Nauki Techniczne

Bulletin of the Polish Academy of Sciences: Technical Sciences

Zawartość

Bulletin of the Polish Academy of Sciences: Technical Sciences | Early Access |

Abstrakt

In times of the COVID-19, reliable tools to simulate the airborne pathogens causing the infection are extremely important to enable the testing of various preventive methods. Advection-diffusion simulations can model the propagation of pathogens in the air. We can represent the concentration of pathogens in the air by “contamination” propagating from the source, by the mechanisms of advection (representing air movement) and diffusion (representing the spontaneous propagation of pathogen particles in the air). The three-dimensional time-dependent advection-diffusion equation is difficult to simulate due to the high computational cost and instabilities of the numerical methods. In this paper, we present alternating directions of implicit isogeometric analysis simulations of the three-dimensional advection-diffusion equations. We introduce three intermediate time steps, where in the differential operator, we separate the derivatives concerning particular spatial directions. We provide a mathematical analysis of the numerical stability of the method. We show well-posedness of each time step formulation, under the assumption of a particular time step size. We utilize the tensor products of one-dimensional B-spline basis functions over the three-dimensional cube shape domain for the spatial discretization. The alternating direction solver is implemented in C++ and parallelized using the GALOIS framework for multi-core processors. We run the simulations within 120 minutes on a laptop equipped with i7 6700 Q processor 2.6 GHz (8 cores with HT) and 16 GB of RAM.
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Autorzy i Afiliacje

Marcin Łoś
Maciej Woźniak
Ignacio Muga
Maciej Paszynski

Abstrakt

We analyze the Google-Apple exposure notification mechanism designed by the Apple-Google consortium and deployed on a large number of Corona-warn apps. At the time of designing it, the most important issue was time-to-market and strict compliance with the privacy protection rules of GDPR. This resulted in a plain but elegant scheme with a high level of privacy protection. In this paper we go into details and propose some extensions of the original design addressing practical issues. Firstly, we point to the danger of a malicious cryptographic random number generator (CRNG) and resulting possibility of unrestricted user tracing. We propose an update that enables verification of unlinkability of pseudonymous identifiers directly by the user. Secondly, we show how to solve the problem of verifying the “same household” situation justifying exempts from distancing rules. We present a solution with MIN-sketches based on rolling proximity identifiers from the Apple-Google scheme. Thirdly, we examine the strategies for revealing temporary exposure keys. We have detected some unexpected phenomena regarding the number of keys for unbalanced binary trees of a small size. These observations may be used in case that the size of the lists of diagnosis keys has to be optimized.
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Autorzy i Afiliacje

Adam Bobowski
Jacek Cichoń
Mirosław Kutyłowski

Abstrakt

Efforts of the scientific community led to the development of multiple screening approaches for COVID-19 that rely on machine learning methods. However, there is a lack of works showing how to tune the classification models used for such a task and what the tuning effect is in terms of various classification quality measures. Understanding the impact of classifier tuning on the results obtained will allow the users to apply the provided tools consciously. Therefore, using a given screening test they will be able to choose the threshold value characterising the classifier that gives, for example, an acceptable balance between sensitivity and specificity. The presented work introduces the optimisation approach and the resulting classifiers obtained for various quality threshold assumptions. As a result of the research, an online service was created that makes the obtained models available and enables the verification of various solutions for different threshold values on new data.
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Autorzy i Afiliacje

Michał Kozielski
Joanna Henzel
Joanna Tobiasz
Aleksandra Gruca
Paweł Foszner
Joanna Zyla
Małgorzata Bach
Aleksandra Werner
Jerzy Jaroszewicz
Joanna Polańska
Marek Sikora

Abstrakt

In the paper, we are analyzing and proposing an improvement to current tools and solutions for supporting fighting with COVID-19. We analyzed the most popular anti-covid tools and COVID prediction Models. We addressed issues of secure data collection, prediction accuracy based on COVID models. What is most important, we proposed a solution for improving the prediction and contract tracing element in these applications. The proof of concept solution to support the fight against a global pandemic is presented, and the future possibilities for its development are discussed.
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Autorzy i Afiliacje

Martyna Gruda
Michal Kedziora

Abstrakt

The ongoing period of the pandemic makes everybody focused on the matters related to fighting this immense problem posed to the societies worldwide. The governments deal with the threat by publishing regulations which should allow to mitigate the pandemic, walking at thin ice as the decision makers do not always know how to properly respond to the threat in order to save people. Computer-based simulations of e.g. parts of the city or rural area should provide a significant help, however there are some requirements to fulfill. The simulation should be verifiable, supported by the urban research and it should be possible to run it in appropriate scale. Thus in this paper we present an interdisciplinary work of urban researchers and computer scientists, proposing a scalable, HPC-grade model of simulation, which was tested in real scenario and may be further used to extend our knowledge about epidemic spread and the results of its counteracting methods. The paper shows the relevant state of the art, discusses the micro-scale simulation model, sketches out the elements of its implementation and provides tangible results gathered for a part of the city of Krakow, Poland.
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Autorzy i Afiliacje

Mateusz Paciorek
Damian Poklewski-Koziełł
Kinga Racoń-Leja
Aleksander Byrski
Mateusz Gyurkovich
Wojciech Turek

