Visnik of the Volodymyr Dahl East Ukrainian National University

Study of the influence of laser radiation adsorbers on the ablation of carbon fiber-reinforced plastic by femtosecond laser pulses

2025-08-03T14:36:58+00:00

Carbon fiber-reinforced plastics (CFRPs) have gained popularity due to their advantageous properties, including a high strength-to-weight ratio, resistance to chemicals, and design flexibility. However, the processing of these composite materials remains challenging due to the heterogeneity between carbon fibers and the polymer matrix. Laser ablation, particularly with ultrafast femtosecond lasers, has emerged as a promising technique for the precise machining of CFRPs. Advantages of this technique include minimal thermal damage and improved ablation precision. However, disparities in ablation rates between the epoxy matrix and carbon fibers frequently impede process efficiency. The present study investigates the use of hydroxyapatite-based additives to enhance laser–material interaction and optimize the ablation behavior of CFRP systems. Specifically, copper-substituted hydroxyapatite (Cu-HAp) microparticles, which are known for their strong absorption in the near-infrared (NIR) region around 1030 nm, were synthesized and introduced into the epoxy matrix. Calcium hydroxyapatite (Ca-HAp), a thermally stable and biocompatible ceramic with low NIR absorption, was utilized as a reference to assess the specific contribution of copper ions. Epoxy composites with 5 wt.% of various filler compositions (100% Cu-HAp, 75% Cu-HAp/25% Ca-HAp, and 50% Cu-HAp/50% Ca-HAp) were prepared and incorporated into CFRP laminates. Femtosecond laser ablation at 1030 nm was performed under optimized conditions for each sample type, followed by evaluation of the resulting surface morphology using optical profilometry and SEM. The findings indicated that the incorporation of Cu-HAp fillers promoted enhanced energy absorption, thereby facilitating more efficient ablation with reduced thermal damage in comparison to unmodified epoxy and Ca-HAp-filled systems. Replacing Cu-HAp with Ca-HAp increased the required laser fluence and energy input. This indicates that copper ions enhance localized heating and energy coupling. SEM imaging showed that Cu-HAp particles had a porous, aggregated morphology that redistributed thermal energy, while Ca-HAp had denser, more homogenous filler structures with reduced porosity. This work shows the potential of Cu-HAp as a functional additive to adjust how femtosecond laser radiation interacts with composite materials and improve micromachining outcomes. The findings support the feasibility of using NIR-absorbing ceramic fillers to deal with common issues associated with laser processing of CFRPs, including heat-affected zones and ablation inhomogeneity.

Liquid-repellent infused surfaces: a review of current trends and prospects

2025-08-05T11:57:23+00:00

The article presents a comprehensive overview of the current state of research in the field of liquid-infused surfaces (LIS), which represent a promising direction in the development of functional coatings with tunable wetting properties. Based on the analysis of recent literature, the key physicochemical principles underlying the formation of infused surfaces are considered, including the presence of a stable lubricant layer retained in a capillary-active porous or textured matrix, the surface energy of the solid substrate, and interfacial interaction mechanisms. The properties of liquid-infused surfaces (LIS) are compared with those of traditional superhydrophobic coatings, particularly in terms of durability, stability under aggressive conditions, as well as self-cleaning, anti-corrosion, and anti-icing performance.

The article systematizes modern approaches to the fabrication of LIS based on both hydrophobic and hydrophilic textures with subsequent infusion of chemically compatible lubricants. Special attention is paid to the use of advanced materials such as polymers, nanostructured metal oxides, and biocompatible lubricating fluids that ensure both functionality and environmental safety of the coatings. The development of adaptive surfaces capable of dynamically altering their properties in response to external stimuli—such as light, temperature, or magnetic field—is also considered. The study highlights key challenges in ensuring mechanical, chemical, and thermal stability of LIS under real-world conditions, including freeze-thaw cycles, dynamic loads, and contact with aggressive liquids.

