Radio Electronics, Computer Science, Control

IMPROVED MULTI-OBJECTIVE OPTIMIZATION IN BUSINESS PROCESS MANAGEMENT USING R-NSGA-II

2023-09-28T14:37:10+03:00

Context. Business process management is a critical component in contemporary organizations for maintaining efficiency and achieving operational objectives. Optimization of these processes in terms of time and cost can lead to significant improvements in overall business performance. However, traditional optimization techniques often face challenges in handling multi-objective problems with a known time-cost trade-off, necessitating more effective solutions. The integration of a business process model and notation for a stochastic process simulation provides a robust foundation for analyzing these business processes and complies with stateof-the-art business process management. In prior studies, we applied several heuristic algorithms, including the evolutionary NSGAII, to find a Pareto-optimal set of solutions. We defined a solution as a pair of cost and time associated with a specific resource allocation. For one of the selected processes, the performance of NSGA-II was subpar compared to other techniques.

Objective. The goal of this study is to improve upon the NSGA-II’s performance and, in turn, enhance the efficiency of multiobjective business process optimization. Specifically, we aim to incorporate reference points into NSGA-II. Our goal is to identify an optimized set of solutions that represent a trade-off between process execution time and the associated cost. We expect this set to have a higher spread and other quality metrics, compared to the prior outputs.

Method. To accomplish our objective, we adopted a two-step approach. Firstly, we modified the original genetic algorithm by selecting and integrating the reference points that served to guide the search towards the Pareto-optimal front. This integration was designed to enhance the exploration and exploitation capabilities of the algorithm. Secondly, we employed the improved algorithm, namely R-NSGA-II, in the stochastic simulations of the business processes. The BPMN provided the input for these simulations, wherein we altered the resource allocation to observe the impact on process time and cost.

Results. Our experimental results demonstrated that the R-NSGA-II significantly outperformed the original NSGA-II algorithm for the given process model, derived from the event log. The modified algorithm was able to identify a wider and more diverse Pareto-optimal front, thus providing a more comprehensive set of optimal solutions concerning cost and time.

Conclusions. The study confirmed and underscored the potential of integrating the reference points into NSGA-II for optimizing business processes. The improved performance of R-NSGA-II, evident from the better Pareto-optimal front it identified, highlights its efficacy in multi-objective optimization problems, as well as the simplicity of the reference-based approaches in the scope of BPM. Our research poses the direction for the further exploration of the heuristics to improve the outcomes of the optimization techniques or their execution performance.

APPLICATION OF BLOW-UP THEORY TO DETERMINE THE SERVICE LIFE OF SMALL-SERIES AND SINGLE ITEMS

2023-09-28T14:48:09+03:00

Context. The actual task of developing a method for determining the service life of small-series and single items based on the blow-up modes theory has been solved.

Objective. Application of the blow-up theory in conditions where there are no statistical data on the dynamics of behaviour during the operation of small-series and single items.

Method. To determine the service life of a particular product manufactured in large series, information obtained for a set of similar products of the same type is used. This information is based on numerous experiments, mathematical statistics and probability theory. When operating small-series and single items, such information is not available. In this case, it is necessary to determine the individual resource of an individual product based on the results of an analysis of its behaviour in the past. The method presented in the article is based on the application for such an analysis of the method used when considering systems operating in blow-up mode. The essence of the technique is to extract the periodic component from the temporal realization of the control parameter. This component is modelled by a Fourier series consisting of log-periodic functions. The main coefficients of these functions are the time equal to the operating time of the product until the end of its service life.

Results. The method under consideration has been successfully tested in determining the service life of the transport-dumping bridge, related to products that are actually single items.

Conclusions. An analysis of the experimental data on the behaviour of the load-bearing elements of a transport-dump bridge confirms the assumption about the behaviour of the bridge structure as a system operating in a blow-up mode. This made it possible to determine in advance the service life of the power units of the bridge and obtain the result directly in units of time, without requiring information about the maximum permissible value of the controlled parameter to obtain this information.

For the first time, the possibility is shown to consider the behaviour of small-series and single items as dynamic systems operating in a blow-up mode.

Practical significance. A solution to the topical problem of determining the service life of small-series and single items is proposed.

USING ESP32 MICROCONTROLLER FOR PHYSICAL SIMULATION OF THE WIRELESS REMOTE CONTROL MODEM

2023-09-28T14:56:58+03:00

Context. Due to the need for practical implementation of the theoretical provisions of the proposed method of the wireless transmission of the commands for controlling a moving object in conditions of intentional interference.

Objective of the work is a practical verification of the possibility of using a phase-pulse modulation of the linear-frequencymodulated signal for transmission a control commands through physical modeling using microcontrollers.

Method. Analytical calculations of the change in time of the voltage at the input and output of the device for optimal processing of the linear frequency-modulated signal were carried out exclusively using the computing capabilities of the microcontroller. The graphs of changes in time of the relevant parameters were built with the help of Excel using the data output to the monitor of the serial port of the Arduino IDE software environment. A digital oscilloscope with a USB host was used to monitor the operation of a wireless modem to transmit control commands to a moving object.

Results. Analytical calculations and physical modeling using a modern microcontroller proved the operability of the lowfrequency part the wireless remote control modem with using phase-pulse modulation of the linear frequency-modulated signal.

