Number of found documents: 16369
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Epidemiologické modely s agenty
Neruda, Roman
2023 - Czech
Tento příspěvek je jemným úvodem do problematiky agentních modelů a jejich aplikací v epidemiologickém modelování. Představíme agentní modely jednak z hlediska informatiky, jednak jako nástroj modelování v jiných vědních disciplínách. V příkladové studii ukážeme model s agenty a sociální sítí jejich kontaktů, který slouží pro simulaci vývoje epidemie a vlivu protiepidemických opatření. Available at various institutes of the ASCR
Epidemiologické modely s agenty

Tento příspěvek je jemným úvodem do problematiky agentních modelů a jejich aplikací v epidemiologickém modelování. Představíme agentní modely jednak z hlediska informatiky, jednak jako nástroj ...

Neruda, Roman
Ústav informatiky, 2023

MAD UFOs: Magnetically Arrested Discs with persistent Ultra-Fast Outflows
Suková, Petra; Zajaček, M.; Karas, Vladimír
2023 - English
We study an outflow that develops in the MAD state in 3D GRMHD simulations. We show that the outflow can be accelerated to\nrelativistic velocities and persist over the course of our simulation. We compare the properties of the outflow from MAD discs with those launched by orbiting secondary at close orbit. The main difference is that the orbiting body launches a more coherent, quasiperiodic ultrafast outflow at lower velocities (v < 0.5c) while the outflow launched in the MAD state (without the body) has a stochastic behaviour and has anapproximately flat velocity distribution between lower anf higher outflow velocities, 0.2c < v < 0.3c and v > 0.5c. Keywords: accretion discs; black holes; active galactic nuclei Fulltext is available at external website.
MAD UFOs: Magnetically Arrested Discs with persistent Ultra-Fast Outflows

We study an outflow that develops in the MAD state in 3D GRMHD simulations. We show that the outflow can be accelerated to\nrelativistic velocities and persist over the course of our simulation. We ...

Suková, Petra; Zajaček, M.; Karas, Vladimír
Astronomický ústav, 2023

Simulating particle-laden flows: from immersed boundaries towards model order reduction
Isoz, Martin; Kubíčková, Lucie; Kotouč Šourek, M.; Studeník, Ondřej; Kovárnová, A.
2023 - English
Particle-laden flow is prevalent both in nature and in industry. Its appearance ranges from the trans-port of riverbed sediments towards the magma flow, from the deposition of catalytic material inside particulate matter filters in automotive exhaust gas aftertreatment towards the slurry transport in dredging operations. In this contribution, we focus on the particle-resolved direct numerical simulation (PR-DNS) of the particle-laden flow. Such a simulation combines the standard Eulerian approach to computational fluid dynamics (CFD) with inclusion of particles via a variant of the immersed boundary method (IBM) and tracking of the particles movement using a discrete element method (DEM). Provided the used DEM allows for collisions of arbitrarily shaped particles, PR-DNS is based (almost) entirely on first principles, and as such it is a truly high-fidelity model. The downside of PR-DNS is its immense computational cost. In this work, we focus on three possibilities of alleviating the computational cost of PR-DNS: (i) replacing PR-DNS by PR-LES or PR-RANS, while the latter requires combining IBM with wall functions, (ii) improving efficiency of DEM contact solution via adaptively refined virtual mesh, and (iii) developing a method of model order reduction specifically tailored to PR-DNS of particle-laden flows. Keywords: particle-laden flow; CFD-DEM; arbitrarily-shaped particles; finite volume method Fulltext is available at external website.
Simulating particle-laden flows: from immersed boundaries towards model order reduction

Particle-laden flow is prevalent both in nature and in industry. Its appearance ranges from the trans-port of riverbed sediments towards the magma flow, from the deposition of catalytic material ...

Isoz, Martin; Kubíčková, Lucie; Kotouč Šourek, M.; Studeník, Ondřej; Kovárnová, A.
Ústav termomechaniky, 2023

On Reynolds-averaged turbulence modeling with immersed boundary method
Kubíčková, Lucie; Isoz, Martin
2023 - English
The immersed boundary (IB) method is an approach in the computational fluid dynamics in which complex geometry conforming meshes are replaced by simple ones and the true simulated geometry is projected onto the simple mesh by a scalar field and adjustment of governing equations. Such an approach is particularly advantageous in topology optimizations (TO) where it allows for substantial speed-up since a single mesh can be used for all the tested topologies. In our previous work, we linked our custom IB variant, the hybrid fictitious domain-immersed boundary method (HFDIB), with a TO framework and successfully carried out an optimization under laminar flow conditions. However, to allow for optimizations of reallife components, the IB approach needs to be coupled with an affordable turbulence modeling. In this contribution, we focus on extending the HFDIB approach by the possibility to perform Reynolds-averaged simulations (RAS). In particular, we implemented the k − ω turbulence model and wall functions for closure variables and velocity. Keywords: immersed boundary; RAS; wall functions; CFD; OpenFOAM Fulltext is available at external website.
On Reynolds-averaged turbulence modeling with immersed boundary method

The immersed boundary (IB) method is an approach in the computational fluid dynamics in which complex geometry conforming meshes are replaced by simple ones and the true simulated geometry is ...