The study analyzes the current application areas of liquid-infused surfaces in modern technical and industrial systems, including anti-icing technologies, corrosion protection, biomedical devices, membrane-based liquid separation, microfluidic components, and low-adhesion coatings. It is shown that LIS possesses significant interdisciplinary potential for implementation in energy, environmental protection, transportation, medicine, and other sectors, provided that existing technical, technological, and environmental barriers are overcome. The prospects for further development of this innovative technology are summarized in the context of materials science, applied engineering, and sustainable manufacturing.

Determination of the possibility of using cold plasma for the oxidation of atmospheric nitrogen into nitrogen oxides and the influence of activating substances on the process

2025-08-05T12:11:42+00:00

The object of study is the process of oxidation of atmospheric nitrogen into nitrogen oxides. The oxidation of atmospheric nitrogen to produce nitric acid is important for the development of new methods of atmospheric nitrogen binding and methane activation, which are fundamental problems in the field of chemical science and technology. The process of molecular nitrogen oxidation and the dependence of nitrogen oxides content on the current strength through an installation with an electric arc low-temperature plasma generator were studied.

To confirm the hypothesis, quantum chemical studies of the reaction activity of nitric acid and its decomposition products were carried out. At the initial stage, quantum chemical DFT calculations were performed to determine the electronic structure and thermodynamic parameters of the ground state of nitric acid and its three known isomers.

To implement the process of producing nitric acid from atmospheric air using reproductive technology, a reactor design for the production of nitrogen oxides by direct oxidation of nitrogen in a cold plasma flow was proposed. It was proposed to use the effect of producing nitrogen oxides in an air mixture with nitric acid vapor and during the thermal decomposition of nitric peroxide with atmospheric nitrogen. The efficiency of using cold plasma for the oxidation of atmospheric nitrogen has been established, which is confirmed by the obtained dependences. The influence of the current strength through the installation in the presence of hydrogen peroxide and alcohols as activators of the process of atmospheric nitrogen oxidation in a high-energy environment was revealed. Studies have shown that with an increase in the current through the plant, the amount of nitrogen oxides increases for all activator substances by 2 to 8 times.

The influence of the nitrogen oxides content on the current strength through the installation with an electric arc low-temperature plasma generator was revealed. It is determined that when comparing activating agents that are capable of forming OH radicals during their decomposition, hydrogen peroxide is the most promising activating agent for the process of oxidation of atmospheric nitrogen in a plasma flow.

Сalibration method for test liquids for measuring surface energy by the Оwens-Wendt method

2025-08-05T12:37:55+00:00

This scientific paper presents a comprehensive study of the surface characteristics of mixed liquids using a graphical analysis method developed by Owens and Wendt, which allows the total surface tension to be quantitatively divided into two main components: the dispersive and polar components. In order to improve the accuracy and reliability of the calculation results, the paper proposes the use of a number of polymer materials with known surface properties as calibration substrates for determining contact wetting angles. This made it possible to extend the application of the Owens–Wendt graphical approach to the analysis of complex multicomponent liquid systems, in particular those containing both nonpolar organic solvents and substances with pronounced polar or hydrogen bonds.

The study investigated the wetting of various mixtures of polymer surfaces based on polyethylene, polypropylene, Teflon, polystyrene and other polymers with different ratios of dispersed and polar components of surface tension. The experimental values of the contact angles obtained made it possible to construct approximate straight lines in the Owens–Wendt method coordinates for each mixture and each surface. This made it possible to calculate the individual components of surface tension for the studied liquid systems with a high degree of accuracy. The influence of the composition of mixtures on the change in the values of polar and dispersive interactions at the phase boundary was analysed.

