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Dependence of mechanical and thermal properties on the composition of lightweight gypsum composites
Get PDFOne of the ways to use the treated gypsum waste is in gypsum mixtures for the production of gypsum blocks. Gypsum blocks can be used in standard interior as well as exterior applications and are made of gypsum, water, PP microfibres and are lightened with foam, which is created from a foaming additive and water. Above all, the amount of foam significantly influences the bulk density of the resulting material, and the bulk density then has a major influence on the mechanical and thermal properties. The use of PP microfibres had a positive effect on the overall stability of the foamed structure, which resulted in an increase in compressive strength while maintaining good thermal insulation properties
Contribution of the Liquid Phase on Direct Current Interruption by a Forced Fluid Flow
Get PDFThe rising amount of medium voltage direct-current systems requires novel solutions for DC switching. The interruption of direct-currents is accomplished by enforcing a current zero, which can only be achieved when the arc voltage of the switching device raises above the grid voltage. On way to achieve this, is to force the arc into narrow channels by an imposed fluid flow. The increasing arc voltage than not only depends on increased cooling due to phase change but also on the mechanical elongation of the arc enforced by the fluid stream. Hence, the interaction of the fluid flow and the arc should be studied in more detail. For this, the switching characteristic of selected dielectric liquids are examined. Using a self developed setup, direct-current interruptions at a constant voltage of 10kV were carried out. Our results indicate, that the process of enforcing a current decay strongly depends on the mechanical resistance of the liquids to deform under the pressure of the electric arc
Research on the Protective Effect of Twin-groyne Arrangement on Riverbank
Get PDFA curved channel with intersecting streams can be easily scoured by incoming flow, and the concave bank is badly damaged. This research showed that the twin-groyne could effectively adjust and optimize the flow velocity distribution, change the shape of the free water surface of the bend, prevent erosion, and promote silting on the concave bank, and it could provide a scouring and silting effect on the convex bank. When the spacing of twin-groyne was increased to more than four times the body length of the single-groyne (spur dike), the protective effect on the concave bank was weakened, and the scouring and silting effect of the convex bank was reduced. Excessive spacing of the twin-groyne could cause local erosion damage to the concave bank. When the distance exceeded the theoretical optimum, it was equivalent to the effect of single-groyne. With the increase in the submergence degree, the velocity of the concave bank decreased first and then increased, while the velocity of convex bank decreased continuously. The protective effect of a non-submerged twin-groyne with a dam spacing of four times the body length of the single-groyne was better than that of other conditions, and it is recommended to be used in practice
ANALYSIS AND OPTIMIZATION OF WIND RESISTANCE PARAMETERS FOR LATTICE-TYPE HIGH-MODULUS SUPPORTS BASED ON THE OPTIMAL CRITERIA METHOD
Get PDFLattice high-molded support can generally be used for cast-in-place support for bridges, but for more than 50 meters of lattice high support, due to the wind, load and other factors, due to the support length and slenderness of the relatively large, relatively light and flexible structure and other characteristics of the role of the wind load is very sensitive. When the lattice high-molded stent construction is used in the typhoon area, it is easy to be damaged by the typhoon, and the structural design of the lattice high-molded stent and the construction of that technology are facing great challenges. In this paper, based on the new construction of a special bridge in Fujian, finite element analysis of four-legged and six-legged lattice bracing is carried out by ANSYS, and the effects of steel pipe diameter, number of columns, longitudinal and transversal spacing of bracing, and diagonal bracing structural parameters on structural performance are analyzed by using the coefficients of buckling stability and the coefficients of critical loading. The results of the study show that the main design variable for displacement sensitivity is the diameter of vertical rod; the main design variable for stress sensitivity is the diameter of diagonal rod; the main design variable for overall stability sensitivity is the diameter of diagonal rod; and the main design variable for overall stability sensitivity of total volume is the diameter of diagonal rod. And the optimal wind resistance parameters are: 4 lattice high-braced columns are selected, the section length should be controlled within 15m, and the total height should not be more than 70m, and the spacing of the columns is controlled between 7m and 8m. This study proposes a set of optimized design process method for wind-resistant lattice structure under the constraints of stiffness, strength and critical load factor, which improves the economy and ensures the reasonableness of the design, and can be used for the design of high-modular lattice bracket in typhoon area
