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Yes (119)
Number of found documents:
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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 - English
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.
Available at various institutes of the ASCR
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 - Czech
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.
Keywords:
water regime; climate change; water resources
Available at various institutes of the ASCR
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 - English
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.
Keywords:
viscosity; flow curve; constitutive equation; empirical modelling
Available at various institutes of the ASCR
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 - Czech
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.
Keywords:
denoising; PIV; time series
Available at various institutes of the ASCR
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 - English
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.
Keywords:
PVB solution; solvents; fumed silica; electrospinning; rheology
Available at various institutes of the ASCR
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 - English
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.
Keywords:
PEO nanofibres; degree of crystallinity; electrospinning
Available at various institutes of the ASCR
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 - English
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.
Keywords:
water retention; radiation balance; potential evapotranspiration (PET)
Available in digital repository of the ASCR
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 ...
Image analysis of particle size: effect of light source type
Formánek, R.; Kysela, Bohuš; Šulc, R.
2018 - English
Agitation of two immiscible liquids or solid-liquid suspension is a frequent operation in chemical and metallurgical industries. The sizes of particles, bubbles or droplets can be determined by the Image Analysis Technique. It is known that the quality of captured images depends significantly on the original image background that is mainly affected by the type of the light source. The aim of this contribution is to investigate the effect of light source type on image quality. The four types of light sources were tested: 1) 1000 W halogen lamp, 2) 72 W LED bar panel, 3) 60 W LED chip, and 4) 90 W LED chip. The illumination intensity and image background quality were investigated for each tested light sources. The effect of the shutter speed on evaluated particle sizes was tested using monodisperse spherical calibration particles having diameter of 1.19 mm. The difference observed between particle sizes evaluated by image analysis for given light source and declared calibration particle diameter was used as a measure of light source quality.
Available at various institutes of the ASCR
Image analysis of particle size: effect of light source type
Agitation of two immiscible liquids or solid-liquid suspension is a frequent operation in chemical and metallurgical industries. The sizes of particles, bubbles or droplets can be determined by the ...
Settling slurry flow near deposition velocity in inclined pipe of negative slope
Kesely, Mikoláš; Matoušek, Václav; Vlasák, Pavel
2018 - English
Pipe flow of sand-water slurry (settling slurry) is sensitive to pipe inclination. The effect of the angle to which the partially stratified flow is inclined from the horizontal has been subject to investigation in numerous studies. However, almost all of them focus on ascending flows, i.e. flows inclined to positive angles of inclination. It is well known that settling slurry flows inclined to negative slopes (descending flows) differ from those inclined to positive slopes, particularly at velocities near the deposition limit. The deposition limit velocity is the flow velocity at which stationary deposit starts to be formed at the bottom of the pipe. We investigate the effect of the negative slope on pipe flow near deposition limit velocity in the broad range of inclination angles. Besides the deposition limit, we focus on the distribution of solids across the pipe cross section. We combine experimental approach with mathematical modelling. Our new experiments with medium-to-coarse sand (mass-medium grain size 0.87 mm) in a 100-mm pipe inclined from 0 to -45 degree provide suitable data for a validation of predictions of our layered model for partially stratified flows in inclined pipes.
Available at various institutes of the ASCR
Settling slurry flow near deposition velocity in inclined pipe of negative slope
Pipe flow of sand-water slurry (settling slurry) is sensitive to pipe inclination. The effect of the angle to which the partially stratified flow is inclined from the horizontal has been subject to ...
Koagulace rozdílných typů látek ze sinic a řas
Novotná, Kateřina; Načeradská, Jana; Barešová, Magdalena; Janda, V.; Pivokonský, Martin
2018 - Czech
Příspěvek se zabývá charakterizací a koagulací rozdílných typů látek produkovaných fytoplanktonem (algal organic matter - AOM), zejména jejich neproteinovou složkou, tvořenou sacharidy aj. Tyto látky byly získány z celulárního organického materiálu zelené řasy Chlorella vulgaris. Při koagulaci neproteinových AOM byla testována dvě různá koagulační činidla na bázi hliníku (síran hlinitý - SH a polyaluminiumchlorid - PACI). Nejúčinnější koagulace bylo v obou případech dosaženo v oblasti kolem neutrálního pH (7,1-7,5 a 7,6-8,0 při použití SH a PACI, resp.), přičemž byly zapotřebí poměrně vysoké dávky činidla (8 a 10 mg.L-1 Al, resp.). I při optimalizovaných podmínkách koagulace však bylo odstraněno max. cca 20% neproteinových AOM. Vhodné podmínky, účinnost i mechanismy koagulace neproteinové složky se značně liší od těch pro AOM peptidy/proteiny, což souvisí s rozdílnými vlastnostmi daných skupin látek (distribuce molekulových hmotností, množství a charakter povrchových funkčních skupin atd.). Pro účinnou optimalizaci koagulace je tedy rozhodující nejen koncentrace, ale právě i charakter AOM. This study focused on coagulation of different algal organic matter (AOM) fractions, especially on its non-proteinaceous fraction. It was derived from cellular organic matter of Chlorella vulgaris, a freshwater algae. Two different Al-based coagulants were employed, i.e. alum and pre-hydrolyzed polyaluminim chloride (PACl). The highest coagulation efficiency was obtained at pH around neutral (pH 7.1-7.5 for alum and pH 7.6-8.0 for PACl) at relatively high dosages of coagulant (8 and 10 mg·L-1 as Al for alum and PACl, resp.). However, the maximum removal reached under the optimized conditions was only approximately 20%. The coagulation behaviour and efficiency of non-proteinaceous matter greatly differ from AOM peptide-proteins, which is discussed in the study.
Keywords:
algal organic matter; Chlorella vulgaris; coagulation; water treatment
Available at various institutes of the ASCR
Koagulace rozdílných typů látek ze sinic a řas
Příspěvek se zabývá charakterizací a koagulací rozdílných typů látek produkovaných fytoplanktonem (algal organic matter - AOM), zejména jejich neproteinovou složkou, tvořenou sacharidy aj. Tyto látky ...
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