Kubíčková, Lucie; Isoz, Martin
Ústav termomechaniky, 2023

Finite element modal analysis of a silicone vocal fold filled with fluid
Hájek, P.; Radolf, Vojtěch; Horáček, Jaromír; Švec, J. G.
2023 - English
A three dimensional (3D) finite element (FE) model of a silicone vocal fold (VF) filled with fluid is presented here. The silicone part of the model is based on partial differential equations of the continuum mechanics and consider large deformations. The fluid domain encapsulated in the silicone VF is defined semianalytically as a lumped-element model describing the fluid in hydrostatic conditions. The elongated and pressurized silicone VF was subjected to perturbed modal analysis. Results showed that the choice of the fluid inside the VF substantially influences the natural frequencies. Namely, the water-filling lowers the natural frequencies approximately by half over the air-filling. Besides, the procedure of reverse engineering for obtaining the geometry of the VF from already 3D-printed mold is introduced. Keywords: perturbed modal analysis; finite element method; vocal folds; reverse engineering; biomechanics of voice Fulltext is available at external website.
Finite element modal analysis of a silicone vocal fold filled with fluid

A three dimensional (3D) finite element (FE) model of a silicone vocal fold (VF) filled with fluid is presented here. The silicone part of the model is based on partial differential equations of the ...

Hájek, P.; Radolf, Vojtěch; Horáček, Jaromír; Švec, J. G.
Ústav termomechaniky, 2023

From John Graunt to Adolphe Quetelet: on the Origins Of Demography
Kalina, Jan
2023 - English
John Graunt (1620-1674) and Adolphe Quetelet (1796-1874) were two important personalities, who contributed to the origins of demography. As they both developed statistical techniques for the analysis of demographic data, they are important also from the point of view of history of statistics. The contributions of both Graunt and Quetelet especially to the development of mortality tables and models are recalled in this paper. Already from the 17th century, the available mortality tables were exploited for computing life annuities. Also the contribution of selected personalities inspired by Graunt are recalled here, the work of Christian Huygens, Jacob Bernoulli, or Abraham de Moivre is discussed to document that the historical development of statistics and probability theory was connected with the development of demography. Keywords: history of demography; history of statistics; probability theory; moral statistics; mortality tables Fulltext is available at external website.
From John Graunt to Adolphe Quetelet: on the Origins Of Demography

John Graunt (1620-1674) and Adolphe Quetelet (1796-1874) were two important personalities, who contributed to the origins of demography. As they both developed statistical techniques for the analysis ...

Kalina, Jan
Ústav informatiky, 2023

Posouzení výpočtové dokumentace zaměřené na hodnocení analýzy dopadu zvýšení výkonu bloků EDU II na vertikální stabilitu a dynamickou odezvu vnitřních částí reaktoru včetně uvažování nehody LOCA DN500
Pták, Svatopluk
2023 - Czech
Tato technická zpráva shrnuje výsledky posouzení výpočtové dokumentace zaměřené na hodnocení analýzy dopadu zvýšení výkonu bloků EDU II v souvislosti s projektem '6729 − Využití projektových rezerv bloků EDU II' na vertikální stabilitu a dynamickou odezvu vnitřních částí reaktoru včetně uvažování nehody LOCA DN500, konkrétně se jedná o posouzení dvou zpráv autorských kolektivů z ÚJV, a. s.: 'M. Klemenc a P. Gál: Analýzy dopadu zvýšení výkonu na dynamické chování VČR při nehodě LOCA DN500, zpráva ÚJV DITI 2301/1242, 12/2020' a M. Švrček a J. Vyčichl: Analýzy dopadu zvýšení výkonu na vertikální stabilitu a vibrační odezvu (vysokocyklovou únavu) VČR, zpráva ÚJV DITI 2301/1307, 08/2021. This technical report summarizes the results of the assessment aimed at evaluation of the impact analysis of the increase in the performance of EDU II units in connection with the project '6729 - Use of design margins of the Dukovany reactor units' on the vertical stability and dynamic response of the reactor internal components, including consideration of the LOCA DN500 event, specifically, it is an assessment of two reports of author collectives from ÚJV, a. s.: M. Klemenc and P. Gál: 'Analyzes of the impact of the power increase on the dynamic behavior of RIC during the LOCA DN500 event, report ÚJV DITI 2301/1242, 12/2020 and M. Švrček a J. Vyčichl: 'Analyzes of the impact of increasing power on vertical stability and vibration response (high-cycle fatigue) of RIC', report ÚJV DITI 2301/1307, 08/2021. Keywords: loss coolant accident; dynamic response; primary pipelime of nuclear reactor; internal parts of nuclear reactor Available at various institutes of the ASCR
Posouzení výpočtové dokumentace zaměřené na hodnocení analýzy dopadu zvýšení výkonu bloků EDU II na vertikální stabilitu a dynamickou odezvu vnitřních částí reaktoru včetně uvažování nehody LOCA DN500

