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Ostatnie pozycje
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Enhancing electrical properties through in-situ controlled nanocrystallization of V2O5–TeO2 glass
- Piotr Okoczuk
- Agnieszka Kwiatkowska
- Leon Murawski
- Tomasz Pietrzak
- Natalia Wójcik
- Fabian Garmroudi
- Leszek Wicikowski
- Barbara Kościelska
V2O5–TeO2 glass–ceramics (VTGC) were prepared by controlled annealing of the V2O5–TeO2 glass (VTG), which illustrates a parent glass matrix with a single charge carrier. The annealing proceeded at six temperatures selected between the glass transition and the maximum of the frst crystallization process to obtain various nanocrystallite sizes. Heat treatment caused an increase in DC conductivity by 2.5–3.5 (250–285 °C) order of magnitude. Using thermal analysis, the crystal growth process was determined to be 1D. Structural studies show that the obtained materials are partially amorphous and polycrystalline with nanometersized crystallites. Subtle thread-like structures were observed using conductive AFM. The activation energy of the conduction process decreased from 0.38 eV in VTG to 0.18–0.11 eV (250–285 °C) in VTGC. The radii of crystallites were calculated based on the theoretical model of electron hopping between connected semiconducting nanocrystallites and vary between 1.7 and 2.8 nm (250–285 °C). Thermoelectric studies indicate constant carrier concentration. Features characteristic of small polaron hopping-governed materials were observed. We suggest V3O7 nanocrystals as conductive media in VTGC.
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Enhancing environmental literacy through urban technology-based learning. The PULA app case
- Ewa Duda
- Helena Anacka
- Hanna Obracht-prondzyńska
- Hanne Cecilie Geirbo
- Jolanta Kowal
This study addresses the need to enhance environmental literacy, focusing on urban adults through mobile applications, based on the example of PULA app that engages early adopters in gamified pro- environmental activities, offering insights into informal learning. Grounded in 'urban pedagogy,' the study combines semi-structured interviews with 17 application testers and quantitative data analysis, unveiling motivations, user feedback, and success aspects. Motivations include a desire for environmental impact, heightened climate awareness, and behavioral transformation. Users perceive knowledge increase as a key benefit, emphasizing educational features, gamification, and social interaction. Success aspects manifest in a sense of belonging, positive behavioral changes, and heightened environmental responsibility. Optimizing the environmentally-friendly app requires continuous gamified content innovation, technical issue resolution, and diverse educational content. Strengthening social interaction features and conducting longitudinal studies are crucial for sustained impact. This study advances our understanding of mobile apps' role in promoting environmental literacy, emphasizing the transformative potential of digital platforms and collaborative efforts for sustainable impact.
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Enhancing nitrogen removal in the partial denitrification/anammox processes for SO4− - Rich wastewater treatment: Insights into autotrophic and mixotrophic strategies
- Dominika Derwis
- Hussein Al-Hazmi
- Joanna Majtacz
- Slawomir Ciesielski
- Jacek Mąkinia
The investigation of partial denitrification/anammox (PD/anammox) processes was conducted under autotrophic (N–S cycle) and mixotrophic (N–S–C cycle) conditions over 180 days. Key findings revealed the remarkable capability of SO42--dependent systems to produce NO2− effectively, supporting anaerobic NH4+ oxidation. Additionally, SO42− served as an additional electron acceptor in sulfate reduction ammonium oxidation (SRAO). Increasing influent SO42− concentrations notably improved ammonia utilization rates (AUR) and NH4+ and total nitrogen (TN) utilization efficiencies, peaking at 57% for SBR1 and nearly 100% for SBR2. Stoichiometric analysis showed a 7.5-fold increase in AUR (SRAO and anammox) in SBR1 following SO42− supplementation. However, the analysis for SBR2 indicated a shift towards SRAO and mixotrophic denitrification, with anammox disappearing entirely by the end of the study. Comparative assessments between SBR1 and SBR2 emphasized the impact of organic compounds (CH3COONa) on transformations within the N–S–C cycle. SBR1 performance primarily involved anammox, SRAO and other SO42− utilization pathways, with minimal S-dependent autotrophic denitrification (SDAD) involvement. In contrast, SBR2 performance encompassed SRAO, mixotrophic denitrification, and other pathways for SO42− production. The SRAO process involved two dominant genera, such as Candidatus Brocadia and PHOS-HE36.
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Enhancing rheological muscle models with stochastic processes
- Bartłomiej Zagrodny
- Wiktoria Wojnicz
- Michał Ludwicki
- Robert Barański
Purpose: Biological musculoskeletal systems operate under variable conditions. Muscle stiffness, activation signals, and loads change during each movement. The presence of noise and different harmonic components in force production significantly influences the behaviour of the muscular system. Therefore, it is essential to consider these factors in numerical simulations. Methods: This study aims to develop a rheological mathematical model that accurately represents the behaviour of the actual muscular system, taking into account the phenomena described by the stochastic model in the form of stationary processes. Stochastic disturbances were applied to simulate variable conditions, in which musculo-skeletal system operates. Numerical simulations were conducted for two dynamic tasks, where we calculated the internal force generated by the system (task 1), and its displacement (task 2). These simulations were performed using two different datasets sourced from the literature. In the next step, simulation results were compared with our own experiment. Results: The considered mathematical model was successfully tuned and compared with both the literature data and our own experimental results. During the analysis of muscle model behavior, depending on the data source for model tuning, we observed distinct frequency characterized by a sine-type pattern and a higher frequencies marked by stochastic perturbations. Conclusions: The proposed model can be customized to simulate systems of varying sizes, levels of maximum voluntary contraction, and the effects of perturbations, closely resembling real-world data. The presented approach can be applied to simulate the behaviour of the musculoskeletal system as well as of individual muscles.
