System technologies

Regression analysis of impulse characteristics shorted supersonic nozzle

Ternova Kateryna — 2023-05-11

When designing and testing rocket engines, an important problem is the choice of the contour of the supersonic part of the nozzle. Recently, with the development of rock-et and space technology, different contours of nozzles have appeared that meet new tasks, requirements for the density of the layout, the need to increase the momentum co-efficient, accounting for various operating conditions, etc. Therefore, the relevance of the work is determined by the need to choose the contour of the supersonic part of the nozzle to increase the impulse characteristics of the flow in the shortened nozzle. The goal of the work is to choose the optimal contour of a shortened nozzle with a bell-shaped nozzle, taking into account geometric and technological parameters. The regres-sion model of the supersonic flow in a shortened nozzle with a nozzle considered in the work was created on the basis of previously obtained simulation results in the ANSYS package. It has been found that the flow patterns in the nozzle are affected by the length of the inlet cone, the total length of the nozzle and the operating conditions of the noz-zle, i.e. inlet pressure and ambient pressure. The nature of the separation flow in the nozzle, and hence the momentum coefficient depends on the degree of expansion of the flow from the shortened nozzle, therefore it is necessary to identify the main geometric and technological parameters of the flows in the shortened nozzle with a bell-shaped tip and determine the dependence of the momentum coefficient on them. Data analysis was carried out on the basis of the STATGRAPHICS Plus program. The influence values of each adopted factor and their mutual influence on increasing the flow impulse charac-teristics in the shortened nozzle are obtained. Three-dimensional graphs of the depend-ence of the momentum coefficient on the geometric parameters, the pressure at the noz-zle inlet, and the pressure of the external environment were obtained. The formula for the dependence of the impulse coefficient on the length of the conical part, the total length of the nozzle, the pressure at the nozzle inlet and the pressure of the external space was determined. It was established that an increase in the pressure of the external space leads to an increase in the impulse characteristic at the average value of the pres-sure at the nozzle inlet. The built regression model allows you to choose the optimal contour of a shortened nozzle with a tip.

Modeling of a neural network-based system for identification and control of technical object parameters

Mykhailenko Vladyslav — 2023-05-11

The article analyzes the effectiveness of a neural network control system for main-taining the pH level in the feedwater of a steam boiler. An intelligent control system im-plements the principle of reverse error propagation through a neural emulator. The sub-system model of steam boiler water tube blowing was used as the research object. The neural network controller and neural emulator were trained on a control system model with a PID controller using the expert correction methodology of tuning coefficients: proportionality, integration constant, and differentiation based on the analysis of tran-sient process quality indicators. The analysis of the transient processes obtained from simulation modeling allows us to state that the trained neural network control system successfully compensates for disturbances over a wide range of changes in the object's parameter values via control channels and disturbances (simulating changes in steam load).

Analysis of vulnerabilities and security problems of web applications

Trofymenko Olena — 2023-05-11

The article provides a comprehensive analysis of vulnerabilities, methods, tools and problems faced by web application security testing. The analysis of scientific research in the field of web application security testing revealed a significant interest of scientists in finding effective ways to minimize site security risks and vulnerabilities. It was found out that the list of the most common web application vulnerabilities includes: broken access control, cryptographic failures, misconfiguration of security, SQL and other injections, insecure design, identification and authentication errors, etc. Specific features of the security vulnerabilities of web applications are highlighted. The problems faced by automated tools for web security testing are separately considered, namely the development of automated tools for web security testing, the use of RIA (Rich Internet Application) web applications, and the use of insecure cryptographic storage. Web application security risks can be associated with the design phase, the development phase, the deployment phase, and the maintenance phase. It is security testing that is used to identify these risks of the web application, to investigate the vulnerabilities and weak points of the web application. The conducted analysis of security vulnerabilities, methods and problems of testing web applications revealed the presence of different approaches to protect software products. A combination of manual and automated web application security testing techniques is advisable, starting with automated security testing and complementing it with manual penetration testing. A comprehensive approach should integrate testing into all stages of the software development life cycle. Such approach helps to use the most appropriate and effective available methods for the current phase of software product development.

