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Gdańsk University of Technology

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Publications from the year 2024

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  • Mesoscopic simulations of a fracture process in reinforced concrete beam in bending using a 2D coupled DEM/micro-CT approach
    • Michał Nitka
    • Andrzej Tejchman-Konarzewski
    2024 Full text ENGINEERING FRACTURE MECHANICS

    W tej pracy zbadano numerycznie w warunkach 2D złożony proces pękania w krótkiej prostokątnej belce betonowej wzmocnionej jednym prętem podłużnym (bez zbrojenia pionowego) i poddanej quasi-statycznemu zginaniu w trzech punktach. Krytyczne pęknięcie poprzeczne w belce spowodowało jej uszkodzenie podczas doświadczenia. Symulacje numeryczne przeprowadzono klasyczną metodą elementów dyskretnych (DEM). Przyjęto trójfazowy opis betonu: kruszywa, zaprawa i międzyfazowe strefy przejściowe (ITZ) wokół kruszyw. W mezoskopowych obliczeniach DEM opartych na skanach rentgenowskich CT 2D przyjęto rzeczywisty kształt i połączenie cząstek kruszywa w betonie. W obliczeniach odtworzono pręt stalowy z żebrami. Założono także ITZ pomiędzy prętem a zaprawą. Bez narzucania prawa poślizgu, uwzględniono warunek geometryczny na granicy pręt/beton. W pracy skupiono się na wykresie siła-ugięcia, procesie pękania, siłach kontaktowych i naprężeniach wzdłuż pręta. Uzyskano dobry poziom zgodności ewolucji siły pionowej w zależności od ugięcia i mechanizmu zniszczenia w analizach DEM w porównaniu z testami laboratoryjnymi pomimo przyjęcia uproszczonych warunków 2D. Wykazano silny wpływ mezostruktury betonu na wzór pęknięcia.

  • Method for prediction of the frost resistance ability of air‐entrained concrete based on the 3D air void characteristics by x‐ray micro‐CT
    • Łukasz Skarżyński
    • Mikołaj Miśkiewicz
    2024 Structural Concrete

    In modern construction, one of the most important factors in the execution of contracts is time. Standard procedures for assessing the frost resistance or concrete are usually very time-consuming and can take up to 40 days. The current paper is experimentally and practically oriented. It presents an alternative testing method, based on air void network, that allows to assess the frost resistance of concrete within just a few days of taking the samples. X-ray micro-CT scans were introduced to obtain the quantitative and qualitative 3D information about the air void microstructure taking into account total air content: A [%], pores of the size below 300 μm in diameter content: A300 [%], specific surface of air voids: α [mm-1] and spacing factor: L [mm] in order to predict the freeze / thaw durability. To verify the assumptions of the frost resistance method, based on the analysis of pore microstructure, tests of freeze / thaw resistance in accordance with Polish supplement to European Standard [46] were carried out. Presented research revealed that the appropriate microstructure of air pores, in particular, content of micropores with the diameter less than 0.3 mm: A300 combined with a spacing factor: L [mm] can constitute a reliable basis for determining concrete freeze / thaw durability. Thus, method proposed in current paper can be effectively used for fast and trustworthy determination of the air-entrained concrete durability in a short time and without any special preparation of the tested sample, that allows immediate preventive or repair actions to be taken if required.

  • Method of Forming Road Surface Replicas Using 3D Printing Technology
    • Wojciech Owczarzak
    • Sławomir Sommer
    • Grzegorz Ronowski
    2024 Coatings

    Rolling resistance is a critical factor that influences vehicle energy consumption, emissions, and overall performance. It directly impacts fuel efficiency, tire longevity, and driving dynamics. Traditional rolling resistance tests are conducted on smooth steel drums, which fail to replicate real-world road surface textures, potentially skewing results. This article presents the process of designing surface replicas using 3D printing technology, which consisted of selecting the internal structure, material, and print parameters of the surface sample. In order to verify the designed structures, an original mechanical strength test was performed. The test was based on pressing the tire onto the test sample with an appropriate force that corresponded to typical conditions during rolling resistance measurements. The test results included surface texture profiles before and after the application of load, which were then superimposed to detect any possible sample deformation. The obtained strength test results confirmed the validity of using 3D printing technology in the process of obtaining road surface replicas.

