Number of found documents: 809
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Synergické efekty svařování laser - TIG
Kubíček, J.; Doležal, P.; Mrňa, Libor; Šebestová, Hana; Horník, Petr
2018 - Czech
Laserové svařování ve srovnání s konvenčními obloukovými metodami je doprovázeno rychlou rychlostí chlazení. To může vést ke vzniku nežádoucí mikrostruktury svařovaného kovu a tepelně postižené zóny některých ocelových tříd, což má negativní dopad na jejich mechanické vlastnosti. Předehřívání je poměrně problematické kvůli vysoké rychlosti svařování laserem. Byla testována možnost předehřívání teplem z obloukového výboje přidruženého hořáku TIG. Přesný držák byl vyroben pro upevnění hořáku na laserovou svařovací hlavu, umožňující umístění TIG elektrody směrem k laserovému paprsku a obrobku. Byla provedena řada ocelových zkoušek S460MC a S700MC s vysokou pevností. Účinek proudění TIG na mikrostrukturální změny byl prokázán. Některé svařovací experimenty byly porovnány s simulacemi svařování SYSWELD. Laser welding compared to conventional arc methods is accompanied by rapid cooling rates. It can lead to the formation of undesirable microstructure of the weld metal and heat affected zone of some steel grades which has a negative impact on their mechanical properties. The preheating is quite problematic because of high speed of laser welding. The possibility of preheating by the heat of the arc discharge of the associated TIG burner has been tested. Precise holder has been fabricated to fix the burner to the laser welding head allowing TIG electrode positioning towards the laser beam and the workpiece. A number of high strength steel S460MC and S700MC welding experiments was performed. The effect of TIG current on microstructural changes has been proven. Some welding experiments were compared to the SYSWELD welding simulations.\n Keywords: laser – TIG welding; cooling rate; HSLA steels; microstructure; tensile strength Available at various institutes of the ASCR
Synergické efekty svařování laser - TIG

Laserové svařování ve srovnání s konvenčními obloukovými metodami je doprovázeno rychlou rychlostí chlazení. To může vést ke vzniku nežádoucí mikrostruktury svařovaného kovu a tepelně postižené zóny ...

Kubíček, J.; Doležal, P.; Mrňa, Libor; Šebestová, Hana; Horník, Petr
Ústav přístrojové techniky, 2018

Fluorescence a povrchem zesílená Ramanova spektroskopie v mikrofluidice pro monitorování enzymatických reakcí
Pilát, Zdeněk; Šmatlo, Filip; Ježek, Jan; Krátký, Stanislav; Zemánek, Pavel
2017 - Czech
Realizovali jsme dva různé systémy detekce koncentrace molekul v mikrofluidních systémech. První způsob využívá optická vlákna a detekuje intenzitu fluorescence, zatímco druhá metoda spočívá v užití povrchem zesílené Ramanovy spektroskopie (surface enhanced Raman spectroscopy, SERS). We have implemented two different systems for detecting the concentration of molecules in microfluidic systems. The first method uses optical fibers and detects the intensity of fluorescence, while the second method is using surface enhanced Raman spectroscopy (SERS). Keywords: optofluidics; biofotonics Available at various institutes of the ASCR
Fluorescence a povrchem zesílená Ramanova spektroskopie v mikrofluidice pro monitorování enzymatických reakcí

Realizovali jsme dva různé systémy detekce koncentrace molekul v mikrofluidních systémech. První způsob využívá optická vlákna a detekuje intenzitu fluorescence, zatímco druhá metoda spočívá v užití ...

