Subject of Research. We compare the effectiveness of the procedure for automatic object classification according to 3d-lidar data, built on the basis of single-photon counting technology, with the efficiency of the classification procedure with the usage of the conventional linear lidar data. Lidars based on the single-photons counting technology (SPCT) significantly exceed the ordinary linear lidars for a whole range of target parameters, including: spatial resolution - by more than an order of magnitude; the performance of the land surface scanning process - by an order of magnitude; by weight and size indicators - few times less. Unlike linear lidars, each laser point in the case of a SPCT-lidar is described not only by its coordinates and the intensity of the reflected signal, but by coordinates and an additional data block that characterizes the surface relief of the probed object in the direction of the probing photon flux. The presence of this additional data block for each laser point makes it possible to consider the received images as 3d-images, that simplifies the solution of not only the photogrammetric problem, but also the task of automatic objects classification on SPCT-image. Method. We consider the automatic object classification task solution based on SPCT-data with the use of the machine learning methods (XGBoost and multilayered neural networks - ANN). Main Results. The results of the numerical simulation carried out within the framework of the present study showed that, other things being equal, the efficiency of solving the classification problem based on SPCT-data, in practically important cases, increases up to 20% compared with the case where the linear-lidar data was used. Practical Relevance. The obtained results can be used in the design of the mobile SPCT-lidars enabling the detection and classification of objects on the Earth's surface in real time with high reliability.

Subject of Research. The paper presents the study of the oral mucosa reaction of experimental animals to fractional laser treatment by diode laser radiation with a wavelength of 980 nm. Methods. A single fractional laser treatment of oral mucosa was carried out in the experiment on Wistar laboratory rats at different exposure regimes: combinations of laser power from the range Р = 5-15 W, pulsewidth tp = 100-120 ms and the filling factor. The animals were taken out of the experiment immediately after exposure, on the 5th, 7th and 28th day after the treatment. For histological evaluation mucosal preparations were stained with hematoxylin and eosin, as well as aniline blue according to Masson. Thickness of mucosa layers and concentration of collagen fibers were defined as a result of computer processing of images of histological samples. Main Results. It was established that the mucous condition  depends significantly on the laser treatment regime and the time elapsed since the fractional treatment. When exposed to pulsed laser radiation with P = 5 W, tp = 100 msor P = 7 W, tp = 120 ms,at the filling factor F = 200±50 microdamages/cm2 the mucous regeneration has been completed on the 28th day after treatment, and for the other studied regimes it continues. After regeneration the thickness of the epithelial layer of the oral mucosa is less, and the thickness of the submucosal layer with lamina propria of mucosaand concentration of collagen fibers in the mucosa correspond to control. Practical Relevance. The obtained results are promising for further research on the reconstruction of thinning oral mucosa. 

Subject of Research.The paper presents the study of blood biochemical composition (bilirubin, creatinine, triglycerides, uric acid) effect on its optical properties, refractive index and absorption coefficient, in terahertz frequency range. Method. To obtain the values of the refractive index and the absorption coefficient, the method of terahertz time-domain spectroscopy was used in the transmission mode. Concentrations of total bilirubin, creatinine and triglycerides were measured in blood serum by the colorimetric method, the pseudokinetic method and the enzymatic method, respectively. The glucose level was determined in blood plasma by the enzyme method. All measurements of blood component concentrations were carried out at the Almazov National Medical Research Centre. Main Results. The optical properties of blood with various biochemical composition were obtained using terahertz time-domain spectroscopy at the frequency of 0.4THz. It is shown that the refractive indices and the absorption coefficients of blood decrease with an increase in the concentration of bilirubin and creatinine. It has also been found that with an increase in the concentration of uric acid and triglycerides, the refractive index of blood increases and the absorption coefficient of blood decreases, respectively. The correlation between the refractive index and the concentration of triglycerides and the correlation between the blood absorption coefficient and the concentration of uric acid were not revealed. Practical Relevance. The observed correlations between the concentrations of blood components and the optical properties are useful in the development of a new technique for blood analysis.

