Publications Repository - Gdańsk University of Technology

Page settings

polski
Publications Repository
Gdańsk University of Technology

Show publications from the year

Publications from the year 2020

Show all
  • Tribological Properties of Ni-P/Si3N4 Nanocomposite Layers Deposited by Chemical Reduction Method on Aluminum Alloy AW-7075
    • Kazimierz Czapczyk
    2020 Full text Materials

    The article presents the results of tribological tests of Ni-P/Si3N4 nanocomposite and Ni-P nickel layers deposited on the AW-7075 aluminum alloy by chemical reduction method, and the AW-7075 alloy without coating. Nanocomposite layers were produced using Si3N4 siliconnitride in the form of a polydisperse powder whose particle sizes ranged from 20 to 25 nm. The influence of the content of the dispersion phase layer material on the abrasive wear, which was determined as the “ball on disc” method, was analyzed. Surface topography was examined by the contact method using a profilometer. The purpose of introducing Si3N4 particles into the Ni-P layer was to increase the wear resistance of AW-7075 aluminum alloy parts with an embedded nanocomposite coating. Based on the obtained test results, it was found that the Ni-P/Si3N4 layers are more resistant to wear than the Ni-P layers and the AW-7075 alloy layers, and are a good barrier against abrasive wear at various loads and environmental conditions.

  • Trimethylamine N-oxide and the reverse cholesterol transport in cardiovascular disease: a cross-sectional study
    • Laura Bordoni
    • Joanna J. Samulak
    • Angelika K. Sawicka
    • Iwona Pelikant-Malecka
    • Adrianna Radulska
    • Lukasz Lewicki
    • Leszek Kalinowski
    • Rosita Gabbianelli
    • Robert Olek
    2020 Full text Scientific Reports

    The early atherosclerotic lesions develop by the accumulation of arterial foam cells derived mainly from cholesterol-loaded macrophages. Therefore, cholesterol and cholesteryl ester transfer protein (CETP) have been considered as causative in atherosclerosis. Moreover, recent studies indicate the role of trimethylamine N-oxide (TMAO) in development of cardiovascular disease (CVD). The current study aimed to investigate the association between TMAO and CETP polymorphisms (rs12720922 and rs247616), previously identified as a genetic determinant of circulating CETP, in a population of coronary artery disease (CAD) patients (n = 394) and control subjects (n = 153). We also considered age, sex, trimethylamine (TMA) levels and glomerular filtration rate (GFR) as other factors that can potentially play a role in this complex picture. We found no association of TMAO with genetically determined CETP in a population of CAD patients and control subjects. Moreover, we noticed no differences between CAD patients and control subjects in plasma TMAO levels. On the contrary, lower levels of TMA in CAD patients respect to controls were observed. Our results indicated a significant correlation between GFR and TMAO, but not TMA. The debate whether TMAO can be a harmful, diagnostic or protective marker in CVD needs to be continued.

  • Tripped at the Finishing Line: The Åland Islands Internet Voting Project
    • David Duenas Cid
    • Iuliia Krivonosova
    • Radu Serrano
    • Marlon Freire
    • Robert Krimmer
    2020 Full text

    The Åland Islands spent years preparing an internet voting system, to be implemented for the first time in October 2019 for Parliamentary Elections. Despite this, the project was canceled the evening before the expected release date. In this paper, we explore the causes of this failure using a two-pronged approach including Information System failure perspectives and the approach to e-voting Mirabilis, focusing on organizational elements which provoked the decision not to use the system.

