Number of found documents: 487
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Virtuální zobrazení vzdálených objektů dlouhofokálními spojkami a konkávními zrcadly
Rail, Zdeněk; Vápenka, David
2016 - Czech
Dlouhofokální spojky a konkávní zrcadla mohou sloužit jako optické prvky, úhlově zvětšující rozměry vzdálených objektů podobně jako dalekohledy. Tyto jejich vlastnosti mohly být pravděpodobně používány pozorovateli dávno před objevem dalekohledu. Naše práce přináší optickou analýzu a výsledky astronomických pozorování soustavou dlouhofokální positivní čočky a lidského oka. The longfocal positive lenses and concave mirrors can serve as optical elements increasing the angular dimensions of the distant objects similarly to telescope.\nThese properties could be probably used by ancient observers before the discovery of telescope.\nOur paper brings optical analysis and results of visual astronomical observations with the longfocal positive lens. Keywords: Real and virtual imaging; Angular magnification; Ibn al-Haytham; Benjamin of Tudela; Roger Bacon; Giambattista della Porta; Johann Lippershey; Galileo; Kepler; Longfocal lens; Lighthouse on Pharos island; Ancient lenses; Šolc mirror; Camera obscura; Longfocal lens observation Fulltext is available at external website.
Virtuální zobrazení vzdálených objektů dlouhofokálními spojkami a konkávními zrcadly

Dlouhofokální spojky a konkávní zrcadla mohou sloužit jako optické prvky, úhlově zvětšující rozměry vzdálených objektů podobně jako dalekohledy. Tyto jejich vlastnosti mohly být pravděpodobně ...

Rail, Zdeněk; Vápenka, David
Ústav fyziky plazmatu, 2016

Black Chromia Plating for the Solar Radiation Absorbers
Brožek, Vlastimil; Březina, Václav; Brom, Petr; Kubatík, Tomáš František; Vilémová, Monika; Mastný, L.; Novák, M.
2016 - English
Black chromia layers were produced on copper, zirconium and aluminium substrates. These layers are aimed to serve as solar collectors. Efficiency of the layers during UV-VIS, UV radiation and WSP® plasma torch radiation is described. The chromia layers were prepared by a new procedure, i.e. deposition of ammonium dichromate solution using plasma torch or so called Liquid Precursor Plasma Spraying (LPPS). Solution of ammonium dichromate is fed into plasma stream, where dissociation takes place under temperatures of 4000 K – 25000 K. Up to nanometric oxide particles can be produced; the resulting size is dependent on solution concentration and feeding nozzle diameter. The particles impact on substrate and form coating. Using 2 wt.% to 5 wt.% solution of ammonium dichromate and feeding nozzle of 0.2 mm in diameter is the size of produced chromia particles about 6 µm which results in formation of 2 µm to 3 µm thick coating, i.e. according to the theory an optimal thickness 2.5 um for absorption layers, necessary condition for formation energy traps for IR radiation emitters up to 100°C. Moreover, black chromia coating is a suitable corrosion barrier of metallic substrates. \n\n Keywords: Solar collector; black chromia; plasma spraying; ceramic coatings Fulltext is available at external website.
Black Chromia Plating for the Solar Radiation Absorbers

Black chromia layers were produced on copper, zirconium and aluminium substrates. These layers are aimed to serve as solar collectors. Efficiency of the layers during UV-VIS, UV radiation and WSP® ...

Brožek, Vlastimil; Březina, Václav; Brom, Petr; Kubatík, Tomáš František; Vilémová, Monika; Mastný, L.; Novák, M.
Ústav fyziky plazmatu, 2016

Black Chromia Coatings on Metal Tubes for the Solar Collectors
Brožek, V.; Mastný, L.; Novák, M.; Vilémová, Monika; Kubatík, Tomáš František
2016 - English
This paper describes the results of the first phase of the study preparation, structure and properties of coatings modification of black chromium oxide on copper, aluminium, iron and zirconium tubes for solar collectors. The coatings are prepared by plasma spraying of liquid chromate method which is known as liquid precursor plasma spraying. Coatings have the function of an energy trap for thermal radiation wavelengths of 1 μm – 3 μm i.e. in the IR region. At the same time, the coating increases the corrosion resistance of metal substrates. The nanometric structure and thickness of the coating depend of the feeding distance and the concentration of chromate precursors. For the deposition of nanometric splats of melt chromiumIII oxide, a new type of feeder that injects precursors into the water stabilized thermal plasma produced by the WSP® generator has been\ndeveloped.\n Keywords: Solar collector; black chromia; plasma spraying; suspension spraying Available at various institutes of the ASCR
Black Chromia Coatings on Metal Tubes for the Solar Collectors

This paper describes the results of the first phase of the study preparation, structure and properties of coatings modification of black chromium oxide on copper, aluminium, iron and zirconium tubes ...

