Abstract: The designs of a warm (uncooled) aperture diaphragm in a gas-filled cryostat with a matrix photodetector sensitive in the infrared spectral range are studied numerically and experimentally. It is shown that for the chosen design of a warm aperture diaphragm, a \(384\times 288\) pixel matrix photodetector is cooled by liquid nitrogen to operating temperatures (85 K) in less than 40 seconds, and by a throttle microcooler in 15 seconds, while maintaining the standard sensitivity of photodetectors based on cadmium–mercury–tellurium (CMT) structures. PubDate: 2020-11-01

Abstract: A modification of the method of digital holographic interferometry for the determination of deformations of an object with a diffuse surface by comparing two complex wavefronts reflected from the object at its two different states is considered. The difference of the proposed method with classical digital holography methods is that digital holograms by which the images are reconstructed have complex values determined by the phase shift method (‘‘complex’’ hologram), while classical digital holograms have only real values. Besides, digital holograms are reconstructed with allowance for inhomogeneity of the reference beam, which improves the reconstruction quality. For this purpose, a tunable neutral optical filter is introduced into the reference arm of the optical scheme of the interferometer. The method is verified experimentally. PubDate: 2020-11-01

Abstract: The peculiarities of image formation of a volume asymmetric ideally absorbing edge, the main fragment of extended (in depth) plates of constant thickness, in diffraction limited projection system are analytically studied with application to the size inspection of 3D objects. The structures and profiles of intensities in the images of the front and rear faces of object are investigated at small and large apertures of the optical system for different relations between the object bevel \(c\) , the size of the Fresnel zone \(\delta_{d}\sim\sqrt{\lambda d}\) ( \(\lambda\) is the wavelength of light and \(d\) is the object thickness), and angular aperture of the optical system \(2\theta_{0}\) . In the case when the bevel \(c\ll\delta_{d}\) , at large focal depth of the system the intensity profile is displaced in the image of the 3D edge in linear proportion to the Fresnel zone and to the bevel size. It is analytically demonstrated that, for large bevels ( \(c\gg\delta_{d}\) ) and small apertures of the system in the plane conjugating with the front face, a sharp image of either the front face (the rear face is shadowed) or the rear face (the front face is shadowed by the rear face) is observed. The formulas for the image profile of the rear face are obtained and studied in the case of significant volume effects, when the focal depth of the system is far smaller than the object thickness. The calculation results are in good agreement with the results of computer modeling. PubDate: 2020-11-01

Abstract: The developed classical machine learning models based on linear models and decision trees, the modern algorithms of convolutional neural networks, and the neural network autoencoder are compared in solving the problem of predictive detection of pre-failure and failure states of aircraft engines. The NASA data set includes the sensor readings reflecting the life cycle of aircraft engines. Several problem formulations are investigated in the study: (i) the problem of binary and multiclass classification, where the normal, pre-failure, and failure states of aircraft engines are predicted; (ii) the regression problem intended to predict the accurate number of working cycles to engine failure; and (iii) the unsupervised learning, where the neural network autoencoder is applied to detect abnormal cycles of aircraft engine operation. The obtained algorithms are combined in a framework useful in analyzing a wide spectrum of data of predictive maintenance. PubDate: 2020-11-01

Abstract: A modification of the fast algorithm for the bandwidth selection of kernel functions in a nonparametric probability density estimate of the Rosenblatt–Parzen type is proposed. Fast algorithms for optimizing kernel estimates of probability densities make it possible to significantly reduce the calculation time when selecting their smoothing parameters (bandwidths) in comparison with the traditional approach, which is especially important when processing large statistical data. The method is based on the analysis of the formula for the optimal calculation of the smoothing parameter of kernel functions and the discovered dependence between the nonlinear functional on the second derivative of the reconstructed probability density and the antikurtosis coefficient. The proposed algorithm for the bandwidth selection provides a decrease in the probability density approximation error in comparison with the traditional approach. The findings are confirmed by the results of computational experiments. Special attention is paid to the dependence of these properties on the amount of initial data. PubDate: 2020-11-01

Abstract: An algorithm for solving an optimal control problem with terminal constraints is developed. The optimal control problem with terminal constraints and constraints on the control parameter is formulated. To solve the problem, a numerical algorithm based on the penalty method and genetic algorithms is described. A computational experiment is performed for the synthesis reaction of phthalic anhydride in order to get the maximum yield of the reaction product under terminal constraints. The optimal temperature regime and optimal concentrations of reagents are obtained. PubDate: 2020-11-01

