2021 - Repozytorium publikacji - Politechnika Gdańska

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A Review of Traffic Analysis Attacks and Countermeasures in Mobile Agents' Networks
- Rafał Leszczyna
2021
For traditional, message-based communication, traffic analysis has been already studied for over three decades and during that time various attacks have been recognised. As far as mobile agents’ networks are concerned only a few, specific-scope studies have been conducted. This leaves a gap that needs to be addressed as nowadays, in the era of Big Data, the Internet of Things, Smart Infrastructures and growing concerns for privacy, the subject gains particular importance. This paper presents the results of a literature study that aimed at identifying traffic analysing attacks and countermeasures in mobile agents’ networks. No limiting assumptions are made in regard to the complexity or size of agent networks. Also, various types of attackers’ configurations have been analysed and referred to each attack. The results enable building appropriate threat models for cybersecurity management or when designing new security solutions.
A review on application of artificial neural network (ANN) for performance and emission characteristics of diesel engine fueled with biodiesel-based fuels
- Anh Tuan Hoang
- Sandro Nižetić
- Hwai Chyuan Ong
- Wiesław Tarełko
- Van Viet Pham
- Tri Hieu Le
- Minh Quang Chau
- Xuan Phuong Nguyen
2021 Sustainable Energy Technologies and Assessments
Biodiesel has been emerging as a potential and promising biofuel for the strategy of reducing toxic emissions and improving engine performance. Computational methods aiming to offer numerical solutions were inevitable as a study methodology which was sometimes considered the only practical method. Artificial neural networks (ANN) were data-processing systems, which were used to tackle many issues in engineering and science, especially in some fields where there was a failure of the conventional modeling approaches. Thus, it was believed that the best choice was the development of a novel approach like the ANN model to anticipate engine performance and exhaust emissions with high accuracy. In this review paper, the structure and applicability of the ANN model were comprehensively evaluated. More importantly, the use of ANN with trained, tested, and validated data was introduced to determine the performance and emission characteristics of a diesel engine fueled with biodiesel-based fuel. In general, the ANN model could supply a relatively high determination coefficient as compared between predicted results and experimental data, showing that the ANN model could have a good ability to predict the engine behaviors with an accuracy higher than 95%.
A review on recent advances in the application of biosurfactants in wastewater treatment
- Surya Teja Malkapuram
- Vikrant Sharma
- Sarang P. Gumfekar
- Shirish H. Sonawane
- Shriram Sonawane
- Grzegorz Boczkaj
- Murali Mohan Seepana
2021 Pełny tekst Sustainable Energy Technologies and Assessments
Microorganisms produce a variety of non-conventional surface-active molecules, known as biosurfactants. The biosurfactants find diverse applications in the oil industry, agriculture, emulsifiers, and wastewater treatment, to name a few. Since they are produced from microbes, advantages such as biodegradability, lower toxicity, and environmental compatibility can be leveraged compared to the chemical surfactants. Recently, biosurfactants found potential usability in treating wastewater generated from various domestic, industrial, and agricultural sources. The application of biosurfactants in wastewater treatment is mainly due to their excellent foaming ability, specific activity, and high selectivity under wide operation window of temperature, pH, and salinity. Wastewater treatment with use of low cost biosurfactant is one of the important suitable goal in treating the wastewater since biosurfactants can be produced from cheap material and cause less damage to the environment by replacing surfactants produced from petroleum crude. This review focuses on the recent developments in biosurfactant production using waste materials such as food and agricultural residues, industrial waste, and animal waste and their application in wastewater treatment processes such as contaminant degradation, oil–water separation, heavy metal removal, and effluent flotation. The characteristics of the biosurfactants produced from cheap materials are compared with that of synthetic surfactants. In fact, the characteristics of both types of surfactants are found to be similar. The ability of biosurfactants for pollution removal from wastewater is extensively reviewed and presented. Finally, the review also evaluates the economic feasibility of biosurfactant production on commercial scale and their industrial scale wastewater treatment application.
A selection of PID type controller settings via LQR approach for two-wheeled balancing robot
- Krzysztof Laddach
- Mateusz Czyżniewski
- Rafał Łangowski
2021 Pełny tekst
The problem of PID type controller tuning has been addressed in this paper. In particular, a method of selection of PD settings based on the solution of linear–quadratic optimisation problem using the energy criterion has been investigated. Thus, the possibility of transforming optimal settings of the linear–quadratic regulator into the settings of the controller in the classical control system has been given. The presented methodology has been used during synthesis of control system for a two–wheeled balancing robot. Finally, the performance of the proposed control system has been validated by simulation in Matlab/Simulink environment with the use of a two–wheeled balancing robot model.
