Repozytorium publikacji - Politechnika Gdańska

Ustawienia strony

english
Repozytorium publikacji
Politechniki Gdańskiej

Pokaż publikacje z roku

Ostatnie pozycje

  • Exhaled breath analysis by resistive gas sensors
    • Tomasz Chludziński
    • Andrzej Kwiatkowski
    2020 Pełny tekst Metrology and Measurement Systems

    Breath analysis has attracted human beings for centuries. It was one of the simplest methods to detect various diseases by using human smell sense only. Advances in technology enable to use more reliable and standardized methods, based on different gas sensing systems. Breath analysis requires the detection of volatile organic compounds (VOCs) of the concentrations below individual ppm (parts per million). Therefore, advanced detection methods have been proposed. Some of these methods use expensive and bulky equipment (e.g. optical sensors, mass spectrometry – MS), and require time-consuming analysis. Less accurate, but much cheaper, are resistive gas sensors. These sensors use porous materials and adsorptiondesorption processes, determining their physical parameters. We consider the problems of applying resistive gas sensors to breath analysis. Recent advances were underlined, showing that these economical gas sensors can be efficiently employed to analyse breath samples. General problems of applying resistive gas sensors are considered and illustrated with examples, predominantly related to commercial sensors and their long-term performance. A setup for collection of breath samples is considered and presented to point out the crucial parts and problematic issues.

  • Expedited antenna optimization with numerical derivatives and gradient change tracking
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    2020 Pełny tekst ENGINEERING COMPUTATIONS

    Design automation has been playing an increasing role in the development of novel antenna structures for various applications. One of its aspects is electromagnetic (EM)-driven design closure, typically applied upon establishing the antenna topology, and aiming at adjustment of geometry parameters to boost the performance figures as much as possible. Parametric optimization is often realized using local methods given usually reasonable quality of the initial designs obtained at the topology evolution stage. The major difficulty here is high computational cost associated with a large number of EM simulations required by conventional methods, both gradient and derivative-free routines. Possible workarounds including surrogate-assisted variable-fidelity methods (e.g., space mapping) face similar problems because the underlying low-fidelity model is often optimized directly. This paper proposes an expedited version of the trust-region (TR) gradient-based algorithm with numerical derivatives. A considerable reduction of the number of EM simulations is achieved by monitoring the behavior of the gradient throughout the algorithm run and omitting the finite-differentiation updates upon detecting stable patterns for particular parameter sensitivities. The proposed approach is benchmarked against the standard TR algorithm as well as the recently reported accelerated TR frameworks. Improved performance is consistently demonstrated for all considered test cases.

  • Expedited Design Closure of Antenna Input Characteristics by Trust Region Gradient Search and Principal Component Analysis
    • Jon Tomasson
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2020 Pełny tekst IEEE Access

    Optimization-based parameter tuning has become an inherent part of contemporary antenna design process. For the sake of reliability, it is typically conducted at the level of full-wave electromagnetic (EM) simulation models. This may incur considerable computational expenses depending on the cost of an individual EM analysis, the number of adjustable variables, the type of task (local, global, single-/multi-objective optimization), and the constraints involved. For these reasons, utilization of conventional algorithms is often impractical. This paper proposes a novel gradient-based algorithm with numerical derivatives for expedited antenna optimization. The improvement of computational efficiency is obtained by employing a rank-one Broyden formula and restricting finite differentiation sensitivity updates to the principal directions of the Jacobian matrix, i.e., those corresponding to the most significant changes of the antenna responses. Comprehensive numerical validation carried out using three wideband antennas indicates that the presented methodology offers considerable savings of sixty percent with respect to the reference trust-region algorithm. At the same time, virtually no degradation of the design quality is observed. Furthermore, algorithm reliability is greatly improved (while offering comparable computational efficiency) over the recent state-of-the-art accelerated gradient-based procedures.

  • Expedited Feature-Based Quasi-Global Optimization of Multi-Band Antenna Input Characteristics with Jacobian Variability Tracking
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2020 Pełny tekst IEEE Access

    Design of modern antennas relies—for reliability reasons—on full-wave electromagnetic simulation tools. In addition, increasingly stringent specifications pertaining to electrical and field performance, growing complexity of antenna topologies, along with the necessity for handling multiple objectives, make numerical optimization of antenna geometry parameters a highly recommended design procedure. Conventional algorithms, particularly global ones, entail often-unmanageable computational costs, so alternative approaches are needed. This work proposes a novel method for cost-efficient globalized design optimization of multi-band antennas incorporating the response feature technology into the trustregion framework. It allows for unequivocal allocation of the antenna resonances even for poor initial designs, where conventional local algorithms fail. Furthermore, the algorithm is accelerated by means of Jacobian variability tracking, which reduces the number of expensive finite-differentiation updates. Two real-world antenna design cases are used for demonstration purposes. The optimization cost is comparable to that of local routines while ensuring nearly global search capabilities.

  • Expedited Globalized Antenna Optimization by Principal Components and Variable-Fidelity EM Simulations: Application to Microstrip Antenna Design
    • Jon Tomasson
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    2020 Pełny tekst Electronics

    Parameter optimization, also referred to as design closure, is imperative in the development of modern antennas. Theoretical considerations along with rough dimension adjustment through supervised parameter sweeping can only yield initial designs that need to be further tuned to boost the antenna performance. The major challenges include handling of multi-dimensional parameter spaces while accounting for several objectives and constraints. Due to complexity of modern antenna topologies, parameter interactions are often involved, leading to multiple local optima as well as difficulties in identifying decent initial designs that can be improved using local procedures. In such cases, global search is required, which is an expensive endeavor, especially if full-wave electromagnetic (EM) analysis is employed for antenna evaluation. This paper proposes a novel technique accommodating the search space exploration using local kriging surrogates and local improvement by means of trust-region gradient search. Computational efficiency of the process is achieved by constructing the metamodels over appropriately defined affine subspaces and incorporation of coarse-mesh EM simulations at the exploratory stages of the optimization process. The resulting framework enables nearly global search capabilities at the costs comparable to conventional gradient-based local optimization. This is demonstrated using two antenna examples and comparative studies involving multiple-start local tuning.

  • Expedited optimization of antenna input characteristics with adaptive Broyden updates
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2020 Pełny tekst ENGINEERING COMPUTATIONS

    Simulation-driven adjustment of geometry and/or material parameters is a necessary step in the design of contemporary antenna structures. Due to their topological complexity, other means, such as supervised parameter sweeping, does not usually lead to satisfactory results. On the other hand, rigorous numerical optimization is computationally expensive due to a high cost of underlying full-wave electromagnetic (EM) analyses, otherwise required to assess antenna performance in a reliable manner. Design closure normally requires a local search, often carried out by means of gradient-based procedures. In this work, accelerated trust-region gradient-search algorithm is proposed for expedited optimization of antenna structures. In our approach, finite differentiation conventionally used to estimate the antenna response Jacobian is replaced, for selected variables, by a rank-one Broyden updating formula. The selection of variables is governed by the alignment between the direction of the recent design relocation and the coordinate system axes. Operation and performance of the algorithm is demonstrated using a set of benchmark wideband antennas. Comprehensive numerical validation indicates significant computational savings of up to 70 percent that can be achieved without compromising the design quality in a significant manner.

  • Expedited Yield Optimization of Narrow- and Multi-Band Antennas Using Performance-Driven Surrogates
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    • Muath Al-hasan
    2020 Pełny tekst IEEE Access

    Uncertainty quantification is an important aspect of engineering design, also pertaining to the development and performance evaluation of antenna systems. Manufacturing tolerances as well as other types of uncertainties, related to material parameters (e.g., substrate permittivity) or operating conditions (e.g., bending) may affect the antenna characteristics. In the case of narrow- or multi-band antennas, this usually leads to frequency shifts of the operating bands. Quantifying these effects is imperative to adequately assess the design quality, either in terms of the statistical moments of the performance parameters or the yield. Reducing the antenna sensitivity to parameter deviations is even more essential when increasing the probability of the system satisfying the prescribed requirements is of concern. The prerequisite of such procedures is statistical analysis, normally carried out at the level of full-wave electromagnetic (EM) analysis. While necessary to ensure reliability, it entails considerable computational expenses, often prohibitive. Following the recently fostered concept of constrained modeling, this paper proposes a simple technique for rapid surrogate-assisted yield optimization of narrow- and multi-band antennas. The keystone of the approach is an appropriate definition of the optimization domain. This is realized by considering a few pre-optimized designs that represent the directions of the major changes of the antenna resonant frequencies and operating bands. Due to a small volume of such a domain, an accurate replacement model can be established therein using a small number of training samples, and employed to improve the antenna yield. Verification results obtained for a ring-slot antenna, a dual-band and a triple-band uniplanar dipoles indicate that the optimization process can be accomplished at low cost of a few dozen of EM simulations: 62, 74 and 132 EM simulations, respectively. Result reliability is validated through comparisons with EM-based Monte Carlo simulations.