  • Methodology Approach for Microplastics Isolation from Samples Containing Sucrose
    • Kornelia Kadac-Czapska
    • Beata Bochentyn
    • Aleksandra Maślarz
    • Sebastian Mahlik
    • Małgorzata Grembecka
    2024 MOLECULES

    The growing production and use of plastics significantly contribute to microplastics (MPs) contamination in the environment. Humans are exposed to MPs primarily through the gastrointestinal route, as these particles are present in beverages and food, e.g., sugar. Effective isolation and identification of MPs from food is essential for their elimination. This study aimed to evaluate factors influencing the isolation of MPs from sucrose solutions to determine optimal conditions for the process. Polyethylene particles were used to test separation methods involving chemical digestion with acids and filtration through membrane filters made of nylon, mixed cellulose ester, and cellulose acetate with pore sizes of 0.8 and 10 µm. The effects of temperature and acid type and its concentration on plastic particles were examined using scanning electron microscopy and µ-Raman spectroscopy. The results indicate that increased temperature reduces solution viscosity and sucrose adherence to MPs’ particles, while higher acid concentrations accelerate sucrose hydrolysis. The optimal conditions for MPs’ isolation were found to be 5% HCl at 70 ◦C for 5 min, followed by filtration using an efficient membrane system. These conditions ensure a high recovery and fast filtration without altering MPs’ surface properties, providing a reliable basis for further analysis of MPs in food.

  • Methodology of generation of CFD meshes and 4D shape reconstruction of coronary arteries from patient-specific dynamic CT
    • Krzysztof Psiuk-Maksymowicz
    • Damian Borys
    • Bartlomiej Melka
    • Maria Gracka
    • Wojciech Adamczyk
    • Marek Rojczyk
    • Jaroslaw Wasilewski
    • Jan Głowacki
    • Mariusz Kruk
    • Marcin Nowak
    • Ziemowit Ostrowski
    • Ryszard Bialecki
    2024 Full text Scientific Reports

    Due to the difficulties in retrieving both the time‑dependent shapes of the vessels and the generation of numerical meshes for such cases, most of the simulations of blood flow in the cardiac arteries use static geometry. The article describes a methodology for generating a sequence of time‑dependent 3D shapes based on images of different resolutions and qualities acquired from ECG‑gated coronary artery CT angiography. The precision of the shape restoration method has been validated using an independent technique. The original proposed approach also generates for each of the retrieved vessel shapes a numerical mesh of the same topology (connectivity matrix), greatly simplifying the CFD blood flow simulations. This feature is of significant importance in practical CFD simulations, as it gives the possibility of using the mesh‑morphing utility, minimizing the computation time and the need of interpolation between boundary meshes at subsequent time instants. The developed technique can be applied to generate numerical meshes in arteries and other organs whose shapes change over time. It is applicable to medical images produced by other than angio‑CT modalities.

  • Methods for Quality Assessment of Window View
    • Barbara Matusiak
    • Filomena Russo
    • Mandana Khanie, Sarey
    • Natalia Sokół
    • Christina Hemauer
    • Klaus Martiny
    • Carlo Volf
    • Siegrun Appelt
    • Natalia Giraldo Vasquez
    • Aicha Diakite-Kortlever
    2024 Full text Land

    This paper summarises findings from two workshops evaluating a series of views in various settings by an interdisciplinary group of experts. In the first one (Trondheim, June 2022), ten experts visited and assessed views from nine rooms. In the second one (Lausanne, June 2023), eleven experts assessed window views from four spaces. The workshops’ main objective was to develop and test multi-method assessments of window views. During both workshops, participants completed a survey that included close and open-ended questions about the perceived quality of the room and the view. Participants also measured lux level, took photographs, made hand drawings of the view, and answered a questionnaire about their mood and the environmental conditions in the room. After the workshop, point-in-time daylight simulations were performed for the visited rooms. The paper describes, compares, and recommends the use of the aforementioned methods depending on the type and complexity of the view, and the space, the evaluators’ professional background, and the type of collected data. It also discusses the overlap of the methods and estimates the preparation time, time spent on site, and the amount of work after the visit. Finally, it recommends the use of the tested methods depending on the application.

