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Gdańsk University of Technology

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Publications from the year 2024

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  • Enhancing seismic performance of steel buildings having semi-rigid connection with infill masonry walls considering soil type effects
    • Farzin Kazemi
    • Neda Asgarkhani
    • Robert Jankowski
    2024 SOIL DYNAMICS AND EARTHQUAKE ENGINEERING

    Unpreventable constructional defects are the main issues in the case of steel Moment-Resisting Frames (MRFs) that mostly occur in the rigidities of beam-to-column connections. The present article aims to investigate the effects of different rigidities of structures and to propose Infill Masonry Walls (IMWs) as retrofitting strategy for the steel damaged buildings. A fault or failure to meet a certain consideration of the soil type beneath the building and the current rigidity of connections can cause mistake in determining the performance of building. Therefore, this study comprehensively explores different conditions of soil types, connection rigidities, and implementing IMWs on the 3-, 5-, 7-, and 9-story MRFs. Two nonlinear analyses, namely Nonlinear Dynamic Analysis (NDA) and Incremental Dynamic Analysis (IDA) were performed on 384 steel MRFs having different conditions of defects and the results of the analysis include 3456 performance curves assuming three ground motion subsets recommended by FEMA P695. The results confirm that the proposed retrofitting procedure can effectively improve the performance levels of MRFs, which the connections rigidity of 90 %, 80 %, 70 %, 60 %, and 50 % can reduce the collapse performance level by 2.86 %, 5.35 %, 9.31 %, 16.56 %, and 34.65 %, respectively.

  • Enhancing the bioconversion rate and end products of black soldier fly (BSF) treatment – A comprehensive review
    • Shahida Anusha Siddiqui
    • Özge Süfer
    • Gülşah Çalışkan Koç
    • Hanif Lutuf
    • Teguh Rahayu
    • Roberto Castro Munoz
    • Ito Fernando
    2024 Full text ENVIRONMENT DEVELOPMENT AND SUSTAINABILITY

    Food security remains a pressing concern in the face of an increasing world population and environmental challenges. As climate change, biodiversity loss, and water scarcity continue to impact agricultural productivity, traditional livestock farming faces limitations in meeting the growing global demand for meat and dairy products. In this context, black soldier fly larvae (BSFL) have emerged as a promising alternative for sustainable food production. BSFL possess several advantages over conventional livestock, including their rapid growth, adaptability to various organic waste substrates, and low environmental impact. Their bioconversion rate, the ability to transform organic waste into valuable products, and final product optimization are key factors that enhance their potential as a nutrient-rich protein source, fertilizer, and biofuel. This review explores strategies to enhance the bioconversion rate and improve the end products derived from BSF treatment. It highlights the benefits of using BSFL over other interventions and underscores the significance of optimizing their bioconversion rate to meet the challenges of global food security sustainably. Despite the promising prospects of BSF-derived products, consumer acceptance and regulatory hurdles remain critical aspects to address in realizing their full market potential. The utilization of BSFL as a sustainable source of food and feed can contribute to waste management, reduce environmental pollution, and address the pressing issue of food security in an environmentally responsible manner. However, there is a need for further research and innovation to ensure the safety, quality, and economic viability of BSF-based products for both animal and human consumption.

  • Entire fracture surface topography parameters for fatigue life assessment of 10H2M steel
    • Wojciech Macek
    • Mateusz Kopec
    • Aleksandra Laska
    • Zbigniew Kowalewski
    2024 JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH

    In this paper, the entire fracture surface approach was used to assess an effect of 280,000 h of exploitation under internal pressure of 2.9 MPa and high temperature of 540 °C on the fatigue response of 10H2M (10CrMo9–10) power engineering steel. The mechanical testing was carried out on the hourglass specimens produced from the as-received, unused pipeline and the same material after long-time exploitation. The uniaxial tensile tests were performed to establish the stress amplitude for subsequent force controlled, fatigue testing in the range from ±250 MPa to ±400 MPa under the frequency of 20 Hz. Since the exploited 10H2M steel was characterized by significantly lower mechanical properties, different damage mechanisms responsible for specimen failure were revealed through fracture surface analysis. The fracture surface topography evaluation was performed with a 3D non-contact measuring system. It was found, that the exploitation state has a strong impact on the fatigue life and fracture characteristics since the significant drop in lifespan of about 300 %–400 % was found for the material after prolonged service. Finally, the proposed surface topography parameter was related to the stress amplitude in order to estimate the fatigue life for the steel in question.

