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Gdańsk University of Technology

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Publications from the year 2018

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  • The validation process of truss model with joint eccentricities
    • Małgorzata Gordziej-Zagórowska
    • Elżbieta Urbańska-Galewska
    • Łukasz Pyrzowski
    2018

    Nowadays, due to the technological reasons in modern lightweight steel trusses, fabricated from cold-formed sections, positive eccentricities appear in the truss nodes, to induce additional forces truss chords. In order to account for the real load-carrying capacity of truss node area the steel structure research was conducted in scale 1:1. As a result of experimental research, the forms of deformation and strains of the walls of the chord made of the hat section in the area of the analyzed joint was determined. The experimental results from the basis for the numerical model validation was presented in the paper.

  • The σ-phase superconductors Nb20.4Rh5.7Ge3.9 and Nb20.4Rh5.7Si3.9
    • Elizabeth M. Carnicom
    • Tai Kong
    • Tomasz Klimczuk
    • R.j. Cava
    2018 SOLID STATE COMMUNICATIONS

    We show that the previously unreported ternary σ phases Nb20.4Rh5.7Ge3.9 and Nb20.4Rh5.7Si3.9 are both superconductors with Tc values of approximately 1.9 K. The superconducting transitions were characterized through temperature-dependent magnetic susceptibility, electrical resistance, and specific heat measurements. The Sommerfeld constants, γ, for Nb20.4Rh5.7Ge3.9 and Nb20.4Rh5.7Si3.9 are 89(1) mJ mol-f.u.−1K−2 and 86(1) mJ mol-f.u.−1K−2 (about 3.0 and 2.9 mJ mol-atom−1 K−2), respectively. The normalized specific heat jumps at Tc, ΔC/γTc, are approximately 1.39 for Nb20.4Rh5.7Ge3.9 and 1.30 for Nb20.4Rh5.7Si3.9, consistent with both materials being weakly coupled BCS type superconductors.

  • Thematic Areas in the Polish Countryside and Their Role in Local Development
    • Anna Górka
    2018

    The article defines the phenomenon of space thematisation with regards to rural areas in Poland. The typology of thematic spaces and criteria of their comparative description have been proposed. Thematic villages, home gardens, amusement parks and housing estates have been distinguished. They have been compared in terms of spatial availability, the degree of user participation and the commercial vs. non-commercial creation purpose. The indicated factors were considered decisive for the sustainability of the thematic project in public space and thus for the degree of its participation in local development. The conclusions indicate poor use of the potential resulting from the material resources of the rural, cultural heritage in the process of thematisation. This translates into high variability and lability of thematic projects, which means their limited impact on improving the quality of life. The significance of the features of local architecture and native greenery was emphasized as visual differentiators for building a permanent image of the town, the identity of its inhabitants and the rural economy. The conclusion has been based on participatory observation, literature review and internet query.

  • Theoretical Investigation of the Electron-Transfer Dynamics and Photodegradation Pathways in a Hydrogen-Evolving Ruthenium-Palladium Photocatalyst
    • Magdalena Staniszewska
    • Stephan Kupfer
    • Julien Guthmuller
    2018 Full text CHEMISTRY-A EUROPEAN JOURNAL

    Time-dependent density functional theory calcula- tions combinedwith the Marcus theory of electron transfer (ET) were app lied on the molecular photocatalys t [(tbbpy) 2 Ru(tpph z)PdC l 2 ] 2 + in order to elucidate thelight-in- duced relaxation pathways populated upon excitation in the longer wavelength range of its absorption spectrum. The computational resultsshow that after the initial excitation, metal (Ru) to ligand (tpphz)chargetransfer (MLCT) triplet states are energeticallyaccessible, but that an ET towardthe catalytic center(PdCl 2 )from thesestates is aslow process, with estimated time constantsabove 1ns. Instead, the cal- culations predict that low-lying Pd-centered states are effi- ciently populated—assoc iated to an energy transfer toward the catalytic center.Thus,itispostulated that thesestates lead to the dissociation of aCl @ and are consequently re- sponsible for the experimentally observed degradation of the catalytic center.Following dissociation, it is shown that the ET rates from the MLCT states to the charge separated statesare significantly increased (i.e. 10 4 –10 6 timeslarger). This demonstrates that alteration of the catalytic center gen- eratesefficientchargeseparation.

