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Gdańsk University of Technology

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  • Stability and phase transition investigation of olanzapine polymorphs
    • Jiequn Tang
    • Yanqiang Han
    • Imran Ali
    • Hongyuan Luo
    • Andrzej Nowak
    • Jinjin Li
    2021 CHEMICAL PHYSICS LETTERS

    We use electrical embedded-fragment QM method with both DFT/ωB97XD/6-31G* and MP2/6-31G* to investigate the phase transformations of olanzapine. Gibbs free energy calculations predict that form I is always the most stable structure and form II is the least stable one, while form IV is more stable than form III below about 200 K but less stable above this temperature, implying a polymorphic phase transformation. This may account for why form IV has only recently been discovered as crystallizing from a polymer-based molecular dispersion. The proposed methods may provide guidance for experiments and thus promote the study of phase transitions of pharmaceutical molecules.

  • Stabilizacja podtorza z wykorzystaniem georusztów heksagonalnych
    • Remigiusz Duszyński
    • Michał Gołos
    2021 Inżynier Budownictwa

    Georuszty wielokierunkowe ograniczją przemieszczenia kruszywa, redukują deformacje podsypki tłuczniowej, wydłużają okres pomiędzy zabiegami utrzymaniowymi

  • Stabilizing forces in trapezoidal sheeting used as a part of the bracing system
    • Natalia Korcz-Konkol
    • Piotr Iwicki
    2021 ce/papers

    In the analysis of bracing systems imperfections of the restrained elements should be considered. According to EC3 this effect can be calculated by means of the equivalent stabilizing force, which replaces (in simplified way) initial bow imperfection of the braced element. However, alternative suggestions of the equivalent stabilizing force calculations can be also found in the literature. In this paper segment of the pitched roof with truss girders, purlins and trapezoidal sheeting was analyzed in two variants: with bar bracing and with trapezoidal cladding as a part of the bracing system (resisting in-plane forces). The influence of the imperfections of the truss girder on the axial forces in the purlins in two cases of the bracing systems were observed. Geometrically nonlinear analysis using shell elements was performed in Abaqus. Initial imperfections of the truss girder were implemented in direct way (by importing imperfect geometry using LBA) and compare to the analytical result according to three selected methods. A few aspects that are omitted in analytical procedures were included in numerical analysis, e.g. the eccentricity between structural elements and the stiffness of selected connections. Results showed discrepancies between numerical and analytical outcomes.

  • Stabilizing forces in trapezoidal sheeting used as a part of the bracing system
    • Natalia Korcz-Konkol
    • Piotr Iwicki
    2021

    In the analysis of bracing systems imperfections of the restrained elements should be considered. According to EC3 this effect can be calculated by means of the equivalent stabilizing force, which replaces (in simplified way) initial bow imperfection of the braced element. However, alternative suggestions of the equivalent stabilizing force calculations can be also found in the literature. In this paper segment of the pitched roof with truss girders, purlins and trapezoidal sheeting was analyzed in two variants: with bar bracing and with trapezoidal cladding as a part of the bracing system (resisting in-plane forces). The influence of the imperfections of the truss girder on the axial forces in the purlins in two cases of the bracing systems were observed. Geometrically nonlinear analysis using shell elements was performed in Abaqus. Initial imperfections of the truss girder were implemented in direct way (by importing imperfect geometry using LBA) and compare to the analytical result according to three selected methods. A few aspects that are omitted in analytical procedures were included in numerical analysis, e.g. the eccentricity between structural elements and the stiffness of selected connections. Results showed discrepancies between numerical and analytical outcomes.

  • Stable Field Electron Emission and Plasma Illumination from Boron and Nitrogen Co‐Doped Edge‐Rich Diamond‐Enhanced Carbon Nanowalls
    • Mateusz Ficek
    • Bartłomiej Dec
    • Kamatchi J Sankaran
    • Krzysztof Gajewski
    • Piotr Tatarczak
    • Igor Wlasny
    • Andrzej Wysmolek
    • Ken Haenen
    • Teodor Gotszalk
    • Robert Bogdanowicz
    2021 Full text Advanced Materials Interfaces

    Superior field electron emission (FEE) characteristics are achieved in edge-rich diamond-enhanced carbon nanowalls (D-ECNWs) grown in a single-step chemical vapor deposition process co-doped with boron and nitrogen. The structure consists of sharp, highly conductive graphene edges supplied by a solid, diamond-rich bottom. The Raman and transmission electron microscopy studies reveal a hybrid nature of sp3-diamond and sp2-graphene in these nanowalls. The ab-initio calculations were carried out to support the experimental observations of diamond-graphene hybrid structure. Finally, this hybrid D-ECNWs is employed as a cathode in an FEE device resulting in a low turn-on field of 3.1 V µm−1, a large field enhancement factor, a high FEE Je of 2.6 mA cm−2, and long lifetime stability of 438 min. Such an enhancement in the FEE originates from the unique materials combination, resulting in good electron transport from the graphene phases and efficient FEE of electrons from the sharp edges on the nanowalls. The prospective application of these materials is displayed by employing these hybrids as cathodes in a microplasma device ensuing a low threshold voltage of 160 V and high plasma stability of 140 min, which confirms the role of these hybrid structured nanowalls in the enhancement of electron emission.

  • Standard and modified falling mass impact tests on preplaced aggregatefibrous concrete and slurry infiltrated fibrous concrete
    • K. Ramakrishnan
    • S.r. Depak
    • K.r. Hariharan
    • Sallal R. Abid
    • G. Murali
    • Daiane Cecchin
    • Roman Fediuk
    • Y.h. Mugahed Amran
    • Hakim Abdelgader
    • Jamal M. Khatibi
    2021 CONSTRUCTION AND BUILDING MATERIALS

    Although several studies have been conducted to evaluate the impact response of concrete using theAmerican Concrete Institute (ACI) 544-2R falling mass impact test, the variations in test results are themain drawback of this testing method. This study aims to reduce the variations in experimental impacttest results by introducing two simple test setup modifications; (1) using coarse or fine aggregate bed-ding as an alternative to the steel base plate, (2) the use of line or cross-notched specimens with a lineor cross-load distributing steel plate. One hundred thirty-five cylindrical discs were prepared withPreplaced Aggregate Fibrous Concrete (PAFC) and Slurry Infiltrated Fibrous Concrete (SIFCON), testedin nine groups to assess the proposed modified techniques. Steel hooked-end (2.5%) and macropolypropylene (8.0%) fibers were used to develop PAFC and SIFCON, respectively. The research findingsrevealed that using aggregate bedding increased the impact resistance by 38 to 429% for no-notch spec-imens and up to 283% for notched specimens. The presence of notches reduced the total energy absorbedby the bedding material. For instance, the specimens with a line notch and sand bedding exhibited 15 to51% lower failure impact numbers than their corresponding no-notch specimens. Considering surface-notched specimens and aggregate bedding led to a lower scattering of the impact test results, whilethe line-notched specimens exhibited lower average scattering than the cross and no-notched specimens.In general, a percentage decrease in the coefficient of variation of 30 to 74% was attained for specimenswith bedding and/or surface notch compared to reference specimens.

  • Stannates, titanates and tantalates modified with carbon and graphene quantum dots for enhancement of visible-light photocatalytic activity
    • Marta Paszkiewicz-Gawron
    • Kowalska Ewa
    • Maya Endo-Kimura
    • Julia Zwara
    • Anna Pancielejko
    • Kunlei Wang
    • Wojciech Lisowski
    • Justyna Łuczak
    • Adriana Zaleska-Medynska
    • Ewelina Grabowska-Musiał
    2021 Full text APPLIED SURFACE SCIENCE

    Most efforts in heterogeneous photocatalysis are focused on development of new and stable photoactive materials efficient in degradation of various pollutants under visible-light irradiation. In this regard, the wide-bandgap perovskite semiconductors, i.e., SrTiO3 (titanate), SrSnO3 (stannate) and AgTaO3 (tantalate), were prepared by a solvothermal method, and then modified with carbon quantum dots (CQDs) or graphene quantum dots (GQDs) co-modified with erbium. The photocactivity was investigated for: (i) toluene degradation (gas phase), (ii) phenol decomposition (aqueous phase), and (iii) inactivation of Escherichia coli K12 bacteria. It has been found that the morphology of semiconductors depends on the synthesis conditions, resulting in the formation of spherical particles, rods and faceted particles for SrTiO3, SnSrO3 and AgTaO3, respectively. Additionally, deposition of CQDs and GQDs/erbium has resulted in an enhancement of light harvesting, thus improved photoactivity under visible-light irradiation. Samples modified with both erbium and GQDs revealed much higher photoactivity than corresponding pristine and CQDs-modified samples. Moreover, all photocatalyst modified with GQDs and Er exhibited a significant antibacterial properties under visible light irradiation (λ>420 nm). Accordingly, it has been proposed that obtained semiconductors modified with QDs and Er are promising candidates as sustainable, clean and cheap materials for environmental purification under solar radiation.

