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Gdańsk University of Technology

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  • TEST METHOD FOR DETERMINING THE CHEMICAL EMISSIONS OF A MARINE DIESEL ENGINE EXHAUST IN OPERATION
    • Zbigniew Korczewski
    2021 Full text Polish Maritime Research

    The article briefly describes the problem of air pollution caused by sea-going ships and the resulting restrictions on the emission of toxic and harmful chemical compounds in the exhaust of marine engines, introduced by the International Maritime Organization (IMO) under the International Convention for the Prevention of Sea Pollution from Ships (MARPOL 73/78). Such emissions provide a significant metrological problem, not only for the owners of operating sea- going ships, but also for shipyards, maritime administration offices and environmental protection inspectors. For this reason, the article’s author is developing research issues related to the diagnosing the exhaust emissions of marine engines under operating conditions, i.e. with limited control (measurement) susceptibility. This is particularly important in the period of intensive implementation of a new category of marine fuel, so-called modified fuels with low sulphur content. As part of the problem, a computational model of the parameters characterising the exhaust emissions of a marine engine in operation is presented in this article. This model is based on the measurement of the engine’s control parameters, using a standard (stationary) measurement system and a portable diagnostic system, configured for the purpose of this research. Presented here are representative measurements and calculation results (both obtained by the author and provided by the manufacturer) from the chemical exhaust gas emissivity of one of the ship engines operated. These confirm the adequacy of the calculation model developed and the diagnostic effectiveness of the measuring equipment applied. The methodology developed for experimental testing may also be implemented for the operation of other types of marine engines, provided that the basic chemical composition of the fuel supply and the engine load characteristics and hourly fuel consumption are known. Moreover, there is the possibility of indicating the cylinders and measuring the chemical composition of exhaust gases in the high-temperature part of the exhaust duct.

  • Testing of Software for the Planning of a Linear Object GNSS Measurement Campaign under Simulated Conditions
    • Sławomir Figiel
    • Cezary Specht
    • Marek Moszyński
    • Andrzej Stateczny
    • Mariusz Specht
    2021 Full text ENERGIES

    The precision of a linear object measurement using satellite techniques is determined by the number and the relative position of the visible satellites by the receiver. The status of the visible constellation is described by DOP. The obtained geometric coefficient values are dependent on many variables. When determining these values, field obstacles at the receiver location and satellite positions changing with time must be taken into account. Carrying out a series of surveys as part of a linear object GNSS measurement campaign requires the optimisation problem to be solved. The manner of the inspection vehicle’s movement should be determined in such a way that the surveys are taken only within the pre-defined time frames and that the geometric coefficient values obtained at subsequent points of the route are as low as possible. The purpose of this article is to develop a software for the planning of a linear object GNSS measurement campaign to implemented in motion and taking into account the terrain model and its coverage. Additionally, it was determined how much the developed program improves DOP values on the planned route under simulated conditions. This software has no equivalent elsewhere in the world, as the current solutions for the planning of a GNSS measurement campaign, e.g., Trimble GNSS Planning, GNSS Mission Planning, or GPS Navigation Toolbox, allow the satellite constellation geometry to be analysed exclusively for specific coordinates and at a specific time. Analysis of the obtained simulation test results indicates that the campaign implementation in accordance with the pre-determined schedule significantly improves the quality of the recorded GNSS data. This is particularly noticeable when determining the position using the GPS and GLONASS satellite constellations at the same time. During the tests conducted on the road along a three-kilometre-long route in Gdańsk, the average value of the obtained PDOP decreased by 22.17% thanks to using the software to plan a linear object GNSS measurement campaign. The largest drop in the geometric coefficient values was noted for an area characterised by a very large number of field obstacles. Under these conditions, the PDOP value decreased by approx. 25%. In areas characterised by a small number of field obstacles (single trees in the vicinity of the track, clusters of trees and buildings located along the track), the changes in the PDOP were slightly smaller and amounted to several percent.

  • Testing of the longest span soil-steel bridge in Europe – new quality in measurements
    • Mikołaj Miśkiewicz
    • Bartosz Sobczyk
    • Paweł Tysiąc
    2021

    The article describes interdisciplinary and comprehensive diagnostic tests of final bridge inspection and acceptance proposed for a soil – steel bridge made of corrugated sheets, being the European span length record holder (25.74 m). As an effect of an original concept a detailed and precise information about the structure response was collected. The load test design was based on the nonlinear numerical simulations performed by means of FEM. The in-situ measurements were done with aid of: inductive sensors, optical total station, terrestrial laser scanner. The results produced by terrestrial laser scanning were used to build a precise image of structure deformation in 3D space during the tests. The precision of laser mapping was additionally significantly increased by means of image tracing (vectorization) and calibration of results through parallel verification of the collected data with the values coming from optic total station and inductive sensors. Thus, new quality in measurements is introduced.

  • Testing Stability of Digital Filters Using Optimization Methods with Phase Analysis
    • Damian Trofimowicz
    • Tomasz Stefański
    2021 Full text ENERGIES

    In this paper, novel methods for the evaluation of digital-filter stability are investigated. The methods are based on phase analysis of a complex function in the characteristic equation of a digital filter. It allows for evaluating stability when a characteristic equation is not based on a polynomial. The operation of these methods relies on sampling the unit circle on the complex plane and extracting the phase quadrant of a function value for each sample. By calculating function-phase quadrants, regions in the immediate vicinity of unstable roots (i.e., zeros), called candidate regions, are determined. In these regions, both real and imaginary parts of complex-function values change signs. Then, the candidate regions are explored. When the sizes of the candidate regions are reduced below an assumed accuracy, then filter instability is verified with the use of discrete Cauchy’s argument principle. Three different algorithms of the unit-circle sampling are benchmarked, i.e., global complex roots and poles finding (GRPF) algorithm, multimodal genetic algorithm with phase analysis (MGA-WPA), and multimodal particle swarm optimization with phase analysis (MPSO-WPA). The algorithms are compared in four benchmarks for integer- and fractional-order digital filters and systems. Each algorithm demonstrates slightly different properties. GRPF is very fast and efficient; however, it requires an initial number of nodes large enough to detect all the roots. MPSO-WPA prevents missing roots due to the usage of stochastic space exploration by subsequent swarms. MGA-WPA converges very effectively by generating a small number of individuals and by limiting the final population size. The conducted research leads to the conclusion that stochastic methods such as MGA-WPA and MPSO-WPA are more likely to detect system instability, especially when they are run multiple times. If the computing time is not vitally important for a user, MPSO-WPA is the right choice, because it significantly prevents missing roots.

  • The adaptive spatio-temporal clustering method in classifying direct labor costs for the manufacturing industry
    • Mateusz Kalinowski
    • Jakub Baran
    • Paweł Weichbroth
    2021 Full text

    Employee productivity is critical to the profitability of not only the manufacturing industry. By capturing employee locations using recent advanced tracking devices, one can analyze and evaluate the time spent during a workday of each individual. However, over time, the quantity of the collected data becomes a burden, and decreases the capabilities of efficient classification of direct labor costs. However, the results obtained from performed experiments show that the existing clustering methods have failed to deliver satisfactory results by taking advantage of spatial data. In contrast to this, the adaptive spatio-temporal clustering (ASTC) method introduced in this paper utilizes both spatial and time data, as well as prior data concerning the position and working status of deployed machines inside a factory. The results show that our method outperforms the bucket of three well-known methods, namely DBSCAN, HDBSCAN and OPTICS. Moreover, in a series of experiments, we also validate the underlying assumptions and design of the ASTC method, as well as its efficiency and scalability. The application of the method can help manufacturing companies analyze and evaluate employees, including the productive times of day and most productive locations.

