2024 - Repozytorium publikacji - Politechnika Gdańska

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Residual current devices in electric vehicles charging installations
- Stanisław Czapp
2024 Pełny tekst Przegląd Elektrotechniczny
The main requirements of national regulations and international standards regarding protection against electric shock in electric vehicle charging installations are presented. The principles of using residual current devices (RCDs) in such installations are discussed. It is pointed out that RCDs are mandatory equipment for safe charging of electric vehicles. It is noted that the standards require the use of RCDs having an appropriate type of tripping, due to the fact that in the event of an earth fault in the charging circuit, a DC component of significant value may appear in the earth fault current. A new type of residual current devices for DC installations (DC-RCD) has been indicated.
Resonant and nonresonant excitation of waves in a planar magnetosonic flow
- Anna Perelomova
2024 CONTRIBUTIONS TO PLASMA PHYSICS
Forced propagation of perturbations in a magnetosonic wave are considered. The driving force may be caused by stimulated Mandelstam–Brillouin scattering of optic waves or by intense magnetosonic exciter. Some heating-cooling function which takes into account radiative cooling and unspecified heating is taken into consideration, as well as nonlinearity of a medium. Both these factors make the excitation particular. The analytical and numerical evaluations reveal that forced oscillations differ essentially from the free propagation and depend on a number of dimensionless parameters such as the ratio of speed of exciter to the eigen speed of excited wave, the ratio of speed of an excited wave to its eigen speed, and the dimensionless magnitude of an exciter. Forced excitation is resonant if speed of an exciter coincides with the eigen speed of excited wave but may give rise to the excited perturbations with the speed different from the eigen one. The preliminary evaluations may be helpful for the controlled excitation of perturbations in natural and laboratory plasma systems and indication of the parameters of an exciter.
Resource constrained neural network training
- Mariusz Pietrołaj
- Marek Blok
2024 Pełny tekst Scientific Reports
Modern applications of neural-network-based AI solutions tend to move from datacenter backends to low-power edge devices. Environmental, computational, and power constraints are inevitable consequences of such a shift. Limiting the bit count of neural network parameters proved to be a valid technique for speeding up and increasing efficiency of the inference process. Hence, it is understandable that a similar approach is gaining momentum in the field of neural network training. In the face of growing complexity of neural network architectures, reducing resources required for preparation of new models would not only improve cost efficiency but also enable a variety of new AI applications on modern personal devices. In this work, we present a deep refinement of neural network parameters limitation with the use of the asymmetric exponent method. In addition to the previous research, we study new techniques of floating-point variables limitation, representation, and rounding. Moreover, by leveraging exponent offset, we present floating-point precision adjustments without an increase in variables’ bit count. The proposed method allowed us to train LeNet, AlexNet and ResNet-18 convolutional neural networks with a custom 8-bit floating-point representation achieving minimal or no results degradation in comparison to baseline 32-bit floating-point variables.
Response Feature Technology for High-Frequency Electronics. Optimization, Modeling, and Design Automation
- Anna Pietrenko-Dąbrowska
- Sławomir Kozieł
2024
This book discusses response feature technology and its applications to modeling, optimization, and computer-aided design of high-frequency structures including antenna and microwave components. By exploring the specific structure of the system outputs, feature-based approaches facilitate simulation-driven design procedures, both in terms of improving their computational efficiency and reliability. These benefits are associated with the weakly nonlinear relationship between feature point coordinates and design variables, which—in the context of optimization—leads to inherent regularization of the objective functions. The book provides an overview of the subject, a definition and extraction of characteristic points, and feature-based design problem reformulation. It also outlines a number of numerical algorithms developed to handle local, global, and multi-criterial design, surrogate modeling, as well as uncertainty quantification. The discussed frameworks are extensively illustrated using examples of real microwave and antenna structures, along with numerous design cases. Introductory material on simulation-driven design, numerical optimization, as well as behavioral and physics-based surrogate modeling is also included. The book will be useful for readers working in the area of high-frequency electronics, including microwave engineering, antenna design, microwave photonics, magnetism and especially those who utilize electromagnetic (EM) simulation models in their daily routines.
