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Comparison between the Wilhelmy surface tension measurement method and the pendant drop shape analysis method
Get PDFSurface tension plays an essential role in various laboratory and industrial processes. The Fluid Metrology Laboratory (Laflu) of the National Institute of Metrology, Quality and Technology (Inmetro) uses the Wilhelmy and DuNoüy methods and has a tensiometer for determining surface tension by the drop shape analysis method in use. One way to ensure the reliability of surface tension measurement results is to compare the methods used. A comparison was made between the Wilhelmy method and the drop shape analysis method. The comparison involved measurements of the surface tension of these liquids: bidistilled water, n-dodecane, and Perfluorocarbon (FC-40), and used the calculation of the Normalized Error (EN), presenting results according to acompatible criterion. Analysing the uncertainties involved, the contribution of the uncertainty of the regression used in the correction of the tensiometer indication was the most relevant
FOREWORD: Šimáně 2024 – International Student Conference on Nuclear Engineering
No full textNuclear-related sciences and technology have a long and rich history within the Czechoslovakia. Even though the Czech Republic and Slovakia have been separated since 1993, wide cooperation on different levels including education and research still exists. In order to support cooperation and good relations between Czech and Slovak students in nuclear engineering and related disciplines, the Department of Nuclear Reactors organizes annually a student conference on nuclear engineering - Šimáně. Students mainly from Czech and Slovakian nuclear institutes are invited to present their research and share their knowledge. Participants from other foreign institutes are welcomed as well.
The conference is named after professor Šimáně, who graduated at the Dr. Edvard Beneš Technical University in Brno. During his early career, he had the opportunity to work with Fréderic Joliot-Curie at College de France. Later, he significantly contributed to the foundation of the nuclear science, industry and education in the Czechoslovakia. He became the first employee of the Institute of Nuclear Physics at the Czechoslovakian Academy of Science, later he became the first director of the Nuclear Research Institute in Řež. Professor Šimáně was well established even on the international level. He was a director at the Joint Institute of Nuclear Research in Dubna or a division director at the International Agency for Atomic Energy. His work was also significantly connected with Faculty of Nuclear Sciences, CTU in Prague where he acted as Dean from 1967 to 1972.
The main objective of the conference is to provide an opportunity for BSc., MSc. and Ph.D. students of nuclear-oriented study programmes to publish and present their scientific results achieved during their university studies. Furthermore, it should give the participants experience in the field of presenting their own research, writing scientific papers and also broaden their knowledge throughout the related fields and to remind them rich Czechoslovakian history in nuclear fields by inviting experienced experts.
The organizing committee would like to thank all participants for their contributions and also to the CTU in Prague for funding this student conference. The committee also hopes that the work achieved and presented will fulfill the heritage of professor Čestmír Šimáně in current as well as future conferences.
Date: June 18 - 19, 2024Venue: Faculty of Mathematics and Physics, Charles University - room T1; V Holešovičkách 747/2, 180 00 Praha 8URL: https://lenochod.fjfi.cvut.cz/simane/
Organized by:Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering
Guest editors:Milan ŠtefánikMartin CesnekPavel SukMartin Ševeček
Scientific committee:Milan ŠtefánikMartin CesnekPavel SukMartin Ševeček
Local organizing committee:Martin ŠevečekPavel SukJán KozicDaniel VlčekMatěj Šikl
Guarantor of the peer review process: Milan Štefánik
Guarantor of language editing: Martin Cesne
Modeling of LTO approach time-in-mode values in MATLAB using the generalized extreme value distribution
Get PDFThe landing and take-off (LTO) cycle, which is used to calculate emissions of aircraft below 3 000 feet, consists of four operating modes, each of which has a standardized time duration or time-in-mode (TIM). In this paper, we model TIM values of the Approach operating mode for two aircraft types (Boeing 737-800 and Airbus A320) arriving on Runway 24 at Prague Václav Havel Airport using the generalized extreme value (GEV) distribution. Predictions of the TIM values are made using the models, and the performance of each model is evaluated. The results show that for both aircraft types, the predicted TIM values lead to total emissions estimates deviating on average by 1 to 2 percent from estimates made using the real TIM values, showing good model performance. The presented approach is also shown to be beneficial in comparison with using the standard TIM value (240 s), highlighting the feasibility of further research in this area as one of the avenues of improving the LTO cycle methodology
Causes of battery fires in railway vehicles and challenges of extinguishing
Get PDFThe aim of this article is to introduce an issue that has not yet been addressed in our region – the fire hazards of BEMU units. The methodology of the Fire Rescue Service of the Czech Republic vehicles was used to establish the basic procedure for extinguishing batteries in railway passenger coaches
Project VALVERDE – validation and verification of computational tools to describe corium spill to improve deterministic analyses of severe accidents
