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Gdańsk University of Technology

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  • Salinity enhances high optically active L-lactate production from co-fermentation of food waste and waste activated sludge: Unveiling the response of microbial community shift and functional profiling
    • Xiang Li
    • Safeena Sadiq
    • Wenjuan Zhang
    • Yiren Chen
    • Xianbao Xu
    • Anees Abbas
    • Shanping Chen
    • Ruina Zhang
    • Gang Xue
    • Dominika Sobotka
    • Jacek Mąkinia
    2020 Full text BIORESOURCE TECHNOLOGY

    Lactic acid (LA), a versatile platform molecule, can be fermented from organic wastes, such as food waste and waste activated sludge. In this study, an efficient approach using salt, a component of food waste as an additive, was proposed to increase LA production. The LA productivity was increased at 10 g NaCl/L and optical pure L-lactate was obtained at 30 g NaCl/L. The enhancement of LA was in accordance with the increased solubilization and the critical hydrolase activities under saline conditions. Moreover, high salinity (30-50 g NaCl/L) changed the common conversion of LA to volatile fatty acids. In addition, the key LA bacteria genera (Bacillus, Enterococcus, Lactobacillus) were selectively enriched under saline conditions. Strong correlations between salinity and functional genes for L-LA production were also observed. This study provides a practical way for the enrichment of L-LA with high optical activity from organic wastes.

  • Scalable Route toward Superior Photoresponse of UV-Laser-Treated TiO2 Nanotubes
    • Łukasz Haryński
    • Katarzyna Grochowska
    • Jakub Karczewski
    • Jacek Ryl
    • Katarzyna Siuzdak
    2020 ACS Applied Materials & Interfaces

    Titanium dioxide nanotubes gain considerable attention as a photoactive material due to chemical stability, photocorrosion resistance, or lowcost manufacturing method. This work presents scalable pulsed laser modification of TiO2 nanotubes resulting in enhanced photoactivity in a system equipped with a motorized table, which allows for modifications of both precisely selected and any-large sample area. Images obtained from scanning electron microscopy along with Raman and UV−vis spectra of laser-treated samples in a good agreement indicate the presence of additional laser-induced shallow states within band gap via degradation of crystalline structure. However, X-ray photoelectron spectroscopy spectra revealed no change of chemical nature of the modified sample surface. Photoelectrochemical measurements demonstrate superior photoresponse of laser-treated samples up to 1.45-fold for an energy beam fluence of 40 mJ/cm2 compared to that of calcined one. According to the obtained results, optimal processing parameters were captured. Mott−Schottky analysis obtained from impedance measurements indicates an enormous (over an order of magnitude) increase of donor density along with a +0.74 V positive shift of flat band potential. Such changes in electronic structure are most likely responsible for enhanced photoactivity. Thus, the elaborated method of laser nanostructuring can be successfully employed to the large-scale modification of titania nanotubes resulting in their superior photoactivity. According to that, the results of our work provide a contribution to wider applications of materials based on titania nanotubes.

  • Scenario-planning solutions for waterfront flood-prone areas
    • Lucyna Nyka
    • Izabela Burda
    2020 Full text Global Journal of Engineering Education

    The aim of this article is to discuss the potential of applying scenario planning to achieve resilient and future-oriented solutions for flood-prone areas. The authors have proposed additions to scenario-planning processes based on the introduction of research-by-design architectural inquiries. Examined in this article is the insight into the testing of such a modified scenario-planning methodology during two courses that accompanied researcher stakeholder workshops organised within the H2020 project SOS Climate Waterfront in the Faculty of Architecture at Gdańsk University of Technology (FA-GUT), Gdańsk, Poland. The task for the students was to propose plausible future scenarios for the flood-prone area of the Polish Hook peninsula in Gdańsk. Based on this experiment, the authors have proposed using research-by-design tools in scenario-planning practices, and they discuss the benefits of research-based learning.

  • Scenariusze w kształtowaniu inteligencji strategicznej województw
    • Jacek Sołtys
    2020

    ..

  • Scientific Collaboration, Citation and Topic Analysis of International Conference on Agile Software Development Papers
    • Muhammad Ahmad
    • Päivi Raulamo-jurvanen
    2020

    The International Conference on Agile Software Development (XP) was established almost sixteen years ago. Based on data from Scopus database, a total of 789 papers have been published in between years of 2002 and 2018. We employed bibliometrics analysis and topic modeling with R/RStudio to analyze these published papers from various dimensions, including the most active authors, collaboration of authorship, most cited papers, used keywords and trends of probable topics from the titles and abstracts of those papers. The results show that the first five years of XP conference cover nearly 40% of the papers published until now and almost 62% of the XP papers have been cited at least once. Mining of XP conference paper titles and abstracts result in these hot research topics: “Coordination”, “Technical Debt”, “Teamwork”, “Startups” and “Agile Practices”, thus strongly focusing on practical issues and problems faced by the practitioners in the industry. The results highlight the most influential researchers and institutions, and the collaboration between the authors in the conference papers. The approach applied in this study can be extended to other software engineering venues and can be applied to large-scale studies.

  • Seabed Topography Changes in the Sopot Pier Zone in 2010–2018 Influenced by Tombolo Phenomenon
    • Artur Makar
    • Cezary Specht
    • Mariusz Specht
    • Paweł Dąbrowski
    • Paweł Burdziakowski
    • Oktawia Lewicka
    2020 Full text SENSORS

    Bathymetric surveys of the same body of water, performed at regular intervals, apart from updating the geospatial information used to create paper and electronic maps, allow for several additional analyses, including an evaluation of geomorphological changes occurring in the coastal zone. This research is particularly important in places where the shape of the coastal zone has been violently disturbed, including by human activity. Tombolo is such a phenomenon and it dynamically shapes the new hydrological conditions of the coastal zone. Apart from natural factors, it may be caused by the construction of hydrotechnical facilities in the littoral zone. It causes a significant disturbance in the balance of the marine environment, resulting in the bottom accretion and dynamic changes in the coastline. This has been the case since 2010 in Sopot, where the rapidly advancing tombolo is not only changing environmental relations but also threatening the health-spa character of the town by stopping the transport of sand along the coast. This paper analyses changes in seabed shape in the pier area in Sopot between 2010 and 2018. In the analysis, both archival maps and bathymetric surveys over a period of 8 years were used; based on these, numerical bottom models were developed and their geospatial changes were analyzed. The results showed that changes in the seabed in this area are progressing very quickly, despite periodic dredging actions organized by administrative bodies.

  • Searching for Solvents with an Increased Carbon Dioxide Solubility Using Multivariate Statistics
    • Marta Bystrzanowska
    • Marek Tobiszewski
    • Francisco Pena-Pereira
    • Vasil Simeonov
    2020 Full text MOLECULES

    Ionic liquids (ILs) are used in various fields of chemistry. One of them is CO2 capture, a process that is quite well described. The solubility of CO2 in ILs can be used as a model to investigate gas absorption processes. The aim is to find the relationships between the solubility of CO2 and other variables—physicochemical properties and parameters related to greenness. In this study, 12 variables are used to describe a dataset consisting of 26 ILs and 16 molecular solvents. We used a cluster analysis, a principal component analysis, and a K-means hierarchical clustering to find the patterns in the dataset and the discriminators between the clusters of compounds. The results showed that ILs and molecular solvents form two well-separated groups, and the variables were well separated into greenness-related and physicochemical properties. Such patterns suggest that the modeling of greenness properties and of the solubility of CO2 on physicochemical properties can be difficult.