  • Experience Based Clinical Decision Support Systems: An Overview and Case Studies
    • Carlos Toro
    • Manuel Grana
    • Eider Sanchez
    • Cesar Sanin
    • Edward Szczerbicki
    2020

    This chapter briefly overviews the evolution of the application of the Decisional DNA and the Set of Experience Knowledge Structure (SOEKS) in the medical domain and in particular in the specific case of the experience-based decision support systems. Decisional DNA, as a knowledge representation structure, offers great possibilities on gathering explicit knowledge of formal decision events as well as a tool for decision making processes. The chapter collates more than 10 years of continuous application of the aforesaid techniques into the medical domain in particular for supporting the clinical decision scenario.

  • Experience-Based Cognition for Driving Behavioral Fingerprint Extraction
    • Haoxi Zhang
    • Fei Li
    • Juan Wang
    • Yang Zhou
    • Cesar Sanin
    • Edward Szczerbicki
    2020 Pełny tekst CYBERNETICS AND SYSTEMS

    ABSTRACT With the rapid progress of information technologies, cars have been made increasingly intelligent. This allows cars to act as cognitive agents, i.e., to acquire knowledge and understanding of the driving habits and behavioral characteristics of drivers (i.e., driving behavioral fingerprint) through experience. Such knowledge can be then reused to facilitate the interaction between a car and its driver, and to develop better and safer car controls. In this paper, we propose a novel approach to extract the driver’s driving behavioral fingerprints based on our conceptual framework Experience-Oriented Intelligent Things (EOIT). EOIT is a learning system that has the potential to enable Internet of Cognitive Things (IoCT) where knowledge can be extracted from experience, stored, evolved, shared, and reused aiming for cognition and thus intelligent functionality of things. By catching driving data, this approach helps cars to collect the driver’s pedal and steering operations and store them as experience; eventually, it uses obtained experience for the driver’s driving behavioral fingerprint extraction. The initial experimental implementation is presented in the paper to demonstrate our idea, and the test results show that it outperforms the Deep Learning approaches (i.e., deep fully connected neural networks and recurrent neural networks/Long Short-Term Memory networks).

  • Experimental analysis of wear resistance of compacts of fine-dispersed iron powder and tungsten monocarbide nanopowder produced by impulse pressing
    • Anatoly Bragov
    • Leonid Igumnov
    • Alexander Konstantinov
    • Andrey Lomunov
    • Evgeny Rusin
    • Victor Eremeev
    2020 Pełny tekst WEAR

    The paper presents the results of studying the structure and wear resistance of compacts produced from fine dispersed reduced iron powder (average particle size 3–mu m) with the addition of tungsten carbide (WC) nanopowder with the average particle size of 25–30 nm. The mass fraction of tungsten carbide (wolfram carbide) in the powder composition was 5% and 10% of the total mass. Impulse pressing was conducted using the modified Kolsky method at compacting temperatures of 20 °C to 300 °C. The produced compacts had relative density of over 90%.

  • Experimental and computational study on mechanical behaviour of carpentry corner log joints
    • Paweł Kłosowski
    • Anna Pestka
    • Marcin Krajewski
    • Izabela Lubowiecka
    2020 Pełny tekst ENGINEERING STRUCTURES

    This work concerns experimental and numerical research on carpentry joints used in historic wooden buildings in southeastern Poland and western Ukraine. These structures are mainly sacred buildings, and the types of corner log joints characteristic of this region are primarily saddle-notch and dovetail joints; thus, these two types of joints were analysed in this study. The modelling of historic timber structures is a complex issue, so the following steps are necessary to obtain accurate solutions: verification, validation and uncertainty quantification. The first and third steps were performed in a previous study, so the current research aimed to validate the numerical models and perform simulations of carpentry joints. Herein, the authors created finite element models of two types of joints and subsequently analysed the mechanical behaviour of these joints. Due to issues concerning model validation, the authors designed a testing stand for corner joints, which formed a part of a biaxial testing machine. The joints were subjected to horizontal loads (deformations), which may cause damage to the connection. Thus, special parts were designed for the stand, which made it possible to fix the joint and prevented eccentric forces that could possibly damage the machine during testing. The authors presented the differences and similarities in the behaviour of both types of joints, emphasizing the corresponding advantages and disadvantages. In addition, the authors determined which type of joint was the most susceptible to damage and what elements failed first. This paper also showed the complexity of modelling timber structures and the accuracy of the proposed numerical models for both types of joints through comparisons of the numerical and experimental results. This work primary addressed the problems in accurately reflecting material, load and boundary conditions in numerical modelling of tested carpentry corner log joints.

  • Experimental and DFT insights into an eco-friendly photocatalytic system toward environmental remediation and hydrogen generation based on AgInS2 quantum dots embedded on Bi2WO6
    • Patrycja Parnicka
    • Alicja Mikolajczyk
    • Henry P. Pinto
    • Wojciech Lisowski
    • Tomasz Klimczuk
    • Grzegorz Trykowski
    • Beata Bajorowicz
    • Adriana Zaleska-Medynska
    2020 APPLIED SURFACE SCIENCE

    Bismuth tungstate (Bi2WO6) can work as a photocatalyst but suffers from rapid recombination of photogenerated charge carriers. Herein, density functional theory (DFT) simulations revealed that the formation of a thermodynamically stable AgInS2(112)/Bi2WO6(010) heterojunction could promote charge separation and enhance the photoactivity of Bi2WO6. To confirm these theoretical predictions, a new type of photocatalysts in the form of Bi2WO6 flower-like microspheres decorated with different amounts of AgInS2 quantum dots (QDs) was obtained using a three-step procedure. The optimized system, obtained by embedding 1 wt% AgInS2 QDs on a Bi2WO6 matrix, possessed an enhanced photocatalytic activity for both phenol degradation and water splitting under visible light irradiation (λ > 420 nm), as well as good reusability and stability during prolonged storage. Finally, DFT calculations of the adsorption energies of reagents (O2, H2O, and H2 molecules) on Bi2WO6 and AgInS2/Bi2WO6 surfaces showed that the surface of the AgInS2(112)/Bi2WO6(010) interface was more active, allowing this system to strongly interact with surrounding species such as H2, O2, and H2O and thereby inducing photocatalytic oxidation of OH– to •OH, reduction of O2 to O2 •– or reduction of H+ to H2.

  • Experimental and Numerical Investigation of Mechanical Properties of Lightweight Concretes (LWCs) with Various Aggregates
    • Marzena Kurpińska
    • Tomasz Ferenc
    2020 Pełny tekst Materials

    High requirements for the properties of construction materials and activities directed at environment protection are reasons to look for new solutions in concrete technology. This research was directed at solutions affecting the reduction of energy consumption and CO2 emissions. The use of lightweight concretes (LWCs) allows one to meet both conditions at the same time. The purpose of the research presented in this paper was to investigate the abilities of using lightweight aggregates (LWAs) of the following types: 2 and 4 mm granulated expanded glass aggregate (GEGA) as ingredients with excellent insulating properties and 8 mm granulated fly ash aggregate (GAA) as an ingredient with a relatively high resistance to crushing. The influence of the percentage participation of each aggregate in all LWCs was variable and amounted to 0%, 25%, 50%, 75%, and 100%. A series of 15 LWC mixes were prepared for various LWA participations and for a constant water–cement ratio (w/c = 0.5). Concrete tests were carried out for the following criteria: density, porosity, compressive strength, and the modulus of elasticity. In order to fully analyze fracture processes in LWCs with the participation of GEGA and GAA and to assess the correctness of the results obtained during the experiments, numerical models that corresponded to both geometrical and load diagrams of elements under research were created. The numerical analyses of the LWCs were conducted by means of the conventional finite element method (FEM).

