Summaries of the Issue
PROCEEDINGS OF THE XXXII SCHOOL ON HOLOGRAPHY. PART II
Pulse recording of dynamic holograms in bismuth silicate crystal in a broad wavelength rangeIvan G. Dadenkov, Alexei L. Tolstik, Yuri I. Miksiuk, Konstantin A. Saechnikov
The formation of dynamic holograms in a photorefractive bismuth silicate crystal by nanosecond laser pulses with a change in the radiation wavelength is studied. An original scheme for recording holograms is proposed to preserve the grating period when operating at different wavelengths. The method of pulsed recording of dynamic gratings based on the proposed optical scheme is applied, which ensures the fulfillment of the Bragg condition for probing radiation. The originality of the scheme lies in the use of the first orders of diffraction of a transmitting diffraction grating as the reference and signal waves, as well as a telescopic system used to fix the period of the recorded grating, regardless of the wavelength used. Kinetic dependences of the diffraction efficiency of dynamic holograms in a photorefractive bismuth silicate crystal are obtained with a change in the wavelength of recording radiation in the actual spectral range (from 450 nm to 600 nm). The effect of the manifestation of competing recording mechanisms of short-lived (hundreds of microseconds) and long-lived (seconds) gratings, the contribution of which depends on the wavelength of the radiation recording the hologram, has been established. The optimal wavelength for obtaining the highest diffraction efficiency of holograms is determined. It is shown that radiation in the blue-green region of the spectrum leads to the predominant recording of a short-lived grating, while long-lived gratings dominate in the red region of the spectrum. The need to study photorefractive crystals of the sillenite family is determined by their use for multiplex recording of dynamic holograms and the implementation of the adaptive interferometry method to track changes in objects in real time.
Hybrid endoscope with television and multispectral image processing for the internal organs cancer early diagnosticsKirill V. Zaichenko, Boris S. Gurevich , Andrey V. Belyaev, Vitaliya I. Svyatkina
Endoscopes are widely used to diagnose various internal diseases. The most advanced endoscopes contain miniature television cameras built into the probe which provide high spatial resolution. However, traditional television cameras significantly distort the spectral composition of the transmitted image because in the RGB system they reproduce only limited width spectral lines. However, the full optical spectrum of an image of an internal organ under examination provides a broader range of information that can be crucial in cancer diagnostics. Thus, the spectral resolution of the image plays an important role. Multispectral processing has been suggested for efficient detection of both spatial and spectral information simultaneously. As a result, a series of monochrome sub-images can be obtained, each of which corresponds to a selected resolved spectral interval. Acousto-optical tunable filters are used as a selective element allowing real-time extraction of sub-images. However, an increase in spectral resolution is accompanied by a decrease in spatial resolution. A new hybrid endoscope was suggested to solve this problem. It implements the method of combined application of a TV camera and a multispectral processing device. It is shown that the suggested method of hybrid endoscopy makes it possible to ensure high resolutions: spatial resolution with a camera and spectral resolution (no less than a hundred of resolvable intervals) due to multispectral processing. The resulting optical images reveal a clear outline of the neoplasm area. The results of multispectral processing diagnose the malignant nature of the neoplasm. A schematic diagram of the proposed endoscope is presented, and the principles of control are shown. The characteristics of the television and multispectral images are determined. An estimation of the linearity characteristics of the acousto-optical filters shows the possibility of transmitting the maximum amount of information due to the linearity of the signal transformation in the filter sections. Implementation of the proposed method in the design of a hybrid endoscope allowed obtaining the most complete spectral information about neoplasms and providing an opportunity of diagnostics of cancer of internal organs at earlier stages of development.
Modelling of a composite waveguide holographic displayDanila Yu. Kharitonov, Damir M. Akhmetov, Eduard R. Muslimov, Aydar R. Gilfanov, Nadezhda K. Pavlycheva
Optical designs of waveguide-type augmented reality displays are investigated. Displays based on volume phase holograms are notable for their small size, large exit pupil and high transmittance both in the projected image channel and in the direct vision channel. However, with an increase of the aperture, field of view and working spectral range, the spread of the values of the beam angle of incidence and the wavelength increases when solving the diffraction problem at different points on the hologram surface which imposes restrictions on spatial resolution and diffraction efficiency. To overcome this phenomenon, it is proposed to use a composite hologram which represents a volume phase grating divided into zones with independently varying parameters of the fringes tilt, their shape, the holographic layer thickness and the refraction index modulation depth. We propose an algorithm that allows ray tracing through a hologram recorded by two coherent point sources using an auxiliary aspherical mirror. The initial ray tracing in the hologram recording scheme is performed using the error function minimization by the orthogonal descent and golden section methods. Based on the results obtained, the directional vectors of the diffracted beam are calculated using the Welford equation. Using the tracing results, the hologram diffraction efficiency is computed with the Kogelnik’s coupled wave theory. The proposed algorithms are implemented in the Zemax Optics Studio software. The application of the proposed composite hologram element and the tools for operation modeling are shown on an example of display operating in the range of 510–530 nm with the field of view of 7°36ʹ × 5°48ʹ and the exit pupil diameter of 8 mm. It is shown that the proposed solutions make it possible to increase the diffraction efficiency by 3.45 times. At the same time, the spatial resolution increases by 12.7 % varying across the field of view in the range of 0ʹ44ʺ–1ʹ6ʺ. The use of composite holograms allows one to create displays with higher spatial resolution and brightness of the projected image as well as uniformity of the characteristics across the field of view.
