2026-03-01
00:49 |
Pokročilá metodika návrhu železničních náprav pro zpřesnění stanovení zbytkové životnosti
Náhlík, Luboš ; Fajkoš, R. ; Pokorný, Pavel ; Dlhý, Pavol ; Hutař, Pavel ; Peter, O.
Metodika slouží jako pokročilý nástroj k výpočetnímu odhadu zbytkové únavové životnosti vlakových náprav. V současné době se vyrábí velké množství různých náprav vyrobených z různých materiálů s různou technologií zpracování, různých designů, provozovaných v různých podmínkách. Metodika dokáže zmíněné faktory zohlednit a určit jejich vliv na únavovou životnost a bezpečnost nápravy. Metodika reaguje na potřebu deklarovat únavovou životnost vlakových náprav při existenci drobné vady v nápravě, protože i přes vyspělost průmyslových technologií a defektoskopických metod nelze vyloučit výskyt drobné vady v nápravě vlivem její nedostatečné detekce při defektoskopické kontrole nebo vlivem vnějších faktorů při samotném provozu nápravy. Silnou stránkou vytvořené metodiky je zahrnutí zbytkových napětí (včetně způsobu jejich stanovení) do procedury odhadu zbytkové únavové životnosti nápravy. Toto představuje klíčový faktor zpřesnění odhadu, neboť u vysoce technologicky zpracovaných náprav představují zbytková napětí dominantní složku zatížení nápravy.
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2026-02-14
00:01 |
Hydride formation in chosen LaNiSn alloys
Král, Lubomír ; Zobač, Ondřej ; Ullattil, Sanjay Gopal ; Roupcová, Pavla ; Zym, M. ; Smetana, B. ; Smajlaj, M. ; Renz, F.
The hydrogen storage properties of ball-milled AB₅-type alloys containing La (a rare earth element) and Ni, Sn \nwere investigated in this study. The experimental alloys were prepared using a compact arc melter under a \nhigh-purity argon atmosphere (99.9999%). The influence of microstructure and phase composition on the \nhydrogen absorption and desorption behavior was examined. The addition of Sn to the LaNi₅ intermetallic \nsignificantly reduced the equilibrium pressure without decreasing the maximum hydrogen absorption capacity, \nup to a Sn content of 10 wt%. Furthermore, increasing the Sn content enhanced the hydrogen absorption rate \nand slightly stabilized the hydride phase H₆LaNi₅.
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2026-02-01
00:15 |
VÝZKUMNÁ ZPRÁVA ÚFM AV ČR ,V.V.I., SHRNUJÍCÍ ROZHODUJÍCÍ VÝSLEDKY ŘEŠENÍ DÍLČÍHO PROJEKTU TN02000018/008 V RÁMCI PROJEKTU TN02000018 NÁRODNÍ CENTRUM KOMPETENCE STROJÍRENSTVÍ V OBDOBÍ 2023-2025.\nSLITINY Zr1%Nb\n
Sklenička, Václav ; Kvapilová, Marie ; Král, Petr ; Dvořák, Jiří
Výzkumná zpráva ÚFM AV ČR, v.v.i. sumarizuje již dosažené výsledky řešení dílčího projektu TN02000018/008 v období 2023-2025, včetně jejich stručného popisu, grafických ilustracích a případné bibliografické dokumentace. Zpráva má zásadní význam pro spoluřešitele UJP PRAHA, a.s. s hlediska koordinace řešení dílčího projektu, zejména pro plánované vytvoření software k výpočtu creepové životnosti zirkoniových povlakových slitin. Zpráva má význam i pro kontrolu a hodnocení průběhu řešení projektu v ÚFM AV ČR. \n
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2026-02-01
00:15 |
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2026-02-01
00:15 |
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2026-02-01
00:15 |
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2025-12-16
16:40 |
NOISY QUANTUM COMPUTING OF ELECTRONIC STRUCTURE OF CRYSTALS
Vašina, Vojtěch ; Miháliková, Ivana ; Friák, Martin
Quantum computing is currently emerging as a useful paradigm for solving highly complex computational \nproblems. Current quantum computers are unfortunately too noisy to provide sufficient accuracy, and quantum\nclassical hybrid algorithms emerged as a solution. Variational Quantum Deflation (VQD) has gained significant \nattention for addressing challenges in quantum chemistry, material science, etc. VQDs typically use multiple \noptimization methods, and the correct choice of optimization method can significantly impact performance. In \nour study, we focused on the comparison of multiple optimization methods used in VQD when applied to the \nelectronic structure of crystals. The quantum part of VQD ran on a classical simulator with imported noise \nmodels from real quantum computers from the IBM Quantum Platform.
