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Gdańsk University of Technology

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  • Structural and Material Determinants Influencing the Behavior of Porous Ti and Its Alloys Made by Additive Manufacturing Techniques for Biomedical Applications
    • Magda Dziaduszewska
    • Andrzej Zieliński
    2021 Full text Materials

    One of the biggest challenges in tissue engineering is the manufacturing of porous structures that are customized in size and shape and that mimic natural bone structure. Additive manufacturing is known as a sufficient method to produce 3D porous structures used as bone substitutes in large segmental bone defects. The literature indicates that the mechanical and biological properties of scaffolds highly depend on geometrical features of structure (pore size, pore shape, porosity), surface morphology, and chemistry. The objective of this review is to present the latest advances and trends in the development of titanium scaffolds concerning the relationships between applied materials, manufacturing methods, and interior architecture determined by porosity, pore shape, and size, and the mechanical, biological, chemical, and physical properties. Such a review is assumed to show the real achievements and, on the other side, shortages in so far research.

  • Structural Changes and Their Implications in Foamed Flexible Polyurethane Composites Filled with Rapeseed Oil-Treated Ground Tire Rubber
    • Paulina Kosmela
    • Adam Olszewski
    • Łukasz Zedler
    • Paulina Burger
    • Krzysztof Formela
    • Aleksander Hejna
    2021 Full text Journal of Composites Science

    The utilization of post-consumer car tires is an essential issue from an ecological andeconomic point of view. One of the simplest and the least harmful methods is their material recyclingresulting in ground tire rubber (GTR), which can be further applied as fillers for polymer-basedcomposites. Nevertheless, insufficient interfacial interactions implicate the necessity of GTR modi-fication before introduction into polymer matrices. In this study, we investigated the influence ofrapeseed oil-assisted thermo-mechanical treatment of GTR using a reactive extrusion process on theprocessing, structure, and performance of flexible polyurethane/GTR composite foams. Appliedmodifications affected the processing of polyurethane systems. They caused a noticeable reductionin the average cell size of foams, which was attributed to the potential nucleating activity of solidparticles and changes in surface tension caused by the presence of oil. Such an effect was especiallypronounced for the waste rapeseed oil, which resulted in the highest content of closed cells. Structuralchanges caused by GTR modification implicated the enhancement of foams’ strength. Mechanicalperformance was significantly affected by the applied modifications due to the changes in glasstransition temperature. Moreover, the incorporation of waste GTR particles into the polyurethanematrix noticeably improved its thermal stability.

  • Structural changes of bacterial cellulose due to incubation in conditions simulating human plasma in the presence of selected pathogens
    • Paulina Dederko-Kantowicz
    • Agata Sommer
    • Hanna Staroszczyk
    2021 Full text CARBOHYDRATE POLYMERS

    Bacterial nanocellulose (BNC) is a natural biomaterial with a wide range of medical applications. However, it cannot be used as a biological implant of the circulatory system without checking whether it is biodegradable under human plasma conditions. This work aimed to investigate the BNC biodegradation by selected pathogens under conditions simulating human plasma. The BNC was incubated in simulated biological fluids with or without Staphylococcus aureus, Candida albicans and Aspergillus fumigatus, and its physicochemical properties were studied. The results showed that the incubation of BNC in simulated body fluid with A. fumigatus con-tributes more to its degradation than that under other conditions tested. The rearrangement of the hydrogen- bond network in this case resulted in a more compact structure, with an increased crystallinity index, reduced thermal stability and looser cross-linking. Therefore, although BNC shows great potential as a cardiovascular implant material, before use for this purpose its biodegradability should be limited.

  • Structural, electrical, and magnetic study of La-, Eu-, and Er- doped bismuth ferrite nanomaterials obtained by solution combustion synthesis
    • Angelika Wrzesińska
    • Alexander Khort
    • Marcin Witkowski
    • Jacek Szczytko
    • Jacek Ryl
    • Jacek Gurgul
    • Dmitry Kharitonov
    • Kazimierz Łątka
    • Tadeusz Szumiata
    • Aleksandra Wypych-puszkarz
    2021 Full text Scientific Reports

    In this work, the multiferroic bismuth ferrite materials Bi0.9RE0.1FeO3 doped by rare-earth (RE = La, Eu, and Er) elements were obtained by the solution combustion synthesis. Structure, electrical, and magnetic properties of prepared samples were investigated by X-ray photoelectron spectroscopy, Mössbauer spectroscopy, electrical hysteresis measurement, broadband dielectric spectroscopy, and SQUID magnetometry. All obtained nanomaterials are characterized by spontaneous electrical polarization, which confirmed their ferroelectric properties. Investigation of magnetic properties at 300.0 K and 2.0 K showed that all investigated Bi0.9RE0.1FeO3 ferrites possess significantly higher magnetization in comparison to bismuth ferrites obtained by different methods. The highest saturation magnetisation of 5.161 emu/g at 300.0 K was observed for the BLaFO sample, while at 2.0 K it was 12.07 emu/g for the BErFO sample. Several possible reasons for these phenomena were proposed and discussed.

  • Structural evaluation of percolating, self-healing polyurethane–polycaprolactone blends doped with metallic, ferromagnetic, and modified graphene fillers
    • Damian Włodarczyk
    • Iwona Żmuda-Trzebiatowska
    • J. Karczewski
    • Martyna Lubinska-Szczygeł
    • Magdalena Urban
    • Antoni Marciniak
    • Anna Kamińska
    • Patrycja Sikorska
    • Magda Graczyk
    • Michał Strankowski
    2021 POLYMERS & POLYMER COMPOSITES

    Composites with differently shaped micro- and nanofillers show various, unique thermal, and physicochemical properties when mixed with carefully chosen polymer matrix. Selected composition holds strategic value in achieving desired properties that is biodegradability, thermoelectric conductivity, and shape memory for organic coating. The main aim of this work is to briefly examine structural changes after reaching percolation threshold and activating healing abilities within exploited (8–2 wt ratio) polyurethane–polycaprolactone thin films mixed up with different types of metallic and ferromagnetic microfillers. They, with applicable dosages of reduced graphene oxide nanoparticles, should enhance materials’ mechanical and conductive properties. Microscopic and spectroscopic techniques accompanied by extensive thermal analysis have been chosen to provide useful information about local changes in surface structure and morphology. Moreover, pristine, percolating surface with inner-formed, metallic structures shows moderate conducting properties within exploited materials which unfortunately diminish after thermal healing stimulus is being applied. This statement is supported by observing the coverage of regional defects and nearby pores with a concise, uniform layer of blend having different PU:PCL ratio. Including the additional fact that apparent filler migration is changing local dopant composition brings up an assumption that both phenomena have negative synergy effect on each other.

  • Structure and magnetic properties of BeO-Fe2O3-Al2O3-TeO2 glass-ceramic composites
    • Natalia Wójcik
    • N Tagiara
    • Sharafat Ali
    • Karolina Górnicka
    • H Segawa
    • Tomasz Klimczuk
    • B Jonson
    • Doris Möncke
    • Efstratios Kamitsos
    2021 Full text JOURNAL OF THE EUROPEAN CERAMIC SOCIETY

    In this work, glass-ceramics in the xBeO–20Fe2O3–(80-x)TeO2 system with x = 0–25 mol% were synthesized by the traditional melt quenching route and studied by inductively coupled plasma optical emission spectroscopy, X-ray diffraction, confocal microscopy, infrared and Raman spectroscopy. BeO addition was found to support the crystallization process of Fe2O3 during melting, and an increased BeO content was associated with an increased fraction of the crystalline Fe2O3 phase and an increased size of these crystallites. Furthermore, samples doped with BeO exhibit an increasing polymerization of the residual tellurite glass network compared to the undoped sample. The magnetic properties and specific heat of all synthesized materials were measured, and the results show that all studied samples behave as spin-glasses. Also, the Morin transition of hematite was observed at 260 K with intensity depending on the material content in Fe2O3 crystalline phase, the formation of which correlates with the amount of added BeO.