  • Miasta Nieskończone. Warsztaty animacji poklatkowej doodle-art. Bałtycki Festiwal Nauki 2024
    • Marta Koperska-Kośmicka
    • Agnieszka Kurkowska
    • Aleksandra Karpińska
    2024

    Warsztaty animacji poklatkowej w technice doodle-art, podczas których uczestnicy stworzyli wspólnie animowany film o mieście marzeń. Warsztaty z animacji poklatkowej są zajęciami rozwijającymi wyobraźnię i kreatywność. Film powstawał zespołowo, poprzez dodawanie nowych elementów rysunku przez każdego z uczestników. Kolejne fazy powstawania wymarzonego miasta zostały uwiecznione na zdjęciach, które po cyfrowej obróbce pozwoliły na stworzenie krótkiego, jednominutowego animowanego filmu.

  • Micro- and nano-Illite to improve strength of untreated-soil as a nano soil-improvement (NSI) technique
    • M Cheraghalikhani,
    • Hamed Niroumand
    • Lech Bałachowski
    2024 Full text Scientific Reports

    Soil stabilization is a technique of improving the geotechnical properties of soils for various engineering applications. However, conventional stabilizers such as cement and lime have some limitations, such as high cost, environmental impact, and durability issues. Therefore, there is a need for alternative and innovative stabilizers that can overcome these challenges. This study introduces nano-Illite, a type of clay mineral, as a novel and efective soil stabilizer. Nano-Illite can form nano-cementation (NC) in soil, which is a process of enhancing the durability of various building materials. NC is also known as nano soil-improvement (NSI), a technique that has been developed in recent years. Four formulations of micro- and nano-Illite with concentrations of 0, 1, 2, and 3% were separately added to soil samples. The unconfned compressive strength (UCS) and the secant modulus at 50% of peak stress (E50) of the treated samples were measured and compared with the untreated samples. The results showed that 3% nano-Illite increased the UCS of soil by more than 2.2 times and the E50 by more than 1.5 times after 7 days of curing. Micro-Illite also improved the UCS and E50 of soil, but to a lesser extent. X-ray fuorescence (XRF), scanning electron microscopy (SEM), and X-ray difraction (XRD) analyses revealed the micro- and nano-structures of the soil specimens and the performance of Illite as a nano-additive. This research demonstrates the efectiveness of nano-Illite in soil improvement as a NSI technique, and its potential to replace or reduce the use of conventional stabilizers. This study also contributes to the understanding of the mechanisms and factors that infuence the NC process in soil.

  • Microbe Cultivation Guidelines to Optimize Rhamnolipid Applications
    • Ilona Kłosowska-Chomiczewska
    • Adam Macierzanka
    • Karol Parchem
    • Pamela Miłosz
    • Sonia Sarach
    • Iga Płaczkowska
    • Weronika Hewelt-Belka
    • Christian Jungnickel
    2024 Full text Scientific Reports

    In the growing landscape of interest in natural surfactants, selecting the appropriate one for specific applications remains challenging. The extensive, yet often unsystematized, knowledge of microbial surfactants, predominantly represented by rhamnolipids (RLs), typically does not translate beyond the conditions presented in scientific publications. This limitation stems from the numerous variables and their interdependencies that characterize microbial surfactant production. We hypothesized that a computational recipe for biosynthesizing RLs with targeted applicational properties could be developed from existing literature and experimental data. We amassed literature data on RL biosynthesis and micellar solubilization and augmented it with our experimental results on the solubilization of triglycerides (TGs), a topic underrepresented in current literature. Utilizing this data, we constructed mathematical models that can predict RL characteristics and solubilization efficiency, represented as logPRL = f(carbon and nitrogen source, parameters of biosynthesis) and logMSR = f(solubilizate, rhamnolipid (e.g. logPRL), parameters of solubilization), respectively. The models, characterized by robust R2 values of respectively 0.581-0.997 and 0.804, enabled the ranking of descriptors based on their significance and impact — positive or negative — on the predicted values. These models have been translated into ready-to-use calculators, tools designed to streamline the selection process for identifying a biosurfactant optimally suited for intended applications.

