Publications Repository - Gdańsk University of Technology

Page settings

polski
Publications Repository
Gdańsk University of Technology

Show publications from the year

Publications from the year 2019

Show all
  • Experimental study on single phase operation of microjet augmented heat exchanger with enhanced heat transfer surface
    • Tomasz Muszyński
    • Rafał Andrzejczyk
    2019 APPLIED THERMAL ENGINEERING

    The article presents experimental investigations on a prototype heat exchanger. Presented research is focused on combined active and passive enhancement techniques of surface modification and microjet impingement. The results were compared to reference plate heat exchanger without microjet impingement. The Wilson plot method was applied to determine the heat transfer coefficients in the single phase operation. The heat exchanger was capable of exchanging 300 W of thermal energy at LMTD of 40 K. The obtained overall heat transfer rates reach 600 W/m2. Introducing knurled surface resulted in ∼10% increase heat transfer area, and similar enhancement in transferred heat in reference to plate heat exchanger geometry. Knurled surface decreased heat transfer in combination with a multi-jet impingement in comparison to a smooth surface. A possible explanation of that effect is that the flow in wall jet region is disrupted by the knurled surface and directed in the bulk of the fluid. Initiating mixing with colder fluid, thicker thermal boundary layer, and affecting local temperature distribution.

  • Experimental tests of lintel hybrid beams
    • Krystyna Nagrodzka-Godycka
    • Maciej Tomasz Solarczyk
    • Marek Wesołowski
    2019

    The results of experimental tests of lintel hybrid beams made of air concrete and prestressed concrete were presented in paper. Blocks of air concrete was a protective element for the construction one. The length of hybrid beams was 3.0 m, while total height 27 cm. It was assumed that hybrid beams will work in the simply-supported scheme (with a 10 cm support) loaded uniformly over the entire length. The object of the tests were beams with the same geometry differing in the position of the prestressed wire. In the first considered case the wire was located at a distance of 6.5 cm from the bottom edge of the construction part (prestressed concrete) of beam, while in the second case: 13 cm from the bottom edge of the construction part of beam. The experimental tests under static monotonous load up to the failure were examined. The paper shortly described the designing stage of project. Hybrid beams were calculated with Limit State Method and Allowable Stress Method. Some assumptions for element calculations were also presented.

  • Experimentally feasible semi-device-independent certification of four-outcome positive-operator-valued measurements
    • Piotr Mironowicz
    • Marcin Pawłowski
    2019 Full text PHYSICAL REVIEW A

    Recently the quantum information science community devoted a lot of attention to the theoretical and practical aspects of generalized measurements, the formalism of all possible quantum operations leading to acquisition of classical information. On the other hand, due to imperfections present in quantum devices, and limited thrust to them, a trend of formulating quantum information tasks in a semi-device-independent manner emerged. In this Rapid Communication we use the concept of quantum random access codes to construct a protocol able to certify the presence of the generalized measurements in a semi-device-independent way without employing quantum entanglement. We use semidefinite programming methods to show robustness of the protocol and characterize its statistical properties. We conclude that it allows for experimental realizations using technology currently available in laboratories.

  • Exploration of Creativity Techniques in Software Engineering in Training-Application-Feedback Cycle
    • Anna Bobkowska
    2019 Lecture Notes in Business Information Processing

    Creativity research has proposed about a hundred and fifty creativity techniques. The question is whether they can be applied in software engineering for creativity training or directing creativity in software projects. This paper aims at answering this question via a quasi-experiment conducted in Training-Application-Feedback cycle in which participants express their opinions about selected creativity techniques after training and an attempt to apply them in software-related context.

  • Extended investigation of performance-energy trade-offs under power capping in HPC environments
    • Adam Krzywaniak
    • Paweł Czarnul
    • Jerzy Proficz
    2019

    —In the paper we present investigation of performance-energy trade-offs under power capping using modern processors. The results are presented for systems targeted at both server and client markets and were collected from Intel Xeon E5 and Intel Xeon Phi server processors as well as from desktop and mobile Intel Core i7 processors. The results, when using power capping, show that we can find various interesting combinations of energy savings and performance drops as well as non-trivial minima of the energy-execution time product. We performed this analysis for a subset of NAS Parallel Benchmark applications: BT, CG, EP and FT and sizes of the computational problem (classes A, B, C, D). We can observe that the energy characteristics visualized by a prototype of our new tool EnergyProfiler do not depend on the size of a computational problem. Consequently, the proposed tool can potentially support quick energy/performance trade-off estimation for codes similar to the tested, well-recognized benchmarks.

