2021 - Repozytorium publikacji - Politechnika Gdańska

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Functionalization of graphene oxide coatings with phosphorus atoms and their corrosion resistance in sodium chloride environment
- Karolina Grajewska
- Marek Lieder
2021 DIAMOND AND RELATED MATERIALS
In this work, we compared corrosion resistance of graphene oxide, and phosphorus functionalized reduced graphene oxide coatings obtained as a result of electrophoretic deposition on the copper substrate. Doping graphene oxide with phosphorus atoms was performed by a hydrothermal method in the presence of different amounts of phosphoric acid. Structural studies confirmed the insertion of phosphorus atoms into the graphene oxide structure. FTIR spectra showed peaks at 1020 cm−1 and 1131–1450 cm−1 which can be assigned to phosphorus groups. XPS analysis indicated that phosphorus atoms were inserted in an amount of around 5%. The stable and uniform suspension of functionalized graphene precursors of coatings allowed electrodeposition. These coatings show good protective properties due to hydrophobic and intact surfaces without significant damages.
Functionalized Peptide Fibrils as a Scaffold for Active Substances in Wound Healing
- Justyna Sawicka
- Emilia Iłowska
- Milena Deptuła
- Paweł Sosnowski
- Piotr Sass
- Katarzyna Czerwiec
- Klaudia Chmielewska
- Aneta Szymańska
- Zuzanna Pietralik-Molińska
- Maciej Kozak
- Paweł Sachadyn
- Michał Pikuła
- Sylwia Rodziewicz-Motowidło
2021 Pełny tekst INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Technological developments in the field of biologically active peptide applications in medicine have increased the need for new methods for peptide delivery. The disadvantage of peptides as drugs is their low biological stability. Recently, great attention has been paid to self-assembling peptides that can form fibrils. Such a formulation makes bioactive peptides more resistant to enzymatic degradation and druggable. Peptide fibrils can be carriers for peptides with interesting biological activities. These features open up prospects for using the peptide fibrils as long-acting drugs and are a valid alternative to conventional peptidic therapies. In our study, we designed new peptide scaffolds that are a hybrid of three interconnected amino acid sequences and are: pro-regenerative, cleavable by neutrophilic elastase, and fibril-forming. We intended to obtain peptides that are stable in the wound environment and that, when applied, would release a biologically active sequence. Our studies showed that the designed hybrid peptides show a high tendency toward regular fibril formation and are able to release the pro-regenerative sequence. Cytotoxicity studies showed that all the designed peptides were safe, did not cause cytotoxic effects and revealed a pro-regenerative potential in human fibroblast and keratinocyte cell lines. In vivo experiments in a dorsal skin injury model in mice indicated that two tested peptides moderately promote tissue repair in their free form. Our research proves that peptide fibrils can be a druggable form and a scaffold for active peptides.
Fundamentals of classical and analytical mechanics
- Krzysztof Lipiński
2021
The book is a monographic description of the present attempt to Newtonian and Lagrangian mechanics. But also, it could be found as a supplementary educational material useful for the graduate courses in mechanics taken by students majoring in mechanical engineering, physics or physical science. In the book you can find a brief introduction to concepts and principles of algebra of vectors; Kinematics of particles, mainly focused on non-Cartesian coordinates used in the description of the kinematics; Dynamics of particles; focused on Newton's laws of motion; motion of particles in one and in three dimensions; description of dynamics in inertial and non-inertial frames of reference; linear and angular momentums; work and energy principles; Kinematics and dynamics of spherical motion of rigid bodies; Euler’s angles; angular velocities and accelerations; conical surfaces of angular velocity vectors, steady precession, angular momentum of bodies that performs spherical motion, Euler’s equations of dynamics for bodies in spherical motion and their kinetic energy formulas; Kinematics and dynamics of general motion of rigid bodies; linear velocity and linear acceleration of points of the bodies; linear and angular momentum of rigid bodies; Newton-Euler’s dynamics equations; kinetic energy; Simplified theory of gyroscope; Mechanics express with the Lagrangian formalism; constraints and the constraint equations; main principles used in classifications of the constraints; generalized coordinates; virtual displacements and consequences of the virtual work principle; virtual velocities and the virtual power; generalized forces and the generalized equation of dynamics (d’Alembert’s principle); two types of Lagrange’s equations; some alternative principles of equilibrium.