In addition, it was demonstrated that an increase in the number of polymer calibration surfaces leads to a reduction in errors in linear approximation and allows avoiding systematic deviations in the determination of surface energy parameters. The results obtained are consistent with the literature data, which confirms the reliability of the developed approach. The presented methodology can be effectively applied to evaluate the surface properties of new composite materials, liquid preparations and functional fluids in various fields of chemistry, biotechnology and materials science. Thus, the study not only expands the possibilities of applying the classical Owens–Wendt approach, but also offers a new tool for a more accurate and convenient assessment of intermolecular interactions in systems with a liquid phase. The presented scientific work carries out a comprehensive study of the surface characteristics of mixed liquids using the graphical analysis method developed by Owens and Wendt, which allows the total surface tension to be quantitatively divided into two main components — the dispersive (London) and polar (dipole-dipole) components. In order to improve the accuracy and reliability of the calculation results, the paper proposes the use of a number of polymer materials with known surface properties as calibration substrates for determining contact wetting angles. This made it possible to extend the application of the Owens–Wendt graphical approach to the analysis of complex multicomponent liquid systems, in particular those containing both nonpolar organic solvents and substances with pronounced polar or hydrogen bonds.

Modern approaches to the utilisation of sludge waste from electroplating as a catalyst for gas flow purification: a review of technologies and prospects

2025-08-05T12:57:07+00:00

An analysis of modern technologies for the utilization of sludge waste from electroplating industries and their use as catalysts for gas stream purification has been conducted. The relevance of the study is due to the growing volume of industrial waste and the need to develop environmentally safe and economically feasible methods of its processing. In this context, special attention is paid to technologies that allow converting sludge waste from electroplating industries not only into by-products, but also into useful catalysts for gas stream cleaning processes. The purpose of the article is to review current approaches to the utilisation of sludge waste from electroplating, in particular, through its use as catalysts for the purification of gas streams. The study involved a systematic analysis of scientific sources, experimental studies of the catalytic properties of materials derived from sludge waste, and a comparative analysis of the economic and environmental parameters of various disposal methods. The main results of the work include an assessment of the effectiveness of various approaches, including thermal, chemical and biotechnological treatment of sludge, as well as the use of nanotechnology to enhance the activity of catalysts. It was found that the best methods are those that provide high catalytic activity at minimal energy consumption. An environmental assessment of modern sludge processing technologies is carried out. It is determined that biotechnological methods of processing are safer for the environment and more promising for small enterprises. The integration of renewable energy sources and the use of the latest materials will contribute to the ecological modernisation of industry and the development of a circular economy. Further research should be aimed at optimising technological processes, improving the efficiency of catalysts and reducing production costs. The integration of renewable energy sources and the use of the latest materials will contribute to the ecological modernisation of industry and the development of the circular economy. The results obtained can be useful for industrial enterprises in choosing waste treatment technologies and improving air purification systems, contributing to the development of environmental safety.

A review of fabrication techniques for superhydrophobic coatings

2025-08-05T13:15:25+00:00

Superhydrophobic surfaces have emerged as a pivotal focus of modern materials science. These surfaces are notable for their unique wetting behavior and wide array of potential applications in fields such as self-cleaning coatings, anti-corrosion protection, drag reduction, anti-icing technologies, and oil-water separation. Inspired by natural models such as lotus leaves, water striders, and Salvinia molesta, these surfaces combine low surface energy materials with hierarchical micro/nanostructures to achieve water contact angles exceeding 150°. This dual scale roughness traps air pockets beneath water droplets, enabling the "lotus effect," whereby droplets roll off surfaces, removing contaminants. The development of superhydrophobic coatings is particularly important in the context of metal corrosion because economic and environmental factors have created a demand for safer, more sustainable alternatives. A wide variety of fabrication techniques have been developed, including top-down methods, such as laser ablation and etching, and bottom-up strategies, such as sol-gel deposition and chemical vapor deposition. However, many approaches are limited by complexity, cost, scalability, or environmental impact. Furthermore, the practical application of these coatings presents challenges concerning durability, material compatibility, performance under environmental stressors, and the use of fluorinated compounds, which pose ecological risks. This review critically examines current methodologies for fabricating superhydrophobic surfaces. It evaluates the underlying principles, advantages, and limitations of these methods with respect to mechanical robustness, scalability, and application-specific demands. Particular emphasis is placed on the importance of multiscale surface structuring and selecting inherently hydrophobic, low-energy materials to create functionally resilient coatings. Additionally, the work explores the limitations of current testing standards and suggests that a unified framework for evaluating mechanical wear, environmental resistance, and hydrophobic retention is essential for accelerating the transfer of technology from the laboratory to the industrial scale. The review highlights novel strategies such as biomimetic design, incorporating self-healing materials, and integrating superhydrophobic coatings with multifunctional technologies as promising future directions. Ultimately, the success of superhydrophobic surface technologies depends on a multidisciplinary effort balancing performance metrics with environmental responsibility and economic feasibility to unlock their transformative potential across diverse sectors.