  • Extremal thermal loading of a bifurcation pipe
    • Bartosz Kraszewski
    • Grzegorz Bzymek
    • Paweł Ziółkowski
    • Janusz Badur
    2019 Full text AIP Conference Proceedings

    The subject of considerations is a spherical bifurcation pipe of a live steam made of steel P91, which is an element of a block of coal-fired power plant working with a 18K370 turbine. As experience shows, it is a very sensitive element of the boiler pipelines. An extreme work scenario for such a block has been adopted, in which the turbine is shutting down to a warm state three times in 24 hours. This is an action dictated by new challenges in the field of electricity network regulation, caused by increasing share of renewable energy sources. A one-sided numerical thermal-FSI analysis was performed. The focus was on hoop stresses as the most significant for the bifurcation pipe durability. The daily runs of these stresses at three points of the thickness of the bifurcation pipe sphere have been presented. Mechanical stresses derived from pressure and thermal stresses derived from temperature changes have been isolated. It has been shown that depending on the thermal load, some areas of the cross section are compressed while adjacent ones are stretched and vice versa. Thus, the mechanical stresses can be reduced under thermal conditions by thermal stresses. It has been proven that the bifurcation pipe is able to withstand the given extreme loads with stresses more than twice smaller than the yield point at a given operating temperature.

  • EXTREME RAINFALLS AS A CAUSE OF URBAN FLASH FLOODS; A CASE STUDY OF THE ERBIL-KURDISTAN REGION OF IRAQ
    • Andam Mustafa
    • Hadi Muhammed
    • Michał Szydłowski
    2019 Full text Acta Scientiarum Polonorum Formatio Circumiectus

    Aim of the study The current paper aims to give a detailed evaluation and analysis of some extreme rainfall events that happened in the last decade in terms of spatial and temporal rainfall distribution, intensity rate, and exceedance probability. Moreover, it examines the effects of each analysed aspect on the resulting flash floods in the studied area. Material and methods In their glossary of meteorology, American Meteorology Society (AMS) subdivided rainfall intensity types into four groups (light, moderate, heavy, and violent). Also, for estimating the exceedance probability, lognormal distribution was applied as a statistical model of the precipitation probability distribution function. Results and conclusions Out of six episodes, five of the analysed events were classified as heavy rainfall. However, the duration of those heavy rainfall events was not more than two hours. Four events of maximum daily rainfall (for a 39-year dataset) were rated at 1–10% of exceedance probability. To conclude, the current study can be an initial step in modelling hydrological events in the studied area, and in the process of transforming precipitation into the outflows of urban basins in the future.

  • Fabrication and Structural Properties of LaNb 1‐x As x O 4 Ceramics
    • Sebastian Wachowski
    • Bartosz Kamecki
    • Piotr Winiarz
    • Kacper Dzierzgowski
    • Michał Jurkowski
    • Jaroslav Dzisevič
    • Aleksandra Mielewczyk-Gryń
    • Maria Gazda
    2019 ChemistrySelect

    Lanthanum niobate substituted with arsenic was synthesized by three methods: solid state reaction from binary oxides and two different methods combining co-precipitation and solidstate reaction. In the first of the combined methods LaNb1- xAsxO4 was synthesized from LaAsO4, obtained from coprecipitation method, and lanthanum and niobium oxides. In the second LaNbO4 was first synthesized from binary oxides and then mixed with LaAsO4 and fired in the second step to obtain the final material. Single phase materials could not be synthesized via solid-state synthesis, whilst it was possible with both of the combined methods. Structural parameters of the materials obtained with both methods were similar what shows that they do not relate to the synthesis method. Ceramics obtained with both combined methods were dense, however, the density of the ceramics formed from LaAsO4 and LaNbO4 was higher.