Subject of Research. The paper presents qualitative analysis of terahertz time-domain spectroscopy application for cancer diagnosis by measurement of the optical properties and spectral characteristics of cancer cells. For this purpose, the cultivation of two cancer cells, U-251 (glioblastoma brain) and A549 (lung adenocarcinoma), were carried out, then their refractive index, absorption coefficient and dielectric constant were measured, and the optical properties of tumor cells were compared with the optical properties of healthy cells (fibroblasts). Tumor cells contain more OH-components in comparison with healthy cells. Since terahertz radiation is heavily absorbed by water, there are differences in the spectra of healthy and oncological cells. Because of the demand for rapid and effective diagnostics of oncology (including intraoperative), the obtained results show that terahertz time-domain spectroscopy can be used for this purpose in the present time.Method. To obtain the optical properties and spectral characteristics of the researched objects, a terahertz time-domain spectroscopy method in the transmission mode was used. The researched cell lines were cultured in vitro. Optical properties and spectral characteristics of the samples were calculated by the thin film method and Fourier transform.Main Results. The results show the differences of refractive index, absorption coefficient and dielectric permittivity between the oncological cell lines U-251, A549 and the healthy cells in the frequency range 0.2-1 THz. It was found that cancer cells have higher values of refractive indices and absorption coefficients than those of healthy cells. Brain glioblastoma (U-251) has a transmission peak at the frequency of 0.24 THz.Practical Relevance. The results obtained in this work can form the basis for the intraoperative diagnosis of brain and lung cancer with the use of terahertz time-domain spectroscopy, and it is also useful in the other studies, for example, the development of biotissue phantoms in the THz frequency range.

The paper proposes the method of integral architecture formation for silica porous films used as solid-state media for different indicators. The formation of sells insulated from each other by barriers in the porous media is performed by direct laser writing using CO2laser source. We study the mechanism of laser induced modification of silica porous film with the thickness of 170±10 nm on glass substrate. We also estimate the laser processing parameters for the formation of barriers with the determined crater depth of 1.5±0.5 μm and beads height of 2.5±0.5 μm, the laser intensities in the range of q = 8.7–11.3 kW/cm2 and scanning speed of υ= 0.1-0.7 mm/s. The dependence of the laser track geometry on scanning speed and laser intensity is analyzed by optical microscopy and contact profilometry. The produced sells were impregnated with aqueous solution of copper (II) nitrate and rhodamine to demonstrate the efficiency of the insulating barriers. Looking ahead this technique can be applied for fabrication of thin film sensing devices containing different metal nanoparticles with unique optical properties.

Subject of Research.The paper presents the study of effect that occurs when pressure is applied to the phase-shifted fiber Bragg gratings perpendicular to the fiber axis. Method. Fiber Bragg gratings inscription was performed using Talbot interferometer, and the introduction of a phase shift – by means of the electrical discharge of an arc fusion splicer. The excimer laser system was used as a radiation source. The change in the reflection spectra at different pressures on the optical fiber is measured. Main Results. Fiber Bragg gratings with a phase shift are obtained by the procedure that excludes the use of high-precision instruments during the phase-shift introduction step. Experiment results are given showing up the distance dependence between the local minima in the reflection spectrum of fiber Bragg grating with a phase shift on the applied mass arising as a result of the induced birefringence. It is shown that the change in spectral characteristics is related to the birefringence effect owing to stresses inside the fiber. As a result, the second local minimum appears in reflectance band. Practical Relevance. Research results can be used in creation of a sensing element of a fiber optic pressure sensor.  This study demonstrates the application possibilities of Bragg gratings with a phase shift as sensing elements in fiber-optic pressure sensors.

Subject of Research. This paper presents analysis of the possibility for establishing all-weather pulse laser altimeters for measuring of low altitudes above the sea surface. We proposed special design features which take into account the random nature of the reflective properties and low reflection coefficient of the water surface. Method. Theoretical analysis and numerical simulation of temporal characteristics of backscattering return and average power reflected from the sea surface were carried out. The method of altitude measuring to the sea surface in conditions of fog and haze is based on the time interval measuring between the emitted pulse drop and the backscattered signal drop when backscattered signal exceeds the certain level.Main Results. A block diagram of pulsed laser altimeter is proposed which makes it possible to measure low altitudes to the sea surface in various meteorological conditions. The ranges of measured altitudes are determined in the clean atmosphere and in the conditions of fog and haze.Practical Relevance. The proposed scheme ensures the navigation of low-flying vehicles above the sea surface under radio interference in all-weather conditions.