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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
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.
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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
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.
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Entire fracture surface topography parameters for fatigue life assessment of 10H2M steel
- Wojciech Macek
- Mateusz Kopec
- Aleksandra Laska
- Zbigniew Kowalewski
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.
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Entrepreneurial intentions of students from Latvia, Poland, and Ukraine: The role of perceived entrepreneurial education results
- Julita Wasilczuk
- Magdalena Licznerska
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.
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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
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.
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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
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.
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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
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.
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Equitable colorings of some variation of corona products of cubic graphs
- Marek Kubale
- Hanna Furmańczyk
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.
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Essays on China's international trade - focus on One-Belt One-Road initiative
- Yuxin Lu
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.
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Estymacja położenia i orientacji w systemie lokalizacyjnym z częściową synchronizacją węzłów referencyjnych
- Jarosław Sadowski
- Jacek Stefański
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.
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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
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.
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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
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.
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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
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.
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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
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.
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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
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%.
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Excitation of Circularly Polarized Wave via Single-Feed Metasurface-Integrated Compact Antenna for Internet of Things
- Shahanawaz Kamal
- Ullah Ubaid
- Sławomir Kozieł
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%.
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Excitation of Waves in a Dispersive Medium. Example of Flow of a Bubbly Liquid
- Anna Perelomova
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
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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
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.
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Expedited Re-Design of Multi-Band Passive Microwave Circuits Using Orthogonal Scaling Directions and Gradient-Based Tuning
- Sławomir Kozieł
- Anna Pietrenko-Dąbrowska
- Ubaid Ullah
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.
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Experimental and Numerical Investigations of the Effect of Curing Conditions on the Temperature Rise of Concrete
- Aleksandra Kuryłowicz-Cudowska
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.
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Experimental and numerical studies on the mechanical response of a piezoelectric nanocomposite-based functionally graded materials
- Mohammad Malikan
- Magdalena Rucka
This work presents an experimental study of piezoelectric structures reinforced by graphene platelets, based on the concept of the functionally graded materials (FGMs). The assumed model is a rectangular beam/plate and the composition is due to the Halpin-Tsai rule. The model is also simulated in the Abaqus software which is the first time that such a structure has been modelled in an FEM package. In addition, a mathematical model based on a beam/plate theory, Lagrangian strains and variational technique is expressed and the derived partial differential equations governing the mechanics of the structure are solved numerically using the differential quadrature method. In terms of the experiments, the nanocomposite is fabricated in the form of layered FGMs using powder metallurgy. The specimens are subjected to two mechanical tests, bending and tensile. To accurately identify the FGM sample cross-section, a scanning electron microscope is used to examine the microstructure of the solid.
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Experimental and numerical study of thermal and electrical potential of BIPV/T collector in the form of air-cooled photovoltaic roof tile
- Jakub Łukasik
- Jan Wajs
Among renewable energy sources, Building-Integrated Photovoltaic/Thermal (BIPV/T) systems are gaining increasing interest. To improve their economic competitiveness, technologies that increase their efficiency are searched for. The paper is devoted to evaluating the impact of various air-cooling configurations on the thermal and electrical performance of a photovoltaic roof tile. A numerical model of the own experimental system was developed in the ANSYS Fluent software for a wide range of input variables. The original approach based on the SST k-ω turbulence model, Discrete Ordinates radiation model, and the use of Solar Load module were proposed. Such a numerical model allows representation of semi-transparent layers and variable solar irradiance, which is a unique realization of real system modelling. Numerous analyses conducted indicate a higher heat recovery potential for an airflow duct with a height of 25 mm for all configurations analysed. The highest value of recovered heat flux was approximately 330 W/m2 under conditions of a volumetric air flow rate of 7.5 m3/h and solar irradiance equal to 900 W/m2. Good agreement of the results of the multivariant CFD simulations with new experimental ones was confirmed. Insight into the flow phenomena behind the achieved thermal results supplemented the knowledge. The highest electrical efficiency obtained experimentally was 5.76 % for a channel with a height of 50 mm, volumetric flow rate equal to 7.5 m3/h and solar irradiance equal to 600 W/m2. The presented methodology and the results obtained can be useful in research devoted to optimising BIPV/T air-based cooling systems, which will then be tested in-situ. Moreover, new experimental data collection can be used for the verification of numerical models.