Application of infrared spectroscopy methods in studying compositions for paper sizingHalima A. Babakhanova , Sadriddinov Аkmal А. , Mansur M. Abnunazarov , Мadina А. Babakhanova, Irina G. Gromyko
The paper proposes a method of infrared spectroscopy for objective control of the adhesive composition in the production of paper. For sizing paper, in order to increase mechanical strength and reduce water absorption, water-repellent materials are used. One of the most effective and used water-repellent material is ordinary pine resin rosin which is in short supply for the Republic of Uzbekistan. The paper investigates the properties of a new adhesive based on rosin from cherry resin for use in mass sizing in order to expand the range of sizing agents and reduce the share of imported components in the structure of local paper production. Infrared spectroscopy was used to identify the rosin-based glue from the resin of the cherry tree. The built-in device with a diamond crystal of the universal and compact Thermo Scientific Nicolet iS50 IR Fourier spectrometer made it possible to register spectra in the mid and far IR ranges up to 100 cm–1. The efficiency of sizing paper samples was studied by standard methods and evaluated by the following properties: density, tensile strength at stretching on a tensile machine, surface absorbency with one-sided wetting. Infrared spectra revealed the identity of the sizing agent from the resin of the cherry tree to the glue from the pine resin, taken for comparison, because their chemical composition is the same. A comparative analysis of the mechanical and surface properties of paper samples confirmed the possibility of using the studied sizing agent, since the obtained values are close to each other, while it is advisable to add in the range from 1 to 1.5 g per 100 g of dry cellulose raw materials. The use of infrared spectroscopy for express analysis of the composition of the sizing agent is promising, since it becomes possible to control the technological process and create glued types of paper products with desired properties that ensure print quality without loss of fine image details.
Distribution optimization method of pixel density by surveillance areaVolkhonskiy Vladimir V., Kovalevskiy Vladislav A.
The task of optimizing the parameters of the video camera matrix to reduce the redundancy of the generated video signal is considered. The relevance of the topic is due to the existing redundancy of video signals generated by matrices in different parts of the observation zone and, as a result, excessive loading of signal transmission, storage and processing devices. The problem is solved by achieving a uniform distribution of pixel density over the observation area. The methodology is based on solving the problem programmatically, unlike existing solutions using hardware methods. It is based on the representation of the view area as a set of subsets of the observation task space with its subsequent fragmentation in accordance with the observation tasks being solved which determine the required minimum pixel density in different fragments. To solve the problem, the matrix is segmented in according to the size of the fragments of the observation area and the specified allowable range of changes in the distribution of pixel density in the viewing area of the camera. Mandatory and additional distribution optimization criteria are proposed. The optimization technique is formulated. In according to the redundancy coefficient of the pixel density distribution in different segments, pixels are combined into groups that are different in different segments. Examples of solving optimization problems according to different criteria are given. The proposed approach makes it possible to minimize the pixel density redundancy and thereby reduce the load on communication channels, the amount of memory in video information storage devices, and the performance requirements for video signal processing devices. In this case, the problem of forming a continuous image of the observation zone is also solved. Results could be used for video signal processing and design of new cameras for video surveillance systems.
AUTOMATIC CONTROL AND ROBOTICS
Evaluation and development of a method for compensating the positioning error of computer numeric control equipmentMuhamad Albani Rizki, Fedosov Yury V
In the manufacturing process, Computer Numerical Control is widely used to process products that require a high level of accuracy. It is found that during product processing, Computer Numerical Control is still unable to fully counteract the influence of vibration and the presence of uneven product surfaces. In this paper, the stabilization mechanism developed, known as the Modified Stewart platform, which has a 3 Degrees of Freedom and can rotate around the X and Y axes and move translationally along the Z axis. This platform can be used to improve the accuracy and stability of the Computer Numeric Control tool. In this research, the positioning accuracy of the Modified Stewart platform has been evaluated. In this research, a mock-up or prototype and a simulation model of the Modified Stewart platform was developed. The data to be studied is the inclination angle of the platform. In the experiment, to determine the positioning error, the variable being changed acquires not only the linear movement, but also the angle of the X-Y plane. By changing the angle contained in the X-Y plane, it can be seen the influence of the X-Y angle on the position error or angle of the Z-A plane. The simulation was carried out on MATLAB. The mathematical model in this study is to find the platform position or angle. To simplify the calculation, the Modified Stewart platform was depicted in the form of a trapezoid. The results of the angle in the simulation will be compared with the result of the angle on the mock-up Modified Stewart platform. The trapezoidal parameter used in the simulation corresponds to the parameters on the mock-up modified Stewart platform. The simulation provided information about the angle of inclination, height, length of its sides, and the relative length of sides. It was found that the position or angle movement of the platform is in accordance with the calculation or simulation model that has been developed, and the positioning error data of the platform is very small and it changes constantly. It should be noted that the presented method can be used to evaluate the platform positioning error and consequential calibration of the mechanisms with spatial kinematic. The positioning error at various mobile links positions is changing, but during the movement in just one direction it remains almost constant. The position error caused by the platform mechanism can be minimized by redesigning the platform and using components that can provide a much more precise movement, moreover, using the preliminary measurements it is possible to build a table containing corrections for the control program to access the correct position of the moving platform. The accuracy and the stability of its movement can be improved and the platform can be applied to Computer Numerical Control. The method developed allows to estimate the moving platform positioning error of the mechanism with spatial kinematic. Thus, the method developed can be eliminated or compensated. It is possible to calibrate the moving platform movements in automatic mode as well.