Subject of Research.The paper presents the study of methods for recognition of pathologies of biological tissues based on the use of gas-discharge visualization process. At the same time, the choice of research method  determines the main differences in biological tissue characteristics, namely, its hypoxia, the rate of cell division and luminescence in a high-frequency electromagnetic field. Method. Six patients underwent gas-discharge visualization of basal cell carcinoma of the skin and a similar healthy site on the opposite side of the face. Photographs of bioptates in a high-frequency field were obtained, clearly representing the differences in the luminescence of affected and healthy tissue areas. A hypothesis was put forward and the dependence of the hypoxia level of biological objects with their luminescence in a high-frequency electromagnetic field was established. The luminescence areas of healthy and affected areas and the rate of their reproduction during anaerobic and aerobic glucose decay were calculated. Main Results. It is shown that at fixed temperature the division of cancer cells is much faster (by 4.6 times) than with normal metabolism in healthy tissues. At the same time, the areas of luminescence obtained from the images as a result of using a high-frequency electromagnetic field in the affected areas are two times greater than in the normal tissues. In this regard, we can speak about the influence of the fission process rate, namely hypoxia, on the cell membrane state, which is fixed by gas-discharge visualization. Practical Relevance. The obtained results can be used to create new safe and accessible methods for detection of pathologies of biological tissues, and, as a consequence, the application of  these processes in medical institutions.

The problem of performance improvement of adaptive output control for linear time-invariant plant is addressed in the paper. The parameters of the plant are assumed to be unknown. A new method based on dynamical extension of regressive error model is proposed for design of the algorithms of controller parameters tuning. With a view of the proposed approach development  the existing solutions to this problem are considered and analyzed. The first solution is based on gradient adaptation algorithm that drives control error to zero, however with arbitrary slow rate of convergence. The second solution uses identification algorithm of dynamical regressor extension. The algorithm has potentially high rate of convergence, however does not ensure decaying of control error. Thus, by modification of aforementioned solutions, namely, by dynamical extension of augmented error model and gradient adaptation algorithm the new algorithm is obtained. The algorithm permitsto increase the rate of the tuning of controller parameters arbitrary and drives control error to zero. The important property of the algorithm is that it does not require parameters identification neither of plant nor of its parameterized representation. This property relaxes the dependence of the control algorithms from persistent excitation condition, that is, the key identifiability condition. The proposed solution is verified in MatLab/ Simulink environment by comparison with solution based on the gradient adaptation algorithm.

The paper discusses modeling and control of mechatronic systems with flexible links, which are widely used for manipulation tasks. At the first stage, a dynamic model of a mechatronic system with a flexible rotational link was obtained based on the Euler-Lagrange equations and the method of the assumed modes. The resulting model has finite dimensionality and can be easily adopted for simulation in order to study the dynamic characteristics of the system and further for trajectories planning and motion control. The algorithm for calculating feedforward control is presented, which enables transition of the link in a horizontal plane from the starting configuration to a given configuration in a finite time. In this case there is minimization of undesirable deformations at the end points of the trajectory caused by the elasticity of the link. The paper presents the results of the algorithm experimental verification on the mechatronic setup Quanser Rotary Flexible Link. The experiments demonstrated that the control goal is achieved for different rotation velocities, as well as they show a match between simulation and experimental results

The paper considers the preparation of film materials based on the chitosan/polyhydroxybutyrate blend by the casting method. The combination of polysaccharide chitosan and polyester polyhydroxybutyrate gives the possibility to decrease the degradation rate and improve biomaterial mechanical characteristics. Acetic acid was used to dissolve biopolymer components. The paper presents compatibility study results for polymers in the blend composition. It was demonstrated that crystallization of polyhydroxybutyrate is suppressed by mixing with chitosan. In order to reduce the film coating solubility, we have studied the application possibility of ionic cross-linking  with the help of calcium chloride. The effect of the calcium chloride content on the structure and morphology of the surface of the film compositions was studied by infrared spectroscopy and optical microscopy. Infrared spectroscopy showed that chemical cross-linking with calcium chloride occurs with the participation of carbonyl groups of polyhydroxybutyrate and hydroxyl groups of chitosan. It has been found that addition of more than 9% calcium chloride provides optically homogeneous surface of the film composition based on the chitosan/polyhydroxybutyrate blend. The obtained polymeric compositions of chitosan/polyhydroxybutyrate/CaCl2 have high perspectives for their further application in the development of medical materials.