  • The added value of using the HEPA PAT for physical activity policy monitoring: a four-country comparison
    • Peter Gelius
    • Sven Messing
    • Sarah Forberger
    • Jeroen Lakerveld
    • Fiona Mansergh
    • Wanda Wendel-Vos
    • Joanna Żukowska
    • Catherine Woods
    2021 Full text Health Research Policy and Systems

    Background Public policy is increasingly recognized as an important component of physical activity promotion. This paper reports on the current status of physical activity policy development and implementation in four European countries based on the Health-Enhancing Physical Activity Policy Audit Tool (HEPA PAT) developed by WHO. It compares the findings to previous studies and discusses the general utility of this tool and its unique features in relation to other instruments. Methods The study was conducted as part of the Policy Evaluation Network (www.jpi-pen.eu) in Germany, Ireland, the Netherlands and Poland. Data collection built upon information obtained via the EU Physical Activity Monitoring Framework survey, additional desk research and expert opinion. Data analysis employed Howlett’s policy cycle framework to map and compare national physical activity policies in the four countries. Results In all countries under study, policy agenda-setting is influenced by prevalence data from national health monitoring systems, and the sport and/or health sector takes the lead in policy formulation. Key policy documents were located mainly in the health sector but also in sport, urban design and transport. Physical activity programmes implemented to meet policy objectives usually cover a broad range of target groups, but currently only a small selection of major policies are evaluated for effectiveness. National experts made several suggestions to other countries wishing to establish physical activity policies, e.g. regarding cross-sectoral support and coordination, comprehensive national action plans, and monitoring/surveillance. Conclusions This study provides a detailed overview of physical activity policies in the four countries. Results show that national governments are already very active in the field but that there is room for improvement in a number of areas, e.g. regarding the contribution of sectors beyond sport and health. Using the HEPA PAT simultaneously in four countries also showed that procedures and timelines have to be adapted to national contexts. Overall, the instrument can make an important contribution to understanding and informing physical activity policy, especially when used as an add-on to regular monitoring tools like the EU HEPA Monitoring Framework.

  • The Analysis of Cross-Polarisation Discrimination for Body Area Networks in Cylindrical Metallic Environment
    • Andrzej Ambroziak
    • Krzysztof Cwalina
    • Piotr Rajchowski
    2021

    The analysis of cross-polarisation discrimination for Body Area Networks in an untypical environment of cylindrical metallic room has been performed in the paper. This analysis was done based on the measurements carried out for dynamic narrowband off-body channels operating at the frequency of 2.45 GHz. The results have shown that there is a strong dependence of the depolarisation effect on the existence of direct component in the radio channel.

  • The assessment of metrological properties of segmental orifice based on simulations and experiments
    • Anna Golijanek-Jędrzejczyk
    • Andrzej Mrowiec
    • Robert Hanus
    • Marcin Zych
    • Marcin Heronimczak
    • Dariusz Świsulski
    2021 Full text MEASUREMENT

    Segmental orifices are often used to measure flows of heterogeneous mixtures, especially in flow meters in the power industry, for example. The orifice (with module m= 0.25) was installed in a stainless-steel pipe with internal diameter of 50 mm, placed in a hydraulic water system. The research was performed for Reynolds numbers ranging from 9,000 to 17,000. The flow characteristics of this orifice obtained based on simulation in SolidWorks Flow Simulation 2014 and experimental data were compared with standard-based calculations. It was determined that relative differences between the obtained flow characteristics did not exceed 1.5% for the experiment and 5.1% for the simulation. The article also presents the results of estimated uncertainty for mass flow measurement qm using the analytical method and the Monte Carlo simulations. The results for both methods proved that the relative expanded uncertainty Urel(qm) does not exceed 1.8% for the tested orifice.

  • The bile salt content of human bile impacts on simulated intestinal proteolysis of β-lactoglobulin
    • Dorota Dulko
    • Robert Staroń
    • Lukasz Krupa
    • Neil Rigby
    • Alan Mackie
    • Krzysztof Gutkowski
    • Andrzej Wasik
    • Adam Macierzanka
    2021 Full text FOOD RESEARCH INTERNATIONAL

    The gastrointestinal hydrolysis of food proteins has been portrayed in scientific literature to predominantly depend on the activity and specificity of proteolytic enzymes. Human bile has not been considered to facilitate proteolysis in the small intestine, but rather to assist in intestinal lipolysis. However, human bile can potentially influence proteins that are largely resistant to gastric digestion, and which are mainly hydrolysed after they have been transferred to the small intestine. We used purified and food-grade bovine milk β-lactoglobulin (βLg) to assess the impact of bile salts (BS) on the in vitro gastrointestinal digestion of this protein. Quantitative analysis showed that the proteolysis rate increased significantly with increasing BS concentration. The effect was consistent regardless of whether individual BS or real human bile samples, varying in BS concentrations, were used. The total BS content of bile was more important than its BS composition in facilitating the proteolysis of βlg. We also show that the impact of human bile observed during the digestion of purified βLg and βLg-rich whey protein isolate can be closely replicated by the use of individual BS mixed with phosphatidylcholine. This could validate simple BS/phosphatidylcholine mixtures as human-relevant substitutes of difficult-to-obtain human bile for in vitro proteolysis studies.

  • The cement-bone bond is weaker than cement-cement bond in cement-in-cement revision arthroplasty. A comparative biomechanical study
    • Marcin Ceynowa
    • Krzysztof Żerdzicki
    • Paweł Kłosowski
    • Maciej Zrodowski
    • Rafał Pankowski
    • Marek Rocławski
    • Tomasz Mazurek
    2021 Full text PLOS ONE

    This study compares the strength of the native bone-cement bond and the old-new cement bond under cyclic loading, using third generation cementing technique, rasping and contamination of the surface of the old cement with biological tissue. The possible advantages of additional drilling of the cement surface is also taken into account. Femoral heads from 21 patients who underwent a total hip arthroplasty performed for hip arthritis were used to prepare bone-cement samples. The following groups of samples were prepared. A bone— cement sample and a composite sample of a 6 weeks old cement part attached to new cement were tested 24 hours after preparation to avoid bone decay. Additionally, a uniform cement sample was prepared as control (6 weeks polymerization time) and 2 groups of cement-cement samples with and without anchoring drill hole on its surface, where the old cement polymerized for 6 weeks before preparing composite samples and then another 6 weeks after preparation. The uniaxial cyclic tension-compression tests were carried out using the Zwick-Roell Z020 testing machine. The uniform cement sample had the highest ultimate force of all specimens (n = 15; Rm = 3149 N). The composite cement sample (n = 15; Rm = 902 N) had higher ultimate force as the bone-cement sample (n = 31; Rm = 284 N; p <0.001). There were no significant differences between composite samples with 24 hours (n = 15; Rm = 902 N) and 6 weeks polymerization periods (n = 22; Rm = 890 N; p = 0.93). The composite cement samples with drill hole (n = 16; Rm = 607 N) were weaker than those without it (n = 22; Rm = 890 N; p < 0.001). This study shows that the bond between the old and new cement was stronger than the bond between cement and bone. This suggests that it is better to leave the cement that is not loosened from the bone and perform cement in cement revision, than compromising bone stock by removal of the old cement with the resulting weaker cement-bone interface. The results support performing cement-in-cement revision arthroplasty The drill holes in the old cement mantle decrease cement binding strength and are not recommended in this type of surgery.

  • The Chemical and Biological Properties of Nanohydroxyapatite Coatings with Antibacterial Nanometals, Obtained in the Electrophoretic Process on the Ti13Zr13Nb Alloy
    • Michał Bartmański
    • Łukasz Pawłowski
    • Anna Belcarz
    • Agata Przekora
    • Grazyna Ginalska
    • Gabriel Strugała
    • Bartłomiej Cieślik
    • Anna Pałubicka
    • Andrzej Zieliński
    2021 Full text INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES

    The risk of an early inflammation after implantation surgery of titanium implants has caused the development of different antimicrobial measures. The present research is aimed at characterizing the effects of nanosilver and nanocopper dispersed in the nanohydroxyapatite coatings, deposited on the Ti13Zr13Nb alloy, and on the chemical and biological properties of the coatings.The one-stage deposition process was performed by the electrophoretic method at different contents of nanomaterials in suspension. The surface topography of the coatings was examined with scanning electron microscopy. The wettability was expressed as the water contact angle. The corrosion behavior was characterized by the potentiodynamic technique. The release rate of copper and silver into the simulated body fluid was investigated by atomic absorption spectrometry. The antibacterial efficiency was evaluated as the survivability and adhesion of the bacteria and the growth of the biofilm. The cytotoxicity was assessed for osteoblasts. The results demonstrate that silver and copper increase the corrosion resistance and hydrophilicity. Both elements together effectively kill bacteria and inhibit biofilm growth but appear to be toxic for osteoblasts. The obtained results show that the nanohydroxyapatite coatings doped with nanosilver and nanocopper in a one-stage electrophoretic process can be valuable for antibacterial coatings.

  • The Cluster Organization. Analyzing the Development of Cooperative Relationships
    • Anna Lis
    • Adrian Lis
    2021

    Cluster organizations are becoming more and more popular, both in developing and developed countries. Considering the development of cluster policy and the related dynamic growth of cluster initiatives in the world, the lack of sufficient knowledge on the development of cooperation in cluster organizations inhibits their development and, in many cases, causes their complete disintegration. 　 The book provides new important elements to the current system of knowledge, filling in cognitive and research gaps in the scientific literature on problems related to cooperation in cluster organizations. The most valuable features for the reader concern the epistemological, methodological, and application aspects. The new element includes a theoretical concept, which refers to the trajectory of development of cooperative relationships in cluster organizations that facilitates the understanding and explanation of mechanisms responsible for cooperation in such organizations. 　 The concept also has great practical advantages, especially for people implementing the idea of "clustering": coordinators, facilitators, and members of cluster organizations as well as politicians and public authorities are responsible for shaping and implementing the cluster policy. It will be of value to researchers, academics, and students in fields with an interest in organizational studies, management of innovation and technology, strategic management, industrial economics, and economic geography.

