Home – Home – Jornals – Advanced Search

This paper presents the results of analysis of the influence of interfering factors on changes in the informative parameter of a single-turn eddy current sensors, which are used as initial data in the study of a system for measuring radial clearances with self-compensation of temperature effects on the sensor. Conversion functions of the measuring circuit with a connected single-turn eddy current sensor are obtained in analytical form. The conversion functions are dependences of the extreme values of codes at the measuring circuit output on radial clearances and temperature effects on the sensor taking into account the influence of interfering factors (neighboring blades, blade temperatures, axial displacements of the gas turbine engine compressor rotor). Quantitative estimates are obtained for the influence functions of these interfering factors on the calculated difference of the extreme values of codes in the system, which characterizes the measured parameter.

Time-optimal algorithms of spatial localization of random pulsed-point sources are proposed, and their parameters are calculated. These sources have a two-step probability density in the search interval and are detected due to generation of instantaneous pulses at random time instants (delta functions). The advantage of the developed optimal localization algorithms over the search procedures that ignore specific features of the spatial distribution of the detected pulsed-point objects is demonstrated.

A problem of detection of 3D objects on the basis of imagery information provided by two or three different sensors is considered. The efficiency of object detection with the use of algorithms of integration and data fusion of information from different sensors and also by means of formation of a unified synthetic image from two initial images is estimated. Conditions are determined at which the use of the information integration algorithm and the method of forming a single synthetic image provides a lower efficiency as compared to the use of only one image among those available for detection.

This paper describes a neural network architecture of edge detection. Different filters for first-layer neurons are compared. Neural network learning based on a cosine measure algorithm shows much worse results than an error backpropagation algorithm. Optimal parameters for first-layer neuron operation are given. The proposed architecture fulfills the stated tasks on edge selection.

The Maxwell equations for a composite two-component layered material with a periodic structure in the field of a time-harmonic source acting along the layer are considered. Two-scale homogenization of the equations is performed with allowance for complex conductivity of interphase layers and their thickness. The boundary-value problem for systems of differential equations with boundary conditions is reduced to a problem in a weakly variational formulation. Unique solvability of the problem is established. The case of low frequencies of interphase surface currents of different intensities with allowance for the frequency-dependent wave length and skin layer length is analyzed. Macro-equations are derived, and effective material constants are determined, such as the magnetic and dielectric permeabilities and electrical conductivity. Conditions at which the effective parameters depend on interphase currents are described. It is found that the effective dielectric permeability can be negative at specially chosen parameters of interphase layers, if the effective dielectric permeability is determined on the basis of the effective wave number.

The rotational motion of finned shaped-charge liners is studied. It is shown that the main factors affecting the rotation of a shaped-charge jet are the position of the jet-forming layer and the distribution of the circumferential velocity in the liner cross-section. The proposed method can be used to estimate the average angular velocity of the jet with consideration of the size of the finned shaped-charge liner and the properties of its material. It is shown that the results are consistent with available experimental data.

A thermodynamically equilibrium model is applied for simulating thermodynamic parameters of shock loading of both pure materials and mixtures of homogeneous and porous materials. The model includes a modified equation of state, which has only one fitting parameter determined on the basis of experimental data. The thermodynamic parameters of shock loading of copper and copper-based mixtures with porosities of 1-10 at pressures above 5 GPa are calculated. The results of these calculations are compared to available experimental data (Hugoniot adiabats, double compression by shock waves, and temperature estimates). The possibility of modeling the compression of the mixture as a whole and each component separately is demonstrated.

Results of studying stability of the Blasius boundary layer on a two-layer compliant coating in the linear formulation are reported. The computations are based on experimental parameters of viscoelasticity of a real coating, which reveal the dependences of its elasticity modulus and loss coefficient on frequency. Parametric investigations of the influence of the coating layer thicknesses and free-stream velocity on flow stability, in particular, on the critical Reynolds number, are performed. Regions of a nonmonotonic behavior of the critical Reynolds number are found, which allow one to determine the optimal thicknesses of the upper and lower layers for intense interaction with the flow. An explanation of this effect is proposed.

Starting of an air-breathing engine with fuel injection distributed along the combustion chamber is numerically simulated. Issues of principal importance are the presence of a compressed are jet generating a throttling effect and preliminary deceleration of the flow to transonic velocities. Averaged Navier-Stokes equations closed by the SST, SST κ-ω, or κ-ε turbulence models are solved. Hydrogen and ethylene combustion is simulated by one reaction. The computations are performed for various values of the turbulent kinetic energy in the flow. A pulsed transonic regime of hydrogen and ethylene combustion is discovered.

This paper considers the possibility of using measuring sections with inductive sensors to detect hypersonic particles in time in the simulation of collisions of objects with space debris. A method for determining the average velocity of hypersonic particles simulating the space debris and a method of starting the recording equipment for optical contactless detection of these particles are proposed. Results of experimental studies of the interaction of particles with a simulator of the mesh shield of the spacecraft.