Summaries of the Issue

EDITORIAL

471
  Dear readers and subscribers of the “Scientific and Technical Journal of Information Technologies, Mechanics and Optics “,   Traditionally, the journal provides its pages for publishing the best works of young scientists. In April 2020, the next All-Russian Congress of Young Scientists was held. This time the Congress was organized in an online format. The current issue of the journal presents some papers by the authors noted by the Congress Organization Committee.   In the framework of the Congress of Young Scientists program, 64 sections were held in the scientific fields presented in our journal. The total number of speakers was 1621 people, representing more than  200 educational institutions, scientific organizations from 60 cities of Russia and Belarus. All papers passed the peer-reviewed procedure.

REVIEW PAPER

BLOCKCHAIN TECHNOLOGY IN 5G NETWORKS
Bezzateev Sergey V, Ivan R. Fedorov
472
The rapid development of mobile networks and the growth of various types of devices connected to them has called forth the integrity and confidentiality ensuring of the transmitted data that now is a high-priority problem. The emergence of cryptocurrency was followed by renewal of interest in blockchain technology and the possibility of its use in various fields. The paper discusses currently existing methods of blockchain technology application in 5G networks in order to solve security problems, network connectivity and productivity improvement, as well as to develop new directions that expand the capabilities of services and applications in fifth-generation networks. The paper presents analysis of modern research works on the blockchain technology integration and key technologies used in the fifth-generation mobile networks. Particular attention is paid to applications of blockchain technology in cloud computing, edge computing, software-defined networking, virtualization of network functions, 5G-slicing and device-to-device communication. Based on the materials presented in the review, the options are outlined that blockchain technology can provide to 5G mobile networks and services through the use of a decentralized architecture and a smart contract algorithm. The materials  of the proposed review is focused on the three main aspects: enhancement of transmitted information security, system performance and resources management. The paper can be useful to specialists and researchers working in the field of information security of the fifth-generation mobile networks, as well as for experts in the field of blockchain technology as an up-to-date overview of various applications of blockchain technology in the fifth-generation networks.

OPTICAL ENGINEERING

485
Subject of Research. The paper presents numerical methods that first studied laser heating of titanium-containing optothermal fiber converter and vein wall, as well as the effect of thermal damage of the vein wall during endovasal laser coagulation with different average power of 980 nm semiconductor laser and the traction speed of the converter inside the vein. Method. Models and conditions for numerical simulation of optical and thermal physical processes were formulated, occurring during endovasal laser coagulation of veins using titanium-containing optothermal fiber converter. The Monte Carlo method was used in optical modeling. The initial-edge task for a non-linear model of radiation-conductive heat transport with moving sources of radiation was analyzed at thermal simulation by the method of finite dispositions. The effect of vein wall thermal damage was assessed as a result of solving the Arrhenius equation. Main Results. The titanium-containing optothermal fiber converter can be used for endovasal laser coagulation of veins by radiation of 980 nm laser with average power up to 20 W. Laser radiation is almost completely absorbed by the converter. With the simultaneous start of laser radiation and the beginning of traction, the temperature of the vein wall does not immediately reach the maximum value; the waiting time can reach units and even tens of seconds. The temperature inside converter exceeds 250 °C. The optimal combinations of average laser power and titanium-containing converter traction speed are defined for uniform coagulation of the vein wall. Practical Relevance. The results can be used in the development of laser methods and devices for endovasal laser coagulation of veins.
EXPERIMENTAL STUDY OF OPTICAL POWER EFFECT ON THE STRUCTURE OF FIBER-OPTICAL DIFFUSER OBTAINED BY FIBER CORE MELTING
Ianina D. Tokareva, Yuri A. Konin, Kirill A. Konnov, Varzhel Sergey V., Andrey A. Dmitriev , Sofya D. Bochkova
494
Subject of Research. The paper presents experimental findings of a fiber-optic diffuser structure formed by optical fiber melting. Method. An optical scheme of ytterbium fiber laser is demonstrated consisting of such main components as: a laser pump diode (980 nm, with power up to 30 W), an active GTWave fiber (24 m), and two fiber Bragg gratings with reflection coefficients of 100 % and 30 %. The presented ytterbium radiation source is used to form a periodic structure of microcavities inside the fiber core using the melting effect of the material. The described technology application provides the creation of scattering structures with a given period without removing the protective acrylate fiber coating. Thus, there is no need for the optical fiber re-coating with a polymer composition, and its strength characteristics are maintained. Main Results. The experimental setup developed during the study gives the possibility to record the scattering structure in the core of the optical fiber by destroying the material using laser radiation. In order to determine the dependence of the properties of the created structures on the input radiation power, a number of samples was obtained recorded for various radiation characteristics. It was established experimentally that with an increase of laser radiation power, the period of localization of microcavities decreases. At the same time, their sizes are reduced, and the uniformity of the structure increases. The optimal radiation power value for the scattering structure formation is established to be about 2 W. Practical Relevance. The studied scattering structures can be used in medical research, laser photodynamic therapy, laser pacemakers, fluorescence diagnostics, and also as a backlight for minimally invasive operations. The fiber optic diffuser can be applicable as a sensor of physical quantities, in particular, for measuring high temperatures, since the upper limit of the diffuser working temperature is comparable to the melting temperature of the optical fiber quartz part.