Conclusions. The possibility of using phase-pulse modulation of the linear-frequency modulated signal for the transmission of control commands is considered. This method of transmitting the information component, unlike the existing methods, does not require changing the parameters of the linear frequency modulated signal. The use in the receiver of optimal processing of a linearfrequency-modulated signal of sufficiently big base will allow of the wireless transmission of the commands for controlling a moving object in conditions of the intentional interference. The use of modern microcontrollers made it possible to conduct a practical test of the functionality of the low-frequency part the wireless remote control modem with phase-pulse modulation of the linear-frequency modulated signal through physical modeling.

POWER SUPPLY OF RING ANTENNA USING DIRECTIONAL COUPLERS

2023-09-25T23:29:11+03:00

Context. The circular polarization of radio waves is used in various electronic systems. This includes, for example, space communications stations, some radio relay communication systems, radar stations, data transmission systems and others. The characteristics of radio wave propagation are studied by using electromagnetic waves separated by circular orthogonal polarization in radiomonitoring and radiocontrol systems. Compared to other antenna types, circularly polarized antennas, such as rings, have superior design simplicity and excellent electrodynamics properties.

Objective. The objective of this study is to analyse the characteristics and application of directional microstrip couplers for supplying power to ring antennas.

Method. To better the performance of microstrip ring antennas, the reasons for their limited operating frequency range are analysed. These causes include the frequency-dependent parameters of the coupler, errors in calculating the directional coupler circuit, and radiation from asymmetric strip lines. To understand how supply lines, affect antenna characteristics, correlations between radiation fields determined in both its coordinate system and that of the primary axis are taken into account.

Results. An analysis of the dependence graphs of the main characteristics of ring microstrip antennas with intricate power supply circuits for directional couplers and comparison with similar characteristics for simple circuits revealed that the shape of the radiation pattern in the higher radiation hemisphere became symmetrical about the axis, especially when symmetrically supplying the ring with branch-line couplers. The frequency band has also widened, at which there was an acceptable degree of deviation in the ellipticity coefficient from unity.

Conclusions. The simulation results of microstrip ring antennas with power lines connected to directional couplers of different types showed that supplying the ring antenna with electricity via the directional coupler ensures circular polarization for the emitted electromagnetic waves. Additionally, the range of operating frequencies where there is only a small discrepancy in ellipticity coefficient remains at an acceptable level of –3 dB is quite broad. By utilizing directional branch-line couplers to power a ring antenna, it is possible to simultaneously emit both right and left circularly polarized waves with the same antenna.

MATHEMATICAL MODEL OF THE CURRENT TIME FOR THREE-FRAGMENT RADAR SIGNAL WITH NON-LINEAR FREQUENCY MODULATION

2023-09-26T13:17:39+03:00

Context. The authors of the article have developed a new mathematical model that allows taking into account frequency and phase distortions that occur in a three-fragment signal during the transition from one fragment to another, when the rate of frequency modulation of the signal changes. The object of research is the process of formation and processing of radar non-linear frequency modulation signals.

Objective. The purpose of the work is to develop and research a mathematical model of current time for a signal with non-linear frequency modulation, which consists of three linear frequency modulated fragments.

Method. The article provides a theoretical justification of the need to develop a mathematical model in the current time for a three-fragment signal with non-linear frequency modulation, capacity for work of the created model is demonstrated on the example of several radio signals that differ in frequency parameters. With the same signal parameters, the obtained results were compared with the results of the known model, for which known methods of spectral and correlation analysis were used. A distinctive feature of the proposed model is the consideration of jumps in the instantaneous frequency and phase of the signal that occur during the transition from one linear-frequency modulated fragment to the next. Such jump-like changes in frequency and phase in known models of signals with non-linear frequency modulation are not compensated for, which causes distortion of their spectra and an increase the side lobes level of auto-correlation (mutual-correlation) functions.

Results. A comparative check of the developed and known signal models indicates a decrease the side lobes level of the autocorrelation function by 3 dB or more, depending on the given frequency-time parameters.

Conclusions. The application of the proposed mathematical model makes it possible to form and process radar signals, which include three linear-frequency modulated fragments. Compensation of jump-like changes in frequency and phase leads to a decrease in the degree of distortion of the spectrum and, as a result, an increase in its effective width, which ensures a narrowing of the main lobe and a decrease the side lobes level of the auto-correlation function.

ENERGY EFFICIENCY RESEARCH OF LPWAN TECHNOLOGIES

2023-09-27T17:25:53+03:00

Context. The emergence of the Internet of Things (IoT) has led to the development of various low-power wide area network (LPWAN) technologies that are designed to provide transmission of small data packets over long distances with minimal energy consumption. The two most well-known LPWAN technologies are LoRaWAN and Sigfox. This study aims to compare the energy efficiency of these two technologies to determine their suitability for use in autonomous solutions.

Objective. The objective of this study is to compare the energy efficiency of LoRaWAN and Sigfox technologies for IoT devices. The comparison will help determine which technology is better for autonomous solutions when devices need to operate for extended periods of time without frequent battery replacements.

Method. In this work, taking into account the specifications of the investigated radio technologies, mathematical modeling of the time of data transmission or reception is used depending on the payload, and information on the power supply current is taken from official datasheets for the components of the investigated devices.