Compensation of output external disturbances for a class of linear systems with control delayVan Huan Bui, Margun Alexei A.
The paper considers the problem of the output external unknown disturbance compensation under unmeasurable state vector for a class of linear systems with the control channel delay. It is assumed that the disturbance is the output of an autonomous linear generator. A special observer was built to estimate the disturbance. A system with an extended state vector is formed on the base of the observer’s estimates. A controller that provides disturbance compensation is proposed. An algorithm for the output external disturbances compensation for a class of linear systems with input delay is presented. This method does not require identification of disturbance parameters. The performance of the proposed algorithm was confirmed using computer simulation in the MATLAB Simulink software. The developed algorithm can be effectively applied to a class of problems related to rocking compensation in ship systems, control of robotic complexes various kinds, etc.
MATERIAL SCIENCE AND NANOTECHNOLOGIES
Luminescence technique for studying the growth of AgInS2 quantum dotsAhmad K. Ahmad, Ammar H. Mohammed, Alexander A. Skaptsov
Although nanoparticle production techniques are well-known, getting nanoparticles with specific characteristics that enable their application as biosensors is an entirely other problem. Many issues occur as a result of employing the method for producing repeatable and time-stable nanostructures. We created AgInS2 nanoparticles as colloidal quantum dots in a variety of methods to test the efficiency of the synthesis process on the optical characteristics of the nanoparticles, as well as their size, composition, absorption, and luminescence spectra. The capillary electrophoresis (CE) approach for AgInS2 production was employed, with modifications in solvent and temperature, to get nanocrystal (NC) particles. The researchers discovered that Ag accumulation in the InS lattice promotes deformation which leads to structural defects. Consequently, the direction of a nanoparticle light band may now be changed. The features of mixed AgInS2 nanoparticles have been examined with respect to different fabrication procedures, surface stability, and metal impurity incorporation. One band dominates in the luminescence spectra of AgxIn1–xS2 nanoparticles. The relationship between the stoichiometric ratio, luminescence amplitude, line width, and the maximum wavelength is investigated. The average size of the received nanocrystals was determined using dynamic light scattering studies. The computed nanoparticle diameter range has an average particle size of 3–3.5 nm.
Peculiarities of pulsed laser deposition of thin InGaAsN films in an active background gas atmosphereDevitsky Oleg V.
III-V-N compounds are a promising class of solid solutions that have the prospect of being used in optoelectronic devices operating in a wide spectral range up to 3 μm, as well as for increasing the efficiency of photodetectors, lasers in fiber-optic communication lines and telecommunication systems. In this work, the features of various methods for obtaining new III-V-N semiconductor materials are investigated. Thin InGaAsN films were obtained by pulsed laser deposition on GaAs (100) and Si (100) substrates in an active background gas atmosphere. Pulsed laser deposition of thin InGaAsN films was carried out using an In0.02Ga0.98As target in an atmosphere of a highly pure argon-nitrogen mixture at a pressure of 2, 5, and 10 Pa. The source of laser radiation was an AYG:Nd3+ laser with a wavelength of 532 nm (second harmonic), laser radiation energy density of 2.3 J/cm2, pulse repetition rate of 15 Hz, and pulse duration of 10 ns. The substrate temperature was 350 °C, the deposition time was 60 minutes. It is shown that the surface of thin films is textured with microdroplets. It has been established that microdroplets on the surface of a thin film are formed by metallic indium. It has been established that the distribution of indium microdroplets over the film surface is mainly ordered in the form of lines. This phenomenon can be explained by the presence of misfit dislocations. The average size of microdroplets on the surface of the InGaAsN film on GaAs (100) was about 30 nm, and their density did not exceed 0.076 μm–2. For comparison, in films obtained on Si substrates at a pressure of 2 Pa, the highest microdroplet density was 0.26 μm–2. The lowest density of microdroplets on the surface (0.17 μm–2) was noted in samples of a thin film of InGaAsN on Si (100) obtained at a pressure of 10 Pa. It is noted that the intensity of the local phonon vibrational mode LVM InN at a frequency of 430 cm–1 increases with increasing pressure of the argon-nitrogen mixture during pulsed laser deposition in the Raman scattering spectra of InGaAsN films on Si. In the Raman spectra of InGaAsN films on Si, second-order phonon modes LVM InN and LVM GaN were detected at frequencies of 450 cm–1 about 470 cm–1, respectively. This confirms the presence of nitrogen in a thin InGaAsN film obtained by pulsed laser deposition. It is shown that an increase in the pressure of the argon-nitrogen gas mixture during pulsed laser deposition contributes to an increase in the nitrogen concentration in thin InGaAsN films on Si. It has been established that the nitrogen concentration in InGaAsN films obtained at a pressure of 10 Pa on GaAs (100) and Si (100) substrates differs insignificantly and amounts to 1.9 % and 1.8 %, respectively. The presented results will make it possible to create highly efficient photoelectric converters and photodetectors for the near and mid-infrared range up to 3 μm based on the obtained InGaAsN thin films.