  • Seashore sediment and water chemistry at the Admiralty Bay (King George Island, Maritime Antarctica) – geochemical analysis and correlations between the concentrations of chemical species
    • Joanna Potapowicz
    • Danuta Szumińska
    • Małgorzata Szopińska
    • Robert Józef Bialik
    • Katarzyna Machowiak
    • Stanisław Chmiel
    • Żaneta Polkowska
    2020 MARINE POLLUTION BULLETIN

    This study covers water and sediment chemical characteristics by the western shore of Admiralty Bay (King George Island, Antarctica) in 2016. Chemical processes between sediment and water have been described based on the determination of ions, metals, non-metals, and TOC concentrations. Rock weathering is an important source of Fe, Ni, Co, Al in the seashore area. The PCA shows the impact of acidification in the release metals from sediment. Our results indicate that riverine mineral fluxes need to be accounted for as the volume of melt increases in response to climate change. Based on geoaccumulation indexes (anthropogenic fingerprint), we observed an increased concentration of Pb (Igeo=1.643), in the lake near station facilities and Cd in the area of Ecology Glacier (Igeo>1.389). Taking into account climate change and the intensification of anthropopressure, our study indicates that Antarctica requires a special focus on the seasonal dynamics of mineral content and pollution assessment.

  • Seasonal contributions of nutrients from small urban and agricultural watersheds in northern Poland
    • Karolina Matej-Łukowicz
    • Ewa Wojciechowska
    • Nicole Nawrot
    • Lidia Dzierzbicka-Głowacka
    2020 Full text PeerJ

    Diffuse sources of pollution like agricultural or urban runoff are important factors in determining the quality of surface waters, although they are more difficult to monitor thanpointsources.Theobjectiveofourstudywastoverifyassumptionsthattheinflow from agricultural nutrient sources is higher than from urbanized ones. It has been done by comparing the nutrients and organic matter concentrations and loads for three small streams in northern Poland (Pomerania Region). Two streams flowing through agricultural catchments and an urban stream flowing through the city of Gdansk were analysed. Concentrations of nutrients: N-NO− 3 N-NH+ 4 , P-PO3− 4 , total phosphorus, total nitrogen and COD were measured 1–3 times per month in the periodfromJuly2017toDecember2018inagriculturalwatershedsandfromOctober 2016 to March 2018 for an urban stream. Seasonal changes in concentrations were analysed with descriptive statistics tools. Principal Component Analysis (PCA) was used to point out the most significant factors determining variations in nutrients and organic matter concentrations with respect to different seasons. The factors included a number of characteristics regarding the catchment and streams: total catchment area, stream length, watershed form ratio, stream slope, flow rate and land use with respecttopavedareas,agriculturalareasandgreenareas(parks,forests,meadowsand pastures). Although concentrations of nitrogen compounds were higher in streams flowing through agricultural areas, our study showed that total concentrations of phosphoruswerehigherintheurbanstream,especiallyinsummer.Inagriculturalareas thesummerconcentrationsofnutrientswerenothigh,whichwasprobablyduetodense vegetation.ThecorrelationbetweenP-PO3− 4 concentrationandsizeofagriculturalarea in the catchment was observed in winter when no vegetation field cover exists. Our study shows an urgent need to monitor the nutrient loads carried with urban streams especially if discharged into receivers prone to eutrophication.

  • Secured wired BPL voice transmission system
    • Grzegorz Debita
    • Przemysław Falkowski-Gilski
    • Marcin Habrych
    • Bogdan Miedziński
    • Jan Wandzio
    • Przemysław Jedlikowski
    2020 Full text Scientific Journal of the Military University of Land Forces

    Designing a secured voice transmission system is not a trivial task. Wired media, thanks to their reliability and resistance to mechanical damage, seem an ideal solution. The BPL (Broadband over Power Line) cable is resistant to electricity stoppage and partial damage of phase conductors, ensuring continuity of transmission in case of an emergency. It seems an appropriate tool for delivering critical data, mostly clear and understandable voice messages. This paper describes such a system that was designed and evaluated in real-time operating conditions. It involved a two-way transmission of speech samples in American English and Polish. The efficiency of the designed solution was evaluated in the subjective study on a group of 15 people.

  • Selected adipocytokines in patients with an incidentally discovered pheochromocytoma
    • Mariusz Kaszubowski
    • Ania Babińska
    • P. Kmieć
    • Krzysztof Sworczak
    2020 Minerva Endocrinologica

    BACKGROUND: Adipose tissue secretes many adipokines and cytokines, which may be an additional risk factor of cardiovascular and metabolic diseases in patients with an incidentally discovered pheochromocytoma (PHEO). The aim of the study was to investigate levels of selected adipocytokines in these patients. METHODS: This prospective study included 12 patients with an incidentally discovered PHEO and 18 healthy participants. In all participants plasma/serum concentrations of triglycerides, HDL and LDL cholesterol, insulin, glucose, adipocytokines (adiponectin, leptin, resistin, TNFα, IL6, and MCP1) were determined, hormonal tests were performed in patients. RESULTS: Patients and controls did not differ significantly in terms of age, sex, and body mass index. Among incidentally discovered PHEO patients, adiponectin levels were lower, while TNFα concentrations higher than in controls. Concentrations of adiponectin correlated with 24-hour urinary excretion of normetanephrine in women. Significantly higher TNFα concentrations were found in hypertensive than in normotensive PHEO patients as well as in non-diabetic PHEO patients than controls. Further, resistin concentration was higher in PHEO patients with diabetes than in non-diabetic ones (p<0.001). Incidentally discovered PHEO tumor size correlated with leptin and IL6 levels. Adiponectin levels were higher, while TNFα and resistin lower among five patients re-examined after tumor resection. CONCLUSIONS: Among patients with an incidentally discovered pheochromocytoma, lower adiponectin, and higher resistin and TNFα levels may constitute additional factors for HT and DM. In our study, for the first time, correlations between incidentally discovered PHEO tumor size and concentrations of leptin as well as IL6 were found.

  • Selected issues of women's participation in labour market and on boards of family entreprises
    • Anita Richert-Kaźmierska
    2020

    The chapter presents cultural determinants of roles attributed to women, as well as their situation in the labour market and in family businesses. The main aim of the study is to trace the changes in the social image of women’s roles in the labour market. The observations made are based on the changes in the value of the economic activity rate among women in the Baltic Sea Region (BSR) countries, as well as on the feminisation rate among managers, employees and successors of family businesses.