  • Trouble in Paradise? Barriers to Open Innovation in Regional Clusters in the Era of the 4th Industrial Revolution
    • Marita Mcphillips
    2020 Full text Journal of Open Innovation: Technology, Market, and Complexity

    The purpose of this paper is to provide an insight into the barriers faced by clusters as open innovation intermediaries. Literature review and an empirical study were performed, involving a nation-wide survey, case studies, and in-depth interviews with cluster actors involved in open innovation activities. This article conceptually links open innovation and clusters in the context of the fourth industrial revolution, empirically identifies barriers hindering open innovation in clusters, and indicates factors that might affect the open innovation processes in networked ecosystems. The findings confirm that the perception of barriers hindering open innovation in clusters differs between clusters already implementing open innovation and those which are still not active in this area. The findings contribute to a comprehensive understanding of the potential roles of clusters as open innovation intermediaries in the context of transitioning economies. With clusters playing a role in open innovation intermediary, public support at cluster level could increase openness to cooperation not only for member companies, but all participants in the regional innovation ecosystem.

  • Trust-Based Model for the Assessment of the Uncertainty of Measurements in Hybrid IoT Networks
    • Piotr Cofta
    • Cezary Orłowski
    • Jacek Lebiedź
    2020 Full text SENSORS

    The aim of this paper is to introduce a NUT model (NUT: network-uncertainty-trust) that aids the decrease of the uncertainty of measurements in autonomous hybrid Internet of Things sensor networks. The problem of uncertainty in such networks is a consequence of various operating conditions and varied quality of measurement nodes, making statistical approach less successful. This paper presents a model for decreasing the uncertainty through the use of socially inspired metaphors of reputation, trust, and confidence that are the untapped latent information. The model described in the paper shows how the individual reputation of each node can be assessed on the basis of opinions provided by other nodes of the hybrid measurement network, and that this method allows to assess the extent of uncertainty the node introduces to the network. This, in turn, allows nodes of low uncertainty to have a greater impact on the reconstruction of values. The verification of the model, as well as examples of its applicability to air quality measurements are presented as well. Simulations demonstrate that the use of the model can decrease the uncertainty by up to 55% while using the EWMA (exponentially weighted moving average) algorithm, as compared to the reference one.

  • Tuning the extraction properties of ionogel-coated Solid-phase microextraction fibers based on the solvation properties of the ionic liquids
    • Kateryna Yavir
    • Karolina Konieczna
    • Łukasz Marcinkowski
    • Adam Kloskowski
    2020 SEPARATION AND PURIFICATION TECHNOLOGY

    A silica-based network was used to immobilize ionic liquid-based ionogels and applied as a fiber coating forsolid-phase microextraction (SPME). The ionogels were prepared by a sol–gel process, using two ionic liquids,triethylsulfonium bis(trifluoromethylsulfonyl)imide ([Set3][TFSI]) and 1-butyl-1-methylpiperidinium bis(tri-fluoromethylsulfonyl)imide ([C4C1Pip][TFSI]), as well as their equimolar mixture. Methyltrimethoxysilane wasused as the sol–gel precursor, and trifluoroacetic acid as a reaction catalyst.The fabricated ionogel fibers were evaluated as sorbent coating in headspace SPME combined with gaschromatography with barrier ionization discharge detection for volatile organic compounds (VOCs). The fibersshowed a high affinity to aromatic VOCs, yielding good sensitivity and precision. Then, the developed methodwas applied to the analysis of aqueous samples.During the study, the main extraction parameters, i.e., salt concentration, extraction time, and temperature,were optimized for maximum fiber sorption and to maximize the enrichment factors. The average limits ofdetection were found to be 0.15 μg L−1, 0.40 μg L−1, and 0.07 μg L−1, and the enrichment factors were in the25700–61000, 33200–84700, and 29100–96500 ranges for [Set3], [C4C1Pip] and [Set3/C4C1Pip], respectively.The single fiber and fiber-to-fiber reproducibilities were below 11.2% and 30.6%, respectively. The results of thiswork suggest the possibility of fabricating selected extractants based on the physicochemical properties of theionic liquids and target analytes.

