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Gdańsk University of Technology

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Publications from the year 2024

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  • Fabrication of the cross-linked PVA/TiO2/C nanocomposite membrane for alkaline direct methanol fuel cells
    • Faiz Khalid
    • Aashis S. Roy
    • Ameena Parveen
    • Roberto Castro Munoz
    2024 MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY (Materials Science and Engineering B-Advanced Functional Solid-State Materials)

    A crosslinked Poly(vinyl alcohol) based composite membrane was developed through a phase inversion process for use in alkaline direct methanol fuel cells (ADMFCs). The titanium dioxide (TiO2) and carbon nanoparticles (NPs) have been incorporated into the PVA polymer matrix to improve the mechanical and thermal properties. The membrane samples were further modified with maleic acid, a carboxylic acid acting as the cross-linker, under controlled temperature and time conditions to enhance electrochemical properties. The mechanical strength and thermal stability of membranes were determined using a Universal testing machine (UTM) and thermogravimetric analysis (TGA), while the crystallographic and morphological features were examined through X-ray diffraction (XRD) and Scanning electron microscopy (SEM), respectively. The proton conductivity (σ), methanol permeability, and water uptake (%) were also assessed. The XRD curves, SEM images, and TGA trends confirmed the successful cross-linking of maleic acid, uniform dispersion of nanoparticles (NPs), and excellent thermal stability in the crosslinked PVA-TiO2-C membrane. This sample also exhibited the highest tensile strength (163 MPa), and lower permeability (45000 Ss/cm3). Moreover, the ionic conductivity was obtained in the order of 10−2 S/cm. These combined characteristics position the cross-linked PVA-TiO2-C membrane as a promising candidate for application in alkaline direct methanol fuel cells (ADMFCs).

  • Facile synthesis and characterization of graphene and N-doped graphene by CVD method from liquid precursors for promising electrode materials
    • Mohammad Taghi Tourchi Moghadam
    • Karolina Cysewska
    2024 MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY (Materials Science and Engineering B-Advanced Functional Solid-State Materials)

    In this study, high-quality and few-layered graphene was synthesized using the chemical vapor deposition (CVD) method from liquid sources. Two different liquid carbon sources, pyridine, and benzene, were used and deposited on nickel foam under heat conditions using a bubbler in a quartz tube. X-ray diffraction (XRD) and Raman analysis confirmed the crystalline properties of graphene and N-doped graphene, demonstrating the high quality and few layers of graphene produced through the synthesis procedure. Energy dispersive X-ray (EDX) confirmed N doping while scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) provided clear sample morphology. The study reports the feasibility of utilizing liquid precursors to produce large-area, continuous, and mostly few-layer graphene, and N-doped graphene, making it a promising candidate for use as an electrode for different applications.

  • Facilitated water transport in composite reduced graphene oxide pervaporation membranes for ethanol upgrading
    • Maksymilian Plata Gryl
    • Grzegorz Boczkaj
    • Alfonso Policicchio
    • Alberto Figoli
    • Francesco Galiano
    • Roberto Castro Munoz
    2024 SEPARATION AND PURIFICATION TECHNOLOGY

    High purity ethanol is one of the most sought-after renewable energy sources. However, standard production methods yield ethanol of insufficient quality. Membrane processes such as pervaporation are recognized as a viable method for upgrading ethanol. Their performance and selectivity depend solely on membrane employed. Hydrophilic polyvinyl alcohol (PVA) membranes are used industrially for this purpose, but there is a trade-off between selectivity and permeability. Among other materials, chemically converted graphene attracts particular attention due to its exceptional water transport properties, however its application is limited by the fabrication of free-standing membranes. In this study, a composite reduced PVA/graphene oxide (rGO) membranes with different rGO content (up to 49 wt%) was synthesized. Polyvinyl alcohol acted as a mediator to improve the mechanical stability of membrane layers by crosslinking rGO flakes with hydrogen bonds. The resulting membranes were fully characterized by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, water contact angle and mechanical tests. Pervaporation tests with water/ethanol mixtures (10/90 wt%) at temperatures between 20 and 50 °C demonstrated an excellent selectivity (over 12 000) of membranes and satisfactory flux, even at high temperatures. The total permeate flux for membranes varied slightly as a function of operating temperature, demonstrating a good thermostability of the reduced graphene oxide-based membranes. The pervaporation separation index (PSI) of synthesized membrane exceed 5000 and surpassed majority of rGO containing membranes reported in the literature. Results indicate that rGO membranes noncovalently strengthened with PVA are a promising material for selective ethanol dehydration via pervaporation.