  • Selected local stability problems of channel section flanges made of aluminium alloys
    • Marcin Kujawa
    2020 Full text CONTINUUM MECHANICS AND THERMODYNAMICS

    The paper addresses the issue of local buckling of compressed flanges of cold-formed thin-walled channel columns and beams with nonstandard flanges composed of aluminium alloys. The material behaviour follows the Ramberg–Osgood law. It should be noted that the proposed solution may be also applied for other materials, for example: stainless steel, carbon steel. The paper is motivated by an increasing interest in nonstandard cold-formed section shaping in local buckling analysis problems. Furthermore, attention is paid to the impact of material characteristics on buckling stresses in a nonlinear domain. The objective of the paper is to propose a finite element method (FEM) model and a relevant numerical procedure in ABAQUS, complemented by an analytical one. It should be noted that the proposed FEM energetic technique makes it possible to compute accurately the critical buckling stresses. The suggested numerical method is intended to accurately follow the entire structural equilibrium path under an active load in elastic and inelastic ranges. The paper is also focused on correct modelling of interactions between sheets of cross section of a possible contact during buckling analysis. Furthermore, the FEM results are compared with the analytical solution. Numerical examples confirm the validity of the proposed FEM procedures and the closed-form analytical solutions. Finally, a brief research summary is presented and the results are discussed further on.

  • Selection of C-Type Filters for Reactive Power Compensation and Filtration of Higher Harmonics Injected into the Transmission System by Arc Furnaces
    • Andrzej, Grzegorz Lange
    • Grzegorz Redlarski
    2020 Full text ENERGIES

    This article presents a method for selecting the elements of a C-type filter working with a conventional LC-type filter for compensating reactive power and filtering out higher harmonics generated by arc furnaces and ladle furnaces. The study was conducted in a steel mill supplied by a 110 kV transmission system, where higher harmonic currents and nonlinear loads were measured. A series of computer simulations were performed under various operating conditions, and an algorithm for selecting the parameters of a third-order C-type filter (for suppressing the second harmonic) and two second-order LC-type filters (for suppressing the third harmonic) was proposed. The filtering system was tested in an arc furnace with the highest rated power, and harmonics in the current spectrum were evaluated. The results of the measurements were used to analyze the effectiveness of the compensation system comprising two passive C-type and LC-type filters at different system configurations. C-type filters significantly influenced current harmonics. The influence of the changes in the number of arc furnace transformers on the true Root Mean Square (RMS) of the currents injected into the 110 kV transmission system and on the voltages of the 110 kV busbars was discussed.

  • Self-standing Nanoarchitectures
    • Siuzdak Katarzyna
    • Łukasz Haryński
    • Jakub Wawrzyniak
    • Piotr Kupracz
    • Katarzyna Grochowska
    2020 Full text

    Despite there are structures invisible for the human eye, they mastered the world of advanced electronic devices, sensors, novel cosmetics or drugs. When the dimensions of the materials go down to the nanometres scale, their properties change dramatically comparing to the observable objects. Because of their tiny size, they gained the name of nanomaterials but simultaneously their importance has significantly grown up. Nanomaterials exhibit superb features such as a distinctive catalytic activity, hydrophobicity, photoconversion activity and biological affinity. Following that, even a small amount of nanomaterials is sufficient to provide unusual properties to the final products such as coatings, active layers in solar cells, clothes, electrodes and electrolytes used for energy storage devices. Owing to the rapid development in the synthesis methods and characterization techniques, especially those used for morphology inspection, we can investigate them in details on the molecular scale and describe the mechanism that stays behind improved antimicrobiological activity, hydrophobicity, capacitance or catalytic properties. Despite the number of usable elements is limited, the diversity of morphologies, namely rods, particles, tubes, planes and the possibility of heterostructures formation, provides researchers the wide room for maneuverer. Sometimes, only small change in the material geometry, structure or a little amount of introduced dopant atoms is enough to obtain completely new nanomaterial that has not been known so far. Therefore, we should not be surprised how fast surrounding environment is changing and our everyday life is supported by the novelties from the nano world. The aim of this chapter is to present the diversity of nanomaterials taking into account their dimensions, shape and composition. Herein, particles, tubes, wires, pores, walls, exhibiting at least one dimension within the nanoscale will be evoked. Moreover, the nanostructures that morphology reminds well known objects from nature are discussed. The description of some interesting examples is supported by the extraordinary SEM images illustrating the beauty unavailable for naked eye.

  • Self-Supervised Learning to Increase the Performance of Skin Lesion Classification
    • Arkadiusz Kwasigroch
    • Michał Grochowski
    • Agnieszka Mikołajczyk
    2020 Full text Electronics

    To successfully train a deep neural network, a large amount of human-labeled data is required. Unfortunately, in many areas, collecting and labeling data is a difficult and tedious task. Several ways have been developed to mitigate the problem associated with the shortage of data, the most common of which is transfer learning. However, in many cases, the use of transfer learning as the only remedy is insufficient. In this study, we improve deep neural models training and increase the classification accuracy under a scarcity of data by the use of the self-supervised learning technique. Self-supervised learning allows an unlabeled dataset to be used for pretraining the network, as opposed to transfer learning that requires labeled datasets. The pretrained network can be then fine-tuned using the annotated data. Moreover, we investigated the effect of combining the self-supervised learning approach with transfer learning. It is shown that this strategy outperforms network training from scratch or with transfer learning. The tests were conducted on a very important and sensitive application (skin lesion classification), but the presented approach can be applied to a broader family of applications, especially in the medical domain where the scarcity of data is a real problem.

  • Sensor Position Estimation Method for IoT Using Mobile Reference Node
    • Jacek Stefański
    • Jarosław Sadowski
    2020 Full text IEEE Access

    The paper proposes an innovative method of locating objects for the Internet of Things (IoT). The proposed method allows the position of a fixed measuring sensor (MS) to be estimated using one mobile base station with a known position moving around the MS. The mathematical analysis of the method, and three algorithms — Newton’s (NA), gradient descent (GD) and genetic (GA) — for solving the system of non-linear positional equations are presented. Next, the analysis of the position dilution of precision (PDoP) parameter for the proposed method, and the Cramér-Rao lower bound (CRLB), limiting the accuracy of the method, are presented. Finally, the results of complex simulation studies on the efficiency of the proposed method for various selected system parameters of the sensor network and convergence of the algorithms used to solve the system of non-linear equations are described.

  • Sensorless five-phase induction motor drive with third harmonic injection and inverter output filter
    • Patrick Strankowski
    • Jarosław Guziński
    • Marcin Morawiec
    • Arkadiusz Lewicki
    • Filip Wilczyński
    2020 Full text Bulletin of the Polish Academy of Sciences-Technical Sciences

    The paper presents a sensorless control approach for a five-phase induction motor drive with third harmonic injection and inverter output filter. In the case of the third harmonic injection being utilised in the control, the physical machine has to be divided into two virtual machines that are controlled separately and independently. The control system structure is presented in conjunction with speed and rotor flux observers that are required for a speed sensorless implementation of the drive. The last section is dedicated to experimental results of the drive system in sensorless operation, and the uninterrupted drive operation for two open-phase faults.