500
Subject of Research. The paper presents the study of various methods of optical radiation coupling from the fiber core into its cladding with the aim of creating a fiber-optic anemometer hot wire. The effectiveness of the described methods is evaluated by analyzing the obtained dependencies. Method. The structures of two optical fibers were studied, one of which was used to transmit an information signal, and the other — to create a hot wire. A Bragg grating was formed in the core of the first fiber, and a radiation coupling region was created in the second fiber. These fiber sections were aligned with each other and fixed by a tin-lead alloy. The temperature was measured by monitoring the spectral characteristics of fiber Bragg gratings inscribed by the phase mask method. The areas of radiation coupling were formed either by changing the fiber geometry using custom modes of the arc fusion splicer, or by creating a SMF-MMF-SMF transition. Main Results. Structures are developed which can be used as a hot wire of a fiber-optic anemometer sensitive element. The dependencies of the Bragg resonance wavelength shift on the pump laser power are obtained; the Bragg wavelength shift varies in the range from 0.15 nm to 3 nm as a result of a hot wire creation. The resulting curves are constructed after three experiments for each type of structure, taking into account the standard deviation. They make it possible to judge the effectiveness of various methods of radiation coupling. Comparative analysis of the studied methods is presented. Practical Relevance. The study describes the capabilities of fiber-optic anemometry when creating point and distributed sensors. The results of this work can be used in the areas where the creation of quasi-distributed and point diffusers is necessary, as well as partial or complete coupling of radiation from a fiber core.
EFFECT OF EXTERNAL RELATIVE PRESSURE ON PHASE SHIFT IN SAGNAC INTERFEROMETER
Azamat B. Mukhtubayev, Aksarin Stanislav Mikhailovich, Nikitenko Aleksander N., Ivan G. Deyneka, Aleynik Artem S
507
Subject of Research. The paper considers the effect of a relative pressure change on the H-parameter value in a birefringent optical fiber with ESC-4 elliptical straining cladding and in Sagnac coil with 140 mm diameter and 700 m length. We analyze the effect of a relative pressure change on the phase shift in Sagnac interferometer. Method. The broadband interferometry method was used for the H-parameter estimation. Michelson polarizing scanning interferometer with a broadband source with a 1560 nm central wavelength and a 45 nm bandwidth was applied. The relative pressure was varied in a special pressure chamber in the range from –80 kPa to +300 kPa. Main Results. It is found out that when the relative pressure changes, random phase jumps occur in Sagnac interferometer. Such random phase jumps are not observed under normal conditions. It is also shown that the effect of increased relative pressure on Sagnac phase shift is more pronounced than the effect of reduced relative pressure; the frequency of phase jumps is greater in case of increased relative pressure. Practical Relevance. Analysis of research results is focused on the problem of high-quality winding and laying of birefringent optical fiber in Sagnac coil, which will improve the accuracy characteristics of fiber- optic sensors based on Sagnac interferometers.

MATERIAL SCIENCE AND NANOTECHNOLOGIES

ABSORPTION CHARACTERISTICS OF SILVER ION-EXCHANGED LAYERS IN CHLORIDE PHOTO-THERMO-REFRACTIVE GLASS
Rawan Semaan, Dmitry V. Marasanov, Sgibnev Evgeniy M, Nikonorov Nikolay V.