  • Structure and properties comparison of poly(ether-urethane)s based on nonpetrochemical and petrochemical polyols obtained by solvent free two-step method
    • Paulina Kasprzyk
    • Ewa Głowińska
    • Janusz Datta
    2021 Full text EUROPEAN POLYMER JOURNAL

    The application of thermoplastic polyurethanes (TPU) is becoming more and more extensive, and the decreasing of used petrochemical monomers and reduction of energy for the polymerization and processing processes is getting increasingly important. In this paper, we confirmed the positive influence of high bio-based monomers contents (by replacing petrochemical polyol and glycol by bio-based counterparts) on processing and properties of obtained materials. A series of partially bio-based thermoplastic poly(ether-urethane)s (bio-based TPU) were obtained from bio- and petrochemical-based polyols, bio-based 1,4-butanediol, and 4,4′-diphenylmethane diisocyanate by the two-step method without using any solvents. Both the monomers’ origin and polyurethane prepolymer processing parameters were taken into account in characterization of the obtained materials. The TPUs' chemical structure was analyzed by FTIR spectroscopy and 1H NMR and the number average molecular weight was examined by 1H NMR and GPC. The measurements of dynamic mechanical thermal analysis, tensile test, hardness, density method, and rheological behavior provided useful information about the properties of prepolymers and TPUs. The processing properties and an activation energy of prepared materials was examined using the melt-flow index. It has been confirmed that despite the origin of polyols obtained thermoplastic poly(ether-urethanes) exhibited comparably good mechanical and thermo-mechanical properties, and an appropriate melt flow index facilitates their processing. Nevertheless, the use of high amount of bio-based monomers resulted in obtaining more eco-friendly materials.

  • Structure and Randomness in Planning and Reinforcement Learning
    • Konrad Czechowski
    • Piotr Januszewski
    • Piotr Kozakowski
    • Łukasz Kuciński
    • Piotr Miłoś
    2021

    Planning in large state spaces inevitably needs to balance the depth and breadth of the search. It has a crucial impact on the performance of a planner and most manage this interplay implicitly. We present a novel method \textit{Shoot Tree Search (STS)}, which makes it possible to control this trade-off more explicitly. Our algorithm can be understood as an interpolation between two celebrated search mechanisms: MCTS and random shooting. It also lets the user control the bias-variance trade-off, akin to TD(n), but in the tree search context. In experiments on challenging domains, we show that STS can get the best of both worlds consistently achieving higher scores.

  • Structure and thermoelectric properties of nickel-doped copper selenide synthesised in a hydrogen atmosphere
    • Agata Ducka
    • Bartosz Trawiński
    • Beata Bochentyn
    • A. Dubiel
    • Bogusław Kusz
    2021 Full text MATERIALS RESEARCH BULLETIN

    Nickel-doped copper selenide—Cu2-xNixSe (x = 0; 0.01; 0.02; 0.03)—materials with high thermoelectric properties were synthesised through reduction of reagents in hydrogen. The impact of the nickel content on both the microstructure and thermoelectric properties was examined. The nickel-doped samples’ microstructure differed significantly from pristine copper selenide. Besides Cu2Se, copper precipitations were present in the materials. The presence of the metallic nanoparticles in the nickel-doped materials enhanced the electrical conductivity without significantly changing the Seebeck coefficient. Above 500 K, the structure of the doped samples also resulted in decreased thermal conductivity. Also, the impact of the Cu2Se phase transition on thermoelectric properties is visible. The highest ZT value, equal to 0.8 at 650 K, was reached for the Cu1.98Ni0.02Se sample.

  • Structure and transport properties of donor-doped barium strontium cobaltites
    • Tadeusz Miruszewski
    • Wojciech Skubida
    • Arkadiusz Dawczak
    • Kacper Dzierzgowski
    • Sebastian Wachowski
    • Aleksandra Mielewczyk-Gryń
    • Maria Gazda
    2021 JOURNAL OF THE EUROPEAN CERAMIC SOCIETY

    In this work, Nb-substituted barium strontium cobaltites Ba0.5Sr0.5Co1-xNbxO3-δ (x = 0 – 0.4) have been fabricated and studied. The structural analysis showed that the Nb content influences the lattice constant as well as the distance between the (Co, Nb) and oxygen atoms. The study of morphology of samples showed that the Nb content does not change the porosity, grain size and morphology of the ceramics. The total electrical conductivity was studied as a function of temperature and pO2/pH2O. It was shown, that total conductivity is influenced by the cobalt to niobium ratio while the conduction mechanism was similar in all analyzed samples. Transport properties and the presence of protonic conductivity were studied in a dry and humidified atmosphere. A non-negligible difference between total conductivities in dry and wet atmospheres below 500 °C was observed what indicates the presence of protonic defects in these structures. Hydrogenation as a predominant protons formation mechanism was proposed.

  • Structure and transport properties of triple-conducting BaxSr1−xTi1−yFeyO3−δ oxides
    • Tadeusz Miruszewski
    • Kacper Dzierzgowski
    • Piotr Winiarz
    • Daniel Jaworski
    • Katarzyna Wiciak-Pawłowska
    • Wojciech Skubida
    • Sebastian Wachowski
    • Aleksandra Mielewczyk-Gryń
    • Maria Gazda
    2021 Full text RSC Advances

    In this work, BaxSr1−xTi1−yFeyO3−δ perovskite-based mixed conducting ceramics (for x = 0, 0.2, 0.5 and y = 0.1, 0.8) were synthesized and studied. The structural analysis based on the X-ray diffraction results showed significant changes in the unit cell volume and Fe(Ti)–O distance as a function of Ba content. The morphology of the synthesized samples studied by means of scanning electron microscopy has shown different microstructures for different contents of barium and iron. Electrochemical impedance spectroscopy studies of transport properties in a wide temperature range in the dry- and wet air confirmed the influence of barium cations on charge transport in the studied samples. The total conductivity values were in the range of 10−3 to 100 S cm−1 at 600 °C. Depending on the barium and iron content, the observed change of conductivity either increases or decreases in humidified air. Thermogravimetric measurements have shown the existence of proton defects in some of the analysed materials. The highest observed molar proton concentration, equal to 5.0 × 10−2 mol mol−1 at 300 °C, was obtained for Ba0.2Sr0.8Ti0.9Fe0.1O2.95. The relations between the structure, morphology and electrical conductivity were discussed.

  • Studies on Aminoanthraquinone-Modified Glassy Carbon Electrode: Synthesis and Electrochemical Performance toward Oxygen Reduction
    • Łukasz Macewicz
    • Grzegorz Skowierzak
    • Paweł Niedziałkowski
    • Jacek Ryl
    • Tadeusz Ossowski
    • Robert Bogdanowicz
    2021 RUSSIAN JOURNAL OF ELECTROCHEMISTRY

    In this paper, 9,10-anthraquinone (AQ) derivative-modified glassy carbon (GC) electrodes were studied towards the electrochemical reduction of oxygen in aqueous and non-aqueous solutions. The reaction of 1-chloro-9,10-anthraquinone with aliphatic diamines was applied for the synthesis of amino-9,10-anthraquinone derivatives. The obtained AQ derivatives were grafted onto the surface of glassy carbon electrodes by electropolymerisation using diazonium salts. The modified GC electrodes are sensitive to oxygen, determined by cyclic voltammetry. Changes in the oxygen determination efficiency depend mostly on the length of the side chain AQ derivative which is grafted to the GC electrode and is nearly double in comparison to a bare GC electrode modified by 1-((2-((2-aminoethyl)amino)ethyl)amino)-9,10-anthraquinone.

