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  • Miniaturized Solid Phase Extraction techniques for different kind of pollutants analysis: State of the art and future perspectives – PART 1
    • Justyna Płotka-Wasylka
    • Natalia Jatkowska
    • Monika Paszkiewicz
    • Magda Caban
    • Michel Y. Fares
    • Aysegul Dogan
    • Salvador Garrigues
    • Natalia Manousi
    • Natasa Kalogiouri
    • Paweł Mateusz Nowak
    • Victoria F. Samanidou
    • Miguel de la Guardia
    2023 TRAC-TRENDS IN ANALYTICAL CHEMISTRY

    Solid Phase Extraction (SPE) has been practiced in a modern form for more than half a century. It was constantly developing, driven by the analysts needs. These needs are coming from the importance to select an appropriate analytical method, which should have satisfactory accuracy, precision and sensitivity. In the case of sorbent-based microextraction techniques, the choice of miniaturized variants that meet these requirements as well as the requirements of GAC is extremely wide. The increasing popularity of the technique has spurred the influx of many manufacturers into the commercial side of the technology, and many columns, cartridges and discs are comercially available. SPE-type techniques which can be connected with quantification techniques, are perfect to be applied for pollution analysis. The purpose of this article is to provide the reader with an updated, comprehensive overview of modern SPE techniques for different kind of pollutants analysis.

  • Miniaturized solid phase extraction techniques for different kind of pollutants analysis: State of the art and future perspectives – PART 2
    • Justyna Płotka-Wasylka
    • Natalia Jatkowska
    • Monika Paszkiewicz
    • Magda Caban
    • Michel Y. Fares
    • Aysegul Dogan
    • Salvador Garrigues
    • Natalia Manousi
    • Natasa Kalogiouri
    • Paweł Mateusz Nowak
    • Victoria F. Samanidou
    • Miguel De la Guardia
    2023 TRAC-TRENDS IN ANALYTICAL CHEMISTRY

    Determination of pollutants present in environmental samples at a low concentration level very often requires the analytical protocol that includes analytes isolation and/or enrichment prior to the final quantification. Miniaturized SPE offers an interesting alternative to LLE. Nowadays, many types of sorbents are available and can be used as selective materials for extraction of varied analytes in different kinds of samples. The characteristic of sorbent plays a crucial role because determines the resulting extraction mechanism of particular technique. SPE techniques have numerous positive features. This review provides an updated, comprehensive overview of new types of sorbents used in SPE-based techniques. In addition, miniaturized SPE techniques applied to environmental problems are described, based on the most recent, relevant, and representative examples of successful application. The perspective of the most promising directions for the development of the SPE technology in the near future, and the greatest challenges that will have to be faced, are also outlined.

  • Mitigating metal-organic framework (MOF) toxicity for biomedical applications
    • Paulina Wiśniewska
    • Józef Haponiuk
    • Mohammad Saeb
    • Navid Rabiee
    • Sidi A. Bencherif
    2023 Pełny tekst CHEMICAL ENGINEERING JOURNAL

    Metal-organic frameworks (MOFs) are a novel class of crystalline porous materials, consisting of metal ions and organic linkers. These hybrid materials are highly porous and have a large specific surface area, making them of great interest for applications in gas separation, energy storage, biomedical imaging, and drug delivery. As MOFs are being explored for biomedical applications, it is essential to comprehensively assess their toxicity. Although nearly ninety thousand MOFs have been investigated, evaluating and optimizing their physico-chemical properties in relevant biological systems remain critical for their clinical translation. In this review article, we first provide a brief classification of MOFs based on their chemical structures. We then conduct a comprehensive evaluation of in vitro and in vivo studies that assess the biocompatibility of MOFs. Additionally, we discuss various approaches to mitigate the critical factors associated with MOF toxicity. To this end, the effects of chemistry, particle size, morphology, and particle aggregation are examined. To better understand MOFs' potential toxicity to living organisms, we also delve into the toxicity mechanisms of nanoparticles (NPs). Furthermore, we introduce and evaluate strategies such as surface modification to reduce the inherent toxicity of MOFs. Finally, we discuss current challenges, the path to clinical trials, and new research directions.