Abstrakt

The COVID-19 pandemic has influenced virtually all aspects of our lives. Across the world, countries have applied various mitigation strategies, based on social, political, and technological instruments. We postulate that multi-agent systems can provide a common platform to study (and balance) their essential properties. We also show how to obtain a comprehensive list of the properties by “distilling” them from media snippets. Finally, we present a preliminary take on their formal specification, using ideas from multi-agent logics.
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Autorzy i Afiliacje

Wojciech Jamroga
David Mestel
Peter B. Roenne
Peter Y.A. Ryan
Marjan Skrobot

Abstrakt

Cloud-based computational environments can offer elastic and flexible services to wide audiences. Małopolska Educational Cloud was originally developed to support the day-to-day collaboration of geographically scattered schools with universities which organized online classes, led by university teachers, as an amendment to face-to-face teaching. Due to the centralized management and ubiquitous access, both the set of services provided by MEC and their usage patterns can be adjusted rapidly. In this paper we show how – during the COVID-19 pandemic – the flexibility of Małopolska Educational Cloud was leveraged to speed up the transition from in-class to remote teaching, both in the classes and schools which were already involved in the MEC project, and newly added ones. We also discuss the actions that were required to support the smooth transition and draw conclusions for the future.
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Autorzy i Afiliacje

Łukasz Czekierda
Filip Malawski
Robert Straś
Krzysztof Zieliński
ORCID: ORCID
Sławomir Zieliński

Abstrakt

The COVID-19 pandemic is accompanied by a cyber pandemic, involving changes in the modi operandi of perpetrators of various crimes, and an infodemic, associated with the spread of disinformation. The article analyses the impact of the COVID-19 pandemic on cybercrime and presents the latest research on the number of cybercrime cases in Poland and their growth dynamics. It determines the factors that contribute to the commission of a crime and prevent easy identification of criminals. It also suggests the legal and organisational changes that could reduce the number and effects of the most frequently recorded cyberattacks at a time of COVID-19. Particular attention is paid to legal problems of the growing phenomenon of identity theft, and the need to ensure better protection of users from phishing, including through education and proactive security measures consisting in blocking Internet domains used for fraudulent attempts to obtain data and financial resources.
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Autorzy i Afiliacje

Agnieszka Gryszczyńska

Abstrakt

This paper aims to discuss the behavior of the proprietary real-time simulator (RTS) during testing the coordination of distance relay protections in power engineering. During the construction process of the simulator, the mapping of various dynamic phenomena occurring in the modeled part of the power system was considered. The main advantage to the solution is a lower cost of construction while maintaining high values of essential parameters, based on the generally available software environment (MATLAB/Simulink). The obtained results are discussed in detail. This paper is important from the point of view of the cost-effectiveness of design procedures, especially in power systems exploitation and when avoiding faults that result from the selection of protection relay devices, electrical devices, system operations, and optimization of operating conditions. The manuscript thoroughly discusses the hardware configuration and sample results, so that the presented real-time simulator can be reproduced by another researcher.
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Autorzy i Afiliacje

Adam Smolarczyk
Sebastian Łapczyński
Michał Szulborski
Łukasz Kolimas
Łukasz Kozarek

Abstrakt

Appropriate modeling of unsteady aerodynamic characteristics is required for the study of aircraft dynamics and stability analysis, especially at higher angles of attack. The article presents an example of using artificial neural networks to model such characteristics. The effectiveness of this approach was demonstrated on the example of a strake-wing micro aerial vehicle. The neural model of unsteady aerodynamic characteristics was identified from the dynamic test cycles conducted in the water tunnel. The aerodynamic coefficients were modeled as function of the flow parameters. The article presents neural models of longitudinal aerodynamic coefficients: lift and pitching moment as functions of angles of attack and reduced frequency. The modeled and trained aerodynamic coefficients show good consistency. This method shows great potential in the construction of aerodynamic models for flight simulation purposes.
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Autorzy i Afiliacje

Dariusz Rykaczewski
Mirosław Nowakowski
Krzysztof Sibilski
Wiesław Wróblewski
Michał Garbowski

Abstrakt

Polyester coatings are among the most commonly used types of powder paints and present a wide range of applications. Apart from its decorative values polyester coating successfully prevents the substrate from environmental deterioration. This work investigates the cavitation erosion (CE) resistance of three commercial polyester coatings electrostatic spray onto AW-6060 aluminium alloy substrate. Effect of coatings repainting (single- and double-layer deposits) and effect of surface finish (matt, silk gloss and structural) on resistance to cavitation were comparatively studied. The following research methods were used: CE testing using ASTM G32 procedure, 3D profilometry evaluation, light optical microscopy, scanning electron microscopy, optical profilometry and FTIR spectroscopy. Electrostatic spray coatings present higher CE resistance than aluminium alloy. The matt finish double-layer (M2) and single-layer silk gloss finish (S1) are the most resistant to CE. The structural paint showed the lowest resistance to cavitation wear which derives from the rougher surface finish. The CE mechanism of polyester coatings relies on the material brittle-ductile behaviour, cracks formation, lateral net-cracking growth and removal of chunk coating material and craters’ growth. Repainting does not harm the properties of the coatings. Therefore, it can be utilised to regenerate or smother the polyester coating finish along with improvement of their CE resistance.
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Autorzy i Afiliacje