  • Factors Associated with Preoperative Anxiety in Patients Undergoing Ambulatory Hand Surgery: A Cross-Sectional Observational Study
    • Justyna Napora
    • Krystian Gryglewski
    • Miłosz Piotrowicz
    • Piotr Lebiedź
    • Tomasz Mazurek
    • Katarzyna Nowicka-Sauer
    2024 Journal of Clinical Medicine

    Background: Studies examining preoperative anxiety in patients awaiting hand surgery are scarce. Preoperative anxiety is a common reaction and can have a negative impact on treatment outcomes. The aim of this study was to assess the level of anxiety in patients undergoing hand surgery as a one-day procedure and to investigate the associations between patients’ preoperative anxiety and selected sociodemographic, psychological, and clinical variables. Methods: We examined 121 patients (77.7% women) who were operated on in an ambulatory setting. The mean age was 52.6 years (range: 24–84 years). Preoperative anxiety was assessed according to the Amsterdam Preoperative Anxiety and Information Scale (APAIS). The Visual Analogue Scale was used to assess irritability, depression, and pain. Results: Univariate analyses showed significant correlations between patients’ preoperative anxiety and increased age, surgery within a year since diagnosis, the presence of rehabilitation in their medical history, higher irritability, and living in rural areas. Multivariate analyses showed significant associations between patients’ anxiety level and diagnosis of up to a year, a history of rehabilitation and the level of irritability. Conclusions: Patients undergoing hand surgery in an ambulatory surgery setting experience some preoperative anxiety. Younger patients, those with a shorter duration of disease, with a history of rehabilitation, those presenting intense irritability, and those living in rural areas may demand special attention.

  • Factors hindering and boosting SDG7 implementation in EU countries
    • Marta Kuc-Czarnecka
    • Iwona Markowicz
    • Agnieszka Sompolska-Rzechuła
    • Alina Stundziene
    2024 Technological and Economic Development of Economy

    One of the sustainable development goals (SDG7) is to ensure access to clean and affordable energy, which is related to most other SDGs and plays a crucial role in eco - nomic development and human well-being. The aim of the article is to identify factors that enhance and delay one of the most crucial goals of sustainable development, SDG7. The study’s originality lies in the spatiotemporal approach to analysing the impact of selected factors on the development of green energy and increasing its availability. Three groups of potential SDG7 determining factors have been identified: ecological, social and eco - nomic. The proposed approach and the use of sensitivity analysis to variables weighting and ranking constructions of EU countries is an innovative aspect of the work and fills the gap in research on SDG7. The study showed that Denmark and Sweden occupy leading positions in the rankings based on the extent of SDG7 implementation. In contrast, Bul- garia, Cyprus and Lithuania occupied one of the last positions. The results of panel-data model estimations showed that in each estimated model, the same “indispensable vari- ables” significantly affect the implementation of SDG7. Among these variables, only the unemployment rate significantly negatively impacted the SDG7 execution.

