National Repository of Grey Literature 17 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Natural aging and early precipitation stages in Al-Mg-Si alloys
Lamač, Marcel ; Čížek, Jakub (advisor) ; Procházka, Ivan (referee)
Modern aluminium alloys 60xx are rich in sillicon and magnesium. They are easy to machine, are weldable, and can be precipitation-hardened, especially se- ries 6061, which we focus on in this thesis. Series 6061 alloy is currently the most general-purpose industrially used aluminium alloy. The purpose of this thesis is to analyze the natural and artificial aging of these alloys through the utilization of positron annihilation spectroscopy and coincidence Doppler broadening of anni- hilation radiation methods. Our goal is precise analysis of precipiation processes, which occur due to natural or artifical aging of the alloy. Although artifical aging in aluminium alloys is a well researched area, understanding and description of key mechanisms controlling the natural aging especially in the early stages of pre- cipitation is not yet sufficiently explained. We use modern methods of positron annihilation spectroscopy to understand and confirm our clustering hypotheses. 1
Microstructure and thermal stability of ultra fine grained Mg-Zn-Y alloys
Vlasák, Tomáš ; Čížek, Jakub (advisor) ; Procházka, Ivan (referee)
The aim of this diploma thesis is to investigate microstructure and thermal stability of ultra fine grained magnesium alloys. The thesis first summarises methods using plastic deformation in order to achieve ultra fine grained structure that are used to process metals. Then experimental methods employed in the experimental part including microhardness testing, scanning electron microscopy and positron annihilation spectroscopy are described. Brief summary of previous research on MgZnY alloys strengthened by quasicrystalline phases and Mg22Gd alloys is given. Finally, results of experimental investigation of MgZnY alloys with various Zn/Y ratios and Mg22Gd alloy are discussed. These results suggest that presence of phases in MgZnY alloys depend on Zn/Y ratio, hardness of these alloys depends on Zn content and that rapid cooling of MgZnY alloys annealed at 500 řC lead to significant increase in volume fraction of quasicrystalline icosahedral phase. In the second section of the experimental part thermal behaviour of Mg22Gd alloy is investigated. Furthermore, formation of GdH2 particles in Mg22Gd is examined and attributed to reaction of hydrogen decomposed from water vapour with gadolinium in areas rich in gadolinium. Finally, significant hardening of Mg22Gd alloy processed by high pressure torsion has been...
Gas electron multiplier based photon detection for Cherenkov imaging applications
Krištof, Michal ; Finger, Michael (advisor) ; Procházka, Ivan (referee)
In the thesis we focus on the methods used to detect photons in Ring Imaging Cherenkov detectors, their description and the basics of the physical phenomena which lie behind them. We provide a brief description of the gaseous detector types and we describe the development of the new Thick GEM based detection system for the RICH-1 of the COMPASS experiment. We provide a detailed description of the latest tests and the convoluted route of the research done in the field. We review the ThGEM-based detector performance in comparison to the other methods of detection. Powered by TCPDF (www.tcpdf.org)
Particle Identification using Ring Cherenkov Detector Technology at Compass Experiment
Roskot, Michal ; Finger, Michael (advisor) ; Procházka, Ivan (referee)
The presented thesis is dedicated to particle identification in COMPASS RICH-1 experiment which is located in European Organization for Nuclear Research (CERN). For particle identification Cherenkov radiation is used, which is described in the thesis together with detection principles. Current aim in detector upgrade is replacing a part of Multi Wire Proportional Chambers (MWPC) in peripheral regions of the detection surface by a suitable photon detector so as to guarantee one-photon detection. For this purpose the hybrid photon detector based on THGEM and MicroMegas technologies was developed. The hybrid detector test results are presented in the thesis.
Low temperature polarized target for spin structure studies of nucleons at COMPASS
Pešek, Michael ; Finger, Miroslav (advisor) ; Procházka, Ivan (referee)
Title: Low temperature polarized target for spin structure studies of nucleons at COMPASS Author: Bc. Michael Pešek Department: Department of low temperature physics Supervisor of the master thesis: prof. Ing. Miroslav Finger, DrSc. Abstract: In presented thesis we describe concept of Deep Inelastic Scattering of leptons on nucleons in context of nucleon spin structure studies. Both polarized and unpolarized cases are discussed and concept of Transverse Momentum Dependent Parton Distribution Functions (TMD PDF) is introduced. The possibility of TMDs measurement using Semi-inclusive DIS (SIDIS) is described along with related results from COMPASS experiment. The future Drell-Yan programme at COMPASS is briefly mentioned and its importance is presented on the universality test i.e. change of sign of T-odd TMDs when measured in Drell-Yan and SIDIS. The importance of Polarized Target (PT) for spin structure studies is highlighted and principles of Dynamic Nuclear Polarization (DNP) are given using both Solid effect and spin temperature concept. COMPASS experiment is described in many details with accent given to PT. Finally the thermal equilibrium (TE) calibration procedure is described and carried out for 2010 and 2011 physics runs at COMPASS. The average polarization measurement results from 2010 and 2011 are...