  • Entrepreneurial intentions of students from Latvia, Poland, and Ukraine: The role of perceived entrepreneurial education results
    • Julita Wasilczuk
    • Magdalena Licznerska
    2024 Full text Journal of Entrepreneurship, Management and Innovation

    Our main aim is to establish which factors influence entrepreneurial intentions, with a particular focus on the role of entrepreneurial education and university support in Central and Eastern European countries (CEE). To verify hypotheses quantitative research was conducted using surveys among 2,085 first-year undergraduate students from three technical universities in three countries: Latvia, Poland and Ukraine. The results of the study indicate that entrepreneurial self- efficacy, perceived entrepreneurial education results, and perceived educational and relational support all influence the intention of students to launch a venture. The research did not provide support for the hypothesis of the impact of perceived structural support (PSS) on intentions. The impact of perceived educational and relational support appeared to be less important than the impact of ESE and PEER on intentions. Additionally, we identified significant differences between students from the analysed countries. Implications for theory and practice: Our research has identified a new factor, not previously used in studies of entrepreneurial intentions, that is, perceived entrepreneurial education results. This new factor can be used in research as a complement to self-efficacy and it refers to hard skills related, in this particular case, to entrepreneurship. The results show the importance of the national context, implying the need to consider this when modelling support policies at a national level. The findings can be used to remodel how this knowledge is delivered to young people. Originality and value: Firstly, we proposed the inclusion of a new education-related component called perceived entrepreneurial education results, which can examine the perceived results of education at any level, in our case, at the secondary school level. Secondly, we showed the stronger influence of factors related to perceptions of one's skills than perceptions of support from the environment. In addition, we demonstrated that making judgements or recommendations about entrepreneurial support for similar countries should be considered separately. Furthermore, we conceptualised the three aspects of ESE, PEER and ESM in a new way.

  • Environmental impacts of food waste management technologies: A critical review of life cycle assessment (LCA) studies
    • Fatima Batool
    • Tonni Agustiono Kurniawan
    • Ayesha Mohyuddin
    • Mohd Hafiz Dzarfan Othman
    • Faissal Aziz
    • Hussein Al-Hazmi
    • Hui Hwang Goh
    • Abdelkader Anouzla
    2024 TRENDS IN FOOD SCIENCE & TECHNOLOGY

    Food waste is a serious global problem. Therefore, it is essential to reduce food waste and adopt recycling strategies to minimize its environmental impacts. However, conventional waste disposal methods emit harmful gases such as dioxin, CH4, N2O, and NH3, which contaminate the air and water resources. This work reviews the environmental consequences of food waste based on lifecycle assessment (LCA) techniques using methods such as anaerobic digestion, composting, and landfilling. It also pays attention to novel techniques like gasification and hydrothermal carbonization. This review critically evaluates and compares the environmental impacts assessed by LCA such as global warming potential (GWP), climate change (CC), marine eutrophication (MEP), human toxicity (HT), terrestrial eco-toxicity (Tecox), terrestrial acidification (TAP), freshwater ecotoxicity (FEW), freshwater eutrophication (FEP), marine ecotoxicity (ME), fossil depletion (FD), ozone layer depletion potential (OLDP), and land occupation (LO) for each method. This study also highlights the importance of technological innovation and the need to improve current food waste valorization practices by focusing on the LCAs of the approaches listed above. With respect to its novelty, this work consolidates a useful comparison among the food waste utilization technologies with respect to environmental impacts based on LCA studies. Furthermore, this work emphasizes the need for in-depth research on the LCA of sustainable techniques such as gasification, fermentation and hydrothermal carbonization to support evidence-based decision-making.