  • Sensorless Rotor Position Estimation of Doubly-Fed Induction Generator Based on Backstepping Technique
    • Marcin Morawiec
    • Krzysztof Blecharz
    • Arkadiusz Lewicki
    2020 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS

    This paper proposes a speed observer algorithm for the sensorless control of a doubly-fed induction generator based on classical adaptive backstepping technique. The sensorless control is shown using classic stator field oriented control which is used to active and reactive power control. Performance of the proposed algorithm of a speed observer is validated by simulation and experimental results obtained using a small-rating generator and bidirectional voltage source converter. The stability analysis of the presented solution with regard to observer gains changes is also considered.

  • Service-based Resilience for Embedded IoT Networks
    • Doganalp Ergenc
    • Jacek Rak
    • Mathias Fischer
    2020

    Embedded IoT networks are the backbone of safety-critical systems like smart factories, autonomous vehicles, and airplanes. Therefore, resilience against failures and attacks should be a prior concern already in their design stage. In this study, we introduce a service-based network model as an MILP optimization problem for the efficient deployment of a service overlay to the embedded network by meeting QoS and resilience requirements. We show the complexity and boundaries of the problem and propose several heuristics to relax the service deployment phase and increase the fault-tolerance against node and link failures. Our results indicate that the heuristics achieve results close to the optimum for small sizes of the problem with up to 10^8 time faster solution time. We also show that the heuristics can solve larger problem sizes and can maintain the service availability for 85% of all potential single node failures.

  • SERVICE-ORIENTED CYBERSPACE FOR IMPROVING CYBERSECURITY
    • Henryk Krawczyk
    2020 Full text TASK Quarterly

    The paper presents a cyberspace model where different categories of IT services are offered and used largely. A general cybersecurity policy is considered and the corresponding cybersecurity strategies are shown. The role of such technologies as: Internet of Things, Cloud Computing and Big Data is analyzed in order to improve the cybersecurity of a cyberspace. A new kind of service oriented cyberspace is proposed and its main properties are emphasized. Two simple examples of such cyberspaces are given and briefly discussed.

  • Set of Experience and Decisional DNA: Experience-Based Knowledge Structures
    • Cesar Sanin
    • Edward Szczerbicki
    2020

    This chapter presents a description of Set of Experience Knowledge Structure (SOEKS) and Decisional DNA (DDNA), argumentation for a knowledge representation, composition, configuration and metrics. SOEKS is a combination of filtered and amalgamated information obtained from formal decision events. It facilitates effective explicit representation of decisional experience taken from different technologies. SOEKS comprises variables, functions, constraints and rules associated in a DNA shape, allowing the construction of enterprises’ fingerprints called Decisional DNA. SOEKS possesses characteristics that potentialize it as a more precise knowledge representation in a world guided by sensitive dependence and uncertainty, that is, SOEKS is a suitable representation for decisional explicit knowledge that has been gifted with capabilities to manage uncertainty, preciseness and incompleteness. Furthermore, SOEKS extends into the so-called DDNA due to the characterization and aggrupation of SOEKS into different classes termed decisional chromosomes. Such decisional chromosomes simulate specialized genes that when placed together create the decisional experience of an enterprise, the Decisional DNA.

  • SEWAGE SYSTEM CONCEPT FOR KAMIEŃ VILLAGE IN THE COMMUNE OF SZEMUD
    • Dominika Grubba
    2020

    The aim of this thesis is to solve a disturbing problem, which is illegal sewage discharge, without any previous treatment in a village Kamień, Szemud commune, Poland, by developing a multivariate sewerage system concept. The introduction submits the theory concerning the division of sewer systems as well as the wastewater treatment’s level. Moreover, there is also the problem of rural sanitation presented and main locality – Kamień description. Furthermore, two variants of the sewage network, meaning: one, that is connecting to an existing network in the village and second one, that is discharging wastewater into the local sewage treatment plant are precisely defined. Calculation part presents all necessary steps to select sewagetubes and wastewater treatment plants. Lastly, there is also a graphic summary of entire solution for the village Kamień presented in this work.

  • Shading, Dusting and Incorrect Positioning of Photovoltaic Modules as Important Factors in Performance Reduction
    • Ewa Klugmann-Radziemska
    2020 Full text ENERGIES

    The amount of solar radiation reaching the front cover of a photovoltaic module is crucial for its performance. A number of factors must be taken into account at the design stage of the solar installation, which will ensure maximum utilization of the potential arising from the location. During the operation of a photovoltaic installation, it is necessary to limit the shading of the modules caused by both dust and shadowing by trees or other objects. The article presents an analysis of the impact of the radiation reaching the surface of the radiation module on the efficiency obtained. Each of the analyzed aspects is important for obtaining the greatest amount of energy in specific geographical conditions. Modules contaminated by settling dust will be less efficient than those without deposits. The results of experimental studies of this effect are presented, depending on the amount of impurities, including their origins and morphologies. In practice, it is impossible to completely eliminate shadowing caused by trees, uneven terrain, other buildings, chimneys, or satellite dishes, and so on, which limits the energy of solar radiation reaching the modules. An analysis of partial shading for the generated power was also carried out. An important way for maximizing the incoming radiation is the correct positioning of the modules relative to the sun. It is considered optimal to position the modules relative to the light source, that is, the sun, so that the rays fall perpendicular to the surfaces of the modules. Any deviation in the direction of the rays results in a loss in the form of a decrease in the available power of the module. The most beneficial option would be to use sun-tracking systems, but they represent an additional investment cost, and their installations require additional space and maintenance. Therefore, the principle was adopted that stationary systems should be oriented to the south, using the optimal angle of inclination of the module surface appropriate for the location. This article presents the dependence of the decrease in obtained power on the angle of deviation from the optimal one.

  • Shallow Water Equations as a Mathematical Model of Whitewater Course Hydrodynamics
    • Michał Szydłowski
    • Patrycja Mikos-Studnicka
    2020 GeoPlanet: Earth and Planetary Sciences

    Predicting the positions of local hydraulic phenomena, as well as accurately esti-mating the depth and velocity of the water flow are necessary to correctly config-ure a whitewater canoeing course. Currently, a laboratory and full 3D CFD model-ing are typically used in the design process to meet these needs. The article points to another possibility which can be useful at the preliminary stage of the design. The authors show that a mathematical model of depth-averaged free-surface flow can reliably predict the basic flow dynamics and location of some hydraulic local effects within a whitewater open channel. The results of a numerical simula-tion of the transcritical flow were compared to the flow parameters measured in a laboratory model of a constriction in an open-channel flow. A satisfactory agreement between the measurements and calculated flow parameters was ob-served along with the proper reconstruction of hydraulic local effects. It can be concluded that the proposed simplified approach to modeling is an efficient method to investigate the main hydraulic features of whitewater flow needed at the concept stage of the design process. This means that cost and time-consuming laboratory and CFD modeling is necessary only at a later stage of the design, after the initial concept of the canoe course has been completed.