Rationality of the Debtor
Procházka, Ivan ; Tuček, Milan (advisor) ; Kuchař, Pavel (referee)
This work deals with the indebtedness of consumers. It examines the causes of the debotrs themselves. Based on a secondary analysis of past research in the area of financial literacy, consumer behavior, statistical data, but also of qualitative research in the form of case study seeks to answer the question why the debtor becomes the debtor, the extent to which the indebtedness and indebtedness viewed as rational behavior but also if the debtor is accompanied by rational reasoning or irrational behavior. It concludes that the debtor can not be considered entirely rational. Applied policy then the issue of over-indebtedness problem takes into account the irrational assumptions by the debtor only marginally and does not reflect as one of its main causes.
Rationality of the Debtor
Procházka, Ivan ; Tuček, Milan (advisor) ; Kuchař, Pavel (referee)
This work deals with the indebtedness of consumers. It examines the causes of the debotrs themselves. Based on a secondary analysis of past research in the area of financial literacy, consumer behavior, statistical data, but also of qualitative research in the form of case study seeks to answer the question why the debtor becomes the debtor, the extent to which the indebtedness and indebtedness viewed as rational behavior but also if the debtor is accompanied by rational reasoning or irrational behavior. It concludes that the debtor can not be considered entirely rational. Applied policy then the issue of over-indebtedness problem takes into account the irrational assumptions by the debtor only marginally and does not reflect as one of its main causes.
Study of thermal stability of Mg-alloys strengthened by quasicrystalline phase
Vlasák, Tomáš ; Čížek, Jakub (advisor) ; Procházka, Ivan (referee)
This bachelor thesis deals with thermal stability of icosahedral phase in Mg-Zn-Y alloys. To study this phenomenon, samples of Mg-3.5Y-35Zn alloy were prepared and equal channel angular pressing method (ECAP) performed at two different temperatures was used to refine their microstructure. Phases in the samples were characterised by scanning electron microscopy and energy-dispersive X- ray spectroscopy. Strengthening effect of icosahedral phase (I-phase) with quasicrystalline structure was examined by measuring Vickers hardness of the samples. Temperatures at which precipitation and dissolution of various phases occur were studied by differential scanning calorimetry. Finally, defect recovery with increasing temperature was investigated by means of positron annihilation lifetime measurement. To identify chemical elements surrounding dislocations coincidence measurements of Doppler broadening of annihilation peak were conducted. Obtained results are as follows. Icosahedral dendritic structures are stable in Mg-3.5Y-35Zn alloy at temperatures up to 350 řC, at higher temperatures they are dissolved in the matrix. Recovery of dislocations takes place in the temperature range from 140 řC to 260 řC and leads to decrease in strength of the alloy processed by ECAP. Concentrations of zinc and yttrium are not enhanced...
Studies of Drell-Yan process with polarized target at COMPASS
Pešková, Markéta ; Finger, Michael (advisor) ; Procházka, Ivan (referee)
Title: Studies of Drell-Yan process with polarized target at COMPASS Author: Markéta Pešková Department / Institute: Department of Low Temperature Physics Supervisor of the bachelor thesis: M.Sc. Michael Finger, CSc. Abstract: The presented thesis intends to give an introduction into the studies of the spin structure of a nucleon. The knowledge about the structure of nucleon has grown in the last few decades; however, its spin structure is still a mystery. One of the concepts that might help solving this spin puzzle is the polarized Drell-Yan process. This process can give us the access to the spin-dependent structure functions of a nucleon via measuring spin asymmetries. In the following text, an outline of the theoretical background of the semi- inclusive Deep Inelastic Scattering and the Drell-Yan is given. The Parton Distribution Functions (PDFs) and the transverse-momentum-dependent PDFs (TMDs) are discussed. And the way of accessing the TMDs via polarized Drell-Yan process is briefly described. This is the goal of the Drell-Yan program at COMPASS experiment, using the transversely polarized target and pion beam in 2014-15. The description of experimental apparatus is given and the system of collecting and processing data is outlined. The data-taking conditions of the 2009 DY beam test and the 2014 DY...
Studies of Drell-Yan process at Compass experiment
Matoušek, Jan ; Finger, Miroslav (advisor) ; Procházka, Ivan (referee)
Hadron structure is not fully understood yet. While the spin-averaged Parton Dis- tribution Functions (PDFs) and the helicity-dependent PDFs are well determined, little is known about the transverzity and some other transverse-momentum de- pendent PDFs (TMDs). The COMPASS experiment at CERN is preparing for studying the TMDs using a Drell-Yan process on transversely polarized target hit by pion beam in 2014-2015. An outline of the parton model of hadrons and of the TMDs is given. The COMPASS spectrometer is described, with emphasis on the modifications for the Drell-Yan program, and its capabilities to measure the TMDs is briefly discussed. A special attention is paid to the polarized target. The dilution refrigerator, the DNP system for polarizing the nuclei and the NMR for polarization measurement are described. The new monitoring system of the refrigerator is described, including the author's contribution to it. Issues of the new NMR coils design are discussed. 1

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See also: similar author names
1 Procházka, I.
2 Procházka, Ivo
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