  • Mobile Networks' Analysis in Terms of QoS Performance Assessment
    • Dariusz Zmysłowski
    • Jan M. Kelner
    • Przemysław Falkowski-Gilski
    2023

    Quality of service (QoS) assessment is one of the basic processes carried out by mobile network operators (MNOs) and regulators of the telecommunications market. Usually, professional companies carry out measurements for various country areas and use cases (scenarios). In this paper, we show exemplary measurement results carried out in drive tests in the vicinity of the Polish capital by a professional company. The measurement campaign included two MNOs and three use cases, i.e., voice calls, video live streaming from YouTube, and web browsing. Various parameters of the received signals and QoS metrics were recorded during the measurements, e.g., reference signal received power, signal-to-interference-plus-noise ratio, mean opinion score (MOS), video MOS, and throughput. One of the MNOs provides services using Universal Mobile Telecommunications Service (UMTS) and Long-Term Evolution (LTE) technologies, while another is based only on LTE technology. The presented results show that higher QoS metrics were obtained for the LTE network than one using UMTS/LTE technologies.

  • Modal Adjustment of Rayleigh Based Structural Damping and Coordinate-Partitioning Algorithm Dedicated to Frictionless Contact Constraints between Multibody System and Structure Modelled with Finite Elements
    • Krzysztof Lipiński
    2023 SSRN Electronic Journal

    The paper presents a dedicated numerical algorithm. The algorithm is advantageous during investigations of the dynamics of a hybrid multibody / finite-elements system. We focus our attention on interactions resulting from mechanical contact. Pointwise contact connects a vertex of the multibody structure and a surface of the elastic reference body. Instead of a positive value of the relative penetration factor, constraint equations model the contact, and Lagrange multipliers model the constraint-associated reactions used in the dynamics equations. In the subsequent steps, the investigated procedure recalls a case-dedicated version of the classic coordinate-portioning algorithm. The dedicated numerical algorithm evaluates the algebraic unknown of the system, i.e., for each set of investigated accelerations, it calculates values of the Lagrange multipliers and values of the selected dependent accelerations resulting from the consistency of the constraint equations. When calculated, the algorithm eliminates them from the remaining equations. Consistently with purely numerical reasons, obtained differential equations are challenging for numerical integration. The paper presents one of the reasons. To solve the misadventure, it proposes an alternative numerically-rational model of the disturbing phenomena. The proposed solution recalls modal adjustment of the damping properties of the elastic subcomponent. We test the efficiency of the paper-proposed methodology with the use of a numerical example. We limit the tests to an example of a purely academic planar structure. Also, we restrict the tested elastic subcomponent to a case of a planar deformable beam. We model it with the use of two-node beam elements. Pin contacts, as well as frictionless pointwise slider-pin contacts, connect the elastic beam and the multibody. The paper presents the case-dedicated constraint equations and their associated Lagrange multipliers. Our initial tests investigate the main consequences of the presence of the uniform Rayleigh model of structural damping. In the subsequent numerical tests, we modify the main parameters of the structural damping. Indicated modification recalls the paper-proposed principles of the abovementioned modal adjustment. Paper-presented figures compare the obtained behaviours with those calculated previously for the Rayleigh model. Even if verified with a purely academic numerical model, the paper-proposed methodology is general.