Funkcjonowanie zespołów napędu hydraulicznego maszyn w niskich temperaturach otoczenia. Wyd.2
- Ryszard Jasiński
2021
W pracy przedstawiono cztery warianty klasyfikacji rozruchów oziębionego napędu hydraulicznego. Pierwsza sytuacja dotyczy zagadnienia, w którym wszystkie zespoły układu napędowego wraz z olejem mają taką samą niską temperaturę podczas rozruchu. Pozostałe warianty odnoszą się do rozruchu w warunkach szoku termicznego wywołanych zasilaniem ciepłym czynnikiem roboczym oziębionych zespołów hydraulicznych. Rozruch zespołów w takich warunkach powoduje wstąpienie wiele niekorzystnych zjawisk. Jednym z nich są zmiany luzów między współpracującymi elementami zespołów hydraulicznych. W Laboratorium Hydrauliki Wydziału Mechanicznego Politechniki Gdańskiej, na stanowiskach w komorach niskich temperatur, przebadano: pompy zębate, tłoczkowe osiowe i promieniowe, siłowniki, silniki satelitowe i orbitalne, silnik tłokowy promieniowy oraz rozdzielacze proporcjonalne i klasyczne oraz serwozawór. Podczas badań zespołów rejestrowano wiele parametrów, na podstawie których uzyskano dane o przebiegach zmian temperatury elementów zespołów hydraulicznych, ciśnienia w kanałach zespołów, prędkości obrotnej, natężenia przepływu, momentu obrotowego w funkcji czasu. Przeprowadzono analizę zjawisk cieplnych typowych zespołów hydraulicznych, uruchamianych w warunkach szoku termicznego. Opracowano i opisano trzy metody do określenia obszarów parametrów prawidłowego lub nieprawidłowego działania zespołu hydraulicznego w warunkach szoku termicznego na podstawie analizy zmian luzów efektywnych między współpracującymi elementami. Tymi metodami są: eksperymentalna, analityczna i symulacji komputerowej. Wyznaczono wartości współczynników przejmowania ciepła w zależności od prędkości obrotowej lub natężenia przepływu. Wyznaczone współczynniki przejmowania ciepła posłużyły do przeprowadzenia symulacji komputerowych procesów nagrzewania zespołów hydraulicznych. Uzyskano rozkłady pól temperatury elementów zespołów hydraulicznych oraz przebiegi temperatury tych elementów potrzebne do wyznaczenia luzów między współpracującymi elementami zespołów. W pracy pokazano rezultaty symulacji komputerowej niektórych zespołów hydraulicznych: pompy wielotłoczkowej osiowej, silnika satelitowego i rozdzielacza proporcjonalnego. Wyniki z symulacji komputerowej porównano z wynikami eksperymentalnymi i uzyskano dużą zbieżność przebiegów temperatury elementów z badań eksperymentalnych i symulacji komputerowych. Przedstawiono kilka sposobów zapobiegania zanikowi efektywnego luzu.
