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Publications Repository
Gdańsk University of Technology

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  • Zachodni front śródmieścia Gdańska. Studium urbanistyczno-konserwatorskie
    • Łukasz Bugalski
    2023

    Zachodni front śródmieścia Gdańska to kluczowy fragment urbanistycznego założenia pierścieniowego, które powstało na przełomie XIX i XX wieku w czasie wielkiej przebudowy miasta. Wtedy to w miejscu nowożytnych bastionów ziemnych, które przez ponad trzy stulecia wyznaczały granicę miasta, zostały wytyczone nowe ulice i place. W ich otoczeniu powstała nowa wielkomiejska zabudowa. W 1945 roku Gdańsk został zniszczony, a po wojnie podjęto próby ponownej zabudowy tego obszaru. Większość przygotowanych projektów nie została jednak zrealizowana lub została zrealizowana fragmentarycznie, co doprowadziło do wyraźnej degradacji zachodniego frontu, który obecnie funkcjonuje głównie jako arteria przelotowa. Łukasz Bugalski podejmuje próbę odczytania nawarstwień składających się na miejskie dziedzictwo zapisane w strukturze urbanistycznej zachodniego frontu śródmieścia Gdańska. Analizując opracowane w kolejnych dekadach plany, projekty i koncepcje przestrzenne, udowadnia, że obszar ten – choć obecnie nieuporządkowany – ma ogromny potencjał.

  • Zachowanie i konserwacja tynków szlachetnych na elewacjach budynków modernistycznych - aktualne doświadczenia z Gdyni
    • Robert Hirsch
    2023

    Artykuł dotyczy kwestii zachowania i rewaloryzacji tynków ozdobnych, ze szczególnym uwzględnieniem wypraw tynkarskich stosowanych w Gdyni po II wojnie światowej. Po wojnie zaczęto stosować w Gdyni inne techniki tynkarskie (np. sgraffito) oraz wprowadzono kolory tynków nie wykorzystywane w okresie międzywojennym np. kolor niebieski. W celu prowadzenia dalszych szerokich badań tynków historycznych autor zaproponował zastosowanie specjalnej KARTY TYNKÓW umożliwiającej ich łatwiejsze dokumentowanie i porównywanie. Wzór karty został zamieszczony w artykule.

  • Zależność wartości współczynnika przepływu C od grubości kryzy z wlotem stożkowym
    • Anna Golijanek-Jędrzejczyk
    2023 Full text Przegląd Elektrotechniczny

    W artykule przedstawiono wyniki badań numerycznych i eksperymentalnych pięciu kryz z wlotem stożkowym o współczynniku przewężenia  równym 0,24, o grubości od 2,5 mm do 31 mm (każda ścięta skośnie pod kątem 45°) umieszczonych w wodnej instalacji hydraulicznej przy przepływach laminarnych i turbulentnych. Uzyskane rezultaty potwierdziły, że wraz ze wzrostem grubości (w badanym zakresie liczb Reynoldsa od 1690 do 14430) tego typu kryzy wartość współczynnika C dąży do wartości 0,9.

  • Zarząd POLSPAR w latach 2020-2023
    • Zdzisław Kowalczuk
    2023 Full text Pomiary Automatyka Robotyka

    W trakcie kadencji 2020-2023 na zebraniach Zarządu Członkowie często podejmowali dyskusję na temat najbardziej dokuczliwych problemów działania uczelni wynikających ze zmian w ustawie Prawo o Szkolnictwie Wyższym i Nauce, kompetencjach i formach naukowej aktywności rad naukowych dyscyplin, procedur nadawania stopni i tytułów naukowych, czy w końcu o nowej nazwie dyscypliny Automatyka, Elektronika, Elektrotechnika i Technologie Kosmiczne (AEEiTK).

  • Zasady prowadzenia napraw kolejowych konstrukcji żelbetowych uszkodzonych wskutek korozji chlorkowej i karbonatyzacji zgodnie z norm PN-EN 1504
    • Anna Banaś
    • Daniel Białecki
    • Marcin Majewski
    • Andrzej Kuryłowicz
    2023

    Uwzględnienie możliwości wystąpienia procesów korozyjnych, czy to na etapie budowy nowych obiektów, czy na etapie remontu konstrukcji już istniejących, jest bardzo istotną kwestią. Ma ona niekiedy decydujący wpływ na powodzenie całej inwestycji oraz na utrzymanie jak najdłuższego czasu eksploatacji samej konstrukcji. Stosowanie innych niż standardowe metod zabezpieczenia stali zbrojeniowej w konstrukcjach żelbetowych kolejowych, powoduje wydłużenie okresu pomiędzy remontami i zmniejsza znacznie ich koszty. Biorąc pod uwagę powstawanie w każdym roku nowych obiektów mostowych, należy zwrócić uwagę, że nawet w prawidłowo zaprojektowanym i wykonanym elemencie żelbetowym, może dojść do procesów korozyjnych stali zbrojeniowej. W przypadku konstrukcji naprawianych, podczas wykonania opinii technicznych, ekspertyz oraz projektów należy zwrócić szczególną uwagę na badania zawartości jonów chlorkowych w konstrukcji oraz głębokość skarbonatyzownia otuliny betonowej. Wykonując naprawy konstrukcji inżynieryjnych kolejowych, w których zostały przekroczone normowe wartości skażenia jonami chlorkowymi, otulina betonowa została skarbonatyzowana, należy dodatkowo wdrażać, zgodne z europejską zharmonizowaną normą PN-EN 1504-9 [7], inne niż tradycyjne metody napraw konstrukcji tj.: • elektrochemiczną realkalizację skarbonatyzowanego betonu (zasada 7, metoda 7.3), • elektrochemiczne usunięcie chlorków (zasada 7, metoda 7.5), • ochronę katodową przy zastosowaniu protektorów cynkowych (zasada 10). Stosowanie się do powyższych zasad i metod spowoduje znaczące wydłużenie żywotności konstrukcji co przełoży się znacząco na zmniejszenie kosztów ponoszonych na remonty pośrednie i główne.

  • Zastosowanie metod uczenia maszynowego w procesie rehabilitacji kończyny górnej
    • Gustaw Rzyman
    2023 Full text

    Celem rozprawy jest opracowanie systemu opartego na metodach uczenia maszynowego, który w przyszłości pozwoli na zautomatyzowanie wybranych procedur w procesie rehabilitacji kończyny górnej. Nośnikiem informacji związanej ze stanem fizjologicznym pacjenta jest biologiczne sprzężenie zwrotne w postaci sygnałów elektromiografi powierzchniowej (ang. sufrace electromigraphy, sEMG). Przypuszcza się, że dzięki zastosowaniu sterowania w pętli zamkniętej sprzężenia zwrotnego pacjent-bioniczna orteza ograniczona zostanie rola terapeuty oraz nastąpi skrócenie czasu niezbędnego na przeprowadzenie procesu rehabilitacji kończyny górnej. Zakres rozprawy obejmuje przeprowadzenie analizy dostępnych rozwiązań bionicznych urządzeń medycznych i rehabilitacyjnych w celu zaplanowania autorskich badań naukowych i opracowaniu autorskich rozwiązań. Tematem przewodnim prezentowanej pracy jest rozpatrzenie możliwości zastosowania metod uczenia maszynowego w zakresie analizy i interpretacji biosygnałów z sEMG. Stąd też w części pierwszej rozprawy zostanie wykonany kompetny przegląd i analiza zarówno od strony medycznej, jak i od strony rozwiązań technicznych ortezy bionicznej. W części drugiej rozprawy zostaną scharakteryzowane metody analizy sygnałów sEMG, a w części trzeciej omówione zostaną badania symulacyjne. Jednym z istotnych zadań rozprawy doktorskiej jest opracowanie bazy biosygnałów pochodzących od osób wymagających rehabilitacji. Badania związane są z eksperymentami przeprowadzanymi na pacjentach, stanowi to dodatkową trudność. Związana jest ona z uzyskaniem specjalnej zgody Komisji Bioetycznej, która nadzoruje daną jednostkę badawczą. Kluczowym elementem rozprawy, stanowiącym jej istotę jest analiza i interpretacja sygnałów biologicznych rejestrowanych za pomocą sEMG na grupie pacjentów. Przeprowadzenie klasyfikacji tych sygnałów stanowi podstawę działania innowacyjnych systemów sterowania ortezą bioniczną. W tym celu koniecznym jest, aby zaproponowane metody bazowały zarówno na najnowszym stanie wiedzy, jak i na dopasowaniu do biologicznych sygnałów.