A Self-Adaptive Complex Root Tracing Algorithm for the Analysis of Propagation and Radiation Problem
- Sebastian Dziedziewicz
- Rafał Lech
- Piotr Kowalczyk
2021 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
An improved complex root tracing algorithm for radiation and propagation issues is proposed. The approach is based on a self-adaptive discretization of Cauchy’s argument principle for a C × R space and requires a reduced number of function calls in comparison to other procedures presented in the literature. A few different examples concerning propagation and radiation problems have been considered to verify the validity and efficiency of the proposed technique.
A sense of security and freedom in a residential environment
- Antoni Taraszkiewicz
- Karolina Taraszkiewicz
2021 Pełny tekst World Transactions on Engineering and Technology Education
The article is based on the results of a survey carried out among students of architecture faculties in several countries, which examined the students’ knowledge of shaping the housing environment in such a way as to enable them to fulfil two basic and, at the same time, seemingly mutually exclusive psychological needs of a person: a sense of security and a sense of freedom. In examining these issues, particular emphasis was placed on the possibility of creating such methods of architectural education that would make students - future engineers - aware of the necessity to understand the needs of the human psyche, and provide an opportunity to develop design skills to create a space that meets those needs. This kind of architectural education is part of the search for an answer to an important question today: how in the contemporary world, in a constantly transformed environment, can a person retain their own identity, find a place to live, find their own existential space?
A Series-Inclined-Slot-Fed Circularly Polarized Antenna for 5G 28-GHz Applications
- Ubaid Ullah
- Muath Al-hasan
- Sławomir Kozieł
- Ismail Mabrouk
2021 Pełny tekst IEEE Antennas and Wireless Propagation Letters
This letter presents the design of a single-point-fed, geometrically simple circularly polarized (CP) antenna for 28 GHz Ka-band applications. The proposed antenna is based on a straight microstrip line printed on one side and coupled with the nearly square patches through a 45-degree inclined V-shape slot aperture on the other side. In order to generate circular polarization, the fundamental radiating mode is degenerated at a slightly different frequency by aligning the patch edges parallel to each arm of the V-slot with orthogonal arms. This configuration yields a relatively small size (10 mm × 27.7 mm), wideband, and high-gain right-hand circularly polarized antenna operating at 28 GHz. The impedance bandwidth of the proposed antenna is from 27.2 GHz to 30.35 GHz and the 3 dB axial ratio (AR) bandwidth from 27.3 GHz to 29.7 GHz with excellent directional characteristics in the broadside direction. The peak realized gain is approximately 11.65 dBic. The performance characteristics in terms of the impedance matching, AR, gain and efficiency of the antenna for wearable applications are also investigated both numerically and experimentally. For practical applications, the small size of the structure allows for implementing the systems that consist of more than one antenna for mobility.
A ship domain-based model of collision risk for near-miss detection and Collision Alert Systems
- Rafał Szłapczyński
- Joanna Szłapczyńska
2021 Pełny tekst RELIABILITY ENGINEERING & SYSTEM SAFETY
The paper presents a new model of ship collision risk, which utilises a ship domain concept and the related domain-based collision risk parameters. An encounter is here described by five variables representing: degree of domain violation (DDV), relative speed of the two vessels, combination of the vessels’ courses, arena violations and encounter complexity. As for the first three variables, their values can be directly computed based on positions, courses and speeds of two vessels. The last two variables require decomposing a close quarters situation into phases. For this purpose the method utilizes a number of auxiliary parameters derived from the concept of ship domain: time of domain violation (TDV), time of domain exit (TDE), timespan of close quarters situation and vessels’ proximity, which is quantified based on the ship arena. The formulas and algorithms for determining all variables’ values are provided in detail. Once all the values are computed, the final collision risk assessment is made. Possible applications of the presented model include: AIS-based near-miss detection, Collision Alert Systems (CAS) and collision avoidance decision support systems (DSS). Case studies for those applications are provided, including examples of encounter classification and quantification of collision risk.