  • Stanowisko badawcze do automatycznej analizy jakości transmisji koncentratora KODEŚ z interfejsami LTE, NB-IoT oraz ISM
    • Olga Błaszkiewicz
    • Robert Burczyk
    • Agnieszka Czapiewska
    • Małgorzata Gajewska
    • Sławomir Gajewski
    • Andrzej Marczak
    • Mariusz Miszewski
    • Jarosław Sadowski
    • Jacek Stefański
    2021 Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

    Zaprezentowano podstawowe właściwości projektowanego koncentratora danych elektroenergetycznych KODEŚ oraz stanowisko badawcze do automatycznych pomiarów jakości transmisji w sieci LTE (Long Term Evolution), opracowane na potrzeby projektu badawczego. Głównym elementem stanowiska jest autorskie oprogramowanie, które umożliwia konfigurowanie urządzeń pomiarowych oraz definiowanie scenariuszy pomiarowych. Dopełnieniem tego jest dodatkowe oprogramowanie zastosowane do graficznej prezentacji otrzymanych wyników badań pomiarowych. W artykule opisano również stanowisko, wykorzystujące technikę radia programowalnego i otwarte oprogramowanie, emulujące funkcje stacji bazowej oraz terminala ruchomego sieci LTE.

  • Starter for Voltage Boost Converter to Harvest Thermoelectric Energy for Body-Worn Sensors
    • Grzegorz Blakiewicz
    • Jacek Jakusz
    • Waldemar Jendernalik
    2021 Full text ENERGIES

    This paper examines the suitability of selected configurations of ultra-low voltage (ULV) oscilla-tors as starters for a voltage boost converter to harvest energy from a thermoelectric generator (TEG). Important properties of particularly promising configurations, suitable for on-chip imple-mentation are compared. On this basis, an improved oscillator with a low startup voltage and a high output voltage swing is proposed. The applicability of n-channel native MOS transistors with negative or near-zero threshold voltage in ULV oscillators is analyzed. The results demonstrate that a near-zero threshold voltage transistor operating in the weak inversion region is most ad-vantageous for the considered application. The obtained results were used as a reference for de-sign of a boost converter starter intended for integration in 180-nm CMOS X-FAB technology. In the selected technology, the most suitable transistor available with a negative threshold voltage was used. Despite using a transistor with a negative threshold voltage, a low startup voltage of 29 mV, a power consumption of 70 µW, and power conversion efficiency of about 1.5% were achieved. A great advantage of the proposed starter is that it eliminates a multistage charge pump necessary to obtain a voltage of sufficient value to supply the boost converter control circuit.

  • State of the Art in Open Platforms for Collaborative Urban Design and Sharing of Resources in Districts and Cities
    • Barry Hayes
    • Dorota Kamrowska-Załuska
    • Aleksandar Petrovski
    • Cristina Jiménez-pulido
    2021 Full text Sustainability

    This work discusses recent developments in sharing economy concepts and collaborative co-design technology platforms applied in districts and cities. These developments are being driven both by new technological advances and by increased environmental awareness. The paper begins by outlining the state of the art in smart technology platforms for collaborative urban design, highlighting a number of recent examples. The case of peer-to-peer trading platforms applied in the energy sector is then used to illustrate how sharing economy concepts and their enabling technologies can accelerate efforts towards more sustainable urban environments. It was found that smart technology platforms can encourage peer-to-peer and collaborative activity, and may have a profound influence on the future development of cities. Many of the research and development projects in this area to date have focused on demonstrations at the building, neighbourhood, and local community scales. Scaling these sharing economy platforms up to the city scale and beyond has the potential to provide a number of positive environment impacts. However, significant technical and regulatory barriers to wider implementation exist, and realising this potential will require radical new approaches to the ownership and governance of urban infrastructure. This paper provides a concise overview of the state of the art in this emerging field, with the aim of identifying the most promising areas for further research.

  • Stateczność kratownic ze sprężystymi podporami bocznymi
    • Marcin Krajewski
    2021 Full text

    W rozprawie doktorskiej podjęto temat stateczności kratownic płaskich, które często stanowią zadaszenie stalowych budynków halowych i innych obiektów budowlanych. Głównym celem pracy było badanie zależności pomiędzy sztywnością na przesuw i obrót, sprężystych podpór bocznych a obciążeniem krytycznym i granicznym kratownic. W pracy przedstawiono rezultaty analiz numerycznych stateczności i nośności rzeczywistych kratownic poddanych obciążeniu grawitacyjnemu i obciążeniu od wiatru. Obliczenia przeprowadzono dla modeli prętowych i powłokowych badanych konstrukcji, metodą elementów skończonych, wykorzystując programy Femap i Autodesk Robot Structural Analysis. Na podstawie liniowych analiz stateczności (LBA) oraz analiz statycznych geometrycznie i fizycznie nieliniowych (GMNIA) wykazano, że w każdym przypadku istniała pewna progowa (minimalna) sztywność sprężystych podpór bocznych kratownicy zapewniająca, że nośność konstrukcji wynosiła 90% lub 95% nośności uzyskanej przy sztywnych stężeniach. W pracy analizowano wpływ kształtu i amplitudy globalnych imperfekcji geometrycznych kratownic, w postaci łukowej krzywizny ściskanych pasów oraz w formie pierwszej postaci wyboczenia, na progowe sztywności stężeń. Analizie poddano również wpływ liczby i wymiarów przewiązek, stosowanych między gałęziami pasów kratownic na nośność prętów o przekrojach złożonych. Ponadto, przeprowadzono badania doświadczalne nośności modelu kratownicy (podpartej sprężyście), poddanej obciążeniu pionowemu skierowanemu ku górze i obciążeniu grawitacyjnemu.

  • Statistical evaluation of physical and index properties of Vistula Marshlands deltaic soft soils
    • Jakub Konkol
    • Lech Bałachowski
    2021 Full text IOP Conference Series: Earth and Environmental Science

    This paper provides statistical evaluation of physical and index parameters of the Vistula Marshlands deltaic soft soils using three datasets. Soft soils from the Vistula Marshlands are grouped into the four categories: (1) silty/sandy loams, (2) organic clays, (3) organic silts and (4) peats. Variability of basic and derivative physical properties as well as Atterberg's limits and plasticity index is studied. It is found that index properties for all soil groups are characterized by large scatter (COV about 50%). The most reliable parameters for silty loams, organic clays and silts are soil density (COV<10%) and specific gravity (COV about 2%). Physical/index parameters of peats are characterized by large scatter, which indicates very local properties and individual formation process. Most of the data points for physical/index quantity are within 1SD range regardless normality of data distribution. In the main body of this paper, the quantitative physical/index properties variability is evaluated and some practical design guidelines concerning variability of deltaic soil in the Vistula Marshlands are given.

  • Sterownik PLC jako urządzenie IED zgodne ze standardem IEC 61850
    • Andrzej Augusiak
    • Mateusz Breza
    • Filip Grabowski
    2021 Full text

    Wraz z rozwojem elektroenergetyki, w stacjach i sieciach elektroenerge- tycznych instalowanych jest coraz więcej cyfrowych urządzeń i układów realizujących złożone funkcje sterowni- cze, nadzorujące i zabezpieczeniowe [1] [2]. Obecnie, większość z tych urządzeń standardowo umożliwia również zdal- ne sterowanie, monitoring i akwizycję danych, wykorzystując jeden z wielu protokołów opracowanych dla prze- mysłowych sieci komunikacyjnych. Jednym z dynamicznie rozwijających się standardów w tym zakresie jest norma IEC 61850 [3], dedykowana dla systemów automatyki w stacjach elek- troenergetycznych. Standaryzuje ona struktury danych opisujących wielo- rakie funkcje w urządzeniach elektro- energetycznych, a także wprowadza jednolite protokoły komunikacji po- między tymi urządzeniami, z wykorzy- staniem przemysłowej sieci ethernet [4]. Dzięki temu możliwa jest stosun- kowo łatwa integracja cyfrowych urzą- dzeń różnych producentów w jednej sieci komunikacyjnej, bez konieczności stosowania urządzeń pośredniczących lub tłumaczących. Wśród dostępnych na rynku urządzeń wykorzystujących standard IEC 61850 (urządzeń IED) na szczególną uwagę zasługują swobodnie programowal- ne sterowniki logiczne (PLC), które umożliwiają oprogramowanie różnych, często bardzo złożonych, funkcji użyt- kowych, a jednocześnie zapewniają zgodność tych funkcji z modelami danych IEC 61850 oraz wymianę in- formacji z innymi urządzeniami i sys- temami obsługującymi komunikację w tym standardzie (w tym z systemami SCADA). Jednym z takich bardzo wszechstron- nych urządzeń IED jest sterownik lo- giczny WAGO PFC200 (750-8212/025- 001) [5], który został udostępniony Politechnice Gdańskiej przez przedsię- biorstwo WAGO ELWAG Sp. z o.o. [6] na potrzeby realizacji projektu Cyfrowego sterownika polowego przeznaczonego do stacji DC [7].