  • Fast EM-Driven Nature-Inspired Optimization of Antenna Input Characteristics Using Response Features and Variable-Resolution Simulation Models
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2024 Full text Scientific Reports

    Utilization of optimization technique is a must in the design of contemporary antenna systems. Often, global search methods are necessary, which are associated with high computational costs when conducted at the level of full-wave electromagnetic (EM) models. In this study, we introduce an innovative method for globally optimizing reflection responses of multi-band antennas. Our approach uses surrogates constructed based on response features, smoothing the objective function landscape processed by the algorithm. We begin with initial parameter space screening and surrogate model construction using coarse-discretization EM analysis. Subsequently, the surrogate evolves iteratively into a co-kriging model, refining itself using accumulated high-fidelity EM simulation results, with the infill criterion focusing on minimizing the predicted objective function. Employing a particle swarm optimizer (PSO) as the underlying search routine, extensive verification case studies showcase the efficiency and superiority of our procedure over benchmarks. The average optimization cost translates to just around ninety high-fidelity EM antenna analyses, showcasing excellent solution repeatability. Leveraging variable-resolution simulations achieves up to a seventy percent speedup compared to the single-fidelity algorithm.

  • Fast Machine-Learning-Enabled Size Reduction of Microwave Components Using Response Features
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    2024 Full text Scientific Reports

    Achieving compact size has emerged as a key consideration in modern microwave design. While structural miniaturization can be accomplished through judicious circuit architecture selection, precise parameter tuning is equally vital to minimize physical dimensions while meeting stringent performance requirements for electrical characteristics. Due to the intricate nature of compact structures, global optimization is recommended, yet hindered by the excessive expenses associated with system evaluation, typically conducted through electromagnetic (EM) simulation. This challenge is further compounded by the fact that size reduction is a constrained problem entailing expensive constraints. This paper introduces an innovative method for cost-effective explicit miniaturization of microwave components on a global scale. Our approach leverages response feature technology, formulating the optimization problem based on a set of characteristic points derived from EM-analyzed responses, combined with an implicit constraint handling approach. Both elements facilitate handling size reduction by transforming it into an unconstrained problem and regularizing the objective function. The core search engine employs a machine-learning framework with kriging-based surrogates refined using the predicted improvement in the objective function as the infill criterion. Our algorithm is demonstrated using two miniaturized couplers and is shown superior over several benchmark routines, encompassing both conventional (gradient-based) and population-based procedures, alongside a machine learning technique. The primary strengths of the proposed framework lie in its reliability, computational efficiency (with a typical optimization cost ranging from 100 to 150 EM circuit analyses), and straightforward setup.

  • Fast Re-Design of Multi-Band Antennas by Means of Orthogonal-Direction Geometry Scaling and Local Parameter Tuning
    • Anna Pietrenko-Dąbrowska
    • Sławomir Kozieł
    2024 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION

    Application-driven design of antenna systems fosters a reuse of structures that have proven competitive in terms of their electrical and field performance, yet have to be re-designed for a new application area. In practice, it most often entails relocation of the operating frequencies or bandwidths, which is an intricate endeavor, normally requiring utilization of numerical optimization techniques. If the center frequencies of the available design reside away from the targets, local routines tend to be inadequate, whereas global procedures incur extraordinary computational costs, which may be unmanageable if antenna characteristics are evaluated using full-wave electromagnetic (EM) analysis. Recently, a procedure involving a combination of joint parameter scaling and intermittent local tuning has been proposed and shown effective in re-design of single-band microwave devices across broad ranges of operational frequencies. Here, we introduce a generalized framework that capitalizes on the aforementioned concept but enables independent scaling of multiple operating frequencies. The fundamental component of the developed approach is identification of orthogonal scaling directions affecting individual center frequencies, which is a non-trivial extension of concurrent parameter adjustment. Our technique has been validated using several multi-band antennas, all re-designed for operating conditions unreachable using conventional tuning methods. Superior performance has been demonstrated for all considered cases in terms of a precise allocation of antenna resonances while maintaining low computational cost, lower than 180 EM antenna analyses on the average. Experimental validation has been also provided.