A Simple Neural Network for Collision Detection of Collaborative Robots
- Michał Czubenko
- Zdzisław Kowalczuk
2021 Pełny tekst SENSORS
Due to the epidemic threat, more and more companies decide to automate their production lines. Given the lack of adequate security or space, in most cases, such companies cannot use classic production robots. The solution to this problem is the use of collaborative robots (cobots). However, the required equipment (force sensors) or alternative methods of detecting a threat to humans are usually quite expensive. The article presents the practical aspect of collision detection with the use of a simple neural architecture. A virtual force and torque sensor, implemented as a neural network, may be useful in a team of collaborative robots. Four different approaches are compared in this article: auto-regressive (AR), recurrent neural network (RNN), convolutional long short-term memory (CNN-LSTM) and mixed convolutional LSTM network (MC-LSTM). These architectures are analyzed at different levels of input regression (motor current, position, speed, control velocity). This sensor was tested on the original CURA6 robot prototype (Cooperative Universal Robotic Assistant 6) by Intema. The test results indicate that the MC-LSTM architecture is the most effective with the regression level set at 12 samples (at 24 Hz). The mean absolute prediction error obtained by the MC-LSTM architecture was approximately 22 Nm. The conducted external test (72 different signals with collisions) shows that the presented architecture can be used as a collision detector. The MC-LSTM collision detection f1 score with the optimal threshold was 0.85. A well-developed virtual sensor based on such a network can be used to detect various types of collisions of cobot or other mobile or stationary systems operating on the basis of human-machine interaction.
A Simulation Model for Risk and Pricing Competition in the Retail Lending Market
- Błażej Kochański
2021 Pełny tekst FINANCE A UVER-CZECH JOURNAL OF ECONOMICS AND FINANCE
We propose a simulation model of the retail lending market with two types of agents: borrowers searching for low interest rates and lenders competing through risk-based pricing. We show that individual banks observe adverse selection, even if every lender applies the same pricing strategy and a credit scoring model of comparable discrimination power. Additionally, the model justifies the reverse-S shape of the response rate curve. According to the model, the benefits of even small increases in the discrimination power of credit scoring are substantial. This effect is more pronounced if the number of offers checked by the applicants before making a decision increases. The simulations illustrate the trade-off between profitability, market share, and credit loss rates. The profit-maximising strategy is to set interest rates slightly lower than the competition; the excessive price reduction turns out to be counterproductive. At the same time, there exists a niche for higher yield players.
A Single-Carrier-Based Pulse-Width Modulation Template for Cascaded H-Bridge Multilevel Inverters
- Charles Ikechukwu Odeh
- Arkadiusz Lewicki
- Marcin Morawiec
2021 Pełny tekst IEEE Access
Multiplicity of the triangular carrier signals is a criterion for the extension of sinusoidal pulsewidth modulation, SPWM, to a number of output voltage levels per phase-leg in cascaded H-bridge (CHB) multilevel inverter (MLI). Considering medium and high voltage applications where appreciable number of output voltage levels from CHB MLI is needed, commensurate high number of carrier signals in either classical level- or phase-shifted SPWM scheme for this inverter is inevitable. High-quality output waveforms from CHB MLI system demands precise synchronization of these multi-carrier signals. Sampling issues, memory constraints and computational delays pose difficulties in achieving this synchronization for real-time digital implementation. This study presents a PWM template for CHB MLI. The developed control concept generates adequate modulation templates for CHB inverter wherein a sinusoidal modulating waveform is modified to fit in a single triangular carrier signal range. These templates can be used on CHB inverter of any level with no further control modification. Nearly even distribution of switching pulses, equal sharing of the overall real power among the constituting power switches and enhanced output voltage quality were achieved with the proposed modulation. For a 3-phase, 7-level CHB, simulation and experimental results, for an R-L load, were presented.
A spline-based FE approach to modelling of high frequency dynamics of 1-D structures
- Arkadiusz Żak
- Wiktor Waszkowiak
2021 Pełny tekst COMPUTERS & MATHEMATICS WITH APPLICATIONS
In this paper a computational methodology leading to the development of a new class of FEs, based on the application of continuous and smooth approximation polynomials, being splines, has been presented. Application of the splines as appropriately defined piecewise elemental shape functions led the authors to the formulation of a new approach for FEM, named as spFEM, where contrary to the well-known NURBS approach, the boundaries of spFEs are well-defined, exactly as it is in the case of the traditional FEM. The current approach has been computationally verified by the authors it terms of high frequency dynamics including such problems as: spectra of natural frequencies, modes of natural vibrations as well as wave propagation problems, especially in the aspect of high frequency responses, all in the case of selected problems involving one- and two-mode theories of 1-D structural elements. The applicability of the proposed approach has been evaluated and compared, in terms of calculated dynamic responses, with the results obtained by the use of well-established FEM approaches: classical FEM as well as TD-SFEM. In all cases investigated by the authors the proposed spFEM approach turned out to be the most accurate approach, free from the main drawback of the other tested FEM approaches thanks to the class of differentiability of approximation polynomials, which guarantees the absence of frequency band gaps in calculated spectra of natural frequencies. A direct consequence of this feature of the proposed approach is that a larger part of the calculated spectra of natural frequency, the same as modes of natural vibrations, can effectively be used for more accurate calculations of dynamic reposes even in the case of multi-mode theories. This in contrast to the other tested FEM approaches.
