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Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna; Bílek, Vojtěch; Haidl, Jan; Isoz, M.; Pivokonský, Martin
2024 - anglický
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.
Klíčová slova:
flocculation tank; stirring; MRF; CFD; OpenFOAM
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
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 ...
Palingeneze - obnovení všeho? (Matouš 19,28)
Dus, Jan A
2024 - český
V Matoušově verzi Ježíšova zaslíbení (Mt 19,28–30) oproti Markovi a Lukášovi chybí výslovná zmínka o přítomnosti: restituce všeho, co Ježíšovi následovníci opustili, se tak posouvá až do budoucnosti, ve které se chopí vlády spolu se Synem člověka. V zaslíbení figuruje raritní pojem „palingeneze“, jehož bližší časové a věcné určení nelze ze samotného souvětí odvodit. Zatímco v Mt 19,28 je palingeneze podle převažujícího výkladu synonymem pro budoucí obnovu veškerenstva, v Tt 3,5 (jediný další výskyt v NZ) odkazuje totéž slovo na znovuzrození některých lidí, ke kterému došlo v minulosti (při křtu). Ani nebiblická literatura nepřináší jednoznačný precedens – palingeneze bývá zasazována jak do minulosti, tak i do budoucnosti, týká se jak světa, tak i jednotlivců či skupin (Izraele). – Syntax a interpunkce řeckého souvětí ukazují, že oba výklady jsou rovnocenné: palingenezi lze vztáhnout buď (A) k následujícímu výrazu pro „usednutí (Syna člověka na trůn)“, tedy do budoucnosti, anebo (B) k předchozímu výrazu pro „následování (učedníků za Ježíšem)“, tedy do minulosti, kromě toho existuje (C) výklad otevřený. V řeckých, latinských a českých verzích ze 16. století jsou zastoupeny všechny možnosti: Erasmus interpunkčně opravuje Vulgátu (B), Beza nejprve respektuje Vulgátu (A), v anotacích však zvažuje druhé řešení (B), ve čtvrtém a pátém vydání nakonec nechává věc otevřenou (C), v dilematu mezi Vulgátou a Erasmem váhají i dva české překlady z první poloviny 16. stol. (náměšťský 1533, melantrišský 1556/57) (C), většina bratrských překladů počínaje Blahoslavem (1564) se odchyluje od Vulgáty (B), jen kralická Šestidílka (1593/94) váhá (C), v Šestidílce i v kralickém Novém zákoně z r. 1601 Bratří věnují oběma výkladům rovnocennou pozornost v poměrně rozsáhlé poznámce, která je pro svou vyváženost pěkným dokladem intelektuální otevřenosti a tolerance, podobně jako Beza připojují k výkladu (B) nový aspekt: palingeneze může znamenat obnovení celého světa díky evangeliu a prvnímu příchodu Mesiáše. – Vzhledem k dynamickému vývoji v 16. století je překvapivé, že všech deset sledovaných českých překladů z období kolem 20. století se shoduje jen na jedné variantě (A). Zdá se, že variantě (B) hrozí nespravedlivé zapomenutí. Proto si na závěr dovolujeme navrhnout nový, poněkud volnější překlad či parafrázi verše Mt 19,28 v kralickém duchu: „Amen, pravím vám, vy jste šli za mnou, když jsem přišel obnovit svět evangeliem, a až Syn člověka usedne na trůn své slávy, budete to zase vy, kdo usednete na dvanáct trůnů a budete soudit dvanáct kmenů Izraele.“ In Matthew’s version of Jesus’ promise (Matthew 19:28–30), in contrast to Mark and Luke, there is no explicit mention of the present time, the restitution of all that the followers of Jesus left behind is thus pushed forward to the future, in which they will take over the reigns with the Son of Man. The promise features the rare term “palingenesis”, whose precise temporal and factual determination cannot be deduced from the sentence itself. While in Mt 19:28 palingenesis is, according to the prevailing interpretation, a synonym for the future restoration of the universe, in Tit 3:5 (the only other occurrence in the NT) the same word refers to the rebirth of some people that took place in the past (at baptism). Even non-biblical literature does not provide a clear precedent - palingenesis tends to be set both in the past and in the future, it concerns both the world and individuals or groups (Israel). – The syntax and punctuation of the Greek sentence show that both interpretations are equally possible: palingenesis can be related either (A) to the following verbal form “sitting (the Son of Man on the throne)”, i.e. to the future, or (B) to the preceding verbal form “following (disciples behind Jesus)”, i.e. into the past, in addition, there is a third, open option (C). In the 16th-century Greek, Latin, and Czech versions, all possibilities are represented: Erasmus punctuates the Vulgate differently (B), Beza first respects the Vulgate (A), but in his Annotations he considers the second solution (B), in the fourth and fifth editions he finally leaves the matter open (C), two Czech translations from the first half of the 16th century (Náměšť 1533, Melantrich 1556/57) hesitate in the dilemma between the Vulgate and Erasmus (C), most Brethren translations starting with Blahoslav (1564) deviate from the Vulgate (B), only the Six-Volume Kralice Bible from 1593/94 (“Kralická Šestidílka”) hesitates (C), in “Kralická Šestidílka” and in the Kralice New Testament from 1601 the Brethren pay equal attention to both interpretations in a rather extensive note, which, for its balance, is a nice proof of intellectual openness and tolerance. Like Beza, the Brethren add a new aspect to interpretation (B): palingenesis can mean the renewal of the whole world thanks to the Gospel and the first coming of the Messiah. – Considering the dynamic development in the 16th century, it is surprising that all ten tracked Czech translations from around the 20th century agree on only one variant (A). Option (B) seems to be in danger of unfair oblivion. Therefore, in conclusion, we allow ourselves to propose a new, somewhat looser translation or paraphrase of verse Mt 19:28 in the spirit of Kralice: “Amen, I say to you, it was you who followed me when I came to renew the world with the gospel, and when the Son of Man sits on the throne of his glory, it will be you again who will sit on twelve thrones and judge the twelve tribes of Israel.”