Response to David Steigmann’s discussion of our paper
- Thang X. Duong
- Mikhail Itskov
- Roger Sauer
2024 Pełny tekst MATHEMATICS AND MECHANICS OF SOLIDS
We respond to David Steigmann's discussion of our paper "A general theory for anisotropic Kirchhoff-Love shells with in-plane bending of embedded fibers, Math. Mech. Solids, 28(5):1274-1317" (arXiv:2101.03122). His discussion allows us to clarify two misleading statements in our original paper, and confirm that its formulation is fully consistent with the formulation of Steigmann. We also demonstrate that some of our original statements criticized by Steigmann are not wrong.
Reverberation divergence in VR applications
- Patryk Rolkowski
- Piotr Odya
- Bartłomiej Mróz
2024 International Journal of Electronics and Telecommunications
This project aimed to investigate the correlation between virtual reality (VR) imagery and ambisonic sound. With the increasing popularity of VR applications, understanding how sound is perceived in virtual environments is crucial for enhancing the immersiveness of the experience. In the experiment, participants were immersed in a virtual environment that replicated a concert hall. Their task was to assess the correspondence between sound scenes (which differed in reverberation times and their characteristics) and the observed invariant visual scene. The research was conducted using paired tests. Participants were asked to identify the sound scene they considered more closely matched the concert hall seen in the VR goggles for each pair. Each sound scene differed in the employed impulse response. All the impulse responses were recorded in real venues such as concert halls, auditoriums, churches, etc. To provide a realistic auditory experience, the sound scenes were processed using third-order ambisonics and decoded using binaural techniques with HRTFs. The virtual concert hall was generated using the Unreal Engine and was the same for all the tests. One of the major conclusions drawn from the conducted research was confirming the role of spatial sound in creating immersive VR experiences. The study demonstrated that appropriately matching spatial sound to the VR visual scene is essential for achieving complete immersion. Additionally, expectations and preferences regarding reverberation characteristics in different types of spaces were discovered. These findings have significant implications for the design of virtual environments, and understanding these aspects can contribute to improving VR technology and creating more immersive and realistic virtual experiences for users.
Review of Recent Advancement on Nature/Bio-inspired Antenna Designs
- Farooq Azam
- Syed Shah
- Shahid Bashir
- Sławomir Kozieł
2024 Pełny tekst IEEE Access
This article presents an extensive examination of antennas rooted in nature and biology, showcasing their remarkable performance across a wide spectrum of frequencies—from microwave to terahertz. The limitations of traditional antenna design have become increasingly evident in the face of burgeoning demands for novel communication technologies. Conventional analytical-equation-based approaches struggle to deliver the combined performance characteristics – encompassing bandwidth, gain, radiation pattern, and miniaturization – that emerging technologies necessitate. This has fueled an explosive interest in bio-inspired antenna designs, a paradigm shift drawing inspiration from the ingenious structural solutions found in the living and non-living world, from plant leaves to bird feathers. These bio-inspired designs offer distinct advantages such as broader bandwidth and reduced sizes, making them highly appealing alternatives to the limitations of conventional antenna designs. This review explores a diverse range of bio-inspired designs. Among them are fractal geometries, inspired by self-repeating patterns in nature, which achieve optimal performance. Numerous designs in this category draw inspiration from nature, incorporating patterns observed in snowflakes, tree branches, clouds, and butterflies. Furthermore, nano-antennas have attracted significant attention for their vast potential applications in microwave and optical frequencies, playing a pivotal role in high-resolution spectroscopy, biomedical diagnosis and sensing, quantum photonics, and solar cell applications. By examining design methodologies and potential benefits, this article highlights the transformative potential of nature-inspired antennas. The compelling advantages of bio-inspired approaches necessitate a thorough exploration of their potential, paving the way for the development of next-generation communication systems with unprecedented capabilities.