  • Two kinds of oxygen vacancies in lithium titaniate doped with copper as detected by EPR
    • Marcin Łapiński
    • Lidia Piekara-Sady
    • Robert Kozioł
    • Wojciech Sadowski
    • Barbara Kościelska
    2020 SOLID STATE SCIENCES

    Lithium titanate (Li1+xTi2-xO4) doped with Cu2+ ions was synthesized by sol-gel processing method. The structure and morphology are characterized by X-ray Diffraction (XRD), X-ray Photoemission Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Electron Paramagnetic Resonance (EPR). Spin Hamiltonian parameters describing Zeeman and hyperfine interaction for 63Cu2+ ions were obtained from EPR spectra simulations. The spectra are characteristic for (Cu-VO)0 close-associate pairs consisting of copper replacing Ti4+ ion and an adjacent doubly ionized oxygen vacancy. These oxygen vacancies serve as charge compensators for the substituting copper ions. However, there are additional narrow EPR signals at g = 2.004 in all samples, including the sample of LiTi2O4 without dopant. These signals are ascribed to single-electron trapped oxygen vacancies VO●. Superconductivity was not confirmed down to 4.2 K by magnetic measurements in all samples studied.

  • Tworzenie wartości wspólnej w uniwersytecie
    • Elżbieta Karwowska
    2020

    Problemem badawczym jest brak definicji pojęcia i modelu teoretycznego tworzenia wartości wspólnej w uniwersytecie, który jest przeszkodą dla przeprowadzenia dyskursu naukowego zmierzającego do zbadania jej możliwości oraz zasadności. Lepsze zrozumienie możliwości i zasadności tworzenia wartości wspólnej w uniwersytecie stworzy zaś nową przestrzeń do opracowania narzędzi wspomagających rozwijanie społecznej odpowiedzialności uniwersytetu. Celem rozprawy jest zdefiniowanie pojęcia oraz zbadanie możliwości i zasadności tworzenia wartości wspólnej w uniwersytecie. Aby osiągnąć przyjęty cel rozprawy, w pierwszej kolejności rozpoznano, jak rozumiane było dotąd pojęcie CSV w kontekście społecznej odpowiedzialności uniwersytetu. Następnie zaproponowano model tworzenia wartości wspólnej w uniwersytecie (CSVU, Creating Shared Value by the University) oraz zdefiniowano to pojęcie w oparciu o zaproponowany model. Kolejnym krokiem było zbadanie możliwości oraz zasadności tworzenia wartości wspólnej w uniwersytecie z perspektywy uczelni oraz z perspektywy jej otoczenia: administracji publicznej oraz biznesu. Eksploracja możliwości i zasadności CSVU z perspektywy uczelni nastąpiła za pomocą analizy tematycznej danych jakościowych zebranych za pomocą wywiadów z reprezentantami uczelni. Możliwość i zasadność CSVU z perspektywy administracji publicznej zbadano na podstawie analizy dokumentów i aktów prawnych, regulujących społeczną odpowiedzialność uczelni i ich relacje z otoczeniem społecznym i gospodarczym. Możliwość i zasadność CSVU z perspektywy biznesu zbadano zaś na podstawie analizy raportów z badań wtórnych, dotyczących opinii przedsiębiorców na temat współpracy z uczelniami. Rezultatem przeprowadzonych analiz jakościowych jest zidentyfikowanie szeregu uwarunkowań, a także szans i zagrożeń, które wpływają na możliwość i zasadność tworzenia wartości wspólnej w uniwersytecie. Wyniki przeprowadzonych badań mają również walor utylitarny, dzięki rekomendacjom w formie listy, która stanowi praktyczne wytyczne dla uniwersytetów, zainteresowanych tworzeniem wartości wspólnej.