  • Experimental and numerical investigations of ultimate strength of imperfect stiffened plates of different slenderness
    • Krzysztof Wołoszyk
    • Yordan Garbatov
    • Jakub Kowalski
    • Leszek Samson
    2020 Pełny tekst Polish Maritime Research

    The objective of this study is to analyse the behaviour of compressed stiffened plates of different slenderness using experimental and numerical methods. The presented results are part of a long-term project to investigate the ultimate strength of geometrically imperfect structures subjected to different degradation phenomena, including corrosion degradation and locked cracks. Several specimens were subjected to a uniaxial compressive force, and the most important quantities related to the structural behaviour were captured and analysed. A finite element model, accounting for material and geometrical nonlinearities and initial geometrical imperfections, was developed using the commercial software ANSYS. The residual welding-induced stresses were measured in the middle cross-section for two specimens. The initial imperfection was identified by employing a close-range photogrammetry approach. It was concluded that the numerical analyses, based on the finite element model, predict the ultimate strength of stiffened plates accurately, although some deviations were also observed. The detailed analysis with the indication of possible uncertainty is presented, and several conclusions are derived.

  • Experimental and Numerical Study on Dynamics of Two Footbridges with Different Shapes of Girders
    • Anna Banaś
    • Robert Jankowski
    2020 Pełny tekst Applied Sciences-Basel

    The paper presents the experimental and numerical results of the dynamic system identification and verification of the behavior of two footbridges in Poland. The experimental part of the study involved vibration testing under different scenarios of human-induced load, impulse load, and excitations induced by vibration exciter. Based on the results obtained, the identification of dynamic parameters of the footbridges was performed using the peak-picking method. With the impulse load applied to both structures, determination of their natural vibration frequencies was possible. Then, based on the design drawings, detailed finite element method (FEM) models were developed, and the numerical analyses were carried out. The comparison between experimental and numerical results obtained from the modal analysis showed a good agreement. The results also indicated that both structures under investigation have the first natural bending frequency of the deck in the range of human-induced excitation. Therefore, the risk of excessive structural vibrations caused by pedestrian loading was then analysed for both structures. The vibration comfort criteria for both footbridges were checked according to Sétra guidelines. In the case of the first footbridge, the results showed that the comfort criteria are fulfilled, regardless of the type of load. For the second footbridge, it was emphasized that the structure meets the assumptions of the guidelines for vibration severability in normal use; nevertheless, it is susceptible to excitations induced by synchronized users, even in the case of a small group of pedestrians.

  • Experimental and predicted physicochemical properties of monopropanolamine-based deep eutectic solvents
    • Bartosz Nowosielski
    • Marzena Jamrógiewicz
    • Justyna Łuczak
    • Maciej Śmiechowski
    • Dorota Warmińska
    2020 Pełny tekst JOURNAL OF MOLECULAR LIQUIDS

    In this work, the novel deep eutectic solvents (DESs) based on 3-amino-1-propanol (AP) as hydrogen bond donor (HBD) and tetrabutylammonium bromide (TBAB) or tetrabutylammonium chloride (TBAC) or tetraethylammonium chloride (TEAC) as hydrogen bond acceptors (HBAs) were synthesized with different molar ratios of 1:4, 1:6 and 1:8 salt to AP. Fourier Transform Infrared Spectroscopy measurements were performed to provide an evidence of any chemical structure changes. Physical properties of the prepared DESs including densities, viscosities, refractive indices and sound velocities were measured within the temperature range of 293.15 – 333.15 K at the pressure of 0.1 MPa. They were analysed in terms of estimating the effect of HBA to HBD molar ratio, anion and length of alkyl chain in a salt, and their temperature dependences were fitted by empirical equations. Thermal expansion coefficients and activation energies for viscous flow were obtained accordingly. Moreover, experimental values of density and refractive index were compared with predicted ones. For prediction of density, Rackett equation modified by Spencer and Danner and the mass connectivity index-based method were used, while refractive index was estimated by the atomic contribution method.

  • Experimental certification of an informationally complete quantum measurement in a device-independent protocol
    • Massimiliano Smania
    • Piotr Mironowicz
    • Mohamed Navareg
    • Marcin Pawłowski
    • Adan Cabello
    • Mohamed Bourennane
    2020 Pełny tekst Optica

    Minimal informationally complete positive operator-valued measures (MIC-POVMs) are special kinds of measurement in quantum theory in which the statistics of their d2-outcomes are enough to reconstruct any d-dimensional quantum state. For this reason, MIC-POVMs are referred to as standard measurements for quantum information.Here, we report an experiment with entangled photon pairs that certifies, for what we believe is the first time, a MIC-POVM for qubits following a device-independent protocol (i.e., modeling the state preparation and the measurement devices as black boxes, and using only the statistics of the inputs and outputs). Our certification is achieved under the assumption of freedom of choice, no communication, and fair sampling.

  • Experimental investigation of joint with positive eccentricity in CFS truss
    • Małgorzata Gordziej-Zagórowska
    • Elżbieta Urbańska-Galewska
    • Patryk Deniziak
    2020 Pełny tekst THIN-WALLED STRUCTURES

    Due to technological restrictions, in the case of trusses made of CFS open cross-sections, positive eccentricities in the truss joints have become very frequent. Therefore studies concerning the load-bearing capacity of truss joints with positive eccentricity were undertaken. It was assumed that the resistance of cold-formed steel (CFS) open cross-section truss joints located on compression chords and with positive eccentricity is greater than that which results from hitherto known methods of steel structure dimensioning. In order to confirm the hypothesis, experimental studies were conducted. A series of 5 full-scale research models was subjected to destructive tests to determine the deformation forms and strains of the hat-section walls in the area of the eccentric joint. Forms of truss chord stability loss under compression and bending were identified. The course of research and analysis of results were described in the article. Than comparative analysis of the outcomes of the experimental tests and the results of analytical calculations carried out according to Eurocode standards was done, and the obtained results confirmed the usefulness of the undertaken research. The obtained results did not allow for explicit confirmation of the research hypothesis at this stage, but constituted the basis for validation of the numerical model which has been elaborated. Currently, the authors carry out a variety of numerical analysis.

  • Experimental Investigations on the Influence of Coil Arrangement on Melting/Solidification Processes
    • Rafał Andrzejczyk
    • Przemysław Kozak
    • Tomasz Muszyński
    2020 Pełny tekst ENERGIES

    The latent heat thermal energy storage units are very popular because of their high energy density and almost close to constant temperature during the charging/discharging. In the present study has been proposed new shell-and-coil geometry with a shifted coil position to enhance the performance of phase change thermal magazine. The experimental investigations have been performed both for the melting and solidification process of coconut oil for constant wall temperature conditions. The experiments have been carried out for cylindrical as well as coil shape geometry of the TES unit. In the case of annular TES, the copper tube with outer diameter d = 10 mm and total length equal to 165 mm were used (4). In the case of shell-and-coil TES the coil has been also made of a copper tube but with an outer diameter d = 6 mm. The total length of the tube was 460 mm. However, the length of the tube element that has been used in the process of bending the coil had a total length equal to 360 mm. The rest of the tube was straight. The coil pitch was 15 mm and the outer coil diameter was 26 mm. The experiments have been conducted for the coil position at the top and the bottom of the tank. The results showed the influence of heat transfer geometry for phase change efficiency. The article presents the thermal characteristic of melting and solidification phenomena as well as their visual analysis. A significant impact of heat transfer geometry at the shape of the melting and solidification profile. The optimal performance has been achieved for shell-and-coil TES with a coil arranged at the top of the tank.