  • Zastosowanie sieci neuronowych do detekcji impulsów o znanym kształcie w obecności silnego szumu i trendu
    • Szymon Betka
    • Marek Blok
    2023 Full text Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

    Detekcja impulsów w odebranym sygnale radiowym, zwłaszcza w obecności silnego szumu oraz trendu, jest trudnym zadaniem. Artykuł przedstawia propozycje rozwiązań wykorzystujących sieci neuronowe do detekcji impulsów o znanym kształcie w obecności silnego szumu i trendu. Na potrzeby realizacji tego zadania zaproponowano dwie architektury. W pracy przedstawiono wyniki badań wpływu kształtu impulsu, mocy zakłóceń szumowych oraz trendu obecnego w sygnałach wejściowych sieci, na skuteczność detekcji zaproponowanych rozwiązań.

  • Zastosowanie wysokopoziomowych języków programowania do wyznaczania nośności przemieszczeniowych pali wkręcanych.
    • Mateusz Domurad
    • Witold Tisler
    2023 Full text Inżynieria Morska i Geotechnika

    W artykule podjęta zostaje problematyka współczesnego, bardziej ekonomicznego projektowania pali. Rozwiązania normowe np. PN-83-B-2482, bazują zazwyczaj na wielkościach takich jak stopień zagęszczenia czy stopień plastyczności. Powoduje to, że dane uzyskane bezpośrednio z badań podłoża są korelowane podwójnie. W niniejszym opracowaniu proponuje się, aby korzystając z funkcji transformacyjnych wyznaczać nośność pala bezpośrednio z sondowania CPT(u) lub badania dylatometrem DMT. Na tej podstawie autor artykułu stworzył program komputerowy w języku Python do prognozowania krzywych osiadania przemieszczeniowych pali wkręcanych. Zaimplementowana metoda oraz jej założenia opierają się na badaniach prowadzonych na Politechnice Gdańskiej w ramach projektu NCBiR, którego kierownikiem jest dr hab. inż. Adam Krasiński. Artykuł zawiera opis wykorzystanej metody obliczeniowej, objaśnienie rozwiązań zawartych w programie oraz przykład obliczeniowy sprawdzający zaimplementowane rozwiązania.

  • Zbiornik z dachem pływającym
    • Aleksander Perliński
    • Wioleta Barcewicz
    2023

    W rozdziale przedstawiono przykład obliczeń statycznych i wymiarowania głównych elementów konstrukcji stalowego zbiornika walcowego o osi pionowej z dachem pływającym.

  • Zdrowie fiskalne jednostek samorządu terytorialnego
    • Maria Jastrzębska
    2023 Full text Optimum. Studia Ekonomiczne

    Cel – Celem artykułu jest określenie istoty i determinant zdrowia fiskalnego jednostek samorządu terytorialnego (JST) w Polsce oraz zakresu jego pomiaru i oceny. Metoda badań – Wykorzystano analizę deskryptywną, analizę porównawczą oraz wnioskowanie indukcyjne i dedukcyjne. Wyniki – W krajowej literaturze przedmiotu poświęcono wiele uwagi problematyce kondycji finansowej i stabilności finansowej JST, ale słabo rozpoznana jest problematyka zdrowia fiskalnego JST. W sposób autorski wyjaśniono istotę zdrowia fiskalnego JST oraz sklasyfikowano jego determinanty, a następnie zaproponowano zakres jego pomiaru i oceny. Oryginalność /wartość /implikacje /rekomendacje – Przeprowadzono badania teoretyczne w zakresie istoty zdrowia fiskalnego JST w kontekście kondycji finansowej i odporności finansowej JST. Zdrowie fiskalne JST jest terminem mniej rozpoznanym w krajowej literaturze przedmiotu niż termin zdrowe finanse publiczne. Odnosi się ono do kondycji finansowej i stabilności finansowej JST, ale nie jest tożsame z tymi terminami. W prak‑ tyce brakuje kompleksowego i powszechnie przyjętego modelu pomiaru i oceny zdrowia fiskalnego JST, co stanowić powinno wyzwanie dla badaczy chcących wypełnić tą lukę.

  • Zeolitic imidazolate framework (ZIF-8) modified cellulose acetate NF membranes for potential water treatment application
    • Vahid Vatanpour
    • Ayse Yuksekdag
    • Meltem Agtas
    • Mohammad Mehrabi
    • Ehsan Salehi
    • Roberto Castro-Muñoz
    • Ismail Koyuncu
    2023 CARBOHYDRATE POLYMERS

    In this study, cellulose acetate (CA)-based nanofiltration membranes, modified with zeolitic imidazole framework-8 (ZIF-8) particles, were prepared with various ZIF-8 contents (0, 0.1, 0.25, 0.5, 1 and 2 wt%), to obtain membranes with improved flux and filtration performance by combining advantages of CA polymer and ZIF-8 metal-organic frameworks. Removal efficiency studies were carried out with bovine serum albumin and two different dyes, along with antifouling performance evaluation. Results of experiments disclosed that as the ZIF-8 ratio increased, the contact angle values decreased. With ZIF-8 addition, the pure water flux of the membranes increased. Besides, the flux recovery ratio value was approximately 85 % for the bare CA membrane, while it increased to above 90 % by blending ZIF-8. Also, in all ZIF-8 doped membranes, a fouling decrease was observed. Importantly, it was observed that the dye removal efficiency increased with the addition of ZIF-8 particles from 95.2 to 97.7 % for Reactive Black 5 dye.

  • Zespół Młodych Naukowców i bariery na PG
    • Agnieszka Lendzion
    2023 Full text Pismo PG

    Artykuł powstał, by zapoznać społeczność PG z "Zespołem monitorującym warunki rozwoju i badań prowadzonych przez młodych naukowców na PG" oraz jego aktywnością. Członkowie Zespołu działają w imieniu ponad 900 młodych badaczy PG. Są zaangażowani w realizację zadań w projekcie IDUB, m.in. związanych z zarządzaniem aktywnością młodych badaczy i rozwiązywaniem konfliktów interesów powstających między młodymi naukowcami a ich otoczeniem naukowym. Opracowują i proponują rozwiązania monitorujące i likwidujące bariery rozwoju kadry akademickiej, w tym w ramach Strategii HR4R PG 2022-2025.

  • Zielona transformacja gospodarki i finansów samorządowych
    • Andrzej Miszczuk
    • Alicja Sekuła
    • Magdalena Miszczuk
    2023 Full text

    Książka wpisuje się w nurt publikacji poświęconych przeciwdziałaniu zmianom klimatu, degradacji środowiska i możliwości wdrażania zrównoważonego rozwoju. Punkt wyjścia rozważań to 2 dokumenty: Agenda 2030 i Europejski Zielony Ład oraz warunki i możliwości ich operacjonalizacji na szczeblu ogólnokrajowym i lokalnym, tj. samorządowym. Zagadnienia omówione w monografii skupiają się na przyczynach i skutkach zmian klimatu, znaczeniu i wytycznych dotyczących zielonego budżetowania oraz stanu zaawansowania tego procesu, głównie w krajach UE, w tym także w Polsce, analizie źródeł samorządowych dochodów z punktu widzenia możliwości wdrażania rozwiązań w zakresie ochrony środowiska i zrównoważonych finansów oraz sposobach pomiaru lokalnej i regionalnej transformacji.

