Nauki Techniczne

Bulletin of the Polish Academy of Sciences: Technical Sciences

Zawartość

Bulletin of the Polish Academy of Sciences: Technical Sciences | 2021 | 69 | No. 2 (i.a. Special Section on Machine modelling and simulations) |

Abstrakt

Artificial intelligence (AI) is changing many areas of technology in the public and private spheres, including the economy. This report reviews issues related to machine modelling and simulations concerning further development of mechanical devices and their control systems as part of novel projects under the Industry 4.0 paradigm. The challenges faced by the industry have generated novel technologies used in the construction of dynamic, intelligent, flexible and open applications, capable of working in real time environments. Thus, in an Industry 4.0 environment, the data generated by sensor networks requires AI/CI to apply close-to-real-time data analysis techniques. In this way industry can face both fresh opportunities and challenges, including predictive analysis using computer tools capable of detecting patterns in the data based on the same rules that can be used to formulate the prediction.
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Autorzy i Afiliacje

Izabela Rojek
Marek Macko
Dariusz Mikołajewski
Milan Sága
Tadeusz Burczyński

Abstrakt

The targeted modification of the material composition is a common procedure used to improve the parameters of the final products. This paper deals with the targeted modification of polymer systems composition using two various types of alternative fillers. The first type of alternative filler (SVD) has been obtained from energetics where it arises as a by-product of flue gas desulfurization. The second alternative filler used (KAL) is based on waste from glass production. The elastomeric systems designed for the production of car tires and solid wheels for transport systems were used in the role of modified polymer systems. Alternative fillers (SVD, KAL) have been applied as a substitution of commonly used fillers (carbon black, silica). The filler – elastomeric matrix interaction, rheology, cure characteristics, as well as hardness and rebound resilience of vulcanizates, which are important parameters for their industrial application, have been studied in the new prepared polymeric systems. The main output of the work is a new formulation of an elastomeric system for industrial applications with high rebound resilience and low rolling resistance, which is the subject of the international patent [1]. The modification of composition using raw material substitution can also bring significant environmental and economic effects.
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Autorzy i Afiliacje

Darina Ondrušová
Ivan Labaj
Mariana Pajtášová
Juliana Vršková
Slavomíra Božeková
Andrea Feriancová
Petra Skalková

Abstrakt

Many researchers in the developed countries have been intensively seeking effective methods of plastic recycling over the past years. Those techniques are necessary to protect our natural environment and save non-renewable resources. This paper presents the concept of an electrostatic separator designed as a test bench dedicated to the separation of mixed plastic waste from the automotive industry. According to the current policy of the European Union on the recycling process of the automotive industry, all these waste materials must be recycled further for re-entering into the life cycle (according to the circular economy). In this paper, the proposed concept and design of the test bench were offered the feasibility to conduct research and technological tests of the electrostatic separation process of mixed plastics. The designed test bench facilitated assessing the impact of positions of high-voltage electrodes, the value and polarity of the high voltage, the variable speed of feeders and drums, and also triboelectrification parameters (like time and intensity) on the process, among others. A specialized computer vision system has been proposed and developed to enable quick and reliable evaluation of the impact of process parameters on the efficiency of electrostatic separation. The preliminary results of the conducted tests indicated that the proposed innovative design of the research stand ensures high research potential, thanks to the high accuracy of mixed plastics in a short time. The results showed the significant impact of the corona electrode position and the value of the applied voltage on the separation process effectiveness. It can be concluded that the results confirmed the ability to determine optimally the values of the studied parameters, in terms of plastic separation effectiveness. This study showed that this concept of an electrostatic separator designed as a test bench dedicated for separation of mixed plastic waste can be widely applied in the recycling plastic industry.
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Autorzy i Afiliacje

Roman Regulski
Dorota Czarnecka-Komorowska
Cezary Jędryczka
Dariusz Sędziak
Dominik Rybarczyk
Krzysztof Netter
Mariusz Barański
Mateusz Barczewski