Brožek, V.; Mastný, L.; Novák, M.; Vilémová, Monika; Kubatík, Tomáš František
Ústav fyziky plazmatu, 2016

Spectroscopic Study of Underwater Electrical Discharge Generated by Nanosecond Pulses
Pongrác, Branislav; Šimek, Milan; Babický, Václav; Člupek, Martin; Lukeš, Petr
2016 - English
Underwater electrical discharge generated by high voltage pulses with nanosecond duration (~110 kV amplitude on the needle, ~5 ns duration (FWHM), 1 Hz repetition rate) has been investigated. Time–resolved optical emission spectroscopy showed different emission spectra profile of the ns–pulsed discharge compared to the μs–pulsed discharges investigated previously. Some characteristic peaks typical for water discharges (Hα, OI) were clearly visible in the spectra. In addition, the integral light emission of the discharge was recorded by photomultiplier tube. Keywords: nanosecond discharge; water discharge; time-resolved emission spectroscopy Available at various institutes of the ASCR
Spectroscopic Study of Underwater Electrical Discharge Generated by Nanosecond Pulses

Underwater electrical discharge generated by high voltage pulses with nanosecond duration (~110 kV amplitude on the needle, ~5 ns duration (FWHM), 1 Hz repetition rate) has been investigated. ...

Pongrác, Branislav; Šimek, Milan; Babický, Václav; Člupek, Martin; Lukeš, Petr
Ústav fyziky plazmatu, 2016

Corrosion behavior of plasma coatings CuAl10 and CuAl50 on magnesium alloy AZ 91
Kubatík, Tomáš František; Stoulil, J.; Stehlíková, K.; Slepička, P.; Janata, Marek
2016 - English
The most common magnesium alloy AZ 91 is widely used as a structural material, but its use is limited at higher temperatures and high humidity. Plasma spraying is a technology that allows to prepare protective metallic and non-metallic coatings on a wide variety of substrates including magnesium and its alloys. In this study, CuAl10 and CuAl50 were plasma sprayed on magnesium alloy AZ 91 with the aim to study corrosion resistance of the plasma sprayed coatings. The corrosion resistance of layers was evaluated by the method of electrochemical potentiodynamic measurement as well as long-term corrosion tests in a condensation chamber with 0.5 mol\nNaCl at the temperature of 35 °C for 1344 hours. Layers with 1, 2, 5 passes and passes of CuAl10 with the thickness ranging from 75 to 716 mm and CuAl50 with the thickness ranging from 64 to 566 mm were prepared. The increased corrosion velocity was observed in the case of thin layers of 2 and 5 passes due to the development of a galvanic corrosion couple. The CuAl10 layer prepared with ten passes has an outstanding corrosion resistance. Keywords: magnesium alloy AZ 91; plasma spraying; corrosion resistance Fulltext is available at external website.
Corrosion behavior of plasma coatings CuAl10 and CuAl50 on magnesium alloy AZ 91

The most common magnesium alloy AZ 91 is widely used as a structural material, but its use is limited at higher temperatures and high humidity. Plasma spraying is a technology that allows to prepare ...

Kubatík, Tomáš František; Stoulil, J.; Stehlíková, K.; Slepička, P.; Janata, Marek
Ústav fyziky plazmatu, 2016

Deposition of Titania from Solution by Hybrid Water-Stabilized Plasma Torch
Mušálek, Radek; Medřický, Jan; Tesař, Tomáš; Kotlan, Jiří; Lukáč, František
2016 - English
Thermal spraying with liquid feedstock presents a novel route for deposition of functional coatings. In this study, possibility of preparation of titania coatings from solution by hybrid water stabilized plasma torch is presented. Coatings were prepared from solution of titanium isopropoxide Ti[OCH(CH3)2]4 in anhydrous ethanol. Fragmentation of feedstock stream in the plasma jet was monitored by shadowgraphy. Deposition was carried out on steel samples mounted to the cooled rotating carousel. Cross-sectional images from SEM microscope showed successful formation of the deposit with dual morphology consisting of fine feather-like features combined with bigger droplets. X-ray diffraction revealed formation of nanometric rutile crystallites. Keywords: Thermal spraying; plasma spraying; titania; solution; liquid feedstock Available at various institutes of the ASCR
Deposition of Titania from Solution by Hybrid Water-Stabilized Plasma Torch

Thermal spraying with liquid feedstock presents a novel route for deposition of functional coatings. In this study, possibility of preparation of titania coatings from solution by hybrid water ...