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Experimental and numerical study on stability loss of innovative geometry steel girder
- Małgorzata Gordziej-Zagórowska
- Wojciech Migda
- Natalia Lasowicz
- Patryk Deniziak
- Alicja Bera
- Jakub Kowalski
This paper presents the experimental and numerical analysis of an innovative plate girder geometry with variable web thicknesses. An idea proposed in this research is to increase the stability of the girder web by increasing its thickness in the compressed zone. This solution can replace commonly used longitudinal stiffeners which are designed to prevent web local loss of stability. Moreover, such an innovative approach requires only one addi- tional butt weld along the entire element, which is technologically a simpler, cheaper and faster operation (due to the possibility of full automation of production) compared to manual welding of individual stiffeners. The experimental and numerical study shows that application of a web with variable thickness in I-shaped plate girder geometry subjected to four-point bending results in a change in failure mechanism from local to global one. Moreover plate girders with single and double-sided longitudinal stiffeners have been tested numerically. The result of the study clearly shows that values of ultimate load estimated for plate girders with longitudinal stiffeners were smaller than those obtained for innovative ones. It confirms that the proposed solution may prevent web from local stability loss and increase plate girder stability due to bending. This innovative method can be also considered as an effective procedure of strengthening the web in its compressive zone compared to commonly used longitudinal stiffeners
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Experimental and theoretical study on high-temperature creep of VT6 titanium alloy under multi-axial loading conditions
- Leonid Igumnov
- Ivan Volkov
- V.a. Kazakov
- Denis Shishulin
- Ivan Modin
- Alexander Belov
- Victor Eremeev
In the framework of damage mechanics, we discuss a new mathematical model that describes the kinetics of the stress–strain state and damage accumulation during material degradation by the mechanism of long-term strength under complex multiaxial stress state. An experimental and theoretical technique is proposed for determination of material parameters and scalar constitutive functions for damaged media based on specially set experiments on laboratory specimens. The results of experimental studies and numerical simulations of short-term high-temperature creep of VT6 titanium alloy under uniaxial and multiaxial loading are presented. Numerical results are compared with the data obtained through experiments. Particular attention is paid to simulating the process of unsteady creep for complex deformation modes, accompanied by rotation of main areas of stress, strain and creep strain tensors. It is shown that the developed version of the constitutive relations of the damaged media enables us to describe the processes of unsteady creep and long-term strength of structural alloys under multiaxial stress with the accuracy sufficient for engineering calculations.
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Experimental investigation of thermal energy storage in shell-and-multi-tube unit with nano-enhanced phase change material
- Maciej Fabrykiewicz
- Janusz Cieśliński
This paper deals with thermal energy storage with use of nanoparticle enhanced phase change material in shell-and-multitube unit. The experiments are conducted under atmospheric pressure. Paraffin wax and two different fatty acids are used as base phase change material. Graphite and multi-walled carbon nanotubes serve as nanoparticles. Graphite nanoparticles are tested at the concentrations of 0.1%, 1% and 5% by weight, while multi-walled carbon nanotubes only at 0.1%wt. Ultrasonic vibration and homogenizer are used in order to stabilize the dispersion of the nanoparticles. Polyvinylpyrrolidone surfactant is used to stabilize the suspension and the tested nano-enhanced phase change material exhibit satisfactory stability. Experimental measurements are performed for a bundle of 7 tubes with outside diameter of 6 mm in a staggered arrangement and a pitch ratio of 4.5. It is found that, regardless of the tested base phase change material, the addition of graphite nanoparticles with mass concentration of 0.1% does not significantly affect the charging and discharging times compared to base phase change material. The differences in charging and discharging times did not exceed 11%. For a graphite nanoparticles mass concentration of 5%, an increase in the charging time by up to 21% and a reduction in the discharging time by 24% was observed, depending on the type of base phase change material. An addition of multi-walled carbon nanotubes with mass concentration of 0.1% shows an increase in charging time regardless of the type base phase change material up to 144% with negligible influence on the discharging time. It was also observed that adding a surfactant to the produced nano-enhanced phase change material results in a reduction in charging time by up to 83% depending on the type of base phase change material.
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Experimental investigation on heat pipes supported by soy wax and lauric acid for electronics cooling
- Paweł Szymański
- Radosław Paluch
This paper presents an experimental study of heat pipes for electronics cooling that were supported by energy storage materials (i.e. phase change materials - PCMs) coated at the adiabatic section. The PCMs utilized included two materials, namely lauric acid and soy wax, the latter being considered as a more cost-effective alternative. The study focused on three different powers: 20 W, 25 W, and 30 W. Both heating, cooling, and thermal cycling experiments were performed in order to compare the thermal performance of cooling units. The experimental results showed that the incorporation of lauric acid as a thermal energy storage material reduced the maximum temperature by 11.6 %, 14.6 %, and 14.5 % for the examined powers. On the other hand, the utilization of soy wax resulted in temperature reductions of 4.3 %, 6.3 %, and 6.8 %. Furthermore, it was observed that lauric acid could store 25 % of the energy during the maximum power dissipation test, whereas soy wax could store 12 %. It was shown that lauric acid improved the thermal performance of the unit by approximately twice as effectively as soy wax. However, it is noteworthy that soy wax exhibits a significantly lower cost, making it a potentially viable alternative for less demanding applications where cost considerations are crucial.
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Experimental investigations on water sorptivity in mortars with the use of X-ray micro-CT system.
