Applied sciences

Bulletin of the Polish Academy of Sciences: Technical Sciences

Content

Bulletin of the Polish Academy of Sciences: Technical Sciences | 2021 | 69 | No. 4 (i.a. Special Section on Computer Science vs. COVID-19) |

Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Łukasz Czekierda
Filip Malawski
Robert Straś
Krzysztof Zieliński
ORCID: ORCID
Sławomir Zieliński
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Agnieszka Gryszczyńska
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Wojciech Jamroga
David Mestel
Peter B. Roenne
Peter Y.A. Ryan
Marjan Skrobot
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Martyna Gruda
Michal Kedziora
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Adam Bobowski
Jacek Cichoń
Mirosław Kutyłowski
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

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

Abstract

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 on 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 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 a 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.
Go to article

Authors and Affiliations

Mateusz Paciorek
Damian Poklewski-Koziełł
Kinga Racoń-Leja
Aleksander Byrski
Mateusz Gyurkovich
Wojciech Turek
Download PDF Download RIS Download Bibtex

Abstract

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 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.
Go to article

Authors and Affiliations

Marcin Łoś
Maciej Woźniak
Ignacio Muga
Maciej Paszynski
Download PDF Download RIS Download Bibtex

Abstract

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 incorporates 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.
Go to article

Authors and Affiliations

V. Suresh
S. Senthil Kumar
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Melih Coban
Suleyman S. Tezcan
Download PDF Download RIS Download Bibtex

Abstract

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 facilitated 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 this paper is to present the selected test results of the laboratory model of the electric system with the power supply.
Go to article

Authors and Affiliations

Michał Gwóźdź
Rafał Wojciechowski
Łukasz Ciepliński
Download PDF Download RIS Download Bibtex

Abstract

Elements of the lightning protection system (LPS) often perform additional 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 LPS design and highlights the ambiguities that may arise during this process. Firstly, the history of changes in national standardization in the field of lightning protection is approximated. Secondly, the individual components of 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 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 account of various materials and assembly technologies.
Go to article

Authors and Affiliations

Anna Dąda
Paweł Błaut
Piotr Miller
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Babak Kiani
Babak Mozafari
Soodabeh Soleymani
Hosein Mohammadnezhad Shourkaei
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Adam Smolarczyk
Sebastian Łapczyński
Michał Szulborski
Łukasz Kolimas
Łukasz Kozarek
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Tadeusz Kaczorek
Download PDF Download RIS Download Bibtex

Abstract

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, facilitate treating a task of stylometric authorship attribution as classification
Go to article

Authors and Affiliations

Urszula Stańczyk
Beata Zielosko
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Hua Yi
Yu-Le Ru
Yin-Yun Dai
Download PDF Download RIS Download Bibtex

Abstract

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).
Go to article

Authors and Affiliations

P. Tharani
A.M. Kalpana
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Michał Nowak
Aron Boguszewski
Download PDF Download RIS Download Bibtex

Abstract

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 a water tunnel. The aerodynamic coefficients were modeled as a 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 manifests great potential in the construction of aerodynamic models for flight simulation purposes
Go to article

Authors and Affiliations

Dariusz Rykaczewski
Mirosław Nowakowski
Krzysztof Sibilski
Wiesław Wróblewski
Michał Garbowski
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Janusz Narkiewicz
Mateusz Sochacki
Adam Rodacki
Damian Grabowski
Download PDF Download RIS Download Bibtex

Abstract

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 welding speed have a significant interaction effect on the tensile strength and elongation of the joints. However, the axial force has a relatively low interaction effect with tool rotational speed and welding speed 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.
Go to article

Authors and Affiliations

M.D. Bindu
P.S. Tide
A.B. Bhasi
K.K. Ramachandran
Download PDF Download RIS Download Bibtex

Abstract

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.
Go to article

Authors and Affiliations

Nadiia Artyukhova
Jan Krmela
Artem Artyukhov
Vladimíra Krmelová
Mária Gavendová
Alžbeta Bakošová
Download PDF Download RIS Download Bibtex

Abstract

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 involve halo nuclei by using a semiclassical approach. The semiclassical and quantum mechanics treatments comprise 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 Vb, the quantum mechanics coupled channels are very similar, according to the experimental results.
Go to article

Authors and Affiliations

Maryam H. Abd Madhi
Fouad A. Majeed
Download PDF Download RIS Download Bibtex

Abstract

This paper presents the results of diagnostic examinations conducted on the coils of super-heaters made of 10CrMo9‒10 steel that were operated in industrial conditions at 480°C for 130 thousand hours. The tube was exposed in a 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 was 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 aging 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 steel on the flue-gas inflow side and identified the main corrosion products and mechanisms.
Go to article

Authors and Affiliations

Monika Gwoździk
Christiane Ullrich
Christian Schimpf
David Rafaja
Sławomir Kulesza
Mirosław Bramowicz
Download PDF Download RIS Download Bibtex

Abstract

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 (SEM), 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.
Go to article

Authors and Affiliations

Mirosław Szala
Aleksander Świetlicki
Weronika Sofińska-Chmiel
Download PDF Download RIS Download Bibtex

Abstract

User authentication is an essential element of any communication system. The paper investigates the vulnerability of the recently published first semiquantum 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
Go to article

Authors and Affiliations

Piotr Zawadzki

This page uses 'cookies'. Learn more