  • Microextraction by packed sorbent: Uncommon detection techniques, sorbents, samples and analytes
    • Vasil Andruch
    • Alina Kalyniukova
    • Tanya Yordanova
    • Justyna Płotka-Wasylka
    • Viera Vojteková
    • Gokhan Zengin
    2024 TRAC-TRENDS IN ANALYTICAL CHEMISTRY

    Among sample preparation approaches, the most desirable are procedures that ensure high efficiency and reproducibility, that are cheap, fast and simple, that minimize the number of operational steps and that require a small amount of sample and solvent and are thus environmentally friendly. Microextraction by packed sorbent (MEPS) is a miniaturized form of solid-phase extraction, the use of which has been continuously expanding since its introduction in 2004. This technique can be considered green, and due to its many advantages, it has been widely accepted and used for sample pretreatment prior to instrumental analysis. This mini-review deals with the presentation and discussion of atypical, less described approaches and solutions with the MEPS technique, especially in regard to the detection techniques and sorbents used, the samples analyzed and the analytes determined. We hope this review will interest, inspire and motivate readers to explore new MEPS applications.

  • Microfluidically Frequency-Reconfigurable Compact Self-Quadruplexing Tunable Antenna with High Isolation Based on Substrate Integrated Waveguide
    • Rusan Kumar Barik
    • Sławomir Kozieł
    2024 Full text Scientific Reports

    This communication presents a novel concept of microfluidically frequency-reconfigurable self-quadruplexing tunable antenna for quad-band applications. At the initial design stage, a substrate-integrated square cavity is divided into four unequal quarter-mode cavity resonators by inserting an X-shaped slot on the top surface of the cavity. Applying four 50-ohm microstrip feed-lines to these four quarter-mode cavity resonators enables quad-band operation with self-quadruplexing capabilities. The feed lines are organized orthogonally and off-center, which leads to port isolation greater than 32.3 dB. An equivalent network model is developed to validate the proposed antenna. To realize frequency reconfigurability, two microfluidic channels corresponding to each port are created by engraving the bottom surface of the cavity. To create a reconfigurable self-quadruplexing antenna, the channels are either filled with air or dielectric liquids of higher permittivity, so that the design offers independent tunability of the operating frequencies. As a proof of concept, the prototype of a self-quadruplexing tunable antenna is fabricated and validated through measurements. The antenna prototype occupies a footprint area of 0.37λg2. The design exhibits frequency tuning ranges of 350 MHz (8.3%), 500 MHz (10.3%), 610 MHz (11.2%), and 845 MHz (14.1%) for the first, second, third, and fourth operating bands, respectively. In all bands and across the entire tuning range, the realized gains of the designed antenna exceed 4.05 dBi. The electromagnetic modeling responses agree extremely well with the measured characteristics.

  • Microfluidically Frequency-Reconfigurable Self-Quadruplexing Antenna Based on Substrate Integrated Square-Cavity
    • Rusan Kumar Barik
    • Sławomir Kozieł
    2024 AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS

    In this article, a novel concept of self-quadruplexing tunable antenna (SQTA) enabled by microfluidic channels is investigated. The operating channels are either filled with air or dielectric liquids to enable frequency tunability. The proposed SQTA is implemented on the substrate-integrated square-cavity (SISC). A swastika-shaped slot is milled on the top-surface of the SISC to create four quarter-mode resonators. The resonators are excited by four 50-Ω microstrip lines to enable independent operating bands with self-quadruplexing properties. The working principle is validated by a custom-developed lumped-circuit model. The port isolations are better than 27dB due to the orthogonal and off-centered port allocation. Subsequently, two microfluidic channels corresponding to each quarter-mode resonator are milled from bottom-surface of the cavity. These two channels are filled with liquids of various permittivity to achieve frequency tunability. As a proof-of-concept, a prototype of the proposed SQTA is fabricated and demonstrated experimentally. The fabricated SQTA operates at 4.05-4.56 GHz, 4.645-5.295 GHz, 5.45-6.325 GHz, and 6.19-7.265 GHz. The measured realized gains of the SQTA are 4.4-4.5 dBi, 4.5-4.6 dBi, 4.8-4.9 dBi, and 4.9-4.95 dBi.