515
Subject of Research. The paper considers effect of chloride in composition of photo-thermo-refractive glass on the spectral properties of silver nanoparticles formed in ion-exchanged layers after heat treatment. Method. Glasses based on Na2O–ZnO–Al2O3–SiO2–F doped with antimony oxide Sb2O3, cerium oxide CeО2 and a variable chloride content (0–1 mol%) were synthesized for the study. Silver ions were introduced by the low-temperature Na+–Ag+    ion exchange method into the synthesized glasses. For this purpose, glass samples were immersed in a mixture of 0.1AgNO3/99.9NaNO3 (mol%) nitrates at the temperature of 320 °С for 15 minutes. After the ion exchange glasses were irradiated with ultraviolet radiation and heat-treated at the temperature of 500 °C for 3 hours to achieve the growth of silver nanoparticles. Main Results. Spectrum properties of chloride photo-thermo-refractive glasses with silver nanoparticles in ion-exchanged layers are studied. It is found that the presence of chloride in the photo-thermo-refractive glass matrix results in a long-wavelength shift of the absorption band of silver nanoparticles. That may be attributed to the growth of the mixed AgCl/NaCl shell on silver nanoparticles. The formation of silver nanoparticles in ion-exchanged layers occurs both in the irradiated and unirradiated regions of the glass. Practical Relevance. The results can be used to create Bragg gratings inside photo-thermo-refractive glass for input and output radiation (pump and signal) into the waveguide structures formed by the ion exchange method, and to create monolithic integrated optical elements on a single substrate, that is very essential for integrated optics
ERBIUM SPECTRAL-LUMINESCENT CHARACTERISTICS IN BROMIDE-FLUORIDE PHOTO-THERMO-REFRACTIVE GLASSES
Khaldoon Nasser, Vladimir A. Aseev, Ignatiev Alexander I , Nikonorov Nikolay V.
520
Subject of Research. The paper presents the study of spectral-luminescent characteristics of erbium ions in bromide- fluoride photo-thermo-refractive glasses with 0.1 mol% of erbium oxide and 1-2 mol% of ytterbium oxide concentration. Such spectroscopic parameters as stimulated emission cross-section of erbium ions at a wavelength of 1.5 microns, the efficiency of energy transfer from ytterbium to erbium ions, and the quantum efficiency are calculated based on the measured absorption spectra of glasses under study. The gain/loss spectra of erbium ions in the infra-red range are calculated for various population inversion values. Methods. Bromide-fluoride photo-thermo-refractive glasses were synthesized in an electric furnace at the temperature of 1480 °C for 5 hours in the air. Judd-Ofelt theory was used for determination of spectroscopic intensity parameters. The amplification spectra were obtained using McCumber theory. Main Results. It was found that the stimulated emission cross-section of erbium ions at a wavelength of 1.5 microns is typical for erbium in silicate glasses. The quantum efficiency of radiation at the same wavelength reached 95 %, and the energy transfer efficiency was 86 %. The gain factor had a positive value when the population inversion parameter was higher than 0.5. Practical Relevance. Bromide-fluoride photo-thermo-refractive glasses activated with erbium and ytterbium ions have spectral-luminescent characteristics comparable with commercial laser silicate glasses. In addition, they allow for recording of highly efficient Bragg gratings. Thus, these glasses can be promising candidates for creating distributed feedback lasers with ultra-narrow spectral lines.

COMPUTER SCIENCE

525
Subject of Research. The paper presents a solution for automatic analysis and recognition of human hand gestures. Recognition of the elements of sign languages is a topical task in the modern information world. The problem of gesture recognition efficiency has not been resolved due to the presence of cultural diversities in the world sign languages, the differences in the conditions for showing gestures. The problem becomes more complicated by the small size of fingers. Method. The presented method is based on the analysis of frame sequences of a video stream obtained using an optical camera. For processing of the obtained video sequences, it is proposed to use a depth map and a combination of modern classifiers based on Single Shot MultiBox Detector deep neural network architectures with a reduced network model of ResNet-10, NASNetMobile and LSTM type. Main Results. Experiments on automatic video analysis of hand movements and gesture recognition in real time show great potential of the proposed method for human-machine interaction tasks. The recognition accuracy of 48 one-handed gestures based on TheRuSLan database is 79 %. This result is better as compared to the other approaches to solving this problem. Practical Relevance. The results can be used in automatic systems for recognition of sign languages, as well as in the situations where contactless interaction of various user groups is necessary, for example, people with hearing and vision impairments, mobile information robots through automatic recognition of sign information.