  • Zintegrowany system monitoringu oddziaływań transportu kolejowego na środowisko
    • Piotr Chrostowski
    • Andrzej Wilk
    • Krzysztof Karwowski
    • Sławomir Grulkowski
    • Roksana Licow
    • Wojciech Rafajłowicz
    • Adam Ratajczak
    • Radosław Idzikowski
    • Marek Szafrański
    • Tadeusz Widerski
    • Karol Daliga
    • Jacek Skibicki
    • Leszek Jarzębowicz
    • Michał Michna
    • Sławomir Judek
    • Natalia Karkosińska-Brzozowska
    • Julia Omilianowicz
    2023

    W artykule przedstawiono działania podejmowane w ramach realizacji projektu badawczego Wspólnego Przedsięwzięcia NCBR i PKP PLK pn. „Badania i Rozwój w Infrastrukturze Kolejowej – BRIK2”. Projekt dotyczy monitoringu szeregu parametrów opisujących oddziaływania transportu kolejowego na środowisko naturalne oraz tereny zurbanizowane. Założono, że na podstawie pomiarów określonych wielkości fizycznych oraz na podstawie szeregu danych o infrastrukturze, jej otoczeniu, taborze i ruchu, możliwe będzie wnioskowanie o oddziaływaniach i zanieczyszczeniu środowiska drganiami i hałasem. Dodatkową, również istotną kwestią będzie możliwość prowadzenia monitoringu szeregu cech technicznych oraz ruchowych, pozwalających na identyfikację i lepsze rozpoznanie przyczyn generowanych zanieczyszczeń środowiskowych. Na tej podstawie opracowano plan badań i przeprowadzono szereg pomiarów terenowych, aby w konsekwencji skutecznie zrealizować cele projektu proponując prototyp systemu pomiarowego oraz metodykę badań, archiwizacji i przetwarzania wyników do wartościowych wskaźników oceny.

  • ZnO-decorated green-synthesized multi-doped carbon dots from Chlorella pyrenoidosa for sustainable photocatalytic carbamazepine degradation
    • Agnieszka Fiszka Borzyszkowska
    • Agnieszka Sulowska
    • Paweł Czaja
    • Aleksandra Bielicka-giełdoń
    • I. Zekker
    • Anna Zielińska-Jurek
    2023 Full text RSC Advances

    The promising green synthesis of carbon dots (CDs) from microalga Chlorella pyrenoidosa was achieved using simple hydrothermal and microwave-assisted methods. Doping of nanomaterials by nonmetals (N, S, and P) was confirmed by X-ray photoelectron spectroscopy (XPS), while the existence of metals in the CDs was confirmed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM), and Mg, Ca, K, and Na were found as the dominant doped metals. The novel nanomaterials with excellent photoluminescence (PL) properties were used for the modification of ZnO obtained by a simple hydrothermal process. In this regard, a series of ZnO decorated with multi-doped carbon dots (xCDs) was prepared and their photocatalytic properties were evaluated. The ZnO-xCD photocatalysts were characterized by various advanced techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), XPS, Brunauer–Emmett–Teller (BET), PL, ultraviolet-visible (UV-vis) spectroscopy and electrochemical impedance spectroscopy (EIS) analysis. The photocatalytic behaviour of the obtained materials was investigated in the degradation of carbamazepine (CBZ). The influence of the synthesis method of xCDs and their content on the activity of the photocatalyst was examined. The photocatalyst ZnO modified with 3% xCDs obtained by the microwave-assisted method revealed the highest effectiveness for CBZ degradation and allowed for a first- order degradation rate of 2.85 times in comparison with non-modified ZnO. The improvement of the photocatalytic process was achieved by support with peroxymonosulphate resulting in up to 3.18 times a first order kinetic rate constant compared with that of simple photocatalysis in the presence of ZnO- xCDs. Taken together, our synthesized multi-doped CDs and their nanohybrids with ZnO, can be considered as promising candidates for photocatalytic applications

  • Zr‐Based Metal‐Organic Framework UiO‐66/Ultem® 1000 Membranes for Effective CO2/H2 Separation
    • Muhammad Imad
    • Roberto Castro Munoz
    • Milan Bernauer
    • Violeta Martin
    • Pavel Izak
    • Vlastimil Fíla
    2023 CHEMICAL ENGINEERING & TECHNOLOGY

    Mixed-matrix membranes (MMMs) using UiO-66 nanofillers as dispersing inorganic phase and polyetherimide (PEI) as continuous polymeric matrix were synthesized. Different UiO-66 loadings of 10, 20, and 30 wt % were applied. The morphology and UiO-66 dispersion over the prepared MMMs were examined. Gas separation measurements were performed for H2/CO2 gas mixture to evaluate the influence of UiO-66 on the separation yield of resulting membranes. When compared with pristine PEI membranes, MMMs containing metal-organic framework (MOF) nanoparticles revealed superior H2 permeability and H2/CO2 separation factor, e.g., maximum permeability values of 14.6 and 5.5 Barrer were observed for H2 and CO2 at a filler loading of 10 wt % and an applied pressure of 4.0 bar.

  • Zwalczanie przestępczości skarbowej jako aktywny sposób minimalizacji ryzyka podatkowego - case study
    • Piotr Kasprzak
    • Witold Witkowski
    • Jarosław Wróblewski
    2023

    Celem pracy jest prezentacja i ocena sposobów zwalczania przestępczości skarbowej jako jeden z podstawowych sposobów minimalizacji ryzyka podatkowego. Metodologia badania - analizie i ocenie poddano wybrane sposoby zwalczania przestępstw skarbowych. Dla osiągnięcia tego celu posłużono się zarówno analizą literatury, jak i materiałów pochodzących ze statystyk sporządzonych przez służby skarbowe oraz policję. Wyniki - wyniki dowodzą, że przestępcy ustawicznie doskonalą istniejące sposoby oszustw podatkowych oraz próbują wymyślić nowe, monitorując i wykorzystując zidentyfikowane luki i niedoskonałości systemu prawnego oraz administracyjnego, problemy w integracji działań poszczególnych służb itd. Istnieje więc potrzeba i konieczność opracowania zestawu skutecznych rozwiązań o charakterze kompleksowym, które będą mogły zostać wykorzystane w obszarze antyryzyka podatkowego. Wartość - praca prezentuje metody oraz narzędzia stosowane w celu zwalczania przestępczości podatkowej i zarządzania ryzykiem skarbowym, a także sposoby ich doskonalenia i integracji oraz koordynacji multidyscyplinarnych oraz wielowymiarowych działań, w celu zwiększenia ich efektywności.

  • 100– lecie urodzin profesora Romualda Kolmana 1922-2016, patrona Konkursu IKAR JAKOŚCI. Kamienie milowe w dorobku twórcy kwalitologii w Polsce
    • Piotr Grudowski
    2022 Full text MAG. Magazyn dla Praktyków

    17 czerwca 2022 roku minęła 100. rocznica urodzin śp. profesora dr. hab. inż. Romualda Kolmana, jednego z najczęściej przywoływanych twórców i krzewicieli Polskiej Szkoły Jakości. Jako podwładny i doktorant profesora w ostatnim, przypadającym na lata 90. XX wieku okresie jego pracy na Wydziale Mechanicznym Technologicznym w Politechnice Gdańskiej, miałem tę możliwość i szczęście, że mogłem zapoznać się z praktycznie całym dorobkiem naukowym jego życia. Dlatego też w związku z tą okrągłą rocznicą chciałbym w dużym skrócie przedstawić najważniejsze jego osiągnięcia związane z kwalitologią – wiedzą o jakości, którą pioniersko systematycznie rozwijał i upowszechniał.