  • Experimental Research on Insufficient Water Lubrication of Marine Stern Tube Journal Bearing with Elastic Polymer Bush
    • Agnieszka Barszczewska
    2020 Pełny tekst Polish Maritime Research

    Water-lubricated bearings with polymer bushes are steadily gaining popularity due to their advantages, including environmental friendliness, relatively simple construction and long-term operation. Nevertheless, in practice instances of damage to such bearings occur due to insufficient or absent flow of the lubricating agent. In this study, experimental tests established that elastic polymer bush bearing is capable of operating without excessive wear for a period of at least 60 minutes under conditions of marginal water flow and typical loads for stern tube journal bearings of small ships.

  • Experimental Studies of Concrete-Filled Composite Tubes under Axial Short- and Long-Term Loads
    • Marcin Abramski
    • Piotr Korzeniowski
    • Krzysztof Klempka
    2020 Pełny tekst Materials

    The paper presents experimental studies on axially compressed columns made of concrete-filled glass fiber reinforced polymer (GFRP) tubes. The infill concrete was C30/37 according to Eurocode 2. The investigated composite pipes were characterized by different angles of fiber winding in relation to the longitudinal axis of the element: 20, 55 and 85 degrees. Columns of two lengths, 0.4 m and 2.0 m, were studied. The internal diameter and wall thickness of all the pipes were identical and amounted to 200 mm and 6 mm, respectively. The mean values of two mechanical properties, elasticity modulus and compression strength, were determined. These properties were determined for longitudinal compression and for circumferential tension. The graphs of longitudinal and peripheral deformations of polymer shells as a function of load level are presented both for empty tubes and for concrete-filled ones. The results of long-term investigations of three identically made 0.4 m high concrete-filled GFRP tubes are also presented.

  • Experimental Study on the Effectiveness of Polyurethane Flexible Adhesive in Reduction of Structural Vibrations
    • Natalia Lasowicz
    • Arkadiusz Kwiecień
    • Robert Jankowski
    2020 Pełny tekst Polymers

    The aim of the present study is to consider the idea of using polyurethane flexible adhesive in to reduce the vibrations in structures exposed to dynamic loads and evaluate their damping properties in relation to large deformations. Firstly, two aluminium cantilever beams, simulating structural elements (without and with polyurethane layer in the form of tape), were analysed, in order to check the damping of the unconstrained polymer layer. In the second stage of the study, a composite beam consisting of two aluminium flat beams bonded with polymer adhesive was considered, so as to check the damping of the constrained polymer layer. Dynamic parameters, such as modes of free vibrations, corresponding natural frequencies and damping ratios, were determined and compared. The third stage of the investigation was aimed at solving the problem of the additional mass of the applied polymer layer, which influences the frequencies and damping of the tested structure. A special separating procedure is proposed that makes it possible to calculate the corrected real values of the polymer layer’s damping. The results of the study clearly show that the response of the composite aluminium beam with and without polymer adhesive layer is mainly influenced by the layers’ thickness and the large strain deformation, in terms of its damping characteristics. The use of polymer adhesive layers in constrained and unconstrained conditions leads to a significant reduction in the vibrations of tested beams, while preserving their stiness at nearly the same level. The applied analysis procedure made it possible for us to separate the damping properties of the analysed polymer layers and evaluate them independently with respect to the influence of integrated structural elements on damping.

  • Experimental study on the selected aspects of bow thruster generated flow field at ship zero-speed conditions
    • Teresa Abramowicz-Gerigk
    • Mirosław Gerigk
    2020 OCEAN ENGINEERING

    The paper presents the results of experimental study on the interaction between the bow thrusters understood as the flow field changes generated by bow tunnel thruster in deep water conditions operated as a single and twin units. The research was limited to zero-speed case for the ship dead in the water. The influence of the hull form and jet spread between the neighbouring thrusters for several combinations of the applied bow thruster propeller revolutions has been discussed. The results of the flow field measurements - velocity field, volume of fluid rate, mean velocity and thrust have been compared with the measurements of hydrodynamic forces generated by the bow thrusters on the hull. Both experiments were conducted at zero-speed using the same large physical man-manned model of a car-passenger ferry in 1:16 scale.

  • Experimental test of nonclassicality with arbitrarily low detection efficiency
    • Alley Hameedi
    • Breno Marque
    • Piotr Mironowicz
    • Debashis Saha
    • Marcin Pawłowski
    • Mohamed Bourennane
    2020 Pełny tekst PHYSICAL REVIEW A

    We theoretically introduce and experimentally demonstrate the realization of a nonclassicality test that allows for arbitrarily low detection efficiency without invoking an extra assumption of independence of the devices. Our test and its implementation is set in a prepare-and-measure scenario with an upper limit on the classical communication capacity of the channel through which the systems are communicated. The essence for our test is the use of two preparation and two measurement devices, which are randomly paired in each round. Our work opens the possibility for experimental realizations of nonclassicality tests with off-the-shelf technology.

  • Explainable AI for Inspecting Adversarial Attacks on Deep Neural Networks
    • Zuzanna Klawikowska
    • Agnieszka Mikołajczyk
    • Michał Grochowski
    2020 Pełny tekst

    Deep Neural Networks (DNN) are state of the art algorithms for image classification. Although significant achievements and perspectives, deep neural networks and accompanying learning algorithms have some important challenges to tackle. However, it appears that it is relatively easy to attack and fool with well-designed input samples called adversarial examples. Adversarial perturba-tions are unnoticeable for humans. Such attacks are a severe threat to the devel-opment of these systems in critical applications, such as medical or military sys-tems. Hence, it is necessary to develop methods of counteracting these attacks. These methods are called defense strategies and aim at increasing the neural mod-el's robustness against adversarial attacks. In this paper, we reviewed the recent findings in adversarial attacks and defense strategies. We also analyzed the ef-fects of attacks and defense strategies applied, using the local and global analyz-ing methods from the family of explainable artificial intelligence.

  • Exploratory analysis and ranking of analytical procedures for short-chain chlorinated paraffins determination in environmental solid samples
    • Mariusz Marć
    • Marta Bystrzanowska
    • Marek Tobiszewski
    2020 Pełny tekst SCIENCE OF THE TOTAL ENVIRONMENT

    Short-chain chlorinated paraffins are ones of the most recent chemical compounds that have been classified as persistent organic pollutants. They have various applications and are emitted to the environment. Despite the fact, that the content levels of these compounds in the environmental compartments should be monitored, there is still a lack of well-defined and validated analytical procedures, proposed or suggested by the national or international environmental protection agencies. Finding an appropriate analytical procedure (sensitive and green at the same time) from many available ones is very often a difficult task. Therefore it can be supported with multicriteria decision analysis. The dataset consisting of 22 procedures was described by 7 criteria, mainly referring to procedures greenness. The data treatment with cluster analysis and principal component analysis revealed the internal structure of the dataset. Moreover, both statistical tools allowed for reduction of dataset criteria to three. This was used for applying ternary plot to show the multicriteria decision analysis results within all possible weights. With the aid of chemometric and multicriteria decision analysis tools it was easy to assess the set of analytical procedure. Depending on the applied weights to assessment criteria different analytical procedures are the most appropriate (winners).

  • Exploring application relationships within enterprise system by matching messages in enterprise log
    • Krzysztof Goczyła
    • Łukasz Korzeniowski
    2020

    With data becoming their key asset, large enterprises require data governance processes to maintain its quality. Because a large portion of business value in enterprise systems is usually delivered by legacy applications without proper documentation, there is a need for a better understanding of these applications and the data produced by them. In this paper, we present an approach to collecting insights into the data managed by enterprise systems by exploring enterprise logs in the search of messages being exchanged between applications. Our method identifies data assets from the extracted messages and finds relationships between them. Based on our professional practice, we verify the method in a generic environment that simulates an enterprise system consisting of applications that exchange XML messages.

  • Exploring Impact of Requirements Engineering on Other IT Project Areas – Case Study
    • Aleksander Jarzębowicz
    • Katarzyna Poniatowska
    2020 Pełny tekst Computer Science

    Requirements Engineering (RE) is recognized as one of the most important (yet difficult) areas of software engineering that has a significant impact on other areas of IT projects and their final outcomes. Empirical studies investigating this impact are hard to conduct, mainly due to the great effort required. It is thus difficult for both researchers and industry practitioners to make evidence-based evaluations about how decisions about RE practices translate into requirement quality and influence other project areas. We propose an idea of a lightweight approach utilizing widely-used tools to enable such an evaluation without extensive effort. This is illustrated with a pilot study where the data from six industrial projects from a single organization were analyzed and three metrics regarding the requirement quality, rework effort, and testing were used to demonstrate the impact of different RE techniques. We also discuss the factors that are important for enabling the broader adoption of the proposed approach.