532
Subject of Research. The paper considers modern approaches to the multiclass intention classification problem. The user intention is the incoming user requests when interacting with voice assistants and chatbots. The algorithm is meant for determination what class the call belongs to. Modern technologies such as transfer learning and transformers can improve significantly the multiclass classification results. Method. This study uses a comparative model analysis technique. In turn, each model is inlined into a common pipeline for data preparing and clearing, and the model training but with regard to its specific requirements. The following models applied in real projects have been selected for comparison: Logistic Regression + TF-IDF, Logistic Regression + FastText, LSTM + FastText, Conv1D + FastText, BERT, and XLM. The sequence of models corresponds to their historical origin, but in practice these models are used without regard to the time period of their creation but depending on the effectiveness of the problem being solved. Main Results. The effectiveness of the multiclass classification models on real data is studied. Comparison results of modern practical approaches are described. In particular, XLM confirms the superiority of transformers over other approaches. An assumption is made considering the reason why the transformers show such a gap. The advantages and disadvantages of modern approaches are described. Practical Relevance. From a practical point of view, the results of this study can be used for projects that require automatic classification of intentions, as part of a complex system (voice assistant, chatbot or other system), as well as an independent system. The pipeline designed during the study can be applied for comparison and selection of the most effective model for specific data sets, both in scientific research and production.
539
Subject of Research. The paper presents the study of methods and approaches to implementation of the modern McEliece cryptosystem based on separable generalized (L, G)-codes. Method. A method is proposed based on the analysis of the well-known public sources on implementation of the modern McEliece cryptosystem that uses the generalized (L, G)-codes with locators of degree greater than or equal to the second one without using an extended field. Mаin Results. Approaches to implementation of the modern McEliece cryptosystem based on the generalized (L, G)-codes are developed, namely: creation of a parity check matrix for the generalized (L, G)-code using a separable Goppa polynomial and locators of various degrees, description of an approach to the implementation of encryption and decryption of messages in the modern McEliece cryptosystem, presentation of the Chein’s procedure for numerators of degree greater than or equal to the second one without expanding the field. Practical Relevance. The proposed methods can be used in the development of cryptographic systems that can withstand attacks from quantum computers and ensure data confidentiality, as well as improve the security and performance of cryptosystems. Aerospace, automobile, railway, network multimedia, telecommunication and mobile information protection systems can also be the scope of the work results.
NORMALIZATION OF KAZAKH LANGUAGE WORDS
Diana R. Rakhimova, Турганбаева А. О.
545
Subject of Research. Models and existing algorithms for normalization of natural language words are considered. The paper describes algorithms for automatic selection of the basic principles for a number of natural languages and possible ways of the normal word form synthesis for the Kazakh language. The research is aimed at creation of a complete classification for the Kazakh language ending system and development of a normalization algorithm for words based on the proposed classification approach for endings and suffixes. Method. Word formation analysis by applying endings for all Kazakh language parts of speech was carried out; a classification of endings and suffixes was presented. The paper discusses all kinds of placement options for endings and suffixes. The total number of various suffixes is 26 526 units and the endings is 3 565 units. All considered types are lexically and semantically valid, but some of them are not applicable. Only those, that are most commonly used, are added to the affix base. The order, that the affixes are added to the base, is presented using sets. Thus, the base is correctly selected. The study does not examine word-forming suffixes, as they change the word stem and contextual interpretation. Basically, word-forming suffixes are added to nouns. Main Results. A complete classification system for endings and suffixes of the Kazakh language has been developed. Deterministic finite automata for various parts of speech are created using all possible options, adding suffixes and endings, taking into account the morphological and lexical features of the Kazakh language grammar. A lexicon-free stemming algorithm is developed using the proposed classification system for endings of the Kazakh language. A normalization system has been implemented, proving the operability of the developed algorithm without a dictionary. The algorithm implementation was tested on the Kazakh language corpus. Punctuation and stop words were initially removed from the specified corpus. Practical Relevance. The results of the work can find application in the text analysis and normalization (lemmatization), as well as in information retrieval systems, in machine translation from the Kazakh language, and other applied problems.