Abstrakt

To model the nonlinear behaviour of vibrating systems, Taylor expansion with integer powers is often used. Some systems, however, are inherently nonlinear. In the case of a non-integer real exponent, the power-law system cannot be linearised around the equilibrium position using Taylor expansion. The approach presented here provides a simple estimate of the principal frequency of free vibration in systems with power-law restoring force. Without seeking the precise mathematical form of the output waveform, we only focus on the principal frequency. The first step is the use of dimensional analysis to reduce the number of parameters. Two independent non-dimensional groups are formed and functional dependence between them is sought using numerical simulations. Once this dependence is known, the principal frequency of free vibration can be readily determined for any system properties and any initial conditions. Finally, we compare the numerical results to analytical expressions for a few restoring force exponents.
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Autorzy i Afiliacje

Ivan Grega
Robert Grega
Jaroslav Homisin

Abstrakt

This paper is focused on the theoretical study of heat conduction in the multi-brake system of the automated guided vehicle (AGV). The study aims to compare the amount of heat generated during braking from 10 m/s until a stop in a brake system based on organic and ceramic friction material. The theoretical study of heat conduction is solved in Matlab computational software using a derived Fourier partial differential equation for nonstationary heat conduction. The results of the simulation of the heat conduction are shown in the diagrams and indicate not only the temperature dependence in the period during braking from a speed of 10 m/s to a stop but also the amount of heat accumulated in the steel disc during braking. The simulation results show that braking in both brake systems generates approximately the same amount of heat. The difference occurs in the period of thermal activity, which was influenced by the length of the braking distance. This is caused by a coefficient of friction that significantly affects the final braking result. Finally, it can be stated that the brake system based on organic material must be equipped with a steel disc with a minimum thickness of 8 mm. This is because the brake system based on organic friction material has a set temperature limit of 160 degrees Celsius. The results presented in this study will help an engineer constructor to choose the right procedures and parameters of geometry for designing the mentioned braking system for the considered AGV.
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Autorzy i Afiliacje

Daniel Varecha
Róbert Kohár
Michal Lukáč

Abstrakt

The article presents the results of the research related to the decomposition of polylactic acid (PLA)/halloysite nanotube (HNTs) biocomposites into a simple organic form. After manufacturing the nanocomposites, the evaluation of the composting process simulation was conducted using the biodegradation method. First, the selected properties of PLA/HNTs biocomposites, such as density, water absorption, and impact strength were tested. Next, the impact of the composting process on the behavior of PLA/HNTs composites was investigated from 30 to 90 days. Finally, the loss of mass of the composites, hardness, and the structural changes of biocomposites under the composting conditions before and after the composting were evaluated using SEM microscopy. The results showed that the PLA modified by HNT particles has biodegradation-friendly properties and therein is fully suitable for organic recycling. Due to this, in the coming years, it may contribute to the replacement of non-biodegradability polymers, i.e. polyolefins and polyesters, and reduction of plastic packaging wastes.
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Autorzy i Afiliacje

Dorota Czarnecka-Komorowska
Katarzyna Bryll
Ewelina Kostecka
Małgorzata Tomasik
Elżbieta Piesowicz
Katarzyna Gawdzińska

Abstrakt

The study aimed to develop a system supporting technological process planning for machining and 3D printing. Such a system should function similarly to the way human experts act in their fields of expertise and should be capable of gathering the necessary knowledge, analysing data, and drawing conclusions to solve problems. This could be done by utilising artificial intelligence (AI) methods available within such systems. The study proved the usefulness of AI methods and their significant effectiveness in supporting technological process planning. The purpose of this article is to show an intelligent system that includes knowledge, models, and procedures supporting the company’s employees as part of machining and 3D printing. Few works are combining these two types of processing. Nowadays, however, these two types of processing overlap each other into a common concept of hybrid processing. Therefore, in the opinion of the authors, such a comprehensive system is necessary. The system-embedded knowledge takes the form of neural networks, decision trees, and facts. The system is presented using the example of a real enterprise. The intelligent expert system is intended for process engineers who have not yet gathered sufficient experience in technological-process planning, or who have just begun their work in a given production enterprise and are not very familiar with its machinery and other means of production.
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Autorzy i Afiliacje

