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Gdańsk University of Technology

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  • On Computing Curlicues Generated by Circle Homeomorphisms
    • Justyna Signerska-Rynkowska
    2022 Full text

    The dataset entitled Computing dynamical curlicues contains values of consecutive points on a curlicue generated, respectively, by rotation on the circle by different angles, the Arnold circle map (with various parameter values) and an exemplary sequence as well as corresponding diameters and Birkhoff averages of these curves. We additionally provide source codes of the Matlab programs which can be used to generate and plot the first N points of curlicues of these types and calculating related quantities. Illustrative figures are included as well.

  • On Decision-Making Strategies for Improved-Reliability Size Reduction of Microwave Passives: Intermittent Correction of Equality Constraints and Adaptive Handling of Inequality Constraints
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    • Marzieh Mahrokh
    2022 KNOWLEDGE-BASED SYSTEMS

    Design optimization of passive microwave components is an intricate process, especially if the primary objective is a reduction of the physical size of the structure. The latter has become an important design consideration for a growing number of modern applications (mobile communications, wearable/implantable devices, internet of things), where miniaturization is imperative due to a limited space allocated for the electronic circuitry. Optimization-based size reduction is a heavily constrained task, with several acceptance thresholds imposed on electrical characteristics of the system. The challenges are pronounced whenever equality constraints are involved (e.g., related to power split ratio requirements), in which case the feasible space is a thin set, thereby difficult to be explored throughout the optimization process. This feature makes conventional methods, such as penalty function approaches or algorithms with explicit constraint handling, of limited reliability. In this paper, we introduce a novel technique for reliable control of equality constraints in simulation-driven size reduction of microwave components. Our methodology involves an intermittent optimization-based correction of equality constraints. This is essentially a knowledge-based decision-making strategy implemented as a supplementary optimization stage, and launched before each iteration of the core algorithm. Constraint violation is reduced without being detrimental to the remaining figures of merit, in particular, the circuit size and inequality constraints. Meanwhile, inequality constraints are handled using a penalty function approach with adaptive adjustment of penalty coefficients. The proposed technique facilitates exploration of the feasible space, and allows for achieving reduced miniaturization rates in comparison to the benchmark methods, while ensuring a reliable control of the design constraints. These advantages have been demonstrated using four microstrip couplers, with consistent results obtained for all considered circuits.

  • ON DYNAMICS OF ELASTIC NETWORKS WITH RIGID JUNCTIONS WITHIN NONLINEAR MICRO-POLAR ELASTICITY
    • Victor Eremeev
    • Emanuele Reccia
    2022 Full text International Journal for Multiscale Computational Engineering

    Within the nonlinear micropolar elasticity we discuss effective dynamic (kinetic) properties of elastic networks with rigid joints. The model of a hyperelastic micropolar continuum is based on two constitutive relations, i.e., static and kinetic ones. They introduce a strain energy density and a kinetic energy density, respectively. Here we consider a three-dimensional elastic network made of three families of elastic fibers connected through massive rigid joints. Effective elastic properties are inherited from the geometry and material properties of the fibers, whereas the kinetic (inertia) properties are determined by the both fibers and joints. Formulae for microinertia tensors are given.

  • On Earth as in Universe
    • Krzysztof Wróblewski
    2022

    On Earth as in Universe Ślady zostawione na podobraziu przygotowanym własnoręcznie przez Kazimierza Ostrowskiego. Kilka pociągnięć pędzlem ciemną farbą na odwrocie płótna, tu i ówdzie przyklejone włosy do powierzchni gruntu, kurz nagromadzony przez lata - słowem każdy element artefaktu, który trafił do mnie, był kapsułą czasu sprzed około pięćdziesięciu lat. Jedyne co mogłem zrobić, to wpisać drobiny obecności Kazimierza Ostrowskiego w strukturę malowanego obrazu. Odnosząc się luźno do twórczości Kacha użyłem dwóch przetworzonych wzorów opracowanych przez Rogera Penrose'a. Ich bazą są symetrie pięcioosiowe wynikające ze złotego podziału. Zarówno na Ziemi jak i w Kosmosie panuje matematyczny porządek, choć na co dzień tego nie dostrzegamy. Na początku XVII wieku mówił o tym Johanes Kepler w Harmonices Mundi twierdząc, że geometryczne obiekty są modelami całego świata. Ówczesne obserwacje i wnioski Keplera potwierdzają współczesne badania, według których gdy weźmiemy dwie planety z Układu Słonecznego, połączymy ich pozycje linią i będziemy na bieżąco monitorować ich wzajemne położenie, to naszym oczom ukażą się wzory o określonych regularnych kształtach. Na lewym marginesie obrazu umieściłem nawiązanie do symetrii występujących w różnych liściach. W górnym lewym rogu kompozycji znajduje się ponadto detal zaprzeczony z jednego obrazów Hilmy af Klint z cyklu zatytułowanego Ewolucja. Artystka była przekonana, że przemianę napędza zasada polaryzacji występująca w różnych formach, takich jak światło i ciemność, dobro i zło, mężczyzna i kobieta. Jej symboliczne, czy wręcz mistyczne malarstwo jest mi szczególnie bliskie. Znajduję też pewne konotacje pomiędzy dokonaniami Hilmy af Klint i Kazimierza Ostrowskiego - choć jego twórczość miała bardziej charakter alegoryczny. Malarstwo Kazimierza Ostrowskiego w moim przekonaniu spajało i monumentalizowało to, czego doświadczamy na Ziemi z tym co dzieje się we Wszechświecie. Nie opierało się ono wprawdzie na rygorystycznej geometrii, ale rządził nim intuicyjny zmysł porządku, wyczucie równowagi i harmonii. Kachu podobnie jak Lèger „dbał o płaszczyznę” a „kompozycja musiała mieć równowagę od brzegu do brzegu” . Krzysztof Wróblewski Gdańsk, 2022

  • On Improved-Reliability Design Optimization of High-Frequency Structures Using Local Search Algorithms
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    • Piotr Płotka
    2022 Full text IEEE Access

    The role of numerical optimization has been continuously growing in the design of high-frequency structures, including microwave and antenna components. At the same time, accurate evaluation of electrical characteristics necessitates full-wave electromagnetic (EM) analysis, which is CPU intensive, especially for complex systems. As rigorous optimization routines involve repetitive EM simulations, the associated cost may be significant. In the design practice, the most widely used EM-driven procedures are by far local (e.g., gradient-based) ones. While typically incurring acceptable expenses that range from dozens to a few hundreds of objective function evaluations, they are prone to failure whenever a decent initial design is not available. Representative scenarios include simulation-based size reduction of compact devices or re-design of structures for operating/material parameters being distant from those at the available design. A standard mitigation approach is the involvement of global search methods, which entails significantly higher computational costs. This paper reviews the recent methodologies introduced to improve the reliability of local parameter tuning algorithms without degrading their computational efficiency. We discuss frequency-based regularization, adaptively adjusted design specification approach, as well as accelerated feature-based optimization. All of these techniques incorporate mechanisms that improve the performance of the search process under challenging scenarios, primarily poor initial conditions. The outline of the mentioned methods is accompanied by illustrative examples including passive microwave circuits and microstrip antennas. Benchmarking against conventional local search is provided as well. Furthermore, the paper discusses the advantages and disadvantages of the reviewed frameworks as well as speculates about future research directions.

  • On proper (1,2)‐dominating sets in graphs
    • Adrian Michalski
    • Iwona Włoch
    • Magda Dettlaff
    • Magdalena Lemańska
    2022 MATHEMATICAL METHODS IN THE APPLIED SCIENCES

    In 2008, Hedetniemi et al. introduced the concept of (1,)-domination and obtained some interesting results for (1,2) -domination. Obviously every (1,1) -dominating set of a graph (known as 2-dominating set) is (1,2) -dominating; to distinguish these concepts, we define a proper (1,2) -dominating set of a graph as follows: a subset is a proper (1,2) -dominating set of a graph if is (1,2) -dominating and it is not a (1,1) -dominating set of a graph. In particular, we introduce proper (1,2) -domination parameters and study their relations with (1,2) -domination parameters and the classical domination numbers.