  • Shallow Water Experiment of OFDM Underwater Acoustic Communications
    • Iwona Kochańska
    • Jan Schmidt
    • Jacek Marszal
    2020 Full text Archives of Acoustics

    The large variability of communication properties of underwater acoustic channels, and especially the strongly varying instantaneous conditions in shallow waters, is a challenge for the designers of underwater acoustic communication (UAC) systems. The use of phase modulated signals does not allow reliable data transmission through such a tough communication channel. However, orthogonal frequency-division multiplexing (OFDM), being a multi-carrier amplitude and phase modulation technique applied successfully in the latest standards of wireless communications, gives the chance of reliable communication with an acceptable error rate. This paper describes communication tests conducted with the use of a laboratory model of an OFDM data transmission system in a shallow water environment in Wdzydze Lake.

  • Shape memory thin films of Polyurethane: Does graphene content affect the recovery behavior of Polyurethane nanocomposites?
    • Maryam Zarghami Dehaghani
    • Babak Kaffashi
    • Józef Haponiuk
    • Łukasz Piszczyk
    2020 POLYMER COMPOSITES

    Thin nanocomposite films of polyurethane have received remarkable attention due to their shape memory properties. As most of the reports focus on the beneficial aspects of the presence of nanofillers such as graphene nanoplatelets (GNPs) introduced into shape memory polymers, some research results reveal the opposite trend. The polyether/polyester-based polyurethane was synthesized through a condensation polymerization and the nanocomposite films containing 0.1, 0.25, 0.5, and 1 wt.% of GNPs were prepared by the solvent casting method. The Fourier transformed infrared (FTIR) spectroscopy was carried out to investigate the chemical structure of nanocomposite films. The properties of nanocomposite films were verified by the differential scanning calorimetry (DSC), X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), tensile test, and the dynamic mechanical analysis (DMA). The shape memory properties were studied through various thermomechanical cycles applied by the DMA apparatus. All the nanocomposite films showed larger glassy storage moduli compared with those of the neat PU films. The nanocomposite film containing 0.25 wt.% GNPs showed the highest shape recovery ratio (92.4%) since the net-point effect of GNPs dominates its slipping effect. While for the other nanocomposite films the slippage effect overcomes the net-point effect.

  • Shaping the competence of future spatial policymakers for small- and medium-sized towns
    • Piotr Lorens
    • Anna Golędzinowska
    2020 Full text World Transactions on Engineering and Technology Education

    In this article, the authors aim to present issues addressed within the framework of the architecture and spatial development courses offered by the Faculty of Architecture at Gdańsk University of Technology (FA-GUT), Gdańsk, Poland. These issues concern competence in the education of future spatial planners and their readiness to deal with the development challenges facing small- and medium-sized towns. Within the article, the similarities and differences are pointed out that relate to curriculum structure and academic outcomes that can influence the professional profile of graduates. Similarities between the two courses enable identification of the most effective model. The article includes a summary of the educational problem, an outline of design studio profiles for both courses, comparison of the results achieved and conclusions regarding future educational efforts, including relevant lessons for other planning and engineering schools. The conclusions focus on the lessons learnt and suggest improvements that can be made worldwide within educational programmes.

  • Shared processor scheduling of multiprocessor jobs
    • Dariusz Dereniowski
    • Wiesław Kubiak
    2020 EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

    We study a problem of shared processor scheduling of multiprocessor weighted jobs. Each job can be executed on its private processor and simultaneously on possibly many processors shared by all jobs. This simultaneous execution reduces their completion times due to the processing time overlap. Each of the m shared processors may charge a different fee but otherwise the processors are identical. The goal is to maximize the total weighted overlap of all jobs. This is a key problem in subcontractor scheduling in extended enterprises and supply chains, and in divisible load scheduling in computing. We introduce synchronized schedules that complete each job that uses some shared processor at the same time on its private and on the shared processors. We prove that, quite surprisingly, the synchronized schedules include optimal ones. We obtain an α-approximation algorithm that runs in strongly polynomial time for the problem, where α = 1/2 + 1/(4(m+1)). This improves the 1/2-approximation reported recently in the literature to 5/8-approximation for a single shared processor problem, m=1. The computational complexity of the problem, both in case of single and multi-shared processor, remains open. We show however an LP-based optimal algorithm for antithetical instances where for any pair of jobs j and i, if the processing time of j is smaller than or equal to the processing time of i, then the weight of j is greater than or equal to the weight of i.

  • Shear Cap Size Selection Method Based on Parametric Analysis of ACI-318 Code and Eurocode 2 Standard
    • Maciej Grabski
    • Andrzej Ambroziak
    2020 Full text Materials

    The scope of the paper is to propose a method for determining the size of shear caps in a slab–column-connections-reinforced concrete structure. Usually, shear heads are used to enhance slab–column connection, especially when the transverse reinforcement does not give the required punching shear load capacity. The dimensions of the shear head should provide the punching shear resistance of the connection inside and outside the enhanced region. The process of selecting the size of the shear head is iterative. The parametric analysis of the ACI 318 code and EC2 standard has the objective of indicating which control perimeter (inside or outside the shear head) has a decisive impact on the punching shear capacity of the connection. Based on the analysis, the authors propose methods for selecting the dimensions of the shear head with practical application examples. The paper is intended to provide scientists, civil engineers, and designers with guidelines to design the process of the slab–column connections with the shear caps.

  • Shear resistance of low height precast concrete lintels
    • Andrzej Ambroziak
    • Jarosław Kondrat
    • Marek Wesołowski
    2020 Full text Archives of Civil Engineering

    The scope of the paper is to investigate analytically and determine experimentally the shear resistance of low height reinforced precast concrete lintels. The chosen procedures included in national and international standards applied for the design of structural concrete elements to an estimation of shear behaviour of reinforced concrete elements are described. The characteristic and designed shear strength of precast concrete lintels are determined and compared with experimentally obtained results. The shear resistance for precast concrete lintels was determined by laboratory tests according to a European standard. The assessment of the in-situ compressive strength of concrete in precast concrete lintel is specified. The designed compressive strength class is confirmed. The real reinforcement distribution is verified to assess the wide scatter of experimentally obtained failure forces. A short literature outlook of the papers concerning investigations on lintels and shear resistance of concrete is given also. The paper can provide scientists, engineers, and designers a theoretical and experimental basis in the field of precast concrete lintels shear resistance.

  • Short and Long Term Measurements in Assessment of FRP Composite Footbridge Behavior
    • Mikołaj Miśkiewicz
    • Łukasz Pyrzowski
    • Bartosz Sobczyk
    2020 Full text Materials

    The paper presents application of different sensors for the purpose of short and long term measurements, as well as a structural health monitoring (SHM) system to assess the behavior of a novel fiber reinforced plastics (FRP) composite footbridge. The aim is to present a thorough and concise description of these sensors networks and results gathered with their aid during in situ measurement of strains, displacements, and vibrations, as only a few works are available in this field. The bridge geometry, material solutions, and properties are described at first. Then the measurement devices composing the system and subsystems of sensors are elaborated on. Subsequently, the bridge research program is described and the results are shown and discussed. Finally, it is concluded that the use of selected sensors is helpful in assessment of the behavior of the novel structure, and moreover in validation of its numerical models. The collected data confirmed many assumptions made during the bridge design process and allowed us to accept it for exploitation.