Mirosław Szala
Aleksander Świetlicki
Weronika Sofińska-Chmiel

Abstrakt

Elements of the lightning protection system (LPS) often also perform other functions in the facility. Correct and economical design of these elements is possible with the fulfillment of specific requirements, close coordination and inter-branch cooperation. The article draws attention to important aspects of the LPS design and highlights the ambiguities that may arise during this process. Firstly, the history of changes in national standardisation in the field of lightning protection is approximated. Secondly, the individual components of the external LPS are presented. Subsequently, the normative material requirements for earthing are compiled, depending on their function (for lightning protection and protection against electric shock in MV and LV installations). The last part of the paper is devoted to the comparison of the protective angle method and the rolling sphere method. The analysis was made on the example of a simple object for which the LPS class I is required. It has been shown that despite the possibility of using both methods, they may result in different solutions. Depending on the choice of method, the difference in the arrangement of the air-termination system is indicated. Examples of generally available LPS solutions are also given, taking into account various materials and assembly technologies.
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Autorzy i Afiliacje

Anna Dąda
Paweł Błaut
Piotr Miller

Abstrakt

The article deals with the technological principles regarding the final drying process of the porous ammonium nitrate (PAN) granules in multistage gravitational shelf dryers. The data on the dryer’s optimal technological operating modes are obtained. PAN samples are studied; the regularity of the porous structure change in the granule depending on the dryer’s hydrodynamic and thermodynamic conditions is established. Experimental data obtained during the research will be used to create a methodology for the engineering calculation of gravitational shelf dryers. Moreover, the data on the optimal operating conditions of the drying machines at the final drying stage will be used to improve the technology to form porous granules from agricultural ammonium nitrate.
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Autorzy i Afiliacje

Nadiia Artyukhova
Jan Krmela
Artem Artyukhov
Vladimíra Krmelová
Mária Gavendová
Alžbeta Bakošová

Abstrakt

When patterns to be recognised are described by features of continuous type, discretisation becomes either an optional or necessary step in the initial data pre-processing stage. Characteristics of data, distribution of data points in the input space, can significantly influence the process of transformation from real-valued into nominal attributes, and the resulting performance of classification systems employing them. If data include several separate sets, their discretisation becomes more complex, as varying numbers of intervals and different ranges can be constructed for the same variables. The paper presents research on irregularities in data distribution, observed in the context of discretisation processes. Selected discretisation methods were used and their effect on the performance of decision algorithms, induced in classical rough set approach, was investigated. The studied input space was defined by measurable style-markers, which, exploited as characteristic features, allow to treat a task of stylometric authorship attribution as classification.
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Autorzy i Afiliacje

Urszula Stańczyk
Beata Zielosko

Abstrakt

This study offers two Support Vector Machine (SVM) models for fault detection and fault classification, respectively. Different short circuit events were generated using a 154 kV transmission line modeled in MATLAB/Simulink software. Discrete Wavelet Transform (DWT) is performed to the measured single terminal current signals before fault detection stage. Three level wavelet energies obtained for each of three-phase currents were used as input features for the detector. After fault detection, half cycle (10 ms) of three-phase current signals was recorded by 20 kHz sampling rate. The recorded currents signals were used as input parameters for the multi class SVM classifier. The results of the validation tests have demonstrated that a quite reliable, fault detection and classification system can be developed using SVM. Generated faults were used to training and testing of the SVM classifiers. SVM based classification and detection model was fully implemented in MATLAB software. These models were comprehensively tested under different conditions. The effects of the fault impedance, fault inception angle, mother wavelet, and fault location were investigated. Finally, simulation results verify that the offered study can be used for fault detection and classification on the transmission line.
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Autorzy i Afiliacje

Melih Coban
Suleyman S. Tezcan

Abstrakt

Time invariant linear operators are the building blocks of signal processing. Weighted circular convolution and signal processing framework in a generalized Fourier domain are introduced by Jorge Martinez. In this paper, we prove that under this new signal processing framework, weighted circular convolution also has a generalized time invariant property. We also give an application of this property to algorithm of continuous wavelet transform(CWT). Specifically, we have previously studied the algorithm of CWT based on generalized Fourier transform with parameter 1. In this paper, we prove that the parameter can take any complex number. Numerical experiments are presented to further demonstrate our analyses.
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Autorzy i Afiliacje

Hua Yi
Yu-Le Ru
Yin-Yun Dai

Abstrakt

The continuing efforts for reduction of the torque and flux ripples using Finite Set Model Predictive Direct Torque Control methods (FS-MPDTC) have been currently drowning a great attention from the academic communities and industrial applications in the field of electrical drives. The major problem of high torque and flux ripples refers to the consideration of just one active voltage vector at the whole control period. Implementation of two or more voltage vectors at each sampling time has recently been adopted as one of the practical techniques to reduce both the torque and flux ripples. Apart from the calculating challenge of the effort control, the parameter dependency and complexity of the duty ratio relationships lead to reduction of the system robustness. those are two outstanding drawbacks of these methods. In this paper, a finite set of the voltage vectors with a finite set of duty cycles are employed to implement the FS-MPDTC of induction motor. Based on so-called Discrete Duty Cycle- based FS-MPDTC (DDC-FS-MPDTC), a base duty ratio is firstly determined based on the equivalent reference voltage. This duty ratio is certainly calculated using the command values of the control system, while the motor parameters are not used in this algorithm. Then, two sets of duty ratios with limit members are constructed for two adjacent active voltage vectors supposed to apply at each control period. Finally, the prediction and the cost function evaluation are performed for all of the preselected voltage vectors and duty ratios. However, the prediction and the optimization operations are performed for only 12 states of inverter. Meanwhile, time consuming calculations related to SVM has been eliminated. So, the robustness and complexity of the control system have been respectively decreased and increased, and both the flux and torque ripples are reduced in all speed ranges. The simulation results have verified the damping performance of the proposed method to reduce the ripples of both the torque and flux, and accordingly the experimental results have strongly validated the aforementioned statement.
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Autorzy i Afiliacje