  • Model studies to identify input parameters of an algorithm controlling electric supply/consumption process by underground iron ore enterprises
    • Oleh Sinchuk
    • Ryszard Strzelecki
    • Tetiana Beridze
    • Ihor Peresunko
    • Vladyslav Baranovskyi
    • Danyil Kobeliatskyi
    • Volodymyr Zapalskyi
    2023 Pełny tekst Mining of Mineral Deposits

    Purpose is the development of the research format of a mathematical model to select and assess input parameters of an algorithm controlling distribution of electric energy flows in the monitoring structure of electricity supply/ consumption by using equipment of mining enterprises engaged in underground iron ore raw materials extraction. Methods. The analytical research involved a theory of random processes adapted to the real conditions. For the purpose, results of experimental measurements have been applied obtained under the conditions of active iron ore enterprises using underground procedures of the raw materials mining. Methods of random functions (i.e. elements of correlation theory) have helped identify the basic input and output parameters characterizing rather completely electric supply consumption as a stochastic process to develop a control algorithm for the process. Originality. The procedure of electric supply/consumption by underground iron ore enterprises has been analyzed in the format of process of a stochastic process of their operation. For the first time, the synthesized mathematical model has been built; both average and disperse stochastic characteristics of electric consumption capacity have been identified; average period of electric energy consumption as a stationary random function during the specified time has been determined; and average number of electric consumption peaks for the interval has been defined as well as average duration of their surges. Analysis of the electric supply/consumption process as a stochastic process has helped solve a problem of the peak influence on the modes of electric energy consumption by receivers of the enterprises. Practical implications. According to the available computing formats, a calculation procedure of the operation parameters of electric supply/consumption is of insufficient accuracy since average values are applied and stochastic nature of the process is ignored, which is typical for the analyzed mining enterprises. The abovementioned restricts the possibility to develop adequate system to control the electric power process in terms of the types of mining enterprises and specificity of their operational technology. The developed methods of electric supply/consumption functioning dynamics as a stochastic process help expand its use while forming and making efficient managerial decisions in the context of the analyzed process.

  • Model zarządzania projektami informatycznymi w jednostkach sądownictwa powszechnego w Polsce
    • Monika Kuźmicz
    2023 Pełny tekst

    Projekty mają istotny wpływ na funkcjonowanie sądów powszechnych. Przyjrzenie się projektom informatycznym realizowanym w sądach wraz z raportem Najwyższej Izby Kontroli dot. sprawności realizowanych projektów informatycznych wymiaru sprawiedliwości doprowadziło do zidentyfikowania głównych problemów podczas realizacji inicjatyw informatycznych. Ponadto przegląd literatury dotyczący zarządzania projektami dla wymiaru sprawiedliwości doprowadził do wskazania luki w tym obszarze. Złożoność i specyfika organizacji publicznych, w szczególności sądów jako ich podzbioru, utrudnia możliwość wykorzystania dostępnych metodyk czy narzędzi wspierających zarządzanie projektami. To doprowadziło do sformułowania procesu badawczego rozprawy, w tym m.in. głównego celu pracy, tj. dostarczenia modelu zarządzania projektami informatycznymi w sądownictwie powszechnym obejmującego przypadki i dobre praktyki, uwzględniającego specyfikę sądów, który w konsekwencji pozwoli na usprawnienie realizacji projektów informatycznych w sądownictwie powszechnym. Do budowy tego modelu wybraną metodę wnioskowania w oparciu o przypadku CBR (ang. Case-Based Reasoning), która zakłada wykorzystywanie doświadczeń dla nowych problemów. W odniesieniu do modelu, CBR pozwala na wykorzystanie dobrych praktyk i przypadków obejmujących procesy, role i artefakty dla nowych projektów. Co więcej metoda ta pozwala na uczenie się i ciągłą rozbudowę modelu, co w przypadku organizacji wrażliwych na ciągłe zmiany otoczenia (np. regulacji prawnych) jakim są sądy jest szczególnie istotne.