Pilát, Zdeněk; Šmatlo, Filip; Ježek, Jan; Krátký, Stanislav; Zemánek, Pavel
Ústav přístrojové techniky, 2017

Laserový standard pro metrologii délky a času
Pravdová, Lenka; Hrabina, Jan; Čížek, Martin; Číp, Ondřej
2017 - Czech
Předkládaná práce popisuje vývoj a dosažené parametry laserového standardu přesného optického kmitočtu pracujícího v IR spektrálním pásmu (okolí 1540 nm). Úkolem bylo vyvinout stabilní a robustní laserový systém umožňující nasazení nejen ve vědeckých a metrologických laboratořích, ale dovolující i distribuci přesných signálů po stávajících telekomunikačních optických spojích do cílových aplikací v průmyslu. We present the development and the achieved parameters of the telecom C-band optical frequency laser standard. Compact and robust laser system based on ultra-narrow linewidth fiber laser achieves relative frequency stabilities from 9e-13/1s down to 8e-14/256s levels and can serve as stable frequency source for applications of dissipation of precise time and frequency, wavelength calibrations in optical telecommunication or laser interferometry measurement systems. Keywords: length and time metrology; laser standards; optical frequency stabilization; acetylene Available at various institutes of the ASCR
Laserový standard pro metrologii délky a času

Předkládaná práce popisuje vývoj a dosažené parametry laserového standardu přesného optického kmitočtu pracujícího v IR spektrálním pásmu (okolí 1540 nm). Úkolem bylo vyvinout stabilní a robustní ...

Pravdová, Lenka; Hrabina, Jan; Čížek, Martin; Číp, Ondřej
Ústav přístrojové techniky, 2017

In vivo study of diatom assemblages using low temperature method for ESEM
Tihlaříková, Eva; Neděla, Vilém; Fránková, Markéta
2017 - English
Diatoms are the most species-rich algal group represented by 12 000 described species and are recognized as powerful bio indicators and used for water quality monitoring. Diatom taxonomy is predominantly based on the morphology of ornate silicified cell wall called frustule composed of two overlapping parts (thecae). This frustule displays intricate patterns and designs unique to each species. For these studies conventional scanning electron microscopy (SEM) was and still is widely used. This method requires cleaning of diatom frustules in strong acids and peroxides followed by conductive coating.This aggressive procedure removes protoplast and damages delicate structures. Environmental scanning electron microscopy (ESEM) brings advantages of observation of fresh diatom material that are presence of whole intact diatom cells, not only empty diatom frustules, extracellular mucilaginous diatom secrets (e.g. pads, stalks, tubes) and whole diatom assemblages directly in situ together with other algal assemblages (e.g. cyanobacteria or green algae). However, in diatom research, ESEM is used mainly for elimination of conductive coating and observation of these organisms in their native wet state adhered directly on the host plant is not yet common. The ESEM observation of native aquatic samples is usually affected with radiation damage that can be lovered by the use of special methods like the Low Temperature Method (LTM) for the ESEM. Keywords: ESEM; diatom; morphology; LTM Available at various institutes of the ASCR
In vivo study of diatom assemblages using low temperature method for ESEM

Diatoms are the most species-rich algal group represented by 12 000 described species and are recognized as powerful bio indicators and used for water quality monitoring. Diatom taxonomy is ...

Tihlaříková, Eva; Neděla, Vilém; Fránková, Markéta
Ústav přístrojové techniky, 2017

Nanopatterning of Silicon Nitride Membranes
Matějka, Milan; Krátký, Stanislav; Řiháček, Tomáš; Kolařík, Vladimír; Chlumská, Jana; Urbánek, Michal
2017 - English
Membranes are typically created by a thin silicon nitride (SIN) layer deposited on a silicon wafer. Both, top and bottom side of the wafer is covered by a thin layer of the silicon nitride. The principle of silicon nitride membranes preparation is based on the wet anisotropic etching of the bottom side of the silicon wafer with crystallographic orientation (100). While the basic procedure for the preparation of such membranes is well known, the nano patterning of thin membranes presents quite important challenges. This is partially due to the mechanical stress which is typically presented within such membranes. The resolution requirements of the\nmembrane patterning have gradually increased. Advanced lithographic techniques and etching procedures had to be developed. This paper summarizes theoretical aspects, technological issues and achieved results. The application potential of silicon nitride membranes as a base for multifunctional micro system (MMS) is also\ndiscussed. Keywords: e-beam writer; silicon nitride membranes; nano patterning; anisotropic etching Available at various institutes of the ASCR
Nanopatterning of Silicon Nitride Membranes

Membranes are typically created by a thin silicon nitride (SIN) layer deposited on a silicon wafer. Both, top and bottom side of the wafer is covered by a thin layer of the silicon nitride. The ...