  • STORMWATER AS AN ALTERNATIVE WATER SOURCE: QUALITY CHANGES WITH RAINFALL DURATION AND IMPLICATIONS FOR TREATMENT APPROACHES
    • Aleksandra Pieniaszek
    • Ewa Wojciechowska
    • Eliza Kulbat
    • Nicole Nawrot
    • Janusz Pempkowiak
    • Hanna Obarska-Pempkowiak
    • Krzysztof Czerwionka
    2021 Full text International Journal of Conservation Science

    The pressure on the world’s water resources is rapidly increasing due to population growth and climatic changes. Valorisation of stormwater as a water resource for non-potable reuse can reduce high-quality water demands and save it for potable uses. In this context, not only roof runoff but also drained stormwater outflow, representing considerably higher pollution levels, should be considered as a potential resource. We analysed the quality of stormwater runoff from the municipal separate sewer system in a residential catchment located in a medium-sized town in Poland. The changes in concentrations of TSS, COD, BOD5, and E. coli with rainfall duration were assessed during 7 torrential rainfalls with an intensity exceeding 15 L/s·ha. The concentrations of contaminants in the “first flush” of stormwater varied from 93 to 1598 mg/L TSS, from 112 to 815 mg O2/L for COD, and from 7 to 48 mg O2/L for BOD5 and significantly dropped with rainfall duration. The number of E.coli in stormwater outflow fluctuated from 2.5·103 to 8.1·105 MPN/100 mL. Rapid filtration on sand filters was applied in laboratory-scale for the treatment of raw stormwater outflow, providing removal efficiencies of 87-88% for COD, 50-90% for TN, and 88-96% for TP. The quality of raw and treated stormwater was discussed with regard to the existing and developing European standards for water reuse. The results from our study show that treated stormwater outflows can be applied for landscape irrigation. Moreover, rapid filtration is appropriate for stormwater treatment and can be applied either with the support of pre-sedimentation or even as the only separation process.

  • Strain sequence effect on fatigue life and fracture surface topography of 7075-T651 aluminium alloy
    • Wojciech Macek
    • Ricardo Branco
    • José Domingos Costa
    • Cândida Pereira
    2021 Full text MECHANICS OF MATERIALS

    The paper studies the effect of strain-loading sequence on fatigue lifetime and fracture surface topographies in 7075-T651 aluminum alloy specimens. Fatigue tests were performed in two ways: (i) constant-amplitude loading and (ii) two series of variable amplitude loading with non-zero mean strain values. The topography of the fatigue fractures was measured over their entire surfaces with the help of an optical confocal measurement system. The results of fatigue tests in the form of equivalent strains, εaeq, such as the weighted mean of strain components, εa1, εa2, and fatigue life, Nf, were used as the sum of the partial number of cycles N1, and N2. This study indicates, inter alia, that the values of the fracture surface parameter core height Sk, found in the two-step loading pro gram, are linearly dependent on the equivalent strain, and logarithmically dependent on the fatigue life.

  • STRAJK!
    • Krzysztof Wróblewski
    2021

    Strajk – według „Słownika wyrazów obcych" (PWN, Warszawa 1999) – to: zbiorowe, dobrowolne zaprzestanie na pewien okres pracy przez pracowników jednego lub wielu zakładów, będące formą walki o zrealizowanie ich żądań ekonomicznych lub politycznych. Lata 70. ubiegłego wieku – dziesięciolecie rządów Gierka i jego ekipy – kończył głęboki kryzys struktur władzy i gospodarki, społeczne rozgoryczenie i brak perspektyw na godne życie. Brakowało żywności, mieszkań, przysłowiowego „papieru toaletowego i sznurka do snopowiązałek". Wszystkiego. (...) 14 sierpnia 1980 roku rozpoczął się strajk w Stoczni Gdańskiej im. Lenina, który błyskawicznie podjęto w stoczniach i fabrykach Gdyni, Szczecina, Elbląga, Słupska, a następnie i innych miejscach w kraju. Oprócz żądań ekonomicznych, związanych z poprawą warunków życia, domagano się wolnych związków zawodowych. Toczyła się znacząca, rozważna gra o przyszłość kraju. Gra, którą wygrali robotnicy. Powstał niezależny, samorządny związek zawodowy SOLIDARNOŚĆ, narodził się spontaniczny ruch społeczny, który doprowadził do zmian ustrojowych i demokratyzacji życia publicznego. Strajki latem 1980 roku zmieniły bieg dziejów Polski. Istotą działań artystycznych tamtego czasu było komentowanie robotniczych i rolniczych strajków i protestów, interpretowanie istniejących w przestrzeni społecznej ograniczeń, zła, niesprawiedliwości, prześladowań. Sztuka odzwierciedlała znaczenie sprzeciwu wobec panującego reżimu, występujących wynaturzeń, rozbudowanych ograniczeń wolności i niezależności. Pomagała w zrozumieniu zachodzących zmian, inspirowała do kolejnych przemian, uświadamiała, że o wolność i dobro trzeba walczyć każdego dnia. Artyści zwracali uwagę na społeczne problemy, niepokoje i rozterki, polityczną rzeczywistość; dokumentowali polską drogę do wolności, podkreślali znaczenie i konieczność dialogu. Wystawa STRAJK! przypomina, że narodziny „Solidarności" poprzedzały Czerwiec '56, Marzec '68, Grudzień '70, Czerwiec '76, które wywołały nie tylko procesy przeobrażeń ustrojowych i społecznych, ale również przeobraziły warunki życia Polek i Polaków; spowodowały, że ludzkie działania ponownie stały się odzwierciedleniem myśli, emocji, marzeń i przekonań.

  • Strategie kontroli biokorozji
    • Edyta Malinowska-Pańczyk
    2021

    W rozdziale omówiono sposoby ograniczania destrukcyjnej działalności mikroorganizmów powodujących biokorozję.

  • Strength analysis of container ship subjected to torsional loading
    • Krzysztof Wołoszyk
    • Mateusz Jabłoński
    • Marian Bogdaniuk
    2021

    The objective of this work is to investigate the torsional response of a container ship, with particular consideration of the warping effect. Two different models are investigated. In the first case, the full length model of a ship is analyzed and a distributed load is applied with the use of a novel approach. The model is supported in the torsional centre of the cross-section, which is derived analytically. In the second case, the three cargo hold model is analyzed, where the influence of fore and aft parts of the ship is simulated by ‘end-constraint beams’. A constant, concentrated torsional moment is applied in the shear centre of the fore and aft end cross-section. The structural responses of these two models are obtained and distributions of normal stress across the critical cross-sections are derived. The studies revealed that three cargo hold model subjected to torsional moment underestimates the level of normal stresses caused by the warping effect when compared to the full-length ship model subjected to a distributed load.

  • Strong ellipticity conditions and infinitesimal stability within nonlinear strain gradient elasticity
    • Victor Eremeev
    2021 Full text MECHANICS RESEARCH COMMUNICATIONS

    We discuss connections between the strong ellipticity condition and the infinitesimal instability within the nonlinear strain gradient elasticity. The strong ellipticity (SE) condition describes the property of equations of statics whereas the infinitesimal stability is introduced as the positive definiteness of the second variation of an energy functional. Here we establish few implications which simplify the further analysis of stability using formulated SE conditions. The results could be useful for the analysis of solutions of homogenized models of beam-lattice materials at different scales.

