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Medium voltage direct current interruption by a high velocity flow of dielectric liquids
Get PDFThe increasing availability of self-sufficient MVDC systems necessitates innovative MVDC switching solutions. Direct current interruption is achieved by inducing a current zero and preventing re-ignition. In addition to complex resonant networks that create oscillating currents with natural current zeros, another method uses a switching device that generates an arc voltage higher than the grid voltage for current limiting. Conventional gas or vacuum interrupters fail at higher voltages. This paper builds upon previous investigations on the contact separation in dielectric liquids for MVDC interruption. A low inertia mass contact mechanism is used and measurements are carried out for 50 A to 250 A direct current interruption at 10 kV. The study investigates the switching performance of synthetic ester and synthetic oil
Evaluation and modelling of the buckling behaviour of SRC composite columns under simultaneous off-axis and lateral loading
Get PDFIn this paper, steel-reinforced composite columns (SRCs) with IPE profiles, commonly used in Iran, have been investigated under lateral and axial loads. The variable parameters in this study are the amount of axial load eccentricity and changes in the ratio of the applied axial load to the lateral load. For this purpose, ABAQUS finite element software has been used. Based on the results, it was observed that as the percentage of eccentricity increased (load to lateral load ratio of 0.5), the buckling load of the composite column has decreased. By increasing the eccentricity from 0 % to 100 %, the buckling load reduction rate for the first mode of the column is equal to 3 % and the amount of critical load reduction in this condition is equal to 21 %. It was also observed that the buckling load of the composite column decreased as the percentage of eccentricity increased (load to lateral load ratio of 1), by increasing the eccentricity from 0% to 100 %, the buckling load reduction rate for the first mode of the column is equal to 4 % and the amount of critical load reduction in this condition is equal to 20 %
Conceptual design of a space nuclear fast reactor
Get PDFThis paper finds an improved combination of fuel, enrichment, and coolant for a fast reactor suitable for nuclear electric propulsion. The study simulates an infinite lattice considering two enrichments, with fuel options (ceramics and metal alloys), and with alkali metals as a coolant. Following this, a simplified core model is developed to ensure long-term reactivity control and safe shutdown at a thermal power of 10 MW for 10 years, focusing on minimising size and mass. The findings indicate two viable fuel and coolant combinations, depending on temperature requirements. For temperatures up to 1 100 K, the U-10Zr and Na combination is preferable due to its smaller critical dimensions and reduced mass. For higher temperatures, up to 1 550 K, the UN and Li combination is suitable. The choice of operating temperature is critical, as heat rejection in space depends only on radiation, covered by the Stefan-Boltzmann law, where heat flux depends on the fourth power of the temperature
Young Transportation Engineers Conference 2024
No full textThe Young Transportation Engineers Conference 2024 was held in Prague, in November 28, 2024.
The conference is focused on the presentation of scientific and research work of PhD students and young scientists not only from Czech Technical University in Prague, Faculty of Transportation Sciences. The main objectives of the conference are to present the results of scientific and research activities of PhD students, to raise awareness of ongoing or upcoming research projects within the Faculty of Transportation Sciences and to provide an opportunity to gain experience in presenting in front of a professionally educated audience for newl PhD students. The conference is thus an opportunity to establish new or increase existing personal and professional contacts and a meeting place for doctoral students, practitioners and faculty staff.
The conference key topics were following:
transport infrastructure,
transport and vehicle safety,
logistics,
transport economics and management,
information and telecommunication technologies in transport,
air transport operations and management.
Scientific comittee:Tomáš TichýLuboš NouzovskýMartin JacuraTomáš DoktorPetr KumpoštStanislav NovotnýZdeněk SvatýMichal Belák
Local organizing comittee:Petr RichterTomáš KohoutMichal DrábekJiří RůžičkaJan KruntorádPetr HadJosef SvobodaVeronika DrechslerováPetr Miloslav Kubíska
Guarantor of the peer review process:Petr Richter
Guarantor of the language editing:Tomáš Kohou
Impact of temperature on tyre hardness
Get PDFThis article deals with the dependence of tyre hardness on temperature. In this study, more than 1 800 temperature-dependent hardness values were measured for 5 samples of summer tyres from different manufacturers and different ages. Using regression analysis, curve equations were determined for each sample. Furthermore, an average curve was determined, which was then applied to the measured values and the error generated by using this average curve was investigated. From the results it is clear that all samples show a polynomial function with a 2nd order polynomial for the temperature range −10 °C to 65 °C. The error of using the average curve reaches values up to 11 % of the average value of the measured hardness of the sample. The lowest error is 2 % of the mean value of the measured hardness of the sample, which corresponds to approximately 1 Shore A. The suitability of using an average curve application depends on the desired output and the required accuracy
Impact of illuminated advertising devices on road traffic safety