  • Studium wprowadzenia elektrycznych zespołów trakcyjnych z zasobnikami energii na częściowo zelektryfikowanej trasie Orunia Górna - Port Oksywie
    • Natalia Karkosińska-Brzozowska
    • Dominika Macedońska
    • Dariusz Karkosiński
    2021 Automatyka Elektryka Zakłócenia

    W artykule rozważono innowacyjny układ przewozów pasażerskich Metropolii Trójmiejskiej. Dla układu z naprzemiennie występującymi odcinkami zelektryfikowanymi i niezelektryfikowanymi wyznaczono zapotrzebowanie energetyczne i dobrano hipotetyczny zasobnik, składający się z baterii akumulatorów oraz superkondesarorów. W wyniku przeprowadzonej analizy wykazano, że zastosowanie elektrycznych zespołów zasobnikowych w stosunku do zespołów z napędem spalinowym oraz budowy sieci trakcyjnej może być ekonomicznie i środowiskowo korzystme

  • Study of a Multicriterion Decision-Making Approach to the MQL Turning of AISI 304 Steel Using Hybrid Nanocutting Fluid
    • Dubey Vineet
    • Kumar Anuj Sharma
    • Prameet Vats
    • Danil Yurievich Pimenov
    • Khaled Giasin
    • Daniel Chuchała
    2021 Full text Materials

    The enormous use of cutting fluid in machining leads to an increase in machining costs, along with different health hazards. Cutting fluid can be used efficiently using the MQL (minimum quantity lubrication) method, which aids in improving the machining performance. This paper contains multiple responses, namely, force, surface roughness, and temperature, so there arises a need for a multicriteria optimization technique. Therefore, in this paper, multiobjective optimization based on ratio analysis (MOORA), VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR), and technique for order of preference by similarity to ideal solution (TOPSIS) are used to solve different multiobjective problems, and response surface methodology is also used for optimization and to validate the results obtained by multicriterion decision-making technique (MCDM) techniques. The design of the experiment is based on the Box–Behnken technique, which used four input parameters: feed rate, depth of cut, cutting speed, and nanofluid concentration, respectively. The experiments were performed on AISI 304 steel in turning with minimum quantity lubrication (MQL) and found that the use of hybrid nanofluid (Alumina–Graphene) reduces response parameters by approximately 13% in forces, 31% in surface roughness, and 14% in temperature, as compared to Alumina nanofluid. The response parameters are analyzed using analysis of variance (ANOVA), where the depth of cut and feed rate showed a major impact on response parameters. After using all three MCDM techniques, it was found that, at fixed weight factor with each MCDM technique, a similar process parameter was achieved (velocity of 90 m/min, feed of 0.08 mm/min, depth of cut of 0.6 mm, and nanoparticle concentration of 1.5%, respectively) for optimum response. The above stated multicriterion techniques employed in this work aid decision makers in selecting optimum parameters depending upon the desired targets. Thus, this work is a novel approach to studying the effectiveness of hybrid nanofluids in the machining of AISI 304 steel using MCDM techniques.

  • STUDY OF ARRAY OF MEMS INERTIAL MEASUREMENT UNITS UNDER QUASI-STATIONARY AND DYNAMIC CONDITIONS
    • Jerzy Demkowicz
    • Krzysztof Bikonis
    2021 Full text Polish Maritime Research

    A measurement system includes all components in a chain of hardware and software that leads from a measured variable to processed data. In that context, the type and quality of the sensors or measuring devices are critical to any measurement system. MEMS/IMU sensors lag behind leading technologies in this respect, but the MEMS/IMU performance rapidly changes while is relatively inexpensive. For this reason, the paper proposes some investigations of currently available MEMS/IMUs, but in an array configuration. The article presents the results of research undertaken on this type of IMU sensor configuration under quasi-stationary and dynamic conditions and answers the question of whether the precision of current MEMS technologies for acceleration and angular velocity sensors is still improved using this kind of approach.

  • Study of Integer Spin S = 1 in the Polar Magnet β-Ni(IO3)2
    • Ebube E. Oyeka
    • Michał Winiarski
    • Thao Tran
    2021 Full text MOLECULES

    Polar magnetic materials exhibiting appreciable asymmetric exchange interactions can potentially host new topological states of matter such as vortex-like spin textures; however, realizations have been mostly limited to half-integer spins due to rare numbers of integer spin systems with broken spatial inversion lattice symmetries. Here, we studied the structure and magnetic properties of the S = 1 integer spin polar magnet β-Ni(IO3)2 (Ni2+, d8, 3F). We synthesized single crystals and bulk polycrystalline samples of β-Ni(IO3)2 by combining low-temperature chemistry techniques and thermal analysis and characterized its crystal structure and physical properties. Single crystal X-ray and powder X-ray diffraction measurements demonstrated that β-Ni(IO3)2 crystallizes in the noncentrosymmetric polar monoclinic structure with space group P21. The combination of the macroscopic electric polarization driven by the coalignment of the (IO3)− trigonal pyramids along the b axis and the S = 1 state of the Ni2+ cation was chosen to investigate integer spin and lattice dynamics in magnetism. The effective magnetic moment of Ni2+ was extracted from magnetization measurements to be 3.2(1) µB, confirming the S = 1 integer spin state of Ni2+ with some orbital contribution. β-Ni(IO3)2 undergoes a magnetic ordering at T = 3 K at a low magnetic field, μ0H = 0.1 T; the phase transition, nevertheless, is suppressed at a higher field, μ0H = 3 T. An anomaly resembling a phase transition is observed at T ≈ 2.7 K in the Cp/T vs. T plot, which is the approximate temperature of the magnetic phase transition of the material, indicating that the transition is magnetically driven. This work offers a useful route for exploring integer spin noncentrosymmetric materials, broadening the phase space of polar magnet candidates, which can harbor new topological spin physics.

  • Study of Multi-Class Classification Algorithms’ Performance on Highly Imbalanced Network Intrusion Datasets
    • Viktoras Bulavas
    • Virginijus Marcinkevičius
    • Jacek Rumiński
    2021 Full text Informatica

    This paper is devoted to the problem of class imbalance in machine learning, focusing on the intrusion detection of rare classes in computer networks. The problem of class imbalance occurs when one class heavily outnumbers examples from the other classes. In this paper, we are particularly interested in classifiers, as pattern recognition and anomaly detection could be solved as a classification problem. As still a major part of data network traffic of any organization network is benign, and malignant traffic is rare, researchers therefore have to deal with a class imbalance problem. Substantial research has been undertaken in order to identify these methods or data features that allow to accurately identify these attacks. But the usual tactic to deal with the imbalance class problem is to label all malignant traffic as one class and then solve the binary classification problem. In this paper, however, we choose not to group or to drop rare classes but instead investigate what could be done in order to achieve good multi-class classification efficiency. Rare class records were up-sampled using SMOTE method (Chawla et al., 2002) to a preset ratio targets. Experiments with the 3 network traffic datasets, namely CIC-IDS2017, CSE-CIC-IDS2018 (Sharafaldin et al., 2018) and LITNET-2020 (Damasevicius et al., 2020) were performed aiming to achieve reliable recognition of rare malignant classes available in these datasets. Popular machine learning algorithms were chosen for comparison of their readiness to support rare class detection. Related algorithm hyper parameters were tuned within a wide range of values, different data feature selection methods were used and tests were executed with and without over-sampling to test the multiple class problem classification performance of rare classes. Machine learning algorithms ranking based on Precision, Balanced Accuracy Score, G¯ , and prediction error Bias and Variance decomposition, show that decision tree ensembles (Adaboost, Random Forest Trees and Gradient Boosting Classifier) performed best on the network intrusion datasets used in this research.

  • Study of Non-Newtonian biomagnetic blood flow in a stenosed bifurcated artery having elastic walls
    • Hasan Shahzad
    • Xinhua Wang
    • Ioannis Sarris
    • Kaleem Iqbal
    • Muhammad Bilal Hafeez
    • Marek Krawczuk
    2021 Full text Scientific Reports

    Fluid structure interaction (FSI) gained attention of researchers and scientist due to its applications in science felds like biomedical engineering, mechanical engineering etc. One of the major application in FSI is to study elastic wall behavior of stenotic arteries. In this paper we discussed an incompressible Non-Newtonian blood fow analysis in an elastic bifurcated artery. A magnetic feld is applied along x direction. For coupling of the problem an Arbitrary Lagrangian–Eulerian formulation is used by twoway fuid structure interaction. To discretize the problem, we employed P2P1 fnite element technique to approximate the velocity, displacement and pressure and then linearized system of equations is solved using Newton iteration method. Analysis is carried out for power law index, Reynolds number and Hartmann number. Hemodynamic efects on elastic walls, stenotic artery and bifurcated region are evaluated by using velocity profle, pressure and loads on the walls. Study shows there is signifcant increase in wall shear stresses with an increase in Power law index and Hartmann number. While as expected increase in Reynolds number decreases the wall shear stresses. Also load on the upper wall is calculated against Hartmann number for diferent values of power law index. Results show load increases as the Hartmann number and power law index increases. From hemodynamic point of view, the load on the walls is minimum for shear thinning case but when power law index increased i.e. for shear thickening case load on the walls increased.