Klíčová slova:
palingenesis; Gospel of Matthew; Kralice Bible; Erasmus of Rotterdam; Theodore Beza; Vulgate; Czech Bible translations
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Palingeneze - obnovení všeho? (Matouš 19,28)
V Matoušově verzi Ježíšova zaslíbení (Mt 19,28–30) oproti Markovi a Lukášovi chybí výslovná zmínka o přítomnosti: restituce všeho, co Ježíšovi následovníci opustili, se tak posouvá až do budoucnosti, ...
COVID-19 and political preferences through stages of the pandemic: the case of the Czech Republic
Bičáková, Alena; Jurajda, Štěpán
2024 - anglický
We track the effects of the COVID-19 pandemic on political preferences through ‘high’ and ‘low’ phases of the pandemic. We ask about the effects of the health and the economic costs of the pandemic measured at both personal and municipality levels. Consistent with the literature, we estimate effects suggestive of political accountability of leaders during ‘high’ pandemic phases. However, we also find that the pandemic political accountability effects are mostly short-lived, and do not extend to the first post-pandemic elections.
Klíčová slova:
COVID-19; political preferences; election outcomes
Dokument je dostupný na externích webových stránkách.
COVID-19 and political preferences through stages of the pandemic: the case of the Czech Republic
We track the effects of the COVID-19 pandemic on political preferences through ‘high’ and ‘low’ phases of the pandemic. We ask about the effects of the health and the economic costs of the pandemic ...
(Ne)zájem žáků o učitelskou profesi: mezinárodní srovnání
Federičová, Miroslava
2024 - český
Mnoho evropských zemí včetně Česka se v současnosti potýká s nedostatkem učitelů, těch kvalitních obzvlášť. Jedním z řešení je podpora učitelských profesních aspirací už u mladých během jejich studia na základní a střední škole. Tato studie empiricky mapuje učitelské aspirace v evropských zemích mezi 15letými žáky na základě dat z mezinárodního šetření PISA. Many European countries, including the Czech Republic, currently face a shortage of teachers, especially quality teachers. One possible solution to this would be to support aspiring teachers at a younger age, during their studies at primary and secondary school. This study provides an empirical overview of teaching aspirations among 15-year-old school pupils in European countries based on data from the international PISA survey.
Klíčová slova:
teachers; teaching aspirations; international comparison
Dokument je dostupný na externích webových stránkách.
(Ne)zájem žáků o učitelskou profesi: mezinárodní srovnání
Mnoho evropských zemí včetně Česka se v současnosti potýká s nedostatkem učitelů, těch kvalitních obzvlášť. Jedním z řešení je podpora učitelských profesních aspirací už u mladých během jejich studia ...
Galloping of insulated bundled overhead line - nonlinear numerical analysis in time domain
Macháček, Michael; Hračov, Stanislav
2024 - anglický
Our contribution focuses on a 3D numerical nonlinear analysis of galloping in a specific bundled overhead line with ice accretion. We studied the susceptibility to this self-excited oscillation, critical onset wind speeds, and global dynamic response of a very low-tensioned line with simulated icing observed on similar real conductors. Due to the highly nonlinear mechanical behavior of such a flexible cable, we employed the Newmark integration method combined with the iterative Newton-Raphson method. We analyzed two numerical models of the overhead line loaded by the wind: one assuming nonlinearity only in the wind load, while retaining the linearity of the mechanical system itself, and the other representing a fully nonlinear system including geometrical nonlinearity. Our analysis revealed that the determined critical wind speeds for the onset of galloping are in relatively close ranges for both models. However, numerical simulations with the fully nonlinear system indicated significantly lower amplitudes of limit cycle oscillations, especially at higher wind speeds, compared to the linear model of the line. This underscores the necessity of using fully nonlinear models during the design stage of such low-tensioned aerial conductors.