Modeling of a multi-circuit system for automated control of the well drilling process based on subcontrollers

2025-08-03T14:03:53+00:00

Decentralized automated control systems (ACS) based on proportional-integral-differential (PID) controllers remain the most common solution for controlling industrial processes with multiple inputs and outputs (MIMO). This is due to their flexibility, simplicity, and inherent fault tolerance compared to centralized control structures. Even when more sophisticated strategies, such as model predictive control (MPC), are applied, PID controllers are usually used at lower control levels of the respective systems. The paper considers an automated control system for the well drilling process implemented on the basis of an electric drive. In the studied hierarchical ACS, a structure is used at its lower level that includes three circuits based on proportional-integral-differential (PID) controllers that provide control of the bit rotation speed RPM, the bit load WOB, and the parameters of the well cleaning system (primarily its performance). Drilling process modeling shows a close relationship between these parameters, which requires appropriate adjustment of each control loop. The optimal tuning of decentralized PID controllers in multi-loop ACS remains a difficult and complex task. Most of the known methods of tuning multi-loop PID controllers are similar in that they use the tuning rules of one loop to obtain initial values for individual controllers, and then detune the individual loops to maintain the stability of the entire system. In the conditions of a real production process, this approach does not always allow achieving the desired performance and control reliability. An algorithm for tuning multicircuit SACs based on PID controllers, which implements the generalized internal model method (IMC), is investigated. A criterion based on determining the parameters of the closed-loop frequency response is used to achieve the desired performance and control reliability. The frequency response of the closed-loop ACS is obtained by calculating the system output signal in response to a sinusoidal input. The results obtained indicate that the tuning of a three-circuit ACS based on PID controllers using the investigated method allows achieving the most accurate compliance with the desired performance and control reliability. The investigated method can be applied to dynamic models of any order. In this case, the feedback characteristics of the closed-loop control are set in advance. In addition, as a result of the corresponding algorithm, information is provided on the stability margins and sensitivity characteristics of the ACS.

Influence of the spread parameter of radial-base networks on the approximation of the main control channels of an acetic acid synthesis reactor

2025-08-03T14:20:18+00:00

The chemical industry is based on chemical reactors. In today's competitive scenario, it is paramount to support the various operating variables and meet product specifications. The continuous stirred tank reactor (CSTR) is widely used in many chemical, pharmaceutical and petroleum industries, as well as in environmental protection and waste management.Neural network models offer the most unified approach to building truly intelligent systems that can provide optimal control for many systems.

Over the past decade, artificial neural networks (ANNs) have gained importance as versatile data-driven structures for modelling nonlinear steady-state and dynamic processes.

To build and study the properties of the neural network, we used statistical data from an acetic acid synthesis reactor operating in a stationary mode. The MATLAB 2021b software simulator environment was used for modelling.

The aim of this work was to build and study the properties of radial basis neural networks RBF and GRNN, according to the main control channels of the acetic acid synthesis reactor, which is a gas-liquid reactor with continuous stirring. The investigated network can be proposed to be used for reactor control.