ANALYSIS OF STRENGTH OF A FORK OF THE FORKLIFT BY NUMERICAL METHODS

V.V. Strelbitskyi — 2023-05-11

Forklift is an industrial power truck, commonly called forklifts or lift trucks, then usually have two forks the can be trial power truck used forklifting and transport materials. Fork-lifts, to this day, the fork strength of a forklift under load still seems to be one of the biggest issues. Fork’s related structural design and detail have a significant impact on the overall performance and reliability of a forklift. In this work, static analyses of a fork forklift were performed using Finite Element Method, on the free software FreeCAD, a multidisciplinary software application that is the result of a long-term active collaboration between develop-ers and users. Open science hardware is cheaper, easier to maintain, and more accessible to more people. In this paper, by calculating the maximum normal stress of the section, the force situation and allowable stress of the fork are analyzed. The fork is made of structural material is 40Cr steel. The output values of the static study consist in establishing the distri-bution of equivalent unitary stresses (stress state) according to the von Mises criterion. The maximum stress of the structure is 128 MPa, which is does not exceed the allowable. Then in order to enhance the structural strength of the weak part, the measures of gradually in-creasing the fillet radius of the fork root were proposed, and the radius were selected as 35mm and 45mm, the weight of the forklift load was still 0,5t. Numerical experiments have shown that by increasing the radius from 25 to 45 mm, stresses decrease by 1.1...1.15 times, which is consistent with the theory of basic mechanics that stress concentration can easily lead to fatigue failure of the structure. Both numerical calculations and visual analysis showed consistency, with stress concentrations observed at the fork neck, demonstrating the accuracy of the established finite element model.

Analysis of the transformation of the microstructure of axial billets after rolling

T.V. Balakhanova — 2023-05-11

The task of improving the quality of metal products of large cross-sections pro-duced from continuous cast billets (CBS) is associated with a number of difficulties. These include the presence of internal defects in the macrostructure of the workpiece (axial looseness, porosity, liquation, crystallization cracks, etc.). Processing from the point of view of deformation of cast workpieces is necessary first of all to eliminate cast defects. An increase in working out contributes not only to the welding of existing mi-crodiscontinuities and, in this connection, to an increase in the density of the metal, but also to the extraction, crushing and reduction of the cross-section of the existing non-metallic inclusions. However, the dimensions of the elements of the primary structure, which are presented on the graphs, are also of the greatest importance. The smallest level of liquation is formed in the surface areas during crystallization. At the same time, as a rule, it is necessary to obtain a homogeneous structure in terms of grain size on the cross-section of large-sized metal products. A study of the features of the structure of axle blanks made of steel grade F (AAR M-101-2017 Axles, carbon steel, heat-treated) after longitudinal rolling on a TPA 5-12" pipe rolling unit with pilgrim mills in three crimping modes (1 mode: Ø 470 → Ø 380 → Ø 260 mm; 2nd mode: Ø 470 → Ø 420 → Ø 260 mm; 3rd mode: Ø 470 →Ø 260 mm). Determination of the features of the distri-bution of deformation work and the formation of the final structure after deformation according to the experimental modes of BLZ Ø470 mm per circle Ø260 mm is the pur-pose of the research. Samples for the structure study were taken both from the original BLZ and the finished draft axle along the entire cross-section. The greatest unevenness of the liquation background, which is observed in the axial blank manufactured using mode No. 1, is also manifested during the study of the microstructure of railway of the axes obtained by the indicated modes. It was determined that the uniformity of the grain structure is the highest after using mode No. 3 (Ø 470 →Ø 260 mm).