  • Fatigue behaviour of SLM maraging steel under variable-amplitude loading
    • Zbigniew Marciniak
    • Ricardo Branco
    • Wojciech Macek
    • Cândida Malça
    2024 Full text Procedia Structural Integrity

    One of the most challenging issues for additive manufactured materials is fatigue endurance. Engineering components often operate under complex, variable amplitude loadings, in which existing technological imperfections promote fatigue cracks growth and damage of elements eventually. In this study the effects of different variable-amplitude strain levels on fatigue life, 18Ni300 steel was tested. The work presents various behaviours of the material depending on the load level.

  • Fault detection in the marine engine using a support vector data description method
    • Klaudia Wrzask
    • Jerzy Kowalski
    • Van Vang Le
    • Van Bac Nguyen
    • Dao Nam Cao
    2024 Journal of Marine Engineering and Technology

    Fast detection and correct diagnosis of any engine condition changes are essential elements of safety andenvironmental protection. Many diagnostic algorithms significantly improve the detection of malfunctions.Studies on diagnostic methods are rarely reported and even less implemented in the marine engine industry.To fill this gap, this paper presents the Support Vector Data Description (SVDD) method as applied to thefault detection of the fuel delivery system of a two-stroke marine engine. The selected diagnostic data is theexhaust gas composition, with four components considered: oxygen, carbon oxide, nitric oxide, and carbondioxide. With these diagnostics, the method distinguishes eight different engine faults from the efficient state.The manuscript presents in detail the methodology for applying the SVDD method in a marine engine. Themethod of obtaining diagnostic data and its scaling is described. The method of training and validating thealgorithm is also presented, along with ready-made algorithms for use. The 100% accuracy of the proposedfault detection method. Based on the obtained results, the proposed fault detection method is promising fora simple application. Moreover, generalised algorithms that may be adapted to different technical solutionsare also presented.

  • Feasibility Study of Three-Phase Modular Converter for Dual-Purpose Application in DC and AC Microgrids
    • Carlos Roncero-Clemente
    • Oleksandr Husev
    • Oleksandr Matiushkin
    • Javier Gutiérrez-Escalona
    • Fermin Barrero-Gonzalez
    • Dmitri Vinnikov
    • Ryszard Strzelecki
    2024 IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS

    The modern concept of a universal converter is intended as a power converter (PC) suitable for application in both dc or ac grids using the same external connectors. This novel family was recently proposed to allow easier integration of renewable energy sources and energy storage systems (ESSs), interfacing with dc/ac grids and/or loads with a minimum redundancy of power switches and passive elements. This kind of solution and applications are expected to be a reality in the nearest decade, as ac and dc low voltage distribution networks will coexist. Nevertheless, the initial solutions proposed as universal converters were focused on ac single-phase power conversion systems. In this sense, this article proposes and describes a new member of the universal converter family suitable for dc–dc and dc–ac power conversion (both in three-phase three-wire and in three-phase four-wire). The proposed power topology is derived as a modular extension from the single buck-boost bidirectional cell. Its main operation modes (buck and boost) are discussed, and a pulsewidth-modulation technique is developed to generate the corresponding switching patterns. The proposed solution is successfully validated in open-loop mode both in simulation and experimentally with a laboratory prototype. The measured efficiency of the PC was above 97% in the dc–ac mode and around 99% in the dc–dc mode.

  • Feasibility Study of Three-Phase Modular Converter for Dual-Purpose Application in DC and AC Microgrids
    • Carlos Roncero-Clemente
    • Oleksandr Husev
    • Oleksandr Matiushkin
    • J. Gutierrez-Escalona
    • Fermin Barrero-Gonzalez
    • D. Vinnikov
    • Ryszard Strzelecki
    2024 IEEE JOURNAL OF EMERGING AND SELECTED TOPICS IN POWER ELECTRONICS

