Articles (RICE)

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http://hdl.handle.net/11025/30065

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Showing 1 - 20 out of 330 results

Room temperature hydrogen sensor for the detection of flammable concentrations based on SWCNT modified by a solid solution of oxygen in Pd nanoparticles
(2025) Šorm, Martin; Štulík, Jiří; Křenek, Tomáš; Koštejn, Martin; Kupčík, Jaroslav; Hamáček, Aleš
Fabricating a high-response sensor for the repeatable detection of a high (flammable) hydrogen concentration (4 %) at room temperature with long-term stability remains a challenge. Here, a hydrogen (H2) sensor based on single-walled carbon nanotubes (SWCNTs) functionalized with palladium (Pd) nanoparticles of a previously unexplored structure is demonstrated. The active sensing layer is fabricated via airbrush deposition of SWCNTs and pulsed laser ablation of Pd in a vacuum. Complementary characterization techniques, including HRTEM, electron diffraction, STEM-EELS, Raman spectroscopy, and XP-spectroscopy, reveal that the Pd nanoparticles form a solid solution of oxygen in metallic Pd (Pd+O), partially covered with a two-dimensional palladium oxide (PdO) layer. The Pd+O/PdO nanoparticles exhibit an expanded face-centered cubic (FCC) and cubic primitive lattice, representing a previously unreported Pd structure. The sensor achieves a repeatable 203 % response to 4 % H2 at room temperature and operates over a wide concentration range (0.05 % – 10 % H2 in air) with long-term stability exceeding 1.5 years. The detection mechanism is hypothesized to involve ionosorption and/or oxygen vacancies in the PdO layer. These findings highlight the undiscovered potential of carbon nanostructure/Pd nanoparticle hybrids for enhanced hydrogen sensing through Pd structure tailoring.
Comparative analysis of printed electronics technologies in RF and microwave circuits
(2025) Lotfi, Saeedeh; Janda, Martin; Řeboun, Jan; Blecha, Tomáš
Printed electronics (PE) present a promising alternative to conventional photolithography by enabling rapid prototyping with reduced costs, material waste, and enhanced design flexibility and advantages, particularly relevant for high-frequency microwave applications. This study presents the design, fabrication, and evaluation of two microstrip low-pass filters (LPFs) with cutoff frequencies of 2.60 GHz and 3.55 GHz serving as representative components for microwave circuits, using three additive manufacturing techniques: Direct-Write (DW), Screen Printing (SP), and Aerosol Jet Printing (AJP). Over 60 filter samples were fabricated and measured to systematically assess performance across different printing methods. The LPFs were designed and analyzed through electromagnetic simulations, complemented by an LC equivalent circuit model based on actual device dimensions to better understand their behavior. Measured frequency responses showed strong agreement with simulations, validating the effectiveness of all three printing methods. Each technique demonstrated unique trade-offs between resolution, fabrication complexity, and electrical performance, emphasizing the need to tailor method selection to specific application requirements. This paper offers valuable insights into the design, analysis, and fabrication of RF and microwave circuits using printed electronics, highlighting the strengths and limitations of each technique. It serves as a practical guide for researchers in selecting suitable methods for high-frequency applications.
Open-source platform for simulation of physical fields: Agros
(2025) Karban, Pavel; Pánek, David; Kaska, Jan
Agros is an open-source software package designed to simulate and analyze physical fields, including electromagnetic, thermal, and mechanical phenomena. The software offers a versatile and intuitive graphical user interface (GUI) and supports multi-physics simulations, making it a valuable tool for academic research and industrial applications. This article provides an overview of agros development, focusing on recent updates that enhance its functionality, modularity, and usability. We discuss agros integration with the deal.II library and Python for advanced customization, which expands the capabilities of its core engine and postprocessor.
A Novel Discrete Resonant Control Method for Cascaded H-Bridge Rail Balancers
(2025) Straka, Miloš; Dragoun, Jaroslav; Talla, Jakub; Blahník, Vojtěch; Pittermann, Martin; Peroutka, Zdeněk
This paper presents the concept of an advanced rail balancer (ARB) for next-generation traction substations (TSSs), along with its control algorithm based on a novel advanced resonant controller. The ARB utilises a cascaded H-bridge (CHB) converter topology and is designed to effectively address several key issues in modern TSSs, including load current symmetrisation in the distribution power grid, reactive power compensation, harmonic currents from railway vehicles and active filtering of higher-order harmonics in the grid current. The proposed asymmetric control of the ARB converter includes individual ARB phase current control using an advanced resonant controller. The resonant controller algorithm provides the desired frequency response without offset and uses direct latency compensation to mitigate the effects of low switching frequency and large control sampling times. Experimental results show very good performance of the proposed control algorithm, especially for grid current harmonics filtration with low ARB switching frequency, large sampling times and control latency.