Future Directions in Quantum Materials Synthesis
- Tyrel McQueen
- Tanya Berry
- Juan Chamorro
- Alireza Ghasemi
- W. Adam Phelan
- Elizabeth Pogue
- Lucas Pressley
- Mekhola Sinha
- Veronica J. Stewart
- Thao Tran
- Hector Vivanco
- Michał Winiarski
2021
The following sections are included: Introduction The Current State of the Art The Frontiers Exploring the Frontiers Conclusion
G2DC-PL+: a gridded 2 km daily climate dataset for the union of the Polish territory and the Vistula and Odra basins
- Mikołaj Piniewski
- Mateusz Szcześniak
- Ignacy Kardel
- Somsubhra Chattopadhyay
- Tomasz Berezowski
2021 Pełny tekst Earth System Science Data
G2DC-PL+, a gridded 2 km daily climate dataset for the union of the Polish territory and the Vistula and Odra basins, is an update and extension of the CHASE-PL Forcing Data – Gridded Daily Precipitation and Temperature Dataset – 5 km (CPLFD-GDPT5). The latter was the first publicly available, high-resolution climate forcing dataset in Poland, used for a range of purposes including hydrological modelling and bias correction of climate projections. While the spatial coverage of the new dataset remained the same, it has undergone several major changes: (1) the time coverage was increased from 1951–2013 to 1951–2019; (2) its spatial resolution increased from 5 to 2 km; (3) the number of stations used for interpolation of temperature and precipitation approximately doubled; and (4) in addition to precipitation and temperature, the dataset consists of relative humidity and wind speed data. The main purpose for developing this product was the need for long-term areal climate data for earth-system modelling, and particularly hydrological modelling. Geostatistical methods (kriging) were used for interpolation of the studied climate variables. The kriging cross-validation revealed improved performance for precipitation compared to the original dataset expressed by the median of the root mean squared errors standardized by standard deviation of observations (0.59 vs. 0.79). Kriging errors were negatively correlated with station density only for the period 1951–1970. Values of the root mean squared error normalized to the standard deviation (RMSEsd) were equal to 0.52 and 0.4 for minimum and maximum temperature, respectively, suggesting a small to moderate improvement over the original dataset. Relative humidity and wind speed exhibited lower performance, with median RMSEsd equal to 0.82 and 0.87, respectively. The dataset is openly available from the 4TU Centre for Research Data at https://doi.org/10.4121/uuid:a3bed3b8-e22a-4b68-8d75-7b87109c9feb (Piniewski et al., 2020).
Galerkin formulations of isogeometric shell analysis: Alleviating locking with Greville quadratures and higher-order elements
- Z. Zou
- T.j.r. Hughes
- M.a. Scott
- Roger Sauer
- E.j. Savitha
2021 COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
We propose new quadrature schemes that asymptotically require only four in-plane points for Reissner–Mindlin shell elements and nine in-plane points for Kirchhoff–Love shell elements in B-spline and NURBS-based isogeometric shell analysis, independent of the polynomial degree p of the elements. The quadrature points are Greville abscissae associated with pth-order B-spline basis functions whose continuities depend on the specific Galerkin formulations, and the quadrature weights are calculated by solving a linear moment fitting problem in each parametric direction. The proposed shell element formulations are shown through numerical studies to be rank sufficient and to be free of spurious modes. The studies reveal comparable accuracy, in terms of both displacement and stress, compared with fully integrated spline-based shell elements, while at the same time reducing storage and computational cost associated with forming element stiffness and mass matrices and force vectors. The high accuracy with low computational cost makes the proposed quadratures along with higher-order spline bases, in particular polynomial orders, p = 5 and 6, good choices for alleviating membrane and shear locking in shells.
Gas mixtures recognition using an array of amperometric gas sensors with drifting or faulty sensors
- Marta Dmitrzak
- Paweł Kalinowski
- Piotr Jasiński
- Grzegorz Jasiński
2021
In this study, the possibility of using selected methods for diagnostics of performance of matrix composed with six amperometric electrochemical gas sensors is investigated. Measurements of sensor responses in selected concentrations of single toxic gases or gas mixtures were performed and were repeated over time to show sensor drift. Additionally, the studies on the sensors’ drift were performed. The drift has been recognized by Principal Component Analysis (PCA). The results show that the methods used in this work can be potentially applied to detect faulty or drifted sensor responses.