Matějka, Milan; Krátký, Stanislav; Řiháček, Tomáš; Kolařík, Vladimír; Chlumská, Jana; Urbánek, Michal
Ústav přístrojové techniky, 2017

Effect of gold coating on emissivity and absorptivity of Ti-6Al-4V alloy
Frolec, Jiří; Králík, Tomáš; Musilová, Věra; Urban, Pavel
2017 - English
The article provides experimental analysis of total hemispherical emissivity and absorptivity of Ti-6Al-4V alloy before and after deposition of 1-2 .pí.m gold layer. We measured their dependences on the temperature of thermal radiation (varying from 20 K to 320 K) and confronted these results with mechanically polished copper, i.e. with material known for extremely low emissivity and absorptivity. Galvanic deposition of pure gold resulted in significant lowering of original emissivity of Ti-6Al-4V bare surfaces from 15.8 percent to 3.4 percent at 300 K and from 4.1 percent to 1.1 percent at 20 K. Our findings about thermal-radiative properties have practical relevance for an improvement of a low temperature part of an ultra-high vacuum scanning probe microscope\n(UHV-SPM) designed by our group and could also be useful for other applications and low temperature systems. Keywords: cryogenics; gold films; heat transfer; thermal radiation Available at various institutes of the ASCR
Effect of gold coating on emissivity and absorptivity of Ti-6Al-4V alloy

The article provides experimental analysis of total hemispherical emissivity and absorptivity of Ti-6Al-4V alloy before and after deposition of 1-2 .pí.m gold layer. We measured their dependences on ...

Frolec, Jiří; Králík, Tomáš; Musilová, Věra; Urban, Pavel
Ústav přístrojové techniky, 2017

Role of the superconductivity in radiative heat transfer
Králík, Tomáš; Musilová, Věra; Srnka, Aleš; Fořt, Tomáš; Frolec, Jiří
2017 - English
The absorption and emission of thermal radiation by metals is related to their electrical properties that are influenced by impurities, defects and temperature. We show by some examples of measurements on common metals how different can be the thermal radiative properties. When the heat is transferred across a microscopic vacuum gap in the near field regime, it is possible to achieve a step-like change of the heat\ntransfer based on a superconducting transition. An interesting feature of this effect is the nonlinear thermal conductivity effecting a change of the sign of the differential thermal conductivity across the vacuum gap. Keywords: thermal radiation; near field; superconductivity Available at various institutes of the ASCR
Role of the superconductivity in radiative heat transfer

The absorption and emission of thermal radiation by metals is related to their electrical properties that are influenced by impurities, defects and temperature. We show by some examples of ...

Králík, Tomáš; Musilová, Věra; Srnka, Aleš; Fořt, Tomáš; Frolec, Jiří
Ústav přístrojové techniky, 2017

Experimentální fluorescenční zařízení pro dielektroforetické třídění kapének v mikrofluidních čipech
Ježek, Jan; Pilát, Zdeněk; Šmatlo, Filip; Zemánek, Pavel
2017 - Czech
V současné době mnoho chemických a biologických oborů využívá pro své pozorování různé formy spektroskopie. Jednou z nejrozšířenějších metod je fluorescenční spektroskopie. Zároveň se v posledních sedmi letech začaly bouřlivě rozvíjet mikrofluidní techniky, které využívají mikrofluidních kanálků, kterými protéká nosná kapalina, která unáší kapénky o průměru od jednotek po desítky až stovky mikrometrů. Tyto kapénky, nemísitelné s nosnou kapalinou, slouží jako kapalné mikrokontejnery, obsahující analyzovaný vzorek a nezbytné reagencie. Pomocí speciálních mikrofluidních technik lze, např. fúzovat kapénky s různým obsahem (řízené spouštění chemických reakcí), vysokou rychlostí měnit koncentrace reaktantů v kapénce (koncentrační gradienty), třídit kapénky podle obsahu (vytváření nových kmenů buněk), apod. At present, many chemical and biological disciplines use different forms of spectroscopy for their observations. One of the most common methods is fluorescence spectroscopy. During the last seven years, microfluidic techniques began developing rapidly, using channels in which two immiscible liquids create droplets with diameters from units to tens to hundreds of micrometers. These droplets serve as liquid microcontainers containing the analysed sample and the necessary reagents. Using special microfluidic techniques, it is possible to fuse droplets with different contents (controlled triggering of chemical reactions), to change the concentration of reactants in the droplet with high speed (concentration gradients), or sort the droplets by content (creation of new cell strains).\n\n Keywords: fiber optics; laser systems; microfluidic chips; microcapades; spectroscopy; dielectrophoretic sorting Available at various institutes of the ASCR
Experimentální fluorescenční zařízení pro dielektroforetické třídění kapének v mikrofluidních čipech

