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Electrical response of multiwall carbon nanotubes (MWCNT) "buckypaper" on deformation
Slobodian, P.; Říha, Pavel; Olejník, R.; Kimmer, D.; Sáha, P.
2009 - English
The network of entangled multiwall carbon nanotubes is shown to be a conductor whose resistance is sensitive to compressive strain both in the course of strain growth and when loading/unloading cycles are imposed. The cycles at first lead at to the resistance decrease but with a higher number of cycles they fade away.
Keywords:
Carbon nanotubes network; electrical resistance; compressive deformation
Available at various institutes of the ASCR
Electrical response of multiwall carbon nanotubes (MWCNT) "buckypaper" on deformation
The network of entangled multiwall carbon nanotubes is shown to be a conductor whose resistance is sensitive to compressive strain both in the course of strain growth and when loading/unloading cycles ...
Polyvinyl chloride catheters with repressed migration of plasticizers
Sedláček, T.; Polášková, M.; Kašpárková, V.; Filip, Petr; Sáha, P.
2009 - English
Impart flexibility and desired softness of polyvinylchloride (PVC) – one of the most widely used polymeric materials for medical device production – is achieved by addition of appropriate amount of plasticizer, usually di(2-ethylhexyl phthalate) (DEHP), into polymer matrix. DEHP is not chemically bonded to PVC and migrates to the surrounding media such as saliva, blood, plasma, or serum resulting in several toxic effects. Migration of DEHP can be significantly suppressed by embedding PVC into another polymer preventing its direct contact with surrounding liquid media. Coextruded TPU-PVC-TPU catheters were prepared with various thicknesses of TPU layers to evaluate its repressing effect on DEHP releasing. Releasing kinetic of DEPH from both three layered catheters and PVC catheters into the acetonitrile was observed in various time intervals and determined using reverse-phase liquid chromatographic technique.
Keywords:
Polyvinyl chloride; catheter; repressed migration of plasticizers
Available at various institutes of the ASCR
Polyvinyl chloride catheters with repressed migration of plasticizers
Impart flexibility and desired softness of polyvinylchloride (PVC) – one of the most widely used polymeric materials for medical device production – is achieved by addition of appropriate amount of ...
Approaches to credible identification of reliable parameters in rainfall-runoff model from long time series
Buchtele, Josef; Košková, Romana
2008 - English
The paper focuses on the issue of the credible identification of parameters of rainfall-runoff models taking into account the length of the calibration period. The benefits of the usage of the long-time observed data series during the model parameter determination have been analysed. The article deals with the uncertainties connected to evolution of the vegetation cover within the simulation of different runoff components. Článek se zabývá problematikou věrohodného stanovení parametrů srážko-odtokového modelu z hlediska volby kalibračního období. Analyzuje přínosy užití dlouhých řad měřených veličin ke stanovení paramterů modelu oproti běžně užívaným pěti až desiteletým řadám. Věnuje se nejasnostem spjatým se simulacemi různých složek odtoku v souvislosti s vývojem vegetačního krytu v jak v rámci roku, tak během několika desetiletí.
Keywords:
land use; rainfall - runoff simulation; vegetation change
Available at various institutes of the ASCR
Approaches to credible identification of reliable parameters in rainfall-runoff model from long time series
The paper focuses on the issue of the credible identification of parameters of rainfall-runoff models taking into account the length of the calibration period. The benefits of the usage of the ...
Comparative study of ADV and LDA measuring techniques
Chára, Zdeněk; Matoušek, V.
2008 - English
The contribution compares measurements of local velocities for water flows of different configurations carried out with the help of the ADV (Acoustic Doppler Velocimeter) and LDA (Laser Doppler Anemometry) measuring techniques. Three different geometrical configurations were tested – open channel flow, flow behind a rectangular cylinder and flow behind a hole in a plate. Příspěvek porovnává měření bodových rychlostí vody za různých konfigurací metodami LDA a ADV. Konfiguracemi jsou: proudění s volnou hladinou, proudění za obtékaným hranolem a úplavu za otvorem ve stěně.
Keywords:
flow measurements; turbulent flow; LDA; ADV
Available at various institutes of the ASCR
Comparative study of ADV and LDA measuring techniques
The contribution compares measurements of local velocities for water flows of different configurations carried out with the help of the ADV (Acoustic Doppler Velocimeter) and LDA (Laser Doppler ...