  • Study of probe signal bandwidth influence on estimation of coherence bandwidth for underwater acoustic communication channel
    • Iwona Kochańska
    • Jan Schmidt
    • Aleksander Schmidt
    2021 Full text APPLIED ACOUSTICS

    A signal transmitted in a shallow Underwater Acoustic Communication (UAC) channel suffers from time dispersion due to the multipath propagation and the refraction phenomena. This causes intersymbol interference of the received signal and frequency-selective fading observed in its spectrum. Coherence bandwidth is one of the key transmission parameters used for designing the physical layer of a data transmission system to minimise the influence of time dispersion on the received signal. It can be calculated on the basis of the channel impulse response, measured with the use of the correlation method and frequency modulated signals or pseudorandom binary sequences. Such signals have a narrow, impulselike autocorrelation function if considered in baseband. However, in the case of bandpass measurements, the influence of the probe signal on the estimate of the impulse response, and thus on the estimate of transmission parameters, is no longer negligible. The paper presents the results of an experimental study on probe signal bandwidth influence on estimation of coherence bandwidth. Simulations were carried out using UAC channel impulse responses measured in an inland reservoir.

  • Study of Slip Effects in Reverse Roll Coating Process Using Non-Isothermal Couple Stress Fluid
    • Hasan Shahzad
    • Xinhua Wang
    • Muhammad Bilal Hafeez
    • Zahir Shah
    • Mohammed Ahmed Alsheri
    2021 Full text Coatings

    The non-isothermal couple stress fluid inside a reverse roll coating geometry is considered. The slip condition is considered at the surfaces of the rolls. To develop the flow equations, the mathematical modelling is performed using conservation of momentum, mass, and energy. The LAT (lubrication approximation theory) is employed to simplify the equations. The closed form solution for velocity, temperature, and pressure gradient is obtained. While the pressure and flow rate are obtained numerically. The impact of involved parameters on important physical quantities such as temperature, pressure, and pressure gradient are elaborated through graphs and in tabular form. The pressure and pressure gradient decreases for variation of the couple stress parameter and velocity ratio parameter K. While the variation of the slip parameter increases the pressure and pressure gradient inside the flow geometry. Additionally, flow rate decreases for the variation of the slip parameter as fluid starts moving rapidly along the roller surface. The most important physical quantity which is responsible for maintaining the quality of the coating and thickness is flow rate. For variation of both the couple stress parameter and the slip parameter, the flow rate decreases compared to the Newtonian case, consequently the coating thickness decreases for the variation of the discussed parameter

  • Study of Statistical Text Representation Methods for Performance Improvement of a Hierarchical Attention Network
    • Adam Wawrzyński
    • Julian Szymański
    2021 Full text Applied Sciences-Basel

    To effectively process textual data, many approaches have been proposed to create text representations. The transformation of a text into a form of numbers that can be computed using computers is crucial for further applications in downstream tasks such as document classification, document summarization, and so forth. In our work, we study the quality of text representations using statistical methods and compare them to approaches based on neural networks. We describe in detail nine different algorithms used for text representation and then we evaluate five diverse datasets: BBCSport, BBC, Ohsumed, 20Newsgroups, and Reuters. The selected statistical models include Bag of Words (BoW), Term Frequency-Inverse Document Frequency (TFIDF) weighting, Latent Semantic Analysis (LSA) and Latent Dirichlet Allocation (LDA). For the second group of deep neural networks, Partition-Smooth Inverse Frequency (P-SIF), Doc2Vec-Distributed Bag of Words Paragraph Vector (Doc2Vec-DBoW), Doc2Vec-Memory Model of Paragraph Vectors (Doc2Vec-DM), Hierarchical Attention Network (HAN) and Longformer were selected. The text representation methods were benchmarked in the document classification task and BoW and TFIDF models were used were used as a baseline. Based on the identified weaknesses of the HAN method, an improvement in the form of a Hierarchical Weighted Attention Network (HWAN) was proposed. The incorporation of statistical features into HAN latent representations improves or provides comparable results on four out of five datasets. The article presents how the length of the processed text affects the results of HAN and variants of HWAN models

  • Study of the Performance of DSSS UAC System Depending on the System Bandwidth and the Spreading Sequence
    • Iwona Kochańska
    • Roman Salamon
    • Jan Schmidt
    • Aleksander Schmidt
    2021 Full text SENSORS

    A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and transmission rate. In such propagation conditions, the Direct-Sequence Spread Spectrum (DSSS) method is one of the solutions that make reliable data transmission possible. In systems with one-to-one communication, it ensures communication with a satisfactory Bit Error Rate (BER). Additionally, it makes it possible to implement the Code-Division Multiple Access (CDMA) protocol in underwater acoustic networks. This paper presents the results of simulation and experimental communication tests on a DSSS-based UAC system using three types of spreading sequence, namely m-sequences, Kasami codes and Gold codes, and occupying different bandwidths from 1 kHz to 8 kHz around a carrier frequency equal to 30 kHz. The UAC channel was simulated by impulse responses calculated by the virtual sources method and the UAC chanel models available in the Watermark simulator. The experimental tests were conducted in a model pool. Based on the obtained results, a transmission rate was estimated, which is possible to achieve in strong multipath propagation conditions, assuming reliability expressed as BER less than 0.001.

  • Study on CPU and RAM Resource Consumption of Mobile Devices using Streaming Services
    • Przemysław Falkowski-Gilski
    • Michał Woźniak
    2021

    Streaming multimedia services have become very popular in recent years, due to the development of wireless networks. With the growing number of mobile devices worldwide, service providers offer dedicated applications that allow to deliver on-demand audio and video content anytime and everywhere. The aim of this study was to compare different streaming services and investigate their impact on the CPU and RAM resources, with respect to type of Internet connection. The paper consists of two parts: theoretical and research. The first part provides a description of current means of wireless communication, including transmission of multimedia in Wi-Fi and cellular systems, as well as principles of operation of popular streaming media available on the marked, including utilized coding algorithm and available bitrates. The second part describes the set of utilized consumer devices, including 50 smartphones, as well as tools, laboratory equipment, and research scenarios. Results of this study may aid both researchers and professionals involved in the digital mobile market, including content and service providers, as well as network operators.

  • Study on Dry Sliding Wear and Friction Behaviour of Al7068/Si3N4/BN Hybrid Composites
    • Kumar Subramanian
    • Sakthivel Murugesan
    • Dhanesh G. Mohan
    • Jacek Tomków
    2021 Full text Materials

    Hybrid aluminium metal matrix composites have the potential to replace single reinforced aluminium metal matrix composites due to improved properties. Moreover, tribological performance is critical for these composites, as they have extensive application areas, such as the automotive, aerospace, marine and defence industries. The present work aims to establish the tribological characteristics of Al7068/Si3N4/BN hybrid metal matrix composites prepared by stir casting route and studied using a pin-on-disc apparatus under dry sliding conditions. The hybrid composite samples were prepared at various weight percentages (0, 5, 10) of Si3N4 and BN particles. To investigate the tribological performance of the prepared composites, the wear experiments were conducted by varying the load (20, 40 and 60 N), sliding velocity (1.5, 2.5 and 3.5 m/s) and sliding distance (500, 1000 and 1500 m). Wear experimental runs were carried out based on the plan of experiments proposed by Taguchi. The minimum wear rate was found with the composite material reinforced with 10 wt. % of Si3N4 and 5 wt. % of BN. Analysis of Variance (ANOVA) was employed to analyse the effect of process parameters on wear rate and coefficient of friction (COF). The ANOVA test revealed that the weight fraction of Si3N4 has more of a contribution percentage (36.60%) on wear rate, and load has more of a contribution percentage (29.73%) on COF. The worn-out surface of the wear test specimens was studied using its corresponding SEM micrograph and correlated with the dry sliding wear experiment results.

  • Study on Microstructural Characterization, Mechanical Properties and Residual Stress of GTAW Dissimilar Joints of P91 and P22 Steels
    • Anupam Sauraw
    • Atul Kumar Sharma
    • Dariusz Fydrych
    • Sachin Sirohi
    • Ankur Gupta
    • Aleksandra Świerczyńska
    • Chandan Pandey
    • Grzegorz Rogalski
    2021 Full text Materials

    This article deals with the dissimilar joining of two different grade Cr-Mo steel (2.25Cr-1Mo: P22 and modified 9Cr-1Mo: P91) for power plant application. The dissimilar butt-welded joint was produced for conventional V groove design by using the gas tungsten arc welding (GTAW) process with the application of an ERNiCrMo-3 Ni-based super alloy filler. A microstructure characterization was performed to measure the inhomogeneity in the microstructure and element diffusion across the interface in a welded joint. The experiments were also performed to evaluate the mechanical properties of the dissimilar welded joint in as-welded (AW) and post-weld heat treatment (PWHT) conditions. An acceptable level of the mechanical properties was obtained for the AW joint. After PWHT, a significant level of the element diffusion across the interface of the weld metal and P22 steel was observed, resulting in heterogeneity in microstructure near the interface, which was also supported by the hardness variation. Inhomogeneity in mechanical properties (impact strength and hardness) was measured across the weldments for the AW joint and was reduced after the PWHT. The tensile test results indicate an acceptable level of tensile properties for the welded joint in both AW and PWHT conditions and failure was noticed in the weak region of the P22 steel instead of the weld metal.