Babak Kiani
Babak Mozafari
Soodabeh Soleymani
Hosein Mohammadnezhad Shourkaei

Abstrakt

Workflow Scheduling is the major problem in Cloud Computing consists of a set of interdependent tasks which is used to solve the various scientific and healthcare issues. In this research work, the cloud based workflow scheduling between different tasks in medical imaging datasets using Machine Learning (ML) and Deep Learning (DL) methods (hybrid classification approach) is proposed for healthcare applications. The main objective of this research work is to develop a system which is used for both workflow computing and scheduling in order to minimize the makespan, execution cost and to segment the cancer region in the classified abnormal images. The workflow computing is performed using different Machine Learning classifiers and the workflow scheduling is carried out using Deep Learning algorithm. The conventional AlexNet Convolutional Neural Networks (CNN) architecture is modified and used for workflow scheduling between different tasks in order to improve the accuracy level. The AlexNet architecture is analyzed and tested on different cloud services Amazon Elastic Compute Cloud- EC2 and Amazon Lightsail with respect to Makespan (MS) and Execution Cost (EC).
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Autorzy i Afiliacje

P. Tharani
A.M. Kalpana

Abstrakt

User authentication is an essential element of any communication system. The paper investigates the vulnerability of the recently published first semi-quantum identity authentication protocol (Quantum Information Processing 18: 197, 2019) to the introduced herein multisession attacks. The impersonation of the legitimate parties by a proper combination of phishing techniques is demonstrated. The improved version that closes the identified loophole is also introduced.
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Autorzy i Afiliacje

Piotr Zawadzki

Abstrakt

This paper presents results of diagnostic examinations carried out on the coils of super-heaters made of 10CrMo9-10 steel that were operated in industrial conditions at 480°C for 130 thousands hours. The tube has been exposed in coal fired boiler. The chemical and phase composition of the oxide/deposit layers formed on both sides of the tube walls (outside – flue-gas side and inside – steam side) and their sequence were examined using optical microscopy, scanning electron microscopy with electron backscatter diffraction and energy-dispersive X-ray spectroscopy, and X-ray diffraction. The changes in the mechanical properties caused by corrosion and ageing processes were concluded from the hardness measurements. In addition, the nature of cracks in the oxide layers caused by pressing a Vickers indenter was determined. The results of these examinations have shown a high degradation of the steel on the flue-gas inflow side, and identified the main corrosion products and mechanisms.
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Autorzy i Afiliacje

Monika Gwoździk
Christiane Ullrich
Christian Schimpf
David Rafaja
Sławomir Kulesza
Mirosław Bramowicz

Abstrakt

The cyclicity of the state matrices of positive linear electrical circuits with the chain structure is considered. Two classes of positive linear electrical circuits with the chain structure and cyclic Metzler state matrices are analyzed. Some new properties of these classes of positive electrical circuits are established. The results are extended to fractional linear electrical circuits.
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Autorzy i Afiliacje

Tadeusz Kaczorek

Abstrakt

In the paper the new paradigm for structural optimization without volume constraint is presented. Since the problem of stiffest design (compliance minimization) has no solution without additional assumptions, usually the volume of the material in the design domain is limited. The biomimetic approach, based on trabecular bone remodeling phenomenon is used to eliminate the volume constraint from the topology optimization procedure. Instead of the volume constraint, the Lagrange multiplier is assumed to have a constant value during the whole optimization procedure. Well known MATLAB topology based optimization code, developed by Ole Sigmund, was used as a tool for the new approach testing. The code was modified and the comparison of the original and the modified optimization algorithm is also presented. With the use of the new optimization paradigm, it is possible to minimize the compliance by obtaining different topologies for different materials. It is also possible to obtain different topologies for different load magnitudes. Both features of the presented approach are crucial for the design of lightweight structures, allowing the actual weight of the structure to be minimized. The final volume is not assumed at the beginning of the optimization process (no material volume constraint), but depends on the material’s properties and the forces acting upon the structure. The cantilever beam example, the classical problem in topology optimization is used to illustrate the presented approach.
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Autorzy i Afiliacje