  • Enzyme Conjugation - A Promising Tool for Bio-catalytic and Biotransformation Applications – A Review
    • Muhammad Asif Muneer
    • Sumaya Fatima
    • Nazim Hussain
    • Tebogo Mashifana
    • Aniqa Sayed
    • Grzegorz Boczkaj
    • Muhammad Shahid Riaz Rajoka
    2024 TOPICS IN CATALYSIS

    Enzymes have revolutionized conventional industrial catalysts as more efficient, eco-friendly, and sustainable substitutes that can be used in different biotechnological processes, food, and pharmaceutical industries. Yet, the enzymes from nature are engineered to make them adapt and enhance their durability in the industrial environment. One promising approach involves the combined use of multiple enzymes that catalyze highly selective and sequential reactions in a single reaction vessel. The multi-enzymatic biocatalytic systems, achieved through gene fusion, fusion proteins, DNA manipulation and bioconjugation, protein engineering, or attachment to solid support materials for immobilization, such as protein-polymer, silica, metal organic framework, Carbon nanotubes or graphene based hybrids, have found widespread utility across various sectors, including the food industry, wastewater treatment, drug delivery, biosensors and methanol production. Enzyme conjugation enables the creation of novel enzymes with improved kinetics and synergistic effects. Researchers can evolve fusion proteins by fusion enzymes which can evolve novel catalytic activities in Biotechnological processes. These engineered enzymes can contribute in synthetic Biology in construction of synthetic system for various applications. Enzyme conjugation helps in metabolic engineering by optimization of pathways. Researchers can develop pathways for production of Bio-sensors, pharmaceuticals, biofuels and other valuable industrial products. This review comprehensively explores the techniques and applications of enzyme conjugation, highlighting its pivotal role in advancing the field of bio-catalysis.

  • Enzyme-linked carbon nanotubes as biocatalytic tools to degrade and mitigate environmental pollutants
    • Muhammad Bilal
    • Anil Kumar Singh
    • Hafiz M.N. Iqbal
    • Jakub Zdarta
    • Anna Chrobok
    • Teofil Jesionowski
    2024 ENVIRONMENTAL RESEARCH

    A wide array of organic compounds have been recognized as pollutants of high concern due to their controlled or uncontrolled presence in environmental matrices. The persistent prevalence of diverse organic pollutants, including pharmaceutical compounds, phenolic compounds, synthetic dyes, and other hazardous substances, necessitates robust measures for their practical and sustainable removal from water bodies. Several bioremediation and biodegradation methods have been invented and deployed, with a wide range of materials wellsuited for diverse environments. Enzyme-linked carbon-based materials have been considered efficient biocatalytic platforms for the remediation of complex organic pollutants, mostly showing over 80% removal efficiency of micropollutants. The advantages of enzyme-linked carbon nanotubes (CNTs) in enzyme immobilization and improved catalytic potential may thus be advantageous for environmental research considering the current need for pollutant removal. This review outlines the perspective of current remediation approaches and highlights the advantageous features of enzyme-linked CNTs in the removal of pollutants, emphasizing their reusability and stability aspects. Furthermore, different applications of enzyme-linked CNTs in environmental research with concluding remarks and future outlooks have been highlighted. Enzyme-linked CNTs serve as a robust biocatalytic platform for the sustainability agenda with the aim of keeping the environment clean and safe from a variety of organic pollutants.

  • Equitable colorings of some variation of corona products of cubic graphs
    • Marek Kubale
    • Hanna Furmańczyk
    2024 Full text Archives of Control Sciences

    The problem of determining the value of equitable chromatic number for multicoronas of cubic graphs is studied. We provide some polynomially solvable cases of cubical multicoronas and give simple linear time algorithms for equitable coloring of such graphs which use almost optimal number of colors in the remaining cases.