  • THE COMPOSITION MODULATION EFFECT IN GaInPAs SOLID SOLUTIONS AS A MANIFESTATION OF ENERGY RESONANCE AFTER MATERIAL'S SPINODAL DECOMPOSITION
    • Pavel Moskvin
    • S.i. Skurativskyi
    • O.a. Gromovyi
    • Wojciech Sadowski
    2021 Full text Journal of Physical Studies

    The Cahn-Hilliard model concepts are extended to describe the spinodal decomposition of Ga$_x$In$_{1-x}$P$_y$As$_{1-y}$ solid solutions grown on the InP substrate. The energy of elastic deformation of the thin layer of a solid solution was calculated on the assumption of its coherent conjugation with the massive InP substrate. The excess energy of component mixing in the solid phase was modeled in accordance with the simple solution model, when the simultaneous substitution of components in the metal and metalloid sub lattices of the sphalerite structure is incorporated. The system of differential equations describing variations of the composition of a semiconductor solid solution after its spinodal decomposition was solved numerically under various thermodynamic conditions.

  • The Concept of Accuracy Analysis of the Vertical Displacements Gained from the Hydrostatic Levelling Systems’ Measurements
    • Waldemar Kamiński
    2021 Full text SENSORS

    Abstract: Nowadays, hydrostatic levelling is a widely used method for the vertical displacements’ determinations of objects such as bridges, viaducts, wharfs, tunnels, high buildings, historical buildings, special engineering objects (e.g., synchrotron), sports and entertainment halls. The measurements’ sensors implemented in the hydrostatic levelling systems (HLSs) consist of the reference sensor (RS) and sensors located on the controlled points (CPs). The reference sensor is the one that is placed at the point that (in theoretical assumptions) is not a subject to vertical displacements and the displacements of controlled points are determined according to its height. The hydrostatic levelling rule comes from the Bernoulli’s law. While using the Bernoulli’s principle in hydrostatic levelling, the following components have to be taken into account: atmospheric pressure, force of gravity, density of liquid used in sensors places at CPs. The parameters mentioned above are determined with some mean errors that influence on the accuracy assessment of vertical displacements. In the subject’s literature, there are some works describing the individual accuracy analyses of the components mentioned above. In this paper, the author proposes the concept of comprehensive determination of mean error of vertical displacement (of each CPs), calculated from the mean errors’ values of components dedicated for specific HLS. The formulas of covariances’ matrix were derived and they enable to make the accuracy assessment of the calculations’ results. The author also presented the subject of modelling of vertical displacements’ gained values. The dependences, enabling to conduct the statistic tests of received model’s parameters, were implemented. The conducted tests make it possible to verify the correctness of used theoretical models of the examined object treated as the rigid body. The practical analyses were conducted for two simulated variants of sensors’ connections in HLS. Variant no. I is the sensors’ serial connection. Variant no. II relies on the connection of each CPs with the reference sensor. The calculations’ results show that more detailed value estimations of the vertical displacements can be obtained using variant no. II.

  • The concept of suspended urban rail vehicle
    • Mateusz Kuczyk
    • Piotr Jędrzejewski
    • Paweł Załuski
    2021 Full text Pojazdy Szynowe

    Niniejsza publikacja została poświęcona szczegółowemu opisowi proponowanej przez autorów koncepcji podwieszanego pojazdu szynowego. W pierwszej kolejności przeanalizowano istniejące rozwiązania, wraz ze wskazaniem ich podstawowych wad i zalet. Następnie opisano proponowaną konstrukcję w zakresie: budowy wagonu, sposobu jego zawieszenia oraz prowadzenia po zadanym torze ruchu. Artykuł ten powstał na podstawie pracy dyplomowej pt. „Koncepcja wagonu silnikowego kolei podwieszanej”, na wydziale Mechanicznym Politechniki Gdańskiej.

  • The Conceptual Research over Low-Switching Modulation Strategy for Matrix Converters with the Coupled Reactors
    • Paweł Szczepankowski
    • Jarosław Łuszcz
    • Aleksander Usoltsev
    • Natalia Strzelecka
    • Enrique Romero-Cadaval
    2021 Full text ENERGIES

    In this paper, different Pulse Width Modulation (PWM) strategies for operating with a low-switching frequency, a topology that combines Conventional Matrix Converters (CMCs), and Coupled Reactors (CRs) are presented and discussed. The principles of the proposed strategies are first discussed by a conceptual analysis and later validated by simulation. The paper shows how the combination of CMCs and CRs could be of special interest for sharing the current among these converters’ modules, being possible to scale this solution to be a modular system. Therefore, the use of coupled reactors allows one to implement phase shifters that give the solution the ability to generate a stair-case load voltage with the desired power quality even the matrix converters are operated with a low-switching frequency close to the grid frequency. The papers also address how the volume and weight of the coupled reactors decrease with the growth of the fundamental output frequency, making this solution especially appropriate for high power applications that are supplied at high AC frequencies (for example, in airport terminals, where a supply of 400 Hz is required).

  • The construction of suspended rail vehicle bogie
    • Mateusz Kuczyk
    • Piotr Jędrzejewski
    • Paweł Załuski
    2021 Full text Pojazdy Szynowe

    Niniejsza publikacja została poświęcona szczegółowemu opisowi wózka, przeznaczonego do wykorzystania w proponowanej przez autorów koncepcji podwieszanego pojazdu szynowego. W pierwszej kolejności skrótowo opisano rzeczony pojazd, ze szczególnym naciskiem na parametry determinujące konstrukcję wózków. Następnie zostały omówione zastosowane rozwiązania konstrukcyjne w zakresie budowy poszczególnych podzespołów wózka, takich jak: zestawy kołowe, rama, dwustopniowe usprężynowanie, układ napędowy i hamulcowy. Artykuł ten powstał na podstawie pracy dyplomowej pt. „Koncepcja wagonu silnikowego kolei podwieszanej”, na wydziale Mechanicznym Politechniki Gdańskiej.

  • The description of non-linear interactions of wave and non-wave modes in a non-adiabatic plasma flow
    • Anna Perelomova
    2021 Full text CONTRIBUTIONS TO PLASMA PHYSICS

    The method of derivation of non-linear equations for interacting modes is explained and applied to a plasma's flow affected by a magnetic field. It is based on the linear projecting of the total perturbation field into specific variations of variables in individual modes of a flow. The method may be applied in many examples of fluid flows with different mechanisms of non-adiabaticity. It is of special importance in complex flows with large number of different modes. A flow of an ionized gas is one of the examples of such flows: it incorporates fast, slow magnetosonic modes, the Alfvén mode and the entropy mode. In the frames of this study, the wave vector may form an arbitrary angle urn:x-wiley:08631042:media:ctpp202100067:ctpp202100067-math-0001 with the straight equilibrium magnetic field. Thermal conduction, dynamic viscosity and a generic heating–cooling function, which is responsible for an energy inflow and radiative losses, are taken into account. Variable urn:x-wiley:08631042:media:ctpp202100067:ctpp202100067-math-0002 and plasma-β, diversity of the wave modes and a balance of different mechanisms of non-adiabaticity make the description of non-linear interaction of modes special. The non-linear excitation of the magnetosonic mode by the entropy mode is considered as an example.

  • The Determinants of False Self-Employment: A Survey of Polish Enterprises
    • Dagmara Nikulin
    2021 EASTERN EUROPEAN ECONOMICS

    The main goal of this article is to advance the emergent research on tax evasion in Poland in the form of false self-employment (FSE), in particular to identify its causes. The dependent character of some self-employed workers is a big problem in the Polish economy, which has been completely unexplored because of the lack of available data. In this article, we use data from a survey of Polish companies. Our empirical results show the highest prevalence of FSE in construction and to lesser extent in the services and retail, at micro and small firms, and at firms whose owners or managers are characterized by lower tax morality.