Modern training courses increasing awareness of environmental protection
(2025) Veg, Lukáš; Jeleń, Michal; Rassölkin, Anton; Stepien, Mariusz; Zygmanowski, Marcin
This paper addresses the increasing global emphasis on environmental protection across various sectors, particularly in education related to electrical engineering, electronics, mechatronics, and automation. It highlights the need for retraining individuals transitioning from the mining industry to high-tech sectors that focus on environmentally sustainable technologies. The paper discusses an international initiative under the Erasmus+ Strategic Partnership program to develop a platform for such retraining courses. Key project goals, outcomes, and the broader impact of this educational initiative on environmental awareness are also explored.
Maximizing Output Voltage of Three-Phase Nine-Leg Multilevel STATCOM by Minimum Infinity Norm Optimization
(2025) Adam, Lukáš; Komrska, Tomáš; Iška, František; Peroutka, Zdeněk
Power converters based on classic three-phase three-leg voltage source inverters (VSIs) that provide a multilevel output voltage are an interesting alternative to multilevel converters that suffer from complexity and higher costs. However, the multiple degrees of freedom of these systems pose a challenge to their optimal control. In this article, the minimum infinity norm algorithm is proposed and implemented for triple three-leg VSI static synchronous compensators (STATCOM) connected to a three-phase power grid. It is shown that the method provides optimal utilization of the dc-link voltage and allows to increase the output voltage by 39% compared to the minimum l2 norm method and by 16% compared to the phase-disposition pulse width modulation (PD-PWM) while keeping total harmonic distortion (THD) below 0.5%. In addition, the algorithm has been optimized for real-time systems, resulting in a very fast algorithm with a worst-case complexity of 39 scalar–scalar multiplications and no division.
Accelerating VVER-440 decommissioning by shortening spent-fuel cooling time for dry-cask storage
(2025) Bůžek, Ondřej; Lovecký, Martin; Škoda, Radek
This study focuses on optimizing the cooling time of spent nuclear fuel in the spent nuclear fuel pool before its placement into a dual-purpose dry cask to reduce the overall cooling duration required to safely store fueldischarged from the VVER-440 reactor. The feasibility of reducing the cooling time is assessed based on the analysis of decay heat and the evaluation of the dose rate equivalent on the cask surface and at a standardizeddistance of 2 m from the cask. To reduce the cooling time, the peripheral layer of spent nuclear fuel in the cask, consisting of 30 storage positions, is replaced with hexagonal fuel dummies made of polyethylene, steel, or their combination. The results obtained apply to standard spent nuclear fuel management practices, particularly in the context of nuclear power plant decommissioning or other scenarios where minimizing the residence time of fuel in the pool is of critical importance.
Spatially Resolved XRD Using Polychromatic Fan Beam and a Hybrid Pixel Detectors Timepix3
(2025) Urban, Ondřej; Georgiev, Vjačeslav; Mašek, Bohuslav; Bartůněk, David
The utilization of hybrid pixelated detectors such as Timepix3 for imaging has already been proven to have many benefits compared to conventional detectors, e.g. CCDs. The proposed work exploits these benefits for material structure analysis using x-ray diffraction (XRD) with a polychromatic fan beam. This allows simultaneous analysis of material properties and thus provides spatially resolved information about differences in the sample structure, e.g. material impurities or uneven sample treatment. The proposed measurement setup utilizes two Timepix3 detectors, an off-the-shelf x-ray tube and a simple geometry, enabling in situ measurements. The data provided by the Timepix3 detector contain both spatial and energy information for each detected photon and therefore advantages of a polychromatic beam can be fully exploited. Thanks to the polychromatic beam, clusters, formed by grain orientation can be tracked and its origin can be restored. This then allows the correct scattering angle calculation while providing location of the corresponding grain. © 2025 IOP Publishing Ltd and Sissa Medialab. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Design of a 65-kW Wireless Charging Station Characterized by Optimal Load Impedance Tracking Control
(2025) Zavřel, Martin; Drábek, Pavel; Kindl, Vladimír; Frivaldský, Michal
This article presents the design and development of a low-level control approach for a wireless charger intended for modern electro-mobility (e-mobility) applications. It outlines future trends in the e-mobility market and technical advancements in wireless power transfer (WPT) systems, aligning them with the proposed wireless charger design methodology. A key advantage of the proposed solution is its full competitiveness with conventional wired charging stations. The primary focus of this work is the control system design for the wireless charging station (WCS), which features active and optimal load impedance tracking. This tracking adapts to varying load parameters (such as battery characteristics) and misalignments in coupling elements, ensuring maximum power transfer efficiency and high-power transfer controlled by supply voltage. The system complies fully with the SAE J2954 standard for wireless charging in e-mobility. The developed test system achieves power transfer of up to 65 kW across an air gap of 15 to 25 cm, with an overall system efficiency exceeding 95.5%.