Results. The results of the study show that both LoRaWAN and Sigfox are energy-saving technologies, but LoRaWAN is generally more energy-efficient than Sigfox. In addition, LoRaWAN has adaptive modes and significantly more manual settings, which in some cases further reduces the energy per bit of data compared to Sigfox.

Conclusions. LoRaWAN is the best choice for autonomous solutions where energy efficiency is crucial. This study provides valuable information for designers and developers of IoT devices, allowing them to make informed decisions when choosing LPWAN technologies for their autonomous solutions.

A METHOD FOR SYNTHESIS OF HIGH PRECISION RADIO TRACKING SYSTEMS WITH SPLIT CONTROL AND FILTERING PROCEDURES

2023-09-27T17:49:26+03:00

Context. In combined automatic control systems (ACS) with the principle of control by disturbance, there are difficulties in controlling disturbances in some objects of radio engineering systems and somewhat lower accuracy. This is especially noticeable when the object is affected by several equal disturbances. Taking them into account requires increasing the complexity and reducing the reliability of the ACS. And neglect sharply reduces the accuracy of the system. Therefore, there is a need to develop a method of synthesis of radio technical tracking systems that eliminates the indicated shortcomings.

Objective. The article presents a synthesis method for high precision radio tracking systems, which are equivalent to combined systems with split control and filtering procedures when the entry useful (preset) action, which is not measured and external disturbances and interferences are present simultaneously.

Method. Methods of automatic control theory were used to achieve the goal of the research.

Results. It has been demonstrated that there is a conflict between the conditions for split synthesis of the evaluation (smoothing) filter and the control filter (regulator) in automatic tracking control systems operating with deviation.

The article offers a solution to the problem of control and evaluation in the framework of two-circuit systems, which are equivalent to combined systems. The second circuit can be presented as a product of a reverse transfer function with an error in the first circuit to the transfer function of Controller, which has a positive feedback from the operator, as well as the reverse transfer function of the control object without integrating links. It is proposed to use for evaluation an evaluation filter with closed filter transfer function instead of an open regulator.

The characteristic polynomial of a two-circuit automatic control system (ACS) excludes the influence of the stable second-circuit evaluation filter on the stability of the entire ACS. The polynomial of the numerator of the transfer function must have the difference of polynomials by error, which ensures the achievement of invariance.

A double-circuit ACS is equivalent to a combined one, since it provides the following: invariance of the error with respect to the preset action without directly measuring it; stability of the first circuit with a stable second circuit.

The synthesized double-circuit ACS is equivalent to a combined one. The author has calculated and constructed the evaluation filter, the influence of this filter on ACS astatism (i. e., on its accuracy) has been analyzed.

Conclusions. The scientific novelty of the developed method of synthesis of high-precision automatic tracking systems with separate control and filtering procedures in conditions where the controlled value is not measured in the presence of disturbances is as follows. Equivalence to combined systems, in contrast to the methods of differential connections, is achieved not by three, but by two control loops. The practical significance lies in the fact that the proposed method is advisable to use for the construction of surveillance radio engineering systems, where the input useful effect is not measured in the presence of external influences and disturbances. In aircraft control systems.

TEST GRAPH-SCHEMES OF THE ALGORITHMS OF FINITE STATE MACHINES WORK FOR ASSESSING THE EFFICIENCY OF AUTOMATED SYNTHESIS IN XILINX VIVADO CAD

2023-09-28T12:40:39+03:00

Context. The problem of evaluating the effectiveness of the automated design of a microprogram finite state machine with the operational transformation of state codes using Xilinx Vivado CAD is considered. The object of the research was graph-schemes of control algorithms implemented by finite state machine and able to prove the effectiveness of the principle of operational transformation of state codes in comparison with standard synthesis methods built into the CAD, in the context of hardware expenses optimization.

Objective. Development and research of graph-schemes of control algorithms in order to substantiate the effectiveness of the application of structure of the finite state machine with datapath of transitions in comparison with the built-in methods of synthesizing finite state machines in Xilinx Vivado CAD in the basis of programmable logic devices.

Method. The research is based on the hypothetical assumption that the Xilinx Vivado CAD has built-in methods of automated design of the circuit of a finite state machine, the effectiveness of which, according to the criterion of hardware expenses, exceeds other known methods of optimizing hardware expenses in the finite state machine circuit. In order to refute this hypothesis, it is proposed to prove that in some cases known methods of hardware expenses optimization in the finite state machine circuit are more effective in comparison with the methods built into CAD. In this work, as a well-known optimization method, the method of operational transformation of state codes, which corresponds to the structure of a finite state machine with datapath of transitions, is chosen. The effectiveness of this method is demonstrated on the example of several test graph-schemes of algorithms, the structure of which is abstract and artificially adapted to the chosen optimization method. The adaptation of the selected graph-schemes of the algorithms consists in the fact that a relatively small number of transition operations is required for their implementation with the help of a finite state machine with datapath of transitions. This contributes to the simplification of the circuit of the finite state machine and the reduction of hardware costs for its implementation. At the same time, the test graph-schemes of the algorithms have the possibility of scaling, which allows to automate the construction of VHDL models of the corresponding finite state machines for graph-schemes of different sizes and to evaluate the optimization of hardware expenses for finite state machines of different complexity.