  • 2D MXene nanocomposites: electrochemical and biomedical applications
    • Marzieh Ramezani Farani
    • Behnam Nourmohammadi Khiarak
    • Rui Tao
    • Zegao Wang
    • Sepideh Ahmadi
    • Mahnaz Hassanpour
    • Mohammad Rabiee
    • Mohammad Saeb
    • Eder C. Lima
    • Navid Rabiee
    2022 Environmental Science-Nano

    In recent years, key questions about the interaction of 2D MXene nanomaterials in electrochemical and biomedical applications have been raised. Most research has focused on clarifying the exclusive properties of the materials; however, only limited reports have described the biomedical applications of 2D nanomaterials. 2D MXenes are monolayer atomic nanosheets resulting from MAX phase ceramics. The hydrophilic properties, metallic conductivity, stability, and exclusive physiochemical performances make them promising materials for electrochemical and biomedical applications, including CO2 reduction, H2 evolution, energy conversion and storage, supercapacitors, stimuli-responsive drug delivery systems, regenerative medicine, and photothermal cancer therapy. In this review paper, we have provided facile approaches to synthesising MXene and characterization of chemical and physical properties. Their potential applications in medicine, ranging from antibacterial agents to targeted drug delivery, cancer photo/chemotherapy, tissue engineering, and electrochemical applications, have not been comprehensively reviewed and discussed—which encouraged us to come up with this work. We also discuss the most common challenges of utilizing MXene-related materials and areas that can be further developed in the future, with possible struggles and limitations one may face.

  • 3D DEM simulations of fracture in reinforced concrete beams
    • Michał Nitka
    • Andrzej Tejchman-Konarzewski
    2022

    Artykuł dotyczy zachowania się belki żelbetowej bez zbrojenia pionowego przy trzypunktowym zginaniu. Belka uległa zniszczeniu wskutek ścinania z powodu obecności nadmiernego zbrojenia podłużnego. Eksperymenty przeprowadzono w skali laboratoryjnej z wykorzystaniem systemu mikro-CT, a następnie odtworzono je w analizach numerycznych stosując metodą elementów dyskretnych 3D (DEM). Zastosowano 4-fazowy model betonu z mezostrukturą, oparty bezpośrednio na obrazach mikro-CT. Uzyskano zadowalającą zgodność między wynikami doświadczalnymi i numerycznymi w odniesieniu do lokalizacji i kierunku krytycznego makropęknięcia.

  • 3D X-ray Micro-CT Analysis of Rebar Corrosion in Reinforced Concrete Subjected to a Chloride-Induced Environment
    • Łukasz Skarżyński
    • Katarzyna Kibort
    • Aleksandra Małachowska
    2022 Full text MOLECULES

    The paper presents experimental investigations of the concrete cover protective ability to coun-teract rebar corrosion in reinforced concrete cubes. To study and quantify the consequences of corrosion a reinforced concrete sample was subjected to chloride-induced environment in order to get corroded and combined with un-corroded sample. Chloride-accelerated technique can in-duce a high degree of corrosion within at a controlled time. Moreover, detailed and thorough experimental measurements and analyses of reinforcement loss due to corrosion and its influ-ence on concrete microstructure was studied by means of 3D X-Ray micro-computed tomogra-phy. Whereas rebar outside the concrete was heavily corroded due to chloride-accelerated test, only local surface corrosion products appeared inside the concrete. It turned out, that in spite of accelerated corrosion environment, concrete cover shows protective ability to counteract rein-forcing steel corrosion mechanism. Moreover, bond strength between reinforcement rebar and concrete was not visibly affected since the failure force in pull-out test and failure mechanisms, observed by 3D X-Ray micro-CT, were similar for corroded and un-corroded sample. Failure took place due to presence of radial cracks with the maximum width equal approximately 0,25 mm.

  • 50’ Sail Catamaran with Hybrid Propulsion, Design, Theoretical and Experimental Studies
    • Wojciech Litwin
    • Daniel Piątek
    • Wojciech Leśniewski
    • Konrad Marszałkowski
    2022 Full text Polish Maritime Research

    The development of modern lithium batteries and propulsion systems now allows the use of complex propulsion systems for vessels of various sizes. As part of the research and implementation project, a parallel hybrid drive system was designed, built and then tested in the laboratory. The experimental studies conducted allowed for the measurements of power, fuel consumption and electric power distribution in various operating modes of the propulsion system. The research proves that in the analysed case, the hybrid parallel system meets the demand for electric energy during a typical cruise scenario, and thus there is no need to install a power generator on the yacht.

  • A breath of fresh air - social cognitive career theory in studying entrepreneurial intentions
    • Magdalena Licznerska
    • Paweł Ziemiański
    2022 International Journal of Entrepreneurship and Small Business

    A pinch of robustness and a pinch of freshness create an interesting story. That is why this study focuses on entrepreneurial intentions from an alternative theoretical perspective in an underexplored context. In this paper, it is argued that social cognitive career theory is relevant to the study of individual entrepreneurial cognition and behaviour, and it offers a solid framework in entrepreneurship research. This paper expands on SCCT’s conceptualisation of environmental determinants, proposing the examination of how a new combination of contextual factors (perceived educational, relational and structural support), entrepreneurial self-efficacy, individual entrepreneurial orientation and negative outcome expectations are related to entrepreneurial intentions. For this exploratory study, a questionnaire completed by a sample of students from Poland, one of the Central and Eastern European countries, was employed. Hierarchical multiple regression analyses revealed support for the role of SCCT variables in predicting entrepreneurial intentions. The results, which offer direct useful indications for further research activities, are presented and discussed.

  • A brief note on monotonic and fatigue fracture events investigation of thin-walled tubular austenitic steel specimens via fracture surface topography analysis (FRASTA)
    • Wojciech Macek
    • Dhinakaran Sampath
    • Łukasz Pejkowski
    • Krzysztof Żak
    2022 Full text ENGINEERING FAILURE ANALYSIS

    The main objective of this short communication is to show the fracture progression in each loading case and complement knowledge about fracture mechanisms underpinning the tensile and fatigue performance of thin-walled tubes. For this purpose, the fracture surface topography analysis (FRASTA) method was used in the thin-walled tubular austenitic stainless-steel specimens. Two cases were analyzed: monotonic tension, and uniaxial fully-reversed fatigue. Furthermore, the fractures topographies were quantified through the profiles over their entire surfaces with the support of an optical confocal measurement system. The results showed the usefulness of the FRASTA method in identifying characteristic zones in the cracking process for the analyzed cases and motivates its development for other materials and complex loading cases.

  • A Case Study on Implementing Agile Techniques and Practices: Rationale, Benefits, Barriers and Business Implications for Hardware Development
    • Paweł Weichbroth
    2022 Full text Applied Sciences-Basel

    Agile methodologies, along with the corresponding tools and practices, are claimed to facilitate teams in managing their work more effectively and conducting their work more efficiently while fostering the highest quality product within the constraints of the budget. Therefore, the rate of awareness and adoption of Agile frameworks both within and outside the software industry has increased significantly. Yet, the latest studies show that the adoption of Agile techniques and practices are not one-size-fits-all, and highlight the challenges, risks, and limitations regarding numerous domains. In this regard, the state-of-the-art literature provides comprehensive reading. However, in the case of hardware manufacturing, it seems to be sparse and fragmented. To fill this gap, the goal of this study is to analyze and present an in-depth account of the implementation of mix agile-oriented tools and practices. To tackle this goal, a single industry case study was undertaken, based on the primary data obtained through the interview protocol and the secondary data extracted from the project’s documentation. The findings concern three areas. First, the rationale behind the implementation of agile for hardware development is explained. Second, the implemented agile techniques and practices are identified, as well as the supporting tools through which their adoption was successfully undertaken. Third, the areas positively impacted by their application are highlighted with the corresponding evaluation measures deployed; moreover, the barriers to adopting Agile practices encountered, and the benefits gained from particular techniques, are further discussed. The presented findings might be of great importance for both researchers and practitioners who are searching for empirical evidence regarding Agile-oriented implementations. Finally, in terms of both benefits and barriers, business implications for hardware development are formulated. Alongside this, numerous open issues and questions present interesting research avenues that concern, in particular, the effectiveness of collaboration and areas of communication through the lens of agile techniques and practices.