Subject of Research. We study the methods for determination of the physical and mechanical characteristics of materials based on parameters recording of a solid body-indenter impact interaction with the surface of the material under test. Among the methods considered, the method of dynamic indentation was chosen for further research. With the development of computing devices and electronic element base this method acquires new opportunities and advantages over the other methods of nondestructive testing. They are: the possibility of portable implementation of the device, an unrestricted control of products, the possibility of F-h diagrams construction and others. Method. We consider the application of the developed algorithm for the primary processing of a measuring signal obtained from a primary converter under dynamic indentation. The results of the algorithm are compared with the results obtained from the ISPG-1 dynamic indentation device, previously developed at the Institute of Applied Physics of the National Academy of Sciences of Belarus. The results of the measuring signal processing were also compared with the results of computer simulation of the process of shock contact interaction by the finite element method. Main Results. An algorithm for processing of dynamic indentation primary signals is proposed. A model of dynamic indentation process is proposed. It is shown that the developed algorithm and model are efficient and show similar results in comparison with the results obtained with the existing dynamic indentation device. Practical Relevance. The obtained results can be used in the development of the domestic analogue of the dynamic indentation device.

Subject of Research.The paper deals with the problem of organization of testing and debugging in complex (full stack) projects of embedded computing systems with heterogeneous structure. The work is aimed at unified formal method development to organize testing and debugging that is applicable to a wide range of embedded systems and invariant to their implementation. The conclusion is drawn about the prospects of using level models of embedded systems representation as a method of unified modeling of complex projects of embedded systems. Method. To develop the method, we used the abstractions of the HLD-methodology of embedded systems design, the "model-process-processor" architectural style and methods of set theory. Main Results. The embedded systems testing and debug method based on level models is developed. We enhanced the "model-process-processor" architectural style, as a part of the method, for a more accurate description of the virtualization relations. The method of embedded systems multi-level testing is developed, which allows describing the test environment at different phases of embedded systems creation in the same style, provides the formalization of the concepts of testing, verification and validation from the embedded systems level representation point of view. Examples of description of multi-level embedded systems using the developed method are given. Practical Relevance. The method provided documentation techniques of embedded systems test environments at different phases of their creation, ways to organize testing, verification, validation and debugging in complex projects of embedded systems.The proposed approach increases requirements control efficiency in the embedded systems projects owing to the end-to-end and transparent project representation as a whole and formalization of the testing and debugging procedures.

We consider computer vision issues with a view to embed it into vehicles and automate the traffic process by detecting of objects and road users. Three basic stages of pattern recognition in the image are enumerated: image preparation for analysis, analysis, object classification. The search of methods that improve pattern recognition quality and provide visual information semantic integrity was carried out respectively for each stage. We propose to use normalization for the first stage, which allows making image objects insensitive to the light changes. For the second stage clustering method based on particle swarm optimization and k-means was developed that provides automatic tuning of clustering parameters. During the third stage Haar cascades with normalized training samples are proposed for application providing object unification and giving an opportunity to use less amount of training samples. Car images provided by Stanford University laboratory and publicly available were used for training and testing. To assess the effectiveness of the developed pattern recognition algorithm, 300 test images were blurred. We compared the results of the proposed algorithm operation with Haar cascades operating results without normalized training samples and without preparation for classification. Haar cascades with non-normalized training images provided correct car recognition in 8% of cases, meanwhile, the proposed algorithm recognized 72% of cases including those 8% of images. Visual information semantic integrity preservation is an important aspect in context of road traffic, because incorrect object detection can cause fatal consequences. The proposed algorithm of image analysis reduces the probability of error occurrences during pattern recognition.

Subject of Research. The paper presents analysis of information interaction of the elements within the group of unmanned aerial vehicles and their vulnerability to destructive information impact. At the moment, this problem is relevant for devices used in civil areas. In addition, the task of identifying hidden destructive information impact is an unsolved problem within the group of unmanned aerial vehicles. Method. A set-theoretical model of information interaction within the group of unmanned aerial vehicles is developed based on comparative evaluation results of the group control strategies. The developed model is analyzed, that gives the possibility to identify and evaluate the vulnerable elements, which carry out information interaction and are subjected to destructive information impact. Experiments are carried out, where destructive information is introduced into the process of information interaction (both internal and external), leading to disruption of the agent or group as a whole. Main Results. The information interaction of unmanned aerial vehicles group requires security factor increasing for contraction of the destructive information impact and a hidden destructive information impact. Hidden destructive information impact cannot be detected by classical approaches to information security, therefore, it is necessary to develop new methods to increase the information interaction security from such attacks. Practical Relevance. The results of the set-theoretical model analysis of information interaction within unmanned aerial vehicles group will enable the development of new information security methods to eliminate specific vulnerabilities associated not only with the classical, but also with the "soft" impact methods. They will be in demand for the use in autonomous robotic systems.