Determination of the electron distribution in thin barrier AlGaAs/GaAs superlattices by capacitance-voltage profilingElena I. Vasilkova, Evgeny V. Pirogov, Maxim S. Sobolev, Artem I. Baranov, Alexander S. Gudovskikh, Alexei D. Bouravleuv
Electron density distribution in uniformly doped AlGaAs/GaAs superlattices with respective layer thicknesses 1.5/10 nm and a different number of quantum wells was investigated. Experimental samples containing 3, 5 and 25 periods with the same layer parameters were grown by molecular beam epitaxy. Capacitance-voltage profiling was used to determine the carrier concentration profiles in the structures both numerically and experimentally. During the analysis of experimental capacitance-voltage characteristics it was found that the maximum electron concentration increases with an increase in the number of quantum wells starting from 7,1∙1016 сm–3 for 3 wells up to 9,2∙1016 сm–3 for 25 wells with overall superlattice doping level of 1017 сm–3. In some samples saturation areas are observed on the concentration profiles, that are associated with the region of superlattice. Concentration values, obtained from computer modeling, correspond to the experimental data with an error of less than 10 %. Capacitance-voltage profiling is a suitable technique for determining the carrier concentration profiles in thin barrier superlattices. Despite the fact that the method provides distribution of the “apparent” carrier concentration profile, it can be used to estimate the dopant atoms distribution in the strongly coupled quantum well heterostructures.
Spectral and kinetic properties of silver sulfide quantum dots in an external electric fieldDaibagya Daniil S. , Sergey A. Ambrozevich, Aleksey S. Perepelitsa, Ivan A. Zakharchuk, Anna V. Osadchenko, Daria M. Bezverkhnyaya, Anton I. Avramenko, Alexandr S. Selyukov
The effect of an external electric field on the luminescence characteristics of silver sulfide nanoparticles embedded in a film based on an optically passive dielectric matrix has been studied. The luminescence characteristics were studied using methods of optical and time-resolved spectroscopy involving the time-correlated single-photon counting technique. The morphology of the nanoparticles was studied using transmission electron microscopy. It was shown that in an external electric field, an increase in the intensity of the recombination luminescence band is observed for silver sulfide nanoparticles, together with an increase in the electronic relaxation rate. This effect is explained by the fact that the electric field enhances the transport of free holes to electron traps which are radiative recombination centers. The observed effects indicate that silver sulfide nanoparticles can be effectively used as active layers of organic light-emitting diodes, where an external field of the order of 500 kV/cm will not lead to a deterioration in their operating luminescence characteristics.
Influence of nano-sized horizontal inhomogeneities on surface profiling by means of XPSDenis S. Lukyantsev, Alexander V. Lubenchenko, Dmitriy A. Ivanov, Olga I. Lubenchenko, Alexandr Alexandr Fedotov
Quantitative analysis of thin films surface is performed by means of X-ray electron spectroscopy (XPS) according to a calculation model assuming surface layers of the target to be homogeneous and parallel. However, almost every surface of an ultra-thin film is rough. A study of such surface using the plane-parallel layer model will lead to incorrect results. This work proposes to use the model of inhomogeneous stochastic nano-structured surface layer for ultra-thin film profiling. Surface stochastic nano-structured inhomogeneities are described by the normal Gauss distribution function. To determine these inhomogeneities, three parameters are specified: dispersion (spread of thicknesses by the layer), mean and maximal thickness of the surface layer. For the first time, the type of X-ray photoelectron spectrum of an inhomogeneous stochastic nano-structured surface is found that is determined by functions of photoelectron production and transmission through that surface layer. The designed model is based on the following assumptions: photoelectrons are produced in substance and travel straight-forward (Straight Line Approximation) along the surface, photoelectron flux density decreases in the layer according to the Bouguer–Lambert law, photoelectrons of different energies lose energy differently, photoelectron energy losses in bulk and on surface differ. Modeling of X-ray photoelectron spectra of an oxidized metal film is performed using different models: homogeneous plane-parallel layers, an island nano-structured surface layer and an inhomogeneous stochastic nano-structured surface layer. Ranges of applicability of plane-parallel layer models and simple periodical nano-structured island surface layer for inhomogeneous stochastic nano-structured surface profiling are determined. The model of homogeneous plane-parallel layers shows satisfactory profiling results by some values of parameters of an inhomogeneous stochastic surface layer. It is shown that the model of a simple periodically nano-structured island layer leads to inadequate results by profiling of an inhomogeneous stochastic surface. The investigation shows that for more accurate profiling of an inhomogeneous ultra-thin film, it is necessary to consider inhomogeneity of a real surface, otherwise the calculated results would not match the true profile.
Organic light-emitting diodes with new dyes based on coumarinAnna V. Osadchenko, Andrey A. Vashchenko, Ivan A. Zakharchuk, Daibagya Daniil S. , Sergey A. Ambrozevich, Nikita Yu. Volodin, Чепцов Д. А., Sergey M. Dolotov, Valery F. Traven, Anton I. Avramenko, Семенова С. Л., Alexandr S. Selyukov
The results of studying the luminescent properties of organic light-emitting diodes based on new luminescent compounds containing a coumarin fragment are presented. The light-emitting diodes were fabricated by spin-coating and thermal evaporation in an argon atmosphere in a clean room. Measurements of the LED characteristics were carried out by optical spectroscopy, as well as by electrical methods. It has been experimentally shown that deposition of an OLED active layer based on luminescent compounds containing a coumarin core can lead to the formation of dimers, the luminescence spectra of which differ significantly from the corresponding spectra of the original materials in toluene. A variation in the structure of the compound leads to a change in both the current-voltage characteristics of the resulting device and the luminescence spectra. These changes appeared due to the difference in the electronic structure of these materials as well as due to different values of charge carrier mobilities and the potential barriers at the heterointerface with other OLED layers. The results obtained may serve as the basis for systematizing knowledge about the dependence of the properties of new luminescent materials, which include a coumarin core, on their structure. The developed structures can become prototypes for industrially produced light-emitting devices that specifically emit white light.