  • The Development of a Combined Method to Quickly Assess Ship Speed and Fuel Consumption at Different Powertrain Load and Sea Conditions
    • Przemysław Krata
    • Aleksander Kniat
    • Roberto Vettor
    • Hubert Krata
    • Carlos Guedes Soares
    2021 Full text TransNav - The International Journal on Marine Navigation and Safety of Sea Transportation

    Decision support systems (DSS) recently have been increasingly in use during ships operation. They require realistic input data regarding different aspects of navigation. To address the optimal weather routing of a ship, which is one of the most promising field of DSS application, it is necessary to accurately predict an actually attainable speed of a ship and corresponding fuel consumption at given loading conditions and predicted weather conditions. In this paper, authors present a combined calculation method to predict those values. First, a deterministic modeling is applied and then an artificial neural network (ANN) is structured and trained to quickly mimic the calculations. The sensitivity of the ANN to adopted settings is analyzed as well. The research results confirm a more than satisfactory quality of reproduction of speed and fuel consumption data as the ANN response meet the calculation results with high accuracy. The ANN-based approach, however, requires a significantly shorter time of execution. The directions of future research are outlined.

  • The Effect of Cobalt Incorporation into Nickel–Iron Oxide/(oxy)hydroxide Catalyst on Electrocatalytic Performance Toward Oxygen Evolution Reaction
    • Karolina Cysewska
    • Marcin Zając
    • Marcin Łapiński
    • Jakub Karczewski
    • Maria Rybarczyk
    • Bartosz Kamecki
    • Piotr Jasiński
    • Sebastian Molin
    2021 Energy Technology

    This work presents a study on the influence of the addition of cobalt into state-of-the-art nickel–iron (NiFe) mixed oxides/hydroxides/(oxy)hydroxides on their structural and morphological properties, and oxygen evolution reaction (OER) catalytic activity. A one-step electrodeposition process is performed without any additives to fabricate NiFe and x cobalt-doped nickel/iron (xCoNiFe) layer-double-hydroxide catalysts directly on nickel foam. The addition of cobalt nitrate in the synthesis solution significantly affects the final form of the catalyst: the addition of 2 mm cobalt nitrate into the aqueous solution of 4 mm nickel and iron nitrate stabilizes the electrochemical synthesis of the catalyst, which leads to the formation of a homogenously spread 3D interconnected structure with a high electroactive surface area (0.07 cm2, 1.1 m2 cm−2: including nickel foam substrate); it induces the formation of Ni3+ desirable for the formation of the catalytically active (oxy)hydroxides, which is not observed for the state-of-the-art NiFe. The significant role of the addition of cobalt translates into improved preliminary OER catalytic stability and activity of the catalyst with an onset potential of 1.40 V, overpotential of 224 mV determined at 10 mA cm−2, and only 0.7% loss in stability after 22 h working in alkaline conditions compared with the initial parameters.

  • The Effect of Conjugation with Octaarginine, a Cell-Penetrating Peptide on Antifungal Activity of Imidazoacridinone Derivative
    • Kamila Rząd
    • Ewa Paluszkiewicz
    • Damian Neubauer
    • Mateusz Olszewski
    • Katarzyna Kozłowska-Tylingo
    • Wojciech Kamysz
    • Iwona Gabriel
    2021 Full text INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES

    Acridine cell-penetrating peptide conjugates are an extremely important family of compounds in antitumor chemotherapy. These conjugates are not so widely analysed in antimicrobial therapy, although bioactive peptides could be used as nanocarriers to smuggle antimicrobial compounds. An octaarginine conjugate of an imidazoacridinone derivative (Compound 1-R8) synthetized by us exhibited high antifungal activity against reference and fluconazole-resistant clinical strains (MICs ≤ 4 μg mL−1). Our results clearly demonstrate the qualitative difference in accumulation of the mother compound and Compound 1-R8 conjugate into fungal cells. Only the latter was transported and accumulated effectively. Microscopic and flow cytometry analysis provide some evidence that the killing activity of Compound 1-R8 may be associated with a change in the permeability of the fungal cell membrane. The conjugate exhibited low cytotoxicity against human embryonic kidney (HEK-293) and human liver (HEPG2) cancer cell lines. Nevertheless, the selectivity index value of the conjugate for human pathogenic strains remained favourable and no hemolytic activity was observed. The inhibitory effect of the analysed compound on yeast topoisomerase II activity suggested its molecular target. In summary, conjugation with R8 effectively increased imidazoacridinone derivative ability to enter the fungal cell and achieve a concentration inside the cell that resulted in a high antifungal effect.

  • The effect of Fe on chemical stability and oxygen evolution performance of high surface area SrTix-1FexO3-δ mixed ionic-electronic conductors in alkaline media
    • Krystian Lankauf
    • Aleksander Mroziński
    • Patryk Błaszczak
    • Karolina Górnicka
    • Justyna Ignaczak
    • Marcin Łapiński
    • Jakub Karczewski
    • Grzegorz Cempura
    • Piotr Jasiński
    • Sebastian Molin
    2021 Full text INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

    Development of environmentally friendly, high performing oxygen evolution reaction (OER) catalysts is an important research challenge. In this work, iron doped strontium titanates with a general formula SrTi1-xFexO3-δ (x = 0.35, 0.50, 0.70, 0.90, and 1.00) denoted as STFx, were synthesized via a solid state reaction technique and characterized in terms of oxygen evolution reaction electrocatalysis in an alkaline electrolyte (0.1 M KOH). The produced powders were characterized by a high specific surface area (>20 m2 g−1), beneficial for OER. The evaluation of specific activity indicated the following trend of increasing performance: STF35 < STF50 < STF70 < SFO < STF90. The lowest overpotential at 10 mAcm−2 GEO of 410 mV (350 mV at 25 μA cm−2OX) was achieved by STF90 with the corresponding Tafel slope of 60 mV dec−1. The two materials with the highest Fe content (i.e. STF90 and SFO) showed, however, poor chemical stability in alkaline solution demonstrated by the dissolution of Sr. Based on the good electrochemical performance (~460 mV at 10 mA cm−2GEO, ~405 mV at 25 μA cm−2OX) and chemical stability for at least 30 days (no Sr dissolution) of STF50, it can be considered an interesting, working at room temperature OER catalyst based on non-toxic and abundant elements.

  • The Effect of Increasing the Amount of Indium Alloying Material on the Efficiency of Sacrificial Aluminium Anodes
    • Krzysztof Żakowski
    • Juliusz Orlikowski
    • Kazimierz Darowicki
    • Marcin Czekajło
    • Piotr Igliński
    • Kinga Domańska
    2021 Full text Materials

    Al-Zn-In alloys having 4.2% zinc content and various indium content in the range of 0.02–0.2% were tested with respect to the most important electrochemical properties of sacrificial anodes in a cathodic protection, i.e., the current capacity and potential of the operating anode. The distribution of In and Zn in the tested alloys was mapped by means of the EDX technique, which demonstrated that these elements dissolve well in the alloy matrix and are evenly distributed within it. The current capacity of such alloys was determined by means of the method of determining the mass loss during the dissolution by a current of known charge. The results obtained demonstrate that the current capacity of Al-Zn-In alloy decreases with the increase in the In content, which results in an increased consumption of anode material and shorter lifetime of anodes. With 0.02% In content, the capacity amounted to approx. 2500 Ah/kg, whereas the alloy with 0.2% In had as much as 30% lower capacity amounting to approx. 1750 Ah/kg. Microscopic examination for the morphology and surface profile of the samples after their exposure demonstrated that a higher indium content in the alloy results in a more uneven general corrosion pattern during the dissolution of such alloy, and the cavities (pits) appearing on the alloy surface are larger and deeper. As the indium content is increased from 0.02% to 0.05%, the Al-Zn-In alloy potential decreases by about 50 mV to −1100 mV vs. Ag/AgCl electrode, which is advantageous in terms of using this alloy as a sacrificial anode. When the indium content is further increased from 0.05% to 0.2%, the potential of the alloy is no longer changed to a more negative one. The results obtained from all these tests demonstrate that alloys containing up to 0.05% of In additive are practically applicable for cathodic protection.

  • The Effect of Protrusions on the Initiation of Partial Discharges in XLPE High Voltage Cables
    • Mohammad AlShaikh Saleh
    • S. Shady Refaat
    • Marek Olesz
    • Haitham Abu-Rub
    • Jarosław Guziński
    2021 Full text Bulletin of the Polish Academy of Sciences-Technical Sciences

    This paper is focusing on 3D Finite Elements Analysis (FEA) based modelling of protrusions as defects or imperfections in the XLPE high voltage cable. This study is aiming to examine the impact protrusions have on the initiation of partial discharges. Spherical and ellipsoidal protrusions with different sizes at the conductor screen of the high voltage cable is an essential content of this paper. In addition, a spherical gas-filled void is placed inside and outside the protrusions, and a water tree produced from protrusions is under consideration. The partial discharge influence taking place at the protrusions and the stress enhancement factor is determined for all the variations mentioned to quantify the rise in the inception of partial discharges due to the protrusions.