  • A Circular Waveguide Dual-Mode Filter With Improved Out-of-Band Performance for Satellite Communication Systems
    • Michał Baranowski
    • Łukasz Balewski
    • Adam Lamęcki
    • Michał Mrozowski
    • Jaione Galdeano
    2022 Full text IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS

    This letter presents a novel design for a 3-D-printed circular waveguide dual-mode (CWDM) filter with a modified cavity shape. The modification leads to a wide spurious-free stopband, which is highly desirable for channel separation in waveguide contiguous output multiplexers (OMUXs) in satellite communication systems. The new resonant cavity design is a result of applying shape deformation to a basic circular cavity in order to move away and suppress parasitic modes. A fourth-order Ku-band channel filter with two transmission zeros (TZs) is designed, fabricated by additive manufacturing (AM) in one piece and measured. In comparison with the state-of-the-art design of a stepped CWDM filter, an improvement of approximately 35% wider spurious-free range is achieved.

  • A city is not a tree: a multi-city study on street network and urban life
    • Jianxiang Huang
    • Yuming Cui
    • Haoliang Chang
    • Hanna Obracht-Prondzyńska
    • Dorota Kamrowska-Załuska
    • Lishuai Li
    2022 Full text LANDSCAPE AND URBAN PLANNING

    Christopher Alexander, a British-American scholar, differentiated an old (natural) city from a new (planned) one by structure. The former resembles a “semilattice”, or a complex system encompassing many interconnected sub-systems. The latter is shaped in a graph-theoretical “tree”, which lacks the structural complexity as its sub-systems are compartmentalized into a single hierarchy. This structural distinction explains why, or perhaps determines “the patina of life” in old urban districts and the lack of such in new ones. His idea, although widely influential, remains contested for its lack of empirical evidence. Subsequent literature failed to distinguish the structural differences between the old and new cities in systematic ways, nor is his hypothesized structure-life relationship verified with statistical rigor. This study aims to test Alexander’s urban structural theory under a comprehensive research framework. We translated his constructs and premises into a mathematically testable form. Qualities of urban spatial structure, such as “semilattice”, “complex network” and “living structure”, were measured using graph-topological indicators computed for street networks. Urban life was measured using a combination of Twitter activities, Point-Of-Interests, and walking trips at the district level. The structure-life relationship was examined using statistical models, after controlling for urban form and socio-demographic confounders including land use, density, block size, parks, income, age, and demographic groups. This research design was implemented in London, New York, Hong Kong, and Gdansk. Our results support Alexander's early works that an old urban district contains more “semilattice” compared with new ones. This quality can be consistently captured by Meshedness Coefficient, a graph-network indicator for semilattice-shaped street network and a strong predictor for urban life. The same cannot be observed for “complex network” with consistency, while we found no independent associations between “living structure” and life, contrary to existing literature. The study shed light on the hidden relationship between urban spatial structure and behavioral evidence in both the virtual and physical world. We uncovered the British-American predilection of Alexander’s theory, which matched data closely in London and New York, but less so in Hong Kong and Gdansk, suggesting the need for a locally-sensitive approach.

  • A coarse‐grained approach to NMR ‐data‐assisted modeling of protein structures
    • Emilia Lubecka
    • Adam Liwo
    2022 Full text JOURNAL OF COMPUTATIONAL CHEMISTRY

    The ESCASA algorithm for analytical estimation of proton positions from coarse-grained geometry developed in our recent work has been implemented in modeling protein structures with the highly coarse-grained UNRES model of polypeptide chains (two sites per residue) and nuclear magnetic resonance (NMR) data. A penalty function with the shape of intersecting gorges was applied to treat ambiguous distance restraints, which automatically selects consistent restraints. Hamiltonian replica exchange molecular dynamics was used to carry out the conformational search. The method was tested with both unambiguous and ambiguous restraints producing good-quality models with GDT_TS from 7.4 units higher to 14.4 units lower than those obtained with the CYANA or MELD software for protein-structure determination from NMR data at the all-atom resolution. The method can thus be applied in modeling the structures of flexible proteins, for which extensive conformational search enabled by coarse-graining is more important than high modeling accuracy.

  • A Compact and Lightweight Microwave Tilt Sensor Based on an SRR-Loaded Microstrip Line
    • Ali Karami Horestani
    • Zahra Shaterian
    • Michał Mrozowski
    2022

    In this paper, the symmetry property of split ring resonators (SRRs) is exploited to develop a tilt sensor. The sensor is composed of an SRR-loaded microstrip line operating at microwave frequencies. It is shown that the depth of notch in the reflection characteristic of the microstrip is a function of the tilt angle of the SRR. Thus, it can be used for sensing inclination. The sensor benefits from very compact size and light weight. Moreover, it is operated at a single frequency, therefore can be used with a simple power meter as the readout circuit. EM simulations show that the proposed sensor exhibits a good average sensitivity of 1 dB/degree while providing a relatively wide span of 25 degrees.

  • A compact spline-enhanced monopole antenna for broadband/multi-band and beyond UWB applications
    • Michał Czyż
    • Jan Olencki
    • Adrian Bekasiewicz
    2022 Full text AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS

    In this work, a compact monopole antenna for broadband/multi-band and beyond ultra- wideband (UWB) communication has been proposed. The structure is based on a spline-enhanced radiator with a broadband feed and a modified ground plane. Rigorous design optimization of the radiator has been performed in a two-stage framework where optimization of the structure with respect to electrical performance is followed by explicit miniaturization using a constrained objective function. Two compact radiators characterized by footprints of 404 mm 2 and 322 mm 2 , as well as frequency ranges from 2.8 GHz to 34.9 GHz and from 2.9 GHz to 33.9 GHz have been designed. Except for a relatively narrow frequency range in Ka band (from 34.9 GHz to 37.8 GHz), the larger structure is capable of operating for up to 80 GHz. Owing to a simple topology, small size and broadband operation, the presented antennas are of potential use in mobile terminals dedicated to support various wireless technologies including Internet of Things, WiFi, or UWB-based localization services. The proposed radiators have been benchmarked against other broadband/beyond UWB antennas from the literature. Electrical and field characteristics of the proposed structures have been confirmed through measurements of the fabricated prototypes.

  • A Comparative Study of Fuzzy SMC with Adaptive Fuzzy PID for Sensorless Speed Control of Six-Phase Induction Motor
    • Lelisa Wogi
    • Tadele Ayana
    • Marcin Morawiec
    • Andrzej Jąderko
    2022 Full text ENERGIES

    Multi-phase motors have recently replaced three-phase induction motors in a variety of applications due to the numerous benefits they provide, and the absence of speed sensors promotes induction motors with variable speed drives. Sensorless speed control minimizes unnecessary speed encoder cost, reduces maintenance, and improves the motor drive’s reliability. The performance comparison of the fuzzy sliding mode controller (FSMC) with adaptive fuzzy proportional integral derivative (AFPID) control methods for sensorless speed control of six-phase induction motors was analyzed in this study, and the proposed control system has an advantage for multiphase machines, specifically six-phase induction motors (IMs) in this study, as they are the current active research area for electric vehicles, hybrid electric vehicles, aerospace, ship propulsion, and high-power applications. The speed control of a six-phase induction motor was performed by using an AFPID controller and FSMC. The comparative performance analysis was based on sensorless speed control of the six-phase induction motor. A proportional integral derivative (PID) controller is commonly employed as it is used to eliminate oscillations, but it has several drawbacks, such as taking a long time to decrease the error and stabilize the system at constant speed. The fuzzy type-2 and PID controllers were hybridized so as to obtain the advantages of both to enhance the system performance. Finally, the comparison result revealed that the FSMC preforms significantly better by achieving good tracking performance. The control technique maintains the sliding mode approach’s robustness while providing reduced overshoots with a smooth control action, and the FSMC revealed good dynamic response under load variations when compared to the AFPID controller.