  • On reliability assessment of ship machinery system in different autonomy degree; A Bayesian-based approach
    • Ahmad BahooToroody
    • Mohammad Mahdi Abaei
    • Osiris Valdez Banda
    • Jakub Montewka
    • Pentti Kujala
    2022 Full text OCEAN ENGINEERING

    Analyzing the reliability of autonomous ships has recently attracted attention mainly due to epistemic uncertainty (lack of knowledge) integrated with automatic operations in the maritime sector. The advent of new random failures with unrecognized failure patterns in autonomous ship operations requires a comprehensive reliability assessment specifically aiming at estimating the time in which the ship can be trusted to be left unattended. While the reliability concept is touched upon well through the literature, the operational trustworthiness needs more elaboration to be established for system safety, especially within the maritime sector. Accordingly, in this paper, a probabilistic approach has been established to estimate the trusted operational time of the ship machinery system through different autonomy degrees. The uncertainty associated with ship operation has been quantified using Markov Chain Monte-Carlo simulation from likelihood function in Bayesian inference. To verify the developed framework, a practical example of a machinery plant used in typical short sea merchant ships is taken into account. This study can be exploited by asset managers to estimate the time in which the ship can be left unattended.

  • On solvability of initial boundary-value problems of micropolar elastic shells with rigid inclusions
    • Victor Eremeev
    • Leonid Lebedev
    • Violetta Konopińska-Zmysłowska
    2022 Full text MATHEMATICS AND MECHANICS OF SOLIDS

    The problem of dynamics of a linear micropolar shell with a finite set of rigid inclusions is considered. The equations of motion consist of the system of partial differential equations (PDEs) describing small deformations of an elastic shell and ordinary differential equations (ODEs) describing the motions of inclusions. Few types of the contact of the shell with inclusions are considered. The weak setup of the problem is formulated and studied. It is proved a theorem of existence and uniqueness of a weak solution for the problem under consideration.

  • On the Bending of Multilayered Plates Considering Surface Viscoelasticity
    • Victor Eremeev
    • Violetta Konopińska-Zmysłowska
    2022

    We discuss the bending resistance of multilayered plates taking into account surface/interfacial viscoelasticity. Within the linear surface viscoelasticity we introduce the surface/interfacial stresses linearly dependent on the history of surface strains. In order to underline the surface viscoelasticity contribution to the bending response we restrict ourselves to the elastic behaviour in the bulk. Using the correspondence principle of the theory of viscoelasticity we present an effective bending relaxation function.

  • On the deformation and frequency analyses of SARS-CoV-2 at nanoscale
    • Shahriar Dastjerdi
    • Mohammad Malikan
    • Bekir Akgöz
    • Ömer Civalek
    • Tomasz Wiczenbach
    • Victor Eremeev
    2022 Full text INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE

    The SARS-CoV-2 virus, which has emerged as a Covid-19 pandemic, has had the most significant impact on people's health, economy, and lifestyle around the world today. In the present study, the SARS-CoV-2 virus is mechanically simulated to obtain its deformation and natural frequencies. The virus under analysis is modeled on a viscoelastic spherical structure. The theory of shell structures in mechanics is used to derive the governing equations. Whereas the virus has nanometric size, using classical theories may give incorrect results. Consequently, the nonlocal elasticity theory is used to consider the effect of interatomic forces on the results. From the mechanical point of view, if a structure vibrates with a natural frequency specific to it, the resonance phenomenon will occur in that structure, leading to the destruction of the structure. Therefore, it is possible that the protein chains of SARS-CoV-2 would be destroyed by vibrating it at natural frequencies. Since the mechanical properties of SARS-CoV-2 are not clearly known due to the new emergence of this virus, deformation and natural frequencies are obtained in a specific interval. Researchers could also use this investigation as a pioneering study to find a non-vaccine treatment solution for the SARS-CoV-2 virus and various viruses, including HIV.

  • On the differential effect of temperature on the Nusselt-Rayleigh relationship in free convection
    • Michał Ryms
    • Grzegorz J. Kwiatkowski
    • Witold Lewandowski
    2022 INTERNATIONAL JOURNAL OF THERMAL SCIENCES

    The aim of and inspiration behind this paper was to explain the reasons, also observed by other researchers, of the discrepancy in the results of experimental free convection, which for small Rayleigh and Nusselt numbers in the initial phase of research can sometimes reach several hundred percent. These discrepancies decrease with increasing heating power and plate surface temperature, in proportion to the increase in Ra and Nu, reaching typical values for this type of research. To explain this phenomenon, a comprehensive theoretical and experimental analysis of the influence of the physical properties of a fluid (air and water) as well as primary (tw and t∞) and secondary (tav and Δt) temperatures on the Rayleigh number was carried out. The impact was found to be unequal. The plate temperature tw is of greater importance, which is much higher than the much lower and almost constant temperature t∞ of the undisturbed area, especially since it causes convective movement, generating differences in fluid density and thus driving the phenomenon. Similarly, the direct contribution of the temperature difference Δt to Ra suggests that it has a greater influence on convective heat transfer than the average temperature of the medium tav. By analysing the effect of each of these temperatures separately, it was possible to show that their mutual, compatible or opposite interaction (tw/t∞) causes a different scattering of results, or may even lead to unusual Rayleigh numbers (Ra temperature dualism). This study led not only to a better understanding of the phenomenon, but even to a prediction of its unusual behaviour, unheard of in typical experimental studies of free convection. For example, if we consider the theoretical convective heat transfer from a plate l = 0.15 m in air in the context of the interaction of tav and Δt, it turns out that for the same Δt = 40 K, the Rayleigh number may assume, depending on tav = (tw + t∞)/2, different values. So, for tw = 50 °C, t∞ = 10 °C and tav = 30 °C, Ra = 1.213.107, whereas for tw = 90 °C, t∞ = 50 °C and tav = 70 °C it is ≈ 1.7 times smaller (Ra = 0.687.107). This hypothetical phenomenon, unheard of in typical experimental studies, which could occur, and maybe even does occur in smelting, thermal energy, etc., forces us to think about the values of Nusselt numbers, heat transfer coefficients and heat fluxes for these two cases. This lies beyond the scope of the present paper, but it is a topic for possible future research.

  • On the Role of Polarimetric Decomposition and Speckle Filtering Methods for C-Band SAR Wetland Classification Purposes
    • Monika Gierszewska
    • Tomasz Berezowski
    2022 Full text IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing

    Previous wetlands studies have thoroughly verified the usefulness of data from synthetic aperture radar (SAR) sensors in various acquisition modes. However, the effect of the processing parameters in wetland classification remains poorly explored. In this study, we investigated the influence of speckle filters and decomposition methods with different combinations of filter and decomposition windows sizes on classification accuracy. We used a C-band Radarsat 2 image acquired over a wetland located in northeast Poland. We processed the SAR data using various speckle filters: boxcar, intensity-driven adaptive-neighborhood (IDAN), improved Lee sigma, refined Lee (in 5×5 to 11×11 pixel window sizes), and a nonlocal NL-SAR. Next, we processed the nonfiltered and filtered data using nine polarimetric decompositions, also in 5×5 to 11×11 pixel window sizes. The extracted polarimetric features were applied as an input dataset in the random forest classification model in single- and multidecomposition scenarios. In the single-decomposition scenario, the Cloude–Pottier decomposition produced the highest (72%) and the Touzi decomposition achieved the lowest (38%) accuracy. The IDAN filter with an 11×11 filter window and a 9×9 decomposition window had the highest, and the nonfiltered data with a 5×5 decomposition window had the lowest accuracy in the multidecomposition scenario. The most important features were the alpha parameter from the Cloude–Pottier decomposition, the polarimetric contribution of the Shannon entropy, and the volume backscattering components. The results stress the importance of appropriate processing parameters in the SAR data classification workflow, and the study guides in selecting the most suitable combination of radar image processing parameters for wetland classification.