552
Subject of Research. Defect detection is an actual and challenging task in the field of additive technologies. This process enables the user to save time and reduce the consumption of material. Also, it prevents the further possible faults and defects. On that account, an automation of surface control process in 3D-printing is an essential step not only or large manufacturing companies but also for private users. The paper proposes an image-based method for quality control of a 3D-printed product by applying machine learning algorithms. Method. 3D-printed item images were taken and processed on an experimental setup composed of a camera and a single board microcomputer. The paper presents a defect detecting method based on development of image preprocessing algorithms and further machine learning by applying support vector machine method. Main Results. The presented method enables the user to find and identify “over-extrusion” and “under-extrusion” defects with high precision on the surface of the manufactured items. Practical Relevance. The developed method is intended to provide practical benefits for the private users of 3D-printing devices and companies manufacturing or applying these devices. There are the following advantages of the method application: the 3D-printing parameters are easy to be set, the reports about the product and its features are saved, the solutions to any problem occurred during printing are simple and fast. The developed method of visual quality control of the 3D-printed item surface can be significantly helpful to the expansion of automation possibilities for fast prototyping processes and take 3D-printing process to a new level.
560
Currently, more and more tasks on image processing and analysis are being solved using convolutional neural networks. Neural networks implemented using high-level programming languages, libraries and frameworks cannot be used in real-time systems, for example, for processing streaming video in cars, due to the low speed and energy efficiency of such implementations. The application of specialized hardware accelerators of neural networks is necessary for these tasks. The design of such accelerators is a complex iterative process requiring highly specialized knowledge and qualification. This consideration makes the creation of automation tools for high-level synthesis of such computers a relevant issue. The purpose of this research is a tool development for the automated synthesis of neural network accelerators from a high-level specification for programmable logic devices (FPGAs), which reduces the development time. A description of networks is used as a high-level specification, which can be obtained using the TensorFlow framework. The several strategies have been researched for optimizing the structure of convolutional networks, methods for organizing the computational process and formats for representing data in neural networks and their effect on the characteristics of the resulting computer. It was shown that structure optimization of neural network fully connected layers on the example of solving the handwritten digit recognition problem from the MNIST set reduces the number of network parameters by 95 % with a loss of accuracy equal to 0.43 %, pipelining of calculations speeds up the calculation by 1.7 times, and parallelization of the computing process individual parts provides the acceleration by almost 20 times, although  it requires 4-6 times more FPGA resources. Applying of fixed-point numbers instead of floating-point numbers in calculations reduces the used FPGA resources by 1.7–2.8 times. The analysis of the obtained results is carried out and a model of an automated synthesis tool is proposed, which performs the indicated optimizations in automatic mode in order to meet the requirements for speed and resources used in the implementation of neural network accelerators on FPGA.
568
Subject of Research. The paper presents research of mechanisms of multipath redundant transmissions in computer networks. Method. The developed application level protocol gives the possibility to increase the probability of timely and faultless data delivery in computer networks which work within the conditions of delivery time limits using multipath redundant transmissions of packet copies via different channels. Main Results. The protocol with redundant multipath transmissions opportunity based on UDP transport protocol is developed. The efficiency analysis of the presented solutions is carried out on the basis of simulation modeling in OMNeT++ environment. Models of the proposed protocol and computer network with redundant transmissions opportunity are developed. Experiments with these models are carried out and efficiency area of the developed protocol application is determined. The multiplicative criterion that shows time reserve of timely and faultless transmitted packets is used as an efficiency indicator. The presented protocol shows efficiency in various working cases with the intensity and redundancy coefficient change of packet arrival. Practical Relevance. The developed algorithms and mechanisms can be used for program implementation of protocol with redundant multipath transmissions aimed at its application in cyberphysic real-time systems.
MODULAR APPROACH APPLICATION IN DEVELOPMENT OF COMPUTER NUMERICAL CONTROL SOFTWARE
Kseniia V. Zimenko, Afanasiev Maksim Ya , Mikhail V. Kolesnikov
576
Subject of Research. The paper proposes an approach to the development of a numerical control kernel. The approach implies creating software from separate modules interacting via a unified programming interface with a high level    of granularity. Thus, a system with a required configuration can be developed in a relatively short time. The study also considers the possibility of using open source computer numerical control systems as a basis, which will further reduce the design time. The approach for computer numerical control development is considered in the context of its application on multipurpose modular equipment. Method. The proposed solution is based on a multi-protocol control system and combines software and hardware components from different manufacturers. Platform independence is also provided. This method allows a prompt development of the numerical control system for any type of processing or other operations according to the requirements of hardware, and also gives wide opportunities for further modifications that increase the equipment efficiency. Main Results. The practical result obtained is a software trajectory-planning library, including geometry analysis, feed rate control and interpolation. Commands for controlling outputs and status of inputs are integrated into the cyclic data of the drive control and transmitted via the same interface. All developed modules are independently designed and can be embedded into other open source systems, as well as be further modified for processing efficiency increase. Practical Relevance. The work is aimed at increasing the economic independence of small design organizations and enterprises. The proposed modular approach allows the development of a required numerical control system for multipurpose modular equipment in a short time, and will significantly expand the capabilities of rapid prototyping and ensure the prompt production of pilot batches.