  • A comparative study of organic pollutants in seawater, sediments and oyster tissues at Hab River Delta, Balochistan coast, Pakistan
    • Sadar Aslam
    • Malik Wajid Hussain Chan
    • Grzegorz Boczkaj
    • Ghazala Siddiqui
    2022

    This chapter is about a Comparative Study of Organic Pollutants in Seawater, Sediments, and Oyster Tissues at Hab River Delta, Balochistan Coast, Pakistan.

  • A Comparative Study on Methods of Distinction Between Near- and Far-Side Defects as Techniques Used Alongside with the Magnetic Flux Leakage Testing
    • Zbigniew Usarek
    • Marek Chmielewski
    • Leszek Piotrowski
    2022 Full text JOURNAL OF NONDESTRUCTIVE EVALUATION

    Results of the finite element analysis show that a far-side defect in a steel plate, with the depth greater by 10% of the plate thickness than a near-side defect, can produce a very similar magnetic flux leakage (MFL) signal. Due to the fact that a measurement of MFL itself can lead to misclassification of a far-side defect as a near-side one, and thus to underestimation of its depth, a comparative study of three complementary magnetic techniques was performed. The following techniques were studied: surface topology air-gap reluctance system (STARS), residual magnetic flux leakage (RMFL) and stray magnetic flux leakage (SMFL). Numerical results showed that in the case of the STARS and SMFL, defect signatures in signals were observed for investigated near-side defects, but not for far-side defects. The signature of the far-side defect in the RMFL was observed, however its peak-to-peak value was only about 8% of the value corresponding to the near-side defect.

  • A comparative study on the decolorization of Tartrazine, Ponceau 4R, and Coomassie Brilliant Blue using persulfate and hydrogen peroxide based Advanced Oxidation Processes combined with Hydrodynamic Cavitation
    • Zahra Askarniya
    • Soroush Baradaran
    • Shirish H. Sonawane
    • Grzegorz Boczkaj
    2022 Full text CHEMICAL ENGINEERING AND PROCESSING

    Decolorization of Ponceau 4R, Tartrazine, and Coomassie Brilliant Blue (CBB) was studied using hybrid processes of hydrodynamic cavitation (HC) with potassium persulfate (KPS) and hydrogen peroxide (H2O2). The different properties of these dyes such as hydrophobicity, molecular structures, and molecular weights provided this opportunity to investigate the effects of these factors by comparing the decolorization values of the dyes. Treatment process was optimized in respect to cavitation number, HC inlet pressure, and the concentration of external oxidants. The application of dual oxidation system under cavitation conditions revealed a synergetic effect. Maximum decolorization values of 92.27%, 50.1%, and 42.3% were obtained applying this combined process for CBB, Tartrazine, and Ponceau 4R, respectively. The different values of decolorization of the dyes were explained based on their different properties. The kinetic study led to first order rate constants of 10−3 min−1, 6.4*10−3 min−1, 9.2*10−3 min−1, and 4.16*10−2 min−1 using KPS, H2O2, HC, and HC-KPS-H2O2, respectively. A synergetic coefficient of 2.51 obtained by HC-KPS-H2O2 proved the effectiveness of this combined process. Analysis of cavitation yield efficiency showed an improvement of 98% for the HC-KPS-H2O2 combined process as compared to sole HC treatment process.

  • A comprehensive overview of software product management challenges
    • Olga Springer
    • Jakub Miler
    2022 Full text EMPIRICAL SOFTWARE ENGINEERING

    The principal focus of software product management is to ensure the economic success of the product, which means to prolong the product life as much as possible with modest expenditures to maximizs profits. Software product managers play an important role in the software development organization while being responsible for the strategy, business case, product roadmap, high-level requirements, product deployment (release-management), and retirement plan. This article explores the problems that affect the software product management process, their perceived frequency and perceived severity. The data were collected by a systematic literature review (5 main databases were analyzed), interviews (10 software product managers from IT companies), and surveys (89 participants). 95 software product management problems assigned nonexclusively to 7 areas were identified. 27 commonly mentioned software product management problems were evaluated for their perceived frequency and perceived severity. The problems perceived as the most frequent are: determining the true value of the product that the customer needs, strategy and priorities change frequently, technical debt, working in silos, and balancing between reactive and proactive work. In total, 95 problems have been identified which have been narrowed down to 27 problems based on their occurrence in at least 3 interviews. These selected problems were prioritized by perceived frequency and perceived severity. Some of the identified problems spanned beyond the software product management process itself, but they all affect the work of software product managers.

  • A comprehensive review on current and emerging technologies toward the valorization of bio‐based wastes and by products from foods
    • Roberto Castro‐Muñoz
    • Elsa Díaz‐Montes
    • Emilia Gontarek-Castro
    • Grzegorz Boczkaj
    • Charis M. Galanakis
    2022 COMPREHENSIVE REVIEWS IN FOOD SCIENCE AND FOOD SAFETY

    Industries in the agro-food sector are the largest generators of waste in the world. Agro-food wastes and by products originate from the natural process of senescence, pretreatment, handling, and manufacturing processes of food and beverage products. Notably, most of the wastes are produced with the transformation of raw materials (such as fruits, vegetables, plants, tubers, cereals, and dairy products) into different processed foods (e.g., jams, sauces, and canned fruits/vegetables), dairy derivatives (e.g., cheese and yogurt), and alcoholic (e.g., wine and beer) and nonalcoholic beverages (e.g., juices and soft drinks). Current research is committed not only to the usage of agro-food wastes and by products as a potential source of high-value bioactive compounds (e.g., phenolic compounds, anthocyanins, and organic acids) but also to the implementation of emerging and innovative technologies that can compete with conventional extraction methods for the efficient extraction of such biomolecules from the residues. Herein, specific valorization technologies, such as membrane-based processes, microwave, ultrasound, pulsed electric-assisted extraction, supercritical/subcritical fluids, and pressurized liquids, have emerged as advanced techniques in extracting various added-value biomolecules, showing multiple advantages (improved extraction yields, reduced process time, and protection to the bioactive properties of the compounds). Hence, this comprehensive review aims to analyze the ongoing research on applying such techniques in valorization protocols. A last-five-year review, together with a featured analysis of the relevant findings in the field, is provided.

  • A comprehensive study on nonlinear hygro-thermo-mechanical analysis of thick functionally graded porous rotating disk based on two quasi three-dimensional theories
    • Shahriar Dastjerdi
    • Yaghoub Tadi Beni
    • Mohammad Malikan
    2022 Full text MECHANICS BASED DESIGN OF STRUCTURES AND MACHINES

    In this paper, a highly efficient quasi three-dimensional theory has been used to study the nonlinear hygro-thermo-mechanical bending analysis of very thick functionally graded material (FGM) rotating disk in hygro-thermal environment considering the porosity as a structural defect. Two applied quasi three-dimensional displacement fields are assumed in which the strain along the thickness is not zero unlike most of the other plate theories. By considering the nonlinear strains (von Kármán’s assumptions) the large deformations have also been taken into account in order to obtain more accurate results. Finally, some factors that affect the results have been studied further.