Izabela Rojek
Dariusz Mikołajewski
Piotr Kotlarz
Marek Macko
Jakub Kopowski

Abstrakt

Biocompatibility, biodegradability and non-toxicity are the main attributes of any material to be used in biomedical applications. Among all the potential stimuli, pH, salt and temperature exist naturally in the internal environment of the human body. Hence internal stimuli responsive hydrogels can be exploited for specific drug delivery and tissue replacement. Poly(vinyl alcohol) (PVA) is the world’s largest volume synthetic polymer, produced for its excellent chemical resistance, physical properties and complete biodegradability, which has resulted in broad practical applications. PVA could be considered a suitable host material due to its good thermo-stability, chemical resistance and film-forming ability. It is also an important material because of its large-scale applications. Novel data analysis techniques were developed to analyze the response of PVA to external stimuli, including temperature and/or pH. The presented non-contact method shows that the PVA polymer gel, physically cross-linked by freezing and thawing, shrinks and swells under the influence of temperature, which is a reversible phenomenon. Under the given conditions, such as temperature, pH and mechanical load, the dominant factor affecting the swelling or contraction of the hydrogel is the change in the temperature of the liquid in which the PVA hydrogel sample is immersed.
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Autorzy i Afiliacje

Katarzyna Kazimierska-Drobny

Abstrakt

This article deals with the design of slewing rings (slewing bearings). A fully parametric, 3D virtual model of a ball slewing ring with four-point contact was created in the PTC/Creo Parametric CAD system. This model was subsequently used for finite-element analysis using Ansys/Workbench CAE software. The purpose of the FEM analysis was to determine the axial stiffness characteristics. Results of FEM analysis were experimentally verified using a test bench. At the end of the article, we present the nomograms of the deformation constant for different pitch diameters, rolling element diameters and contact angles.
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Autorzy i Afiliacje

Slavomir Hrcek
Robert Kohar
Jan Steininger

Abstrakt

The fiber-cement and cellulose boards are materials commonly used in architectural engineering for exterior and interior applications such as building facades or as wall and roof covering materials. The aim of the study was to present the ultrasonic non-contact method of testing fiber-cement boards with Lamb waves and to discuss the results and limitations of the method in context of quality control of the material. The experiments were performed for the corrugated boards using a laboratory non-contact ultrasonic scanner. Lamb waves were generated in the tested materials by a transmitter excited by a chirp signal with a linearly modulated frequency. Waves transmitted through the tested material are acquired by the receiver and registered by the PC based acquisition system. The tests were done on reference plate board and the corrugated boards. As the main descriptor to assess the quality of tested boards the maximum amplitude of transmitted Lamb waves was selected. The significant role of boundary effects and frequency of waves was noticed. The obtained results have confirmed the usefulness of the applied ultrasonic method for testing macroscopic inhomogeneity of corrugated fiber-cement boards.
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Autorzy i Afiliacje

Radosław Drelich
Michał Rosiak
Michał Pakula

Abstrakt

Groundings are necessary parts included in lightning and shock protection. In the case of a surge current, high current phenomena are observed inside the grounding. They are result of the electrical discharges around the electrode when the critical field is exceeded in a soil. An available mathematical model of grounding was used to conduct computer simulations and to evaluate the influence of current peak value on horizontal grounding parameters in two cases. In the first simulations, electrode placed in two different soils were considered. The second case was a test of the influence of current peak value on grounding electrodes of various lengths. Simulation results show that as soil resistivity increases in value, the surge impedance to static resistance ratio decreases. In the case of grounding electrodes lengths, it was confirmed that there is a need to use an operating parameter named effective grounding electrode length, because when it is exceeded, the characteristics of grounding is not significantly improved during conductance of lightning surges. The mathematical model used in the paper was verified in a comparison with laboratory tests conducted by K.S. Stiefanow and with mathematical model described by L. Grcev.
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Autorzy i Afiliacje

Artur Łukaszewski
Łukasz Nogal

Abstrakt

The escalating prevalence of rooftop solar PVs and DC powered home appliances are the driving forces for the research in the field of DC distribution at residential level. The current research work presents comparative analyses of AC and DC distribution systems considering various scenarios for the specific purpose of efficiency/energy savings. A modern Bakersfield CA, USA home is considered for the analyses. The loads are classified according to the power demand. Rooftop solar PVs are also included in each residential building. Mathematical equations are devised for the efficiency analysis of residential buildings powered with AC as well as DC. The results reveal strong dependence of the efficiency values on the utilization/types of loads, efficiencies of the power electronic converters (PECs), solar capacity and seasonal conditions, as a function of the time of day. It is concluded that AC system presents better efficiency values as compared to the DC counterpart except during the time periods when solar power is available and when the penetration of variable speed drive (VSD) based loads is high.
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Autorzy i Afiliacje