Results. Using the example of several graph-schemes of algorithms, it is demonstrated that in some cases none of the finite state machine synthesis methods built into the Xilinx Vivado CAD is able to surpass the method of operational transformation of state codes according to the criterion of hardware expenses for the implementation of a finite state machine circuit. At the same time, a several-fold gain in hardware expenses can be achieved, which indicates the expediency of using this method under certain conditions. The formal definition of such conditions for the considered and other known optimization methods is a separate unsolved scientific problem.

Conclusions. The conducted experiments confirmed that in some cases, the known methods of synthesis of finite state machines allow to obtain circuits with lower hardware expenses than when using the methods of synthesis of finite state machines contained in Xilinx Vivado CAD. This testifies to the general expediency of using existing and developing new methods of hardware expenses optimization in the circuit of the finite state machines and the current relevance of the theory of the synthesis of digital automata as a scientific direction.

INFORMATION TECHNOLOGY OF FORMING THE EDUCATIONAL NETWORK OF THE TERRITORIAL COMMUNITY

2023-09-28T12:56:43+03:00

Context. Local government organizations have significant decision-making power in the field of education. This requires the development of understandable tools that help form a network of educational institutions that provide high-quality educational services. The object of the study was the process of forming an educational network (ENW) of the community in the implementation of territorial development projects as part of the reform of local self-government.

Objective. The goal of the work is to increase objectivity of decisions made in the formation of the ENW territorial community, summarizing demographic, infrastructural, personnel, economic factors when choosing the location of ENW facilities.

Method. The study of the classical placement problem and its further adaptation to real problems arising from the implementation of the education reform made it possible to represent ENW territorial communities as a set of independent complete bipartite graphs. In this case, to solve the problem of choosing the location of an educational institution on the network, an information technology (IT) was developed to form an ENW territorial community. Based on the adapted p-median model and methods of geospatial analysis, generalizing the requirements of the current legislation, a set of input and output parameters of IT and a set of its operations are formed. The representation of the IT structure in the form of an IDEF0-model clearly explains how a combination of various factors is processed and generalized when making decisions while creating ENW and looking for ways to improve it.

Results. The developed IT was investigated in solving the problem of forming a network of lyceums in the Kharkiv region using geospatial information, open statistical data and data on lyceums. The proposed accommodation options make it possible to achieve a general level of accessibility of specialized secondary education of almost 94%. IT has additional tools for solving the problems of transporting students to the place of study and home.

Conclusions. The experiments carried out confirmed the operability of the proposed IT. The generalization of the results obtained makes it possible to recommend it for practical use in solving the problems of analyzing the current state of ENW, finding ways to improve it and possible directions for development, as well as evaluating solutions related to the spatial planning of ENW.

ON THE RECURSIVE ALGORITHM FOR SOLVING THE TRAVELING SALESMAN PROBLEM ON THE BASIS OF THE DATA FLOW OPTIMIZATION METHOD

2023-09-28T13:14:13+03:00

Context. The article considers a technique for the sequential application of flow schemes for distributing a homogeneous resource for solving the traveling salesman problem, which is formulated as the problem of finding a route to visit a given number of cities without repetitions with a minimum duration of movement. The task of formalizing the algorithm for solving the traveling salesman problem by the method of streaming resource distribution using the backtracking scheme is posed. The use of Orlin’s method to optimize the flow distribution on the graph is proposed.

Objective. The goal of the work is to develop an algorithm for solving the traveling salesman problem based on the implementation of the method of streaming resource distribution and the backtracking scheme with the minimum duration of movement along the route.

Method. This paper proposes a method for solving the traveling salesman problem by the method of streaming resource distribution with the backtracking scheme. A scheme for formalizing the procedure for solving the traveling salesman problem with the minimum duration of movement along the route is described. A variant of accelerating the speed of the developed algorithm is proposed, which consists in using a greedy technique in the procedure for selecting route sections: planning each subsequent stage of movement is determined based on the choice of the fastest direction of movement. The results of the proposed algorithm for calculating solutions to the traveling salesman problem with minimization of the duration of movement are presented, the obtained solutions are compared with the solutions found by other exact and heuristic methods.

Results. The method for solving the traveling salesman problem using the method of streaming resource allocation and using the backtracking scheme is developed. A variant of accelerating the speed of the developed algorithm is proposed, which consists in using a greedy technique in the procedure for selecting route sections: planning each subsequent stage of movement is determined based on the choice of the fastest direction of movement. The application of the greedy approach makes it possible to obtain a constructive scheme for solving the traveling salesman problem. The results of the proposed algorithm for calculating solutions to the traveling salesman problem with minimization of the duration of movement are presented, the obtained solutions are compared with the solutions found by other exact and heuristic methods.

Conclusions. The paper considers a method for formalizing the algorithm for solving the traveling salesman problem using the method of streaming resource allocation and the backtracking scheme. The use of Orlin’s method to optimize the flow distribution on the graph is proposed. The scheme of formalization of the procedure for using the method with the implementation of the backtracking scheme for solving the traveling salesman problem with the minimum duration of movement along the route is briefly described. A variant of accelerating the speed of the developed algorithm is proposed.