- Łukasz Skarżyński
- Andrzej Tejchman-Konarzewski
W pracy doswiadczalnej zbadano zjawisko sorpcji wody w pryzmatycznych próbkach zapraw, które jest ściśle powiązane z trwałością materiału. Sorpcyjność oceniana na etapie ustalonym w połączeniu z warunkami zewnętrznymi może być wykorzystana do przewidywania okresu użytkowania. Sorpcyjność początkową i wtórną wody w próbkach zapraw nienasyconych zmierzono w badaniach laboratoryjnych zgodnie z normą amerykańską ASTM C 1585–04. Wpływ porowatości początkowej na sorpcyjność zbadano poprzez zmianę stosunku cementu do piasku (c/s) i stosunku wody do cementu (w/c). Dodatkowo zmieniono powierzchnię napływu wody, która miała orientację pionową lub poziomą. Nowością była wizualizacja rozkładu wody w badanych próbkach za pomocą aparatu rentgenowskiego mikro-CT 3D SkyScan 1173. Stwierdzono, że na sorpcyjność zaprawy silnie reaguje współczynnik c/s, wahający się do 100%, przy czym umiarkowany wpływ na nią ma współczynnik w/c zmieniający się aż do 25% i powierzchnia napływu wody zmienny od 25% do 45%. Sorpcyjność wzrastała wraz ze spadkiem współczynnika c/s (zgodnie z istniejącymi danymi literaturowymi) i stosunku w/c (w przeciwieństwie do istniejących danych literaturowych). Na podstawie zdjęć mikro-CT stwierdzono, że rozkład wody w próbkach zapraw był nierównomierny, a ich większa porowatość wpływała na wzrost poziomu wody, ale nie na całkowitą objętość pochłoniętej wody (w przeciwieństwie do danych literaturowych). Do odrywania cząstek wody doszło przed jej głównym frontem.
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Experimental observations on the creep behaviour of frozen soil
- Katarzyna Staszewska
- Andrzej Niemunis
- Marcin Cudny
Constitutive models in the literature for creep of frozen soil are based on the direct use of time counted from the onset of creep. An explicit time dependence in a constitutive equation violates the principles of rational mechanics. No change in stress or temperature is allowed for during creep, using the time-based formulations. Moreover, the existing descriptions need much verification and improvement on the experimental side as well. Creep behaviour of artificially frozen sand was evaluated experimentally. Novel testing methods were used, and new insights into the creep behaviour of frozen soil were gained. Creep rate under uniaxial compression was examined with different kinds of interruptions, like unloadings or overloadings. Experimental creep curves were presented as functions of creep strain. They were brought to a dimensionless form which describes the creep universally, despite changes in stress or temperature. Possible anisotropy of frozen soil was revealed in the creep tests on cubic samples with changes of the loading direction. Using the particle image velocimetry (PIV) technique, information on the lateral deformation and the uniformity of creep were obtained. Volumetric creep of unsaturated frozen soil under isotropic compression was demonstrated to be due to the presence of air bubbles only.
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Experimental study and numerical simulation on porosity dependent direct reducibility of high-grade iron oxide pellets in hydrogen
- Behzad Sadeghi
- Pasquale Cavaliere
- Mutlucan Bayat
- Niloofar Ebrahimzadeh Esfahani
- Aleksandra Laska
- Damian Koszelow
The transition to more environmentally friendly steel production methods has intensified research into hydrogen-based direct reduction (HyDR) of iron oxide pellets. The aim of this study is to systematically investigate the kinetics of the reduction process, the evolution of porosity and the resulting microstructural changes on the reduction behavior of high-quality pellets during HyDR of iron ore at different temperatures. A modified mathematical model is developed based on the shrinkage kernel model, taking into account both mass and heat transport in a hydrogen atmosphere. The effects of temperature, particle size and time on the reduction behavior of the pellets are investigated. The simulated results are validated and discussed by the results of a batch of iron oxide pellets consisting of ten almost spherical pellets subjected to the direct reduction process with pure hydrogen. The results show that the total energy input to the HyDR process is a complex balance of factors, including chemical reaction rates, diffusion dynamics and entropy generation. The increase in free volume and simultaneous decrease in pore diameter reflect the dynamic nature of the microstructure, which includes additional free volume and defects due to the volume discrepancies and associated stresses between the reactant and product phases. Furthermore, the data show that higher temperatures accelerate the reduction reactions, especially the transformation of wustite into metallic iron. This phase transition is characterized by a significant volume change that cannot be accommodated by elastic deformation alone, leading to the development of lattice defects such as cracks, creep pores and dislocations that serve as stress relief mechanisms. The trends for porosity change at 950 °C and 1000 °C observed in the experimental results are correct and in good agreement with the numerical and simulated results.
