     

Mechanochemical modification of the phase diagrams of hexagonal oxide ferrimagnets

Mechanical activation and fine comminution of hexagonal oxide ferrimagnets by milling to a nanocrystalline state (ultradisperse powder), followed by sintering, leads to significant changes in the phase diagram, the temperature of synthesis, and the magnetic properties as compared to those of the materials obtained by traditional ceramic technology. The final material structure is formed through “chemical assembly”—sequential consolidation of nanodimensional particles (structure-forming blocks)—rather than through the formation of low-temperature phases and their decomposition with increasing temperature.     

Non-parametric maximum-likelihood channel estimator and detector for OFDM in presence of interference

A maximum-likelihood channel estimator for the orthogonal frequency division multiplexing communication environments, in the presence of interference is discussed here. In a training-based scenario, the channel is estimated based on pilots that precede the transmission of the information. To reduce the number of estimation parameters, the channel is estimated iteratively in time-domain. Since interference from other users provide no useful information, parameters of the interference are neither estimated nor the effect of the interference neglected, instead interference along with Gaussian noise is perceived as non-Gaussian noise process. The algorithm assumes no a priori knowledge about the interfering channel and signal at the receiver, further no assumption on the statistical properties of the interferer is assumed, which makes this algorithm robust. The estimated channel information along with the estimated distribution are then utilised to equalise the subsequent data blocks. The strength of the algorithm is in its robustness to both synchronous and asynchronous interference, which is confirmed by the simulation results for both flat and multipath fading channels in presence of synchronous and asynchronous interference.     

Effect of spontaneous polarization on the energy levels in quantum wells formed at the contact between cubic and noncubic silicon carbide polytypes

We have studied the effect of spontaneous polarization, which is inherent in noncubic silicon carbide (SiC) polytypes, on the characteristics of quantum wells (QWs) formed in the cubic region at the heterojunction. The analysis is performed for various QW models, including triangular, parabolic, and exponential. Conditions for the appearance of a two-dimensional electron gas at the interface are briefly discussed.     

Microhardness of silicon layers grown by liquid phase epitaxy

The microhardness of silicon epilayers grown from Sn fluxes is found to be lower than that of the silicon substrates and to significantly depend on the crystallographic orientation of the substrates. The microhardness values follow a Gaussian distribution in all of the epilayers. Unintentional impurities are shown to have a significant effect on the microhardness of the epilayers. The addition of ytterbium to the high-temperature solution reduces the microhardness of the epilayers.     

The behavior of a cloud of emissions of high moisture content in the surface layer of the atmosphere

The propagation in the atmosphere of instantaneous emissions which largely consist of water vapor is treated in a three-dimensional formulation. The regularities are studied of the evolution of the hydrodynamic, concentration, and temperature fields depending on the parameters which define the state of the atmosphere (temperature and humidity), as well as on the temperature and moisture content of the cloud of emissions.     

The fractal structure of a carbon deposit formed during graphite spraying in an electric arc

Experimental data obtained by atomic force microscopy showing that a carbon deposit formed during graphite spraying in an electric arc possesses a fractal structure. The deposit is composed of clusters with dimensions on the order of 1–5 nm. The surface and profile of the deposit exhibit a self-affine fractal structure. The fractal dimensions of the deposit surface and profile, as well as the Hurst index characterizing the self-affine fractal, are determined.     

Navigation of a Mobile System with Parametrically Uncertain State Vector

Navigation of a mobile system with parametrically uncertain state vector is studied. The required navigation accuracy is attained through orientation control of the gyrostabilized platform and identification of the parameters of the model of the platform drift. A wide range of functionals that depend on the a posteriori distribution density can be used as the optimization criteria since the solution is general. In the numerical example, the Shannon criterion is used as the optimization criterion.