  • On the Use of Selected 4th Generation Nuclear Reactors in Marine Power Plants
    • Marta Drosińska-Komor
    • Jerzy Głuch
    • Łukasz Breńkacz
    • Paweł Ziółkowski
    2022 Full text Polish Maritime Research

    This article provides a review of the possibility of using different types of reactors to power ships. The analyses were carried out for three different large vessels: a container ship, a liquid gas carrier and a bulk carrier. A novelty of this work is the analysis of the proposal to adapt marine power plants to ecological requirements in shipping by replacing the conventional propulsion system based on internal combustion engines with nuclear propulsion. The subjects of comparison are primarily the dimensions of the most important devices of the nuclear power plant and the preliminary fitness analysis. It was assumed for this purpose that the nuclear power plant fits in the engine room compartment and uses the space left after the removal of the combustion engines. At the same time, this propulsion provides at all times sufficient energy for port, technological and shipping operations at an economically justifiable speed. For deep-sea vessels, which are supposed to reach null emissions of CO, CO2, NOx, SOx and H2O, this is one of the most reasonable solutions. Finally the paper proves that all the above-mentioned marine functions could be effectively applied in power plants equipped with 4th generation nuclear reactors.

  • On the use of the cumulative strain energy density for fatigue life assessment in advanced high-strength steels
    • Ricardo Branco
    • Rui F. Martins
    • José A.F.O. Correia
    • Zbigniew Marciniak
    • Wojciech Macek
    • J. Jesus
    2022 Full text INTERNATIONAL JOURNAL OF FATIGUE

    In this paper, the applicability of the cumulative strain energy density is explored as a fatigue indicator parameter for advanced high-strength steels subjected to strain-controlled conditions. Firstly, the cyclic stress-strain responses of nine steels, selected from three multiphase families, encompassing different elemental compositions and different heat treatment routes, were studied. Then, the predictive capabilities of the proposed model were compared to those of other strain-based and energy-based approaches. It was found that the cumulative strain energy density decreases as the strain amplitude rises and it can be correlated with the fatigue life via a power function. In addition, the dialectical relationship between the cumulative strain energy and the fatigue life was not significantly affected by the elemental composition or the heat treatment route. Furthermore, the fatigue lives computed through the cumulative strain energy density concept were close to those of the other models but were slightly more conservative.

  • On weak solutions of the boundary value problem within linear dilatational strain gradient elasticity for polyhedral Lipschitz domains
    • Victor Eremeev
    • Francesco dell'Isola
    2022 Full text MATHEMATICS AND MECHANICS OF SOLIDS

    We provide the proof of an existence and uniqueness theorem for weak solutions of the equilibrium problem in linear dilatational strain gradient elasticity for bodies occupying, in the reference configuration, Lipschitz domains with edges. The considered elastic model belongs to the class of so-called incomplete strain gradient continua whose potential energy density depends quadratically on linear strains and on the gradient of dilatation only. Such a model has many applications, e.g., to describe phenomena of interest in poroelasticity or in some situations where media with scalar microstructure are necessary. We present an extension of the previous results by Eremeyev et al. (2020 Z angew Math Phys 71(6): 1–16) to the case of domains with edges and when external line forces are applied. Let us note that the interest paid to Lipschitz polyhedra-type domains is at least twofold. First, it is known that geometrical singularity of the boundary may essentially influence singularity of solutions. On the other hand, the analysis of weak solutions in polyhedral domains is of great significance for design of optimal computations using a finite-element method and for the analysis of convergence of numerical solutions.

  • On zero-error codes produced by greedy algorithms
    • Marcin Jurkiewicz
    2022 Full text JOURNAL OF COMBINATORIAL OPTIMIZATION

    We present two greedy algorithms that determine zero-error codes and lower bounds on the zero-error capacity. These algorithms have many advantages, e.g., they do not store a whole product graph in a computer memory and they use the so-called distributions in all dimensions to get better approximations of the zero-error capacity. We also show an additional application of our algorithms.

  • Online Volatile Compound Emissions Analysis Using a Microchamber/Thermal Extractor Coupled to Proton Transfer Reaction-Mass Spectrometry
    • Y Lan Pham
    • Wojciech Wojnowski
    • Jonathan Beauchamp
    2022 Full text ANALYTICAL CHEMISTRY

    Indoor air is a complex and dynamic mixture comprising manifold volatile organic compounds (VOCs) that may cause physiological and/or psychological discomfort, depending on the nature of exposure. This technical note presents a novel approach to analyze VOC emissions by coupling a microchamber/thermal extractor (μ-CTE) system to a proton transfer reaction-mass spectrometer (PTR-MS). This configuration provides an alternative to conventional emissions testing of small objects. The dynamic emission profiles of VOCs from a representative 3D-printed model are presented as a proof-of-concept analysis. Emission profiles are related to the target compound volatility, whereby 2-propanol and acetaldehyde exhibited the highest emissions and most rapid changes compared to the less volatile vinyl crotonate, 2-hydroxymethyl methacrylate, and mesitaldehyde, which were present at lower concentrations and showed different dynamics. Comparative measurements of the emission profiles of these compounds either with or without prior static equilibration yielded stark differences in their dynamics, albeit converging to similar values after 15 min of sampling time. Further, the utility of this system to determine the time required to capture a specific proportion of volatile emissions over the sampling period was demonstrated, with a mean duration of 8.4 ± 0.3 min to sample 50% of emissions across all compounds. This novel configuration provides a means to characterize the dynamic nature of VOC emissions from small objects and is especially suited to measuring highly volatile compounds, which can present a challenge for conventional sampling and analysis approaches. Further, it represents an opportunity for rapid, targeted emissions analyses of products to screen for potentially harmful volatiles.

  • Open-Set Speaker Identification Using Closed-Set Pretrained Embeddings
    • Michał Affek
    • Marek Tatara
    2022 Full text

    The paper proposes an approach for extending deep neural networks-based solutions to closed-set speaker identification toward the open-set problem. The idea is built on the characteristics of deep neural networks trained for the classification tasks, where there is a layer consisting of a set of deep features extracted from the analyzed inputs. By extracting this vector and performing anomaly detection against the set of known speakers, new speakers can be detected and modeled for further re-identification. The approach is tested on the basis of NeMo toolkit with SpeakerNet architecture. The algorithm is shown to be working with multiple new speakers introduced.

  • Opracowanie deskryptora nawierzchni drogowej do oceny oporu toczenia opon samochodowych
    • Sławomir Sommer
    2022 Full text

    Na początku niniejszej pracy pt. „Opracowanie deskryptora nawierzchni drogowej do oceny oporu toczenia opon samochodowych” przedstawiono zagadnienia dotyczące oporów ruchu pojazdu. Omówiono metody zarówno drogowe, jak i laboratoryjne badań oporu toczenia opon samochodowych. Zaprezentowano przykładowe wartości współczynników oporu toczenia opon na różnych rodzajach nawierzchni. Kolejno omówiono metody pomiaru tekstury nawierzchni. W dalszej części przedstawiono obowiązującą procedurę określania średniej głębokości profilu (Mean Profile Depth- MPD) wykonywaną zgodnie z normą ISO 13473-1. Przedstawiono wpływ tekstury nawierzchni na opór toczenia opon samochodowych. W pracy doktorskiej wykazano, że parametr MPD źle koreluje się ze współczynnikiem oporu toczenia opon. W celu przeprowadzenia analiz tekstur nawierzchni opracowano autorskie stanowiska badawcze: do pomiaru profilu tekstur nawierzchni oraz wykonanych na nich odcisków opon, a także do pomiaru sztywności dynamicznej bieżnika opony w warunkach penetracji przez elementy tekstury nawierzchni. Przeanalizowano szereg parametrów geometrycznych związanych z teksturą nawierzchni w aspekcie oporu toczenia. W efekcie opracowano parametr Descriptor of Pavament Texture (DPT50), który lepiej niż MPD koreluje się z oporem toczenia. W dalszej części przedstawiono model matematyczny opisujący ten parametr. W wyniku przeprowadzonych analiz opracowano wzorcową nawierzchnię, która ma posłużyć do prowadzenia normatywnych badań opon w warunkach laboratoryjnych. Na zakończenie pracy przedstawiono autorską technologię wytwarzania replik nawierzchni rzeczywistych, jak i wzorcowych przeznaczonych do pokrywania stalowych bębnów maszyn bieżnych.