Subject of Research. The paper presents research of numerical image simulation for objects with known edge contour, considering optical diffraction blur and image sensor spatial sampling. Computationally effective solution is proposed under restriction of edge contour approximation by a set of straight lines.Method. Proposed method is based on the analytical numerical computation of the Fourier transform for the object bounding polygon. Calculus bandwidthis defined by the optical system diffraction limit and spatial frequency response of the object and background textures.Main Result. Proposed technical solution results in 2-3 order less computation time compared to a subpixel image simulation in spatial domain with subpixel sampling step value of 10-2 pixel.Computational complexity of the proposed approach is invariant with respect to a subpixel accuracy of simulated object geometry representation.Practical Relevance. Proposedapproach may be applied to a solution of inverse problems in the field of optical geometrical measurements and to a study of image processing algorithms with geometrical parameters representation error on the order of 10-1-10-4 pixel.

The paper presents analysis of modern network covert channels. The authors set forward a hypothesis of effective streaming protocol usage for covert channel creating. Covert channel technique for open networks is proposed. RTP-based covert channel functional model is described. Estimated characteristics of software prototype are reported. The results of stegano system software prototype operational testing in laboratory conditions and the Internet are described.  Software prototype demonstrated high covertness with allowable capacity for many tasks. At the same time transfer characteristics decrease with the complication of network topology. Obtained research results have two application domains of prime importance. On the one hand, illegal covert channel detection methods can be used by DLP-systems developers, law-enforcement agencies and defense establishments. On the other hand, the proposed method for covert information transmission can be used in telemetered covert channel creation, for example, satellite communication.

Subject of Research. The paper proposes models that make it possible to extend the Internet of things life cycle as a result of the sensory field clustering and the transfer of the interaction functions from the base station to the head node of the cluster. The efficiency of the clustered wireless sensor network was evaluated in comparison with the nonclustered one in terms of the residual energy parameter and the network lifetime. Methods. The Internet of things sensory field clustering method was used. The method is based on the idea of​equiprobable rotation of the head nodes, taking into account the level of nodes residual energy and the distance from the sensor devices to the head node. The time division multiple accessmechanism in the interaction of sensory devices with the head node of the cluster minimizes the probability of data transmission collision. Simulation modeling provides a tool for selecting clustering parameters while providing the required characteristics of the functioning of the Internet of things. Main Results. A wireless sensor network simulation model is proposed, which can find application in the Internet of things designing tasks. Estimations are given demonstrating the clustering expediency of  the Internet of things sensory field at sensory field sizes exceeding the distance from the most remote node to the base station. Practical Relevance.Sensor field clustering provides the increase of the Internet of things life cycle. The proposed models will be useful in the early stages of the Internet of things design.

Subject of Research.The paper deals with the practical aspects of distant speech acquisition in complex noisy environments using dual microphone arrays (MA2). The non-adaptive frequency-domain algorithms are described. The theory of MA2 is well developed so far, but the application of MA2 in specific conditions requires special consideration. The scenarios of point coherent interference and spatially distributed noise are studied.Methods. The comparison of differential algorithms and delay-and-sum algorithm is presented. The main properties of MA2 with summation algorithm and differential algorithms are researched on the basis of analytical models. Algorithms were tested on anechoic chamber recordings. The efficiency of the algorithms has been studied on recordings made near the street with intensive traffic. Main Results. The experimental results show the advantage of differential algorithms over delay-and-sum algorithm of both noise and interference suppression. For different variants of differential algorithms, street noise suppression about 10-12 dB is achieved. An additional advantage of differential algorithms is the possibility of null forming in the direction of a point source of interference. Practical Relevance. The results obtained may be used in hands free communication devices, camera equipment, portable recording devices, in acoustic monitoring systems. The results of the analysis of MA2 algorithms can also be used in the development of compact microphone arrays, as well as microphone arrays with a large number of elements.