  • Fabrication methods of smart composite coatings - review
    • Łukasz Pawłowski
    • Michał Bartmański
    • Andrzej Zieliński
    2019 Full text European Journal of Medical Technologies

    Postoperative bacterial infections are one of the main reasons for unsuccessful implantation of long-term implants. The development of bacterial infection requires antibiotic therapy, in extreme cases a reimplantation procedure is necessary. In order to provide materials for implants with antibacterial properties, they are subjected to modifications to create a coating that will release the drug substance, when the inflammation occurs. Significant interest is now gained by the so-called smart polymers, that react to the stimuli from the external environment such as pH change, temperature change, the influence of UV-VIS radiation or interaction of electric and magnetic fields. When designing drug delivery systems, the characteristics of the inflamed tissue may be taken into account, because they are characterized by increased temperature and reduced pH. It would, therefore, be reasonable to create biopolymer coatings that under these conditions degrade and release the drug substance. However, the problem is the controlled release of the drug substance trapped in the biopolymer matrix. This review paper presents most often used methods of smart biopolymer coatings production, which release the drug substance in a controlled manner. Methods such as electrophoretic deposition, dip-coating, spin-coating, and layer-by-layer are discussed, including process parameters, steps of the coating production, possible post-processing and examples of smart coatings produced using these methods. Each of these methods offers a wide range of process parameters, by changing these parameters it is possible to fine-tune the properties of the coatings produced to the desired values. Extensive research is needed to determine the optimal process parameters that will allow the production of coatings with the desired properties.

  • Fading Analysis in Off-Body Channels in a Straight Metallic Corridor in a Passenger Ferry Environment
    • Paweł Tomasz Kosz
    • Sławomir Ambroziak
    • Luis M. Correia
    • Jacek Stefański
    2019

    This paper presents a fading analysis for Body Area Networks off-body communications at 2.45 GHz in a passenger ferry environment. The results are based on measurements performed for dynamic scenarios in a straight metallic corridor. Two components, extracted from instantaneous system loss values, have been analysed: small- and large-scales fading, separately for each scenario. Well-known probability distribution functions have been fitted to the empirical distributions by using Goodness of Fit tests. The slow fading component is best modelled by the Lognormal Distribution, with 0 dB mean and [1.22, 2.88] dB standard deviation parameters, while the fast fading one is by the Nakagami-m Distribution with [0.78, 0.91] shape and [1.9, 2.18] scale parameters.

  • Fake News: Possibility of Identification in Post-Truth Media Ecology System
    • Jan Kreft
    2019 Full text Zarządzanie Mediami

    The main aim of the article is identification of the attitudes towards the processes of identification and verification of fake news in the environment of digital media. The subject of the research refers to the users’ attitudes towards fake news. As indicated by the research, the attitudes towards fake news are not unambiguous. About 2/3 of the respondents claim that they are not able to distinguish fake news from true information; only every twelfth respondent declares that they know tools for verification of information, although the research survey has been carried out among students of media management, journalism and marketing – students who deal with information in social media.

  • Fake News: Possibility of Identification in Post-Truth Media Ecology System
    • Jan Kreft
    • Monika Hapek
    2019 Full text

    Information comes as basic good which affects social well-being. A modern society and a modern state – its administration, education, culture, national economy and armed forces – cannot function efficiently without a rationally developed field of information. The quality of the functioning of that system depends on a specific feature of information, that is namely: its reliability which makes it possible for us to evaluate accuracy, completeness, valence and trust towards information. A part of information conveyed in social media is fake news that is namely: distorted signals not correlated with the truth, which may mislead their recipients. Such information comes as an element of info-environment defined by the term of post-truth. The main aim of the article is identification of the attitudes towards the processes of identification and verification of fake news in the environment of digital media. The subject of the research refers to the users’ attitudes towards fake news. As indicated by the research, the attitudes towards fake news are not unambiguous. About 2/3 of the respondents claim that they are not able to distinguish fake news from true information; only every twelfth respondent declares that they know tools for verification of information, although the research survey has been carried out among students of media management, journalism and marketing – students who deal with information in social media

  • Fast Basis Function Estimators for Identification of Nonstationary Stochastic Processes
    • Maciej Niedźwiecki
    • Marcin Ciołek
    • Artur Gańcza
    2019

    The problem of identification of a linear nonsta-tionary stochastic process is considered and solved using theapproach based on functional series approximation of time-varying parameter trajectories. The proposed fast basis func-tion estimators are computationally attractive and yield resultsthat are better than those provided by the local least squaresalgorithms. It is shown that two important design parameters –the number of basis functions and the size of the local analysisinterval – can be selected on-line in an adaptive way.