PERFORMANCE ANALYSIS OF WIRELESS COMPUTER NETWORKS IN CONDITIONS OF HIGH INTERFERENCE INTENSITY

2023-09-28T13:27:23+03:00

Context. The decrease in the probability of successful frame transmission in the infrastructure domain of IEEE 802.11 DCF wireless network is caused both by the influence of the collision intensity and by the impact of external interference in the radio path. Using the Markov chain approach as a baseline, we explicitly expressed the dependence of the network throughput on the number of operating stations, bit error rate (BER), and the frame fragmentation factor.

Objective. The purpose of this article is to study the influence of interference intensity on the throughput of a wireless network domain in a wide range of the number of operating stations when transmitting frames of various lengths in the absence and with the use of the fragmentation mechanism.

Method. The performed mathematical modelling showed, that in the range of increased and high noise intensity (BER = 10–5 – 10–4), a decrease in the length of the frame data field from the standard length of 12000 bits to 3000 bits is accompanied by a decrease in the throughput for all values of the number of competing stations. At the same time, it must be noted that as the amount of the frame data decreases, the throughput becomes less susceptible to an increase in the noise intensity. Qualitatively different results are obtained in the region of very high interference intensity (BER = 2·10–4). A significant increase in the probability of frame transmission in this region observed with a decrease in the standard length of the frame data field by 2–3 times, made it possible to increase the throughput compared to the original one. This effect is especially pronounced when the length is halved.

Results. The study of the standard frame transmitting process, but with a fragmented data field, showed that if for BER = 5·10–5 and less with an increase in fragmentation factor, the throughput values decrease, in the entire range of the number of stations due to the predominant increase in overhead costs, then in the region of high (BER = 10–4) and very high noise intensity (BER = 2·10–4) we have the opposite effect. To the greatest extent, the throughput increases when the frame data is transmitted in two equal fragments. We have made a comparison of the network throughput determined by simply reducing the length of the frame data field and using fragmentation of a standard frame. The comparison showed that the use of the fragmentation mechanism is more beneficial both when throughput is stabilized under conditions of increased noise intensity and when the throughput is increased under conditions of high and very high noise intensity.

Conclusions. In this article, a mathematical model has been modified for direct calculation of the wireless network throughput. Using this model, we studied the changes in throughput over a wide range of BER and a number of operation stations for various values of the transmitted frame fragmentation factor. The conditions for increasing the throughput are determined.

MODIFIED GENETIC ALGORITHM APPROACH FOR SOLVING THE TWO-STAGE LOCATION PROBLEM

2023-09-28T13:44:29+03:00

Context. Optimization of logistics processes is one of the important tasks of supply chain management in various fields, including medicine. Effective coordination in medical logistics is essential to ensure public health and prosperity. This is especially essential during global emergencies when the rapid and efficient distribution of medicines is critical. In addition, professional logistics management is critical to delivering humanitarian aid, where the timely transportation of medical supplies and resources can be lifesaving. The most advanced technologies and algorithms are being used to improve medical logistics processes. This paper considers modifying the genetic algorithm for solving the two-stage location problem in supply chain management in the distribution of medicines and medical equipment.

Objective. The work aims to build a model and develop an algorithm for solving a two-stage location problem in the context of the medical logistics problem with further analysis of their applications and performance.

Method. We propose to use a genetic algorithm to solve a two-stage logistics problem. The peculiarities of this algorithm are the modification of evaluation procedures and the use of mixed mutation, which allows for solving the problem effectively, considering irregularities in the statement regarding the subject – the limits on the centers’ location at several stages of the logistic process.

Results. The paper deals with a two-stage location problem with constraints on the maximum number of centers. Considering the specific requirements of medical logistics in the transportation context of medicines and medical equipment, a mathematical model and modification of the genetic algorithm are proposed. The developed algorithm is tested on model tasks and can produce effective solutions for problems ranging in size from 25 to 1000. The solution process takes longer for larger problems with dimensions from 1001 to 2035. Additionally, the influence of increasing the maximum generations number on the time of execution is investigated. When the maximum generation value increases from 50 to 100 and from 100 to 150 generations, the algorithm’s execution time increases by 45.69% and 51.68%, respectively. 73% of the total execution time is dedicated to the evaluation procedure. The algorithm is applied to the medical logistics problem in the Dnipropetrovsk region (Ukraine). An efficient solution is obtained within an acceptable execution time.

Conclusions. A mathematical model for a two-stage location problem in the context of medical logistics is introduced. It considers the peculiarities of the medical field. A solution algorithm based on a genetic approach is developed and applied to the medical logistics problem. The algorithm has been tested on model tasks of varying sizes, with a comprehensive analysis conducted on the correlation between the problem size and the algorithm’s running time. In addition, it is investigated how the maximum number of generations affects the algorithm’s execution time. The role of each stage in the genetic algorithm research towards the overall effectiveness of the algorithm is researched. The obtained results indicate high efficiency and wide application possibilities of the proposed mathematical model and algorithm. The developed method demonstrates high performance and reliability.

USER EVALUATION-DRIVEN RANKING CONCEPT

2023-09-28T13:59:47+03:00

Context. The problem of personalizing search engine results, empowering users with search result management tools and developing new ranking models based on user’s subjective information needs. The object of the study was to modeling information search results in the Internet based on user ratings.