In this paper, we investigated the effect of the SPREAD parameter on the structure of the radial basis network and the quality of approximation. To model the radial basis networks RBF and GRNN for controlling an acetic acid synthesis reactor for each control channel, an iterative procedure for forming networks was used.

The relative error was used to quantify the quality of the approximation of the initial parameters. The SPREAD influence parameter for the radial basis function (RBF) network was determined to be 0.01, 0.1, 0.7, 2.0, 5.0, 10.0, 20.0, 50.0, 100.0. For the radial basis network GRNN, the values of the influence parameter SPREAD were taken to be 0.7, 2.5, 10, 20, 50, 100. The modelling of the radial basis networks RBF and GRNN for controlling the acetic acid synthesis reactor for each control channel using the iterative procedure for forming networks in MATLAB 2021b showed a satisfactory quality of approximation of the original data.

It can also be said that the radial basis networks RBF and GRNN can be used to improve the control of the acetic acid synthesis reactor by all the main control channels.

Integrated approach to diagnosing complex technical systems: experimental validation and multidimensional efficiency assessment

2025-07-10T14:17:01+00:00

This paper presents a comprehensive experimental validation of an integrated approach to the diagnosis of the technical condition (TC) of complex technical systems (CTS), using ship power plants (SPPs) as an example. The proposed methodology combines precedent-based logic (Case Based Reasoning – CBR), probabilistic forecasting using Bayesian networks and Markov chains, and simulation modeling of degradation scenarios and cascading failures. Testing was conducted under three scenarios: normal operating mode, high-load mode, and a scenario with limited data availability, which enabled a thorough assessment of the algorithms' adaptability and resilience to changing operational factors. Classical binary classification metrics (Accuracy, Precision, Recall, and F1 score) were used for quantitative evaluation of diagnostic quality, along with newly introduced extended indicators: weighted accuracy (WAcc), F1 score accounting for the criticality of component failures (F1W), recall weighted by failure risk (RecallR), cost-adjusted precision for false alarms (PrecisionC), and the Diagnostic Stability Index (DSI). The results of the multi-scenario experiment showed a consistent improvement in all major indicators: Accuracy increased from 78.5% to 85.3%, Precision from 75.2% to 83.1%, Recall from 80.1% to 87.6%, F1 score from 77.5% to 85.3%, RecallR reached 91.0%, and DSI was 0.983. Five-fold cross-validation yielded a standard deviation of F1 score at 2.2%, confirming the reproducibility and reliability of the proposed method for experimental testing of the integrated diagnostic approach for CTS. The implementation of a cyclic procedure "simulation, probabilities, CBR adaptation" significantly reduced the number of false alarms and missed critical failures in SPP equipment. The practical significance of the approach lies in its potential integration into SCADA/PMS systems of marine CTS and ground power stations, facilitating a shift to intelligent predictive maintenance, thereby reducing unplanned downtime, lowering costs, and enhancing equipment reliability. Future research prospects include increasing the adaptability of the approach, expanding the precedent base, and developing tools for automated processing of heterogeneous data.

Conceptual model of information security of educational computer laboratories

2025-08-03T13:04:16+00:00

In conditions of martial law and rapid development of ICT, effective counteraction to cyberattacks as an element of hybrid warfare requires joint efforts of state institutions, critical infrastructure facilities, industrial enterprises and educational institutions. Under such circumstances, it becomes important to review the foundations of information security. The article is devoted to the study and classification of information security models used to build effective information protection systems. The paper considers three main types of models: conceptual model, mathematical model and functional model.

Conceptual model – serves as a basis for formulating general processes for creating a security system, determines key areas and structure of information protection.

In addition to analyzing models, the work highlights the features of implementing information protection systems in educational institutions. Among the main problems identified are: lack of specialized departments and persons responsible for information security; insufficient level of training of teaching and support staff; large differences in user qualifications; difficulty in ensuring security with the openness of the educational process and increasing requirements for the implementation of distance education technologies.