Review of Segmentation Methods for Coastline Detection in SAR Images
- Marcin Ciecholewski
2024 Pełny tekst ARCHIVES OF COMPUTATIONAL METHODS IN ENGINEERING
Synthetic aperture radar (SAR) images acquired by airborne sensors or remote sensing satellites contain the necessary information that can be used to investigate various objects of interest on the surface of the Earth, including coastlines. The coastal zone is of great economic importance and is also very densely populated. The intensive and increasing use of coasts and changes of coastlines motivate researchers to try to assess the pace of these changes. As remote sensing develops, coastlines are detected using various image processing and analysis methods, including segmentation methods. Segmentation is to allow separating water and land areas in order to obtain contours representing the shorelines of coasts. Its result has direct impact on the accuracy of the obtained contours and is one of the most important steps in image processing. This article presents an overview of state-of-the-art segmentation methods used for detecting and extracting coastlines from SAR images, taking into account the evaluation metrics used in them. Segmentation methods can be divided into three main groups: thresholding methods, active contours, and machine learning approaches. This article presents the theoretical and practical properties of individual groups of segmentation methods, their advantages and disadvantages, and also promising research directions. This article is intended to give researchers insight into existing approaches and to help them propose new, better solutions
RF Input-Quasi-Reflectionless Dispersive-Delay Structures Based on Complementary-Diplexer Circuits
- Maciej Jasiński
- Adam Lamęcki
- Roberto Gómez-García
- Michał Mrozowski
2024
A class of RF dispersive-delay structures (DDSs) with input-quasi-reflectionless behavior is reported. It is based on the exploitation of complementary-diplexer circuit networks, in which the out-of-band RF-input-power echoes reflected by the main bandpass-filter-(BPF)-type channel are dissipated by the resistively-terminated auxiliary bandstop-filter-(BSF)-type channel. Specifically, it is shown that the influence of the absorptive auxiliary channel over the in-band transmission-phase response of the main channel can be compensated to obtain the desired transmission-phase profile in the overall RF device. Thus, a multi-functional RF component with co-integrated DDS, BPF, and low-RF-input-reflection capabilities can be designed. Optimization-based synthesis examples at the coupling-routing-diagram level of third-and fifth-order input-quasi-reflectionless BPF-based DDSs, for which the in-band group-delay pattern increases linearly with frequency, are presented. Moreover, for practical-validation purposes, a 2-GHz microstrip prototype is built and measured.
Rhodotorulic Acid and its Derivatives: Synthesis, Properties, and Applications
- Joanna Stefaniak-Skorupa
- Michał Nowak
- Andrzej Skwarecki
2024 CURRENT MEDICINAL CHEMISTRY
Siderophores are low molecular weight compounds produced by microorganisms to scavenge iron in iron-deficient environments. Rhodotorulic acid (RA), a natural hydroxamate siderophore, plays a vital role in iron acquisition for fungi and bacteria. As the simplest natural hydroxamate siderophore, RA exhibits a high affinity for ferric ions, enabling it to form stable complexes that facilitate iron uptake and transport within microorganisms. Insights into RA derivatives reveal distinct biological effects and applications, with potential in various fields, from antioxidants to antifungals. Rhodotorulic acid and its derivatives show promise for novel therapies, plant protection strategies, and iron supplementation in agriculture. Understanding their properties could advance science and medicine with sustainable practices.
