CTU Open Journal Systems (Czech Technical University, Prague / České vysoké učení technické v Praze)
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Classical and quantum superintegrable systems on the sphere and the hyperbolic 2-space
Get PDFWe present two superintegrable Hamiltonian systems in two dimensions, defined on the sphere and on the hyperbolic plane. These systems are generalised à la Tremblay-Turbiner-Winternitz (TTW), involving the introduction of a real parameter k > 0, with the aim of extending superintegrable Hamiltonian systems to curved spaces in a way similar to the TTW system on the plane. We carry out both classical and quantum analyses of these new systems. We prove that the superintegrability of the initial systems (i.e. when k = 1) is preserved when k is rational, as in the TTW case. A detailed study of their classical counterparts and trajectories is also included
Dispersion type metal-metal based high-density fuels for nuclear reactors – sample preparation, analysis and examination of LOCA behaviour
Get PDFMetal-based nulear fuels have been proposed as an alternative to UO2 partly in response to increasing pressure to continually improve nuclear system safety. In this work, a set of High-Density Fuel samples manufactured from depleted uranium alloys and Zr-based matrix have been manufactured and evaluated in the as-manufactured and post-LOCA conditions. A qualitative analysis of the samples showed that the matrix and fuel behaviour is mostly consistent with theory and available research while quantitative analysis revealed a major impact of fuel element geometry on packing density and distribution. Fuel–matrix–cladding interactions of varying intensity have also been observed during fabrication and under LOCA conditions
Thermal diffusivity of ATF cladding materials using laser flash technique
Get PDFAccident tolerant fuel (ATF) cladding materials are designed to improve the fuel behavior in normal operation while further enhancing the material performance in accidental scenarios. The paper presents experimental data on thermal diffusivity for five advanced cladding candidates considered as ATFs, evaluated over a wide temperature range using the laser flash technique. The measured data were evaluated to identify trends in thermophysical behavior in the investigated temperature range. Based on the results, correlations were established to describe the temperature dependence of thermal diffusivity for each material. The analysis also revealed characteristic differences in the thermal diffusivity for various candidates. These findings provide a comparative perspective on the heat transfer capabilities of the tested materials and offer a fundamental experimental basis for their further optimization in accident tolerant fuel applications
EVALUATION OF SIMPLIFIED MECHANICAL POWER AND DISSIPATED ENERGY CALCULATIONS IN PHYSICAL RESPIRATORY MODELS WITH TISSUE AND AIRWAY RESISTANCE
Get PDFMechanical power (MP) calculation is a promising predictor of ventilator-induced lung injury, yet simplified bedside equations rely on airway opening pressure, potentially missing key information about tissue-level stresses, and involve unclear contributions of PEEP and airway flow resistance. This study compared simplified MP equations in physical models of the respiratory system with either tissue viscoelastic (Rt) or airway flow (Raw) resistance, evaluating how pressure measurement location affects delivered and dissipated energy estimates. Six physical models (No-resistance, Tissue resistance, Flow resistance, and three combinations of Rt with different Raw) were ventilated with the same volume-controlled parameters. Pressure was measured at the airway opening and at an artificial lung level with vital signs monitor, sampled at 100 Hz. Mechanical energy was calculated using both simplified equations and a geometric method based on the pressure-volume loops. Simplified MP equations produced similar mechanical energy estimates for Tissue resistance model and Flow resistance model (Raw = 5 cmH2O·s·L-1) when pressure was measured at the airway opening. However, measurements at the artificial lung level revealed marked differences in delivered and dissipated energy. Simplified MP equations may misrepresent tissue-level energy, particularly when Raw dominates. Future studies should focus on refining energy estimation methods, considering driving transpulmonary pressures, inspiratory hold duration, and tissue versus flow resistance
Characterizing the diffuse vacuum arc voltage for MVDC circuit breaker applications: experiment, data, and empirical model
Get PDFProposed hybrid DC circuit breaker concepts rely on the arc voltage in vacuum interrupters to commutate fault currents to parallel branches. This paper presents an extensive experimental investigation of the diffuse vacuum arc voltage of an industrially manufactured vacuum interrupter which is connected to a Thomson coil actuator. By independently varying the opening speed and arc current, an empirical model describing the diffuse vacuum arc voltage as a function of contact distance and current is derived. The model limits are evaluated by discussing the transition phase towards high-current anode mode formation
Traffic accident analysis using EDR data: a case study of a multicollision event
Get PDFThis paper focusses on the importance of using Event Data Recorder (EDR) data in the reconstruction of traffic accidents. It presents a case study of a highway accident in which aggressive overtaking led to a series of collisions between three vehicles. Although the speed recorded at certain moments was not accurate due to vehicle skidding, the EDR data allowed confirmation of key manoeuvres and movements of the vehicles prior to the collision. The paper highlights the importance of EDRs in accident analysis, where they helped reconstruct the drivers’ manoeuvres and decisions, contributing to the elucidation of the causes of the accident. The mandatory introduction of EDRs in new vehicles from 2024 is an important step towards better crash analysis and improved road safety