  • A Comprehensive Survey on Antennas On-Chip Based on Metamaterial, Metasurface, and Substrate Integrated Waveguide Principles for Millimeter-Waves and Terahertz Integrated Circuits and Systems
    • Mohammad Alibakhshikenari
    • Esraa Mousra Ali
    • Mohammad Soruri
    • Mariana Dalarsson
    • Mohammad Naser-moghadasi
    • Bal S. Virdee
    • Caslav Stefanovic
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    • Stanisław Szczepański
    • Ernesto Limiti
    2022 Full text IEEE Access

    Antennas on-chip are a particular type of radiating elements valued for their small footprint. They are most commonly integrated in circuit boards to electromagnetically interface free space, which is necessary for wireless communications. Antennas on-chip radiate and receive electromagnetic (EM) energy as any conventional antennas, but what distinguishes them is their miniaturized size. This means they can be integrated inside electronic devices. Although on-chip antennas have a limited range, they are suitable for cell phones, tablet computers, headsets, global positioning system (GPS) devices, and WiFi and WLAN routers. Typically, on-chip antennas are handicapped by narrow bandwidth (less than 10%) and low radiation efficiency. This survey provides an overview of recent techniques and technologies investigated in the literature, to implement high performance on-chip antennas for millimeter-waves (mmWave) and terahertz (THz) integrated-circuit (IC) applications. The technologies discussed here include metamaterial (MTM), metasurface (MTS), and substrate integrated waveguides (SIW). The antenna designs described here are implemented on various substrate layers such as Silicon, Graphene, Polyimide, and GaAs to facilitate integration on ICs. Some of the antennas described here employ innovative excitation mechanisms, for example comprising open-circuited microstrip-line that is electromagnetically coupled to radiating elements through narrow dielectric slots. This excitation mechanism is shown to suppress surface wave propagation and reduce substrate loss. Other techniques described like SIW are shown to significantly attenuate surface waves and minimise loss. Radiation elements based on the MTM and MTS inspired technologies are shown to extend the effective aperture of the antenna without compromising the antenna’s form factor. Moreover, the on-chip antennas designed using the above technologies exhibit significantly improved impedance match, bandwidth, gain and radiation efficiency compared to previously used technologies. These features make such antennas a prime candidate for mmWave and THz on-chip integration. This review provides a thorough reference source for specialist antenna designers.

  • A conceptual framework for digital tax administration - A systematic review
    • Edidiong Bassey
    • Emer Mulligan
    • Adegboyega Ojo
    2022 Full text GOVERNMENT INFORMATION QUARTERLY

    Tax administrations worldwide have become highly digitised with a diverse and sophisticated array of e-services to enhance the taxpayer experience. Nevertheless, given the high rates of failure of e-government services, it is critical to understand the factors that are essential to the success of a digital tax system. Drawing on a systematic review of ninety-six publications across the digital taxation, taxation, and information systems (IS) literature, a comprehensive conceptual framework is developed to improve our success of digital services in tax administration. The conceptual framework identifies fifteen themes for consideration by policymakers when designing digital services in tax administrations clustered around four categories – Context, Stakeholders, Technology and Demonstrated Results. The framework should also serve as a reference point in successfully developing strategies and measures to embed digital services in tax administrations. Future research directions are also proposed based on the conceptual framework that will help advance our understanding of digital services in tax administration beyond technology acceptance models.

  • A Control Theoretical Approach to Spectral Factorization is Unstable
    • Michał Meller
    • Adam Lasota
    2022 Full text CIRCUITS SYSTEMS AND SIGNAL PROCESSING

    Local stability analysis of a recently proposed recursive feedback-based approach to spectral factorization is performed. The method is found not to give stability guarantees. Interestingly enough, its global behavior often allows one to obtain reasonable approximations of spectral factorizations if a suitable stopping criterion is employed.

  • A convergence result for mountain pass periodic solutions of perturbed Hamiltonian systems
    • Marek Izydorek
    • Joanna Janczewska
    • Pedro Soares
    2022 Full text COMMUNICATIONS IN CONTEMPORARY MATHEMATICS

    In this work, we study second-order Hamiltonian systems under small perturbations. We assume that the main term of the system has a mountain pass structure, but do not suppose any condition on the perturbation. We prove the existence of a periodic solution. Moreover, we show that periodic solutions of perturbed systems converge to periodic solutions of the unperturbed systems if the perturbation tends to zero. The assumption on the potential that guarantees the mountain pass geometry of the corresponding action functional is of independent interest as it is more general than those by Rabinowitz [Homoclinic orbits for a class of Hamiltonian systems, Proc. R. Soc. Edinburgh A 114 (1990) 33–38] and the authors [M. Izydorek and J. Janczewska, Homoclinic solutions for a class of the second-order Hamiltonian systems, J. Differ. Equ. 219 (2005) 375–389].

  • A Cost-Effective Method for Reconstructing City-Building 3D Models from Sparse Lidar Point Clouds
    • Marek Kulawiak
    2022 Full text Remote Sensing

    The recent popularization of airborne lidar scanners has provided a steady source of point cloud datasets containing the altitudes of bare earth surface and vegetation features as well as man-made structures. In contrast to terrestrial lidar, which produces dense point clouds of small areas, airborne laser sensors usually deliver sparse datasets that cover large municipalities. The latter are very useful in constructing digital representations of cities; however, reconstructing 3D building shapes from a sparse point cloud is a time-consuming process because automatic shape reconstruction methods work best with dense point clouds and usually cannot be applied for this purpose. Moreover, existing methods dedicated to reconstructing simplified 3D buildings from sparse point clouds are optimized for detecting simple building shapes, and they exhibit problems when dealing with more complex structures such as towers, spires, and large ornamental features, which are commonly found e.g., in buildings from the renaissance era. In the above context, this paper proposes a novel method of reconstructing 3D building shapes from sparse point clouds. The proposed algorithm has been optimized to work with incomplete point cloud data in order to provide a cost-effective way of generating representative 3D city models. The algorithm has been tested on lidar point clouds representing buildings in the city of Gdansk, Poland.

  • A Cross-Polarisation Discrimination Analysis of Off-Body Channels in Passenger Ferryboat Environments
    • Sławomir Ambroziak
    • Krzysztof Cwalina
    • Piotr Rajchowski
    • Filipe D. Cardoso
    • Manuel M. Ferreira
    • Luis M. Correia
    2022 Full text IEEE Access

    There is a need for investigating radio channels for Body Area Networks considering the depolarisation phenomenon and new types of environments, since these aspects are becoming very important for systems design and deployment. This paper presents an analysis of cross-polarisation discrimination for off-body channels based on a measurement campaign performed in a passenger ferryboat, i.e., where all walls, floors and ceilings are made of metal. Firstly, the measurement campaign, including test-bench and scenarios, as well as the analysis approach, including classification of mutual antennas’ orientation and definition of parameters are described. The analysis of results includes distance, on-body antennas location and several scenarios, addressing statistical parameters. Mean values for the cross-polarisation discrimination are in the range of [3.7, 6.8] dB while the standard deviation is around 10.0 dB. There is no dependence of the cross-polarisation discrimination on distance, within the measured range (up to 16 m). It is found that there is no correlation between radio signals received by vertically and horizontally polarised receiving antennas, hence, enabling the application of polarisation diversity in Body Area Networks. The Normal Distribution is the best fit for describing cross-polarisation discrimination, as shown by the analysis of goodness of fit parameters, since it passes many of the tests.

  • A Direct Modulation for Matrix Converters based on the Onecycle Atomic operation developed in Verilog HDL.
    • Paweł Szczepankowski
    • Wojciech Śleszyński
    • Tomasz Bajdecki
    2022 Full text IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS

    This paper presents a fast direct Pulse Width Modulation (PWM) algorithm for the Conventional Matrix Converters (CMC) developed in Verilog Hardware Description language (HDL). All PWM duty cycle calculations are performed in one cycle by an atomic operation designed as a digital module using FPGA basic blocks. The algorithm can be extended to any number of output phase. The improved version of the discontinuous Direct Analytic Voltage PWM (DAV–PWM) method is proposed, in which the use of trigonometry, angles and program loops has been eliminated. The proposed DAV-PWM is equivalent to the Space Vector Modulation (SVM), it can be applied during input asymmetry and also allows for the control of the displacement input angle. The proposal has been verified using the circuit simulation in PSIM, digital structure modelling in ModelSim, and finally through an experiment.