Objective. The goal of the work is to form unique expert groups for each user, based on calculating the measure of agreement between the current user’s opinions and potential experts.

Method. Introducing a novel method for ranking search results based on user ratings, which takes a subjective approach to the ranking process. This approach involves the formation of distinct expert groups tailored to individual users. Experts are selected based on the level of agreement between their opinions and the current user, determined by shared ratings on a specific set of web resources. User selection for the expert group is based on their weight relative to the current user, serving as a measure of agreement.

The proposed methodology offers a fresh approach to forming unique expert groups for each user, utilizing three different strategies depending on the presence of shared ratings on a particular set of web resources between the user and potential experts.

The developed ranking method ensures that each user receives a personalized list of web resources with a distinct order. This is accomplished by incorporating unique ratings from the expert group members associated with each user. Furthermore, each rating contributes to the ranking model of web resources with an individual weight, calculated based on an analysis of their past system activity.

Results. The developed methods have been implemented in software and investigated for complex web data operation in real time.

Conclusions. The conducted experiments have confirmed the effectiveness of the proposed software and recommend its practical use for solving complex web data operation in real time. Prospects for further research may include optimizing software implementations and conducting experimental investigations of the proposed methods on more complex practical tasks of various nature and dimensions

RECOGNITION OF REFERENCE SIGNALS AND DETERMINATION OF THEIR WEIGHTING COEFFICIENTS IF AN ADDITIVE INTERFERENCE PRESENTS

2023-09-27T22:13:28+03:00

Context. The subject matter of the article is the recognition of a reference signal in the presence of additive interference.

Objective. The recognition of the reference signal by the obtained value of its weighting factor in conditions where additive interference is imposed on the spectrum of the reference signal at unknown random frequencies. The task is the development of a method for recognizing a reference signal for the case when the interference consists of an unknown periodic signal that can be represented by a finite sum of basis functions. In addition, interference may also include deterministic signals from a given set with unknown weighting coefficients, which are simultaneously transmitted over the communication channel with the reference signal.

Method. The method of approximating the unknown periodic component of the interference by the sum of basis functions is used. The current number of values of the signal that enters the recognition system depends on the number of basis functions. This signal is the sum of the basis functions and the reference signal with unknown weighting coefficients. To obtain the values of these coefficients, the method based on the properties of the disproportion functions is used. The recognition process is reduced to the calculation of the weight coefficient of the reference signal. If it is zero, it indicates that the reference signal is not part of the signal being analyzed. The recognition system is multi-level. The number of levels depends on the number of basis functions.

Results. The obtained results show that, provided that the reference signal differs by at least one component from the given set of basis functions, the recognition is successful. The given examples show that the system recognizes the reference signal even in conditions where the weighting coefficient of the interference is almost 1000 times greater than the coefficient for the reference signal. The recognition system also works successfully in conditions where the interference includes the sum of deterministic signals from a given set, which are simultaneously transmitted over the communication channel.

Conclusions. The scientific novelty of the obtained results is that a method for recognizing the reference signal has been developed in conditions where only an upper estimate of its maximum frequency is known for the periodic component of the interference. Also, recognition occurs when, in addition to unknown periodic interference, the signals from a given set with unknown weighting coefficients are superimposed on the reference signal. In the process of recognition, in addition to the weighting factor for the reference signal, the factors for the interference components are also obtained.

K-NN’S NEAREST NEIGHBORS METHOD FOR CLASSIFYING TEXT DOCUMENTS BY THEIR TOPICS

2023-09-27T22:30:19+03:00

Context. Optimization of the method of nearest neighbors k-NN for the classification of text documents by their topics and experimentally solving the problem based on the method.

Objective. The study aims to study the method of nearest neighbors k-NN for classifying text documents by their topics. The task of the study is to classify text documents by their topics based on a dataset for the optimal time and with high accuracy.

Method. The k-nearest neighbors (k-NN) method is a metric algorithm for automatic object classification or regression. The k-NN algorithm stores all existing data and categorizes the new point based on the distance between the new point and all points in the training set. For this, a certain distance metric, such as Euclidean distance, is used. In the learning process, k-NN stores all the data from the training set, so it belongs to the “lazy” algorithms since learning takes place at the time of classification. The algorithm makes no assumptions about the distribution of data and it is nonparametric. The task of the k-NN algorithm is to assign a certain category to the test document x based on the categories k of the nearest neighbors from the training dataset. The similarity between the test document x and each of the closest neighbors is scored by the category to which the neighbor belongs. If several of k’s closest neighbors belong to the same category, then the similarity score of that category for the test document x is calculated as the sum of the category scores for each of these closest neighbors. After that, the categories are ranked by score, and the test document is assigned to the category with the highest score.

Results. The k-NN method for classifying text documents has been successfully implemented. Experiments have been conducted with various methods that affect the efficiency of k-NN, such as the choice of algorithm and metrics. The results of the experiments showed that the use of certain methods can improve the accuracy of classification and the efficiency of the model.

Conclusions. Displaying the results on different metrics and algorithms showed that choosing a particular algorithm and metric can have a significant impact on the accuracy of predictions. The application of the ball tree algorithm, as well as the use of different metrics, such as Manhattan or Euclidean distance, can lead to improved results. Using clustering before applying k-NN has been shown to have a positive effect on results and allows for better grouping of data and reduces the impact of noise or misclassified points, which leads to improved accuracy and class distribution.