  • The Effect of Surface Treatment with Isocyanate and Aromatic Carbodiimide of Thermally Expanded Vermiculite Used as a Functional Filler for Polylactide-Based Composites
    • Mateusz Barczewski
    • Olga Mysiukiewicz
    • Aleksander Hejna
    • Radosław Biskup
    • Joanna Szulc
    • Sławomir Michałowski
    • Adam Piasecki
    • Arkadiusz Kloziński
    2021 Full text Polymers

    In this work, thermally expanded vermiculite (TE-VMT) was surface modified and used as a filler for composites with a polylactide (PLA) matrix. Modification of vermiculite was realized by simultaneous ball milling with the presence of two PLA chain extenders, aromatic carbodiimide (KI), and 4,4’-methylenebis(phenyl isocyanate) (MDI). In addition to analyzing the particle size of the filler subjected to processing, the efficiency of mechanochemical modification was evaluated by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The composites of PLA with three vermiculite types were prepared by melt mixing and subjected to mechanical, thermomechanical, thermal, and structural evaluation. The structure of composites containing a constant amount of the filler (20 wt%) was assessed using FTIR spectroscopy and SEM analysis supplemented by evaluating the final injection-molded samples’ physicochemical properties. Mechanical behavior of the composites was assessed by static tensile test and impact strength hardness measurements. Heat deflection temperature (HDT) test and dynamic thermomechanical analysis (DMTA) were applied to evaluate the influence of the filler addition and its functionalization on thermomechanical properties of PLA-based composites. Thermal properties were assessed by differential scanning calorimetry (DSC), pyrolysis combustion flow calorimetry (PCFC), and thermogravimetric analysis (TGA). The use of filler-reactive chain extenders (CE) made it possible to change the vermiculite structure and obtain an improvement in interfacial adhesion and more favorable filler dispersions in the matrix. This translated into an improvement in impact strength and an increase in thermo-mechanical stability and heat release capacity of composites containing modified vermiculites.

  • The Effect of the Selection of Three-Dimensional Random Numerical Soil Models on Strip Foundation Settlements
    • Kamil Żyliński
    • Karol Winkelmann
    • Jarosław Górski
    2021 Full text Applied Sciences-Basel

    This paper delivers a probabilistic attempt to prove that the selection of a random three-dimensional finite element (FE) model of a subsoil affects the computed settlements. Parametricanalysis of a random soil block is conducted, assuming a variable subsoil Young’s modulus inparticular finite elements. The modulus is represented by a random field or different-sized setsof random variables; in both cases, the same truncated Gaussian model is assumed. Mean valuesand standard deviations of random soil settlement are estimated by a Monte Carlo simulationprocedure. With regard to the adopted FE model, the estimated settlement mean values do notvary significantly, but standard deviations do strongly. Similarities also appear in the diagrams ofrandom field correlation length versus settlement standard deviation and the diagrams displayinga total number of model random variables versus settlement standard deviation. Thus, relevantsingle random variable models represent the random field approach well with regard to settlementparameter estimation. This remark is verified upon a settlement analysis of a three-dimensional FEmodel of a hypothetical strip foundation. Following the preliminary model observations, variousprobabilistic geotechnical analyses may be supported, e.g., continuous footing design, slope stabilityanalysis, and foundation reliability assessment.

  • The Effectiveness of Basic Resuscitation Activities Carried out by Combat Paramedics of the Police, as Exemplified by Polish Counterterrorist Units
    • Waldemar Zubrzycki
    • Jarosław Przyjemczak
    • Beata Świeczko-Żurek
    2021 Full text Internal Security

    The tasks carried out by Police officers are often accompanied by dangerous situations that threaten the life and health of the people involved, the police themselves, and bystanders. It concerns especially counter-terrorism police units whose activities are aimed at terrorists and particularly dangerous criminals, and their course is violent and aggressive. In conjunction with the inability to bring civilian rescue services into the action zone, this results in the need to expand the assault team by including one more specialisation — combat paramedic, having the appropriate knowledge, skills and qualifications, as well as equipment that allows for independent first aid while the operations are underway. A paramedic’s preparation must be versatile, but the key to effective action is the ability to perform basic activities, including cardiopulmonary resuscitation, after the diagnosis of sudden cardiac arrest. The study aims to present the results of research conducted on a fairly unique research sample regarding the effectiveness of indirect heart massage by combat paramedics of police special units and conclusions resulting from empirical research and their comparison with the results of similar studies, in relation to other professional groups. The knowledge and skills acquired during the training quickly become obsolete, requiring systematic consolidation and improvement. Therefore, cyclical repetition of exercises in the area of rescue activities plays a key role in maintaining the required quality of life support. The collected material may be a premise for further research, indicating their potential directions.

  • The efficiency of turbomachinery in the zero-and three-dimensional approaches
    • Paweł Ziółkowski
    • Tomasz Kowalczyk
    • Janusz Badur
    • Michel Feidt
    2021 Entropie

    Efficiency of turbomachinery is usually defined using an isentropic process. This approach provides a reliable reference point only when pressure and temperature measurements are available, e.g. at the casing inlet and outlet. In the case of a single stage internal efficiency determination the reference point is difficult. Computational fluid dynamics allows for an exact calculation of values of losses occurring in a turbine stage from turbine blades geometry, clearances, uneven steam distribution and other. Present method is a three-dimensional polytrophic approach based on work comparison of a turbine stage using real and ideal working fluid. The reference state is estimated by iterative simulation of considered geometry using the Eulerian model of compressible fluid. This approach is more convenient and feels natural when using 3D modeling. Moreover, calculations conducted for a control stage indicated differences between results attained using those two approaches less than 0.2%.

  • The Energy of Finance in Refining of Medical Surge Capacity
    • Oleksandr Melnychenko
    2021 Full text ENERGIES

    The availability of resources and their concentration in the place of greatest need, will not allow us to successfully overcome a medical surge without the energy required to activate these resources and activities, and increase their quantities if necessary, that is why the staff and management of healthcare institutions are forced to making ethical crisis decisions about who wins and who loses. This study highlights the versatility of the concept of ‘energy’ by attributing it to money or financial resources, which are highly essential in dealing with surges as the healthcare system adopts the appropriate capacity level. This study considers the means (space, staff, supplies, and specific resources) at the disposal of healthcare institutions for the control of diseases as economic resources to identify ways for enhancing their capacity, especially during periods of medical surges such as that caused by the coronavirus disease (COVID-19). The medical resources are dependent on ‘energy’, albeit not in the strictest sense of the term. The article, thus, points out that while limited resources are the norm in economic theory, a medical surge provides an opportunity to sufficiently extend the resources within the health system capacity through increased funding.

  • The equivariant spectral flow and bifurcation of periodic solutions of Hamiltonian systems
    • Marek Izydorek
    • Joanna Janczewska
    • Nils Waterstraat
    2021 Full text NONLINEAR ANALYSIS-THEORY METHODS & APPLICATIONS

    We define a spectral flow for paths of selfadjoint Fredholm operators that are equivariant under the orthogonal action of a compact Lie group as an element of the representation ring of the latter. This G-equivariant spectral flow shares all common properties of the integer valued classical spectral flow, and it can be non-trivial even if the classical spectral flow vanishes. Our main theorem uses the G-equivariant spectral flow to study bifurcation of periodic solutions for autonomous Hamiltonian systems with symmetries.

  • The evidence for the impact of policy on physical activity outcomes within the school setting: A systematic review
    • Catherine Woods
    • Kevin Volf
    • Liam Kelly
    • Bláthín Casey
    • Peter Gelius
    • Sven Messing
    • Sarah Forberger
    • Jeroen Lakerveld
    • Joanna Żukowska
    • Enrique García Bengoechea
    2021 Full text Journal of Sport and Health Science

    Purpose Despite the well-established health benefits of physical activity (PA) for young people (aged 4–19 years), most do not meet PA guidelines. Policies that support PA in schools may be promising, but their impact on PA behavior is poorly understood. The aim of this systematic review is to ascertain the level and type of evidence reported in the international scientific literature for policies within the school setting that contribute directly or indirectly to increasing PA. Methods This systematic review is compliant with Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. Six databases were searched using key concepts of policy, school, evaluation, and PA. Following title and abstract screening of 2323 studies, 25 progressed to data synthesis. Methodological quality was assessed using standardized tools, and the strength of the evidence of policy impact was described based on pre-determined codes: positive, negative, inconclusive, or untested statistically. Results Evidence emerged for 9 policy areas that had a direct or indirect effect on PA within the school setting. These were whole school PA policy, physical education, sport/extracurricular PA, classroom-based PA, active breaks, physical environment, shared use agreements, and active school transport and surveillance. The bulk of the evidence was significantly positive (54%), 27% was inconclusive, 9% was significantly negative, and 11% was untested (due to rounding, some numbers add to 99 or 101). Frequency of evidence was highest in the primary setting (41%), 34% in the secondary setting, and 24% in primary/secondary combined school settings. By policy area, frequency of evidence was highest for sport/extracurricular PA (35%), 17% for physical education PA, and 12% for whole school PA policy, with evidence for shared use agreements between schools and local communities rarely reported (2%). Comparing relative strength of evidence, the evidence for shared use agreements, though sparse, was 100% positive, 60% of the evidence for whole school PA policy was positive, 59% of the evidence for sport/extracurricular PA was positive, 57% of the evidence for physical education was positive, and 50% of the evidence for PA in classroom and for active breaks/recess was positive.