Michał Nowak
Aron Boguszewski

Abstrakt

Hybridization of meta-heuristic algorithms plays a major role in the optimization problem. In this paper, a new hybrid meta-heuristic algorithm called hybrid pathfinder algorithm (HPFA) is proposed to solve the optimal reactive power dispatch (ORPD) problem. The superiority of the Differential Evolution (DE) algorithm is the fast convergence speed, a mutation operator in the DE algorithm incorporate into the pathfinder algorithm (PFA). The main objective of this research is to minimize the real power losses and subject to equality and inequality constraints. The HPFA is used to find optimal control variables such as generator voltage magnitude, transformer tap settings and capacitor banks. The proposed HPFA is implemented through several simulation cases on the IEEE 118-bus system and IEEE 300-bus power system. Results show the superiority of the proposed algorithm with good quality of optimal solutions over existing optimization techniques, and hence confirm its potential to solve the ORPD problem.
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Autorzy i Afiliacje

V. Suresh
S. Senthil Kumar

Abstrakt

In the current work the calculations of the reaction cross section of total fusion σ fus, the fusion barrier distribution D fus, and the probability P fus were achieved for systems ⁶He+⁶⁴Zn, ⁸B+⁵⁸Ni and ⁸He+¹⁹⁷Au which involving halo nuclei by using a semiclassical approach. The semiclassical and quantum mechanics treatments is comprising the approximation of WKB for describing the relative motion among projectile nuclei and target nuclei, and the method of CDCC (Continuum Discretized Coupled Channel) for describing the intrinsic motion for the projectile and target nuclei. Our semiclassical calculations yielded findings that were compared to obtainable experimental data as well as quantum mechanics calculations. For fusion cross sections σ fus below and above the Coulomb barrier V b, the quantum mechanics Coupled-Channels is very similar, according to the experimental results.
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Autorzy i Afiliacje

Maryam H. Abd Madhi
Fouad A. Majeed

Abstrakt

The objective of the research was to investigate the efficiency of selected methods of data fusion from visual sensors used on-board satellites for attitude measurements. Data from a sun sensor, an earth sensor, and a star tracker were fused, and selected methods were applied to calculate satellite attitude. First, a direct numerical solution, a numerical and analytical solution of the Wahba problem, and the TRIAD method for attitude calculation were compared used for integrating data produced by a sun sensor and an earth sensor. Next, attitude data from the star tracker and earth/sun sensors were integrated using two methods: weighted average and Kalman filter. All algorithms were coded in the MATLAB environment and tested using simulation models of visual sensors. The results of simulations may be used as an indication for the best data fusion in real satellite systems. The algorithms developed may be extended to incorporate other attitude sensors like inertial and/or GNSS to form a complete satellite attitude system.
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Janusz Narkiewicz
Mateusz Sochacki
Adam Rodacki
Damian Grabowski

Abstrakt

In this investigation, high specific strength precipitation hardenable alloy AA7068-T6 was joined using friction stir welding. Experiments were carried out using the three factor- three level central composite face-centered design of Response Surface Methodology. Regression models were developed to assess the influence of tool rotational speed, welding speed, and axial force on ultimate tensile strength and elongation of the fabricated joints. The validity of the developed models was tested using the analysis of variance (ANOVA), actual and adjusted values of the regression coefficients, and experimental trials. The analysis of the developed models together with microstructural studies of typical cases showed that the tool rotational speed and axial force have significant interaction effect on the tensile strength and elongation of the joints. However, the axial force has relatively low interaction effect with tool rotational speed and axial force on the strength and elongation of the joints. The process variables were optimized using the desirability function analysis. The optimized values of joint tensile strength and elongation- 516 MPa and 21.57% respectively were obtained at a tool rotational speed of 1218 rpm, welding speed of 47 mm/min, and an axial force of 5.3 kN.
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Autorzy i Afiliacje

M.D. Bindu
P.S. Tide
A.B. Bhasi
K.K. Ramachandran

Abstrakt

In this paper thermal oxidation resistance of the silicide coated niobium substrates was tested in temperature range 1300÷1450°C using HVOF burner. Pure niobium specimens were coated using pack cementation CVD method. Three different silicide thickness coatings were deposited. Thermal oxidation resistance of the coated niobium substrates was tested in temperature range 1300÷1450°C using HVOF burner. All samples that passed the test showed their ability to stabilize the temperature in time of 30 s during the thermal test. The rise time of substrate temperature takes about 10 s after which keeps constant values. In order to assess the quality of the Nb-Si coatings before and after the thermal test, a light microscopy, Scanning Electron Microscopy (SEM) and chemical analysis (EDS), X-ray diffraction XRD and Vickers hardness test investigation were performed. Results confirmed the presence of substrate compounds Nb as well as Si addition. The oxygen compounds are result of high temperature intense oxidizing environment that causes the generation of SiO phase in the form of quartz and cristobalite during thermal test. Except one specimen all substrates surfaces pass the high temperature oxidation test with no damages.
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Autorzy i Afiliacje

Radoslaw Szklarek
Tomasz Tanski
Boguslaw Mendala
Marcin Staszuk
Lukasz Krzeminski
Pawel Nuckowski
Kamil Sobczak