  • Microplastics in water resources: Global pollution circle, possible technological solutions, legislations, and future horizon
    • Saeed S. Albaseer
    • Hussein Al-Hazmi
    • Tonni Agustiono Kurniawan
    • Xianbao Xu
    • Sameer A.M. Abdulrahman
    • Peyman Ezzati
    • Sajjad Habibzadeh
    • Henner Hollert
    • Navid Rabiee
    • Eder C. Lima
    • Michael Badawi
    • Mohammad Saeb
    2024 SCIENCE OF THE TOTAL ENVIRONMENT

    Beneath the surface of our ecosystems, microplastics (MPs) silently loom as a significant threat. These minuscule pollutants, invisible to the naked eye, wreak havoc on living organisms and disrupt the delicate balance of our environment. As we delve into a trove of data and reports, a troubling narrative unfolds: MPs pose a grave risk to both health and food chains with their diverse compositions and chemical characteristics. Nevertheless, the peril extends further. MPs infiltrate the environment and intertwine with other pollutants. Worldwide, microplastic levels fluctuate dramatically, ranging from 0.001 to 140 particles.m-3 in water and 0.2 to 8766 particles.g-1 in sediment, painting a stark picture of pervasive pollution. Coastal and marine ecosystems bear the brunt, with each organism laden with thousands of microplastic particles. MPs possess a remarkable ability to absorb a plethora of contaminants, and their environmental behavior is influenced by factors such as molecular weight and pH. Reported adsorption capacities of MPs vary greatly, spanning from 0.001 to 12,700 μg·g−1. These distressing figures serve as a clarion call, demanding immediate action and heightened environmental consciousness. Legislation, innovation, and sustainable practices stand as indispensable defenses against this encroaching menace. Grasping the intricate interplay between microplastics and pollutants is paramount, guiding us toward effective mitigation strategies and preserving our health ecosystems.

  • Microstructural evolution and mechanical behavior of activated tungsten inert gas welded joint between P91 steel and Incoloy 800HT
    • Vishwa Bhanu
    • J. Manoj
    • Ankur Gupta
    • Dariusz Fydrych
    • Chandan Pandey
    2024 INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY

    This study examines the welded joint between P91 steel and Incoloy 800HT using the Activated Tungsten Inert Gas (A-TIG) welding process. The focus is on analyzing the microstructure and evaluating the mechanical properties of joints made with different compositions of activating flux. Owing to the reversal of the Marangoni effect in which the conventional direction of molten metal flow in the weld pool is reversed due to the application of oxide-based fluxes, a complete depth of penetration of 8 mm was successfully achieved. Conducting mechanical tests, such as microhardness, tensile, and Charpy impact toughness tests, elucidates the behavior of the welded specimens under different loading conditions. The findings highlight the effects of grain size, dislocations, and the evolution of fine-sized precipitates in the high-temperature matrix. This study highlights the importance of choosing suitable flux compositions to achieve consistent penetration and dilution in the base metals. Insights into different failure modes and the influence of temperature on the tensile strength were evaluated. Beneficial mechanical properties of the joints (meeting the criteria of ISO and ASTM standards) were found: ultimate tensile strength of 585 ± 5 MPa, elongation 38 ± 2%, impact toughness of 96  5 J, and maximum microhardness of 345 ± 5 HV.

  • Microstructure and mechanical properties of a dissimilar metal welded joint of Inconel 617 and P92 steel with Inconel 82 buttering layer for AUSC boiler application
    • Amit Kumar
    • Sachin Sirohi
    • Manohar Singh
    • Dariusz Fydrych
    • Chandan Pandey
    2024 INTERNATIONAL JOURNAL OF PRESSURE VESSELS AND PIPING