Faraz Ahmad
Faizan Dastgeer
Hasan E. Gelani
Sidra Khan
Mashood Nasir

Abstrakt

Installation and operation of rail vehicles powered by multiple system voltages forces the construction of multi-system traction substation. The article describes a traction substation power supply with 15 kV output voltage and frequency Hz and 25 kV at 50 Hz. The topology of the power electronics system and the control structure of the power supply enables parallel connection of several power supplies. The selected topology and control structure ensures minimizing the rms value of the LCRL filter capacitor current used at the output of the inverters. The article analyses the influence of harmonics consumed by the active front end (AFE) rectifier used in traction vehicles on the rms current of the LCRL filter capacitor.
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Autorzy i Afiliacje

Tadeusz Płatek
Tomasz Osypinski
Zdziaław Chłodnicki

Abstrakt

PIC microcontroller has a vital role in various types of controllers and nowadays the presence of PIC microcontroller is unavoidable in most control applications. This paper describes the enhancement of soft starting of induction motors using PIC microcontroller. Soft starting is required for the induction motors with reduced applied voltages so that the peak starting current is reduced and the startup of the motor is smooth with controlled torque and reduced mechanical vibrations, reduced starting current with correspondingly reduced bus voltage drops. While many of the available schemes of soft starting offer better results in view of smooth starting process, the proposed methodology offers soft starting as well as it cares about the source current quality. In contrast to the conventional multistep starting scheme, in this work a continuously controlled starting scheme is proposed. The three phase AC voltage controller topology is used as the core controller. In each of the half cycles, instead of a single conduction period with a single delay angle, the proposed AC voltage controller is switched symmetrically in each half cycle with multiple pulses in each quarter cycle. Symmetrically placed fixed numbers of switching pulses are used. The paper also describes the various time ratio controls namely the phase angle controller, the extinction angle controller and the symmetrical angle controller. The design aspects of the proposed soft starting scheme and the validation of the proposed system in the MATLAB SIMULINK environment are presented in this paper.
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Autorzy i Afiliacje

S. Selvaperumal
N. Krishnamoorthy
G. Prabhakar

Abstrakt

In this article, an analytical-numerical approach to calculating a stationary thermal field in the elliptical region is presented. The eigenfunctions of the Laplace operator were determined analytically, whereas the coefficients of the eigenfunctions were obtained numerically. The cooling was modeled with 3rd kind (Hankel’s) boundary condition, where the total heat transfer coefficient was the sum of the convective and radiative components. The method was used to analyze the thermal field in an elliptical conductor and a dielectrically heated elliptical column. The basic parameters of these systems, i.e. their steady-state current rating and the maximum charge temperature, were determined. The results were verified using the finite element method and have been presented graphically.
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Autorzy i Afiliacje

Jerzy Gołębiowski
Marek Zaręba

Abstrakt

The paper features a grid-tied converter with a repetitive current controller. Our goal here is to demonstrate the complete design workflow for a repetitive controller, including phase lead, filtering and conditional learning. All key parameters, i.e., controller gain, filter and fractional phase lead, are designed in a single optimization procedure, which is a novel approach. The description of the design and optimization process, as well as experimental verification of the entire control system, are the most important contributions of the paper. Additionally, one more novelty in the context of power converters is verified in the physical system – a conditional learning algorithm to improve transient states to abrupt reference and disturbance changes. The resulting control system is tested experimentally in a 10 kW converter.
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Autorzy i Afiliacje

Bartlomiej Ufnalski
Andrzej Straś
Lech M. Grzesiak

Abstrakt

The paper presents issues associated with the impact of electromagnetic interference on track-side cabinets of a closed-circuit television system (CCTV) functioning in a railway transport environment. The measurements of an electromagnetic field emitted by a track-side CCTV cabinet were presented. Designs of this kind are operated in railway facilities; therefore, they should not disturb the functioning of other equipment, the rail traffic control systems, in particular (so-called inner compatibility). An analysis of the obtained results enabled developing a research model, and a further reliability and operational analysis, taking into account electromagnetic interference. This enabled determining a relationship allowing the determination of the probability of a track-side CCTV cabinet staying in a state of full ability. The presented discussions regarding a track-side CCTV cabinet, taking into account electromagnetic interference, allow for the numerical assessment of different types of solutions (technical and organizational), which can be implemented in order to mitigate the impact of electromagnetic interference on a system’s functioning.
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Autorzy i Afiliacje