Klíčová slova:
aerial bundled conductors; wind effects; galloping; limit cycle oscillation
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Galloping of insulated bundled overhead line - nonlinear numerical analysis in time domain
Our contribution focuses on a 3D numerical nonlinear analysis of galloping in a specific bundled overhead line with ice accretion. We studied the susceptibility to this self-excited oscillation, ...
Electrochemical Properties of Pretomanid. New drug for Tuberculosis Treatment
Deri, M.; Vespi, M.; Giannarelli, S.; Hromadová, Magdaléna
2024 - anglický
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.
Klíčová slova:
pretomanid; dimetridazole; cyclic voltammetry; reduction mechanism
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
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 - anglický
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.
Klíčová slova:
pyrene; cyclohexene; conjugation
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
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 ...
Electrochemical Valorization of Lignocellulosic Biomass Amination of Furfural and 5-Hydroxymethylfurfural
Donkeng Dazie, Joel; Koláčná, Lucie; Urban, Jiří; Lamač, Martin; Ludvík, Jiří
2024 - anglický
Furfural (FF) and 5-hydroxymethylfurfural (HMF) isolated from waste lignocellulosic biomass represent renewable sources. The present contribution deals with the transformation of FF and HMF into furfuryl amines which are important precursors namely for pharmaceutical synthesis. First, FF and HMF underwent condensation reactions with various amines which were electrochemically monitored to optimize the process. The resulting Schiff bases were identified by NMR and subsequently electrochemically reduced in basic media. The vicinal diamine (aminopinacol) was the main product besides the expected furfuryl amines. This reaction is a contribution to green synthesis because it was performed electrochemically, in water, and without any metallic catalysts.
Klíčová slova:
furfural; 5-hydroxymethylfurfural; (di)amines
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Electrochemical Valorization of Lignocellulosic Biomass Amination of Furfural and 5-Hydroxymethylfurfural
Furfural (FF) and 5-hydroxymethylfurfural (HMF) isolated from waste lignocellulosic biomass represent renewable sources. The present contribution deals with the transformation of FF and HMF into ...
Electrochemical Properties of Newly Synthesized Selaginpulvilins
Dostálová, L.; Sokolová, Romana; Schwarzová-Pecková, K.; Rýček, L.
2024 - anglický
The electrochemical properties of newly synthesized selaginpulvilin were investigated by cyclic voltammetry and UV-Vis spectroelectrochemistry. The subject of the study were two\nselaginpulvilins differing in the presence of a hydroxyl group in the media of 0.1 mol L-1 tetrabutylammonium hexafluorophosphate as supporting electrolyte in anhydrous acetonitrile. Both\ncompounds provided an oxidative signal in the positive region until +2.0 V.
Klíčová slova:
oxidation; cyclic voltammetry; selaginpulvilins
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
Electrochemical Properties of Newly Synthesized Selaginpulvilins
The electrochemical properties of newly synthesized selaginpulvilin were investigated by cyclic voltammetry and UV-Vis spectroelectrochemistry. The subject of the study were two\nselaginpulvilins ...
3D-printed Electrodes with Nearly Ideal Charge Transfer Characteristics
Vaněčková, Eva; Sebechlebská, Táňa; Kolivoška, Viliam
2024 - anglický
3D printing is an outstanding manufacturing tool for prototyping customized designs at reduced time and costs, having found applications in fields such as medicine or the automotive industry. The development of printable electrically conductive composite materials brought a revolution to electrochemistry, with 3D-printed electrodes being intensively studied from the viewpoint of\nanalytical performance and stability. However, it is often reported that 3D-printed electrodes have poor charge transfer characteristics, typically due to limited exposure of the electrically conductive phase at the composite surface to the surrounding solution. In this work, we devise and apply simple electrochemical activation procedures that lead to a significant improvement of charge transfer characteristics of 3D printed electrodes.
Klíčová slova:
three-dimensional printing; electrochemistry; electrodes
Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
3D-printed Electrodes with Nearly Ideal Charge Transfer Characteristics
3D printing is an outstanding manufacturing tool for prototyping customized designs at reduced time and costs, having found applications in fields such as medicine or the automotive industry. The ...
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