  • Thermal and Chemical Expansion in Proton Ceramic Electrolytes and Compatible Electrodes
    • Andreas Løken
    • Sandrine Ricote
    • Sebastian Lech Wachowski
    2018 Full text Crystals

    This review paper focuses on the phenomenon of thermochemical expansion of two specific categories of conducting ceramics: Proton Conducting Ceramics (PCC) and Mixed Ionic-Electronic Conductors (MIEC). The theory of thermal expansion of ceramics is underlined from microscopic to macroscopic points of view while the chemical expansion is explained based on crystallography and defect chemistry. Modelling methods are used to predict the thermochemical expansion of PCCs and MIECs with two examples: hydration of barium zirconate (BaZr1−xYxO3−δ) and oxidation/reduction of La1−xSrxCo0.2Fe0.8O3−δ. While it is unusual for a review paper, we conducted experiments to evaluate the influence of the heating rate in determining expansion coefficients experimentally. This was motivated by the discrepancy of some values in literature. The conclusions are that the heating rate has little to no effect on the obtained values. Models for the expansion coefficients of a composite material are presented and include the effect of porosity. A set of data comprising thermal and chemical expansion coefficients has been gathered from the literature and presented here divided into two groups: protonic electrolytes and mixed ionic-electronic conductors. Finally, the methods of mitigation of the thermal mismatch problem are discussed

  • Thermal and hydraulic phenomena in boundary layer of minijets impingement on curved surfaces
    • Tomasz Kura
    • Elżbieta Fornalik-Wajs
    • Jan Wajs
    2018 Full text Archives of Thermodynamics

    Presented work considers flow and thermal phenomena occurring during the single minijet impingement on curved surfaces, heated with a constant heat flux, as well as the array of minijets. Numerical analyses, based on the mass, momentum and energy conservation laws, were conducted, regarding single phase and two-phase simulations. Focus was placed on the proper model construction, in which turbulence and boundary layer modeling was crucial. Calculations were done for various inlet parameters. Initial single minijet results served as the basis for the main calculations, which were conducted for two jet arrays, with flat and curved heated surfaces. Such complex geometries came from the cooling systems of electrical devices, and the geometry of cylindrical heat exchanger. The results, regarding Nusselt number, heated surface temperature, turbulence kinetic energy, production of entropy and vorticity, were presented and discussed. For assumed geometrical parameters similar results were obtained.

  • Thermal and physical properties of ZrO2–AlO(OH) nanopowders synthesised by microwave hydrothermal method
    • Iwona Koltsov
    • Marta Prześniak-Welenc
    • Jacek Wojnarowicz
    • Anna Rogowska
    • Jan Mizeracki
    • Maria Malysa
    • Giora Kimmel
    2018 Full text JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY

    Industrially relevant nanopowder was synthesised by microwave hydrothermal synthesis to obtain well-controlled composition (ZrO2–AlO(OH) system) which was found to determine a number of physical and thermal characteristics. This study reports variation of particle size, density, specific surface area (SSABET), as well as thermal behaviour of nanopowder mixtures of ZrO2–AlO(OH) in the whole range of compositions. It was found that the onset temperature (Ton) of physically and chemically bounded water desorption depends on the Al3+/or AlO(OH) content. The lower content of Al3+ in the ZrO2–AlO(OH) system, the higher Ton of physically bound water desorption. There are three distinct temperature regions for water decomposition for nanomaterials investigated in air (at approximately 50, 250 and 450 °C). These temperature ranges depend on particle size and chemical composition of ZrO2–AlO(OH) nanopowders. Materials were divided into three groups characterised by different properties: (1) ZrO2 with 2–12% of Al3+, where particle sizes are from 4 to 8 nm, (2) ZrO2 with 30–67% of AlO(OH), where particle sizes are from 10 to 13 nm, and (3) ZrO2 with 80–99% of AlO(OH), where particle sizes are from 13 to 23 nm. AlO(OH) content determines thermal and physico-chemical properties of synthesised ZrO2–AlO(OH) nanopowders.