Jacek Paś
Adam Rosiński
Kamil Białek

Abstrakt

This work evaluates the influence of gate drive circuitry to cascode GaN device’s switching waveforms. This is done by comparing three PCBs using three double-pulse-test (DPT) with different gate driving loop design. Among important parasitic elements, source-side inductance shows a significant impact to gate-source voltage waveform. A simulation model based on experimental measurement of the cascode GaNFET used in this work is modified by author. The simulation model is implemented in a synchronous buck converter topology and hereby to assess the impact of gate driving loop of cascode GaN device in both continuous conduction mode (CCM) and critical conduction mode (CRM). Apart from simulation, a synchronous buck converter prototype is presented for experimental evaluation, which shows a 99.15% efficiency at 5A under soft-switching operation (CRM) with a 59ns dead-time.
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Autorzy i Afiliacje

Q.Y. Tan
E.M.S. Narayanan

Abstrakt

The article presents a new generation of ultra-fast hybrid switching systems (USH) for reliable, ultra-fast protection of various medium and low voltage DC systems (MVDC and LVDC). The DC switch-off takes place in a vacuum chamber (VC) cooperating with a semiconductor module using current commutation of natural or forced type. Against the background of the current state of science and technology, the paper depicts the basic scopes of USH applications and their particular suitability for operation in high magnetic energy DC circuits. In the case of DC system failures, this magnetic energy should be dissipated outside the system as soon as possible. Usually, magnetic blow-out switches (MBOS) with relatively low operating speed are used for this purpose. The article describes the theoretical basis and principles of construction of two types of novel USH systems: a direct current switching system (DCSS) and a direct current ultra-fast hybrid modular switch (DCU-HM). The DCSS family is designed for quench protection of superconducting electromagnets’ coils in all areas of application. The DCU-HM family is designed for the protection of all systems or vehicles of DC electrical traction and for related industrial applications. The conducted comparative analysis of the effectiveness of USH with respect to MBOS shows clear technical advantages of the new generation switching systems over MBOS. List of abbreviations used in the article is provided at the end.
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Autorzy i Afiliacje

Marek Bartosik
Piotr Borkowski
Franciszek Wójcik

Abstrakt

The electrical properties and behaviour in constant magnetic field of fourfold expanded GaSe matrix intercalated with SmCl 3 guest were investigated by means of impedance spectroscopy and cyclic voltammetry. It was determined that the synthesized GaSe< SmCl 3> clathrate of 4-fold expansion demonstrates the coexistence of mechanisms of generation, transformation and accumulation of electric energy on a quantum level. These mechanisms are driven from external sources of magnetic, thermal and electric field without Faradaic reactions. Therefore, investigated GaSe< SmCl 3> structure is of great attraction in multivoltaics as a prototype of new class of materials. Quantum mechanical model of electro motive force of spin nature is proposed. The main focus of work lies in the prospects of synthesized clathrates for the development of power nanosources and gyrator-free delay nanolines controlled by means of magnetic field.
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Autorzy i Afiliacje

Fedir Ivashchyshyn
Anna Pidluzhna
Dariusz Calus
Orest Hryhorchak
Piotr Chabecki
Oleksandr Makarchuk
23 38

Abstrakt

Polymer coatings are increasingly used in varied fields and applications from simple coatings of barrier to intricated nanotechnology based composite. In the present study, polyvinylidene fluoride(PVDF)/Hydroxyapatite (HA )coatings were produced by spin coating technique over 316L SS. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to observe the coated 316L SS substrates surface morphology. The corrosion protection efficiency of pure polyvinylidene fluoride and polyvinylidene fluoride/HA nanocomposite coatings on 316L SS was inspected using potentiodynamic polarization along with the ions release techniques in Hank’s solution. A superior biocompatibility and an improved protection performance against corrosion were obtained for the 316L SS samples with nanocomposite coatings compared with the pure polyvinylidene fluoride coatings and pristine 316L SS counterparts. The 316L SS samples coated by PVDF/HA nanocomposite showed enhanced corrosion protection within Hank’s solution. The corrosion of 316L SS samples within Hank’s solution increased from 92.99% to 99.99% when using 3wt% HA due to increasing the PVDF inhibition efficiency. Good agreements in the electrochemical corrosion parameters were obtained from using ions release and potentiodynamic polarization tests.
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Autorzy i Afiliacje

