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Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna; Bílek, Vojtěch; Haidl, Jan; Isoz, M.; Pivokonský, Martin
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 in digital repository 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 ...
EFFECT OF STEEL COMPOSITION ON ITS BEHAVIOUR IN THE LIQUID LEAD ENVIRONMENT
Pazderova, M.; Hojná, A.; Vít, J.; Hadraba, Hynek; Čižek, J.
2024 - English
Ferritic-martensitic Eurofer-97 and oxide dispersion strengthened (ODS) Eurofer steels are potential candidates for structural applications in advanced nuclear reactors. Influence of scandium, yttrium, and aluminum addition was studied at 600 degrees C using 10-6 wt.% oxygen concentration. Microstructure and corrosion behaviour was evaluated after 500 h and 1000 h of exposure to liquid lead. Microscopical investigation identified oxidation, solution- based attack, and Pb penetration into the material. Addition of scandium and aluminum changed the mechanism of corrosion attack. Eurofer-97 was partially protected by outer oxide and inner oxidation and Pb penetration was found. In contrast ODS-Eurofer steels after 1000 h of exposure showed mainly inner oxidation and SBA including Pb penetration into the steel. The inner oxidation consisted of Pb+Cr-O and Cr-O+Al-O layers mixture. Degradation of ODS steel was significantly lower than Eurofer-97. It seems that the inner oxidation layer beneath the surface did not prevent the Pb penetration but protected the surface from dissolution.
Keywords:
corrosion behavior; flowing lead; ods steels; pb; Ferritic-martensitic steel; ods; liquid Pb; oxidation; nuclear application
Available at various institutes of the ASCR
EFFECT OF STEEL COMPOSITION ON ITS BEHAVIOUR IN THE LIQUID LEAD ENVIRONMENT
Ferritic-martensitic Eurofer-97 and oxide dispersion strengthened (ODS) Eurofer steels are potential candidates for structural applications in advanced nuclear reactors. Influence of scandium, ...
QUANTUM-COMPUTING STUDY OF THE ELECTRONIC STRUCTURE OF CRYSTALS: THE CASE STUDY OF SI
Ďuriška, Michal; Miháliková, Ivana; Friák, Martin
2024 - English
Quantum computing is newly emerging information-processing technology which is foreseen to be exponentially faster than classical supercomputers. Current quantum processors are nevertheless very limited in their availability and performance and many important software tools for them do not exist yet. Therefore, various systems are studied by simulating the run of quantum computers. Building upon our previous experience with quantum computing of small molecular systems (see I. Mihalikova et al., Molecules 27 (2022) 597, and I. Mihalikova et al., Nanomaterials 2022, 12, 243), we have recently focused on computing electronic structure of periodic crystalline materials. Being inspired by the work of Cerasoli et al. (Phys. Chem. Chem. Phys., 2020, 22, 21816), we have used hybrid variational quantum eigensolver (VQE) algorithm, which combined classical and quantum information processing. Employing tight-binding type of crystal description, we present our results for crystalline diamond-structure silicon. In particular, we focus on the states along the lowest occupied band within the electronic structure of Si and compare the results with values obtained by classical means. While we demonstrate an excellence agreement between classical and quantum-computed results in most of our calculations, we further critically check the sensitivity of our results with respect to computational set-up in our quantum-computing study. A few results were obtained also using quantum processors provided by the IBM.
Keywords:
computation; Quantum computing; crystals; tight-binding method; quantum-mechanical calculations
Available at various institutes of the ASCR
QUANTUM-COMPUTING STUDY OF THE ELECTRONIC STRUCTURE OF CRYSTALS: THE CASE STUDY OF SI
Quantum computing is newly emerging information-processing technology which is foreseen to be exponentially faster than classical supercomputers. Current quantum processors are nevertheless very ...
The heterogeneous consequences of reduced labor costs on firm productivity
Del Prato, F.; Zacchia, Paolo
2024 - English
We document how a reduction in labor costs led to heterogeneous effects on the total factor productivity (TFP) of manufacturing firms. Leveraging an Italian labor legislation reform and unique institutional features of the local collective bargaining system, we show that such effects vary along the TFP distribution. Relative to the counterfactual, TFP markedly declines on the left tail, which we explain via selection mechanisms, on the right, TFP mildly increases as firms are able to expand and reallocate their workforce. To guide the evaluation of welfare implications, we develop a general equilibrium model featuring firm selection and frictions in input markets.
Keywords:
labor costs; productivity; collective bargaining
Fulltext is available at external website.
The heterogeneous consequences of reduced labor costs on firm productivity
We document how a reduction in labor costs led to heterogeneous effects on the total factor productivity (TFP) of manufacturing firms. Leveraging an Italian labor legislation reform and unique ...