V současné době mnoho chemických a biologických oborů využívá pro své pozorování různé formy spektroskopie. Jednou z nejrozšířenějších metod je fluorescenční spektroskopie. Zároveň se v posledních ...

Ježek, Jan; Pilát, Zdeněk; Šmatlo, Filip; Zemánek, Pavel
Ústav přístrojové techniky, 2017

Parameter Optimization of Multi-Level Diffraction Gratings
Matějka, Milan; Kolařík, Vladimír; Horáček, Miroslav; Král, Stanislav
2017 - English
Originally, the e-beam lithography (EBL) is a technique for creating high-resolution black and white masks for the optical lithography. Multi-level relief structures can be also prepared using EBL patterning. Their preparation is based on the image patterning with a gradient of exposure doses. Large-area multi-level structures can be effectively prepared using the electron beam pattern generator with a variable shaped beam. We present several writing strategies. Basically, the main writing strategy uses one stamp (i.e. one elementary exposure of the shaped electron beam) per one elementary area with the same exposure dose. This simple approach is fast and flexible, however it does not guarantee optimal results. The main problem is an imperfection of the stamps (size, shape, and homogeneity). Advanced algorithms are based on multiple\nexposure of the same elementary area, the total local exposure dose is a sum of several different elementary exposures (stamps). Using these algorithms, a smoother surface of the structure can be achieved. On the other hand, the writing speed is considerably decreased. Tradeoff between the achieved parameters and the writing speed is discussed for selected set of writing strategy algorithms. Keywords: e-beam pattern generator; variable shaped beam; grayscale lithography; multi-level grating Available at various institutes of the ASCR
Parameter Optimization of Multi-Level Diffraction Gratings

Originally, the e-beam lithography (EBL) is a technique for creating high-resolution black and white masks for the optical lithography. Multi-level relief structures can be also prepared using EBL ...

Matějka, Milan; Kolařík, Vladimír; Horáček, Miroslav; Král, Stanislav
Ústav přístrojové techniky, 2017

Noise behaviour of field emission cathode based on lead pencil graphite
Knápek, Alexandr; Horáček, Miroslav; Hrubý, František; Šikula, J.; Kuparowitz, T.; Sobola, D.
2017 - English
The paper describes electrical noise of experimental field emission cathodes based on “polymer” pencil leads which have a high content of hybridized carbon with a low degree of surface oxidation and silicon monoxide (SiO). Charge transport within experimental samples is evaluated based on results provided by the noise spectroscopy method. The paper also briefly describes the experimental preparation method of graphite tips based on ion milling which allow obtaining ultrasharp tips of a diameter lower than 100 nm. Keywords: field emission; lead pencil graphite; noise spectroscopy Available at various institutes of the ASCR
Noise behaviour of field emission cathode based on lead pencil graphite

The paper describes electrical noise of experimental field emission cathodes based on “polymer” pencil leads which have a high content of hybridized carbon with a low degree of surface oxidation and ...

Knápek, Alexandr; Horáček, Miroslav; Hrubý, František; Šikula, J.; Kuparowitz, T.; Sobola, D.
Ústav přístrojové techniky, 2017

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