A cloud of geographically distributed data centers developed by ITMO University (ifmo.ru) is presented.To increase reliability, as well as to collect statistical data, a special monitoring system is created that monitors the state of systems and the utilization of hardware resources. In addition to building a map of statistical data, information on resource utilization is suggested for the provider to perform a billing. An approach to monitoring system with asynchronous communication is proposed. An option with message broker implementation is shown. Out of two basic billing models, billing by quotas and billing by actual usage, we propose a model for organizing a dialogue between the administrator and the monitoring system in order to obtain data on resource utilization by actual usage. The use of a database for storing requests and responses is proposed, as well as the asynchronous dialogue using queues technology and message broker. Approbation was carried out on testing equipment with an actual infrastructure simulation. Unique asynchronous multi-agent system was obtained for statistics gathering on data center resources utilization. RabbitMQ message broker, PostgreSQL database and Zabbix monitoring system implementations are shown. The dialogue system was optimized with the help of Python code. The designed model can be recommended for implementation aimed at utilization of data obtained in different data centers, including distributed ones. Suggested model can be used in high-loaded systems  providing virtual resources as a service.

Subject of Research. One of the ways of automatic text analysis is the construction of subordination trees, in which the words of a sentence are connected with each other by semantic-syntactic links. The field of research is Russian-language texts, which have a general political, artistic and highly specialized character. Special attention is paid to the cases when the words are connected being far from each other at a considerable distance. Method. The subordination trees were built with the help of semantic-syntactical parser.Then the calculation of the distribution of links of different types by lengths was performed. The appearance frequencies of nonlocal links are studied. Main Results. It is shown that the fraction of non-local connections depending on the type can reach up to tens of percent. This is especially important for links coming from predicate nodes (subject, adverbial, etc.), as well as for anaphoric ones. It is noted that publicly available semantic classifiers and thesaurus have limited applicability for solving the problem of correct linking of remoted words in a sentence. Practical Relevance. It is shown that when solving the problem of extracting information that is ontological or scenario-based, as well as coreference, the long syntactic links that form the non-local semantic context cannot be neglected. The conclusion is drawn that the analysis of n-grams only is insufficient for the adequate selection of information from the text that is ontological or scenario. In this regard, there is a need to compile micro-dictionaries, focused on certain syntactic structures.

This paper deals with the examination of features of methods for determination of special points on electronic module images aimed at evaluating their application possibility for determination of an overlapping region. The conclusion is drawn about an insufficiency of the application of these methods for the unique determination of an overlapping region presence. Also this research considers features of the transformation to the uniform center of coordinates of electronic module image regions which do not have an overlapping region. We study a matrix decomposition of projective image transformation to the superposition of simple geometrical transformations for the image obtained within the conditions of formation of electronic module image regions. We propose an algorithm which determines an overlapping region presence of a couple of image regions of electronic modules based on the analysis of a projective transformation matrix and determination of parameters of an affine and projective transformation of images in case of their coercion to the uniform center of coordinates. The proposed algorithm is invariant with respect to scale changes and orientation of a pair of crosslinking images of electronic module regions and allows excluding images obtained with the distortions, which exceed admissible values, during the image stitching. The developed algorithm can be used for optimization of automated computer algorithms of processing of electronic module images and an acquisition of a large-scale electronic module image of the required quality.

Subject of Research.The results of emoji research are presented. Emoji are small electronic symbolic images used for expression of emotions and thoughts in an electronic message. We performed a search for dependencies between the use of emoji in messages and the degree of attention they attract. The main attention in the study is given to the Russian-speaking Internet community. Method. "VKontakte" social network and its four most popular thematic areas were chosen for the study. By structure research of the communities taken for the study, obvious indicators of the person's response to a post were highlighted. The graphs of the emotion frequency ratio in the post and the interest in it were constructed. Main Results. Adecreasing tendency is observed forthe interest in the post with the increase in the frequency of emoji for all types of communities. The greatest response was given to the posts that did not contain emoji. They made up the bulk of the researched array. Fan communities have become an exception: they are also the subject to this trend, but the process of interest decreasing is slower than in the similar posts of other orientations. Entertaining and motivational communities also contain peaks of slow decline of interest, but they are less clear and less frequent. Practical Relevance. Obtained research results give the possibility not only to understand the current trends in the use of emoji in "VKontakte" Russian-language social network, the dynamics and distribution of their use, but also the psychological perception of emoji by a person. The dependence was revealed between the use of emoji in messages and the degree of attracted attention. It shows how the use of emoji affects the perception of various kinds of information.