  • Opracowanie technologii naprawy nieciągłości metalicznych w połączeniach spawanych, w konstrukcji podpór przednich pras filtracyjnych położonych na terenie Grupowej Oczyszczalni Ścieków Dębogórze
    • Wojciech Kiełczyński
    • Kamil Wilk
    • Maciej Kiełczyński
    2022

    Celem niniejszej pracy jest opracowanie wytycznych technologicznych, których wdrożenie pozwoli na usunięcie istniejących pęknięć, co przyczyni się do stabilizacji wymiarowej podpór oraz całej konstrukcji pras. Osiągniecie tego celu wymaga podjęcia następujących działań: - ocenę stanu technicznego naprawianego komponentu- podpór przednich trzech pras filtracyjnych, - określenie własności spawalniczych materiału naprawianego, - określenie warunków eksploatacji i wymogów dotyczących spawania, - zdeterminowanie norm i przepisów dedykowanych naprawianej konstrukcji, - opracowania zaleceń i wytycznych do opisu procedur spawalniczych, - kwalifikacji procedur – czyli oceny jakości spoin próbnych, - opracowanie procedur kontroli jakości na poszczególnych etapach realizacji naprawy, - sporządzenie dokumentacji końcowej.

  • Optimal placement of IMU sensor for the detection of children activity
    • Magdalena Madej
    • Jacek Rumiński
    2022

    In this paper an investigation to determine the optimal placement of IMU sensors for the purpose of children characteristic activity detection is presented. The article compares four different placement of two IMU sensors on human body. Ten healthy volunteers participated within the study. Data were collected firstly from two wireless 9-axial IMU sensors placed at the left and right wrists, then sensors were placed at lower back and hip (dominant hand side). Activities included jumping, rotating, walking, walking on tiptoe, running, clapping hands, standing still, sitting still and dancing. Several parameters such as mean, standard deviation, skewness, kurtosis, energy, correlations, Hjorth parameters (activity, mobility and complexity) and spectra purity index, were calculated from measured data. Data from all locations provided similar levels of accuracy in differentiate analyzed activities.

  • Optimal reshaping and stress controlling of double-layer spherical structures under vertical loadings
    • Ahmed Manguri
    • Najmadeen Saeed
    • Aram Mahmood
    • Javad Katebi
    • Robert Jankowski
    2022 Full text Archives of Civil Engineering

    Optimal reshaping and stress controlling of double-layer spherical structures under vertical loadings

  • Optimal state feedback controller for balancing cube
    • Adam Kowalczyk
    • Robert Piotrowski
    2022 Full text Journal of Automation, Mobile Robotics and Intelligent Systems - JAMRIS

    In this paper, a nonlinear balancing cube system is considered, the concept for which is based on an inverted pendulum. The main purpose of this work was the modelling and construction of a balancing cube with the synthesis of the control system. The control objectives included swing-up and stabilization of the cube on its vertex at an unstable equilibrium. Execution of the intended purpose required, first, deriving a cognitive mathematical model. It was based on the Lagrange method. Next, a mathematical model for control purposes was derived. The project of the physical model of the balancing cube was presented. A stabilization system based on a linear quadratic regulator (LQR) was developed. Moreover, a swing-up mechanism was used to bring the cube close to the upper equilibrium point. The algorithm switching condition was important to enable the correct functioning of the system. The developed control system was verified in the Matlab environment. Finally, verifying experiments and comparisons among models (mathematical and physical) were performed.

  • Optimally regularized local basis function approach to identification of time-varying systems
    • Maciej Niedźwiecki
    • Artur Gańcza
    2022

    Accurate identification of stochastic systems with fast-varying parameters is a challenging task which cannot be accomplished using model-free estimation methods, such as weighted least squares, which assume only that system coefficients can be regarded as locally constant. The current state of the art solutions are based on the assumption that system parameters can be locally approximated by a linear combination of appropriately chosen basis functions. The paper shows that when the internal correlation structure of estimated parameters is known, the tracking performance of the local basis function estimation algorithms can be further improved by means of regularization. The optimal form of the regularization matrix is derived analytically and it is shown that the best settings of the regularized algorithm can be determined in the computationally efficient way using cross-validation.

  • Optimization of biocorrosion resistance and mechanical properties of PM Ti–XAl–2Fe–3Cu alloys by response surface methodology
    • Mojtaba Najafizadeh
    • Mehran Ghasempour-Mouziraji
    • Morteza Hosseinzadeh
    • Sahar Yazdi
    • Ahmadreza Sarrafan
    • Mansoor Bozorg
    • Pasquale Cavaliere
    • Aleksandra Laska
    • Marek Szkodo
    2022 Full text JOURNAL OF MATERIALS SCIENCE

    In the current study, the biocorrosion resistance and mechanical properties of the Ti–XAl–2Fe–3Cu (wt%) (X = 6, 4, 2 wt%) alloy produced by powder compact extrusion of blended elemental powders were optimized by using the response surface methodology in order to gain the best combination of processing parameters. To run the optimization process, central composite design with three equal levels of oxygen, hydrogen and aluminum was used and, by employing ANOVA, the analysis of variance was implemented. The results showed that the content of aluminum has a significant effect on the microstructure, mechanical properties, biocorrosion resistance and fracture behavior of the extruded rods. The highest aluminum content corresponds to the highest alloy strength and biocorrosion resistance. This was due to the reduction of the lamella thickness and of the material colonies as the aluminum content increases. Also, by running the experimental and optimization tests, the mechanical properties resulted 1245 MPa in yield strength and 1340 MPa in ultimate tensile strength with 0.1 lAcm-2 in corrosion current.

  • Optimization-Based High-Frequency Circuit Miniaturization through Implicit and Explicit Constraint Handling: Recent Advances
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    • Marzieh Mahrokh
    2022 Full text ENERGIES

    Miniaturization trends in high-frequency electronics have led to accommodation challenges in the integration of the corresponding components. Size reduction thereof has become a practical necessity. At the same time, the increasing performance demands imposed on electronic systems remain in conflict with component miniaturization. On the practical side, the challenges related to handling design constraints are aggravated by the high cost of system evaluation, normally requiring full-wave electromagnetic (EM) analysis. Some of these issues can be alleviated by implicit constraint handling using the penalty function approach. Yet, its performance depends on the arrangement of the penalty factors, necessitating a costly trial-and-error procedure to identify their optimum setup. A workaround is offered by the recently proposed algorithms with automatic adaptation of the penalty factors using different adjustment schemes. However, these intricate strategies require a continuous problem-dependent adaptation of the penalty function throughout the entire optimization process. Alternative methodologies have been proposed by taking an explicit approach to handle the inequality constraints, along with correc-tion-based control over equality conditions, combination of which proves to be demonstrably competitive for some miniaturization tasks. Nevertheless, optimization-based miniaturization, whether using implicit or explicit constraint handling, remains a computationally expensive task. A reliable way of reducing the aforementioned costs is the incorporation of mul-ti-resolution EM fidelity models into the miniaturization procedure. Therein, the principal op-eration is based on a simultaneous monitoring of factors such as quality of the constraint satis-faction, as well as algorithm convergence status. This paper provides an overview of the abovementioned size-reduction algorithms, in which theoretical considerations are illustrated using a number of antenna and microwave circuit case studies.