CREDIBILISTIC ROBUST ONLINE FUZZY CLUSTERING IN DATA STREAM MINING TASKS

2023-09-27T22:52:43+03:00

Context. The task of clustering-classification without a teacher of data arrays occupies an important place in the general problem of Data Mining, and for its solution there exists currently many approaches, methods and algorithms. There are quite a lot of situations where the real data to be clustered are corrupted with anomalous outliers or disturbances with non-Gaussian distributions. It is clear that “classical” methods of artificial intelligence (both batch and online) are ineffective in this situation. The goal of the paper is to develop a credibilistic robust online fuzzy clustering method that combines the advantages of credibilistic and robust approaches in fuzzy clustering tasks.

Objective. The goal of the work is online credibilistic fuzzy clustering of distorted data, using of credibility theory in data stream mining.

Method. The procedure of fuzzy clustering of data using credibilistic approach based on the use of both robust goal functions of a special type, insensitive to outliers and designed to work both in batch and its recurrent online version designed to solve Data Stream Mining problems when data are fed to processing sequentially in real time.

Results. Analyzing the obtained results overall accuracy of clustering methods and algorithm, proposed method similar with result of credibilistic fuzzy clustering method, but has time superiority regardless of the number observations that fed on clustering process.

Conclusions. The problem of fuzzy clustering of data streams contaminated by anomalous non-Gaussian distributions is considered. A recurrent credibilistic online algorithm based on the objective function of a special form is introduced, which suppresses these outliers by using the hyperbolic tangent function, which, in addition to neural networks, is used in robust estimation tasks. The proposed algorithm is quite simple in numerical implementation and is a generalization of some well-known online fuzzy clustering procedures intended for solving Data Stream Mining problems.

SENTIMENT ANALYSIS TECHNOLOGY FOR USER FEEDBACK SUPPORT IN E-COMMERCE SYSTEMS BASED ON MACHINE LEARNING

2023-09-27T23:15:40+03:00

Context. The interaction between a company and its target audience has been studied for centuries. From the very beginning of commercial relations, the relationship between the service provider and the recipient has been valued almost above all else. Trade is built on trust and respect. The image of an entrepreneur is often more important than the product he sells. For hundreds of years, the relationship between the merchant and the buyer, the entrepreneur and the client has not lost its importance, and in the era of mass digitalization, the quality of the relationship between the company and the target audience of different sizes and professional feedback support with clients often start the success of e-business. To provide these additional tools and information technologies to help businessmen monitor e-business development opportunities in a specific location, as well as establish feedback with users through social networks and mass media. Obtaining such tools will significantly expand the vision of market opportunities for ebusiness, it will clarify which of them make sense to invest in, and which ones are not worth paying time for. Also see what idea has the future and what business model needs to be implemented/maintained/developed for the rapid development of territorial/interregional e-business. It will also help to understand which levers have the greatest effect for business changes: what not to touch, and what policies to change to ensure high speed in the implementation of the plan based on the analysis of relevant research results, for example, to receive: direct feedback from customers, the dynamics of changes in overall satisfaction or interest of the target audience and advantages/disadvantages from users using NLP analysis; support for the development of e-business in relation to the location of their enterprise and the best directions; – graphs of business development (improvement/deterioration) depending on the content of comments.

Objective of the study is to develop information technology to support the development of e-business by analyzing business locations, processing feedback from users, analyzing and classifying customer feedback in real time from social networks: Twitter, Reddit, Facebook and others using deep learning and Natural methods. Language Processing of Ukrainian-speaking and Englishspeaking texts.

Method. NLP-methods were used to analyze the opinions of users and customers. Among the methods of implementing the main functions of English-language news classification, the following machine learning methods are used: naive Bayesian classifier, logistic regression, and the method of support vectors. The Naive Bayes algorithm was used to classify Ukrainian-language user feedback, as it performs well on small amounts of data, is easy to train and operate, and works well with text data. Naive Bayes classifier is a very good option for our system and considering that the number of responses in the dataset is smaller compared to the averages.

Results. A machine learning model was developed for the analysis and classification of Ukrainian- and English-language reviews from users of e-commerce systems.

Conclusions. The created model shows excellent classification results on test data. The overall accuracy of the sentimental model for the analysis of Ukrainian-language content is quite satisfactory, 92.3%. The logistic regression method coped best with the task of analyzing the impact of English-language news on the financial market, which showed an accuracy of 75.67%. This is certainly not the desired result, but it is the largest indicator of all considered. The support vector method (SVM) coped somewhat worse with the task, which showed an accuracy of 72.78%, which is a slightly worse result than the one obtained thanks to the logistic regression method. And the naïve Bayesian classifier method did the worst with the task, which achieved an accuracy of 71.13%, which is less than the two previous methods.