    The modern concept of a universal converter is intended as a power converter suitable for application in both dc or ac grids using the same external connectors. This novel family was recently proposed to allow an easier integration of renewable energy sources and energy storage systems, interfacing with dc/ac grids and/or loads with a minimum redundancy of power switches and passive elements. This kind of solution and applications are expected to be a reality in the nearest decade, as ac and dc low voltage distribution networks will coexist. Nevertheless, the initial solutions proposed as universal converter were focused on ac single-phase power conversion systems. In this sense, this article proposes and describes a new member of the universal converter family suitable for dc to dc and dc to ac power conversion (both in three-phase three-wire and in three-phase four-wire). The proposed power topology is derived as a modular extension from the single buck-boost bidirectional cell. Its main operation modes (buck and boost) are discussed, and a pulse-width-modulation technique is developed to generate the corresponding switching patterns. The proposed solution is successfully validated in open-loop mode both in simulation and experimentally with a laboratory prototype. The measured efficiency of the power converter was above 97% in the dc to ac mode and around 99% in the dc to dc mode

  • Feasibility Study on the Potential Using of Ferrocement for Constructing Floats
    • Beata Zima
    • Artur Karczewski
    2024

    In recent years, there has been a significant increase in interest in ferrocement as a material for various engineering constructions. Due to its ease of shaping complex forms, it has been used previously, for example, in constructing ship hulls or tank walls. Apart from the advantages associated with the ability to shape thin elements, improved mechanical properties compared to concrete, and resistance to chemical actions, ferrocement is becoming an increasingly attractive solution for both economic and ecological reasons. The paper presents the results of preliminary analysis aimed at determining the potential use of ferrocement as a material for constructing floats for houseboats. The assumptions regarding the load-bearing structure are presented, and the dimensioning process is described. Due to the lack of standards for the ferrocement structures, the calculations were based on the guidelines of the European standards for concrete and reinforced concrete structures. Subsequently, the focus was on the problems associated with determining the ferrocement strength parameters, as well as discussing the consequences of applying reinforced concrete theory to its calculations. Also, the areas that required reformulation due to the strictly adopted assumptions related to the concrete behavior and the method of load transfer through reinforced sections have been indicated.

  • Feedback Control of Doubly-Fed Generator Connected to Current Source Converter
    • Marcin Morawiec
    • Pawel Kroplewski
    • Filip Wilczyński
    2024 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS

    Doubly-fed induction generator (DFIG) system supplied by current source converter (CSC) is considered in this article. The DFIG can work in two independent modes: AC grid connection and stand-alone mode. The DFIG is connected to the ac grid directly through its stator and the CSC links the rotor side. In this mode, the active and reactive powers of the DFIG must be controlled. This article proposes two control system structures for the DFIG working in the generator mode. Both control structures are based on nonlinear transformations but on different state-feedback control variables. The selection of the variables is similar to the input–output linearization but more complicated due to the CSC and “voltage control” involved. Both proposed control structures ensure independent control of the active and reactive powers with different accuracies; as evidenced in the simulation and experimental results. The proposed approach can be named by voltage control of the DFIG because the control variables are the voltage in the dc-link and the angular speed of the output current vector from the inverter. For both proposed control structures, the current in the dc-link is not a constant value, but depends on the dynamic states and values of the controlled powers; thus, it varies accordingly. The proposed control strategy can be applied to low- and high-power DFIG systems. Simulation and experimental results from a 2-kW generator validate theoretical propositions.

  • FEM simulations applied to the failure analysis of RC structure under the influence of municipal sewage pressure
    • Łukasz Skarżyński
    • Ireneusz Marzec
    2024 ENGINEERING FAILURE ANALYSIS

