Some Aspects of the Inverse Problem of Determination of Cr^(4+) :YAG Absorption Cross Sections Using Experimental Data of Transmission

Mathematical modelling of nonlinear transmission of Cr4+:YAG crystals excited by Nd:YAG laser pulses of different duration are reported. Numerical simulation of transmission using a five-level scheme which included finite excitation lifetimes in Cr4+:YAG, focusing and diffraction of transversely nonhomogeneous pump radiation allowed to specify more precisely the limits of applicability of the four-level model. Critical analysis of typical simplifications commonly used for solving an inverse problem of determination of absorption cross sections is undertaken. It is shown that some of these assumptions that seem plausible enough might lead to considerable deviations of the determined absorption cross sections from their “true” values. A technique for determination of confidence intervals in case of the nonlinear regression is emphasized

Pulse Shape Influence on the Accuracy of Z-scan Measurements

Although the laser pulses with durations ranging from nanoseconds to femtoseconds and various pulse shapes are utilized for the Z-scan measurements, the influence of the temporal pulse shape on the measurement results is often neglected. In this paper, we tried to differentiate the influence of the temporal pulse shape on the common Z-scan technique with a small on-axis aperture in two cases: when the pulse peak intensity at the beam waist is known (for relatively long pulses), or when the total pulse energy and full width at half maximum (FWHM) of the correlation functions or FWHM of pulse durations are known (for short pulses)

Numerical Analysis of Short Pulse Optical Parametric Amplification Using Type I Phase Matching

The possibilities of efficient amplification and additional shortening of faster moving short fundamental harmonic pulses by the more slowly moving longer second harmonic pulses for type I phase matching are numerically analyzed for initially collimated axially symmetric beams, taking into account diffraction, group velocity mismatch and dispersion of the pulses

Intelligent System of Relay Protection of Electrical Network 6-10 kV with the Implementation of Automatic Correction of the Operation Set Point

The purpose of the study is to develop the architecture and working algorithm of intelligent relay protection of an electrical network with an isolated neutral. “Intellectualization” of relay protection is necessary to increase its sensitivity and reliability. This problem is relevant due to the accident rate of overhead power lines and incorrect operation of traditional relays. This is due to the fact that the set point is not adjusted according to the deviation of the line parameters with changing environmental and load conditions. The purpose of the study is achieved by solving the following problems: the concept of supplementing an electronic relay with a mechanism for correcting the operation set point is proposed. The use of the digital shadow of the electrical network is substantiated. The digital shadow interrogates the sensor system. The advantage of using a digital shadow as part of relay protection has been proven. This allows emulating faults and estimating currents to correct the setpoint. The most significant result of the study is an example of the implementation of intelligent relay protection using a digital shadow in the form of an artificial neural network. The application of a neural network for approximating the current function of a two-phase short circuit is demonstrated. The significance of the results lies in the improvement of the sensitivity and selectivity of current protection due to the digital shadow for working out emergency modes. The convenience of operating and reproducing a digital shadow in the form of a neural network is noted

Stochastic Cooling Overview

The status of stochastic cooling and developments over the years are reviewed with reference to much of the original work. Both theoretical and technological subjects are considered.Comment: 10 pages. Includes an extensive bibliograph

Capture of particles of dust by convective flow

Interaction of particles of dust with vortex convective flows is under theoretical consideration. It is assumed that the volume fraction of solid phase is small, variations of density due to nonuniform distribution of particles and those caused by temperature nonisothermality of medium are comparable. Equations for the description of thermal buoyancy convection of a dusty medium are developed in the framework of the generalized Boussinesq approximation taking into account finite velocity of particle sedimentation. The capture of a cloud of dust particles by a vortex convective flow is considered, general criterion for the formation of such a cloud is obtained. The peculiarities of a steady state in the form of a dust cloud and backward influence of the solid phase on the carrier flow are studied in detail for a vertical layer heated from the sidewalls. It is shown that in the case, when this backward influence is essential, a hysteresis behavior is possible. The stability analysis of the steady state is performed. It turns out that there is a narrow range of governing parameters, in which such a steady state is stable.Comment: 14 pages, 10 figures, published in Physics of Fluid

Increasing Requirements for Information Culture and Competencies in The Digitalization of The Economy

The amount and complexity of information is constantly increasing, changing in the process of digitalization of the economy, where professionals with a high information culture can create a competitive advantage in the company in relation to other players in the market. To get the full effect of information technology implementation, management and specialists must understand what they are working with in order to avoid loss of profits in the company.Количество и сложность информации постоянно возрастает, меняется в процессе цифровизации экономики, где специалисты, обладающие высокой информационной культурой способны создавать конкурентное преимущество в компании относительно других игроков на рынке. Чтобы получать полный эффект от внедрения информационных технологий, руководство и специалисты должны понимать с чем работают во избежание потери прибыли в компании