  • Strong-coupling superconductivity of SrIr2 and SrRh2 : Phonon engineering of metallic Ir and Rh
    • Sylwia Gutowska
    • Karolina Górnicka
    • Paweł Wójcik
    • Tomasz Klimczuk
    • Bartlomiej Wiendlocha
    2021 PHYSICAL REVIEW B

    Experimental and theoretical studies on superconductivity in SrIr2 and SrRh2 Laves phases are presented. The measured resistivity, heat capacity, and magnetic susceptibility confirm the superconductivity of these compounds with Tc = 6.07 and 5.41 K, respectively. Electronic structure calculations show that the Fermi surface is mostly contributed by 5d (4d) electrons of Ir (Rh), with Sr atoms playing the role of electron donors. The effect of the spin-orbit coupling is analyzed and found to be important in both materials. Lattice dynamics and electron-phonon coupling (EPC) are studied and the strong electron-phonon interaction is found, contributed mostly by the low-frequency Ir and Rh vibrations. The enhancement of EPC, when compared to weakly coupled metallic Ir and Rh, is explained by the strong modifications in the propagation of phonons in the network of Ir (Rh) tetrahedrons, which are the building blocks of the Laves phase, and originate from the metallic fcc structures of elemental iridium and rhodium.

  • Structural Adaptive, Self-Separating Material for Removing Ibuprofen from Waters and Sewage
    • Anna Skwierawska
    • Dominika Nowacka
    • Paulina Nowicka
    • Sandra Rosa
    • Katarzyna Kozłowska-Tylingo
    2021 Full text Materials

    -cyclodextrin nanosponge (CDM) was used for the adsorption of ibuprofen (IBU) from water and sewage. The obtained material was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), Barrett– Joyner–Halenda (BJH), Harkins and Jura t-Plot, zeta potential, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and elementary analysis (EA). Batch adsorption experiments were employed to investigate the effects of the adsorbent dose, initial IBU concentration, contact time, electrolyte ions and humic acids, and sewage over adsorption efficiency. The experimental isotherms were show off using Langmuir, Freundlich, Hill, Halsey and Sips isotherm models and thermodynamic analysis. The fits of the results were estimated according to the Sips isotherm, with a maximum adsorption capacity of 86.21 mg g1. The experimental kinetics were studied by pseudofirst- order, pseudo-second-order, Elovich, modified Freundlich, Weber Morris, Bangham’s pore diffusion, and liquid film diffusion models. The performed experiments revealed that the adsorption process fits perfectly to the pseudo-second-order model. The Elovich and Freundlich models indicate chemisorption, and the kinetic adsorption model itself is complex. The data obtained throughout the study prove that this nanosponge (NS) is extremely stable, self-separating, and adjusting to the guest structure. It also represents a potential biodegradable adsorbent for the removal IBU from wastewaters.

  • Structural analysis as a supporting method for the research of the medieval brick architecture
    • Piotr Samól
    • Piotr Iwicki
    • Jarosław Przewłócki
    2021

    Chronology of brick historical buildings might be established much more precisely than the chronology of stone ones due to the architectural and metrical analysis of bricks, mortars and brickworks. Comparison of historical sources allows to reconstruct the previous stages of constructing monuments. Causations between transformations and developments of monuments are usually interpreted as the results of artistic or ideological influence rather than pragmatic decisions. Such explanations neglect, however, the impact of structural disasters and imperfections. Experience, delivered by the previous erroneous solutions or failures, undoubtedly influenced the further development of architecture. In this paper the authors present how numerical modelling and structural analysis of complex historical brick buildings and different stages of their alterations might be used as a supporting method for the research of their history. Consequently, modern numerical tools for structural analysis can also be useful in investigating of the process of creating architectural solutions [1]. Because more accurate historical analyses belong to the qualitative research, it is not possible to examine very wide group of different monuments. Therefore the authors chose for that purpose the homogeneous group of the mendicant orders’ medieval churches in the former State of Teutonic Order in Prussia, which have been the subject of authors’ in situ research since 2009 [2]. This group is thought to be representative for the medieval techniques of the brick architecture in northern Europe and Baltic Sea Region. The aim of this research is to find out whether structural analysis might be carried out in a historical building in which consecutive transformations partially erased its original form (reconstructed on the base of the architectural and archaeological research)? A positive answer to that question allows to put another one – about whether the numerical modelling of the structure of monument might give some additional information on its history? The results of described research might give a new tool for conservators, architects, archaeologists and engineers in their research and other conducting works.

  • Structural and Material Determinants Influencing the Behavior of Porous Ti and Its Alloys Made by Additive Manufacturing Techniques for Biomedical Applications
    • Magda Dziaduszewska
    • Andrzej Zieliński
    2021 Full text Materials

    One of the biggest challenges in tissue engineering is the manufacturing of porous structures that are customized in size and shape and that mimic natural bone structure. Additive manufacturing is known as a sufficient method to produce 3D porous structures used as bone substitutes in large segmental bone defects. The literature indicates that the mechanical and biological properties of scaffolds highly depend on geometrical features of structure (pore size, pore shape, porosity), surface morphology, and chemistry. The objective of this review is to present the latest advances and trends in the development of titanium scaffolds concerning the relationships between applied materials, manufacturing methods, and interior architecture determined by porosity, pore shape, and size, and the mechanical, biological, chemical, and physical properties. Such a review is assumed to show the real achievements and, on the other side, shortages in so far research.

  • Structural Changes and Their Implications in Foamed Flexible Polyurethane Composites Filled with Rapeseed Oil-Treated Ground Tire Rubber
    • Paulina Kosmela
    • Adam Olszewski
    • Łukasz Zedler
    • Paulina Burger
    • Krzysztof Formela
    • Aleksander Hejna
    2021 Full text Journal of Composites Science

    The utilization of post-consumer car tires is an essential issue from an ecological andeconomic point of view. One of the simplest and the least harmful methods is their material recyclingresulting in ground tire rubber (GTR), which can be further applied as fillers for polymer-basedcomposites. Nevertheless, insufficient interfacial interactions implicate the necessity of GTR modi-fication before introduction into polymer matrices. In this study, we investigated the influence ofrapeseed oil-assisted thermo-mechanical treatment of GTR using a reactive extrusion process on theprocessing, structure, and performance of flexible polyurethane/GTR composite foams. Appliedmodifications affected the processing of polyurethane systems. They caused a noticeable reductionin the average cell size of foams, which was attributed to the potential nucleating activity of solidparticles and changes in surface tension caused by the presence of oil. Such an effect was especiallypronounced for the waste rapeseed oil, which resulted in the highest content of closed cells. Structuralchanges caused by GTR modification implicated the enhancement of foams’ strength. Mechanicalperformance was significantly affected by the applied modifications due to the changes in glasstransition temperature. Moreover, the incorporation of waste GTR particles into the polyurethanematrix noticeably improved its thermal stability.

  • Structural changes of bacterial cellulose due to incubation in conditions simulating human plasma in the presence of selected pathogens
    • Paulina Dederko-Kantowicz
    • Agata Sommer
    • Hanna Staroszczyk
    2021 Full text CARBOHYDRATE POLYMERS

    Bacterial nanocellulose (BNC) is a natural biomaterial with a wide range of medical applications. However, it cannot be used as a biological implant of the circulatory system without checking whether it is biodegradable under human plasma conditions. This work aimed to investigate the BNC biodegradation by selected pathogens under conditions simulating human plasma. The BNC was incubated in simulated biological fluids with or without Staphylococcus aureus, Candida albicans and Aspergillus fumigatus, and its physicochemical properties were studied. The results showed that the incubation of BNC in simulated body fluid with A. fumigatus con-tributes more to its degradation than that under other conditions tested. The rearrangement of the hydrogen- bond network in this case resulted in a more compact structure, with an increased crystallinity index, reduced thermal stability and looser cross-linking. Therefore, although BNC shows great potential as a cardiovascular implant material, before use for this purpose its biodegradability should be limited.

  • Structural, electrical, and magnetic study of La-, Eu-, and Er- doped bismuth ferrite nanomaterials obtained by solution combustion synthesis
    • Angelika Wrzesińska
    • Alexander Khort
    • Marcin Witkowski
    • Jacek Szczytko
    • Jacek Ryl
    • Jacek Gurgul
    • Dmitry Kharitonov
    • Kazimierz Łątka
    • Tadeusz Szumiata
    • Aleksandra Wypych-puszkarz
    2021 Full text Scientific Reports

    In this work, the multiferroic bismuth ferrite materials Bi0.9RE0.1FeO3 doped by rare-earth (RE = La, Eu, and Er) elements were obtained by the solution combustion synthesis. Structure, electrical, and magnetic properties of prepared samples were investigated by X-ray photoelectron spectroscopy, Mössbauer spectroscopy, electrical hysteresis measurement, broadband dielectric spectroscopy, and SQUID magnetometry. All obtained nanomaterials are characterized by spontaneous electrical polarization, which confirmed their ferroelectric properties. Investigation of magnetic properties at 300.0 K and 2.0 K showed that all investigated Bi0.9RE0.1FeO3 ferrites possess significantly higher magnetization in comparison to bismuth ferrites obtained by different methods. The highest saturation magnetisation of 5.161 emu/g at 300.0 K was observed for the BLaFO sample, while at 2.0 K it was 12.07 emu/g for the BErFO sample. Several possible reasons for these phenomena were proposed and discussed.