    The paper discusses a failure mechanism of reinforced concrete (RC) structure with steel cover that failed under the influence of municipal sewage pressure. To explain the reasons of failure, in-situ measurements, laboratory experiments and comprehensive Finite Element Method (FEM) computations were performed. Non-destructive in-situ scanning tests were carried out to determine quantity and cover thickness of embedded reinforcement bars, simultaneously, laboratory tests regarding concrete and shotcrete thickness, density and compressive strength were performed on samples prepared from core drills taken from the RC structure. FEM computations were carried out with the constitutive continuum model for concrete and steel with material parameters designated on the basis of stress-strain curves in uniaxial compression and uniaxial tension, respectively. An isotropic coupled elasto-plastic-damage formulation based on the strain equivalence hypothesis was used. In order to describe strain localization in concrete, model was enhanced in a softening regime by a characteristic length of micro-structure by means of a non-local theory. FEM analyses were carried out for different values of sewage pressure. The main attention was paid to the evolution of steel cover deformation and strain localization of the RC ceiling slab. FEM results revealed strong dependence between a bond-slip between anchors and steel cover deformation as well as between sewage pressure value and strain localization pattern of RC structure. Mechanism of the structure failure under complex loading conditions was realistically captured and its reasons were discussed in detail.

  • Femtosecond laser ablated trench array for improving performance of commercial solid oxide cell
    • Mohamed A. Baba
    • Bartłomiej Lemieszek
    • Mantas Sriubas
    • Brigita Abakevičiene
    • Sigitas Tamulevičius
    • Sebastian Molin
    • Tomas Tamulevičius
    2024 JOURNAL OF POWER SOURCES

    The performance of electrode-supported solid oxide cells (SOCs) is limited adversely by gas diffusion impedance in thick and porous support. This work focuses on the improvement of gas transport properties of commercial Ni-YSZ anode-supported SOFC by femtosecond laser-based micromachining where micro-holes of identical depth but different hole separations pitches with minimal heated affected zones were imposed. The polarization resistance calculations and DRT analysis revealed that the presence of the micro-holes improves fuel transport in the anode active zone of commercial SOFC. The presence of the micro-holes resulted in up to 20.8 % and up to 17.2 % reduction in polarization resistance for dry H2 and wet H2 gas-fueled SOFC samples, respectively. Moreover, the decrease in intensity of peaks responsible for fuel diffusion with increasing micro-holed density was observed. Therefore, dense and sparse cells exhibited a performance augmentation of 25 % and 11 % in dry H2 and enhancement of 16 % and 15.6 % in wet H2, respectively. Fs-laser ablation appeared as a unique capability for the post-processing of SOFC elements via imposing different gas channel geometries.

  • Ferromagnetism and structural phase transition in rhombohedral PrIr3
    • Karolina Górnicka
    • Michał Winiarski
    • Robert J. Cava
    • Michael A. McGuire
    • Tomasz Klimczuk
    2024 PHYSICAL REVIEW B

    The synthesis, structural, magnetic, thermal, and transport properties are reported for polycrystalline PrIr3. At room temperature PrIr3 displays the rhombohedral space group R-3m and a PuNi3-type structure. At around 70 K a phase transition to a monoclinic C2/m structure is observed and continued cooling reveals temperature independent behavior of the unit cell volume. Further, PrIr3 undergoes a paramagnetic to ferromagnetic transition with Tc = 7.5K. The temperature dependent magnetic susceptibility follows the Curie-Weiss law with a positive Curie-Weiss temperature, and an effective moment that is close to the theoretical effective moment for a free Pr+3 ion. The structural transition introduces further complexity into the behavior of PuNi3-type materials and highlights the importance of temperature-dependent structural studies to complement physical property measurements in intermetallic compounds.