Abstract: The method for reconstructing object images in cross-sections using a circular antenna array when sounding space by an ultrasonic monochromatic wave is proposed. The image reconstruction is carried out by scanning the internal structure of the object placed inside the circle controlled by the focus of the circular antenna array. An algorithm for controlling the phase shift modules in the elementary radiator channels of the circular antenna array for changing the focus position is presented. Model results of the reconstruction of the image of the simplest point objects are presented. The problems of implementation of a circular array are discussed. PubDate: 2020-11-01

Abstract: High-speed algorithms for detecting and localizing randomly distributed pulse point objects capable of generating instantaneous delta pulses at random time instances. The search is carried out using the reception device (detector), which can freely move within the search interval and dynamically adjust the size of the scanning window. In this work the a priori information about the distribution of the sought signal source is limited by the single-mode functions with a stepwise probability density function, which provides that the algorithms are physically implementable. The parameters of the optimal search are computed in dependence on the a priori probability density function of the sought signal source and the required localization accuracy. PubDate: 2020-11-01

Abstract: A simple-to-implement technique for measuring radial clearances with controlled precision due to decreasing random components of errors is considered. The quantitative estimates of precision, performance, and efficiency of the proposed technique are provided. This technique is stochastic, is based on characteristics of random errors and on periodicity of blade wheel rotation, and allows obtaining the measurement results with uniform precision in the entire range of rotation speeds of the turbomachine rotor. The considered technique makes it possible to avoid procedures for approximating numerical readouts. PubDate: 2020-11-01

Abstract: A new algorithm of 6-coordinate tracking of a moving object on a sequence of RGB-images that is based on the convolutional neural network is proposed. Training the neural network is carried out by using the synthesized data of the object with a dynamic model of motion. A Kalman filter is included into the feedback from the network output to its input to obtain a smoothed estimate of the object coordinates. Preliminary results of object tracking on synthesized images demonstrates the efficiency of the proposed approach. PubDate: 2020-11-01

Abstract: A dynamic clustering algorithm for temperature signals is considered. It is used for solving the problem of distinguishing climatic regions characterized by a certain homogeneous climate type within the boundaries of the region on the Earth’s surface. A numerical experiment implemented with the aim of estimating its stability is described. The reference signal model used in the numerical experiment is presented as a sum of harmonic components. Additive components of the noise are formed in the frequency region. In the numerical experiment, the noise magnitude and sample size are measured. Estimates of root-mean-square deviations and stability of the dynamic clustering algorithm are presented. PubDate: 2020-11-01

Abstract: A method for reconstructing functionally defined surfaces by stereo images of real objects is proposed. A known approach to the computation of 3D models by silhouette images in the object space is used for preprocessing. The depth map is calculated using a well-known algorithm based on area with correlation of image intensity levels. In order to reconstruct a smooth surface with a compact description, a new method of transformation into a functionally defined model is proposed. PubDate: 2020-11-01

Abstract: Processes of acoustooptical interaction at infralow frequencies with the use of seismic vibrators as sources of low-frequency acoustic oscillations propagating in the atmosphere and laser measuring lines as optical receivers of oscillations are studied. The proposed types of the source and receiver in the interest of studying the acoustooptical interaction determine the novelty and originality of the proposed approach. Results of experiments on estimating characteristics of the acoustooptical interaction at infralow frequencies in problems of laser ecological monitoring of the environment are presented. PubDate: 2020-11-01

Abstract: Using the previously developed numerical-analytic method for describing input and output parameters of a the multidimensional dynamical object for the given domain of admissibility (Part I), the paper develops a method for optimal estimating the values of continuous linear functionals (numerical characteristics) of measurable parameters based on incorrect data that contains not only fluctuation error, but also singular interference (Part II). The method provides maximally maximal decomposition of computation, does not require performing standard linearization scheme and choosing initial condition, and also is not related with spectral coefficient calculation in finite linear combinations (with given basis functions) describing integral curves of the differential equation, measured parameters, and singular interference. Casual and method errors are analyzed, and an illustrative context and recommendations for a practical application of the results are provided. PubDate: 2020-11-01

