Number of found documents: 634
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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

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

Recent Trends in Charged Particle Optics and Surface Physics Instrumentation. Proceedings of the 16th International Seminar
Mika, Filip; Pokorná, Zuzana
2018 - English
The origins of the seminar “Recent Trends in Charged Particle Optics and Surface Physics Instrumentation” date back into the eighties, when as a part of the isolated “Eastern Bloc”, we were short of English-language books, papers and conferences. In 1990, at the second Seminar, there were as many as 30 participants from 5 countries. The third Seminar in 1992 was moved to hotel Skalský dvur in the Bohemian-Moravian Highlands where it has been held as a biannual meeting ever since.\nThe Seminar takes place in a secluded lakeside hotel surrounded by beautiful nature and calm forests, so all participants have a great possibility to see each other every day and to discuss their topics of interest in more detail. This is a great advantage compared to the huge bustling conferences with their many parallel sections, which are a lively celebration of science but\nsometimes it is difficult to meet there the person with whom you want to discuss a particular scientific topic in more detail.\nFrom the very beginning, the Seminar has been conceived as a meeting devoted more to asking questions not answered yet, than to reporting results. This spirit is usually less present in the introductory presentations and posters but is dominant in the following discussions.\n Keywords: charged particle optics; surface physics; instrumentation Available at various institutes of the ASCR
Recent Trends in Charged Particle Optics and Surface Physics Instrumentation. Proceedings of the 16th International Seminar

The origins of the seminar “Recent Trends in Charged Particle Optics and Surface Physics Instrumentation” date back into the eighties, when as a part of the isolated “Eastern Bloc”, we were short of ...

Mika, Filip; Pokorná, Zuzana
Ústav přístrojové techniky, 2018

Very low energy electron transmission spectromicroscopy
Daniel, Benjamin; Radlička, Tomáš; Piňos, Jakub; Mikmeková, Šárka; Konvalina, Ivo; Frank, Luděk; Müllerová, Ilona
2018 - English
For more than 25 years, Scanning Low Energy Electron Microscopy (SLEEM) has been\ndeveloped at the Institute of Scientific Instruments (ISI), with several commercially available SEMs adapted with a cathode lens for SLEEM use, as well as a dedicated self-built UHVSLEEM setup.\nFor a better understanding of contrast formation at low energies, especially at very low energies below 50 eV, where the local density of states plays an important role, more general knowledge about the interaction of (very) low energy electrons with solids is required. This will be achieved using a newly developed ultra-high vacuum (UHV SLEEM) setup which includes several enhancements compared to other available machines. Data processing is presented in, and processed data will be further used and tested with the Monte Carlosimulation package BRUCE, which is being developed by Werner et al. at TU Vienna. Keywords: low energy scanning electron microscopy; electron microscopy; time of flight; electron energy lost spectroscopy Available at various institutes of the ASCR
Very low energy electron transmission spectromicroscopy

For more than 25 years, Scanning Low Energy Electron Microscopy (SLEEM) has been\ndeveloped at the Institute of Scientific Instruments (ISI), with several commercially available SEMs adapted with a ...

Daniel, Benjamin; Radlička, Tomáš; Piňos, Jakub; Mikmeková, Šárka; Konvalina, Ivo; Frank, Luděk; Müllerová, Ilona
Ústav přístrojové techniky, 2018

Hiding e-beam exposure fields by deterministic 2D pattering
Horáček, Miroslav; Knápek, Alexandr; Matějka, Milan; Krátký, Stanislav; Urbánek, M.; Mika, Filip; Kolařík, Vladimír
2018 - English
The high stability and good current homogeneity in the spot of the e-beam writer is crucial to\nthe exposure quality, particularly in the case of large-area structures when gray-scale\nlithography is used. Even though the deflection field distortion is calibrated regularly and\nbeam focus and beam astigmatism is dynamically corrected over the entire deflection field, we can observe disturbances in the exposed relief.\nRecently, we presented a method that makes use of e–beam exposure imperfection by\nintroducing marginally visible high–frequency diffraction gratings of variable pitch that fill in\nseparate orthogonal exposure fields. The actually presented approach follows up our\nresearch on aperiodic arrangements of optical primitives, especially on the phyllotactic–\nlike arrangement of sub–micron relief optical elements. This approach is extended from the\ndiffraction element arrangement to the higher level of exposure fields arrangements. Keywords: phyllotaxis; electron beam lithography Available at various institutes of the ASCR
Hiding e-beam exposure fields by deterministic 2D pattering

The high stability and good current homogeneity in the spot of the e-beam writer is crucial to\nthe exposure quality, particularly in the case of large-area structures when gray-scale\nlithography is ...

Horáček, Miroslav; Knápek, Alexandr; Matějka, Milan; Krátký, Stanislav; Urbánek, M.; Mika, Filip; Kolařík, Vladimír
Ústav přístrojové techniky, 2018

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