Number of found documents: 911
Published from to

Měření absorpčních spekter HCN metodami laserové spektroskopie
Hošek, Martin; Hrabina, Jan; Řeřucha, Šimon; Pravdová, Lenka; Lazar, Josef; Číp, Ondřej
2021 - Czech
Kyanovodík (konkrétně izotop H13C14N) jakožto absorpční médium má velký potenciál pro realizaci frekvenčně stabilizovaných laserů, protože jeho absorpční spektrum pokrývá téměř celé telekomunikační pásmo C (1530-1565 nm). Široké absorpční spektrum lze s výhodou využít nejen pro kalibrace přístrojů v optických telekomunikacích ale i při nasazení moderních interferometrických metod pro odměřování velkoobjemových objektů (např. FSI - frekvenční skenovací interferometrie). Cílem našeho výzkumu je přesná charakterizace spektrálních profilů HCN a experimentální určení optických frekvencí odpovídajících středům absorpčních čar. Hydrogen Cyanide (specifically isotope H13C14N) has significant potential as an absorption medium for the frequency stabilised lasers’ realisation because its absorption spectrum covers the whole telecommunication C-band (1530-1565 nm). The broad absorption spectrum can be used not only for calibration of optical telecommunication devices but also for modern interferometric methods that are useful for measuring macroscale objects (e.g., FSI - frequency scanning interferometry). Our research aims to precisely characterise the profile of HCN’s spectral lines and determine the optical frequency of absorption lines’ corresponding centres. Keywords: absorption spectroscopy; HCN; laser standard Available at various institutes of the ASCR
Měření absorpčních spekter HCN metodami laserové spektroskopie

Kyanovodík (konkrétně izotop H13C14N) jakožto absorpční médium má velký potenciál pro realizaci frekvenčně stabilizovaných laserů, protože jeho absorpční spektrum pokrývá téměř celé telekomunikační ...

Hošek, Martin; Hrabina, Jan; Řeřucha, Šimon; Pravdová, Lenka; Lazar, Josef; Číp, Ondřej
Ústav přístrojové techniky, 2021

Svařování vysokopevnostní pohliníkované oceli 22MnB5
Šebestová, Hana; Horník, Petr; Mikmeková, Šárka; Novotný, Jan; Mrňa, Libor
2021 - Czech
Povlaky na bázi Al-Si jsou hojně používány jako povrchová ochrana ocelových plechů 22MnB5 proti oxidaci během procesu kalení při lisování, při kterém získávají svoji pevnost. Laserové svařování je vhodnou technologií spojování kalených výlisků, protože při něm nevzniká široká tepelně ovlivněná oblast s degradovanou mikrostrukturou. Díky vysoce koncentrované energii svazku dochází k velmi rychlému ohřevu i následnému ochlazování materiálu. Důsledkem je ale nedostatečná homogenizace svarového kovu. V místech bohatých na hliník z povlaku vznikají v martenzitické matrici feritické pásy, které snižují pevnost svaru o více než třetinu oproti základnímu materiálu. Zařazením elektrického oblouku s nízkou energií bezprostředně za laserový svazek je možné dosáhnout pomalejšího ochlazování svarového kovu, redukce feritických pásů a zvýšení pevnosti svarových spojů až na 90 % meze pevnosti základního materiálu. Al-Si-based coatings are widely used as surface protection of steel sheets against high-temperature oxidation during the hot stamping process. Laser welding is a suitable technology for hardened components joining because it does not produce a wide heat-affected zone with a degraded microstructure. The highly concentrated energy of the laser beam is responsible for rapid heating and subsequent rapid cooling of material which results in insufficient homogenization of the weld metal. In Al-rich areas (Al originates from the coating), ferritic bands are formed in the dominantly martensitic matrix. These bands decrease the strength of laser weld by more than one third compared to the base metal. The low-power electric arc placed immediately behind the laser beam can help to achieve a slower cooling of the weld metal, reduce the ferritic bands and increase the strength of weld joints up to 90 % of base metal tensile strength. Keywords: laser welding; laser-TIG welding; high-strength steel; cooling rate; microstructure; microhardness; tensile strength Available at various institutes of the ASCR
Svařování vysokopevnostní pohliníkované oceli 22MnB5

Povlaky na bázi Al-Si jsou hojně používány jako povrchová ochrana ocelových plechů 22MnB5 proti oxidaci během procesu kalení při lisování, při kterém získávají svoji pevnost. Laserové svařování je ...