Abstract: Wavelet filtration algorithms are widely used for image processing; the majority of them are of threshold character: the wavelet decomposition coefficient whose value is smaller than some threshold value is equated to zero, otherwise, this coefficient is subjected to some (mostly nonlinear) transform which is defined by the used threshold function. When filtering contrast images, such treatment of decomposition coefficients may lead to the so-called artefacts in the filtered image — in the neighborhood of the stepwise change in the amplitude of the filtered image, the pulses appear that are absent in the initial image, which significantly worsens the filtration quality. To eliminate such artefacts, several approaches are considered in this study and a method is proposed whose gist consists in posttreatment of the result of wavelet filtration of images by means of nonlinear spatial filtering algorithms. The calculation experiment performed in this study has made it possible to come to the conclusion that the proposed method is efficient to eliminate the artefacts of wavelet filtration of contrast images. PubDate: 2020-11-01

Abstract: The effect of the different surface treatment of Hg \({}_{1-x}\) Cd \({}_{x}\) Te (CMT) films before the atomic layer deposition of Al \({}_{2}\) O \({}_{3}\) dielectric on the charge at the dielectric–semiconductor interface has been studied. Metal–dielectric–semiconductor (MDS) structures with different surface treatment before the deposition of a dielectric have been manufactured. The capacitance–voltage characteristics of CMT based MDS structures have been measured alongside with the surface charge density. The surface charge is non-uniformly distributed over the surface of films with \(x=0.22\) and a natural oxide layer and equal to \((0.8{-}1.8)\times 10^{-8}\) C/cm \({}^{2}\) , and this may lead to the inversion of the surface conductivity type. The exposure of these CMT structures in mercury vapor at room temperature leads to the formation of a negative charge within a range of \(-(0.4{-}1.6)\times 10^{-8}\) C/cm \({}^{2}\) . PubDate: 2020-09-01

Abstract: The paper states the operating principles of subminiature semiconductor emitters and offers the research results of the performance for those emitters that were developed and manufactured at the Rzhanov Institute of Semiconductor physics of SB RAS over the last three years. Single photon emitter based on Al \({}_{x}\) In \({}_{1-x}\) As/Al \({}_{y}\) Ga \({}_{1-y}\) As quantum dots has been developed. Hanbury Brown and Twiss experiment has been carried out to measure the photon statistics. The photon correlation function demonstrates a clear photon antibunching effect ( \(g^{2}\) (0) \(\approx\) 0.04), which is a direct evidence of single photon emission by single Al \({}_{x}\) In \({}_{1-x}\) As quantum dots. The results of developing single-mode vertical-cavity surface-emitting lasers with a wavelength of 794.8 nm future-oriented for application in chip-scale atomic clock and operating at the transition 5S \({}_{1/2}\to\) 5P \({}_{1/2}\) of Rb \({}^{87}\) are reported. PubDate: 2020-09-01

Abstract: The characteristics of MIS structures based on insulating PbSnTe:In films grown by molecular beam epitaxy (MBE) with compositions near the band inversion are studied. It is shown that a number of their features can be induced by a ferroelectric phase transition with the Curie temperature in the range of 15-20 K. The injection and detection of spin-polarized electrons in PbSnTe:In are studied by using ferromagnetic contacts Co and Co \({}_{40}\) Fe \({}_{40}\) B \({}_{20}\) . A spin-valve effect is discovered by measuring the magnetoresistance in local geometry at a distance of more than 30 \(mu\) m from ferromagnetic contacts. The presence of a surface spin-polarized state with a linear dispersion law is demonstrated by means of the photoemission with angular and spin resolution. PubDate: 2020-09-01

Abstract: It is demonstrated that it is possible to use the ammonia molecular beam epitaxy for growing structurally perfect high-ohmic GaN layers which allow generating SiN/Al(Ga)N/GaN heterostructures for transistors with a high mobility of electrons. The growth conditions are determined for GaN layers with smooth surface morphology (with a mean-squared deviation of \({\sim}\) 2 nm) appropriate for creating sharp heteroboundaries. The possibility of improving the crystalline perfection of GaN layer due to the use of buffer high-temperature AlN layer (with the growth temperature above 940 \({}^{\circ}\) C) is demonstrated. It was shown that in situ surface passivation of Al(Ga)N/GaN heterostructures by the ultrathin SiN layer allows generating normally closed transistors with unprecedented low values of the current collapse ( \({\sim}1\%\) ). PubDate: 2020-09-01

Abstract: The paper reviews studies of the Laboratory of Theoretical Physics of the Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences. Two research directions are discussed: transport properties of two-dimensional excitonic systems and electron transport in two-dimensional topological insulators. Particular attention is given to excitonic systems in the mode of Bose–Einstein condensate and to the theory of conductivity of two-dimensional topogical insulator with a thickness close to the critical one caused by developed network of edge states permeating the sample. PubDate: 2020-09-01