Risk Assessment at Unsignalized Intersections Based on Human-Road-Environment-Vehicle System Applying Fuzzy Logic
- Ievgen Medvediev
- Dmitriy Muzylyov
- Vitalii Ivanov
- Jakub Montewka
- Justyna Trojanowska
2024
The constant increase in motorization level and traffic density increases risks due to dangerous situations for road participants. Therefore, assessing the accident level of road network elements has been an urgent task over the past decades. However, existing approaches mainly rely on traffic flow parameters and account for dynamic vehicle characteristics. The research aims to design a model accounting for uncertain factors (weather conditions and pedestrian wear color) that directly impact the accident rate. For this, the mathematical toolkit of fuzzy logic is used. The study presented in this paper has yielded a model for assessing accident risk at unsignalized intersections. This model, known as the Fuzzy Model, considers various factors such as human behavior, road conditions, environmental factors, and vehicle characteristics. The model proposes accounting for the factors included in the four subsystems (Human-Road-Environment-Vehicle) that determine the transport mega system. Fuzzy Logic MATLAB Toolbox was used for modeling, and the model was assembled using Simulink Environment tools. The simulation used a full-factor experiment 34 for four factors at three variation levels for each parameter. A set of accident risk factors was obtained for 81 conducted tests. Based on the modeling, a 3-level table of accident risk measurement was formed at unsignalized intersections depending on the pedestrian's clothing color, intersection equipment level (illumination), weather conditions, and vehicle speed. The study results are due to a novel accident risk system that can be used for operational measures to increase safety levels at an unsignalized intersection.
Risk Assessment Due To Customs Delays In Supply Chains By Fuzzy Logic
- Ievgen Medvediev
- Dmitriy Muzylyov
- Jakub Montewka
2024
Due to violations of existing trade relations, cargo flows between the European Union and Ukraine have been redistributed. As a result, new supply chains have been created that have increased the tension on ground transport, including road and rail. Unfortunately, this has caused significant delays when crossing the border, which has led to a greater increase in the total delivery time of goods. Therefore, to plan for effective delivery, it is important to consider risks associated with increased border passing time. A detailed study of the challenge revealed that these risks are caused by various hazards, which are often fuzzy. To address these risks, a modern mathematical approach is required. Fuzzy logic has proven to be successful in dealing with such research questions. According to the above, this study aims to design a fuzzy model that proactively assesses the risks of customs delays caused by operational, technical, human, and political hazards when crossing borders. The study identified four categories of hazards that can lead to delays or refusals in customs operations, resulting in increased border crossing times. These hazards are technical failures of the control system, border blocking due to human factors, formation of a queue for technological failures, and political influence. The proposed approach can take into account both quantitative and non-quantitative threats arising at the border. The study resulted in a decision support system that allows carriers to calculate possible risks and select the best alternative border crossing point in advance, reducing the risk of supply chain disruptions due to customs waivers.
Risk factor assessment in agricultural supply chain by fuzzy logic
- Dmitriy Muzylyov
- Ievgen Medvediev
- Olexiy Pavlenko
2024
Significant uncertainty characterizes the harvest period. This aspect is due to various risks impacting agrifood supply chains. The occurrence of risks is due to hazards: technological failures, technical breakdowns, or adverse weather conditions. Hence, the operational time of the agricultural supply chain during the harvest period increases due to such risk factors. In essence, some hazards are fuzzy, and the nature of most threats is characterized by significant uncertainty. Classical risk assessment methods do not allow assessing simultaneously the impact of various risks, especially those expressed fuzzy (weather conditions). Therefore, the study objective is to design a fuzzy model assessing risk factors that impact the increase in the operating time of the agrifood supply chain during the harvest period. As initial parameters in the indistinct model, three groups of risk factors were accepted: weather conditions, technological failures and technical malfunctions. The MATLAB Fuzzy Toolbox is used to design the fuzzy model, and the model architecture is implemented in Simulink. The modelling results can be used to create the necessary reserves of the harvesting and transport complex to ensure timely harvesting and reduce the negative impact of hazards on the agricultural supply chain operating.