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Experimental study of the impact of notches and holes made in the front edge of adherends on the properties of static and fatigue strength of adhesive joints
- Andrzej Kubit
- Wojciech Macek
- Władysław Zielecki
- Paulina Szawara
- Piotr Myśliwiec
The paper presents the results of experimental studies aimed at determining the effect of holes and notches at the front edge of adherends on the strength of adhesive joints. Single-lap joints made of S235JR steel sheets joined with Araldite 2014-2 epoxy adhesive were tested. Comparative tests of static strength in the shear test as well as high-cycle fatigue strength tests were carried out. Joints with three holes with a diameter of 3 mm filled with adhesive and notches 3 mm wide and 4 mm long also filled with adhesive were tested and compared with reference joints, i.e. without modification. The assumption was that the structural changes applied were to contribute to the reduction of the peak of peel and shear stresses that typically occur in this type of joint. Based on the static strength tests, no significant effect of the applied modifications on the strength of the connections was demonstrated. However, in the case of fatigue strength, a significant improvement in fatigue lifetime was demonstrated, which in the area of low cycle fatigue increased by 328.6 % for the joint with notches and by 640.8 % for the variant with holes. For the fatigue fracture surfaces, a topography analysis was carried out by determining the roughness parameters. Significant differences were exposed since at the leading edge, the selected parameters were significantly lower for the reference variant than for variants with notches and holes.
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Experimental study of the multi-disc negative brake for a hydraulic motor
- Paweł Śliwiński
- Ryszard Jasiński
This paper describes the methodology for experimental testing of a multi-disc brake. The construction of this brake was also present. The brake is dedicated to hydraulic motors with a small working volume. Experimental tests were carried out on a brake with plates immersed in oil and, for comparison, tests were carried out on a dry brake. As a result of the tests, the permissible torque (load) that is able to transfer the brake and the pressure required to release the brake were determined. The temperature rise in the chamber of the uncoupled brake (both wet and dry brake), whose shaft with active discs was rotated at speed of 1,500 rpm, was also examined. The influence of the deformation of the brake discs on the characteristics of the torque of friction in these discs was also observed.
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Experimental study on the feasibility of alternative materials for tilting pad thrust bearings operating in transition to mixed friction
- Michał Wasilczuk
- Michał Wodtke
In hydrodynamic bearings traditional bearing alloys: Babbitts and bronzes are most frequently utilized. Polymer sliding layers are sometimes applied as a valuable alternative. Hard diamond-like carbon (DLC) coatings, which are also considered for certain applications may show some advantages, as well. Although material selection is of secondary importance in a full film lubrication regime it becomes important in mixed friction conditions, which is crucial for bearings with frequent starts and stops. Experimental research aimed at studying the performance of fluid film bearings in the specific operating regime, including the transition to mixed friction, is described in the paper. The tests were carried out on four tilting pad bearings of different material compositions: Steel/bronze, DLC/steel, steel/polyether ether ketone (PEEK), and steel/Babbitt. The tests comprised stopping under load and reproduction of the Stribeck curve by decreasing rotational speed to very low values, and observing the changes of friction force during the transition to mixed friction regime. Analysis of the transition conditions and other results showed clear differences between the tested bearings, illustrating the feasibility of less popular material compositions for bearings operating in specific conditions. More specifically, the DLC/steel bearing was demonstrating superior performance, i.e. lower friction, transition to mixed friction occurring at higher load, and more stable performance at start-stop regime over the other tested bearings.
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Experimental test results of an automatic voltage regulator with independent phase voltage controllers
- Wojciech Śleszyński
- Artur Cichowski
- Krzysztof Jakub Szwarc
- Robert Małkowski
- Paweł Szczepankowski
- Andrzej Augusiak
- Dariusz Karkosiński
- Ryszard Strzelecki
The growing number of distributed renewable energy sources and dynamic constant-power loads (e.g. electric vehicle charging stations) pose new challenges for network operators. These changes result in alterations to network load profiles and load flows, leading to greater voltage volatility. One effective solution to these problems can be the use of automatic voltage regulators (AVRs), which stabilize and symmetrize voltage output, whether at distribution transformers (DTs) or elsewhere in the distribution network. The device developed by the authors consists of two bidirectional power converters and three single-phase transformers connected in series to the low-voltage grid as a stabilizer. The proposed control system provides accurate and fast regulation of the AVR’s output voltage (within the range of ±10% of the nominal grid voltage), with each phase being independently adjusted, regardless of the type of power load. The article includes test results demonstrating selected functionalities of the developed AVR. The physical model of the device discussed in the article is a research componentof the LINTE2 laboratory of the Gda´nsk University of Technology
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Experimental tests of steel double-type balcony connections
- Maciej Tomasz Solarczyk
- Paweł Michał Piotrkowski
- Maciej Niedostatkiewicz
The paper presents analysis and results of experimental tests of full scale prefabricated balcony sets with dimensions (width × length × height): 2.0 m × 2.78 m × 0.186 m (in slope to 0.17 m). The sets consists of reinforced concrete slabs (balcony and ceiling) connected with each other by double-type balcony connections. The paper analyses the impact of variable parameters on the load carry capacity of elements. Additionally an overview of current scientific and technical papers in the field of balcony connections is provided.