Tato technická zpráva shrnuje výsledky posouzení výpočtové dokumentace zaměřené na hodnocení analýzy dopadu zvýšení výkonu bloků EDU II v souvislosti s projektem '6729 − Využití projektových rezerv ...

Pták, Svatopluk
Ústav termomechaniky, 2023

Souhrnná zpráva zakázky OZM-LCF-2023: Experimentální hodnocení vlastností oceli 1.4529 z hlediska nízkocyklové únavy
Štefan, Jan; Parma, Slavomír
2023 - Czech
Tato technická zpráva byla zpracována v rámci zakázky „OZM-LCF-2023: Experimentální hodnocení vlastností oceli 1.4529 z hlediska nízkocyklové únavy“. Ve zprávě jsou přehledně zdokumentovány všechny podstatné informace týkající se odborného plnění zakázky počínaje návrhem experimentálního programu, přes protokoly o provedených experimentech až po souhrnné vyhodnocení programu vč. návrhů pro případné rozšíření zakázky a navazující experimentální činnost. This technical report was prepared within the framework of the contract "OZM-LCF-2023: Experimental evaluation of the properties of steel 1.4529 in terms of low cycle fatigue". The report clearly documents all relevant information concerning the technical performance of the contract, starting from the design of the experimental program, through the protocols of the experiments performed, to the summary evaluation of the program, including proposals for possible contract extension and follow-up experimental activities. Keywords: material testing; low-cycle fatigue; austenitic stainless steels Available at various institutes of the ASCR
Souhrnná zpráva zakázky OZM-LCF-2023: Experimentální hodnocení vlastností oceli 1.4529 z hlediska nízkocyklové únavy

Tato technická zpráva byla zpracována v rámci zakázky „OZM-LCF-2023: Experimentální hodnocení vlastností oceli 1.4529 z hlediska nízkocyklové únavy“. Ve zprávě jsou přehledně zdokumentovány všechny ...

Štefan, Jan; Parma, Slavomír
Ústav termomechaniky, 2023

Measurements on KR-D-11B Optimized Subsonic Blade Cascade
Šimurda, David; Hála, Jindřich
2023 - English
This report contains results and evaluation of aerodynamic measurements conducted on a subsonic compressor blade cascade. Keywords: compressor blade cascade; experiment; subsonic flow; optimized profile Available at various institutes of the ASCR
Measurements on KR-D-11B Optimized Subsonic Blade Cascade

This report contains results and evaluation of aerodynamic measurements conducted on a subsonic compressor blade cascade.

Šimurda, David; Hála, Jindřich
Ústav termomechaniky, 2023

COMPUTER SIMULATION STUDY OF THE STABILITY OF UNDERACTUATED BIPEDAL ROBOT MODELS (motivated by Griffin and Grizzle, 2017)
Polach, P.; Anderle, Milan; Zezula, Pavel; Papáček, Štěpán
2023 - English
A key feature for bipedal walkers (robots and humans as well) is their stability or disturbance rejection defined as the ability to deal with unexpected disturbances. The paper by Griffin and Grizzle (2017) have significantly contributed to the shift from flat ground to slopes and steps when evaluating the walking efficiency of their robots. Similarly, in this contribution, based on the appropriate model of robot dynamics and control law, we examine the stability of walking-without-falling for different ground perturbations for a threelink compass gait walker. I.e., we perform the sensitivity analysis of the walking stability of underactuated bipedal walker with respect to certain disturbation using the alaska/MultibodyDynamics simulation tool. Keywords: Mechatronics; Bipedal robot; Multibody dynamics; Acrobot; Control applications Fulltext is available at external website.
COMPUTER SIMULATION STUDY OF THE STABILITY OF UNDERACTUATED BIPEDAL ROBOT MODELS (motivated by Griffin and Grizzle, 2017)

A key feature for bipedal walkers (robots and humans as well) is their stability or disturbance rejection defined as the ability to deal with unexpected disturbances. The paper by Griffin and Grizzle ...

Polach, P.; Anderle, Milan; Zezula, Pavel; Papáček, Štěpán
Ústav teorie informace a automatizace, 2023

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