Improving Manufacturing Processes through Artificial Intelligence - Example of Printed Circuit Board Manufacturing
(2025) Tupa, Jiří; Benešová, Andrea; Steiner, František; Řeřicha, Tomáš
The advent of Artificial Intelligence (AI) in manufacturing has heralded a new era of industrial revolution, characterised by unprecedented efficiency, productivity, and innovation. This critical review delves into the application of AI technologies in the manufacturing sector, scrutinising their impact on process enhancement and addressing the spectrum of opportunities and challenges they present. By thoroughly analysing recent studies, industry reports, and case examples, this paper outlines the transformative potential of AI in various manufacturing domains, including predictive maintenance, supply chain optimisation, quality control, and intelligent manufacturing. However, the paper does not shy away from discussing the critical challenges facing the deployment of AI in manufacturing. These include technical limitations, data privacy and security concerns, the need for substantial investment, and the socio-economic implications of workforce displacement and skill gaps. Concluding with a forward-looking perspective, the review suggests practical strategies for overcoming these hurdles, such as fostering public-private partnerships, investing in AI literacy and training, and adopting ethical guidelines for AI use.
Proton reconstruction with the TOTEM Roman pot detectors for high-β∗ LHC data
(2025) Hayrapetyan, A.; Georgiev, Vjačeslav; Hammerbauer, Jiří; Linhart, Richard; Peroutka, Zdeněk; Urban, Ondřej; Vavroch, Ondřej; Zich, Jan; CMS, Collaboration; TOTEM, Collaboration
The TOTEM Roman pot detectors are used to reconstruct the transverse momentum of scattered protons and to estimate the transverse location of the primary interaction. This paper presents new methods of track reconstruction, measurements of strip-level detection efficiencies, cross-checks of the LHC beam optics, and detector alignment techniques, along with their application in the selection of signal collision events. The track reconstruction is performed by exploiting hit cluster information through a novel method using a common polygonal area in the intercept-slope plane. The technique is applied in the relative alignment of detector layers with μm precision. A tag-and-probe method is used to extract strip-level detection efficiencies. The alignment of the Roman pot system is performed through time-dependent adjustments, resulting in a position accuracy of 3 μm in the horizontal and 60 μm in the vertical directions. The goal is to provide an optimal reconstruction tool for central exclusive physics analyses based on the high-β* data-taking period at √(s) = 13 TeV in 2018.
Transmission energy dispersive X-ray diffraction as a tool for the laboratory study of fast processes in metals
(2025) Vavřík, Daniel; Georgiev, Vjačeslav; Jakubek, Jan; Mašek, Bohuslav; Urban, Ondřej; Sleichrt, Jan; Kytyr, Daniel
In this work, an in-situ study of phase transitions in low-carbon steel is presented. The phase changes were monitored by the transmission energy dispersive X-ray diffraction technique during the heating, annealing and quenching cycle of the sample under standard laboratory conditions. During energy dispersive X-ray diffraction, the sample volume was transmitted with a pencil beam generated by a standard polychromatic X-ray tube without any spectral filtering. Two-dimensional polychromatic diffraction images were acquired by a Timepix 3 pixelated detector. This detector is capable of achieving a throughput of up to 38 Mhits/s in continuous stream mode using USB 3.0 interface. For each detected photon, its position is known with an accuracy of 55 μm in the detector plane and its energy with a resolution of 4 keV at 60 keV. The recorded polychromatic data is then recomputed to get the equivalent monochromatic XRD pattern that would be produced using a monochromatic X-ray source. Thanks to the 90 kV voltage potential of the X-ray tube, the polychromatic pencil beam wasable to pass through a highly attenuating sample made of 1.5 thick steel sheet. In addition, by utilizing the entire X-ray spectrum, the pencil beam has a sufficiently high brilliance to obtain XRD patterns rapidly enough to investigate relatively fast processes with temporal resolution of 10 s. It made to possible to analyze the phase transitions in a polycrystalline sample during its temperature treatment under standard laboratory conditions.
