The Study Methods of Increase Efficiency Algorithms Pulse width Modulation in AC Electric Drives

In the paper describes the AC electric drive, which consists of the induction motor and the semiconductor converter. Structure of the frequency converter, which includes a three-phase bridge inverter on based fully controlled transistors, is considered. The algorithm of pulse width modulation, which used in the majority of the electric drives, is discussed. The characteristics and shortcomings of the algorithm is shows. Algorithmically methods to improve the efficiency of the inverter – promodulation control signal. The efficiency of this method in different variations is given. The level electromagnetic compatibility inverter and efficiency various control algorithms are analyzed. The conclusions about feasibility of using the method promodulation

Nonadiabatic generation of spin currents in a quantum ring with Rashba and Dresselhaus spin-orbit interactions

When subjected to a linearly polarized terahertz pulse, a mesoscopic ring endowed with spin-orbit interaction (SOI) of the Rashba-Dresselhaus type exhibits nonuniform azimuthal charge and spin distributions. Both types of SOI couplings are considered linear in the electron momentum. Our results are obtained within a formalism based on the equation of motion satisfied by the density operator which is solved numerically for different values of the angle $\phi$, the angle determining the polarization direction of the laser pulse. Solutions thus obtained are later employed in determining the time-dependent charge and spin currents, whose values are calculated in the stationary limit. Both these currents exhibit an oscillatory behavior complicated in the case of the spin current by a beating pattern. We explain this occurrence on account of the two spin-orbit interactions which force the electron spin to oscillate between the two spin quantization axes corresponding to Rashba and Dresselhaus interactions. The oscillation frequencies are explained using the single particle spectrum.Comment: 9 pages, 5 figures, Conference "Advanced many-body and statistical methods in mesoscopic systems", June 27 -July 2, 2011, Constanta, Romani

Influence of Milk Thistle Shot on Quality Parameters of the Sour-milk Beverage

Modern complicated ecological conditions cause a general necessity in improving the food structure of the population due to improving the quality, biological value and taste characteristics of products. Just that is why, the aim of the work was to study the influence of milk thistle shot on quality parameters of the sour-milk beverage – kefir. It was established, that it had the homogenous consistence with a broken clot and color from white to creamy with shot particles. The increase of the milk thistle shot dose to 3 % and 4 % results in the taste with the brightly expressed milk thistle smack and brown color with the expressed milk thistle content. The viscosity of kefir with fms 2,5 % changes during seven days of storage, although remains rather high at 8 day, namely 47 s. The increase of the viscosity of kefir with milk thistle shot is explained by its hygroscopic properties, in which result free moisture of the product is bound. The analysis of microbiological parameters in the process of storage of kefir with milk thistle shot allows to make a conclusion about the satisfactory sanitary condition of the new product and its harmlessness for consumer's health. In the kefir with milk thistle shot the general amount of amino acids grew by 11,6 %, including irreplaceable ones – by 10,1 %, replaceable – by 12,6 %, that indicates its biological value.Addition of milk thistle shot to kefir didn't cause changes of the biological value of the protein component of the combined product. It is testified by the mean value of amino acid scores of control (129,3 %) and experimental (127,9 %) samples of kefir. Some growth of the valine score (3,6 %) can be noted.So, the combined product is characterized by the balanced amino acid composition. Due to adding milk thistle shot, consumption of amino acids, necessary for synthesis of proteins and essential number of compounds, vitally important for the human organism, grew

Investigation of the Influence of “Amaranth” Cryoadditive on Organoleptic and Microbiological Parameters of Processed Cheeses

There was grounded the expedience of using “Amaranth” cryoadditive in the technology of processed cheeses. “Amaranth” cryoadditive contains necessary vitamins and microelements of the natural origin. The use of “Amaranth” cryopowder in the processed cheeses technology allows to enrich them with vitamins, mineral substances and food fibers. The main factors of introducing “Amaranth” cryoadditive were: the normative organoleptic estimation of a product and its daily need.Introduction of “Amaranth” cryopowder in cheese masses results in the energetic value growth along with the treating-prophylactic effect. The complicated complex of chemical and biochemical compounds, included in the composition of “Amaranth” cryopowder, allows to relate it to products with the wide spectrum of treating-prophylactic and radio-protective properties.Organoleptic characteristics of processed cheeses with cryopowder “Amaranth” testified that experimental samples of cheese keep the tender, elastic and resilient consistence. They have the specific original taste and smell (of cream butter). They had the homogenous picture on the cut, paste of the light-yellow or yellow color with separate dots of amaranth (black-red color). The surface of experimental samples was clean, shiny, correspondent to standards.Experimental samples had the pleasant commodity look. Processed cheese, produced using “Amaranth” cryopowder, combines in itself traditional consumption properties with technological possibilities of functional-technological ingredients of the vegetable origin.The offered products widen the assortment of milk products of the treating-prophylactic direction