  • Study on Microstructure and Mechanical Properties of Laser Welded Dissimilar Joint of P91 Steel and INCOLOY 800HT Nickel Alloy
    • Vishwa Bhanu
    • Dariusz Fydrych
    • Ankur Gupta
    • Chandan Pandey
    2021 Full text Materials

    This investigation attempts to explore the weld characteristics of a laser welded dissimilar joint of ferritic/martensitic 9Cr-1Mo-V-Nb (P91) steel and Incoloy 800HT austenitic nickel alloy. This dissimilar joint is essential in power generating nuclear and thermal plants operating at 600–650 °C. In such critical operating conditions, it is essential for a dissimilar joint to preserve its characteristics and be free from any kind of defect. The difference between the physical properties of P91 and Incoloy 800HT makes their weldability challenging. Thus, the need for detailed characterization of this dissimilar weld arises. The present work intends to explore the usage of an unconventional welding process (i.e., laser beam welding) and its effect on the joint’s characteristics. The single-pass laser welding technique was employed to obtain maximum penetration through the keyhole mode. The welded joint morphology and mechanical properties were studied in as-welded (AW) and post-weld heat treatment (PWHT) conditions. The macro-optical examination shows the complete penetrations with no inclusion and porosities in the weld. The microstructural study was done in order to observe the precipitation and segregation of elements in dendritic and interface regions. Solidification cracks were observed in the weld fusion zone, confirming the susceptibility of Incoloy 800HT to such cracks due to a mismatch between the melting point and thermal conductivity of the base metals. Failure from base metal was observed in tensile test results of standard AW specimen with a yield stress of 265 MPa, and after PWHT, the value increased to 297 MPa. The peak hardness of 391 HV was observed in the P91 coarse grain heat-affected zone (CGHAZ), and PWHT confirmed the reduction in hardness. The impact toughness results that were obtained were inadequate, as the maximum value of impact toughness was obtained for AW P91 heat-affected zone (HAZ) 108 J and the minimum for PWHT Incoloy 800HT HAZ 45 J. Thus, difficulty in obtaining a dissimilar joint with Incoloy 800HT using the laser beam welding technique was observed due to its susceptibility to solidification cracking.

  • Study on Speech Transmission under Varying QoS Parameters in a OFDM Communication System
    • Monika Zamłyńska
    • Przemysław Falkowski-Gilski
    • Grzegorz Debita
    • Bogdan Miedziński
    2021

    Although there has been an outbreak of multiple multimedia platforms worldwide, speech communication is still the most essential and important type of service. With the spoken word we can exchange ideas, provide descriptive information, as well as aid to another person. As the amount of available bandwidth continues to shrink, researchers focus on novel types of transmission, based most often on multi-valued modulations, multiple channels and related sub-carriers. Currently, OFDM (Orthogonal Frequency Division Multiplexing) is widely utilized both in wired and wireless transmission. It includes terrestrial and online digital services, such as cellular systems and broadcasting standards. This paper is focused on varying QoS (Quality of Service) aspects, related with the OFDM telecommunication system, with respect to speech signals. It involves a group of four language sets, namely: American English, British English, German, and Polish. Results of this study may aid both researchers and professionals involved in designing everyday communication services as well as supplementary back-up services.

  • Study on Strategy in University Laboratory Class Teaching
    • Edward Szczerbicki
    • Haoxi Zhang
    2021 Full text

    Laboratory teaching is a critical way to ensure the effective input of techniques in engineering learning. Laboratory teaching not only contributes to improving course quality but also helps enrich comprehensive engineering application ability. However, there are some typical problems in current university laboratory teaching, such as rigid and isolated course design, outdated contents and materials, and not encouraging innovation and real-world problem solving. To overcome these challenges, a three-step teaching reconstruction strategy has been proposed to enhance university educators’ teaching effects, including introduce new laboratory teaching methods, updating contents and materials, and organizing innovative and multi-discipline Learning. Through efforts made by university teachers, students, and industry partners, the goal can be achieved by following the proposed strategy

  • Study on the Positioning Accuracy of GNSS/INS Systems Supported by DGPS and RTK Receivers for Hydrographic Surveys
    • Andrzej Stateczny
    • Cezary Specht
    • Mariusz Specht
    • David Brčić
    • Alen Jugović
    • Szymon Widźgowski
    • Marta Wiśniewska
    • Oktawia Lewicka
    2021 Full text ENERGIES

    Hydrographic surveys, in accordance with the International Hydrographic Organization (IHO) S-44 standard, can be carried out in the following five orders: Exclusive, Special, 1a, 1b and 2, for which minimum accuracy requirements for the applied positioning system have been set out. They are as follows, respectively: 1, 2, 5, 5 and 20 m, with a confidence level of 95% in twodimensional space. The Global Navigation Satellite System (GNSS) network solutions (accuracy: 2–3 cm (p = 0.95)) and the Differential Global Positioning System (DGPS) (accuracy: 1–2 m (p = 0.95)) are now commonly used positioning methods in hydrography. Due to the fact that a new order of hydrographic surveys has appeared in the IHO S-44 standard from 2020—Exclusive, looking at the current positioning accuracy of the DGPS system, it is not known whether it can be used in it. The aim of this article is to determine the usefulness of GNSS/Inertial Navigation Systems (INS) for hydrographic surveys. During the research, the following two INSs were used: Ekinox2-U and Ellipse- D by the SBG Systems, which were supported by DGPS and Real Time Kinematic (RTK) receivers. GNSS/INS measurements were carried out during the manoeuvring of the Autonomous/Unmanned Surface Vehicle (ASV/USV) named “HydroDron” on Kłodno lake in Zawory. The acquired data were processed using the mathematical model that allows us to assess whether any positioning system at a given point in time meets (or not) the accuracy requirements for each IHO order. The model was verified taking into account the historical and current test results of the DGPS and RTK systems. Tests have confirmed that the RTK system meets the requirements of all the IHO orders, even in situations where it is not functioning 100% properly. Moreover, it was proven that the DGPS system does not only meet the requirements provided for the most stringent IHO order, i.e., the Exclusive Order (horizontal position error 1 m (p = 0.95)). Statistical analyses showed that it was only a few centimetres away from meeting this criterion. Therefore, it can be expected that soon it will be used in all the IHO orders.

  • Study on the prevalence of mobile phone use by car drivers – the case of Poland
    • Paulina Szrywer
    • Joanna Wachnicka
    • Wojciech Kustra
    • Orazio Pellegrino
    2021 Full text Archives of Civil Engineering

    : Distracted driving is a significant factor affecting road safety and it can occur as a result of using mobile phones while driving. The aim of the current research is to present the prevalence of mobile phone use by Polish car drivers, based on the roadside and online survey. The field study showed that 11.6% of 1867 drivers were using mobile phones while being in motion and 26.1% of 203 drivers when stopped in front of traffic lights. While moving, 8.9% were manipulating the device by hand and 2.6% – holding it to ear. During the stop, 14.2% of the observed motorists were manipulating it, 3.0% – holding it to the ear, and 8.9% – talking through a hands-free or headset. To determine how many people generally use mobile phones while driving (not only during momentary observation), a questionnaire was also carried out. The vast majority of 252 surveyed drivers (82.9%) admitted to using mobile phones while driving, and an equally large proportion considered this behavior as dangerous for transport safety (81.3%). Most of the motorists reported using cell phones: rarely (44.4%), both when stopped and being in motion (58.9%), in a built-up area (63.6%), holding it in hand (43.5%) and in order to chat or write messages (81.8%). The majority of drivers using cell phones while driving were male and in the 25–44 or 18–24 age group. None of the respondents caused an accident due to the use of these devices, but 1.6% were guilty of a collision caused by this reason