A study about daylighting knowledge and education in Europe. Results from the first phase of the DAYKE project
- Federica Giuliani
- Natalia Sokół
- Valerio R.M. Lo Verso
- Raquel Viula
- Federica Caffaro
- Bernard Paule
- Aicha Diakite
- Yannick Sutter
2021 Pełny tekst Architectural Science Review
This paper presents selected results from the first stage of DAYKE (Daylight Knowledge in Europe), a 3- phase project that investigates the knowledge on daylighting in buildings among architecture students and practitioners across Europe. Subjective judgements from 561 students from 8 architecture universities in the EU, collected through two surveys in 2018. The key findings are: (i) the spatial distribution of comfort and mood in the classrooms varied depending on sky conditions and distance from windows; (ii) the average daylight factor DFm showed a good agreement with subjective judgements on the amount of daylight in a space; (iii) experts and non-experts provided similar judgements on the perception of a daylit environment; (iv) a general lack of knowledge about daylighting metrics, regulations, assessment tools and software was highlighted. Furthermore a difficulty in implementing daylighting into the design practice is also identified.
A study of jet impingement cooling enhancement by concave and convex heat sink shape modifications
- Marcin Froissart
- Paweł Ziółkowski
- Janusz Badur
2021 Pełny tekst E3S Web of Conferences
The rising demand for efficient cooling technologies is a strong driver of extensive research in this area. This trend is particularly strong in turbines and microprocessors technology. Presented study is focused on the jet impingement cooling concept, which is used in various configurations for many years. The potential of the heat sink shape modification is not yet fully explored. Available literature suggests that average Nusselt number can be improved by more than 10% by adding conical shape in the stagnation region. This refers to the axisymmetric case where cold-water jet impinges the surface of heated aluminium. Presented results are based on 2D axisymmetric thermal-FSI (Fluid-Solid Interaction) model, which was validated against the experiment. The objective of the presented analysis is to determine the correlation between cooling effectiveness (Nusselt number) and chosen examples of concave and convex shapes located in the jet stagnation area.
A study on diagnosing both isotropic and orthotropic, intentionally damaged laminates
- Khadijeh Askaripour
- Arkadiusz Żak
2021 Nondestructive Testing and Evaluation
Being the most detrimental mode in laminated structures, delamination initially degrades local structural strength, and lastly causes global structural failure, thus necessitating delamination identification at its incipient stages. For identification purposes, a comprehensive numerical and experimental study on delamination within both the laminated isotropic acrylic-glass and orthotropic epoxyglass plates is presented. As the first step, frequency variations in the acrylic-glass plate induced by different-sized delamination are examined at varying the in-plane or out-of-plane location as well as boundary conditions of delamination. Tiny delamination is identified by the use of processed signals of Lamb wave simulated by spectral finite element (SFE) technique in the next step when noticing the delamination-induced changes of frequency to be inefficient for detection purposes. While utilising absorbing layers with the obtained mechanical properties along the axis of symmetry, a quarter of the plate in the SFE domain is modelled. The study is concluded with finding the accurate location and shape of small delamination using A0 or S0 modes. The preference of A0 mode for the delamination identification compared to S0 mode is indicated. Finally, for verification purposes of Lamb wave patterns in real-life applications, a composite epoxy-glass plate is experimentally investigated via laser Doppler vibrometer (LDV).