General stochastic separation theorems with optimal bounds

Phenomenon of stochastic separability was revealed and used in machine learning to correct errors of Artificial Intelligence (AI) systems and analyze AI instabilities. In high-dimensional datasets under broad assumptions each point can be separated from the rest of the set by simple and robust Fisher's discriminant (is Fisher separable). Errors or clusters of errors can be separated from the rest of the data. The ability to correct an AI system also opens up the possibility of an attack on it, and the high dimensionality induces vulnerabilities caused by the same stochastic separability that holds the keys to understanding the fundamentals of robustness and adaptivity in high-dimensional data-driven AI. To manage errors and analyze vulnerabilities, the stochastic separation theorems should evaluate the probability that the dataset will be Fisher separable in given dimensionality and for a given class of distributions. Explicit and optimal estimates of these separation probabilities are required, and this problem is solved in present work. The general stochastic separation theorems with optimal probability estimates are obtained for important classes of distributions: log-concave distribution, their convex combinations and product distributions. The standard i.i.d. assumption was significantly relaxed. These theorems and estimates can be used both for correction of high-dimensional data driven AI systems and for analysis of their vulnerabilities. The third area of application is the emergence of memories in ensembles of neurons, the phenomena of grandmother's cells and sparse coding in the brain, and explanation of unexpected effectiveness of small neural ensembles in high-dimensional brain.Comment: Numerical examples and illustrations are added, minor corrections extended discussion and the bibliograph

Taking into Account Material Damping in Seismic Analysis of Structures

The purpose of this paper is to justify that it is necessary to take into account physical and mechanical properties of soil and different materials of erected structures for damping vibrations in dynamic loads, and to suggest tools for modelling the damping effect (natural or engineering induced) between foundation and soil. A technique is suggested for modelling the behavior of structure in time history analysis taking into account material damping. When solving this problem, the following results were obtained: the physical meaning of material damping was described; Rayleigh damping coefficients were computed through modal damping coefficients. Numerical analysis was carried out for the structure together with soil in earthquake load. Time history analysis was carried out for the problem. Peak values of displacement, speed and acceleration at the roof levels were compared. Analysis results were compared (with and without taking into account material damping). Significant influence of damping on the stress-strain state of the structure has been confirmed

Spin Current in Spin-Orbit Coupling Systems

We present a simple and pedagogical derivation of the spin current as the linear response to an external electric field for both Rashba and Luttinger spin-orbital coupling Hamiltonians. Except for the adiabatic approximation, our derivation is exact to the linear order of the electric field for both models. The spin current is a direct result of the difference in occupation levels between different bands. Moreover, we show a general topological spin current can be defined for a broad class of spin-orbit coupling systems

Vibration spectra of benzene-like models with Hooke's law interactions

The harmonic oscillations of a spring-ball model of benzene-like nanosystems with Hooke's law interactions between nearest, second, and third neighbors are explored. We show that in the cylindrical coordinates the dynamics of this cyclic hexagonal system is described by the Lagrange equations similar to those of the one-dimensional two-component crystal model. We expose that the vibration frequencies of the hexagonal model lie on the branches of the dispersion law of the associated lattice model, and their positions are determined by the cyclic Born-Von Karman condition. The hexagonal model is generalized to one describing the benzene molecule and the fully deuterated and halogenated benzenes. The effect of hybridization of vibration modes and the pushing apart of spectral branches in the crossover situation is revealed. All the discrete frequency spectrum and normal modes of oscillations and their explicit dependencies on all the constants of elastic interactions are exactly found.Comment: 25 pages, 10 figure

On the locality of MHD turbulence scale fluxes

The scale locality of energy fluxes for magnetohydrodynamics (MHD) is investigated numerically for stationary states of turbulence. Two types of forces are used to drive turbulence, a kinetic force that acts only on the velocity field and a kinetic-inductive forcing mechanism, which acts on the velocity and magnetic fields alike. The analysis is performed in spectral space, which is decomposed into a series of shells following a power law for the boundaries. The triadic transfers occurring among these shells are computed and the fluxes and locality functions are recovered by partial summation over the relevant shells. Employing Kraichnan locality functions, values of 1/3 and 2/3 for the scaling exponents of the four MHD energy fluxes are found. These values are smaller compared with the value of 4/3 found for hydrodynamic turbulence. To better understand these results, an in depth analysis is performed on the total energy flux.Comment: submitted to Physics of Plasmas, 10 pages, 8 figure