  • The fate and contamination of trace metals in soils exposed to a railroad used by Diesel Multiple Units: Assessment of the railroad contribution with multi-tool source tracking
    • Jacek Szmagliński
    • Nicole Nawrot
    • Ksenia Pazdro
    • Jolanta Walkusz-miotk
    • Ewa Wojciechowska
    2021 Full text SCIENCE OF THE TOTAL ENVIRONMENT

    Soil samples from cut slopes from lightly loaded railway lines used by Diesel Multiple Units for 5 years in Gdansk (Poland) were collected and analyzed for trace metals (TMs): Zn, Pb, Cd, Ni, Cr, Cu, and Fe. The main aim was to assess soil enrichment, contamination status, and distribution of TMs relative to the distance from the railway track. Extensive source tracking analyses were performed using cluster analysis (CA) and the Pb isotope ratios approach (206Pb, 207Pb, and 208Pb). Soil samples were affected by Cr, Cu, Pb, and Zn (max values in mg/kg d.w.: 31.1, 145, 80.5, and 115, respectively). The Enrichment Factor showed moderate (Cr, Zn, Pb) to very severe (Cu) enrichment. CA allowed TMs to be divided into two general groups: a) containing Zn, Pb, Cd with slight interaction with Cu; and b) containing Fe and Niwith slight interactionwith Cr. Correlation analyses indicated Cr as an outlying TM delivered from a separate source associated with the specificity of the construction of railroad 248, where alloys containing Cr were used to counteract increasing wear-and-tear of the rails. Pb isotopic ratios in the ranges of 1.16–1.20 (206Pb/207Pb) and 2.05–2.10 (208Pb/206Pb) corresponded to anthropogenic supplementation (coal combustion, road vehicles, and railroad transport) of Pb and Pb-correlated TMs (Zn, Cd, and partly Cu). Despite the research focus on the impact of the railroad contribution, a comparison with other forms of transport indicated that road transport appeared to have a higher contributing factor to TM pollution at the investigated site. This general conclusion againemphasizes the lower environmental footprint exhibited by railway transport in comparison to road transport.

  • The Green Approach to the Synthesis of Bio-Based Thermoplastic Polyurethane Elastomers with Partially Bio-Based Hard Blocks
    • Ewa Głowińska
    • Paulina Kasprzyk
    • Janusz Datta
    2021 Full text Materials

    Bio-based polymeric materials and green routes for their preparation are current issues of many research works. In this work, we used the diisocyanate mixture based on partially bio-based diisocyanate origin and typical petrochemical diisocyanate for the preparation of novel bio-based thermoplastic polyurethane elastomers (bio-TPUs). We studied the influence of the diisocyanate mixture composition on the chemical structure, thermal, thermomechanical, and mechanical properties of obtained bio-TPUs. Diisocyanate mixture and bio-based 1,4-butanediol (as a low molecular chain extender) created bio-based hard blocks (HS). The diisocyanate mixture contained up to 75 wt % of partially bio-based diisocyanate. It is worth mentioning that the structure and amount of HS impact the phase separation, processing, thermal or mechanical properties of polyurethanes. The soft blocks (SS) in the bio-TPU’s materials were built from α,ω-oligo(ethylene-butylene adipate) diol. Hereby, bio-TPUs differed in hard segments content (c.a. 30; 34; 40, and 53%). We found that already increase of bio-based diisocyanate content of the bio-TPU impact the changes in their thermal stability which was measured by TGA. Based on DMTA results we observed changes in the viscoelastic behavior of bio-TPUs. The DSC analysis revealed decreasing in glass transition temperature and melting temperature of hard segments. In general, obtained materials were characterized by good mechanical properties. The results confirmed the validity of undertaken research problem related to obtaining bio-TPUs consist of bio-based hard building blocks. The application of partially bio-based diisocyanate mixtures and bio-based chain extender for bio-TPU synthesis leads to sustainable chemistry. Therefore the total level of “green carbons” increases with the increase of bio-based diisocyanate content in the bio-TPU structure. Obtained results constitute promising data for further works related to the preparation of fully bio-based thermoplastic polyurethane elastomers and development in the field of bio-based polymeric materials

  • The image of the City on social media: A comparative study using “Big Data” and “Small Data” methods in the Tri-City Region in Poland
    • Jianxiang Huang
    • Hanna Obracht-Prondzyńska
    • Dorota Kamrowska-Załuska
    • Yiming Sun
    • Lishuai Li
    2021 Full text LANDSCAPE AND URBAN PLANNING

    “The Image of the City” by Kevin Lynch is a landmark planning theory of lasting influence; its scientific rigor and relevance in the digital age were in dispute. The rise of social media and other digital technologies offers new opportunities to study the perception of urban environments. Questions remain as to whether social media analytics can provide a reliable measure of perceived city images? If yes, what implication does it hold for urban planners? This paper describes a study on the perception of city images using a combination of “big data” and “small data” methods in the Tri-City Region in Poland. The aims were to 1) test the hypothesis whether social media analytics can elicit Lynchian elements of city image in consistency with conventional methods, and 2) develop and evaluate social media-based indicators of Imageability for planning practice. Geo-tagged images and texts were collected from Instagram and Twitter, two popular social media platforms in Poland. Text-Mining, Image Processing, Clustering Analysis, Kernel Density Estimation, and Sentiment Analysis were used. Results were compared with benchmarks constructed from official GIS database, questionnaire responses and sketch maps. “District”, “landmark”, and “path” identified on social media were in good agreements with benchmarks, less so for “edge” and “node”. Two social media-based indicators have influenced the perception of a place: Instagramability, the frequency of a place captured on Instagram, was linked to its perception as an architectural landmark and tourist attraction, while Twitterability, the frequency of a place mentioned on Twitter by name, was linked to its perceived niceness and relevance to everyday life of communities. Methods developed in this study have theoretical and practical implications for urban planners.

  • The Impact of Covid-19 on the Performance of Exchange Traded Funds on Developed and Emerging Markets
    • Krystian Zawadzki
    2021 Full text

    In this paper an endeavour was made to evaluate the impact of Covid-19 on the achievement of the investment objectives by selected ETFs in developed and emerging markets. For this purpose, the tracking errors calculated for 18 different ETFs operating on the basis of American, Asian and European stock indexes were analyzed. The time range of the research was selected in such a way as to compare the period before the pandemic(pre-Covid) and the period after the pandemic (post-Covid). The research results show that the outbreak of the coronavirus pandemic has not had a negative impact on the degree of implementation of the investment objective, regardless of the degree of market development. For each of the analyzed markets, the calculated tracking errors were not higher in the post-Covid period as compared to the pre-Covid period. In the vast majority of cases, they were even lower. This means that the management of the ETF has run smoothly in the most turbulent period of the 21st century.

  • The Impact of Decommissioning Cemeteries on the Urban Ecosystem
    • Anna Myślińska
    • Jakub Szczepański
    • Witold Dłubakowski
    2021 Full text Sustainability

    The decommissioning of cemeteries noticeably transforms the urban fabric. The purpose of this article was to determine what impact the decommissioning of cemeteries has on the urban ecosystem. For this purpose, it was necessary to assess the value of cemeteries within the urban ecosystem. Cemeteries are classified as urban green spaces, and their value as preservers of flora and fauna in local ecosystems has been proven. However, numerous decaying bodies in one place could have adverse effects on the environment. In order to assess the impact of transforming cemetery areas for other uses in the context of sustainable city development, it is necessary to define what these other functions might be. This article presents the main reasons for decommissioning cemeteries and links them with subsequent land use. The history of cemetery locations in five major Polish cities was analyzed to determine the extent to which cemeteries were decommissioned. In the two cities with the highest number of decommissioned cemeteries, further research was carried out in order to establish the typical land use of these former cemeteries, whether this usage is related to the size or type of the former cemetery, and whether change in land use is an advantage or a disadvantage for the urban ecosystem.