  • SHORT REVIEW AND 3-D FEM ANALYSIS OF BASIC TYPES OF FOUNDATION FOR OFFSHORE WIND TURBINES
    • Piotr Iwicki
    • Jarosław Przewłócki
    2020 Full text Polish Maritime Research

    Some problems of the foundations of offshore wind turbines are considered in this paper. A short review is presented on the two basic types of foundations, i.e. monopiles and gravity foundations, including their basic features and applications as well as general design considerations. Also, some issues regarding analysis are discussed, including geotechnical problems and modelling techniques. A numerical model of offshores turbine and some preliminary computations are presented. Finite element analysis was carried out for wind turbines supported on both gravity and monopile foundations. The wind turbine tower, blades (simplified model), gravity foundation and part of the surrounding soil are included in the model. The turbine was loaded by wind and loads induced by waves, inertia and gravity. Both non-linear static and dynamic analysis of the wind turbine was performed. The displacements and stresses under the tower foundations were calculated and a comparison analysis carried out.

  • Short-range order structure and free volume distribution in liquid bismuth: X-ray diffraction and computer simulations studies
    • Valeriy Plechystyy
    • Ihor Shtablavyi
    • Szymon Winczewski
    • Kamil Rybacki
    • Stepan Mudry
    • Jarosław Rybicki
    2020 PHILOSOPHICAL MAGAZINE

    The structure of liquid bismuth was studied by X-ray diffraction and computer simulation methods. The contraction of the atomic structure within the first coordination sphere in the temperature interval of 575- 1225 K is reported. The temperature dependencies of the coordination numbers and of the free volume are analysed. On the basis of the temperature dependencies of the free volume, the temperature dependencies of viscosity and the self-diffusion coefficient were calculated to be in the ranges from 1.17 to 0.86 mPa s and from 2.18 × 10 −9 to 5.44 × 10 −9 m 2 /s, respectively. The free volume – extracted results are in fair agreement with the experimental data and with the results obtained in the molecular dynamics simulations

  • Short-term Price Reaction to Involuntary Bankruptcies Filed in Bad Faith: Empirical Evidence from Poland
    • Błażej Prusak
    • Marcin Potrykus
    2020 Full text European Research Studies Journal

    Purpose: Assessing the reaction of the prices of shares of companies listed in the Warsaw Stock Exchange to the public disclosure of information about the filing a bankruptcy petition in bad faith by creditors. Design/Methodology/Approach: Event study analysis. Findings: It can therefore be assumed that the filing of an unfounded bankruptcy petition does not, in the short term, have a statistically significant negative impact on the share price of the company being the subject of the petition Practical Implications: When information about the filing a bankruptcy petition appears and creditors submitted it in bad faith, it has not a negative impact on the share price in short term. It can be said that submitting such information is not an opportunity for an investor to receive an abnormal rate of return. Originality/value: Although there are many research results using event study analysis most of them are related to the US market. The originality of this paper is that this research is dedicated to petitions in bad faith for a selected developing country.

  • Shoulder ultrasound in the diagnosis of the suprascapular neuropathy in athletes
    • Barbara Igielska-Bela
    • Boguslaw Baczkowski
    • Karol Flisikowski
    2020 Full text Open Medicine

    Purpose: Shoulder pain and weakness are common symptoms in athletes who play sports connected with overhead throwing. Suprascapular neuropathy may be one of the reason of such signs.The aim of the study was to find out if ultrasound examination of the shoulder in athletes reveals signs of suprascapular neuropathy. Methods: This was a cross-sectional study in which 67 pro- fessional volleyball, handball and rugby players of polish teams without shoulder disorders, which have played sport for 10 or more years, were included. An ultrasound examination of both shoulders was performed. Exclud- ing criteria were recent shoulder and/or neck trauma and neurological disorders. Results: No ultrasound signs of suprascapular neuropathy were seen in any player. The only finding was enthesop- athy of supraspinatus muscle and this finding was con- nected with athletes’ age, type of sport and with dominant hand. It had statistical significance with p-value respec- tively 0.01 for athletes’ age, 0.0208 for sport type and 0.03 for dominant hand. Conclusions: Ultrasonography should not be used as the screening examination of shoulders in athletes, but it can sometimes be an additional tool to help to diagnose shoul- der disorders.

  • SiC-Based Power Electronic Traction Transformer (PETT) for 3 kV DC Rail Traction
    • Marek Adamowicz
    • Janusz Szewczyk
    2020 Full text ENERGIES

    The design of rolling stock plays a key role in the attractiveness of the rail transport. Train design must strictly meet the requirements of rail operators to ensure high quality and cost-eective services. Semiconductor power devices made from silicon carbide (SiC) have reached a level of technology enabling their widespread use in traction power converters. SiC transistors oering energy savings, quieter operation, improved reliability and reduced maintenance costs have become the choice for the next-generation railway power converters and are quickly replacing the IGBT technology which has been used for decades. The paper describes the design and development of a novel SiC-based DC power electronic traction transformer (PETT) intended for electric multiple units (EMUs) operated in 3 kV DC rail traction. The details related to the 0.5 MVA peak power medium voltage prototype, including the electrical design of the main building blocks are presented in the first part of the paper. The second part deals with the implementation of the developed SiC-based DC PETT into a regional train operating on a 3 kV DC traction system. The experimental results obtained during the testing are presented to demonstrate the performance of the developed 3 kV DC PETT prototype.

  • Signal propagation in electromagnetic media described by fractional-order models
    • Tomasz Stefański
    • Jacek Gulgowski
    2020 Communications in Nonlinear Science and Numerical Simulation

    In this paper, signal propagation is analysed in electromagnetic media described by fractional-order (FO) models (FOMs). Maxwell’s equations with FO constitutive relations are introduced in the time domain. Then, their phasor representation is derived for one-dimensional case of the plane wave propagation. With the use of the Fourier transformation, the algorithm for simulation of the non-monochromatic wave propagation is introduced. Its implementation in Matlab allows for generation of time-domain waveforms of signals propagating in the media described by FOMs. It is demonstrated that despite high attenuation, a small perturbation of the time-derivative orders in Maxwell’s equations allows for tuning of the time of signal arrival to the observation point. In all the cases studied, the rate of pulse advancement increases, with simultaneous decrease of the value of the time-derivative orders in FO Maxwell’s equations.

