2020 - Repozytorium publikacji - Politechnika Gdańska

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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.