The paper proposes a model of floated gyro drift, used in a platform-based inertial navigation system, which takes into account temperature effects. We consider a problem of unknown parameters identification in a mathematical model of floated gyro drift. The presence of nonlinearity in the dynamics equations is expected. It is proposed to solve the formulated identification problem by Kalman-type filter application. This filter is characterized by the linearization point variation in course of solving the problem. The problem is solved for the gyro drift model which takes into account the temperature effect. The results of the model unknown parameters identification are compared using two algorithms. The first proposed algorithm is based on Kalman-like filter and the second one is based on the least squares method. The analysis of simulation results showed that the accuracy of unknown parameters identification by the algorithm based on linearized Kalman filter is commensurable with the algorithm based on the least squares method. However, linearized Kalman filter is efficient in solving the problem of identification of a gyro error model represented by combination of a few random processes.

Subject of Research. The paper presents an algorithm for pseudorandom number generationbased on properties of cellular automata. Cellular automata have high potential, high speed of calculations, especially at realization in parallel architecture. Method. In the presented algorithm pseudorandom numbers are generated by means of rules of transitions in cells of the cellular automaton depending on templates of the neighborhood and the output data of cells of "neighbors". Through several transitions at the choice of a generation technique the sequence of pseudorandom numbers turns out from zeroes and units. Main Results. The developed algorithm is tested on NIST-tests. The results of testing have shown that the algorithm makes the sequence with uniform distribution with probability of 99-100%. Comparison of the proposed algorithm with linearly congruent method, the main up-to-date method of generation of pseudorandom numbers, is carried out on NIST-tests. According to all tests the developed generator of pseudorandom numbers has shown the best results. The algorithm has the high speed, easy realization and also scaling possibility. Practical Relevance. The generator can be used in various applications, such as the theory of coding or lightweight cryptography. The cryptographic firmness is reached at tests by standard quality estimation techniques for the generator of pseudorandom numbers.

Subject of Research. The development and creation of a measurement system for determination and monitoring of the location and bends of extended objects in space are actual at the moment.We propose the creation of a sensitive part of fiber-optic measurement system based on chirped fiber Bragg gratings (FBGs) inscribed in a multi-core fiber. Method. The method essencelies independence determination of the grating period change in each core on the bending radius of the fiber, that gives the possibility to reconstruct remotely the trajectory of  the optical fiber laying in space.Main Results. The paper presents experiment results with a single-mode fiber with an array of chirped FBGs. The experimental optical scheme and the reflection spectra before and after the single-core optical fiber bending are shown. The geometry and computer model of multi-core fiber section with a given radius bend are described. Practical Relevance. Unlike the other existing fiber-optic measurement systems, a system with multi-core optical fiber with chirped FBGs array makes it possible to determine the trajectory of fiber-optic light guide laying in space without using methods of optical frequency domain reflectometry, which determine the location of the Bragg gratings along the optical fiber length.

The paper proposes an algorithm for frequency estimation of a pulse signal with constant beat under significant distortion conditions with the use of spectral analysis methods. The sequential processing of the signal based on the recurrent usage of discrete Fourier transform is shown. The initial pulse signal is represented as a fragment of the Dirac comb. Its Fourier spectrum also contains a fragment of the Dirac comb. To reduce the effect of leakage due to the application of Fourier transform to the finite sequence, a convolution of the signal with a weight window is used. To increase the signal-to-noise ratio and reduce the side lobe level, the spectrum of the initial signal is taken as the original for Fourier transform with an increased number of spectral lines. The necessity of recurrent transformation usage is brought about by the noise of the initial signal and the resulting spectrum after the first application of Fourier transform. In comparison with a single application of the transformation, this approach provides an opportunity to recognize a useful signal both against the background of Gaussian and aperiodic impulse noise, and against the background of signals containing such noise in the Fourier spectrum. We give a method for checking the local maxima of the amplitudes of the obtained discrete Fourier transform for periodicity. The frequency of a pulse signal with constant beat is determined by the element index with the largest number of fulfillment of the periodicity condition.