Small-scale variation of hydraulic properties in pine forest soil near Sekule, south-western Slovakia
Orfánus, T.; Lichner, Ľ.; Šír, Miloslav; Tesař, Miroslav
2008 - English
The variability of water repellency of pine-forest arenic Regosols and its influence on the infiltration process were estimated at the locality of Mláky II near Sekule in south-west Slovakia. The water drop penetration time (WDPT) tests of soil water repellency and infiltration tests with a miniaturized tension infiltrometer (3 mm diameter) at single-sample scale (100 cm3 volume, 22 cm2 surface) were performed. Extreme heterogeneity of water repellency and infiltration velocity was recorded. All the results suggested that the hydraulic properties of the soil are changing at millimetre scale due to the presence of unevenly distributed hydrophobic material. Na lokalitě Mláky II v blízkosti obce Sekule na jihozápadním Slovensku byla stanovena variabilita vodoodpudivosti půdy pod borovicovým lesem. Laboratorně byl testován vliv vodoodpudivosti půdy na infiltraci vody do půdy pomocí kapkového testu a pomocí podtlakového miniinfiltrometru o průměru 3 mm. Byly testovány vzorky půdy ve válci o objemu 100 cm3 a ploše podstavy 22 cm2. Na podstavě vzorku byla pozorována velká prostorová heterogenita vodoodpudivosti a rychlosti infiltrace vody. Výsledky ukazují, že v milimetrovém měřítku se hydraulické vlastnosti půdy výrazně mění vlivem nerovnoměrného zastoupení hydrofobního materiálu.
Keywords:
spatial variability; water repellency; WDPT test; infiltration; sorptivity
Available at various institutes of the ASCR
Small-scale variation of hydraulic properties in pine forest soil near Sekule, south-western Slovakia
The variability of water repellency of pine-forest arenic Regosols and its influence on the infiltration process were estimated at the locality of Mláky II near Sekule in south-west Slovakia. The ...
CFD and experimental study of aerodynamic degradation of iced airfoils
Horák, V.; Rozehnal, D.; Chára, Zdeněk; Hyll, A.
2008 - English
Paper deals with an aerodynamic degradation of iced airfoils. There are presented results of the lift coefficient solution in dependence on angle of attack, for NACA 0012 airfoil. Two different ice shapes chosen from available experimental data were tested. Příspěvek se zabývá aerodynamickou degradací na křídle s námrazou. Jsou prezentovány výsledky pro vztlakový koeficient v závislosti na úhlu náběhu pro křídlo NACA 0012. Byly testovány dva různé typy námrazy.
Keywords:
CFD; lift coefficient; iced airfoil
Available at various institutes of the ASCR
CFD and experimental study of aerodynamic degradation of iced airfoils
Paper deals with an aerodynamic degradation of iced airfoils. There are presented results of the lift coefficient solution in dependence on angle of attack, for NACA 0012 airfoil. Two different ice ...
On the measurement of elongational viscosity using SER universal testing platform
Švrčinová, Petra; Kharlamov, Alexander; Filip, Petr
2008 - English
The goal of this contribution is to present measurements of elongational viscosity for polyethylene material using SER Universal Testing Platform. The attention is paid to the possibilities how to check potential sagging of the samples measured and how to accelerate measurements for selected materials with the aim to eliminate possible material degradation. Cílem příspěvku je presentovat měření elongační viskozity polyethylénů pomozí tzv. SER Universal Testing Platform. Pozornost je věnována možnostem jak kontrolovat možné prověšování měřených vzorků a jak urychlit měření pro vybrané materiály s cíle eliminovat nástup možné degradace materiálu.
Keywords:
elongational viscosity
Available at various institutes of the ASCR
On the measurement of elongational viscosity using SER universal testing platform
The goal of this contribution is to present measurements of elongational viscosity for polyethylene material using SER Universal Testing Platform. The attention is paid to the possibilities how to ...
Experimental investigation of Magnus force acting on smooth sphere at high Reynolds numbers
Kharlamov, Alexander; Chára, Zdeněk; Vlasák, Pavel
2008 - English
The paper describes the results of experimental research dealing with rotating smooth spherical particles moving quasi-steadily in calm water. The motion of the particles was recorded by a digital video camera. The kinematics of the particles motion was analyzed numerically. The dimensionless Magnus force coefficient, the Reynolds number Re and spin parameter Γ (ratio of peripheral sphere velocity and translational velocity) were evaluated from the time series of the particle coordinates and its angle of rotation. The Magnus force was determined as a function of the Reynolds number and spin parameter for 3000 < Re < 42000 and 0.1 < Γ <7. The results were compared with results from literature and overall data were fitted by a simple function valid for 0.5 < Re < 140000 and 0.1 < Γ <10. Článek popisuje výsledky pokusů s rotující hladkou kulovou částicí při kvazi-stabilním pohybu v klidné vodě. Pohyb částice byl zaznamenán digitální videokamerou a kinematické parametry pohybu částice numericky analyzovány. Bezrozměrný součinitel Magnusovy síly, Reynoldsovo číslo a spin parametr Γ (poměr obvodové rychlosti rotující částice a její translační rychlosti) byly vyhodnoceny z časových řad souřadnic a úhlů rotace částice. Magnusova síla byla určena v závislosti na Reynoldsově čísle a spin parametru pro oblast 3000 < Re < 42000 a 0,1 < Γ <7. Výsledky byly porovnány s literárními údaji a data byly aproximovány jednoduchou funkcí platnou pro oblast 0,5 < Re < 140000 a 0,1 < Γ <10.