  • Modele i algorytmy dla grafowych struktur defensywnych
    • Robert Lewoń
    2023 Pełny tekst

    W niniejszej pracy przeprowadzono analizę złożoności istnienia struktur defensywnych oraz równowag strategicznych w grafach. W przypadku struktur defensywnych badano modele koalicji defensywnych, zbiorów defensywnych i koalicji krawędziowych – każdy z nich w wersji globalnej, tj. z wymogiem dominacji całego grafu. W przypadku modeli równowagi strategicznej badano równowagę strategiczną koalicji defensywnych, równowagę strategiczną zbiorów defensywnych i równowagę strategiczną koalicji krawędziowych. Przedstawiono wielomianowe algorytmy konstruujące najmniejsze struktury defensywne oraz weryfikujące ich istnienie i konstruujące równowagi strategiczne w przypadku drzew. Dodatkowo zweryfikowano trudność obliczeniową badanych problemów poprzez wykazanie ich NP–zupełności dla możliwie wąskich klas grafów. W ten sposób określono zakres stosowalności modeli w przypadku dużych grafów, a dalsze badania skierowano w kierunku podejść aproksymacyjnych, które poszerzą zakres zastosowań dyskutowanych modeli w praktyce. Przebadano również własności teoretyczne modeli, takie jak oszacowania rozmiaru badanych struktur i związki między nimi. Zaproponowano także ogólną koncepcję stanowiącą wspólny trzon dla dyskutowanych modeli, otwierając tym samym kierunki badań w obrębie tego zagadnienia.

  • Modeling and optimization of chemical-treated torrefaction of wheat straw to improve energy density by response surface methodology
    • Samuel Latebo Majamo
    • Temesgen Amibo
    2023 Pełny tekst Biomass Conversion and Biorefinery

    Today, torrefaction is important technique for extending the potential of biomass for improvement of energy density. The independent variables investigated for torrefaction study were temperature, retention time, acid concentration, and particle size. The experiment was designed by central composite design (CCD) method using design expert (version 11). The three dependent variables were higher heating value (HHV), energy enhancement factor (EEF), and mass yield (MY) were carried out. Numerical optimization using response surface method (RSM) to maximize the HHV and EEF with lowest MY was carried out. The maximum HHV of 25.05MJ/kg, lowest MY of 60.15%wt and highest EEF of 1.593 were obtained at 299.99°C, 31.89min of retention time, 0.75g/l of acid concentration and 0.20mm of particle size. Proximate analysis, bulk density, hydrophobicity, energy density, and ultimate analysis of raw and torrefed biomass were determined to analyze the physiochemical properties of the fuel. In addition, thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and X-ray difractometer (XRD) were done to distinguish the behavior of raw and torrefed wheat straw. The results implied that energy density of torrefed biomass was well improved when compared with raw biomass. All in all, energy density of torrefed biomass was improved, which can be used as an alternative energy.

  • Modeling and simulation of blood flow under the influence of radioactive materials having slip with MHD and nonlinear mixed convection
    • Sidra Afzal
    • Mubashir Qayyum
    • Muhammad Riaz
    • Adam Wojciechowski
    2023 Pełny tekst Alexandria Engineering Journal

    Radioactive materials are widely in industry, nuclear plants and medical treatments. Scientists and workers in these fields are mostly exposed to such materials, and adverse effects on blood and temperature profiles are observed. In this regard, objective of the current study is to model and simulate blood based nanofluid with three very important radioactive materials, named as Uranium dioxide (UO2), Thorium dioxide (ThO2) and Radium (Rd). In this modeling blood based nanofluid is considered under the influence of magneto hydrodynamic effect, non-linear mixed convection and thermal radiation, Joule heating, along with velocity and temperature slip. A three-dimensional fluid model is considered in bounded domain to justify flow geometry in arteries. System of partial differential equations are converted to highly nonlinear coupled ordinary differential equations by using suitable transformations. The obtained system is solved numerically using Fehlberg Runge–Kutta algorithm. Validity and convergence of the obtained solutions are confirmed through residual errors, numerical uncertainties and comparison with experimental data. Moreover, effect of pertinent fluid parameters on the velocity (radial, axial, tangential) and temperature profiles of blood flow are analyzed graphically. Furthermore, Skin friction and Nusselt number are also analyzed graphically against volume fraction of involved radioactive materials for the case of UO2;ThO2 and Rd comparatively. Analysis reveals that increase in volume fraction of radioactive elements results in increased blood flow through walls in both radial and tangential directions. In case of slip at fluid solid-interface, the highest skin fraction is observed in case of Radium nanoparticles.