    The application of the novel dissimilar metal welded (DMW) joint, utilizing Inconel 617 and P92 steel, was showcased in the advanced ultra-supercritical (AUSC) boiler. The work has been performed to investigate the effect of Inconel 82 (ERNiCr-3) buttering layer on microstructure and mechanical properties (high-temperature tensile strength, impact strength and microhardness) of gas tungsten arc welded (GTAW) dissimilar joint between Inconel 617 and P92 steel fabricated using the Inconel 617 (ERNiCrCoMo-1) filler. For optical microscopy and scanning electron microscopy (SEM), samples were machined along a transverse direction which comprised the butter layer, weld metal, and heat-affected zone of both sides. The energy-dispersive X-ray spectroscopy (EDS) was used to map the interface of the buttering layer and weld metal and butter layer and P92 steel. The high-temperature tensile testing and Charpy impact testing at room temperature were conducted for the integrity assessment of the welded joint. The examination of microstructure and hardness revealed that the buttering layer of Inconel 82 filler successfully mitigated a significant portion of the brittle martensitic microstructure from the coarse-grained heat-affected zone (CGHAZ), along with hardness peaks on the side of P92 steel. The conventional method of DMW joint fabrication, without the use of a buttering layer, has been demonstrated to be less favourable compared to the new fabrication method, which incorporates a buttering layer. The TiC/NbC carbides were identified in the Inconel 82 buttering layer, whereas M23C6 and Mo6C carbides were found in the Inconel 617 filler weld. Near the interface of the Inconel 82 buttering layer and P92 steel, the formation of peninsula and island structures, as well as Type I and Type II boundaries, were confirmed. Additionally, element diffusion of Ni, Cr, and Fe was observed. The tensile test results indicated an ultimate tensile strength of 620 ± 4 MPa and % elongation of 19 ± 4 % at room temperature, with fracture occurring in the buttering layer near the interface of the buttering layer and P92 steel. At temperatures of 550 °C and 650 °C, the ultimate tensile strength decreased to 448 MPa and 326 MPa, respectively, with fractures occurring in the P92 steel, irrespective of temperature. The hardness of the Inconel 82 buttering layer and Inconel 617 filler weld were 219 ± 10 HV and 248 ± 11 HV, respectively.

  • Microwave-Induced Processing of Free-Standing 3D Printouts: An Effortless Route to High-Redox Kinetics in Electroanalysis
    • Kornelia Kozłowska
    • Mateusz Cieślik
    • Adrian Koterwa
    • Krzysztof Formela
    • Jacek Ryl
    • Paweł Niedziałkowski
    2024 Materials

    3D-printable composites have become an attractive option used for the design and manufacture of electrochemical sensors. However, to ensure proper charge-transfer kinetics at the electrode/electrolyte interface, activation is often required, with this step consisting of polymer removal to reveal the conductive nanofiller. In this work, we present a novel effective method for the activation of composites consisting of poly(lactic acid) filled with carbon black (CB-PLA) using microwave radiation. A microwave synthesizer used in chemical laboratories (CEM, Matthews, NC, USA) was used for this purpose, establishing that the appropriate activation time for CB-PLA electrodes is 15 min at 70 °C with a microwave power of 100 W. However, the usefulness of an 80 W kitchen microwave oven is also presented for the first time and discussed as a more sustainable approach to CB-PLA electrode activation. It has been established that 10 min in a kitchen microwave oven is adequate to activate the electrode. The electrochemical properties of the microwave-activated electrodes were determined by electrochemical techniques, and their topography was characterized using scanning electron microscopy (SEM), Raman spectroscopy, and contact-angle measurements. This study confirms that during microwave activation, PLAs decompose to uncover the conductive carbon-black filler. We deliver a proof-of-concept of the utility of kitchen microwave-oven activation of a 3D-printed, free-standing electrochemical cell (FSEC) in paracetamol electroanalysis in aqueous electrolyte solution. We established satisfactory limits of linearity for paracetamol detection using voltammetry, ranging from 1.9 μM to 1 mM, with a detection limit (LOD) of 1.31 μM.

  • Mieszanki betonowe stosowane w technologii druku trójwymiarowego
    • Andrzej Ambroziak
    2024 Przegląd Budowlany

    W niniejszej pracy dokonano przeglądu literatury z zakresu mieszanek i zapraw betonowych stosowanych w druku trójwymiarowym. Przegląd literatury przygotowano z zachowaniem chronologii pojawienia się danej publikacji (daty publikacji). Na podstawie przeprowadzonego przeglądu dokonano tabelarycznego zestawienia receptur mieszanek wykorzystywanych w wydrukach trójwymiarowych (3D). Przedstawiony przegląd literatury z zakresu mieszanek i zapraw betonowych stosowanych w druku trójwymiarowym można traktować jako wstęp do szczegółowych badań związanych z projektowaniem nowych typów mieszanek i receptur.