  • A dual-control strategy based on electrode material and electrolyte optimization to construct an asymmetric supercapacitor with high energy density
    • Xianyu Chu
    • Fanling Meng
    • Wei Zhang
    • He Yang
    • Xu Zou
    • Sebastian Molin
    • Piotr Jasiński
    • Xiangcheng Sun
    • Weitao Zheng
    2022 NANOTECHNOLOGY

    Metal-organic frames (MOFs) are regarded as excellent candidates for supercapacitors that have attracted much attention because of their diversity, adjustability and porosity. However, both poor structural stability in aqueous alkaline electrolytes and the low electrical conductivity of MOF materials constrain their practical implementation in supercapacitors. In this study, bimetallic CoNi-MOF were synthesized to enhance the electrical conductivity and electrochemical activity of nickel-based MOF, as well as the electrochemical performance of the CoNi-MOF in multiple alkaline electrolytes was investigated. The CoNi-MOF/active carbon device, as-fabricated with a 1 M KOH electrolyte, possesses a high energy density of 35 W h kg−1 with a power density of 1450 W kg−1, exhibiting outstanding cycling stability of 95% over 10,000 cycles. The design of MOF-based electrode materials and the optimization selection of electrolytes pave the way for constructing high-performance supercapacitors.

  • A Dual-Polarized 39 GHz 4x4 Microstrip Antenna Array for 5G MU-MIMO Airflight Cabin Connectivity
    • Kamil Trzebiatowski
    • Jan Fromme
    • Damian Duraj
    • Łukasz Kulas
    • Krzysztof Nyka
    2022 Full text

    This paper presents the design, fabrication, and experimental validation of a 39 GHz dual-polarized 4x4 microstrip antenna array. The array consists of 16 slot coupled circular microstrip patches, fed through SMPS connectors. The procedure requiring a reduced number of cables for measurement of the uniformly excited antenna array is also presented. The array exhibits 18 dBi peak gain and 2.9 GHz reflection bandwidth and is intended for use in a 5G base station inside an airplane. The presented antenna is characterized by a simple feeding system which results in a reduced number of via-holes and dielectric layers.

  • A facile approach to fabricate load-bearing porous polymer scaffolds for bone tissue engineering
    • Tairong Kuang
    • Shaowei Chen
    • Zhipeng Gu
    • Zhisen Shen
    • Aleksander Hejna
    • Mohammad Saeb
    • Feng Chen
    • Mingqiang Zhong
    • Tong Liu
    2022 Advanced Composites and Hybrid Materials

    Biodegradable porous scaffolds with oriented interconnected pores and high mechanical are load-bearing biomaterials for bone tissue engineering. Herein, we report a simple, non-toxic, and cost-effective method to fabricate high-strength porous biodegradable scaffolds, composed of a polymer matrix of polycaprolactone (PCL) and water-soluble poly (ethylene oxide) (PEO) as a sacrificial material by integrating annealing treatment, pressure-induced flow (PIF) processing and particulate leaching techniques. The microstructure, crystal orientation, and crystallization behavior were studied by scanning electron microscope (SEM), 2D X-ray techniques, and differential scanning calorimetry (DSC). Through the analysis of SEM and 2D X-ray results, the proposed hybrid strategy aided formation of porous PCL scaffolds with highly oriented pore structures as well as suitable pore size and pore connectivity. Owing to the improvement of crystal orientation and crystallinity after PIF processing, the obtained scaffolds exhibited higher tensile strength (14.1 MPa), compressive strength (6.6 MPa), bending strength (5.9 MPa), and elongation at break (above 150%) compared with the non-oriented porous scaffolds. In addition, NIH-3T3 fibroblast cell culture unveiled in vitro biocompatibility of the scaffolds. Overall, the obtained oriented porous PCL scaffolds exhibited good biocompatibility, elongated cell morphology, and highly strengthened oriented structure for load-bearing bone tissue applications.

  • A facile method for Tauc exponent and corresponding electronic transitions determination in semiconductors directly from UV–Vis spectroscopy data
    • Łukasz Haryński
    • Adrian Olejnik
    • Katarzyna Grochowska
    • Katarzyna Siuzdak
    2022 OPTICAL MATERIALS

    In this work, a facile method allowing for estimation of the exponent in the Tauc equation directly from the UV–vis spectra is presented. It is based on the Taylor expansion of the logarithmic version of the Tauc equation. The Tauc exponent is calculated from the tangent slope of the absorption data. Knowledge of this coefficient provides information about the optical transition types and is used as an input for the calculations of the band gap. As an exemplar material, TiO2 in form of thin film and nanotubes as well as their nanocomposites with other metal oxides are chosen. For the transparent thin 15 nm film of TiO2, two linear ranges with n = 2.0 and 1.2 are found. The first is assigned to the well-established indirect (allowed) transition. In the case of the second one, the n does not correspond to typically used values. Therefore, it is speculated that more than one transition is probable. This consideration is supported with ab-initio DFT calculations of the band structure of TiO2 with Hubbard U correction. Similar results are found for TiO2 nanotubes using diffuse reflectance spectroscopy indicating that the presented method applies both to transmission and reflection.

  • A facile structural manipulation strategy to prepare ultra-strong, super-tough, and thermally stable polylactide/nucleating agent composites
    • Tairong Kuang
    • Jiajun Ju
    • Tong Liu
    • Aleksander Hejna
    • Mohammad Saeb
    • Shuidong Zhang
    • Xiangfang Peng
    2022 Advanced Composites and Hybrid Materials

    Polylactide (PLA) is a biodegradable thermoplastic widely used in diferent felds, but it should be adequately modifed considering high-performance applications. However, the current processes for developing PLA materials achieve high strength at the expense of toughness or ductility of the materials. Therefore, there is need to develop new strategies for generation of PLA materials with high strength, great toughness, good ductility, and high heat resistance. The present study reported a facile and cost-efective structural manipulation strategy for fabricating high-performance PLA composites that involved addition of 0.5 wt% self-assembled nucleation agent (TMC-306). During the structural manipulation process, the nucleation agent (TMC-306 shish) initially induced the PLA materials to develop a random shish-kebab crystal structure. A chain-like interlocking shish-kebab crystal structure with gradients in both length and thickness was then achieved through semi-solid high-pressure molding. The resulting super-PLA product showed excellent tensile strength (98.7 MPa), superb toughness (82.7 kJ/m2 ), and high elongation at break (117.5%). The reported qualities of the super-PLA materials were superior to that of most commercially available commodity polymers and were comparable to engineering plastics. In addition, PLA composites exhibited a lower thermal deformation variable and a higher Vicat softening temperature (112.4 °C) than neat PLA (62.1 °C). The facile strategy reported in the present study allows development of strong, tough, ductile, and thermally stable PLA, making it a potential alternative plastic material to commodity and engineering plastics used in many technical felds.

  • A finite element analysis of thermal energy inclination based on ternary hybrid nanoparticles influenced by induced magnetic field
    • Muhammad Bilal Hafeez
    • Marek Krawczuk
    • Sooppy Nisar Kottakkaran
    • Wasim Jamshed
    • Amjad Ali Pasha
    2022 Full text INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER

    The use of hybrid nanoparticles to improve thermal processes is a key method that has implications for a variety of interventions utilized in many sectors. This paper aimed to look into the impacts of ternary nanoparticles on hyperbolic tangent materials to establish their thermal characteristics. Flow describing equations have been explored in the presence of heat production, non-Fourier heat flux, and an induced magnetic field. Boundary layer analysis, which generates partial differential equations, was used to model the physical situation under several major physical properties (PDEs). The flow rheology is expanded and calculated in a rotating frame by supposing that the flow is created by a spinning disk. The solution of complicated generated PDEs was calculated using the Galerkin finite element technique (G-FEM) after translating them into corresponding ODEs. Several major bodily repercussions have been seen and documented because of increasing the implicated influencing factors.