Risks caused by microbiologically influenced corrosion in diesel fuel storage tanks
- Michał Kuna
- Andrzej Miszczyk
2024 Ochrona przed Korozją
Microbiologically influenced corrosion (MIC) poses serious problems for the petrochemical and refinery industries. Particularly favourable conditions for MIC arise in storage tanks and transmission pipelines for mixtures of diesel oil with the addition of a biocomponent (in Poland 7%). The best conditions for the development of MIC occur at the fuel-water interface, where microorganisms are provided with a source of food and water, the presence of which is one of the basic conditions for the development of microorganisms. The development of microbiological deposits leads to the formation of sludge, causing fuel deterioration and corrosion that occurs under the resulting biomass. Studies have shown that biodiesel, alone as a substitute and as an additive to traditional fuels, increases the corrosion rate of carbon steel used in pipelines, storage tanks and other fuel infrastructure. Therefore, there is an increasing demand for research on methods of protecting steel surfaces in these conditions. The phenomena causing the corrosion of tanks and directions of research related to the protection against corrosion of infrastructure will be discussed.
Robust asymptotic super twisting sliding mode observer for non-linear uncertain biochemical systems
- Mateusz Czyżniewski
- Rafał Łangowski
2024 JOURNAL OF PROCESS CONTROL
The problem of state estimation (reconstruction of the state vector) for a given class of biochemical systems under uncertain system dynamics has been addressed in this paper. In detail, the bioreactor at a water resource recovery facility represents the considered biochemical systems. The biochemical processes taking place in the bioreactor have been modelled using an activated sludge model. Based on this model, an appropriate utility model has been derived for estimation purposes. The internal dynamics of the model have been burdened with unstructured and parametric uncertainty due to the unknown reaction kinetics functions. Taking this uncertainty into account, an analysis of the observability and detectability of the utility model has been carried out. The utility model and the available set of inputs and measured outputs have been used to design a new robust non-linear observer that allows the estimation of state variables in the presence of uncertainty. In the synthesis of the observer, the asymptotic observer methodology has been combined with a second-order sliding mode observer, a so-called super twisting algorithm. The developed observer generates not only robust and stable estimates of the state variables but also enables the reconstruction of unknown kinetic functions. The stability of the designed observer has been proven using the Lyapunov stability theory. The observer has been implemented in the Matlab/Simulink environment. The comprehensive simulation studies carried out show the high efficiency of the estimation process using the developed state observer.
Rotating rod and ball
- Sergey Kryzhevich
- Alexander Plakhov
2024 JOURNAL OF MATHEMATICAL ANALYSIS AND APPLICATIONS
We consider a mechanical system consisting of an infinite rod (a straight line) and a ball (a massless point) on the plane. The rod rotates uniformly around one of its points. The ball is reflected elastically when colliding with the rod and moves freely between consecutive hits. A sliding motion along the rod is also allowed. We prove the existence and uniqueness of the motion with a given position and velocity at a certain time instant. We prove that only 5 kinds of motion are possible: a billiard motion; a sliding motion; a billiard motion followed by sliding; a sliding motion followed by a billiard one; and a constant motion when the ball is at the center of rotation. The asymptotic behaviors of time intervals between consecutive hits and of distances between the points of hits on the rod are determined.
Rotational stiffness of a connection made using a single prestressed bolt
- Paweł Pieczka
- Piotr Iwicki
2024 Pełny tekst ENGINEERING STRUCTURES
The often overlooked rotational stiffness of connections utilizing a single prestressed bolt leads to the common assumption of treating such connections as pinned or even modeling them as rigid. Nevertheless, considering the friction between interconnected elements, it is evident that the actual rotational stiffness lies between these simplified assumptions. This study is dedicated to quantifying this stiffness and addressing the question of whether simplifying such connections to pinned or rigid is justifiable. Experimental, theoretical, and numerical analyses were conducted. The results reveal a substantial variability in this phenomenon, which can be effectively described by a normal distribution. Illustrated through a case study involving built-up battened columns, it was demonstrated that the maximum normal force in the column, when considering rotational stiffness of connections, significantly surpasses that obtained for a model assuming pinned connections. This underscores the necessity of employing a model with nonlinear rotational stiffness for an accurate analysis of such constructions.