  • Essays on China's international trade - focus on One-Belt One-Road initiative
    • Yuxin Lu
    2024 Full text

    This thesis explores China's international trade from trade, global value chains (GVCs) and export diversity, focusing on the "One-Belt One-Road" (OBOR) initiative proposed at the end of 2013. Specifically, I verify the potential association of OBOR with bilateral imports and exports in the first chapter. Then the relationship between OBOR and GVCs has been explored in Chapter 2. And I have extended the research in GVCs to China's province level and checked the linkages with labour markets. Finally, Chapter 3 focuses on OBOR's role in export diversity and the relationship between capital and Chinese firms' extensive margins. The result indicates 1) the positive association between OBOR and trade, value-added and GVCs. China-Pakistan (CP) and Bangladesh-China-India-Myanmar (BCIM) economic corridors play a more vital promoter role. 2) For China's labour market, wages and productivity (employment) are positively correlated, but employment and productivity are negatively associated. And GVCs' participation hinders the development of employment and productivity. 3) The relationship between OBOR and export diversity is negative. State-owned and private capital positively associate with extensive margins at the Chinese firm's level.

  • Estymacja położenia i orientacji w systemie lokalizacyjnym z częściową synchronizacją węzłów referencyjnych
    • Jarosław Sadowski
    • Jacek Stefański
    2024 Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

    W referacie przedstawiono koncepcję systemu lokalizacyjnego do jednoczesnej estymacji położenia i orientacji obiektów. Obiekt ruchomy jest wyposażony w zestaw zsynchronizowanych odbiorników. Nadajniki referencyjne systemu są podzielone na grupy i pracują synchronicznie tylko w obrębie swojej grupy, bez zachowania synchronizacji pomiędzy grupami nadajników.

  • Evaluating the impact of ZnO doping on electrical and thermal properties of calcium-aluminosilicate oxynitride glass-ceramics
    • Abbas Saeed Hakeem
    • Natalia Wójcik
    • Stefania Wolff
    • Sharafat Ali
    2024 CERAMICS INTERNATIONAL

    This study aimed to investigate the impact of ZnO content on the structure, thermal, and electrical properties of oxynitride glass-ceramic(s) within the Ca–Al–Si–O–N (CASON) system. The base glass had the composition of Ca7Al14Si17O52N7, with ZnO additions ranging from 3 to 15 % by weight. A pristine Ca7Al14Si17O52N7 glass was successfully prepared by melt-quenching technique followed by converted into glass-ceramic by incorporating various amounts of ZnO using the field-assisted sintering technique. XRD and FESEM analysis confirmed that increasing the amount of Zn increases the crystallinity in the glass matrix. The observed crystalline phases were formed mostly from ZnO and showed higher conductivity than the remaining dielectric matrix. IR spectra confirmed the presence of bands correlated with the presence of Zn and suggested the progressive depolymerization of the silicate-aluminate network as a consequence of increasing Zn content. Density values varied between 2.75 and 2.94 gcm 3 and increased with increasing the Zn content in the glass-ceramic. The thermal expansion and thermal conductivity values increased and decreased, respectively, with the increase of Zn content in the matrix. The electrical properties of the samples were investigated using impedance spectroscopy over a wide range of frequencies (10 mHz to 1 MHz) and temperatures (153 K–623 K). The results showed that in the glass without ZnO and glass-ceramic(s) with a small addition of ZnO, the conductivity is mainly dominated by the transfer of oxygen ions and, to a small extent, by the presence of electronic conductivity. As the ZnO content increases, continuous conduction paths are formed between the ZnO crystallites, and the electrical conductivity increases rapidly and becomes dominated by electron transfer.