Asra Ali Hussein
Nawal Mohammed Dawood
Ammar Emad Al-kawaz

Abstrakt

The mechanical and tribological properties of the Al/CNT composites could be controlled and improved by the method of its fabrication process. This research article deals with the optimization of mechanical and tribological properties of Al/CNT composites, which are fabricated using the mechanical alloying process with the different weight percentage of multi-walled CNT reinforcement. The phase change and the presence of CNT are identified using the X-Ray Diffraction (XRD) analysis. The influence of mechanical alloying process and the multi-walled CNT reinforcement on the mechanical, and tribological behaviours of the Al/CNT composites are studied. The optimal mechanical alloying process parameters and the weight percentage of multi-walled CNT reinforcement for the Al/CNT composite are identified using the Response Surface Methodology (RSM), which exhibits the better hardness, compressive strength, wear rate and Coefficient of Friction (CoF). The Al/CNT composite with 1.1 wt.% of CNT has achieved the optimal responses at the milling speed 301 rpm and milling time 492 minutes with the ball to powder weight ratio 9.7:1, which is 98% equal to the experimental result. This research also reveals that the adhesive wear is the dominant wear mechanism for the Al/CNT composite against EN31 stainless steel but the optimal Al/CNT composite with 1.1 wt.% of multi-walled CNT has experienced a mild abrasive wear.
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Autorzy i Afiliacje

P. Manikandan
A. Elayaperumal
R. Franklin Issac

Abstrakt

Plasma sprayed ceramic coatings serve as protective layers and are frequently exposed to aggressive wear, corrosion, or high-temperature environment. Currently, alumina and alumina-titania are some of the most popular protective ceramic composite coatings used in the industry. The present work deals with the investigation of the influence of TiO₂ content in the feedstock powder on the resulting microstructure and properties of Al₂O₃, Al₂O₃ + 3 wt% TiO₂, Al₂O₃ + 13 wt% TiO₂ and Al₂O₃ + 40 wt% TiO₂ coatings developed via atmospheric plasma spraying (APS). Specifically, the phase composition, morphology, and microstructure, as well as the mechanical and tribological performance of the coatings were examined. Results revealed that higher content of TiO₂ induced the transformation of phases, leading to the formation of intermediary Al₂TiO₅ and Al₂- xTi₁- xO₅ phases. Also, the dominant α–Al₂O₃ to γ–Al₂O₃ transformation confirmed the formulation of well-melted lamellas within the coating structure. It was also shown that the increase in TiO₂ content decreased the micro-hardness of the coatings due to the formation of the intermediary phases as mentioned above and thus, affected their tribological performance. The lowest volumetric wear, equal to 7.2×10⁻⁵ mm³/(N m), was reported for Al₂O₃ + 13 wt% TiO₂ coating.
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Autorzy i Afiliacje

Monika Michalak
Leszek Łatka
Paweł Sokołowski
Rolando T. Candidato Jr.
Andrzej Ambroziak

Abstrakt

The development of combustion systems construction is associated with the possibility of increasing the thermal or overall efficiency of an internal combustion engine. The combustion systems currently in use (mainly related to direct fuel injection) are increasingly being replaced by hybrid systems, including direct and indirect injection. Another alternative is the use of prechambers in new combustion systems. This article concerns the thermodynamic aspect of this issue – namely, the assessment of the inter-chamber flow of a marine engine equipped with a prechamber combustion spark ignition system. The research was carried out using mainly one-dimensional simulation apparatus, and detailed analyses were presented using three-dimensional modeling. The tests included the engine model at medium load. Differences in mass flows were shown at different diameters and different numbers of holes from the preliminary chamber (while maintaining the same cross-sectional area). Similar values of excess air coefficient during ignition of the fuel dose in the prechamber were observed, which resulted in changes in the flow between the prechamber and the main chamber. The differences in mass flow affected the temperatures achieved in the individual combustion chambers. Based on three-dimensional analyses, the mass transfer rate between the chambers and the temperature distribution were assessed during fuel ignition initiated in the prechamber.
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Autorzy i Afiliacje