  • Exploring the Role of Social Media Use Motives, Psychological Well-Being, Self-Esteem, and Affect in Problematic Social Media Use
    • Bruno Schivinski
    • Magdalena Brzozowska-Woś
    • Ellena Stansbury
    • Jason Satel
    • Christian Montag
    • Halley M. Pontes
    2020 Pełny tekst Frontiers in Psychology

    Given recent advances in technology, connectivity, and the popularity of social media platforms, recent literature has devoted great attention to problematic Facebook use. However, exploring the potential predictors of problematic social media use beyond Facebook use has become paramount given the increasing popularity of multiple alternative platforms. In this study, a sample of 584 social media users (Mage = 32.28 years; 67.81% female) was recruited to complete an online survey assessing sociodemographic characteristics, patterns, and preferences of social media use, problematic social media use (PSMU), social media use motives, psychological well-being, self-esteem, and positive and negative affect. Results indicated that 6.68% (n = 39) of all respondents could be potentially classed as problematic users. Moreover, further analysis indicated that intrapersonal motive (β = 0.38), negative affect (β = 0.22), daily social media use (β = 0.18), surveillance motive (β = 0.12), and positive affect (β = −0.09) each predicted PSMU. These variables accounted for about 37% of the total variance in PSMU, with intrapersonal motive driving the greatest predictive contribution, over and above the effects of patterns of social media use and sociodemographic variables. These findings contribute to the increasing literature on PSMU. The results of this study are discussed in light of the existing literature on PSMU.

  • Exploring thiophene-2-acetate and thiophene-3-acetate binding modes towards the molecular and supramolecular structures and photoluminescence properties of Pb(ii) polymers
    • Mateusz Kowalik
    • Joanna Masternak
    • Katarzyna Kazimierczuk
    • Bogumiła Kupcewicz
    • Oleksiy Khavryuchenko
    • Barbara Barszcz
    2020 CRYSTENGCOMM

    To evaluate the impact of the flexible positional isomeric ligands thiophene-2-acetate (2tpacCOO) andthiophene-3-acetate (3tpacCOO) on the construction and self-assembly process of Pb(II) polymers, twonovel compounds, [Pb(2tpacCOO)2(H2O)]n(1) and [Pb(3tpacCOO)2]n(2), were preparedviaanonhydro-thermal method with respect to green chemistry rules. The obtained polymers were fully characterized byelemental analysis, TG/DTG and PXRD, FT-IR, solid-state photoluminescence, DFT calculations and single-crystal X-ray diffraction. Each Pb(II)centreof1is 7-coordinated as a {PbO7} chromophore while the Pb(II)centre of2is 6-coordinated as a {PbO6} structure. The coordination polyhedron of1is best described as adistorted monocapped pentagonal pyramid, and2has a distorted trigonal prismatic shape. The crystallo-graphic analysis and DFT calculations indicated the stereoactivity of the lone electron pair, which contrib-uted to the hemidirected geometry of the Pb(II) environment. Due to the versatile binding modes of the li-gands, complex1forms 1D stair-like chains with an SP 1-periodic net (4,4)(2,0) topology, and theunderlying net of2is determined to have a 1D 2,4C4 topology. It is worth noting that the crystal structuresof the obtained polymers are stabilized mainly by many hydrogen bonds as well as Pb⋯SandPb⋯πtetrelinteractions. Moreover, the PL data demonstrate the different influences of the isomers of linkers onphotoluminescence properties. Polymer1might be a good candidate for obtaining solid-state photo-luminescent materials.

  • Exposure of a small Arctic seabird, the little auk (Alle alle) breeding in Svalbard, to selected elements throughout the course of a year
    • Aneta Pacyna-Kuchta
    • Dariusz Jakubas
    • Marcin Frankowski
    • Żaneta Polkowska
    • Katarzyna Wojczulanis-Jakubas
    2020 Pełny tekst SCIENCE OF THE TOTAL ENVIRONMENT

    The Arctic marine ecosystem can be altered by processes of natural and anthropogenic origin. Spatio-temporal variation in species exposure to contamination is still poorly understood. Here, we studied elemental concentrations in the non-lethally collected samples from the most numerous seabird in European Arctic, the little auk (Alle alle) nesting in one breeding colony in Svalbard. This seabird spent the breeding season in the high-Arctic zone and the non-breeding period in sub-Arctic areas what may implicate spatio-temporal variation in elements bioaccumulation. We determined concentrations of 19 elements in adults feathers to determine levels of exposure during part of the pre-breeding (n = 74) and post-breeding (n = 74) seasons, feathers from nestlings (n=18) to determine local contamination, and chick down (n=16) and post-hatching eggshells (n = 18) to determine maternal input to offspring. During the pre-breeding period adults accumulated in their feathers significantly more Hg (one third of feathers exceeded the established toxicity threshold), Se and Mn compared to the post-breeding period. It reflects a higher exposition of birds to contaminants in pre-breeding moult areas outside the High Arctic compared to the post-breeding moult in the High Arctic. Sex differences in adult feathers representing the post-breeding period were found only for Ca and Zn with higher values in females. Chick down was characterized by high levels of several essential elements, an intermediate level of Hg and Se, and the highest Se:Hg molar ratios of all groups. Chick body feathers had the highest level of Cu and K among all the studied groups. Post-hatching eggshells were characterized by high Sr level (exceeding 2000 μg/g). Concentrations of several non-essential elements (Bi, Cd, Cr, Hg, Ni and Pb) in them were below method detection limits.

  • Exsolution of Ni nanoparticles on the surface of cerium and nickel co-doped lanthanum strontium titanate as a new anodic layer for DIR-SOFC. Anti-coking potential and H2S poisoning resistance of the prepared material
    • Patryk Błaszczak
    • Marcin Łapiński
    • Sea-Fue Wang
    • Piotr Jasiński
    • Beata Bochentyn
    2020 Pełny tekst INTERNATIONAL JOURNAL OF HYDROGEN ENERGY

    The aim of this study was to evaluate a new catalytic material for biogas fueled DIR-SOFC. This material was a perovskite-type SrTiO3 doped with La, Ce and Ni of a general formula La0.27Sr0.54Ce0.09Ni0.1Ti0.9O3-σ (LSCNT). Additional preparation steps were undertaken to promote a nickel exsolution process. Heat post-treatment of powders in a humidified H2 resulted in an intensive growth of nickel nanoparticles (NPs) while the temperature of reduction was increased gradually from 800 to 1200 oC. Selected reduction temperature equal to 900 oC gave NPs of an average size 22 nm. The prepared material was used as a functional layer deposited onto the anodic site of Ni/YSZ supported SOFC to promote an effective reforming of synthetic and H2S-contaminated biogas at 750 oC. It was found that after 130 h of operation in 60% CH4/40% CO2 mixture, the fuel cell with additional LSCNT layer showed higher power density and no carbon deposits were observed. However, 20 ppm of H2S present in fuel caused a full deactivation of both reference and SOFC with LSCNT layer. Cyclic tests in sour biogas revealed that fabricated anodic layer is much more resistant to sulfur poisoning compared to bare Ni/YSZ anode. Recovery of overall performance after 3 poisoning cycles was nearly 90% for a fuel cell with LSCNT layer, while for unmodified one reached only 75%. Concentrations of exhaust gases such as CH4, CO2 and CO were continuously measured in situ using a FTIR-based technique. The thermochemical analysis revealed that investigated material ensures much better biogas reforming stability over whole testing time and strongly promotes catalytic reactions.