  • The impact of freeze-thaw processes on a cliff recession rate in the face of temperate zone climate change
    • Halina Kaczmarek
    • Arkadiusz Bartczak
    • Sebastian Tyszkowski
    • Michał Badocha
    • Michał Krzemiński
    2021 CATENA

    Freeze-thaw action is a common type of geomorphological processes eroding cliff faces in the temperate climate zone. In our previous study, we assessed the geomorphological effects of freeze-thaw fluctuations occurring within the cliff of Jeziorsko Reservoir (central Poland). Based on those findings, we have now determined the number of freeze-thaw cycles to assess their historical impact on the studied cliff. We have also traced the directions and the pace of changes in freeze-thaw processes in Poland. The results reveal a gradually decreasing role of freeze-thaw action in the process of the recession of the cliff of Jeziorsko Reservoir throughout its existence. The same is true nearly across Poland, although with some regional variation. Within 1951–2018, the impact of freeze-thaw action declined most significantly in north-western and central Poland, i.e. the area with the smallest annual number of freeze-thaw cycles. Consequently, this is also where the impact of geomorphological results of freeze-thaw cycles will be the least pronounced. It was only in the north-eastern edges of the country, which are under the dominant influence of continental air masses, where no significant changes in the impact of freeze-thaw processes were identified. The obtained results strongly legitimise the conclusion that global warming in the mid-latitude zone of the temperate climate has reduced the role of freeze-thaw processes in the geomorphological transformation of cliffs developed within river banks and lake or water reservoir shores.

  • The Impact of Ground Tire Rubber Oxidation with H2O2 and KMnO4 on the Structure and Performance of Flexible Polyurethane/Ground Tire Rubber Composite Foams
    • Aleksander Hejna
    • Adam Olszewski
    • Łukasz Zedler
    • Paulina Kosmela
    • Krzysztof Formela
    2021 Full text Materials

    The use of waste tires is a very critical issue, considering their environmental and economic implications. One of the simplest and the least harmful methods is conversion of tires into ground tire rubber (GTR), which can be introduced into different polymer matrices as a filler. However, these applications often require proper modifications to provide compatibility with the polymer matrix. In this study, we examined the impact of GTR oxidation with hydrogen peroxide and potassium permanganate on the processing and properties of flexible polyurethane/GTR composite foams. Applied treatments caused oxidation and introduction of hydroxyl groups onto the surface of rubber particles, expressed by the broad range of their hydroxyl numbers. It resulted in noticeable differences in the processing of the polyurethane system and affected the structure of flexible composite foams. Treatment with H2O2 resulted in a 31% rise of apparent density, while the catalytic activity of potassium ions enhanced foaming of system decreased density by 25% and increased the open cell content. Better mechanical performance was noted for H2O2 modifications (even by 100% higher normalized compressive strength), because of the voids in cell walls and incompletely developed structure during polymerization, accelerated by KMnO4 treatment. This paper shows that modification of ground tire rubber is a very promising approach, and when properly performed may be applied to engineer the structure and performance of polyurethane composite foams.

  • The Impact of Thermal Stresses on Volume Resistivity: Performance Comparison between TR-XLPE and XLPE Cables
    • Jasem Mohammed
    • Shady S. Refaat
    • Haitham Abu-Rub
    • Marek Olesz
    • Jarosław Guziński
    2021

    Most failures in electric power cables are attributed to the development of water trees inside the insulating materials. Thus, the development and utilization of Tree Retardant Cross-Linked Polyethylene (TR-XLPE) based cables have recently been given great attention to overcome the treeing issues. TR-XLPE cables use low-density polyethylene compounds suppressing the formation of water trees while retaining excellent electrical, physical, and processing attributes. This paper investigates and analyzes the impact of thermal stress on a 33kV three-core power cable with TR-XLPE and XLPE insulations in the presence of different types, shapes and sizes of voids. The results have been obtained after 500 hours of the accelerated aging test. The obtained results confirm the superiority of TR-XLPE over XLPE cables in terms of retaining higher volume resistivity. Results obtained from simulations conclude that TR-XLPE insulated cable retains 6% more dielectric strength when compared to XLPE insulated cable.

  • The Influence of a Photovoltaic Micro-Installation on the Low-Frequency Parameters of Electricity at PCC and Its Impact on the Thermal Characteristics of Selected Devices
    • Stanisław Galla
    • Mirosław Włas
    2021 Full text ENERGIES

    This manuscript illustrates the measurement results of parameters describing the quality of energy at the PCC (point of common coupling) of a photovoltaic micro-installation that can significantly affect devices in the same power grid. The analyses reflecting heating of selected devices used in domestic installations, which were performed in an isolated laboratory environment, are also indicated. The conducted study aimed at checking the thermal characteristics of the chosen equipment, i.e., AC/DC power supply, LED and fluorescent light sources, a step-down transformer at synergistically higher voltage harmonics and constant component in the network voltage. The tests were carried out at the disturbance levels recorded at the site of the photovoltaic micro-installation. The conducted tests aimed at indicating the presence of an increased level of synergetic disturbances in the vicinity of micro-photovoltaic installations. Based on the research, recommendations were made for photovoltaic micro-installations.

  • The Influence of Antitumor Unsymmetrical Bisacridines on 3D Cancer Spheroids Growth and Viability
    • Jolanta Kulesza
    • Monika Pawłowska
    • Ewa Augustin
    2021 Full text MOLECULES

    The culture of 3D spheroids is a promising tool in drug development and testing. Recently, we synthesized a new group of compounds, unsymmetrical bisacridines (UAs), which exhibit high cytotoxicity against various human cell lines and antitumor potency against several xenografts. Here, we describe the ability of four UAs—C-2028, C-2041, C-2045, and C-2053—to influence the growth of HCT116 and H460 spheres and the viability of HCT116 cells in 3D culture compared with that in 2D standard monolayer culture. Spheroids were generated using ultra-low-attachment plates. The morphology and diameters of the obtained spheroids and those treated with UAs were observed and measured under the microscope. The viability of cells exposed to UAs at different concentrations and for different incubation times in 2D and 3D cultures was assessed using 7-AAD staining. All UAs managed to significantly inhibit the growth of HCT116 and H460 spheroids. C-2045 and C-2053 caused the death of the largest population of HCT116 spheroid cells. Although C-2041 seemed to be the most effective in the 2D monolayer experiments, in 3D conditions, it turned out to be the weakest compound. The 3D spheroid culture seems to be a suitable method to examine the efficiency of new antitumor compounds, such as unsymmetrical bisacridines.

  • The influence of atmospheric circulation on the occurrence of dry and wet periods in Central Poland in 1954–2018
    • Andrzej Araźny
    • Arkadiusz Bartczak
    • Rafał Maszewski
    • Michał Krzemiński
    2021 Full text THEORETICAL AND APPLIED CLIMATOLOGY

    This work presents the influence of atmospheric circulation on the occurrence of dry and wet periods in the central Polish region of Kujawy. The material on which the authors relied encompassed monthly totals of precipitation obtained from 10 weather stations in the period 1954–2018. Both dry and wet periods have been identified on the basis of monthly values of the Standardised Precipitation Index (SPI). Additionally, the calendar of circulation types over Central Poland was used to determine the atmospheric circulation indices: western (W), southern (S) and cyclonicity (C). The analyses have indicated that the region concerned experiences low precipitation totals in comparison with the rest of Poland. According to the circulation indices W, S and C, for Central Poland, the air mass advection from the West prevails over that from the East. Moreover, a slightly more frequent inflow of air from the South than from the North has been observed. The frequency of anticyclonic situations is higher than that of the cyclonic types in this part of Europe. Drought spells occurred in the study area at a clear dominance of anticyclonic circulation, with the inflow of air mostly from the North and with increased westerly circulation. On the other hand, the occurrence of wet periods was mainly influenced by cyclonic circulation during the advection of the masses from the South and West. Dry and wet periods accounted for 28% and 27% of the study period, respectively.

