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Vliv organických látek na charakter agregátů tvořených koagulací/flokulací při úpravě vody
Filipenská, Monika; Pivokonská, Lenka; Vašatová, Petra; Pivokonský, Martin
2018 - český
Cílem práce bylo popsat vliv různých znečišťujících příměsí (kaolinitové částice, COM peptidy/proteiny a jejich směs) na velikost, velikostní distribuci, tvar a strukturu agregátů tvořených v proměnných hydrodynamických podmínkách (různá gradient rychlosti) v konečné fázi vývoje agregace, tzv. steady state. Jako míchací zařízení byl zvolen Taylor-Couettův reaktor, který umožňuje neinvazivní pozorování agregátů. Vlastnosti agregátů byly vyhodnocovány metodou obrazové analýzy. Bylo zjištěno, že velikost a tvar agregátů je závislá na typu koagulačního činidla, typu koagulované přímesi a aplikovaném gradientu rychlosti. Železité koagulační činidlo produkuje větší a méně pravidelné agregáty než činidlo hlinité. Podle příměsi roste velikost (zároveň klesá kompaktnost a roste neuspořádanost) agregátů v pořadí kaolinit < COM < kaolinit + COM. Bylo zjištěno, že velikost agregátů se na aplikovaném gradientu rychlosti nemění plynule, jak bylo doposud předpokládání, ale při překročení hodnoty tzv. kritických gradientů rychlosti, dochází k její prudké změně. Změny ve velikosti agregátů se liší v závislosti na charakteru koagulovaných příměsí a byly vysvětleny pomocí rozdílných interakcí mezi znečišťující příměsí a koagulačním činidlem. Characteristics of aggregates (size, shape, density and porosity) affect separation efficiency. These characteristics come from properties of impurities (molecular weight and structure, charge density, affinity to water, etc.), coagulation parameters (pH, type and concentration of coagulants, etc.) and by physical conditions (shear rate and time of mixing). In this work, we describe relations between the size of aggregates and shear rate and moreover dependency on the characteristics of coagulated compounds. In order to understand dependency on compounds, flocs formed by kaolinite, Algal Organic Matter (AOM) and a mixture of the same were studied. There was found aggregates are bigger and more porous when AOM is present. The most striking result is that aggregates size changes in dependence on shear rate are not smooth in progress. A rapid change for the kaolinite-coagulant suspension and two rapid changes for the suspensions containing AOM were observed. These were attributed to various intermolecular interactions between floc components participating in coagulation at the different shear rate.
Klíčová slova:
AOM; Algal Organic Matter; coagulation; aggregation; shear rate; aggregate structure; water treatment
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Vliv organických látek na charakter agregátů tvořených koagulací/flokulací při úpravě vody
Cílem práce bylo popsat vliv různých znečišťujících příměsí (kaolinitové částice, COM peptidy/proteiny a jejich směs) na velikost, velikostní distribuci, tvar a strukturu agregátů tvořených v ...
Analýza vzniku kritické situace ohrožení kulturního dědictví přírodní pohromou
Hnilicová, Soňa; Šípek, Václav
2018 - český
Analýza vzniku různých typů povodňových situací a hodnocení faktorů ovlivňující tvar povodňové vlny. Mechanismus komplexní protipovodňové ochrany včetně konkrétních opatření na území hl. m. Prahy. Floods are one of the most occurring natural hazards causing damage of cultural heritage. Factors influencing flood formation and the shape of flood wave are analysed. Mechanism of complex flood control protection is described including planned and realised measured in the capital city Prague.
Klíčová slova:
flood causing factor; flood wave; flood control protection
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Analýza vzniku kritické situace ohrožení kulturního dědictví přírodní pohromou
Analýza vzniku různých typů povodňových situací a hodnocení faktorů ovlivňující tvar povodňové vlny. Mechanismus komplexní protipovodňové ochrany včetně konkrétních opatření na území hl. m. ...
Dispersion kinetics in mechanically agitated vessel
Bucciarelli, E.; Formánek, R.; Kysela, Bohuš; Fořt, I.; Šulc, R.