  • Evaluation of high-frequency roughness measurement errors for composite and ceramic surfaces after machining
    • Przemysław Podulka
    • Wojciech Macek
    • Mirosław Szala
    • Andrzej Kubit
    • Kinkar Chandra Das
    • Grzegorz Królczyk
    2024 Full text Journal of Manufacturing Processes

    Precise characterisation of surface topography is of the greatest importance since many factors directly affect the accuracy of the whole measurement process. In this paper, the variety of surface topographies from machined composite and ceramic workpieces was studied with a special emphasis on the measurement results. Surfaces were subjected to the ground diamond, honing and milling processes. Measurement results were analysed in terms of the application of the procedure for the removal of the high-frequency noise. Bandwidth characteristics were supported by the studies of autocorrelation and power spectral functions. It was found, that examination of noisy data, especially its isotropic properties, is crucial in the enhancement of the noise-removal methods. The proposed procedure was validated through direction and profile characterisation. The spline filtering technique with a 7.5 μm cut-off was encouraged against other generally used filtering techniques for the reduction of high-frequency measurement noise considering the study based on the power spectral, autocorrelation and direction functions. The proposed methodology was validated by comparing it to the averaged results of 3 time repeated measurements of the composite and ceramic surfaces after machining. The main advantage of the proposal is reducing the time of data processing due to the fast and easy-to-implement usage of general surface topography analysis functions, available in the commercial software of the measuring instrument.

  • Evaluation of Terpene Decomposition in Kaffir Lime Juice during Storage Using Gas Chromatography–Mass Spectrometry and Proton Transfer Reaction–Mass Spectrometry
    • Martyna Lubinska-Szczygeł
    • Żaneta Polkowska
    • Bianka Tobolkova
    • Tomasz Majchrzak
    • Martin Polovka
    • Parichart Promchote
    • Shela Gorinstein
    2024 MOLECULES

    Kaffir lime juice, often treated as production waste, can be a good source of terpenes. These compounds undergo various decomposition processes under the influence of external factors, especially during transportation and storage. In this paper, it was possible to monitor changes in the terpene profile of kaffir lime juice under different storage conditions, namely, 4 ◦C, 20 ◦C, and 35 ◦C. The identification of key decomposition products was achieved using gas chromatography–mass spectrometry (GC–MS) and a data mining protocol. It was followed by tracing those products in different storage conditions using a high-throughput proton transfer reaction mass spectrometry (PTR–MS) approach. Based on our findings, degradation pathways were presented, showing that the main products resulting from storage are p-cymene, p-cymenene, terpinene-4-ol, and α-terpineol. It was shown that conversion to p-cymenene occurs after 5 days of storage. Terpinene-4-ol and α-terpineol were found to be the final products of the conversion at all temperatures. Changes in the composition of terpenes are important from the point of view of their bioactive properties.

  • Evolution of charge density wave order in continuous solid solutions Lu(Ni1-xCox)C2
    • Herwig Michor
    • Marta Roman
    • Lisa Reisinger
    • Maria Fritthum
    • Jana Schmelzenbart
    • Alexander Vock
    • Volodymyr Levytskyi
    • Volodymyr Babizhetskyy
    • Bogdan Kotur
    2024 Full text JOURNAL OF ALLOYS AND COMPOUNDS

    Pseudo-ternary solid solutions, Lu(Ni1-xCox)C2 (0 ≤ x ≤ 1), were studied by means of powder X-ray diffraction, differential thermal analysis as well as electrical resistivity and heat capacity measurements. The crystal structure of the Lu(Ni1-xCox)C2 series, as investigated by means of X-ray powder diffraction, is of structure type CeNiC2, space group Amm2, Pearson symbol oS8. The structural analysis reveals a non-monotonous evolution, in particular for the a- and c-lattice parameters, resulting in a non-linear decrease of the unit cell volume, markedly deviating from Vegard’s rule, due to non-isoelectronic substitution of Ni by Co. Utilizing differential thermal analysis (DTA) data, a pseudo-binary phase diagram LuNiC2–LuCoC2 has been constructed. The evolution of charge density wave order in Lu(Ni1-xCox)C2, which reaches an ordering temperature TCDW ≅ 450 K for LuNiC2, was studied by means of electrical resistivity and heat capacity measurements. For solid solutions prepared via the floating-zone melting technique it became feasible to trace charge density wave (CDW) features of the temperature dependent electrical resistivity, thus, indicating a critical composition for the suppression of CDW order in Lu(Ni1-xCox)C2 at around x ≈ 0.15 – 0.17, which matches with a distinct drop of the composition dependent electronic Sommerfeld coefficient of the low temperature heat capacity of Ni-rich solid solutions.

