Influence of ball material on the resulting fatigue life of thermal sprayed HVOF coatings in dynamic impact testing
Duliškovič, J.; Daniel, Josef; Houdková, Š.
2024 - English Dynamic impact wear, i.e. contact between two components in the presence of high cyclic local loads, is a challenging failure mode that occurs in many mechanical applications. Many previous studies have confirmed that dynamic impact testing is suitable for evaluating the contact fatigue of thermal sprayed coatings. However, the effect of the test parameters on the resulting lifetime is unclear. The aim of this study describes the effect of the ball material used in the dynamic impact test on the resulting fatigue life of the HVOF thermal sprayed coating. Three test balls made of WC/Co alloy, Si3N4 silicon nitride and 440 C steel were chosen for this study. Dynamic impaction testing was carried out on the Cr3C2-NiCr coating, which was sprayed by HVOF on a 1.2376 high-speed steel substrate. The impact lifetime was described by the number of critical impacts, i.e. the number of impacts before coating fatigue occurs. Furthermore, the depth and volume of impact craters were measured. Using scanning electron microscopy (SEM), the surface of the impacts as well as the microstructure of the coating on the cross-section in the region of the impacts were observed. Furthermore, the mechanism of crack propagation in the coating and the microstructure of the indentor were investigated. Keywords: dynamic impact test; HVOF; Cr3C2-NiCr; fatigue Available at various institutes of the ASCR Influence of ball material on the resulting fatigue life of thermal sprayed HVOF coatings in dynamic impact testing

Dynamic impact wear, i.e. contact between two components in the presence of high cyclic local loads, is a challenging failure mode that occurs in many mechanical applications. Many previous studies ...

Duliškovič, J.; Daniel, Josef; Houdková, Š.
Ústav přístrojové techniky, 2024

14th International Bordetella Symposium
Šebo, Peter
2024 - English We shall discuss the latest research achievements in the Bordatella/pertussis filed and how to tackle the challenge of current pertussis resurgence. We will assess what needs to be done to overcome the limitations of current acellular pertussis vaccines in order to curb the resurgence and transmission of whoopong cough. Keywords: bordetella; petrussis; vaccine Available in digital repository of the ASCR 14th International Bordetella Symposium

We shall discuss the latest research achievements in the Bordatella/pertussis filed and how to tackle the challenge of current pertussis resurgence. We will assess what needs to be done to overcome ...

Šebo, Peter
Mikrobiologický ústav, 2024

Forced migration and crime: evidence from the 2014 immigration wave to Russia
Shcherbov, Arsenii
2024 - English Recent years have spurred significant migration movements, underscoring the need to understand their impacts. This study explores a widely-debated correlation between crime and migration. Specifically, I investigate the 2014 migration wave, studying the response of Russian crime rates to the influx of immigrants from Ukraine. I approximate local crime rates using court data on sentencing decisions and describe relevant migration flows with internet search activity. The application of the difference-in-differences method reveals positive effects for property crime sentencing and the heterogeneous response of violent crime sentencing. The findings of this study are policy-relevant and could prove beneficial in understanding and mitigating the effects of future migration waves. Keywords: crime; migration; Russia Fulltext is available at external website. Forced migration and crime: evidence from the 2014 immigration wave to Russia

Recent years have spurred significant migration movements, underscoring the need to understand their impacts. This study explores a widely-debated correlation between crime and migration. ...