  • Modeling of entrained flow steam gasification of sewage sludge
    • Jakub Mularski
    • Kamil Stasiak
    • Michał Ostrycharczyk
    • Michał Czerep
    • Mateusz Wnukowski
    • Krystian Krochmalny
    • Marcin Baranowski
    • Paweł Ziółkowski
    • Mateusz Kowal
    • Łukasz Niedźwiecki
    • Halina Pawlak-kruczek
    • Dariusz Mikielewicz
    2023 Pełny tekst

    Proper management of sewage sludge becomes increasingly problematic due to legal requirements aiming at diminishing environmental impact, as well as rationalizing the utilization from the point of view of logistics. Steam gasification of sewage sludge can result in very good quality of the producer gas. So far, the works have been focused on the gasification in fixed bed gasifiers. However, this does not allow to take full advantage of the effect of scale, as the scalability of fixed ed gasifiers is limited. Entrained flow gasifiers are scalable up to the order of magnitude of hundreds of megawatts, which was proven for the gasification of coal. Therefore, it seems plausible to suspect that such scalability would allow building gasifiers big enough, to work as a part of bioenergy with carbon capture and storage plants, operating in an economically feasible manner, fully utilizing the effect of scale. However, the optimized design of such units would require robust modeling. This work focuses on different models for sewage sludge steam gasification, allowing accurate predictions of the producer’s gas quality. The core part of this work is a comparison between the results obtained using advanced CFD models in Fluent, as well as two different equilibrium models. Results from all the models are experimentally validated, by entrained flow steam gasification in a 3 m long reactor, with an addition of CO2.

  • Modeling of low calorific gas burning in a deficient oxygen environment and high-temperature oxidizer
    • Jan Stąsiek
    • Marcin Jewartowski
    • Jacek Barański
    • Jan Wajs
    2023 Pełny tekst INTERNATIONAL JOURNAL OF PHYSICS RESEARCH AND APPLICATIONS

    The experimental research will be performed using the experimental facility with a combustion chamber. The oxygen concentration in combustion oxidizers will be varied from 21% by volume (normal) air to 2%. The test combustion chamber will be fed with propane or methane as the reference fuel, then with low calorific fuels as test gases obtained by mixing various combustible components, e.g. H2, CH4, CO, and neutral gases, e.g. N2, CO2. Gaseous fuels prepared in this way will be burned in the atmosphere of a deficient oxidizer with a temperature changing from 800 °C to 1100 °C. Oxidizers will be heated up to a certain temperature using two methods: by flue gas heat exchanger and kanthal rod electric preheater. Different burner geometry will be used. The burner will be equipped with annular swirl vanes for co-axial or under different angles, fuel, and oxidizers flow to have a high swirl number achieved by flow aerodynamics and mixing. Experimental data will be verified with numerical simulations with the use of ANSYS CFD Fluent code.