  • External Security Strategies of Belarus
    • Krystyna Gomółka
    2020 Pełny tekst Annales Universitatis Mariae-Curie Skłodowska, sectio K – Politologia

    Under President Lukashenko, three Belarusian national security strategies have been announced: the first in 1995, the second in 2001 and the third in 2011. The first proposal, formulated after Lukashenko’s victory in the presidential elections in 1994, outlined Belarus as a neutral state, unbound to any military block in the absence of external enemies. The direction of the foreign policy pursued by the president of Belarus was reflected in the second strategy, where security against NATO and EU member states was sought in a federal state with the Russian Federation. Under the third national security scheme Belarus was to remain in Russia’s military security system. Nevertheless, an important security factor was considered to be the modernisation of the economy with foreign capital participation and the need to diversify the supplies of fuels, thus reducing the country’s dependence on its earlier partner. The subsequently issued documents: the military doctrine of the State, whose assumptions were published on 20 July 2016, and the Concept of security of the Belarusian state borders for the period 2018–2022, prioritised further development of relations with the Russian Federation and the member states of the Collective Security Treaty Organisation. A new element of the 2019 defence plan is the prevention of external aggression and internal disturbance that contribute to the destabilisation of the state.

  • Extractive detoxification of feedstocks for the production of biofuels using new hydrophobic deep eutectic solvents – Experimental and theoretical studies
    • Patrycja Makoś
    • Edyta Słupek
    • Jacek Gębicki
    2020 Pełny tekst JOURNAL OF MOLECULAR LIQUIDS

    The paper presents a synthesis of novel hydrophobic deep eutectic solvents (DESs) composed of natural components, which were used for removal of furfural (FF) and 5-hydroxymethylfurfural (HMF) from lignocellulosic hydrolysates. The main physicochemical properties of DESs were determined, followed by explanation of the DES formation mechanism, using 1H NMR, 13C NMR and FT-IR analysis and density functional theory (DFT). The most important extraction parameters were optimized. Reusability, regeneration of DES, multistage extraction, influence of FF and HMF concentration, as well as possibility of sugars loss were also investigated. The experimental studies revealed high extraction efficiency resulting in 79.2% and 87.9% removal of FF and HMF respectively from model hydrolysates and in the range of 74.2–76.1% and 87.8–82.3% from real samples in one-step extraction. The yield of bio‑hydrogen production via dark fermentation after the DES extraction was comparable to the results obtained using enzymatic hydrolysis. The theoretical studies on the extraction mechanism revealed that hydrogen bonds and van der Waals interactions were the main driving force for detoxification of lignocellulosic biomass.

  • Fabrication of anti-corrosion nitrogen doped graphene oxide coatings by electrophoretic deposition
    • Karolina Ollik
    • Maria Rybarczyk
    • Jakub Karczewski
    • Marek Lieder
    2020 APPLIED SURFACE SCIENCE

    This work assesses anti-corrosion properties of graphene and N-doped graphene coatings deposited on copper by an electrophoretic method. Graphene oxide (GO) precursor was synthesized by an improved Hummers' method, whereas N-doping was performed hydrothermally in the presence of ammonia. After nitrogenation, doped graphene oxide samples (NGO) contained a reduced amount of oxygen and about 9% w/w nitrogen as pyridinic, pyrrole, and graphitic groups. Nevertheless, it was possible to obtain a stable aqueous dispersion of NGOs, a prerequisite for the EPD process. According to SEM images, the EPD coatings were compact with minor defects. On the contrary, GO coating possessed cracks and large pores that resulted from gas evolution during electrolysis. Electrochemical studies showed that all coatings prevented copper from corrosion in saline solution, however, the nitrogenated coatings did not exhibit better anti-corrosion properties than reduced graphene oxide coating. A reasonable explanation of this finding is that some positive properties of the nitrogenated coatings, in terms of anti-corrosion action, like low hydrophilicity and good adhesion, were counteracted by their catalytic activity towards oxygen reduction reaction.

  • Fabrication of Durable Ordered Ta2O5 Nanotube Arrays Decorated with Bi2S3 Quantum Dots
    • Mateusz Baluk
    • Marek Kobylański
    • Wojciech Lisowski
    • Grzegorz Trykowski
    • Tomasz Klimczuk
    • Marek Mazierski
    • Adriana Zaleska-Medynska
    • Mateusz Adam Baluk
    2020 Pełny tekst Nanomaterials

    One of the most important challenges in the fabrication of ordered tantalum pentaoxide (Ta2O5) nanotube arrays (NTs) via the electrochemical method is the formation of nanotubes that adhere well to the Ta substrate. In this paper, we propose a new protocol that allows tight-fitting Ta2O5 nanotubes to be obtained through the anodic oxidation of tantalum foil. Moreover, to enhance their activity in the photocatalytic reaction, in this study, they have been decorated by nontoxic bismuth sulfide (Bi2S3) quantum dots (QDs) via a simple successive ionic layer adsorption and reaction (SILAR) method. Transmission electron microscopy (TEM) analysis revealed that quantum dots with a size in the range of 6-11 nm were located both inside and on the external surfaces of the Ta2O5 NTs. The effect of the anodization time and annealing conditions, as well as the effect of cycle numbers in the SILAR method, on the surface properties and photoactivity of Ta2O5 nanotubes and Bi2S3/Ta2O5 composites have been investigated. The Ta2O5 nanotubes decorated with Bi2S3 QDs exhibit high photocatalytic activity in the toluene degradation reaction, i.e., 99% of toluene (C0 = 200 ppm) was degraded after 5 min of UV-Vis irradiation. Therefore, the proposed anodic oxidation of tantalum (Ta) foil followed by SILAR decorating allows a photocatalytic surface, ready to use for pollutant degradation in the gas phase, to be obtained.

  • Fabrication of exfoliated graphite reinforced silicone rubber composites - Mechanical, tribological and dielectric properties
    • Józef Haponiuk
    • P. S. Sarath
    • Sohil Vargese Samson
    • Rakesh Reghunath
    • Mrituanjay Kumar Pandey
    • Sabu Thomas
    • Soney C. George
    2020 Pełny tekst POLYMER TESTING

    The effect of exfoliated graphite (EG) on the mechanical, tribological and dielectric properties of the silicone rubber (QM) composites has been systematically investigated and analysed. Morphological analysis of the composites helps to understand the interfacial interaction between the filler and the rubber matrix as well as wear mechanism respectively. An enhancement in the mechanical, tribological and dielectric properties was observed with an increase in filler loading and better performance was observed at 7 phr of filler loading. The improvement in performance is attributed to the better interaction between the QM chains and the EG layers as evident from the AFM and TEM analysis. It is also evident from the Kraus plot which supports the reinforcing effect of EG in QM matrix.

  • Fabrication of exfoliated graphite reinforced silicone rubber composites - Mechanical, tribological and dielectric properties
    • P. S. Sarath
    • Sohil Vargese Samson
    • Rakesh Reghunath
    • Mrituanjay Kumar Pandey
    • Józef Haponiuk
    • Sabu Thomas
    • Soney C. George
    2020 Pełny tekst POLYMER TESTING

    The effect of exfoliated graphite (EG) on the mechanical, tribological and dielectric properties of the silicone rubber (QM) composites has been systematically investigated and analysed. Morphological analysis of the composites helps to understand the interfacial interaction between the filler and the rubber matrix as well as wear mechanism respectively. An enhancement in the mechanical, tribological and dielectric properties was observed with an increase in filler loading and better performance was observed at 7 phr of filler loading. The improvement in performance is attributed to the better interaction between the QM chains and the EG layers as evident from the AFM and TEM analysis. It is also evident from the Kraus plot which supports the reinforcing effect of EG in QM matrix.