Shcherbov, Arsenii
Národohospodářský ústav, 2024

Surfactant-free silver nanofluids as liquid systems with neuromorphic potential
Nikitin, D.; Biliak, K.; Lemke, J.; Protsak, M.; Pleskunov, P.; Tosca, M.; Ali-Ogly, S.; Červenková, V.; Adejube, B.; Bajtošová, L.; Černochová, Zulfiya; Prokeš, J.; Křivka, I.; Biederman, H.; Faupel, F.; Vahl, A.; Choukourov, A.
2024 - English Neuromorphic engineering is a rapidly developing branch of science that aims to implement the unique attributes of biological neural networks in artificial devices. Most neuromorphic devices are based on the resistive switching effect, which involves changing the device’s conductivity in response to an external electric field. For instance, percolating nanoparticle (NP) networks produced by gas aggregation cluster sources (GAS) show collective spiking behavior in conductivity reminiscent of brain-like dynamics. Nevertheless, the problem of dynamic spatial reconfiguration in solid-state neuromorphic systems remains unsolved. Herein, novel nanofluids with resistive switching properties are proposed as neuromorphic media. They are produced by depositing silver NPs from GAS into vacuum-compatible liquids (paraffin, silicon oil, and PEG) without the use of surfactants or other chemicals. When the electric field is applied between two electrodes, the migration of NPs toward biased electrode is detected in all liquids. The electrophoretic nature of the NP movement was proved by means of ζ-potential measurements. Such movement led to the self-assembly of NPs in conductive paths connecting the electrodes and, as a result, to resistive switching. The electrical response was strongly dependent on the dielectric constant of the base liquid. The Ag-PEG nanofluid demonstrated the best switching performance reproducible during several tens of current-voltage cycles. The growth of flexible and reconfigurable conductive filaments in nanofluids makes them suitable media for potential realization of 3D neural networks. Keywords: nanofluid; gas aggregation cluster source; ζ-potential, electrophoresis Available at various institutes of the ASCR Surfactant-free silver nanofluids as liquid systems with neuromorphic potential

Neuromorphic engineering is a rapidly developing branch of science that aims to implement the unique attributes of biological neural networks in artificial devices. Most neuromorphic devices are based ...

Nikitin, D.; Biliak, K.; Lemke, J.; Protsak, M.; Pleskunov, P.; Tosca, M.; Ali-Ogly, S.; Červenková, V.; Adejube, B.; Bajtošová, L.; Černochová, Zulfiya; Prokeš, J.; Křivka, I.; Biederman, H.; Faupel, F.; Vahl, A.; Choukourov, A.
Ústav makromolekulární chemie, 2024

QUANTUM-MECHANICAL STUDY OF INTERNAL STRUCTURAL TRANSFORMATIONS IN Pb-SUPERSATURATED Pb-Sn ALLOYS
Friák, Martin; Čípek, Petr; Pavlů, J.; Roupcová, Pavla; Miháliková, Ivana; Msallamová, Š.; Michalcová, A.
2024 - English Motivated by a decades-long controversy related to the crystal structure of Pb-supersaturated solid solutions of Pb in Sn, we have performed a quantum-mechanical study of these materials. Focusing on both body-centred-tetragonal beta-Sn and simple-hexagonal gamma-Sn structures, we have computed properties of two alloys with the chemical composition Pb5Sn11, i.e. 31.25 at. % Pb, which is close to the composition of the experimentally found alloy (30 at. % Pb). The 16-atom computational supercells were designed as multiples of the elemental beta- and gamma-Sn unit cells, where the Pb atoms were distributed according to the special quasi-random structure (SQS) concept. Full structural relaxations of both beta- and gamma-phase-based alloys resulted in very significant re-arrangements into structures which do not exhibit any apparent structural features typical for the original alloys, and are, therefore, difficult to classify. The formation energies of the beta- and gamma-phase-originating equilibrium phases are 50 meV/atom and 53 meV/atom, respectively. Therefore, they are not stable with respect to the decomposition into the elemental lead and tin. Moreover, our calculations of elastic constants of both phases revealed that they are close to mechanical instability. Our results indicate that the studied Pb-supersaturated Pb-Sn solid solutions may be prone to structural instability, transformations into different phases and decomposition. Our findings may contribute into the identification of the reason why the subsequent experimental studies did not reproduce the initial published data. Keywords: tin; crystal; Pb-Sn alloys; stability; supersaturation; quantum-mechanical calculations Available at various institutes of the ASCR QUANTUM-MECHANICAL STUDY OF INTERNAL STRUCTURAL TRANSFORMATIONS IN Pb-SUPERSATURATED Pb-Sn ALLOYS

Motivated by a decades-long controversy related to the crystal structure of Pb-supersaturated solid solutions of Pb in Sn, we have performed a quantum-mechanical study of these materials. Focusing on ...