  • Fast geometry scaling of miniaturized microwave couplers with power split correction
    • Sławomir Kozieł
    • Adrian Bekasiewicz
    2019 INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING

    Redesigning a microwave circuit for various operating conditions is a practically important yet challenging problem. The purpose of this article is development and presentation of a technique for fast geometry scaling of miniaturized microwave couplers with respect to operating frequency. Our approach exploits an inverse surrogate model constructed using several reference designs that are optimized for a set of operating frequencies within a range of interest. For the sake of computational efficiency, the reference designs are obtained for an equivalent network model of the coupler. The surrogate directly predicts the optimum values of geometry parameters of the structure at hand corresponding to a requested operating frequency. By introducing appropriate correction, the model allows for coupler scaling at the EM simulation model level. Because the surrogate does not carry information about the power split ratio of the coupler, an additional analytical corrective procedure is developed to ensure an equal power split of scaled structure. The computational cost of the scaling procedure corresponds to only two EM analyses of the circuit at hand (including both correction steps). The operation and performance of our technique is demonstrated using a compact microstrip rat‐race coupler scaled for the operating frequency range of 0.5‐2.5 GHz. Experimental validation is also provided.

  • Fast surrogate-assisted frequency scaling of planar antennas with circular polarisation
    • Sławomir Kozieł
    • Adrian Bekasiewicz
    2019 IET Microwaves Antennas & Propagation

    In this work, the problem of computationally efficient frequency scaling (re-design) of circular polarisation antennas is addressed using surrogate-assisted techniques. The task is challenging and requires the identification of the optimum geometry parameters to enable the operation of the re-designed structure at a selected (required) centre frequency. This involves handling several performance figures such as the antenna gain, the impedance bandwidth, as well as the axial ratio bandwidth. The design technique described here involves two types of surrogate models: an inverse surrogate (utilised to find the initial design) and a forward surrogate of the structure response sensitivities, necessary to realise post-scaling design correction. The entire re-design process is fast and only requires a few full-wave electromagnetic simulations of the antenna. The proposed dimension scaling method is demonstrated using a patch antenna with circular polarisation fed through a branch-line coupler. The structure is re-designed within the operating frequency range of 4.5–6.5 GHz. Numerical results are validated experimentally.

  • Fast tolerance-aware design optimization of miniaturized microstrip couplers using variable-fidelity EM simulations and re-sponse features
    • Sławomir Kozieł
    • Adrian Bekasiewicz
    2019 ENGINEERING COMPUTATIONS

    Manufacturing tolerances and other types of uncertainties may considerably affect operation and performance of microwave components and systems. Quantification of these effects is therefore an important part of the design process. It is even more important to obtain designs whose sensitivity to parameter deviations is reduced as much as possible. All of these require statistical analysis carried out at the level of electromagnetic (EM) simulation models, which may be prohibitively expensive when executed directly, e.g., through Monte Carlo simulations. In this work, a technique for fast yield optimization of compact microstrip couplers is proposed. Our methodology involves variable-fidelity EM models, local surrogates constructed using a response feature approach, as well as a sequential approximation optimization framework. A combination of these tools permits yield optimization at a remarkably low cost corresponding to less than a dozen of high-fidelity EM analyses of the circuit under design. The proposed approach is demonstrated using a miniaturized equal-split rat-rate coupler operating at 1 GHz. Reliability of results is validated using direct (high-fidelity) Monte Carlo simulations of the initial and optimized designs.

  • FE analysis of support-specimen interaction of compressive experimental test
    • Krzysztof Wołoszyk
    • Yordan Garbatov
    2019

    The objective of this work is to investigate the support-specimen interaction during the compressive experimental testing of stiffened plates. The interaction is analyzed employing the nonlinear Finite Element Method using the commercial software ANSYS. The connection between the stiffened plate and testing supports is modelled with the use of contact elements, where several possible interaction scenarios are investigated, and their impact on the ultimate strength is evaluated. The sensitivity of the modelling of the testing support structure to the boundary conditions as generated by the finite element model and the structural behavior of stiffened plates during the test are also investigated, and several conclusions are derived.

