Práce prostřednictvím platforem
VÚBP
2024 - Czech Ekonomika digitálních platforem v EU i ČR roste. V průběhu pandemie covidu-19 nabrala tato práce na dynamice a stala se běžnou záležitostí. Digitální pracovní platformy používají algoritmy pro řízení lidských zdrojů. Keywords: platformy; digitalizace; online platformy Available in a digital repository NRGL Práce prostřednictvím platforem

Ekonomika digitálních platforem v EU i ČR roste. V průběhu pandemie covidu-19 nabrala tato práce na dynamice a stala se běžnou záležitostí. Digitální pracovní platformy používají algoritmy pro řízení ...

VÚBP
Výzkumný ústav bezpečnosti práce, v.v.i., 2024

Computational and experimental assessment of natural frequencies in a bladed disk system
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Maturkanič, Dušan; Voronova, Evgeniya; Hodboď, Robert
2024 - English This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring natural frequencies and mode shapes under different operational conditions. A comparative analysis is conducted to assess modal properties obtained from both analytical and experimental approaches, while also considering the influence of rotation speed. Additionally, Finite Element Method (FEM) outputs are used to accurately position the strain gauge. Integrating these techniques provides a comprehensive understanding of the bladed disk's behaviour under varying rotational speeds, enhancing result accuracy and facilitating thorough investigation within rotating machinery systems. Keywords: natural frequencies; FEM; LDV; strain gauge Available at various institutes of the ASCR Computational and experimental assessment of natural frequencies in a bladed disk system

This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring ...

Mekhalfia, Mohammed Lamine; Procházka, Pavel; Maturkanič, Dušan; Voronova, Evgeniya; Hodboď, Robert
Ústav termomechaniky, 2024

Numerické optimalizační metody
Lukšan, Ladislav
2024 - Czech Tato zpráva popisuje teoretické i praktické vlastnosti numerických metod pro nepodmíněnou optimalizaci. Studují se metody pro obecné i speciální optimalizační úlohy, mezi které patří minimalizace součtu čtverců, součtu absolutních hodnot, maximní hodnoty a dalších nehladkých funkcí. Kromě metod pro standardní úlohy středních rozměrů jsou studovány i metody pro rozsáhlé řídké a strukturované úlohy. Velká pozornost je věnována soustavám nelineárních rovnic.\n Keywords: Numerická optimalizace; nelineární aproximace; systémy nelineárních rovnic; algoritmy Available on request at various institutes of the ASCR Numerické optimalizační metody

Tato zpráva popisuje teoretické i praktické vlastnosti numerických metod pro nepodmíněnou optimalizaci. Studují se metody pro obecné i speciální optimalizační úlohy, mezi které patří minimalizace ...

Lukšan, Ladislav
Ústav informatiky, 2024

Analysis of the 2024 state budget revenue in light of the 2019 pre-crisis year
Janský, Petr; Kolář, Daniel
2024 - Czech This analysis compares planned state budget revenues in 2024 with the state budget outcomes of 2019. It charts a period in which the Czech economy and public budgets have been heavily impacted by the consequences of several major crises (coronavirus, the invasion of Ukraine and the war, an energy crisis, and an inflationary wave) as well as by significant parametric changes in the Czech tax system. 2019 can be considered the last pre-crisis year and 2024 the first post-crisis year, so they correspond to 'normal times' more closely than the years in between. This analysis builds on a previous analysis of the state budget expenditure development between 2019 and 2024 and includes a brief synthesis of findings on revenues and expenditures. Tato analýza srovnává plánované příjmy státního rozpočtu na rok 2024 s výsledky státního rozpočtu v roce 2019. Mapuje období, během něhož na českou ekonomiku a veřejné rozpočty silně dopadly jak důsledky několika zásadních krizí (koronavirus, napadení Ukrajiny a válka, energetická krize a inflační vlna), tak výrazné parametrické změny českého daňového systému. Rok 2019 lze považovat za poslední předkrizový a rok 2024 za první pokrizový, takže odpovídají ‘normálním časům‘ lépe než roky mezi nimi. Tato analýza svým pojetím navazuje na předchozí analýzu vývoje výdajů státního rozpočtu mezi roky 2019 a 2024 a obsahuje i stručnou syntézu zjištění o vývoji příjmů a výdajů. Keywords: budget proposal; budget revenues; Czech Republic Fulltext is available at external website. Analysis of the 2024 state budget revenue in light of the 2019 pre-crisis year

This analysis compares planned state budget revenues in 2024 with the state budget outcomes of 2019. It charts a period in which the Czech economy and public budgets have been heavily impacted by the ...

Janský, Petr; Kolář, Daniel
Národohospodářský ústav, 2024

Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna; Bílek, V.; Haidl, J.; Isoz, Martin; Pivokonský, M.
2024 - English Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and savings of operational costs. However, it is currently based on trial-and-error experimental approaches. In this contribution, we focus on flow modeling in stirred flocculation tanks that would, after coupling with a calibrated model of particle aggregation, enable simulationbased flocculation optimization. Despite the abundance of literature on stirred tank modeling, there is no universal agreement on the methodology used to describe turbulence nor on the approach to the computational mesh creation. Consequently, there is no unified methodology for simulations and their validation. To address this, we present a best-practice methodology for economical, yet reliable flow simulations in the said device. This methodology includes the choice of the turbulence model, the approach to the design of a high quality mesh suitable for arbitrary geometries, and results evaluation. It is developed based on an extensive literature review, a multitude of flow simulations using several meshes of progressively higher quality and resolution, and various strategies to converge to steady-state flow conditions. The simulation quality indicators used here involve comparison with the experimental data on fluid velocity, stirrer power output, and flow rate through the impeller zone. Additionally, the resulting flow simulation models are compared using tracer transport simulations, hinting at their potential for coupling with particle aggregation models. Keywords: flocculation tank; stirring; MRF; CFD; OpenFOAM Available at various institutes of the ASCR Flow simulations approach for flocculation tanks

Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and ...