  • STUDY ON THE RELATIONSHIP BETWEEN VEHICLE MAINTENANCE AND FUEL CONSUMPTION
    • Olha Sakno
    • Ievgen Medvediev
    • Tatiana Kolesnikova
    2021 Full text Zeszyty Naukowe Politechniki Śląskiej. Seria: Transport

    A contemporary road vehicle (RV) is a rather complex system, consisting of a large number of subsystems, assemblies, units, and elements (parts). While operating, an RV interacts with the environment, and its elements interact with each other. Consequently, the properties (parameters) of these elements change in the process - hardness, roughness, size, relative position, gapping, etc. A partial solution to the presented problems can be the search for a technique for assessing the RV technical condition by a generalised criterion, which is quite sensitive to changes in the technical state. One of these criteria may be fuel consumption in litres per 100 kilometres. This paper investigates the possibilities of using the fuel consumption indicator as a criterion for assessing the technical condition of the vehicle and the vehicle maintenance and repair technologies have been generalised to obtain a given technical solution. Thus, the possibility of using the fuel consumption indicator as a criterion for assessing the technical condition of the vehicles was explored using the Volkswagen Touran 1.9 TDI operating in urban conditions using a driving cycle. A clear correlation between the fuel consumption and the service lifetime of the vehicle has been established; therefore, it depends on the frequency and quality of the maintenance and repair (MR). The vehicle MR technology has been generalised to obtain a specified technical solution. The process of creating an RV MR Technology model is implemented based on an iterative approach (repetition) with the possibility to specify their features.

  • Subiektywny pomiar jakości sygnałów mowy i muzyki w lokalnych multipleksach radiofonii DAB+ w Gdańsku i Wrocławiu
    • Przemysław Falkowski-Gilski
    • Stefan Brachmański
    2021

    Radiofonia cyfrowa DAB+ (Digital Audio Broadcasting plus) dostępna jest dla słuchaczy w Polsce od 2013 r. Standard ten oferuje szerokie możliwości konfiguracji multipleksów lokalnych nie tylko pod względem liczby, lecz także jakości nadawanych programów radiowych. Dzięki temu możliwe jest dostosowanie parametrów emitowanych sygnałów w celu sprostania oczekiwaniom odbiorców końcowych. W przeciwieństwie do radiofonii analogowej FM sygnały audio pochodzące od różnych nadawców grupowane są w zbiór określany - ensemble. W pracy przedstawiono wyniki subiektywnych testów oceny jakości programów radiowych obejmujących sygnały mowy oraz muzyki. Badania przeprowadzono na lokalnych wariantach cyfrowego multipleksu dla Gdańska i Wrocławia. Opisano rezultaty ocen tych samych programów radiowych nadających jednakowy materiał dźwiękowy w technice analogowej FM i cyfrowej DAB+ (tzw. simulcast). Wyniki obejmowały zarówno pierwszy multipleks polskiego nadawcy (Gdańsk), jak i pionierski multipleks jednoczęstotliwościowy (Wrocław).

  • Sugar Fee in Poland as an Example of New Fiscal Burdens and Stimulation of Consumer Behaviour
    • Piotr Kasprzak
    2021

    During the economic downturn caused by the COVID-19 pandemic, the amount and structure of tax burdens imposed by the state on businesses continue to increase, as shown on the example of the newly introduced sugar fee. A new tax-related burden imposed on businesses and consumers producing and consuming sugar-sweetened beverages appeared at the beginning of 2021. The aim of the paper is to present the fiscal burdens that accompany the introduction of the sugar fee along with the justification for its introduction and its impact on the functioning of the sweetened beverage market.

  • Sulfate reducing ammonium oxidation (SULFAMMOX) process under anaerobic conditions
    • Dominika Grubba
    • Joanna Majtacz
    • Jacek Mąkinia
    2021 Full text Environmental Technology & Innovation

    Sulfate (SO42-) can be an electron acceptor for ammonium nitrogen (NH4+) oxidation under anaerobic conditions. The process is known as sulfammox and can be a viable alternative to conventional, nitrite (NO2-) dependent, anammox. Two bacterial species, including Bacillus Benzoevorans and Brocadia Anammoxoglobus Sulfate, can perform that process. With sulfammox, an economically inefficient pre-nitration step (due to aeration) is not required. There are more than 10 different systems in which sulfammox has been studied, including suspended growth, biofilm, granular and hybrid reactors. A combination of anammox and sulfur related processes (sulfammox and autotrophic denitrification) would especially be appropriate for specific industrial wastewater with high content of nitrogen compounds and SO42-. The results of recent studies suggest that very high removal efficiencies could simultaneously be achieved with respect to both NH4+ (92-99%) and SO42- (53-60%).

  • Sulfurization of phosphanylphosphinidene ligand: Access to phosphinothioyltrithiophosphonato platinum(II) complexes
    • Anna Ordyszewska
    • Natalia Szynkiewicz
    • Jarosław Chojnacki
    • Rafał Grubba
    • Jerzy Pikies
    2021 Full text INORGANICA CHIMICA ACTA

    The reactivity of phosphanylphosphinidene Pt(0) complexes [DppePt(η2-P–PtBu2)] (1) and [(pTol3P)2Pt(η2-P–PtBu2)] (2) toward sulfur was studied. Reactions of 1 and 2 with an excess of sulfur led to the formation of the first transition metal complexes 3 and 4 with phosphinothioyltrithiophosphonato ligands with the formula [tBu2P(=S)–P(=S)S2]2-. In contrast to previous reports on the phosphanylphosphinidene moiety sulfurization, the P–P bond was not cleaved during these reactions. The structures of sulfurization products 3 and 4 were elucidated using NMR spectroscopy, X-ray diffraction, and DFT calculations.

  • Sum-over-state expressions including second-order Herzberg–Teller effects for the calculation of absorption and resonance Raman intensities
    • Julien Guthmuller
    2021 Full text JOURNAL OF CHEMICAL PHYSICS

    The sum-over-state expressions are derived to calculate the second-order Herzberg–Teller (HT) effects in absorption and resonance Raman spectroscopies. These effects depend on the second derivatives of the transition dipole moment with respect to the vibrational coordinates. The method is applied to the molecule of 1,3-butadiene using density functional theory calculations. It is found that the second-order HT effects are significant for both absorption and resonance Raman intensities, and that the calculated spectra are in good agreement with the experimental data. The second-order HT effects originate from diagonal elements of the second derivatives matrix, whereas non-diagonal elements have a negligible impact on the intensities of 1,3-butadiene.

  • Superconductivity in LiGa2Ir Heusler type compound with VEC = 16
    • Karolina Górnicka
    • Gabriel Kuderowicz
    • Michał Winiarski
    • Bartłomiej Wiendlocha
    • Tomasz Klimczuk
    2021 Full text Scientific Reports

    Polycrystalline LiGa2Ir has been prepared by a solid state reaction method. A Rietveld refnement of powder x-ray difraction data confrms a previously reported Heusler-type crystal structure (space group Fm-3m, No. 225) with lattice parameter a= 6.0322(1) Å. The normal and superconducting state properties were studied by magnetic susceptibility, heat capacity, and electrical resistivity techniques. A bulk superconductivity with Tc= 2.94 K was confrmed by detailed heat capacity studies. The measurements indicate that LiGa2Ir is a weak-coupling type-II superconductor (e–p = 0.57, C/γTc= 1.4). Electronic structure, lattice dynamics, and the electron–phonon interaction are studied from frst principles calculations. Ir and two Ga atoms equally contribute to the Fermi surface with a minor contribution from Li. The phonon spectrum contains separated high frequency Li modes, which are seen clearly as an Einstein-like contribution in the specifc heat. The calculated electron–phonon coupling constant e–p = 0.68 confrms the electron–phonon mechanism for the superconductivity. LiGa2Ir and recently reported isoelectronic LiGa2Rh are the only two known representatives of the Heusler superconductors with the valence electron count VEC= 16.

  • Superconductivity in the Endohedral Ga Cluster Compound PdGa5
    • Zuzanna Ryżyńska
    • Piotr Wiśniewski
    • Dariusz Kaczorowski
    • Weiwei Xie
    • Robert J. Cava
    • Tomasz Klimczuk
    • Michał Winiarski
    2021 Full text Journal of Physical Chemistry C

    Superconductivity is observed below Tc = 1.6 K in an endohedral Ga cluster compound PdGa5 using magnetization and heat capacity measurements. Electronic structure calculations show that the density of states (DOS) at the Fermi level is dominated by Ga s and p states and that the overall shape of DOS is similar to what was found in other endohedral Ga cluster superconductors, such as MoxGa5x+1, ReGa5, and T2Ga9 (T = Rh and Ir). Our results provide a more complete picture of the relationship between the valence electron count and superconductivity in the family of endohedral Ga cluster superconductors.