  • FEA analysis of the multicell piezoelectric motor
    • Roland Ryndzionek
    • Łukasz Sienkiewicz
    • Michał Michna
    • Filip Kutt
    • Grzegorz Kostro
    • Mieczysław Ronkowski
    2019 Full text

    The presented paper concerns a design, modeling and chosen tests of the prototype multicell piezoelectric motor (MPM). The principle of operation based on three independent traveling wave actuators is presented. The main materials and technologies used in the fabrication process are described. The structure of the motor is modeled using static and modal FEM analysis. The process of traveling wave generation in the MPM structure is demonstrated. Finally, the main results of the simulation are validated by measurements of MPM prototype. The natural frequencies of three actuators are measured along with the corresponding displacements at two locations.

  • Feedline Alterations for Optimization-Based Design of Compact Super-Wideband MIMO Antennas in Parallel Configuration
    • Muhammad ul Haq
    • Sławomir Kozieł
    2019 IEEE Antennas and Wireless Propagation Letters

    This letter presents a technique for size reduction of wideband multiple-input-multiple-output (MIMO) antennas. Our approach is a two-stage procedure. At the first stage, the antenna structure is modified to improve its impedance matching. This is achieved through incorporation of an n-section tapered feedline, followed by reoptimization of geometry parameters. Reducing the maximum in-band reflection well beyond the acceptance level of -10 dB creates room for size reduction, realized in the second stage as explicit footprint area minimization with the constraints imposed on the maximum in-band reflection level (|S 11 | ≤ -10 dB) and element isolation (|Sε| ≤ -20 dB). The technique is generic and can be applied to various monopole-based MIMO structures. It is validated using two antenna structures operating from 2.8 to 20 GHz. Various complexities of the tapered lines are also investigated, from n = 1 to 5. To the best of the authors' knowledge, the obtained footprints (452 and 546 mm 2 , respectively) are the smallest to date while ensuring acceptable performance, specifically impedance matching, isolation, envelope correlation coefficient (<;0.005), and diversity gain (>9.99 dB).

  • Fermentative Conversion of Two-Step Pre-Treated Lignocellulosic Biomass to Hydrogen
    • Karolina Kucharska
    • Hubert Cieśliński
    • Piotr Rybarczyk
    • Edyta Słupek
    • Rałał Łukajtis
    • Katarzyna Wychodnik
    • Marian Kamiński
    2019 Full text Catalysts

    Fermentative hydrogen production via dark fermentation with the application of lignocellulosic biomass requires a multistep pre-treatment procedure, due to the complexed structure of the raw material. Hence, the comparison of the hydrogen productivity potential of different lignocellulosic materials (LCMs) in relation to the lignocellulosic biomass composition is often considered as an interesting field of research. In this study, several types of biomass, representing woods, cereals and grass were processed by means of mechanical pre-treatment and alkaline and enzymatic hydrolysis. Hydrolysates were used in fermentative hydrogen production via dark fermentation process with Enterobacter aerogenes (model organism). The differences in the hydrogen productivity regarding different materials hydrolysates were analyzed using chemometric methods with respect to a wide dataset collected throughout this study. Hydrogen formation, as expected, was positively correlated with glucose concentration and total reducing sugars amount (YTRS) in enzymatic hydrolysates of LCMs, and negatively correlated with concentrations of enzymatic inhibitors i.e., HMF, furfural and total phenolic compounds in alkaline-hydrolysates LCMs, respectively. Interestingly, high hydrogen productivity was positively correlated with lignin content in raw LCMs and smaller mass loss of LCM after pre-treatment step. Besides results of chemometric analysis, the presented data analysis seems to confirm that the structure and chemical composition of lignin and hemicellulose present in the lignocellulosic material is more important to design the process of its bioconversion than the proportion between the cellulose, hemicellulose and lignin content in this material. For analyzed LCMs we found remarkable higher potential of hydrogen production via bioconversion process of woods i.e., beech (24.01 mL H2/g biomass), energetic poplar (23.41 mL H2/g biomass) or energetic willow (25.44 mL H2/g biomass) than for cereals i.e., triticale (17.82 mL H2/g biomass) and corn (14.37 mL H2/g biomass) or for meadow grass (7.22 mL H2/g biomass).