Šebestová, Hana; Horník, Petr; Mikmeková, Šárka; Novotný, Jan; Mrňa, Libor
Ústav přístrojové techniky, 2021

Adhesion of PVD Coatings on Surface of Small Arm
Joska, Z.; Rak, L.; Daniel, Josef; Horníček, J.; Tříska, V.; Nguyen, C.H.
2020 - English
This work deals with the possibility of increasing the utility properties of the functional part of the weapon by deposition of PVD coating. These coatings are widely known for their high hardness and abrasion resistance without affecting the anticorrosion properties. The experimental part evaluates the created duplex coating on the piston of the assault rifle Sa vz. 58. Duplex coating adhesion, surface morphology and coating thickness was evaluated on opto digital microscope Olympus DSX 500. The impact resistance of the coating was evaluated by dynamic impact test. The durability tests of the coatings were carried out during the training of students in the military training. The results showed the application of PVD coating significantly reduced piston head wear and increased user comfort in the form of shortening time of the cleaning and maintenance process after firing. Keywords: adhesion of PVD Coatings Available at various institutes of the ASCR
Adhesion of PVD Coatings on Surface of Small Arm

This work deals with the possibility of increasing the utility properties of the functional part of the weapon by deposition of PVD coating. These coatings are widely known for their high hardness and ...

Joska, Z.; Rak, L.; Daniel, Josef; Horníček, J.; Tříska, V.; Nguyen, C.H.
Ústav přístrojové techniky, 2020

Trip steel specimen preparation for advanced sem and EBSD
Ambrož, Ondřej; Mikmeková, Šárka; Hegrová, J.; Aoyama, T.
2020 - English
Modern scanning electron microscopy (SEM) allows observations of specimens with high surface sensitivity. The surface sensitivity is significantly affected by the accelerating voltages. With the development of the scanning electron microscopy, the requirements for the surface quality of samples increase. Metallographic methods originally intended for light microscopy become insufficient. The problem occurs especially with multiphase materials having a fine-grained structure. The investigated TRIP steel consists of a ferritic-bainitic matrix, retained austenite and martensite phases. The sizes of the smallest phases are nanometer units. The volume of residual austenite was determined by X-ray diffraction. The basic preparation of all tested samples involved conventional metallographic grinding and very fine mechanical polishing. One sample was analysed in this state. Other samples were subsequently chemically polished, electropolished and chemical-mechanically polished. The specimens were observed in the SEM using a SE and a BSE detector at low energies immediately after the preparation. An EBSD was performed in the same areas to characterize the retained austenite. Topographical imaging by special AFM, integrated into the SEM, demonstrated that the mechanical polishing results in surface deformation and residual austenite is transformed. All other methods have their specifics and for modern sensitive SEM instruments it is necessary to optimize individual procedures. Keywords: TRIP steel; metallography; SEM; EBSD; AFM Available at various institutes of the ASCR
Trip steel specimen preparation for advanced sem and EBSD

Modern scanning electron microscopy (SEM) allows observations of specimens with high surface sensitivity. The surface sensitivity is significantly affected by the accelerating voltages. With the ...

Ambrož, Ondřej; Mikmeková, Šárka; Hegrová, J.; Aoyama, T.
Ústav přístrojové techniky, 2020

Dynamic impact wear and impact resistance of W-B-C coatings
Daniel, Josef; Grossman, Jan; Buršíková, V.; Zábranský, L.; Souček, P.; Mirzaei, S.; Vašina, P.
2020 - English
Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. Aim of this paper is to describe the method of dynamic impact testing and the novel concepts of evaluation of the impact test results, such as the impact resistance and the impact deformation rate. All of the presented results were obtained by testing two W-B-C coatings with different C/W ratio. Different impact test results are discussed with respect to the coatings microstructure, the chemical and phase composition, and the mechanical properties. It is shown that coating adhesion to the HSS substrate played a crucial role in the coatings. Keywords: boron carbide W-B-C; fracture resistance; impact wear; W-B-C Available at various institutes of the ASCR
Dynamic impact wear and impact resistance of W-B-C coatings

Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. ...