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Experimentally Aided Operational Virtual Prototyping to Predict Best Clamping Conditions for Face Milling of Large-Size Structures
- Krzysztof Kaliński
- Marek Galewski
- Michał Mazur
- Natalia Stawicka-Morawska
Vibrations occurring during milling operations are one of the main issues disturbing the pursuit of better efficiency of milling operations and product quality. Even in the case of a stable cutting process, vibration reduction is still an important goal. One of the possible solutions to obtain it is selection of the favorable conditions for clamping the workpiece to the machine table. In this paper, a method for predicting and selecting the clamping condition of a large-size workpiece for the reduction in vibrations during milling is presented. A modal test of the workpiece is performed first for a selected set of tightening screw settings. Next, one milling pass is performed to obtain reference data which are then used to tune the hybrid computational model. In the subsequent step, milling simulations are performed for a set of tightening variants, and the best one is selected, providing the lowest vibrations, assessed as the root mean square (RMS) of vibration displacements. In this paper, the description of the clamping selection procedure, key elements of the simulation model, and simulation and experimental results obtained for the milling of the test workpiece performed for a set of different clamping conditions are provided. The proposed method accurately predicts not only the best but also the worst clamping conditions.
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Expermental investigation on adsorption of methylene blue dye from waste water using corncob cellulose-based hydrogel
- Samuel Latebo Majamo
- Temesgen Amibo
- Dereje Tadesse Mekonnen
Hydrogel from corncob cellulose was synthesized in this investigation. The synthesized Hydrogel was characterized by SEM, XRD, and FTIR instruments. As the results indicate the synthesized hydrogel has required and important features, these suggest the suitability of hydrogel for the adsorption of methylene blue dye (MBD). Three important process variables (dosage, contact time, and initial concentration) with three levels were studied during the adsorption process at 30 °C and neutral pH. The efficiency of hydrogel for adsorption of MBD was determined in each experiment. The experimental results were statistically analyzed and interpreted. The maximum removal efficiency was achieved at 2.22 g/L of dosage, 80.36 min of contact time, and 74.54 mg/L of initial concentration. At this condition, 98.25% of MBD was achieved through experimental tests. Kinetics, isotherm, and thermodynamics studies were performed. Langmuir isotherm is more suitable to describe the adsorption process and the Pseudo second-order kinetic model fits this process. From the thermodynamics studies, all negative values of change in Gibbs free energy (ΔG°), and positive value of change in enthalpy (ΔH°), and change in entropy (ΔS°) indicate that the carried out experimental process is a spontaneous and endothermic. Moreover, the regeneration experiment for adsorbent was performed. The treatment of real textile industry waste water was conducted and the removal efficiency of hydrogel was 64.76%. This removal percentage reduction from sythetic aqueous solution is due to involvement of other pollutants in the real waste water. The synthesized hydrogel adsorbent is suitable up to the third cycle without significant loss in removal efficiency.
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Exploring avian exposure to parent polycyclic aromatic hydrocarbons (PAHs): Using the common eider Somateria mollissima in a global context
- Aneta Pacyna-Kuchta
- Juliana Souza-Kasprzyk
- Svend Erik Garbus
- Igor Eulaers
- Christian Sonne
- Dariusz Jakubas
Compared to other organic contaminants, birds are rarely studied for their exposure to polycyclic aromatic hydrocarbons (PAHs), mainly due to their effective metabolization of parent PAHs. However, as some studies suggest, exposure to PAHs may result in adverse health effects including decreased survival, especially following oil spills. In the present study, we analyzed samples from a sea duck, the common eider Somateria mollissima including feathers, preen oil, blood, liver and bile, to evaluate whether non- lethally collected samples could be reliably used for avian biomonitoring strategies. Phenanthrene was the only individual PAH detected across sample types, with the highest concentration found in preen gland and the lowest in blood. Significant differences in concentrations were observed between bile vs preen gland and liver vs preen gland, while for most compounds neither blood nor feathers showed detectable levels of parent PAHs. Therefore, the utility of those sample types for PAH exposure assessment may be limited and should be interpreted with caution, moreover as several physiological factors may affect them. Additionally, we also provide a comparison with the available literature to review current avian PAH exposure assessment and outline future research focused needs.
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Exploring Cause-and-Effect Relationships Between Public Company Press Releases and Their Stock Prices
- Filip Grzonkowski
- Paweł Weichbroth
The aim of the work is to design and implement a method of exploring the cause-and-effect relationships between company announcements and the stock prices on NASDAQ stock exchange, followed by a brief discussion. For this purpose, it was necessary to download the stock quotes of selected companies from the NASDAQ market from public web sources. Additionally, media messages related to selected companies had to be downloaded, and then a news sentiment analysis mechanism had to be prepared. The mechanism of sentiment analysis was prepared based on the supervised machine learning approach. The implemented method was used to analyze the sentiment of a set of stock exchange announcements and it was correlated with changes in the share prices of selected companies. Based on the collected data, the association rules were extracted using the Apriori algorithm. While the obtained results are very promising, however, one should also estimate the rate of return for the interrelated transactions to determine the true and ultimate value of discovered relationships.