Gasification of Densified Biomass (DB) and Municipal Solid Wastes (MSW) Using HTA/SG Technology
- Jan Stąsiek
- Jacek Barański
- Marcin Jewartowski
- Jan Wajs
2021 Pełny tekst Processes
The necessity of economical and rational use of natural energy sources caused a rapid development of research on the possibilities of using non‐conventional energy resources. Taking the above into account, a new technological process of thermochemical conversion of biomass and communal waste, commonly known as High Temperature Air/Steam Gasification (HTA/SG) and Multi‐Staged Enthalpy Extraction Technology (HTAG‐MEET), was developed. In relation to traditional techniques of gasification or combustion of hydrocarbon fuels, the presented concept is characterized by higher thermal efficiency of the process, low emission of harmful compounds of carbon, sulfur, nitrogen, dioxins, furans and heavy metals. The use of a high‐temperature gasification factor causes an increased thermochemical decomposition of solid fuels, biomass and municipal waste into gaseous fuel (syngas), also with increased hydrogen content and Lower Calorific Value (LCV). In this study, the possibility of using a batch type reactor (countercurrent gasifier) was analyzed for gasification of biomass and municipal waste in terms of energy recovery and environmental protection. The proposed research topic was aimed at examining the possibility of using the thermal utilization of biomass and municipal waste through their high‐temperature decomposition in the presence of air, a mixture of air and steam. The main goals of the research were achieved during the implementation of several parallel stages of the schedule, which included, primarily: (a) study of the possibility of using thermal utilization of biomass and municipal waste through their high‐temperature gasification in the presence of air or a mixture of air and steam and, secondary (b) analytical and numerical modeling of high‐temperature gasification of biomass and municipal waste with the use of ANSYS CFD Fluent 6.3 software. Selected results of the experimental and numerical studies are properly presented. The higher temperature gasification concept shows the capability of this technology for maximizing the gaseous product yield in an up‐draft fixed bed gasifier. It was also observed that at a high temperature, steam addition contributed to the thermal conversion of biofuels to gas with higher production of hydrogen.
Gdyńskie perły czyli więcej niż modernizm
- Patrycja Wójcik
- Maria Sołtysik
- Agata Abramowicz
- Jacek Friedrich
2021
Monografia przedstawia różne tendencje stylowe w gdyńskie architekturze, zarówno w okresie międzywojennym jak i w latach powojennych
Gender and support Polish women at the beginning of their professional career in IT
- Agnieszka Wałachowska
2021
The development of ICT should be understood not only as an increase in the number of users skilled in the use of new technologies, but also as an ever-increasing demand for qualified professionals capable of creating, administering, supporting, and servicing ICT systems. With regard to the continuous development of innovative technologies, there is a noticeably low share of women who actively create and co-create this sector, while at the same time providing an opportunity to increase efficiency in terms of adapting technologies to the expectations of a wider audience. In Poland, the share of women preparing to become ICT specialists by studying computer science is low, although constantly growing. The aim of the chapter is to notice the differences in the abilities and perception of their skills and professional ambitions between female and male IT students on the example of empirical data from the Gdańsk WSB University in the field of Computer Sciences and to indicate the initiative that helps to eliminate these differences. After outlining the problems underlying the dominance of men in the ICT sector, we show that even when women take up the challenge of studying IT, they still need support to overcome stereotypes. The IT for SHE initiative is described as an example of a program that offers such support. It is assessed in terms of diversity, flexibility, and an area directly related to strengthening the mentality. The conclusion of the work is that, because they have low self-esteem of their professional skills, talented IT students need help to enter the labor market and the diverse support programs are not indifferent in this role.