  • Structural evaluation of percolating, self-healing polyurethane–polycaprolactone blends doped with metallic, ferromagnetic, and modified graphene fillers
    • Damian Włodarczyk
    • Iwona Żmuda-Trzebiatowska
    • J. Karczewski
    • Martyna Lubinska-Szczygeł
    • Magdalena Urban
    • Antoni Marciniak
    • Anna Kamińska
    • Patrycja Sikorska
    • Magda Graczyk
    • Michał Strankowski
    2021 POLYMERS & POLYMER COMPOSITES

    Composites with differently shaped micro- and nanofillers show various, unique thermal, and physicochemical properties when mixed with carefully chosen polymer matrix. Selected composition holds strategic value in achieving desired properties that is biodegradability, thermoelectric conductivity, and shape memory for organic coating. The main aim of this work is to briefly examine structural changes after reaching percolation threshold and activating healing abilities within exploited (8–2 wt ratio) polyurethane–polycaprolactone thin films mixed up with different types of metallic and ferromagnetic microfillers. They, with applicable dosages of reduced graphene oxide nanoparticles, should enhance materials’ mechanical and conductive properties. Microscopic and spectroscopic techniques accompanied by extensive thermal analysis have been chosen to provide useful information about local changes in surface structure and morphology. Moreover, pristine, percolating surface with inner-formed, metallic structures shows moderate conducting properties within exploited materials which unfortunately diminish after thermal healing stimulus is being applied. This statement is supported by observing the coverage of regional defects and nearby pores with a concise, uniform layer of blend having different PU:PCL ratio. Including the additional fact that apparent filler migration is changing local dopant composition brings up an assumption that both phenomena have negative synergy effect on each other.

  • Structure and magnetic properties of BeO-Fe2O3-Al2O3-TeO2 glass-ceramic composites
    • Natalia Wójcik
    • N Tagiara
    • Sharafat Ali
    • Karolina Górnicka
    • H Segawa
    • Tomasz Klimczuk
    • B Jonson
    • Doris Möncke
    • Efstratios Kamitsos
    2021 Full text JOURNAL OF THE EUROPEAN CERAMIC SOCIETY

    In this work, glass-ceramics in the xBeO–20Fe2O3–(80-x)TeO2 system with x = 0–25 mol% were synthesized by the traditional melt quenching route and studied by inductively coupled plasma optical emission spectroscopy, X-ray diffraction, confocal microscopy, infrared and Raman spectroscopy. BeO addition was found to support the crystallization process of Fe2O3 during melting, and an increased BeO content was associated with an increased fraction of the crystalline Fe2O3 phase and an increased size of these crystallites. Furthermore, samples doped with BeO exhibit an increasing polymerization of the residual tellurite glass network compared to the undoped sample. The magnetic properties and specific heat of all synthesized materials were measured, and the results show that all studied samples behave as spin-glasses. Also, the Morin transition of hematite was observed at 260 K with intensity depending on the material content in Fe2O3 crystalline phase, the formation of which correlates with the amount of added BeO.

  • Structure and properties comparison of poly(ether-urethane)s based on nonpetrochemical and petrochemical polyols obtained by solvent free two-step method
    • Paulina Kasprzyk
    • Ewa Głowińska
    • Janusz Datta
    2021 Full text EUROPEAN POLYMER JOURNAL

    The application of thermoplastic polyurethanes (TPU) is becoming more and more extensive, and the decreasing of used petrochemical monomers and reduction of energy for the polymerization and processing processes is getting increasingly important. In this paper, we confirmed the positive influence of high bio-based monomers contents (by replacing petrochemical polyol and glycol by bio-based counterparts) on processing and properties of obtained materials. A series of partially bio-based thermoplastic poly(ether-urethane)s (bio-based TPU) were obtained from bio- and petrochemical-based polyols, bio-based 1,4-butanediol, and 4,4′-diphenylmethane diisocyanate by the two-step method without using any solvents. Both the monomers’ origin and polyurethane prepolymer processing parameters were taken into account in characterization of the obtained materials. The TPUs' chemical structure was analyzed by FTIR spectroscopy and 1H NMR and the number average molecular weight was examined by 1H NMR and GPC. The measurements of dynamic mechanical thermal analysis, tensile test, hardness, density method, and rheological behavior provided useful information about the properties of prepolymers and TPUs. The processing properties and an activation energy of prepared materials was examined using the melt-flow index. It has been confirmed that despite the origin of polyols obtained thermoplastic poly(ether-urethanes) exhibited comparably good mechanical and thermo-mechanical properties, and an appropriate melt flow index facilitates their processing. Nevertheless, the use of high amount of bio-based monomers resulted in obtaining more eco-friendly materials.

  • Structure and Randomness in Planning and Reinforcement Learning
    • Konrad Czechowski
    • Piotr Januszewski
    • Piotr Kozakowski
    • Łukasz Kuciński
    • Piotr Miłoś
    2021

    Planning in large state spaces inevitably needs to balance the depth and breadth of the search. It has a crucial impact on the performance of a planner and most manage this interplay implicitly. We present a novel method \textit{Shoot Tree Search (STS)}, which makes it possible to control this trade-off more explicitly. Our algorithm can be understood as an interpolation between two celebrated search mechanisms: MCTS and random shooting. It also lets the user control the bias-variance trade-off, akin to TD(n), but in the tree search context. In experiments on challenging domains, we show that STS can get the best of both worlds consistently achieving higher scores.

  • Structure and thermoelectric properties of nickel-doped copper selenide synthesised in a hydrogen atmosphere
    • Agata Ducka
    • Bartosz Trawiński
    • Beata Bochentyn
    • A. Dubiel
    • Bogusław Kusz
    2021 Full text MATERIALS RESEARCH BULLETIN

    Nickel-doped copper selenide—Cu2-xNixSe (x = 0; 0.01; 0.02; 0.03)—materials with high thermoelectric properties were synthesised through reduction of reagents in hydrogen. The impact of the nickel content on both the microstructure and thermoelectric properties was examined. The nickel-doped samples’ microstructure differed significantly from pristine copper selenide. Besides Cu2Se, copper precipitations were present in the materials. The presence of the metallic nanoparticles in the nickel-doped materials enhanced the electrical conductivity without significantly changing the Seebeck coefficient. Above 500 K, the structure of the doped samples also resulted in decreased thermal conductivity. Also, the impact of the Cu2Se phase transition on thermoelectric properties is visible. The highest ZT value, equal to 0.8 at 650 K, was reached for the Cu1.98Ni0.02Se sample.

  • Structure and transport properties of donor-doped barium strontium cobaltites
    • Tadeusz Miruszewski
    • Wojciech Skubida
    • Arkadiusz Dawczak
    • Kacper Dzierzgowski
    • Sebastian Wachowski
    • Aleksandra Mielewczyk-Gryń
    • Maria Gazda
    2021 JOURNAL OF THE EUROPEAN CERAMIC SOCIETY

    In this work, Nb-substituted barium strontium cobaltites Ba0.5Sr0.5Co1-xNbxO3-δ (x = 0 – 0.4) have been fabricated and studied. The structural analysis showed that the Nb content influences the lattice constant as well as the distance between the (Co, Nb) and oxygen atoms. The study of morphology of samples showed that the Nb content does not change the porosity, grain size and morphology of the ceramics. The total electrical conductivity was studied as a function of temperature and pO2/pH2O. It was shown, that total conductivity is influenced by the cobalt to niobium ratio while the conduction mechanism was similar in all analyzed samples. Transport properties and the presence of protonic conductivity were studied in a dry and humidified atmosphere. A non-negligible difference between total conductivities in dry and wet atmospheres below 500 °C was observed what indicates the presence of protonic defects in these structures. Hydrogenation as a predominant protons formation mechanism was proposed.