Overloadability improvement of electric motorcycle eDrive by using a five-phase PMSM
(2025) Frank, Zdeněk; Laksar, Jan; Hruška, Karel
This article addresses the replacement of the original three-phase permanent magnet synchronous motor for an electric motorcycle by a five-phase PMSM in terms of improving its verloadability and efficiency. The overloadability improvement is achieved by a novel approach utilizing the fundamental pro erties of the multiphase windings while keeping possibly most similar magnetic circuit topology. On the basis of previous work, a five-phase machine is designed, manufactured, measured and compared with the original three-phase machine. On the basis of measured data and calculated machine characteristics, the benefits of an increased number of machine phases are discussed as well as the proof of usability and benefits of used design approach.
Effect of open phase condition on asynchronous machine
(2025) Skala, Bohumil; Kindl, Vladimír; Frivaldský, Michal; Sobotka, Lukáš; Zavřel, Martin
This paper investigates the influence of an asymmetrical power supply on induction machines, focusing on key parameters such as temperature rise, torque, efficiency, and power factor. Various three-phase voltage asymmetries are examined to determine their impact on the magnitude of the negative-sequence voltage component. The study further explores how a drop in phase voltage leads to a significant negative component, the effect of phasor rotation from its ideal position, and the number of phases subject to voltage drops or phase shift errors. A voltage synthesis approach is employed to analyse the roles of the positive and negative components, with one component held constant to evaluate the resulting changes in power factor, efficiency, and torque. In addition, a dynamic thermal model is implemented to assess the machine’s temperature rise under load conditions.
Decay Heat Uncertainty Analysis for VVER Spent Nuclear Fuel
(2025) Lovecký, Martin; Závorka, Jiří; Kořínek, Tomáš; Škoda, Radek
Total Monte Carlo (TMC) extends the Monte Carlo method, using stochastic techniques and random sampling to solve the Boltzmann transport equation in spent nuclear fuel (SNF) depletion analysis. TMC evaluates the impact of uncertainties in nuclear data, such as cross sections and fission product yields, on SNF characteristics, focusing on decay heat, which is crucial for SNF handling and management. TMC generates random nuclear data variations within uncertainty ranges for Monte Carlo simulations, resulting in outcome distributions (e.g., decay heat) that reflect real-world behavior uncertainties. The uncertainty analysis examined a standard VVER-440 nuclear fuel. Using the serpent 2 code and referencing the endf/b-viii.0 and tendl nuclear data libraries, the study focused on the impact of cross sections and fission product yield nuclear data uncertainty on the decay heat of a standard VVER-440 nuclear fuel. The time frame chosen for both post-reactor shutdown and long-term for spent fuel cask loading is chosen, providing a comprehensive view of the nuclear fuel cycle.
Partial discharge behavior and insulation failures detection in electrical devices subjected to impulse voltage excitation
(2025) Eckert, Manuel; Mraz, Petr; Ballweg, Christof; Pihera, Josef
Partial discharges can occur within an insulating system due to flaws in the material and can cause continuous deterioration until a full breakdown occurs. Modern insulating systems are subjected to various forms of pulse voltage excitation, mainly due to the switching of modern power electronics. The recent introduction of wide-bandgap semiconductors increases this stress by enabling higher operating voltages and steeper switching transients than silicon-based semiconductors. Within this paper, partial discharge measurements are performed to investigate the discharge behavior of different partial discharge sources at impulse voltage excitation, aiming to find characteristic features. The presented method relies on measuring the conducted electrical signal of a partial discharge and can, therefore, access all quantities known from partial discharge measurements at sinusoidal voltage. This article introduces the high voltage measurement setup and the signal processing required. Experiments on four different partial discharge sources are performed, and the measured data are evaluated for the information they possess regarding the active discharge mechanisms. With the results obtained, the fault analysis can be extended to recognizing the fault type active at pulse voltage, utilizing partial discharge measurements.