  • Few-Layer Black Phosphorus/Chitosan Nanocomposite Electrodes via Controlled Electrodeposition for Enhanced Electrochemical Kinetic Performance
    • Paweł Jakóbczyk
    • Iwona Kaczmarzyk
    • Robert Bogdanowicz
    2024 Journal of Physical Chemistry C

    This study presents the preparation and characterization of few-layer black phosphorus (FLBP) chitosan electrodes by controlled electrochemical deposition of chitosan nanoparticles on FLBP-modified glassy carbon electrodes. FLBP was prepared by solvent-assisted exfoliation of bulk BP and was further modified with chitosan forming together a nanocomposite, including easy cross-linking with nanomaterials and film-forming properties. Cyclic voltammetry was employed to analyze the kinetic properties of electrodes fabricated at different electrochemical deposition durations of chitosan, revealing distinct reduction and oxidation peaks using 10 V. The electrochemical impedance spectroscopy technique was employed to further characterize the investigated FLBP-chitosan nanocomposites, which provides valuable insights into the electrode material properties. The controlled electrochemical deposition of chitosan nanoparticles on FLBP-modified glassy carbon electrodes opens up possibilities for developing a wide range of electrochemical sensors and devices for energy storage applications.

  • Field Calibration of Low-Cost Particulate Matter Sensors Using Artificial Neural Networks and Affine Response Correction
    • Sławomir Kozieł
    • Anna Pietrenko-Dąbrowska
    • Marek Wójcikowski
    • Bogdan Pankiewicz
    2024 Full text MEASUREMENT

    Due to detrimental effects of atmospheric particulate matter (PM), its accurate monitoring is of paramount importance, especially in densely populated urban areas. However, precise measurement of PM levels requires expensive and sophisticated equipment. Although low-cost alternatives are gaining popularity, their reliability is questionable, attributed to sensitivity to environmental conditions, inherent instability, and manufacturing imperfections. The objectives of this paper include (i) introduction of an innovative approach to field calibration for low-cost PM sensors using artificial intelligence methods, (ii) implementation of the calibration procedure involving optimized artificial neural network (ANN) and combined multiplicative and additive correction of the low-cost sensor readings, (iii) demonstrating the efficacy of the presented technique using a custom-designed portable PM monitoring platform and reference data acquired from public measurement stations. The results obtained through comprehensive experiments conducted using the aforementioned low-cost sensor and reference data demonstrate remarkable accuracy for the calibrated sensor, with correlation coefficients of 0.86 for PM1 and PM2.5, and 0.76 PM10 (particles categorized as having diameter equal to or less than 1m, 2.5m, and 10m, respectively), along with low RMSE values of only 3.1, 4.1, and 4.9 µg/m³.

  • Fine-Tuning the Photocatalytic Activity of the Anatase {1 0 1} Facet through Dopant-Controlled Reduction of the Spontaneously Present Donor State Density
    • Szymon Dudziak
    • Jakub Karczewski
    • Adam Ostrowski
    • Grzegorz Trykowski
    • Kostiantyn Nikiforow
    • Anna Zielińska-Jurek
    2024 Full text ACS Materials Au

    The present study highlights the importance of the net density of charge carriers at the ground state on photocatalytic activity of the faceted particles, which can be seen as a highly underexplored problem. To investigate it in detail, we have systematically doped {1 0 1} enclosed anatase nanoparticles with Gd3+ ions to manipulate the charge carrier concentration. Furthermore, control experiments using an analogical Nb5+ doped sample were performed to discuss photocatalytic activity in the increased range of free electrons. Overall results showed significant enhancement of phenol degradation rate and coumarin hydroxylation, together with an increase of the designed Gd/Ti ratio up to 0.5 at. %. Simultaneously, the mineralization efficiency, measured as a TOC reduction, was controlled between the samples. The observed activity enhancement is connected with the controlled decrease of the donor state density within the materials, being the net effect of the spontaneously present defects and introduced dopants, witch reduce hydroxylation and the hole trapping ability of the {1 0 1} facets. This allows to fine-tune multi-/single-electron processes occurring over the prepared samples, leading to clear activity maxima for 4-nitrophenol reduction, H2O2 generation, and ·OH formation observed for different donor densities. The optimized material exceeds the activity of the TiO2 P25 for phenol degradation by 52% (377% after surface normalization), showing its suitable design for water treatment. These results present a promising approach to boost photocatalyst activity as the combined result of the exposed crystal facet and dopant-optimized density of ground-state charge carriers.