Ireneusz Pielecha

Abstrakt

In this paper we explore the mechanics of infinitesimal gyroscopes (test bodies with internal degrees of freedom) moving on an arbitrary member of the helicoid-catenoid family of minimal surfaces. As the configurational spaces within this family are far from being trivial manifolds, the problem of finding the geodesic and geodetic motions presents a real challenge. We have succeeded in finding the solutions to those motions in an explicit parametric form. It is shown that in both cases the solutions can be expressed through the elliptic integrals and elliptic functions, but in the geodetic case some appropriately chosen compatibility conditions for glueing together different branches of the solution are needed. Additionally, an action-angle analysis of the corresponding Hamilton-Jacobi equations is performed for external potentials that are well-suited to the geometry of the problem under consideration. As a result, five different sets of conditions between the three action variables and the total energy of the infinitesimal gyroscopes are obtained.
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Autorzy i Afiliacje

Vasyl Kovalchuk
Barbara Gołubowska
Ivaïlo M. Mladenov

Abstrakt

This study describes the methodology for modelling a worm and worm wheel of a double enveloping worm gear with the use of a CAD system. An algorithm for generating a globoid helix is described. In addition, the methodology for modelling an hourglass worm thread with a straight axial tooth profile is presented. The shape of the hourglass worm tooth end with and without a trace modification is proposed. Moreover, a method for achieving a geometric modification of the tooth trace was developed. Next, the method for modelling the worm wheel teeth is described. A solid model of using a machining worm as a hob is applied. Owing to the limitations of a CAD system, which prevents the use of a direct machining simulation, an indirect modelling method is introduced. In the present study, different CAD techniques, both solid and surface, are applied. Knowledge of the correct modelling of the hourglass worm and worm wheel facilitates their generation and conducting various analyses, including a tooth contact analysis. CAD models are utilised to analyse the geometrical contact pattern in a CAD environment, to carry out FEM analysis, to manufacture real parts or to prototype models using the technique of rapid prototyping. They can be also used as master models for measurement, e.g. in optical technics.
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Autorzy i Afiliacje

Piotr Połowniak
Mariusz Sobolak
Adam Marciniec

Abstrakt

The Lagrange-Sylvester formula is applied to the computation of the solutions of state equations of fractional continuous-time and discrete-time linear systems. The solutions are given as finite sums with their numbers of components equal to the degrees of the minimal characteristics polynomials of state matrices of the systems. Procedures for computations of the solutions are given and illustrated by numerical examples of continuous-time and discrete-time fractional linear systems.
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Autorzy i Afiliacje

Tadeusz Kaczorek

Abstrakt

Very often, a digital system includes sequential blocks which can be represented using a model of the finite state machine (FSM). It is very important to improve such FSM characteristics as the number of used logic elements, operating frequency and consumed energy. The paper proposes a novel technology-dependant design method targeting LUT-based Mealy FSMs. It belongs to the group of structural decomposition methods. The method is based on encoding the product terms of Boolean functions representing the FSM circuit. To diminish the number of LUTs, a partition of the set of internal states is constructed. It leads to three-level logic circuits of Mealy FSMs. Each function from the first level requires only a single LUT to be implemented. The method of constructing the partition with the minimum amount of classes is proposed. There is given an example of FSM synthesis with the proposed method. The experiments with standard benchmarks were conducted. They show that the proposed method can improve such FSM characteristics as the number of used LUTs. This improvement is accompanied by a decrease in performance. A positive side effect of the proposed method is a reduction in power consumption compared with FSMs obtained with other design methods.
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Autorzy i Afiliacje

