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Gdańsk University of Technology

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Publications from the year 2024

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  • Maximizing SDN resilience to node‐targeted attacks through joint optimization of the primary and backup controllers placements
    • Michał Pióro
    • Mariusz Mycek
    • Artur Tomaszewski
    • Amaro de Sousa
    2024 NETWORKS

    In Software Defined Networks (SDN) packet data switches are configured by a limited number of SDN controllers, which respond to queries for packet forwarding decisions from the switches. To enable optimal control of switches in real time the placement of controllers at network nodes must guarantee that the controller-to-controller and switch-to-controller communications delays are bounded. Apart from the primary controllers that control the switches in the nominal state, separate backup controllers can be introduced that take over when the primary controllers are unavailable, and whose delay bounds are relaxed. In this paper we present optimization models to jointly optimize the placement of primary and backup controllers in long-distance SDN networks, aimed at maximizing the network's resilience to node-targeted attacks. Applying the models to two well-known network topologies and running a broad numerical study we show that, when compared with the standard approach of using only primary controllers, the use of backup controllers provides significant resilience gains, in particular in case of strict delay bounds.

  • Measuring Tilt with an IMU Using the Taylor Algorithm
    • Jerzy Demkowicz
    2024 Remote Sensing

    This article addresses the important problem of tilt measurement and stabilization. This is particularly important in the case of drone stabilization and navigation in underwater environments, multibeam sonar mapping, aerial photogrammetry in densely urbanized areas, etc. The tilt measurement process involves the fusion of information from at least two different sensors. Inertial sensors (IMUs) are unique in this context because they are both autonomous and passive at the same time and are therefore very attractive. Their calibration and systematic errors or bias are known problems, briefly discussed in the article due to their importance, and are relatively simple to solve. However, problems related to the accumulation of these errors over time and their autonomous and dynamic correction remain. This article proposes a solution to the problem of IMU tilt calibration, i.e., the pitch and roll and the accelerometer bias correction in dynamic conditions, and presents the process of calculating these parameters based on combined accelerometer and gyroscope records using a new approach based on measuring increments or differences in tilt measurement. Verification was performed by simulation under typical conditions and for many different inertial units, i.e., IMU devices, which brings the proposed method closer to the real application context. The article also addresses, to some extent, the issue of navigation, especially in the context of dead reckoning.

  • Mechanical Properties of 3D Printed Parts and Their Injection Molded Alternatives Subjected to Environmental Aging
    • Angela Jadwiga Andrzejewska
    2024 3D Printing and Additive Manufacturing

    Additive manufacturing is the technology used in medical, industrial, or lifestyle applications. The scientific literature include works reporting various manufacturing parameters’ influence on changes in additive manufacturing components’ mechanical behavior, especially with fused filament fabrication (FFF). The changes in mechanical strength and toughness of FFF compared to injection molding parts were studied. In the study, the FFF and injection molded parts were aged in buffered saline solution in temperature of 37C. The results show that by differentiating the orientation of the fibers during fabricating, it is possible to reach strength values similar to injection molded parts. Therefore, it was reported that the mechanical strength and toughness changed significantly after aging, and the FFF components lost strength more quickly than their injected alternatives. The research results can be useful during the fabrication of mechanically stable and biodegradable components, which can be more easily recycled than their injected alternatives when used with warmer temperatures and humidity. This article completes the present state of the art on the problem of environmental aging of parts produced from biodegradable materials. Especially, the research was related to the multilayer laminate structure.

  • Mechanical Properties of Additively Manufactured Polymeric Materials—PLA and PETG—For Biomechanical Applications
    • Rui F. Martins
    • Ricardo Branco
    • Miguel Martins
    • Wojciech Macek
    • Zbigniew Marciniak
    • Rui Silva
    • Daniela Trindade
    • Carla Moura
    • Margarida Franco
    • Cândida Malça
    2024 Full text Polymers

    The study presented herein concerns the mechanical properties of two common polymers for potential biomedical applications, PLA and PETG, processed through fused filament fabrication (FFF)—Material Extrusion (ME). For the uniaxial tension tests carried out, two printing orientations—XY (Horizontal, H) and YZ (Vertical, V)—were considered according to the general principles for part positioning, coordinates, and orientation typically used in additive manufacturing (AM). In addition, six specimens were tested for each printing orientation and material, providing insights into mechanical properties such as Tensile Strength, Young’s Modulus, and Ultimate Strain, suggesting the materials’ potential for biomedical applications. The experimental results were then compared with correspondent mechanical properties obtained from the literature for other polymers like ASA, PC, PP, ULTEM 9085, Copolyester, and Nylon. Thereafter, fatigue resistance curves (S-N curves) for PLA and PETG, printed along 45°, were determined at room temperature for a load ratio, R, of 0.2. Scanning electron microscope observations revealed fibre arrangements, compression/adhesion between layers, and fracture zones, shedding light on the failure mechanisms involved in the fatigue crack propagation of such materials and giving design reference values for future applications. In addition, fractographic analyses of the fatigue fracture surfaces were carried out, as well as X-ray Computed Tomography (XCT) and Thermogravimetric (TGA)/Differential Scanning Calorimetric (DSC) tests.