Fabrication and characterization of hybrid composite of Al6082/SiC/rice husk powder using friction stir processingNitesh Kumar, Prateek Gupta, Rakesh Kumar Singh
Friction Stir Processing (FSP) is a technology in which the microstructure of a material, as well as the mechanical properties of this material, is enhanced by the action of friction with a special tool. There are many applications for FSP materials which are in high demand in various industries, including aerospace, shipbuilding, instrumentation, and many others. The paper presents a study of a hybrid composite made from silicon carbide powder and rice husk (RHP) as reinforcement, included in the Al6082 aluminum alloy. The study of the characteristics of the fabricated composite was performed using an optical microscope, field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) method. Tensile strength (UTS) and hardness were determined. It was revealed by microscopy that a modification of the microstructure occurs on the surface of the composite. X-ray diffraction analysis showed the presence in the spectrum of elements similar to the Al/SiC/RHP hybrid composition. It is shown that UTS tensile strength and Brinell hardness is being increased by factors of 1.36 and 1.75, respectively, compared to base aluminum material.
A multi-path secure routing for the detection of node capturing attack in wireless sensor networkJayaraman Kolangiappan, Angamuthu Senthil Kumar
Over the past few years, the devices in Wireless Sensor Networks (WSN) are growing exponentially due to the emergence of many sophisticated applications. This tremendous growth leads to serious security challenges, and the devices of WSN should be protected from various attacks. WSN can be configured dynamically without fixed infrastructure and the devices can be talked with one another in an ad-hoc manner. Due to the dynamic nature of WSN, routing is considered as the challenging task that should be performed efficiently with robust routing mechanism. Even though many routing schemes have been emerged for WSN, they are not well scalable in very large-scale environment. This work introduces multi path routing strategy, and the routing will be selected based on trusted nodes. First, the trusted nodes are identified using trusted metrics of each node in the network. These metrics are calculated based on the threshold value of nodes. Then, secure routing is established by isolating node capturing attacks from the path. The performance of the work is analyzed in terms of packet loss, computational time and throughput. The paper compares the performance with the state-of-the-art routing schemes such as EMBTR (Enhanced Multi Attribute Based Attack Resistance), TSRM (Trust based secure routing model), and TARF (Trust-aware routing framework for WSNs). The outcome of the simulation shows that the proposed scheme outperforms the other state-of-the-work in terms of computational cost, throughput, and delay.
A method for documenting architectural solutions of computing platformsYaroslav G. Gorbachev
The article describes a method for documenting the principles of functioning and internal organization of computing platforms, including reconfigurable computing systems and non-standard processor architectures. The novelty is in using of unified tools to describe: the design process and the computing process, hardware, software and tools, computing components of different granularity. The proposed approach is to describe computing platform as an ideal model that represents abstract algorithms for fulfilling functional requirements without specifying of how to implement it. Then the iterative model refinement follows including selection of physical implementation options, specifying the technological stacks, and additional mechanisms that provide the specified system qualities. A feature of the method is a kernel used for structuring information, classifying and describing the computational mechanisms the system consists of. The kernel includes elements common for different systems and is based on the analysis of a large number of computing architectures. The method describes the principles of the organization of platforms which are usually not considered together. These are: generalized processors with classical architecture which is an evolution of the von Neumann principles; systems based on microcontrollers; operating systems; large- and small-granular reconfigurable systems; specialized processors and accelerators; artificial neural networks. The proposed method can be used to structure information in both traditional and rapidly developing areas: reconfigurable systems and specialized processors. Based on the method, it is possible to create a common database of computing mechanisms suitable for use in different functional units of the system and at different levels of granularity. The results of the work can be useful for system architects to describe complex computing mechanisms consisting of software, hardware and dynamically generated adaptive “intelligent” components which will simplify their reuse and can be used to generate new architectural solutions. Also, the proposed method can be used in the process of training specialists, for a visual demonstration of the basic principles of computer technology.
Improving out of vocabulary words recognition accuracy for an end-to-end Russian speech recognition systemAndrei Yu. Andrusenko, Romanenko Alexei N.
Automatic Speech Recognition (ASR) systems are experiencing an active introduction into our daily lives, simplifying the way we interact with electronic devices. The advent of end-to-end approaches has only accelerated this process. However, the constant evolution and a high degree of inflection of the Russian language lead to the problem of recognizing new words outside the vocabulary (Out Of Vocabulary, OOV) because they did not take part in the training process of the ASR system. In such a case, the ASR model tends to predict the most similar word from the training data which leads to a recognition error. This is especially true for ASR models that use decoding based on a Weighted Finite State Transducer (WFST), since they are obviously limited by the list of vocabulary words that may appear as a result of recognition. In this paper, this problem is investigated on the basis of an open data set of the Russian language (common voice) and an integrated ASR system using the WFST decoder. A method for retraining an integral ASR system based on the discriminative loss function MMI (maximum mutual information) and a method for decoding the integral model using a TG graph are proposed. Discriminative learning allows smoothing the probability distribution of acoustic class prediction, thus adding more variability in the recognition results. Decoding using the TG graph, in turn, is not limited to recognizing only vocabulary words and allows the use of a language model trained on a large amount of external text data. An eight-hour subset from the common voice base is used as a test set. The total number of OOV words in this test sample is 18.1 %. The results show that the use of the proposed methods allows to reduce the word recognition error (Word Error Rate, WER) by 3 % in absolute value relative to the standard method of decoding integral models (beam search), while maintaining the ability to recognize OOV words at a comparable level. The use of the proposed methods should improve the overall quality of recognition of ASR systems and make such systems more resistant to the recognition of new words that were not involved in the learning process.