A Survey of Fast-Recovery Mechanisms in Packet-Switched Networks
- Marco Chiesa
- Andrzej Kamisinski
- Jacek Rak
- Gabor Retvari
- Stefan Schmid
2021 Pełny tekst IEEE Communications Surveys and Tutorials
In order to meet their stringent dependability requirements, most modern packet-switched communication networks support fast-recovery mechanisms in the data plane. While reactions to failures in the data plane can be significantly faster compared to control plane mechanisms, implementing fast recovery in the data plane is challenging, and has recently received much attention in the literature. This survey presents a systematic, tutorial-like overview of packet-based fast-recovery mechanisms in the data plane, focusing on concepts but structured around different networking technologies, from traditional link-layer and IP-based mechanisms, over BGP and MPLS to emerging software-defined networks and programmable data planes. We examine the evolution of fast-recovery standards and mechanisms over time, and identify and discuss the fundamental principles and algorithms underlying different mechanisms. We then present a taxonomy of the state of the art, summarize the main lessons learned, and propose a few concrete future directions.
A Systematic Literature Review on Implementing Non-functional Requirements in Agile Software Development: Issues and Facilitating Practices
- Aleksander Jarzębowicz
- Paweł Weichbroth
2021 Pełny tekst Lecture Notes in Business Information Processing
Agile Software Development methods have become a widespread approach used by the software industry. Non-functional requirements (NFRs) are often reported to be a problematic issue for such methods. We aimed to identify (within the context of Agile projects): (1) the issues (challenges and problems) reported as affecting the implementation of NFRs; and (2) practices that facilitate the successful implementation of NFRs. We conducted a systematic literature review and processed its results to obtain a comprehensive summary. We were able to present two lists, dedicated to issues and practices, respectively. Most items from both lists, but not all, are related to the requirements engineering area. We found out that the issues reported are mostly related to the common themes of: NFR documentation techniques, NFR traceability, elicitation and communication activities. The facilitating practices mostly cover similar topics and the recommendation is to start focusing on NFRs early in the project.
A technique of experiment aided virtual prototyping to obtain the best spindle speed during face milling of large-size structures
- Krzysztof Kaliński
- Marek Galewski
- Michał Mazur
- Natalia Morawska
2021 Pełny tekst MECCANICA
The paper presents an original method concerning vibration suppression problem during milling of large-size and geometrically complicated workpieces with the use of novel way of selecting the spindle speed. This consists in repetitive simulations of the cutting process for subsequent values of the spindle speed, until the best vibration state of the workpiece is reached. An appropriate method of obtaining a computational model, called a modal approach, consists in identifying the parameters of the workpiece model created using the Finite Element Method (FEM). Thanks to the results of the identification of the modal subsystem obtained by the Experimental Modal Analysis (EMA) method, it can be stated that the parameters obtained from the experiment and delivered from the computational model have been correctly determined and constitute reliable process data for the simulation tests. The Root Mean Square (RMS) values of time domain displacements are evaluated. The efficiency of the proposed approach is evidenced by chosen technique of mechatronic design, called Experiment Aided Virtual Prototyping (EAVP). The proposed method is verified on the basis of the results of the experimental research of the relevant milling process.
A Universal Gains Selection Method for Speed Observers of Induction Machine
- Daniel Wachowiak
2021 Pełny tekst ENERGIES
Properties of state observers depend on proper gains selection. Each method of state estimation may require the implementation of specific techniques of finding those gains. The aim of this study is to propose a universal method of automatic gains selection and perform its verification on an induction machine speed observer. The method utilizes a genetic algorithm with fitness function which is directly based on the impulse response of the observer. System identification using least-squares estimation is implemented to determine the dynamic properties of the observer based on the estimation error signal. The influence of sampling time as well as signal length on the system identification has been studied. The results of gains selection using the proposed method have been compared with results obtained using the approach based on the placement of the poles of linearized estimation error equations. The introduced method delivers results comparable with analytical methods and does not require prior preparation specific to the implemented speed observer, such as linearization.
A variational approach of homogenization of piezoelectric composites towards piezoelectric and flexoelectric effective media
- Nagham Mawassy
- Hilal Reda
- Jean-François Ganghoffer
- Victor Eremeev
- Hassan Lakiss
2021 Pełny tekst INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
The effective piezoelectric properties of heterogeneous materials are evaluated in the context of periodic homogenization, whereby a variational formulation is developed, articulated with the extended Hill macrohomogeneity condition. The entire set of homogenized piezoelectric moduli is obtained as the volumetric averages of the microscopic properties of the individual constituents weighted by the displacement and polarization localization operators. This framework is extended in a second part of the paper to the computation of the flexoelectric effective properties, thereby accounting for higher gradient effects that may be induced by a strong contrast of properties of the composite constituents. The effective properties of inclusion-based composites are evaluated numerically as an illustration of the general homogenization theory and the respective effect of the volume fraction and relative tensile modulus of the reinforcement is assessed numerically.