2020 - Repozytorium publikacji - Politechnika Gdańska

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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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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 Pełny tekst 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%.