  • Structure and transport properties of triple-conducting BaxSr1−xTi1−yFeyO3−δ oxides
    • Tadeusz Miruszewski
    • Kacper Dzierzgowski
    • Piotr Winiarz
    • Daniel Jaworski
    • Katarzyna Wiciak-Pawłowska
    • Wojciech Skubida
    • Sebastian Wachowski
    • Aleksandra Mielewczyk-Gryń
    • Maria Gazda
    2021 Full text RSC Advances

    In this work, BaxSr1−xTi1−yFeyO3−δ perovskite-based mixed conducting ceramics (for x = 0, 0.2, 0.5 and y = 0.1, 0.8) were synthesized and studied. The structural analysis based on the X-ray diffraction results showed significant changes in the unit cell volume and Fe(Ti)–O distance as a function of Ba content. The morphology of the synthesized samples studied by means of scanning electron microscopy has shown different microstructures for different contents of barium and iron. Electrochemical impedance spectroscopy studies of transport properties in a wide temperature range in the dry- and wet air confirmed the influence of barium cations on charge transport in the studied samples. The total conductivity values were in the range of 10−3 to 100 S cm−1 at 600 °C. Depending on the barium and iron content, the observed change of conductivity either increases or decreases in humidified air. Thermogravimetric measurements have shown the existence of proton defects in some of the analysed materials. The highest observed molar proton concentration, equal to 5.0 × 10−2 mol mol−1 at 300 °C, was obtained for Ba0.2Sr0.8Ti0.9Fe0.1O2.95. The relations between the structure, morphology and electrical conductivity were discussed.

  • Studies on Aminoanthraquinone-Modified Glassy Carbon Electrode: Synthesis and Electrochemical Performance toward Oxygen Reduction
    • Łukasz Macewicz
    • Grzegorz Skowierzak
    • Paweł Niedziałkowski
    • Jacek Ryl
    • Tadeusz Ossowski
    • Robert Bogdanowicz
    2021 RUSSIAN JOURNAL OF ELECTROCHEMISTRY

    In this paper, 9,10-anthraquinone (AQ) derivative-modified glassy carbon (GC) electrodes were studied towards the electrochemical reduction of oxygen in aqueous and non-aqueous solutions. The reaction of 1-chloro-9,10-anthraquinone with aliphatic diamines was applied for the synthesis of amino-9,10-anthraquinone derivatives. The obtained AQ derivatives were grafted onto the surface of glassy carbon electrodes by electropolymerisation using diazonium salts. The modified GC electrodes are sensitive to oxygen, determined by cyclic voltammetry. Changes in the oxygen determination efficiency depend mostly on the length of the side chain AQ derivative which is grafted to the GC electrode and is nearly double in comparison to a bare GC electrode modified by 1-((2-((2-aminoethyl)amino)ethyl)amino)-9,10-anthraquinone.

  • Studium wprowadzenia elektrycznych zespołów trakcyjnych z zasobnikami energii na częściowo zelektryfikowanej trasie Orunia Górna - Port Oksywie
    • Natalia Karkosińska-Brzozowska
    • Dominika Macedońska
    • Dariusz Karkosiński
    2021 Automatyka Elektryka Zakłócenia

    W artykule rozważono innowacyjny układ przewozów pasażerskich Metropolii Trójmiejskiej. Dla układu z naprzemiennie występującymi odcinkami zelektryfikowanymi i niezelektryfikowanymi wyznaczono zapotrzebowanie energetyczne i dobrano hipotetyczny zasobnik, składający się z baterii akumulatorów oraz superkondesarorów. W wyniku przeprowadzonej analizy wykazano, że zastosowanie elektrycznych zespołów zasobnikowych w stosunku do zespołów z napędem spalinowym oraz budowy sieci trakcyjnej może być ekonomicznie i środowiskowo korzystme

  • Study of a Multicriterion Decision-Making Approach to the MQL Turning of AISI 304 Steel Using Hybrid Nanocutting Fluid
    • Dubey Vineet
    • Kumar Anuj Sharma
    • Prameet Vats
    • Danil Yurievich Pimenov
    • Khaled Giasin
    • Daniel Chuchała
    2021 Full text Materials

    The enormous use of cutting fluid in machining leads to an increase in machining costs, along with different health hazards. Cutting fluid can be used efficiently using the MQL (minimum quantity lubrication) method, which aids in improving the machining performance. This paper contains multiple responses, namely, force, surface roughness, and temperature, so there arises a need for a multicriteria optimization technique. Therefore, in this paper, multiobjective optimization based on ratio analysis (MOORA), VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR), and technique for order of preference by similarity to ideal solution (TOPSIS) are used to solve different multiobjective problems, and response surface methodology is also used for optimization and to validate the results obtained by multicriterion decision-making technique (MCDM) techniques. The design of the experiment is based on the Box–Behnken technique, which used four input parameters: feed rate, depth of cut, cutting speed, and nanofluid concentration, respectively. The experiments were performed on AISI 304 steel in turning with minimum quantity lubrication (MQL) and found that the use of hybrid nanofluid (Alumina–Graphene) reduces response parameters by approximately 13% in forces, 31% in surface roughness, and 14% in temperature, as compared to Alumina nanofluid. The response parameters are analyzed using analysis of variance (ANOVA), where the depth of cut and feed rate showed a major impact on response parameters. After using all three MCDM techniques, it was found that, at fixed weight factor with each MCDM technique, a similar process parameter was achieved (velocity of 90 m/min, feed of 0.08 mm/min, depth of cut of 0.6 mm, and nanoparticle concentration of 1.5%, respectively) for optimum response. The above stated multicriterion techniques employed in this work aid decision makers in selecting optimum parameters depending upon the desired targets. Thus, this work is a novel approach to studying the effectiveness of hybrid nanofluids in the machining of AISI 304 steel using MCDM techniques.

  • STUDY OF ARRAY OF MEMS INERTIAL MEASUREMENT UNITS UNDER QUASI-STATIONARY AND DYNAMIC CONDITIONS
    • Jerzy Demkowicz
    • Krzysztof Bikonis
    2021 Full text Polish Maritime Research

    A measurement system includes all components in a chain of hardware and software that leads from a measured variable to processed data. In that context, the type and quality of the sensors or measuring devices are critical to any measurement system. MEMS/IMU sensors lag behind leading technologies in this respect, but the MEMS/IMU performance rapidly changes while is relatively inexpensive. For this reason, the paper proposes some investigations of currently available MEMS/IMUs, but in an array configuration. The article presents the results of research undertaken on this type of IMU sensor configuration under quasi-stationary and dynamic conditions and answers the question of whether the precision of current MEMS technologies for acceleration and angular velocity sensors is still improved using this kind of approach.

  • Study of Integer Spin S = 1 in the Polar Magnet β-Ni(IO3)2
    • Ebube E. Oyeka
    • Michał Winiarski
    • Thao Tran
    2021 Full text MOLECULES

    Polar magnetic materials exhibiting appreciable asymmetric exchange interactions can potentially host new topological states of matter such as vortex-like spin textures; however, realizations have been mostly limited to half-integer spins due to rare numbers of integer spin systems with broken spatial inversion lattice symmetries. Here, we studied the structure and magnetic properties of the S = 1 integer spin polar magnet β-Ni(IO3)2 (Ni2+, d8, 3F). We synthesized single crystals and bulk polycrystalline samples of β-Ni(IO3)2 by combining low-temperature chemistry techniques and thermal analysis and characterized its crystal structure and physical properties. Single crystal X-ray and powder X-ray diffraction measurements demonstrated that β-Ni(IO3)2 crystallizes in the noncentrosymmetric polar monoclinic structure with space group P21. The combination of the macroscopic electric polarization driven by the coalignment of the (IO3)− trigonal pyramids along the b axis and the S = 1 state of the Ni2+ cation was chosen to investigate integer spin and lattice dynamics in magnetism. The effective magnetic moment of Ni2+ was extracted from magnetization measurements to be 3.2(1) µB, confirming the S = 1 integer spin state of Ni2+ with some orbital contribution. β-Ni(IO3)2 undergoes a magnetic ordering at T = 3 K at a low magnetic field, μ0H = 0.1 T; the phase transition, nevertheless, is suppressed at a higher field, μ0H = 3 T. An anomaly resembling a phase transition is observed at T ≈ 2.7 K in the Cp/T vs. T plot, which is the approximate temperature of the magnetic phase transition of the material, indicating that the transition is magnetically driven. This work offers a useful route for exploring integer spin noncentrosymmetric materials, broadening the phase space of polar magnet candidates, which can harbor new topological spin physics.