Generalization of Kramers-Krönig relations for evaluation of causality in power-law media
- Jacek Gulgowski
- Tomasz Stefański
2021 Communications in Nonlinear Science and Numerical Simulation
Classical Kramers-Krönig (K–K) relations connect real and imaginary parts of the frequency-domain response of a system. The K–K relations also hold between the logarithm of modulus and the argument of the response, e.g. between the attenuation and the phase shift of a solution to a wave-propagation problem. For square-integrable functions of frequency, the satisfaction of classical K–K relations implies causality in the time domain. On the other hand, when the K–K relations are checked for the logarithm of the system response, the function is not a square integrable one. Then one can employ classical K–K relations with subtractions, but their satisfaction for the logarithm of the system response does not imply causality of the original function. In this paper, the K–K relations are generalized towards functions which are not square-integrable, also allowing for causality evaluation when the logarithm of the system response is considered. That is, we propose generalization of the K–K relations with subtractions, whose validity for the logarithm of the system response and the satisfaction of additional assumptions imply causality of the originally considered function. The derived theory is then applied to electromagnetic media characterized by power-law frequency dispersion, i.e. the media which are described by fractional-order models (FOMs). In this case, the subtraction procedure generates functions which may be not square integrable, or even not locally integrable. However, we can rigorously analyse causality of the media described by FOM using the derived theory, as well as the parameter ranges for which such models are causal.
Generalized temperature dependence model for anammox process kinetics
- Dominika Sobotka
- Jun Zhai
- Jacek Mąkinia
2021 Pełny tekst SCIENCE OF THE TOTAL ENVIRONMENT
Temperature is a key operational factor influencing the anammox process kinetics. In particular, at temperatures below 15 °C, the specific anammox activity (SAA) considerably decreases. This study aimed to describe the temperature dependence of the anammox process kinetics in the temperature range from 10 to 55 °C, including the specific characteristics of“cold anammox”. The commonly used Arrhenius and extended and modifiedRatkowsky equations were examined. The Ratkowskyequationsyieldedastrong correlation (coefficient of determination, R2= 0.93–0.96) between the measured and predicted data over the analyzed temperature range(10–55 °C). However, these equations could not correctly reflect the anammox temperature dependence at temperatures below 15 °C (R2= 0.36–0.48). Therefore, a new generalized temperature model was proposed. The generalized temperature equation (GTE) considered the division of the analyzed temperature range into three temperature ranges: 10–15 °C, 15–35 °C and 35–55 °C. The ranges correspond to“cold anammox”,“(low)mesophilic anammox” and “thermophilic anammox”. The applied approach yielded a strong correlation between the measured and predicted SAA (R2= 0.97) over the temperature range from 10 to 55 °C and over the low-temperature range from 10 to 15 °C (R2= 0.99). Overall, the GTE could enhance the predictions of the temperature dependence of the anammox process kinetics. The GTE can help examine anammox-based bioaugmentation systems operating at both high temperatures (sidestream reactors) and low temperatures (mainstream reactors).
Generation-recombination and 1/f noise in carbon nanotube networks
- A. Rehman
- A. Krajewska
- B. Stonio
- K. Pavlov
- G. Cywinski
- D. Lioubtchenko
- W. Knap
- S. Rumyantsev
- Janusz Smulko
2021 Pełny tekst APPLIED PHYSICS LETTERS
The low-frequency noise is of special interest for carbon nanotubes devices, which are building blocks for a variety of sensors, including radio frequency and terahertz detectors. We studied noise in as-fabricated and aged carbon nanotube networks (CNNs) field-effect transistors. Contrary to the majority of previous publications, as-fabricated devices demonstrated the superposition of generation-recombination (GR) and 1/f noise spectra at a low-frequency range. Although all the devices revealed identical current–voltage characteristics, GR noise was different for different transistors. This effect is explained by the different properties and concentrations of trap levels responsible for the noise. Unexpectedly, exposure of these devices to the atmosphere reduced both the resistance and GR noise due to nanotube’s p-doping by adsorbed water molecules from the ambient atmosphere. The presence of the generation recombination noise and its dependences on the environment provides the basis for selective gas sensing based on the noise measurements. Our study reveals the noise properties of CNNs that need to be considered when developing carbon nanotubes-based selective gas sensors.
Generowanie tekstu z użyciem sieci typu Transformer
- Julian Szymański
- Michał Wilk
- Radosław Baziak
2021
Opisano działanie wybranych modeli uczenia maszynowego znajdujących zastosowanie w przetwarzaniu języka naturalnego w szczególności wy- korzystywanych do generowania tekstu. Przedstawiono również model BERT i jego różne wersje, a także praktyczne wykorzystanie modeli typu Transformer. Przedstawiono ich działanie w aplikacji zmieniającej nastrój tekstu w sposób sekwencyjny.