Abstrakt

In this scientific publication, research results of two newly developed hot-rolled Fe-Mn-Al-C (X105) and Fe-Mn-Al-Nb-Ti-C (X98) steels were compared. These steels are characterized by an average density of 6.68 g/cm3, a value 15% lower compared to the conventional structural steels. Hot rolling was carried out on a semi-industrial line to evaluate the effect of hot plastic deformation conditions with different cooling variants on the structure. The detailed analysis of the phase composition as well as the microstructure allows to state that the investigated steels are characterized by austenitic-ferritic structure with carbides precipitates. The results of the transmission electron microscopy (TEM) tests of both steels after hot rolling showed the occurrence of various deformation effects such as shear bands, micro bands and lens twins in the microstructure. Based on the research undertaken with the use of transmission electron microscopy, it was found that the hardening mechanism of the X98 and X105 steels is deformation-induced plasticity by the formation of shear bands (SIP) and micro shear bands (MBIP).
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Liwia Sozańska-Jędrasik
Wojciech Borek
Janusz Mazurkiewicz

Abstrakt

The S304H steel is used in the construction of pressure components of boilers with supercritical operating parameters. The paper presents the results of the research on the microstructure after ageing for 30,000 hours at 650 and 700°C. The microstructure examination was performed using scanning and transmission electron microscopy. The precipitates were identifies using transmission electron microscopy. The paper analyses the precipitation process and its dynamics depending on the temperature and ageing time in detail. The MX carbonitrides and the ε_Cu phase were shown to be the most stable phase, regardless of the test temperature. It was also showed that the M 23C 6 carbide precipitates in the tested steel and the intermetallic sigma phase (σ) may play a significant role in the loss of durability of the tested steel. It is related to their significant increase due to the influence of elevated temperature, and their coagulation and coalescence dynamics strongly depend on the ageing/operating temperature level. The qualitative and quantitative identification of the secondary phase precipitation processes described in the study is important in the analysis of the loss of durability of the tested steel under creep conditions.
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Autorzy i Afiliacje

Adam Zieliński
Robert Wersta
Marek Sroka

Abstrakt

The growing interest in one-dimensional tin oxide-based nanomaterials, boost research in both high-quality nanomaterials as well as in production methods. This is due to the fact that they present unique electrical and optical properties, that enable their application in various (opto)electronic devices. Thus, the aim of the paper was to produce ceramic SnO₂ nanowires using electrospinning with calcination method and to investigate the influence of the calcination temperature on the morphology, structure, and optical properties of the obtained material. A scanning electron microscope (SEM)) and Fourier-transform infrared spectroscopy (FTIR) were used to examine the morphology and chemical structure of obtained nanomaterials. The optical properties of manufactured one-dimensional nanostructures were investigated using UV–Vis spectroscopy. Moreover, based on the UV–Vis spectra, the energy band gap of the prepared nanowires was determined. The analysis of the morphology of the obtained nanowires showed that both the concentration of the precursor in the spinning solution and the calcination temperature have a significant impact on the diameter of the nanowires and, consequently, on their optical properties.
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Autorzy i Afiliacje

Tomasz Tański
Weronika Smok
Wiktor Matysiak

Abstrakt

Magnesium alloys are recently more and more popular in many sectors of the industry due to their unique properties, such as low density, high specific strength, vibration damping ability, also their recyclability, and excellent machinability. Nowadays, thin films have been attracting more attention in applications that improve mechanical and corrosion properties. The following alloys were used for the coated: Mg-Al-RE and the ultra-light magnesium-lithium alloy of the Mg-Li-Al-RE type. A single layer of TiO₂ was deposited using the atomic layer deposition ALD method. Multilayer layers of the Ti/TiO₂ and Ti/TiO₂/Ti/TiO₂ type were obtained by the MS-PVD magnetron sputtering technique. Samples were investigated by scanning and transmission electron microscope (SEM, TEM) and their morphology by atomic forces microscope (AFM). Further examinations like electrochemical corrosion, roughness, and tribology were carried out. As a result of the research, it was found that the best electrochemical properties are exhibited by single TiO₂ layers obtained by the ALD method. Moreover, it was found that Ti/TiO₂/Ti/TiO₂ double film has better properties than Ti/TiO₂ film.
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Autorzy i Afiliacje

Marcin Staszuk
Łukasz Reimann
Aleksandra Ściślak
Justyna Jaworska
Mirosława Pawlyta
Tomasz Mikuszewski
Dariusz Kuc
Tomasz Tański
Antonín Kříž

Abstrakt

Magnesium-based alloys are widely used in the construction of the automotive, aviation and medical industries. There are many parameters that can be modified during the synthesis in order to obtain an alloy with the desired microstructure and advantageous properties. Modifications to the chemical composition and parameters of the synthesis process are of key importance. In this work, Mg-based alloy with a rare-earth element addition was synthesized by mechanical alloying (MA). The aim of this work was to study the effect of milling times on Mg based alloy with a rare-earth addition on the structure and microhardness. A powder mixture of pure elements was milled in a SPEX 8000D high energy shaker ball mill under an argon atmosphere using a stainless steel container and balls. The sample was mechanically alloyed at milling times: 3, 5, 8 and 13 h with 0.5 h interruptions. The microstructure and hardness of samples were investigated. The Mg-based powder alloy was examined by an X-ray diffraction (XRD), scanning electron microscopy (SEM) and a Vickers microhardness test. The results showed that the microhardness of the sample milled for 13 h was higher than that of milling time of 3, 5 and 8 h.
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Autorzy i Afiliacje

Sabina Lesz
Bartłomiej Hrapkowicz
Klaudiusz Gołombek
Małgorzata Karolus
Patrycja Janiak