Dynamic wireless power transfer in E-mobility using AC power bus and matrix converter: implementation suitability study
(2025) Zavřel, Martin; Kindl, Vladimír; Frivaldský, Michal; Skala, Bohumil
Presented paper discusses power distribution bus of dynamic wireless charging track for e-mobility applications. The focus is applied to the matrix converter and AC power distribution bus adaptation. The key behavior of matrix one-to-one phase converter and three-to-one phase converter is presented to get topologies for adaptation. Get matrix converter features are discussed regarding to the wireless power transfer and dynamic charging in electromobility. Feasibility of power topologies and control approaches are discussed as well. Proposed dynamic charging using three-phase matrix converter adaptation is compared to the conventional topologies using DC power distribution bus and corresponding inverters topologies. Knowledge taken from literature and theoretical discussion is verified by MATLAB–Simulink simulations and by basic experiments. Finally, feasibility study decisions are made in conclusion.
Special Experimental Environment for Generation IV Reactors with Graphite Reflector
(2024) Vilímová, Eva; Peltan, Tomáš; Škoda, Radek
Nowadays, there is an increasing demand for new small modular reactors (SMR) reactors with a wide range of applications, often classified as a new Generation-IV reactors. Unfortunately, there is no commercially operating nuclear reactor meeting the characteristics of Generation-IV reactors in its technical design and features. However, Generation-IV nuclear reactors are intensively developed worldwide, including the Czech Republic. To support research activities linked with the development of these reactors, an appropriate experimental environment and resources simulating conditions expected in Generation-IV reactors with graphite are needed This work builds on previous research and presents a special arrangement of the LR-0 reactor core with a double-row graphite reflector, on which the influence of graphite on the neutron field shaping and power distribution was experimentally and computationally verified. The main reason for this article is to investigate the effect of the graphite reflector, which will serve as a support for the development of neutron instrumentation for Generation-IV reactors and other support for Generation-IV research activities. The results confirm the conclusions of previous research and also provide a better knowledge of the double-row graphite reflector neutron field. The presented and tested LR-0 core arrangement is included in a set of experiments supporting the research of reactor cores with graphite reflectors.
Electrically switchable magnetic elastomer
(2025) Sodomka, Ondřej; Mach, František
The magnetorheologic elastomers (MREs) have emerged as valuable materials in soft robotics, especially on small scales, where their responsive magnetic properties enable precise control and enhanced adaptability. In this paper, we focus on the design, composition, and magnetic properties of a multicomponent electropermanent elastomer (EPE) that can be switched between on and off states by an external magnetic field source. The EPE is composed of two ferromagnetically hard NdFeB particles coupled together with strontium ferrite microparticles (SF-D360) with different magnetic coercivity and remanent flux density. The resulting EPE has a bistable magnetic behavior, enabling the device to be energy efficient. This unique feature positions EPEs as highly efficient alternatives to conventional electromagnetic systems in fields such as robotics, automation and medical devices, where precise magnetic control and low power requirements factors are essential.
Lifetime Behavior of Turn Insulation in Rotating Machines Under Repetitive Pulsed Stress
(2025) Zedan, Ousama Ahmed Abdalla; Haller, Rainer; Trnka, Pavel; Bärnklau, Hans
Insulation materials are critical for the reliability and performance of electrical power systems, particularly in high-voltage rotating machines. While failures can arise from thermal, mechanical, or electrical stress, they predominantly manifest as electrical breakdowns. Prior research has primarily concentrated on aging in straight winding sections, despite evidence indicating that failures frequently occur in the bending regions of turn insulation. This study explores the influence of high-frequency pulsed electrical stress on the lifetime behavior of Type II insulation systems used in high-voltage rotating machines. Practical samples, designed with geometric configurations and technology akin to that in rotating machines, were tested under conditions characterized by voltage slew rates (dv/dt) exceeding 10 kV/mu s, with variations in frequency and waveform shape. The findings reveal that the rate of electrical aging remains consistent across differing pulse widths, risetimes, and polarities, displaying a similar lifetime exponent. Nonetheless, insulation durability is markedly more compromised under pulsed conditions. At the identical times-to-failure, the sinusoidal waveform necessitated nearly twice the applied peak voltage as the bipolar pulse waveform. This finding clearly suggests that pulsed excitation exacerbates insulation degradation more effectively due to the sharp rise times and high (dv/dt) rates imposing substantial electrical stress on dielectric materials.

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