Genetic Background and Antibiotic Resistance Profiles of K. pneumoniae NDM-1 Strains Isolated from UTI, ABU, and the GI Tract, from One Hospital in Poland, in Relation to Strains Nationally and Worldwide
- Magdalena Wysocka
- Roxana Zamudio
- Marco R Oggioni
- Justyna Gołębiewska
- Marek Bronk
- Beata Krawczyk
2021 Pełny tekst Genes
In recent years, there has been an observed increase in infections caused by carbapenem-resistant Klebsiella pneumonia (Kp) strains. The aim of this study was the phenotypic and genotypic analysis of eight K. pneumoniae NDM (Kp NDM) isolates, recovered in Poland during the years 2016 and 2018 from seven patients with urinary tract infections (UTIs), asymptomatic bacteriuria (ABU), or colonization of the gut. PCR melting profile genotyping indicated a close relationship between the strains derived from 2018, which were not related to the strain isolated in 2016. WGS results were analyzed in relation to international Kp isolates. Clonal and phylogenetic analyses were performed based on multilocus sequence typing (MLST) and single nucleotide polymorphisms (SNPs) of the core genome. The metallo-β-lactamase was assigned to the NDM-1 type and the sequence was identified as ST11. Eleven antimicrobial resistance genes were detected, mostly from plasmid contigs. Unprecedented profiles of plasmid replicons were described with the IncFII/pKPX-1 dominant replicon. In terms of the KL24 and O2v1 capsular antigen profiles, these isolates corresponded to Greek strains. Strains isolated from UTI, ABU, and colonization GI tract patients were not carrying environment-specific virulence genes. Based on the assessment of strain relationships at the genome level and their direction of evolution, the international character of the sublines was demonstrated, with a documented epidemic potential in Poland and Greece. In con-clusion, some groups of patients, e.g., renal transplant recipients or those with complicated UTIs, who are frequently hospitalized and undergoing antibiotic therapy, should be monitored not only for the risk of UTI, but also for colonization by Kp NDM strains.
Geo-Questionnaire for Environmental Planning: The Case of Ecosystem Services Delivered by Trees in Poland
- Patrycja Przewoźna
- Adam Inglot
- Marcin Mielewczyk
- Krzysztof Mączka
- Piotr Matczak
- Piotr Wężyk
2021 Pełny tekst Data
Studies on society and the environment interface are often based on simple questionnaires that do not allow for an in-depth analysis. Research conducted with geo-questionnaires is an increasingly common method. However, even if data collected via a geo-questionnaire are available, the shared databases provide limited information due to personal data protection. In the article, we present open databases that overcome those limitations. They are the result of the iTre-es project concerning public opinion on the benefits provided by trees and shrubs in four different research areas. The databases provide information on the location of trees that are valuable to the residents, the distances from the respondents’ residence place, their attitude toward tree removal, socio-demographic variables, attachment to the place of life, and environmental attitudes. The presentation of all these aspects was possible thanks to the appropriate aggregation of the results. A method to anonymize the respondents is presented. We discuss the collected data and their possible areas of application.