Friák, Martin; Čípek, Petr; Pavlů, J.; Roupcová, Pavla; Miháliková, Ivana; Msallamová, Š.; Michalcová, A.
Ústav fyziky materiálů, 2024

IPC-IOPC 2024: Abstract book
Bek, Jiří; Votočková Frojdová, Jana
2024 - English Keywords: Palaeobotany; palynology; plants; spores Available at various institutes of the ASCR IPC-IOPC 2024: Abstract book

Bek, Jiří; Votočková Frojdová, Jana
Geologický ústav, 2024

Functional Tungsten-based thin films and their characterization
Košelová, Zuzana; Horáková, L.; Sobola, Dinara; Burda, Daniel; Knápek, Alexandr; Fohlerová, Z.
2024 - English Anodizing is a technique by which thin oxide layers can be formed on a surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten is still a common choice for cold field emitters in commercial microscopy applications. Its suitable quality can be further improved by thin film deposition. Not only the emission characteristic can be improved, but also the emitter operating time can be extended. Tungsten oxide is known for its excellent resistance to corrosion and chemical attack due to its stable crystal structure and strong chemical bonds between tungsten and oxygen atoms. Many techniques with different advantages and disadvantages have been used for this purpose. Anodization was chosen for this work because of the controllable uniform coverage of the material and its easy availability without the need for expensive complex equipment. The anodizing process involves applying an electrical potential to tungsten while it is immersed in an electrolyte solution. This creates a thin layer of tungsten oxide on the surface of the metal. The thickness and properties of the resulting oxide layer can be controlled by adjusting the anodization conditions, such as the electrolyte solution, voltage, and the duration of the process. In this work, H3PO4 was used as the electrolyte to test whether these tungsten oxide layers would be useful for electron emitters, for use in electron guns and other devices that require high-quality electron emitters. The properties were evaluated using appropriate techniques. In general, anodization of tungsten to form thin layers of tungsten oxide layers is a promising technique for producing high quality electron emitters. Keywords: cold-field emission; thin layer deposition; tungsten oxide; resonance enhanced tunneling; anodization Available at various institutes of the ASCR Functional Tungsten-based thin films and their characterization

Anodizing is a technique by which thin oxide layers can be formed on a surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten ...

Košelová, Zuzana; Horáková, L.; Sobola, Dinara; Burda, Daniel; Knápek, Alexandr; Fohlerová, Z.
Ústav přístrojové techniky, 2024

Winning culture, winning future: the effects of early-career success on long-run performance
Trestcov, Ivan; Rakhmetova, Aizhamal
2024 - English This paper investigates the influence of early-career environments on long-run performance. Utilizing quasi-randomness of the NBA Draft Lottery system, we isolate the impacts of initial team success, coaching experience, and the presence of a star player during a basketball player’s debut season. Our findings underscore the significant positive effects of early team wins and experienced coaches on future player performance. Surprisingly, playing alongside a star player in the first year does not show a strong influence. This study offers insights that extend beyond sports, emphasizing the lasting effects of early professional experience and mentorship on career trajectories. Keywords: early-career success; NBA draft lottery; long-term performance Fulltext is available at external website. Winning culture, winning future: the effects of early-career success on long-run performance

This paper investigates the influence of early-career environments on long-run performance. Utilizing quasi-randomness of the NBA Draft Lottery system, we isolate the impacts of initial team success, ...

Trestcov, Ivan; Rakhmetova, Aizhamal
Národohospodářský ústav, 2024

Brno lingvistické
Vykypěl, Bohumil
2024 - Czech Keywords: Moravia; personality; linguistics Available at various institutes of the ASCR Brno lingvistické

Vykypěl, Bohumil
Ústav pro jazyk český, 2024

František Martin Pelcel jako etymolog: výklady českých názvů měsíců v Pelcelově mluvnici
Vykypělová, Taťána
2024 - Czech Keywords: etymology Available at various institutes of the ASCR František Martin Pelcel jako etymolog: výklady českých názvů měsíců v Pelcelově mluvnici

Vykypělová, Taťána
Ústav pro jazyk český, 2024