  • The Influence of Cement Type on Early Properties of Cold In-Place Recycled Mixtures
    • Bohdan Dołżycki
    • Mariusz Jaczewski
    • Cezary Szydłowski
    2021 Full text

    Cold in-place recycling is a commonly used maintenance treatment in rehabilitation of low and medium volume roads in Poland. Typically, two types of binding agents are used—cement and bituminous emulsion (or foamed bitumen).Due to the harsh Polish climate with many freeze/thaw cycles and frequent occurrence of saturated conditions, the used amounts of cement are higher than those commonly used in warmer parts of Europe. While there is usually only one type of bituminous emulsion dedicated for cold recycling on the market, there are numerous types of cements, which differ in chemical composition and properties. The conducted research presents possible development of cold recycled mixture properties over curing time, taking into account the type of cement used. Two types of cement were tested in laboratory investigation—common Portland CEM I 32.5 R cement and Portland-fly ash CEM II 32.5 B-V cement with longer setting time. Cold recycled mixtures were designed with the same composition and amount of binding agents, but differed in the type of cement used. For both mixtures, indirect tensile strength and modulus were tested after 7, 28 and 90 days of curing in laboratory conditions. The laboratory tests confirmed lower values of strength and modulus for the fly ash cement after 7 and 28 days in comparison to the typical cement, but after 90 days the properties of both tested mixtures presented similar values. If the overall predicted fatigue life and long-term mechanical properties are the same, the use of slow-setting cementsmay result in reduction of reflective cracking on the surface of the pavement. In the case of low and medium volume roads, where there is no need for fast paving of the asphalt layers and more time may be allowed for the cold-recycled mixture to achieve the required initial strength, slow-setting cements should be considered as a viable treatment for reduction of the risk of reflective cracking.

  • The influence of climate change on the life insurance in the EU: A panel data approach
    • Oleksandr Melnychenko
    • Tetyana Kalna-Dubinyuk
    • Olha Vovchak
    • Tetiana Girchenko
    2021 Full text E3S Web of Conferences

    The financial sector, as one of the most sensitive economic sectors, is alert to all trends and changes in the environment. The aim of the article is to study the impact of climate change on the life insurance market using panel data from 28 countries of the European Union (EU) for the last 9 years. This study is based on a panel model, where the amount of premiums under life insurance contracts is defined as a function of the fundamental factor of climate change - greenhouse gas emissions. According to empirical findings, an increase in greenhouse gas emissions per thousand tons leads to an increase in the amount of life insurance premiums by 0.1786 million euros. It has also been found that an increase in greenhouse gas emissions per thousand tons leads to an increase in deaths in the European Union by 1.0442 people, and these consequences are statistically significant. In general, our results suggest that the life insurance market as well as the nonlife insurance market is dependent on climate change. The empirical results of this study provide valuable insight into how greenhouse gas emissions affect mortality in the European Union.

  • The Influence of Co-Fermentation of Agri-Food Waste with Primary Sludge on Biogas Production and Composition of the Liquid Fraction of Digestate
    • Anna Wilińska-Lisowska
    • Monika Ossowska
    • Krzysztof Czerwionka
    2021 Full text ENERGIES

    Energy self-sufficiency is a current trend in wastewater treatment plants. This effect can be achieved by increasing the production of electricity from biogas and by reducing energy consumption for technological processes. One idea, in line with the circular economy concept, is the use of waste rich in organic matter as co-substrates for the fermentation process. The aim of this study was to determine the effect of waste co-fermentation on biogas production and nitrogen concentration in the reject water. A co-fermentation process with flotate or flotate and vegetables increased biogas production compared to primary sludge by 162 and 180%, respectively. During the tests, there was no inhibition of the fermentation process. Hydrolysis of organic compounds contained in flotate and vegetables resulted in a significant increase in ammonium nitrogen (by 80–100%) and dissolved organic nitrogen concentration (by 170–180%). The biogas and methane production rate as well as the ammonium and total nitrogen release rate were calculated. An energy balance was made, which took into account the variable amount of electric energy production depending on the efficiency of the cogeneration systems and energy consumption for supplying oxygen necessary to remove nitrogen contained in the reject water. A positive energy balance was obtained for all analyses.

  • The Influence of Drying Temperature on Color Change of Hornbeam and Maple Wood Used as Surface and Inner Layers of Wood Composites
    • Ivan Klement
    • Peter Vilkovský
    • Tatiana Vilkovská
    • Kazimierz Orłowski
    • Jacek Barański
    • Daniel Chuchała
    • Aleksandra Suchta
    2021 Full text Applied Sciences-Basel

    The thermal treatment of wood changes its structure due to the degradation of wood polymers (cellulose, hemicellulose and lignin), so the physical properties of wood are either improved or degraded. Color changes apply not only to natural wood, but also to such wood composites for which some amount of glue is used in their construction (e.g., plywood, blockboard or laminboard). This article is focused on the analysis of hornbeam and field maple wood color changes influenced by drying temperature. Two types of drying modes were used: hot-air mode where the temperature of the drying environment was 60 C, and high-temperature mode with a drying temperature of 120 C. The drying mode was divided into two phases depending on the moisture content of the wood. The compared woods had similar values of color coordinates at the beginning of drying. During hot-air drying, the largest changes in color coordinates occurred during the first 24 h. The total color difference between the color at the end and the beginning of drying was 7.3 for hornbeam and 11.1 for maple. The overall color difference between the compared woods was minimal. During high-temperature drying (120 C), the color changes of the dried woods were more pronounced. In the case of maple wood, there was a very significant change in color and the value of DE* was twice as high as for hornbeam. The total color difference between the color at the end and at the beginning of drying was 8.7 for hornbeam and 18.9 for maple.

  • The Influence of External Additional Loading on the Muscle Activity and Ground Reaction Forces during Gait
    • Bartłomiej Zagrodny
    • Michał Ludwicki
    • Wiktoria Wojnicz
    2021 Full text Applied Bionics and Biomechanics

    Asymmetrical external loading acting on the usculoskeletal system is generally considered unhealthy. Despite this knowledge, carrying loads in an asymmetrical manner like carrying on one shoulder, with one hand, or on the strap across the torso is a common practice. This study is aimed at presenting the effects of the mentioned load carrying methods on muscle activity assessed by using thermal field and ground reaction forces. Infrared thermography and pedobarographic force platform (ground reaction force/pressure measurement) were used in this study. Experimental results point out an increased load-dependent asymmetry of temperature distribution on the chosen areas of torso and the influence of external loading on ground reaction forces. Results point out that wearing an asymmetrical load should be avoided and are showing which type of carrying the external load is potentially less and the most harmful.

  • The Influence of External Load on the Performance of Microbial Fuel Cells
    • Szymon Potrykus
    • León-Fernández Fernando Luis
    • Janusz Nieznański
    • Dariusz Karkosiński
    • Francisco-Jesus Fernandez-Morales
    2021 Full text ENERGIES

    In this work, the effect of the external load on the current and power generation, as well as on the pollutant removal by microbial fuel cells (MFCs), has been studied by step-wise modifying the external load. The load changes included a direct scan, in which the external resistance was increased from 120 Ω to 3300 Ω, and a subsequent reverse scan, in which the external resistance was decreased back to 120 Ω. The reduction in the current, experienced when increasing the external resistance, was maintained even in the reverse scan when the external resistance was step-wise decreased. Regarding the power exerted, when the external resistance was increased below the value of the internal resistance, an enhancement in the power exerted was observed. However, when operating near the value of the internal resistance, a stable power exerted of about 1.6 µW was reached. These current and power responses can be explained by the change in population distribution, which shifts to a more fermentative than electrogenic culture, as was confirmed by the population analyses. Regarding the pollutant removal, the effluent chemical oxygen demand (COD) decreased when the external resistance increased up to the internal resistance value. However, the effluent COD increased when the external resistance was higher than the internal resistance. This behavior was maintained in the reverse scan, which confirmed the modification in the microbial population of the MFC.

  • The influence of intermolecular correlations on the infrared spectrum of liquid dimethyl sulfoxide
    • Maciej Śmiechowski
    2021 Full text SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY

    Dimethyl sulfoxide (DMSO) is routinely applied as an excellent, water-miscible solvent and chemical reagent. Some of the most important data concerning its liquid structure were obtained using infrared (IR) spectroscopy. However, the actual extent of intermolecular correlations that connect the isolated monomer spectrum to the IR response of the bulk liquid is poorly studied thus far. Using ab initio molecular dynamics (AIMD) simulations, IR spectra of liquid DMSO are obtained here from first principles and further analyzed using an array of sophisticated spectral decomposition techniques. The calculated spectra when unfolded in space reveal non-trivial spatial correlations underlying the IR response of liquid DMSO. It is unequivocally demonstrated that some of the fundamental vibrations visible in the intramolecular limit are effectively suppressed by the solvation environment due to symmetry reasons and thus disappear in the bulk limit, escaping experimental detection. Overall, DMSO as an aprotic solvent with dominant dipole–dipole interactions displays strong intermolecular correlations that contribute significantly to the IR spectra, on par with the situation observed in strongly associated liquids, such as water.