Daniel, Josef; Grossman, Jan; Buršíková, V.; Zábranský, L.; Souček, P.; Mirzaei, S.; Vašina, P.
Ústav přístrojové techniky, 2020

Study of secondary phases in trip steel by advanced sem and afm techniques
Mikmeková, Šárka; Ambrož, Ondřej; Hegrová, J.; Aoyama, T.
2020 - English
The paper aims to demonstrate a modern scanning electron microscope (SEM) as a powerful tool for visualization of the secondary phases in TRIP steel. The TRIP steel specimens prepared by various metallographic techniques were imaged by the SEM and the secondary phases presence was confirmed by an electron back-scattered diffraction (EBSD) technique. The chemical polishing by 5 % HF in H2O2 for 10 seconds results in selective etching for each individual phase, as confirmed by an atomic force microscopy (AFM) and hybrid AFM-in-SEM techniques. The phases are easily distinguishable in the SEM micrographs created by the low energy high take-off angle signal electrons. The proposed sample preparation technique together with special SEM imaging conditions enables us accurate analysis of distribution of secondary phases within the TRIP steel matrix and moreover, the retained austenite is distinguishable from the martensite phase. Keywords: TRIP steel; advanced SEM; metallography Available at various institutes of the ASCR
Study of secondary phases in trip steel by advanced sem and afm techniques

The paper aims to demonstrate a modern scanning electron microscope (SEM) as a powerful tool for visualization of the secondary phases in TRIP steel. The TRIP steel specimens prepared by various ...

Mikmeková, Šárka; Ambrož, Ondřej; Hegrová, J.; Aoyama, T.
Ústav přístrojové techniky, 2020

Deep learning for magnetic resonance spectroscopy quantification: A time frequency analysis approach
Shamaei, Amirmohammad
2020 - English
Magnetic resonance spectroscopy (MRS) is a technique capable of detecting chemical compounds from localized volumes in living tissues. Quantification of MRS signals is required for obtaining the metabolite concentrations of the tissue under investigation. However, reliable quantification of MRS is difficult. Recently deep learning (DL) has been used for metabolite quantification of MRS signals in the frequency domain. In another study, it was shown that DL in combination with time-frequency analysis could be used for artifact detection in MRS. In this study, we verify the hypothesis that DL in combination with time-frequency analysis can also be used for metabolite quantification and yields results more robust than DL trained with MR signals in the frequency domain. We used the complex matrix of absolute wavelet coefficients (WC) for the time-frequency representation of the signal, and convolutional neural network (CNN) implementation for DL. The comparison with DL used for quantification of data in the frequency domain is presented. Keywords: magnetic resonance spectroscop; quantification; deep learning; machine learning Fulltext is available at external website.
Deep learning for magnetic resonance spectroscopy quantification: A time frequency analysis approach

Magnetic resonance spectroscopy (MRS) is a technique capable of detecting chemical compounds from localized volumes in living tissues. Quantification of MRS signals is required for obtaining the ...

Shamaei, Amirmohammad
Ústav přístrojové techniky, 2020

Pokročilé metody přípravy vzorků TRIP ocelí a jejich zobrazování moderními technikami rastrovacího elektronového mikroskopu
Ambrož, Ondřej; Mikmeková, Šárka
2019 - Czech
Vícefázové oceli, mezi něž patří i TRIP oceli, vynikají svými excelentními mechanickými vlastnostmi a nacházejí uplatnění v mnoha odvětvích, jako je například automobilový průmysl. Studium mikrostruktury takovýchto materiálů je velmi obtížné, především s ohledem na rozlišení jednotlivých fází. U současně vyvíjených TRIP ocelí, vyznačujících se přítomností nano-fází ve struktuře, běžné charakterizační techniky selhávají a vzniká poptávka po vývoji nových technik, které umožní precizní charakterizaci fází v nano- měřítku. V této práci bude demonstrován přínos moderní rastrovací elektronové mikroskopie pro charakterizaci jednotlivých fází ve vybrané TRIP oceli. Multiphase steels, including TRIP steels, excel in their mechanical properties and find application in many sectors, such as the automotive industry. Studying the microstructure of such materials is very difficult, especially with regard to the differentiation of phases. Current TRIP steels are failing in conventional characterization techniques and there is a demand for the development of new techniques that will enable precise characterization of phases on a nanoscale. The aim of this paper is to use benefit of modern scanning electron microscopy to characterize of individual phases in selected TRIP steel. Keywords: TRIP steels, scanning electron microscopy, metallography Available at various institutes of the ASCR
Pokročilé metody přípravy vzorků TRIP ocelí a jejich zobrazování moderními technikami rastrovacího elektronového mikroskopu