Get PDFThe VALVERDE project focuses on the investigation of the melt flow characteristics of the core melt simulant material and the subsequent development of suitable procedures and methodologies for the description of the melt flow of the simulant in a defined geometry. The main aim is to develop an experimental setup in which the melt spreading of the corium will be performed using suitable simulants. The current version of the experimental setup and the CFD simulations of the spreading of the reactor core melt simulant will be presented
Adaptation of SUBCAL subchannel code for square-lattice rod bundles using PSBT benchmark
Get PDFSubchannel analysis is a commonly used approach for simulating heat transfer and coolant flow in nuclear reactor cores. This paper presents the adaptation of the SUBCAL computational code, originally developed for reactors with a triangular lattice, to configurations with a square lattice. Geometry-dependent computational relations, models and correlations were identified and analyzed based on the research. The selected relations for the square lattice were implemented into the SUBCAL code, and the computational model was optimized for the recalculation of the PSBT benchmark. Verification of the proposed changes was carried out by evaluating the results of the benchmark recalculation against experimental data and through code-to-code comparisons with results from other participating organizations. These modifications and the recalculated PSBT benchmark represent the starting point for validating the SUBCAL code for this type of analysis
Study on the mechanical properties of large diameter and long distance reinforced concrete pipe jacking in weak strata
Get PDF In order to study the mechanical properties of large diameter and long distance reinforced concrete pipe during jacking in weak strata, field monitoring of jacking force, contact pressure, slurry pressure and pipe strain was carried out on based on the Tangxun Lake sewage pipe jacking project in Wuhan. The results showed that during the jacking process, the axial stress of the pipe was mainly compressive stress, and there are some areas of stress concentration. As the jacking distance increases, the axial stress of the pipe first increases and then remains relatively stable. The hoop strain of pipe is mainly compressive strain, which is mainly affected by earth pressure and axis deviation. Under the slurry pressure, the hoop strain at the top and bottom of the pipe increases, while the left and right sides decrease. The bottom of the pipe is in contact with the soil, and the contact pressure is the largest, while the left and right sides are in full or partial contact with the slurry. The crown of the pipe is in contact with the slurry and the contact pressure is affected by the mud pressure. In addition, the contact pressure is not directly related to the jacking distance.
Received: 18.12.2023
Received in revised form: 23.9.2024
Accepted: 13.8.202
High performance concrete with recycled concrete aggregates: effect of production technology on mechanical properties and shrinkage
Get PDFThe research deals with the possibility of using fine recycled concrete aggregates in high performance (HPC) concrete. The main objectives include the verification of mechanical properties, the effect of shrinkage and production technology – method of water dosage. The partial goal of the research task is to verify the potential of internal curing based on the use of fine recycled concrete aggregates. The experimental program gives an account of experiments with concrete mixtures of varying content of recycled material and water. Compressive and bending strength of the concretes were measured. All samples were subjected to shrinkage measurements in time interval 1 to 28 days. The experiments evidenced that used recycled concrete aggregates affect strengths and also relative deformation of concrete.
Received: 4.6.2024
Received in revised form: 18.3.2025
Accepted: 30.8.202
Flexural Performance of Concrete T-Beams Reinforced with UHPC: Experimental and Theoretical Analysis
Get PDFThis study investigates the flexural performance of concrete T-beams reinforced with thin layers of ultra-high-performance concrete (UHPC) through a combination of experimental testing and theoretical analysis. Three T-beam specimens with varying UHPC thicknesses were fabricated and subjected to loading to evaluate their failure modes, load-displacement responses, and strain distributions. The experimental results show that the incorporation of UHPC reinforcing-layers significantly enhances the flexural performance of the T-beams. As the layer thickness increased from 0 mm to 50 mm, the flexural stiffness of the T-beams increased by 167.8%, the initial cracking load of the T-beams rose by 241.0%, and the ultimate flexural resistance of the T-beams improved by 40.8%. Based on these findings, a predictive model for the flexural resistance of UHPC-reinforced T-beams was developed. The model\u27s predictions showed a relative error of less than 10% when compared to experimental results, confirming its reliability and adequate safety margin. These findings provide valuable insights for the design of deficient concrete T-beams flexurally strengthened using UHPC thin layers.
Received: 03.02.2025
Received in revised form: 11.09.2025
Accepted: 02.12.202
Progress versus tradition – traditional craftsmanship and attempts at industrial tower clock production in the Czech lands in the 19th century
Get PDFWith the growing need for accurate timekeeping, the demand for clocks on public buildings increased in the 19th century. The only way to meet the demand, however, was to produce individual items by hand. Due to the conservative and protectionist influence of the clockmaker’s guilds and the absence of a specialised clockmaking education, technical innovations from abroad were slow to be adopted. Despite this, there are significant innovative watchmaking personalities, such as Josef Božek at the beginning and Václav Krečmer in the second half of the century. There were also several attempts at factory mass production of tower clocks, which, however, were not developed until the 1880s by the company of Ludvík Hainz