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2025-12-16
16:40 |
Study of nanostructures coupled with a superconducting lead via the neural-network quantum states methods.\n
Kodrlová, J. ; Žonda, M. ; Friák, Martin
The Neural-Network Quantum States (NNQS) method is rapidly emerging as a powerful tool for investigating \nquantum many-body physics. By combining variational Monte Carlo techniques with neural network-based \nvariational functions, this approach leverages the remarkable advancements in deep learning achieved in \nrecent years. While substantial progress has been made in simulating magnetic systems on lattices, simple \nmolecules, and even continuous systems, the ab initio simulation of complex strongly correlated electron \nsystems continues to pose significant challenges. With the help of the generalized atomic limit (GAL) – a \nrecently developed model describing a system of quantum dots coupled to a superconducting lead – we \nattempt to show the efficiency and accuracy of NNQS, mainly the Restricted Boltzmann Machine, by comparing \nthe acquired results to other available methods such as exact diagonalization. The simultaneous study of the \nsystem’s properties such as the energy spectrum and quantum phase transitions could bring advancements \nin electronics, sensors or the design of high-quality qubits used in quantum computers.
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2025-12-16
16:40 |
COMBINED EXPERIMENTAL AND THEORETICAL STUDY OF STABILITY OF La2Ni7
Zobač, Ondřej ; Friák, Martin ; Kovaříková Oweis, Sabina ; Pavlů, Jana ; Holec, D. ; Zlá, S. ; Kawuloková, M. ; Smetana, B. ; Watson, A.
The La-Ni binary system, and in particular the LaNi5 binary intermetallic phase, has been intensively studied \nin recent decades, especially as a promising hydrogen storage material. Knowledge of phase equilibria is very \nimportant for the possible optimization of material properties. This work is focused on the study of the \nthermodynamic properties of the La2Ni7 phase, which occurs in phase equilibrium with the LaNi5 phase and \ncan therefore influence the capacity and dynamics of these hydrogen storage materials in real materials. The \nalloy samples were prepared from pure elements using a gravity melting furnace in an inert Ar-6N atmosphere. \nThe overall composition and chemical composition of the phases were analyzed by SEM-EDX. The crystal \nstructure of the phases was confirmed by powder XRD. Our experiments were complemented by quantum\nmechanical calculations implementing the density functional theory (DFT) within the generalized gradient \napproximation (GGA) to determine the ground-state structural, electronic, thermodynamic, and elastic \nproperties of La2Ni7. A computational unit cell of La2Ni7 contains 36 atoms and has a strongly anisotropic \nshape. The computed results obtained for static lattices indicate that La2Ni7 is thermodynamically stable with \nrespect to the decomposition into elemental end members. The stress-strain method was used to address the \nmechanical stability by computing a full tensor of the second-order elastic constants and La2Ni7 has been found \nto be mechanically stable.
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2025-12-16
16:40 |
QUANTUM-MECHANICAL STUDY OF HLaNiSn INTERMETALLIC PHASE
Kovaříková Oweis, Sabina ; Pavlů, Jana ; Zobač, Ondřej ; Kawuloková, M. ; Zlá, S. ; Friák, Martin ; Smetana, B.
Energy storage remains a central challenge in realizing a complete transition to renewable energy sources, \nwith hydrogen storage emerging as a particularly promising solution. Metal hydrides offer a viable platform due \nto their high volumetric density of hydrogen and safety. However, further research is needed to identify \ncompositions that combine high hydrogen capacity with fast hydrogen uptake and release at reasonable \noperating temperatures. The La-Ni-Sn system exhibits notable structural and electronic properties, making it \na candidate for hydrogen storage and energy applications. The binary compound LaNi₅ and the ternary phase \nLaNiSn are known to form multiple hydrides, many of which remain poorly characterized. Using a quantum\nmechanical approach, this study focuses on the stoichiometric H₁LaNiSn phase, namely its stability, \nequilibrium properties, phonons, electronic structure and hydrogen absorption behavior. These results offer \ncritical insight into the thermodynamic stability and electronic structure of H₁LaNiSn, enhancing the \nunderstanding of its potential in hydrogen storage applications. We determined the ground-state properties, \nincluding the lattice parameters, the electronic density of states and the phonon band structure. Additionally, \nwe evaluated the temperature dependencies of key thermodynamic quantities (free energy, entropy and heat \ncapacity) within the harmonic approximation. Importantly, the H₁LaNiSn phase was found to be mechanically \nstable, supporting its viability as a hydrogen storage material.
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