Evaluation of the efficiency of implementation of asynchronous computing algorithms using coroutines and threads in С++

H.Ia. Vokhmianin — 2023-05-11

Modern multi-core systems are most effective when used in large server centers and for cloud computing. However, despite the known complexity of software implemen-tation, parallel computing on multiprocessors is increasingly used in computer model-ling. Advanced mechanisms of synchronous and multithreaded programming are in-creasingly used to improve the productivity of numerical studies, reducing the time of computer models implementation. One such mechanism is coroutines, a convenient tool for managing asynchronous operations introduced in the C++20 standard. A special feature of coroutines is the ability to suspend a function at a certain stage, saving its state, and after some time resume its execution from the previous stop. The aim of this research is to improve the performance of computer modelling by using coroutines and data threads. As a result of the work, a test algorithm for multiplying a matrix by a vector and its modified asynchronous version using the coroutine mechanism and splitting into two data threads was developed, which allowed to achieve 1.94 times increase in the com-puting speed when the matrix dimension is 15000 (2.25×106 elements). It has been found that at a small matrix dimension, the developed asynchronous algorithm using coroutines and splitting into two threads is less efficient than the single thread algo-rithm. This is due to the fact that the compiler needs some time to create threads and start execution simultaneously. With a large dimensionality, the performance of the asynchronous algorithm increases significantly. With a matrix dimension of more than 1200, the use of an asynchronous algorithm divided into two threads is guaranteed to be more efficient than a single-threaded. The data obtained are consistent with the results of similar studies of the problem of increasing the efficiency of computer modelling using alternative software and hard-ware. The new method of solving the problems of asynchronous programming provides a more efficient and simple mechanism for managing asynchronous operations.

Іntelligent classification system based on ensemble methods

O.P. Hozhyi — 2023-05-11

In the paper, based on machine learning methods, the solution of the classification task was investigated using a two-level structure of ensembles of models. To improve forecasting results, an ensemble approach was used: several basic models were trained to solve the same problem, with subsequent aggregation and improvement of the ob-tained results. The problem of classification was studied. The architecture of the intelli-gent classification system is proposed. The system consists of the following components: a subsystem of preprocessing and data analysis, a subsystem of data distribution, a subsystem of building basic models, a subsystem of building and evaluating ensembles of models. A two-level ensemble structure was used to find a compromise between bias and variance inherent in machine learning models. At the first level, an ensemble based on stacking is implemented using a logistic regression model as a metamodel. The pre-dictions that are generated by the underlying models are used as input for training in the first layer. The following basic models of the first layer were chosen: decision trees (DecisionTree), naive Bayesian classifier (NB), quadratic discriminant analysis (QDA), logistic regression (LR), support vector method (SVM), random forest model (RF). The bagging method based on the Bagged CART algorithm was used in the second layer. The algorithm creates N regression trees using M initial training sets and averages the re-sulting predictions. As the basic models of the second layer, the following were chosen: the first-level model (Stacking LR), the model of artificial neural networks (ANN); the linear discriminant analysis (LDA) model and the nearest neighbor (KNN) model. A study of basic classification models and ensemble models based on stacking and bag-ging, as well as metrics for evaluating the effectiveness of the use of basic classifiers and models of the first and second level, was conducted. The following parameters were de-termined for all the methods in the work: prediction accuracy and error rate, Kappa statistic, sensitivity and specificity, accuracy and completeness, F-measure and area under the ROC curve. The advantages and effectiveness of the ensemble of models in comparison with each basic model are determined.

Alternative to mean and least squares methods used in processing the results of scientific and technical experiments

V.U. Ihnatkin — 2023-05-11

The nomenclature of controlled parameters and norms of measurement accuracy determines the reliability of control and its laboriousness. On average, the labor-intensiveness of control is about 10% of the total labor-intensiveness of manufacturing objects, and in a number of industries it is much higher (aerospace engineering). The simplest task in determining a rational nomenclature of controlled parameters of ob-jects is the exclusion of excessive parameters, while it is necessary to determine the probability that the deviations of some Х2 parameter within the specified tolerances are the same as the deviations of the Х1 parameter within its specified tolerances. At the same time, inequalities are defined that determine the smallest value of this probability. The general principle of solving this problem is the determination of conditional proba-bilities (if two parameters are considered) P Р11, Р12; , or Р21, Р22. At the same time, if the obtained values: Р11, Р12, are more likely than (or equal to) the permissible value of Rdop, then it is advisable to control only parameter Х1, and exclude Х2 from the no-menclature of parameters. If: Р21, Р22 , are greater than (or equal to) the permissible value of Rdop, then Х1 is turned off. An example of the exclusion of a redundant control parameter is given. The method can be generalized for any number of parameters, for which it is necessary to use correlation matrices or a simple enumeration of parameter combinations. A computer program has been developed that can be used if the following information is available: 1) the number of controlled parameters (n); 2) values of toler-ances (Xni, Xvi), which parameters are subject to control; 3) numerical characteristics of distributions of parameter values within the specified tolerances - the average value of and the average squared deviation σХі,; 4) types of distribution laws of parameter values; 5) data on correlations between parameters and values of pairwise correlation coefficients ( rij ); 6) the value of the probabilities of control errors Р12, Р21 (with two parameters). Calculations should be adjusted as statistical data accumulate.

