Number of found documents: 859
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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\ndynamic impact load. The dynamic impact test is a suitable method for the\nstudy of thin protective coatings under such conditions. Aim of this paper\nis to describe the method of dynamic impact testing and the novel concepts\nof evaluation of the impact test results, such as the impact resistance and\nthe impact deformation rate. All of the presented results were obtained by\ntesting two W-B-C coatings with different C/W ratio. Different impact test\nresults are discussed with respect to the coatings microstructure, the\nchemical and phase composition, and the mechanical properties. It is shown\nthat coating adhesion to the HSS substrate played a crucial role in the\ncoatings.\n 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\ndynamic impact load. The dynamic impact test is a suitable method for the\nstudy 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

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

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

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

Měření a simulace zpětně odraženého záření při penetračním laserovém svařování
Horník, Petr; Mrňa, Libor; Šarbort, Martin; Šebestová, Hana
2019 - Czech
Laserový svařovací proces je doprovázen množství záření, jak ve viditelné části spektra, tak tepelné záření svarové lázně a v neposlední řadě i vlastní laserové záření. Při laserovém svařování se často používá penetrační režim, při kterém se tvoří paroplynový kanál – keyhole. Většina laserového záření je vícenásobným odrazem pohlcena uvnitř keyhole, avšak malá část se odráží zpět a prochází optickou soustavou svařovací hlavy a dopravním vláknem. Zpětně odražené laserové záření je také monitorováno přímo v laseru z důvodu ochrany rezonátoru a dalších optických komponent. Signál je snadno přístupný a takto získaných dat se dá využít i během svařovacího procesu. Proto byl navržen experiment, při kterém byla zjišťována souvislost mezi rozměry svaru, polohou ohniska a zpětně odraženým laserovým zářením. Dále pak byly výsledky měření porovnány se simulací. The laser welding process is accompanied by a wide range of radiation, both in the visible part of the spectrum and thermal radiation of the weld pool, and last but not least, the laser radiation itself. During penetration laser welding mode, which is often used, the keyhole is created. Most of the laser radiation is absorbed by the multiple reflections inside the keyhole, but a small portion is reflected back and passes through the welding head and the optical fiber. Back-reflected laser radiation is also monitored directly in the laser to protect the resonator and other optical components. The signal is easily accessible and obtained data can be used for monitoring during the welding process. Therefore, we designed experiment in which the relationship between weld dimensions, focal position, and back-reflected laser radiation was investigated. Furthermore, the measurement results were compared with the simulation. Keywords: laser welding; focus position; back-reflected radiation; ray-tracing simulation Fulltext is available at external website.
Měření a simulace zpětně odraženého záření při penetračním laserovém svařování

Laserový svařovací proces je doprovázen množství záření, jak ve viditelné části spektra, tak tepelné záření svarové lázně a v neposlední řadě i vlastní laserové záření. Při laserovém svařování se ...

Horník, Petr; Mrňa, Libor; Šarbort, Martin; Šebestová, Hana
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

Vliv teploty na spektrální valstnosti optických tenkých vrstev v laserové spetroskopii s absorpčními kyvetami
Oulehla, Jindřich; Pokorný, Pavel; Hrabina, Jan; Holá, Miroslava; Číp, Ondřej; Lazar, Josef
2019 - Czech
Studujeme vlic teploty na spektrální vlastnosti optických tenkých vrstev, které jsou využívány v laserové spektroskopii s absorpčními kyvetami. Jedná se zejména o vliv teploty na polohu minima zbytkové odrazivosti ve spektru a na pronikání pracovního plynu do struktury tenké vrstvy v závislosti na použité depoziční technologii.\n We stude the influence of thermal annealing on the optical performance of thin film coatings used in laser spectroscopy with iodine-filled absorption cells. We are particulary interested in the temperature influence on the position of the residual reflection minimum in the spectrum and on the permeation of the working gas into the coating structure depending on the coating technology used.\n Keywords: absolute frequency-measurement standard; thin film optics, coatings; evaporation; PIAD Fulltext is available at external website.
Vliv teploty na spektrální valstnosti optických tenkých vrstev v laserové spetroskopii s absorpčními kyvetami

Studujeme vlic teploty na spektrální vlastnosti optických tenkých vrstev, které jsou využívány v laserové spektroskopii s absorpčními kyvetami. Jedná se zejména o vliv teploty na polohu minima ...

Oulehla, Jindřich; Pokorný, Pavel; Hrabina, Jan; Holá, Miroslava; Číp, Ondřej; Lazar, Josef
Ústav přístrojové techniky, 2019

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