  • Fabrication of ILs-Assisted AgTaO3 Nanoparticles for the Water Splitting Reaction: The Effect of ILs on Morphology and Photoactivity
    • Julia Zwara
    • Anna Pancielejko
    • Marta Paszkiewicz-Gawron
    • Justyna Łuczak
    • Magdalena Miodynska
    • Wojciech Lisowski
    • Adriana Zaleska-Medynska
    • Ewelina Grabowska-Musiał
    2020 Pełny tekst Materials

    The design of an active, stable and ecient photocatalyst that is able to be used for hydrogen production is of great interest nowadays. Therefore, four methods of AgTaO3 perovskite synthesis, such as hydrothermal, solvothermal, sol-gel and solid state reactions, were proposed in this study to identify the one with the highest hydrogen generation eciency by the water splitting reaction. The comprehensive results clearly show that the solid state reaction (SSR) led to the obtainment of a sample with an almost seven times higher photocatalytic activity than the other methods. Furthermore, four ionic liquids, all possessing nitrogen in the form of organic cations (two imidazoliums with dierent anions, ammonium and tetrazolium), were used for the first time to prepare composites consisting of AgTaO3 modified with IL and Pt, simultaneously. The eect of the ionic liquids (ILs) and Pt nanoparticles’ presence on the structure, morphology, optical properties, elemental composition and the eectiveness of the hydrogen generation was investigated and discussed. The morphology investigation revealed that the AgTaO3 photocatalysts with the application of [OMIM]-cation based ILs created smaller granules (<500 nm), whereas [TBA] [Cl] and [TPTZ] [Cl] ILs caused the formation of larger particles (up to 2 m). We found that various ILs used for the synthesis did not improve the photocatalytic activity of the obtained samples in comparison with pristine AgTaO3. It was detected that the compound with the highest ability for hydrogen generation under UV-Vis irradiation was the AgTaO3_0.2% Pt (248.5 molg1), having an almost 13 times higher eciency in comparison with the non-modified pristine sample. It is evidenced that the enhanced photocatalytic activity of modified composites originated mainly from the presence of the platinum particles. The mechanism of photocatalytic H2 production under UV-Vis light irradiation in the presence of an AgTaO3_IL_Pt composite in the water splitting reaction was also proposed.

  • Facebook, YouTube, Instagram... jako arbitrzy prawdy. Deepfake – na szlaku dystopii i łasce korporacji
    • Jan Kreft
    2020

    Zidentyfikowano ich w 2019 roku w sieci blisko 15 tysięcy . Zwykle nie dotyczą polityki, choć to przede wszystkim w środowisku politycznym budzą strach i zwątpienie. Strach przed dewastacja resztek społecznego zaufania, jakimi politycy się cieszą, zwątpienie – bo zwalczanie ich przekracza polityczne możliwości władz ujmowanych w kartezjańskim podziale władzy. Deepfake – bo o nich mowa – są przełomową innowacją wyznaczającą nowe granice możliwości poznawczych ludzi w cyfrowym środowisku, technologią która wykorzystywana jest z różnymi intencjami, od „mowy (wideo) nienawiści”, po szczytne kampanie społeczne i kładzie podwaliny pod „koniec prawdy” w mediach. Ich identyfikacja i usuwanie ukazuje kluczowy problem współczesnego zarządzania organizacjami mediano – technologicznymi w relacjach z otoczeniem. Jest nową odsłoną asymetrii zależności między użytkownikiem, a organizacją - platformą nowomedialną, nowej relacji władzy i konieczności zdania się na dobrą wolę, determinację oraz potencjał badawczy organizacji medialno – technologicznych.

  • Factors Affecting the Effectiveness of Military Training in Virtual Reality Environment
    • Małgorzata Gawlik-Kobylińska
    • Paweł Maciejewski
    • Jacek Lebiedź
    • Aneta Wysokińska-Senkus
    2020

    In this paper, we explored the factors influencing the effectiveness of military trainings performed in a virtual reality environment. The rationale for taking up the topic is the fact that such trainings are often conducted under specific operational procedures. These procedures may create rigorous frameworks for all elements of the learning environment, including the teacher’s performance. Therefore, to ensure the most conducive conditions of training and, thus, its effectiveness, it is necessary to identify critical factors to be taken into account while designing the training process. On the basis of literature review, we selected, analysed, and categorized the most relevant factors concerning the learner, the teacher, as well as didactic tools and the content. We limited our considerations to the learning environment and the teaching process. We did not explore the organizational level. Another implication concerns the development of a tool for training effectiveness assessment based on the identified factors.

  • Factors of successful client co-production in knowledge-intensive business services
    • Małgorzata Zięba
    • Paweł Kończyński
    2020 Pełny tekst KYBERNETES

    Purpose This paper aims to explore the topic of client co-production in knowledge-intensive business services (KIBS). The paper first sketches a theoretical background and reviews previous studies on factors affecting successful client co-production in such companies and then examines these factors via case study research among a small KIBS company and its five customers. Design/methodology/approach The paper is based on an in-depth analysis of literature devoted to client co-production in KIBS firms and on the results of case studies analysis. The authors explore theoretically and empirically the perception of factors behind a successful client co-production process of a KIBS company from the point of view of both customers and service provider. The examination resulted in the clarification of what a successful client-KIBS firm cooperation should look like and what kind of actions KIBS firms should undertake to provide it. Findings As the analysis shows, to perceive client-KIBS firm cooperation as successful, customers desire on hand immediate effects that would justify and compensate their time and money investments (e.g. new clients or brand recognition) and on the other hand, some of them desire positive changes in longer-term, which tangible form is associated with the newly obtained knowledge and more importantly, freshly developed and written strategy. Among the factors that influence the co-production process one can list teamwork, trust, communication and knowledge flows. Research limitations/implications Research results are limited to one KIBS company operating in Poland and its five customers. As such, they are not conclusive for the whole KIBS sector. The findings of both literature review and case study analysis indicate that there are several outcomes that are expected from the point of view of a KIBS customer when selecting the service of a KIBS company. The paper examines important aspect of service co-production and provides practical guidelines how cooperation between KIBS firms and their customers should look like. Practical implications The paper examines the relationship between a client and a KIBS company and explores the factors influencing the successful outcome of this relation. The paper provides guidelines on how this type of relation should be handled by managers or owners of KIBS firms.

  • Failures and a concept of corrosion protection system for spiral classifiers at KGHM Polska Miedź S.A. Ore Concentration Plant
    • Marcin Czekajło
    • Krzysztof Żakowski
    2020 Pełny tekst ENGINEERING FAILURE ANALYSIS

    The Ore Concentration Plant, where the process of flotation is carried out as well as the final production of copper concentrate, plays a key role in the entire production line of KGHM Polska Miedź S.A. Majority of operations related to the run-of-mine preparation to copper flotation enrichment are carried out in a water environment. The maintaining of production process continuity requires to pursue minimisation of many production limitations. The corrosive action of the technological medium, being a salted water suspension of ground copper ore, is one of them. The concept of spiral classifiers cathodic protection presented in this paper may become an alternative to the anti-corrosion protection methods of machinery and equipment used now at the KGHM. The obtained results of research indicate a possibility of significant reduction of classifiers corrosion rate at the application of cathodic protection and of a few times extension of the period of spiral classifiers operation, which replacement generates substantial operating costs.

  • Falowniki napięcia z quasi-rezonansowym obwodem pośredniczącym w układach napędowych
    • Marek Turzyński
    2020

    W monografii przedstawiono zagadnienia związane z wykorzystaniem pośrednich przemienników częstotliwości z rezonansowymi oraz quasi-rezonansowymi obwodami pośredniczącymi w układach napędowych. Omówiono wpływ przełączania „twardego” przy niezerowych prądach i napięciach łączników na właściwości eksploatacyjne elektrycznego układu napędowego. Ponadto dokonano przeglądu wybranych topologii przekształtników DC/AC, zapewniających techniki „miękkiego” przełączania łączników w stanach bezprądowych lub beznapięciowych. Omówiono mechanizm powstawania składowych napięć wspólnych oddziałujących na silnik elektryczny i związane z nimi zjawisko prądów łożyskowych, a także przedstawiono wyniki eksperymentalnej weryfikacji skuteczności powszechnie stosowanych metod tłumienia składowych napięcia wspólnego w układach falowników napięcia z komutacją twardą. W ramach monografii zaproponowano autorską strukturę falownika napięcia z quasi-rezonansowym obwodem pośredniczącym, umożliwiającą redukcję poziomów napięć wspólnych, ograniczenie wielkości prądów doziemnych oraz poprawę warunków zasilania maszyny elektrycznej, co zostało pozytywnie zweryfikowane w przeprowadzonych badaniach eksperymentalnych.