MODELING AND SIMULATION

584
The paper considers the solution of the inverse heat conduction problem by parametric identification of differential- difference models of heat transfer in one-dimensional bodies. Differential-difference models is a system of differential ordinary equations of the first order with respect to the state vector. In this case, the direct and inverse heat conduction problems are solved, and the Kalman recurrent digital filter algorithm is used in terms of parameters for discrepancy minimization between the measured and model parameters values. The paper considers the Kalman algorithm application for two specific problems, namely: an experiment estimation and planning for restoration of heat transfer boundary conditions for a system of bodies. When planning an experiment or during field studies, the task parametrization is carried out initially and then parametric identification, as well. To determine the confidence area for measuring the desired parameters, the Gram matrix (Fisher information matrix) is used, involving the components which are sensitivity functions that represent all significant factors of heat metering: the type of heat transfer in the system, the number and location of temperature measurement points, the quality of channels for recording measured values, and the features of input actions, time measurement section and the number of measurement time points in this section. The paper gives an example of Kalman recurrent digital filter, considers the battery transformer of unsteady heat flux, for which the creation of the differential-difference model is carried out, shows the results of unsteady heat flux restoration, changing according to an arbitrary law. Confidence areas of the desired parameters are established.
SELECTION OF COMPOSITE MATERIAL IN ELECTROMAGNETIC LOG SENSOR
Voronov Alexander S., Evstifeev Michail I.
589
Subject of Research. The paper considers the issues of choosing an insulating material for a deep-sea electromagnetic log sensor. The effect of the insulating material characteristics on the operational factors of the sensor is studied. Method. Matlab program was used to analyze the effect of design parameters on the instrumental error of the sensor. For this purpose a mathematical model of the instrumental error component was built, and its evaluation was carried out. The stress-strain state of the sensor was simulated by the finite element method in the ANSYS Workbench application package. Analysis of insulating material peeling from the case during shrinkage was carried out in the Static Structural module. Fill simulation was performed in the Fluid Flow module. All materials are taken to be isotropic at calculations. Main Results. The effect of the insulating material characteristics on the instrumental error of the electromagnetic log sensor is shown. The design and technological issues of the insulating material choice are described. Recommendations on the choice of design parameters are given to reduce peeling of the material and the occurrence of sensors emptiness formed by filling with composite material. The validity of the recommendations is confirmed by computer simulation and experiments. Practical Relevance. The results obtained can be applied in the modernization, design and construction of new electromagnetic log sensors.
MODELING OF LIQUEFIED NATURAL GAS EVAPORATION IN MOBILE RESERVOIRS
Aleksandr Yu. Baranov, Kseniia A. Valentinova, Ivanov L. V.
595
The paper presents the analysis of isothermal storage of liquefied natural gas within the conditions of river navigation. The effect of constructive and technological solutions on the safety and profitability of liquefied natural gas application as an alternative to petroleum products is studied. The technique principle consists in a cryogenic storage modeling based on the energy equation of the vapor and liquid fractions and comparative analysis of several options for transportation of liquefied natural gas by river transport. In consequence of the study results, data were obtained on the relationship between the insulation thickness and the degree of tank filling having an effect on transport characteristics. It was revealed that transportation of liquefied natural gas in gas-insulated storage facilities is technically possible and satisfactory by combining the optimal specific volume of cryogenic liquid in the tank and sufficient thickness of thermal insulation. The results obtained can be used in the development of autonomous floating containers with a large insulation thickness, which will be towed along rivers without the use of carrier vessels.