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Exploring hydrogen energy systems: A comprehensive review of technologies, applications, prevailing trends, and associated challenges
- Muhammad Kamran
- Marek Turzyński
Exploring hydrogen energy and its associated technologies is a pivotal pathway towards achieving carbon neutrality. This article comprehensively reviews hydrogen production technologies, storage technologies, and end-use applications of hydrogen, based on the input energy source, operating conditions, conversion efficiency, energy density, and unit investment cost. The review also highlights the advantages, disadvantages, and technological readiness of hydrogen production technologies, and storage methods. The selected hydrogen production methods include pyrolysis, gasification, fermentation, biophotolysis, electrolysis, thermolysis, and photolysis, while the selected hydrogen storage technologies are compressed, liquid, cryo-compressed, adsorption, and hydrides. Water electrolysis, highly efficient at 55–80 % and versatile, comes with a higher cost of $4.15–$10.30/kg. In contrast, pyrolysis offers more cost-effective solutions with moderate efficiency (35–50 %) and a reasonable yield (25–65 g/kg), making it suitable for budget-sensitive projects. Compressed, liquid, and cryo-compressed hydrogen offer high efficiency with the added benefit of compact storage due to their high volumetric and gravimetric densities. Metal and chemical hydrides provide excellent safety and efficiency, with metal hydrides also delivering high volumetric density for more compact solutions. Furthermore, the review explores the applications of hydrogen energy in renewable energy systems, support to existing grid, transportation, cogeneration and tri-generation, and metallurgy along with insights from pilot projects. Moreover, the article examines the challenges and opportunities encountered in hydrogen production, storage methods, and end-use applications. Finally, the article conducts a SWOT analysis, pinpointing key aspects crucial for the successful adoption of hydrogen in the future. The conclusions indicate that ongoing efforts in performance enhancement, scaling up, and technical advancements are essential to establish a cost-effective hydrogen economy.
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Exploring Mechanism of Corrosion Inhibition of WE43 and AZ31 Alloys by Aqueous Molybdate in Hank’s Solution by Multisine Impedimetric Monitoring
- Maria Osipenko
- Jakub Karczewski
- Michał Dominów
- Marta Prześniak-Welenc
- Jacek Gurgul
- Irina Kurilo
- Jacek Ryl
- Dmitry Kharitonov
The concept of utilizing multisine dynamic electrochemical impedance spectroscopy to monitor effectiveness of a model molybdate inhibitor for AZ31 and WE43 Mg alloys is proposed. The corrosion kinetics and instantaneous values of inhibition efficiency (IE) of molybdate at concentrations up to 150 mM were examined. The inhibitor provides inhibition in Hank’s solution at concentrations starting from ca. 25 mM, with the IE of about 90%. These data together with results of the surface analysis allowed to propose the mechanism of the corrosion inhibition of AZ31 and WE43 Mg alloys by aqueous molybdate in Hank’s solution.
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Exploring music listening patterns: an online survey
- Barbara Szyca
- Bartosz Wejda
- Marta Muchewicz
- Bożena Kostek
An online survey was carried out to explore how respondents listen to music recordings. It was anticipated that the listener’s preferences would be influenced by various factors, such as age, music genre, the contexts in which they listen, and their favored methods of music consumption. Consequently, the data were collected to analyze these relationships. The survey, structured as a web application, encompassed 23 questions, with seven specifically aimed at defining the respondents and the remainder contributing to the dataset for analysis. The results reveal a prevailing preference for listening to music via streaming platforms. Respondents predominantly engage in passive listening, where music becomes a background presence without commanding their focused attention. Moreover, the data also highlight a noteworthy correlation between preferred music genres and the age of the listeners.
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Exploring Neural Networks for Musical Instrument Identification in Polyphonic Audio
- Maciej Blaszke
- Grazina Korvel
- Bożena Kostek
The purpose of this paper is to introduce neural network-based methods that surpass state-of-the-art (SOTA) models, either by training faster or having simpler architecture, while maintaining comparable effectiveness in musical instrument identification in polyphonic music. Several approaches are presented, including two authors’ proposals, i.e., spiking neural networks (SNN) and a modular deep learning model named FMCNN (Fully Modular Convolutional Neural Network). First, a convolutional neural network (CNN) and convolutional-recurrent neural network (CRNN), adapted from literature, are built to detect up to 13 different instruments in polyphonic music. Furthermore, FMCNN and SNN are explored. The results obtained demonstrate that both FMCNN and SNN outperform traditional CNN and CRNN in terms of accurate instrument identification. Moreover, the SNN architecture is much less complex compared to other model sizes. These findings highlight the efficacy of the methods proposed in musical instrument identification in polyphonic audio.
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Exploring novel Cd(ii) complexes with 5-methyl-4-imidazolecarboxaldehyde: synthesis, structure, computational insights, and affinity to DNA through switchSense methodology
- Mateusz Kowalik
- Paulina Nowicka
- Jakub Brzeski
- Natalia Żukowska
- Joanna Masternak
- Katarzyna Kazimierczuk
- Mariusz Makowski
A series of four Cd(II) complexes with 5-methyl-4-imidazolecarboxaldehyde (L) with different inorganic anions within or outside the coordination sphere of general formula: [CdCl2 L2 ] (1), [CdBr2 L 2] (2), [CdI2L 2] (3), and [CdL4 ](PF6 )2 ·3H2 O (4) was synthesized through one-step and two-step reactions, respectively. All complexes were obtained as colorless crystals without the need for recrystallization and exhibited solubi- lity in aqueous solutions. Structural analysis revealed different coordination environments for each complex, with variations in bond lengths and angles. The crystal packing of the complexes was stabilized by hydrogen bonding and π–π stacking interactions. FT-IR analysis indicated coordination of the ligand to the metal ion, and UV-Vis studies confirmed the stability of the complexes in solution. Computational analysis has revealed the polar nature of the complexes and their favorable stability constants. Affinity studies with DNA using the switchSense technique demonstrated rapid association and dissociation pro- cesses for all complexes, with temperature-dependent binding constants. Thermodynamic analysis suggested spontaneous with positive entropy change and endothermic formation processes for the com- plexes. Overall, the study underscores the synthesis, examination, and interaction with DNA of Cd(II ) com- plexes, demonstrating their promise within medicinal chemistry.