  • Example of Using Particle Swarm Optimization Algorithm with Nelder–Mead Method for Flow Improvement in Axial Last Stage of Gas–Steam Turbine
    • Paweł Ziółkowski
    • Łukasz Witanowski
    • Stanisław Głuch
    • Piotr Klonowicz
    • Michel Feidt
    • Aimad Koulali
    2024 Full text ENERGIES

    This article focuses principally on the comparison baseline and the optimized flow efficiency of the final stage of an axial turbine operating on a gas–steam mixture by applying a hybrid Nelder– Mead and the particle swarm optimization method. Optimization algorithms are combined with CFD calculations to determine the flowpaths and thermodynamic parameters. The working fluid in this study is a mixture of steam and gas produced in a wet combustion chamber, therefore the new turbine type is currently undergoing theoretical research. The purpose of this work is to redesign and examine the last stage of the gas–steam turbine’s flow characteristics. Among the optimized variables, there are parameters characterizing the shape of the endwall contours within the rotor domain. The values of the maximized objective function, which is the isentropic efficiency of the turbine stage, are found from the 3D RANS computation of the flowpath geometry changing during the improvement scheme. The optimization process allows the stage efficiency to be increased by almost 4 percentage points. To achieve high-quality results, a mesh of over 20 million elements is used, where the percentage error in efficiency between the previous and current mesh sizes drops below 0.05%.

  • Excitation of Circularly Polarized Wave via Single-Feed Metasurface-Integrated Compact Antenna for Internet of Things
    • Shahanawaz Kamal
    • Ullah Ubaid
    • Sławomir Kozieł
    2024 AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS

    A compact circularly polarized (CP) quasi-omnidirectional antenna is introduced for internet of things (IoT). The structure consists of two components implemented on FR-4 substrates, and sep-arated by an air gap: one printed with a rectangular patch fed through a matching network, and another with a metasurface and a ground plane. Two different methods for impedance matching are employed. An equivalent circuit model of the antenna is developed to facilitate the analysis. The design procedure, operating principle, and experimental validation of the antenna are de-scribed. The optimized antenna occupies 0.3λ × 0.1λ footprint and 0.04λ height at 16 GHz and exhibits the impedance bandwidth of ∼2 GHz, axial ratio of <3dB, realized gain of 6 dBi and efficiency of ~80%.

  • Excitation of Waves in a Dispersive Medium. Example of Flow of a Bubbly Liquid
    • Anna Perelomova
    2024 Full text ACTA PHYSICA POLONICA A

    The excitation of wave motion by an external source and the interaction of modes inherent to a ow in a dispersive medium are considered. Dispersion is caused by the presence of gaseous bubbles in a liquid. A large variety of steady excited waveforms is possible when the exciting wave is also steady and propagates at a constant velocity. The velocities of the exciter and forced waves may be dierent. This leads to a variety of non-stationary excitations

  • Expedited Machine-Learning-Based Global Design Optimization of Antenna Systems Using Response Features and Multi-Fidelity EM Analysis
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    • Leifur Leifsson
    2024