Get PDFThis article examines the impact of illuminated advertising devices on road safety in urban environments. By measuring the light parameters of advertising displays and comparing them to public lighting, the study analyzes how the brightness and dynamic elements of these devices affect driver attention, reaction times, and overall ability to perceive traffic situations. The findings indicate that high-brightness, dynamic advertising displays can significantly increase the risk of traffic accidents, especially during nighttime driving. The study also highlights the insufficiency of current legislative regulations, which primarily focus on public lighting systems, and suggests that more comprehensive guidelines should be established to address the specific characteristics of illuminated advertising devices. Two measurement methods were employed: horizontal illumination of roadways and a gradient luminance analysis, both of which provided insights into the disruptive influence of these devices on road safety. The article concludes by recommending specific legislative changes, improved regulation of advertising installations, and the development of further research to better understand the long-term effects of these devices on accident rates. By addressing these challenges, this research aims to contribute to safer road environments and minimize the negative impact of illuminated advertisements on traffic flow and driver behavior
Augmented Reality as a 3D Land Cover Visualisation Technique
Get PDFAugmented Reality (AR) is an established technique for both 2D and 3D visualisations in several fields such as sports, entertainment or culture (museums). However, in cartography or in GIS, it is still considered as a minor niche visualisation technique. Therefore, the aim of this paper is to present AR as a 3D visualisation method for land cover development. The presented output is a part of a mobile application for Android. Land cover GIS data obtained from historical and contemporary large-scale maps are processed using City Engine, resulting in the creation of several 3D models viewed via augmented reality. Procedural modelling in City Engine is used to visualise 3D land cover data such as buildings or forests (including coniferous, deciduous and mixed). Other land cover types (e.g. arable land, grassland or roads) are displayed as 2D textures. In this way, the user can experience an innovative perspective of land cover changes over time in a study area of Chudenice (a village in the southwest of Czechia). The 3D land cover maps are presented in two time periods (1837 and 2023). The 3D models are accompanied by a map legend, scale, north arrow and title, so that the user can keep track of the current model without the need for additional essential map information
Insights from the 18th INTEGRAL/BART Workshop & AHEAD Summer School
No full textThe 18th INTEGRAL/BART Workshop, held from 13th to 17th May 2024, was a milestone event that contributed significantly to the advancement of high-energy astrophysics and CubeSat technology. This year\u27s event was uniquely integrated with the AHEAD Summer School, fostering an enriched environment for knowledge exchange and collaboration.
This year the workshop attracted 49 participants from six European countries and was kindly hosted and supported by the grammar school (Gymnázium Cheb) and the secondary school (Integrovaná střední škola Cheb) in Cheb. The diverse programme covered a wide range of topics, including gamma-ray bursts, black holes, active galactic nuclei and gravitational waves. Discussions covered detection methods for X-ray emissions, the design and implementation of novel detectors and payloads, and missions ranging from balloon experiments and small satellite ventures to large-scale international collaborations.
Thanks to the funding from the European Union’s Horizon 2020 programme under the AHEAD2020 project (Grant Agreement No. 871158), the event was enriched by the integration of the AHEAD Summer School. This collaboration has particularly increased the participation of international students and young researchers, giving them the opportunity to present their projects and to interact directly with experts in the field, as well as to attend insightful lectures given by nine invited speakers, including:
Rosa Poggiani, University of Pisa, Italy
Dorota Rosinska, University of Warsaw, Poland
András Pál, Konkoly Observatory, Hungary
Klaus Schilling, Zentrum für Telematik, Germany
Martin Jelinek, Astronomical Institute of the Czech Academy of Sciences, Czech Republic
Filip Münz, Masaryk University, Faculty of Science, Czech Republic
Jiří Svoboda, Astronomical Institute of the Czech Academy of Sciences, Czech Republic
Enrico Bozzo, University of Geneva, Switzerland
Karl Mannheim, University of Würzburg, Germany
These experts provided invaluable insights, bridging theoretical concepts with practical demonstrations, such as those presented - for example, the THESEUS mission.
The 18th INTEGRAL/BART Workshop and AHEAD Summer School were held under the auspices of the Astronomical Institute of the Czech Academy of Sciences and the Czech Technical University in Prague. The success of this workshop was underpinned by the generous support of the key partner Rigaku Innovative Technologies Europe s.r.o. Additional support was provided by Huld and GCI.
We are pleased to present this special issue, which contains peer-reviewed papers submitted by participants of the workshop and summer school. The diversity of the contributions underscores the wide range of topics discussed and highlights the role of the workshop in fostering international collaboration in space science.
We would like to sincerely thank all speakers, participants, and partners for their commitment, dedication and enthusiasm. We look forward to continued success and fruitful collaboration in future endeavours
Quantum graphs featuring unusual self-adjoint extensions
Get PDFWe present an example of a simple quantum graph with “vertices at infinity”, which appear due a strongly attractive potential making the spectral problem quantum-mechanically incomplete. We construct the appropriate self-adjoint extensions of the formal graph Hamiltonian, and derive their spectral properties
The scientific legacy of Miloslav Havlíček
Get PDFWe review the main research achievements of Miloslav Havl´ıˇcek in algebraic methods in Quantum Theory, his extensive work on realisations of Lie algebras and superalgebras and their representation theory, quantum groups and differential equations