  • Family business succession – the practical or also theoretical problem. Bibliometric analysis
    • Marzena Grzesiak
    2020

    Family businesses, in various forms, have existed since societies began to be created. However, family business research has a decidedly shorter tradition. In favorable conditions, family enterprises develop for many generations, and their fate is intertwined with the fate of the families. The topics of family businesses are raised by researchers around the world. Estimates regarding the number of family businesses are a frequent subject of scientific disputes. Differences in the results of scientific research result, among others, from a different understanding of the concept of family accessibility. This requires uniformity in decisions regarding the definitions of this term. Most family businesses are micro and small service companies, but there are also many large family enterprises in the world (e.g. Anderson R., Reeb D 2003: in the US, families control 1/3 of the richest companies comprising the S&P 500 index). The averaged international stock exchange estimates show that about 44% of the listed companies are in the hands of families. In the USA and Canada, the share of family businesses in the population is estimated at 80–90%, while in Europe — at around 75%. The aim of this chapter is to analyze the directions of research in the field of family businesses with particular attention to the process of succession. This goal will be achieved through a review of articles dedicated to family businesses as well as through the usage of bibliometric analysis tools. The work starts with a general review of the literature concerning the issues of family businesses, in order to indicate the main trends of research. Next, the results of reports dealing with the problem of statistics of family enterprises are presented, focusing on the succession issue. Bibliometric research has been used for the synthetic analysis of publications addressing the succession and made it possible to search for the regularity in the structure of scientific achievements in this field. The author used two bibliometric methods. On the basis of standard indicators generated by the tools offered by Scopus, a descriptive analysis of the publication structure was made. Next, in order to identify the main research topics, the analysis of the co-occurrence of words was carried out using the Vosviewer tool.

  • Fast Antenna Optimization Using Gradient Monitoring and Variable-Fidelity EM Models
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2020 APPLIED COMPUTATIONAL ELECTROMAGNETICS SOCIETY JOURNAL

    Accelerated simulation-driven design optimization of antenna structures is proposed. Variable-fidelity electromagnetic (EM) analysis is used as well as the trust-region framework with limited sensitivity updates. The latter are controlled by monitoring the changes of the antenna response gradients. Our methodology is verified using three compact wideband antennas. Comprehensive benchmarking demonstrates its superiority over both conventional and surrogate-assisted algorithms.

  • Fast Fading Characterization for Body Area Networks in Circular Metallic Indoor Environments
    • Filipe D. Cardoso
    • Paweł Kosz
    • Manuel M. Ferreira
    • Sławomir Ambroziak
    • Luis M. Correia
    2020 Pełny tekst IEEE Access

    With the increasing development of 5G and Body Area Network based systems being implemented in unusual environments, propagation inside metallic structures is a key aspect to characterize propagation effects inside ships and other similar environments, mostly composed of metallic walls. In this paper, indoor propagation inside circular metallic structures is addressed and fast fading statistical distributions parameters are obtained from simulation, being assessed with measurements at 2.45 GHz in a passenger ferry discotheque with an 8 m diameter circular shape. It is observed that, in this kind of environments, second order reflections are particularly relevant due to the walls’ high reflective nature. Globally, it is concluded that the Rayleigh distribution can be used to characterize fast fading effects with no significant loss of accuracy compared to the Rice one, since a low value of the Rice parameter is observed, being below 3.1 dB, even under Line-of-Sight conditions. Moreover, it is observed that, from the fast fading viewpoint, the best transmitter position is at the circle center.

  • Fast Multi-Objective Aerodynamic Optimization Using Sequential Domain Patching and Multifidelity Models
    • Anand Amrit
    • Leifur Leifsson
    • Sławomir Kozieł
    2020 Pełny tekst JOURNAL OF AIRCRAFT

    Exploration of design tradeoffs for aerodynamic surfaces requires solving of multi-objective optimization (MOO) problems. The major bottleneck here is the time-consuming evaluations of the computational fluid dynamics (CFD) model used to capture the nonlinear physics involved in designing aerodynamic surfaces. This, in conjunction with a large number of simulations necessary to yield a set of designs representing the best possible tradeoffs between conflicting objectives (referred to as a Pareto front), makes CFD-driven MOO very challenging. This paper presents a computationally efficient methodology aimed at expediting the MOO process for aerodynamic design problems. The extreme points of the Pareto front are obtained quickly using single-objective optimizations. Starting from these extreme points, identification of an initial set of Pareto-optimal designs is carried out using a sequential domain patching algorithm. Refinement of the Pareto front, originally obtained at the level of the low-fidelity CFD model, is carried out using local response surface approximations and adaptive corrections. The proposed algorithm is validated using a few multi-objective analytical problems and an aerodynamic problem involving MOO of two-dimensional transonic airfoil shapes where the figures of interest are the drag and pitching moment coefficients. A multifidelity model is constructed using CFD model and control points parameterizing the shape of the airfoil. The results demonstrate that an entire or a part of the Pareto front can be obtained at a low cost when considering up to eight design variables.

  • Fast multi-objective design optimization of microwave and antenna structures using data-driven surrogates and domain segmentation
    • Sławomir Kozieł
    • Adrian Bekasiewicz
    2020 Pełny tekst ENGINEERING COMPUTATIONS

    Purpose Strategies and algorithms for expedited design optimization of microwave and antenna structures in multi-objective setup are investigated. Design/methodology/approach Formulation of the multi-objective design problem oriented towards execution of the population-based metaheuristic algorithm within the segmented search space is investigated. Described algorithmic framework exploit variable fidelity modeling, physics- and approximation-based representation of the structure, as well as model correction techniques. The considered approach is suitable for handling various problems pertinent to design of microwave and antenna structures. Numerical case studies are provided demonstrating feasibility of the segmentation-based framework for design of real-world structures in setups with two and three objectives. Findings Formulation of appropriate design problem enables identification of the search space region containing Pareto front which can be further divided into a set of compartments characterized by small combined volume. Approximation model of each segment can be constructed using a small number of training samples and then optimized, at a negligible computational cost, using population-based metaheuristics. Introduction of segmentation mechanism to multi-objective design framework is important to facilitate low cost optimization of many-parameter structures represented by numerically expensive computational models. Further reduction of the design cost can be achieved by enforcing equal-volumes of the search space segments. Research limitations/implications The study summarizes recent advances in low-cost multi-objective design of microwave and antenna structures. The investigated techniques exceed capabilities of conventional design approaches involving direct evaluation of physics-based models for determination of trade-offs between the design objectives, particularly in terms of reliability and reduction of the computational cost. Studies on scalability of segmentation mechanism indicate that computational benefits of the approach decrease with the number of search space segments.

  • Fast multi-objective optimization of antenna structures by means of data-driven surrogates and dimensionality reduction
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2020 Pełny tekst IEEE Access

    Design of contemporary antenna structures needs to account for several and often conflicting objectives. These are pertinent to both electrical and field properties of the antenna but also its geometry (e.g., footprint minimization). For practical reasons, especially to facilitate efficient optimization, single-objective formulations are most often employed, through either a priori preference articulation, objective aggregation, or casting all but one (primary) objective into constraints. Notwithstanding, the knowledge of the best possible design trade-offs provides a more comprehensive insight into the properties of the antenna structure at hand. Genuine multi-objective optimization is a proper way of acquiring such data, typically rendered in the form of a Pareto set that represents the mentioned trade-off solutions. In antenna design, the fundamental challenge is high computational cost of multi-objective optimization, normally carried out using population-based metaheuristic algorithms. In most practical cases, the use of reliable, yet costly, full-wave electromagnetic models is imperative to ensure evaluation reliability, which makes conventional multi-objective optimization procedures prohibitively expensive. The employment of fast surrogates (or metamodels) can alleviate these difficulties, yet, construction of metamodels faces considerable challenges by itself, mostly related to the curse of dimensionality. This work proposes a novel surrogate-assisted approach to multi-objective optimization, where the data-driven model is only rendered in a small region spanned by the selected principal components of the extreme Pareto-optimal design set obtained using local search routines. The region is limited in terms of parameter ranges but also dimensionality, yet contains the majority of Pareto front, therefore surrogate construction therein does not incur considerable costs. The typical cost of identifying the Pareto set is just a few hundred of full-wave analyses of the antenna under design. Our technique is validated using two antenna examples (a planar Yagi and an ultra-wideband monopole antenna) and favorably compared to state-of-the-art surrogate-assisted multi-objective optimization methods.