Abstrakt

Magnesium-based materials are promising alternatives for medical applications, due to their characteristics, such as good mechanical and biological properties. Which opens many possibilities for biodegradable materials to be used as lessinvasive options for treatment. The degradation is prompted by its chemical composition and microstructure. Both those aspects can be finely adjusted by proper manufacturing process, such as mechanical alloying (MA). Furthermore, MA allows for alloying of elements, that normally would be really hard to mix due to their very different properties. Magnesium usually needs various alloying elements, which can further increase its. Alloying magnesium with rare earth elements is considered to greatly improve the aforementioned properties. Due to that fact erbium was used as one of the alloying elements, alongside zinc and calcium to obtain Mg64Zn30Ca4Er1 alloy via mechanical alloying. The alloy was milled in the SPEX 8000 Dual Mixer/Mill high energy mill under an argon atmosphere for 8, 13, and 20 hours. It was assessed by X-ray diffraction, energy dispersive spectroscopy, granulometric analysis, and hardness. The hardness values reached 232, 250, and 302 HV respectively, which is closely related to their particle size. The average particle sizes were 15, 16, and 17 μm respectively.
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Autorzy i Afiliacje

Bartłomiej Hrapkowicz
Sabina Lesz
Marek Kremzer
Małgorzata Karolus
Wojciech Pakieła

Abstrakt

The paper is the second part of the work, devoted to a DC power supply with a power factor correction function. The power supply is equipped additionally with a shunt active power filter function, which enables the compensation of reactive and distortion power, generated by loads, connected to the same power grid node. A tunable inductive filter, included at the input of the power electronics current source – the main block of the power supply – allows for an improvement of the quality of the system control, compared to the device with a fixed inductive filter. This improvement was possible by extending the current source “frequency response”, which let for increasing the dynamics of current changes at the power supply input. The second part of the work briefly reminds the reader of the principle of operation and the structures of both the power supply control system and its power stage. The main purpose of the current work is to present the selected test results of the laboratory model of the electric system with the power supply.
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Autorzy i Afiliacje

Michał Gwóźdź
Rafał Wojciechowski
Łukasz Ciepliński

Abstrakt

The increasing demand for electricity and global attention to the environment has led energy planners and developers to explore developing control techniques for energy stability. The main objective function of this research in an interconnected electrical power system to increase the stability of the system with the proposed RRVR technique is evaluated in terms of the different constraints like THD (%), steady-state error (%), settling time (sec), Overshoot (%), efficiency (%) and to maintain the Frequency at a predetermined value, and controlling the change of the power flow of control between the areas renewable energy generation (Solar, wind, and fuel cell with battery management system) based smart grid system. To provide high-quality, reliable and stable electrical power, the designed controller should perform satisfactorily, that is, suppress the deviation of the load frequency. The performance of linear controllers on non-linear power system has not yet been found to be effective in overcoming this problem. In this work, a Fractional High-Order Differential Feedback controller (FHODFC) is proposed for the LFC problems in a multi-area power system. The gains of FHODFC are best adjusted by Resilience Random Variance Reduction Technique (RRVR) designed to minimize the overall weighted absolute error performance exponential time. Therefore, the controller circuit automatically adjusts the duty cycle value to obtain a desired constant output voltage value, despite all the source voltage and load output changes in grid system. The proposed interconnected multi generation energy generation topology is established in MATLAB 2017b software.
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Autorzy i Afiliacje

B. Prakash Ayyappan
R. Kanimozhi

Abstrakt

Self-Healing Grids are one of the most developing concepts applied in electrical engineering Each restoration strategy requires advanced algorithms responsible for the creation of local power systems. Multi-agent automation solutions dedicated for smart grids are mostly based on Prim’s algorithm. Graph theory in that field also leaves many open problems. This paper is focused on a variation of Prim’s algorithm utility for a multi-sourced power system topology. The logic described in the paper is a novel concept combined with a proposal of a multi parametrized weight calculation formula representing transmission features of energy delivered to loads present in a considered grid. The weight is expressed as the combination of three elements: real power, reactive power, and real power losses. The proposal of a novel algorithm was verified in a simulation model of a power system. The new restoration logic was compared with the proposal of strategy presented in other recently published articles. The novel concept of restoration strategy dedicated to multi-sourced power systems was verified positively by simulations. The proposed solution proved its usefulness and applicability.
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Autorzy i Afiliacje

Artur Łukaszewski
Łukasz Nogal

Abstrakt

In the paper we propose a fractional-, piecewise-constant-order PID controller and discuss the stability and robustness of a closed loop system. In stability analysis we use the transform method and include the Nyquist-like criteria. Simulations for designed controllers are performed for the second order plant with a delay.
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Autorzy i Afiliacje

Piotr Oziablo
Dorota Mozyrska
Malgorzata Wyrwas

Abstrakt

The paper presents the main issues of management of electrical grids. Selected information technology tools supporting for electrical grids maintenance are presented. In electrical infrastructure maintenance of power companies the geographic information systems are increasingly used to support the management of theirs resources. Their functionalities in terms creating comprehensive databases for electrical infrastructure of power sector are described. The important information technology tools regarding spatial systems for supporting maintenance and operation management electrical grids and the conditions of their implementation are presented. This paper also attempts to innovative multidimensional evaluate the technical and economic benefits resulting from the use of modern information technology tools for the management of energy infrastructure.
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Autorzy i Afiliacje