GENERALIZED FRACTIONAL GAUSSIAN NOISE PREDICTION BASED ON THE WALSH FUNCTIONS

2023-09-27T19:09:04+03:00

Context. Some of the authors’ recent papers were devoted to the Kolmogorov-Wiener filter for telecommunication traffic prediction in some stationary models, such as the fractional Gaussian noise model, the power-law structure function model, and the GFSD (Gaussian fractional sum-difference) model. Recently, the so-called generalized fractional Gaussian noise model was proposed for stationary telecommunication traffic description in some cases. So, in this paper the theoretical fundamentals of the continuous Kolmogorov-Wiener filter used for the prediction of the generalized fractional Gaussian noise are investigated.

Objective. The aim of the work is to obtain the filter weight function as an approximate solution of the corresponding Wiener– Hopf integral equation with the kernel equal to the generalized fractional Gaussian noise correlation function.

Method. A truncated Walsh function expansion is proposed in order to obtain the corresponding solution. This expansion is a special case of the Galerkin method, in the framework of which the unknown function is sought as a truncated series in orthogonal functions. The integral brackets and the results for the mean absolute percentage errors, which are a measure of discrepancy between the left-hand side and the right-hand side of the Wiener-Hopf integral equation, are calculated numerically on the basis of the Wolfram Mathematica package.

Results. The investigation is made for approximations up to sixty four Walsh functions. Different model parameters are investigated. It is shown that for different model parameters the proposed method is convergent and leads to small mean absolute percentage errors for approximations of rather large numbers of Walsh functions.

Conclusions. The paper is devoted to a theoretical construction of the continuous Kolmogorov-Wiener filter weight function for the prediction of a stationary random process described by the generalized fractional Gaussian noise model. As is known, this model may give a good description of some actual telecommunication traffic data in systems with packet data transfer. The corresponding weight function is sought on the basis of the truncated Walsh function expansion method. The corresponding discrepancy errors are small and the method is convergent.

GROWING TREE METHOD FOR OPTIMISATION OF MULTIFACTORIAL EXPERIMENTS

2023-09-27T19:27:27+03:00

Context. The task of planning multifactorial experiments is important in science and industrial production. In the context of competition, rising costs, and increasing efficiency, it is necessary to optimize plans for multifactorial experiments in terms of cost and time. To solve this problem, there are a number of approaches and methods, the choice of which for a competitive technical task is an important and difficult task. In this regard, there is a need to develop new methods for optimizing the cost (time) of multifactorial experiment plans, compare them with existing methods, and give recommendations for practical application in the study of real objects.

Objective. The purpose of the study is to develop and test the method of growing trees, to evaluate its effectiveness in comparison with other methods. The following tasks has been solved to achieve this goal: the proposed method of growing trees has been implemented in the form of software; the method has been used to optimize plans for multifactorial experiments in the study of real objects; its effectiveness has been evaluated in comparison with other methods; recommendations for its use were given.

Method. The proposed method of growing trees is based on the application of graph theory. The advantage of the method is the reduction of time for solving optimization problems related to the construction of optimal plans for multifactorial experiments in terms of cost (time) expenses. Another characteristic feature is the high accuracy of solving optimization problems.

Results. The results of experiments and comparisons with other optimization methods confirm the efficiency and effectiveness of the proposed method and allow us to recommend it for the study of objects with the number of significant factors k ≤ 7. It is promising to further expand the range of scientific and industrial objects for their study using this method.

Conclusions. A growing tree method has been developed for the optimization of multifactorial experimental plans in terms of cost and time expenditures, along with software that implements it using the Angular framework and the TypeScript programming language.

The effectiveness of the growing tree method is shown in comparison with the following methods: complete and limited enumeration, monkey search, modified Gray code application, and bacterial optimization. The growing tree method is faster than complete enumeration and can be applied to optimize multifactorial experimental plans in terms of cost (time) expenses for objects with a number of factors k ≤ 7. In solving optimization problems, the method of growing trees gives better results compared to monkey search, limited enumeration and bacterial optimization.

POLYNOMIAL ESTIMATION OF DATA MODEL PARAMETERS WITH NEGATIVE KURTOSIS

2023-09-27T21:51:19+03:00

Context. The paper focuses on the problem of estimating the center of distribution of the random component of experimental data for density models with a negative kurtosis.

Objective. The goal of this research is to develop methods to improve the efficiency of polynomial estimation of parameters of experimental data with a negative kurtosis coefficient.

Method. The study applies a relatively new approach to obtaining estimates for the center of the probability distribution from the results of experimental data with a stochastic component. This approach is based on polynomial estimation methods that rely on the mathematical apparatus of Kunchenko's stochastic polynomials and the description of random variables by higher-order statistics (moments or cumulants). A number of probability density distributions with a negative kurtosis coefficient are used as models of the random component.

As a measure of efficiency, the ratio of variance of the estimates for the center of the distribution found using polynomial and classical methods based on the parameter of amount of information obtained is used.

The relative accuracy of polynomial estimates in comparison with the estimates of the mean, median and quantile estimates (center of curvature) is researched using the Monte Carlo method for multiple tests.

Results. Polynomial methods for estimating the distribution center parameter for data models of probability distribution density with a negative kurtosis coefficient have been constructed.

Conclusions. The research carried out in this paper confirms the potentially high efficiency of polynomial estimates of the coordinates of the center of the experimental data, which are adequately described by model distributions with a negative kurtosis. Statistical modeling has confirmed the effectiveness of the obtained estimates in comparison with the known non-parametric estimates based on the statistics of the mean, median, and quantile, even with small sample sizes.