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Dielectric recovery of electric arcs confined between PTFE and PA6,6 walls
Full text linkPlastic ablation plays a key role in the quenching of arcs in low-voltage switchgear. Here, we compare experimentally the arc quenching capacity of polyamide 6,6 (PA6,6) and polytetrafluoroethylene (PTFE). Using a set-up with a topology close to that of a hybrid breaker, we evaluate the impact of the plastic ablation on the current limitation during arcing as well as on the dielectric recovery after current interruption. Our results, supported with the calculations of the transport properties of vapors consisting of ablated PA6,6 and PTFE, demonstrate the superiority of PA6,6 for arc quenching in low-voltage applications
Mechanical properties of cement composites with plasma-treated waste glass aggregate
Full text linkThis research focuses on evaluating the effect of low-temperature plasma surface treatment of finely ground recycled glass on the mechanical properties of cement composites. The use of waste glass in construction represents an environmentally friendly alternative, but its application may cause alkalisilica reaction (ASR), leading to material degradation. To prevent this phenomenon, plasma treatment was applied with the aim of improving the adhesion of glass particles to the cement matrix, enabling the partial replacement of traditional filler materials. In cement composites, glass primarily functions as an alternative fine aggregate. Its use offers several potential advantages, including improving the pozzolanic properties of the composite, meaning it reacts with calcium hydroxide, thereby contributing to the formation of additional binding phases. In this way, glass not only replaces traditional fillers but also enhances the long-term mechanical properties of the material. However, inappropriate particle size or high reactivity of the glass may lead to ASR, which causes cracking and degradation of the material. Plasma treatment was employed to mitigate these negative effects by enhancing the adhesion between glass particles and the cement matrix, thereby increasing the overall cohesion, strength, and resistance of the composite to environmental influences and degradation. The samples were tested for compressive strength and bulk density after 28, and 168 days of curing. The results indicated that plasma treatment, particularly with oxygen, led to a moderate improvement in mechanical properties compared to untreated samples, but the values did not reach the levels observed in the reference sample without glass powder
Microstructural and mechanical property characterization of high-density uranium fuel for light-water reactors
Full text linkOne of the key concepts in the development of accident-tolerant fuels (ATFs) involves the use of high-density fuels, aimed at improving the safety and economics of light-water reactors. This work focuses on the microstructural and mechanical characterization of experimentally fabricated segments of dispersion-type high-density uranium fuels with a zirconium matrix and Zr-based cladding, intended for future testing in research reactors. Both U-Mo alloys and pure uranium metal were investigated, with particular attention given to the influence of thermal treatment on the phase composition and microstructure of the fuel segments. In addition, changes resulting from thermal exposure were evaluated. The research includes the identification of newly formed phases during transient conditions and the analysis of diffusion phenomena in the material. Mechanical properties were evaluated through microhardness measurements, and the results will serve as input parameters for computational simulations using the Serpent code to support the introduction of these fuels in the VR-2 research reactor
Experimental study of the Leidenfrost effect in the context of high heat flux cooling
Full text linkThe behavior of water droplet on heated surfaces is experimentally observed to investigate the properties of the insulating vapor layer, a key element of the boiling crisis phenomenon. The lifetime of droplets on the heated surface is measured and compared with analytical models to examine the formation of the insulating vapor layer thickness between the coolant and the heated wall. The potential for reducing the Leidenfrost effect and increasing the critical heat flux by adjusting the surface roughness is examined to improve the thermohydraulic properties of the first-wall cooling channels. The behavior of water droplets on the heated surface with variable roughness is observed through the acoustic emission method. The behavior of water droplets on heated copper surfaces was experimentally studied using inductive and electrical heating with thermocouple temperature control, camera recording and acoustic emission analysis. The measured droplet lifetimes were compared with analytical models to evaluate the insulating vapor layer thickness. The practical relevance lies in reducing the Leidenfrost effect and increasing the critical heat flux, which can improve the cooling performance of high heat flux components such as tokamak first-wall channels
Publicly available spatial data as a source of coordinates for ground control points
Full text linkNowadays, direct georeferencing methods, utilizing GNSS receivers and Inertial Measurement Units (IMUs) on aircraft carriers, are commonly employed to generate products from aerial imagery, including orthophotos and digital elevation models. However, certain scenarios necessitate the utilization of signalized ground control points, such as when higher accuracy is required, large areas need coverage, or GNSS correction data is unavailable. This paper explores leveraging publicly available data, such as orthophotos and digital elevation models, for photogrammetric projects. The methodology involves identifying identical points suitable for embedding from both publicly available data and acquired aerial photographs, retrieving X, Y coordinates from orthophotos, and Z coordinates from elevation (LiDAR) data. Evaluation using advanced geostatistical methods in urban areas and application to landscape documentation in Bohemian Switzerland National Park with diverse photogrammetric sensors demonstrate that the resulting data falls within the accuracy class, meeting standards possibly sufficient even for cadaster needs (based on the national decrees). This approach accelerates photogrammetric imaging preparation and implementation, particularly when aerial vehicles with IMUs are impractical. Moreover, it contributes to reducing the carbon footprint of aerial imaging by limiting motor vehicle movement within the area of interest.