2018 - anglický
Agitation of two immiscible liquids or solid-liquid suspension is a frequent operation in chemical and metallurgical industries. Prediction of mean drop/particle size and drop/particle size distribution (DSD) is vital for emulsification, suspension polymerization, solid particle dispersion or crystallization. Simulation of particulate systems requires the knowledge of DSD and its time evolution. The time evolution of drop size distribution was investigated in baffled vessel mechanically agitated by a Rushton turbine and a high-shear tooth impeller. The system water –silicone oil was used as a model liquid. The volume fraction of the dispersed phase was 0.047 %. The drop sizes were determined by image analysis. The time evolution of the drops size dp32 was studied for both impellers tested. The model used involves the first order kinetics. Finally, the following correlations predicted by the Kolmogorov-Hinze theory were evaluated at steady state: dp32/D = C1.We-0.6 and dpmax/D = C2.We-0.6, where We is the impeller Weber number.
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Dispersion kinetics in mechanically agitated vessel
Agitation of two immiscible liquids or solid-liquid suspension is a frequent operation in chemical and metallurgical industries. Prediction of mean drop/particle size and drop/particle size ...
Measurement of drop size distribution time rate for liquid-liquid dispersion using IPI method
Jašíková, D.; Kotek, M.; Kysela, Bohuš; Šulc, R.; Kopecký, V.
2018 - anglický
The liquid-liquid dispersion properties are studied mainly by image analysis (IA) and Interferometric Particle Imaging (IPI). Drop sizes will be investigated in dilute dispersion since in this case the break up phenomena is the dominating and is not affected by phase fraction. Characteristics of the size distribution and the evolution of two liquid-liquid phase’s disintegration were studied. The IPI method was used for subsequent detailed study of the disintegrated droplets. We compared two liquids: Rhodosil Oil 47V50, and Silicone Oil AP1000 under stirrer rate of 540 rpm, and 760 rpm. The experiment run in the scaled model of agitated tank with Rushton turbine.
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurement of drop size distribution time rate for liquid-liquid dispersion using IPI method
The liquid-liquid dispersion properties are studied mainly by image analysis (IA) and Interferometric Particle Imaging (IPI). Drop sizes will be investigated in dilute dispersion since in this case ...
Vodní režim v minulosti a současnosti – postřehy k zamyšlení
Buchtele, Josef; Slámová, Romana; Chlumecký, M.
2018 - český
The variability of the water regime is ascertained as being influenced by the frequent natural evolutions in the span of decades and also by some abrupt changes in the recent periods, including the damages or grows of vegetation cover or human influence in the historical decades. Analysis of such natural or man-made impacts in the context of historical evolution could clarify uncertainties and oscillations in basin water regime. The events as changes in vegetation cover, resp. evapotranspiration, land-use changes, building of new reservoirs and disappearing the old ones, effect of water management changing the condition of the water supply should be evaluated taking into account the influencing of the natural water regime. The modeling of rainfall-runoff process could be used to identify such impacts, especially for the cases when the long term complex monitoring is missing. The difference between observed and simulated streams flow appears as the helpful tool for the assessments of the resulting water regime. The variability of the water regime is ascertained as being influenced by the frequent natural evolutions in the span of decades and also by some abrupt changes in the recent periods, including the damages or grows of vegetation cover or human influence in the historical decades. Analysis of such natural or man-made impacts in the context of historical evolution could clarify uncertainties and oscillations in basin water regime. The events as changes in vegetation cover, resp. evapotranspiration, land-use changes, building of new reservoirs and disappearing the old ones, effect of water management changing the condition of the water supply should be evaluated taking into account the influencing of the natural water regime. The modeling of rainfall-runoff process could be used to identify such impacts, especially for the cases when the long term complex monitoring is missing. The difference between observed and simulated streams flow appears as the helpful tool for the assessments of the resulting water regime.
Klíčová slova:
water regime; climate change; water resources
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Vodní režim v minulosti a současnosti – postřehy k zamyšlení
The variability of the water regime is ascertained as being influenced by the frequent natural evolutions in the span of decades and also by some abrupt changes in the recent periods, including the ...
Modelling of non-monotonous course of shear viscosity
Filip, Petr
2018 - anglický
A number of parameters appearing in the 'classical' empirical constitutive equations usually oscillate between two and five. With the onset of new rheologically more complex materials exhibiting non-monotonous behaviour of flow curves this range (2-5) is no longer tenable and more additional parameters are required for a proper description of the flow curves. An 8-parameter model is presented and testified.
Klíčová slova:
viscosity; flow curve; constitutive equation; empirical modelling
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modelling of non-monotonous course of shear viscosity
A number of parameters appearing in the 'classical' empirical constitutive equations usually oscillate between two and five. With the onset of new rheologically more complex materials exhibiting ...