Alexander Barkalov
Larysa Titarenko
Małgorzata Mazurkiewicz
Kazimierz Krzywicki

Abstrakt

The paper concerns the utilization of hydrated lime and zeolites as additives in warm mix asphalt produced with foamed bitumen. The mentioned additives were added to the mixtures in exchange for specific quantities of mineral filler, which amounted to 0.4% and 1.2% of hydrated lime or 0.4% of water-modified and 1.0% of air-dry zeolites in mineral mix. The study investigated warm-produced mixtures with 4.5% and 4.8% binder content and production and compaction temperatures set at 120⁰C and 100⁰C respectively. Additionally, reference hot and warm mixtures were evaluated. The testing included: air void content, indirect tensile strength in dry state and after one freeze-thaw cycle as well as the resulting resistance to moisture and frost damage index. The mixtures incorporating hydrated lime and lower bitumen content of 4.5% exhibited increased air voids and mostly unchanged mechanical performance when compared to the reference warm mix. Increased bitumen content has resulted in significantly improved performance in moisture resistance and compactability which could be compared to that of the reference hot-produced mixture. On the other hand, the incorporation of zeolites in the foamed bitumen mixtures resulted in all cases in increased air void content in the samples. This has apparently led to decreased indirect tensile strength, in both the dry state and after the freeze-thaw cycle. Based on the results it was concluded that the production temperature of the zeolite-bearing mixtures was too low for the zeolite water to significantly improve the mix’ workability and therefore positively affect its mechanical parameters.
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Autorzy i Afiliacje

Anna Chomicz-Kowalska
Krzysztof Maciejewski
Mateusz Marek Iwański
Karolina Janus

Abstrakt

The paper discusses service load measurements (weight of construction materials, small equipment and workers) conducted on 120 frame scaffoldings all over Poland in 2016‒2018. Despite the fact that the scaffolding should ensure the safety of its users, most accidents on construction sites are caused by fall from height. Service loads are one of the elements affecting the safety of scaffolding use. On the basis of the studies, maximum load on one platform and maximum load on a vertical scaffolding module for one day were obtained. They were treated as the random variables of the maximum values. Histograms and probability density functions were determined for these variables. The selection of a probability distribution consisted in the selection of a probability density function by means of fitting curves to the study result histograms using the method of least squares. The analysis was performed for distribution Weibull and Gumbel probability density functions which are applied for maximum values of random variables. Parameters of these functions can be used for the purposes of the reliability analysis to calibrate partial safety factors in simulation of service load during the scaffolding failure risk assessment. Besides, the probability of not exceeding the standard loads provided for frame scaffoldings for 120 weeks was established on the aforementioned basis. The results of the presented research show that in Poland there is a high probability of exceeding the permissible service loads in one year and thus there is a high risk of scaffolding damage.
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Autorzy i Afiliacje

Ewa Błazik-Borowa
ORCID: ORCID
Michał Pieńko
Iwona Szer
ORCID: ORCID
Bożena Hoła
ORCID: ORCID
Krzysztof Czarnocki

Abstrakt

Specific emitter identification (SEI) is the process of identifying individual emitters by analyzing the radio frequency emissions, based on the fact that each device contains unique hardware imperfections. While the majority of previous research focuses on obtaining features that are discriminative, the reliability of the features is rarely considered. For example, since device characteristics of the same emitter vary when it is operating at different carrier frequencies, the performance of SEI approaches may degrade when the training data and the test data are collected from the same emitters with different frequencies. To improve performance of SEI under varying frequency, we propose an approach based on continuous wavelet transform (CWT) and domain adversarial neural network (DANN). The proposed approach exploits unlabeled test data in addition to labeled training data, in order to learn representations that are discriminative for individual emitters and invariant for varying frequencies. Experiments are conducted on received signals of five emitters under three carrier frequencies. The results demonstrate the superior performance of the proposed approach when the carrier frequencies of the training data and the test data differ.
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Autorzy i Afiliacje

Keju Huang
Junan Yang
Hui Liu
Pengjiang Hu

Abstrakt

Individual identification of similar communication emitters in the complex electromagnetic environment has great research value and significance in both military and civilian fields. In this paper, a feature extraction method called HVG-NTE is proposed based on the idea of system nonlinearity. The shape of the degree distribution, based on the extraction of HVG degree distribution, is quantified with NTE to improve the anti-noise performance. Then XGBoost is used to build a classifier for communication emitter identification. Our method achieves better recognition performance than the state-of-the-art technology of the transient signal data set of radio stations with the same plant, batch, and model, and is suitable for a small sample size.
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Autorzy i Afiliacje

Ke Li
Wei Ge
Xiaoya Yang
Zhengrong Xu

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