Search and assessment of urban heat islands on digital satellite images

V.Iu. Kashtan — 2023-05-11

Formulation of the problem. The development of urbanization processes resulted in Urban Heat Islands (UHI) - ur-ban areas of high temperatures due to the dominance of artificial surfaces that absorb and retain heat. UHIs adversely affect the environmen-tal conditions of cities and people's health. Satellite images in the thermal infrared range of the electromagnetic spectrum allow identifying areas of the high thermal back-ground of urbanized territories for management decisions support aimed at improving urban landscapes. The aim of the work is to develop a methodology for temperature anomalies analy-sis and urban heat islands detection on digital space images from Landsat 8 satellite in the thermal infrared range of the electromagnetic spectrum. Methodology of UHI detection. The methodology proposed in the paper includes a sequence of stages of collecting, and preprocessing satellite data, generating land sur-face temperature maps, identifying temperature anomalies, comprehensive analysis of high-temperature zones based on different-time data, and identifying areas of high temperatures stable over time. Land Surface Temperature estimation. Land Surface Temperature (LST) is esti-mated from the band 10 data of space images from the Landsat 8 satellite. The initial data are subjected to atmospheric correction, after which the spectral radiation in the band is converted to brightness temperature, and then to LST (Celsius degrees). UHI mapping. On each survey date, UHIs are identified as temperature anomalies - LST map pixels with values higher than the LST mean plus standard deviation within the study area. Time series analysis of satellite images. UHI mapping is based on a time series of Landsat 8 images acquired during the warm season (when ambient temperatures are above zero) to eliminate the effect of snow and ice on the observation results. According to the time series of LST maps of different years, stable temperature anomalies are dis-tinguished - UHIs presented on all images of the time series. Conclusions. Time-stable UHIs of the urbanized territory are mapped and ana-lyzed using Landsat 8 LST data time series. The areas of the high thermal background are compared with the classes of the earth's surface. It is concluded that increasing ur-ban density contributes to the accumulation of heat and increases the ambient tem-perature. The maps of LST distribution, vegetation indices, and UHI generated in the work can be used in urban planning tasks together with traditional sources of spatial information to obtain new information on improving the city's resistance to heat waves. UHI observation data are necessary for zoning areas with different land use types, for example, increasing the amount of open space and greenery, and improving the thermal comfort of citizens.

Optimal control of the belt conveyor as part of the technological process of ore mass transportation by controlling the belt tension

I.D. Kurganov — 2023-05-11

Optimum control of the conveyor in the transport flow due to the change of the belt tension is proposed in order to reduce the costs of transporting goods by increasing the life of the belt and reducing energy consumption costs. It is suggested to use tape tension control to eliminate the accidental slippage of the tape on the drum and its excessive abrasion during the transportation of the ore mass. To implement the control method being developed, it is necessary to use a mathe-matical model with distributed parameters, on the basis of which an optimal control model will be formed using the control principles considered in the work. Control of this kind of objects is determined by the technological need to compen-sate for the slippage of the belt on the drive drum of the conveyor, which is based on the process of transmission of motion using friction, and is implemented by changing the thermal field on the arc of the girth by changing the tension of the conveyor belt or the speed of rotation of the drum. Thus, from the point of view of the theory of control of systems with distributed pa-rameters, in the process of controlling the thermal field of the drive drum and belt, the controlled coordinate is the temperature or its distribution on the girth arc. As a result of a change in the circumferential force on the drive drum, the pressure of the tape on the lining of the drum changes, which leads to a change in the value of the heat flow both in terms of amplitude and spatial distribution (the value of the working sliding arc changes, i.e. the area of elastic interaction), which is compensated by con-trolling the tension ribbons