Redukce šumu z experimentálních časových řad
Chára, Zdeněk; Kysela, Bohuš
2018 - český
Příspěvek se zabývá redukcí šumu z časových řad. Pozornost je zaměřena především na časové řady získané metodou PIV. Metoda redukce šumu je testována pro PIV data získaná při měření rychlostních polí v míchané nádobě. This article deals with the denoising of experimental time series. Attention is focused primarily on the time series obtained by the PIV method. The noise reduction method is tested for the PIV data obtained by measuring the velocity fields in the stirred vessel.
Klíčová slova:
denoising; PIV; time series
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Redukce šumu z experimentálních časových řad
Příspěvek se zabývá redukcí šumu z časových řad. Pozornost je zaměřena především na časové řady získané metodou PIV. Metoda redukce šumu je testována pro PIV data získaná při měření rychlostních polí ...
The role of solvents in the preparation of hydrophobic nanofibrous membrane containing fumed silica
Peer, Petra; Polášková, M.; Musilová, I.; Filip, Petr
2018 - anglický
It is well-known that a type of used fumed silica nanoparticles plays a dominant role in wettability of the corresponding nanofibrous mats. As a result, the desired contact angle can be approximately achieved by a choice of adequate fumed silica nanoparticles. However, less attention has been hitherto paid to an active role of solvents in connection with the tailoring this contact angle. For analysis we used poly(vinyl butyral) representing electrospun-friendly material, various types of fumed silica nanoparticles and two solvents - methanol and ethanol. It is demonstrated that a choice of polymer solvents plays a significant role in contact angle changes. Hence, in combination of the type of fumed silica nanoparticles and the type of solvent it is possible to achieve a finer partition of the required contact angles.
Klíčová slova:
PVB solution; solvents; fumed silica; electrospinning; rheology
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The role of solvents in the preparation of hydrophobic nanofibrous membrane containing fumed silica
It is well-known that a type of used fumed silica nanoparticles plays a dominant role in wettability of the corresponding nanofibrous mats. As a result, the desired contact angle can be approximately ...
Thermal induced morphological changes of poly(ethylene oxide) nanofibrous webs
Polášková, M.; Peer, Petra; Ponížil, P.; Čermák, R.
2018 - anglický
The crystallinity of fibres prepared by electrospinning shows lower level in comparison with samples processed by common technologies such as moulding or film casting. Thus, the attempts to improve the structure of electrospun fibres in order to increase physical and mechanical properties of nonwoven webs are obvious. Post-process thermal treatment is one of the possibilities of the crystallinity enhancement that can be easily included to the finishing operation of final products. For the experiment we used poly(ethylene oxide) representing electrospun-friendly material and two solvents - methanol and water, both ensuring good electrospinnability. It is demonstrated that a choice of polymer solvents plays a significant role in fibre diameter and their capabilities to resist applied heat. However, in all cases the enhancement of crystallinity is detected at the short time of thermal exposure.
Klíčová slova:
PEO nanofibres; degree of crystallinity; electrospinning
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Thermal induced morphological changes of poly(ethylene oxide) nanofibrous webs
The crystallinity of fibres prepared by electrospinning shows lower level in comparison with samples processed by common technologies such as moulding or film casting. Thus, the attempts to improve ...
The importance of the radiation balance for water retention of the landscape
Kofroňová, Jitka
2018 - anglický
As part of the radiation balance, longwave radiation is one of the factors needed to estimate potential evapotranspiration (PET). Since the longwave radiation balance is rarely measured, many computational methods have been designed. In this study, we report on the difference between the observed longwave radiation balance and modelling results obtained using the two main procedures outlined in Manuals 24 and 56 of the FAO. The performance of these equations was evaluated in the warmer months (April to October) over eight years at the Liz experimental catchment in the Bohemian Forest (Czech Republic). The coefficients of both methods were also calibrated based on local conditions. Four commonly used methods were used to calculate the PET (Penman-Monteith, Pristley and Taylor, Kimberley-Penman, Thom and Oliver). The use of default coefficient values gave errors of 40 100 mm and 0 20 mm for the seasonal PET estimates for FAO56 and FAO24, respectively (the PET was usually overestimated). Parameter calibration decreased the FAO56 error to less than 20 mm per season (FAO24 remained unaffected by the calibration). The FAO56 approach with calibrated coefficients proved to be more suitable for estimation of the longwave radiation balance.
Klíčová slova:
water retention; radiation balance; potential evapotranspiration (PET)
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
The importance of the radiation balance for water retention of the landscape
As part of the radiation balance, longwave radiation is one of the factors needed to estimate potential evapotranspiration (PET). Since the longwave radiation balance is rarely measured, many ...
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