    The design of antenna systems poses a significant challenge due to stringent per-formance requirements dictated by contemporary applications and the high com-putational costs associated with models, particularly full-wave electromagnetic (EM) analysis. Presently, EM simulation plays a crucial role in all design phases, encompassing topology development, parametric studies, and the final adjustment of antenna dimensions. The latter stage is especially critical as rigorous numerical optimization becomes essential for achieving optimal performance. In an increas-ing number of instances, global parameter tuning is necessary. Unfortunately, the use of nature-inspired algorithms, the prevalent choice for global design, is hin-dered by their poor computational efficiency. This article presents an innovative approach to cost-efficient global optimization of antenna input characteristics. Our methodology leverages response feature technology, ensuring inherent regulariza-tion of the optimization task by exploring the nearly-linear dependence between the coordinates of feature points and the antenna's dimensions. The optimization process is structured as a machine learning (ML) procedure, utilizing a kriging surrogate model rendering response features to generate promising candidate de-signs (infill points). This model is iteratively refined using accumulated EM simulation data. Further acceleration is achieved by incorporating multi-fidelity EM analysis, where initial sampling and surrogate model construction use low-fidelity EM simulations, and the ML optimization loop employs high-fidelity EM analysis. The multi-fidelity EM simulation data is blended into a single surrogate using co-kriging. Extensive verification of the presented algorithm demonstrates its remarkable computational efficiency, with an average running cost not exceed-ing ninety EM simulations per run and up to a seventy percent relative speedup over the single-fidelity procedure.

  • Expedited Re-Design of Multi-Band Passive Microwave Circuits Using Orthogonal Scaling Directions and Gradient-Based Tuning
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    • Ubaid Ullah
    2024 Full text Scientific Reports

    Geometry scaling of microwave circuits is an essential but challenging task. In particular, the employment of a given passive structure in a different application area often requires re-adjustment of the operating frequencies/bands while maintaining top performance. Achieving this necessitates utilization of numerical optimization methods. Nonetheless, if the intended frequencies are distant from the ones at the starting point, local search procedures tend to fail, whereas global search algorithms are computationally expensive. As recently demonstrated, a combination of large-scale concurrent geometry parameter scaling with intermittent local tuning allows for dependable re-design of high-frequency circuits at low CPU costs. Unfortunately, the procedure is only applicable to single-band structures due to synchronized modifications of all operating bands under scaling. This article discusses a novel procedure that leverages a similar overall concept, but allows for independent control of all center frequencies. To achieve this goal, an automated decision-making procedure is developed in which a set of orthogonal scaling directions are determined based on their effect on individual circuit bands, and using auxiliary optimization sub-problems. The scaling range is then automatically computed by solving and appropriately-defined least-square design relocation problem. The methodology introduced in the work is illustrated using two planar passive devices. In both cases, wide-range operating frequency re-design has been demonstrated and favorably compared to conventional gradient-based tuning. Furthermore, the presented procedure has been shown to be computationally efficient. It is also easy to implement and integrate with a variety of gradient-based optimization procedures of a descent type.

  • Experimental and Numerical Investigations of the Effect of Curing Conditions on the Temperature Rise of Concrete
    • Aleksandra Kuryłowicz-Cudowska
    2024 Full text International Journal of Civil Engineering

    This paper presents experimental and numerical studies investigating the impact of three curing conditions on temperature evolution in concrete cubes. The tests were performed on samples of the same volume (3.375 dm3) under different curing conditions: room temperature, insulation boxes, and adiabatic calorimeter. Various cements (Portland cement, Portland composite cement, and blast furnace slag cement) and aggregates (gravel and basalt) were examined. The temperature evolution for all mixtures was analyzed, revealing a correlation between temperature increase and concrete type. Under insulation and adiabatic curing, Portland cement with gravel aggregate exhibited the highest temperature rise, while blast furnace slag cement with basalt aggregate showed the lowest increase. The incorporation of slag, ash, or other mineral additives reduced temperature rise. Additionally, basalt aggregate’s higher heat capacity and thermal energy accumulation led to a decreased temperature increase compared to gravel. Using recorded thermal data, a numerical procedure predicting temperature development in nonadiabatic conditions through direct adiabatic tests is proposed. Comparisons between experimental and numerical temperature evolutions confirmed the model’s accuracy.