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Analysis of punches in top boxing competitions
Čížek, Jakub ; Zdobinský, Adam (advisor) ; Stich, Jaroslav (referee)
Title: Analysis of punches in top boxing competitions Objectives: The main objective of this work was to analyze the total number of punches, their efficiency and the use of punches on the body at two weight categories. The specific categories studied were velterweight and light heavyweight. Methods: An observation method was used to create statistics from watched videos. Two consecutive World championships served as a data source. The first one took place in 2013 in Almaty, the second two years later in Doha. MS Excel was used to process data. Results: It was found that more active in terms of attacks was the weight category up to 69 kg, but not more successful. More precise hits have been used by the light heavyweight category. The most commonly used technique was a direct followed by a hook and uppercut. Punches to the body were in the sum total of about 12 % and they were much more effective than strikes to head. Keywords: punch techniques, tactical concept, boxing, comparison, weight categories
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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
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Investigation of defects in quasicrystals
Vlček, Marián ; Čížek, Jakub (advisor)
Název práce: Studium defekt· v kvazikrystalech Autor: Marián Vlček Katedra: Katedra fyziky nízkých teplot Vedoucí disertační práce: doc. Mgr. Jakub ížek, Ph.D., Katedra fyziky nízkých teplot Abstrakt: V predloženej práci boli pomocou spektroskopie doby života poz- itrónov a koincidenčnej spektroskopie Dopplerovského rozšírenia anihilačného píku študované zliatiny WE43 s prídavkom zinku a ternárne zliatiny Mg-Zn-Y. V týchto zliatinách bola nedávno zistená prítomnos' ikosahedrálnej fázy Mg3Zn6Y1 s kvázikryštalickou štruktúrou, čo pritiahlo pozornos' výskumníkov. Spektroskopia doby života pozitrónov preukázala prítomnos' unikátnych vakanciám podobných defektov na rozhraní ikosahedrálnej fázy a horčíkovej matrice, ktoré sú charakter- istické pre horčíkové zliatiny obsahujúce ikosahedrálnu fázu. Tepelné spracovanie skúmaných zliatin vedie k významným zmenám morfológie hraničných fáz. Ke¤že vakanciám podobné defekty spojené s ikosahedrálnou fázou sa vyskytujú na jej rozhraní s horčíkovou matricou, zmeny v morfológii ikosahedrálnej fázy vedú k výrazným zmenám koncentrácie týchto defektov. "alej boli skúmané vzorky pripravené uhlovým pretláčaním kanálom rovnakého prierezu. Typy defektov prítomné v týchto zliatinách a ich teplotná stabilita bola určená pomocou spektroskopie doby života pozitrónov a merania tvrdosti...
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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...
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Výzkum interakce vodíku s vakacemi, dislokacemi a hranicemi zrn v Ti
Knapp, Jan ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
This thesis deals with the system of titanium and hydrogen. Interstitial hydrogen alloys and hydrides are subject to intensive investigation, both theoretical and experimental. It has been proved, that absorbed hydrogen lowers the formation energy of defects in metals, and thus works as the so called 'defactant'. Surfactants on the surfaces of liquids lower the surface tension; defactants in solids lower the formation energy of defects. It has also been proved, that titanium absorbs hydrogen readily, when exposed to high temperature, or high pressure (fugacity); while different loading conditions lead to different features of the final sample. Beside ordinary coarse grained titanium, ultra-fine grained titanium shall be studied in present work, due to its high content of defects. Positron Annihilation Life-time Spectroscopy, a non-destructive technique sensitive on open-volume defects, shall be of prime importance in our investigation. We shall further use the X-ray diffraction, Micro-hardness measurements and Differential Scanning Calorimetry together with Thermogravimetry. Lastly, we shall strongly benefit from using existing computational tools like the Vienna ab-initio Simulation Package, or Pos330; a program for positron life--times calculations.
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Investigation of vacancies in Fe-Al alloys
Lukáč, František ; Čížek, Jakub (advisor) ; Král, Robert (referee) ; Schneeweiss, Oldřich (referee)
Title: Investigation of vacancies in Fe-Al alloys Author: RNDr. František Lukáč Department: Department of Low Temperature Physics Supervisor: doc. Mgr. Jakub Čížek, Ph.D., Department of Low Temperature Physics, Faculty of Mathematics and Physics Abstract: Fe-Al alloys exhibit relatively high vacancy concentrations, which significantly influence the mechanical properties of these alloys. Positron annihi- lation spectroscopy was employed for investigations of vacancies in this work and the vacancy concentrations in Fe-Al alloys were determined by positron lifetime spectroscopy and measurements of positron diffusion length of implanted mono- genergetic positrons. The correlation of hardness with the vacancy concentration was characterized by determination of the vacancy hardening coefficient in Fe- Al alloys. The thermal evolutions of hardness and the vacancy concentration were compared during the annealing of the Fe-Al alloys with various composi- tions. Coincidence Doppler broadening of annihilation peak was employed for determination of the chemical composition of quenched-in vacancies in Fe-Al al- loys. Increased concentration of Al atoms in surrounding vacancies in Fe-Al alloys was related to the attractive interaction between the Al atoms and the vacancy. Quantum mechanical ab initio calculations were...