  • Thermal boundary conditions to simulate friction layers and coatings at sliding contacts
    • Oleksii Nosko
    2018 Full text INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER

    A brief review of the thermal boundary conditions specified at sliding interfaces was performed. New thermal boundary conditions were derived aimed at solving problems of sliding with account of surface layers representing friction layers and tribological coatings. Based on the assumption of linear temperature distributions in the surface layers, the proposed conditions enable one to simplify simulations by eliminating the surface layers from consideration and merging thermally the bulk bodies. A problem of non-stationary heat conduction in two sliding semispaces with the proposed conditions at their interface was solved analytically. The particular cases of the solution were shown to coincide with the exact temperature expressions obtained for different well-known boundary conditions. The temperature influence of the basic parameters was analysed in dimensionless form on example of a decelerative sliding between a semispace covered with a surface layer and a semispace of constant temperature. An estimation of the error introduced by the proposed conditions was done. It was found that the error is below 1% for a wide class of friction layers and coatings met in practice.

  • Thermal degradation kinetics of poly(propylene succinate) prepared with the use of natural origin monomers
    • Paulina Parcheta
    • Iwona Koltsov
    • Ewa Głowińska
    • Janusz Datta
    2018 Full text Polimery

    Linear biobased polyester polyols were prepared with the use of succinic acid and 1,3-pro- panediol (both with natural origin). Tetraisopropyl orthotitanate (TPT) was used as a catalyst. In order to determine the effect of various synthesis temperature conditions on the thermal degradation kinet- ics, nine sequences of temperature conditions were used during two-step polycondensation reaction. Thermogravimetric analysis was conducted with the use of DSC-TG/QMS method (differential scanning calorimetry-coupled with thermogravimetry and quadrupole mass spectrometry). The results indicated high thermal stability of the obtained materials. They undergo a one-step thermal decomposition with the temperature of maximum rate of weight loss at ca. 405 °C. Moreover, the thermal degradation kinet- ics was determined with the use of Ozawa, Flynn and Wall as well as Kissinger methods. The highest thermal degradation activation energy was equal to 196.4 kJ/mol.

  • Thermal energy storage using stearic acid as PCM material
    • Janusz Cieśliński
    • Maciej Fabrykiewicz
    2018 Full text Journal of Mechanical and Energy Engineering

    This work presents an experimental study of thermal energy storage by use of PCM. The aim of the study was to establish the influence of different inlet temperature of heat transfer fluid (HTF) and different Reynolds number of HTF on intensity of charging process. The PCM used in this study was stearic acid and water was used as HTF. A copper helical coil mounted in cylindrical container served as a heat transfer surface.

  • Thermo-Chemical Decomposition Study of Polyurethane Elastomer Through Glycerolysis Route with Using Crude and Refined Glycerine as a Transesterification Agent
    • Janusz Datta
    • Patrycja Jutrzenka Trzebiatowska
    • Diego Simón
    • Juan F. Rodríguez
    2018 Full text JOURNAL OF POLYMERS AND THE ENVIRONMENT

    Due to the increasing amount of polyurethane waste, chemical recycling of these materials is a topic of growing interest for many researchers. The primary pur- pose of polyurethane feedstock recycling is to recover the starting polyol. In this study glycerolysis using glycerine from two sources and two purity grades is proposed as a method of chemical recycling. The main effort of this paper focuses on the employment of commercial glycerine of analytical grade and waste glycerine without purification derived from the biodiesel production, as a decomposing agent for polyurethane recycling. In this study, the influ- ence of polyurethane to glycerine mass ratio (PU/GL) and the type of decomposing agent on the chemical structure by FTIR, 1H NMR and GPC was examined. FTIR analy- sis of the glycerolysates showed absorption peaks similar to the virgin polyol. Those results are in compliance with GPC chromatograms, which showed for all samples, well- defined peak at ca. 13 min of retention time. The molec- ular weight of glycerolysates was ranging from 800 to 1300 g mol−1 depending on PU/GL mass ratio. The novel decomposition agent, namely waste glycerine derived from biodiesel production was successfully used in glycerolysis process.