  • Optimization-Based Robustness Enhancement of Compact Microwave Component Designs with Response Feature Regression Surrogates
    • Anna Pietrenko-Dąbrowska
    • Julia Kozieł
    2022 Full text KNOWLEDGE-BASED SYSTEMS

    The ability to evaluate the effects of fabrication tolerances and other types of uncertainties is a critical part of microwave design process. Improving the immunity of the device to parameter deviations is equally important, especially when the performance specifications are stringent and can barely be met even assuming a perfect manufacturing process. In the case of modern miniaturized microwave components of complex topologies, it is of paramount importance to carry out tolerance-aware design at the highest available accuracy level (i.e., with the use of full-wave electromagnetic (EM) simulations). Although reliable, EM-driven tolerance-aware design is extremely costly if conventional techniques are to be applied (e.g., Monte Carlo simulation). To overcome this setback, this paper proposes a simple and computationally efficient algorithm for robustness enhancement of compact microwave component designs. The objective is to increase the allowed deviations of geometry parameter values (described using the coefficients of an underlying probability distributions, e.g., the variance) so that the prescribed performance specifications are still fulfilled. The presented approach incorporates knowledge-based surrogate models, constructed using the characteristic points (response features) of EM-simulated system outputs, and utilized for low-cost prediction of the fabrication yield. The parameter vector of the microwave circuit of interest is adjusted within the trust-region (TR) framework to identify the maximum levels of deviations still ensuring 100-percent yield. The employment of TR also permits the adaptive control of design relocation and ensures convergence of the optimization process. Numerical verification of the presented methodology is carried out using three miniaturized microstrip circuits, including two equal-split couplers and a wideband filter. The major finding is that incorporating knowledge-based feature surrogates allows for achieving a significant improvement of the acceptable input tolerance levels (nearly two fold on the average) at a remarkably low cost of few dozen EM simulations.

  • Optimized Stress and Geometry Control of Spherical structures under Lateral Loadings
    • Aram Mahmood
    • Javad Katebi
    • Najmadeen Saeed
    • Ahmed Manguri
    2022

    In this paper, a numerical model of a double-layer spherical structure has been examined under lateral loadings. When the structure has been distorted due to loadings, the dislocated joints have been moved to their original positions utilizing the adjustment techniques based on the force method. Meanwhile, the members’ internal forces were kept in the desired domain. Optimization techniques were also implemented in order to minimalize the amount of actuation and the number of actuators to reduce the cost of the controlling process. The results of the work confirm that the adjustment and optimization techniques can be easily applied to spherical structures to control their shape and stress in members. The optimization and actuation were obtained from MATLAB and the results were verified by SAP2000.

  • Optymalizacja procesów biologicznych w oczyszczalni ścieków typu SBR
    • Robert Piotrowski
    2022

    Obiektem zainteresowania jest biologiczna, sekwencyjna oczyszczalnia ścieków (Sequ-encing Batch Reactor – SBR). Jest to złożony system sterowania z powodu nieliniowej dyna-miki, niepewności, wielu skal czasu, wielowymiarowości i braku wystarczającej liczby pomia-rów. Warunkiem koniecznym zachodzenia większości procesów biologicznych jest dostar-czenie bakteriom oczyszczającym ścieki, odpowiedniej ilości tlenu, za pomocą instalacji na-powietrzającej. Napowietrzanie spełnia bardzo ważną rolę w oczyszczalni ścieków. Powietrze dostarczane do oczyszczalni ścieków z jednej strony służy jako pokarm dla bakterii oczyszcza-jących ścieki, z drugiej strony pomaga w procesach mieszania ścieków. Koszty napowietrzania są wysokie i stanowią główny składnik kosztów operacyjnych w oczyszczalni ścieków, dlate-go bardzo ważne jest ich zmniejszanie, z jednoczesną poprawą jakości oczyszczania ścieków. W zakresie sterowania, w praktyce eksploatacyjnej oczyszczalni ścieków w dalszym cią-gu stosuje się proste algorytmy sterowania stężeniem tlenu oparte na regułach i regulatorach typu PI ze stałymi wartościami nastaw. Ze względu na złożoność problemu sterowania i różne punkty pracy są one niewystarczające. Wynika to z faktu, iż zapotrzebowanie na tlen, a tym samym na ilość powietrza dostarczanego przez instalację napowietrzającą, jest zmienne w cza-sie. W monografii zaprojektowano dwa nowoczesne, zaawansowanwane algorytmy stero-wania stężeniem tlenu: adaptacyjnego z nadrzędnym regulatorem regułowym i adaptacyjnego z nadrzędnym regulatorem heurystycznym. Układy regulacji oparto o pomiary stężenia tlenu, azotu amonowego i azotanów. Następnie zaproponowano i rozwiązano trzy zadania optymali-zacji procesów biologicznych. Przeprowadzono analizę symulacyjną efektywności zapropo-nowanych struktur i algorytmów optymalizacji dla różnych warunków obciążeń oczyszczalni ścieków w Swarzewie. Zaproponowane rozwiązania przyniosły znaczącą poprawę efektywno-ści oczyszczania ścieków, z równoczesną redukcją kosztów operacyjnych pracy tego złożone-go systemu przemysłowego.

  • Optymalizacja procesów prefabrykacyjnych przyszłością branży budowlanej
    • Rafał Ziółkowski
    • Marzena Kurpińska
    2022 Full text Materiały Budowlane

    Intensywny rozwój technologiczny w zakładach prefabrykacji będzie miał wpływ na: krótszy czas wznoszenia obiektów; lepszą jakość końcową obiektów uzyskiwaną dzięki wprowadzeniu automatyzacji linii produkcyjnych w zakładach prefabrykacji; ochronę środowiska przez lepsze zarządzanie surowcami; wprowadzanie nowych rozwiązań technologicznych pozwalających na produkcję m.in. smuklejszych elementów, przez co możliwe będzie uzyskanie większej powierzchni użytkowej obiektów budowlanych; zmniejszenie liczby wypadków na budowach; możliwość zmniejszenia liczby pracowników na placu budowy przez przeniesienie części pracochłonnych i czasochłonnych procesów do zakładów prefabrykacji; zmniejszenie wpływu warunków atmosferycznych na prowadzone prace na budowie. Rozwój zakładów prefabrykacji oznacza przyjęcie nowych strategii zarządzania zarówno w samych zakładach, jak i na budowach. Pozwoli to na zaspokojenie potrzeb inicjatyw co do ochrony, utrzymywania i podnoszenia wartości ludzkich oraz zasobów naturalnych, które będą potrzebne w przyszłości – zarównoważenia interesów ekonomicznych, społecznych i ekologicznych.

  • Organic solvents aggregating and shaping structural folding of protein, a case study of the protease enzyme
    • Monikaben Padariya
    • Maciej Bagiński
    • Minofar Babak
    • Umesh Kalathiya
    2022 Full text BIOPHYSICAL CHEMISTRY

    Low solubility of reactants or products in aqueous solutions can result in the enzymatic catalytic reactions that can occur in non-aqueous solutions. In current study we investigated aqueous solutions containing different organic solvents / deep eutectic solvents (DESs) that can influence the protease enzyme's activity, structural, and thermal stabilities. Retroviral aspartic protease enzyme is responsible for the cleavage of the polypeptide pre- cursors into mature viral components, a very crucial step for virus life cycle. In molecular dynamic simulations (MDS), the complex of the protease enzyme with Darunavirwas found highly stable in urea aqueous solution compared to when with the ethylene glycol (EG) or glycerol solvents. Particularly, in different organic solvents the presence of Darunavir induced protein-protein interactions within the protease homodimer. For the systems with EG or glycerol solvents, the flap domains of the enzyme formed an “open” conformation which lead to a weak binding affinity with the drug. Conserved D25 and G27 residues among this family of the aspartic protease enzymes made a stable binding with Darunavir in the urea systems. Unfolding of the protease dimer was initiated due to self-aggregation for the EG or glycerol organic solvents, which formed an “open” conformation for the flap domains. On the contrary lack of such clustering in urea solvent, the protease showed conventional structural folding in the presence or absence of the drug molecule. These novel findings may help to better understand the protease enzymes, which could be controlled by deep eutectic solvents.