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Exploring Relationships Between Data in Enterprise Information Systems by Analysis of Log Contents
- Łukasz Korzeniowski
- Krzysztof Goczyła
Enterprise systems are inherently complex and maintaining their full, up-to-date overview poses a serious challenge to the enterprise architects’ teams. This problem encourages the search for automated means of discovering knowledge about such systems. An important aspect of this knowledge is understanding the data that are processed by applications and their relationships. In our previous work, we used application logs of an enterprise system to derive knowledge about the interactions taking place between applications. In this paper, we further explore logs to discover correspondence between data processed by different applications. Our contribution is the following: we propose a method for discovering relationships between data using log analysis, we validate our method against a real-life system running at Nordea Bank, we provide detailed insights into a real-life dataset, we analyze the influence of log quality on the results provided by our method, and we provide recommendations for developers on logging practices that can support the log analysis.
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Exploring the Antitumor Efficacy of N-Heterocyclic Nitrilotriacetate Oxidovanadium(IV) Salts on Prostate and Breast Cancer Cells
- Katarzyna Chmur
- Aleksandra Tesmar
- Magdalena Zdrowowicz
- Damian Rosiak
- Jarosław Chojnacki
- Dariusz Wyrzykowski
The crystal structures of two newly synthesized nitrilotriacetate oxidovanadium(IV) salts, namely [QH][VO(nta)(H2O)](H2O)2 (I) and [(acr)H][VO(nta)(H2O)](H2O)2 (II), were determined. Additionally, the cytotoxic effects of four N-heterocyclic nitrilotriacetate oxidovanadium(IV) salts— 1,10-phenanthrolinium, [(phen)H][VO(nta)(H2O)](H2O)0.5 (III), 2,2′-bipyridinium [(bpy)H][VO(nta)(H2O)](H2O) (IV), and two newly synthesized compounds (I) and (II)—were evaluated against prostate cancer (PC3) and breast cancer (MCF-7) cells. All the compounds exhibited strong cytotoxic effects on cancer cells and normal cells (HaCaT human keratinocytes). The structure–activity relationship analysis revealed that the number and arrangement of conjugated aromatic rings in the counterion had an impact on the antitumor effect. The compound (III), the 1,10-phenanthrolinium analogue, exhibited the greatest activity, whereas the acridinium salt (II), with a different arrangement of three conjugated aromatic rings, showed the lowest toxicity. The increased concentrations of the compounds resulted in alterations to the cell cycle distribution with different effects in MCF-7 and PC3 cells. In MCF-7 cells, compounds I and II were observed to block the G2/M phase, while compounds III and IV were found to arrest the cell cycle in the G0/G1 phase. In PC3 cells, all compounds increased the rates of cells in the G0/G1 phase.
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Exploring the Beam Squint Effects on Reflectarray Perfromance: A Comprehensive Analysis of the Specular and Scattered Reflection of the Unit Cell
- Manzoor Elahi
- Amir Altaf
- Sławomir Kozieł
- Anna Pietrenko-Dąbrowska
In this article, the phenomena of beam deviation in reflectarray is discussed. The radiation pattern of the unit cell, which plays a vital role in shaping the beam of the reflectarray, is analyzed by considering undesired specular and scattered reflections. These unwanted reflections adversely affect the pattern of the single unit cell, thereby reducing the overall performance of the reflectarray. To conduct our investigations, three cases of reflectarray, i.e., (i) a center-fed with broadside beam (Case-I), (ii) a center-fed with the beam at 30∘ (Case-II), and (iii) off-center fed with the beam at 30∘ reciprocal to feed position with reference to the broadside direction (Case-III), are simulated. Different degrees of beam deviation are analyzed in each reflectarray by assessing the radiation pattern of a single element. The significance of specular reflections is further confirmed by half (left half and right half) aperture analysis of Case-II. This involves simulating the half-plane aperture illuminated by horn antenna, resulting in a distinct beam angle at the same frequency. Although the analysis specifically focuses on the three cases of the reflectarray, the proposed methodology is applicable to any type of reflectarray. The study presented in this work provides an important insight into the practical aspects of reflectarray operation, particularly in terms of quantifying undesirable effects that are normally overlooked in the design of this class of arrays. Moreover, this work holds significant potential for remote sensing satellite systems as beam deviation can adversely impact data collection accuracy and compromize observation precision, resulting in distorted images, reduced data quality, and overall hindrance to the system’s performance in capturing reliable information.