  • Two-step mechanism of J-domain action in driving Hsp70 function
    • Bartlomiej Tomiczek
    • Wojciech Delewski
    • Łukasz Nierzwicki
    • Milena Stolarska
    • Igor Grochowina
    • Brenda Schilke
    • Rafal Dutkiewicz
    • Marta A. Uzarska
    • Szymon Ciesielski
    • Jacek Czub
    • Elizabeth Craig
    • Jaroslaw Marszalek
    2020 Full text PLoS Computational Biology

    J-domain proteins (JDPs), obligatory Hsp70 cochaperones, play critical roles in protein homeostasis. They promote key allosteric transitions that stabilize Hsp70 interaction with substrate polypeptides upon hydrolysis of its bound ATP. Although a recent crystal structure revealed the physical mode of interaction between a J-domain and an Hsp70, the structural and dynamic consequences of J-domain action once bound and how Hsp70s discriminate among its multiple JDP partners remain enigmatic. We combined free energy simulations, biochemical assays and evolutionary analyses to address these issues. Our results indicate that the invariant aspartate of the J-domain perturbs a conserved intramolecular Hsp70 network of contacts that crosses domains. This perturbation leads to destabilization of the domain-domain interface—thereby promoting the allosteric transition that triggers ATP hydrolysis. While this mechanistic step is driven by conserved residues, evolutionarily variable residues are key to initial JDP/Hsp70 recognition—via electrostatic interactions between oppositely charged surfaces. We speculate that these variable residues allow an Hsp70 to discriminate amongst JDP partners, as many of them have coevolved. Together, our data points to a two-step mode of J-domain action, a recognition stage followed by a mechanistic stage.

  • Tynki - wykonywanie i pielęgnacja
    • Maciej Niedostatkiewicz
    • Tomasz Majewski
    2020 Full text Inżynier Budownictwa

    W artykule przedstawiono podstawowe wymagania jakie powinny być zachowane podczas realizacji oraz późniejszej eksploatacji tynków tak aby jak najdłużej zachowac je w stanie wysokiej sprawności technicznej

  • Udział Biblioteki Politechniki Gdańskiej w procesie umiędzynarodowiania uczelni
    • Urszula Szybowska
    2020 Full text Pismo PG

    Umiędzynarodowienie szkolnictwa wyższego definiowane jest zasadniczo jako podejmowanie studiów na zagranicznych uczelniach oraz udział w międzynarodowych projektach badawczych i szkoleniowych. Umiędzynarodowienie szkół wyższych jest jednym z elementarnych wskaźników, które określają dziś rozwój nauki i szkolnictwa wyższego. Biblioteka PG na różnych polach wspiera uczelnię w procesie internacjonalizacji. Strategia rozwoju usług Biblioteki PG funkcjonującej w międzynarodowym środowisku opiera się zasadniczo na trzech filarach: dostosowaniu swoich zbiorów i usług do potrzeb użytkowników zagranicznych, uczestniczeniu w programie Erasmus+ oraz dynamicznym rozwijaniu współpracy z organizacjami międzynarodowymi.

  • Udział w wystawie zbiorowej WETWARE: PROLIFERACJA I PRZECZUCIE
    • Patryk Różycki
    2020

    „WETWARE: PROLIFERACJA I PRZECZUCIE” Wystawa w Instytucie Cybernetyki Sztuki Dzieła sztuki w ich materialnym aspekcie możemy postrzegać jako nośniki informacji programujące i stymulujące przebieg procesów społecznych. Wystawa proponuje namysł nad dziełami sztuki i aktywnościami artystycznymi poprzez pryzmat terminu WETWARE – rozrostu struktur biologicznych i fizycznych umożliwiających przejawianie się procesów mentalnych. Psycholog Karl H. Pribram ukuł termin „wetware”1, dla podkreślenia specyfiki biologicznej w zakresie zdolności przenoszenia poprzez struktury biologiczne (neurony) różnego rodzaju informacji. Marek Rogulski artystki i artyści: Marcin Bożek, Marta Branicka, Flora Ćwirko + Jan Maurycy Adamski, Jowan Czerkas, Urszula Dulewicz, Dorota Grubba Thiede + Danuta Ćwirko Godycka, Tomasz Kopcewicz, Marta Koniarska, Maria Krupa, Monika Krygier + Stefan Krygier + Włodzimierz Pietrzyk, Przemysław Kryszk, Ryszard Ługowski, Krzysztof Malec, Anna Malinowska, Andrzej Egon Fietke Miastkowski, Piotr Tadeusz Mosur, Mateusz Pęk, Katarzyna Podpora, Marek Rogulski, Magdalena Rosman, Patryk Różycki, Wojtek Sosnowski, Urszula Śliz, Xenia Uranova, Marcelo Zammenhoff, Sofia Żezmer.