  • Organic Vapor Sensing Mechanisms by Large-Area Graphene Back-Gated Field-Effect Transistors under UV Irradiation
    • Katarzyna Drozdowska
    • Adil Rehman
    • Pavlo Sai
    • Bartłomiej Stonio
    • Aleksandra Krajewska
    • Maksym Dub
    • Jacek Kacperski
    • Grzegorz Cywiński
    • Maciej Haras
    • Sergey Rumyantsev
    • Lars Österlund
    • Janusz Smulko
    • Andrzej Kwiatkowski
    2022 Full text ACS Sensors

    The gas sensing properties of graphene back-gated field-effect transistor (GFET) sensors toward acetonitrile, tetrahydrofuran, and chloroform vapors were investigated with the focus on unfolding possible gas detection mechanisms. The FET configuration of the sensor device enabled gate voltage tuning for enhanced measurements of changes in DC electrical characteristics. Electrical measurements were combined with a fluctuation-enhanced sensing methodology and intermittent UV irradiation. Distinctly different features in 1/f noise spectra for the organic gases measured under UV irradiation and in the dark were observed. The most intense response observed for tetrahydrofuran prompted the decomposition of the DC characteristic, revealing the photoconductive and photogating effect occurring in the graphene channel with the dominance of the latter. Our observations shed light on understanding surface processes at the interface between graphene and volatile organic compounds for graphene-based sensors in ambient conditions that yield enhanced sensitivity and selectivity.

  • Osiedle Naturia/Toruń
    • Agnieszka Błażko
    2022 Full text Architektura-Murator

    Osiedle Jar, zlokalizowane na leśnych terenach powojskowych, to niezwykle atrakcyjny i dynamicznie rozwijający się obszar budownictwa mieszkaniowego w Toruniu. W jego północnej części, w miejscu ograniczonym ulicami Strobanda, Grasera i Watzenrodego powstaje zanurzony w zieleni zespół wielorodzinnych budynków mieszkalnych autorstwa KURYŁOWICZ & ASSOCIATES - egzemplifikacja modernistycznego modelu zespołu mieszkalnego złożonego z otoczonych zielenią wolnostojących domów, z odpowiednio nasłonecznionymi i przewietrzanymi mieszkaniami różnych typów. Główną ideą projektu odwołującą się chociażby do tonącego w zieleni Hansaviertel w Berlin Mitte było takie wpisanie budynków mieszkalnych w piękne leśne otoczenie aby możliwe było zachowanie i wyeksponowanie jak największej liczby drzew i naturalnego, urozmaiconego ukształtowania terenu.

  • OVERALL SET OF BANDSAW TEETH VERSUS METHODS OF MEASUREMENTS
    • Dawid Stenka
    • Kazimierz Orłowski
    • Daniel Chuchała
    2022 Full text Trieskove a Beztrieskove Obrabanie Dreva

    This article deals with the impact of the manual methods of measurement on the overall set measurement results. It describes the results of the measurement of bandsaw teeth kerf with the use of a micrometer and a digital calliper. It is commonly known that the cutting process causes the wear of cutting tools. The wear of the cutting edge depends on the cutting conditions as well as on the mechanical properties of the processed material. One of the methods used to estimate the state of saw teeth uses kerf measurements. The overall set of teeth of the bandsaw Prime ST 0.8/1.2 by Wintersteiger, which was used in the oak wood re-saving process, was measured using a micrometer and a digital calliper. The results of different measurements were compared to estimate the accuracy and precision of those methods. It was shown that micrometer measurements were much more precise than calliper measurements. It was also noted that the kerf varied between two tooth ranges

  • Overcoming carboxylic acid inhibition by granular consortia in high-load liquefied food waste fermentation for efficient lactate accumulation
    • Xianbao Xu
    • Xia Gu
    • Tingting Ye
    • Yanbiao Liu
    • Yanan Liu
    • Gang Xue
    • Xiang Li
    • Jacek Mąkinia
    2022 JOURNAL OF CLEANER PRODUCTION

    Granular sludge, a self-aggregating spherical biofilm, possesses better stability compared to flocculent sludge under extreme conditions. This study compared the ability of anaerobic granular sludge (AnGS) and flocculent waste activated sludge (WAS) to convert food waste (FW) into highly-valuable optically active lactic acid (LA), a central and versatile intermediate platform molecule. Different loadings (30–60 g volatile suspended solids (VSS)/L) were applied and LA was accumulated to 52.7 g chemical oxygen demand (COD)/L on day 7 with optical activity (OA) of 77% using granular consortia under the highest FW loading, exhibiting a 48% increase in the yield over flocculent WAS on day 6. An initially delayed utilization of carbohydrates and subsequently enhanced glycolysis occurred with AnGS, which was in line with its high accumulation of LA. Furthermore, the AnGS consortia were dominated by LA bacteria (81%), including Bacillus, Lactobacillus, and Bifidobacterium, much higher than the WAS consortia (48%). The AnGS was more tolerant to LA inhibition, preventing cytoplasmic pH decrease (intracellular H+ in AnGS was 42% lower than in WAS) from the dissociation of carboxylic acid inside the cells. This might be due to its particular multi-layered aggregate extracellular polymeric substance structure and the enhancement of H+-transporting ATPase (increased by 120% in AnGS). This study provides a practical way to overcome carboxylic acid inhibition and increase the recovery of value-added platform molecules from organic wastes.

  • Overcoming gender bias in the digital economy. Empirical evidence for European countries
    • Ewa Lechman
    • Magdalena Popowska
    2022 Gender, Technology and Development

    This study aims to contribute to understanding the gender biases that emerge in the digital technology-related field. More specifically we concentrate on examining whether gender gaps are diminishing or are persistent in terms of women’s enrollment in technology-related programs at the tertiary level of education and for female STEM graduates. Next, this evidence is confronted with gender biases in the labor market regarding changing female and male employment in high-tech sectors; we detect whether gender gaps grow or diminish in this respect. Our data cover 29 European countries in the period 2011–2020 and are extracted from World Economic Forum reports, Eurostat, and UNESCO databases. Our methodological framework combines time trends analysis, cross-country inequalities, distributional changes, and non-parametric approximations examining relationships between variables. Our major conclusions support the view of negligibly diminishing gender inequalities in technology-related education and demonstrate increasing gender gaps regarding high-tech employment.

  • Overview of Approaches for Compensating Inherent Metamaterials Losses
    • Bashar Esmail
    • Sławomir Kozieł
    • Stanisław Szczepański
    • Huda Majid
    2022 Full text IEEE Access

    Metamaterials are synthetic composite structures with extraordinary electromagnetic properties not readily accessible in ordinary materials. These media attracted massive attention due to their exotic characteristics. However, several issues have been encountered, such as the narrow bandwidth and inherent losses that restrict the spectrum and the variety of their applications. The losses have become the principal limiting factor when employing metamaterials in real-world applications. Consequently, overcoming them is crucially important and of practical necessity. This paper discusses the practical applications of metamaterials in constructing functional devices and the effects of the losses on such devices. In more depth, it reviews the available approaches for reducing the metamaterial losses developed over the last two decades in the light of available literature. These approaches include the utilization of the principles of electromagnetically induced transparency (EIT), geometric tailoring of the metamaterial structures, and embedding gain materials. Further, computational optimization techniques, such as particle swarm optimization (PSO) and genetic algorithm (GA), are also discussed to design low-loss metamaterials. The EIT-like metamaterial and the including of gain materials are systematic and universal approaches exhibiting low loss approaching zero. In contrast, the other two are not systematic and universal approaches.

  • Overview of Knowledge Management in Occupational Safety, Health, and Ergonomics
    • Syed Imran
    • Edward Szczerbicki
    • Cesar Sanin
    2022

    Occupational safety, health, and ergonomics (OSHE) are strategic pillars of contemporary organizations. In order to provide safer workplace, it is vital to manage the organizational knowledge, so that effective decision making along with absolute compliance to standards can be executed. The critical challenge for OSHE in modern industry is management of existing individual knowledge (experience), structure knowledge, and organizational knowledge in the vast domains of practical applications. This paper firstly investigates the requirements for effective knowledge management (KM) in OSHE, secondly it reviews the present knowledge models and finally proposes a new knowledge model in OSHE. The proposed model is based on a technique called set of experience knowledge structure (SOEKS); it is not only capable of knowledge creation, distribution, elaboration, and consolidation but also possesses features to review and reflect decisions taken in past.