Method for monitoring the state of elements of cyber-physical systems based on time series analysisSemenov Victor V.
The wide spread of cyber-physical systems, as well as the widespread integration of computing resources into physical entities, have led to an increase in the risks of deliberate and accidental security incidents. In this regard, the development of new methods and tools and improvement of the existing ones for monitoring such systems is of particular relevance. The methods being created and modernized should have increased recall and precision of identification, especially for critical infrastructure objects. An original method for processing data for monitoring the state of cyber-physical systems based on time series analysis using significance weights as a post-processing of classification results was proposed. The method differs from the existing ones by the combined approach that combines the use events of information security and functional safety in monitoring systems. It is characterized by the use of an ensemble of decision trees as well as parallel classifiers and Fishburn weight coefficients in the analysis of the set of the most informative features obtained from time series. The applicability of the method was substantiated by conducting of a computational experiment on a known data set which characterizes the functioning of the information and physical components in the implementation of various types of attacks on the components of the experimental stand of the cyber-physical water treatment system. When using the developed method, the identification precision increased by 1.45 % compared to the best approaches presented in other scientific works, and the recall increased by 4.45 % and amounted to 99.85 % for both indicators. The results obtained are adapted for practical use in systems for identifying the state of cyber-physical systems. The theoretical significance lies in the possibility of using the results of the study in the design of systems for monitoring the information security and functional safety of cyber-physical systems.
Application of the text wave model to the sentiment analysis problemAnastasia S. Gruzdeva, Iurev N. Iurev, Bessmertny Igor Alexandrovich
Authors researched the wave model of text representation which is one of the implementations of distributive semantics. This model takes into account not only the frequency of words occurrence in the text, but also their mutual location. The purpose of the study: to increase the accuracy of the analysis of the tonality of short texts based on the wave model. The method of determining the relationship between the text and the term is based on the calculation of the probability amplitude of the text and term proximity using a wave model. The term with the highest probability amplitude is considered to correspond most closely to the meaning of the text. The wave model allowed taking into account the fact that well-known methods define antonyms as semantically close lexical units. For the experimental study of this technique, a solution to the problem of sentiment analysis was chosen, exactly, finding the correspondence of user reviews about the product to the classes “positive” and “negative”. As a result, the accuracy of the text tonality defining was obtained up to 76.4 %, which exceeds the accuracy of the classical approach as well as the well-known methods of sentiment analysis for the Russian language. In addition, authors detected significant influence on classification accuracy of such model parameters as the choice of a basic distributive semantic model, the choice of a control point for calculating wave numbers, taking into account the influence of antonyms. The presented model has shown high accuracy in identifying the relationships of the text with concepts that are not explicitly present in it and can be successfully used as a mathematical basis for solving problems of sentiment analysis. In addition, the results obtained indicate the potential use of the wave model in other areas that require the classification of texts by indirect signs, for example, to determine the elements of author psychological portrait.
Automated evaluation of ECG parameters during the COVID-19 pandemicAlexandra S. Vatyan, Gusarova Natalya Fedorovna, Dobrenko Natalia V. , Danil A. Zmievsky, Maxim A. Kabyshev, Tatyana A. Polevaya, Anna A. Tatarinova, Ivan V. Tomilov
Algorithms for prompt automated evaluation of electrocardiogram parameters in the absence of specialized equipment and specialized specialists are considered. The patient’s electrocardiogram is recorded on a paper tape, then it is photographed on the primary care doctor’s mobile phone and processed by a specialized application. The application digitizes the photographed image of the electrocardiogram, evaluates its main parameters as well as calculates criteria for the differential diagnosis of certain diseases using approximate formulas. In addition, the digitized electrocardiogram image is transmitted to the server and processed using a machine learning system. Algorithms for digitizing and analyzing an electrocardiogram have been developed that make it possible to evaluate its elements that are important for diagnosis, and the average error in determining the position of the most complex (smoothed) peaks — P and T waves — was no more than 0.1 mm. An algorithm for the criteria analysis of an electrocardiogram is proposed to support the differential diagnosis of acute myocardial infarction with ST segment elevation and early ventricular repolarization syndrome which provides accuracy values of 0.85 and F-scores of 0.74. An alternative algorithm based on a deep neural network is proposed which provides the best values — 0.96 and 0.88, respectively, but requires large computing resources and is executed on the server. The algorithms are implemented as a set of library functions. They can be used both independently and as part of a full-scale clinical decision support system for automated evaluation of electrocardiogram parameters based on a client-server architecture. In addition, all calculation results, together with a photograph of the original electrocardiogram, can be promptly transferred to a qualified cardiologist in order to receive an advisory opinion remotely.
Multi-agent adaptive routing by multi-headattention-based twin agents using reinforcement learningTimofey A. Gribanov, Andrey A. Filchenkov , Artur A. Azarov, Shalyto Anatoly A.