Mušálek, Radek; Medřický, Jan; Tesař, Tomáš; Kotlan, Jiří; Lukáč, František
Ústav fyziky plazmatu, 2016

Formation of RONS in cold air plasma activazed water and their effects on cell membranes of Escherichia coli
Tarabová, B.; Machala, Z.; Doležalová, Eva; Lukeš, Petr
2016 - English
In this work, we focused on the detection of secondary reactive oxygen and nitrogen species (RONS) formed by cold plasma induced gas-liquid chemistry in air discharge activated water and liquids. Plasma induced chemical changes in plasma activated water (PAW) were correlated with the antibacterial effect, sublethal injury of bacterial cells and peroxidation of membrane lipids. The contribution of the electric field induced by the plasma treatment was evaluated by the detection of membrane permeabilization. The bactericidal effects of direct (plasma and PAW) and indirect (only PAW) treatments were compared with long-term preservation of the PAW with its antibacterial properties Keywords: cold air plasma; plasma activated water; sublethal injury; lipoperoxidation Available at various institutes of the ASCR
Formation of RONS in cold air plasma activazed water and their effects on cell membranes of Escherichia coli

In this work, we focused on the detection of secondary reactive oxygen and nitrogen species (RONS) formed by cold plasma induced gas-liquid chemistry in air discharge activated water and liquids. ...

Tarabová, B.; Machala, Z.; Doležalová, Eva; Lukeš, Petr
Ústav fyziky plazmatu, 2016

Gap – gep – mezera?
Obdržálek, J.; Bílková, Petra; Mlynář, Jan
2016 - Czech
Jsou prezentovány obecné terminologické obtíže v odborném jazyce fyziky kontinua. Zvláště se příspěvek zabývá výhodami a nevýhodami velkého vlivu angličtiny z hlediska grafického (typologického) a fonetického. They presented the general terminological difficulties in technical language continuum physics. In particular it deals with the advantages and disadvantages of the great influence of English in terms of graphical (typological) and phonetic Keywords: phonetics; typology Available at various institutes of the ASCR
Gap – gep – mezera?

Jsou prezentovány obecné terminologické obtíže v odborném jazyce fyziky kontinua. Zvláště se příspěvek zabývá výhodami a nevýhodami velkého vlivu angličtiny z hlediska grafického (typologického) a ...

Obdržálek, J.; Bílková, Petra; Mlynář, Jan
Ústav fyziky plazmatu, 2016

Arc–Anode Attachment Area in DC Arc Plasma Torch at Low Pressure
Ondáč, Peter; Mašláni, Alan; Hrabovský, Milan
2016 - English
Studying the processes in the anode attachment area of a DC arc plasma torch helps to extend the lifetime of the anode, stabilize the plasma flow for plasma spraying and better understand the movement of the anode attachment. In this work, such processes were studied at low pressure, by a non-disturbing method, using a high-speed camera and a high voltage probe. We also found pressure ranges, in which the following transitions were observed: the constricted/diffuse anode attachment, and subsonic/supersonic plasma jet\n Keywords: Arc Plasma Torch; Arc–Anode Attachment; Low Pressure Available at various institutes of the ASCR
Arc–Anode Attachment Area in DC Arc Plasma Torch at Low Pressure

Studying the processes in the anode attachment area of a DC arc plasma torch helps to extend the lifetime of the anode, stabilize the plasma flow for plasma spraying and better understand the movement ...

Ondáč, Peter; Mašláni, Alan; Hrabovský, Milan
Ústav fyziky plazmatu, 2016

Sférochromatické vada Clarkova objektivu z observatoře v Ondřejově
Rail, Zdeněk; Šrajer, Bohdan; Jareš, Daniel; Vápenka, David; Pintr, Pavel
2016 - Czech
V naší práci jsou předloženy výsledky matematické simulace zbytkových vad Clarkova objektivu o průměru 8 palců (203.2 mm). Tento achromatický dublet je používán na observatoři v Ondřejově více než 100 let k pozorování Slunce. In our paper the results of mathematical simulations of the residual aberrations of Clark‘s 8 inch (diameter 203.2 mm) objective lens are presented. This achromatic dublet has been used at the Ondřejov Observatory for more than 100 years mostly for solar observation. Keywords: Alvan Clark doublet; Achromatic objective; Spherochromatic aberration; Longitudal chromatic aberration; Dispersion curve; Non aplanatic dublet; Spotdiagrams; Solar photosphere photography; Ondrejov observatory Fulltext is available at external website.
Sférochromatické vada Clarkova objektivu z observatoře v Ondřejově

V naší práci jsou předloženy výsledky matematické simulace zbytkových vad Clarkova objektivu o průměru 8 palců (203.2 mm). Tento achromatický dublet je používán na observatoři v Ondřejově více než 100 ...

Rail, Zdeněk; Šrajer, Bohdan; Jareš, Daniel; Vápenka, David; Pintr, Pavel
Ústav fyziky plazmatu, 2016

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