  • Overview of Metamaterials-Integrated Antennas for Beam Manipulation Applications: The Two Decades of Progress
    • Bashar Esmail
    • Sławomir Kozieł
    • Łukasz Gołuński
    • Huda Majid
    • Rusan Kumar Barik
    2022 Full text IEEE Access

    Metamaterials (MMs) are synthetic composite structures with superior properties not found in naturally occurring materials. MMs have gained massive attention over the last two decades because of their extraordinary properties, such as negative permittivity and permeability. These materials enable many applications in communication subsystems, especially in the field of antenna design, to enhance gain, bandwidth, and efficiency, reduce the size, and deflect the radiation pattern. The demand for beam-deflection antennas is significant in modern wireless communication research studies due to their importance in enhancing service quality, system security, avoiding interference, and economizing power. The MM structures are usually included in the vicinity of the radiating element or incorporated in the antenna substrate for controlling the radiation pattern. This review study provides an introduction to MMs, focusing on their electromagnetic properties, classification, and design approaches. Furthermore, a detailed study of using the MMs to manipulate the radiation is carried out, where different properties such as the positive/negative refractive index, epsilon-near-zero (ENZ), and mu near-zero (MNZ) are employed to achieve a beam-deflection antenna. Reconfigurable MMs are also loaded to the antenna to achieve multi-directional beam deflection with negligible effect on the antenna's physical size. Moreover, the gradient-index (GRIN) based on MMs is used to obtain high deflection angles with minor effects on other antenna properties.

  • Overview of planar antenna loading metamaterials for gain performance enhancement: the two decades of progress
    • Bashar Esmail
    • Sławomir Kozieł
    • Stanisław Szczepański
    2022 Full text IEEE Access

    Metamaterials (MTMs) are artificially engineered materials with unique electromagnetic properties not occurring in natural materials. MTMs have gained considerable attention owing to their exotic electromagnetic characteristics such as negative permittivity and permeability, thereby a negative refraction index. These extraordinary properties enable many practical applications such as super-lenses, and cloaking technology, and are used to design different electromagnetic devices like filters, polarization converters, sensors, and absorbers. Advances in MTMs have made new application fields to emerge in communication subsystems, especially in the field of antennas. MTMs are usually arranged in front or above the radiating element, or incorporated in the same substrate to improve the performance of planar antennas, in terms of improving directivity, gain, bandwidth, and efficiency, reducing the size and mutual coupling, and deflecting the radiation characteristics. High gain antennas are demanded in modern wireless communication systems. Their importance is in improving the signal strength by reducing the interference and alleviating the free space path loss. This review paper provides a brief introduction to MTMs, with the focus on their operating principles. Furthermore, a detailed study of antenna gain enhancement based on the various properties of MTMs is carried out. MTMs with low values of constitutive parameters; zero-index material (ZIM), low-index material (LIM), epsilon-near-zero (ENZ), and mu-near-zero (MNZ) are discussed in detail in the context of their capability to enhance the gain of a broad class of planar antennas. The low impedance property and lensing property, which is achieved by three different characteristics: high refractive index (HRI), gradient refractive index (GRIN), and negative refractive index (NRI) materials, are loaded to planar antennas for gain enhancement. The scope of this review has been limited to antennas that were experimentally validated in the respective source papers.

  • Oznakowanie robót drogowych – studium przypadków
    • Natalia Konkel
    • Joanna Wachnicka
    2022 Drogownictwo

    W artykule przedstawiono zagadnienia związane ze sposobami oznaczania stref robót drogowych oraz stanem technicznym zastosowanych znaków pionowych i urządzeń bezpieczeństwa ruchu drogowego. Wpływ na bezpieczeństwo, oprócz nieodpowiedniego umiejscowienia oznakowania, ma również jego odblaskowość oraz czytelność. Omawiane niespełnienie wymagań przedmiotowych cech wynika z nienależytego dbania o zapewnienie właściwych parametrów i stanu technicznego używanych znaków pionowych i urządzeń bezpieczeństwa ruchu drogowego do oznakowania tymczasowych organizacji ruchu oraz w całym okresie ich stosowania. W głównej części artykułu opisano inwentaryzację istniejącego oznakowania na drogach w czasie prowadzenia prac budowlanych oraz przeprowadzono analizę zastosowanej organizacji ruchu, stanu technicznego znaków drogowych i wpływu tych elementów na bezpieczeństwo użytkowników ruchu drogowego.

  • Paired domination versus domination and packing number in graphs
    • Magda Dettlaff
    • Didem Gözüpek
    • Joanna Raczek
    2022 Full text JOURNAL OF COMBINATORIAL OPTIMIZATION

    Given a graph G = (V(G), E(G)), the size of a minimum dominating set, minimum paired dominating set, and a minimum total dominating set of a graph G are denoted by γ (G), γpr(G), and γt(G), respectively. For a positive integer k, a k-packing in G is a set S ⊆ V(G) such that for every pair of distinct vertices u and v in S, the distance between u and v is at least k + 1. The k-packing number is the order of a largest kpacking and is denoted by ρk (G). It is well known that γpr(G) ≤ 2γ (G). In this paper, we prove that it is NP-hard to determine whether γpr(G) = 2γ (G) even for bipartite graphs. We provide a simple characterization of trees with γpr(G) = 2γ (G), implying a polynomial-time recognition algorithm. We also prove that even for a bipartite graph, it is NP-hard to determine whether γpr(G) = γt(G). We finally prove that it is both NP-hard to determine whether γpr(G) = 2ρ4(G) and whether γpr(G) = 2ρ3(G).

  • Participatory co-design approach for Greencoin educational tool shaping urban green behaviors.
    • Ewa Duda
    • Helena Anacka
    • Jolanta Kowal
    • Hanna Obracht-Prondzynska
    2022 Full text

    Our main goal is to prepare assumptions of the Greencoin (GC) cybernetic system, implying pro-ecological attitudes and behavior of city residents. We used qualitative methods, including a literature review and action research -workshops attended by academics, representatives of private and business sectors, urban movements, municipal institutions’ partners, and residents. Our results defined functionalities of the GC, identified main climate challenges, and confronted city’s possibilities and expectations of its residents. Application modules were proposed to help shape pro-ecological attitudes and behaviors of city residents. The modules include educational solutions fitting into the circular economy, and metabolic approach, enabling broader inclusion in the community. Our studies contribute to and fill the gap in the stream of research and knowledge on implementations in the co-creation of application solutions that promote pro-environmental attitudes and behavior.

  • Particle Swarm Optimization Based Optimal Design of Six-Phase Induction Motor for Electric Propulsion of Submarines
    • Lelisa Wogi
    • Amruth Thelkar
    • Tesfabirhan Tahiro
    • Tadele Ayana
    • Shabana Urooj
    • Samia Larguech
    2022 Full text ENERGIES

    Abstract: Recent research reveals that multi-phase motors in electric propulsion systems are highly recommended due to their improved reliability and efficiency over traditional three phase motors. This research presented a comparison of optimal model design of a six phase squirrel cage induction motor (IM) for electric propulsion by using Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). A six phase squirrel cage induction motor is designed and simulated by ANSYS Motor-CAD. In order to find the best fit method, simulation results are compared and applied to the motors for electric propulsion, considering the influence of design upon the motor performance. The six-phase squirrel cage induction motor is more energy efficient, reliable and cost effective for the electric propulsion compared to the conventional three phase motor. In this study, first the initial parameters of the six phase squirrel cage induction motor have been determined and then these parameters have been compared with optimized values by Genetic Algorithm (GA) and PSO optimization. The motor designed is optimized using efficiency and power losses as the fitness function. The six phase squirrel cage induction motor is designed using ANSYS Motor-CAD and the simulation results were also presented along with two-dimensional and three-dimensional geometry. The result shows that the weight and power loss are reduced to 161 kg and 0.9359 Kw respectively, while the efficiency and power factor are increased to 0.95 and 0.87 respectively when PSO is used. This shows that the result is promising.