A regular condition, typical for packet routing, for the problem of cargo transportation, and for the problem of flow control, is the variability of the graph. Reinforcement learning based adaptive routing algorithms are designed to solve the routing problem with this condition. However, with significant changes in the graph, the existing routing algorithms require complete retraining. To handle this challenge, we propose a novel method based on multi-agent modeling with twin-agents for which new neural network architecture with multi-headed internal attention is proposed, pre-trained within the framework of the multi-view learning paradigm. An agent in such a paradigm uses a vertex as an input, twins of the main agent are placed at the vertices of the graph and select a neighbor to which the object should be transferred. We carried out a comparative analysis with the existing DQN-LE-routing multi-agent routing algorithm on two stages: pre-training and simulation. In both cases, launches were considered by changing the topology during testing or simulation. Experiments have shown that the proposed adaptability enhancement method provides global adaptability by increasing delivery time only by 14.5 % after global changes occur. The proposed method can be used to solve routing problems with complex path evaluation functions and dynamically changing graph topologies, for example, in transport logistics and for managing conveyor belts in production.
Joint learning of agents and graph embeddings in a conveyor belt control problemKonstantin E. Rybkin, Andrey A. Filchenkov , Artur A. Azarov, Zabashta Alexey S, Shalyto Anatoly A.
We focus on the problem of routing a conveyor belts system based on a multi-agent approach. Most of these airport baggage belt conveyor systems use routing algorithms based on manual simulation of conveyor behavior. This approach does not scale well, and new research in machine learning proposes to solve the routing problem using reinforcement learning. To solve this problem, we propose an approach to joint learning of agents and vector representations of a graph. Within this approach, we develop a QSDNE algorithm, which uses DQN agents and SDNE embeddings. A comparative analysis was carried out with multi-agent routing algorithms without joint learning. The results of the QSDNE algorithm showed its effectiveness in optimizing the delivery time and energy consumption in conveyor systems as it helped to reduce mean delivery time by 6 %. The proposed approach can be used to solve routing problems with complex path estimation functions and dynamically changing graph topologies, and the proposed algorithm can be used to control conveyor belts at airports and in manufacturing workshops.
MODELING AND SIMULATION
Simulation of radiative transfer in gas-liquid foamsIsaeva Anna A., Isaeva Elena A. , Pantyukov Aleksey V.
The results of the radiation light transfer in the gas-liquid foams are presented. To study the probing light transfer in gas-liquid foam-like media at different stages of aging, a Monte Carlo numerical simulation method is proposed. To take into account the re-reflections at the phase interfaces, the approach based on the Fresnel formula is applied. Kelvin cells structures are considered as a model medium, imitating gas bubbles in a liquid matrix during aging (coarsening), which represents the transition of a foam-like medium from “wet” to “dry”. Such transition is caused by the slow liquid flow along the gas cells walls and Plateau-Gibbs channels due to the influence of the gravitational force in an isolated system. During the evolution process, the volume fraction of the liquid phase decreases and the average size of the gas cells of the foam-like medium increases. The three-dimensional cellular structure at different evolution stages is represented as a system of close-packed ordered spheres or tetradecahedrons of various geometric sizes depending on the aging process duration. The Monte Carlo modeling of the radiation light transfer in scattering two-phase foam-like media, taking into account the redistribution at the interfaces of two phases by use of Fresnel formulas at different coursing stages, is presented. The transmittance and backscattering coefficients of a probing light are obtained using the Monte Carlo numerical simulations and Fresnel formulas for the gas-liquid foams. The obtained results are well correlated with the spectrometric measurements of the foamed liquid produced by Gillete (Gillete shaving cream). The influence of the anisotropy factor on the optical length of the probing light was carried out. The development of the theoretical approaches to the diagnostics of the two-phase foam-like materials makes it possible to synthesize foamed materials with established rheological and structural properties to increase and improve the efficiency of evaluating of the functional characteristics for such materials.
The effect of signal-to-noise ratio value on the error in measuring acoustic emission parameters: statistical assessmentFedorov Alexei V, Yeldos Altay, Ksenia A. Stepanova, Dmitry O. Kuzivanov
Modern acoustic emission diagnostic systems and complexes are a sensitive tool for detecting developing defects at an early stage when monitoring the technical condition of objects under operational loads. A significant limitation of the application acoustic emission method is the difficulty in isolating signals against the background of acoustic and electromagnetic interference. The effect of interference during acoustic emission recording significantly complicates the interpretation of parameters that characterize the technical condition of the test object. To increase the value signal-to-noise ratio and increase the reliability of the results of acoustic emission testing in the quantitative assessment of parameters, filtering methods are used. The subject of this study is the study of the effect of signal-to-noise ratio value on the measurement error acoustic emission parameters formatted during noise compensation using the polynomial filtering method. The basis of the statistical model characterizing the effect of signal-to-noise ratio value on the measurement error acoustic emission parameters is based on the machine learning method — linear regression. The dependence of the measurement error on the signal-to-noise ratio value was approximated by the least-squares method and visualized using a scattergram. It was found that when using the Butterworth filter, the relative measurement error acoustic emission parameters do not exceed 3 %, which are orders of magnitude lower than the values obtained for the Bessel filter and Daubechies mother functions 8 based on wavelet filter. A high inverse non-random correlation was established (r > 0.9), due to a decrease in the values of the relative measurement error emission parameters and an increase in the signal-to-noise ratio value. The developed statistical model describes the effect of the signal-to-noise ratio value on the value relative error in estimating the acoustic emission parameters. The adequacy of the developed model was confirmed by calculating the coefficient of determination and checking its statistical significance. It is shown that the use of Butterworth filter to compensate for interference significantly increases the information content of the results of measurements of acoustic emission parameters. The developed statistical model can be used in the development of new or improvement of existing complexes and systems for processing acoustic emission data to improve the reliability of the results of acoustic testing.
