The article describes a method for suppressing harmonic current distortion in a power line without direct measurement , to which a nonlinear load is connected, using a device, which not requiring a continuous current spectral analysis. The oscillograms of currents in the connection node of the device for suppressing higher harmonic currents, obtained as a result of simulation modeling of the operation of the power system with a nonlinear load and a Matlab / Simulink filter, are presented. A mathematical description of the proposed principle of suppressing the highest current harmonics is presented.
Keywords: suppression device, harmonic distortion, simulation, power line, impedance, electromagnetic interferencer
In this paper, a numerical study of the optimized body shape with minimal aerodynamic drag has been carried out. A computational experiment involves the transition from the study of a real object to the study of its mathematical model, for the study of such processes, a full-scale study of which is impossible, for some reason is difficult or expensive. The conditions for comparing the forms of bodies in a computational experiment are that they are kept constant for all bodies: the volume and shape of the working area; distances from sources, drains and centers of bodies; gas flow rates; body mass and other secondary characteristics besides just the very shape of the surface.
Keywords: aerodynamic resistance, optimized body shape, numerical simulation, computational experiment, temperature field, convective heat transfer
In this work, a study was made of the efficiency of the heat sink surface of a volumetric body with an internal heat source. An electrostatic analog of the distribution of the thermal field is chosen. A model of the convective flow is proposed, under certain initial and boundary conditions, the thermal conductivity of the medium transforming into heat removal. The conclusion is made about the ineffectiveness of the heat-conducting surface in the form of whip, finned and other designs of existing heat sinks, increasing only the mass, technological complexity of manufacture, thermal resistance and temperature of the heat-loaded element.
Keywords: Temperature field, convective heat transfer, effective heat sink area, electrostatic analog, similarity theory
In this paper, the temperature distribution from a point source of heat under convective heat transfer is studied. The Navier-Stokes equation describing the steady two-dimensional laminar motion of a fluid is solved numerically. The distribution of the temperature field of a heat-loaded point source is obtained under appropriate boundary conditions, supplemented by the boundary conditions for the flow velocity to equal zero on the paraboloid walls by numerical integration using the control volume method.
Keywords: Radiator protrusion shape, thermal conductivity, thermal apparatus mode, the temperature of the heat source
In work on the basis of one of the methods of nonlinear acoustics (method of successive approximations) is considered environment as a set of orthogonal plane layers. The analysis is conducted with the division generated total field into components parallel and orthogonal to the direction of its propagation. It is recognized as the primary distribution field distribution along the longitudinal direction with the introduction of the aperture factor and orthogonal to the introduction of the cross-aperture factor. It determines the range of changes of the parameters for biological environments in the case of the nonlinear interaction of acoustic waves in them.
Keywords: nonlinear interaction, quadratic nonlinearity, different layered media, immersion method, transverse aperture factor.
The article describes the method of controlling the parameters of the focused ultrasound field by means of the transition layer with desired acoustic characteristics. The article describes the experimental setup and the technological scheme. The description of the program and the formulas used for computer modeling. Presented and evaluated the results of experimental studies and computer modeling: the displacement of the focal point position on the width of the focal spot at the level of 0.707 of the maximum, location and the level of additional peaks. Summarizing the results of experimental setup and computer modeling can be concluded about the possibility of using the transition layer to control the formation of the focal spot.
Keywords: Ultrasound, experimental assembly, layered medium, refraction, computer modelling, transition layer, parameter control, focused ultrasound
The mathematical basics of the non-classical approach to the logical synthesis of k-valued digital structures, based on the replacement of the classic mathematical apparatus of logic synthesis (Boolean algebra) to the proposed mathematical apparatus - linear algebra are considered. The limiting properties of Boolean algebra, preventing further improve the technical ICs characteristics are discussed. One of the possible directions of overcoming these properties is the transition to a multi-valued logic. A new in a logical synthesis concept of linear synthesis of digital structures is proposed. A strong definition of linear algebra and its basic properties are shown. The logic synthesis process of two valued and multi-valued digital structures in linear algebra, including the formation of bases of a linear space, the original representation of the implemented logical function, obtaining decomposition of logic function according to the system of basis vectors are considered.
Keywords: multi-valued logic, Boolean algebra, linear algebra, linear logic synthesis, linear digital structures, bases of the linear space, decomposition of logic functions, logical variable, logical synthesis, digital logical elements
One of the parameters determining the efficiency of cleaning the blood in hemodialysis therapy is an effective mass transfer processes of metabolites through the dialyzer, which is defined by the mechanism of molecular diffusion and convection of low and medium weight substances in the blood. The article presents an analysis of modern mass transport models: streaming and kinetic; the analytical expressions of the spatial and temporal distribution of metabolites in the dialyzer. The results of mathematical modeling showed that these models do not reflect the full extent of the entire mechanism of mass transfer and must be supplemented. This is primarily due to the fact that blood is a non-Newtonian fluid. In addition, during hemodialysis, there is a change of the rheological properties of the blood - viscosity aggregated and deformability of erythrocytes, which ultimately affects the dialyzer mass transfer processes, reduces its clearance and thus reduces the efficiency of hemodialysis. The authors consider that the solution to this problem might be to develop a space-time mathematical model of mass transfer (the so-called distributed model of mass transfer), built with the influence of the driving forces behind the transfer of substances through the membrane dialyzer basic parameters and characteristics of fibers and rheological blood properties. In our view, the space-time dependence of the distribution of concentrations of metabolites in the blood and dialysate hemodialyzers allow to predict normalization the concentration of metabolites in the blood, and thus improve the accuracy of assessing the quality of dialysis.
Keywords: hemodialysis, mathematical modeling, spatial distribution, the time dependence, the space-time model
The article describes the experimental setup is designed to test the ability of manage the ultrasonic beam as it passes through the layered media. In this paper we consider a methodology of research, justified the choice of material for the simulation layers of biological tissues. The article describes the characteristics of the developed installation and positioning methods acoustic transducer. Solution of the experimental research allowed us to estimate the deviation of the "maximum" acoustic pressure (in the transverse distribution) by passing through the layered media and to determine the influence of the sound velocity in the transition layer on the distribution of acoustic energy in the region of space.
Keywords: Ultrasound, experimental assembly, layered medium, refraction.
The system that provides suppression external to the object magnetic disturbances during magnetoencephalography was developed. Register magnetic fields of the brain can detect features of the functioning of the CNS and to determine normal or pathological activity in human regulation systems, reflecting the functional state of human health. The designed system consists of a device for registration of external magnetic fields - fluxgate magnetometer, compensation module external magnetic field - coils Helmholtz, device register magnetic fields of the brain and compensate for a homogeneously magnetic field generated by the device of compensation of external magnetic fields.
Keywords: Magnetoencephalography, fluxgate magnetometer, coils Helmholtz, induction magnetometer