603
Subject of Research. The paper proposes a model for predicting evaporation of liquefied natural gas (LNG) stored in tanks of regasification terminals. The model is a combination of the strict thermodynamic LNG vapor-liquid equilibrium and heat transfer realistic models. Analysis of the initial composition effect and the stock of LNG, the initial content of nitrogen and the value of the outside air temperature on the LNG evaporation rate is carried out. Method. A numerical experiment using a mathematical model of the LNG evaporation process was based on the LNG composition data and its storage time in aboveground tanks. The proposed method provided a number of advantages compared to previously developed models: the heat input to the low-temperature part of the LNG storage tank was calculated taking into account the outdoor temperature and the LNG composition; the evaporation coefficient was not an input parameter, but was calculated as part of the simulation; the LNG density was calculated by experimental correlation. Main Results. An important parameter in assessing the LNG loss from its evaporation is the nitrogen content in the liquid, which evaporates at a higher rate than methane, the main LNG component. Analysis of the initial composition effect on the LNG evaporation rate has shown that the growth of the nitrogen content in the initial mixture causes noticeable decrease in the evaporation rate due to the nitrogen priority evaporation and, as a consequence, the growth of latent mixture heat vaporization. Analysis of the initial LNG supply value at the evaporation rate has shown that a large degree of the tank filling causes an outstripping reduction in losses from evaporation. The result is an earlier reduction in the amount of boil-off gas (BOG, stripping gas) for more filled tank. Analysis of the outdoor temperature effect on the rate of LNG evaporation has shown that the ambient temperature change of 1 °C leads to the decrease in the BOG amount by 0.2 %. Practical Relevance. The proposed mathematical model of the LNG evaporation process reduces BOG formation during long-term storage, maintain the original LNG quality, optimizes the operational parameters of regasification terminals, and provides the consumers with reliable supply of high-quality natural gas.
611
Subject of Research. Composites are unique materials combining lightness and strength, which makes them popular in the materials industry. Mathematical modeling of these materials is necessary to predict their behavior underspecific loads. The paper proposes a meshless method for mathematical modeling of anisotropic composite materials based on their representation as a set of meta-particles with spring-like bonds. Special feature of the presented work  is the applicability of the same equations for the multi-scale modeling: on micro-scale (single fiber and an elementary volume of the compound) and macro-scale (cross-section of the whole composite part). Method. The method is based on Verlet-like time integration of particle displacements with consequent resolving of a system of elastic bonds with pre-calculated mass and stiffness. The method estimates temporal dynamics of composite deformations under applied mechanical load. The code for solution of motion equations and result visualization is written in pure JavaScript without any dependencies. Main Results. Elastic deformations of a simplified 2D model of carbon-fiber-reinforced plastic have been simulated (with a mixture of epoxy and polyester resins as a compound) under static mechanical load using the proposed method. Calculations on the micro-and macro-scales with different directions of fiber layering: at the angles of 0° and 90°. Flat layering type is selected. The results are verified via the ANSYS Composite PrepPost solver under equivalent conditions. The coincidence of the calculation results by the meta-particle method of the developed solver and the finite element method is 89 %. Practical Relevance. The results obtained can be used in the development of new types of composite materials at the modeling and forecasting stage, and can also allow simulations of composites taking into account micro-processes for exclusion of pore formation and other defects that cannot be resolved using macro-scale modeling.
617
Subject of Research. The paper proposes a method of muscle activity filtering measurements for a mobile hardware- software appliance used in surface electromyography. The method extends the dynamic range of measurements by capacity growth of analog-to-digital converter aimed at the increase of recognition accuracy and range of muscle activity. Method. A filter model for signals from sensors for a muscle activity controller was developed in the Proteus Design Suite software package. The filter of the signal carrier component based on the RC high-pass filter provides isolation of the measuring unit from the reference voltage of the sensor. An active low-pass filter amplifies the signal from the sensor and filters out the noise higher than the frequency range of muscle activity signals. Main Results. Filtering of the signal carrier component and increasing the order of low-pass filter show positive results in simulation. The paper presents amplitude-frequency characteristics plots and model structures with and without RC filter, with an active low-pass filter of the first order and an active low-pass filter of the second order. An amplifier unit electrical circuit for a muscle activity controller is developed based on the methodology for muscle activity measurement filtering. The results obtained are applicable for improvement of the prototype for the mobile hardware-software appliance used in surface electromyography. Practical Relevance. The developed complex can be applied in a system for muscle activity measuring and monitoring as the rehabilitation process maintenance during the movement of patients with injuries and disorders of the musculoskeletal system. This complex can be used in various neurophysiological studies where the monitoring of muscle activity dynamics in the process of the examined subject movement is required.
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