Simulating the process of steady-state thermoreflectance for measuring the thermal conductivity of materialsAnastasiia S. Tukmakova, Petr S. Demchenko, Ivan L. Tkhorzhevskiy, Novotelnova Anna V. , Khodzitskiy Mikhail K
The measurement of thermal conductivity by the method of steady-state thermoreflectance is based on the effect of heating the sample by laser radiation. The power of reflected radiation from the sample is measured using an additional probe laser. The change in the reflection coefficient of the studied material due to the heating is proportional to the change of the sample temperature. The radiation power absorbed by the material acts as a volumetric heat source. The value of thermal conductivity is calculated according to the Fourier’s law of thermal conductivity. A steady-state thermoreflectance setup requires calibration, i.e., thermal conductivity measurement of reference samples. The value of the calibration coefficient, in turn, depends on the characteristics of the lasers used in the setup. In this work, a numerical model of sample heating is proposed which allows considering the shape and diameter of the incident radiation beam, the distribution of radiation power over the beam area, and the absorption and reflection coefficients of the material. A methodology for samples reflection and absorption coefficients determination, including measurements and calculations considering the Fabry-Perot effect, is proposed. The study was performed for the samples of germanium, silicon, gallium arsenide, and sitall. The irradiation was performed with a continuous wave single-mode diode laser with a wavelength of 980 nm. The incident radiation power distribution over the beam area was approximated according to the Gaussian function in the OriginPro software. The radiation power that passed through the samples and reflected from them was measured. The temperature of the samples during irradiation was measured with a thermal imager. The reflection and absorption coefficients of the samples were determined from the results of radiation power measurements using a mathematical model of the interaction of plane-polarized TE electromagnetic radiation with the material. Comparison of the calculation results with the literature data for germanium, silicon, and sitall samples showed their correspondence. For gallium arsenide there was a discrepancy between the calculation results and the literature data. For gallium arsenide samples, a model considering the Fabry-Perot effect was used, and the optical properties were determined numerically by searching for the minimum modules of the transfer functions of the transmitted and reflected radiation in the Matlab program. The model of electromagnetic heating of the investigated samples was implemented in the COMSOL Multiphysics software. A method for the determination of the reflection and absorption coefficients of materials investigated by the steady-state thermorflectance is proposed. The proposed model allows considering beam shape, width and distribution of the radiation power as well as the value of the absorbed radiation power for each sample. The difference between the calculated values of the sample temperature and the measurement results does not exceed 9 %. The model can be applied to measure the thermal conductivity of bulk and thin-film materials with unknown properties.
Modeling and simulation ofone- and two-row six-bladed ducted fansSergey Yu. Dudnikov , Bulat Mikhail P., Vokin Leonid O. , Pavel N. Kuznetsov, Pavel S. Chernyshov
The problem of simulation of efficient ducted fan type propulsors is considered. From experience of operation of twin blades in fantails of helicopters, it is known that this configuration creates less noise compared to a uniform arrangement of the blades around the circumference. However, the flow behind such fan is less uniform than that of a conventional ducted fan. For multicopter-type unmanned aircraft and air taxis, the key problem is flight in take-off and landing modes as well as acoustic and vortex fields created by propulsors in these modes. The decrease in the noise level in propellers with twin blades can potentially be accompanied by an increase in non-stationary vortex effects on the aircraft as well as a decrease in specific thrust. The objectives were to develop a method for simulation of ducted fan propellers in the takeoff and landing mode, to determine the optimal angle between the blades, and to compare a ducted fan with twin X-shaped blades to conventional blade position. Turbulent flows were calculated using transient Reynold-averaged Navier-Stokes equations, complemented by SST turbulence model, and large eddy simulation with WALE subgrid viscosity model. The calculations used the modification γ–Reθ Transition SST of the Langtry-Menter turbulence model, where there are relations for the intermittency criterion, which made it possible to consider the laminar-turbulent transition and the appearance of thin laminar separation bubbles that affect both the thrust of the propeller and the non-uniformity of the flow behind it. Testing was carried out on four-bladed propellers according to the known results of the TsAGI reference experiments. Testing of the γ–Reθ Transition SST Langtry-Menter turbulence model showed that it reproduces the dependence of the thrust coefficient and power factor on the blade angle better than the standard SST model. Calculations have shown that there is a clearly defined optimum angle between the paired blades. A comparison of three-bladed, six-bladed single and six-bladed propellers with twin blades showed that the latter option has slightly better thrust characteristics and creates a significantly lower noise level on the ground. The studied characteristics of ducted fans demonstrate the prospects for the use of propellers with twin blades in aircraft with vertical takeoff and landing. The developed numerical method can be directly used for industrial calculations of propellers and fans.
Differential-difference model of heat transfer in solids using the method of parametric identificationPilipenko Nikolay V., Pavel A. Kolodiychuk, Yury P. Zarichnyack
The paper considers the problem of parametric identification of a differential-difference model of the heat transfer process in a spherical body. When developing the model, the original extended Kalman filter is used which allows taking into account the dependence of the thermophysical properties of the object under study on temperature. This formulation and the obtained solution of the problem make it possible to take into account the different nature of the external thermal effect and the processes occurring inside the bodies, in particular, during phase transitions in systems of bodies. The research results obtained using parametric identification and Ansys software are in good agreement. However, the method we have considered, in contrast to the Ansys software, allows not only to determine the temperature at different points of the object, but also to restore the non-stationary heat flow at the object boundary as well as to refine its thermophysical properties. The considered method of parametric identification of the differential-difference model of heat transfer can be successfully used in determining the efficiency of heat energy storage devices.