Received: 13.03.2025
Received in revised form: 19.06.2025
Accepted: 02.12.202
Photogrammetric image processing and comparison of experimental result with laser diffraction and the PDA method
Full text linkOptical methods have been established as a standard tool for aerosol size measurement. The aim of this paper is to compare the results of two commercial optical instruments based on Phase Doppler Anemometry (PDA) and Laser Diffraction (LD) with an in-house optical photogrammetric measurement method. For the purpose of this comparison, a new in-house image processing procedure was developed with the use of a MATLAB script. The accuracy of the method was tested on several calibration particle samples as well as on PDA and LD commercial instruments. The analysis of the measurements with calibration standard particles was done using the Bias-Variance decomposition method. All three methods were tested on the polydisperse sand particle sample. The results are applicable to determine the benefits and drawbacks of these methods in their application to the broader field of aerosol technology
Use of the thermo-hydraulic system code RELAP5/MOD3.2 to transient analysis events of the VR-1 reactor
Full text linkThe article explores the application of the RELAP5 thermo-hydraulic code for transient simulations on the VR-1 research reactor, focusing on reactor vessel nodalisation and coolant stratification above the core. The study investigates Reactivity-Initiated Accidents (RIAs) at the VR-1 reactor, triggered by various initiating events such as inadvertent control rod withdrawal or experimental channel flooding. By comparing several nodalisation models for protected and unprotected RIAs, the study discusses the impact of the nodalisation approach. Key findings highlight the significant influence of user effects and reactor vessel nodalisation on the accuracy and reliability of these predictions. The article also examines two-phase flow flashing instability and the reactor SCRAM delay effect. The conclusions drawn from different nodalisation approaches may offer insights into optimising research reactor safety analysis and the simulation of natural circulation systems
The influence of road marking visibility on lateral vehicle position and driving speed
Full text linkRoad markings are a vital element of horizontal signalling, forming an integral part of traffic signalling. Their role in traffic safety involves providing timely warnings, safe guidance, and necessary information to ensure the safe movement of all road users. Under conditions of reduced visibility, often due to weather (night, fog, rain, etc.), road markings are often the only guide for drivers to determine the direction of the road. Research conducted using a driving simulator demonstrated the influence of road markings on driver behaviour, specifically on lateral vehicle position and driving speed. The results indicated that drivers behave differently depending on the visibility of road markings. A total of 31 participants took part in the study, with data collected on driving speed and lateral vehicle position for three different visibility levels of road markings on a straight road and on a right and left curve
Burnout in agile software development
Full text linkThis article examines the relationship between personality traits measured by the HEXACO model and the prevalence of burnout syndrome as measured by the Maslach Burnout Inventory (MBI). The research was conducted on a sample of nine developers working in the IT sector, who were divided into two groups according to project management methods – the agile Scrum methodology and the traditional waterfall approach. The aim of the study was to determine whether the implementation of the Scrum method can contribute to reducing the risk of burnout and how individual personality traits correlate with selected dimensions of burnout syndrome. The results show that individuals with higher extraversion and conscientiousness show lower levels of emotional exhaustion and depersonalization, while honesty-humility and agreeableness have less influence on burnout syndrome. At the same time, the introduction of the Scrum methodology contributed to better work stress management and work organization in most cases. The results are limited by the small sample size, but they can provide valuable insights for further research as a pilot study
Multi-mode secure data communication for real-time robot arm control with Li-Fi technology
Full text linkThis work explores the secure data transmission approach to control a robotic arm using Li-Fi technology. Although Li-Fi offers built-in security by keeping the light within the walls of the environment, where it is used, leaks through windows are a concern. The proposed system addresses this concern by using a multi-mode approach with three options: without encryption, Rivest Cipher 4 (RC4) encryption, and Advanced Rivest Cipher 4 (ARC4) encryption. Users can choose the appropriate mode based on data sensitivity and processing constraints. The system transmits the movement commands to the robotic arm via a controller and transmitter. In used encryption modes, the received data is decrypted before instructing the robotic arm to perform the designated action. This secure Li-Fi system offers a promising solution for reliable and secure communication in industrial environments, addressing the limitations of traditional RF communication and improving data security