  • Układy dynamiczne w analizie zachowania się geosyntetyków w kolejowych konstrukcjach inżynierskich
    • Eligiusz Mieloszyk
    • Anita Milewska
    • Sławomir Grulkowski
    2020 Full text Przegląd Komunikacyjny

    W analizie współpracy geosyntetyków z elementami konstrukcji inżynierskiej możemy je traktować jako membrany sprężyste lub powłoki posadowione na różnych rodzajach podłoża. Modelowanie układu rzeczywistego oznacza jego idealizację pod kątem uwzględnienia tych cech ośrodka i jego elementów, które wydają się najistotniejsze z punktu widzenia analizowanego problemu. Zbudowany zostanie model fizyczny, a następnie matematyczny przedstawiony w postaci uogólnionego układu dynamicznego. W tym opisie wykorzystuje się różne operatory. Prowadzą one do układów ciągłych o parametrach rozłożonych. Rozpoczynając od opisu z wykorzystaniem układów dynamicznych ciągłych można przejść do układów dynamicznych dyskretnych. Pozwala na to teoria uogólnionych układów dynamicznych, poprzez wykorzystanie innych operatorów. Takie podejście umożliwia prowadzenie analizy problemu z wykorzystaniem sygnałów ciągłych i dyskretnych. Otrzymane wyniki pozwalają też wyznaczać odpowiedzi analizowanych układów metodami analitycznymi, numerycznymi lub hybrydowymi.

  • Ultrafast degradation of brilliant cresyl blue under hydrodynamic cavitation based advanced oxidation processes (AOPs)
    • Elvana Cako
    • Kumaravel Dinesh Gunasekaran
    • Reza Darvishi Cheshmeh Soltani
    • Grzegorz Boczkaj
    2020 Full text Water Resources and Industry

    The study highlights effectiveness of hydrodynamic cavitation (HC) in the degradation of effluents polluted by Brilliant Cresyl Blue (BCB) dye. Optimal process parameters were cavitation number 0.27, inlet pressure 1.70 bar, temperature 20 °C and pH 7. The efficiency of HC was investigated in combination with other advanced oxidation processes, including the addition of external oxidants (hydrogen peroxide, ozone, and sodium persulfate) and photooxidation. A detailed investigation of reactive radical species present in the system is also presented. Hybrid processes based on HC revealed the highest synergism. Finally, ultrafast degradation of target oxazine dye (decolorization efficiency of 100%) within the short treatment time of 1 min was developed. The most effective process was a combination of hydrodynamic cavitation and ozonation with a synergistic coefficient of 1.84 and electrical energy per order EEO of 0.03 kWh m⁻³ order⁻¹. The presented solution is ready to be implemented as technology for industrial practice.

  • Ultrasound assisted solvent extraction of porous membrane-packed samples followed by liquid chromatography-tandem mass spectrometry for determination of BADGE, BFDGE and their derivatives in packed vegetables
    • Natalia Szczepańska
    • Paweł Kubica
    • Justyna Płotka-Wasylka
    • Błażej Kudłak
    • Jacek Namieśnik
    2020 Full text SCIENCE OF THE TOTAL ENVIRONMENT