  • Study of Multi-Class Classification Algorithms’ Performance on Highly Imbalanced Network Intrusion Datasets
    • Viktoras Bulavas
    • Virginijus Marcinkevičius
    • Jacek Rumiński
    2021 Full text Informatica

    This paper is devoted to the problem of class imbalance in machine learning, focusing on the intrusion detection of rare classes in computer networks. The problem of class imbalance occurs when one class heavily outnumbers examples from the other classes. In this paper, we are particularly interested in classifiers, as pattern recognition and anomaly detection could be solved as a classification problem. As still a major part of data network traffic of any organization network is benign, and malignant traffic is rare, researchers therefore have to deal with a class imbalance problem. Substantial research has been undertaken in order to identify these methods or data features that allow to accurately identify these attacks. But the usual tactic to deal with the imbalance class problem is to label all malignant traffic as one class and then solve the binary classification problem. In this paper, however, we choose not to group or to drop rare classes but instead investigate what could be done in order to achieve good multi-class classification efficiency. Rare class records were up-sampled using SMOTE method (Chawla et al., 2002) to a preset ratio targets. Experiments with the 3 network traffic datasets, namely CIC-IDS2017, CSE-CIC-IDS2018 (Sharafaldin et al., 2018) and LITNET-2020 (Damasevicius et al., 2020) were performed aiming to achieve reliable recognition of rare malignant classes available in these datasets. Popular machine learning algorithms were chosen for comparison of their readiness to support rare class detection. Related algorithm hyper parameters were tuned within a wide range of values, different data feature selection methods were used and tests were executed with and without over-sampling to test the multiple class problem classification performance of rare classes. Machine learning algorithms ranking based on Precision, Balanced Accuracy Score, G¯ , and prediction error Bias and Variance decomposition, show that decision tree ensembles (Adaboost, Random Forest Trees and Gradient Boosting Classifier) performed best on the network intrusion datasets used in this research.

  • Study of Non-Newtonian biomagnetic blood flow in a stenosed bifurcated artery having elastic walls
    • Hasan Shahzad
    • Xinhua Wang
    • Ioannis Sarris
    • Kaleem Iqbal
    • Muhammad Bilal Hafeez
    • Marek Krawczuk
    2021 Full text Scientific Reports

    Fluid structure interaction (FSI) gained attention of researchers and scientist due to its applications in science felds like biomedical engineering, mechanical engineering etc. One of the major application in FSI is to study elastic wall behavior of stenotic arteries. In this paper we discussed an incompressible Non-Newtonian blood fow analysis in an elastic bifurcated artery. A magnetic feld is applied along x direction. For coupling of the problem an Arbitrary Lagrangian–Eulerian formulation is used by twoway fuid structure interaction. To discretize the problem, we employed P2P1 fnite element technique to approximate the velocity, displacement and pressure and then linearized system of equations is solved using Newton iteration method. Analysis is carried out for power law index, Reynolds number and Hartmann number. Hemodynamic efects on elastic walls, stenotic artery and bifurcated region are evaluated by using velocity profle, pressure and loads on the walls. Study shows there is signifcant increase in wall shear stresses with an increase in Power law index and Hartmann number. While as expected increase in Reynolds number decreases the wall shear stresses. Also load on the upper wall is calculated against Hartmann number for diferent values of power law index. Results show load increases as the Hartmann number and power law index increases. From hemodynamic point of view, the load on the walls is minimum for shear thinning case but when power law index increased i.e. for shear thickening case load on the walls increased.

  • Study of probe signal bandwidth influence on estimation of coherence bandwidth for underwater acoustic communication channel
    • Iwona Kochańska
    • Jan Schmidt
    • Aleksander Schmidt
    2021 Full text APPLIED ACOUSTICS

    A signal transmitted in a shallow Underwater Acoustic Communication (UAC) channel suffers from time dispersion due to the multipath propagation and the refraction phenomena. This causes intersymbol interference of the received signal and frequency-selective fading observed in its spectrum. Coherence bandwidth is one of the key transmission parameters used for designing the physical layer of a data transmission system to minimise the influence of time dispersion on the received signal. It can be calculated on the basis of the channel impulse response, measured with the use of the correlation method and frequency modulated signals or pseudorandom binary sequences. Such signals have a narrow, impulselike autocorrelation function if considered in baseband. However, in the case of bandpass measurements, the influence of the probe signal on the estimate of the impulse response, and thus on the estimate of transmission parameters, is no longer negligible. The paper presents the results of an experimental study on probe signal bandwidth influence on estimation of coherence bandwidth. Simulations were carried out using UAC channel impulse responses measured in an inland reservoir.

  • Study of Slip Effects in Reverse Roll Coating Process Using Non-Isothermal Couple Stress Fluid
    • Hasan Shahzad
    • Xinhua Wang
    • Muhammad Bilal Hafeez
    • Zahir Shah
    • Mohammed Ahmed Alsheri
    2021 Full text Coatings

    The non-isothermal couple stress fluid inside a reverse roll coating geometry is considered. The slip condition is considered at the surfaces of the rolls. To develop the flow equations, the mathematical modelling is performed using conservation of momentum, mass, and energy. The LAT (lubrication approximation theory) is employed to simplify the equations. The closed form solution for velocity, temperature, and pressure gradient is obtained. While the pressure and flow rate are obtained numerically. The impact of involved parameters on important physical quantities such as temperature, pressure, and pressure gradient are elaborated through graphs and in tabular form. The pressure and pressure gradient decreases for variation of the couple stress parameter and velocity ratio parameter K. While the variation of the slip parameter increases the pressure and pressure gradient inside the flow geometry. Additionally, flow rate decreases for the variation of the slip parameter as fluid starts moving rapidly along the roller surface. The most important physical quantity which is responsible for maintaining the quality of the coating and thickness is flow rate. For variation of both the couple stress parameter and the slip parameter, the flow rate decreases compared to the Newtonian case, consequently the coating thickness decreases for the variation of the discussed parameter

  • Study of Statistical Text Representation Methods for Performance Improvement of a Hierarchical Attention Network
    • Adam Wawrzyński
    • Julian Szymański
    2021 Full text Applied Sciences-Basel

    To effectively process textual data, many approaches have been proposed to create text representations. The transformation of a text into a form of numbers that can be computed using computers is crucial for further applications in downstream tasks such as document classification, document summarization, and so forth. In our work, we study the quality of text representations using statistical methods and compare them to approaches based on neural networks. We describe in detail nine different algorithms used for text representation and then we evaluate five diverse datasets: BBCSport, BBC, Ohsumed, 20Newsgroups, and Reuters. The selected statistical models include Bag of Words (BoW), Term Frequency-Inverse Document Frequency (TFIDF) weighting, Latent Semantic Analysis (LSA) and Latent Dirichlet Allocation (LDA). For the second group of deep neural networks, Partition-Smooth Inverse Frequency (P-SIF), Doc2Vec-Distributed Bag of Words Paragraph Vector (Doc2Vec-DBoW), Doc2Vec-Memory Model of Paragraph Vectors (Doc2Vec-DM), Hierarchical Attention Network (HAN) and Longformer were selected. The text representation methods were benchmarked in the document classification task and BoW and TFIDF models were used were used as a baseline. Based on the identified weaknesses of the HAN method, an improvement in the form of a Hierarchical Weighted Attention Network (HWAN) was proposed. The incorporation of statistical features into HAN latent representations improves or provides comparable results on four out of five datasets. The article presents how the length of the processed text affects the results of HAN and variants of HWAN models

  • Study of the Performance of DSSS UAC System Depending on the System Bandwidth and the Spreading Sequence
    • Iwona Kochańska
    • Roman Salamon
    • Jan Schmidt
    • Aleksander Schmidt
    2021 Full text SENSORS

    A signal transmitted in an Underwater Acoustic Communication (UAC) system operating in a shallow-water channel suffers from strong time dispersion due to multipath propagation. This causes the Inter-Symbol Interference (ISI) observed in the received signal, which significantly limits the communication system’s reliability and transmission rate. In such propagation conditions, the Direct-Sequence Spread Spectrum (DSSS) method is one of the solutions that make reliable data transmission possible. In systems with one-to-one communication, it ensures communication with a satisfactory Bit Error Rate (BER). Additionally, it makes it possible to implement the Code-Division Multiple Access (CDMA) protocol in underwater acoustic networks. This paper presents the results of simulation and experimental communication tests on a DSSS-based UAC system using three types of spreading sequence, namely m-sequences, Kasami codes and Gold codes, and occupying different bandwidths from 1 kHz to 8 kHz around a carrier frequency equal to 30 kHz. The UAC channel was simulated by impulse responses calculated by the virtual sources method and the UAC chanel models available in the Watermark simulator. The experimental tests were conducted in a model pool. Based on the obtained results, a transmission rate was estimated, which is possible to achieve in strong multipath propagation conditions, assuming reliability expressed as BER less than 0.001.