Idžakovičová, Kristýna; Bílek, V.; Haidl, J.; Isoz, Martin; Pivokonský, M.
Ústav termomechaniky, 2024

Improvement of an unbaffled stirred tank mixing characteristics using variable speed impeller
Gebouský, Ondřej; Haidl, Jan; Bodnár, J.; Pivokonský, Martin
2024 - English Unbaffled mixing tanks with magnetically driven impellers are increasingly used in biotechnological and pharmaceutical industries, combining the benefits of a closed, sterile environment with easy equipment cleanability. On the other hand, missing internals, such as baffles or cooling coils, have an adverse effect on the equipment mixing characteristics, namely the batch\nhomogenization time. In our previous research, we uncovered that the eccentricity and inclination of the impeller – both employed routinely to enhance the mixing characteristics of unbaffled vessels – are not fully effective in the suppression of central vortex formation resulting in the increase in the homogenization time. In this work, we propose a simple solution to counteract the central vortex formation – a periodical variation of impeller rotational speed. This approach destabilizes the central vortex, significantly reducing homogenization time while maintaining the benefits of the original unbaffled setup. This innovation can seamlessly integrate into existing industrial setups, promising efficiency gains for biotech and pharmaceutical production. Keywords: unbaffled mixing tanks; variable rotational speed; vortex destabilization; mixing time improvement Available in digital repository of the ASCR Improvement of an unbaffled stirred tank mixing characteristics using variable speed impeller

Unbaffled mixing tanks with magnetically driven impellers are increasingly used in biotechnological and pharmaceutical industries, combining the benefits of a closed, sterile environment with easy ...

Gebouský, Ondřej; Haidl, Jan; Bodnár, J.; Pivokonský, Martin
Ústav pro hydrodynamiku, 2024

Posouzení stavu a měření mechanických vlastností dřevěné konstrukce krovu a stropu 1. patra státního zámku Hrádek u Nechanic, rejstř. číslo kult. památky: 18278/6‐619
Kloiber, Michal; Drdácký, Miloš
2024 - Czech Available at various institutes of the ASCR Posouzení stavu a měření mechanických vlastností dřevěné konstrukce krovu a stropu 1. patra státního zámku Hrádek u Nechanic, rejstř. číslo kult. památky: 18278/6‐619

Kloiber, Michal; Drdácký, Miloš
Ústav teoretické a aplikované mechaniky, 2024

Zoological days Ostrava 2024: book of abstracts
Drozd, P.; Ožana, S.; Bryja, Josef
2024 - Czech Keywords: zoology; conference Fulltext is available at external website. Zoological days Ostrava 2024: book of abstracts

Drozd, P.; Ožana, S.; Bryja, Josef
Ústav biologie obratlovců, 2024

Applying a two degree of freedom model for drive-by identification
Bayer, Jan
2024 - English A new concept of drive-by identification is examined applying the analogy with a Two Degree Of Freedom (DOF) system where the bridge is considered the ground-supported spring-mass and the moving spring-mass the second DOF. The response of the moving spring-mass is simulated on a bridge model using different road profiles and compared to parameters of the corresponding two DOF system. The focus is the spectral shift that can be observed on the moving spring-mass during its passage along the bridge and could possibly be applied for drive-by identification. The accuracy mainly depends on the relation of the moving spring-mass to the bridge mass and the relation between the natural frequency of the spring-mass and those of the bridge. The simulations showed that road profile can significantly reduce the accuracy of identified results, which imposes limits on practical applications. Keywords: drive-by identification; structural health monitoring; finite element analysis; road roughness; two DOF system Available in digital repository of the ASCR Applying a two degree of freedom model for drive-by identification

A new concept of drive-by identification is examined applying the analogy with a Two Degree Of Freedom (DOF) system where the bridge is considered the ground-supported spring-mass and the moving ...

Bayer, Jan
Ústav teoretické a aplikované mechaniky, 2024

Solution methods for an aeroelastic problem with combined harmonic and stochastic excitation
Fischer, Cyril; Náprstek, Jiří
2024 - English Assessing responses in slender engineering structures facing both deterministic harmonic and stochastic excitation is often based on an approximation by the single-degree-of-freedom van der Pol-type nonlinear model. Determining the response probability density function involves solving the Fokker-Planck equation, which is generally a challenging task. Hence, semi-analytical and numerical methods come into play. This contribution reviews several possible techniques and spotlights the exponential-polynomial-closure method. The shown results are limited, as the paper reflects an early stage of the relevant research direction. Keywords: Fokker-Planck equation; stochastic averaging; numerical solution; Galerkin approximation; van der Pol-type oscillator; partial amplitudes; exponential-polynomial-closure method Available in digital repository of the ASCR Solution methods for an aeroelastic problem with combined harmonic and stochastic excitation

Assessing responses in slender engineering structures facing both deterministic harmonic and stochastic excitation is often based on an approximation by the single-degree-of-freedom van der Pol-type ...

Fischer, Cyril; Náprstek, Jiří
Ústav teoretické a aplikované mechaniky, 2024