  • Mechanical response of human thoracic spine ligaments under quasi-static loading: An experimental study
    • Radosław Wolny
    • Tomasz Wiczenbach
    • Angela Andrzejewska
    • Jan Henryk Spodnik
    2024 Journal of the Mechanical Behavior of Biomedical Materials

    Purpose This study aimed to investigate the geometrical and mechanical properties of human thoracic spine ligaments subjected to uniaxial quasi-static tensile test. Methods Four human thoracic spines, obtained through a body donation program, were utilized for the study. The anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), capsular ligament (CL), ligamenta flava (LF), and the interspinous ligament and supraspinous ligament complex (ISL + SSL), were investigated. The samples underwent specimen preparation, including dissection, cleaning, and reinforcement, before being immersed in epoxy resin. Uniaxial tensile tests were performed using a custom-designed mechanical testing machine equipped with an environmental chamber (T = 36.6 °C; humidity 95%). Then, the obtained tensile curves were averaged preserving the characteristic regions of typical ligaments response. Results Geometrical and mechanical properties, such as initial length and width, failure load, and failure elongation, were measured. Analysis of variance (ANOVA) revealed significant differences among the ligaments for all investigated parameters. Pairwise comparisons using Tukey's post-hoc test indicated differences in initial length and width. ALL and PLL exhibited higher failure forces compared to CL and LF. ALL and ISL + SSL demonstrated biggest failure elongation. Comparisons with other studies showed variations in initial length, failure force, and failure elongation across different ligaments. The subsystem (Th1 – Th6 and Th7 – Th12) analysis revealed increases in initial length, width, failure force, and elongation for certain ligaments. Conclusions Variations of both the geometric and mechanical properties of the ligaments were noticed, highlighting their unique characteristics and response to tensile force. Presented results extend very limited experimental data base of thoracic spine ligaments existing in the literature. The obtained geometrical and mechanical properties can help in the development of more precise human body models (HBMs).

  • Melanoma skin cancer detection using mask-RCNN with modified GRU model
    • K. M. Monica
    • J. Shreeharsha
    • Przemysław Falkowski-Gilski
    • Bożena Falkowska-Gilska
    • Mohan Awasthy
    • Rekha Phadk
    2024 Full text Frontiers in Physiology

    Introduction: Melanoma Skin Cancer (MSC) is a type of cancer in the human body; therefore, early disease diagnosis is essential for reducing the mortality rate. However, dermoscopic image analysis poses challenges due to factors such as color illumination, light reflections, and the varying sizes and shapes of lesions. To overcome these challenges, an automated framework is proposed in this manuscript. Methods: Initially, dermoscopic images are acquired from two online benchmark datasets: International Skin Imaging Collaboration (ISIC) 2020 and Human against Machine (HAM) 10000. Subsequently, a normalization technique is employed on the dermoscopic images to decrease noise impact, outliers, and variations in the pixels. Furthermore, cancerous regions in the pre-processed images are segmented utilizing the mask-faster Region based Convolutional Neural Network (RCNN) model. The mask-RCNN model offers precise pixellevel segmentation by accurately delineating object boundaries. From the partitioned cancerous regions, discriminative feature vectors are extracted by applying three pre-trained CNN models, namely ResNeXt101, Xception, and InceptionV3. These feature vectors are passed into the modified Gated Recurrent Unit (GRU) model for MSC classification. In the modified GRU model, a swish-Rectified Linear Unit (ReLU) activation function is incorporated that efficiently stabilizes the learning process with better convergence rate during training. Results and discussion: The empirical investigation demonstrate that the modified GRU model attained an accuracy of 99.95% and 99.98% on the ISIC 2020 and HAM 10000 datasets, where the obtained results surpass the conventional detection models.

  • Meldrum’s acid assisted formation of tetrahydroquinolin‑2‑one derivatives a short synthetic pathway to the biologically useful scaffold
    • Małgorzata Ryczkowska
    • Alicja Trocka
    • Anna Hromova
    • Sławomir Makowiec
    2024 Full text Scientific Reports

    A new method for the preparation of tetrahydroquinolin-2-one derivatives is presented. This approach involves a two-step reaction between enaminones and acylating agents, immediately followed by electrophilic cyclization, all within a single synthesis procedure, eliminating the need to isolate intermediates. The entire process is facilitated by the use of acyl Meldrum’s acids which not only shortens the preparation time of the substrates but also easily extends the range of substituents That can be used. The method’s scope and limitations were evaluated with various reagent combinations thus demonstrating its general applicability to the synthesis of tetrahydroquinolin-2-one core. Interestingly, some exceptions to the regular reaction pathway were observed when a strong EDG (electron donating group) was introduced via acyl Meldrum’s acids. The underlying mechanism of this phenomenon was elucidated during the investigation.

  • Merton-type default risk and financial performance: the dynamic panel moderation of firm size
    • Muhammad Mushafiq
    • Syed Ahmad Sami
    • Muhammad Khalid Sohail
    • Muzammal Ilyas Sindhu
    2024 Journal of Economic and Administrative Sciences

    Purpose – The main purpose of this study is to evaluate the probability of default and examine the relationship between default risk and financial performance, with dynamic panel moderation of firm size. Design/methodology/approach – This study utilizes a total of 1,500 firm-year observations from 2013 to 2018 using dynamic panel data approach of generalized method of moments to test the relationship between default risk and financial performance with the moderation effect of the firm size. Findings – This study establishes the findings that default risk significantly impacts the financial performance. The relationship between distance-to-default (DD) and financial performance is positive, which means the relationship of the independent and dependent variable is inverse. Moreover, this study finds that the firm size is a significant positive moderator between DD and financial performance. Practical implications – This study provides new and useful insight into the literature on the relationship between default risk and financial performance. The results of this study provide investors and businesses related to nonfinancial firms in the Pakistan Stock Exchange (PSX) with significant default risk’s impact on performance. This study finds, on average, the default probability in KSE ALL indexed companies is 6.12%. Originality/value – The evidence of the default risk and financial performance on samples of nonfinancial firms has been minimal; mainly, it has been limited to the banking sector. Moreover, the existing studies have only catered the direct effect of only. This study fills that gap and evaluates this relationship in nonfinancial firms. This study also helps in the evaluation of Merton model’s performance in the nonfinancial firms.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.