  • Signature of Oxide-Ion Conduction in Alkaline-Earth-Metal-Doped Y3GaO6
    • Pragati Singh
    • Raghvendra Pandey
    • Tadeusz Miruszewski
    • Kacper Dzierzgowski
    • Aleksandra Mielewczyk-Gryń
    • Prabhakar Singh
    2020 Full text ACS Omega

    We have studied alkaline-earth-metal-doped Y3GaO6 as a new family of oxide-ion conductor. Solid solutions of Y3GaO6 and 2% −Ca2+-, −Sr2+-, and −Ba2+-doped Y3GaO6, i.e., Y(3−0.06)M0.06GaO6−δ (M = Ca2+, Sr2+, and Ba2+), were prepared via a conventional solid-state reaction route. X-ray Rietveld refined diffractograms of all the compositions showed the formation of an orthorhombic structure having the Cmc21 space group. Scanning electron microscopy (SEM) images revealed that the substitution of alkaline-earth metal ions promotes grain growth. Aliovalent doping of Ca2+, Sr2+, and Ba2+ enhanced the conductivity by increasing the oxygen vacancy concentration. However, among all of the studied dopants, 2% Ca2+-doped Y3GaO6 was found to be more effective in increasing the ionic conductivity as ionic radii mismatch is minimum for Y3+/Ca2+. The total conductivity of 2% Ca-doped Y3GaO6 composition calculated using the complex impedance plot was found to be ∼0.14 × 10−3 S cm−1 at 700 °C, which is comparable to many other reported solid electrolytes at the same temperature, making it a potential candidate for future electrolyte material for solid oxide fuel cells (SOFCs). Total electrical conductivity measurement as a function of oxygen partial pressure suggests dominating oxide-ion conduction in a wide range of oxygen partial pressure (ca. 10−20−10−4 atm). The oxygen-ion transport is attributed to the presence of oxygen vacancies that arise from doping and conducting oxide-ion layers of one, two-, or three-dimensional channels within the crystal structure. The oxide-ion migration pathways were analyzed by the bond valence site energy (BVSE)-based approach. Photoluminescence analysis, dilatometry, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy studies were also performed to verify the experimental findings.

  • Signature Partitioning Using Selected Population-Based Algorithms
    • Marcin Zalasiński
    • Krzysztof Cpałka
    • Tacjana Niksa-Rynkiewicz
    • Yoichi Hayashi
    2020

    Dynamic signature is a biometric attribute which is commonly used for identity verification. Artificial intelligence methods, especially population-based algorithms (PBAs), can be very useful in the dynamic signature verification process. They are able to, among others, support selection of the most characteristic descriptors of the signature or perform signature partitioning. In this paper, we focus on creating the most characteristic signature partitions using different PBAs and comparing their effectiveness. The simulations whose results are presented in this paper were performed using the BioSecure DS2 database distributed by the BioSecure Association.

  • Silica Gel Impregnated by Deep Eutectic Solvents for Adsorptive Removal of BTEX from Gas Streams
    • Patrycja Makoś
    • Edyta Słupek
    • Aleksandra Małachowska
    2020 Full text Materials

    The paper presents the preparation of new adsorbents based on silica gel (SiO2) impregnated with deep eutectic solvents (DESs) to increase benzene, toluene, ethylbenzene, and p-xylene (BTEX) adsorption efficiency from gas streams. The DESs were synthesized by means of choline chloride, tetrapropylammonium bromide, levulinic acid, lactic acid, and phenol. The physico-chemical properties of new sorbent materials, including surface morphology and structures, as well as porosity, were studied by means of thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller analysis. The effect of DESs type, flow rate, and initial concentration of BTEX were also investigated followed by regeneration and reusability of adsorbents. The results indicate that SiO2 impregnated with tetrapropylammonium bromide and lactic acid in a 1:2 molar ratio have great potential for the removal of BTEX from gas streams. Its adsorption capacity was higher than the pure SiO2 and other developed SiO2-DES adsorbents. This result can be explained by the specific interaction between DESs and BTEX, i.e., hydrogen bonds interaction.

  • Silicon Oxycarbide-Graphite Electrodes for High-Power Energy Storage Devices
    • Dominik Knozowski
    • Magdalena Graczyk-Zajac
    • Grzegorz Trykowski
    • Monika Wilamowska-Zawłocka
    2020 Full text Materials

    Herein we present a study on polymer-derived silicon oxycarbide (SiOC)/graphite composites for a potential application as an electrode in high power energy storage devices, such as Lithium-Ion Capacitor (LIC). The composites were processed using high power ultrasound-assisted sol-gel synthesis followed by pyrolysis. The intensive sonication enhances gelation and drying process, improving the homogenous distribution of the graphitic flakes in the preceramic blends. The physicochemical investigation of SiOC/graphite composites using X-ray diffraction, 29Si solid state NMR and Raman spectroscopy indicated no reaction occurring between the components. The electrochemical measurements revealed enhanced capacity (by up to 63%) at high current rates (1.86 A g−1) recorded for SiOC/graphite composite compared to the pure components. Moreover, the addition of graphite to the SiOC matrix decreased the value of delithiation potential, which is a desirable feature for anodes in LIC.

  • Simplified Approach for Broadband RF Testing of Low Loss Magneto-Dielectric Samples
    • Nilesh K. Tiwari
    • Surya P. Singh
    • Abhishek Jha
    • M. Jaleel Akhtar
    2020 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT

    In this paper, an attractive measurement techniqueis proposed to retrieve the broadband permittivity and permeabil-ity of the magneto-dielectric materials. The proposed techniqueis quite novel which mitigates the major problems associatedwith the conventional broadband RF material characterizationtechniques such as numerical instability and phase uncertaintywhen the length of the sample exceeds the integer multipleof half-wavelength. The approach adopted in this paper isquite unique as it alleviates the error normally caused by thesensitive phase measurement, since it only employs the relativeamplitude of the scattering parameters, thus minimizing themeasurement uncertainty. The proposed methodology here isbased on the development of a unified scheme for the retrieval ofdielectric and magnetic properties of magneto-dielectric samples,which is first tested for a number of reference samples usingthe numerically generated scattering coefficient data. Finally,the proposed technique is experimentally validated by measuringa number of standard samples over a broad microwave frequencyrange with the help of the coaxial line and the network analyzer.The dielectric and magnetic properties of samples retrieved usingthe proposed approach is always found to be in good agreementwith their actual values available in the literature

  • Simulating Power Generation from Photovoltaics in the Polish Power System Based on Ground Meteorological Measurements—First Tests Based on Transmission System Operator Data
    • Jakub Jurasz
    • Marcin Wdowikowski
    • Mariusz Figurski
    2020 Full text ENERGIES

    The Polish power system is undergoing a slow process of transformation from coal to one that is renewables dominated. Although coal will remain a fundamental fuel in the coming years, the recent upsurge in installed capacity of photovoltaic (PV) systems should draw significant attention. Owning to the fact that the Polish Transmission System Operator recently published the PV hourly generation time series in this article, we aim to explore how well those can be modeled based on the meteorological measurements provided by the Institute of Meteorology and Water Management. The hourly time series of PV generation on a country level and irradiation, wind speed, and temperature measurements from 23 meteorological stations covering one month are used as inputs to create an artificial neural network. The analysis indicates that available measurements combined with artificial neural networks can simulate PV generation on a national level with a mean percentage error of 3.2%.