The peculiarities of building a security system in educational institutions are the need to find a compromise solution between the openness of the educational process and student-centered learning; ensuring comfortable conditions for access to all materials of the educational process and strict provisions for the leakage of confidential and official information. The paper proposes one of the options for developing a conceptual security model as a basis for the further implementation of effective protection measures, taking into account the specifics of the work of educational institutions and their information environment. The creation of this model is an important first step in building a security system. Based on the analysis, it is proposed to review the main approaches to information security in educational institutions, especially taking into account the specifics of distance learning and the openness of educational processes.

Web service integration with social network

2025-08-03T13:37:49+00:00

The article is devoted to the consideration of the creation of a web-service that organizes the work of an electronic queue and has the functionality of interaction with a social network. An electronic queue is a software and hardware complex that allows you to formalize and optimize the management of the flow of visitors. The article considers the software implementation of the electronic queue system "E-queue" with functionality integrated with a social network, which can have the following areas of application: bank operating rooms; insurance company payment centers; operator client centers, stationary operators; state institutions (for example, tax and registration services, embassies and consular offices); pension funds; medical centers; travel companies; visa centers; car dealerships, car services; notary and law offices; airline and railway ticket offices; operating rooms of communication departments; multifunctional centers for the provision of state and municipal services. To identify users in the system, it is proposed to create a QR code in personal accounts, with subsequent data administration using a QR code scanner. A convenient and fast way to provide users with additional functionality is to use social network bots, which have become an integral part of any online service, online store, information portal or blog. The developed software functionality consists of both receiving content and creating processes that directly relate to services and resources. Additional use of social network functionality for notifications allows users to quickly and conveniently receive up-to-date information in real time without the need to download the system's web service interface. This creates flexibility and convenience of interaction with the service for users, which provides more effective management of customer time and resources. In this regard, the integration of the functionality of web-systems for managing customer flows with social networks becomes an urgent task. The proposed methods for implementing the system when creating a service use a modern and proven stack of web programming technologies, which allows you to create web services that have a high level of security when working in an electronic system.

Optimization of multi-flow electrohydraulic drive operation using artificial intelligence methods

2025-08-03T13:47:47+00:00

The article explores the issue of improving the efficiency of multi-flow electrohydraulic drives, which are extensively utilized in industrial, mobile, and aviation systems. These systems are characterized by nonlinear dynamics, parameter uncertainties, and the complexity of mathematical modeling, which create significant challenges for conventional control methods. To address these difficulties, a comprehensive approach is introduced, combining artificial intelligence methods such as neural networks, fuzzy logic, and genetic algorithms to optimize system performance.

A critical aspect of the research is the development of a neural network model that enables accurate identification of drive parameters and reliable prediction of its dynamic behavior. This approach significantly surpasses traditional modeling techniques in precision and adaptability. The hybrid neuro-fuzzy control system integrates expert knowledge with the flexibility of neural networks, providing enhanced positioning accuracy, improved energy efficiency, and increased resilience to external disturbances. Additionally, the implementation of genetic algorithms for multi-criteria optimization allows for an effective balance between motion accuracy, energy consumption, and smooth operation of the mechanism.

Another key contribution is the diagnostic and technical condition forecasting system based on machine learning. This system demonstrates high reliability in detecting anomalies, contributing to reduced maintenance costs and prolonged operational lifespan. Experimental studies validate the effectiveness of the proposed methods: under substantial load variations, deterioration in positioning accuracy is reduced by three times compared to traditional control systems. The proposed algorithms lead to lower operating costs, higher equipment productivity, and improved reliability of automated control systems.

The results of this study have practical applications in industrial automation, robotic complexes, aviation, and military technologies, as well as in mechatronic systems where precision control, energy efficiency, and operational reliability are crucial. Future research may focus on refining machine learning algorithms for real-time applications and integrating these approaches into the industrial Internet of Things (IIoT) framework. By advancing these methodologies, this study contributes to the development of intelligent control systems capable of meeting the evolving demands of modern automation and mechatronics.