  • Thermodynamic, Anticoagulant, and Antiproliferative Properties of Thrombin Binding Aptamer Containing Novel UNA Derivative
    • Weronika Kotkowiak
    • Jolanta Lisowiec-Wachnicka
    • Jakub Grynda
    • Ryszard Kierzek
    • Jesper Wengel
    • Anna Pasternak
    2018 Full text Molecular Therapy-Nucleic Acids

    Thrombin is a serine protease that plays a crucial role in hemostasis, fibrinolysis, cell proliferation, and migration. Thrombin binding aptamer (TBA) is able to inhibit the activity of thrombin molecule via binding to its exosite I. This 15-nt DNA oligonucleotide forms an intramolecular, antiparallel G-quadruplex structure with a chair-like conformation. In this paper, we report on our investigations on the influence of certain modified nucleotide residues on thermodynamic stability, folding topology, and biological properties of TBA variants. In particular, the effect of single incorporation of a novel 4-thiouracil derivative of unlocked nucleic acid (UNA), as well as single incorporation of 4-thiouridine and all four canonical UNAs, was evaluated. The studies presented herein have shown that 4-thiouridine in RNA and UNA series, as well as all four canonical UNAs, can efficiently modulate G-quadruplex thermodynamic and biological stability, and that the effect is strongly position dependent. Interestingly, TBA variants containing the modified nucleotide residues are characterized by unchanged folding topology. Thrombin time assay revealed that incorporation of certain UNA residues may improve G-quadruplex anticoagulant properties. Noteworthy, some TBA variants, characterized by decreased ability to inhibit thrombin activity, possess significant antiproliferative properties reducing the viability of the HeLa cell line even by 95% at 10 μM concentration.

  • Thermoplastic Elastomers Filled With GTR
    • Krzysztof Formela
    • Józef Haponiuk
    • Shifeng Wang
    • Xavier Colom
    2018

    In recent years, searching for new and cost-effective methods of recycling waste tires has been a subject of research in many laboratories worldwide. This is due to regulations in the law and environmental factors, which have both stimulated industry to re-use high quality rubber found in ground tire rubber (GTR). One of the most promising solutions in this area seems to be thermoplastic elastomers (TPEs) filled with GTR, which are economical and a pro-ecological alternative for commercially available TPEs. This chapter describes the recent advances in processing and characterization of thermoplastic elastomers filled with GTR. Special attention has been focused on the structure–properties relationships and compatibilization strategies of the studied TPEs. Moreover, the future trends in the development of TPEs filled with GTR are proposed and discussed.

  • Threats to Rural Landscape and Its Protection in Poland
    • Anna Górka
    2018 Full text Environments

    The article describes the premises and conditions for the implementation of a pro-landscape spatial policy in rural areas in Poland. It presents the erosion of spatial order in a large part of the country’s territory. Firstly, the state of protection of the rural landscape and the legal aspects of shaping the space of rural areas are described. Secondly, the location is depicted, and the main physiognomic and environmental threats in the rural areas are discussed. It is then questioned whether the statutory regulations that have been introduced into the spatial planning system and adapt the Polish law to the requirements of the European Landscape Convention will stop the degradation of the landscape. Deep systemic changes are needed, as they will lead to the involvement of public policy in shaping the landscape and the introduction of tools and procedures for the management of visual landscape resources. They would constitute a convenient space for mediation in the relations between actors operating in space and an open knowledge laboratory of the environment, which would be useful in the participatory planning process. The presented arguments and conclusions result from the review and analysis of research results, which are mainly in the field of landscape protection and rural area management.

  • Three levels of fail-safe mode in MPI I/O NVRAM distributed cache
    • Artur Malinowski
    • Paweł Czarnul
    2018 Full text Procedia Computer Science

    The paper presents architecture and design of three versions for fail-safe data storage in a distributed cache using NVRAM in cluster nodes. In the first one, cache consistency is assured through additional buffering write requests. The second one is based on additional write log managers running on different nodes. The third one benefits from synchronization with a Parallel File System (PFS) for saving data into a new file which allows to keep file history at the cost of space. We have shown that the three level fail-safe mode incorporating these versions does introduce minimal overhead for a random walk microbenchmark application for a 1GB file and checkpoints created every 2000 iterations, computing powers of a graph with 10000 vertices and up to 20% overhead for parallel processing of images up to 1000 megapixels compared to the basic NVRAM cache without fail-safe modes. We also presented times for checkpoint creation and restoring for sizes up to 10GBs.