Geologická a geotechnická charakterizace horninového prostředí – PVP Bukov II – třetí průběžná zpráva
Soejono, I.; Bukovská, Z.; Rukavičková, L.; Švagera, O.; Chabr, T.; Souček, Kamil; Vavro, Martin; Morávek, R.; Levý, O.; Sosna, K.; Kryl, J.; Řihošek, J.; Zelinková, T.; Dobeš, P.; Hanák, J.; Čermák, F.; Kašpar, R.; Mareček, L.; Nedvěd, J.; Vavro, Leona; Myška, O.; Janeček, Ivan
2024 - Czech
Tato zpráva popisuje práce zhotovené v třetím roce řešení veřejné zakázky Geologická a geotechnická charakterizace horninového prostředí – PVP Bukov II. Charakterizační a popisné práce přímo navazují na ražbu prostor pro budoucí podzemní laboratoř a zahrnují zejména: geologické a geotechnické dokumentace čeleb a stěn díla, petrografickou, mineralogickou a strukturně geologickou dokumentaci, hydrogeologickou charakterizaci prostředí, dále stanovení fyzikálně-mechanických vlastností horninového masivu in situ a v laboratoři, geofyzikální charakterizaci, monitoring seismických účinků trhacích prací a charakterizaci EDZ. Zpráva také obsahuje nově navržený klasifikační systém horninových bloků a výsledky jeho testování na prostředí PVP Bukov II. Zpráva je doplněna stručným přehledem prací plánovaných pro následující rok řešení projektu. This report describes the work carried out in the third year of the public contract Geological and geotechnical characterisation of the rock environment – the Bukov URF II. The characterisation and descriptive works are directly related to the excavation of the premises for the future underground laboratory. These include in particular: geological and geotechnical documentation of the faces and walls of the workings, petrographic, mineralogical and structural geological documentation, hydrogeological characterisation of the environment, as well as determination of the physical and mechanical properties of the rock-mass in situ and in the laboratory, geophysical characterisation and monitoring of the seismic effects of blasting. The report also includes the newly developed rock mass\nclassification system and the results of its testing on the Bukov URF II site. The report includes also brief overview of the work planned for the following year of the project.
Keywords:
Bukov URF; geological documentation; 3D model; petrography; geochemistry; petrophysical data; natural radioactivity; physico-mechanical and geotechnical properties; seismic tomography; excavation induced vibration measurement; rock mass classification system
Available on request at various institutes of the ASCR
Geologická a geotechnická charakterizace horninového prostředí – PVP Bukov II – třetí průběžná zpráva
Tato zpráva popisuje práce zhotovené v třetím roce řešení veřejné zakázky Geologická a geotechnická charakterizace horninového prostředí – PVP Bukov II. Charakterizační a popisné práce přímo navazují ...
Stanovení in-situ napjatosti v PVP Bukov II – rešerše metod měření napjatosti a studie jejich využití v procesu výstavby a provozu hlubinného úložiště
Vavro, Martin; Waclawik, Petr; Souček, Kamil; Staš, Lubomír; Koníček, Petr; Jiránková, Eva; Schuchová, Kristýna; Kukutsch, Radovan; Kajzar, Vlastimil
2024 - Czech
Rešerše prezentuje hlavní metody měření a jim odpovídající technickou instrumentaci, které byly v minulosti použity pro stanovení napětí horninového masivu, a to jak v podmínkách PVP Bukov I, respektive dolu Rožná, tak zejména v prostředí vybraných zahraničních podzemních výzkumných laboratoří. Shrnuty jsou rovněž stěžejní výsledky, které byly při těchto měřeních získány. Zjištěné poznatky jsou pak reflektovány v návrhu způsobu měření a monitoringu napětí v různých fázích procesu přípravy a provozu hlubinného úložiště (HÚ) v ČR. Z provedené rešerše stěžejních publikovaných studií a výsledků in situ experimentů vyplývá, že celosvětově nejčastěji používanými způsoby napěťových měření jsou zejména hydraulické štěpení stěn vrtů (hydrofracturing) a metoda odlehčeného vrtného jádra (overcoring). Tyto dvě metody byly rovněž navrženy jako nejvhodnější pro fázi výběru finální lokality HÚ v ČR. Ve fázi budování HÚ bylo doporučeno jejich rozšíření o metodu inverzní analýzy konvergenčních měření. Pro účely měření změn napětí ve stádiu přípravy a provozu HÚ byl jako nejvhodnější doporučen monitoring pomocí tenzometrických CCBM sond. The presented search summarizes main measurement methods and their corresponding technical instrumentation, which were used in the past to determine the stress state of the rock\nmass, both in the conditions of Bukov URF I or the Rožná mine respectively, and especially in the environment of selected foreign underground research laboratories. The key results obtained during these stress measurements are also compiled. The findings are then reflected in the proposed method of rock mass stress measurement and monitoring in various stages of the process of preparing and operating a deep geological repository (DGR) in the Czech Republic. From the conducted search of the crucial published studies and the results of in situ experiments, it follows that the most commonly used methods of stress measurement worldwide are mainly hydraulic fracturing of borehole walls (hydrofracturing) and the overcoring method. These two methods were also proposed as the most suitable for the stage of selecting the final site of the DGR in the Czech Republic. In the phase of construction the DGR, it was recommended to extend them by the method of inverse analysis of convergence measurements. For the purposes of measuring stress changes during the construction and operation of the DGR, monitoring using conical tensometric CCBM probes was recommended as the most suitable.