  • Simulation of Signal Propagation Along Fractional-Order Transmission Lines
    • Tomasz Stefański
    • Damian Trofimowicz
    • Jacek Gulgowski
    2020

    In this paper, the simulation method of signal propagation along fractional-order (FO) transmission lines is presented. Initially, fractional calculus and the model of FO transmission line are introduced. Then, the algorithm allowing for simulation of the nonmonochromatic wave propagation along FO transmission lines is presented. It employs computations in the frequency domain, i.e., an analytical excitation is transformed to the frequency domain, multiplications with phase factors are executed, and finally the result is transformed back to the time domain. This algorithm involves elementary functions only and the fast Fourier transformation, hence, computations are numerically efficient and accurate. However, applicability of the method is limited by the sampling theorem. Numerical results are presented allowing for the evaluation of the method.

  • Simulation of Wave Propagation in Media Described by Fractional-Order Models
    • Tomasz Stefanski
    • Jacek Gulgowski
    2020 Full text

    In this paper, algorithms for simulation of the wave propagation in electromagnetic media described by fractional-order (FO) models (FOMs) are presented. Initially, fractional calculus and FO Maxwell's equations are introduced. The problem of the wave propagation is formulated for media described by FOMs. Then, algorithms for simulation of the non-monochromatic wave propagation are presented which employ computations in the time domain (TD) and the frequency domain (FD). In the TD algorithm, the electromagnetic field is computed as a convolution of an excitation with Green's function formulated based on an improper integral and the Mittag-Leffler function. On the other hand, the FD algorithm transforms an analytic excitation to FD, executes multiplications with phase factors, and finally transfers back result to TD. This algorithm involves elementary functions only, hence, computations are significantly faster and accurate with its use. However, applicability of the FD algorithm is limited by the sampling theorem. Numerical results and computation times obtained with the use of both algorithms are presented and discussed in detail.

  • Simulation-Driven Antenna Modeling by Means of Response Features and Confined Domains of Reduced Dimensionality
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    2020 Full text IEEE Access

    In recent years, the employment of full-wave electromagnetic (EM) simulation tools has become imperative in the antenna design mainly for reliability reasons. While the CPU cost of a single simulation is rarely an issue, the computational overhead associated with EM-driven tasks that require massive EM analyses may become a serious bottleneck. A widely used approach to lessen this cost is the employment of surrogate models, especially data-driven ones: versatile and easily accessible. Yet, one of the unresolved issues remains the curse of dimensionality. Standard modeling techniques are merely capable of rendering surrogates for low-dimensional cases within narrow parameter ranges. In pursuit to overcome these limitations, a novel technique has been recently proposed, where the overall modeling process is carried out within a confined domain, set up based on performance specifications and spectral analysis of an auxiliary set of reference designs. This work offers a further development of the aforementioned method. Instead of tackling the entire antenna responses, only the selected characteristic points (relevant to the figures of interest considered in the antenna design process) are handled. This allows for achieving excellent model accuracy at a low computational cost. The proposed approach can be an attractive modeling alternative for systems with well-structured characteristics.

  • Simulations of hydro-fracking in rock mass at meso-scale using fully coupled DEM/CFD approach
    • Marek Krzaczek
    • Michał Nitka
    • Jan Kozicki
    • Andrzej Tejchman-Konarzewski
    2020 Full text Acta Geotechnica

    The paper deals with two-dimensional (2D) numerical modelling of hydro-fracking (hydraulic fracturing) in rocks at the meso-scale. A numerical model was developed to characterize the properties of fluid-driven fractures in rocks by combining the discrete element method (DEM) with computational fluid dynamics (CFD). The mechanical behaviour of the rock matrix was simulated with DEM and the behaviour of the fracturing fluid flow in newly developed and pre- existing fractures with CFD. The changes in the void geometry in the rock matrix were taken into account. The initial 2D hydro-fracking simulation tests were carried out for a rock segment under biaxial compression with one injection slot in order to validate the numerical model. The qualitative effect of several parameters on the propagation of a hydraulic fracture was studied: initial porosity of the rock matrix, dynamic viscosity of the fracking fluid, rock strength and pre- existing fracture. The characteristic features of a fractured rock mass due to a high-pressure injection of fluid were realistically modelled by the proposed coupled approach.

  • Simultaneous optical and electrochemical label-free biosensing with ITO-coated lossy-mode resonance sensor
    • Mateusz Śmietana
    • Marcin Koba
    • Petr Sezemsky
    • Katarzyna Szot-Karpińska
    • Dariusz Burnat
    • Vitezslav Stranak
    • Joanna Niedziółka-Jönsson
    • Robert Bogdanowicz
    2020 Full text BIOSENSORS & BIOELECTRONICS

    In this work we discuss a new label-free biosensing device based on indium tin oxide (ITO) overlaid section of a multimode optical fiber fused silica core. The sensor has been used to optical measurements also simultaneously interrogated electrochemically (EC). Due to optimized thickness and optical properties of ITO film, a lossy-mode resonance (LMR) could be observed in the optical domain, where electrical properties of the film allowed for application of the sensor as a working electrode in an EC setup. It has been confirmed that the LMR response depends on optical properties of the external medium, as well as potential applied to the electrode during cyclic voltammetry. After the ITO surface functionalization with amine groups and covalently attached biotin, the device has been applied for label-free biosensing of avidin in both the domains simultaneously. On the example of biotin-avidin detection system it was demonstrated that when avidin concentration increases a decrease in current and increase in LMR wavelength shift were recorded in EC and optical domain, respectively. Both optical and EC responses follow the protein interaction process, and thus can be used as cross-verification of the readouts. Moreover, an extended information has been achieved comparing to solely EC interrogation, i.e., the grafting process of biotin and avidin was directly monitored optically displaying individual steps of an incubation procedure.

  • Simultaneous Removal of Hexane and Ethanol from Air in a Biotrickling Filter—Process Performance and Monitoring Using Electronic Nose
    • Piotr Rybarczyk
    • Bartosz Szulczyński
    • Jacek Gębicki
    2020 Full text Sustainability

    Biofiltration is a well-accepted method for the removal of malodorous compounds from air streams. Interestingly, the mechanisms underlying this process are not fully understood. The aim of this paper was to investigate the simultaneous removal of hydrophobic hexane with hydrophilic ethanol, resulting in the enhanced removal of hexane in the presence of ethanol. Investigations were performed in a peat-perlite packed biotrickling filter and the process performance was monitored using both gas chromatography and electronic nose techniques. The results indicate that the length as well as the eciency of biofiltration during the start-up period depend on the feed composition, with higher eciency obtained when hexane and ethanol were fed together from the process initiation. The experiments in the steady-state period present the biofilter performance when dierent ratios of hydrophilic to hydrophobic compounds were fed to the biofilter. The obtained results show the synergistic eects of the addition of a hydrophilic compound on the removal eciency of hydrophobic hexane. The influence of the ratio of hydrophilic to hydrophobic compounds is discussed in terms of enhancing the mass transfer phenomena for hydrophobic volatile organic compounds.