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A note to the measurement of extensional viscosity using SER Universal Testing Platform with different shapes of polymer samples
Švrčinová, Petra; Filip, Petr; Kharlamov, Alexander
2009 - anglický
For polymer melts, with respect to their numerical simulations, there were recommended to apply polymer samples (rectangles) with a width not exceeding 8 mm and a thickness less than 0.4 mm. The aim of this contribution is to document - for material used (LDPE Escorene, Exxon, USA) - the invariantness of the elongational viscosity measured with respect to sample dimensions including its width and thickness. The width of the samples used consecutively attained 12.7, 11.0, 9.3, and 7.4 mm; the thickness also ranged across a sufficiently broad interval (0.3-1.1mm). Temperature was set to 180, 190, and 200oC. For the measurements there were used the SER Universal Testing Platform from the Xpansion Instruments; the model SER-HV-P01 was applied with a Physica MCR501 rotational rheometer host system. The results obtained justify usage of a 'classical' width 12.7 mm (1/2") more suitable for better manipulation with a sample, especially its fixing to both drums perpendicularly to the clamps.
Klíčová slova:
extensional viscosity; SER Universal Testing Platform; LDPE
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
A note to the measurement of extensional viscosity using SER Universal Testing Platform with different shapes of polymer samples
For polymer melts, with respect to their numerical simulations, there were recommended to apply polymer samples (rectangles) with a width not exceeding 8 mm and a thickness less than 0.4 mm. The aim ...
Electrical response of multiwall carbon nanotubes (MWCNT) "buckypaper" on deformation
Slobodian, P.; Říha, Pavel; Olejník, R.; Kimmer, D.; Sáha, P.
2009 - anglický
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.
Klíčová slova:
Carbon nanotubes network; electrical resistance; compressive deformation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
Polyvinyl chloride; catheter; repressed migration of plasticizers
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
land use; rainfall - runoff simulation; vegetation change
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
flow measurements; turbulent flow; LDA; ADV
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
spatial variability; water repellency; WDPT test; infiltration; sorptivity
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 - anglický
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.
Klíčová slova:
CFD; lift coefficient; iced airfoil
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
22nd Symposium on Anemometry - Proceedings
Chára, Zdeněk; Klaboch, L.
2008 - anglický
Proceedings of 22nd Symposium on Anemometry. The conference was oriented on the experimental techniques applied in fluid mechanics. Sborník z konference 22. symposium o anemometrii. Konference byla zamřena na experimentální techniky používané v mechanice tekutin.
Klíčová slova:
anemometry; conference; proceedings
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
22nd Symposium on Anemometry - Proceedings
Proceedings of 22nd Symposium on Anemometry. The conference was oriented on the experimental techniques applied in fluid mechanics....
6th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering
Chára, Zdeněk; Bareš, V.
2008 - anglický
The conference was concentrated on the ultrasound Doppler shift based measurements of velocity profiles and flow mapping in the field of fluid and hydraulics engineering, environmental flow, and industrial and biomedical applications. Konference byla zaměřena na ultrazvukové metody měření rychlostního pole založené na dopplerově efektu ve vodním hospodářství, v průmyslových, biomedicínských a dalších odvětvích.
Klíčová slova:
ultrasonic; flow measurements; conference
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
6th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering
The conference was concentrated on the ultrasound Doppler shift based measurements of velocity profiles and flow mapping in the field of fluid and hydraulics engineering, environmental flow, and ...
On the measurement of elongational viscosity using SER universal testing platform
Švrčinová, Petra; Kharlamov, Alexander; Filip, Petr
2008 - anglický
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.
Klíčová slova:
elongational viscosity
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
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