Keywords:
Magnus force; smooth spherical particle; particle rotation; Reynolds numbers; experimental investigation
Available at various institutes of the ASCR
Experimental investigation of Magnus force acting on smooth sphere at high Reynolds numbers
The paper describes the results of experimental research dealing with rotating smooth spherical particles moving quasi-steadily in calm water. The motion of the particles was recorded by a digital ...
Soil water dynamics in the Šumava Mts. and in the Krkonoše Mts. in August 2002
Tesař, Miroslav; Krejča, M.; Polívka, Jiří; Šír, Miloslav
2008 - English
The soil water movement during extreme rain is analysed in the Doupě and Kout catchment (Šumava Mts, Southern Bohemia) and in the Modrý Důl catchment (Krkonoše Mts., Northern Bohemia). Two cyclones, which moved from Hungary to Poland, caused extreme rainfall and subsequent extreme runoff in August, 2002. Precipitation, air and soil temperature, and tensiometric pressure were recorded in catchments. The analysis showed that the huge rain amount in August 2002 exceeded the retention capacity of the catchment covered by mature spruce forest and dwarf pine forest (Modrý Důl), dead forest and herb undergrowth (Kout), clearing covered by herbs (Doupě). It means that the plant cover played a negligible role in the runoff generation. The soil cover was not able to prevent the country from catastrophic runoff because its retention capacity is rather low (60 – 90 mm). V článku je analyzován pohyb vody v půdě při extrémních deštích v povodích Doupě a Kout (Šumava, Jižní Čechy) a v povodí Modrý potok (Krkonoše, Severní Čechy). Dvě cyklóny, které se přesouvaly z Maďarska směrem k Polsku, způsobily extrémní srážky a následné extrémní odtoky v srpnu 2002. V povodích jsou zaznamenávány srážky, teploty vzduchu a půdy a tenzometrické tlaky. Analýza ukázala, že vysoký srážkový úhrn v srpnu 2002 přesáhl retenční kapacitu povodí krytého dospělým smrkovým lesem a klečí (Modrý Důl), mrtvým lesem a bylinným podrostem (Kout) a porostem bylin na pasece (Doupě). To znamená, že vegetační kryt hrál zanedbatelnou roli při formování odtoku. V důsledku poměrně nízké retenční kapacity (60 – 90 mm) nebyl půdní kryt schopen zabránit katastrofickému odtoku.
Keywords:
mountain hydrology; extreme rain; soil-water movement
Available at various institutes of the ASCR
Soil water dynamics in the Šumava Mts. and in the Krkonoše Mts. in August 2002
The soil water movement during extreme rain is analysed in the Doupě and Kout catchment (Šumava Mts, Southern Bohemia) and in the Modrý Důl catchment (Krkonoše Mts., Northern Bohemia). Two cyclones, ...
Runoff formation in Senotín: a revitalised sub-mountain headwater area
Tesař, Miroslav; Syrovátka, O.; Lichner, Ľ.
2008 - English
The purpose of the Senotín pilot project (1993–2000) was to determine methods of revitalisation of a sub-mountain headwater area (0.38 km2) in the Novobystřická Vysočina Highlands (610–725 m a. s. l.). Seven underground clay shields stopped pipe drainage, and four balks prevented surface and subsurface runoff. These adaptations improved the water retention capacity of the whole catchment, as demonstrated by the formation of runoff in the revitalised area. A typical rainstorm (amount 15 mm, duration 5.6 hours, max. intensity 1.8 mm/20 minutes) and consequent runoff was analysed, along with the role of soil in runoff retardation and water retention. The time course of the contributing area was also quantified. The contributing area was formed in the surface soil layer with a thickness of about 40 cm. Runoff retardation lasted two hours after the rain began. Retention reached 98% of the total rainfall. Runoff lasted for 85 hours. Účelem projektu Senotín (1993–2000) bylo nalézt metody revitalizace podhorské pramenné oblasti (0,38 km2) v Novobystřické pahorkatině (610–725 m n. m.). Bylo vystavěno sedm podzemních jílových stěn, které přerušily trubní drenáž. Čtyři meze zabraňují povrchovému a podpovrchovému odtoku. Tyto terénní úpravy zlepšily vodní retenční kapacitu celého povodí, což je demonstrováno na příkladu formování odtoku z přívalového deště. Bylo analyzováno formování odtoku z deště o úhrnu 15 mm, trvání 5,6 hodin a maximální intenzitě 1,8 mm za 20 minut. Byl stanoven časový průběh retence vody v povodí a průběh velikosti zdrojové plochy. Zdrojová plocha se vytvořila v povrchové půdní vrstvě o mocnosti asi 40 cm. Retardace odtoku trvala asi 2 hodiny po začátku deště. Retence vody v povodí dosáhla 98 % srážkového úhrnu. Odtoková vlna trvala 85 hodin.
Keywords:
headwater area; landscape revitalisation; runoff formation
Available at various institutes of the ASCR
Runoff formation in Senotín: a revitalised sub-mountain headwater area
The purpose of the Senotín pilot project (1993–2000) was to determine methods of revitalisation of a sub-mountain headwater area (0.38 km2) in the Novobystřická Vysočina Highlands (610–725 m a. s. ...
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