    The problem of the presence of trace organic pollutants in food is of growing importance due to increasing awareness about their impact on newborns, infants and adults of reproductive age. Despite the fact that packaged food products offer many advantages, packaging can be a source of contamination for stored food. Thus, monitoring such pollution in food is of high importance. In this work, a novel methodology based on the solvent extraction of porous membrane-packed samples followed by liquid chromatography-tandem mass spectrometry was applied for the determination of bisphenol A diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives in packed vegetables. Several parameters of the extraction process were optimized, including the volume and type of extraction solvent as well as the sonication time. Due to advantages such as simplicity of use, short analysis time, and a reduction in the required amount solvent, the developed procedure can be considered green. In addition, the developed methodology was characterized by good validation parameters. Limit if quantitation (LOQ) was found to be in the range of 0.8 to 1.5 ng/g. The obtained recoveries varied from 78.3% to 111.2%. The repeatability of the extraction ranged between 0.6% and 5.8% (RSD). The proposed method was successfully applied to determine the presence of BADGE, BFDGE and their derivative compounds in the vegetable samples stored in different types of containers. The obtained data indicate that the majority of investigated samples were contaminated by chlorinated and hydroxyl derivatives of BADGE.

  • Ultrasound assisted synthesis of 3-alkynyl substituted 2-chloroquinoxaline derivatives: Their in silico assessment as potential ligands for N-protein of SARS-CoV-2
    • Shaik Shahinshavali
    • Kazi Hossain
    • Abbaraju Venkata Durga Nagendra Kumar
    • Alugubelli Gopi Reddy
    • Deepti Kolli
    • Ali Nakhi
    • Mandava Venkata Basaveswara Rao
    • Manojit Pal
    2020 TETRAHEDRON LETTERS

    In view of recent global pandemic the 3-alkynyl substituted 2-chloroquinoxaline framework has been explored as a potential template for the design of molecules targeting COVID-19. Initial in silico studies of representative compounds to assess their binding affinities via docking into the N-terminal RNA-binding domain (NTD) of N-protein of SARS-CoV-2 prompted further study of these molecules. Thus building of a small library of molecules based on the said template became essential for this purpose. Accordingly, a convenient and environmentally safer method has been developed for the rapid synthesis of 3-alkynyl substituted 2-chloroquinoxaline derivatives under Cu-catalysis assisted by ultrasound. This simple and straightforward method involved the coupling of 2,3-dichloroquinoxaline with commercially available terminal alkynes in the presence of CuI, PPh3 and K2CO3 in PEG-400. Further in silico studies revealed some remarkable observations and established a virtual SAR (Structure Activity Relationship) within the series. Three compounds appeared as potential agents for further studies.

  • Ultrasound-assisted heterogeneous activation of persulfate and peroxymonosulfate by asphaltenes for the degradation of BTEX in water
    • Kirill Fedorov
    • Maksymilian Plata-Gryl
    • Javed Khan
    • Grzegorz Boczkaj
    2020 Full text JOURNAL OF HAZARDOUS MATERIALS

    This study investigated – for the first time - the simultaneous degradation of benzene, toluene, ethylbenzene and o-xylene (BTEX) by persulfate (PS) and peroxymonosulfate (PMS) activated by asphaltenes (Asph) under ultrasound (US) irradiation. Advantageous properties such as high thermal stability, low production cost and extensive availability make asphaltenes as an appealing carbonaceous material for heterogeneous catalysis. The application of asphaltenes in PS/US increased the degradation of BTEXs from 31%, 34%, 35%, 32% to 78%, 94%, 98% and 98%, while the removal of these compounds in PMS/US system was improved from 26%, 27%, 24%, 20% to 76%, 91%, 97%, 97%, respectively. PS and PMS activation followed a typical sulfate-radical based advanced oxidation processes. In terms of activation of PS and PMS, the particles of asphaltenes intensified formation of reactive radicals by creating additional centers of cavitational events. Moreover, owing to π–π stacking interaction between asphaltenes and sp2-hybridized systems of BTEX, the contaminants undergo adsorption on the surface of asphaltenes and subsequent oxidation by formed radicals. The radical route of BTEX degradation in both PS/US/Asph and PMS/US/Asph systems was mainly contributed by sulfate (SO4•−) and hydroxyl radicals (HO•) and coexisting superoxide radical anions (O2•−) played a minor role.