Saint-Venant torsion based on strain gradient theory
- Przemysław Podulka
- Wojciech Macek
2024 INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
In this study, the Saint-Venant torsion problem based on strain gradient theory is developed. A total form of Mindlin's strain gradient theory is used to acquire a general Saint-Venant torsion problem of micro-bars formulation. A new Finite Element formulation based on strain gradient elasticity theory is presented to solve the Saint-Venant torsion problem of micro-bars. Moreover, the problem is solved for both micro and macro scale. In addition, six different cross sections in solid and hollow condition are considered, which the Saint-Venant torsion problem is solved on them. Torsional response of micro-bars is predicted by using the modified couple stress theory and the strain gradient theory of Aifantis which both of them employ only one length scale parameter. Some micro-bars with different cross-sectional area are investigated to show the performance of current study and conclusions are drawn from the micron-scale torsional feedback for micro-bars.
Sampling-based novel heterogeneous multi-layer stacking ensemble method for telecom customer churn prediction
- Fatima E. Usman-Hamza
- Abdullateef O. Balogun
- Ramoni Tirimisiyu Amosa
- Luiz Fernando Capretz
- Hammed Mojeed
- Shakirat A. Salihu
- Abimbola G. Akintola
- Modinat Abolore Mabayoje
2024 Pełny tekst Scientific African
In recent times, customer churn has become one of the most significant issues in business-oriented sectors with telecommunication being no exception. Maintaining current customers is particularly valuable due to the high degree of rivalry among telecommunication companies and the costs of acquiring new ones. The early prediction of churned customers may help telecommunication companies to identify the causes of churn and design industrial tactics to address or mitigate the churn problem. Controlling customer churn by developing efficient and reliable customer churn prediction (CCP) solutions is essential to achieving this objective. Findings from existing CCP studies have shown that numerous methods, such as rule-based and machine-learning (ML) mechanisms, have been devised to solve the CCP problem. Nonetheless, the problems of adaptability and the resilience of rule-based CCP solutions are its major weaknesses, and the skewed pattern of churn datasets (class imbalance) is detrimental to the prediction performances of conventional ML models in CCP. Hence, this research developed a robust heterogeneous multi-layer stacking ensemble method (HMSE) for effective CCP. Specifically, in the HMSE method, the prediction prowess of five ML classifiers (Random Forest (RF), Bayesian network (BN), Support Vector Machine (SVM), K-Nearest Neighbour (KNN), and Repeated Incremental Pruning to Produce Error Reduction (RIPPER)) with distinct computational characteristics are ensembled based on stacking and the resulting model is further enhanced using a forest penalizing attribute (FPA) model. The synthetic minority oversampling technique (SMOTE) is integrated with the proposed HMSE to balance the skewed class label present in the original experimental datasets. Extensive tests were carried out to determine the effectiveness of the proposed HMSE and S-HMSE on standard telecom CCP datasets. Observed findings from the experimental results showed that HMSE and S-HMSE can effectively predict churners even with the class imbalance (skewed datasets) problem. In addition, comparison studies demonstrated that the suggested S-HMSE offered improved prediction performance and optimum solutions for CCP in the telecom sector in comparison with baseline classifiers, homogeneous ensemble methods, and current CCP approaches.
Schemat powstawania rys na przykładzie osiowo rozciąganego pręta żelbetowego
- Marek Wesołowski
- Maciej Solarczyk
2024 Pełny tekst Inżynieria i Budownictwo
W artykule przedstawiono w sposób schematyczny ideę powstawania kolejnych rys w konstrukcjach żelbetowych na przykładzie osiowo rozciąganego pręta. Opisano początkowy oraz końcowy stan zarysowania. Wyprowadzono wzór na szerokość rysy. Przedstawiono interpretację geometryczną rys dla fazy początkowego zarysowania oraz efekt tension stiffening na przykładzie elementu osiowo rozciąganego. Przedstawiono przykładowe obliczenia miary efektu tension stiffening, szerokości rys oraz średnich naprężeń przyczepności dla fazy początkowych rys.