  • Migration of trace elements and radioisotopes to various fractions of solid wastes generated as a result of the sewage sludge incineration process
    • Oskar Ronda
    • Bartłomiej Cieślik
    • Barbara Piotrowska
    • Krzysztof Isajenko
    • Satoki Okabayashi
    • Koichi Chiba
    • Motohiro Tsuboi
    • Justyna Płotka-Wasylka
    2024 Full text WASTE MANAGEMENT

    The research was aimed at providing new knowledge in the field of chemical characteristics of solid waste generated in the process of combustion of sewage sludge in fluidized bed furnaces. The research material consisted of disposed fluidized beds (DFB), sewage sludge ash (SSA) and air pollution control residues (APC) from three Polish installations for the thermal treatment of sewage sludge. Natural radionuclides as well as anthropogenic isotope 137Cs were determined in the tested materials and the migration of a wide spectrum of trace elements to various waste fractions generated in the process of sewage sludge combustion was examined. It was observed that both radioisotopes and most of the trace elements determined accumulate in SSA and DFB, while the APC fraction contains a much smaller amount of them. The exceptions are mercury and selenium, whose volatile compounds migrate to the exhaust gas dedusting system and accumulate in the APC fraction (up to 40 mg/kg and 13 mg/kg, respectively). A potential threat from the 226Ra isotope in SSA is identified in the context of the management of this waste in the production of building materials because the typical activity of 226Ra in SSA collected from areas with very low Ra content in natural environment exceeds 1.5–6 times the activity of this isotope in conventional cement mixtures. When managing SSA and DFB, special attention should be paid to the content of metalloids such as As, B and Se, due to the high content of mobile forms of these elements in the mentioned materials.

  • Millimeter Wave Negative Refractive Index Metamaterial Antenna Array
    • Rao Aziz
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2024 Full text Scientific Reports

    In this paper, a novel negative refractive index metamaterial (NIM) is developed and characterized. The proposed metamaterial exhibits negative effective permittivity (εeffe) and negative effective permeability (µeffe) at millimeter wave frequency of 28GHz. This attractive feature is utilized to enhance the gain of a microstrip patch antenna (MPA). Two thin layers of 5  5 subwavelength unit cell array of NIM are placed above a single MPA to enhance the gain of the antenna. Each unit cell has an area of 3.4  3.4 mm2. A gain increase of 7.9dBi has been observed when using the proposed NIM as a superstrate. Furthermore, the NIM array is placed over a 2  2 array of MPAs with four ports to demonstrate versatility of the metamaterial. The total size of the 2  2 antenna array system with N-MTM is about 61.1  34  16mm3 (5.71λ  3.18λ  1.5λ, where λ is the free-space wavelength at 28 GHz). The measurement result indicate that the maximum gain of the antenna array is 13.5dBi. A gain enhancement of 7.55 dB in E-Plane and 7.25 dB in H-Plane at the resonant frequency of 28 GHz is obtained. The proposed antenna structure is suitable for 5G millimeter wave communications, in particular, for possible implementation in future millimeter wave access points and cellular base stations.

  • Millimeter Wave Retrodirective Van Atta Arrays in LTCC Technology
    • Kamil Trzebiatowski
    • Martin Ihle
    • Benedykt Sikorski
    • Łukasz Kulas
    • Krzysztof Nyka
    2024 Full text

    The millimeter wave Van Atta arrays, intended for chipless RFID applications and fabricated in LTCC technology, are presented in this paper. The arrays are designed for 24 GHz and 60 GHz bands. The method for an easy modification of the RCS characteristic by increasing the number of single-dimensional arrays, intended for increasing the RCS level, is also presented. The LTCC manufacturing process is described in detail. The fabricated arrays are characterized in an anechoic chamber and exhibit RCS levels up to -26 dBsm with a small 51 x 17 mm footprint.