  • Ultrastructural analysis of the submandibular sialoliths: Raman spectroscopy and electron back-scatter studies
    • Dmitry Tretiakov
    • Andrzej Skorek
    • Jacek Ryl
    • Joanna Wysocka
    • Kazimierz Darowicki
    • Dmitry Tretiakow
    2020 Full text ULTRASTRUCTURAL PATHOLOGY

    The aim of work was the epidemiological analysis of the occurrence of sialolithiasis of the submandibular gland in adults and the evaluation of the ultrastructure of salivary stones. The study sample consisted of 44 sialoliths. Analysis of the structure and chemical composition of sialoliths was performed using a Scanning Electron Microscope and Raman Spectroscopy. Comparing our results with the literature we can say that the epidemiology of sialolithiasis has not changed significantly over the past 50 years. A wide variety of sialoliths structure was observed. In 75% (33) cases a layered structure of salivary stones was observed, while in 25% (11) – homogeneous structure. The various distribution of organic and inorganic components was observed among all the analyzed sialoliths. Raman spectroscopy allows for preliminary analysis of the sialoliths structure with only a qualitative assessment of their composition, which significantly reduces the research value of this method. The presence of organic and inorganic compounds in the core and inner layers of the salivary glands stones confirms 2 basic theories of the formation of sialoliths: inflammation and deposition of the inorganic component as a result of disruption of saliva flow in the salivary glands.

  • Uncertainty of mass flow measurement using centric and eccentric orifice for Reynolds number in the range 10,000 ≤ Re ≤ 20,000
    • Anna Golijanek-Jędrzejczyk
    • Andrzej Mrowiec
    • Robert Hanus
    • Marcin Zych
    • Dariusz Świsulski
    2020 Full text MEASUREMENT

    The article analyses the impact of the Reynolds number on the estimated uncertainty of the mass flow rate measurement using an orifice plate. The objects of the research were two types of orifices: centric (ISA) and eccentric, with the diameter ratio β = 0.5. Studies were performed by Monte Carlo simulation and experiments for Reynolds numbers in the range 10,000 ≤ Re ≤ 20,000. The obtained results have shown that for both orifice types, the results obtained from the experiments and from the Monte Carlo simulation are similar. The nature of changes in the expanded uncertainty of the flow measurement is very similar for each type. For the both types of orifices, the value of the expanded uncertainty of the flow measurement increases linearly with the increasing Reynolds number.

  • Underfrequency Load Shedding: An Innovative Algorithm Based on Fuzzy Logic
    • Robert Małkowski
    • Janusz Nieznański
    2020 Full text ENERGIES

    In contemporary power systems, the load shedding schemes are typically based on disconnecting a pre-specified amount of load after the frequency drops below a predetermined value. The actual conditions at the time of disturbance may largely dier from the assumptions, which can lead to non-optimal or ineective operation of the load shedding scheme. For many years, increasing the eectiveness of the underfrequency load shedding (UFLS) schemes has been the subject of research around the world. Unfortunately, the proposed solutions often require costly technical resources and/or large amounts of real-time data monitoring. This paper puts forth an UFLS scheme characterized by increased eectiveness in the case of large disturbances and reduced disconnected power in the case of small and medium disturbances compared to the conventional load-shedding solutions. These advantages are achieved by replacing time-consuming consecutive load dropping with the simultaneous load dropping mechanism and by replacing ineective fixed-frequency activation thresholds independent of the state of the system with implicit adaptive thresholds based on fuzzy logic computations. The proposed algorithm does not require complex and costly technical solutions. The performance of the proposed scheme was validated using multivariate computer simulations. Selected test results are included in this paper.