  • Three-dimensional geographically weighted inverse regression (3GWR) model for satellite derived bathymetry using Sentinel-2 observations
    • Andrzej Chybicki
    2018 Full text MARINE GEODESY

    Current trends of development of satellite derived bathymetry (SDB) models rely on applying calibration techniques including analytical approaches, neuro-fuzzy systems, regression optimization and others. In most of the cases, the SDB models are calibrated and verified for test sites, that provide favourable conditions for the remote derivation of bathymetry such as high water clarity, homogenous bottom type, low amount of sediment in the water and other factors. In this paper, a novel 3-dimensional geographical weighted regression (3GWR) SDB technique is presented, it binds together methods already presented in other studies, the geographically weighted local regression (GWR) model, with depth dependent inverse optimization. The proposed SDB model was calibrated and verified on a relatively difficult test site of the South Baltic near-shore areas with the use of multispectral observations acquired by a recently launched Sentinel-2 satellite observation system. By conducted experiments, it was shown that the proposed SDB model is capable of obtaining satisfactory results of RMSE ranging from 0.88 to 1.23[m] depending on the observation and can derive bathymetry for depths up to 12m. It was also shown, that the proposed approach may be used operationally, for instance, in the continuous assessment of temporal bathymetry changes, for areas important in the context of ensuring local maritime safety.

  • Three-objective antenna optimization by means of kriging surrogates and domain segmentation
    • Sławomir Kozieł
    • Adrian Bekasiewicz
    2018 Full text

    In this paper, an optimization framework for multi-objective design of antenna structures is discussed which exploits data-driven surrogates, a multi-objective evolutionary algorithm, response correction techniques for design refinement, as well as generalized domain segmentation. The last mechanism is introduced to constrain the design space region subjected to sampling, which permits reduction of the number of training data samples required for surrogate model identification. The generalized segmentation technique works for any number of design objectives. Here, it is demonstrated using a three-objective case study of a UWB monopole optimized for best in-band reflection, minimum gain variability, and minimum size. The numerical results indicate that segmentation leads to reducing the cost of initial Pareto identification by around 21 percent as compared to the conventional surrogate-assisted approach.

  • Threshold Attendance under Soft-Crash Model: TAG Protocol and Markovian Analysis
    • Jerzy Konorski
    2018 Full text

    A realistic and systematic network evaluation should subsume an availability model and a failure model. We combine a "hard availability" model we call threshold attendance, whereby a certain minimum number of network elements must be present at any time, with a soft-crash failure model, whereby after experiencing a failure, a network element is still able to function correctly for a while in an emergency mode at a risk of a major crash. A Threshold Attendance Guarantee (TAG) protocol, earlier studied from a security viewpoint, is deployed to ensure threshold attendance while controlling the duration of the emergency mode. We study the network under TAG using an "isolated" node-type Markovian analysis, offering insights into the tradeoffs between some relevant availability and reliability characteristics, and showing a simple model-free way to account for a positive correlation between the network elements' behavior that can reflect mass disasters.

  • Tight bounds on the complexity of semi-equitable coloring of cubic and subcubic graphs
    • Hanna Furmańczyk
    • Marek Kubale
    2018 Full text DISCRETE APPLIED MATHEMATICS

    We consider the complexity of semi-equitable k-coloring, k>3, of the vertices of a cubic or subcubic graph G. In particular, we show that, given a n-vertex subcubic graph G, it is NP-complete to obtain a semi-equitable k-coloring of G whose non-equitable color class is of size s if s>n/3, and it is polynomially solvable if s, n/3.

  • Timber frame houses resistant to dynamic loads - seismic analysis
    • Marcin Szczepański
    • Wojciech Migda
    2018 Full text MATEC Web of Conferences

    The aim of the article is to present results of seismic analysis results of two real-sized timber frame buildings subjected to seismic excitations. The first model was insulated with mineral wool, the second one with polyurethane foam. Technology and specifications involved in both models construction is based on the previously conducted experimental research on timber frame houses, including wall panels tests, wall numerical models and study on material properties and precisely reflect results of the those research. During the seismic analysis reference node located in buildings were selected. In selected node displacement values were measured and compared between two analyzed models. The results of the numerical analysis presented in the article indicate that the application of polyurethane foam for a skeleton filling of the timber-frame building leads to the increase in stiffness as well as damping of the whole structure, which results in a considerable increase in the seismic resistance of the structure.