Šimáně 2023 – 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 12 - 13, 2023Venue: Prague, Czech RepublicURL: http://simane.fjfi.cvut.cz
Organized by:Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering
Guest editor:Martin Ševeček
Scientific committee:Milan ŠtefánikMartin Ševeček
Local organizing committee:Martin CesnekOndřej NovákPavel Suk
Guarantor of the peer review process: Milan Štefánik
Guarantor of language editing: Ondřej Nová
Evaluation of ATLHAMC12 subchannel code for total loss of flow scenario
Get PDFThe ALTHAMC12 subchannel code is a new subchannel code developed by the ALVEL company. The code is intended for DNBR safety analyses of the Czech nuclear power plants. In order to validate the code, a code to code comparison with THALES and VIPRE-01 is provided in this work. The reactor core model was developed and set of initial and boundary conditions has been adopted from a reference study. The comparison is done for steady state nominal parameters and Total Loss of Flow (TLOF) type of accident. The results show that ALTHAMC12 provides a good agreement with the reference codes in the terms of MDNBR value and its positions in the reactor core
Simulation of the compression test of the Zr1Nb fuel cladding ring
Get PDFFuel cladding is a first protective barrier against the loss of fission products that must withstand extreme conditions, from normal operation to final and interim dry storage. This hostile environment results in mechanical and microstructural damage of cladding caused by different stress levels, temperature, corrosion, hydrogen pick up and other degradation processes further enhanced by radiation. For this reason, the integrity of the cladding is a critical issue. The aim of this work is to simulate a ring compression test to evaluate the stress-strain behavior and hoop fracture properties of a zirconium-based alloy with niobium, which was chosen because it is widely used as fuel cladding in light water nuclear reactors
Quality improvement by application of a revised standard – feasibility studies on 2500 soundings
Get PDFCPT is a geotechnical investigation method that, depending on the geology, has been proved to be an essential tool to establish the Geotechnical Design Model. However, doubt has been raised about the quality of the data. Hence, the feasibility to use data from CPT to evaluate reliable parameters for the Geotechnical Design Model also needs investigation. Currently, the international standard EN ISO 22476-1 [1] is being revised, and the revised version will be published in winter 2022. It will include new requirements related to quality parameters such as zero stability, zero-shift, temperature, and pore pressure response. In addition, there will be updated requirements related to the calibration of the cone penetrometer. All this is to improve the quality of the CPT data, thereby increasing the reliability of parameters evaluated from CPT. This paper presents a feasibility study. It compares the zero-shift variation depending on the type of cone penetrometer, the operator, and the geology. More than 2 500 soundings from Sweden, Norway and Finland were the basis for this comparison. The results indicate that the data quality is strongly linked to the type of cone penetrometer, its calibration, and the management of the cone penetrometer in the field
SURFACE BIOCOMPATIBILITY OF POROUS TITANIUM STRUCTURES WITH STEM CELLS
Get PDFSuccessful tissue regeneration requires scaffolds with mechanical stability or biodegradability, surface roughness, and porosity to provide a suitable microenvironment for sufficient cell interaction, migration, cell proliferation, and differentiation. This study features the design, fabrication, and biocompatibility testing of Ti-6Al-4V titanium alloy scaffolds. Cylindrical titanium samples were tested, where each sample had a porous structure with pore sizes of 0.4 mm, 0.8 mm, and 1.0 mm respectively, which were seeded with chorionic-derived mesenchymal stem cells (CMSCs). The viability of the seeded CMSCs was evaluated using the MTT test. The aim of the study was to evaluate the cytotoxic effect and biocompatibility of porous titanium scaffolds. CMSCs showed the highest viability, adhesion to surfaces, and good proliferation on samples with 0.4 mm pore size, on the other hand, the pore size of 1.0 mm showed relatively lowest compatibility with cells and their proliferation. However, the viability of cells on all tested sizes of porous titanium scaffolds showed sufficient viability for future use in regenerative medicine
Mechanical properties of basalt: a study on compressive loading at different strain rates using SHPB
Get PDFThis article focuses on the mechanical properties of basalt in compressive loading at different strain-rates. The study employs advanced instrumentation for the evaluation of the results in dynamic conditions, while standard uni-axial loading device is used for evaluation in quasi-static conditions. Basalt specimens were subjected to four different loading-rates from 200–600 s−1 on which the stress-strain dependence was evaluated together with DIC analysis of crack initiation and disintegration process. Understanding the mechanical properties of basalt can provide insights for engineers and designers in creating structures that are durable and able to withstand different loading conditions. The findings of this study can have implications for a wide range of industries, including aerospace, automotive, and construction, among others