Keywords:
high level radioactive waste; geological disposal; deep repository; long-term stability of the repository; Bukov URF; rock mass stress; hydrofracturing; overcoring method; tensometric conical probes; acoustic logging; optical logging; long-term stress monitoring; convergence measurement; numerical modelling
Available on request at various institutes of the ASCR
Stanovení in-situ napjatosti v PVP Bukov II – rešerše metod měření napjatosti a studie jejich využití v procesu výstavby a provozu hlubinného úložiště
Rešerše prezentuje hlavní metody měření a jim odpovídající technickou instrumentaci, které byly v minulosti použity pro stanovení napětí horninového masivu, a to jak v podmínkách PVP Bukov I, ...
Growth and Phosphorus Dynamics During Tolypothrix tenuis Cultivation – a Cyanobacterium of Biotechnological Potential
Mušálková, Petra
2024 - English
Here I investigated the course of biomass growth, phosphorus uptake and changes in intracellular phosphorus content in T. tenuis in a batch cultivation. Cultivation experiment was held in multiple bubble columns during a light regime (alternating light and dark periods 16 and 8h). Thanks to this experiment I was able to obtain a growth curve of T. tenuis. The decrease of phosphorus concentration in the medium was disproportionally faster\nthan biomass growth resulting in significant oscillations of phosphorus content in the biomass, which are typical characteristics for LPU. It was also observed, that after all phosphorus was removed from the medium, the algae growth continues over time, while obviously utilizing intracellular phosphorus reserves. These findings are valuable in course of using this cyanobacterium for efficient bioremediation of eutrophic water based on phosphorus removal by targeted algae cultivation.
Available in a digital repository NRGL
Growth and Phosphorus Dynamics During Tolypothrix tenuis Cultivation – a Cyanobacterium of Biotechnological Potential
Here I investigated the course of biomass growth, phosphorus uptake and changes in intracellular phosphorus content in T. tenuis in a batch cultivation. Cultivation experiment was held in multiple ...
Influence of Material Properties and Mixing Dynamics on Heat Transport in Granular Materials
Kokavcová, Anna
2024 - English
This study evaluates the effect of rotational speed on heat transfer and analyzes particle motion at different stirrer rotational frequencies to understand how primary and secondary flows affect heat transfer efficiency. It also examines the effect of Young’s modulus on heat transfer at different agitator\noperating speeds. Key simulation parameters and their influence 33 on heat transfer efficiency are detailed to improve the reproducibility and applicability of the results.
Keywords:
granular mixing; heat transfer; DEM
Available in digital repository of the ASCR
Influence of Material Properties and Mixing Dynamics on Heat Transport in Granular Materials
This study evaluates the effect of rotational speed on heat transfer and analyzes particle motion at different stirrer rotational frequencies to understand how primary and secondary flows affect heat ...
Electrochemical Properties of Pretomanid. New drug for Tuberculosis Treatment
Deri, M.; Vespi, M.; Giannarelli, S.; Hromadová, Magdaléna
2024 - English
The electrochemical behavior of Pretomanid (PA 824) has been investigated in acetonitrile by cyclic voltammetry at different scan rates and compared to dimetridazole reduction in order to elucidate its redox mechanism. Both compounds show similar reduction behavior in the aprotic solvent that involves one electron transfer to the nitro group. The reduction of Pretomanid is more difficult and the stability of its nitro anion radical is much lower compared to the dimetridazole molecule.
Keywords:
pretomanid; dimetridazole; cyclic voltammetry; reduction mechanism
Available on request at various institutes of the ASCR
Electrochemical Properties of Pretomanid. New drug for Tuberculosis Treatment
The electrochemical behavior of Pretomanid (PA 824) has been investigated in acetonitrile by cyclic voltammetry at different scan rates and compared to dimetridazole reduction in order to elucidate ...
Redox Properties of Pyrene-Cyclohexene Conjugates – Electrochemical Study
Koláčná, Lucie; Čubiňák, M.; Tobrman, T.; Ludvík, Jiří
2024 - English
The series of 16 compounds for "organic electronics" comprising the double-bond cyclohexene core extended by pyrene and/or other aromatics were electrochemically characterized by rotating disk voltammetry in N,N-dimethylformamide. Due to multiple substitutions, the resulting potential gap represents the sum of all substituent effects. Different combinations of substituents can be used to achieve the desired properties of cyclohexene-pyrene derivatives. The electrochemical data presented in this contribution facilitate further tuning of properties of these molecules and systems to achieve features required in material chemistry just by means of chemical modification.
Keywords:
pyrene; cyclohexene; conjugation
Available on request at various institutes of the ASCR
Redox Properties of Pyrene-Cyclohexene Conjugates – Electrochemical Study
The series of 16 compounds for "organic electronics" comprising the double-bond cyclohexene core extended by pyrene and/or other aromatics were electrochemically characterized by rotating disk ...
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