  • SUPPORT FOR OLDER ADULTS DURING COVID19 PANDEMIC – HOW DID LOCAL AUTHORITIES IN THE POMERANIAN REGION RESPOND TO THE CHALLENGE?
    • Anita Richert-Kaźmierska
    2021

    The COVID-19 pandemic, apart from health threats, has shown the problem of older adults’ social isolation and loneliness in aging societies that has been progressing for several decades. Older adults’ singularisation, loosening family relations, diminishing families’ caring potential, caused that during the lockdown, many older adults – without the neighbours’ or NGOs’ support or the activities undertaken by local authorities – would be left without meeting their basic life and social needs. Authors draw their attention to the different aspects of population aging process and its socio-economic consequences. Nevertheless, the subject of older adults’ loneliness and the growing role of institutions (coordinated by local government authorities) in providing them different care services still seems insufficiently researched in the Polish-language literature. In Polish society, citizens prefer that the informal care needs of older adults are assiduously met by family members. However, the months of the COVID-19 pandemic lockdown have clearly shown that this traditional model of informal care is not always possible in practice, and that family members are increasingly turning to regional local authorities to assist them in the care requirements of older and frail relatives. Many family members are not always ready to provide care for older relatives at home due to a lack of appropriate knowledge and assistive aids.

  • Surface and interfacial anti-plane waves in micropolar solids with surface energy
    • Mriganka Shekhtar Chaki
    • Victor Eremeev
    • Abhishek K Singh
    2021 MATHEMATICS AND MECHANICS OF SOLIDS

    In this work, the propagation behaviour of a surface wave in a micropolar elastic half-space with surface strain and kinetic energies localized at the surface and the propagation behaviour of an interfacial anti-plane wave between two micropolar elastic half-spaces with interfacial strain and kinetic energies localized at the interface have been studied. The Gurtin–Murdoch model has been adopted for surface and interfacial elasticity. Dispersion equations for both models have been obtained in algebraic form for two types of anti-plane wave, i.e. a Love-type wave and a new type of surface wave (due to micropolarity). The angular frequency and phase velocity of anti-plane waves have been analysed through a numerical study within cut-off frequencies. The obtained results may find suitable applications in thin film technology, non-destructive analysis or biomechanics, where the models discussed here may serve as theoretical frameworks for similar types of phenomena.

  • Surface modification of PMMA polymer and its composites with PC61BM fullerene derivative using an atmospheric pressure microwave argon plasma sheet
    • Andrzej Sikora
    • Dariusz Czylkowski
    • Bartosz Hrycak
    • Magdalena Moczała-Dusanowska
    • Marcin Łapiński
    • Mirosław Dors
    • Mariusz Jasiński
    2021 Full text Scientific Reports

    This paper presents the results of experimental investigations of the plasma surface modification of a poly(methyl methacrylate) (PMMA) polymer and PMMA composites with a [6,6]-phenyl-C61-butyric acid methyl ester fullerene derivative (PC61BM). An atmospheric pressure microwave (2.45 GHz) argon plasma sheet was used. The experimental parameters were: an argon (Ar) flow rate (up to 20 NL/min), microwave power (up to 530 W), number of plasma scans (up to 3) and, the kind of treated material. In order to assess the plasma effect, the possible changes in the wettability, roughness, chemical composition, and mechanical properties of the plasma-treated samples’ surfaces were evaluated by water contact angle goniometry (WCA), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The best result concerning the water contact angle reduction was from 83° to 29.7° for the PMMA material. The ageing studies of the PMMA plasma-modified surface showed long term (100 h) improved wettability. As a result of plasma treating, changes in the samples surface roughness parameters were observed, however their dependence on the number of plasma scans is irregular. The ATR-FTIR spectra of the PMMA plasma-treated surfaces showed only slight changes in comparison with the spectra of an untreated sample. The more significant differences were demonstrated by XPS measurements indicating the surface chemical composition changes after plasma treatment and revealing the oxygen to carbon ratio increase from 0.1 to 0.4.

  • Surface quality control of a thin SiN layer by optical measurements
    • Jakub Gierowski
    • Sandra Pawłowska
    2021 Full text Photonics Letters of Poland

    Fiber optic interferometers have a wide range of applications, including biological and chemical measurements. Nevertheless, in the case of a reflective interferometer setup, standard silver mirrors cannot be used in every measurement, due to their chemical activity. This work investigates the surface quality of a thin optical layer of silicon nitride (SiN), which can serve as an alternative material for silver mirrors. We present measurements carried out with a Fabry-Perot fiber-optic interferometer working in a reflective mode. Measurement results allow us to determine the surface quality of the investigated layer.

  • Surface Roughness Evaluation in Thin EN AW-6086-T6 Alloy Plates after Face Milling Process with Different Strategies
    • Daniel Chuchała
    • Michał Dobrzyński
    • Danil Yurievich Pimenov
    • Kazimierz Orłowski
    • Grzegorz Królczyk
    • Khaled Giasin
    2021 Full text Materials

    Lightweight alloys made from aluminium are used to manufacture cars, trains and planes. The main parts most often manufactured from thin sheets requiring the use of milling in the manufacturing process are front panels for control systems, housing parts for electrical and electronic components. As a result of the final phase of the manufacturing process, cold rolling, residual stresses remain in the surface layers, which can influence the cutting processes carried out on these materials. The main aim of this study was to verify whether the strategy of removing the outer material layers of aluminium alloy sheets affects the surface roughness after the face milling process. EN AW-6082-T6 aluminium alloy thin plates with three different thicknesses and with two directions relative to the cold rolling process direction (longitudinal and transverse) were analysed. Three different strategies for removing the outer layers of the material by face milling were considered. Noticeable differences in surface roughness 2D and 3D parameters were found among all machining strategies and for both rolling directions, but these differences were not statistically significant. The lowest values of Ra = 0.34 µm were measured for the S#3 strategy, which asymmetrically removed material from both sides of the plate (main and back), for an 8-mm-thick plate in the transverse rolling direction. The highest values of Ra = 0.48 µm were measured for a 6-mm-thick plate milled with the S#2 strategy, which symmetrically removed material from both sides of the plate, in the longitudinal rolling direction. However, the position of the face cutter axis during the machining process was observed to have a significant effect on the surface roughness. A higher surface roughness was measured in the areas of the tool point transition from the up-milling direction to the down-milling direction (tool axis path) for all analysed strategies (Ra = 0.63–0.68 µm). The best values were obtained for the up-milling direction, but in the area of the smooth execution of the process (Ra = 0.26–0.29 µm), not in the area of the blade entry into the material. A similar relationship was obtained for analysed medians of the arithmetic mean height (Sa) and the root-mean-square height (Sq). However, in the case of the S#3 strategy, the spreads of results were the lowest.

  • Surface Texture after Turning for Various Workpiece Rigidities
    • Michał Dobrzyński
    • Karolina Miętka
    2021 Full text Machines

    In the paper, we present an analysis of the surface texture of turned parts with L/D (length/diameter) ratios of 6 and 12 and various rigidity values. The studies were carried out on samples made of S355JR steel and AISI 304 stainless steel. A detailed analysis of 2D surface profiles was carried out by using a large number of parameters that allowed us to distinguish significant differences in the surface microgeometry, which confirmed that determining surface characteristics from one height parameter (Ra—arithmetical mean height) is far from sufficient. The obtained results indicate significantly better roughness and waviness values of the AISI 304 steel surfaces in terms of its size, periodicity, and regularity. Therefore, the turning process of AISI 304 shafts with low rigidity allows one to be able to achieve better quality texture and have a positive effect on the general properties of a workpiece. In all tested samples, surface irregularities decreased along with the distance from the tailstock. The shafts with an L/D ratio of 12 had worse surfaces in the first two sections due to lower rigidity. The results received close to the three-jaw chuck, regardless of the L/D ratio and material type, demonstrated similar waviness and roughness parameters and profiles.