  • Pedestrian detection in low-resolution thermal images
    • Aleksandra Górska
    • Patrycja Guzal
    • Iga Namiotko
    • Jacek Rumiński
    • Martyna Włoszczyńska
    • Jacek Rumiński
    2022

    Over one million people die in car accidents worldwide each year. A solution that will be able to reduce situations in which pedestrian safety is at risk has been sought for a long time. One of the techniques for detecting pedestrians on the road is the use of artificial intelligence in connection with thermal imaging. The purpose of this work was to design a system to assist the safety of people and car intelligence with the use of automatic detection of pedestrians in low-resolution thermal image sequences. The data acquisition system was designed and used to collect thermal images for the needs of training of machine learning methods. The created new dataset consists of 9178 annotated, low-resolution images of pedestrians in different traffic conditions. Several deep, object detection models were adapted and trained using the new dataset together with public datasets. The best model turned out to be the adapted Faster R-CNN ResNet50 FPN (Faster Region-based Convolutional, Neural Networks Residual network50, Feature Pyramid Network) model with mean Average Precision (mAP) equal to 94.00%. It was also shown that the use of transfer learning based on the features learned from the RGB images results in mAP greater than 85.00% for all investigated algorithms. The designed system finds practical application in increasing road safety through the potential use of autonomous cars and city monitoring.

  • Pedestrian Safety at Midblock Crossings on Dual Carriageway Roads in Polish Cities
    • Piotr Szagała
    • Andrzej Brzeziński
    • Mariusz Kieć
    • Marcin Budzyński
    • Joanna Wachnicka
    • Sylwia Pazdan
    2022 Full text Sustainability

    Road crossings across two or more lanes in one direction are particularly dangerous due to limited sight distance and high vehicle speeds. To improve their safety, road authorities should provide safety treatments. These may include additional measures to reduce speed and narrow the road cross-section and the introduction of active pedestrian crossings. Equipped with flashing lights activated automatically when a pedestrian is detected, the crossings are painted red and have an anti-skid surface on approaches. The article presents an analysis of road user behaviour at pedestrian crossings on dual carriageways with a varying provision of road safety measures in some Polish cities. It also evaluates the effectiveness of the measures over time. The study was conducted before, immediately after and one year after the additional signage was introduced. The evaluation is based on how vehicle speeds changed before the pedestrian crossing, how pedestrians behaved versus the vehicle and their readiness to cross the street. The number of conflicts on selected crossings was also evaluated. The safety treatments under analysis were found to be less effective than the traditional pedestrian safety measures such as speed cushions or roads narrowed to one lane. This suggests that if used on dual carriageways the measures should only be temporary and should ultimately be replaced with traffic lights or a grade separated solution (a footbridge or tunnel) on exits from urban areas. No clear-cut conclusions about pedestrian safety can be drawn based on the traffic conflicts in question. The article is divided into the following sections: introduction with a review of the literature on pedestrian and driver behaviour studies at pedestrian crossings, including midblock crossings and dual carriageways; a description of the research method and test sites, the results, discussion of the results and conclusion.

  • Performance Analysis of Machine Learning Methods with Class Imbalance Problem in Android Malware Detection
    • Abimbola G. Akintola
    • Abdullateef O. Balogun
    • Hammed Mojeed
    • Fatima Usman-Hamza
    • Shakirat A. Salihu
    • Kayode S. Adewole
    • Ghaniyyat B. Balogun
    • Peter O. Sadiku
    2022 Full text International Journal of Interactive Mobile Technologies

    Due to the exponential rise of mobile technology, a slew of new mobile security concerns has surfaced recently. To address the hazards connected with malware, many approaches have been developed. Signature-based detection is the most widely used approach for detecting Android malware. This approach has the disadvantage of being unable to identify unknown malware. As a result of this issue, machine learning (ML) for detecting malware apps was created. Conventional ML methods are concerned with increasing classification accuracy. However, the standard classification method performs poorly in recognizing malware applications due to the unbalanced real-world datasets. In this study, an empirical analysis of the detection performance of ML methods in the presence of class imbalance is conducted. Specifically, eleven (11) ML methods with diverse computational complexities were investigated. Also, the synthetic minority oversampling technique (SMOTE) and random undersampling (RUS) are deployed to address the class imbalance in the Android malware datasets. The experimented ML methods are tested using the Malgenome and Drebin Android malware datasets that contain features gathered from both static and dynamic malware approaches. According to the experimental findings, the performance of each experimented ML method varies across the datasets. Moreover, the presence of class imbalance deteriorated the performance of the ML methods as their performances were amplified with the deployment of data sampling methods (SMOTE and RUS) used to alleviate the class imbalance problem. Besides, ML models with SMOTE technique are superior to ML models based on the RUS method. It is therefore recommended to address the inherent class imbalance problem in Android Malware detection

  • Performance Analysis of the OpenCL Environment on Mobile Platforms
    • Przemysław Falkowski-Gilski
    • Maciej Plewka
    2022

    Today’s smartphones have more and more features that so far were only assigned to personal computers. Every year these devices are composed of better and more efficient components. Everything indicates that modern smartphones are replacing ordinary computers in various activities. High computing power is required for tasks such as image processing, speech recognition and object detection. This paper analyses the performance of the OpenCL (Open Compute Language) environment on mobile devices, which is a library dedicated to high-speed parallel computing. This paper examines how smartphones can access a library that, as it turned out, is not officially supported on the Android platform, and briefly describes the evaluated library. As a part of the study, this API (Application Programming Interface) was tested in the context of the achieved computing power, memory flow rate, speed of matrix multiplication and the possibility of processing the image from the camera in real-time. The obta ined results were presented in graphical format, described and commented. We also provide an insight on applications that use this API for teaching deep neural networks, image processing, etc.

  • Performance Assessment of Using Docker for Selected MPI Applications in a Parallel Environment Based on Commodity Hardware
    • Tomasz Kononowicz
    • Paweł Czarnul
    2022 Full text Applied Sciences-Basel

    In the paper, we perform detailed performance analysis of three parallel MPI applications run in a parallel environment based on commodity hardware, using Docker and bare-metal configurations. The testbed applications are representative of the most typical parallel processing paradigms: master–slave, geometric Single Program Multiple Data (SPMD) as well as divide-and-conquer and feature characteristic computational and communication schemes. We perform analysis selecting best configurations considering various optimization flags for the applications and best execution times and speed-ups in terms of the number of nodes and overhead of the virtualized environment. We have concluded that for the configurations giving the shortest execution times the overheads of Docker versus bare-metal for the applications are as follows: 7.59% for master–slave run using 64 processes (number of physical cores), 15.30% for geometric SPMD run using 128 processes (number of logical cores) and 13.29% for divide-and-conquer run using 256 processes. Finally, we compare results obtained using gcc V9 and V7 compiler versions.

  • Performance evaluation and model-based optimization of the mainstream deammonification in an integrated fixed-film activated sludge reactor
    • Mohammad Javad Mehrani
    • Mohammad Azari
    • Burkhard Teichgraber
    • Peter Jagemann
    • Jens Schoth
    • Martin Denecke
    • Jacek Mąkinia
    2022 Full text BIORESOURCE TECHNOLOGY

    This study aimed to model and optimize mainstream deammonification in an integrated fixed-film activated sludge (IFAS) pilot plant under natural seasonal temperature variations. The effect of gradually decreasing temperature on the performance was evaluated during a winter season and a transition period to summer conditions, and the correlation of the performance parameters was investigated using principal component analysis (PCA). The optimization of intermittent aeration in the long-term (30 days) dynamic conditions with on/ off ratio and dissolved oxygen (DO) set-point control was used to maximize the N-removal rate (NRR) and Nremoval efficiency (NRE). Optimization results (DO set-point of 0.2–0.25 mgO2/L, and on/off ratio of 0.05)