Gigantic electro-chemo-mechanical properties of nanostructured praseodymium doped ceria
- Victor Buratto Tinti
- Ahsanul Kabir
- Jin Kyu Han
- Sebastian Molin
- Vincenzo Esposito
2021 NANOSCALE
Some oxygen defective fluorites are non-Newnham electrostrictors, i.e., the electromechanical response does not depend on their dielectric properties. Here, we show gigantic electrostriction in nanocrystalline 25 mol% praseodymium doped ceria (PCO) bulk ceramics. The material was fabricated with a fieldassisted spark plasma sintering (SPS) process from high-purity nanoscale PCO powders (<20 nm). The SPS process consolidates the powders into a single-phase, highly dense material with a homogeneous microstructure and large grain boundary extension. Various thermally and chemically stable ionic defects are incorporated into the nanostructure, leading to superior electrical conductivity. The material shows an electrostriction strain coefficient (M33) of ∼10−16 m2 V−2 at frequencies below 100 Hz at room temperature. Such performance is comparable and even superior to Newnham’s electrostrictors, such as ferroelectric ceramics and polymeric actuators. Comparative analysis with polycrystals suggests that nanostructured PCO possesses electromechanically active nanodomains of Pr3+–VO pairs. Such results are unexpected and open novel insights on non-Newnham electrostrictors
Glass-ceramic sealants and steel interconnects: accelerated interfacial stability and reactivity tests at high temperature
- Agnieszka Drewniak
- Damian Koszelow
- Patryk Błaszczak
- Karolina Górnicka
- Kacper Jurak
- Hassan Javed
- Antonio Gianfranco Sabato
- Piotr Jasiński
- Sebastian Molin
- Federico Smeacetto
2021 Pełny tekst MATERIALS & DESIGN
High-temperature reactions between glass-ceramic sealants and Fe-Cr alloy interconnects may lead to the formation of undesirable phases, and consequently degradation of solid oxide fuel/electrolyser devices. In this work, three different glass-ceramic sealants (Na-containing, Ba-containing, Sr-containing compositions) and Fe22Cr stainless steel powders (raw and pre-oxidised) are considered in order to test their chemical reactivity at 750°C and 850 °C for 500 h in static air. The novelty of this approach is related to the use of powder mixtures instead of studying the reactivity on planar interfaces, which allows a better evaluation the materials’ reactivity. Oxidation tests indicate that the Sr-containing glass-ceramic/steel couple is the least reactive among the aged samples. For the Ba-containing samples, the formation of an undesirable phase of BaCrO4 is observed by diffractometry and photoelectron spectroscopy analyses. The present research explores, for the first time, the effects of exposing the high surface area of the alloy powder and glass-ceramic sealant interface, assessed by oxidation testing and microstructural analysis. The results show that by using mixed powders with large interface surface areas, degradation of the materials can be observed after relatively short times, allowing accelerated screening of the reactivity of materials, and thus their further development.
Global EM-Driven Optimization of Multi-Band Antennas Using Knowledge-Based Inverse Response-Feature Surrogates
- Sławomir Kozieł
- Anna Pietrenko-Dąbrowska
2021 Pełny tekst KNOWLEDGE-BASED SYSTEMS
Electromagnetic simulation tools have been playing an increasing role in the design of contemporary antenna structures. The employment of electromagnetic analysis ensures reliability of evaluating antenna characteristics but also incurs considerable computational expenses whenever massive simulations are involved (e.g., parametric optimization, uncertainty quantification). This high cost is the most serious bottleneck of simulation-driven design procedures, and may be troublesome even for local tuning of geometry parameters, let alone global optimization. On the one hand, globalized search is often necessary because the design problem might be multimodal (i.e., the objective function features multiple local optima) or a reasonably good initial design may not be available. On the other hand, the computational efficiency of popular algorithmic approaches, primarily, nature-inspired population-based algorithms, is generally poor. Combining metaheuristics procedures with surrogate modeling techniques and sequential sampling methods alleviates the problem to a certain extent but modeling of nonlinear antenna responses over broad frequency ranges is extremely challenging, and the aforementioned solutions are normally limited to rather simple structures described by a few parameters. This paper proposes a novel approach to global optimization of multi-band antennas. The major component of the presented framework is the knowledge-based inverse surrogate constructed at the level of response features (e.g., frequency and level locations of the antenna resonances). The surrogate facilitates decision-making process of inexpensive identification of the most promising regions of the parameter space, and a rendition of the good-quality initial design for further local tuning. Our methodology is validated using three examples of dual- and triple-band antennas. The average optimization cost is only 150 full-wave antenna analyzes while ensuring precise allocation of the antenna resonances at the target frequencies. This performance is demonstrated superior over both local optimizers and population-based metaheuristics.