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Investigation of defects in quasicrystals
Vlček, Marián ; Čížek, Jakub (advisor) ; Hnilica, František (referee) ; Petriska, Martin (referee)
Název práce: Studium defekt· v kvazikrystalech Autor: Marián Vlček Katedra: Katedra fyziky nízkých teplot Vedoucí disertační práce: doc. Mgr. Jakub ížek, Ph.D., Katedra fyziky nízkých teplot Abstrakt: V predloženej práci boli pomocou spektroskopie doby života poz- itrónov a koincidenčnej spektroskopie Dopplerovského rozšírenia anihilačného píku študované zliatiny WE43 s prídavkom zinku a ternárne zliatiny Mg-Zn-Y. V týchto zliatinách bola nedávno zistená prítomnos' ikosahedrálnej fázy Mg3Zn6Y1 s kvázikryštalickou štruktúrou, čo pritiahlo pozornos' výskumníkov. Spektroskopia doby života pozitrónov preukázala prítomnos' unikátnych vakanciám podobných defektov na rozhraní ikosahedrálnej fázy a horčíkovej matrice, ktoré sú charakter- istické pre horčíkové zliatiny obsahujúce ikosahedrálnu fázu. Tepelné spracovanie skúmaných zliatin vedie k významným zmenám morfológie hraničných fáz. Ke¤že vakanciám podobné defekty spojené s ikosahedrálnou fázou sa vyskytujú na jej rozhraní s horčíkovou matricou, zmeny v morfológii ikosahedrálnej fázy vedú k výrazným zmenám koncentrácie týchto defektov. "alej boli skúmané vzorky pripravené uhlovým pretláčaním kanálom rovnakého prierezu. Typy defektov prítomné v týchto zliatinách a ich teplotná stabilita bola určená pomocou spektroskopie doby života pozitrónov a merania tvrdosti...
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Hydrogen-induced defects in titanium
Knapp, Jan ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
Titanium is a very important industrial material with quite a versatile use. This thesis examines the influence of hydrogen absorbed in metal lattice of titanium on defects inside the lattice. In this work titanium samples were loaded with hydrogen using two different methods: electrochemical charging, where titanium sample was immersed in solution of H3PO4 and glycerin as a cathode. The anode was be made of platinum and constant electrical current in order of miliampers was run throw the solution. The H+ cations went to the cathode and were neutralized to a hydrogen atom there. The hydrogen atoms subsequently penetrated into the titanium lattice by diffusion. Gas loading was used as the second method of hydrogen doping. Titanium samples were put into hydrogen atmosphere with defined pressure and kept at constant temperature. Hydrogen loaded samples were examined by positron lifetime spectroscopy which represents a non-destructive technique for studying defects in materials. Analysis of phase composition was performed by X- ray diffraction. Developments of mechanical properties of hydrogen loaded samples were monitored by Vickers micro-hardness testing. Differential Scanning calorimetry was employed for investigation of thermal stability of absorbed hydrogen.
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Study of free volumes in Nafion using positronium
Košinová, Lucie ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
Title: Study of free volumes in Nafion using positronium Author: Lucie Košinová Department: Department of Low-Temperature Physics Supervisor: doc. Mgr. Jakub Čížek, Ph.D., Department of Low-Temperature Physics Abstract: The object of this thesis is investigation of the absorption of water in Nafion and the influence of temperature on the absorption and desorption kinetics. Study of the absorption and desorption of water was carried out either measurement of changes in the macroscopic physical properties of Nafion (weighing, differential scanning calorimetry) either by microscopic characterization of the size distribution of free volume that arises as a consequence of an imperfect arrangement of polymer chains. For this purpose I used a non- destructive method used positron annihilation spectroscopy, which is currently the only technique capable of determination of the size distribution of free volumes having the free volume distribution by size of a few Å. The development of the size distribution and the concentration free volumes in the sample were determined on the based on the measurement of lifetime spectra of positrons annihilating in the sample of Nafion. The results obtained in this thesis can be further used in research of Nafion, which is widely used as a semipermeable membrane during industrial...
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Investigation of defects in thin metallic films
Hruška, Petr ; Čížek, Jakub (advisor)
In the present work Mg films prepared by RF magnetron sputtering were studied. Variable energy positron annihilation spectroscopy (VEPAS) was employed for investigation of defects in the Mg films. VEPAS characterization was combined with scanning electron microscopy and X-ray diffraction in order to determine grain size, phase composition and texture. The effect of different deposition rate and deposition temperature, annealing, various substrates and film thickness on the structure and amount of defects present in the Mg films was examined. Defect studies by VEPAS showed that positrons in studied Mg films are trapped at misfit dislocations and at vacancy-like defects in grain boundaries and their density can be reduced by the deposition at elevated temperature. 1
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