  • Modeling of Surface Roughness in Honing Processes by UsingFuzzy Artificial Neural Networks
    • Irene Buj - Corral
    • Piotr Sender
    • Carmelo J. Luis-Pérez Luis-Pérez
    2023 Pełny tekst Journal of Manufacturing and Materials Processing

    Honing processes are abrasive machining processes which are commonly employed to improve the surface of manufactured parts such as hydraulic or combustion engine cylinders. These processes can be employed to obtain a cross-hatched pattern on the internal surfaces of cylinders. In this present study, fuzzy artificial neural networks are employed for modeling surface roughness parameters obtained in finishing honing operations. As a general trend, main factors influencing roughness parameters are grain size and pressure. Mean spacing between profile peaks at the mean line parameter, on the contrary, depends mainly on tangential and linear velocity. Grain Size of 30 and pressure of 600 N/cm 2 lead to the highest values of core roughness (Rk) and reduced valley depth (Rvk), which were 1.741 µm and 0.884 µm, respectively. On the other hand, the maximum peak-to-valley roughness parameter (Rz) so obtained was 4.44 µm, which is close to the maximum value of 4.47 µm. On the other hand, values of the grain size equal to 14 and density equal to 20, along with pressure 600 N/cm 2 and both tangential and linear speed of 20 m/min and 40 m/min, respectively, lead to the minimum values of core roughness, reduced peak height (Rpk), reduced valley depth and maximum peak-to-valley height of the profile within a sampling length, which were, respectively, 0.141 µm, 0.065 µm, 0.142 µm, and 0.584 µm.

  • Modeling the application of steel slag in stabilizing expansive soil
    • Worku Firomsa Kabeta
    • Hinsene Lemma
    2023 Pełny tekst Modeling Earth Systems and Environment

    The objective of this study was to evaluate the suitability of steel slag as an additive to the engineering properties of weak clay soil. Different geotechnical laboratory tests were conducted on both stabilized and natural soils. Steel slag (SS) was added at a rate of 0, 5, 10, 15, 20, and 25% to the soil. Specific gravity, grain size analysis, Atterberg limit test, compaction test, free swell, California bearing ratio (CBR), and unconfined compression strength (UCS) are among the tests that were performed. The Atterberg limit test result shows that the liquid limit decreases from 90.8 to 65.2%, the plastic limit decreases from 60.3 to 42.5%, and the plasticity index decreases from 30.5 to 22.7% as the steel slag of 25% was added to the expansive soil. With 25% steel slag content, the specific gravity increases from 2.67 to 3.05. The free swell value decreased from 104.6 to 58.2%. In the Standard Proctor compaction test, the maximum dry density rises from 1.504 to 1.692 g/cm3, while optimum moisture content falls from 19.77 to 12.09%. From the UCS test, mixing 25% steel slag into the soil increases the unconfined compressive strength from 64.3 to 170.6 kPa. Additionally, the CBR value increases from 3.64 to 6.82% as 25% of steel slag is mixed with the soil. As a result, steel slag has been found to improve expansive soil properties for geotechnical applications.

  • Modeling the debonding process of osseointegrated implants due to coupled adhesion and friction
    • Katharina Immel
    • Vu-Hieu Nguyen
    • Guillaume Haiat
    • Roger Sauer
    2023 Pełny tekst Biomechanics and Modeling in Mechanobiology

    Cementless implants have become widely used for total hip replacement surgery. The long-term stability of these implants is achieved by bone growing around and into the rough surface of the implant, a process called osseointegration. However, debonding of the bone–implant interface can still occur due to aseptic implant loosening and insufficient osseointegration, which may have dramatic consequences. The aim of this work is to describe a new 3D finite element frictional contact formulation for the debonding of partially osseointegrated implants. The contact model is based on a modified Coulomb friction law by Immel et al. (2020), that takes into account the tangential debonding of the bone-implant interface. This model is extended in the direction normal to the bone-implant interface by considering a cohesive zone model, to account for adhesion phenomena in the normal direction and for adhesive friction of partially bonded interfaces. The model is applied to simulate the debonding of an acetabular cup implant. The influence of partial osseointegration and adhesive effects on the long-term stability of the implant is assessed. The influence of different patient- and implant-specific parameters such as the friction coefficient mu_b , the trabecular Young’s modulus E_b , and the interference fit IF is also analyzed, in order to determinethe optimal stability for different configurations. Furthermore, this work provides guidelines for future experimental and computational studies that are necessary for further parameter calibration.