  • Study on CPU and RAM Resource Consumption of Mobile Devices using Streaming Services
    • Przemysław Falkowski-Gilski
    • Michał Woźniak
    2021

    Streaming multimedia services have become very popular in recent years, due to the development of wireless networks. With the growing number of mobile devices worldwide, service providers offer dedicated applications that allow to deliver on-demand audio and video content anytime and everywhere. The aim of this study was to compare different streaming services and investigate their impact on the CPU and RAM resources, with respect to type of Internet connection. The paper consists of two parts: theoretical and research. The first part provides a description of current means of wireless communication, including transmission of multimedia in Wi-Fi and cellular systems, as well as principles of operation of popular streaming media available on the marked, including utilized coding algorithm and available bitrates. The second part describes the set of utilized consumer devices, including 50 smartphones, as well as tools, laboratory equipment, and research scenarios. Results of this study may aid both researchers and professionals involved in the digital mobile market, including content and service providers, as well as network operators.

  • Study on Dry Sliding Wear and Friction Behaviour of Al7068/Si3N4/BN Hybrid Composites
    • Kumar Subramanian
    • Sakthivel Murugesan
    • Dhanesh G. Mohan
    • Jacek Tomków
    2021 Full text Materials

    Hybrid aluminium metal matrix composites have the potential to replace single reinforced aluminium metal matrix composites due to improved properties. Moreover, tribological performance is critical for these composites, as they have extensive application areas, such as the automotive, aerospace, marine and defence industries. The present work aims to establish the tribological characteristics of Al7068/Si3N4/BN hybrid metal matrix composites prepared by stir casting route and studied using a pin-on-disc apparatus under dry sliding conditions. The hybrid composite samples were prepared at various weight percentages (0, 5, 10) of Si3N4 and BN particles. To investigate the tribological performance of the prepared composites, the wear experiments were conducted by varying the load (20, 40 and 60 N), sliding velocity (1.5, 2.5 and 3.5 m/s) and sliding distance (500, 1000 and 1500 m). Wear experimental runs were carried out based on the plan of experiments proposed by Taguchi. The minimum wear rate was found with the composite material reinforced with 10 wt. % of Si3N4 and 5 wt. % of BN. Analysis of Variance (ANOVA) was employed to analyse the effect of process parameters on wear rate and coefficient of friction (COF). The ANOVA test revealed that the weight fraction of Si3N4 has more of a contribution percentage (36.60%) on wear rate, and load has more of a contribution percentage (29.73%) on COF. The worn-out surface of the wear test specimens was studied using its corresponding SEM micrograph and correlated with the dry sliding wear experiment results.

  • Study on Microstructural Characterization, Mechanical Properties and Residual Stress of GTAW Dissimilar Joints of P91 and P22 Steels
    • Anupam Sauraw
    • Atul Kumar Sharma
    • Dariusz Fydrych
    • Sachin Sirohi
    • Ankur Gupta
    • Aleksandra Świerczyńska
    • Chandan Pandey
    • Grzegorz Rogalski
    2021 Full text Materials

    This article deals with the dissimilar joining of two different grade Cr-Mo steel (2.25Cr-1Mo: P22 and modified 9Cr-1Mo: P91) for power plant application. The dissimilar butt-welded joint was produced for conventional V groove design by using the gas tungsten arc welding (GTAW) process with the application of an ERNiCrMo-3 Ni-based super alloy filler. A microstructure characterization was performed to measure the inhomogeneity in the microstructure and element diffusion across the interface in a welded joint. The experiments were also performed to evaluate the mechanical properties of the dissimilar welded joint in as-welded (AW) and post-weld heat treatment (PWHT) conditions. An acceptable level of the mechanical properties was obtained for the AW joint. After PWHT, a significant level of the element diffusion across the interface of the weld metal and P22 steel was observed, resulting in heterogeneity in microstructure near the interface, which was also supported by the hardness variation. Inhomogeneity in mechanical properties (impact strength and hardness) was measured across the weldments for the AW joint and was reduced after the PWHT. The tensile test results indicate an acceptable level of tensile properties for the welded joint in both AW and PWHT conditions and failure was noticed in the weak region of the P22 steel instead of the weld metal.

  • Study on Microstructure and Mechanical Properties of Laser Welded Dissimilar Joint of P91 Steel and INCOLOY 800HT Nickel Alloy
    • Vishwa Bhanu
    • Dariusz Fydrych
    • Ankur Gupta
    • Chandan Pandey
    2021 Full text Materials

    This investigation attempts to explore the weld characteristics of a laser welded dissimilar joint of ferritic/martensitic 9Cr-1Mo-V-Nb (P91) steel and Incoloy 800HT austenitic nickel alloy. This dissimilar joint is essential in power generating nuclear and thermal plants operating at 600–650 °C. In such critical operating conditions, it is essential for a dissimilar joint to preserve its characteristics and be free from any kind of defect. The difference between the physical properties of P91 and Incoloy 800HT makes their weldability challenging. Thus, the need for detailed characterization of this dissimilar weld arises. The present work intends to explore the usage of an unconventional welding process (i.e., laser beam welding) and its effect on the joint’s characteristics. The single-pass laser welding technique was employed to obtain maximum penetration through the keyhole mode. The welded joint morphology and mechanical properties were studied in as-welded (AW) and post-weld heat treatment (PWHT) conditions. The macro-optical examination shows the complete penetrations with no inclusion and porosities in the weld. The microstructural study was done in order to observe the precipitation and segregation of elements in dendritic and interface regions. Solidification cracks were observed in the weld fusion zone, confirming the susceptibility of Incoloy 800HT to such cracks due to a mismatch between the melting point and thermal conductivity of the base metals. Failure from base metal was observed in tensile test results of standard AW specimen with a yield stress of 265 MPa, and after PWHT, the value increased to 297 MPa. The peak hardness of 391 HV was observed in the P91 coarse grain heat-affected zone (CGHAZ), and PWHT confirmed the reduction in hardness. The impact toughness results that were obtained were inadequate, as the maximum value of impact toughness was obtained for AW P91 heat-affected zone (HAZ) 108 J and the minimum for PWHT Incoloy 800HT HAZ 45 J. Thus, difficulty in obtaining a dissimilar joint with Incoloy 800HT using the laser beam welding technique was observed due to its susceptibility to solidification cracking.

  • Study on Speech Transmission under Varying QoS Parameters in a OFDM Communication System
    • Monika Zamłyńska
    • Przemysław Falkowski-Gilski
    • Grzegorz Debita
    • Bogdan Miedziński
    2021

    Although there has been an outbreak of multiple multimedia platforms worldwide, speech communication is still the most essential and important type of service. With the spoken word we can exchange ideas, provide descriptive information, as well as aid to another person. As the amount of available bandwidth continues to shrink, researchers focus on novel types of transmission, based most often on multi-valued modulations, multiple channels and related sub-carriers. Currently, OFDM (Orthogonal Frequency Division Multiplexing) is widely utilized both in wired and wireless transmission. It includes terrestrial and online digital services, such as cellular systems and broadcasting standards. This paper is focused on varying QoS (Quality of Service) aspects, related with the OFDM telecommunication system, with respect to speech signals. It involves a group of four language sets, namely: American English, British English, German, and Polish. Results of this study may aid both researchers and professionals involved in designing everyday communication services as well as supplementary back-up services.

  • Study on Strategy in University Laboratory Class Teaching
    • Edward Szczerbicki
    • Haoxi Zhang
    2021 Full text

    Laboratory teaching is a critical way to ensure the effective input of techniques in engineering learning. Laboratory teaching not only contributes to improving course quality but also helps enrich comprehensive engineering application ability. However, there are some typical problems in current university laboratory teaching, such as rigid and isolated course design, outdated contents and materials, and not encouraging innovation and real-world problem solving. To overcome these challenges, a three-step teaching reconstruction strategy has been proposed to enhance university educators’ teaching effects, including introduce new laboratory teaching methods, updating contents and materials, and organizing innovative and multi-discipline Learning. Through efforts made by university teachers, students, and industry partners, the goal can be achieved by following the proposed strategy