  • Surpassing the Line: Urban-Oriented Strategies in the Development of Business Complexes in Poland
    • Piotr Lorens
    • Joanna Bach-Głowińska
    • Michał Habier
    • Paweł Rzepecki
    2021 Full text Urban Planning

    Development trends regarding the business-related urban complexes seem to evolve from the “big-box” towards the more “multi-use” types of structures. Within it, the special role is reserved for places, which—due to economic, political, and geographical reasons—have not been previously considered as major business hubs. Only recently, places like cities in Central and Eastern Europe have become attractive locations for business complexes. These could offer centrally located and attractive locations for new structures, which resulted in the development of the new type of commercial centers—in the form of multi-use districts, walkable, and complemented by other uses. Therefore, to some extent, these cities “surpassed the development line” of the commercial and business complexes, and have become home to something much more advanced. Within the article, the cases from Poland, including Gdańsk, Warsaw, Cracow, and Wroclaw, are discussed. Not only is the urban arrangement of selected complexes presented, but the planning and socio-economic, legal, and infrastructural aspects of these developments are also discussed.

  • Surrogate-Assisted Design of Checkerboard Metasurface for Broadband Radar Cross-Section Reduction
    • Muhammad Abdullah
    • Sławomir Kozieł
    2021 Full text IEEE Access

    Metasurfaces have been extensively exploited in stealth applications to reduce radar cross section (RCS). They rely on the manipulation of backward scattering of electromagnetic (EM) waves into various oblique angles. However, arbitrary control of the scattering properties poses a significant challenge as a design task. Yet it is a principal requirement for making RCS reduction possible. This article introduces a surrogate-based approach for rapid design optimization of checkerboard metasurfaces. Our methodology involves fast metamodels, and a combination of surrogate-assisted global optimization with local, gradient-based tuning. It permits an efficient control of the EM wave reflection characteristics, and ensures arriving at that the globally optimum solution within the assumed parameter space. The design procedure is fully automated. The framework is employed to develop a novel broadband checkerboard metasurface, where the RCS reduction is fundamentally based on the backward scattering manipulation carefully controlled by simultaneous adjustment of the unit cell dimensions. The properties of the structure are demonstrated using simulated monostatic and bistatic RCSs. The proposed metasurface exhibits 6 dB RCS reduction within the frequency range from 16 to 37 GHz. The numerical results are validated using physical measurements of the fabricated prototype. Experimental data indicates that the relative RCS reduction bandwidth is 83 percent, which makes the proposed structure outperforming the designs reported in the literature.

  • Survey on opportunities and barriers in lighting controls
    • Bruno Bueno Unzeta
    • Jan de Boer
    • Ruben Delvaeye
    • Bertrand Deroisy
    • Marc Fontoynont
    • David Geisler-Moroder,
    • Niko Gentile,
    • Tao Luo
    • Daniel Neves Pimenta
    • Per Reinhold
    • Michelangelo Scorpio
    • Sergio Sibilio
    • Natalia Sokół
    • Sophie Stoffer
    • Robert Weitlaner
    2021

    This report summarizes a survey performed in eight countries on the status quo of daylight and electric lighting control systems. Feedback from more than 100 international experts (building / facility managers and planers) was evaluated. The aim of the survey was to identify the perception of the different possibilities of the current lighting control solutions and the expectations about the control systems. The survey aims to provide a mapping of the current lighting control systems available at the market and an overview of which functions are perceived as most important and which areas are found to be improved. Participants of the survey had to rank each question in relation to the perceived importance and the need for improvement. The survey enclosed five general topics; energy, operational aspects, occupant control, occupant comfort and control functionality. The findings from the summary suggest, that the two main reasons for the implementation of lighting control systems are: 1. The possibility to reduce the electric lighting consumptions and 2. The opportunity to increase the user’s well-being and thereby reduce complaints from the users. From a user perspective, this means that the lighting system must ensure visual acuity and comfort by providing a sufficient level of illuminance and the ability to regulate the light level. Always in relation to the task and the ambient light in the space, and thereby creating a pleasant and comfortable light environment. Research suggests, when giving the users some manual control possibilities, the satisfaction with the lighting conditions in general increases The users should be able to both increase and dim the light levels or completely turn it off. This suggests, if the lighting control system is designed to regulate the illuminance automatically, it should be provided some kind of manual override. This is supported by the findings in the surveys, where all countries in one way or another find it important to provide the users with some possibility of user control. This as well applies to the control of the shading system in relation to avoid glare from high daylight intensities and undesired solar radiation coming into the space.

  • Sustainable development model for measuring and managing sustainability in the automotive sector
    • Dominik Jasiński
    • James Meredith
    • Kerry Kirwan
    2021 Full text SUSTAINABLE DEVELOPMENT

    A growing number of organizations across a variety of industries are now pursuing sustainable management business goals to improve business efficiency, manage stakeholder expectations, or for legislative compliance. This is also the case for automotive manufacturing organizations who are under pressure from their stakeholders to manage and improve sustainability performance. This requires the development of credible measurement tools and systems to enable capture and monitoring of sustainability. This paper describes the development process for an innovative model, named the Automotive Sustainability Assessment Model (A-SAM), to drive sustainable decision-making in the automotive sector. The process of developing the model consisted of four major steps, each of which contained series of intermediate steps, individual objectives, and research methods. The model measures, quantifies, and translates a broad range of external effects (both positive and negative) into their monetary equivalents, enabling large car manufacturers to evaluate options, identify win–wins, and optimize trade-off, while making complex and multidisciplinary sustainability decisions. It allows managers and design engineers in the automotive sector to develop a better understanding of the environmental, resource, and social impacts of their activities, products, processes, and materials used, while still ensuring cost-effectiveness when making decisions. The A-SAM shows promise as an effective tool for supporting sustainability decisions in a business environment. Although developed in the context of the automotive industry, it can be adapted by organizations of any type, operating across many different sectors for managing sustainability in a more holistic, comprehensive, and integrated manner.

  • Sustainable Fashion in Poland—Too Early or Too Late?
    • Magdalena Popowska
    • Aleksandra Sinkiewicz
    2021 Full text Sustainability

    This article presents an analysis of the concept of sustainable fashion from the Polish consumer’s perspective. The aim of this research is to investigate how Polish fashion consumers approach the concepts of sustainability, such as organic, fair-trade, and carbon emissions. Exploring the experience of the Polish consumption context provides a richer understanding of the evolution of fashion sustainability concepts in this and similar countries. The research methods applied comprise the literature review, including the theoretical and empirical items, and the survey conducted among Polish clothing consumers. According to our findings, they declare caring more about the general environment but do not pay attention to sustainable development in the clothing industry. It is also worth noting that Poles, compared to other consumers in selected markets, have an unfavourable opinion of their own nation on the approach to sustainable development in the garment industry.

  • Sustainable recovery of plant essential Nitrogen and Phosphorus from human urine using industrial coal fly ash
    • Mahesh Ganesapillai
    • Jakub Drewnowski
    • Shivendu Ranjan
    • Thirumalini Selvaraj
    2021 Environmental Technology & Innovation

    Coal-based thermal power plants play a pivotal role in meeting global energy demand. The amount of fly ash generated from these plants increases every year, and its successful use has posed a significant environmental risk in the last decade. In this study, coal fly ash was packed in a fixed-bed adsorption column to remove Urea–N from synthetic human urine. To assess the efficacy of fly ash in the removal of Nitrogen, various process parameters were tested, including initial urea concentration in urine (20, 40, 60%), fly ash loading in column (100, 150, 200 g), and urine flow rate through the column (2, 4, 6 L.h−1). The initial urea concentration and bed height were found to have a major impact on nutrient recovery. Following nitrogen removal, the effluent urine was de-phosphatized using struvite precipitation and approximately 83% of phosphorus was recovered. High inlet urine concentration (60%), high flow rate (6 L.h−1) and minimal adsorbent loading (100 g) resulted in maximum struvite precipitation. The column breakthrough and characteristic parameters of four different models were predicted using kinetic modelling of the adsorption data, in which Yoon-Nelson and Thomas’ models suggested efficient removal and recovery of plant essential nutrients. As a result of the findings, coal fly ash appears to be a promising adsorbent for extracting these important plant nutrients. The effect of initial urine concentration, fly ash loading in the column, and urine flow rate on dephospatisation was calculated. The findings of this study will shed light on the process of nutrient adsorption process selection and detail the comparative differences between continuous and batch nutrient recovery of human urine.