Applicability of the SAF operation – case study of a Czech registered business aircraft operator on flights within Europe
Get PDFThe aim of this paper is to develop a fundamental model for assessing the potential of Sustainable Aviation Fuel (SAF) utilization in business aviation. It investigates the feasibility and strategic integration of SAF within Czech registered business aircraft operator on flights within Europe, with a focus on its environmental and economic implications. The study evaluates the carriers’ networks by establishing two refueling strategies and identifying key factors for calculating emissions and costs. Specifically, the Minimum Refueling Strategy and Maximum SAF Refueling Strategy are analyzed. Through a thorough analysis, this research aims to offer actionable insights for aviation companies, highlighting the dual benefits of SAF in promoting both sustainability and cost efficiency. Current EU ETS regulations exempt operators emitting less than 10 000 tonnes of CO2 annually, a threshold many operators aim to stay below. However, as the EU intensifies its climate targets, smaller operators must anticipate greater regulatory and financial pressures related to emissions. This represents a pivotal move toward a more inclusive and stringent emissions trading system, aligned with sustainability goals. SAF adoption emerges as a promising solution for business aviation, as its use would significantly reduce CO2 emissions and associated costs for operators. By offering a comprehensive overview and strategic recommendations, this study aims to contribute to the ongoing discussion on sustainable aviation practices and assist stakeholders in making informed decisions regarding the adoption of SAF
Implementation of a hydrogen fuel cell in a small urban vehicle
Get PDFThe transition to sustainable urban mobility is a key priority for Europe as countries seek to reduce greenhouse gas emissions and combat climate change. Electric vehicles (EVs) have become a popular trend offering a cleaner alternative to traditional combustion engines. However, despite their advantages, EVs face challenges related to the difficult extraction of raw materials for battery production, energy storage and long charging times. Hydrogen fuel cells (HFCs) are another possible alternative, offering longer range and shorter refueling times while maintaining zero local emissions. This paper discusses the integration of hydrogen fuel cell technology into a small urban vehicle and evaluates its potential in terms of sufficient power and efficiency. The study focuses on the design and implementation of the fuel cell system in a specific prototype vehicle, with the biggest challenge being the placement of the components and definition of sufficient power of fuel cell system integrated as range extender
Simulation of RC-T Beam Reinforced by Steel Wire Mesh and Polyurethane Cement Composite (SWM-PUC) P
Get PDFIn this paper, the flexural performance of seven steel wire mesh and polyurethane cement (SWM-PUC) composite strengthened beams was investigated experimentally. The variation law of flexural performance of reinforced beams is clarified. Based on the experimental research, the deflection and stress analysis of SWM-PUC composite strengthened reinforced concrete beams was conducted using finite element analysis software ABAQUS. The Bending properties of reinforced beams with different steel wire mesh (SWM) reinforcement rates and different polyurethane cement (PUC) thickness parameters were researched. The reinforcement ratios of SWM are 0.064%, 0.087%, 0.114%, 0.144%, and 0.178%, respectively. The PUC thickness is 20mm, 25mm, 30mm, 35mm and 40mm. The finite element analysis shows that as the reinforcement ratio of the SWM increases, the yield and ultimate loads gradually increase and the deflection then gradually decreases. When the reinforcement ratio reaches a certain level, the increase in yield load decreases with the increase of reinforcement ratio. In the case of 0.114% increase in the reinforcement ratio of the SWM, the ultimate load of the simulated beams was increased by 47% compared to the simulated beams with 0.064% reinforcement ratio of the SWM. As the thickness of the PUC increases, the yield limit and ultimate load gradually increase, and the deflection value decreases continuously. The ultimate load of the reinforced beam with PUC at 40mm thickness was increased by 20.5% compared to the reinforced beam with 30cm thickness. The optimum configuration of the SWM -PUC composite reinforcement layer was given through the finite element analysis
Point cloud local neighborhood features - a review
No full textPoint clouds are essential for 3D spatial analysis and widely used in geodesy, photogrammetry, and remote sensing. While modern technologies simplify their collection, processing remains challenging due to data size, irregularity, and noise. Classification is critical for object identification and noise removal.
This paper explores geometric features of points derived from their local 3D neighbourhoods. It examines neighbourhood definitions, feature computation via principal component analysis (PCA), and their impact on real dataset classification. Using a test point cloud with natural and anthropogenic features, we analyze feature dependencies, identify redundancies, and highlight key metrics. Additionally, we propose new approaches for noise filtering, contributing to more efficient point cloud processing and practical applications