Waldemar Kamrat

Abstrakt

This paper considers the problem of the accurate task space finite-time control susceptible to both undesirable disturbance forces exerted on the end-effector and unknown friction forces coming from joints directly driven by the actuators as well as unstructured forces resulting from the kinematic singularities appearing on the mechanism trajectory. We obtain a class of estimated extended transposed Jacobian controllers which seem to successfully counteract the external disturbance forces on the basis of a suitably defined task-space non-singular terminal sliding manifold (TSM) and the Lyapunov stability theory. Moreover, in order to overcome (or to minimise) the undesirable chattering effects, the proposed robust control law involves the second-order sliding technique. The numerical simulations (closely related to an experiment) ran for a mobile manipulator consisting of a non-holononic platform of (2;0) type and a holonomic manipulator of two revolute kinematic pairs show the performance of the proposed controllers and make a comparison with other well-known control schemes.
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Autorzy i Afiliacje

Mirosław Galicki

Abstrakt

The rotating machines with overhung rotors form a wide class of devices used in many types of industry. For this kind of rotor machines in the paper there is investigated an influence of dynamic and static unbalance of a rotor, parallel and angular misalignments of shafts as well as inner anisotropy of rigid couplings on system dynamic responses. The considerations are performed by means of a hybrid structural model of the machine rotor-shaft system, which consists of continuous beam finite elements and discrete oscillators. Numerical calculations are carried out for parameters characterizing a heavy blower applied in the mining industry. The main goal of the research is to assess a sensitivity of the above-mentioned imperfections on excitation severity of rotor-shaft lateral vibrations and on motion stability of the machine in question.
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Autorzy i Afiliacje

Tomasz Szolc
Robert Konowrocki

Abstrakt

A gyroscopic rotor exposed to unbalance is studied and controlled with an active piezoelectrical bearing in this paper. A model is required in order to design a suited controller. Due to the lack of related publications utilizing piezoelectrical bearings and obtaining a modal model purely exploiting experimental modal analysis, this paper reveals a method to receive a modal model of a gyroscopic rotor system with an active piezoelectrical bearing. The properties of the retrieved model are then incorporated into the design of an originally model-free control approach for unbalance vibration elimination, which consists of a simple feedback control and an adaptive feedforward control. After the discussion on the limitations of the model-free control, a modified controller using the priorly identified modal model is implemented on an elementary rotor test-rig comparing its performance to the original model-free controller.
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Autorzy i Afiliacje

Jens Jungblut
Christian Fischer
Stephan Rinderknecht

Abstrakt

Rotors of rotating machines are often mounted in hydrodynamic bearings. Loading alternating between the idling and full load magnitudes leads to variation of the rotor journal eccentricity in the bearing gap. To avoid taking place of undesirable operating regimes, its magnitude must be kept in a certain interval. This is offered by the hydrodynamic bearings lubricated with smart oils, the viscosity of which can be changed by action of a magnetic field. A new design of a hydrodynamic bearing lubricated with magnetically sensitive composite fluid is presented in this paper. Generated in the electric coil, the magnetic flux passes through the bearing housing and the layer of lubricant and then returns back to the coil core. Action of the magnetic field on the lubricant affects the fluid apparent viscosity and thus position of the rotor journal in the bearing gap. The developed mathematical model of the bearing is based on application of the Reynolds equation that has been adapted for the case of lubricants exhibiting the yielding shear stress. The results of the performed simulations confirmed that the change of magnetic induction makes it possible to change the bearing load capacity and thus to keep the rotor journal eccentricity in the required range. The extent of control has its limitations. High increase in the loading capacity can arrive at the loss of stability of the rotor forced vibration and at inducing oscillation of large amplitude.
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Autorzy i Afiliacje

Jaroslav Zapoměll
Petr Ferfecki

Abstrakt

In this paper, the performance and frequency bandwidth of the piezoelectric energy harvester (PZEH) is improved by introducing two permanent magnets, which is attached to the proof mass of a dual beam structure. Both magnets are in the vicinity of each other and attached in such as a way to proof mass of a dual-beam, so that they create a magnetic field around each other. The generated magnetic field develops a repulsive force between the magnets, which improves not only electrical output but also enhances the bandwidth of harvester. The simple rectangular cantilever structure with and without magnetic tip mass has the frequency bandwidth of 4 Hz and 4.5 Hz respectively. The proposed structure generates a peak voltage of 20 V at a frequency of 114.51 Hz at an excitation acceleration of 1g (g = 9.8 m/s2). The peak output power of a proposed structure is 12.2 μW. The operational frequency range of a proposed dual-beam cantilever with magnetic tip mass of 30 mT is from 102.51 Hz to 120.51 Hz i.e., 18 Hz. The operational frequency range of a dual-beam cantilever without magnetic tip mass is from 104.18 Hz to 118.18 Hz i.e., 14 Hz. There is an improvement of 22.22% in the frequency bandwidth of proposed dual-beam cantilever with magnetic tip mass of 30 mT than the dual-beam without magnetic tip mass.
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Autorzy i Afiliacje

Ashutosh Anand
Srikanta Pal
Sudip Kundu

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