  • Modeling the effect of electric vehicles on noise levels in the vicinity of rural road sections
    • Maciej Hałucha
    • Janusz Bohatkiewicz
    • Piotr Mioduszewski
    2023 Pełny tekst Archives of Civil Engineering

    Numerous European countries experience a steady increase in the share of electric (EV) and hybrid electric (HEV) vehicles in the traffic stream. These vehicles, often referred to as low- or zero-emission vehicles, significantly reduce air pollution in the road environment. They also have a positive effect on noise levels in city centers and in the surroundings of low-speed roads. Nevertheless, issues related to modeling noise from electric and hybrid vehicles in the outdoor environment are still not fully explored, especially in the rural road settings. The article attempts to assess the degree of noise reduction around these roads based on different percentages of EVs in the traffic stream. Input data for noise modeling was obtained from 133 sections of homogeneous rural roads in Poland. Based on their analysis, it was first determined on how many of these road sections electric-vehicle-induced noise reduction would be possible, taking into account the traffic speeds occurring on them. Next, a computational algorithm that can be used to calculate noise reduction in the CNOSSOS-EU model is presented, and noise modeling is performed based on it for different percentages of electric vehicles in the traffic stream.

  • Modelling and optimisation of MXene-derived TiO2/Ti3C2 synthesis parameters using Response Surface Methodology based on the Box–Behnken factorial design. Enhanced carbamazepine degradation by the Cu-modified TiO2/Ti3C2 photocatalyst
    • Anna Grzegórska
    • Jakub Karczewski
    • Anna Zielińska-Jurek
    2023 Pełny tekst PROCESS SAFETY AND ENVIRONMENTAL PROTECTION

    In the present study, a hydrothermal method in a water/ethanol environment was used for the first time to obtain novel Cu/TiO2/Ti3C2 composites with high photocatalytic activity for the degradation of carbamazepine (CBZ) under simulated solar light. The Box–Behnken factorial design was coupled with Response Surface Methodology (RSM) for synthesis parameter optimisation. The effect of different synthesis parameters, including temperature, time and water/ethanol ratio, was for the first time studied in detail. The analysis of variance (ANOVA) was used to verify the adequacy of the proposed model. The water/ethanol ratio was the most influential parameter for anatase crystallite growth and the efficiency of carbamazepine degradation. The TiO2/Ti3C2 sample prepared under the optimised conditions (synthesis time of 17 h, temperature of 220 ◦C, and water/ethanol ratio of 58:42 v/v) revealed almost 100% of CBZ degradation within 60 min. Furthermore, the surface modification of this sample with 0.25% - 1 wt% of copper resulted in improved photocatalytic activity. For TiO2/Ti3C2 modified with 0.5% of Cu, almost complete CBZ degradation was observed in 40 min of the photodegradation process. Finally, the combination of the photodegradation process with the activation of peroxymonosulphate (PMS) by Cu-TiO2/ Ti3C2 resulted in markedly improved carbamazepine degradation and reached 100% within 20 min under simulated solar light irradiation. The degradation mechanism of CBZ was proposed based on trapping experiments, which revealed that •O2 and •SO4 are the main oxidising species involved in carbamazepine degradation. Moreover, the hybrid system exhibited high recyclability and stability during subsequent photodegradation cycles.