Transformation in the system of residual number classes from one system of modules to another

Yu.D. Poliskyi — 2023-05-11

The purpose of the study. The purpose of the study is an analytical consideration of the system of residual classes for the implementation of the operation of converting numbers from one system of residual classes to another. Method. System analysis, number theory, and the Chinese remainder theorem are tools of the research methodology. The method uses the representation of the number both by its remainders and in the polyadic code. The methodology is based on determining the positional characteristics for this module on the basis of the received positional characteristics for the remaining modules of the original system, with the subsequent construction on their basis of the residuals for the modules of the sought system. The proposed method is algorithmically simple. The results. The theoretical substantiation of the considered approach to obtain an effective solution of the non-modular transformation operation in the system of residual classes for the transition from the representation of a number by one system of modules to its representation by another system of modules is performed. It is shown that the proposed method provides the desired result. On the basis of the proposed approach, an increase in the performance of the conversion operation is achieved. Scientific novelty. The theoretical justification of the presented approach to the solution of the non-modular transformation operation in the system of residual classes for the transition from the representation of a number in one system of modules to its representation in another system of modules is proposed. It seems appropriate to apply the proposed approach as a prospective direction of research of complex operations in the system of residual classes. Practical significance. It follows from the importance of theoretical conclusions and obtained research results.It is based on the fact that there is a reasonably simple and effective approach to solving the problem of performing a non-modular conversion operation in the system of residual classes for the transition from the representation of a number in one system of modules to its representation in another system of modules. The considered solutions have high speed and can be effective in the development of modular computing structures for promising information technologies.

Research in machine learning methods for solving problems of the medical profile

K.Iu. Ostrovska — 2023-05-11

The work is devoted to the study of machine learning methods for solving medical problems. The aim of the work is to analyze machine learning methods to improve the accuracy and reduce the time for diagnosing diseases of the genitourinary system in children. The object of research is machine learning methods. The subject of the study is a classifier of diseases of the genitourinary system of patients of the Dnipropetrovsk Re-gional Children's Clinical Hospital "Dnepropetrovsk Regional Council". As a result of the study, the following tasks were solved: an analysis of the literature on the applica-tion of machine learning methods to diseases of the genitourinary system was made; a program was developed to extract the necessary information on statements in a semi-automatic mode; Python libraries and part of machine learning methods were analyzed; primary analysis and processing of data was carried out; applied methods of classifica-tion, feature selection and filling in missing values; the obtained results were analyzed and the substantiation of the research results in the subject area was made.

Software system of automatic identification and distributed storage of patient medical data

Ye.S. Sulema — 2023-05-11

Due to the rapid development of information technologies, informatization in the medical industry is essential. The main component of electronic health care is medical information systems designed for the accumulation, processing, analysis and transmis-sion of medical data. In the medical field, specialized software products are used to per-form diagnostic studies, process the results of laboratory tests, and make decisions at the stage of establishing a diagnosis. The use of mobile devices in medical information systems is developing. However, the degree of automation of processes in the provision of medical services and the protection of the personal and medical data of patients is still insufficient. The purpose of the research is to create a basic architecture of a software system that would simplify the process of developing software for automated input, processing, search and confidential patient access to their medical data in a medical information system based on multi-color barcoding of information using mobile devices. The architecture of the software system is proposed, in which, based on the princi-ples of distribution, anonymization, and data ownership, a patient can provide access to medical personnel to their medical data by reading a multi-color interference-resistant barcode from one smartphone (patient’s) by the camera of another smartphone (doctor’s). It is shown that in order to ensure the reliability of such transmission, it is neces-sary to use an interference-resistant barcode, which would ensure the integrity of the data in the conditions of possible distortion of the barcode image (change in lighting, scanning angle, trembling of the operator's hand, blurring or skewing of the image, etc.). The use of mobile devices for the barcode method of transmission and processing of data allows providing the protected electronic co-operating of a patient and a doctor both directly and remotely. It guarantees high reliability and confidentiality of the ex-change of data. The proposed technical solutions make it possible to improve the quality of medi-cal care and strengthen the protection of the patient's medical data.