Vícefázové oceli, mezi něž patří i TRIP oceli, vynikají svými excelentními mechanickými vlastnostmi a nacházejí uplatnění v mnoha odvětvích, jako je například automobilový průmysl. Studium ...

Ambrož, Ondřej; Mikmeková, Šárka
Ústav přístrojové techniky, 2019

Determination of thickness refinement using STEM detector segments
Skoupý, Radim; Krzyžánek, Vladislav
2019 - English
Quantitative STEM imaging together with Monte Carlo simulations of electron scattering in solids can bring interesting results about properties of many thin samples. It is possible to determine thickness of a sample, to calculate mass of particles and measure mass per length/area. Appropriate calibration is one of the crucial parts of the method. Even a small error or inaccuracy in detector response to electron beam either blanked or full brings significant error into thickness determination. This problem can be overcome by parallel STEM imaging in more segments of the detector. Comparing more segments gives a possibility to use a signal from different segments for different thicknesses of a sample. Accuracy of individual parts of the detector depends on the captured signal quantity. It is desirable to use such a STEM detector segment that provides the greatest signal change to a unit of thickness. To demonstrate the usage, we used a sample of Latex nanospheres placed on thin carbon lacey film, diameter of the nanospheres was around 600 nm in order to compare the results from different detector segments. Thanks to the known thickness of the sample (calculated from its geometrical shape), it is possible to estimate the optimal acquisition settings and post processing steps with the known and the true state of the sample. Keywords: electron-microscopy; Quantitative STEM; thickness determination; detector segments; Monte Carlo simulation Available at various institutes of the ASCR
Determination of thickness refinement using STEM detector segments

Quantitative STEM imaging together with Monte Carlo simulations of electron scattering in solids can bring interesting results about properties of many thin samples. It is possible to determine ...

Skoupý, Radim; Krzyžánek, Vladislav
Ústav přístrojové techniky, 2019

An appropriate method for assessing hydrogel pore sizes by cryo-sem
Adámková, Kateřina; Trudicová, M.; Hrubanová, Kamila; Sedláček, P.; Krzyžánek, Vladislav
2019 - English
The aim of our work was to examine and describe ultrastructure of the agarose hydrogel and any possible structural concentration dependencies, and to assess the distribution and size of pores of agarose hydrogel in dependence on its concentration. Four concentrations were prepared (0.5 %, 1.0 %, 2.0 % and 4.0 % of dry weight content) and cryo-SEM and turbidimetry methods were executed on wet (original) samples in order to image the ultrastructure and measure the pore sizes within. \nReasonable results were obtained for the wet samples as they were closer to their native state they are usually used for applications in. Cryo-SEM and turbidimetry provided comparable results of pore diameters and allowed to compare pore diameters dependant on the concentrations, moreover, it showed more detailed and realistic structure. Keywords: hydrogelcryo-SEM; agarose; cryo-SEM; freezing methods; image analysis Available at various institutes of the ASCR
An appropriate method for assessing hydrogel pore sizes by cryo-sem

The aim of our work was to examine and describe ultrastructure of the agarose hydrogel and any possible structural concentration dependencies, and to assess the distribution and size of pores of ...

Adámková, Kateřina; Trudicová, M.; Hrubanová, Kamila; Sedláček, P.; Krzyžánek, Vladislav
Ústav přístrojové techniky, 2019

About project

NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web

Send your suggestions and comments to nusl@techlib.cz

Provider

http://www.techlib.cz

Facebook

Other bases