  • Modelling hydraulic and capillary-driven two-phase fluid flow in unsaturated concretes at the meso-scale with a unique coupled DEM-CFD technique
    • Marek Krzaczek
    • Michał Nitka
    • Andrzej Tejchman-Konarzewski
    2023 INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS

    The goal of the research was to demonstrate the impact of thin porous interfacial transition zones (ITZs) between aggregates and cement matrix on fluid flow in unsaturated concrete caused by hydraulic/capillary pressure. To demonstrate this impact, a novel coupled approach to simulate the two-phase (water and moist air) flow of hydraulically and capillary-driven fluid in unsaturated concrete was developed. By merging the discrete element method (DEM) with computational fluid dynamics (CFD) under isothermal settings, the process was numerically studied at the meso-scale in two-dimensional conditions. A flow network was used to describe fluid behaviour in a continuous domain between particles. Small concrete specimens of a simplified particle mesostructure were subjected to fully coupled hydro-mechanical simulation tests. A simple uniaxial compression test was used to calibrate the pure DEM represented by bonded spheres, while a permeability and sorptivity test for an assembly of spheres was used to calibrate the pure CFD. For simplified specimens of the pure cement matrix, cement matrix with aggregate, and cement matrix with aggregate and ITZ of a given thickness, DEM/CFD simulations were performed sequentially. The numerical results of permeability and sorptivity were directly compared to the data found in the literature. A satisfactory agreement was achieved. Porous ITZs in concrete were found to reduce sorption by slowing the capillary-driven fluid flow, and to speed the full saturation of pores when sufficiently high hydraulic water pressures were dominant.

  • Modelling of Capillary Pressure-driven Water Flow in Unsaturated Concrete Using Coupled DEM/CFD Approach.
    • Marek Krzaczek
    • Michał Nitka
    • Andrzej Tejchman-Konarzewski
    2023

    Sformułowano nowatorskie, połączone podejście do modelowania dwufazowego przepływu wody napędzanego kapilarami w nienasyconym betonie. Dzięki połączeniu metody elementów dyskretnych (DEM) z obliczeniową dynamiką płynów (CFD) w warunkach izotermicznych proces został zbadany numerycznie w mezoskali w warunkach dwuwymiarowych. Niewielkie próbki betonu o uproszczonej mezostrukturze cząstek poddano w pełni sprzężonym hydromechanicznym testom symulacyjnym w warunkach izotermicznych. Do kalibracji czystego DEM reprezentowanego przez związane kulki zastosowano prosty jednoosiowy test ściskania, podczas gdy do kalibracji czystego CFD zastosowano testy przepuszczalności i sorpcji dla zespołu połączonych kulek. Dla uproszczonych próbek czystej zaprawy, zaprawy z kruszywem i zaprawy z kruszywem i przejściową strefą międzyfazową (ITZ) o pewnej szerokości wykonano sekwencyjnie symulacje DEM/CFD. Liczbowe wyniki przepuszczalności i sorpcyjności porównano z danymi literaturowymi. Podstawowym celem badań było wykazanie wpływu ITZ na przepływ płynu w betonie nienasyconym pod wpływem ciśnienia kapilarnego.

  • Modelling of Hydraulic Fracturing in Rocks in Non-isothermal Conditions Using Coupled DEM/CFD Approach with Two-Phase Fluid Flow Model
    • Marek Krzaczek
    • Michał Nitka
    • Andrzej Tejchman-Konarzewski
    2023

    Skała łupkowa jest materiałem silnie niejednorodnym, nieciągłym i porowatym. W warunkach nieizotermicznych ruch płynu w układzie porów i kapilar jest silnie sprzężony z przenoszeniem ciepła. Przebieg szczeliny hydraulicznej silnie zależy od stopnia nasycenia skały. Opracowano innowacyjny model termo-hydro-mechaniczny oparty na modelu DEM w celu szczegółowego śledzenia frakcji ciecz/gaz w porach i pęknięciach pod kątem ich różnej geometrii, rozmiaru, położenia i temperatury. Wygenerowano gruboziarnistą siatkę 2D, aby utworzyć sieć przepływu płynów i rozwiązać równanie zachowania energii. Wreszcie, znaczenie w pełni sprzężonego modelu termo-hydro-mechanicznego ilustruje symulacja wtryskiwania zimnego płynu podczas szczelinowania hydraulicznego w macierzy skalnej o różnym stopniu nasycenia wodą.